Polyacetal Gears Research Articles

20310 籾殻焼成粉体を配合した射出成形プラスチック歯車の寿命に及ぼす負荷トルクの影響(GS-12【耐久性】)

The injection-molded-plastic-gears are used in such many fields as home electric appliances. Information processing equipments, automobiles and so on. Many factors have an effect on load carrying characteristics of an injection-molded-plastic-gear pair. Among others, the materials and the temperature of plastics are the most important factors, because the plastic physical property is greatly different in each plastics type. and the high temperature causes the decrease in Young's modulus of plastics. Therefore. the plastic gears are mixed with the reinforcing materials, which are glass fibers, chemical fibers, and graphite for keeping strength even in high temperature. On the other hand, natural materials are used to focus on the ecological recycling. Based on the above background, the authors focused on using a rice-hull-silica-carbon (RHSC) with a reinforcing material in plastics. In this study, the strength of the plastic filled RHSC gears was compared with the polyacetal (POM) gears.

Operating Characteristics of Gear by Low Elastictity Polyacetal

The demands for noise reduction of plastic gears in OA machines, etc. were increased recently because of the strong demands of lowering noise level in environment. The usual way to reduce the noise of polyacetal gears, mainly used as plastic gears, was dependent on lubricant additives only. We newly developed low elastic polyacetal by modifying the molecule chain itself with adding lubricant. In this study, we investigated the characteristics of the gears using the new polyacetal above mentioned in operation on various conditions, and found out the profitability in characteristics of those gears by comparing with the gears made by Nylon 12 (PA 12), well known as a suitable plastic material for low noise gears.

A Study on Plastic Gear of Reducing Friction Paired with Steel Gear.

Plastic gears are generally used as plastic/plastic gear pairs in a gear train except when paired with an input gear connected to a motor. For the input gear, a metal gear is usually used to bear its severe condition while this surely causes the wear at the meshing plastic gear to be largest in the gear train. To overcome this, a polyacetal containing fatty acid(MM), which has reduced coefficient of friction against a metal, is considered as a gear material. Operational tests were conducted on gears made of MM to examine basic characteristics such as life, tooth wear and tooth surface temperature. Applicability of this plastic material for practical use was discussed by comparing the results with those of regular and friction reduced polyacetal gears.

タルクを充てんしたポリアセタール歯車の研究

Recently, not only high strength, but also high rigidity have been demanded of plastic gears. At present, a high-rigidity, composite polyacetal gear filled with a talc has been developed. However, filling with inorganic talc results in increased rigidity and a decreased sliding potential compared to polyacetal. Therefore, the applicability of talc to gear materials has been questionable. This study was carried out to elucidate the above phenomenon by manufacturing two kinds of composite polyacetal gears changing the filling amount of talc and by comparing the characteristics of these gears during operation. Furthermore, these characteristics were compared with those of other polyacetal gears which are known to be suitable for many applications, and the potential for practical use of this composite polyacetal gear was investigated.

A Study on Polyacetal Gears Filled with Glass Fibers.

When glass fiber filled plastic is injection molded into gears through a conventional metal mold, there is a possibility that the end of the filled fiber will face and damage the tooth surface of the mating gear. In order to prevent the above damage and to increase the bending strength of teeth by arranging filled fibers uniformly in the direction of tooth form, we devised a metal mold in which as many fibers as possible can be arranged uniformly in the direction of tooth form at the time of injection molding. In this research, both kinds of composite plastic gears, containing 25% or 40% glass fibers respectively in polyacetal, were injection molded through this metal mold. Together with examining the bending fatigue strength and running characteristics of the teeth of the above gears by experiments, we performed the same experiments for composite plastic gears which were injection molded through a conventional metal mold. Comparing these results, we studied the profitability of the devised metal mold.

Polymer Alloy Gears. Polymer Alloy Gears Consisting of Polyacetal and Polyurethane.

Based on the fabrication of polymer alloys, a new plastic consisting of 50% polyacetal and 50% polyurethane (called FU polymer alloy) has been developed as a material for gears. For the FU polymer alloy gear, it has been predicted that its noise level becomes lower than that of polyacetal gear ; however, since the FU polymer alloy is weaker than polyacetal, problems arise in terms of the load capacity when it is used as a gear and some doubt still remains regarding its practical application. Because of these findings, in this study, operation tests of FU polymer alloy gears have been carried out under various conditions, and the operating characteristics such as noise level, wear and tooth profile change were investigated. Then these results were compared with those for polyacetal gears, and applicability of FU polymer alloy as a plastic gear material was evaluated.

