Award
Winning
Products

2020“CHO” MONODZUKURI Innovative Parts and Components Award,
Mobility Components Award

Low Friction HUB Bearing Ⅲ
Makoto SEKI

The “Low Friction HUB Bearing Ⅲ”1), which reduces
rotational friction while driving by 62 % comparedwith conventional products, received the 2020 “CHO”
MONODZUKURI Innovative Parts and Components
Award, Mobility Components Award sponsored by
MONODZUKURI. Nippon. Conference and Nikkan
Kogyo Shimbun, Ltd.
NTN developed bearing internal grease in pursuit of
low friction, and combined with the latest low friction
seals, was able to reduce rotational friction by 62 %when compared with conventional products2). Using
this product on the wheels at both sides of a vehicle
is expected to improve vehicle fuel efficiency byapproximately 0.53 %.

２. Structure
Fig. 1 shows a schematic drawing of Low Friction
HUB Bearing Ⅲ.

《New development》● Low friction grease・Low viscosity base oil
・Revised additive● Low friction seal
・Labyrinth structure
・Seal dedicated grease is applied
・Optimized lip contact[Outer seal][Inner seal]
Assist lip

Labyrinth
Assist lip

Slinger

Running torque comparison

1. Introduction

Hub bearing (overall)
Running torque is reduced by 62 %1

Sealfriction
0.50Bearingfriction

-70 %

NTN
conventional
product

Low Friction HUB
Bearing Ⅲ(Developed product)

Fig. 2 Hub bearing running torque comparison(an example)

4. Summary
To support stricter emission regulations on CO2
and improve vehicle fuel efficiency throughout
the world, NTN has developed a hub bearing withsignificantly lower friction over conventional products
while meeting the requirements for service life andstrength. NTN will continue to develop the market
for this product, which is expected to improve vehicle
fuel and power consumption efficiency, and also
contribute towards reducing the impact on the global
environment.
References
1) Makoto Seki, Low Friction HUB Bearing Ⅲ,
NTN TECHNICAL REVIEW, No.87, (2019) 63-67.
2) Makoto Seki, Low Friction HUB Bearing,NTN TECHNICAL REVIEW, No.85, (2017) 67-71.

Fig. 1 Structure of Low Friction HUB Bearing Ⅲ

3. Features

Photo of author

The following are the features of Low Friction HUB
Bearing Ⅲ.
(1) Application of newly developed low friction
grease(2) Application of new seal structure with labyrinth(3) Application of seal dedicated grease(4) Optimization of seal lip contact surface
As shown in Fig. 2, these features reduce bearing
friction and outer/inner seal friction to achieve a runningtorque reduction of 62 % for the entire hub bearing.

106

NTN TECHNICAL REVIEW No.89-56 %Makoto SEKI
Axle Unit Products
Development Dept.,
Axle Products Unit,
Automotive Business
Headquarters

AwardWinning
Products

Nippon Brand Award of 2021 “CHO” MONODZUKURI Innovative Parts
and Components Award

High Speed Deep Groove Ball Bearing for EV/HEV
Katsuaki SASAKI

1. Introduction
NTNʼs “High Speed Deep Groove Ball Bearing for EV/HEV”1),
has achieved the worldʼs highest level of allowable speed by
the Nippon Brand Award of 2021 “CHO” MONODZUKURI
Innovative Parts and Components Award sponsored by
MONODZUKURI. Nippon. Conference and Nikkan Kogyo
Shimbun, Ltd.
This product was developed using technology that optimizes
the shape and material of the bearing cage to minimize theenergy lost due to friction. As motors become smaller andfaster to accommodate the continued electrification of theindustry, there is a growing need for bearings that can support
high-speed rotation of 1.8 million d mn*1.
Furthermore, with the aim of improving performance ofdeep groove ball bearings, high regard is placed on such things
as the creativity of designers and development concepts
that provide verification of results after planning detailed
improvements.

