The new engine starter is developed for the purpose of downsizing and the improvement of the response time. A feed screw is utilized in this device. The behaviors of this device are follows: The motor shaft connected to the feed screw rotates, and the pinion gear with an inner groove moves along an axial axis. The ring gear connected to the engine is put into the axial position where the pinion gear is stopped. Therefore the pinion gear is engaged with the ring gear, so the engine is turned over. The conventional starter needs a solenoid actuator for the gear engagement. On the other hand, a solenoid actuator is not necessary for this device. But, there is a problem that the rotational speed of the motor shaft decreases when the pinion gear is engaged. Running tests are conducted after the countermeasure for that problem is implemented. According to the test results, we have found that the response time of the new engine starter is 15% faster than the conventional one, and the size of the new engine starter is about 10% smaller than the conventional one.

View full abstract

High strength and high thermal resistance magnesium (Mg) alloy bolt by using the wrought 9Al-Zn-2Ca alloy was developed for the purpose of fastening the Mg parts of the transportation industry. In the application to vehicles, both loosening and creep properties of the bolt are critical due to the vibration loading and thermal history subjected to the bolts. In this report, we focused on the loosening properties and relaxation of a fastening system using Mg alloy bolts in comparison with ordinal steel bolts. The experimental results revealed Mg bolt has higher resistance against bolt loosening than ordinal steels, which is also supported by theoretical review. Then the Mg bolt-Mg parts-Mg nut system was experimented to investigate the influence of thermal history on the axial force in the bolt. Finite element analysis was executed to explain the decrease of axial force in this fastening system. The result indicated Mg alloy bolt maintains the axial force at low initial clamping force more than steel bolts.

View full abstract

Effect of creep deformation on the tightening behavior of nonferrous bolt was studied in order to understand the tightening performance of nonferrous bolt in various conditions. Creep test under 100 degrees of Celsius was conducted for two kind of magnesium bolt, AZ31 and AZX912. The results show that the elongation of bolt after 45 h from the test start was 0.74 mm in AZ31, and that was 0.19 mm in AZX912. It is shown by a simple numerical analysis for the changes in tightening force with time that the tightening force after 5000 h from the start in AZ31 decrease to 6 % of the initial force, and that after 9000 h from the start in AZX912 decrease to 9 % of the initial force.

View full abstract

In a bolt tightening, it is well known that the cause of tightening error of the torque control method is a variation of the frictional coefficients of thread surfaces and bearing surfaces. In this study, an influence of the squareness error of bolt bearing surface on the clamping force error has been investigated. The results showed that the squareness error of bearing surface causes the clamping force error. The results also showed that the clamping force error increased with an increase in the squareness error.

View full abstract

The bolts and nuts are widely used in various field s as an important joining machine element. To ensure the structure safety, a lot of special bolts and nuts were studied previously, and most of the researches focus on the anti-loosening performance. It is known that failures usually happen at the root of the first bolt thread, where the maximum stress concentration occurs. The previous experimental results showed that the fatigue strength may be improved under suitable pitch error existing between bolt and nut. However, the effect of the pitch difference on the stress and stress amplitude at each bolt thread has not been clarified. In this paper, at the first place, the fatigue experiment was performed with varying the pitch difference. The fatigue lives and fracture positions of different specimens were discussed. Then, the finite element method was applied to simulate the fatigue experiment and the stress status at the roots of bolt threads was obtained. As a result, it is found that when the stress amplitude is over the fatigue limit, the fatigue life of the bolt can be extended by introducing pitch difference.

