• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for producing a sintered gear with a gear body on which at least one elastomeric element is arranged, after which a green compact is produced by pressing a powder sintered the green compact to the gear body and by carburization and subsequent quenching or sintering and subsequent quenching with a gas is hardened and then the at least one elastomeric element is vulcanized onto the gear body.
    公开号:AT518831A1
    申请号:T50632/2016
    申请日:2016-07-15
    公开日:2018-01-15
    发明作者:
    申请人:Miba Sinter Austria Gmbh；
    IPC主号:
    专利说明:

    Summary
    The invention relates to a method for producing a sintered gearwheel with a gearwheel body on which at least one elastomer element is arranged, after which a green compact is produced by pressing a powder, the green compact is sintered to the gearwheel body and by carburizing and subsequent quenching or sinter hardening and subsequent quenching with a gas is cured and then the at least one elastomer element is vulcanized onto the gear body.
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    N2016 / 09500 AT-00
    The invention relates to a method for producing a sintered gearwheel with a gearwheel body on which at least one elastomer element is arranged, after which a green compact is produced by pressing a powder, the green compact is sintered to form the gearwheel body and hardened by carburizing and subsequent quenching or sinter hardening and subsequent quenching, and then the at least one elastomer element is vulcanized onto the gear body.
    Sintered gears with elastomer elements are already known from the prior art. The elastomer elements serve a wide variety of purposes. For example, AT 508 701 B1 describes a split gear arrangement with vulcanized spring elements. These spring elements serve to preload in the circumferential direction of the rotatable gear against the fixed gear.
    The AT 514 570 B1 and the AT 514 590 B1 describe gear wheels divided in the radial direction, in which the two gear parts are connected to one another via vulcanized-on elastomer rings.
    What these gears have in common is that the elastomer elements are subject to high loads during operation of the gears. Especially when the elastomer elements are exposed to changing shear and tensile forces, the connection point between the metal and the elastomer is of great importance, since there is a risk that the elastomer elements will come off when overloaded.
    For the production of gearwheels with vulcanized-on elastomer elements, complex and costly machining steps of the gearwheels / 15 are therefore necessary
    N2016 / 09500-AT-00 required to ensure a high adhesive strength of the elastomer element on the metallic
    To reach the gear body.
    Proceeding from this, it is the object of the invention to provide a simpler or more cost-effective way of producing a sintered gear which achieves at least as good an adhesive strength of the elastomer element on the metallic substrate as in the prior art.
    The object of the invention is achieved in the above-mentioned method in that the hardened gear body is quenched with a gas.
    Gas quenching avoids quenching oils or generally liquid cooling media. It is thus avoided that these liquid media accumulate in the pores of the sintered toothed wheel and subsequently only have to be laboriously removed from these pores. The gear body is therefore already dry after the heat treatment and gas quenching, so that it can be fed directly to the vulcanization of the elastomer element without further processing steps. Although gas quenching is generally slower than oil quenching due to the lack of evaporation capability of the cooling medium, the process engineering advantage that can be achieved outweighs this disadvantage. As a side effect, the slower quenching results in a lower core hardness, so that a sintered gear wheel is obtained which on the one hand has a relatively high hardness in the areas close to the surface and on the other hand also has a relatively high toughness in the core and thus withstands alternating loads better ,
    According to an embodiment variant of the method it can be provided that the carburizing of the gear body is carried out by means of low pressure carburizing. This has the advantage that even with sintering gears that are very narrow in the axial direction, hardness profiles can be set in a very targeted manner in comparison to other carburizing processes, such as carbonitriding. It is also possible with these sintered gears to obtain a softer core.
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    N2016 / 09500 AT-00
    A sinter-hardenable powder is preferably used to produce the green compact. The use of sinter-hardenable powders helps to avoid liquid cooling media in order to achieve relatively high hardness of the surface layers of the sintered gear wheel that are subject to wear. In addition, better tooth quality and, consequently, smooth running of the sintered gear can be achieved.
