Rolling Bearings Contribute to the Environment Japan Bearing Association Global environment committee
1. Introduction Environmental problems the world over, beginning with depletion of the ozone layer in the 1980s, have lead to global warming, stripping of natural resources, toxic waste, and so on. The progress we enjoy now may spell out the ultimate demise of our very existence as humans in general. Global environmental issues are related to the activities of every individual. Although not readily apparent, rolling bearings, being an essential element in various industries, also have an impact on the environment. Originally designed to use less energy and save natural resources through their entire life, rolling bearings are environmentally friendly and have little negative impact on the environment. Specifically, one distinctive feature of bearings is low friction. This contributes to the use of less energy of all rolling areas. Regarding bearing production, recycled steel from scrap is mostly used for the raw material of bearing steel, and machining grids. Chips at the production process are also melted and recycled. With these points in mind, we want to discuss and touch on the topic of the environmentally friendly aspects of rolling bearings.
2. Energy Conservation Since the industrial revolution, energy consumption has grown significantly. Most energy requirements are filled by the consumption of fossil fuels, such as petroleum products, and coal. These energy sources are limited, though, and will eventually be depleted in the future. During the 1970s oil crisis, attention was focused on energy conservation measures, with the realization that fossil fuels are finite. In the later half of the 1990s, a new theme, the reduction of carbon dioxide, was proposed with the primary focus on global warming and what industries can do to achieve further savings in energy utilization. Rolling bearings, which we produce, play a significant role in energy conservation. This has been our contribution since ancient times. Once we understood the basic concepts, we were moving hefty objects of wood or stone on rollers. We learned that this required much less effort than just sliding. We finally understood that using rollers could reduce frictional resistance, thus contributing to energy conservation. From day one, rolling bearings have been contributing to energy conservation. Though indirect, the contribution our products make to industries in regards to their energy conservation is enormous. Since this effect is difficult to measure in numbers, the average person might not be aware of the contributions bearings make. The loss and waste of energy through frictional resistance of rolling bearings has to be reduced even further to its barest minimum. Therefore, bearing manufacturers need to increase their efforts to further their contributions to industries. Here are some examples of how bearings contribute to energy conservation. 2.1 Energy Conservation by Rolling The most basic characteristic of rolling bearings is low friction. Compared to sliding bearings, substantial savings in energy can be attained by replacing sliding bearings with rolling bearings. 2.1.1 Contribution of Automotive Rolling Bearings Figure 1 shows the torque loss of sliding bearings and rolling bearings. As shown in Figure 1, the torque loss of rolling bearings is small for the entire range of speed. This clearly indicates that rolling bearings contribute to energy conservation. For example, if all the automobiles in Japan only used sliding bearings and ran at the speed of 60 km/h, which is the point of least torque loss difference, the increased amount of fuel consumption would be 480,000 kl (crude oil). The number of barrels of oil, when stacked one of top of the other, would be 240 times higher than Mt. Everest.
Torque loss (N·m)
8.0 Sliding bearings (Rolling bearings are not used)
6.0 4.0
Energy conservation by rolling bearings
2.0 Rolling bearings
0.0 0
30
60
90
Car speed (km/h)
Figure 1 Comparison of energy consumption for vehicles with and without rolling bearings.
2.1.2 Contribution of Rolling Contact for Roller Tappets and Rocker Arms Originally, the roller in an engine would slide on the cam. Now, many engines use roller tappets that have a hardened steel roller turning on needle bearings. This reduces friction and improves fuel economy (Figures 2 and 3). For most sedans, engine rpm is mostly in the low and medium ranges. In these ranges, since the loss of the valve system is relatively high among entire engine frictional loss, introduction of rolling bearings in valve system has contributed to better fuel economy (Figure 4). Conventional rocker arm (Sliding type)
Rocker arm with needle bearings
Figure 2 Design of rocker arms (See Document 1)
Running torque (N·m)
Test conditions Actual engine motoring Oil temperature: 100°C Sliding rocker arm Rolling rocker arm
Camshaft speed (rpm)
Figure 3 Running torque of actual engine head motoring
Field fuel
100km/h 80km/h 60km/h 40km/h 10-mode fuel consumption Idling fuel consumption
0
1
2
3
4
5
6
7
8
9
Fuel efficiency (%) Figure 4 Improved fuel economy with rocker arms and needle bearings (See Document 1) 2.1.3 Contribution of Automotive Transmission Rolling Bearings Needle roller bearings are used in transmission gear shafts (Figure 5). In the past, sliding bearings had been used for these applications. Rolling bearings replaced the sliding bearings with no change to space requirements. Frictional torque has been reduced by about one-tenth with increased machine and fuel efficiency resulting in greater energy conservation.
