U.S. patent number RE30,188 [Application Number 05/889,145] was granted by the patent office on 1980-01-15 for valve train for internal combustion engine.
Invention is credited to Wilfred F. Predhome, Jr..
United States Patent |
RE30,188 |
Predhome, Jr. |
January 15, 1980 |
Valve train for internal combustion engine
Abstract
A system for varying valve timing; i.e. the rotational angle of
the crankshaft during which an intake or an exhaust valve of a
cylinder of a reciprocating internal combustion engine is open
which results in varying valve overlap, and for varying valve lift
of such intake and exhaust valves. A desmodromic cam and cam
follower convert rotation of a cam shaft to reciprocating rotation,
or oscillation, of the cam follower. The reciprocating rotation of
the cam follower is converted by the interaction of a secondary
cylindrical cam, a cylindrical control ring, and a reciprocating
member to linear motion of the reciprocating member which
reciprocating member is operatively connected to a poppet valve.
Timing and lift of the reciprocating member and valve are variable
over predetermined limits as a function of engine rpm and load by
rotation of the cylindrical control ring. Each valve train
positively closes as well as opens its associated valve.
Inventors: |
Predhome, Jr.; Wilfred F.
(Aurora, CO) |
Family
ID: |
27104784 |
Appl.
No.: |
05/889,145 |
Filed: |
March 22, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
691429 |
Jun 1, 1976 |
04061115 |
Dec 6, 1977 |
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Current U.S.
Class: |
123/90.16;
123/90.21; 123/90.24; 123/90.26; 74/57 |
Current CPC
Class: |
F01L
1/047 (20130101); F01L 1/0532 (20130101); F01L
1/181 (20130101); F01L 1/30 (20130101); F01L
13/0015 (20130101); F01L 1/04 (20130101); F01L
1/14 (20130101); F01L 1/146 (20130101); F01L
2001/0535 (20130101); F01L 2001/054 (20130101); Y10T
74/18312 (20150115); F01L 1/042 (20130101) |
Current International
Class: |
F01L
1/00 (20060101); F01L 13/00 (20060101); F01L
1/30 (20060101); F01L 001/34 () |
Field of
Search: |
;123/90.2,90.26,90.25,90.17,90.21,90.24,90.15,90.16,90.6
;74/57,568 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Yates; Jeffrey L.
Attorney, Agent or Firm: Sheridan, Ross, Fields &
McIntosh
Claims
What is claimed is:
1. A valve train for a poppet valve of a reciprocating internal
combustion engine comprising:
an internal combustion engine;
a cam shaft having an axis of rotation and being mounted on said
engine for rotation about its axis at angular velocities which are
a function of engine rpm;
means forming a cam surface on said shaft;
a cam follower having an axis of rotation;
means for mounting said cam follower on said engine in engagement
with the cam surface of said cam shaft to convert rotation of said
cam shaft into reciprocating rotation of said cam follower about
its axis of rotation;
a reciprocating member having projecting means;
cam means operatively connected to said cam follower;
movable control means concentrically mounted with respect to said
cam means;
said cam means, control means and projecting means interacting to
convert reciprocal rotation of said cam follower to reciprocating
linear motion of the reciprocating member substantially along the
axis of rotation of said cam follower;
said cam means and control means varying the amplification and
timing of said reciprocating member with respect to the angular
position of the cam shaft as a function of the position of said
control means with respect to said engine;
servo means operatively connected to the control means to vary the
control means position to vary the amplitude and timing of the
reciprocating member as a function of engine rpm and load;
a poppet valve; and
means for operatively connecting said valve to said reciprocating
member.
2. The valve train of claim 1 in which the means for operatively
connecting said valve to said reciprocating member include a rocker
arm pivotally mounted on said engine.
