JP2006063916A - Rocker arm structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rocker arm structure having a compact rolling bearing and a light and compact rocker arm while achieving longer rolling fatigue and surface damage life. <P>SOLUTION: The steel rocker arm 1 is mounted on a rocker arm shaft 5. A forked roller supporting part 14 abuts on one end 1a of the rocker arm 1, and the end of a valve 9 abuts on the other end 1b thereof. A roller shaft (an inner ring) 2 is fixed to the forked roller supporting part 14, and a roller (an outer ring) 4 is supported via a roller (a rolling element) 3 on the roller shaft (the inner ring) 2. At least one member of the outer ring 4, the inner ring 2 and the rolling element 3 has a nitrogen enriched layer. The grain size number of austenite crystal grains in the nitrogen enriched layer is in a range exceeding 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rocker arm used for opening and closing an intake valve and an exhaust valve of an automobile engine and a rocker arm structure having a rolling bearing used for the rocker arm, and more specifically, various performances of the bearing are improved. The present invention relates to a rocker arm structure that can reduce the weight of the rocker arm.

  In recent years, environmental problems have been highlighted, and automobiles have become legally required to reduce fuel consumption and are strongly demanded. Along with this, each component constituting the engine is required to be lightweight and compact. Accordingly, there is a demand for lighter and more compact rocker arms used for opening and closing engine intake valves and exhaust valves. In order to make the rocker arm lightweight and compact, it is necessary to make the bearing used in the rocker arm compact.

  Therefore, the bearing used for the rocker arm is often used for high-speed and high-load applications while being a full-roller type.

  Conventionally, the status of research and development on rolling bearings used for rocker arms is as follows.

  In applications where the outer peripheral surface of the outer ring is in rolling contact with the cam, such as bearings used in rocker arms used to open and close engine intake valves and exhaust valves, the conventional method has been mainly aimed at improving the outer peripheral surface of the outer ring. There was much development. For example, compressive residual stress due to processing such as shot peening and long life due to high hardness due to high-concentration carburizing have been performed mainly to improve the outer peripheral surface of the outer ring that is in rolling contact with the mating cam.

  For example, the following measures have been taken in the conventional technology.

  (1) A bearing component in which shot peening is applied to the bearing ring of the bearing component in order to improve the rolling fatigue life, and a reinforcing layer, a retained austenite-containing layer, and a hardened hardening layer are sequentially provided from the surface to the inside (Japanese Patent Laid-Open No. 2-168022). Issue gazette).

  (2) Technology for efficiently adjusting the size, area ratio, retained austenite amount and hardness of carbides in the martensite structure by shot peening (Japanese Patent Laid-Open No. 2001-65576).

  (3) Technology for matching the peak height and distribution of residual compressive stress due to shot peening to the maximum shear stress and depth of action acting during use in order to improve the rolling fatigue life (JP-A-3-199716).

  (4) For carburized bearings, the combination of residual compressive stress σ (MPa) and residual austenite γ (%) on the surface after shot peening is applied to extend the life and final surface finishing is performed. A control method that satisfies 001σ + 0.3γ ≧ 1.0.

  (5) A cam follower device in which the outer peripheral surface abutting on the cam of the cam follower outer ring has the same hardness as that of the mating cam and the inner peripheral surface of the outer ring is harder than the outer peripheral surface (Japanese Utility Model Laid-Open No. 3-119508).

(6) In a part that is in rolling contact or rolling and sliding contact with other parts facing each other, the maximum compressive stress of the surface layer at a depth of 0 to 50 μm from the surface is 50 to 110 kgf / mm ² , and the hardness is HV 830 to 960, The residual austenite is 7% or more, the average wavelength of the surface roughness is 25 μm or less, and these are achieved by shot peening (Japanese Patent No. 3125434).

  In addition, although there are few improvements to extend the rolling life of the shaft, rollers, or the entire bearing corresponding to the inner ring, as shown below, heat resistance and microstructure stability by carbonitriding are given, and hardness is increased as shown below There is an example in which the life of the bearing is extended by the above.

  (D1) A bearing for a cam follower device for a valve mechanism of an engine having a calculation life of 1000 hours or more at a rated engine speed (Japanese Patent Laid-Open No. 2000-38907).

  (D2) For a cam follower device in which the carbide ratio is 10 to 25%, the decomposition ratio with respect to the initial value of retained austenite is 1/10 to 3/10, the end surface hardness is HV830 to 960, and the average surface roughness wavelength is 25 μm or less. A bearing steel subjected to carbonitriding and hard shot peening to realize a bearing shaft (Japanese Patent Laid-Open No. 10-47334).

  (D3) A cam follower shaft in which a solid lubricating film such as a polymer compound is formed on the shaft in order to improve the wear resistance of the shaft (Japanese Patent Laid-Open No. 10-103339).

  (D4) A cam follower shaft made of tool steel or the like and made hard by ion nitriding or ion plating at a temperature lower than the tempering temperature (Japanese Patent Laid-Open No. 10-110720).

  (D5) A bearing for a cam follower device for a valve operating mechanism of an engine having a bending stress with respect to a shaft of 150 MPa or less (Japanese Patent Laid-Open No. 2000-38906).

  (D6) A cam follower for an engine valve mechanism in which a phosphate coating excellent in lubricating oil retention is attached to the rolling surface of a bearing component (Japanese Patent Laid-Open No. 2002-3212).

  (D7) A cam follower for a valve mechanism of an engine having a crowned roller rolling region (Japanese Utility Model Laid-Open No. 63-185917).

  (D8) Carburized shaft with high-concentration carburizing treatment or carbonitriding treatment in which the carbon concentration in the surface of the rolling surface of the shaft is 1.2% to 1.7% C, and the internal hardness is HV300 194438).

  As another problem associated with the rocker arm, there is a case where both ends of the roller shaft are caulked to be caulked on the roller support member. In this case, the rolling surface of the roller shaft requires high hardness, but the end portion needs to be soft so that it can be crimped. Moreover, after caulking and fixing, strength (hardness) is required so as not to loosen during use. The following disclosure is made with respect to one that enables caulking to both ends of the roller shaft of the roller rocker.

  (D9) A method in which the outer peripheral surface of the roller shaft is uniformly induction-hardened and tempered, and then both ends are subjected to induction annealing to soften both ends (Japanese Patent Laid-Open No. 5-179350).

