月: 2022年12月

What Is Vacuum Insulation?

Vacuum insulation refers to insulation that has been vacuumed by decompressing the inside of the insulation material.

Specifically, it refers to a material with heat-insulating properties, such as glass wool that is covered with a laminated film and then vacuumed by further depressurizing the interior.

Uses of Vacuum Insulations

Vacuum insulation is used in household refrigerators, electric hot water pots, vending machines, cold storage boxes for transportation, etc. With the conservation law revisions, companies are actively considering the introduction of vacuum insulation to improve the thermal efficiency of various equipment. In addition, vacuum heat insulators are used as heat insulators.

Vacuum insulation is also advantageous in that the insulation part is vacuumed and its thickness is extremely thin, allowing it to be placed in narrow spaces. Therefore, it can be used for a wide range of products, from small to large in size.

Principle of Vacuum Insulation

Heat conduction, in which heat is transferred from one object to another, requires a medium (gas, liquid, or solid) to transfer heat. When these materials heat up, the molecules inside the medium vibrate, which propagates the heat to the neighboring molecules.

Thermal conductivity expresses the ease with which heat propagates. If this thermal conductivity is small, it means that heat is difficult to propagate. In other words, the smaller the thermal conductivity of the medium, the less heat is transferred and the better the insulation. In general, glass wool and polystyrene are used as materials with thermal insulation properties. The thermal conductivity of these materials themselves is relatively small, but since they contain air inside, heat conduction by the air also occurs.

Vacuum insulation uses glass wool, which is conventionally used as the core material, and then covers it with laminated film to remove the air inside, resulting in almost no heat conduction by the air. Vacuum insulation is therefore less prone to thermal conduction than conventional glass wool insulation and has extremely high thermal insulation properties.

However, if a hole develops in the laminated film of vacuum insulation, air can enter the interior, resulting in a rapid loss of performance as an insulator. In addition, since there is a possibility of vacuum breakage due to deterioration over time, care must be taken when using the material for long periods of time.

Other Information on Vacuum Insulation

1. Improvement of Heat Resistance and Durability in Vacuum Insulation

In recent years, as attention has focused on countermeasures against global warming and energy issues, products with superior heat resistance and durability have been developed for vacuum insulation. One example is a vacuum insulation material with a glass wool core inside and stainless steel foil as an outer wrapping material.

The heat resistance of stainless steel foil is 300°C or higher, which is a significant improvement over conventional vacuum insulation materials that use a resin laminate film as the outer packaging material. In addition, in conventional vacuum insulation, the resin laminate film allows a slight permeation of gas, and the heat conduction of the gas inside the glass wool, which serves as the insulating portion, causes the insulation performance to deteriorate.

However, by using stainless steel foil as the outer wrapping material, gas permeability has been improved and the durability of vacuum insulation has been greatly enhanced.

2. Vacuum Insulation for Residential Use

Vacuum insulation is also used in housing. For example, a core material consisting of glass wool is used for the interior, which is wrapped with a laminated film and has a porous structure with a vacuum inside. Vacuum insulation materials are only a few millimeters thick but can achieve the same thermal insulation effect as glass wool which is several dozen times thicker.

Such excellent heat insulation performance is achieved by making each porous material pore a large space. This is because the larger each pore is, the greater the vacuum area in the area of the glass wool, and thus the thermal conduction by the air, can be suppressed.

To make each porous hole a large space, the core material is compressed under pressure. During this process, the fibers of the core material are fixed in layers, forming a structure in which the fibers are in contact with each other at points, and large spaces (gaps) are formed in the core material. This increases the vacuum portion of the glass wool core, which results in a higher thermal insulation performance.

Vacuum insulation is made by placing the core material in a laminated film bag, creating a vacuum, and thermocompressing the open end. Vacuum insulation materials have also been developed by applying this structure, where a single sheet of vacuum insulation material is divided into multiple blocks by thermo-compression bonding of laminated film, and each block is vacuumed.

What Is a Vacuum Dryer?

A vacuum dryer is an apparatus that creates a vacuum or reduced-pressure environment within a sealed space to facilitate drying.

