Information
-
Patent Grant
-
6637399
-
Patent Number
6,637,399
-
Date Filed
Wednesday, February 13, 200223 years ago
-
Date Issued
Tuesday, October 28, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Yuen; Henry C.
- Benton; Jason
Agents
- Arent Fox Kintner Plotkin & Kahn, PLLC
-
CPC
-
US Classifications
Field of Search
US
- 123 196 R
- 123 196 M
- 123 196 S
- 123 1935
-
International Classifications
-
Abstract
An OHC engine includes a valve operation system housed in a valve operation chamber formed between a cylinder head and a head cover joined to the cylinder head. The valve operation system includes a valve-operating cam and is cooperatively connected to an intake valve and an exhaust valve. The OHC engine also includes timing transmitting device disposed between the valve operation system and a crankshaft, the timing transmitting means including a driven wheel that rotates together with the valve-operating cam and a transmission belt that is wrapped around the driven wheel so that oil within a crankcase can accompany the transmission belt and be supplied to the valve operation chamber. The head cover is provided with an arc-form curved cover part for covering the upper part of the driven wheel. The curved cover part integrally includes above the driven wheel a plurality of oil splashing ribs that are positioned at intervals along the rotational direction of the driven wheel to project toward the side that is closer to the transmission belt, thereby allowing oil to be supplied uniformly to each section of the valve operation system.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an OHC engine in which a valve operation system is housed in a valve operation chamber formed between a cylinder head and a head cover joined to the cylinder head. The valve operation system includes a valve-operating cam that is rotatably supported by the cylinder head and is cooperatively connected to an intake valve and an exhaust valve; and timing transmitting means disposed between the valve operation system and a crankshaft. The timing transmitting means includes a driven wheel that rotates together with the valve-operating cam and a transmission belt that is wrapped around the driven wheel, so that oil within a crankcase is carried by the transmission belt and is supplied to the valve operation chamber. In particular, it relates to an improvement of a lubrication structure for the valve operation system.
2. Description of the Prior Art
A conventional lubrication structure for an OHC engine is already known in, for example, Japanese Patent Application Laid-open No. 8-177441, wherein oil is supplied to a valve operation system by means of the oil being carried by a timing belt that is for transmitting the rotational power of a crankshaft to the valve operation system.
In order to lubricate a valve operation system with the oil supplied to a valve operation chamber by means of a timing belt, etc., it is necessary to splash the oil within the valve operation chamber. In the above-mentioned conventional arrangement, the oil is splashed by means of inertial force and centrifugal force imposed on the oil in the section where the timing belt is wrapped around a driven pulley, but in order to satisfy the lubrication requirements that become more strict as the load and rotational speed of an engine increase, it is necessary to splash the oil more finely.
In a lubrication structure disclosed in Japanese Patent Application Laid-open No. 9-151720, a wall is provided on a head cover, in a section where a timing belt is wrapped around a driven pulley, at a position on a line that extends over the slack side of the timing belt, the oil that has separated from the timing belt due to inertial force collides with the wall, and the oil is thereby atomized so as to fill a valve operation chamber.
Even in accordance with the lubrication structure of Japanese Patent Application Laid-open No. 9-151720, it is difficult to splash the oil uniformly within the valve operation chamber, and there is a possibility that, among the members forming the valve operation system, oil supply to the member that is positioned on the tensioned side of the timing belt might become insufficient.
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 lubrication structure in an OHC engine that can supply oil uniformly to each section of a valve operation system.
In order to accomplish this object, in accordance with a first aspect of the present invention, there is proposed a lubrication structure in an OHC engine. The lubrication structure includes a valve operation system housed in a valve operation chamber formed between a cylinder head and a head cover joined to the cylinder head, the valve operation system including a valve-operating cam that is rotatably supported by the cylinder head and is cooperatively connected to an intake valve and an exhaust valve. The lubrication structure also includes timing transmitting means disposed between the valve operation system and a crankshaft, the timing transmitting means including a driven wheel that rotates together with the valve-operating cam and a transmission belt that is wrapped around the driven wheel, so that oil within a crankcase can be carried by the transmission belt and be supplied to the valve operation chamber. The head cover is provided with an arc-form curved cover part for covering the upper part of the driven wheel, and the curved cover part above the driven wheel is provided integrally with a plurality of oil splashing ribs that are placed at intervals along the rotational direction of the driven wheel to project toward the side that is closer to the transmission belt.
In accordance with the above-mentioned arrangement, the oil that has been conveyed to the valve operation chamber while attached to the transmission belt is made to separate from the transmission belt due to centrifugal force in the section where the transmission belt is wrapped around the driven wheel, and the oil so detached collides with the oil splashing ribs and is atomized. Since the oil splashing ribs are provided on the curved cover part of the head cover at a plurality of positions at intervals along the rotational direction of the driven wheel, when the transmission belt runs in the section where it is wrapped around the driven wheel, the oil that has passed by one oil splashing rib collides with a following oil splashing rib and is splashed, thereby reliably splashing the oil at a plurality of positions and ensuring that the oil can reliably reach each part of the valve operation system. Moreover, the plurality of oil splashing ribs also have the function of reinforcing the head cover.
Furthermore, in accordance with a second aspect of the present invention, there is proposed a lubrication system in an OHC engine, wherein the valve operation system further includes intake side and exhaust side rocker arms cooperatively connected to the corresponding intake valve and exhaust valve and individually in sliding contact with the lower part of the valve-operating cam at positions on opposite sides of, and an equal distance from, a vertical line passing through the rotational axis of the valve-operating cam coaxially and integrally formed with the driven wheel. A pair of the oil splashing ribs are placed outside a pair of vertical lines, in a projection on a vertical plane that is orthogonal to the rotational axis of the valve-operating cam, that pass through the parts of the rocker arms that are in sliding contact with the valve-operating cam. In accordance with the arrangement, the oil that has collided with the pair of oil splashing ribs can reliably reach the sections where the intake side and exhaust side rocker arms slide on the valve-operating cam. Reliable lubrication of the valve operation system can thereby be carried out by means of a small number of oil splashing ribs.
