U.S. patent application number 16/775459 was filed with the patent office on 2020-10-15 for internal combustion engine, straddled vehicle, and method for manufacturing internal combustion engine.
This patent application is currently assigned to YAMAHA HATSUDOKI KABUSHIKI KAISHA. The applicant listed for this patent is YAMAHA HATSUDOKI KABUSHIKI KAISHA. Invention is credited to Manabu MIYATA.
Application Number | 20200325845 16/775459 |
Document ID | / |
Family ID | 1000004657539 |
Filed Date | 2020-10-15 |
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United States Patent
Application |
20200325845 |
Kind Code |
A1 |
MIYATA; Manabu |
October 15, 2020 |
INTERNAL COMBUSTION ENGINE, STRADDLED VEHICLE, AND METHOD FOR
MANUFACTURING INTERNAL COMBUSTION ENGINE
Abstract
An internal combustion engine includes a cylinder head including
a first valve lifter hole, a first camshaft rotatably supported on
the cylinder head, a first valve lifter inserted in the first valve
lifter hole, a first valve spring that biases the first valve
lifter toward the first cam of the first camshaft, and an oil
supply passage having a first oil supply port formed on the inner
circumferential surface of the first valve lifter hole and a first
passage connected to the first oil supply port. An upper end of the
first oil supply port is located upward relative to the upper
surface of the first valve lifter when the first valve lifter is in
the lower position. A lower end of the first oil supply port is
located downward relative to the upper surface of the first valve
lifter when the first valve lifter is in the upper position.
Inventors: |
MIYATA; Manabu; (Iwata-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YAMAHA HATSUDOKI KABUSHIKI KAISHA |
Iwata-shi |
|
JP |
|
|
Assignee: |
YAMAHA HATSUDOKI KABUSHIKI
KAISHA
Iwata-shi
JP
|
Family ID: |
1000004657539 |
Appl. No.: |
16/775459 |
Filed: |
January 29, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/12 20130101; F16J
10/02 20130101; F01L 1/462 20130101; F01M 9/10 20130101; B33Y 80/00
20141201; F02F 1/4214 20130101; B62K 11/04 20130101; B22D 25/02
20130101; F01L 1/047 20130101; F01M 11/02 20130101; B22C 9/10
20130101 |
International
Class: |
F02F 1/42 20060101
F02F001/42; F01L 1/047 20060101 F01L001/047; F01L 1/46 20060101
F01L001/46; F01M 9/10 20060101 F01M009/10; F01L 1/12 20060101
F01L001/12; B62K 11/04 20060101 B62K011/04; F01M 11/02 20060101
F01M011/02; F16J 10/02 20060101 F16J010/02; B22D 25/02 20060101
B22D025/02; B22C 9/10 20060101 B22C009/10; B33Y 80/00 20060101
B33Y080/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2019 |
JP |
2019-076319 |
Claims
1. An internal combustion engine comprising: a cylinder head
including a first valve lifter hole having an inner circumferential
surface; a first camshaft having a first cam, the first camshaft
rotatably supported on the cylinder head; a first valve lifter in
the first valve lifter hole and having an outer circumferential
surface in contact with the inner circumferential surface of the
first valve lifter hole, the first valve lifter having an upper
surface in contact with the first cam; a first valve spring that
biases the first valve lifter toward the first cam so that the
first valve lifter reciprocates within the first valve lifter hole,
based on rotation of the first cam, between a lower position and an
upper position that is closer to the first camshaft than the lower
position; and an oil supply passage having a first oil supply port
formed on the inner circumferential surface of the first valve
lifter hole and a first passage connected to the first oil supply
port, wherein lubricant oil flows through the oil supply passage,
wherein: an upper end of the first oil supply port is located
upward relative to the upper surface of the first valve lifter when
the first valve lifter is in the lower position; and a lower end of
the first oil supply port is located downward relative to the upper
surface of the first valve lifter when the first valve lifter is in
the upper position.
2. The internal combustion engine according to claim 1, wherein the
lower end of the first oil supply port is located upward relative
to the upper surface of first valve lifter when the first valve
lifter is in the lower position.
3. The internal combustion engine according to claim 1, wherein as
viewed along a center line of the first valve lifter hole, an angle
formed between a straight line that connects together a center of
the first valve lifter hole and the first oil supply port and a
center line of the camshaft is within 45 degrees.
4. The internal combustion engine according to claim 3, wherein the
angle is within 10 degrees.
5. The internal combustion engine according to claim 1, wherein as
viewed along a center line of the first valve lifter hole, a
straight line that connects together a center of the first valve
lifter hole and a center of the first oil supply port coincides
with a center line of the camshaft.
6. The internal combustion engine according to claim 1, wherein a
rotation angle range of the first camshaft when the upper surface
of the first valve lifter is located downward relative to the upper
end of the first oil supply port is 50% or more, and less than
100%, with respect to a rotation angle range of the first camshaft
from when the first valve lifter starts moving from the upper
position until the first valve lifter returns to the upper
position.
7. The internal combustion engine according to claim 1, wherein the
first passage of the oil supply passage extends in a direction
perpendicular to a center line of the first valve lifter hole.
8. The internal combustion engine according to claim 1, wherein:
the cylinder head includes a second valve lifter hole having an
inner circumferential surface; the first camshaft has a second cam;
the internal combustion engine comprises: a second valve lifter in
the second valve lifter hole and having an outer circumferential
surface in contact with the inner circumferential surface of the
second valve lifter hole and an upper surface in contact with the
second cam; and a second valve spring that biases the second valve
lifter toward the second cam so that the second valve lifter
reciprocates within the second valve lifter hole, based on rotation
of the second cam, between a lower position and an upper position
that is closer to the first camshaft than the lower position; the
oil supply passage has a second oil supply port formed on the inner
circumferential surface of the second valve lifter hole and a
second passage connected to the second oil supply port; as viewed
along a center line of the first valve lifter hole, the first
passage is arranged on the second valve lifter hole side relative
to a center of the first valve lifter hole; as viewed along a
center line of the second valve lifter hole, the second passage is
arranged on the first valve lifter hole side relative to a center
of the second valve lifter hole; and the oil supply passage
includes a first vertical passage that is arranged on the second
valve lifter hole side relative to the first valve lifter hole and
on the first valve lifter hole side relative to the second valve
lifter hole, extends in a direction perpendicular to the first
camshaft, and is connected to the first passage and the second
passage.
9. The internal combustion engine according to claim 8, wherein:
the cylinder head includes third and fourth valve lifter holes each
having an inner circumferential surface; the internal combustion
engine comprises: a second camshaft having a third cam and a fourth
cam and rotatably supported on the cylinder head; a third valve
lifter in the third valve lifter hole and having an outer
circumferential surface in contact with the inner circumferential
surface of the third valve lifter hole, the third valve lifter
having an upper surface in contact with the third cam; a fourth
valve lifter in the fourth valve lifter hole and having an outer
circumferential surface in contact with the inner circumferential
surface of the fourth valve lifter hole, the fourth valve lifter
having an upper surface in contact with the fourth cam; a third
valve spring that biases the third valve lifter toward the third
cam so that the third valve lifter reciprocates within the third
valve lifter hole, based on rotation of the third cam, between a
lower position and an upper position that is closer to the second
camshaft than the lower position; and a fourth valve spring that
biases the fourth valve lifter toward the fourth cam so that the
fourth valve lifter reciprocates within the fourth valve lifter
hole, based on rotation of the fourth cam, between a lower position
and an upper position that is closer to the second camshaft than
the lower position; the oil supply passage includes a third oil
supply port formed on the inner circumferential surface of the
third valve lifter hole, a third passage connected to the third oil
supply port, a fourth oil supply port formed on the inner
circumferential surface of the fourth valve lifter hole, and a
fourth passage connected to the fourth oil supply port; as viewed
along a center line of the third valve lifter hole, the third
passage is arranged on the fourth valve lifter hole side relative
to a center of the third valve lifter hole; as viewed along a
center line of the fourth valve lifter hole, the fourth passage is
arranged on the third valve lifter hole side relative to a center
of the fourth valve lifter hole; and the oil supply passage
includes: a second vertical passage that is arranged on the fourth
valve lifter hole side relative to the third valve lifter hole and
on the third valve lifter hole side relative to the fourth valve
lifter hole, extends in a direction perpendicular to the second
camshaft, and is connected to the third passage and the fourth
passage; and an upstream passage that communicates with the first
vertical passage and the second vertical passage.
10. The internal combustion engine according to claim 1, wherein
the cylinder head includes a depression formed along a peripheral
portion of the first valve lifter hole of the cylinder head and
downward of the first cam.
11. A straddled vehicle comprising the internal combustion engine
according to claim 1.
12. A method for manufacturing the internal combustion engine
according to claim 1, comprising: producing a core having the same
shape as the oil supply passage by using a three-dimensional
modeling device; and casting the cylinder head with the core fitted
in a cast.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to Japanese
Patent Application No. 2019-076319 filed on Apr. 12, 2019, the
entire contents of which are hereby incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to an internal combustion
engine, a straddled vehicle, and a method for manufacturing an
internal combustion engine.
Description of the Related Art
[0003] Conventional internal combustion engines that open/close
valves by means of rotating cams are known in the art. Valves are
movable parts. In order to prevent the wear and seizure of valves,
there is a need to appropriately supply lubricant oil to sliding
surfaces of the valves.
