Unique SKF taper roller bearings: Solutions for demanding operating conditions and long service life.

Transcription

1 Unique SKF taper roller bearings: Solutions for demanding operating conditions and long service life. SKF TQ-Line SKF CL7C SKF Explorer

2 SKF taper roller bearings Performance classes The design and production of technical products are subject to ever-increasing quality and performance requirements. More robust and easy-to-use, more energy-saving and longer lasting, more precise and sophisticated all these demands apply to today s bearing arrangements for vehicle transmissions and wheels as well as stationary transmissions (e.g. wind turbines, rail-bound vehicles, hoisting equipment or escalators). Taper roller bearings are usually the best and most economic solution in these fields. They are capable of accommodating combined radial and axial loads. SKF taper roller bearings enable very stiff bearing arrangements and are easily adaptable to the ideal load conditions during operation. SKF TQ-Line SKF TQ-Line taper roller bearings have been tried and proven over many years: With this type of bearing, SKF customers can achieve operating characteristics that are clearly set apart from competitors products. The TQ-Line, recognisable by its SKF designation suffix Q, is the basis for CL7C and SKF Explorer bearings. SKF CL7C taper roller bearings These high-performance bearings with the SKF designation suffix CL7C are ideal for applications requiring high stiffness, low friction and very high speeds. Moreover this performance class offers high operational reliability even where boundary lubrication conditions may apply. SKF Explorer taper roller bearings SKF Explorer taper roller bearings represent a completely new performance class with significantly improved performance parameters. Technologically they offer clear advantages over both the TQ-Line and the CL7C performance classes. Their significantly longer service life has been verified in various inhouse and independent tests. The quality of the inner and outer ring raceway surfaces as well as of the rollers has been further optimised, as have been the contact profiles. The bearing steel is subject to stringent inspections. A 1 % inspection of the most important parameter ensures production in compliance with the Zero Defect principle. This results in higher load carrying capacity and reference speeds, much longer service life in other words, a plus in economic efficiency. SKF taper roller bearings TQ-Line Design features and customer benefits The optimised internal geometry of these SKF taper roller bearings enables the incorporation of more rollers and thus results in extra load carrying capacity. Thanks to the optimisation of roller end/flange contact and internal geometry, TQ-Line bearings offer a plus in safety during running-in and ensure a controlled low spread of the unavoidable initial preload loss. When the application can benefit from higher stiffness or precision of the axial position, then a higher preload capability is crucially important. Higher stiffness also reduces noise and friction both in the bearing and the entire assembly. Lubricant film formation is actively supported, so avoiding an excessive rise in temperature and the related risk during running-in. Best-in-class rollers with optimised surface typography and minimum spread in diameter dimensions lead to even stress distribution in the bearing. This forms the basis for very long service life and low noise. The optimised logarithmic contact profile ensures even load distribution between rollers and raceways. This leads to a reduction of stress peaks in extreme applications. Applications requiring high bearing stiffness benefit in the form of service life increase. Preload extends the bearing service life and ensures optimum gear mesh with low friction and long service life. SKF TQ-Line taper roller bearings comprise high surface hardness, even load distribution, homogenous material and hardness structures as well as high ductility of the bearing rings. All these benefits result in high resistance to contaminated lubricating oils and ensure long service life. Low spread in adjustment behaviour is a consequence of the minimal spread in dimension of each individual component. This is a decisive contribution to long bearing service life and also facilitates the adjustment process and increases safety. 2

3 SKF taper roller bearings TQ-Line Long service life and high performance density Explore new limits! Service life Preload suitability influences service life Highest performance capability verified in comparative tests CL7C Service life index 1,4 TQ-Line 1,,8 Premium brand taper roller bearing (standard design) Running-in Spread High preload possible in combination with low determinable temperature behaviour during running-in Optimised contact profile between roller end and ring flange as well as optimum contact between roller and raceway Very high roller quality,6,4 Non-optimised bearings Optimised surface topography high medium medium high Preload in operation Clearance Heat-treated to latest findings High-grade steel Temperature during running-in T ( C) 15 High degree of metallic contact due to poor roller/flange contact zone Competitors with boundary lubrication in the roller/flange contact zone Reliable assessment of service life and critical stresses - in specific customer applications - based on SKF bearing features 1 5 CL7C 5 TQ-Line t (h) Bearing adjustment can be targeted at maximum service life and controlled temperature balance Controlled temperature behaviour - during running-in - during operation SKF taper roller bearings TQ-Line Low noise and vibration levels, high running accuracy Applications Escalator gearboxes 1 % in-flow noise check by means of frequency analysis for taper roller bearings of up to 16 mm outside diameter Very low dimensional spread and deviation of dimensions of important ring and roller parameters through continuous material flow and separation of components Very high roller quality Optimised surface topography Separation of components systematically avoids damage during production and assembly Positioning accuracy in drum scanners and printing machines Where bearing noise is directly perceived (e.g. car and escalator gearboxes) Where precise positioning of the bearing axis is required, for instance to avoid moiré effects during printing. Professional drum scanners also require high positioning accuracy to enable high-quality scans. Moiré effects 3

