The traditional methods for computation of the efficiency of cylindrical gear transmissions are based on the hypotheses of constant friction coefficient and uniform load distribution along the line of contact. However, the changing rigidity of the pair of teeth along the path of contact produces a non-uniform load distribution, which has significant influence on the friction losses, due to the different relative sliding at any point of the line of contact. In previous works, the authors obtained a non-uniform model of load distribution based on the minimum elastic potential criterion. This load distribution was applied to compute the efficiency of spur and helical gears, resulting in slightly greater values of the efficiency than those obtained if the load distribution along the line of contact is assumed to be uniform. In this work, this non-uniform model of load distribution is applied to study the efficiency of involute spur gears with transverse contact ratio greater than 2 (named high transverse contact ratio gears). In this kind of gear transmissions, the load is shared among two or three pairs of teeth, reducing significantly the load, and consequently the friction losses, at the contact points in which the relative sliding is greater. Analytical expressions for the power losses due to friction, for the transmitted power and for the efficiency are presented, as well as a study of the influence of some transmission parameters (as the gear ratio, the pressure angle, etc.) on the efficiency.

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In this study, the influence of basic design parameters and tooth surface modifications on the mechanical (friction induced) power losses of a helical gear pair is studied. A helical gear mechanical efficiency model based on elastohydrodynamic lubrication (EHL) is introduced. The model is used to simulate the gear contact conditions of an example helical gear pair within the ranges of basic design parameters such as pressure and helix angles, numbers of teeth (module), and major diameters to quantify their impact on mechanical power losses. Variation of gear efficiency with these parameters are then weighed against other functional requirements such as transmission error amplitudes, and contact and bending stresses to demonstrate that many designs that have high efficiency might perform poorly in terms of noise, pitting, and tooth breakage. A representative design that is acceptable in all aspects is considered next with varying amounts of tooth modifications to demonstrate their impact on power losses. At the end, recommendations are made on how to reduce helical gear mechanical power losses while meeting other functional requirements as well.

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Environmental issues are leading to a growing interest in bio-lubricants, which can have similar or even better performance than mineral and synthetic oils. In this work the biodegradability and toxicity characteristics of ester-based gear oils are discussed and their physical, chemical and wear properties are compared with those of a commercial mineral oil. Power loss tests were performed on the FZG test rig, using carburized (C) and high pressure nitrided (N) gears and two different lubricants. The operating temperatures of the oil and of the FZG gearbox wall were measured for different values of the input torque and speed. At the end of the tests, the gear mass loss and the oil viscosity were measured, and the tooth flanks were inspected, looking for typical surface failure mechanisms. An energetic model of the FZG test gearbox was developed, taking into account the power loss mechanisms inside the gearbox and the heat flow mechanisms from the gearbox to the surrounding environment. Using this model it was possible to quantify the influence of lubricant formulation and gear materials on the average friction coefficient between gear teeth. Gear micropitting tests were performed on the FZG test rig, using carburized (C) and high pressure nitrided (N) gears and two different oils. Post test analysis included the mass loss measurement of the gear and the ferrometric analysis of lubricant samples. The tooth flanks were inspected using surface topography measurements to assess the number and depth of micro-pits. Metallurgical cuts were done to observe contact fatigue crack initiation and propagation using scanning electron microscopy. If carefully formulated, biodegradable low-toxicity ester-based gear oils, beside their environmental advantages, enhance gear performance when compared with the mineral lubricant providing (i) lower friction coefficients and lower operating temperatures of gearboxes and (ii) less tooth flank micropits and shallower micropits.

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C-N films were deposited on the 20CrMo alloy steel substrate by the Plasma Source Ion Implantation (PSII) method and TiN films were coated on the same material by the Physical Vapor Deposition (PVD) method. It was found that friction coefficient of C-N coating were relatively lower than that of TiN coating, and the friction coefficients of C-N and TiN coating decreased with increasing load. Then the author puts forward the test rig, working under the conditions of 1,800 rpm, 20 N-m for 100 h. The observations by microscope showed the wear reduced. The anti-wearing performance enhanced prominently. But the TiN coated gear had a more serious friction phenomenon than C-N coated gear. This is caused by that coating of TiN, which was made at a high temperature about 500℃. And the high temperature led to the substrate intenerated and the surface hardness decreased 850 HV to 630 HV. PSII method eliminates the tempering problem of the coating of C-N films, which had higher wear resistance than TiN films. The friction and wear resistance of gears while coated by C-N films ameliorated significantly.

