WO2018162324A1 - Cam follower roller, cam follower, valve train, and internal combustion engine - Google Patents

Abstract

The invention relates to a cam follower roller for a positively controlled cam follower of the valve train of an internal combustion engine, having a running surface. The invention is characterized in that the running surface has a plurality of, in particular two, partial running surfaces (11, 12) for axially divided cams (13, 14) of an assembled camshaft, the partial running surfaces (11, 12) being separately rounded such that the running surface has a plurality of rounded sections.

Description

 Cam follower roller, cam follower, valve train and internal combustion engine

description

The invention relates to a cam follower roller having the features of the preamble of claim 1. Such a cam follower roller is known for example from EP 2 574 744 AI. The invention further relates to a cam follower, a

Valve train and an internal combustion engine.

Modern internal combustion engines are increasingly subject to stricter regulations of pollutant and C0 ₂ emissions. The variability in the valvetrain is a key technology to meet the legal requirements for pollutant and C0 ₂ emissions by optimizing the combustion and charge exchange process.

An example of a continuously variable valvetrain system is the so-called ConcentricCam technology developed by the Applicant which leads to a significant improvement in the efficiency and environmental friendliness of internal combustion engines. Specifically, from the aforementioned EP 2 574 744 AI, which is based on the applicant, a built camshaft with an outer tube and a concentric inner shaft known. The cams of

Inner shaft are rotatable relative to the cams of the outer tube, wherein in each case a cam of the inner shaft with a cam of the outer tube form a partial cam pair, which is non-positively connected to a cam follower. By adjusting the inner shaft, the partial cams of the partial cam pair are spread, so that the opening duration of the actuated by the cam follower valve can be varied continuously. Broadening the valve lift curve will reduce NO _x emissions and thus exhaust aftertreatment costs. The required for the spread of the cam division of the cam profile in two parallel juxtaposed partial cam leads to a

asymmetric force application and thus to a contact point from the roll side, directed in the direction of the symmetry axis tilting moment as soon as the cam follower roller passes over one of the two partial cams.

From the prior art, the use of cam follower rollers is also known, which have a spherical surface in the axial direction to avoid edge beams and concomitant damage to the running surfaces of the contact partners. The use of such cam follower rollers in the above-described cam system leads to a reinforcement of the

Tilting moment.

The previous measures to limit the overturning moment can not be sufficiently reliably avoided due to manufacturing tolerances, systemic play and resiliency in the valve train in double cam systems edge bearer.

The invention is based on the object to improve a cam follower roller of the type mentioned in that tilting moments are reduced when used in variable valve trains in a simple manner. The invention is further based on the object to provide a cam follower, a valve train and an internal combustion engine.

According to the invention this object is achieved by a cam follower roller according to claim 1. With a view to the cam follower, this task is accomplished by the

Subject of claim 8 solved. Regarding valve train and

Internal combustion engine is the task in each case by the objects of the

Claims 11, 13 solved.

The cam follower roller according to the invention is for a positively controlled

Cam follower of the valve train of an internal combustion engine and includes a tread. The tread has a plurality, in particular two, partial contact surfaces for axially divided cams of a built-up camshaft. The partial contact surfaces are each formed separately spherical, so that the tread has several crowns. In contrast to the prior art, the tread is not continuously convex, ie formed with a single crown, but has a plurality of crowns, which extend side by side in the axial direction of the cam follower roller. Each crown corresponds to a partial run area. The single crown extends in the axial direction of the cam follower roller and forms a

A lateral surface with a vertex which is spaced from the inner and outer edges of the associated Teilaufauffläche. The vertex is raised relative to the inner and outer edges. In contrast to a cam follower roller with a single crown and a single vertex, the invention has several, in particular two vertices.

Preferably, the cam follower roller has two crowns. It is also possible that the cam follower roller has three crowns. The number of crowns corresponds to the number of partial cams per cam follower roller.