Noise Comparison of Polyacetal Gears Based on Differences of Gear Processing Methods.

The mass production of plastic gears by injection molding has many advantages ; however, hobbing has been used in cases where injection molding could not be applied due to economical problems of mold shrinkage in the small-volume production of a wide variety of gears and technical problems in the processing of large-sized thick gears. It has been said that there are differences in the magnitude of noises between injection-molded plastic gears and hobbed plastic gears causing a difference in acoustic characteristics based on the difference of crystallinity of their gear surfaces. In this study, by using a polyacetal gear, and by measuring noises of both gears at each point of time when the properties of their gear surfaces were changed by the wear during a long period of operation, the difference of noises based on the difference of plastic gear processing methods was verified quantitatively based on experimental results.

Study on Liquid Crystal-Polymer Gears.

Attention has been paid to liquid-crystal polymers (hereinafter called LCP) as plastics of the next generation since these have features of high rigidity and small thermal expansion coefficient in addition to excellent heat resistance. Accordingly, in industry, application of LCP to gear materials has been attempted, but at present, data for investigation of its suitability are insufficient. From this fact, in this study, LCP gears were made by injection molding, and by performing experiments on them, gear life, tooth wear and change in tooth profile accompanying wear were examined and compared with those of polyacetal gears, for which there are actual results. In this way, the industrial applicability of LCP gears was confirmed.

Biodegradable Plastic Gears.

Presently, we often hear the phrase "plastics friendly to the global environment", and that a biodegradable plastic is being developed. However, no case has been reported up to now of mechanical parts being made of such plastics. Therefore, focusing the characteristics of this plastic, we have carried out a study to utilize this plastic for gears. In the study, first, biodegradable plastic gears were formed by injection molding similarly to commercial plastic gears, and their operation tests were carried out to investigate operating life, wear of teeth, tooth profile change, and tooth surface roughness. The results were compared with those of commonly used polyacetal gears, and the practicability of biodegradable plastic gears was examined.

Development of Polyacetal Gears Emitting Low Noise. 2nd Report. Polyacetal Gears Filled with Polyolefin and Synthetic Oil.

In the previous study, in order to reduce the noise of polyacetal gears, a composite polyacetal (called FO) made by filling several percent of low-molecular-weight polyolefin and mineral oil to polyacetal was developed. In these FO gears, noise was reduced as compared with polyacetal gears, but recently, gears with greater noise reduction than FO gears have been demanded. As a result, the authors developed a composite polyacetal (called FX) made by filling several percent of low-molecular-weight polyolefin and synthetic oil to polyacetal. In this study, the noise reduction in these FX gears was confirmed, and the wear of teeth, the change of tooth profile, the temperature on tooth surfaces and other characteristics were examined.

Basic Characteristics of Plastic Gears Lubricated with Water

Recently, plastic gears have been used in water, but depending on the kind of plastic, there are some gears which show a great deal of wear when they are used in water. However, it is important to note that in water or in places where moisture exists, water functions as a lubricant, and wear decreases as compared with the case without lubrication. To date, some reports have addressed this phenomenon but few have presented data on the design of plastic gears for use in water. In light of this situation, in this study, nylon gears and polyacetal gears, which are widely used plastic gears, were operated in water and with a small number of water drops, and various characteristics such as the wear of the teeth, the change in the tooth profile, the tooth surface roughness and so on, due to the difference in the quantity of bathing water were examined.

Development of Polyacetal Gears Emitting Low Noise. 1st Report, Two Kinds of Polyacetal Gears Filled with Different Additives.

Polyacetal gears have excellent characteristics, but there is one demerit in that they make as much noise as plastic gears. Therefore, for the purpose of reducing the noise of these gears, two kinds of composite polyacetal, filled with various additives, were developed. In this study, gears were made of these composite polyacetals, and the effect of reducing the noise was confirmed. Also, operation tests were carried out for long hours under various conditions, and various characteristics such as the wear of the teeth and the change of the tooth profile were examined and compared with those of polyacetal gears for which results of practical use were available. In this way, their practicality as power transmission gears was investigated.

Water Lubrication Characteristics of Polyacetal Gears Filled with Carbon Fibers

To obtain a polyacetal with high strength and rigidity, we should select a composite polyacetal filled with, for example, carbon fibers. However, this may not be true in the case when this kind of composite polyacetal is used in water. That is, it is considered that the sliding Characteristics might decrease because water enters into the bonding space between carbon fibers and polyacetal and between carbon fibers themselves. In this study, operating tests of a polyacetal gear filled with carbon fibers in water and with water drops were performed and the wear of the gear and the change of the tooth profile were determined. By comparing these results with those of an unfilled polyacetal gear, we investigated the usefulness of polyacetal gears filled with carbon fibers in water or humid environments.

