Bearing Arrangement for a Camshaft of an Internal Combustion Engine and Crankcase with Same

This is a continuation of PCT application no. PCT/EP2023/085434, entitled “BEARING ASSEMBLY FOR A CAMSHAFT OF AN INTERNAL COMBUSTION ENGINE, AND CRANKCASE COMPRISING SAME”, filed Dec. 12, 2023, which is incorporated herein by reference. PCT application no. PCT/EP2023/085434 claims priority to German patent application no. 10 2022 133 736.7, filed Dec. 16, 2022, which is incorporated herein by reference.

The present invention relates to internal combustion engines.

Bearing arrangements of the aforementioned type are generally known and are used in engine construction to ensure an operationally stable and positionally precise arrangement of the camshaft in the crankcase. Since the camshaft controls the timing sequence of the engine's ignition points, a smooth operation and high reliability are of great importance.

While the known bearing arrangements generally perform their purpose satisfactorily, there is nevertheless a desire to improve the bearing arrangements in terms of cost efficiency, without compromising the quality and operational reliability of the bearing arrangement.

Accordingly, what is needed in the art is to reduce the disadvantages described above as far as possible in a bearing arrangement of the type mentioned at the outset. In particular, what is needed in the art is a bearing arrangement that allows for simplified maintenance and assembly without impairing the running quality of the camshaft.

The present invention relates to a bearing arrangement for a camshaft of an internal combustion engine, wherein the internal combustion engine has a crankcase, the camshaft has a camshaft gear wheel and a shaft end allocated to the cam shaft gear wheel, and wherein the bearing arrangement has an axial bearing which is designed to support the camshaft on the side of the shaft end.

The present invention provides a bearing arrangement for a camshaft of an internal combustion engine, wherein the internal combustion engine has a crankcase and a camshaft which has a camshaft gear wheel and a shaft end allocated to a cam shaft gear wheel, and wherein the bearing arrangement has an axial bearing which is designed to support the camshaft on a side of the shaft end, characterized in that the axial bearing has a crescent-shaped plain bearing body designed to axially support the camshaft and to be attached to the crankcase by way of a mounting interface.

In a first further development, the camshaft has a bearing groove that is circumferentially incorporated into the camshaft. The crescent-shaped plain bearing body is designed to be inserted into the bearing groove for axial support of the camshaft, to support the camshaft axially when inserted, and to be attached—in the inserted state—to the crankcase by way of the mounting interface when inserted.

Alternatively, the present invention proposes that instead of the camshaft, the plain bearing body is equipped with the bearing groove and is designed to be slid onto a corresponding shoulder of the camshaft for axial support of the camshaft, to axially support the camshaft in the slid-on state, and to be attached to the crankcase in the slid-on state by way of a mounting interface. Accordingly, the following considerations and optional embodiments also apply to this alternative.

The present invention is based on the realization that conventional axial bearings-due to their reduced number of parts compared to roller bearings, which however overall is still quite high-involve an assembly effort that can be optimized. In conventional axial bearings, where rotating parts are to be supported axially on stationary parts, the axial bearings were designed as dedicated components, whereby always a stationary part had be attached to a first component and a rotating part was attached to the second, rotating component, wherein these stationary and rotating components of the axial bearing were designed as single or multiple parts respectively, and frequently had additional interaction elements, forming the sliding surface or other bearing surfaces.

The present invention separates from the conventional concept in that the axial bearing is formed by only two mechanical elements when including the camshaft. Strictly speaking, the axial bearing consists of only one single component, namely the crescent-shaped plain bearing body, which engages in the groove with its bearing surfaces which are adapted to the groove.

In the concept of the current invention the term crescent-shape is understood to mean that the plain bearing body has a section with a substantially semicircular contour that conforms to the surrounding bearing groove, in particular has an identical curvature.

Optimization of cost efficiency has already been achieved through parts reduction.

A further optimization of cost efficiency is achieved in that the crescent-shaped plain bearing can be laterally inserted into the bearing groove, namely in a radial or radial/tangential motion. This allows for the camshaft and crankcase to be mounted and to be inserted into the predetermined position in the crankcase. Once the bearing groove is arranged approximately in the designated assembly position, the plain bearing body can be meshed with the camshaft by inserting it into the bearing groove. Since the camshaft is still movable in the axial direction at this point, assembly of the unit consisting of camshaft and plain bearing body can then be accomplished in a single step by attaching the plain bearing body with the mounting interface to the crankcase.

This also expedites and simplifies assembly, resulting in a further improvement in cost efficiency. At the same time, the plain bearing body remains more easily accessible for maintenance work.

If reference is made to an axial direction in connection with the present invention, this is to be understood to be the direction of the rotational axis of the camshaft. Equally, a radial or tangential movement is always understood as a movement relative to the rotational axis of the camshaft.

The present invention is advantageously further developed in that the mounting interface has a contact surface, wherein the crankcase has a corresponding contact surface, which is arranged optionally on a wall of the crankcase.

