JP4855432B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification device that purifies engine exhaust, and more particularly, to an exhaust gas purification device that includes a urea water tank that stores urea water for supplying ammonia to an ammonia selective reduction type NOx catalyst.

As an exhaust purification device for purifying NOx (nitrogen oxide), which is one of the pollutants contained in engine exhaust, an ammonia selective reduction type NOx catalyst is disposed in the exhaust passage of the engine, and ammonia as a reducing agent. There is known an exhaust gas purification device that purifies exhaust gas by reducing NOx by supplying NOx to an ammonia selective reduction type NOx catalyst.
In such an exhaust purification apparatus, in order to supply ammonia to the ammonia selective reduction type NOx catalyst, it is common to supply urea water, which is easier to handle than ammonia, into the exhaust gas. The urea water supply system into the exhaust includes a so-called air assist system that injects urea water together with compressed air, and a so-called airless system that injects only urea water without using compressed air.

  In the case of the latter airless system, if the distance between the solenoid valve for adjusting the supply amount of urea water into the exhaust and the nozzle to which urea water is actually injected is long, the solenoid valve is closed after the solenoid valve is closed. Since urea water remaining between the valve and the nozzle may solidify and cause clogging, a urea water injector in which the solenoid valve and the nozzle are integrated is used. Therefore, in the urea water injector in which the solenoid valve and the nozzle are integrated, a drive solenoid for the solenoid valve is incorporated in the urea water injector.

  In order to inject urea water into the exhaust gas, the urea water injector is mounted in an exhaust passage that becomes hot due to the heat of the exhaust. However, if the temperature of the drive solenoid rises excessively, problems such as poor insulation and seizure occur. There is a fear. Therefore, in order to prevent the temperature of the drive solenoid from rising excessively, a part of the urea water supplied to the urea water injector is injected into the exhaust gas, and the urea water injector is cooled by the remaining portion of the supplied urea water. A urea water injector with a cooling mechanism has been developed. In the exhaust gas purification apparatus using such a urea water injector with a cooling mechanism, the urea water used for cooling the urea water injector is returned to the urea water tank for storing the urea water.

On the other hand, as a urea water tank for storing urea water, for example, the one shown in Patent Document 1 is known, and urea water is stored in a simple sealed box-shaped urea water tank. It is like that.
JP-A-2005-337112

  However, when the urea water injector with the cooling mechanism described above is used to inject the urea water supplied from the urea water tank into the exhaust gas, the urea water that has been used for cooling the urea water injector and whose temperature has risen is reduced. Since it is returned to the urea water tank, the temperature of the urea water in the urea water tank gradually increases. On the other hand, the amount of urea water remaining in the urea water tank decreases as the urea water consumption progresses, but the amount of heat released from the urea water tank wall as the urea water level in the urea water tank decreases. Will decrease. For this reason, when the urea water tank as shown in the above-mentioned patent document 1 is used and the urea water in the urea water tank decreases, when the urea water whose temperature has increased as described above is returned to the urea water tank, There is a possibility that the temperature of the urea water in the urea water tank rises excessively.

  In particular, in the case of an exhaust gas purification device in which a particulate filter that collects particulates in exhaust gas is disposed upstream of the ammonia selective reduction type NOx catalyst, selective ammonia reduction is performed when the particulate filter is forcibly regenerated. Since the temperature of the exhaust gas flowing into the NOx catalyst rises to around 600 ° C, the temperature of the urea water in the urea water tank rises excessively when the urea water that has received the heat of the hot exhaust gas is returned to the urea water tank It becomes easy to do.

When the temperature of the urea water in the urea water tank rises excessively in this way, there arises a problem that the urea water injector cannot be cooled effectively.
In order to avoid such problems, if urea water is replenished to keep the urea water level in the urea water tank always high, the urea water must be replenished frequently. Arise.

  This invention is made | formed in view of such a subject, The place made into the objective is to provide the exhaust gas purification apparatus which can prevent the excessive temperature rise of urea water in a urea water tank. is there.

  In order to achieve the above object, an exhaust emission control device according to the present invention stores an ammonia selective reduction type NOx catalyst that is interposed in an exhaust passage of an engine and selectively reduces NOx in exhaust gas using ammonia as a reducing agent, and urea water. A urea water tank is provided in the exhaust passage, and a part of the urea water supplied from the urea water tank is injected into the exhaust gas upstream of the ammonia selective reduction type NOx catalyst, and the remaining portion of the urea water A urea water injector for returning the urea water tank to the urea water tank, wherein the urea water tank has at least a part of a wall portion provided in the vertical direction out of the wall portions forming the urea water tank. A double wall structure comprising a first wall portion serving as an outer shell and a second wall portion provided inside the first wall portion, and urea water returned from the urea water injector is used as the double wall structure. The Then, an inflow portion that flows into the first housing portion formed between the first wall portion and the second wall portion, and an opposite side of the first housing portion across the second wall portion are formed. A communication portion for allowing the urea water in the first storage portion to flow into the second storage portion, and an outflow portion for allowing the urea water supplied to the urea water injector to flow out of the second storage portion. (Claim 1).

  According to the exhaust purification apparatus configured as described above, a part of the urea water supplied from the urea water tank is supplied from the urea water injector into the exhaust gas upstream of the ammonia selective reduction type NOx catalyst. The urea water supplied in the exhaust gas is hydrolyzed by the heat of the exhaust gas to generate ammonia, and the generated ammonia is supplied as a reducing agent to the ammonia selective reduction type NOx catalyst and used for the reduction of NOx in the exhaust gas. The On the other hand, the remaining portion of the urea water supplied from the urea water tank is returned to the urea water tank after cooling the urea water injector.

  The urea water returned from the urea water injector to the urea water tank passes through the inflow portion, and the inside of the first housing portion formed between the first wall portion and the second wall portion forming the double wall structure of the urea water tank. Flow into. The urea water once flowing into the first housing part in this way flows into the second housing part through the communication part. And the urea water in a 2nd accommodating part flows out out of an outflow part again, and is supplied to a urea water injector.

Further, in the exhaust purification apparatus, the communication unit causes the urea water to flow from the first storage unit into the second storage unit when the water level of the urea water in the first storage unit exceeds a predetermined level. (Claim 2).
According to the exhaust gas purification apparatus configured as described above, when the urea water returned from the urea water injector flows into the first housing portion, and the water level of the urea water in the first housing portion exceeds a predetermined level, the communication portion causes The urea water in the first housing part flows into the second housing part.

Specifically, in such an exhaust purification device, the communication portion communicates with the first housing portion at a first position which is the lower end side of the first housing portion, and is located above the first position. The second housing portion is in communication with the second housing portion (claim 3).
According to the exhaust gas purification apparatus configured as described above, the urea water is returned from the urea water injector because the first storage portion and the communication portion communicate with each other at the first position on the lower end side of the first storage portion. As the water level of the urea water in the first housing portion rises, the urea water also flows into the communication portion at the first position, and the water level of the urea water in the communication portion rises as in the first housing portion. Go. When the water level of the urea water in the communication portion rises to reach the second position and further urea water flows into the first storage portion, the urea water in the communication portion flows into the second storage portion.

  More specifically, in such an exhaust emission control device, the communication part covers a part of the wall surface of the second wall part in the second housing part with a cover member, thereby A communication passage formed in a passage shape starting from the bottom surface and extending upward, and opening into the second housing portion at the second position, which is lower than the upper end of the second wall portion; and A communication hole that is formed in the second wall portion to be formed and opens at the first position lower than the second position to communicate the first storage portion with the inside of the communication passage is provided ( Claim 4).

According to the exhaust emission control device configured as described above, a part of the wall surface of the second wall portion in the second accommodating portion is used to cover the cover member so as to form a passage, and the second position is the second position. The communication portion is configured by a communication passage that opens into the housing portion and a communication hole that opens at the first position of the second wall portion that forms the communication passage and connects the first storage portion and the communication passage.
More specifically, in such an exhaust emission control device, the second housing portion has a box shape having an opening at the upper end and a corner portion extending in the vertical direction, and the communication portion includes the corner portion in the first portion. (2) It is formed by covering with a flat cover member from the bottom surface of the housing portion to the second position (Claim 5).

According to the exhaust gas purification apparatus configured as described above, the second housing portion has a box shape having an upper end opened and a corner portion extending in the vertical direction, and the corner portion of the second housing portion is utilized. A communication path is formed by covering with a flat cover member.
Alternatively, the communicating portion communicates with the first accommodating portion at the first position on the lower end side of the first accommodating portion, and communicates with the second accommodating portion at the second position located above the first position. Specifically, the communication part is formed in the shape of a passage extending in the vertical direction using a part of the wall surface of the second wall part in the first housing part, and the first communication part. A communication passage that opens into the first housing portion at the first position, which is the lower end side of the housing portion, and a second wall portion that forms the communication passage, and the second position is higher than the first position. An opening is provided to open and connect the second housing portion and the communication passage (Claim 6).

