Information
-
Patent Grant
-
6422194
-
Patent Number
6,422,194
-
Date Filed
Friday, March 9, 200123 years ago
-
Date Issued
Tuesday, July 23, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- McMahon; Marguerite
- Ali; Hyder
Agents
- Armstrong, Westerman & Hattori, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 572
- 123 658
- 123 9039
- 123 9048
- 123 4165
- 123 417
- 123 196 R
- 123 196 M
-
International Classifications
-
Abstract
With regard to a handheld type four-cycle engine including, in a side wall of a cylinder block, an intake valve, an exhaust valve and a valve operation mechanism operable in association with a crankshaft so as to open and close the above-mentioned valves and, an oil tank is formed in one side wall of the cylinder block, and the oil tank houses the valve operation mechanism and oil mist generation means for generating an oil mist from stored oil. It is thus possible to reliably lubricate the valve operation mechanism regardless of the operational position of the engine while allowing the size and weight of the engine main body to be reduced.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvement of handheld type four-cycle engines which can desirably be used mainly as a power source for machines for portable operation such as trimmers.
2. Description of the Relevant Art
With regard to conventional handheld type four-cycle engines, one in which an oil mist generated from the oil stored in an oil reservoir is circulated inside the engine in order to lubricate the inside of the engine regardless of the operational position of the engine is already known in Japanese Patent Application Laid-open No. 10-288019.
However, the lubrication system disclosed in the above-mentioned patent publication has a comparatively long and complicated circulation route in which the oil mist is circulated from the oil tank to the crank chamber, then to the valve operation chamber and is then returned to the oil tank. Such a long and complicated circulation route for the oil mist causes an increase in the size of the engine main body, which includes the circulation route, and makes it difficult to reduce the weight thereof. Weight reduction is one of the important issues when considering improvements in the operability of, in particular, handheld type four-cycle engines.
SUMMARY OF THE INVENTION
The present invention has been carried out in view of the above-mentioned circumstances, and it is an object of the present invention to provide a handheld type four-cycle engine which can reliably lubricate the valve operation mechanism regardless of the operational position of the engine while making the engine main body more compact and lighter.
In accordance with a first characteristic of the present invention in order to achieve the above-mentioned objective, there is proposed a handheld type four-cycle engine including a crankcase having a crank chamber housing a crankshaft; a cylinder block having a cylinder bore; and an intake valve, an exhaust valve and a valve operation mechanism provided in a side wall of the cylinder block, the valve operation mechanism being operable in association with the crankshaft so as to open and close the intake valve and the exhaust valve, wherein an oil tank for storing oil is provided in one side wall running the length of the crankcase and the cylinder block, and the oil tank houses the valve operation mechanism and oil mist generation means for generating oil mist from the stored oil.
In accordance with the above-mentioned first characteristic, since the oil tank can be filled with the oil mist generated by the oil mist generation means, each part of the valve operation mechanism disposed inside the oil tank can be lubricated reliably by the above-mentioned oil mist regardless of the operational position of the engine. It is therefore unnecessary to provide the engine main body with a special oil supply passage for lubricating the valve operation mechanism, and the size and weight of the engine can thus be reduced. Moreover, since the oil tank is provided in one side wall running the length of the crankcase and the cylinder block, it is unnecessary to provide an oil reservoir in the lower part of the crankcase, and the total height of the engine can thus be reduced and the size of the engine can be further reduced.
In accordance with a second characteristic of the present invention, in addition to the above-mentioned first characteristic, there is proposed a handheld type four-cycle engine wherein an outward route and an return route are provided for communication between the oil tank and the crank chamber above the oil stored in the oil tank, and valve means is provided for introducing the positive pressure component of pressure pulsations generated in the crank chamber into the side of the oil tank.
The above-mentioned valve means corresponds to the one-way valve
51
described in the embodiment of the present invention below.