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In order to improve the weakness of poor wear resistance and low strength of bronze worm-gear, new functional coating on the steel worm-gear by tooth surface reformation is investigated. The tooth surface of the steel worm gearing is treated by superfine manganese phosphate conversion coating, ferrous sulfide solid lubricant coating and MoS2 shot peening, respectively. The steel worm gearings with the three treatments are tested on the test-bed. The experimental results show that steel worm gear with the surface reformation can reduce the running-in time, and improve the transmission efficiency and anti-scuffing capacity. This investigation provides an approach to replace bronze worm-gear by steel worm-gear with surface reformations.

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Increasing gear performance through applying a thin film coating on gear tooth flanks is attracting considerably attention. Several different gear tests show an increase in carrying load capacity or prolonged lifetime with tungsten-carbide doped DLC (W-DLC) coated gears, however the exact mechanisms by which the performance additives work in lubricated W-DLC coated contact are still unclear. In general, there are no guidelines for selection of lubricant for coated machine components subjected to high loads. The conventional lubricants have been primarily developed or tailored to interact with ferrous materials and are probably far from optimal for amorphous carbon-based coatings. In this paper, several different base oils and functional oil blends with single additives were tested on a ball-on-disc test rig with W-DLC/W-DLC coated specimens. One perspective oil blend was identified and was subjected to the further investigation on FZG gear test rig. Under conditions of reduced oil immersion depth scuffing load carrying capacity was determined.

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DLC films have attracted considerable attention for its excellent mechanical and tribological properties such as low friction cofficient, high wear resistance, and high hardness. DLC films are expected using in tribological and protective applications and improve the robustness and sustainability of machine elements. However, adhesion of DLC films is weak because these are consisted of stable C bond and have large residual stresses in themselves. Therefore, DLC films cannot be used in strict condition and these are not adopted in major machine elements such as gears and bearings. Adhesion of DLC films were evaluated by adhesion energy equation proposed in our previous study. And these films were tested in high surface pressure, and the surface durability of films was evaluated. structures of films were designed and optimized from these results. Films using in the test were deposited by Unbalanced Magnetron Sputtering with various conditions. As Young's modulus of films decreased, adhesion increased and hardness decreased. Wear resistance seemed to decrease with hardness decreasing. Therefore, both adhesion and wear resistance had to be considered into development of DLC films.

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The Gear oils and automatic transmission fluids (ATFs) for passenger cars are required to have lower viscosity in order to achieve better fuel economy. In general, when the viscosity of lubricant is reduced, the pitting life of the bearing tends to decrease. In this study, the effect of lubricating oil additive on the pitting life was determined by the radial needle bearing pitting test machine that assumed the needle bearing in the planetary sun gear was produced. Three kinds of and-wear additive were selected, and the individual effect of each additive and the combined effect of two kinds of additives were evaluated. The chemical composition of the additive film formed on the rolling contact surface was analyzed by XPS, and the hardness of the film was measured using a nano-indenter. It is understood that the combination of phosphorus and sulfur additives gives the longest pitting life of all tested samples, and that the additive that forms a softer film on the rolling surface tends to extend the pitting life.

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Rolling contact fatigue test with five kinds of lubricating oils was carried out in order to clarify the influence of viscosity characteristics of lubricating oil on rolling contact fatigue strength of steel roller. The viscosity at the operating temperature was adjusted to almost the same with three kinds of base oils and the quantity of viscosity index improver. In addition, two kinds of additives were used and the rolling contact fatigue behavior was compared. The failure mode was the typical pitting caused by surface cracking. In case of the test under the lubricating oils with equivalent kinematic viscosity at the operating temperature, the rolling contact fatigue life depended on the base oil viscosity and was longer in case of the base oil of the lubricating oil with higher kinematic viscosity. In case of the rolling fatigue test under the lubricating oil blended with the same base oil, the rolling contact fatigue life was longer in case of the lubricating oil with higher kinematic viscosity. The rolling contact fatigue strength tended to increase with increasing film parameter.

