• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.36-42
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• 2021

This study was conducted to analyze the effect of the gear specification and gear quality corresponding to the macro geometry on the gear transmission error. The two pairs of gears with large and small transmission errors were selected for calculation, and two pairs of gears were manufactured with different gear quality. The test gears were manufactured by two different gear specifications with ISO 5 and 8 gear quality, respectively. The transmission error measurement system consists of an input motor, reducer, encoders, gearbox, torque meter, and powder brake. To confirm the repeatability of the test results, repeatability was confirmed by performing three repetitions under all conditions, and the average value was used to compare the transmission error results. The transmission errors of the gears were analyzed and compared with the test results. When the gear quality was high, the transmission error was generally low depending on the load, and the load at which the decreasing transmission error phenomenon was completed was also lower. Even when the design transmission error according to the gear specification was different, the difference of the minimum transmission error was not large. The transmission error at the load larger than the minimum transmission error load increased to a slope similar to the slope of the analysis result.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.799-806
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• 2007

One method for improving the torque capacity of the CVT is to use a split-powered CVT(SPCVT) to reduce the power transmitted into a continuously variable unit(CVU). A variable bridge SPCVT with two planetary gear units(PGUs), which are composed of a sun gear, a ring gear, and carrier and planetary gears, can minimize the power to the CVU. However, a SPCVT with a conventional CVT should possess a dual mode, which would allow the conventional CVT to be used at high speeds and an additional gear train to be used at low speeds. The inner-spherical CVU(ISCVU) with an inner and outer spherical contact mechanism developed in this study can cover the range from low to high speeds. The rated power and the overall speed ratios were 100 kW and $0.09{\sim}0.36$, respectively. Power efficiency was numerically calculated to be over 90% over the speed ratio range of $0.1{\sim}0.29$. The maximum shear stress at the two contact areas of the rotor pairs, the minimum life and the overall size were estimated to be 700 MPa, 276 kh and $350{\times}350{\times}400mm^3$, respectively. This study shows that an ISCVU and a variable bridge type PGU can realize the SPCVT with a single mode for a vehicle.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.286-293
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• 2004

This paper presents the result of a study on the starter control for a turbo generator. Because a starter in gear box type turbo-generator system is composed of gearbox and brush DC motor, it should be replaced with High Speed Generator(HSG)) in HSG type Turbo-generator. There-ore, it is necessary to design a new starting algorithm and starter. In gearbox type system, brush DC motor is rotated to the designed speed using low voltage-high current battery power. After brush DC motor speed is increased to several times by gearbox, gas turbine engine can be rotated to designed starting speed. If we implement a starter with High Speed Generator(HSG), it is necessary to drive high-speed generator to high-speed motor. High-speed generator with permanent magnet on rotor has a low leakage inductance fur driving high-speed rotation, and it is necessary high DC link voltage for inverter when High-speed generator is driven to high speed. This paper presents result of development of the boost converter for converting high voltage DC from low battery voltage and design of the inverter for controlling a high frequency current to be injected to motor winding. Also, we show performance of the designed starter by driving the turbo generator.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.95-101
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• 2014

In this study, an ISM (immersed solid method) was used for investigating the mass flow rate and efficiency of an involute-gear pump featuring very high rotational speed. For considering circulation flow at the gear pump and housing, fluid flow was assumed as turbulent, and the rotational speed of the gear pump increased under the condition of constant pressure at both the inlet and outlet. The efficiency and mass flow rate of the gear pump were studied by varying its rotational speed and the clearance between the gear tip and the housing. In the simulation results, as the rotational speed were increased, the average mass flow rate and efficiency increased. Furthermore, as the clearance between the gear tip and the housing was increased, the average mass flow rate and efficiency decreased. The efficiency was 85.11, 90.94, and 93.62 at rotational speeds of 6,000 rpm, 8,000 rpm, and 10,000 rpm, respectively, under the condition that there was no clearance. In addition, the efficiency was 93.62, 93.29, and 92.74 at clearances of 0 m, 0.00001 m, and 0.00003 m respectively.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.309-314
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• 2003

High-efficiency turboblowers in the next generation have been successfully developed and commercialized first in the world, using the high-speed BLDC motors and the foil air bearings. About 20-35% savings in electricity consumption in the field are found in comparison with the conventional roots rotary blowers and the integral gear-driven turboblowers. Current TB75 and TB150 products are replacing the existing blowers in the worldwide market.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.17-17
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• 2017

