Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2002-06-14
2003-06-03
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090480, C123S090240, C123S090260, C074S569000
Reexamination Certificate
active
06571758
ABSTRACT:
BACKGROUND OF THE INVENTION
CROSS-REFERENCES TO RELATED APPLICATIONS
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2001-215688 filed in Japan on Jul. 16, 2001, the entirety of which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a valve pause mechanism, and more particularly to a valve pause mechanism fitted between a valve lifter in reciprocating contact with a valve cam of a four-stroke internal combustion engine and a valve stem of a poppet valve.
2. Description of the Background Art
Japanese published unexamined patent application No. Hei 10-184327, the entirety of which is hereby incorporated by reference, describes an example of a valve pause mechanism of the background art.
As seen in
FIGS. 14
to
16
of the present application, a valve lifter
03
fitted is into a cylinder head
01
of a four-stroke internal combustion engine so that the valve lifter
03
can slide in contact with a valve cam
02
. The valve lifter
03
is also pressed by a lifter spring
04
. A slide pin holder
05
is fitted into the valve lifter
03
and a slide pin
06
is inserted into the slide pin holder
05
so that the slide pin
06
can slide perpendicularly to a direction in which the valve lifter
03
is moved.
As shown in
FIG. 15
, the slide pin
06
is cylindrical. A stem working face
06
a
is formed by a part of the side of the slide pin
06
cut out flat. A stem through hole
06
b
is made perpendicularly to the central axis of the cylinder next to the stem working face
06
a
. The slide pin
06
pressed by a spring
07
is slid by oil pressure. A valve stem
08
is arranged so as to be pressed by a valve spring
09
so that the top end faces the stem working face
06
a
, or the stem through hole
06
b
respectively adjacent to the slide pin
06
.
Therefore, where the slide pin
06
is located in a position in which the stem working face
06
a
faces the top end of the valve stem
08
(see FIG.
16
), the valve stem
08
can be lowered via the slide pin
06
. The valve can be opened or closed by lifting or lowering the valve stem
08
together with the valve lifter
03
lifted or lowered by the rotation of the valve cam
02
.
When the slide pin
06
is moved and is located in a position in which the stem through hole
06
b
faces the top end of the valve stem
08
(a state shown in FIG.
14
), the valve stem
08
is not untracked from the stem through hole
06
b
and cannot be lowered. Accordingly, the operation of the valve can be paused with the aforementioned arrangement.
The present inventors have determined that the inertial weight of a valve system increases by a quantity representative of the additional weight of the valve pause mechanism. A load of the valve spring is required to be increased corresponding to the increase in inertial weight and as a result, friction between the cam and the lifter increases.
As shown in
FIG. 16
, e.g., in the case of the slide pin
06
having the above-mentioned arrangement, the top end of the valve stem
08
is in contact with the stem working face
06
a
of the slide pin
06
in a valve operation state and a load is applied thereto. Stress is apt to concentrate on the deepest point P of an opening slightly within the stem through hole
06
b
at the back of the stem working face
06
a.
Therefore, the present inventors have also determined that durability of the slide pin against the bending stress in the valve operation state should be considered based upon the dimensional relation between the outside diameter of the slide pin and the stem through hole, and the relation of a load from the valve spring.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
An object of the present invention is to provide a valve pause mechanism provided with a durable slide pin of lightweight.
One or more of the objects of the present invention is accomplished by a valve pause mechanism for a four-stroke internal combustion engine comprising a valve cam; a poppet valve having a valve stem; a lifter spring; a valve lifter fitted between the valve cam and the valve stem, wherein the poppet valve is always pressed in a direction in which the valve lifter remains in an operating contact position with the valve cam by the lifter spring; a slide pin holder being fitted within the valve lifter; a slide pin being fitted into the slide pin holder, the slide pin being capable of sliding in a reciprocating motion in a direction perpendicular to the valve stem and having an upper surface and a lower surface; a stem working face on the lower surface of the slide pin; a stem through hole adjacent to the stem working face; a slide pin driving mechanism, the slide pin driving mechanism selectively applying the stem working face and the stem through hole to the valve stem by sliding the slide pin in the reciprocating motion; a chamfered portion being formed along the upper surface of the slide pin and extending along a portion of the stem through hole.
One or more of the objects of the present invention is also accomplished by a slide pin holder assembly for a valve pause mechanism of a four-stroke internal combustion engine comprising a valve lifter having a valve lifter spring; a slide pin holder being fitted within the valve lifter; a cylindrical slide pin being fitted into the slide pin holder, the slide pin being capable of sliding in a reciprocating motion in a direction perpendicular to the valve stem and having an upper surface and a lower surface; a stem working face on the lower surface of the slide pin; a stem through hole adjacent to the stem working face; a chamfered portion being formed along the upper surface of the slide pin and extending along a portion of the stem through hole.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4770137 (1988-09-01), Okabe et al.
patent: 5488934 (1996-02-01), Shirai et al.
patent: 5758612 (1998-06-01), Tsuzuku et al.
patent: 6302070 (2001-10-01), Tsukui et al.
patent: 6386163 (2002-05-01), Tsukui et al.
patent: 199 41 367 (2000-03-01), None
patent: 100 00 239 (2000-07-01), None
patent: 1 020 619 (2000-07-01), None
patent: 10184327 (1998-07-01), None
Iino Kazuaki
Nagahashi Yoshiki
Tsukui Takaaki
Birch & Stewart Kolasch & Birch, LLP
Chang Ching
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
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