JP2008064159A - Method of manufacturing track member, method of manufacturing valve gear, and track member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a track member capable of suppressing the increase of a manufacturing cost, sufficiently increasing the hardness of an area including a rolling surface, ensuring the sufficient rolling fatigue lifetime by giving the high resistance against the rolling fatigue, and consistently controlling the hardness of an area of the plastic deformation. <P>SOLUTION: The method of manufacturing the track member includes a steel member preparing step of preparing a steel member for suppressing the carbon content and the chromium content, a heat treatment step, and a finishing step. The heat treatment step includes a carbo-nitiriding step of heating and carbo-nitiriding the steel member, a hardening step of performing the hardening by cooling the steel member at the temperature below M<SB>S</SB>point, a high-temperature tempering step of performing the tempering by heating the steel member at the temperature of ≥650°C and <650°C, and below A<SB>1</SB>point, and an induction hardening step of performing the induction hardening of a high-hardness area of the steel member without any hardening of a low-hardness area other than the high-hardness area including an area to be formed as a rolling surface of the track member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for manufacturing a track member, a method for manufacturing a valve operating device, and a track member, and more specifically, a track member that is fixed to an adjacent member by plastic deformation of a part thereof, and a method for manufacturing the track member. And a method of manufacturing a valve gear including a cam follower having the track member.

  In general, a rolling bearing includes race members such as an outer ring and an inner ring, and rolling elements such as balls and rollers arranged in contact with the race member. In the rolling bearing, at least one of the race members such as the inner ring and the outer race is fixed to another member adjacent to the race member. Here, the race member is fixed by fitting the race member to another adjacent member, or by plastically deforming a part of the race member, for example, by caulking. There is also a case.

  The fixing of the raceway member using plastic deformation does not require a new member for fixing as compared with the fixing by fitting, and thus has advantages such as cost reduction and downsizing. ing.

  In order to fix the race member using plastic deformation, it is necessary to pay sufficient attention to the hardness distribution in the race member. That is, when fixing using plastic deformation, the region that is plastically deformed in the raceway member needs to have a relatively low hardness, for example, 300 HV or less, from the viewpoint of suppressing the occurrence of cracks during plastic deformation. . On the other hand, with the recent high performance of industrial machines, transportation machines, and the like in which rolling bearings are used, rolling bearings are required to have a long life. For this reason, in the race member, a rolling surface that is a surface in contact with the rolling element is required to have high hardness, for example, 653HV (58HRC) or higher, and high resistance to rolling fatigue.

The fixing of the raceway member using plastic deformation has been widely adopted in recent years because it has the advantages as described above. For example, a full-roller type (a type that does not have a cage) radial roller bearing, which is a kind of rolling bearing, may be employed as a cam follower with a roller for a valve operating device that operates an intake / exhaust valve of an engine. Also in the attachment of the cam follower with a roller, the cam follower can be attached to the holding member by plastically deforming a part of the track member constituting the cam follower and fixing it to the holding member. Therefore, with regard to a rolling bearing that can be used as a cam follower with a roller, many studies have been made on extending the life and the like (see, for example, Patent Documents 1 to 9), and at the same time, improving the life and fixing using plastic deformation. The proposal regarding this is made | formed (for example, refer patent documents 10-12).
JP 2000-38907 A Japanese Patent Laid-Open No. 10-47334 Japanese Patent Laid-Open No. 10-103339 JP-A-10-110720 JP 2000-38906 A JP 2000-205284 A JP 2002-3212 A Japanese Utility Model Publication No. 63-185917 JP 2002-194438 A JP-A-5-321616 JP-A-62-7908 JP 2005-299914 A

  As described above, in a race member fixed to another member by plastic deformation of a part of the region, the region including the rolling surface has sufficient hardness and at the same time plastic deformation. It is required that the region to be processed has a hardness that can be plastically deformed without causing cracks or the like. However, as described in Patent Documents 10 to 12 described above, the hardness of the plastically deformed region is not sufficiently controlled only by simply quenching and hardening the region that undergoes plastic deformation. For this reason, the hardness of the plastically deformed region varies depending on the shape of the race member, the number of heat treatments, and the like, and the hardness of the region cannot be stably set to a preferable range. As a result, in an actual mass production process, fixing using plastic deformation may be difficult.

  Further, in recent years, the usage environment of rolling bearings has become severe, and there is a demand for further extending the service life of the race members constituting the rolling bearings. On the other hand, it is considered that a countermeasure for extending the life by subjecting the conventional raceway member to heat treatment such as carbonitriding is effective. However, the carbonitriding process with high processing cost is simply applied to a conventional raceway member made of a relatively expensive steel such as bearing steel (for example, JIS SUJ2) or carburized steel (alloy steel) (for example, JIS SCM420). When combined, the increase in manufacturing cost increases. Therefore, in view of the price competitiveness of the track member, the above measures are not necessarily complete measures.

  Therefore, an object of the present invention is to sufficiently increase the hardness of the region including the rolling surface while suppressing an increase in manufacturing cost, and to provide a high resistance to rolling fatigue to provide a sufficient rolling fatigue life. An object of the present invention is to provide a method for manufacturing a raceway member that can be secured and can stably control the hardness of a plastically deformed region. Another object of the present invention is that the raceway member has sufficient resistance to rolling fatigue while suppressing an increase in manufacturing cost, and has sufficient durability and plastic deformation. It is providing the manufacturing method of the valve operating apparatus with which the attachment of the cam follower using this is easy. Still another object of the present invention is to provide sufficient rolling resistance by suppressing the increase in manufacturing cost and having sufficiently high hardness in the region including the rolling surface and at the same time having high resistance to rolling fatigue. It is an object of the present invention to provide a race member in which a dynamic fatigue life is ensured and the hardness of a plastic deformation region is stably controlled.

  The manufacturing method of the raceway member according to the present invention includes carbon of 0.5 mass% or more and 0.7 mass% or less, silicon of 0.15 mass% or more and 0.35 mass% or less, and 0.6 mass% or more. A member made of steel containing 0.9% by mass or less of manganese, the balance iron and inevitable impurities, the chromium content being suppressed to 0.3% by mass or less, and formed into a rough shape of the race member A steel member preparation step in which the steel member is prepared, a heat treatment step in which the steel member is heat-treated, and a finishing process in which the steel member heat-treated in the heat treatment step is finished. .

The heat treatment process includes a carbonitriding process, a quench hardening process, a high temperature tempering process, and an induction hardening process. In the carbonitriding step, the steel member is heated to a carbonitriding temperature that is a temperature of _one point A or higher and carbonitrided. In the quench hardening process, the steel member carbonitrided in the carbonitriding process is cooled from the carbonitriding temperature to a temperature equal to or lower than the _MS point and is hardened by hardening. In the high temperature tempering step, the steel member that has been quenched and hardened in the quench hardening step is heated to a temperature of 650 ° C. or more and less than A ₁ point and tempered. In the induction hardening process, in the steel member tempered in the high temperature tempering process, the low hardness region, which is a region other than the high hardness region including the region to be the rolling surface of the race member, is quenched and hardened. In addition, the high hardness region is induction hardened.

