SE1550958A1 - A rocker arm and a rocker arm assembly - Google Patents

A rocker arm and a rocker arm assembly Download PDF

Info

Publication number
SE1550958A1
SE1550958A1 SE1550958A SE1550958A SE1550958A1 SE 1550958 A1 SE1550958 A1 SE 1550958A1 SE 1550958 A SE1550958 A SE 1550958A SE 1550958 A SE1550958 A SE 1550958A SE 1550958 A1 SE1550958 A1 SE 1550958A1
Authority
SE
Sweden
Prior art keywords
rocker arm
zone
support shaft
bearing surface
steel
Prior art date
Application number
SE1550958A
Other languages
Swedish (sv)
Inventor
Wessman Linnéa
Fahlkrans Johan
Hansen Thorbjörn
Original Assignee
Scania Cv Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scania Cv Ab filed Critical Scania Cv Ab
Priority to SE1550958A priority Critical patent/SE1550958A1/en
Priority to PCT/SE2016/050601 priority patent/WO2017007397A1/en
Publication of SE1550958A1 publication Critical patent/SE1550958A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
    • C23C8/30—Carbo-nitriding
    • C23C8/32—Carbo-nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/36—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases using ionised gases, e.g. ionitriding
    • C23C8/38—Treatment of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
    • C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
    • C23C8/48—Nitriding
    • C23C8/50—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
    • C23C8/52—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions more than one element being applied in one step
    • C23C8/54—Carbo-nitriding
    • C23C8/56—Carbo-nitriding of ferrous surfaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/18—Rocking arms or levers
    • F01L1/181—Centre pivot rocking arms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
    • F16C33/121—Use of special materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/14—Tappets; Push rods
    • F01L1/146—Push-rods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/20—Adjusting or compensating clearance
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/06—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for braking
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2301/00—Using particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2303/00—Manufacturing of components used in valve arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2820/00—Details on specific features characterising valve gear arrangements
    • F01L2820/01—Absolute values
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2202/00—Solid materials defined by their properties
    • F16C2202/02—Mechanical properties
    • F16C2202/04—Hardness
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2223/00—Surface treatments; Hardening; Coating
    • F16C2223/10—Hardening, e.g. carburizing, carbo-nitriding
    • F16C2223/14—Hardening, e.g. carburizing, carbo-nitriding with nitriding

Abstract

A rocker arm (1) and a rocker arm assembly, wherein the rocker arm has a through-hole for rotatably receiving a support shaft (2). The rocker arm is manufactured from steel and the through-hole is delimited by an outer surface (3) of a bearing surface zone comprising an elevated amount of nitrogen and having an increased hardness with respect to a steel matrix below the bearing surface zone. The support shaft is preferably manufactured from ductile cast iron.(Fig. 1)