This device leverages the principle that lower air pressure decreases the temperature required for moisture evaporation. Compared to conventional hot-air dryers, vacuum dryers enable drying at lower temperatures, offering efficient and rapid drying solutions.

Notably, vacuum dryers preserve the surface integrity of the dried object, making them a preferred choice in university laboratories, science and engineering fields, and the food processing industry. Effective drying requires pre-drying due to the temperature drop caused by evaporative cooling.

Applications of Vacuum Dryers

Vacuum dryers are used for:

• Quick drying of moisture-rich objects
• Drying porous materials that trap moisture
• Non-destructive drying to maintain surface quality

Specific fields of application include the following:

1. Food Products

Used in freeze-dried product manufacturing, vacuum dryers preserve the taste and freshness of food. They are also integral in producing instant coffee, powdered seasonings, and dairy products.

2. Molding Processing

Suitable for resin processing, vacuum drying ensures uniform low-temperature drying, essential for maintaining the quality of molded products. During the molding process, excess moisture can lead to resin hydrolysis, accelerated thermal decomposition, and cracking.

3. Electrical and Electronic Components

For components like motor coils and transformers, vacuum drying prevents insulation failure and moisture damage, ensuring quality maintenance.

4. Metal and Machined Parts

Effective for drying sintered parts and metal powders, vacuum drying ensures even drying from the inside, crucial for complex-shaped precision parts.

Principle of Vacuum Dryer

Vacuum dryers operate by reducing atmospheric pressure in a sealed container, thus lowering the boiling point for efficient drying. They typically comprise a sealed container, electric heater, gas exchange valve, and vacuum gauge. Some models include a cooling trap to recondense vaporized water, preventing vacuum pump damage.

Types of Vacuum Dryers

Vacuum pumps in these dryers come in two main types: gas transport and gas hoarding. Gas transport pumps expel gas externally and are categorized into volumetric transfer and momentum transfer types. Common pumps include oil-sealed rotary pumps and dry pumps.

1. Oil-Sealed Rotary Pump

These pumps use lubricating oil for efficient operation but require periodic oil replacement.

2. Dry Pump

Dry pumps, containing a three-leaf rotor, discharge air without lubricating oil, minimizing environmental impact.

What Is a Vacuum Blower?

A vacuum blower is a type of vacuum generator. There are three types of vacuum generators: ejectors, vacuum pumps, and vacuum blowers. Each is used for a different purpose. The main applications of vacuum are adsorption by suction pads and degassing by depressurizing the system.

Vacuum pumps and vacuum blowers, on the other hand, are electrically driven and can create a vacuum efficiently. Ejectors can also be used in areas where hazardous materials are used by using air as the driving force.

Uses of Vacuum Blowers

One application of a vacuum blower is to suction with suction pads. This is used to lift a workpiece by adsorbing it when transporting it with a robot or other equipment. Another application is degassing by reducing the pressure in a system. For example, if a material is susceptible to oxidation, removing air (oxygen) from the material prevents oxidation.

Vacuum blowers are used for the adsorption of vented workpieces. Vacuum blowers are also characterized by their ability to generate a large flow rate, which allows a large suction volume to be obtained.

Principle of Vacuum Blowers

Vacuum blowers rotate a built-in blade (impeller) by turning a motor. The rotation of the impeller draws in gas. The gas is drawn into the housing, which accelerates and compresses the gas. This means that mechanical energy is transferred from the impeller to the air. Air is sucked in by the impeller blades, creating a vacuum on the vacuum side.

Vacuum blowers are characterized by their large suction volume. On the other hand, however, the vacuum generated is low. Also, in principle, the more air permeable the workpiece to be vacuumed is, the more efficiently it can be used.

The vacuum blower creates a vacuum to enable suction by the suction pad. When the ambient pressure is higher than the pressure existing between the suction pad and the workpiece, the workpiece is fixed to the pad by the atmospheric pressure. The suction force of the suction pad is directly proportional to the pressure difference between atmospheric pressure and the pressure inside the pad. The pressure inside the suction pad is removed using the power of the vacuum blower.

