OUTLOOKAssimilation and Evolution of Basic Technologies:
Weight Reduction of Automobile Parts
S. TAKEUCHI

This paper describes weight reducing technology for automotive parts in order to reduce CO2 and improvefuel consumption of automobiles in response to environment problems. It also explains the importance ofbasic technologies (material development, measurement and simulation analysis, efficiency technology, andmanufacturing technology) and the need for future research, using examples of developed technologies, both
directly and indirectly related the weight reduction.

1. Introduction
Together with raising awareness about sustainability,
we greet a great turning point in energy and automobilerelated industries concurrent with the radical changes
in the environment surrounding automobiles. It would
appear that we evolve from the vehicles to the mobility,
then from simply moving and means of transportation tothings such as the creation of greater values, including
services. Furthermore, the rapid growth of developing
countries is intensifying competition across all industries,
making it a necessity to create new ideas for technologicalinnovations that defy the successful experiences and1)
common knowledge of the past .
In the midst of these circumstances, at the research anddevelopment field at JTEKT is mainly working on thedevelopment of fundamental element technologies withthe aim of improving product competitiveness of current
business products, and pursuing the creation of novel
technologies for new domain. This report introduces
examples of the efforts of fundamental researchconcerning the environmental friendliness of automobile
parts within the direction of automobiles, focusing inparticular on weight reduction.

2. Improvements in Energy and Fuel
Consumption for Environmental Friendliness
As an environmental problem, global warming stands
in an extremely important position, together with natural
resource and energy issues. In an effort to reduce theamount of the global warming factor CO2, there exist
2)worldwide reduction goals for automobiles (Fig. 1) , and8

Amount of CO2 emissions, g/km

Key Words: weight reduction, basic technology, material substitution, measurement, simulation, efficiency
technology, manufacturing technology

250

EuropeJapan
China
United States

200
150
100
50
0
2005

2010

2015

2020

2025 Year

Fig. 1 Trends of fuel efficiency regulation (amount of CO2
emission)2)

developments in fuel consumption improvement alike areintensifying within automobile parts as well.
Recently, with advancements in electronization
as seen in EV and HEV automobiles, decelerationenergy recovery and idling stop mechanisms, and withdownsizing from the development of next-generationinternal combustion and the shift to small emissions(with superchargers), fuel consumption has improved
drastically. It can be expected that the rate of cars
equipped with such devices will continue to increase.
Efforts by JTEKT to switch from hydraulic power
steering to electric power steering (EPS) have led to afuel consumption improvement of approximately 3% (insmall-size automobiles). In addition, motor size reduction,
harness curtailment and the utilization of aluminum
columns have achieved weight reduction of approximately
15% (Fig. 2). Electronically controlled 4WD coupling has
also led to approximately 38% reduction in weight, andconsumed energy was reduced by 47% due to the 30%
size reduction of the motor, using a 2012 mass-produced

JTEKT ENGINEERING JOURNAL English Edition No. 1011E (2014)

−Assimilation and Evolution of Basic Technologies: Weight Reduction of Automobile Parts−

electronic oil pump for idling stop 3). The achievement ofthese results forms the background for the accumulationof technologies through the fusion and evolution ofcultivated fundamental technologies.

Use ofaluminum
columns

Reduction in numberof clutches due tospecial-purpose oil

Adoption ofcompact motor

Thinner cover

Fuel consumption, km/L

40.0

Reduction in number of parts due to review
of attaching method for propeller shaft
Harness reduction
due to union of
motor and ECU

As shown in Fig. 4, there is an inversely proportionate
tendency between automobile mass and fuel consumption,
and weight reduction is effective in improving fuelconsumption.

