U.S. patent application number 09/820927 was filed with the patent office on 2001-08-16 for lubricating system in a 4-cycle engine.
This patent application is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Honda, Souhei, Nishida, Takao, Ryu, Yasutake, Tsugekawa, Takanori.
Application Number | 20010013327 09/820927 |
Document ID | / |
Family ID | 27480397 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013327 |
Kind Code |
A1 |
Ryu, Yasutake ; et
al. |
August 16, 2001 |
Lubricating system in a 4-cycle engine
Abstract
An oil reservoir chamber, a crank chamber and a valve-operating
chamber are provided in an engine body. The oil reservoir chamber
and the crank chamber are in communication with each other through
a through-hole, and the crank chamber and the valve-operating
chamber are in communication with the each other through a one-way
valve which is opened upon rising of the pressure in the crank
chamber. The valve-operating chamber and the oil reservoir chamber
are in communication with each other through an orifice. By
utilizing a pressure pulsation in the crank chamber, an oil mist
produced in the oil reservoir chamber is circulated from the oil
reservoir chamber to the crank chamber, the valve-operating chamber
and the oil reservoir chamber. Thus, in any operational attitude of
an engine, the lubricating oil can be circulated without use of
special oil pump.
Inventors: |
Ryu, Yasutake; (Wako-Shi,
JP) ; Honda, Souhei; (Wako-Shi, JP) ; Nishida,
Takao; (Wako-Shi, JP) ; Tsugekawa, Takanori;
(Wako-Shi, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN, HATTORI,
MCLELAND & NAUGHTON, LLP
1725 K STREET, NW, SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha
|
Family ID: |
27480397 |
Appl. No.: |
09/820927 |
Filed: |
March 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09820927 |
Mar 30, 2001 |
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09285252 |
Apr 2, 1999 |
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6213078 |
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09285252 |
Apr 2, 1999 |
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08764813 |
Dec 12, 1996 |
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5947075 |
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Current U.S.
Class: |
123/196R ;
123/196M |
Current CPC
Class: |
F02B 2075/027 20130101;
F02B 2275/30 20130101; F01M 9/06 20130101; F01M 1/04 20130101; F02B
2275/34 20130101; F01M 11/064 20130101; F02B 63/02 20130101; F02F
1/002 20130101 |
Class at
Publication: |
123/196.00R ;
123/196.00M |
International
Class: |
F01M 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 1995 |
JP |
327665/95 |
Dec 15, 1995 |
JP |
327667/95 |
Dec 20, 1995 |
JP |
331602/95 |
Dec 26, 1995 |
JP |
339373/95 |
Claims
What is claimed is:
1. A system for lubricating a 4-cycle engine, comprising: an oil
reservoir chamber which stores a lubricating oil therein and has an
oil mist producing means contained therein for producing an oil
mist from the lubricating oil; a crank chamber having a crank
portion of a crankshaft contained therein; and a valve-operating
chamber having a valve-operating device contained therein, said oil
reservoir chamber, said crank chamber and said valve-operating
chamber being provided in an engine body, said oil reservoir
chamber and said crank chamber being in communication with each
other through a through-hole above an oil level in said oil
reservoir chamber, said crank chamber and said valve-operating
chamber being in communication with each other through a control
valve which is opened upon rising of the pressure in said crank
chamber and closed upon reduction of the pressure in said crank
chamber, said valve-operating chamber being substantially in
communication at its upper portion with the atmosphere and at its
bottom portion with said oil reservoir chamber through an orifice,
and the following expression is established during operation of the
engine:Pc.ltoreq.Po<Pvwherein Pc is a pressure in the crank
chamber; Po is a pressure in the oil reservoir chamber; and Pv is a
pressure in the valve operating chamber.
2. A system for lubricating a 4-cycle engine according to claim 1,
further including an uppermost chamber which occupies a position
above the valve-operating chamber and to communicate with the
valve-operating chamber through an orifice and also communicate
with said oil reservoir chamber or said crank chamber through an
oil passage, and the following expression is established during
operation of the engine:Pc.ltoreq.Po.lto- req.Pt<Pvwherein Pt is
a pressure in said uppermost chamber.
3. A system for lubricating a 4-cycle engine according to claim 1
or 2, wherein said oil mist producing means comprises an oil
slinger which is rotated by said crankshaft to agitate and scatter
the lubricating oil in said oil reservoir chamber at all times,
irrespective of the inclined state of the engine.
4. A system for lubricating a 4-cycle engine according to claim 1,
wherein said control valve comprises a one-way valve of
pressure-responsive type.
5. A system for lubricating a 4-cycle engine according to claim 1,
wherein said control valve comprises a rotary valve which is opened
upon the lowering movement of a piston operatively associated with
the rotation of the crankshaft and closed upon the elevating
movement of the piston.
6. A system for lubricating a 4-cycle engine according to claim 5,
wherein the opening duration of said rotary valve is approximately
180.degree. in terms of a crank angle, and the start point of
opening of said rotary valve is set in a range of from a middle
point between top and bottom dead centers of the piston to a
lowering-piston position of 45.degree. of said piston in terms of
the crank angle.
7. A system for lubricating an air-cooled 4-cycle engine
comprising: a shroud covering an outer periphery of a cylinder
block and defining a cooling-air passage between the shroud and the
outer periphery of the cylinder block; a cooling blade mounted at
one end of a crankshaft supported in a crankcase for feeding
cooling air into the cooling-air passage; and a recoil type starter
which is mounted to the crankcase to protrude the outside of the
shroud and which is capable of cranking the other end of the
crankshaft, wherein said lubricating system further includes an oil
reservoir chamber formed in the crankcase and disposed between the
recoil type starter and a crank chamber in said crankcase having a
crank portion of the crankshaft contained therein for storing a
lubricating oil, an oil mist producing means contained in said oil
reservoir chamber for agitating the lubricating oil to produce an
oil mist, and the oil mist produced in the oil reservoir chamber is
supplied to the crank chamber and the various portions of the
engine.
