U.S. patent application number 14/440996 was filed with the patent office on 2015-10-22 for camshaft for a variable-stroke exchange valve train.
This patent application is currently assigned to Schaeffler Technologies AG & Co. KG. The applicant listed for this patent is Schaeffler Technologies AG & Co. KG. Invention is credited to Andreas Wedel.
Application Number | 20150300216 14/440996 |
Document ID | / |
Family ID | 49765242 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150300216 |
Kind Code |
A1 |
Wedel; Andreas |
October 22, 2015 |
CAMSHAFT FOR A VARIABLE-STROKE EXCHANGE VALVE TRAIN
Abstract
A camshaft of a sliding cam valve train in an internal
combustion engine is provided. A cam piece (2), which has cam
strokes of different lengths and can be displaced on a carrier
shaft (1), is mounted on a rolling bearing at a camshaft bearing
point (12) of the internal combustion engine. The outer race (16)
of the rolling bearing (13) is formed by a one-piece bearing ring
(17) which surrounds the cam piece and said race is smaller than a
revolution radius of the longer stroke h2.
Inventors: |
Wedel; Andreas; (Emskirchen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schaeffler Technologies AG & Co. KG |
Herzogenaruach |
|
DE |
|
|
Assignee: |
Schaeffler Technologies AG &
Co. KG
Herzogenaurach
DE
|
Family ID: |
49765242 |
Appl. No.: |
14/440996 |
Filed: |
October 25, 2013 |
PCT Filed: |
October 25, 2013 |
PCT NO: |
PCT/DE2013/200245 |
371 Date: |
May 6, 2015 |
Current U.S.
Class: |
123/90.18 |
Current CPC
Class: |
F01L 2001/0476 20130101;
F01L 2303/00 20200501; F01L 1/08 20130101; F01L 2013/0052 20130101;
F01L 13/0036 20130101; F01L 2001/0473 20130101 |
International
Class: |
F01L 13/00 20060101
F01L013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2012 |
DE |
10 2012 220 210.2 |
Claims
1. A camshaft of a variable stroke gas exchange valve train of an
internal combustion engine, comprising a carrier shaft and a cam
part that is supported locked in rotation and axially displaceable
on the carrier shaft and has at least one first cam group of at
least two directly adjacent cams with different strokes (h1, h2)
and an axial connecting link in which an actuation element is
couplable for shifting the cam part on the carrier shaft, and a
bearing journal that runs between the first cam group and the axial
connecting link and on which a roller bearing supporting the cam
part is held so that for rotation at a camshaft bearing point of
the internal combustion engine, an inner raceway of the roller
bearing is formed by the bearing journal, an outer raceway of the
roller bearing is formed by a one-part bearing ring, and the cam
part and the bearing ring have the following geometric properties:
a) h.sub.1<h.sub.2 b) max {r.sub.HK;
r.sub.GK+h.sub.1}<r.sub.L<r.sub.GK+h.sub.2 c)
r.sub.L<r.sub.AK where h.sub.1=the stroke of the cam adjacent to
the bearing journal in the first cam group, h.sub.2=the stroke of
the other cam of the first cam group, r.sub.HK=a common enveloping
circle radius of the cams of the first cam group, r.sub.GK=a base
circle radius of the cams of the first cam group, r.sub.L=a radius
of the outer raceway, and r.sub.AK=a circumferential radius of the
axial connecting link.
2. The camshaft according to claim 1, wherein the roller bodies of
the roller bearing are held in a roller bearing cage that is open
on a periphery.
3. The camshaft according to claim 2, wherein the bearing journal
has a radial step with a raised inner raceway, and at least one end
sides of the radial step supports the roller bearing cage
axially.
4. The camshaft according to claim 2, wherein the cam part has a
second cam group of at least two directly adjacent cams with
different strokes (h.sub.1, h.sub.2), wherein at least one end side
facing each other of the cams adjacent to the bearing journal in
the cam groups supports the roller bearing cage axially.
5. The camshaft according to claim 4, wherein the cam end sides
directly support the roller bearing cage axially.
6. The camshaft according to claim 4, wherein at least one of the
cam end sides supports the roller bearing cage axially by a spacer
ring that is open on a periphery.
Description
BACKGROUND
[0001] The invention relates to a camshaft of a variable stroke gas
exchange valve train of an internal combustion engine. The camshaft
comprises a carrier shaft and a cam part that is supported locked
in rotation and axially displaceable on the carrier shaft and has
at least one first cam group of at least two directly adjacent cams
with different strokes and an axial connecting link in which an
actuation element for shifting the cam part on the carrier shaft
can be coupled, as well as a bearing journal that runs between the
first cam group and the axial connecting link and on which a roller
bearing supporting the cam part is held so that it can rotate in a
camshaft bearing point of the internal combustion engine.
