Patent Application
20150308299
This application claims priority to German Patent Application No. 10 2013 207 573.1, filed Apr. 25, 2013, the contents of which are hereby incorporated by reference in their entirety.
The present invention relates to a bearing frame or a cylinder head cover of an internal combustion engine, comprising at least one camshaft mounted therein according to the preamble of the claim 1. The invention also relates to an internal combustion engine comprising such a bearing frame or such a cylinder head cover.
Closed bearing frames or cylinder head covers principally offer the great advantage that they can be pre-assembled in a cost-effective manner. Moreover, they are relatively stiff and light, which is a decisive advantage in particular when used in motor vehicles. However, assembling a camshaft in such a closed bearing frame or such a cylinder head cover requires holding the individual components, for example cams, in their joining position and subsequent inserting a shaft tube of the camshaft, which is complicated and prone to error. Under certain circumstances, this can result in a high reject rate which, of course, has to be avoided. As an alternative, it is also conceivable to manufacture the camshafts separately, i.e., to join the cams and functional components separately on the shaft tube, as a result of which the reject rate can be reduced significantly. However, for a desired tunnel mounting, such completely pre-assembled camshafts require that comparatively large bearing openings are provided through which the camshaft together with the cams can be slid. Thus, the bearing diameter is significantly larger than the shaft diameter, which is contrary to the desire of minimizing friction. When using antifriction bearings, the mentioned friction problem is even more serious in the case of a large diameter of the bearing.
The present invention therefore is concerned with the problem of providing an improved embodiment for a bearing frame or a cylinder head cover of the generic kind, which avoids the disadvantages known from the prior art.
This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are subject matter of the dependent claims.
The present invention is based on the general idea of utilizing each of the advantages of previous assembly methods separately and thereby to implement overall a simplified and improved assembly of a prefabricated camshaft in a bearing frame or a cylinder head cover. The bearing frame according to the invention or the cylinder head cover according to the invention thus enables high-quality separate manufacturing of the camshafts which are subsequently installed in the pre-assembled state in the respective bearing frame or in the respective cylinder head cover and are tunnel-mounted therein, wherein comparatively small bearing diameters are sufficient. Accordingly, the bearing frame according to the invention or the cylinder head cover according to the invention comprise at least one camshaft that is mounted therein and is tunnel-mounted in at least two bearing openings arranged along a bearing channel. On the camshaft, there are arranged at least two radial bearings, each of which has an outer bearing shell, wherein the respective outer bearing shells of at least two radial bearings have different outer diameters that are in each case formed complementary to an inner diameter of the associated bearing opening. Here, the inner diameters of the bearing openings decrease in the direction of assembly of the camshaft in the bearing frame or in the cylinder head cover so that the previously separately pre-fabricated camshaft can be slid as a whole into the bearing openings that form the bearing channel of the cylinder head cover or the bearing frame. By assembling also the outer bearing shell on the camshaft and, at the same time, by the stepped formation of the individual radial bearings, simple and yet high-quality assembling of the camshaft in the bearing frame or the cylinder head cover can be achieved. Here, a standard radial bearing for radially supporting the camshaft in the bearing openings can usually be assembled between individual cams, wherein the standard radial bearing is covered by a bearing ring and thereabove by the already-mentioned bearing shell which, in a particularly advantageous embodiment, is made from the same material as the bearing frame or the cylinder head cover. The bearing ring, however, is usually made from hardened steel that is typically used for bearing surfaces. This also minimizes problems caused by thermal expansion since the bearing frame or the cylinder head cover usually is made of an aluminum material.
In another advantageous embodiment of the solution according to the invention, the bearing shell is arranged in a positive-locking and rotationally fixed manner in the associated bearing opening in the bearing frame or in the cylinder head cover. For this purpose, the bearing shell may have a round outer contour with or without a relief-ground area, an angular outer contour, in particular a triangular or quadrangular or an octagonal contour. For example, due to the round outer contour having a relief-ground area and the angular outer contours, rotating of the bearing shell in the associated bearing opening can be reliably excluded. At the same time, a predefined angular position during assembly can be ensured.
Advantageously, the radial bearing is configured as a sliding bearing or as an antifriction bearing. In particular the configuration as an antifriction bearing, for example as a needle bearing, allows a comparatively smooth-running mounting of the camshaft in the cylinder head cover or in the bearing frame, wherein, of course, sliding bearings are also conceivable, for example a plastic sliding bearing, in particular from a polymer material by means of which optimum sliding properties can be achieved. Of course, it is also conceivable that a metallic sliding bearing is provided which is coated with a polymer material that has good sliding properties.
