Optimization of Contact Pattern Position on the Worm Wheel Teeth by Axial Shift in Worm Wheel Axis

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by Axial Shift in Worm Wheel Axis Ehsan Soury Arash Houshmand

1 From the SelectedWorks of Arash Houshmand Spring March, 04 Optimization of Contact Pattern Position on the Worm Wheel Teeth by Axial Shift in Worm Wheel Axis Ehsan Soury Arash Houshmand Alireza Nezamabadi Available at:

2 Indian J.Sci.Res.() : 55-57, 04 ISSN:50-038(Online) ISSN : (Print) OPTIMIZATION OF CONTACT PATTERN POTION ON THE WORM WHEEL TEETH BY AXIAL SHIFT IN WORM WHEEL AXIS EHSAN SOURY a, ARASH HOUSHMAND b, AND ALI REZA NEZAMABADI c a PhD, Department of Mechanical Engineering, University of Arak, Arak, Iran b MSc, Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Arak, Iran c PhD, Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Arak, Iran ABSTRACT In industrial applications Lubricant temperature decrease is a desired aim in the case of lubricant and gears performance. In this paper the procedure of optimization of worm gears performance by considering the proper contact pattern position had been performed. In accordance with required axial shift in worm wheel axis the contact pattern optimized and as a result the lubricant temperature decreased. This procedure leads to increase gears efficiency and their effective life. KEYWORDS: Worm Gears, Contact Pattern, Lubricant Temperatur In industrial power transmit applications, optimization plays an important role to achieve maximum required life and economize on time and cost. The most important precision characteristic of the power-transmitting worm gears is the contact pattern. Great number of parameters are influencing on shape and position of contact pattern like process and accurate of production, real geometry of gear box, selection of slidingcontact method and exploitation conditions. The load capacity of worm gear drives is mainly influenced by the size and the position of the contact pattern. The worm gear contact pattern is a visual determination of the worm gear axial location to achieve the desired position of the gear element and provide the initial contact pattern to carry the design load on the gear elements profiles and allow for oil entry gap. The different positions of the contact area, including the correct one, can be seen in Figure. Regarding the symbols used in the figure, it should be noted that the arrows facing in the same direction represent the meshing direction of rotation. Two different worm gears mated with the same worm are symbolized by different direction of hatching lines. In the case of left-hand teeth, the adjustment of elements should plainly be carried out as a mirror view shown in Figure. Figure : Right-hand teething; adjustment of correct contact area The kinematic action of worm gears ensures that the wheel component is almost stationary relative to the contact point, and the gears essentially operate in a simple sliding mode. As a result, the softer wheel component is subject to wear due to the sliding action of the worm over its surface (Sharif ET AL., 006). Lubricants are introduced into the worm and worm gear mesh to reduce friction and heat and to prevent metal-tometal contact, thereby reducing or eliminating wear (60- C93, 993). In first hours of utilizing worm gear drives, it is common that in accordance with worm gears size, lubricant temperature rises and then after several hours of working it will have a constant value. EXPERIMENTS Two experiments were performed in the worm gears of a reciprocating pump which is shown in figure. The basic manufacturing specifications of worm gears are shown in table. The lubricant oil specifications which are used in experiments are shown in table. Corresponding author

