Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2002-06-06
2003-10-28
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S639000, C266S099000, C266S129000, C266S258000, C219S639000, C219S652000
Reexamination Certificate
active
06638379
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a procedure for hardening the bearing surfaces of a shaft or axle, in particular a crankshaft or camshaft. In addition, the invention relates to a device for hardening the bearing surfaces of shafts or axles that rotate around their longitudinal axis during hardening, in particular of crankshafts and camshafts.
In particular when hardening the bearing surfaces of crankshafts, the problem is that the crankshaft becomes distorted due to the respective locally limited exposure to heat. This distortion becomes particularly evident when hardening a main bearing of the crankshaft.
DE 31 37 398 C1 proposed a procedure and a device of the aforementioned kind, which enable a hardening of crankshafts with a minimal distortion. In this prior art, the distortion that arises during inductive heating of the respective bearing surface is ascertained. To this end, a measuring device is provided, which monitors the lift of the inductor carried on a pendulum bearing that abuts the bearing surface. If the lift is delayed, the heat output of the inductor is increased. By contrast, if a reduction in lift is detected, the heat output is also reduced. At the same time, the crankshaft is clamped on either side of the bearing to be hardened in a collar plate. These support surfaces encompass three rollers sitting on the crankshaft in regular angular intervals, via which the respective support force is exerted on the crankshaft. As a result of the interaction between the support forces exerted by the collar plates and variable heat output, the distortion of the crankshaft that accompanies the hardening is kept to a minimum.
It has been found in practice that, in particular when the surfaces of the lifting and main bearing of a crankshaft are hardened in sequence, the minimization of distortion achieved with the known procedures or known device is insufficient to satisfy the increased requirements placed on the dimensional stability of shafts hardened in this way.
SUMMARY OF THE INVENTION
Proceeding from these problems, the object of the invention is to develop a procedure and a device of the kind described above in which the distortion of a shaft or axle that arises as the bearing surfaces are hardened is further reduced.
On the one hand, this object is achieved with a procedure for hardening the bearing surfaces of a shaft or axle, in particular a crankshaft or camshaft, in which the bearing surfaces to be hardened are hardened sequentially with the shaft or axle turning around their longitudinal axis by means of a heating or quenching device, in which the distortion of the shaft or axle that arises in the area of the respective bearing surface during the course of hardening is determined, in which the shaft or axle is supported by at least one supporting device during hardening, which is placed against a previously hardened bearing surface, and in which the position of the supporting device is regulated taking into account the distortion determined for the bearing surface, against which the supporting device is placed.
On the other hand, the above object is achieved by a device for hardening the bearing surfaces of shafts or axles that rotate around their longitudinal axis during hardening, in particular of crankshafts or camshafts, which is equipped with a heating and quenching device, a supporting device for supporting the shaft or axle during hardening of the bearing surfaces, and with a device for determining the distortion of the respective shaft or axle, wherein a controller with a memory for storing the result of determining the distortion is present, and the supporting device encompasses a setting device linked with the controller, which changes the setting of the supporting device taking into account the stored measured values.
The invention is based on the idea that the distortion that arises when hardening a bearing surface is also taken into account if a supporting device is placed against the respective bearing point to support the shaft or axle while hardening the next bearing surface to be machined. As a result, the setting device is guided as a function of the distortion of the shaft or axle respectively present in the area of the supporting point. In this way, the supporting forces applied by the supporting device can be adjusted to the actual circumstances.
One the one hand, this makes it possible to adjust the supporting forces acting on the shaft or axle in such a way as to avoid undesired additional deformations of the shaft or axle. These deformations can also be caused by motions of the supporting devices that have not been adjusted to the actual circumstances. On the other hand, supporting forces can be exerted on the shaft or axle in a targeted fashion by appropriately controlling the setting of the supporting device, in order to achieve a deformation of the shaft or axle suitable for counterbalancing the distortion.
In this case, the setting of the supporting device is regulated as a function of the rotational setting of the shaft or axle that rotates around its longitudinal axis during the hardening process. In this way, the invention makes it possible to control the support of the machined shaft or axle as a function of rotational angle, while at the same time balancing out those deformations that set in due to the preceding hardenings initiated at another point. By taking into account the deformations that arise during the hardening of the bearing surfaces of a shaft or axle as specified by the invention, distortion of the shaft or axle is minimized after all bearing surfaces have been hardened.
The respective distortion of the individual bearing points taken into account while adjusting the setting of the supporting device can be determined by ascertaining the respective distortion that arises while hardening the bearing surfaces using a pattern shaft or pattern axle, and, while hardening the subsequently machined shafts or axles, regulating the setting of the supporting device placed against a bearing surface of the machined shafts or axles respectively hardened beforehand, taking into account the distortion determined using the pattern shaft for the respectively corresponding bearing surface. In this embodiment of the invention, it is assumed that the same distortion always arises when hardening the bearing points of shafts or axles in a large series of work pieces with identical geometry. For this reason, the distortion that arises when hardening each bearing point is determined using a pattern. Once determined in this way, the distortion is taken into account when regulating the setting of the supporting device during the hardening of all subsequently machined shafts or axles in the same series. The cost for determining distortion can be minimized in this way.
The accuracy with which the arising distortion is counterbalanced can be improved by determining the respective distortion that arises while hardening a bearing surface (H
1
), by placing the supporting device against the hardened bearing surface after the bearing surface has been hardened in order to support the shaft or axle while hardening the next bearing surface, and by regulating the setting of the supporting device taking into account the distortion determined for the hardened bearing point. In this embodiment of the invention, the respective distortion that actually arises on the individual bearing surfaces is determined for each shaft or axle. This distortion is then taken into account when supporting the shaft or axle while hardening the bearing surface machined next. In this way, all deformations of the shaft or axle that accompany the hardening process are directly counterbalanced, taking into account the actual circumstances existing for each individual work piece.
Regardless of how the distortion is determined, the distortion should be ascertained with respect to its magnitude and relative position, so that the supporting forces applied by the supporting device can be easily controlled depending on the rotational angle according to the inventio
Gezarzick Waldemar
Leissner Hans-Jürgen
Schulte Peter
Elotherm GmbH
Proskauer Rose LLP
Yee Deborah
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