U.S. patent application number 13/060206 was filed with the patent office on 2012-12-20 for tappet roller bearing.
This patent application is currently assigned to NSK LTD.. Invention is credited to Satoshi Hachisuka, Tomohiro Kudo.
Application Number | 20120318216 13/060206 |
Document ID | / |
Family ID | 44563248 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120318216 |
Kind Code |
A1 |
Kudo; Tomohiro ; et
al. |
December 20, 2012 |
TAPPET ROLLER BEARING
Abstract
A tappet roller bearing 10 includes a support shaft 20 to be
supported on a locker arm 4, and first and second rollers 11 and 12
which can be respectively supported rotatably on the periphery of
the support shaft 20 and are arranged together in the axial
direction of the support shaft 20. The first roller 11 constitutes
a plain bearing, and the second roller 12 constitutes a full type
roller bearing or a plain bearing. Due to this, the tappet roller
bearing 10 can extend its life, can enhance its assembling
efficiency and can reduce its manufacturing cost.
Inventors: |
Kudo; Tomohiro; (Gunma,
JP) ; Hachisuka; Satoshi; (Gunma, JP) |
Assignee: |
NSK LTD.
Tokyo
JP
|
Family ID: |
44563248 |
Appl. No.: |
13/060206 |
Filed: |
January 18, 2011 |
PCT Filed: |
January 18, 2011 |
PCT NO: |
PCT/JP2011/050763 |
371 Date: |
June 7, 2011 |
Current U.S.
Class: |
123/90.5 |
Current CPC
Class: |
F01L 2305/02 20200501;
F01L 1/181 20130101; F01L 2305/00 20200501; F01L 1/18 20130101 |
Class at
Publication: |
123/90.5 |
International
Class: |
F01L 1/14 20060101
F01L001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2010 |
JP |
2010-055650 |
Jan 14, 2011 |
JP |
2011-006244 |
Claims
1. A tappet roller bearing, comprising: a support shaft to be fixed
to a locker arm for receiving the movement of a cam to be supported
on the cam shaft of an engine; and first and second rollers
respectively supported rotatably on the periphery of the support
shaft and arranged in the axial direction of the support shaft,
wherein: the first roller constitutes a plain bearing; and the
second roller constitutes a full type roller bearing or a plain
bearing.
2. The tappet roller bearing according to claim 1, wherein: the cam
includes a high speed cam and a low speed cam respectively disposed
on the cam shaft slidably in the axial direction of the cam shaft;
the first roller constituting the plain bearing is contacted with
the high speed cam; and the second roller constituting the full
type roller bearing is contacted with the low speed cam.
3. The tappet roller bearing according to claim 1, wherein: the cam
includes a high speed cam and a low speed cam respectively disposed
on the cam shaft slidably in the axial direction of the cam shaft;
the outer peripheral surface of the first roller to be contacted
with the high speed cam is formed by barrel working to be carried
out after polish finishing; and the outer peripheral surface of the
second roller to be contacted with the low speed cam is formed by
polish finishing without being barrel worked.
4. The tappet roller bearing according to claim 1, wherein the
outer peripheral surfaces of the first and second rollers are not
crowning worked but have a uniform diameter in the axial direction
thereof.
5. The tappet roller bearing according claim 1, wherein at least
one of the first and second rollers is structured so that an axial
direction end face has a convex shape.
6. The tappet roller bearing according to claim 5, wherein: at
least one of the first and second rollers, the axial direction end
face of which is formed to have the convex shape, constitutes a
double roller; and the inner roller of the double roller is
structured so that an axial direction end face has a convex
shape.
7. The tappet roller bearing according to claim 5, wherein: the
second roller constitutes a full type roller bearing; and the
multiple rollers of the roller bearing, together with the second
roller, are structured so that respective axial direction end faces
have a convex shape.
8. The tappet roller bearing according to claim 1, wherein: the
support shaft is formed to have a staged shape including first and
second shaft portions different from each other in the outside
diameter dimension thereof; the first roller is disposed on the
periphery of the first shaft portion; and the second roller is
disposed on the periphery of the second shaft portion.
9. The tappet roller bearing according to claim 1, wherein the
first and second rollers are different from each other in the axial
direction width thereof
10. The tappet roller bearing according to claim 1, wherein the
first and second rollers are different from each other in the
roller diameter thereof
11. The tappet roller bearing according to claim 1, further
comprising a third roller rotatably supported on the periphery of
the support shaft and arranged together with the first and second
rollers in the axial direction of the support shaft.
12. The tappet roller bearing according to claim 1, further
comprising a third roller rotatably supported on the periphery of
the support shaft and arranged together with the first and second
rollers in the axial direction of the support shaft, wherein in a
case that the second roller constitutes a roller bearing, the third
roller is situated on the opposite side to the second roller with
respect to the first roller.
13. The tappet roller bearing according to claim 11, wherein the
outer peripheral surface of at least one of the first to third
rollers is crowning worked.
Description
TECHNICAL FIELD
[0001] The present invention relates to a tappet roller bearing
and, specifically, the invention relates to a tappet roller bearing
to be mounted into a cam follow apparatus which is used in the
variable valve mechanism of an engine.
