U.S. patent application number 09/866716 was filed with the patent office on 2001-12-06 for power unit of motorcycle.
This patent application is currently assigned to Suzuki Kabushiki Kaisha. Invention is credited to Tsutsumikoshi, Shinobu.
Application Number | 20010047901 09/866716 |
Document ID | / |
Family ID | 18664880 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047901 |
Kind Code |
A1 |
Tsutsumikoshi, Shinobu |
December 6, 2001 |
Power unit of motorcycle
Abstract
A power unit of the motorcycle is provided with an engine unit
in which a counter shaft is pivoted to a rear portion in a casing
of an engine body provided with a crankshaft disposed along a
motorcycle body width direction and a bracket having a fitting hole
extending rearward so as to pass through in the width direction is
formed in a rear portion outside the casing, a transmission unit
and a bevel unit which are pivoted in a manner to be independent
from the engine unit. One side surface of a front portion of the
transmission unit is fixed to one side surface of a rear portion of
the casing in the engine unit so as to connect the counter shaft to
the input shaft to be integrally rotatable, the same side surface
of the rear portion in the transmission unit is fitted and fixed to
one side surface of the bracket so as to fit and fix the bevel unit
to another side surface of the bracket. Thus, the output shaft is
connected to a bevel input shaft to be integrally rotatable.
Inventors: |
Tsutsumikoshi, Shinobu;
(Hamamatsu-shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
Suzuki Kabushiki Kaisha
300, Takatsuka-sho Shizuoka-ken
Hamamatsu-shi
JP
|
Family ID: |
18664880 |
Appl. No.: |
09/866716 |
Filed: |
May 30, 2001 |
Current U.S.
Class: |
180/219 |
Current CPC
Class: |
B62K 11/10 20130101;
F02B 2275/18 20130101; F02B 61/02 20130101; F02F 2001/245 20130101;
F02B 75/20 20130101; F02B 2075/1808 20130101 |
Class at
Publication: |
180/219 |
International
Class: |
B62K 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2000 |
JP |
2000-160732 |
Claims
What is claimed is:
1. A power unit of a motorcycle comprising: an engine unit in which
a counter shaft rotating, while interlocking with a crankshaft, is
supported in parallel at a rear portion in a casing of an engine
body provided with the crankshaft disposed along a width direction
of a motorcycle body and a bracket portion having a fitting hole
extending rearward so as to pass through in the width direction of
the motorcycle body is formed in a rear portion outside the casing;
a transmission unit in which an input shaft and an output shaft are
pivoted at front and rear portions in another casing different from
the casing of the engine unit so as to constitute a transmission
device; and a bevel unit receiving a bevel input shaft disposed
along the width direction of the motorcycle body, a bevel output
shaft disposed along a longitudinal direction of the motorcycle
body and a bevel gear which are all disposed in a further casing so
as to take out an engine output rearward from the bevel output
shaft, wherein one side surface of a front portion, in the
longitudinal direction of the motorcycle body, of the transmission
unit is fixed to one side surface of a rear portion of the casing
in the engine unit so as to connect the counter shaft to the input
shaft to be integrally rotatable, a bearing boss of the output
shaft is closely fitted to the fitting hole in the bracket portion
with one side surface of the rear portion of the transmission unit
being disposed adjacent to one side surface of the bracket portion
of the engine unit, and the bearing boss of the bevel input shaft
is closely fitted and fixed to the fitting hole of the bracket
portion with the bevel unit being disposed adjacent to another side
surface of the bracket portion so as to connect the output shaft to
the bevel input shaft to be integrally rotatable.
2. A power unit of a motorcycle according to claim 1, wherein the
counter shaft receiving portion of the engine unit is arranged, in
an offset manner, close to one side with respect to a center line
of the motorcycle body in a plan view and the bracket portion is
extended to a rear portion thereof so as to provide a plan shape of
the engine unit to be a substantially L-shape and a plan shape of
the transmission unit to be a substantially L-shape to thereby
arrange the transmission unit on a side of the center line of the
motorcycle body in the bracket portion so as to assemble
substantially L-shaped portions of the engine unit and the
transmission unit with each other to provide a substantially
rectangular shape, and on the other hand, the bevel unit is
arranged on a side opposite to the center line of the vehicle body
in the bracket portion.