2. Structure
Fig. 1 shows a schematic drawing of a cage for the High
Speed Deep Groove Ball Bearing for EV/HEV.

Yukihiro ISHIDA

Large

Standard
cage

Developed
cage
Optimized material
removalFig. 1 Structure of developed cage

3. Features
NTNʼs “High Speed Deep Groove Ball Bearing for EV/HEV”
contains the following features:(1) The worldʼs highest allowable speed of 1.8 million d mn
: Over 3 times that of a standard deep groove ballbearingStandard cage
Developed cage

Ball interference

Small

Cage pocket clearance0

Increased thickness(strength)
Optimized lubrication
grooveKazunori MURANUSHI(2) Superior cage strength (compared to standard cage)
1.6 times: Tensile strength: Centrifugal force deformation
1/8: Heat resistance temperature improved by 30 °C
Fig. 2 shows the results of analyzing the amount of cage
deformation (outer radial displacement) due to centrifugal
force under bearing inner ring rotating conditions. NTNʼs“High Speed Deep Groove Ball Bearing for EV/HEV” has an
optimized resin material and resin cage design that preventsball interference at high speeds. Note that the developed
product can operate at speeds up to 3 times higher than aconventional bearing and still maintain sufficient clearancewith the cage pocket. This also prevents increased bearing
torque and temperature rise during operation.

Outer radialdisplacement

Goro NAKAO

10 000

20 00030 000Inner ring rotational speed [min-1]

Fig.2 Difference in deformation due to centrifugal force(standard cage vs. developed “high speed” cage)

4. Summary
Increasing the speed of the motor is the most effective wayof improving EV motor efficiency. This product responds todemands from customers to increase the speed of bearings,
and also contributes towards achieving a decarbonizedsociety. Furthermore, NTN has recently achieved a d mn valueof 2.2 million due to the optimization of heat balance.2) In the
future, NTN will continue to support the need for increased
allowable speeds using our expert knowledge in high speed
operating technology.
References
1） Masahiko Satoda, Goro Nakao, Grease Lubricated Highspeed Deep Groove Ball Bearing for EV and HEV Motor,
NTN TECHNICAL REVIEW, No.83, (2015) 81-85.
2） Single page in Nikkan Kogyo Shimbun dated April 28, 2022.

Photo of authors*1

Goro NAKAO

Katsuaki SASAKI

Yukihiro ISHIDA

d mn value refers to an index that represents
bearing rotational performance, and is thebearing pitch diameter (mm) × rotational
speed (min-1).

Kazunori MURANUSHI

Automotive Bearing
Automotive Bearing
Automotive Bearing
Automotive Bearing
Engineering Dept.,
Engineering Dept.,
Engineering Dept.,
Engineering Dept.,
Automotive Bearing Products Unit, Automotive Bearing Products Unit, Automotive Bearing Products Unit, Automotive Bearing Products Unit,
Automotive Business Headquarters Automotive Business Headquarters Automotive Business Headquarters Automotive Business Headquarters

NTN TECHNICAL REVIEW No.89

107

AwardWinning
Products

2020 Japanese Society of Tribologists (JAST) Technology Award

Development of Super Long-Life Tapered Roller
Bearings for Automobile
Hiroki FUJIWARA

Takashi KAWAI

1. Introduction

Chikara OHKI

3. Features

NTN has developed “Super Long-Life” Tapered Roller
Bearings that can be used on automobile transmissions anddifferentials as well as in electric drive devices (reducers for
e-Axle). This product received the 2020 Technology Award
from the Japanese Society of Tribologists.
This bearing has an increased resistance to misalignmentand contamination and a higher allowable speed. Theseadvancements are possible due to improvements madeto the shape of sliding contact areas, the heat treatment
method for grain refinement of crystal grain in bearing steel,and the technology used to design the shape of rollers thatminimizes the contact stress at the rolling contact surfaceof roller elements and the raceway surface. These factors
enable the automobile drive device to be more compact
and lighter in weight, which has been praised for its ability
to improve both fuel and power consumption efficiency.
The product that received the award was commercialized
as “ULTAGE Tapered Roller Bearing for Automotive
Application” (Fig. 1).

