1. Field of the Invention
The present invention relates to a method for producing a conical pulley for a belt-driven conical-pulley transmission, to a conical pulley for a belt-driven conical-pulley transmission, and to a belt-driven conical-pulley transmission that includes such a conical pulley.
2. Description of the Related Art
The use of belt-driven conical-pulley transmissions, which allow a continuously variable transmission ratio adjustment, was limited for a long time to vehicles having engines with low torque output. Modern, further advanced belt-driven conical-pulley transmissions can transfer torques of over 300 Nm, so that such belt-driven conical-pulley transmissions are now also being used with high-torque-output engines and in high-powered vehicles, in particular in passenger cars.
An input pinion 20 that is driven by an internal combustion engine (not shown) is supported on the input shaft 10, and non-rotatably connected with a torque sensor unit 22. Input pinion 20 transmits the input torque to the axially movable disk 14, which influences the axial adjustment of the axially movable disk 14, which is performed by hydraulic pressure.
The additional details and the function of the illustrated embodiment are not further described herein because they are known in principle. An endless torque-transmitting means 34 runs between the conical disks 12 and 14 and another conical disk pair that is disposed at radial distance from the illustrated conical disk pair. The transmission ratio of the belt-driven conical-pulley transmission is changed by opposite adjustment of the axial distances between the conical disks of the conical disk pairs.
The conical pulleys and the axle components connected therewith are highly stressed mechanically in certain operating regions. Thus, conical surfaces of the conical disks that face each other are stressed with respect to their strength and also with respect to wear, as a consequence of their frictional engagement with the endless torque-transmitting means. Thus, the spline connected portions, the left end portion of the hollow shaft section 16 illustrated in
It is furthermore known to case harden in particular the above-mentioned portions, similar to regular transmission components, e.g., shafts or gears. Because the conical disks and their associated shaft components have a significant volume and are bulky components, case hardening is expensive due to the complex oven loading process and due to the long carbonization times.
It is an object of the present invention to reduce the cost associated with the manufacture of a belt-driven conical-pulley transmission, without degradation of the functional quality.
The object is achieved by a method for producing a conical disk for a belt-driven conical-pulley transmission, by which method at least partial portions of the surface of the conical disk are hardened, and wherein other partial portions of the surface of the conical disk are induction hardened.
In the known induction hardening method, the surface portions of the conical disk to be hardened are heated by an induction coil, wherein the depth of hardening and the temperature can be adjusted. Induction hardening can also be performed cost effectively on components that are complex and that have a significant volume in a manner that is adapted to the special requirements of the components.
The cost can be reduced further by machining at least partial portions of the hardened portions to a finish before hardening, so that no machining is required after hardening.
Another solution to the object of the present invention is achieved for a conical disk for a belt-driven conical-pulley transmission in which a conical surface of a conical disk of the conical pulley, provided for frictional engagement with an endless torque-transmitting means, is induction hardened.
The axially movable conical disk includes a coaxial stub shaft that includes a through-opening for sliding the axially movable conical pulley onto a shaft, wherein the inside of the through-opening is provided with axial recesses and/or axial projections for an axially movable and non-rotatable connection with the shaft, and is induction hardened at least in the region of the axial recesses and/or axial projections.
It is advantageous for the surface of the above-described conical disk to be induction hardened in further surface regions that are exposed to particularly high mechanical stresses.
The conical disk and the stub shaft can be made from different materials and connected to each other in a rigid manner.
The axially fixed conical disk can include a shaft on which the stub shaft of the axially movable conical disk is slidably received, wherein the outer surface of the shaft is provided with recesses and/or projections for an axially movable and non-rotatable connection with the hollow stub shaft, and can be induction hardened in at least the region of the recesses and/or projections.
It is advantageous for the surface of the conical disk to be induction hardened on additional mechanically highly stressed surface portions.
The conical disk and the shaft can be made of different materials and can be rigidly connected to each other.
Particular degrees of freedom with respect to hardening arise as a result when the conical pulley includes a conical disk and a shaft component, each of which is made of a different material and is hardened differently.
A belt-driven conical-pulley transmission having conical disks and whose conical surfaces are induction hardened, is preferably operated with a rocker joint chain, that is, a plate-link chain, as an endless torque-transmitting means, whose pressure piece end surfaces are in frictional engagement with the induction hardened conical surfaces.
The end surfaces of the pressure pieces can include a planar surface inclined at an angle of between 6° and 13° to the axis of rotation, preferably 11°, corresponding approximately to the conical angle, relative to the axis of rotation, of the conical surfaces of the conical disks.
Alternatively, the end surfaces of the pressure pieces can be of convex or spherical form.
The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which:
It will be appreciated that the axially movable disk 14 can also be assembled from two different materials that are adapted to the respective requirements and hardened in an optimum manner.
By providing the conical pulleys as conical pulley disks and shaft components initially from different materials, the shaft components can be easily case hardened because of their simple configuration, and they can be connected with the conical pulley disks in a rigid manner after hardening, wherein conical pulley disks are induction hardened either previously or subsequently.
When in the belt-driven conical-pulley transmission that has been previously described, as it has been developed by the applicant of the present patent application and whose general configuration is known, the conical surfaces of its conical pulleys 12 and 14 are induction hardened, in particular in conjunction with a rocker joint chain 34 (also referred to as a plate-link chain), provides excellent operating characteristics, such as long service life, torque-transmitting capacity, and the like. Such a rocker joint chain 34 includes pressure pieces 36 that are connected by particular link plates 38 that extend in the in longitudinal direction of the rocker joint chain 34, wherein the pressure pieces 36 roll in a rocking movement within the link plates 38 when the rocker joint chain 34 is curved. The end surfaces 40 of the pressure pieces 36 are in frictional engagement with the conical surfaces 42 of the conical disks 12 and 14. Preferably, conical angles α (see
It is preferred to form the end surfaces convexly or spherically, so that there is no risk of an overload at their edges.
Although particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.
Number | Date | Country | |
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60921350 | Apr 2007 | US | |
60923968 | Apr 2007 | US |