Information
-
Patent Grant
-
6708652
-
Patent Number
6,708,652
-
Date Filed
Friday, December 21, 200122 years ago
-
Date Issued
Tuesday, March 23, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Yuen; Henry C.
- Benton; Jason
Agents
- Birch, Stewart, Kolasch & Birch, LLP
-
CPC
-
US Classifications
Field of Search
US
- 123 4149
- 123 198 R
- 123 9031
- 123 196 R
-
International Classifications
-
Abstract
A valve timing transmission apparatus is disclosed that increases the freedom of attachment positions for a pivot pin supporting a one end of timing chain and enables arrangement of a chain tensioner in an optimum position for tensioning of the timing chain. An opening having a diameter greater than a sprocket is provided on the drive sprocket side of an outer side wall of a timing chamber which is formed in one side wall of an engine main body and which accommodates the timing chain. A lid plate is removably secured to the engine main body so as to close the opening. Support bosses supporting both ends of the pivot pin are formed in opposite walls of the engine main body and the lid plate.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2000-403155 filed in Japan on Dec. 28, 2000, the entirety of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine valve timing transmission apparatus, and more particularly, to an apparatus where a timing chain is arranged around a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft. An end of a tensioner, press-contacted with an outer side surface of the timing chain to apply tension to the chain is swingably attached to an engine main body via a pivot pin.
2. Description of the Background Art
A similar engine valve timing transmission apparatus is described in Japanese Published Unexamined Patent Application No. Hei 7-71543. In this type of engine valve timing transmission apparatus, a pivot pin of a tensioner is held between junction surfaces of a crankcase divided in two halves to rotatably hold a crankshaft.
However, the pivot pin is too close to a timing chain, and the tensioner cannot be provided in an optimum position for tensioning of the timing chain. Further, since the pivot pin must be attached between the junction surfaces of the crankcase when the crankshaft is held between the two halves of the divided crankcase, assembly is difficult and unreliable.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
An object of the present invention is to provide an engine valve timing transmission apparatus which increases freedom of attachment positions of the pivot pin.
A further object of the present invention is to enable placement of the chain tensioner in an optimum position for easy, reliable tensioning of the timing chain.
A further object of the present invention is to enable attachment of the pivot pin after assembly of the crankcase in order to improve the ease of assembly.
These and other objects are accomplished by an engine valve timing transmission apparatus comprising a timing chain engaging with a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft; a chain tensioner, the chain tensioner having a first end press-contacted with an outer side surface of the timing chain to apply tension to the timing chain and swingably attached to an engine main body via a pivot pin; a timing chamber formed in a side wall of the engine main body for accommodating the timing chain; an opening having a diameter greater than the drive sprocket is provided on a side of the drive sprocket on an outer side wall of the timing chamber; and a lid plate for covering the opening is removably secured to the engine main body.
The pivot pin is held between opposite walls of the engine main body and the lid plate. The pivot pin can be reliably supported by the engine main body and the lid plate without special dropping preventing means. Further, the freedom of attachment position of the pivot pin in opposite walls of the engine main body and the lid plate increases, the pivot pin can be provided in a desired position, and the chain tensioner can be provided in an optimum position for tension of the timing chain. Furthermore, since the attachment of the pivot pin is made upon attachment of the lid plate, e.g. after assembly of the engine main body, ease of reliable assembly is improved.
Further, according to a second feature of the present invention, the engine main body is constructed with a cylinder block, a first crankcase half body connected to one end of the cylinder block, and a second crankcase half body connected to and in cooperation with the first crankcase half body and rotatably holding the crankshaft. The timing chamber is formed from the cylinder block to the second crankcase half body. The opening is provided over the first and second crankcase half bodies, and the pivot pin is held between opposite walls of the lid plate to close the opening and the second crankcase half body.
The pivot pin can be provided sufficiently away from the drive sprocket to the opposite side of the driven sprocket. Accordingly, a sufficient length of the chain tensioner can be ensured. The timing chain can be held under an approximately constant tension without influence by the extension of the chain, and the durability of the timing chain can be improved.
