CN1993561A - Rolling bearing for rocker arm - Google Patents

Abstract

A rolling bearing (50) for a rocker arm, comprising a roller (4) in rolling contact with the cam (6) of an engine, a roller shaft (2) positioned on the inside of the roller (4) and fixed to the rocker arm (1), and a plurality of rollers (3) interposed between the roller (4) and the roller shaft (2). At least one member of the roller (4), the roller shaft (2), and the rollers (3) comprises a nitrogen-enriched layer, the grain size number of the austenitic crystal grain of the member is within the range of exceeding 10, and the surface hardness Hv of the member is 653 or higher. Thus, the life of the rolling bearing can be increased.

Description

Rolling bearing for rocker arm

Technical field

The present invention relates to the rolling bearing for rocker arm that a kind of suction valve or outlet valve that is used for car engine opens and closes, especially relate to the rolling bearing for rocker arm that to realize long lifetime.

Background technique

In nearest rolling bearing, the bearing that on the rocking arm that opens and closes at the suction valve or the outlet valve that are used for engine, uses for example, though be full dress roller (Japanese: Gross こ ろ) type have many at a high speed, the bearings that use in the high loading purposes.Especially in not having the full dress roller-type bearing of retainer,, thereby cause the crooked of roller easily because roller produces interference to each other, or can not successfully control roller position.In addition, when lubricant oil can not be well to the bearing internal feed, be easy to generate the situation of poor lubrication.The result is, causes the rising of slippage heating and local surface pressure, although have big load bearing capacity in the calculating, but is easy to generate surface failure (peel off, abrade, surperficial starting point type peel off) and inner starting point type is peeled off.

The bearing that uses on the rocking arm that opens and closes at the suction valve or the outlet valve that are used for engine, in the external diameter of its outer ring and cam rolled the purposes that contact, had a lot mainly was the improving technology that the external diameter of outer ring is improved in the past.For example, the residual stress of the compression that brings of processing such as shot peening, high hardness (processing effect) that high-concentration carburized nitrogenize brings and the long lifetime realized etc. all mainly carry out in order to improve with the object cam outer ring external diameter that contacts that rolls.

In known technology in the past, take following measure.

(1) in order to improve rolling fatigue life, the lasso of bearing part is implemented shot peening, be provided with strengthened layer successively, contain the bearing part (Japanese patent laid-open 2-168022 communique (patent documentation 1)) of retained austenite floor, laser quenching hardened layer from the surface to inside.

(2) technology of size, area ratio, retained austenite amount and the hardness of carbide in the martensitic structure efficiently being adjusted by shot peening (the Japan Patent spy opens 2001-065576 communique (patent documentation 2)).

(3), make the residual compression stress peak height that shot peening causes and the maximum that acts on when using that distributes is cut off stress and the consistent technology (Japanese patent laid-open 3-199716 communique (patent documentation 3)) of depth of interaction in order to improve rolling fatigue life.

(4) in soaking the carbon bearing, implement shot peening in order to realize long lifetime, applying the controlling method that makes residual compression stress σ (MPa) and the combination of retained austenite γ (%) satisfy the condition of 0.001 σ+0.3 γ 〉=1.0 on the surface of final surface finishing.

(5) make the hardness and the object cam of external diameter of cam follower outer ring basic identical, and make the hardness of the internal diameter of outer ring be higher than the cam follower device (rocker arm bearing) (the real flat 3-119508 communique (patent documentation 4) of opening of Japan Patent) of the hardness of external diameter.

(6) rolling in parts of contact or rolling slippage contact with relative another parts, making the maximal compressed stress of the skin section of distance surface 0～50 μ m degree of depth by shot peening is 50～110kgf/mm ², hardness is HV830～960, retained austenite is more than 7%, the technology (Japan special permission No. 3125434 communique (patent documentation 5)) of the mean wavelength of surface roughness below 25 μ m.

Though for the improvement in rolling life-span of prolonging the roll shaft, roller or the bearing integral that are equivalent to inner ring seldom, but as described below, also have from the material aspect by carrying out nitrocarburizing and improve the example that heat resistance, microstructure stability, high hardnessization wait the long lifetime of realizing bearing.

(7) the valve mechanism of engine with cam follower device with bearing (rocker arm bearing) in, make bearing the mathematic(al) expectation under the rated speed of engine the technology more than 1000 hours (the Japan Patent spy opens 2000-038907 communique (patent documentation 6)).

(8) for the ratio of realizing carbide is 10～25%, retained austenite with respect to the mean wavelength that the resolution ratio of initial value is 1/10～3/10, end hardness is HV830～960, surface roughness be cam follower device below the 25 μ m with bearing shaft (rocker arm bearing), and Bearing Steel is implemented the technology (Japanese patent laid-open 10-047334 communique (patent documentation 7)) of nitrocarburizing and hard shot peening.

(9) in order to improve the wearability of axle, on axle, be formed with the cam follower axle (rocker arm bearing parts) (Japanese patent laid-open 10-103339 communique (patent documentation 8)) of solid lubricant film such as polymeric compound.

(10) form, be lower than the cam follower axle (rocker arm bearing parts) (Japanese patent laid-open 10-110720 communique (patent documentation 9)) that obtains high hardness under the temperature of tempering temperature by plasma nitriding or ion plating by tool steel etc.

(11) to the flexural stress of axle be the valve mechanism of the engine below the 150MPa with cam follower device with bearing (rocker arm bearing parts) (the Japan Patent spy opens 2000-038906 communique (patent documentation 10)).

(12) on the roller surface of bearing component parts, be formed with the valve mechanism of engine of the good phosphate coating film of lubricant oil retentivity with cam follower (valve mechanism rolling bearing) (the Japan Patent spy opens 2002-031212 communique (patent documentation 11)).

(13) valve mechanism that is formed with crowning in the roller scroll zones of axle is with cam follower (valve mechanism rolling bearing) (the real clear 63-185917 communique (patent documentation 12) of opening of Japan Patent).

(14) make the concentration of carbon on roller surface top layer of axle be the high concentration of 1.2%～1.7%C soak that carbon is handled or nitrocarburizing handle, make inner hardness be HV300 soak carbon axle (the Japan Patent spy opens 2002-194438 communique (patent documentation 13)).

As the other problems that rocking arm produces, sometimes riveted joint is implemented at the roll shaft two end part and be shaped, thereby be riveted on the roller supporting member.At this moment, the roller surface of roll shaft needs high hardness, but the end need have the ductility that can rivet shaping.In addition, need after the riveted fixing, do not produce lax intensity (hardness) in using.In the device that can rivet shaping to the roll shaft two end part of rocking arm, disclose following technology.

(15) outer circumferential face to roll shaft carries out high frequency hardening equably, after the tempering, only high frequency annealing is carried out at two end part and makes the softening method (Japanese patent laid-open 5-179350 communique (patent documentation 14)) in two end part.

But in recent years, environmental problem is by extensive concern, to the automobile low burnupization of strong request that also begins to make laws.Simultaneously, each parts for constituting engine also require lightweight, compactness.Therefore, the rocking arm for the suction valve or the outlet valve that are used for engine open and close also requires lightweight, compactness, also requires lightweight, compactness for rocker arm bearing naturally.

As making the light-weighted method of bearing, for example specially permit the 4th, 727, disclose a kind of method that inner ring is formed the drum (pipe) of hollow in No. 832 (patent documentation 15) in the U.S., in addition, the compactness method as bearing has the method that reduces bearing size.But the size of bearing reduces to be subjected to the shape of cam and the lift quantitative limitation of valve opening and closing, therefore, can not reduce diameter simply, is to reduce the width direction size of (axially) mostly.Thus, lightweight, the compactness method as bearing all is the size that inner ring is formed the hollow cylinder shape and reduce width direction mostly.

At this, when the lightweight of implementing bearing, compactness, the problem of existence is that the fracture fatigue strength of outer ring or inner ring and the rolling fatigue life of roller or inner ring descend.

Before this, the applicant is by the improvement heat treatment technology, successfully carried out the improvement of fracture fatigue strength and rolling fatigue life to outer ring, roller and by being pressed into or selling the inner ring (inner ring of whole sclerosis) that fixing etc. (beyond the riveted joint processing) be fixed on the rocking arm.Thus, for by the inner ring of riveted joint fixed processing on rocking arm, need to improve fracture fatigue strength and rolling fatigue life.

The applicant has been also successfully to having carried out the improvement of rolling fatigue life by the riveted joint inner ring of fixed processing on rocking arm, but residual technical problem is the improvement of fracture fatigue strength of the inner ring of hollow cylinder shape.

In the past, for passing through the inner ring of riveted joint fixed processing on rocking arm, because of manufacturing procedure increases, so do not use the drum of hollow, and be to use solid drum, in order to rivet processing and only to handle by high frequency heat the roller surface as the roller of rolling element is carried out surface hardening to end face.This technology for example is disclosed in the Japan Patent spy and opens in clear 62-007908 communique (patent documentation 16), the Japanese patent laid-open 5-321616 communique (patent documentation 17) etc.