According to the exhaust gas purification apparatus configured as described above, a continuous passage is formed in a passage shape by using a part of the wall surface of the second wall portion in the first housing portion, and opens into the first housing portion at the first position. The communication portion is configured by the passage and the opening that opens at the second position of the second wall portion that forms the communication passage and communicates the second housing portion and the inside of the communication passage.
More specifically, in such an exhaust emission control device, the communication path includes two partition members that are spanned and spaced from each other between the wall surface of the first wall portion and the wall surface of the second wall portion. The first housing portion is formed by partitioning, and the lower end of at least one of the partition members is located above the bottom surface of the first housing portion so that the first housing portion is opened at the first position, and the second housing is formed. The portion is formed in a box shape with an upper end opened, and the opening is formed by cutting out the upper end of the second wall portion that forms the communication path (Claim 7).

  According to the exhaust gas purification apparatus configured as described above, the communication passage is first formed by two partition members that are spanned and spaced from each other between the inner wall surface of the first wall portion and the outer wall surface of the second wall portion. It is formed by partitioning the accommodating portion. And the lower end of at least one of a partition member is located above the bottom face of a 1st accommodating part, and is opening in the 1st position. The second housing part is formed in a box shape with an upper end opened, and an opening is formed by cutting out the upper end of the second wall part forming the communication path.

Alternatively, as an exhaust gas purification device provided with a communication part that allows urea water to flow from the first housing part to the second housing part when the level of urea water in the first housing part exceeds a predetermined level, specifically, The second accommodating portion is formed in a box shape having an open upper end, and the communication portion is a notch formed at the upper end of the second wall portion.
According to the exhaust gas purification apparatus configured as described above, the urea water is returned from the urea water injector, whereby the level of the urea water in the first housing portion rises and reaches the notch formed at the upper end of the second wall portion. Then, with the further inflow of urea water into the first housing portion, the urea water in the first housing portion is second accommodated through a notch formed at the upper end of the second wall portion forming the first housing portion. Flows into the club.

Alternatively, as an exhaust gas purification device provided with a communication part that allows urea water to flow from the first housing part to the second housing part when the level of urea water in the first housing part exceeds a predetermined level, specifically, The second housing part is formed in a box shape having an open upper end, and the communication part is an upper end part of the second wall part (claim 9).
According to the exhaust gas purification apparatus configured as above, when the urea water is returned from the urea water injector and the water level of the urea water in the first housing portion rises and reaches the upper end of the second wall portion, the further Along with the inflow of urea water into the first housing part, the urea water in the first housing part flows into the second housing part from the upper end of the second wall part forming the first housing part.

  According to the exhaust gas purification apparatus of the present invention, the urea water returned from the urea water injector to the urea water tank is formed between the first wall portion and the second wall portion forming the double wall structure of the urea water tank. After flowing into the first housing part, the communication part flows into the second housing part formed on the opposite side of the first housing part across the second wall part. Accordingly, the urea water returned from the urea water injector to the urea water tank flows into the first housing portion and then flows into the second housing portion through the first wall portion that is in contact with the outside air. Heat release from the urea water is performed, and the temperature of the urea water can be effectively reduced. As a result, even if the amount of urea water in the urea water tank decreases, it is possible to prevent an excessive temperature rise of the urea water in the urea water tank, and the urea water injector can be effectively cooled. it can. In addition, it is not necessary to replenish urea water frequently before the water level of the urea water drops to suppress the temperature rise of the urea water in the urea water tank.

  Further, according to the exhaust purification device of the second to ninth aspects, the urea water in the first housing portion does not flow into the second housing portion by the communicating portion until the water level of the urea water in the first housing portion exceeds a predetermined level. Therefore, even if the total amount of urea water stored in the urea water tank is relatively small, the urea water in the first housing portion is kept at a high level after the urea water level in the first housing portion is maintained high. 2 will flow into the housing. Therefore, the state in which the contact area between the urea water and the first wall portion is ensured to be large can be maintained for a long time, and the heat from the urea water through the first wall portion that is in contact with the outside air allows the urea water to be maintained. Cooling can be performed more effectively.

Particularly, in the case of the exhaust emission control device configured as in claim 3, the communication portion communicates with the first housing portion at the first position which is the lower end side of the first housing portion, and more than the first position. It is only necessary to provide a communication portion that communicates with the second housing portion at the second position located above, and such an effect can be obtained while the communication portion has a simple structure.
In particular, in the case of the exhaust emission control device configured as in claim 4 or claim 5, since the communication portion is constituted by a part of the second wall portion and the cover member, urea in the first accommodating portion is formed. As described above, there is no need to perform piping or the like in order to allow urea water to flow from the first storage portion into the second storage portion in accordance with the water level, and the communication portion has a simpler structure as described above. It is possible to obtain an effect that the urea water level in the section is increased to maintain a state in which the contact area between the urea water and the first wall portion is ensured for a long time, and the urea water can be efficiently cooled. .

  Particularly, in the case of the exhaust emission control device configured as in claim 5, the communication passage is formed by covering with a flat cover member using the corner portion of the second housing portion. While having a very simple structure, as described above, the level of the urea water in the first housing portion is increased to maintain the state in which the contact area between the urea water and the first wall portion is ensured for a long time. The effect that cooling can be performed efficiently can be acquired.

  Further, in the case of the exhaust emission control device configured as in the sixth and seventh aspects in particular, since the communication portion is configured by using a part of the second wall portion, the urea water in the first accommodating portion is formed. As described above, there is no need to perform piping or the like in order to allow urea water to flow from the first container to the second container according to the water level, and the communication part has a simpler structure. It is possible to obtain an effect that the urea water can be efficiently cooled by increasing the water level of the urea water and maintaining a state in which a large contact area between the urea water and the first wall portion is ensured.

  In particular, in the case of the exhaust emission control device configured as in claim 7, the communication portion is formed by using a part of the first wall portion and the second wall portion and the two partition members. While having a simple structure, as described above, the level of the urea water in the first housing portion is increased to maintain a state in which the contact area between the urea water and the first wall portion is large, and the urea water is cooled. The effect that it can carry out efficiently can be acquired.

  Further, according to the exhaust gas purification apparatus configured as in claim 8, the urea water in the first storage portion is stored in the second storage until the level of the urea water in the first storage portion reaches the notch in the second wall portion. Therefore, even if the amount of urea water stored in the urea water tank is relatively small, the urea water in the first storage unit is maintained after the urea water level in the first storage unit is kept high. Will flow into the second housing part. Accordingly, a large contact area between the urea water and the first wall portion can be secured, and the cooling of the urea water can be further effectively performed by heat radiation from the urea water through the first wall portion in contact with the outside air. Can be done.

  In addition, such an effect is obtained by a very simple structure in which the second housing portion is formed in a box shape with the upper end opened and a notch is formed at the upper end of the second wall portion forming the first housing portion. In addition to being possible, it is not necessary to provide a communication path for allowing urea water to flow from the first storage unit to the second storage unit according to the level of urea water in the first storage unit. The limited space can be used effectively.

  Further, according to the exhaust emission control device configured as in claim 9, the inside of the first housing portion is kept until the urea water level in the first housing portion reaches the upper end of the second wall portion forming the first housing portion. The urea water does not flow into the second storage part, so even if the amount of urea water stored in the urea water tank is relatively small, the urea water level in the first storage part is maintained high. The urea water in the first housing part flows into the second housing part. Accordingly, a large contact area between the urea water and the first wall portion can be secured, and the cooling of the urea water can be further effectively performed by heat radiation from the urea water through the first wall portion in contact with the outside air. Can be done.

  In addition, such an effect can be obtained not only by an extremely simple structure in which the second housing part is formed in a box shape having an open upper end, but also depending on the level of urea water in the first housing part. Thus, it is not necessary to provide a communication path for allowing urea water to flow from the first housing portion to the second housing portion, and the limited space in the urea water tank can be effectively utilized.

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. The exhaust purification device according to the present invention is based on FIG. The configuration 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 high-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is supplied to an injector 4 provided in each cylinder. Then, fuel is injected from each injector 4 into each cylinder.

  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 from the intake passage 6, and the intake air supercharged by the compressor 8a is intercooler. 10 and the intake control valve 12 are introduced into the intake manifold 14. An intake air amount sensor 16 for detecting an intake air flow rate to the engine 1 is provided upstream of the compressor 8a in the intake passage 6.

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 24 that communicates the exhaust manifold 18 and the intake manifold 14 via the EGR valve 22 is provided between the exhaust manifold 18 and the intake manifold 14.
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. The rotating shaft of the turbine 8b is connected to the rotating shaft of the compressor 8a so that the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and drives the compressor 8a.

