Dynamic behavior of ambient medium, or air, of mesh recessing region of a pair of helical gears is demonstrated to give suggestions to realize high performance lubrication,. The behavior was observed by means of pressure variation measurement of tooth-to-tooth space by embedding a pressure gage at the bottom of the space and dependency of longitudinal position was revealed. It is discovered that strong negative pressure exists and sucking action is expected. Smoke wire method along with a high speed camera was also applied to view detailed movement of the air, that revealed actual movement going into tooth spaces against the direction of pitch line velocity. In addition the movement of medium was examined by shooting an oil droplet axially into the region, which also indicated there that the medium tends to stay close to mesh recess region and travels axially from the leading end to the trailing end of gears.

View full abstract

This paper described 2-dimensional molecular dynamics simulation application for evaluating wear and adhesion behavior of rolling-sliding machine elements under non-lubricating condition. The wear simulation model is that movement atom slide on substrate atom. The adhesion simulation model is that movement atom indent into the substrate atom and draw from the substrate atoms. Morse potential function was used in the simulations. The atom that slide and indented was Ni or Fe, and the substrate atom was Ni. The wear of combination Ni and Fe was larger than that of combination Ni and Ni. And the adhesion of combination Ni and Fe was smaller than that of combination Ni and Ni. The tribological behavior in the simulation was similar to that in the cross-cylinder test by using electroless Ni alloy plated cylinder and carbon steel cylinder.

View full abstract

For carburized gears, shot-peening method is widely used for improvement bending fatigue strength. But, the effect of shot-peening on tooth surface strength of carburized gears has not been clarified due to its complicated mechanism. In this study, the author investigated the influence of the shot-peening on surface strength of roller using a disk machine with rolling and sliding. Fatigue tests were carried out with carburized SCM420 steel rollers whose two type conditions of shot-peened rollers; ultrasonic shot-peening and air shot-peening. As a result of experiments, the shot-peening deteriorates surface strength of roller; in particular deterioration of surface strength of air shot-peened roller is remarkable. Former failure patterns like pitting or spalling does not observed. In this experiment, mainly observed failures were micro pitting. Shot-peening causes increasing of surface roughness, then lubricated condition became boundary lubrication. Most cracks were generated from contact surface. During operating, asperities of surface roughness were directly contacted, then cracks were generated and propagated and it became micro pitting.

View full abstract

To clarify the scoring resistance of SCM415H gears with plasma carburizing and SACM645 gears with plasma nitriding and radical nitriding, a gear tests was carried out using a power- circulating gear machine under forced lubrication. From the test, the following results were obtained. (1) In the case of SCM415H gears, the scoring resistance of the gears with plasma carburizing was 785 N/mm and it was 2.2 times as large as that of the gears with gas carburizing. (2) In the case of SACM645 gears, the scoring resistance of the gears with plasma nitriding was 721 N/mm and that of the gears with radical nitriding was 657 N/mm.

View full abstract

A silent chain drive and a synchronous belt drive are similar in the features of winding around and meshing with a sprocket or toothed pulley. In this paper a comparison study on noise generation mechanisms of these two kinds of transmission system is carried out experimentally. The results show that the resonant noise in a silent chain drive comes from the structural resonant vibration of drive system, but the resonant noise in a synchronous belt drive comes from the resonant vibration of belt string.

View full abstract

In this paper, the influence of the natural shape in the storage of belts and the eccentricity of the pulley on the driving torque and the shaft load are experimentally discussed. The fluctuation of the driving torque is small for the belt preserved in the condition which was approximate to the round shape. The comparatively large torque loss is generated, even for a light-load flexible belt.

View full abstract

A precise analysis has been made for the designing and manufacturing method of a pinion cutter for non-involute internal gear, especially in the case the profile of the gear is given as a series of dispersive points. When the profile of a relief grinding wheel is given as a dispersive points, theoretical equations are derived from them which represent the profile of the cutting edge after the resharpening. The calculation is made for the profile of the non-involute internal gear, which is cut by using the reshaepened pinion cutter. Finally it is clarified thai the relationship between the resharpening quantity and the profile error of the pinion cutter.

