U.S. patent application number 15/423876 was filed with the patent office on 2017-10-26 for muffler for engine.
This patent application is currently assigned to MAKITA CORPORATION. The applicant listed for this patent is MAKITA CORPORATION. Invention is credited to Masayoshi OKUMI.
Application Number | 20170306817 15/423876 |
Document ID | / |
Family ID | 60021136 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306817 |
Kind Code |
A1 |
OKUMI; Masayoshi |
October 26, 2017 |
MUFFLER FOR ENGINE
Abstract
A muffler for an engine is provided. A muffler (50) according to
an embodiment of the present invention includes a box-shaped
housing (51), and a partition (56) that divides the inside of the
housing (51) into a first chamber (61) and a second chamber (62).
The partition (56) includes a main body portion (56a) in the form
of a flat plate, and a concave portion (56b) that protrudes toward
the second chamber (62). Exhaust gas, having flowed from an inlet
(52a) of the housing (51) into the first chamber (61), passed a
through hole (57) of the main body portion (56a), and reached one
side in the second chamber (62), flows inside the second chamber
(62) so as to bypass a second concave portion (56b2) of the concave
portion (56b) and then passes the other side in the second chamber
(62) to reach an outlet (53a) of the housing (51).
Inventors: |
OKUMI; Masayoshi; (Anjo-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAKITA CORPORATION |
Anjo-shi |
|
JP |
|
|
Assignee: |
MAKITA CORPORATION
Anjo-shi
JP
|
Family ID: |
60021136 |
Appl. No.: |
15/423876 |
Filed: |
February 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 2590/06 20130101;
F01N 1/083 20130101 |
International
Class: |
F01N 1/08 20060101
F01N001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2016 |
JP |
2016-087945 |
Claims
1. A muffler for an engine, comprising: a box-shaped housing having
an inlet that is connected with an exhaust port of the engine to
allow exhaust gas to flow in, and an outlet for discharging the
exhaust gas having flowed in; and a partition for dividing the
inside of the housing into a first chamber with the inlet and a
second chamber with the outlet, wherein the partition includes a
main body portion in the form of a flat plate, and a concave
portion that protrudes toward the second chamber from the main body
portion, the main body portion has, on one side thereof, at least
one through hole that communicates between the first and second
chambers, at least a portion of the bottom of the concave portion
contacts an inner surface of the second chamber in the housing, and
exhaust gas having flowed from the inlet into the first chamber,
passed the through hole, and reached one side in the second
chamber, flows inside the second chamber so as to bypass the
concave portion and then passes the other side in the second
chamber to reach the outlet.
2. The muffler for an engine according to claim 1, wherein the
concave portion is positioned between the outlet and the through
hole.
3. The muffler for an engine according to claim 1, wherein the
concave portion faces the inlet.
4. The muffler for an engine according to claim 3, wherein the
inlet is formed at an upper portion of the first chamber, and the
concave portion receives exhaust gas having flowed from the inlet
into the first chamber and guides the gas downward.
5. The muffler for an engine according to claim 1, wherein the main
body portion has the through hole on one horizontal side thereof,
and exhaust gas having flowed from the inlet into the first
chamber, passed the through hole, and reached one horizontal side
in the second chamber, flows inside the second chamber so as to
pass above and/or below the concave portion and then passes the
other horizontal side in the second chamber to reach the
outlet.
6. The muffler for an engine according to claim 1, wherein the
housing includes a convex portion that protrudes outward so as to
cover the outlet, and the convex portion has an opening, and a
tubular exhaust gas passage for guiding exhaust gas from the outlet
to the opening is defined by the convex portion and a portion of
the bottom of the concave portion, which partially blocks the
outlet.
7. A muffler for an engine, comprising: a box-shaped housing having
an inlet that is connected with an exhaust port of the engine to
allow exhaust gas to flow in, and an outlet for discharging the
exhaust gas having flowed in; a partition for dividing the inside
of the housing into a first chamber with the inlet and a second
chamber with the outlet; and a flow regulating part for partially
regulating the flow of exhaust gas inside the second chamber,
wherein the partition has, on one side thereof, at least one
through hole that communicates between the first and second
chambers, and exhaust gas having flowed from the inlet into the
first chamber, passed the through hole, and reached one side in the
second chamber, flows inside the second chamber so as to bypass the
flow regulating part and then passes the other side in the second
chamber to reach the outlet.
8. The muffler for an engine according to claim 7, wherein the flow
regulating part is positioned between the outlet and the through
hole.
9. The muffler for an engine according to claim 7, wherein the
partition has, on one horizontal side thereof, the through hole,
and exhaust gas having flowed from the inlet into the first
chamber, passed the through hole, and reached one horizontal side
in the second chamber, flows inside the second chamber so as to
pass above and/or below the flow regulating part and then passes
the other horizontal side in the second chamber to reach the
outlet.
10. The muffler for an engine according to claim 7, wherein the
flow regulating part constitutes a portion of the partition or a
portion of the housing.