  Generally, JIS SUJ2, which is a high-carbon chromium bearing steel, is widely used as the steel constituting the raceway member of a rolling bearing. Since SUJ2 has a high carbon content and chromium content, it is easy to quench and has a high hardness after quenching, so it is relatively excellent in resistance to rolling fatigue. However, in view of the severe use environment of rolling bearings in recent years, simply using SUJ2 as a material does not necessarily provide sufficient resistance to rolling fatigue.

  On the other hand, it is considered that a countermeasure for improving the resistance to rolling fatigue by carbonitriding a SUJ2 raceway member is effective. However, if carbonitriding is further performed on SUJ2, which is a relatively expensive steel type with a high chromium content, the manufacturing cost of the race member and the rolling bearing provided with the raceway member increases. This is contrary to the recent demand for cost reduction of rolling bearings.

  Moreover, JIS SCM420 and SCr420 which are carburized steel (alloy steel) may be used as steel which comprises a rolling bearing. However, as in the case of SUJ2, taking into account the recent harsh use of rolling bearings, simply using them as materials does not necessarily provide sufficient resistance to rolling fatigue. Furthermore, these steel types are relatively expensive steel types, similar to SUJ2, and when combined with carbonitriding, an increase in manufacturing costs becomes a problem.

  On the other hand, the present inventor examines in detail the composition of steel constituting the race member, and improves resistance to rolling fatigue while suppressing an increase in manufacturing cost by combination with surface treatment. We have intensively studied the manufacturing method of the raceway member that can be used. As a result, the following findings were obtained. That is, normally, the rolling surface of the race member constituting the rolling bearing is formed by removing a 0.1 to 0.2 mm region of the surface layer portion by grinding or the like in the finishing process after the heat treatment. Therefore, improving the resistance to rolling fatigue in a region deeper than the region removed in the finishing step in the heat treatment step is effective in extending the life of the race member and the rolling bearing.

  Here, by reducing the carbon content and chromium content of the steel constituting the raceway member to a predetermined value or less, it becomes easier for nitrogen to enter the raceway member in the carbonitriding process. It became clear. That is, by reducing the amount of carbon and chromium in the steel constituting the raceway member to a predetermined value or less, a nitrogen-enriched layer having a sufficient nitrogen concentration and thickness can be obtained without extending the treatment time for carbonitriding. It becomes possible to form. As a result, the manufacturing cost can be suppressed while improving the resistance to rolling fatigue of the raceway surface of the raceway member even if grinding or superfinishing in the finishing process is taken into consideration. Furthermore, by reducing the content of chromium, which is a relatively expensive alloy element, the cost of the material can be suppressed.

  That is, in the track member manufacturing method of the present invention, a steel member made of steel having the above-described composition is used instead of a steel type having a high chromium content such as JIS SUJ2, SCM420, and SCr420 that have been conventionally employed. Nitrogen-enriched layer having sufficient nitrogen concentration and thickness without extending the processing time of carbonitriding treatment by preparing the steel member in the carbonitriding step and carbonitriding the steel member in the carbonitriding step While being able to form, the cost of a raw material can be reduced. In addition, the detail of the reason which limited the component range of steel to the above-mentioned range is mentioned later. And the resistance with respect to rolling fatigue | fatigue of a rolling surface can be improved by induction-hardening the high hardness area | region which should become a rolling surface.

  Here, the surface layer portion refers to a region of the raceway member whose distance from the surface is 0.2 mm or less. Further, the nitrogen-enriched layer is a layer having a higher nitrogen content than the core portion of the race member formed on the surface layer portion of the race member, and is formed by a process such as carbonitriding, nitriding, or nitrogenation. be able to.

On the other hand, when it is desired to soften a steel member for the purpose of ensuring the ease of plastic working, the steel member is generally allowed to cool from a temperature of A ₁ point or higher. However, in that case, even when the same heat treatment equipment is used, the cooling rate of the steel member varies depending on the shape and size of the steel member, the amount of the steel member to be processed at the same time, and the like. Depending on the shape of the steel member, the cooling rate may vary depending on the portion of the steel member.

Here, the hardness of the steel member is suppressed by coarsening and agglomerating iron carbide (cementite; Fe ₃ C; hereinafter referred to as carbide) in the steel structure constituting the steel member, for example, 300 HV or less. Hardness. Here, in order to coarsen and agglomerate the carbide, it is effective to reduce the cooling rate (temperature decrease per unit time) when the steel member is cooled.

  However, as described above, considering the change in the cooling rate due to the shape of the steel member and the difference in the cooling rate depending on the part in the steel member, the necessary cooling conditions change depending on the shape of the steel member. For this reason, it is not easy to stably control the hardness of the region of the raceway member that undergoes plastic deformation. Further, if the cooling rate is reduced to an unlimited level, the hardness of the plastically deformed region can be stably suppressed, but the time required for the heat treatment becomes longer, so the production efficiency is lowered and the manufacturing cost is increased. is there.

  On the other hand, the present inventor stabilizes the hardness of the region not subjected to induction hardening (low hardness region) after carbonitriding regardless of the shape and size of the steel member, the amount of the steel member processed at the same time, and the like. The heat treatment history was examined in detail. As a result, the following knowledge was obtained.

That is, carbonitriding has been the cooling rate of the steel member is reduced rather than soften the steel member, once hardened steel member is carbonitrided, high temperature sintering followed by heating to a temperature just below A ₁ point It has been found that the steel member can be stably softened in a relatively short time by carrying out the return. Here, it is less than the high-temperature tempering temperature is 650 ° C. for a long time required for tempering, in order to lead to decrease in production efficiency, is the high-temperature tempering is carried out at a temperature of less than ₁ point 650 ° C. or higher A Preferably, it is more preferably performed at a temperature of 680 ° C. or more and less than A ₁ point.

That is, the steel member carbonitrided in the carbonitriding process is quenched once in the quench hardening process and then heated to a temperature of 650 ° C. or higher and less than A ₁ point in the high temperature tempering process. In FIG. 2, the density of dislocations introduced into the steel constituting the steel member is reduced, and the carbides are coarsened and agglomerated. As a result, the steel member has a hardness that can be uniformly and stably plastically deformed without causing cracks. Then, in the subsequent induction hardening step, the high hardness region, which is the region including the region that becomes the rolling surface of the carbonitrided raceway member as described above, is induction hardened and partially hardened, thereby quenching. It is possible to achieve both ease of plastic working in a region that is not hardened and resistance to rolling fatigue on the rolling surface of the raceway member.

  As described above, according to the race member manufacturing method of the present invention, while suppressing an increase in manufacturing cost, the hardness of the region including the rolling surface is sufficiently increased, and high resistance to rolling fatigue is provided. A sufficient rolling fatigue life can be secured, and the hardness of the plastic deformation region can be stably controlled.

  Next, the detail of the reason for having limited the steel component range which comprises the steel member prepared in a steel member preparation process to the above-mentioned range is demonstrated.

Carbon: 0.5% by mass or more and 0.7% by mass or less When the carbon content increases, coarse carbides (cementite; Fe ₃ C) are formed in the steel constituting the raceway member. Even when the carbonitriding process is performed, the coarse carbide does not dissolve in the steel substrate, and inhibits nitrogen from entering the raceway member. When the amount of carbon exceeds 0.7% by mass, the above-described influence increases.