What Is a Vacuum Flange?

A vacuum flange is an essential component used in vacuum systems to connect various parts of the equipment while maintaining an airtight seal. It is a plate-shaped element that can be circular or square and features threaded holes or grooves for bolting purposes. Vacuum flanges play a critical role in creating a vacuum environment within the system, adhering to standards such as NW, KF, and JIS.

Uses of Vacuum Flanges

Vacuum flanges find application across industries that depend on vacuum environments for their processes, including:

1. Semiconductor Industry

Vacuum conditions are crucial for wafer fabrication in the semiconductor industry, where processes like deposition and etching are performed. Vacuum flanges ensure the chamber is sealed off from impurities while allowing the introduction of necessary gases and reactants.

2. Optical Device Industry

In optical equipment manufacturing, vacuum flanges are indispensable during the coating process of components like lenses and mirrors, enabling the precise and uniform application of thin films to enhance optical performance.

3. Power Generation

Vacuum flanges are used in steam turbines within condensers to convert steam back into water, maintaining a vacuum that enhances efficiency and performance.

4. Materials Research and Development

In R&D, particularly in physics and chemistry, vacuum flanges are crucial for conducting experiments under vacuum conditions to prevent contamination and accurately study the properties of materials.

Principles of Vacuum Flanges

Vacuum flanges ensure the airtightness of vacuum systems by using gaskets or packings at the joints, preventing external gas leakage. Materials like stainless steel (e.g., SUS316L, SUS304) or nickel alloys are used for their construction, with teflon packing or copper gaskets often employed as sealing materials to achieve optimal airtightness.

Types of Vacuum Flanges

Vacuum flanges are categorized by their standards and applications, including:

1. KF and NW Flanges

These modular flanges are suited for medium to high vacuum applications, utilizing sealing materials and clamps for hermetic connections, making them ideal for systems requiring frequent reconfiguration.

2. Conflat (CF Flange

CF vacuum flanges are designed for ultra-high vacuum applications, using metal gaskets for connections that withstand thermal cycling and chemical corrosion, ensuring high levels of tightness.

3. ANSI Flange

Adhering to the American National Standards Institute, these flanges are used in low vacuum and general piping systems, typically connected with bolts and nuts.

4. JIS Flange

JIS standard flanges are prevalent in vacuum equipment, offering standards for a wide range of industrial products and technologies.

What Is a Vacuum Chuck?

A vacuum chuck is a fixture that secures objects using negative pressure created by a vacuum, ideal for diverse industrial applications.

Typically table-shaped, these chucks feature several small holes linked to an internal vacuum. This design enables them to firmly hold objects via the negative pressure generated through these holes.

Due to their ability to adsorb objects with flat, non-porous surfaces, vacuum chucks offer broader material compatibility compared to magnetic chucks, which are limited to magnetic materials.

Applications of Vacuum Chucks

Vacuum chucks play a crucial role in securing materials during processes like polishing and packaging. They are perfect for handling delicate precision parts, hygiene-critical food containers, non-magnetic materials such as stainless steel and aluminum, and electronic components susceptible to magnetic fields.

These chucks are especially vital in the handling of semiconductor materials during processing and coating operations, as semiconductors are prone to damage, dust-sensitive, and adversely affected by magnetic fields. They can also be used to float workpieces by switching to positive pressure.

Principle of Vacuum Chuck

The vacuum chuck operates by creating a vacuum inside the table, generating suction through small holes on its surface. This suction force, due to atmospheric pressure differences, firmly secures objects to the table. Releasing the vacuum also releases the suction.

A vacuum is created either by a vacuum pump or through a vacuum ejector, using compressed air. The system’s scale varies based on the object’s size, material, and the required suction force.

Structure of Vacuum Chuck

The efficacy of a vacuum chuck depends on the small holes’ arrangement and size. Factors like the disparity in size between the chuck and the workpiece’s flat area, and the workpiece’s thinness, can impact its ability to securely hold the workpiece.

Types of Vacuum Chucks

Ceramic vacuum chucks excel in handling partial suction due to their high-precision small holes. These chucks are adept at managing thin workpieces and can be used atop standard chucks for improved functionality or in cylindrical forms for transport applications.