In accordance with the above-mentioned second characteristic, since the oil mist generated in the oil tank is circulated between the oil tank and the crank chamber by utilising the pressure pulsations of the crank chamber, the crankshaft and the piston can be lubricated regardless of the operational position of the engine. Moreover, since it is sufficient for the oil mist to merely circulate between the two chambers, that is to say, the oil tank and the crank chamber, the outward and return routes for providing communication between the two chambers can be made comparatively short and simple, and the size and weight of the engine can be further reduced.
In accordance with a third characteristic of the present invention, in addition to the above-mentioned first or second characteristics, there is proposed a handheld type four-cycle engine wherein a breather chamber is communicated with the return route between the valve means and the oil tank, and the breather chamber is communicated with an air cleaner of an intake system on one side and with a suction chamber communicated with the oil tank via an orifice on the other side.
In accordance with the above-mentioned third characteristic, the blowby gas generated in the crank chamber is transferred to the breather chamber together with the oil mist, and separated into gas and liquid. Then, the blowby gas is discharged to the air cleaner, and the liquefied oil flows into the suction chamber via the orifice and can be returned to the low pressure oil tank.
Furthermore, in accordance with a fourth characteristic of the present invention, there is proposed a handheld type four-cycle engine including a crankcase having a crank chamber housing a crankshaft; a cylinder block having a cylinder bore; and an intake valve, an exhaust valve and a valve operation mechanism provided in a side wall of the cylinder block, the valve operation mechanism being operable in association with the crankshaft so as to open and close the intake valve and the exhaust valve, characterised in that an oil tank for storing oil that is separate from the crank chamber is provided in one side wall running the length of the crankcase and the cylinder block, the oil tank houses the valve operation mechanism and oil mist generation means for generating oil mist from the stored oil and is arranged so that the oil mist generated inside the oil tank can be supplied to the crank chamber, a cooling fan driven by the crankshaft is placed so as to adjoin the oil tank, and a power output mechanism is provided on the crankshaft so that the crankcase is interposed between the power output mechanism and the oil tank.
In accordance with the above-mentioned fourth characteristic, since the oil tank is provided in one side wall running the length of the crankcase and the cylinder block, it is unnecessary to provide an oil reservoir in the lower part of the crankcase, the total height of the engine can thus be reduced and the engine can be made compact. Moreover, since the oil tank is filled with the oil mist generated by the oil mist generation means and the oil mist is supplied to the crank chamber, each component inside the crank chamber as well as the valve operation mechanism placed inside the oil tank can be lubricated reliably regardless of the operational position of the engine.
Furthermore, since the cooling fan is placed so as to adjoin the oil tank, the oil tank and, therefore, the stored oil and the oil mist inside the oil tank can be cooled effectively by the cooling air generated by the cooling fan, thus efficiently carrying out lubrication and cooling of each component.
Moreover, since the valve operation mechanism and the power output mechanism are linked to the two ends of the crankshaft, the loads arising from the valve operation mechanism and the power output mechanism, during operation of the engine, are applied to the two separate ends of the crankshaft, it is thus possible to prevent the load applied to the crankshaft, its bearings and the side wall of the crankcase from being localised and the durability thereof can be enhanced.
In accordance with a fifth characteristic of the present invention, in addition to the above-mentioned first or fourth characteristic, there is proposed a handheld type four-cycle engine wherein a carburettor and an exhaust muffler are placed on the two sides of the cylinder block along a direction perpendicular to the axes of both the cylinder bore and the crankshaft.
In accordance with the above-mentioned fifth characteristic, the carburettor and the exhaust muffler can be easily arranged without any obstruction from the oil tank, the cooling fan or the power output mechanism thus helping to make the engine more compact.
The above-mentioned oil mist generation means corresponds to the oil slingers
36
to
41
described in the embodiment of the present invention below, and the above-mentioned power output mechanism corresponds to the centrifugal clutch
31
described in the embodiment below.