The exhaust aftertreatment device 28 includes an upstream casing 30 and a downstream casing 34 connected to the downstream side of the upstream casing 30 via an exhaust communication passage 32. In this embodiment, the upstream casing 30 and the exhaust casing 28 are exhausted. The communication passage 32 and the downstream casing 34 correspond to the exhaust passage of the present invention.
A pre-stage oxidation catalyst 36 is accommodated in the upstream casing 30, and a particulate filter (hereinafter referred to as a filter) 38 is accommodated on the downstream side of the pre-stage oxidation catalyst 36. The filter 38 is provided to purify the exhaust of the engine 1 by collecting particulates in the exhaust. Further, the front-stage oxidation catalyst 36 oxidizes NO (nitrogen monoxide) in the exhaust gas to generate NO ₂ (nitrogen dioxide). Thus, by arranging the front-stage oxidation catalyst 36 and the filter 38 in this way, the filter 38 Particulates collected and accumulated in the catalyst react with NO ₂ supplied from the pre-stage oxidation catalyst 36 to be oxidized, and the filter 38 is continuously regenerated.

On the other hand, an ammonia selective reduction type NOx catalyst (hereinafter referred to as an SCR catalyst) that adsorbs ammonia in the downstream casing 34 and selectively reduces NOx (nitrogen oxide) in the exhaust gas by using the adsorbed ammonia as a reducing agent to purify the exhaust gas. 40) and a downstream oxidation catalyst 42 for removing ammonia flowing out from the SCR catalyst 40 is housed downstream of the SCR catalyst 40. The post-stage oxidation catalyst 42 also has a function of oxidizing CO (carbon monoxide) generated when particulates are incinerated by forced regeneration of the filter 38 and discharging it into the atmosphere as CO ₂ (carbon dioxide). Yes.

  The exhaust communication passage 32 is provided with a urea water injector 44 for injecting and supplying urea water into the exhaust gas in the exhaust communication passage 32. The urea water injector 44 injects urea water by opening and closing a valve mechanism (not shown), and a drive solenoid (not shown) for opening and closing the valve mechanism is incorporated. The urea water injector 44 injects a part of the supplied urea water into the exhaust gas by opening and closing the valve mechanism and uses the remaining part for cooling. The temperature of the drive solenoid of the urea water injector 44 receives the heat of the exhaust gas. It is trying not to rise excessively. In addition, since such urea water injector 44 is already known, the description about the detailed structure is abbreviate | omitted here.

  The urea water injector 44 is connected to the urea water tank 50 by a urea water supply pipe 46 and a urea water return pipe 48, and the urea water tank 50 is connected to the urea water tank 50 by a urea water supply pump 52 interposed in the urea water supply pipe 46. The stored urea water is supplied to the urea water injector 44 through the urea water supply pipe 46. As described above, a part of the urea water supplied to the urea water injector 44 drives the drive solenoid provided in the urea water injector 44 to open and close the valve mechanism, whereby the exhaust gas in the exhaust communication passage 32 is exhausted. It is injected inside. On the other hand, the remaining portion of the urea water supplied to the urea water injector 44 is returned to the urea water tank 50 via the urea water return pipe 48 after cooling the urea water injector 44.

The atomized urea water injected from the urea water injector 44 is hydrolyzed by the heat of the exhaust to become ammonia, and is supplied to the SCR catalyst 40. The SCR catalyst 40 adsorbs the supplied ammonia and promotes a denitration reaction between the adsorbed ammonia and NOx in the exhaust, thereby purifying NOx to be harmless N ₂ . At this time, if ammonia flows out of the SCR catalyst 40 without reacting with NOx, this ammonia is removed by the post-stage oxidation catalyst 42.

  Further, the temperature of the urea water used for cooling the urea water injector 44 is increased by the heat taken from the urea water injector 44, and the urea water tank 50 is returned to the urea water tank 50 by returning the urea water to the urea water tank 50. The temperature of the urea water inside gradually increases. In particular, when the filter 38 is forcibly regenerated to remove particulates accumulated on the filter 38, the temperature of the exhaust gas flowing out from the filter 38 and flowing into the SCR catalyst 40 rises to around 600 ° C. The temperature of the urea water in the water tank 50 also greatly increases as compared with the case where the filter 38 is not forcibly regenerated.

If the temperature of the urea water in the urea water tank 50 rises excessively, the urea water injector 44 may not be effectively cooled. For this reason, in this embodiment, even if the urea water whose temperature has risen due to the heat of the exhaust gas is returned to the urea water tank 50, the urea water tank does not exceed the predetermined temperature in the urea water tank 50. 50 is configured.
Hereinafter, such a urea water tank 50 will be described in order as first to fourth embodiments of the present invention. In each embodiment, only the internal structure of the urea water tank 50 is different, and each configuration including the exhaust gas purification device shown in FIG. 1 is common to each embodiment. Therefore, except for the urea water tank 50, common reference numerals are used for the configuration shown in FIG. 1, and the reference numerals in each embodiment of the urea water tank 50 shown in FIG. It replaces with and demonstrates.

First, as a urea water tank 50 in FIG. 1, a urea water tank 150 of an exhaust gas purification apparatus according to a first embodiment of the present invention will be described based on FIGS. 2 to 5.
FIG. 2 is a schematic configuration diagram in which a part of the urea water tank 150 in the first embodiment is cut away, FIG. 3 is a cross-sectional view of the urea water tank 150 taken along line III-III in FIG. 2, and FIG. It is sectional drawing of the urea water tank 150 which follows the IV-IV line in the inside.

  As shown in FIGS. 2 to 4, the urea water tank 150 is formed in a box shape closed by the first wall 102 serving as an outer shell of the urea water tank 150, and stores urea water therein. A space is provided. As shown in FIGS. 3 and 4, a cylindrical second wall portion 104 is erected from the bottom surface of the urea water tank 150 inside the first wall portion 102, and the wall portion of the urea water tank 150 is Among them, the side wall portion extending in the vertical direction has a double wall structure by the first wall portion 102 and the second wall portion 104. By providing the second wall portion 104 inside the first wall portion 102 in this manner, the urea water 106 is accommodated between the first wall portion 102 and the second wall portion 104 that form a double wall structure. A second housing portion is formed for housing the urea water 110 inside the second wall portion 104, which is formed on the opposite side of the first housing portion 108 with the second wall portion 104 interposed therebetween. 112 is formed. As shown in FIG. 4, the upper end of the second wall portion 104 is located at a position lower than the upper surface of the urea water tank 150, and the second storage portion 112 has a box shape with the upper end opened.

As shown in FIG. 4, an inlet 114 for replenishing the urea water in the urea water tank 150 is provided on the upper surface of the urea water tank 150 at a position above the second housing portion 112. . A cap 116 that has a ventilation mechanism (not shown) for maintaining the internal pressure of the urea water tank 150 at atmospheric pressure and plugs the injection port 114 is attached to the injection port 114.
A return port (inflow part) 118 to which a urea water return pipe 48 is connected is provided on the upper surface of the urea water tank 150 above the first housing portion 108 and used for cooling the urea water injector 44. The urea water thus made passes through the urea water return pipe 48 and flows into the first accommodating portion 108 of the urea water tank 150 from the return port 118.

  On the other hand, a portion of the bottom surface of the urea water tank 150 that serves as the bottom surface of the first housing portion 108 is provided with a first drain port 120 as shown in FIGS. The first drain port 120 is used to remove dust in the first accommodating portion 108 and can be opened and closed by the first drain cock 122. Note that the first drain cock 122 is closed in a normal use state except when the first drain port 120 is used for dust removal or the like.

  Furthermore, a suction port (outflow portion) 124 and a second drain port 126 are provided on the portion of the bottom surface of the urea water tank 150 that becomes the bottom surface of the second housing portion 112, as shown in FIGS. ing. A urea water supply pipe 46 is connected to the suction port 124, and the urea water 110 in the second housing portion 112 flows out of the suction port 124 and then passes through the urea water supply pipe 46 by the urea water supply pump 52. It is supplied to the urea water injector 44. The second drain port 126 is used to remove dust in the second housing portion 112 and can be opened and closed by the second drain cock 128. Note that the second drain cock 128 is closed in a normal use state except when the second drain port 126 is used for dust removal or the like.

  As shown in FIG. 3, four corners extending in the vertical direction are formed in the second housing portion 112 by the second wall portion 104, and one of these four corners has a flat plate shape. The cover member 130 is attached so as to cover the corner. As shown in FIG. 4, the cover member 130 extends upward from the bottom surface of the second housing portion 112, and a passage (communication passage) is formed by the cover member 130 and the second wall portion 104 that forms a corner portion. ) 132 is formed.

