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 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.
Because of the geometrical character of the tooth geometry Globoid pinion can mesh not only with the mating enveloping gear but also with a properly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is usually common in reduced cost in applications such as for example automotive electric powered gear actuators. The globoid worm significant cost advantage comes because of the possibility to injection mold the helical plastic gear. The load capability of the simplified helical/Globoid transmission is decreased to the particular level below the strain capacity of the standard worm gear. However the driving efficiency is still better compare to the standard worm gear.
There are just a few suppliers of the Globoid gear. division of Textron, located in Traverse Town, MI. The detailed details about procedures utilized at Cone Drive for making of its gear could not be found. However, based on publicly released details it can be understood that the apparatus is produced by CNC milling with use a little 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 gear CAD versions can be used in numerous CNC machining shops for producing globoid gear at considerably reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that production of the Globoid gear is more complex compare to production of the Globoid pinion. The Globoid pinion can 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 in order to produce the enveloping shape.
The newer production methods are under advancement. The most promising production method of the Globoid pinion is certainly continues grinding process, which includes a grinding wheel (gemstone or CBN plated) with specific Ever-power simulated geometry. The complication of the novel process is the difficulties with simulation of the geometry of the grinding device. The grinding tooth would have to generate a correct form of the Globoid pinion without tilting so the production rate and the production price would be considerably reduced. Ever-power is rolling out a computer based device for producing 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 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 already been cut by a particular hub, which replicated the shape of the Globoid Pinion. Special machines for creating the trimming hubs have been developed. As the modern motor vehicle steering systems started 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 based on:
Classic
gear
theory
Direct
Digital
Simulation
Rack geometry calculation precision is:
Limited by the boundaries of the classic gear theory
Unlimited
Capability to produce the vr-rack with not involute form for reduced noise
NO
YES
Capability to generate vr-rack with increased ratio gain is:
Limited
YES
Cost of vr-rack style 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 generation of Globoid gears. In 1999 Ever-power presented a skew axis Globoid gear as a higher load capability and increased driving efficiency option to the classic Globoid gear.
Ever-power skew axis (wormoid) gear.
It has to be noted that the name WORMOID does not relate to any scientific term and it is a product of Dr. Stepan V. Lunin, who was simply the first in proposing this design and, more importantly, he was the 1st who produces a precise functioning model of the gear in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID gear has proved the capability of the concept such as for example conjugated transmission actions and significant increase of number of teeth in the get in touch with 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 based on Ever-power wormoid technology.
It has to be noted that wormoid equipment style from Ever-power is obviously promising unique advantages review to the classic Globoid (double enveloping) equipment. One of the obvious advantages is elevated load capacity because of increased number of the teeth in the mesh. The gear torque is normally carried by more teeth so the load on every individual tooth is reduced. The other obvious advantage is increase driving efficiency. As one can see, the part of the pinion with bigger diameter is driving the corresponding portion of the gear, that includes a larger diameter as well. Such of exclusive feature of Ever-power wormoid is usually missing in the traditional Globoid gear and results in higher sliding velocities and higher friction drug on the classic globoid gear. An experienced in the artwork engineer would immediately 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 generally used on modern automobiles. Because of the bigger driving efficiency, wormoid equipment set can be made with increase ration and provide the same driving performance as the original worm or dual enveloping worm gear. For example NSK worm equipment steering actuator with a ration around 20:1 provides about 80% of traveling efficiency. The plastic gear would hold about 80 Hm of torque. An alternative 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 increase of the guts distance between the gear and the pinion.