U.S. patent application number 12/753391 was filed with the patent office on 2010-10-07 for valve drive of an internal combustion engine.
This patent application is currently assigned to SCHAEFFLER TECHNOLOGIES GMBH & CO. KG. Invention is credited to Harald Elendt, Andreas Nendel.
Application Number | 20100251982 12/753391 |
Document ID | / |
Family ID | 42675222 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100251982 |
Kind Code |
A1 |
Elendt; Harald ; et
al. |
October 7, 2010 |
VALVE DRIVE OF AN INTERNAL COMBUSTION ENGINE
Abstract
A valve drive (1, 1') of an internal combustion engine with
stroke-variable gas-exchange valve activation is provided. The
valve drive includes a camshaft (2, 2') with a carrier shaft (3)
and a cam piece (4, 4') that is arranged in a rotationally locked
way on the carrier shaft and that can move between axial positions
and that has a cam group of directly adjacent cams (14a-c, 15a-c)
with different lobes and a groove-shaped axial link (16, 16') and
an activation element (18, 19) that can be coupled in the axial
link for shifting the cam piece on the carrier shaft. The cam piece
is provided with a bearing journal (12, 13, or 12') on which the
camshaft is supported in the radial direction at a camshaft bearing
point (9, 10, or 9') of the internal combustion engine. Here, the
axial link is constructed overlapping with the camshaft bearing
point on the bearing journal in the axial direction, and the
activation element runs in the camshaft bearing point.
Inventors: |
Elendt; Harald; (Altendorf,
DE) ; Nendel; Andreas; (Hessdorf, DE) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
UNITED PLAZA, 30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
SCHAEFFLER TECHNOLOGIES GMBH &
CO. KG
Herzogenaurach
DE
|
Family ID: |
42675222 |
Appl. No.: |
12/753391 |
Filed: |
April 2, 2010 |
Current U.S.
Class: |
123/90.18 |
Current CPC
Class: |
F01L 2001/0473 20130101;
F01L 2013/0052 20130101; F01L 1/047 20130101; F01L 13/0036
20130101; F01L 13/0005 20130101 |
Class at
Publication: |
123/90.18 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2009 |
DE |
10 2009 016 463.4 |
Claims
1. A valve drive of an internal combustion engine with
stroke-variable gas-exchange valve activation, comprising a
camshaft with a carrier shaft and a cam piece that is arranged in a
rotationally locked manner on the carrier shaft and is moveable
between axial positions and that has a cam group of directly
adjacent cams with different lobes and a groove-shaped axial link,
an activation element that is coupleable in the axial link for
shifting the cam piece on the carrier shaft, the cam piece is
provided with a bearing journal on which the camshaft is supported
in a radial direction at a camshaft bearing point of the internal
combustion engine, the axial link is constructed overlapping with
the camshaft bearing point on the bearing journal in an axial
direction, and the activation element runs in the camshaft bearing
point.
2. The valve drive according to claim 1, wherein the bearing
journal with the camshaft bearing point forms a sliding bearing,
the bearing journal has sliding surface sections on both sides of
the axial link in the axial direction.
3. The valve drive according to claim 1, wherein a bearing diameter
of the bearing journal is larger than a surrounding diameter of the
cam lying closest to the bearing journal, and the cam lying closet
to the bearing journal and the camshaft bearing point overlap in
the axial direction in one of the axial positions of the cam
piece.
4. The valve drive according to claim 1, wherein the cam piece has
two of the bearing journals that are constructed on axial end
sections thereof and two cam groups are arranged between the
bearing journals.
5. The valve drive according to claim 1, wherein the cam piece has
two of the cam groups constructed on axial end sections thereof and
the bearing journal consists of a single bearing journal arranged
between the cam groups.
6. The valve drive according to claim 1, wherein the cam piece
includes a single one of the axial links that is constructed in a
bidirectional way with two connecting paths running in an opposite
sense in the axial direction.
7. The valve drive according to claim 6, wherein the two connecting
paths are arranged one next to the other in a peripheral direction
of the bearing journal and cross one another in a middle area.