11. The muffler for an engine according to claim 7, wherein the
flow regulating part is positioned inside the second chamber,
between the housing and the partition.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The application claims priority to Japanese Patent
Application No. 2016-087945 filed on Apr. 26, 2016, the entire
contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a muffler for an engine
(internal combustion engine).
2. Description of Related Art
[0003] A muffler for an engine installed in a portable work machine
such as a brush/weed cutter includes a box-shaped housing having,
for example, an inlet that is connected to an exhaust port of the
engine to allow exhaust gas to flow in, and an outlet for
discharging the exhaust gas having flowed in. The inside of the
housing is divided by a partition into a first chamber with the
inlet and a second chamber with the outlet. The partition has
plural through holes that communicate between the first and second
chambers. Such engine muffler is disclosed in JP 2014-181580 A.
[0004] In the muffler disclosed in JP 2014-181580 A, however, the
substantial distance the exhaust gas has to flow (move) from the
through hole of the partition to the outlet of the housing is
relatively short. This makes it difficult to efficiently reduce the
pressure of the exhaust gas within the second chamber, and
resultantly achieve a satisfactory noise-reduction effect of the
muffler.
SUMMARY OF THE INVENTION
[0005] In view of the above circumstances, the present invention
has been accomplished and an object of the present invention is to
enhance the noise-reduction effect of the muffler.
[0006] According to a first aspect of the present invention, there
is provided a muffler for an engine, which includes: a box-shaped
housing having an inlet that is connected with an exhaust port of
the engine to allow exhaust gas to flow in, and an outlet for
discharging the exhaust gas having flowed in; and a partition for
dividing the inside of the housing into a first chamber with the
inlet and a second chamber with the outlet. The partition includes
a main body portion in the form of a flat plate, and a concave
portion that protrudes toward the second chamber from the main body
portion. The main body portion has, on one side thereof, at least
one through hole that communicates between the first and second
chambers. At least a portion of the bottom of the concave portion
contacts an inner surface of the second chamber in the housing.
Exhaust gas, having flowed from the inlet into the first chamber,
passed the through hole, and reached one side in the second
chamber, flows inside the second chamber so as to bypass the
concave portion and then passes the other side in the second
chamber to reach the outlet.
[0007] According to a second aspect of the present invention, there
is provided a muffler for an engine, which includes: a box-shaped
housing having an inlet that is connected with an exhaust port of
the engine to allow exhaust gas to flow in, and an outlet for
discharging the exhaust gas having flowed in; a partition for
dividing the inside of the housing into a first chamber with the
inlet and a second chamber with the outlet; and a flow regulating
part for partially regulating the flow of exhaust gas inside the
second chamber. The partition has, on one side thereof, at least
one through hole that communicates between the first and second
chambers. Exhaust gas, having flowed from the inlet into the first
chamber, passed the through hole, and reached one side in the
second chamber, flows inside the second chamber so as to bypass the
flow regulating part and then passes the other side in the second
chamber to reach the outlet.
[0008] Other objects and features of aspects of the present
invention will be understood from the following description with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a brush/weed cutter
according to an embodiment of the present invention.
[0010] FIG. 2 is an explanatory view of the brush/weed cutter in
use according to the embodiment.
[0011] FIG. 3 is a schematic cross-sectional view of an engine and
a muffler according to the embodiment.
[0012] FIG. 4 is a front view of the muffler according to the
embodiment.
[0013] FIG. 5 is a cross-sectional view of the muffler taken at
line I-I in FIG. 4.
[0014] FIG. 6 is a cross-sectional view of the muffler taken at
line II-II in FIG. 4.
[0015] FIG. 7 is a front view of a partition according to the
embodiment.
[0016] FIGS. 8A and 8B illustrate the flow of exhaust gas in the
muffler according to the embodiment.
[0017] FIGS. 9A and 9B illustrate the flow of exhaust gas in the
muffler according to the embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Embodiments of the present invention will be described below
in detail with reference to the accompanying drawings.
[0019] FIG. 1 is a perspective view of a brush/weed cutter
according to an embodiment of the present invention. FIG. 2 is an
explanatory view of the brush/weed cutter in use. Note that in the
present embodiment, the brush/weed cutter is illustrated as an
example of a portable work machine in which a muffler for an engine
of the present invention is installed, but the muffler for an
engine of the present invention can be installed in any other
portable work machines.
[0020] A brush/weed cutter 1 includes an operation shaft 2 in the
form of a long pipe. An engine module 3 is provided as a power
source at the rear end of the operation shaft 2. A tool attachment
base 4 is disposed, as a working portion, at the tip of the
operation shaft 2.
[0021] The tool is replaceably attached to the tool attachment base
4. The tool attachment base 4 is connected to the engine module 3
by means of a drive shaft incorporated in the operation shaft 2.
The tool attachment base 4 is rotated by the engine module 3 (more
specifically, an engine 21).
