U.S. patent application number 11/997646 was filed with the patent office on 2009-03-05 for direct-acting type valve lifter for internal-combustion engines.
This patent application is currently assigned to NITTAN VALVE CO., LTD.. Invention is credited to Teruaki Ando, Masayasu Nagado.
Application Number | 20090056659 11/997646 |
Document ID | / |
Family ID | 37708598 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090056659 |
Kind Code |
A1 |
Nagado; Masayasu ; et
al. |
March 5, 2009 |
DIRECT-ACTING TYPE VALVE LIFTER FOR INTERNAL-COMBUSTION ENGINES
Abstract
Objects: To provide a direct-acting type valve lifter that is
simple in structure, involves a small number of components, and is
capable of switching its valve lift between a high and a low lift.
Means for Carrying Out the Invention: The valve lifter is mounted
between a cam unit (20) and a valve stem (15). The cam unit (20)
comprises a high-lift cam (22) and a low-lift cam (24) integrated
to the high-lift cam. The valve lifter (30) is equipped with a side
lifter (32) for slidably lifting the low-lift cams (24), a center
lifter (40) for slidably lifting the high-lift cam, and hydraulic
means (oil groove) (11b) for sliding the center lifter (40) so as
to switch the valve lift in two levels, i.e. to switch between a
high and a low lift. A cylindrical body of the valve lifter is
provided on the top end thereof with a slit (33) for allowing the
high-lift cam to freely rotate therein, and with sliding surfaces
(32a) serving as a side lifter (32) to be in sliding contact with
the low lift cam. Formed in the body of the valve lifter (lifter
body) is a through-hole 34 perpendicular to the slit (33), which
accommodate therein the piston type center lifter (40) such that
the center lifter (40) can be slidably moved by a hydraulic
pressure. When the center lifter (40) is located at a position
aligned with the slit (33), the cam unit assumes a high lift mode.
On the other hand, at a position well offset from the slit (33),
the cam unit assumes a low lift mode. Thus, the valve lifter of the
invention is composed of a small number of components, so that
dimension tolerance demanded for the respective components are much
relaxed, which permits easy assembly of the parts.
Inventors: |
Nagado; Masayasu;
(Hadano-shi, JP) ; Ando; Teruaki; (Hadano-shi,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
NITTAN VALVE CO., LTD.
Hadano-shi, Kanagawa
JP
|
Family ID: |
37708598 |
Appl. No.: |
11/997646 |
Filed: |
August 26, 2005 |
PCT Filed: |
August 26, 2005 |
PCT NO: |
PCT/JP2005/015520 |
371 Date: |
September 19, 2008 |
Current U.S.
Class: |
123/90.48 |
Current CPC
Class: |
F01L 13/0036 20130101;
F01L 1/143 20130101; F01L 1/25 20130101; F01L 1/08 20130101 |
Class at
Publication: |
123/90.48 |
International
Class: |
F01L 13/00 20060101
F01L013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2005 |
JP |
2005-222462 |
Claims
1. A cylindrical direct acting type valve lifter for use with an
internal-combustion engine, provided between the cam unit and the
valve stem constituting a valve mechanism of said internal
combustion engine, said cam unit formed of a high-lift cam (center
cam) and a pair of low-lift cams integral with said high-lift cam,
and said valve lifter having: a side lifter that can be in sliding
contact with said low-lift cams; a center lifter that can be in
sliding contact with said high-lift cam; and hydraulic means for
actuating said center lifter to switch the valve lift of said valve
lifter between a high and a low lift, said valve lifter
characterized in that said cylindrical valve lifter is provided
with: a center cam slit for allowing said center cam to freely
rotate therein, said center cam slit formed in the top end of the
lifter body and extending in the direction of the sliding motion of
said center cam; sliding surfaces formed on the top end of said
side lifter for said low-lift cams; a circular through-hole formed
in said lifter body, extending in the direction perpendicular to
said center cam slit; and a cylindrical piston type center lifter
slidably fitted in said through-hole under hydraulic pressure.