They also feature air-blowing functions to facilitate object movement and continuous air discharge to prevent foreign matter from entering the holes.

What Is a Vacuum Seal?

A vacuum seal is a sealing device that utilizes the properties of a liquid called magnetic fluid, which is attracted by a magnet.

The magnetic fluid is attracted to the magnet like iron sand while holding the fluid. The magnets in the vacuum seal hold the magnetic fluid, sealing the gap between the device and the joint. This prevents air, gases, and particulates from entering the sealed object, thereby maintaining a vacuum environment.

The holding force of the magnetic fluid is determined by the strength of the magnet (magnetic force), so the stronger the magnetic force, the greater the pressure resistance of the ring of magnetic fluid.

Use of Vacuum Seals

Vacuum seals are used to maintain quality when manufacturing products in which impurities, air, or moisture are strictly prohibited. Due to their high effectiveness in blocking fluid magnetism, they are often used in manufacturing industries with high vacuum, such as semiconductor, solar cell, or OLED panel manufacturing for smart phones.

Under these manufacturing conditions, vacuum seals have a very wide range of applications, as they are required to save energy and make manufacturing equipment more compact.

1. Semiconductors

In semiconductor manufacturing, vacuum seals are used in sputtering, CVD, and ion implantation equipment. These require a high-vacuum environment with vacuum seals to form uniform thin films and to control the electrical properties of semiconductors through ion implantation.

2. Solar Cells

They are also used in monocrystalline pulling equipment for the production of silicon ingots, which are indispensable for the manufacture of solar cells. Silicon ingots are vacuumed to prevent contamination from dust and dirt and oxidation by air during the manufacturing process. Vacuum seals are utilized to maintain a vacuum environment inside the equipment.

3. Organic EL

In OLED, vacuum seals are required for vacuum deposition to form thin films of OLED elements. In recent years, the demand for vacuum seals has increased as the demand for OLED has grown from LCDs.

Principle of Vacuum Seals

Vacuum seals use a liquid called magnetic fluid. A magnetic fluid consists of three components: magnetic nano-sized particles (magnetic particles), a surfactant, and a base liquid, such as water or oil.

Magnetic particles usually agglomerate with each other like magnets (spiking phenomenon), and surfactants are generally used to prevent this. Since surfactants have polarity, the same polarity repels each other. As a result, it is possible to create a stable magnetic fluid as a colloidal solution without agglomeration.

In addition to the magnetic fluid, the vacuum seal uses a permanent magnet and a rotating shaft. The vacuum seal has a mechanism that seals while rotating at high speed, but prevents contact between the rotating shaft and the magnetic pole material or permanent magnet. Since solids do not come into contact with each other like oil sheets, there is no need to worry about friction.

Structure of Vacuum Seals

A wide range of shaft shapes of seals are manufactured, from small products of a few millimeters to large products of several meters in scale. Vacuum seals consist of a rotating shaft and a pole piece with strong magnetism, and a magnetic field is generated in the gap between the two materials.

By guiding the magnetic fluid through the gap in this magnetic field, the magnetic fluid forms an O-ring and adheres closely to the pole piece, preventing intrusion from the outside.

Features of Vacuum Seal

Because of the contact between the rotating shaft and the fluid, the rotating shaft can be rotated as desired without abrasion. Furthermore, since the magnetic fluid seals the gap along the magnetic force lines, it does not flow out due to pressure differences, thus enabling the maintenance of a vacuum environment.

The greater the magnetic force, the higher the pressure resistance of the ring formed by the magnetic fluid. By forming the ring in several stages, a pressure-resistant vacuum seal is completed and can withstand greater pressures.

The inert nature of the magnetic fluid and its low vapor pressure also have a bearing on the life of the vacuum seal. The advantage of using a magnetic fluid that does not react easily is that it is resistant to deterioration and can be used for a long period.

What Is an Expanded Polystyrene (EPS) Densifier?

An expanded polystyrene (EPS) densifier is a device that melts styrene foam to reduce its original volume using an on-board heat source without using fire or solvents.