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This study is related to Analysis and Experiment of WN helical Rack and Pinion .Tooth contact Analysis and calculation of Hertzian stress was made. By these results, new type WN Rack & Pinion is proposed. Radius of rack is larger than that of conventional design. The authors decided the best radius of concave radius of rack, from both views of sensibility of tooth contact and Hertzian stress in the case of changing the tooth contact mark caused by the misalignment.

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Mathematical models of the ZK-type worm and ZN-type worm wheel are developed based on their respective generating mechanisms. Kinematic errors (KEs) of the proposed worm gear drive under a non-ninety-degree crossing angle are calculated by applying the tooth contact analysis (TCA) method. Contact ratios (CR), instantaneous contact teeth (ICT) and average contact ratio (ACR) are investigated by applying the TCA method. It is found that the CR, ICT and ACR of the proposed worm gear drive are increased significantly when the crossing angle is chosen as 60 degrees. The effects of gear parameters on the ICT, CR, ACR and KEs under various crossing angle of the worm gear drive are demonstrated by an illustrative example.

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Some design conditions can have a negative or serious effect on vibration, efficiency and life of the transmission components. Gears and bearing lubrication and cooling methods may produce losses in efficiency, vibration and reduced life if not properly applied. Some gear design methods may cause a much lower life than expected when improperly applied. An example of a large gear design is discussed showing the results of poor design practice Other examples of bearing and gear applications are presented with reasons for failure and with improved design methods for solutions.

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The calculation of gears especially planetary gears can just be carried out by the consideration of influences of the whole drive train and the analysis of all relevant machine elements. In this case the gear is more than the sum of its machine elements. Relevant interactions need to be considered under real conditions. The standardized calculations are decisive for the safe dimensioning of the machine elements with the consideration of realistic load assumptions. But they need to be completed by extended analysis of load distribution, flank pressure, root stress, transmission error and contact temperature.

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In this paper, a dynamically controlled/powered walking support system was described. Certain requirements must be met when developing a walking support system; it must be light weight and safe. Particularly, in this paper, emphasis is placed on maintaining natural appearance by a simple, small, and lightweight device. To meet the requirements of the walking support system using a simply designed device, development must be conducted considering muscular activity. Muscular activity revealed that the anterior muscles are activated during balancing, and that the tibialis anterior muscle is the most important muscle for assist during walking. Based on these results, a walking support system with dynamic motion assist functions for the ankle and knee joint was successfully developed. The system exhibits suitable functionality and maintains the natural appearance by using flexible shafts for power transmission.

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The number of people who need of nursing care become difficult to various activities of daily living is increasing. The movement to stand up has much frequency in particular in daily living. And standing up action causes pain to the joints as people get older. In this research, we develop the device whose seat plate follows a motion of the thigh in general standing up action for the purpose of relieving the burden of the joint and reducing a care worker's effort. The device is designed using a planar five-link mechanism and a gear train, only one input is needed to drive the device. The lengths of links are determined by method of comparing the motion of the seat plate of the device with the motion of human thigh in standing up action. And this device is expected to make users stand in a natural form also in the state when the body is left to seat plate, and to guide the subjective standing motion of users.

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In order to suppress the variation of driving torque of planar link mechanisms with a single degree of freedom due to inertial and gravitational forces acting on moving links, a single coil spring with revolute pairs on its both ends is attached between moving links or a moving link and a frame. Based on inverse dynamics calculation, the optimum stiffness and fixing positions of the coil spring are determined so as to minimize the maximum driving torque with simplex method. For an example, the proposed method is applied to a 4-bar crank-rocker mechanism. It is confirmed that the arrangement between coupler link and frame or between crank and rocker links are most effective. The effective range of crank speed around its designed value is also discussed by simulations.