View full abstract

Numerical data are calculated and used for CAD/CAM Systems for forging of Spiral Bevel Gears. New idea for crowning of tooth surface to obtain point contact for forging gears is proposed. Tooth contact of proposed gearing are confirmed by 3D drawing of tooth surfaces.

View full abstract

The curvilinear-tooth gear was developed as a gear having the same function as the double helical gear. The double helical gear has disadvantages that necessitate a special bobbing machine for fabrication and a high-grade technique for assembly. The curvilinear-tooth gear was devised as a solution to these disadvantages. In general, curvilinear-tooth gears were previously fabricated using gear-mill cutters. However, the authors have devised a bobbing method that uses a CNC bobbing machine. The present report introduces a method of hobbing a curvilinear-tooth gear.

View full abstract

Plastic gears have several advantages such as light weight, reduce noise, and high degree of freedom in gear geometry, in comparison with metal gears. They are generally used without lubrication. Therefore the amount of used of plastic gears are increasing, and used for motion and power transmission. But the study for strength of plastic gears is not done. The demand to power transmission for plastic gears will become high from now on, since it has been used with emphasis on an actual result. The abrasion and damage of the tooth of plastic gears has become a problem. This paper describes the strength of Injection molded plastic helical gears. In early reports, we carried out high load, high speed gear test. But, resulting in these test gear life is below 1.0×10^7. Generally, this is inappropriateness for design life. In this study, we carried out low load, low speed gear test expect to enlarge gear life. As a result, remarkable gear life extension is confirmed.

View full abstract

The deflection of the plastic gear is larger than the deflection of the metal gear. These deflections greatly influence that calculation, when the strength of plastic gear is regarded as an exothermic reaction. In this calculation, all calculation has been handled in the static deflection. However, the dynamic deflection becomes actually a problem. In this study, in the first, this research examined theoretical calculation and the experiment method of static and dynamic deflections. Next, the result which compared static deflection with dynamic deflection was described. The equilibrium temperature of the tooth of plastic gear was calculated and was compared as an application.

View full abstract

The plastic gear receives the effect of friction heat by the contact between tooth surface and hysteresis heat for viscoelastic material. Especially, the friction between tooth surface greatly affects the plastic gear when used oil-free often. In the research on the exothermic reaction of plastic gear, the average friction coefficient is often used. However, by knowing the friction coefficient in the tooth form position, the experiment of the gear becomes unnecessary in this method.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The rack corresponding with straight-sided splines has been shown by M. Naruse and T. Matsuyama in 1942. However, they have not designed the hob on the basis of the rack. It is proper that they should not analyze the grinding wheel profile to grind the flank of spline hob. This paper shows that the grinding wheel profile is determined theoretically by considering the normal lines of the flank at the cutting edge of hob.

View full abstract

To content high productivity and low manufacturing cost, it is believed that direct dry hobbing after gear material heat treatment is the best manufacturing method. First, 0.45% carbon steel of round bar gear material was hardened to HRC53-56 by high frequency induction heat treatment till the specified depth. Next, the high-hardened material was directly hobbed by special carbide hob installed on a highly rigid CNC hobbing machine without using cutting oils. Thus, the author have developed Direct Dry Hobbing of High hardened Material, called the RGC (Round bar Gear Cutting) Method. The gears applying the RGC Method were module 0.8 to 1.25 and of helix angle 25°. The gear profile accuracy was JIS Grade 1-2. Gear motors incorporating gears manufactured by the RGC Method are now receiving remarkable customers satisfaction as low noise and low vibration gear motors.

View full abstract

In this paper, to aim at the decrease of processing cost and the improvement of productivity, a high efficient hard hobbing (the flank finish of high hardened gears by coated finishing multi-thread carbide hob of CNC hobbing machine) is examined for the flank finish of high hardened small pitch gears. The examination is focused on the accuracy of hobbing and tool life of carbide hob. As a result, high efficient hard hobbing is found effective for the flank finish of high hardened small pitch gears.