3. A power unit of a motorcycle according to claim 1, wherein the
bracket portion of the engine unit, the transmission unit and the
bevel unit are fastened together by a fastening member disposed
along the width direction of the motorcycle body.
4. A power unit of a motorcycle according to claim 1, wherein the
motorcycle body frame fixing portion of the power unit is formed to
the bracket portion of the engine unit.
5. A power unit of a motorcycle according to claim 1, wherein said
transmission device is a belt-type change gear device disposed in
the another casing having a three-piece structure.
6. A power unit of a motorcycle according to claim 5, wherein said
belt-type change gear device includes an input shaft supported in
parallel to the crankshaft of the engine unit and the input shaft
is operatively coupled with the bevel input shaft.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a power unit of a
motorcycle such as a scooter-type vehicle or the like.
[0002] Generally, the power unit of the scooter-type vehicle has a
structure in which a belt-type transmission unit (speed change
mechanism or change gear) is integrally connected to a rear portion
of an engine and a rear wheel is directly pivoted to a most rear
section of the transmission unit. A front portion of the power unit
is pivoted to a body frame of a motorcycle (which may be called
vehicle body frame, hereinlater) and a rear portion thereof is
suspended to the vehicle body frame by means of a shock absorber,
so that a whole of the power unit is swung entirely vertically
together with the rear wheel so as to achieve a part of a swing arm
of the rear wheel.
[0003] In accordance with the structure mentioned above, it becomes
advantageous that a capacity of a luggage space placed above the
power unit can be secured to be increased and a riding function
(running felling) can be improved by making an engine vibration
hard to be transmitted to the frame side. However, on the contrary,
since a weight of the whole of the power unit becomes heavy in the
case that a displacement of the engine is increased, a shared
weight of the rear wheel is increased, a weight may be improperly
distributed between front and rear wheels and a support rigidity of
the rear wheel becomes insufficient. In such case, arrangement or
layout of respective parts or elements of a motorcycle may be
restricted.
[0004] Then, as shown in Japanese Patent Laid-Open Publications
Nos. HEI 10-324287 (Prior Art 1) and HEI 11-129969 (Prior Art 2),
there have been developed a scooter-type vehicle in which an engine
and a transmission unit are fixed to a vehicle body frame side and
only a shaft drive apparatus extending rearward from the
transmission unit is made vertically swingable so as to drive the
rear wheel. Accordingly, it is possible to mount an engine
corresponding to a heavy load, which is the same as that in the
normal motorcycle to a front side of the vehicle body frame so as
to make a weight distribution between the front and rear wheels
proper.
[0005] However, in the structure described in the above Prior Art
1, since a drive pulley, a driven pulley, a belt and the like in
the transmission unit are exposed, the transmission is easily
damaged by foreign materials such as dirt, sands, stones or the
like splashed by the rear wheel during a running of a
motorcycle.
[0006] On the contrary, in the structure described in the above
Prior Art 2, since a drive pulley of the transmission unit is
coaxially provided in a crankshaft of an engine, a whole of the
transmission unit protrudes sideward. Accordingly, this apparatus
lacks a compact size.
[0007] Further, since the engine, the transmission and a bevel gear
mechanism corresponding to an output take-out portion are received
within one casing so as to be united, it is necessary to produce
and assemble all of the parts mentioned above at the same
production site, so that a productivity is significantly made
worse. Further, in the case of intending to change any one of
specifications such as an engine output, a gear ratio or the like,
it is necessary to change a whole of the unit, so that it is hard
to apply the unit to various kinds of vehicles. Additionally, in
the case of performing maintenance of any one portion, it is
necessary to disassemble a whole of the unit, which may deteriorate
the ease maintenance.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to substantially
eliminate disadvantages or inconveniences encountered in the prior
arts mentioned above and to provide a power unit of a motorcycle
capable of making a power unit compact, improving a productivity
thereof, making ease of maintenance, improving a manufacturing
quality and the like, and moreover, the present invention makes it
possible to be applied to various kinds of vehicles to reduce
processing man-hours. It also becomes possible to well secure a
rigidity of the power unit itself and a support rigidity of the
power unit to the vehicle body frame.