8. A system for lubricating an air-cooled 4-cycle engine
comprising: an oil reservoir chamber provided in an engine body
having a crank chamber and a valve-operating chamber for
sequentially supplying a lubricating oil to said crank chamber and
said valve-operating chamber, said valve-operating chamber and said
oil reservoir chamber being in communication with each other
through an oil circulating passage for returning the lubricating
oil from said valve-operating chamber to said oil reservoir
chamber, wherein an opening of the oil circulating passage into the
oil reservoir chamber is disposed such that it is exposed above an
oil level of the lubricating oil in the oil reservoir chamber in a
sideways-fallen state or an inverted state of the engine in which
the valve-operating chamber comes below the oil reservoir
chamber.
9. A system for lubricating a 4-cycle engine comprising: a crank
chamber having a crank portion of a crankshaft contained therein
and storing a lubricating oil therein, a valve operating chamber
having a valve-operating device contained therein, said crank
chamber and said valve-operating chamber being provided in an
engine body, an oil mist producing means provided in said crank
chamber for producing an oil mist from the lubricating oil, said
crank chamber and said valve operating chamber being in
communication with each other above an oil level of the lubricating
oil in the crank chamber through a control valve which is opened
upon rising of the pressure in said crank chamber and closed upon
reduction of the pressure in said crank chamber, said
valve-operating chamber being substantially in communication at its
upper portion with atmosphere, and in communication at its bottom
with said crank chamber through an orifice, and the following
expression is established during operation of the
engine:Pc<Pvwherein Pc in a pressure in said crank chamber, and
Pv is a pressure in the valve-operating chamber.
10. A system for lubricating a 4-cycle engine according to claim 9,
further including an uppermost chamber provided the engine body to
occupy a position above said valve-operating chamber and to
communicate with said valve-operating chamber through an orifice
and also with said crank chamber through an oil circulating
passage, and the following expression is
established:Pc.ltoreq.Pt<Pvwherein Pt is a pressure in said
uppermost chamber.
11. A system for lubricating a 4-cycle engine according to claim 9,
wherein said control valve comprises a rotary valve which is opened
upon the lowering movement of a piston operatively associated with
the rotation of the crankshaft and closed upon the elevating
movement of the piston.
12. A system for lubricating a 4-cycle engine according to claim
11, wherein the opening duration of said rotary valve is
approximately 180.degree. in terms of a crank angle, and the start
point of opening of said rotary valve is set in a range or from a
middle point between top and bottom dead centers of the piston to a
lowering-piston position of 45.degree. of said piston in terms of
the crank angle.
13. A system for lubricating a 4-cycle engine according to claim 9,
wherein said crank chamber comprises an inner chamber in which the
crank portion of the crankshaft is disposed, and an outer chamber
adjoining opposite sides of said inner chamber on opposite sides of
a partition wall and communicating with a bottom of said inner
chamber, and wherein much of the lubricating oil in said crank
chamber is received in said outer chamber when the engine is fallen
sideways or inverted.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a system for lubricating a
hand-held type 4-cycle engine used as a power source mainly for a
trimmer or a chain saw.
[0003] 2. Description of the Related Art
[0004] The conventional hand-held type engine widely used in these
applications is a 2-cycle engine capable of exhibiting a
lubricating function in any operational attitude of the engine such
as inclined and sideways-fallen attitudes.
[0005] However, as such a hand-held type engine, it is desirable to
use a 4-cycle engine from the viewpoint of an exhaust emission
control. In the 4-cycle engine, however, it is necessary to store
an oil exclusively used for lubrication. Therefore, if the 4-cycle
engine is used as the hand-held type engine, it is necessary to
reliably lubricate various portion of the engine in any operational
attitude of the engine.
SUMMARY OF THE INVENTION
[0006] Accordingly, it is one object of the present invention to
provide a 4-cycle engine lubricating system capable of satisfying
the above requirements for use in hand-held tools.
[0007] To achieve the above object, according to a first aspect and
feature of the present invention, there is provided a system for
lubricating a 4-cycle engine, comprising: an oil reservoir chamber
which stores a lubricating oil therein and has an oil mist
producing means contained therein for producing an oil mist from
the lubricating oil; a crank chamber having a crank portion of a
crankshaft contained therein; and a valve-operating chamber having
a valve-operating device contained therein, the oil reservoir
chamber, the crank chamber and the valve operating chamber being
provided in an engine body, the oil reservoir chamber and the crank
chamber being in communication with each other through a
through-hole above an oil level in the oil reservoir chamber, the
crank chamber and the valve operating chamber being in
communication with each other through a control valve which is
opened upon rising of the pressure in the crank chamber and closed
upon reduction of the pressure in the crank chamber, the
valve-operating chamber being substantially in communication at its
upper portion with the atmosphere and at its bottom portion with
the oil reservoir chamber through an orifice, and the following
expression is established during operation of the engine;
Pc.ltoreq.Po<Pv
[0008] wherein Pc is a pressure in the crank chamber; Po is a
pressure in the oil reservoir chamber; and Pv is a pressure in the
valve-operating chamber.
[0009] With the first feature of the present invention, in any
inclined state of the engine, the oil mist can be constantly
circulated to the oil reservoir chamber, the crank chamber, the
valve-operating chamber and the oil reservoir chamber and the oil
liquified in the valve-operating chamber can be circulated to the
oil reservoir chamber by utilizing the magnitude of the differences
between the pressures in the chambers, thereby insuring a good
lubricating state. Moreover, an expensive oil pump is not required
and hence, this lubricating system is convenient even in a respect
of cost.
[0010] According to a second aspect and feature of the present
invention, in addition to the above first feature, the system
further includes an uppermost chamber which occupies a position
above the valve-operating chamber and to communicate with the
valve-operating chamber through an orifice end also communicate
with the oil reservoir chamber or the crank chamber through an oil
passage, and the following expression is established during
operation of the engine:
Pc.ltoreq.Po.about..ltoreq.Pt<Pv
[0011] wherein Pt is a pressure in the uppermost chamber.
[0012] With the above second feature of the present invention, not
only the circulation of the oil mist but also the circulation of
the oil liquified and accumulated in the uppermost chamber can be
reliably performed, and a good lubricating state can be
insured.
[0013] According to a third aspect and feature of the present
invention, in addition to the above first feature, the oil mist
producing means comprises an oil slinger which is rotated by the
crankshaft to agitate and scatter the lubricating oil in the oil
reservoir chamber at all times irrespective of the inclined state
of the.
