Note: Descriptions are shown in the official language in which they were submitted.
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POWER UNIT FOR VEHICLE
FIELD OF THE INVENTION
The present invention relates to a power unit for a vehicle having a
crankcase, a
crankshaft rotatably supported to the crankcase, a power transmission path for
transmitting a rotational drive force of the crankshaft to a drive wheel, a
clutch
provided in the power transmission path for switching between the connection
and disconnection of the transmission of power, and a clutch actuator mounted
on an engine body for controlling the switching between an engaged condition
and disengaged condition of the clutch.
BACKGROUND OF THE INVENTION
Such a power unit for a vehicle is known from Japanese Patent Laid-Open No.
Hei 11-222043, for example.
In the power unit disclosed in Japanese Patent Laid-Open No. Hei 11-222043, a
clutch actuator is provided on a rearmost portion of an engine body, so that
the
longitudinal size of the engine body tends to be increased and the
longitudinal
size of a vehicle body accordingly tends to be increased.
It is accordingly an object of the present invention to provide a power unit
for a
vehicle which can avoid an increase in longitudinal size of an engine body and
a
vehicle body due to the provision of a clutch actuator.
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SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a power unit for a
vehicle having a crankcase, a crankshaft rotatably supported to the crankcase,
a
power transmission path for transmitting a rotational drive force of the
crankshaft to a drive wheel, a clutch provided in the power transmission path
for
switching between the connection and disconnection of the transmission of
power, a clutch cover joined to a side portion of the crankcase, a clutch
chamber
formed between the crankcase and the clutch cover for accommodating the
clutch, an engine body including the crankcase and the clutch cover, and a
clutch
actuator mounted on the engine body for controlling the switching between an
engaged condition and disengaged condition of the clutch, wherein the clutch
actuator is provided on an upper portion of the clutch cover.
According to the present invention, the clutch cover is joined to the side
portion
of the crankcase to define the clutch chamber for accommodating the clutch
between the crankcase and the clutch cover, and the clutch actuator is
provided
on the upper portion of the clutch cover. Accordingly, the clutch actuator can
be
located by effectively utilizing the space above the clutch cover as avoiding
an
increase in longitudinal size of the engine body and the vehicle body.
Further,
the distance between the clutch and the clutch actuator is short, so that the
path
for transmitting a control force from the clutch actuator to the clutch can be
made
compact. Further, the clutch actuator can readily receive a running wind
during
running of the vehicle, so that the cooling effect for the clutch actuator can
be
improved.
In accordance with an aspect of the invention including the configuration as
defined above, the engine body further includes a cylinder block joined to the
crankcase, and the clutch actuator is located so that at least a part of the
clutch
actuator overlaps the cylinder block as viewed in side elevation of the
vehicle.
According to this aspect of the invention, at least a part of the clutch
actuator is
located on one lateral side of the cylinder block. Accordingly, the clutch
actuator
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can more readily receive a running wind, so that the cooling effect for the
clutch
actuator can be more improved.
In accordance with another aspect of the invention including the configuration
as
defined above, the clutch actuator is positioned inside of the laterally
outermost
end of the clutch cover.
According to this aspect of the invention, the projection of the clutch
actuator
from the engine body in the lateral direction can be avoided to thereby
prevent
an increase in lateral size of the engine.
In accordance with yet another aspect of the invention including the
configuration as defined above, the outer surface of the upper portion of the
clutch cover has a mounting seat for mounting the clutch actuator, the
mounting
seat being inclined laterally inward to the upper side, so that the clutch
actuator
is inclined laterally inward to the upper side along the upper portion of the
clutch cover.
According to this aspect of the invention, the projection of the clutch
actuator
from the clutch cover can be suppressed to thereby contribute to a reduction
in
overall size of the engine.
In accordance with a further aspect of the invention including the
configuration
as defined above, the crankcase is composed of an upper case half and a lower
case half joined to each other, and the clutch cover is composed of an upper
cover half integral with the upper case half and a lower cover half integral
with
the lower case half, the upper cover half and the lower cover half being
joined to
each other to form the clutch cover by joining the upper case half and the
lower
case half.
According to this aspect of the invention, the clutch cover is integral with
the
crankcase. That is, no separate clutch cover is required, so that the number
of
parts can be reduced.