[0002] A gas exchange valve train which is also often called a
sliding cam valve train with such a camshaft is known from DE 10
2009 030 373 A1. The cam parts supported with a central bearing
journal between two intake or exhaust valves of an engine cylinder
comprise two identical cam groups each with three cams and an
end-side axial connecting link in which two actuation pins for
shifting the cam part into the three axial positions can be coupled
selectively. The publication alternatively proposes a roller
bearing for the cam part in addition to the hydrodynamic sliding
bearing.
[0003] Despite the three-stage stroke variability, the known valve
train has a very compact axial construction. This is achieved in
that the cams adjacent to the bearing journals can dip into the
camshaft bearing point when they are not instantaneously active. A
geometric requirement here is a corresponding dimensioning of the
rotational bearing, whose diameter must be greater than the
surrounding circle of the cams entering within this circle. In the
case of a roller bearing of the cam part, this dimensioning would,
however, lead to a camshaft bearing point with an undesirably large
radial construction.
SUMMARY
[0004] The present invention is based on the objective of improving
a camshaft of the type noted above such that, despite the roller
bearing of the cam part, it allows the most compact radial
construction possible.
[0005] This objective is met in that the inner raceway of the
roller bearing is formed by the bearing journal, the outer raceway
of the roller bearing is formed by a one-part bearing ring, and the
cam part and the bearing ring have the following geometric
properties:
a) h.sub.1<h.sub.2
b) max {r.sub.HK;
r.sub.GK+h.sub.1}<r.sub.L<r.sub.GK+h.sub.2
c) r.sub.L<r.sub.AK
[0006] Where:
[0007] h.sub.1=Stroke of the cam adjacent to the bearing journal in
the first cam group
[0008] h.sub.2=Stroke of the other cam of the first cam group
[0009] r.sub.HK=Common enveloping circle radius of the cams of the
first cam group
[0010] r.sub.GK=Base circle radius of the cams of the first cam
group
[0011] r.sub.L=Radius of the outer raceway
[0012] r.sub.AK=Circumferential radius of the axial connecting
link
[0013] These geometric relationships allow the radius r.sub.L of
the outer raceway to be less than the circumferential radius
r.sub.GK+h.sub.2 of the large stroke h.sub.2 but nevertheless the
one-part bearing ring can be mounted on the bearing journal past
the cams. The installation is performed such that the bearing ring
is first threaded into a position on the cams eccentric to the
rotational axis of the cam part and then centered on the rolling
bodies in the area of the bearing journal. The rolling bodies are
advantageously held in a roller body cage that is open on the
periphery and is mounted on the bearing journal before installation
of the bearing ring in the elastically expanded state.
Alternatively, a multiple-part cage could also be used.
[0014] The invention could also be used in non-variable,
roller-supported standard camshafts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Additional features of the invention come from the following
description and drawings, in which the geometric relationships
specified above are illustrated and explained in more detail using
embodiments. If not mentioned otherwise, identical or functionally
identical features or components are provided with identical
reference numbers. The hundreds place of three digit reference
numbers refers to the figure number. Shown are:
[0016] FIG. 1 a known variable stroke gas exchange valve train,
[0017] FIG. 2 a first embodiment of a cam part according to the
invention in perspective view,
[0018] FIGS. 2a-e the first cam part in different mounting
positions of the bearing ring,
[0019] FIG. 3 the geometry of a cam part according to the invention
in schematic view A according to FIG. 2,
[0020] FIG. 4 a second embodiment of a cam part according to the
invention in perspective view,
[0021] FIGS. 4a-f the second cam part from FIG. 4 in different
mounting positions of the bearing ring,
[0022] FIG. 5 a third embodiment of a cam part according to the
invention in longitudinal section,
[0023] FIG. 6 a fourth embodiment of a cam part according to the
invention in longitudinal section,
[0024] FIG. 7 a fifth embodiment of a cam part according to the
invention in longitudinal section.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The invention will be explained starting from FIG. 1, which
shows a three-stage variable stroke gas exchange valve train of an
internal combustion engine. The basic functional principle of this
known valve train can be summarized in that a conventionally rigid
camshaft is replaced by a camshaft with a carrier shaft 1 with
external teeth and--cam parts 102 arranged locked in rotation on
this carrier shaft--corresponding to the number of cylinders of the
internal combustion engine--and displaceable between three axial
positions. Each cam part has two identical groups of directly
adjacent cams 103 to 105 that have different strokes with identical
reference circle radii. The cam lift is performed by roller cam
followers 6 that transfer the cam travels selectively to gas
exchange valves 7.
