DE102011001711B4 - Valve train for an internal combustion engine and method of manufacturing the same - Google Patents

Abstract

Valve drive for an internal combustion engine with several cylinders, wherein at least one camshaft (1) rotatably mounted in camshaft bearings (2, 3) with at least one sliding cam (5) that can be displaced axially on the respective camshaft (1) is provided for actuating gas exchange valves of the internal combustion engine, wherein the respective sliding cam (5) is mounted in such a way that, despite the axial displaceability of the respective sliding cam (5) relative to the respective camshaft (1), on the one hand a centering of the respective sliding cam (5) and on the other hand a torque transmission to the respective sliding cam (5) is ensured , wherein the respective sliding cam (5) is mounted on the respective camshaft (1) via a sliding sleeve (15) that can be moved axially on the respective camshaft (1) in such a way that it can be moved axially in such a way that the respective sliding sleeve (15), which, seen in the radial direction, is between the respective camshaft (1) and the respective sliding cam (5) and which is firmly connected to a central section (16) of the respective sliding cam (5), viewed in the axial direction, serves to transmit torque to the respective sliding cam (5), the respective sliding cams (5) via lateral sections (17) protruding laterally opposite the respective sliding sleeve (15), viewed in the axial direction, on bearing sleeves (8) of the camshaft bearings (2, 3) fixed axially immovably on the camshaft (1) opposite the bearing sleeves (8 ), which serve to center the respective sliding cam (5), is mounted in an axially displaceable manner, characterized in that the bearing sleeves (8) and the sliding sleeves (15) each have a plurality of flattened areas (20, 21) on an outer circumference thereof, which outer circumference carrying shoulders (22, 23), wherein the flattened areas (20) of the bearing sleeves (8) are offset relative to the flattened areas (21) of the sliding sleeves (15) viewed in the circumferential direction.

Description

The invention relates to a valve train for an internal combustion engine with multiple cylinders according to the preamble of patent claim 1 and a method for manufacturing such a valve train.

In modern internal combustion engines, variable valve drives are used to optimize the charge movement in the combustion chamber, with which different valve lifts can be set in the gas exchange valves of the internal combustion engine.

From the DE 196 11 641 C1 a valve drive of an internal combustion engine is known, with which the actuation of a gas exchange valve with several different lift curves is made possible. For this purpose, a sliding cam with several cam tracks is mounted on the camshaft in a rotationally fixed but axially displaceable manner. The sliding cam has a connecting link section in which an actuating element of an actuator in the form of a pin engages to generate an axial displacement of the sliding cam. Due to the axial displacement of the sliding cam, a different valve lift is set for the respective gas exchange valve. After DE 196 11 641 C1 the sliding cam can be locked in place by a locking device after it has been axially displaced relative to the camshaft.

From the DE 10 2007 027 979 A1 a valve drive for an internal combustion engine with a sliding cam that can be displaced axially on a camshaft is also known. According to this prior art, the sliding cam has an internal toothing which, for mounting the sliding cam on the camshaft, interacts with an external toothing of the camshaft in such a way that, despite the axial displaceability of the sliding cam relative to the camshaft, the sliding cam is centered on the camshaft on the one hand and torque is transmitted on the other from the camshaft to the sliding cams is guaranteed.

According to the prior art, the function of centering and the function of torque transmission are therefore taken over by one and the same internal toothing of the sliding cam and external toothing of the camshaft. This type of storage, which simultaneously assumes the centering function and the torque transmission function, is very sensitive to tolerances and can only be manufactured with great effort.

DE 199 08 286 A1 discloses a valve train for a multi-cylinder internal combustion engine according to the preamble of claim 1.

DE 195 19 048 A1 and DE 10 2008 024 876 A1 disclose further prior art.

The object of the invention is to improve a valve train according to the preamble of patent claim 1 in such a way that the same is less sensitive to tolerances and can be produced with less effort. Furthermore, a simple method for manufacturing such a valve train should be created.

According to the invention, this object is achieved by a valve drive having the features of patent claim 1 .