As the material of the rocker arm, there are currently used rocker arms made of steel and rocker arms made of light alloy such as aluminum. A light alloy rocker arm is weaker in strength than a steel rocker arm, and its compacting effect is slightly reduced. The price is also slightly higher. Therefore, the rocker arm made of steel is the most suitable material for the rocker arm that is both lightweight and compact. The rocker arm made of steel includes a rocker arm manufactured by forging, casting, MIM (Metal Injection Molding) or press forming from a steel plate.
Japanese Patent Laid-Open No. 2-168022 JP 2001-65576 A Japanese Patent Laid-Open No. 3-199716 Japanese Utility Model Publication No. 3-119508 Japanese Patent No. 3125434 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 2002-3212 A Japanese Utility Model Publication No. 63-185917 JP 2002-194438 A JP-A-5-179350

  As described above, the rocker arm used for opening and closing the intake valve and the exhaust valve of the engine is required to be lightweight and compact.

  However, in a full-roller type bearing without a retainer, which is a bearing used for a rocker arm, the rollers may interfere with each other, or the roller position may not be controlled smoothly, and roller skew is likely to occur. In addition, the lubricating oil is not supplied well into the bearing, resulting in poor lubrication conditions. As a result, sliding heat generation, local surface pressure increase, or insufficient lubrication occurs, and there is a large load capacity in the calculation. Even though the life is sufficient for the required life, surface damage (peeling, smearing) , Surface-origin type separation) or internal origin-type peeling occurs, and often fails to function as a bearing. Unless such a problem is solved, it is difficult to reduce the weight of the steel rocker arm.

  In addition to the usual load-dependent rolling fatigue life, the factors governing the life of the bearing under such conditions include the life of surface damage due to metal contact caused by slipping and oil film breakage. Therefore, it is necessary to extend both lifetimes. However, until now, no technology has been established that significantly extends both lifetimes.

  Therefore, the object of the present invention is to increase the life of surface damage due to metal contact caused by slipping or oil film breakage in addition to the usual load-dependent rolling fatigue life in rolling bearings used for rocker arms. An object is to provide a rocker arm structure that realizes a long life and enables compactness of the rolling bearing, thereby making the rocker arm light and compact.

  One rocker arm structure of the present invention includes a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring positioned inside the outer ring, and a plurality of rollers interposed between the outer ring and the inner ring. A rocker arm structure having a rolling bearing provided with rolling elements and having a rocker arm made of steel. The rocker arm is attached to a rocker arm shaft positioned between one end and the other end. One end of the rocker arm is provided with a bifurcated inner ring support, the other end is in contact with the end of an engine opening / closing valve, and the bifurcated inner ring support corresponds to the inner ring. The outer ring, the inner ring and the rolling element have a nitrogen-enriched layer, and the grain size number of the austenite crystal grains in the nitrogen-enriched layer is in a range exceeding # 10. It is an butterfly.

  Another rocker arm structure of the present invention includes a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring located inside the outer ring, and a plurality of intervenes between the outer ring and the inner ring. In a rocker arm structure having a rolling bearing provided with rolling elements and having a rocker arm made of steel, a pivot is in contact with one end of the rocker arm, and one end of the rocker arm A rolling bearing is provided between the other end and the other end is in contact with the end of an engine opening / closing valve, and at least one member of the outer ring, inner ring and rolling element is a nitrogen-enriched layer. And the grain size number of the austenite crystal grains in the nitrogen-enriched layer is in a range exceeding # 10.

  Still another rocker arm structure according to the present invention includes a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring located inside the outer ring, and a plurality of rollers interposed between the outer ring and the inner ring. And a rocker arm structure having a steel rocker arm, the rocker arm is attached to a rocker arm shaft positioned between one end and the other end. One end of the rocker arm is in contact with one end of the interlocking rod that transmits the force from the camshaft, and the other end is in contact with the end of the valve for opening and closing the engine The other end of the interlocking rod is provided with a rolling bearing, and at least one member of the outer ring, the inner ring and the rolling element has a nitrogen-enriched layer, and the particle size number of the austenite crystal grains in the nitrogen-enriched layer is 10 Turn It is characterized in that the range to obtain.

  According to any of the above three rocker arm structures of the present invention, the rolling fatigue life is greatly improved because the austenite grain size number exceeds 10 and the austenite grain size is fine. Can do. When the austenite grain size number is 10 or less, the rolling fatigue life is not greatly improved. Usually 11 or more. Austenite grains are preferably finer, but it is usually difficult to obtain a grain number exceeding 13th.

  The nitrogen-enriched layer can also improve the surface damage life.

  The three rocker arm structures are common in that the driving force from the cam is transmitted to the valve of the engine, but the structures thereof are different from each other and can correspond to different engine types.

  The nitrogen-enriched layer is a layer having an increased nitrogen content formed on the outer ring, the inner ring, or the surface layer of the rolling element, and can be formed by a process such as carbonitriding, nitriding, or nitriding.

  Further, the austenite crystal grains of the outer ring, the inner ring, or the rolling element do not change in the surface layer portion where the nitrogen-enriched layer exists or in the inner part thereof. Therefore, the target position of the above crystal grain size number range is the surface layer portion and the inside. Here, the austenite crystal grain is a crystal grain based on the trace of the austenite crystal grain boundary immediately before quenching after the quenching treatment.

  In the above rocker arm structure, the amount of retained austenite in the nitrogen-enriched layer is preferably in the range of 11% by volume to 25% by volume.

  When the amount of retained austenite is about 11% by volume, the surface damage life is reduced, and when the amount is less than 11%, it tends to be further reduced. On the other hand, when the amount of retained austenite is more than 25% by volume, the amount of retained austenite is not different from that of ordinary carbonitriding treatment, so that the dimensional change over time becomes worse.

  The amount of retained austenite is a value in the surface layer of 50 μm of the rolling surface after grinding, and can be measured, for example, by comparing the diffraction intensities of martensite α (211) and retained austenite γ (220) by X-ray diffraction. .

  In the above rocker arm structure, the nitrogen content in the nitrogen-enriched layer is preferably in the range of 0.1% by mass to 0.7% by mass.

  When the nitrogen content in the nitrogen-enriched layer is less than 0.1%, there is no effect of nitrogen content, and in particular, the surface damage life is reduced. When the nitrogen content is more than 0.7%, voids called voids are formed, or the amount of retained austenite increases so that the hardness does not come out, resulting in a short life.

  The nitrogen content of the nitrogen-enriched layer is a value at the surface layer of 50 μm of the rolling surface after grinding, and can be measured by, for example, EPMA (wavelength dispersion type X-ray microanalyzer).

  In the rocker arm structure described above, the surface hardness of the nitrogen-enriched layer is preferably in the range of HV653 or more.

  When the surface hardness is as high as HV653 or more, the rolling fatigue life can be greatly improved. If the surface hardness is less than HV653, the rolling fatigue life is not greatly improved, but rather deteriorates. Usually, the range of surface hardness is HV720-800. A higher surface hardness is desirable, but it is usually difficult to obtain a surface hardness exceeding HV900.

  In the above rocker arm structure, the area ratio of the spheroidized carbide in the nitrogen-enriched layer is preferably in the range of 10% to 25%.