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Realization of mechanical softness is an important issue for a safe and adaptive control of robots in the real world. However, because the robot also requires stiffness for task execution, the simultaneous realization of softness and stiffness is necessary. In this paper, we design a nonlinear passive stiffness using closed kinematic chain. Because the proposed mechanism utilizes linear spring and nonlinearity of the closed kinematic chain, we can easily design the nonlinearity of the stiffness by changing the link parameters of members. The proposed mechanism is used for the leg of a robot and the mechanical parameters (length of members) are optimized so that the impact force on landing is reduced. The effectiveness of the proposed mechanism and optimization method are evaluated by simulations.

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Our team has developed a prototype for a walking assistance apparatus for the elderly or rehabilitants; that uses a spatial parallel link mechanism. Its flat steps of our apparatus move in parallel with the ground and can support the whole legs of the person including his/her soles. By using a flexible link which is made from stainless steel and rubber, the apparatus can achieve the twisting motions of the waist and ankle. By using this developed apparatus, the wearing experiment was carried out and the effectiveness of the apparatus was evaluated by the IEMG (Integrated Electromyography). As a result, muscle activity of the RF (the Rectus Femoris muscle) and the TA (the Tibialis Anterior muscle) while wearing the apparatus decreased to sixty percent. Therefore, the muscles on the front of the leg were especially affected by using the apparatus. Furthermore, in order to assist walking indoors, we investigated the assistance methods of walking on a slope or stairs. The apparatus was equipped with a gyro sensor and an ultrasonic sensor; the angle of the slope and the size of stairs could be recognized and the apparatus could be adapted accordingly to the signals from the sensors. As a result of our experiment, the equipped person wearing the apparatus could walk on a slope and stairs at will.

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Nonholonomic mechanical system can be recognized as variable-speed drives, contained in many complex systems of modern techniques. This type of transmission has the connections of differential character between transmissions elements. The aim of this paper is to give one general approach to dynamical description of the behavior of one general example of transmissions with nonholonomic characteristics and to estimate stability of working system with changeable working regime. For dynamical description of the mechanical nonholonomic system Appell's differential equations are used. By numerical solving differential equations of motion an answer concerning the working stability as well as the dynamical and kinematics behavior of observed system can be get. The obtained results will serve as one of the constraint in choosing optimal parameters in the synthesis of such power transmissions.

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Based on the Lie-group-algebraic properties of the displacement set and intrinsic coordinate-free geometry, all general primitive generators of Schoenflies (X) motion are first outlined and then we synthesize Oldham-style constant-velocity shaft couplings (CVSCs) from these X-motion generators. Their constant velocity (CV) transmissions with homokinetic property are further verified by group-algebraic approach. Nine general CVSCs are creatively proposed for the potential application of transmitting the uniform motion between two parallel axes with a constant or variable distance. Seven simpler general ones with one cylindrical pair are introduced too. Four special findings derived from them are recommended for easy uses.

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Plate cam mechanism can easily produce the positive and functional motions in contact of cam and follower. Generally cam mechanism is used in many fields of mechanical control, automation, and industrial machinery. To obtain the accurate motion of follower, the profile of cam must be designed and machined precisely. This paper proposes an instant velocity center method for the profile design and a biarc fitting method for the profile machining for plate cam mechanism with reciprocating roller follower. The key of this paper is the introduction of a hybrid system combined the design procedures and the manufacturing procedures. The main idea is that the minimum machining data are built by biarc curves fitted accurately from the design parameters. The radial direction angles toward biarc centers for the accurate biarc curve fitting can be defined directly by the contact angle of cam and follower roller given in the design procedures. An application of the proposed approach is verified the accurate shapes of a designed cam and a machining cam using the minimum NC data within a given machining tolerance.

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The quest for smoother, more accurate and quieter operation has led to many different designs of reducers in power transfer machines. Between them, the roller type reducers are very smooth and accurate. For this type of reducers to work, it is very important to calculate the preload in between the rollers and the outer ring, so as to eliminate their slip and be able to transfer the requested amount of torque. To this end, this paper includes the derivation of the analytical equations that give the deformations of the outer ring under internal radial loads. The theoretical model is validated against experimental results. The measuring technique used, the problems encountered and the measures taken to overcome them are also presented. The final agreement between the theoretical and experimental results is very good and thus the final validated equations are used during the initial design studies of a roller reducer.