View full abstract

In a sandwich-belt conveyor there are tow belts, one is driving belt and another driven belt, used to pinch and convey media. In this paper, finite elements analysis considering media conveyance is carried out. The influence of media conveyance on driving torque, belt tensions and slip of belt and pulley are discussed. It is found that the media conveyance causes some change in driving torque, belt tension and pulley slip only when the media pass through the contact area, and there could be a very large instantaneous slip when there is torque load.

View full abstract

Euler's formula is the fundamental of theory of flat belt transmission, which gives the tension distribution of a single belt winding on a pulley. In a sandwich-belt conveyor system, however, there is at least one pulley on which two belts wind, and the conventional Euler's formula can not be applied in so called twofold winding. In this paper, a theoretical analysis on twofold winding of belts is carried out and the formulas for calculating belt tension are derived. The theoretical analysis is verified by using FEM through a calculation example.

View full abstract

The sandwich belt conveyance mechanism is used in various conveying systems such as ATM machines and post conveying machine. It is imort ant to gras belt tension and sli of belts and ulleys in design of this mechanism. For this uro se some studies using F or ulti-body ynamics have been reort ed. o solve this rob lem using methods such as F it reuir es enormous time to comu te contact between the belts. In this a er a method using is rovid ed and a solver which can reduce time is develo ed.

View full abstract

This paper describes a development of practical face reverse mechanism, adapt to variety of flexible media. Dynamic simulation shows instability of media behavior on the conventional switch back mechanism. According to the research, we developed a new switch back mechanism using reversible rollers. Experiments prove that performance for poor quality media is improved.

View full abstract

In this research, a laminate material (a phenolic resin reinforced by plain woven cotton cloth) was used for the gear material. The gear was produced by hobbing. In this paper, we addressed the bending strength of gear teeth in the basic design process. First, Vibration characteristics between metal gear and metal gear and cotton fiber-reinforced plastic gear and metal gear when the gears meshed are compared. Second, bending fractures in teeth, were examined by a line load applied to the tooth root fillet and tooth breakage in this area during bending was investigated. Third, to investigate the repetition fatigue strength of teeth, a fatigue test was performed. Forth, tension, uniaxial compression, 3-point and 4-point bending, and shearing tests were performed for the gear materials used in order to investigate the destruction strength of the gear shape and the primary factors in the destruction form.

View full abstract

Molding conditions influences the thickness of deformed layer of plastic gear. The authors have demonstrated that the noise level of the gear with thick deformed layer becomes low. In this study, the operation tests by using the pair of gears of same resin and the pair of gears of different resin were performed to confirm noise and wear. This experiment also showed that noise level of a gear pair of a different material became lower than the gear pair of the same material, and that the amount of wear of driving gear increased rather than the driven gear with comparatively high torque.

View full abstract

The models of normal force on teeth surface of gears are important to decide the contact ratio factor or the temperature rising on teeth surface. The real contact ratio εR of Plastic/Plastic gears are often above 2, and the distributions of normal force are alike mountain instead of step of steel gears. According to Prof. YELLE' theory and experimental study, a model as ε_R under 2 and 3 models as ε_R above 2 are considered. Using model-based reasoning, the equivalent contact ratio factor Yε' and the temperature rising Δθ are studied. When ε_R under 2, Yε' of plastic gears are as same as steel gears. But ε_R above 2, they are more than them of steel gears. The more ε_R rises the more Δθ. When ε_R under 2, Δθ change rapidly, but ε_R above 2, slowly by any more models.

View full abstract

Many factors have effect on load carrying characteristics of the injection molded plastic spur gear pair. One of them is the plastic materials. In especial, the temperature in plastic materials is the most important item, because high temperature in plastic materials causes decrease in the modulus of longitudinal elasticity. Therefore, the effect of each condition, such as the transmitting torque and the kind of plastic materials, on the bulk temperature of gear was investigated. In addition, the measurements of strength and noise of gear were done. The test gears were made from standard POM and POM included new porous carbon materials. As a result, the effects of plastic materials were found.

View full abstract

The present report describes a new method for numerical analysis of tooth forms of a shaved gear. The simulation program evaluates depth of cut in all calculating points on all tooth flanks of work gear, which and a target tooth contact with cutter flank simultaneously. Consequently, to reduce the simulation time, eliminate calculation if these points are not contact with cutter flank. The author evaluated the contact area by generator of tooth flanks of gear pair, select the flank which contacts and select the calculation points. As a result, the calculation time was reduced about 60%.

