TECHNICAL REPORTHigh Efficiency and Lightweight Technology of*1
Automotive Parts for Energy Saving
H. MATSUYAMAHigh efficiency and lightweight of automotive parts such as rolling bearings, steering systems and driveline
units is a significant contribution to reduction of CO2 emissions by vehicle fuel efficiency. JTEKT has introduced a"JTEKT Ecology Package" for 2.5 L class AWD vehicles for the purpose of achieving energy saving in vehicles. The
paradigms of ecologically friendly products which constitute the "JTEKT Ecology Package", in particular rolling
bearings and their fundamental technologies, have been presented for their high efficiency and lightweight quality.
It is expected that the total fuel efficiency improvement from the "Ecology Package" is 10.7 percent.
Key Words: rolling bearings, automobiles, tribology, low friction, high efficiency, lightweight, energy saving

1. Introduction
The demands on vehicles are changing significantly.
Conventionally, vehicle development focused on thethree aspects of “safety”, “comfort” and “environment”,
but now many new demands have emerged, including
responses to the following:1) environmental issues such as the prevention of global
warming,2) energy issues made apparent by soaring oil prices,
3) resource issues such as rare metal4) competing on a global market in line with market
expansion in emerging countries.
In particular, the response of automobiles toenvironmental and energy issues is an important
theme which will have impact upon the fate of theautomotive industry moving forward. It would not be anoverstatement to say that improving fuel efficiency andreducing CO2 emissions are the most important issues
related to global warming and energy conservation.
In this situation, JTEKT proposes a total package
for improving fuel efficiency, we call “JTEKT Ecology
Package”, which comprises of automotive parts suchas rolling bearings, steering systems, driveline unitsetc., which contribute to energy-saving of vehicles, orin other words, the reduction of CO2 emissions throughimproved fuel efficiency. In this paper, we introduce
the ecologically-friendly products and their respective*1 This paper was prepared based on proceeding of Tribology
Kenkyukai, No. 42 (2013) 45-48.

46

element technologies, which have developed to realize
high-efficiency and lightweight of vehicles.

2. Response to Environmental and Energy
Issues
It is common knowledge that Japan, Europe and the
U.S. alike are becoming more stringent in regards tovehicle fuel efficiency (CO2 emissions) regulations in
response to global warming and in line with the rapid
industrial development of emerging countries. In July
2015, the Japanese government finalized a draft proposalof Japan’s commitment to achieve a 26% reduction
in greenhouse gases from a 2013 baseline by the year
2030 and submitted this draft to the United Nations
Framework Convention on Climate Change. CO 2
emissions originating from energy constitute 90% ofJapan’s greenhouse gas emissions, and the transportation
sector, which produces around 20% of all CO2 emissions,is required to achieve a reduction of 28% compared to2013 results. In order to meet such a requirement, there isa need to promote energy-saving initiatives for vehicles,
which occupy the majority of the transportation sector.
If attempts to curb vehicle energy consumption focusedon the vehicle in isolation, it would only be a matter ofthe extent to which fossil fuel consumption could be
minimized during a vehicle’s operation, that is, improving
fuel efficiency.
Figure 1 shows the percentages of energy loss when a
1)
U.S. gasoline-driven vehicle is travelling . The JapaneseSociety of Tribologists have also conducted a similar2)
investigation and obtained loss distribution percentages

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

−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−for each element roughly the same as Fig. 1. Aside fromreducing vehicle weight, many technologies have beendeveloped for the improvement of fuel economy. Effective
areas of focus are:1) Improving engine efficiency
2) Reducing idling loss3) Improving power transmission efficiency
4) Reducing travel resistance5) Reducing auxiliary device loss
JTEKT engages in the development of technologies
to achieve the above outcomes and satisfy demands for3)high-efficiency and lightweight needs .

3. JTEKT Ecology Package
Figure 2 shows the JTEKT Ecology Package
assuming a 2.5 L-class AWD vehicle. The percentage
values shown in this figure represent the fuel efficiency
improvement rate as a result of increased efficiency andweight reduction. In the following, the representative
ecologically-friendly products and their respective
element technologies to configure them in chassis,
powertrain and drivetrain systems, have been presented.