Further, according to a third feature of the present invention, a stator of a generator driven by the crankshaft is fixed to the lid plate. The lid plate also serves as a support base of the stator of the generator. This third feature permits a reduction in the number of parts.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
FIG. 1
is a side view of a scooter type motorcycle according to a first embodiment of the present invention;
FIG. 2
is a cross-sectional view taken along line
2
—
2
in
FIG. 1
;
FIG. 3
is a side view taken along arrows
3
—
3
in
FIG. 2
;
FIG. 4
is a side view corresponding to the view of
FIG. 3
shown without a radiator cover;
FIG. 5
is a cross-sectional view taken along line
5
—
5
in
FIG. 3
;
FIG. 6
is a side view corresponding to the view of
FIG. 3
shown without a radiator and a generator;
FIG. 7
is a cross-sectional view taken along line
7
—
7
in
FIG. 2
; and
FIG. 8
is a cross-sectional view taken along line
8
—
8
in FIG.
6
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will hereinafter be described with reference to the accompanying drawings.
FIG. 1
is a side view of a scooter type motorcycle according to a first embodiment of the present invention.
FIG. 2
is a cross-sectional view taken along line
2
—
2
in FIG.
1
.
FIG. 3
is a side view taken along arrows
3
—
3
in FIG.
2
.
FIG. 4
is a side view corresponding to the view of
FIG. 3
shown without a radiator cover.
FIG. 5
is a cross-sectional view taken along line
5
—
5
in FIG.
3
.
FIG. 6
is a side view corresponding to the view of
FIG. 3
shown without a radiator and a generator.
FIG. 7
is a cross-sectional view taken along line
7
—
7
in FIG.
2
.
FIG. 8
is a cross-sectional view taken along line
8
—
8
in
FIG. 6. A
working example according to an embodiment of the present invention will be described hereinafter with reference to the accompanying drawings.
In
FIG. 1
, a vehicle body frame F of a scooter type motorcycle V having a front wheel Wf steered by a steering handle
11
, and a rear wheel Wr driven by a swing type power unit P, is divided into three parts: a front frame
12
, a center frame
13
and a rear frame
14
. The front frame
12
includes an aluminum alloy casted member integrally provided with a head pipe
12
a
, a down tube
12
b
and a step floor
12
c.
The center frame
13
, on which the power unit P can be upwardly-and-downwardly swung via a pivot pin
15
, also includes an aluminum alloy casted member. The center frame
13
is connected to a rear end of the front frame
12
. The rear frame
14
, extending at a rear and upper position from the power unit P, includes a ring-shaped pipe member.
A fuel tank
16
is supported by the rear frame
14
such that the tank is surrounded by the rear frame
14
. A helmet case
17
is supported on an upper surface of the center frame
13
, and the helmet case
17
is openably/closably covered with a lid
19
integrally provided with a seat
18
.
The power unit P has a water-cooling, monocylinder 4-cycle engine E and a belt-type continuously variable transmission T extending from a left side surface of the engine E toward the rear of the vehicle body. A rear upper surface of the continuously variable transmission T is connected to a rear end of the center frame
13
via a rear cushion (shock absorber)
20
. An air cleaner
21
is supported on an upper surface of the continuously variable transmission T, a muffler
22
is supported on a right side surface of the continuously variable transmission T, and a main stand
23
which can be set upright and tilted downward is supported on a lower surface of the engine E.
In FIG.
2
through
FIG. 4
, an engine main body
25
of the engine E has an engine block
32
and a rear crankcase half body
33
b
divided by a dividing surface extending in upward and rearward directions along an axial line of the crankshaft
31
. The engine block
32
is integrally provided with a cylinder block
32
a
having a cylinder bore
41
, and a front crankcase half body
33
a
. The front crankcase half body
33
a
and the rear crankcase half body
33
b
form the crankcase
33
. A cylinder head
34
is connected to a front end of the engine block
32
, and a head cover
35
is connected to a front end of the cylinder head
34
.
This engine main body
25
is mounted on the vehicle body frame F approximately along frontward and rearward directions of the vehicle body frame F, with a front part of an axial line L of the cylinder bore
41
being slightly raised off a centerline. A bracket
27
provided in an upper part of the engine block
32
is swingably connected to the pivot pin
15
fixed to the center frame
13
of the vehicle body frame F via a rubber mount
28
.
The continuously variable belt-type transmission T has a right casing
37
and a left casing
38
connected to each other. A front right side surface of the right casing
37
is connected to a left side surface of the front and rear crankcase half bodies
32
and
33
. Further, a deceleration casing
39
is connected to a rear right side surface of the right casing
37
.
