U.S. patent application number 10/075066 was filed with the patent office on 2002-06-20 for valve mechanism, in particular for internal combustion engines.
Invention is credited to Battlogg, Stefan.
Application Number | 20020073948 10/075066 |
Document ID | / |
Family ID | 27146996 |
Filed Date | 2002-06-20 |
United States Patent
Application |
20020073948 |
Kind Code |
A1 |
Battlogg, Stefan |
June 20, 2002 |
Valve mechanism, in particular for internal combustion engines
Abstract
The valve drive mechanism is particularly suitable for internal
combustion engines of motor vehicles. The mechanism has at least
one driven cam element and a valve control member which is moved
(translationally or rotationally) by the cam element. The cam
element is rotatingly mounted in a flexible surround element which
is connected to the valve control member in a plane orthogonal to
the axis of rotation of the cam element. The surround element can
be reversably extended, such as elastically extended, to enable a
variation in the resulting valve lift.
Inventors: |
Battlogg, Stefan; (St.
Anton/Montafon, AT) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
POST OFFICE BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Family ID: |
27146996 |
Appl. No.: |
10/075066 |
Filed: |
February 12, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10075066 |
Feb 12, 2002 |
|
|
|
PCT/AT00/00215 |
Feb 8, 2000 |
|
|
|
Current U.S.
Class: |
123/90.16 ;
123/90.44; 123/90.6 |
Current CPC
Class: |
F01L 1/08 20130101; F01L
1/46 20130101; F01L 2301/00 20200501; Y10T 74/2107 20150115; F01L
1/26 20130101; Y10T 74/2101 20150115; F01L 1/0532 20130101; F01L
1/04 20130101; F01L 1/30 20130101; F01L 1/053 20130101; F01L 1/047
20130101; F16H 53/02 20130101; F16H 53/06 20130101; F01L 1/024
20130101 |
Class at
Publication: |
123/90.16 ;
123/90.6; 123/90.44 |
International
Class: |
F01L 001/34; F01L
001/18; F01L 001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 1998 |
AT |
A 1027/98 |
Jun 10, 1999 |
DE |
299 10170.3 |
Jun 10, 1999 |
DE |
299 16 363.6 |
Claims
I claim:
1. A valve mechanism, comprising: at least one driven cam element
and a valve actuator driven by said cam element; a flexible
surround element, said cam element being rotatably disposed in said
flexible surround element about an axis of rotation and said
flexible surround element being movably connected to said valve
actuator for movement in a plane perpendicular to said axis of
rotation of said cam element, and wherein said surround element is
configured to be reversibly lengthened for adjusting a valve lift
of said valve actuator.
2. The valve mechanism according to claim 1, wherein said surround
element is composed of two different materials, and at least one of
said materials is an elastically stretchable material.
3. The valve mechanism according to claim 1, wherein said surround
element consists of an elastically stretchable material.
4. The valve mechanism according to claim 1, wherein said surround
element is formed of at least one elastically stretchable material,
and a stretch-limiting device is assigned to said elastically
stretchable material.
5. The valve mechanism according to claim 4, wherein the mechanism
is disposed to drive a valve of an internal combustion engine
having a given maximum rotational speed, and said stretch-limiting
device is active at approximately 60%-70% of the maximum rotational
speed of the internal combustion engine.
6. The valve mechanism according to claim 1, wherein said surround
element includes a strip comprising a textile-bound sheet material
having two ends connected to a holder for said valve actuator.
7. The valve mechanism according to claim 6, wherein said two ends
of said strip are formed with plug-in openings for a connecting
element.
8. The valve mechanism according to claim 7, wherein said two ends
of said strip which are provided with plug-in openings are formed
with cutout regions engaged inside one another.
9. The valve mechanism according to claim 7, wherein said strip
comprises a continuous loop guided backward and forward about said
cam element and having reversal points forming said plug-in
openings.
10. The valve mechanism according to claim 6, wherein said surround
element has a nonstretch region, said sheet material is a woven
fabric containing filaments of aramid fibers extending in a
circumferential direction of said cam element, and said holder
consists of an elastically stretchable material.
11. The valve mechanism according to claim 1, wherein said surround
element comprises a seamless, continuous sheet material produced in
a textile circular working process and provided with a holder for
said valve actuator.
12. The valve mechanism according to claim 6, wherein said
textile-bound sheet material is adhesively bonded to said
holder.
13. The valve mechanism according to claim 1, wherein said cam
element is formed with a central circumferential groove and said
surround element is an elastically stretchable cord laid into said
central circumferential groove in said cam element.
14. The valve mechanism according to claim 13, wherein said cord is
guided through an eyelet formed in said valve actuator.
15. The valve mechanism according to claim 1, wherein said surround
element is an elastically stretchable plastic ring.
16. The valve mechanism according to claim 15, wherein said plastic
ring is formed with a recess, and a bearing pin of said valve
actuator is disposed in said recess.
17. The valve mechanism according to claim 1, wherein said surround
element has an elastically stretchable region including filaments
of aramid fibers extending in a circumferential direction of said
cam element and serving as a stretch-limiting device.
18. The valve mechanism according to claim 1, wherein said surround
element has an elastically stretchable region formed from a
material with a modulus of elasticity of between 1 and 4000
N/mm.sup.2.
