192 clutches and power-stop control – Elements – Engaging surfaces
Reexamination Certificate
1999-01-19
2001-06-12
Marmor, Charles A (Department: 3681)
192 clutches and power-stop control
Elements
Engaging surfaces
C192S11400R
Reexamination Certificate
active
06244413
ABSTRACT:
The invention concerns a morphology matrix for forming the cross-sectional shape of a short gearing tooth, in particular on toothed wheels of motor vehicle gearboxes, the short gearing teeth being formed on a cylindrical section of a gear wheel or gear wheel sleeve, the axis of this section coinciding with the displacement axis of the gear shift sleeve, each tooth comprising a tip which is chamfered in a roof-like manner and lateral flanks which terminate in a radiused tooth base and comprise an undercut section that extends at least over part of the flank height.
The above-mentioned short gearing morphology is described in the relevant technical literature and has been translated into practice.
An essential characteristic to be achieved in a short gearing system consists in the smoothest possible shifting between two gear wheels already moving synchronously, i.e. in limiting friction to an absolute minimum; especially reducing the occurrence and duration of frontal contact between the gear tips of two short gearing units. However, neither axial contact nor the safe axial stability of the selected gearshift mechanism may be sacrificed in favor of such shifting comfort. Instead, specially shaped lateral tooth flanks are used, the tooth flanks comprising an undercut section so that at least part of the lateral tooth flank tapers towards the tooth base. Two corresponding interacting short gearing units thus designed ensure that neighboring undercut lateral tooth flanks are appropriately protected against axial displacement and the resulting undesired undoing of the shifting connection.
The expert is familiar with the fact that individual teeth in a conventionally designed short gearing system are over their entire height attached to a cylindrical section and can also be attached to a base. Additionally, the expert is familiar with the fact that a radiused tooth base can improve the resistance of the teeth and that roof-like chamfering of the tooth tip can facilitate the meshing of the teeth.
However, as there are many different possibilities for application of short gearing systems which are characterised by different loads and load changing patterns and as different shifting comfort and shifting safety requirements must be met in practice, also requiring a number of criteria in connection with the metal forming method to be met, it can be assumed that the expert will usually find it difficult to identify the most appropriate solution for every single case.
In view thereof, one of the objectives of the present invention consists in providing an overview of the layout and design criteria for short gearing units, i.e. in offering the expert a means by which he can easily and reliably identify the solutions meeting the applicable requirements in every specific case.
The proposed invention is not limited to the identification of a single solution for each case but consists of a morphology matrix for the adequate designing of the cross-sectional shapes of short gearing teeth.
Additionally, the morphology matrix mentioned above is characterised by the fact that all teeth or a part thereof defined according to a regularly changing pattern are characterised by at least one of the two following features defining the design of the lateral tooth flanks:
a) Between the lower edge of the tooth roof surface of the tooth tip and the undercut section of the tooth flank an upper spur toothing section in the shape of a guiding surface (flat) largely parallel to the longitudinal axis of the tooth is provided, the guiding surface being either narrow or wide.
b) Between the undercut section of the tooth flank and the radiused tooth base a lower spur toothing section is provided in the form of a tooth base reinforcement with a supporting surface largely parallel to the longitudinal axis of the tooth, the supporting surface being either low or high.
The matrix which constitutes the object of the present invention is based on the assumption that said invention facilitates, in addition to the undercut flank section, depending on a specific application, one or two spur gear sections in particular, consisting of additional sections on each lateral flank, namely either an upper spur toothing section above the undercut section of the flank and/or a lower spur toothing section below the undercut section of the flank.
The upper spur toothing section constitutes a guiding surface, also called “flat”, which becomes effective when the teeth begin to engage and reinforces, in the initial contact area, the most lateral sections of the flank, thus prolonging the service life of the toothing. The guiding surfaces reduce the so-called “backlash”, i.e. the forces occurring as a response to the shifting movement are reduced without increasing the face clearance.
The guiding surfaces can be narrow or wide (seen in the longitudinal direction of the tooth). The guiding surface (
5
) of the first width, measured in the direction of the tooth height can measure less than one sixth of the remaining height of the tooth tip above. The guidance surface (
6
) of the second width measured in the direction of the tooth height, may be shorter than the overall tooth height, but longer than half of the remaining height of the tooth tip above. The choice between narrow and wide guiding surfaces has a significant impact on the size of the relief angle of undercut because a wide guiding surface implies a larger and, thus, more effective relief angle than a narrow guiding surface. At the same time, the width of the guiding surface must be considered a function of the load, i.e. of the occurring torques.
However, the teaching of the present invention is not limited to an upper spur toothing section only. Instead, a lower spur toothing section located below the undercut flank section can be provided in addition to or instead of the upper spur toothing section. The lower spur toothing section reinforces the tooth base, consisting of a supporting surface parallel to the longitudinal axis of the tooth which counteracts the tapering of the tooth caused by the undercut tooth section. This kind of supporting surface thus directly increases the strength of the entire tooth, especially of the portion near the tooth base.
In cases where particularly high torque loads occur those learned in the art will, within the limits of the morphology proposed in the framework of the invention, combine an upper and a lower spur toothing section in order to benefit from a combination of both guiding surfaces and supporting surfaces.
The supporting surface of each tooth flank can be either high or low. The choice between high or low will mainly depend on the relief angle chosen by the expert.
If only one upper spur toothing section—with a narrow or wide guiding surface—is intended, a relief angle of up to 9 angular degrees is recommended according to the correlation 0≦&agr;≦9.
If a lower spur toothing section with a low supporting surface—with or without an additional upper spur toothing section—is provided, a relief angle between 3 and 12 angular degrees is recommended according to the correlation 3≦&agr;≦12.
If a lower spur toothing section with a high supporting surface—with or without an upper spur toothing section—is intended, a relief angle between 6 and 60 angular degrees is recommended according to the correlation 6≦&agr;≦60. The largest relief angles are realised by selecting an upper spur toothing section in the form of a wide guiding surface and a lower spur toothing section in the form of a high supporting surface.
Supporting surface (
7
) of the low type, measured from the tooth base can be wider than the guiding surface of the wide type but is lower than half the tooth height measured from the tooth base (
1
) to the lower edge of the roof surface. The supporting surface (
8
) of the high type, measured from the tooth base, is approximately half as long as the overall tooth height. These rules can be derived on the basis of the overall geometry and are only valid when teeth with an identical overall tooth height or tooth tip height
Gutmann Peter
Tauschek Georg
Weissmann Gerd
BLW Praezisionsschmiede GmbH
Helfgott & Karas P.C.
Marmor Charles A
Parekh Ankur
LandOfFree
Gearing tooth form does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gearing tooth form, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gearing tooth form will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543979