4 SKF taper roller bearings TQ-Line Surface profile: Longer bearing life through optimised surfaces Surface topography Competitor product Oil film Critical area in rolling contact SKF TQ-Line taper roller bearing Reduced surface roughness No risk that asperities cut the lubricant film Lubricant reservoir close to surface Evenly smooth surface topography Safe operation even with low-viscosity oils No lubricant film breakdown even at high environmental temperatures Quick formation of separating lubricant film Safe start-up even at low temperatures Low operating temperature Reduced noise and vibration levels Longer service life SKF taper roller bearings TQ-Line Roller end/flange contact profile: SKF technological leadership Contact profile between roller end and flange Optimised geometry of contact zone and surfaces Lubricant film Running-in zone Lubricant film formation is actively supported immediately after start-up, even at low speeds No excessive temperature rise during running-in avoids risk at start-up Roller Ring Safe operation under preload Small controlled initial loss of preload (low spread) targeted adjustment value achieved in operation Minimised wear avoids the need for special running-in procedures and critical preload loss Consistent friction behaviour facilitates bearing adjustment Service life extension possible - higher preload - improved temperature balance More reliable bearing adjustment during mounting Faulty adjustment is one of the main reasons for premature bearing failure! 4

5 SKF taper roller bearings TQ-Line Roller/raceway contact: Reduced stress peaks Roller/raceway contact Logarithmic profile Light load Larger load zone gives higher effective carrying capacity Optimised internal geometry with maximum number of rollers Optimised for different load conditions Light: - no stress concentration Heavy: - long line contact - low edge stresses Misalignment: - reduced stress peaks Smooth transition towards the end of the raceways No sharp edges and thus no stress peak Heavy load Ability to accommodate critical operating conditions: strength of the Forgiving taper roller bearing from SKF Less sensitive to extreme load variations, misalignment and cornering combined with shock loads High load carrying capacity Heavy load plus misalignment Carrying capacity reserve for shock and peak loads Sufficient lubricant film even in hot environment Typical bearing failure causes are systematically avoided SKF taper roller bearings TQ-Line Rollers Low dimensional variation Dimensional variation of rollers Optimum load distribution Optimum load distribution thanks to minimal size and form variations - very small dimensional variations of the bearing rollers positively influence load and stress distribution - optimum load carrying capacity and roller guidance thanks to even load distribution Low run-out (roller end wobble) and low waviness Optimised roughness and structure of surfaces support formation of hydrodynamic lubricant film Minimised radial and axial run-out Optimised surface High load carrying capacity Longer service life Ability to accommodate high initial preload on adjustment without risk of bearing damage and peak temperatures positive effect on bearing life Lower friction and heat generation Low noise and vibration levels High running accuracy (low radial and axial run-out) Safe start-up even at low temperatures instant formation of lubricant film Safe operation even with thin lubricant film 5

6 SKF taper roller bearings TQ-Line Bearing steel: Specifically selected to ensure long life Steel quality Micro inclusion limits for 1Cr6 through hardened steel SKF specifications for bearing steels tighter than those in DIN/ISO 3 2,5 2 1,5 1,5 ISO SKF Special focus on homogeneity and restricting inclusions Even distribution of contact stresses at the surface and in the critical subsurface loaded zone no local stress peaks Minimal material alterations under load A B C D Inclusion type Inclusions cause steel subsurface fatigue Customer benefit Typical causes for bearing failure are systematically avoided 5 Conventional Reasons for premature bearing failure ruled out Steel purity has a major impact on survival probability 1 SKF with high steel purity 1 5 SKF taper roller bearings TQ-Line Support for a correct installation/adjustment process Adjustment Spread of resulting preload after running-in F o [N] Premium manufacturers Sufficient design SKF TQ- Line Target preload during operation Spread of readings during adjustment 5 1 Competitor Wettbewerber SKF TQ-line SKF CL7C Axialkraft load [kn] t [h] Optimum roller end/flange contact profile Optimum rollers Improved surface topography Low variations and spread Preload suitability Controlled temperature behaviour High repeating accuracy Reliability Targeted preload/clearance value in operation is achieved with low spread Limited temperature rise during start-up Reserve for erroneously set excessive preload Run-down position of bearing clearly recognisable Economic efficiency No special running-in procedure required Less time/efforts for adjustment and, possibly, subsequent readjustment Time for verification tests after mounting can be reduced 6