Furthermore, in accordance with a third aspect of the present invention, there is proposed an OHC engine wherein each of the oil splashing ribs is provided integrally with the curved cover part extending in a direction orthogonal to the rotational direction of the driven wheel. In accordance with the above-mentioned arrangement, the oil can collide with the oil splashing ribs at right angles, and the oil can thereby be splashed more finely.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1
to
14
illustrate one embodiment of the present invention.
FIG. 1
is a side view of a portable engine generator.
FIG. 2
is a view from line
2
—
2
in FIG.
1
.
FIG. 3
is a cross section at line
3
—
3
in FIG.
2
.
FIG. 4
is a cross section at line
4
—
4
in FIG.
2
.
FIG. 5
is a cross section at line
5
—
5
in FIG.
4
.
FIG. 6
is a longitudinal cross section viewed from the same direction as in FIG.
3
.
FIG. 7
is a cross section at line
7
—
7
in FIG.
6
.
FIG. 8
is a magnified cross section at line
8
—
8
in FIG.
6
.
FIG. 9
is a magnified view of an essential part in FIG.
6
.
FIG. 10
is a magnified view from arrow
10
in FIG.
6
.
FIG. 11
is a cross section at line
11
—
11
in FIG.
6
.
FIG. 12
is a magnified cross section at line
12
—
12
in FIG.
7
.
FIG. 13
is a magnified cross section at line
13
—
13
in FIG.
7
.
FIG. 14
is a cross section corresponding to
FIG. 11
while changing the attitude of the engine when in a laid-sideways state in 90° steps.
DESCRIPTION OF PREFERRED EMBODIMENTS
One embodiment of the present invention is explained below by reference to
FIGS. 1
to
14
. Referring to
FIGS. 1
to
4
, a synthetic resin case
11
forms an outer shell of a portable engine generator, which is a portable engine-operated machine. The case
11
is formed from a left side cover
12
, a right side cover
13
, a front cover
14
, a rear cover
15
and a under cover
16
, which are joined to each other. Provided on the upper parts of the left and right side covers
12
and
13
is a carrying handle
17
for carrying the engine generator. Radial reinforcing ribs
17
a
are formed within the carrying handle
17
as shown in FIG.
4
.
The left side cover
12
is provided with a lid
12
a,
which can be opened and closed, for replacing a spark plug. The right side cover
13
is provided with a lid
13
a,
which can be opened and closed, for maintenance. The front cover
14
is provided with a control panel
18
. Provided on the inside face of the control panel
18
is a control unit
19
for controlling the operation of an engine E and a generator G that is driven by the engine E. Provided behind the control unit
19
is an inverter unit
20
for controlling the output frequency of the generator G. The front cover
14
is provided with a cooling air inlet
14
a
positioned above the control panel
18
and a cooling air inlet
14
b
positioned beneath the control panel
18
and further with a guide part
14
c
connected to the cooling air inlet
14
b.
The rear cover
15
is provided with an exhaust gas outlet
15
a
for discharging the exhaust gas from the engine E and a cooling air outlet
15
b
for discharging the cooling air from the case
11
. The under cover
16
is provided with four rubber support legs
21
that make contact with the ground or a floor when the engine generator is placed thereon.
Referring also to
FIG. 5
, left and right reinforcing frames
26
and
27
made of FRP are disposed within a front part of the case
11
. The left reinforcing frame
26
is formed in an inverted L-shape, rising upward along the inner face of the left side cover
12
and extending inward in the lateral direction in the upper part. The lower end of the left reinforcing frame
26
is secured to the under cover
16
by means of a bolt
28
. The right reinforcing frame
27
is also formed in an inverted L-shape, rising upward along the inner face of the right side cover
13
and extending inward in the lateral direction in the upper part. The lower end of the right reinforcing frame
27
is secured to the under cover
16
by means of a bolt
29
. Integrally provided on the upper ends of the left and right reinforcing frames
26
and
27
are mounting parts
26
a
and
27
a
that are bent upward to contact each other. The left and right reinforcing frames
26
and
27
together form an arch shape, in which the mounting parts
26
a
and
27
a
make contact with each other. The mounting parts
26
a
and
27
a
are clamped between the left and right side covers
12
and
13
in the front part of the carrying handle
17
and fastened by means of a bolt
30
a
and a nut
30
b
together with the left and right side covers
12
and
13
.
A rubber seal
31
is attached to a part where the left and right side covers
12
and
13
and the upper part of the front cover
14
are joined together. A fuel tank
32
is arranged above the inverter unit
20
on one side at the front of the engine E. The fuel tank
32
has a refueling inlet
32
a
on its top, and the refueling inlet
32
a
runs through the seal
31
, projects above the case
11
and is blocked with a detachable cap
33
.
Projectingly provided on the left and right side faces of the fuel tank
32
are projections
32
b
and
32
c,
which are in a loose fit with fuel tank supports
26
b
and
27
b
of the left and right reinforcing frames
26
and
27
, thereby positioning and supporting the fuel tank
32
in the left and right reinforcing frames
26
and
27
in a non-vibrating manner.
