The Experts below are selected from a list of 1107 Experts worldwide ranked by ideXlab platform
Yohichi Nakao - One of the best experts on this subject based on the ideXlab platform.
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Dynamic characteristics of spindle with water-lubricated Hydrostatic Bearings for ultra-precision machine tools
Precision Engineering, 2020Co-Authors: Dmytro Fedorynenko, Rei Kirigaya, Yohichi NakaoAbstract:Abstract A key component of ultra-precision machine tools is the spindle. The motivation for this study was to improve machining accuracies in precision cutting and grinding by pursuing improvements in the spindle characteristics by designing a sophisticated spindle with water-lubricated Hydrostatic Bearings. The static bearing stiffness of the developed spindle was investigated in previous studies. In addition to the static bearing stiffness, the dynamic characteristics regarding bearing stiffness also affect significantly on the machining results. In this study, dynamic characteristics of the developed spindle with water-lubricated Hydrostatic Bearings were investigated via simulations and experiments. Not only bearing dynamics but also rotor dynamics were considered in this study. In the simulation studies, the spindle dynamic characteristics were analysed based on the transfer matrix method. A spindle rotor supported with Hydrostatic Bearings was represented by discrete sections of the rotor. The mathematical model of transverse linear vibrations of the spindle rotor was derived with distributed parameters for these discretized rotor sections. As a result of the analysis on the amplitude-frequency characteristic, radial displacements of the rotor due to bearing displacement and bending deformation were defined. Then, the frequency characteristics were represented with Nyquist plots. Resonant frequencies and amplitudes formation in the transverse vibration of the rotor were determined. The influence of rotor bending deformations on spindle compliance was assessed. Furthermore, the study examined the influences of the supply pressure of the lubricating fluid, radial clearance and journal diameter of the Hydrostatic Bearings on the amplitude of the rotor vibration, and the resonance frequency of the system. Furthermore, the dynamic characteristics of the spindle were examined experimentally. The simulation results were in good agreement with the actual spindle dynamics obtained experimentally. The influence of the structural parameters of the rotor and the operating parameters of the Bearings on the spindle dynamic characteristics was also determined. It was verified that the amplitude of the vibration of the rotor overhang part was dominantly affected not by bearing stiffness but by bending stiffness of the bearing journal of the front bearing and the length of the rotor overhang. Then it was verified that the resultant displacement of the rotor in the radial direction due to the influence of the bearing characteristics and the structural effect of the rotor is significantly small. Practical recommendations to improve the spindle design in terms of the dynamic characteristics of the spindle with water-lubricated Hydrostatic Bearings were also derived.
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Thermal Characteristics of Spindle Supported with Water-Lubricated Hydrostatic Bearings
International Journal of Automation Technology, 2019Co-Authors: Yohichi Nakao, Dmytro Fedorynenko, Rei Kirigaya, Akio Hayashi, Kenji SuzukiAbstract:Characteristics of a spindle supported with water-lubricated Hydrostatic Bearings were experimentally investigated. In particular, this paper focuses on the thermal characteristics of the spindle. The flowrates of water as the lubricating fluid were measured separately for the radial and thrust Bearings, in relation to the supply pressure. Fluid power losses owing to pressure losses of the lubricating fluid were then introduced. Furthermore, the power losses owing to the water viscosity were determined by measuring the spindle torque and angular velocity. The experiments revealed that the total power loss of the spindle is approximately 300 W. The cooling effect of the lubricating water was then examined by introducing a temperature increase between the supply and drain water. The experimental results verified that the water temperature increased by approximately 0.8°C, at a spindle speed of 3000 min-1. Based on the temperature increase of the water, the power removed from the spindle by the water flow was estimated. By comparing the generated total power loss and the power transferred by the water flow, the cooling efficiency of the flow of lubricating-water was defined in this paper. If the cooling efficiency is 100%, the temperature change of the spindle can be zero regardless of the power loss, achieving ideal thermal stability of the spindle. Experimental results revealed that the cooling efficiency of the tested spindle was over 80%. This indicates that the flow of water as a lubricating fluid removes generated heat from the spindle effectively, and achieves improved thermal stability of the spindle.