  FIG. 5 is a perspective view showing only the second wall portion 104 and the cover member 130 of the urea water tank 150. As shown in FIGS. 4 and 5, the upper end of the cover member 130 is the second wall portion. 104, that is, a position lower than the upper end of the second accommodating portion 112, the passage 132 opens into the second accommodating portion 112 at a position where the upper end is lower than the upper end of the second wall portion 112 (second position). The second housing part 112 is in communication.

  On the other hand, as shown in FIGS. 2, 4, and 5, the lower end portion of the corner of the second wall portion 104 that forms the passage 132 together with the cover member 130 is the The communication hole 134 is provided by cutting out between the two connecting portions. Thus, by providing the communication hole 134 by notching the second wall portion 104, the passage 132 communicates with the first accommodating portion 108 at a position (first position) serving as a lower end thereof. Accordingly, the passage 132 serves as a communication passage communicating with the first housing portion 108 and the second housing portion 112.

  In the urea water tank 150 configured as described above, the urea water returned from the urea water injector 44 to the urea water tank 150 via the urea water return pipe 48 flows into the first housing portion 108 from the return port 118. . At this time, the passage 132 communicates with the first storage portion 108 through the communication hole 134 provided at the lower end thereof, so the level of the urea water 106 in the first storage portion 108 and the urea water in the passage 132 It is substantially coincident with the water level of 136.

  In addition, the passage 132 opens into the second housing portion 112 at the upper end portion thereof and communicates with the inside of the second housing portion 112, so that the first passage regardless of the amount of the urea water 110 in the second housing portion 112. Until the water level of the urea water 106 in the storage unit 108 rises and reaches the same height as the upper end of the passage 132, that is, the level indicated by the two-dot chain line in FIG. 4, the urea water 106 in the first storage unit 108 It does not flow into the second housing part 112 through the passage 132.

  Therefore, even if the urea water whose temperature has been increased by being used for cooling the urea water injector 44 is returned to the urea water tank 150 and flows into the first accommodating portion 108 from the return port 118, the urea water is not 1 until the water level of the urea water 106 in the storage portion 108 reaches the same height as the upper end of the passage 132, and stays in the first storage portion 108, and during this time, the first wall portion 102 is in contact with the outside air. The heat of the urea water 106 in the first storage unit 108 is released, and the urea water 106 is effectively cooled.

  In addition, when the urea water 106 in the first storage portion 108 reaches the same height as the upper end of the passage 132 and the inflow of urea water from the return port 118 into the first storage portion 108 continues, The urea water 136 cooled in the first storage unit 108 and flowing into the passage 132 flows into the second storage unit 112 from the upper end of the passage 132. Accordingly, the passage 132 and the communication hole 134 correspond to the communication portion of the present invention.

At this time, since the water level of the urea water 106 in the first accommodating portion 108 is maintained at a high position, a large heat radiation area of the urea water 106 to the outside air through the first wall portion 102 is secured, and continues. The urea water 106 is effectively cooled, and the urea water thus cooled flows into the second accommodating portion 112 through the passage 132.
Further, the urea water 106 cooled in the first housing portion 108 has a higher density and is distributed below the first housing portion 108 as the temperature of the urea water becomes lower. Since the urea water 106 in the first storage portion 108 flows into the second storage portion 112 after flowing into the passage 132 through the communication hole 134 provided at the lower end of the passage 132, the urea water in the first storage portion 108. Of the water 106, urea water having a relatively low temperature is supplied to the second storage unit 112.

  Therefore, by using the urea water tank 150 having such a configuration, regardless of the amount of urea water in the urea water tank 150, the urea water returned from the urea water injector 44 into the urea water tank 150 is effectively used. It is possible to cool and prevent an excessive temperature rise of the urea water stored in the urea water tank 150. As a result, the urea water injector 44 can be effectively cooled by the urea water, and deviation from an appropriate concentration due to the concentration of the urea water can be prevented, and ammonia can be generated in the urea water tank 150. It becomes possible to suppress. Furthermore, it is not necessary to replenish the urea water frequently before the water level of the urea water decreases to suppress the temperature rise of the urea water in the urea water tank 150.

  In the urea water tank 150 of the first embodiment, a part of the second wall portion 104 is covered with a flat cover member 130 using the corners of the second storage portion 112 formed by the second wall portion 104. Since the passage 132 is formed by covering, piping or the like for communicating the first housing portion 108 and the second housing portion 112 becomes unnecessary, and the above-described effects can be obtained with a simple structure.

  In the first embodiment, the upper end of the second wall portion 104 is made lower than the upper surface of the urea water tank 150 and the second storage portion 112 is formed in a box shape opened at the upper end. The portion 104 may be extended to the upper surface of the urea water tank 150 so that the upper surface of the urea water tank 150 covers the upper portion of the second storage portion 112. Also in this case, the passage 132 and the communication hole 134 can be similarly configured.

  In the first embodiment, the corner 132 of the second housing portion 112 formed by the second wall portion 104 is covered with the cover member 130 to form the passage 132. However, the second wall other than the corner portion is formed. For example, a cover member having a U-shaped cross section may be attached to the inner side surface of the portion 104, and a passage similar to that in the first embodiment may be formed by the cover member and the second wall portion 104. In this case, by setting the upper end portion of the cover member to a position lower than the upper end of the second wall portion 104, the passage is opened in the second accommodating portion 112, and at the lower end portion of the second wall portion forming the passage. What is necessary is just to provide the communicating hole which forms a notch and connects a channel | path and a 1st accommodating part.

In the first embodiment, the upper end of the cover member 130 is made lower than the upper end of the second wall portion 104 so that the passage 132 is opened in the second accommodating portion 112. A through hole may be provided in the middle of the member 130 in the vertical direction so that the passage 132 is opened in the second housing portion 112.
Furthermore, in the first embodiment, the first housing portion 108 and the passage 132 are communicated with each other by providing a notch at the lower end of the second wall portion 104 that forms the passage 132. A through hole may be provided in the middle of the second wall portion 104 forming the 132 in the vertical direction, and this may be used as a communication hole.

  In addition to this, when the through hole is provided in the middle portion of the cover member 130 and the passage 132 is opened in the second accommodating portion 112 as described above, the through hole provided in the cover member 130 is By being at a position higher than the through hole provided in the second wall portion 104, the same effect as described above can be obtained. However, in order to cool the urea water more effectively, it is desirable that the passage 132 opens into the second housing portion 112 at the upper end and communicates with the first housing portion 108 at the lower end.

Next, as a urea water tank 50 in FIG. 1, a urea water tank 250 of an exhaust gas purification apparatus according to a second embodiment of the present invention will be described based on FIGS. 6 to 9.
6 is a schematic configuration diagram showing a part of the urea water tank 250 in the second embodiment by cutting away, FIG. 7 is a sectional view of the urea water tank 250 along the line VII-VII in FIG. 6, and FIG. It is sectional drawing of the urea water tank 250 which follows the middle VIII-VIII line.

  As shown in FIGS. 6 to 8, the urea water tank 250 is formed in a box shape closed by the first wall 202 that is an outer shell of the urea water tank 250, and stores urea water therein. A space is provided. As shown in FIGS. 7 and 8, a cylindrical second wall portion 204 is erected from the bottom surface of the urea water tank 250 inside the first wall portion 202. Among these, the side wall portion extending in the vertical direction has a double wall structure by the first wall portion 202 and the second wall portion 204. Thus, by providing the 2nd wall part 204 inside the 1st wall part 202, it is for accommodating the urea water 206 between the 1st wall part 202 and the 2nd wall part 204 which make a double wall structure. A second housing portion for housing urea water 210 inside the second wall portion 204, which is formed on the opposite side of the first housing portion 208 with the second wall portion 204 interposed therebetween, is formed. 212 is formed. As shown in FIG. 8, the upper end of the second wall portion 204 is at a position lower than the upper surface of the urea water tank 250, and the second storage portion 212 has a box shape with the upper end opened.

As shown in FIG. 8, an injection port 214 is provided on the upper surface of the urea water tank 250 at a position above the second housing portion 212, and a cap 216 is attached to the injection port 214. The inlet 214 and the cap 216 have the same structure and function as the inlet 114 and the cap 116 in the first embodiment described above.
In addition, a return port (inflow part) 218 to which a urea water return pipe 48 is connected is provided at a position above the first housing portion 208 on the upper surface of the urea water tank 250 and used for cooling the urea water injector 44. The urea water thus passed through the urea water return pipe 48 flows into the first storage portion 208 of the urea water tank 250 from the return port 218.

  On the other hand, a portion of the bottom surface of the urea water tank 250 that becomes the bottom surface of the first accommodating portion 208 is provided with a first drain port 220 as shown in FIGS. 222 can be opened and closed. The first drain port 220 and the first drain cock 222 have the same structure and function as the first drain port 120 and the first drain cock 122 in the first embodiment described above.