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In accordance with another aspect of the invention including the configuration
as
defined above, the clutch actuator mounted on the upper portion of the clutch
cover controls the oil pressure applied to the clutch for switching between
the
connection and disconnection of the transmission of power according to the
application and cancellation of hydraulic pressure, and the clutch cover is
formed
with an oil passage constituting at least a part of a hydraulic path for
connecting
the clutch actuator and the clutch.
According to this aspect of the invention, a mechanism for operating the
clutch
can be configured compactly in the vicinity of the clutch cover, and the
maintainability of this mechanism can be improved owing to such a compact
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings, wherein:
FIG. 1 is a partially cutaway, left side view of a power unit according to a
first
preferred embodiment of the present invention.
FIG. 2 is a right side view of the power unit shown in FIG. 1.
FIG. 3 is a cross section taken along the line 3-3 in FIG. 1.
FIG. 4 is an enlarged view of an essential part shown in FIG. 3.
FIG. 5 is a view similar to FIG. 2, showing a modification of the first
preferred
embodiment.
FIG. 6 is a right side view of a power unit according to a second preferred
embodiment of the present invention.
FIG. 7 is a view taken in the direction shown by an arrow 7 in FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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Some preferred embodiments of the present invention will now be described
with reference to the attached drawings.
FIGS. 1 to 4 show a first preferred embodiment of the present invention,
wherein
FIG. 1 is a partially cutaway, left side view of a power unit PA according to
the
first preferred embodiment, FIG. 2 is a right side view of the power unit PA,
FIG.
3 is a cross section taken along the line 3-3 in FIG. 1, and FIG. 4 is an
enlarged
view of an essential part shown in FIG. 3.
Referring now to FIGS. 1 and 2, the power unit PA is composed generally of an
engine EA and a transmission TA for transmitting power from the engine EA as
shifting. The power unit PA is adapted to be mounted on a vehicle such as a
motorcycle. The engine EA has an engine body 11, which includes a crankcase 13
for rotatably supporting a crankshaft 12 extending in the lateral direction of
the
motorcycle, a cylinder block 14 joined to the crankcase 13 and having a
cylinder
bore 17 in which a piston 18 connected through a connecting rod 19 to the
crankshaft 12 is slidably fitted, a cylinder head 15 joined to the cylinder
block 14
so that a combustion chamber 20 to which the top of the piston 18 is exposed
is
formed between the cylinder block 14 and the cylinder head 15, and a head
cover
16 joined to the cylinder head 15.
The crankcase 13 is composed of an upper case half 13a and a lower case half
13b
joined to each other. The upper case half 13a is formed integrally with the
cylinder block 14. The axis of the crankshaft 12 lies on the plane formed by a
joint surface between the upper case half 13a and the lower case half 13b.
The axis C of the cylinder bore 17 is inclined frontward in the condition
where
the power unit PA is mounted on the motorcycle. An intake valve 21 and an
exhaust valve 22 are operatively provided in the cylinder head 15, and a valve
train 23 for operating the intake valve 21 and the exhaust valve 22 is
accommodated in the space defined between the cylinder head 15 and the head
cover 16.
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Referring next to FIG. 3, the transmission TA is composed of a gear shifting
mechanism 25 and first and second clutches 37 and 38 provided between the gear
shifting mechanism 25 and the crankshaft 12. The first and second clutches 37
and 38 function to switch between an engaged condition where the power from
the crankshaft 12 is transmitted to the gear shifting mechanism 25 and a
disengaged condition where the transmission of power from the crankshaft 12 to
the gear shifting mechanism 25 is cut off according to the application or
cancellation of hydraulic pressure. The first and second clutches 37 and 38
are
located in a power transmission path for transmitting a rotational drive force
of
the crankshaft 12 to a drive wheel, i.e., a rear wheel (not shown) of the
motorcycle.
The gear shifting mechanism 25 is accommodated in the crankcase 13 and
includes a plurality of gear trains respectively corresponding to a plurality
of
shift positions, e.g., a first speed gear train G1, a second speed gear train
G2, a
third speed gear train G3, a fourth speed gear train G4, a fifth speed gear
train
G5, and a sixth speed gear train G6, which can be selectively established.