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Effects of Shaft-Bore Water Flow Cooling of High-Speed Spindle Supported With Water-Lubricated Hydrostatic Bearings on Thermal Stability
Volume 3A: Fluid Applications and Systems, 2019Co-Authors: Yohichi Nakao, Dmytro Fedorynenko, Tsubasa Yaguchi, Junpei KusuyamaAbstract:Abstract In this paper, the thermal stability of a spindle with water-lubricated Hydrostatic Bearings was investigated. In order to improve the thermal stability of the spindle, a center bore water cooling structure was designed in the rotor. Influences of the center bore water cooling on not only thermal stability but also temperature control performance of the spindle was studied via simulations and experiments. Power losses due to water flows in the spindle were considered. Based on a derived lumped parameter model, the temperature changes of the water flow and spindle were predicted. As used in many machine tool components, it was verified that the center bore cooling are effective to improve the thermal stability of the spindle. An influence of structural change of the rotor due to the center bore on the heat capacity and time constant was investigated. As a result, the time constant in terms of the thermal characteristics is decreased due to the center bore structure. Because of this feature, the temperature control performance can be improved.
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Ultra-Precision Machine Tool, Bearing Stiffness
2015Co-Authors: Yohichi Nakao, Fumiyuki Kobayashi, Yuji SagesakaAbstract:Spindles used for recent diamond turning machines are typically supported by Hydrostatic Bearings. Especially, air Hydrostatic Bearings are the most common because of low viscosity of air. Low viscosity of lubricant fluid is an important requirement for operating the spindle in a range of higher rotational speeds. However, from a stiffness viewpoint of the Bearings, higher compressibilit
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Design of Short-Pipe Restrictor of Hydrostatic Thrust Bearings
Volume 3: Design Materials and Manufacturing Parts A B and C, 2012Co-Authors: Yohichi Nakao, Shota Nakatsugawa, Masataka Komori, Kenji SuzukiAbstract:High stiffness Hydrostatic Bearings are needed in order to achieve precise motions of the machine components of ultra-precision machine tools or other precision machines. Design procedure of restrictors of Hydrostatic thrust Bearings, making bearing stiffness maximize under given conditions, is considered in the paper. In particular, the paper focuses on design of short pipe restrictors that are used in the Hydrostatic thrust Bearings in many industrial applications. Derived mathematical model predicting load capacity and stiffness of the Hydrostatic Bearings with short pipe restrictors are verified by compared with experimental results. Based on the derived mathematical model, an optimum condition of a ratio between the diameter and length of the short pipe restrictor is then derived. Designed short pipe restrictors are used in a water Hydrostatic thrust bearing. Then the experimental results show that the bearing stiffness significantly increased. It is noted that the optimum condition of the restrictors is represented by defined non-dimensional parameters.Copyright © 2012 by ASME
Dmytro Fedorynenko - One of the best experts on this subject based on the ideXlab platform.