[0026] The displacement of the cam part 102 required for operating
point-dependent activation of each cam 103, 104, or 105 on the
carrier shaft 1 is realized by a groove-shaped axial connecting
link 108 in which, depending on the instantaneous axial position of
the cam part, one of two pin-shaped actuation elements 9, 10 of an
electromagnetic actuator (not shown) is coupled, in order to
displace the cam part within the common reference circle phase of
the cam. To stabilize the cam part in the axial positions, a
locking device is used that runs (not visible here) in the interior
of the carrier shaft 1 and locks in the interior of the cam
part.
[0027] For the radial support of the camshaft in the internal
combustion engine, the cam part 102 is provided between the two cam
groups with a bearing journal 111 that is supported so that it can
rotate in a camshaft bearing point 12 arranged locked in position
and cylindrically centered in the internal combustion engine. This
is a split camshaft bearing point with a screwed-on bearing cover
not shown here. Shown is a hydrodynamic sliding bearing of the
bearing journal in the camshaft bearing point, wherein the bearing
could also be formed in a known way as a roller bearing.
[0028] FIG. 2 shows a first embodiment of a cam part 202 for a
two-stage variable stroke gas exchange valve, wherein the bearing
journal 211 of the cam part is enclosed by a roller bearing 213 in
a way according to the invention. Differently than in the known cam
part 102 in FIG. 1, the cam strokes of the first cam group arranged
at a distance to the axial connecting link 208 are oriented so that
the stroke h.sub.1 of the one cam 203 adjacent to the bearing
journal is smaller than the stroke h.sub.2 of the other cam 204.
For this first cam group, the following relationship is then
applicable:
a) h.sub.1<h.sub.2 (see also FIG. 3)
[0029] The cutaway and greatly simplified roller bearing 213 is a
needle bearing with cage-supported needles 214, whose inner raceway
215 is formed by the bearing journal 211 and whose outer raceway
216 is formed by a one-part bearing ring 217 drawn onto the cam
part 202. The plastic needle cage 218 is shown as needle ring 19
below in connection with the needles held therein, i.e., as 219 in
FIG. 2. The width of the bearing ring 217 is approximately twice as
large as the length of the needles 214 that roll, depending on the
axial position of the cam part, either in one axial raceway half or
in the other axial raceway half of the bearing ring mounted in the
internal combustion engine.
[0030] FIG. 3 illustrates the geometric radii or diameter
relationships on the cam part 202 (cam parts 402 to 702
accordingly) that are projected according to view A in FIG. 2 in
the plane of the sheet. The two cams 203 and 204 have a common
enveloping circle with radius r.sub.HK that encloses the same
reference circle radius r.sub.GK and the two different strokes
h.sub.1 and h.sub.2 of this cam. In the shown case, however, the
smaller stroke h.sub.1 runs, with respect to its angular position,
not completely within the larger stroke h.sub.2, and the
circumferential radius r.sub.GK+h.sub.1 of the cam 203 rotating
about the camshaft axis 20 is greater than the common enveloping
circle radius r.sub.HK. The smallest possible radius r.sub.L of the
outer raceway 216 for the installation of the bearing ring 217 is
now generally the larger value of these two radii r.sub.GK+h.sub.1
and r.sub.HK, so that the following relationship is also
applicable:
b1) max {r.sub.HK; r.sub.GK+h.sub.1}<r.sub.L
[0031] On the other hand, in order to keep the radial installation
space of the cam part 202 with the needle bearing 213 as small as
possible, the relationship, according to which the outer raceway
radius r.sub.L is smaller than the revolution radius of the greater
cam 204 about the camshaft axis 20, is also applicable:
b2) r.sub.L<r.sub.GK+h.sub.2
[0032] Example calculation for the outer raceway radius r.sub.L for
the cam geometry according to FIG. 3:
[0033] From
[0034] r.sub.GK: 15.0 mm
[0035] h.sub.1: 6.4 mm
[0036] h.sub.2: 11.3 mm
[0037] gives
[0038] r.sub.HK: 20.6 mm
[0039] r.sub.GK+h.sub.1: 21.4 mm
[0040] max {r.sub.HK; r.sub.GK+h.sub.1}=21.4 mm
[0041] r.sub.GK+h.sub.2: 26.3 mm
[0042] and the following size relationship is applicable for the
outer raceway radius:
[0043] 21.4 mm<r.sub.L<26.3 mm
[0044] The drawing of the bearing ring 217 on the cam part 202 will
be explained with reference to FIGS. 2a to 2e.
