Title of Invention

ENGINE FASTENING STRUCTURE

Abstract An engine fastening structure for laminating and fastening a cylinder body and a cylinder head to a crank case, a flange (3b) on the case side formed in the end of the cylinder body (3) on the crank case side is fastened to the crank case (2) by a case bolt (30a), and at least part of a head bolt (30c) for fastening the cylinder head (4) and cylinder body (3) is threadedly inserted into the flange (3b) on the case side. (FIG. - 1)
Full Text Description
Technical Field
The present invention relates to an engine fastening
structure in which a cylinder body and a cylinder head are stacked
on and fastened to a crankcase, and more particular to an engine
fastening structure which can improve the durability of the
cylinder body by reducing the load due to combustion pressure
which is applied to the cylinder body.
Background Art
As a fastening structure for a motorcycle engine, for
example, there exists an engine fastening structure in which
a crankcase side flange portion of a cylinder body is fastened
to a crankcase with bolts and a cylinder head side flange portion
of the cylinder body is fastened to a cylinder head with bolts.
With the conventional construction, however, in the case
of a single cylinder and large displacement engine that is
subjected to a large load due to combustion pressure, the large
load eventually generates a large tensile stress at an axially
intermediate portion of the cylinder body.
Then, conventionally, it is a generally acceptedpractice
to secure a required durability by increasing the thickness
of the axially intermediate portion of the cylinder body.
However, increasing the thickness of the cylinder body like
this constitutes a cause for an increase in the weight of the
engine.
On the other hand, as a conventional engine fastening
structure which can avoid the increase in the engine weight,
there exists, for example, an engine fastening structure
disclosed in JP-A-8-28-210 . In this engine fastening structure,
a crankcase side flange portion of a cylinder body 2 is fastened
and fixed to a crankcase 3, 4 with case bolts 11, and a cylinder
head side flange portion of the cylinder body 2 is fastened
and fixed to a cylinder head with bolts 15. Furthermore, the
cylinder head 1 is fastened and fixed to the crankcase 3, 4
with bolts 17 which screw through the cylinder body 2.
In the case of the engine fastening structure disclosed
in the above publication, since the cylinder head 1 is fastened
and fixed to the crankcase 3, 4 with the bolts 17 which screw
through the cylinder body 2, part of a combustion pressure
applied to the cylinder body is borne by the bolts 17, and stress
generated in the cylinder body can be reduced accordingly,
thereby making it possible to improve the durability of the
cylinder body.
With the engine fastening structure disclosed in the
publication, however, while the head bolts are screwed into
the crankcase at positions which align with fixing positions
of the cylinder head, since there exist cooling water jackets
in the cylinder head, the head bolts have to be disposed outwardly
so as to avoid the cooling water jackets. Due to this, as seen
from the top, the crankcase is fastened at positions which are
apart from the axis of a cylinder, and hence the crankcase has
to be enlarged accordingly, which would otherwise be unnecessary.
In addition, the construction is adopted in which the head bolts
are screwed into the crankcase, since the head-bolts have to
be disposed at positions where they do not interfere with a
web of a crankshaft and the fixing positions of the cylinder
head and fixing positions of the crankcase have to be aligned
with each other, the degree of freedom in design is reduced.
The present invention was made in view of the problems
inherent in the conventional engine fastening structure, and
an object of the invention is to provide an engine fastening
structure which can secure the durability of an engine without
needing to enlarge a crankcase unnecessarily and without needing
to reduce the degree of freedom in arrangement of head bolts.
Disclosure of the Invention
According to a first aspect of the invention, there is
provided an engine fastening structure in which a cylinder body
and a cylinder head are stacked on and fastened to a crankcase,
characterized in that a case side flange portion formed at a
crankcase side end portion of the cylinder body is fastened
to the crankcase with case bolts, and in that at least part
of head bolts which fasten the cylinder head and the cylinder
body together is made to be a flange screw-through head bolt
which is screwed into the case side flange portion.
According to a second aspect of the invention, there is
provided an engine fastening structure as set forth in the first
aspect of the invention, characterized in that the flange
screw-through head bolt and the case bolt overlap each other
by a distance which is substantially the same as the thickness
of the case side flange portion in the axial direction of a
cylinder bore.
According to a third aspect of the invention, there is
provided an engine fastening structure as set forth in the first
or second aspect of the invention, characterized in that the
flange screw-through bolt and the case bolt are disposed close
to each other, when viewed in the axial direction of the cylinder
bore.
According to a fourth aspect of the invention, there is
provided an engine fastening structure as set forth in any of
the first to third aspects of the invention, characterized in
that the case bolt is disposed such that a distance from the
case bolt to a first straight line which passes through the
axis of the cylinder bore and which is normal to a crankshaft
becomes shorter than a distance from the flange screw-through
head bolt to the first straight line, when viewed in the axial
direction of the cylinder bore.
According to a fifth aspect of the invention, there is
provided an engine fastening structure as set forth in any of
the first to fourth aspects of the invention, characterized
in that the flange screw-through head bolt is disposed such
that a distance from the head bolt to a second straight line
which passes through the axis of a cylinder bore and which is
parallel to the crankshaft becomes shorter than a distance from
the case bolt to the second straight line, when viewed in the
axial direction of the cylinder bore.
According to a sixth aspect of the invention, there is
provided an engine fastening structure as set forth in any of
the first to fifth aspects of the invention, characterized in
that an axial part of the flange screw-through head bolt is
exposed to the outside.
According to a seventh aspect of the invention, there
is provided an engine fastening structure as set forth in any
of the first to sixth aspects of the invention, characterized
in that at least three head bolts are disposed on either side
of the cylinder bore across the second straight line, when viewed
in the axial direction of the cylinder bore, and in that the
central head bolt along the second straight line is set to have
a length which does not reach the case side flange portion.
According to an eighth aspect of the invention, there
is provided an engine fastening structure as set forth in any
of the first to seventh aspects of the invention, characterized
in that the flange screw-through head bolt is disposed between
a chain compartment formed on a side to the cylinder bore in
which a camshaft driving chain which connects the crankshaft
to a camshaft is disposed and the cylinder bore.
According to a ninth aspect of the invention, there is
provided an engine fastening structure as set forth in any of
the first to eighth aspects of the invention, characterized
in that the flange screw-through head bolt is screwed into the
case side flange portion at one end and is fastened and fixed
to the cylinder head with a cap nut at the other end thereof.
Brief Description of the Drawings
Fig. 1 is a right-hand side view of an engine according
to an embodiment of the invention.
Fig. 2 is a sectional plan view showing a development
of the engine.
Fig. 3 is a left-hand side view showing a valve train
device of the engine.
Fig. 4 is a sectional rear elevation of the valve train
device.
Fig. 5 is a sectional plan view showing a development
of a balance shaft of the engine.
Fig. 6 is a bottom view of a cylinder head of the engine.
Fig. 7 is a bottom view of a cylinder body of the engine.
Fig. 8 is a sectional side view showing a portion where
the cylinder head of the engine is connected to the cylinder
body.
Fig. 9 is a sectional side view showing a portion where
the cylinder body of the engine is connected to the crankcase.
Fig. 10 is another sectional side view showing a portion
where the cylinder body of the engine is connected to the
crankcase.
Fig. 11 is a left-hand side view showing a balancer unit
of the engine.
Fig. 12 is an enlarged cross-sectional view of a portion
where a holding lever of the balancer unit is attached.
Fig. 13 is a side view of constituent components of a
rotational lever of the balancer unit.
Fig. 14 is a side view showing a damping construction
of a balancer drive gear of the balancer unit.
Fig. 15 is a right-hand side view of the balancer unit.
Fig. 16 is a sectional right-hand side view of a bearing
bracket of the engine.
Fig. 17 is a sectional left-hand side view of a bearing
bracket.
Fig. 18 is an explanatory drawing showing the construction
of a lubrication system of the engine.
Fig. 19 is a drawing showing the construction of the
lubrication system.
Fig. 20 is a sectional side view of an area surrounding
a lubricating oil pump of the lubrication system.
Fig. 21 is a sectional left-hand side view of the
lubrication system.
Best Mode for Carrying out the Invention
Hereinafter, an embodiment of the invention will be
described with reference to the accompanying drawings.
Figs. 1 to 21 are drawings for describing an embodiment
of the invention. In the drawings, reference numeral 1 denotes
a water-cooled, 4-cycle, single cylinder, 5-valve engine, and
in general, the engine has a construction in which a cylinder
body 3, a cylinder head 4 and a cylinder head cover 5 are stacked
on and fastened to a crankcase 2, and a piston 6 slidably disposed
in a cylinder bore 3a in the cylinder body 3 is connected to
a crankshaft 8 via a connecting rod 7.
The cylinder body 3 and the crankcase 2 are securely
connected together by screwing four case bolts 30a which pass
through a lower flange portion (a case side flange portion)
3b into a cylinder side mating surface 2e of the crankcase 2.
To be more specific, the case bolts 30a are screwed into bolt
connectingportions (connectingbossportions) 12cof iron alloy
bearing brackets 12, 12" (which will be described later on)
embedded in left and right wall portions of the aluminum alloy
crankcase 2, respectively, through insert casting. Note that
reference numeral 31a in Fig. 10 denotes a positioning dowel
pin for positioning the crankcase 2 and the cylinder body 3.
In addition, the cylinder body 3 and the cylinder head
4 are connected together with two short head bolts 30b and four
long head bolts (flange screw-through head bolts) 30c. The
short head bolt 30b is screwed to be planted in a portion below
an induction port 4c and a portion below an exhaust port in
the cylinder head 4, extends downwardly to pass throughan upper
flange portion 3f of the cylinder block 3 and protrudes
downwardly therefrom. Then, a cap nut 32a is screwed on the
downwardlyprotrudingportion of the short headbolt 30b, whereby
the upper flange portion 3f and hence the cylinder body 3 are
fastened to a cylinder side mating surface 4a of the cylinder
head 4.
In addition, the long headbolt 30c is screwed to be planted
in the lower flange portion 3b of the cylinder body 3, extends
upwardly to pass from the upper flange portion 3f of the cylinder
block 3 through a flange portion 4b of the cylinder head 4 and
protrudes upwardly therefrom. Then, a cap nut 32b is screwed
on the upwardly protruding portion of the long head bolt 30c,
whereby the lower flange portion 3b and hence the cylinder body
are fastened to the cylinder side mating surface 4a of the
cylinder head 4 . Note that a portion 30c" of the long head bolt
30c which is situated between the lower flange portion 3b and
the upper flange portion 3f of the cylinder body 3 is exposed
to the outside.
Here, when viewed in a direction normal to the axis A
of the cylinder bore (refer to Fig. 10), the long head bolt
30c and the case bolt 30a overlap each other by a distance which
is substantially the same as the thickness of the lower flange
portion (the case side flange portion) 3b along the axis A of
the cylinder bore.
In addition, when viewed in a direction along the axis
A of the cylinder bore (refer to Figs. 6, 7), the long head
bolt 30c and the case bolt 30a are disposed so as to establish
the following relationship and close to each other. Namely,
the case bolt 30a is disposed such that a distance a1 from the
case bolt 30a to a first straight line C1 which passes through
the axis A of the cylinder bore and which is normal to the
crankshaft becomes shorter than a distance a2 from the head
bolt 30c to the first straight line C1 or such that the case
bolt 30a is situated closer to the center of the cylinder bore
as viewed in the direction of the crankshaft.
In addition, the head bolt 30c is disposed such that a
distance b2 from the head bolt 30c to a second straight line
C2 which passes through the axis A of the cylinder bore and
which is parallel to the crankshaft is shorter than a distance
b1 from the case bolt 30a to the second straight line C2 or
such that the head bolt is situated closer to the crankshaft
side.