Similarly, in use during the inner ring of Kong drum, also only handled the roller surface as the roller of rolling element was carried out surface hardening in order to rivet processing in the past by high frequency heat to end face.This technology for example is disclosed in Japanese patent laid-open 3-031503 communique (patent documentation 18), the Japan Patent spy opens in 2000-038906 communique (patent documentation 10) etc.

Especially, compare with the inner ring of solid drum, the flexural stress that the shape of the inner ring of the drum of hollow causes is bigger, therefore a kind of this flexural stress that makes is arranged at 15kgf/mm ²Below to prevent damaged method (opening the 2000-038906 communique) with reference to the Japan Patent spy.But this method can make shape be restricted, thereby hinders lightweight, the compactness of bearing.

In addition, there is the problem of strength deficiency in the inner ring of simple hollow cylinder shape because of above-mentioned reason, so a kind of method to the additional reinforcing material of inside diameter (with reference to the real flat 3-063703 communique (patent documentation 19) of opening of Japan Patent) is arranged.But this method can make manufacturing procedure increase, and comparatively complicated, so the shortcoming that exists the price of bearing to rise.

Patent documentation 1: Japanese patent laid-open 2-168022 communique

Patent documentation 2: the Japan Patent spy opens the 2001-065576 communique

Patent documentation 3: Japanese patent laid-open 3-199716 communique

Patent documentation 4: Japan Patent is opened flat 3-119508 communique in fact

Patent documentation 5: No. 3125434 communique of Japan's special permission

Patent documentation 6: the Japan Patent spy opens the 2000-038907 communique

Patent documentation 7: Japanese patent laid-open 10-47334 communique

Patent documentation 8: Japanese patent laid-open 10-103339 communique

Patent documentation 9: Japanese patent laid-open 10-110720 communique

Patent documentation 10: the Japan Patent spy opens the 2000-038906 communique

Patent documentation 11: the Japan Patent spy opens the 2002-031212 communique

Patent documentation 12: Japan Patent is opened clear 63-185917 communique in fact

Patent documentation 13: the Japan Patent spy opens the 2002-194438 communique

Patent documentation 14: Japanese patent laid-open 5-179350 communique

Patent documentation 15: the U.S. speciallys permit the 4th, 727, No. 832 specifications

Patent documentation 16: the Japan Patent spy opens clear 62-007908 communique

Patent documentation 17: Japanese patent laid-open 5-321616 communique

Patent documentation 18: Japanese patent laid-open 3-031503 communique

Patent documentation 19: Japan Patent is opened flat 3-063703 communique in fact

Disclosure of the Invention

Invent technical problem to be solved

From now on, being used for rolling bearing for rocker arm that suction valve or outlet valve to engine open and close also can be the same with common bearing, constantly advance the lowering viscousity of the speed up when using, big loadization, lubricant oil.The principal element of propping up the life-span that fits over the bearing that uses under this condition also has at the surface failure life-span because of slippage or the not enough Metal Contact that produces of oil film except that the rolling fatigue life of common dependence load type.For the long lifetime of realizing rolling bearing for rocker arm just needs to prolong these life-spans, but also do not make the technology that two life-spans significantly prolong now simultaneously.In addition, the interference and the crooked life-span that causes that also can produce the peculiar roller of full dress roller-type bearing shortens.

Known technology in the past mainly is to utilize high hardness, high compression stress to improve the life-span of rolling, or the rolling surface of improvement and object member.When with these technology practical applications on bearing the time, though this effect in outer ring there is the wearability of diametric plane outside the fatigue strength of purposes of flexural stress and the outer ring effective, and obtained good effect, but only may not necessarily play big effect to the axle that is equivalent to bearing inner race and the prolongation of the rolling fatigue life of roller by these technology.

Therefore, first purpose of the present invention is to provide a kind of rolling bearing for rocker arm of realizing long lifetime.In addition, second purpose of the present invention is to provide a kind of suction valve or outlet valve that is used for engine to open and close, can prolong rolling fatigue life under the service condition of speed up, big loadization, lubricant oil lowering viscousity and the rolling bearing for rocker arm in the surface failure life-span of the surface failure that causes at Metal Contact.

In addition, in recent years, owing to adopted valve lift amount changeable mechanism and valve time changeable mechanism, thus valve mechanism is constantly complicated.In addition, constantly require the lightweight of movable member and engine self.Because these reasons, rocking arm shared space in valve mechanism is restricted.Therefore, also require to be contained in rolling bearing on the rocking arm than compactness in the past.

But if make the rolling bearing for rocker arm compactness, the load that then unit area applied increases, thereby has the problem of life-span decline.Therefore, can not in the compactness of realizing rolling bearing for rocker arm, suppress the reduction in life-span.

Therefore, the 3rd purpose of the present invention is to provide a kind of rolling bearing for rocker arm that can suppress the life-span reduction when realizing compactness.

Moreover, as mentioned above, the bearing for using on the rocking arm that opens and closes at the suction valve or the outlet valve that are used for engine also requires lightweight, compactness, but do not improve by above-mentioned explanation as can be known, the scheme of fracture fatigue strength of the inner ring of hollow cylinder shape.

Therefore, the 4th purpose of the present invention is: the bearing that uses on the rocking arm that opens and closes at the suction valve or the outlet valve that are used for engine provides a kind of and inner ring can be formed the rolling bearing for rocker arm that the hollow cylinder shape realizes lightweight, compactness and can improve fracture fatigue strength and rolling fatigue life.

The technological scheme that is used for the technical solution problem

The rolling bearing for rocker arm of first aspect present invention, comprise: with the camshaft of engine roll the outer ring that contact, the inboard of outer ring and be fixed on the inner ring on the rocking arm and be folded in the outer ring and inner ring between a plurality of rolling elements, at least one member in outer ring, inner ring and the rolling element has nitrogen-enriched layer (Japanese: Chisso richness ), the grain size category of the austenite crystal grain of this member is in surpassing 10 grades scope, and surface hardness Hv is more than 653.

Austenite crystal to above-mentioned member carries out miniaturization, makes its grain size category surpass 10 grades, therefore can significantly improve rolling fatigue life.If the grain size category of austenite particle diameter then can not significantly improve rolling fatigue life below 10 grades, therefore make it in surpassing 10 grades scope.Usually, be preferably more than 11 grades.In addition, also can make the average crystallite particle diameter below 6 μ m.Though the austenite particle diameter is the smaller the better, be difficult to obtain surpassing 13 grades grain size category usually.

Above-mentioned austinite grain size can be tried to achieve by the usual way of JIS regulation, also can convert then by the Mean particle diameter that microtomy etc. is tried to achieve corresponding above-mentioned crystal size grade and try to achieve.Above-mentioned austinite grain size grade is as long as satisfy in nitrogen-enriched layer.But generally, the steel body that is in nitrocarburizing layer inboard also satisfies the benchmark of above-mentioned austenite crystal grain miniaturization.

In addition, so-called austenite crystal grain is meant in quenching and adds the austenitic crystal grain of having pined for taking place phase transformation that still the form (Japanese: carry out Artworks) with the past is remaining after being phase-changed into martensite because of cooling for it.In addition, in this manual, so-called " inner ring " is the meaning that comprises the axle of solid axle and hollow.

In addition, because surface hardness Hv more than 653, therefore can significantly improve rolling fatigue life.If surface hardness Hv is less than 653, then especially foreign matter life-span of sneaking under the condition reduces.Preferably make surface hardness Hv more than 720 and below 800.Though surface hardness Hv is high more good more, if surface hardness Hv surpasses 800, then carbide becomes big easily, may become stress raiser.

(a1) above-mentioned rolling bearing for rocker arm can constitute: the rocking arm rotation is installed in freely on the running shaft between one square end portion and the opposing party end, the switching of one square end portion and engine is with the end butt of valve; rocking arm has two forked inner ring supporting portions in the opposing party end, and the inner ring of rolling bearing for rocker arm of the present invention is fixed on this two forked inner ring supporting portion.

(a2) above-mentioned rolling bearing for rocker arm can constitute: rolling bearing for rocker arm is located between the square end portion and the opposing party end of rocking arm, inner ring is fixed in the inner ring hole between two sidewalls that are in rocking arm; a square end portion of rocking arm and the switching of engine are with the end butt of valve, the opposing party end of rocking arm and pivot butt.

(a3) above-mentioned rolling bearing for rocker arm can constitute: rocking arm can have rocking arm body and the continuous motion stem that transmits from the stress of camshaft; the rotation of rocking arm body is installed in freely in a square end portion and the running shaft between the opposing party end of rocking arm body; a square end portion of rocking arm body and the switching of the engine end butt of valve; a square end portion butt of the opposing party end of rocking arm body and continuous motion stem, the inner ring of rolling bearing of the present invention is fixed on the opposing party end of continuous motion stem.

The identical point of above-mentioned (a1), (a2) rocking arm (a3) is from the valve transmission to engine of the driving force of cam, but its structure difference can be distinguished corresponding different engine models.

In addition, rolling bearing for rocker arm can be the needle bearing of full dress roller form.

