Exhaust emission control device

Provided is an exhaust emission control device in which only a casing for a particulate filter can be easily taken out of position with a casing for a selective reduction catalyst being left on a vehicle body in a reliably supported state.The exhaust emission control device has a particulate filter 5 and a selective reduction catalyst 6 housed in casings 7 and 8, respectively, and arranged side by side with entry ends of them are directed in one and the same direction, and an S-shaped communication passage 9 which interconnects the casings 7 and 8 and is intermediately provided with urea water addition means 10. The communication passage 9 is intermediately provided with a separable portion for suitable separate-off, and the casing 8 for the selective reduction catalyst 6 is supported by a frame 15 on a vehicle body independently of the casing 7 for the particulate filter 5. The casing 7 for the particulate filter 5 is detachably mounted and supported on the vehicle body and on the casing 8 for the selective reduction catalyst 6.

TECHNICAL FIELD

The present invention relates to an exhaust emission control device.

BACKGROUND ART

It has been recently proposed that a particulate filter for capturing particulates in exhaust gas is incorporated in an exhaust pipe and a selective reduction catalyst capable of selectively reacting NOxwith ammonia even in the presence of oxygen is arranged downstream of the particulate filter, urea water as reducing agent being added between the particulate filter and the selective reduction catalyst, thereby attaining lessening of both the particulates and NOx.

Such addition of the urea water to the selective reduction catalyst is conducted between the particulate filter and the selective reduction catalyst, so that in order to ensure sufficient reaction time for pyrolysis of the urea water added to the exhaust gas into ammonia and carbon dioxide gas, it is necessary to prolong a distance between a urea water added position and the selective reduction catalyst. However, such arrangement of the particulate filter and the selective reduction catalyst substantially spaced apart from each other will extremely impair the mountability on a vehicle.

In order to overcome this, a compact exhaust emission control device as shown inFIG. 1has been proposed by the applicant as JP 2008-196328A. In the exhaust emission control device of the prior application shown, incorporated in an exhaust pipe4through which exhaust gas3flows from a diesel engine1via an exhaust manifold2is a particulate filter5housed in a casing7to capture particles in the exhaust gas3; arranged downstream of and in parallel with the particulate filter5and housed in a casing8is a selective reduction catalyst6having a property capable of selectively reacting NOxwith ammonia even in the presence of oxygen. A discharge end of the particulate filter5is connected to an entry end of the selective reduction catalyst6through an S-shaped communication passage9with a urea water addition means10at its upstream side such that the exhaust gas3discharged through the discharge end of the particulate filter5is reversely curved back into the entry end of the adjacent selective reduction catalyst6.

Arranged in the casing7and in front of the particulate filter5is an oxidation catalyst11for oxidization treatment of unburned fuel in the exhaust gas3, and arranged in the casing8and behind the selective reduction catalyst6is an ammonia reducing catalyst12for oxidization treatment of surplus ammonia.

With such construction being employed, particulates in the exhaust gas3are captured by the particulate filter5. The urea water is added into the exhaust gas3upstream of the communication passage9by the urea water addition means10and is pyrolyzed into ammonia and carbon dioxide gas, so that NOxin the exhaust gas3is favorably reduced and depurated by the ammonia on the selective reduction catalyst6. As a result, both the particulates and NOxin the exhaust gas3are lessened.

In this case, the exhaust gas3discharged through the discharge end of the particulate filter5is reversely curved back by the communication passage9into the entry end of the adjacent selective reduction catalyst6. As a result, enough reaction time is ensured for production of ammonia from the urea water since a long distance between the selective reduction catalyst6and the urea water added position by the urea water addition means10is ensured and the flow of the exhaust gas3becomes turbulent due to the reversed curving to facilitate mixing of the urea water with the exhaust gas3.

Moreover, the particulate filter5and selective reduction catalyst6are arranged in parallel with each other and the communication passage9is arranged between and along the filter5and catalyst6, so that the whole structure becomes compact in size to substantially improve its mountability on a vehicle.

