[0001] The present invention refers to a system for continuously varying the lift and the
phase of the valves in an alternating internal combustion engine.
[0002] As known, in internal combustion engines the opening and closing of the intake and
discharge valves of each cylinder is commanded by special eccentrics, known as cams,
normally fitted onto a so-called camshaft. The camshaft is actuated by the drive shaft,
with respect to which it rotates at half the angular speed and to which it is connected
through a chain or a belt or else, more rarely, through a cascade of gears.
[0003] The shape of the eccentrics is a defining characteristic for the performance of an
engine, since it has an influence both on the opening time, or phase, of each valve,
and upon the excursion, expressed in millimetres, of the valve itself. Moreover, the
shape of the eccentrics is also a defining characteristic for the noisiness of the
engine, since it regulates the impact between the valves and the respective seats.
[0004] For the regulation of the phases of each valve known devices have therefore been
made like phase variators, which indeed allow the opening time of the valves themselves
to be varied. By increasing such an opening time for the valve or the intake valves
of each cylinder there is greater filling of the combustion chamber, with a consequent
increase in the power delivered. The variation of the discharge phase, on the other
hand, allows the crossing over of valves, in other words the phase in which both the
intake valves and the discharge valves are open simultaneously after the burning of
the mixture, to be increased, so that the unburnt gases are expelled outside of the
chamber thanks to the entry of the new mixture. In this delicate phase a small percentage
of mixture is lost, but the advantage that is obtained is a good washing of the combustion
chamber that thus, at each burn, is always clean and cooled as it should be.
[0005] In order to modify the excursion of the valves , on the other hand, it is possible
to foresee suitable lift variators that, usually through hydraulic actuation means,
are able to increase or decrease the excursion of the valves themselves, thus allowing
the power delivered by the engine to be best adjusted.
[0006] Such valve control systems, normally made separately and with different technologies,
are however expensive and delicate, especially when actuated hydraulically, and therefore
are only intended for use on certain high-performance vehicles.
[0007] The purpose of the present invention is therefore to make a system that is able to
simultaneously and completely mechanically vary both the lift and the phase of the
valves of an internal combustion engine.
[0008] Another purpose of the invention is to make a system for continuously varying the
lift and the phase of the valves in an internal combustion engine that is quick and
simple to adjust.
[0009] These purposes according to the present invention are accomplished by making a system
for continuously varying the lift and the phase of the valves in an internal combustion
engine as outlined in claim 1.
[0010] Further characteristics of the invention are outlined by the subsequent claims.
[0011] The characteristics and advantages of a system for continuously varying the lift
and the phase of the valves in an internal combustion engine according to the present
invention shall become clearer from the following description, given as a non-limiting
example, referring to the attached schematic drawings, in which:
figure 1 is a front view of a first example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention;
figure 2 is a side view of the system shown in figure 1;
figure 3 is a rear view of the system shown in figure 1;
figures 4 to 6 are perspective views of the system shown in figure 1;
figure 7 is a front view of a second example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention;
figure 8 is a side view of the system shown in figure 7;
figure 9 is a rear view of the system shown in figure 7;
figure 10 is a front view of a third example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention;
figure 11 is a side view of the system shown in figure 10;
figure 12 is a rear view of the system shown in figure 10;
figure 13 is a front view of a fourth example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention;
figure 14 is a side view of the system shown in figure 13;
figure 15 is a rear view of the system shown in figure 13; and
figures 16 to 18 are perspective views of the system shown in figure 13.
[0012] With reference to figures 1 to 6, a pair of valves belonging to a generic internal
combustion engine (not shown) is shown, which can be equipped with one or more cylinders.
Such valves 10 and 12, which can be for intake or else discharge, have a first embodiment
of the system for continuously varying the lift and phase according to the present
invention applied to them.
[0013] Each valve 10, 12 is directly commanded by a rocker arm 14, of the so-called finger
type, provided or not with a roller 16 for reducing friction. In the example embodiment
illustrated, the clearances of each valve 10, 12 can be controlled through a hydraulic
recovery mechanism 18. In addition, between each valve 10, 12 and the respective finger
rocker arm 14 a capsule or tablet 20 (figure 6) can possibly be arranged for adjusting
the clearances.
