DE102012220210A1 - Camshaft of a variable-displacement gas exchange valve train - Google Patents

Abstract

A camshaft of a slide cam valve train of an internal combustion engine is proposed. A cam piece (2), which can be displaced on a carrier shaft (1) and has different cam strokes, is roller-mounted in a camshaft bearing point (12) of the internal combustion engine. The outer raceway (16) of the roller bearing (13) is formed by a one-piece bearing ring (17) surrounding the cam piece and is smaller than the circumferential radius of the larger stroke h2.

Description

The invention relates to a camshaft of a variable-displacement gas exchange valve drive of an internal combustion engine. The camshaft comprises a carrier shaft and a cam piece, which is mounted rotatably and axially displaceably on the carrier shaft and at least a first cam group of at least two immediately adjacent cams with different strokes and an axial slide into which an actuating element for moving the cam piece can be coupled onto the carrier shaft, and a bearing pin extending between the first cam group and the axial cam, on which a rolling bearing bearing the cam piece in a camshaft bearing point of the internal combustion engine is accommodated.

Background of the invention

A frequently referred to as a sliding cam valve train gas exchange valve drive with such a camshaft is from the DE 10 2009 030 373 A1 known. The bearing with a central journal between two intake or exhaust valves of an engine cylinder cam pieces comprise two identical groups of cams with three cams and an end axial slide, in which two actuating pins for moving the cam piece in the three axial positions are selectively coupled. The document suggests, in addition to the hydrodynamic sliding bearing, alternatively, a roller bearing for the cam piece.

Despite the three-stage Hubvariabilität the known valve train builds axially very compact. This is accomplished by allowing the cams adjacent to the trunnions to dip into the camshaft bearing location when they are not currently active. Geometric prerequisite for this is a corresponding dimensioning of the pivot bearing whose diameter must be greater than the circulation circuit of the immersing cams therein. In the case of rolling bearing of the cam piece, however, this dimensioning would lead to a radially undesirable large-scale camshaft bearing.

Object of the invention

The present invention has the object, a camshaft of the type mentioned in such a way that despite the rolling bearing of the cam piece a radially as compact construction is possible.

Summary of the invention

• a) h₁ < h₂
• b) max{r_HK; r_GK + h₁} < r_L < r_GK + h₂
• c) r_L < r_AK

The solution to this problem results from the fact that the inner race of the rolling bearing is formed by the journal, that the outer race of the rolling bearing is formed by a one-piece bearing ring and that the cam piece and the bearing ring have the following geometric features:

• a) h ₁ <h ₂
• b) max {r _HK ; r _GK + h ₁ } <r _L <r _GK + h ₂
• c) r _L <r _AK

h1

= Hub des an den Lagerzapfen angrenzenden einen Nockens der ersten Nockengruppe

h2

= Hub des anderen Nockens der ersten Nockengruppe

r_HK

= gemeinsamer Hüllkreisradius der Nocken der ersten Nockengruppe

r_GK

= Grundkreisradius der Nocken der ersten Nockengruppe

r_L

= Radius der Außenlaufbahn

r_AK

= Umlaufradius der Axialkulisse

Here are:

h1

= Hub of the cam adjacent to a cam of the first cam group

h2

= Stroke of the other cam of the first cam group

r _HK

= common envelope circle radius of the cams of the first cam group

r _GK

= Base circle radius of the cams of the first cam group

r _L

= Radius of the outer raceway

r _AK

= Radius of rotation of the axial slide

These geometric relationships allow the radius r _{L of} the outer race to be smaller than the radius of rotation r _GK + h _{2 of} the large stroke h ₂ , and the one-piece bearing ring can still be mounted over the cams on the journal. The assembly takes place in such a way that the bearing ring is first threaded onto the cams in a position eccentric to the axis of rotation of the cam piece and then centered in the region of the bearing journal on the rolling bodies. The rolling elements are preferably mounted in a roller bearing cage, which is open at the periphery and is mounted on the bearing journal before assembly of the bearing ring in the elastically expanded state. Alternatively, a multi-part cage can be used.

