Influence of Undercut on the Load Capacity for Involute Teeth With Small Pressure Angle

2003 ◽  
Author(s):  
Jose´ I. Pedrero ◽  
Mariano Arte´s ◽  
Carlos Garci´a-Masia´
Keyword(s):  
Load Capacity ◽  
Geometrical Parameters ◽  
Contact Ratio ◽  
Helical Gears ◽  
Small Pressure ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number

The minimum number of teeth to avoid undercut on involute spur and helical gears depends on the pressure angle, among some other geometrical parameters. Higher number of teeth is required if the pressure angle becomes smaller. However, the contact ratio may be increased by reducing the pressure angle, which means the load is distributed along a longer line of contact. In many cases, even if undercut arises and teeth are weakened, both effects may result in higher load capacity for the gears. This paper presents a study on the influence of the pressure angle on the contact ratio, and through it on the length of contact and the load capacity, including a discussion on the condition to improve the load capacity by reducing the pressure angle beyond the undercut limit.

GEAR DESIGN

Engevista ◽  
2014 ◽  
Vol 16 (4) ◽  
pp. 313
Author(s):  
Florian Ion Petrescu ◽  
Relly Victoria Petrescu
Keyword(s):  
Inclination Angle ◽  
Normal Pressure ◽  
Original Method ◽  
Gear Design ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number ◽  
Gear Efficiency ◽  
Driving Wheel ◽  
Tooth Inclination

The paper presents an original method to determine the efficiency of the gear, the forces of the gearing, the velocities and the powers. The originality of this method relies on the eliminated friction modulus. The first chapters are analyzing the influence of a few parameters concerning gear efficiency.  These parameters are:  z1   - the number of teeth for the primary wheel of gear; z2   - the number of teeth of the secondary wheel of gear; alpha0 - the normal pressure angle on the divided circle; beta - the inclination angle. With the relations presented in this paper, it can synthesize the gear’s mechanisms. Today, the gears are present everywhere, in the mechanical’s world (In vehicle’s industries, in electronics and electro-technique equipments, in energetically industries, etc.). Optimizing this mechanism (the gears mechanism), we can improve the functionality of the transmissions with gears. At the gear mechanisms an important problem is the interference of the teeth. To avoid the interference between teeth, we must know the minimum number of teeth of the driving wheel, in function of the pressure angle (normal on the pitch circle, alpha0), in function of the tooth inclination angle (beta), and in function transmission ratio (i). The last chapter presents an original method to make the geometric synthesis of the gear, having in view the minimum number of teeth of the driving wheel. The classical methods use many different relations to determine the minimum number of teeth of the driving wheel. By this paper we want to give a unitary method to determine the minimum number of teeth of the driving wheel 1, to avoid the interference between the teeth of the two wheels (of the gear).

The Undercutting of Hobbed Spur Gear Teeth

1983 ◽  
Vol 105 (1) ◽  
pp. 122-128 ◽  
Author(s):  
R. G. Mitchiner ◽  
H. H. Mabie ◽  
H. Moosavi-Rad
Keyword(s):  
Spur Gear ◽  
Gear Teeth ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Minimum Number ◽  
Straight Portion ◽  
Base Circle ◽  
Tooth Flank ◽  
General Method

A general method is presented for the determination of the minimum number of teeth that can be cut in a spur gear without undercutting by a rounded-tooth tip hob. The minimum number of teeth to produce undercutting was investigated for three trochoid/tooth-profile relations: (1) trochoid tangent to the involute profile at the base circle, (2) trochoid tangent to a straight portion of the tooth flank, and (3) trochoid intersecting the involute profile at the base circle. It was found that in order to avoid undercutting, the minimum number of teeth cut into a gear occurs when the trochoid is tangent to the involute at the base circle. There is no set of hob parameters such that the trochoid intersects the involute profile at the base circle nor does the case of the trochoid being tangent to a straight flank exist. A set of figures representing the variation of the amount of undercutting versus the number of teeth, radius of hob-tooth tip, hob addendum, cutting pressure angle, and the corresponding derivatives are included for a typical gear.

Modal Analysis and Parameters Research of Internal Helical Gears Based on AWE

2011 ◽  
Vol 86 ◽  
pp. 904-907 ◽  
Author(s):  
Yan Jun Gong ◽  
Xue Yao Wang ◽  
Han Zhao ◽  
Kang Huang
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Helix Angle ◽  
Helical Gear ◽  
Vibration Characteristics ◽  
Helical Gears ◽  
Pressure Angle ◽  
Number Of Teeth ◽  
Gear Change

The paper conducted a modal analysis of an internal helical gear based on AWE, and obtained its first 6 order natural frequency. Then the paper analyzed the influence of its parameters on the vibration characteristics of the internal helical gear, found that if the helix angle, the normal module, the number of teeth of the internal helical gear change, its vibration characteristics will change, but the change of the pressure angle doesn’t influence its vibration characteristics.

Efficiency of the High Contact Ratio Involute Spur Gears With Asymmetric Teeth

2010 ◽  
Author(s):  
F. Karpat ◽  
S. Ekwaro-Osire
Keyword(s):  
High Performance ◽  
Load Capacity ◽  
Design Parameters ◽  
Spur Gears ◽  
Contact Ratio ◽  
Pressure Angle ◽  
Low Weight ◽  
Standard Design ◽  
Load Carrying ◽  
The Impact

Gears with asymmetric teeth have unique potential for application in gearboxes, particularly when uni-directional loading is applied. Most recently, gears with asymmetric teeth have received much attention for use in applications that require high performance due to increased load capacity. Such applications include aircraft and wind turbine. These gears offer flexibility to designers due to their non-standard design. In asymmetric teeth, the geometry of the drive side is not to be symmetric to the coast side. In other words, the pressure angle on the drive side is greater or smaller than that on the coast side. Asymmetry between tooth sides provide vital in obtaining key properties, such as high load carrying capacity, low weight, low wear or low vibration. In order to effectively design asymmetric teeth, it is necessary to perform analyses on the efficiency of these gears under various loading. In this study, the results obtained on high contact ratio involute spur gears with asymmetric teeth are presented and discussed. The impact of a few design parameters, such as pressure angle or tooth height, on sliding velocities and friction is investigated and illustrated with numerical examples.

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