[0004] Japanese Laid-Open Patent Publication No. H05-306609
discloses an internal combustion engine that includes three intake
valves actuated by a direct-type valve mechanism or a swing
arm-type valve mechanism and includes openings for supplying oil
onto the inner circumferential surface of the valve lifter holes of
the intake valves. Each opening is connected to a single oil
passage. With this internal combustion engine, lubricant oil can be
directly supplied, through the oil passage, between the inner
circumferential surface of the valve lifter hole and the outer
circumferential surface of the valve lifter.
[0005] Japanese Laid-Open Patent Publication No. H08-226315
discloses an internal combustion engine that includes a reflector
wall for supplying lubricant oil toward the sliding surface between
the cam and the cam slipper, and a lubricant oil supply pipe having
a spray hole for spraying lubricant oil toward the reflector wall.
The lubricant oil supply pipe is arranged upward of the cam. The
reflector wall is arranged beside the cam so that the sprayed
lubricant oil is unlikely to hit the cam. With this internal
combustion engine, since the lubricant oil path extending from the
spray hole to the sliding surface does not interfere with the area
of cam rotation, it is possible to prevent lubricant oil from being
spattered by the cam.
[0006] As described above, with the internal combustion engine
disclosed in Japanese Laid-Open Patent Publication No. H05-306609,
it is possible to directly supply lubricant oil between the inner
circumferential surface of the valve lifter hole and the outer
circumferential surface of the valve lifter. The valve lifter hole
serves to guide the valve lifter so that the valve lifter does not
incline from the valve center line when the valve lifter
reciprocates. The gap between the inner circumferential surface of
the valve lifter hole and the outer circumferential surface of the
valve lifter is designed to be very small so that the valve lifter
reciprocates straight in the valve lifter hole. Therefore,
lubricant oil in the oil passage is unlikely to flow toward between
the inner circumferential surface of the valve lifter hole and the
outer circumferential surface of the valve lifter. In order to
stably supply lubricant oil, there is a need for a high-power oil
pump.
[0007] With the internal combustion engine disclosed in Japanese
Laid-Open Patent Publication No. H05-306609, lubricant oil cannot
be directly supplied between the cam and the upper surface of the
valve lifter. On the other hand, with the internal combustion
engine disclosed in Japanese Laid-Open Patent Publication No.
H08-226315, lubricant oil can be directly supplied to the sliding
surface of the cam. Thus, one may consider supplying lubricant oil
between the cam and the upper surface of the valve lifter by adding
the lubricant oil supply pipe and the reflector wall disclosed in
Japanese Laid-Open Patent Publication No. H08-226315 to the
internal combustion engine disclosed in Japanese Laid-Open Patent
Publication No. H05-306609.
[0008] In that case, however, with the addition of new members,
i.e., a lubricant oil supply pipe and a reflector wall, there is a
need to ensure a sufficient clearance between the lubricant oil
supply pipe and the reflector wall and other members. However,
since the internal space of the internal combustion engine is
small, the installment of the lubricant oil supply pipe and the
reflector wall is likely to entail design restrictions and make it
difficult to realize a size reduction. As lubricant oil hits the
reflector wall, the speed of the lubricant oil decreases
significantly. The lubricant oil whose speed has been decreased
drips by gravity so as to be supplied to intended portions. Now, a
straddled vehicle may take an inclined attitude. For example, a
straddled vehicle may take an inclined attitude, e.g., when banking
and wheeling, under particular circumstances such as during a
motocross race. When the internal combustion engine described above
is installed on a straddled vehicle, the attitude of the internal
combustion engine may change. However, when the internal combustion
engine is inclined, lubricant oil reflected by the reflector wall
may no longer be supplied accurately to the intended portions,
making the lubricant oil supply unstable. The internal combustion
engine disclosed in Japanese Laid-Open Patent Publication No.
H08-226315 includes a swing arm-type valve mechanism. Now, the area
of the upper surface of the valve lifter of a direct-type valve
mechanism is smaller than the area of the cam slipper (the portion
of the swing arm that contacts the cam) of a swing arm-type valve
mechanism. When a lubricant oil supply pipe and a reflector wall
are provided in an internal combustion engine having a direct-type
valve mechanism, there is a need to supply lubricant oil reflected
by the reflector wall to a portion of a smaller area (i.e., between
the cam and the upper surface of the valve lifter). In view also of
changes in the attitude of the internal combustion engine, the
lubricant oil supply may be even more unstable.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide an internal
combustion engine having a direct-type valve mechanism, wherein
lubricant oil is stably supplied to a sliding surface of a valve
lifter that slides against a valve lifter hole and to a sliding
surface of the valve lifter that slides against a cam, while
preventing the internal combustion engine from becoming larger.
[0010] An internal combustion engine disclosed herein includes a
cylinder head, a first camshaft, a first valve lifter, a first
valve spring, and an oil supply passage. The cylinder head includes
a first valve lifter hole having an inner circumferential surface.
The first camshaft has a first cam and is rotatably supported on
the cylinder head. The first valve lifter is inserted in the first
valve lifter hole and has an outer circumferential surface in
contact with the inner circumferential surface of the first valve
lifter hole and an upper surface in contact with the first cam. The
first valve spring biases the first valve lifter toward the first
cam so that the first valve lifter reciprocates, following rotation
of the first cam, between a lower position and an upper position
that is closer to the first camshaft than the lower position. The
oil supply passage has a first oil supply port formed on the inner
circumferential surface of the first valve lifter hole and a first
passage connected to the first oil supply port. The oil supply
passage carries lubricant oil flowing therethrough. An upper end of
the first oil supply port is located upward relative to the upper
surface of the first valve lifter when the first valve lifter is in
the lower position. A lower end of the first oil supply port is
located downward relative to the upper surface of the first valve
lifter when the first valve lifter is in the upper position.
[0011] Note that the term "upward" as used herein refers to the
direction in which the valve lifter moves toward the center line of
the camshaft, and the term "downward" refers to the direction in
which the valve lifter moves away from the center line of the
camshaft.
[0012] With the internal combustion engine described above, when
the first valve lifter is in the lower position, the upper end of
the first oil supply port is located upward relative to the upper
surface of the first valve lifter. When the first valve lifter
reciprocates between the upper position and the lower position, the
first oil supply port is at least partially exposed. Therefore,
lubricant oil is directly supplied to the upper surface of the
first valve lifter from the first passage of the oil supply passage
through the first oil supply port. The upper surface of the first
valve lifter is a sliding surface that slides against the first
cam. With the internal combustion engine described above, it is
possible to stably supply lubricant oil to the sliding surface of
the first valve lifter that slides against the first cam.
[0013] As the first valve lifter ascends, the lubricant oil
supplied to the upper surface of the first valve lifter flows over
the periphery of the upper surface of the first valve lifter down
between the outer circumferential surface of the first valve lifter
and the first inner circumferential surface of the valve lifter
hole. The outer circumferential surface of the first valve lifter
is a sliding surface that slides against the first valve lifter
hole. Thus, it is possible to supply lubricant oil to the sliding
surface of the first valve lifter that slides against the first
valve lifter hole. In addition, with the internal combustion engine
described above, when the first valve lifter is in the upper
position, the lower end of the first oil supply port is located
downward relative to the upper surface of the first valve lifter.
When the first valve lifter reciprocates between the upper position
and the lower position, the first oil supply port at least
partially faces the outer circumferential surface of the first
valve lifter. Therefore, lubricant oil is directly supplied to the
outer circumferential surface of the first valve lifter from the
first passage of the oil supply passage through the first oil
supply port. Therefore, it is possible to directly supply lubricant
oil to the sliding surface of the first valve lifter that slides
against the first valve lifter hole. With the internal combustion
engine described above, it is possible to stably supply lubricant
oil to the sliding surface of the first valve lifter that slides
against the first valve lifter hole.
[0014] With the internal combustion engine described above, there
is no need for the lubricant oil supply pipe and the reflector wall
described above. Therefore, it is possible to prevent the internal
combustion engine from becoming larger.
[0015] Therefore, with the internal combustion engine described
above, it is possible to prevent the internal combustion engine
from becoming larger, and it is possible to stably supply lubricant
oil to the sliding surface of the first valve lifter that slides
against the first valve lifter hole and to the sliding surface of
the first valve lifter that slides against the first cam.
[0016] According to one preferred aspect, the lower end of the
first oil supply port is located upward relative to the upper
surface of first valve lifter being in the lower position.
[0017] According to this aspect, when the first valve lifter
reciprocates between the upper position and the lower position, the
first oil supply port is entirely exposed. Therefore, it is
possible to directly supply more lubricant oil to the upper surface
of the first valve lifter from the first passage of the oil supply
passage through the first oil supply port. Therefore, it is
possible to stably supply lubricant oil to the sliding surface of
the first valve lifter that slides against the first cam.
[0018] According to one preferred aspect, as viewed along a center
line of the first valve lifter hole, an angle formed between a
straight line that connects together a center of the first valve
lifter hole and the first oil supply port and a center line of the
first camshaft is within 45 degrees.
[0019] According to this aspect, the first oil supply port is
provided at a position that is relatively far away from the first
cam. Therefore, lubricant oil supplied from the first oil supply
port is unlikely to be spattered by the first cam. Thus, it is
possible to more stably supply lubricant oil to the upper surface
of the first valve lifter from the first oil supply port.
