JP2007120391A - Exhaust muffler and construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increase in size of a muffler for a construction machine. <P>SOLUTION: This muffler is provided with a silencing muffler 20 provided in an exhaust path for discharging exhaust fluid exhausted from an engine 11 of the construction machine to an outside of the machine, a passage forming member 21 forming an exhaust passage 210 along the exhaust path outside of the muffler 20, and resonance mufflers 213-215 communicating to the exhaust passage 210 and provided on the passage forming member 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust silencer and a construction machine that reduce exhaust noise caused by exhaust gas discharged from an engine.

  Some exhaust silencers of this type are provided with a resonator for the purpose of reducing noise at a predetermined frequency. For example, in the apparatus described in Patent Document 1, a resonator is provided inside the muffler so that engine explosion sound and the like are muted in the resonator.

JP 2002-23552 A

  However, in the apparatus described in Patent Document 1, since the resonator is provided inside the muffler, the muffler becomes large and the degree of freedom of arrangement of the muffler is impaired.

An exhaust silencer according to the present invention includes a muffler for silencing provided in an exhaust path for discharging exhaust fluid discharged from an engine of a construction machine to the outside of the fuselage, and an exhaust passage along the exhaust path outside the muffler. And a resonance type silencer provided in the passage forming member so as to communicate with the exhaust passage.
It is preferable to provide a resonance type silencer in the tail pipe that forms the end of the exhaust path.
A sound absorbing material may be provided on the passage forming member so as to surround the exhaust passage.
The muffler can be arranged in the engine compartment, and the tail pipe can be attached to an openable and closable engine compartment cover that forms the engine compartment.
A construction machine according to the present invention includes an engine that is driven at a constant rotational speed during work, a muffler for silencing provided in an exhaust path for discharging exhaust fluid discharged from the engine to the outside of the fuselage, and an outside of the muffler In the above, a passage forming member that forms an exhaust passage along the exhaust path, and a resonance type silencer that communicates with the exhaust passage and is provided in the passage forming member. The resonance frequency is provided so as to coincide with the corresponding noise frequency.

  According to the present invention, since the resonance silencer is provided in the passage forming member so as to communicate with the exhaust passage outside the muffler, it is possible to prevent the muffler from becoming large.

-First embodiment-
Hereinafter, a first embodiment of an exhaust silencer according to the present invention will be described with reference to FIGS.
FIG. 1 is an external side view of a hydraulic excavator to which the present invention is applied. A swivel body 2 is mounted on the traveling body 1 so as to be turnable. A working front 3 including a boom 3A, an arm 3B, and a bucket 3C is attached to the front portion of the frame (swivel frame 4) of the revolving structure 2, and a counterweight 5 is attached to the rear end portion of the revolving frame 4. Yes. A cab 6 is provided on the left side of the front part of the turning frame, and an engine bay 7 is provided behind the cab 6.

  2 is a cross-sectional view taken along the line II-II in FIG. The engine 10 is supported in the engine chamber via a vibration isolation mount 12 by a bracket 11 provided on the turning frame 4. A cooling fan 13 is disposed on the side of the engine 10, and a heat exchanger 14 is disposed further on the side. The rotation of the engine crankshaft is transmitted to the cooling fan 13 via the belt 16, and the cooling fan 13 is rotated by driving the engine 10. When the cooling fan 13 rotates, cooling air is sucked into the engine compartment, and the sucked air passes through the heat exchanger 14 and passes through the inside of the shroud 15 to flow through the engine compartment. A hydraulic pump 17 is provided on the opposite side of the cooling fan 13 of the engine 10, and the hydraulic pump 17 is rotated by driving the engine 10.

  The engine 10 is, for example, a four-cylinder four-cycle diesel engine, and exhaust gas from the engine 10 is discharged to the outside through the following exhaust path. That is, an exhaust manifold 18 is installed in the upper part of the engine, and exhaust gas from the exhaust port of each cylinder gathers in the exhaust manifold 18 and is guided to the muffler 20 above the engine via the exhaust pipe 19. Then, after passing through the muffler 20, it passes through the tail pipe 21 and is discharged out of the engine compartment. The upper cover 22 of the engine compartment 7 can be opened and closed via a hinge 22a, and maintenance of each part in the engine compartment is possible with the upper cover 22 opened.