A piston
42
slidably engaged in the cylinder bore
41
of the engine block
32
is connected to the crankshaft
31
via a connecting rod
43
. A camshaft
44
is rotatably supported in the cylinder head
34
. An intake valve and an exhaust valve (not shown) provided in the cylinder head
34
are opened/closed by the camshaft
44
.
As shown in
FIG. 2
, and FIG.
5
through
FIG. 8
, a timing chamber
40
is formed in one side wall of the crankcase
33
, cylinder block
32
a
and the cylinder head
34
. The timing chamber
40
accommodates an endless timing chain
45
, placed around a drive sprocket
46
provided on the crankshaft
31
and a driven sprocket
47
provided on the camshaft
44
. The drive sprocket
46
, the driven sprocket
47
and the timing chain
45
forms a timing transmission apparatus Ti to reduce the rotation of the crankshaft
31
by half and to transmit this rotational force to the camshaft
44
. The camshaft
44
then opens/closes the intake and exhaust valves (not shown) by its controlled rotation.
Further, a chain guide
48
for guiding the running of the timing chain
45
on the tension side, and a chain tensioner
49
for applying tension to the timing chain
45
on the loose side, are also provided in the timing chamber
40
. The chain guide
48
is bent into an arc shape. One end of the chain guide is received by a shelf-shaped support
113
on an inner wall of the rear crankcase half body
33
b
and the other end of the chain guide is swingably attached to the cylinder block
32
a
with a bolt
36
such that the chain guide is in sliding contact with the outer side surface of the timing chain
45
on the tension side, approximately over the entire length.
The chain tensioner
49
is also bent to have an arc shape, with a curvature greater than that of the chain guide
48
. The chain tensioner
49
mainly presses a central portion of the outer side surface of the timing chain
45
on the loose side. A bush
50
connected to one end of the tensioner via a ring-shaped elastic member
51
is rotatably supported by the pivot pin
112
provided in a position away from the drive sprocket
46
to the opposite side to the driven sprocket
47
(an attaching structure of the pivot pin will be described later), and the other end of the chain tensioner
49
is a free end. A lifter
52
to press a central portion rear surface of the chain tensioner
49
against the timing chain
45
side by a constant pressing force is provided in the cylinder block
32
a
. Thus, the timing chain
45
is provided with a constant tension from the chain tensioner
49
.
The front and rear crankcase half bodies
33
a
and
33
b
are provided with an opening
53
having a diameter sufficiently greater than the drive sprocket
46
around the crankshaft
31
in a portion corresponding to an outer side wall of the timing chamber
40
. The timing chain
45
is secured in a position around the drive sprocket
46
through the opening
53
. A lid plate
73
fixed to the front and rear crankcase half bodies
33
a
and
33
b
with a plurality of bolts
74
closes the opening
53
.
An O-ring
110
is inserted between junction surfaces of both crankcase half bodies
33
a
,
33
b
and the lid plate
73
. An oil seal
111
in tight contact with an outer peripheral surface of the crankshaft
31
is applied to a through hole
73
a
of the lid plate
73
formed through the crankshaft
31
. Accordingly, the timing chamber
40
is securely maintained with an oil seal.
The attachment structure of the pivot pin
112
supporting the chain tensioner
49
will be described hereinafter. As clearly shown in FIG.
6
through
FIG. 8
, a pair of support bosses
125
and
126
with bottomed holes
125
a
and
126
a
opposite to each other in desired position of the pivot pin
112
are integrally projected from opposite walls of the lid plate
73
and the crankcase
33
. The bush
50
of the chain tensioner
49
is provided between both support bosses
125
and
126
, and both ends of the pivot pin
112
rotatably inserted through the bush
50
are engaged with the bottomed holes
125
a
and
126
a
of the support bosses
125
and
126
. These bottoms prevent movement of the pivot pin
112
in an axial direction.
Accordingly, the pivot pin
112
is reliably supported by the crankcase
33
and the lid plate
73
without special dropping prevention means. Further, as the crankcase
33
and the lid plate
73
are arranged in positions opposite to each other in a wide range around the drive sprocket
46
, the freedom of arrangement for the support bosses
125
and
126
supporting the pivot pin
112
increases. The pivot pin
112
can be supported at a desired position, and the chain tensioner can be provided in an optimum position for tensioning of the timing chain.