BACKGROUND ART
[0002] In recent years, there has been increasing an engine
employing a variable valve mechanism which changes the opening and
closing timing of one or both of a suction valve or an exhaust
valve according to the changes of the rotation speed of the engine.
Such variable valve mechanism is generally constituted of a cam
follower apparatus including a locker arm for a high speed cam and
a locker arm for a low speed cam. Also, in order to make compact
the structure of an engine in the axial direction thereof and to
reduce the number of parts of the engine to thereby reduce the cost
of the engine, there is also proposed a cam follower apparatus
which includes a lock arm for high speed and low speed cams and
also which, in operation, slides these cams in the axial direction
thereof to thereby switch the high speed and low speed cams over to
each other.
[0003] The cam follower apparatus includes a locker arm which is
disposed opposed to a cam fixed to a cam shaft rotatable in
synchronization with the crankshaft of the engine and has a roller
to receive the movement of the cam (see, for example, the patent
reference 1 to 3). According to a cam follower apparatus disclosed
in the patent reference 1, in the intermediate portion of a locker
arm, there is provided a support shaft and, on this support shaft,
there are rotatably supported multiple tappet rollers which can be
contacted with the cam fixed to the cam shaft. According to a cam
follower apparatus which is disclosed in the patent reference 2 and
is mounted on the end portion of a locker arm, there are included:
a shaft the two end portions of which are respectively supported on
a pair of support plates and also which is used to constitute an
inner race; three outer races respectively interposed between the
pair of support plates; and, multiple rollers respectively
interposed between the shaft and three outer races and each having
a length extending over the whole of the three outer races. Also,
according to a cam follower apparatus which is disclosed in the
patent reference 3 and is mounted on the end portion of a locker
arm, there are included: a shaft the two end portions of which are
respectively supported on a pair of support plates and also which
is used to constitute an inner race; two outer races respectively
interposed between the pair of support plates; and, multiple
rollers respectively interposed between the shaft and two outer
races and each having a length extending over the whole of the two
outer races.
[0004] Further, according to a roller bearing disclosed in the
patent reference 4, there are included: a shaft the two end
portions of which are respectively supported on a pair of support
plates and also which is used to constitute an inner race; an outer
race interposed between the pair of support plates through a
washer; and, multiple rollers respectively interposed between the
shaft and outer race and arranged in two lines in the axial
direction of the roller bearing through a spacer.
RELATED ART REFERENCE
Patent Reference
[0005] Patent Reference 1: U.S. Pat. No. 6,532,920
Specification
[0006] Patent Reference 2: German Patent Application No.
102006018512 Specification
[0007] Patent Reference 3: Japanese Patent Publication No.
2009-293392
[0008] Patent Reference 4: U.S. Pat. No. 3,674,325
Specification
SUMMARY OF THE INVENTION
Problem that the Invention is to Solve
[0009] Here, according to the cam follower apparatus disclosed in
the patent reference 1, since the rollers are separated from each
other by the side walls of the locker arm, there is raised a
problem that the space of the locker arm in the axial direction
thereof is large. Also, in the patent reference 2 or 3, since, for
each of the rollers of the locker arm, there are disposed two or
three outer races in such a manner that the they straddle over the
roller, there is a possibility that an edge load can occur in the
end portions of the respective outer races. Further, in the roller
bearing disclosed in the patent reference 4, the washer is
interposed between the outer race and the side wall of the locker
arm, and the spacer is interposed between the two lines of rollers.
This complicates the assembling operation of the roller bearing and
also increases the space thereof in the axial direction.
[0010] The present invention aims at solving the problems found in
the above prior art technology. Thus, it is an object of the
invention to provide a tappet roller bearing which can extend its
life, can enhance its assembling efficiency and can reduce its
manufacturing cost. Also, it is another object of the invention to
provide a tappet roller bearing which, for use in a cam follower
apparatus for sliding high speed and low speed cams in the axial
direction thereof to thereby switch them over to each other, can
extend its life, can enhance its rotation performance and its
assembling efficiency, and can reduce its manufacturing cost.
Means for Solving the Problem
[0011] The above objects of the invention can be attained by the
following structures.
[0012] (1) A tappet roller bearing, including:
[0013] a support shaft to be fixed to a locker arm for receiving
the movement of a cam to be supported on the cam shaft of an
engine; and
[0014] first and second rollers respectively supported rotatably on
the periphery of the support shaft and arranged in the axial
direction of the support shaft, wherein:
[0015] the first roller constitutes a plain bearing; and
[0016] the second roller constitutes a full type roller bearing or
a plain bearing.
[0017] (2) The tappet roller bearing according to article (1),
wherein:
[0018] the cam includes a high speed cam and a low speed cam
respectively disposed on the cam shaft slidably in the axial
direction of the cam shaft;
[0019] the first roller constituting the plain bearing is contacted
with the high speed cam; and
[0020] the second roller constituting the full type roller bearing
is contacted with the low speed cam.