The invention can also be applied to non-variable standard roller bearings with standard bearings.

Brief description of the drawings

Further features of the invention will become apparent from the following description and from the drawings, in which the aforementioned geometry relationships are illustrated and explained in more detail in exemplary embodiments. Unless otherwise stated, the same or functionally identical features or components are provided with the same reference numbers. The hundreds of three-digit reference numbers refers to the number of the figure. Show it:

1 a known variable displacement gas exchange valve drive;

2 a first embodiment of a cam piece according to the invention in a perspective view;

2a -E the first cam piece in different mounting positions of the bearing ring;

3 the geometry of a cam piece according to the invention in a schematic view A according to 2 ;

4 a second embodiment of a cam piece according to the invention in a perspective view;

4a -F the second cam piece 4 in different mounting positions of the bearing ring;

5 a third embodiment of a cam piece according to the invention in longitudinal section;

6 a fourth embodiment of a cam piece according to the invention in longitudinal section;

7 a fifth embodiment of a cam piece according to the invention in longitudinal section.

Detailed description of the drawings

The invention is based on 1 which shows a three-stage variable-displacement gas exchange valve drive of an internal combustion engine. The basic operating principle of this known valve train can be summarized to the effect that a conventional rigid camshaft formed by a camshaft with an externally toothed carrier shaft 1 and - the number of cylinders of the internal combustion engine accordingly - rotatably and between three axial positions slidably arranged cam pieces 102 is replaced. Each cam piece has two identical groups of immediately adjacent cams 103 to 105 on, which have different strokes with the same base circle radius. The cam tapping takes place via roller cam followers 6 The cam strokes selectively on gas exchange valves 7 transfer.

The operating point-dependent activation of the respective cam 103 . 104 or 105 required displacement of the cam piece 102 on the carrier shaft 1 takes place via a groove-shaped axial slide 108 in which, depending on the instantaneous axial position of the cam piece, one of two pin-shaped actuating elements 9 . 10 an electromagnetic actuator (not shown) is coupled to move the cam piece within the common base circle phase of the cam. To stabilize the cam piece in the axial positions is a Rastiervorrichtung, which (not visible here) in the interior of the carrier shaft 1 runs and snaps into the interior of the cam piece.

For radial mounting of the camshaft in the internal combustion engine is the cam piece 102 between the two cam groups with a journal 111 provided in a stationary and cylinder center arranged in internal combustion engine camshaft bearing 12 is mounted rotating. It is a split camshaft bearing with a screwed, not shown bearing cap. Shown is a hydrodynamic sliding bearing of the journal in the camshaft bearing, the bearing can be known to be designed as a rolling bearing.

2 shows a first embodiment of a cam piece 202 for a two-stage variable-stroke gas exchange valve drive, wherein the bearing pin 211 of the cam piece in accordance with the invention of a rolling bearing 213 is enclosed. Unlike the known cam piece 102 in 1 are the cam strokes of the Axialkulisse 208 distant arranged first cam group oriented so that the stroke h ₁ of the bearing pin adjacent to a cam 203 is smaller than the stroke h _{2 of} the other cam 204 , The relationship then applies to this first cam group:

a) h ₁ <h ₂ (see also FIG. 3)

The cut and greatly simplified illustrated rolling bearing 213 is a needle bearing with cage-supported needles 214 whose inner career 215 through the journal 211 and their outer career 216 through one on the cam piece 202 mounted one-piece bearing ring 217 is formed. The plastic needle cage 218 is in connection with the held therein needles below as needle ring 19 ie in the 2 With 219 designated. The width of the bearing ring 217 is about twice the length of the needles 214 which roll depending on the axial position of the cam piece either in one axial raceway half or in the other axial raceway half of the bearing ring mounted in the engine.