View full abstract

Ball screw is a precision mechanical linear actuator that uses steel balls between a screw shaft and a nut to transfer the motion which convert rotary into linear movement when screw is rotated. Different from any conventional power transmission screw, which needs to overcome sliding friction between the screw and the nut threads, ball screw operates similar to bearing components could achieve high mechanical efficiency since it moves in relatively low rolling friction. As a tried and tested technology, ball screw drive systems are still used in a majority of machine tools which can meet the demands of higher productivity and tight part tolerances due to their low cost and high degree of stiffness. High speed ball screw drive system generates more heat and it results in greater positioning error, adversely affecting the accuracy of high precision machined parts. In consideration of the complicated unpredictable working condition of the ball screw drive system, a well designed nut/screw air cooling ball screw system was developed and be applied to a mass produced ball screw used in a high precision CNC machine tool which can avoid thermal error that affect the positioning accuracy and the temperature rise of in all working conditions. In order to discuss the effectiveness of the developed high speed/high precision nut/screw air cooling ball screw system, a series of tests was carried out in several kind of working condition. As results, the thermal deformation improved 58.7%〜80.1% by nut cooling, screw cooling and nut/screw cooling at the 2500 s moment. Similar with the thermal deformation case, relatively big temperature rising presented through the whole test process in no cooling condition and "Learning curve" phenomenon presented in the cooling cases. The dominated temperature rising area covered the nut moving range completely. Even the cooling methods can control the heat that distribute on the screw surface very well, the cooling performance in the bearing parts is uncertain. Despite excellent positioning accuracy and cooling performance of the ball screw introduced in this research, the average noise elevates 6.25% in the nut cooling, 14.1% in the screw cooling and 15.3% in the nut/screw cooling comparing with the no cooling case.

View full abstract

Gear couplings are widely used as connecting elements that can allow axis displacements caused between two axes. The recent demands to gear couplings are as follow, they are the increase in load capacity, the increase in allowable shaft angle and the reduction in vibration and noise. In order to satisfy these demands, authors have proposed a method of new tooth contact analysis. In this paper,' the test gear couplings with the various profiles are used. The internal gears were manufactured by the CNC gear form grinding machine. The external gears were finished by the form grinding and the hobbing. The tooth contact tests were conducted under the axis displacements. The tooth contact patterns and sound levels were measured. As the results, the influence of tooth contact on the noise of the gear couplings almost was not found.

View full abstract

Synchronous belt drives generate resonance on the belt spanning between the driving and driven pulleys when the transverse natural frequency of the belt approaches the meshing frequency of the pulley and belt teeth. This resonance affects the accuracy of the rotation transmission device installed in the drive system. In a previous report, it was found that the transmission error caused by first mode vibration due to resonance in synchronous belt drives was generated with a period of 1/2 of the pitch of the pulley. However, transmission errors are also generated with a period of one pitch of the pulley, a case which has not yet been examined. In the present study, a transmission error comprising both periods of one pitch and 1/2 of the pitch of the pulley in a synchronous belt drive was experimentally investigated for the case in which the belt at the span generates first mode vibration due to resonance. The installation tension was varied while the rotation speed of the pulleys was fixed, maintaining a speed ratio between the pulleys of 1:1. Analyses of the transmission error based on the experimental results were carried out, and the calculated results of the transmission error were compared with the experimental results. The agreement obtained confirmed the validity of the analyses. It was found that the transmission error of a period of one pitch of the pulley was generated by the difference in belt length between the upper and lower spans due to the resonance.

View full abstract

In late years, dry bobbing without the cutting oil is adopted for consideration for a global environment and the work environment, and a cost cut. This paper presents the experimental results of dry bobbing where four hobs with different coating film were tested. Under the cutting conditions, each hob demonstrates a considerably satisfactory performance although the TiAlN coating seems to be somewhat more favorable than the others, i.e. TiN, TiSiN and AlCrSiN. Another meaningful result suggests that excellent tool life may be expected for higher cutting speed with these hobs.

View full abstract

Direct dry hobbing is the method to cut gear materials after having finished heat treatment without cutting oils. This method is capable of high productivity and low manufacturing cost, and it is effective method to reduce the cutting oils' environmental pollutions. To use this method more effectively, it is necessary to study the cutting states when the gear materials' hardness changed. The purpose of this study is to clarify the optimal work hardness in the dry cutting condition. In this paper, we measure cutting forces and surface roughness of root surface of the gear blanks whose hardness are from HRC28 to 56, and compare them between the dry and wet hobbing condition. We report that the cutting force fluctuation and surface roughness are minimum at HRC56 in the dry hobbing.