Furthermore, three head bolts 30c, 30b, 30c are disposed
on either side of the cylinder bore across the second straight
line C2, and of these three head bolts, the head bolt situated
centrally along the direction of the second straight line C2
is made to be the short head bolt 30b. This short head bolt
30b is set to have a length which corresponds to the upper flange
portion 3f and which does not reach the lower flange portion
3b.
Then, the long head bolts 30c, 30c are disposed on either
side of the cylinder bore across the second straight line C2 .
Here, on one side of the cylinder bore 3a along the direction
of the crankshaft (on a left-hand side of Fig. 7), a chain
compartment 3d is formed in which a camshaft driving chain 40
for transmitting the rotation of the crankshaft to the camshaft
is disposed. The long head bolts 30c situated on the one side
of the cylinder bore along the direction of the second straight
line C2 are disposed between the chain compartment 3d and the
cylinder bore 3a.
Thus, in connecting the cylinder body 3 and the cylinder
head 4 together, since not only is the upper flange portion
3f of the cylinder body 3 fastened and fixed to the cylinder
head 4 with the short head bolts 30b and cap nuts 32a but also
the long head bolts 30c are planted in the lower flange portion
3b which is bolted and connected to the mating surface 2e of
the crankcase 2, so that the cylinder body 3 is fastened and
fixed to the flange portion 4b of the cylinder head 4 with the
long head bolts 30c so planted and cap nuts 32b, the tensile
load due to the combustion pressure is borne by the cylinder
body 3 and the four long head bolts 30c, and therefore, the
load applied to the cylinder body 3 can be reduced accordingly.
As a result, the stress generated at, in particular, the axially
intermediate portion of the cylinder body 3 can be reduced,
and even in the event that the thickness of the cylinder body
3 is reduced, the durability can be secured.
Incidentally, in the event that only the upper flange
portion 3f of the cylinder body 3 is connected to the cylinder
head 4, an excessive tensile stress is generated at the axially
intermediate portion of the cylinder body 3, and in the worst
case, there is caused a concern that a crack is generated at
the relevant portion. According to the embodiment, however,
the generation of such an excessive stress at the intermediate
portion of the cylinder body can be avoided due to the existence
of the long head bolts 30c, thereby making it possible to prevent
the generation of such a crack.
In addition, in planting the long head bolts 30c in the
lower flange portion, since the long head bolt 30c is disposed
close to the case bolt 30a for fastening the crankcase, the
long head bolt 30c transmits part of the load generated by the
combustion pressure to the case side flange portion 3b, and
furthermore, the case side flange portion 3b transmits the load
so transmitted thereto to the crankcase 2 via the case bolt
30a, whereby the load applied to the cylinder body 3 can be
reduced in an ensured fashion. From this point of view, the
durability of the cylinder body 3 against the load can be
improved.
In addition, since the long head bolt 30c and the case
bolt 30a are made to overlap each other by the distance which
is substantially the same as the thickness of the case side
flange portion 3b in the axial direction of the cylinder bore,
the long head bolt 30c can ensure the transmission of part of
the load generated by the combustion pressure to the case side
flange portion 3b, thereby making it possible to reduce the
load applied to the intermediate portion of the cylinder body
3.
Additionally, since the case bolt 30a is disposed such
that the distance a1 to the first straight line C1 which passes
through the axis of the cylinder bore and which is normal to
the crankshaft becomes shorter than the distance from the long
cylinder bolt 30c to the first straight line C1 or such that
the case bolt 30a is situated closer to the center of the cylinder
bore in the direction of the crankshaft, when viewed in the
direction of the axis A of the cylinder bore, as shown in
double-dashed lines in Fig. 7, the dimension of the mating
surface 2e of the crankcase 2 that is attached to the cylinder
body in the crankshaft direction can be reduced to the vicinity
of positions where the long head bolts 30c are disposed, and
as a result, the dimension of the crankcase 2 in the crankshaft
direction can be reduced.
Furthermore, since the construction is adopted in which
the long head bolts 30c are screwed into the case side flange
portion 3b of the cylinder body 3 or the long head bolts 30c
are not screwed into the mating surface 2e of the crankcase
2 which is attached to the cylinder body, there is no risk of
causing a problem that the long head bolts 30c interfere with
the web 8b of the crankshaft 8, and the long head bolt 30c can
be disposed such that the distance b2 to the second straight
line C2 which passes through the center of the cylinder and
which is parallel to the crankshaft becomes shorter than the
distance b1 from the case bolt 30a to the second straight line
C2 or such that the long head bolt 30c is situated closer to
the crankshaft side, thereby making it possible to reduce the
dimension of the cylinder head 4 and the cylinder body 3 in
the direction normal to the crankshaft.
In addition, since the axial part 30c" of the long head
bolt 30c is exposed to the outside from the side wall of the
cylinder body 3, the wall which surrounds the long head bolt
30c can be reduced, and hence the weight of the cylinder body
can be reduced accordingly.
Additionally, since the three head bolts are disposed
on either side of the cylinder bore across the second straight
line C2, while the head bolt 30b situated centrally along the
direction of the second straight line C2 is situated apart from
the axis A of the cylinder bore in the direction normal to the
crankshaft, the case side flange portion 3b can be minimized
with respect to a portion corresponding to the central head
bolt 30b due to the head bolt 30b being set to have the length
that does not reach the case side flange portion 3b, thereby
making it possible to avoid the enlargement of the crankease.
In addition, since the long head bolts 30c are disposed
between the cylinder bore 3a and the chain compartment 3d formed
on the side to the cylinder bore 3a, the long head bolts 30c
can be disposed by making an effective use of a dead space formed
therebtween.
Furthermore, since the long head bolt 30c is screwed into
the case side flange portion 3b at the one end and is fastened
and fixed to the cylinder head with the cap nut 32b at the other
end thereof, the cylinder head can be removed without securing
a large space above the cylinder head, thereby making it possible
to secure the maintenance properties of the engine.
Here, as shown in Figs. 5, 16, the right-side bearing
bracket 12" has a boss portion 12b in which a right-side bearing
11a" of the crankshaft 8 is inserted to be fitted in a bearing
hole 12a through press fit. Then, the bolt connecting portions
12c, 12c extend upwardly from front and rear portions of the
boss portion 12b which are situated opposite to each other across
the crankshaft 8 as viewed in the direction in which the
crankshaft 8 extends to the vicinity of the cylinder-side mating
surface 2e of the crankcase 2.
In addition, in the left-side bearing bracket 12, as shown
in Figs. 5, 17, the bolt connecting portions 12c, 12c extend
upwardly fromfront andrearportions which are situatedopposite
to each other across the crankshaft 8 as viewed in the direction
in which the crankshaft 8 extends to the vicinity of the
cylinder-side mating surface 2e of the crankcase 2 . In addition,
a collar hole 12e is formed in the boss portion 12b into which
an iron bearing collar 12d having an outside diameter larger
than the that of a balancer driving gear 25a, which will be
described later on, is press fitted. Then, a left-side
crankshaft bearing 11a is inserted to be fitted in the bearing
hole 12a of the bearing collar 12d.
Here, the bearing collar 12d is such as to facilitate
the assembly of the crankshaft 8 in the crankcase 2 with a gear
unit 25 having the balancer driving gear 25a being press fitted
on the crankshaft 8.
In addition, as shown in Fig. 5, a seal plate 25d is
interposed between the gear unit 25 on a left shaft portion
8c of the crankshaft 8 and the bearing 11a. An inside diameter
side portion of the seal plate 25d is held by the gear unit
25 and an inner race of the bearing lla, and a slight gap is
provided between an outside diameter side portion thereof and
an outer race of the bearing 11a for avoiding the interference
therebetween. In addition, an outer circumferential surface
of the seal plate 25d is brought into sliding contact with an
inner circumferential surface of a flange portion 12h of the
bearing collar 12d.
Furthermore, a seal tube 17i is interposed between the
bearing 11a" of a right shaft portion 8c" of the crankshaft
8 and a cover plate 17g. An inner circumferential surface of
the seal tube 17i is fixedly fitted on the right shaft portion
8c" . In addition, a seal groove having a labyrinth construction
is formed in an outer circumferential surface of the seal tube
17i, and the outer circumferential surface of the seal tube
17i is brought into sliding contact with an inner circumferential
surface of a seal hole 2p formed in the right case portion 2b.
Thus, the leakage of pressure within a crank compartment
2c is prevented by interposing the seal plate 25d and the seal
tube 17i on the outside of the bearings 11a, 11a" of the left
and right shaft portions 8c, 8c" of the crankshaft 8.
Thus, according to the embodiment, since the bolt
connecting portions (the connecting boss portions) 12c, 12c
which extend toward the cylinder body 3 side are integrally
formed on the sides situated opposite to each other across the
axis A of the cylinder bore of each of the iron alloy crankshaft
supporting bearing members 12, 12" which are insert cast in
the aluminum alloy crankcase 2 and the case bolts 30a for
connecting the cylinder body 3 to the crankcase 2 are screwed
into the bolt connecting portions 12c, respectively, the load
generated by virtue of the combustion pressure can be borne
uniformly by the two front and rear bolt connecting portions
12c which are situated opposite to each other across the axis
A of the cylinder bore, whereby the connecting rigidity between
the cylinder body 3 and the crankcase 2 can be improved.
In addition, since the balance shafts 22, 22" which are
disposed in parallel with the crankshaft 8 in the vicinity of
thereof are supported by the iron alloy bearing members 12,
12" at at least one ends thereof, the supporting rigidity of
the balance shafts 22, 22" can be enhanced.
Furthermore, in embedding the iron alloy bearing brackets
12, 12" in the aluminum alloy crankcase 2, since the upper end
face 12f of the bolt connecting portion 12c is positioned
inwardly without being exposed to the cylinder side mating
surface 2e of the crankcase 2, there is no risk that metallic
members which are different in hardness and material exist in
a mixed fashion at a joint between the crankcase 2 and the cylinder
block 3, thereby making it possible to avoid a reduction in
sealing properties. Namely, in the event that the upper end
face 12f of the bolt connecting portion 12c is made to abut
with a case side mating surface 3c formed on the lower flange
3b of the aluminum alloy cylinder body 3, the sealing properties
are reduced due to a difference in thermal expansion
coefficients.
In addition, in the left-side bearing bracket 12, since
the bearing collar 12 having the outside diameter larger than
that of the balancer driving gear 25a is attached to the outer
circumference of the bearing 11a, when assembling the crankshaft
8 in the crankcase 2 with the balancer driving gear 25a with
the balancer driving gear 25a being attached to be fixed onto
the crankshaft 8 through press fit or the like (or the balancer
driving gear 25a may of course be integrally formed on the
crankshaft 8) , there is caused no risk that the balancer driving
gear 25a is brought into interference with a minimum inside
diameter portion of the boss portion 12b of the bearing bracket
12, and hence, the assembling of the crankshaft 8 can be
implemented without any problem.
The crankcase 2 is a two-piece type in which the crankcase
2 is divided into the left and right case portions 2a, 2b. A
left case cover 9 is detachably attached to the left case portion
2a, and a space surrounded by the left case portion 2a and the
left case cover 9 constitutes a flywheel magnet compartment
9a. A flywheel magnetic generator 35 attached to the left and
portion of the crankshaft 8 is accommodated in this flywheel
magnet compartment 9a. Note that the flywheel magnet
compartment 9a communicates with a camshaft arranging
compartment via the chain compartments 3d, 4d, which will be
described later on, whereby most of the lubricating oil which
has been used to lubricate the camshafts falls into the flywheel
magnet compartment 9a via the chain compartments 3d, 4d.
In addition, a right case cover 10 is detachably attached
to the right case portion 2b, and a space surrounded by the
right case portion 2b and the right case cover 10 constitutes
a clutch compartment 10a.
The crank compartment 2c and a transmission compartment
2d are formed at front and rear portions of the crankcase 2,
respectively. The crank compartment 2c is made to open to the
cylinder bore 3a but is defined substantially to be separated
from the other compartments such as the transmission compartment
2d. Due to this, the pressure within the transmission
compartment 2d is caused to fluctuate as the piston reciprocates
vertically, thereby allowing the transmission compartment 2d
to function as a pump.
A transmission 13 is accommodated and arranged in the
transmission compartment 2d. The transmission 13 is such as
to have a constant mesh construction in which a main shaft 14
and a drive shaft 15 are provided and arranged in parallel with
the crankshaft 8, and first-speed to fifth-speed gears 1p to
5p attached to the main shaft 14 are made to constantly mesh
with first-speed to fifth-speed gears 1w to 5w attached to the
drive shaft 15.
The main shaft 14 is rotationally supported by the left
and right case portions 2a, 2b via main shaft bearings 11b,
11b, whereas the drive shaft 15 is rotationally supported by
the left and right case portions 2a, 2b via drive shaft bearings
11c, 11c.
A right end portion of the main shaft 14 passes through
the right case portion 2b and protrudes to the right side, and
a clutch mechanism 16 is attached to the protruding portion,
and this clutch mechanism 16 is located within the clutch
compartment 10a. Then, a large reduction gear (an input gear)
16a of the clutch mechanism 16 meshes with a small reduction
gear 17 fixedly attached to the right end portion of the
crankshaft 8.
A left end portion of the drive shaft 15 protrudes outwardly
from the left case portion 2a and a driving sprocket 18 is attached
to the protruding portion. This driving sprocket 18 is
connected to a driven sprocket on a rear wheel.
A balancer unit 19 according to the embodiment includes
front and rear balancers 20, 20" disposed opposite across the
crankshaft 8 and having substantially the same construction.
The front and rear balancers 20, 20" include the balance shaft
22, 22" which do not rotate and weights 24, 24 which are
rotationally supported on the balance shat via bearings 23,
23.
Here the balance shafts 22, 22" are made to double as
the case bolts (the connecting bolts) for fastening and
connecting the left and right case portions 2a, 2b together
in the direction of the crankshaft. The respective balance
shafts 22, 22" function to connect the left and right case
portions 2a, 2b together by causing flange portions 22a formed
on insides of the rotationally supported weights 24 in a
transverse direction of the engine to abut with boss portions
12g integrally formed on the bearing brackets 12, 12" which
are insert cast into the left and right case portions 2a, 2b
and screwing fixing nuts 21b, 21a on opposite end portions of
the respective balance shafts 22, 22".
The weight 24 includes a semi-circular weight main body
24a and a circular gear supporting portion 24b which is
integrally formed on the weight main body, and a ring-shaped
balancer driven gear 24c is fixedly attached to the gear
supporting portion 24b. Note that reference numeral 24b
denotes a hole made in a part of the weight 24 which is situated
opposite to the weight main body 24a so as to reduce the weight
of the part to as low a level as possible.
The balancer driven gear 24c attached to the rear balancer
20" meshes with the balancer driving gear 25a which is
rotationally attached relative to the gear unit 25 which is
securely attached to the left shaft portion 8c of the crankcase
8 through press fit.
Note that reference numeral 25b denotes a timing chain
driving sprocket integrally formed on the gear unit 15 and has,
as shown in Fig. 11, an aligning or timing mark 25c for alignment
of timing marks for valve timing. The gear unit 25 is press
fitted on the crankshaft 8 such that the timing mark 25c aligns
with the cylinder bore axis A as viewed in the direction in
which the crankshaft extends when the crankshaft 8 is situated
at a top dead center of a compression stroke.
In addition, the balancer driven gear 24c attached to
the front balancer 20 meshes with a balancer driving gear 17a
which is supported rotationally relative to the small reduction
gear 17 which is fixedly attached to the right shaft portion
8c" of the crankshaft 8.
Here, the rear balancer driving gear 25a is supported
rotationally relative to the gear unit 25, and the front balancer
driving gear 17a is supported rotationally relative to the small
reduction gear 17. Then, U-shaped damper springs 33 each made
up of a plate spring are interposed between the balancer driving
gears 25a, 17a and the gear unit 25 and the small reduction
gear 17, respectively, to thereby restrain the transmission
of impact generated due to a torque fluctuation occurring in
the engine to the balancers 20, 20" is restrained from being
transmitted.
Here, while the balancer driving gear 17a for driving
the front balancer 20 will be described in detail by reference
to Fig. 14, the same description would be given if the balancer
driving gear 25a for driving the rear balancer were described.
The balancer driving gear 17a is formed into a ring shape and
is supported by a sliding surface 17b formed so as to have a
smaller diameter than the small reduction gear 17 rotationally
relative to a side of the small reduction gear 17. Then, a
number of U-shaped spring retaining grooves 17c are formed in
the sliding surface 17b by setting them back into the surface
thereof in a radial fashion about the center of the crankshaft,
and the U-shaped damper springs 33 are arranged to be inserted
in place within the spring retaining grooves 17c. Opening side
end portions 33a, 33a of the damper spring 33 are locked at
front and rear stepped portions formed in a locking recessed
portion 17d formed in an inner circumferential surface of the
balancer driving gear 17a.
When a relative rotation is generated between the small
reduction gear 17 and the balancer driving gear 17a due to a
torque fluctuation, the damper springs 33 resiliently deform
in a direction in which the space between the end portions 33a,
33a narrows so as to absorb the torque fluctuation so generated.
Note that reference numeral 17g denotes a cover plate for
retaining the damper springs 33 within the retaining grooves
17c, reference numeral 17h denotes a key for connecting the
small reduction gear 1 with the crankshaft 8, and reference
numerals 17e, 17f denote, respectively, alignment marks for
use in assembling the small reduction gear 17 and the balancer
driving gear 17a.
A mechanism for adjusting a backlash between the balancer
driven gears 24c, 24c and the balancer driving gears 25a, 17a
is provided on the balancers 20, 20". This adjusting mechanism
is constructed such that the balancer axis of the balance shaft
22, 22" slightly deviates from the rotational center of the
balancer driven gear 24c. Namely, when the balance shaft 22,
22" is made to rotate about the balancer axis, the space between
the rotational center line of the balancer driven gear 24c and
the rotational center line of the balancer driving gear 25a,
17a changes slightly, whereby the backlash is changed.
Here, a mechanism for rotating the balance shaft 22, 22"
differs between the front balancer 20 and the rear balancer
20". Firstly, in the rear balancer 20", a hexagonal locking
protruding portion 22b is formed on a left end portion of the
rearbalance shaft 22", and a spline-like (apolygonalstar-like)
locking hole 26a formed in one end of a rotational lever 26
is locked on the locking protruding portion 22b. In addition,
an arc-like bolt hole 2 6b is formed in the other end portion
of the rotational lever 26 in such a manner as to extend about
the balancer axis.
A fixing bolt 27a passed through the bolt hole 26b is
planted in a guide plate 28. The guide plate 28 is generally
formed into an arc-like shape and is fixedly bolted to the
crankcase 2. Note that the guide plate 28 has also a function
to control the flow of lubricating oil.
The adjustment of the backlash of the rear balancer 20"
is implemented by rotating the rotational lever 2 6 so as to
bring the backlash to an appropriate state with the fixing nut
21a being loosened and thereafter by fixing the rotational lever
26 with the fixing bolt 27a and a fixing nut 27b, and thereafter,
the fixing nut 21a is refastened.
A grip portion 22f having an oval cross section, which
is formed by forming a flat portion 22e on both sides of a
cross-sectionally circular shape, is formed on a left endportion
of the front balance shaft 22 (refer to Fig. 12). A collar
29a having an inner circumferential shape which matches an outer
circumferential shape of the grip portion 22f is attached to
the grip portion 22f, and furthermore, a holding portion 29b
of a holding lever 29 is attached to an outside of the collar
29a in such a manner as to move axially but as not to rotate
relatively. A distal end portion 29e of the holding lever 29
is fixed to a boss portion 2f of the left case portion 2a with
a bolt 29f. In addition, a tightening slit 29c is formed in
the holding portion 29b of the holding lever 29, so that the
rotation of the collar 29 and hence of the balance shaft 22
is preventedby tightening up the fixing bolt 29d. Furthermore,
the fixing nut 21b is screwed on the balance shaft 22 to an
outer side of the collar 29 so as to be secured thereto via
washer.
The adjustment of the backlash of the front balancer 20
is implemented by loosening the fixing nut 21b or preferably
removing the same, griping the grip portion 22f of the balance
shaft 22 with a tool to rotate the shaft so as to bring the
backlash to an appropriate state, and thereafter tightening
up the fixing bolt 29d, and thereafter, the fixing nut 21b is
fastened.
In addition, a lubricating oil introducing portion 22c
is formed in an upper portion of the locking protruding portion
22b by cutting out the upper in an arc. A guide bore 22d is
made to open to the introducing portion 22c, and the guide bore
extends into the balance shaft 22 and passes therethrough to
below an outer circumferential surface of the balance shaft
22, whereby the lubricating oil introducing portion 22c is made
to communicate with an inner circumferential surface of the
balancer bearing 23. Thus, lubricating oil that has fallen
in the lubricating oil introducing portion 22c is supplied to
the balancer bearing 23.
Here, while the weight 24 and the balancer driven gear
24c are disposed at the right end portion along the direction
in which the crankshaft extends in the front balancer 20, in
the rear balancer 20", they are disposed at the left end portion.
In addition, the balancer driven gear 24c is located rightward
relative to the weight 24 in both the front and rear balancers
20, 20", and therefore, the weight 24 and the balancer driven
gear 24c are set into the same configuration in both the front
and rear balancers.

