Crown Gear Research Articles

Crown Gear Reducer with Seesaw Motion of Transmission Shaft

Crown Gear Reducer with Seesaw Motion of Transmission Shaft

Theoretical investigations of the load distribution of small sized crown gear sets different material pairings

An analytical approach for the calculation of the load distribution on the flank of crown gears, based on the theory according Placzek, is proposed. The teeth of the face gear and the pinion are divided into equidistant slices perpendicular to the normal plane, where the local forces, resulting from the acting torque, are calculated under consideration of the local deformation behavior of the gear system. By considering the geometrical conditions like radii of curvature, etc., the local Hertian stresses can be determined. Based on these considerations, the impact of the stiffness, the helix angle and the offset on the local force or load distribution is illustrated. Finally the lubricant film thickness is calculated by using the EHD-theory.

Preventive and conservative prosthodontic treatment using overdenture and Richmond crown

Prosthodontic treatment aims to restore the chewing function (rehabilitation) and to prevent tooth decay and bone resorption (preventive and conservative). As an example, treatment by overdenture and Richmond crown. Overdenture is a partial or complete removable denture covered and supported by one or more teeth, the tooth roots and/or dental implants. Richmond crown is fixed denture by post and crown system, in which the post part goes into the root canal and its crown covers the entire of original tooth crown surface. By retaining the original teeth and/or roots, it could improve the stability and retention of the denture, and defend proprioseptic of teeth and vertical dimensions. To provide information about preventive prosthodontic treatment and prevention by using overdenture and Richmond crown. Case Report: A 50 year old woman only has 44 teeth on the mandible which is indicated for the overdenture construction and loss teeth 13, 14, 17 and 27 on the maxilla with deep caries in teeth 22 which is indicated for a removable partial denture (RPDs) construction by Richmond crown gear 22. On an early stage study, printing models is done. Then treatment of the root canal on teeth 22 and 44, followed by root canal preparation, core construction (cast post) and Richmond crown on tooth 22 and bareroot preparation on tooth 44 for overdenture construction. The procedure followed by printing, recording bite to insertion. Choosing treatment either overdenture or Richmond crown is very important because it could mantain remain original teeth, thus it can help to improve the retention and stabilization.

Mathematical definition and computerized modeling of spherical involute and octoidal bevel gears generated by crown gear

The involute profile is the most commonly used tooth profile for cylindrical gears. However, its counterpart for bevel gears is not commonly used because its generation is not compatible with the use of easy-to-manufacture cutting tools and market-oriented generation methods. Nowadays, with additive manufacturing technology growing across industries to manufacture parts and full-scale products, the spherical involute profile deserves to be given the possibility to become the reference profile for bevel gears generated by additive manufacturing, forging or plastic molding. In this work, both the spherical involute and the octoidal form systems for bevel gears are mathematically defined. The geometry of their respective crown-gears for generation is derived and the computerized modeling of the geometries of the generated bevel gears presented. The comparison between the obtained gear tooth geometries is performed from the point of view of the obtained geometric deviations, their behavior to the change of the shaft angle and the evolution of contact and bending stresses for different values of torque applied to the pinion. The results showed that the spherical involute profile can handle better with the changes in the shaft angle, although the octoidal profile presents lower contact and bending stresses.

Experimental Setup and Methodology to Carryout Fatigue Testing of Spiral Bevel Gears Used in Differential Gear Box Using NVH Approach

Currently the fatigue testing of bevel gears are being done by using non rotating type of fixtures that applies fatigue load on a single tooth, which does not resemble the actual loading condition in an automotive differential gear box. This paper discusses the experimental setup with the noise and vibration analysis approach to determine the signature of failures of spiral bevel gears. The proposed experimental setup seems promising for further research and development in the fatigue testing of spiral bevel gears. The Crown pinion and wheel assembly is used for the testing. The pinion is connected to the electric 3 phase AC motor of 75HP with a suitable coupling and the crown wheel is mounted on the half axle shaft, which in turn is connected to an electric dynamometer. The speed/torque of electric motor and the load applied by the dynamometer can be varied. The acoustic sensor is mounted near the differential gear box and the accelerometers are mounted on the Pinion bearing, Crown wheel bearing and the half axle bearing. A four channel data acquisition system is used to log data in time domain (raw data) by three accelerometers and an acoustic sensor. The variations of sound pressure(dB) v/s time, sound Pressure(FFT-(RMS)) amplitude v/s Frequency, Acceleration v/s Time, Octave analysis i.e., Band power v/s Frequency, Noise spectrum Power v/s Frequency, Histogram, Power density v/s Time can be obtained. These data are then used to plot vibration and SPP levels in frequency domain to develop the noise and vibration signature of that crown pinion for given cycles of operation. The tests on Bevel pinion and gear set were performed in the BEC, Bagalkot NVH lab facility. The gear set run successfully at double the rated torque for 30 million pinion cycles. And the signature of pinion failure was obtained. The results demonstrated the suitability of using the given bevel crown pinion and gears set for specified speed, high load application in differential gear box of an automobile.

