TECHNICAL REPORTTechnical Trends Regarding Rolling Bearings Used with Balancer
Shaft Systems in European Engine Applications
S. MESCHER

In present automotive and heavy-duty engine applications, plain bearings are primarily used and, vice versa,
rolling bearings, such as ball or needle bearings, are of minor relevance. However, the share of plain bearings will
be decreased in automotive applications because they are gradually replaced by rolling bearings. This is, on theone hand, owed to more stringent CO2-emission standards set by European governments and, on the other hand, tothe customers’ desire for a reduced fuel consumption of the car. An increased benefit value implies a reduced energy
demand with simultaneously minimized friction losses which, consequently, lead to reduced engine emissions. Since
the changes as for bearing technology requirements lead to an increased demand for rolling bearings in automotiveengines, JTEKT has committed itself to developing special bearings for automotive engines. The development
process of rolling bearings for balancer shaft systems is introduced in this journal.
Key Words: automotive, engine, balancer shaft, rolling bearing, low friction, CO2-emission reduction

1. Introduction
The automotive industry is currently facing major
challenges in terms of structural and technologicalchange. One of these challenges is the new and more
stringent CO2-emission requirements set by the Europeangovernments. Increasing the power and efficiency of theengine by reducing internal frictional losses is a major
1)target of the European automotive manufacturers.
Another important issue is the continuous enhancement2)of the engine’s level of comfort and running smoothness.
One of the European car manufacturers’ options
to achieve these targets consists in replacing plain
bearings on balancer-, cam- and crankshaft by rolling
bearings. These operations lead to an increased demand
for rolling bearings for engine applications, such as3)4)
Needle Roller Bearings and special Ball Bearings.
Consequently, JTEKT has developed particular bearings
for automotive engines to fulfill the customer needs, suchas compensating annoying vibrations and uncomfortablenoise related to engine operation. Specific rolling bearing
solutions for automotive balancer shafts will be presentedin the next chapters.

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2. Balancer shaft design concepts in
European engine applications
Modern diesel and gasoline engines have been released
from annoying vibrations and uncomfortable noise due tothe implementation of balancer shafts and balancer shaft
units (add-on). A balancer shaft system can be developedby the European automotive manufacturers themselves
or in a development partnership between European
automotive manufacturers and the suppliers of balancer
shafts and bearings.
The balancer shaft is a mass compensation systemdesigned to reduce and to eliminate second-order massforces which, in a fired engine, result from engine
operation. With the help of extensive FEM calculations
that are based on the initial CAD draft models of all
engine components, an optimal compromise between
rigidity (positive effect on noise and vibration), strength
and weight of the balancing system is achieved. Since theengine manufacturers aim at reducing friction losses anddecreasing engine weight as well, they try to optimize thebalancer shaft design as for mass saving and limitation ofits deformation in operation. This results in, e.g., a partlycircumferential inner race (so-called 180° shaft, covering
an angle of 180°).
The balancer shaft bearings are used in different engine
architectures, such as L2, L3 L4 or V6 engines, see Fig. 1.
Depending on the engine concept, one or two shafts areincluded in the respective application, running at single or
double engine speed.

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

−Technical Trends Regarding Rolling Bearings Used with Balancer Shaft Systems in European Engine Applications−Balancer shaft design overview

L2

3. Rolling Bearing Design DevelopmentThe design of balancer shafts and the corresponding
bearings requires a consideration of all the underlying
conditions, including the balancer shaft housing and thedrive system as well as the oil supply and oil system.
These aspects are discussed in detail in the following
sections.

L3 or V6

3. 1 Operating conditions considered in thecalculation

L4

During the process of calculating and developing(Fig. 4) the optimal bearings for the investigated balancer
shaft, loads and speeds occurring in engine operationneed to be considered – these characteristics effectmisalignment (shaft deformation & tolerance sensitivity)
on each bearing position. As well, the expected bearing
lifetime is affected by temperature and lubrication (Oilgrade, quantity, contamination…).

Identified risks and design parameters

Fig. 1 Balancer shaft design architecture overview

Regarding the system architecture, there are two basicbalancer shaft concepts on the market. The first concept
called “tunnel assembly” means integrating a balancer
shaft system in the engine block (Fig. 2).
The second concept is a balancer shaft module,
Fig. 3, which is separately attached to the engine block.
Depending on the balancer shaft design different bearing
types can be applied.

• The main goal is an adequate bearing having sufficient
dynamic capacity: bearing dimensions and life target
are to be balanced.
• In order to provide robust bearing operation for all
application conditions, stress resistance related toboth, inner and outer race, is specified: material &heat treatment definition, specific race & rolling
element profile for stress balancing, also shaft design
improvement as for limiting deformation.
• High speed bearing capability => definition of
optimized cage design type; e.g. cage guidance byouter race or by rolling element and rolling element
size.
• Bearing mounting in housing (Retention, stressin housing) => housing material, interference andminimum outer race thickness, housing design are
optimised as for enduring all application conditions.
• Clearance management => system geometry, sorting &selective assembly.
• NVH level => system assembly, raceway geometry andsurface finish, clearance management are investigated.