  When the area ratio of the spheroidized carbide is 10% or more, the rolling fatigue life can be greatly improved. If the area ratio of the spheroidized carbide is less than 10%, the rolling fatigue life is not greatly improved, so the range is made 10% or more. The larger the area ratio of the spheroidized carbide, the better. However, usually, if an area ratio exceeding 25% is obtained, the toughness of the material deteriorates due to coarsening and agglomeration of the carbide. Therefore, it is preferably in the range of 10% to 25%. .

  The area ratio of the spheroidized carbide is a value in the surface layer of 50 μm of the rolling surface after grinding, and after corroding with a picric acid alcohol solution (picral), it can be observed with an optical microscope (400 times). Here, although it is simply expressed as spheroidized carbide, it is actually a combination of carbide / nitride.

  In the rocker arm structure described above, the rolling bearing is preferably a full-roller type needle bearing.

  The shaft corresponding to the inner ring in the present invention includes both a solid shaft and a hollow shaft.

  As described above, according to the rocker arm structure of the present invention, in a rolling bearing used for a rocker arm, a normal load-dependent rolling fatigue life and a surface damage life due to metal contact caused by slipping or oil film breakage Therefore, the rolling bearing can be made compact, and the steel rocker arm can be made lighter and more compact.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic front view showing a configuration of a cam follower with a roller of an engine according to an embodiment of the present invention, and FIG. 2 is a view corresponding to a cross section taken along line II-II of FIG. Referring to FIGS. 1 and 2, rocker arm 1 is made of steel, and rocker arm shaft 5 via a bearing metal or the like at a central portion located between one end 1a and the other end 1b. It is supported by. The rocker arm 1 swings around the rocker arm shaft 5.

  An adjustment screw 7 is screwed into the other end 1 b of the rocker arm 1. The adjustment screw 7 is fixed by a lock nut 8 and is in contact with the upper end of a supply valve or exhaust valve (engine opening / closing valve) 9 of the internal combustion engine at the lower end thereof. The valve 9 is biased by the elastic force of the spring 10.

  The rocker arm 1 integrally has a roller support portion 14 formed in a bifurcated shape at one end portion 1a. This bifurcated roller support portion 14 is provided with a full-roller type rolling bearing (needle bearing) 50 having a roller shaft 2 corresponding to an inner ring, a roller 3 serving as a rolling element, and a roller 4 corresponding to an outer ring. Has been.

  Both ends of the roller shaft 2 are caulked into roller shaft holes formed in the bifurcated roller support portion 14 and fixed by press-fitting or retaining rings. A roller 4 is rotatably supported at the center of the outer peripheral surface of the roller shaft 2 via a roller 3. The axial direction of the roller 3 is arranged parallel to the axis of the roller shaft 2. The outer peripheral surface of the roller 4 is in contact with the cam surface of the cam 6 provided on the cam shaft by the urging force of the spring 10. In this embodiment, the roller shaft 2 is a hollow shaft, but may be a solid shaft.

  In the present specification, there is no particular distinction between one and the other, and there is only a meaning that one end is an end that will be described earlier in the order of description.

  As described above, the rolling bearing 50 including the roller shaft (inner ring) 2, the rollers (rolling elements) 3, and the rollers (outer rings) 4 is used as a full roller bearing for the rocker arm. In general, when a cage is not used, the bearing is called a full roller bearing. The rocker arm full roller bearing 50 supports the outer ring 4 so that the roller 4 rotates while contacting the cam 6, and the pressing force and impact force of the cam 6 act on the outer ring 4. The rocker arm structure in the present embodiment includes the rocker arm full roller bearing 50 and the rocker arm 1.

  FIG. 3 is a view showing a cam follower with a roller of an engine according to another embodiment of the present invention. In this cam follower, a rocker arm full roller bearing 50 is disposed between one end 1a and the other end 1b of a rocker arm 1 made of steel. The rolling bearing 50 includes a roller shaft 2 corresponding to an inner ring, rollers 3 as rolling elements, and a roller 4 corresponding to an outer ring.

  The roller shaft 2 is fixed by inserting both ends into roller shaft holes (not shown) formed in each of the side walls on both sides of the rocker arm 1. A roller 4 is rotatably supported at the center of the outer peripheral surface of the roller shaft 2 via a roller 3. The axial direction of the roller 3 is arranged parallel to the axis of the roller shaft 2. The outer peripheral surface of the roller 4 is in contact with the cam surface of the cam 6 provided on the cam shaft by the urging force of the spring 10.

  The other end 1b of the rocker arm 1 is in contact with the end of the valve 9 for opening and closing the engine, and a pivot hole 15 is provided in order to contact a pivot (not shown) with one end 1a. The rocker arm 1 is urged by a spring 10 in a predetermined direction around the pivot, receives the driving force transmitted from the cam 6 by the roller 4, and moves the valve 9 against the urging force of the spring 10.

  FIG. 4 is a view showing a cam follower with a roller of an engine according to still another embodiment of the present invention. FIG. 5 is an enlarged view of a portion including the rocker arm rolling bearing of FIG. Referring to FIG. 4, a rocker arm shaft 5 is disposed at a central portion located between one end 1 a and the other end 1 b of the steel rocker arm 1, and the rocker arm shaft 5 is the center. A rocker arm 1 is supported. The other end 1 b of the rocker arm 1 is in contact with the end of the opening / closing valve 9 of the engine, and one end 1 a is in contact with one end of the interlocking rod 16. An adjustment screw 8 is attached to one end 1 a of the rocker arm 1. The adjustment screw 8 has a function of adjusting the contact position between one end 1 a of the rocker arm 1 and the interlocking rod 16.

  A hollow bearing mounting portion 16 a is located at the other end portion (lower end in the figure) of the interlocking rod 16. A rocker arm full roller bearing 50 is mounted to the bearing mounting portion 16 a by a mounting member 17.

  Referring to FIG. 5, this rolling bearing 50 includes a roller shaft 2 corresponding to an inner ring, a roller 3 that is a rolling element, and a roller 4 that corresponds to an outer ring. Both ends of the roller shaft 2 are fixed to the mounting member 17. A roller 4 is rotatably supported at the center of the outer peripheral surface of the roller shaft 2 via a roller 3. The axial direction of the roller 3 is arranged parallel to the axis of the roller shaft 2.

  Referring to FIG. 4, the outer peripheral surface of roller 4 is in contact with the cam surface of cam 6 by the urging force of spring 10, and cam 6 is in contact with roller 4 of rolling bearing 50 as shown in FIG. Then, the driving force is transmitted to the interlocking rod 16. The driving force of the cam shaft having the cam 6 is transmitted to the rocker arm 1 by the interlocking rod 16.