35.0

MT car
AT carCVT carHybrid car
Standard level for FY2010

30.0
25.0
20.0
15.0
10.0
5.0
0.0
500

750

1 000 1 250 1 500 1 750 2 000 2 250 2 500 2 750
Automobile mass, kg

Conventional
product
Developed
product

0

Conventional
product 38% reduction
15% reduction
Developed
product
5
10 15 200
5
10Mass, kg
Mass, kg

Fig. 4 Relationship between vehicle weight and fuelconsumption4)
15

Fig. 2 Examples of weight reduction efforts3)

3. Approach to Fundamental Technology
R&D for Weight Reduction
We have summarized the general outline of efforts for
improving fuel consumption in Fig. 3. Most importantare 1) technologies for improving efficacy in power trains
and drive trains, 2) technologies for improving efficacy
in energy input and output for the whole vehicle, and 3)
weight reduction technologies for decreasing mass. In
this report, we will discuss approaches for fundamental
technology research as well as its direction, covering 3) inparticular.

Also, with weight reduction, it is understood that there
are other performance-related merits besides reduced fuel5)
consumption , as shown in Table 1. Within automobiles
and mobility based on "Run", "Stop", "Turn", mass is
an extremely important element in regards to motive
ability, and therefore it is necessary to focus particularly
on weight reduction technologies. For the formulas
expressing rolling resistance in tires, acceleration,
braking, and resistance during rotation, each is related tototal mass of the automobile, and it can be said that mass
has a considerable influence on energy loss.
Table 1 Advantages of weight reduction5)
Results of the effects of a trial calculation for a passenger vehicle
achieving 10% weight reduction at 1 500 kg with a capacity of 5
peopleItem
Fuel consumption improvement
1) Technologies for improving efficacy in power trains/drive trains(Including support technologies for electronization into EV/HEV)
2) Technologies for improving efficacy in energy input and output
for the whole vehicle (Air resistance/rolling resistance reductions,energy management, etc.)
3) Weight reduction technologies for decreasing mass
(1) Material replacement(2) Size reduction• Analysis/Measuring• Machine efficiency, electrical efficiency• Machine processing

Fundamental Element Technology R&D• Material innovation • Monozukuri innovation

Fig. 3 Outline of the approach to improve fuel consumption

JTEKT ENGINEERING JOURNAL English Edition No. 1011E (2014)

Emission gas

Result
CO

−4.5％

HC

−2.5％

NOX

−8.8％

Fuel consumption performance(10 and 15 mode)−3.8％

Starting acceleration performance＋8％

Brake stopping distance−5％

Comfort(Steering eﬀort at micro-low speeds)＋6％

Durability(Fatigue strength leading to cracks)＋70％

Fundamental technologies directly and indirectly
related to weight reduction will be discussed below.

9−Assimilation and Evolution of Basic Technologies: Weight Reduction of Automobile Parts−

3. 1 Material Replacement
Material replacement is the most directly effective
method for weight reduction. The replacement of ironwith aluminum and resin has been steadily increasing
and expanding. Efforts to change to resin for weight
reduction has been quicker than those for aluminum, atendency which has accelerated in recent years. Resinholds high marks in recyclability, but the problem is how
to accommodate its differences with iron in strength,
durability, rigidity, heat and thermal shock resistance,
dimension stability, and age-related deterioration, etc.
This makes fundamental technologies such as those forphysical property analysis, analysis and measuring, andforming and machining very important. For example,
while partially resin parts for the steering gear box are
mass produced, as structural components that undergo
mounting to the inside of the engine room and receiverack thrust, ensuring reliability against the abovementioned issues has become a developmental point. Dueto this, the change to aluminum has been advancing fromearly on.
Peripheral technologies have been progressing recently,
and like automobiles, the anticipation for magnesium
within these technologies is increasing, and attention is
4)
being drawn to new materials such as FRP . However,cost, including manufacturing processes, is essential inproceeding with material replacement, and more researchand development is expected for balancing weight
reduction with cost.

3. 2 Size Reduction
When pursuing size reduction, simply thinning the
housing is not enough. It is difficult to achieve largescale reduction in size without reviewing basic design,
such as combined unification of housing components.
This requires stress analysis and measuring technologies
for ensuring strength, as well as analysis and evaluation
technologies concerning friction and abrasion within thefield of tribology, and energy analysis technologies within
the field of electricity. Technology from new machining
methods is also necessary for improving shape generation
and accuracy.
Examples of research details of these fundamental
6-13)
technologies are introduced below .