[0020] Since the first cam rotates about the center line of the
first camshaft, the first valve lifter, which receives a force from
the first cam, is likely to receive a force in a direction that is
perpendicular to the center line of the first camshaft. The
pressure that the inner circumferential surface of the first valve
lifter hole of the cylinder head receives from the outer
circumferential surface of the first valve lifter is greater in
portions thereof that are closer to a line that is perpendicular to
the center line of the first camshaft. According to this aspect,
the first oil supply port is provided at a position that is
relatively far away from the line perpendicular to the center line
of the first camshaft. Therefore, even though the first oil supply
port is formed on the inner circumferential surface of the first
valve lifter hole, it is possible to maintain a sufficient
mechanical strength of the peripheral portion of the first valve
lifter hole.
[0021] According to one preferred aspect, the angle is within 10
degrees.
[0022] According to one preferred aspect, as viewed along a center
line of the first valve lifter hole, a straight line that connects
together a center of the first valve lifter hole and a center of
the first oil supply port coincides with a center line of the first
camshaft.
[0023] According to one preferred aspect, a rotation angle range of
the first camshaft when the upper surface of the first valve lifter
is located downward relative to the upper end of the first oil
supply port is 50% or more and less than 100% with respect to a
rotation angle range of the first camshaft from when the first
valve lifter starts moving from the upper position until the first
valve lifter returns to the upper position.
[0024] According to this aspect, it is possible to sufficiently
supply lubricant oil to the upper surface of the first valve
lifter, and it is possible to stably supply lubricant oil to the
sliding surface of the first valve lifter that slides against the
first cam.
[0025] According to one preferred aspect, the first passage of the
oil supply passage extends in a direction perpendicular to a center
line of the first valve lifter hole.
[0026] According to this aspect, the area of the first oil supply
port is smaller as compared with a case where the first passage
extends in a direction inclined relative to the center line of the
first valve lifter hole. Therefore, it is possible to ensure a
large area of the inner circumferential surface of the first valve
lifter hole. Thus, it is possible to maintain a sufficient
mechanical strength of the peripheral portion of the first valve
lifter hole of the cylinder head.
[0027] According to one preferred aspect, the cylinder head
includes a second valve lifter hole having an inner circumferential
surface. The first camshaft has a second cam. The internal
combustion engine includes a second valve lifter inserted in the
second valve lifter hole and having an outer circumferential
surface in contact with the inner circumferential surface of the
second valve lifter hole and an upper surface in contact with the
second cam. The internal combustion engine includes a second valve
spring that biases the second valve lifter toward the second cam so
that the second valve lifter reciprocates, following rotation of
the second cam, between a lower position and an upper position that
is closer to the first camshaft than the lower position. The oil
supply passage has a second oil supply port formed on the inner
circumferential surface of the second valve lifter hole and a
second passage connected to the second oil supply port. As viewed
along a center line of the first valve lifter hole, the first
passage is arranged on the second valve lifter hole side relative
to a center of the first valve lifter hole. As viewed along a
center line of the second valve lifter hole, the second passage is
arranged on the first valve lifter hole side relative to a center
of the second valve lifter hole. The oil supply passage includes a
first vertical passage that is arranged on the second valve lifter
hole side relative to the first valve lifter hole and on the first
valve lifter hole side relative to the second valve lifter hole,
extends in a direction perpendicular to the first camshaft, and is
connected to the first passage and the second passage.
[0028] According to this aspect, the first passage and the second
passage branch off a single vertical passage. Therefore, it is
possible to shorten the overall length of the oil supply passage.
Thus, it is possible to prevent a pressure decrease of lubricant
oil in the first passage and the second passage. Therefore, it is
possible to stably supply lubricant oil to the sliding surface of
the first valve lifter that slides against the first valve lifter
hole, the sliding surface of the first valve lifter that slides
against the first cam, the sliding surface of the second valve
lifter that slides against the second valve lifter hole, and the
sliding surface of the second valve lifter that slides against the
second cam, while preventing the internal combustion engine from
becoming larger. The first vertical passage is formed between the
first valve lifter hole and the second valve lifter hole, and
extends in a direction perpendicular to the first camshaft. This
makes it more likely that lubricant oil is evenly supplied to the
first oil supply port and the second oil supply port.
[0029] According to one preferred aspect, the cylinder head
includes third and fourth valve lifter holes each having an inner
circumferential surface. The internal combustion engine includes a
second camshaft having a third cam and a fourth cam and rotatably
supported on the cylinder head. The internal combustion engine
includes a third valve lifter inserted in the third valve lifter
hole and having an outer circumferential surface in contact with
the inner circumferential surface of the third valve lifter hole
and an upper surface in contact with the third cam. The internal
combustion engine includes a fourth valve lifter inserted in the
fourth valve lifter hole and having an outer circumferential
surface in contact with the inner circumferential surface of the
fourth valve lifter hole and an upper surface in contact with the
fourth cam. The internal combustion engine includes a third valve
spring that biases the third valve lifter toward the third cam so
that the third valve lifter reciprocates, following rotation of the
third cam, between a lower position and an upper position that is
closer to the second camshaft than the lower position. The internal
combustion engine includes a fourth valve spring that biases the
fourth valve lifter toward the fourth cam so that the fourth valve
lifter reciprocates, following rotation of the fourth cam, between
a lower position and an upper position that is closer to the second
camshaft than the lower position. The oil supply passage includes a
third oil supply port formed on the inner circumferential surface
of the third valve lifter hole, a third passage connected to the
third oil supply port, a fourth oil supply port formed on the inner
circumferential surface of the fourth valve lifter hole, and a
fourth passage connected to the fourth oil supply port. As viewed
along a center line of the third valve lifter hole, the third
passage is arranged on the fourth valve lifter hole side relative
to a center of the third valve lifter hole. As viewed along a
center line of the fourth valve lifter hole, the fourth passage is
arranged on the third valve lifter hole side relative to a center
of the fourth valve lifter hole. The oil supply passage includes a
second vertical passage that is arranged on the fourth valve lifter
hole side relative to the third valve lifter hole and on the third
valve lifter hole side relative to the fourth valve lifter hole,
extends in a direction perpendicular to the second camshaft, and is
connected to the third passage and the fourth passage. The oil
supply passage includes an upstream passage that communicates with
the first vertical passage and the second vertical passage.
[0030] According to this aspect, it is also possible to stably
supply lubricant oil to the sliding surface of the third valve
lifter that slides against the third valve lifter hole, the sliding
surface of the third valve lifter that slides against the third
cam, the sliding surface of the fourth valve lifter that slides
against the fourth valve lifter hole, and the sliding surface of
the fourth valve lifter that slides against the fourth cam.
[0031] According to one preferred aspect, a depression that is
depressed downward is formed along a peripheral portion of the
first valve lifter hole of the cylinder head and downward of the
first cam.
[0032] According to this aspect, the peripheral portion of the
first valve lifter hole can be prevented from interferring with the
rotating first cam. Since it is possible to ensure a sufficient
height of a portion, other than the depression, of the peripheral
portion, it is possible to increase the area of the inner
circumferential surface of the first valve lifter hole. Therefore,
it is possible to reduce the pressure that the inner
circumferential surface of the first valve lifter hole receives
from the outer circumferential surface of the first valve lifter,
and it is possible to maintain a sufficient mechanical strength of
the peripheral portion of the first valve lifter hole.
[0033] Now, if an excess of lubricant oil remains on the upper
surface of the first valve lifter, it may possibly increase the
resistance against the rotation of the first cam. According to this
aspect, however, even if lubricant oil remains on the upper surface
of the first valve lifter, any excess of lubricant oil is likely to
flow over the upper surface via the depression. Thus, it is
possible to reduce the resistance against the rotation of the first
cam.
[0034] According to this aspect, with the provision of the
depression, a portion of the outer circumferential surface of the
first valve lifter (specifically, a portion that is adjacent to the
depression) does not come into contact with the inner
circumferential surface of the first valve lifter hole when the
first valve lifter is in the upper position. Lubricant oil is
temporarily not supplied to said portion. However, since lubricant
oil is directly supplied to the sliding surface of the first valve
lifter that slides against the first valve lifter hole from the oil
supply passage, lubricant oil is sufficiently supplied to said
portion while the first valve lifter moves from the upper position
toward the lower position. When the first valve lifter comes back
from the lower position to the upper position, lubricant oil that
has remained on the upper surface of the first valve lifter is
supplied to the lubricating surface. Therefore, it is possible to
also well lubricate said portion of the outer circumferential
surface of the first valve lifter (i.e., a portion that is adjacent
to the depression when the first valve lifter is in the upper
position). Despite the provision of the depression, it is possible
to desirably supply lubricant oil to the sliding surface of the
first valve lifter that slides against the first valve lifter
hole.
[0035] A straddled vehicle disclosed herein includes the internal
combustion engine set forth above.
[0036] A method for manufacturing the internal combustion engine
disclosed herein includes: producing a core having the same shape
as the oil supply passage by using a three-dimensional modeling
device; and casting the cylinder head with the core fitted in a
cast.
[0037] With the method described above, it is possible to form the
oil supply passage without performing a drilling process. Even an
oil supply passage having a complicated shape can be manufactured
with ease and high precision.