Referring also to
FIGS. 6 and 7
, an engine main body
41
of the engine E, which is a four-cycle, single-cylinder, OHC engine, includes a crankcase
45
, a cylinder barrel
47
, and a cylinder head
50
. The crankcase
45
forms a crank chamber
43
for storing oil
42
and supports a crankshaft
44
whose axis is substantially horizontal when the generator G is in use. The cylinder barrel
47
has a cylinder bore
46
which has an axis which is substantially vertical when the generator G is in use. Formed between the cylinder head
50
and the top of a piston
48
is a combustion chamber
49
, the piston
48
being slidably fitted in the cylinder bore
46
.
The crankcase
45
is formed by connecting first and second case halves
52
and
53
to each other by means of a plurality of bolts
54
, the case halves
52
and
53
being separable from each other along a separation plane
51
that intersects the axis of the crankshaft
44
obliquely. The first case half
52
, the cylinder barrel
47
and the cylinder head
50
are made as one piece by casting, thereby forming an engine block
55
.
The piston
48
is connected to a crankpin
44
a
of the crankshaft
44
via a connecting rod
56
. Formed integrally on the larger end of the connecting rod
56
is an oil dipper
58
for splashing the oil
42
within the crank chamber
43
.
One end of the crankshaft
44
projects out of the crankcase
45
with a ball bearing
59
and an annular seal
60
disposed between the first case half
52
and the one end of the crankshaft
44
. Fixed to the one end of the crankshaft
44
outside the crankcase
45
is a flywheel
62
integrally having a cooling fan
61
.
The other end of the crankshaft
44
is supported in the second case half
53
via a ball bearing
63
with an annular seal
64
disposed between the other end of the crankshaft
44
and the second case half
53
.
The generator G is of an outer rotor type and is provided in cantilever form on the one end of the crankshaft
44
projecting forward, out of the crankcase
45
. The generator G includes a stator
66
and a rotor
68
. The stator
66
has a coil
65
and is fixed to the front face of the crankcase
45
. The rotor
68
is formed from the flywheel
62
and a plurality of permanent magnets
67
fixed to the inner face of the flywheel
62
.
Provided in the cylinder head
50
are an intake port
70
and an exhaust port
71
, which can communicate with the combustion chamber
49
. An intake system
74
including an air cleaner
72
and a carburetor
73
, is supported on the cylinder head
50
to communicate with the intake port
70
. The intake system
74
is placed on the right side of the cylinder head
50
. Placed on the left side of the cylinder head
50
is an exhaust system
77
including an exhaust pipe
75
and an exhaust muffler
76
. The exhaust pipe
75
is connected to the exhaust port
71
and the exhaust muffler
76
is connected to the downstream end of the exhaust pipe
75
. An exhaust outlet
76
a
of the exhaust muffler
76
is placed to face the exhaust gas outlet
15
a
of the rear cover
15
.
The fuel tank
32
has a fuel outlet
32
d
on a lower part thereof. Fuel is fed from the fuel outlet
32
d
to the carburetor
73
which is positioned above the fuel outlet
32
d,
by means of a fuel pump
78
supported on the inner face of an upper part of the right reinforcing frame
27
. A fuel cock
79
and an engine switch
80
are supported on the outer face of a lower part of the right reinforcing frame
27
. The fuel cock
79
is connected to the fuel outlet
32
d
of the fuel tank
32
via a fuel pipeline
81
and also to an inlet
78
a
of the fuel pump
78
via a fuel pipeline
82
. An operating knob
79
a
for opening and closing the fuel cock
79
runs through the right side cover
13
and is exposed externally.
The fuel pump
78
is of a diaphragm type in which a pumping operation is carried out in response to pressure pulsations generated within the crank chamber
43
of the engine main body
41
. An outlet
78
b
of the fuel pump
78
is connected to the carburetor
73
of the intake system
74
via a fuel pipeline
83
and the pressure pulsations generated within the crank chamber
43
are transmitted to the fuel pump
78
via the pressure pipeline
84
.
The engine E is covered with a shroud
85
, which is formed by joining left and right shroud halves
86
and
87
made of a synthetic resin. The left shroud half
86
is secured to the left side faces of the crankcase
45
and the cylinder barrel
47
of the engine main body
41
by means of bolts
88
. The right shroud half
87
is secured to the right side faces of the crankcase
45
and the cylinder barrel
47
by means of bolts
89
.
The shroud
85
is formed so that it is open at the front and rear. The exhaust muffler
76
is disposed in the rear aperture of the shroud
85
. A die-cast aluminum fan cover
90
is fitted around the front aperture to cover the generator G and the cooling fan
61
. The upper part of the fan cover
90
is secured to the cylinder head
50
of the engine main body
41
by a bolt
91
, and the lower part of the fan cover
90
is secured to the crankcase
45
of the engine main body
41
by bolts
92
.
Fixed to a central aperture of the fan cover
90
by means of a plurality of bolts
93
is a recoil starter cover
95
for a recoil starter
94
. The recoil starter
94
includes the recoil starter cover
95
, a reel
96
rotatably supported on the recoil starter cover
95
, a cable
97
, an operating knob
98
, and a drive member
99
provided on the reel
96
so that it can engage with a driven member
61
a
that is integral with the cooling fan
61
. One end of the cable
97
is wound around the reel
96
. The other end of the cable
97
runs through the right reinforcing frame
27
and the right side cover
13
and is provided with the operating knob
98
.
Cooling air inlets
95
a
are formed in the recoil starter cover
95
. Moreover, a cooling air inlet
100
is formed between the lower end of the recoil starter cover
95
and the lower part of the shroud
85
.
When the reel
96
is rotated by pulling the cable
97
by means of the operating knob
98
, the drive member
99
engages with the driven member
61
a
by means of a cam mechanism (not illustrated), thus rotating the cooling fan
61
and thereby cranking the crankshaft
44
connected to the cooling fan
61
via the flywheel
62
to start the engine E. When the operating knob
98
is released, the drive member
99
disengages from the driven member
61
a,
and the reel
96
returns to its original position due to the spring force of a return spring (not illustrated) while winding up the cable
97
.
