U.S. patent application number 11/305768 was filed with the patent office on 2006-06-22 for variable cam system.
Invention is credited to Dong Chul Lee.
Application Number | 20060130791 11/305768 |
Document ID | / |
Family ID | 36594144 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060130791 |
Kind Code |
A1 |
Lee; Dong Chul |
June 22, 2006 |
Variable cam system
Abstract
A variable cam system which in one embodiment includes cams
having a contacting surface formed by an involute curve, a cam
shaft, and an actuator for moving the shaft in a longitudinal
direction. The operating displacement of the cams may be varied by
longitudinally moving the cam shaft.
Inventors: |
Lee; Dong Chul;
(Anyang-city, KR) |
Correspondence
Address: |
MORGAN, LEWIS & BOCKIUS LLP (SF)
2 PALO ALTO SQUARE
3000 El Camino Real, Suite 700
PALO ALTO
CA
94306
US
|
Family ID: |
36594144 |
Appl. No.: |
11/305768 |
Filed: |
December 15, 2005 |
Current U.S.
Class: |
123/90.18 ;
123/90.15 |
Current CPC
Class: |
F01L 1/34416 20130101;
F01L 1/143 20130101; F01L 13/0042 20130101; F01L 1/022 20130101;
F01L 1/08 20130101; F01L 1/0532 20130101 |
Class at
Publication: |
123/090.18 ;
123/090.15 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2004 |
KR |
10-2004-0107588 |
Claims
1. A variable cam system variably opening/closing intake and
exhaust valves comprising: a cam shaft coupled to a timing gear
movable in a longitudinal direction thereof; an actuator moving the
cam shaft in the longitudinal direction of the cam shaft; and a
plurality of cams secured to the cam shaft to open/close the valves
by rotating, a contacting surface of each cam formed as a curved
surface along the longitudinal direction of the cam shaft such that
an operating displacement of the cam is varied corresponding to a
longitudinal direction movement of the cam shaft.
2. The system of claim 1, wherein the contacting surface of each
cam is formed as an involute curve.
3. The system of claim 1, further comprising uppermost points on
the contacting surface of each cam formed at both ends of the cam
such that an operating displacement of the cam increases as it goes
from a center portion to either end along the longitudinal
direction of the cam shaft; and the uppermost points deviate from
each other by a predetermined angle with respect to a rotating
direction of the cam shaft.
4. The system of claim 1, wherein a bearing is disposed at an end
of a tappet of each valve contacting the contacting surface of each
cam.
5. The system of claim 4, wherein the bearing is a ball
bearing.
6. A variable cam system for opening and closing intake and exhaust
valves comprising: a cam shaft defining a longitudinal direction;
an actuator coupled to the shaft and operable to move the shaft
back and forth in the longitudinal direction; a plurality of
V-shaped cams attached to the shaft in a spaced-apart relationship
to each other, each cam having a center portion and an end on
either side of the center portion; the ends being higher than the
center portion; at least one valve operably coupled to each cam and
displaceable by rotational movement of the cam; wherein a relative
longitudinal position of each cam is adjustable in relation to each
at least one respective valve by the actuator.
7. The system of claim 6, wherein each valve is connected to a
tappet having a bearing at one end that contacts one of the cams,
each tappet displaceable up and down by rotational movement of each
cam.
8. The system of claim 6, wherein each cam is shaped as an involute
curve.
9. The system of claim 7, wherein a maximum displacement of each
tappet occurs when an end of the cam contacts the bearing.
10. They system of claim 6, further comprising the actuator
including a rack and a pin.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2004-0107588 filed in the Korean
Intellectual Property Office on Dec. 17, 2004, the entire contents
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] (a) Field of the Invention
[0003] The present invention relates to a variable cam system of a
vehicle. More particularly, the present invention relates to a
variable cam system for enhancing fuel efficiency and output of a
vehicle.
