Showing papers on "Pressure angle published in 2002"

Gear Crack Propagation Path Studies-Guidelines for Ultra-Safe Design

Abstract: Design guidelines have been established to prevent catastrophic rim fracture failure modes when considering gear tooth bending fatigue. Analysis was performed using the finite element method with principles of linear elastic fracture mechanics. Crack propagation paths were predicted for a variety of gear tooth and rim configurations. The effects of rim and web thicknesses, initial crack locations, and gear tooth geometry factors such as diametral pitch, number of teeth, pitch radius, and tooth pressure angle were considered. Design maps of tooth/rim fracture modes including effects of gear geometry, applied load, crack size, and material properties were developed. The occurrence of rim fractures significantly increased as the backup ratio (rim thickness divided by tooth height) decreased. The occurrence of rim fractures also increased as the initial crack location was moved down the root of the tooth. Increased rim and web compliance increased the occurrence of rim fractures. For gears with constant pitch radii, coarser-pitch teeth increased the occurrence of tooth fractures over rim fractures. Also, 25 deg pressure angle teeth had an increased occurrence of tooth fractures over rim fractures when compared to 20 deg pressure angle teeth. For gears with constant number of teeth or gears with constant diametral pitch, varying size had little or no effect on crack propagation paths.

Direct Gear Design for Spur and Helical Involute Gears

Abstract: analysis and design of spur and helical involute gears. Introduction Modern gear design is generally based on standard tools. This makes gear design quite simple (almost like selecting fasteners), economical, and available for everyone, reducing tooling expenses and inventory. At the same time, it is well known that universal standard tools provide gears with less than optimum performance and— in some cases—do not allow for finding acceptable gear solutions. Application specifics, including low noise and vibration, high density of power transmission (lighter weight, smaller size) and others, require gears with nonstandard parameters. That’s why, for example, aviation gear transmissions use tool profiles with custom proportions, such as pressure angle, addendum, and whole depth. The following considerations make application of nonstandard gears suitable and cost-efficient: • CNC cutting machines and CMM gear inspection equipment make production of nonstandard gears as easy as production of standard ones. • Cost of the custom cutting tool is not much higher than that of the cutting tool for standard gears and can be amortized if production quantity is large enough. • The custom gear performance advantage makes a product more competitive and justifies larger tooling inventory, especially in mass production. • Gear grinding is adaptable to custom tooth shapes. • Metal and plastic gear molding cost largely does not depend on tooth shape. This article presents the direct gear design method, which separates gear geometry definition from tool selection, to achieve the best possible performance for a particular product and application. The direct design approach that is commonly used for most parts of mechanisms and machines (for example, cams, linkages, compressor or turbine blades, etc.) determines their profiles according to the operating conditions and desired performance. Ancient engineers used the same Direct Gear Design for Spur and Helical Involute Gears

The efficiency and friction of plastic cylindrical gears Part 2: Influence of tooth geometry

Abstract: In Part 1 the influences of materials and material combinations on the efficiency of plastic gears were investigated. In this paper, the effect of changes to plastic gear tooth geometry is investigated. Using a gear tooth form of standard proportions as the benchmark gear, gears were moulded to a number of different specifications. These changes in geometry included speed ratio, module, pressure angle, addendum, integer contact ratios and tip relief. Sensitivity to centre distance variations was investigated on the benchmark geometry. A helical gear was also tested for comparison with a spur gear of comparable specification. Using measured efficiencies, coefficients of friction were determined for a number of the gear geometries examined.

The Influence of Gear Design Parameters on Gear Tooth Damage Detection Sensitivity

Abstract: This paper develops an analytical model to simulate the gear mesh contact for a spur gear pair with and without tooth damage. Three common gear tooth faults are simulated including pitting, wear and root cracks. The effect of tooth face width on detection sensitivity for pitting and the effect of crack width on detection sensitivity for crack are investigated. Using static performance measures, such as transmission error results suggest that basic gear design parameters, such as diametral pitch, pressure angle and number of teeth, may have a significant effect on damage detection sensitivity. It appears that a decrease in diametral pitch will enhance damage detection sensitivity for all the three types of damage. An increase in pressure angle or number of teeth will enhance detection sensitivity for pitting damage, but tends to decrease the sensitivity to crack or wear damage.

