ypical 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 on 25:1 ratio) and increased loading capacity (on the subject of 30%).
The disadvantage of a globoid gear is higher production 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 gear but also with a correctly designed cylindrical helical gear. Using a helical gear with a Globoid pinion can be common in lower cost in applications such as for example automotive electric powered gear actuators. The significant cost advantage comes because of the possibility to injection mold the helical plastic material gear. The load capacity of the simplified helical/Globoid transmitting is reduced to the level below the strain capacity of the standard worm gear. Nevertheless the driving efficiency is still better compare to the regular worm gear.
There are just a few suppliers of the Globoid gear. division of Textron, located in Traverse Town, MI. The detailed information regarding procedures used at Cone Drive for making of its gear cannot be found. However, based on publicly released information it can be understood that the apparatus is manufactured by CNC milling with use a little ball shaped cutter.
Ever-power has capability to design, prototype and supply Globoid gear items. The experience 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 gear CAD models can be used in numerous CNC machining shops for producing globoid gear at significantly reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It needs to be noted that production of the Globoid gear is more technical compare to production of the Globoid pinion. The Globoid pinion can be produced in high amounts by turning, whirling or grinding. During the machining procedure for the Globoid pinion the reducing tool has to be capable to tilt in order to produce the enveloping shape.
The newer production methods are under development. The most promising production approach to the Globoid pinion is continues globoid worm grinding procedure, 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 generate a correct form of the Globoid pinion without tilting therefore the production price and the production price would be significantly reduced. Ever-power is rolling out a computer based device for making of 3-dimensional CAD types of grinding tools for high volume production 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 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 producing the trimming hubs have been developed. Because the modern automotive steering systems began to use classic Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears offers been reduced.
Variable ratio technology comparison
Bishop
Ever-power
Vr-rack technology was introduced:
Before 2000
2000
Underlying mathematical model is based on:
Classic
gear
theory
Direct
Digital
Simulation
Rack geometry calculation accuracy is:
Tied to the boundaries of the classic gear theory
Unlimited
Capability to produce the vr-rack with not involute type for reduced noise
NO
YES
Capacity to generate vr-rack with increased 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 noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another era of Globoid gears. In 1999 Ever-power launched a skew axis Globoid gear as a high load capacity and increased driving efficiency alternative to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It has to be noted that the name WORMOID does not relate to any scientific term in fact it is something of Dr. Stepan V. Lunin, who was the 1st in proposing this style and, moreover, he was the initial who produces a precise 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 idea such as conjugated transmission action and significant boost 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 style and development of items predicated on Ever-power wormoid technology.
It needs to be noted that wormoid equipment style from Ever-power is obviously promising unique advantages compare to the basic Globoid (double enveloping) gear. One of the obvious advantages is improved load capacity because of increased number of one’s teeth in the mesh. The apparatus torque can be carried by more teeth so the load on each individual tooth is decreased. The other apparent advantage is boost driving efficiency. As one can see, the part of the pinion with bigger diameter is generating the corresponding part of the gear, that includes a larger diameter aswell. Such of unique feature of Ever-power wormoid is usually missing in the traditional Globoid gear and outcomes in higher sliding velocities and higher friction drug on the traditional globoid gear. An experienced in the artwork engineer would immediately derive possible design benefits of the wormoid gear. For instance, using of the wormoid equipment can significantly reduce price of electric powered support mechanisms that are generally used on modern automobiles. Due to the bigger driving efficiency, wormoid gear set can be designed with increase ration and provide the same driving effectiveness as the initial worm or double enveloping worm gear. For example NSK worm equipment steering actuator with a ration around 20:1 delivers about 80% of driving efficiency. The plastic equipment would hold about 80 Hm of torque. An alternative solution wormoid gear design from Ever-power would be capable to increase the ratio up to 30:1 and the torque on the apparatus up to 150 Hm without enhance of the guts distance between the equipment and the pinion.