2. The direct-acting type valve lifter according to claim 1,
characterized in that the width of said high-lift cam slit is
substantially the same as the width (thickness) of said high-lift
cam.
3. (canceled)
Description
[0001] This invention relates to the cylindrical direct-acting type
valve lifter provided between the cam and the valve stem which
constitute a valve mechanism of an internal-combustion engine, and
more particularly, to a direct-acting type valve lifter for use
with an internal combustion engines, said valve lifter comprising:
a side lifter having a sliding surface to be in sliding contact
with a low-lift cam of a cam unit; and a center lifter having a
sliding surface to be in contact with a high-lift cam integral with
the low-lift cam, such that the valve lifter is capable of
switching the valve lift between a high and a low lift.
BACKGROUND ART
[0002] A typical direct-acting type valve lifter is disclosed in,
for example, a patent document 1 cited below, and as shown in FIG.
11. This prior art valve lifter is provided with: a cylindrical
body (referred to as lifter body) 1 separated into a central center
lifter 2 having a circular sliding surface 2a to be in sliding
contact with a low-lift center cam and a cylindrical side lifter 3
having a ring-shaped sliding surface 3a to be in contact with
high-lift side cams; a first link pin provided in through-holes 4a
and 4b that extend through the center lifter 2 and the side lifter
3; and a second link pin 5b provided in through-holes 4b and 4c
that extend through the center lifter 2 and the side lifter 3.
Reference numeral 6 refers to a spring member for returning the
first and second link pins 5a and 5b, respectively, back to their
predetermined positions. Reference numeral 7 refers to a spring
member provided between a spring bearing 2b at the end of the
center lifter 2 and the spring bearing 3b of the side lifter 3 to
support the center lifter 2 at a predetermined vertical position
relative to the side lifter 3.
[0003] When the first link pin 5a is located within the
through-hole 4a, the center lifter 2 and the side lifter 3 are
separated in the axial direction of the valve lifter (vertical
direction in FIG. 11) (such that the side lifter 3 can `sink`
relative to the center lifter 2, as shown in FIG. 11), thereby
causing the movement of the center cam (undergoing a low-lift cam
movement) to be transmitted to the lifter body 1 via the sliding
surface 2a. On the other hand, under hydraulic pressure, when the
first and second link pins 5a and 5b, respectively, are moved (to
the right in FIG. 11) against the biasing force of the spring 7 to
the respective positions where the first link pin 5a lies in the
through-hole 4a and 4b and the second link pin 5b lies in the
through-hole 4b and 4c, the center lifter 2 and the side lifter 3
are operably coupled in the axial direction of the valve lifter via
the first and second link pins 5a and 5b, respectively, thereby
transmitting the movement of the side cam (undergoing a high lift
cam operation) to the lifter body 1 via the sliding surface 3a.
Patent document 1: Pat Table 2002-509219 (FIGS. 1 and 2)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0004] However, in the prior art as disclosed in the
above-mentioned patent document 1, the cylindrical lifter body 1
accommodates many components including the center lifter 2, side
lifter 3, first link pin 5a, second link pin 5b, and spring members
6 and 7.
[0005] Therefore, in order for this lifter to be smoothly operable,
the link pins and through-holes must have a high degree of accuracy
regarding their relative positions. To attain this accuracy, the
dimensions of the shaped lifter body 1 and all other components
mounted in the lifter body 1 including the first link pin 5a, a
receiver that abuts on the link pin 5a, the second link pin 5b, and
the through-holes, must be of high precision. Therefore, mass
production of high precision valve lifters is difficult and not
cost effective.
[0006] Moreover, since the spring member 7 is inevitable between
the center lifter 2 and the side lifter 3 to hold the center lifter
2 at a predetermined vertical position relative to the side lifter
3, a further problem exists in that the spring force exerted by the
spring member 7 always adds extra sling friction to the valve
lifter, thereby preventing smooth operation of the lifter,
particularly when the cam is in a high-speed rotational motion in a
low-lift mode (in which the center lifter 2 and the side lifter 3
are operably disconnected in the axial direction so that the side
lifter 3 can sink with respect to the center lifter 2).