  On the other hand, the amount of carbon greatly affects the hardness of steel after quenching. When the carbon content is low, in order to function as a race member, it is preferable to increase the carbon concentration to 0.8% by mass or more in the surface layer portion of the race member, particularly in the vicinity of the rolling surface. If the amount of carbon is less than 0.5% by mass, the time required to increase the carbon concentration becomes long, leading to an increase in manufacturing cost. Therefore, the carbon content is 0.5 mass% or more and 0.7 mass% or less.

Silicon: 0.15% by mass or more and 0.3% by mass or less In the usage environment of the raceway member, there may be a problem that the temperature rises during use and the raceway member hardness decreases. When the steel which comprises a track member contains silicon, the effect (temper softening resistance) which prevents this improves. When the silicon content of the steel constituting the race member is less than 0.15% by mass, the temper softening resistance of the race member may be insufficient. In addition, silicon is an element added to reduce the content of oxygen harmful to steel characteristics in the steel manufacturing process, and reducing it to less than 0.15% by mass causes an increase in manufacturing cost. There is a possibility. On the other hand, when the silicon content of the steel constituting the raceway member exceeds 0.3% by mass, the hardness of the material increases and the cold workability decreases. For the above reasons, the silicon content is 0.15 mass% or more and 0.3 mass% or less.

Manganese: 0.6 mass% or more and 0.9 mass% or less Manganese has an effect of improving the easiness of quenching of the race member by being contained in the steel constituting the race member. In addition, manganese combines with sulfur inevitably contained in the steel constituting the race member to form manganese sulfide, suppressing the segregation of sulfur to the crystal grain boundaries in the microstructure, and reducing the properties of the race member. Has the effect of avoiding. When the manganese content is less than 0.6% by mass, the above effects cannot be sufficiently achieved. On the other hand, when the manganese content of the steel constituting the raceway member exceeds 0.9% by mass, the hardness of the material increases and the cold workability decreases, so that the processing cost increases. Therefore, the amount of manganese is 0.6 mass% or more and 0.9 mass% or less.

Chromium: 0.3 mass% or less Chromium inhibits solid solution of carbide in the steel base when carbonitriding is performed. And the carbide | carbonized_material which remain | survives at the time of carbonitriding inhibits the penetration | invasion of nitrogen to the inside of a track member. When the amount of chromium exceeds 0.3% by mass, the above effect becomes large, so the amount of chromium is 0.3% by mass or less. In order to facilitate nitrogen intrusion during carbonitriding and to form a sufficient nitrogen-enriched layer in a shorter time, the chromium content is preferably 0.2% by mass or less.

  Moreover, the steel which comprises the steel member prepared in the steel member preparatory process of this invention is what satisfy | fills the conditions of the above-mentioned composition among the carbon steel for mechanical structures prescribed | regulated to JISG4051, or other standards. It is preferable that the carbon steel is specified. Specifically, JIS S50C, S53C, S55C, S58C, and SAE 1050, 1055, 1060, 1065, 1070 satisfy the above-described compositional conditions. By adopting standard steel, it becomes easy to obtain the raw material and the cost of the raw material can be reduced.

  A method for manufacturing a valve operating apparatus according to the present invention is a method for manufacturing a valve operating apparatus that includes a cam follower and a holding member that holds the cam follower, and operates at least one of an intake valve and an exhaust valve of an engine. is there. This method for manufacturing a valve operating apparatus includes a cam follower manufacturing process for manufacturing a cam follower, a holding member manufacturing process for preparing a holding member, and an attaching process for attaching the cam follower to the holding member. And in a cam follower manufacturing process, the track member which comprises a cam follower is manufactured by the manufacturing method of the above-mentioned track member. In the attaching step, the low hardness region is plastically processed, whereby the raceway member is fixed to the holding member, and the cam follower is attached to the holding member.

  According to the method for manufacturing a valve gear of the present invention, since the race member constituting the cam follower is produced by the race member production method described above, the rolling surface is suppressed while suppressing an increase in the production cost of the race member. Can be sufficiently increased, high resistance to rolling fatigue can be imparted to ensure a sufficient rolling fatigue life, and the hardness of the plastic deformation region can be stably controlled. The low hardness region of the raceway member whose hardness is stably controlled is plastically processed, whereby the raceway member is fixed to the holding member, and the cam follower is attached to the holding member. Therefore, while suppressing an increase in manufacturing cost, the raceway member has sufficient durability due to sufficient resistance to rolling fatigue, and it is easy to attach a cam follower using plastic deformation. A method for manufacturing a simple valve operating apparatus can be provided.

  The track member according to the present invention is manufactured by the above-described track member manufacturing method. According to the track member of the present invention, since it is manufactured by the method for manufacturing the track member of the present invention described above, the hardness of the region including the rolling surface is sufficiently high while suppressing an increase in manufacturing cost. By having high resistance to rolling fatigue, it is possible to provide a race member in which a sufficient rolling fatigue life is ensured and the hardness of the plastic deformation region is stably controlled.

  As is clear from the above description, according to the raceway member manufacturing method of the present invention, while suppressing an increase in manufacturing cost, the hardness of the region including the rolling surface is sufficiently increased and high against rolling fatigue. It is possible to provide a method for manufacturing a race member that can provide resistance to ensure a sufficient rolling fatigue life and stably control the hardness of a plastically deformed region. Moreover, according to the manufacturing method of the valve gear of the present invention, the raceway member has sufficient durability due to sufficient resistance to rolling fatigue while suppressing an increase in manufacturing cost. In addition, it is possible to provide a method for manufacturing a valve operating device that is easy to attach a cam follower using plastic deformation. Further, according to the race member of the present invention, the increase in manufacturing cost is suppressed, and the hardness of the region including the rolling surface is sufficiently high, and at the same time, the rolling member has sufficient resistance to rolling fatigue. It is possible to provide a race member in which the fatigue life is ensured and the hardness of the plastic deformation region is stably controlled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating a configuration of a valve operating apparatus including a cam follower including a track member according to the first embodiment which is an embodiment of the present invention. FIG. 2 is a schematic sectional view taken along line II-II in FIG. FIG. 3 is an enlarged schematic partial cross-sectional view showing the vicinity of the cam follower in FIG. With reference to FIGS. 1-3, the valve gear provided with the cam follower containing the track member in Embodiment 1 of this invention is demonstrated.

  Referring to FIGS. 1 and 2, a valve operating apparatus 10 includes a cam follower 1 that is a full-roller type radial roller bearing, a rocker arm 2 as a holding member that holds the cam follower 1 at one end 2B, and a cam follower. A lock nut 8 is inserted into a cam 5 disposed so as to be in contact with the outer peripheral surface of the roller 11 as an outer ring 1 on the outer peripheral surface 5B and a through hole 2D formed in the other end 2C of the rocker arm 2. The adjusting screw 9 fixed to the rocker arm 2 is provided with a valve 6 which is an engine supply or exhaust valve connected to one end of the adjusting screw 9 at one end.

  The cam follower 1 includes an annular roller 11 as an outer ring, a hollow cylindrical shaft 12 penetrating the roller 11, and a plurality of rollers 13 disposed between the roller 11 and the shaft 12. The rocker arm 2 is held by the rocker arm shaft 3 via a bearing metal 4 or the like at the center, and is rotatable about the rocker arm shaft 3 as a fulcrum. The valve 6 is biased in the direction of the arrow 7 </ b> A by the elastic force of the spring 7. Therefore, the cam follower 1 is always pressed against the outer peripheral surface 5 </ b> B of the cam 5 by the elastic force of the spring 7 through the adjustment screw 9 and the rocker arm 2. The cam 5 has an oval cross-sectional shape in a cross section perpendicular to the axial direction of the shaft 12 that is an inner ring of the cam follower 1. The cam 5 is formed integrally with the camshaft 5A, and is configured to be rotatable about the camshaft 5A.