  Further, a suction port (outflow portion) 224 and a second drain port 226 are provided on the bottom surface of the urea water tank 250 at the bottom surface of the second storage portion 212 as shown in FIGS. It has been. A urea water supply pipe 46 is connected to the suction port 224, and the urea water 210 in the second housing portion 212 flows out of the suction port 224 and then passes through the urea water supply pipe 46 by the urea water supply pump 52. It is supplied to the urea water injector 44. The second drain port 226 can be opened and closed by the second drain cock 228. The second drain port 226 and the second drain cock 228 are the second drain port 126 and the second drain port 126 in the first embodiment described above. The second drain cock 128 has the same structure and function.

As shown in FIG. 7, four corners extending in the vertical direction are formed in the second housing portion 212 by the second wall portion 204, and one of these four corners has a pair. The flat partition members 230 are spanned between the first wall portion 202 and the second wall portion 204 so as to be spaced apart from each other with the corner portion interposed therebetween.
FIG. 9 is a perspective view showing only the second wall portion 204 and the partition member 230 of the urea water tank 250, and the both partition members 230 are shown in FIG. 8 and FIG. A lower end portion is provided above the bottom surface of the second wall portion 204 and extends to the upper end of the second wall portion 204, and a passage (communication passage) 232 is formed between the two partition members 230. As described above, since the lower end of each partition member 230 is above the bottom surface of the first housing portion 208, the passage 232 opens at the position of the lower end portion (first position) and communicates with the inside of the first housing portion 208. is doing.

  On the other hand, as shown in FIGS. 6, 8, and 9, the upper end portion of the corner of the second wall portion 204 that forms the passage 232 together with the pair of partition members 230 corresponds to the pair of partition members 230. The opening part 234 is provided by notching between them. By thus notching the second wall portion 204 and providing the opening 234, the passage 232 opens at a position (second position) higher than the opening position in the first housing portion 208, and the inside of the second housing portion 212. Communicating with Accordingly, the passage 232 serves as a communication passage that communicates the first storage portion 208 and the second storage portion 212.

  In the urea water tank 250 configured as described above, the urea water returned from the urea water injector 44 to the urea water tank 250 via the urea water return pipe 48 flows into the first accommodating portion 208 from the return port 218. . At this time, since the passage 232 is opened at the lower end thereof and communicates with the first storage portion 208, the water level of the urea water 206 in the first storage portion 208 and the water level of the urea water 236 in the passage 232 are substantially the same. Is consistent.

  Further, since the passage 232 communicates with the inside of the second housing part 212 through the opening 234 at the upper end thereof, the inside of the first housing part 208 regardless of the amount of the urea water 210 in the second housing part 212. Until the water level of the urea water 206 rises and reaches the same level as the lower end of the opening 234, that is, the level indicated by the two-dot chain line in FIG. 8, the urea water 206 in the first container 208 passes through the passage 232. Therefore, it does not flow into the second housing part 212.

  Therefore, even if the urea water whose temperature has been increased by being used for cooling the urea water injector 44 is returned to the urea water tank 250 and flows into the first accommodating portion 208 from the return port 218, the urea water is not The urea water 206 in the first storage unit 208 stays in the first storage unit 208 until the water level reaches the same height as the lower end of the opening 234. During this time, the heat of the urea water 206 in the first accommodating portion 208 is released through the first wall portion 202 in contact with the outside air, and the urea water 206 is effectively cooled.

  Moreover, even after the water level of the urea water 206 in the first storage unit 208 reaches the same height as the lower end of the opening 234, the inflow of urea water from the return port 218 into the first storage unit 208 continues. The urea water 136 cooled in the first housing part 108 and flowing into the passage 132 flows into the second housing part 212 through the opening 234. Therefore, the passage 232 and the opening 234 correspond to the communication portion of the present invention.

At this time, since the water level of the urea water 206 in the first storage unit 208 is maintained at a high position, a large heat radiation area of the urea water 206 to the outside air through the first wall 202 is ensured, and continues. The urea water 206 is effectively cooled, and the urea water thus cooled flows into the second housing portion 212 through the passage 232.
Furthermore, the urea water 206 cooled in the first storage unit 208 has a higher density as the temperature of the urea water becomes lower, and is distributed below the first storage unit 208. Since the urea water 206 in the first storage portion 208 flows into the second storage portion 212 after flowing into the passage 232 from the lower end of the passage 232, the temperature of the urea water 206 in the first storage portion 208 is relatively low. The urea water is supplied to the second storage unit 212.

  Therefore, by using the urea water tank 250 having such a configuration, regardless of the amount of urea water in the urea water tank 250, the urea water returned from the urea water injector 44 into the urea water tank 250 can be effectively used. It is possible to cool and prevent an excessive increase in the temperature of the urea water stored in the urea water tank 250. As a result, the urea water injector 44 can be effectively cooled by the urea water, and deviation from an appropriate concentration due to the concentration of the urea water can be prevented, and ammonia can be generated in the urea water tank 250. It becomes possible to suppress. Furthermore, it is not necessary to replenish the urea water frequently before the urea water level drops in order to suppress the temperature rise of the urea water in the urea water tank 250.

Further, in the urea water tank 250 of the second embodiment, the passage 132 is formed by spanning the pair of partition members 230 between the first wall portion 202 and the second wall portion 204, respectively. The piping for connecting the first housing portion 208 and the second housing portion 212 is not necessary, and the above-described effects can be obtained with a simple structure.
In the second embodiment, the upper end of the second wall portion 204 is made lower than the upper surface of the urea water tank 250 and the second storage portion 212 is formed in a box shape opened at the upper end. The portion 204 may be extended to the upper surface of the urea water tank 250 so that the upper surface of the urea water tank 250 covers the upper portion of the second storage portion 212. Also in this case, the passage 232 and the opening 134 can be similarly configured.

  Moreover, in the said 2nd Embodiment, although the channel | path 232 was formed so that the corner | angular part of the 2nd accommodating part 212 formed of the 2nd wall part 204 might be pinched | interposed with a pair of partition members 230, 2nd walls other than a corner | angular part are formed. A pair of partition members may be spaced apart from each other between the portion 204 and the first wall portion 202 to form a passage similar to the passage 232 of the second embodiment. In this case, the lower end of each partition member is located above the lower surface of the first accommodating portion 208 to open the passage into the first accommodating portion 208 and to cut out the upper end portion of the second wall portion forming the passage. And an opening for communicating the passage and the second housing portion 212 may be provided.

In the second embodiment, the lower end of each partition member 230 is positioned above the bottom surface of the first housing portion 208 so that the passage 232 is opened in the first housing portion 208. Thus, a through hole may be provided in the middle of the partition member 230 in the vertical direction so that the passage 232 is opened in the first housing portion 208.
Furthermore, in the second embodiment, by forming a notch at the upper end of the second wall portion 204 forming the passage 232 and providing an opening 234, the inside of the second accommodating portion 212 and the passage 232 are communicated. However, instead of this, a through hole may be provided in the middle of the second wall portion 204 forming the passage 232 in the vertical direction, and this may be used as the opening.

  In addition to this, as described above, when a through hole is provided in the middle part of the partition member 130 and the passage 232 is opened in the first accommodating portion 208, the through hole provided in the partition member 130 is By being at a position lower than the through hole provided in the second wall portion 204, the same effect as described above can be obtained. However, in order to cool the urea water more effectively, it is desirable that the opening 234 is provided at the upper end of the passage 232 and the passage 232 communicates with the first accommodating portion 208 at the lower end.

  Further, in the second embodiment, the lower ends of the pair of partition members 230 are made higher than the bottom surface of the first housing portion 208 so that the passage 232 is opened in the first housing portion 208. Only one of the pair of partition members 230 may be configured such that the passage 232 is opened in the first housing portion 208 by setting the lower end thereof to be higher than the bottom surface of the first housing portion 208.

Next, the urea water tank 350 of the exhaust gas purification apparatus according to the third embodiment of the present invention will be described as the urea water tank 50 in FIG. 1 with reference to FIGS. 10 to 12.
FIG. 10 is a horizontal cross-sectional view of the middle portion of the urea water tank 350 in the vertical direction, and FIG. 11 is a cross-sectional view of the urea water tank 350 taken along line XI-XI in FIG.
As shown in FIGS. 10 and 11, the urea water tank 350 is formed in a box shape closed by a first wall 302 that is an outer shell of the urea water tank 350, and stores urea water therein. A space is provided. As shown in FIG. 11, a cylindrical second wall portion 304 is erected from the bottom surface of the urea water tank 350 inside the first wall portion 302. The first side wall 302 and the second wall 304 form a double wall structure. By providing the second wall portion 304 inside the first wall portion 302 in this manner, the urea water 306 is accommodated between the first wall portion 302 and the second wall portion 304 forming a double wall structure. A second housing portion for housing urea water 310 inside the second wall portion 304, which is formed on the opposite side of the first housing portion 308 with the second wall portion 304 interposed therebetween, is formed. 312 is formed. As shown in FIG. 11, the upper end of the second wall portion 304 is at a position lower than the upper surface of the urea water tank 350, and the second storage portion 312 has a box shape with the upper end opened.