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Dynamic characteristics of spindle with water-lubricated Hydrostatic Bearings for ultra-precision machine tools
Precision Engineering, 2020Co-Authors: Dmytro Fedorynenko, Rei Kirigaya, Yohichi NakaoAbstract:Abstract A key component of ultra-precision machine tools is the spindle. The motivation for this study was to improve machining accuracies in precision cutting and grinding by pursuing improvements in the spindle characteristics by designing a sophisticated spindle with water-lubricated Hydrostatic Bearings. The static bearing stiffness of the developed spindle was investigated in previous studies. In addition to the static bearing stiffness, the dynamic characteristics regarding bearing stiffness also affect significantly on the machining results. In this study, dynamic characteristics of the developed spindle with water-lubricated Hydrostatic Bearings were investigated via simulations and experiments. Not only bearing dynamics but also rotor dynamics were considered in this study. In the simulation studies, the spindle dynamic characteristics were analysed based on the transfer matrix method. A spindle rotor supported with Hydrostatic Bearings was represented by discrete sections of the rotor. The mathematical model of transverse linear vibrations of the spindle rotor was derived with distributed parameters for these discretized rotor sections. As a result of the analysis on the amplitude-frequency characteristic, radial displacements of the rotor due to bearing displacement and bending deformation were defined. Then, the frequency characteristics were represented with Nyquist plots. Resonant frequencies and amplitudes formation in the transverse vibration of the rotor were determined. The influence of rotor bending deformations on spindle compliance was assessed. Furthermore, the study examined the influences of the supply pressure of the lubricating fluid, radial clearance and journal diameter of the Hydrostatic Bearings on the amplitude of the rotor vibration, and the resonance frequency of the system. Furthermore, the dynamic characteristics of the spindle were examined experimentally. The simulation results were in good agreement with the actual spindle dynamics obtained experimentally. The influence of the structural parameters of the rotor and the operating parameters of the Bearings on the spindle dynamic characteristics was also determined. It was verified that the amplitude of the vibration of the rotor overhang part was dominantly affected not by bearing stiffness but by bending stiffness of the bearing journal of the front bearing and the length of the rotor overhang. Then it was verified that the resultant displacement of the rotor in the radial direction due to the influence of the bearing characteristics and the structural effect of the rotor is significantly small. Practical recommendations to improve the spindle design in terms of the dynamic characteristics of the spindle with water-lubricated Hydrostatic Bearings were also derived.
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Thermal Characteristics of Spindle Supported with Water-Lubricated Hydrostatic Bearings
International Journal of Automation Technology, 2019Co-Authors: Yohichi Nakao, Dmytro Fedorynenko, Rei Kirigaya, Akio Hayashi, Kenji SuzukiAbstract:Characteristics of a spindle supported with water-lubricated Hydrostatic Bearings were experimentally investigated. In particular, this paper focuses on the thermal characteristics of the spindle. The flowrates of water as the lubricating fluid were measured separately for the radial and thrust Bearings, in relation to the supply pressure. Fluid power losses owing to pressure losses of the lubricating fluid were then introduced. Furthermore, the power losses owing to the water viscosity were determined by measuring the spindle torque and angular velocity. The experiments revealed that the total power loss of the spindle is approximately 300 W. The cooling effect of the lubricating water was then examined by introducing a temperature increase between the supply and drain water. The experimental results verified that the water temperature increased by approximately 0.8°C, at a spindle speed of 3000 min-1. Based on the temperature increase of the water, the power removed from the spindle by the water flow was estimated. By comparing the generated total power loss and the power transferred by the water flow, the cooling efficiency of the flow of lubricating-water was defined in this paper. If the cooling efficiency is 100%, the temperature change of the spindle can be zero regardless of the power loss, achieving ideal thermal stability of the spindle. Experimental results revealed that the cooling efficiency of the tested spindle was over 80%. This indicates that the flow of water as a lubricating fluid removes generated heat from the spindle effectively, and achieves improved thermal stability of the spindle.
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Effects of Shaft-Bore Water Flow Cooling of High-Speed Spindle Supported With Water-Lubricated Hydrostatic Bearings on Thermal Stability
Volume 3A: Fluid Applications and Systems, 2019Co-Authors: Yohichi Nakao, Dmytro Fedorynenko, Tsubasa Yaguchi, Junpei KusuyamaAbstract:Abstract In this paper, the thermal stability of a spindle with water-lubricated Hydrostatic Bearings was investigated. In order to improve the thermal stability of the spindle, a center bore water cooling structure was designed in the rotor. Influences of the center bore water cooling on not only thermal stability but also temperature control performance of the spindle was studied via simulations and experiments. Power losses due to water flows in the spindle were considered. Based on a derived lumped parameter model, the temperature changes of the water flow and spindle were predicted. As used in many machine tool components, it was verified that the center bore cooling are effective to improve the thermal stability of the spindle. An influence of structural change of the rotor due to the center bore on the heat capacity and time constant was investigated. As a result, the time constant in terms of the thermal characteristics is decreased due to the center bore structure. Because of this feature, the temperature control performance can be improved.