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The elasto-mechanical behavior of a rubber V-belt in the neighborhood of the seating and unseating regions of the pulley is affected by the transverse belt compliance, which produces a gradual radial penetration into the groove and by the shear-flexural deformation, which arches the belt line along the free strand away from the ideal straight path. These effects are always analyzed separately in the literature, but are in close correlation with each other. This lecture describes the matching between the free strand and the wrap region, showing a remarkable reduction of the belt arching and of the contact losses, with respect to the conventional theory.

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The fatigue failure mechanism has been investigated for the rubber CVT (continuously variable transmission) belts. There are three major failure modes, namely the adhesive rubber failure, the backing rubber failure and the bottomland failure. Especially, the adhesive rubber failure is the important mode to strengthen the rubber CVT belts, because the failure is hard to find out during the driving. The authors have revealed that the adhesive rubber failure is further branched into two failure initiation types, i.e. the interface de-bonding and the surface-crack initiation. In this study, the authors focused on the surface-crack initiation type. The damage for the surface-crack initiation was accumulated by the shearing between the belt cord and the belt side-surface, where the torque was transformed by the friction between the belt and pulley. The extent of the shearing stress was estimated by a simplified mechanical model, which was proposed basing on Euler's theory for the friction.

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Lubricants for metal V-belt pushing type continuously variable transmissions (B-CVTFs) are required to give greater transmittable torque capacity between the belt and pulley in the CVT. In this study, the impact of base stocks used in B-CVTFs on the torque capacity of a B-CVT was experimentally investigated using a commercial CVT unit with a metal belt assembly and pulley design. As a result, synthetic naphthene base stock (SN) demonstrated 10 % greater than polyalphaolefin (PAO) under the conditions of secondary pulley clamping force from 17 to 34 kN and oil temperature 45 to 100℃ at a reduction speed ratio. Furthermore, the traction characteristic of tested oils was evaluated utilizing a rolling/sliding type tribometer at contacting pressure of 400 MPa, corresponding to the pressure between the belt segment and pulley. The traction coefficient of sample SN increased with increasing slip ratio while PAO did not show a distinct increase in the traction coefficient. This result implies that the difference in torque capacity between the two base stocks depends on the oil film shearing stress caused by slipping between the belt and pulley in the CVT.

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In this paper, a rate-dependent belt creep theory is developed by introducing a Kelvin solid as a rate-dependent material model in order to predict the effect of the rate-dependence of material constitutive law on the creep behavior in a multipulley belt drive system. First, the general Cosserat rod theory is reviewed, and then the governing equations of an extensible string for belt creep theory is de-rived from the rod theory by assuming unshearable rod and neglecting the bending stiffness. Next, the creep behavior of a belt over pulley is determined by using the derived governing equations and the effect of the rate-dependence of material constitutive law on the creep behavior are discussed. It is shown that the creep behavior of the belt with rate-dependence of material constitutive law is equivalent to that of classical creep theory by newly introducing the effective friction coefficient.

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A belt-drive model using an absolute nodal coordinate formulation is presented. The aim of this paper is to introduce a damping mechanism into the belt-drive model and to verify it against experimental data. Different damping mechanisms are proposed for the damping of the longitudinal and bending deformations and several experiments were conducted in order to obtain the damping properties. Good agreement between the numerical result and the experimentally obtained data was found.

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The aim of this paper is to present an efficient and realistic numerical model in order to predict the dynamic response of belt drives. The belt was modeled as a planar beam element based on an absolute nodal coordinate formulation. A viscoelastic material was adopted for the belt and the corresponding damping and stiffness matrices were determined. The belt-pulley contact was formulated as a linear complementarity problem, together with a penalty method. This made it possible to accurately predict the contact forces, including the stick and slip zones between the belt and the pulley. The belt-drive model was verified by comparing it with available analytical solutions, and good agreement was found. Finally, the applicability of the method was demonstrated by con-sidering non-steady belt-drive operating conditions.