[0014] Each finger rocker arm 14 is in turn commanded by the camshaft 22 through the interposition
of a second rocker arm 24, or intermediate rocker arm. In practice, each cam 26 actuates
the relative intermediate rocker arm 24 that transmits the motion to the finger rocker
arm 14 and, consequently, to the valves 10 and 12.
[0015] The intermediate rocker arm 24 has the special characteristic of having the contact
surface 28 with the roller 16 of the finger rocker arm 14 equipped with a specific
profile. In detail, at least one portion 28a of such a contact surface 28, in other
words the portion along which the motion for adjusting/varying the phase and the lift,
has its centre of curvature coinciding with the rotation axis C of the camshaft 22,
as can be seen in figure 2. A second portion 28b, possibly not present, of the contact
surface 28, on the other hand, has a different centre of curvature to the centre C.
What has been stated up to now is only valid should the contact between the roller
30 of the intermediate rocker arm 24 and the relative cam 26 of the camshaft 22 take
place along the base circle of the cam 26 itself. Should the second portion 28b of
the contact surface 28 be present, its curvature can also not be constant.
[0016] Each intermediate rocker arm 24 is hinged on a pin 32 supported by a support 34.
In turn, the support 34 is hinged on the camshaft 22, with the possibility of rotating
with respect to it, and it is formed of a top part 34a and a bottom part 34b, joined
together by means of a plurality of screws 36.
[0017] The maintaining of the contact between each roller 30 and the relative cam 26 is
aided by the action of a spring 38 fixedly connected to each intermediate rocker arm
24. Such a spring 38 has a fixed reaction point on the support 34 and is housed on
the support 34 itself. The axial check of the intermediate rocker arm 24 is thus carried
out through a washer 40 and a stop ring 42 of the Seeger
® type, both applied in a position opposite that in which the spring 38 is located.
[0018] The angular positioning of the support 34 and, consequently, of the intermediate
rocker arms 24 is carried out through a control eccentric 44 fixedly connected to
a drive shaft 46 supported by the structure of the head (not shown) of the engine.
The camshaft 22 and the seats 48 of each valve 10, 12 are also supported, in a conventional
manner, on the head. The eccentric 44 is engaged by pressure with a control roller
50 hinged onto the support 34. The contact between the eccentric 44 and the control
roller 50 is kept constant thanks to the action of a spring 52, connected to the support
34 and having a fixed reaction point on the head of the engine or on another fixed
component.
[0019] Therefore, according to the position taken up by the eccentric 44 and, consequently,
by the support 34 of the intermediate rocker arms 24, it varies the relative angular
position between the camshaft 22 and the intermediate rocker arms 24 themselves. Such
a variation in the angular position, during the actuation of each valve 10, 12 and
with respect to a predetermined initial position, or start position, shall create
a dephasing of the lift law.
[0020] In addition, again with respect to the start position, it is possible to obtain a
variation of the lever arm with which the intermediate rocker arm 24 actuates the
rocker arm 14 for commanding the valves 10 and 12. By virtue of such an arm variation
there shall be a lift variation of each valve 10, 12.
[0021] The correct sizing of the portions 28a and 28b of each contact surface 28, as well
as of the cams 26 and the relative orientation between the pairs of command and intermediate
rocker arms 14, 24, shall achieve the desired relationship between the variation in
lift and the variation in phase of each valve 10, 12, and without affecting the predetermined
maximum and minimum lift range.
[0022] Figures 7, 8 and 9 show a second example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention. In this example embodiment, the command rocker arm 14 of
each valve 10, 12 lacks the hydraulic clearance recovery mechanism 18. The command
rocker arm 14 is thus pivoted on a pin 54, supported by the structure of the head
or else by another member that is fixed with respect to the engine. The adjustment
of the clearances can be carried out through a suitable calibrated thickness 56 (figure
7) arranged between each valve 10, 12 and the relative command rocker arm 14.