A mounting bracket
101
is fixed to the lower rear part of the crankcase
45
of the engine main body
41
. The mounting bracket
101
is resiliently supported on a mounting rib
16
a
provided on the upper face of a rear part of the under cover
16
of the case
11
. A mounting bracket
90
a
is formed integrally on the lower part of the fan cover
90
. The mounting bracket
90
a
is resiliently supported on a mounting rib
16
b
provided on the upper face of a front part of the under cover
16
of the case
11
.
Referring also to
FIG. 8
, a centrifugal speed governor
102
is mounted on the second case half
53
of the crankcase
45
in a position that is beneath the crankshaft
44
when the generator G is in use. The centrifugal governor
102
is formed from a rotary disc
104
, a tubular slider
105
and a pair of pendular centrifugal weights
106
. The rotary disc
104
is rotatably supported by a support shaft
103
fixed to the inner face of the second case half
53
. The slider
105
is slidably fitted around the support shaft
103
. The centrifugal weights
106
are swingably supported on the rotary disc
104
with the slider
105
interposed between the weights
106
. Each of the centrifugal weights
106
is provided with an operating arm
106
a
that slides the slider
105
in one direction when the corresponding centrifugal weight
106
swings outward in the radial direction of the rotary disc
104
due to centrifugal force.
A driven gear
107
and oil splashing vanes
108
are formed integrally around the outer circumference of the rotary disc
104
. The driven gear
107
is meshed with a drive gear
109
fixed to the crankshaft
44
. The support shaft
103
is provided in the second case half
53
at a position such that the oil splashing vanes
108
on the outer circumference of the rotary disc
104
are immersed in the oil
42
within the crank chamber
43
.
In the centrifugal speed governor
102
, the slider
105
slides in one axial direction of the support shaft
103
in response to rotation of the rotary disc
104
accompanying the rotation of the crankshaft
44
. The sliding action of the slider
105
is transmitted to a throttle valve (not illustrated) of the carburetor
73
via a link (not illustrated), thereby controlling the engine rotational speed at a predetermined value.
An intake valve
110
and an exhaust valve
111
are disposed in the cylinder head
50
so that they can be made to open and close, the intake valve
110
controlling the provision and blockage of communication between the intake port
70
and the combustion chamber
49
, and the exhaust valve
111
controlling the provision and blockage of communication between the combustion chamber
49
and the exhaust port
71
. The cylinder head
50
is also provided with a spark plug
112
facing the interior of the combustion chamber
49
.
Referring also to
FIG. 9
, the intake valve
110
and the exhaust valve
111
are made to open and close by a valve operation system
113
. The valve operation system
113
is housed in a valve operation chamber
116
formed between the cylinder head
50
and a head cover
115
secured to the cylinder head
50
by a plurality of bolts
114
.
The head cover
115
projects upward through an aperture
117
formed between the upper parts of the shroud
85
and the fan cover
90
. Provided integrally on the front part of the head cover
115
is an air guide plate
119
forming an air guide passage
118
between the front part of the cylinder head
50
and itself. A guide member
120
for inserting the spark plug
112
into the cylinder head
50
and removing it therefrom is attached to the air guide plate
119
. The aperture of the upper end of the guide member
120
is blocked with a detachable cap
121
. An ignition coil
122
is mounted on the upper part of the fan cover
90
in the vicinity of the spark plug
112
.
A plate-form support
115
a
is projectingly provided on the head cover
115
. The support
115
a
is resiliently supported by the left and right side covers
12
and
13
.
The valve operation system
113
housed in the valve operation chamber
116
includes intake side and exhaust side rocker arms
124
and
125
and a valve-operating cam
126
rotatably supported by the cylinder head
50
so as to be in sliding contact with these rocker arms
124
and
125
. The intake side and exhaust side rocker arms
124
and
125
are operatively connected to the intake valve
110
and the exhaust valve
111
respectively and rockably supported in the head cover
115
.
Provided between the valve-operating cam
126
of the valve operation system
113
and the crankshaft
44
is a timing transmitting means
127
for transmitting the rotational power of the crankshaft
44
to the valve-operating cam
126
with a reduction in speed of ½. The timing transmitting means
127
is housed in a housing passage
128
provided in the cylinder barrel
47
and the cylinder head
50
of the engine main body
41
, the housing passage
128
connecting the valve operation chamber
116
and the crank chamber
43
.
The timing transmitting means
127
includes a drive timing pulley
129
, a driven timing pulley
131
as the driven wheel, and an endless timing belt
132
. The drive timing pulley
129
is fixed to the crankshaft
44
. The driven timing pulley
131
is a driven wheel rotatably supported on the support shaft
130
fixedly supported in the cylinder head. The endless timing belt
132
is wrapped around the drive timing pulley
129
and the driven timing pulley
131
. The driven timing pulley
131
is formed integrally with the valve-operating cam
126
of the valve operation system
113
.
The timing transmitting means
127
can supply the oil
42
within the crank chamber
43
to the valve operation chamber
116
by means of the oil attached to and accompanying the timing belt
132
. The second case half
53
of the crankcase
45
is provided with a guide wall
133
and a guide wall
134
. The guide wall
133
is curved so as to cover the side of the centrifugal governor
102
beneath the timing transmitting means
127
, thereby guiding the oil
42
splashed up by the oil splashing vanes
108
of the centrifugal governor
102
to the lower part of the timing transmitting means
127
. The guide wall
134
faces the timing belt
123
in the lower part of the timing transmitting means
127
to guide to the timing belt
123
side, the splashed oil that has collided with the guide wall
133
.