クラウン減速機の精度向上のための歯形の設計

Generally, low backlash mechanisms are required for robot joints to perform tasks accurately, so we are proposing a new concept of a low backlash reducer using precessing crown gears. We call it the crown reducer. The features of this reducer are low backlash, high reduction ratio and ease of downsizing which we believe will contribute to the design of small mechanisms such as finger joints of robot hands. This paper describes a design of tooth profile for improvement of accurate motion. Firstly, we propose the clearance of tooth profile for stator gear to avoid increasing input torque. Secondary, we change design of the rotor gear with coaxial double circular gear to single circular gear for reduction of manufacturing cost. Finally, we discuss the effect using manufactured prototype reducers.

An Approach for Determination of Basic Machine-Tool Settings From Blank Data in Face-Hobbed and Face-Milled Hypoid Gears

The conditions of meshing and contact in hypoid gear drives depend substantially on the machine-tool settings to be applied. Determination of gear geometry is the first step in the design process of a hypoid gear drive. An approach for determination of basic machine-tool settings for face-hobbed and face-milled hypoid gears is proposed, covering the cases when the gear is generated and nongenerated. Gear basic machine-tool settings are determined from the blank data that can be obtained from application of Standard ANSI/AGMA 2005-C96. Some machine-tool settings are determined analytically considering the imaginary generation of the gear by a crown gear. Some other machine-tool settings are obtained numerically in order to provide some given blank data as the normal chordal tooth thickness and the normal pressure angles of the gear teeth. The developed theory is illustrated with numerical examples.

Kinematic Modeling for the Nutation Drive Based on Screw Theory

The paper describes a study of a relative screw motion of a pair of internal and external spiral bevel gears with double circular-arc tooth profile in a nutation drive by screw theory and focuses on the kinematic modeling for the nutation drive. According to the instantaneous screw motion theory, the meshing function of the nutation drive for the kinematic modeling is developed based on the gear meshing theory and the coordinate system transformation between a crown gear and an internal or an external spiral bevel gear. The equations for the tooth profile of the crown gear, internal and external spiral bevel gears are further obtained based on the standard double circular-arc tooth profile and equal strength principles. Finally, the controllable precision three dimension modeling method for the tooth profile of the external and internal spiral bevel gears is further proposed.

1P1-B01 クラウン減速機の精度向上のための歯形の設計 : 歯形パラメータに対する出力軸のヒステリシスロス

Generally, low backlash mechanisms are required for robot joints to perform tasks accurately, so we are proposing a new concept of a low backlash reducer using precessing crown gears. We call it the crown reducer. The features of this reducer are low backlash, high reduction ratio and ease of downsizing which we believe will contribute to the design of small mechanisms such as finger joints of robot hands. This paper describes a design of tooth profile for improvement of accurate motion. Firstly, we estimate the effect of tooth profile parameters on the hysteresis loss and the start-up torque. Then, we discuss the effect using manufactured prototype reducers.

Dynamics for an electromechanical integrated harmonic piezodrive system

The Authors propose an electromechanical integrated harmonic piezodrive system. The dynamics behavior of the movable tooth drive has important effects on its operating performance. Here, the dynamic equations of the movable tooth drive for the drive system are presented. Using the equations, the natural frequencies and vibrating modes of the movable tooth drive are investigated. Results show that five vibrating modes occur for the movable tooth drive which include system modes, static crown gear modes, movable tooth modes, translating rotor modes and translating crown gear modes. Eccentric center, thickness and length of the flexible ring, diameter of the movable tooth and speed ratio have significant effects on the natural frequencies of the movable tooth drive and should be selected properly.

2A1-N03 クラウン減速機のプレスロータの設計(アクチュエータの機構と制御(1))

Generally, low backlash mechanisms are required for robot joints to perform tasks accurately, so we are proposing a new concept of a low backlash reducer using precessing crown gears. We call it the crown reducer. The features of this reducer are low backlash, high reduction ratio and ease of downsizing which we believe will contribute to the design of small mechanisms such as finger joints of robot hands. This paper describes a improvement of input mechanism (press rotor) for increasing durability itself. Evaluations of the performance of a prototype reducer will be discussed.

Mathematical Model and 3D Modeling of Involute Spiral Bevel Gears for Nutation Drive

The mathematical model and 3D modeling of involute spiral bevel gears for nutation drive are considered. The basic tooth profile of involute is composed of involute curve and dedendum transition curve, and the equations have been established. The mathematical model of crown gear with involute profile is obtained, and then the mathematical models of the involute spiral bevel gears are developed. The tooth surface modeling of involute spiral bevel gear is proposed, and the 3D modeling of the involute spiral bevel gear for nutation drive is illustrated.