View full abstract

This paper deals with the effect of minimal quantity lubrication (MQL) of cutting oil in terms of quantity of oil supply, viscosity grade of oil and concentration of EP additives. Experiments were conducted by simulating bobbing by fly tool cutting on a milling machine. The results obtained are summarized as follows. (1)The quantities of oil supply of 1mL/h to 15mL/h in the MQL system are suitable for the bobbing with regard to decreasing the flank wear. (2)The polyol ester having low viscosity grade of 19.1mm^2/s is suitable for the MQL system. (3)Sulfurized fatty oil, of which the concentration is 1.0%, is suitable for the MQL system.

View full abstract

Gear skiving using the meshing of crossed helical gears attracts attention as the hopeful gear cutting method available to cut efficiently both internal and external gears. In this case, it is known that three kinds of tool gears are used. In this paper, the calculation method of these tool gear profiles are developed, and also the characteristics of gear skiving are discussed through the calculation examples, especially when the cylindrical gear type cutters are used.

View full abstract

In order to develop the economical and environmental manufacturing processes and to obtain the high load-carrying capacity of case-carburized gears, the tooth surface-finishing method using the volcanic-ashes was studied. In this paper, the tooth surface textures of shaved gears and finish-hobbed gears were compared with those of surface-finished gears which were manufactured using the volcanic-ashes. First, the test gear tooth was finished by use of the volcanic-ashes which flowed on the tooth surface. Secondly, the three-dimensional curve and surface texture of test gear tooth were investigated using a surface texture measuring instrument. By applying the designed tooth surface-finishing method to the case-carburized tooth surface, the following results are obtained: The random asperities of the shaved tooth surface almost disappear. The vertical interval of concave-convex shape on the tooth surface becomes small. The convex regions of the finish-hobbed tooth surface become smooth. The maximum peak height of the roughness profile on the tooth surface decreases. Therefore, it is found that the tooth surface-finishing method using the volcanic-ashes is a useful manufacturing process from the viewpoint of surface texture and surface durability of power transmission gears.

View full abstract

The objective of this research is to develop a gear lapping machine which can simultaneously make all tooth flanks of an internal gear smooth in a short time. A work gear is meshing with two lap gears as crossed helical gears and supported by a guide gear during the lapping. The two lap gears and the guide gear are made of nylon. Lapping slurry containing abrasive grains is supplied to the meshing teeth. The structure of the lapping machine designed and manufactured by the authors is shown. The work gears are lapped using lap gears which have tooth trace modified based on the calculated results to prevent the interference. They are evaluated with regard to the tooth roughness and the accuracy of the tooth profile. The results are as follows. (1) A work gear meshed with lap gears without the occurrence of the interference. (2) Tooth flanks of work gears were finished smooth as a maximum peak-valley height (Rz) of less than 1μm by this process. (3) It is necessary to enable to finish in shorter lapping time.

View full abstract

Precise micromodule small gears are necessary to realize high-strength low-noise compact geared motors. In the gear manufacturing process, burrs and nicks are generated at the edge or ridgeline of the work gear tooth and they get the gear accuracy worse. Therefore a removal method of burrs and nicks is important. However, it is difficult to remove them from small gears by using usual tools and usual processing devices because the tooth groove of small gears is narrow. In order to solve these problems, FRP gear-shaped tool and finishing device for small gears using oscillation have been developed in this research. Experiments are carried out and it is confirmed that the proposed method can remove burrs and nicks from small gears.

View full abstract

Double helical gears sometimes counteract or nullify the forces to overcome axial thrust and are usually generated using a special generator. However, the phase difference of oncoming gears must be controlled with high accuracy and the machining of the gears is restricted due to tooth arrangement. In this paper, the double helical gears are manufactured using a multi-axis control and multi-tasking machine tool in order overcome these problems. This manufacturing method has some advantages as arbitrarily modification of tooth surface and machining of the part except tooth surface in addition to only one machine settings. The gears were manufactured by a swarf cutting using a coated carbide end mill and the tooth profile errors, tooth trace errors, and pitch errors of manufactured double helical gears were measured. As a result, the validity of this manufacturing method was confirmed.