[0021] (3) The tappet roller bearing according to article (1) or
(2), wherein:
[0022] the cam includes a high speed cam and a low speed cam
respectively disposed on the cam shaft slidably in the axial
direction of the cam shaft;
[0023] the outer peripheral surface of the first roller to be
contacted with the high speed cam is formed by barrel working to be
carried out after polish finishing; and
[0024] the outer peripheral surface of the second roller to be
contacted with the low speed cam is formed by polish finishing
without being barrel worked.
[0025] (4) The tappet roller bearing according to any one of
articles (1) to (3), wherein
[0026] the outer peripheral surfaces of the first and second
rollers are not crowning worked but have a uniform diameter in the
axial direction thereof.
[0027] (5) The tappet roller bearing according to anyone of
articles (1) to (4), wherein
[0028] at least one of the first and second rollers is structured
so that an axial direction end face has a convex shape.
[0029] (6) The tappet roller bearing according to article (5),
wherein:
[0030] at least one of the first and second rollers, the axial
direction end face of which is formed to have the convex shape,
constitutes a double roller; and
[0031] the inner roller of the double roller is structured so that
an axial direction end face has a convex shape.
[0032] (7) The tappet roller bearing according to article (5),
wherein:
[0033] the second roller constitutes a full type roller bearing;
and
[0034] the multiple rollers of the roller bearing, together with
the second roller, are structured so that respective axial
direction end faces have a convex shape.
[0035] (8) The tappet roller bearing according to any one of
articles (1) to (7), wherein:
[0036] the support shaft is formed to have a staged shape including
first and second shaft portions different from each other in the
outside diameter dimension thereof;
[0037] the first roller is disposed on the periphery of the first
shaft portion; and
[0038] the second roller is disposed on the periphery of the second
shaft portion.
[0039] (9) The tappet roller bearing according to any one of
articles (1) to (8), wherein
[0040] the first and second rollers are different from each other
in the axial direction width thereof.
[0041] (10) The tappet roller bearing according to any one of
articles (1) to (9), wherein
[0042] the first and second rollers are different from each other
in the roller diameter thereof.
[0043] (11) The tappet roller bearing according to any one of
articles (1) to (10), further comprising
[0044] a third roller rotatably supported on the periphery of the
support shaft and arranged together with the first and second
rollers in the axial direction of the support shaft.
[0045] (12) The tappet roller bearing according to any one of
articles (1) to (10), further comprising
[0046] a third roller rotatably supported on the periphery of the
support shaft and arranged together with the first and second
rollers in the axial direction of the support shaft, wherein
[0047] in a case that the second roller constitutes a roller
bearing, the third roller is situated on the opposite side to the
second roller with respect to the first roller.
[0048] (13) The tappet roller bearing according to article (11) or
(12), wherein
[0049] the outer peripheral surface of at least one of the first to
third rollers is crowning worked.
ADVANTAGE OF THE INVENTION
[0050] According to a tappet roller bearing of the invention, in
the first and second rollers which are respectively supported
rotatably on the periphery of the support shaft and are arranged
together in the axial direction of the support shaft, the first
roller constitutes a plain bearing, while the second roller 12
constitutes a full type roller bearing or a plain bearing. Thanks
to this structure, the present tappet roller bearing can extend its
life, can enhance its assembling efficiency, and can reduce its
manufacturing cost.
[0051] Also, according to the invention, in the cam follower
apparatus which slides the high speed and low speed cams in the
axial direction thereof to thereby switch these cams over to each
other, the first roller constituting the plain bearing can be
contacted with the high speed cam, while the second roller
constituting the full type roller bearing can be contacted with the
low speed cam. Thanks to this structure, the present cam follower
apparatus can extend its life, can enhance its rotation performance
and its assembling efficiency, and can reduce its manufacturing
cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] FIG. 1 is a partially cut-away side view of a cam follower
apparatus into which a tappet roller bearing according to a first
embodiment of the invention is assembled.
[0053] FIG. 2 is a perspective view of the tappet roller bearing
shown in FIG. 1.
[0054] FIG. 3 is a section view taken along the A-A arrow line
shown in FIG. 1.
[0055] FIG. 4 is a perspective view of a tappet roller bearing
according to a first modification of the first embodiment of the
invention.
[0056] FIG. 5 is a section view of the tappet roller bearing
according to the first modification of the first embodiment of the
invention.
[0057] FIGS. 6A to 6C are respectively section views of the tappet
roller bearing according to a second modification of the first
embodiment of the invention, showing the combinations of two lines
of rollers included therein.
[0058] FIGS. 7A to 7H are respectively section views of the tappet
roller bearing according to a third modification of the first
embodiment of the invention, showing the combinations of three
lines of rollers included therein.
[0059] FIGS. 8A to 8E are respectively section views of the tappet
roller bearing according to a second embodiment of the invention,
showing the combinations of two lines of rollers included
therein.
[0060] FIGS. 9A and 9B are respectively section views of the tappet
roller bearing according to the second embodiment of the invention,
showing the other combinations of the two lines f rollers included
therein.
[0061] FIGS. 10A and 10B are respectively section views of the
tappet roller bearing according to a modification of the second
embodiment of the invention, showing the other combinations of the
two lines of rollers included therein.
[0062] FIGS. 11A to 11H are respectively section views of the
tappet roller bearing according to a second modification of the
second embodiment of the invention, showing the combinations of
three lines of rollers included therein.