[0009] This and other objects can be achieved according to the
present invention by providing a power unit of a motorcycle
comprising:
[0010] an engine unit in which a counter shaft rotating while
interlocking with a crankshaft is supported in parallel at a rear
portion in a casing of an engine body provided with the crankshaft
disposed along a width direction of a motorcycle body, and a
bracket portion having a fitting hole extending rearward so as to
pass through in the width direction of the motorcycle body is
formed in a rear portion outside the casing;
[0011] a transmission unit in which an input shaft and an output
shaft are pivoted at front and rear portions in another casing
different from the casing of the engine unit so as to constitute a
transmission device; and
[0012] a bevel unit receiving a bevel input shaft disposed along
the width direction of the motorcycle body, a bevel output shaft
disposed along a longitudinal direction of the motorcycle body and
a bevel gear which are all disposed in a further casing so as to
take out an engine output rearward from the bevel output shaft,
[0013] wherein one side surface of a front portion, in the
longitudinal direction of the motorcycle body, of the transmission
unit is fixed to one side surface of a rear portion of the casing
in the engine unit so as to connect the counter shaft to the input
shaft to be integrally rotatable, a bearing boss of the output
shaft is closely fitted to the fitting hole in the bracket portion
with one side surface of the rear portion of the transmission unit
being disposed adjacent to one side surface of the bracket portion
of the engine unit, and the bearing boss of the bevel input shaft
is closely fitted and fixed to the fitting hole of the bracket
portion with the bevel unit being disposed adjacent to another side
surface of the bracket portion so as to connect the output shaft to
the bevel input shaft to be integrally rotatable.
[0014] In a preferred embodiment of the above aspect, the counter
shaft receiving portion of the engine unit is arranged, in an
offset manner, close to one side with respect to a center line of
the motorcycle body in a plan view and the bracket portion is
extended to a rear portion thereof so as to provide a plan shape of
the engine unit to be a substantially L shape and a plan shape of
the transmission unit is formed in a substantially L shape to
thereby arrange the transmission unit on a side of the center line
of the motorcycle body in the bracket portion so as to assemble
substantially L-shaped portions of the engine unit and the
transmission unit with each other to provide a substantially
rectangular shape, and on the other hand, the bevel unit is
arranged on a side opposite to the center line of the vehicle body
in the bracket portion.
[0015] The bracket portion of the engine unit, the transmission
unit and the bevel unit are fastened together by a fastening member
disposed along the width direction of the motorcycle body.
[0016] The motorcycle body frame fixing portion of the power unit
is formed to the bracket portion of the engine unit.
[0017] The transmission device is a belt-type change gear device
disposed in the another casing having a three-piece structure. The
belt-type change gear device includes an input shaft supported in
parallel to the crankshaft of the engine unit and the input shaft
is operatively coupled with the bevel input shaft.
[0018] According to the structures and characters of the power unit
of the motorcycle such as scooter-type vehicle of the present
invention mentioned above, since the engine unit, the transmission
unit and the bevel unit can be respectively manufactured in
different production sites, a productivity and ease of maintenance
of the power unit are improved and it is possible to apply to
various kinds of vehicles. Furthermore, since the structure is made
such that the transmission unit and the bevel unit are coaxially
fitted and fixed to the fitting hole of the bracket portion in the
engine unit, a manufacturing quality can be improved and processing
man-hours can be reduced, and further a rigidity of a whole of the
power unit is increased.
[0019] Furthermore, in accordance with the structure mentioned
above, since no dead space is generated between the engine unit and
the transmission unit, and there is no case that any one of the
transmission unit and the bevel unit arranged laterally at the back
of the engine unit protrudes widely to a side direction from a
lateral width of the engine unit, sizes in a longitudinal direction
and a width direction of the power unit can be made compact.