  Referring to FIG. 2, one end 2B side of rocker arm 2 has a bifurcated shape in which a pair of side walls 21 are formed. Each of the pair of side walls 21 is formed with a coaxial cylindrical through hole 21A. The shaft 12 of the cam follower 1 is fitted so as to penetrate both the through holes 21A of the pair of side walls 21. An axial rolling surface 12A is formed on the outer peripheral surface of the shaft 12, and a plurality of rollers 13 are arranged so as to contact the axial rolling surface 12A on a roller rolling surface 13A that is an outer peripheral surface. Further, the roller 11 is disposed between the pair of side walls 21, and the roller rolling surface 11 </ b> A is formed on the inner peripheral surface so as to face the shaft rolling surface 12 </ b> A. And the roller 13 is arrange | positioned so that the roller rolling surface 11A may be contacted in the roller rolling surface 13A. As a result, the roller 11 is held rotatably with respect to the shaft 12.

  Further, referring to FIG. 3, a tapered portion 21 </ b> B having a gradually increasing diameter in a cross section perpendicular to the axial direction of the shaft 12 is formed in the vicinity of each outer wall side opening of the through hole 21 </ b> A. The both ends of the shaft 12 are low hardness regions 12C having a hardness of 300 HV or less, and are deformed along the tapered portion 21B by caulking which is plastic working. Thereby, the shaft 12 as the track member is fixed to the rocker arm 2 as the holding member. On the other hand, the annular region including the shaft rolling surface 12A of the shaft 12 is a high hardness region 12B that is induction hardened and has a hardness of 653 HV or higher.

  1 to 3 show a case where the hollow shaft 12 is employed for weight reduction, the solid shaft 12 may be employed with emphasis on strength and rigidity.

  Next, the operation of the valve gear 10 in the first embodiment will be described. Referring to FIG. 1, when cam 5 rotates together with cam shaft 5A about cam shaft 5A, the distance from cam shaft 5A to the contact portion between cam 5 and cam follower 1 changes periodically. Therefore, the rocker arm 2 swings around the rocker arm shaft 3 as a fulcrum. As a result, the valve 6 reciprocates through the adjustment screw 9. Thereby, the intake valve or exhaust valve of the engine opens and closes.

  Next, a method for manufacturing the shaft 12 of the cam follower 1 and the valve gear 10 as the track member in the first embodiment will be described. FIG. 4 is a diagram showing an outline of a method of manufacturing the cam follower shaft in the first embodiment.

  Referring to FIG. 4, in the method for manufacturing the cam follower shaft in the first embodiment, first, carbon of 0.5 mass% or more and 0.7 mass% or less, and 0.15 mass% or more and 0.35 mass% or less are obtained. Comprising 0.6 mass% or more and 0.9 mass% or less of manganese, consisting of the balance iron and inevitable impurities, consisting of steel with a chromium content suppressed to 0.3 mass% or less, A steel member preparation step is performed in which a steel member, which is a member formed in the schematic shape of the shaft 12 as a race member, is prepared. Specifically, steel having the above-described component composition, for example, a steel material made of JIS standard S53C is processed by forging, cutting, or the like to produce a steel member.

  Next, a heat treatment step is performed in which the steel member prepared in the steel member preparation step is heat treated. The heat treatment process includes a carbonitriding process, a quench hardening process, a high temperature tempering process, an induction quenching process, and a low temperature tempering process. Details of this heat treatment step will be described later.

  And the finishing process in which the steel member heat-processed in the heat processing process is finished is implemented. Specifically, the shaft 12 of the cam follower 1 is completed by performing a finishing process such as a grinding process or a super-finishing process on the steel member that has been heat-treated.

  Next, details of the heat treatment step included in the method for manufacturing the cam follower shaft in the first embodiment will be described. FIG. 5 is a diagram showing a heat treatment step included in the method for manufacturing the cam follower shaft in the first embodiment. In FIG. 5, the horizontal direction indicates time, and the time elapses toward the right. In FIG. 5, the vertical direction indicates the temperature, and the higher the temperature, the higher the temperature.

Referring to FIG. 5, in the heat treatment step, first, a carbonitriding step is performed in which the steel member is heated to a carbonitriding temperature that is a temperature equal to or higher than point A ₁ and carbonitrided. Specifically, the steel member prepared in the steel member preparation step is heated to a temperature of 800 ° C. or higher and 1000 ° C. or lower, which is a temperature of _one point or higher, for example, 850 ° C., and is 60 minutes or longer and 300 minutes or shorter. Hold for a time, eg 150 minutes. At this time, by heating in an atmosphere in which ammonia (NH ₃ ) is added to RX gas, the carbon concentration and the nitrogen concentration in the surface layer portion of the steel member are adjusted to desired concentrations.

  Here, a steel member composed of steel in which the carbon and chromium contents are suppressed to 0.7 mass% or less and 0.3 mass% or less as described above is prepared in the steel member preparation step, By carbonitriding the steel member in the carbonitriding step, it becomes possible to form a nitrogen-enriched layer having a sufficient nitrogen concentration and thickness without extending the carbonitriding time. , Material costs can be reduced.

Next, the steel member carbonitrided in the carbonitriding step is cooled to a temperature not higher than the _MS point by being immersed (oil-cooled) in, for example, oil from the carbonitriding temperature, and is hardened and hardened. A quench hardening process is performed. At this time, the steel constituting the steel member undergoes martensitic transformation by being cooled to a temperature equal to or lower than the _MS point, and high-density dislocations are introduced into the steel and hardened.

Next, referring to FIG. 5, the steel member is quench-hardened in quench-hardening step is heated to a temperature of less than ₁ point 650 ° C. or higher A high temperature tempering step being tempered is carried out. Specifically, the hardened steel member is held at a temperature of, for example, 650 ° C. or more and 680 ° C. or less, for example, 650 ° C. for 60 minutes or more and 180 minutes or less, for example, 120 minutes, and then released in the air. Tempering is performed after cooling (air cooling). At this time, the density of dislocations introduced into the steel constituting the steel member in the quench hardening process decreases, and the coarsening and agglomeration of the carbide progress.

Thereby, regardless of the shape and size of the steel member, the amount of the steel member processed at the same time, and regardless of the site, the hardness of the steel member is reduced uniformly, for example, to a hardness of 300 HV or less. . In addition, by performing the tempering at a temperature of A ₁ point or less and 650 ° C. or higher, preferably 680 ° C. or higher, a hardness that can be plastically deformed without generating cracks in a relatively short time. It is possible to soften the steel member. As a result, the hardness of the low hardness region 12C in the shaft 12 can be stably controlled, and the shaft 12 having the low hardness region 12C that can be plastically processed without generating cracks is stably manufactured. be able to.