Fig. 1 ULTAGE Tapered Roller Bearing for Automotive Application

2. Structure
Fig. 2 shows a schematic drawing of ULTAGE
Tapered Roller Bearing for Automotive Application.
Optimized shape of the sliding contact area
provides control for temperature increases1)

Optimized roller
shape minimizes
the contact
surface pressure2)

Outer
ring

(1) The worldʼs highest level in high-load capacity: Basic dynamic load rating4) 1.3 times(2) Long operating life (comparing basic rating life4)): Standard heat treated type 2.5 times or more
: Grain refinement heat treated type 3.8 times or more
(3) The worldʼs highest level in high rotational speed
performance: Allowable speed5) Improvement of approx. 10 %(4) Allowable misalignment5) (misalignment amount): Allowable misalignment Up to 4 times

4. Summary
This product was developed to allow for longer
operating life for tapered roller bearings. The bearing
can also be made smaller dimensionally and achieve
the same previous service life. This contributes tomaking automobile drive devices smaller and lighter,and can also make automobiles more efficient interms of fuel and power consumption. Furthermore,
the longer operating life technology we havedeveloped for this product can also be applied toother areas, which we hope will greatly contributetowards higher optimization of various machines andachieve carbon neutrality.
References
1) Yasuhito Fujikake, Takanori Ishikawa, Susumu
Miyairi, ULTAGE Tapered Roller Bearing for
Automotive Application, NTN TECHNICALREVIEW, No. 85, (2017) 51-55.
２) H. Fujiwara et al., Optimized Logarithmic Roller
Crowning Design of Cylindrical Roller Bearings
and Its Experimental Demonstration, Tribol.
Trans., 53 (2010) 909-916.
３) C. Ooki, Improving Rolling Contact Fatigue Life of
Bearing Steels Through Grain Refinement, SAE
Technical Paper Series, 2004-01-0634.
４) JIS B 1518 (2013)５) NTN “Ball and Roller Bearings Catalog” (CAT. No. 2203/J)
Photo of authors

Cage

Application of grain refinement
heat treatment improves surface
initiated damage life3)

Inner
ring

RollerFig. 2 Structure of ULTAGE Tapered Roller Bearing for
Automotive Application

108

NTN TECHNICAL REVIEW No.89

Hiroki FUJIWARA

Takashi KAWAI

Chikara OHKI

CAE R&D Center

Automotive Bearing
Engineering Dept.,
Automotive Bearing Products Unit,
Automotive Business Headquarters

Advanced
Technology R&D
CenterAwardWinning
Products

2021 Japanese Society of Tribologists (JAST) Technology Award

Low Friction Technology of Sealed Ball Bearings forTransmission
Katsuaki SASAKI Takahiro WAKUDA

1. Introduction
Lower torque and long operating life are needed forautomotive transmission bearings to achieve carbon
neutrality. The lubricating oil inside a transmission
has contaminants such as gear wear debris which
can cause the service life of a rolling bearing to
decline. Therefore, countermeasures are provided
using methods such as ① preventing contaminantsfrom entering the bearing using a contact seal and ②
applying special heat treatment to the rolling bearing
ring to improve the service life against contaminants.
However, ① places restrictions on the allowable speed
due to increased running torque due to the seal andheat generated at the seal. Furthermore, ② is not
sufficiently effective at suppressing the decline inservice life in comparison with the bearing service life
in an environment with no contaminants.
To respond to these issues, NTN has developed
technology to reduce running torque while
maintaining sufficient service life even whencontaminants are present in the lubricating oil1,2). This
technology received the “2021 Japanese Society of
Tribologists Technology Award”, which is given for
excellent new technology in the field of tribology. This
paper introduces this technology.

2. Overview of award-winning technology
With conventional contact seals, the seal sliding
surface contacts the inner ring and because a sufficientoil film does not form at the operational speed range,
there is a comparatively high drag resistance torqueat the seal. In contrast, this technology provides arcshaped micro convexities on the contact seal sliding
surface as shown in Fig. 1. These micro convexities
generate a fluid film due to the “wedge film effect”
between the seal sliding surface and inner ring under
oil lubrication. This results in a fluid lubrication state at
the operational speed range which reduces the runningtorque by 80 % when compared to conventional
contact seals, as shown in Fig. 2. This can achieve
the same low torque performance as a non-contact
seal despite it being a contact seal. Furthermore, theconvexities are of a micro height so they can prevent
contaminants of sizes that would cause the service life
to decline from entering the bearing. This enables thebearing to maintain a service life equal to a bearing
used in an environment with no contaminants.

Bearing running torque N . m

Tomohiro SUGAI

0.4

Developed seal
Conventional non-contact seal

0.3

Conventional contact seal

0.2
0.1
0.0
20

40

60

80

100

120

140

Bearing temperature °C

Fig. 2 Bearing running torque experimental results
Additionally, this seal reduces sliding heat generated
at the seal contact area so it can also be used underperipheral speed conditions that are two or moretimes greater than that of a conventional contact seal.