[0022] A handle 5 is attached at the center of the operation shaft
2 in its longitudinal direction. A vibration-proofing housing 6 is
disposed between the handle 5 and the engine module 3. A hanger 7
is provided around the outer periphery of the vibration-proofing
housing 6.
[0023] The brush/weed cutter 1 is slung by a holder 8 over the
shoulder of an operator M. The holder 8 includes a harness 9 and a
loop 10. The operator M wears the harness 9 on his upper body. In
FIG. 2, the loop 10 is hung on the right side of the operator M.
The operator M hooks the hanger 7 over the loop 10 and operates the
thus-suspended brush/weed cutter 1. The operator M grips the handle
5 of the brush/weed cutter 1 with his hands and moves the
brush/weed cutter 1 to cut weeds.
[0024] The engine module 3 is mainly composed of a cover 11 as its
armor, the engine 21 covered with the cover 11 (see FIG. 3 as
below), and a muffler 50. Here, the muffler 50 corresponds to a
"muffler for an engine" of the present invention. The cover 11 is
made of, for example, resin.
[0025] FIG. 3 is a schematic cross-sectional view of the engine 21
and the muffler 50. FIG. 3 illustrates the engine 21 in case a
piston 25 is positioned near a top dead center. Furthermore, in the
present embodiment, the term "upper side" substantially corresponds
to a vertically upper side of the engine 21 in such a posture that
the engine 21 stands (upright posture), when in use, for the
longest period of time.
[0026] The engine 21 is an overhead valve (OHV) 4-stroke,
air-cooled engine. The engine 21 has a cylinder part 22, a crank
case 23 disposed below the cylinder part 22, and an oil tank 24
disposed below the crank case 23.
[0027] The cylinder part 22 has cylindrical space through which the
piston 25 slidably moves in the vertical direction in FIG. 3. The
piston 25 is inserted into the space with a clearance that allows
vertical sliding in FIG. 3.
[0028] The cylinder part 22, the crankcase 23, and the piston 25
constitute a crank chamber 27. More specifically, the cylindrical
space on the crankcase 23 side as defined by the side surface of
the cylinder part 22 and the piston 25 and the internal space of
the crankcase 23 form the crank chamber 27. In the crank chamber
27, its internal volume changes along with the sliding movement of
the piston 25.
[0029] The cylinder head 28, the cylinder part 22, and the piston
25 constitute a combustion chamber 29. The oil tank 24 is defined
by an oil tank case and provided separately of the crankcase 23.
The oil tank 24 retains lubricating oil.
[0030] A check valve 30 is disposed between the oil tank 24 and the
crankcase 23, which only allows oil to flow into the oil tank 24
from the crankcase 23 (crank chamber 27).
[0031] In this example, as the piston 25 moves from a bottom dead
center to the top dead center, the pressure in the crank chamber 27
becomes a negative pressure. In contrast, along with the movement
of the piston 25 from the top dead center to the bottom dead
center, the pressure in the crank chamber 27 becomes a positive
pressure. Thus, when the pressure of the crank chamber 27 is
positive, the check valve 30 opens to let oil flow from the crank
chamber 27 to the oil tank 24. If the pressure of the crank chamber
27 is negative, the check valve 30 closes.
[0032] A crank 33 is rotatably supported inside the crankcase 23.
The crank 33 is composed of a crank shaft 33a as the rotational
center, a counter weight, etc. The piston 25 and the crank 33 are
connected together by means of a connecting rod 34. The connecting
rod 34 and the piston 25 are oscillatably connected. The connecting
rod 34 and the crank 33 are rotatably connected. Such configuration
ensures that the piston 25 reciprocates inside the cylinder part
22.
[0033] A cylinder head 28 is provided on an upper wall of the
cylinder part 22. The cylinder head 28 is equipped with an intake
port 35 and an exhaust port 36. The intake port 35 is in
communication with a carburetor (not shown) by means of an
insulator (not shown). An air cleaner (not shown) is provided
upstream of the carburetor. Note that the engine module 3 further
includes the aforementioned insulator, carburetor, and air cleaner,
and a fuel storage tank (not shown). The above insulator,
carburetor, and air cleaner are covered with the cover 11. The
carburetor is a device for mixing a fuel with the air past the air
cleaner to generate an air-fuel mixture.
[0034] The muffler 50 has a vertically-elongated thin form. In the
present embodiment, the muffler 50 is directly connected to the
exhaust port 36 of the engine 21, communicating with the exhaust
port 36. The muffler 50 is detailed below with reference to FIGS. 4
to 7.
[0035] The cylinder head 28 is equipped with an intake valve 37 for
opening/closing the intake port 35. Moreover, the cylinder head 28
is equipped with an exhaust valve 38 for opening/closing the
exhaust port 36. The intake valve 37 and the exhaust valve 38
open/close the combustion chamber 29.