R: Radial type S: Axial type
Figure 5 Application of rolling bearings in a sedan transmission
2.1.4 Contribution of Fan Motor Miniature Ball Bearings Let’s compare the consumption of electricity for two 80-mm fan motors, each running at 2,550 rpm. One fan incorporates miniature ball bearings (Bearing number: 693) and the other incorporates sliding bearings (Sintered metal). The results are as follows: Miniature ball bearings: 0.9 w Sliding bearings: 1.2 w These results show that if 100 million fan motors ran for 8 hours a day, 250 days a year, the total energy conservation would be 6 million kw·h/year. If powered by plants using fossil fuels, the reduction in carbon dioxide emissions would be 5,280 tons. 2.2 Energy Conservation by Reducing Torque in Rolling Bearings In our efforts to further conserve energy, we have made efforts to reduce bearing torque loss. 2.2.1 Contribution of Low-Friction Tapered Roller Bearings
Tapered roller bearings used in automotive powertrains have rather high frictional resistance compared to other rolling bearings. The bearing running torque has been reduced 20 to 50% by reducing friction coefficient between the large head of the roller and the rib surface, and by applying crowning on the outer ring raceway (Figure 6).
Bearing bore: ø30, ø50 mm Axial load: 3.92 kN Lubricant viscosity: 23.3 mm²/s Running torque N·m
Conventional bearings Improved bearing I Improved bearing II
Speed (rpm) Figure 6 Running torque of low-torque tapered roller bearings
2.2.2 Contribution of Power Hand Tool Bearings Hand tools include tools powered by electric motors, such as grinders, drills, cutters, etc. Figure 7 shows the bearing application for a grinder. Running conditions for these types of bearings are harsh and require superior wear and corrosion resistance. Various conditions include operating under high speeds (some tools exceeding 20,000 rpm), and exposure to dust, water and mist. Sealed deep-groove ball bearings are most popular for hand tools. If dust or water resistance is required, contact-type seals are often incorporated. The very nature of hand tools requires that they are light in weight, have low vibration, and generate as little heat as possible. These requirements extend directly to the bearings of such tools. In order for the tools to meet user requirements, the bearings, too, must have low vibration, and generate as little heat as possible (low torque). Power hand tools that meet the above requirements also require smaller motors resulting in less energy consumption. To achieve all of these, the following innovations have seen a 50% increase in improvements: (1) Adoption of low-torque contact seals (2) Selection and quantity of greases suitable for high speeds (3) Low torque design of bearing interiors
Figure 7 Bearing arrangements in a power grinder
2.2.3 Contribution of Seal and Seal Recess Improvements (Standard deep groove ball bearings) for Low Torque Bearings Running torque has been reduced 20% by redesigning the seal and seal recess of sealed deep groove ball bearings (Figure 8).
Running torque ( %)
Ball bearing: 6908, both sides sealed Inner ring rotation: n = 1800 rpm
Conventional
New
100
0
Conventional New
Figure 8 Low torque achieved by improvements in the seal recess The examples and information provided thus far clearly indicate the positive impact that bearings have had on saving natural resources, and show how bearings can assist various industries in lowering energy consumption. As suppliers of such bearings, we promise to maintain our endeavor to develop optimum bearings to meet various needs of both industry and the environment. 3. Saving of Natural Resources 3.1 Light Weight 3.1.1 Streamlining Massive Bulk In the past era of excess, emphasis was on performance while structural size was ignored. Current trends require that we review the past era of waste and excess. To meet modern requirements of efficiency, reliable design and production technologies are indispensable. In comparison to the overall size of the machine or equipment, bearing weight or size is not so great. However, production of compact and light bearings, while maintaining reliability, allows for more freedom in end-product design, substantially contributes to making machines and equipment more lightweight. Figure 9 shows the axle bearings of Japan’s shinkansen “bullet” train. Forty years ago, the 0-series model (Maximum speed: 250 km) utilized an axle bearing that consisted of one double-row cylindrical roller bearing for radial load, and one deep groove ball bearing for axial load. A single axle bearing weighed in at 75 kg. Then, 30 years later, the 300-series model (Maximum speed: 300 km) was introduced. Bearing mass was drastically reduced to only 31 kg by utilizing improved materials and by design reviews. The most obvious change was in eliminating the deep groove ball bearing for axial load and applying all the axle load to double-row cylindrical roller bearings instead. Bearing mass of the latest mode, the 700-series, is only 25 kg. Since each coach is installed with 8 sets of bearings, coach mass is directly reduced by 400 kg (75 – 25) × 8). Furthermore, bearing size has also been reduced. The lighter and smaller bearings allow for even greater energy conservation of the bullet train.