19. The valve mechanism according to claim 18, wherein the modulus
of elasticity is between 600 and 2000 N/mm.sup.2.
20. The valve mechanism according to claim 1, wherein the mechanism
is disposed to drive a valve of an internal combustion engine
having a given maximum rotational speed, and the elastically
stretchable material is designed for an additional valve lift of
10% to 30% of the valve lift at idling speed of the internal
combustion engine.
21. The valve mechanism according to claim 1, wherein said surround
element has a protuberance formed by an elastically resilient
constriction and wherein a holder for said valve actuator is
arranged.
22. The valve mechanism according to claim 21, wherein said
constriction is formed by two clamping jaws that are externally
stressed with respect to one another.
23. The valve mechanism according to claim 21, wherein said
constriction is formed by an elastically deformable eyelet.
24. The valve mechanism according to claim 1, wherein said surround
element has one of the following three configurations: the surround
element includes a strip comprising a textile-bound sheet material
having two ends connected to a holder for said valve actuator, said
surround element comprises a seamless, continuous sheet material
produced in a textile circular working process and provided with a
holder for said valve actuator, and said surround element has a
protuberance formed by an elastically resilient constriction and
wherein a holder for said valve actuator is arranged, and wherein
said holder is composed of two parts enclosing said valve
actuator.
25. The valve mechanism according to claim 24, wherein said valve
actuator is arranged on said holder to be adjustable in length.
26. The valve mechanism according to claim 24, wherein said valve
actuator is rotatably arranged in said holder.
27. The valve mechanism according to claim 1, wherein a feed
opening for a friction-reducing medium is formed in one of a
circumferential surface of said cam element and an inner surface of
said flexible surround element.
28. The valve mechanism according to claim 27, which comprises a
hollow support shaft supporting said cam element and having at
least one bore formed therein, and wherein, for an internal supply
of the friction-reducing medium, said cam element is formed with at
least one bore that extends radially with respect to the axis of
rotation and is aligned with said at least one bore in said support
shaft.
29. The valve mechanism according to claim 28, wherein said cam
element is formed with a central circumferential groove and said
surround element is an elastically stretchable cord laid into said
central circumferential groove in said cam element, and wherein
said feed opening for the friction-reducing medium is formed in
said circumferential groove in the cam element.
30. The valve mechanism according to claim 1, which comprises a
support shaft supporting said cam element, wherein said cam element
is fixed on said support shaft against twisting with a pin inserted
into bores in said cam element and said support shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of copending
International Application PCT/AT00/00215, filed Aug. 8, 2000, which
designated the United States.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to a valve mechanism, in particular
for internal combustion engines of motor vehicles, having at least
one driven cam element and having a valve actuator, which can be
displaced or pivoted by the cam element, the cam element being
arranged rotatably in a flexible surround element which is
connected to the valve actuator in such a manner that it can move
in a plane which is perpendicular to the axis of rotation of the
cam element.
[0003] Valve mechanisms for controlling the valves of internal
combustion engines, in particular for motor vehicles, usually have
a device (spring, hydraulic element, etc.) which is used to load
the valve toward its closed position. In this position, a valve
actuator (valve lifter, drag lever, rocker lever or the like) is
pressed against a continuous valve control surface, which in part
runs eccentrically with respect to the shaft axis. When the valve
is closing, it should be ensured that the valve disk does not
strike the valve seat too quickly, since otherwise it will rebound.
This requires relatively complex matching between the shape of the
cam, the masses which are to be moved, the forces which are
generated, the materials properties, etc.
[0004] Therefore, there is no lack of proposals concerning forced
guidance of the valve actuator on the cam element; various
embodiments have been developed, which are each based on two
eccentric valve control surfaces instead of the restoring spring.
Specific designs are to be found, for example, in British patent
specifications GB 19,193 (1913) and GB 434,247, wherein the cam
element, on at least one end face, has a groove, the two side walls
of which form the valve control surfaces. A roller or the like
which is arranged at the end of the valve actuator engages in the
groove from the side. A cam element which has a web which can be
gripped around is known, for example, from European publication EP
429 277 A.
[0005] A further proposal for a desmodromic valve mechanism,
wherein a space-saving, lightweight and inexpensive design is
achieved, is to be found in published German patent application DE
37 00 715 A which describes the generic type referred to in the
introduction. In this design, a surround element is provided, which
surrounds the circumference of the cam element without significant
play, so that it always matches the shape of the cam, yet the cam
element, on account of the nature of the surround element, can
rotate inside the latter. Since the surround element connected to
the valve actuator cannot rotate with the cam element, the movement
of the cam region about the axis of rotation of the cam element is
converted into a lifting or reciprocating movement of the valve
actuator which is mounted displaceably or pivotably in the cylinder
head. The valve actuator does not execute a movement as long as the
connecting region of the surround element together with the valve
actuator rests against the base circle region of the rotating cam
element, is then moved away from the axis of rotation of the cam
element in the radial direction and finally is returned again,
while the cam region of the cam element moves past the connecting
region of the surround element and the valve actuator. The moveable
connection of the surround element to the valve actuator allows the
pivoting or tilting movement of the surround element in the cam
region, so that the required freedom of movement of the valve
actuator in its sliding or pivot bearing is preserved. In the first
exemplary embodiment, the surround element is formed by two
flexible rings, between which needle-shaped rolling bodies are
provided in order to reduce the friction. A second embodiment
provides a plastic strip having an inner ceramic slip layer.
