JPH11257045A - Exhaust device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling efficiency inside the engine compartment while reducing noises emitted by exhaust gas into the environment in an exhaust device wherein a discharge pipe end portion of a silencer connected to an engine for a construction machine is disposed inside a flared shape of a tail pipe end portion, by providing rectifying means inside the tail pipe. SOLUTION: A lower end portion 30A of a tail pipe 30 installed so as to penetrate through a through hole 14B of an engine cover 14 of a construction machine is formed into a flared shape and a discharge pipe end portion 12b of a muffler is inserted into the flared shape. This makes it possible to intake the air outside the discharge pipe end portion 12b into a tail pipe 30 by an ejector effect of a flow velocity of an exhaust gas 27. Accordingly, a cooling wind 39 for cooling around the muffler is induced and cooling efficiency inside the engine compartment is improved thereby. Also, a wire netting 32 is provided inside a straight pipe portion 30B of a tail pipe 30 that is located above the lower end portion 30A of the flared shape. Accordingly, a plurality of passage are formed along the flow direction. Flow resistance of substantially equivalent magnitude is applied to each passage to reduce the flow noise generated at the tail pipe 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust device for a construction machine, and more particularly, to an exhaust device for a construction machine capable of improving the cooling efficiency of an engine room while sufficiently reducing noise to the surrounding environment due to exhaust gas. About.

[0002]

2. Description of the Related Art Auxiliary equipment related to an engine provided in a construction machine is usually arranged together with the engine in an engine room whose upper part is covered by an engine cover. For example, a muffler for silencing exhaust gas of an engine is disposed above the engine in the engine compartment. Exhaust gas silenced by the muffler is guided to a discharge pipe (exit pipe) above the muffler and then discharged. The exhaust gas is discharged to the outside of the engine room via a tail pipe connected above the pipe. Further, for example, a heat exchanger such as a radiator that dissipates heat of the cooling water of the engine is arranged substantially horizontally in the engine room at substantially the same height position as the engine. During the operation of the construction machine, the cooling fan is driven by the driving force of the engine to generate cooling air for cooling each device. This cooling air is mainly generated by the engine and the heat exchanger in the engine room. Etc., and is not so guided to the muffler located in the upper part of the engine compartment. Therefore, heat is trapped around the muffler and the temperature tends to be high, which is not sufficient in terms of improving the cooling efficiency in the engine room. In order to solve this point,
As described in JP-A-111313, the end of the tail pipe connected to the discharge pipe of the muffler on the muffler side has an expanded shape, and the end of the discharge pipe is inserted into the expanded shape of the tail pipe. A configuration has been proposed. The prior art described above uses the ejector effect by the flow velocity when exhaust gas from the discharge pipe flows into the tail pipe by adopting a structure in which the end of the discharge pipe is inserted into the expanded shape of the tail pipe. Then, air outside the discharge pipe is sucked into the tail pipe. This induces cooling air that cools around the muffler, thereby improving the cooling efficiency in the engine compartment.

On the other hand, when the exhaust gas from the engine is led to the discharge pipe of the muffler, of the exhaust gas flowing in the pipe, the flow velocity is slow due to the flow resistance in the vicinity of the pipe wall, and the flow velocity is high in the vicinity of the central part due to the flow resistance. . Due to such non-uniform flow velocity distribution, air flow noise increases, and noise due to exhaust gas increases. In addition, it is generally known that air flow noise generated by air flow in a pipe is generated in proportion to the sixth to eighth powers of the maximum flow velocity in the pipe. The airflow noise is further increased by the flow velocity, and the noise due to the exhaust gas is increased. In order to solve this problem, as described in Japanese Utility Model Laid-Open No. 2-139317, a large number of partitions are provided at the outlet end of the discharge pipe of the muffler of a general-purpose small engine, and the exhaust gas flow path is directed in the flow direction. Has been proposed. In the above-mentioned prior art, a large number of partitions are provided at the outlet side end of the discharge pipe, and the flow paths are subdivided along the flow direction, and substantially equal flow resistance is given to each flow path, thereby making the flow velocity distribution uniform. At the same time, the maximum flow velocity in the pipe is reduced to reduce air flow noise.

