Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
TITLE OF THE INVENTION
LUBRICATION SYSTEM FOR CRANX:SHAFT
BACKGROUND OF THE INASNTION
The present invention relates to a lubrication system for a
crankshaft, which is lubricated between a crankpin of the
crankshaft and a connecting rod.
An engine includes a piston reciprocating in a cylinder, and
a crankshaft rotatably mounted in a crankcase, wherein a piston.
and the crankshaft are connected through a connecting rod. To
supply lubricating oil to contact portions of respective members
constituting the engine, an oil pump is driven by the crankshaft.
In a four-cycle engine, the lubricating oil from the oil pump is
supplied also to contact portions between a crankpin of the
crankshaft and a bearing incorporated in an end portion of the
connecting rod.
In an assembly-type crankshaft formed by a plurality of
members so that they are linked through the crankpin, a hollow
crankpin can be used. Thus, in the crankshaft using the hollow
crankpin, as described in patent document 1, a communication hole
for communicating with a hollow hole and an outside periphery of
the crankpin is formed in a diameter direction thereof, and the
lubricating oil from the oil pump is supplied., through the hollow
hole and the communication hole, to a contact portion between a
rolling bearing fitted to the crankpin and the crankpin, whereby
the lubricating oil is directly discharged into an outside
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periphery of a rotating body of the rolling bearing.
Meanwhile, in a connecting rod of such a type that a sliding
bearing is incorporated between the crankshaft and an end portion
of a crankshaft side of the connecting rod, as described in patent
document 2, a supply hole of the lubricating oil is fozmed in the
connecting rod so as to communicate with an inner surface of the
sliding bearing and an inner surface of a fitting hole to which a
piston pin is fitted.
[Patent Document 1]
Japanese Patent Laid-Open (TOKUKAIHEI) rlo. 7-119428
[Patent Document 2]
Japanese Patent Laid-Open (TOKUKAIHEI) No. 5-106630
SUMMARY OF TtiS INV8~1TION
As described above, to supply the lubricating oil to the
contact portion between the crankpin and the bearing fitted
thereto, durability tests have been performed for the engine
provided with the crankshaft in which an opening of a lubricating-
oil supply path is formed on the outside periphery of the crankpin
so as to face to an inner surface of the bearing. As a result of
observation of the crankshaft after driving the engine over a long
terns, it has been found out that a flaking phenomenon occurs at a
fringe, i.e., an edge of the opening of the lubricating-oil supply
path formed in the crankpin. This flaking phenomenon is one in
which the fringe of the opening a.s worn away, and if the flaking
phenomenon occurs, the lubricating oil cannot be appropriately
supplied to the contact portion.
Investigations of the reason for the occurrence of the
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flaking phenomenon have shown that when a rolling bearing such as
a roller bearing is mounted to the crankpin, a rotating body such
as a roller of the rolling bearing rolls and contacts to the
outside periphery of the crankpin, whereby a surface pressure
applied to the outside periphery of the crankpin from this
rotating body is such that the fringe of the opening is several
times higher in the surface pressure than other portions. Thus,
it is thought that when the high surface pressure is applied to
the fringe of the opening, the flaking phenomenon occurs at the
fringe at the very first due to the high surface pressure. If the
flaking phenomenon occurs at the fringe at the very first, desired
lubrication performance cannot be maintained even though there are
no defects in other parts, and so the durability of the crankshaft
is lost.
An object of the present invention is to provide a
lubrication system for a crankshaft, which is capable of improving
the durability of the crankshaft.
A lubrication system for a crankshaft according to the
present invention is one which lubricates a connecting portion
between a crankshaft rotatably mounted in a crankcase and
connected to a piston in a cylinder via a connecting rod and said
connecting rod, said lubrication system comprising: a crankpin
attached to a crank web integrally provided with a journal portion
to form said crankshaft; a bearing mounted on an end portion of
said connecting rod and fitted to said crankpin; and a
lubricating-oil discharging opening communicating with a
lubricating-oil supply path formed in said crankshaft, said
opening being formed on an end face of said crank web, wherein the
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lubricating oil is discharged from said opening to an end portion
of said bearing.
In the lubrication system of a crankshaft according to the
present invention, said bearing is a rolling bearing having a
rotating body. Further, in the lubrication system of a crankshaft
according to the present invention, said crankshaft is formed by:
a plurality of shaft elements each having a iournal portion and a
crank web integrally fornned therewith; and a crankpin connecting
the shaft elements attached to an attachment hole formed in each
of the crank webs, and connecting the crank elements.
In the present invention, since the opening of the
lubricating-oil supply path foamed in the crankshaft is formed on
the end face of the crank web, the lubricating oil can be supplied,
through the end portion of the bearing, to the sliding portion
between the bearing fitted to the crankpin and the crankpin.
