Constructional design of the body shape of large gear wheels

The development of modern machines and means of production is characterized by ever-increasing performance parameters with decreasing equipment weight. When designing large gears, it is also necessary to consider the influence of the body shape of the gear wheel. The body shape of gear wheel must meet the basic requirements of stiffness and strength with the lightest possible construction of the gear wheel body. The work is focused on large gears, made with relief. Such gears can be forged, cast, or made by welding. The shape of the gear wheel body depends on several factors such as the size of the wheel, the material, the method of manufacture or use. The paper provides an overview of the body shapes used by large spur gears. These body shapes of spur gears will be the subject of further research, where suitability will be assessed based on stiffness of teeth and wheel weight.

Increased efficiency of eccentric cycloidal engagement

Gears with eccentric cycloidal engagement have large gear ratios, small overall dimensions, low noise and vibration levels. A relatively low efficiency factor limits their use in transmissions mechanisms, where involute gearing with gear ratios up to 10 and high efficiency (over 0.98) are in demand. The power losses of the eccentric cycloidal engagement are caused by friction in the jointly working kinematic pairs, which are formed by the gear with at least half of the pins, and the latter form the pairs with axles or sockets in the housing. It is possible to reduce the power loss by reducing the number of jointly working kinematic gear-pin pairs, which is done by modifying the theoretical profile of the gear. The modified profile is obtained from the theoretical one by removing the tops of the protrusions so that the remaining parts of the profile provide a smooth transfer of the load to a given number of pins. The study introduces a method for calculating power losses and the efficiency of eccentric cycloidal gearing for theoretical and modified gear profiles. Findings of research show that the modification of the cycloidal gear makes it possible to reduce the power loss in the engagement by more than 60% and to increase the efficiency by 0.03 ... 0.04 without a significant decrease in the strength of the working surfaces. The obtained result confirmed the possibility of increasing the efficiency of eccentric cycloidal gearing for it to be used in transmissions of transport vehicles.

Method for determining the optimal parameters of the chain transmission, taking into account the design of the drive chain

Goal . Develop the design of the drive plate chain and methods for determining the optimal parameters of the chain transmission. Methods. Analysis of the designs of standard drive bushing and roller chains, as well as the drive plate chain with internal engagement. Determination of ways to increase the durability of these chains and chain gears from the condition of ensuring the wear resistance of their hinges and increasing their technical and economic indicators. Results . The analysis of designs of standard drive bushing-roller chains and drive plate chains with internal gearing is performed. A promising design of the drive plate chain has been developed. The optimization of transmission parameters, both with standard chains, and with the chain proposed by the authors, providing an increase in their durability and efficiency. In this regard, a method has been developed for determining the greatest elongation of standard chain links, as well as the chain developed by the authors, from the condition of wear resistance of their hinges. A method for determining the optimal transmission ratio of these chain gears has also been developed. It is established that the gear ratio of the transmission with the drive plate chain developed by the authors is determined primarily by the accuracy of manufacturing its hinges. With sufficiently precise manufacturing of chain hinge parts, the gear ratio can be significantly increased, up to u=10 and higher. This will allow you to use gears equipped with this chain in drives with a large gear ratio.

Suitable Material Selection for Large Size Cylindrical Gears*

Globalization and international supply chains constantly challenge gear- and steel manufacturers. In the case of large gear units in particular, expensive alloy contents have a direct impact on the material price. Steels with lower alloy contents and therefore cheaper steels are therefore becoming the focus of attention in order to further improve competitiveness. This article therefore compares two materials with different alloying elements and contents and thus different hardenability behaviour. For this purpose, extensive material characterizations as well as pulsator tests were carried out on case-hardened large gears. The aim of these tests was to determine the tooth root load-bearing capacity of the two material variants. Finally, the results are compared, discussed and recommendations for industrial application are derived, taking into account the hardenability of large gears. ◼

Study of geometric characteristics of the arc teeth semi-rolled cylindrical gear meshing

In the conditions of unbraced machine body parts, arc teeth cylindrical gears have a higher load capacity, durability and reliability as well as the ability to compensate for the twist angle by self-adjustment of one of the wheels compared to straight and helical teeth gears. Use of such gears in a semi-rolled version allows simplifying significantly the technological process of cutting wheels and making gears with large gear ratios. In this article, mathematical models of wheel and gear arc teeth forming process are built for a semi-rolled cylindrical gear. The geometric characteristics of the gear arc teeth meshing in the presence of errors in the wheel and gear relative position, required to solve the problem of calculating the gear load capacity and durability, have been determined.