[0004]

Generally, there are various types of noise generated from construction machines. For example, noise generated by driving an engine disposed in an engine room, wind noise generated by a cooling fan in an engine room, and noise generated by an engine. There is noise etc. based on exhaust gas. Although it is preferable to reduce these noises as much as possible, in particular, in recent years, there has been a strong demand for further reducing the noise to the surroundings due to demands for preserving the living environment. For example, in the past, noise was measured when the construction machine was stationary, but the noise was measured while the construction machine was operating, and an inspection was performed to determine whether the measured value was within the reference value. Is in a situation where

The conventional structure described in the above-mentioned Japanese Patent Publication No. 58-111313 is intended to improve the cooling efficiency in the engine room by utilizing the ejector effect of the exhaust gas. However, special consideration is given to the reduction of noise due to the exhaust gas. It has not been. Therefore,
It is conceivable to apply the conventional structure described in Japanese Utility Model Laid-Open No. 2-139317 to this conventional structure. That is, the end of the discharge pipe is inserted into the expanded shape of the tail pipe, and a large number of partitions are provided at the end of the discharge pipe on the outlet side, thereby making the flow velocity distribution in the discharge pipe uniform and reducing airflow noise. In addition, the air outside the outlet pipe is sucked into the tail pipe to induce cooling air for cooling around the muffler, thereby improving the cooling efficiency in the engine room. However, in such a structure, although the flow velocity distribution in the discharge pipe can be made uniform at the outlet end of the discharge pipe, external air flows from the end of the expanded shape of the tail pipe downstream of the discharge pipe. When the air is sucked into the pipe, the turbulence generated by the suction causes the flow velocity distribution in the tail pipe to be insufficiently uniform, so the air flow noise in the tail pipe increases and the exhaust gas reduces noise to the surrounding environment. There is a regret that will be insufficient. In particular, when the construction machine performs work, the engine speed increases and the exhaust gas flow rate also increases, so that the noise is considerably increased.
Also, the tone at this time deteriorates, resulting in a very unpleasant sound.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust device for a construction machine capable of improving the cooling efficiency of an engine room while sufficiently reducing noise to the surrounding environment due to exhaust gas.

[0007]

According to the present invention, in order to achieve the above object, the end of a discharge pipe of a muffler connected to an engine of a construction machine is formed by expanding an end of a tail pipe facing the discharge pipe. An exhaust device for a construction machine, wherein exhaust gas discharged from the discharge pipe flows into the tail pipe and is discharged to the outside air, wherein a straightening means is provided in the tail pipe. In the device. The exhaust pipe end of the silencer is arranged in the widened shape of the tail pipe end, and the exhaust gas discharged from the discharge pipe flows into the tail pipe. Air outside the tube can be sucked into the tail tube. This induces cooling air that cools the surroundings of the muffler, thereby improving the cooling efficiency of the engine room. At this time,
The exhaust gas discharged from the discharge pipe and the air sucked by the ejector effect of the exhaust gas merge and flow in. Of these flows, those near the pipe wall have a low flow velocity due to flow resistance, and near the center. In this case, the flow velocity becomes high, and the flow velocity distribution becomes non-uniform. In the present invention, unlike the conventional structure in which the rectifying means is provided in the discharge pipe, the rectifying means is provided in the tail pipe into which the two flows merge to flow, thereby preventing disturbance caused by suction from the end of the tail pipe. Since the rectifying action can also be performed to sufficiently uniform the flow velocity distribution in the tailpipe, the airflow noise of the tailpipe can be reduced. Also, at this time, the maximum flow velocity in the tail tube can be surely reduced as compared with the case where no rectifying means is provided, so that the airflow noise can also be reduced. As a result, noise to the surrounding environment due to exhaust gas can be sufficiently reduced.

