DE102011001660B4 - Valve drive for an internal combustion engine - Google Patents

Abstract

Valve drive for an internal combustion engine with several cylinders, at least one rotatably mounted camshaft (6) with at least one sliding cam (7) axially displaceable on the respective camshaft (6) being provided for actuating the gas exchange valves of the internal combustion engine, the respective sliding cam (7) opening the respective camshaft (6) is mounted in such a way that despite the axial displaceability of the respective sliding cam (7) relative to the respective camshaft (6), on the one hand, a centering of the respective sliding cam (7) on the respective camshaft (6) and, on the other hand, a torque transmission from the respective camshaft (6) is guaranteed on the respective sliding cam (7), whereby a) for centering the respective sliding cam (7) on the respective camshaft (6) a centering section (16) is formed in such a way that radially outside on the respective camshaft ( 6) several centering projections distributed over the circumference of the same (18) which rest on a radially inner surface (19) of the respective sliding cam (7); b) axially spaced from the centering section (16) for the torque transmission between the respective camshaft (6) and the respective sliding cam (7) a torque transmission section (17) is designed in such a way that torque transmission projections (20) distributed over an outer circumference of the respective camshaft (6) in torque transmission depressions (21) of the respective slide cam (7) and torque transmission projections (7) distributed over an inner circumference of the respective slide cam (7) 22) engage in torque transmission depressions (23) of the respective camshaft (6); c) grooves (24) in the radially inner surface (19) of the centering section (16) of the respective sliding cam (7) on which the centering projections (18) rest ) are introduced into which during the assembly of the respective sliding cam (7) on the respective camshaft (6) the centering projections (18) engage with radial play, the grooves (24) made in the radially inner surface (19) of the respective sliding cam (7) extending over the entire axial width of the same in the area of the centering section (16) and the torque transmission section (17) extend; d) on the respective camshaft (6) axially between the centering projections (18) of the centering section (16) and the torque transmission projections (20) of the torque transmission section (17) a clearance section (25) is formed, the radius of which is smaller than a head radius of the torque transmission projections (22) of the respective slide cam (7).

Description

The invention relates to a valve drive for an internal combustion engine with several cylinders.

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 link section into which an actuating element of an actuator in the form of a pin engages to generate an axial displacement of the sliding cam. The axial displacement of the sliding cam sets a different valve lift 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 axial displacement of the same relative to the camshaft.

From the DE 10 2007 027 979 A1 a valve drive for an internal combustion engine with a sliding cam axially displaceable on a camshaft is also known. According to this prior art, the sliding cam has internal teeth which, for mounting the sliding cam on the camshaft, interact with external teeth of the camshaft in such a way that despite the axial displaceability of the sliding cam relative to the camshaft, on the one hand, centering of the sliding cam on the camshaft and, on the other hand, a Torque transmission from the camshaft to the sliding cam is guaranteed.

According to the state of the art, the centering function and the torque transmission function are 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 takes on the centering function and the torque transmission function, is very sensitive to tolerances and can only be manufactured with great effort.

From the DE 10 2008 035 935 A1 another valve train is known. This valve drive has a rotatably mounted camshaft and at least one slide cam that is axially displaceable on the camshaft. At least one centering section is configured for centering the sliding cam on the camshaft and at least one torque transmission section is configured for torque transmission.

The object of the invention is to improve a valve train in such a way that it is less sensitive to tolerances and easy to manufacture.

This object is achieved according to the invention by a valve drive with the features of claim 1. For centering the respective sliding cam on the respective camshaft, a centering section is designed such that a plurality of radially outer centering projections are formed on the respective camshaft distributed over the circumference of the respective camshaft and bear against a radially inner surface of the respective sliding cam. Axially spaced from the centering section for the torque transmission, a torque transmission section is formed between the respective camshaft and the respective slide cam such that torque transmission projections distributed over an outer circumference of the respective camshaft in torque transmission recesses of the respective slide cam and torque transmission projections distributed over an inner circumference of the respective slide cam in the torque transmission recesses engage the respective camshaft. In the radially inner surface of a centering section of the respective sliding cam, on which the centering projections rest, grooves are made, in which the centering projections engage with radial play when the respective sliding cam is mounted on the respective camshaft, the centering projections being introduced into the radially inner surface of the sliding cam Grooves extend over the entire axial width of the same in the region of the centering section and the torque transmission section. On the respective camshaft, a clearance section is axially formed between the centering projections of the centering section and the torque transmission projections of the torque transmission section, the radius of which is smaller than a head radius of the torque transmission projections of the respective sliding cam.