More
specifically, the second, fourth, and sixth speed gear trains G2, G4, and G6
are
provided between a first main shaft 26 and a counter shaft 28 connected to the
rear wheel. The first, third, and fifth speed gear trains G1, G3, and G5 are
provided between a second main shaft 27 and the counter shaft 28. The second
main shaft 27 coaxially extends through the first main shaft 26 so as to be
rotatable relative thereto.
The crankcase 13 has a pair of side walls 13c and 13d opposed to each other
with
a given space in the lateral direction along the axis of the crankshaft 12.
The first
main shaft 26 is cylindrical and has an axis parallel to the axis of the
crankshaft
12. The first main shaft 26 is rotatably inserted at its intermediate portion
through the right side wall 13c of the crankcase 13 in such a manner that a
ball
bearing 29 is interposed between the right side wall 13c and the first main
shaft
26. The second main shaft 27 has the same axis as that of the first main shaft
26
parallel to the axis of the crankshaft 12. The second main shaft 27 is
inserted
through the first main shaft 26 in such a manner that the axial position of
the
second main shaft 27 relative to the first main shaft 26 is fixed and that the
first
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and second main shafts 26 and 27 are rotatable relative to each other. That
is, a
plurality of needle bearings 30 are interposed between the first main shaft 26
and
the second main shaft 27. The second main shaft 27 is rotatably supported at
its
left end portion through a ball bearing 31 to the left side wall 13d of the
crankcase 13.
The counter shaft 28 has an axis parallel to the axis of the crankshaft 12.
The
counter shaft 28 is rotatably supported at its right end portion through a
ball
bearing 32 to the right side wall 13c. The left end portion of the counter
shaft 28
is rotatably inserted through the left side wall 13d in such a manner that a
ball
bearing 33 and an annular seal member 34 are interposed between the left side
wall 13d and the counter shaft 28. A drive sprocket 35 is fixed to the
projecting
end portion of the counter shaft 28 projecting leftward from the left side
wall
13d, and a chain 36 for transmitting a drive force from the counter shaft 28
to the
rear wheel is wrapped around the drive sprocket 35.
Referring also to FIG. 4, a clutch cover 65 is joined to a right side portion
of the
crankcase 13 as viewed in a forward running direction of the motorcycle. A
clutch chamber 45 is defined between the crankcase 13 and the clutch cover 65.
The first and second clutches 37 and 38 are accommodated in the clutch chamber
45.
The first clutch 37 is provided between the crankshaft 12 and the right end
portion of the first main shaft 26, and the second clutch 38 is provided
between
the crankshaft 12 and the right end portion of the second main shaft 27. The
drive force from the crankshaft 12 is input through a primary speed reduction
device 40 and a damper spring 41 to a common outer member 39 of the first and
second clutches 37 and 38. The primary speed reduction device 40 is composed
of a drive gear 42 provided on the crankshaft 12 and a driven gear 43
relatively
rotatably supported to the first main shaft 26 and meshing with the drive gear
42.
The driven gear 43 is connected through the damper spring 41 to the outer
member 39.
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The first clutch 37 includes the outer member 39, a first inner member 46
coaxially surrounded by the outer member 39 and relatively nonrotatably
connected to the first main shaft 26, a plurality of first friction plates 47
relatively
nonrotatably engaged with the outer member 39, a plurality of second friction
plates 48 relatively nonrotatably engaged with the first inner member 46 and
arranged in alternate relationship with the first friction plates 47, a first
pressure
receiving plate 49 formed integrally with the first inner member 46 so as to
be
opposed to the stack of the first and second friction plates 47 and 48, a
first piston
50 located axially opposite to the first pressure receiving plate 49 in such a
manner that the stack of the first and second friction plates 47 and 48 is
interposed between the first piston 50 and the first pressure receiving plate
49,
and a first spring 51 for biasing the first piston 50.
A first end wall member 53 is fixedly mounted on the first inner member 46 in
such a manner that a first oil pressure chamber 52 is defined between the back
surface of the first piston 50 and the first end wall member 53. With an
increase
in oil pressure in the first oil pressure chamber 52, the first piston 50 is
moved to
apply pressure to the stack of the first and second friction plates 47 and 48
against the first pressure receiving plate 49, thereby obtaining the engaged
condition where the power from the crankshaft 12 is transmitted through the
outer member 39, the first and second friction plates 47 and 48, and the first
inner
member 46 to the first main shaft 26. On the other hand, a first canceler
chamber
54 is defined between the first inner member 46 and the front surface of the
first
piston 50. The first spring 51 is accommodated in the first canceler chamber
54 so
as to bias the first piston 50 in such a direction that the volume of the
first oil
pressure chamber 52 is decreased.