The rolling bearing for rocker arm of second aspect present invention comprises: being fixed on being used between the valve that is located in engine and the cam regulates the axle that is equivalent to inner ring on the rocking arm of air-breathing, exhaust; Be positioned at the foreign side of inner ring and the outer ring that contacts with cam; And a plurality of rolling elements between outer ring and inner ring.And, at least one member in outer ring, inner ring and the rolling element has nitrogen-enriched layer, the grain size category of the austenite crystal grain in this nitrogen-enriched layer in surpassing 10 grades scope, and the retained austenite amount of nitrogen-enriched layer at the top layer of rolling surface after the grinding 50 μ m everywhere in the scope of 11～25 volume %.

The above-mentioned axle that is equivalent to inner ring can be solid axle, also can be the axle of hollow.These axles that are equivalent to inner ring are called inner ring.

The austenite crystal grain of described outer ring, inner ring or rolling element does not change in skin section that has nitrogen-enriched layer and the inside that is in the skin section inboard.Therefore, the position that meets the scope of above-mentioned crystal size grade is skin section and/or inside.At this, the austenite crystal grain is meant the vestige of still residual the austenite grain boundary before will carrying out that quenches after carrying out Quenching Treatment, based on the crystal grain of this vestige.Its grain size category is as implement can be based on mensuration such as JIS specifications as described in the form.

In the formation of the invention described above second aspect, if the retained austenite amount is more than 11 volume %, then can generate compressive stress,, also can not produce damage because of retained austenite is phase-changed into martensitic volumetric expansion even apply stress and/or the strain that produces the local damage degree.Therefore, the surface failure life-span improves.If the retained austenite amount is less than 11 volume %, then the raising in surface failure life-span is less.On the other hand, when retained austenite amount during greater than 25 volume %, then retained austenite amount and common nitrocarburizing are handled and are not had difference, and excessive to the volumetric expansion that martensitic phase transformation causes from above-mentioned retained austenite, the timeliness dimensional changes increases, so not good.Therefore, retained austenite is 11 volume %～25 volume %.Preferred range is 15 volume %～25 volume %.

Retained austenite amount 11 volume %～25 volume % or 15 volume %～25 volume % are values of the skin section of rolling surface after the grinding.

The nitrogen content of described nitrogen-enriched layer is preferably in the scope of 0.1 weight %～0.7 weight %.Nitrogen-enriched layer is the layer that the nitrogen content on the top layer that is formed on described outer ring, inner ring or rolling element is increased, for example can be by nitrocarburizing, nitrogenize, soak processing such as nitrogen and form.The nitrogen content of nitrogen-enriched layer is preferably in the scope of 0.1 weight %～0.7 weight %.If nitrogen content is less than 0.1 weight %, then the effect to the generation of retained austenite, high hardnessization etc. is little, and especially the surface failure life-span can reduce.If nitrogen content more than 0.7 weight %, the emptying aperture of shrinkage cavity then can occur being called, or because of the retained austenite amount does not too much show hardness, thereby the life-span is shorter.The nitrogen content of nitrogen-enriched layer is the value of the skin section of rolling surface after the grinding.In addition, nitrogen content also can be described as nitrogenous rate.

(b1) above-mentioned rolling bearing for rocker arm can constitute: the rocking arm rotation is supported on freely on the running shaft between one square end portion and the opposing party end, one square end portion has two forked inner ring supporting portions, inner ring is fixed on this two forked inner ring supporting portion, the end butt of the valve of the opposing party end and engine.

(b2) above-mentioned rolling bearing for rocker arm can constitute: the end butt of a square end portion of rocking arm and the valve of engine, be combined with pivot in the opposing party end, inner ring is fixed on the inner ring of two the relative sidewalls between the square end portion that is in rocking arm and the opposing party end with in the hole.

(b3) above-mentioned rolling bearing for rocker arm can constitute: the rocking arm rotation is supported on freely on the running shaft between one square end portion and the opposing party end, the end butt of the valve of this square end portion and engine, the opposing party end and the square end portion butt of transmission; the inner ring of rolling bearing for rocker arm is fixed on the opposing party end of continuous motion stem, and its outer ring contacts with cam from the continuous motion stem of the stress of camshaft.

Above-mentioned (b1), (b2) rocking arm and the identical point of the combination of rolling bearing (b3) is from the valve transmission to engine of the driving force of cam, but its structure difference can be distinguished corresponding different engine models.

The rolling bearing for rocker arm of third aspect present invention, comprise: with the camshaft of engine roll the outer ring that contact, the inboard of outer ring and be fixed on the inner ring on the rocking arm and be folded in the outer ring and inner ring between a plurality of rolling elements, outer ring, inner ring and rolling element all have nitrogen-enriched layer.The grain size category of the austenite crystal grain of the nitrogen-enriched layer of at least one member in inner ring and the rolling element is in surpassing 10 grades scope, and the retained austenite amount of described member is more than the 11 volume % and below the 25 volume %, and the nitrogen content of described member is more than the 0.1 quality % and below the 0.7 quality %.

The austenite crystal grain does not change in skin section that has nitrogen-enriched layer and the inside that is in the skin section inboard.Therefore, the position of object that becomes the scope of above-mentioned crystal size grade is skin section and inside.At this, the austenite crystal grain is meant in quenching and adds the austenitic crystal grain of having pined for producing phase transformation that still the form with the past is remaining after being phase-changed into martensite because of cooling for it.

If the retained austenite amount is less than 11 volume %, then there is the tendency that declines to a great extent in the surface failure life-span, if the retained austenite amount is more than 25 volume %, then the retained austenite amount does not have difference with the occasion of carrying out common nitrocarburizing processing, thereby the timeliness dimensional changes is relatively poor.

The retained austenite amount is the value at the 50 μ m places, top layer of rolling surface after the grinding, and martensite α (211) measures with the diffracted intensity of retained austenite γ (220) in the time of for example can be by X-ray diffraction relatively.In addition, because austenite is nonmagnetic material mutually, ferritic phase is the strong magnetism body, measures so also can utilize magnetic balance etc. to try to achieve magnetizing force.Moreover, also can use the testing apparatus of selling on the market to measure simply.

Nitrogen-enriched layer is the layer that the nitrogen content that is formed on the top layer is increased, for example can be by nitrocarburizing, nitrogenize, soak processing such as nitrogen and form.If the nitrogen content of nitrogen-enriched layer is less than 0.1 quality %, then there is not effect, especially the surface failure life-span can reduce.If nitrogen content more than 0.7 quality %, the emptying aperture of shrinkage cavity then can occur being called, or because of the retained austenite amount does not too much show hardness, thereby the life-span is shorter.The nitrogen content of nitrogen-enriched layer is the value at the 50 μ m places, top layer of rolling surface after the grinding, for example can pass through EPMA (Electron ProbeMicro-Analysis: wavelength dispersion type X-ray microanalysis instrument) measure.

As mentioned above, adopt rolling bearing for rocker arm of the present invention can realize long lifetime, therefore, even compactness also can not make the life-span of bearing lower than in the past.Thus, can realize compactness, suppress the reduction in life-span.

(c1) above-mentioned rolling bearing for rocker arm can constitute: rocking arm is installed on the pitman arm shaft between one square end portion and the opposing party end, the switching of one square end portion and engine is with the end butt of valve; rocking arm has two forked inner ring supporting portions in the opposing party end, and the inner ring of rolling bearing for rocker arm of the present invention is fixed on this two forked inner ring supporting portion.

(c2) above-mentioned rolling bearing for rocker arm can constitute: rolling bearing for rocker arm of the present invention is located between the square end portion and the opposing party end of rocking arm, inner ring is fixed in the inner ring hole between two sidewalls that are in rocking arm; a square end portion of rocking arm and the switching of engine are with the end butt of valve, the opposing party end of rocking arm and pivot butt.

(c3) above-mentioned rolling bearing for rocker arm can constitute: rocking arm has rocking arm body and the continuous motion stem that transmits from the stress of camshaft; the rocking arm body is installed in a square end portion and the pitman arm shaft between the opposing party end of rocking arm body; a square end portion of rocking arm body and the switching of the engine end butt of valve; a square end portion butt of the opposing party end of rocking arm body and continuous motion stem, the inner ring of rolling bearing for rocker arm of the present invention is fixed on the opposing party end of continuous motion stem.

The identical point of above-mentioned (c1), (c2) rocking arm (c3) is from the valve transmission to engine of the driving force of cam, but its structure difference can be distinguished corresponding different engine models.

In addition, in this manual, so-called " inner ring " is the meaning that comprises the axle of solid axle and hollow.

The rolling bearing for rocker arm of fourth aspect present invention, comprise: with the camshaft of engine roll the outer ring that contact, the inboard of outer ring and be fixed on the inner ring on the rocking arm and be folded in the outer ring and inner ring between a plurality of rolling elements, at least one member in outer ring, inner ring and the rolling element has nitrogen-enriched layer, the grain size category of austenite crystal grain of member with nitrogen-enriched layer is in surpassing 10 grades scope, and the area ratio of spheroidization carbide of member with nitrogen-enriched layer is more than 10%.