3. In a reciprocating internal combustion engine having a cam shaft
mounted on the engine for rotation around the cam shaft's
longitudinal axis as a function of engine rpm, the improvements
comprising:
means forming a circular cam surface on said cam shaft;
a cam follower having an axis of rotation;
means for mounting the cam follower on the engine to engage the
circular cam surface of the cam shaft to convert rotation of the
cam shaft into oscillations of said first cam follower through
substantially an angle alpha about the cam follower's axis of
rotation for each complete rotation of the cam shaft;
first and second hollow cylindrical members, each member having a
longitudinal axis, the members being dimensioned so that one
slidably fits within the others so when they are so positioned
their longitudinal axes substantially coincide;
means forming a pair of cam slots in the first cylindrical member,
each slot extending substantially over an angle beta with respect
to the first member's axis of rotation, a portion of each slot at
corresponding portions extending over an angle gamma with respect
to the first member's axis of rotation being substantially
horizontal;
means adapted to operationally connect said first member to the cam
follower so that the longitudinal axis of the first member
substantially coincides with the axis of rotation of the cam
follower;
means forming a pair of guide slots in the second member, the slots
being substantially parallel to the longitudinal axis of the second
member;
resilient means for maintaining said second member concentric with
the first member, for slidably engaging the first member and for
positioning the first member in operational connection with the cam
follower so that the first member oscillates with the cam
follower;
a reciprocating member mounted within said first and second
members, the reciprocating member having means for engaging the cam
and guide slots of said first and second members; and
means for positioning the second member relative to the engine as a
function of engine rpm and load to vary the timing and magnitude of
movement of the reciprocating member with respect to the same
shaft;
a poppet valve; and
means for operatively connecting the valve to the reciprocating
member.
4. In the engine of claim 3 in which the means for operatively
connecting the valve to the reciprocating member include a rocker
arm pivotally mounted on the engine.
5. In the engine of claim 3 in which the angle alpha is 90.degree.,
the angle beta is 120.degree., and the angle gamma is
30.degree..
6. A valve operating mechanism for a reciprocating internal
combustion engine, which mechanism converts rotational motion of a
cam shaft which rotates around its longitudinal axis as a function
of engine rpm into reciprocating linear motion of a reciprocating
member operatively connected to a valve, and varies the timing and
magnitude of movement of the valve as a function of engine rpm and
load, comprising:
means forming a circular cam surface on said cam shaft;
a cam follower having an axis of rotation;
a pin having a longitudinal axis, the pin being mounted on the cam
follower so that its longitudinal axis is substantially parallel to
the axis of rotation of the cam follower but offset from it;
a bushing mounted on the pin;
means for mounting the cam follower with respect to the cam shaft
so that the bushing engages the circular cam surface to convert
rotation of the cam shaft into reciprocal rotation of the cam
follower about its axis of rotation;
a first hollow cylindrical member having a longitudinal axis;
means forming a pair of cam slots in the first member;
means adapted to operationally connect the first member to the cam
follower to cause the first member to oscillate about its
longitudinal axis with the cam follower;
a second hollow cylindrical member having a longitudinal axis;
means forming a pair of guide slots in the second member, said
slots being substantially parallel to the second member's
longitudinal axis;
resilient means for mounting the second member so that it is
substantially concentric with the first cylindrical member and so
that the first member is operatively connected to the cam
follower;
a reciprocating member;
projecting means formed on the reciprocating member;
the reciprocating member being positioned within the first and
second members with its projecting means engaging the cam slots and
guide slots of the first and second members;
means for rotating the second member about its axis relative to the
means for mounting the cam follower as a function of the speed and
load mechanism of the engine;
a poppet valve; and
means for operatively connecting the valve to the reciprocating
member.
7. The valve operating mechanism of claim 6 in which the resilient
means is a coil spring.
8. The valve operating mechanism of claim 6 in which the means for
operatively connecting the valve to the reciprocating member
include a rocker arm pivotally mounted on the engine.
