valve stem
DESCRIPTION
skfTRANSCRIPT
VALVE STEM SEALS
Design and Select ion
CONTENTS VALVE STEM SEALS
CONTENTS
DESIGN AND SELECTION 3What i s a Valve Stem Seal?
OIL METERING RATE 5The most important funct ion
TYPES 6What Valve Stem Seal des igns are there?
THE DESIGN 7Based on modern CAE systems
VALVE STEM SEAL QUESTIONNAIRE 10Information needed for us to ass i st you
CHECK LIST FOR ASSEMBLY LINE 11Your indiv idual solut ion
INSTALLATION 12Simple but important
THE CR PRODUCT RANGE 13Complete automotive seal ing solut ions
CHICAGO RAWHIDE – LOCATIONS 14A world-wide network
2
DESIGN AND SELECTION VALVE STEM SEALS
DESIGN AND SELECTION
What i s a Valve Stem Seal?
Valve stem seals are not seals at all, but finely engineered
devices designed to provide a defined metering rate of
oil to the valve stem / valve guide interface of combu-
stion engines.
If the metering rate is too high, then engine emissions
are adversely affected and carbon can build up on the
valves resulting, in extreme cases, to valves sticking.
If the metering rate is too low, then the valves are
insufficiently lubricated and scuffing can occur. The ideal
metering rate lies between these two extremes.
The valve, valve guide andseal work as a system
3
DESIGN AND SELECTION VALVE STEM SEALS
4
Quality is our top priority
valve stem seal withintegrated spring seat
Although the requirements for each engine differ accor-
ding to the design parameters and operating conditions,
the oil metering rate is generally within the range
0.1 - 1.0 mg per valve per hour.
These values have been developed through extensive
comparative testing on cylinder heads using the standard
CR test cycle.
Should there be specific customer requirements on
oil metering, then we are in a position to finely tune the
design of the seal to provide the optimum oil metering
rate for the application.
VALVE STEM SEALSOIL METERING RATE
Oil metering to the valve guide/stem interface is the
prime function of a valve stem seal.
Experience has shown that the standard CR design
provides the correct oil metering rate for most applications.
This is true for diesel and gasoline applications as well
as for intake and exhaust valves.
There are however applications where the oil mete-
ring rate must be adjusted. This can be tuned to the exact
requirements of a specific engine by changing the geo-
metry of the sealing lip.
The major factors are the radius of the sealing lip and
the lip angle to the oil side.
The radial force of the seal, while being important
for assuring lip contact to the valve stem under
operating conditions, is not a major factor in deter-
mining the oil metering rate.
SEAL FACTORS INFLUENCING
OIL METERING RATE
5
OIL METERING RATE
The most important funct ion
VALVE STEM SEALSTYPES
BASIC DESIGNS
Two basic designs of state of the art valve stem seal
are offered:
THE NON-INTEGRATED SEAL
This seal (types 866 & 861) fulfils the function of
metering rate only. Type 866 is the standard seal.
Type 861 is used for large differences between valve
stem and guide diameters.
THE INTEGRATED SEAL
This seal (type 863) additionally incorporates a
spring seat to prevent wear on the cylinder head.
All seals incorporate the same dynamic and static sealing
properties enabling reliable function over the life of the
engine. The integrated seal additionally includes a spring
seat, thereby eliminating the separate spring seat (advan-
tages at installation, warehousing, logistics).
All designs use our specially formulated fluorpolymer
materials. These materials provide excellent chemical and
temperature resistance as well as mechanical properties,
to ensure minimal wear and high reliability.
TYPES
What Valve Stem Seal des igns are there?
6
Type 866
Type 861
Type 863
A
A
A
B
B
VALVE STEM SEALSTHE DESIGN
THE DESIGN
Based on modern CAE systems
7
HOW DO WE DESIGN A VALVE STEM SEAL?
All valve stem seals are designed using the most modern
CAE systems. This includes the analysis and prediction
of installation forces with the use of FEAmethods.
As a result, data useful for the layout of the installa-
tion equipment is available at the start of the programme.
The FEAtools can also be used for other aspects of
the seal design. For example, design variations with
differing oil metering rates can be tested for pressure
dependence.
Example: FEA calculation ofpressure influence
VALVE STEM SEAL INSTALLED ON
VALVE GUIDE
VALVE STEM SEALSTHE DESIGN
DESIGN CONSIDERATIONS FOR THE
VALVE STEM
Normal surface treatments are acceptable
(e.g. chrome plating).
Surface roughness Rz ≤ 3 µm / Rmax = 4 µm.
No lettering on the running surface permissible.
DESIGN CONSIDERATIONS FOR THE
VALVE GUIDE
OD tolerance ± 0.05 mm for standard designs.