Since styrene foam is melted without using flames or solvents, carbon monoxide from incomplete combustion and harmful gases generated from solvents are not generated, and styrene foam can be melted safely.

In addition, when styrene foam is dissolved by high-temperature heat treatment or solvents, it is difficult to recycle due to deterioration caused by heat and solvents. With expanded polystyrene (EPS) densifiers, there is almost no such deterioration, making it possible to recycle.

Uses of Expanded Polystyrene (EPS) Densifiers

Styrofoam is used throughout our daily lives as containers for seafood and agricultural products, cushioning materials, containers for keeping food hot or cold, and as the inner container of cooler boxes and other containers due to its water resistance.

Styrofoam is a mixture of polystyrene and other resins with air bubbles in them, making it lightweight, but its volume is large, and it is very costly to transport styrofoam as waste material in bulk.

Expanded polystyrene (EPS) densifiers can significantly reduce transportation costs by reducing the volume of styrene foam, and since styrene foam is dissolved at a lower temperature than when it is burned, it can be recycled.

Principle of Expanded Polystyrene (EPS) Densifiers

The main treatment process with expanded polystyrene (EPS) densifiers consists of three steps: crushing, dissolving, and cooling and forming.

First, the styrene foam to be processed is crushed into small pieces by a built-in crusher. In this way, the styrofoam can be dissolved more efficiently.

The crushed styrofoam is then dissolved at relatively low temperatures (~140 degrees Celsius) by frictional heat generated by electric heaters and rotating specially shaped disks, or by warm water, which removes air from the styrofoam. With the air removed, the styrofoam is reduced in size by up to 1/100th of its original volume.

The melted de-foamed resin is then formed into bars or ingots. This shape allows the treated styrofoam to be stored without taking up too much space.

The average size expanded polystyrene (EPS) densifier can process about 40 to 50 kg of styrene foam per hour, and its power consumption can be reduced to about one-fourth that of conventional heat and solvent treatment, making it an extremely energy-saving and environmentally friendly solution.

What Is an Environmental Tester?

An environmental tester is a device that simulates various environmental conditions to measure changes in the environment of the test object.

Environmental testing is used to verify the reliability of components and materials mounted on various types of equipment. Environmental testers are devices that artificially create various environments to which components and materials may be exposed.

Environmental testers measure the change and resistance of parts and materials in the environment they create. For example, we check the operation of parts before and after exposure to a given environment to see if there are any problems with their resistance to the environment.

Applications of Environmental Testers

Environmental testers are used in various fields to test the environmental resistance of various components and materials. In addition to testing the resistance of various components in use, environmental testing is also used to detect defects in the design and manufacturing of various components during development.

Environmental test results are also necessary for quality assurance. Furthermore, the results of environmental resistance in the use of various components serve as a guide for customers to select products at the time of purchase.

Various equipment and components have various regulations that must be observed depending on the environment in which they are used and the characteristics of the products. The domestic standards are JIS (Japanese Industrial Standards), while the global standards are IEC (International Electrotechnical Commission) standards. These standards have regulations for each type of equipment and operating conditions, and since environmental testing is included in these regulations, environmental testers are also used to determine whether a product passes or fails the standard.

Principles of Environmental Testers

Environmental Ttesters include temperature and humidity testers that change the conditions of temperature and humidity, and water resistance testers that spray water. This section describes the main types of environmental testers.

1. Temperature/Humidity Testers

In temperature/humidity testers, various devices, parts, and materials to be tested are placed inside a temperature/humidity tester for testing. The equipment is then set to the upper and lower temperature and humidity limits specified in the product specifications and standards, and the test is switched to the upper and lower temperature and humidity conditions at regular intervals.

The operation of the equipment and parts is checked before the test and again after the test, and if the operation is confirmed to be the same as before the test or within the specified range, the test is completed.

2. Thermal Shock Tester

In the thermal shock tester test, the temperature setting is switched between low and high temperatures for a short period to observe changes in the equipment and components. When environmental temperatures change rapidly, thermal expansion and contraction occur in individual components of parts and equipment. Failures such as cracks in joints and surfaces occur, which are caused by differences in the thermal expansion coefficients of the individual components. The degree of these defects determines whether the test passes or fails.