Link plate for a silent chain

Abstract: A link plate for silent chains 10 includes a pair of teeth or toes 10 a each formed of an inside flank 11 and an outside flank 12 and a pair of pin apertures 10 b to insert connecting pins 3 thereinto. A moment M around a pin 3 is shown as follows: M=F×Lo where F is a force applied by a tooth 21 of a sprocket 20 against a meshing point 12 e on the outside flank 12, and Lo is a length of a perpendicular drawn from a center O of a pin aperture 10 b to an action line m of the force F. In order to decrease this moment M, the length Lo of the perpendicular is shortened, said link plate having an engaging point E with a tooth of a sprocket on an intersection between a straight line n and a flank, said straight line n and the direction of a central line connecting each center O of pin apertures forming a pressure angle α, and being in contact with a circle C, said circle C having a center located at a center O of said pin aperture and a radius r≦0.25×P, where P is a pin aperture pitch. Also, a pressure angle α of the outside flank is determined to satisfy an inequality, 32°≦α≦34°, to lessen the force F.

Gear machining method and device thereof

Abstract: PROBLEM TO BE SOLVED: To improve workability in gear grinding work in a gear machining method and a device thereof. SOLUTION: Upon completion of grinding machining, a probe 17 measures and computes pressure angle errors ΔfaL, ΔfaR on the left and right in a workpiece (gear) W, error ΔL in the direction of tooth trace, and tooth thickness error Δth. A lead compensation amount ΔP is calculated from the measured error ΔL in the direction of tooth trace using dichotomy. Grinding wheel center position compensation amount ΔX, ΔY and grinding wheel mounting angle error ΔΣ are calculated from the measured pressure angle errors ΔfaL, ΔfaR and tooth thickness error Δth using a glide simplex method so that evaluation function f becomes the minimum by taking the lead compensation amount ΔP into account. COPYRIGHT: (C)2003,JPO

Study for the Forming Principle of Logix Gear Tooth Profile and Its Mesh Performance

Abstract: In recent years, a new type of gear named Logix gea r was developed. Actually, the tooth profile of this new type of gear is composed of lots of micro-segment involute curves, and on the profile, there exist lots of points, which their relative curvatures are equal to zero. This can result in the sliding coefficient smaller between two meshed Logix gears, and the mesh ch aracteristic becomes almost rolling transmission from sliding transmission accor dingly. So, this new type of gear has lots of advantages such as higher contact intensity, longer useful life and can easily realize power transfer of bigger tr ansmission ratio than standard involute gear. Study results showed that the cont act fatigue strength is 3 times larger, the bend fatigue strength is 2.5 times l arger, and the minimum tooth number can be decreased to 3, much smaller than tha t of standard involute gear. In this paper, following studies had been done: 1) The formation principle of Logix gear tooth profile was studied. The theoreti cal models describing the geometrical formations of this type of gear and its re lative Logix rack had been deduced. 2) While cutting a Logix gear, its tooth profile is decided by its normal tooth profile of Logix rack. Besides the basic parameters of standard involute gear, L ogix rack has its own specific parameters such as preliminary pressure angle, re lative pressure angle, and preliminary referential circle radius etc. So, the in fluence of connatural parameters of Logix rack on the tooth profile of Logix gea r had been farther studied. Reasonable selection for these parameters had been d iscussed. 3) Several kinds of transition curves for gear's tooth profile had been introdu ced, its selection used by Logix gear had been described, and also its mathemati cal description model had been deduced. 4) The mesh theories of Logix gears had been developed. It had been proved that the transmission performance between Logix gears coincides with E-W theorem as that of ordinary standard involute gears. The formula calculating superposition coefficient was deduced according to its definition. Different from standard inv olute gears, the parameter of gear number has no effect on the superposition coe fficient of the Logix gears. Accordingly, bigger ratio transmission can be acqui red by means of decreasing the gear number, and its minimum gear number can be r eached to 3, much smaller than the minimum gear number of ordinary standard invo lute gear: 14～17. This is very important to realize the miniaturization of prod uction design. 5) The CAD special software was developed to design all kinds of Logix gears, an d a solid design example was offered. To sum up, by means of above study, the system info about Logix gear had been de veloped and enriched. This has most significant impact on its widely promotion a nd practical application, on the improvement of carrying capacity, miniaturizati on, and life of kinetic transmission products.