The spatially and functionally separate sections for centering and torque transmission can each be designed independently of one another according to requirements, whereby the tolerance sensitivity can be significantly reduced. Furthermore, the manufacturing requirements can be reduced and thus manufacturing costs can be saved. The valve train is easy to manufacture with high accuracy.

• 1 einen schematischen Querschnitt durch eine Brennkraftmaschine im Bereich eines Ventiltriebs;
• 2 einen perspektivischen teilweisen Querschnitt aus einem Ventiltrieb im Bereich einer Nockenwelle und eines Schiebenockens;
• 3 einen perspektivischen Ausschnitt aus der Nockenwelle des Ventiltriebs der 2;
• 4 einen perspektivischen Querschnitt durch den Schiebenocken des Ventiltriebs der
• 2; 5 eine perspektivischen Ansicht des Schiebenockens des Ventiltriebs der 2;
• 6a bis 6c unterschiedliche Zustände des Ventiltriebs der 2 bei der Montage desselben; und
• 7 einen Querschnitt durch den Ventiltrieb der 2 an einer Axialposition.
• 1 zeigt einen ausschnittsweisen Querschnitt durch eine Brennkraftmaschine im Bereich eines Zylinderkopfs 1, der nach außen von einem im Ausführungsbeispiel gegenüber dem Zylinderkopf 1 getrennten Zylinderkopfdeckel 2 begrenzt ist. Der Zylinderkopf 1 setzt sich im Ausführungsbeispiel aus einem Zylinderkopfunterteil 3 und einem Nockenwellengehäuse 4 zusammen. Es sei darauf hingewiesen, dass auch andere Bauformen von Brennkraftmaschinen möglich sind, so z.B. eine Bauform, in welcher der Zylinderkopfdeckel 2 und der Zylinderkopf 1 einstückig ausgebildet sind.

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

• 1 a schematic cross section through an internal combustion engine in the area of a valve drive;
• 2 a perspective partial cross-section of a valve drive in the area of a camshaft and a sliding cam;
• 3 a perspective section of the camshaft of the valve train of 2 ;
• 4th a perspective cross section through the sliding cam of the valve train of the
• 2 ; 5 a perspective view of the slide cam of the valve train of FIG 2 ;
• 6a to 6c different states of the valve train of the 2 when assembling the same; and
• 7th a cross section through the valve train of the 2 at an axial position.
• 1 shows a partial cross section through an internal combustion engine in the area of a cylinder head 1 , the outward from one in the exemplary embodiment opposite the cylinder head 1 separate cylinder head cover 2 is limited. The cylinder head 1 consists in the exemplary embodiment of a cylinder head lower part 3 and a camshaft housing 4th together. It should be pointed out that other designs of internal combustion engines are also possible, for example a design in which the cylinder head cover 2 and the cylinder head 1 are integrally formed.

According to 1 is in the camshaft housing 4th for controlling inlet valves 5 of the internal combustion engine, an intake camshaft 6th stored. An exhaust camshaft (not shown) is located in the camshaft housing to control exhaust valves (not shown) of the internal combustion engine 4th stored. There are preferably two inlet valves per cylinder 5 and two exhaust valves (not shown) are provided, the intake valves 5 from the intake camshaft 6th be actuated controlled in a known manner. The exhaust valves are actuated in a controlled manner by the exhaust camshaft (not shown). For this purpose, the in the camshaft housing 4th bearing intake camshaft 6th or the exhaust camshaft (not shown) each has a plurality of sliding cams 7th on. At the inlet valves 5 and exhaust valves are gas exchange valves of the internal combustion engine.

To store the in 1 visible intake camshaft 6th are radial bearing devices 8th provided which has a lower bearing ring body 9 include, which in the embodiment shown is integral with the camshaft housing 4th is trained. Furthermore, each radial bearing device comprises 8th an individual bearing cap 10 , the one with the lower bearing ring body 9 with the help of z. B. Screws on the camshaft housing 4th is attached. The position cover 10 can also be combined to form a storage bridge. According to 1 actuates the intake camshaft 6th the inlet valves 5 with the help of roller cam followers 11 .