[0014] With the third feature of the present invention, the oil
mist can be reliably produced in the oil reservoir chamber by the
rotation of the oil slinger in any operational attitude of the
engine and moreover, the structure of the oil slinger is relatively
simple.
[0015] According to a fourth aspect and feature of the present
invention, in addition to the first or second feature, the control
valve comprises a one-way valve of a pressure responsive type.
[0016] With the fourth feature, the one-way valve can be opened and
closed in operative association with the pressure pulsation in the
crank chamber to transfer the oil mist from the crank chamber into
the valve-operating chamber and to maintain the crank chamber in an
averagely negative pressure state. Particularly, the sealing is
good during closing of the one-way valve and hence, the lubricating
system is effective for an engine rotating at relatively lower
speeds.
[0017] According to a fifth aspect and feature of the present
invention, in addition to the first or second feature, the control
valve comprises a rotary valve which is opened upon the lowering
movement of a piston operatively associated with the rotation of
the crankshaft and closed upon the elevating movement of the
piston.
[0018] With the fifth feature, the rotary valve can be opened and
closed in mechanically operative association with the rotation of
the crankshaft to transfer the oil mist from the crank chamber into
the valve-operating chamber and to maintain the crank chamber in an
averagely negative pressure state. Particularly, a deviation in
timing of opening and closing of the rotary valve cannot be
produced and hence, the lubricating system is effective for a
relatively lower-speed rotated type engine.
[0019] According to a sixth aspect and feature of the present
invention, in addition to the fifth feature, the opening duration
of the rotary valve is approximately 180.degree. in terms of a
crank angle, and the start point of opening of the rotary valve is
set in a range of from a middle point between top and bottom dead
centers of the piston to a lowering-piston position of 45.degree.
of the piston in terms of the crank angle.
[0020] With the sixth feature of the present invention, the
discharge of a positive pressure from the crank chamber into the
valve-operating chamber can be effectively performed by utilizing
an inertial effect of a gas during rotation of the engine at a high
speed. Therefore, the transferring of the oil mist and insuring of
the negative pressure state of the crank chamber can be more
reliable.
[0021] The above and other objects, features and advantages of the
invention will become apparent from the following description of
preferred embodiments taken in conjunction with be accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1 to 10 show a first embodiment of the present
invention, wherein
[0023] FIG. 1 is an illustration for explaining the service state
of a power trimmer equipped with an engine including one
lubricating system according to the invention;
[0024] FIG. 2 is a vertical sectional front view of the engine;
[0025] FIG. 3 is a sectional view taken along the line 3-3 in FIG.
2;
[0026] FIG. 4 is a sectional view taken along the line 4-4 in FIG.
2;
[0027] FIG. 5 is a sectional view taken along the line 5-5 in FIG.
2;
[0028] FIG. 6 is a sectional view taken along the line 6-6 in FIG.
2;
[0029] FIG. 7 is a sectional view taken along the line 7-7 in FIG.
2;
[0030] FIG. 8 is a sectional view taken along the line 8-8 in FIG.
2;
[0031] FIG. 9 is a sectional view taken along the line 9-9 in FIG.
2; and
[0032] FIGS. 10A and 10B are sectional views illustrating the
position between a level of oil stored in an oil reservoir chamber
and a circulating passage in a sideways fallen state (10A) and a
turned upside-down or inverted state (10B) of the engine;
[0033] FIGS. 11 to 14 show a modification of the engine, wherein
FIG. 11 is a vertical sectional view of an engine;
[0034] FIG. 12 is a sectional view taken along the line 12-12 in
FIG. 11;
[0035] FIG. 13 is a sectional view showing an opened state of the
rotary valve; and
[0036] FIG. 14 is a diagram illustrating the opening and closing
timing of the rotary valve;
[0037] FIGS. 15 to 25 show a second embodiment of the present
invention, wherein
[0038] FIG. 15 is a side view of an engine including a lubricating
system;
[0039] FIG. 16 is a vertical sectional front view of the
engine;
[0040] FIG. 17 is an enlarged view of an essential portion shown in
FIG. 16;
[0041] FIG. 18 is a sectional view similar to FIG. 17, but
illustrating a different operational state of the rotary valve;
[0042] FIG. 19 is a sectional view taken along the line 13-19 in
FIG. 16;
[0043] FIG. 20 is a sectional view taken along the line 20-20 in
FIG. 16;
[0044] FIG. 21 is a sectional view taken along the line 21-21 in
FIG. 16;
[0045] FIG. 22 is a sectional view taken along the line 22-22 in
FIG. 16;
[0046] FIG. 23 is a sectional view taken along the line 23-23 in
FIG. 17;
[0047] FIG. 24 is a sectional view showing the state of a
lubricating oil in a crank chamber when the engine is fallen
sideways; and
[0048] FIG. 25 is a sectional view showing the state of the
lubricating oil in the crank chamber when the engine is inverted or
turned upside down.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] The present invention will now be described by way of
preferred embodiments with reference to the accompanying
drawings.
[0050] A first embodiment of the present invention shown in FIGS. 1
to 10 will be first described. Referring to FIG. 1, a hand-held
type 4-cycle engine E is mounted, for example, as a power source
for a power trimmer T, to a drive section of the power trimmer T.
The power trimmer T is used with its cutter turned in each of
various directions depending upon its working state and hence, is
largely inclined or turned upside down, wherein its working state
is not constant.
[0051] Referring to FIGS. 2 and 3, a carburetor 2 and an exhaust
muffler 3 are mounted in front and rear portions of an engine body
1 of the engine E, and an air cleaner 4 is mounted in an inlet of
an intake passage in the carburetor 2. A fuel tank 5 is mounted to
a lower surface of the engine body 1. The carburetor 2 includes a
diaphragm pump for pumping fuel from the fuel tank 5 by utilizing a
pressure pulsation in a crank chamber (which will be described
hereinafter) of the engine E to circulate the surplus fuel to the
tank 5, so that the fuel can be supplied to an intake port in the
engine E in any attitude.
[0052] As shown in FIGS. 2 and 3, the engine body 1 includes a
cylinder block integral with a head, and a crankcase 7 bonded to a
lower end face of the cylinder block 6. The cylinder block 6
includes a single cylinder 9 having a piston 8 received therein,
and a large number of cooling fins 10 around its outer
periphery.
