In the production of camshafts, different components are produced separately and joined onto a prefabricated shaft. For joining purposes, the components on the shaft are moved axially on to a widened portion of the shaft. This is done typically using a tool referred to as a clamping nest. Such a tool is known from DE 102009060349 A1. Using the tool referred to in said document as an aligning unit, the tool is gripped and moved along the shaft, i.e. in the axial direction. The aligning unit additionally has various elements which adjust the angled position of the component. In the axial direction, the aligning unit disclosed in said document has just one stop to fix the component in a form-fitting manner in the axial direction. The component can thus be moved, by way of the aligning unit, only in one axial direction. Once the component has been fastened, the aligning unit is moved in the opposite axial direction until it is separated from the component, and can then be removed. In the case of modern engines, the amount of installation space on and around the camshaft, however, is vastly restricted. Movement in the axial direction for removing the tool is therefore always not possible.
It is therefore an object of the present invention to provide a clamping nest which, following installation of the component, can be removed in the radial direction. This object is achieved by a clamping nest for positioning a component on a shaft, and joining it thereto, wherein the component has a central part with a circular-cylindrical aperture for accommodating the shaft. The clamping nest here has a fork-shaped region for accommodating the component, said region comprising a plurality of clamping elements, which secure the angled position of the component within the fork-shaped region. The fork-shaped region additionally comprises two opposite bearing surfaces, which secure the axial position of the component in a form-fitting manner in both axial directions. As a result of the two opposite bearing surfaces, the component is retained reliably in the fork-shaped region and the clamping nest, following installation, can be removed in the radial direction. In addition, this construction has the advantage that the component, during installation, can be moved in both axial directions with the aid of the clamping nest.
Within the context of this application, the axial direction is understood to be the direction in which the shaft extends. This is therefore the direction of the axis of rotation of the shaft. As seen in relation to a component, this is therefore the direction of the axis of symmetry of the circular-cylindrical aperture for accommodating the shaft.
The radial direction is understood to be any direction which is located perpendicularly to the axial direction.
The component is often a cam. The component then has at least one extension, which extends radially away from the shaft. Other components such as sensor wheels are likewise possible.
In the case of a developed embodiment, the plurality of clamping elements are arranged such that the component can be accommodated in an orientation in which the extension is oriented essentially along the fork axis in the direction of the clamping nest. This allows the clamping nest to be of particularly narrow configuration in a direction which runs perpendicularly to the fork axis and perpendicularly to the axial direction.
In some methods for producing camshafts, the component first of all is positioned in the vicinity of a widened portion of the shaft and then is pressed onto said widened portion by means of the clamping nest, so that the component is fixed there. The widened portion may be, in particular, a rolled formation. This pressing-on operation requires a relatively large amount of force. It is therefore advantageous if the bearing surfaces are of solid configuration such that the component can be pressed onto a widened portion of the shaft by means of the clamping nest.
It is also advantageous if at least one of the two bearing surfaces comprises a fixing element on the side directed toward the other bearing surface, in order to fix the axial position of the component between the bearing surfaces by a press fit. The fixing element may be formed, for example, by a leaf spring which, when the component is pushed into the clamping nest, is compressed and thus pushes the component onto the opposite bearing surface. As an alternative, the fixing element may also be formed by a flexible plastics material which likewise, when the component is pushed into the clamping nest, is compressed and thus pushes the component in the direction of the opposite bearing surface. The leaf spring, which is typically produced from a metal, has the additional advantage that it is less sensitive to high temperatures which may occur during the joining process.
In the case of some embodiments, at least one of the clamping elements is configured in the form of a ball bearing. This has the advantage that, in comparison with a single-piece clamping element, the friction of the clamping nest is reduced. Friction occurs, for example, when the component is rotated into a predetermined angled position with the aid of the clamping elements, by way of a kind of funnel effect, as described herein below. The surface of the component here slides along the clamping elements. Friction may thus give rise to the clamping nest being subjected to wear. This is reduced by the ball bearings according to the invention.
