ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm gear due to increased driving efficiency ( 6-10% higher on 25:1 ratio) and increased loading capacity (about 30%).
The disadvantage of a globoid gear is higher manufacturing cost and sensitivity of the enveloping globoid worm Pinion to the axial location.
Because of the geometrical nature of the tooth geometry Globoid pinion can mesh not only with the mating enveloping equipment but also with a properly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is normally common in lower cost in applications such as for example automotive electric powered gear actuators. The significant cost advantage comes due to the likelihood to injection mold the helical plastic material gear. The load capacity of the simplified helical/Globoid transmission is reduced to the particular level below the load capacity of the regular worm gear. Nevertheless the driving efficiency is still better compare to the standard worm gear.
There are only a few suppliers of the Globoid gear. division of Textron, situated in Traverse Town, MI. The detailed details about procedures used at Cone Drive for manufacturing of its gear could not be found. However, predicated on publicly released information it can be understood that the apparatus is produced by CNC milling with make use of a small ball shaped cutter.
Ever-power has capacity to design, prototype and supply 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 creating globoid gear at considerably reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that manufacturing of the Globoid equipment is more complex compare to manufacturing of the Globoid pinion. The Globoid pinion could be produced in high quantities by turning, whirling or grinding. During the machining procedure for the Globoid pinion the trimming tool needs to be capable to tilt in order 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 procedure, which incorporates a grinding steering wheel (diamond or CBN plated) with particular Ever-power simulated geometry. The complication of the novel procedure is the difficulties with simulation of the geometry of the grinding tool. The grinding tooth would need to generate a correct form of the Globoid pinion without tilting therefore the production rate and the production price would be significantly reduced. Ever-power has developed a computer based tool for creating of 3-dimensional CAD models of grinding tools for high volume production of the Globoid products.
The most common usage 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 made by grinding with a tilting grinding wheel. The Globoid gears have been cut by a special hub, which replicated the form of the Globoid Pinion. Special machines for creating the trimming hubs have already been developed. As the modern motor vehicle steering systems began to use traditional Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears has been reduced.
Variable ratio technology comparison
Bishop
Ever-power
Vr-rack technology was introduced:
Before 2000
2000
Underlying mathematical model is founded on:
Classic
gear
theory
Direct
Digital
Simulation
Rack geometry calculation accuracy is:
Limited by the boundaries of the traditional gear theory
Unlimited
Capacity to produce the vr-rack with not involute form for reduced noise
NO
YES
Capacity to generate vr-rack with an increase of ratio gain is:
Limited
YES
Cost of vr-rack design is:
High
Low
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 introduced a skew axis Globoid gear as a high load capacity and increased driving performance alternative to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It has to be noted that the name WORMOID will not relate to any scientific term in fact it is something of Dr. Stepan V. Lunin, who was simply the first in proposing this style and, more importantly, he was the initial who produces an accurate working model of the gear in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID gear has proved the ability of the concept such as conjugated transmission action and significant increase of number of tooth in the get in touch with compare to the classic Globoid gear.
CAD 3-d model of Ever-power wormoid gear.
Ever-power is currently offering assistance for design and development of items predicated on Ever-power wormoid technology.
It has to be noted that wormoid gear style from Ever-power is actually promising unique advantages review to the classic Globoid (double enveloping) equipment. Among the obvious advantages is increased load capacity due to increased number of one’s teeth in the mesh. The apparatus torque is carried by even more teeth so the load on every individual tooth is reduced. The other apparent advantage is increase driving efficiency. As one can see, the portion of the pinion with bigger diameter is driving the corresponding portion of the gear, that includes a larger diameter as well. Such of unique feature of Ever-power wormoid is missing in the classic Globoid gear and outcomes in higher sliding velocities and higher friction medication on the classic globoid gear. An experienced in the artwork engineer would immediately derive possible design benefits of the wormoid gear. For instance, using of the wormoid gear can significantly reduce cost of electric powered assist mechanisms that are commonly applied to modern automobiles. Because of the higher driving efficiency, wormoid equipment set can be designed with increase ration and offer the same driving effectiveness as the initial worm or dual enveloping worm gear. For example NSK worm equipment steering actuator with a ration around 20:1 provides about 80% of driving efficiency. The plastic equipment would hold about 80 Hm of torque. An alternative wormoid gear style from Ever-power would be capable to boost the ratio up to 30:1 and the torque on the apparatus up to 150 Hm without enhance of the guts distance between the gear and the pinion.