  Of the members constituting the full roller bearing 50 of the cam follower with roller of each engine shown in FIGS. 1 to 5, the roller 3 as a rolling element, the roller shaft 2 corresponding to the inner ring, and the roller 4 corresponding to the outer ring At least one member is made of steel, and is subjected to a heat treatment of a low-temperature secondary quenching method to be described below to form fine austenite grains.

  Next, heat treatment including carbonitriding performed on at least one bearing part of the outer ring (roller), inner ring (roller shaft) and rolling element of the rolling bearing will be described. FIG. 6 is a diagram for explaining a heat treatment method according to the embodiment of the present invention. Moreover, FIG. 7 is a figure explaining the modification of the heat processing method in embodiment of this invention.

FIG. 6 is a heat treatment pattern showing a method of performing the primary quenching and the secondary quenching, and FIG. 7 is a method in which the material is cooled to below the A ₁ transformation point temperature during quenching, and then reheated and finally quenched. It is the heat processing pattern which shows. Both are exemplary embodiments of the present invention.

Referring to FIG. 6, first, for example, steel for bearing parts is heated to a carbonitriding temperature (for example, 845 ° C.) exceeding the A ₁ transformation point, and carbon for the bearing parts is subjected to carbonitriding at that temperature. The In the temperature treatment T ₁ , carbon and nitrogen are diffused in the steel base, and the carbon is sufficiently dissolved in the steel. Thereafter, the steel for bearing parts is subjected to oil quenching from the temperature of treatment T ₁ and cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 180 ° C., but this tempering can be omitted.

Thereafter, the steel for the bearing component is reheated to a temperature lower than the temperature of the carbonitriding process (for example, 800 ° C.) at a temperature equal to or higher than the A ₁ transformation point, and the process T ₂ is performed by holding at that temperature. After that, oil quenching is performed from the temperature of the treatment T ₂ , and it is cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 180 ° C.

Referring to FIG. 7, first, for example, steel for bearing parts is heated to a carbonitriding temperature (for example, 845 ° C.) exceeding the A ₁ transformation point, and carbon for the bearing parts is subjected to carbonitriding at that temperature. The In the temperature treatment T ₁ , carbon and nitrogen are diffused in the steel base, and the carbon is sufficiently dissolved in the steel. Thereafter, the steel for bearing parts is not quenched and cooled to a temperature below the A ₁ transformation point. Thereafter, the steel for the bearing component is reheated to a temperature lower than the temperature of the carbonitriding process (for example, 800 ° C.) at a temperature equal to or higher than the A ₁ transformation point, and the process T ₂ is performed by holding at that temperature. After that, oil quenching is performed from the temperature of the treatment T ₂ , and it is cooled to a temperature below the A ₁ transformation point. Tempering is then performed at 180 ° C.

  The above heat treatment can improve the cracking strength and reduce the aging dimensional change rate while carbonitriding the surface layer portion, rather than normal quenching (ie, quenching as it is after the carbonitriding process). As described above, according to the heat treatment method described above, it is possible to obtain a microstructure in which the austenite crystal grains have a particle size of 1/2 or less of the conventional one. Rolling bearings using bearing parts that have undergone the above heat treatment have a long rolling fatigue life characteristic, can improve crack strength, and can also reduce the rate of change over time.

  In either of the heat treatments described above, a nitrogen-enriched layer that is a “carbonitriding layer” is formed on the surface by carbonitriding. Since the carbon concentration of steel used as a material in the carbonitriding process is high, carbon may not easily enter the steel surface from the normal carbonitriding process atmosphere. For example, in the case of steel with a high carbon concentration (steel of about 1% by mass), a carburized layer with a higher carbon concentration may be generated, or a carburized layer with a higher carbon concentration may be difficult to generate. However, although the nitrogen concentration depends on the Cr concentration, etc., it is as low as 0.025% by mass or less for normal steel, so a nitrogen-enriched layer is clearly formed regardless of the carbon concentration of the raw steel. The Needless to say, the nitrogen-enriched layer may be enriched with carbon.

  The amount of retained austenite in the nitrogen-enriched layer is 11% by volume or more and 25% by volume or less, and the nitrogen content is in the range of 0.1% by mass or more and 0.7% by mass or less. The surface hardness in the nitrogen-enriched layer is in the range of HV653 or more, and the area ratio of the spheroidized carbide in the nitrogen-enriched layer is in the range of 10% to 25%.

  FIG. 8A shows a microstructure showing the austenite grain size of the bearing steel to which the heat treatment pattern shown in FIG. 6 is applied. For comparison, FIG. 8B shows a microstructure showing the austenite grain size of bearing steel by a conventional heat treatment method. FIGS. 9 (a) and 9 (b) show the austenite crystal grain sizes illustrated in FIGS. 8 (a) and 8 (b). From the structure showing the austenite grain size, the conventional austenite grain size is No. 10 in the JIS standard grain size number, and according to the heat treatment method of the present invention, No. 12 fine grains can be obtained in a range exceeding No. 10. it can. Moreover, the average particle diameter of Fig.8 (a) was 5.6 micrometers as a result of measuring by the intercept method.

  Next, examples of the present invention will be described.

Example 1
A bearing for a rolling fatigue test was manufactured using JIS standard SUJ2. The bearing was a full roller type needle bearing used for a rocker arm. The inner ring had an outer diameter φ14.64 mm × width L 17.3 mm, and the outer ring had an inner diameter φ18.64 mm × outer diameter φ24 mm × width L6.9 mm. The rollers used were 26 rollers with an outer diameter of φ2 mm and a length of L6.8 mm, and had a full roller type configuration without using a cage. The basic dynamic load rating of this bearing is 8.6 kN, and the basic static load rating is 12.9 kN.

  The manufacturing history of each test bearing is as follows.

  Test bearing No. 1-3 (Invention Example): In the heat treatment pattern shown in FIG. 6, the carbonitriding temperature was 850 ° C. and the holding time was 150 minutes. The atmosphere at that time was a mixed gas of RX gas and ammonia gas. At that time, test bearing No. The processing was performed by changing the mixing ratio of RX gas and ammonia gas in 1 to 3. Thereafter, in the heat treatment pattern shown in FIG. 6, primary quenching is performed from a carbonitriding temperature of 850 ° C., followed by secondary quenching by heating at a temperature 800 ° C. lower than the carbonitriding temperature, and then at 180 ° C. Tempering was performed for 90 minutes.

  Test bearing No. 4 (Comparative example): Standard heat treatment was performed. That is, in an RX gas atmosphere, heating was performed at a heating temperature of 840 ° C. and a holding time of 20 minutes, followed by quenching, and then tempering at 180 ° C. for 90 minutes.