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One of the most outstanding features of synchronous belt drives is their ability to transmit rotation accurately. However, when synchronous belt drives are operated at high speeds, a transmission error occurs due to the inertial force of the pulley and the shaft, and belt vibration. This study investigates experimentally transmission errors in synchronous belts with regard to the influence of pulley speed under dynamic conditions. The results of our experiments show that the magnitude of transmission errors with a period of one rotation of both the belt and pulley does not affect the pulley speed. In addition, the transmission error per single pitch of the pulley increases markedly when the belt span causes a resonance of the meshing frequency and a transverse vibration natural frequency. In the study, we also determine a method to estimate this transmission error resulting from the resonance of string vibration.

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Further improvement of durability has been required for timing chain system for automobile use. Development of a technology for predicting timing chain load is indispensable, as is fulfillment of low vibration and low noise requirements. Although software for estimating timing chain load is already available on the market, the analysis method and influences of required parameter are not very clear for users. As described in this paper, a one-dimensional vibration model of a chain system, in which the timing chain is approximated by spring and damper elements, is proposed to contribute to determination of timing chain system specifications as the final target. Furthermore, numerical analyses will be performed of motion equations introduced herein. Obtained chain load will be compared with experimental results for discussion.

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Authors describe technologies to improve the efficiency of toroidal CVT. Firstly, technologies to improve the efficiency of toroidal variator are discussed. Improvements of Power Roller design and loading force optimization show higher efficiency than conventional toroidal variator. One of the important points in the traction drive system is to use high traction coefficient as much as possible. The influences of new technologies which can make traction coefficient higher are discussed. The toroidal variator efficiency of 97% at the maximum input torque will come true with this research. Secondly authors describe efficiency of power recirculation system which is composed of toroidal variator and planetary gear mechanism. The influence of the efficiency of variator and planetary gear mechanism upon the whole transmission efficiency is discussed. Comparison between belt variator and toroidal variator is also discussed. These variator have different characteristic of efficiency on rotation speed and transmitting torque each other.

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Traction fluid changes its property from liquid to solid by controlling the pressure. This phenomenon has potential to be applied to a new type of mechanical engaging or disengaging element as a starter-generator of an aircraft engine. This paper examines fundamental engaging characteristics of a half-toroidal variator on focusing the synchronization of 4 power rollers, power loss and corresponding temperature rise during liquid to solid drive transition by using a 350Nm torque capacity variator with an electro-hydraulic loading mechanism.

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Whilst full-toroidal traction drives (IVT and TCVT) have demonstrated the ability to provide significant fuel economy, emissions and cost benefits across a wide range of applications, increased emphasis is now being placed on power density. Increased power density places increased demands on the variator elements and traction fluid to withstand the heavily loaded rolling contact conditions and the corresponding contact temperature increase. In this paper, the ability of the full-toroidal traction drive to meet the accelerated durability testing requirements of 50,000km at max vehicle speed is experimentally investigated, demonstrating traction fluid 'fill for life' and excellent high temperature durability of the variator disc and roller material. In addition, a rigid-perfectly plastic traction model is compared to the measured roller metal temperature data and used to calculate the metal and fluid contact flash temperature.

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Continuously variable transmissions (CVTs) in automotive powertrains permit an optimization of the engine operating point resulting in significant fuel economy. A wide ratio spread and a fast shifting response are prerequisites to achieving both the system efficiency and the required driveability. The full toroidal variator fulfills these requirements along with offering the highest torque capacity of all CVTs. Moreover, this variator is torque controlled, enabling the operation of an IVT (Infinitely Variable Transmission) in geared neutral. The ability of shuttling a vehicle without slipping a clutch extends the application range to off-highway vehicles. The motivation of using this transmission is therefore not only concerned with improving the fuel efficiency, but also in enhancing the maneuverability. This paper explores various control configurations that can be applied to a powertrain. Different vehicle applications and their control objectives are reviewed with the most appropriate control.