3. 2. 1 Analysis and Measuring
As with material replacement, shape changes suchas size reduction and thinning generally employ stress
distribution and thermal displacement in regular FEM
analysis, distortion, review of natural vibration, and theprocesses of design, trial production and evaluation.
Depending on how accurate actual phenomena areperceived to be, the influence from development may belarge.

10

Stress measurement generally involves the use of astress gauge, but in this research we have developed a
new method of measurement which specifies the largest
stress generated within structural components, as wellas the place of generation. This contributes to productsize reduction by providing feedback of the results to theanalysis model. An example of this technology applied tothe constant velocity joint (CVJ) of a power train system
6)is shown in Fig. 5 .

Measured results
Cage

Rolling
elements

Analysis results

Fig. 5 Example of stress distribution measurement using infrared

The CVJ has been given even greater high-accuracy
calculation ability due to enabled visualization of stress
distribution inside the joint. Thus, the newly-developed
compact CVJ achieves 300 to 900 g in weight reduction
for a single vehicle. Also, when applied to the steeringintermediate shaft, this technology adds the influenceof coupled force generated by the mounting state of thevehicle, enabling the calculation of the internal stress
distribution inside the slide mechanism part.

3. 2. 2 Machine Efficiency
Raising energy efficiency leads directly to theimprovement of automobile fuel efficiency, and enables
plans for the size reduction of the improved component
through efficiency improvements in unit devices.
Losses caused by gear meshing and friction within
the gear and sliding part of the unit devices greatly
affect machine efficiency, to which there are tribologicalcontributing factors.
We have focused on reducing friction in the
bearings most used within automobiles, based onelastohydrodynamic lubrication (EHL) and analysis offactors in friction generation, and promote streamlining
and the reduction of friction torque through independent
technologies. We must also consider decreases in strengthand rigidity, etc. for the compaction of the bearings
themselves. Though these are difficult points, reducing
friction reduces the required output for the output powerof unit devices such as the motor, and this may lead to the

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−Assimilation and Evolution of Basic Technologies: Weight Reduction of Automobile Parts−

For DLC films, we are also contemplating plans to
expand automobile parts and other components (Fig. 8).
On the other hand, although we utilize the plasma CVD
superior in mass production for forming films, we havealso developed a treatment method that further improvesmass productiveness with low heat.

1

Plasma CVD method

Torque ratio

0.8

58% reduction

Formingfilm gas

0.6

Glowdischarge
sample (component)

0.4
0.2
0
Conventional productDeveloped productFig. 6 Reduction of tapered roller bearing friction torquethrough parameter optimization7)

We also conducted the development of grease tobalance the reduced resistance in sliding parts of the unit
devices with improvements of damping characteristics forsilencing (Fig. 7).

Average friction coefficientcompaction of output devices equivalent to this reduction.
As an example, we have achieved large-scale friction
reduction in tapered roller bearings by clarifying therelationship of friction resistance to all parameters andthrough optimization of all contradicting characteristics.
(Fig. 6).

0.3
0.2

35% reduction

0.1
0Untreated DLC

Fig. 8 Friction reduction using DLC films9)

3. 2. 3 Electrical Efficiency
Unit devices receive power supply from the battery,and outputs of torque and thrust are generated; however
in terms of energy efficiency, the electricity efficiency is
as an important factor as the abovementioned machine
efficiency. Figure 9 shows EPS energy loss as an
example.

[Contribution to features and low friction]

Additive agent

Solid contact prevention throughhighly-absorbent additive agent

Base oil

Improved oil film thickness throughviscosity optimization (Adaptability toresin materials due to non-polarization)
Prevention of grease shortage throughlowered grease viscosity

Thickener

Abrasion reduction
Technologies
reducing shear stress

Friction coefficient

0.08

68% reduction

0.06
0.04
0.02
0

(3) Wiring (between ECU and motor)(1) Wiring (between battery and ECU)

Technologies
improvement oil film

0.12
0.10

Reduction gear

Base material +General-purpose +General-purpose
additive agent
additive agent+Stearate-related A

Fig. 7 Low-friction grease8)

Another method we have focused on for low friction
research involving surface treatment is the improvement
and application of the Diamond-like Carbon (DLC)
9)
film . Power train system electronically controlled
4WD coupling (ITCC: Intelligent Torque Controlled
Coupling) used in practical application achieved greater
size reduction through their low friction characteristics.