The first canceler chamber 54 is in communication with a first oil line 55
formed
in the second main shaft 27 so as to extend coaxially therewith. The first oil
line
55 functions to supply a lubricating oil to various portions of the gear
shifting
mechanism 25 and to between the first and second main shafts 26 and 27. Even
when a centrifugal force due to rotation is applied to the oil in the first
oil
pressure chamber 52 in its pressure reduced condition to move the first piston
50,
a centrifugal force is similarly applied to the oil in the first canceler
chamber 54 to
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resist the movement of the first piston 50, so that such undesired movement of
the first piston 50 in the pressure applying direction to the stack of the
first and
second friction plates 47 and 48 can be avoided by the first canceler chamber
54.
The second clutch 38 is arranged axially adjacent to the first clutch 37 in
the axial
direction of the second main shaft 27 in such a manner that the first clutch
37 is
interposed between the second clutch 38 and the primary speed reduction device
40. As similar to the first clutch 37, the second clutch 38 includes the outer
member 39, a second inner member 56 coaxially surrounded by the outer
member 39 and relatively nonrotatably connected to the second main shaft 27, a
plurality of third friction plates 57 relatively nonrotatably engaged with the
outer
member 39, a plurality of fourth friction plates 58 relatively nonrotatably
engaged with the second inner member 56 and arranged in alternate relationship
with the third friction plates 57, a second pressure receiving plate 59 formed
integrally with the second inner member 56 so as to be opposed to the stack of
the third and fourth friction plates 57 and 58, a second piston 60 located
axially
opposite to the second pressure receiving plate 59 in such a manner that the
stack
of the third and fourth friction plates 57 and 58 is interposed between the
second
piston 60 and the second pressure receiving plate 59, and a second spring 61
for
biasing the second piston 60.
A second end wall member 63 is fixedly mounted on the second inner member 56
in such a manner that a second oil pressure chamber 62 is defined between the
back surface of the second piston 60 and the second end wall member 63. With
an increase in oil pressure in the second oil pressure chamber 62, the second
piston 60 is moved to apply pressure to the stack of the third and fourth
friction
plates 57 and 58 against the second pressure receiving plate 59, thereby
obtaining
the engaged condition where the power from the crankshaft 12 is transmitted
through the outer member 39, to the second main shaft 27. On the other hand, a
second canceler chamber 64 is defined between the second inner member 56 and
the front surface of the second piston 60. The second spring 61 is
accommodated
in the second canceler chamber 64 so as to bias the second piston 60 in such a
direction that the volume of the second oil pressure chamber 62 is decreased.
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The second canceler chamber 64 is in communication with a second oil line 71
to
be hereinafter described. Even when a centrifugal force due to rotation is
applied
to the oil in the second oil pressure chamber 62 in its pressure reduced
condition
to move the second piston 60, a centrifugal force is similarly applied to the
oil in
the second canceler chamber 64 to resist the movement of the second piston 60,
so that such undesired movement of the second piston 60 in the pressure
applying direction to the stack of the third and fourth friction plates 57 and
58
can be avoided by the second canceler chamber 64.
First, second, and third partition members 66, 67, and 68 are mounted on the
inside surface of the clutch cover 65 covering the first and second clutches
37 and
38. The first, second, and third partition members 66, 67, and 68 are arranged
in
this order from the right side as viewed in the forward running direction of
the
motorcycle. A first cylindrical member 70 for forming a first oil passage 69
communicating with the first oil pressure chamber 52 of the first clutch 37 is
provided between the second main shaft 27 and the first partition member 66. A
second cylindrical member 72 is provided between the second main shaft 27 and
the second partition member 67 so as to coaxially surround the first
cylindrical
member 70 in such a manner that an annular second oil line 71 communicating
with the second canceler chamber 64 of the second clutch 38 is formed between
the first cylindrical member 70 and the second cylindrical member 72. A third
cylindrical member 74 is provided between the second main shaft 27 and the
third partition member 68 so as to coaxially surround the second cylindrical
member 72 in such a manner that an annular second oil passage 73
communicating with the second oil pressure chamber 62 of the second clutch 38
is formed between the second cylindrical member 72 and the third cylindrical
member 73.