[0053] The crankcase 7 includes a pair of upper and lower case
halves 7a and 7b coupled to each other by a plurality of bolts 11
arranged in their peripheral edges. A crankshaft 13 is connected to
the piston 8 through a connecting rod 12 and supported between the
case halves 7a and 7b in the following manner:
[0054] The upper case half 7a is integrally provided with a pair of
left and right upper journal support walls 14 and 14' depending
from a ceiling wall, and the lower case half 7b is integrally
provided with a pair of left and right lower journal support walls
15 and 15' rising from its bottom wall and opposed to the upper
journal walls 14 and 14'. A left journal portion of the crankshaft
13 is clamped between the left upper and right journal support
walls 14 and 15 with a plane bearing 16 interposed therebetween,
and a right journal portion of the crankshaft 13 is clamped between
the right upper and lower journal support walls 14' and 15' with a
ball bearing 17 interposed therebetween. A total of four bolt bores
18 are made in each of the upper and lower journal support walls
14' and 15' in an arrangement on opposite sides of the plane
bearing 16 or the ball bearing 17, and vertically passed through
the crankcase 7. Four stud bolts 19 are embedded in a lower end
face of the cylinder block 6 and passed through the bolt bores 18.
A nut 20 is threadedly fitted over a lower end of each of the stud
bolts 19 protruding from a lower surface of the crankcase 7. In
this manner, the upper and lower journal support walls 14, 14', and
15, 15' are coupled to each other, and the cylinder block 6 and the
crankcase 7 are also coupled to each other.
[0055] Such coupling structure does not interfere with the cooling
fins 10 provided around the outer periphery of the cylinder block 6
and hence, the number, the extent and the like of the cooling fins
10 can be freely selected, and the cooling effect for the engine
can be enhanced sufficiently. The support rigidity of the crankcase
7 to the crankshaft 13 can be also enhanced.
[0056] Oil seals 21 and 21' are mounted at opposite end walls of
the crankcase 7 at portions through which the crankshaft 13 is
passed.
[0057] The inside of the crankcase 7 is divided into a left oil
reservoir chamber 22, a central rank chamber 23 and a right
valve-operating chamber 24, as viewed in FIG. 2. A crank portion
13a of the crankshaft 13 is disposed in the crank chamber 23. A
defined amount of lubricating oil 0 is stored in the oil reservoir
chamber 22, and an oil slinger 25 (which is an oil mist generating
means) for agitating and scattering the lubricating oil 0 is
secured to the crankshaft 13.
[0058] As shown in FIGS. 2 and 4, the oil slinger 25 includes a
boss 25a fitted over the crankshaft 13, a plurality of longer-arm
blades 25b and a plurality of shorter-arm blades 25c both
protruding from an outer periphery of the boss 25a. Tip ends of the
blades 25b and 25c are bent in axially opposite directions.
[0059] The oil slinger 25 having such structure is capable of
agitating the oil stored in the oil reservoir chamber 22 by the
rotation of both the blades 25b and 25c in any operational attitude
of the engine E to produce an oil mist at all times.
[0060] The valve-operating chamber 24 extends through one side of
the cylinder block 6 to the head of the cylinder block 6. An upper
portion or the valve-operating chamber 24 is capable of being
opened and closed by a head cover 26 coupled to the head of the
cylinder block 6.
[0061] As shown in FIGS. 2 and 5, the head of the cylinder block 6
is provided with exhaust ports 27 and 28 connected to the
carburetor 2 and the exhaust muffler 3, and intake and exhaust
valves 29 and 30 for opening and closing the intake and exhaust
ports 27 and 28. A valve-operating device 31 for opening and
closing the intake and exhaust valves 29 and 30 is disposed in the
valve-operating chamber 24.
[0062] The valve-operating device 31 includes a follower timing
gear 33 which is rotatably carried on a support shaft 34 supported
between coupled surfaces of the cylinder block and the crankcase 7
and which is driven at a speed-reduction ratio of 2/1 from a
driving timing gear 32, a cam 35 integrally connected to one end of
the follower timing gear 33, a pair of cam followers 37 and 38
carried on a cam follower shaft 36 mounted in the cylinder block 6,
so that they are swung by the cam 35, a pair of rocker arms 40 and
41 carried on a rocker shaft 39 mounted in the head of the cylinder
block 6 with their one ends abutting against valve heads of the
intake and exhaust valves 29 and 30, a pair of push rods 42 and 43
connecting the can followers 37 and 38 to the other ends of the
rocker arms 40 and 41, and valve springs 44 and 45 for biasing the
intake end exhaust valves 29 and 30 in closing directions. During
an intake stroke of the piston 8, the intake valve 29 can be
opened, and during an exhaust stroke of the piston 8, the exhaust
valve 30 can be opened.
[0063] The oil reservoir chamber 22 and the crank chamber 23
communicate with each other through a through-hole 46 provided in
the crank shaft 13. In this case, an opening of the through-hole
into the oil reservoir chamber 22 is disposed at a center portion
of the oil reservoir chamber 22. The amount of lubricating oil O
stored in the oil reservoir chamber 22 is set so that the opening
is submerged into the oil even in any inclined or inverted state of
the engine. Alternatively, the through-hole 46 may be provided in
the plane bearing 16 or a partition wall between the oil reservoir
chamber 22 and the crank chamber 23.
[0064] As shown in FIGS. 2 and 7, a valve chamber 47 is defined
under a lower surface of the crankcase 7 and connected to the
valve-operating chamber 24. The valve chamber 47 communicates with
a bottom of the crank chamber 23 through a valve bore 48. A one-way
valve 49 is mounted in the valve chamber 47 as a control valve for
opening and closing valve bore 48 and is moved in response to the
pressure pulsation in the crank chamber 23, so that the valve bore
48 is closed upon a reduction in pressure and opened upon a
pressure rise.
[0065] A U-shaped oil return chamber 50 is defined under the lower
surface of the crankcase 7 to surround the valve chamber 47. The
oil return chamber 50 communicates with the bottom of the
valve-operating chamber 24 through a pair of orifices 51 disposed
spaced apart from each other to the utmost, and also communicates
with the oil reservoir chamber 22 through the pair of through-hole
46. The total sectional area of the through holes 46 is set
sufficiently larger than the total sectional area of the orifices
51.