3 EHSAN SOURY ET AL.: OPTIMIZATION OF CONTACT PATTERN POTION ON THE WORM WHEEL TEETH BY AXIAL SHIFT IN WORM Worm Wheel Width Material - - (mm) b 44. CuSn-C- GZ Table : The specifications of experiments used lubricant oil Figure : The reciprocating pump which is used to perform experiments Table : The basic manufacturing specifications of used right-hand worm gears in experiments Worm &Worm Wheel Joint Specifications Addendum coefficient Dedendum coefficient Transverse Module ul ul (mm) * h ap * h fp.5 m t 6.5 Pressure angle ( ) a n 0 Mean Lead Angle ( ) γ 5. Center distance (mm) a 88.9 Shape of flank - - ZI Worm Specifications Physical- Chemical Specifications Test Method Experiments Oil (ISO VG 50) Viscosity (cst) Viscosity Index 00 C 40 C D-445 D-70 Flash Point ( C) D-9 Pour Point ( C) Density at 5 C 3 ( kg m ) D- D In the case of condition of tests, the pump was under working condition with an electromotor with 0.37 (KW) power which rotates worm in clockwise direction with 435(rpm) Angular velocity and this condition leads to 0 Bars pressure exist on pump's plunger with 7(mm) diameter. In specific period of time the temperature of oil was measured with a digital thermometer. After hours of gears running on, the lubricant temperature stays at a constant value for each test. RESULTS AND DISCUSON After creating a thin layer of color in worm wheel teeth, test was performed in same condition as described above. The lubricant temperature diagram and worm wheel contact pattern position have been shown in Figure 3 and Figure 4. Pitch Diameter (mm) d 47.8 Number of threads - N Facewidth (mm) b 74.6 Material - - 7NiCrMo6 Worm Wheel Specifications Pitch Diameter (mm) d 30 Number of teeth - N 0 Figure 3: Resultant lubricant temperature diagram test Facewidth (mm) b Indian J.Sci.Res.() : 55-57, 04 56

Figure for a right-hand worm gear set, we can find that axial shift in worm wheel axis is needed.

4 EHSAN SOURY ET AL.: OPTIMIZATION OF CONTACT PATTERN POTION ON THE WORM WHEEL TEETH BY AXIAL SHIFT IN WORM Figure 4: Resultant worm wheel contact pattern position of test By considering the proper contact pattern in Figure for a right-hand worm gear set, we can find that axial shift in worm wheel axis is needed. The required worm wheel axis shift direction created by changing the position of a worm wheel's washer forms one side to other side. This displacement leads to.mm worm wheel axis shift in true direction. After creating axial shift in worm wheel axis, test was performed. The results in case of lubricant temperature diagram and worm wheel contact pattern position have been shown in Figure 5 and Figure 6. The worm wheel axis shift by changing the position of a worm wheel's washer to achieve the desired contact pattern position. Figure 5: Contact pattern optimization after axial shift in worm wheel axis in test As indicated in Figure 6, the final result of Contact pattern optimization with worm wheel axial shift in this experiment leads to C decrease in lubricant temperature. This decreased value is more considerable in the biggest worm gear sets. CONCLUON Lubricant temperature decrease is a desired aim in the case of lubricant and gears performance. By considering the instruction of proper contact pattern achievement procedure and by performing worm wheel Adaptable axis shift, the desired contact pattern in this experiment achieved and as a result lubricant temperature decreased. ACKNOWLEDGEMENT Figure 6: The effect of Contact pattern optimization after axial shift in lubricant temperature diagram in test in compare with test This work was supported in part by "NEEV" company in IRAN. The authors gratefully acknowledge the support of Mr. K. Ghaffari (head of R&D department of NEEV group) for his supports. Indian J.Sci.Res.() : 55-57, 04 57

5 EHSAN SOURY ET AL.: OPTIMIZATION OF CONTACT PATTERN POTION ON THE WORM WHEEL TEETH BY AXIAL SHIFT IN WORM REFERENCES Miltenović A.; 005. Contact pattern optimization of worm gear pairs," Konstruisanje mašina, 8: 33-40, 005. Höhn B.-R, Steingröver K., and Lutz M.; 00. Determination and optimization of the Contact Pattern of Worm Gears," in International Conference on Gears,: C93,; 993. Manual for Cylindrical Worm Gearing," ed. USA: American Gear Manufacturers Association, Inc., 993. Dudas I..; 000. The Theory and Practice of Worm Gear Drrives", London: Penton Press. Sharif K., Evans H., and Snidle R,;L 006. Prediction of the wear pattern in worm gears," Wear, vol. 6: Indian J.Sci.Res.() : 55-57,

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