Working machine

A working machine is provided with a revolving upperstructure, working equipment, an engine compartment, a counterweight, a muffler, and an exhaust path for releasing exhaust gas, which has been discharged from the muffler, to an outer side of the revolving upperstructure. The exhaust path includes a tailpipe connected to the muffler and an exhaust pipe for releasing exhaust gas, which has been discharged from the tailpipe, to the outer side of the revolving upperstructure. The counterweight is utilized for the formation of the exhaust path. The exhaust path includes a passage formed in the counterweight and accommodating an upper end portion of the tailpipe inserted therein with a predetermined clearance formed around the upper end portion such that the exhaust gas discharged from the tailpipe can be guided to the exhaust pipe.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of Japanese Patent Application 2010-203461 filed Sep. 10, 2010, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a working machine such as a compact excavator, which is provided with an exhaust path for releasing exhaust gas, which has been discharged from a muffler, to an outer side of a revolving upperstructure and makes use of a counterweight for the formation of the exhaust path.

2. Description of the Related Art

As a conventional technology of this kind, there is the technology disclosed in JP-A-2002-70077. This conventional technology is applied to a hydraulic excavator provided with a travel base, a revolving upperstructure mounted on the travel base, and working equipment attached pivotally in up and down directions to the revolving upperstructure and including a boom, an arm, and a bucket or the like. In this hydraulic excavator, an exhaust gas silencer for silencing exhaust gas discharged from an engine, that is, a muffler is accommodated in a recess formed in a counterweight. An exhaust pipe connected to the muffler, specifically a tailpipe is formed of a straight pipe extending in a vertical direction. An upper end portion of the tailpipe is inserted with a predetermined clearance in a guide pipe, in other words, an exhaust pipe that releases exhaust gas, which has been discharged from the tailpipe, to an outer side of the revolving upperstructure. The exhaust pipe in which the upper end portion of the tailpipe is inserted is provided in a vicinity of a lower end thereof with a flange, and this flange is fixed by bolts on a cover plate fixedly secured on the counterweight such that the above-mentioned recess of the counterweight is covered up. Exhaust gas from the engine is guided via the muffler and tailpipe into the exhaust pipe in which the tailpipe is inserted, and is then released from the exhaust pipe to an outer side of the revolving upperstructure.

According to the above-described conventional technology, intense heat of exhaust gas is transferred to the counterweight via the exhaust pipe in which the upper end portion of the tailpipe is inserted and also via the cover plate on which the exhaust pipe is fixed. The conventional technology, therefore, contributes to lowering the temperature of exhaust gas which is to be released to the outer side of the revolving upper structure. However, the conventional technology involves a problem in that sufficient heat transfer effect can be hardly obtained by the counterweight because the intense heat of the exhaust gas is conducted to the counterweight by way of the exhaust pipe and cover plate.

In this conventional technology, the intense heat of the exhaust gas guided to the exhaust pipe via the tailpipe is conducted to the cover plate that holds the exhaust pipe in place, and the thickness dimension of the cover plate is set small. There is, accordingly, a potential problem that the cover plate may undergo a deflection under the intense heat. If such a deflection occurs, a problem may arise in that the exhaust pipe held in place by the cover plate may lean to change the releasing direction of exhaust gas.

SUMMARY OF THE INVENTION

With the above-described circumstances of the conventional technology in view, the present invention has as an object thereof the provision of a working machine which can more efficiently lower the temperature of exhaust gas to be released from an exhaust pipe to an outside of a revolving upperstructure.

To achieve the above-described object, the present invention provides, in one aspect thereof, a working machine provided with a revolving upperstructure, working equipment attached to the revolving upperstructure, an engine compartment arranged on the revolving upperstructure, a counterweight disposed behind the engine compartment, a muffler for silencing exhaust gas discharged from an engine accommodated in the engine compartment, and an exhaust path for releasing exhaust gas, which has been discharged from the muffler, to an outer side of the revolving upperstructure, said exhaust path including a tailpipe connected to the muffler and an exhaust pipe for releasing exhaust gas, which has been discharged from the tailpipe, to the outer side of the revolving upperstructure, and said counterweight being utilized for the formation of the exhaust path, wherein the exhaust path comprises a passage formed in the counterweight and accommodating an upper end portion of the tailpipe inserted therein with a predetermined clearance formed around the upper end portion such that the exhaust gas discharged from the tailpipe can be guided to the exhaust pipe.