Thus, according to the embodiment, since the weight main
body 24a and the balancer driven gear 24c of the balancer 20
are disposed on the right-hand side (one side) of the front
balance shaft (the primary balance shaft) 22 along the direction
in which the crankshaft extends and the weight main body 24a
and the balancer driven gear 24c are disposed on the left-hand
side (the other side) of the rear balance shaft (the secondary
balance shaft) 22" along the direction in which the crankshaft
extends, the reduction in balance in weight in the crankshaft
direction that would result when providing a two-shaft balancer
unit can be avoided.
In addition, since the front and rear balance shafts 22,
22" are made to double as the case bolts for connecting the
left and right case portions 2a, 2b together, when adopting
a two-shaft balancer unit, the connecting rigidity of the
crankcase can be enhanced while restraining the construction
of the engine from becoming complex and the number of components
from being increased.
Additionally, since the balancer weight main body 24a
and the balancer driven gear 24c are made integral and are
supported rotationally by the balance shafts 22, 22",
respectively, only the weight made up of the balancer weight
main body 24a and the balancer driven gear 24c may be driven
to rotate, and therefore, the engine output can be attempted
to be used effectively to such an extent that the balance shafts
themselves do not need to be driven to rotate.
In addition, the degree of freedom in assembling can be
improved when compared with an engine construction in which
a balancer weight and a balance shaft are made integral.
Additionally, since the rotational center lines of the
balancer driven gears 24c are caused to deviate relative to
the axes of the balance shafts 22, 22", the backlash between
the balancer driven gears 24c and the balancer driving gears
25a, 27a on the crankshaft 8 side can be adjusted by the simple
construction or only by a simple operation of rotating the
balance shafts, thereby making it possible to prevent the
generation of noise.
On the front balance shaft 22, the backlash adjustment
is implemented by gripping the grip portion 22f formed on the
left-hand side of the balance shaft 22 with a tool so as to
rotate the balance shaft 22, and on the rear balance shaft 22",
the backlash adjustment is implemented by rotating the
rotational lever 26 provided on the left-hand side of the balance
shaft 22" . Thus, on either of the front and rear balance shafts
22, 22", the backlash can be adjusted from the left-hand side
of the engine, and hence the backlash adjusting work can be
implemented efficiently.
Additionally, since the balancer driving gear 17a on the
crankshaft 8 side which meshes with the balancer driven gear
24c is constructed to be disposed in such a manner as to rotate
relatively to the sliding surface 17b of the small reduction
gear 17 which is fixed to the crankshaft 8 and the U-shaped
damper springs 33 are disposed in the spring retaining grooves
17c formed by setting them back from the sliding surface 17b,
the impact generated due to the torque fluctuation in the engine
can be absorbed by the compact construction so that the balancer
unit can be operated smoothly. Note that the same description
can be made with respect to the balancer drive gear 25a.
Furthermore, a coolant pump 48 is disposed at the right
end portion of the front balance shaft 22 coaxially therewith.
A rotating shaft of the coolant pump 48 is connected to the
balance shaft 22 by an Oldham"s coupling which has a similar
construction to that of a lubricating oil pump 52, which will
be described later on, in such a manner that a slight deviation
between the centers of the rotating shaft and the balance shaft
22 can be absorbed.
In a valve train device of the embodiment, an intake
camshaft 36 and an exhaust camshaft 37 which are disposed within
the cylinder head cover 5 are constructed to be driven to rotate
by the crankshaft 8. To be specific, a crankshaft sprocket
25b of the gear unit 25 press fitted on the left shaft portion
8c of the crankshaft 8 so as to be attached thereto and an
intermediate sprocket 38a rotationally supported by a support
shaft 39 planted in the cylinder head 4 are connected by a timing
chain 40, and an intermediate gear 38 formed integrally on the
intermediate sprocket 38a and having a smaller diameter than
that of the intermediate sprocket 38a meshes with intake and
exhaust gears 41, 42 secured to end portions of the intake and
the exhaust camshafts 36, 37. Note that the timing chain 40
is disposed so as to pass through the chain compartments 3d,
4d formed on the left walls of the cylinder block 3 and the
cylinder head 4.
The intermediate sprocket 38a and the intermediate gear
38b are rotationally supported by the support shaft 39 which
passes through the chain compartment 4d on the cylinder head
4 in the direction in which the crankshaft extend along the
cylinder bore axis A via two sets of needle bearings 44. The
support shaft 39 is fixed at a flange portion 39a thereof to
the cylinder head 4 with two bolts 39b. Note that reference
numerals 39c, 39d denote a sealing gasket, respectively.
Here, commercially available (standard) bearings are
adopted for the two sets of needle bearings 44, 44. A space
adjusting collar 44 a is disposed between the respective bearings
44, 44, and thrust washers 44b, 44b for receiving thrust load
are provided at ends of the bearings. The thrust washer 44b
is formed into a stepped shape having a large diameter portion
which is brought into sliding contact with an end face of the
intermediate sprocket and a stepped portion which protrudes
axially toward the needle bearing 44.
Thus, since the space adjusting collar 44a is interposed
between the two sets of bearings 44, 44, commercially available
standard bearings can be adopted for the needle bearings by
adjusting the length of the collar 44a, thereby making it
possible to reduce costs.
In addition, since the washer having the stepped
configuration is adoptedas the thrust washer 44b, the assembling
work of the intermediate sprocket 38a can be improved. Namely,
in assembling the intermediate sprocket 38a, while the support
shaft 39 is inserted from the outside in a state in which the
intermediate sprocket 38a and the intermediate gear 38b are
disposed within the chain compartment 4d with the thrust washers
being positioned at the ends of the intermediate sprocket 38a
and the intermediate gear 38b in such a manner as not to fall
therefrom, the thrust washer 44b can be prevented from falling
by allowing the stepped portion of the thrust washer 44b to
be locked in a shaft hole in the intermediate sprocket 38a,
and hence the assembling properties can be improved.
In addition, an oil hole 39e is formed in the support
shaft 39 for supplying lubricating oil introduced from the cam
compartment via an oil introducing bore 4e formed in the cylinder
head 4 to the needle bearing 44.
Additionally, four weight reduction holes 38c and two
inspection holes 38c adapted to be used at the time of assembling
and made to double as weight reduction holes are formed at
intervals of 60 degrees. Then, an alignment or timing mark
38d is stamped on a tooth situated substantially at the center
of the inspection hole 38c" for the intermediate gear 38b, and
timing marks 41a, 42a are also stamped on two teeth of intake
and exhaust camshaft gears 41, 42 which correspond to the timing
marks 38d. Here, when aligning the left and right timing marks
38d, 38d with the timing marks 41a, 42a, the intake and exhaust
camshafts gears 41, 42 are located at positions, respectively,
which correspond to a top dead center of a compression stroke.
Furthermore, timing marks 38e, 38e are also formed at
portions of the intermediate sprocket 38a which are situated
on a cover side mating surface 4f of the cylinder head 4 when
the timing marks 38d align with 41a, 42a.
To align valve timings, firstly, the crankshaft 8 is held
at a top dead center of a compression stroke by aligning the
timing mark 25c (refer to Fig. 11) with the cylinder bore axis
A. In addition, the intermediate sprocket 38a and the
intermediate ear 38b which are attached to the cylinder head
4 via the support shaft 39 are positioned so that the timing
mark 38e of the intermediate sprocket 38a aligns with the cover
side mating surface 4f, and in this state, the crankshaft
sprocket 25b and the intermediate sprocket 38a are connected
by the timing chain 40. Then, the intake and exhaust camshaft
gears 41, 42 on the intake and exhaust camshafts 36, 37 are
brought into mesh engagement with the intermediate gear 38b
while confirming through the inspection hole 38c" that the timing
marks 41a, 42a align with the timing mark 38d on the intermediate
gear 38b, and the intake and exhaust camshafts 36, 37 are fixed
to an upper surface of the cylinder head 4 via cam carriers.
Thus, since the inspection holes 38c" made to double as
the weight reduction holes to reduce the weight of the large
diameter intermediate sprocket 38a are provided in the
intermediate sprocket 3 8a, so that the alignment of the timing
marks 38d on the small-diameter intermediate gear 38b which
is set on the back of the intermediate sprocket 38a with the
timingmarks 41a, 42aon the camshaft gears 41, 42 canbe confirmed
through the inspection holes 38c", the meshing positions of
the intermediate gear 38b with the camshaft gears 41, 42 can
visually confirmed in an easy and ensured fashion while the
small diameter intermediate gear 38b is placed on the back of
the large diameter intermediate sprocket 38a, thereby making
it possible to align the valve timings without any problem.
In addition, since the intermediate gear 38b can be
disposed on the back side of the intermediate sprocket 38a,
the dimension from the camshaft gears 41, 42 which mesh with
the intermediate gear 38b to a cam nose 36a can be made shorter,
whereby the torsional angle of the camshaft can be made smaller
to such an extent that the dimension is made so shorter, thereby
making it possible to make compact an area surrounding the
camshafts.
Namely, for example, in a case where the intermediate
gear 38b is disposed on a front side of the intermediate sprocket
38a, while the valve timings can easily be aligned, the dimension
from the camshaft gears 41, 42 to the cam nose becomes long,
and the torsional angle of the camshafts becomes large to such
an extent that the dimension is extended, thereby reducing the
control accuracy of valve opening and closing timings.
In addition, in a case where the intermediate gear 38b
is disposed in front of the-intermediate sprocket 38a, a space
between the intermediate sprocket support shaft 39 and the
camshafts 36, 37 needs to be expanded in order to avoid any
interference between the intermediate sprocket 38a and the
camshaft 36, 37, this causing a concern that the area surrounding
the camshafts is enlarged.
Here, a backlash adjusting mechanism is provided between
the intermediate gear 38b and the camshaft gears 41, 42. This
adjusting mechanism has a construction in which the intake
camshaft gear 41 and the exhaust camshaft gear 42 are made up
of two gears such as a driving gear (a power transmission gear)
46 and a shift gear (an adjusting gear) 45 and the angular
positions of the driving gear 46 and the shift gear 45 can be
adjusted.
Namely, the shift gear 45 and the driving gear 46 are
fixed to flange portions 36b, 37b formed at end portions of
the camshafts 36, 37, respectively, in such a manner that the
angular positions thereof can be adjusted by four
circumferentially long elongated holes 45a, 46a and four long
bolts 68a. A clearance portion 46b is cut and formed in the
driving gear 46 that is disposed outwardly, and only the shift
gear 45 is fixed in such a manner that the angular position
thereof can be adjusted two elongated holes 45b and two short
bolts 68b by making use of the clearance portion 46.
A backlash adjustment is implemented according to the
following procedure. Note that in the engine according to the
embodiment, the intermediate gear 38b rotates counterclockwise
as shown in Fig. 3 when viewed from the left-hand side of the
engine. Consequently, both the intake camshaft gear 41 and
the exhaust camshaft gear 42 rotate clockwise. In addition,
here, while the backlash adjustment will be described with
respect to the intake camshaft gear 41, the same description
would be made with respect to the exhaust camshaft gear 42.
Firstly, all the fixing bolts 68a, 68b of the intake
camshaft gear 41 are loosened, and the shift gear 45 is rotated
clockwise so that front side surfaces of teeth of the shift
gear 45 in the clockwise direction slightly abut with rear side
surfaces of teeth of the intermediate gear 38b in the
counterclockwise direction. In this state, the shift gear 45
is fixed to the flange portion 36b of the camshaft 36 with two
short bolts 68b. Then, the driving gear 46 is rotated
counterclockwise in such a manner that front side surfaces
(driven surfaces) of teeth of the driving gear 46 in the
counterclockwise direction abut with front side surfaces
(driving surfaces) of the intermediate gear 38b in the
counterclockwise direction so as to obtain a required backlash,
and in this state, four long bolts 68a are tightened up, whereby
the driving gear 46 and the shift gear 45 are fixed to the intake
camshaft 36.
Thus, since the intake and exhaust camshaft gears 41,
42 are made up of the driving gear (power transmission gear)
46 and the shift (adjusting gear ) 45 adapted to rotate relatively
to the driving gear, respectively, the backlash can be adjusted
by rotating the shift gear 45 relatively to the driving gear
4 6 forward or backward in the rotating directions.
Note that while, in this embodiment, both the driving
gear 46 and the shift gear 45 which constitute the camshaft
gears 41, 42 are described as being able to rotate relatively
to the camshafts, one of the driving gear 46 and the shift gear
45 may be adapted to rotate relatively and the other gear may
be integrated into the camshaft. In this case, it is desirable
that the gear integrated into the camshaft constitutes the power
transmission gear. Even if constructed in this way, similar
function and advantage to those obtained by the embodiment can
be obtained.
In addition, while in the embodiment, the invention is
described as being applied to the construction in which the
chain drive method is adopted, the invention can of course be
applied to a drive method using a toothed belt.
Next, a lubricating construction will be described.
A lubrication system 50 of the engine according to the embodiment
is constructed such that lubricatingoil stored within a separate
lubricating oil tank 51 is picked up and pressurized by a
lubricating oil pump 52 via a down tube 56c on a vehicle body
frame, lubricating oil discharged from the pump 52 is divided
into three systems such as a cam lubricating system 53, a
transmission lubricating system 54 and a crank lubricating
system 55 so as to be supplied to parts needing to be lubricated
at the respective systems, and lubricating oil used for
lubricating the respective parts needing lubrication is
returned to the lubricating oil tank 51 by making use of pressure
fluctuation occurring within the crank compartment 2c as the
piston 6 reciprocates vertically.
The lubricating oil tank 51 is formed integrally within
a space surrounded by a head pipe 56a, a main tube 56b, the
down tube 56c and a reinforcement bracket 56d of the vehicle
body frame 56. This lubricating oil tank 51 communicates with
a cross pipe 56e which connects lower portions of the down tube
56c via the down tube 56c.
Then, the cross pipe 56e communicates with a pick-up port
of the lubricating oil pump 52 via an outlet tube 56f connected
thereto, anoilhose 57a, a joint pipe 57b andapick-up passageway
58a formed in a crankcase cover 10. A discharge port of the

