ypical globoid worm Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm equipment due to increased driving efficiency ( 6-10% higher in 25:1 ratio) and increased loading capacity (about 30%).
The disadvantage of a globoid gear is higher manufacturing cost and sensitivity of the enveloping pinion to the axial location.
Because of the geometrical nature of the tooth geometry Globoid pinion may mesh not only with the mating enveloping equipment but also with a correctly designed cylindrical helical gear. Using a helical equipment with a Globoid pinion is certainly common in lower cost in applications such as automotive electric powered gear actuators. The significant cost advantage comes due to the possibility to injection mold the helical plastic material gear. The load capability of the simplified helical/Globoid transmitting is reduced to the particular level below the strain capacity of the regular worm gear. However the driving efficiency is still better evaluate to the regular worm gear.
There are just a few suppliers of the Globoid gear. division of Textron, situated in Traverse City, MI. The detailed information about processes used at Cone Drive for manufacturing of its gear could not be found. However, based on publicly released info it can be understood that the gear is produced by CNC milling with make use of a small ball shaped cutter.
Ever-power has capacity to design, prototype and offer Globoid gear products. The knowledge of Ever-power is 3-dimentional simulation and modeling of the Globoid and double enveloping tooth geometry. Ever-power 3-dimentional Globoid and double enveloping equipment CAD versions can be used in numerous CNC machining shops for producing globoid gear at significantly reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that manufacturing of the Globoid gear is more technical compare to manufacturing of the Globoid pinion. The Globoid pinion could be produced in high amounts by turning, whirling or grinding. Through the machining procedure for the Globoid pinion the reducing tool has to be able to tilt to be able to produce the enveloping form.
The newer production methods are under development. The most promising creation approach to the Globoid pinion is normally continues grinding process, which includes a grinding steering wheel (gemstone or CBN plated) with particular Ever-power simulated geometry. The complication of the novel process is the difficulties with simulation of the geometry of the grinding tool. The grinding tooth would have to generate a correct type of the Globoid pinion without tilting so the production rate and the production cost would be considerably reduced. Ever-power has developed a computer based tool for generating of 3-dimensional CAD models of grinding tools for high volume production of the Globoid items.
The most common use of the Globoid gear set was seen in 1961-1989 on automotive steering systems in Italy and in Soviet Union.
VAZ-2101 with Globoid steering technology.
The Globoid pinions have already been produced by grinding with a tilting grinding wheel. The Globoid gears have been cut by a particular hub, which replicated the shape of the Globoid Pinion. Special machines for generating the slicing hubs have already been developed. Because the modern automotive steering systems started to use traditional Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears provides been reduced.
Variable ratio technology comparison
Vr-rack technology was introduced:
Underlying mathematical model is founded on:
Rack geometry calculation accuracy is:
Limited by the boundaries of the classic gear theory
Capability to produce the vr-rack with not involute form for reduced noise
Capacity to generate vr-rack with increased ratio gain is:
Cost of vr-rack design is:
Ever-power advanced Variable Ratio rack and pinion high ratio gain technology for electric motor sport racing applications.
Ever-power low sound Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of the next generation of Globoid gears. In 1999 Ever-power presented a skew axis Globoid gear as a higher load capability and increased driving performance alternative to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It needs to be noted that the name WORMOID will not relate with any scientific term and it is a product of Dr. Stepan V. Lunin, who was simply the initial in proposing this style and, moreover, he was the first who produces an accurate functioning model of the apparatus in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID equipment has proved the ability of the idea such as for example conjugated transmission action and significant increase of number of tooth in the contact compare to the classic Globoid gear.
CAD 3-d model of Ever-power wormoid gear.
Ever-power happens to be offering assistance for style and development of items predicated on Ever-power wormoid technology.
It has to be noted that wormoid gear design from Ever-power is actually promising unique advantages review to the basic Globoid (double enveloping) gear. Among the obvious advantages is elevated load capacity because of increased number of one’s teeth in the mesh. The apparatus torque is certainly carried by more teeth so the load on every individual tooth is decreased. The other obvious advantage is boost driving efficiency. As one can see, the part of the pinion with larger diameter is traveling the corresponding portion of the gear, that includes a larger diameter aswell. Such of exclusive feature of Ever-power wormoid is missing in the traditional Globoid gear and results in higher sliding velocities and higher friction medication on the classic globoid gear. An experienced in the art engineer would immediately derive possible design benefits of the wormoid equipment. For example, using of the wormoid gear can significantly reduce cost of electric powered help mechanisms that are generally used on modern automobiles. Because of the bigger driving efficiency, wormoid equipment set can be designed with increase ration and provide the same driving efficiency as the initial worm or dual enveloping worm equipment. For instance NSK worm equipment steering actuator with a ration around 20:1 provides about 80% of generating efficiency. The plastic gear would hold about 80 Hm of torque. An alternative solution wormoid gear style from Ever-power will be capable to raise the ratio up to 30:1 and the torque on the apparatus up to 150 Hm without enhance of the center distance between the equipment and the pinion.
ypical globoid worm Globoid gear.