[0038] The present invention provides an internal combustion engine
having a direct-type valve mechanism, wherein lubricant oil is
stably supplied to a sliding surface of a valve lifter that slides
against a valve lifter hole and to a sliding surface of the valve
lifter that slides against a cam, while preventing the internal
combustion engine from becoming larger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a side view of a motorcycle according to an
embodiment.
[0040] FIG. 2 is a cross-sectional view of a part of an internal
combustion engine, taken along line II-II of FIG. 4.
[0041] FIG. 3 is a cross-sectional view of a part of an internal
combustion engine, taken along line of FIG. 4.
[0042] FIG. 4 is a plan view schematically showing a part of an
internal combustion engine as viewed along the cylinder axial
line.
[0043] FIG. 5 is a perspective view showing a configuration of an
oil supply passage.
[0044] FIG. 6 is a cross-sectional view of a part of an internal
combustion engine, taken along line VI-VI of FIG. 5.
[0045] FIG. 7 is a cross-sectional view of a part of an internal
combustion engine where the first valve lifter and the second valve
lifter are in their lower positions, taken along line VII-VII of
FIG. 5.
[0046] FIG. 8 is a cross-sectional view of a part of an internal
combustion engine where the first valve lifter and the second valve
lifter are in their upper positions, taken along line VII-VII of
FIG. 5.
[0047] FIG. 9 shows the lift characteristics of the first valve
lifter.
[0048] FIG. 10 shows the position of the first oil supply port as
viewed along the center line of the first valve lifter hole.
[0049] FIG. 11 is a perspective view of a core manufactured by a
three-dimensional modeling device.
[0050] FIG. 12 shows the position of the first oil supply port as
viewed along the center line of the first valve lifter hole
according to a variation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] An embodiment will now be described with reference to the
drawings. A motorcycle 1 shown in FIG. 1 will be described below as
an example of the straddled vehicle.
[0052] The motorcycle 1 includes a body frame 2, an internal
combustion engine (hereinafter referred to as an engine) 5
supported on the body frame 2, a seat 11 supported on the body
frame 2, a front wheel 3, and a rear wheel 4. The body frame 2
includes a head pipe 6, and a main frame 7 extending rearward from
the head pipe 6. The engine 5 is supported on the main frame 7. The
head pipe 6 supports a steering shaft 8 so that the steering shaft
8 can rotate left and right. A handle 9 is secured on an upper
portion of the steering shaft 8. A front fork 10 is provided on a
lower portion of the steering shaft 8. The front wheel 3 is
rotatably supported on the front fork 10. A pivot shaft 12 is
provided on the main frame 7. A front end portion of a rear arm 13
is pivotally connected to the pivot shaft 12. The rear wheel 4 is
supported on the rear end portion of the rear arm 13. The rear
wheel 4 and the engine 5 are linked together by a chain 14, which
is an example of the power transmission member.
[0053] The engine 5 includes a crank case 15 accommodating a crank
shaft (not shown) therein, a cylinder body 16 connected to the
crank case 15, a cylinder head 17 connected to the cylinder body
16, and a cylinder head cover 18 connected to the cylinder head 17.
A cylinder 16a (see FIG. 2) is provided inside the cylinder body
16. A piston (not shown) is arranged in the cylinder 16a. The
piston and the crank shaft are linked together by a connecting rod
(not shown). An intake pipe 19 and an exhaust pipe 20 are connected
to the cylinder head 17.
[0054] FIG. 2 is a cross-sectional view of a part of the engine 5.
FIG. 3 is a cross-sectional view of another part of the engine 5.
FIG. 4 is a plan view schematically showing a part of the engine 5
as viewed along the axial line (hereinafter referred to as a
cylinder axial line) 16c of the cylinder 16a. Note that FIG. 2 and
FIG. 3 are cross-sectional views taken along line II-II and line
respectively, of FIG. 4.
[0055] As shown in FIG. 2, the cylinder head 17 includes a first
intake port 27A having a first intake opening 26A that is facing
toward a combustion chamber 25, and a first exhaust port 29A having
a first exhaust opening 28A that is facing toward the combustion
chamber 25. As shown in FIG. 3, the cylinder head 17 further
includes a second intake port 27B having a second intake opening
26B that is facing toward the combustion chamber 25, and a second
exhaust port 29B having a second exhaust opening 28B that is facing
toward the combustion chamber 25.
[0056] As shown in FIG. 2 and FIG. 3, the engine 5 includes a first
intake valve 37A that opens/closes the first intake opening 26A, a
second intake valve 37B that opens/closes the second intake opening
26B, a first exhaust valve 39A that opens/closes the first exhaust
opening 28A, and a second exhaust valve 39B that opens/closes the
second exhaust opening 28B. The engine 5 includes a first camshaft
31 having a first intake cam 31A and a second intake cam 31B, and a
second camshaft 32 having a first exhaust cam 32A and a second
exhaust cam 32B. The first camshaft 31 and the second camshaft 32
are rotatably supported on the cylinder head 17. The first camshaft
31 and the second camshaft 32 are arranged in parallel to each
other.
[0057] As shown in FIG. 2, the cylinder head 17 includes a first
valve lifter hole 21 having an inner circumferential surface 21a.
The first valve lifter 41 is inserted in the first valve lifter
hole 21. In the first valve lifter hole 21, the first valve lifter
41 can reciprocate toward and away from a center line 31c of the
first camshaft 31. The term "upward" as used herein for a valve
lifter refers to the direction toward the axis of the camshaft of
the cam in contact with the valve lifter, and the term "downward"
refers to the direction away from the axis of the camshaft. For
example, for the first valve lifter 41, the direction in which the
first valve lifter 41 moves toward the center line 31c of the first
camshaft 31 is referred to as "upward", and the direction in which
the first valve lifter 41 moves away from the center line 31c of
the first camshaft 31 is referred to as "downward". This similarly
applies to other valve lifters 42 to 44 to be discussed later. The
first valve lifter 41 reciprocates between a predetermined lower
position and a predetermined upper position. The first valve lifter
41 includes an outer circumferential surface 41a in contact with
the inner circumferential surface 21a of the first valve lifter
hole 21, and an upper surface 41b in contact with the first intake
cam 31A.
[0058] The first intake valve 37A is a so-called poppet valve. The
first intake valve 37A includes a valve stem end 81, a valve stem
82 extending in a straight line from the valve stem end 81, and a
valve body 83 provided at the tip portion of the valve stem 82. A
cylindrical valve guide 86 is supported on the cylinder head 17.
The valve stem 82 extends through the valve guide 86 and is
slidably supported on the valve guide 86. The first intake valve
37A ascends and descends as the valve stem 82 slides against the
valve guide 86.
[0059] A valve spring seat 84 is supported on the cylinder head 17.
A valve spring seat 85 is supported on the valve stem end 81. A
first valve spring 51 is arranged between the valve spring seat 84
and the valve spring seat 85. One end portion of the first valve
spring 51 is supported on the valve spring seat 85, and the other
end portion thereof is supported on the valve spring seat 84. The
valve stem end 81 is in contact with the first valve lifter 41. The
first valve spring 51 biases the valve lifter 41 toward the first
intake cam 31A via the valve spring seat 85 and the first intake
valve 37A.
[0060] As shown in FIG. 2 and FIG. 3, the cylinder head 17 includes
a second valve lifter hole 22 having an inner circumferential
surface 22a, a third valve lifter hole 23 having an inner
circumferential surface 23a, and a fourth valve lifter hole 24
having an inner circumferential surface 24a. A second valve lifter
42 is inserted in the second valve lifter hole 22, a third valve
lifter 43 is inserted in the third valve lifter hole 23, and a
fourth valve lifter 44 is inserted in the fourth valve lifter hole
24. The second to fourth valve lifters 42 to 44 can reciprocate up
and down in the second to fourth valve lifter holes 22 to 24,
respectively. The second to fourth valve lifters 42 to 44 each
reciprocate between its predetermined lower position and its
predetermined upper position. The second to fourth valve lifters 42
to 44 are configured as is the first valve lifter 41. The second
valve lifter 42 includes an outer circumferential surface 42a in
contact with the inner circumferential surface 22a of the second
valve lifter hole 22, and an upper surface 42b in contact with the
second intake cam 31B. The third valve lifter 43 includes an outer
circumferential surface 43a in contact with the inner
circumferential surface 23a of the third valve lifter hole 23, and
an upper surface 43b in contact with the first exhaust cam 32A. The
fourth valve lifter 44 includes an outer circumferential surface
44a in contact with the inner circumferential surface 24a of the
fourth valve lifter hole 24, and an upper surface 44b in contact
with the second exhaust cam 32B.
[0061] The second intake valve 37B, the first exhaust valve 39A and
the second exhaust valve 39B are configured as is the first intake
valve 37A. The second intake valve 37B, the first exhaust valve 39A
and the second exhaust valve 39B are supported on the cylinder head
17, as is the first intake valve 37A. Thus, like elements to those
already described above are denoted by like reference signs and
will not be further described below.
[0062] A second valve spring 52 is provided between the second
valve lifter 42 and the cylinder head 17. The second valve spring
52 biases the second valve lifter 42 toward the second intake cam
31B. A third valve spring 53 is provided between the third valve
lifter 43 and the cylinder head 17. The third valve spring 53
biases the third valve lifter 43 toward the first exhaust cam 32A.