[0020] In comparison with the case that the transmission unit and
the bevel unit are respectively fastened by exclusive fastening
members, since the number of the fastening members is reduced, and
assembling man-hours can be reduced accordingly, a productivity of
the power unit can be improved.
[0021] Still furthermore, since the connecting portions of the
respective units constituting the power unit are fixed to the
vehicle body frame, the supporting rigidity of the whole of the
power unit can be increased.
[0022] As mentioned above, in summary, in accordance with the power
unit of the motorcycle of the present invention, it is possible to
make a power unit compact, to improve a productivity, ease of
maintenance, a manufacturing quality and the like, to make it
possible to be applied to various kinds of vehicles, to reduce
processing man-hours, and to secure a rigidity of the power unit
itself and a support rigidity of the power unit to the vehicle body
frame.
[0023] The nature and further characteristic features of the
present invention will be made more clear from the following
descriptions made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In the accompanying drawings:
[0025] FIG. 1 is a left side elevational view showing an embodiment
of a scooter-type motorcycle on which a power unit according to the
present invention is mounted;
[0026] FIG. 2 is a left side elevational view showing an internal
structure of the motorcycle;
[0027] FIG. 3 is a plan view of the motorcycle showing the internal
structure of the motorcycle;
[0028] FIG. 4 is a left side view of the power unit showing an
internal structure thereof;
[0029] FIG. 5 is a schematic plan view of the power unit;
[0030] FIG. 6 is a plan view of the power unit; and
[0031] FIG. 7 is a horizontal sectional view of a power unit of the
embodiment according to the present invention taken along a line
VII-VII in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] A description will be given of an embodiment in accordance
with the present invention with reference to the accompanying
drawings.
[0033] With reference to FIGS. 1 to 3, a motorcycle 1 is provided
with a vehicle body frame 2 made of a steel pipe. The vehicle body
frame 2 is provided with a head pipe 3 positioned in a front end
(left-side end in the longitudinal direction of the motorcycle
body, the same being applied hereinlater) thereof, a pair of right
and left down pipes 4, upper pipes 5 and middle pipes 6 extending
rearward from the head pipe 3, a rear pipe 7 and a rear stay 8
connected to a portion near a rear end of the down pipe 4, a pair
of right and left seat pipes 9, and a pair of right and left pivot
plates 10 positioned in a substantially central portion so as to
provide a substantially underbone-type structure. In this case, a
pair of right and left pipe members (4, 5, 6) are connected by a
plurality of bridge pipes 11, 12 . . . (the others are not shown)
extending in a width direction of the vehicle body (motorcycle
body).
[0034] A front fork 15 supporting a front wheel 14 is pivoted to
the head pipe 3 together with a handle bar 16 or the like, a pivot
shaft 17 is provided between the right and left pivot plates 10,
and a swing transmission unit 19 supporting a rear wheel 18 is
pivoted to the pivot shaft 17 so as to be suspended by a suspension
mechanism 20. Further, a power unit 21 is suspended and supported
by the down pipe 4, the middle pipe 6 and the pivot plate 10, and a
power thereof is transmitted to the rear wheel 18 through the swing
transmission unit 19.
[0035] An interval between the right and left middle pipes 6 is
made narrower than an interval between the down pipes 4. The middle
pipes 6 extend above the power unit 21 and the down pipes 4 extend
along both side portions of the power unit 21. Further, a seat
hinge 25 is provided in an upper end of a seat stay 24 extending
upward from the bridge pipe 11 provided near a bent point of the
middle pipe 6, and a front end of a seat 26 is supported to the
seat hinge 25. The seat 26 opens and closes around the seat hinge
25, and a fuel tank 27 and a luggage space 30 capable of receiving
helmets 28 and 29 and the like therein are formed below the seat
26.
