OUTLOOKTechnological Trends and Outlook of Automotive Bearings
K. YOKOTA

Global awareness of environmental improvement has been growing in recent years, and therefore it is necessary
to continue responding to environmental issues on an industry-wide scale. To achieve this, it is important tounderstand the evolution and transformation of motor vehicles precisely, as well as assess bearing technologicaltrends that respond to this evolution and transformation, and advance the development of fundamental technology.
This paper presents the trends of automotive bearings and introduces the evolution of technologies for powertrain
bearings, drivetrain bearings and chassis bearings which respond to these trends.
Key Words: automotive bearing, trends, bearing technology, tribology

1. Introduction

170

160

140

CO2 Emissions, g/km

Due to increasing global awareness about
environmental conservation in recent years, further
efforts for environmental response are necessary in the
future in all industries. In particular, extremely stringent
environmental regulations are placed upon the automotive
industry, and requirements for low friction torque inbearings used within automobiles are rising as this greatly
contributes to CO 2 reduction by improving efficiency
within automobiles. Furthermore, power units (HV, EV,
FCV, diesel, and engine downsizing + turbocharger) havebeen diversified by automakers, so that it is essential todevelop bearings and bearing unit products that support
the function and performance of those power units(Fig. 1)

150
130
110
EU
USA
China
Saudi
Japan

90
70
50
2015

2020

2025

2030

Year

Fig. 1 Transition of CO2 restrictions for cars

(millions)・88 million automobiles in 2015. Slow growth just short of 90 million.
・In the market of advanced nations, the sales volume stays at around 40 million.
・Will expand to 60 million in emerging nations in 2021.

120

70%

60%

50%
Middle and Near East
AfricaRatio for emerging nations
100

40%

80

30%

60

20%

40

10%

20

0%

China

Asia
East Europe/Russia
Central and South America
Advanced nations in Asia
(Japan/South Korea/Australia/
New Zealand/Singapore)
Advanced nations in West Europe

Advanced nations in North America
0
1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

2021

2023

2025

Fig. 2 Global trend in automobile market1)

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−Technological Trends and Outlook of Automotive Bearings−

Year
2020

Long life

Safety and Security
・Bearings for ADAS

Support for
preventative safety

Improved
quietness

2015

2010

2005

Comfort and Convenience
Support forhigh speeds

・Anti-creep ball bearing for outer ring・BB supporting
high rotational speed(two-piece cage)
Higher・BB for electric
・NRB for planetary gear with long life
rigiditysupercharger
・Isolated thrust NRB ・NRB for high-speed
・Improved reliability of hub unit outer seal
planetary gear・Resin magnetic encoder
・Water-resistant idler BB・High-rigidity HUB
・Bearing forwith different PCDs
peeling-resistant rocker arm

Environment and Efficiency
Lower friction
torque・Lower friction torquein chassis bearings

・High-speed BB for HVs ・Third-generation TRB-HUB
・Tapered roller
bearing with・ KE Ⅱ bearing
・Low friction torque thrust NRB
resin cage
Super-low・Alternator pulley with one-way clutch
・Low friction torque BB・friction torque・Rubber magnetic encoder
・Lightweight low friction torque HUB
TRB・Super-low friction torque TRB (LFT Ⅲ)
・Change balance shaft bearing to rolling bearing
・Most lightweight HUB
・NRB for planetary gear side face
2005

2010

2015

Response to environmentallyfriendly vehicles

Downsizing andlighter weight

2020YearFig. 3 Technical trends of automotive bearings

methods during bearing development, technicalinnovations in simulation have progressed recently,
allowing simulation to be utilized for more detailed anddiverse verification. In particular, the flow of lubricant,which is difficult to measure, has been visualized throughfluid simulation, and effects caused by the differencesin shape, fluid properties, and boundary conditions havebeen quantified, which have contributed to lower friction
torque and longer life of bearings. In the next-generation
super-low friction torque tapered roller bearing (LFTIV), the optimal shape has been determined throughthe application of fluid simulation technology, reducing
development time and enhancing reliability (Fig. 4).
−＋
Outer ringA

JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)

Inner ring

D

Cage

Inner ring

Fast
large

Flow velocity

Although the duties required of automobiles arelargely divided into “Safety and Security”, “Comfort
and Convenience”, and “Environment and Efficiency”,
technical trends of automotive bearings differ according
to their applications. This paper introduces the technicaltrends and responding technologies for powertrains,
drivetrains and chassis applications starting in Chapter 3(Fig. 3). Furthermore, as for evaluation and verification