Surface roughness Rz 10 - 25 µm / Rmax = 30 µm
for the non-integrated seal. Less is no concern for the
integrated seal as it is retained by the valve spring.
A lead-in chamfer is required and most designs,
including the newer symmetrical guides (chamfer the
same at both ends), can be used with CR seals.
Traditional valve guide materials as well as newer
sintered materials incorporating solid lubricants are
fully acceptable for CR seals.
A misalignment of 0.3 mm between guide ID and
OD is acceptable. Special seal designs may be
required for values exceeding this.
OTHER DESIGN CONSIDERATIONS
When the valve is fully open, the gap between the
top of the valve stem seal and the bottom of the
spring retainer should exceed 1.5 mm.
From a timing viewpoint, we should be contacted as
early as possible in the development stage, so that
technical support on design and installation of the
seal and surrounding components can be provided.
VALVE STEM SEAL VALIDATION
The validation procedure varies according to customer
requirements, however the usual procedure for a new
design is to test the oil metering rate and installation
suitability.
Oil metering rate is tested by running an original
customer cylinder head with an electric motor. The tem-
perature, speed, pressures, oil type etc. are decided with
the customer, or the standard CR-Test can be used.
For the installation, the forces needed to press on
the seal and to remove the seal from the valve guide are
measured.
It is normal that these tests are performed, however
they do not replace the tests the customer makes in the
actual engine. This is the final proof of suitability as the
bench tests cannot fully simulate the characteristics of
a fired engine.
WHAT SIZES ARE ALREADY AVAILABLE?
The strong market position of the SKF Seals Division
means that there are already many sizes being
manufactured. Should it not be possible to use a current
seal, then tooling may have to be made for a seal
designed to your specification. Our representative can
advise you.
8
VALVE STEM SEALSTHE DESIGN
9
MANUFACTURING
The SKF Seals Division has invested heavily in unique
state of the art manufacturing technology. The high level
of automation enables us to provide the highest quality
at the lowest price and has been a contributing factor for
CR valve stem seals being the number 1 in Europe.
A very important aspect of our production process is
the visual inspection. All seals are inspected fully auto-
matically using computer vision techniques to ensure
that the critical areas for the function of the seal are with-
out defects.
THE QUALITY ISSUES
As the European leader in valve stem seals and a certified
supplier according to QS 9000, VDA 6.1, DIN EN ISO
9001 and DIN EN ISO 14001, the SKF Seals Division is
well placed to meet the most stringent requirements of
our customers. The most advanced manufacturing techni-
ques, including 100% automatic visual inspection of the
finished parts, ensure the highest level of quality and re-
liability. The characteristics responsible for the function
of the seals are controlled using statistical methods.
WHAT INFORMATION DO WE NEED TO DESIGN
A NEW VALVE STEM SEAL?
A questionnaire (see page 10) has been developed which
details all the information required to design a valve stem
seal. The completed questionnaire should be returned to
us together with drawings of the valve, valve guide,
valve spring and assembly drawing, if available. The
preference for either an integrated or non-integrated seal
should also be given.
CR VALVE STEM SEAL PRICE
Pricing can only be given on an individual basis as this
is very dependant on the design of seal and the annual
requirement. For standard seals, there is no tooling charge.
LEAD TIMES
Detailed lead times can only be given on an individual
basis, but under normal circumstances for a new design,
samples can be supplied within 10 weeks and production
parts 6 months after receipt of the order. For existing
parts, the lead times are significantly lower depending
on stock levels.
VALVE STEM SEALSVALVE STEM SEAL QUESTIONNAIRE
10
Designation
Projected annual engine quantity
Arrangement & no. of cylinders
Inclination of head to horizontal
Is the engine naturally aspirated?
No. of valves per cylinder
– Inlet
– Exhaust
OHV or OHC
Diameter D1
Surface treatment
Surface hardness
Surface roughness
Step diameter (if present) D2
Step height (if present) H2
Outer diameter D3
Protrusion H1
Chamfer length C1
Chamfer angle C2
Concentricity – guide OD to guide ID
Surface roughness
Material
Is a seal retention groove included in the design?
Inner diameter D4
Wire diameter D5
Gap between head & spring cap (valve open) H3
Spot face diameter for spring seat (integrated seal) D6
Pressure range
Mean temperatur
Max. temperature
Max. camshaft speed
Oil type
ENGINE:
VALVE STEM:
VALVE GUIDE:
VALVE SPRING:
SEAL LOCATION:
COMMENTS:
dim. Intake Tol. Exhaust Tol.
mm
mm
mm
mm
mm
mm
°
mm
if yes then please specify
mm
mm
mm
mm
bar
°C
°C
rpm
Please sketch here details of any groove in the valve guide or include a drawing
CR Elastomere GmbH, Düsseldorfer Straße 121, D-51379 Leverkusen, Germany, Tel. +49 (0)2171 713-821, Fax +49 (0)2171 713-860
VALVE STEM SEALSCHECK LIST
11
CHECK LIST FOR ASSEMBLY LINE
Your indiv idual solut ion
SEAL DESIGN:
For an existing seal, please provide a drawing.
