• Title/Summary/Keyword: Friction torque

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A Study on the Flow Path Position Design of Waviness Friction Pad for Drag Torque Reduction in Wet Type DCT (파형 습식클러치의 드래그 토크 저감을 위한 파형내 유로 위치 설정 설계 연구)

  • Cho, Junghee;Han, Juneyeol;Kim, Woojung;Jang, Siyoul
    • Tribology and Lubricants
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    • v.33 no.1
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    • pp.1-8
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    • 2017
  • Drag torque reduction in a wet clutch pack is a key aspect of the design process of the dual clutch transmission (DCT) system. In order to reduce the drag torque caused by lubricant shear resistance, recently developed wet clutch pack systems of DCT, as well as automatic transmission and other four-wheel drive (4WD) couplings, frequently utilize wavy wet clutch pads. Therefore, wavy shape of friction pad are made on the groove patterns like waffle pattern for the reduction of drag torque. Additionally, the groove patterns are designed with larger channels at several locations on the friction pad to facilitate faster outflow of lubricant. However, channel performance is a function of the waviness of the friction pad at the location of the particular channel. This is because the discharge sectional area varies according to the waviness amplitude at the location of the particular channel. The higher location of the additional channel on the friction pad results in a larger cross-sectional area, which allows for a larger flow discharge rate. This results in reduction of the drag torque caused by the shear resistance of DCTF, because of marginal volume fraction of fluid (VOF) in the space between the friction pad and separator. This study computes the VOF in the space between the friction pad and separator, the hydrodynamic pressure developed, and the shear resistance of friction torque, by using CFD software (FLUENT). In addition, the study investigates the dependence of these parameters on the location and waviness amplitude of the channel pattern on the friction pad. The paper presents design guidelines on the proper location of high waviness amplitude on wavy friction pads.

A Performance Improvement Method of PMSM Torque Control Considering DC-link Voltage Variation (DC-link 전압변동을 고려한 PMSM 토크제어의 성능 향상 방법)

  • Lee, Jung-Hyo;Won, Chung-Yuen
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.11
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    • pp.112-122
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    • 2014
  • This paper proposes a PMSM torque control method considering DC-link voltage variation and friction torque. In general EV/HEV application, two dimensions look-up table(2D-LUT) is used for reference current generation due to its stable and robust torque control performance. Conventionally, this 2D-LUT is established by flux-torque table to overcome the DC-link voltage variation. However, the flux table establishment is more complex than the speed table establishment. Moreover, one flux data reflects several speed conditions in variable DC-link voltage, friction torque cannot be considered by using the flux table. In this paper, speed-torque 2D-LUT is used for current reference generation. With this table, PMSM torque control is well achieved regardless of DC-link voltage variation by the proposed control method. Simulation and experimental results validate improvement of torque control error through friction torque compensation.

Study on Torque Analysis of Micro-Electromagnetic Clutch by Using FEM (FEM을 이용한 Micro-Electromagnetic Clutch 토크해석)

  • Piao Changhao;Cho Chongdu;Kim Myunggu;Pan Qiang
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.2
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    • pp.60-65
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    • 2005
  • This study tries to analyzes the static friction torque that generated in a micro-electromagnetic clutch by using FEM. For the purpose of design change and optimization of the micro-electromagnetic clutch, the static friction torque prediction is very important. We construct the axi symmetric FEM model for analyze the static friction torque and the real material properties are substituted to the FEM model. For a test, predicted static friction torque is compared with experimental one to discuss the rationality of torque analysis process. The analytical result agrees well to experimental data. explaining the validity of the mathematical process and FEM model.