[0006] Particularly when the valve mechanism is used in internal
combustion engines, a surround element is subject to high loads,
and it is necessary to rule out temperature-or fatigue-related
plastic lengthening of the surround element. An irreversible
increase in the size of the gap between the circumference of the
cam element and the surround element affects in particular the
valve-closing position.
[0007] Furthermore, the term variable valve control has revealed a
wide range of different structures which can be used to change the
opening and closing time and the lift of the valve, in order to
improve the performance, the exhaust emissions, the torque, etc. of
an internal combustion engine. Compared to the non-adjustable valve
control with fixed values, the filling of a cylinder is improved if
the valve is opened later and closed earlier at low rotational
speeds and is opened earlier and closed later at higher rotational
speeds. It is therefore possible, by means of a speed-dependent
adjustment of the valve control, to optimize the exhaust emissions,
the torque, the engine performance, etc. All the variable valve
control arrangements which have been revealed to date change the
position of the actuating surface of the valve actuator relative to
the eccentric valve control surface through rotation, linear
displacement or enlargement of the cam element. These adjustment
mechanisms are relatively complex and, in some cases, also require
considerable adjustment forces, since they have to operate counter
to the restoring elements of the valves.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
valve lifting mechanism, particularly for an internal combustion
engine, which overcomes the above-mentioned disadvantages of the
heretofore-known devices and methods of this general type and which
provides for a variable forced valve control.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a valve mechanism,
comprising:
[0010] at least one driven cam element and a valve actuator driven
by said cam element;
[0011] a flexible surround element, said cam element being
rotatably disposed in said flexible surround element about an axis
of rotation and said flexible surround element being movably
connected to said valve actuator for movement in a plane
perpendicular to said axis of rotation of said cam element, and
wherein said surround element is configured to the reversibly
lengthened for adjusting a valve lift of said valve actuator.
[0012] In other words, the objects of the invention are achieved,
in a valve mechanism of the type described in the introduction, in
that the surround element is designed so that it can be lengthened
reversibly.
[0013] The cam element rotating in the surround element generates
tensile forces, which rise as a function of rotational speed, at
the connecting point to the valve actuator, so that the surround
element, which bears against the circumference of the cam element
virtually without play at idling speed, is lifted increasingly
further away from the circumference as the rotational speed rises,
thus adopting positions which correspond to cam elements with
greater circumferential lengths. Since, in this way, the distance
between the axis of rotation of the cam element and the connecting
point between the surround element and the valve actuator
increases, an additional valve lift which is dependent on
rotational speed is produced.
[0014] In a first embodiment, the reversible lengthening of the
surround element is achieved by elastic stretchability of at least
a partial region of the surround element, so that the play which is
formed between the cam circumference and the surround element is
reduced further as the rotational speed falls. Moreover, it allows
advantageous, slight prestressing of the surround element in the
at-rest state, in order to ensure that the valve-closing position
is reached outside the cam region despite any temperature-related
changes in length.
[0015] The surround element may consist of an elastically
stretchable material or may be composed of two materials with
different properties, at least one of which can stretch
elastically. By way of example, a non-stretch strip may be closed
with respect to the surround element by an elastically stretchable
intermediate piece, wherein case a holder for the valve actuator
may be provided either in the nonstretch region or in the
elastically stretchable region. If the holder is in the elastically
stretchable region, it may itself also consist of an elastically
stretchable material and, if appropriate, may also form the elastic
region.
[0016] For internal combustion engines of motor vehicles, the
elastically stretchable material is preferably designed for an
additional valve lift of 10% to 30% of the valve lift at idling
speed. In order, in a preferred embodiment, to ensure an upper
limit value of the elastic stretching, which can be selected for a
permissible maximum rotational speed or a rotational speed above
which an additional valve lift is of subordinate importance, a
stretch-limiting means can be assigned to the elastically
stretchable material by arranging nonstretch filaments or fibers,
the length of which corresponds to the length of the elastic
material which has been stretched to the limit, in or parallel to
the stretchable material.
[0017] In a second embodiment, the surround element has a
protuberance which is formed by an elastically resilient
constriction, the tensile forces acting on the holder of the valve
actuator causing the elastically resilient constriction to widen.
The reduction of the constriction lengthens the surround element,
which in this embodiment may itself be of nonstretch design. The
holder is preferably arranged in the protuberance, with the result
that the two regions of the surround element, which, at idling
speed, come into contact with one another between the cam element
and the holder, move away from one another as the rotational speed
increases and move closer to one another as the rotational speed
falls.
[0018] In a further embodiment, it is provided that the surround
element has a strip comprising a textile-bound sheet material, in
particular comprising a woven fabric, the two ends of which are
connected to a holder for the valve actuator. When the two ends of
the strip penetrate through one another or project from the cam
element in contact with one another, the flexibility of the
material of the surround element means that a physical axis in the
connection to the valve actuator may be unnecessary, since the two
ends together can be bent to both sides to the required extent. For
connection to the valve actuator, it is preferable for the two ends
of the strip to have plug-in openings for a connecting element. The
plug-in openings may be formed by winding round and--depending on
the material used for the strip--sewing, adhesively bonding or
welding the wrapped-around end, or the like. A particularly
advantageous embodiment provides for the strip to comprise a
continuous loop which is guided backward and forward about the cam
element and the reversal points of which form the plug-in openings.