However, with such structure having the heavy particulate filter5and heavy selective reduction catalyst6arranged side by side and interconnected by the S-shaped communication passage9, relative twisting tends to be caused between the filter5and the catalyst6, so that stress may be concentrated to connections and curved portions of the communication passage9. In order to overcome this, as shown inFIG. 2, the casings7and8for the particulate filter5and selective reduction catalyst6are interconnected at plural axial positions through connections13and14on upper and lower sides so as not to be relatively twisted. Then, the casings7and8are arranged between a pair of brackets16and17fixed to a frame15on a vehicle body and are supported through connections18and19by the brackets16and17, respectively.

As a prior art literature pertinent to the invention, there exists, for example, the following Patent Literature 1.[Patent Literature 1] JP 2005-155404A

SUMMARY OF INVENTION

Technical Problems

Since ash derived from the lubricant oil and produced through combustion in the cylinders gradually accumulates in the particulate filter5, the casing7has to be taken out of position so as to make the particulate filter5directly cleaned by, for example, air or water cleaning or so as to substitute a new particulate filter5. However, it is difficult to take out only the casing7for the particulate filter5since both the casings7and8are interconnected through the S-shaped communication passage9. Moreover, in the above-mentioned support shown inFIG. 2, taking-out of only the casing7for the particulate filter5would cause the casing8for the selective reduction catalyst6to be supported in a cantilever manner, failing in keeping the casing8in a favorably supported state. Thus, the whole of the exhaust emission control device including the casings7and8has to be taken out all at once, which disadvantageously results in considerable labor required for maintenance of the particulate filter5.

The invention was made in view of the above and has its object to provide an exhaust emission control device which makes it possible to easily take a casing for a particulate filter out of position with a casing for a selective reduction catalyst being left on a vehicle body in a reliably supported state.

Solution to Problems

The invention is directed to an exhaust emission control device wherein a particulate filter and a selective reduction catalyst arranged downstream of said particulate filter and capable of selectively reacting NOxwith ammonia even in the presence of oxygen are housed in casings, respectively, and arranged side by side such that entry ends of the particulate filter and the selective reduction catalyst are oriented to one and the same direction, an S-shaped communication passage being provided for introduction of the exhaust gas discharged from a discharge end of the particulate filter to the entry end of the adjacent selective reduction catalyst through reversed turnabout, urea water being addible intermediately of said communication passage, characterized by comprising a separable portion for suitable separate-off arranged intermediately of the communication passage, the casing for the selective reduction catalyst being supported on a vehicle body independently of the casing for the particulate filter, the casing for the particulate filter being detachably mounted and supported on the vehicle body and on the casing for the selective reduction catalyst.

Thus, in this manner, separation through the separable portion intermediately of the communication passage and disconnection of the casing for the particulate filter from the vehicle body and from the casing for the selective reduction catalyst make it possible to take the casing for the selective reduction catalyst out of position on the vehicle body with the casing for the particulate filter being left on the vehicle body in a reliably supported state, which is less troublesome than the conventional taking-out of the whole of the exhaust emission control device all at once, leading to lessening in workload.

In order to conduct the invention more specifically, it is preferable that the casing for the selective reduction catalyst is arranged between and attached to both of a pair of brackets fixed to a frame on a vehicle body, the casing for the particulate filter being arranged downward of the casing for the selective reduction catalyst and being detachably mounted on one of the brackets and on the casing for the selective reduction catalyst.

ADVANTAGEOUS EFFECTS OF INVENTION

The above-mentioned exhaust emission control device of the invention, in which only the casing for the particulate filter can be easily taken out of position with the casing for the selective reduction catalyst being left on the vehicle body in a reliably supported state, can exert an excellent effect that labor for maintenance of the particulate filter can be substantially lessened in comparison with the conventional taking-out of the whole of the exhaust emission control device all at once.

REFERENCE SIGNS LIST

DESCRIPTION OF EMBODIMENT

An embodiment of the invention will be described in conjunction with the drawings.

