Innovative solutions for the cylinder head in modern gasoline engines

Innovative solutions for the cylinder head in
modern gasoline engines
Jürgen Meusel
Abstract
Motorcycles follow, or are sometimes ahead of automotive standard
technologies in engine design.
The development trends of advanced motorcycle and automotive engines are
towards high power and torque and reduction mass, which in itself contradicts
the requirements regarding reduced fuel consumption and emissions.
This paper deals with innovations in the cylinder head by the group
ThyssenKrupp Presta Camshafts. The technologies in the camshafts give a
potential for reduction in weight and emissions and higher performance in
power and torque.
1. Introduction
The gasoline engine is situated in a stress field which is constituted on the one
hand by demands for higher power/ torque, low fuel consumption and low
emissions and on the other hand by the demands for low production costs, low
engine weight and higher durability. (Fig 1)
Fig. 1
Area of conflicts in gasoline engines and Requirements of camshafts
The group ThyssenKrupp Presta Camshafts is the market leader in assembled
camshafts for the automotive sector. The production stands at 21 Mio
camshafts per year. The group has five locations, two of which are in Germany,
one in Lichtenstein, USA and China.
The R&D team develop new solutions in the cylinder head and has solutions in
-Light weight and flexible- , -Component and function integration- , -Variability in
the valve train. (Fig. 2.)
The Presta Camshafts team is also a competent partner in development of light
weight components like rotor and gear shafts for electro mobility.
Developments are tested for function and durability in our own test department.
Engine tests are carried out with partners and OEM´s.
Fig. 2
Development Technologies in the cylinder head by Thyssenkrupp
Presta Camshafts
2. Camshafts technology state of the art
2.1. One piece camshafts
One-piece camshafts can be manufactured by casting or forging. In gasoline
engines casted camshafts and partly forged camshafts are most commonly
used. Casted camshafts can be completely manufactured as hollow or as less
expensive full shafts and forged shafts. In order to reduce the weight, it is
possible to drill them hollow. Fig. 3 shows the pro- and contra factors for one
piece camshafts.
.Fig. 3 Pro- and contra factors for one piece camshafts
2.2. Assembled camshafts
Constantly increasing requirements have led to the use of assembled
camshafts Fig 4.
Fig. 4 Requirements from the engine producers
Fig. 5 shows the Presta Camshafts “press and form fits” technology. The
components are mounted in sequence on a tube. The weight of the camshafts
is reduced by 30% compared to casted or forged shafts.
This technology enables the camshafts to be produced with components of
various materials, so achieving an optimum in both function and costs.
Fig. 5
Technology and manufacturing process of ThyssenKrupp Presta
Camshaft
The processes are automated and all manufacturing data is archived (Fig. 6).
Fig. 6
Quality process in the assembly of ThyssenKrupp Presta Camshaft
Fig. 7
Manufacturing spectrum in assembled camshafts
The manufacturing spectrum in assembled camshafts ranges from a motorcycle
with a length of 120 mm to heavy duty engines with a possible length of 2,200
mm in the mass production. (Fig. 7)
3. Innovative Solutions in Camshafts & Valve Train
The following pages show an overview of the innovations which are currently in
development at ThyssenKrupp Presta Camshafts. These products and
technologies are also being tested in the preliminary development for gasoline
engines. Some of our latest projects are also interesting for motorcycles. The
aims are reduction of fuel consumption/emissions, higher flexibility in
production, reduction in cost and weight (Fig. 8).
- The reference in the cylinder head Light weight
and
Flexibility
Variability
in
Valvetrain
Component and
Functional Integration
Fig. 8 Innovative developments and products in the cylinder head
3.1. Lightweight camshaft
In addition to Presta assembly technology we are also developing camshafts
using the hydro-forming technology. This technology enables the bearing
diameter and the base circle diameter from the cam lob to be designed/
manufactured in the same size. At the same time an advantage in weight is
achieved (Fig. 9).
Fig. 9 Innovative developments with hydro-forming technology
3.2. Camshaft for tappet application
Presta is continually researching new material possibilities and has carried out
extensive testing with different materials for tappet applications.
Current examples of Presta camshafts for tappet applications include:
-
sintered cam lobes (Kia)
100Cr6 steel cam lobes (Ford)
combined sinter and 100Cr6 (Porsche)
In Fig. 10 shows a shiftable tappet and a cam lobe application with different
material.
As cast iron cams have dominated the tappet market up until now, Presta has
also developed the application of assembled cast iron cam lobes.
100Cr6
Sinter
Sinter
Fig. 10 Tappet application with different material
3.3. PICA - cylinder head concepts
The cylinder head concept gives several possibilities for potential in innovation.
The Presta Integrated Camshaft Assembly (PICA) is one of a highly efficient
and flexible system.
Today’s technology is:
Complex casting of cylinder head,
Complex machining of journal bores and
Assembly and disassembly of upper cam halves required
-
Presta Integrated Cam Assembly (PICA) solution has advantages in:
Flexible & multi-functional solution kit regarding material & bearing type
Lowered system-costs of cylinder head due to machining and
assembly advantages
Weight reduction of the cylinder head
Lowered fuel consumption due to reduced friction
Less number of parts for the engine manufacturer because of modular
reference
-
The following Fig 11 shows the reference and the closed bearing system with
potential of reduction in weigh
Fig. 11 References and potential of Presta integrated camshafts
assembly PICA® with potential of weight reduction
The Presta Integrated Camshaft Assembly (PICA) gives a high
flexibility in application and layout of cylinder head designs. The development of
a modular “construction kit” is the basis for the flexibility (Fig. 12).