8. The valve drive according to claim 6, wherein the two connecting
paths are arranged one behind the other in a peripheral direction
of the bearing journal, and each starting point of one of the
connecting paths is adjacent to an end point of the other of the
connecting paths.
9. The valve drive according to claim 1, wherein there are three
directly adjacent cams for each of the cam groups and two
activation elements that are coupleable alternately in the same
axial link.
10. The valve drive according to claim 9, wherein one of the three
cams is free of lobes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of German Patent
Application No. 10 2009 016 463.4, filed Apr. 4, 2009, which is
incorporated herein by reference as if fully set forth.
[0002] 1. Field of the Invention
[0003] The invention relates to a valve drive of an internal
combustion engine with stroke-variable gas-exchange valve
activation. The valve drive comprises a camshaft with a carrier
shaft and a cam piece that is arranged in a rotationally locked
manner on the carrier shaft and that can move between axial
positions and that has a cam group of directly adjacent cams with
different lobes and a groove-shaped axial link extending on the
outer periphery and an activation element that can be coupled in
the axial link for shifting the cam piece on the carrier shaft. The
cam piece is provided with a bearing journal on which the camshaft
is supported in the radial direction at a camshaft bearing point of
the internal combustion engine.
[0004] 2. Background of the Invention
[0005] The stroke variability of such a valve drive is based in a
known way on a cam piece with cams that are directly arranged on
this cam piece and whose different lobes are transferred
selectively onto a gas-exchange valve by a conventional, rigidly
constructed cam follower. For the operating-point-dependent
activation of each lobe, the cam piece is arranged on a carrier
shaft in a rotationally locked way but can move between two or more
axial positions and has axial connecting paths running in the
opposite sense in the form of spiral grooves. The shifting of the
cam piece is realized according to the construction of the
connecting paths by one or more activation elements that are
coupled selectively in the spiral grooves. The axial profile of the
spiral groove engaged with the activation element has the result
that, during the common (lobe-free) base-circle phase of the cam of
a cam group, the cam piece is shifted in a self-controlled and
camshaft-angle-true way from one axial position to the next. The
radial profile of one spiral groove is usually shaped so that this
becomes increasingly flatter at the end of a shifting process and
shifts the currently engaged activation element into its disengaged
rest position.
[0006] Among other things, a valve drive according to the class
with two-stage stroke variability emerges from DE 101 48 179 A1.
One essential property of this valve drive is that the individual
cam pieces are provided with bearing journals that are supported in
a sliding manner both in the radial and also axial directions at
associated camshaft bearing points of the internal combustion
engine. Accordingly, the camshaft bearing of the valve drives
disclosed in DE 101 48 177 A1 and DE 10 2004 022 832 A1 is realized
directly on the carrier shafts. In this case, while the length of a
cam piece is definitely defined by the number of cams and the
connecting paths, as well as their spatial arrangement relative to
each other, in the first case, the length of the bearing journal or
possibly the length of the bearing journals is also to be taken
into account. Under consideration of various structural parameters
of the internal combustion engine, in particular, the cylinder and
gas-exchange valve spacing, the number and width of the cams, and
also the middle or end camshaft bearing position with respect to a
cylinder, however, the required length of the cam piece quickly
conflicts with the installation space available for this piece.
This applies to an elevated degree for three-stage stroke
variability.
SUMMARY
[0007] Therefore, the present invention is based on the objective
of refining a valve drive of the type named above so that the cam
piece is constructed with the most compact possible structure in
the axial direction, so that the valve drive not only can be used
widely also in small-volume internal combustion engines, but there
is also a high potential for stroke variability with more than two
stages, in particular, three stages.
[0008] The objective is met with the arrangement according to the
invention, while advantageous refinements and constructions of the
invention are also provided. Accordingly, the axial link should be
constructed overlapping with the camshaft bearing point on the
bearing journal in the axial direction, wherein the activation
element runs in the camshaft bearing point. In other words, the
idea forming the basis of the invention provides that the spatial
separation of the bearing journal and axial link is to be
eliminated and these are to be "fused" with each other in the axial
direction, in order to be able to reduce the axial structural space
of the cam piece accordingly and/or in order to be able to provide
the cam group with an additional cam.