As shown in FIG. 11, an inlet 314 is provided on the upper surface of the urea water tank 350 at a position above the second housing portion 312, and a cap 316 is attached to the inlet 314. The inlet 314 and the cap 316 have the same structure and function as the inlet 114 and the cap 116 in the first embodiment described above.
In addition, a return port (inflow part) 318 to which a urea water return pipe 48 is connected is provided at a position above the first housing part 308 on the upper surface of the urea water tank 350 and used for cooling the urea water injector 44. The urea water thus made passes through the urea water return pipe 48 and flows into the first housing portion 308 of the urea water tank 350 from the return port 318.

  On the other hand, a portion of the bottom surface of the urea water tank 350 that becomes the bottom surface of the first housing portion 308 is provided with a first drain port 320 as shown in FIGS. It can be opened and closed by 322. The first drain port 320 and the first drain cock 322 have the same structure and function as the first drain port 120 and the first drain cock 122 in the first embodiment described above.

  Further, a suction port (outflow portion) 324 and a second drain port 326 are provided in a portion of the bottom surface of the urea water tank 350 which is the bottom surface of the second housing portion 312 as shown in FIGS. 10 and 11. It has been. A urea water supply pipe 46 is connected to the suction port 324, and the urea water 310 in the second housing portion 312 flows out of the suction port 324 and then passes through the urea water supply pipe 46 by the urea water supply pump 52. It is supplied to the urea water injector 44. The second drain port 326 can be opened and closed by a second drain cock 328. These second drain port 326 and second drain cock 328 are connected to the second drain port 126 and the second drain port 126 in the first embodiment described above. The second drain cock 128 has the same structure and function.

  As shown in FIG. 10, the second accommodating portion 312 has a horizontal cross section formed in a quadrangular shape by the second wall portion 304. FIG. 12 is a perspective view showing only the second wall portion 304 of the urea water tank 350 taken out, but as shown in FIGS. 11 and 12, 4 of the second housing portion 312 having a horizontal cross section having a quadrangular shape. A notch 330 is formed at the upper end of the second wall 304 forming one of the two side surfaces.

  In the urea water tank 350 configured as described above, the urea water returned from the urea water injector 44 to the urea water tank 350 via the urea water return pipe 48 flows into the first housing portion 308 from the return port 318. . Since the first storage portion 308 and the second storage portion 312 are separated by the second wall portion 304 that forms the second storage portion 312, regardless of the amount of urea water 310 in the second storage portion 312, Until the water level of the urea water 306 in the first accommodating portion 308 rises and reaches the same height as the lower end of the notch 330 formed at the upper end of the second wall portion 304, that is, the level indicated by the two-dot chain line in FIG. The urea water 306 in the first housing part 308 does not flow into the second housing part 312 through the notch 330.

  Therefore, even if the urea water whose temperature has been increased by being used for cooling the urea water injector 44 is returned to the urea water tank 350 and flows into the first housing portion 308 from the return port 318, the urea water is not The urea water 306 in the first accommodating portion 308 remains in the first accommodating portion 308 until the water level reaches the same height as the lower end of the notch 330. During this time, the heat of the urea water 306 in the first housing portion 308 is released through the first wall portion 302 in contact with the outside air, and the urea water 306 is effectively cooled.

In addition, even after the water level of the urea water 306 in the first housing portion 308 reaches the same height as the lower end of the notch 330, the inflow of urea water from the return port 318 into the first housing portion 308 continues. The urea water 306 in the first storage unit 308 flows into the second storage unit 312 via 330. Therefore, the notch 330 corresponds to the communication portion of the present invention.
At this time, since the water level of the urea water 306 in the first storage portion 308 is maintained at a high position, a large heat radiation area of the urea water 306 to the outside air through the first wall portion 302 is ensured, and continues. The urea water 306 is effectively cooled. Note that the urea water that has flowed into the first housing portion 308 from the return port 318 once flows downward in the first housing portion 308 due to inertia, and thus is effective due to heat radiation to the outside air via the first wall portion 302. Cooled. Thus, the urea water cooled in the first housing part 308 flows into the second housing part 312 through the notch 330.

  Therefore, by using the urea water tank 350 having such a configuration, regardless of the amount of urea water in the urea water tank 350, the urea water returned from the urea water injector 44 into the urea water tank 350 can be effectively used. It is possible to cool and prevent an excessive increase in temperature of the urea water stored in the urea water tank 350. As a result, the urea water injector 44 can be effectively cooled by the urea water, and deviation from an appropriate concentration accompanying the concentration of the urea water can be prevented, and ammonia can be generated in the urea water tank 350. It becomes possible to suppress. Furthermore, it is not necessary to replenish the urea water frequently before the water level of the urea water decreases to suppress the temperature rise of the urea water in the urea water tank 350.

  Further, in the urea water tank 350 of the third embodiment, it is only necessary to provide the notch 330 at the upper end of the second wall portion 304 that forms the second housing portion 312, so that the first housing portion 308, the second housing portion 312, A pipe or the like for communicating is unnecessary, and the above-described effects can be obtained with an extremely simple structure. Moreover, the passage 132 is formed by using a part of the second housing portion 112 as in the first embodiment described above, or the passage is formed by using a part of the first housing portion 208 as in the second embodiment. Since it is not necessary to form H.232, the first storage unit 308 and the second storage unit 312 can be utilized to the maximum extent for cooling and storing urea water.

  In the third embodiment, the upper end of the second wall portion 304 is made lower than the upper surface of the urea water tank 350 and the second storage portion 312 is formed in a box shape opened at the upper end. The portion 304 may be extended to the upper surface of the urea water tank 350 and the upper surface of the urea water tank 350 may be closed above the second storage unit 312. In this case as well, a similar notch may be provided at the upper end of the second wall portion 304 that forms the second housing portion 312.

  Further, in the third embodiment, the notch 330 is formed in a part of the upper end of the second wall portion 304 that forms one of the four side surfaces of the second housing portion 312 having a quadrangular horizontal cross section. A notch may be provided over the entire upper end of one side surface, or a notch may be provided at the upper end of a plurality of side surfaces. Further, a plurality of notches may be provided instead of the single notch 330 as in the third embodiment.

  In the third embodiment, as described above, the notch 330 is formed at the upper end of the second wall portion 304 so that the urea water 306 in the first storage portion 308 flows into the second storage portion 312. However, instead of this, a through-hole may be provided in the middle of the second wall portion 304 in the vertical direction so that the urea water 306 in the first storage portion 308 flows into the second storage portion 312. Good. However, in order to more effectively cool the urea water, it is desirable to provide the notch 330 at the upper end of the second wall portion 304.

Next, as a urea water tank 50 in FIG. 1, a urea water tank 450 of an exhaust gas purification apparatus according to a fourth embodiment of the present invention will be described based on FIGS. 13 to 15.
13 is a horizontal cross-sectional view of the middle portion of the urea water tank 450 in the vertical direction, and FIG. 14 is a cross-sectional view of the urea water tank 450 taken along line XIV-XIV in FIG.
As shown in FIG. 13 and FIG. 14, the urea water tank 450 is formed in a box shape closed by the first wall 402 serving as an outer shell of the urea water tank 450, and stores urea water therein. A space is provided. A box-shaped second wall 404 having an opening at the top and a bottom is provided inside the first wall 402, and is supported above the bottom of the urea water tank 450 through four spacers 404a. ing. Therefore, a side wall portion and a bottom surface portion extending in the vertical direction in the wall portion of the urea water tank 450 have a double wall structure by the first wall portion 402 and the second wall portion 404. Thus, by providing the second wall portion 404 inside the first wall portion 402, the urea water 406 is accommodated between the first wall portion 402 and the second wall portion 404 forming a double wall structure. A second accommodating portion for accommodating urea water 410 inside the second wall portion 404 that is opposite to the first accommodating portion 408 with the second accommodating portion 408 interposed therebetween. 412 is formed. As described above, the second accommodating portion 412 has a box shape with the upper end opened by the second wall portion 404, and the upper end of the second wall portion 404 is the upper surface of the urea water tank 450 as shown in FIG. 14. It is in a lower position.