9. In a reciprocating internal combustion engine having a
crankshaft, a valve train comprising:
a cam shaft having an axis of rotation;
bearing means on the engine mounting the cam shaft for rotation
around its axis;
means connecting the cam shaft to the crankshaft of the engine so
that the angular velocity of the cam shaft is one-half that of the
crankshaft;
a cam surface of circular cross section formed on the cam
shaft;
a cam follower having a cylindrical portion, the cylindrical
portion having an axis of rotation;
a pin having a longitudinal axis, the pin being mounted on one end
of the cylindrical portion so that the pin's longitudinal axis is
substantially parallel to the cylindrical portion's axis of
rotation but displaced a fixed distance;
a cam follower bushing mounted on the pin;
a cylindrical disk attached to the other end of the cylindrical
portion of the cylindrical portion of the cam follower;
means forming a plurality of notches around the periphery of the
cylindrical disk of the cam follower;
a journal bearing in the engine, the cylindrical portion of the cam
follower mounted in the journal bearing for rotation about its axis
of rotation and with the cam follower bushing contacting the cam
surface of the cam shaft, the path of the cam surface being such
that rotation of the cam shaft causes the cam follower to oscillate
through a predetermined angle about its axis of rotation;
a secondary cam having cylindrical walls and longitudinal axis;
means forming a pair of cam slots in the walls of the secondary
cam;
a plurality of lugs formed on the secondary cam;
a control ring having cylindrical walls and a longitudinal
axis;
a cylindrical disk attached near the bottom of the control
ring;
means forming a pair of guide slots in the cylindrical walls of the
control ring, said slots being substantially parallel to its
longitudinal axis;
the diameter of the outer cylindrical wall of the control ring
being slightly less than the diameter of the inner cylindrical wall
of the secondary cam;
the secondary cam being mounted around the exterior of the
cylindrical walls of the control ring, the lugs on the secondary
cam adapted to fit into the means forming notches of the cam
follower;
a coil spring positioned between the engine and the bottom surface
of the cylindrical disk of the control ring or maintaining the lugs
of the secondary cam in the means forming notches in the
cylindrical disk of the cam follower so that they will oscillate
together;
a valve keeper positioned for linear movement within the inner
cylindrical wall of the control ring;
means forming a transverse bore through the keeper;
means forming a vertical bore through the keeper;
a cross pin located in the transverse bore and engaging the means
forming cam slots in the secondary cam and the means forming guide
slots in the control ring;
a poppet valve;
key means for fixedly securing the valve to the valve keeper;
a drive pin mounted on the cylindrical disk of the control ring;
and
a servo mechanism connected to the drive pin, the servo mechanism
also being connected to the engine and responsive to engine rpm and
load for varying the angular position of the control ring with
respect to the engine as a function of engine rpm and load, whereby
the timing and lift of the valve varies as a function of engine rpm
and .[.speed.]. .Iadd.load.Iaddend.. .Iadd. 10. A valve train for a
poppet valve of a reciprocating piston engine comprising:
a piston engine;
a cam shaft having an axis of rotation and being mounted on said
engine for rotation about its axis at angular velocities which are
a function of engine rpm;
means forming a cam surface on said shaft;
a cam follower having an axis of rotation;
means for mounting said cam follower on said engine in engagement
with the cam surface of said cam shaft to convert rotation of said
cam shaft into reciprocating rotation of said cam follower about
its axis of rotation;
a reciprocating member having projecting means;
cam means operatively connected to said cam follower;
movable control means concentrically mounted with respect to said
cam means;
said cam means, control means and projecting means interacting to
convert reciprocal rotation of said cam follower to reciprocating
linear motion of the reciprocating member substantially along the
axis of rotation of said cam follower;
said cam means and control means varying the timing of said
reciprocating member with respect to the angular position of the
cam shaft as a function of the position of said control means with
respect to said engine;
means operatively connected to the control means to vary the
control means position to vary the timing of the reciprocating
member;
a poppet valve; and
means for operatively connecting said valve to said reciprocating
member.
.Iaddend. .Iadd. 11. A valve train for a poppet valve of a
reciprocating piston engine comprising:
an internal combustion engine;
a cam shaft having an axis of rotation and being mounted on said
engine for rotation about its axis at angular velocities which are
a function of engine rpm;
means forming a cam surface on said shaft;
a cam follower having an axis of rotation;
means for mounting said cam follower on said engine in engagement
with the cam surface of said cam shaft to convert rotation of said
cam shaft into reciprocating rotation of said cam follower about
its axis of rotation;
a reciprocating member having projecting means;
cam means operatively connected to said cam follower;
movable control means concentrically mounted with respect to said
cam means;
said cam means, control means and projecting means interacting to
convert reciprocal rotation of said cam follower to reciprocating
linear motion of the reciprocating member substantially along the
axis of rotation of said cam follower;
said cam means and control means varying the timing of said
reciprocating member with respect to the angular position of the
cam shaft as a function of the position of said control means with
respect to said engine;
servo means operatively connected to the control means to vary the
control means position to vary the timing of the reciprocating
member as a function of engine rpm;
a poppet valve; and
means for operatively connecting said valve to said reciprocating
member. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is in the field of valve train or valve operating
mechanisms for internal combustion engines and more particularly
variable valve timing and valve lift mechanisms.