The above-mentioned objectives, other objectives, characteristics and advantages of the present invention will become apparent from an explanation of preferable embodiments which will be described in detail below by reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an oblique view showing one embodiment of the handheld type four-cycle engine of the present invention in practical use.
FIG. 2
is a vertically sectioned view of the above-mentioned four-cycle engine.
FIG. 3
is a cross-sectional view at line
3
—
3
in FIG.
2
.
FIG. 4
is a cross-sectional view at line
4
—
4
in FIG.
3
.
FIG. 5
is a cross-sectional view at line
5
—
5
in FIG.
4
.
FIG. 6
is a cross-sectional view at line
6
—
6
in FIG.
5
.
DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in
FIG. 1
, a handheld type four-cycle engine E to which the present invention is applied is fitted as the source of power to the driving section of, for example, a powered trimmer T. Since the powered trimmer T is used in a manner in which a cutter C is positioned in various directions according to the operational conditions, the engine E is also tilted to a large extent or turned upside-down as a result, and the operational position is unstable.
As shown in
FIGS. 2 and 3
, the engine main body
1
of the above-mentioned handheld type four-cycle engine E includes a crankcase
6
having a crank chamber
6
a
, a cylinder block
7
having one cylinder bore
7
a,
and a cylinder head
8
having a combustion chamber
8
a
, and a large number of cooling fins
11
are formed on the outer peripheries of the cylinder block
7
and the cylinder head
8
.
The crankshaft
12
housed in the crank chamber
6
a
is supported in right and left side walls of the crankcase
6
in a rotatable manner via ball bearings
14
and
14
′ and is also connected to a piston
15
fitted in the cylinder bore
7
a
via a connecting rod
16
.
An oil tank
13
is provided as a continuation of the left side wall running the length of the crankcase
6
and the cylinder block
7
. The oil tank
13
includes a tank inner half
13
a
and a tank outer half
13
b,
the tank inner half
13
a
being linked integrally to the crankcase
6
and the cylinder block
7
, and the tank outer half
13
b
being bolt-joined to the tank inner half
13
a.
The left-hand end of the crankshaft
12
runs through and projects out of the oil tank
13
, and an oil seal
17
in close contact with the outer circumference of the crankshaft
12
is fitted in the tank outer half
13
b.
A flywheel
24
having a large number of cooling vanes
25
is fixed to the left-hand end of the crankshaft
12
projecting out of the oil tank
13
, the flywheel
24
functioning also as a cooling fan, and a recoil type starter
26
is placed outside the flywheel
24
.
An oil seal
17
′ is fitted in the right side wall of the crankcase
6
so as to adjoin the outside of the bearing
14
′, the right-hand end of the crankshaft
12
runs through and projects out of the oil seal
17
′, a drive plate
27
is fixed to the right hand end of the crankshaft
12
, and a plurality of centrifugal shoes
28
(one thereof is shown in the figure) are pivotally supported on the drive plate
27
in a rockable manner. These centrifugal shoes
28
, together with a clutch drum
30
connected to the drive shaft
29
for driving the aforementioned cutter C, form a centrifugal clutch
31
. When the rotational rate of the crankshaft
12
exceeds a predetermined value, the centrifugal shoes
28
are pressed onto the inner periphery of the clutch drum
30
due to the centrifugal force of the shoes, thereby transmitting the output torque of the crankshaft
12
to the drive shaft
29
.
The cylinder block
7
and the cylinder head
8
share an overhang section
19
which overhangs on the side of the oil tank
13
, and the lower part of the overhang section
19
forms a part of the upper wall of the tank inner half
13
a.
The combustion chamber
8
a
is formed in the part of the cylinder head
8
corresponding to this overhang section
19
, and an intake port
9
i
and an exhaust port
9
e
communicated with the combustion chamber
8
a
are formed in the cylinder block
7
. An ignition plug
10
is screwed into the cylinder head
8
, the electrodes of the ignition plug
10
projecting into the combustion chamber
8
a.