In another advantageous embodiment of the solution according to the invention, the radial bearing is formed as an antifriction bearing comprising rolling elements, for example needles, running directly on the camshaft, a bearing ring enclosing said needles, and the outer bearing shell. In this case, it is of course also possible that the camshaft is coated or hardened in the region of the radial bearing so as to improve the bearing properties. As an alternative, it is also conceivable that in the region of the radial bearing, an inner bearing ring is arranged on the camshaft, on which inner bearing ring the actual rolling elements, for example, the needles roll. Here, the bearing ring encloses the rolling elements in a manner similar to a bearing cage.
Advantageously, the bearing shell has a stepped outer contour, and the bearing opening has a stepped inner contour formed complementary to the outer contour. This embodiment indicates that the outer contour of the bearing shell can be formed not only as a continuous cylinder surface but, moreover, can be formed from a plurality of cylinder surfaces that are arranged in a step-like manner with respect to each other.
Fixing the bearing shell via a circular spline connection is also possible. Here, the bearing shells are slid into bearing openings and are subsequently press-fitted in the bearing frame or the cylinder head cover by rotating the bearing shells.
Likewise, it is conceivable that at least one bearing shell can be fixed via a bayonet lock in the associated bearing opening of the bearing frame or the cylinder head cover. Through this, disassembling the respective bearing shell and thus also disassembling the camshaft can be simplified. Fixing the respective bayonet locks takes place here by axially inserting the camshaft and rotating it relative to the bearing frame or the cylinder head cover in the rotational direction of the camshaft, whereby self-locking of the bearing shell during operation of the internal combustion engine and yet simple disassembling can be achieved. Of course, as an alternative, it is also conceivable that the bearing shells are arranged in the respective bearing opening of the bearing frame or the cylinder head cover by means of thermal joining or by means of press-fitting.
Further important features and advantages of the invention arise from the sub-claims, from the drawings, and from the associated description of the figures based on the drawings.
It is to be understood that the above-mentioned features and the features still to be explained hereinafter are usable not only in the respective mentioned combination, but also in other combinations or alone, without departing from the context of the present invention.
Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein identical reference numbers refer to identical or similar or functionally identical components.
In the Figures, schematically:
a, b show different detailed views of a radial bearing of the camshaft in the cylinder head cover or the bearing frame,
a-d show a sectional view through the bearing frame shown according to
a-d show different assembly steps for assembling the camshaft in the cylinder head cover or in the bearing frame,
According to the
In the bearing frame 2 illustrated according to the
The individual bearing shells 8 are arranged in a positive-locking and, at the same time, rotationally fixed manner in the associated bearing opening 6 in the bearing frame 2 or in the cylinder head cover 4, wherein the bearing shell 8 may have a round outer contour with a relief-ground area 11, as illustrated according to
The radial bearing 7 can generally be configured as an antifriction bearing, in particular as a needle bearing, and alternatively also as a sliding bearing. If the radial bearing 7 is configured as an antifriction bearing, it is conceivable here that rolling elements thereof, for example needles, roll directly on the camshaft and are enclosed by a bearing ring similar to a bearing cage. The bearing shell 8 is arranged so as to enclose the bearing ring. Of course, also conceivable is an embodiment in which the individual rolling elements roll on an inner bearing ring, which is not described in detail here, which is arranged on the camshaft 3. However, in order to be able to minimize the diameter of the individual radial bearings 7, the embodiment in which the individual rolling elements run directly on the camshaft 3 is to be preferred.
Lubricating the individual radial bearings 7 can optionally be carried out via the bearing frame 2 or the cylinder head cover 4, but also via the camshaft 3, wherein in this case, corresponding oil feed channels or oil feed holes have to be provided in the bearing frame 2 or the cylinder head cover 4 and/or in the camshaft 3.
When viewing
According to the
With the bearing frame 2 according to the invention or the cylinder head cover 4 according to the invention, the advantages of standardized and high-quality camshaft production, which previously had to be implemented separately, can now be combined with the advantages of a tunnel mounting of such a camshaft 3 in the cylinder head cover 4 or the bearing frame 2.
During installation, the bearing shells 8 are slid into the bearing openings 6 and subsequently press-fitted or clamped into the bearing frame 2 or the cylinder head cover 4 by rotating the bearing shells 8.