[0063] FIGS. 12A to 12C are respectively section views of the
tappet roller bearing according to a third modification of the
second embodiment of the invention, showing the combinations of
three lines of rollers included therein.
[0064] FIGS. 13A to 13D are respectively section views of the
tappet roller bearing according to a fourth modification of the
second embodiment of the invention, showing the combinations of
three lines of rollers included therein.
[0065] FIG. 14 is a section view of a tappet roller bearing
including two lines of rollers respectively arranged around shafts
having different diameters according a third embodiment of the
invention. FIGS. 15A to 15C are respectively explanatory views of
the tappet roller bearing shown in FIG. 14, showing the assembling
steps of the tappet roller bearing.
[0066] FIG. 16A is a section view of a modification of the tappet
roller bearing of the third embodiment of the invention including
two lines of rollers, and FIG. 16B is a section view of another
modification of the tappet roller bearing of the third embodiment
of the invention including three lines of rollers.
[0067] FIG. 17 is a section view of a tappet roller bearing
including two lines of rollers having different roller diameters
according to a fourth embodiment of the invention.
[0068] FIG. 18 is a section view of a tappet roller bearing
including two lines of rollers having different roller diameters
according to a modification of the fourth embodiment of the
invention.
[0069] FIG. 19 is an explanatory side view of a modification of a
locker arm.
MODE FOR IMPLEMENTING THE INVENTION
[0070] Now, description will be given below specifically of a
tappet roller bearing according to the respective embodiments of
the invention with reference to the drawings.
First Embodiment
[0071] Firstly, description will be given below of a cam follower
apparatus 1 with reference to FIG. 1. In this cam follower
apparatus 1, on a cam shaft 2 which can be rotated synchronously
with the crank shaft of an engine (not shown), there are
respectively supported a high speed cam 3a and a low speed cam 3b
in such a manner that they can be slid in the axial direction of
the cam shaft 2 (in FIG. 1, in the front and back direction of the
sheet of FIG. 1). Also, at the position that is disposed opposed to
the high speed cam 3a or low speed cam 3b slidably in the axial
direction thereof, there is arranged a locker arm 4 which is used
to receive the movements of these cams 3a and 3b. The locker arm 4
has a shaft hole 4a formed in the longitudinal direction
intermediate portion thereof (in FIG. 1, in the right and left
direction), while the lock arm 4 can be rotatably supported on a
cylinder head (not shown) through a locker shaft 5 inserted through
the shaft hole 4a.
[0072] Also, with the base end portion (in FIG. 1, the left end
portion) of the locker arm 4, there is threadedly engaged an adjust
bolt 6, while the adjust bolt 6 can be fastened and fixed to such
base end portion using a lock nut 6a. And, with the end portion of
the adjust bolt 6 (in FIG. 1, the lower end portion thereof), there
is contacted the end portion (in FIG. 1, the upper end portion) of
an engine valve 7 serving as a suction valve or an exhaust valve
supported on a cylinder head (not shown) in such a manner that it
can be moved reciprocatingly. The engine valve 7 is always
energized by a valve spring 8 in a valve closing direction (a
direction where the engine valve 7 is contacted with the adjust
bolt 6). Therefore, the locker arm 4 is always energized clockwise
in FIG. 1.
[0073] On the other hand, in the leading end portion (in FIG. 1, in
the right end portion) of the locker arm 4, there are provided a
pair of support wall portions 9 which are spaced from each other.
On the pair of support wall portions 9, there is mounted a tappet
roller bearing 10 according to the present embodiment.
[0074] The tappet roller bearing 10 according to the present
embodiment, as shown in FIGS. 1.about.3, includes: a first roller
11 and a second roller 12 which are respectively interposed between
the paired support wall portions 9, while the first roller 11 can
be contacted with the high speed cam 3a and second roller 12 can be
contacted with the low speed cam 3b; and, a support shaft 20 the
two end portions of which are supported in the shaft holes 9a of
the paired support wall portions 9 and also which supports the
first and rollers 11 and 12 rotatably.
[0075] The support shaft 20 is constituted of a steel-made hollow
or solid shaft member and, when the two end portions of the support
shaft 20 are caulked into the shaft holes 9a formed in the paired
support wall portions 9, the support shaft 20 can be fixed to the
support wall portions 9.
[0076] Here, the first roller 11, with which the high speed cam 3a
can be contacted, constitutes a single roller serving as a plain
bearing which can be slidingly contacted with the outer peripheral
surface of the support shaft 20. Also, the second roller 12, with
which the low speed cam 3b can be contacted, constitutes the outer
race of a roller bearing including multiple rollers 13 which are
interposed in a full type roller manner between the roller bearing
and support shaft 20.
[0077] The first and second rollers 11 and 12 are substantially
equal to each other in the outside diameter dimension thereof. The
first and second rollers 11 and 12 may be made of metal such as
bearing steel or carbon steel, provided that the metal can secure
necessary hardness through the heat treatment thereof. And, they
may be constituted of the same material or may be constituted of
different materials. For example, by using materials which are
different in the carbon contents thereof, they may be prevented
from biting into each other.