As in the illustrated example, if the support bosses
125
and
126
are provided on opposite walls of the rear crankcase half body
33
b
and the lid plate
73
, the pivot pin
112
supported by the bosses can be provided sufficiently away from the drive sprocket
46
to the opposite side to the driven sprocket
47
. As a result, a sufficient length of the chain tensioner
49
, e.g. a sufficient distance between the pivot pin
112
and the lifter
52
, is ensured. The timing chain
45
can be held under an approximately constant tension without influence by the extension of the chain, thus the durability of the timing chain
45
can be improved.
Further, since the attachment of the pivot pin
112
is performed upon attachment of the lid plate
73
to the front and rear crankcase half bodies
33
a
and
33
b
, after connection of the front and rear crankcase half bodies holding the crankshaft
31
, assembly can be easily made.
In
FIG. 8
, a bearing boss
127
projecting toward the timing chamber
40
side is integrally formed with the lid plate
73
and rotatably supports a rotor shaft
129
of an oil pump
128
. In this manner, the lid plate
73
also serves as a support member of the rotor shaft
129
, which contributes to a reduction of the number of required parts and assembly steps of the oil pump
128
. The rotor shaft
129
is driven from the crankshaft
31
via a large-diameter gear
130
fixed to the rotor shaft and a small-diameter gear
131
integrally connected to one end of the drive sprocket
46
.
In
FIG. 5
, a rotor
69
is fixed to the right end side of the crankshaft
31
. A stator
70
, forming an alternator
68
in combination with the rotor
69
, is fixed to the lid plate
73
with plural bolts
74
. The rotor
69
surrounds the stator
70
. Accordingly, the lid plate
73
also serves as an attachment base of the stator
70
, and contributes to the reduction of the number of parts.
A cooling fan
71
is fixed to a right end of the crankshaft
31
in a position exterior to the alternator
68
. A radiator
72
is provided so as to hold the cooling fan
71
between the radiator
72
and the alternator
68
. The radiator
72
is attached to the engine main body
25
via a shroud
81
surrounding the cooling fan
71
.
The radiator
72
is constructed with upper and lower tanks
77
and
78
, provided at an interval, and a radiating core
79
connecting these tanks
77
and
78
while mutually communicating with the inside of these tanks. The radiating core
79
is made of metal having high radiation qualities. Respective pairs of connection projection pieces
101
,
101
;
102
,
102
are projected leftward and rightward from both upper and lower ends. The upper connection projection pieces
101
,
101
are swaged with both left and right ends of the upper tank
77
having its lower surface opened, with seal members
103
,
103
held therebetween. The lower connection projection pieces
102
,
102
are swaged with both left and right ends of the lower tank
78
having its upper surface opened, with seal members
104
,
104
held therebetween. The upper and lower tanks
77
and
78
are formed of synthetic resin.
Connection flanges
105
and
106
are integrally formed with the upper and lower tanks
77
and
78
, and one end of the shroud
81
of elastic material such as synthetic resin is fixed to these flanges with a plurality of rivets
107
. A connection flange
81
a
is integrally formed with the other end of the shroud
81
, and the connection flange
81
a
is fixed to the engine main body
25
with a plurality of bolts
108
.
The outer periphery of the radiator
72
is covered with a radiator cover
75
of synthetic resin fixed to the shroud
81
with a plurality of screws
109
. A grille
75
a
integrally formed with the radiator cover
75
is provided in a position opposite to a front surface of the radiating core
79
. A cooling wind is introduced from the outside through the grille
75
a
to the radiating core
79
.
Referring to FIG.
6
and
FIG. 8
, plural discharge ports
76
are provided in the shroud
81
at the side of the cooling fan
71
. Upon actuation of the cooling fan
71
, air introduced from the grille
75
a
is passed through the radiating core
79
of the radiator
72
, and the radiating core
79
is cooled down. The air is discharged from the discharge ports
76
to the outside. Thus, cooling water in the radiator
72
is also cooled.
The radiator
72
forms a part of a cooling device
83
to circulate cooling water in a water jacket
82
provided in the cylinder block
32
a
of the engine block
32
and the cylinder head
34
in the engine main body
25
. The cooling device
83
includes a water pump
84
for supplying cooling water to the water jacket
82
. The radiator
72
is inserted between the water jacket
82
and an intake port of the water pump
84
. A thermostat
85
selects an operating state for either restoring the cooling water from the water jacket
82
to the water pump
84
(thereby avoiding the radiator
72
) or restoring the cooling water from the water jacket
82
through the radiator
72
to the water pump
84
in accordance with the cooling water temperature.