Preferably, in the exhaust device for a construction machine, the rectifying means is a lattice member that divides the tail pipe into a plurality of parallel flow paths along a flow direction. In the device. By providing substantially the same flow resistance to each flow path by the lattice member, it is possible to realize a configuration in which the flow velocity distribution in the tail pipe is made uniform and the maximum flow velocity is reduced.

More preferably, in the exhaust device for a construction machine, the lattice member is a wire mesh.

Preferably, in the exhaust device for a construction machine, when the grid member has a grid width of d [mm] and a grid pitch of 1 [mm], 1.12 ≦ d ≦ 1.2.
5. An exhaust device for a construction machine, wherein 2.00 ≦ l ≦ 2.36. It is known that, in a grid member such as a wire mesh, the flow velocity distribution becomes uniform when the resistance coefficient K becomes 2.76, and the flow velocity distribution becomes more uniform as the resistance coefficient K approaches this. This resistance coefficient K is the lattice width d.
The aperture ratio β calculated from β = (1−d / l) ² based on the lattice pitch l and the Reynolds number Re of the flow in the tailpipe is determined. The Reynolds number Re is expressed as Re = U · d / ν where U is a flow velocity, d is a representative dimension, and ν is a kinematic viscosity of air. In a typical working state of a construction machine, for example, Re ≒ 15
It becomes 0. In this case, in order to make the resistance coefficient K close to 2.76, the aperture ratio β ≒ 0.4 to 0.45 may be set, so that the grid width d and the grid pitch 1 are appropriately set within such a range. Just choose. However, if the grid width d and the grid pitch l are too large, a vortex street is generated on the back side of the grid, which causes an increase in noise and loss. Conversely, if the grid width d and the grid pitch l are too small, the pressure loss increases. And clogging. Therefore, in the present invention, 1.12 ≦ d
By setting ≦ 1.25 and 2.00 ≦ l ≦ 2.36, the resistance coefficient K is set to 2.76 while preventing these adverse effects.
To make the flow velocity distribution uniform,
Noise to the surrounding environment due to exhaust gas during construction machine operation can be reliably reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a hydraulic excavator will be described below with reference to FIGS.

FIG. 1 shows a hydraulic excavator to which the present invention is applied. A hydraulic excavator 1 includes a traveling body 3, a revolving body 4 mounted on the traveling body 3 so as to be pivotable, and a revolving body. And a work front 5 connected to the work front 4 so as to be vertically rotatable.

The traveling body 3 has left and right crawler tracks 2L and 2R as running means, and these crawler tracks 2L and 2R are driven by left and right running motors (not shown). Driven by force. The revolving superstructure 4 has a cab 6 as an operator's cab and an engine (not shown, see FIG. 2 described later) located behind the cab 6.
Are provided, and a counter weight 9 is provided further rearward than the engine room 8 to maintain a weight balance. A turning motor (not shown) is provided at the center of the turning body 4.
Thus, the revolving unit 4 is revolved with respect to the traveling unit 3. The work front 5 includes a boom 5a rotatably connected to the swing body 4, an arm 5b rotatably connected to the boom 5a, and a bucket rotatably connected to the arm 5b. The boom 5a, the arm 5b, and the bucket 5c are operated by a boom cylinder 10a, an arm cylinder 10b, and a bucket cylinder 10c, respectively.

The boom cylinder 10a, arm cylinder 10b, bucket cylinder 10c, and driving devices (hydraulic actuators) such as the above-described turning motor and left / right running motor are not described in detail. Is driven by a configuration known as a hydraulic drive. That is, pressure oil from an oil pump (not shown, see FIG. 2 described later) driven by the engine in the engine compartment is applied to each of the above-mentioned hydraulic actuators based on the operation lever operation of the operator in the cab 6. Supplied and each hydraulic actuator is driven accordingly.