According to 1 is the sliding cam 7th from a backdrop section positioned in the middle 12 and two outer cam sections 13 educated. Any outer cam section 13 includes three cam tracks 14th , with each of the cam tracks 14th a different valve lift is set. The in 1 shown sliding cam 7th accordingly comprises a cam section for each valve 13 with three cam tracks 14th that is axially displaceable. There can also be several link sections laterally outside next to the cam sections 13 to be available.

Every sliding cam 7th an actuator, not shown, is assigned which has pins which are attached to a lateral surface of the link section 12 trained grooves 15th of the sliding cam 7th work together. This results in an axial displacement of the sliding cam 7th in an area between two camshaft bearings. Due to the axial displacement of the sliding cam 7th the respective gas exchange valve is targeted with a specific cam track 14th operated so that a different valve lift setting takes place. The interaction of the pins of the actuator, not shown, with the grooves 15th of the scenery section 12 is familiar to the person skilled in the art addressed here.

To in particular after an axial displacement of the respective slide cam 7th on the respective intake camshaft 6th the relative position of the sliding cam 7th and thus a specific cam track 14th of the or each cam section 13 of the sliding cam 7th relative to an inlet valve to be actuated 5 To lock, a locking device, not shown, is provided, which has at least one first locking element, not shown, with a plurality of locking recesses and a spring-loaded second locking element, not shown, which interacts with the first locking element.

To despite the axial displaceability of the sliding cam 7th relative to the intake camshaft 6th To ensure proper functioning of the valve drive, the sliding cam must be centered on the one hand 7th on the intake camshaft 6th and on the other hand a torque transmission from the intake camshaft 6th on the sliding cam 7th to be guaranteed. This is done on the inlet camshaft 6th and the sliding cam 7th for the centering and for the torque transmission each spatially and functionally separate sections 16 or. 17th formed, namely at least one Centering section 16 for centering and at least one torque transmission section 17th for torque transmission. The functions of torque transmission and centering between the intake camshaft 6th and sliding cams 7th are therefore functionally and spatially separated from each other. This makes it possible to use these sections 16 and 17th to be designed according to requirements and thus to reduce the tolerance sensitivity of the valve drive according to the invention. Furthermore, manufacturing requirements and manufacturing costs can be reduced.

In the embodiment shown are for centering the slide cam shown 7th on the intake camshaft shown 6th two centering sections 16 present, being for torque transmission from the intake camshaft 6th on the sliding cam 7th only a single torque transmission section 17th is present in the axial direction of the intake camshaft 6th seen between the centering sections 16 is positioned.

The centering sections 16 are designed so that on the intake camshaft 6th A plurality of centering projections distributed radially outward over the circumference thereof 18th are formed on a radially inner surface 19th of the respective sliding cam 7th almost without radial play.

The axially between the centering sections 16 positioned torque transmission section 17th is designed in such a way that over an outer circumference of the intake camshaft 6th distributed torque transmission protrusions 20th in torque transmission depressions 21st of the respective sliding cam 7th and over an inner circumference of the respective slide cam 7th distributed torque transmission protrusions 22nd in torque transmission depressions 23 of the respective intake camshaft 6th intervene with almost no circumferential play.

The torque transmission depressions 23 the intake camshaft 6th are each of two torque transmission projections 20th same limited. The torque transmission depressions 21st of the sliding cam 7th are each of two torque transmission projections 22nd the same limited.

The centering sections 16 therefore have almost no radial play, whereas the torque transmission section 17th has almost no scope game.

In the radially inner surface 19th of the centering section 16 of the sliding cam 7th on which centering protrusions 18th the intake camshaft 6th that are in contact with almost no radial play are grooves 24 introduced, which extend in the axial direction, with in the grooves 24 when assembling the sliding cam 7th on the intake camshaft 6th the centering protrusions 18th engage with radial play. How best 4th and 5 can be removed, these grooves extend 24 into which when assembling the sliding cam 7th on the intake camshaft 6th the centering protrusions 18th the intake camshaft 6th engage with radial play across the entire axial width of the sliding cam 7th , so both over the centering sections 16 as well as via the torque transmission section 17th same.

The centering protrusions 18th the intake camshaft 6th have a head radius R3 (please refer 3 ), which is larger than a head radius R2 (please refer 3 ) the torque transmission projections 20th the intake camshaft 6th ..