Which dimensions are critical for the feeding system?
INSTALLATION PROCESS:
Is the valve inserted before the seal is installed?
What is the maximum installation force per seal?
What is the minimum installation force per seal?
What is the installation speed?
Is the cylinder head rotated after the seal installation?
Is a lubrication process included? If yes, please specify.
Is the presence of the garter spring on the seal
checked? If so, how?
Is the final position of the installed seal checked?
If so, how?
Is the final position of the seal determined by force?
Is a minimum seal removal force specified?
VALVE STEM SEALSINSTALLATION
INSTALLATION
Simple but important
12
1 2
A typical installation procedure.
As our designs incorporate a metal ring bonded directly
to the rubber elements, all CR valve stem seals can be
easily installed, either by hand for small quantities, or
fully automatically for high volumes. However, in order
to ensure the correct function in the engine, the installati-
on procedure is very important.
This begins with the designs of the seal and valve
guide, which must be tuned to each other for the best re-
sults. The seal must sit at the correct position and remain
there for the life of the engine.
For a new application, we would be pleased to recom-
mend an installation tool design and to advise on the
installation procedure.
For an application where installation equipment is
already available, it is important that the design of seal
takes this into consideration, so minimising (or elimina-
ting) equipment change costs. In this case, details of the
existing equipment will be required.
THE CR PRODUCT RANGE
Complete automotive seal ing solut ions
Innovative sealing modules for automotive transmissions
are also part of the CR product range.
In addition to sealing products, our advanced rubber
technology has also been applied to the field of sensors.
SKF is a leading supplier of ABS bearing systems and
these systems include tone rings with a magnetised rub-
ber coating, which provide an accurate signal for rotatio-
nal sensors. The use of these tone rings is expanding into
engine and transmission applications.
INTERESTED IN ADDITIONAL PRODUCTS?
In addition to valve stem seals, CR products provide
complete automotive sealing solutions for engine, trans-
mission, driveline, steering and suspension systems. This
single source approach is possible through a world-wide
network offering one-source accountability.
CR sealing products include dynamic radial seals for
engine, driveline and wheel end systems; Moulded In
Place (MIP) seals for valve covers, oil pans and other
covers; seals for gas springs and shock absorbers; and
RotostatTM Sealing Modules - dynamic and static seals
bonded directly to covers to form a single easily installed
component.
13
VALVE STEM SEALSADDITIONAL PRODUCT RANGE
CONTACTS
The product centre for valve stem seals is.
CR Elastomere GmbH
Düsseldorfer Str. 121
51379 Leverkusen-Opladen
Germany
Phone +49 (0)2171 713-821
Fax +49 (0)2171 713-860
E-Mail: [email protected]
14
VALVE STEM SEALSLOCATIONS
CHICAGO RAWHIDE – LOCATIONS
A world-wide network
SALES AND MANUFACTURING
Brazil 1 plant
China 1 plant
Germany 1 plant
India 1 plant
Italy 2 plants
Korea 1 plant
Mexico 1 plant
Ukraine 1 plant
USA 6 plants
SALES AND DISTRIBUTION CENTRES
Australia
Belgium
Denmark
France
Japan
Poland
Sweden
United Kingdom
additional sales via regional SKF offices
in over 130 countries
Beijing
CR-manufacturing sites
Leverkusen
Göteborg
E-Mail: [email protected]
www.skf.com
© Copyright SKF 2001Every care has been taken to ensure the accuracy of the information contained in this publication but no liability can be accepted for any loss or damage whether direct, indirect or consequential arising out of the use of the informationcontained herein.
SKF Publication 5166E
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AMERICA
Chicago Rawhide
900 North State Street
Elgin, Illinois 60123-2193
USA
Phone +1 847 742-0700
Fax +1 847 742-7845
EUROPE
CR Elastomere GmbH
Düsseldorfer Str. 121
D-51379 Leverkusen-Opladen
Germany
Phone +49 (0)2171 713-821
Fax +49 (0)2171 713-860
ASIA-PACIFIC
CR Asia-Pacific
3-2, Shin Yokohama Kouhoku-Ku
Yokohama Kanagawa 222-0033
Japan
Phone +81 (0)45 473-4823
Fax +81 (0)45 473-3475