lubricating oil pump 52 is connected to an oil filter 59 via
an oil discharge passageway 58b, an external portion connecting
chamber 58c and an oil passageway 58d and is divided into the
three lubrication systems 53, 54, 55 on a secondary side of
the oil filter 59.
The oil filter 59 is constructed such that an oil element
59e is disposed in a filter compartment 59d def inedby detachably
attaching a portion of a cover 47 to a filter recessed portion
10b provided in the right case cover 10 by setting part thereof
further back from the rest.
The cam lubricating system 53 has a construction which
is generally constructed such that a lower end of a vertical
member 53a of a T-shaped lubricating oil pipe is connected to
a cam side outlet 59a of an oil passageway formed on the outside
of the filter recessed portion 10b, whereas left and right ends
of a horizontal member 53b of the lubricating oil pipe are
connected to a camshaft oil supply passageway 53c, so that
lubricating oil is supplied to parts such as bearings of the
camshafts 36, 37 which need to be lubricated via the passageway
53c.
The transmission lubrication system 54 has the following
construction. A right transmission oil supply passageway 54a
formed within the right case portion 2b is connected to a
transmission side outlet 59b of the oil filter 59, and the oil
supply passageway 54a communicates with the interior of a main
shaft bore 14a formed in the main shaft 14 along the axial center
thereof via a left transmission oil passageway 54b formed in
the left case portion 2a. Then, this main shaft bore 14a
communicates with sliding portions between the main shaft 14
and change-speed gears via a plurality of branch bores 14b,
whereby lubricating oil supplied to the main shaft bore 14a
passes through the branch bores 14b to be supplied to the sliding
portions.
In addition, an intermediate portion of the left
transmission oil passageway 54b communicates with a bolt bore
60a through which a case bolt 60 for connecting the left and
right case portions 2a, 2b together is allowed to pass. This
bolt bore 60a is such as to be formed by forming a bore having
an inside diameter which is slightly larger than the outside
diameter of the case bolt 60 in tubular boss portions 60c, 60c
which are formed so as to face and abut with each other on the
mating surface between the left and right case portions 2a,
2b. The boss portion 60c is situated in the vicinity of a portion
where a gear train on the main shaft 14 meshes with a gear train
on the drive shaft 15, and a plurality of branch bores 60b are
formed from which lubricating oil within the bolt bore 60a is
spouted out toward the gear trains meshing portion. Note that
the bolts 60 shown in Fig. 19 as being developed into the left
and right case portions are the same bolt.
Furthermore, a right end portion of the bolt bore 60a
communicates with a drive shaft bore 15a formed in the drive
shaft 15 along the axial center thereof via a communication
bore54c. Then, the drive shaft bore 15a is closedby apartition
wall 15c at a left-hand side portion and communicates with
sliding portions between the drive shaft 15 and driving gears
via a plurality of branch bores 15b. Thus, lubricating oil
supplied into the drive shaft bore 15a passes through the branch
bores 15b to be supplied to the sliding portions.
The crank lubricating system 55 has the following
construction. A crank oil supply passageway 55a is formed in
the filter cover 47 in such a manner as to extend from a crank
side outlet 59c toward the lubricating oil pump 52, and the
passageway 55 is made to communicate with a communication bore
62a which is formed in a rotating shaft 62 of the lubricating
oil pump 52 to pass therethrough along the axial center thereof.
Furthermore, the communication bore 62a communicates with a
crank oil supply bore 8e formed in the crankshaft 8 to pass
therethrough along the axial center thereof via a connecting
pie 64. Then, this crank oil supply bore 8e communicates with
the interior of a pin bore 65a in a crank pin 65 via a branch
bore 8f, and the pin bore 65a is made to open to the rotating
surface of a needle bearing 7b at a big end portion 7a of a
connecting rod 7 via a branch bore 65b. Thus, lubricating oil
filtered in the oil filter 59 is supplied to the rotating surface
of the needle bearing 7b.
The lubricating oil pump 52 has the following construction.
A pump compartment 61c is provided in a right case 61b of a
two-piece casing made up of left and right cases 61a, 61b by
setting a relevant portion of the case further back from the
rest, and a rotor 63 is disposed rotationally within the pump
compartment 61. The rotating shaft 62 is inserted into the
rotor 63 along the axial center thereof in such a manner as
to pass therethrough to be disposed in place therein, and the
rotating shaft 62 and the rotor 63 are fixed together with a
pin 63a. Note that the oil pick-up passageway 58a and oil
discharge passageway 58b are connected to a pump compartment
upstream side and a pump compartment downstream side of the
left case 61a, respectively. In addition, reference numeral
66 denotes a relief valve for retaining the discharge pressure
of the lubricating oil pump 52 to a predetermined value of lower
and adapted to relieve the pressure on the discharge side of
the lubricating oil pump 52 to the oil pick-up passageway 58a
side when the pressure on the discharge side reaches or exceeds
the predetermined value.
The rotating shaft 62 is a tubular shaft which passes
through the pump case 61 in the axial direction and opens to
the crank oil supplypassageway 55a at a right end portion thereof
as shown in the drawing. In addition, a power transmitting
flange portion 62b is formed integrally at a left end portion
of the rotating shaft 62 as shown in the drawing. The flange
portion 62b faces a right end face of the crankshaft 8, and
the flange portion 62b and the crankshaft 8 are connected
together by an Oldham" s coupling 61 in such a manner as to absorb
a slight deviation of the centers of the shafts.
The Oldham"s coupling 67 is constructed such that a
coupling plate 67a is disposed between the crankshaft 8 and
the flange portion 62b, a pin 67b planted in the end face of
the crankshaft 8 and a pin 67c planted in the flange portion
62b are inserted into a connecting bore 67d in the coupling
plate 67a.
In addition, the connecting pipe 64 is such as to connect
a right end opening in the crankshaft 8 to a left end opening
in the rotating shaft 62, and sealing is provided by an oil
seal 64a between the inner circumference of the crankshaft
opening and the inner circumference of the rotating shaft opening
and the outer circumference of the connecting pipe 64.
Here, as has been described above, the crank compartment
2c is defined separately from the other transmission compartment
2d, the flywheel magnet compartment 9a and the clutch compartment
10a, whereby an oil return mechanism is constructed in which
the pressure within the crank compartment 2c is fluctuated to
be positive and negative as the piston 6 strokes, so that
lubricating oil in the respective compartments is returned to
the lubricating oil tank 51 by virtue of the pressure
fluctuation.