According to the present invention constructed as described above, the exhaust gas from the engine passes through the passage formed in the counterweight while being guided to the exhaust pipe via the muffler and tailpipe. In this passage, intense heat of the exhaust gas can thus be transferred to the counterweight. As a result, the temperature of the exhaust gas to be released from the exhaust pipe to the outside of the revolving upperstructure can be lowered more efficiently.

Preferably, the passage formed in the counterweight may comprise a restricted passage having a diameter dimension that progressively decreases toward an upper end thereof; and the exhaust pipe may have a flange for securing the exhaust pipe on an upper surface of the counterweight such that the restricted passage is maintained in communication with the exhaust pipe.

According to the present invention constructed as described immediately above, in the restricted passage formed in the counterweight, the intense heat of the exhaust gas guided to the restricted passage can be transferred to the counterweight, and owing to this restricted passage, the flow rate of the exhaust gas is increased so that the exhaust gas can be vigorously released from the exhaust pipe. As the flange of the exhaust pipe is secured on the upper surface of the counterweight, the intense heat of the exhaust gas that passes through the exhaust pipe can be conducted to the counterweight via the flange. By this conduction, the temperature of the exhaust gas can be also lowered. Further, the exhaust pipe can be always maintained in a stable upright position, because the exhaust pipe is held via the flange on the counterweight which has a thickness sufficient to form the restricted passage and is at low risk of thermal deformation.

Preferably, the tailpipe may comprise a straight pipe extending in a vertical direction, and the restricted passage may have a vertical cross-section in a trapezoidal shape formed by vertically cutting a truncated circular cone.

According to the present invention constructed as described immediately above, the tailpipe and the restricted passage formed in the counterweight can be formed in relatively simple shapes.

Preferably, the tailpipe may comprise a vertical section connected to the muffler and extending in a vertical direction, and an inclined section arranged in conjunction with the vertical section, progressively extending rearward toward an upper end thereof and having an upper end portion inserted in the restricted passage formed in the counterweight; and the restricted passage may comprise an inclined path having an inclination such that the restricted passage progressively extends rearward toward an upper end thereof.

According to the present invention constructed as described immediately above, the angle between the vertical section and inclined section of the tailpipe and the length dimensions of the vertical section and inclined section can be set depending on the layout and position of the muffler.

Preferably, the working machine may be further provided with an exhaust-pipe holding member fixed on the counterweight and holding the exhaust pipe in place; the passage formed in the counterweight may comprise an exhaust passage set at a same diameter dimension over an entire length thereof; the exhaust-pipe holding member may be provided with a restricted passage communicating to the exhaust passage and having a diameter dimension that progressively decreases toward an upper end thereof; and the exhaust pipe may have a flange for securing the exhaust pipe on an upper surface of the exhaust-pipe holding member such that the restricted passage of the exhaust-pipe holding member is maintained in communication with the exhaust pipe.

According to the present invention constructed as described immediately above, at the exhaust passage formed in the counterweight, the intense heat of the exhaust gas can be transferred to the counterweight, whereby the temperature of the exhaust gas can be lowered. Further, heat can also be transferred to the counterweight via the restricted passage of the exhaust-pipe holding member arranged integrally with the counterweight, and through this restricted passage of the exhaust-pipe holding member, the flow rate of the exhaust gas is increased so that the exhaust gas can be vigorously released from the exhaust pipe. The heat of the exhaust gas, which has been conducted from the flange of the exhaust pipe, can also be transferred to the counterweight. Further, the fabrication of the counterweight is easy as the exhaust passage formed in the counterweight is set at the same diameter dimension over the entire length thereof. Furthermore, the exhaust pipe can be always maintained in a stable upright position, because the exhaust pipe is held via the flange on the counterweight which has a thickness sufficient to form the restricted passage and is at low risk of thermal deformation.