A contribution to the optimal choice of the HCR-gears regarding frictional losses

Abstract: High transverse contact ratio (HCR) gears are non-standard involute gears with a transverse contact ratio ea > 2 which proved adequate for use in automobiles, trucks, aircrafts and ships. The paper deals with the dependence of the sliding friction losses on HCR spur gears geometry: pressure angle, tooth height, gears centre distance resp. addendum modification coefficients sum, addendum modification coefficients sum distribution and other parameters. The calculations are based on the comparison between the values of the sliding friction loss geometrical factor, which comprises the influence of the magnitude and form of the toothing. A proper choice of these parameters is necessary for achieving good gearbox efficiency. The results of the calculations are shown in diagrams that can be a tribological guideline for the designer to choose gears optimal geometrical parameters.

Gear of motor-driven power steering device

Abstract: PROBLEM TO BE SOLVED: To provide a gear of a motor-driven power steering device capable of further reducing the quantity of abrasion from a view-point different from a traditional one. SOLUTION: Since the pressure angle αn of a worm wheel 107 on the addendum side is larger than that on the dedendum side, the local abutting of the gear can be controlled and the abrasion of the worm wheel 107 on the dedendum side can be reduced, and therefore, such problems as the increase of the initial backlash can be avoided.

Inscribed engagement planetary gear mechanism

Abstract: PROBLEM TO BE SOLVED: To make a pressure angle smaller and increase transmission efficiency of an outer and inner toothed gears because the shapes of conventional toothed wheels have large pressure angles with low transmission efficiency due to formation by curves such as a prolate epicycloid, a prolate hypocycloid, a curtate epicycloid, or a curtate hypocycloid. SOLUTION: The inscribed engagement planetary gear mechanism is equipped with a first shaft 1, an outer toothed gear 3 eccentrically rotatable relative to the first shaft 1 through an eccentric part 2 of the first shaft 1, an inner toothed gear 4 inscribed and engaged to the outer toothed gear 3, and a second shaft 6 connected through a transmitting means 5 for transmitting only the rotation component of the outer toothed gear 3. The forms of both the teeth of the outer toothed gear 3 and the inner toothed gear 4 are provided with the tooth form of the inside of a pitch circle as a hypocycloid, and the form of the outside of the pitch circle as an epicycloid. Thereby, the pressure angles of the outer toothed gear 3 and the inner toothed gear 4 can be made smaller, and transmission efficiency can be increased. COPYRIGHT: (C)2004,JPO

Drum shape teeth type coupling

Abstract: The utility model discloses a drum tooth-shaped coupling, comprising an external tooth axle sleeve, an annular ring gear and a bolt used for reaming, and the utility model is characterized in that an inner tooth and an external tooth are meshed with an involute spline with a drum shape, an angle of a pressure angle between the inner tooth and the external tooth ranges from 28 degrees to 30 degrees, a tooth length direction of the external tooth takes a shape of a three-segment arc and a middle arc radius is larger than the arc radius of two ends. The utility model has the advantages of high transmission ability, big angle offset and long service life and convenient for production.

Forging gear, method of manufacturing the same, and mould for forging gear

Abstract: PROBLEM TO BE SOLVED: To inexpensively provide a gear which eliminates warping in configuration of the gear induced from influence in manufacturing error and distortion of heat treatment and restrains the gear from occurring noise. SOLUTION: The forging gear 1 is configured to form at least one of tooth thickness and pressure angle of basic tooth profile 2 by aligning tooth varying within gear required precision along with the basic tooth profile. The tooth thickness and the pressure angle of thinner tooth profile 3 and those of thicker tooth profile 4 relative to the basic tooth profile 2 are determined so as to become optimal increased and decreased amount at every tooth within the gear required precision. In addition, error of gear shape inducing to gear noise and assembled error of the gear are adjusted at every tooth and engagement due to every tooth is made to optimal condition. Alteration in the gear shape at every tooth of the forging gear 1 can perform by adjusting surface shape of product in forging mould concerned to manufacture of the forging gear. Once determining the shape of the mount, it is possible to inexpensively provide a majority of the gears which restrain the gear from occurring the noise. COPYRIGHT: (C)2004,JPO