An intake valve
18
i
and an exhaust valve
18
e
are mounted in the overhang
19
, that is to say, the upper wall of the tank inner half
13
a,
in a freely ascending and descending manner so that their valve heads project into the oil tank
13
, the intake valve
18
i
and the exhaust valve
18
e
opening and closing the intake port
9
i
and the exhaust port
9
e
respectively. A valve operation mechanism
23
for operating the intake valve
18
i
and the exhaust valve
18
e
so as to open and close them is disposed inside the oil tank
13
.
The valve operation mechanism
23
includes a drive gear
32
fixed to the crankshaft
12
, a pair of driven gears
36
and
37
supported in a rotatable manner on a pair of support shafts
33
and
34
provided in the oil tank
13
above the crankshaft
12
and driven by the drive gear
32
with a reduction ratio of 1/2, an intake cam
21
i
and an exhaust cam
21
e
formed integrally with the driven gears
36
and
37
respectively, an intake cam follower
22
i
pivotally supported in the oil tank
13
in a rockable manner and provided between the intake cam
21
i
and the intake valve
18
i,
an exhaust cam follower
22
e
pivotally supported in the oil tank
13
in a rockable manner and provided between the exhaust cam
21
e
and the exhaust valve
18
e,
and valve springs
20
i
and
20
e
forcing the intake valve
18
i
and the exhaust valve
18
e
towards the closing direction. The engine E is thus arranged to be of the side valve type.
The driven gear
36
and the intake cam
21
i,
and also the driven gear
37
and the exhaust cam
21
e
are placed distant from each other in the axial direction so that they closely adjoin the left and right side walls respectively of the toil tank
13
. Gear type oil slingers
39
and
40
are formed integrally with the intake cam
21
i
and the exhaust cam
21
e
respectively so as to adjoin them.
Another support shaft
35
is provided in the oil tank
13
at a position beneath the crankshaft
12
, and this support shaft
35
supports a driven gear
38
and a vane type oil slinger
41
in a rotatable manner, the driven gear
38
being driven by the drive gear
32
and the oil slinger
41
being integral with the driven gear
38
. The driven gear
38
and the oil slinger
41
are positioned distant from each other in the axial direction so that they closely adjoin the left and right inner walls respectively of the oil tank
13
.
A predetermined amount of lubricating oil O is stored in the oil tank
13
, at least one of the three driven gears
36
to
38
or the three oil slingers
39
to
41
is partially immersed in the stored oil O regardless of the operational position of the engine E, and the stored oil O is scattered by the rotation thereof so generating an oil mist. The three driven gears
36
to
38
therefore also function as oil slingers, and in fact, the three support shafts
33
,
34
and
35
support a pair of oil slingers
36
and
39
;
37
and
40
; and
38
and
41
respectively, the oil slingers of each pair being distant from each other in the axial direction.
As shown in
FIG. 3
, the intake port
9
i
is connected to a carburettor
2
and an air cleaner
4
in that order, and the exhaust port
9
e
is connected to an exhaust muffler
3
. The carburettor
2
and the exhaust muffler
3
are placed along a direction perpendicular to the axes of both the crankshaft
12
and the cylinder bore
7
a.
The route for the circulation of oil mist between the oil tank
13
and the crank chamber
6
a
is explained below by reference to
FIGS. 2 and 4
to
6
.
An outward route
45
and an return route
46
for circulating the oil mist generated inside the oil tank
13
between the oil tank
13
and the crank chamber
6
a
are provided between the above-mentioned two chambers
13
and
6
a.
The outward route
45
includes a through hole formed in the crankshaft
12
and providing communication between the oil tank
13
and the crank chamber
6
a.
The return route
46
includes a valve hole
47
in the bottom wall of the crankcase
6
, a valve chamber
48
communicated with the crank camber
6
a
via the valve hole
47
, and a first return pipe
49
providing communication between the valve chamber
48
and the oil tank
13
. A one-way valve
51
is provided in the valve chamber
48
, the one-way valve
51
including a reed valve for blocking and unblocking the valve hole
47
. The one-way valve
51
opens so as to unblock the valve hole
47
when a positive pressure is generated in the crank chamber
6
a
accompanying the ascending and descending movement of the piston
15
, and the one-way valve
51
closes so as to close the valve hole
47
when a negative pressure is generated.