2. Description of the Prior Art
The desirability of varying valve timing and valve overlap; i.e.,
the angle of rotation of the crankshaft of a reciprocating internal
combustion engine during which both exhaust and intake valves of a
cylinder are open, as a function of speed and load to optimize the
efficiency of a reciprocating internal combustion engine under any
given operating condition has been recognized. The prior art
solutions teach the use of a valve train including a single lobed
cam on a rotating cam shaft with a tappet engaging the lobed cam to
convert circular motion to reciprocating linear motion of a tappet
which is operatively connected directly to a valve as in an
overhead cam shaft type engine or through a rocker arm. A heavy
duty spring biases the valves closed and the tappet against the cam
surface. Changes in timing are accomplished by changing the length
of an element in the valve train, the location of the cam shaft
lobe to the tappet, or by varying the axis of rotation of rocker
arms.
SUMMARY OF THE INVENTION
The present invention provides a valve train that does not use a
lobed cam surface on a rotating cam shaft but rather a cam surface
in the form of a groove of constant radius in the shaft which
causes a cam follower engaging said groove to convert rotation of
the cam shaft into reciprocal rotation, or oscillation, of the cam
follower. The reciprocal rotation of the cam follower is converted
by a secondary cam reciprocally rotated by the cam follower and a
control ring into reciprocal linear motion of a reciprocating
member which is operationally connected directly to a poppet valve
or through a rocker arm. Movement of the control ring changes the
valve timing as measured by crankshaft position and valve lift so
that optimum valve timing and valve lift for substantially all
operating conditions of a reciprocating internal combustion engine
can be achieved.
It is, therefore, an object of this invention to provide a valve
train which provides optimum valve timing and valve lift over all
engine speeds and loads for which a reciprocating internal
combustion engine is designed which will reduce engine emissions
below that experienced with conventional valve trains.
It is another object of this invention to provide a valve train
that requires significantly less power to operate a valve.
It is still another object of the invention to provide a valve
train which is relatively quiet.
It is a further object of this invention to provide a valve train
in which the mass of the valve train in reciprocating linear motion
is minimized.
It is another object of the invention to provide a valve train
which can be manufactured economically.
BRIEF DESCRIPTION OF THE DRAWING
Other objects, features and advantages of the invention will be
readily apparent from the following description of certain
preferred embodiments thereof, taken in conjunction with the
accompanying drawings, although variations and modifications may be
effected without departing from the spirit and scope of the novel
concepts of the disclosure, and in which:
FIG. 1 is a fragmentary view in section of a conventional internal
combustion engine of the overhead cam type showing the valve trains
or valve operating mechanisms for one cylinder of an engine;
FIG. 2 is a fragmentary side view of a portion of the engine
illustrated in FIG. 1;
FIG. 3 is a fragmentary plan view taken on line 3--3 of FIG. 1;
FIG. 4 is a plan view of the cam shaft illustrated in FIG. 1;
FIG. 5 is an enlarged fragmentary view disclosing details of the
valve train of my invention;
FIG. 6 is a section taken on line 6--6 of FIG. 5;
FIG. 7 is an exploded view of the components of one embodiment of a
valve train assembly;
FIG. 8 is a graph of valve lift vs. crankshaft angle produced by an
embodiment of a valve train of this invention in a reciprocating
internal combustion engine; and
FIG. 9 is a fragmentary view partially in section of a modification
of the valve train of my invention in which a valve is connected to
the valve train through a rocker arm.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, reciprocating internal combustion engine 10
has a cylinder block 12, a cylinder head 14 which defines a
combustion chamber 16. Piston 18 is mounted for reciprocating
movement in cylinder 20 formed in block 12. A connecting rod 22 is
pivotally secured to piston 18 by means of a conventional wrist pin
24. The lower end of connecting rod 22 is connected to a
conventional crankshaft, which is not illustrated. Cam shaft 26 is
mounted on engine 10 for rotation about its axis of rotation 28 by
conventional journal bearings, which are not illustrated, and is
driven by the crankshaft, for example, by means of a timing belt
and pulley which are also not illustrated since they are
conventional and well known to those skilled in this art. Cam shaft
28 normally completes one revolution for every two revolutions of
the crankshaft of engine 10.
Cam shaft 26 is provided with a plurality of grooves 30, or cam
surfaces, one for each valve of engine 10 driven by cam shaft 26,
for example. It should be noted that cam surface 30 is a circular
cam of constant radius with respect to the axis of rotation 28 of
cam shaft 26 compared with lobed cams conventionally used in the
valve trains of reciprocating internal combustion engines in which
the radius to various points on the surface of a lobe varies as a
function of the angle.