The first and second oil passages 69 and 73 are connected to a clutch actuator
76,
so that the oil pressures in the first and second oil passages 69 and 73, or
in the
first and second oil pressure chambers 52 and 62 are controlled by the clutch
actuator 76 to thereby control the switching between the engaged condition and
the disengaged condition of each of the first and second clutches 37 and 38.
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The clutch actuator 76 is composed of a first electromagnetic control valve 77
for
switching between the application and cancellation of the oil pressure to the
first
oil pressure chamber 52 of the first clutch 37 and a second electromagnetic
control valve 78 for switching between the application and cancellation of the
oil
pressure to the second oil pressure chamber 62 of the second clutch 38. The
clutch cover 65 is integrally formed with a mounting plate portion 65a
extending
upward from an upper portion of the clutch cover 65. A supporting plate 79 for
commonly supporting the first and second electromagnetic control valves 77 and
78 is fixedly mounted on the mounting plate portion 65a of the clutch cover 65
by
means of a plurality of bolts 80.
The clutch actuator 76 is mounted on the upper portion of the clutch cover 65
in
such a manner that at least a part of the clutch actuator 76 overlaps the
cylinder
block 14 as viewed in side elevation of the vehicle. More specifically, as
shown in
FIG. 2, the first and second electromagnetic control valves 77 and 78 are
mounted
on the upper portion of the clutch cover 65 in such a manner that a part of
solenoid portions 77a and 78a respectively constituting the first and second
electromagnetic control valves 77 and 78 overlaps the cylinder block 14 as
viewed in side elevation of the motorcycle.
As shown in FIG. 2, an oil pump 81 adapted to be operated by the power
transmitted from the crankshaft 12 is accommodated in the crankcase 13 at a
position below the gear shifting mechanism 25. A third oil passage 82 for
supplying the oil discharged from the oil pump 81 to the first and second
electromagnetic control valves 77 and 78 is formed in the clutch cover 65. The
clutch cover 65 is further formed with an oil passage constituting at least a
part of
a hydraulic path for connecting the first and second clutches 37 and 38 to the
clutch actuator 76. More specifically, the clutch cover 65 is formed with a
fourth
oil passage 83 for connecting the first oil passage 69 communicating with the
first
oil pressure chamber 52 of the first clutch 37 to the first electromagnetic
control
valve 77 and is also formed with a fifth oil passage 84 for connecting the
second
oil passage 73 communicating with the second oil pressure chamber 62 of the
second clutch 38 to the second electromagnetic control valve 78.
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As shown in FIG. 3, the fourth speed gear train G4, the sixth speed gear train
G6,
and the second speed gear train G2 are juxtaposed in this order from the
opposite side of the first and second clutches 37 and 38 so as to be provided
between the first main shaft 26 and the counter shaft 28. The second speed
gear
train G2 is composed of a second speed drive gear 87 formed integrally with
the
first main shaft 26 and a second speed driven gear 88 relatively rotatably
supported to the counter shaft 28 and meshing with the second speed drive gear
87. The sixth speed gear train G6 is composed of a sixth speed drive gear 89
relatively rotatably supported to the first main shaft 26 and a sixth speed
driven
gear 90 axially slidably and relatively nonrotatably supported to the counter
shaft 28 and meshing with the sixth speed drive gear 89. The fourth speed gear
train G4 is composed of a fourth speed drive gear 91 axially slidably and
relatively nonrotatably supported to the first main shaft 26 and a fourth
speed
driven gear 92 relatively rotatably supported to the counter shaft 28 and
meshing
with the fourth speed drive gear 91.