To describe this in detail, a discharge port 2g and a
suction or pick-up port 2h are formed in the crank compartment
2c. A discharge port reed valve 69 adapted to open when the
pressure within the crank compartment is positive is disposed
in the discharge port 2g, and a pick-up port reed valve 70 adapted
to open when the pressure within the crank compartment is
negative is disposed in the pick-up port 2h.
Then, the discharge port 2g communicates with the clutch
compartment 10a from the crank compartment 2c via a communication
bore 2i and then communicates with the transmission compartment
2d from the clutch compartment 10a via a communication bore
2j . Furthermore, the transmission compartment 2d communicates
with the flywheel magnet compartment 9a via a communication
bore 2k. A return port 2m formed so as to communicate with
the flywheel magnet compartment 9a communicates with the
lubricating oil tank 51 via a return hose 57c, an oil strainer
57d and a return hose 57e.
Here, a guide plate 2n is provided at the return port
2m. This guide plate 2n has a function to ensure the discharge
of lubricating oil by modifying the return port 2m so as to
provide a narrow gap a between a bottom plate 2p and itself
and to secure a wide width b.
Additionally, an oil separating mechanism for separating
oil mists contained in the air within the tank by virtue of
centrifugal force so as to return oil mists so separated to
the crank compartment 2c. This oil separating mechanism has
a construction in which an introduction hose 72a which is
connected to an upper portion of the lubricating oil tank 51
at one end thereof is tangentially connected to an upper portion
of a cone-shaped separating compartment 71 at the other end
and a return hose 72b connected to a bottom portion of the
separating compartment 71 is connected to the pick-up port 2h
of the crank compartment 2c. Note that the air from which the
oil mists are separated is discharged to the atmosphere via
an exhaust hole 72c.
Thus, according to the embodiment, since the crank chamber
2c is made to be a substantially closed space so that the pressure
therein fluctuates as the piston 6 reciprocates vertically,
whereby lubricating oil that has flowed into the crank
compartment 2c is sent back to the lubricating oil tank 51 by
virtue of pressure fluctuation within the crank compartment
2c, the necessity of an exclusive oil sending pump (a scavenging
pump) can be obviated, and hence the construction of the engine
can be simplified and costs can be attempted to be reduced.
Inaddition, since the discharge port reed valve (anoutlet
side check valve) 69 adapted to open when the pressure in the
crank compartment increases and to close when the pressure lowers
is disposed in the vicinity of where the oil sending passageway
is connected to the crank compartment 2c, the lubricating oil
within the crank compartment 2c can be sent back to the
lubricating oil storage tank 51 in a more ensured fashion.
In addition, since an portion above the oil level within
the lubricating oil storage tank 51 is connected to the crank
compartment 2 via the return hoses 72a, 72b and the discharge
port reed valve (a pick-up side check valve) 70 adapted to open
when the pressure in the crank compartment 2c lowers and to
close when the pressure increases is provided in the vicinity
where the return hoses are connected to the-crank compartment
2c, air required is picked up into the crank compartment 2c
when the piston 6 moves upwardly, whereas the inside pressure
of the crank compartment 2c increases as the piston 6 lowers,
whereby lubricating oil within the crank compartment 2c can
be sent tout in a more ensured fashion.
Incidentally, in a case where there is provided no air
supply path from the outside to the interior of the crank
compartment 2c, only a negative pressure or a lower positive
pressure is formed inside the crank compartment, this causing
a concern that there occurs a case where oil cannot be sent
out properly.
Furthermore, since the centrifugal lubricating oil mist
separating mechanism 71 for separating lubricating oil mist
is interposed at the intermediate position along the length
of the return passageways 72a, 72b, so that lubricating oil
mist so separated is returned to the crank compartment 2c via
the return hose 72b, whereas air from which the mist content