Description

A rocker arm and a rocker arm assemblv TECHNICAL FIELD OF THE INVENTION The present invention relates to a rocker arm according to thepreamble of claim 1 and a rocker arm assembly according to thepreamble of claim 8. Such a rocker arm and rocker arm assemblyare used in motor vehicles, in particular in vehicles comprising an internal combustion engine.
BACKGROUND AND PRIOR ART A conventional internal combustion engine of piston type, a so-called piston engine, is provided with one or more cylinders. lneach cylinder a piston is configured to reciprocate under the actionof the pressure which occurs upon ignition of a fuel-air mixtureintroduced into the cylinder. ln a piston engine of four-stroke type,each cylinder is provided with at least one inlet valve via which thefuel-air mixture is drawn into the cylinder, and at least one exhaustvalve via which combustion gases are removed from the cylinder.For this purpose, the inlet valve and the outlet valve are movablebetween a closed an open position. The valves may also beactuated for other reasons than for the inlet and outlet related tocombustion. An example of this function is decompression braking,in which the valves are engaged without combustion to obtain a retarding effect of the crankshaft.
The inlet valve and the exhaust valve are each spring-loaded to aclosed position and are each movable from closed to open positionby the action of a control cam on a rotating camshaft. The controlcam is normally configured to act upon the valve via a so-calledrocker arm, which is provided with a through-hole for rotatablyreceiving a support shaft or a bearing bracket. The rocker arm iscommonly manufactured from steel or cast iron and the supportshaft is commonly manufactured from steel. However, if the valvesare to be used also for decompression braking, the demands onthe mechanical strength of the rocker arm increases and it is usually not possible to use a cast iron rocker arm.
A plain bearing is usually provided between the support shaft andthe through-hole to minimise the risk of seizure and wear duringrelative motion of the parts arising during relative rotationalmotion. Such plain bearings used between the rocker arm and thesupport shaft include sleeve bearings typically comprising leadedbronze, providing a lubricating film of lead at the bearing interface.However, for environmental reasons and in order to meetincreasingly strict legal requirements regarding leaded products, itis desirable to develop an alternative solution to the use of suchbearings. Furthermore, bronze sleeve bearings, including lead-free such bearings, exhibit an impaired performance in acidenvironments. Modern engine oils have less ability to buffer acids,resulting from oxidation of the engine oil and contamination viacondensation and combustion by-products. Thus, the performanceof the bearings is negatively affected, especially for lead-containing bearings and bearings based on bronze or other yellow metals.
A further problem with bronze sleeve bearings, in particular forheavy motor vehicles such as trucks and buses, is that high weararises when the vehicle is equipped with a so-called stop-startsystem. Such a system is increasingly common and automaticallyshuts down the combustion engine when the vehicle is stopped in order to save fuel and to reduce emissions.
SUMMARY OF THE INVENTION lt is a primary objective of the present invention to provide a rockerarm and a rocker arm assembly which are in at least some aspectimproved with respect to known such components. ln particular, itis an objective to provide a rocker arm and a rocker arm assemblyby means of which the above mentioned problems are overcome.Another objective is to provide a rocker arm and a rocker armassembly with a mechanical strength such that the rocker arm andthe rocker arm assembly are suitable for use in connection with decompression brakes.
At least the primary objective is, according to a first aspect of thepresent invention, achieved by a rocker arm having a through-holefor rotatably receiving a support shaft, wherein the rocker arm ismanufactured from steel and wherein the through-hole is delimitedby an outer surface of a bearing surface zone, which ischaracterised in that the bearing surface zone comprises anelevated amount of nitrogen and has an increased hardness with respect to a steel matrix below the bearing surface zone.
The hardened surface zone at least around the through-hole together with the steel core of the rocker arm provides a combination of core toughness and surface hardness. The rockerarm has a high mechanical strength and is thereby suitable forbeing used in connection with compression braking. The hardenedsurface zone provides increased wear resistance and resistanceto seizure in the bearing interface between the rocker arm bearingsurface zone and a contact surface of a support shaft mounted inthe through-hole, and it also reduces the friction arising uponrelative movement of the parts. Such a surface zone withincreased hardness can be in the form of a conversion coatingformed on the steel matrix of the rocker arm. The hardened surfacezone may, apart from nitrogen, also comprise an elevated amount of carbon.
The steel should be a steel suitable for being subjected to anitriding or a nitrocarburising process, such as a steel forquenching and tempering with a typical hardness in the rangebetween 150 to 350 HV. The steel is preferably such that acompound layer is provided when the steel is subjected to anitriding process. The hardness of the bearing surface zone shouldpreferably be at least 500 HV, and can be significantly higher, such as 1000 HV and above.
According to one embodiment of the invention, the bearing surfacezone has been formed in a nitriding process or in a nitrocarburisingprocess. There are a plurality of different suitable nitriding andnitrocarburising processes which result in an increased hardnessof the surface zone. Nitriding and nitrocarburising have theadvantage over other surface hardening methods that the requiredprocess temperature is low, typically 400-650°C, of which nitridingtypically 480-550°C, temperatures are and nitrocarburising temperatures are typically 550-650°C. The rocker arm can therebybe nitrided in a fully hardened and tempered condition without thecore properties of the steel being adversely affected. Nitridinggenerally diffuses nitrogen into the surface zone, thus increasingthe concentration of nitrogen, while nitrocarburising also diffusescarbon into the surface zone. lt is possible to mask part of therocker arm during the nitriding or nitrocarburising process if it isdesired that only the surface zone delimiting the through-holeshould be hardened. However, it is also possible to leave therocker arm unmasked and obtain a surface layer of increased hardness on the entire rocker arm.
According to one embodiment of the invention, the bearing surfacezone is a nitrided surface zone. Such a nitrided surface zone canbe achieved by e.g. gas nitriding and exhibits the desiredproperties regarding resistance to seizure, hardness and wear resistance.
According to one embodiment of the invention, the bearing surfacezone comprises an outer compound zone having a thickness withina range of 5-50 um. Such a compound zone, sometimes referredto as a “white layer”, is a phase transformed layer achieved duringa nitriding or a nitrocarburising process and provides excellentresistance to seizure, wear resistance and corrosion resistance tothe bearing surface zone. With a thickness of at least 5 um,sufficient wear resistance and durability is achieved. Making thecompound zone too thick requires very long processing times, andfurthermore reduces the quality of the compound layer. Preferably,the outer compound zone has a thickness within a range of 10-20 um.