[0023] Figures 10, 11 and 12, on the other hand, show a third example embodiment of the
system for continuously varying the lift and the phase of the valves in an internal
combustion engine according to the present invention. In this example embodiment,
in which there may or may not be the hydraulic clearance recovery mechanism 18, the
angular positioning of the support 34 and of the intermediate rocker arms 24 hinged
onto it takes place through a gearwheel sector 58 applied onto the support 34 itself.
For controlling the variation system, the gearwheel sector 58 is able to operate both
autonomously, and through the interposition of reducing gears.
[0024] Finally, figures 13 to 18 show a fourth example embodiment of the system for continuously
varying the lift and the phase of the valves in an internal combustion engine according
to the present invention, intended in particular for being used on racing engines.
The system illustrated in such figures is conceptually identical to the previous ones,
but it is specifically designed to keep the mass to a bare minimum.
[0025] Each valve 10 and 12 is still directly commanded by the finger rocker arm 14, in
turn actuated by the intermediate rocker arm 24 that receives the motion from the
camshaft 22. Each intermediate rocker arm 24 is thus hinged on the relative pin 32
supported by the support 34.
[0026] In this example embodiment, each finger rocker arm 14 is hinged, at an end thereof,
on a small shaft 60 fixedly connected to the head of the engine, whereas the support
34 of the intermediate rocker arms 24 is again configured in such a way as to be able
to rotate about the camshaft 22. In particular, the support 34 is provided, in addition
to the rotation seat on the camshaft 22, with a further circular surface portion or
raceway 62 concentric to the rotation axis of the camshaft 22 itself. The support
34 can thus rotate about the camshaft 22 making the raceway 62 slide on the circular
portion 44a of the control eccentric 44 that, in this example embodiment, is rigidly
fixed, removably or not, onto the small pivoting shaft 60 of the command rocker arms
14. Therefore, in this particular example embodiment, the small shaft 60, free to
rotate in its own support seat and with respect to the rocker arms 14, also acts as
a drive shaft, thus contributing to reducing the number of components and, therefore,
the mass.
[0027] The rotation of the small shaft 60 pulls with it the control eccentric 44, which
sets the angular position of the support 34 through the effect of the contact of a
portion 44b thereof with a roller 64 (figure 18) hinged onto the support 34 itself.
Therefore, as the angular position of the control eccentric 44 varies, the support
34 shall take up different positions around the camshaft 22 taking the intermediate
rocker arms 24 with it.
[0028] The preloading spring 52, hooked to the support 34 and connected to the structure
of the head or to another fixed member, shall keep the contact between the roller
64 and the control eccentric 44 constant, thus making the adjustment of the position
of the support 34 and, consequently, of the lift and phasing of the valves 10 and
12 stable.
[0029] The correct clearance between the base circle of each cam 26 and the relative intermediate
rocker arm 24 can be adjusted by the screw system 36 of the support 34 that, in this
embodiment, is formed of a single piece and stays in position because it is held by
the contact with the roller 64, by the contact between the raceways 62 and the raceways
44a, and with the housing on the cam axis 22.
[0030] The system illustrated in figures 13 to 18 can also be made in further configurations,
whilst still respecting the same operating principle. For example, the portion 44b
of the control eccentric 44 could be replaced by a small gearwheel, without affecting
the containment function performed by the circular portion 44a of the control eccentric
44 itself. Such a gearwheel could engage with a toothed sector present on the support
34 instead of the roller 64.
[0031] It has thus been seen that the system for continuously varying the lift and the phase
of the valves in an internal combustion engine according to the present invention
achieves the purposes highlighted previously, being able to simultaneously and completely
mechanically vary both the lift and the phase of the valves of an internal combustion
engine.
[0032] The system for continuously varying the lift and the phase of the valves in an internal
combustion engine of the present invention thus conceived can in any case undergo
numerous modifications and variants, all of which are covered by the same inventive
concept; moreover, all of the details can be replaced by technically equivalent elements.
In practice, the materials used, as well as the shapes and sizes, can be whatever
according to the technical requirements.
[0033] The scope of protection of the invention is therefore defined by the attached claims.