Above-mentioned austinite grain size can be tried to achieve by the usual way of JIS regulation, also can convert then by the Mean particle diameter that microtomy etc. is tried to achieve corresponding above-mentioned crystal size grade and try to achieve.Above-mentioned austinite grain size grade is as long as satisfy in the nitrocarburizing layer.But generally, the steel body that is in nitrocarburizing layer inboard also satisfies the benchmark of above-mentioned austenite crystal grain miniaturization.

In addition, so-called austenite crystal grain is meant in quenching and adds the austenitic crystal grain of having pined for taking place phase transformation that still the form with the past is remaining after being phase-changed into martensite because of cooling for it.In addition, in this manual, so-called " inner ring " is the meaning that comprises the axle of solid axle and hollow.

In addition, because therefore the area ratio of spheroidization carbide of member with nitrogen-enriched layer can significantly improve rolling fatigue life more than 10%.If the area ratio of spheroidization carbide then can not significantly improve rolling fatigue life less than 10%, therefore in the scope more than 10%.Though the area ratio of spheroidization carbide is the bigger the better, usually if area ratio surpasses 25%, then therefore the toughness deterioration that can cause material because of thickization and the cohesion of carbide is preferably in more than 10% and in the scope below 25%.

(d1) above-mentioned rolling bearing for rocker arm can constitute: the rocking arm rotation is installed in freely on the running shaft between one square end portion and the opposing party end, the switching of one square end portion and engine is with the end butt of valve; rocking arm has two forked inner ring supporting portions in the opposing party end, and the inner ring of rolling bearing for rocker arm of the present invention is fixed on this two forked inner ring supporting portion.

(d2) above-mentioned rolling bearing for rocker arm can constitute: rolling bearing for rocker arm is located between the square end portion and the opposing party end of rocking arm, inner ring is fixed in the inner ring hole between two sidewalls that are in rocking arm; a square end portion of rocking arm and the switching of engine are with the end butt of valve, the opposing party end of rocking arm and pivot butt.

(d3) above-mentioned rolling bearing for rocker arm can constitute: rocking arm has rocking arm body and the continuous motion stem that transmits from the stress of camshaft; the rotation of rocking arm body is installed in freely in a square end portion and the running shaft between the opposing party end of rocking arm body; a square end portion of rocking arm body and the switching of the engine end butt of valve; a square end portion butt of the opposing party end of rocking arm body and continuous motion stem, the inner ring of rolling bearing for rocker arm of the present invention is fixed on the opposing party end of continuous motion stem.

The identical point of above-mentioned (d1), (d2) rocking arm (d3) is from the valve transmission to engine of the driving force of cam, but its structure difference can be distinguished corresponding different engine models.

In addition, rolling bearing for rocker arm can be the needle bearing of full dress roller form.

The rolling bearing for rocker arm of fifth aspect present invention, comprise: with the camshaft of engine roll the outer ring that contacts, the inner ring of the inboard of outer ring and be folded in the outer ring and inner ring between a plurality of rolling elements, it is characterized in that, inner ring is made of the steel that contains the carbon more than the 0.50 quality %, drum with hollow, end face has the hardness that HV200 is above and HV300 is following, and the whole footpath to aperture surface upwards has hardened layer on the rolling surface surface of the inner ring that rolls from rotor.

Adopt the rolling bearing for rocker arm of fifth aspect present invention, because the whole footpath to its internal diameter upwards is formed with hardened layer on the rolling surface surface of the inner ring that rolls from rotor, so can improve static rupture strength and the fatigue strength that ruptures.In addition, because inner ring is the hollow cylinder shape, so can make rolling bearing lightweight, compactness.

Handle owing to carry out high frequency heat, make rolling surface, be the hardness (more than the HV653) that the external diameter surface of inner ring hardens into appropriateness that the carbon amount that therefore constitutes the steel of inner ring need be more than 0.5 quality % as the roller of rolling element.

Since be fixed on the rocking arm etc. by the inner ring end face being riveted processing, therefore, in the scope of the hardness of inner ring end face more than the HV200 that can rivet processing and below the HV300.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: the grain size category of the austenite crystal grain of the rolling surface skin section of inner ring is in surpassing 10 grades scope, and the grain size category of this austenite crystal grain is the value at the 50 μ m places, top layer of rolling surface after the grinding.

Because the grain size category of austenite crystal grain surpasses 10 grades, the particle diameter of austenite crystal grain is very fine, therefore can significantly improve rolling fatigue life.If the grain size category of austenite crystal grain below 10 grades, then can not significantly improve rupture fatigue life, rolling fatigue life, therefore make it in surpassing 10 grades scope.Usually, be more than 11 grades.

At this, the austenite crystal grain is meant the vestige of still residual the austenite grain boundary before will carrying out that quenches after carrying out Quenching Treatment, based on the crystal grain of this vestige.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: inner ring has nitrogen-enriched layer in skin section.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: the retained austenite amount of the rolling surface skin section of inner ring is more than 11 volume % and in the scope below the 40 volume %, the value at the 50 μ m places, top layer that this retained austenite amount is a rolling surface after the grinding.

If the retained austenite amount is about 11 volume %, then the surface failure life-span reduces, if less than 11 volume % lower tendency is arranged then.On the other hand, if the retained austenite amount more than 40 volume %, then can cause the reduction of surface hardness, cause rolling fatigue life to worsen.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: the nitrogen content of nitrogen-enriched layer is more than 0.1 quality % and in the scope below the 0.7 quality %, and this nitrogen content is the value at the 50 μ m places, top layer of rolling surface after the grinding.

Nitrogen-enriched layer is the layer that the nitrogen content on the top layer that is formed on inner ring is increased, for example can be by nitrocarburizing, nitrogenize, soak processing such as nitrogen and form.If nitrogen content is less than 0.1 quality %, then there is not effect, especially the surface failure life-span can reduce.If nitrogen content more than 0.7 quality %, the emptying aperture of shrinkage cavity then can occur being called, or because of the retained austenite amount does not too much show hardness, thereby the life-span is shorter.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: the surface hardness of the rolling surface of inner ring is more than HV653.

Because surface hardness is higher, more than HV653, therefore can significantly improve rolling fatigue life.If surface hardness less than HV653, then can not significantly be improved rolling fatigue life, make its deterioration on the contrary.Usually, the scope of surface hardness is more than the HV720 and below the HV800.Though surface hardness is high more good more, be difficult to obtain surpassing the surface hardness of HV900 usually.

The rolling bearing for rocker arm of fifth aspect present invention preferably constitutes: the area ratio of the spheroidization carbide of the nitrogen-enriched layer of the rolling surface skin section of inner ring is more than 10%, and the area ratio of this spheroidization carbide is the value at the 50 μ m places, top layer of rolling surface after the grinding.

Because the area ratio of spheroidization carbide more than 10%, therefore can significantly be improved rolling fatigue life.If the area ratio of spheroidization carbide then can not significantly improve rolling fatigue life less than 10%, therefore in the scope more than 10%.Though the area ratio of spheroidization carbide is the bigger the better, usually if area ratio surpasses 25%, then therefore the toughness deterioration that can cause material because of thickization and the cohesion of carbide is preferably in more than 10% and in the scope below 25%.The area ratio of spheroidization carbide is the value at the 50 μ m places, top layer of rolling surface after the grinding, and after corroding with picric acid alcohol solution (picral), available optical microscope (400 times) is observed.

At this, be called the spheroidization carbide simply, but be actually the combination of carbide.

These each characteristics of area ratio of the hardness of above-mentioned retained austenite amount, the nitrogen content in the nitrogen-enriched layer, hardened layer and spheroidization carbide can be improved rolling fatigue life by the rupture strength of improving inner ring.

(e1) above-mentioned rolling bearing for rocker arm preferably constitutes: rocking arm is installed on the pitman arm shaft between a square end portion and the opposing party end, square end portion at rocking arm is provided with two forked inner ring supporting portions, the switching of the opposing party end and engine is with the end butt of valve, and inner ring is fixed on the two forked inner ring supporting portions.

(e2) above-mentioned rolling bearing for rocker arm preferably constitutes: a square end portion and the pivot butt of rocking arm, rolling bearing are located between the square end portion and the opposing party end of rocking arm body, the switching of the opposing party end and the engine end butt of valve.

(e3) above-mentioned rolling bearing for rocker arm preferably constitutes: rocking arm is installed on the pitman arm shaft between a square end portion and the opposing party end; a square end portion of rocking arm and the square end portion butt of transmission from the continuous motion stem of the power of camshaft; the switching of the opposing party end and the engine end butt of valve, rolling bearing is located on the opposing party end of continuous motion stem.

Above-mentioned (e1), (e2) (e3) identical point of each form are from the valve transmission to engine of the driving force of cam, but its structure difference can be distinguished corresponding different engine models.

Above-mentioned rolling bearing for rocker arm preferably constitutes: rolling bearing is the needle bearing of full dress roller form.