[0066] The valve chamber 47 and the oil return chamber 50 are
defined by closing a recess defined in the lower surface of the
crankcase 7 by a bottom plate 53. The bottom plate 53 is clamped to
the crankcase 7 by the stud bolts 19 and the nuts 20.
[0067] An upper portion of the valve-operating chamber 24
communicates with an inside of the air cleaner 4 through a breather
tube 54 made of rubber and mounted through one-side wall of the
head cover 26. In this case, that end of the breather tube 54 which
is opened into the valve-operating chamber 24 is disposed to
protrude into the valve-operating chamber 24 over a predetermined
length. Therefore, the oil somewhat accumulated in the
valve-operating chamber 24 can be prevented from flowing out of the
chamber 24 into the breather tube 54 in any operational attitude of
the engine E.
[0068] As shown in FIGS. 2, 8 and 9, an outer cover 55 is coupled
to the head cover 26, so that it is fitted over an outer periphery
of the head cover 26. A flat uppermost chamber 56 is defined
between ceiling walls of the covers 26 and 55 and communicates with
the valve-operating chamber 24 through a pair of orifices 57
provided in the ceiling wall of the head cover 26 at diagonal
locations (desirably at four corners). The uppermost chamber 56
also communicates with the oil return chamber 50 through a single
oil passage 58 provided in the cylinder block 6 and the crankcase
7. The oil passage 58 has a sectional area larger than the total
sectional area of the pair of orifices 57.
[0069] The orifices 51 and 57, the uppermost chamber 56, the oil
passage 58, the oil return chamber 50 and the through-holes 46
constitute a circulating passageway L for returning the lubricating
oil from the valve-operating chamber 24 to the oil reservoir
chamber 22. An opening 52 of the circulating passageway into the
oil reservoir chamber 22, i.e. an outlet end of the through-hole 52
is located at a longitudinally and laterally central portion of the
oil reservoir chamber 22 and below a vertically central portion of
the oil reservoir chamber 2 and below a vertically central portion
of the chamber 22. Thus, as shown in FIGS. 10A and 10B, such
opening is exposed above the stored oil level in the oil reservoir
chamber 22 in a sideways-fallen or inverted state of the engine E
in which the valve-operating chamber 24 is located below the oil
reservoir chamber 22.
[0070] If the rotation of the crankshaft 13 causes the lubricating
oil O to be agitated in the oil reservoir chamber by the oil
slinger 25 during operation of the engine E to produce an oil mist,
when the pressure in the crank chamber is reduced by the elevating
movement of the piston 8, the oil mist is drawn through the
through-holes 46 into the crank chamber 23 to lubricate portions
around the crank portion 13a and the piston 8. Then, when the
pressure in the crank chamber 23 increases by the lowering movement
of the piston 8, the one-way valve 49 is opened to permit the oil
mist to be supplied along with blow-by gas generated in the crank
chamber 23 from the valve bore 48 into the valve chamber 47 and
thus into the valve operating chamber 24, where the oil mist and
the blow-by gas are separated from each other. Thus, the oil mist
lubricates the various portions of the valve-operating device 31,
while the blow-by gas is discharged through the breather tube 54
into the air cleaner 4.
[0071] The pressure in the crank chamber 23 is pulsated by the
elevating and lowering movements of the piston 5 between positive
and negative pressures alternately repeated. Under the positive
pressure, the one-way valve 49 is opened to permit the positive
pressure to be released toward the valve chamber 47. Under the
negative pressure, the one-way valve 49 is closed to inhibit the
back-flow of the positive pressure from the valve chamber 47 and
hence, the pressure in the crank chamber 23 is kept negative on an
average.
[0072] On the other hand, the valve-operating chamber 24 and the
valve chamber 47 connected to each other communicate with the
inside of the air cleaner 4 which is in an atmospheric pressure
state, through the breather tube 54 and hence, the pressures in
both the chambers 24 and 47 are substantially equal to atmospheric
pressure.
[0073] The oil reservoir chamber 22 communicates with the crank
chamber 23 through the through-holes 46 and hence, the pressure in
the oil reservoir chamber 22 is equal to or slightly higher than
the pressure in the crank chamber 23.
[0074] The oil return chamber 50 communicates with the oil
reservoir chamber 22 through the through-hole 52 and also with the
valve-operating chamber 24 through the orifices 51 and hence, the
pressure in the oil return chamber 50 is equal to or slightly
higher than the pressure in the oil reservoir chamber 22.
[0075] The uppermost chamber 56 communicates with the oil return
chamber 50 through the oil passage 58 and also with the
valve-operating chamber 24 through the orifices 57 and hence, the
pressure in the uppermost chamber 56 is equal to or slightly higher
than the pressure in the oil return chamber 50.
[0076] The magnitude relationship between the pressures in the
chambers can be represented by the following expression:
Pc.ltoreq.Po.ltoreq.Pr.ltoreq.Pt<Pv
[0077] wherein,
[0078] Pc represents pressure in the crank chamber 23,
[0079] Po represents pressure in the oil reservoir chamber 22,
[0080] Pr represents pressure in the oil return chamber 50,
[0081] Pt represents pressure in the upper most chamber 56, and
[0082] Pv represents pressure in the valve-operating chamber
24.
[0083] As a result, during operation of the engine, the pressure
flows through a path which will be shown below:
1 Valve-operating chamber 24 Uppermost chamber 56 Oil return
chamber 50 Oil reservoir chamber 22 Crank chamber 23
[0084] Therefore, the oil mist fed to the valve-operating chamber
24 is circulated via the pressure path to the oil reservoir chamber
22, and the oil liquefied in the valve-operating chamber 24 is
circulated via the orifices 51 to the oil return chamber 50 and the
oil reservoir chamber 22. Such circulation of the oil mist and the
liquefied oil is performed without hindrance even when the engine E
is inclined in any attitude.
[0085] In the inverted operational state of the engine E, the upper
most chamber 56 is located below the valve-operating chamber 24 and
hence, the oil liquefied in the valve-operating chamber 24 flows
through the orifices 57 into the uppermost chamber 24 and is drawn
upwards through the oil passage 58 into the oil return chamber 50
and circulated into the oil reservoir chamber 22.