A first shifter 93 is axially slidably and relatively nonrotatably supported
to the
counter shaft 28 between the second speed driven gear 88 and the fourth speed
driven gear 92 in such a manner as to switch among a condition where the first
shifter 93 is engaged with the second speed driven gear 88, a condition where
the
first shifter 93 is engaged with the fourth speed driven gear 92, and a
neutral
condition where the first shifter 93 is engaged with neither the second gear
driven gear 88 nor the fourth speed driven gear 92. The first shifter 93 is
integrally formed with the sixth speed driven gear 90. Further, a second
shifter
94 is axially slidably and relatively nonrotatably supported to the first main
shaft
26. The second shifter 94 is integrally formed with the fourth speed drive
gear
91. The second shifter 94 is movable in the axial direction of the first main
shaft
26 so as to switch between a condition where the second shifter 94 is engaged
with the sixth speed drive gear 89 and a condition where the second shifter 94
is
disengaged from the sixth speed drive gear 89.
When the first shifter 93 is brought into engagement with the second speed
driven gear 88 in the condition where the second shifter 94 is disengaged from
the sixth speed drive gear 89, the second speed gear train G2 is established.
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When the first shifter 93 is brought into engagement with the fourth speed
driven gear 92 in the condition where the second shifter 94 is disengaged from
the sixth speed drive gear 89, the fourth speed gear train G4 is established.
When
the second shifter 94 is brought into engagement with the sixth speed drive
gear
89 in the neutral condition of the first shifter 93, the sixth speed gear
train G6 is
established.
The first speed gear train G1, the fifth speed gear train G5, and the third
speed
gear train G3 are juxtaposed in this order from the opposite side of the first
and
second clutches 37 and 38 in FIG. 3 so as to be provided between the counter
shaft 28 and a left portion of the second main shaft 27 projecting leftward
from
the left end of the first main shaft 26. The third speed gear train G3 is
composed
of a third speed drive gear 95 axially slidably and relatively nonrotatably
supported to the second main shaft 27 and a third speed driven gear 96
relatively
rotatably supported to the counter shaft 28 and meshing with the third speed
drive gear 95. The fifth speed gear train G5 is composed of a fifth speed
drive
gear 97 relatively rotatably supported to the second main shaft 27 and a fifth
speed driven gear 98 axially slidably and relatively nonrotatably supported to
the counter shaft 28 and meshing with the fifth speed drive gear 97. The first
speed gear train G1 is composed of a first speed drive gear 99 formed
integrally
with the second main shaft 27 and a first speed driven gear 100 relatively
rotatably supported to the counter shaft 28 and meshing with the first speed
drive gear 99.
A third shifter 101 is axially slidably and relatively nonrotatably supported
to the
second main shaft 27. The third shifter 101 is integrally formed with the
third
speed drive gear 95. The third shifter 101 is movable in the axial direction
of the
second main shaft 27 so as to switch between a condition where the third
shifter
101 is engaged with the fifth speed drive gear 97 and a condition where the
third
shifter 101 is disengaged from the fifth speed drive gear 97. A fourth shifter
102
is axially slidably and relatively nonrotatably supported to the counter shaft
28
between the third speed driven gear 96 and the first speed driven gear 100 so
as
to switch among a condition where the fourth shifter 102 is engaged with the
third speed driven gear 96, a condition where the fourth shifter 102 is
engaged
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with the first speed driven gear 100, and a neutral condition where the fourth
shifter 102 is engaged with neither the third speed driven gear 96 nor the
first
speed driven gear 100. The fourth shifter 102 is integrally formed with the
fifth
speed driven gear 98.
When the fourth shifter 102 is brought into engagement with the first speed
driven gear 100 in the condition where the third shifter 101 is disengaged
from
the fifth speed drive gear 97, the first speed gear train G1 is established.
When
the fourth shifter 102 is brought into engagement with the third speed driven
gear 96 in the condition where the third shifter 101 is disengaged from the
fifth
speed drive gear 97, the third speed gear train G3 is established. When the
third
shifter 101 is brought into engagement with the fifth speed drive gear 97 in
the
neutral condition of the fourth shifter 102, the fifth speed gear train G5 is
established.
The first, second, third, and fourth shifters 93, 94, 101, and 102 are
rotatably
retained to first, second, third, and fourth shift forks 103, 104, 105, and
106,
respectively. The first, second, third, and fourth shift forks 103, 104, 105,
and 106
are selectively driven in the axial direction of the first and second main
shafts 26
and 27 and the counter shaft 28, thereby axially moving the first, second,
third,
and fourth shifters 93, 94, 101, and 102.