In the case of a developed variant of the clamping nest, one of the two bearing surfaces is formed by an adjustable slide, which can be moved in the radial direction between a bracing position and an accommodating position. In the bracing position, the slide and the other bearing surface delimit the axial position of the component in both axial directions. In contrast, in the accommodating position, the slide, in comparison with the bracing position, is drawn back from the fork end of the clamping nest. The axial position of the component, in the accommodating position, is thus secured in a form-fitting manner only in one axial direction. Designing the one bearing surface in the form of a slide makes it possible for the component to be introduced axially into the clamping nest while the slide is located in the accommodating position. Once the slide has then been moved into the bracing position, the axial position of the component is secured in a form-fitting manner in both axial directions, so that the component can be moved in both axial directions on the shaft. Once the component has been moved axially to the desired position of the shaft, it is fastened there. In some methods, the fastening and movement operations take place in one step, the component being pressed onto a widened portion of the shaft. Once the component has been fastened on the shaft, the slide can be moved into the accommodating position, so that the clamping nest can be removed either in the axial direction or the radial direction or by a combined axial/radial movement, as is explained herein below. This therefore allows the clamping nest according to the invention to be used in a particularly flexible manner
Advantageously at least one first clamping element of the plurality of clamping elements is connected to the slide and a second clamping element of the plurality of clamping elements is connected to the opposite bearing surface of the two bearing surfaces. When the slide is moved into the bracing position, the radial distance between the first clamping element and the second clamping element is therefore reduced. The reduction of this distance brings a previously introduced component into contact with the first clamping element and the second clamping element and thus fixes the same in the radial direction, that is to say clamps it in between the first and the second clamping elements. In the case of a preferred development, the first clamping element and the second clamping element are designed, and positioned, such that, in the bracing position, the component has a secure angled position within the fork-shaped region. In addition to the component being fixed in a form-fitting manner in the axial direction by the two opposite bearing surfaces and being fixed in a form-fitting manner in the radial direction by the first clamping element and the second clamping element, it is therefore additionally the case that the first clamping element and the second clamping element additionally prevent the component from being rotated about the axial direction. Since the angled position of the components, in particular of cams, on a shaft is important for the subsequent engine control, it is necessary for there to be no undesired rotation of the components during the installation process. Furthermore, there are specific installation processes which involve axial rotation of the components about the axial direction. It may therefore be advantageous, possibly following temporary preliminary positioning, to join the components on to a widened portion of the shaft and then to rotate the same axially at this position. The friction between the shaft and components gives rise to diffusion processes in the two contact surfaces. This increases the amount of torque which can be transmitted from the shaft to the component. This means that, using the clamping nest according to the invention, it is possible not just to prevent undesired rotation, but additionally to bring about desired rotation by the component being rotated about the axial direction, with the aid of the clamping nest, once it has been pressed on.
Fixing to particularly good effect in the radial direction can be achieved if the first clamping element is spaced apart from the fork end of the slide to the extent where, in the bracing position, it acts on the extension of the component, and the second clamping element is arranged in such proximity to the fork end of the other bearing surface that, in the bracing position, it acts on the central part.
In order to prevent the component from rotating about both axial directions, the clamping nest advantageously has two first clamping elements of the plurality of clamping elements, both connected to the slide and spaced apart from the fork end of the slide to the extent where, in the bracing position, they act on the extension of the component, said two clamping elements being spaced apart from one another by such a distance that the extension of the component, in the bracing position, ends up located between the two first clamping elements.
In the case of the installation process described above, which involves rotation of the component about the axial direction, relatively high forces are transmitted via the component. It is therefore advantageous if the forces are introduced uniformly into the component. In order to achieve this, the clamping element advantageously has two second clamping elements of the plurality of clamping elements, both connected to the bearing surface located opposite the slide. The two second clamping elements here are arranged in such proximity to the fork end that, in the bracing position, they act on the central part of the component in respective contact regions, wherein the distance between the two contact regions is between 50° and 130°, in particular between 70° and 110°, as seen in relation to the axis of rotation of the shaft. The points where the forces act during rotation are thus distributed over the circumference of the component.
In the case of a particularly preferred variant of the invention, the first clamping element and the second clamping element are designed, and positioned, such that a component accommodated therein is rotated into a predetermined angled position by virtue of the slide being moved from the accommodating position into the bracing position. The first clamping element, which is connected to the slide, gives rise, so to speak, to a kind of funnel effect when the slide is moved from the accommodating position into the bracing position. During this rotation, the component is supported on the second clamping element. This arrangement has the advantage that the component need not be introduced precisely into the clamping nest; rather, an amount of angular inaccuracy can be tolerated here. The precise angular adjustment which is necessary is then carried out automatically when the slide is moved into the bracing position. This simplifies the installation process considerably.