Flat die for form rolling

Abstract: PROBLEM TO BE SOLVED: To provide a flat die for form rolling capable of rolling a screw and a worm that can suppress a bend of the material to be processed as little as possible by improving processing accuracy of the material to be processed. SOLUTION: The flat die for form rolling is provided with a biting section I, a semi-finishing section II and a finishing section III and the tooth profile a of the biting section I is composed of the two sections of the root of tooth and the tooth blank 11 near the tooth bottom and the tooth top and the tooth blank 12 near the tooth top and the relationship between the pressure angle α1 of the root of tooth and the tooth blank 11 near the tooth bottom and the pressure angle α2 the tooth top and the tooth blank 12 near the tooth top is α2 >α1 and 25 deg.<α2 <45 deg. and the tooth top of the biting section I is point shaped and roundness R is given in the top end, and the roundness R has a configuration of R<2.0.

Gearshifter for automobile

Abstract: The utility model discloses a car derailleur. A casing 2 is provided with a second axis 15, a middle axis 20 and a plurality of gears and synchronizers at the second axis 15 and the middle axis 20. The utility model is characterized in that the modulus of the gear in the derailleur is 4 to 5, the pressure angle is 25.5 DEG and the helical angle is 18 DEG to 23 DEG. The parameter improves the intensity of the gears and reduces the noise. The gears of two to six all have synchronizers except for the gear one and the reverse gear, wherein, the synchronizer of the gear two has a large capability and reduces the shift force with convenient operation. And a gear anti-disengaging device is adopted to improve the working reliability of the derailleur. The gears of the first axis 1 and the second axis 15 are respectively provided with an oil hole and an oil groove and the inner side top of the casing 2 is provided with an oil guiding groove 26. The middle of the casing 2 is provided with an oil-isolating wall 27 whose bottom is provided with a throttling hole 28. When in working, the front oil face debases and the back oil face arises so as to lubricate the back of the derailleur completely. Besides, the gear of the second axis 15 all adopts a needle bearing 29, which reduces the tearing damage. The reference input torsion distance of the utility model is 75 kilogram meter and the centre distance between the second axis 15 and the middle axis 20 is 138mm. The derailleur is enginery six gears derailleur and is applicable for the cars of 7 tons or more.

Gear Crack Propagation Path Studies-- Guidelines Developed for Ultrasafe Design

Abstract: Effective gear designs balance strength, durability, reliability, size, weight, and cost. However, unexpected gear failures may occur even with adequate gear tooth design. To design an extremely safe system, the designer must ask and address the question "What happens when a failure occurs?" With regard to gear-tooth bending fatigue, tooth or rim fractures may occur. For aircraft, a crack that propagated through a rim would be catastrophic, leading to the disengagement of a rotor or propeller, the loss of an aircraft, and possible fatalities. This failure mode should be avoided. However, a crack that propagated through a tooth might or might not be catastrophic, depending on the design and operating conditions. Also, early warning of this failure mode might be possible because of advances in modern diagnostic systems. An analysis was performed at the NASA Glenn Research Center to develop design guidelines to prevent catastrophic rim fracture failure modes in the event of gear-tooth bending fatigue. The finite element method was used with principles of linear elastic fracture mechanics. Crack propagation paths were predicted for a variety of gear tooth and rim configurations. The effects of rim and web thicknesses, initial crack locations, and gear-tooth geometry factors such as diametral pitch, number of teeth, pitch radius, and tooth pressure angle were considered. Design maps of tooth and rim fracture modes, including the effects of gear geometry, applied load, crack size, and material properties were developed. The occurrence of rim fractures significantly increased as the backup ratio (rim thickness divided by tooth height) decreased. The occurrence of rim fractures also increased as the initial crack location was moved down the root of the tooth. Increased rim and web compliance increased the occurrence of rim fractures. For gears with constant-pitch radii, coarser-pitch teeth increased the occurrence of tooth fractures over rim fractures. Also, 25 degree pressure angle teeth increased the occurrence of tooth fractures over rim fractures in comparison to 20 pressure angle teeth. For gears with a constant number of teeth or for gears with constant diametral pitch, varying size had little or no effect on crack propagation paths.

