Proceedings

Abstract

The invention relates to a method for producing cams (1) for a camshaft, in which - the cam (1) is finish-forged with at least one chamfer (4), - the chamfer (4) is not reworked. This allows the cam (1) to be manufactured much faster and more cost-effectively, as there is no need for time-consuming reworking of the chamfers (4).

Description

[0001] The present invention relates to a method for producing cams for a camshaft. The invention also relates to a cam produced by this method.

[0002] EP 1 707 763 A1 discloses a method for producing a cam for a camshaft. In several individual cold-forging steps, a cam blank with a pre-forged cam chamfer is produced. This cam chamfer, like the running surface, is then reworked by a subsequent turning and / or milling process. Generally, with forged cam chamfers, it is unavoidable that the chamfered facets, typically produced at an angle of between 30° and 60°, will cause burrs to form in the area of ​​the side surface / running surface of the cam chamfer. The resulting burr poses an increased risk of injury and therefore requires rework.

[0003] The remachining of cam chamfers represents a considerable additional effort, which significantly increases the unit costs for such cams.

[0004] The present invention therefore addresses the problem of providing a method by means of which cams with chamfers can be manufactured significantly more cost-effectively, but still precisely.

[0005] This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0006] The present invention is based on the general idea of ​​no longer only pre-forging a cam with a chamfer located between a running surface and a side surface, as was previously the case, and then subsequently finishing it with a complex and cost-intensive milling or turning operation, but for the first time already finish-forging it and not finishing the chamfer. The angle and width of the cam chamfers are thus pre-forged and finish-forged during the forging process. All dimensions are designed to the technically reasonable and feasible forging tolerance, for example a component width, a chamfer width, a chamfer depth, a chamfer angle or radii. By finish-forging the cams with the chamfers and eliminating the need for post-machining of the chamfers, the cam itself can be manufactured significantly faster and more cost-effectively.

[0007] In an advantageous development of the method according to the invention, the cam is finish-forged to form a cam running surface with a chamfer having an angle α between 5 and 40°. In general, the chamfer angle α can be finish-forged to form a cam running surface between 10 and 80°, very preferably between 8 and 37°. In a particularly preferred embodiment of the method according to the invention, the cam is finish-forged to form a cam running surface with a chamfer having an angle α of 10° ≤ α ≤ 30°. The aforementioned angle ranges cover all commonly occurring angles between the chamfer and the cam running surface, so that preferably all cams can be produced using the method according to the invention.

[0008] In a particularly preferred embodiment of the method according to the invention, the chamfer is finish-forged with a region having a radius of R ≤ 2.0 mm. The chamfer itself therefore does not have to have a linear surface in cross-section, but can also form an arc. In theory, even chamfers with both a straight and a curved section in cross-section are conceivable. With the method according to the invention, in which the chamfer is finish-forged regardless of its shape and not reworked, almost any chamfer can be produced depending on the forging tool used.

[0009] In a particularly preferred embodiment of the method according to the invention, the side surfaces of the cam are ground. By grinding the side surfaces, which can alternatively be replaced by turning, a flat side surface can be created and, at the same time, any unevenness caused by forging can be compensated for. It is conceivable that the two side surfaces can be machined in parallel, i.e., simultaneously. The side surface machining offers the significant advantage that pre-machining of the cam bore can be eliminated. By eliminating pre-machining of the cam bore, the cam can be manufactured more cost-effectively.

[0010] In an advantageous development of the method according to the invention, the cam is cold forged. This offers the great advantage that the forging of the cam can be carried out with significantly less energy and thus significantly more cost-effectively than hot forging.

[0011] In a particularly preferred embodiment of the method according to the invention, the cam is finish-forged with a chamfer in a single forging step. This significantly streamlines the forging process and thus shortens cycle times.

[0012] The present invention is further based on the general idea of ​​producing a cam according to the method described in the previous paragraphs. This allows the advantages described with regard to the method to be transferred to the cam according to the invention. Specifically, these advantages lie in the fact that the cam, which is finished with the chamfers, can preferably be used without further post-machining of the chamfers. In particular, no turning or milling of the chamfers is required, making the cam according to the invention less complex and thus significantly more cost-effective to produce.