The connecting element may also be of elastically resilient design
and consist, for example, of spring steel.
[0019] If the surround element consists of two different materials,
the textile-bound sheet material may have a nonstretch region,
wherein it contains filaments of Kevlar.RTM., glass, carbon or
aramid fibers, or the like, substantially constant-length fibers,
extending in the circumferential direction of the cam element.
[0020] A surround element which forms a continuous loop may consist
in particular of a sheet material which is produced using a textile
circular working technique (circular weaving, circular knitting,
etc.) and is provided with a holder for the valve actuator.
[0021] The elastic stretching of the loop may be selected to be
linear, progressive or degressive, for example by incorporating
filaments with different stretching properties, which become active
simultaneously or in succession.
[0022] Further possible options provide an elastically stretchable
cord or an elastically stretchable ring made from plastic, which is
preferably provided with a recess for a bearing pin of the valve
actuator. The plastic ring may be fiber-reinforced and/or provided
with a slip-reducing metal coating. As an alternative, it is also
possible to use a flat belt, in particular a ribbed belt, between
the transverse ribs of which there is space for the bearing pin of
the valve actuator, which is fixed by an adhesively bonded cover
strip or the like. The ribbed belt may also be fitted in such a way
that the ribs are internal, which eliminates the need for
additional fixing of the bearing pin.
[0023] Materials which are particularly suitable for a surround
element which has at least elastically stretchable partial regions
have a modulus of elasticity of between 1 and 4000 N/mm.sup.2.
Rubber-like materials have low moduli of elasticity and are
preferably provided with a stretch-limiting means. Materials such
as plastics which have higher moduli of elasticity, in particular
between 600 and 2000 N/mm.sup.2, preferably between 800 and 1200
N/mm.sup.2, do not generally require a stretch-limiting means,
although it is, of course, possible to provide such means.
[0024] A simple possible option for the stretch-limiting means
consists in assigning nonstretch filaments of Kevlar.RTM., glass,
aramid fibers or the like, which extend in the circumferential
direction and are, for example, woven into a strip, to the surround
element or the elastically stretchable region of the surround
element. Specifically in this design, it would also be possible to
use an elastomeric plastic, which is vulcanized to the strip, for
the ring or flat belt.
[0025] For internal combustion engines wherein the cylinders have
two intake or discharge valves which operate in parallel, the valve
pairs may have different stretching levels, for example one
stretch-limited valve under partial load and the other valve
without stretch-limiting means or with stretch-limiting means at
full load.
[0026] If the surround element consists of a material with a
low-friction surface or a surface which has been provided with a
low-friction coating, it may be that lubrication of the sliding
surfaces, i.e. of the circumferential surface of the cam element
and of the inner surface of the surround element which bears
against it, will not be required. If lubrication is required or
desirable, it is preferable for the cam element to have at least
one oil bore which runs radially with respect to the axis of
rotation and opens out on the circumference of the cam element,
inside the flexible surround element. Since the surround element
does not rotate, external supply of oil through the surround
element via a flexible line is also conceivable.
[0027] Instead of a film of lubricating oil, it is also possible to
build up an air cushion surrounding the cam element by means of
compressed air. This may be advantageous in particular in the case
of a surround element made from plastic or woven plastic
fabric.
[0028] In the valve mechanism according to the invention, the
masses which have to be accelerated are reduced by the elimination
of the valve spring and spring disk and by a significantly lighter
design of the valve lifter or rocker lever. The use of light
metals, ceramics or plastics for the valve and/or the valve
actuator allows the masses which have to be accelerated and
decelerated to be reduced by from 50% to 80% of the value for a
valve lifter with restoring spring and hydraulic play compensation.
The high values result in particular in the part-load range, since
the valve springs have to be designed to be able to withstand full
load. Furthermore, the valve may be of shorter design, since the
bulky valve spring is eliminated.
[0029] It is also possible for the cam element to be of shorter
design. It also becomes possible to form plastic cam elements or
camshafts which are produced completely from plastic, for example
by injection molding. The use of other lightweight materials for
the production of the camshafts or of the cam elements, for example
aluminum, also becomes possible. On account of the reduction in
mass and the lubrication, fuel savings of 5% and more are to be
expected.
[0030] Particularly if valve actuators are actuated together, it is
possible to provide a weak spring for acting on each closed
valve.
[0031] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0032] Although the invention is illustrated and described herein
as embodied in a valve mechanism, in particular for internal
combustion engines, it is nevertheless not intended to be limited
to the details shown, since various modifications and structural
changes may be made therein without departing from the spirit of
the invention and within the scope and range of equivalents of the
claims.