View full abstract

Gear design calculation and drawing software have been developed based on AutoCAD Visual Basic language included in AutoCAD. With the developed software, a pair of spur gears, helical gears and internal gears can be calculated simply in AutoCAD surrounding. The software developments have also been made for some special gear devices, such as trochoidal gear reducers and strain-wave gearing. Two-dimensional (2D), exact tooth profile shapes and drawings of the designed gears can be drawn automatically and immediately on the template of AutoCAD when the developed software are run. Then three-dimensional (3D) drawings of the designed gears can be made by 3D commands included in AutoCAD. The developed software can also be used to calculate gear bending and contact strength in AutoCAD surrounding based on the JGMA and ISO standards.

View full abstract

Mechanism design becomes more complicated to achieve higher mechanical functions. It is necessary to create appropriate configuration and geometry at upstream design stage to satisfy design specifications at detail design stage. In our study, a design system is developed for generating gear trains under design constraints on a specified area. The design specifications are input position, output position, input torque, output torque, rotation direction and so on. Spur gear trains are generated by using random method combined with local optimization method based on the conjugate gradient method. The objective function evaluates weight, efficiency and life of generated gear train. Multi-objective design optimizations in spur gear train generation problems are examined by using Satisficing Trade-off Method. For several examples, optimal gear trains are generated successfully. Trade-off relationships in spur gear train design are examined by the optimization system. The effectiveness of the mechanism generation algorithm is reported.

View full abstract

There are innumerable solutions when the pitch surface of hypoid gear is solved from requirement of two cones. The pitch angle is decided as the tooth lengthwise curvature is corresponding to the cutter radius by the Gleason method. In this study, using the new tooth geometry, the new design method which can optimize the contact ratio is proposed. The effectiveness of the optimum design method is confirmed by measuring transmission errors. A gear design example of reducing spiral angle is shown.

View full abstract

Typically, the circular-arc tooth-trace (CATT) gears are considered as a special type of spiral bevel gears whose shaft-angle is zero. Conventional circular face-mill gear-cutters are used to make these gears. In this paper, the characteristic of the new CATT gears designed by the author with 3D-CAD/CAM were studied; the tooth profile of pinion gears have the same involute curve at the any section through the face-width. Similarly the tooth profile of the CATT's rack is a straight line at the both ends of the face-width.

View full abstract

The present paper describes characteristics of asymmetric gears. A large pressure angle gear enables a load-capability to increase without changing its size and the material. However, the larger pressure angle is, the narrower top land is. Therefore, the asymmetric tooth profile gears were noticed. Contact stress, transverse contact ratio, sliding ratio and bearing load were calculated with changing pressure angle. As a result, contact stress and sliding ratio of asymmetric gears were decreased with increasing pressure angle, and these were less than symmetric gears. However, contact ratio was also decreased and bearing load was increased compared with symmetric gears. Moreover, bending stress, contact stress, friction coefficient, flash temperature, oil film thickness, damage probability and efficiency were calculated. It was found that asymmetric gears have advantages compared with symmetric gear.

View full abstract

Like recent automatic transmission, our latest CVT is demanded to be lightweight and downsizing from standpoints of fuel efficiency improvement and collision safety. Its gears, shafts that support gear, bearings and case are smaller than conventional specification, and gears operate at higher mesh force than ever before. So we developed balanced tooth flank form to match load capacity and noise performance. We measured tooth stress in load condition using CVT to investigate relation between load and tooth deformation. Considering the relation of tooth deformation, we simulated tooth contact pressure in heavy load and transmission error in light load. As a result of the simulation we founded a balanced tooth flank form that could reduce tooth contact pressure and keep same level of transmission error. We verified these simulated results experimentally using CVT.

View full abstract

Root stresses in meshing process from the beginning of engagement to the end of engagement of thin-rimmed helical gears with symmetric and asymmetric web arrangement of helix angle helix angle β_0=10 and 30°, which were meshed with solid helical gears, were measured by means of the strain gage method. The changes of root stresses in the meshing process, the maximum root stress, the position of the maximum root stress and the worst meshing position (the meshing position where the maximum root stress occurs) were examined, and then the effects of rim and web thickness, web structure, and helix angle on root stresses were determined by comparing with the results of β_0=20°. Furthermore, the results obtained were compared with those of solid helical gears.