As the exhaust path for releasing exhaust gas, which has been discharged from the muffler, to the outer side of the revolving upperstructure includes the passage formed in the counterweight and accommodating the upper end portion of the tailpipe inserted therein with the predetermined clearance formed around the upper end portion such that the exhaust gas discharged from the tailpipe can be guided to the exhaust pipe. At this passage, the intense heat of the exhaust gas can thus be transferred to the counterweight so that the temperature of the exhaust gas can be lowered more efficiently. Compared with before, it is hence possible to lessen the adverse effects which the heat of exhaust gas released to the outer side of the revolving upperstructure gives to the surrounding environment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The embodiments of the working machine according to the present invention will hereinafter be described with reference to the accompanying drawings.

Referring first toFIGS. 1 and 2, the working machine to which the present invention can be applied is, for example, a compact excavator as a small machine. This compact excavator is provided with a travel base1, a revolving upperstructure mounted on the travel base1, and working equipment3attached pivotally in up and down directions to the revolving upperstructure2and including a boom, an arm, and a bucket or the like to perform digging work of earth or sand or like work. On the revolving upperstructure2, a seat4is arranged. Laterally to the seat4, control devices5are arranged to operate the working equipment3and revolving upperstructure2, respectively. In front of the seat4, a travel lever6is arranged to operate the travel base1. A space above the seat4is covered by a canopy7. Behind the seat4, a cast counterweight8is disposed to assure a static balance. Between the seat4and the counterweight2, an engine compartment is arranged to accommodate an engine, hydraulic pumps and the like none of which are shown in the drawings.

With reference toFIGS. 3 through 6, a description will next be made of a compact excavator as the first embodiment of the working machine according to the present invention. The compact excavator as the first embodiment is provided with a muffler12for silencing exhaust gas discharged from the unillustrated engine accommodated in the engine compartment11. This compact excavator is also provided with an exhaust path for releasing exhaust gas, which has been discharged from the muffler12, to an outer side of the revolving upperstructure2. This exhaust path includes a tailpipe13connected to the muffler12and an exhaust pipe15for releasing exhaust gas, which has been discharged from the tailpipe13, to the outer side of the revolving upperstructure2.

The exhaust path also includes a passage14formed in an upper part of the counterweight8and accommodating an upper end portion of the tailpipe13inserted therein with a predetermined clearance14aformed around the upper end portion such that the exhaust gas discharged from the tailpipe13can be guided to the exhaust pipe15, for example, a restricted passage14having a diameter dimension that progressively decreases toward an upper end thereof.

The exhaust pipe15has a flange16for securing the exhaust pipe15on an upper surface9of the counterweight8such that the restricted passage14is maintained in communication with the exhaust pipe15. The flange16of the exhaust pipe15is formed, for example, in a rectangular shape, and is fixed by plural bolts17on the upper surface9of the counterweight8.

The tailpipe13is formed, for example, of a straight pipe extending in a vertical direction. The restricted passage14of the counterweight8has a vertical cross-section, for example, in a trapezoidal shape formed by vertically cutting a truncated circular cone.

According to the compact excavator as the first embodiment, the exhaust gas from the engine is silenced in the muffler12, is guided to the restricted passage14of the counterweight8from the tailpipe13connected to the muffler12, is guided further to the exhaust pipe15, and is then released to the outer side of the revolving upperstructure2.

Along the muffler12and the exhaust path, vibrations of a vibration system, which includes the muffler12arranged integrally with the unillustrated engine and the tailpipe13, and those of another vibration system, which includes the counterweight8and exhaust pipe15, are allowed in the clearance14abetween the tailpipe13and the restricted passage14of the counterweight8, and therefore, these vibration systems can be maintained independent from each other without restraining each other. Owing to this feature, vibrations of the another vibration system including the counterweight8and exhaust pipe15are not transmitted to mounting parts for the unillustrated engine and the muffler12so that the mounting parts for these unillustrated engine and muffler12can be protected.