The oil thus attached to the timing belt
132
is thereby splashed within the valve operation chamber
116
from the timing belt
132
due to the action of inertial force and centrifugal force in the section where the timing belt
132
is wrapped around the timing pulley
131
. Provided in the head cover
115
is a curved cover part
115
b
that is retained in an arc form so as to cover the upper part of the driven timing pulley
131
. Provided integrally on the curved cover part
115
b
are a plurality, for example, a pair of oil splashing ribs
136
and
137
at intervals along the rotational direction
135
of the driven timing pulley
131
to project toward the side that is closer to the timing belt
132
.
The intake side and exhaust side rocker arms
124
and
125
of the valve operation system
113
are individually in sliding contact with the lower part of the valve-operating cam
126
at positions on opposite sides of, and an equal distance from, a vertical line
138
passing through the rotational axis of the valve-operating cam
126
. In a projection on a vertical plane that is orthogonal to the rotational axis of the valve-operating cam
126
(a plane parallel to the plane of the paper in FIG.
8
), the pair of oil splashing ribs
136
and
137
are placed outside a pair of vertical lines
139
and
140
that pass through the parts of the rocker arms
124
and
125
that are in sliding contact with the valve-operating cam
126
. The oil splashing ribs
136
and
137
are provided integrally with the curved cover part
115
b
so as to extend in a directions orthogonal to the rotational direction
135
of the driven timing pulley
131
.
Provided on the upper part of the cylinder head
50
are an internal shaft support
50
a
and an external shaft support
50
b
with the housing passage
128
interposed therebetween. The internal shaft support
50
a
supports one end of the support shaft
130
that rotatably supports the valve-operating cam
126
and the driven timing pulley
131
, which are integral with each other. The external shaft support
50
b
supports the other end of the support shaft
130
. An annular seal
141
is disposed between the shaft support
50
b
and the support shaft
130
.
The other end of the support shaft
130
is positioned so as to face outside the cylinder head
50
. An engagement plate
115
c
provided in the head cover
115
engages with the other end of the support shaft
130
, thereby preventing the support shaft
130
from moving away from the cylinder head
50
and from rotating about its axis.
Provided between the internal shaft support
50
a
and the one end of the support shaft
130
is an oil intake passage
142
the upper end of which opens upward on the base of the valve operation chamber
116
and lower end of which is closed. Provided on the outside of the lower part of the support shaft
130
is a flat surface
130
a
that extends from the one end of the support shaft
130
to a position corresponding to the external shaft support
50
b.
Formed between the flat surface
130
a
and the valve-operating cam
126
and driven timing pulley
131
is an oil passage
143
, one end of which communicates with the oil intake passage
142
. The other end of the oil passage
143
opens downward between the external shaft support
50
b
and the driven timing pulley
131
and communicates with the housing passage
128
housing the timing transmitting means
127
.
Referring also to
FIGS. 10 and 11
, the engine block
55
in the engine main body
41
is provided with a first breather chamber
144
, a first communicating passage
145
, a second breather chamber
146
, a second communicating passage
147
, and a connecting passage
148
connecting the first and second breather chambers
144
and
146
. The first breather chamber
144
is placed at a position that is approximately 180° from a position corresponding to the intake system
74
along the circumferential direction of the cylinder bore
46
. The first communicating passage
145
provides communication between the first breather chamber
144
and the interior of the crank chamber
143
. The second breather chamber
146
is positioned in the vicinity of the intake system
74
on the side substantially opposite to the first breather chamber
144
relative to the axis of the cylinder bore
46
. The second communicating passage
147
provides communication between the second breather chamber
146
and the interior of the crank chamber
43
. The second breather chamber
146
is connected to the air cleaner
72
of the intake system
74
via a gas pipeline
149
such as a rubber hose.
Referring also to
FIG. 12
, a recess
150
is provided on the outside of the first case half
52
in the engine block
55
on the side opposite to the side where the intake system
74
is placed. A cover
151
for covering the recess
150
is secured to the outside of the first case half
52
. The first breather chamber
144
is thereby formed between the first case half
52
and the cover
151
, the first breather chamber
144
being positioned above the oil level within the crank chamber
43
when the generator G is in use. The first communicating passage
145
communicates with the lower part of the first breather chamber
144
when the generator G is in use and is bored in the first case half
52
so that its open end in the crank chamber
43
, is divided into two.
The connecting passage
148
is provided in the first case half
52
so that it is positioned in a plane that is orthogonal to the axis of the cylinder bore
46
. One end of the connecting passage
148
opens within the recess
150
so as to communicate with the first breather chamber
144
.
A boss
152
is projectingly provided on the outside of the first case half
52
in a substantially central part within the recess
150
. The cover
151
is secured to the first case half
52
by a bolt
153
that is screwed into the boss
152
. Furthermore, projectingly provided on the outside of the first case half
52
within the recess
150
are a plurality of labyrinth-forming walls
154
that are in contact with the cover
151
. These labyrinth-forming walls
154
form a labyrinth providing communication between the first communicating passage
145
and the connecting passage
148
. When the generator G is in use, the breather gas enters the first breather chamber
144
from the crank chamber
43
via the first communicating passage
145
and then reaches the connecting passage
148
through the labyrinth within the first breather chamber
144
. The accompanying oil is separated from the breather gas while the breather gas changes its direction of flow in the labyrinth. That is to say, the first breather chamber
144
is formed to have a gas-liquid separation mechanism. Moreover, provided in the labyrinth-forming walls
154
that are positioned lower than the open end of the connecting passage
148
in a section of the labyrinth on the connecting passage
148
side are return holes
155
whose flow areas are narrowed to suppress the flow of the breather gas to a minimum, the return holes
155
returning the separated oil to the first communicating passage
145
side.