FIGS. 3-5show the embodiment of the invention in whichFIG. 3is a front view of the exhaust emission control device according to the embodiment looking axially of casings7and8;FIG. 4, a perspective view of the exhaust emission control device shown inFIG. 3looking slantwise from above; andFIG. 5, an exploded view showing particulars of a structure supporting the exhaust emission control device shown inFIG. 4.

The embodiment illustrated is substantially similar to the above-mentioned structure shown inFIG. 1in that an exhaust emission control device comprises a particulate filter5and a selective reduction catalyst6which are housed in casings7and8, respectively, and are arranged side by side such that entry ends of the filter and the catalyst are directed in one and the same direction, and an S-shaped communication passage9which guides exhaust gas3discharged from a discharge end of the particulate filter5to an entry end of the adjacent selective reduction catalyst6through reversed turnabout, urea water being addible by urea water addition means10intermediately of the communication passage9. The communication passage9has an intermediate separable portion20for suitable separate-off (seeFIGS. 4 and 5). The casing8for the selective reduction catalyst6is supported on a vehicle body independently of the casing7for the particulate filter5, and the casing7for the particulate filter5is detachably mounted and supported on the vehicle body and the casing8for the selective reduction catalyst6.

Specifically, the communication passage9is intermediately divided and divided ends are provided with flanges21and22, respectively, which in turn are detachably bolted together to thereby provide the separable portion20. The casing8for the selective reduction catalyst6is arranged between a pair of brackets16and17fixed to a frame15on the vehicle body, and is attached at plural axial positions through connections23and24on lateral sides to both of the brackets16and17, and the casing7for the particulate filter5is arranged downward of the casing8for the selective reduction catalyst6and is detachably mounted through connections25and26on the one16of the brackets and on the casing8for the selective reduction catalyst6.

The connections23and24for attachment of the casing8for the selective reduction catalyst6to both of the respective brackets16and17comprise extensions27and28formed on parts of flanges at two separate axial positions on the casing8, and bracket pieces29and30fixed to the respective brackets16and17for bolting in overlapped relationship with the extensions27and28, respectively. The bracket pieces29are fixed to the one bracket16through intermediate brackets31which are referred to hereinafter, and the bracket pieces30are directly fixed to the other bracket17.

Further, the connection25through which the casing7for the particulate filter5is mounted on the one bracket16comprises extensions32formed on parts of flanges at two separate axial positions on the casing7and the intermediate brackets31fixed to the one bracket16so as to be bolted together in overlapped relationship with the extensions32.

The connection26through which the casing7for the particulate filter5is mounted on the casing8for the selective reduction catalyst6comprises extensions33formed on the flanges with the extensions32and at positions different from those for the extensions32, and extensions34formed on the flanges with the extensions27and28and at positions different from those for the extensions so as to be bolted together in overlapped relationship with the extensions33.

Thus, when the particulate filter5is to be taken out so as to be directly cleaned through, for example, air or water cleaning or so as to be replaced with a new particulate filter5, the bolting of the flanges21and22at intermediately of the communication passage9is released to separate off the separable portion20; and then, the bolting of the extensions32and the intermediate brackets31and the bolting of the extensions33and34are released to separate the casing7for the particulate filter5from the vehicle body and from the casing8for the selective reduction catalyst6, so that the casing7for the particulate filter5can be taken out of position on the vehicle body with the casing8for the selective reduction catalyst6being left on the vehicle body in a reliably supported state, which is less troublesome than the conventional taking-out of the whole of the exhaust emission control device all at once, leading to lessening in workload.

Thus, according to the above embodiment, only the casing7for the particulate filter5can be easily taken out of position with the casing8for the selective reduction catalyst6being left on the vehicle body in a reliably supported state, so that labor required for maintenance of the particulate filter5can be substantially lessened in comparison with the conventional taking-out of the whole of the exhaust emission control device all at once.

Industrial Applicability

An exhaust emission control device of the invention is not limited to the above embodiment and that various changes and modifications may be made without departing from the scope of the invention. For example, the separable portion for the communication passage, the support of the casing for the selective reduction catalyst on the vehicle body and detachable mounting of the casing for the particulate filter on the vehicle body and on the casing for the selective reduction catalyst are not always restricted to those illustrated in the drawings.