ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm gear because of increased driving efficiency ( 6-10% higher about 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 may mesh not merely with the mating enveloping equipment but also with a correctly designed cylindrical helical gear. Using a helical equipment with a Globoid pinion can be common in lower cost in applications such as automotive electric powered gear actuators. The significant price advantage comes because of the probability to injection mold the helical plastic material 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, positioned in Traverse City, MI. The detailed information about procedures utilized at Cone Drive for developing of its gear could not be found. However, predicated 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 offer Globoid gear items. 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 models 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 production of the Globoid equipment is more technical compare to manufacturing 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 slicing tool needs to be able to tilt to be able to produce the enveloping form.
The newer production methods are under advancement. The most promising creation approach to the Globoid pinion is continues grinding process, which includes a grinding steering wheel (gemstone or CBN plated) with specific 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 have to generate a correct kind of the Globoid pinion without tilting therefore the production rate and the production cost would be significantly reduced. Ever-power is rolling out a computer based device for creating of 3-dimensional CAD types of grinding equipment for high volume production of the Globoid items.
The most common usage 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 made by grinding with a tilting grinding wheel. The Globoid gears have already been cut by a particular hub, which replicated the form of the Globoid Pinion. Special machines for creating the cutting hubs have already been developed. Because the modern automotive steering systems began 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
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
Capability 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 noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another generation of Globoid gears. In 1999 Ever-power released a skew axis Globoid gear as a higher load capability and increased driving performance option to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It needs to be noted that the name WORMOID does not relate with any scientific term and it is a product of Dr. Stepan V. Lunin, who was the 1st in proposing this style and, moreover, he was the first who produces an accurate operating model of the apparatus in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID equipment has proved the capability of the concept 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 style of Ever-power wormoid gear.
Ever-power happens to be offering assistance for style and development of products predicated on Ever-power wormoid technology.
It needs to be noted that wormoid equipment design from Ever-power is actually promising unique advantages review to the common Globoid (double enveloping) equipment. Among the obvious advantages is elevated load capacity due to increased number of one’s teeth in the mesh. The gear torque is carried by more teeth therefore the load on each individual tooth is reduced. The other apparent advantage is increase driving efficiency. As one can see, the portion of the pinion with larger diameter is generating the corresponding part of the gear, which has a larger diameter as well. Such of exclusive feature of Ever-power wormoid is normally missing in the traditional Globoid gear and outcomes in higher sliding velocities and higher friction medication on the traditional globoid gear. An experienced in the art engineer would instantly derive possible design benefits of the wormoid gear. For example, using of the wormoid equipment can significantly reduce cost of electric powered aid mechanisms that are generally applied to modern automobiles. Due to the bigger driving efficiency, wormoid gear set can be made with increase ration and offer the same driving performance as the initial worm or dual enveloping worm gear. For instance NSK worm gear steering globoid worm actuator with a ration of about 20:1 provides about 80% of generating 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 gear up to 150 Hm without increase of the guts distance between the gear and the pinion.