The main aim of gearing technology, at its present state of maturity as an applied science, should be a continued effort to minimize noise and vibration in two industries where they are especially critical: office-automation equipment and automobile production. One obstacle facing the advancement of this technology is the decline in qualified gear-engineering specialists from the workforce. A solution to this problem is presented in this paper as a simplified means of analyzing low-vibration parallel gear pairs through computer-aided-design, vibration-performance diagrams. Through the development of more sophisticated computer-simulated analysis techniques, the shortage of qualified engineers may be offset by allowing less-qualified engineers greater access to this important but highly specialized technology.

View full abstract

After giving a brief explanation of the difference between "predictive" and "descriptive" theories in metal cutting, two examples of representative "predictive" theories of orthogonal cutting are presented. The predicted or experimentally obtained data of orthogonal cutting may be applied under some assumptions to predict three-dimensional cutting performance, although plastic flow in the cutting is not the flow in plane strain. This type of theory is then discussed since it appears only the practical approach at present. Besides the predictions mentioned above, machining troubles such as chatter vibration and cutting tool failure must be also predicted in order to obtain optimum cutting conditions for a given operation. These problems of prediction sre also reviewed in some detail. Finally, it is pointed out that an expert system using nonalgorithmic artificisl intelligence is indispens able at present in order to complement and utilize our metal cutting theories in practical problems such as determination of optimum cutting conditions.

View full abstract

This paper proposes an oil damper with a variable damping mechanism. The piston of the damper has a fan-shaped orifice as a flow channel for the oil. The magnitude of damping can be regulated continuously by varying the area of the orifice. Another merit of this damper is that its damping can be regulated as viscous, enabling a theoretical approach to be used in its study. We have analyzed the oil damper by assuming the flow of oil to be laminar and oscillatory. However, it is too difficult to obtain an analytical solution from the basic equation, so the analysis was accomplished numerically using the finite difference method. It was confirmed that the theoretical results agree well with the experimental ones.

View full abstract

The object of this paper is to study a method for passing through the critical speeds of rotating shaft systems, and in particular, to search for optimal turning points and returning points for minimizing the maximum flexural amplitude by changing the driving acceleration after the initial start-up. This method is based on the following idea. A large acceleration is available during transition through critical speeds because the maximum amplitudes of flexural deflection are reduced ; however it is unsuitable except the region of critical speed because the torsional deflection increases. In order to realize the optimal operating curve, a linear optimal tracking system is applied. This control system consists of optimal state feedback and a compensation input. It has been proved that this control system reduces transient torsional vibration due to sudden torque change and torsional resonance vibration when the shaft passes through its resonance region.

View full abstract

For the vibration control of a main structure subjected to a random input with a dominant frequency, an active dynamic vibration absorber is manufactured, which is equipped with a linear motor as an actuator and is digitally controlled by means of optimal feedback and feedforward links. First, by performing impulse excitation, the usefulness of the optimal feedback control is verified. Second, in the frequency responses obtained from a stationary random excitation, the effectiveness of the optimal feedforward link is demonstrated in comparison with a feedback link only. Further, in a nonstationary random excitation in which the same nonstationary random wave can be realized every time, it is confirmed that the active dynamic vibration absorber is useful also for a nonstationary random input.

View full abstract

A new position measurement method for conduit pipelines buried under public roads is proposed. In this method, two modules, a vehicle and a probe move inside a pipeline. The probe measures the pipeline inclination and radius of curvature. The position of the pipeline is calculated by cumulating the inclination and the attitude angle from the radius of the curvature measurement. Position measurement accuracy is analyzed and evaluated with standard deviations of the inclination and radius of curvature. This method of measurement is confirmed to be useful by experiments with a pipeline 40 m long with an internal diameter of 80 mm. The error in the horizontal and vertical measurements is smaller than 20 cm.

View full abstract

In order to make vibration analysis an easily input, automated task for designers, it is desirable to develop an interactive vibration analysis system, using personal computers or engineering work stations which have a user-friendly interface for easy input of the vibration model, and which can perform automatic generation of equations of motion, and automatic numerical analysis of them. As the first step towards such a system, an automatic generation system of equations of motion was developed for two-dimensional vibrations of multibody systems. The system is written in Smalltalk-80, which is a typical object-oriented language having the following advantages : (1) user-friendly interface for graphic input of a vibration model, enabling users to make a variety of configurations of a vibration model on the display by choosing the vibration model elements listed in the menu with a pointing device (mouse) ; (2) applicability to extensive models of two-dimensional vibrations of multibody systems which contain various constraints and nonlinear elements.

View full abstract

A theoretical and experimental study is presented for the displacement control of a one-link flexible arm with an end-point payload, The tip displacement of the arm is measured by a gap sensor fixed in space and controlled by a D. C. motor located at the other end of the arm, where the motor is driven by a feedback signal composed of the tip displacement and the velocity. As an example, the problem of shifting the end-point of the arm from its initial position to the commanded position by the amount of w^*_d is considered. Solutions derived by applying the method of the Laplace transform to the governing equations are calculated by the method of numerical inversion. Experimental results are obtained and compared with the theoretical ones, showing both results in good agreement for a wide range of parameters.

