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One of the demands regarding reciprocating seals is to minimize the leakage from machineries due to global environmental issue. Especially in these years, rising in efficiency and downsizing of the machineries make the operating conditions of the seals severer than ever. Therefore, it becomes more important to know the sealing performance with high accuracy under actual operating conditions. In order to meet the request, a new method based on visualization and spectroscopy is presented. In this paper the description of the technique and the first results obtained with general reciprocating seals are shown.

This paper reports on a new concept for static seal designs taking into consideration the surface roughness of sealing surfaces. The concept focuses on fluid penetration from the interstices between the seal and counterface caused by surface roughness. In the study, we investigated the relation between the leakage and surface roughness of the sealing surface of the elastomer seal. At the same time, we also analyzed the contact state of the elastomer seal based on the equations of Ishiwata et al. on deformation of elastomer surface into rough surfaces [1]. The micro-leakage testing machine (SMLA) developed by the authors was used to measure micro-leakage at high precision and in a short time [2]. The results showed that the sealing phenomena were related to the ratio of seal surface contact pressure Ps / elastic modulus of seal E, determined by the compression ratio of seals, and does not depend on the chemical structure and hardness of the elastomer used.

Several number of ball joints are used in the suspension system. For these ball joints, rubber dust covers are used in order to maintain sufficient lubrication and protect the ball joint from contaminants such as water and dusts. In recent years, the number of breakage or grease leakage of the dust cover used under ultralow temperature is increasing with the growth of automobile selling in developing countries. In this research, we have studied the mechanism of dust cover breakage under ultralow temperature by focusing on the low temperature behavior of a rubber material.

In this study, we have developed two type of low friction seal rings (S/R). The first of developed product is textured seal ring. The surface textures with the side of seal ring are designed by using numerical analysis of hydrodynamic, and attempt to reduce the friction coefficient by lubrication improvement of sliding surface. Low friction effect is confirmed by friction torque and oil film thickness measurement, and it was discussed from analysis and experiments. The second is outer sliding type seal ring. This seal ring is unaffected by the environmental factors, it is possible to a pressure-receiving area reduction by changing the sliding surface from the side to the outer. Friction characteristics and sealing performance have been evaluated by the sliding test. Also both developed seal rings were confirmed that the low-torque effect compared to conventional one (T-shaped cross section seal ring) is obtained.

This paper presents a measuring technique, a test result and a finite element analysis result of a surface temperature of rotary lip seals. A thermocouple embedded in the surface of a shaft and radio transmission systems provide wireless measurement for the temperature of the rotary shaft, which is driven up to 6000 rpm. Relationships between shaft temperature, lip temperature and sliding speed were shown. Torque of PTFE coated seals is about 23 % lower than that of conventional seals at 22 m/s. At that time, the shaft temperature of PTFE coated seals is about 7 K lower than that of conventional seals. And, Lip temperature of PTFE coated seals is about 1 K lower. In the analysis result, high temperature part of the shaft is larger than that of the lip, that is, heat is concentrated in the sealing edge of the lip. Temperature rise of the analysis result is consistent with those of the test result.

The effects of cross section shape of the seal, rubber material property and their combination on the friction force of reciprocating seals were investigated. O-ring, D-ring and Oval-ring were prepared as different cross section shape of the reciprocating seal. In particular, D-ring and Oval-ring were designed to be narrow width to save the space. The seals were made from rubber material with different mechanical property and low temperature property. The friction forces of the seals were measured at −40 to 150°C. The O-ring made from rubber material with lower rubber hardness and lower TR10 reduced the friction force. The friction force of Oval-ring was decreased in comparison with those of O-ring and D-ring. The decrease in the friction force was caused by leaning in the groove. The combination of Oval-ring and rubber material property reduced the friction force of the reciprocating seal. The seal was reciprocated for 1 million cycles as a durability test.

Leakage occurs between contact surfaces due to the surface roughness. In general, soft materials such as rubber are used to perform a sealing function. Softmetal used as an engine seal material, is a stainless steel plate coated with rubber. In order to seal a fluid, it is necessary to design the rubber coating and the contact pressure with consideration of the surface roughness. In this study, leak tests are conducted with the softmetal, and the effects of contact conditions, such as surface roughness, load, rubber thickness and rubber material are investigated. A differential pressure system using nitrogen gas was constructed for the leak test, and a surface of anisotropic roughness is adopted. The size of the clearance due to the geometrical shape of surface asperities is calculated from an indentation test. A model of rubber compliance to surface asperities is proposed, which predicts the sealing contact pressure with the rubber thickness.

In developing engine oils, it is crucial to consider their compatibility with the rubbers used for seals. Among the different seal rubbers, silicone rubber is particularly susceptible to attack by acids and bases, which means it would be more likely to be affected by certain engine oil additives. In this study, the effects of some major additives, namely detergents, zinc dialkyl-dithiophopshate (ZDDP) and molybdenum dithiocarbamate (MoDTC), on silicone rubber were investigated. Silicone rubber test specimens were immersed in sample oils containing these additives for a prescribed period at 150°C, then the physical properties of the test specimens were measured to compare the effects of the different additives. It was found that ZDDPs dramatically reduce the tensile strength of silicone rubber, with primary ZDDP having a greater effect than secondary ZDDP.