[0036] A whole of the vehicle body is covered by a front cowling 32
and a frame cover 33 made of synthetic resin, so that internal
devices or equipments can be protected as well as an outer
appearance of the motorcycle 1 is improved. Furthermore, a pair of
right and left step boards 34 (refer to FIG. 1) positioned above
the down pipe 4 are integrally formed in the frame cover 33, and
the middle pipes 6 and the power unit 21 are received within a
center console 35 formed therebetween. An upper space of the center
console 35 forms a foot space 36 used when a rider rides on the
seat 26.
[0037] In this case, a radiator 37 for cooling an engine unit 41
mentioned below is provided in the down pipe 4 so as to be
positioned immediately at the rear portion of the front wheel 14,
and an exhaust muffler 38 connected to a cylinder head 46 of the
engine unit 41 is provided in a right side of the rear wheel
18.
[0038] Next, with reference to FIGS. 5 to 7, the power unit 21
according to the described embodiment is a composite body in which
the engine unit 41, a transmission unit 42 and a bevel unit 43 are
combined.
[0039] A casing 44 of the engine unit 41 has a structure in which a
head cover 45, a cylinder head 46, a cylinder block 47, a crankcase
48 and a rear cover 49 are combined from a forward portion in this
order, a vertical-plate-shaped bracket portion 51 extending
rearward is integrally formed in a rear portion of the rear cover
49, and a fitting hole 52 extending through in a direction of
vehicle width is pierced in the bracket portion 51.
[0040] As shown in FIGS. 4 and 7, the cylinder head 46 is fastened
and fixed to the cylinder block 47 by six long fixing bolts 54 and
one short fixing bolt 55, and the crankcase 48 and the rear cover
49 are fastened to the cylinder block 47 by means of six through
bolts 56 and a plurality of fixing bolts 57. Since these six
through bolts 56 are fastened to the cylinder block 47 after
passing through the rear cover 49 and the crankcase 48 from the
rear side, the rear cover 49 and the crankcase 48 are fastened
together to the cylinder block 47. In this case, the rear cover 49
is also fastened and fixed to the crankcase 48 by other plural
fixing bolts 58.
[0041] Since a crankshaft 61 disposed along the direction of the
vehicle width is pivoted between the cylinder block 47 and the
crankcase 48, two right and left cylinder bores 62 are formed
within the cylinder block 47. A piston 63 (a piston pin 64) and the
crankshaft 61 (a crank pin 65) inserted thereto are connected
through a connecting rod 66, a sliding motion of the piston 63
within the cylinder bore 62 is converted into a rotating motion of
the crankshaft 61 so as to generate an output of the engine unit
41. In this case, a balancer shaft 67 for canceling an engine
vibration is pivoted above the crankshaft 61. This balancer shaft
67 is also pivoted between the cylinder block 47 and the crankcase
48 and is rotated and driven by means of uniform gears 68a and
68b.
[0042] On the contrary, two camshafts 69 and a valve system 70 are
received in an inner portion of the cylinder head 46. Each of the
cam shafts 69 is driven to the crankshaft 61 via a timing chain 71
and operates the valve system 70 at a predetermined timing so as to
promote an intake and exhaust operation of the engine unit within
the cylinder bore 62.
[0043] On the other hand, a counter shaft 72 parallel to the
crankshaft 61 is pivoted between the crankcase 48 and the rear
cover 49. An axial length of the counter shaft 72 is widely shorter
than that of the crankshaft 61, the rear portion of the crankcase
48 corresponding to a receiving portion of the counter shaft 72 and
the rear cover 49 are arranged, in an offset manner, close to one
side (for example, close to a left side) with respect to a center
line C of the vehicle body, and a plan shape of the engine unit 41
is formed in a substantially L-shape together with the bracket
portion 51 positioned at the rear thereof in FIG. 7.
[0044] Further, since a counter driven gear 74 pivoted to a left
end side of the counter shaft 72 through a buffer (absorbing)
mechanism 73 is engaged with a counter drive gear 75 formed in a
crank web at a left end portion of the crankshaft 61, the counter
shaft 72 backward rotates while interlocking with the forward
rotating crankshaft 61, whereby a shock or the like generated
together with a torque fluctuation of the crankshaft 61 is absorbed
by the buffer mechanism 73.