As shown in FIG. 14, an inlet 414 is provided on the upper surface of the urea water tank 450 at a position above the second housing portion 412, and a cap 416 is attached to the inlet 414. The injection port 414 and the cap 416 have the same structure and function as the injection port 114 and the cap 116 in the first embodiment described above.
A return port (inflow part) 418 to which a urea water return pipe 48 is connected is provided at a position above the first housing part 408 on the upper surface of the urea water tank 450 and used for cooling the urea water injector 44. The urea water thus made passes through the urea water return pipe 48 and flows into the first housing portion 408 of the urea water tank 450 from the return port 418.

  On the other hand, a first drain port 420 is provided in a portion of the first wall portion 402 that becomes the bottom surface of the first accommodating portion 408, as shown in FIGS. 13 and 14, and is formed by the first drain cock 422. It can be opened and closed. The first drain port 420 and the first drain cock 422 have the same structure and function as the first drain port 120 and the first drain cock 122 in the first embodiment described above.

  Furthermore, a suction port (outflow portion) 424 and a second drain port 426 are provided in a portion of the second wall portion 404 that becomes the bottom surface of the second housing portion 412 as shown in FIGS. 13 and 14. ing. The suction port 424 and the second drain port 426 pass through the first wall portion 402 that forms the bottom surface of the first accommodating portion 408 and project outward from the urea water tank 450. A urea water supply pipe 46 is connected to the suction port 424, and the urea water 410 in the second housing portion 412 flows out of the suction port 424 and then passes through the urea water supply pipe 46 by the urea water supply pump 52. It is supplied to the urea water injector 44. The second drain port 426 can be opened and closed by a second drain cock 428 provided outside the urea water tank 450. The function of the second drain port 426 and the structure and function of the second drain cock 428 are the same as those of the second drain port 126 and the second drain cock 128 in the first embodiment described above, respectively.

  The second housing portion 412 formed by the second wall portion 404 is substantially the same as the second housing portion 312 in the third embodiment described above except that the second housing portion 412 has a bottom surface formed by the second wall portion 404 as described above. Are similar in shape. That is, as shown in FIG. 13, the second accommodating portion 412 is formed in a quadrangular horizontal section by the second wall portion 404. FIG. 15 is a perspective view showing only the second wall portion 404 of the urea water tank 450 taken out, but as shown in FIGS. 14 and 15, 4 of the second storage portion 412 whose horizontal cross section has a quadrangular shape. A notch 430 is formed at the upper end of the second wall portion 404 forming one of the two side surfaces.

  In the urea water tank 450 configured as described above, the urea water returned from the urea water injector 44 to the urea water tank 450 via the urea water return pipe 48 flows into the first housing portion 408 from the return port 418. . Since the 1st accommodating part 408 and the 2nd accommodating part 412 are separated by the 2nd wall part 404 which forms the 2nd accommodating part 412, regardless of the quantity of the urea water 410 in the 2nd accommodating part 412, Until the water level of the urea water 406 in the first accommodating portion 408 rises and reaches the same height as the lower end of the notch 430 formed at the upper end of the second wall portion 404, that is, the level indicated by the two-dot chain line in FIG. The urea water 406 in the first housing part 408 does not flow into the second housing part 412 through the notch 430.

  Therefore, even if the urea water whose temperature has been increased by being used for cooling the urea water injector 44 is returned to the urea water tank 450 and flows into the first housing portion 408 from the return port 418, the urea water is not The urea water 406 in the first accommodating portion 408 remains in the first accommodating portion 408 until the water level reaches the same height as the lower end of the notch 430. During this time, the heat of the urea water 406 in the first housing portion 408 is released through the first wall portion 402 in contact with the outside air, and the urea water 406 is effectively cooled.

Further, even if the urea water 406 in the first housing portion 408 reaches the same height as the lower end of the notch 430 and the inflow of urea water from the return port 418 into the first housing portion 408 continues, The urea water 406 in the first storage unit 408 flows into the second storage unit 412 through 430. Therefore, the notch 430 corresponds to the communication portion of the present invention.
At this time, since the water level of the urea water 406 in the first accommodating portion 408 is maintained at a high position, a large heat radiation area of the urea water 406 to the outside air through the first wall portion 402 is secured, and subsequently The urea water 406 is effectively cooled. Note that the urea water that has flowed into the first housing portion 408 from the return port 418 once flows downward in the first housing portion 408 due to inertia, and thus is effective due to heat radiation to the outside air through the first wall portion 402. Cooled. Thus, the urea water cooled in the first housing part 408 flows into the second housing part 412 through the notch 430.

  Therefore, by using the urea water tank 450 having such a configuration, the urea water returned from the urea water injector 44 into the urea water tank 450 can be effectively used regardless of the amount of urea water in the urea water tank 450. It is possible to cool and prevent an excessive increase in the temperature of the urea water stored in the urea water tank 450. As a result, the urea water injector 44 can be effectively cooled by the urea water, and deviation from an appropriate concentration due to the concentration of the urea water can be prevented, and ammonia can be generated in the urea water tank 450. It becomes possible to suppress. Furthermore, it is not necessary to replenish the urea water frequently before the urea water level drops to suppress the temperature rise of the urea water in the urea water tank 450.

  Further, in the urea water tank 450 of the fourth embodiment, since it is only necessary to provide the notch 430 at the upper end of the second wall portion 404 that forms the second housing portion 412, the first housing portion 408 and the second housing portion 412 A pipe or the like for communicating is unnecessary, and the above-described effects can be obtained with a simple structure. Moreover, the passage 132 is formed by using a part of the second housing portion 112 as in the first embodiment described above, or the passage is formed by using a part of the first housing portion 208 as in the second embodiment. Since it is not necessary to form 232, the first storage portion 408 and the second storage portion 412 can be utilized to the maximum extent for cooling and storing urea water.

  Furthermore, in the urea water tank 450 of the fourth embodiment, the bottom surface of the second storage portion 412 formed by the second wall portion 404 is separated upward from the bottom surface of the first storage portion 408 by the spacer 404a, and the urea water Since the bottom surface of the tank 450 also has a double wall structure, a larger contact area between the first wall portion 402 and the urea water 406 in the first accommodating portion 408 can be secured, and cooling of the urea water is more effective. Can be done.

  In the fourth embodiment, the upper end of the second wall portion 404 is made lower than the upper surface of the urea water tank 450 and the second storage portion 412 is formed in a box shape opened at the upper end. The portion 404 may be extended to the upper surface of the urea water tank 450 and the upper surface of the urea water tank 450 may be closed above the second storage portion 412. In this case as well, a similar notch may be provided at the upper end of the second wall portion 404 forming the second accommodating portion 412.

  Further, in the fourth embodiment, the notch 430 is formed in a part of the upper end of the second wall portion 404 that forms one of the four side surfaces of the second housing portion 412 having a quadrangular horizontal cross section. A notch may be provided over the entire upper end of one side surface, or a notch may be provided at the upper end of a plurality of side surfaces. Furthermore, instead of the single notch 430 as in the fourth embodiment, a plurality of notches may be provided.

  In the fourth embodiment, as described above, the notch 430 is formed at the upper end of the second wall portion 404 so that the urea water 406 in the first storage portion 408 flows into the second storage portion 412. However, instead of this, a through hole may be provided in the middle of the second wall 404 in the vertical direction so that the urea water 406 in the first housing 408 flows into the second housing 412. Good. However, in order to more effectively cool the urea water, it is desirable to provide the notch 430 at the upper end of the second wall portion 404.

Although the description of the exhaust emission control device according to the embodiment of the present invention has been completed above, the present invention is not limited to the first to fourth embodiments described above.
For example, in the first to third embodiments, the second wall portion is erected from the bottom surface of the urea water tank, and the bottom surface of the second housing portion is formed by the first wall portion. Similarly, the box-shaped second housing part having the bottom surface may be formed by the second wall part, and the second housing part may be separated upward from the bottom surface of the first housing part by the spacer. However, when the bottom surface of the second accommodating portion is formed by the first wall portion as in the first to third embodiments, the suction port and the second drain port are directly connected to the bottom surface of the second accommodating portion. Therefore, the structure is simplified and it is not necessary to provide a seal member or the like, and the volume of the second housing portion can be secured relatively large.

  Moreover, in the said 1st thru | or 4th embodiment, although it was set as the double wall structure which consists of a 1st wall part and a 2nd wall part over the perimeter of the side part of a urea water tank, a perimeter is made into a double wall structure. It does not have to be. That is, the horizontal cross-sectional shape of the second wall portion forming the second storage portion is, for example, U-shaped or L-shaped, and the second storage portion is formed by the combination of the second wall portion and the first wall portion. And it is good also considering only a part of side part of a urea water tank as a double wall structure by comprising a part of side wall of a 2nd accommodating part in a 1st wall part. In this case, the same structure as in the first to fourth embodiments may be applied to the portion having a double wall structure. However, in order to effectively cool the urea water, the double wall composed of the first wall portion and the second wall portion over the entire circumference of the side surface portion of the urea water tank as in the first to fourth embodiments. It is desirable to form a 1st accommodating part as a wall structure.