The invention has the advantage that edge bearers (Hertzian pressure) of the cam follower roller on the raceways of the partial cams are avoided. By dividing the tread into several partial contact surfaces, each with its own crowning is achieved that the cam follower role when tilting a

load-appropriate contact surface to the cam profile has, so that a

Excessive surface pressure is prevented. With that

Reduced wear problems. The invention thus does not avoid the tilting of the cam follower by the eccentric force input, but adjusts the running surface of the cam follower roller to the change in position. This is made possible by dividing the tread into partial treads.

The invention is more compact in comparison to other solutions which aim for symmetrical cam-to-cam follower contact.

in particular in the axial direction of the camshaft. In addition, the invention avoids that in order to stabilize the cam follower, the number of components of the valve train is increased, so that it forms an economically viable solution without increased production costs and increased production costs.

Without being limited thereto, the invention improves the application of the economic double cam design for positively driven cam followers

(ConcentricCam type 2). The invention is applicable to all types of cam followers Applicable, which have a cam follower role, for example. Toggle, drag lever, rocker arm and plunger, for example, tappets.

Preferably, the cam follower roller forms a single, in particular one-piece role. The partial contact surfaces are thus arranged on a common cam follower roller and together form the running surface of the cam follower roller.

It is also possible that the cam follower roller is constructed of a plurality, in particular two, sub-rollers, which are arranged axially next to one another and are rotatable independently of one another. Each sub-roll is assigned to a sub-cam and has a lateral surface with its own crown and a vertex. The

Partial roles form the Teilaufaufflächen, which together form the running surface of the cam follower roller. The multiply spherical contour of the divided

Cam follower roller corresponds to the multi-spherical contour of the one-piece

Cam follower role.

The design of the single single cam follower roller with two crowns is advantageous in comparison to the two juxtaposed separate sub-rollers (one per sub-cam) in that the single cam follower roller makes permanent contact with the overall cam contour, i. owns the two partial cams. As a result, the cam follower roller is always in a rotational movement about its roller axis. Just for the commonly used storage of the cam follower roller by means of bearing needles is a discontinuous

Rotational movement due to separate sub-roles unfavorable. On the one hand, it can come between the contact surfaces of roller and cam for the demolition of the lubricating film. On the other hand lead uneven, sometimes bumpy

Rotational movement in the needle bearing itself to damage.

The split cam follower roller is included in the invention, but has the above disadvantages compared to the common, in particular one-piece cam follower roller.

Preferred embodiments of the invention are specified in the subclaims.

Thus, the crowning of at least one partial contact surface may be asymmetrical, so that the tilting moment due to the asymmetrically introduced forces can be well balanced, since the partial operating surface of the tilting movement is adjusted.

Preferably, the vertex of the crown of the partial contact surface is off-center and arranged offset to the outer edge of the partial operating surface. This is particularly well taken into account the fact that due to the

eccentric force entry the tilting moment inwards, ie acts in the direction of the symmetry line of the cam follower and thereby the largest possible contact surface is formed when tilting.

In a further embodiment, the crowning of at least one partial operating surface has a plurality of different radii. As a result, the shape or contour of the respective partial operating surface even better to the combined movement of the

Partial cams are adjusted.

Particularly preferably, the crown in the region of the outer edge of the

Teilaufauffläche on a first radius, which is smaller than a second radius of the crown of the part tread. In other words, the outer edge of the part tread has a small curvature and the inner region has a large curvature. Since the contour area at the outer edge of the partial operating surface only at

Transfer point between the sub-cam in contact with the cam track occurs and the cam normal force is then divided on both sub-cam, the surface pressure is not increased by the small curvature. Subsequently, the contact area shifts back inward to the larger curvature.

Preferably, the crowns of the partial contact surfaces are formed symmetrically to each other. Particularly preferably, the partial contact surfaces are mirror-symmetrical, based on a center plane of the cam follower roller, which runs perpendicular to the axis of rotation of the cam follower roller. Alternatively, the crowns of the partial contact surfaces can be designed differently.

Between the partial contact surfaces may be formed an annular recess. This has the advantage that edge supports are avoided in the case of strong tilting movements on the inside of the part cams.