When the exhaust gas is guided from the tailpipe13to the restricted passage14of the counterweight8, an air stream around the tailpipe13is drawn into the restricted passage14through the clearance14a. By this air stream, the intense heat of the exhaust gas is cooled.

According to the compact excavator constructed as the first embodiment as described above, the exhaust gas from the unillustrated engine passes through the restricted passage14formed in the counterweight8while being guided to the exhaust pipe15via the muffler12and tailpipe13. At this restricted passage, the intense heat of the exhaust gas can hence be transferred to the counterweight8. As a consequence, the temperature of exhaust gas to be released from the exhaust pipe15to the outer side of the revolving upperstructure2can be lowered more efficiently.

As the flange16of the exhaust pipe15is secured on the upper surface9of the counterweight8, the heat of the exhaust gas that passes through the exhaust pipe15can be conducted to the counterweight8via the flange16. These transfer and conduction of heat can lessen the adverse effects which the heat of exhaust gas released to the outer side of the revolving upperstructure gives to the surrounding environment.

Owing to the restricted passage14formed in the counterweight8, the flow rate of the exhaust gas is increased so that the exhaust gas can be vigorously released from the exhaust pipe15. As a consequence, excellent releasing performance can be assured for exhaust gas.

Further, the exhaust pipe15can be always maintained in a stable upright position, because the exhaust pipe15is held via the flange16on the counterweight8which has a thickness sufficient to form the restricted passage14and is at low risk of thermal deformation. As a consequence, a highly-reliable holding structure has been realized for the exhaust pipe15. As the exhaust pipe15can be stably held, the length dimension of the exhaust pipe15can be increased to realize an enlargement of the exhaust pipe15. For the compact excavator that the position of an exhaust-gas release port of the exhaust pipe15tends to be located close to the ground plane, it is especially effective to increase the length dimension of the exhaust pipe15as described above. When designed to release exhaust gas at as high a position as possible, it is possible to realize the protection of plants of relatively low height, which are planted around the compact excavator, from the intense heat of exhaust gas.

According to this first embodiment, the tailpipe13and the restricted passage14formed in the counterweight8can be formed in relatively simple shapes. Accordingly, the first embodiment is easy to manufacture, and has high practical utility.

Referring next toFIGS. 7 through 9, a compact excavator as a second embodiment of the present invention will be described hereinafter.

The working machine according to this second embodiment is also a similar compact excavator as in the above-described first embodiment. In the compact excavator as the second embodiment, a tailpipe20connected to the muffler12is formed of a vertical section20aand an inclined section20b. The vertical section20ais connected to the muffler12and extends in a vertical direction. The inclined section20bis arranged in conjunction with the vertical section20a,progressively extends rearward toward an upper end thereof, and has an upper end portion inserted in a restricted passage21formed in the counterweight8.

In this restricted passage21, the upper end portion20bof the tailpipe20is inserted with a predetermined clearance21aformed around the upper end portion such that the exhaust gas discharged from the tailpipe20can be guided to the exhaust pipe15. As depicted inFIG. 8, the restricted passage21is formed of an inclined path having an inclination such that the inclined path progressively extends rearward toward an upper end thereof. As illustrated inFIG. 9, a flange22of the exhaust pipe15is formed, for example, in a substantially oval shape in view of the shape of an upper edge portion of the counterweight8. The flange22is fixed by bolts23on the upper surface9of the counterweight8to hold the exhaust pipe15on the counterweight8. The remaining construction is equal to the corresponding construction in the above-described first embodiment.

In this compact excavator as the second embodiment, the counterweight8is also provided with the restricted passage21in which the upper end portion of the inclined section20bof the tailpipe20is inserted. Similar to the above-described first embodiment, the intense heat of exhaust gas can therefore be transferred to the counterweight8at the restricted passage21. Further, the flange22of the exhaust pipe15is fixed on the upper surface9of the counterweight8so that the heat of exhaust gas guided to the exhaust pipe15can be transferred to the counterweight8via the flange22. The second embodiment can, therefore, bring about similar advantageous effects as the first embodiment.