In optional embodiments, a side wall, end wall, or another separating wall in the crankcase is used as the crankcase wall. The wall can close off partial volumes of the crankcase or the entire crankcase, or only certain areas of the crankcase. As an alternative to a wall, other structures that provide rigidity to the crankcase, such as struts or ribs for supporting the camshaft in general, and the axial bearing in particular, can also be used.

In one optional embodiment, the plain bearing body is designed to be axially screwed to the crankcase. The position of the plain bearing body on the crankcase can be very precisely defined by mechanical processing of the contact surfaces of the mounting interface and the crankcase. This avoids establishment of longer tolerance chains, which are unavoidable in conventional axial bearings. The axial screw connection of the plain bearing body to the crankcase also facilitates assembly of the unit consisting of camshaft and plain bearing body.

In a further optional embodiment, the mounting interface on the plain bearing body has a number of through-bores in a predetermined pattern, which extend in axial direction from a first side that faces away from the contact surface to a second side of the plain bearing body that faces toward the contact surface, and wherein the crankcase has a number of threaded holes in the same pattern.

It can be advantageous to introduce the round holes that define the pattern in a single processing step into the plain bearing body and the crankcase. In optional embodiments, the holes of the pattern, in other words the through-bores in the plain bearing body and the threaded holes in the crankcase, are arranged on a common pitch circle around the camshaft axis.

In a further optional embodiment, the plain bearing body features an increased material thickness in axial direction in the region of the mounting interface, optionally designed as a protrusion on the first side. The regions of increased material thickness advantageously result in an increase in the grip length for the screw connection. The material reinforcements can be designed to be integral on the plain bearing body if, for example, it is a cast part. Alternatively, they can also be provided additionally on the plain bearing body, for instance, by way of discs or sleeves that are arranged on the plain bearing body or are firmly connected to it.

In an optional version, the plain bearing body can be provided as a cast part, or in another optional version as a sheet metal part; in both versions, precise shaping and machining of the relevant contact surfaces and bearing surfaces is possible even in high quantities.

In a further optional embodiment, the plain bearing body has a first bearing surface and a second bearing surface opposite the first bearing surface, the bearing groove has two opposite groove edges, and the bearing surfaces each face one of the groove edges in the inserted state of the plain bearing body. The groove edges and the plain bearing surfaces are optionally arranged parallel to each other. A surface of the plain bearing body, and a groove edge facing toward the latter respectively provide a plain bearing surface pairing.

In an optional embodiment, the (first) axial distance between the opposite groove edges is greater than the (second) axial distance between the opposite bearing surfaces of the plain bearing body, wherein the first axial distance is optionally greater within a range of 0.01 to 0.5 mm than the second distance, so that, in the inserted state, an axial bearing gap can form between the bearing surfaces and the groove edges respectively. Furthermore, the axial bearing gap on both sides of the bearing surfaces is optionally 0.025 mm to 0.4 mm or more, especially optionally 0.05 mm to 0.2 mm.

In a further optional embodiment, the axial bearing is a fluid-lubricated axial bearing, and the plain bearing body has a fluid channel that can be connected in a fluid-conducting manner to a lubricant supply, wherein the fluid channel has at least one outlet for each bearing surface that opens into the bearing surface. The output of lubricant to both bearing surfaces via the fluid channel has the advantage that a fluid film can form on both sides of the plain bearing body at the respective groove edges, which simultaneously favors or causes a hydrodynamic centering of the plain bearing body in the bearing gap that is formed by the groove edges. It is particularly optional if the outlets of the fluid channel are each aligned symmetrically, and especially optional if they are aligned with each other towards the opposite sides of the plain bearing body.

In a further optional embodiment, the plain bearing body has an inlet side and an outlet side in circumferential direction relative to the direction of rotation of the camshaft. In the context of the present invention, direction of rotation refers to the direction in which the camshaft rotates for the majority of the operating time in normal operation of the engine.

The outlets of the fluid channel are optionally positioned closer to the inlet side than to the outlet side. This is advantageous for lubricant distribution along the bearing gaps.

As previously indicated, the outlets of the fluid channel are optionally aligned coaxially to one another in an optional embodiment.

In a further optional embodiment, the bearing surfaces have an end face in circumferential direction at their inlet end, where a chamfer is formed at each, wherein the chamfer optionally has an angle of 2° to 10°, especially optionally of 4° to 6°, so that the plain bearing body is tapered in a wedge shape at the inlet end. The wedge-shaped taper provided by the chamfers has the advantage that the assembly, in other words, insertion of the plain bearing body into the bearing groove, is clearly simplified. On the other hand, the wedge-shaped taper contributes to the fact that during operation, i.e., when the camshaft is rotating, lubricant that is not introduced into the gap through the fluid channel, but rather is swirled up due to the rotating parts in the engine housing and impacts the inlet side of the axial bearing, is drawn into the wedge acting as a funnel due to the rotation of the camshaft, which further improves the lubrication of the axial bearing.