In a cam follower for a valve train of an internal combustion engine, the cam follower has a contact surface for cams. In the context of this invention the contact surface has several, in particular two, partial contact surfaces for axially divided cams of a built-up camshaft. Here are the

Part contact surfaces each formed separately spherical, so that the contact surface has a plurality of crowns.

In one embodiment, the above are

Part contact surfaces of the cam follower to partial contact surfaces. The cam follower may include, for example, a cam follower roller or a pickup roller, or the like.

In another embodiment, the above-mentioned partial contact surfaces of the cam follower are partial sliding surfaces of a cam follower with sliding tappet. For example, the cam follower includes a sliding tappet

Cup tappets or valve tappets and the like.

The valve train according to the invention for an internal combustion engine has a built camshaft with axially split cams, cam followers and gas exchange valves, in particular intake valves, which are to be actuated by cam follower according to the invention. For the advantages of the valve train reference is made to the comments on the cam follower.

The cam surfaces of the cams associated with a cam follower may each extend at an angle to the cam axis of rotation. In other words, the cam surfaces do not extend parallel to

Cam rotation axis. The cam running surfaces can thus be formed obliquely. The angle to the cam rotation axis is concrete between an imaginary one

Extension of the oblique cam surface and the cam rotation axis formed. The two cam surfaces are inclined inwards, so that

a balanced surface contact between cam and cam follower role is further favored. For axially split cams, the respective

Cam running surfaces also be mirror-symmetrical, based on a center plane which is perpendicular to the cam axis of rotation.

The invention will be explained in more detail below with reference to an embodiment with reference to the accompanying schematic drawings.

In these show: 1 shows a cross section of a cam follower roller according to an embodiment of the invention and associated partial cams in different positions.

FIG. 2 shows a contour of a partial cam for the cam follower roller according to FIG. 1; FIG.

Fig. 3 is a detail A of the position C of FIG. 1 and

4 shows a detailed detail B of the position B according to FIG. 1

Fig. 1 shows a pairing of a cam follower roller 10, specifically the outer ring of the cam follower roller 10, and the associated part cam 13, 14 which are non-positively connected to the cam follower roller 10 in a conventional manner.

The cam follower roller 10 and associated part cam 13, 14 form part of a continuously variable valve train, in which a built camshaft for

Inlet valves of an internal combustion engine comprising an outer tube and an inner shaft, which are arranged concentrically with each other and can rotate individually by means of a phaser relative to each other (not shown). The outer tube and the inner shaft each drive their own cams with their own profiles. Two partial cams 13, 14 are provided for each intake valve, wherein a first partial cam 13 is connected to the inner shaft and a second partial cam 14 is connected to the outer tube. The first part cam 13 forms the adjusting cam, the second part cam 14 the fixed cams. Together, the partial cams 13, 14 adjustable expansion cams, which cause a variable cam profile. A relative rotational movement between the outer tube and the inner shaft thus leads to a variation of the cam profile effective for the cam follower and thus to the variation of the Ventilhubverlaufs.

This can be well understood using the example of the first part cam 13 according to FIG. 2. In the area of the positions B, C forms the tread of the first

Teilnockens 13 a plateau that to a substantially constant

Opening position of the inlet valve leads and thus determines the opening time. In addition, at the positions B, C, the transfer of the tap takes place

Cam follower roller on the second part cam 14 (contact change between adjusting cam 13 and fixed cam 14). By adjusting the angle of rotation between the two sub-cams 13, 14, these are spread and the entire, ie combined plateau length changed, resulting in a change of

Overall cam profile leads. This feature is known per se and will be available in the

Framework of the ConcentricCam technology, as described, for example, in EP 2 574 744 AI realized.

The partial cams 13, 14 are connected to the cam follower roller 10 of a cam follower (not shown) which converts the rotary cam motion into a linear motion and drives the associated inlet valve. In the example, the cam follower is a rocker arm. Other cam followers, such as swivel and swing levers or bucket tappets, each with cam follower rollers are possible. The invention is not limited to the control of intake valves, but extends generally to gas exchange valves.