[0078] The respective outer peripheral surfaces of the first and
second rollers 11 and 12 have been crowning worked, which can
prevent an excessive surface pressure due to an edge load from
acting on the rolling contact portions of the rollers with the cams
3a and 3b and also which makes it possible for the rollers to deal
with the inclination of the cams 3a, 3b and tappet roller bearing
10.
[0079] The crowning may include any of full crowning, partial
crowning, logarithmic arc crowning and composite arc crowning.
Also, the radius of curvature of the crowning may be different
between the first and second rollers 11 and 12. Preferably, the
radius of curvature of the first roller 11 to be contacted by the
high speed cam 3a may be set smaller than the radius of curvature
of the second roller 12 to be contacted by the low speed cam 3b,
and large crowning may be carried out on the first roller 11 with
which the high speed cam 3a can be contacted.
[0080] The allowable surface pressure of the respective cams 3a and
3b is up to 2 GPa or so, while the allowable surface pressure of
the tappet roller bearing 10 is set higher than the allowable
surface pressure of the respective cams 3a and 3b. In the case that
the surface pressure of these members 3a and 3b exceeds the
allowable surface pressure, there occurs a peeling phenomenon in
these members. Therefore, the crowning working is carried out on
the outer peripheral surfaces of the cams 3a and 3b in order to
prevent their respective contact surface pressures from exceeding
their respective allowable surface pressures.
[0081] However, when there is little possibility that misalignment
can occur, the crowning working can be omitted. In this case, the
outer peripheral surfaces of the first and second rollers 11 and 12
respectively have a uniform diameter in the axial direction
thereof.
[0082] Also, the second roller 12 to be contacted by the low speed
cam 3b, after it is polish finished, may not receive additional
surface working such as barrel working. On the other hand, on the
first roller 11 to be contacted by the high speed cam 3a, there are
carried out not only polish finishing but also additional surface
working such as barrel working.
[0083] Here, in FIG. 2 and also in FIGS. 4, 6, 7 and the like which
will be described later, the illustration of the support wall
portion 9 for supporting the support shaft 20 is omitted.
[0084] In the cam follower apparatus 1 structured in the
above-mentioned manner, the outer peripheral surface of the first
or second roller 11 or 12 is contacted with the outer peripheral
surface of the high speed cam 3a or low speed cam 3b due to the
energizing force of the valve spring 8. In this state, the rotation
of the cam shaft 2 is converted to the reciprocating oscillatory
motion of the locker arm 4 about the locker shaft 5, and the engine
valve 7 is moved or reciprocated in the axial direction thereof
against the energizing force of the valve spring 8 or due to the
energizing force of the valve spring 8, while the lift amount of
the engine valve 7 is variable. Thanks to this, a suction port or
an exhaust port to be formed in a cylinder head (not shown) can be
opened and closed.
[0085] Also, in the tappet roller bearing 10, since the first
roller 11 is used as a plain bearing and the second roller 12 is
used a roller bearing, there is eliminated the need to provide a
washer, which is necessary when the two rollers are respectively
constituted of roller bearings, for prevention of mutual
interference between the two rollers in the axial direction
thereof. Therefore, the tappet roller bearing 10 is enhanced in the
assembling efficiency thereof and also can reduce the manufacturing
cost thereof.
[0086] Further, a plain bearing has a problem that it has such
sufficient durability as can neglect the need to consider the life
of the bearing but it provides large frictional resistance in the
low speed rotation area. However, in the high speed rotation area,
the frictional resistance of the plain bearing is low and is
substantially equal to that of a roller bearing.
[0087] Therefore, in the tappet roller bearing 10, the second
roller 12 for contact with the low speed cam 3b is constituted of a
roller bearing to thereby be able to reduce the frictional
resistance in the low speed rotation time, while the first roller
11 for contact with the high speed cam 3a is constituted of a plain
bearing to thereby be able to eliminate a possibility that a high
load in the high speed rotation time can have an influence on the
life of the bearing.
[0088] Accordingly, since the first and second rollers 11 and 12
are structured as in the present embodiment according to the high
speed cam 3a and low speed cam 3b, the enhanced rotation
performance (dynamic torque) due to the reduced frictional
resistance and the increased life of the bearing can be attained at
the same time.
[0089] Now, FIGS. 4 and 5 respectively show a tappet roller bearing
10 according to a modification of the present embodiment. In this
tappet roller bearing 10, a first roller 11a constitutes the outer
roller of a double roller (plain bearing) including an inner roller
14 which is interposed between a support shaft 20 and first roller
11a. In the case that the first roller 11a functions as an outer
roller and cooperates together with the inner roller 14 to
constitute a double roller in this manner, when compared with the
single roller 11 according to the first embodiment, the frictional
resistance can be reduced.
[0090] Also, FIGS. 6 and 7 respectively show another modification
of the tappet roller bearing according to the first embodiment.