Tooth Contact Analysis and Manufacture on Multitasking Machine of Large-Sized Straight Bevel Gears With Equi-Depth Teeth

Straight bevel gears are widely used in the plant of large-sized power generation when the gears have large size. The purpose of this study is to manufacture the large-sized straight bevel gears with equi-depth teeth on a multitasking machine. The manufacturing method has the advantages of arbitrary modification of the tooth surface and machining of the part without the tooth surface. For this study, first, the mathematical model of straight bevel gears by complementary crown gears considering manufacture on multitasking machine is proposed, and the tooth contact pattern and transmission errors of these straight bevel gears with modified tooth surfaces are analyzed in order to clarify the meshing and contact of these gears. Next, the numerical coordinates on the tooth surfaces of the bevel gears are calculated and the tooth profiles are modeled using a 3D-Computer-Aided Design (CAD) system. Five-axis control machines were utilized. The gear-work was machined by a swarf cutting using a coated carbide end mill. After rough cutting, the gear-work was heat-treated, and it was finished based on a Computer-Aided Manufacturing (CAM) process through the calculated numerical coordinates. The pinion was also machined similarly. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. As a result, the obtained tooth flank form errors were small. In addition, the tooth contact pattern of the manufactured large-sized straight bevel gears was compared with those of tooth contact analysis. The data showed good agreement.

ВплиВ об'ємУ гідромоторА нА параметрИ гідрооб'ємно-меХанічниХ трансмісіЙ (схемА “диференціаЛ нА вході”)

When creating a new hydrovolumetric-mechanical transmission developers face a number of difficult issues: the choice of optimal structural chart, determination of necessary parameters of hydrovolumetric transmission and many others. The article studies the influence of volume of a hydromotor on the main parameters of hydrovolumetric and mechanical transmissions, working according to the chart at the input. The article presents the kinematic charts of hydrovolumetric-mechanical transmissions with different connections of mechanical and hydraulic branches with links of the planetary train (with a sun gear, a crown gear, and a drove). We have defined the kinematic, force and energy parameters of the transmissions, efficiency of the hydrovolumetric transmission and transmission in general at different volumes of the hydromotor. The analysis of the hydrovolumetric-mechanical transmission with the differential at the input showed: the reviewed hydrovolumetric-mechanical transmissions with unregulated hydromotor (whether the maximum hydraulic capacity is 130 cm 3 or 250 cm 3 ), according to all parameters (efficiency , engine power, pressure drop), yield to similar hydrovolumetric-mechanical transmissions with adjustable hydromotor. When using hydromotor with the maximum volume of 250 cm 3 instead of 130 cm 3 , we have observed, depending on the circuit, the reduction of the maximum value of the pressure drop at 1.18 - 20, 53%, of the maximum value of efficiency at 0.35 - 3.16%, of the maximum angular velocity of the shaft of the hydromotor at 17.38 - 38.92%, and the increase of the maximum engine power at 0.77 - 4.12%. Other parameters have not undergone significant changes (the maximum angular velocity of satellites, the maximum angular velocity of the shaft of the hydromotor)

2A2-D11 浮遊ロータ歯車を用いたクラウン減速機の開発と評価(アクチュエータの機構と制御(2))

Generally, low backlash mechanisms are required for robot joints to perform tasks accurately. we are developing a new concept of a low backlash reducer using precessing crown gears. We call it the crown reducer. The features of this reducer are low backlash, high reduction ratio and ease of downsizing which we believe will contribute to the design of small mechanisms such as finger joints of robot hands. This paper describes a improvement of output mechanism for increasing rigidity and transmission torque of the output shaft. Evaluation of the performance of a prototype reducer will be discussed.

Effect of Pressure and Oil Mist on Windage Power Loss of a Shrouded Spiral Bevel Gear