CF
E

Roller

2. Trends of automotive bearings andbearing units

Outer ringB

Cage

Outer ring
Cage

Flow rate

On the other hand, automobile sales will increase in
the global automobile market due to market expansion
following the spread of automobiles in emerging nations.
Automobile sales are not forecasted to increase verymuch in advanced nations, however. Requirements forautomobiles vary greatly depending on the market: In
emerging nations requirements focus on reliability inharsh outside environments, and in advanced nations
requirements center on low fuel consumption and lightweight, as well as the expansion of electronization,
integrated controls, and the Advanced Driving Assist
System (ADAS). The polarization of these markets is
expected to continue (Fig. 2).
This paper will introduce the trends of development of
automotive bearings in the aforementioned environment,
as well as JTEKT bearing products and evaluation
technologies which satisfy required functions andperformances, by their respective applications.

Optimal value
small

small
small
Slow

B
C

large large

Fig. 4 Shape optimization using fluid simulation15

−Technological Trends and Outlook of Automotive Bearings−

3. Powertrain bearings
To respond to fuel economy and emissions regulations,
initiatives are being taken by automakers towards thedownsizing and high efficiency of engines, and the
expansion of HVs. With this comes the necessity of
responding to further low friction torque and high speeds
for powertrain bearings.
The downsizing of the gasoline engine, which began
in Europe, has been progressing recently within Japan
as well, and downsized engines are already being massproduced. For downsizing, supercharger technology
utilizing a turbocharger is necessary in order tocompensate for insufficient output. Turbochargers havebeen used for diesel engines since the past; however it isnecessary to improve turbocharger efficiency as a measurefor fuel economy and emissions regulations. The adoptionof rolling bearings to support the turbine shaft is therefore
expanding to facilitate this improvement.
In the past, sliding bearings were used for turbochargers;
however the large amount of frictional resistance during
acceleration caused a time lag (turbo lag) until the boostpressure rose, creating an uncomfortable response felt by
the driver and worsening fuel economy. Changing fromsliding bearings to ball bearings, which have smaller
frictional resistance, drastically reduced turbo lag andimproved fuel economy. Bearings for turbochargers areused under extremely harsh conditions, such as ultra−1
high speeds (max. 200 000 min ) and high temperatures(max. 350℃). JTEKT is the first bearing manufacturer
that put ball bearings with ceramic balls into practicaluse for turbochargers after providing optimal internal
design and improving the heat resistance of bearing ringand cage materials. JTEKT is currently developing aball bearing unit which unitizes the bearing, housing andspacer, improving installability and stabilizing bearing
performance (Fig. 5). In addition, with the recent ongoingdevelopment of motor-driven superchargers in order toimprove turbocharger efficiency, JTEKT is promoting
the development of bearings able to endure sudden

Intake air

Compressor side

acceleration into high rotational speeds.
Another initiative for achieving high engine efficiency
is a variable valve system. There are two types of variable
valve system: variable valve timing type and variable
valve lift type. Both systems have become electronized.
Ball bearings are used for the spindle of the electric
actuator as well as the reduction gear, which require low
friction torque, fretting resistance, and high rigidity. To
respond to these requirements, JTEKT has developedand is currently mass-producing specially heat-treatedbearings whose internal design features low friction
torque and high rigidity, and which use long-life materials
that improve cleanliness and grease with excellent fretting
resistance, among other features (Fig. 6).

Fig. 6 Example of bearings for variable valve controlled
by ectric motor

The ISG (Integrated Starter Generator) for startup,
electricity generation, and power assist is currently
mass-produced as a means for achieving high efficiency
through auxiliary equipment. Ball bearings are used tosupport the spindle of this generator. The required bearing
performance for this application includes the hightemperature and high-speed durability and vibration andspalling resistance required of bearings for alternators,
as well as water resistance, low friction torque, frequent
startup for the start-stop function, and long-term
durability. It is necessary to consider all of these factors
in the design of this bearing. JTEKT contributes to better
ISG performance through the development of an originalhigh-performance grease, low friction torque seal withhigh sealing capability, and low friction torque cage
(Fig. 7).