3. Water Resistance Tester

Water testers are used to evaluate the water resistance and water resistance of electronic components and small electronic products when subjected to wind, rain, or splashing water. Tests are conducted by sprinkling, fountaining, or flooding the test object. 

4. Accelerated Weathering Resistance Tester

Accelerated weathering testers simulate indoor and outdoor conditions such as sunlight, rainfall, temperature, and humidity to accelerate the deterioration of test objects. The tester performs indoor testing using an artificial light source and produces results in a short period.

5. Corrosion Tester

Corrosion testers are used to examine the effects of gases, chemicals, acid rain, and salt water on test objects. The most famous tester is the CASS tester, which measures the degree of corrosion using a sodium chloride solution with copper chloride added to acetic acid.

Gas corrosion testers, which use corrosive gases such as hydrogen sulfide (H2S), sulfur dioxide (SO2), nitrogen dioxide (NO2), or chlorine (Cl2) to measure corrosion, are also often used.

More Environmental Tester Information

Other Environmental Testers

Environmental testers are used to evaluate physical properties without controlling temperature or humidity.

1. Vibration Testers
Vibration testers subject equipment and components to vibration conditions that exceed those expected during transportation or in relatively vibration-prone locations such as factories. Operation is checked before and after the test, and the test is completed when similar results are obtained.

2. Drop Tester
A drop tester is a device that drops test items naturally while repeatedly maintaining the specified conditions to examine the impact and effects of dropping the test object. It is used to check the impact resistance of heavy cargo or packaging materials.

What Is an Environmental Laboratory?

An environmental laboratory is a test room designed to simulate various environmental conditions. They are used to confirm in advance that various devices and components mounted on devices will operate according to specifications without problems when used under various assumed conditions.

Environmental tests are conducted using the following types of environmental testing equipment.

Vibration testers can generate specific vibrations based on the surrounding environment and vibration during movement, and drop testers simulate the case where equipment is dropped. Electrostatic testers that simulate static electricity that may be generated in the operating environment, noise testers that simulate noise contamination from surrounding electrical and electronic equipment, power supplies, etc., and surge testers are used.

In addition to these testers, there are temperature and humidity testers that can change the temperature and humidity conditions, but if the device under test is large, such as a television, refrigerator, or washing machine, it will not fit inside the environmental tester. Environmental laboratories are used in such cases.

Uses of Environmental Laboratories

Environmental laboratories are used to test various types of equipment and components in a test chamber.

Various types of equipment and parts are used under various environmental conditions. In the case of equipment intended for the domestic market, it must operate normally under temperature conditions ranging from Hokkaido in the middle of winter to Okinawa in the middle of summer. Therefore, since normal consumer products are tested in temperatures ranging from -10 to +40 degrees Celsius, environmental laboratories can be set to produce such conditions in temperatures ranging from minus several tens of degrees Celsius to plus 50 degrees Celsius or more.

Using such a test chamber, we set the upper and lower temperature and humidity limits specified in the product specifications or standards, and switch to these upper and lower temperature and humidity conditions at regular intervals. The operation of the equipment and components is checked before the test, and the same checks are made again after the test is completed.

Principle of Environmental Laboratories

Equipment and various components are sold with the obligation to agree on product specifications and guarantee these specifications to the purchaser. Purchasers purchase products after confirming the manufacturer’s specifications and use the products according to their intended purposes.

Additionally, various equipment and parts must adhere to specific regulations depending on the environment in which they are used and their product characteristics. The International Electrotechnical Commission (IEC) provides global standards. Manufacturers must ensure that their products meet the individual requirements for each device and usage condition.

Environmental testing is not limited to testing a product with the specific testing equipment designed for that product. Product designers must consider variations in component characteristics. Therefore, it is essential to design products with a certain level of tolerance to standards, assuming that some components may have characteristics that make them more likely to meet the standard. In product design, designers often set a margin beyond the standard values under rigorous conditions and consider the design complete when the product passes the test.