A fourth valve spring 54 is provided between the fourth valve
lifter 44 and the cylinder head 17. The fourth valve spring 54
biases the fourth valve lifter 44 toward the second exhaust cam
32B.
[0063] The first intake cam 31A rotates following the rotation of
the first camshaft 31. When a cam nose 38 of the first intake cam
31A pushes the first valve lifter 41 downward, the first valve
lifter 41 and the first intake valve 37A move downward, thereby
opening the first intake opening 26A. When the first intake cam 31A
further rotates and the cam nose 38 comes off the first valve
lifter 41, the first intake valve 37A and the first valve lifter 41
ascend due to the urging of the first valve spring 51, thereby
closing the first intake opening 26A. The first intake cam 31A, the
first valve lifter 41, the first intake valve 37A and the first
valve spring 51 cyclically repeats such an operation. Thus, the
first intake opening 26A is cyclically opened/closed. In this
operation, the outer circumferential surface 41a of the first valve
lifter 41 slides against the inner circumferential surface 21a of
the first valve lifter hole 21. The upper surface 41b of the first
valve lifter 41 slides against the first intake cam 31A. Therefore,
in order to prevent the wear of the outer circumferential surface
41a and the upper surface 41b of the first valve lifter 41, there
is a need to supply lubricant oil to the outer circumferential
surface 41a and the upper surface 41b.
[0064] Similarly, the second valve lifter 42, the third valve
lifter 43 and the fourth valve lifter 44 reciprocate following the
rotation of the second intake cam 31B, the first exhaust cam 32A
and the second exhaust cam 32B, respectively, thereby cyclically
opening/closing the second intake valve 37B, the first exhaust
valve 39A and the second exhaust valve 39B, respectively. The outer
circumferential surface 42a of the second valve lifter 42 slides
against the inner circumferential surface 22a of the second valve
lifter hole 22, and the upper surface 42b thereof slides against
the second intake cam 31B. The outer circumferential surface 43a
the third valve lifter 43 slides against the inner circumferential
surface 23a of the third valve lifter hole 23, and the upper
surface 43b thereof slides against the first exhaust cam 32A. The
outer circumferential surface 44a of the fourth valve lifter 44
slides against the inner circumferential surface 24a of the fourth
valve lifter hole 24, and the upper surface 44b thereof slides
against the second exhaust cam 32B. Therefore, there is a need to
supply lubricant oil also to the outer circumferential surface 42a
and the upper surface 42b of the second valve lifter 42, the outer
circumferential surface 43a and the upper surface 43b of the third
valve lifter 43, and the outer circumferential surface 44a and the
upper surface 44b of the fourth valve lifter 44.
[0065] In view of this, the cylinder head 17 of the engine 5
includes an oil supply passage 70 to be described below. Next, the
configuration of the oil supply passage 70 will be described.
[0066] FIG. 5 shows the configuration of the oil supply passage 70.
Although the oil supply passage 70 is actually a passage formed
inside the cylinder head 17 (see FIG. 6), the oil supply passage 70
is shown as being a pipe in FIG. 5 for easier understanding of the
configuration. Although the first to fourth valve lifter holes 21
to 24 are actually holes formed in the cylinder head 17, they are
shown as being cylinders in FIG. 5. As shown in FIG. 5, the oil
supply passage 70 includes an upstream passage 77, a first vertical
passage 75, a second vertical passage 76, a first passage 71, a
second passage 72, a third passage 73, and a fourth passage 74.
[0067] The upstream passage 77 is a passage for carrying lubricant
oil sent from an oil pump (not shown). The upstream passage 77 is
formed downward relative to the center line 31c of the first
camshaft 31 and a center line 32c of the second camshaft 32. The
upstream passage 77 is formed in a portion of the cylinder head 17
that is closer to the cylinder 16a with respect to the center line
31c of the first camshaft 31 and the center line 32c of the second
camshaft 32. Although there is no limitation on the configuration
of the upstream passage 77, the upstream passage 77 herein includes
first to seventh upstream passages 77A to 77F. As viewed along a
cylinder axial line 16c, the first upstream passage 77A extends
perpendicular to the center line 31c of the first camshaft 31 and
the center line 32c of the second camshaft 32. The second upstream
passage 77B extends from the first upstream passage 77A toward the
cylinder axial line 16c. The second upstream passage 77B is formed
between the second valve lifter hole 22 and the fourth valve lifter
hole 24. The second upstream passage 77B is parallel to the center
line 31c of the first camshaft 31 and the center line 32c of the
second camshaft 32. The third upstream passage 77C and the fifth
upstream passage 77E branch off the second upstream passage 77B.
The third upstream passage 77C and the fifth upstream passage 77E
are each formed in a quarter circle arc centered at the cylinder
axial line 16c. The third upstream passage 77C extends from the
second upstream passage 77B toward the first valve lifter hole 21
and the second valve lifter hole 22. As viewed along the cylinder
axial line 16c, the fourth upstream passage 77D extends from the
third upstream passage 77C toward the middle point between the
first valve lifter hole 21 and the second valve lifter hole 22. The
fifth upstream passage 77E extends from the second upstream passage
77B toward the third valve lifter hole 23 and the fourth valve
lifter hole 24. As viewed from the cylinder axial line 16c, the
sixth upstream passage 77F extends from the fifth upstream passage
77E toward the middle point between the third valve lifter hole 23
and the fourth valve lifter hole 24. As viewed along the cylinder
axial line 16c, the fourth upstream passage 77D and the sixth
upstream passage 77F are perpendicular to the center line 31c of
the first camshaft 31 and the center line 32c of the second
camshaft 32.
[0068] The first vertical passage 75 extends upward from the fourth
upstream passage 77D. The first vertical passage 75 extends from
the fourth upstream passage 77D toward the center line 31c of the
first camshaft 31. The first vertical passage 75 is parallel to the
first valve lifter hole 21 and the second valve lifter hole 22. The
first vertical passage 75 extends straight. The second vertical
passage 76 extends upward from the sixth upstream passage 77F. The
second vertical passage 76 extends from the sixth upstream passage
77F toward the center line 32c of the second camshaft 32. The
second vertical passage 76 is parallel to the third valve lifter
hole 23 and the fourth valve lifter hole 24. The second vertical
passage 76 extends straight.
[0069] The first passage 71 and the second passage 72 branch off
the first vertical passage 75. The first passage 71 extends from
the first vertical passage 75 toward a center line 21c of the first
valve lifter hole 21. The second passage 72 extends from the first
vertical passage 75 toward a center line 22c of the second valve
lifter hole 22. The third passage 73 and the fourth passage 74
branch off the second vertical passage 76. The third passage 73
extends from the second vertical passage 76 toward a center line
23c of the third valve lifter hole 23. The fourth passage 74
extends from the second vertical passage 76 toward a center line
24c of the fourth valve lifter hole 24. The first passage 71 and
the second passage 72 are parallel to the center line 31c of the
first camshaft. The third passage 73 and the fourth passage 74 are
parallel to the center line 32c of the second camshaft 32. The
first to fourth passages 71 to 74 each extend straight.
[0070] A first oil supply port 61 is formed on the inner
circumferential surface 21a of the first valve lifter hole 21. A
second oil supply port 62 is formed on the inner circumferential
surface 22a of the second valve lifter hole 22. A third oil supply
port 63 is formed on the inner circumferential surface 23a of the
third valve lifter hole 23. A fourth oil supply port 64 is formed
on the inner circumferential surface 24a of the fourth valve lifter
hole 24. The first oil supply port 61 is connected to the first
passage 71. The second oil supply port 62 is connected to the
second passage 72. The third oil supply port 63 is connected to the
third passage 73. The fourth oil supply port 64 is connected to the
fourth passage 74.
[0071] FIG. 7 and FIG. 8 are vertical cross-sectional views of the
cylinder head 17, taken along line VII-VII of FIG. 5. FIG. 7 shows
a state where the first valve lifter 41 and the second valve lifter
42 are at their lower positions, and FIG. 8 shows a state where the
first valve lifter 41 and the second valve lifter 42 are at their
upper positions. As described above, the first valve lifter 41 and
the second valve lifter 42 each repeatedly reciprocate between the
upper position and the lower position. The upper positions are
positions reached by the first valve lifter 41 and the second valve
lifter 42 having fully ascended. The lower positions are positions
reached by the first valve lifter 41 and the second valve lifter 42
having fully descended.
[0072] As shown in FIG. 7, an upper end 61t of the first oil supply
port 61 is located upward relative to the upper surface 41b of the
first valve lifter 41 being in the lower position. When the first
valve lifter 41 is in the lower position, the first oil supply port
61 at least partially does not face the outer circumferential
surface 41a of the first valve lifter 41. In the description below,
the state where an oil supply port does not face the outer
circumferential surface of a valve lifter will be described as "the
oil supply port is exposed". When the first valve lifter 41 is in
the lower position, the first oil supply port 61 is at least
partially exposed. Similarly, the upper end of the second oil
supply port 62 is located upward relative to the upper surface 42b
of the second valve lifter 42 being in the lower position. When the
second valve lifter 42 reciprocates, the second oil supply port 62
is at least partially exposed. Although not shown in the figures,
the upper end of the third oil supply port 63 is located upward
relative to the upper surface 43b of the third valve lifter 43
being in the lower position. The upper end of the fourth oil supply
port 64 is located upward relative to the upper surface 44b of the
fourth valve lifter 44 being in the lower position. When the third
valve lifter 43 and the fourth valve lifter 44 reciprocate, the
third oil supply port 63 and the fourth oil supply port 64 are at
least partially exposed.