  Test bearing No. 5, 6 (comparative example): Carbonitriding was performed. That is, heating was performed in a mixed gas atmosphere of RX gas and ammonia gas at a heating temperature of 850 ° C. and a holding time of 150 minutes. At that time, test bearing No. 5 and 6 were performed by changing the mixing ratio of RX gas and ammonia gas. Then, it hardened from 850 degreeC and then tempered at 180 degreeC for 90 minutes.

  Test bearing No. manufactured by each manufacturing method described above. Table 1 shows the material investigation results and function evaluation test results of the inner rings 1-6.

  Next, a material investigation method and a function evaluation test method will be described.

(1) Austenite grain size The austenite grain size was measured based on the austenite grain size test method for steel of JIS G 0551.

(2) Amount of retained austenite The amount of retained austenite was measured by comparing the diffraction intensities of martensite α (211) and retained austenite γ (220) by X-ray diffraction. As the amount of retained austenite, the value at the surface layer of 50 μm of the rolling surface after grinding was adopted.

(3) Nitrogen content The nitrogen content was measured using EPMA. For the nitrogen content, the value at the surface layer of 50 μm of the rolling surface after grinding was adopted.

(4) Surface hardness The surface hardness was measured using a Vickers hardness meter (1 kgf).

(5) Area ratio of spheroidized carbide The area ratio of spheroidized carbide was measured by observation with an optical microscope (400 times) after corrosion using a picric acid alcohol solution (picral). As the area ratio of the spheroidized carbide, the value at the surface layer of 50 μm of the rolling surface after grinding was adopted.

(6) Rolling fatigue life The rolling fatigue life was performed under the test conditions shown in Table 2 using the test test apparatus shown in FIG. The test apparatus shown in FIG. 10 is an outer ring rotating test apparatus. Referring to FIG. 10, a configuration in which a plurality of needle rollers 53 (3) are arranged so as to roll between an inner ring 52 (2) and an outer ring 54 (4) incorporated in the testing machine is used. A rolling fatigue test was performed by rotating the outer ring 54 at a predetermined speed while applying a radial load by the members 55 and 56.

(7) Static crack strength test Using the outer ring of the test bearing, a static crack strength test was performed by applying a load with an Amsler tester alone.

(8) Crack fatigue strength test A crack fatigue strength test was conducted under the test conditions shown in Table 3 using the outer ring of the test bearing.

  The results of the rolling fatigue life test, static crack strength test, and crack fatigue strength test are shown in the standard heat-treated product No. The value of 4 was set to 1, and the result of each test bearing was expressed as a ratio.

  The test results shown in Table 1 will be described.

(1) Austenite crystal grain size 1-3 are remarkably refined with a grain size number of 11-12. Standard heat treated product and conventional carbonitrided product No. Nos. 4 to 6 are austenite grains having a grain size number of 8 to 9 and coarser than those of the present invention.

(2) Amount of retained austenite The amount of retained austenite of 1 to 3 is 12 to 24% by volume, and moderate austenite is present in these samples. Standard heat treatment No. The amount of retained austenite 4 is 8% by volume, which is less than that of the present invention. In addition, the conventional carbonitriding product No. The amount of retained austenite of 5 and 6 is 29% by volume and 36% by volume, which is larger than that of the present invention. The austenite amount of the product of the present invention is the amount of retained austenite between the standard heat treated product and the conventional carbonitrided product.

(3) Nitrogen content Product No. The nitrogen content of 1 to 3 is 0.12 to 0.62% by mass. Standard heat treatment No. Since no carbonitriding treatment was performed on No. 4, the nitrogen content was 0%. In addition, the conventional carbonitriding product No. The nitrogen contents of 5 and 6 were 0.31% by mass and 0.70% by mass. The nitrogen content of the product of the present invention tended to be slightly lower than that of the conventional carbonitrided product. This is because the product of the present invention performs secondary quenching at a temperature of 800 ° C. lower than the carbonitriding temperature after conventional carbonitriding.

(4) Surface hardness This product No. The surface hardness of 1-3 is HV730-780. Standard heat treatment No. 4 is HV740. In addition, the conventional carbonitriding product No. Nos. 5 and 6 are HV760 and HV650. Regarding No. 6, the amount of retained austenite is too large and the hardness is not obtained.

(5) Area ratio of spheroidized carbide The area ratio of the spheroidized carbides in 1 to 3 is 11.4 to 13.6%. Standard heat treated product and conventional carbonitrided product No. The area ratios of spheroidized carbides in 4, 5, and 6 are 7.9%, 9.6%, and 8.8%. Compared with the standard heat-treated product and the conventional carbonitrided product, the product of the present invention has a larger area ratio of the spheroidized carbide, is refined, and has a larger amount. This is because the product of the present invention performs secondary quenching at a temperature of 800 ° C. lower than the carbonitriding temperature after conventional carbonitriding.

(6) Rolling fatigue life test No. 1-3 are standard heat-treated products No. Compared with No. 4, it has a rolling fatigue life of 3 times or more. Compared with 5, 6, it has a rolling fatigue life of 1.5 times or more. In addition, carbonitrided product No. Nos. 5 and 6 are standard heat treated product Nos. Compared to 4, it has a rolling fatigue life slightly less than twice.

(7) Static crack strength test The static crack strength of Nos. 1 to 3 is the standard heat treated product No. Compared to 4, it is equivalent or slightly improved. In addition, carbonitrided product No. In Nos. 5 and 6, the standard heat treatment product No. Compared to 4, the static crack strength is reduced. This is considered to be caused by the coarsening of the nitrogen-enriched layer and austenite crystal grains in the surface layer portion.

(8) Crack fatigue strength test 1-3 are standard heat-treated products No. Compared to 4, it is improved by 20% or more. In addition, carbonitrided product No. Nos. 5 and 6 are standard heat-treated product Nos. Compared to 4, it is improved by 20% or more. This is considered to be caused by the formation of compressive residual stress in the surface layer due to the penetration of nitrogen into the surface.

  In summary, the product No. 1 to 3 have a nitrogen-enriched layer in the surface layer portion, have austenite crystals refined to a particle size number of 11 or more (greater than 10), have moderately retained austenite, and have an appropriate surface Since it has hardness and the area ratio of spheroidized carbide is large, the usual load-dependent rolling fatigue life and crack fatigue strength are improved.

(Example 2)
Peeling and smearing specimens were manufactured using JIS standard SUJ2. The test piece had an outer diameter of φ40 mm × width L12. The manufacturing history of each test bearing is as follows.

  Test bearing No. 1 (Invention Example): In the heat treatment pattern shown in FIG. 6, the carbonitriding temperature was 850 ° C. and the holding time was 150 minutes. The atmosphere at that time was a mixed gas of RX gas and ammonia gas. Thereafter, in the heat treatment pattern shown in FIG. 6, primary quenching is performed from a carbonitriding temperature of 850 ° C., followed by secondary quenching by heating at a temperature 800 ° C. lower than the carbonitriding temperature, and then at 180 ° C. Tempering was performed for 90 minutes.