is removed is discharged to the atmosphere, only lubricating
oil mist can be returned to the crank compartment, whereby the
reduction in oil sending efficiency can be avoided which would
occur when an excessive amount of air is allowed to flow into
the crank compartment, thereby making it possible to send out
lubricating oil in the crank compartment in an ensured fashion
while preventing the atmospheric pollution.
In addition, since the lubricating oil pump-52 is disposed
so as to be connected to the one end of the crankshaft 8 and
the discharge port of the lubricating oil pump 52 is made to
communicate with the crank oil supply bore (an in-crankshaft
oil supply passageway) 8e formed within the crankshaft 8 via
the communication bore (an in-pump oil supply passageway) 62a
formed within the lubricating oil pump 52 and the connecting
pipe 64, the lubricating oil can be supplied to the parts of
the crankshaft 8 which need to be lubricated by the simple and
compact construction.
In addition, since the crankshaft 8 and the lubricating
oil pump 52 are connected together by the Oldham"s coupling
67 which can absorb the displacement of the shafts in the
direction normal thereto and the communication bore 62a and
the crank oil supply bore 8e are made to communicate with each
other via the connecting pipe 64 with the 0 rings 64a having
elasticity being interposed between the connecting pipe 64 and
the communicating bore 62a, the crank oil supply bore 8e, even
in the event that the centers of the crankshaft 8 and the pump
shaft 62 are caused to deviate slightly from each other,
lubricating oil can be supplied to the parts needing to be
lubricated without any problem, thereby making it possible to
secure the required lubricating properties.
Furthermore, since the tubular boss portion 60c is formed
in the vicinity of the main shaft 14 and the drive shaft 15
which constitute the transmission, the crankcase connecting
case bolt 60 is inserted into the bolt bore 60a in the boss
portion 60c so that the space between the inner circumferential
surface of the bolt bore 60a and the outer circumferential
surface of the case bolt 60 is made to form the lubricating
oil passageway, and the branch bore (the lubricating oil supply
bore) 60b is formed which is directed to the change-speed gears
at the boss portion 60c, lubricating oil can be supplied to
the meshing surfaces of the change-speed gears while obviating
the necessity of providing an exclusive lubricating oil supply
passageway.
In addition, since the other end of the lubricating oil
passageway defined by the inner circumferential surface of the
bolt bore 60c and the outer circumferential surface of the case
bolt 60 is made to communicate with an opening of the drive
shaft bore (the lubricating oil passageway) 15a formed within
the drive shaft 15 which is situated opposite to an outlet side
of the bore, lubricating oil can be supplied to the portions
on the drive shaft 15 which are brought into sliding contact
with the change-speed gears while obviating the necessity of
providing an exclusive lubricating oil supply passageway.
Industrial Applicability
According to the first aspect of the invention, since
at least the part of head bolts which fasten the cylinder head
and the cylinder body together are screwed into the case side
flange portion, the load applied to the cylinder body is reduced
by such an extent that the load generated by the combustion
pressure is partially borne by the head bolts, and hence the
stress generated in the cylinder body can be reduced accordingly,
thereby making it possible to improve the durability of the
cylinder body.
Namely, in the case of a construction, for example, in
which a head side flange portion of a cylinder body and a cylinder
head are simply fastened together with bolts and a case side
flange portion and a crankcase are simply fastened together
with bolts, the load generated by the combustion pressure is
totally applied to the cylinder body, and the durability of
the cylinder body becomes insufficient depending upon the
thickness of the cylinder body, and in the worst case, there
exists a concern that a crack is generated in the cylinder body.
According to the invention, however, a problem like this can
be avoided.