A head radius R1 the one in the radially inner surface 19th of the sliding cam 7th introduced grooves 24 (please refer 5 ) is larger than the head radius R3 the centering protrusions 18th the intake camshaft 6th , with the circumferential width of these grooves 24 is greater than the circumferential width of the centering projections 18th the intake camshaft 6th so that when assembling the sliding cam 7th on the intake camshaft 6th , in which the centering projections 18th the intake camshaft 6th in the grooves 24 at least temporarily protrude with radial play in the grooves 24 are positioned.

After the sliding cam has been installed 7th on the intake camshaft 6th are the centering protrusions 18th the intake camshaft 6th out of the grooves 24 of the sliding cam 7th moved out and lie on the inner surface with almost no radial play 19th of the sliding cam 7th at.

As already stated, there are two centering sections in the exemplary embodiment shown 16 present, which are spaced apart from one another as seen in the axial direction, with between the two centering sections 16 the torque transmission section 17th is available. How best 2 can be found is between the in 2 left centering section 16 and the torque transmission section 17th an outdoor section 25th on the intake camshaft 6th formed whose radius is smaller than a head radius of the torque transmission projections 22nd of the sliding cam 7th . An axial width of the clearance portion 25th the intake camshaft 6th is at least as large as the axial width of the torque transmission projections 22nd of the sliding cam 7th .

Due to the above configuration of the intake camshaft 6th and sliding cams 7th will the in 6a to 6c clarified assembly of the Sliding cam 7th on the intake camshaft 6th guaranteed, according to 6a the sliding cam 7th starting from the left side of the intake camshaft 6th on the intake camshaft 6th in the axial direction (see arrow A1 in 6a) is pushed, namely in such a way that the centering projections 18th of the left centering section 16 in the grooves 24 of the sliding cam 7th Engage with radial play so that, starting from the left side, the sliding cam 7th simply axially on the intake camshaft 6th up to the in 6a relative position shown between sliding cams 7th and intake camshaft 6th can be pushed out.

In the in 6a relative position shown between sliding cams 7th and intake camshaft 6th then engage the torque transmission projections 22nd of the sliding cam 7th in the free passage 25th the intake camshaft 6th with radial play.

For further assembly of the sliding cam 7th on the intake camshaft 6th then takes place according to 6b a relative rotation (see arrow U in 6b) between inlet camshaft 6th and sliding cams 7th .

As a result of this relative rotation, the torque transmission projections 22nd of the sliding cam 7th such relative to the torque transfer depressions 23 the intake camshaft 6th or the torque transmission projections 20th the intake camshaft 6th relative to the torque transfer depressions 21st of the sliding cam 7th aligned that subsequently the sliding cam 7th in the axial direction (see arrow A2 in 6c ) on to the intake camshaft 6th can be postponed, as a result of this relative rotation between the inlet camshaft 6th and sliding cams 7th the centering protrusions 18th the intake camshaft 6th out of the grooves 24 of the sliding cam 7th are moved out and then with almost no radial play on the inner surface 19th of the sliding cam 7th come to the plant.

As 7th can be seen, which shows a cross section through the valve train according to the invention in the area of an intake camshaft 6th and one on the intake camshaft 6th positioned sliding cam 7th shows, have the centering projections 18th the intake camshaft 6th not only over a larger head radius R3 than the head radius R2 the torque transmission projections 20th the same, but rather have the centering projections 18th the intake camshaft 6th also over a larger circumferential width than the torque transmission projections 20th the same.

The circumferential width of the grooves 24 of the respective sliding cam 7th is accordingly larger, preferably many times larger, than the circumferential width of the torque transmission projections 20th of the respective intake camshaft 6th .

In the area of the torque transmission section 17th exists between the torque transmission projections 20th , 22nd and torque transfer depressions 21st , 23 one radial play in each case, but almost no circumferential play, so that in the area of the torque transmission section 17th Flanks 26th the torque transmission projections 20th , 22nd and torque transfer depressions 21st , 23 lie against one another in the circumferential direction almost without play

The centering of the sliding cam 7th on the intake camshaft 6th is accordingly carried out as head centering and the torque transmission as flank centering. These areas or sections are axially spaced from one another and accordingly spatially and functionally separated from one another.