In this specification, the work front 5 side (the left side in FIG. 1) when the revolving superstructure 4 is at the position shown in FIG. 1 is referred to as the front or the front side, and the counterweight 9 side (FIG. 1). 1 right side) is called the rear side or the rear side. The left-right direction when the front-rear direction is determined in this way is simply referred to as a left side and a right side.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 showing the internal structure of the engine compartment 8 provided with an embodiment of the exhaust device of the present invention. Reference numerals indicate the same parts. In FIG. 2, an engine 11 as a prime mover is provided in an engine room 8, and exhaust gas from the engine 11 is guided to a muffler 12 as a muffler.

An engine cover 14 forming a substantially box-shaped lid is provided above the engine room 8 so as to cover the engine 11 and the muffler 12. One side of this engine cover 14 is fixed with a hinge 15,
As a result, it is configured to be openable and closable as indicated by the arrow in the figure, and convenience during maintenance is achieved. Although not particularly shown, a locking member for hooking the engine cover 14 to the fixed cover 7 is provided on the other side of the engine cover 14.

The driving force of the crankshaft 11A of the engine 11 is transmitted to an auxiliary rotating shaft 32, which is a rotating shaft of the fan 19, via a V-belt 18 stretched over a pulley 16a and a pulley 16b. As a result, cooling air 20a, 20b is induced, and so-called suction-type engine cooling is performed. That is, the cooling air 20a
Is sucked into the engine room 8 from the ventilation inlet 21,
Heat exchange is performed by an oil cooler 22 that cools hydraulic oil that drives each hydraulic actuator described above, and a radiator 23 that cools cooling water of the engine 11, and a shroud attached to the radiator 23 to improve the suction efficiency of the fan 19. It flows into the fan 19 via 24. Then, after flowing out of the fan 19 and flowing around the engine 11 to cool it, it flows out of the engine room 8 through the ventilation outlets 25a and 25b. After the cooling air 20b is sucked into the engine room 8 from the ventilation suction port 21,
The periphery of the engine cover 14 is cooled to some extent through an upper space inside the engine cover 14, and flows out of the engine cover 14 through a ventilation discharge port 14 </ b> A formed on the left end surface. The oil pump 26, which is driven by the engine 11 and supplies hydraulic oil to each hydraulic actuator, is provided on the side of the engine 11 opposite to the fan 19.

The muffler 12 is fixed to an outer wall of the engine room 8 via a bracket 17. FIG. 3 is a side cross-sectional view from the right side showing a detailed structure near the muffler 12 of the engine room 8 provided with the embodiment of the exhaust device of the present invention shown in FIG. Those indicate the same parts. In FIG. 3, the right side corresponds to the front side, and the left side corresponds to the rear side. In FIG. 3, the exhaust gas 2 from the engine 11
7 is guided from an exhaust manifold 11B of the engine 11 through a bracket 28 to an exhaust pipe 29 fixed to an upper portion of the engine 11 as indicated by an arrow, and further, an inlet pipe 12a of the muffler 12 fitted to the exhaust pipe 29. Through the muffler body 12c. And the exhaust gas 27
Passes through the inside of the muffler body 12c and the muffler body 1
Discharge is performed outside the muffler 12 via a discharge pipe 12b protruding upward (downstream) of 2c.
At this time, the tail pipe 30 for discharging the exhaust gas to the outside air so as to penetrate the through hole 14B of the engine cover 14.
Is attached via a bracket 31. The lower end portion 30A of the tail pipe 30 has an expanded shape, and the muffler discharge pipe 12b is disposed so as to be inserted into the expanded shape, thereby discharging from the discharge pipe 12b. The exhaust gas 27 flowing into the tail pipe 30 is discharged to the outside air via the tail pipe 30.

FIG. 4 is an enlarged longitudinal sectional view showing a detailed structure near a connection portion between a tail pipe and a muffler discharge pipe which is a main part of one embodiment of the exhaust device of the present invention shown in FIG.
FIG. 4 is a cross-sectional view taken along the line BB in FIG. 4 showing the internal structure of the tailpipe according to an embodiment of the exhaust device of the present invention, and the same components as those in FIG. 4 and 5, a wire mesh 32 as a flow straightening means is provided in a straight tube portion 30B provided above the lower end portion 30A of the expanded shape in the tail tube 30. As shown in FIG. 5, the wire mesh 32 subdivides the straight pipe portion 30B of the tail pipe 30 into a number of parallel flow paths 33 along the flow direction, and has a lattice width (wire diameter). Is a steel wire, iron wire, or the like in which d is regularly arranged in a grid pattern at a grid pitch l.