[0033] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 shows a graph illustrating a speed-dependent change
in length of the surround element;
[0035] FIG. 2 shows components of a first embodiment of a forcibly
controlled variable valve mechanism in perspective;
[0036] FIGS. 3 to 5 show cross-sectional illustrations of various
angular position s of the first embodiment of the valve
mechanism;
[0037] FIGS. 6 and 7 show longitudinal sections through the first
embodiment, FIG. 6 illustrating the valve actuator at idling speed
and FIG. 7 illustrating the valve actuator at a higher speed;
[0038] FIG. 8 shows components of a second design of a valve
mechanism, in a perspective view,
[0039] FIG. 9 shows a longitudinal section through the third
embodiment; and
[0040] FIG. 10 shows a side view of the third embodiment, in each
case at idling speed;
[0041] FIG. 11 shows components of a fourth embodiment of a valve
mechanism, in a perspective view;
[0042] FIG. 12 shows a side view of the fourth embodiment; and
[0043] FIG. 13 shows a cross section through the fourth embodiment,
in each case at idling speed;
[0044] FIG. 14 shows a perspective view of components of a fifth
embodiment;
[0045] FIGS. 15 and 16 show cross sections through the fifth
embodiment, FIG. 15 showing the valve actuator at idling speed and
FIG. 16 showing the valve actuator at a higher speed;
[0046] FIG. 17 shows a perspective view of components of a sixth
embodiment;
[0047] FIG. 18 shows a perspective view of the sixth embodiment in
the closed position;
[0048] FIG. 19 shows a longitudinal section through the sixth
embodiment;
[0049] FIG. 20 shows a perspective view of components of a seventh
embodiment;
[0050] FIG. 21 shows a cross section through the seventh
embodiment;
[0051] FIG. 22 shows an enlarged detailed view of part of FIG.
21;
[0052] FIG. 23 shows a perspective view of the seventh
embodiment;
[0053] FIG. 24 shows a perspective view of components of an eighth
embodiment;
[0054] FIG. 25 shows a longitudinal section through the eighth
embodiment;
[0055] FIG. 26 shows a perspective view of components of a ninth
embodiment;
[0056] FIG. 27 shows a cross section through the ninth
embodiment;
[0057] FIG. 28 shows a perspective view of components of a tenth
embodiment;
[0058] FIG. 29 shows a perspective view of the tenth
embodiment;
[0059] FIG. 30 shows a perspective view of components of an
eleventh embodiment;
[0060] FIG. 31 shows a cross section through the eleventh
embodiment;
[0061] FIG. 32 shows an enlarged detailed view of part of FIG.
31;
[0062] FIG. 33 shows a perspective view of components of a twelfth
embodiment;
[0063] FIG. 34 shows a longitudinal section through the twelfth
embodiment; and
[0064] FIG. 35 shows an enlarged detailed illustration of part of
the twelfth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0065] The drawings in each case show a forcibly guided valve
mechanism, wherein a valve mechanism used for an internal
combustion engine of a motor vehicle has, on the support shaft 1,
the number of cam elements 2 which are required for the valves. A
supply of oil in order to build up a film of oil or of air in order
to build up an air cushion on the circumferencial surface of the
cam element 2 can be effected via a hollow support shaft, radial
openings 30 in the support shaft 1 and via bores 3 in the cam
element 2. An arrangement of openings 30 and bores 3 can also, as
shown in FIGS. 8 to 10, be used to secure the cam element 2 on the
support shaft 1 when a fixing pin 20 is inserted. The valve lift,
the increase wherein as a function of the rotational speed is
illustrated in the diagram shown in FIG. 1, can be seen from a
comparison of FIGS. 3 to 5. The diagram shown in FIG. 1 illustrates
the change in length of the surround element 4; the eccentric range
0 to 1 of the cam element 2, starting and ending at the base circle
region (not shown), wherein the valve-closing position is produced,
is plotted on the abscissa. Depending on the selected conditions,
the eccentric range extends over an angle of approximately one
third to two thirds of the circumference of the cam element 4, for
example over an angle of approximately 150.degree., as shown in the
figures. At a rotational speed of the camshaft of 400 revolutions
per minute, which corresponds to the engine idling, the diagram
shows a valve lift of 9.7 mm, denoted as 100%. If the rotational
speed increases, the lift should become greater, for example
reaching an additional valve lift of 1.75 mm at a maximum of 4000
revolutions per minute, corresponding to an increase of
approximately 18% in valve lift. The speeds indicated, in this
figure and below, always refer to the rotational speeds of the
camshaft itself, which in the case of internal combustion engines
for motor vehicles are generally half as great as the engine
speeds, i.e. in the example indicated the idling speed of the
engine is 800 and the maximum speed 8000 revolutions per
minute.
[0066] In order, despite forced control, to increase the valve lift
as a function of the rotational speed, the cam element 2 is
surrounded by a surround element 4, which can be reversibly
lengthened and substantially bears against the circumferential
surface, it being possible for the cam element 2 to rotate in the
surround element 4, about its axis of rotation 8, with continuous
pulsed deformation of the surround element 4. In the figures, the
cross-sectional shape of the surround element 4 is in each case
illustrated matched to the cam element 2, since in these figures
the valve mechanism is shown in an exploded view. As an individual
element, the surround element 4 is only in the form of a ring if
the material is sufficiently elastic and thick, while otherwise it
forms a collapsed oval or the like. The surround element 4 is
prevented from rotating by the connection to a valve actuator 10,
which in the case of the valve lifter is mounted in such a manner
that it can be moved in translation in a sliding-contact bearing,
while in the case of a rocker or drag lever is mounted so that it
can be pivoted in a pivot bearing. This also permits an embodiment
wherein a lubricant is supplied through the stationary surround
element 4. The surround element 4 is connected to the valve
actuator 10 in such a manner that it can tilt or pivot about an
axis 15, so that, when the cam of the cam element 2 passes through
the connecting region of the valve actuator 10, it is possible for
the surround element 4 to pivot relative to the valve actuator 10.