3. Summary
This technology can reduce the running torque oftransmission bearings while maintaining sufficient
service life even with contaminants in the lubricatingoil. This can contribute towards better fuel economy
in automobiles. Furthermore, the bearing size can besmaller due to improved reliability which can makeautomobiles lighter in weight. It can also respond to
the demand for speed increases that accompany theelectrification of vehicles.
References
1） Katsuaki Sasaki, Takahiro Wakuda, Tomohiro
Sugai, Ultra-Low Friction Sealed Ball Bearing forTransmission, NTN TECHNICAL REVIEW, No.85,(2017) 62-66.
2） Tomohiro Sugai, Katsuaki Sasaki, Takahiro Wakuda,
Low Friction Technology of Sealed Ball Bearings
for Transmission, Tribology Congress, 2022 Spring
Tokyo Proceedings, (2022) B6 85-86.
Photo of authors

Tomohiro SUGAI Katsuaki SASAKI Takahiro WAKUDA
Arc-shaped
micro convexity

Fig. 1 Schematic drawing of developed seal

Advanced
Technology R&D
CenterAutomotive Bearing Automotive Bearing
Engineering Dept.,
Engineering Dept.,
Automotive Bearing Automotive Bearing
Products Unit,
Products Unit,
Automotive Business Automotive Business
Headquarters
Headquarters
NTN TECHNICAL REVIEW No.89

109

AwardWinning
Products

2021 Japanese Society of Tribologists (JAST) Best Paper Award

Estimation Method of Micropitting Life from S-NCurve Established by Residual Stress Measurements
and Numerical Contact Analysis
Takumi FUJITA

Michimasa UCHIDATE

1. Introduction
The above-mentioned paper1) submitted to
the Japanese Society of Tribologists (non-profit
organization) academic journal “Tribology Online”
received the 2021 Best Paper Award. The content of
this paper is introduced below.

2. Overview
Peeling (referred to as micropitting in the paper)is the typical damage seen on bearings under severe
lubrication conditions. It refers to a concentration of
micro spalling caused by cyclic contact of projections
on rough surface. This paper proposed a new peelinglife estimation method utilizing experimental results.
This method estimates the peeling life using thefollowing procedure.
1) A rolling fatigue test is conducted under various
operating conditions. Time series data (hereafter,
stress history) for cyclic stress at areas ofprojection contact and peeling life during each testis acquired. The stress history is estimated using
the measurement results of surface roughness
and residual stress during the operation.
2) Regression analysis is performed on the obtained
data, and a S-N curve that shows the relationshipbetween cyclic stress and peeling life is created.
3) A preliminary test simulating the subject
operating conditions is conducted. Stress history
under those conditions is obtained. The peelinglife is then estimated using the S-N curve createdin 2) above and Minerʼs rule.
To estimate peeling life under various conditions,actual measured data was utilized to increase theprecision of life estimation. Furthermore, anotherfeature of this method is that it considers the effectof residual stress on life, something that was difficult
to do in the past. However, it must be noted that theapplication range of this estimation method is limited
to pure rolling and boundary lubrication conditions.
Fig. 11) shows the relationship between the actual
life Lact and the peeling life Lest estimated using thismethod. The median, minimum value and maximum

Masayoshi ABO

Hiroshi KINOSHITA

value of the life ratio (Lact / Lest) is 0.89, 0.49 and 1.82
respectively. This precision is comparable to or better
than the generally used spalling life estimation of therolling bearing. This method is considered sufficiently
applicable as an estimation method for peeling life.

Estimated life (Lest)×106 cycles

Naoya HASEGAWA

10

4
1

1

8

3

9

2

Lact / Lest (All test)

6

0.1

0.01
0.01

7

Median: 0.89
Min.: 0.49
Max.: 1.82

5

0.1

1

Fig. 1 Relationship between estimated life and actual life1)

3. Summary
Even greater progress is expected in the future toachieve higher efficiency of machines for achievingcarbon neutrality by lowering the viscosity of
lubricating oils. This increases the likelihood ofbearings being used under thin lubrication conditions.
Life estimation under conditions similar to those usedin this study will become an important technology for
maintaining the reliability of bearing life prediction. In
the future, NTN will strive to increase the application
range of this estimation method and further improve
its accuracy.
References
1） N. Hasegawa, T. Fujita, M. Uchidate, M. Abo & H.
Kinoshita: Estimation Method of Micropitting Life
from S-N Curve Established by Residual StressMeasurements and Numerical Contact Analysis,
Tribology Online, 14, 3 (2019) 131.