In some embodiments, the second clamping element, in the axial direction, has an extent which is smaller than the distance between the opposite bearing surfaces. This makes it more straight-forward to remove the clamping nest following installation. In the embodiments in which the second clamping element is arranged in such proximity to the fork end of the bearing surface located opposite the slide, it is not necessarily possible for the clamping nest, following movement of the slide into the accommodating position, to be removed immediately in the radial direction. Depending on the specific arrangement of the second clamping element, it may be the case that there is a form fit present between the second clamping element and component preventing the clamping nest from being removed in the radial direction. In these cases, the clamping nest is moved first of all in the axial direction, until there is no longer any form fit present in the radial direction between the component and all the clamping elements of the clamping nest, and the clamping nest is then removed in the radial direction. The smaller the extent of the second clamping element in the axial direction, the smaller is the distance which the clamping nest has to be moved in the axial direction until there is no longer any form fit present in the radial direction. The variant in which the second clamping element, in the axial direction, therefore has an extent which is smaller than the distance between the opposite bearing surfaces thus has the advantage that a smaller amount of installation space is necessary in the axial direction in order to remove the clamping nest following installation of the component.
The invention likewise relates to a method of positioning a component on a shaft, and joining it thereto, by means of an above described clamping nest, comprising the following steps:
Furthermore, the invention also relates to a method of positioning a component on a shaft, and joining it thereto, by means of a clamping nest, comprising the following steps:
The two methods have the advantages which have already been described previously in relation to the clamping nest itself.
The invention will be explained in more detail with reference to the figures, in which:
a shows a plan view along an axial direction of a clamping nest according to the invention with a slide in the bracing position.
b shows a plan view along an axial direction of a clamping nest according to the invention with a slide in the accommodating position.
a shows a schematic illustration of the operation of pressing a component onto a widened portion.
b shows a schematic illustration of the operation of adjusting the angle of a component on a widened portion of a shaft.
c shows a schematic illustration of the combined operations of adjusting the angle of a component and pressing onto a shaft.
a illustrates a plan view along an axial direction of a clamping nest 1 according to the invention. The axial direction is illustrated, for example, in
The two second clamping elements 4 act on the central part 20 of the component 7 at the respective contact regions 21. The two contact regions 21 are spaced apart by an angular distance a, as seen in relation to the axis of rotation B of the shaft, of, in the present case, for example approximately 100°. The first clamping elements 5 and the second clamping elements 4 are arranged such that the component 7 can be accommodated in an orientation in which the extension 19 is oriented essentially along the fork axis A in the direction of the clamping nest 1. In addition, the two first clamping elements 5 are spaced apart from one another by such a distance that the extension 19 of the component 7, in the bracing position, ends up located between the two first clamping elements 5.
b shows the clamping nest 1 according to the invention in the accommodating position. In this case, the slide 3, in comparison with the bracing position, is pulled back from the fork end of the clamping nest 1. For this purpose, the clamping nest 1 has an adjusting unit 8. Whereas the second clamping elements 4, in the case of the embodiment illustrated, are formed in one piece with the bearing surface 2, the first clamping elements 5 are connected to the slide 3 via fastening elements 15. As an alternative, it is also possible for the second clamping elements 4 to be configured separately and to be connected to the bearing surface 2 via fastening elements 13. This is illustrated, for example, in
Once the component 7 has been fastened on the shaft 16, the slide 3 is moved radially away from the shaft 16, and therefore the clamping nest 1 is moved into the accommodating position again. The clamping nest 1 cannot then readily be removed in the radial direction since, on account of the extent D of the second clamping elements 4, there is a form fit present between the clamping nest 1 and the component 7. Therefore, the clamping nest 1 is moved first of all in the axial direction, until there is no longer any form fit present in the radial direction since the second clamping elements 4, in the axial direction, have an extent D which is smaller than the distance between the opposite bearing surfaces 2, 3. It is thus possible for the clamping nest 1 to be used even if the operating distances involved are small. The clamping nest 1 is then removed in the radial direction.
a-7c show schematically, the different variants for fastening a component 7 on the shaft 16. The shaft 16 has a respective widened portion 22, the diameter of which is larger than the internal diameter of the circular-cylindrical aperture 12 of the component. The component is pressed onto the widened portion 22 by means of the clamping nest, which is not illustrated in
Number | Date | Country | Kind |
---|---|---|---|
10 2013 005 713.2 | Mar 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2014/000839 | 3/28/2014 | WO | 00 |