A thermostat case
86
accommodating the thermostat
85
is connected to a right side surface of the cylinder head
34
. The water pump
84
is provided on a right end of the camshaft
44
and is accommodated in a space surrounded by the cylinder head
34
and the thermostat case
86
.
An upwardly-extending water supply port tube
87
is integrally provided with one end of the upper tank
77
along the frontward and rearward directions of the vehicle body frame F (in this embodiment, a rear end). A water supply cap
88
opened/closed by rotational operation is attached to an upper end of the water supply port tube
87
. Further, a forwardly-projecting connection pipe
89
is integrally provided with the other end of the lower tank
78
along the frontward and rearward directions of the vehicle body frame F (in this embodiment, a front end).
This radiator
72
is attached to the engine main body
25
as described above in a position tilted at an angle a to the axial line L of the cylinder bore
41
of the engine main body
25
. When the engine main body
25
is mounted on the vehicle body frame F, the radiator
72
is frontwardly tilted at an angle b to a horizontal plane. The water supply cap
88
is provided in the highest position in the cooling device
83
and the connection pipe
89
is provided in the lowest position in the cooling device
83
.
The foregoing arrangement avoids increases in cost by forming the radiator
72
in a special shape and providing a water supply cap in a tank connected to the radiator
72
and provided aside from the radiator
72
, attains a comparatively large head difference in the cooling device
83
upon water supply from the water supply port tube
87
, and improves air removal characteristics and water supply performance from the water supply port tube
87
.
Further, in the case where the radiator
72
is tilted at an angle a to the axial line L of the cylinder bore
41
as described above, the radiator
72
can be provided to avoid the pivot pin
25
to support the engine main body
25
on the vehicle body frame F. Further, adequate space to hold an exhaust pipe
90
connected to an exhaust port of the cylinder head
32
is ensured in the rear of the radiator
72
and the freedom of arrangement of the exhaust pipe
90
can be improved.
One end of a flexible first conduit
91
comprising a rubber hose or the like, to guide the cooling water in the radiator
72
to the thermostat
85
side, is connected to the connection pipe
89
of the radiator
72
. The other end of the first conduit
91
is connected to the thermostat case
86
.
The radiator
72
is provided in a position where at least a part (a front part in this embodiment) of the upper tank
77
is overlapped with the cylinder block
32
a
of the engine main body
25
, in a side view. A connection hole
115
connected to the inside of the upper tank
77
and a connection hole
116
connected to an exit
82
in an upper part of the water jacket
82
are provided in the upper tank
77
and the cylinder block
32
a
, within a region where the upper tank
77
and the cylinder block
32
a
overlap with each other (as seen in a side view).
Both ends of a second conduit
92
comprising a metal pipe or the like having rigidity are engaged with these connection holes
115
and
116
along a fastening direction of the bolts
108
via seal members
117
and
118
, e.g. O-rings. The second conduit
92
is provided so as to be inserted through a through hole
119
provided in the shroud
81
in a non-contact state. Further, a gap to allow swing movement of the second conduit
92
at a slight angle while elastically deforming the seal members
117
and
118
is provided in an engagement portion between the second conduit
92
and the connection holes
115
and
116
.
Further, one end of a flexible third conduit
93
comprising a rubber hose or the like, to guide the cooling water from the water pump
84
, is connected to the thermostat case
86
. The other end of the third conduit
93
is connected to an entrance
82
i
in a lower part of the water jacket
82
projected from a lower surface of the cylinder block
32
a.
A pipe line (not shown) to guide the cooling water from the water jacket
82
so as to humidify a carburetor
95
is connected to the carburetor
95
connected to an inlet port of the cylinder head
32
. A flexible fourth conduit
96
comprising a rubber hose or the like, to guide the cooling water, which humidified the carburetor
95
to the thermostat
85
, is connected to the thermostat case
86
.
A flexible fifth conduit
97
comprising a rubber hose or the like, to remove air from the water pump
84
, is connected to an upper part of the thermostat case
86
. The fifth conduit
97
and a conduit (not shown) connected to the upper part of the cylinder block
32
a
to remove air from an upper part in the water jacket
82
are connected to a flexible sixth conduit
98
comprising a rubber hose or the like. The sixth conduit
98
is connected to a rear side upper part of the upper tank
77
in the radiator
72
.