In one optional embodiment, the bearing arrangement includes a radial bearing for the camshaft, particularly in the region of the shaft end, wherein the radial bearing supports the camshaft radially at the crankcase. In this type of embodiment, the radial bearing is optionally arranged in a bearing seat of the crankcase, and the axial bearing is arranged in axial direction between the radial bearing and the camshaft gear.

In an optional embodiment, the radial bearing is arranged in the wall of the crankcase, to which the axial bearing with its mounting interface is also attached from the direction of one of the axial end faces. Thus, the camshaft gear wheel and the axial bearing are located optionally on the same side relative to the wall of the crankcase where the radial bearing is located, which further simplifies both assembly and maintenance. To service or replace the axial bearing, simply remove the camshaft gear from the face of the shaft end, and the entire axial bearing is exposed on the wall of the crankcase.

The axial bearing is optionally aligned such that the plain bearing body engages under the camshaft. In other words, the plain bearing body wraps around the camshaft-with respect to the direction of gravity in the operational orientation of the crankcase-from below. The crescent shape causes the plain bearing body to form a trough. This has the advantage that less oil escapes both during operation and at standstill. This is particularly advantageous after standstill periods, in that emergency lubrication is ensured until sufficient oil pressure in the lubrication supply of the bearing arrangement is established after engine start, optionally within 15 to 20 seconds after engine start.

The present invention was described above in a first aspect, with reference to a bearing arrangement. In a second aspect, the present invention further relates to a crankcase of an internal combustion engine, with a camshaft, a camshaft gear wheel, fixed to the camshaft for driving the camshaft, and a bearing arrangement.

According to the second aspect, the present invention further provides that the bearing arrangement is designed according to one of the previously described embodiments.

The present invention exploits the same advantages concerning the second aspect as the bearing arrangement according to the first aspect. Optional embodiments of the bearing arrangement of the first aspect are also optional embodiments of the crankcase according to the second aspect and vice versa, which is why reference is made to the above descriptions in order to avoid repetitions.

Due to the fact that, in the crankcase according to the present invention, the camshaft has the camshaft gear wheel and a shaft end allocated to the camshaft gear wheel, and that the bearing arrangement includes the axial bearing, which axially supports the camshaft on the side of the shaft end, whereby the camshaft has the bearing groove that is circumferentially introduced into the camshaft, and the axial bearing has the crescent-shaped plain bearing body that is inserted into the bearing groove for axial support of the camshaft, axially supports the camshaft and is fixed to the crankcase via the mounting interface, a reliable support of the camshaft is achieved, which, compared to conventional axial bearings, is significantly easier to install and maintain without including the quality of the axial positioning of the camshaft.

The plain bearing body does not need to be pressed in but can be screwed axially to the crankcase. The fluid channel of the plain bearing body can be connected to a lubrication supply with minimal effort, wherein the fluid channel ensures lubrication of the plain bearing.

Embodiments of the present invention are described below with reference to the drawings in comparison to the prior art, which is also partially illustrated.

With regard to additions to the teachings that can be directly inferred from the drawings, reference is made to the relevant state of the art. It is thereby to be considered that numerous modifications and changes regarding the design and detail of an embodiment can be made without departing from the general concept of the present invention.

The general concept of the present invention is not limited to the exact design or detail of the optional embodiment shown and described below, nor is it limited to an object that would be restricted compared to the object claimed in the claims. In the case of specified measurement ranges, values within the stated limits are to be disclosed as threshold values that can be used and claimed randomly.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

shows crankcaseof internal combustion engine. Crankcasehas a wallin which camshaftis mounted by way of a bearing arrangement (seeto).

Camshafthas shaft endto which camshaft gear wheelis attached. Camshaft gear wheelis designed to be driven by way of a transmission and to rotate camshaftin direction of rotation B about a rotation axis A. Crankcasecan be closed with one or more covers which however are not necessary for explanation of the present invention and are therefore not shown.

As can be seen fromto, axial bearingis arranged between camshaft gear wheeland wall. Axial bearinghas a crescent-shaped plain bearing body. Plain bearing bodyhas a bearing sectionthat is inserted into bearing groove, which is provided circumferentially on camshaft.

Plain bearing bodymoreover has a mounting interface, by way of which plain bearing bodyis attached to wall.

The assembly optionally is performed in such a way that camshaftis pushed into its approximate designated operating position in the direction of axis A. Then, optionally with camshaft gear wheelnot yet assembled, plain bearing bodyis engaged laterally with camshaftso that bearing portiondips into bearing groove.

Plain bearing bodyis then brought into contact with wallvia the mounting interface and attached, for example, axially screw-fastened, as shown in the present design example. For this purpose, the bearing arrangement has a number, in particular a plurality, of screwsthat are installed along a predetermined pattern on plain bearing bodyand on wall.

To accommodate plain bearing body, wallhas a contact surfacecorresponding to mounting interfaceof the latter, which can be designed as one piece or segmented into several spaced-apart parts. After mounting plain bearing bodyand securing it to wall, camshaft gear wheelcan finally be connected in a known manner with shaft endof camshaft.

Meshing of plain bearing bodyinto camshaft, particularly into its bearing groove, is shown in more detail inand.