[0007] In view of the problems pertinent to the prior art, the
present invention seeks to provide a direct-acting type valve
lifter for use with an internal combustion engine, said valve
lifter comprising a small number of components arranged in a simple
configuration and capable of switching its valve lift between a
high lift and a low lift, thereby enabling smooth operation of the
valve lifter.
Means for Solving the Problems
[0008] To fulfill the object above, there is provided, in
accordance with one aspect of the invention as recited in claim 1,
a direct-acting type cylindrical valve lifter of an internal
combustion engine to be mounted between the cam unit and the valve
stem that together constitute a valve mechanism of the internal
combustion engine, said cam unit formed of a high-lift cam and a
pair of low-lift cams integral with said high-lift cam, said valve
lifter having: a side lifter that can be in sliding contact with
said low-lift cams; a center lifter in sliding contact with said
high-lift cam; and hydraulic means for actuating said center lifter
to switch the valve lift of said valve lifter between a high and a
low lift, said valve lifter characterized in that
[0009] said cylindrical valve lifter is provided with:
[0010] a slit (referred to as center cam slit) for allowing said
center cam to freely rotate therein, said center cam slit formed in
the top end of the body of the valve lifter (referred to as lifter
body) and extending in the direction of the sliding motion of said
center cam;
[0011] sliding surfaces formed on the top end of said side lifter
for said low-lift cams;
[0012] a through-hole formed in said lifter body, extending in the
direction perpendicular to said center cam slit; and
[0013] a piston type center lifter, slidably fitted in said
circular through-hole under hydraulic pressure.
[0014] (Function) The piston type center lifter is adapted to slide
in the through-hole when actuated by a hydraulic pressure. At the
position where the center lifter is well aligned with the slit, the
high-lift cam comes into contact with the center lifter, thereby
giving a high-lift to the valve stem via the center lifter and the
side lifter (lifter body). On the other hand, when the center
lifter comes to a position where it is well offset from the slit,
the high-lift cam freely rotates in the slit, while the low-lift
cams come into sliding contact with the side lifter, thereby giving
a low-lift to the valve stem via the side lifter (lifter body).
[0015] Thus, the center lifter is slid in the through-hole by
hydraulic pressure, and takes on either a first state where it can
be in contact with the center-cam or a second state where it does
not come to contact with the center cam.
[0016] Thus, the valve lifter is composed of a small number of
components. It is composed mainly of: a cylindrical body of the
lifter (referred to as valve lifter body) serving as the side
lifter; and a piston type center lifter slidably fitted in the
through-hole formed in the valve lifter body and actuated by
hydraulic pressure. As a result dimension tolerance demanded for
the respective components are much relaxed, thereby permitting easy
assembly of the parts.
[0017] Moreover, unlike prior art valve lifters, no spring member
is used to support the center lifter in position relative to the
lifter body (side lifter). Hence, no spring force will act on the
valve lifter as a load. As a consequence, in the low-lift mode,
where the high-lift cam is not involved in cam motion, smooth valve
lifter motion can be secured for the cam undergoing a high-speed
rotation.
[0018] In the direct-acting valve lifter for use with an internal
combustion engine as recited in claim 1, the through-hole may have
a circular cross section and said center lifter may have a
cylindrical shape, as recited in claim 2. (Function) Because the
cylindrical piston type center lifter has a curved sliding surface
that comes into contact with the center cam, the sliding surface
has a minimum length to give a predetermined lift, which enables
the center lifter to have a minimum size in the direction of the
cam movement. This adds more degrees of freedom to the design of
the center cam.
[0019] The width of the high-lift cam slit recited in claim 1 or 2
may be substantially the same as the width (thickness) of the
high-lift cam, as recited in claim 3.
[0020] (Function) It is in general necessary to provide the
cylindrical lifter body with rotation stopping means (for example,
a protrusion formed on the lifter body for slidable engagement with
a longitudinal groove formed in the cylinder bore). In the
invention, however, if the cam is designed to have such profile
that the center cam is in engagement with the high-lift cam slit at
all times, the high-lift cam slit and the center cam work together
as rotation stopping means for stopping the rotation of the lifter
body relative to the cylinder bore, since the width of the
high-lift cam slit is substantially the same as the width
(thickness) of the center cam.