The open ends of the above-mentioned outward route
45
and the first return pipe
49
inside the oil tank
13
are arranged so that they are always above the liquid level of the stored oil O regardless of the operational position of the engine E.
A breather chamber
53
is provided on one side of the valve chamber
48
, the breather chamber
53
being communicated with the valve chamber
48
via a link hole
52
. The breather chamber
53
is partitioned into a plurality of expansion chambers
53
a,
53
b
(two chambers in the figure) by means of a wall
54
. These expansion chambers
53
a
and
53
b
are communicated with each other via throttle passages
55
and
55
on both sides of the wall
54
, and the expansion chamber
53
b
furthest from the link hole
52
is communicated with the above-mentioned air cleaner
4
via a breather pipe
56
.
A horizontally flattened chamber
57
a
is provided immediately below the breather chamber
53
, a vertically flattened chamber
57
b
is provided in the side wall of the breather chamber
53
on the side of the oil tank
13
, the vertically flattened chamber
57
b
rising at one end of the horizontally flattened chamber
57
a,
and a suction chamber
57
is formed by the two flattened chambers
57
a
and
57
b.
The horizontally flattened chamber
57
a
is communicated with the breather chamber
53
via orifices
58
,
58
. . . separately placed at several positions, and the vertically flattened chamber
57
b
is also communicated with the breather chamber
53
via orifices
58
,
58
. . . provided close to the ceiling of the breather chamber
53
.
The suction chamber
57
is communicated with the inside of the oil tank
13
via a second return pipe
59
. In the same way as for the first return pipe
49
, in this case the second return pipe
59
is arranged so that the open end thereof inside the oil tank
13
is always above the liquid level of the stored oil O regardless of the operational position of the engine E.
The above-mentioned valve chamber
48
and the breather chamber
53
are formed between a surrounding wall
60
and a gasket
61
, the surrounding wall
60
being formed integrally with the lower part of the crankcase
6
and the gasket
61
being joined to the lower end of the surrounding wall
60
. The horizontally flattened chamber
57
a
is formed between the gasket
61
and a base plate
62
joined to the surrounding wall
60
in such a way that the periphery of the gasket
61
is interposed between the base plate
62
and the surrounding wall
60
. The vertically flattened chamber
57
b
is formed in the dividing wall present between the breather chamber
53
and the oil tank
13
.
Referring again to
FIG. 2
, an engine cover
65
is fixed to the engine main body
1
so as to cover it, a recoil type starter
26
is supported in the cover
65
, and an air inlet
66
is provided in the engine cover
65
around the recoil type starter
26
so as to face cooling vanes
25
of the flywheel
24
.
The action of the embodiment is explained below.
When the drive gear
32
rotates together with the crankshaft
12
during operation of the engine E, this rotation makes the three sets of oil slingers
36
and
39
;
37
and
40
;
38
and
41
supported in the three support shafts
33
,
34
,
35
rotate together. Since at least one of the oil slingers reliably scatters the stored oil O so as to generate an oil mist regardless of the operational position of the engine E, the inside of the oil tank
13
can always be filled with oil mist. The valve operation mechanism
23
is provided inside such an oil tank
13
, the intake cam
21
i
and the exhaust cam
21
e
rotating together with the upper driven gears
36
and
37
operate the intake valve
18
i
and the exhaust valve
18
e
so as to open and close them with appropriate timing via the cam followers
22
i
and
22
e
while working co-operatively with the valve springs
20
i
and
20
e,
and each component of the valve operation mechanism
23
can therefore be lubricated effectively by the above-mentioned oil mist. It is therefore unnecessary to provide the engine main body
1
with a special oil supply passage for lubricating the valve operation mechanism
23
, and the size and weight of the engine E can thus be reduced. Moreover, since the oil tank
13
is provided in one side wall running the length of the crankcase
6
and the cylinder block
7
, it is unnecessary to provide an oil reservoir in the lower part of the crankcase
6
, the total height of the engine E can be reduced and the size of the engine can further be reduced.