Referring also to
FIG. 13
, provided on the outside of the first case half
52
in the engine block
55
is a recess
156
positioned in the vicinity of the intake system
74
at the side substantially opposite to the first breather chamber
144
relative to the axis of the cylinder bore
46
. A cover
157
for covering the recess
156
is secured to the outside of the first case half
52
. The second breather chamber
146
, which is positioned above the oil level within the crank chamber
43
when the generator G is in use, is thereby formed between the first case half
52
and the cover
157
. The other end of the connecting passage
148
opens in the recess
156
so as to communicate with the upper part of the second breather chamber
146
when the generator G is in use.
A boss
158
is projectingly provided on the outside of the first case half
152
in substantially the central part within the recess
156
. The cover
157
is secured to the first case half
52
by a bolt
159
screwed into the boss
158
. Mounted on the first case half
52
within the recess
156
is a reed valve
160
that inhibits the flow of breather gas from the second breather chamber
146
to the connecting passage
148
side, in a manner such that it blocks the open end at the other end of the connecting passage
148
.
A projection
161
is projectingly provided on the outside of the first case half
52
in an area to the side of the connecting passage
148
that, when the generator G is in use, is on the upper part of the second breather chamber
146
. The projection
161
receives one end of the gas pipeline
149
fitted in an airtight manner in a through hole
162
provided in the cover
157
, in a manner such that the whole opening at the one end of the gas pipeline
149
is not closed.
Projectingly provided on the outside of the first case half
52
within the recess
156
are labyrinth-forming walls
163
and
164
, which are in contact with the cover
157
. One labyrinth-forming wall
163
forms a labyrinth providing a connection between the connecting passage
148
and the gas pipeline
149
within the second breather chamber
146
. The other labyrinth-forming wall
164
forms a labyrinth providing a connection between the second communicating passage
147
and the gas pipeline
149
within the second breather chamber
146
. These labyrinths allow the second breather chamber
146
also to have a gas-liquid separation mechanism.
One end of a pressure pipeline
84
is connected to the cover
157
to communicate with the second breather chamber
146
beneath the labyrinth-forming walls
163
and
164
. The other end of the pressure pipeline
84
is connected to the fuel pump
78
. On the lower part of the labyrinth-forming walls
163
and
164
within the second breather chamber
146
there opens a branch passage
165
that branches off from the connecting passage
148
to bypass the reed valve
160
. Formed between the lower parts of the labyrinth-forming walls
163
and
164
is a throttle hole
166
that is disposed between the upper and lower parts of the labyrinth-forming walls
163
and
164
within the second breather chamber
146
.
The second communicating passage
147
communicates with the lower part of the second breather chamber
146
when the generator G is in use and is formed from a passage hole
167
and a pipe
168
. The passage hole
167
is bored directly in the first case half
52
to communicate with the second breather chamber
146
. The pipe
168
is secured to the first case half
52
to communicate with the passage hole
167
. A flat mounting seat
169
is formed on the first case half
52
, in a part that is positioned beneath the second breather chamber
146
when the generator G is in use, to face the crank chamber
168
. The passage hole
167
is bored in the first case half
52
, providing a connection between the second breather chamber
146
and the mounting seat
169
. The pipe
168
is made in a substantially L-shaped form having a flange part
168
a
that is in contact with the mounting seat
169
. The flange part
168
a
is secured to the mounting seat
169
by a bolt
170
, and one end of the pipe
168
is fitted in a liquid-tight manner to an end, on the mounting seat
169
side, of the passage hole
167
.
When the generator G is not in use, as shown in
FIG. 14
, the engine main body
41
can be in a laid-sideways attitude so that the axis of the cylinder bore
46
is substantially horizontal. The second communicating passage
147
is formed so that the open end thereof within the crank chamber
43
is always above the oil level L within the crank chamber
43
regardless of the attitude of the engine main body
41
as shown in
FIGS. 14A
to
14
D when the engine main body
41
is in a laid-sideways state where the axis of the cylinder bore
46
is substantially horizontal.
In a state in which the engine main body
41
is in a laid-sideways state in which the connecting passage
148
is positioned beneath the axis of the cylinder bore
46
, that is, in a state shown in
FIG. 14A
, the oil level L of the oil
42
is at a position that allows the oil
42
to be guided into the first breather chamber
144
via a section of the first communicating passage
145
. There is therefore a possibility that the oil
42
might flow from the first breather chamber
144
to the second breather chamber
146
side via the connecting passage
148
. However, the route extending from the first communicating passage
145
to the connecting passage
148
via the first breather chamber
144
is formed in a shape that prevents the oil
42
within the crank chamber
43
from entering the connecting passage
148
. That is, in the present embodiment, the oil level is at a position denoted by the broken chain line L in
FIG. 12
when the engine main body
41
is in a laid-sideways state in which the connecting passage
148
is positioned beneath the axis of the cylinder bore
46
, and the labyrinth-forming walls
154
provided in the first case half
52
for forming the labyrinth within the first breather chamber
144
are formed in a shape that prevents the oil
42
that has flowed into the first breather chamber
144
through the first communicating passage
145
from entering the connecting passage
148
.
The action of the present embodiment is explained below. The first case half
52
of the engine main body
41
is provided with the first breather chamber
144
, the first communicating passage
145
that provides communication between the first breather chamber
144
and the crank chamber
43
, the second breather chamber
146
that is placed in the vicinity of the intake system
74
on the side that is substantially opposite to the first breather chamber
144
relative to the axis of the cylinder bore
46
, the second communicating passage
147
that provides communication between the second breather chamber
146
and the crank chamber
43
, and the connecting passage
148
that provides a connection between the first and second breather chambers
144
and
146
, so that the first and second communicating passages
145
and
147
communicate with the lower parts of the first and second breather chambers
144
and
146
that are positioned above the oil level L within the crank chamber
43
when the generator G is in use and the connecting passage
148
opens in the upper part of the second breather chamber
146
. The gas pipeline
149
communicating with the upper part of the second breather chamber
146
when the generator G is in use is connected to the air cleaner
72
of the intake system
74
.