  Test bearing No. 2 (Comparative example): Standard heat treatment was performed. That is, in an RX gas atmosphere, heating was performed at a heating temperature of 840 ° C. and a holding time of 20 minutes, followed by quenching, and then tempering at 180 ° C. for 90 minutes.

  Test bearing No. 3 (Comparative example): Carbonitriding was performed. That is, after heating in a mixed gas atmosphere of RX gas and ammonia gas at a heating temperature of 850 ° C. and a holding time of 150 minutes, quenching was performed from 850 ° C., and then tempering was performed at 180 ° C. for 90 minutes.

  Table 4 shows the results of the material investigation, the peeling test, and the smearing test of the test piece manufactured by the manufacturing method.

  Next, the function evaluation test method will be described.

(1) Peeling test Generated on the test piece when the test piece and the counterpart test piece are brought into rolling contact under the test conditions shown in Table 5 with a standard heat treatment product of JIS standard SUJ2 having a rough surface as the counterpart test piece. The area ratio of peeling (aggregate of fine peeling) to be measured was measured as peeling strength. The peel strength ratio is the standard heat treatment product No. The value of 2 was set to 1, and the result of each test bearing was represented by the reciprocal of the ratio.

(2) Smearing test Under the test conditions shown in Table 6, both the test piece and the counterpart test piece were made of the same material in rolling contact with each other, and the rotational speed of only the test piece was increased at a constant rate. In this case, the relative rotation speed between the test pieces at the moment when the generated sound became larger than a certain value was defined as the smearing strength. The smearing strength ratio is the standard heat treatment product no. The value of 2 was set to 1, and the result of each test bearing was expressed as a ratio.

  The test results shown in Table 4 will be described.

(1) Peeling test Product No. No. 1 is a standard heat treatment product No. Compared with No. 2, it has a peeling strength of 1.8 times. Compared to 3, it is the same or slightly improved. This has a nitrogen-enriched layer in the surface layer part, the austenite crystal is refined to a grain size number of 11 or more, the amount of retained austenite is moderately, it has an appropriate surface hardness, and the area of spheroidized carbide A large ratio is considered to have increased toughness and resistance to crack initiation and propagation.

(2) Smearing test Product No. No. 1 is a standard heat treatment product No. Compared with No. 2, it has 1.7 times the smearing strength. Compared to 3, it is the same or slightly improved. This has a nitrogen-enriched layer in the surface layer part, the austenite crystal is refined to a grain size number of 11 or more, the amount of retained austenite is moderately, it has an appropriate surface hardness, and the area of spheroidized carbide A large ratio is considered to suppress the plastic flow of the surface layer under large sliding conditions and to improve the seizure resistance.

  In summary, the product No. No. 1 is better than conventional bearing materials in both peeling test and smearing test.

  In addition, the lubrication conditions are poor, the rollers interfere with each other, the roller position is not controlled smoothly, and the surface damage life due to roller skew is improved.

  The product of the present invention has a nitrogen-enriched layer in the surface layer part, the austenite crystal is refined to a particle size number of 11 or more, the amount of retained austenite is moderately, the surface hardness is appropriate, and the spheroidized carbide Therefore, the resistance to the occurrence and development of cracks is very large, and the generation of surface cracks due to surface heat generation and tangential force due to sliding can be suppressed.

(Example 3)
Using JIS standard SUJ2 material (1.0% by mass C-0.25% by mass Si-0.4% by mass Mn-1.5% by mass Cr), (1) measurement of hydrogen content, (2) crystal grain size (3) Charpy impact test, (4) Fracture stress value measurement, and (5) Rolling fatigue test. Table 7 shows the results.

  The manufacturing history of each sample is as follows.

  Samples A to D (examples of the present invention): In the heat treatment pattern shown in FIG. 6, the carbonitriding temperature was 850 ° C., and the holding time was 150 minutes. The atmosphere at that time was a mixed gas of RX gas and ammonia gas. In the heat treatment pattern shown in FIG. 6, primary quenching was performed from a carbonitriding temperature of 850 ° C., followed by secondary quenching by heating to a temperature range of 780 ° C. to 830 ° C. lower than the carbonitriding temperature. However, Sample A having a secondary quenching temperature of 780 ° C. was excluded from the test because of insufficient quenching.

  Samples E and F (comparative examples): The carbonitriding treatment was carried out with the same history as the invention examples A to D, and the secondary quenching temperature was 850 ° C to 870 ° C, which is a carbonitriding temperature of 850 ° C or higher.

  Conventional carbonitrided product (comparative example): Carbonitriding was performed. That is, after heating at a heating temperature of 850 ° C. and a holding time of 150 minutes in a mixed gas atmosphere of RX gas and ammonia gas, quenching was performed as it was from the carbonitriding temperature of 850 ° C., and secondary quenching was not performed.

  Normal quenching product (comparative example): without any carbonitriding treatment, it was quenched by heating to 850 ° C. Secondary quenching was not performed.

  Next, the test method will be described.

(1) Measurement of hydrogen amount The amount of hydrogen was determined by analyzing the amount of non-diffusible hydrogen in the steel using a DH-103 type hydrogen analyzer manufactured by LECO. The amount of diffusible hydrogen is not measured. The specification of this LECO DH-103 type hydrogen analyzer is shown below.

Analysis range: 0.01 to 50.00 ppm
Analysis accuracy: ± 0.1 ppm or ± 3% H (whichever is greater)
Analysis sensitivity: 0.01ppm
Detection method: Thermal conductivity method Sample weight size: 10 mg to 35 mg (maximum: diameter 12 mm × length 100 mm)
Heating furnace temperature range: 50 ° C to 1100 ° C
Reagents: Anhydrone Mg (ClO ₄ ) ₂ , Ascarite NaOH
Carrier gas: nitrogen gas, gas dosing gas: hydrogen gas, both gases have a purity of 99.99% or more and a pressure of 40 psi (2.8 kgf / cm ² ).

  The outline of the measurement procedure is as follows. A sample collected with a dedicated sampler is inserted into the hydrogen analyzer together with the sampler. Internal diffusible hydrogen is directed to the thermal conductivity detector by a nitrogen carrier gas. This diffusible hydrogen is not measured in this example. Next, a sample is taken out from the sampler, heated in a resistance heating furnace, and non-diffusible hydrogen is guided to the thermal conductivity detector by nitrogen carrier gas. The amount of non-diffusible hydrogen can be known by measuring the thermal conductivity with a thermal conductivity detector.

(2) Measurement of crystal grain size The crystal grain size was measured based on the JIS G 0551 steel austenite grain size test method.

(3) Charpy impact test The Charpy impact test was performed based on the Charpy impact test method of the metal material of JIS Z2242. As a test piece, a U-notch test piece (JIS No. 3 test piece) shown in JIS Z 2202 was used.

