On a gear tooth surface, there may be some certain points which contact twice with its mating gear tooth surface. This phenomenon is called secondary action. In this paper, applying this phenomenon in cycloid drive, a new type of double-enveloping cycloid drive is generated based on gear geometry theory, and the torsional stiffness is calculated. The new conjugated tooth profile is composed by an external cycloid tooth profile and a new generated internal ring gear tooth profile. The main characteristic of the new tooth profile is that there are double contact lines simultaneously between on tooth pair in a certain meshing area. In this paper, firstly the generation method of the new conjugated tooth profile is present, and the meshing characteristics are investigated. Secondly, the torsional stiffness calculation model for double-enveloping cycloid drive is established. The normal stiffness, the arm length of the meshing force and the torsional stiffness are calculated. Finally, based on a numerical example, the calculation results are present, and the torsional stiffness of double-enveloping cycloid drive is compared with that of the conventional cycloid drive both on single tooth pair and whole gear mesh.
This research report discusses how to derive a path of contact on a face gear. A sample was manufactured, in which tooth modification is taken into account, and the sample was investigated as to whether it is robust against alignment errors. It has been verified that the assembly operation can be improved in mass production line.
In a two-stroke cycle engine, the piston and its piston rings slide over the cylinder wall and its cylinder ports. This study investigates how those piston rings project and catch in cylinder ports, and examines the effects of engine speed and round chamfered ports on projection and catching. Strain gauges were installed on the bottom of the top and second rings, over the intake and exhaust ports. The variation of strain was then observed over each engine cycle. The piston behavior was then analyzed to consider ring projection and catching in ports. Results suggest the rings indeed project and catch in the ports, immediately after the piston moves from the intake port side to the exhaust port side, and again when the piston continues moving along the exhaust port on the upward stroke. Engine speed had a minimal effect on this projection and catching. However, larger round chamfered ports might decrease the second ring projection and catching in the exhaust port.
In this study, steel rollers and gears were treated by the cavitation peening with processing times of 1 min and 5 min, and they were fatigue-tested using a roller testing machine and a gear testing machine. The surface hardness and the compressive residual stress of the rollers and gears were increased by the cavitation peening, while, the surface roughness of the cavitation-peened rollers and gears was almost the same as that of the non-peened ones. As a result of the fatigue tests, the fatigue strength of the test specimens were improved by the increase in surface hardness due to the cavitation peening, and those without the increase in surface hardness were not increased so much. The fatigue strength of the cavitation-peened test specimens was similar to that of the shot-peened ones obtained by the previous fatigue tests. This study revealed that the cavitation peening is expected to put to practical use in the improvement in fatigue strength of steel gears.
In stereolithography, parts are fabricated by curing photopolymeric resins with light. The application of stereolithography can now be extended to a very small scale. The process, called microstereolithography, can fabricate parts on a microscale without any further consideration of geometry complexity. In particular, projection-type microstereolithography can perform quite rapid fabrication that cures a specific cross section in one exposure to light without movement. However, in the case where the light source has a nonuniform intensity or an aberration caused by its optics, the part might have some distortion, and this is commonly the case. Because the material experiences shrinkage when it is cured, the light intensity over the entire cross section should be uniform. This study utilizes a Dynamic Mirror Device, which is mainly used for beam shaping, to control the beam intensity also. This control makes the beam intensity profile flat and reduces the distortion to a great degree. This paper presents the concept of an exposure time control method that makes the beam intensity uniform, and it also presents some experimental results.
For generating holes on carbon fiber reinforced plastic (CFRP) composites, drilling is one of the most commonly applied processes. However, machining defects caused by delamination occur frequently during this kind of process. To realize defect-free drilling of CFRP composites, we propose to apply feedback control based on thrust force, because the degree of thrust force is directly related to the occurrence of delamination. In this study, we have developed a machining system which can be operated at a predetermined cutting force by changing the feed rate based on cutting force signals measured by a piezoelectric cutting dynamometer, and the basic performances of the developed system have been confirmed through evaluation tests. In addition, drilling tests with the developed system were carried out, in order to consider the possibility of defect-free drilling of CFRP composites with feedback control based on cutting force. In the drilling tests, we used a conventional twist drill, and the work-piece was a quasi-isotropic laminate composite, which is a stack of unidirectional plies consisting of high-strength carbon fibers T800S and high-toughness matrix resin 3900-2b. We have confirmed, under specific conditions through drilling tests, that the feedback control process can machine through-holes without causing significant machining defects on CFRP composites.