According to the invention, the bearing sleeves and the sliding sleeves each have a plurality of flattened areas on an outer circumference thereof, which delimit support shoulders on the outer circumference, the flattened areas of the bearing sleeves being offset relative to the flattened areas of the sliding sleeves, viewed in the circumferential direction. This supports simple manufacture and assembly of the valve train.

The function of centering the respective sliding cam and the function of torque transmission to the respective sliding cam are not only functionally and spatially separate, rather different component combinations are involved in these functions, namely the camshaft, sliding sleeve and sliding cam in the torque transmission function and the camshaft, bearing sleeves and in the centering function sliding cam. This allows a needs-specific design of the respective components involved, a reduction in tolerance sensitivity and easy manufacturability of the valve train.

The method for manufacturing such a valve train is defined in claim 9 and comprises at least the following steps: a) providing at least one camshaft having external teeth, b) providing bearing sleeves for camshaft bearings having internal teeth and at least one sliding sleeve having internal teeth; c) providing at least one sliding cam; d) arranging and fixing a bearing sleeve on the respective camshaft, then arranging a sliding sleeve on the respective camshaft and then arranging and fixing another bearing sleeve on the respective camshaft, this being repeated until all sliding sleeves and bearing sleeves are positioned on the respective camshaft are; e) Finish-machining of the bearing sleeves arranged on the respective camshaft and of the sliding sleeve or of each sliding sleeve arranged on the respective camshaft while eliminating concentricity deviations; f) formation of grooves, in particular longitudinal grooves, preferably by means of material accumulation, on an outer surface of the or each sliding sleeve; g) arranging and fixing the respective sliding cam on the respective sliding sleeve.

• 1 einen schematischen Ausschnitt aus einem Ventiltrieb einer Brennkraftmaschine;
• 2 ein Detail des Ventiltriebs der 1 in teilgefertigtem Zustand;
• 3 einen Querschnitt durch den Ventiltrieb der 2 entlang der Schnittrichtung A-A; und
• 4 einen Querschnitt durch den Ventiltrieb der 2 entlang der Schnittrichtung B-B.

Further features and combinations of features result from the description. Concrete exemplary embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it:

• 1 a schematic section of a valve train of an internal combustion engine;
• 2 a detail of the valve train 1 in semi-finished condition;
• 3 a cross section through the valve train 2 along the cutting direction AA; and
• 4 a cross section through the valve train 2 along the cutting direction BB.

1 shows a cross section through an internal combustion engine in the area of a camshaft 1 of a valve train of the internal combustion engine. In the 1 Camshaft 1 shown is mounted via camshaft bearings 2, 3 in a cylinder head, not shown, of the internal combustion engine, which is preferably composed of a cylinder head base and a camshaft housing. The lower part of the cylinder head and the camshaft housing can also be designed in one piece.

In the 1 Camshaft 1 shown is designed as an intake camshaft and is used to control intake valves 4 of the internal combustion engine with the aid of roller rocker arms, not shown. An exhaust camshaft, not shown, is provided for controlling exhaust valves, not shown, of the internal combustion engine. The inlet valves and outlet valves are gas exchange valves of the internal combustion engine.

Two intake valves 4 and two exhaust valves (not shown) are preferably provided per cylinder, the intake valves 4 being actuated in a known manner by the intake camshaft 1 in a controlled manner. The exhaust valves are actuated in a known manner in a controlled manner by the exhaust camshaft (not shown). For this purpose, the intake camshaft 1 and the exhaust camshaft (not shown) each have a plurality of sliding cams 5 .

To store the in 1 Visible intake camshaft 1 is provided with the camshaft bearings 2, 3 already mentioned and designed as radial bearing devices, which comprise a lower bearing ring body 6, which can be designed in one piece with the camshaft housing. Furthermore, each camshaft bearing 2, 3 comprises an individual bearing cap 7 which is attached to the lower bearing ring body 6 with the aid of z. B. screws is attached, and attached to the intake camshaft 1 bearing sleeve 8. The position cover 7 can be combined to form a bearing bridge.