[0091] For example, as shown in FIGS. 6A.about.6C, in the case that
the first and second rollers are both constituted of plain
bearings, the tappet roller bearing can be structured with no
provision of a washer. Specifically, as shown in FIG. 6A, the first
and second rollers 11 and 12a may be respectively constituted of
plain bearings formed as single rollers; as shown in FIG. 6B, the
first roller 11a may be constituted of a double roller including an
inner roller 14, and the second roller 12 may be constituted of a
single roller; and, as shown in FIG. 6C, the first and second
rollers 11a and 12b may be both constituted of double rollers
respectively including inner rollers 14 and 15. In the case of such
double roller as shown in FIG. 6C, the materials of the first and
second rollers 11a, 12b and inner rollers 14, 15 may be changed
respectively.
[0092] Also, the tappet roller bearing 10, as shown in FIGS.
7A.about.7H, may further include a third roller 16, 16a, 16b which
is rotatably supported on the periphery of a support shaft 20 and
is arranged in the axial direction of the support shaft 20 together
with the first and second rollers 11, 12. In this case, preferably,
the types of the rollers to be arranged on both sides in the axial
direction of the support shaft 20 may be the same.
[0093] Specifically, as shown in FIGS. 7A.about.7F, in the case
that the third roller 16, 16a is constituted of a plain bearing,
when the third roller 16, 16a and the first roller 11, 11a
constituted of a plain bearing are arranged on both sides in the
axial direction of the support shaft 20, the second roller 12, 12a,
12b may be constituted of a full type roller bearing or may be
constituted of a plain bearing. In this case, it is unnecessary to
consider interference between the rollers and unnecessary to
dispose a washer.
[0094] On the other hand, as shown in FIGS. 7G and 7H, in the case
that the third roller 16b is constituted of a full type roller
bearing and the second roller 12 is also constituted of a full type
roller bearing, in order that interference between the rollers can
be prevented without provision of a washer, the third roller 16b
may be arranged such that it is situated on the opposite side to
the second roller 12 with respect to the first roller 11, 11a, that
is, the third roller 16b and second roller 12 may be arranged on
both sides in the axial direction of the support shaft 20.
Second Embodiment
[0095] Next, description will be given below of a tappet roller
bearing according to a second embodiment of the invention with
reference to FIGS. 8.about.13. Here, in the following description,
in the case that a plain bearing is constituted of a single roller,
the single roller itself may also be referred to as the composing
element of the bearing; in the case that a plain bearing is
constituted of a double roller, the outer roller and inner roller
may also be referred to as the composing elements of the bearing;
and, in the case of a full type roller bearing, the roller
constituting the outer race and multiple rollers may also be
referred to as the composing elements of the bearing.
[0096] In a tappet roller bearing according to the present
embodiment, the axial direction two end faces of at least first and
second rollers 11, 11a and 12, 12a are formed to have a convex
shape. Owing to this, bearings, which are respectively constituted
of the first and second rollers 11, 11a, 12, 12a, can be prevented
from moving together, thereby being able to reduce sliding torque
which can be generated between the mutually opposing end faces of
the rollers. Also, there can also be reduced sliding torque which
can be generated between the first and second rollers 11, 11a, 12,
12a and a pair of support wall portions 9 of a locker arm
respectively disposed opposed to the first and second rollers on
the outside in the axial direction of the support shaft 20.
Further, supply of a lubricant to the support shaft 20 can be
facilitated and thus the support shaft 20 can be prevented against
abrasion and seizure.
[0097] The above structure according to the present embodiment can
be applied to an arbitrary tappet roller bearing 10 according to
the first embodiment. That is, for example, similarly to FIG. 3, in
a tappet roller 10 shown in FIG. 8A in which a first roller 11
constitutes a single roller and a second roller 12 constitutes a
full type roller bearing, the axial direction two end faces of the
second roller 12 and multiple rollers 13 are respectively formed to
have a convex shape (a convex-shaped partially spherical
surface).
[0098] Also, in a tappet roller bearing 10 as well which is shown
in FIG. 8B and in which a first roller 11a constitutes the outer
roller of a double roller and a second roller 12 constitutes a full
type roller bearing, the axial direction two end faces of the
second roller 12 and multiple rollers 13 are formed to have a
convex shape (a convex-shaped partially spherical surface).
[0099] Further, FIGS. 8C.about.8E, similarly to FIGS. 6A.about.6C,
respectively show a structure in which, in the case that first and
second rollers 11, 11a, 12a, 12b are both constituted of a plain
bearing, the axial direction end faces of one of the first and
second rollers are respectively formed to have a convex shape.
However, as shown in FIG. 8D, in the case that the tappet roller
bearing 10 is constituted of a single roller and a double roller,
in order to prevent the mutually opposing axial direction end faces
of the rollers from surface contacting with each other, preferably,
the axial direction two end faces of the inner and outer rollers of
the double roller may be respectively formed to have a convex
shape.
[0100] Also, although, in FIGS. 8A.about.8E, there is shown a
structure in which the axial direction two end faces of one of the
first and second rollers 11, 11a, 12a, 12b are respectively formed
to have a convex shape, the axial direction two end faces of both
the first and second rollers 11, 11a, 12a, 12b may also be
respectively formed to have a convex shape. That is, as shown in
FIG. 9A, in a tappet roller bearing having a similar structure to
FIG. 8B, the axial direction two end faces of the first roller 11a
(the outer roller of the double roller) and inner roller 14 as well
as the axial direction two end faces of the second roller 12 and
multiple rollers 13 are respectively formed to have a convex shape
(a convex-shaped partially spherical surface). Also, as shown in
FIG. 9B, in a tappet roller bearing having a similar structure to
FIG. 8C, the axial direction two end faces of first and second
rollers 11 and 12a respectively constituting a single roller are
formed to have a convex shape.