Therefore, it is unnecessary to fornn the opening of the
lubricating-oil supply path on the outside periphery of the
crankpin, and the surface pressure applied to the crankpin from
the bearing becomes almost uniform over the entirety of the
outside periphery of the crankpin. Accordingly, without the
occurrence of the flaking phenomenon on the outside periphery of
the crankpin, the durability of the crankshaft can be improved.
DESCRIPTION OF TIC DRAWINGS
FIG. 1 is a schematic diagram showing an engine in which a
lubrication system for a crankshaft according to an embodiment of
the present invention is incorporated.
FIG. 2 is an enlarged sectional view showing a part of FIG. 1.
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FIG. 3 is a perspective view showing one shaft element
constituting a crankshaft.
FIG. 4 is a sectional view showing a part of a crankpin and a
connecting rod as a comparison example.
DESCRIPTIOI~i OF TIC PRBFERRSD EMBODI~NTS
Hereinafter, an embodiment of the present invention will be
described in detail based on the drawings. lE'IG. 1 is a schematic
diagram showing an engine in which a lubrication system for a
crankshaft according to an embodiment of the present invention is
incorporated, and FIG. 2 is an enlarged sectional view showing a
part of FIG. 1.
This engine is a four-cycle single-cylinder one and can be
applied as an engine of a vehicle such as a 1'DUggy, more
specifically, applied as an engine of an ATV, namely, all-terrain
vehicle. As shown in FIG. 1, this engine includes a crankcase 12
rotatably supporting crankshafts 11, and a piston 14 reciprocally
incorporated in a cylinder 13 mounted in the crankcase 12. To
transmit the reciprocating motion of the piston 14 to the rotary
motion of the crankshaft 11, a connecting rod 17 is connected
between a piston pin 15 fixed to the piston .14 and a crankpin 16
fixed to the crankshafts 11.
A cylinder head 18 is attached to the cylinder 13, and the
cylinder head 18 and the piston 14 form a combustion chamber 19 in
the cylinder 13. A suction port communicating with the combustion
chamber 19 and supporting an air-fuel mixture and an exhaust part
exhausting an combustion gas are fo:cmed in the cylinder head 18.
An not shown suction valve for opening/closing the suction port
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and an not shown exhaust valve for opening/c)_osing the exhaust
port are formed in the cylinder head 18, respectively. To
open/close-drive the suction valve and the exhaust valve, a
camshaft 20 is rotatably attached to the cylinder head 18, and a
sprocket 21 fixed to the camshaft 20 is connected to a sprocket 22
fixed to the crankshaft 11 via a chain 23. Therefore, the
camshaft 20 is driven by the crankshaft 11.
A rocker shaft 24 parallel to the camshaft 20 is rotatably
mounted in the cylinder head 18, and a rocket: arm 25 for
open/close-driving the suction valve and a rocker a.rm 26 for
open/close-driving the exhaust valve are rotatably mounted on the
rocker shaft 24. One end portions of the rocker arms 25 and 26
come in contact with valve-operating cams 27 and 28, respectively,
and the suction valve grad the exhaust valve are attached to the
other end portions thereof.
In the engine shown in FIG. 1, a generai=or c~.se 31 is
attached to the crankcase 12, and a generator 32 is mounted in
this generator case 31. The generator 32 includes an outer rotor
34 provided with magnets 33 and a stator 36 provided with coils 35,
wherein the outer rotor 34 is fixed to the crankshaft 11 and the
stator 36 is fixed to the generator case 31. The electric power
generated by the rotation of the crankshaft 11 is supplied to an
not shown battery from this generator 32, whereby the battery is
charged.
As shown in FIG. 2, the crankshaft 11 is rotatably mounted in
the crankcase 12 by bearings 37 and 38 attached to the crankcase
12. The crankshaft 11 shown in FIG. 2 has tvao shaft elements 11a
and 11b, and one shaft element 11a is shown in FIG. 3. As shown
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in FIG. 3, the shaft element 11a is provided with a journal
portion 41a rotatably supported by the bearing 38, and a crank web
42a integrally formed with an end portion of the journal portion
41a. The crank web 42a has a crank arm portion 43a protruding in
a diameter direction, and a balance weight portion 44a protruding
in a direction opposite to that of the crank arm portion 43a,
wherein an attachment hole 45a is formed in the crank arm portion
43a. Similarly, also in the other shaft element 7.1b, a crank web
42b integrally provided with a journal portion 41b includes a
crank arm portion 43b and a balance weight portion 44b, wherein an
attachment hole 45b is formed in the crank a.~zrt portion 43b.