According to 1 the sliding cam 5 is formed from a link section 9 positioned in the middle and two outer cam sections 10 . Each outer cam section 10 comprises three cam tracks 11, with each of the cam tracks 11 setting a different valve lift. the inside 1 The shifting cam 5 shown therefore comprises, for each valve, a cam section 10 with three cam tracks 11, which is axially displaceable. There can also be several connecting link sections on the outside next to the cam sections 10 . Each sliding cam 5 is assigned an actuator 12 which has pins 13 which interact with grooves 14 of the sliding cam 5 formed on a lateral surface of the connecting link section 9 . This results in an axial displacement of the sliding cam 5 in an area between two camshaft bearings 2, 3.

Due to the axial displacement of the sliding cam 5, the respective gas exchange valve is actuated in a targeted manner with a specific cam track 11, so that a different valve lift adjustment takes place. The person skilled in the art addressed here is familiar with the interaction of the pins 13 of the actuator 12 with the grooves 14 of the link section 9 .

To ensure proper functioning of the valve train, the respective shift cam 5 must be centered relative to the camshaft 1 on the one hand, and torque transmission from the camshaft 1 to the respective shift cam 5 must be ensured on the other hand.

In order to provide the torque transmission function from the camshaft 1 to the sliding cam 5, the in 1 The sliding cam 5 shown is mounted on the camshaft 1 in an axially displaceable manner via a sliding sleeve 15 which is mounted in an axially displaceable manner on the camshaft 1 .

The sliding sleeve 15 is positioned between the camshaft 1 and the sliding cam 5 viewed in the radial direction, the sliding sleeve 15 being connected to a central section 16 of the sliding cam 5 in a rotationally fixed manner. The torque is therefore transmitted from the camshaft 1 to the sliding cam 5 starting from the camshaft 1 to the sliding sleeve 15 and via the sliding sleeve 15 ultimately to the sliding cam 5.

The provision of the centering of the sliding cam 5 on the camshaft 1 takes place via the bearing sleeves 8 fastened on the camshaft 1 in an axially non-displaceable manner, the in 1 Sliding cam 5 shown is mounted axially displaceably on sections of the bearing sleeves 8 of the camshaft bearings 2, 3, which are fixed axially immovably on the camshaft 1, via lateral sections 17 protruding in the axial direction opposite the sliding sleeve 15 relative to the bearing sleeves 8.

The centering of the sliding cam 5 on the camshaft 1 is therefore carried out via the bearing sleeves 8, which are fixed axially non-displaceably on the camshaft 1, and against which the sliding cam 5 via the sliding sleeve 15 is axially displaceable.

The torque transmission function and the centering function for the respective sliding cam 5 are therefore not only functionally and spatially separate from one another, rather these functions are provided by different component combinations.

The torque transmission function is provided by the camshaft 1, the sliding sleeve 15 which is arranged on the camshaft 1 in an axially displaceable but non-rotating manner and the sliding cam 5 which is arranged on the sliding sleeve 15 in an axially fixed and non-rotating manner.

The centering function is provided by the camshaft 1 , the bearing sleeves 8 which are arranged axially fixed and torsionally fixed on the camshaft 1 and the sliding cam 5 which is axially displaceable relative to the bearing sleeves 8 .

The camshaft 1 has an external toothing 18 which interacts with an internal toothing 19 of the sliding sleeve 15, these toothings 18, 19 meshing and the axial displaceability of the sliding sleeve 15 on the camshaft 1 as well as the non-rotatability of the sliding sleeve 15 to the camshaft 1 and thus provide the axial displaceability of the sliding cam 5 on the camshaft and the torque transmission from the camshaft 1 via the sliding sleeve 15 to the sliding cam 5.

The bearing sleeves 8 are non-positively connected to the camshaft 1, in particular by being pressed onto the camshaft 1, the bearing sleeves 8 being connected to the camshaft 1 so that they cannot be displaced in the axial direction on the one hand and are non-rotatably or non-rotatably connected to the camshaft 1 on the other hand in the circumferential direction relative to the camshaft 1. The respective sliding cam 5 is mounted axially displaceably on the bearing sleeves 8 of the camshaft bearings 2 , 3 relative to the bearing sleeves 8 via the lateral sections 17 protruding laterally relative to the respective sliding sleeve 15 , as seen in the axial direction.