What Is a Spherical Bearing?

Spherical bearings are bearings in which the inner and outer rings are in spherical contact.

They are mainly used for oscillating, tilting, and low-speed rotational motion. Spherical bearings are spherical and can support large radial loads and axial loads in both directions at the same time.

There are two main types: lubricating type, which requires lubrication of the spherical surface of the sliding portion in contact with the bearing, and non-lubricating type, which does not. They excel in wear resistance and are used in joints of industrial and construction machinery and other locations where large loads are applied.

The lubrication-free type is maintenance-free and is best suited for applications where oil is not required, such as in food processing machinery, or parts of machinery that cannot be lubricated.

Applications of Spherical Bearings

Oilless spherical bearings have excellent resistance to wear and are capable of carrying large loads. Examples of applications include industrial machinery and construction equipment.

Oilless spherical bearings have low creep deformation when supporting compressed loads and have excellent resistance to wear. In addition, they do not require lubrication and do not require maintenance.

Oilless spherical bearings are suitable for supporting axial loads in one direction and are used in areas where oil is used, such as in food products, and in locations where lubrication maintenance is difficult.

Principle of Spherical Bearings

1. Oil-Supplied Bearings

Spherical bearings are generally made of high-carbon chromium bearing steel for both the inner and outer rings, and the sliding surfaces are treated with a phosphate coating. In addition, many are covered with a dry coating of molybdenum disulfide. These bearings operate at low torque and have a large load capacity with excellent wear resistance.

The sliding portion between the inner and outer rings is characterized by spherical contact and the absence of the grooves necessary to incorporate the inner ring, which allows for a large load capacity and can be used where impact or alternating loads are applied. If the sliding surfaces where the inner ring and outer ring contact each other are poorly lubricated, heat generation and other problems can occur.

2. Oilless Spherical Bearings

An example of an oilless spherical bearing is a combination of a special PTFE liner reinforced with copper alloy adhered to the sliding surface of the outer ring and hard chrome plating on the sliding surface of the inner ring. High lubricity is added to the sliding surface itself.

Even without lubrication, large loads can be supported by applying a process such as adhering to a material with excellent resistance to wear.

Other Information on Spherical Bearings

1. How to Fix Spherical Bearings

When using spherical bearings, the housing in which the spherical bearing is mounted and the shaft that is inserted into the spherical bearing are dimensionally toleranced according to the application. Care must also be taken to ensure that the housing has sufficient wall thickness to prevent deformation due to load.

When mounting in a housing, only the outer ring should be pushed in so that no force is applied to the inner ring. It is also important to push only the inner ring into the shaft as well so that no force is applied to the outer ring. Poor mounting may result in uneven loading due to deformation of the bearing, resulting in shortened service life and rattling.

There are four different conditions of use when determining the dimensional tolerances of the housing and shaft of a spherical bearing: inner ring rotating load, outer ring rotating load, normal load, and heavy load.

Dimensional Tolerances for Oilless Type
For the inner ring rotating load, the recommended tolerance for the shaft under normal load is k6, and for heavy load is m6. For both housings, H7 is recommended for steel and J7 for light alloys.

For the outer ring rotating load, the dimensional tolerance of the shaft is h6 for both normal and heavy loads, and the housing is k7 for steel and m7 for light alloy for normal loads; for heavy loads, m7 for steel and no light alloy is specified.

Dimensional Tolerance for Oil-Filled Type
There are slight differences in dimensional tolerances for oil-feeding types, so it is necessary to check the manufacturer’s technical data before determining dimensional tolerances.

2. Examples of Spherical Bearing Applications

Spherical bearings are used in a wide range of applications, with the most common use being in large equipment. In the use of shaft couplings, a shaft is connected with a coupling having two spherical bearings. This allows the eccentricity and misalignment of the two shafts to be absorbed.

An example of use in heavy construction equipment such as power shovels is the rod ends of hydraulic cylinders used in each joint. Other applications include coupling parts of cranes and suspension parts of trucks, which are often used under heavy loads with vibration and shock.