Between the grooves 24 of the sliding cam 7th in the area of the centering sections 16 cylindrical surfaces are designed with a relatively large circumferential extent on which the sliding cam 7th can be safely and reliably picked up or clamped for machining so that the sliding cam can be machined 7th especially in the area of the lift curves 14th exact reference points can be provided. This can cause a sliding cam 7th be manufactured for the valve train according to the invention with little effort and high accuracy.

List of reference symbols

1

Cylinder head

2

Cylinder head cover

3

Cylinder head lower part

4th

Camshaft housing

5

Inlet valve

6th

Camshaft, intake camshaft

7th

Sliding cam

8th

Radial bearing devices

9

Bearing ring body

10

Bearing cap

11

Roller rocker arm

12

Scenery section

13

Cam section

14th

Cam track

15th

Groove

16

Section, centering section

17th

Section, torque transmission section

18th

Centering protrusion

19th

area

20th

Torque transfer projection

21st

Torque transmission recess

22nd

Torque transfer projection

23

Torque transmission recess

24

Groove

25th

Free passage

26th

Flank

R1

Head radius

R2

Head radius

R3

Head radius

Claims (6)

Valve drive for an internal combustion engine with several cylinders, at least one rotatably mounted camshaft (6) with at least one sliding cam (7) axially displaceable on the respective camshaft (6) being provided for actuating the gas exchange valves of the internal combustion engine, the respective sliding cam (7) opening the respective camshaft (6) is mounted in such a way that despite the axial displaceability of the respective sliding cam (7) relative to the respective camshaft (6), on the one hand, a centering of the respective sliding cam (7) on the respective camshaft (6) and, on the other hand, a torque transmission from the respective camshaft (6) on the respective sliding cam (7) is guaranteed, wherein a) for centering the respective sliding cam (7) on the respective camshaft (6), a centering section (16) is formed in such a way that a plurality of centering projections (18) are formed radially outward on the respective camshaft (6) distributed over the circumference thereof, which abut against a radially inner surface (19) of the respective slide cam (7); b) axially spaced from the centering section (16) for the torque transmission between the respective camshaft (6) and the respective sliding cam (7), a torque transmission section (17) is formed such that torque transmission projections (6) distributed over an outer circumference of the respective camshaft (6) 20) in torque transmission recesses (21) of the respective slide cam (7) and torque transmission projections (22) distributed over an inner circumference of the respective slide cam (7) engage in torque transmission recesses (23) of the respective camshaft (6); c) in the radially inner surface (19) of the centering section (16) of the respective sliding cam (7), on which the centering projections (18) rest, grooves (24) are made, in which grooves are made during the assembly of the respective sliding cam (7) of the respective camshaft (6), the centering projections (18) engage with radial play, the grooves (24) made in the radially inner surface (19) of the respective sliding cam (7) extending over the entire axial width of the same in the area of the centering section (16) and the torque transmission portion (17) extend; d) on the respective camshaft (6) axially between the centering projections (18) of the centering section (16) and the torque transmission projections (20) of the torque transmission section (17), a clearance section (25) is formed whose radius is smaller than a head radius of the torque transmission projections ( 22) of the respective sliding cam (7). Valve train according to Claim 1 , characterized in that two centering sections (16) are formed for the centering, and that a single torque transmission section (17) is formed for the torque transmission, which is positioned in the axial direction between the centering sections (16). Valve train according to Claim 1 or 2 , characterized in that a head radius R3 of the centering projections (18) of the respective camshaft (6) is greater than a head radius R2 of the torque transmission projections (20) of the respective camshaft (6), and that a head radius R1 of the in the radially inner surface (19 ) of the respective sliding cam (7) introduced grooves (24) is greater than the head radius R3 of the centering projections (18) of the respective camshaft (6). Valve train according to one of the Claims 1 to 3 , characterized in that an axial width of the clearance section (25) of the respective camshaft (6) is at least as large as an axial width of the torque transmission projections (22) of the respective slide cam (7). Valve train according to one of the Claims 1 to 4th , characterized in that a circumferential width of the centering projections (18) of the respective camshaft (6) is greater than a circumferential width of the Torque transmission projections (20) of the respective camshaft (6). Valve train according to one of the Claims 1 to 5 , characterized in that a circumferential width of the grooves (24) of the respective sliding cam (7) is greater than a circumferential width of the torque transmission projections (20) of the respective camshaft (6).

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