The invention effect

The rolling bearing for rocker arm of first aspect present invention austenite crystal is carried out miniaturization so that its grain size category above 10 grades, and has the surface hardness Hv more than 653, therefore, rolling fatigue life significantly improves, and can obtain good anti-rupture strength and anti-timeliness dimensional changes.

Adopt the rolling bearing for rocker arm of second aspect present invention, under the service condition of speed up, big loadization, lubricant oil lowering viscousity, not only can prolong rolling fatigue life, but surface failure life-span of extension pin surface failure that Metal Contact is caused also.

Adopt the rolling bearing for rocker arm of third aspect present invention, can realize compactness, suppress the reduction in life-span.

The rolling bearing for rocker arm of fourth aspect present invention, austenite crystal is carried out miniaturization so that its grain size category surpasses 10 grades, and therefore the area ratio of spheroidization carbide is more than 10%,, rolling fatigue life significantly improves, and can obtain good anti-rupture strength and anti-timeliness dimensional changes.

Adopt the rolling bearing for rocker arm of fifth aspect present invention, because the whole footpath from the rolling surface surface of rolling for rotor of inner ring to its internal diameter upwards is formed with hardened layer, so can improve static rupture strength and the fatigue strength that ruptures.In addition, because inner ring is the hollow cylinder shape, so can make rolling bearing lightweight, compactness.In addition, has nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category to surpass 10 grades by miniaturization, and has an an amount of retained austenite amount, surface hardness with appropriateness, therefore the area ratio height of spheroidization carbide, can improve the rolling fatigue life of common dependence load type and simultaneously at the surface failure life-span because of the not enough Metal Contact that produces of slippage or oil film.

Description of drawings

Fig. 1 is the general principal view of user mode of the rolling bearing for rocker arm of expression the invention process form 1.

Fig. 2 is the sectional view along the II-II line of Fig. 1.

Fig. 3 is the general principal view of user mode of another rolling bearing for rocker arm of expression the invention process form 1.

Fig. 4 is the general principal view of user mode of the another rolling bearing for rocker arm of expression the invention process form 1.

Fig. 5 comprises the enlarged view of the rolling bearing for rocker arm of Fig. 4 in interior part.

Fig. 6 is the figure of the heat treatment method of explanation the invention process form 1.

Fig. 7 is the figure of variation of the heat treatment method of explanation the invention process form 1.

Fig. 8 is the figure of microstructure, the especially austenite crystal of expression bearing part, (a) is the bearing part of example of the present invention, (b) is bearing part in the past.

Fig. 9 (a) is the figure of the austenite grain boundary behind expression diagram Fig. 8 (a), and Fig. 9 (b) is the figure of the austenite grain boundary behind expression diagram Fig. 8 (b).

Figure 10 is the sectional block diagram that is used to illustrate the pattern of hardened layer in the past.

Figure 11 is the sectional block diagram of pattern that is used to illustrate the hardened layer of the invention process form 2.

Figure 12 is the figure of the heat treatment method of explanation the invention process form 2.

Figure 13 is the figure of another heat treatment method of explanation the invention process form 2.

Figure 14 is the figure that the heating curve H1 of Figure 12 has been added actual conditions.

Figure 15 is the figure that the heating curve H2 of Figure 13 has been added actual conditions.

Figure 16 is the figure of the rolling contact fatigue testing machine of expression outer ring rotation.

Figure 17 is the figure of the test film of expression static pressure breakdown strength test (mensuration of failure stress values).

Figure 18 is the skeleton diagram of rolling fatigue life testing machine, (a) is plan view, (b) is side view.

Figure 19 is the static figure that destroys the test film of toughness test of expression.

Figure 20 is the sectional view of structure (size) of test portion 1～test portion 6 of expression embodiment 5.

Figure 21 is the sectional view of structure (size) of test portion 7～test portion 11 of expression embodiment 5.

Figure 22 is the plan view that the major component of life test apparatus is peeled off in expression.

Figure 23 is the sectional view along the XXIII-XXIII line of Figure 22.

(symbol description)

1 rocking arm 1a, 1b rocking arm end

1c sidewall 2,52 roll shafts (inner ring)

The outer diametric plane of 2a hardened layer 2b

2c aperture surface 2d end face

3,53 rollers (needle-like roller), 4,54 rollers (outer ring)

5 pitman arm shafts (running shaft), 6 cams

7 adjust screw 8 locking nut

9 valve 9a valves upper end

10 springs, 11 rocking arm bodies

11a, 11b rocking arm body end 14 inner ring supporting portions (roller supporting portion)

15 pivot holes, 16 continuous motion stems

The 16a Bearing Installation 16b of portion continuous motion stem upper end portion

17 installation components, 50 rolling bearings

55,56 members, 101 head rolls

111 head rolls, 112 guide roller

113 balls, 121 rolling fatigue life test films

Embodiment

With reference to the accompanying drawings example of the present invention is described.

(example 1)

Fig. 1 is the general principal view of user mode of the rolling bearing for rocker arm of expression the invention process form 1, and Fig. 2 is the sectional view along the II-II line of Fig. 1.As shown in Figures 1 and 2, the rocking arm 1 as rotary member is supported on the pitman arm shaft 5 by bearing lining tile etc. at the central part between a 1a of square end portion and the opposing party end 1b with rotating freely.Rocking arm 1 is that oscillating motion is carried out at the center with pitman arm shaft 5.Screwing on a 1b of square end portion of this rocking arm 1 has the screw 7 of adjustment.It is fixing by locking nut 8 that this adjusts screw 7, the upper end portion 9a butt of the steam supply valve of its lower end and internal-combustion engine or the valve of outlet valve (the switching valve of engine) 9.This valve 9 is by the elastic force application of force of spring 10.

Rocking arm 1 has integratedly with the inner ring supporting portion (roller supporting portion) 14 on the two forked the opposing party of being formed on end 1a.Riveted joint in the roll shaft hole on being opened in this two forked inner ring supporting portion 14, be pressed into or be fixed with the two ends of the roll shaft 2 that is equivalent to inner ring by back-up ring.Roll shaft 2 has the drum of hollow.Outer circumferential face central part at this roll shaft 2 is supported with the roller 4 that constitutes the outer ring with rotating freely by a plurality of rollers 3 as rolling element.That is, between roll shaft 2 and roller 4, be folded with a plurality of rollers 3.That is, on this two forked roller supporting portion 14, dispose comprise the roll shaft 2 that is equivalent to inner ring, as the roller 3 of rolling element and be equivalent to the rolling bearing (needle bearing) 50 of full dress roller-type of the roller 4 of outer ring.The parallel axes ground configuration of the axial direction of roller 3 and roll shaft 2.The outer circumferential face of this roller 4 is because of the application of force of spring 10 and the camming surface butt of the cam 6 of being located at camshaft.In other words, cam 6 rolls with roller 4 and contacts.

During cam 6 rotations, rocking arm 1 is pushed by cam 6 and vibration along the vertical direction, and this vibration is that fulcrum transmits to valve 9 with pitman arm shaft 5, and valve 9 carries out on-off action.The rolling bearing for rocker arm 50 of this example is the full dress roller bearing that does not use retainer, is made of roll shaft 2, a plurality of roller 3 and roller 4.Rolling bearing for rocker arm 50 plays the friction that reduces between rocking arm 1 and the cam 6, the effect that improves wearability.Because rolling bearing for rocker arm 50 contacts rotation on one side on one side with cam 6, so on roller 4, act on pushing force and the impact force that cam 6 is arranged.

Fig. 3 is the general principal view of user mode of another rolling bearing for rocker arm of expression the invention process form 1.As shown in Figure 3, between a 1b of square end portion of rocking arm 1 and the opposing party end 1a, be provided with rolling bearing for rocker arm 50.In addition, between two sidewall 1c of rocking arm 1, be formed with roller hole (not shown) as inner ring hole.And, roll shaft 2 is arranged at this roller hole internal fixation.

Roll shaft 2 has the drum of hollow, by two ends being inserted in the roll shaft hole (not shown) on each sidewall that is opened in rocking arm 1 both sides and riveting processing and fixed.Outer diametric plane central part at this roll shaft 2 is supported with roller 4 by roller 3 with rotating freely.The parallel axes ground configuration of the axial direction of roller 3 and roll shaft 2.The outer diametric plane of this roller 4 is because of the application of force of spring 10 and the camming surface butt of the cam 6 of being located at camshaft.

One 1b of square end portion of rocking arm 1 and the switching of the engine upper end portion 9a butt of valve 9, the opposing party end 1a of rocking arm 1 is provided with pivot hole 15.Pivot hole 15 and not shown pivot butt.The rocking arm 1 that is provided with pivot hole 15 is by the prescribed direction application of force of spring 10 around pivot.Accept by roller 4 from the driving force that cam 6 transmits, make valve 9 overcome the force application movement of spring 10.

Fig. 4 is the general principal view of user mode of the another rolling bearing for rocker arm of expression the invention process form 1.Fig. 5 comprises the enlarged view of the rolling bearing for rocker arm of Fig. 4 in interior part.