Next, referring to FIG. 5, in the steel member, the low hardness region 12C (both ends) which is a region other than the high hardness region 12B including the region to be the axial rolling surface 12A of the shaft 12 as the raceway member. Induction hardening is performed in which the high hardness region 12B is induction hardened without being hardened. Specifically, referring to FIG. 3, the steel member is set in a high-frequency hardening apparatus so that the surface of the high hardness region 12B faces the induction coil, and a high-frequency current is passed through the induction coil. The hardness region 12B is induction-heated to a temperature of 800 ° C. or higher and 1000 ° C. or lower, which is a temperature of A ₁ point or higher, for example, 900 ° C. Thereafter, the temperature range of not lower than A ₁ point to a temperature below M _S point, is quenched by being for example oil cooling or water cooling. Thereby, the high hardness region 12B is hardened by hardening without quenching the low hardness region 12C. Here, the surface layer portion of the steel member including the high hardness region 12B is carbonitrided in the carbonitriding process. Therefore, when the high hardness region 12B is induction-hardened in the induction hardening process, the shaft rolling surface 12A becomes a region having high resistance to rolling fatigue, and imparts excellent rolling fatigue life characteristics to the shaft 12. Can do.

  Further, the surface layer portion immediately below the axial rolling surface 12A is carbonitrided and then induction-quenched so that it is 10% by volume to 50% by volume, or a more preferable range of 15% by volume to 35% by volume. The steel structure includes the amount of retained austenite and an austenite grain size of 11 or more (former austenite grain size number: JIS G 0551). Therefore, the rolling fatigue life characteristics of the shaft 12 are further improved.

  Here, the induction heating in the induction hardening process is realized by the generation of heat corresponding to the work due to the Joule heat generated by the eddy current and the hysteresis loss generated in the shaft 12 that is the object to be processed. By controlling the frequency of the high-frequency current flowing through the power source, the output of the power source, the heating time, etc., only a desired portion of the shaft 12 can be locally heated. Therefore, the high hardness region 12B can be hardened and hardened relatively easily without quenching and hardening the low hardness region 12C.

Next, referring to FIG. 5, a low temperature tempering step is performed. Specifically, the steel member subjected to the induction hardening process is heated to a temperature of 150 ° C. or higher and 350 ° C. or lower, which is a temperature below A ₁ point, for example, 180 ° C., and a time of 30 minutes or longer and 240 minutes or shorter. For example, it is held for 120 minutes and then allowed to cool in air at room temperature (air cooling). By the above procedure, the heat treatment process included in the manufacturing process of the raceway member in the first embodiment is completed.

  According to the method for manufacturing the shaft 12 as the raceway member in the first embodiment, the hardness of the high hardness region 12B including the shaft rolling surface 12A is sufficiently increased while rolling is suppressed while suppressing an increase in manufacturing cost. High resistance to fatigue can be imparted to ensure a sufficient rolling fatigue life, and the hardness of the low hardness region 12C, which is both ends of the shaft 12, can be stably controlled and suppressed. As a result, both ends of the shaft 12 (low hardness region 12C) can be plastically deformed while avoiding the occurrence of cracks, and the shaft 12 that can be easily fixed by plastic deformation can be manufactured.

  And the axis | shaft 12 as the track member in Embodiment 1 of this invention manufactured with the manufacturing method of the track member in the said Embodiment 1 suppresses the raise of manufacturing cost, and the hardness of the area | region containing a rolling surface is suppressed. Is sufficiently high and at the same time has high resistance to rolling fatigue. As a result, the shaft 12 is a track member in which a sufficient rolling fatigue life is ensured and the hardness of the plastic deformation region is stably controlled.

Here, the point A ₁ in the case of heating the steel refers to a point that the structure of the steel corresponds to the temperature to start the transformation from ferrite to austenite. Further, the M _S point when the steel was austenitized is cooled, it refers to a point corresponding to a temperature to initiate the martensite.

  Next, the manufacturing method of the valve gear 10 in Embodiment 1 is demonstrated. FIG. 6 is a diagram showing an outline of a method for manufacturing the valve gear 10 in the first embodiment.

  Referring to FIGS. 1 and 6, the method for manufacturing valve gear 10 in Embodiment 1 includes cam follower 1 and rocker arm 2 as a holding member that holds cam follower 1, and an engine (not shown). This is a method of manufacturing a valve operating apparatus that operates the valve 6 that is an air supply valve or an exhaust valve. The manufacturing method of the valve operating apparatus 10 includes a cam follower manufacturing process for manufacturing the cam follower 1, a holding member manufacturing process for manufacturing the rocker arm 2 as a holding member, and an attachment for attaching the cam follower 1 to the rocker arm 2 as a holding member. A process, and an assembly process of assembling the valve operating apparatus 10 by combining the rocker arm 2 to which the cam follower is attached and the cam 5, the valve 6, the spring 7 and the like separately prepared.

  Here, in the cam follower manufacturing process, the shaft 12 as the track member constituting the cam follower 1 is manufactured by the track member manufacturing method in the first embodiment.

  Further, in the attaching process, referring to FIG. 3, the low hardness region 12C, which is both ends of the shaft 12, is plastically processed, so that the shaft 12 is fixed to the rocker arm 2 and the cam follower 1 is locked to the rocker. It is attached to the arm 2. More specifically, the roller 11 and a plurality of rollers 13 arranged so as to be in contact with the roller rolling surface 11A of the roller 11 are formed on one end 2B side of the rocker arm 2 of the pair of side walls 21. Inserted between. Thereafter, the shaft 12 is inserted so that the through holes 21 </ b> A formed in each of the pair of side walls 21 are simultaneously penetrated and the shaft rolling surface 12 </ b> A is in contact with the plurality of rollers 13. Then, the low hardness region 12 </ b> C that is both ends of the shaft 12 is caulked by plastic working, whereby the shaft 12 is fixed to the rocker arm 2, and the cam follower 1 is attached to the rocker arm 2.

  In the manufacturing method of the valve gear 10 in the first embodiment, the shaft 12 is manufactured by the method for manufacturing the raceway member in the first embodiment, and the shaft 12 is caulked so that the shaft 12 is rocker arm. The cam follower 1 is attached to the rocker arm 2. Therefore, according to the manufacturing method of valve gear 10 in the first embodiment, the shaft 12 as the raceway member has sufficient resistance against rolling fatigue while suppressing an increase in manufacturing cost. It is possible to provide a method of manufacturing the valve gear 10 that has excellent durability and can easily mount the cam follower using plastic deformation.

(Embodiment 2)
FIG. 7 is a schematic diagram showing a configuration of a valve gear including a cam follower including a track member according to the second embodiment which is an embodiment of the present invention. With reference to FIG. 7, the valve operating apparatus provided with the cam follower containing the track member in Embodiment 2, and its manufacturing method are demonstrated.

  Referring to FIG. 7, valve gear 10 in the second embodiment has basically the same configuration as valve gear 10 in the first embodiment described above. However, the valve gear 10 in the second embodiment is different from the valve gear 10 in the first embodiment in that the pivot point of the rocker arm 2 is one end 2B of the rocker arm 2. .

  That is, in the valve operating apparatus 10 according to the second embodiment, the pivot abutting portion 22 with which a pivot (not shown) abuts is formed on the one end 2B side of the rocker arm 2. The rocker arm 2 is rotatably held with the pivot contact portion 22 as a fulcrum.