  In the third and fourth embodiments, a notch is formed in a part of the upper end of the second wall portion, and urea water in the first accommodating portion is caused to flow into the second accommodating portion through the notch. However, such a notch may be omitted. In this case, the urea water flows into the first housing part from the return port, and the urea water continues to flow into the first housing part even after the urea water level in the first housing part reaches the upper end of the second wall part. Then, the urea water in the first housing part flows into the second housing part from the upper end of the second wall part. Therefore, in this case, the upper end portion of the second wall portion corresponds to the communication portion of the present invention.

  Even when the notch is omitted in this manner, as in the case of the third and fourth embodiments, the urea water level in the first accommodating portion is in contact with the outside air until reaching the upper end of the second wall portion. The heat of the urea water in the first housing portion is released through the one wall portion, and the urea water is effectively cooled. And even if the urea water in the first housing portion flows into the second housing portion from the upper end of the second wall portion, the urea water flowing in from the return port once enters the lower portion in the first housing portion due to inertia. During the period from the upper end of the second wall portion to the second housing portion, the heat is effectively cooled by the heat radiation from the first wall portion. At this time, in order to specify the position of the urea water flowing into the second storage portion from the first storage portion, the upper end of the second wall portion is not made the same height over the entire circumference, but at least partially in the continuous state. You may make it vary in height.

Moreover, you may make it provide a pipe-shaped flow path separately as a communicating part for making urea water flow in into a 2nd accommodating part from a 1st accommodating part, without using a 2nd wall part. In this case, it is preferable that the pipe-shaped flow path opens into the first housing portion at the lower end side of the first housing portion and opens into the second housing portion at a position higher than the opening position in the first housing portion. .
In the first to fourth embodiments, the outer shape of the urea water tank formed by the first wall portion and the outer shape of the second housing portion formed by the second wall portion are both rectangular parallelepiped. These shapes can be arbitrarily changed, and various shapes can be applied without departing from the conditions required for the configuration of the present invention.

  Furthermore, about the space | interval of a 1st wall part and a 2nd wall part, it can change variously as needed. That is, in the first to fourth embodiments, in order to clearly show the configuration of the urea water tank, the second wall portion is disposed at a relatively large interval with respect to the first wall portion. Thus, the second wall portion may be disposed with respect to the first wall portion, or conversely, the second wall portion may be disposed with respect to the first wall portion at a larger interval. Furthermore, you may make it change according to a position, without making the space | interval of a 1st wall part and a 2nd wall part uniform.

Further, various modifications can be made to the exhaust gas purification device other than the urea water tank 50 shown in FIG. 1, for example, in the case of using a urea water injector in which urea water is injected into the exhaust together with compressed air. Even in such a case, when a part of the urea water is returned from the urea water injector to the urea water tank, the present invention can be similarly applied.
In the above-described embodiment, the upstream oxidation catalyst 36 and the filter 38 are accommodated in the upstream casing 30, and the SCR catalyst 40 and the downstream oxidation catalyst 42 are accommodated in the downstream casing 34 to constitute the exhaust aftertreatment device 28. However, the configuration of the exhaust aftertreatment device 28 is not limited to this. In other words, the exhaust aftertreatment device 28 may include the SCR catalyst 40 and the urea water injector 44 provided on the upstream side of the SCR catalyst 40.

  Furthermore, 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 a schematic block diagram which cuts and shows a part of urea water tank in the exhaust gas purification apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of the urea water tank which follows the III-III line in FIG. It is sectional drawing of the urea water tank which follows the IV-IV line in FIG. It is a perspective view which shows the 2nd wall part and cover member of the urea water tank of FIG. It is a schematic block diagram which notches and shows a part of urea water tank in the exhaust gas purification apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing of the urea water tank which follows the VII-VII line in FIG. It is sectional drawing of the urea water tank which follows the VIII-VIII line in FIG. It is a perspective view which shows the 2nd wall part and partition member of the urea water tank of FIG. It is sectional drawing of the horizontal direction in the up-down direction intermediate part of the urea water tank in the exhaust gas purification apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing of the urea water tank which follows the XI-XI line in FIG. It is a perspective view which shows the 2nd wall part of the urea water tank of FIG. It is sectional drawing of the horizontal direction in the up-down direction intermediate part of the urea water tank in the exhaust gas purification apparatus which concerns on 4th Embodiment of this invention. It is sectional drawing of the urea water tank which follows the XIV-XIV line | wire in FIG. It is a perspective view which shows the 2nd wall part of the urea water tank of FIG.

Explanation of symbols

1 Engine 30 Upstream casing (exhaust passage)
32 Exhaust communication passage (exhaust passage)
34 Downstream casing (exhaust passage)
40 SCR catalyst (ammonia selective reduction type NOx catalyst)
44 Urea water injector 50, 150, 250, 350, 450 Urea water tank 102, 202, 302, 402 First wall 104, 204, 304, 404 Second wall 106, 206, 306, 406 Urea water 108, 208 , 308, 408 First accommodating portion 110, 210, 310, 410 Urea water 112, 212, 312, 412 Second accommodating portion 118, 218, 318, 418 Return port (inflow portion)
124, 224, 324, 424 Suction port (outflow part)
130 cover member 132,232 passage (communication passage)
134 Communication hole 136,236 Urea solution 230 Partition member 234 Opening 330,430 Notch (communication part)

Claims (9)

An ammonia selective reduction type NOx catalyst that is interposed in the exhaust passage of the engine and selectively reduces NOx in the exhaust gas using ammonia as a reducing agent;
A urea water tank for storing urea water;
A portion of the urea water provided in the exhaust passage and supplied from the urea water tank is injected into the exhaust on the upstream side of the ammonia selective reduction type NOx catalyst, and the remaining portion of the urea water is injected into the urea water tank. A urea water injector to return to
The urea water tank is
Among the wall portions forming the urea water tank, at least a part of the wall portion provided in the vertical direction is provided on the inner side of the first wall portion serving as an outer shell of the urea water tank and the first wall portion. A double wall structure consisting of a second wall portion,
An inflow part for causing urea water returned from the urea water injector to flow into a first housing part formed between the first wall part and the second wall part in the double wall structure;
A communicating part for allowing urea water in the first accommodating part to flow into a second accommodating part formed on the opposite side of the first accommodating part across the second wall part;
An exhaust gas purification apparatus comprising: an outflow part that causes the urea water supplied to the urea water injector to flow out of the second housing part.   2. The communication unit according to claim 1, wherein when the water level of the urea water in the first storage unit exceeds a predetermined level, the communication unit causes the urea water to flow into the second storage unit from the first storage unit. Exhaust purification device.   The communication portion communicates with the first accommodation portion at a first position on the lower end side of the first accommodation portion, and communicates with the second accommodation portion at a second position located above the first position. The exhaust emission control device according to claim 2, wherein The communication part is
By covering a part of the wall surface of the second wall portion in the second housing portion with a cover member, a passage shape starting from the bottom surface of the second housing portion is formed and extended upward. A communication path that opens into the second housing part at the second position, which is lower than the upper end of the two wall parts;
A communication hole that is formed in the second wall portion that forms the communication path, opens at the first position lower than the second position, and communicates the first storage section with the inside of the communication path. The exhaust emission control device according to claim 3, wherein The second housing portion has a box shape with a corner portion having an upper end opened and extending vertically.
The exhaust purification device according to claim 4, wherein the communication portion is formed by covering the corner portion with a flat cover member from the bottom surface of the second housing portion to the second position. The communication part is
A passage extending in the up-down direction using a part of the wall surface of the second wall portion in the first housing portion, and in the first housing portion at the first position which is the lower end side of the first housing portion. A communication passage opening to
An opening that is provided in the second wall portion that forms the communication path, opens at the second position higher than the first position, and communicates between the second housing section and the communication path. The exhaust emission control device according to claim 3, wherein The communication path is formed by partitioning the first housing portion with two partition members that are spaced apart from each other between the wall surface of the first wall portion and the wall surface of the second wall portion, The lower end of at least one of the partition members is located above the bottom surface of the first housing portion, and thus opens at the first position.
The second accommodating portion is formed in a box shape having an open upper end,
The exhaust purification device according to claim 6, wherein the opening is formed by notching an upper end of the second wall portion that forms the communication path. The second accommodating portion is formed in a box shape having an upper end opened.
The exhaust purification apparatus according to claim 2, wherein the communication part is a notch formed at an upper end of the second wall part. The second accommodating portion is formed in a box shape having an upper end opened.
The exhaust purification device according to claim 2, wherein the communication part is an upper end part of the second wall part.

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