As Fig. 4 and shown in Figure 5, rocking arm 1 has rocking arm body 11 and the continuous motion stem 16 that transmits from the stress of cam 6.Between the 11b of square end portion and the opposing party end 11a of rocking arm body 11, promptly the central part at rocking arm body 11 disposes pitman arm shaft (running shaft) 5, rocking arm body 11 rotates around it.One 11b of square end portion of rocking arm body 11 and the upper end portion 9a butt of valve 9, valve 9 is by the elastic force application of force of spring 10.In addition, the upper end portion 16b butt of the opposing party end 11a of rocking arm body 11 and continuous motion stem 16.On the 11a of the opposing party end of rocking arm body 11, be equipped with and adjust screw 7.Adjust the function that screw 7 has the butt position of regulating rocking arm body 11 and continuous motion stem 16.The roll shaft 2 of rolling bearing for rocker arm 50 is installed by installation component 17 on the 16a of Bearing Installation portion of the hollow that is positioned at continuous motion stem 16 underparts.Roller 4 butts of cam 6 and rolling bearing for rocker arm 50 pass to continuous motion stem 16 with driving force.

Rolling bearing 50 comprises the roll shaft 2 that is equivalent to inner ring, as the roller 3 of rolling element and be equivalent to the roller 4 of outer ring.Roll shaft 2 has the drum of hollow.The two ends of this roll shaft 2 are by riveting fixed processing on installation component 17.Central part is supported with roller 4 by roller 3 with rotating freely in the periphery footpath of this roll shaft 2.The parallel axes ground configuration of the axial direction of roller 3 and roll shaft 2.

The outer diametric plane of roller 4 is because of the application of force of spring 10 and the camming surface butt of cam 6, and roller 4 butts of cam 6 and rolling bearing 50 pass to continuous motion stem 16 with driving force.The driving force of utilizing this continuous motion stem 16 will have the camshaft of cam 6 passes to rocking arm 1.

In Fig. 1～Fig. 5, to not doing special difference between a side and the opposing party, just the end that will more early illustrate on the order of explanation is called a square end portion.

In constituting the member of above-mentioned rolling bearing for rocker arm 50, implement the heat treatment of low temperature secondary quenching method described later to roller 3, roll shaft 2 and as at least one member in the roller 4 of outer ring, thereby become fine austenite crystal.The result is, roll shaft 2 among above-mentioned Fig. 1～Fig. 5, has nitrogen-enriched layer as the roller 3 of rolling element and as at least one member in the roller 4 of outer ring as inner ring, its skin section is implemented high frequency hardening, become the ultra tiny state of austinite grain size, and hardness is more than HV653 in (based on the JIS specification) more than 11 grades.

In addition, in the member of the rocker arm bearing that constitutes above-mentioned engine, at least one member in roller 3, roll shaft 2 and the roller 4 is implemented the heat treatment of low temperature secondary quenching method described later, thereby the grain size category of austenite crystal grain is in surpassing 10 grades scope, and accounts for 11 volume %～25 volume % in the skin section of the rolling surface of retained austenite amount after grinding of nitrogen-enriched layer.

In addition, in the member that constitutes above-mentioned rolling bearing for rocker arm 50, roller 4, roll shaft 2 and roller 3 all have nitrogen-enriched layer.In addition, at least one member in roll shaft 2 and the roller 3 is implemented the heat treatment of low temperature secondary quenching method described later, thereby the grain size category of the austenite crystal grain of the nitrogen-enriched layer of at least one member in roll shaft 2 and the roller 3 is in surpassing 10 grades scope, and the retained austenite amount is more than the 11 volume % and below the 25 volume %, and nitrogen content is more than the 0.1 quality % and below the 0.7 quality %.

In addition, in the member that constitutes above-mentioned rolling bearing for rocker arm 50, to roller 3, roll shaft 2 and implement the heat treatment of low temperature secondary quenching method described later as at least one member in the roller 4 of outer ring, thereby the grain size category of austenite crystal grain is in surpassing 10 grades scope, and the area ratio of spheroidization carbide is more than 10%.

Below the nitrocarburizing processing that comprises that at least one bearing part carried out in outer ring (roller 4), inner ring (roll shaft 2) and the rolling element (roller 3) of these rolling bearings is described in interior heat treatment.Fig. 6 is the figure of the heat treatment method of explanation the invention process form 1.Fig. 7 is the figure of variation of the heat treatment method of explanation the invention process form 1.Fig. 6 is that the heat treatment cycle curve of primary quenching and Qa method is carried out in expression, and Fig. 7 is illustrated in the way of quenching A that material cooled arrived ₁The temperature of transformation temperature, reheat and the heat treatment cycle curve of the method for finally quenching then.The both is an example example of the present invention.Processing T at these figure ₁In, carbon and nitrogen are diffused in the matrix of steel, and after the dissolving of carbon is fully carried out, are cooled to less than A ₁The temperature of transformation temperature.Then, processing T in the drawings ₂In, reheat than handling T ₁Low temperature is implemented oil quench afterwards.

Compare with the situation of carrying out normal quenching, promptly after nitrocarburizing is handled, directly carry out primary quenching, but above-mentioned processing his-and-hers watches layer segment carries out nitrocarburizing, and can improve rupture strength, reduce the timeliness size changing rate.As mentioned above, adopt above-mentioned heat treatment method, the particle diameter that can obtain the austenite crystal grain is in the past the microstructure below 1/2nd.Carry out above-mentioned heat treated bearing part and can obtain long-life rolling contact fatigue characteristic, and can improve rupture strength, reduced the timeliness size changing rate.

Fig. 8 is the figure of microstructure, the especially austenite crystal of expression bearing part.Fig. 8 (a) is the bearing part of example of the present invention, and Fig. 8 (b) is a bearing part in the past.That is, the austinite grain size of the Bearing Steel of above-mentioned heat treatment cycle curve shown in Figure 6 has been used in Fig. 8 (a) expression.In addition, in order to compare, the austinite grain size of the Bearing Steel of heat treatment method has in the past been adopted in Fig. 8 (b) expression.Fig. 9 (a) and Fig. 9 (b) are respectively the figure of the austenite grain boundary behind expression above-mentioned Fig. 8 of diagram (a) and Fig. 8 (b).By organizing as can be known of these expression austinite grain sizes, with the grain size category of JIS specification, austenite particle diameter in the past is the grade below 10 grades, adopts heat treatment method of the present invention then can obtain 12 grades particulate.The Mean particle diameter of the Fig. 8 (a) that measures with microtomy is 5.6 μ m.

(example 2)

As Fig. 1～shown in Figure 5, the inner ring 2 of the rolling bearing for rocker arm 50 of this example is made of the steel that contains the carbon more than the 0.50 quality %, has the drum of hollow, and end face has the hardness that HV200 is above and HV300 is following.Shown in Figure 11 (a) and (b), the inner ring 2 of each rolling bearing 50 upwards has hardened layer in the surperficial whole footpath to aperture surface 2c of the rolling surface of the inner ring 2 that rolls from roller (rotor) 3.This hardened layer is preferably formed on the whole circumference direction of inner ring 2.

As the pattern of this hardened layer, open in the 2000-38906 communique the Japan Patent spy, as shown in figure 10, only the rolling surface skin section of the outer diametric plane 2b of inner ring 2 is hardened layer 2a, the skin section of the skin section of aperture surface 2c and end face 2d is unhardened layer.When adopting the pattern of this hardened layer 2a,, then compare, be mixed with little, the easy deformation of intensity of the inner ring 2 of hardened layer 2a and unhardened layer with the inner ring 2 that all is hardened layer 2a if bearing is subjected to load, therefore, in the big tensile stress of central part generation of aperture surface 2c.And when imposed load repeatedly, because the skin section of aperture surface 2c is unhardened layer, to compare fatigue strength little with hardened layer 2a, therefore, many times can produce the crack because of the effect of little tensile stress, causes the inner ring breakage.

On the other hand, shown in Figure 11 (a) and (b), in the pattern of the hardened layer 2a of this example, the whole footpath from the rolling surface skin section of the outer diametric plane 2b of inner ring 2 to aperture surface 2c all is hardened layer 2a upwards, and the part of unhardened layer is only near the skin section of end face 2d.When adopting the pattern of this hardened layer 2a, compare with inner ring 2 shown in Figure 10 because the zone of hardened layer 2a is many, so intensity greatly, not yielding.Even when imposed load repeatedly, because the central part of aperture surface 2c is hardened layer 2a, fatigue strength is big, therefore, can prevent to produce the crack, causes the possibility of inner ring 2 breakages low.

Compare with Figure 11 (a), in the hardened layer pattern of Figure 11 (b), the zone of the hardened layer 2a among the aperture surface 2c is big, and is comparatively favourable to intensity.In addition, the tensile stress that produces during for imposed load repeatedly, can in the big zone of aperture surface 2c, prevent to produce the crack, thus with only prevent that at the central part of aperture surface 2c the situation that produces the crack from comparing, also comparatively favourable when the instability action because of rocking arm 1 is subjected to eccentric load.