View full abstract

Recently, two steps bending phenomenon of S-N curve for the bending fatigue strength of cast iron gear is reported, and the fatigue phenomenon in long life region over 10,000,000 time number of cycles is discussed. However, the surface durability in long life region has not been clarified until now. In this paper, surface durability of cast iron rollers in long life region is investigated using a disk machine which simulates the rolling and sliding action of gears. Furthermore, fatigue limit for surface durability of ADI is estimated by observations with crack initiation and propagation.

View full abstract

This paper presents a study on the bending fatigue strength and surface durability of high strength sintered metal gears. Bending fatigue tests and running tests for newly developed carburized Fe-Ni-Mo and Fe-Ni-Cr-Mo sintered metal gears were carried out and the bending fatigue strengths and surface durabilities of these gears were determined. The results were compared with those of conventional high density sintered metal gears and carburized wrought steel gears. The experimental results show that the load bearing capacity of newly developed sintered metal gear with surface-densification is comparable to that of a carburized wrought steel gear.

View full abstract

Because of light weight and high power of transmission, carburized and quenched gears are used as power transmission gear. Surface durability of carburized and quenched gears has been related with their tooth surface properties. The influence of abnormal carburized layer on the surface durability, however, has not been clarified. In this study, tested pinions were of two types: gear carburized and quenched after grinding, and gears carburized and quenched before grinding with two different surface roughness. In case of gears with equivalent surface roughness, the surface durability of the gear with abnormal carburized layer was longer than or almost the same as those without abnormal carburized layer. This would be because the abnormal carburized layer at the edge of tooth surface was worn during the fatigue tests.

View full abstract

In order to investigate the influence of tooth surface form on fatigue strength of steel gears, the case-hardened steel gears with non-ground tooth surfaces, ground tooth surfaces and crowned ground tooth surfaces were fatigue-tested using a gear testing machine. In the fatigue tests, the surface failure of the gear with a crown radius of 300 mm started to occur in the center of the tooth surfaces, and that of the gears with non-ground and ground tooth surfaces started to occur at the edge of the tooth surfaces. The fatigue strength using Hertzian contact stress of the gear with a crown radius of 300 mm was the highest, followed by those of the gear with ground tooth surfaces, the gear with a crown radius of 600 mm and the gear with non-ground tooth surfaces. On the other hand, the fatigue strength using normal load of the gear with ground tooth surfaces was the highest, and those of the other gears were almost the same. Therefore, it was found that the fatigue strength using Hertzian contact stress of the steel gears depends heavily on a crown radius of tooth surface, and that using normal load has little influence on it in this experimental range.

View full abstract

The measurement of hardened layer and the impact tests were carried out for gas and vacuum case-carburized SNC815 steel gears and induction hardened gears made of thermally refined and as-rolled S35C steels. The effective hardened depth (HV400) and the case depth (HV550), the relation between impact energy and the increment of sector span of test gears were obtained. Relationships between the hardened depth, the case depth and the impact strength of case-carburized and induction hardened gears were examined, and the method for selecting the suitable case-carburizing and induction hardening condition for impact strength was proposed.

View full abstract

Macro and micro-structure and hardness of hardened layer of induction hardened SUJ2 steel gears were measured, and profiles of hardened layers and effective hardened depths were obtained. Bending fatigue tests of induction hardened SUJ2 steel gears were carried out and S-N curves and bending fatigue limits were obtained. On the basis of these results, effects of heating time, pre-treatment and tempering on effective hardened depth and bending fatigue limits of induction hardened SUJ2 steel gears were clarified. Furthermore, these results were also compared with those of induction hardened S35C steel gears.

View full abstract

The development of bending fatigue can be divided into the fatigue crack initiation stage and the crack growth stage, and the fatigue crack initiation life predominantly determines the total fatigue life. After a fatigue crack initiated on a power transmission element such as a gear, the crack will always grow until a fatigue break, so, none of fatigue break can be considered practically as none of fatigue crack initiation; and the bending fatigue strength can also be defined as the stress under that the fatigue crack will not initiate. The purpose of this research is to estimate bending fatigue strength based on the crack initiation. A practical method for the detection of a fatigue crack initiation using an ion-sputtered film was used in bending fatigue tests. The ratio of the fatigue crack initiation life among the total fatigue life was investigated. The ratios are clarified that increase with the decrease of bending stress, and reach the maximum value of 1.0 at the fatigue limit. The bending fatigue strength can be estimation based on the relationship between the relationship between the ratio and bending stress, and the appropriate number of load cycles to judge that the fatigue break will not happen can also be determined from the relationship between the ratio and fatigue life.