[0036] Next, the muffler 50 is described in more detail with
reference to FIGS. 4 to 7 together with FIG. 3 as referenced above.
FIG. 4 is a front view of the muffler 50. FIG. 5 is a
cross-sectional view taken at line I-I of FIG. 4. FIG. 6 is a
cross-sectional view taken at line II-II of FIG. 4. FIG. 7 is a
front view of a partition (partition plate) 56. In the following,
the upper and lower sides and the right and left sides are defined
as illustrated in FIGS. 4 to 7 for ease of explanation.
Furthermore, the intake side is defined as being on the engine 21
side, and the discharge side is defined as being opposite to the
engine 21 side (i.e., on the side far from the engine 21). The
"upper side" in FIGS. 4 to 7 substantially corresponds to a
vertically upper side of the engine 21 in such a posture that the
engine 21 stands (upright posture), when in use, for the longest
period of time. Moreover, the "left side" in FIG. 4 to 7
corresponds to "one side" or "one horizontal side" of the present
invention, whereas the "right side" corresponds to "the other side"
or "the other horizontal side".
[0037] The muffler 50 includes a housing 51, the partition 56, and
a guide member 58. The housing 51 is provided in the form of
substantially a rectangular box and composed of a first container
52 and a second container 53. In the present embodiment, the first
container 52 and the second container 53 are made of metal but may
be alternatively made of resin resistant to high temperature like
fiber reinforced plastics (FRP), etc.
[0038] The first container 52 defines the intake side of the
housing 51. The first container 52 has substantially a rectangular
box shape that opens at its discharge side. The first container 52
has an external flange portion 54 that extends outward at its
peripheral edge on the discharge side. An inlet 52a is formed at an
upper portion of the first container 52. The inlet 52a is connected
to the exhaust port 36. Owing to the inlet 52a provided at the
upper portion of the first container 52, the muffler 50 does not so
much extend upward beyond the engine 21.
[0039] The second container 53 defines the discharge side of the
housing 51. The second container 53 has substantially a rectangular
box shape that opens at its intake side. The second container 53
has an external flange portion 55 extending outward at its
peripheral edge on the intake side. A convex portion 53p protrudes
outward (opposite to a second chamber 62) at a somewhat lower
position than the center of the second container 53 in the vertical
direction. As illustrated in FIG. 4, the convex portion 53p has a
horizontally elongated rectangular form as viewed from the front.
The convex portion 53p has substantially a U shape in cross section
and extends in the horizontal direction (right-left direction). The
convex portion 53p has an opening 53q at the left end. Here, the
substantially rectangular opening at the intake side end of the
convex portion 53p (i.e., the substantially rectangular opening at
the proximal-end-side end of the convex portion 53p) corresponds to
the outlet 53a. Thus, the convex portion 53p protrudes outward to
cover the outlet 53a and also includes the opening 53q.
[0040] The metal or resin partition 56 is composed of a main body
portion 56a in the form of substantially a rectangular flat plate
and a concave portion 56b formed at the center in the horizontal
direction (right-left direction). The peripheral edge of the main
body portion 56a of the partition 56 is fixed to the first
container 52 and the second container 53 by means of a swage while
being clamped between the external flange portion 54 of the first
container 52 and the external flange portion 55 of the second
container 53. Accordingly, in the housing 51, a first chamber 61 is
defined by the first container 52 and the partition 56, and the
second chamber 62 is defined by the second container 53 and the
partition 56. In this example, the first chamber 61 includes the
inlet 52a. On the other hand, the second chamber 62 includes the
outlet 53a. In addition, the first chamber 61 communicates with the
exhaust port 36 through the inlet 52a.
[0041] The concave portion 56b of the partition 56 is composed of a
first concave portion 56b1 that forms the upper portion thereof and
a second concave portion 56b2 that forms the central and lower
portions thereof in the vertical direction. The first concave
portion 56b1 faces the inlet 52a of the first container 52 across
the guide member 58. In other words, the first concave portion 56b1
and the inlet 52a of the first container 52 face each other with
the guide member 58 being interposed between them.
[0042] The first concave portion 56b1 is curved downward in the arc
shape from the inlet 52a side to the discharge side (i.e., from the
intake side to the discharge side). In this example, the first
concave portion 56b1 has the function of receiving exhaust gas
having flowed into the first chamber 61 from the inlet 52a and
guiding the gas downward (for example, to the second concave
portion 56b2).
[0043] The lower end of the first concave portion 56b1 is
continuous to the upper end of the second concave portion 56b2. The
second concave portion 56b2 protrudes toward the discharge side as
compared to the first concave portion 56b1. The second concave
portion 56b2 has substantially a rectangular shape as viewed from
the front as shown in FIG. 7. At least a portion (see, for example,
portion P of FIG. 6) of its bottom 56bt is in contact with the
inner surface of the second container 53. In other words, at least
a portion of the bottom 56bt of the concave portion 56b is in
contact with the inner surface of the second chamber 62 in the
housing 51. The bottom 56bt constitutes an end wall on the
discharge side, out of the second concave portion 56b2 of the
concave portion 56b.