Further, one end of a flexible seventh conduit
100
comprising a rubber hose or the like is connected to the water supply port tube
87
, and the other end of the seventh conduit
100
is connected to a reservoir (not shown), opened in atmosphere and provided aside from the radiator
72
. When the temperature of the cooling water in the radiator
72
becomes high and the water expands, excessive cooling water overflows to the reservoir. When the temperature of the cooling water in the radiator
72
becomes low, the cooling water is restored from the reservoir to the radiator
72
. By this movement of cooling water between the radiator
72
and the reservoir, air stored in the water supply port tube
87
is discharged to the reservoir. That is, adequate air removal from the cooling device
83
can be achieved even when the engine E is running.
Then, in a status where warming up of the engine E is complete, the cooling water discharged from the water pump
84
driven by the camshaft
44
is supplied through the thermostat case
86
and the third conduit
93
to the water jacket
82
in the engine block
32
and the cylinder head
34
. When the cooling water passes through the water jacket
82
, it cools the engine E. The cooling water then is sent via the second conduit
92
to the upper tank
77
of the radiator
72
. Then, the cooling water, the temperature of which has been lowered when the water flowed from the upper tank
77
via the cooling core
79
to the lower tank
78
, is taken into the water pump
84
via the first conduit
91
and the thermostat
85
.
On the other hand, when the engine E is warmed up and the temperature of the cooling water is low, the thermostat
85
is actuated to circulate the cooling water while avoiding the radiator
72
. The cooling water is circulated, without passing through the radiator
72
, through the water jacket
82
, the carburetor
95
and the water pump
84
, in order to raise the temperature rapidly.
Since the upper and lower tanks
77
and
78
of the radiator
72
are made of light-weight synthetic resin, the weight of the radiator
72
can be greatly reduced. Further, since the shroud
81
to guide the cooling wind that passed through the radiator
72
to the outside from the discharge ports
76
is made of elastic material and the radiator
72
is attached to the engine main body
25
via the shroud, the shroud
81
absorbs engine E vibration by its own elasticity, and prevents additional vibration from being transferred from the engine E to the radiator
72
.
The shroud
81
serves a role of vibration isolation by blocking transmission of vibration from the engine E to the radiator
72
in addition to its original function to guide the cooling wind from the radiator
72
. Accordingly, specialized vibration isolation means for the radiator
72
is unnecessary, and simplification of the structure and subsequent cost reduction can be attained.
Further, since the radiator
72
is light weight as described above, the load capacitance of the shroud
81
can be reduced. Accordingly, the thickness of the shroud
81
can be reduced, and by extension, further improvement in vibration isolation function and weight reduction can be attained. Since the radiator
72
is attached to the engine E in the power unit P, which connected to the vehicle body frame F via the pivot pin
15
and supported via the rear cushion
20
, and which swings upwardly and downwardly with the rear wheel Wr, the above-described weight reduction of the radiator
72
and the shroud
81
reduces spring load and contributes to improvement in driving feeling.
Again referring to
FIG. 2
, a drive pulley
54
is provided at a left end of the crankshaft
31
projecting inside the right casing
37
and the left casing
38
. The drive pulley
54
has a fixed pulley half body
55
fixed to the crankshaft
31
and a movable pulley half body
56
approachable/withdrawable to/from the fixed pulley half body
55
. The movable pulley
56
is pressed, by a centrifugal weight
57
moving radial-outwardly in correspondence with increments in the number of revolutions of the crankshaft
31
, in a direction approaching to the fixed pulley half body
55
.
A driven pulley
59
, provided on an output shaft
58
supported between a rear part of the right casing
37
and the deceleration casing
39
, has a fixed pulley half body
60
rotatably supported relatively to the output shaft
58
. A movable pulley half body
61
approachable/withdrawable to/from the fixed pulley half body
60
, and the movable pulley half body
61
is pressed by a spring
62
toward the fixed pulley half body
60
. Further, a take-off clutch
63
is provided between the fixed pulley half body
60
and the output shaft
58
. An endless V-belt
64
is placed around the drive pulley
54
and the driven pulley
59
.