Cam follower 32 has a central cylindrical portion 34 and a disk
portion 36 rigidly attached to cylindrical portion 34. A plurality
of notches 38 are formed in the perimeter of disk 36. Cam follower
32 has an axis of rotation 40. Pin 42 is mounted on the upper end
of cylinder 34 remote from disk 36. As can be seen in FIG. 7, the
longitudinal axis 44 of cylindrical pin 42 is substantially
parallel to but offset from axis 40 of cam follower 32 by a fixed
amount. Follower bushing 46 fits on pin 42 and its outer surfaces
are designed to engage cam surfaces 30 formed on cam shaft 26.
As can be seen in FIGS. 1, 2 and 5, cam follower 32 is journaled in
a bore 48 in support member 49 which is illustrated in FIG. 2 as
being bolted to cylinder head 14. Cam follower 32 while mounted in
bore 48 is free to rotate reciprocally, or oscillate, about its
axis of rotation 40 and is mounted so that follower bushing 46
engages groove 30 in cam shaft 26.
Secondary cam 50 is comprised of hollow cylindrical member 52 in
the cylindrical walls of which are formed a pair of cam slots 54. A
plurality of lugs 56 are located on the upper end of member 52 and
are shaped and located to fit into notches 38 of cam follower 32.
The shape and dimension of secondary cam slots 54 are chosen to
provide a range of valve timing and valve lift for optimum engine
operation over the entire range of operating conditions of the
engine in which the valve trains are installed.
Control ring 58 consists of a hollow cylindrical member 60 with a
cylindrical disk 62 located near the bottom of member 60. The
dimension of cylinder member 60 is such that it has a sliding low
friction, fit within cylindrical member 52. The axis 64 of
cylindrical member 52 and the axis 66 of cylindrical member 60
substantially coincide when the cylinder 60 is located within
cylinder member 52. A pair of slots 68 are formed in the
cylindrical walls of member 60 substantially parallel to axis 66. A
drive pin 70 is located near the outer perimeter of disk 62. Pin 70
is operatively connected by shaft 69 to a conventional engine rpm
or vacuum control, or servo, 72 so that the position of control
ring 58 with respect to cylinder head 14, or any similar element of
engine 10 that is fixed, can be varied as a function of engine
speed, or rpm, and load, intake manifold pressure, as will be
described below.
Reciprocating member, or valve keeper, 74 has a portion 76 which
has a sliding fit within control ring 58. Transverse bore 78 is
formed in member 74 into which cross pin 80 can be inserted.
Projecting means, or cross pin 80, when the valve train is
assembled, as is illustrated in FIG. 5, for example, passes through
slots 68 in control ring 58 and engage cam slots 54 of secondary
cam 50.
Poppet valve 82, which is provided with a groove 84 located toward
the upper end of its stem 86 is mechanically, or fixedly, secured
to reciprocating member 74 by a pair of keys 88 which are held in
place in vertical bore 89 by pin 80 when pin 80 is mounted in bores
78 in reciprocating member 74.
Cam follower 32, secondary cam 50 and control ring 58 are held
together by the force of coil spring 90 which is illustrated in
FIG. 5, for example, as being compressed between the underside of
disk 62 of control ring 58 and cylinder head 14.
In FIG. 4 the shape of the grooves 30 in cam shaft 26 are best
illustrated. Each groove 30 has a substantially straight section 92
and a curved portion 94 in which the groove 30 deviates from a
circular path in a plane normal to the axis of rotation 28 of cam
shaft 26. As shaft 26 rotates in the direction of arrow 96 in FIG.
4 the follower bushing 46 mounted on cam follower 32 engages the
surfaces of groove 30 as seen in FIG. 1. Rotation of shaft 26 one
complete revolution will cause cam followers 32 to oscillate
through an angle alpha as illustrated in FIG. 3. The excursion of
cam surfaces 30 from a true circle, the distance between the axis
of rotation 40 of follower 32 and axis 44 of pin 42 on which
bushing 46 is mounted and the position of the center of shaft 26
with respect to axis 40 of cam follower 32 as seen in FIG. 2
determine the magnitude of alpha. In a preferred embodiment alpha
is 90.degree.. Since cam follower 32 is forced to oscillate about
its axis by cam surfaces 30, this type of cam and cam follower is
called a desmodromic cam.