4. Chassis
4. 1 Steering
In 1988, JTEKT was the first in the world to begin mass
production of column type electric power steering (EPS).
With the conventional hydraulic power steering (HPS),
there was a need to constantly run a hydraulic pump withengine driving force. In contrast, an EPS system only
requires the motor to be operated when the vehicle isbeing steered, therefore energy consumption is small, at
a mere one-sixth compared to HPS, which translates to a4, 5)fuel efficiency improvement of 2.5% (Fig. 3) . Looking
at overall global vehicle production by steering type, HPS

Air resistance 3％

Rolling resistance 4％

Accessories 2％

Inertia (braking) 6％
Drivetrain loss
6％

Engineloss
62％

Idling loss 17％

Fig. 1 Percentages of energy loss in traveling gasoline engine
vehiclesImproved fuel eﬃciency 10.7％

EPS: Electric power steering system
Ratio to HPS

2.5%

Ratio to HPS‫ڎ‬2.5%‫ڎ‬1.5%**Sum of % values of ‫ڎ‬item's
AWD vehicle of 2.5 L-class1.6%‫ڎ‬0.6%
Head side

Dual pinion type
EPS (DP-EPS)

Column type EPS(C-EPS)

Super-low friction torque tapered
roller bearing (LFT-III)

Low friction torqueball bearing

ً803 g/Platform

0.03%

Tail sideLow friction torquebearing for differential

High capacity tapered
roller bearing (KE-II)‫ڎ‬0.1%‫ڎ‬0.8%

Drivetrain

ً640 g/Platform

Chassis/Steering

Low friction torque thrustneedle roller bearing

Low friction torque &lightweight hub unit0.05%

‫ڎ‬0.6%

Chassis/Wheel
ً1 300 g/
Platform
Compact TORSEN®
Type CPowertrain

Super-low friction seal
for wheel bearings‫ڎ‬0.5%‫ڎ‬0.01%
コンプレッサ側‫ڎ‬0.1%As an idle
reduction system

4.0%

ً330 g/Platform

タービン側

ً500 g/Platform
Differentialside‫ڎ‬0.02%

Full-time AWD ψ‫ڎ‬4.0%During ITCC on-demand
AWD

Wheel
side

コンプレッサインペラ
セラミック玉軸受

Roller finger follower

タービンインペラ

Ceramic ball bearing
for turbochargers

Low friction torqueoil seal

Electric oil pump for idle
reduction system (EOP)

Compact CVJ

ITCC®
(electronically-controlled AWD coupling)

Fig. 2 JTEKT Ecology Package

JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)47

−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−

was used on the majority of vehicles produced aroundthe 2000s, however by 2014, EPS was used on half,
6)demonstrating the rapidly accelerating shift to EPS .
Due to being adopting on a higher number andbroader range of vehicles, various types of EPS havebeen produced, and the system has become high-output
and high-functionality. The dual pinion type EPS (DPEPS) has an assist mechanism in the engine chamber tosimultaneously achieve higher output and improvementof vehicle mountability. In recent years, the developed
column type EPS (C-EPS) has achieved a weight
reduction of 15% (2.7 kg) compared to the conventional
7)
model due to motor/ECU integration , a smaller brushless
motor and other measures.

The worm gears used in EPS motor reducers are
made from resin worm wheels and steel worm shafts,
and the sliding portions of these (Fig. 4) are lubricatedwith grease. In recent years, a new grease low-friction
8)
technology has been developed with optimized additives
and improvement of influx to sliding portions. As shown9)
in Fig. 5 , by adding stearate-based additives to enhanceoiliness (A, B) to an aliphatic diurea grease (U), it would
be possible to reduce friction compared to conventional
Ba complex soap grease (BC). This is also effective in
minimizing any change to resin material properties causedby high temperatures. By adopting this technology, it ispossible to achieve low temperature rising of the worm
shaft, improved resin gear durability and enhanced
reducer efficiency.

4. 2 Wheel
Fuel consumption

3%

3.0%
2.5%
2.0%

2%

1.0%

1%
0%

0.5%
HPS
HPS
(Conventional) (High pressure)

H-EPS

H-EPS
(Idle & Go)

EPS

Fig. 3 Comparison of energy consumption in steering systems

Steelworm shaft

As Fig. 6 shows, the hub unit comprises of peripheral
components such as the wheel bearing and hub shaft, allintegrated into one. This has significantly contributed
to reducing components and weight. Currently, the 3rd
generation hub unit is mainstream and is characterized byintegrating one inner ring with the hub shaft. For the 3rd
generation hub unit, JTEKT utilized a lightweight designand “monozukuri” technology using CAE analysis which
included the configuration of surrounding sections toachieve a 25% weight reduction while securing strength3)
and rigidity (Fig. 7) . Moreover, a total friction torquereduction of 55% was achieved by reducing seal sliding
resistance, which accounts for half of the hub unit’s
overall friction torque, in addition to reducing rolling
resistance through minimizing preload and improving
dimensional/assembly accuracy.