[0086] Even in any operational attitude such as inclined and
inverted attitudes of the engine E, the circulation of the
lubricating oil can be conducted without interruption to insure a
good lubricating state at all times. Therefore, it is possible for
the engine to resist the working of the power trimmer T in all
directions. Moreover, since the pressure pulsation in the crank
chamber 23 is utilized for the circulation of the lubricating oil,
the expense of an oil pump is not required.
[0087] After completion of the working, the operation of the engine
E is stopped to leave the power trimmer to stand, the engine E may
be fallen sideways or inverted in some cases, as shown in FIGS. 10A
and 10B. However, in such a state, the opening of the circulating
path L connected to the valve-operating chamber 24 into the oil
reservoir chamber 22, i.e., the outlet end of the through-hole 52
is exposed above the oil level of the lubricating oil O stored in
the oil reservoir chamber 22 and hence, the lubricating oil 0 in
the oil reservoir chamber 22 can be prevented from flowing
backwards through the circulating path L into the valve-operating
chamber 24. Therefore, it is possible to avoid the leakage of the
lubricating oil from the valve-operating chamber 24 into the
breather tube 54.
[0088] Referring again to FIG. 2, a rotor 61 of a flywheel magneto
59 with a cooling blade 60 is secured to an outer end of the
crankshaft 13 adjacent the valve-operating chamber 24, and an
ignition coil 62 cooperating with the rotor 61 is secured to the
cylinder block 6. A centrifugal clutch 64 is interposed between the
rotor 61 and a working machine driving shaft 63. The centrifugal
clutch 64 includes a plurality of clutch shoes 65 expandably
carried on the rotor 61, a clutch spring 66 for biasing the clutch
shoes 65 in a contracting direction, and a clutch drum 67 secured
to the driving shaft 63 to surround the clutch shoes 65. When the
rotor 61 is rotated in a predetermined number of rotations or more,
the clutch shoes 65 are expanded to come into pressure contact with
an inner peripheral surface of the clutch drum 67, thereby
transmitting an output torque from the crankshaft 13 to the driving
shaft 63.
[0089] A shroud 69 is mounted to the engine body 1 to cover the
head portion of the engine body 1 and the flywheel magneto 59 and
to define a cooling air passage 68 between the shroud and the head
portion of the engine body 1 and the flywheel magneto 59. An inlet
68I into the cooling air passage 68 is mounted in an annular
configuration between the centrifugal clutch 64 and the shroud 69,
and an outlet 68o is mounted in the shroud 69 on the opposite side
from the inlet 68I.
[0090] Thus, during rotation of the rotor 61, wind produced by the
cooling blade 60 flows through the cooling air passage 68 to cool
the various portions of the engine E.
[0091] The oil reservoir chamber 22 adjoining one side of the crank
chamber 23 is disposed to protrude from the outer surface of the
cylinder block 6 to face the cooling air passage 68, and known coil
starter 70 capable of cranking the crankshaft 13 is mounted to the
outer surface of the crankcase 7 adjacent the oil reservoir chamber
22. The starter 70 is disposed to protrude to the outside of the
shroud 69, so that the shroud 69 does not interfere with operation
of a starter rope of the starter 70.
[0092] When the rotor 61 is rotated along with the crankshaft 13,
wind produced by the cooling blade 60 flows through the cooling air
passage 68 to cool the various portions of the engine E, but
particularly, since the oil reservoir chamber 22 faces the cooling
air passage 68, the oil reservoir chamber 22 is also cooled by the
cooling air, whereby the cooling of the lubricating oil O can be
effectively performed. Moreover, the oil reservoir chamber 22 is
disposed in a space between the crank chamber 23 and the
recoil-type starter 70, which is conventionally a dead space, and
hence, the size of the engine E is not increased by the presence of
the oil reservoir chamber 72.
[0093] FIGS. 11 to 14 show a modification to the engine, which
employs a rotary valve 71 in place of the one-way valve 49. In
FIGS. 11 to 13, the rotary valve 71 includes a pair of fan-shaped
valve members 72 formed in a bulged manner on an opposite side of
the follower timing gear 33 of the valve-operating devise 31 from
the cam 35 and arranged on a diametrical line, and a pair of
recesses 73 circumferentially located between the valve members 72.
The rotary valve 71 is opposed to a valve bore 74 provided in a
partition wall between the crankshaft chamber 23 and the
valve-operating chamber 24 to open and close the valve bore 74 by
the rotation of the follower timing gear 33.
[0094] Each of the valve members 72 and the recesses 73 has a
center angle of approximately 90.degree., but because the follower
timing gear 33 is driven with a reduction ratio of 1/2 from the
driving gear 32 rotated in unison with the crankshaft 13, each of
the durations of closing and opening of the valve bore 74 by the
valve members 72 and the recesses 73 is of approximately
180.degree. in terms of a crank angle.
[0095] Moreover, as shown in FIG. 14, the valve member 72 and the
recess 73 are disposed so that they cause the valve to be opened
(see FIG. 13) during the lowering stroke of the piston 8 and to be
closed (see FIG. 11) during the elevating stroke of the piston 8.
Particularly, a desirable disposition is such that the valve bore
74 is opened in a range of from the middle point P between top and
bottom dead points of the piston 8 to a lowering-piston position
corresponding to 45.degree. in terms of the crank angle, and closed
in a range of from such middle point P to an elevating-piston
position of 45.degree. in terms of the crank angle.
[0096] Other arrangements are similar to those in the above
described embodiment, except that the valve chamber 47 is
eliminated, and in FIGS. 11-14, portions or components
corresponding to those in the above-described first embodiment are
designated by like reference characters.
[0097] The rotary valve 71 opens and closes the valve bore 74 in
mechanically operative association with the rotation of the
crankshaft 13 and hence, even during rotation of the engine E at a
high speed, a deviation in a predetermined timing for opening and
closing the valve bore 74 cannot be produced, and by effectively
utilizing in inertial effect of the flowing gas, the oil mist can
be efficiently supplied from the crank chamber 23 into the
valve-operating chamber 24 and at the same time, an average
negative pressure state of the crank chamber 23 can be insured.
[0098] A second embodiment of the present invention will now be
described with reference to FIGS. 15 to 25.