View full abstract

For the gears installed in machines and equipment, the alignment errors of the gear shaft due to the manufacturing of the gear box, the assembling of the gears, and the elastic deformation and backlash of the unit are usually unknown. The exact state of manufacturing errors of gears is also often unknown. This research proposes a new method to estimate the state of vibration of gears at arbitrary operating conditions from the data of vibrational acceleration measured at some definite reference operating condition when the manufacturing and alignment errors of gears are unknown. The paper explains the proposed method of estimation for the rotational vibration of gears with unknown accuracy and examines the validity of this method by the comparison between the estimated value and value of computer-simulation, and by the comparison with experimental results as well. It is confirmed that the state of vibration of gears with unknown manufacturing and alignment errors can be estimated by this method, if very high accuracy of estimation is not demanded.

View full abstract

The quasi-static vibratory analysis of a rotor supported by cylindrical roller bearings is presented. The system is an ideal cylindrical roller bearing in which the inner ring moves in a radial plane with two degrees of freedom under a constant radial load. The load-deformation relationship for elastic contact is expressed by a function with an arbitrary power index, and the motion of the inner ring center due to the roller revolution is analyzed in detail. The case using a one-sided linear spring is also analyzed. The results show that the inner ring motion has complicated features which change significantly with the design and operating conditions. All the computed results are arranged in charts in which approximate waveforms of the inner ring motion and its magnitudes are presented together with the loaded states of rollers. These may be useful in design processes to examine the rigidity, the critical speed, and the vibratory nature of a rotor system.

View full abstract

The influence of tooth profile modification on the surface durability of spur gears has been studied using mirror-like finished gears with a high accuracy (≒0.1 μm R_max, JIS M 00 class). In order to explain the effectiveness of tooth profile modification, the durations of the elastohydrodynamic lubrication (EHL) condition at the point of contact were measured utilizing an electric resistance method. The results clearly show that the duration of the EHL condition on gear pairs with tooth profile modification have been improved, especially at the beginning and the end points of contact. Even when low hardness gears are used, it is necessary to modify the tooth profile in order to form the lubricating oil film between the meshing teeth and to reduce the surface distress.

View full abstract

A globoidal worm gear of a new type which consists of a wheel having cylindrical pins as teeth and a worm with an arc-shaped groove is proposed. The gear has merits of easy manufacturing and maintenance. The geometrical characteristics are examined in the first section of this study. A slightly skewed shaft angle is proposed to realize good performance of lubrication and a design example is shown. The second section deals with an experiment of lubrication between a cylindrical pin and a rotating roller with an arc-shaped groove to obtain the optimum groove profile of the worm. A method of machining the worm gear unit is presented in the third section and two pairs of the units with a gear ratio of 1/24 are manufactured for trial using a hobbing machine. The last section deals with a performance test of the worm gear units. A transmission efficiency of 80% max. is obtained showing satisfactory abilities of the units for practical use.

View full abstract

This paper presents a general approach for solving the Reynolds equation, in which the Reynolds equation is reduced analytically without approximation to infinite dimensional linear equations (matrix form) with unknowns related to eigenvalues of operator R=∇·[(h³/6η)∇]. The paper presents applications of the method to journal bearing problems under a quasi-Reynolds boundary condition in which the trailing boundary line is given by a straight line and the bulk flow across this line is ensured to be continuous. It is shown that the present method requires much less computational time than ordinary FDM for obtaining accurate predictions.

View full abstract

In this paper, two analytical models for an externally pressurized circular thrust bearing with a central supply hole are presented when the gas flow is choked at the inlet to the clearance space. These models can be modified for an unchoked condition and enable one to analyze the dynamic performance of the bearing over a wide range of design conditions. From the experiment, it is concluded that the effects of the inertia forces are considerable when the feeding parameter is small, and that the presented analyses yield good predictions of both the bearing stiffness and the damping coefficient.

View full abstract

In the long-term endurance test of Shinkansen electric cars at the speed of 240 km/h, the shape of the wheels and vibration of the cars were measured periodically. This test was continued up to a running distance nearly equal to that which requires an overhaul of the trucks. From the data of the wheel shapes, the wear characteristics were analyzed, and their quantitative effects on the running vibrations were researched. As a result, the following matters were clarified. (1) During the tested running distance, the riding quality level of lateral vibration grew 2∼3 dB because of the increased play between the flange and the rail-side caused by flange wear. (2) In the case of present trucks, tread wear did not dominantly affect the running vibration. Thus, it is supposed that the lateral shift of the contact point between the wheel tread and rail-head caused by the worn wheel played an important role in this result.

View full abstract

A stress sensor for detecting pressure and frictional stress acting on a roll surface during rolling has been developed. Using this sensor, not only the pressure, but also the frictional stress in the rolling direction and in the width direction can be detected at the same time. The measuring performance of this sensor is investigated and an example of the measurement during rolling is shown. The accuracy of the measured data is confirmed.

View full abstract

This paper describes how to increase the stiffness of a servomechanism in a direct- drive NC hobbing machine. Since the equivalent inertia moment of the work-table is very small in the direct-drive NC hobbing machine, the rotating vibration caused by the torque fluctuation of load becomes very large. To solve this problem, the authors tried to apply damping torque to the servomechanism by using an inertial damper. This increased the stiffness without any resonance over a wide frequency range of exciting force. The effect of this inertial damper is verified by theoretical analysis and experiments. Gear-cutting experiments proved that this easy method is practical and useful in decreasing the rotating vibration of the worktable in the cutting process.

View full abstract