According to one embodiment of the invention, a diffusion zonewith an inward gradually decreasing hardness is formed betweenthe outer compound zone and the steel matrix, said diffusion zonehaving a thickness within a range of 50-800 pm, preferably 100-400 pm. Such a diffusion layer provides a gradual transition fromthe high hardness of the surface to the relatively low hardness ofthe steel matrix of the core and thereby increases the structuralstrength of the rocker arm. Preferably, the hardness of thediffusion zone at an interface toward the outer compound zone isat least 450 HV.
According to another aspect of the present invention, at least theabove mentioned primary objective is achieved by means of arocker arm assembly comprising a support shaft and at least onerocker arm as proposed, wherein the rocker arm is configured tobe rotatably mounted around the support shaft. Advantages andadvantageous embodiments of such an assembly appear from theabove description of the proposed rocker arm. The support shaftcan be in the form of a long support shaft supporting several rockerarms, or in the form of one or several bearing brackets having anintegrated shaft member, depending on the design of the enginein which the rocker arm assembly is operating. Normally, thesupport shaft is fixed in the rocker arm assembly, and the rocker arm rotationally pivots around the support shaft.
According to one embodiment of this aspect of the invention, theouter surface of the bearing surface zone of the at least one rockerarm is in rotational contact with a peripheral surface of the supportshafi.
According to one embodiment of this aspect of the invention, thesupport shaft is manufactured from cast iron. Preferably, the castiron is in the form of ductile cast iron. Ductile cast iron, alsoreferred to as e.g. spherulitic graphite cast iron and nodulargraphite cast iron, contains graphite which provides to somedegree a lubricating film at the bearing interface between therocker arm and the support shaft. The steel with the bearingsurface zone provides resistance to seizure in the bearinginterface. The combination of the two materials provides a bearinginterface without having to use an intermediate p|ain bearingcomponent, such as a sleeve. This combination of materials thusprovides excellent strength and hardness of the rocker arm incombination with the lubricating properties of the support shaft.The ductile cast iron preferably has a minimum tensile strength of350 MPa and an elongation A5 of minimum 3%. The elongation A5is defined as the elongation up to the point of fracture of a bar, measured over an initial gauge length of 5 times the bar diameter.
Further advantages and advantageous features of the invention will appear from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example withreference to the appended drawings, in which:Fig.1 shows an exploded view of a rocker arm assembly according to an embodiment of the invention, Fig. 2 shows a perspective view of the rocker arm assemblyin fig. 1, andFig. 3 schematically shows a sectional view of a surface zone of a rocker arm according to an embodiment of the invenüon.
DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION An exploded view of a rocker arm assembly according to anembodiment of the invention is schematically shown in fig. 1. Therocker arm assembly comprises two rocker arms 1 and a supportshaft 2, which extends along a central axis. Each of the rockerarms 1 comprises a through-hole for rotatably receiving thesupport shaft 2, such as shown in fig. 2. The rocker arms 1 canthereby rotate around the support shaft 2. Fastening members 5for fastening the support shaft 2 are provided outside of the rocker arms 1.
The through-hole of each rocker arm is delimited by an outersurface 3 of a bearing surface zone 4, schematically shown in fig.3. The outer surface 3 is in direct contact with a peripheral surface6 of the support shaft 2, so that a rotational plain bearing is formedby the outer surface 3 of the bearing surface zone 4 of the rocker arm 1 and the peripheral surface 6 of the support shaft 2.
The rocker arms 1 are manufactured from steel and are, afterhardening and tempering, preferably surface hardened by anitriding or nitrocarburising process. The steel grade should therefore be suitable for being subjected to such a process, such as a steel for quenching and tempering with a typical hardness inthe range between 150 to 350 HV. Suitable steel grades for thispurpose fulfill the requirements listed in Swedish standard SS-EN10083. The support shaft 2 is preferably manufactured from ductilecast iron, i.e. cast iron containing graphite which can act as alubricant between the peripheral surface 6 and the outer surface 3 of the bearing surface zone 4.
The bearing surface zone 4 of the rocker arm 1, in comparison witha steel matrix 9, comprises an elevated amount of nitrogen, and insome cases also of carbon, as a result of the nitriding ornitrocarburising process. The bearing surface zone 4, as shown infig. 3, comprises an outer compound zone 7 having a hardness ofat least 500 HV, as compared to the core hardness of the steelmatrix 9 of the rocker arm 1 of between 150 and 350 HV. Thehardness of the compound zone 7 depends on the steel gradeused, wherein high-alloy steel grades generally give a compoundsuch as 1000 HV or above. The compound zone typically consists of non-metallic phases formed zone of higher hardness, by iron and nitrogen, such as v-phase iron nitride (Fe4N),containing up to 6 wt. % N, and s-phase (Fe2-3N) containing up to11 wt. % N. ln the case when the bearing surface zone 4 has beenformed in a nitrocarburising process, the compound zone 7 alsocomprises iron-carbonitrides. Between the steel matrix 9 and thecompound zone 7, a diffusion zone 8 is formed. The diffusion zone8 has a hardness which gradually decreases from the compoundzone 7 and toward the steel matrix 9. The hardness of the diffusionzone 8 at the interface toward the outer compound zone 7 should at least be 450 HV. The diffusion zone contains nitrogen in solid solution as well as stable metal nitrides formed by alloying elements of the steel.
The thickness of the compound zone 7 is typically in the range 5-50 pm, preferably 10-20 pm. The thickness of the compound zone7 increases with processing time and the ideal thickness istherefore dependent on desired lead times in the production aswell as on desired material properties of the rocker arm 1. Thediffusion zone 8 typically has a thickness within a range of 50-800 um, preferably 100-400 um.
The nitriding or nitrocarburising process used to form the bearingsurface zone 4 can be any suitable process used in the field, suchas salt bath nitrocarburising, gas nitriding, gas nitrocarburising,low pressure nitriding, low pressure nitrocarburising, plasma nitriding, or plasma nitrocarburising.
The rocker arm assembly may of course comprise a differentnumber of rocker arms than described above, and the supportshaft may be accordingly configured. The support shaft can e.g.be in the form of one or more bearing brackets with an integratedshaft member, or a long shaft configured to hold several rockerarms depending on the design of the engine in which the rocker arm assembly is mounted.
The invention is of course not in any way restricted to theembodiments described above. On the contrary, many possibilitiesto modifications thereof will be apparent to a person with ordinaryskill in the art without departing from the basic idea of the invention such as defined in the appended claims.