To reduce the management cost and environmental load of water-soluble coolants, the authors have been studying a metabolic system for these coolants. In the metabolic system, water resources are recovered from water-soluble coolant waste and reused as a diluent for a new coolant. In this study, we focused on the recycled use of amine-free water-soluble coolants. Most water-soluble coolants contain alkanolamines for corrosion inhibition and pH maintenance. However, alkanolamines are difficult to eliminate from water-soluble coolants in waste treatment by both chemical and physical processes. Some amine-free water-soluble coolants have been developed and are commercially available, and are regarded as environmentally friendly cutting fluids compared with conventional coolants. We examined the recyclability, lubrication, cooling performance, as well as the ability change of amine-free water-soluble coolants. The amine-free water-soluble coolants showed an equivalent lubrication and cooling performance as amine-containing coolants. The recycling processing time of the amine-free coolants decreased by half with our recycling process. The fluctuations in Brix and pH during long-time usage have also been similar to those in conventional coolants. However, the corrosion inhibition performance of amine-free coolants has been inferior to that of amine-containing coolants.
This paper presents a flexure revolute joint with a large range of motion which can be used as a joint in a parallel robot with a large workspace. We proposed a new structure of flexure revolute joint. The joint consists of leaf springs which are symmetrically arranged between two frames. The shape of the frame is like a spiral stairs. Arrangement of leaf springs was proposed taking into consideration the axis drift and stiffness characteristics of the joint while achieving a large range of motion. Characteristics of the proposed joint were investigated by Finite Element Analysis (FEA) and experiments. A planar parallel robot with two degrees of freedom using the proposed joints was designed and fabricated. Its workspace, position repeatability and stiffness were experimentally investigated.
The meshing model and the method used for estimation of sliding loss in a parallel-axis gear pair are presented. First the sliding loss model for single tooth meshing spur gear is constructed. The sliding loss is attributed to the deviation in direction of force from the line of action due to friction. Afterwards the sliding loss of a helical gear pair is considered. The helical gear is modeled as the multi-section spur gears aligned slantwise along with base helix angle. Thus the sliding loss of each section can be considered as same as the loss of the spur gear pair. Then the total sliding loss is estimated by combining the losses of all sections together. To verify the method, the estimated results were compared with the experimental results and estimated results done by the other researchers. The estimated results agree with the experimental results. The sliding loss increases with loads and speeds. The gear with larger module has higher sliding loss. Increasing the helix angle, the sliding loss will be increased, but increasing the transverse pressure angle the sliding loss will be decreased. Various empirical formulae of friction coefficient are used in this paper, and the accuracies of various formulae are shown.
Ultralow temperature environments are important for advanced scientific research areas, for example, chemical analysis technology. Some devices need to be operated in an ultralow temperature environment. However, actuators used in such an environment have low output power. As a result, some applications in an ultralow temperature environment have limited functions. This research aims to achieve a piezoelectric actuator having high output power at an ultralow temperature. A bolt-clamped Langevin-type transducer for an ultrasonic motor used in an ultralow temperature environment is proposed. The piezoelectric materials used in the transducer are affected by thermal stress when the temperature decreases from room temperature to an ultralow one. As a result, the materials break down or the performance of the transducer decreases. Thermal stress was simulated with the finite element method using some non-linear properties of materials in the transducer. The influence of the stress was evaluated by driving a transducer at an ultralow temperature obtained by using helium gas. An ultrasonic motor for use at an ultralow temperature was fabricated and evaluated. The maximum diameter and the height of the motor are 22 and 30.5 mm, respectively. The motor was successfully rotated at an ultralow temperature.