[0101] However, as shown in FIG. 10A, in a tappet roller bearing
having a similar structure to FIG. 8A, also in the case that the
axial direction two end faces of the second roller 12 and multiple
rollers 13 are respectively formed to have a convex shape, there is
a possibility that the mutually opposing axial direction end faces
of the rollers can be surface contacted with each other. Therefore,
the axial direction end face of the first roller 11 must be formed
to have such a two-stage convex shape as shown in FIG. 10B which is
recessed in the diameter direction at the same diameter direction
positions of the inside diameter of the second roller 12.
[0102] Also, the structure according to the present embodiment,
similarly to FIGS. 7A.about.7H according to the first embodiment,
can also be applied to a structure including a third roller 16, 16a
constituted of a full type roller bearing or a plain bearing. That
is, a second roller 12 and multiple rollers 13 respectively
constituting a full type roller bearing, first or second roller 11
or 12a constituting a single roller, first or second roller 11a or
12b constituting the outer roller of a double roller and inner
roller 14 or 15 of the double roller, which are respectively
situated in the axial direction intermediate portion of the tappet
roller bearing in FIGS. 11A.about.11H, are respectively formed such
that the axial direction two end faces thereof respectively have a
convex shape. Or, as shown in FIGS. 12A.about.12C, a convex shape
may also be formed in the axial direction two end faces of two
bearing composing elements respectively situated on both sides in
the axial direction of the support shaft 20. Or, as shown in FIGS.
13A.about.13D, a convex shape may also be formed in the axial
direction two end faces of three bearing composing elements.
However, the second roller 12a shown in FIG. 11F and the first
roller 11 shown in FIG. 11H respectively have a convex-shaped axial
direction end faces which are similar to the FIG. 11B.
Third Embodiment
[0103] Next, description will be given below of a tappet roller
bearing according to a third embodiment of the invention with
reference to FIGS. 14.about.16.
[0104] According to the present embodiment, there is provided a
structure which can prevent a tappet roller bearing 10 against
wrong assembly when it is assembled. In the previously described
embodiments, it is difficult to judge from the outside which of the
first and second rollers 11, 11a, 12, 12a, 12b is a roller to be
contacted with the high speed cam or low speed cam. Therefore, in
the case that the first and second rollers are different from each
other only in the crowning shape thereof, it is difficult to judge
visually which one of the rollers is the roller to be contacted.
Also, in the case that the first and second rollers 11, 11a, 12,
12a, 12b are different from each other in the surface treatment
thereof, even when they respectively constitute the same bearing
composing elements, it is necessary to judge whether they are to be
contacted with the high speed or low speed cam, which makes it
necessary to take measures against wrong assembly.
[0105] Therefore, in the case that a tappet roller bearing 10 shown
in FIG. 14 is composed of a combination of a plain bearing
including a first roller 11 constituted of a single roller and a
full type roller bearing including a second roller 12 constituting
the outer race of the roller bearing, a support shaft 20 is formed
to have a staged shape including a first shaft portion 20a and a
second shaft portion 20b respectively adjoining each other and
having different outside diameter dimensions. The first roller 11
is disposed on the periphery of the first shaft portion 20a, while
the second roller 12 is disposed on the periphery of the second
shaft portion 20b.
[0106] Here, since a load to be applied to the second roller 12
from the low speed cam 3b is smaller than a load to be applied
thereto from the high speed cam 3a, stress involved with the
support shaft 20 is also low and an oil film may be formed small.
In view of this, the second roller 12 to be contacted with the low
speed cam 3b is disposed on the periphery of the second shaft
portion 20b having a smaller diameter than the first shaft portion
20a.
[0107] Also, the outside diameter dimensions of the first and
second rollers 11 and 12 are set equal to each other. Therefore,
the sum of the diameter direction dimension (thickness) of the
second roller 12 and the diameter direction dimension (roller
diameter) of multiple rollers 13 can be set larger than the
diameter direction dimension (thickness) of the first roller 11.
Here, in this case, preferably, the thickness of the second roller
12 may be set larger than the roller diameter.
[0108] Specifically, the tappet roller bearing 10 shown in FIG. 14
is assembled to the locker arm 4 using a method shown in FIG. 15.
Firstly, as shown in FIG. 15A, before assembled to the locker arm
4, the tappet roller bearing 10 is held by a staged stop plug 50
including a shaft portion having an outside diameter substantially
equal to the axial direction width of the tappet roller bearing 10
and also substantially equal to the first and second shaft portions
20a, 20b of the support shaft 20. And, the tappet roller bearing
10, while it remains held by the stop plug 50, is interposed
between the support wall portions 9 of the locker arm 4; and, the
stop plug 50 is pushed out from the small diameter side thereof
using a jig 51 having an outside diameter dimension substantially
equal to the small diameter side outside diameter of the stop plug
50. And, after the stop plug 50 is removed from the locker arm 4,
the support shaft 20 is inserted from the side where the stop plug
50 has been pushed out to thereby remove the jig 51, so that the
tappet roller bearing 10 is assembled to the locker arm 4 without
wrong assembly.