The first to fourth shift forks 103 to 106 are engaged with the outer
circumference
of a shift drum 107 (see FIG. 1) rotatably supported to the crankcase 13 and
having an axis parallel to the axis of the crankshaft 12. By rotating the
shift drum
107, the first to fourth shift forks 103 to 106 are selectively slid.
The shift drum 107 is rotatably driven by a shift actuator 108 having an
electric
motor 109. The shift actuator 108 is mounted on the crankcase 13 on the left
side
opposite to the clutch cover 65.
The operation of the first preferred embodiment mentioned above will now be
described. The first and second clutches 37 and 38 are accommodated in the
clutch chamber 45 formed between the crankcase 13 and the clutch cover 65
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joined to the right side portion of the crankcase 13 as viewed in the forward
running direction of the motorcycle. Further, the clutch actuator 76 for
controlling the switching between the engaged condition and disengaged
condition of the first and second clutches 37 and 38 is provided on the upper
portion of the clutch cover 65.
Accordingly, the clutch actuator 76 can be located by effectively utilizing
the
space above the clutch cover 65 as avoiding an increase in longitudinal size
of the
engine body 11 and the vehicle body. Further, the distance between the first
and
second clutches 37 and 38 and the clutch actuator 76 is short, so that the
path for
transmitting a control force from the clutch actuator 76 to the first and
second
clutches 37 and 38 can be made compact. Further, the clutch actuator 76 can
readily receive a running wind during running of the vehicle, so that the
cooling
effect for the clutch actuator 76 can be improved.
Further, the clutch cover 65 is formed with an oil passage constituting at
least a
part of a hydraulic path for connecting the first and second clutches 37 and
38 for
switching between the connection and disconnection of the transmission of
power according to the application or cancellation of hydraulic pressure to
the
clutch actuator 76 for controlling the oil pressures applied to the first and
second
clutches 37 and 38. More specifically, the clutch cover 65 is formed with the
fourth oil passage 83 for connecting the first oil passage 69 communicating
with
the first oil pressure chamber 52 of the first clutch 37 to the first
electromagnetic
control valve 77 and is also formed with the fifth oil passage 84 for
connecting
the second oil passage 73 communicating with the second oil pressure chamber
62 of the second clutch 38 to the second electromagnetic control valve 78.
Accordingly, a mechanism for operating the first and second clutches 37 and 38
can be configured compactly in the vicinity of the clutch cover 65, and the
maintainability of this mechanism can be improved owing to such a compact
configuration.
Further, the clutch actuator 76 is located in such a manner that at least a
part of
the clutch actuator 76 overlaps the cylinder block 14 as viewed in side
elevation
of the vehicle. Accordingly, the clutch actuator 76 can more readily receive a
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running wind, so that the cooling effect for the clutch actuator 76 can be
more
improved.
FIG. 5 shows a modification of the first preferred embodiment, wherein
substantially the same parts as those of the first preferred embodiment are
denoted by the same reference numerals, and the detailed description thereof
will be omitted herein.
The power unit PA' is composed generally of an engine EA' and a transmission
TA for transmitting power from the engine EA' as shifting. A clutch cover 65'
constitutes a part of an engine body 11' of the engine EA' and is joined to a
crankcase 13. The clutch cover 65' is composed of an upper cover half 85
integral
with the upper case half 13a of the crankcase 13 and a lower cover half 86
integral with the lower case half 13b of the crankcase 13. The upper case half
13a
and the lower case half 13b are joined to each other to thereby form the
crankcase
13, thus forming the clutch cover 65'. A clutch actuator 76 is mounted on an
upper portion of the clutch cover 65', i.e., an upper portion of the upper
cover
half 85.
According to this modification, the clutch cover 65' is formed by a part of
the
crankcase 13, so that any members for constituting the clutch cover 65' are
not
necessary, so that the number of parts can be reduced.
FIGS. 6 and 7 show a second preferred embodiment of the present invention,
wherein FIG. 6 is a right side view of a power unit PB according to the second
preferred embodiment, and FIG. 7 is a view taken in the direction shown by an
arrow 7 in FIG. 6. In FIGS. 6 and 7, substantially the same parts as those of
the
first preferred embodiment are denoted by the same reference numerals, and the
detailed description thereof will be omitted herein.