[0009] With respect to the stability and durability of the camshaft
bearing, which is obviously still to be guaranteed, in one
refinement of the invention it is provided that the bearing journal
with the camshaft bearing point forms a sliding bearing, wherein
the bearing journal has sliding surface sections on both sides of
the axial link in the axial direction.
[0010] In addition, the bearing diameter of the bearing journal
should be larger than the surrounding diameter of the cam lying
closest to the bearing journal, wherein this cam and the camshaft
bearing point overlap in the axial direction in one of the axial
positions of the cam piece. The insertion of the cam group made
possible in this manner into the camshaft bearing point is
especially preferred or even necessary when the cam piece has two
cam groups for activating two gas-exchange valves that are arranged
with a small spacing relative to the camshaft bearing point and
when, in addition, a three-stage stroke variability is provided
with three cams for each cam group.
[0011] With respect to the bearing arrangement of the camshaft, the
cam piece should have two bearing journals constructed on its axial
end sections and two cam groups arranged between the bearing
journals. This bearing arrangement correlates with camshaft bearing
points that are arranged between the cylinders of an internal
combustion engine with multi-valve technology. Unidirectional axial
links with a single connecting path according to DE 101 48 179 A1
cited above could be provided on both bearing journals in which
activation elements running in both associated camshaft bearing
points can be coupled.
[0012] In an alternative construction of the invention hereto, the
cam piece should have two cam groups constructed on its axial end
sections and only one bearing journal arranged between the cam
groups. This bearing arrangement correlates with camshaft bearing
points that are arranged between the gas-exchange valves of a
cylinder of an internal combustion engine with multi-valve
technology.
[0013] In addition, it is provided that the cam piece has exactly
one axial link that has a bidirectional construction with two
connecting paths running in the opposite sense in the axial
direction. One construction of such an axial link is already known
from DE 101 48 177 A1 cited above: here the two connecting paths
are arranged one next to the other in the peripheral direction of
the bearing journal and cross in their middle. The essential
advantage relative to the spatially separated, unidirectional
connecting paths consists, on one hand, in the comparatively small,
axial structural space requirements for the axial link and, on the
other hand, in that a single activation element is sufficient for
both directions of movement.
[0014] This also applies for a bidirectional axial link according
to an alternative second construction. In this case, the two
connecting paths should be arranged one behind the other in the
peripheral direction of the bearing journal, wherein each starting
point of one of the connecting paths is adjacent to the end point
of the other connecting path. The kinematics of such an axial link
emerges in detail from DE 10 2009 009 080 A1 of the applicant,
which is not a prior publication, whose entire contents are
incorporated herein by reference as if fully set forth.
[0015] In addition, the two constructions named above allow a
comparatively easily performed expansion of the stroke variability
from two to three stages in that two activation elements are
coupled selectively in the bidirectional axial links. This is
disclosed in detail in DE 10 2007 051 739 A1 of the applicant,
which is also not a prior publication, for the construction with
crossing connecting paths. The entire contents of that publication
are also incorporated herein by reference as if fully set
forth.
[0016] In the case of three-stage stroke variability, it is
provided that one of the three cams of a cam group is free of
lobes. This cam involves a so-called base-circle cam that leads to
the shutdown of the gas-exchange valve due to its purely
cylindrical shape.
[0017] The features and constructions of the invention should also
be capable of being combined with each other arbitrarily as far as
possible and useful.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Additional features of the invention emerge in the following
description and from the drawings in which embodiments of the
invention are shown partially simplified. If not mentioned
differently, here identical or functionally identical features or
components are provided with identical reference symbols. Shown
are:
[0019] FIG. 1 is a perspective, assembled view of cutout section of
a cylinder head of an internal combustion engine with a first
construction of a valve drive according to the invention;
[0020] FIG. 2 is the view of FIG. 1 without camshaft bearing
cover;
[0021] FIG. 3 is a perspective, longitudinal cross-sectional view
of the arrangement according to FIGS. 1 and 2;
[0022] FIG. 4 is a first perspective view of the axial link
according to FIGS. 1 to 3;
[0023] FIG. 5 is a second (ca. 180.degree. rotated) perspective
view of the axial link according to FIG. 4;
[0024] FIG. 6 is perspective view of a cutout section of a cylinder
head of an internal combustion engine with a second construction of
a valve drive according to the invention;
[0025] FIG. 7 is a perspective view of the cutout section from FIG.