A simplified model related to microtopography on CMP pad and prediction of real contact area between the pad and wafers is presented in this paper. The model has been developed on the basis of the analysis of the pad surface roughness and contact mechanics. The bearing area curve, representing tribological properties of the surface, is used to formulate the model. The pad microtopography which is expressed in the model is uniform and simple. Particularly, the important characteristics of the pad microtopography for the CMP process are emphasized in the model. It provides more convenient way to perceive the situation of the pad surface during the CMP process. The progress of the pad surface wear and the real contact area can be easily taken and connected each other by using the model. The model is also verified by comparing the tendency of actual removal rates with those theoretically anticipated. Finally, authors could get the efficient link between the pad surface wear and the real contact area, which results in a strong tool to understand the fundamental CMP mechanism of material removal.
In the present paper, tribological properties of DLC films deposited by UBM sputtering were investigated by rolling contact friction tests under approximately 2.86GPa of high contact pressure. DLC films were deposited by UBM sputtering under substrate bias voltages such as 0 to -300V. Friction coefficients of DLC films deposited under low bias voltage were unstable. And it was found that this unstable friction coefficient occurred when the counterpart ball began to contact with sliding. From observation of the cross section of DLC films after occurring unstable friction coefficients using SEM, the films were fractured in the a-C:H or Cr/C gradient interlayer. Moreover, these fractures had already occurred before sliding. DLC films were thought to be damaged by rolling with slightly sliding contact with high pressure in very short time. It was clear that DLC film deposited under substrate bias voltage -300V has the best performance for high contact pressure. And the change in Young's modulus of Cr/C gradient interlayer at the interface continuously seemed to be important to prevent the fracture of DLC film due to high pressure.
Most of the existing service robots employ electric actuators with harmonic reducers to drive the upper arm joints. Due to the limited size of elbow joint and shoulder joint, such actuators need to be small. To match the capability of human arm, they also need to be powerful. Such requirements on the actuators lead to high cost. In this work, a new joint actuation system is presented. Based on biomimetic approach, the system is arranged along the length of the upper arm as well as in the upper body. The system represents the functions of human biceps and triceps for elbow joint and of the shoulder muscles including deltoid, pectoralis major, latissimus dorsi and etc. The space for the elbow muscles and the shoulder muscles is much larger than that of each joint. With relieved spatial constraint on the actuation system, economic design is possible with standard industrial components. The new system consists of gears, a timing belt, pulleys and a feed-drive (screw-nut). The feed drive offers high joint torque with high reduction as well as self-locking. Since friction loss is inherent to the feed drive, an attempt is made for design improvement with TRIZ approach. Technical contradiction analysis of TRIZ on the 1st design suggests several invention principles including ‘Nesting’ that was implemented in the 2nd design. Experiments show that the 2nd design is about 330% more efficient than the 1st design.
The overhead pantograph for the high speed train is a mechanical and electrical part mounted on the train roof to supply the train with electrical power from the catenary system. So, the interaction between the pantograph and the catenary system is very important to prevent contact loss and overload to the contact wire. The contact force generally includes the static force by pneumatic pressure supplied from the compressor and the aerodynamic force on the pantograph structure by increasing speed. The on-line test for evaluation of pantograph performance was executed on the Kyoung-Bu high speed line by measuring the contact force between the contact strip of the pantograph and the contact wire of the catenary system. This paper introduces the methodology of measuring system and the procedure of analysis for the final evaluation results, and shows that it was useful and acceptable considering the environmental conditions of the on-line test with the commercial line, not test track.