Reciprocal rotation of follower 32 about its axis of rotation 40
causes a similar rotation, or oscillation, of secondary cam 50
about its axis 64. The engagement of lugs 56 of cam 50 into notches
38 in cam follower 32 provides the mechanical coupling of the two
devices which when assembled results in axis 64 of cylinder 52
substantially coinciding with axis 40. The hollow cylindrical
member 60 of control ring 58 fits inside hollow cylindrical member
52 of secondary cam 50 with axis 66 of cylindrical member 60
substantially coinciding with axis 64 of secondary cam 50 and the
axis of rotation 40 of cam follower 32. The bottom surface of
secondary cam 50 engages the top surface of disk 62 of control ring
58. Reciprocating member 74 is located within cylindrical member 60
with projecting means 80 passing through slots 68 of control ring
50 and engaging cam slots 54. Oscillation of secondary cam 50
causes the reciprocating member 74 to move in a reciprocating, or
oscillating, linear path along axis 64, for example, since rotation
of reciprocating member 74 is prevented by vertical guide slots 68
in control ring 58 which is held in place by shaft 69 which is
operatively connected to servo 72.
Coil spring 90 biases control ring 58 toward cam follower 32. When
engine 10 is cold, a gap of a few thousandths of an inch exist
between the top surfaces of control ring 58, secondary cam 50, and
the bottom surface of disk 36 of cam follower 32 to provide for
expansion of valve 82 mounted in reciprocating member 74 as well as
the other components of a valve train such as are illustrated in
FIG. 7, for example.
The shape of cam slots 54 in secondary cam 50 is chosen so that the
timing of the valve 82 of a given cylinder of a reciprocating
internal combustion engine will fall within the curves illustrated
in FIG. 8. In a preferred embodiment the slots 54 extend through or
determine an angle beta of 120.degree. with the portion of the slot
extending over an angle gamma, in a preferred case gamma equals
30.degree., being substantially horizontal as seen in FIG. 7, for
example, and with a smaller flat, or horizontal, portion at the
other end. The curved portion is chosen to provide optimum valve
timing and valve lift as is well known to those skilled in the
art.
Servo mechanism 72 and the linkage between it and control ring 58
is designed, in a preferred embodiment, to rotate control ring 58
through an angle delta, in a preferred embodiment delta is
30.degree., as a function of the rpm of engine 10 .[.and its.].
.Iadd.which may vary with .Iaddend.load. Valve timing and valve
lift of the valves of a given cylinder vary for exhaust valves from
those for minimum engine speed, curve 98, to those for maximum
engine speed, curve 100, and for intake valves from those for
minimum speed, curve 102, to those for maximum speed, curve 104.
The extent of valve overlap at maximum speed in the embodiment
illustrated is approximately 168.degree.. .Iadd.Thus, timing will
change depending on the initial position of projecting means 80
along the portion of the slot 54 extending over the angle gamma.
The amplitude or lift will vary if the final position of the
projecting means varies along the diagonal portion of slot 54. If
this final position is along the lower horizontal position of slot
54 with each initial position of projecting means 80, there will be
no amplitude variation..Iaddend.
In FIG. 9 there is illustrated a modification of my invention in
which poppet valve 82 is operatively connected to reciprocating
member 74 by means of rocker arm 106 which is pivotally mounted on
cylinder head 14. Valve 82 is held between the jaws 108, 110 of
rocker arm 106 with jaw 110 which is pivotally mounted on rocker
arm 106 forced toward jaw 108 through the action of torsion spring
112. The significant changes between the embodiment illustrated in
FIG. 1 and that of FIG. 9 is that the cylindrical portion 34 of cam
follower 32 is extended and what would be the bottom surface of
control ring in FIG. 5 is provided with a cover 114 against which
the closing force of valve 82 and rocker arm 106 react.
From the foregoing it is clear that the desmodromic cam drive of my
invention positively closes as well as opens poppet valves. Thus,
it is not necessary for the desmodromic valve train of my invention
to overcome the resistance of coil springs conventionally used to
bias valves closed and to keep tappets in contact with a lobed cam.
This results in a considerable reduction in the amount of energy
consumed by the engines and thus increases engine efficiency.
The valve train of my invention also significantly reduces the mass
of material undergoing linear oscillation since rotational motion
of the cam follower is translated to linear motion in close
proximity to the valve to be driven which reduces the forces acting
on the components of a drive train.
The secondary cam and the control ring as a result of their design
can be fabricated by stamping which minimizes their cost of
production. Further the valve operating mechanism varies valve
timing and valve lift of a valve in a reciprocating internal
combustion engine as a function of engine rpm or speed and load
which greatly enhances engine efficiency.
It should be obvious that various modifications can be made to the
embodiments of my invention as disclosed herein without departing
from the scope of the present invention.
* * * * *