Resinworm wheel
Generation Ⅰ

Generation Ⅱ

Generation Ⅲ

Fig. 4 Worm gear for EPS motor reducer

Polyamide/Steel, 39.2 N, 1mm/s

Friction coefficient

0.15

RT
80℃
0.1

0.05

0

Fig. 6 Transition of hub units
U

U＋A

U＋B

BC

Fig. 5 Comparison of friction characteristics between
lubricating greases with different thickeners andadditives

48

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−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−

conditions, good heat resistance, high-speed ability andimproved durability (Fig. 10). As Fig. 11 shows, by
switching to a rolling type for the developed bearing,
friction loss has been reduced, the use of low viscosity
lubricant has been made possible, less lubricant isrequired and acceleration response has been improved.
Fig. 7 Example of CAE analysis of hub unit flange

Ra 0.2 0.2mm
3D roughness

2D roughness

Ra 0.1 0.2mm
3D roughness

2 µm

Features of double-sided lip●Lower contact load
(low friction)
Double-sided lip●Favorable tracking
performance
Radial lip(improved muddy water
resistance)●Optimized lip shape(CAE analysis)(a) Conventional seal(b) Developed seal

Developed

2 µm

Conventional

2D roughness

Special barreling (Tetratekt)

Shot blasting & barrelingFig. 9 Special barreling (Tetratekt)Fig. 8 Super-low friction seal
Outer ring (heat-resistant steel)

In order to reduce engine loss, which accounts foraround 60% of total vehicle energy loss, the technology is
being developed to replace the bearing from widely usedsliding type to rolling type. In regards to the rocker arm, amajor component of the valve system, low-speed friction
torque, which has particularly large friction loss, has been
reduced through adoption of a rolling type rocker arm,
meaning that the roller finger follower uses needle rollers
as the rolling elements. As Fig. 9 shows, by applying
a special barreling treatment (Tetratekt) to harden only
the topmost layer of the roller’s outer surface, whichcontacts by rolling while sliding with the camshaft, at thesame time as suppressing surface roughness, it has beenpossible to reduce the aggressiveness on the camshaft, as
well as reduce friction torque.
In regards to the turbocharger, which is an effectivemeans in reducing engine size, studies are being carriedout to enhance efficiency and acceleration response
through using a rolling bearing for turbine support. To
3)handle this issue, the ceramic ball bearing has been
adopted due to having low friction torque at high-speed

JTEKT ENGINEERING JOURNAL English Edition No. 1014E (2017)Ball (ceramics)
Inner ring (heat-resistant steel)Fig. 10 Ceramic ball bearing for turbocharger[Test conditions] Compressed air pressure: 0.3 MPa
SeizureRotational speed, ×104 min−1

5. Powertrain

Cage (heat-resistant resin)

10

Steel ball bearing

SeizureFull-floating
bearing

5
Ceramic ball bearing
00.05 0.1

0.5

1

5

Amount of Lubrication, L/min(a) Anti-seizure performance[Test conditions] Compressed air pressure: 0.25 MPa
Rotational speed, ×104 min−1

In the super-low friction torque seal used in hub units
and wheel bearings, a double-sided lip was adopted
to achieve both good muddy water resistance and low
10)friction torque . As shown in Fig. 8, the radial lip, whichlargely contributes to contact load, particularly friction
torque, has been abolished on the developed seal, and two
axial lips, which help to improve muddy water resistance,
were adopted. This has reduced the friction torque by
50% compared to the conventional low friction torqueseal, and 70% compared to the standard seal, at the sametime as doubling muddy water resistance.

Ceramic ball bearing
10
Full-floating
bearing

5

20% improvement
0

2

4

6

8

Time, s(b) Acceleration response

Fig. 11 Performance of developed bearing49

−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−

Furthermore, a low friction torque oil seal with
optimized tension design and a coating on its sliding
surfaces has also been effective.

has been adopted to control the lubricating oil flow, asshown in Table 1, thus ultimately reducing friction torque15)
by 40% compared to the conventional ball bearing . The
profile of the developed cage was optimized to suppress
the influx of oil into the bearing and make it easier for oil
inside the bearing to be discharged. Moreover, a different
pitch circle diameter was adopted on the double row
angular contact ball bearing, which has the same contact
angle direction, to produce the tandem-type angular
16)
contact ball bearing (Tandem AC) with enhanced load
capacity and rigidity. As Fig. 14 shows, by using LFT-III
and Tandem AC in combination, the differential can be
expected to achieve even higher efficiency.