In many aeroengines the accessory power offtake is achieved using a spiral bevel gear set running off one of the main shafts. The crown and bevel gears are housed in an internal gearbox and there is significant heat generation within this chamber, some of which is attributed to windage power loss (WPL) generated by the gear. Over the past few years the University of Nottingham Technology Centre (UTC) in Gas Turbine Transmissions has been researching spiral bevel gear windage power loss, both computationally and experimentally, using a purpose-built test rig at the UTC. In this study the test rig has been adapted such that chamber pressures up to 8 bar can be generated. Test data has been obtained that shows the effect on the WPL of chamber pressure, advancing understanding of the relationship between data obtained at ambient and pressurized conditions. Three configurations have been studied: unshrouded gear, a gear with 360 deg shroud and a shrouded crown and pinion meshing pair. Furthermore, the effect of oil mist within the chamber on the WPL has been studied. An oil mist generation system was developed for introducing a fine mist into the chamber and results are presented for varying mist flowrates. A mist measurement system was developed to sample mist mass fraction within the chamber and the data obtained is used to calculate an effective (oil/gas mixture) chamber density. Increasing chamber pressure increases the Reynolds number, moving the system behavior further along the moment coefficient-Reynolds number correlation. The Cm-Re correlation is similar in form to that for a shrouded cone, showing transitional behavior around Re = 2 × 106. Beyond this transition, Cm decreases with increasing Re. Introducing an oil spray has two effects: a reduction in chamber temperature and an increase in the effective density of the chamber fluid. Both effects can be accounted for by calculating Re and Cm based on mixture properties but it seems highly likely that the properties of the fluid under the shroud differ from those of the fluid in the external chamber.

Influence of hydromotor volume on basic parameters of hydrovolumetric mechanical transmissions, working according to the scheme “output differential”

Every year the number of selfpropelled machines equipped with hydrovolumetric mechanical transmissions increases. In the process of creation of new hydrovolumetric mechanical transmission the designers faced a number of difficult issues: the choice of optimal structural chart, determination of necessary parameters of hydrovolumetric transmission, etc. The article examines the influence of hydromotor volume on the main parameters of hydovolumetric mechanical transmissions working according to the scheme differential. The article represents the kinematic scheme of hydrovolumetric mechanical transmissions with different connection of mechanical and hydraulic strand with units of planetary train (sun gear, crown gear, cage). There are definitions of kinematic, force and energy parameters of given transmission, efficiency of hydrovolumetric transmission and transmission in general at different volumes of hydromotors. The analysis of hydrovolumetric mechanical transmission with output differential showed that using hydromotor of maximum volume of 250 cm 3 instead of 130 cm 3 we can observe the reduction of the maximum pressure to 0.04 - 17.92% , the maximum power output to0.14 - 6.54%, the maximum angular velocity of hydromotor shaft to 36.96 - 49.74%, the increase of maximum angular velocity of the shaft of hydropump to 0.0 - 15.72%, the change of maximum efficiency value in the range 2.23 - 0.80%, the change of maximum angular velocity of satellites in the range -48.45 - 4.15%.

General Mathematical Model of Internal Meshing Spiral Bevel Gears for Nutation Drive

The general mathematical model of internal meshing spiral bevel gears for nutation drive is studied. Based on conventional enveloping theory and transmission principle, the meshing of two spiral bevel gears in nutation drive was substituted by the meshing of an imaginary rotating crown gear engaging with the external and internal bevel gear respectively. The general mathematical model of crown gear was established. Then the general mathematical model of internal meshing spiral bevel gears is obtained by matrix transformation, which is suitable for a variety of gear tooth profiles. Finally, the mathematical model and 3D modeling of double circular-arc spiral bevel gears are developed.

Influence of tooth modifications on tooth contact in face-hobbed spiral bevel gears

In this study the influence of tooth modifications induced by machine tool setting and head-cutter profile variations on tooth contact characteristics in face-hobbed spiral bevel gears is investigated. The concept of face-hobbed spiral bevel gear generation by an imaginary generating crown gear is applied. The modifications of tooth surfaces are introduced into the teeth of both members. The lengthwise crowning of teeth is achieved by applying a slightly bigger radius of lengthwise tooth flank curvature of the crown gear generating the concave side of pinion/gear tooth-surfaces, and by the variation of machine tool settings in the generation of pinion/gear teeth. The ease-off in the tooth height direction of meshing tooth surfaces is achieved by applying a head-cutter whose profile consists of two circular arcs, instead of a straight-line. The method of tooth contact analysis applied determines the path of contact, the potential contact lines, the separations along these lines, and the transmission errors. A computer program implements the method. By using this program the influence of the variation of machine tool settings and of head-cutter geometry on tooth contact is investigated and discussed.

Design and Finite Element Analysis on Crown Gear Coupling of High Torque Considering Radial Restriction

In order to meet the requirements of high torque and small center distance of the twin screw pulping extruder, an improved design method of the crown gear coupling (CGC) was studied. Based on the preliminary structural design, the paper selected parameters of tooth form of the crown gear firstly, and according to the contact strength solved the tooth width, then the discussed influences of radius of displacement circle and unilateral thinning amount on tooth thickness, finally through the finite element analysis verified the design results. The results show that under the condition of radial restriction the most effective ways to increase load-bearing capability of the CGC are to improve the tooth stiffness and increase the tooth width, and the increasing of tooth width should consider the tip strength of the crown gear and avoid over-cutting. The CGC design method of the paper can meet the requirements of the twin screw extruder.