Patent Application
20070264913
They show, each in schematic diagrams:
According to
To achieve and adjustment of the first cams 2 with respect to the second cams 3, the first cams 2 are fixedly connected to the inner shaft 5 while the second cams 3 are fixedly connected to the outer shaft 4. The connection between the second cams 3 and the outer shaft 4 may be accomplished by means of a shrink fit, for example. The connection of the first cams 2 to the inner shaft 5 is usually implemented via connecting pins 7 which are arranged essentially across the longitudinal axis 6 and the outer shaft 4 passes through longitudinal holes arranged in the circumferential direction therein. The length of the longitudinal hole aligned in the circumferential direction limits the angle of adjustment between the first cams 2 and the second cams 3. Since the first cams 2 are arranged so they are rotatable with respect to the outer shaft 4, there must be an interspace 8, even if minimal, designed in the form of a ring gap between the first cam 2 and the outer shaft 4. The camshaft 1 shown in
Before installation of the camshaft 1 in a corresponding crankcase (not shown) it is necessary for the cam profiles of the first and second cams 2, 3 to be ground. Cam profiles are understood to refer to a circumferential lateral surface of the cams 2, 3. In grinding the cam profiles, there is the problem that grinding dust can enter the interspace/ring gap 8 between the first cam 2 and the outer shaft 4 and thereby can impair the subsequent functionality of the camshaft 1. This is where the inventive method for grinding of cam profiles offers a remedy.
According to the inventive method, during and/or after the grinding operation, a fluid under pressure is forced into the outer shaft 4, i.e., into a cavity 9 and therefore penetration of grinding dust into the interspace 8 between the first cams 3 and the outer shaft 4 is prevented or grinding dust that has already penetrated is flushed out again.
A fluid should be understood to refer in general to a liquid, in particular a hydraulic oil, or a gas, in particular air or compressed air.
When fluid is forced into the outer shaft 4 and/or the hollow space 9 during the grinding operation, it continuously penetrates outward through the interspace 8, creating a volume flow in the interspace 8, thereby preventing grinding dust from entering. Grinding dust could then penetrate only if it moves against the volume flow outward from the hollow space 9 through the interspace 8 to the outside, which is physically impossible. Additionally or alternatively, it is possible to provide for the fluid under pressure to be pressed into the outer shaft 4 after the grinding operation and thereby to rinse the grinding dust that has penetrated into the interspace 8 back out of it again during the grinding process without any application of fluid. In both cases, it may be assumed that no grinding dust is to be encountered in the interspace 8 after the cam profile grinding operation and/or after rinsing out the interspace 8, so no impairment of the function of the finished camshaft 1 need be expected.
When the fluid is forced into the shaft, in particular in the form of a liquid, during the grinding process, the injection pressure may be set so high that the outer shaft 4 undergoes elastic deformation and the interspaces 8 and/or the ring gaps 8 between the first cams 2 and the outer shaft 4 are at least reduced in size. Reduction of the interspace 8 at an elevated pressure results in the velocity of flow increasing in the interspace 8, thereby reliably suppressing any penetration of grinding dust. For the case when, only after the grinding operation, the fluid is forced under pressure into the outer shaft 4, the elastic deformation of the outer shaft 4 produces a smaller cross section of flow in the interspace 8 and therefore an increased velocity of flow, thereby improving the cleaning effect in the interspace 8.
When the pressure of the fluid is increased, i.e., in particular the pressure of the liquid, during the grinding operation, it is possible to achieve the result that the outer shaft 4 undergoes elastic deformation so that the first cams 2 are in close contact with an outer lateral surface of the outer shaft 4 and therefore the interspaces 8 are closed. Thus, penetration of grinding dust into the interspaces 8 is entirely impossible.
In both variants in which the pressure of the fluid leads to elastic deformation of the outer shaft 4, releasing the pressure results in an elastic re-deformation of the outer shaft 4, so that the first cams 2 can again be turned with respect to the outer shaft 4 with no problem. Fluid is forced in preferably from an axial end face 10, 10′ of the camshaft 1, whereby openings 11 that run radially, such as an oil channel, may be sealed in advance in the bearings. It is also conceivable for an injection of fluid through the opening 11 to take place, in which case then the camshaft 1 is sealed at the end. It is important here that the same pressure is applied preferably on both ends of a seal 12 so that the seal 12 is not displaced.
To be able to increase the quality of the grinding process, filtered oil is preferably used as the fluid. This uncontaminated oil ensures that both the hollow space 9 and the interspace 8 are supplied with high-quality clean oil so that cleaning after the grinding operation may be omitted. In addition, it is conceivable that oil escaping due to the pressure might take up the dust and then be cleaned, i.e., filtered again to be able to be forced back into the hollow space 9 in the outer shaft 4.
As an alternative to this, in a particularly preferred embodiment, the fluid used is air, in particular compressed air. Compressed air is inexpensive on the one hand and on the other hand can easily be discharged into the environment after the grinding process without polluting the environment. Purification or expensive disposal, such as that which is required with a hydraulic medium, for example, may be omitted, so the grinding process can be implemented inexpensively.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 022 405.1 | May 2006 | DE | national |
| 10 2006 044 010.2 | Sep 2006 | DE | national |