RESULTS OF THE INVENTION
[0021] As will be apparent from the description given above, the
direct-action type valve lifter of the invention has a small number
of components, as recited in claim 1, so that the dimension
tolerance demanded for the respective components is greatly
relaxed, and assembling these components is very simple, thereby
enabling manufacture of cost-effective valve lifters.
[0022] Further, the invention can secure smooth motion of the valve
lifter even in a high-speed cam operation in a low-lift mode,
thereby circumventing a conventional problem that hinders smooth
operation of lifters in a low-lift mode and preventing the lopsided
wear problem pertinent to existing valve lifters. In addition,
since no spring member is needed to hold the high-lift valve lifter
in position, there is no need to worry about limitations of the
rotational frequency of cams imposed by a spring force and
permanent set in fatigue of the spring, which also adds more
degrees of freedom to the design of engines.
[0023] As recited in claim 2, since the size of the center cam can
be reduced in the direction of the sliding motion thereof as
recited in claim 2, the size of the valve lifter can be also
reduced accordingly, thereby adding more degrees of freedom to the
design of cams and valve lifters.
[0024] Given a high-lift cam configured to fit in the high-lift cam
slit at all times as recited in claim 3, the lifter body can be
prevented from rotating with respect to the cylinder bore without
any rotation stopping means between the body of the lifter and the
cylinder bore. Then, the body of the lifter and cylinder bore can
be simplified in structure accordingly.
BEST MODE FOR CARRYING OUT THE INVENTION
[0025] Preferred embodiments of the invention will now be described
with reference to the accompanying drawings.
[0026] FIGS. 1-5 are cross sections of a first embodiment of the
invention, with
[0027] FIG. 1 showing a cross section of a direct-acting type valve
lifter and its surrounding components of a valve mechanism for use
with an internal-combustion engine in accordance with a first
embodiment of the invention;
[0028] FIG. 2 showing a cross section of the valve lifter, with a
center lifter being well offset from the slit of the side
lifter;
[0029] FIG. 3 showing a side elevation view of the valve lifter (as
seen from the right in FIG. 2);
[0030] FIG. 4 showing an exploded perspective view of the valve
lifter; and
[0031] FIG. 5 showing a cross section of the valve lifter, with the
center lifter being well aligned with the slit of the side
lifter.
[0032] In these figures, reference numeral 12 refers to an air
intake port formed in the cylinder head 10 of an automobile engine;
numeral 14 to an inlet valve provided in the air intake port 12.
The valve stem 15 of the air intake valve 14, extending in the
cylinder bore 11 near the air intake port 12, is urged by the
spring force of a compressed coil spring 16 in one direction to
close the air intake port 12.
[0033] Reference numeral 20 refers to a cam unit formed of low-lift
side cams 22 and 24 integrated to the opposite sides of a high-lift
center cam 22. The cam unit 20 is arranged on the top end of the
cylinder bore 11. Provided between the cam unit 20 and the valve
stem 15 is a valve lifter 30 that is vertically slidable in the
bore 11.
[0034] As shown in FIG. 4, the valve lifter 30 is mainly provided
with: a slit 33 (referred to as center cam slit) for allowing the
center cam 22 to rotate freely therein; a side lifter (lifter body)
32 having a pair of side cam sliding surfaces 32a; a piston type
center lifter 40 that is slidable in a through-hole 34 formed in
the side lifter 32 in the direction perpendicular to the vertical
slit 33; and a compression spring 39 for holding the center lifter
40 in position. The through-hole 34 has a circular cross section.
The center lifter 40 is a hollow circular cylinder having a closed
end and slidably engages the through-hole 34. The outer peripheral
surface of the center lifter 40 serves as a sliding surface 40a for
the center cam.