Claims (11)

1. A rocker arm (1) having a through-hole for rotatably receivinga support shaft (2), wherein the rocker arm (1) is manufacturedfrom steel and wherein the through-hole is delimited by an outersurface (3) of a bearing surface zone (4), characterised in thatthe bearing surface zone (4) comprises an elevated amount ofnitrogen and has an increased hardness with respect to a steel matrix (9) below the bearing surface zone (4).
2. The rocker arm according to c|aim 1, wherein the bearingsurface zone (4) has been formed in a nitriding process or in a nitrocarburising process.
3. The rocker arm according to c|aim 2, wherein the bearing surface zone (4) is a nitrided surface zone.
4. The rocker arm according to c|aim 2 or 3, wherein the bearingsurface zone (4) comprises an outer compound zone (7) having a thickness within a range of 5-50 pm.
5. The rocker arm according to c|aim 4, wherein the outer compound zone (7) has a thickness within a range of 10-20 pm.
6. The rocker arm according to c|aim 4 or 5, wherein a diffusionzone (8) with an inward gradually decreasing hardness is formedbetween the outer compound zone (7) and the steel matrix (9),said diffusion zone (8) having a thickness within a range of 50-800 um. 12
7. The rocker arm according to claim 6, wherein the diffusion zone (8) has a thickness within a range of 100-400 um.
8. A rocker arm assembly comprising a support shaft (2) and atleast one rocker arm (1) according to any one of the precedingclaims, wherein the rocker arm (1) is configured to be rotatably mounted around the support shaft (2).
9. The rocker arm assembly according to claim 8, wherein theouter surface (3) of the bearing surface zone (4) of the at least onerocker arm (1) is in rotational contact with a peripheral surface (6)of the support shaft (2).
10. The rocker arm assembly according to claim 8 or 9, whereinthe support shaft (2) is manufactured from cast iron.
11. The rocker arm assembly according to claim 10, wherein the cast iron is in the form of ductile cast iron.
SE1550958A 2015-07-03 2015-07-03 A rocker arm and a rocker arm assembly SE1550958A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
SE1550958A SE1550958A1 (en) 2015-07-03 2015-07-03 A rocker arm and a rocker arm assembly
PCT/SE2016/050601 WO2017007397A1 (en) 2015-07-03 2016-06-22 A rocker arm and a rocker arm assembly