The division of the cam profile into two parallel juxtaposed partial cams 13, 14 leads to an asymmetrical force application and thus to a contact point from the roll side, directed in the direction of the symmetry axis of the cam profile tilting moment as soon as the cam follower roller 10 one of the two partial cams 13, 14 passes over. This is shown in the positions A, B and D shown in FIG. 1. In position C am

Transfer point between the partial cams 13, 14 and in the overlapping region of the base circle are the two partial cams 13, 14 at the same height and the

Cam Follower Roller 10 is free of tilting torque. The contact change begins already at position B, in which both partial cams 13, 14 abut the cam follower roller 10, but have different height position, so that a tilting moment is applied. The eccentric force entry takes place in the positions A and D, if only the first part cam 13 (position A) or only the second part cam 14 the

Cam follower roller 10 acted upon by a force. Each inward, i. to the symmetry axis of the partial cams 13, 14 acting, changing tilting moment M is shown (position A, B clockwise, position D in

Counterclockwise).

As seen in Fig. 3, the cam follower roller 10 forms a one-piece roller with a tread, which is divided into two partial contact surfaces 11, 12. each

Part contact surface 11, 12 is designed to be spherical, so has its own

Crowning. The running surface thus has in each case a spherical partial contact surface 11, 12 for the two partial cams 13, 14. If more than two partial cams per Cam follower roller 10 are used, the number of increases

Part contact surfaces and thus the crowns accordingly.

Due to the multiple crowning, specifically double crowning, it is achieved that the cam follower roller maintains a load-compatible contact surface with the cam profile during tilting. As a result, the tilts occurring in positions A and D according to FIG. 1 occurring in opposite directions and edge beams are avoided.

A further improvement of the contact surface between the component pairs is achieved by the asymmetrical formation of the crown of each partial contact surface 11, 12, which is shown in detail A of FIG. 3. In this case, the center of the crown is offset so that for the tilting moment-free case that occurs at the transfer point between the partial cams 13, 14 and in the overlap region of the base circle, by manufacturing tolerances and by molding and

Lag deviations caused tilting of the cam follower roller 10 is designed in the direction away from the tilting direction of the crown symmetry line. In other words, the symmetry axis of the crown 20 is inclined relative to the normal to the axis of rotation 22 of the cam follower roller 10. Concretely, the symmetry axis of the crown 20 is outward, i. to the outer edge or the outer edge 16 of the respective part of the tread 11, 12 inclined towards. The vertex of the crown is thus off-center and offset from the outer edge 16 of the partial support surface 11, 12 out.

The resulting from the vertex inwardly extending segment of the crown is thereby compared to a symmetrical

Predominantly extended, so that in the case of the end positions of the cam follower roller 10 according to positions A, D a position-optimized design of the center position of the crown contour is achieved. Thus, it is avoided that the cam follower roller 10 due to the tilting moment and the component games and elasticities resulting tilt on the tilting side runs on the roller edge and a sufficient size of the contact surface is present.

As illustrated in FIG. 4, the crowning of the second partial contact surface 12 has a plurality of different radii. In other words, a contour with different contiguous curvatures is used for the crown. Concretely, the crown in the region of the outer edge 16 of the second Part run area 12 to a first radius which is smaller than a second radius of the crown of the partial support surface 12. At the outer region of the crown contour, therefore, a small curvature 23 is used. Since this contour area is only on

Transfer point between fixed and adjustable cam in contact with the

Cam track occurs, splits the cam normal force on both partial cams, whereby the surface pressure is not increased by the small curvature 23 (see Fig. 1, position B). Subsequently, the contact area shifts back inward to the larger curvature (see Fig. 1, position A and D).

In order to achieve a balanced surface contact on the respective part cam 13, 14, the cam surfaces 18, 19 at an angle to

Cam axle be executed. As a result, the extend

Cam running surfaces 18, 19 are not parallel to the cam axis of rotation, but are formed obliquely (not shown). In this example, with axially split cams, the respective cam surfaces 18, 19 are mirror-symmetrical, with respect to a median plane perpendicular to the

Cam pivot axis extends.