Exhaust gas
Turbine side

Rolling bearings
Exhibited at Tokyo Motor Show 2015＊

Fig. 5 Example of turbocharger structure with rolling bearing

16

Fig. 7 Bearing for ISG

JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)

Motor speed is being increased to achieve HVs withlow fuel consumption, low cost, high output, and compact
drive unit. With this comes increasing requirements forhigher speeds for bearings as well, and thus JTEKT has
developed a bearing that endures high rotational speeds*1(Fig. 8) with a d mn value of over two million whenused with oil lubrication. This bearing employs a newlydeveloped high-rigidity resin cage. The conventional
single-support shape of this cage has been changed to adual-support shape to increase rigidity. This new cage
has been designed to prevent interference between thecage and balls from occurring due to cage deformation
caused by centrifugal force during high-speed rotation.
In addition, the cage is assembled from two identicallyshaped parts, in consideration of productivity.
*1 d mn value: bearing P.C.D. (mm) × rotational speed−1(min )

Fig. 8 High rotational speed ball bearing

As a means of reducing fuel consumption to combat
the environmental problems that have come forth inrecent years, there are rising demands for change fromsliding bearings to rolling bearings. Automobile engines
in particular employ a relatively high number of sliding
bearings, an example of which is on the balance shaft.
Due to the application of sliding bearings, it is necessary
to supply lubrication oil to the bearing part by generatinghigh oil pressure in the oil pump. However, this pressure
will not rise to a high level in the low-speed rotation zone.
This prevents sufficient lubrication oil supply, creating
the problem of large sliding frictional resistance. JTEKT
therefore proposes initiatives to reduce sliding frictional
resistance. Figure 9 shows a measurement example ofrunning torque.
Changing from sliding bearings to rolling bearings
eliminates the need for high oil pressure, and thus,
reduces the oil pump volume, which enables the pump
to be downsized. Furthermore, the start-stop function
is easier to employ with rolling bearings as these allow
startup with low friction torque. This allows the engine
to stop, which contributes to a dramatic reduction in fuelconsumption.

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Running torque comparison−Technological Trends and Outlook of Automotive Bearings−−1

Oil temperature: 90ºC, Balance shaft: average for 1 600−4 000 min▲16%

Sliding bearing▲23%

Rolling bearing(Same oil amountas sliding bearing)

Rolling bearing(1/10 of oil amountof sliding bearing)

Fig. 9 Example of torque reduction

4. Drivetrain bearings
In the trend of electronization nowadays, it is thetransmission mechanism in the drivetrain which is mostaffected. There are numerous transmission mechanisms
used, ranging from the conventional manual transmission(MT) and automatic transmission (AT) to transmissionsfor HVs and FCVs, all of which are currently being
improved. There are also many performance requirements
for the bearings which are utilized within transmissions;however, the primary requirement is smooth support for
the gear shaft which transfers rotation and torque fromthe engine and motor. The reduction of running torqueremains the issue with the topmost priority for drivetrain
bearings.
Tapered roller bearings (TRB), which are a main
product of JTEKT, are used in great numbers fortransmission mechanisms. This is because TRBs havea high load carrying capacity against both radial andaxial loads which occur at gear meshing, and allow a
combination of high rigidity and space-saving. On theother hand, TRBs have relatively high torque loss, andtherefore JTEKT has worked for long time towards the
reduction of friction torque in order to overcome thisdisadvantage, and commercialized this technology as theⅠ, Ⅱ and Ⅲ of the LFT (Low Friction Torque) series.
The “super-low friction torque TRB (LFT-Ⅲ)” wasdeveloped with a focus on reducing lubrication oil
churning loss, and dramatically reduces bearing losses by
suppressing the amount of lubrication oil that flows into
the bearing, thereby contributing to better fuel economyof the automobile. JTEKT pursued the reduction ofchurning loss thoroughly and developed the “nextgeneration super-low friction torque TRB (LFT-IV)”(Fig. 10) by evolving this technology in order to respondto CO2 regulations which will continue to increase instringency. This bearing employs a resign cage with ahigh level of design freedom, achieving a maximum ofover 50 percent reduction in losses compared with the
JTEKT “standard low friction torque TRB” of the same
size, by optimizing the cage shape using oil flow analysis
via CAE.

17

−Technological Trends and Outlook of Automotive Bearings−＊

Presented at Tokyo Motor Show 2015

Fig. 10 Next-generation super-low friction torque tapered
roller bearing (LFT-IV)

Table 1 Comparison of standard and long life (KE-Ⅱ)
bearings
Long-life (KE-Ⅱ)
bearing
KCr620:Optimization ofsilicon/manganese/
chromium
Super carburized
quenching/tempering
Average 0.2 μm,
approx. 10% in area
ratio

Standard bearing

Material

SAE5120

Heat
treatment

Carburized
quenching/tempering

Structure

Additionally, JTEKT has developed the tandem
angular contact ball bearing (Fig. 11) and high axial loadcompatible ball bearing (Fig. 12) as a means of achieving
low friction torque by changing from roller bearings toball bearings. The tandem angular contact ball bearing
has the structure of a double-row ball bearing withdifferent pitch circle diameters and the same direction ofcontact angle, and in particular can operate with smaller
running torque in low load ranges. This bearing has
both high load capacity and rigidity, and is used mainly
to support differential drive pinion shafts. Combining
this bearing with the aforementioned low friction torquetapered roller bearing enables the achievement of a shaft
support mechanism suited for the characteristics of thedifferential. The high axial load-compatible ball bearing
has improved axial load capacity obtained by raising
the height of diagonally opposite inner and outer ringshoulders of a deep groove ball bearing, and can be usedin parts of the transmission that receive high axial loads.

