Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/16—Both compacting and sintering in successive or repeated steps
  • B22F3/164—Partial deformation or calibration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/08—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of toothed articles, e.g. gear wheels; of cam discs
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
• • 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
  • F16H—GEARING
  • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
  • F16H55/02—Toothed members; Worms
  • F16H55/30—Chain-wheels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/02—Compacting only
  • B22F2003/023—Lubricant mixed with the metal powder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F2003/248—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • 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
  • F01L1/02—Valve drive
  • F01L1/022—Chain drive
• • 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
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
  • F16H55/02—Toothed members; Worms
  • F16H55/06—Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties

Definitions

• the invention relates to a sintered sprocket to be used for a sprocket of a cam shaft timing chain of an automobile and to a production method therefor.
• Patent Document No. 2 Furthermore, techniques involving densifying the gear teeth of sintered bodies made of ferrous materials with similar compositions by forming by rolling and then case hardening and tempering have been proposed (reference to Japanese Patent Application Laid-Open No. 2002-129295, page 2; hereinafter referred to as Patent Document No. 2).
• a sprocket for a silent chain has a structure of interlocking gears and transmitting the rotation by the interlocking of the gears, as compared with that of a common sprocket for a roller chain, the interlocking contact pressure of the sprocket for a silent chain is high. Therefore, the sprocket for a silent chain is required to have a high density in the gears as compared with that of a sprocket for a roller chain and also to have a high hardness by hardening.
• 1 and 2 are obtained by means of adding Ni, Mo, and Cu for increasing the material strength and hardenability, increasing the density by warm-compacting and forming by rolling, and accordingly improving the wear resistance and the fatigue strength. Accordingly, in terms of the production cost and the process simplification, it has been required to develop a technique of producing a sprocket by using a material containing fewer addition elements and employing a simple densifying means.
• the invention was made under the above-mentioned circumstances and aims to provide a sintered sprocket for a silent chain by using a material containing a few addition elements and employing a simple densifying means and a method for producing such a sintered sprocket for a silent chain.
• the sintered sprocket for a silent chain of the invention is produced from an atomized iron powder with a good compressibility and having a simple composition containing Cu and C so as to satisfy the above required properties and characteristics by densifying essential parts, without employing warm-compacting or forming by rolling, by a common powder compacting and sintering method and hardening and tempering the essential parts.
• the sintered sprocket for a silent chain of the invention is made of an iron alloy having an overall composition containing Cu at 1 to 2%, C at 0.5 to 0.8%, Mn as an inevitable impurity at 0.10% or less, and the balance of Fe and other inevitable impurities, has a density of 7.1 Mg/m 3 or higher, HRA 65 or higher as a hardness in the gear teeth, and a martensite, sorbite, bainite, or their mixed structure as a cross-sectional microscopic structure in at least the gear teeth and the peripheral area of the gear teeth.
• the density of the gear teeth and peripheral parts of the gear teeth be 7.1 Mg/m 3 or higher and that the density of other parts be lower than that of the gear teeth and peripheral parts of the gear teeth and be 6.6 Mg/m 3 or higher.
• the production method for the sintered sprocket for a silent chain of the invention involves compacting a powder mixture containing an atomized iron powder, a Cu powder at 1 to 2% by mass in the entire composition, a graphite powder at 0.6 to 1.0% by mass, and a lubricant powder at 1% by mass or less into a sprocket shape having a density of 7.1 Mg/m 3 or higher at least in the gear teeth and peripheral parts of the gear teeth; sintering the green compact in a non-oxidizing gas atmosphere; and hardening and tempering at least the gear teeth of the sintered body.
• the above-mentioned atomized iron powder have a green density of 7.05 Mg/m 3 or higher in the case in which the powder mixed with a zinc stearate powder of 0.75% by mass is compacted by a pressure of 490.3 MPa and it is also preferable, as described in a fifth aspect of the invention, that the composition of the above-mentioned atomized iron powder contains Mn at 0.10% by mass or less and 0 (oxygen) at 0.10% by mass or less as inevitable impurities.