A negative pressure and a positive pressure are generated alternately in the crank chamber
6
a
accompanying the ascending and descending movement of the piston
15
so causing pressure pulsations; when a negative pressure is generated, the one-way valve
51
closes so as to block the valve hole
47
and at the same time the oil mist inside the oil tank
13
is drawn up into the crank chamber
6
a
through the through hole of the crankshaft
12
, that is to say, the outward route
45
thus lubricating the crankshaft
12
and the piston
15
. At this stage, the pressure of the oil tank
13
becomes negative due to the oil mist drawn up into the crank chamber
6
a.
When a positive pressure is generated, the one-way valve
51
opens so as to unblock the valve hole
47
, and the oil mist inside the crank chamber
6
a
is returned to the oil tank
13
having a low pressure through the return route
46
, that is to say, the valve hole
47
, the valve chamber
48
and the first return pipe
49
. It is thus sufficient for the oil mist to circulate merely between the two chambers, namely the oil tank
13
and the crank chamber
6
a,
the outward route
45
and the return route
46
providing communication between the above-mentioned two chambers
13
and
6
a
can be made comparatively short and simple, and the size and weight of the engine main body
1
can be reduced.
Meanwhile, the blowby gas generated in the crank chamber
6
a
is transferred to the valve chamber
48
together with the oil mist and further to the breather chamber
53
through the link hole
52
, and separated into gas and liquid while passing through the first and second expansion chambers
53
a
and
53
b,
and the blowby gas alone is discharged to the air cleaner
4
via the breather pipe
56
.
The oil separated and liquefied in the breather chamber
53
flows into the suction chamber
57
via the orifice
58
,
58
. . . Since the first suction chamber
57
a
and the second suction chamber
57
b
are communicated with the inside of the oil tank
13
having a low pressure via the second return pipe
59
, the oil transferred to the suction chamber
57
is drawn up into the oil tank
13
through the second return pipe
59
. Since the suction chamber
57
includes, in particular, the horizontally flattened chamber
57
a
and the vertically flattened chamber
57
b
rising at one end of the horizontally flattened chamber
57
a
as mentioned above, and each of the two chambers
57
a
and
57
b
is communicated with the breather chamber
53
via the orifices
58
,
58
, . . . , the oil stored in the breather chamber
53
can flow into the suction chamber
57
and return to the oil tank
13
even in the case where the engine E is tilted horizontally so positioning the vertically flattened chamber
57
b
downwards, as well of course in the case where the engine E is upright so positioning the horizontally flattened chamber
57
a
downwards.
Furthermore, since the flywheel
24
having the cooling vanes
25
driven by the crankshaft
12
is placed outside the oil tank
13
so as to adjoin it, cooling air drawn in through the air inlet
66
of the engine cover
65
by rotation of the cooling vanes
25
is directly applied to the oil tank
13
, the oil mist and the oil O stored inside the oil tank can be cooled effectively and the lubrication and cooling of each part can be carried out efficiently.
Moreover, since the valve operation mechanism
23
and the centrifugal clutch
31
are linked to the two ends of the crankshaft
12
with the engine main body
1
disposed therebetween, the loads arising from the valve operation mechanism
23
and the drive shaft
29
during operation of the engine E separately work on the two ends of the crankshaft
12
. It is therefore possible to prevent the load from being localised on the crankshaft
12
, its bearings
14
and
14
′ and the side wall of the crankcase
6
, and the durability thereof can thus be enhanced. Furthermore, since it is unnecessary to specially increase the load capacity of these parts, the engine E can be made more compact.