55
215
170
210
165
155
0-series (1964) Mass 75 kg
300-series (1992) 31 kg
φ220
φ120
φ230
φ120
φ280
φ130
φ125
φ260
130
700-series (1999) 25 kg
Figure 9 Evolution of axle bearings for Japanese shinkansen “bullet” trains Figure 10 provides an example of a hard disk drive (HDD) used for data storage devices in personal computers. During the 1970s, HDDs grew in popularity as data storage devices for large computers. Disk diameter was larger than 10 inches, and the spindle was supported by precision angular contact ball bearings of around 40 mm bores. Recently, the density of personal computer HDDs has drastically increased. Disk diameter was reduced to 3.5 inches, and then 2.5 inches and 1.8-inch disks are appeared. To meet the demand for reduced disk sizes, bearings installed into the disk support became small, extra small ball, and finally miniature. Now, miniature ball bearings are industry standard. High precision bearings have helped make high-density, compact, and high-speed HDDs a reality. The dynamic running accuracy (NRRO: non-repetitive runout) of support bearings for HDDs has improved to the 0.01 µm-level (Figure 11) Miniature ball bearings
NRRO, µm
Figure 10 Cross-sectional view of a HDD spindle motor
Spindle motor
Bearing
Year Figure 11 Required NRRO for HDD spindle motors and bearings 3.1.2 Integration or Built-in Surrounding Parts (Unification) The amount of space used by a part, its mass, or the number of related components, can be reduced by integrating or unifying the bearings and other surrounding components. Direct use of the mating shafts can result in resource and energy conservation. Figure 12 shows an example of automotive wheel hub unit. 40 years ago, a pair of tapered roller bearings, or angular contact ball bearings, were used. Specifically, automakers assembled the bearings with the housing and the hub shaft. The original configuration evolved to double-row angular contact ball bearings. With the second and third generations, bearings were being integrated into the surrounding components. Hub mass is reduced by 20% owing to the reduction of components. The lighter weight contributes to improved fuel economy, and integration of hub components contributes to labor cost savings for automakers. Moreover, variations in tightening torque at the automaker’s bearing assembly line is simplified and more accurate. Overall performance, quality, stability, and safety of the vehicles are enhanced.
Second generation + constant velocity joint
Third generation + constant velocity joint
Integrated constant velocity joint
Figure 12 Evolution of wheel hub unit bearings Figure 13 shows an example of needle roller bearings. Needle roller bearings have less cross-section height compared to cylindrical roller bearings and are more lightweight. The example shows installation of needle rollers with a cage and drawn-cup needle roller bearings. By utilizing the housing or shaft of mating machines as a bearing ring, these bearings can reduce bearing height. K: Needle rollers with cage and rollers T: Drawn-cup needle roller bearing
Figure 13 Needle roller bearings in a planetary gear reducer
3.1.3 Thin Cross-section of Standard Bearings Deep groove ball bearings, which are easy to use, are most common for the 60, 62 and 63 series. Ever since bearing manufacturers started producing the 67 series, in addition to the 68 and 69 series of which cross-section is small, users can easily procure thin cross-section bearings. Thin cross-section bearings, as shown in Figure 14, have a smaller outside diameter and width if the bore diameter is the same. Therefore, they are more lightweight and compact.
64 series 63 series 62 series 60 series 69 series 68 series 67 series
Figure 14 Comparison of cross sections of bearing series 3.1.4 Adoption of Pressed Steel Bearing rings can be made of pressed steel if the application is limited and the pressed part can fulfill the reliability required for bearings. For these types of bearings, the rings are thinner and the bearing mass can be reduced. Figure 15 shows an automotive clutch release bearing whose rings are replaced with pressed rings. Mass reduction is about 10%.
Conventional (Machined rings)
(interchangeable)
Pressed steel (Pressed rings)
Figure 15 Clutch release bearings
3.2 Long Life Bearing manufacturers have tried to improve and develop bearing materials through cooperative research with steel manufacturers to extend bearing life and improve reliability. Research includes reduction of impurities and oxygen in steel, special materials for special applications, development of special heat treatment, and surface modification. The results are lightweight and long-life bearings that contribute to energy conservation. Further efforts for longer life are continuously being promoted to support all industries in the future. The following are examples contributing to resource conservation.