A Nonlinear Friction Torque Compensation of Servo System with Double Speed Controller (이중 속도 제어 구조에 의한 서보 제어기의 비선형 마찰 토크 보상)

  • Lee Dong-Hee;Choi Cheol;Kim Cheul-U
    • The Transactions of the Korean Institute of Power Electronics
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    • v.9 no.6
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    • pp.612-619
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    • 2004
  • Servo motor systems with ball-screw and timing-belt are widely used in NC, robot, FA and industrial applications. However, the nonlinear friction torque and damping effect in machine elements reduce the control performance. Especially tracking errors in trajectory control and very low velocity control range are serious due to the break-away friction and Stribeck effects. In this paper, a new double speed controller is proposed for compensation of the nonlinear friction torque. The proposed double speed controller has outer speed controller and inner friction torque compensator. The proposed friction torque compensator compensates the nonlinear friction torque with actual speed and speed error information. Due to the actual information for friction torque compensator without parameters and mathematical model of motor, proposed compensator is very simple structure and the stability is very high. The proposed compensator is verified by simulation and experimental results.

Evaluation of Running Friction Torque of Tapered Roller Bearings Considering Geometric Uncertainty of Roller (롤러의 형상 불확실성을 고려한 테이퍼 롤러 베어링의 구동마찰토크 평가)

  • Jungsoo Park;Seungpyo Lee
    • Tribology and Lubricants
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    • v.39 no.5
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    • pp.183-189
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    • 2023
  • A bearing is a mechanical component that transmits rotation and supports loads. According to the type of rotating mechanism, bearings are categorized into ball bearings and tapered roller bearings. Tapered roller bearings have higher load-bearing capabilities than ball bearings. They are used in applications where high loads need to be supported, such as wheel bearings for commercial vehicles and trucks, aircraft and high-speed trains, and heavy-duty spindles for heavy machinery. In recent times, the demand for reducing the driving friction torque in automobiles has been increasing owing to the CO2 emission regulations and fuel efficiency requirements. Accordingly, the research on the driving friction torque of bearings has become more essential. Researchers have conducted various studies on the lubrication, friction, and contact in tapered roller bearings. Although researchers have conducted numerous studies on the friction in the lips and on roller misalignment and skew, studies considering the influence of roller shape, specifically roller shape errors including lips, are few. This study investigates the driving friction torque of tapered roller bearings considering roller geometric uncertainties. Initially, the study calculates the driving friction torque of tapered roller bearings when subjected to axial loads and compares it with experimental results. Additionally, it performs Monte Carlo simulations to evaluate the influence of roller geometric uncertainties (i.e., the effects of roller geometric deviations) on the driving friction torque of the bearings. It then analyzes the results of these simulations.

Heat Treatment of Stator Core in Permanent Magnet Type Motor for Reduction of Friction Torque and Analysis of Their Cause (영구자석형 모터의 프릭션 토크 저감을 위한 고정자 철심의 열처리 및 발생원 분석)

  • Ha, Kyung-Ho;Lim, Yang-Su;Kwon, Oh-Yeoul;Kim, Ji-Hyun;Kim, Jae-Kwan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.10
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    • pp.1752-1758
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    • 2008
  • This paper deals with the reduction of friction torque in permanent magnet motors by using the heat treatment of stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress acting on the edge of stator tooth induces significant plastic and elastic deformation and then cause the change of magnetization properties. Then, the mechanical and magnetic unbalance in the sheared region of stator tooth produced by material cutting has influence on the friction torque. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation, and then proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

Effects of Friction Plate Area and Clearance on the Drag Torque in a Wet Clutch for an Automatic Transmission (클러치 드래그 토크에 미치는 마찰재 면적 및 클리어런스의 영향)

  • Ryu, Jin Seok;Sung, In-Ha
    • Tribology and Lubricants
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    • v.30 no.6
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    • pp.337-342
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    • 2014
  • The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrow gap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects of the friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of air and oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speed increases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. The clearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearance causes a decrease in shear stress; thus, the drag torque also decreases according to Newton's law of viscosity. An observation of the effect of the area of contact between transmission fluid and friction plate shows that the drag torque increases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of the fluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum size of the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It is expected that the results from this study can be very useful as a database for clutch design and to predict the drag torque for the initial design with respect to various clutch parameters.