[0044] The bottom 56bt of the second concave portion 56b2 includes
an exhaust gas passage forming portion 56bt1 that protrudes
somewhat toward the discharge side. The exhaust gas passage forming
portion 56bt1 blocks a portion of the above outlet 53a (in the
present embodiment, at least left portion). Here, the remaining
portion of the outlet 53a, which is not blocked by the exhaust gas
passage forming portion 56bt1, constitutes a substantial opening
53a1 of the outlet 53a. Furthermore, the exhaust gas passage
forming portion 56bt1 corresponds to "a portion of the bottom of
the concave portion, which partially blocks the outlet" of the
present invention.
[0045] The second concave portion 56b2 has an exhaust gas guide
portion 56bt2 adjoining the right side of the exhaust gas passage
forming portion 56bt1. As illustrated in FIG. 7, the exhaust gas
guide portion 56bt2 is formed like a groove that is recessed toward
the first chamber 61 side as viewed from the front. The exhaust gas
guide portion 56bt2 has the function of guiding the exhaust gas
inside the second chamber 62 to the substantial opening 53a1 of the
outlet 53a.
[0046] As shown in FIG. 7, plural (ten in FIG. 7) through holes 57
are formed on the left side of the main body portion 56a of the
partition 56. In this example, the through holes 57 are positioned
lower than the inlet 52a of the first container 52. In FIG. 7, the
ten through holes 57 are illustrated, but the number of through
holes 57 is not limited to ten.
[0047] Also, in the present embodiment, as shown in FIG. 6, the
concave portion 56b (especially, second concave portion 56b2) is
positioned between the outlet 53a (especially, the substantial
opening 53a1) and the plural through holes 57 in the horizontal
direction (right-left direction). In the present embodiment, as
shown in FIG. 7, a C-shaped region 56bt3 is in contact with the
inner surface of the second chamber 62 in the housing 51. The
region 56bt3 extends covering the upper side, the lower side, and
the left side of the exhaust gas passage forming portion 56bt1 out
of the bottom 56bt of the second concave portion 56b2 of the
concave portion 56b.
[0048] The tubular exhaust gas passage 67 of the substantially
rectangular cross-sectional shape is defined by the convex portion
53p of the second container 53 and the exhaust gas passage forming
portion 56bt1 of the second concave portion 56b2 of the partition
56. The exhaust gas passage 67 extends in the horizontal direction
(right-left direction) and communicates with, on the right side
thereof, the second chamber 62 through the outlet 53a (especially,
the substantial opening 53a1). The left end of the exhaust gas
passage 67 corresponds to the above opening 53q. The exhaust gas
passage 67 serves to guide exhaust gas from the outlet 53a
(especially, the substantial opening 53a1) to the opening 53q.
[0049] At least one (two in FIGS. 4 and 6) cylindrical portion 65
penetrates the housing 51. The cylindrical portion 65 is formed to
penetrate the first container 52, the second container 53, and the
partition 56. A bolt (not shown) for fixing the housing 51 to the
engine 21 may be inserted into the cylindrical portion 65. Note
that FIGS. 4 and 6 show the two cylindrical portions 65, but the
number of cylindrical portions 65 is not limited to two. Also, FIG.
7 shows through holes 65a in each of which the cylindrical portion
65 is inserted.
[0050] The guide member 58 is made of metal or resin and attached
to the inlet 52a of the first container 52. The guide member 58 has
the U-shaped sectional shape that opens at its lower end and
extends toward the discharge side from the inlet 52a of the first
container 52.
[0051] The guide member 58 has the function of smoothly guiding to
the concave portion 56b of the partition 56 the exhaust gas having
flowed into the first chamber 61 through the inlet 52a from the
exhaust port 36.
[0052] In the present embodiment, the concave portion 56b of the
partition 56 (especially, the second concave portion 56b2)
functions as a flow regulating part 70 so as to partially regulate
the flow of the exhaust gas inside the second chamber 62. The flow
regulating part 70 regulates, especially, the flow of the exhaust
gas that flows straight inside the second chamber 62 from the
through hole 57 to the outlet 53a (especially, the substantial
opening 53a1) in the horizontal direction. Moreover, in the present
embodiment, the flow regulating part 70 partially constitutes the
partition 56 (the concave portion 56b (especially the second
concave portion 56b2)). The flow regulating part 70 is interposed
between the housing 51 (especially, the second container 53) and
the partition 56 (especially, the main body portion 56a) inside the
second chamber 62.
[0053] In the present embodiment, as shown in FIG. 5, the partition
56 is placed in the housing 51 so that a flow direction F1 of the
exhaust gas at the inlet 52a of the first container 52 forms obtuse
angle .theta.1 with a direction F2 extending from the lower end to
the upper end of the main body portion 56a of the partition 56. The
obtuse angle .theta.1 is preferably within a range of 95.degree. to
125.degree., more preferably 100.degree. to 120.degree..