This is necessary since, as illustrated in FIGS. 3 to 5, the
sliding-contact bearing of the valve stem 11 does not allow any
lateral deflection, and the valve stem 11 has to be directed
radially toward the axis of rotation 8.
[0067] The higher the rotational speed of the cam element 2, the
greater the tensile forces which are produced in the surround
element 4, these forces, on account of the fact that the surround
element 4 can be lengthened reversibly, leading to the distance
between the axis of rotation 8 and the axis 15, at which a valve
actuator 10 is articulatedly mounted, increasing. This increase in
distance produces an additional valve lift.
[0068] In the first embodiment, shown in FIGS. 2 to 7, the surround
element 4 is formed by a ring made from a flexible, elastically
stretchable and, if appropriate, fiber-reinforced plastic, which
has only a low resistance to deformation. At one point, the ring
contains a window 5, wherein a bearing pin 14, which runs parallel
to the axis of rotation 8 of the cam element 2 and lies in the axis
15, passes through the valve stem 11. On the inner surface of the
ring, which surrounds the cam element 2, there is a continuous thin
loop of a friction-reducing strip 22, wherein the cam element 2
rotates. The strip 22 may likewise be elastically stretchable and
may consist, for example, of a low-friction plastic, a woven fabric
or the like. As shown in FIG. 6, a small gap 31 remains between the
strip 22 and the circumferential surface of the cam element 2,
generally if only for assembly reasons, wherein gap a film of oil
can be formed for lubrication purposes. As the rotational speed
rises, the elastic stretching of the surround element 4 means that
the gap 31 increases in size, as can be seen from a comparison
between FIGS. 6 and 7, so that the valve lift is increased.
[0069] FIGS. 8 to 10 show an embodiment wherein a holder 12 is
formed in the shape of an "iron", the bearing pin 18, in a similar
manner to that shown in FIG. 2, being arranged between the
elastically stretchable strip 22 and the ring 4 made from
elastically stretchable plastic or the like and forming the axis
15. The end section of the bearing pin 18 widens slightly, in order
to prevent axial slipping in the surround element 4, the opposite
region of the holding body 12 being beveled, in order for it to be
possible to push the holding body 12 in laterally. The holding body
12 has a threaded bore, into which the valve stem 11, which has a
screw thread 28, can be screwed and fixed adjustably by a locking
nut 27. As has been mentioned, FIGS. 8 to 10 also show a possible
way of fixing the cam element 2 on the support shaft 1 by means of
a pin 20, which is fitted through bores 30 in the shaft 1 and bores
3 in the cam element 2.
[0070] FIGS. 11 to 13 show an embodiment wherein the surround
element 4 is formed by a continuous loop of an elastically
stretchable cord, which is arranged slideably in a groove 16 in the
circumferential surface of the cam element 2. The cam element 2 is
divided into two cam regions 43 which are spaced apart from one
another in the axial direction, the groove 16, wherein the oil
bores 3 of the cam element 2 open out, forming the central region.
The valve stem 11 of the valve actuator 10 is provided with an, in
particular laterally open, hook-like eyelet 17, wherein the cord
loop is suspended, and is rounded on the top side parallel to the
axis 15, in order to allow the pivoting, as can be seen in
particular from FIG. 13. The eyelet 17 may also be of closed
design, if a piece of a cord is only closed up to form the cord
loop after it has been threaded into the eyelet 17. In this
embodiment, the surround element 4 is slightly larger than the cam
circumference, since it is also guided through the eyelet 17. The
elastic stretchability also compensates for the changes in the
surround length which result from rotation of the cam element on
account of the eyelet 17 holding the cord at a distance from the
circumference.
[0071] FIGS. 14 to 16 show an embodiment wherein the surround
element 4 is formed from a strip of elastically stretchable sheet
structure with textile binding, in particular a woven fabric or the
like. For connection to the valve actuator 10, a protuberance 6 is
formed on the surround element 4, which protuberance can be fitted
into a slot 29 in the valve stem 11. Connection is effected by
means of a cotter pin 19, which passes through the bores 25 in the
valve stem 11 and the protuberance 6. The surround element 4 may be
a single, continuous loop or turn with a protuberance 6 which has
been pressed flat. The single loop or turn may also be formed by
bringing together both ends 13 of a strip, which when in contact
with one another form the protuberance 6 and together are inserted
into the slot 29. In this embodiment, the axis 15 is not physically
embodied, but rather results from the bending region between the
protuberance 6 and that part of the surround element 4 which
surrounds the circumferential surface of the cam element 2. FIG. 15
shows the position of the valve stem 11 in the closed position, and
FIG. 16 shows a position at a high rotational speed, wherein the
two ends 13 of the strip have been moved away from one another
between the upper end of the valve stem 11 and the cam element.