According to the second aspect of the invention, since
the flange screw-through head bolt and the case bolt overlap
each other by the distance which is substantially the same as
the thickness of the case side flange portion, the flange
screw-through head bolts can ensure the transmission of part
of the load generated by the combustion pressure to the case
side flange portion, thereby making it possible to reduce the
load applied to the intermediate portion of the cylinder body.
According to the third aspect of the invention, since
the flange screw-through bolt and the case bolt are disposed
close to each other, when viewed in the axial direction of the
cylinder bore, the flange screw-through head bolts can ensure
further the transmission of part of the load generated by the
combustion pressure to the case side flange portion, and
furthermore, the case side flange portion can in turn ensure
the transmission of the load so transmitted thereto to the
crankcase via the case bolts, thereby making it possible to
reduce the load applied to the cylinder body in an ensured
fashion.
According to the fourth aspect of the invention, since
the case bolt is disposed such that the distance from the case
bolt to the first straight line which passes through the axis
of the cylinder bore and which is normal to the crankshaft becomes
shorter than the distance from the flange screw-through head
bolt to the first straight line, when viewed in the axial
direction of the cylinder bore, or such that the case bolts
are situated closer to the center of the cylinder bore in the
crankshaft direction, the dimension in the crankshaft direction
of the mating surface of the crankcase which is attached to
the cylinder body can be reduced to the vicinity of the positions
where the flange screw-through head bolts are disposed, and
as a result, the dimension in the crankshaft direction of the
crankcase can be reduced.
According to the fifth aspect of the invention, since
the construction is adopted in which the flange screw-through
head bolts are screwed into the case side flange portion of
the cylinder body or the flange screw-through head bolts are
not screwed into the crankcase, there exists no risk that a
problem is caused of the flange screw-through head bolts
interfering with the crankshaft web incorporated in the
crankcase, so that the flange screw-through head bolts can be
disposed such that the distance to the second straight line
which passes through the axis of the cylinder bore and which
is parallel to the crankshaft becomes shorter than the distance
from the case bolt to the second straight line or such that
the flange screw-through head bolts can be situated closer to
the crankshaft side, whereby the dimension of the cylinder body
in the direction normal to the crankshaft can be reduced.
According to the sixth aspect of the invention, since
the axial part of the flange screw-through head bolt is exposed
to the outside, the weight of the cylinder body can be reduced.
According to the seventh aspect of the invention, since
at least the three head bolts are disposed on either side of
the cylinder bore across the second straight line, the central
head bolt along the second straight line is caused to be situated
apart from the axis of the cylinder. However, since the head
bolt is set to have the length which does not reach the case
side flange portion, the portion of the case side flange portion
which corresponds to the center can be minimized, thereby making
it possible to avoid the enlargement of the cylinder body and
the crankcase.
According to the eighth aspect of the invention, since
the flange screw-through head bolt is disposed between the
cylinder bore and the chain compartment formed on the side to
the cylinder bore, the flange screw-through head bolt can be
disposed by making the effective use of the dead space formed
therebetween.
According to the ninth aspect of the invention, since
the flange screw-through head bolt is screwed into the case
side flange portion at one end and is fastened and fixed to
the cylinder head with the cap nut at the other end thereof,
the cylinder head can be removed without securing a large space
above the cylinder head, thereby making it possible to secure
the maintenance properties of the engine.