  Here, when the cam 5 rotates together with the cam shaft 5A about the cam shaft 5A, the distance from the cam shaft 5A to the contact portion between the cam 5 and the cam follower 1 changes periodically. Therefore, the rocker arm 2 swings with the pivot contact portion 22 as a fulcrum. As a result, the valve 6 reciprocates, and the intake valve or exhaust valve of the engine opens and closes.

  The shaft 12 and the valve operating device 10 as the raceway members in the second embodiment basically have the same configuration as the shaft 12 and the valve operating device 10 in the first embodiment as described above. It can be manufactured by the same manufacturing method.

(Embodiment 3)
FIG. 8 is a schematic view showing a configuration of a valve gear including a cam follower including a track member according to the third embodiment which is an embodiment of the present invention. FIG. 9 is an enlarged schematic view showing the periphery of the cam follower in FIG. With reference to FIG. 8 and FIG. 9, the valve operating apparatus provided with the cam follower containing the track member in Embodiment 3, and its manufacturing method are demonstrated.

  Referring to FIGS. 8 and 9, valve operating apparatus 10 in the third embodiment has basically the same configuration as valve operating apparatus 10 in the first embodiment described above. However, in the valve operating apparatus 10 according to the third embodiment, the cam follower 1 is not directly attached to the rocker arm 2, but the push rod 90 is interposed between the rocker arm 2 and the cam follower 1, and the cam follower 1 is pushed to the push rod 90. Is different from the valve gear 10 of the first embodiment.

  That is, a push rod 90 having a rod-like shape is coupled to one end 2B of the rocker arm 2 via an adjusting screw 80 and a coupling member 81 fixed to the rocker arm 2 by a lock nut 82. Yes. In the push rod 90 as the holding member, the cam follower 1 is attached to an end portion on the opposite side to the side connected to the rocker arm 2. And the cam 5 is arrange | positioned so that the outer peripheral surface of the roller 11 of the cam follower 1 may contact in outer peripheral surface 5B.

  Here, when the cam 5 rotates together with the cam shaft 5A about the cam shaft 5A, the distance from the cam shaft 5A to the contact portion between the cam 5 and the cam follower 1 changes periodically. Therefore, the rocker arm 2 swings about the rocker arm shaft 3 as a fulcrum when one end 2B is pushed by the push rod 90. As a result, the valve 6 reciprocates, and the intake valve or exhaust valve of the engine opens and closes.

  In addition, the shaft 12 and the valve operating apparatus 10 as the track members in the third embodiment basically have the same configuration as the shaft 12 and the valve operating apparatus 10 in the first embodiment as described above. It can be manufactured by the same manufacturing method.

  Embodiment 1 of the present invention will be described below. A test was performed in which the nitrogen concentration distribution of the raceway member of the present invention was compared with the nitrogen concentration distribution of a raceway member subjected to carbonitriding using SUJ2 which is a general bearing steel. The test procedure is as follows.

  First, a method for producing a test piece to be tested will be described. JIS S53C was adopted as the steel constituting the race member of the example of the present invention, and JIS SUJ2 was adopted as the steel constituting the race member of the comparative example. And the said steel material was processed into the steel member which has a rough shape of the bearing inner ring | wheel of 6303 model number (JISB1513) which is a track member.

  Thereafter, the steel member was carbonitrided by holding at 850 ° C. for 150 minutes in an atmosphere in which ammonia gas was added to RX gas. Then, the steel member is cut in a cross section perpendicular to the surface, and the distribution of nitrogen concentration and carbon concentration in the direction perpendicular to the surface is measured from the surface toward the inside by EPMA (Electron Probe Micro Analysis). did.

  FIG. 10 is a diagram showing the relationship between the depth from the surface and the nitrogen concentration in the carbonitrided steel member. FIG. 11 is a diagram showing the relationship between the depth from the surface and the carbon concentration in the carbonitrided steel member. 10 and 11, the horizontal axis represents the depth from the surface, and the vertical axis represents the nitrogen concentration and the carbon concentration, respectively. 10 and 11, the measurement result of the steel member made of S53C is shown by a solid line, and the measurement result of the steel member made of SUJ2 is shown by a broken line. The nitrogen concentration distribution of the carbonitrided steel member will be described with reference to FIGS.

  Referring to FIG. 10, the nitrogen concentration in the steel member made of S53C which is an example of the present invention and the steel member made of SUJ2 which is a comparative example is decreasing from the surface toward the inside. And in the outermost layer part, the nitrogen concentration of the SUJ2 steel-made member as a comparative example exceeds the nitrogen concentration of the S53C steel-made member as an example. However, the nitrogen concentration of the SUJ2 steel member rapidly decreases inside the inner ring, and in the region where the depth from the surface exceeds 0.15 mm, the nitrogen concentration of the S53C steel member is the nitrogen concentration of the SUJ2 steel member. Is over. This is considered to be due to the following reasons.

Referring to FIG. 11, the carbon concentration of the S53C steel member, which is an example, decreases almost linearly toward the inside, whereas the carbon concentration of the SUJ2 steel member, which is a comparative example, is the outermost layer. It has the largest peak in the part and has many peaks toward the inside. This is because the carbide (cementite; Fe ₃ C) exists in the microstructure of SUJ2, which is a hypereutectoid steel, and because SUJ2 contains a large amount of chromium (Cr), it is carbonitrided. This is due to the fact that Cr carbonitride is deposited on the surface layer. And these carbide | carbonized_material and carbonitride inhibit the penetration | invasion of the inside of nitrogen in a carbonitriding process, and it is thought that it was the cause of the above-mentioned rapid fall of nitrogen concentration.

  Here, usually, on the rolling surface of the race member constituting the rolling bearing, the 0.1 to 0.2 mm region of the surface layer portion is removed by grinding in the finishing process after the heat treatment. Therefore, the nitrogen concentration of the race member made of S53C, which is an example of the present invention, is higher than the nitrogen concentration of the race member made of SUJ2, which is a comparative example, at and near the rolling surface where resistance to rolling fatigue is required. Will be higher. For example, in the finishing process after heat treatment, even when the 0.2 mm region of the surface layer portion is removed by grinding, in the raceway member made of S53C, the nitrogen concentration in the region within a depth of 0.05 mm from the rolling surface Can be 0.14 mass% or more. Further, in order to increase the nitrogen concentration on the rolling surface of the SUJ2 raceway member, a measure to increase the carbonitriding time can be considered, but in that case, there is a problem that the manufacturing cost increases.

  From the above, the raceway member of the present invention that has been carbonitrided using S53C as a raw material is near the rolling surface while suppressing an increase in manufacturing cost compared to the raceway member of a comparative example that has been carbonitrided using SUJ2 as a raw material. It can be seen that the nitrogen concentration can be increased. And it is thought by this that according to the track member of the present invention, it is possible to improve the resistance to rolling fatigue of the rolling surface.

  Embodiment 2 of the present invention will be described below. A test for evaluating the characteristics of the track member manufactured by the track member manufacturing method of the present invention was conducted. The test procedure is as follows.

