Hirth coupling

Hirth serration made of aluminum, anodized in color to show the meshing of the teeth

The Hirth toothing is an axially effective, face-side toothing . It was invented by Albert Hirth at the beginning of the 20th century . In mechanical engineering , the Hirth coupling is one of the form-fitting connections between shaft and shaft and there it belongs to the class of fixed, but detachable couplings . It has no involute toothing and is also called face serration . The teeth are statically and flat against one another in the sense of a form-fitting coupling, are arranged radially, conically and center the components. It is the smallest of all detachable couplings. It is suitable for connecting shaft ends with gears, disks and crank webs or directly between gears with gears, as well as disks without a shaft. Axial bracing is necessary for full frictional engagement , which in turn limits the torque transmission.

She was z. This is used, for example, when a crankshaft had to be able to be dismantled for assembly purposes in order to be able to install the connecting rod in one piece instead of the "normal" design with a split base.

Because of the high manufacturing costs, a mechanically processed Hirth coupling was rarely used. An application example in the 1950s was the crankshafts of the two-cylinder engines of the German motorcycle manufacturer Adler .

By stringing together parts of single-cylinder crankshafts, crankshafts for three-cylinder and four-cylinder engines that were assembled at the customer's site were easily assembled in the past, to meet the higher performance requirements of the time.

Today the construction element of the Hirth coupling is used for B. used between the carriers of the compressor of turbine engines for aircraft and in stationary systems ( gas turbine ).

The Hirth coupling is also used in the crankset of racing bicycles . At the component manufacturer Campagnolo , a two-piece hollow axle, which is connected via a Hirth coupling, replaces the one-piece square axle. Bicycle manufacturer Specialized has presented a similar system ; there, however, the axle halves are connected with less fine teeth.

Another use of the Hirth serration is indexing the indexing table of rotary indexing tables in machine tools . Due to the self-centering effect of the Hirth coupling, the highest indexing accuracies of up to one arc second are achieved.

More recently, the automotive industry has been increasingly researching the serial application of the Hirth coupling for built crankshafts.

For the connection of individual components, such as B. Vibration dampers and timing chain sprockets , the Hirth coupling has already found its way into the series production of car engines. Alternative manufacturing processes, such as sintering and extrusion , have been adapted to manufacture the gears .

Manufacturing

Thanks to modern machine tools and manufacturing processes, the component can now also be implemented cost-effectively. The following manufacturing processes are used:

• Milling
• Profile grinding for high-precision connections ( grinding )
• Injection molding
• Drop forging
• Flow pressing
• Sintering

Geometrically, a 60 ° spur gear is placed on the shaft end. The tooth tip rises radially from the inside to the outside and the tooth base drops radially from the inside to the outside. Alternatively, an angle can also be at right angles to the axis of rotation of the shaft. In order to be able to introduce the same toothing on both front sides, the angle from the radial rise of the tooth tip must be equal to the angle of the descent of the tooth base. This angle only depends on the number of teeth. The tooth depth depends on the number of teeth and the diameter of the Hirth toothing.

Sources / literature

• G. Niemann: machine elements. Published by Springer-Verlag, Berlin / Göttingen / Heidelberg 1960, 4th reprint
• Dubbel - paperback for mechanical engineering, published by Springer-Verlag, Berlin / Göttingen / Heidelberg 1958

Web links

• Hirth coupling applications
• Hirth coupling on racing bikes (technical description and pictures)
• Use of the Hirth coupling in rotary indexing tables
• Catalog excerpt from Voith-Hirth
• Hirth serration in technical brushes for mechanical engineering

Individual evidence

1. ↑ [1]
2. ↑ Archived copy ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.