    It is particularly preferred to use a sinter-curable powder which has a chromium content of between 1% by weight and 5% by weight. The effects mentioned can be further improved by the chrome. Chromium significantly improves the hardenability in the gas quenching described.
    According to a further embodiment variant of the method, the gear body is compressed to a density between 6.8 g / cm 3 and 7.4 g / cm 3 . The advantage here is that particularly good strength can be produced very cost-effectively.
    It can further be provided that the gear body is manufactured with a roughness depth of its surface that is between Rz1 and Rz10. The adhesion of the elastomer element to the gear body can thus be significantly increased.
    The carburizing is preferably carried out to a depth of the gear body, measured from the surface thereof, which is selected from a range from 100 μm to 2000 μm, in particular to a depth of 100 μm to 1000 μm, depending on the tooth geometry and those that occur Herzt pressings. The wear resistance can thus be significantly improved since a correspondingly high hardened layer thickness can be made available by the subsequent hardening. This in turn can improve the adhesion of the elastomer element to the gear body.
    According to a further embodiment variant of the method, gas quenching is carried out using N2, N2 / H2 or He as the gas. The use of N2, N2 / H2 or He compared to other gases has the advantage that higher cooling rates can be achieved.
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    N2016 / 09500 AT-00
    The gear body can be cooled at a quenching rate selected from a range of 1 ° C / s to 7 ° C / s. The result is that an at least partially martensitic structure is established.
    For a better understanding of the invention, this will be explained in more detail with reference to the following description.
    The invention relates to a method for producing a sintered gear.
    The sintered gearwheel per se can be, for example, a sintered gearwheel for a belt drive, such as in particular a chain wheel, or a sintered gearwheel for a gearwheel drive in which the sintered gearwheel interacts with at least one further gearwheel. It can also have straight or helical teeth. The sintered gear wheel preferably has a spur toothing. The sintered gear can also have one or more tracks.
    Furthermore, the sintered gear has at least one elastomer element which is vulcanized onto the metallic gear body of the sintered gear.
    In the preferred embodiment variant, a chain wheel is produced that has an elastomer track in the axial direction on one or both sides (immediately) next to the toothing for the chain drive. The elastomer track can be designed with depressions and (nub-like) elevations. The elastomer track serves to dampen noise when the chain runs into the teeth of the chain wheel track. The elastomer track preferably extends continuously over the entire circumference of the gear body.
    The elastomer element consists at least partially of a rubber-elastic material, for example of an (X) NBR ((carboxylated) acrylonitrile butadiene rubber), HNBR (hydrogenated nitrile rubber), a silicone rubber (VMQ), EPDM (ethylene propylene diene Rubber), CR (chloroprene rubber), SBR (styrene butadiene rubber) etc., whereby material mixtures can also be used.
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    N2016 / 09500 AT-00
    By "at least partially" it is meant that in the elastomer element e.g. Stiffening elements, e.g. Fibers and / or particles, for example made of metal,
    Plastic, natural fibers, etc., or rods, etc. can be stored. However, the elastomer element preferably consists exclusively of a rubber-elastic material.
    The metallic gear body is manufactured using a powder metallurgical process (sintering process). Such methods are already well known from the prior art, so that a detailed discussion of the basic features of this method is unnecessary. It should only be said that the method essentially comprises the steps of powder mixing, pressing the powder into a green body, dewaxing and sintering the green body to the gear body in one or more stages.
    In the course of the method for producing the sintered gear, it is further provided that the gear body is hardened by carburizing and then controlled cooling or by sinter hardening. Carburizing increases the carbon content in the gear body. The carburizing can be carried out after the sintering or during the sintering.
    In principle, carburizing can be carried out by various methods, all methods having in common that a gas or gas mixture is used as the carbon source. For example, methane, propane, acetylene, etc. can be used as the gas.
    The carburizing can take place, for example, by carbonizing. However, carburizing is preferably carried out by a low-pressure carburizing process.
    After carburizing, the carbon content of the gear body is preferably between 0.4% by weight and 1.0% by weight.
    In particular, the carburizing is carried out to a depth of the gear body, measured from its surface, which is selected from a range from 100 μm to 2000 μm; preferably from a range of 100 μm to 1000 μm. The preferred carbon content referred to above relates to / 15
    N2016 / 09500-AT-00 refer to this carburizing depth. Areas of the gearwheel body lying underneath consequently have a lower carbon content.
    If necessary, mechanical post-processing can take place after sintering and / or after hardening.
    After hardening, the at least one elastomer element is vulcanized (directly) onto the metallic gear body. An adhesion promoter (1-component or 2-component system) can be applied directly to the powder-metallurgical gearwheel without further washing operations after a blasting step (e.g. with hard cast iron, steel gravel, sand, carborundum, grain sizes in the range from 0.6 to 1 mm) to avoid renewed oxide formation). Due to the dry and clean gear body, an improved adhesion to the metal can be achieved by providing the largest possible effective surface. The type of bonding agent depends on the materials to be bonded. The adhesion promoter should be selected so that it has a lower surface tension compared to the metal surface in order to enable complete wetting.
    After the adhesion promoter has dried, the elastomer is vulcanized at a temperature between 90 ° C. and 250 ° C. within a period of 1 minute to 20 minutes. It is advantageous if no liquid escapes in the form of oil or hardening emulsion, otherwise the coupling agent will lose its function. The method according to the invention shows its advantage particularly in these critical steps, since the vulcanization takes place with completely dry, powder-metallurgical components. The temperature control should be selected in such a way that the necessary surface hardness remains from the heat treatment of the sintered steel.
    In order to improve the adhesive strength of the elastomer element on the metallic gear body, it is now provided that the hardened gear body is quenched with a gas after carburizing.
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    N2016 / 09500 AT-00
    The gas quenching is preferably quenched with N2, N2 / H2 or He as the gas.
    According to an embodiment variant, it can be provided that the gear wheel body is quenched at a quenching speed which is selected from a range of 1 ° C / s to 7 ° C / s.
    The at least one elastomer element is preferably vulcanized onto the gear body immediately after quenching.
    According to a preferred embodiment variant of the method, it can be provided that a sinter-hardenable powder is used to produce the green compact. It is understood to mean an iron or steel powder which has a proportion of at least one alloy element which delays the eutectoid conversion from austenite to ferrite and pearlite. For example, the powder may contain chromium, nickel and / or molybdenum. The proportion of the at least one element in the powder for producing the green compact can be between 0.4% by weight and 5% by weight.
    In the preferred variant of the method, chromium is added as the alloying element in order to obtain the sinter-hardenable powder. The proportion of chromium in the powder can be between 1% by weight and 5% by weight.
    For example, powders of the following composition can be used in the process: Fe + 1.8% Cr + 0.2% C; or Fe + 3% Cr + 0.5% Mo + 0.2% Cr
    It is further preferred if the gear body is compressed to a density between 6.8 g / cm 3 and 7.4 g / cm 3 . For this purpose, the surface can be redensified by means of rollers, or the entire cross-section during calibration after sintering. However, a corresponding density can also be achieved when pressing.
    According to another embodiment variant, the gear body with a roughness depth according to DIN EN ISO 4287: 1998 and DIN EN ISO 11562: 1998 on its surface / 15
    N2016 / 09500-AT-00, which is between Rz1 and Rz10. This can be done, for example, by pressing and sintering, or press sintering and other compression methods.
    Some examples of the manufacture of the sintered gear are given below.
    Such a powder-metallurgical gear is produced by pressing a Cr-alloyed powder with a composition of Fe + 3% Cr + 0.5% Mo + 0.5% C or also Fe + 1.8% Cr + 2% Ni + 0 .5% C to a density between 6.8 g / cm 3 and 7.3 g / cm 3 . The subsequent sintering takes place at a sintering temperature between 1120 ° C and 1300 ° C in an N2 / H2 / C atmosphere for about 10 minutes to 30 minutes at temperature. The subsequent cooling is carried out by quenching from the sintering heat by means of gas quenching, with cooling rates of between 1 ° C./7 and 7 ° C./s being achieved depending on the temperature range. The components sinter-hardened in this way have, at least in part, a martensitic structure and do not require any additional hardening. The roughness depth Rz is about 5.
    Another type of manufacture of such a powder-metallurgical gear is carried out by pressing a Cr-alloyed powder with a composition of Fe + 1.8% Cr + 0.2% C or also Fe + 1.8% Cr + 2% Ni + 0, 2% C to a density between 6.8 g / cm3 and 7.3 g / cm3. The subsequent sintering takes place at a sintering temperature between 1120 ° C and -1300 ° C in an N2 / H2 atmosphere for about 10 minutes to 30 minutes at temperature. Subsequent to the sintering, the entire cross section of the component is partially compressed during calibration, or the surface is rolled or calibrated. The components are subjected to an additional carburization in the form of a low-pressure carburization with high-pressure gas quenching with 20 bar N2 or He. The surface roughness Rz of the surface here is approximately 2. An increased surface roughness proves to be helpful for the adhesion.
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    N2016 / 09500 AT-00
    A subsequent vulcanization takes place for both process routes without any further necessary washing and / or chemical cleaning steps, since the components are completely dry and, in particular, oil-free after sinter hardening.
    The resulting adhesive strength between metal and elastomer is analyzed using squeeze tests. For this purpose, extrusion tests are carried out, in which an attempt is made to loosen the rubber / metal connection by applying an axial force to the sintered gear. These show results on special geometries of> 30 kN.
    The exemplary embodiments describe possible embodiment variants of the method, it being noted at this point that various combinations of the individual embodiment variants with one another are also possible.
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    N2016 / 09500 AT-00
    权利要求:
    Claims (9)
    [1]
    claims
    1. A method for producing a sintered gearwheel with a gearwheel body on which at least one elastomer element is arranged, after which a green compact is produced by pressing a powder, the green compact is sintered into the gearwheel body and hardened by carburizing and subsequent quenching or sinter hardening and subsequent quenching and then on the gear body the at least one elastomer element is vulcanized, characterized in that the hardened gear body is quenched with a gas.
    [2]
    2. The method according to claim 1, characterized in that the carburizing of the gear body is carried out by means of low pressure carburizing.
    [3]
    3. The method according to claim 1 or 2, characterized in that a sinter-hardenable powder is used to produce the green compact.
    [4]
    4. The method according to claim 3, characterized in that a sinter-hardenable powder is used, which has a proportion of chromium, which is between 1 wt .-% and 5 wt .-%.
    [5]
    5. The method according to any one of claims 1 to 4, characterized in that the gear body is compressed to a density between 6.8 g / cm 3 and 7.4 g / cm 3 .
    [6]
    6. The method according to any one of claims 1 to 5, characterized in that the gear body is made with a roughness depth of its surface which is between Rz1 and Rz10.
    [7]
    7. The method according to any one of claims 1 to 6, characterized in that the carburizing is carried out to a depth of the gear body
    11/15
    N2016 / 09500-AT-00 from its surface, which is selected from a range from 100 μm to
    2000 μm.
    [8]
    8. The method according to any one of claims 1 to 7, characterized in that the gas quenching with N2, N2 / H2 or He is carried out as a gas.
    [9]
    9. The method according to any one of claims 1 to 8, characterized in that the gear body is quenched at a quenching speed which is selected from a range of 1 ° C / s to 7 ° C / s.
    12/15
    N2016 / 09500-AT-00 Austrian
    Patent Office
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    引用文献:
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    法律状态:
    优先权:
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    US15/630,209| US10919093B2|2016-07-15|2017-06-22|Method for the production of a sintered gear|
    DE102017113918.4A| DE102017113918A1|2016-07-15|2017-06-23|Process for producing a sintered gear|
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