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Continuously variable transmission technology currently offers the greatest potential to reduce automotive emissions. The torque-controlled CVT shown here offers a novel solution to several drawbacks currently shown in other CVT designs. In an attempt to improve and optimize the design without using the costly 'trial and error' design method, a fully detailed drive-train model has been created. Stepping away from the traditional approach of using pre-existing software packages, everything within this model has been created from first principles, allowing a high level of customization and control. The process described has successfully been used to predict how the CVT would behave were it placed in a real automotive situation.

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This paper describes the details of a new traction drive transmission, which features a self-loading mechanism to achieve high efficiency and a simple ratio-change system without synchronizers. An accurate model of the dynamic behavior of this transmission was constructed and tests using components or an assembly were executed to analyze power transmission efficiency and ratio-change performance, which are fundamental attributes of transmissions. An analysis of power transmission efficiency based on calculations and measurements confirmed that this transmission has a high potential, achieving high efficiency equal to that of gears while the power transmission unit generates less heat than gears. Ratio-change performance was investigated using a kinematic model consisting of kinematic equations of the rollers, including the translational motion that is characteristic of this mechanism, and ratio-change logic for controlling clutch operations so as to decrease heat generation on the rollers and achieve smooth ratio changes. Bench test results showed that the ratio-change logic operated correctly.

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The novel mechanism CVT (Shaft Drive CVT, S-CVT) was developed by the authors. It transmits power by a traction drive same as the Half Toroidal CVT. S-CVT has parallel input/output shafts with conical disks and the idler shaft having conical rollers at both ends, which is placed perpendicularly to the input/output shafts. All disks and rollers can move along each axis directions, and these movements produce the ratio changing by the changes of the rotational radii of disks and rollers. The efficiency is the key evaluation function of CVT, but that of first prototype S-CVT was less than 90%. To improve the efficiency, the backup roller mechanism was devised. Its effectiveness was confirmed by the theoretical calculation and the experiment, and the efficiency of 95% was obtained by modified prototype S-CVT. The improvement of power to weight ratio, namely the increase of transmitted power with downsizing and lightening, is also important to apply the S-CVT to automobiles. To achieve this objective, the new concave disk, named the zero-spin disk, was devised. Because of the decreasing the spin angular velocity ratio and the contact pressure, this disk decreases the slip ratio and increases the torque capacity with downsizing. In this report, the efficiency of the zero-spin disk and roller was estimated by the calculation and the experiment. The theoretical efficiency of S-CVT using the zero-spin disk was calculated by considering the power transmission of the backup roller based on the traction curve. The calculated efficiency and speed efficiency were 87.7 to 92.7% and 99.0 to 99.4%, respectively. These efficiencies were also measured by the experiment using the prototype S-CVT equipped with the zero-spin disk and backup roller. The results of 79.6% to 95.2% and 99.0 to 99.1%, respectively, showed agreement with the calculated results.

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This paper describes a new low-cost CVT micro-traction-drive system utilizing commercially available tapered bearing. Driving low-cost type CVT to be able to adjust preload were done by arranging loading cam of slipping method combined back to back, and the following results were obtained. (1) The expression from which the rotational speed and the flow of power of developed low-cost type CVT micro-traction-drive system was clarified. (2) Preload generated when the load torque is 9Nm is about 1200N, and it agreed to the value of expectations of the assumption of the coefficient of friction on the cam surface 0.12. (3) Hysteresis phenomenon by friction on the cam surface is generated when the load torque is increased and when it decreases. (4) Hysteresis phenomenon become small since the coefficient of friction was decreased by putting Teflon film on the cam surface, and it was confirmed that the coefficient of friction was a important factor of hysteresis.