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE1550958A SE1550958A1 (en) 2015-07-03 2015-07-03 A rocker arm and a rocker arm assembly

Publications (1)

Publication Number Publication Date
SE1550958A1 true SE1550958A1 (en) 2017-01-04

Family

ID=57685404

Family Applications (1)

Application Number Title Priority Date Filing Date
SE1550958A SE1550958A1 (en) 2015-07-03 2015-07-03 A rocker arm and a rocker arm assembly

Country Status (2)

Country Link
SE (1) SE1550958A1 (en)
WO (1) WO2017007397A1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111972033A (en) 2018-02-16 2020-11-20 瑞典爱立信有限公司 Communication node and method performed thereby
FR3096419B1 (en) * 2019-05-22 2021-04-23 Hydromecanique & Frottement Guide member, mechanical system comprising such a guide member, and method of manufacturing such a guide member
CN114260321A (en) * 2022-01-04 2022-04-01 新疆八一钢铁股份有限公司 Method for improving stability of standard sample box of thickness gauge

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5884961A (en) * 1981-11-16 1983-05-21 Toyota Motor Corp Rocker arm
DE4205647C2 (en) * 1992-02-25 1996-08-01 Schaeffler Waelzlager Kg Process for the thermochemical-thermal treatment of case-hardening steels
JP2594505B2 (en) * 1993-09-10 1997-03-26 日本ピストンリング株式会社 Rocker arm
US5575064A (en) * 1994-12-06 1996-11-19 Honda Giken Kogyo Kabushiki Kaisha Process for producing rocker arm for internal combustion engine
JP3149104B2 (en) * 1996-11-15 2001-03-26 株式会社リケン Gearing
JP5898092B2 (en) * 2010-12-13 2016-04-06 川崎重工業株式会社 DRIVE CAM, MANUFACTURING METHOD THEREOF AND ENGINE VALVE DEVICE

Also Published As

Publication number Publication date
WO2017007397A1 (en) 2017-01-12

Similar Documents

Publication Publication Date Title
EP0878647B1 (en) Piston ring made of cast iron
US20080044646A1 (en) Wear-resistant coating and process for producing it
US5605126A (en) Piston for internal combustion engines, especially diesel engines
US20150176691A1 (en) Cam follower roller device
BRPI0920375B1 (en) sliding element in an internal combustion engine
JP2014001732A (en) Coating with nonconstant thickness for cylinder liner
US10145409B2 (en) Bearing apparatus of crankshaft for internal combustion engine
SE1550958A1 (en) A rocker arm and a rocker arm assembly
BR102013031072A2 (en) slip set
EP2162561B1 (en) Piston ring with a sulphonitriding treatment
JPH11264468A (en) Piston ring and its combination
JP6424951B2 (en) Sliding component and sliding structure
US9903236B2 (en) Adjustable camshaft
US7299777B2 (en) Fastening of a bearing bolt to a roller tappet
US9726270B2 (en) Cam follower roller device, notably for a fuel injection pump
US9291192B2 (en) Connecting rod with bearing-less large end
JP2012097727A (en) Roller tappet, and roller bolt for roller tappet
US11680538B2 (en) Cylinder sleeve for an internal combustion engine
US5458097A (en) Light weight valve lifter
JPS6327572B2 (en)
US4342293A (en) Valve guide and method for making same
JP3143835B2 (en) Combination of piston rings
KR20040023506A (en) Exhaust valve guide for engine
EP0618351A1 (en) Tappets for use in internal combustion engines
JPS6082654A (en) Sliding member

Legal Events

Date Code Title Description
NAV Patent application has lapsed