[0099] Referring to FIG. 15, a carburetor 102 and an exhaust
muffler 103 are mounted to front and rear portions of an engine
body 101 of a hand-held type 4-cycle engine 10E, respectively, and
an air cleaner 104 is mounted at an intake inlet of the carburetor
102. A fuel tank 105 is mounted to a lower surface of the engine
body 101. The carburetor 102 includes a diaphragm pump for pumping
fuel from the fuel tank 105 by utilizing a pressure pulsation in a
crank chamber which will be described and for circulating the
surplus fuel to the fuel tank, so that the fuel can be supplied to
an intake port of the engine 10E in any attitude of the engine.
[0100] Referring to FIGS. 16, 17, 19 and 20, the engine body 101
includes a crankcase 106 comprised of a pair of left and right case
halves 106a and 106b coupled to each other by bolts, and an
integral head-type cylinder block 107 bolted to an upper end face
of the crank case 106. The case halves 106a and 106b carry a
crankshaft 108 horizontally, and a piston 110 is connected to a
crank pin of the crankshaft 108 through a connecting rod 109 and
slidably received in a cylinder 107a which is defined in the
cylinder block 107.
[0101] A top wall of the cylinder 107a includes intake port 111 and
an exhaust port 112 defined therein and connected to the carburetor
102 and the exhaust muffler 103, and intake and exhaust valves 113
and 114 provided therein for opening and closing the intake and
exhaust ports 111 and 112. A valve-operating device 115 for driving
the intake and exhaust valves 113 and 114 is disposed in a
valve-operating chamber 116 which is defined to extend from the
crankcase 106 and the side of the cylinder block 107 to the top of
the cylinder block 107. The valve-operating chamber 116 is capable
of being opened and closed by a head cover 121 coupled to the head
of the cylinder block 107.
[0102] The valve-operating device 115 includes a driving timing
gear 117 secured to the crankshaft 108, a follower driving gear 118
which is carried on a support shaft 119 mounted to the crankcase
106 at an intermediate portion of the valve-operating chamber 116
and which is driven at a reduction ratio of 1/2 from the driving
timing gear 117, a cam 120 integrally connected to one end of the
follower timing gear 118, a pair of cam followers 123 and 124
carried on a cam follower shaft 122 mounted in the cylinder head
107, a pair of rocker arms 126 and 127 supported by a rocker shaft
125 mounted in the head of the cylinder block 107 with their one
ends abutting against valve heads of the intake and exhaust valves
113 and 114, a pair of push rods 128 and 129 which connect the cam
followers 123 and 124 to the other ends of the rocker arms 126 and
127, and valve springs 130 and 131 for biasing the intake and
exhaust valves 113 and 114 in a closing direction, so that the
intake is opened during an intake stroke of the piston 110 and the
exhaust valve 114 is opened during an exhaust stroke of the piston
114.
[0103] A crankcase 132 is defined in the crankcase 106 and includes
a cylindrical inner chamber 132a in which a crank portion 108a of
the crankshaft 108 is disposed, and an outer chamber 132b having a
U-shape in section and surrounding the inner chamber 132 over from
its bottom to its circumferentially opposite sides. An opening 133
is provided in a partition wall 134 between the inner and outer
chambers 132a and 132b at the bottom of the crank chamber 132 and
permits the inner and outer chambers 132a and 132b to communicate
with each other.
[0104] A lubricating oil O is stored in the bottom of the crank
chamber 132, and the amount of lubricating oil stored is set at a
value such that the oil surface slightly contacts with an outer
periphery of the crank portion 108a. An oil dipper 135 is formed at
an enlarged end of the connecting rod 109 as an oil mist producing
mans for producing an oil mist by agitating and scattering the
lubricating oil O during rotation of the crankshaft 108.
[0105] As shown in FIGS. 17 and 23, the crank chamber 132 and the
valve-operating chamber 116 communicate with each other through
first and second oil supply passages 136 and 137 provided in the
crankshaft 108 and the crankcase 106 above the oil level in the
crank chamber 132, respectively. The valve-operating chamber 116
also communicates at its bottom with the crank chamber 132 through
an orifice 138.
[0106] A rotary valve 139 is mounted between the first and second
oil supply passage 136 and 137 as a control valve. The rotary valve
139 includes an arcuate groove 160 of approximately 180.degree.
made in an outer periphery of a journal portion 108b at one side of
the crankshaft 108, and a valve bore 162 which is provided in a
bearing portion 161 of the crankcase 106 for bearing the journal
portion 108b to communicate with the arcuate groove 160. The first
oil supply passage 136 in the crankshaft 108 is connected to the
arcuate groove 160, and the second oil supply passage 137 in the
crankcase 106 is connected to the valve bore 162. Thus, every time
the crankshaft is rotated through approximately 180.degree. the
arcuate groove 160 and the valve bore 162 are brought alternately
repeatedly into and out of communication with each other, but the
rotary valve is disposed, so that it is opened (see FIG. 18) during
a lowering stroke of the piston 110 and closed (see FIG. 17) during
a elevating stroke of the piston 110. Particularly, a desirable
disposition is such that the opening of the rotary valve is started
in a range of from a middle point P between top and bottom dead
points of the piston 8 to a lowering-piston position corresponding
to 45.degree. in terms of the crank angle, and the opening of the
rotary valve is completed in a range of from such middle point P to
an elevating-piston position of 45.degree. in terms of the crank
angle, as in the above-described modification (see FIG. 14).
[0107] As shown in FIG. 20, an upper portion of the valve operating
chamber 124 communicates with the inside of the air cleaner 104
through a breather tube 142 made of a rubber and mounted through
one side wall of the head cover 121. In this case, that end of the
breather tube 142 which is opened into the valve-operating chamber
116 is disposed to protrude into the valve-operating chamber 116
over a predetermined length. Therefore, the oil somewhat
accumulated in the valve-operating chamber 116 can be prevented
from flowing out of the chamber 116 into the breather tube 142 in
any operational attitude of the engine 10E.
[0108] As shown in FIGS. 16, 21 and 22, an outer cover 163 is
coupled the head cover 121, so that it is fitted over an outer
periphery of the head cover 121. A flat uppermost chamber 164 is
defined between ceiling walls of the covers 121 and 163 and
communicates with the valve-operating chamber 116 through a pair of
orifices 165 provided in the ceiling wall of the head cover 121 at
diagonal locations (desirably at four corners). The upper most
chamber 164 also communicates with the inner chamber 132a of the
crank chamber 132 through a series of circulating oil passages 166
provided in the cylinder block 107 and the crankcase 106. The
circulating oil passages 166 have a sectional area larger than the
total sectional area of the pair of orifices 165.