[0035] Reference numeral 36 refers to a plug (serving as a spring
bearing) force fitted in a bore 35 formed near the lower opening of
the through-hole 34 in parallel to the through-hole 34. The plug 36
is a hollow cylinder and has a closed end. Projecting from one end
of the plug 36 is a pin (rotation stopping pin) 37 which engages
with the longitudinal groove 11a formed in the wall of the cylinder
bore 11 to serve as rotation stopping means for stopping the
rotation of the valve lifter 30 relative to the cylinder bore 11
and cams 22 and 24.
[0036] Provided inside the plug 36 is a cylindrical hollow slide
pin 38 that has a closed end and is slidable in the axial direction
of the plug 36. A compression spring 39 is arranged between the
plug 36 and the slide pin 38 to urge the center lifter 40 away from
the plug 36 (to the left in FIG. 2).
[0037] Reference numeral 11b refers to an oil groove formed in the
cylinder head 10. The oil groove 11b has an opening in the cylinder
bore 11 in opposition to the longitudinal groove 11a formed in the
cylindrical bore 11 (the opening facing the center lifter 40 of the
valve lifter 30). Under the hydraulic pressure of the engine oil
supplied from this oil groove 11b, the center lifter 40 can slide
in the through-hole 34 to change the lift of the valve 14.
[0038] That is, under a (high) hydraulic pressure applied to the
center lifter 40 via the oil groove 11b, the center lifter 40
slides in the through-hole 34 against the spring force exerted by
the spring 39. When the center lifter 40 assumes a position where
it is aligned with the slit 33 as shown in FIG. 5, the high-lift
center cam 22 comes into sliding contact with (the sliding surface
of) the center lifter 40. As a consequence, a high lift is given to
the valve stem 15 via the center lifter 40 and the side lifter 32
(lifter body).
[0039] On the other hand, as the hydraulic pressure acting on the
center lifter 40 is reduced, the center lifter 40 returns to its
home position where the center lifter 40 is well offset from the
slit 33 by the spring force exerted by the spring 39, thereby
permitting the high-lift center cam 22 to freely rotate in the slit
33, as shown in FIG. 2. At the same time, the low-lift side cam 24
comes into sliding contact with (the sliding surface of) the side
lifter 32, thereby transmitting a low lift to the valve stem 15 via
the side lifter (lifter body) 32.
[0040] In this way, in response to the hydraulic pressure acting on
the center lifter 40, the center lifter 40 selectively assumes one
position where it is in sliding contact with the center cam 24 or
the other position where it does not come into contact with the
center cam 24.
[0041] It is noted that, because the center lifter 40 is formed to
have an arcuate cylindrical sliding surface 40a, the length of the
sliding surface 40a can be short for a given cam lift, so that the
size of the center lifter 40 in the direction of the cam movement
thereof, or equivalently the outer diameter of the center lifter
40, can be reduced accordingly. Hence, the degrees of freedom in
the design of the center cam 24 and valve lifter 30 can be
increased.
[0042] Referring to FIGS. 6 and 7, there is shown a direct-acting
type valve lifter for use with an internal combustion engine in
accordance with a second embodiment of the invention. More
particularly, FIG. 6 shows a cross section of the valve lifter with
its center lifter well aligned with the center cam slit formed in
the side lifter, and FIG. 7 shows a cross section of the valve
lifter with the center lifter completely offset from the center cam
slit.
[0043] As compared with a first embodiment described above which is
provided with the rotation stopping means for stopping the rotation
of the valve lifter 30 (and side lifter 32) that consists of the
rotation stopping pin 37 and the longitudinal groove 11a of the
cylinder bore 11, the present embodiment requires no such rotation
stopping means (no longitudinal groove 11a nor rotation stopping
pin 37) due to the fact that, in this embodiment, the width d of
the high-lift cam slit 33 for the center cam is configured to have
substantially the same width (thickness) t of the center cam 22 and
that the center cam 22 is configured to have a profile that engages
the slit 33 at all times, so that the slit 33 and the center cam 22
together serve as the rotation stopping means for stopping the
rotation of the valve lifter 30 relative to the cylinder bore 11
(or relative to the cam unit 20). As a result, the structures of
the valve lifter 30A and the cylinder bore 11 are simplified
accordingly.