3 illustrates the geometric radii or diameter ratios on the cam piece 202 (Cam elements 402 to 702 accordingly), which according to the view A in 2 projected into the leaf plane. The two cams 203 and 204 have a common envelope circle with radius r _HK , which covers the identical base circle radius r _GK and the two different strokes h ₁ and h _{2 of} these cams. In the case shown, however, the smaller stroke h ₁ does not extend completely within the larger stroke h ₂ with respect to its angular position, and the circumferential radius r _GK + h ₁ of the camshaft axis 20 rotating cam 203 is bigger than the common one Enveloping circle radius h _HK . The for the mounting of the bearing ring 217 smallest possible radius r _{L of} the outer raceway 216 Now, in general, the greater value of these two radii r _GK + h ₁ and r _HK , so that the following relationship holds:

b1) max {r _HK ; r _GK + h ₁ } <r _L

On the other hand, the radial space of the cam piece 202 with the needle bearing 213 To keep as small as possible, the relationship applies, according to which the outer race radius r _{L is} smaller than the radius of rotation of the larger cam 204 around the camshaft axis 20 is:

b2) r _L <r _GK + h ₂

Example calculation for the outer race radius r _L for the cam geometry according to 3 :
out
r _GK : 15.0 mm
h ₁ : 6.4 mm
h ₂ : 11.3 mm
surrendered
r _HK : 20.6 mm
r _GK + h ₁ : 21.4 mm
max {r _HK ; r _GK + h ₁ } = 21.4 mm
r _GK + h ₂ : 26.3 mm
and consequently, the size relationship applies to the outer race radius:
21.4 mm <r _L <26.3 mm

The mounting of the bearing ring 217 on the cam piece 202 be based on the 2a to 2e explained.

2a : the perimeter open needle ring 219 is radially expanded elastically and from the side to the journal 211 snapped. The width of the needle cage 218 and the width of the trunnion are substantially equal, so that the needle cage from the facing end faces 221 and 222 of the inner cam adjacent to the journal 204 the second cam group or the cam 203 the first cam group is supported directly axially.

2 B : the bearing ring 217 is eccentric to the camshaft axis 20 on the outer cam 204 threaded. In this case, the smaller stroke h ₁ extends with respect to its angular position completely within the larger stroke h ₂ , and the radius r _{L of} the outer race 216 is slightly larger than the common Hüllkreisradius r _{HK of} the cam 203 . 204 with r _HK = 1/2 (2r _GK + h ₂ ). The drawn radius r _AK denotes the outer radius of rotation of the axial slide 208 and is also greater than the outer race radius r _L :

c) r _L <r _AK

2c : the bearing ring 217 will be in the eccentric position over the outer cams 203 . 204 pushed until the outer cam 204 is free.

2d : the bearing ring 217 is on the camshaft axis 20 centered.

2e : the bearing ring 217 is over the needles 214 pushed.

4 shows a second embodiment of a cam piece according to the invention 402 , This differs from the cam piece explained above 202 essentially by the axial support of the needle cage 418 , The mounting of the bearing ring 417 on the cam piece is based on the 4a to 4f explained.

4a : the bearing ring 417 is eccentric to the camshaft axis 20 on the outer cam 404 Threaded and over the outer cam 403 and 404 pushed until the outer cam 404 is free. The needle wreath 419 is displaced toward the inner cam group to allow axial clearance for the bearing ring 417 to accomplish.

4b : the needle wreath 419 and the camshaft axis 20 centered bearing ring 417 are pushed together.

4c : a spacer ring open at the circumference 423 made of plastic is expanded radially elastic and from the side to the journal 411 snapped.

4d : the spacer ring 423 is in an annular groove 424 between the inner raceway 415 and the inner cam 404 used the second cam group.

4e : the bearing ring 417 becomes the inner cam 404 shifted until another ring groove 425 between the inner raceway 415 and the outer cam 403 is freely accessible.

4f : as in 4c will be another spacer ring 423 in the further annular groove 425 used so that the facing cam faces 421 and 422 the needle cage 418 by means of spacer rings 423 support axially.

5 shows a third embodiment of a cam piece according to the invention 502 , In this case, the journal is 511 with a raised inner race 515 radially strongly stepped formed, both end faces 526 and 527 the radial stage the this encompassing needle cage 518 support axially.