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Accuracy of spindle units with Hydrostatic Bearings
Acta Mechanica et Automatica, 2016Co-Authors: Dmytro Fedorynenko, Serhii Sapon, Sergiy BoykoAbstract:The work is devoted to the research of precision regularities in a spindle unit by the trajectory of the spindle installed on Hydrostatic Bearings. The mathematical model of trajectories spindle with lumped parameters that allows to define the position of the spindle with regard the simultaneous influence of design parameters, geometrical deviations ofform, temperature deformation bearing surfaces, the random nature of operational parameters and technical loads of Hydrostatic Bearings has been developed. Based on the results of numerical modeling the influence of shape errors of bearing surface of Hydrostatic bearing on the statistical characteristics of the radius vector trajectories of the spindle by varying the values rotational speed of the spindle and oil pressure in front Hydrostatic bearing has been developed. The obtained statistical regularities of precision spindle unit have been confirmed experimentally. It has been shown that an effective way to increase the precision of spindle units is to regulate the size of the gap in Hydrostatic spindle Bearings. The new design of an adjustable Hydrostatic bearing, which can improve the accuracy of regulation size gap has been proposed.
E. Urata - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Hydrostatic bearing for water hydraulic servovalve
1999Co-Authors: K. Suzuki, E. UrataAbstract:This paper deals with characteristics of Hydrostatic Bearings used in a water hydraulic servovalve. In this servovalve, the Hydrostatic Bearings support a spool to avoid wear and sticking of spool to the sleeve. Water in the Hydrostatic Bearings is led to a nozzle through the spool clearance and the end of the spool. The Hydrostatic Bearings should have a sufficient spring constant for the supporting. In addition, the Bearings must supply the flow for spool positioning, while minimizing leakage through the clearance between the spool and the sleeve. To satisfy these requirements, one must know precise dimensions of the Hydrostatic bearing and the clearance. Pressure distribution in the clearance and port pressures must be determined in terms of known dimensions. To find the pressure distribution in the clearance, we apply a relaxation method to Reynolds' equation. An iterative method is applied to find port pressures corresponding to the pressure distribution. Results of the calculation are given in nondimensional form. These data will be used for the design of the Hydrostatic bearing in the water hydraulic servovalve.
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Development of a Water Hydraulic Servovalve
JSME International Journal Series B, 1998Co-Authors: E. Urata, S. Miyakawa, Yohichi Nakao, Chishiro Yamashina, Yuhichi Usami, Masao ShinodaAbstract:An electrohydraulic servovalve that uses fresh water as a pressure medium (water hydraulic servovalve) is developed. conventional electrohydraulic servovalve cannot be operated with such a hostile fluid. In this paper, we explain the structure and functions of components, and the relationship between them, as well as the developmental procedure of the water hydraulic servovalve. The basic idea for the servovalve is to support the spool of the valve with Hydrostatic Bearings and to lead the water from the Bearings to the flapper-nozzle system. The Hydrostatic Bearings constitute a laminar restriction that takes the place of the turbulent restriction in the conventional flapper-nozzle system. We also explain the design procedure of the Hydrostatic bearing in the valve and the relationship between electromagnetic elements and fluidic elements. The water hydraulic servovalves fabricated show good characteristics of smooth motion, endurance and controllability, as well as good dynamic characteristics.
Kenji Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Thermal Characteristics of Spindle Supported with Water-Lubricated Hydrostatic Bearings
International Journal of Automation Technology, 2019Co-Authors: Yohichi Nakao, Dmytro Fedorynenko, Rei Kirigaya, Akio Hayashi, Kenji SuzukiAbstract:Characteristics of a spindle supported with water-lubricated Hydrostatic Bearings were experimentally investigated. In particular, this paper focuses on the thermal characteristics of the spindle. The flowrates of water as the lubricating fluid were measured separately for the radial and thrust Bearings, in relation to the supply pressure. Fluid power losses owing to pressure losses of the lubricating fluid were then introduced. Furthermore, the power losses owing to the water viscosity were determined by measuring the spindle torque and angular velocity. The experiments revealed that the total power loss of the spindle is approximately 300 W. The cooling effect of the lubricating water was then examined by introducing a temperature increase between the supply and drain water. The experimental results verified that the water temperature increased by approximately 0.8°C, at a spindle speed of 3000 min-1. Based on the temperature increase of the water, the power removed from the spindle by the water flow was estimated. By comparing the generated total power loss and the power transferred by the water flow, the cooling efficiency of the flow of lubricating-water was defined in this paper. If the cooling efficiency is 100%, the temperature change of the spindle can be zero regardless of the power loss, achieving ideal thermal stability of the spindle. Experimental results revealed that the cooling efficiency of the tested spindle was over 80%. This indicates that the flow of water as a lubricating fluid removes generated heat from the spindle effectively, and achieves improved thermal stability of the spindle.