[0054] In the present embodiment, distance L1 is set longer than
distance L2; the distance L1 is from a portion of the inner wall at
the lower end of the first chamber 61, which faces the lower end of
the main body portion 56a of the partition 56, to the lower end of
the main body portion 56a of the partition 56, and the distance L2
is from a portion of the inner wall at the lower end of the second
chamber 62, which faces the lower end of the main body portion 56a
of the partition 56, to the lower end of the main body portion 56a
of the partition 56. In addition, the partition 56 includes the
concave portion 56b. Thereby, the first chamber 61 can ensure large
volume enough to let high-temperature and high-pressure exhaust gas
flow in.
[0055] Next, the flow of the exhaust gas discharged to the outside
from the exhaust port 36 via the muffler 50 is described. FIGS. 8A
and 8B and FIGS. 9A, and 9B show the flow of exhaust gas inside the
muffler 50 of the present embodiment. FIG. 8A corresponds to FIG. 5
as referenced above. FIG. 9A corresponds to FIG. 6 as referenced
above. FIGS. 8B and 9B correspond to FIG. 7 as referenced
above.
[0056] The flow direction of exhaust gas having flowed into the
first chamber 61 from the exhaust port 36 through the inlet 52a of
the muffler 50 is directed downward by the concave portion 56b of
the partition 56 (especially, the first concave portion 56b1) (see
flow S1 of the exhaust gas as indicated by arrows in FIGS. 8A and
8B). In this example, the concave portion 56b of the partition 56
(especially, the first concave portion 56b 1) can function to
receive the exhaust gas having flowed into the first chamber 61
from the inlet 52a and guide the gas downward.
[0057] After dispersed into the first chamber 61 and cooled, the
exhaust gas passes through the through hole 57 of the partition 56
and flows into the left side of the second chamber 62 (see flow S2
of the exhaust gas as indicated by arrows in FIGS. 8A, 8B, and 9A).
The exhaust gas having flowed into the left side of the second
chamber 62 flows inside the second chamber 62 so as to pass above
and below the concave portion 56b of the partition 56 (especially,
the second concave portion 56b2) and reaches the right side of the
second chamber 62 (see flows S3 and S4 of the exhaust gas as
indicated by arrows in FIGS. 9A and 9B). Note that the exhaust gas
can be dispersed and cooled in the second chamber 62 as well.
[0058] Subsequently, the exhaust gas passes the exhaust gas guide
portion 56bt2 of the partition 56 and the outlet 53a (especially,
substantial opening 53a1) and further the exhaust gas passage 67
and then is discharged from the opening 53q of the exhaust gas
passage 67 to the outside (see flow S5 of the exhaust gas as
indicated by arrows in FIGS. 9A and 9B). Note that the first
container 52, the second container 53, and the partition 56
receives heat of the exhaust gas passing through the muffler 50 and
releases the received heat to the outside from outer surfaces of
the first container 52 and the second container 53.
[0059] According to the present embodiment, the muffler 50
includes: the box-shaped housing 51 having the inlet 52a that is
connected to the exhaust port 36 of the engine 21 to allow the
exhaust gas to flow in, and the outlet 53a for discharging the
exhaust gas having flowed in; and the partition 56 for dividing the
inside of the housing 51 into the first chamber 61 with the inlet
52a and the second chamber 62 with the outlet 53a. The partition 56
includes the main body portion 56a in the form of a flat plate and
the concave portion 56b protruding from the main body portion 56a
toward the second chamber 62 side. The main body portion 56a has,
on one side thereof (left side), at least one through hole 57 that
communicates between the first chamber 61 and the second chamber
62. At least a portion of the bottom 56bt (e.g., the region 56bt3)
of the concave portion 56b contacts the inner surface of the second
chamber 62 in the housing 51. The exhaust gas, having flowed into
the first chamber 61 from the inlet 52a, passed the through hole
57, and reached one side (left side) in the second chamber 62,
flows inside the second chamber 62 so as to bypass the concave
portion 56b (especially, second concave portion 56b2). Then, the
gas passes the other side (right side) in the second chamber 62 to
reach the outlet 53a (especially, substantial opening 53a1) (see
flows S1-S5 of the exhaust gas in FIGS. 8A and 8B and FIGS. 9A and
9B). This makes it possible to relatively increase the substantial
distance the exhaust gas flows (moves), from the through hole 57 of
the partition 56 to the outlet 53a of the housing 51, contributing
to efficient reduction of the exhaust gas pressure in the second
chamber 62 and further to enhancement of the noise-reduction effect
of the muffler.
[0060] According to the present embodiment, the concave portion 56b
(especially, second concave portion 56b2) is positioned between the
outlet 53a (especially, substantial opening 53a1) and the through
hole 57. This makes it possible to ensure, with simple structure,
the relatively long substantial distance the exhaust gas flows
(moves), from the through hole 57 of the partition 56 to the outlet
53a of the housing 51.