The hardness of hardened layer 2a more than HV653, inner ring 2 comprise end face 2d in the hardness of interior unhardened layer more than the HV200 and below the HV300.Between hardened layer 2a and unhardened layer, there is mesosphere (hardness is more than the HV300 and below the HV653).

Preferably inner ring 2 has nitrogen-enriched layer in skin section, and its skin section is implemented high frequency hardening, becomes the ultra tiny state that austinite grain size surpasses 10 grades (based on JIS specifications).

The surface hardness of the rolling surface of inner ring 2 is more than HV653.Because the skin section of inner ring 2 has been implemented high frequency hardening, best retained austenite amount accounts for more than the 11 volume % and below the 40 volume %.In addition, the nitrogen content in the nitrogen-enriched layer is preferably in more than the 0.1 quality % and below the 0.7 quality %.These retained austenite amounts and nitrogen content are the values at the 50 μ m places, top layer of rolling surface after the grinding.The result is, is difficult for producing surface failure and inner starting point type is peeled off in skin section, on the other hand, at other positions because hardness is low so rivet processing easily.Therefore, though not shown, processing is riveted at the two ends of roll shaft, the chamfered section in the roll shaft supporting portion is formed with riveted joint fixed processing portion.

The nitrocarburizing that comprises that the inner ring 2 of these rolling bearings 50 is carried out is handled and is described in interior heat treatment below.

Figure 12 is the figure of the heat treatment method of explanation the invention process form 2.Figure 13 is the figure of another heat treatment method of explanation the invention process form 2.Figure 12 carries out nitrocarburizing to handle back, the direct heat treatment cycle curve of slow cool down more than the A1 point, Figure 13 is chilling after carrying out nitrocarburizing handle more than A1 point, carries out the heat treatment cycle curve that quenching with Subsequent tempering is a temper then under the temperature of ordering less than A1.Slow cool down in the heat treatment cycle curve of Figure 12 handle or Figure 13 in quenching with Subsequent tempering in correspondence with each other so that the hardness of the part beyond the skin section reduces.The heat treatment cycle curve of Figure 12 and Figure 13 all be after the skin section with rolling surface is implemented high frequency hardening, implement low-temperature tempering then.

Below how respectively handling of Figure 12 and Figure 13 being generated microstructure describes.At first, in the heating curve of Figure 12 and Figure 13, all the steel of the hollow cylinder shape that is made of the steel that contains the carbon more than the 0.50 quality % are for example carried out nitrocarburizing more than the A1 point and handle.In this nitrocarburizing is handled, on the object member (inner ring) of rolling bearing, be formed with nitrogen-enriched layer.In this nitrogen-enriched layer, be the C that enters the type element, enter to the N hypereutectoid with respect to iron atom Fe, for example carbide precipitate (two-phase coexistent) in austenite.That is, form hypereutectoid steel at nitrogen-enriched layer.In addition, do not carrying out the inside that nitrocarburizing is handled, owing to be the composition as raw-material original steel, thereby be the austenite phase.In addition, also can carry out nitrocarburizing under the temperature of the state that is in ferrite and this two-phase of austenite or austenite and this two-phase coexistent of cementite as raw-material steel handles.

Then, when cooling off, in the heating curve (being called heating curve H1) of Figure 12, begin slow cool down from the nitrocarburizing treatment temperature.The purpose of this slow cool down is to make organization softening, improves processability.In this slow cool down, inner generate the pearlite that constitutes by ferrite and cementite from above-mentioned austenite, but owing to do not make the cementite stratiformization in the pearlite but make it condense thickization, thereby can promote to soften.Therefore, the temperature province of slow cool down can arrive about nitrocarburizing treatment temperature～(A1 point-100 ℃).Even slow cool down to the temperature lower than this temperature, can not be realized thickization of cohesion of cementite, just lose time, lower efficiency.Can arrive about 620 ℃ as standard.Then,, air cooling can be carried out, also water-cooled or oil cooling can be carried out for the shortening time.

In nitrogen-enriched layer, generate pearlite from carbide+austenitic austenite, carbide wherein condenses thickization.

In the heating curve (being called heating curve H2) of Figure 13, begin for example to quench by oil cooling etc. from the nitrocarburizing treatment temperature.At this moment, generate martensite etc. inner the composition from austenite by initial steel.This martensitic structure is harder.Under this state, because the riveted joint processing difficulties, so carry out above-mentioned temper (quenching with Subsequent tempering).Temper is promptly being carried out below the A1 point and under the temperature of as far as possible ordering near A1.That is, carry out high-temperature tempering.Therefore, tempering can be in ℃ scope of A1 point～650, more preferably carry out in ℃ scope of A1 point～680.By this tempering, dislocation density higher in the martensitic structure disappears, the tissue of the cementite after obtaining the lower ferrite of dislocation density and condensing thickization.

In addition, in the nitrocarburizing layer, by the austenite generation martensite of quenchings such as oil cooling from (carbide+austenite).Martensite is by above-mentioned tempering, and the martensite that generates with inside similarly is softened.The carbide that initially has produces cohesion.

In the explanation of above-mentioned microstructure,, as mentioned above, nitrogen and the secondary cause in the actual microstructure of complexity have comparatively been ignored for the ease of understanding.

Then, in heating curve H1 and H2, all carry out high frequency hardening.In stage before this high frequency hardening, nitrogen-enriched layer is carbide (large percentage) and the ferritic tissue that is mixed with cohesion.Heated rapidly in high frequency hardening, at this moment, carbide solid solution on one side nucleation on one side produces austenite.Because the density of the carbide that disperses is very high, so the austenite nucleation density is very high, the crystal grain that the austenite of generation converges the austenite structure of formation mutually is ultra tiny state.In addition, because nitrogen-enriched layer is hypereutectoid steel, thus the carbide coexistence, thus stop the growth of ultramicrofine austenite crystal because of the appearance of this carbide.Therefore, in nitrogen-enriched layer, can obtain ultramicrofine austenite crystal.Along with the temperature rising of rapid heating, the carbide solid solution, a large amount of carbon is solidly soluted in the ultra tiny austenite.

Then, when quenching after heating rapidly, ultra tiny austenite phase transformation becomes martensite.At this moment, because a large amount of solid solution has carbon, austenite is more stable, so the residual austenite that not phase transformation is arranged in the fine zone between martensite.Here it is retained austenite.This retained austenite is formed between the martensite, so very fine.With volume fraction, retained austenite accounts for 11～40 volume %.

Then, about 180 ℃, carry out the tempering that hardness not too descends.In the tempering about these 180 ℃, maintain the state that highdensity dislocation disappears hardly.This tempering to be organized stabilization and is carried out in order to make.In this tempering, do not produce the cohesion of cementite, also produce softening hardly.Also can save this tempering according to the steel difference.

The high frequency hardening that contains above-mentioned retained austenite is organized more tough, even also can realize the long lifetime under harsh service condition.

By carrying out above-mentioned heat treatment, can make the austenitic grain size of skin section become the ultrafine dust that (surpasses 10 grades scope) more than 11 grades, and can make inner microstructure become the line and staff control of ferrite and carbide.In addition, the hardness that can make skin section makes retained austenite account for 11～40 volume % more than HV635.In addition, shown in Figure 11 (a) or Figure 11 (b), the whole footpath that hardened layer (hardness is more than HV635) can be formed on from the rolling surface surface of inner ring aperture surface upwards.

On the other hand, can make the hardness of hardened layer unhardened layer part (end face that comprises inner ring) in addition more than the HV200 and below the HV300.Therefore, carried out above-mentioned heat treated inner ring and had long-life rolling contact fatigue characteristic, and riveted processing easily.

In addition, can make nitrogen content in the nitrogen-enriched layer more than the 0.1 quality % and below the 0.7 quality %, the area ratio that makes the spheroidization carbide in the nitrogen-enriched layer is more than 10%.

Below each actual conditions among Figure 12 and heating curve H1, the H2 shown in Figure 13 is described.

Figure 14 is the figure that the heating curve H1 of Figure 12 has been added actual conditions, and Figure 15 is the figure that the heating curve H2 of Figure 13 has been added actual conditions.As shown in figure 14, nitrocarburizing is handled and is for example carried out under 850 ℃ * 90 minutes condition.Slow cool down after nitrocarburizing is handled is for example by after being as cold as 650 ℃ from nitrocarburizing treatment temperature stove, be as cold as 500 ℃, carry out air cooling then and carry out from 650 ℃ of stoves.High frequency hardening for example carries out water-cooled after 800～1000 ℃ the temperature and carries out by being heated to rapidly.Tempering is for example carried out under 180 ℃ * 120 minutes condition, carries out air cooling then.

As shown in figure 15, nitrocarburizing is handled and is for example carried out under 850 ℃ * 90 minutes condition.After handling, nitrocarburizing for example is cooled to 100 ℃ by oil cooling.Temper (quenching with Subsequent tempering) is for example carried out under 700 ℃ * 120 minutes condition, carries out air cooling then.High frequency hardening for example carries out water-cooled after 800～1000 ℃ the temperature and carries out by being heated to rapidly.Tempering is for example carried out under 180 ℃ * 120 minutes condition, carries out air cooling then.