In the above description, the discharge pipe 12b forms the discharge pipe of the silencer, and the wire mesh 32 forms the lattice member.

In this embodiment constructed as described above, the end of the discharge pipe 12b of the muffler 12 is disposed within the expanded shape of the tail pipe end 30A, and the exhaust gas 27 discharged from the discharge pipe 12b is 4 (see FIG. 4) flows into the tailpipe 30, whereby the ejector effect (= converting the velocity energy of the high-speed fluid into pressure energy and sucking another fluid) by the flow velocity of the exhaust gas 27 at this time is obtained. The air outside the discharge pipe 12b can be sucked into the tail pipe 30. Thereby, the cooling air 39 (see FIGS. 3 and 4) that mainly cools the periphery of the muffler 12 can be induced, so that the cooling air 20b passing near the muffler 12 (see FIG. 2) is reinforced. In this manner, the cooling in the vicinity of the muffler 12 above the engine room 8 where heat is easily stored can be promoted, and the cooling efficiency in the engine room 8 can be improved. Further, the exhaust gas 27 discharged from the discharge pipe 12b and the cooling air 39 sucked by the ejector effect of the exhaust gas 27 merge and flow into the tail pipe 30.
Among these flows, the flow near the pipe wall has a low flow velocity due to the flow resistance, and the flow near the center has a high flow velocity, and the flow velocity distribution is not uniform. In this embodiment, the wire mesh 3
2 is provided to divide the flow path 33 into a number of parallel flow paths 33 along the flow direction, so that each flow path 33 has substantially the same flow resistance. As a result of this resistance, the flow is damped to some extent. As a result, the static pressure near the radially central portion where the flow velocity is fast becomes higher than the static pressure near the pipe wall where the flow velocity is slow at the upstream side immediately before the wire mesh 32, and the gas flow near the central portion where the flow velocity is fast is reduced. Part of the flow merges with the gas flow near the slow pipe wall, so that the flow velocity distribution can be made uniform. At this time, since the wire mesh 32 is provided in the straight pipe portion 30B of the tail pipe 30 into which the two flows merge and flows, unlike the conventional structure in which the discharge pipe is provided with the rectification means, suction from the tail pipe end 30A is performed. A rectifying effect is also applied to the turbulence caused by the turbulence, and the flow velocity distribution in the tail tube 30 can be made sufficiently uniform. Therefore, the airflow noise generated in the tail pipe 30 can be reduced. Further, at this time, the maximum flow velocity in the tail pipe 30 can be surely reduced as compared with the case where the wire netting 32 is not provided in the tail pipe 30, so that the airflow noise can also be reduced. As a result, noise to the surrounding environment due to exhaust gas can be sufficiently reduced.