6. Drivetrain
6. 1 Bearings
Drivetrain units such as transmissions and differentials
utilize many different types of rolling bearing. In order
to increase the power transmission efficiency of each
unit, reducing the friction torque of rolling bearings is
considered as important as extending bearing service
life. As a leading company in tapered roller bearings,
JTEKT has been offering a low friction torque tapered
roller bearing (LFT) on the market for over thirty years.
11)
Figure 12 shows the transition of LFT bearings. LFT-I
has reduced sliding resistance between the cone rib and12)
the roller end faces, while LFT-II has reduced rolling
resistance between the rollers and the raceway. For thesuper-low friction torque tapered roller bearing, LFT13)
III , rolling resistance has been reduced through the
optimization of internal geometry, including the numberof rollers, roller length, roller diameter and contact
14)
angle and so on. Furthermore, as shown in Fig. 13 ,lubricating oil has been considered as another bearing
component and its flow controlled to reduce agitating
resistance. In addition, rolling fatigue life has been
maintained by applying long-life technology based on
special carburizing heat treatment, while the bearing has
been made more compact, thus reducing both rolling
and agitating resistance. LFT-III has 50% less friction
torque than a standard bearing of identical size, and 80%
less friction torque when the effects of size reduction areincorporated, thereby surpassing the ball bearing. A 1.5%
improvement in fuel efficiency can be expected if the
LFT-III is used on a rear axle differential.
For ball bearings, the design concept of LFT-III wasapplied to achieve optimization of internal geometry,
including ball configuration (number of balls, balldiameter, pitch circle diameter of balls), raceway curve
radius and raceway surface roughness, and a resin cage
LFT-Ⅰ
(1983)①Restriction of oil
inﬂow②Easy discharge ofoil inside bearing

Smaller cage bore
diameterLarger contact
angle

Specialized shapeof cone rib

Smaller numberof rollers

Oil ﬂow

Larger roller
diameterFig. 13 Lubricating oil flow control for reducing agitating resistance

Table 1 Cage shape of low friction torque ball bearing
Current cage
Steel cage

Developed cage

Resin snap cage

②
①
②

②
①

①

①Oil inﬂux easily increasing theamount of oil inside the bearing②Small amount discharged frominside the bearing

R

LFT-Ⅱ
(1994)

Cone

Friction torque ratio(vs. standard bearing)90％①Optimized internal
geometry②Lubricating oil flow
control③Compactness(long-life heat
treatment)

Special crowning
profile80％

Ideas for the cage
guide surface, backface angle and I.D.
form
①Suppress oil inﬂux②Encourage
discharge ofoil from insidebearing← ←：Oil ﬂow

LFT-Ⅲ(2005)

R
Specialprocessing

①

①

Cup
Roller

Low-torque resin cage

20％

Fig. 12 Transition of LFT bearings

50

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

−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−<Condition>−1・Input torque: 200 N･m・Rotational speed: 2 000 min
・Lubricant: SAE75W-90 gear oil ・Oil temperature: 50℃
Head bearing

Tail bearing

LFT-II(Conventional)

Improved fuel efficiency (reduced CO2)

Tandem AC

1.2%（▲2.7 g/km）

LFT-III

1.5%（▲3.4 g/km）

LFT-III+(head)
Tandem AC(tail)
0.0

1.7%（▲3.8 g/km）
0.2

0.4

0.6

0.8

1.0

Torque ratio

Fig. 14 Degree of environmental contribution withcombination of drive pinion bearings

A high number of thrust needle roller bearings areused particularly in regards to automatic transmissions,needs for friction torque reduction are particularly high.
JTEKT has optimized cage design to reduce the sliding
resistance between the rollers and the cage, achieving
50% less torque without compromising on life, high17)
speed performance and wear resistance (Fig. 15) .
Increasing load carrying capacity of the bearing byapplying heat treatment technology allows the bearing to
be made more compactness whilst maintaining the life,
thereby contributing not only to weight reduction but also
higher efficiency due to lower friction torque and a morecompact drive unit. On the high-capacity tapered roller
18)
bearing (KE-II) , a higher load carrying capacity has
been obtained by refining and evenly distributing carbides
through carbide dispersion carburizing technique,improving the bearing life by 4 times in clean oil and15 times in contaminated oil as compared with theconventional bearings.