Minimum dimension design of disc cam mechanism with upright installed concave arc bottomed translating follower

Abstract: AbstrcatStarting from the expression of pressure angle,via constructing corresponding analogous velocity chart of mechanism,a clear solving thinking and steps for determining minimum basic dimension of mechanism according firstly to the condition of pressure angle α≤,αr≤r and secondly to the condition of curvature radius ρ≥,thus the theoretical task of minimum dimension design of upright installed concave arc bottomed translating follower disc cam mechanism is solved satisfactorily.

Evaluation of Ring Gear Tooth Stress

Abstract: To optimize the operating speeds of the low spool of a gas turbine engine together with the overall transmitted horsepower to weight ratio, an epicyclic gear train is used to transmit power from the turbine section to the propeller shaft (as in PWC PT6 engine) or to the fan shaft (as in Honeywell TFE-731 engine). In order to achieve an optimum design in view of structural integrity, the stress characteristics of each component of the epicyclic gear train needs to be optimized. In general, the external gear mesh (as in the sun and planet mesh), needs a back up rim to tooth thickness ratio of not less than 1.2. However, this is not always the case for internal gear mesh such as the ring gear. The objective of this paper is to present analytical results on the stress behavior of the ring gear under different loading conditions. Three dimensional finite element method is employed to study the internal tooth fillet stress under the effects of fillet radius, gear rim thickness, pressure angle and helix angle. This study is the first part of a work aiming to determine the failure mode of the ring gear and leading to design optimization of epicyclic systems.Copyright © 2002 by ASME

Research on Cycloidal Characteristics

Abstract: Based on cycloidal mathematic equation, I derived equations for tangent line and normal line of a point in cycloidal, and obtained the intersection coordinate by the normal lines of each surface contact point in cycloidal pin wheel reducer when it is in high motion. Finally, the pressure angle formula of a point in cycloidal is established according to its motion form.

Numerical simulation analysis of die deflection in net shape forming of bevel gear

Abstract: Elastic deflection of die profile is an important factor to influence the accuracy of the formed component in precision forming.In the paper,the profile deflection of die used in bevel gear precision forming process is studied quantitatively by means of numerical simulation method.It is found that,in both prestressing state and process state,the deflection may be big enough to ruin gear accuracy counted in μm.The analysis results prove that the deflection on tooth flank is not distributed uniformly.Therefore,it can not reach accurate compensation of tooth error to simply modify pressure angle of die in single value.

Screw compressor gearing

Abstract: FIELD: compressor technology. SUBSTANCE: gearing is formed by two parallel to rotors with interrounded screw surfaces and large and small numbers of starts each in end face section having tooth profile asymmetric to straight line running through tooth point and rotor rotation center. Tooth profile of rotor screw part with small number of starts on side of lower pressure from addendum circle to pitch circle is formed by successively located connected curves. Sections of profile of rotor screw part with large number of starts are rounding the respective rotor sections with small number of starts. EFFECT: higher efficiency of gearing due to increased length of gas throttling path over tooth point and increased pressure angle on profile from low pressure side. 3 dwg

Control method of cam system for manufacturing nc-code of spur gear

Abstract: PURPOSE: A control method of a cam system for generation of NC(numerical control) code of spur gear is provided to reduce interval number and NC code length and therefore working time of the spur gear through optimization of interval length by maintaining error in all intervals into permissible error range using GSS(golden section search) method. CONSTITUTION: In a step(S1), tooth number, module, pressure angle, arbitrary permissible error are inputted by a console. In a step(S2), variable such as angle at pitch circle, basic circle, root circle radius and arbitrary point related to tooth configuration of the gear is produced. In a step(S3), interval variable is initialized with substitution of 1. In a step(S4), interval error between corresponding interval length and predetermined interval length is produced by using GSS method. In a step(S5), the step S4 is repeated if the produced error length is larger than permissible error, and, if not, corresponding interval length is stored with adding of 1 to interval variable. In a step(S6), the step S4 is repeated if interval length corresponding to interval variable added with 1 is larger than 1 micrometer, and if not, length of last interval is stored. In a step(S7), NC code is generated according to position of a point between intervals.