7 SKF taper roller bearings TQ-Line Heat treatment: Adapted to the specific application requirements Heat treatment Balance between hardness and dimensional stability Hardness HRC SN SQS S S1, S2, Structural strength: Through hardening vs. surface hardening J Relative ring growth over temperature/time C HRC surface hardness with SQS heat treatment (Special Quenching + Stabilising) for bearings up to and incl. 16 mm outside diameter resulting in - very high hardness for better resistance to contaminated lubricants - optimum balance between high hardness and dimensional stability. Focus for bearings >16mm outside diameter is on higher dimensional stability, therefore S hardening. Through-hardened (martensitic) rings for homogeneous material and hardening structure Case hardening is recommended - where a soft core is required and is achievable from the dimensional point of view - where heavy and frequent shock loads occur DIN 17 MnCr5 Case hardening steel SAE 521 Bainite hardening Martensitic through hardening High hardness enables high resistance to surface damage Long-term dimensional stability balanced with maximum available hardness % A ratio of > 2% between case depth and ring cross section gives no difference in hardness. Customer-specific requirements can be met with targeted choice of heat treatment SKF CL7C high-performance quality bearings Design features and customer benefits The quasi run-in behaviour of the roller end/flange contact zone results in minimal wear and loss of preload during runningin so that there is a high probability that the targeted adjustment under operating conditions can be achieved. Higher preload of the CL7C bearings may be applied without risk as long as the total temperature balance is controlled. The instant lubricant film formation, required especially with high preloads, reduces the risk of lubricant starvation and enables higher load carrying capacity. Extreme preload capability combined with minimal and predictable loss of initial preload minimises the risk of faulty gear mesh. This results in defined high stiffness, low noise and vibration and optimum service life of bearings and gears, which makes SKF taper roller bearings a precision class of their own. Low waviness of the bearing rings and rollers results in reduced friction and lower operating temperatures as well as low vibration and noise. Moreover it facilitates bearing adjustment. For bearing adjustment with the help of friction torque measurement, the linear friction characteristic simplifies the mounting process, making it more reliable and precise. When using an SKF preservative, this characteristic prevails as long as no other lubricant enters the bearing during adjustment. 7

8 SKF CL7C high-performance quality bearings The solution for very stiff bearing arrangements SKF CL7C high-performance bearings permit significantly higher preload compared to conventional taper roller bearings. This ensures long service life. Calculated life [km] CL7C TQ-Line Premium manufacturers Very high preload capability Minimal initial loss of preload due to - quasi running-in behaviour of roller end/flange contact - low spread (tolerances and behaviour) supported by highly precise dimensions and running accuracy Instant lubricant film formation even on adjustment and/or low temperatures Low waviness of rings and rollers (Q5) Linear friction characteristic established by special preservative and lubricant, selected by SKF Preload Bearing clearance F Preload Preload loss mainly through setting of surrounding parts Preload loss through smoothing and wear with spread CL7C high-performance bearings TQ-Line Premium manufacturers Sufficient and risky performance capability λ m km Reduction of wear, temperatures and noise with full service life by - constant optimum contact point, e.g. in the gear mesh of toothed gears and - precise positioning of shaft Low temperature generated in the bearing and the entire assembly Operational reliability of the bearing even under difficult lubrication conditions Reliable and safe adjustment reduces the total costs through - stable friction behaviour during friction torque adjustment in series assembly Extreme speeds and loads possible SKF CL7C high-performance quality bearings Temperature generation Temperature during running-in New bearings nearly optimally run in T ( C) 15 High degree of metallic contact due to poor roller/flange contact zone Competitors with boundary lubrication in the roller/flange contact zone Significantly lower heat generation and friction than with conventional bearings during running-in Defined frictional behaviour with very limited spread 1 5 CL7C TQ-Line Favourable friction characteristics for bearing adjustment thanks to special preservative developed by SKF Increased running accuracy t (h) Reduced noise level Noise check Controlled temperature behaviour even during initial operating hours High load carrying capacity and operational reliability from very early on Design permits very precise bearing adjustment Very smooth and low-noise bearing arrangement Frequencies 8