The breather gas generated in the crank chamber
43
is therefore guided, when the generator G is in use, from the first communicating passage
145
to the intake system
74
via the first breather chamber
144
, the connecting passage
148
, the second breather chamber
146
and the gas pipeline
149
and also from the second communicating passage
147
to the intake system
74
via the second breather chamber
146
and the gas pipeline
149
.
Moreover, since the labyrinths are formed within the first and second breather chambers
144
and
146
, the oil can be separated from the breather gas while passing through the labyrinths and returned to the crank chamber
43
via the first and second communicating passages
145
and
147
, thereby enhancing the gas-liquid separation performance.
Furthermore, since the second communicating passage
147
is formed so that the open end of the second communicating passage
147
within the crank chamber
43
is positioned above the oil level L within the crank chamber
43
regardless of the attitude of the engine main body
41
when the engine main body
41
is in a laid-sideways state where the axis of the cylinder bore
46
is substantially horizontal, the oil
42
within the crank chamber
43
can be prevented from entering the second breather chamber
146
via the second communicating passage
147
regardless of the attitude of the engine main body
41
when the engine main body
41
is laid sideways where the axis of the cylinder bore
46
is substantially horizontal.
Furthermore, since the route from the first communicating passage
145
to the connecting passage
148
via the first breather chamber
144
is formed in a shape that can prevent the oil
42
within the crank chamber
43
from entering the connecting passage
148
when the engine main body
41
is in a laid-sideways state in which the connecting passage
148
is positioned beneath the axis of the cylinder bore
46
, the oil
42
within the crank chamber
43
does not enter the second breather chamber
146
from the first communicating passage
145
via the first breather chamber
114
and the connecting passage
148
.
The oil
42
within the crank chamber
43
therefore does not enter the second breather chamber
146
regardless of the attitude of the engine main body
41
when it is in a laid-sideways state so that the axis of the cylinder bore
46
is substantially horizontal, and it is possible to reliably prevent the oil
42
from entering the intake system
74
and this contributes to an enhancement of the exhaust performance while discharging no white smoke through the exhaust muffler
40
when starting the engine E.
Moreover, the first and second breather chambers
144
and
146
are provided in the engine main body
41
, and the overall dimensions of the engine E do not increase.
Furthermore, the second communicating passage
147
is formed from the passage hole
167
that is bored directly in the first case half
52
of the engine main body
41
to communicate with the second breather chamber
146
, and the pipe
168
secured to the first case half
52
communicates with the passage hole
167
. It is possible to easily form the second communicating passage
147
having a complicated shape that allows its open end to be positioned above the oil level within the crank chamber
43
regardless of the attitude of the engine main body
41
when the engine main body
41
is in a laid-sideways state so that the axis of the cylinder bore
46
is substantially horizontal.
The fuel tank
32
is positioned on the side of the engine main body
41
, thereby making the portable engine-operated machine lower and more compact. It can therefore be carried around easily, thereby enhancing the user convenience.
Furthermore, since the fuel pump
78
, which is required because the fuel exit
32
a
of the fuel tank
32
is positioned lower than the carburetor
73
, is of a diaphragm type, the pressure pulsations generated within the crank chamber
43
of the engine E can be utilized effectively to drive the fuel pump
78
. Moreover, since the pressure pipeline
84
for transmitting the pressure pulsations to the fuel pump
78
is connected to the second breather chamber
146
, as in the case of the breather gas, the pressure pulsations generated in the crank chamber
43
are transmitted from the first communicating passage
145
to the pressure pipeline
84
via the first breather chamber
144
, the connecting passage
148
, and the second breather chamber
146
and act on the fuel pump
78
, thereby preventing the oil from entering the fuel pump
78
as far as is possible.
The gas-liquid separation mechanism is thus shared by the breather gas and the fuel pump
78
and its installation in the engine main body
41
can be rationalized, thereby simplifying the structure of the engine main body
41
and making it more compact.
The valve operation system
113
is housed in the valve operation chamber
116
formed between the cylinder head
50
and the head cover
115
of the engine E. The power from the crankshaft
44
is transmitted to the valve operation system
113
via the timing transmitting means
127
having the driven timing pulley
131
and the timing belt
132
wrapped around the driven timing pulley
131
, which is rotated together with the valve-operating cam
126
of the valve operation system
113
. The oil
42
is supplied to the valve operation chamber
116
by the oil
42
within the crankcase
43
accompanying the timing belt
132
.
Moreover, the arc-shaped curved cover part
115
b
covering the upper part of the driven timing pulley
131
is provided on the head cover
115
, and a plurality (a pair in this embodiment) of oil splashing ribs
136
and
137
are provided integrally with the curved cover part
115
b
above the driven timing pulley
131
at intervals along the rotational direction
135
of the driven timing pulley
131
so as to project toward the timing belt
132
.
When the oil that has been conveyed to the valve operation chamber
116
while attached to the timing belt
132
is separated from the timing belt
132
due to the action of inertial force and centrifugal force, the oil so detached collides with the oil splashing ribs
136
and
137
and is atomized. Since the oil splashing ribs
136
and
137
are provided on the curved cover part
115
b
of the head cover
115
at a plurality of positions at intervals along the rotational direction
135
of the driven timing pulley
131
, the oil that has passed by one oil splashing rib
136
collides with the following oil splashing rib
137
and is splashed, thereby reliably splashing the oil at a plurality of positions and ensuring that the oil can reliably reach each part of the valve operation system
113
. The oil splashing ribs
136
and
137
also have the function of reinforcing the head cover
115
.