Another large technical issue in bearings for drivetrainsis the improvement of contamination resistance. These
bearings are used with oil lubrication that contains hardcontaminants such as powder created from material
wear during gear meshing of the transmission. A bearing
failure mode under this environmental condition is asurface spalling originated from a ridge at the edge ofan indentation caused by the entry of foreign matteror surface layer spalling accompanied by wear, which
shortens the bearing life to one half to one tenth of that ofa standard bearing with clean lubrication oil. In responseto these issues, JTEKT has developed a new material andheat treatment technology to achieve the development oflong-life tapered roller bearings (KE, KE-Ⅱ) (Table 1).
These bearings have high contaminant resistance, whichenables downsizing of bearings used with contaminatedlubrication oil.

Finecarbide

None

Outer
appearance

Fig. 11 Tandem angular contact ball bearing

Life incontaminatedoil

Cumulative failure rate, ％

5µm
90
50

10

Standard bearing
Developed bearing

KE bearing
10

50

100

500 1 000

Bearing life, hLoad : Fr=20.6 kN, Fa=13.7 kN
Rotational speed : 2 000 min ー1
Lubrication : Gear oil 85 W 90
Contaminants : Hardness 830HV 0.06 wt ％Hardness 700HV 0.06 wt ％Fig. 12 High axial load-compatible ball bearing

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−Technological Trends and Outlook of Automotive Bearings−

improvement of NV characteristics (Fig. 15) throughthe installation of an isolator with a thickness and agroove shape designed to have a large damping effect on
vibration transfer (Fig. 14).

5. Chassis bearings

Fig. 13 Thrust needle roller bearing isolator for automatictransmission (AT)Type−CAs shown in Fig. 16, wheel bearings have evolved fromthe first generation with an integrated outer ring which
can withstand radial load and bidirectional axial load by
combining two angular contact ball bearings to the thirdgeneration hub unit which incorporates a mounting flange
and other peripheral components. The third-generation
hub unit in particular is a bearing unit that can contributeto omitting the time and effort taken by troublesome
preload and gap adjustment within the assembly lines ofautomakers through shaft clinching and a built-in ABS
sensor.
First generation

Third generation

2mmFig. 14 Isolated needle roller bearing
90

Shaft clinching+ built-in sensor

Fig. 16 Evolution of wheel bearing

Decibels, dB

85−9.7 dB(ً11.3%)8075
70Bearing
Only

3mm
No groove

2mm Type−C

Fig. 15 NV-related benefits

Amidst rising automobile requirements for passenger
comfort in recent years, the automobile, which is acomplex assembly of many parts, contains numerous
sources of noise and vibration (NV) which hinder
comfort. Rolling bearings used in drivetrains are one ofthe parts which impacts NV, as well as thrust needle roller
bearings (Fig. 13) used in ATs.
JTEKT worked to develop the isolated thrustneedle roller bearing with a focus on the transfer ofvibration within the AT, with the goal of improving NV
characteristics by reducing vibration transfer within the
bearing alone. This bearing utilizes a high-polymericmaterial with excellent damping characteristics between
the bearing and the housing, and is able to contributeto passenger comfort in automobiles by enabling the

JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)

It is known that the reduction of automobile weight iseffective in improving fuel economy, and thus there arestill heavy demands to downsize and reduce the weightof the hub unit as well. Reduced weight and strength/
rigidity are contravening design elements for the hubunit. A simply lightweight design may lower strength andrigidity. The third-generation hub unit has an integrated
mounting flange for the knuckle and that for the brakerotor and wheel. Using a model that includes the knuckle
and the brake rotor, coupling analysis is conducted byhigh-accuracy CAE to promote the optimal design fromall aspects of strength, rigidity, and weight reduction.
As with weight reduction, reduction of rolling loss
in tires is also an essential technology for fuel economy
improvement in automobiles, and it is also necessary to
reduce running torque in wheel bearings, which is one of
the factors of rolling loss in tires. The running torque ofthe hub unit is divided into seal torque for maintaining
bearing function against mud and muddy water on
the suspension of the car, and torque from the bearing
part. For the seal part, JTEKT has developed a doubleaxial seal (Fig. 17) with reduced lip friction torqueby examining the optimal seal shape through analysis
of super-flexibility that imitates the characteristics ofrubber materials. Furthermore, to reduce running torque19