[0044] It will be recalled that in the first embodiment the piston
type center lifter 40 is initially held at the position well offset
from the slit 33 by the spring force of the compressed coil spring
39 when no (high) hydraulic pressure acts on the center lifter 40,
as shown in FIG. 2. (Thus, the low-lift side cams 24 are in
operation in the low-lift transmission mode). When a (high)
hydraulic pressure is applied to the center lifter 40, it is moved
to the position where it is well aligned with the slit 33, thereby
placing the high-lift side cam 22 in the high-lift transmission
mode. It is noted that in the second embodiment described herein,
two lift transmission modes are switched over by the hydraulic
pressure in the opposite manner as compared with the first
embodiment. That is, in the initial stage where no hydraulic
pressure is applied onto the center lifter 40A, it is held by the
spring force of the compressed coil spring 39 at the position where
it is well aligned with the slit 33 (where driving power of the
high-lift side cam 22 is available), as shown in FIG. 6. On the
other hand, when a hydraulic pressure acts on the center lifter
40A, it is moved to the position well offset from the slit 33,
thereby placing the low-lift side cam 24 in operation in the
low-lift transmission mode, as shown in FIG. 7.
[0045] A cylindrical slide pin 38A arranged in the bore 35 has a
closed end. There is provided in the cylinder head 10 an oil groove
11c, which has an opening in the wall of the cylinder bore 11
facing the slide pin 38A of the valve lifter 30A (or the bore 35).
Located at one end of the through-hole 34, remote from the slide
pin 38A, is a cap 44 having a substantially semi-spherical outer
surface. A compression coil spring 39 is provided between the cap
44 and the piston type center lifter 40A to cause the center lifter
40A to abut against the slide pin 38A. As a consequence, the center
lifter 40A is held at a predetermined position where it is well
aligned with the slit 33.
[0046] Specifically, when a (high) hydraulic pressure is applied
onto the slide pin 38A via the oil groove 11c, the center lifter
40A is caused to slide in the through-hole 34 against the spring
force of the spring 39A, and reaches a position where the slide pin
38A is well offset from the slit 33 as shown in FIG. 7. Then, the
high-lift center cam 22 undergoes free rotation in the slit 33 and
the low-lift side cams 24 come into sliding contact with the side
lifter 32, thereby transmitting a low lift to the valve stem 15 via
the side lifter (lifter body 32). On the other hand, as the
hydraulic pressure acting on the slide pin 38A is reduced, the
slide pin 38A is returned by the spring force of the spring 39 to
the home position where it is well aligned with the slit 33,--so
that the high-lift center cam 22 comes into sliding contact with
the center lifter 40A as shown in FIG. 6, thereby transmitting a
high lift to the valve stem 15 via the center lifter 40A and side
lifter (lifter body) 32.
[0047] The rest of the operation of this cam unit is the same as
those of the first embodiment. To avoid duplication of description,
like components in the two embodiments are respectively indicated
by like reference numerals, and further details of the second
embodiment will be omitted.
[0048] Referring to FIGS. 8 and 9, there is shown a direct-acting
type valve lifter for use with an internal combustion engine in
accordance with a third embodiment of the invention. More
particularly, FIG. 8 shows a cross section of the valve lifter_with
its center lifter well offset from the side lifter slit. FIG. 9
shows a side elevation view of the valve lifter shown in FIG.
8.
[0049] This third embodiment is an improved variation of the first
embodiment. It will be recalled that in the first embodiment the
spring force of the compression coil spring 39 acts on the piston
type center lifter 40 via the slide pin 38. In the third embodiment
shown herein, a plug 36 having a rotation stopping pin 37 that
projects from one end of the cylindrical plug 36 is adapted to
slide in the bore 35 formed along the central axis of the
through-hole 34. The center lifter 40B is provided at the axial
center thereof with a spring bearing 41 that projects to engage the
plug 36 such that the resilient force of the compression coil
spring 39 directly acts on the center lifter 40B. Thus, the valve
lifter 30B has less constituents than the preceding
embodiments.