[0109] Thus, by allowing the oil dipper 135 at the enlarged end of
the connecting rod 109 to be swung while being vertically moved
through the opening 133 between the inner and outer chambers 132a
and 132b of the crank chamber 132 with the rotation of the
crankshaft 108 during operation of the engine 10E the lubricating
oil is agitated and scattered to produce an oil mist in the crank
chamber 122. This oil mist first lubricates the peripheral portions
of the crank portions 108a and the piston 110, and upon opening of
the rotary valve 139, is then supplied along with a blow-by gas
through the first and second oil supply passages 136 and 137 into
the valve-operating chamber 116, where the oil mist, and the
blow-by gas are separated from each other. The oil mist lubricates
the various portions of the valve operating device 115, and the
blow-by gas is discharged through the breather tube 142 into the
air cleaner 104.
[0110] The pressure in the crank chamber 132 is pulsated between
positive and negative pressures alternatively repeated by elevating
and lowering movements of the piston 110. When the positive
pressure is generated, the rotary valve 139 is opened to permit the
positive pressure to be released via the first end second oil
supply passages 136 and 137 into the valve-operating chamber 116.
When the negative pressure is generated, the rotary valve 139 is
closed to inhibit the back-flow of the positive pressure from the
valve-operating chamber 116 and hence, the pressure in the crank
chamber 23 is kept negative on an average.
[0111] On the other hand, the valve-operating chamber 116
communicates with the inside of the air cleaner 104 which is in an
atmospheric pressure state, through the breather tube 142 and
hence, the pressure in the valve-operating chamber 116 is
substantially equal to atmospheric pressure.
[0112] The uppermost chamber 164 communicates with the crank
chamber 132 through the oil circulating passage 166 and also with
the valve-operating chamber 116 through the orifices 165 and hence,
the pressure in the uppermost chamber 164 is equal to or slightly
higher than the pressure in the crank chamber 132.
[0113] The magnitude relationship between the pressures in the
chambers can be represented by the following expression:
Pc.ltoreq.Pt<Pv
[0114] wherein,
[0115] Pc represents pressure in the crank chamber 132,
[0116] Pt represents pressure in the uppermost chamber 164, and
[0117] Pv pressure in the valve-operating chamber 116.
[0118] As a result, during operation of the engine 10E, the
pressure flows through a path which will be shown below:
2 Valve-operating chamber 116 Orifice 138 Orifice 165 Crank chamber
132 Uppermost chamber 164 Oil circulating passage 166
[0119] Therefore, the oil mist fed from the crank chamber 132 to
the valve-operating chamber 116 is circulated via the path back to
the crank chamber 132. The circulation of such oil mist and the
liquefied oil is performed without hindrance even when the engine E
is inclined in any attitude.
[0120] When the engine 10E is fallen sideways or inverted during
operation of the engine 10E, as shown in FIGS. 24 and 25, much of
the lubricating oil O in the crank chamber 132 flows in a direction
to close the outer chamber 132b, and the lubricating oil O remains
in a smaller amount in the inner chamber 132a. Thus, it is possible
to prevent the piston 110 from being dipped in the oil end to avoid
the entering of the oil into a combustion chamber.
[0121] In the operational state of the engine 10E in the
sideways-fallen or inverted attitude, the oil liquefied in the
valve-operating chamber 116 flows through the orifices 165 into the
uppermost chamber 164. However, the pressure relationship between
the chambers is maintained and hence, the oil accumulated in the
uppermost chamber 164 is drawn through the oil circulating passage
166 into the inner chamber 132a in the crank chamber 132.
[0122] On the other hand, the oil dipper 135 of the connecting rod
109 is incapable of agitating the lubricating oil in such case, but
the oil returned through the oil circulating passage 166 into the
inner chamber 132a strikes the crank portion 108a of the crankshaft
108 and the piston 110 and as a result, such oil is scattered to
produce an oil mist again. Therefore, the lubrication of the
various portions of the engine 10E cannot be impeded.
[0123] Even in any operational attitude such as inclined and
inverted attitudes of the engine E, the circulation of the
lubricating oil can be conducted without interruption to insure a
good lubricating state at all times.
[0124] Referring again to FIG. 16, a recoil type starter 143
capable of cranking the crankshaft, 108 is mounted to an outer
surface of the crankcase 106 on the opposite side from the
valve-operating chamber 116. A rotor 146 of a flywheel magneto 144
with a cooling blade 145 is secured to an outer end of the
crankshaft 108 adjacent the valve-operating chamber 116, and an
ignition coil 147 cooperating with the rotor 146 is secured to the
cylinder block 107. A centrifugal clutch 149 is interposed between
the rotor 146 and a working machine driving shaft 148. The
centrifugal clutch 149 includes a plurality of clutch shoes 150
expandably carried on the rotor 146, a clutch spring 151 for
biasing the clutch shoes 150 in a contracting direction, and a
clutch drum 152 secured to the driving shaft 148 to surround the
clutch shoes 150. When the rotor 146 is rotated in a predetermined
number of rotations or more, the clutch shoes 150 are expanded to
come into pressure contact with an inner peripheral surface of the
crutch drum 152, thereby transmitting an output torque from the
crankshaft 108 to the driving shaft 148.
[0125] A shroud 153 is mounted to the engine body 101 to cover the
head portion of the engine body 101 and the flywheel magneto 144
and to define a cooling air passage 154 between the shroud and the
head portion of the engine body 1 and the flywheel magneto 59. An
inlet 154a into the cooling air passage 154 is mounted in an
annular configuration between the centrifugal clutch 149 and the
shroud 153, and an outlet 154b is mounted in the shroud 153 on the
opposite side from the inlet 154a.
[0126] Thus, during rotation of the rotor 146, wind produced by the
cooling blade 145 flows through the cooling air passage 154 to cool
the various portions of the engine 10E.
[0127] Although the embodiments of the present invention have been
described in detail, it will be understood that the present
invention is not limited to the above-described embodiments, and
various modifications may made without departing from the spirit
and scope of the invention as defined in the claims.
* * * * *