(4) Measurement of Fracture Stress Value FIG. 11 is a diagram showing a test piece for a static crush strength test (measurement of a fracture stress value). The load until it is broken by applying a load in the P direction in the figure is measured. Thereafter, the obtained fracture load is converted into a stress value by the following bending beam stress calculation formula. In addition, a test piece is not restricted to the test piece shown in FIG. 11, You may use the test piece of another shape.

Sigma ₁ a fiber stress on the convex surface of the test piece of Figure 11, when the fiber stress and sigma ₂ in concave surface, sigma ₁ and sigma ₂ is determined by the following formula (Mechanical Engineering Handbook A4 Part material Mechanics A4-40) . Here, N is the axial force of the cross section including the axis of the annular specimen, A is the cross-sectional area, e ₁ is the outer radius, and e ₂ is the inner radius. Further, κ is a section modulus of the curved beam.

σ ₁ = (N / A) + {M / (Aρ ₀ )} [1 + e ₁ / {κ (ρ ₀ + e ₁ )}]
σ ₂ = (N / A) + {M / (Aρ ₀ )} [1-e ₂ / {κ (ρ ₀ −e ₂ )}]
κ = − (1 / A) ∫A {η / (ρ ₀ + η)} dA
(5) Rolling fatigue life Table 8 shows the test conditions for the rolling fatigue life test. FIG. 12 is a schematic view of a rolling fatigue life tester. FIG. 12A is a front view, and FIG. 12B is a side view. In FIG. 12A and FIG. 12B, the rolling fatigue life test piece 31 is driven by the drive roll 21 and rotates in contact with the ball 23. The ball 23 is a 3/4 inch ball and is guided by the guide roll 22 to roll while exerting a high surface pressure with the rolling fatigue life test piece 31.

  The test results shown in Table 1 will be described as follows.

(1) Amount of hydrogen Conventional carbonitrided products that have undergone carbonitriding have a very high value of 0.72 ppm. This is thought to be because ammonia (NH ₃ ) contained in the carbonitriding atmosphere decomposed and hydrogen entered the steel. On the other hand, in Samples B to D, the hydrogen content is reduced to almost half of 0.37 to 0.40 ppm. This amount of hydrogen is at the same level as that of ordinary hardened products.

  By reducing the amount of hydrogen described above, embrittlement of steel due to hydrogen solid solution can be reduced. That is, the reduction in the amount of hydrogen greatly improves the Charpy impact value of Samples B to D of the present invention example.

(2) Crystal grain size When the secondary quenching temperature is lower than the quenching (primary quenching) temperature during carbonitriding, that is, in the case of Samples B to D, the austenite grains are prominent as the grain size numbers 11 to 12. Has been refined. The austenite grains of the samples E and F, the conventional carbonitrided product and the normal quenching product have a crystal grain size number 10, and are coarser than the samples B to D of the examples of the present invention.

(3) Charpy impact test According to Table 1, the Charpy impact value of the samples B to D of the present invention example is 6 compared to the Charpy impact value of the conventional carbonitrided product being 5.33 J / cm ^2. A high value of .30 to 6.65 J / cm ² is obtained. Among these, the one where secondary quenching temperature is low shows the tendency for a Charpy impact value to become high. The normally hardened product has a high Charpy impact value of 6.70 J / cm ² .

(4) Measurement of fracture stress value The fracture stress value corresponds to the crack resistance strength. According to Table 1, the conventional carbonitrided product has a fracture stress value of 2330 MPa. Compared to this, the fracture stress values of Samples B to D were improved to 2650 to 2840 MPa. The fracture stress value of the normal quenching product is 2770 MPa, and the improved cracking resistance strength of Samples B to D is estimated to have a great effect by reducing the hydrogen content, along with the refinement of austenite crystal grains.

(5) According to the rolling contact fatigue test Table 1, normally hardened product to reflect to have no carbonitrided layer in the surface layer portion, the rolling fatigue life L ₁₀ is the lowest. Compared to this, the rolling fatigue life of the conventional carbonitrided product is 3.1 times. The rolling fatigue life of Samples B to D is significantly improved as compared with the conventional carbonitrided product. Samples E and F are almost equivalent to conventional carbonitrided products.

  In summary, Samples B to D of the present invention have a reduced hydrogen content, an austenite crystal grain size of 11 or more, and improved Charpy impact value, crack resistance strength and rolling fatigue life. .

Example 4
Next, Example 4 will be described. A series of tests were performed on the following X material, Y material, and Z material. JIS standard SUJ2 material (1.0% by mass C-0.25% by mass Si-0.4% by mass Mn-1.5% by mass Cr) is used for the material for heat treatment, which is common to X material to Z material. did. The manufacturing history of the X material to the Z material is as follows.

  X material (comparative example): Only normal quenching (not carbonitriding).

  Y material (comparative example): quenching directly after carbonitriding (conventional carbonitriding quenching). The carbonitriding temperature was 845 ° C. and the holding time was 150 minutes. The atmosphere of the carbonitriding process was a mixed gas of RX gas and ammonia gas.

  Z material (example of the present invention): bearing steel subjected to the heat treatment pattern of FIG. The carbonitriding temperature was 845 ° C. and the holding time was 150 minutes. The carbonitriding atmosphere was a mixed gas of RX gas and ammonia gas. The final quenching temperature was 800 ° C.

(1) Rolling fatigue life Test conditions and test equipment for rolling fatigue life are as shown in Table 8 and FIG. 12, as described above. The rolling fatigue life test results are shown in Table 9.

According to Table 9, the Y material of the comparative example shows 3.1 times the L ₁₀ life of the X material that has been subjected only to normal quenching in the comparative example (the life that one of the 10 test pieces breaks), The effect of extending the life by carbonitriding is recognized. On the other hand, the Z material of the example of the present invention has a long life of 1.74 times that of the Y material and 5.4 times that of the X material. The main reason for this improvement is thought to be the refinement of the microstructure.

(2) Charpy impact test The Charpy impact test was performed by the method according to the above-mentioned JIS Z 2242 using the U notch test piece. The test results are shown in Table 10.

  The Charpy impact value of the Y material (comparative example) subjected to carbonitriding was not higher than that of the normal quenching X material (comparative example), but the Z material obtained the same value as the X material.

(3) Test of Static Fracture Toughness Value FIG. 13 is a diagram showing a test piece of a static fracture toughness test. About 1 mm of pre-crack was introduced into the notch portion of the test piece, and then a static load by three-point bending was applied to determine the fracture load P. The following formula (I) was used for calculation of the fracture toughness value (K ₁ c value). The test results are shown in Table 11.