Appraisement of Polycarbonate Used as the Gear Material.

Polycarbonate is a general-purpose engineering plastic which has been widely used, together with nylon and polyacetal. In this plastic, the rate of contraction in molding is small, and the water-absorbing property is low ; therefore, the accuracy of finishing products is high. However, there are defects such as low fatigue strength and brittle fracture, and it has not frequently been used for the gears for power transmission. In this research, for the purpose of extending the practical use of polycarbonate to gears, gears were manufactured of polycarbonate without filling (natural) and of polycarbonate in which the amount of carbon fiber filling was varied, and operation tests were carried out. In this way, such factors as the load-bearing capacity, the wear of teeth and the change of tooth. profile were investigated. These results were compared with those on polyacetal gears previously, reported. Thus the evaluation of polycarbonate as a gear material was carried out.

Water Lubrication characteristics of Polyacetal Gears Filled with Carbon Fiber.

For a polyacetal with high strength and rigidity, we should select a composite polyacetal filled with, for example, carbon fiber. However, this may not be true in the case when this kind of composite polyacetal is used in water. That is, it is considered that the sliding characteristics might decrease because water enters into the bonding space of carbon fibers and polyacetal and of carbon fibers with each other. In this study, operation tests of a polyacetal gear filled with carbon fiber in water and with water drops were examined and the wear of the gear and the change of the tooth profile were determined. By comparing these results with those of an unfilled polyacetal gear, we investigated the usefulness of polyacetal gears filled with carbon fiber in water or steamy environments.

Basic Characteristics of Plastic Gears Lubricated with Water.

Recently, plastic gears have become to be used also in water, but according to the kinds of plastics, there are some which show a great deal of wear when they are used in water. However, it is considered also that in water or in the place where moisture exists, water performs lubricating action, and wear decreases as compared with the case without lubricathon. At present, the report which can answer this problem, and can become the design data for the plastic gears lubricated with water is scarcely found. Due to the situation like this, in this study, the nylon gears and polyacetal gears which have been used widely as plastic gears were operated in water and with small quantity of water drops, and the various characteristics such as the wear of the teeth, the change of the tooth profile, the roughness of the tooth surfaces and so on due to the difference of the bathing water quantity were examined.

Effect of reducing friction of polyacetal in gears. 1st report, Polyacetal filled with fluorine-containing resin.

It has already been reported that when nylon (MC nylon) was filled with synthetic wax, the coefficient of friction decreased, and in the case of using such wax-filled nylon for gears, the wear of teeth was reduced, and the amount of gouging of the teeth roots by the top corners of teeth on matching steel gears decreased: accordingly, the change of pressure angle became less. In order to confirm whether phenomena such as these may also occur in polyacetal or not, gears were made with material having a small coefficient of friction by filling polyacetal with fluorine-containing resin, and trial operation was carried out. The wear of teeth, change of teeth profile and other properties were examined, and by comparing them with those in the case of polyacetal gears without filling, the effect of reducing friction was investigated.

Fundamental characteristics of plastic gears made of thermoplastic resin filled with various fibers.

This study aimed to elucidate the fundamental characteristics of the composite plastics that adopt thermoplastic resin as the matrix (basic material), and in which various fibers are filled, when they are applied to gears. In this case, polyacetal was used as the matrix, and glass fibers, carbon fibers or potassium titanate whiskers were used to fill it in. Gears were made with these composite materials, and the wear of teeth, the change of the tooth profile, the temperature on tooth surfaces and other characteristics of the respective gears were examined. In this way, the features were elucidated by comparison with those in the case of polyacetal gears.

A study of fiber-filled plastic gears. (3rd report. Fundamental characteristics of plastic gears made of thermoplastic resin filled with various fibers).

This study aimed to elucidate the fundamental characteristics of the composite plastics that adopt thermoplastic resin as the basic material, and in which various fibers are filled, when they are applied to gears. In this case, polyacetal was used as the basic material, and glass fibers, carbon fibers or potassium titanate whiskers were used to fill it in. Gears were made with these composite materials, and the wear of teeth, the change of the tooth profile, the temperature on tooth surfaces and so on of the respective gears were examined. In this way, the features were elucidated by comparing those with the case of polyacetal gears.