−Technological Trends and Outlook of Automotive Bearings−

maintaining reliability in the harsh environments (suchas muddy roads and cold regions) of Asia and Russia,
where automobile demands are increasing significantly,
we JTEKT utilized our Iga Proving Ground to analyze
the water exposure state of the hub unit when muddy
water splashes up from the tires, and developed adeflector structure based on these results. By conducting
improvements for the water exposure environment
surrounding the seal, JTEKT has achieved simplificationof the seal lip (Fig. 18) as well as a reduction in seal
torque.

Conventional

Double axial

Fig. 17 Structure of seal for hub unit

Double axial lip

Single axial lip

Fig. 18 Structure of deflector

For torque loss in the bearing part, JTEKT focusedon lubrication as well as optimization of preload of the
bearing part, and developed a hub unit with extremely
low friction torque performance utilizing a synthetic oilwith low viscosity as the grease base oil.
Hub units introduced so far are mainly ball bearing
types for passenger vehicles. However, a TRB type hub
unit, which evolved from wheel support utilizing two
conventional TRBs is also employed for the wheels of
pickup trucks.
SUVs and pickup trucks are often driven on unpaved
roads, and are used in harsher environments comparedwith passenger vehicles, and thus are required to haveextremely long life and high durability, as well as sealingability. In addition, like passenger vehicles, there arestrong demands for weight reduction and lower friction
torque to improve fuel economy. To respond to suchneeds, we JTEKT also produce the third-generation TRB
hub unit (Fig. 19) that employs raceway crowning and
LFT technology able to reduce torque loss at the innerring rib, both of which have been fostered in our tapered
roller bearings, as well as a long-life seal with high20

Fig. 19 Third-generation TRB hub unit

sealing capability and weight reduction technology.
Furthermore, automatic operation has developed
remarkably as a next-generation technology, transitioning
from Levels 1 and 2 where the driver monitors the driving
environment to automated monitoring of the driving
environment in Levels 3 and 4. Within this field as well,
JTEKT has developed a sensing system that monitorsroad surface conditions utilizing the characteristic of the
hub unit that it has a stationary outer ring and is locatedclosest to the tire, and is steadily progressing with thedevelopment of new technologies which respond totechnical development trends in automobiles, such as in
the development of in-wheel motors that allow rotational
speed control of each of four tires independently.

6. Conclusion
JTEKT has been promoting technological development
to enable both automobile convenience and global
environmental conservation for the future. It is believedthat vehicles with ordinary gasoline and diesel engines
will continue to account for the majority of those withinemerging nations, and it is vital to reduce CO2 emitted
from these automobiles. Therefore, JTEKT will further
deepen and pursue tribology technology. On the other
hand, in advanced nations, technologies responding
to the transition to steer-by-wire due to the spread of
HVs, EVs and similar automobiles will be introduced
into the market. In addition, with the forecast of rapid
sophistication of automobile functions through ADAS andrelated technology, we JTEKT will aim to develop No.
1 & Only One technologies combined with our bearing
technology, steering technology and driveline-related
technology. Through the development of bearing products,
we JTEKT will continue to contribute to the creation of,even a part of it, a future vision of an automobile society
where all users can safely travel to their destinations andwhere more comfortable driving can be achieved throughthe latest technologies.
*1 LFT is a registered trademark of JTEKT Corporation.

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−Technological Trends and Outlook of Automotive Bearings−

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2)

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Y. Tanaka: New Trend of Global Automotive Market
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M . K awa m u r a : L a t e s t Te c h n o l o g i c a l Tr e n d o f
Automotive Bearings, Kikai Sekkei, Vol. 60 No. 1 (2016)(in Japanese)
K. Kouda: CO 2 Reduction Technology throughDownsizing and Torque Reduction of Tapered Roller
Bearings for Automotive Drive Line, THE TRIBOLOGY,
No. 338 (2015) (in Japanese)
Y. Sankai, K.Yoshizaki, T. Ogimoto: Achieving Low
Torque by Applying Low Viscosity Synthetic Grease to
Hub-unit Bearing, International Tribology Conference,
Tokyo 2015
M. Murakami, Y. Takahashi, D. Okamoto: JTEKTENGINEERING JOURNAL, No. 1011 (2013) 39
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K. YOKOTA**JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)

Executive Managing Officer21