Oxygen in steel, ppm
3.2.1 Longer Life by Improving Purity of Bearing Steel To meet the requirements of lightweight and fuel efficient cars, maintenance-free steel mill equipment, and bullet train related equipment, bearing running conditions have been severe. The demand for longer life is never-ending. By the early 90s, steel life was seven times of that from the late 60s. The purity of steel was improved by reducing oxygen content and non-metallic incursions (oxide impurity which is origin of fatigue flaking) in bearing steel (SUJ steel: equivalent to AISI 52100) (Figures 16 and 17).
LD introduced
LD: Ladle vacuum degassing RH: RH vacuum degassing LF: Ladle refining CC: Continuous casting EBT: Eccentric bottom tapping EBT introduced
RH introduced
LF introduced CC introduced
Years
Figure 16 Reduction of oxygen in bearing steel
Continuous casting
Bearing life, h
Ladle refining
> 7 times ßRated life
Vacuum degassing
Years Figure 17 Evolution of rolling fatigue life of bearing steel (ball bearing: 6206)
Accumulated failure probability, %
3.2.2 Longer Life by Development of Special Bearing Steels To restrict cracking extension, bearing manufacturers have developed bearings whose life is six times longer compared to conventional bearings. Bearing steel structural phase and temper resistance are strengthened by adding Ni and Si in cooperation with steel manufacturers (Figure 18).
● Clean oil lubrication Test bearings: 6206 ball bearings Load: 9 kN Lubricating oil: #68 turbine oil
Calculated life
General bearing steel
Highstrength bearing steel
Life, h Figure 18 Fatigue life test results of high-strength bearing steel
3.2.3 Longer Life at High Temperature with Special Bearing Steel Development One of the requirements of the steel mill process is longer life at high temperatures. This is in addition to the already severe conditions of rolling bearings. By developing special bearing steel with an added alloy component, longer life can be achieved for up to 250°C. Life is 3.5 times at room temperature and 30 times at 200°C compared to conventional bearing
steel (Figure 19).
Accumulated failure probability, %
99
Test temperature: 200°C Test-piece: ø47 × 7 mm plate Used balls: ø6.35 (1/4”) Si3Ni4 balls Contact stress: 5.5 GPa Loading speed (frequency): 3000 times/min Lubricant: Ether-base oil
SUJ2 80
STJ2
50
20 10 5
1
105
103
108
107
Life (× 105)
Life ratio
SUJ2
9.1
1
STJ2
No flaking
> 30
Life (load cycle) Figure 19 Life test at 200°C
Accumulated failure probability, %
3.2.4 Longer Life Under Contaminated Lubricating Oil for Special Heat-Treated Bearing Steel To satisfy longer life requirements of transmission bearings, which are used under severe running conditions, that is, running under contaminated oil with steel chips, we developed bearings with a life that is 10-times longer compared to conventional bearings. This was accomplished by applying special heat treatment to obtain the optimum retained austenite and to form an improved hard surface (Figure 20).
● Contaminated oil lubrication Specimen: TRA0607RYR Load: Fa = 13.7 kN Fr = 20.7 kN Speed: 2000 rpm Foreign particles: Total 0.12 wt% (1.1 g/l) General bearings
Improved bearings
Life (h) Figure 20 Fatigue life test of tapered roller bearings with optimum steel and heat treatment under contaminated oil
3.2.5 Longer Life by Insulated Layer (Film) Electric corrosion (scales and chips) occurs in bearings for railway traction motors due to the passing of an electric current through the bearings. Scales and chips decrease bearing life. To prevent passing of the current, an insulated layer (sputtering of ceramic or PPS injection molding) is provided on the exterior of the outer ring. By applying high insulation (more than 1000 MΩ), bearing life is extended two to three times longer than conventional bearings (Photos 1 and 2).
Photo 1 Ceramic-insulated bearings
Photo 2 PPS-insulated bearings
3.3 High Speeds Rolling bearings used to support rolling parts of all industries are constantly being developed to meet the requirements of high speeds and performance year after year. Figure 21 shows the history of high speeds for rolling bearings of machine tool main spindles. Figure 22 shows the present conditions of high-speed bearings by industry.