9 SKF Explorer taper roller bearings Design features and customer benefits There is a strong correlation between oxygen content and rolling contact fatigue. As a result, extremely clean and homogenous bearing steel of minimal oxygen content is used for SKF Explorer bearings, which makes it possible to achieve even longer service life in spite of unfavourable environmental conditions such as extreme contamination. The stringent material specifications used for so long by SKF have been further tightened here. The rings of SKF Explorer taper roller bearings have an optimised surface topography which reduces the stress peaks in the micro contact and permits the buildup of a separating lubricant film in the rolling contact zone even under difficult lubrication conditions. Processes and in-flow measurements eliminate outliers and safeguard a very small spread in dimensions. Tightened and targeted processes and specification parameters, together with major investments in tools and machines, secure the superior performance of SKF Explorer taper roller bearings. The optimised surface roughness of SKF Explorer taper roller bearings supports the lubricant film formation even under difficult conditions such as high speeds or lower shear forces. The quick build-up of the lubricant film enables the bearing to run at high speeds with low risk of lubricant starvation and excessive temperatures. The quality of the separating lubricant film is crucial for the service life of bearings and gears. SKF Explorer taper roller bearings Service life Endurance test Calculated L 1-lives Tested L 1-lives L 1 [Mrev] C/P = 1,5; clean conditions High preload with positive effect on service life is possible Optimised surfaces in the rolling contact Low spread in dimensions and adjustment behaviour Optimised design Standard Beacon Life ASKF = 1,8 SKF Explorer Beacon Life ASKF = 2,5 24 Competitor Test life SKF Explorer Test life Improved manufacturing processes consistently high product quality Weibull probability F % Wettbewerber Competitor ( ) ( ) ( ) ( ) SKF Reliable methods for evaluating - performance density - service life extension Significant service life increase - verified by in-house and independent endurance tests - product comparison tests - application results Extended maintenance intervals possible Low noise level Life [Mrevs]

10 SKF Explorer taper roller bearings Improved working contact surfaces Profiles Inspection of raceway form Consistency of profiles and structures over the full contact length thanks to improved manufacturing processes Grinding speed and pressure adapted to SKF Explorer quality standards New generation of grinding wheels used Uniform honing result over full profile length through permanent computerised analysis of raceway profiles Grinding monitoring and control Rough grinding Fine grinding Further increase in service life potential Less friction and heat generation - in the bearing and - in the total assembly Higher speeds and longer service life possible Reduced sensitivity to misalignment Sparking out SKF Explorer taper roller bearings Improved working contact surfaces Rings Ring surface structure Optimised ring surface structure Reduced roughness before: Peak elimination Long carrying contact areas Randomly distributed valleys (lubricant reservoir) Reduced friction and heat generation after: Large contact area Suitable for use also in difficult lubrication conditions, for example Low viscosity oils Synthetic lubricants being trimmed more to shearing forces (gear mesh) than to line contact (rolling bearings) Low temperatures Lubricant reservoir 1

11 SKF Explorer taper roller bearings Zero Defect target Quality control Control of main dimensions Masters 1 % computerised, fully automatic in-process quality control Main dimensions Noise testing through dynamic frequency measurement and root cause analysis Visual inspection of surfaces Basis for process control and continuous improvement Reduced costs and downtimes with a Zero Defect supplier Full traceability of the production process Low spread and hence high reliability Reduced mounting costs Noise and vibration test device SKF Explorer taper roller bearings Extremely high performance density High-purity steel with extremely homogeneous structure - made to significantly tighter tolerances than prescribed by DIN/ISO optimised surface topography J J2/Q J2/Q SKF explorer taper roller bearing Manufacturing processes further improved Consistently high product quality Low spread in dimensions and adjustment behaviour Quick formation of a separating lubricant film Higher load ratings (+15 %) Less mounting space for identical performance or Higher performance in same mounting space Higher reference speeds (+1 %) 11

12 For further information: SKF is a registered trademark of the SKF Group. SKF 25 The contents of this publication are the copyright of the publisher and may not be reproduced (even extracts) unless permission is granted. Every 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 information contained herein. Publication 6216 EN Printed in Germany.