Determination of the mean base circle radius of gears by optical multi-distance measurements

The required reliability of wind turbine gearboxes increases the requirements for large gear measurements. Extensive measurements to reliably assess the geometry of large gears in the single micrometer range are necessary. Due to an individually fixed measuring volume, standard methods like coordinate and gear measuring instruments reach their limits for large gears with diameters > 1 m. Therefore, a scalable optical measurement approach consisting of a single sensor in combination with a rotary table for multi-distance measurements with subsequent model-based evaluation of shape parameters of gears is presented. The scalable measurement approach is to be extended to a multisensory system in further work. As a fundamental shape parameter the mean base circle radius using the example of spur gears is determined. The base circle radius is used due to the geometric relationship to further shape parameters for example to the profile slope deviation. The theoretically achievable measurement uncertainty of the mean base circle radius due to sensor noise is estimated to less than 5 µm (k=2) for a small and a large gear, which verifies the scalability of the sensor system. In order to show a general proof of principle, two series of optical measurements on a gear with a diameter of 0.105 m are performed and referenced with a tactile measurement. As a result, random errors of 1.2 µm for k=2 are determined. The remaining systematic deviations to the reference value amount to 4.3 and 1.6 µm, respectively. Hence, the total measurement uncertainty is currently limited by systematic effects, and the defined aim of a total uncertainty of less than 5 µm (k=2) is narrowly missed by 1.5 µm. The random errors of 1.2 µm (k=2) show, however, that an adequate measurement precision is achieved and that the multi-distance measurement approach has the potential to reach the aimed measurement uncertainty with appropriate strategies to compensate for the systematic influences. The experimental and theoretical results prove the principle applicability of the proposed single sensor multi-distance approach for the precise inspection of gears.

Study on Swing Movable Teeth Drive with External Generating Wave Mode

An external generating wave swing movable teeth drive based on sinusoidal acceleration and quintic polynomial motion has been newly developed. This drive consists of a wave generator as the input cam, a train of movable rollers which are uniformly distributed on the fixed separator, and a ring gear as the output cam. The teeth difference between the ring gear and the rollers is two. The input and output cam are engaged with the train of rollers simultaneously. The drive thus has the advantages of large gear ratio, compact structure, high torsional rigid and steady rotation, can be integrated with pulley drive to form a pulley reducer. In this paper, the motion principle is studied and the tooth profiles are derived. On this foundation, curvature of the ring gear and pressure angles of the drive are conducted. And kinematic simulation is also carried out. A physical prototype is manufactured to demonstrate the feasibility and correctness of the theoretical analysis model of the drive. This drive can be integrated with pulley drive to form a pulley reducer, which is promising for the fields needing compact structure and large transmission ratio.

Detailed analyses of stall force generation inMycoplasma mobilegliding

ABSTRACTMycoplasma mobileis a bacterium that uses a unique mechanism to glide on solid surfaces at a velocity of up to 4.5 µm/s. Its gliding machinery comprises hundreds of units that generate the force for gliding based on the energy derived from ATP; the units catch and pull on sialylated oligosaccharides fixed to solid surfaces. In the present study, we measured the stall force of wild-type and mutant strains ofM. mobilecarrying a bead manipulated using optical tweezers. The strains that had been enhanced for binding exhibited weaker stall forces than the wild-type strain, indicating that stall force is related to force generation rather than to binding. The stall force of the wild-type strain decreased linearly from 113 to 19 pN following the addition of 0–0.5 mM free sialyllactose (a sialylated oligosaccharide), with a decrease in the number of working units. Following the addition of 0.5 mM sialyllactose, the cells carrying a bead loaded using optical tweezers exhibited stepwise movements with force increments. The force increments ranged from 1 to 2 pN. Considering the 70-nm step size, this small unit force may be explained by the large gear ratio involved in theM. mobilegliding machinery.SIGNIFICANCEMycoplasmais a genus of bacteria that parasitizes animals. Dozens ofMycoplasmaspecies glide over the tissues of their hosts during infection. The gliding machinery ofMycoplasma mobile, the fastest species, includes intracellular motors and hundreds of legs on the cell surface. In the present study, we precisely measured force generation using a highly focused laser beam arrangement (referred to as optical tweezers) under various conditions. The measurements obtained in this study suggest that the rapid gliding exhibited byM. mobilearises from the large gear ratio of its gliding machinery.