Cam for composite camshaft

Abstract

A cam with a bore that has a funnel-shaped core-insertion section. To ensure that the cam will rest more securely against the core and remain more precisely centered, the section (5) comprises at least two mutually aligned conical extents (6 & 7), each expanding outward at a different apical angle.

Description

[0001] The present invention concerns the design of a cam for a composite camshaft for controlling the valves in internal-combustion engine and featuring the characteristics recited in the preamble to claim 1.

[0002] Cams and camshaft of this genus are described in German 4 121 951 C2. The core of the shaft differs in thickness along its length, and, to facilitate sliding the cam over it, the cam is provided with a cavity that tapers out like a funnel at least part-way along at least one side. The outside diameter of the opening into the cavity is at least as long as the ridges or webs that constitute the thicker sections of the core. The conical expansion extends at least ⅕ of the thickness of the cam and has an apical angle of approximately 20 •.

[0003] This design has drawbacks. First, in spite of the funnel-shaped expansion, considerable force is required to mount the cams. Furthermore, it is difficult to keep the cams precisely centered on the core.

[0004] The object of the present invention is a cam with a bore that has a funnel-shaped core-insertion section ensuring that the cam will rest more securely against the core and remain more precisely centered.

[0005] This object is attained in accordance with the present invention by the characteristics recited in the body of claim 1.

[0006] Advantageous further and more advance embodiments are addressed in the subsidiary claims, 2 through 8.

[0007] One embodiment of the present invention will now be specified by way of example with reference to the accompanying drawing, wherein

[0008] FIG. 1 is a perspective view of q composite camshaft,

[0009] FIG. 2 a view of a single cam,

[0010] FIG. 3 illustrates a cam and a core before the core has been forced onto it,

[0011] FIG. 4 illustrates the cam forced onto the core,

[0012] FIG. 5 is a section through the cam, and

[0013] FIG. 6 is a larger-scale depiction of the detail VI in FIG. 5.

[0014] The composite camshaft illustrated in FIGS. 1 through 4 comprises a core 1 that cams 2 can be forced onto. The shape of each cam 2 and its orientation in relation to core 1 will be dictated by the specifications of the particular internal-combustion engine. The core 1 of the illustrated embodiment is a hollow cylinder with corrugations 3 that constitute seats for cams 2. Each cam 2 is provided with a bore 4 that is essentially narrower than corrugations 3. The cam's core-insertion section 5 is funnel-shaped and at least as wide as corrugations 3. Corrugations 3 are compressed when cams 2 are forced over them, resulting in a plastic but resilient deformation that ensures a tight fit between the cams and the core. Cams 2 are, at least in the vicinity of bore 4, usually harder than core 1.

[0015] FIGS. 5 and 6 illustrate the core-insertion section 5 of a cam 2 in detail. Section 5 comprises two conical extents 6 and 7 of different length and apical angle. Apical semi-angle 8 is 2 •. The apical angle of outer conical extent 7 is 20 •, its semi-angle 9 accordingly equaling 10 •.

[0016] The length 10 of outer conical extent 7 is 0.09 the thickness 11 of a cam 2.

[0017] Depending on the specifications, core-insertion section 5 may comprise more than two mutually aligned conical extents. This feature can be particularly practical when cams 2 have a very considerable thickness 11.

Claims

1. Core-insertion section in the shape of a funnel in the bore (4) of a cam (2) that can be forced over the core (1) of a composite camshaft, characterized in that the section (5) comprises at least two mutually aligned conical extents (6 & 7), each expanding outward at a different apical angle.

2. Core-insertion section as in claim 1, characterized in that the mutually aligned conical extents (6 & 7) expand by s factor of three to five.

3. Core-insertion section as in claim 1, characterized in that the mutually aligned conical extents (6 & 7) expand by a factor of five.

4. Core-insertion section as in claim 1, characterized in that, when there are two mutually aligned conical extents (6 & 7), the apical angle of the inner conical extent (6) is 3 to 5 • and that of the outer conical extent (7) is 15 to 25 •.

5. Core-insertion section as in claim 1, characterized in that, when there are two mutually aligned conical extents (6 & 7), the apical angle of the inner conical extent (6) is 4 • and that of the outer conical extent (7) is 20 •.

6. Core-insertion section as in claims 1 to 4, characterized in that the mutually aligned conical extents are reduced from inside to outside.

7. Core-insertion section as in claim 6, characterized in that, when there are two mutually aligned conical extents (6 & 7), the length (12) of the inner conical extent (6) is 0.30 to 0.40 and the length (10) of the outer conical extent (7) is 0.08 to 0.12 times the thickness (11) of the cam (2).

8. Core-insertion section as in claim 6, characterized in that, when there are two mutually aligned conical extents (6 & 7), the length (12) of the inner conical extent (6) is 1 to 3 mm and the length (10) of the outer conical extent (7) 3 to 6 mm.