We Claim
---------------
1. An engine fastening device in which a cylinder body (3) and a cylinder
head (4) are stacked on and fastened to a crankcase (2), characterized in
that atleast one case bolt (30a) passes through a case side flange portion
(3b) formed at a crankcase side end portion of the cylinder body (3) and
are screwed into a cylinder body side end portion of the crankcase (2) to
fasten the cylinder body (3) to the crankcase (2), in that at least part of
atleast one head bolt (30c) which fastens the cylinder head (4) and the
cylinder body (3) together is made to be a flange screw-through head
bolt, and in that the flange screw-through head bolt (30c) is screwed into
a screw portion formed in the case side flange portion (3b).
2. An engine fastening device as claimed in claim 1, wherein flange screw-
through head bolt (30c) and the case bolt (30a) overlap each other by a
distance which is substantially the same as the thickness of the case side
flange portion (3b) in the axial direction of a cylinder bore (3a).
3. An engine fastening device as claimed in claim 1 or 2, wherein the flange
screw-through head bolt (30c) and the case bolt (30a) are disposed close to
each other, when viewed in the axial direction of the cylinder bore (3a).
4. An engine fastening device as claimed in any of claims 1 to 3, wherein the
case bolt (30a) is disposed such that a distance from the case bolt to a
first straight line (c1) which passes through the axis (A) of the cylinder
bore (3a) and which is normal to a crankshaft (8) becomes shorter than a
distance (a2) from the flange screw-through head bolt (30c) to the first
straight line (c1), when viewed in the axial direction of the cylinder bore
(3a)
5. An engine fastening device as claimed in any of claims 1 to 4, wherein the
flange screw-through head bolt (30c) is disposed such that the a distance
(b2) from the head bolt (30c) to a second straight line (c2) which passes
through the axis (A) of the cylinder bore (3a) and which is parallel to the
crankshaft (8) becomes shorter than a distance (b1) from the case bolt
(30a) to the second straight line (c2), when viewed in the axial direction
of the cylinder bore (3a).
6. An engine fastening device as claimed in any of claims 1 to 5, wherein an
upper flange portion (3f) is formed at a cylinder head side (4) end portion
of the cylinder body (3), wherein the flange screw-through head bolt
(30c) passes the upper flange (3f) portion and is screwed into the case
side flange portion (30a), and wherein a part of the flange screw-through
head bolt (30c) which is between the case side flange portion (30a) and
the upper flange portion (3f) is exposed to the outside.
7. An engine fastening device as claimed in any of claims 1 to 6, wherein at
least three head bolts (30c, 30b, 30e) are disposed on either side of the
cylinder bore (3a) across the second straight line (c2), when viewed in the
axial direction of the cylinder bore (3a), and wherein the central head bolt
(30b) along the second straight line (c2) is set to have a length which
does not reach the case side flange portion (3b).
8. An engine fastening device as claimed in any of claims 1 to 7, wherein the
flange screw-through head bolt (30c) is disposed between a chain
compartment (3d) and the cylinder bore (3a), the chain compartment
being formed on a side to the cylinder bore (3a) in which a camshaft
driving chain (40) which connects the crankshaft (8) to a camshaft is
disposed.
9. An engine fastening device as claimed in any of claims 1 to 8, wherein the
flange screw-through head bolt (30c) is screwed into the case side flange
portion (30a) at one end and is fastened and fixed to the cylinder head
(4) with a cap nut (32a) at the other end thereof.
10. An engine fastening device as claimed in claim 1, wherein a tip of the
flange screw-through head bolt (30c) is positioned closer to a cylinder
body side than a cylinder body side end surface to the crankcase (2).
This invention relates to an engine fastening device in
which a cylinder body (3) and a cylinder head (4) are stacked on
and fastened to a crankcase (2). Atleast one case bolt (30a)
passes through a case side flange portion (3b) formed at a
crankcase side end portion of the cylinder body (3) and are
screwed into a cylinder body side end portion of the crankcase
(2) to fasten the cylinder body (3) to the crankcase (2), in that
at least part of atleast one head bolt (30c) which fastens the
cylinder head (4) and the cylinder body (3) altogether is made to
be a flange screw-through head bolt, and in that the flange
screw-through head bolt (30c) is screwed into a screw portion
formed in the case side flange portion (3b).

Documents:

1157-kolnp-2004-granted-abstract.pdf

1157-kolnp-2004-granted-claims.pdf

1157-kolnp-2004-granted-correspondence.pdf

1157-kolnp-2004-granted-description (complete).pdf

1157-kolnp-2004-granted-drawings.pdf

1157-kolnp-2004-granted-form 1.pdf

1157-kolnp-2004-granted-form 18.pdf

1157-kolnp-2004-granted-form 2.pdf

1157-kolnp-2004-granted-form 3.pdf

1157-kolnp-2004-granted-form 5.pdf

1157-kolnp-2004-granted-letter patent.pdf

1157-kolnp-2004-granted-pa.pdf

1157-kolnp-2004-granted-reply to examination report.pdf

1157-kolnp-2004-granted-specification.pdf


Patent Number 212691
Indian Patent Application Number 01157/KOLNP/2004
PG Journal Number 50/2007
Publication Date 14-Dec-2007
Grant Date 12-Dec-2007
Date of Filing 11-Aug-2004
Name of Patentee YAMAHA HATSUDOKI KABUSHIKI KAISHA
Applicant Address 2500 SHINGAI, IWATA SHI SHIZUOKA 438 8501 JAPAN.
Inventors:
# Inventor's Name Inventor's Address
1 UTSUMI YOJI C/0 YAMAHA HATSUDOKI KABUSHIKI KAISHA 2500 SHINBAIU IWAT SHI SHIZUOKA 438 8501 JAPAN.
2 ITO MASAHIRO C/O. YAMAHA HATSUDOKI KABJUSHIKI KAISHA 2500 SHINGAI IWTA SHI SHIZUOKA 438 8501 JAPAN.
PCT International Classification Number F0F1/00
PCT International Application Number PCT/JP03/01607
PCT International Filing date 2003-02-14
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2002-43837 2002-02-20 Japan