2.5
Angular contact ball bearings Cylindrical roller bearings
2.0
Ultra high-speed or high rigidity machining centers
(Jet lubrication)
d·n value× 106
.
1.5
High-speed angular contact ball bearings High-speed machining centers
Ceramic ball bearings (Oil-air lubrication)
High-speed machining centers
1.0 Ball bearings with ceramic balls (Grease lubrication) Machining centers, NC lathes and milling machines
0.5 Lathes and milling machines Tapered roller bearings (Forced lubricating oil circulation)
0
1965
70
Angular contact ball bearings Cylindrical roller bearings (Grease lubrication)
75
80 Years
85
90
95
2000
Figure 21 History of rolling bearing speeds for machine tool main spindles d·n value: Bearing bore diameter, d (mm) × speed, n (rpm)
Present Near future Bearing bore
Speed
Lubrication method
d·n value (× 106)
Application
Machine tools
Aircraft
Jet Oil- Mist Grease air
1
2
3
4
Jet engines Machining centers Internal grinders
Cars
Magnetic clutches
Electric appliances
Turbochargers Cleaner motors
Figure 22 The present conditions of high-speed bearings by industry To achieve such high speed running of rolling bearings, optimum design of rolling bearings and related technologies (lubrication, cooling, etc.) play important roles. Bearing preload switching technology, low-heat generation interior design, ceramic balls, and low dynamic loss minute lubrication (oil-air lubrication) are the key points for attaining high speeds. Besides the contribution to industrial production activities, bearings used in transportation and information equipment have also improved to meet requirements of high speed. This has helped reduce costs and has contributed to energy conservation. The tendency of high speed requirements will increase steadily and we are enthusiastically promoting the development such high-speed technology. 4. Recycling of Bearing Components Refuse of bearing materials at the press process is reprocessed as steel scrap. Machining chips and burrs from processing, which are about 100 thousand tons per year in Japan, are removed from water and oil and recycled as raw material for steel (Photos 3 and 4).
Photo 3 Billets of grinding chips
Photo 4 Billeting machine of grinding chips In addition to the above, recycling systems for plastic materials have been established. We continue to make efforts to reduce or reuse the exhaust or used oils at the production process. Rolling bearings are made of steel. The bearings in cars and home electric appliances, which are major application items, are reclaimed and recycled as an iron resource. The Japan Bearing Association increased recycling by 75%, 10 years ahead of schedule. We are now working on targeting new activities and establishing new goals. 5. Improvement of Noise Characteristics 5.1 Air conditioners Applications which require low noise are home electric appliances, information equipment, audio-visual equipment, etc. Fan motors in air conditioners or air cleaners, which are used during night or while people are sleeping, must be quiet in operation. Figure 23 shows the change of noise level of air conditioners and Figure 24 shows the change of sound level of bearings for air conditioner fan motors. Clearly, advancements made in ball bearing noise has lead to quieter air conditioners.
60 50 Exterior equipment B
40
Figure 23 Evolution of air conditioner noise levels
100 Ball bearings (100 at 1980)
Vibration*1 %
80
60
40
20
0 1980
1985
1990
1995
Years
2000
1
* Vibration: Anderon value
Figure 24 Evolution of fan motor bearing sound levels 5.2 Traction Drives Figure 25 shows a traction drive reducer system which utilizes rolling traction force with ring and rollers in a conventional planetary gear device. Planetary rollers
Sun roller
Low speed side
High speed side
Ａ
Ａ－Ａ
Ring
Ａ
Figure 25 Traction drive reducer system
By replacing gears with rolling contact, noise and vibration are reduced compared to a conventional power transfer system as shown in Figure 26. 20
15
Vibration m/s
2
Planetary gears 10
5
Traction drive
0 0
1000
2000
3000
4000
5000
Sun roller speed, rpm Figure 26 Comparison of vibration 5.3 CT Scanners A CT scanner (Photo 5), which is one of many valuable medical devices, consists of a patient bench and inspection unit. As shown in Figure 27, the cathode-ray tube and detector (imagery system), are attached to a rotating frame of the inspection unit. A bearing of 1 m in diameter supports the rotating frame. Though the mechanism is encapsulated, the bearing must still operate quietly. Bearing speed is increasing to shorten the inspection time and to improve image accuracy. This helps to reduce stress and burden of the patient.