6 without the camshaft bearing cover;
[0026] FIG. 8 is a perspective, detailed partial view of the cam
piece according to FIGS. 6 and 7;
[0027] FIG. 9 is a first perspective view of the axial link
according to FIGS. 6 to 8;
[0028] FIG. 10 is a second (ca. 120.degree. rotated) perspective
view of the axial link according to FIG. 9; and
[0029] FIG. 11 is a third (ca. 240.degree. rotated) perspective
view the axial link according to FIG. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] In FIGS. 1 to 3, a cutout section of a valve drive 1 of an
internal combustion engine that is essential for understanding the
invention is disclosed with stroke-variable gas-exchange valve
activation and four-valve technology. A component that is central
to the function of the valve drive 1 is a camshaft 2 that comprises
a carrier shaft 3 and also cam pieces 4 that are arranged in a
rotationally locked way on the carrier shaft and that can move
between three axial positions--corresponding to the number of
cylinders of the internal combustion engine. For the purpose of
axial shifting, the carrier shaft 3 is provided with outer
longitudinal teeth and each cam piece 4 is provided with
corresponding inner longitudinal teeth. The teeth 5 and 6 can be
seen in FIGS. 3 and 8. The intermediate spaces that can be seen
between the axial end sections 7 and 8 allow the separate shifting
of the cam pieces 4 in sync with the ignition sequence of the
internal combustion engine into an adjacent axial position. The
radial bearing of the camshaft 2 is realized in camshaft bearing
points 9 and 10 that are arranged, in this embodiment, between the
cylinders of the internal combustion engine. The cam followers 11
that can be seen between the camshaft bearing points 9, 10 activate
the two intake valves of a cylinder not shown here.
[0031] As emerges from FIG. 2--the same cutout section is shown as
in FIG. 1, but without the top camshaft bearing cover--the cam
piece 4 is provided on its end sections 7, 8 with bearing journals
12 and 13 of different widths that are supported in a sliding way
both in the radial and also axial directions on the inner lateral
surfaces of the camshaft bearing points 9, 10. Cam groups running
between the bearing journals 12, 13 each include three directly
adjacent cams 14a-c and 15a-c that have different lobes for the
same base-circle radius. These are transmitted to the gas-exchange
valves by the cam follower 11 selectively, i.e., as a function of
the instantaneous axial position of the cam piece 4. The different
lobes are to be understood as different magnitudes of each cam
stroke and/or different valve control times of the cams 14a-c and
15a-c. For example, the cams 14a and 15a involve so-called
base-circle cams that are free of lobes and that each lead to
shutdown of the gas-exchange valve.
[0032] The shifting of the cam piece 4 between its axial positions
is realized outside of the lobes during the common base-circle
angle of the cams 14a-c and 15a-c. The functional principle known,
in principle, for example, from DE 101 48 179 A1 cited above for
the actuator mechanism required here touches upon a groove-shaped
axial link 16 on the cam piece 4 and an activation element in the
form of a cylindrical actuator pin that is arranged fixed in
position in the axial direction relative to the camshaft 2 but can
move in the radial direction toward the camshaft 2 in the internal
combustion engine and can be coupled in the axial link 16 for the
purpose of shifting the cam piece 4.