[0004] (b) Description of the Related Art
[0005] Generally, one or two intake valves and an exhaust valve are
mounted to one cylinder of a 4-stroke-cycle engine. An overhead
valve type and an overhead cam shaft type of valve opening/closing
apparatus is generally utilized. The overhead valve type is where a
push rod is pushed by a valve lifter contacted to a surface of a
cam of a cam shaft, the push rod operates a rocker arm, and the
rocker arm selectively opens/closes a valve. The overhead cam shaft
type is where a valve is selectively opened/closed by a cam, which
is connected to a cam shaft directly, operating a rocker arm.
[0006] However, the foregoing cam system cannot be varied to an
optimized position to correspond to a variable running state.
Therefore, fuel efficiency and output of a vehicle may
deteriorate.
SUMMARY OF THE INVENTION
[0007] The present invention provides a variable cam system having
advantages of enhancing fuel efficiency and output of a vehicle. An
exemplary variable cam system variably opening/closing intake and
exhaust valves according to an embodiment of the present invention
may include a cam shaft coupled to a timing gear movable in a
longitudinal direction thereof, an actuator moving the cam shaft in
the longitudinal direction of the cam shaft, and cams secured to
the cam shaft to open/close the valves by rotating, a contacting
surface of each cam being formed as a curved surface along the
longitudinal direction of the cam shaft such that an operating
displacement of each cam is varied corresponding to a longitudinal
direction movement of the cam shaft. The contacting surface of each
cam may be formed as an involute curve. In one embodiment,
uppermost points of the contacting surface of each cam may be
formed at both ends of the contacting surface of the cam such that
an operating displacement of the cam increases as it goes from a
center portion, which may be a lower-most point, to either end
along the longitudinal direction of the cam shaft, and the
uppermost points may deviate from each other by a predetermined
angle with respect to a rotating direction of the cam shaft. A
bearing may be disposed at an end of a tappet of each valve
contacting the contacting surface of each cam. The bearing may be a
ball bearing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows a variable cam system according to an exemplary
embodiment of the present invention.
[0009] FIG. 2A and 2B shows a cam of a variable cam system
according to an exemplary embodiment of the present invention.
[0010] FIG. 3 illustrates an amount of displacement per unit of
time of a valve operated by a variable cam system according to an
exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0011] An exemplary embodiment of the present invention will
hereinafter be described in detail with reference to the
accompanying drawings.
[0012] As shown in FIG. 1, according to an exemplary embodiment of
the present invention, a variable cam system variably
opening/closing intake and exhaust valves 15 includes a cam shaft
10 defining a longitudinal direction, an actuator 13, and cams 11.
The cam shaft 10 is coupled to a timing gear 14 movable in a
longitudinal direction of the cam shaft 10 and the actuator 13
moves the cam shaft 10 in the longitudinal direction of the cam
shaft 10. The cams 11 are secured to the cam shaft 10 to open/close
the valves 15 by rotating, and a contacting surface 16 of each cam
11 is formed as a curved surface in one embodiment along a
longitudinal direction of the cam shaft 10 such that an operating
displacement of the cam 11 is varied corresponding to a
longitudinal direction movement of the cam shaft 10.
[0013] As shown in FIG. 1, the timing gear 14 defines a hole 17
that the cam shaft 10 is inserted into and gear teeth may be formed
to the hole 17. An end of the cam shaft 10 is inserted into the
hole 17 of the timing gear 14 such that the cam shaft 10 can move
in the longitudinal direction thereof. Gear teeth corresponding to
the gear teeth of the hole 17 of the timing gear 14 may be formed
to the end of the cam shaft 10 and a torque is transmitted from the
timing gear 14 to the cam shaft 10 by the gear teeth of the hole 17
and the cam shaft 10.
[0014] The actuator 13 moves the cam shaft 10 in the longitudinal
direction of the cam shaft 10, and in an exemplary embodiment of
the present invention, the actuator 13 may be realized as a motor.
Actuator 13 may be controlled by a controller based on various
appropriate input parameters as may be selected and programmed by a
person of ordinary skill in the art.
[0015] The timing gear 14 may be connected to a crank shaft (not
shown) by a timing chain 18. Therefore, the timing gear 14 receives
power from the crank shaft by the timing chain 18.