• the sintered alloy a common Fe—Cu—C type alloy will be used.
• the contents of Cu at 1 to 2% by mass and C at 0.5 to 0.8% by mass and more preferably Cu at 1.5% by mass and C (bonding carbon) at 0.7% by mass.
• the iron powder to be used for the sintered sprocket is an atomized iron powder and among a variety of commercialized atomized iron powders, those mixed with 0.75% zinc stearate powder and having a compressibility so as to have a density of 7.05 Mg/m 3 or higher in the case in which they are compacted by a pressure of 490.3 MPa may be mentioned.
• the density of the green compacts obtained in the above-mentioned compacting manner becomes 7.0 Mg/m 3 or lower, and therefore, they are not preferable.
• the content of Mn among the inevitable impurities in the iron powders is 0.10% by mass or less and the content of 0 (oxygen) is 0.10% by mass or less.
• the content of Mn is 0.14 to 0.20% by mass and the content of 0 (oxygen) is 0.12 to 0.25% by mass.
• the average value of an iron powder to be used for the embodiments of the invention is lower and the maximum value is about 110 HV, so that it cannot be said that there is a significant difference from the cross section hardness of a common atomized iron powder. Furthermore, from the cross section microscopic structures of the atomized iron powders, there is no considerable difference found in the size of crystal grains. However, in the case of etching with nital, the common atomized iron powders are etched at a high rate at the crystal grain faces, and on the other hand, the atomized iron powders to be used for the invention are hardly etched.
• the powder mixture to be compacted is obtained by mixing prescribed amounts of a copper powder, a graphite powder, and a common lubricant powder such as zinc stearate powder with the above-mentioned atomized iron powder.
• the similar types of a copper powder and a graphite powder to those conventionally used for the production of iron-based sintered alloys may be used.
• the copper powder contains 60 to 90% by mass of copper grains under 350 mesh.
• the content of the lubricant added to the powder mixture is 1% by mass or less.
• the theoretical density of the powder mixture containing the copper powder 1.5% by mass and the graphite powder at 0.8% by mass in the iron powder is 7.72 Mg/m 3 in the case in which no zinc stearate is added and 7.30 Mg/m 3 in the case in which 1% by mass of zinc stearate is added. Therefore, in the case a higher density is desired, the content of the lubricant should be set to be less. However, in the case in which the content of the lubricant is very low, the pressure of ejecting a green compact from a die becomes high, and accordingly the content is preferably adjusted to be 0.4% or higher by mass.
• the powder compacting is generally performed by a die.
• the green density is adjusted to be 7.1 Mg/m 3 or more in the gear teeth and in the peripheral parts of the gear teeth. Since it is desirable that the mechanical strength and the contact fatigue strength be high in the gear teeth, the density is more preferably adjusted to be about 7.3 Mg/m 3 .
• the parts other than the gear teeth and the peripheral parts of the gear teeth may have a density similar to that of the gear teeth, and if they have sufficient strength required for common mechanical elements, they can perform their functions sufficiently. Therefore, the density of these parts may be sufficiently 6.6 Mg/m 3 or higher. In general, if the density is lower, the amount of the raw material to be consumed is less and the product can be more lightweight and the vibration damping capacity is increased. Furthermore, the die life is prolonged more than if the density were increased more only in the needed parts and that results in greater economy, saves energy, and reduces material consumption, and is advantageous in terms of environmental conservation.
• the green compact weight is 7.2 g less than that if the overall density were adjusted to be 7.1 Mg/m 3 .
• the powder mixture of the invention is provided with an excellent compressibility as compared with that of a conventional powder mixture. This is due to, as described above, the quality of the atomized iron powder being different.
• the compacting pressure is about 500 MPa to obtain the green density 7.1 Mg/m 3 .
• the above-mentioned compacting pressure is about 600 MPa and therefore a similar density can be obtained at a pressure lower by 100 MPa.