Moreover, since the carburettor
2
and the exhaust muffler
3
are placed along a direction perpendicular to the axes of both the crankshaft
12
and the cylinder bore
7
a,
the carburettor
2
and the exhaust muffler
3
can easily be arranged without any obstruction from the oil tank
13
, the flywheel
24
or the centrifugal clutch
31
which are arranged along the axis of the crankshaft
12
thus helping to make the engine E more compact.
The present invention is not limited to the above-mentioned embodiment and can be modified in a variety of ways without departing from the spirit and scope of the invention, For example, a rotary valve operable in association with the crankshaft
12
and operating so as to unblock the outward pipe
45
when the piston
15
descends, and to block the outward pipe
45
when the piston
15
ascends can be provided instead of the one-way valve
51
.
Claims
- 1. A handheld side-valve type four-cycle engine including:a crankcase having a crank chamber housing a crankshaft; a cylinder block having a cylinder bore; and an intake valve, an exhaust valve and a valve operation mechanism provided in a side wall extending along the crankcase and the cylinder block, the valve operation mechanism being operable in association with the crankshaft so as to open and close the intake valve and the exhaust valve; wherein an oil tank for storing oil is provided in said side wall extending along the crankcase and the cylinder block, the oil tank houses therein the valve operation mechanism and oil mist generation means for generating oil mist from the stored oil, and said intake and exhaust valves project partly into said oil tank.
- 2. A handheld side-valve type four-cycle engine according to claim 1 wherein an outward route and a return route are provided for communication between the oil tank and the crank chamber above the oil stored in the oil tank, and valve means is provided in the return route, the valve means introducing the positive pressure component of pressure pulsations generated in the crank chamber into the side of the oil tank.
- 3. A handheld side-valve type four-cycle engine according to claim 1 or 2 wherein a breather chamber is communicated with a return route between valve means and the oil tank, and the breather chamber is communicated with an air cleaner of an intake system on one side and with a suction chamber communicated with the oil tank via an orifice on the other side.
- 4. A handheld side-valve type four-cycle engine including:a crankcase having a crank chamber housing a crankshaft; a cylinder block having a cylinder bore; and an intake valve, an exhaust valve and a valve operation mechanism provided in a side wall extending along the crankcase and the cylinder block, the valve operation mechanism being operable in association with the crankshaft so as to open and close the intake valve and the exhaust valve; wherein an oil tank for storing oil that is separate from the crank chamber is provided in said side wall extending along the crankcase and the cylinder block and said intake and exhaust valves project partly into said oil tank, the oil tank houses therein the valve operation mechanism and oil mist generation means for generating oil mist from the stored oil and is arranged so that the oil mist generated inside the oil tank can be supplied to the crank chamber, a cooling fan driven by the crankshaft is placed so as to adjoin the oil tank, and a power output mechanism is provided on the crankshaft so that the crankcase is interposed between the power output mechanism and the oil tank.
- 5. A handheld side-valve type four-cycle engine according to claim 1 or 4 wherein a carburettor and an exhaust muffler are placed along a direction perpendicular to the axes of both the cylinder bore and the crankshaft on the two sides of the cylinder block.
- 6. A handheld side-valve type four-cycle engine according to claim 4, wherein said cooling fan is disposed outside said oil tank.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2000-79307 |
Mar 2000 |
JP |
|
2000-79308 |
Mar 2000 |
JP |
|
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
4424772 |
Porter |
Jan 1984 |
A |
4813408 |
Katsumoto et al. |
Mar 1989 |
A |
5947068 |
Akaki |
Sep 1999 |
A |
6152098 |
Becker et al. |
Nov 2000 |
A |
Foreign Referenced Citations (5)
Number |
Date |
Country |
0 779 412 |
Jun 1997 |
EP |
0 887 520 |
Dec 1998 |
EP |
0 962 630 |
Dec 1999 |
EP |
10-288019 |
Oct 1998 |
JP |
WO 9902824 |
Jan 1999 |
WO |