K ₁ c = (PL√a / BW ² ) {5.8−9.2 (a / W) +43.6 (a / W) ² −75.3 (a / W) ³ +77.5 (a / W) ⁴ } (I)

  Since the precrack depth is larger than the carbonitrided layer depth, there is no difference between the X material and the Y material of the comparative example. However, the Z material of the present invention example was able to obtain a value about 1.2 times that of the comparative example.

(4) Static Crush Strength Test A static crush strength test piece having the shape shown in FIG. 11 was used as described above. In the figure, a static crushing strength test was performed by applying a load in the P direction. The test results are shown in Table 12.

  The Y material subjected to carbonitriding has a slightly lower value than the normal quenching X material. However, the Z material of the present invention has higher static crushing strength than the Y material, and a level comparable to that of the X material is obtained.

(5) Aged dimensional change rate The measurement results of the aged dimensional change rate at a holding temperature of 130 ° C. and a holding time of 500 hours are shown in Table 13 together with the surface hardness and the retained austenite amount (50 μm depth).

  It can be seen that the Z material of the example of the present invention is suppressed to half or less compared to the dimensional change rate of the Y material having a large amount of retained austenite.

(6) Rolling life test under the presence of foreign matter Using a ball bearing 6206, the rolling fatigue life under the presence of foreign matter mixed with a predetermined amount of standard foreign matter was evaluated. Table 14 shows the test conditions and Table 15 shows the test results.

  Compared to the X material, the Y material subjected to the conventional carbonitriding treatment is about 2.5 times longer, and the Z material of the present invention example has a long life of about 2.3 times. Although the Z material of the present invention has less retained austenite than the Y material of the comparative example, a substantially equivalent long life is obtained due to the intrusion of nitrogen and the effect of the refined microstructure.

  From the above results, the Z material, that is, the present invention example, simultaneously satisfies the three items of the rolling fatigue life extension, crack strength improvement, and reduction of aging dimensional change rate, which were difficult in the conventional carbonitriding process. I found out that I can do it.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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.

  INDUSTRIAL APPLICABILITY The present invention can be particularly advantageously applied to a rocker arm structure having a rocker arm used for opening and closing an intake valve and an exhaust valve of an automobile engine and a rolling bearing used for the rocker arm.

It is a figure which shows the cam follower with a roller of the engine in embodiment of this invention. It is sectional drawing which follows the II-II line in FIG. It is a figure which shows the cam follower with a roller of the engine in other embodiment of this invention. It is a figure which shows the cam follower with a roller of the engine in other embodiment of this invention. It is an enlarged view of the part of the full roller bearing which contacts the cam of the cam follower with a roller of the engine of FIG. It is a figure explaining the heat processing method in embodiment of this invention. It is a figure explaining the modification of the heat processing method in embodiment of this invention. It is a figure which shows the microstructure of a bearing component, especially an austenite grain. (A) is a bearing component of the present invention example, and (b) is a conventional bearing component. (A) shows the austenite grain boundary illustrated in FIG. 8 (a), and (b) shows the austenite grain boundary illustrated in FIG. 8 (b). It is a figure which shows the rolling fatigue testing machine of outer ring | wheel rotation. It is a figure which shows the test piece of a static crushing strength test (measurement of a fracture stress value). It is the schematic of a rolling fatigue life tester. (A) is a front view, (b) is a side view. It is a figure which shows the test piece of a static fracture toughness test.

Explanation of symbols

  1 Rocker arm, 1a One end, 1b The other end, 2 Roller shaft (inner ring), 3 Roller (rolling element), 4 Roller (outer ring), 5 Rocker arm shaft, 6 Cam, 7 Adjustment screw, 8 Lock Nut, 9 Engine valve, 10 Spring, 14 Roller support part, 15 Pivot hole, 16 Interlocking rod, 16a Bearing mounting part, 17 Mounting member, 21 Drive roll, 22 Guide roll, 23 Ball, 31 Rolling fatigue life test piece, 50 Rolling bearing, 52 Inner ring, 54 Outer ring, 55 Member.

Claims (8)

A rolling bearing comprising a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring located inside the outer ring, and a plurality of rolling elements interposed between the outer ring and the inner ring. And a rocker arm structure having a steel rocker arm,
The rocker arm is attached to a rocker arm shaft positioned between one end and the other end, the one end of the rocker arm is provided with a bifurcated inner ring support, and the other The end of the valve for opening and closing the engine contacts the end, and the shaft corresponding to the inner ring is fixed to the bifurcated inner ring support part,
A rocker arm structure in which at least one member of the outer ring, the inner ring, and the rolling element has a nitrogen-enriched layer, and the grain size number of the austenite crystal grains in the nitrogen-enriched layer is in a range exceeding 10. A rolling bearing comprising a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring located inside the outer ring, and a plurality of rolling elements interposed between the outer ring and the inner ring. And a rocker arm structure having a steel rocker arm,
A pivot is in contact with one end of the rocker arm, the rolling bearing is provided between the one end and the other end of the rocker arm, and the other end is The end of the valve for opening and closing the engine is in contact,
A rocker arm structure in which at least one member of the outer ring, the inner ring, and the rolling element has a nitrogen-enriched layer, and the grain size number of the austenite crystal grains in the nitrogen-enriched layer is in a range exceeding 10. A rolling bearing comprising a roller corresponding to an outer ring that is in rolling contact with a camshaft of an engine, a shaft corresponding to an inner ring located inside the outer ring, and a plurality of rolling elements interposed between the outer ring and the inner ring. And a rocker arm structure having a steel rocker arm,
The rocker arm is attached to a rocker arm shaft positioned between one end and the other end, and one end of an interlocking rod that transmits a force from the cam shaft to the one end of the rocker arm. An end portion is in contact, the other end portion is in contact with an end portion of the opening / closing valve of the engine, and the other end portion of the interlocking rod is provided with the rolling bearing,
A rocker arm structure in which at least one member of the outer ring, the inner ring, and the rolling element has a nitrogen-enriched layer, and the grain size number of the austenite crystal grains in the nitrogen-enriched layer is in a range exceeding 10.   The rocker arm structure according to any one of claims 1 to 3, wherein the amount of retained austenite in the nitrogen-enriched layer is in a range of 11 vol% or more and 25 vol% or less.   The rocker arm structure according to any one of claims 1 to 4, wherein a nitrogen content in the nitrogen-enriched layer is in a range of 0.1 mass% or more and 0.7 mass% or less.   The rocker arm structure according to any one of claims 1 to 5, wherein a surface hardness of the nitrogen-enriched layer is in a range of HV653 or more.   The rocker arm structure according to any one of claims 1 to 6, wherein the area ratio of the spheroidized carbide in the nitrogen-enriched layer is in the range of 10% to 25%.   The rocker arm structure according to any one of claims 1 to 7, wherein the rolling bearing is a full-roller type needle bearing.

Images