• the powder mixture of the invention is used for compacting by the same pressure of 600 Ma, a density of about 7.2 Mg/m 3 can be obtained.
• the sintering can be performed in common conditions.
• a common non-oxidizing gas atmosphere of nitrogen gas, a nitrogen-hydrogen gas, or a converted butane gas can be employed.
• the sintering temperature can be adjusted to be 1,100 to 1,150° C.
• the sintered body has a iron-based matrix in which 1 to 2% by mass of Cu is almost all dispersed and the structure is a pearlitic structure containing 0.5 to 0.8% by mass of bonding carbon amount.
• the physical properties of the sintered body are as follows: the surface hardness is about 82 HRB, the tensile strength is about 550 MPa, and the elongation about 3.5% in the case the density is 7.1 Mg/m 3 .
• the sintered body may be subjected to sizing or cutting processes.
• the sizing increases the production cost, it is therefore desirable not to employ the sizing, if possible.
• the quenching may be performed by a method for heating the entire body and then quenching it or a method for heating the gear teeth in the outer circumference and their peripheral parts by high frequency heating and then quenching these parts.
• a key way exists in the axial hole of the sprocket it is possible that no desirable size precision can be obtained owing to dimensional change by the former hardening method, and therefore the latter method is preferably employed.
• the former hardening method a common case hardening can be employed. In such a case, the carbon amount of the sintered body is adjusted to be slightly less and the carbon amount in the material surface can be increased by the carburization in the hardening step.
• the tempering can be performed at a temperature of around 180° C.
• the surface hardness of the gear teeth is adjusted to be 65 HRA or higher to ensure the wear resistance.
• the heat treatment conditions are set so as to adjust the cross sectional micro hardness of the iron alloy matrix to be about 650 HV or higher in at least 0.2 mm depth from the gear surface.
• the physical properties of the heat treated product are as follows: the tensile strength is about 1,110 MPa and the elongation about 0.8% in the case in which the density is about 7.1 Mg/m 3 .
• the heat treated product can be used without any additional treatment. If shot-peening is performed for at least gear teeth and their peripheral parts, the fatigue strength in their surface can be improved to yield more excellent fatigue strength.
• the iron powders employed were an atomized iron powder A (trade name: Atomel 300 M) manufactured by Kobe Steel, Ltd. as a general iron powder to be used conventionally for producing an iron sintered product such as a gear or the like; an atomized iron powder B (trade name: ABC 100-30) manufactured by Hoeganaes AB. and an atomized iron powder C (trade name: Atomel 300 NH) manufactured by Kobe Steel, Ltd. as iron powders to be used for the invention and an electrolytic copper powder (trade name: CE 15) manufactured by Fukuda Metal Foil and Powder Co., Ltd., was used.
• atomized iron powder A (trade name: Atomel 300 M) manufactured by Kobe Steel, Ltd. as a general iron powder to be used conventionally for producing an iron sintered product such as a gear or the like
• an atomized iron powder B (trade name: ABC 100-30) manufactured by Hoeganaes AB.
• an atomized iron powder C (trade name: Atomel 300 NH)
• the main impurities, the apparent density, the grain size distribution, and the compressibility of the atomized iron powders are as shown in Table 1.
• the particle size distribution was calculated by carrying out a sieving analysis test.
• the compressibility is evaluated on the basis of the density of a powder containing an iron powder and 0.75% by mass of zinc stearate and compacted at 490.3 MPa.
• the respective three types of the atomized iron powders were mixed independently with a copper powder at 1.5% by mass, a graphite powder at 0.8% by mass, and zinc stearate at 0.4% or 0.8% by mass as a lubricant to obtain powder mixtures.
• the compressibilities (Mg/m 3 ) of these powder mixtures is shown in Table 2.
• the compressibilities were in the case in which the diameter of the respective test specimens was adjusted to be 11.3 mm.