The intake side and exhaust side rocker arms
124
and
125
of the valve operation system
113
are in sliding contact with the lower part of the valve-operating cam
126
at positions on opposite sides of, and an equal distance from, the vertical line
138
passing through the rotational axis of the valve-operating cam
126
. In the projection on the vertical plane that is orthogonal to the rotational axis of the valve-operating cam
126
, the pair of oil splashing ribs
136
and
137
are placed outside the pair of vertical lines
139
and
140
that pass through the parts of the two rocker arms
124
and
125
where they are in sliding contact with the valve-operating cam
126
. The oil that has collided with the oil splashing rib
136
and been splashed is supplied effectively to the area where the exhaust side rocker arm
125
slides on the valve-operating cam
126
. The oil that has collided with the oil splashing rib
137
and been splashed is supplied effectively to the area where the intake side rocker arm
124
slides on the valve-operating cam
126
. The valve operation system
113
can thereby be lubricated reliably by a small number of oil splashing ribs
136
and
137
.
Each of the oil splashing ribs
136
and
137
is provided integrally with the curved cover part
115
b
to extend in a direction orthogonal to the rotational direction
135
of the driven timing pulley
131
. The oil can collide with the oil splashing ribs
136
and
137
at right angles, thereby splashing the oil in an atomized manner.
Furthermore, the valve-operating cam
126
of the valve operation system
113
and the driven timing pulley
131
of the timing transmitting means
127
are formed integrally with each other and are rotatably supported by the support shaft
130
, the opposite ends of the support shaft
130
being fixedly supported in the cylinder head
50
, which is an upper part of the engine main body
41
.
Provided between the cylinder head
50
and one end of the support shaft
130
is the oil intake passage
142
the upper end of which opens upward on the base of the valve operation chamber
116
and the lower end of which is closed. Provided on the outside of the lower part of the support shaft
130
is the flat surface
130
a
that forms the oil passage
143
between the flat surface
130
a
and the valve-operating cam
126
and driven timing pulley
131
, one end of the oil passage
143
communicating with the oil intake passage
142
. The other end of the oil passage
143
opens downward and communicates with the housing passage
128
housing the timing transmitting means
127
.
In accordance with the above-mentioned arrangement, together with the use of the splash lubrication system in which the oil that has been splashed in and fills the valve operation chamber
116
, falls down within the valve operation chamber
116
and is guided to the oil intake passage
142
by free fall, the oil is further guided from the oil intake passage
142
to one end of the oil passage
143
that is formed between the outside of the lower part of the support shaft
130
and the valve-operating cam
126
and driven timing pulley
131
. The oil can further flow from the other end of the oil passage
143
toward the housing passage
128
and return to the lower part of the engine main body
41
.
The oil passage
142
is formed by providing the flat surface
130
a
on the outside of the lower part of the support shaft
130
and, while suppressing any increase in the machining cost by simplifying the machining of the support shaft
130
, setting the flow areas of the oil intake passage
142
and the oil passage
143
to be comparatively large allows a sufficient amount of oil to be supplied to the lubrication area between the support shaft
130
and the valve-operating cam
126
and driven timing pulley
131
, thereby suppressing the generation of heat due to rotation at higher speed.
The application of the present invention is not limited to an OHC engine for an engine generator but the present invention can be put into practice widely in relation to an OHC engine.
Although an embodiment of the present invention has been explained above, the present invention is not limited by the above-mentioned embodiment, and the present invention can be modified in a variety of ways without departing from the spirit and scope of the present invention described in the appended claims.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, to be embraced therein.
Claims
- 1. A lubrication structure in an OHC engine having a cylinder head, a head cover connected to the cylinder head, a valve operation chamber formed between the cylinder head and the head cover, an intake valve, an exhaust valve, a crankshaft, and a crankcase, the lubricating structure comprising:a valve operation system housed in the valve operation chamber, the valve operation system comprising a valve-operating cam rotatably supported by the cylinder head and is cooperatively connected to the intake valve and the exhaust valve; and timing transmitting means disposed between the valve operation system and the crankshaft, the timing transmitting means comprising a driven wheel rotating together with the valve-operating cam and a transmission belt wrapped around the driven wheel, wherein oil within the crankcase, is carried by the transmission belt and is supplied to the valve operation chamber; wherein the head cover includes an arc-form curved cover part for covering the upper part of the driven wheel; wherein the curved cover part integrally comprises above the driven wheel a plurality of oil splashing ribs positioned at intervals along the rotational direction of the driven wheel projecting toward the side that is closer to the transmission belt; and wherein each of the oil splashing ribs is integral with the curved cover part and extends in a direction orthogonal to the rotational direction of the driven wheel, thereby reinforcing said head cover.
- 2. The lubrication structure in an OHC engine according to claim 1, wherein the valve operation system further comprises:intake side and exhaust side rocker arms cooperatively connected to the corresponding intake valve and exhaust valve and individually in sliding contact with the lower part of the valve-operating cam at positions on opposite sides of, and an equal distance from, a vertical line passing through the rotational axis of the valve-operating cam coaxially and integrally formed with the driven wheel, a pair of the oil splashing ribs being positioned outside of a pair of vertical lines, in a projection on a vertical plane that is orthogonal to the rotational axis of the valve-operating cam, that pass through the parts of the rocker arms that are in sliding contact with the valve-operating cam.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2001-036556 |
Feb 2001 |
JP |
|
US Referenced Citations (5)
Foreign Referenced Citations (2)
Number |
Date |
Country |
8-177441 |
Jul 1996 |
JP |
9-151720 |
Jun 1997 |
JP |