Photo 5 CT scanner
Cathode-ray tube
Rotating frame
Bearing
Patient bench Fixed frame
Detector
Drive belt
Figure 27 Structure of CT scanner In medium and low speed models (rotating speed: 40 ~ 90 rpm), a 4-point contact ball bearing (Figure 28) is usually used. To obtain low noise operation, a resin cage is used in the bearing and internal clearance is settled so that the balls at the unloaded zone generate little or no noise. In medium- and high-speed models (rotating speed: 80 ~ 120 rpm), a back-to-back arrangement of angular contact ball bearings with resin cages (Figure 29), or preloaded double-row angular contact ball bearings (Figure 30), are used to restrict noise by increasing bearing rigidity. Moreover, the double-row angular contact ball bearings, which are integrated with surrounding part, enable low noise running with high accuracy.
Figure 28 4-point contact ball bearing
Figure 29 Back-to-back angular contact ball bearings
Figure 30 Integrated double-row angular contact ball bearings
6. Reduction of Materials Inflicting an Environmental Burden Chemical materials, which are dissolved from product waste and garbage, such as mercury, lead, cadmium, arsenic, sexivalent chrome, etc, cause an environmental burden. Rolling bearings, whose major component materials is steel, contain little such materials. Used bearings are usually recycled together with installed machines, thus, bearings have little effect on environment. However, some bearing lubricants place a burden on the environment. Usage is very little, as is the case with lead-based, extreme pressure additives that are contained in lubricating greases. Regardless, we are now replacing such greases with non-lead type greases to reduce any additional burden on the environment. In addition, we will continue to develop and make modification to our grease. We have developed and marketed environmentally conscientious greases that have excellent decomposition characteristics. This is accomplished utilizing the bacteria that occur naturally in the water and soil of fields, rivers, lakes, and oceans. We have developed greases with safety in mind and. Results of living organism impact tests of our greases confirm that we achieved a mark of less than one-tenth of the new eco-mark criteria set for fish (Figures 31 and 32).
Natural decomposition
Natural decomposition rate %
Natural decomposition capability is very high and environmental-friendly (natural decomposition rate: 97.3%)
Natural decomposition grease
Lithium-mineral oil grease (general grease)
Figure 31 Natural decomposition of greases
Low impact on ecology system Acute poisonous test using killifish LC50 value after 96 hours: more than 1000 mg/l (New criteria for eco-mark: 100 mg/l)
Judging criteria of poison against ecology
LC50: 50%-fatal dose density of test on live organism
Relative poisonous level Relatively nonpoisonous Actually nonpoisonous Slightly poisonous Poisonous Very poisonous
LC50 value (mg/l) > 1000 100 ~ 1000 10 ~ 100 1 ~ 10 < 1.0
Figure 32 Impact on ecology
Special fron and 1.1.1-trichroloethane have been used at bearing production lines for cleaning purposes. They are being replaced or eliminated by new environmentally friendly cleaning methods or equipment, such as a pure water cleaning device (Photo 6), and a cleaning device using hydrocarbon-base agent, etc.
Photo 6 Pure water cleaning system Although rolling bearings contain few materials that create an environmental burden, we steadily make efforts to reduce further environmental impact in areas that are not so readily visible. 7. Futures Taking this all into consideration, we believe you can understand the great contribution to the Earth's environment of rolling bearings that are used in all rotating equipment and devices. In the 21st century, laws to prevent further global warming will be rapidly expanded to not only affect home appliances, but also all other industries including those related to transportation and IT. Therefore, the ultrahigh rigidity or ultra long life of rolling bearings should be achieved under the development of zero-impurity next-generation bearing materials. Ultra-low torque bearings with optimum geometric design and extremely low viscosity greases should be also studied. Together with the promotion of a recycling-oriented society, separable rolling bearings with easily classified reclaiming of components will become major bearings and the synthetic rubber for seals will be replaced with paper. Grease base oils will be replaced with animal fat or vegetable oil and environmental contaminated materials will be eliminated from all products. It is not a dream that all the components will be reused or recycled. At the rolling bearing production process, wet cutting or grinding using oil or water-based coolants will be changed to dry cutting or grinding, free of oil mist. This will create a comfortable working environment and zero garbage at the production process, thus achievement of zero emissions is feasible. With bearing industry action plans, together with member companies considering the above conditions, the Japan Bearing Association, Global environment committee is aggressively promoting energy conservation and garbage reduction. We will study to make environmentally friendly products a long-term goal utilizing the lifecycle assessment (LCA) analysis.
Document 1: N. Miyamura, S. Nagano, K. Asano, I. Tanaka, “Development of needle roller type rocker arms”(Japanese language), Internal Combustion Engines, 26 (1987)