[0045] In this case, a right end portion of the crankshaft 61 is
covered by a case cover 44a, and a one-way clutch mechanism 77
receiving a power output from a starter motor 76 for starting the
engine shown in FIG. 4 is arranged in the inner side thereof. On
the contrary, a left end portion of the crankshaft 61 is covered by
a case cover 44b, a flywheel 78 and a belt pulley 79 are arranged
respectively in the inside and outside of the left end portion of
the crankshaft 61 in such a manner as to integrally rotate with the
crankshaft 61, and an alternator 80 (refer to FIG. 2) for
generating a power is driven by the belt pulley 79 via a belt 81.
The alternator 80 is placed above the power unit 21.
[0046] Furthermore, a water pump 82 for circulating a cooling water
is provided in a left end portion of the counter shaft 72 and a
left side portion of the rear cover 49. An oil pump 83 for
supplying an engine oil is provided in a right end portion of the
counter shaft 72 and an inner portion of the rear cover 49. These
pumps 82 and 83 are directly driven by the counter shaft 72.
[0047] On the contrary, the transmission unit (change gear unit) 42
has a structure in which a belt-type transmission (for example,
CVT) 85 is placed within a casing separately provided from the
engine unit 41. A casing 84 is formed as a three-piece structure
comprising an inner case 86 positioned in an inner side in a
direction of vehicle width, an outer case 87 attached to an outer
side thereof in a liquid tight manner and a case cover 88 attached
to an outer side thereof.
[0048] The belt-type transmission 85 comprises: an input shaft 89
and an output shaft 90 pivoted in a front portion and a rear
portion within the casing 84 in parallel to the crankshaft 61; an
input V pulley 91 and an output V pulley 92 respectively pivoted to
the shafts 89 and 90 so as to integrally rotate; a V belt (or a
metal belt) 93 wound between both of the V pulleys 91 and 92; and a
facing drive mechanism 94 coaxially provided with the input V
pulley 91.
[0049] The input V pulley 91 has a stationary facing 95 integrally
formed with the input shaft 89 and a movable facing 96 provided so
as to move in an axial direction, and a position of the movable
facing 96 is determined by the facing drive mechanism 94. Further,
the output V pulley 92 also has a stationary facing 97 and a
movable facing 98, and the movable facing 98 is always pressed to a
side of the stationary facing 97 through a spring 99.
[0050] In this case, the input V pulley 91 is arranged close to a
left end of the input shaft 89, and the output V pulley 92 is
arranged close to a right end of the output shaft 90. The input V
pulley 91 and the output V pulley 92 are arranged in such a manner
as to be aligned in a longitudinal direction. The facing drive
mechanism 94 is arranged in a right side of the input V pulley 91,
and a blower composed of the case cover 88 is provided at the rear
side of the facing drive mechanism 94 and in a right side of the
output V pulley 92. Accordingly, the transmission unit 42 is formed
in a substantially L-shape in a plan view.
[0051] Furthermore, a bearing boss 101 provided on a front left
side surface of the transmission unit 42 (the inner case 86) is
closely fitted and fixed to a right side surface of a connecting
portion between the crankcase 48 and the rear cover 49 of the
engine unit 41. The input shaft 89 extending through the bearing
boss 101 and the counter shaft 72 of the engine unit 41 are
connected through a spline connection or the like so as to
integrally rotate. On the contrary, a rear left side surface or the
transmission unit 42 (86) is arranged in adjacent to a right side
surface (on a side of the center line C of the vehicle body) of the
bracket 51 in the engine unit 41, and a bearing boss 102 of the
output shaft 90 is closely fitted to the fitting hole 52 of the
bracket 51.
[0052] As mentioned above, the engine unit 41 and the transmission
unit 42 are formed in a substantially L-shape in a plan view, both
the substantially L-shaped portions are combined with each other so
as to be formed in a substantially rectangular shape.