[0073] In the present embodiment, a lower end 61b of the first oil
supply port 61 is located upward relative to the upper surface 41b
of the first valve lifter 41 being in the lower position.
Therefore, when the first valve lifter 41 reciprocates, the first
oil supply port 61 is temporarily entirely exposed. Similarly, the
lower end of the second oil supply port 62 is located upward
relative to the upper surface 42b of the second valve lifter 42
being in the lower position. The lower end of the third oil supply
port 63 is located upward relative to the upper surface 43b of the
third valve lifter 43 being in the lower position. The lower end of
the fourth oil supply port 64 is located upward relative to the
upper surface 44b of the fourth valve lifter 44 being in the lower
position. Therefore, when the second to fourth valve lifters 42 to
44 reciprocate, the second to fourth oil supply ports 62 to 64 are
temporarily entirely exposed.
[0074] As shown in FIG. 8, the lower end 61b of the first oil
supply port 61 is located downward relative to the upper surface
41b of the first valve lifter 41 being in the upper position. When
the first valve lifter 41 is in the upper position, the first oil
supply port 61 at least partially faces the outer circumferential
surface 41a of the first valve lifter 41. In the description below,
the state where an oil supply port faces the outer circumferential
surface of a valve lifter will be described as "the oil supply port
is covered". When the first valve lifter 41 is in the upper
position, the first oil supply port 61 is at least partially
covered. Similarly, the lower end of the second oil supply port 62
is located downward relative to the upper surface 42b of the second
valve lifter 42 being in the upper position. The lower end of the
third oil supply port 63 is located downward relative to the upper
surface 43b of the third valve lifter 43 being in the upper
position. The lower end of the fourth oil supply port 64 is located
downward relative to the upper surface 44b of the fourth valve
lifter 44 being in the upper position. When the second to fourth
valve lifters 42 to 44 reciprocate, the second to fourth oil supply
ports 62 to 64 are at least partially covered.
[0075] In the present embodiment, the upper end 61t of the first
oil supply port 61 is located downward relative to the upper
surface 41b of the first valve lifter 41 being in the upper
position. When the first valve lifter 41 is in the upper position,
the first oil supply port 61 is entirely covered. When the first
valve lifter 41 reciprocates, the first oil supply port 61 is
temporarily entirely covered. Similarly, the upper end of the
second oil supply port 62 is located downward relative to the upper
surface 42b of the second valve lifter 42 being in the upper
position. The upper end of the third oil supply port 63 is located
downward relative to the upper surface 43b of the third valve
lifter 43 being in the upper position. The upper end of the fourth
oil supply port 64 is located downward relative to the upper
surface 44b of the fourth valve lifter 44 being in the upper
position. Therefore, when the second to fourth valve lifters 42 to
44 reciprocate, the second to fourth oil supply ports 62 to 64 are
temporarily entirely covered.
[0076] The oil supply passage 70 is filled with lubricant oil. As
shown in FIG. 7, as the first valve lifter 41 descends, the first
oil supply port 61 is exposed, thereby directly supplying lubricant
oil from the first oil supply port 61 to the upper surface 41b of
the first valve lifter 41. As the second valve lifter 42 descends,
the second oil supply port 62 is exposed, thereby directly
supplying lubricant oil from the second oil supply port 62 to the
upper surface 42b of the second valve lifter 42. As shown in FIG.
8, as the first valve lifter 41 ascends, the first oil supply port
61 is covered, thereby directly supplying lubricant oil from the
first oil supply port 61 to the outer circumferential surface 41a
of the first valve lifter 41. As the second valve lifter 42
ascends, the second oil supply port 62 is covered, thereby directly
supplying lubricant oil from the second oil supply port 62 to the
outer circumferential surface 42a of the second valve lifter 42.
The first valve lifter 41 and the second valve lifter 42 repeatedly
move up and down. Thus, lubricant oil is cyclically supplied
directly to the upper surface 41b and the outer circumferential
surface 41a of the first valve lifter 41 and to the upper surface
42b and the outer circumferential surface 42a of the second valve
lifter 42.
[0077] Although not shown in the figures, this similarly applies
also to the third valve lifter 43 and the fourth valve lifter 44.
That is, as the third valve lifter 43 and the fourth valve lifter
44 descend, lubricant oil is directly supplied from the third oil
supply port 63 to the upper surface 43b of the third valve lifter
43, and lubricant oil is directly supplied from the fourth oil
supply port 64 to the upper surface 44b of the fourth valve lifter
44. As the third valve lifter 43 and the fourth valve lifter 44
ascend, lubricant oil is directly supplied from the third oil
supply port 63 to the outer circumferential surface 43a the third
valve lifter 43, and lubricant oil is directly supplied from the
fourth oil supply port 64 to the outer circumferential surface 44a
of the fourth valve lifter 44. Lubricant oil is cyclically supplied
directly also to the upper surface 43b and the outer
circumferential surface 43a of the third valve lifter 43 and to the
upper surface 44b and the outer circumferential surface 44a of the
fourth valve lifter 44.
[0078] The amount of time the first oil supply port 61 is exposed
is dictated by the position in the direction along the center line
21c of the first valve lifter hole 21 of the first oil supply port
61. By adjusting the position of the first oil supply port 61, it
is possible to adjust the amount of time the first oil supply port
61 is exposed. Thus, it is possible to adjust the balance between
the amount of lubricant oil directly supplied to the upper surface
41b of the first valve lifter 41 and the amount of lubricant oil
directly supplied the outer circumferential surface 41a. Similarly,
by adjusting the positions of the second to fourth oil supply ports
62 to 64, it is possible to adjust the amount of time the second to
fourth oil supply ports 62 to 64 are exposed, and it is possible to
adjust the balance between the amount of lubricant oil directly
supplied to the upper surfaces 42b to 44b of the second to fourth
valve lifters 42 to 44 and the amount of lubricant oil directly
supplied to the outer circumferential surfaces 42a to 44a.
[0079] The amount of time the first oil supply port 61 is exposed
is determined by the rotation angle range of the first camshaft 31
over which the first oil supply port 61 is exposed. Although there
is no particular limitation on the amount of time the first oil
supply port 61 is exposed, as shown in FIG. 9, the rotation angle
range T1 of the first camshaft 31 over which the upper surface 41b
of the first valve lifter 41 is located downward relative to the
upper end 61t of the first oil supply port 61 is preferably 50% or
more and less than 100% with respect to the rotation angle range T2
of the first camshaft 31 from when the first valve lifter 41 starts
moving from the upper position until it returns to the upper
position. In FIG. 9, the horizontal axis represents the rotation
angle .alpha. of the first camshaft 31, and the vertical axis
represents the lift amount VL of the first valve lifter 41. Note
that T1 is the rotation angle range over which the first oil supply
port 61 is at least partially exposed. T2 is the rotation angle
range over which the cam nose 38 of the first intake cam 31A (see
FIG. 2) is pushing the first valve lifter 41. In the present
embodiment, T2 is 170 degrees. In this case, T1 is preferably 85
degrees or more and less than 170 degrees. Note however that there
is no particular limitation. T1 and T2 shown in FIG. 9 are merely
illustrative. T1 and T2 can be set appropriately. This similarly
applies also to the amounts of time the second to fourth oil supply
ports 62 to 64 are exposed, which will therefore not be further
described below.
[0080] As shown in FIG. 7, when the first oil supply port 61 is
exposed, lubricant oil is sprayed from the first oil supply port 61
toward the first intake cam 31A. If the first intake cam 31A were
in the vicinity of the first oil supply port 61, lubricant oil
would be hindered by the first intake cam 31A and unlikely to be
evenly supplied across the entire upper surface 41b of the first
valve lifter 41. FIG. 10 shows the position of the first oil supply
port 61 as viewed along the center line 21c of the first valve
lifter hole 21. In the present embodiment, in FIG. 10, a straight
line L1 that connects together the center 21c of the first valve
lifter hole 21 and a center 61c of the first oil supply port 61
coincides with the center line 31c of the first camshaft 31. The
first oil supply port 61 is provided at a position that is
relatively far away from the first intake cam 31A. Therefore,
lubricant oil supplied from the first oil supply port 61 is
unlikely to be spattered by the first intake cam 31A (see FIG. 7).
Lubricant oil supplied from the first oil supply port 61 is
unlikely to be hindered by the first intake cam 31A and is likely
to be evenly supplied across the entire upper surface 41b of the
first valve lifter 41. Therefore, it is possible to more stably
supply lubricant oil from the first oil supply port 61 to the upper
surface 41b of the first valve lifter 41.
[0081] As shown in FIG. 5, a depression 35A that is depressed
downward is formed along a peripheral portion of the first valve
lifter hole 21 of the cylinder head 17. The depression 35A is
formed downward of the first intake cam 31A. Specifically, the
depression 35A is formed directly under the first intake cam 31A.
With the depression 35A, the rotating first intake cam 31A does not
hit the peripheral portion of the first valve lifter hole 21.