  FIG. 3 is an enlarged view of the muffler 20 of FIG. 2 as viewed from the side of the fuselage. The muffler 20 has a substantially cylindrical shape as a whole, and a peripheral surface thereof is fixed to a bracket 23 (see FIG. 2) provided on the upper part of the engine by a U-shaped bolt 24. On the peripheral surface of the muffler 20, an inflow pipe 201 into which exhaust gas from the exhaust pipe 19 flows and a discharge pipe 202 through which exhaust gas flows out to the tail pipe 21 through a through hole 22 b provided in the upper cover 22 protrude. It is installed.

  The tail tube 21 has a substantially cylindrical outer tube 211 whose upper end surface is obliquely cut toward the rear of the body, and an outlet tube 212 welded to the upper end surface of the outer tube 211. In order to prevent intrusion of rainwater or the like, an exhaust port 21a is opened rearward and slightly downward. A flange portion 21b is provided at the bottom of the outer tube 211, and the flange portion 21b is fastened with a bolt to the upper surface of the upper cover 22 so as to close the through hole 22b.

  By attaching the tail pipe 21 to the upper cover 22 via the flange portion 21b in this way, the vicinity of the through hole 22b of the upper cover 22 is reinforced, the rigidity of the upper cover 22 is increased, and noise in the engine compartment is discharged from the outflow pipe. Leakage to the outside can be prevented through a gap between 202 and the through hole 22b. On the other hand, when the tail pipe 21 is continuously connected to the tip of the discharge pipe 202 by welding or the like, a gap is required between the through hole 22b and the tail pipe 21 in order to open and close the upper cover 22. The rigidity of the cover 22 is reduced, and noise is likely to leak outside through the gap.

  Next, the silencing structure of the muffler 20 will be described. FIG. 4 is a diagram schematically showing the internal configuration of the muffler 20. The inside of the muffler 20 is divided into a first chamber 205, a second chamber 206, and a third chamber 207 by partition walls 203 and 204. The end of the inflow pipe 201 is inserted into the first chamber 205, and the end of the discharge pipe 202 is inserted into the third chamber 207. An inner pipe 208 is disposed from the first chamber 205 to the third chamber 207 through the partition walls 203 and 204.

  The end surfaces of the inflow pipe 201 and the outflow pipe 202 are closed by blocking walls 201a and 207a, respectively. On the peripheral surfaces of the inflow pipe 201 and the outflow pipe 202, a plurality of communication holes 201b and 207b are opened facing the first chamber 205 and the third chamber 207, respectively. A blocking wall 208a is provided inside the inner tube 208, and the passage in the inner tube 208 is blocked by the blocking wall 208a. On the peripheral surface of the inner pipe 208, communication holes 208b and 208c are opened so as to face the second chamber 206 with the blocking wall 208 interposed therebetween.

  The arrows in FIG. 4 indicate the flow of exhaust gas. Exhaust gas introduced into the muffler through the inflow pipe 201 flows out into the first chamber 205 through the communication hole 201b. The exhaust gas in the first chamber 205 flows into the inner pipe 208 and flows out into the second chamber 206 through the communication hole 208b. The exhaust gas in the second chamber 206 flows into the internal pipe 208 again through the communication hole 208 c and flows out into the third chamber 207 through the internal pipe 208. The exhaust gas in the third chamber 207 flows into the discharge pipe 202 through the communication hole 207 b and flows out to the tail pipe 21. As a result, the exhaust gas is repeatedly expanded and compressed in the muffler, and the exhaust noise is reduced.

  In the present embodiment, a resonator is provided in the tail tube 21 as a characteristic configuration. Hereinafter, this point will be described. FIG. 5A is a diagram schematically showing the internal configuration of the tail tube 21 according to the first embodiment, and FIG. 5B is a cross-sectional view taken along the line bb of FIG. 5A. Inside the tail tube 21 (inside the outer tube 211), a substantially cylindrical inner tube 213 is disposed from the lower end surface along the flow direction of the exhaust gas over a predetermined length. The end of the discharge pipe 202 is inserted into the gas passage part 210. That is, the tail tube 21 has a double tube structure having an outer tube 211 and an inner tube 213.

  A substantially ring-shaped upper plate 214 and lower plate 215 are fixed to the upper and lower end surfaces of the inner tube 213 so as to close the gap between the inner tube 213 and the outer tube 211, respectively. The plate 214 and the lower plate 215 form a substantially cylindrical resonance chamber 216. The inner tube 213 has a through hole 217 at one location in the circumferential direction. The through hole 217 serves as a neck portion that communicates the gas passage portion 210 and the resonance chamber 216 to form a resonator.