[0109] Also, according to a modification of the present embodiment,
as shown in FIGS. 16A and 16B, the first and second rollers 11 and
12 may be formed such that they are different from each other in
the axial direction width thereof, thereby being able to visually
prevent the wrong assembly of the tappet roller bearing 10. That
is, as shown in FIG. 16A, the axial direction width a of the first
roller 11 receiving a large load from the high speed cam 3a may be
formed set larger than the axial direction width b of the second
roller 12.
[0110] Also, as shown in FIG. 16B, in the case that the tappet
roller bearing 10 is constituted of a combination of a plain
bearing including the first roller 11 constituting a single roller
and a full type roller bearing including the second and third
rollers 12 and 16b constituting the outer race of the roller
bearing, the axial direction width a of the first roller 11 may
also be set larger than the axial direction width b of the second
and third rollers 12 and 16b.
[0111] Further, according to a further modification of the present
embodiment, the tappet roller bearing may also be structured such
that the first and second rollers 11 and 12 are formed different
from each other in the roller diameter thereof, whereby the wrong
assembly of the tappet roller bearing can be prevented visually.
For example, as shown in FIG. 17, in the case that the surface
pressure of the first roller 11 is high, the roller diameter of the
first roller 11 is set larger than that of the second roller 12 to
thereby reduce the surface pressure. On the other hand, in the case
that the surface pressure of the second roller 12, the roller
diameter of the second roller 12 may be increased.
[0112] Also, as shown in FIG. 18, the tappet roller bearing may
also be structured by combining together the two structures
respectively shown in FIGS. 14 and 17. That is, the support shaft
20 is formed to have a staged shape which includes first and second
shaft portions 20a and 20b respectively having mutually different
outside diameter dimensions, the first roller 11 is disposed on the
periphery of the first shaft portion 20a, while the second roller
12 is disposed on the periphery of the second shaft portion 20b.
Also, the first and second rollers 11 and 12 are structured such
that their respective roller diameters (outside diameters) are
different from each other.
[0113] Also, according to the present embodiment, there can also be
employed a structure in which both bearings are constituted of
plain bearings and, there can also be employed in a structure which
includes such first to third rollers as shown in FIG. 7. That is,
to any of the above-mentioned embodiments, there can also be
applied the following structures: for example, a structure in which
rollers are respectively disposed in the shaft portions of the
support shaft 20 having different axial diameters; and, a structure
in which rollers are formed such that their respective axial
direction widths are different from each other. Also, a structure
in which the axial direction widths of the respective rollers are
different from each other can be applied to any of the above
embodiments. Or, at least one of the rollers may also be formed to
have a roller diameter which is different from the roller diameters
of the remaining rollers.
[0114] Here, the invention is not limited to the above-mentioned
embodiments but it can be changed properly without departing from
the subject matter of the invention.
[0115] In the above embodiments, there is illustrated an example in
which the tappet roller bearing 10 is mounted on the leading end
portion of the locker arm 4. However, as shown in FIG. 19, the
tappet roller bearing 10 may also be mounted onto the intermediate
portion of a locker arm 40. In this case, the locker arm 40
includes a shaft hole 41 which is formed in the intermediate
portion of the locker arm 40 and to the inner surface of which the
two end portions of the support shaft 20 of the tappet roller
bearing 10 can be fitted and fixed. Also, on one end portion (in
FIG. 19, the right end portion) of the locker arm 40 in the
longitudinal direction thereof, there is provided a substantially
semi-cylindrical projecting portion 42 against which the end
portion of the engine valve 7 (see FIG. 1) can be butted, whereas,
in the other end portion of the locker arm 40, there is formed a
spherical recessed portion against which the end portion of a rush
adjuster (not shown) can be butted against.
[0116] Here, the invention is based on the Japanese Patent
Application (Patent Application No. 2010-055650) filed on Mar. 12,
2010 and the Japanese Patent Application (Patent Application No.
2011-006244) filed on Jan. 14, 2011 and thus the contents thereof
are incorporated herein for reference.
MODE FOR IMPLEMENTING THE INVENTION
[0117] 1: Cam follower apparatus [0118] 2: Cam shaft [0119] 3a, 3b:
Cam [0120] 4, 40: Locker arm [0121] 9: Support wall portion [0122]
10: Tappet roller bearing [0123] 11: First roller (plain bearing)
[0124] 11a: First roller (plain bearing, outer roller) [0125] 12:
Second roller (outer race of roller bearing) [0126] 12a: Second
roller (plain bearing) [0127] 12b: Second roller (plain bearing,
outer roller) [0128] 16: Third roller (plain bearing) [0129] 16a:
Third roller (plain bearing, outer roller) [0130] 16b: Third roller
(outer race of roller bearing) [0131] 20: Support shaft
* * * * *