As shown in FIG. 3, the two partial contact surfaces 11, 12 are separated by an annular recess 17, which adjoins the inner edge of the partial contact surfaces 11, 12, respectively. If one of the two sub-cams is run over by the cam follower roller, this leads to an asymmetrical force application and thus to a contact point from the roll side, directed in the direction of the symmetry axis tilting moment. In this recess 17, the cam edge can dip during tilting, without getting into contact with the cam follower roller, whereby edge beams are avoided.

The invention is generally applicable to cam followers having a contact surface for cams. In the context of this invention, this contact surface is characterized in that the contact surface has a plurality, preferably two, partial contact surfaces 11, 12 for axially divided cams 13, 14 of a built-up camshaft. The partial contact surfaces 11, 12 are each formed separately spherical, so that the contact surfaces have multiple crowns.

The partial contact surfaces 11, 12 may be partial contact surfaces 11, 12 of a

Be cam follower role. For this purpose, reference is made to the above explanations to the cam follower role. The cam follower according to the invention is not limited to cam follower rollers, but also includes cam followers with Gleitabgriff as bucket tappets, valve tappets, or the like. The partial contact surfaces of the cam follower are then formed by the Teilgleitflächen.

LIST OF REFERENCE NUMBERS

10 cam follower roller

 11 first partial contact surface (first partial contact surface)

 12 second partial contact surface (second partial contact surface)

 13 first part cams

 14 second part cams

 15 free

 16 outer edge

 17 recess

 18 cam surfaces

 19 cam surfaces

 20 symmetry axis of the crown

 21 inclination of the crown axis

 22 normal to the axis of the picking roller

 23 Small curvature

Claims

claims A cam follower roller for a positively controlled cam follower of a valvetrain of an internal combustion engine, the cam follower roller having a tread  dad u rch nets that net  the running surface has a plurality, in particular two, partial running surfaces (11, 12) for axially divided cams (13, 14) of a built-up camshaft, wherein the part running surfaces (11, 12) are each formed separately spherical so that the running surface has a plurality of crowns. 2. cam follower roller according to claim 1  dad u rch nets that net  the crowning of at least one partial contact surface (11, 12) is asymmetrical. 3. cam follower roller according to claim 2  dad u rch nets that net  the apex of the crowning of the partial contact surface (11, 12) is off-center and offset towards an outer edge (16) of the partial contact surface (11, 12). 4. cam follower roller according to one of claims 1 to 3  dad u rch nets that net the crowning of at least one partial running surface (11, 12) has a plurality of different radii. 5. cam follower roller according to claim 4  dad u rch nets that net  the crown in the region of an outer edge (16) of the partial contact surface (11, 12) has a first radius which is smaller than a second radius of the crown of the partial contact surface (11, 12). 6. cam follower roller according to one of claims 1 to 5  dad u rch nets that net  the crowns of the partial contact surfaces (11, 12) are symmetrical to each other. 7. cam follower roller according to one of claims 1 to 6  dad u rch nets that net  an annular recess (17) between the partial contact surfaces (11, 12) is formed. 8. cam follower for a valve train of an internal combustion engine, which  Cam follower has a contact surface for cams  dad u rch nets that net  the contact surface has a plurality of, in particular two, partial contact surfaces (11, 12) for axially divided cams (13, 14) of a built-up camshaft, wherein the partial contact surfaces (11, 12) are formed separately crowned, so that the contact surface has a plurality of crowns. 9. cam follower according to claim 8  dad u rch nets that net  the partial contact surfaces comprise partial contact surfaces. 10. cam follower according to claim 8  dad u rch nets that net  the partial contact surfaces include partial sliding surfaces. 11. A valvetrain for an internal combustion engine with a built camshaft having axially split cams (13, 14), cam followers and Gas exchange valves, which are each operated by a cam follower according to claim 8. 12. Valve drive according to claim 11  dad u rch nets that net  the cam surfaces (18, 19) of the cams (13, 14) associated with a cam follower each extend at an angle to the cam axis of rotation. 13. Internal combustion engine with a valve drive according to claim 11.