[0033] The current used actuator 17 that can be seen only hidden in
FIGS. 1 and 2 emerges more clearly from the longitudinal cutout in
FIG. 3. The actuator 17 comprises two actuator pins 18 and 19 that
are spaced apart with a cam width and that are driven selectively
out from a common actuator housing by an electromagnetically
activated locking mechanism and that are alternately coupled in the
single axial link 16 for each cam piece 4. The structural
configuration of this actuator 17 emerges in detail from DE 10 2009
010 949 A1 of the applicant, which is not a prior publication,
whose entire contents are also incorporated herein by reference as
if fully set forth.
[0034] The axial link 16 shown in FIGS. 4 and 5 as details from two
opposite perspective views is constructed with bidirectional action
with two connecting paths 20 and 21 running in opposite sense in
the axial direction, wherein the two connecting paths 20, 21 are
arranged one next to the other in the peripheral direction and
cross in their middle. While such an axial link 16 is known in
principle, the connecting paths 20, 21 in the present embodiment
are offset in height relative to each other in the radial
direction, in order to generate two-sided positive guidance of the
coupled actuator pin 18 or 19 along the connecting path 20 that is
lower in the radial direction. In this way, also for a lower
camshaft rotational speed and a correspondingly lower axial mass
inertia of the cam piece 4 whose shifting process along the
connecting path 20 lower in the radial direction can be completed
after passing the crossing point.
[0035] Concerning the functioning of the actuator mechanism:
coupling of the actuator pin 18 in the connecting path 20 leads to
a shift of the cam piece 4 to the left (in FIG. 3) and--starting
from its shown axial position in which the cam followers 11 are
loaded by the middle cams 14b and 15b--to an activation of the cams
14c and 15c. Conversely, coupling of the actuator pin 19 in the
connecting path 21 leads to a shift of the cam piece 4 to the right
and--starting from the shown axial position--to an activation of
the cams 14a and 15a. Two coupling processes of the same actuator
pin 18 or 19 immediately following each other lead to a back and
forth shifting of the cam piece 4 into the original axial position.
In contrast, alternating coupling processes of the actuator pins 18
and 19 immediately following each other in the same connecting path
20 or 21 leads to a rectified shift of the cam piece 4 about two
axial positions. Thus, for setting the three axial positions of the
cam piece 4, only one actuator 17 with the two actuator pins 18 and
19 and one axial link 16 are required.
[0036] The cam piece 4 is secured against uncontrolled shifting in
its axial position by a locking device. The known locking device
not shown here in detail comprises a spring-loaded pressure piece
22 that is supported in a cross borehole 23 of the carrier shaft 3
and--according to the axial position of the cam piece 4--engages in
one of three peripheral grooves 24, 25, and 26 on the inner
periphery of the cam piece 4.
[0037] The actuator 17 runs according to the invention within the
axial longitudinal extent of the camshaft bearing point 9. This
means that its inner lateral surface is cut from a borehole for
holding the actuator 17 and the axial link 16 constructed on the
periphery of the bearing journal 12 and the camshaft bearing point
9 overlap in the axial direction. Sliding surface sections 27 and
28 on both sides of the axial link 16 are used for forming the
sliding bearing of the bearing journal 12 in the camshaft bearing
point 9. The bearing journal 13 is constructed significantly more
narrowly and as a complete cylinder relative to the bearing journal
12 with the axial link 16 running on this journal.
[0038] An alternative construction of a stroke-variable valve drive
1' emerges from FIGS. 6 to 8, wherein the following statements are
largely limited to the structural differences with the valve drive
1. For the valve drive 1', the camshaft bearing points 9' are not
located between the cylinders, but instead between the gas-exchange
valves 29 of a cylinder. Accordingly, the two cam groups with the
cams 14a-c and 15a-c are arranged on the two end sections 7, 8 of
the cam piece 4' that has only one bearing journal 12' running
in-between for the radial bearing of the camshaft 2' in the
associated camshaft bearing point 9'. The actuator 17 known from
FIGS. 1 to 3 is held in this case in the top camshaft bearing cover
30.