View full abstract

The conical involute gears have been applied to automotive parts such as 4WD transfer. The conical gear pair has characteristic large ease off and this is equivalent to meshing of cylindrical gears which has large crowning for lead direction. Consequently, the trochoidal interference is thought to be caused because of tooth stiffness reduction. In this study, to clarify the influence of the tooth flank modification on the tooth surface damage, tooth surface endurance test with several tooth flank modification shapes is experimented. As a result, the gear pair with crowning for tooth profile direction and reverse crowning for lead direction can extend the pitting fatigue life because of the edge load reduction of tip or root.

View full abstract

When a gear tooth form is given, conjugated tooth form is usually calculated using equation of meshing. Solution of the equation is constituted into equation of a tooth form in the other gear coordinate system, and points represent conjugated tooth form can be obtained. However, these points lie randomly. So, in order to use them for points represent tooth flank, mathematical interpolation method with high accuracy is necessary. In the present paper, Lagrange Polynomials are proposed for interpolation of tooth form. As a result, it was found that maximum deviations were very small and lower than submicron order using Lagrange Polynomials.

View full abstract

The gear was deal with electron beam, and microhardness, roughness, topography and organization structure and stress on gear surface was measure and their effect to gear bending fatigue strength was analyzed and discussed. Experimental of gear bending fatigue strength was accomplished and contrasted before and after they were dealt with pulsed electron beam after grinding tooth surface. The surface hardness of 40Cr can be changed within in 2 mm under the surface. For grinding gear which was treated by electron beam, tooth surface roughness has a certain degree of enhancement. Because electron beam has the polishing effect, so many small scratches on the root surface of the grinding gear have disappeared, and the grain size in the material's surface has been refined. The results demonstrated that gear bending fatigue strength after irradiation was improved 6.1% than that before irradiation at the condition of reliability 50%.

View full abstract

Engineering plastic which has heat-resistance, shock-resistance and chemical-resistance has been applied in various fields, such as automobile, machine parts, electronic components and chemical components. As one of examples, the Electric Power Steering (EPS) has been equipped for a steering assistance in an automobile. And worm wheel of EPS is made of engineering plastic. However, the reports and papers about the load carrying capacity of the engineering plastic worm wheel are hardly seen. In this study, some running tests were executed with the worm wheels made of 4 types of engineering plastics. The precepts for designing engineering plastic worm wheel were obtained and discussed in this paper.

View full abstract

In the plastic crossed helical gear, there are two types of failure modes. They are excessive wear and tooth breakage. In case of the excessive wear, the lifetime can be evaluated by average meshing teeth temperature. On the other hand, in case of the tooth breakage, the lifetime can be evaluated by the stress ratio, which is the ratio of the tooth root stress and the allowable bending stress of plastics at meshing teeth temperature. Therefore, regardless the gear failure mode, it is possible to estimate the lifetime of plastic crossed helical gear if meshing teeth temperature can be predicted. With regard to this meshing teeth temperature of plastic crossed helical gear, we reported that there is a good correlation between the increase in meshing teeth temperature and the mean flash temperature using Coleman's method. However, this report was the contents about limited conditions. In this study, the meshing teeth temperature of the crossed helical gear when number of teeth of driving and driven gear differs was investigated experimentally. As a result, within the dimensions of the plastic gear which was generally used, we clarified that the mean flash temperature was a useful parameter for evaluating on the increase in meshing teeth temperature of plastic crossed helical gear.