The bearing sleeves 8 and the sliding sleeve 15 each have a plurality of flat areas 20 and 21 on an outer circumference thereof, which delimit the same support shoulders 22 and 23 on the outer circumference.

So can 3 can be seen that over the outer circumference of the bearing sleeves 8 three flattened areas 20 are distributed, which are distributed over the circumference of the respective bearing sleeve 8 in each case delimit three support shoulders 22 from one another. 4 it can be seen that in an analogous manner on the outer circumference of the respective sliding sleeve 15 three flattened areas 21 are distributed, which limit the three support shoulders 23 from one another.

The flattened areas 20 of the bearing sleeves 8 are offset relative to one another relative to the flattened areas 21 of the sliding sleeve 15 and thus the supporting shoulders 22 of the bearing sleeves 8 relative to the supporting shoulders 23 of the sliding sleeve 15 in the circumferential direction, namely in such a way that viewed in the axial projection (see 4 ) the supporting shoulders 22 of the bearing sleeves 8 are aligned with flat areas 21 of the sliding sleeve 15, and that the supporting shoulders 23 of the sliding sleeve 15 are aligned with flat areas 20 of the bearing sleeves 8.

An outer radius of the bearing shoulders 22 of the bearing sleeves 8 corresponds to an outer radius of the bearing shoulders 23 of the sliding sleeve 15 and an inner radius of the sliding cam 5.

The sliding cam 5 is non-positively and positively connected to the sliding sleeve 15 by forming grooves in particular on the support shoulders 23 of the sliding sleeve and by subsequently pressing the sliding cam 5 onto the sliding sleeve 15, namely in such a way that the sliding cam is neither displaced in the axial direction relative to the sliding sleeve nor in the circumferential direction can be rotated relative to the same.

As already mentioned, the axial displacement of the in 1 shown sliding cam 5 on the camshaft 1 with the sliding cam 5, the actuator 12 together, namely one of the pins 13 with one of the grooves 14 of the slide section 9 of the sliding cam 5, the actual axial displacement of the sliding cam 5 on the camshaft 1 being provided via the sliding sleeve 15 . In order to move the sliding sleeve 15, after an axial displacement thereof on the camshaft 1, into its axial relative position on the camshaft 1 and thus to lock the sliding cam 5 in its axial relative position relative to an intake valve 4 to be actuated, the valve train has a locking device 24 (see in particular 2 ).

The locking device 24 acts between the camshaft 1 and the sliding sleeve 15 in such a way that locking balls 27 accommodated in a transverse bore 25 of the camshaft 1 and acted upon by at least one spring element 26 interact with locking depressions 28 formed on an inner surface of the sliding sleeve 15 in such a way that the locking balls are used for locking 27 of the camshaft 1 engage in one of the locking recesses 28 of the sliding sleeve 15. In 1 and 2 two locking balls 27 are shown. There can also be only one such locking ball 27 per sliding sleeve 15 .

For the production of the in 1 until 4 valve drive shown in different representations, the procedure is such that first a camshaft 1 with external teeth 18 is provided, bearing sleeves 8 with internal teeth and sliding sleeves 15 with internal teeth and sliding cams 5 are also provided.

A first bearing sleeve 8, which at the same time provides a so-called camshaft head 29, is then positioned on the camshaft 1 and positively connected to the camshaft 1 by pressing on.

A sliding sleeve 15 with the internal toothing 19 is then pushed onto the external toothing 18 of the camshaft 1 and locked in a relative axial position on the camshaft 1 via a corresponding locking device 24 .

A further bearing sleeve 8 is then arranged on the camshaft 1 and fixed in a non-positive manner on the camshaft 1 by pressing.

This alternating positioning of bearing sleeves 8 and sliding sleeves 15 on camshaft 1 is repeated until all sliding sleeves 15 and bearing sleeves 8 are positioned on camshaft 1 in question.