In this embodiment, the wire mesh 32
Although there is no particular limitation on the dimensions and shape of the above, when the grid width is d [mm] and the grid pitch is 1 [mm],
It is preferable to set the value in the range of 12 ≦ d ≦ 1.25 and 2.00 ≦ l ≦ 2.36. The reason will be described below. For example, as shown in the technical document “Fluid resistance of pipes and ducts” (The Japan Society of Mechanical Engineers, 1979), p. ∞ is expressed by using a resistance coefficient K as follows: A （= (1 + α−αK) / (1 + α + K) (Equation 1) Further, when K> 0.7, between α and K, α = 1.1 (1 + K) ^−1/2 (Equation 2) From these (Equation 1) and (Equation 2), when the resistance coefficient K becomes 2.76, A∞ = 0, the disturbance completely disappears, and the flow velocity distribution becomes uniform.
In addition, the closer to K = 2.76, the more uniform the flow velocity distribution. This resistance coefficient K is the lattice width d.
And the lattice pitch l, the opening ratio β calculated by β = (1−d / l) ² (Equation 3), the flow velocity U, the tail pipe inner diameter dt,
Assuming that the kinematic viscosity of the air is ν, it is determined by the Reynolds number Re of the flow in the tail pipe calculated by Re = U · dt / ν (Equation 4). By the way, in the working state of a typical hydraulic excavator,
Considering the value of the Reynolds number Re specifically, for example, in the case of a large hydraulic excavator of the 50t class, the tail pipe inner diameter dt is set to dt = 127.8 [mm], and the exhaust gas is exhausted. Assuming that the gas flow rate Q is Q = 1 [m ³ / s], the flow velocity U is Becomes In addition, according to actual measurements by the inventors of the present application, the exhaust gas temperature in the tail pipe 30 was 380 ° C. under general operating conditions. Since the kinematic viscosity of air at this temperature is ν = 606 × 10 ⁻⁶ [m ² / s], the Reynolds number Re at this time is given by the above (Equation 4). Becomes Here, when Re ≧ 150, K ≒ 0.85 (1−β) / β is set between the resistance coefficient K and the aperture ratio β, as shown on P112 of the technical data described above. Since there is a relation of ² , it can be seen that the opening ratio β should be set to β ≒ 0.4 to 0.45 (Equation 5) in order to make the resistance coefficient K close to 2.76. Therefore, the grating width d and the grating pitch 1 may be appropriately selected within such a range. As described above, since the aperture ratio β is expressed using (Equation 3) based on the grating width d and the grating pitch 1, 1
The combination of the grating width d and the grating pitch l for two values of the aperture ratio β is such that the larger the grating width d, the greater the grating pitch l
And the lattice pitch l is made smaller as the lattice width d is made smaller. However, some dimensions are actually determined by the JIS standard as a commercially available lattice member. In the case of a wire mesh, a standard size is determined by a wire diameter d corresponding to a lattice width and a standard aperture size x determined by x = ld (Equation 6). The aperture reference dimension x is, for example, x = 1.7.
0, 1.80, 2.00, 2.24, 2.36, 2.5
0, 2.80, 3.15... Are determined. However, if x becomes too large, the grid pitch l becomes large and vortex streets are generated on the back side of the grid, causing noise and loss to increase. Conversely, if x is too small, the lattice pitch l becomes small, which may lead to an increase in pressure loss and clogging. From the viewpoint of arranging the tail pipe 30 in the construction machine, the inventors of the present invention have to set x = 2.00,
Three standard dimensions of 2.24 and 2.36 were judged to be preferable. The JIS standard also defines the standard of the wire diameter d when x is these values, and when x = 2.00, d =
0.50, 0.56, 0.80, 0.90, 1.12,
In the six cases of 1.60, when x = 2.24, d = 0.5
6, 0.63, 0.90, 1.40, 2.00, and when x = 2.36, d = 0.50, 0.80,
There are four types, 1.00 and 1.25. The present inventors calculated β using (Equation 3) and (Equation 6) for these combined dimensions of x and d.
1.12 [mm], l = 3.12 [mm] (x = 2.0
0 [mm]), β ≒ 0.411, and d
= 1.25 [mm], l = 3.61 [mm] (x = 2.
36 [mm]), β ≒ 0.427, and it was found that both values satisfied Expression (5). Therefore, 1.12 ≦ d ≦ 1.25 and 2.00 ≦ l ≦
It has been found that by setting 2.36, the resistance coefficient K can be brought close to 2.76 while preventing an increase in noise and loss or an increase in pressure loss and clogging due to the vortex street. This makes it possible to reliably reduce noise to the surrounding environment due to exhaust gas during construction machine work, and to suppress deterioration in tone.