A Study on Setting of Torque for Compressor Jointing Bolt (컴프레서 체결용 볼트의 적정 토크 설정에 관한 연구)

  • Kong, Yu Sik;Kim, Tae Wan
    • Tribology and Lubricants
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    • v.29 no.5
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    • pp.286-290
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    • 2013
  • When a threaded fastener is tightened, the torque-tension relationship is highly sensitive to two friction components: thread friction and head friction. In this study, we carried out friction experiments and analyses to determine the optimum clamping torque setting for bolt joints. First, we measured the coefficients of thread friction and head friction under the same running conditions of the bolt clamping process for lubricated and non-lubricated bolts. We also measured axial tension through bolt clamping tests using lubricated and non-lubricated bolts attached to a strain gauge. Finally, we compared the experiment and theoretical results.

Accuracy of spring-style and friction-style mechanical implant torque wrench (스프링형과 마찰형 기계식 임플란트 토크 렌치의 정확도에 관한 연구)

  • Cha, Dong-Hee;Oh, Sang-Chun
    • The Journal of Korean Academy of Prosthodontics
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    • v.54 no.1
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    • pp.8-13
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    • 2016
  • Purpose: The aim of this study was to compare the accuracy of two different styles of mechanical implant torque wrenches before and after sterilization and repeated use. Materials and methods: Thirty new spring-style and friction-style mechanical implant torque wrenches from five different manufacturers were selected as subjects of study and assessed in terms of accuracy. Three manufacturers produced, spring-style (Dio, Neobiotech, Osstem) torque wrenches, and other three manufactures produced friction-style (Dentium, Osstem, Shinhung) torque wrenches. The procedure of target torque measurement was performed 10 times for each device and a digital torque gauge (MGT-12, Mark-10 Corp, USA) was used to record the measurements. All torque wrenches were used repeatedly for 20 times and then sterilized. This whole procedure was repeated 100 times and all torque wrenches were retested. The collected data was analyzed using a SPSS Statistics Analysis program to evaluate the accuracy of the torque wrenches and Mann-Whitney-U test was used for a comparative analysis. Results: After sterilization and repeated use procedure, results did not show any significant difference between error values in the spring-style torque wrench group. However, the results demonstrated an increase in error values within the friction-style torque wrench group (P<.05). Conclusion: There was no difference between the accuracy of new spring-style torque wrenches before and after 100 cycles of sterilization and repeated use (P>.05). There was significant difference between the accuracy of new friction-style torque wrenches before and after 100 cycles of sterilization and repeated use (P<.05). Within the limitation of this study, spring-style torque wrenches were more accurate than friction-style torque wrenches in delivering target torque values.

Modeling of High-speed Tapping Touque Considering Friction Force (마찰력을 고려한 고속탭핑 토크 모델링)

  • Lee, Don-Jin;Gang, Ji-Ung;Jeon, Hyeon-Bae;Kim, Seon-Ho;An, Jung-Hwan
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.11
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    • pp.67-73
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    • 2001
  • This paper aims at developing a torque model for the high-speed tapping with small-diameter taps. As recent industries such as automobile and information technology grows, taps smaller than 5mm in diameter are needed much more. In that occasion, the friction force between a tap surface and a workpiece plays much more important role in the tapping torque than in he larger tapping. Tapping mechanism was analysed based on the tap geometry. It has two steps : one is a forward cutting composed of the chamfered threading and full threading and the other is the backward cutting. The torque by the cutting force in the chamfered threading is calculated using the cutting area and the specific cutting force while the torque by the friction force, which is rather dominant than the cutting force both in the full threading and in the backward cutting, is calculated using the normal force on the threads and the friction coefficient. The experiment has shown that the results by the proposed torque model fit quite well with the acutal measurements within the error of 10%.

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