  The tail tube 21 is manufactured as follows, for example. Before welding the outlet pipe 212 to the upper end surface of the outer pipe 211, first, the upper plate 214 is welded to the inner peripheral surface of the outer pipe 211. Next, the upper end surface of the inner tube 213 is welded to the end portion of the upper plate 214. Next, the lower plate 215 is welded to the lower end surfaces of the outer tube 211 and the inner tube 213, and finally the outlet tube 212 is welded to the upper end surface of the outer tube 211.

When the cross-sectional area of the neck (through hole 217) is S, the length of the neck is L, the volume of the resonance chamber 216 is V, and the speed of sound is c, the noise frequency F1, which is reduced by the resonator, that is, the resonance frequency is It can be expressed by the following formula (I).
F1 = c × (S / LV) 1/2 / 2π (I)
On the other hand, assuming that the number of engine cylinders is k (= 4) and the engine speed is N (rpm), the frequency F2 of the primary explosion sound of the engine 10 can be expressed by the following equation (II).
F2 = (k / 2) × N / 60 (II)

  Normally, excavation work or the like is performed with a hydraulic excavator in a state where the engine speed N is constant (for example, 2000 rpm). Therefore, in the present embodiment, the engine rotation sound frequency F2 is obtained by substituting the engine speed N at the time of normal excavation work into the above formula (II), so that this F2 and the resonance frequency F1 are equal. The cross-sectional area S, the length L, and the volume V of the resonance chamber 216 are appropriately set. As a result, exhaust noise due to engine explosion during work can be reduced.

  The main operation of this embodiment will be described. When excavation work is performed at a predetermined engine speed N, the exhaust gas discharged from the engine 10 flows into the muffler 20 through the exhaust pipe 19 and is muffled by repeatedly expanding and compressing in the muffler. Further, the exhaust gas that has passed through the muffler 20 flows into the gas passage portion 210 of the tail pipe 21, flows through the gas passage portion 210 toward the exhaust port 21a, and is discharged from the exhaust port 21a. At this time, the amplitude of the air in the neck with respect to the sound wave in the vicinity of the resonance frequency F1 increases, and air friction occurs. As a result, the noise in the resonance frequency range, that is, the exhaust noise corresponding to the frequency F2 of engine explosion sound during work can be reduced, and a sufficient silencing effect of the exhaust sound can be obtained.

According to 1st Embodiment, there can exist the following effects.
(1) Since the resonance chamber 216 is provided inside the tail tube 21 to form a resonator, an increase in exhaust pressure (exhaust gas pressure) is suppressed, and noise of a specific frequency due to engine explosion or the like is effectively prevented. Can be reduced.
(2) It is not necessary to increase the size of the muffler 20, and the degree of freedom of arrangement of the muffler 20 can be secured.
(3) Since the tail tube 21 having the resonator is provided outside the engine room 7, it is not necessary to enlarge the engine room itself.
(4) Since the tail pipe 21 having the resonator is fixed to the upper surface of the upper cover 22, the rigidity of the upper cover 22 is increased, and noise in the engine compartment is generated between the outflow pipe 202 and the through hole 22b. It is possible to prevent leakage to the outside through the.
(5) Since the dimensions of the resonator are set so that the resonance frequency F1 coincides with the noise frequency F2 corresponding to the engine speed at the time of work, the effect of the noise of a hydraulic excavator that is often operated at a constant engine speed is effective. Can be reduced.

-Second Embodiment-
A second embodiment of the exhaust silencer according to the present invention will be described with reference to FIG.
In the second embodiment, a resonator is provided inside the tail tube 21 and a sound absorbing material is installed. FIG. 6 is a diagram schematically showing the internal configuration of the tail tube 21 according to the second embodiment. In addition, the same code | symbol is attached | subjected to the location same as FIG. 5, and the difference with 1st Embodiment is mainly demonstrated below.

  As shown in FIG. 6, a substantially cylindrical perforated pipe 218 in which a plurality of communication holes 218 a are opened over the entire peripheral surface is disposed above the inner pipe 213. The diameter of the perforated pipe 218 is equal to the diameter of the inner pipe 213, and the lower end surface of the perforated pipe 218 is welded to the upper plate 214 so that there is no step between the inner pipe 213. A sound absorbing material 220 such as glass wool or rock wool is filled between the perforated pipe 218 and the outer pipe 211, and an upper plate 219 is provided above the sound absorbing material, and the upper plate 219 is connected to the inner peripheral surface of the outer pipe 211. It is welded to the upper end surface of the perforated pipe 218.