View full abstract

We investigated the effect of swelling of polyamide gear on the gear accuracy and noise generation. For the influence of swelling on the gear accuracy, we examined the changes in the tooth profile and tooth trace of test gear by water immersion test. Gear swelling caused large negative pressure angle errors on the tooth profiles of test gear and the error increased with the immersion time. Changes in the tooth profile were approximately similar in each tooth of the test gear. For the influence of swelling on the gear noise, we examined by comparing the noise of swelled gear and that of non-swelled gear using a gear tester. In this study, we attached a polyamide gear to the driven shaft and a steel gear to the driving shaft, and carried out gear tests under the conditions of tangential force F/b = 6.5, 13.0, 19.6 N/mm (the nominal load torque = 19.6, 39.2, 58.8 Nm). The change in tooth profile due to swelling influenced the noise generation, however the influence was limitative and swelling had no very influence on the gear noise generation except for the case operated under low load condition.

View full abstract

The present paper illustrates evaluation of DLC (Diamond-like Carbon) film strength using cyclic plunge load. DLC film strength is generally evaluated using Rockwell hardness measurement, or scratch test. However, these evaluations may not be effective method for DLC film strength which is subjected to cyclic load. Therefore, cyclic plunge load test is proposed for strength evaluation. As a result, it was found that DLC film did not show failure by 27.5N plunge load (number of cycles 10^4) and 65.0N (number of cycles 10^3). And DLC film shows failure by 65.0N plunge load (number of cycles 10^4). In addition, failure points were thought to be inside near by surface of indentation.

View full abstract

In the recent years, Face gear becomes an alternative mechanical element of Bevel gear or Hypoid gear due to easy for assembling. In this paper, we propose new tool specialized for the cutting face gear flank. This tool is constructed from spur gear that has same axial plane tooth profile as a helical pinion gear meshed with a face gear to be cut. This tool synchronously rotates with face gear blank and feeds the tool axis to cut face gear flank. Its cutting edge appears on spur gear axial profile and this edge scrapes face gear flank by synchronous rotation and feeding. This method can be applied for producing face gear which meshes a pinion gear on arbitrary angle without outstanding difficulty.

View full abstract

This research proposes the method of manufacturing wheels which changed the number of teeth by the same hob. The designed hourglass worm gear requires the center distance corresponding to number of teeth. A design-criteria point is located in the throat of the standard hourglass worm. And center distance is defined when a wheel and a worm fulfill the conditions of contact. The geometric performance of the designed hourglass worm gears is investigated. Compared with cylindrical worm gears, it is high performance and the validity of the proposed method became clear.

View full abstract

To protect the global emvironment and for energy saving, it is needed to improve the fuel consumption of vehicle. It is a means of improvement of fuel consumption to reduce the friction of hypoid gear. Generally, it is known that hypoid gear meshing friction has opposite performance to NVH and strength. In this paper, the prediction method of hypoid gear friction is shown which is based on the formula proposed by Wells Coleman and using the experimental formula as the coefficient of friction of meshing. And the facter effect of hypoid gear dimension parameter to friction loss is considered using the prediction method. From this consideration, spiral angle and pinion offset have big effect to meshing friction. By optimizing spiral angle, pinion offset and face with which has big effort to NVH and strength, dimension example is cleared which has equal performance of both of NVH and strength, and better performance of meshing friction compared with current hypoid gear.

View full abstract

A multibody dynamics method has been developed to evaluate effects of bearing clearances on a planetary gear vibration. The numerical method solves the equation of motion by modal superposition using local floating frame. Gear mesh is calculated by numerical surfaces considering surface modification. Bearing clearance is modeled by nonlinear springs and dampers. Numerical examinations reveal that the radial clearance of the carrier affects the torsional vibration of the carrier. The clearance of the carrier should be small to reduce the excitation force of the carrier of the meshing frequency. Numerical results show that the unbalanced load sharing of the pinions increases the torsional vibration of the carrier.

View full abstract

As a component of fuel cell vehicle, compact and high pressure ratio compressor has been developed. Development target of it is driven by an electric motor using normal bearings. The authors have developed a planetary gear system with gear ratio of 11.33 times. These features of planetary gear are 0.5 modules, special gear process, and duplicated directly gear and bearing by oil spray. And rotation speed of output shaft is very high, so bearing was made by special race and ceramic ball. The prototype has made and estimated. The pressure ratio of 3.4 has been achieved by impeller speed of 153,000rpm. Durability of the unit is continuing to be estimated and have confirmed to no trouble the early periods.

View full abstract