New Geometry of Generating Spiral Bevel Gear

New geometry of generating spiral bevel gear is proposed. The key idea of the new proposed geometry is that the gear tooth surface geometry can be investigated in a developed curved surface based on the planar engagement principle. It is proved that the profile curve on the back of generating cone surface is a conical involute curve. The equations of generated gear tooth surface are achieved by the conical involute curve sweeping along the tooth trace of gear. The obtained equations are explicit and independent of the machine-tool settings. This differs from previous studies. The developed theory is illustrated with numerical examples to compare with the previous method, the comparison approves that the method is possible in this way. The new method indicates that there are new solutions to the design the production of spiral bevel gear.

Observation of Fatigue Damage to Gear Tooth Using Image Processing

The detection of damage in early stage of fatigue is important for a reliable evaluation of gear life and strength. From this point of view, the variation of strain distribution in a tooth due to cyclic load contains useful information because the fatigue crack will initiate as a result of the accumulation of plastic strain. Meanwhile, digital image equipments are widely used in our life and the performance is in progress. We took digital pictures of cyclic loaded tooth by the digital camera and compared with the picture of no load to find displacement. The strain distribution of tooth is calculated by the correlation method using those pictures. The initiation of a micro crack is observed by the method. It is also confirmed by the detection of acoustic emission wave with higher energy. The variation of stress-strain diagram in fatigue process is presented, and this illustrates the increase of strain in the final stage of fatigue.

Expansion of Ratio Range of Shaft Drive CVT by Using Zero-Spin Disk

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 or concave 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. The efficiency is the key evaluation function of CVT. To improve the efficiency, the backup roller mechanism was devised. Its effectiveness was confirmed by the experiment, and the efficiency of 95% was obtained by modified prototype S-CVT. This paper deals with the expansion of ratio range of S-CVT. In case of using the present disks, S-CVT has a difficulty to expand the narrow ratio range of 4 (0.5 to 2) because of the large slip brought by the spin. To expand the ratio range, the zero-spin disk/roller was devised. The shape of zero-spin disk/roller satisfies the condition that the spin does not occur at any speed ratio. According to the calculation, the slip rate becomes less than 1% at any speed ratio. To confirm the effectiveness, the prototype S-CVT with zero-spin disk was manufactured. It has the ratio range of 0.43 to 2.35. To obtain the slip rate the experiments were carried out at the speed ratio of 0.43, 1 and 2.35. At each speed ratio, the slip rate of less than 1% was obtained, and the effect of the zerospin disk was confirmed.

Virtual Clutch Development Model

In a world of constant development and where competition grows stronger for every minute, there is a need to work smart to stay on the market. Product development in the automotive business is not an exception. It is though not enough to adapt new technology and new ideas, one has to apply it to the organization in the smartest way to be able to achieve one of the most wanted goals; shortened lead-time in combination with improved product quality. As well known, virtual prototyping is a mean to achieve the above stated goal. This paper describes how this method has been the basis for a new product development approach in the clutch system area in an automotive company. The new virtual development approach is enabled by creation of the Virtual Clutch Development Model (VCDM). The main benefit of the simulation model is that several clutch performance phenomena can easily be investigated at once to get an overview of the performance of the clutch system, this in an early phase of the development process. This will facilitate trade off decisions and avoid suboptimization and thus shorten lead-times and improve product quality.

The Mechanism and Solution of Harmonic Gear Whine Noise in Automotive Transmission Systems

Since gear noise in automotive is one of the most unpleasant noises for passengers, various solutions, such as gear design optimization, tooth modification and transfer path reformations in the vehicle have been developed. But, these attempts are mainly focused on the fundamental mesh excitation of the gear set without any consideration of their harmonic noise (1st, 2nd or higher). Harmonic gear whine noise is easily audible in the vehicle because of their high frequency characteristics in spite of low sound pressure level. This annoying pure-tone noise is usually issued in the transmission system composed of the gears produced by grinding process. This paper will present the main sources of this harmonic gear whine noise with the test results of gears with identical design parameters but having different surface structure (roughness parameters, wave patterns). Additionally, manufacturing guidelines of gear surface structure will be proposed at the end of this paper.

Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

Bending Strength of Carburized Forged Spur Gear

This paper deals with the evaluation of influence of the manufacturing methods precision forging and conventional hobbing on the bending fatigue strength of carburized gears. The forging has advantages in productivity and strength. The forged gear has a continuous directed fiber flow which runs along the gear profile. To clarify the effect of strength enhancement, a bending fatigue test is performed for the forged and the hobbed gears. The material of test gears is SCr420H in the JIS and all gears are carburized. The electrohydraulic servo-controlled fatigue tester is used in the constant stress-amplitude fatigue test. The strength is expressed by the fillet stress level, which is calculated by FEM. The obtained strengths of forged and hobbed gear are 1613 MPa and 1490 MPa, respectively. The strength of forged gear is increased 8% in comparison with that of the hobbed gear. The surface hardness is higher and the surface roughness is smaller in the forged gear, however, the residual stress is approximately same. The effect of improvement of the roughness by forging on the strength is small in 1%, and the main reason of the improvement of fatigue strength is considered as the continuous fiber flow.

Modification of an Involute Gearing and Its Effect on a Loading Capacity

A modification of an involute gearing is presented by a modification of an involute and a longitudinal modification along the face width. In the contribution both of the modifications are presented and theoretical and practical methods for determination of their parameters are shown. Experimental methods of setting up of input data for design of modifications are brought in then. These data are prepared on the basis of measuring of deformations of gearwheels bodies, shafts and shafts supports. An attention is given to the influence on a size and position of a zone of contact of meshing teeth. A separate part deals with the appreciation of an influence of modification on a size of a noise and vibrations of involute gears. As far as a loading capacity of modified involute gearings, the attention is first given to the loading capacity in a contact stress between teeth faces. The comparison is made between loading capacity of an involute gearing with no modification and a gearing modified by various types of modifications. This comparison is made both by using a FEM and by experiment. Experiment is based on lifetime test of these gearing.

Effects of Rolling on Load Bearing Capacity of Sintered Metal Gears

This paper describes the effects of surface rolling on the load bearing capacity of sintered metal gears. Sintered metal gears and rollers were surface-rolled under various amounts of rolling. The effects of rolling on the surface properties were examined by measuring the porosities and hardness near the surfaces of the rolled gear teeth and rollers. Bending fatigue tests for the surface-rolled sintered metal gears and contact fatigue tests for the rollers were carried out. The effects of the amount of rolling on the load bearing capacity of sintered metal gears and rollers were determined, and these results were compared with the results for as-sintered and wrought steel gears and rollers.

Optimal Construction of a Hydraulic Pump With Elliptic Rotated Piston by Kakeya-Besicovitch Application

The paper has presented an application of Kakeya-Besicovitch, third example about commutation of finite element beam endpoints inside of arbitrary small zone. This area is a hypocycloid with three cusped points at that inner tangent has a constant length independent by the point position of its inner tangent, which being rotated in clock-way it’s came back to its original position with its endpoints reversed. The application is a hydraulic pump compound by one rotated piston with elliptical section which is rolling in a fixed chamber with hypocycloid form and three cusped rounded tips after a curvature equal with major axe ellipse endpoints curvatures. The rolling motion is imposed by eccentric exterior source that acting inside of cylindrical pocket located in the center of elliptic piston, which divided the hypocycloid in three equal parts at 120° from each other. The pump could be working as a hydraulic motor which is endowed with rotating distributor that can feed each chamber with variable volume one by one due to moving the piston. The pump’s relevance is given by its efficiency, allowing a large flow capacity to a lower spindle speed, ensured a constant ratio spindle speed which working silence and a large stability.