[0045] FIG. 2a: The needle ring 219 open on the periphery is
expanded elastically in the radial direction and is snapped onto
the bearing journal 211 from the lateral direction. The width of
the needle cage 218 and the width of the bearing journal are
essentially the same size, so that the needle cage is supported
directly in the axial direction from the facing end sides 221 and
222 of the inner cam 204 of the second cam group and cam 203,
respectively, adjacent to the bearing journal.
[0046] FIG. 2b: The bearing ring 217 is threaded eccentric to the
camshaft axis 20 onto the outer cam 204. In this case, the smaller
stroke h.sub.1 extends with respect to its angular position
completely within the larger stroke h.sub.2, and the radius r.sub.L
of the outer raceway 216 is slightly greater than the common
enveloping circle radius r.sub.HK of the cam 203, 204 with
r.sub.HK=1/2 (2 r.sub.GK+h.sub.2). The drawn radius r.sub.AK
designates the outer circumferential radius of the axial connecting
link 208 and is also greater than the outer raceway radius
r.sub.L:
c) r.sub.L<r.sub.AK
[0047] FIG. 2c: The bearing ring 217 is pushed into the eccentric
position over the outer cams 203, 204 until the outer cam 204 is
free.
[0048] FIG. 2d: The bearing ring 217 is centered on the camshaft
axis 20.
[0049] FIG. 2e: The bearing ring 217 is pushed over the needles
214.
[0050] FIG. 4 shows a second embodiment of a cam part 402 according
to the invention. This differs from the previously explained cam
part 202 essentially by the axial support of the needle cage 418.
Pulling the bearing ring 417 onto the cam part will be explained
with reference to FIGS. 4a to 4f.
[0051] FIG. 4a: The bearing ring 417 is threaded eccentric to the
camshaft axis 20 onto the outer cam 404 and pushed over the outer
cams 403 and 404 until the outer cam 404 is free. The needle ring
419 is pushed toward the inner cam group to create an axial opening
for the bearing ring 417.
[0052] FIG. 4b: The needle ring 419 and the bearing ring 417
centered relative to the camshaft axis 20 are pushed one onto the
other.
[0053] FIG. 4c: A plastic spacer ring 423 that is open on the
periphery is expanded elastically in the radial direction and
snapped onto the bearing journal 411 from the lateral
direction.
[0054] FIG. 4d: The spacer ring 423 is inserted into a ring groove
424 between the inner raceway 415 and the inner cam 404 of the
second cam group.
[0055] FIG. 4e: The bearing ring 417 is displaced toward the inner
cam 404 until another ring groove 425 is freely accessible between
the inner raceway 415 and the outer cam 403.
[0056] FIG. 4f: As in FIG. 4c, another spacer ring 423 is inserted
into the other ring groove 425 so that the facing cam end sides 421
and 422 support the needle cage 418 in the axial direction by means
of the spacer rings 423.
[0057] FIG. 5 shows a third embodiment of a cam part 502 according
to the invention. In this case, the bearing journal 511 is formed
with large steps in the radial direction with a raised inner
raceway 515, wherein both end sides 526 and 527 of the radial step
support the needle cage 518 surrounding these sides in the axial
direction.
[0058] FIG. 6 shows a fourth embodiment of a cam part 602 according
to the invention. In this fourth embodiment, the axial support of
the needle cage 618 is formed from a combination of the support in
the second embodiment and the third embodiment: The axial support
is realized on one side on the cam end side 621 by means of the
spacer ring 623 and on the other side directly on the end side 626
of the radial step.
[0059] FIG. 7 shows a fifth embodiment of a cam part 702 according
to the invention. This fifth embodiment is a variant of the fourth
embodiment in the way that the spacer ring 723 is formed in one
piece on the needle cage 718.
LIST OF REFERENCE NUMBERS
[0060] (without the hundreds place, which refers to the figure
number) [0061] 1 Carrier shaft [0062] 2 Cam part [0063] 3 Cam
[0064] 4 Cam [0065] 5 Cam [0066] 6 Roller cam follower [0067] 7 Gas
exchange valve [0068] 8 Axial connecting link [0069] 9 Actuation
element [0070] 10 Actuation element [0071] 11 Bearing journal
[0072] 12 Camshaft bearing point [0073] 13 Roller bearing/needle
bearing [0074] 14 Roller body/needle [0075] 15 Inner raceway [0076]
16 Outer raceway [0077] 17 Bearing ring [0078] 18 Roller bearing
cage/needle cage [0079] 19 Needle ring [0080] 20 Camshaft axis
[0081] 21 Cam end side [0082] 22 Cam end side [0083] 23 Spacer ring
[0084] 24 Annular groove [0085] 25 Additional annular groove [0086]
26 End side of radial step [0087] 27 End side of radial step
* * * * *