[0050] It is noted that the sliding motion of the center lifter 40B
is smooth since the spring force of the compression spring 39 acts
on the central section of the center lifter 40B.
[0051] The rest of the features of the third embodiment are the
same as those of the first embodiment. To avoid duplication of
description, like components in the two embodiments are
respectively indicated by like reference numerals, and further
details of the third embodiment will be omitted.
[0052] It should be understood, however, that although the
through-holes 34 and the center lifters 40, 40A, and 40B of the
first-third embodiments are shown to have cylindrical cross
sections, they can be formed to have square cross sections.
[0053] In the first-third embodiments, although the resilient force
of a spring is employed along with hydraulic pressure to actuate
the piston, the spring can be removed by applying a hydraulic
pressure to the piston from the opposite side of the piston.
[0054] The invention has been described above in connection with a
valve lifter that constitutes the valve mechanism for use with an
air inlet valve installed in an air inlet port in accordance with
the first through third embodiments. It will be apparent, however,
that the invention can be equally applied to the valve lifter that
constitutes the valve mechanism for use with an exhaust valve
installed in an air exhaust port.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 is a cross section of a direct-acting type valve
lifter and its surrounding components of a valve mechanism for use
with an internal-combustion engine in accordance with a first
embodiment of the invention.
[0056] FIG. 2 is a cross section of the valve lifter shown in FIG.
1, with the center lifter well offset from the side lifter
slit.
[0057] FIG. 3 is a side elevation view of the valve lifter (as seen
from the right in FIG. 2).
[0058] FIG. 4 is an exploded perspective view of the valve
lifter.
[0059] FIG. 5 shows a cross section of the valve lifter, with the
center lifter well aligned with the center cam slit formed in the
lifter body.
[0060] FIG. 6 shows a cross section of a direct-acting type valve
lifter for use with an internal combustion engine in accordance
with a second embodiment of the invention, with the valve lifter
well aligned with the center cam slit formed in the lifter
body.
[0061] FIG. 7 is a cross section of the valve lifter with the
center lifter well offset from the center cam slit formed in the
lifter body.
[0062] FIG. 8 is a cross section of a direct-acting type valve
lifter for use with an internal combustion engine in accordance
with a third embodiment of the invention, with the center lifter
well offset from the center cam slit formed in the lifter body.
[0063] FIG. 9 is a right side elevation view of the valve lifter of
FIG. 8.
[0064] FIG. 10 is a cross section of the valve lifter of FIG. 9,
with the center lifter well aligned with the center cam slit formed
in the lifter body.
[0065] FIG. 11 is a cross section of a conventional valve
lifter.
DESCRIPTION OF THE SYMBOLS
[0066] 10 CYLINDER HEAD [0067] 11 CYLINDER BORE [0068] 11a
LONGITUDINAL GROOVE [0069] 11b & 11c OIL GROOVES [0070] 14 AIR
INLET VALVE CONSTITUTING A VALVE MECHANISM [0071] 15 VALVE STEM
[0072] 20 CAM UNIT CONSTITUTING A VALVE MECHANISM [0073] 22
HIGH-LIFT CENTER CAM [0074] 24 LOW-LIFT SIDE CAMS [0075] 30, 30A,
30B DIRECT-ACTING TYPE VALVE LIFTER [0076] 32 LIFTER BODY (SIDE
LIFTER) [0077] 32a SLIDING SURFACE OF THE SIDE CAM [0078] 33 SLIT
FOR ALLOWING FREE ROTATION OF CENTER CAM (CENTER CAM SLIT) [0079]
34 THROUGH-HOLE [0080] 39 COMPRESSION COIL SPRING [0081] 40, 40A,
40B PISTON TYPE CENTER LIFTER [0082] 40a SLIDING SURFACE OF THE
CENTER CAM [0083] d WIDTH OF CENTER CAM SLIT [0084] t WIDTH
(THICKNESS) OF CENTER CAM
* * * * *