6. 2 Driveline Unit
Contact areas between roller end faces and cage
(The peripheries of roller and faces contact the cage.)Contact area between
roller end
face and cage
Pocket cross-section

Cage pocket(a) Conventional

Contact areas between roller end faces and cage
(Area near the centers of roller end faces contact
the cage.)Contact area between
roller end
face and cage
Cage pocket

Pocket cross-section(b) Developed productFig. 15 Low friction torque thrust needle roller bearing

New electromagnetic clutch●High hardness Hv 2000
●High wear resistance●Doesn't abrademating parts so much

Outer (nitrided) Inner (DLC-Si)

8 times longer electromagnetic clutch life

Fig. 16 Electronically controlled AWD coupling

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

With attention focused on highly fuel efficient,environmentally-friendly vehicles, there is a demandfor driving stability, safety and enhanced fuel efficiency
on the powerful and popular AWD. In order to satisfy
such demands, JTEKT was quick to develop the®
Intelligent Torque Controlled Coupling (ITCC ) as anelectronically-controlled AWD coupling. The ITCC
suppresses power loss when travelling in 2WD mode
under normal conditions, while providing the optimal
torque distribution necessary as an AWD when starting
the vehicle in snow, or other slippery road surfaces. Thismeans that both torque transmission frequency and power
loss are reduced, thus enabling driveline units such as thepropeller shaft and rear differential to be made lighter andmore compactness, as well as improving fuel efficiency.
Two issues which arose from the outset of ITCC
development were the wear resistance and durability ofthe electromagnetic clutch inside the coupling. As such,
JTEKT developed a high-performance electromagnetic
clutch with a coating made from Silicon Containing
19)
Diamond-Like Carbon (DLC-Si) (Fig. 16) . This DLCSi coating had the effect of significantly improving
durability by 8 times and enabling the coupling to bemade smaller and lighter. JTEKT then developed the20)
3rd generation coupling (Gen3) on which increases indrag torque and transmission torque at low temperature
had been reduced by modifying the surface texture of
the electromagnetic clutch, hence allowing the driveline
to be made even smaller and lighter (Fig. 17). Driveline
units such as the compact, lightweight constant velocity
joint (CVJ) and planetary gear-type torque sensitive LSD®
(Torsen Type C) also contributed to size and weight
reduction.

51

−High Efficiency and Lightweight Technology of Automotive Parts for Energy Saving−

Gen2

Inner Plate

Appearance

W/O crowning

Gen3

With crowning

Outer Plate

Crowning: Macroscopic profile in theorder of tens of µm

Expansion of micro-groove pitch
Micro groove: Microscopic profile in theorder of several µm

Fig. 17 Comparison of surface profiles in magnetic clutch

6. 3 Electric Oil Pump
The idle reduction system that stops the engine when
the car is stationary at traffic lights, etc. is one form oftechnology to reduce fuel consumption, however the
instantaneous engagement of the transmission clutch isnecessary to ensure a smooth takeoff when the engine
restarts. For this purpose, an electrical oil pump (EOP) to
supply hydraulic pressure to the transmission when theengine is stopped is necessary. The electric oil pump for
21, 22)
idle reduction system developed by JTEKT (Fig. 18)
adopts a compact brushless motor and reduces the lengthof the bearing inside the motor rotor to achieve 30%
size reduction compared with the conventional pump.
Motor power consumption has also been reduced by up
to 47%. This product will facilitate the popularization andexpansion of vehicles with the idle reduction system andcontribute to 4% improvement in fuel efficiency.

7. Conclusion
A p p l y i n g t r i b o l o g i c a l t e c h n o l o g y t o ve h i c l ecomponents does not only increases the efficiency ofcomponents due to reduced friction of sliding surfaces,
but also contributes to reducing the size and weightof components and units through enhanced durability,
anti-seizure performance and wear resistance, thus
significantly contributing to energy saving. If the
reductions in fuel consumption achieved by the JTEKT
Ecology Package shown in Fig. 2 are simply summed
up, an overall improvement of 10.7% is obtained, whichis equivalent to reducing CO2 emissions by 25.4 g/km.
A tentative calculation based on the number of vehicles
produced in the world’s major countries shows that CO2
emissions would be reduced by 11 million tons per year.
Electric vehicles and fuel cell vehicles are already being
introduced as a measure to reduce CO2 emissions, and it
can be predicted that by the year 2020, technologies toimprove the fuel efficiency of conventional, fuel-driven
vehicles will be of extreme importance. JTEKT wishes
to continue developing technology able to contribute toenergy saving, hence alleviate the environmental burdens.

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Fig. 18 Structure of electric oil pump for idle reduction system

8)52

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H. MATSUYAMA**

Material R&D Dept., Research & Development
Headquarters

53