The research study experimented and analyzed the relation between a super rough surface and the seal of the gasket. It groped for the relation of the seal by the seal testing and FEM by using several different type of jig and gaskets. As for the seal of the gasket, the thing that greatly depends on the contact range and seal side has been understood. The improvement of the seal was tried by using not only upper and lower sides but also sides that were the concepts of a general seal as a sealing surface.

A new valve stem seal design has been developed to achieve superior control of the oil flow rate to valve guide. This design exhibits increased performance in the control of the oil flow rate under high pressures of the inlet or exhaust port and under high valve stem eccentricity. The recent demands of stable function, minimized oil consumption, and more efficient emission controls are achieved by this new design.

This paper describes that the effect of surface texture of sealing lip on lubrication and sealing performance examined experimentally on practical aspect. Hub seals of PAC type were used in this study. A test apparatus and operating procedure were shown. The seal which had texture on the lip had lower frictional torque than plain one. The effect of friction reduction with the textured surface preserved up to 15 cycles, which was equivalent to a travel distance of 30,000 km. The textured surface 10 μmRz with grease on the lip kept sealing performance up to -0.10 MPa in static and dynamic conditions. The endurance time of sealing of the textured surface was almost the same as that of the plain surface in seal endurance test with muddy water.

This paper describes a new measurement method using fluorescence analysis to measure oil pump rates of radial lip seals for small shaft diameters. A test apparatus and operating procedure for measurement of pump rate were shown. First results of pump rates obtained with seals for 8 mm shaft diameter were shown. As a result, the oil pump rates under various shaft speeds and sump pressures ranged from 4 to 160 mg/h.

We developed a measurement method to evaluate the sealing performance for narrow gap between a metal shaft and a fitted sleeve quantitatively in a brief time. We examined the effect of the chamfer shape and the surface roughness of the shaft on the leakage rate. We also conducted liquid leakage test in order to compare the leakage rate of gas with that of the liquid. From this comparison, we showed that it is possible to evaluate the sealing performance for liquid by measuring leakage rate of gas. In addition, we discussed the leakage rate of fluid through the gap by assuming viscous flow. The estimated leakage rate of the liquid derived from the leakage rate of air by converting viscosity of air into that of the liquid was totally proportional to the measured leakage rate of the liquid. Therefore, we concluded that the leakage rate of liquid can be estimated by measuring that of air.

The correlation between the micro surface roughness and sealability of O-rings was experimentally analyzed. We developed a SMLA (Seal Micro Leakage Analyzer) for observing the contact of micro asperities using a micro-prism glass plate, and a micro-leakage measurement device for O-rings. Using the SMLA, the contact of micro asperities of O-rings surfaces ranging from 1.6 microns to 16.3 microns was clearly visualized. We also measured the contact area and leakage amount at the same time, and studied the sealing mechanism. The visualized images of the contact area were analyzed by image processing. The results showed that the micro asperites on the O-ring surfaces were squashed elastically to form a band which sealed in the fluid.

SOFT METAL (SUS plate coated with rubber) is used for cylinder head gasket (CHG). Conventionally, this SUS plate is preprocessed using coating chromate. When this was changed to chrome-free agent, the rubber was peeled off from the plate. There are found that this may be due to the electrochemical reaction caused by the contact between different metals-Al of the engine block and Fe (SUS) of CHG.

This paper addresses the temperature dependence of friction properties in seals (O-rings and D-rings) for use in reciprocating motions. The narrower focus here is on several factors: the effects of a lubrication state, the change in dimension and the physical properties of a rubber material. It can be assumed that they influence the temperature dependence of a frictional force. As shown in this study, A frictional force has a profile characterized by temperatures. It is revealed that the profile of a frictional force is mainly attributable to the deformation of a rubber material in motion-the physical properties (elastic modulus) of a rubber materials-and the rate of recovery in elasticity of a rubber material. In addition, a temperature showing the maximum frictional force is largely attributable to the low-temperature properties of a rubber material. It is revealed that the temperature dependence of a frictional force is mainly influenced by the material properties of rubber.

Seal rings are used as shaft seals in automatic transmissions, where they act as a dam to direct pressurized fluid flow to hydraulic circuits. Conventionally, cast-iron seal rings were used, but over the past two decades, this material has been switched to resins like PTFE and PEEK to satisfy performance requirements such as low leakage and low frictional torque. However in using resin seal rings, the shaft sometimes undergoes the so-called three body abrasive wear due to invasion of hard particles, such as wear particles and dust, into the sliding portion between the seal ring and the shaft. To prevent such wear of the shaft, it is important to prevent invasion of hard particles into the sliding portion, and also to promptly discharge hard particles from the sliding portion. We therefore designed a seal ring taking into consideration these needs and investigated its shaft wear reduction effects.