[0053] On the other hand, the bevel unit 43 has a structure in
which a bevel input shaft 105 extending along the width direction
of the vehicle body and a bevel output shaft 106 extending along
the longitudinal direction of the vehicle body are pivoted to an
inner portion of an independent casing 104. An input bevel gear 107
and an output bevel gear 108 engaged with the input bevel gear 107
are respectively provided in the bevel input shaft 105 and the
bevel output shaft 106 so as to integrally rotate.
[0054] Then, the bevel unit 43 is arranged on a left side surface
(on a side opposite to the center line C of the vehicle body) of
the bracket portion 51 in the engine unit 41 so as to be adjacent
to the bracket portion 51. A bearing boss 109 of the bevel input
shaft 105 is closely fitted and fixed to the fitting hole 52 of the
bracket portion 51, and the output shaft 90 and the bevel input
shaft 105 are connected through a spline connection or the like so
as to be integrally rotated.
[0055] As shown in FIG. 7, a fastening member such as a through
bolt 111 or the like is fastened to the transmission unit 42 from a
left side through the bevel unit 43 and the bracket portion 51, and
the bevel unit 43 and the bracket portion 51 are fastened together
to the transmission unit 42 by the through bolt 111. In this case,
totally four through bolts 111 are used, and each of the through
bolts 111 extends through a through hole 112 formed around the
fitting hole 52 of the bracket 51 at an equal distance as shown in
FIG. 4.
[0056] In this case, for example, three frame fixing portions 113
are formed around the bracket portion 51. These frame fixing
portions 113, one frame fixing portion 114 provided in the cylinder
block 47 as shown in FIG. 4 and two frame fixing portions 115
provided in the cylinder head 46 are respectively fastened to
fastening portions provided in the down pipes 4, the middle pipes 6
and the pivot plate 10 in the vehicle body frame 2 by fixing bolts
116 (refer to FIG. 7). According to the structure mentioned above,
the whole structure of the power unit 21 is fixed to the vehicle
body frame 2.
[0057] In the described power unit 21, the rotation of the
crankshaft 61 of the engine unit 41 is transmitted to the counter
shaft 72, the input shaft 89 of the transmission unit 42 and the
input V pulley 91, and the rotation of the input V pulley 91 is
transmitted to the output V pulley 92 and the output shaft 90 by
the V belt 93. Further, the rotation of the output shaft 90 is
transmitted to the bevel output shaft 106 via the bevel input shaft
105, the input bevel gear 107 and the output bevel gear 108 in the
bevel unit 43, and an engine output is taken out rearward from the
bevel output shaft 106.
[0058] In this case, since the tooth number of the counter drive
gear 75 is smaller than the tooth number of the counter driven gear
74, the rotational speed of the crankshaft 61 is primarily reduced
when being transmitted to the counter shaft 72. Furthermore, since
the tooth number of the input bevel gear 107 is smaller than the
tooth number of the output bevel gear 108, a secondary speed
reduction is hence performed.
[0059] Then, a rotation of the bevel output shaft 106 is
transmitted to a drive shaft 118 pivoted within the swing
transmission unit 19 via a universal joint 117 (refer to FIGS. 3, 5
and 6), and a rotation of the drive shaft 118 is transmitted to the
rear wheel 18 via a rear bevel gear mechanism 119. In this case,
for example, an electromagnetic type starter clutch 120 is arranged
to a middle portion of the drive shaft 118, and a power of the
engine unit 41 is transmitted and interrupted with respect to the
rear wheel 18 in accordance with an ON-OFF operation of the starter
clutch 120.
[0060] In this case, the facing drive mechanism 94 of the belt-type
transmission 85 in the transmission unit 42 moves the movable
facing 96 of the input V pulley 91 in an axial direction in
accordance with the various conditions such as a vehicle speed, a
throttle opening degree, an engine load or the like of the
motorcycle 1, on the basis of a power of an actuator controlled by
control means (not shown).
[0061] For example, at a time when the engine unit of the
motorcycle 1 starts, the facing drive mechanism 94 moves the
movable facing 96 apart from the stationary facing 95 so as to make
minimum an effective diameter of the input V pulley 91 for winding
the belt. Together with this operation, since the movable facing 98
is pressed, on the output V pulley 92 side, to the side of the
stationary facing 97 due to an urging force of the spring 99 and
the effective diameter for winding belt becomes maximum, a gear
ratio becomes high and, hence, it becomes possible to easily
start.