[0061] According to the present embodiment, the concave portion 56b
(especially, first concave portion 56b1) faces the inlet 52a,
whereby the concave portion 56b (especially, first concave portion
56b1) can smoothly receive the exhaust gas having flowed from the
inlet 52a into the first chamber 61.
[0062] According to the present embodiment, the inlet 52a is
provided at an upper portion of the first chamber 61. The concave
portion 56b receives the exhaust gas having flowed from the inlet
52a into the first chamber 61 and guides it downward. As a result,
the exhaust gas can be appropriately dispersed and cooled inside
the first chamber 61.
[0063] According to the present embodiment, the main body portion
56a has the through hole 57 on one horizontal side thereof (left
side). The exhaust gas, having flowed from the inlet 52a into the
first chamber 61, passed the through hole 57, and reached one
horizontal side (left side) in the second chamber 62, flows inside
the second chamber 62 so as to pass above and below the concave
portion 56b (especially, second concave portion 56b2), passes the
other horizontal side (right side) in the second chamber 62, and
reaches the outlet 53a (especially, substantial opening 53a1) (see
flows S1-S5 of the exhaust gas in FIGS. 8A and 8B and FIGS. 9A and
9B). This makes it possible to relatively increase the substantial
distance the exhaust gas flows (moves), from the through hole 57 of
the partition 56 to the outlet 53a of the housing 51, contributing
to efficient reduction of the exhaust gas pressure in the second
chamber 62 and further to enhancement of the noise-reduction effect
of the muffler.
[0064] According to the present embodiment, the housing 51
(especially, second container 53) includes the convex portion 53p
that protrudes outward to cover the outlet 53a, and the convex
portion 53p has the opening 53q. The tubular exhaust gas passage 67
for guiding the exhaust gas from the outlet 53a (especially,
substantial opening 53a1) to the opening 53q is defined by the
convex portion 53p and a portion (exhaust gas passage forming
portion 56bt1) of the bottom 56bt of the concave portion 56b, which
partially blocks the outlet 53a. Thus, an exhaust duct usually
attached as an external member to the outer surface of the housing
51 (especially, second container 53) can be omitted and
functionally replaced by the exhaust gas passage 67. The total
number of components can be accordingly reduced by the number of
components for the duct. Moreover, the portion functioning as the
duct can be prepared only by combining the convex portion 53p of
the housing 51 and the exhaust gas passage forming portion 56bt1 of
the partition 56, whereby the production time for the duct can be
considerably reduced as compared to the conventional
configuration.
[0065] According to the present embodiment, the muffler 50
includes: the box-shaped housing 51 having the inlet 52a that is
connected to the exhaust port 36 of the engine 21 to allow the
exhaust gas to flow in, and the outlet 53a for discharging the
exhaust gas having flowed in; the partition 56 for dividing the
inside of the housing 51 into the first chamber 61 with the inlet
52a and the second chamber 62 with the outlet 53a; and the flow
regulating part 70 for partially regulating the flow of the exhaust
gas inside the second chamber 62. The partition 56 has, on one side
thereof (left side), at least one through hole 57 that communicates
between the first chamber 61 and the second chamber 62. The exhaust
gas having flowed from the inlet 52a into the first chamber 61,
passed the through hole 57, and reached one side (left side) in the
second chamber 62, flows inside the second chamber 62 so as to
bypass the flow regulating part 70 and then passes the other side
(right side) in the second chamber 62 to reach the outlet 53a
(especially, substantial opening 53a1) (see flows S1-S5 of the
exhaust gas in FIGS. 8A and 8B and FIGS. 9A and 9B). This makes it
possible to relatively increase the substantial distance the
exhaust gas flows (moves), from the through hole 57 of the
partition 56 to the outlet 53a of the housing 51, contributing to
efficient reduction of the exhaust gas pressure in the second
chamber 62 and further to enhancement of the noise-reduction effect
of the muffler.
[0066] According to the present embodiment, the flow regulating
part 70 is positioned between the outlet 53a (especially,
substantial opening 53a1) and the through hole 57. This makes it
possible to ensure, with simple structure, the relatively long
substantial distance the exhaust gas flows (moves), from the
through hole 57 of the partition 56 to the outlet 53a of the
housing 51.
[0067] According to the present embodiment, the main body portion
56a has the through hole 57 on one horizontal side thereof (left
side). The exhaust gas, having flowed from the inlet 52a into the
first chamber 61, passed the through hole 57, and reached one
horizontal side (left side) in the second chamber 62, flows inside
the second chamber 62 so as to pass above and below the flow
regulating part 70, passes the other horizontal side (right side)
in the second chamber 62, and reaches the outlet 53a (especially,
substantial opening 53a1) (see flows S1-S5 of the exhaust gas in
FIGS. 8A and 8B and FIGS. 9A and 9B). This makes it possible to
relatively increase the substantial distance the exhaust gas flows
(moves), from the through hole 57 of the partition 56 to the outlet
53a of the housing 51, contributing to efficient reduction of the
exhaust gas pressure in the second chamber 62 and further to
enhancement of the noise-reduction effect of the muffler.