Referring now to FIG. 6, the power unit PB is composed generally of an engine
EB and a transmission TB for transmitting power from the engine EB as
shifting.
The power unit PB is adapted to be mounted on a vehicle such as a motorcycle.
The engine EB has a V-shaped engine body 111 including a front bank BF located
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at a front position in the condition that the engine EB is mounted on the
motorcycle and a rear bank BR located on the rear side of the front bank BF. A
crankshaft 112 extending in the lateral direction of the motorcycle is
rotatably
supported to a crankcase 113 common to the front and rear banks BF and BR.
The crankcase 113 is composed of an upper case half 113a and a lower case half
113b joined to each other. Front and rear cylinder blocks 114F and 114R are
integrally formed to have a V-shaped configuration and joined to the crankcase
113. The front bank BF is composed of the front cylinder block 114F, a front
cylinder head 115F joined to the front cylinder block 114F, and a front head
cover
116F joined to the front cylinder head 115F. Similarly, the rear bank BR is
composed of the rear cylinder block 114R, a rear cylinder head 115R joined to
the
rear cylinder block 114R, and a rear head cover 116R joined to the rear
cylinder
head 115R.
The transmission TB is similar to the transmission TA in the first preferred
embodiment. That is, front and second clutches 37 and 38 for switching between
an engaged condition and a disengaged condition according to the application
or
cancellation of hydraulic pressure are located in a power transmission path
for
transmitting a rotational drive force of the crankshaft 112 to a drive wheel,
i.e., a
rear wheel (not shown) of the motorcycle. Further, a clutch cover 118 is
joined to
a right side portion of the crankcase 113 as viewed in the forward running
direction of the motorcycle, and a clutch actuator 76 for controlling the
switching
between the engaged condition and disengaged condition of the first and second
clutches 37 and 38 is mounted on an upper portion of the clutch cover 118 by
means of a plurality of bolts 80.
As shown in FIG. 7, the outer surface of the upper portion of the clutch cover
118
has a flat mounting seat 118a for mounting the supporting plate 79 for the
clutch
actuator 76 by using the bolts 80. The flat mounting seat 118a is inclined
laterally
inward to the upper side. Accordingly, the clutch actuator 76 mounted on the
upper portion of the clutch cover 118 is inclined laterally inward to the
upper
side along the upper portion of the clutch cover 118. Furthermore, the clutch
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actuator 76 is positioned inside of the laterally outermost end of the clutch
cover
118.
Further, the clutch actuator 76 is located in such a manner that at least a
part of
the clutch actuator 76 overlaps the front and rear cylinder blocks 114F and
114R
as viewed in side elevation of the vehicle.
According to the second preferred embodiment, the clutch actuator 76 can be
located by effectively utilizing the space above the clutch cover 118 as
avoiding
an increase in longitudinal size of the engine body 111 and the vehicle body.
Further, the path for transmitting a control force from the clutch actuator 76
to
the first and second clutches 37 and 38 can be made compact. Further, the
clutch
actuator 76 can readily receive a running wind during running of the vehicle,
so
that the cooling effect for the clutch actuator 76 can be improved.
Further, a mechanism for operating the first and second clutches 37 and 38 can
be
configured compactly in the vicinity of the clutch cover 118, and the
maintainability of this mechanism can be improved owing to such a compact
configuration. Further, at least a part of the clutch actuator 76 overlaps the
front
and rear cylinder blocks 114F and 114R as viewed in side elevation of the
vehicle.
Accordingly, the clutch actuator 76 can more readily receive a running wind,
so
that the cooling effect for the clutch actuator 76 can be more improved.
Further, the clutch actuator 76 is positioned inside of the laterally
outermost end
of the clutch cover 118. Accordingly, the projection of the clutch actuator 76
from
the engine body 111 in the lateral direction can be avoided to thereby prevent
an
increase in lateral size of the engine EB. Further, the clutch actuator 76 is
inclined
laterally inward along the upper portion of the clutch cover 118. Accordingly,
the projection of the clutch actuator 76 from the clutch cover 118 can be
suppressed to thereby contribute to a reduction in overall size of the engine
EB.
While the specific preferred embodiments of the present invention have been
described above, it should be noted that the present invention is not limited
to
the above preferred embodiments, but various modifications may be made
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without departing from the scope of the present invention as defined in the
appended claims.
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