[0062] Further, during the acceleration of the motorcycle 1, the
facing drive mechanism 94 gradually moves the movable facing 96 of
the input V pulley 91 close to the side of the stationary facing 95
so as to increase the effective diameter of the input V pulley 91
for winding the belt. Then, in the output V pulley 92 side, since
the movable facing 98 moves apart from the stationary facing 97
against the urging force of the spring 99, and the effective
diameter for winding the belt is reduced, the gear ratio becomes
low and a vehicle speed is increased.
[0063] As mentioned above, according to the power unit 21 of the
present invention, the engine unit 41, the transmission unit 42 and
the bevel unit 43, which are independently provided and formed in a
sealed manner, are integrally combined, it is possible to
manufacture the respective units 41, 42 and 43 in different
production sites and it is also possible to ensure a significantly
high productivity.
[0064] Furthermore, in the case of changing the specification such
as the engine output, the gear ratio or the like or maintaining a
specific portion, only one of three units 41, 42 and 43 may be
disassembled or replaced, so that the maintenance can be easily
made and it is possible to be easily applied to various kinds of
vehicles.
[0065] In addition, since the bearing boss 102 of the variable
change unit 42 and the bearing boss 109 of the bevel unit 43 are
coaxially fitted and fixed to the fitting holes 52 of the bracket
portion 51 in the engine unit 41, it is unnecessary to form many
fitting portions, fixing portions or the like, so that it is
possible to improve a manufacturing quality and reduce processing
working, and further it is possible to increase an assembling
rigidity of the whole structure of the power unit 21.
[0066] Furthermore, since the engine unit 41 and the transmission
unit 42 which are formed in substantially L-shape in a plan view
are combined with each other so as to be formed in substantially
rectangular shape in a plan view, no dead space is generated
between the engine unit 41 and the transmission unit 42.
Furthermore, since the transmission unit 42 is arranged on the side
of the center line C of the vehicle body (the right side) of the
bracket 51 arranged, in an offset manner, close to one side (in
this case, close to the left side) with respect to the center line
C of the vehicle body. The bevel unit 43 having a lateral width
smaller than that of the transmission unit 42 is arranged in the
side opposite to the center line C of the vehicle body (the left
side) of the bracket portion 51. Any one of the transmission unit
42 and the bevel unit 43 does not protrude sideward more largely
than the lateral width of the engine unit 41. Accordingly, it is
possible to make compact the sizes of the power unit 21 in the
longitudinal direction and the width direction.
[0067] Further, in this power unit 21, since the bracket portion
51, the transmission unit 42 and the bevel unit 43 in the engine
unit 41 are fastened together by the through bolts 111 disposed
along the direction of the vehicle width, it is possible to widely
reduce the number of the fastening members (the through bolts 111)
and simultaneously reduce the number of the assembling time and
labor of workers so as to widely increase a productivity of the
power unit 21, in comparison with the case that the transmission
unit 42 and the bevel unit 43 are respectively fastened to the
bracket portion 51 by using the exclusive fastening members.
[0068] On the contrary, since the frame fixing portion 113 for
fixing the power unit 21 to the vehicle body frame 2 is formed in
the bracket portion 51 of the engine unit 41, the connecting
portion (that is, the bracket portion 51) of three units 41, 42 and
43, constituting the power unit 21, is firmly fixed to the vehicle
body frame 2. Thus, it is possible to increase a supporting
rigidity of the whole of the power unit 21 to the vehicle body
frame 2.
[0069] In the present invention, the power unit 21 is not limited
to the structure of the scooter-type motorcycle and may be also
applied to a power unit for other types of motorcycles or other
kinds of vehicles.
[0070] That is, it is to be noted that the present invention is not
limited to the described embodiment and many other changes and
modifications may be made without departing from the scopes of the
appended claims.
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