Photo of authors

Naoya HASEGAWA
Advanced
Technology R&D
Center110

Takumi FUJITA

Michimasa UCHIDATE

Masayoshi ABO

Hiroshi KINOSHITA

Product and Business Faculty of Science andEngineering,
Strategic Planning
Iwate University
Dept.

School ofEngineering,
University of Hyogo

School ofEngineering,
University of Hyogo

NTN TECHNICAL REVIEW No.89

10

Actual life (Lact)×106 cycles

AwardWinning
Products

2021 New Energy Awards, New Energy Foundation Chairman Award(products and services category)

DLC Coating Spherical Roller Bearing for Wind Turbine
Main Shaft

Kazumasa SEKO

Takashi YAMAMOTO

1. Introduction“DLC Coating Spherical Roller Bearing for Wind
Turbine Main Shaft” received the “New Energy
Foundation Chairman Award (products and services
category)” of the 2021 New Energy Awards sponsoredby the New Energy Foundation.
The award-winning product substantially improves
the wear resistance of the raceway surface and rolling
contact surface of rolling elements by applying a
DLC (diamond-like carbon) coating* to the rolling
contact surface of rolling elements. This has beenhighly regarded for its significant contribution towards
improving the reliability of wind turbines.

Masaki NAKANISHI

confirmed that wear depth on the outer ring raceway
surface was suppressed by 1/9 or less in comparison witha conventional product (Fig. 2).
Test bearing

Wear depth progress
50 h
50 h
100 h
100 h

Conventional product

20
20

30
30

40
40

50
50

10
10

20
20

30
30

40
40

50
50

50 h
50 h

DLC coating product2. Structure

10
10Wear depth µm
Wear depth µm

100 h
100 h

* A hard film consisting of a mixture of a diamond structure andgraphite structure

150 h
150 h
0
0

150 h
150 h
0
0

Wear depth µm
Wear depth µm

Fig. 2 Wear test results

Fig. 1 shows the structure of the DLC Coating
Spherical Roller Bearing for Wind Turbine Main Shaft.
RollerCage

DLC coating

Outer
ring

Inner
ring

Suppresses wear due to the DLC coating on therolling contact surface of rolling elements

Fig. 1 DLC Coating Spherical Roller Bearing for Wind
Turbine Main Shaft

3. Features
When there is insufficient lubrication during operation
with conventional spherical roller bearings, metal on theroller raceway surface and rolling contact surface of rolling
elements makes contact, resulting in wear on the raceway
surface. This contact and resultant wear causes spallingand cracks to occur.
The DLC Coating Spherical Roller Bearing for Wind
Turbine Main Shaft can suppress wear on the raceway
surface even under harsh lubrication conditions byapplying a DLC coating. The DLC coating has a 3-layer
structure that provides excellent adhesion to the basematerial on the rolling contact surface of rolling elements.
During a wear test on smaller sized bearings, NTN

4. Summary
The main bearings on a wind turbine repeatedly rotateand stop based on wind conditions, and are used underharsh lubrication conditions. Moreover, replacing the main
bearings is not an easy task. Therefore, it is necessary to
avoid spalling and cracks due to wear on the main bearings
because such factors are directly linked to a drop in thereliability of wind turbines.
DLC Coating Spherical Roller Bearing for Wind Turbine
Main Shaft is a product that responds to these issues, andcan contribute towards improving the reliability of windturbines by developing the market for this type of product.
References
1） Michio Hori, Yusuke Yamada, New Products andImproved Reliability of Main Bearings for Wind
Turbine Generators, NTN TECHNICAL REVIEW,
No.88, (2021) 15-20.
Photo of authors

Kazumasa SEKO Takashi YAMAMOTO Masaki NAKANISHI
Application
Engineering Dept.,
Industrial Business
Headquarters

Product Design
Dept.,
Industrial Business
Headquarters

Advanced
Technology R&D
CenterNTN TECHNICAL REVIEW No.89

111