[0072] In the embodiment shown in FIGS. 17 to 19, the cam element 2
is provided with a circumferential groove 16, the base of which is
concentric with respect to the support shaft 1. In this way, the
cam element 2 is divided into two cam regions 43, which are
connected by means of a material-saving central region. The
surround element 4, which in this embodiment is formed by a
continuous loop of an elastically stretchable strip, has at one
point an adhesively bonded or sewn tab 45 which defines a plug-in
opening 47. In the central region the loop and the tab 45 are
provided with a window 5. In the securing region, the valve
actuator 10 has a bore 46, so that, after insertion into the window
5, a connecting element 48, in the form of a pin or cotter pin, can
be pushed through the plug-in opening 47 and the bore 46. The pin
in turn forms the axis 15, which extends parallel to the support
shaft 1. The free end of the valve stem 11 in this case projects
into the circumferential groove 16, resulting in axial guidance
also being provided. The seamless woven strip of the surround
element 4, which is preferably produced using a textile circular
working technique (circular weaving, circular knitting or the like)
contains carbon, Kevlar.RTM. or aramid filaments or fibers or the
like to protect against excessive stretching, since this produces a
highly constant length and a good thermal stability. The nonstretch
filaments have a length which corresponds to the normal
circumferential length and may be the weft filaments, running in
the circumferential direction, of the woven-fabric ring or
additional filaments which, for example, in the unstretched state
are connected to the woven-fabric ring in waves or zigzag form. The
woven fabric may also be provided with a low-friction coating.
[0073] FIGS. 20 to 23 show a similar design, wherein, once again, a
circular-worked, in particular circular-woven strip is used to
produce the surround element 4. The strip circumference
substantially corresponds to twice the circumference of the cam
element 2 and is brought together so as to form a double-layer open
loop. The reversal points of the strip at the ends 13 of the open
loop form the plug-in openings 47 for the hollow connecting element
48, which in this embodiment is bent into a U shape. Both ends 13
are cut out in the central region 52, and the two cutouts
complement one another to form the window 5 through which the end
of the valve stem 11 projects into the circumferential groove 16 of
the cam element. As a result, the installation position of the
valve actuator 11 can lie laterally offset, parallel to the axial
plane, as can be seen from FIG. 21, which may result in advantages
with regard to a change in the rolling and contact lines. Of
course, the valve stem 11 may also lie in the axial plane, so that
the two plug-in openings 47 are not symmetrical. A second part 53
which is bent into a U shape is inserted into the hollow connecting
element 48 and is, for example, adhesively bonded, so that the
connection between the surround element 4 and the valve actuator 10
is ensured.
[0074] Instead of using the U-shaped connecting element 48, the two
ends 13 of the open loop could also be connected by an element
which is similar to a belt buckle and has one or two slots through
which the ends 13 are guided and are fixed by pins inserted into
their plug-in openings 47. The belt-buckle-like element forms the
holder 12 for the valve actuator, into which it is screwed or
latched.
[0075] An elastically stretchable connection of the two ends 13 can
also be achieved by connecting the protruding ends of pins which
have been inserted into the plug-in openings 47 by two tension
springs made from steel.
[0076] In the embodiment shown in FIGS. 24 and 25, a sleeve 55,
which is provided with a pair of connecting tabs 56 and projects
inward into the circumferential groove 16, is inserted into the
window 5 in the surround element 4, which is formed by a continuous
loop of a woven strip or the like. The connecting tabs 56 are
adhesively bonded or welded or joined in some other way to the
surrounding area of the window 5. At the free end, the valve stem
11 has a screw thread 28, and the stem can be screwed into a screw
thread in the sleeve 55 to an adjustable depth and can be clamped
by means of a mating nut 27. In this embodiment, the cam element 2
comprises two cam regions 43, which are not connected to one
another, but rather are fixed separately on the support shaft.
Instead of the screw connection, it would also be possible to form
a latching or snap-action connection between the sleeve 55 and the
valve stem 11, so that rotation about the axis of the valve stem 11
is possible. The axis 15 about which the surround element 4 has to
be pivoted backward and forward to a limited extent with respect to
the valve actuator 10 runs between the connecting tabs 56, on
account of the flexibility of the material used.
[0077] In the embodiments shown in FIGS. 26 to 32, the surround
element 4 is in each case designed as a continuous loop with a
protuberance 6, which is divided from the cam element by a
constriction which is, for example, adhesively bonded, sewn or
clamped, and accommodates an insert 54 which serves as holder 12 of
the valve actuator 10. Particularly in these embodiments, the
surround element may also be of constant-length design, if the
constriction between the holder 12 and the cam element 2 is of
elastically resilient design. In this way it is possible, for
example, to sew the constriction by means of rubber filaments or
the like.
[0078] FIGS. 26 and 27 show an embodiment wherein the constriction
of the surround element 4 is effected by an elastically widenable
eyelet 50, through which the protuberance 6, which has been pressed
flat, is threaded. The insert 54 which has been pushed into the
protuberance 6 has a latching or threaded bore 57, into which the
latchable or threaded end 28 of the valve stem 11 can be pushed or
screwed. In the latter case, a mating nut 27 is used for adjusting
and fixing the length of the valve actuator 10. The tensile forces,
which rise at higher rotational speeds, widen the eyelet, so that
the regions which are in contact with one another in the
constriction move away from one another, and the constriction is
stretched.