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Design of Short-Pipe Restrictor of Hydrostatic Thrust Bearings
Volume 3: Design Materials and Manufacturing Parts A B and C, 2012Co-Authors: Yohichi Nakao, Shota Nakatsugawa, Masataka Komori, Kenji SuzukiAbstract:High stiffness Hydrostatic Bearings are needed in order to achieve precise motions of the machine components of ultra-precision machine tools or other precision machines. Design procedure of restrictors of Hydrostatic thrust Bearings, making bearing stiffness maximize under given conditions, is considered in the paper. In particular, the paper focuses on design of short pipe restrictors that are used in the Hydrostatic thrust Bearings in many industrial applications. Derived mathematical model predicting load capacity and stiffness of the Hydrostatic Bearings with short pipe restrictors are verified by compared with experimental results. Based on the derived mathematical model, an optimum condition of a ratio between the diameter and length of the short pipe restrictor is then derived. Designed short pipe restrictors are used in a water Hydrostatic thrust bearing. Then the experimental results show that the bearing stiffness significantly increased. It is noted that the optimum condition of the restrictors is represented by defined non-dimensional parameters.Copyright © 2012 by ASME
Jakub Łagodziński - One of the best experts on this subject based on the ideXlab platform.
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High-Speed Hermetic Turbogenerator with a Hybrid Bearing System
Journal of Vibration Engineering & Technologies, 2018Co-Authors: Eliza Tkacz, Zbigniew Kozanecki, Jakub ŁagodzińskiAbstract:In the power industry, the most commonly used Hydrostatic Bearings are usually oil lubricated. On the contrary, for a distributed combined heat and power production, in the working machine—a hermetic high-speed turbogenerator—an oil-free bearing system is required. For this purpose, Hydrostatic Bearings lubricated with an organic, oil-free working fluid have been designed. Characterized by its limited lift force, Hydrostatic bearing system can be used in small-power turbomachinery. To expand the functionality of the application, a new type of bearing—a hybrid bearing—was designed, built, and tested. In this new bearing, both Hydrostatic and hydrodynamic effects are combined. In addition, a magnetic thrust bearing has been designed, so that the whole hybrid bearing system is characterized by Hydrostatic, hydrodynamic, and magnetic effects. To confirm the good stability of rotor dynamics, numerical calculations and experimental tests have been conducted. The presented design resulted in good bearing lift and reliability of the bearing system.
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High-Speed Hermetic Turbogenerator with a Hybrid Bearing System
Journal of Vibration Engineering & Technologies, 2018Co-Authors: Eliza Tkacz, Zbigniew Kozanecki, Jakub ŁagodzińskiAbstract:Purpose In the power industry, the most commonly used Hydrostatic Bearings are usually oil lubricated. On the contrary, for a distributed combined heat and power production, in the working machine—a hermetic high-speed turbogenerator—an oil-free bearing system is required. Method For this purpose, Hydrostatic Bearings lubricated with an organic, oil-free working fluid have been designed. Characterized by its limited lift force, Hydrostatic bearing system can be used in small-power turbomachinery. To expand the functionality of the application, a new type of bearing—a hybrid bearing—was designed, built, and tested. In this new bearing, both Hydrostatic and hydrodynamic effects are combined. In addition, a magnetic thrust bearing has been designed, so that the whole hybrid bearing system is characterized by Hydrostatic, hydrodynamic, and magnetic effects. Results To confirm the good stability of rotor dynamics, numerical calculations and experimental tests have been conducted. The presented design resulted in good bearing lift and reliability of the bearing system.