First, a method for producing a test piece to be tested will be described. As an example of the present invention, JIS S53C, S58C, and SAE1070, which are carbon steels, are adopted as materials, and the same method as the method of manufacturing the shaft 12 as the race member in the first embodiment described with reference to FIGS. 4 and 5 is used. A solid cylindrical test piece (cam follower shaft) having an outer diameter of 14.6 mm and a length of 17.3 mm was produced by the production method. In the heat treatment step, referring to FIG. 5, after carbonitriding by heating to 850 ° C., which is a temperature of _one point A or higher, and holding in an atmosphere in which ammonia is added to RX gas (carbonitriding step) ), oil cooled by hardened by cooling to a temperature below M _S point (quench-hardening step) was performed tempering holds then 650 ° C. 120 min (high-temperature tempering step). Furthermore, after performing induction hardening (frequency 80 kHz) for quenching and hardening the region including the region to be the rolling surface (frequency quenching step), tempering is performed by heating to 180 ° C. and holding for 120 minutes. Performed (low temperature tempering step), and the heat treatment step was completed (Examples A to C).

  On the other hand, as a comparative example outside the scope of the present invention, S53C is adopted as a material, and in the same process as the above test piece, the carbonitriding process, quench hardening process and high temperature tempering process of the heat treatment process are omitted and induction tempering is performed. A test piece that was subjected only to the entering step and the low-temperature tempering step was also produced (Comparative Example A).

  Next, a characteristic evaluation method will be described. The hardness of the outer peripheral surface of the test piece, the amount of retained austenite on the rolling surface, and the austenite grain size number were investigated. FIG. 12 is a diagram showing the measurement position of the hardness of the test piece. Referring to FIG. 12, the hardness of the outer peripheral surface of the shaft 30 of the cam follower as the test piece is a position away from the end of the outer peripheral surface by 8.65 mm, 5.0 mm, 2.0 mm, and 1.0 mm in the longitudinal direction, respectively. Measurement positions A, B, C and D were measured with a Vickers hardness tester. Here, the measurement positions A and B are positions included in the rolling surface 31 that is the surface of the high hardness region 32, and the measurement positions C and D are positions included in a region other than the rolling surface 31.

  The amount of retained austenite on the rolling surface 31 is calculated by measuring the diffraction intensities of the martensite α (211) plane and the austenite γ (220) plane of the part using an X-ray diffractometer (XRD). did. Moreover, the austenite crystal grain size number was measured by the measuring method of the grain size number of the former austenite crystal grain described in JIS G 0551.

  Table 1 shows the results of the characteristic evaluation. Referring to Table 1, in Examples A to C produced by the manufacturing method of the example of the present invention, the hardness at measurement positions A and B included in the rolling surface 31 is 775 to 790 HV, which is sufficient The hardness can be expected to have a good rolling fatigue life. Moreover, the hardness in the measurement positions C and D which are areas | regions other than the rolling surface 31 is 220-250HV, and is 300HV or less which is a hardness range which can implement plastic processing, such as crimping, without generating a crack. It has become.

  On the other hand, Comparative Example A produced by a conventional manufacturing method that is outside the scope of the present invention has a hardness of 700 to 705 HV at measurement positions A and B included in the rolling surface 31. The reason why the hardness is lower than that of Example A is considered to be due to the fact that the test piece of Comparative Example A is not carbonitrided. Further, the hardness at the measurement positions C and D, which is a region other than the rolling surface 31, is 180 to 185HV.

  In Examples A to C, the amount of retained austenite on the rolling surface 31 is 29.5 to 35% by volume. This is a rolling fatigue life, particularly 10 volume% or more and 50 volume, which is a preferable range in order to achieve both the improvement of the rolling fatigue life in a foreign matter mixed environment where hard foreign matter is mixed in the lubricant and the dimensional stability. % Or less, which is a particularly preferable range of 15 volume% or more and 35 volume% or less.

  On the other hand, in Comparative Example A, the amount of retained austenite on the rolling surface 31 is 5.5% by volume. It is considered that the amount of retained austenite is smaller than that in Example A because the test piece of Comparative Example A is not carbonitrided. As a result, the amount of retained austenite of Comparative Example A is 10% by volume to 50% which is a preferable range for achieving both rolling fatigue life, particularly improvement of rolling fatigue life in a foreign matter mixed environment, and dimensional stability. % Or less.

  In Examples A to C, the austenite grain size number on the rolling surface 31 is 11, which is 11 or more, which is a preferable range for improving rolling fatigue life, toughness, and the like.

  On the other hand, in Comparative Example A, the grain size number of the austenite crystal grains on the rolling surface 31 is 9. The grain size number is smaller than that of Example A (the former austenite crystal grains are large) because the test piece of Comparative Example A is not carbonitrided, and therefore the austenite crystal grain generation site during induction hardening This is considered to be due to the fact that the number density of the resulting carbide was smaller than in Examples A to C.

  As described above, the race member produced by the method for producing a race member according to the present invention has a rolling surface hardness and austenite grain size number larger than those of conventional race members, and the amount of retained austenite is in a preferred range. A region where plastic processing is easy is formed. Therefore, the race member produced by the method for producing a race member of the present invention has an excellent rolling fatigue life of the raceway surface, and it becomes easy to fix the race member using plastic working such as caulking. It was confirmed that

  Embodiment 3 of the present invention will be described below. The test which investigates the rolling fatigue life of the track member manufactured by the manufacturing method of the track member of this invention was done. The test procedure is as follows.

  An outer ring rotation type rolling fatigue life test was carried out using the cam follower shaft, which is the test piece shown in FIG. In addition, the shaft of the cam follower made from JIS SUJ2 produced by the heat treatment process similar to the comparative example A was added to the test object as the comparative example B. FIG. 13 is a schematic view showing a main part of a rolling fatigue life tester used in the test of Example 3. With reference to FIG. 13, the test method of the rolling fatigue life test of Example 3 will be described.

  Referring to FIG. 13, the rolling fatigue life tester 40 has a rotating shaft 41 connected to a power source (not shown), and the rotating shaft 41 passes through an area including the center so that the rotating shaft 41 can rotate integrally with the rotating shaft 41. A disk-shaped drive roller 42 is provided, and a pair of bearings 45 that support the rotary shaft 41 so as to be rotatable about the axis.

  An annular outer ring 43 is disposed so as to contact the outer peripheral surface 42 </ b> A of the driving roller on the outer peripheral surface, and a plurality of rollers 44 are disposed so as to contact the inner peripheral surface of the outer ring 43 on the outer peripheral surface. The Further, referring to FIGS. 12 and 13, cam follower shaft 30 as a test piece is fixed and arranged so as to penetrate outer ring 43 and contact roller 44 on rolling surface 31.

  When the rotating shaft 41 rotates around the axis by a power source (not shown), the driving roller 42 rotates integrally with the rotating shaft 41. Then, driven by the drive roller 42, the outer ring 43 rotates. As a result, the roller 44 rolls on the rolling surface 31 of the shaft 30 of the fixed cam follower. Here, the load applied to the shaft 30 of the cam follower is 2200 N, the rotation speed of the outer ring 43 is 7000 rpm, the lubricating oil is engine oil (SAE viscosity standard: 10 W-30), and the oil temperature is 100 ° C. The test was carried out. According to this condition, either surface damage or internal origin delamination occurs during the test. Therefore, the life of both surface damage and internal origin peeling can be confirmed by this test. Then, the time (rolling fatigue life) until peeling occurred on the cam follower shaft 30 was investigated. Furthermore, the rolling fatigue life obtained as a result of the experiment was statistically analyzed, and the time until the 10% test piece peeled (L10 life) was calculated. Table 2 shows the test results.