[0068] According to the present embodiment, the flow regulating
part 70 partially constitutes the partition 56 (concave portion 56b
(especially, second concave portion 56b2)). This eliminates the
necessity for preparing the flow regulating part 70 by use of any
other member and consequently contributes to reduction in the total
number of components.
[0069] According to the present embodiment, the flow regulating
part 70 is positioned, inside the second chamber 62, between the
housing 51 (especially, second container 53) and the partition 56
(especially, main body portion 56a). Thus, the exhaust gas flowing
from the left to the right inside the second chamber 62 can pass,
in mid-flow, above and below the flow regulating part 70.
[0070] In the present embodiment, described is the case that the
exhaust gas flowing from the left to the right inside the second
chamber 62 passes, in mid-flow, above and below the flow regulating
part 70 (concave portion 56b of the partition 56 (especially,
second concave portion 56b2)). As regards the bypass routes of the
exhaust gas, however, the gas has only to pass either above or
below the flow regulating part 70 (concave portion 56b of the
partition 56 (especially, second concave portion 56b2)). More
specifically, the exhaust gas flowing from the left to the right
inside the second chamber 62 can pass, in mid-flow, above or below
the flow regulating part 70 (concave portion 56b of the partition
56 (especially, second concave portion 56b2)).
[0071] In the present embodiment, the concave portion 56b of the
partition 56 (especially, second concave portion 56b2) is described
as an example of the flow regulating part 70. However, the
configuration of the flow regulating part 70 is not limited to the
above.
[0072] As another example of the flow regulating part 70, the
second container 53 can be, instead of forming the second concave
portion 56b2 in the partition 56, integrally molded to include any
substitute for the second concave portion 56b2. In this case, the
flow regulating part 70 partially constitutes the housing 51
(especially, second container 53).
[0073] To give still another example of the flow regulating part
70, the partition 56 is composed of the plate-like main body
portion 56a alone and the aforementioned other member substitutable
for the second concave portion 56b2 is interposed between the main
body portion 56a of the partition 56 and the inner surface of the
second container 53. In this example, the aforementioned other
member corresponds to the flow regulating part 70, which is
disposed inside the second chamber 62, and which is held between
the housing 51 (especially, second container 53) and the partition
56.
[0074] In the present embodiment, the brush/weed cutter is
described as an example of the portable work machine in which the
muffler 50 is installed. However, the muffler 50 can be installed
in any other portable work machines. For example, the muffler 50
can be installed in portable work machines such as a hole-digging
machine and a concrete cutter. Alternatively, the muffler 50 can be
installed in backpack work machines such as a backpack blower, a
sprayer (spray), a dust blower, and a backpack brush/weed
cutter.
[0075] In the present embodiment, the OHV type 4-stroke engine is
described as an example of the engine 21. However, the
configuration of the engine 21 is not limited thereto. For example,
the engine 21 could be an OHC-type engine.
[0076] In the present embodiment, the cylinder head 28 and the
cylinder part 22 are separately provided in the engine 21 by way of
example. Alternatively, the cylinder head and the cylinder part can
be integrated.
[0077] In the muffler for an engine according to the first aspect
of the present invention, at least a portion of the bottom of the
concave portion of the partition is in contact with the inner
surface of the second chamber in the housing. Moreover, the exhaust
gas, having flowed from the inlet of the housing into the first
chamber, passed the through hole of the partition, and reached one
side in the second chamber, flows inside the second chamber so as
to bypass the concave portion of the partition, passes the other
side in the second chamber, and reaches the outlet of the housing.
This makes it possible to relatively increase the substantial
distance the exhaust gas flows (moves), from the through hole of
the partition to the outlet of the housing, contributing to
efficient reduction of the exhaust gas pressure in the second
chamber and further to enhancement of the noise-reduction effect of
the muffler.
[0078] In the muffler for an engine according to the second aspect
of the present invention, the flow regulating part partially
regulates the exhaust gas flow inside the second chamber.
Furthermore, the exhaust gas, having flowed from the inlet of the
housing into the first chamber, passed the through hole of the
partition, and reached one side in the second chamber, flows inside
the second chamber so as to bypass the flow regulating part, passes
the other side in the second chamber, and reaches the outlet of the
housing. This makes it possible to relatively increase the
substantial distance the exhaust gas flows (moves), from the
through hole of the partition to the outlet of the housing,
contributing to efficient reduction of the exhaust gas pressure in
the second chamber and further to enhancement of the
noise-reduction effect of the muffler.
[0079] The embodiments of the present invention are described above
but the present invention is not limited to these embodiments. As
is needless to say, various changes and modifications can be made
based on the technical idea of the present invention.
* * * * *