[0079] FIGS. 28 and 29 show a similar connection between the
surround element 4 and the valve actuator 10, wherein the
constriction of the protuberance 6 is effected by two clamping jaws
49 which are clamped to one another, in particular resiliently. The
two clamping jaws 49 may also be of identical design, so that in
each case one connecting screw is inserted into a clamping jaw 49.
If appropriate, the spring prestressing may also be adjustable.
[0080] Instead of the eyelet 50 or the clamping jaws 49 in the
embodiments shown in FIGS. 26 to 29, a latchable, elastically
widenable constricting device is also conceivable, for example by
clipping together two parts which are of identical design and are
provided with latching hooks and latching openings.
[0081] In FIGS. 26 to 29, the insert 54 may also comprise a rubber
or a rubber-sheathed metal or plastic core, which is pinched into
an oval shape by the tensile forces, which rise in the surround
element 4 at higher rotational speeds, on account of the rising
mass forces of the valve. This likewise leads to an elastic
increase in the distance between the axis of rotation 8 and the
pivot axis 15 of the valve actuator 10.
[0082] FIGS. 30 to 32 show a possible way of producing a latching
connection between the valve stem 11 and the holder 12, which
allows the valve stem 11 to rotate about its axis. The end of the
valve stem 11 is provided with a polygonal, conical or rounded
annular groove 59, and the insert 54 is provided with two webs,
which are resilient on account of a slot 51 and on which polygonal,
conical or rounded ribs 60 are formed. The valve stem is pushed
into the bore 57, so that the insert 54 is widened, until the ribs
60 latch into the annular groove 59 (FIG. 32). The connecting
element 48, which is responsible for the constriction and is in the
form of a U-shaped hollow bracket, is then pushed on and secured by
the U-shaped mating piece 53, which is adhesively bonded or pinched
in place. In FIGS. 26 to 32, the constriction in each case forms an
elastic, flexible connection, wherein the axis 15 is embodied.
[0083] FIGS. 33 to 35 show an embodiment wherein the surround
element 4, in a similar manner to the embodiment shown in FIGS. 20
to 23, comprises a continuous strip of an elastically stretchable
woven fabric which is laid together so as to form an open,
two-layer loop and the reversal points of which once again form
plug-in openings 47. The ends 13 of the open loop are cut out in
such a way that they can be fitted into one another. In this
embodiment, the holder 12 is assembled from two parts 12' each of
which has a pin-like section 48' of the connecting element 48, a
receiving part and a threaded sleeve for a threaded screw 61. Two
ribs 60, which engage in a circumferential groove 59 in the valve
stem 11, which is once again held rotatably, project into the
opening 57, which is likewise divided. The two pin-like sections
48' engage in the mutually aligned plug-in openings 47 in the
mutually engaging ends 18 and come into contact with one another in
the center, is as can be seen from FIG. 34. In this embodiment, the
cam element 2 is not shown as a part which can be mounted
individually, but rather the cam shaft is produced as a single part
using a conventional process.
[0084] Since the variable forced guidance of the valve actuator
allows the valve mechanism to be of very lightweight design, it is
also possible for the entire camshaft to be of very lightweight
design. Therefore, it can even be produced in a single piece from
an optionally reinforced plastic or other lightweight
materials.
[0085] If a woven-fabric strip is used for the surround element 4,
its ends can either be sewn, adhesively bonded or welded together
to form a continuous loop, or can be wrapped around and sewn,
adhesively bonded or welded, in order to form plug-in openings 47
of the open loop. The windows 5 or edge and center cutouts 52 can
readily be formed in a woven fabric which has been treated in this
manner.
[0086] A holder 12 as shown in FIGS. 8 to 10 or 26 to 35 is
preferably formed from inelastic material, so that an elastically
stretchable surround element 4 or an elastically widenable
constriction of the surround element 4 is provided for the purpose
of changing the distance between the axis of rotation 8 of the
support shaft 1 and the articulation axis 15 of the valve actuator
10.
[0087] However, it is also possible for the holder 12 to consist of
an elastically stretchable, rubber-like material, which can in
particular be permanently adhesively bonded or vulcanized onto a
woven-fabric strip or its ends. The rubber-like material, which is
preferably of varying thickness according to the stress profile,
effects damping of the surrounding squeezing movement in the
surround element 4 which is produced by the cam peaks and good
transfer, without stress peaks, of the shear forces from the
surround element 4 to the valve actuator.
[0088] As has already been mentioned, the surround element may be
composed of an elastically stretchable material and a substantially
nonstretch material. In this connection, embodiments wherein the
elastically stretchable region is provided opposite the holder 12
are also possible, with the result that any weakening in the
connecting area between the valve actuator and the surround element
4 is avoided. A design of this type is illustrated in FIG. 24,
wherein the region of the surround element 4 which lies opposite
the opening 5, between the dashed lines, can stretch
elastically.
[0089] In all embodiments, the valve mechanism is shown with a
valve lifter as valve actuator 10. However, the valve actuator 10
may equally well comprise a pivotably mounted rocker or drag lever,
on one end of which the surround element 4 is arranged in such a
manner that it can pivot about the axis 15. A camshaft for use with
internal combustion engines usually has a plurality of valve
mechanisms of this type, wherein the cam elements are arranged in
an angularly offset manner.
* * * * *