[0016] Each cam 11 rotates by the cam shaft 10 and a tappet 23 is
mounted between each cam 11 and the intake/exhaust valves 15. The
cam shaft 10 moves in a predetermined range by the actuator 13 such
that the tappets 23 can transmit the driving torque of the cams 11
to the intake/exhaust valves 15. The predetermined range in which
the cam shaft 10 moves can be varied by a person of ordinary skill
in the art.
[0017] According to an exemplary embodiment of the present
invention, an operating displacement of the cams 11 is varied
corresponding to a movement in the longitudinal direction of the
cam shaft 10. The operating displacement means a displacement in
which each tappet 23 moves up and down by a rotation of each cam
11. That is, as shown in FIG. 1, 2A, and 2B, a contacting surface
16 of each cam 11, which the tappets 23 contact to, may have a
different operating displacement depending on a position of the
contacting surface 16 of each cam 11.
[0018] In one embodiment, the contacting surface 16 of the cams 11
may be formed as an involute curve. An involute curve means a
curved line which an end of a thread draws when a thread wound to a
cylinder is drawn out therefrom. Therefore, the tappets 23 operate
more easily and smoothly by the movement of the cams 11.
[0019] As shown in FIGS. 1, 2A and 2B, according to an exemplary
embodiment of the present invention, each cam 11 may define two
uppermost points 20 which may be at both ends thereof in one
embodiment. Tappets 23 operate at a longest operating displacement
when the tappets 23 contact to the uppermost points 20. Because,
uppermost points 20 of the contacting surface 16 of each cam 11 are
formed at both ends of the contacting surface 16 of each cam 11,
the operating displacement of each cam 11 increases as it goes from
a center portion, which may correspond to a lowermost point 22 in
one embodiment, to either end along the longitudinal direction of
the cam shaft 10. As shown in FIGS. 2A and 2B, the uppermost points
20 may deviate from each other by a predetermined angle with
respect to a rotating direction of the cam shaft 10 (see, e.g.,
FIG. 2B).
[0020] The predetermined angle may be changed and varied by a
person of ordinary skill in the art. In one possible embodiment,
lowermost point 22 may be formed at a center portion of cam 11
equally spaced between the uppermost points 20.
[0021] According to an exemplary embodiment of the present
invention, a bearing 12 may be mounted to an end of the tappet 23
of each valve 15. Bearing 12 may be realized as a ball bearing in
one possible embodiment. Therefore, each tappet 23 can be more
easily contacted to the cams 11 when the cams 11 move rightward and
leftward or rotate, and advantageously occurrence of an impact
noise by a contact can be reduced and a loss of power by the
contact can be minimized.
[0022] Referring to FIG. 3, according to an exemplary embodiment of
the present invention, a variable cam system is described
hereinafter. Because the cam shaft 10 can move in a longitudinal
direction thereof, in a rightward and leftward direction in the
drawings, the cams 11, having variable displacement, can also move
in a rightward and leftward direction together with the cam shaft
10. Therefore, because displacement of the tappets 23 is variably
changed, a valve lift and valve timing, that is, displacement of
the valves 15 and opening/closing times of the valves 15, may be
realized to correspond to variable driving conditions. According to
an exemplary embodiment of the present invention, the
opening/closing time of each valve and the displacement of each
valve may be variably realized corresponding to a shape of the
contacting surface 16 of each cam 11. Furthermore, because the
contacting surface of each cam 11 is formed as a smooth curved
surface, preferably, as an involute curve in one embodiment, an
impact noise and an impact vibration can be reduced while the
operating displacement varies. Therefore, because variable states
of the intake/exhaust valves corresponding to variable driving
conditions can be realized, fuel efficiency and output of a vehicle
may advantageously be enhanced.
[0023] It will be appreciated that the shape of cam 11 and the
height and position of the lowermost point 22 and uppermost points
20 may be varied from that shown and described. Therefore, other
suitable cam configurations are possible and contemplated according
to principles of the present invention.
[0024] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
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