Conversely, a portion 35B, other than the depression 35A, of the
peripheral portion of the first valve lifter hole 21 is extended
upward relative to the depression 35A. The upper end of the portion
35B is located upward relative to the lower end of the rotation
path of the first intake cam 31A (the lower end of the first intake
cam 31A of FIG. 7). With the provision of the portion 35B, which is
extended upward, the area of the inner circumferential surface 21a
of the first valve lifter hole 21 is relatively large.
[0082] The motorcycle 1 and the engine 5 are configured as
described above. As described above, the cylinder head 17 of the
engine 5 includes the oil supply passage 70. Although there is no
particular limitation on the machining method for the oil supply
passage 70, it is only possible to form a hole of a straight line
shape with a drilling process in which a hole is made by using a
drill. When forming a passage that is bent in the cylinder head 17,
for example, there is a need to form two straight line-shaped holes
that cross each other, and then plug a part of a hole. In view of
this, in the present embodiment, the cylinder head 17 is
manufactured as follows. First, as shown in FIG. 11, a core 70B
having the same shape as the oil supply passage 70 is produced by
using a three-dimensional modeling device (not shown). Then, the
cylinder head 17 is cast with the core 70B fitted in the cast.
Thus, it is possible to obtain the cylinder head 17 in which the
oil supply passage 70 is precisely formed.
[0083] The drilling process needs to be a precise process in order
to ensure a sufficient circularity of the valve lifter holes 21 to
24. In view of this, a core that includes the core 70B having the
same shape as the oil supply passage 70 and a core having the same
shape as the valve lifter holes 21 to 24 may be produced by using a
three-dimensional modeling device, and the cylinder head 17 may be
cast with this core fitted in the cast. Thus, it is possible to
obtain the cylinder head 17 in which the oil supply passage 70 and
the valve lifter holes 21 to 24 are precisely formed.
[0084] As described above, with the engine 5 according to the
present embodiment, lubricant oil is directly supplied to the upper
surface 41b of the first valve lifter 41 from the first passage 71
of the oil supply passage 70 through the first oil supply port 61.
Now, the upper surface 41b of the first valve lifter 41 is a
sliding surface that slides against the first intake cam 31A.
According to the present embodiment, it is possible to stably
supply lubricant oil to the sliding surface of the first valve
lifter 41 that slides against the first intake cam 31A.
[0085] As the first valve lifter 41 ascends, the lubricant oil
having been supplied to the upper surface 41b of the first valve
lifter 41 flows over the periphery of the upper surface 41b down
between the outer circumferential surface 41a of the first valve
lifter 41 and the inner circumferential surface 21a of the first
valve lifter hole 21. Now, the outer circumferential surface 41a of
the first valve lifter 41 is a sliding surface that slides against
the first valve lifter hole 21. With the engine 5, it is possible
to supply lubricant oil to the sliding surface of the first valve
lifter 41 that slides against the first valve lifter hole 21 by
utilizing the ascension of the first valve lifter 41. In addition,
with the engine 5, when the first valve lifter 41 reciprocates
between the upper position and the lower position, the first oil
supply port 61 faces the outer circumferential surface 41a of the
first valve lifter 41. Therefore, lubricant oil is directly
supplied to the outer circumferential surface 41a of the first
valve lifter 41 from the first passage 71 through the first oil
supply port 61. Lubricant oil is directly supplied to the sliding
surface of the first valve lifter 41 that slides against the first
valve lifter hole 21. Therefore, according to the present
embodiment, it is possible to stably supply lubricant oil to the
sliding surface of the first valve lifter 41 that slides against
the first valve lifter hole 21.
[0086] On the other hand, the present embodiment does not require a
lubricant oil supply pipe and a reflector wall, which have been
used with conventional techniques. Thus, it is possible to prevent
the engine 5 from becoming larger.
[0087] Therefore, according to the present embodiment, it is
possible to stably supply lubricant oil to the sliding surface of
the first valve lifter 41 that slides against the first valve
lifter hole 21 and the sliding surface thereof that slides against
the first intake cam 31A while preventing the engine 5 having a
direct-type valve mechanism from becoming larger. Therefore, it is
possible to well prevent the wear of the first valve lifter 41, the
first valve lifter hole 21 and the first intake cam 31A. It is also
possible to sufficiently cool the first valve lifter 41, the first
valve lifter hole 21 and the first intake cam 31A.
[0088] Similarly, it is possible to stably supply lubricant oil to
the sliding surface of the second valve lifter 42 that slides
against the second valve lifter hole 22 and the sliding surface
thereof that slides against the second intake cam 31B. It is
possible to stably supply lubricant oil to the sliding surface of
the third valve lifter 43 that slides against the third valve
lifter hole 23 and the sliding surface thereof that slides against
the first exhaust cam 32A. It is possible to stably supply
lubricant oil to the sliding surface of the fourth valve lifter 44
that slides against the fourth valve lifter hole 24 and the sliding
surface thereof that slides against the second exhaust cam 32B.
Therefore, it is possible to well prevent the wear of the second to
fourth valve lifters 42 to 44, the second to fourth valve lifter
holes 22 to 24, the second intake cam 31B, the first exhaust cam
32A and the second exhaust cam 32B, and to sufficiently cool these
parts.
[0089] The motorcycle 1 may take an inclined attitude, e.g., when
banking and wheeling, under particular circumstances such as during
a motocross race. In that case, the engine 5 also takes an inclined
attitude. However, with the engine 5 according to the present
embodiment, it is possible to directly supply lubricant oil to the
sliding portions of the first to fourth valve lifters 41 to 44, as
described above. Therefore, even when the motorcycle 1 takes an
inclined attitude, it is possible to sufficiently prevent the wear
of the first to fourth valve lifters 41 to 44, etc.
[0090] According to the present embodiment, as shown in FIG. 10,
the straight line L1 that connects together the center 21c of the
first valve lifter hole 21 and the center 61c of the first oil
supply port 61 coincides with the center line 31c of the first
camshaft 31. The first oil supply port 61 is provided at a position
that is far away from the first intake cam 31A. Therefore, it is
possible to more stably supply lubricant oil to the upper surface
41b of the first valve lifter 41 through the first oil supply port
61.
[0091] Since the first intake cam 31A rotates about the center line
31c of the first camshaft 31, the first valve lifter 41, which
receives a force from the first intake cam 31A, is likely to
receive a force in a direction that is perpendicular to the center
line 31c of the first camshaft 31. The pressure that the inner
circumferential surface 21a of the first valve lifter hole 21 of
the cylinder head 17 receives from the outer circumferential
surface 41a of the first valve lifter 41 is greater in portions
thereof that are closer to a line 31d that is perpendicular to the
center line 31c of the first camshaft 31. In the present
embodiment, the first oil supply port 61 is provided at a position
that is far away from the line 31d perpendicular to the center line
31c of the first camshaft 31. Therefore, even though the first oil
supply port 61 is formed on the inner circumferential surface 21a
of the first valve lifter hole 21, it is possible to maintain a
sufficient mechanical strength of the peripheral portion of the
first valve lifter hole 21.
[0092] Note that the straight line L1 that connects together the
center 21c of the first valve lifter hole 21 and the center 61c of
the first oil supply port 61 does not need to coincide with, or be
co-planar with, the center line 31c of the first camshaft 31. As
shown in FIG. 12, .theta. denotes the angle formed between the
straight line L1 and the center line 31c of the first camshaft 31,
as seen in a plan view along the center line 21c of the first valve
lifter hole 21, .theta. may be within 10 degrees. Note that "within
10 degrees" as used in the present specification and claims means
that it is in the range of -10 degrees or more and +10 degrees or
less, where a positive value represents an angle in the
counterclockwise direction with respect to the center line 31c of
the first camshaft 31. In other words, the line L1 connecting the
center 21c of the first valve lifter hole 21 and the center 61c of
the first oil supply port 61 may be arranged relative to the center
line 31c of the first camshaft 31, as seen in a plan view, in the
range from -10 degrees to +10 degrees. Alternatively, the angle
.theta. may be within 45 degrees. That is, it may be -45 degrees or
more and +45 degrees or less, where a positive value represents an
angle in the counterclockwise direction with respect to the center
line 31c of the first camshaft 31.
[0093] Similarly, although not shown in the figures, in the present
embodiment, as viewed in a plan view along the center line 22c of
the second valve lifter hole 22, the straight line that connects
together the center 22c of the second valve lifter hole 22 and the
center of the second oil supply port 62 coincides with the center
line 31c of the first camshaft 31. As viewed in a plan view along
the center line 23c of the third valve lifter hole 23, the straight
line that connects together the center 23c of the third valve
lifter hole 23 and the center of the third oil supply port 63
coincides with the center line 32c of the second camshaft 32. As
viewed in a plan view along the center line 24c of the fourth valve
lifter hole 24, the straight line that connects together the center
24c of the fourth valve lifter hole 24 and the center of the fourth
oil supply port 64 coincides with the center line 32c of the second
camshaft 32. Note however that as viewed in a plan view along the
center line 22c of the second valve lifter hole 22, the angle
formed between the straight line that connects together the center
22c of the second valve lifter hole 22 and the center of the second
oil supply port 62 and the center line 31c of the first camshaft 31
may be within 45 degrees. In one embodiment, the angle formed
between the straight line that connects together the center 22c of
the second valve lifter hole 22 and the center of the second oil
supply port 62 and the center line 31c of the first camshaft 31 may
be within 10 degrees. As viewed in a plan view along the center
line 23c of the third valve lifter hole 23, the angle formed
between the straight line that connects together the center 23c of
the third valve lifter hole 23 and the center of the third oil
supply port 63 and the center line 32c of the second camshaft 32
may be within 45 degrees. In one embodiment, the angle formed
between the straight line that connects together the center 23c of
the third valve lifter hole 23 and the center of the third oil
supply port 63, and the center line 32c of the second camshaft 32
may be within 10 degrees. As viewed in a plan view along the center
line 24c of the fourth valve lifter hole 24, the angle formed
between the straight line that connects together the center 24c of
the fourth valve lifter hole 24 and the center of the fourth oil
supply port 64 and the center line 32c of the second camshaft 32
may be within 45 degrees. In one embodiment, the angle formed
between the straight line that connects together the center 24c of
the fourth valve lifter hole 24 and the center of the fourth oil
supply port 64 and the center line 32c of the second camshaft 32
may be within 10 degrees.