In electric agricultural machine the gearhead is needed to convert the high speed low torque rotation motion generated by DC motor to lower speed high torque motion used by the vehicle. The gearhead consist of several spur gears works as reduction gears. Spur gear have straight tooth and are parallel to the axis of the wheel. Spur gears are the most easily visualized gears that transmit motion between two parallel shafts and easy to produce. The modeling and simulation of spur gears in DC motor gearhead is important to predict the actual motion behavior. A pair of spur gear tooth in action is generally subjected to two types of cyclic stress: contact stress and bending stress including bending fatigue. The stress may not attain their maximum values at the same point of contact fatigue. These types of failure can be minimized by analysis of the problem during the design stage and creating proper tooth surface profile with proper manufacturing methods. To improve its life expectation in this study modal and stress analysis of gearhead is simulated using ansys work bench software based on finite element method (FEM). The modal analysis was done to understand gearhead deformation behaviour when vibration occurs. FEM static stress analysis is also simulated on gearhead to simulate the gear teeth bending stress and contact stress behavior. This methodology serves as an approach for gearhead design evaluation, and the study of gear stress behavior in DC motor gearhead which is needed in the small workshop scale industries.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1056-1061
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• 2004

The vibration of rotor systems is caused by various factors, such as misalignment, unbalance, gear meshing, error of assembly, etc. Modal test and TDA/ODS analysis were done. The dynamic analysis of the armature was done with SAMCEF which is a commercial software for finite element and kinematic analysis. The transient response of the armature is calculated by the SAMCEF with the consideration of magnetic force and bearing stiffness, which are the essential elements for the design of high speed cutter. Main frequency of the vibration is due to the unbalance of the armature. The FEM analysis model considering unbalance and the high speed cutter have same vibration properties. The vibration sources of the high speed cutter is proved to be unbalance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.301-307
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• 2013

MRU(motor reduction unit) for KTX is a assembled complex structure that is equipped with a lot of parts at the express train KTX and that is the core power source operating variable speeds. This study is recorded the dynamic characteristics analysis results tested by EMA which is done through the parts and assembly test, transient analysis and stoped train test in order to design the online monitoring system for KTX MRU. And the mode shapes result from critical vibration frequency explain the relation with variable speeds of express train over 250 km/hr. Also these variable speeds make variable operational frequencies at pinion, axle gear mesh frequency and normal bearing fault frequencies. As the specified speed can make resonance with natural frequencies of the MRU, for the train operating stability, this study also presents the MRU's critical speeds calculated by the each train speed.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.116-123
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• 1999

A case of the axle gear box which was one of tile power transmission components of high speed train was supported by the bearings installed in axle and the reaction arm connected in bogie frame. Structural analyses of this case were executed for investigation the application of aluminum for weight reduction. The evaluations of the material strength, the thermal strength and deformation, and the stability of natural vibration were carried out according to computer simulation. It was found out that the steel case was safe from the structural failure. For the aluminum case, there was no worry about the vibration resonance and the static failure, but some efforts to reduce tile deformation of the bearing mounting part.

• Journal of Drive and Control
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• v.12 no.4
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• pp.28-34
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• 2015

Because heavy-duty construction vehicles such as excavators are required for good engine-room cooling capacity, a hydraulic gear motor is adopted in the cooling fan drive mechanism to actively control the output speed, instead of adopting the conventional ON/OFF type belt drive. While gear motors are normally limited to 140bars of operating pressure, those for the cooling fan are capable of operating at continuous pressures of up to 220bars. After assembly, all gear motors for high pressure must pass an aging test which is a kind of the wearing process between the gear teeth and motor housing. During the aging process with gradual pressure increments, gear sticking sometimes occurs due to abnormal wear, resulting in defects. This paper focuses on a gear-sticking free aging test controller that is designed together with the knowledge of an experienced operator and the analysis results of experimental data of the gear jamming phenomenon. From the aging experiment, it is demonstrated that the developed controller that can alter the setting pressure of the load pump is effective for stabilizing the abrupt increase in the motor input pressure, thus preventing the hydraulic motor from stopping. This is expected to be helpful for the reduction of defects and increase in productivity.