[0039] Both valve drives 1' and 1 have in common that the
gas-exchange valves 29 and thus also the cam followers 11 run
spaced closely apart to the camshaft bearing point or points 9' or
9 and 10. The axial free travel of the cam groups required for the
three-stage stroke variability relative to the camshaft bearing
point 9' is created such that according to the axial position of
the cam piece 4', the cam groups with their cams 14a and 15c lying
closest to the bearing journal 12' are inserted into the camshaft
bearing point 9'. In the axial position of the cam piece 4' shown
in FIG. 7, the gas-exchange valves 29 are instantaneously loaded by
the cams 14c and 15c, while the base-circle cam 14a and the
camshaft bearing point 9' overlap in the axial direction. The
opposite axial position of the cam piece 4' here with the then
effective base-circle cams 14a and 15a equally requires an
insertion of the cam 15c into the camshaft bearing point 9'.
[0040] As is clear in FIG. 8, the axial free travel of the cam
groups relative to the camshaft bearing point 9' is produced
structurally such that the bearing diameter of the bearing journal
12' is larger than the surrounding diameter 31 drawn with dotted
lines of the cam 15c lying closest to the bearing journal 12' and
is also larger than the base-circle diameter of the cam 14a. This
geometric construction occurs with respect to the cams 14c and 15a
in a corresponding way for the valve drive 1 according to FIGS. 1
to 5.
[0041] The axial link 16' constructed on the periphery of the
bearing journal 12' is likewise constructed with bidirectional
action with two connecting paths 20' and 21' running in the
opposite sense in the axial direction and is limited on both sides
by the sliding surface sections 27, 28 that form a sliding bearing
with the camshaft bearing point 9'. Relative to the axial link 16,
however, the connecting paths 20', 21' are not arranged one next to
the other with identical starting and end points, but are instead
arranged one behind the other in the peripheral direction of the
bearing journal 12'. As becomes clear from FIGS. 9 to 11 with an
axial link 16' each rotated by approximately 120.degree., the
starting point 32 of the connecting path 20' is adjacent to the end
point 33 of the connecting path 21', and the starting point 34 of
the connecting path 21' is adjacent to the end point 35 of the
connecting path 20'. Also, in this case, for switching between the
three axial positions of the cam piece 4', two actuator pins 18, 19
spaced apart by a cam width are sufficient (see FIG. 3) that are
coupled alternately in this axial link 16' corresponding to the
previous explanation. The camshaft angle available for the shifting
of the cam piece 4' is indeed significantly smaller relative to the
axial link 16 with the crossing connecting paths 20, 21, but there
is a significant advantage in the continuous positive guidance of
each coupled actuator pin 18 or 19, so that secure shifting of the
cam piece 4' is also possible without its supporting mass inertia,
i.e., for the smallest camshaft rotational speeds.
LIST OF REFERENCE SYMBOLS
[0042] 1. Valve drive
[0043] 2. Camshaft
[0044] 3. Carrier shaft
[0045] 4. Cam piece
[0046] 5. Outer longitudinal teeth
[0047] 6. Inner longitudinal teeth
[0048] 7. Axial end section of the cam piece
[0049] 8. Axial end section of the cam piece
[0050] 9. Camshaft bearing point
[0051] 10. Camshaft bearing point
[0052] 11. Cam follower
[0053] 12. Bearing journal
[0054] 13. Bearing journal
[0055] 14. Cam group with cams 14a-c
[0056] 15. Cam group with cams 15a-c
[0057] 16. Axial link
[0058] 17. Actuator
[0059] 18. Actuator pin/activation element
[0060] 19. Actuator pin/activation element
[0061] 20. Connecting path
[0062] 21. Connecting path
[0063] 22. Pressure piece
[0064] 23. Cross borehole of the carrier shaft
[0065] 24. Circumferential groove
[0066] 25. Circumferential groove
[0067] 26. Circumferential groove
[0068] 27. Sliding surface section
[0069] 28. Sliding surface section
[0070] 29. Gas-exchange valve
[0071] 30. Camshaft bearing cover
[0072] 31. Surrounding diameter
[0073] 32. Starting point of one connecting path
[0074] 33. End point of the other connecting path
[0075] 34. Starting point of the other connecting path
[0076] 35. End point of one connecting path
* * * * *