An intermediate shaft
65
and a vehicle axle
66
parallel to the output shaft
58
are supported between the right casing
37
and the deceleration casing
39
. A deceleration gear array
67
is provided among the output shaft
58
, the intermediate shaft
65
and the vehicle axle
66
. The rear wheel Wr is spline-engaged with a right end of the vehicle axle
66
projecting rightward through the deceleration casing
39
.
Therefore, the rotation power of the crankshaft
31
is transmitted to the drive pulley
54
. The rotational energy is then transmitted from the drive pulley
54
, via the V belt
64
, the driven pulley
59
, the take-off clutch
63
and the deceleration gear array
67
, to the rear wheel Wr.
Upon low-speed revolution of the engine E, as a centrifugal force acting on the centrifugal weight
57
of the drive pulley
54
is small, a groove width between the fixed pulley half body
60
and the movable pulley half body
61
is reduced by the spring
62
of the driven pulley
59
. The transmission gear ratio is LOW in this arrangement. From this state, if the number of revolutions of the crankshaft
31
is increased, the centrifugal force acting upon the centrifugal weight
57
increases and a groove width between the fixed pulley half body
55
and the movable pulley half body
56
of the drive pulley
54
decreases. The groove width between the fixed pulley half body
60
and the movable pulley half body
61
of the driven pulley
59
increases. Accordingly, the transmission gear ratio continuously varies from LOW toward TOP (HIGH).
The present invention is not limited to the above described embodiments, but various design changes can be made without departing from the scope of subject matter of the present invention. For example, the present invention is applicable to various vehicles such as an automatic three-wheeled vehicle other than the above motorcycle V or scooter type vehicle.
As described above, according to the first feature of the present invention, in an engine valve timing transmission apparatus, a timing chain is placed around a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft. An end of a tensioner, press-contacted with an outer side surface of the timing chain to apply tension to the chain, is swingably attached to an engine main body via a pivot pin. An opening having a diameter greater than the sprocket is provided on the side of the drive sprocket on an outer side wall of a timing chamber accommodating the timing chain, formed in one side wall of the engine main body. A lid plate to close the opening is removably fixed to the engine main body.
The pivot pin is held between opposite walls of the engine main body and the lid plate. The pivot pin can be reliably supported by the engine main body and the lid plate without special dropping preventing means. Further, the freedom of attachment position of the pivot pin in opposite walls of the engine main body and the lid plate increases, the pivot pin can be provided in a desired position, and the chain tensioner can be provided in an optimum position for tension of the timing chain. Furthermore, since the attachment of the pivot pin is made upon attachment of the lid plate, e.g. after assembly of the engine main body, ease of reliable assembly is improved.
Further, according to a second feature of the present invention, the engine main body is constructed with a cylinder block, a first crankcase half body connected to one end of the cylinder block, and a second crankcase half body connected to and in cooperation with the first crankcase half body and rotatably holding the crankshaft. The timing chamber is formed from the cylinder block to the second crankcase half body. The opening is provided over the first and second crankcase half bodies, and the pivot pin is held between opposite walls of the lid plate to close the opening and the second crankcase half body.
The pivot pin can be provided sufficiently away from the drive sprocket to the opposite side of the driven sprocket. Accordingly, a sufficient length of the chain tensioner can be ensured. The timing chain can be held under an approximately constant tension without influence by the extension of the chain, and the durability of the timing chain can be improved.
Further, according to a third feature of the present invention, a stator of a generator driven by the crankshaft is fixed to the lid plate. The lid plate also serves as a support base of the stator of the generator. This third feature permits a reduction in the number of parts.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
- 1. An engine valve timing transmission apparatus comprising:a timing chain engaging with a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft; a chain tensioner, said chain tensioner having a first end press-contacted with an outer side surface of the timing chain to apply tension to the timing chain and swingably attached to an engine main body via a pivot pin; a timing chamber formed in a side wall of the engine main body for accommodating the timing chain; an opening having a diameter greater than the drive sprocket is provided on a side of the drive sprocket on an outer side wall of the timing chamber; a lid plate for covering the opening is removably secured to the engine main body; and a bearing boss projecting toward the timing chamber and integrally formed with the lid plate, said bearing boss rotatably supporting a rotor shaft of an oil pump.