6 shows a fourth embodiment of a cam piece according to the invention 602 , In this fourth embodiment, the axial support of the needle cage 618 formed from a combination of the support in the second embodiment and the third embodiment: the axial support takes place on the one hand on the cam face 621 by means of the spacer ring 623 and on the other hand directly on the front side 626 the radial stage.

7 shows a fifth embodiment of a cam piece according to the invention 702 , This fifth embodiment is a variant of the fourth embodiment in such a way that the spacer ring 723 in one piece on the needle cage 718 is formed.

LIST OF REFERENCE NUMBERS

1

 carrier wave

2

 cam piece

3

 cam

4

 cam

5

 cam

6

 Roller cam

7

 Gas exchange valve

8th

 axial slotted

9

 actuator

10

 actuator

11

 pivot

12

 Camshaft bearing

13

 Rolling bearings / needle roller bearings

14

 Rolling element / needle

15

 Inner raceway

16

 Outer race

17

 bearing ring

18

 Rolling bearing cage / needle cage

19

 needle bearing

20

 camshaft axis

21

 Cam face

22

 Cam face

23

 spacer

24

 ring groove

25

 another ring groove

26

 Front side of the radial stage

27

 Front side of the radial stage

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009030373 A1 [0002]

Claims (6)

Camshaft of a variable-displacement gas exchange valve drive of an internal combustion engine, comprising a carrier shaft ( 1 ) and a cam piece ( 2 ), the rotationally fixed and axially displaceable on the carrier shaft ( 1 ) is mounted and at least a first cam group of at least two immediately adjacent cam ( 3 . 4 ) with different strokes (h ₁ , h ₂ ) and a Axialkulisse ( 8th ) into which an actuating element ( 9 . 10 ) for moving the cam piece ( 2 ) on the carrier shaft ( 1 ) can be coupled, and one between the first cam group and the axial slide ( 8th ) extending trunnions ( 11 ), on which a cam piece ( 2 ) in a camshaft bearing ( 12 ) of the internal combustion engine rotatably rolling bearings ( 13 ), characterized in that the inner raceway ( 15 ) of the rolling bearing ( 13 ) through the bearing journal ( 11 ) that the outer raceway ( 16 ) of the rolling bearing ( 13 ) by a one-piece bearing ring ( 17 ) is formed and that the cam piece ( 2 ) and the bearing ring ( 17 ) have the following geometric features: a) h ₁ <h ₂ b) max {r _HK ; r _GK + h ₁ } <r _L <r _GK + h ₂ c) r _L <r _AK h ₁ = stroke of the bearing journal ( 11 ) adjacent a cam ( 3 ) of the first cam group h ₂ = stroke of the other cam ( 4 ) of the first cam group r _HK = common envelope circle radius of the cams ( 3 . 4 ) of the first cam group r _GK = base circle radius of the cams ( 3 . 4 ) of the first cam group r _L = radius of the outer raceway ( 16 ) r _AK = radius of rotation of the axial slide ( 8th ) Camshaft according to claim 1, characterized in that the rolling elements ( 14 ) of the rolling bearing ( 13 ) in a circumferentially open rolling bearing cage ( 18 ) are held. Camshaft according to claim 2, characterized in that the bearing journal ( 11 ) with a raised inner raceway ( 15 ) is radially stepped, wherein at least one of the end faces ( 26 . 27 ) of the radial stage the rolling bearing cage ( 18 ) is axially supported. Camshaft according to claim 2, characterized in that the cam piece ( 2 ) a second cam group of at least two immediately adjacent cams ( 3 . 4 ) with different strokes (h ₁ , h ₂ ), wherein at least one of the mutually facing end faces ( 21 . 22 ) at the journal ( 11 ) adjacent cams ( 3 . 4 ) of the cam groups the rolling bearing cage ( 18 ) is axially supported. Camshaft according to claim 4, characterized in that the cam end faces ( 21 . 22 ) the rolling bearing cage ( 18 ) directly axially support. Camshaft according to claim 4, characterized in that at least one of the cam end faces ( 21 . 22 ) the rolling bearing cage ( 18 ) by means of a circumferentially open spacer ring ( 23 ) is axially supported.

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