• the respective powder mixtures are shown as A, B, and C correspond to the types of the atomized iron powders shown in Table 1. As is clear from Table 2, the densities of the iron powder B and the iron powder C were high.
• a sprocket was produced from the powder B containing 0.4% by mass of the lubricant.
• the sprocket had 44 gear teeth, a gear tip diameter of 89 mm, an inner diameter of 19 mm, an average thickness of 8.5 mm and was formed into a shape having steps in the peripheral part of the gears and in the peripheral part of the inner diameter and a key way with a width of 6 mm and a depth of 10 mm from the inner diameter part toward the outer circumference.
• a common die apparatus composed of a die, a core rod, and a pair of upper and lower punches divided into inner and outer punches was used.
• the partial density of the sprocket green compact was adjusted to be 7.15 Mg/m 3 in the gear teeth and the area in the outer circumferential side from the center with about 80 mm diameter and to be 6.8 Mg/m 3 in the inner side from the center with about 80 mm diameter.
• the green compact was sintered at temperature of 1,120° C. in a hydrogen-nitrogen atmosphere.
• the density of the gear teeth of the sintered body was 7.11 Mg/m 3 and the bonding carbon content was found to be 0.7% from the microscopic structure of the cross-section.
• the sintered body was oil quenched after being heated for a prescribed period by a high frequency heating apparatus and tempered at 180 C.
• the surface hardness of the gear teeth was 68 to 70 HRA.
• the microscopic structure of the cross-section was found containing mainly martensite in the gear teeth and gradually changing to a region comprising finely deformed troostite and pearlite toward the axial center and finally to a pearlitic structure in the sintered state.
• the inner diameter part of the heat treated product was subjected to the machining in a prescribed size so as to fit the inner diameter part of the heat treated product with an axis and accordingly complete the sintered sprocket.
• the gear teeth had a structure of mainly martensite; however, in the case in which the conditions of the tempering temperature and the temperature duration were changed, a mixed structure containing sorbite, bainite, or either of them may be formed in some cases.
• a sintered sprocket for comparison was that described in Japanese Patent Application Laid-Open No. 2001-295915. More particularly, the sprocket was produced by mixing an iron alloy powder containing Ni at 4% by mass, Mo at 0.5% by mass, and Cu at 1.5% by mass, which were respectively diffused and joined therein, with a graphite powder and a lubricant; heating the powder mixture at 130° C.; compacting the powder mixture by the die heated to 150° C. (warm-compacting) for obtaining the sprocket-shaped green compact with a green density of 7.15 Mg/m 3 ; and then sintering the sprocket-shaped body at 1,195° C. After that, the inner diameter part of the sintered body was formed by a machining process to adjust the dimensions, and the sintered body was case hardened and tempered.
• the above-mentioned sintered sprocket of Example and the sintered sprocket for comparison were mounted in gasoline engines to investigate the wear state.
• the driving conditions of the engines were as follows: the silent chain tension (tensile force) was 1,500 N; the engine rotation speed was 6,000 rpm; and the driving duration was 100 hours. As a result, no difference was found in the wear loss of both sprockets.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Powder Metallurgy (AREA)
• Gears, Cams (AREA)

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• 2003
  • 2003-07-22 JP JP2003277289A patent/JP4570066B2/ja not_active Expired - Lifetime
• 2004
  • 2004-07-06 US US10/883,721 patent/US20050028641A1/en not_active Abandoned
  • 2004-07-13 AT AT04016477T patent/ATE460507T1/de active
  • 2004-07-13 DE DE602004025882T patent/DE602004025882D1/de active Active
  • 2004-07-13 EP EP04016477A patent/EP1500714B1/en not_active Expired - Fee Related
  • 2004-07-22 CN CNB2004100545211A patent/CN100338374C/zh active Active
  • 2004-07-22 KR KR1020040057342A patent/KR100665168B1/ko active IP Right Grant
• 2006
  • 2006-04-05 US US11/397,702 patent/US7309465B2/en active Active

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