Fig. 12 The modular “construction kit” of Presta integrated camshafts
assembly PICA®
Fundamental investigations on plain bearings based on Elasto-hydro-dynamic
simulations (EHD simulations) show high potential in friction reduction.
The Fig. 13 shows the result by rotation of camshaft at 2750rpm, with maximum
bearing gap, maximum concentricity deviation and bearing cap offset.
The results in bearing 5 (drive train) are not dominated by bearing cap offset.
There is mixed friction due to bearing cap offset in all other bearings (Fig. 13).
Fig. 13 Results on EHD simulation in friction with bearing cap and closed
bearings
A further analysis of temperature influence on the tribological situation in the
camshaft bearing (adjustment of the thermal expansion coefficient of the
bearing blocks) shows in addition possible savings in friction power as well as
oil flow in the camshaft bearings (Fig. 14).
Fig. 14 Results on EHD simulation in friction and oil flow with adjustment of
thermal expansion coefficient of bearings
3.4. POSS® - Presta Oil Separation System
ThyssenKrupp Presta Camshafts has a new highly efficient oil separation
system integrated in a hollow camshaft for diesel and gasoline engines (Fig 15).
The benefits to Customers are:
- Package and weight saving
- Fewer emissions due to better oil separation rate
- Decreased risk of freezing by integration
into cylinder head
- Small component part complexity due to modular solution
The following Fig. 15 shows the design solution with the function parts. The oil
separation works in two steps.
Fig. 15 Presta Oil Separation System is integrated in the camshaft
There is a pressure downward slope between the engine inside with blow by
gases and the engine intake air system.
The raw gases flow through to holes into the camshaft tube.
The centrifugal force accelerates the big oil particles outward in the 1st
separation stage, where they precipitate as a film on the tube wall.
The small particles are separated in the second separation stage in the oil
separator rings.
The separated oil (oil film) flows into the oil chamber of the cleaned gas
passage and back in the crankcase.
The cleaned gas streams through the gas passage to the engine intake air
system.
The particle capacity and size of raw gas and the cleaned gas is shown in Fig.
16.
Fig. 16 Particle capacity and size of raw gas and the cleaned gas
The Presta Presta Oil Separation System is optimized in functionality, package
and integrated in assembled camshaft.
3.5. Concentric Cam - variable valve timing system
Following the automotive requirements for optimized load- and speeddependent valve train variability, TK Presta Camshafts Concentric Cam
development was focussed on applying more functionality and variability to the
camshaft itself.
Reduction of fuel consumption by same or better torque and power distribution,
also reduction of exhaust emissions are targets and main potential of ConCam
technology.
Concentric Cam design consists in principal of a second shaft in concentric
position inside a standard assembled camshaft, having fix lobes on the outer
shaft and moveable lobes connected to the inner shaft (Fig. 17).
Driven by a camshaft phaser, the two shafts are rotatable to each other,
performing a continuously variable phasing of valve event/ timing between fix
lobes and moveable lobes.
Fig. 17 Concentric Cam principle.
Two robust, durable and cost competitive systems of Concentric Cam,
o
Type I for variable phasing of valve timing and
o
Type II for variable duration of valve timing,
developed, tested and proven by ThyssenKrupp Presta Camshafts, are
applicable to SOHC- as well as DOHC- engines.
The following Fig. 18 and 19 show the design characteristics of the Concentric
Cam Type I and II system.
Fig. 18 Concentric Cam Type I: Design characteristics
Fig. 19 Concentric Cam Type II: Design characteristics
Depending on engine type (Gasoline or Diesel) and construction (SOHC- or
DOHC- engine), Concentric Cam technology is capable for several strategies of
VT- variability and shows significant potential in reduction of fuel consumption
and/ or emissions, furthermore optimized or increased torque and power
distribution.
Functional strategies and benefits using ConCam technologies are shown at
following Fig. 20.
Fig. 20 Functional strategies and advantages Concentric Cam Type I and II
Substantial investigations, in a first stage by combustion simulation and
analysis, clearly indicated the achievable potential and customer benefit of
described strategies using ConCam technology.
Essential simulation results could be proven by real fired engine tests
performed on reference engines.
3.6 Shiftable Camshaft/ lobe technology
Another potential system of VT- variability with camshafts shows shiftable lobe
mechanism, so called shiftable camshaft/ lobes.
System consists of camshaft with tooth profiles at cam position, supporting and
guiding axial moveable lobe pieces, which carry 2 or 3 different cam profiles
close in parallel at relevant valve position.
Dependend on engine load and speed, driven by engaging actuator, the
slideable lobes can be shifted to get related cam profile in contact to the valve
train, including feasibility for partly cylinder deactivation.
System design and TK Presta camshafts cooperation for development/
industrilization is shown at Fig. 21.
Fig. 21 System design shiftable camshaft/ lobe technology
Characteristics of slideable lobe variability are discrete cam profiles (2 to 3), but
different in valve lift, timing and phasing, adapted to main engine running
conditions like part load, full load etc.
Based on engine type and strategy for VT- variability, for optimization of engine
efficiency, shiftable camshaft/ lobe technology provides similar results and
benefits regarding fuel consumption, power and torque distribution and exhaust
emissions.
Conclusions
Existing and new engine technologies in the automotive and motorcycle
industries vary significantly in some systems. Both powertrains have the same
target however, maximum performance in power/torque but by low weight, low
costs and reduced emissions. The ThyssenKrupp Presta Camshafts systems
show possible solutions on the way to achieving these targets.
Some systems give a new identity to the engine, with higher unique features.
Some systems can be integrated with relatively little effort.
The Presta Camshafts group is the marked leader and tier 1 supplier in
assembled camshafts and a development partner in camshaft- and valve train
systems, also for motorcycle powertrains.