ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage pitched against a traditional worm gear 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 production cost and sensitivity of the enveloping pinion to the axial location.
Due to the geometrical character of the tooth geometry Globoid pinion can mesh not only with the mating enveloping equipment but also with a correctly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is definitely common in lower cost in applications such as for example automotive electric powered gear actuators. The significant price advantage comes due to the probability to injection mold the helical plastic gear. The load capability of the simplified helical/Globoid transmission is decreased to the level below the strain capacity of the standard worm gear. Nevertheless the driving efficiency continues to be better compare to the regular worm gear.
There are only a few suppliers of the Globoid gear. division of Textron, situated in Traverse City, MI. The detailed information regarding processes used at Cone Drive for making of its gear cannot be found. However, predicated on publicly released information it can be understood that the gear is manufactured 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 expertise of Ever-power is 3-dimentional simulation and modeling of the Globoid and dual enveloping tooth geometry. Ever-power 3-dimentional Globoid and double enveloping gear CAD models can be used in various CNC machining shops for creating globoid gear at significantly reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that production of the Globoid equipment is more complex compare to production of the Globoid pinion. The Globoid pinion could be produced in high quantities by turning, whirling or grinding. Through the machining process of the Globoid pinion the reducing tool has to be able to tilt in order to produce the enveloping shape.
The newer production methods are under development. The most promising creation method of the Globoid pinion is certainly 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 problems with simulation of the geometry of the grinding device. The grinding tooth would need to globoid worm generate a correct kind of the Globoid pinion without tilting so the production rate and the production price would be considerably reduced. Ever-power has developed a computer based device for making of 3-dimensional CAD models of grinding equipment for high volume creation of the Globoid products.
The most common utilization of the Globoid gear set was noticed 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 special hub, which replicated the form of the Globoid Pinion. Special machines for generating the trimming hubs have already been developed. Because the modern automotive steering systems started to use traditional Bishop or advanced Ever-power variable ratio rack and pinion technology, the demand for the Globoid gears provides 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 precision 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 motor sport racing applications.
Ever-power low noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another era of Globoid gears. In 1999 Ever-power introduced a skew axis Globoid gear as a higher load capacity 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 to any scientific term and it is something of Dr. Stepan V. Lunin, who was simply the first in proposing this style and, moreover, he was the first who produces an accurate working model of the apparatus in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID equipment has proved the ability of the concept such as conjugated transmission actions and significant increase of number of tooth in the contact compare to the traditional Globoid gear.
CAD 3-d style of Ever-power wormoid gear.
Ever-power is currently offering assistance for design and development of products predicated on Ever-power wormoid technology.
It needs to be noted that wormoid equipment style from Ever-power is actually promising unique advantages review to the vintage Globoid (double enveloping) equipment. One of the obvious advantages is improved load capacity due to increased number of one’s teeth in the mesh. The apparatus torque is certainly carried by even more teeth so the load on every individual tooth is reduced. The other apparent advantage is boost driving efficiency. As you can see, the portion of the pinion with bigger diameter is generating the corresponding part of the gear, which has a larger diameter aswell. Such of exclusive feature of Ever-power wormoid can be missing in the classic Globoid gear and outcomes in higher sliding velocities and higher friction drug on the classic globoid gear. A skilled in the art engineer would instantly derive possible design advantages of the wormoid equipment. For example, using of the wormoid equipment can significantly reduce price of electric powered help mechanisms that are commonly applied to modern automobiles. Because of the bigger driving efficiency, wormoid gear set can be designed with increase ration and provide 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 gear would hold about 80 Hm of torque. An alternative solution wormoid gear design from Ever-power will be capable to boost the ratio up to 30:1 and the torque on the gear up to 150 Hm without enhance of the center distance between the gear and the pinion.