  In Table 2, the life ratio of each test piece when the L10 life of Comparative Example A is set to 1 is shown. Referring to Table 2, the cam follower shafts of Examples A to C, which are examples of the present invention, have a rolling fatigue life of about 5 to 6 times that of Comparative Example A which is a conventional cam follower shaft. is doing. In Example A, it is considered that the carbonitriding treatment is performed in Example A, and as described above, the austenite crystal grain size is small and the amount of retained austenite is in a preferable range. . In addition, Examples A to C have a rolling fatigue life of about 1.5 to 1.7 times that of the shaft of a SUJ2 cam follower that is a bearing steel.

  Embodiment 4 of the present invention will be described below. The test which investigates the relationship between the heating temperature in the high temperature tempering process in the manufacturing method of the raceway member of the present invention, and the heating time required in order to soften to desired hardness was done. The test procedure is as follows.

  In the cam follower shaft manufacturing method according to the first embodiment described with reference to FIGS. 4 and 5, a steel member (cam follower shaft; JIS) subjected to a steel member preparation step, a carbonitriding step, and a quench hardening step is performed. S53C) was prepared as a test piece, and a high-temperature tempering step was performed by changing the tempering parameters (temperature and time) on the test piece. The tempering temperature is 600 ° C. to 700 ° C., the holding time at the tempering temperature is changed, and the hardness of the test piece is 250 HV or less which is a preferable hardness for carrying out plastic working without generating cracks. The retention time required for this was investigated. The results of the test are shown in Table 3.

  Referring to Table 3, when the tempering temperature is 650 ° C., the holding time necessary for setting the hardness to 250 HV is 1.00 hour, whereas at 600 ° C., the holding time is 2.5 times 2.50. It takes time. For this reason, when the tempering temperature is set to 600 ° C. in the actual production process, the production efficiency may be lowered. Therefore, it can be said that the tempering temperature in the high-temperature tempering step is preferably 650 ° C. or higher. Furthermore, when the tempering temperature is 680 ° C., it becomes 0.67 hours, which is 2/3 of the tempering temperature of 650 ° C., and tempering in a shorter time is possible. On the other hand, when the tempering temperature is 700 ° C., the holding time is 0.21 hours, and further tempering is possible, but if the holding time is shorter than this, in the actual production process There is a risk that the variation in hardness between products and the variation in hardness depending on the site inside the product will increase. For this reason, it is considered that the tempering temperature in the high-temperature tempering step is preferably 700 ° C. or lower.

  From the results of Examples 1 to 4 above, according to the track member manufacturing method of the present invention, carbonitriding and induction hardening are suppressed while suppressing an increase in manufacturing cost by suppressing the number and time of heat treatment steps. The material including the rolling surface is made of a material having sufficiently high hardness and high resistance to rolling fatigue, and the hardness of the region other than the rolling surface is stably controlled and suppressed, and plastic deformation of the region is performed. It was confirmed that a track member that can be easily fixed using the track can be manufactured.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The track member and the track member manufacturing method of the present invention can be applied particularly advantageously to a track member fixed to an adjacent member by plastic deformation of a part of the track member and the method of manufacturing the track member. In addition, the method for manufacturing a valve operating apparatus according to the present invention is particularly advantageous for a method for manufacturing a valve operating apparatus including a cam follower having a track member that is fixed to an adjacent member by plastic deformation of a part thereof. Can be applied.

FIG. 3 is a schematic diagram illustrating a configuration of a valve gear including a cam follower including a track member in the first embodiment. It is a schematic sectional drawing in alignment with line segment II-II of FIG. FIG. 3 is a schematic partial cross-sectional view showing an enlargement of the vicinity of the cam follower in FIG. 2. FIG. 3 is a diagram showing an outline of a method for manufacturing a cam follower shaft in the first embodiment. FIG. 6 is a diagram showing a heat treatment step included in the method for manufacturing the cam follower shaft in the first embodiment. It is a figure which shows the outline of the manufacturing method of the valve gear in Embodiment 1. FIG. 6 is a schematic diagram illustrating a configuration of a valve gear including a cam follower including a raceway member in Embodiment 2. FIG. FIG. 6 is a schematic diagram illustrating a configuration of a valve gear including a cam follower including a raceway member in a third embodiment. It is the schematic which expanded and showed the cam follower periphery of FIG. It is a figure which shows the relationship between the depth from the surface in a carbonitrided steel member, and nitrogen concentration. It is a figure which shows the relationship between the depth from the surface in carbon steel nitrided steel member, and carbon concentration. It is a figure which shows the measurement position of the hardness of a test piece. FIG. 5 is a schematic view showing the main part of a rolling fatigue life tester used in the test of Example 3.

Explanation of symbols

  1 cam follower, 2 rocker arm, 2B one end, 2C other end, 2D through hole, 3 rocker arm shaft, 4 bearing metal, 5 cam, 5A camshaft, 5B outer peripheral surface, 6 valve, 7 spring, 8 Lock nut, 9 adjustment screw, 10 valve gear, 11 roller, 11A roller rolling surface, 12 shafts, 12A shaft rolling surface, 12B high hardness region, 12C low hardness region, 13 rollers, 13A roller rolling surface, 21 Side wall, 21A through hole, 21B taper part, 22 pivot contact part, 30 cam follower shaft, 31 rolling surface, 32 high hardness region, 40 rolling fatigue life tester, 41 rotating shaft, 42 driving roller, 42A outer peripheral surface , 43 Outer ring, 44 Roller, 45 Bearing, 80 Adjustment screw, 81 Connecting member, 82 Lock nut, 90 Push lock De.

Claims (3)

0.5% by mass or more and 0.7% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.6% by mass or more and 0.9% by mass or less of manganese. A steel member comprising a balance iron and unavoidable impurities, a steel whose chromium content is suppressed to 0.3% by mass or less, and a steel member which is a member formed into a schematic shape of a raceway member A preparation process;
A heat treatment step in which the steel member is heat treated;
The steel member that has been heat-treated in the heat treatment step includes a finishing process for finishing.
The heat treatment step includes
A carbonitriding step in which the steel member is heated to a carbonitriding temperature which is a temperature of _one point A or more and carbonitrided;
A quench hardening step in which the steel member carbonitrided in the carbonitriding step is quenched and hardened by cooling from the carbonitriding temperature to a temperature below the _MS point;
A high temperature tempering step in which the steel member quenched and hardened in the quench hardening step is tempered by being heated to a temperature of 650 ° C. or more and less than A ₁ point;
In the steel member tempered in the high-temperature tempering step, the low-hardness region that is a region other than the high-hardness region including the region that should become the rolling surface of the raceway member is not quenched and hardened, A method for manufacturing a raceway member, including an induction hardening process in which a high hardness region is induction hardened. A method for manufacturing a valve operating device having a cam follower and a holding member for holding the cam follower, and operating at least one of an intake valve and an exhaust valve of an engine,
A cam follower manufacturing process for manufacturing the cam follower;
A holding member manufacturing process for manufacturing the holding member;
An attachment step of attaching the cam follower to the holding member;
In the cam follower manufacturing process, the track member constituting the cam follower is manufactured by the track member manufacturing method according to claim 1,
In the attachment step, the low hardness region is plastically processed, whereby the track member is fixed to the holding member, and the cam follower is attached to the holding member.   A track member manufactured by the method for manufacturing a track member according to claim 1.

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