JTEKT ENGINEERING JOURNAL English Edition No. 1011E (2014)(4) Motor
rotation energy(2) ECURack
thrustBattery power(input)BatteryMotor output(output)(4) Motor thermal loss
(3) Wiring thermal loss (ECU/motor)(2) ECU thermal loss
(1) Wiring thermal loss (battery/ECU)

Fig. 9 Energy loss within the EPS system10)

Losses from batteries, harnesses, ECU (Electronic
Control Unit), motor harnesses, and loss within the motor
part influences electricity efficiency, and efficiency issought for each of these in turn. The standalone ECU
and motor were integrated or united into a harnessless
structure, contributing to a weight reduction of 35%
compared with the conventional motor through magnetic
circuit optimization, more efficient coil space factor, andthe development of cyclic technologies to raise motor
10)
efficiency .

11

High coil space factor

Magnetic circuit optimization
Throttle
opening

Double (parallel)star winding

MagnetSize reduction
100

0

30%
reduction

Conventional Developed
product
product

Weight reduction
1000

F n = a·Dactual+b
Infeed amount Dactual

Calculation ofdeflection amount fromgrinding force duringcommand infeed
Infeed positioning
Execution of control
cutting cycle

D (t )Infeed amount Dactual Grinding force Fn

Conventional
firstmachining
for wheel contact
stiffness assuming a

Feedback for each machining session

Figure 10 is an example of compaction enabledthrough overcoming problems by promoting development
within production technologies in response to highcoil space factor (a main factor in bottlenecking within
motor design) and magnetic circuit optimization. Thissuggests that monozukuri innovations within production
development hold a vital existence.

Grinding force Fn−Assimilation and Evolution of Basic Technologies: Weight Reduction of Automobile Parts−

Fn (t )Kt

Time

Dactual(t )TimeCalculated actual infeed amount

D/A

Update and wheel contact
stiffness assuming a

Fig. 11 Feed control based on calculations of workpiece
deflection11)

35%
reduction

Compensation command forthermal displacement amount
CNC

Conventional Developed
product
product

Fig. 10 Case example of motor downsizing/weight reduction10)

PC
Assumed calculation forthermal displacement amount3. 2. 4 Machine Processing
Within the structures of unit devices, there is theissue that division or thickening must be conducted onparts in accordance with restrictive conditions from tool
path, secured accuracy and dispersion reduction withinconventional machining methods. In other words, there is
the possibility of compaction by applying new machining
methods. Our company must leverage our strength as amachine tools maker, promoting the development of parts
machining element technology to pave the way to size
reduction. For high machining accuracy, we developed
technologies that compensate for workpiece heatdistortion and deflection amount by improving machine
rigidity, and confirmed their results (Fig. 11, 12). From
here, we will use these confirmed results to create adesign feedback loop and capitalize on compact design.

12

Temperature measurement data for some points

Fig. 12 Thermal deformation compensation12), 13)

4. Conclusion
The need for weight reduction will undoubtedly
increase further in years to come. In this report, we
introduced technology examples both directly andindirectly necessary to weight reduction. On theother hand, cost remains extremely important even if
revolutionary weight reduction is achieved, and it goes
without saying that balancing these two factors is mostimportant.
Regardless of the framework of not only automobile,
but bearings, machine tools and mechatronics operations,research and development matched to the needs andinnovative technologies of the customer is vital; createdthrough the fusion and evolution of fundamental
technologies such as material development, measuring
and analysis, efficient technologies, and production
technologies. We wish to connect the achievements ofresearch and development with the improved value of
attractive products, while continuing to strengthen the ties
between each of our operations headquarters.

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−Assimilation and Evolution of Basic Technologies: Weight Reduction of Automobile Parts−

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S. TAKEUCHI**JTEKT ENGINEERING JOURNAL English Edition No. 1011E (2014)

R&D Planning Dept., Research & Development
Headquarters

13