[0013] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

[0014] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the present invention. Components mentioned above and to be mentioned below of a higher-level unit, such as a device, an apparatus, or an arrangement, which are designated separately, may form separate parts or components of this unit or be integral areas or sections of this unit, even if this is shown differently in the drawings.

[0015] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0016] They show, schematically, Fig. 1 a view of a cam produced by a method according to the invention with finished forged chamfers, Fig. 2 a detailed view A from Fig. 1 with a linear chamfer surface in section, Fig. 3 a representation as in Fig. 2, but with a bevel surface curved in cross-section.

[0017] According to the Fig. 1-3, a cam 1 according to the invention has a cam running surface 2, two side surfaces 3, and two chamfers 4. The cam 1 according to the invention is used, for example, on a camshaft of an internal combustion engine, in particular in a motor vehicle.

[0018] According to the invention, the cam 1 is now finish-forged, preferably in a single step, together with at least one chamfer 4, preferably with both chamfers 4, so that, in comparison to cams previously known from the prior art, reworking of the chamfers 4 is no longer necessary. Purely theoretically, it is also conceivable that the cam 1 is finish-forged, preferably in a single step, together with only one chamfer 4, so that, in comparison to cams previously known from the prior art, reworking of this chamfer 4 is no longer necessary.

[0019] This makes it possible to manufacture cam 1 not only faster and less complex, but also significantly more cost-effectively.

[0020] If we look at the Fig. 2, the cam 1 can be finish-forged with a chamfer 4 with an angle α of 5° ≤ α ≤ 40°, preferably with an angle α of 8° ≤ α ≤ 37°, and most preferably with an angle α of 10° ≤ α ≤ 30° to the cam running surface 2. The smaller the angle α, the lower the tendency to burr formation during grinding of the running surface (the chamfer remains unmachined). At α = 10° to 30°, subsequent deburring can be omitted.

[0021] The chamfer 4 can also have an area with a radius R ≤ 2 mm and be finish-forged with such a radius R (compare Fig. 3). It is also conceivable that a chamfer 4 is finish-forged, which has an area with a linear chamfer surface in cross-section (cf. Fig. 2) and a curved chamfer surface in cross-section (cf. Fig. 3). This creates a mixed form of the chamfers 4 from the Fig. 2 and Fig. 3.

[0022] The side surfaces 3 can be further machined, in particular turned, milled, or ground, by which the overall width of the cam 1 can also be adjusted. The grinding of the side surfaces 3 can be achieved, for example, by disc grinding, in which the plane-parallel cams 1 are ground with the side surfaces 3 of the grinding tool. The decisive factor in this process is the combination of the forged chamfer and disc grinding. Cost reduction is achieved by grinding at least two cams simultaneously. This was previously not possible with milling or turning.

[0023] Typically, the cam 1 is cold forged using the method according to the invention, which enables longer service life of the forging tools.

[0024] With the method according to the invention and the cam 1 produced according to this method according to the invention, ie with at least one finish-forged chamfer 4, the production of such cams 1 can be carried out significantly less complexly and thus significantly more cost-effectively. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 1 707 763 A1

[0002]

Claims

[1] Method for producing cams (1) for a camshaft, in which - the cam (1) is finish-forged with a chamfer (4), - the chamfer (4) is not reworked. [2] Method according to claim 1, characterized by that the cam (1) is finish-forged with a chamfer (4) with an angle α of 5° ≤ α ≤ 40° to a cam running surface (2). [3] Method according to claim 1 or 2, characterized by that the cam (1) is finish-forged with a chamfer (4) with an angle α of 8° ≤ α ≤ 37° to a cam running surface (2). [4] Method according to one of the preceding claims, characterized by that the cam (1) is finish-forged with a chamfer (4) with an angle α of 10° ≤ α ≤ 30° to a cam running surface (2). [5] Method according to one of the preceding claims, characterized by that the chamfer (4) is finish-forged at least in an area with a radius R of R ≤ 2.0 mm. [6] Method according to one of the preceding claims, characterized by that the side surfaces (3) of the cam (1) are ground. [7] Method according to one of the preceding claims, characterized by that the cam (1) is cold forged. [8] Method according to one of the preceding claims, characterized by that the cam (1) is finished with a chamfer (4) in a single forging step, [9] Cam (1) manufactured by the method according to one of the preceding claims.

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