Fig. 2 Balancer shaft tunnel system

Fig. 3 Balancer shaft module

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−Technical Trends Regarding Rolling Bearings Used with Balancer Shaft Systems in European Engine Applications−Fig. 4 Balance shaft analytical development process - e.g. balancer shaft module

4. Balancer Shaft Bearing – design
overview
As shown in Fig. 5, bearing design is characterised bya balance of the bearing capacity on the one hand andload conditions and durability target on the other. As
well considered are assembly conditions, the operatingclearance management, friction and NVH requirements
and other customer needs.

Fig. 6 Needle roller bearing

Advantages:• Flat cross section, low diameter• NVH convenient with polymer cage
• Low cost
Drawn cup
bearing withpolymer cage

Cylindrical roller Ball bearing
Split polymer cage with
with a axial
drawn sleeve or machined bearing withload support
solid race
ring. Cage roller or outercapability
diameter guided.

Fig. 5 Balancer shaft bearings-design overview

Drawbacks:• Limited capacity, no extremely loaded configuration• Sensitive to misalignment in case of long rollers• NVH risks due to housing geometry effects

4. 1 Needle Roller Bearing

4. 2 Cage and Roller

A Needle Roller Bearing is designed for radial loads
exclusively and has a drawn cup to form the outer
raceways in most cases. A particularly thick-walled “heavyduty” drawn cup can be used to cover even extremely
loaded mountings in aluminum housings/engine blocks.
A broad variety of cage design according to application
speed and cage material (steel or polymer) can be applied.

A Cage & Roller Assembly is a bearing designed forradial loads only. One variant suitable for balancer shaftsin particular has a split polymer cage – it allows themounting on a fully assembled shaft in a conclusive step.
A solid ring could serve as an inner race, and a machined
ring or drawn sleeve could constitute the outer race.
For ideal operating conditions the outer and inner races
need to be properly specified for a rolling contact (heattreatment and clearance management).

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−Technical Trends Regarding Rolling Bearings Used with Balancer Shaft Systems in European Engine Applications−

4. 4 Ball Bearing
Commonly used in balancer shaft applications are aswell single or double row ball bearings, characterized bysteel cages and specially customized material and heattreatment.

Fig. 7 Cage and roller

Advantages:• Assembly in a conclusive process feasible (split
polymer cage)• Clearance management with machined outer ring
• NVH capabilities (polymer cage and solid race withcustomized surface finish)

Fig. 9 Ball bearing

Drawbacks:• Sensitive to misalignment in case of long rollers• Limited NVH capabilities in combination withdrawn outer sleeves (sensitive to housing geometry)

Advantages:• Thrust load capacity and axial positioning• Low sensibility to misalignment• Low friction

4. 3 Cylindrical Roller Bearings

Drawbacks:• Bearing dimensions• Low radial capacity, compared to needle roller or
cylindrical roller bearing

Characteristic of Cylindrical Roller Bearings is, in
relation to their length, the large diameter of the rollers
which generally roll on massive, thick-walled raceways.
Usually they are operated in balancer shaft applications
which involve high radial loads. Several configurations
are possible, e.g. a steel or polymer cage type, with orwithout an inner ring. A thick-walled drawn cup may also
be applied in combination with cylindrical rollers.

Fig. 8 Cylindrical roller bearing

5. Conclusion
The development of special rolling bearings forbalancer shaft systems in European engines has
successfully supported the European automotive
manufacturers in various ways: reducing the CO 2e m i s s i o n s o f t h e i r c a r- f l e e t t o m e e t E u r o p e a ngovernmental emission standards, and satisfying thecustomers’ desire for improved fuel consumption. As forthe specific rolling bearings for balancer shaft application,
volume production has now been implemented in Europe.
Regarding rolling bearings used in future automotiveengine applications, the JTEKT European Bearing
Technical Centre will fully use its expertise and advanceinnovative solutions and valuable technologies.

Advantages:• High capacity, high expected life in high radial loadcondition• Support axial load in some cases• Clearance management with solid races• Friction and NVH capabilities (solid race, polymercage)
Drawbacks:• Larger outer diameter• High costs for the case that drawn cups are notapplicable• Extra load at high speed (Roller mass) and slippagerisks

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−Technical Trends Regarding Rolling Bearings Used with Balancer Shaft Systems in European Engine Applications−

References
1)
2)

3)
4)

T. Koch: Paradigmenwechsel in der Automobilindustrie,
MTZ worldwide, Volume 63 (2002).
BMW: The Balancer Shafts on the New Four-Cylinder
Diesel Engine from BMW, MTZ worldwide, Volume 63(2002).
Daimler: Diesel Engines for new E-Class MTZworldwide, Volume 63 (2002).
K. Hoag, B. Dondlinger, Vehicular Engine Design,Powertrain (2016).

S. MESCHER**78

KOYO BEARINGS DEUTSCHLAND GMBH

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