The crankshaft 11 is formed, by coupling the two shaft
elements lla and 11b through the crankpin 16 fitted into the
attachment holes 45a and 45b, and the crankpin 16 has a
communication hole 47 therein and so becomes hollow. In the
connecting rod 17 connecting the crankshaft :L1 and the piston 14,
a link end portion 49 having a fitting hole 49a to which the
piston pin 15 fixed to the piston 14 is fitted is provided on one
end thereof. In a link end portion 51 provided at the other end
thereof, a fitting hole 51a to which a bearing 50 fitted to the
crankpin 16 is fitted is formed. The bearing 50 is provided with
a plurality of rotating bodies such as rollers 52, and a retainer
53 having a groove rotatably accommodating the respective rollers
52.
A lubricating-oil supply path 55 having an opening 54 on an
end face of the crank web 42a is formed in the shaft element 11a
of the crankshaft 11, and the lubricating-oil supply path 55
communicates with an not shown discharge port: of the oil pump.
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The lubricating-oil supply path 55 and the discharge port of the
oil pump may communicate with each other through an oil path
formed in the crankcase 12, or through a joint portion provided at
the end portion of the crankshaft 11. The opening 54 of the
lubricating-oil supply path 55 is formed so as to face to an end
face of the bearing 50. The lubricating oil discharged from the
oil pump serving as a lubricating-oil supply source is supplied
into the inside of the bearing 50 from a side of the end portion
of the bearing 50, and the outside periphery of the crankpin 16
and the roller 52 rolling along the outside periphery thereof are
contacted via an oil film.
The lubricating-oil supply path 55 communicates with the
communication hole 47 in the crankpin 16, through a communication
oil path 56 formed in the crankshaft 11 and a~ communication hole
56a formed in the r,.rankpin 16 so as to communicate with the oil
path, whereby the lubricating oil is supplied to the communication
hole 47. Plugs 57a and 57b are fixed at both. ends of the
communication hole 47 of the crankpin 16, and a discharge hole 58
for supplying the lubricating oil to the bearing 37 is formed in
the plug 57a. However, if the lubricating oil can be supplied to
the bearing 37 through the other oil path, it is unnecessary to
provide the communication oil path 56 and the communication hole
47.
As described above, the opening for discharging the
lubricating oil is not formed in a partial one on which the roller
52 rolls in the entire outside periphery of the crankpin 16,
whereby the outside periphery of the crankpin 16 becomes wholly
flat. As a result, without locally increasing the surface
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pressure at the outside periphery of the crankpin 16 by loads
applied from the roller 52, the wholly unifoxm surface pressure is
applied to the outside periphery of the crankpin 16. Therefore,
the flaking phenomenon on the outside periphery of the crankpin 16
does not occur even after the engine has been used over a long
term, whereby the durability of the crankshaft 11 can be improved.
FIG. 4 is a sectional view showing a part of the crankpin 16
and the connecting rod 17 as a comparison example. In this
comparison example, to supply the lubricating oil to the bearing
50 from the communication hole 47 similarly to the conventional
ones, a lubricating-oil supply path 60 opening to the outside
periphery of the roller 52 of the bearing 50 is formed in the
crankpin 16. When the lubricating-oil supply path 60 is thus
foamed in the crankshaft 16 by opening to the outside periphery of
the roller 52, the roller 52 contacts to a fringe of such an
opening with some large surface pressure. Therefore, a flaking
phenomenon 61 occurs at the fringe of the opening due to secular
change in the crankpin 16, and the lubrication perforlnance,is
changed. However, such a flaking phenomenon does not occur in the
crankshaft 11 of the present invention, whereby the durability of
the crankshaft 11 can be improved.
The present invention is not limited to the above-mentioned
embodiment, and can be variously modified and changed without
departing from the gist thereof. For example, the crankshaft 11
illustrated in the drawings is for the single-cylinder engine.
However, the present invention can also be applied to a crankshaft
for rnulti-cylinder engine. Further, the engine provided with the
crankshaft I1 can be applied as an engine for motorcycle or a
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mufti-purpose engine for, generator besides the ATV. Furthernnore,
the crankshaft 11 illustrated in the drawings is of such an
assembly type as to connect the shaft elements 11a and 11b through
the crankpin 16. However, it is also possible to apply the
present invention to a crankshaft of an integrally formed type.
Additionally, a needle bearing can be used as the rolling bearing
as well as the roller bearing.
According to the present invention, since the opening of the
lubricating-oil supply path formed in the crankshaft is formed on
the end face of the crank web, it is possible to supply the
lubricating oil to the sliding portion between the bearing fitted
to the crankpin and the crankpin, through the end portion of the
bearing. Therefore, without the occurrence of the flaking
phenomenon on the outside periphery of the crankpin, the
durability of the crankshaft can be improved.
The entire disclosure of a Japanese Patent Application No.
2003-087522, filed on March 27, 2003 including specification,
claims, drawings and su~nnary, on which the Convention priority of
the present application is based, are incorporated herein by
reference in its entirety.