The bearing sleeves 8 and the respective sliding sleeve 15 are in the axial direction of the camshaft 1 (see in particular 1 ) spaced apart from one another, namely in such a way that the respective sliding sleeve 15 and thus the sliding cam 5 accommodated on the respective sliding sleeve 15 can be displaced axially in the axial direction of the camshaft 1 .

The camshaft 1 preassembled in this way with the bearing sleeves 8 and the sliding sleeves 15 is then subjected to finish-machining in the area of the outer peripheral surfaces of the bearing sleeves 8 and the sliding sleeves 15, for example by grinding. Here, concentricity deviations in the area of the bearing sleeves 8 and sliding sleeves 15 are eliminated.

Following this, grooves are formed in the area of the sliding sleeves 15, namely in the area of the supporting shoulders 23 of the same, preferably by rolling, as a result of which material is thrown up in the area of the supporting shoulders 23.

A sliding cam 5 is then arranged on the respective sliding sleeve 15 by sliding it on axially and pressed with the same, with the material of the sliding sleeve 15 thrown up during rolling or forming the grooves digging into the sliding cam 5 and thus forming a non-positive and positive connection between them.

Since when the sliding cam 5 is pushed axially onto the sliding sleeve 15 provided with the grooves, material is also thrown up in the area of a radially inner surface of the sliding sleeve 15 , the flat areas 20 are formed in the area of the bearing sleeves 8 .

Since the assembly takes place from an axial side, a bearing sleeve 8 with the flattened areas 20 must only be present on one axial side of each sliding cam 5 in the area of the section of the bearing sleeve 8 on which the respective lateral section 17 of the sliding cam 5 acts in an axially displaceable manner. On the opposite side of the sliding cam 5, the bearing sleeve 8 can do without such flattened portions 20 in relation to the respective sliding cam 5 on the respective section thereof on which the sliding cam 5 acts in an axially displaceable manner via the respective section 17.

During the final machining of the bearing sleeves 8 and sliding sleeves 15 arranged on the preassembled camshaft 1, the flattened areas 20, 21 and the support shoulders 22, 23 are also machined.

After assembly or production is complete, the sliding cams 5 are firmly connected to the sliding sleeves 15 and are slidably mounted on the bearing sleeves 8 with minimal concentricity deviation.

The sliding cams 5 can be axially displaced relative to the camshaft 1 and the bearing sleeves 8 via the sliding sleeves 15 on the camshaft 1 . The sliding cams 5 can be positioned precisely in the respective end positions via a stop, not shown, of the sliding sleeves 15 on the bearing sleeves 8 .

The valve drive according to the invention allows precise centering and torque transmission to the sliding cam 5. Since different component combinations are involved in providing the centering function and torque transmission function, the respective components can be designed individually as required, so that the tolerance sensitivity of the valve drive can be reduced. Furthermore, a simple production of the valve train is guaranteed.

Reference List

1

camshaft

2

camshaft bearings

3

camshaft bearings

4

intake valve

5

sliding cam

6

bearing ring body

7

location cover

8th

bearing sleeve

9

scenery section

10

cam sections

11

cam track

12

actuator

13

Pen

14

groove

15

sliding sleeve

16

Section

17

Section

18

external teeth

19

internal teeth

20

flattening

21

flattening

22

carrying shoulder

23

carrying shoulder

24

locking device

25

cross bore

26

spring element

27

detent ball

28

detent recess

29

camshaft head

Claims (10)

