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 on 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 gear but also with a correctly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is certainly common in reduced cost in applications such as for example automotive electric powered gear actuators. The significant cost advantage comes because of the likelihood to injection mold the helical plastic material gear. The load capacity of the simplified helical/Globoid transmission is reduced to the level below the load capacity of the standard worm gear. Nevertheless the driving efficiency continues to be better evaluate to the regular worm gear.
There are simply a few suppliers of the Globoid gear. division of Textron, located in Traverse City, MI. The detailed information about processes utilized at Cone Drive for manufacturing of its gear cannot be found. However, based on publicly released information it can be understood that the gear is manufactured by CNC milling with use 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 dual enveloping tooth geometry. Ever-power 3-dimentional Globoid and double enveloping gear CAD versions can be used in various 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 equipment is more complex compare to manufacturing of the Globoid pinion. The Globoid pinion can be produced in high quantities by turning, whirling or grinding. During the machining process of the Globoid pinion the reducing tool has to be able to tilt to be able to produce the enveloping form.
The newer production methods are under advancement. The most promising production method of the Globoid pinion is certainly continues grinding procedure, which includes a grinding 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 device. The grinding tooth would have to generate a correct kind of the Globoid pinion globoid worm without tilting therefore the production rate and the production cost would be significantly reduced. Ever-power has developed a computer based device for generating of 3-dimensional CAD models of grinding tools for high volume creation of the Globoid products.
The most common use 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 made 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 making the slicing hubs have been developed. Because the modern motor vehicle steering systems started to use classic Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears provides been reduced.
Variable ratio technology comparison
Vr-rack technology was introduced:
Underlying mathematical model is based on:
Rack geometry calculation precision is:
Limited by the boundaries of the classic gear theory
Capacity to produce the vr-rack with not involute type for reduced noise
Capacity to generate vr-rack with an increase of ratio gain is:
Cost of vr-rack design is:
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 generation of Globoid gears. In 1999 Ever-power released a skew axis Globoid gear as a high load capability 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 with any scientific term and it is a product of Dr. Stepan V. Lunin, who was simply the first in proposing this style and, moreover, he was the 1st who produces an accurate functioning 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 action and significant boost of number of tooth 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 design and development of items based 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 basic Globoid (double enveloping) gear. One of 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 therefore the load on each individual tooth is decreased. The other apparent advantage is boost 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 exclusive feature of Ever-power wormoid is usually missing in the traditional Globoid gear and results in higher sliding velocities and higher friction medication on the traditional globoid gear. A skilled in the art engineer would instantly derive possible design advantages of the wormoid equipment. For example, using of the wormoid gear can significantly reduce cost of electric powered aid mechanisms that are generally applied to modern automobiles. Because of the higher driving efficiency, wormoid gear set can be made with increase ration and offer the same driving efficiency as the original worm or dual enveloping worm gear. For example NSK worm equipment steering actuator with a ration of about 20:1 provides about 80% of generating efficiency. The plastic equipment would hold about 80 Hm of torque. An alternative solution wormoid gear style from Ever-power will be capable to raise the ratio up to 30:1 and the torque on the apparatus up to 150 Hm without increase of the guts distance between the equipment and the pinion.
ypical Globoid gear.