1. System for continuously varying the lift and the phase of the valves in an internal
combustion engine of the type comprising at least one camshaft (22) provided with
at least one pair of cams (26), at least one intake valve (10) and at least one discharge
valve (12) each commanded by a rocker arm (14) provided with a roller (16), characterised in that each of said rocker arms (14) is commanded by the respective cam (26) of said camshaft
(22) through the interposition of at least one intermediate rocker arm (24).
2. System according to claim 1, characterised in that at least one first portion (28a) of the contact surface (28) of said intermediate
rocker arm (24) with said roller (16) of each rocker arm (14) has a centre of curvature
coinciding with the rotation axis (C) of said camshaft (22).
3. System according to claim 2, characterised in that said contact surface (28) has at least one second portion (28b) having a different
centre of curvature to said centre of curvature (C) of said at least one first portion
(28a).
4. System according to claim 1, characterised in that each of said intermediate rocker arms (24) is hinged on a pin (32) supported by a
support (34).
5. System according to claim 4, characterised in that said support (34) is hinged on said camshaft (22), with the possibility of rotating
with respect to it.
6. System according to claim 5, characterised in that said support (34) is formed of a top part (34a) and a bottom part (34b) joined together
by means of a plurality of screws (36).
7. System according to claim 4, characterised in that the maintaining of the contact between the roller (30) of each of said intermediate
rocker arms (24) and the relative cam (26) is aided by the action of a spring (38)
fixedly connected to each of said intermediate rocker arms (24).
8. System according to claim 7, characterised in that said spring (38) has a fixed reaction point on said support (34) and is housed on
said support (34).
9. System according to claim 7, characterised in that the axial check of each of said intermediate rocker arms (24) is obtained through
at least one washer (40) and at least one stop ring (42).
10. System according to claim 9, characterised in that said at least one washer (40) and said at least one stop ring (42) are applied in
a position opposite that where said spring (38) is located.
11. System according to claim 4, characterised in that the angular positioning of said support (34) and of said intermediate rocker arms
(24) is carried out through at least one control eccentric (44) fixedly connected
to a drive shaft (46) supported by the structure of the head of said internal combustion
engine.
12. System according to claim 11, characterised in that said control eccentric (44) is engaged by pressure with a control roller (50) hinged
on said support (34).
13. System according to claim 12, characterised in that the contact between said control eccentric (44) and said control roller (50) is kept
constant thanks to the action of a spring (52) connected to said support (34) and
having a fixed reaction point on said head of said internal combustion engine.
14. System according to claim 1, characterised in that the clearances of each of said valves (10, 12) can be controlled through a hydraulic
recovery mechanism (18).
15. System according to claim 14, characterised in that between each of said valves (10, 12) and the respective rocker arm (14) at least
one capsule or tablet (20) is arranged to adjust the clearances.
16. System according to claim 1, characterised in that the clearances of each of said valves (10, 12) can be controlled through a calibrated
thickness (56) arranged between each of said valves (10, 12) and the respective rocker
arm (14).
17. System according to claim 4, characterised in that the angular positioning of said support (34) and of said intermediate rocker arms
(24) is carried out through at least one gearwheel sector (58) applied onto said support
(34).
18. System according to claim 17, characterised in that said gearwheel sector (58) is able to operate through the interposition of reducing
gears.
19. System according to claim 4, characterised in that each of said rocker arms (14) is hinged, at an end thereof, on a small shaft (60)
fixedly connected to the head of said internal combustion engine.
20. System according to claim 19, characterised in that said support (34) is provided, as well as the rotation seat on said camshaft (22),
with a further circular surface portion or raceway (62) concentric to the rotation
axis of said camshaft (22).
21. System according to claim 20, characterised in that said support (34) rotates around said camshaft (22) making said raceway (62) slide
on the circular portion (44a) of a control eccentric (44) rigidly fixed on said small
shaft (60).
22. System according to claim 21, characterised in that the rotation of said small shaft (60) pulls said control eccentric (44) with it,
which sets the angular position of said support (34) through the effect of the contact
of a portion (44b) of said control eccentric (44) with a roller (64) hinged onto said
support (34).