In this embodiment, the wire mesh 32 is used as the lattice member. However, the present invention is not limited to this, and another material may be used. This modification will be described with reference to FIGS.
FIG. 6 is an enlarged vertical sectional view showing a detailed structure in the vicinity of a connection portion between a tail pipe and a muffler discharge pipe which is a main part of a modification of the embodiment of the exhaust device of the present invention, and FIG. 6 showing an internal structure of a tailpipe of a modified example of one embodiment of the exhaust device of FIG.
FIG. 6 is a transverse cross-sectional view taken along a middle CC section, and is a view substantially corresponding to FIGS. 4 and 5 described above. 4 and 5 indicate the same parts. 6 and 7, in this modified example, a flow path grid 34 having a predetermined length in the axial direction is provided as a grid member (rectifying means). The flow path grid 34 is formed integrally by, for example, casting, and is similar to the above-described embodiment of the present invention.
The straight pipe portion 30B of the tail pipe 30 is subdivided into a number of parallel flow paths 33 along the flow direction. According to this modified example, similarly to the above-described embodiment of the present invention, the flow velocity distribution in the tail pipe 30 can be sufficiently uniformized, and the maximum flow velocity in the tail pipe 30 can be reliably reduced. Therefore, noise to the surrounding environment due to the exhaust gas can be sufficiently reduced.

Further, in this embodiment, the case where the present invention is applied to the engine room 8 using a so-called suction type fan has been described. However, the present invention is not limited to this. May be applied. In this case, a similar effect is obtained.

[0026]

According to the present invention, it is possible to improve the cooling efficiency of the engine compartment while sufficiently reducing the noise to the surrounding environment due to the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a structure of a hydraulic shovel to which the present invention is applied.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 showing a structure inside an engine room provided with an embodiment of the exhaust device of the present invention.

3 is a right side sectional view showing a detailed structure near a muffler of an engine room provided with the embodiment of the exhaust device of the present invention shown in FIG. 2;

FIG. 4 is an enlarged vertical sectional view showing a detailed structure near a connection portion between a tail pipe and a muffler discharge pipe, which is a main part of one embodiment of the exhaust device of the present invention shown in FIG.

FIG. 5 is a cross-sectional view taken along the line BB in FIG. 4 illustrating the internal structure of the tailpipe according to the embodiment of the exhaust device of the present invention.

FIG. 6 is an enlarged vertical sectional view showing a detailed structure near a connection portion between a tail pipe and a muffler discharge pipe, which is a main part of a modification of the exhaust device according to one embodiment of the present invention.

FIG. 7 is a cross-sectional view taken along a line CC in FIG. 6, showing an internal structure of a tailpipe of a modified example of the exhaust device of one embodiment of the present invention.

[Explanation of symbols]

11 ... engine, 12 ... muffler (silencer), 12b ...
Muffler discharge pipe (discharge pipe), 27 ... exhaust gas, 30
... Tail tube, 30A ... Tail tube end, 30B ... Tail tube straight tube part, 32
... wire mesh (lattice member, rectifying means), 33 ... parallel flow path, 34
... Channel grid (grid member, rectifying means), d: wire mesh wire diameter (grid width), l: wire mesh pitch (grid pitch).

Claims (4)

[Claims] An end of a discharge pipe of a silencer connected to an engine of a construction machine is disposed within an expanded shape of an end of a tail pipe facing the end of the muffler, and the exhaust gas discharged from the discharge pipe is discharged from the discharge pipe. An exhaust device for a construction machine for flowing into a tailpipe and discharging to the outside air, wherein a rectifying means is provided in the tailpipe. 2. An exhaust system for a construction machine according to claim 1, wherein said rectifying means is a lattice member which divides the inside of the tail pipe into a plurality of parallel flow paths along a flow direction. Machine exhaust system. 3. The exhaust device for a construction machine according to claim 2, wherein said lattice member is a wire mesh. 4. The exhaust device for a construction machine according to claim 2, wherein the grid member has a grid width d [mm] and a grid pitch l [mm]. 1.12 ≦ d ≦ 1 .25 2.00 ≦ l ≦ 2.36. An exhaust device for a construction machine, wherein: