Classifications

• • 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
  • C23C8/08—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
  • C23C8/02—Pretreatment of the material to be coated
• • 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
  • C23C8/34—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 more than one step
• • 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
• • 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
  • F01L1/16—Silencing impact; Reducing wear
• • 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

Definitions

• the present invention relates to a valve operating system component of an internal combustion engine, which is a nitrided palbrifter, and a method of manufacturing the same. Furthermore, it relates to a combination of a valve lifter and a cam. Background art
• a valve lifter 1 that converts the rotation of a cam 11 into a reciprocating motion of a valve 12 is driven by a reciprocating motion with a cylinder block 14.
• the shim 3 or crown 2 that comes into contact with the cam 11 receives sliding and impact at high surface pressure, resulting in excellent wear and impact resistance.
• the cam 11 is made of a material having abrasion resistance and impact resistance, and in order to reduce the aggressiveness to the pallet lifter 1 and to prevent boundary lubrication in which the lubrication form is unstable, the surface of the sliding portion is formed. It is necessary to improve the surface roughness.
• nitriding treatment As a simple means of improving the wear resistance of the valve lifter 1, a nitriding treatment is generally used. However, a compound layer formed on the outermost surface by nitriding (also called a white layer by those skilled in the art) is Because of its high hardness and very brittle properties, it has been conventionally used in a state where it is removed by grinding, polishing, etc., leaving only the nitrided diffusion layer.
• a process is performed for several hours at a temperature of about 570 ° C. with a target of forming a compound layer of about 10 m.
• a porous layer is generated, and not only a brittle ⁇ phase (F e 2 to 3 N) is generated, but also the processed product is greatly deformed and the surface roughness is significantly increased. The problem is that it gets worse.
• the compound layer in the conventional nitriding treatment wherein the outermost layer of porous ⁇ -phase (F e 2 ⁇ 3 N) , as well as dense ⁇ 5 phase thereunder (F e 4 N) and / or ⁇ -phase and ⁇ These are mixed phases, which form relatively coarse columnar crystals oriented almost perpendicular to the surface.
• the polishing treatment after nitriding is indispensable to reduce the aggressiveness to the mating material. Since the thickness is not uniform, it is necessary to set a relatively large polishing allowance. Furthermore, since uniform polishing is difficult due to variations in hardness and the like, a porous layer may remain after polishing. On the crown surface of a valve lifter that is subject to sliding and impact at high surface pressure, if the porous layer remains after polishing, the porous layer peels off and causes trouble.
• a polishing means such as a puff is used as a means for removing a porous layer and adjusting the thickness and surface roughness of a compound layer. It consists of ⁇ phase (F e 2 to 3 N) and dense ⁇ ′ phase (F e 4 N) and / or mixed phase of ⁇ phase and ⁇ ′ phase, and the polishing amount depends on the distribution state of each phase and hardness variation. Since it is not uniform, a portion where the compound layer is entirely removed or a portion where the porous layer remains on the same polished surface is likely to be generated, and a uniform compound layer cannot be obtained. For this reason, there is a problem in that the wear resistance varies and the effect of reducing the friction torque cannot be obtained.
• JP-A-2002-97563 there is a problem in improving the surface roughness even if a uniform compound layer is polished along the surface undulation. Further, there is a problem that the above polishing treatment is very expensive.
• the cam that slides with the valve lifter is used after polishing the sliding surface, but the surface roughness is relatively rough, the lubrication mode is boundary lubrication, and the crown surface of the valve lifter having a brittle compound layer is used. Increase surface roughness. For this reason, in order to suppress the friction torque from the initial operation and prevent the lubrication form from becoming unstable boundary lubrication, in addition to general polishing, expensive equipment such as one-par lap finishing is required. There is a problem that requires expensive means requiring a long processing time.
• the present invention solves the above problems by forming a uniform, dense, highly wear-resistant compound layer on the surface at the stage of nitriding treatment, and increasing and treating the surface roughness in the nitriding treatment.
• An object of the present invention is to provide a valve lifter in which the deformation of the object is small and which does not require polishing treatment for improving abrasion resistance and improving surface roughness and dimensional accuracy, and a method for manufacturing the same.
• paper on the cam surface An object of the present invention is to provide a valve lifter that can be used in combination with a cam without requiring lapping or the like.
• a diffusion layer having a relatively low nitrogen concentration and a compound layer having a high nitrogen concentration are formed in layers. If the nitriding temperature is high, the compound layer is formed thick and the outermost surface becomes brittle and porous.Therefore, in order to reduce this as much as possible, the processing temperature may be set to a low value.
• the diffusion layer also becomes thin. In the valve lifter, since the thickness of the diffusion layer is required to be 50 to 100, a compound having a predetermined hardness and a low surface friction, which has a high hardness and a low friction coefficient, is required to have a thickness of 50 to 100 m. It is desired to obtain a layer.
• the present inventors have conducted intensive studies and found that the surface roughness of the crown surface of the valve lifter before nitriding was reduced, and the thickness of the compound layer due to nitriding was reduced, so that the surface roughness of the crown surface after nitriding was reduced.
• the surface roughness of the cam can be reduced by the leveling operation without the need for expensive finishing work such as paper wrap, and overall wear resistance is improved. It has been found that a combination of a valve lifter and a cam that is excellent and has reduced friction torque can be realized, and at the same time, the cost can be reduced.
• the compound layer formed by nitriding on the outermost surface has a thickness of 1 to 5 m, and the formed compound layer has a surface roughness a 0. 05 or less.
• the method for manufacturing a valve lifter according to the present invention is characterized in that the surface roughness of the crown surface before nitriding is polished to Ra 0.01 to 0.03. By nitriding the valve lifter polished in this way and selecting a nitriding condition that makes the surface compound layer thickness 1 to 5 nm, high hardness can be achieved.
• a valve lifter having a nitride compound layer having a low coefficient of friction on the outermost surface of the crown surface and having a surface roughness R a 0.05 or less is obtained.
• the thickness of the compound layer after nitriding is 1 xm or less, the wear resistance and friction torque reduction effect cannot be obtained. If the thickness is 5 im or more, the formation of a porous layer, an increase in surface roughness, and a thick compound layer are required.
• the upper limit is set to 5 m because of the problem of peeling of the compound layer during use due to the above.
• the surface roughness is less than RaO.05, it can be used as a sliding part without any problem.
• the surface roughness is R a O.05 or more, the aggressiveness of the counterpart material increases, and the effect of reducing the friction torque cannot be obtained. Therefore, in the present invention, the crown surface roughness is set to R a 0.05 or less. I have.
• the surface roughness is more preferable when the surface roughness is R a O.045 or less, because it has a function of polishing the cam of the mating member and thus has an effect of reducing the friction torque.
• the porosity of the compound layer after nitriding is 5% or less, and for example, as shown in FIG. Not observed, forming a relatively dense compound layer.
• the porosity is set to 5% or less in the present invention. If the porosity is more than 5%, the surface roughness is affected, and the wear resistance and friction torque reduction effect cannot be obtained.
• the surface has a large number of protrusions made of fine carbides, nitrides, sulfides or oxides having an average diameter of 0.5 m or less, or two or more of the above compounds.
• These protrusions when slid in combination with the cam, improve the cam surface roughness to RaO.02 or less by the polishing function, and disengage without increasing the surface roughness of the valve lift itself. And leave dimples on the surface.
• the surface roughness of the sliding surface that slides on the cam is 0.2 Rz to 0.7 Rz. However, it is shown that the surface roughness is not improved below 0.2 Rz, and the structure is different.
• the mating material cam to be combined with the valve lifter according to the present invention is generally used for a camshaft, such as iron, steel, and chill, carburizing, quenching, and the like. It can be used after quenching.
• a porous layer harmful to the valve lifter is not generated in the nitriding treatment.
• a nitrogen compound layer containing a uniform and dense equiaxed crystal composed of 1 to 5 ⁇ ′ phase and / or a mixed phase of ⁇ ′ phase and ⁇ phase is formed, and the crown surface is roughened.
• the value is less than Ra 0.05 and there is almost no deformation. This not only eliminates the need for polishing after nitriding, but also eliminates polishing residue of the porous layer and excessive removal of the necessary nitrogen compound layer caused by polishing when removing the porous layer.
• the valve lifter is characterized in that the crown surface has a uniform surface hardness of Hv660 or more due to the dense compound layer having a uniform thickness formed by nitriding.
• a method of manufacturing a valve lifter according to the present invention is characterized in that the valve lifter has a nitriding temperature of 500 to 560. If the nitriding temperature is lower than 500, the nitriding rate is too slow to form a sufficient nitrogen compound layer, and if it exceeds 560 ° C, a porous layer is formed, and the nitrogen layer is removed after the nitriding process. Polishing is required. Further, the present invention is characterized in that an a ′ phase and a mixed phase of a Z or a ′ phase and an ⁇ phase are formed on the crown surface of a valve lift by appropriately adjusting the atmosphere of the nitriding treatment. Further, the nitride compound layer is characterized by including an equiaxed crystal.
• valve lifter carbon steel for machine structural use, alloy steel, tool steel, and the like generally used for valve lifters can be used as a base material. Wear.
• nitriding method used for the above-mentioned materials examples include ion nitriding, radical nitriding and salt bath nitriding in addition to gas nitriding and gas soft nitriding. Is extremely low and there is no merit in cost, and the salt bath nitriding method is not preferable because of environmental problems and difficulty in securing surface roughness.In the present invention, gas nitriding and gas soft nitriding are suitable. .
• the gas nitriding and gas nitrocarburizing treatment generally uses NH 3 , but may use a substance such as urea that forms an atmosphere that exhibits nitriding action on steel. Further, in the present invention are using the N 2 gas, for adjusting the atmosphere, the decomposition gas of the subject 3, reformed gas (RX gas), to supply the required amount of N 2 gas or the like alone or in combination Is also good. While using the co 2 gas as a gas for soft-nitriding in yet present invention, it may also use the gas containing CO, such as reformed gas.
• the nitrogen compound layer formed on the surface has a T ′ phase and / or a 7 ′′ phase.
• the effect of the present invention is exhibited if the phase is a mixture of the and ⁇ phases.
• the nitriding temperature, time, atmosphere, etc. are adjusted by using gas nitriding and gas nitrocarburizing methods, and after the nitriding treatment, there is no porous layer and the porosity is 5% or less.
• a dense nitride compound layer is formed.
• a compound layer having a uniform thickness can be obtained without the need for adjusting the thickness of the compound layer after nitriding, adjusting the surface roughness, and polishing for removing the porous layer, thereby securing stable wear resistance. it can.
• valve lifters There are two types of valve lifters: one is a shim that is installed between the upper surface of the valve body and the cam and the other is a shim that slides on the cam.
• the valve lifter of the present invention and a method of manufacturing the valve lifter can be applied to both types of valve lifters.
• the present invention can be applied to a valve lifter provided with an oil hole or a hole for another purpose, a chamfer, a groove, or the like on a crown surface of the valve lifter.
• the present invention can be applied to the boss portion 4 of the valve lifter that slides the compound layer by the valve lifter and the method of manufacturing the same according to the present invention on the stem end of the valve.
• FIG. 1 is a cross-sectional view of an example of a valve lifter (shimless) to which the present invention can be applied.
• FIG. 2 is a sectional view of another example of a valve lifter (with shim) to which the present invention can be applied.
• FIG. 3 is a micrograph (magnification: 800,000) of a crown cross section after nitriding of a valprift according to the present invention.
• FIG. 4 is a sectional view clearly showing the compound layer of FIG.
• FIG. 5 is a micrograph (magnification: 800,000) of a crown cross section after nitriding of a conventional valve lifter.
• FIG. 6 is a sectional view clearly showing the porous layer of FIG.
• FIG. 7 is a micrograph (magnification: 800,000) of the crown surface after nitriding of the valve lifter according to the present invention.
• FIG. 8 is a micrograph (magnification: 800,000) of the crown surface after nitriding of a conventional valve lifter.
• FIG. 9 is a graph showing the relationship between the cam rotation speed and the friction torque.
• FIG. 10 is a sectional view showing a usage example of a valve lift.
• FIG. 11 is a TEM observation photograph (magnification: 30000) of a cross section of the crown face after nitriding of the palbrifter according to the present invention.
• Fig. 12 is a TEM observation photograph (magnification: 30000) of a crown cross section in which the porous layer has been removed after nitriding of a conventional valve lifter.
• FIG. 13 is a micrograph ( ⁇ 800) of the crown surface after the sliding test of the valve lifter according to the present invention.
• FIG. 14 is a diagram showing a change in surface roughness before and after the leveling operation of the valp lifter and the mating material cam according to the present invention and the prior art.
• FIG. 15 is a diagram showing a change in surface roughness before and after a sliding test between a valve lifter and a mating member cam according to the present invention.
• the valve lifter 1 of the present invention shown in FIG. 1 and FIG. 2 is provided between a cam 11 and a valve 12 in a direct-acting valve train of an internal combustion engine.
• This is a sliding part that converts the rotation of 1 into the reciprocating movement of the valve 12.
• the manufacturing method of the valve lifter 1 of the present invention is used for a sliding surface 2 that slides on a cam (not shown) of the valve lifter 1.
• the present invention is also applied to the sliding surface 2 of the shim 3 which is in direct sliding contact with the cam as shown in FIG.
• valve lifter 1 A specific example of the valve lifter 1 according to the present invention will be described below.
• a material obtained by forging an SCM material is subjected to carburizing, quenching and tempering so that the surface hardness is HRC 58 or more and the effective hardened layer depth is about 1.0 mm.
• the surface roughness of the moving surface 2 is processed to Ra0.01 to 0.03 using a grinder using a grindstone and an abrasive, but preferably, the surface roughness of the sliding surface 2 is adjusted.
• the crown surface finish processing is performed so that becomes R a 0.02.
• gas soft nitriding was performed at a treatment temperature of 520 and a treatment time of 70 minutes so that the surface hardness of the sliding surface 2 was Hv 660 or more and the thickness of the compound layer 6 (see FIG. 4) was 1 to 5 m. I do.
• the gas used for the gas nitrocarburizing process is a mixed gas of NH 3, N 2 and CO 2 .
• the compound layer is formed uniformly in the range of 1 to 5 m and the compound layer has no porous layer, so that the deformation is further reduced and the surface roughness is Ra 0.05 or less. Therefore, be careful of temperature uniformity and stirring of atmospheric gas. It is also important to control the composition of the atmosphere gas and the decomposition rate of NH 3 in order to form a compound layer uniformly in the range of 1 to 5 zm and obtain a compound layer without a bolus layer.
• the pulverizer is nitrided in an atmosphere having a predetermined NH 3 decomposition rate.
• the decomposition rate of NH 3 can be controlled by the gas exchange rate (flow rate) or the composition ratio of the mixed gas.
• the nitriding treatment may be performed in another furnace using a gas whose atmosphere is adjusted to a predetermined NH 3 decomposition rate.
• the decomposition rate of NH 3 in this example was 23%.
• gas nitrocarburizing is performed under the above-mentioned processing conditions.
• the processing temperature is 560 ° C and the processing time is 30 minutes, and the processing temperature is 500 ° C and the processing time is 150 minutes, each of them is 3.5 times. m and 2.5 m of a compound layer without a porous layer were obtained.
• the decomposition rate of NH 3 had to be increased at the treatment temperature of 560 ° C as compared with the 520 ° C treatment, but was the same at 500 ° C.
• the decomposition rate of NH 3 is controlled in the range of 5 to 50% according to the nitriding temperature of 500 to 560 ° C.
• valve lifters were arranged in a jig and gas nitrocarburizing treatment was performed so as to uniformly contact the atmosphere gas. As a result, a valve lifter having a uniform compound layer with less deformation was obtained. It should be noted that gas nitrocarburizing at a temperature exceeding 560 In the chemical treatment, the treatment time was short to obtain the required compound layer of 1 to 5 Aim, and it was not possible to adjust the atmosphere to an appropriate one.
• a diffusion layer 7 on the base material and a porous layer on the surface were formed on the crown surface of the valve lifter by the gas nitrocarburizing treatment in which the temperature, time and atmosphere of the nitriding treatment were controlled.
• a nitride layer composed of a dense compound layer 6 having a porosity of 5% or less was formed without being formed.
• fine protrusions composed of fine carbides, nitrides, sulfides or oxides having an average diameter of 0.5 m or less, or two or more of the above compounds are provided. have.
• the surface roughness at this time is Ra 0.05 or less.
• the nitrogen compound layer contains equiaxed crystals of 0.5 m or less.
• Table 1 shows examples of changes in the surface roughness of the sliding surface 2 before and after the nitriding treatment at this time.
• the surface roughness of the sliding surface before nitriding is polished to Ra 0.012 to 0.028
• the surface roughness of the sliding surface after nitriding is set to Ra It turns out that it can be made into 0.024-0.045.
• the surface roughness of the sliding surface before nitriding was Ra If it exceeds 0.03, the surface roughness after nitriding exceeds Ra 0.05.
• FIG. 5, FIG. 12 and FIG. 8 show the cross section and surface after nitriding of the valve lift of Comparative Example 4 according to the prior art.
• the valve lift of Comparative Example 4 is gas-nitrogenated at a general temperature of 570 ° C., has a thick compound layer 6 containing columnar crystals, and has a coarse porous layer 8. (See Figure 6).
• Fig. 12 shows the TEM structure of the cross section of the valve lifter from which the porous layer has been removed by processing, and has relatively coarse columnar crystals oriented almost perpendicularly from the surface.
• Table 2 shows the change in dimensional accuracy and the thickness of the compound layer and porous layer before and after nitriding of the valve lifters of Example 2 and Comparative Example 4.
• the deformation shows the maximum displacement after nitriding of the valve lifter crown surface shape before nitriding with reference to the outer periphery.
• the surface roughness is not increased and the deformation is very small after the nitriding treatment.
• the porous layer is not formed in the compound layer. This eliminates the need for polishing as a post-process, so that there is no variation in the thickness of the compound layer due to polishing.
• FIG. 14 shows changes in the surface roughness of the crown surface of the valve lifter and the cam (cam nose portion) of the sliding partner before and after the leveling operation of the valve lifter according to the present invention and the prior art.
• the valve lifter according to the present invention can improve (reduce) the surface roughness on the cam side by its polishing function without causing an increase in its own surface roughness.
• the surface roughness of the valve lifter itself significantly increases before and after the running-in operation.
• FIG. 15 shows changes in the surface roughness of the crown surface of the valve lifter and the cam (cam nose portion) of the mating material after the valve lifter according to the present invention before the running-in operation and after the durability evaluation.
• the surface roughness of the crown surface of the valve lifter according to the present invention hardly changes, while the surface roughness of the cam side of the mating material is improved to Ra of 0.02 m by its polishing function.
• the root mean square of the surface roughness used for the evaluation of the total sliding of the valve lifter and cam also tends to converge.
• FIG. 13 shows the sliding surface of the valve lifter of the present invention after durability evaluation.
• FIG. 9 is a graph showing the relationship between the rotational speed and the friction torque.
• the valve lifter according to the present invention has almost no change in its own surface roughness before and after the running-in operation and in the durability evaluation, and the surface roughness on the cam side is improved by the polishing function. It is clear that the sliding resistance is superior to that of the above.
• the valve lifter according to the present invention has a compound layer thickness after nitriding of 1 to 5 m and a crown roughness after nitriding of Ra 0.05 or less. Furthermore, since a porous layer is not formed on the surface of the compound layer, buffing is basically not required. In the valve lifter 1 manufactured in this manner, a high-cost compound layer having a high hardness and a low friction coefficient can be uniformly present on the sliding surface 2 without basically requiring an expensive polishing treatment after the nitriding treatment. Therefore, its abrasion resistance is stable, and it is possible to significantly reduce manufacturing costs while maintaining high performance.
• the surface roughness of the cam side can be improved by the polishing function without increasing the surface roughness of the val-prifter itself. Also, expensive equipment such as paper wrap finishing and expensive means requiring long processing time are not required.
• a dense and hard nitride compound layer of 1 to 5 m without a porous layer is formed, the surface roughness hardly increases before and after nitriding, and the strain deformation is extremely small
• polishing for adjusting the compound layer after the nitriding treatment such as adjusting the surface roughness and removing the porous layer, is not required. This ensures uniform and stable surface properties The improved wear resistance can be secured.
• the friction torque can be reduced as compared with the valve lifter according to the prior art. Furthermore, since no expensive polishing treatment is required, a low-cost valve lifter can be obtained.
• the surface roughness of the cam can be improved by the polishing function without increasing the surface roughness of the valve lifter itself, so that the wear resistance and friction torque are improved.
• the cam side can be reduced in cost.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Valve-Gear Or Valve Arrangements (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

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Citations (7)

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• 2004
  • 2004-03-09 US US10/546,902 patent/US20060144359A1/en not_active Abandoned
  • 2004-03-09 EP EP04718747A patent/EP1602743B1/en not_active Expired - Lifetime
  • 2004-03-09 ES ES04718747T patent/ES2295833T3/es not_active Expired - Lifetime
  • 2004-03-09 WO PCT/JP2004/003022 patent/WO2004081252A1/ja active IP Right Grant
  • 2004-03-09 DE DE602004010890T patent/DE602004010890T2/de not_active Expired - Lifetime
  • 2004-03-09 KR KR1020057016812A patent/KR20050118175A/ko not_active Application Discontinuation
  • 2004-03-09 TW TW093106196A patent/TW200506181A/zh unknown
  • 2004-03-09 JP JP2005503522A patent/JP4141473B2/ja not_active Expired - Fee Related
  • 2004-03-09 CN CN2004800126733A patent/CN1784505B/zh not_active Expired - Fee Related
• 2007
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