View full abstract

In the present study, a simulation program of Fassler gear honing have been developed. Fassler gear honing consists of two differrent processes, dressing and honing. The present report describes a new grinding model for each process based on a fundamental experiments. In these models, the following concepts are considered: (1) In the dressing process, amount of stock removal depends on depth of cut, but they could have no definite relationship. (2) In the honing process, amount of stock removal depends on the edge sharpness of abbrasive grain, surface texture of grinding wheel, and so on. The simulation program into which the new cutting models are incorporated has developed. Using the program, tooth forms of internal gear hone dressed with a dress gear and finished tooth forms of work gear honed with the internal gear hone were calculated, and are compared with the measured ones. As a result, the proposed models are confirmed in usefulness.

View full abstract

A method of calculating additional motions in form grinding for finishing the gears with the modified tooth surface is proposed. The method can calculate three kinds of additional motions with consideration of changes in the contact line between the grinding wheel and work gear. As examples of calculation, the modifications of tooth surfaces with symmetrical and bias-in shapes are investigated. Consequently, it was found that the improvement by using the three kinds of motions is small in comparison of using the two kinds of motions.

View full abstract

Gear units have been developed to attain the lower running noise and higher durability under higher revolutions and heavier loads in recent years. It is known that the running noise of gears is reduced and the load carrying capacity is improved through having the high precision and the smooth tooth surfaces. The lapping machine designed and manufactured by the authors is able to make the tooth surfaces of hardened gears smooth like a mirror in a short time. The structure and hardness of surface layer of lapped teeth were researched and residual compression stresses at the lapped surface were measured. In addition, the new lapping device was developed to finish tooth surfaces of pinions with small module for gear reducers. The mechanism of the machine and results of lapping tests were stated.

View full abstract

This paper discusses the bobbing of chip crush, which has become one of object of attention as diy cut. In the cutting tests using a fly-tool, the dimensions of the work piece were 500mm in length and SCM420. The hardness of that material is HB170. The tool was made of high-speed steel and TiAlN coated. As a result, the following conclusions were obtained: (1) TiAlN coated fly-tool was the wear track of the tooth flank in both cutting in and cutting out. (2) Up cut is better than down cut in the machined surface with TiAlN full coated fly-tool.

View full abstract

The degradation of tooth surfaces and the unusual tool wear sometimes occurs in dry nobbing. This paper investigates the transient phenomenon of chip generations and behavior in hobbing by using high-speed video camera. The location of the ending point of cut on a cutting edge influences chip movements at the take-off from the tooth flank. Many chips rotate around the fulcrum of the ending point of cut. Some chips produced with the regular cutting tooth flow to the opposite side frequently when the ending point of cut exists at the trailing side in the conventional hobbing. When the chips flow to the opposite side flank, the chips strike against the tooth surface. There is possibility of jamming into the space between tooth surface and cutter relief surface. Two jamming patterns are found in the fundamental tests; (1) the chip attached on the cutting edge before one revolution is jammed into the space between work and cutting edge when it pushed by the new chip, (2) the end portion of chip newly produced is jammed during cutting.

View full abstract

The simulation program developed that calculates the clearance between cutting edge of hob and tooth flank of gear blank is applied to some practical industrial problems of dry hob cutting, i.e. to chipping failure of cutting edge of carbide hob and bad coarse surface finish of hobbed tooth flank of product gears. The output of the simulation explains the mechanism of such actual failures in detail. The "Distance of Single Edge Cutting" of a hob tooth is proposed to be an index of chipping failure of hob cutting edge due to chip intrusion into the clearance between hob cutting edge and tooth flank of gear blank. Combination of DTL and LRC condition is found to be an index of rough scratched hobbed flank due to chip intrusion. Influencing factors on it is investigated and the bases for finding countermeasures are shown. This method has been applied to some practical cases of problem in mass-production of automotive gears, and good result was confirmed.

View full abstract