Rotating machinerys have problems at bearings to support a rotor such as seismic ACROSS transmitters. The ACROSS ( Accurately Controlled Routinely Operated Signal System ) is a new technical method to detect subtle changes in the physical state of Earth's structure using precise and continuous signal transmitter-receiver systems. The signal is a type of sinusoidal elastic waves, which is generated by a large unbalanced rotor. The rotor is supported by rolling contact bearings. The bearings in the transmitters, large heat generation occur caused by the high frictional loss. In order to solve this problem, use of hydrostatic gas bearings was studied. Effectiveness of the gas bearings was clarified by the test for decrease of frictional loss. However, large gas flow rate was required to support large load. In this paper, asymmetric supply type hydrostatic journal gas bearing is developed to support large load with decreasing of gas flow rate. Numerical calculation of the bearing characteristics is conducted and the results are compared with previously studied and conventional bearing. The test bearing and a rig were made and the test was conducted. Availability of the bearing is verified by the test.
The present study describes tribological properties of copper based porous alloy containing nano-sized sulfide particles. The porous alloy was fabricated with sintering on the steel plate using the developed powders consisted from Cu with dispersed sulfides. The micro structure of the alloys consisted from micro sized open pores and sintered particles. The measurement of tribological properties were carried out with a ring on disc testing apparatus with a steel ring as the mating specimen. First, comparison of friction behavior between the developed material and the lead-bronze alloy used as traditional materials for bearings are evaluated. As results, the friction coefficient of the developed material was stable and lower than that of the lead one and larger adhesion resulted in the higher friction resistance was found on the ring surface. In order to enhance porous structure on the reduction and stabilization of the friction resistance, graphite powder was penetrated into the pores by rubbing with the graphite rod. It was found that the further reduction of friction resistance was obtained.
In the present paper, we describe the measurement of brain activation response during lathe operation in a VR lathe environment and an actual lathe environment by near-infrared spectroscopy. In the frontal lobes and the motor cortex, oxyHb tended to increase during the operation in both the VR lathe environment and the actual lathe environment. The results show that the brain activation response during the performance of lathe operation in the VR lathe environment was very similar to that which occurs during lathe operation in the actual lathe environment.
Wireless driving of a micromirror device is achieved by electromagnetic excitation tuned to the mechanical resonance of the mirror rotation. The micromirror used is designed for low-voltage-driving. Static mirror rotation angle is 7.7 deg. at 12 V bias. The micromirror is connected to a coil for receiving the driving energy through electromagnetic induction. Magnetic field of 19.3 mT at the surface of the first coil induces 0.6 V at the second coil that is 24 mm apart from the first coil. An LC resonance circuit is incorporated in the second coil system to enhance the induced voltage. The LC resonance frequency is tuned to induce the mechanical resonance of the micromirror device. When the separation distance between the first and second coils is 24 mm, the voltage induced by the LC resonance is 1.43 V. Mirror rotation angle is 0.3 deg. for half stroke is achieved. It is expected that the rotation angle is expanded by increasing the Q factors of the electrical circuit and mechanical resonance of the micromirror. These will be achieved by reducing the loss in the electrical circuits and packaging the micromirror device in vacuum with hermetic seal.
The residual stress at the thread root of a bolt is one of the major factors influencing the fatigue strength. Some hypotheses have been proposed to predict the fatigue strength from the local stress on the thread root. However, these have not yet been verified quantitatively since the residual stress induced by thread rolling and locally acting on the thread root can neither be measured nor estimated with sufficient accuracy. This study aims to clarify the relationship between the fatigue strength and the local stress around the thread root taking into account the effect of residual stress. For this purpose, a method is proposed where the residual stress, which can be estimated by FE analysis, is induced on the thread root of an axi-symmetrical bolt in bolt/adapter assembly model by preloading. The results from fatigue test show that the preloaded specimen has the higher fatigue strength than non-preloaded one. This shows that the compressive residual stress could improve the fatigue strength as anticipated from Yoshimoto's hypothesis. On the other hand, the fatigue strength of a bolt calculated by FE analysis based on the local stress distribution using Ishibashi's hypothesis was smaller than that of notch-free specimen. However, experimental investigation showed that the bending stress are acting on the bolt thread root due to the construction of threaded adapter or the fatigue test device. Finally, it can be concluded that the fatigue strength of the axi-symmetrical bolt model can be predicted by using the hypotheses taking into account the bending effect.