Crown gear

The crown is a special gear and part of a crown. Crown-gear used to transmit rotary motion and torque. A characteristic feature is the angle to one another the input and output shafts, the axes of which usually have a common intersection.

For crown- there are similar applications such as for bevel gear.

History

In earlier times, lacked the calculation bases and possibilities to transmit rotary movements with gears uniform. Expenses incurred during this time teeth are sometimes called crown. The rack and pinion gearing used in this case falls far short of the performance of a modern involute back and does not transmit uniform, but is technically simple and can also be realized in wood.

Your application can still be seen today in the historic mills, where the crown engages the cog wheel and the vertical shaft drives.

In the 1940s, crown wheels were developed that allowed a uniform motion transmission and used for example for Rear- which consisted of Hypoidsatz (conventional) and differential ( crown ).

The rediscovery of the crown wheel ( sometimes called crown wheel ) for technical applications began in the 1990s as an alternative to bevel gears, as manufacturing and calculation methods were available to crown gears automatically to manufacture in large quantities.

Construction

The diagram below illustrates the essential difference when used in angle drives crown wheels instead of bevel gears: When bevel gear both gears must have the shape of a cone. Trouble-free operation is only guaranteed when the peaks of the imaginary center line of the bevel gears in a point ("0" ) cut. During assembly, the bevel gears must be set accordingly so that they are exactly in the direction of the axes A and B in the correct position and the teeth running noise and wear.

Among crown on the other hand, a toothed wheel ( Z ) is cylindrical and the other is a crown wheel (K). The gear (Z ) can therefore be moved along the axis A without problems arise when running behavior. This allows for some very elegant technical solutions. With a straight-toothed cylindrical gear wheel ( Z ) are produced under load, no axial forces ( along the axis A), as opposed to the bevel gear a special support of the cylindrical gear wheel ( Z ) only for helical gearing is required.

Examples of tooth shapes

Various examples of the structure of another image shows Kronenradpaarungen:

• The red circles show that the cylindrical gear can be moved along its axis (position 1 and position 2 on the outside inside on), without the function is impaired. The helical spur gears in the picture additionally cause a phase shift when they are axially displaced on the crown.
• Spur (A) in which the axes intersect at right angles,
• With helical gearing (B ) in which the axes intersect at right angles, and
• Helical teeth (C), in which the axes are offset.

The enlarged detail shows the peculiar shape of the tooth crown gears.

Variations in the design

In principle, one can crown gears manufactured in the following versions:

• Straight toothing of the cylindrical wheel, so that an axial displacement is possible. This allows for example a simple length adjustment to achieve, the cylindrical gear to move axially, thus preventing tension.
• The cylindrical gear is helically toothed, its axial displacement causes a small rotation of the crown wheel, which is superimposed on the rotational movement. In this way, can be easily implemented phase shifts. Example camshaft adjustment: Leafs to the camshaft at the outlet of a 4- valve engine with a chain and drives the camshaft for the intake via a face gear with helically spur on, this is how the phase shift of the intake camshaft by simple axial displacement of the cylindrical gear realize.
• With an appropriate design can be realized also a axis offset, as it (mostly in rear-wheel drive vehicles ) is common in hypoid gears in the rear axle by axle drives.

A crown is part of a crown. The special feature of this transmission part are located on the one side of the wheel teeth, so that it looks like a crown.

Applications

The example shows two rollers W1 and W2, which are driven by the crown wheels of K1 and K2. The rollers rotate in opposite directions so that they can be used for guidance of paper or tape or steel for rolling dough into a certain thickness. With the crown teeth, it is now possible to move the roller W1 during operation so ( red dashed line), the distance can be continuously adjusted to the medium which is to be guided by the rollers.

Numerous other applications relate to differentials in motor vehicles. In principle, application advantages found in each planetary gear that is otherwise constructed with bevel gears.