  As described above, by providing the perforated pipe 218 inside the tail pipe 21 and housing the sound absorbing material 220 between the perforated pipe 218 and the outer pipe 211, the noise of the broadband frequency component is absorbed by the sound absorbing material 220. . Therefore, exhaust noise having a predetermined frequency can be reduced by the resonator, and broadband exhaust noise can be reduced by the sound absorbing material 20. Since the perforated pipe 218 is connected to the upper end of the inner pipe 213, there is no step at the connecting portion between the inner pipe 213 and the perforated pipe 218, and noise can be efficiently absorbed in a short passage.

  In the above embodiment, a so-called Helmholtz type resonator is provided in communication with the gas passage part 210 of the tail tube 21. However, another resonance type silencer such as a side branch type resonator may be provided. When the side branch type resonator is provided, for example, as shown in FIG. 7, the side branch 25 may be branched and connected to the tail tube 21, and the side branch 25 may be communicated with the gas passage portion 210. In the example of FIG. 7, the side branch 25 penetrates the flange portion 21 b and the upper cover 22 and extends along the inner side of the upper cover 22. What is necessary is just to set the pipe line length of the side branch 25 to 1/4 wavelength of the frequency of engine explosion sound, for example.

  If these resonators are provided outside the muffler 20, that is, if provided in a passage forming member (tail pipe 21 or exhaust pipe 19) that forms an exhaust passage along the exhaust path outside the muffler 20, You may provide in places other than the above-mentioned. If the resonator is not provided inside the muffler 20, the configuration of the muffler 20 for silencing is not limited to that shown in FIG. Although the tail tube 21 is attached to the upper cover 22, it may be attached to other than the upper cover. Although the sound absorbing material 220 is installed around the gas passage portion 210 of the tail pipe 21, the sound absorbing material 220 may be installed in another place surrounding the exhaust passage.

  Although the above embodiment is applied to a hydraulic excavator, other construction machines having an exhaust path for exhausting exhaust fluid discharged from the engine 10 to the outside of the fuselage, in particular, working frequently with a constant engine speed. The present invention can be similarly applied to other construction machines. That is, the present invention is not limited to the exhaust silencer of the embodiment as long as the features and functions of the present invention can be realized. The above description is merely an example, and when interpreting the invention, there is no limitation or restriction on the correspondence between the items described in the embodiment and the items described in the claims.

1 is an external side view of a hydraulic excavator to which the present invention is applied. II-II sectional view taken on the line of FIG. The enlarged view which looked at the muffler of FIG. 2 from the side of the body. The figure which showed the internal structure of the muffler of FIG. The figure which shows the principal part structure of the exhaust silencer which concerns on 1st Embodiment. The figure which shows the principal part structure of the exhaust silencer which concerns on 2nd Embodiment. The figure which shows the modification of this invention.

Explanation of symbols

7 Engine chamber 10 Engine 20 Muffler 21 Tail tube 22 Upper cover 25 Side branch 211 Outer tube 213 Inner tube 217 Through hole 220 Sound absorbing material

Claims (5)

A muffler for silencing provided in an exhaust path for discharging exhaust fluid discharged from the engine of the construction machine to the outside of the fuselage,
A passage forming member that forms an exhaust passage along the exhaust path outside the muffler;
An exhaust silencer comprising: a resonance silencer that communicates with the exhaust passage and is provided in the passage forming member. The exhaust silencer according to claim 1,
The exhaust silencer, wherein the resonance silencer is provided in a tail pipe that forms a terminal portion of the exhaust path. The exhaust silencer according to claim 1 or 2,
An exhaust silencer, wherein a sound absorbing material is provided on the passage forming member so as to surround the exhaust passage. The exhaust silencer according to claim 2 or 3,
The exhaust muffler according to claim 1, wherein the muffler is disposed in an engine compartment, and the tail pipe is attached to an openable / closable engine compartment cover that forms an engine compartment. An engine that is driven at a fixed speed during work;
A muffler for silencing provided in an exhaust path for discharging the exhaust fluid discharged from the engine to the outside of the fuselage,
A passage forming member that forms an exhaust passage along the exhaust path outside the muffler;
A resonance silencer provided in the passage forming member in communication with the exhaust passage;
The construction machine according to claim 1, wherein the resonance silencer is provided so that a resonance frequency coincides with a noise frequency corresponding to an engine speed during the work.

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