- 2. An engine valve timing transmission apparatus comprising:a timing chain engaging with a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft; a chain tensioner, said chain tensioner having a first end press-contacted with an outer side surface of the timing chain to apply tension to the timing chain and swingably attached to an engine main body via a pivot pin; a timing chamber formed in a side wall of the engine main body for accommodating the timing chain; an opening having a diameter greater than the drive sprocket is provided on a side of the drive sprocket on an outer side wall of the timing chamber; a lid plate for covering the opening is removably secured to the engine main body; and a pair of support bosses being integrally formed with said lid plate and a crankcase of said engine main body, wherein the pivot pin is held between opposite walls of the engine main body and the lid plate by said support bosses.
- 3. The engine valve timing transmission apparatus according to claim 2, wherein the engine main body includes a cylinder block, a first crankcase half body connected to a one end of the cylinder block, and a second crankcase half body connected to and in cooperation with the first crankcase half body, said first and second crankcase half bodies rotatably holding the crankshaft.
- 4. The engine valve timing transmission apparatus according to claim 3, wherein the timing chamber is formed from the cylinder block to the second crankcase half body.
- 5. The engine valve timing transmission apparatus according to claim 3, wherein said opening is provided over the first and second crankcase half bodies.
- 6. The engine valve timing transmission apparatus according to claim 4, wherein said opening is provided over the first and second crankcase half bodies.
- 7. The engine valve timing transmission apparatus according to claim 3, wherein said pivot pin is held between opposite walls of said lid plate in a position covering the opening and the second crankcase half body.
- 8. The engine valve timing transmission apparatus according to claim 4, wherein said pivot pin is held between opposite walls of said lid plate in a position covering the opening and the second crankcase half body.
- 9. The engine valve timing transmission apparatus according to claim 6, wherein said pivot pin is held between opposite walls of said lid plate in a position covering the opening and the second crankcase half body.
- 10. The engine valve timing transmission apparatus according to claim 1, further comprising a generator driveably engaging with the crankshaft, said generator including a stator fixed to said lid plate.
- 11. The engine valve timing transmission apparatus according to claim 2, further comprising a generator driveably engaging with the crankshaft, said generator including a stator fixed to said lid plate.
- 12. The engine valve timing transmission apparatus according to claim 8, further comprising a generator driveably engaging with the crankshaft, said generator including a stator fixed to said lid plate.
- 13. The engine valve timing transmission apparatus according to claim 9, further comprising a generator driveably engaging with the crankshaft, said generator including a stator fixed to said lid plate.
- 14. An engine valve timing transmission apparatus comprising:a timing chain engaging with a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft; a chain tensioner, said chain tensioner having a first end press-contacted with an outer side surface of the timing chain to apply tension to the timing chain and swingably attached to an engine main body via a pivot pin; a timing chamber formed in a side wall of the engine main body for accommodating the timing chain; an opening having a diameter greater than the drive sprocket is provided on a side of the drive sprocket on an outer side wall of the timing chamber; a lid plate for covering the opening is removably secured to the engine main body, wherein the pivot pin is held between opposite walls of the engine main body and the lid plate; and a bearing boss projecting toward the timing chamber and integrally formed with the lid plate, said bearing boss rotatably supporting a rotor shaft of an oil pump.
- 15. An engine valve timing transmission apparatus comprising:a timing chain engaging with a drive sprocket and a driven sprocket respectively fixed to a crankshaft and a valve camshaft; a chain tensioner, said chain tensioner having a first end press-contacted with an outer side surface of the timing chain to apply tension to the timing chain and swingably attached to an engine main body via a pivot pin; a timing chamber formed in a side wall of the engine main body for accommodating the timing chain; an opening having a diameter greater than the drive sprocket is provided on a side of the drive sprocket on an outer side wall of the timing chamber; a lid plate for covering the opening is removably secured to the engine main body, wherein the pivot pin is held between opposite walls of the engine main body and the lid plate; a generator driveably engaging with the crankshaft, said generator including a stator fixed to said lid plate; and a cooling fan fixedly secured to a right end of the crankshaft in a position exterior to said generator.
- 16. The engine valve timing transmission apparatus according to claim 15, further comprising a radiator securing said cooling fan in a position between said radiator and said generator, wherein said radiator is secured to said engine main body.
- 17. The engine valve timing apparatus according to claim 2, further comprising a bush pivotably supporting said chain tensioner and being provided between said support bosses.
- 18. The engine valve timing apparatus according to claim 17, wherein said pivot pin is rotatably inserted within said bush.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-403155 |
Dec 2000 |
JP |
|
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
Country |
7-71543 |
Mar 1995 |
JP |