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The Milner continuously variable transmission (MCVT) is a traction drive transmission based on rolling contacts analogous to those found in angular contact roller bearings. The MCVT is applicable to very high power density applications or those with demanding packaging constraints, due primarily to the existence of multiple traction contacts on each of the rolling elements. This paper details the application of a design of experiments approach to optimising the design of the MCVT. An Analytical model including the contact mechanics and Elasto-hydrodynamics of the traction contacts has been developed and interrogated using design of experiments. Furthermore, the results of the technique have been applied to develop a design tool based on multi dimensional response surface models of pertinent transmission performance criteria. The use of the design tool is then demonstrated to derive future geometry iterations of the MCVT based on the tradeoffs between efficiency, ratio range and transmission life requirements. Inputs to the design tool include geometry parameters, number of rolling elements, design torque and speed ratings and required traction coefficient. Outputs from the design tool include assessment of ratio range, spin effects, traction efficiency and material stress levels.

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M-MATE (Measuring Machine for the Angular Transmission Error) is the systems which measure the performance of gears including the angular transmission error (ATE). The Performance of M-MATE is changed by the selection of parts. It is possible that the System accuracy of ATE is less than ±2arc-sec or the measuring rotational speed of the input shaft is more than 1000rpm. M-MATE can measure not only ATE but also the rotational fluctuation generated by gears, backlash and shaft torque simultaneously. *1 [arc-sec]=1/3600[deg]=4.85 [μrad]

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Romax capabilities in NVH extend from the development of advanced software tools that provide an all in one solution for the modelling, simulation and analysis of geared transmission systems. Romax can be involved at the concept design or development stages as well as during refinement or problem solving on existing applications. The Romax approach is to simulate the whole system including bearing, gears, housings and shafts in order to take into account the many different influences within the analysis. Both static and dynamic analysis can be carried out including calculation of system displacements with gear/bearing misalignments due to applied torque load and modal analysis to determine system mode shapes and natural frequencies. Transmission error (TE) is the ultimate source of gear whine noise. Romax NVH capabilities allow calculation for static deflections of the system under a given loading condition. The resulting gear mesh misalignments are used, along with gear micro-geometry to predict the TE in each loaded gear mesh either for a single gear mesh or a complete planetary gear set. The vibration response of the entire system to the TE excitation is obtained from an automatically generated dynamic model. The relative phase of the TE excitations can be critical and so is included in all analysis. In any gearbox, it is impossible to avoid variations in mesh misalignment, since the gearbox experiences different speeds and different torques. However, it is possible to modify the gear geometry to minimise the transmission error over its range of operating conditions. Gear macro-geometry can be modified to maximise the contact ratio in gears, thereby improving the noise characteristics of the gear. However, micro-geometry modifications are also necessary since the gear undergoes elastic deflection and must be able to accommodate variations in mesh misalignment. Romax have a great deal of experience to define optimised gear geometry with an evolutionary optimisation process to quickly and easily analyse gear mesh micro-geometry and predict the transmission error as well as gear contact patterns and loads. After using the optimiser to determine the ideal micro-geometry design, it can also be used to investigate the sensitivity of the design to manufacturing errors and tolerances. Transmission designers are also increasingly turning to virtual simulation solutions to address the challenges of noise caused by gear meshes termed gear rattle. In many applications both gear whine and gear rattle noise problems occur simultaneously and often only become apparent when complete transmission prototypes are built and tested which often leads to product launch delays and considerable additional expense. Romax can consider gear whine and gear rattle analysis together in a single environment and on the same virtual model. Rattle problems can then be addressed in parallel with whine issues at an early development stage with consequent savings of time and resources. Concept designs can have their potential susceptibility to rattle behaviour quantified and remedied by Romax before any prototypes are made.

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The Micro-Traction-Drive is made of modified rolling bearings. It is developed for the purpose of transmitting high torque with small drive size. Structure of the Micro-Traction-Drive is as follows: The traction force is generated by the thrust preload between inner race and outer race. The retainer connected to the output shaft transmits the driving torque. The retainer is specially designed. Two types of Micro-Traction-Drive are developed. The test-runs of angular contact ball type Micro-Traction- Drive (outer ring diameter 30mm) and tapered roller type Micro-Traction- Drive (outer ring diameter 47mm) have been carried out (reduction ratio 2.6, 2.3). According to the results of tests, we have found that the angular contact ball type can transmit higher torque with higher efficiency than same size planetary gearhead. The tapered roller type can transmit torque bigger than 1.5 or more times of angular contact ball type.

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