New Development /New Product

New Ceramic Ball Bearings
for Electric Motors
Our newly developed, first in Japan
ceramic material makes ceramic bearings
available for more applications.

Ceramic rolling elements
prevent electrical pitting
in bearingsfor electric motors

Our newly developed ceramic has onlya slight difference in linear expansion
coefficient from the inner and outerring material (bearing steel SUJ2),
thus creating minimal internal clearances
due to temperature change, allowing
ceramic bearing use in an environment
with a wide range of temperatures.
（※）※

Change in a material’s length in response to a change intemperature of 1 degree Celsius.

Our newly developed ceramic has
similar insulation properties, strength,and durability (little change in acoustic value)with conventional silicon nitride material(Si3N4).
(See the table below for details.)■ Material properties
New ceramic

Bearing steel(SUJ2)

Standard ceramic(Si3 N4 )Density (g/cm3)

6

7.8

3.2

Linear expansion
coefficient (1/°C)

10.5×10−6

12.5×10−6

3.2×10−6

Vickers hardness (HV)

1280

750

1500

Module of longitudinalelasticity (GPa)

210

208

320Poisson's ratio

0.31

0.30

0.29

1200−

1100

5〜6−

6Insulator

Conductor

Insulator

3-point bending
strength (MPa)Fracture toughness(MPa･m1/2)
Conductivity

■ Rolling fatigue life evaluation results■ High-temperature Noise comparison test results

More than 3 times longer than calculated fatigue life

Noise comparison test results (150°C)

430

Noise value

Fatigue life

32

[VG]

New ceramic

Bearingsteel(SUJ2)

Standardceramic(Si3N4)20

101

Calculated fatigue life

Test equipment

Test result

0Test conditions

Test conditions

Contact stress

4.2 GPa

Lubrication

Oil bathLoad■ Crushing load test
Crushing loadF

Schematic ofcrushing load test

3000

4000

No significant
deterioration of
the acoustic valueof our new ceramic
after 3600 hours■ Wave-like wear by electrical pitting

40【Electrical pitting】

Load causing
1/10000
deformationof ball diameterfor bearing steel(SUJ2)

29.93024.7

201002000

Time [h]Lubrication KVC (urea-based grease)
Ambient
temperature Outer ring temperature 150°C
Load
Fa＝0.16kN
Rotational 3000 min−1speed
Calculated 3600 hgrease life
Test duration 3600 h

Ball size 3/8 inch

[kN]

F

1000

0.17kN

New ceramic Standard ceramic(Si3N4)

Crushing load test results

Inner ring raceway surface

This new ceramic has strength equivalent
to conventional silicon nitride ceramic (Si3N4).

Due to the nature of electric motors,
harmful voltage is generated byhigh-frequency current during
operation, and above a certain
voltage can produce arcing
between the bearing raceway
surface and rolling elements.
Electrical pitting occurs when asurface in rolling contact is locallymelted due to the arcing, reducingbearing service life. To avoid such
pitting, using an insulating ceramicrolling element is one of the mostreliable solutions. Our newly
developed ceramic has insulation
properties equivalent to those of
conventional silicon nitride ceramic(Si3N4).

Applications

Inverter motors

Fan motors

Inquiries:

PUBLISHERJTEKT CORPORATION NAGOYA HEAD OFFICE
No.7-1, Meieki 4-chome, Nakamura-ku, Nagoya, Aichi 450-8515, JAPANTEL:81-52-527-1900

FAX:81-52-527-1911

TEL:81-6-6271-8451

FAX:81-6-6245-3712

TEL:81-6-6245-6087

FAX:81-6-6244-9007

JTEKT CORPORATION OSAKA HEAD OFFICE
No.5-8, Minamisemba 3-chome, Chuo-ku, Osaka, 542-8502, JAPANSales & Marketing Headquarters
No.5-8, Minamisemba 3-chome, Chuo-ku, Osaka, 542-8502, JAPAN･Information in this catalog is subject to change without notice due to continual improvements.

CAT.NO.B1017E,

Printed in Japan 16.11-1CM