Owing to the restricted passage21formed in the counterweight8, excellent releasing performance can be obtained for exhaust gas as in the first embodiment.

Further, the exhaust pipe15can be always maintained in a stable upright position on the upper surface9of the counterweight8via the flange22. In this respect too, the second embodiment can bring about similar advantageous effects as the first embodiment.

In the compact excavator as the second embodiment, the angle between the vertical section20aand inclined section20bof the tailpipe20and the length dimensions of the vertical section20aand inclined section20bcan be set depending on the layout and position of the muffler12. A higher degree of freedom or tolerance can, therefore, be enjoyed as to the layout designing of the muffler12.

With reference toFIGS. 10 through 13, a description will next be made of a compact excavator as a third embodiment of the present invention.

The working machine according to this third embodiment is also a similar compact excavator as in the above-described first embodiment. The compact excavator as the third embodiment is provided with an exhaust-pipe holding member32which is fixed on the counterweight8and holds the exhaust pipe15in place. This exhaust-pipe holding member32is made of a similar cast iron as the counterweight8. Similar to the second embodiment, a tailpipe30connected to the muffler12is formed of a vertical section30aconnected to the muffler12and an inclined section30barranged in conjunction with the vertical section30a. Further, an exhaust passage31is formed in the counterweight8. In this exhaust passage31, an upper end portion of the inclined section30bof the tailpipe30is inserted with a predetermined clearance31asuch that the exhaust gas discharged from the tailpipe30can be guided to the exhaust pipe15. This exhaust passage31is set at the same diameter dimension along the entire length thereof.

The exhaust-pipe holding member32is provided with a restricted passage33formed such that the restricted passage33is maintained in communication with the exhaust passage31and has a diameter dimension progressively decreasing toward an upper end thereof. Further, the exhaust pipe15has a flange35via which the exhaust pipe15is fixed on an upper surface34of the exhaust-pipe holding member32such that the restricted passage33of the exhaust-pipe holding member32is maintained in communication with the exhaust pipe15. This flange35is fixed by plural bolts36on the upper surface34of the exhaust-pipe holding member32. As depicted inFIG. 12, the exhaust-pipe holding member32is fixed by plural bolts37on an upper part of a rear wall of the counterweight8. The remaining construction is equal to the corresponding construction in the above-described first embodiment.

In this compact excavator as the third embodiment, the counterweight8is also provided with the exhaust passage31in which the upper end portion of the inclined section30bof the tailpipe30is inserted. Similar to the above-described first embodiment, the intense heat of exhaust gas can therefore be transferred at the exhaust passage31to the counterweight8via the exhaust-pipe holding member32. Further, the heat of exhaust gas guided to the exhaust pipe15can be transferred to the counterweight8via the flange35of the exhaust pipe15and the exhaust-pipe holding member32. The second embodiment can, therefore, bring about similar advantageous effects as the first embodiment.

Owing to the restricted passage33formed in the exhaust-pipe holding member32, excellent releasing performance can be obtained for exhaust gas as in the first embodiment.

The angle between the vertical section30aand inclined section30bof the tailpipe30and the length dimensions of the vertical section30aand inclined section30bcan be set depending on the layout and position of the muffler12. Similar to the second embodiment, a higher degree of freedom or tolerance can, therefore, be enjoyed as to the layout designing of the muffler12.

The exhaust passage31formed in the counterweight8is set at the same diameter dimension over the entire length thereof. Therefore, the manufacture of the counterweight8is easy, and the manufacturing cost of the counterweight8can be limited low.

Further, the exhaust pipe15can be always maintained in a stable upright position, because the exhaust pipe15is held via the flange35on the exhaust-pipe holding member32which has a thickness sufficient to form the restricted passage33and is at low risk of thermal deformation. In this respect too, the second embodiment can bring about similar advantageous effects as the first embodiment.

It is to be noted that despite the formation of the exhaust passage31in the counterweight8, this third embodiment is effective especially in the case of a small compact excavator in which the thickness dimension of the counterweight8has to be set relatively small or a small compact excavator in which a layout space can be hardly found for the exhaust pipe15on the upper surface of the counterweight8.