[0094] According to the present embodiment, as shown in FIG. 9, the
rotation angle range T1 of the first camshaft 31 when the upper
surface 41b of the first valve lifter 41 is located downward
relative to the upper end 61t of the first oil supply port 61 is
50% or more, and less than 100%, with respect to the rotation angle
range T2 of the first camshaft 31 from when the first valve lifter
41 starts moving from the upper position until it returns to the
upper position. Thus, it is possible to stably supply lubricant oil
to the upper surface 41b of the first valve lifter 41, which is the
sliding surface that slides against the first intake cam 31A.
[0095] According to the present embodiment, as shown in FIG. 7, the
first passage 71 of the oil supply passage 70 extends in a
direction perpendicular to the center line 21c of the first valve
lifter hole 21. The area of the first oil supply port 61 is smaller
as compared with a case where the first passage 71 extends in a
direction inclined relative to the center line 21c of the first
valve lifter hole 21. Therefore, it is possible to ensure a large
area of the inner circumferential surface 21a of the first valve
lifter hole 21. Thus, it is possible to maintain a sufficient
mechanical strength of the peripheral portion of the first valve
lifter hole 21 of the cylinder head 17. In the present embodiment,
as shown in FIG. 10, the first passage 71 is provided at a position
that is far away from the line 31d perpendicular to the center line
31c of the first camshaft 31. This also contributes to maintaining
a sufficient mechanical strength of the peripheral portion of the
first valve lifter hole 21 of the cylinder head 17.
[0096] According to the present embodiment, as shown in FIG. 5, the
first passage 71 and the second passage 72 of the oil supply
passage 70 branch off a single first vertical passage 75.
Therefore, it is possible to shorten the overall length of the oil
supply passage 70 as compared with a case where a vertical passage
connected to the first passage 71 and a vertical passage connected
to the second passage 72 are provided separately from each other.
Since it is possible to shorten the length of the oil supply
passage 70, it is possible to prevent a pressure decrease of
lubricant oil in the first passage 71 and the second passage 72.
This also contributes to stably supplying lubricant oil to the
sliding surface of the first valve lifter 41 that slides against
the first valve lifter hole 21 and the sliding surface thereof that
slides against the first intake cam 31A and to the sliding surface
of the second valve lifter 42 that slides against the second valve
lifter hole 22 and the sliding surface thereof that slides against
the second intake cam 31B, while preventing the engine 5 from
becoming larger. The first vertical passage 75 is formed between
the first valve lifter hole 21 and the second valve lifter hole 22,
and extends in a direction perpendicular to the first camshaft 31.
This makes it more likely that lubricant oil is evenly supplied to
the first oil supply port 61 and the second oil supply port 62.
[0097] Similarly, according to the present embodiment, the third
passage 73 and the fourth passage 74 of the oil supply passage 70
branch off the second vertical passage 76. It is possible to stably
supply lubricant oil to the sliding surface of the third valve
lifter 43 that slides against the third valve lifter hole 23 and
the sliding surface thereof that slides against the first exhaust
cam 32A and to the sliding surface of the fourth valve lifter 44
that slides against the fourth valve lifter hole 24 and the sliding
surface thereof that slides against the second exhaust cam 32B.
[0098] According to the present embodiment, the depression 35A that
is depressed downward is formed along the peripheral portion of the
first valve lifter hole 21 of the cylinder head 17 and downward of
the first intake cam 31A. Thus, the peripheral portion of the first
valve lifter hole 21 can be prevented from interferring with the
rotating first intake cam 31A. Since it is possible to ensure a
sufficient height of the portion 35B, other than the depression
35A, of the peripheral portion, it is possible to increase the area
of the inner circumferential surface 21a of the first valve lifter
hole 21. Therefore, it is possible to reduce the pressure that the
inner circumferential surface 21a of the first valve lifter hole 21
receives from the outer circumferential surface 41a of the first
valve lifter 41, and it is possible to maintain a sufficient
mechanical strength of the peripheral portion of the first valve
lifter hole 21.
[0099] Now, if an excess of lubricant oil remains on the upper
surface 41b of the first valve lifter 41, it may possibly increase
the resistance against the rotation of the first intake cam 31A.
According to the present embodiment, however, even if lubricant oil
remains on the upper surface 41b of the first valve lifter 41, any
excess of lubricant oil is likely to flow over the upper surface
41b via the depression 35A. Thus, it is possible to reduce the
resistance against the rotation of the first intake cam 31A.
[0100] In the present embodiment, with the provision of the
depression 35A, a portion of the outer circumferential surface 41a
of the first valve lifter 41 (specifically, a portion that is
adjacent to the depression 35A) does not come into contact with the
inner circumferential surface 21a of the first valve lifter hole 21
when the first valve lifter 41 is in the upper position. Lubricant
oil is temporarily not supplied to said portion. However, since
lubricant oil is directly supplied to the sliding surface of the
first valve lifter 41 that slides against the first valve lifter
hole 21 (i.e., the outer circumferential surface 41a) from the oil
supply passage 70, lubricant oil is sufficiently supplied to said
portion while the first valve lifter 41 moves from the upper
position toward the lower position. When the first valve lifter 41
comes back from the lower position to the upper position, lubricant
oil that has remained on the upper surface 41b of the first valve
lifter 41 is supplied to the lubricating surface (the outer
circumferential surface 41a). Therefore, it is possible to also
well lubricate said portion of the outer circumferential surface
41a of the first valve lifter 41 (i.e., a portion that is adjacent
to the depression 35A when the first valve lifter 41 is in the
upper position). Despite the provision of the depression 35A, it is
possible to desirably supply lubricant oil to the sliding surface
of the first valve lifter 41 that slides against the first valve
lifter hole 21.
[0101] Note that this similarly applies also to the peripheral
portion of the second valve lifter hole 22, the peripheral portion
of the third valve lifter hole 23, and the peripheral portion of
the fourth valve lifter hole 24 of the cylinder head 17.
[0102] According to the present embodiment, for manufacturing the
engine 5, a three-dimensional modeling device is used to produce
the core 70B having the same shape as the oil supply passage 70
(see FIG. 11), and the cylinder head 17 is cast with the core 70B
fitted in the cast. Therefore, it is possible to form the oil
supply passage 70 without performing a drilling process. Even an
oil supply passage 70 having a complicated shape can be
manufactured with ease and high precision.
[0103] One embodiment has been described above. However, the
embodiment described above is merely an example. Various other
embodiments are possible.
[0104] In the embodiment described above, four valve lifters 41 to
44 are provided in the cylinder head 17. However, there is no
limitation on the number of valve lifters.
[0105] The shape of the oil supply passage 70 of the embodiment
described above is merely an example. There is no limitation on the
shape of the oil supply passage 70.
[0106] In the embodiment described above, the oil supply ports 61
to 64 each have a circular shape. However, the shape is not limited
to this. For example, the oil supply ports 61 to 64 may each have
an elliptical shape or a quadrangular shape. The oil supply ports
61 to 64 may have the same dimension or different dimensions. The
oil supply ports 61 to 64 may have the same upper/lower positions
or different upper/lower positions.
[0107] In the embodiment described above, the depression 35A is
formed along the peripheral portion of each of the first to fourth
valve lifter holes 21 to 24. However, the depression 35A may not be
necessary. The depression 35A may be absent.
[0108] While a straddled vehicle refers to a vehicle to be
straddled by a passenger, the straddled vehicle is not limited to a
motorcycle. The straddled vehicle may be other vehicles to be
straddled by a passenger, e.g., a motortricycle, an ATV (all
terrain vehicle), etc.
[0109] The terms and expressions used herein are used for
explanation purposes and should not be construed as being
restrictive. It should be appreciated that the terms and
expressions used herein do not eliminate any equivalents of
features illustrated and mentioned herein, but include various
modifications falling within the claimed scope of the present
invention. The present invention may be embodied in many different
forms. The present disclosure is to be considered as providing
examples of the principles of the invention. These examples are
described herein with the understanding that such examples are not
intended to limit the present invention to preferred embodiments
described herein and/or illustrated herein. Hence, the present
invention is not limited to the preferred embodiments described
herein. The present invention includes any and all preferred
embodiments including equivalent elements, modifications,
omissions, combinations, adaptations and/or alterations as would be
appreciated by those skilled in the art on the basis of the present
disclosure. The limitations in the claims are to be interpreted
broadly based on the language included in the claims and not
limited to examples described in the present specification or
during the prosecution of the application.
* * * * *