Valve drive for an internal combustion engine with several cylinders, wherein at least one camshaft (1) rotatably mounted in camshaft bearings (2, 3) with at least one sliding cam (5) that can be displaced axially on the respective camshaft (1) is provided for actuating gas exchange valves of the internal combustion engine, wherein the respective sliding cam (5) is mounted in such a way that, despite the axial displaceability of the respective sliding cam (5) relative to the respective camshaft (1), on the one hand a centering of the respective sliding cam (5) and on the other hand a torque transmission to the respective sliding cam (5) is ensured , wherein the respective sliding cam (5) is mounted on the respective camshaft (1) via a sliding sleeve (15) that can be moved axially on the respective camshaft (1) in such a way that it can be moved axially in such a way that the respective sliding sleeve (15), which, seen in the radial direction, is between the respective camshaft (1) and the respective sliding cam (5) and which is firmly connected to a central section (16) of the respective sliding cam (5), viewed in the axial direction, serves to transmit torque to the respective sliding cam (5), the respective sliding cams (5) via lateral sections (17) protruding laterally opposite the respective sliding sleeve (15), viewed in the axial direction, on bearing sleeves (8) of the camshaft bearings (2, 3) fixed axially immovably on the camshaft (1) opposite the bearing sleeves (8 ), which serve to center the respective sliding cam (5), is mounted in an axially displaceable manner, characterized in that the bearing sleeves (8) and the sliding sleeves (15) each have a plurality of flat areas (20, 21) on an outer circumference thereof, which outer circumference carrying shoulders (22, 23), wherein the flattened areas (20) of the bearing sleeves (8) are offset relative to the flattened areas (21) of the sliding sleeves (15) viewed in the circumferential direction. valve train after claim 1 , characterized in that the camshaft (1) has external teeth (18) and the respective sliding sleeve (15) has internal teeth (19), these intermeshing teeth (18, 19) the axial displaceability of the respective sliding sleeve (15) and thus of the respective sliding cam (5) on the respective camshaft (1) and the torque transmission from the respective camshaft (1) via the respective sliding sleeve (15) to the respective sliding cam (5). valve train after claim 1 or 2 , characterized in that the bearing sleeves (8) with the respective camshaft (1) are non-positively connected. valve train after claim 3 , characterized in that the bearing sleeves (8) are non-positively connected to the respective camshaft (1) by being pressed onto the respective camshaft (1). Valve train according to one of Claims 1 until 4 , characterized in that the respective sliding sleeve (15) after an axial displacement thereof on the respective camshaft (1) in its axial relative position on the respective camshaft (1) and thus the respective sliding cam (5) in its axial relative position relative to a actuating gas exchange valve can be locked by a locking device (24). valve train after claim 5 , characterized in that spring-loaded locking balls (27) of the locking device are received in a transverse bore (25) of the respective camshaft (1) and for locking the respective sliding sleeve (15) on the respective camshaft (1) in locking recesses (28) of the respective sliding sleeve (15) intervene. Valve train according to one of Claims 1 until 6 , characterized in that an outer radius of the bearing shoulders (22) of the bearing sleeves (8) corresponds to an outer radius of the bearing shoulders (23) of the respective sliding sleeve (15) and an inner radius of the respective sliding cam (5). Valve train according to one of Claims 1 until 7 , characterized in that the respective sliding cam (5) with the respective sliding sleeve (15) by forming grooves on the support shoulders (23) of the respective sliding sleeve (15) and by pressing the respective sliding cam (5) onto the respective sliding sleeve (15) is positively and positively connected. Method for manufacturing a valve train according to one of Claims 1 until 8th , having the following steps: a) providing at least one camshaft (1) having external teeth (18), b) providing bearing sleeves (8) having internal teeth (19) for camshaft bearings (2, 3) and at least one camshaft having internal teeth (19) having sliding sleeve (15); c) providing at least one sliding cam (5); d) arranging and fixing a bearing sleeve (8) on the respective camshaft (1), then arranging a sliding sleeve (15) on the respective camshaft (1) and then arranging and fixing a further bearing sleeve (8) on the respective camshaft (1) , this being repeated until all sliding sleeves (15) and bearing sleeves (8) are positioned on the respective camshaft (1); e) Finish-machining of the bearing sleeves (8) arranged on the respective camshaft (1) and of the or each sliding sleeve (15) arranged on the respective camshaft (1) while eliminating concentricity deviations; f) scoring an outer surface of the or each sliding sleeve (15); g) arranging and fixing the respective sliding cam (5) on the respective sliding sleeve (15). procedure after claim 9 , characterized in that when the bearing sleeves (8) arranged on the respective camshaft (1) and the or each sliding sleeve (15) arranged on the respective camshaft (1) are machined to their final dimensions, a plurality of flattened areas (20, 21) are formed on an outer circumference thereof that limit the outer circumference of the bearing shoulders (22, 23) are processed.

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