Below embodiments of the invention are described.

(embodiment 1)

Use JIS specification SUJ2 to make the rolling bearing for rocker arm of rolling contact fatigue test usefulness.Bearing is the needle bearing of the full dress roller-type that uses on rocking arm.Inner ring is of a size of external diameter φ 14.64mm * wide L17.3mm, and the outer ring is of a size of internal diameter φ 18.64mm * external diameter φ 24mm * wide L6.9mm.Roller is of a size of external diameter φ 2mm * long L6.8mm, uses 26 rollers.In addition, constitute the full dress roller-type that does not use retainer.The basic dynamic rated load of this bearing is 8.6kN, and basic static rated load is 12.9kN.

The manufacture process of each test bearing is as described below.

Test bearing No.1～No.3 (embodiment of the invention): in the nitrocarburizing treatment temperature is that 850 ℃, endurance are to carry out nitrocarburizing under 150 minutes the condition to handle.Nitrocarburizing is handled in the environment of the mixed gas of RX gas and ammonia and is carried out.At this moment, corresponding to each test bearing No.1～No.3, change respectively and carry out nitrocarburizing after the proportions of ingredients of RX gas and ammonia and handle.Then,, carry out primary quenching, then carried out secondary quenching in 20 minutes, carry out tempering in 90 minutes with 180 ℃ then with 800 ℃ of heating that are lower than the nitrocarburizing treatment temperature since 850 ℃ nitrocarburizing treatment temperature according to heat treatment cycle curve shown in Figure 6.

Test bearing No.4: carry out standard heat treatment.That is, in the RX gaseous environment, after heating with 840 ℃ heating-up temperatures, endurance of 20 minutes, quench, carry out tempering in 90 minutes with 180 ℃ then.

Test bearing No.5,6: in the nitrocarburizing treatment temperature is that 850 ℃, endurance are to carry out nitrocarburizing under 150 minutes the condition to handle.Nitrocarburizing is handled in the environment of the mixed gas of RX gas and ammonia and is carried out.At this moment, corresponding to each test bearing No.5, No.6, change respectively and carry out nitrocarburizing after the proportions of ingredients of RX gas and ammonia and handle.Then, quench since 850 ℃, then carry out tempering in 90 minutes with 180 ℃.

Table 1 is represented material investigation result and the functional evaluation test result with the inner ring of the test bearing No.1～No.6 of above-mentioned manufacture method making.

Table 1:

No.	Austinite grain size (JIS)	Retained austenite amount (volume %)	Nitrogen content (quality %)	Surface hardness (HV)	The area ratio of spheroidization carbide (%)	The rolling fatigue life ratio	The rupture strength ratio	The fracture fatigue ratio	Remarks
											1	12	12	0.12	780	13.6	3.2	1.1	1.2	The embodiment of the invention 1
2	12	20	0.28	770	13.0	3.5	1.1	1.2	The embodiment of the invention 2
										3	11	24	0.62	730	11.4	3.3	1.1	1.3	The embodiment of the invention 3
4	9	8	0	740	7.9	1	1	1	Comparative example 1
										5	8	29	0.31	760	9.6	1.9	0.8	1.2	Comparative example 2
6	8	36	0.70	650	8.8	1.2	0.8	1.3	Comparative example 3

Below material investigation method and functional evaluation test method are described.

(1) austinite grain size: the mensuration of austinite grain size is carried out based on the austinite grain size test method of steel among the JIS G 0551.

(2) retained austenite amount: the mensuration of retained austenite amount during by X-ray diffraction relatively the diffracted intensity of martensite α (211) and retained austenite γ (220) carry out.The value at the 50 μ m places, top layer of rolling surface after the retained austenite amount employing grinding.

(3) nitrogen content: the mensuration of nitrogen content uses EPMA to carry out.The value at the 50 μ m places, top layer of rolling surface after the nitrogen content employing grinding.

(4) surface hardness: the mensuration of surface hardness uses Vickers hardness tester (1kgf) to carry out.

(5) area ratio of spheroidization carbide: the area ratio of spheroidization carbide corrodes the back, observes with optical microscope (400 times) and measure by using picric acid alcohol solution (picral).The value at the 50 μ m places, top layer of rolling surface after the area ratio employing grinding of spheroidization carbide.

(6) rolling fatigue life test: the rolling fatigue life testing apparatus as shown in figure 16, test conditions is as shown in table 2.This testing apparatus is the rotary-type testing apparatus in outer ring.As shown in figure 16, rollably dispose a plurality of needle-like rollers 53 being contained between roll shaft 52 on the testing machine and the roller 54, make this roller 54 under the situation that applies radial load by member 55,56 with the fixing speed rotation, carry out the rolling contact fatigue test thus.

Table 2:

The rolling life test condition of bearing

Testing machine	The rotary-type life test machine in outer ring
		Test film	The rocker bearing assembly
Load (N)	2580N(0.3C)
		The outer ring rotational speed	7000rpm
Lubricated	Engine lubricating oil 10W-30
		The oil temperature	100℃
Life-span	Peel off the life-span

(7) static fracture strength test: the outer ring of service test bearing, with monomer form Amsler tester imposed load, carry out static fracture strength test.

(8) fracture Stromeyer test: the outer ring of service test bearing, Stromeyer test ruptures under the test conditions shown in the table 3.

Table 3:

Ring fracture fatigue test condition

Testing machine	The oil pressure servo type is encouraged the machine that shakes
		Test film	φ18.64×φ24×L6.9
Load (N)	Between 3000～5000, carry out various variations
		Load frequency (Hz)	20～50 (according to load change)
Estimate	In the S/N line chart 10 5Inferior intensity

For the result of (6) rolling fatigue life test, (7) static fracture strength test and (8) fracture Stromeyer test, No.4 is made as 1 with the standard heat treatment product, and the result of each test bearing is represented with the form of ratio.

Test result shown in the following his-and-hers watches 1 describes.

(1) austinite grain size: the crystal size grade of product No.1～No.3 of the present invention is 11～12, by miniaturization significantly.The crystal size grade of standard heat treatment product and nitrocarburizing treatment product No.4～No.6 in the past is 8～9, is the austenite crystal grain thicker than the present invention product.

(2) retained austenite amount: product No.1～No.3 of the present invention is 12～24%, has the austenite of appropriateness.Standard heat treatment product No.4 is 8%, lacks than product of the present invention.In the past nitrocarburizing treatment product No.5, No.6 are 29～36%, and be more than product of the present invention.The Ovshinsky scale of construction of product of the present invention is the retained austenite amount that is between standard heat treatment product and the nitrocarburizing treatment product in the past.

(3) nitrogen content: product No.1～No.3 of the present invention is 0.12～0.62%.Standard heat treatment product No.4 does not handle owing to not carrying out nitrocarburizing, so nitrogen content is 0%.In the past nitrocarburizing treatment product No.5, No.6 are 0.31～0.70%.Compare with nitrocarburizing treatment product in the past, the nitrogen content of product of the present invention is low slightly.Can think that this is to carry out Qa cause because product of the present invention is handled the back in the past nitrocarburizing to be lower than 800 ℃ of nitrocarburizing treatment temperature.

(4) surface hardness: product No.1～No.3 of the present invention is HV730～780.Standard heat treatment product No.4 is HV740.In the past nitrocarburizing treatment product No.5, No.6 are respectively HV760, HV650, are because the retained austenite amount too much and not shows hardness for No.6.

(5) area ratio of spheroidization carbide: product No.1～No.3 of the present invention is 11.4～13.6%.Standard heat treatment product and nitrocarburizing treatment product No.4～No.6 in the past are 7.9～9.6%.Compare with standard heat treatment product and nitrocarburizing treatment product in the past, the area ratio of the spheroidization carbide of product of the present invention is big, and by miniaturization, measures also many.Can think that this is to carry out Qa cause because product of the present invention is handled the back in the past nitrocarburizing to be lower than 800 ℃ of nitrocarburizing treatment temperature.

(6) rolling fatigue life test: No.4 compares with the standard heat treatment product, product No.1～No.3 of the present invention has the rolling fatigue life more than 3 times, even if compare with in the past nitrocarburizing treatment product No.5, No.6, product No.1～No.3 of the present invention also has the rolling fatigue life more than 1.5 times.In addition, No.4 compares with the standard heat treatment product, and nitrocarburizing treatment product No.5, No.6 have the rolling fatigue life less than 2 times.

(7) static fracture strength test: product No.1～No.3 of the present invention compares basic identical with standard heat treatment product No.4 or improvement is arranged slightly.In addition, No.4 compares with the standard heat treatment product, and the static rupture strength of nitrocarburizing treatment product No.5, No.6 descends.Can think that this is because the nitrogen-enriched layer of skin section and thickization of austenite crystal grain cause.

(8) fracture Stromeyer test: No.4 compares with the standard heat treatment product, and product No.1～No.3 of the present invention has improved more than 20%.In addition, No.4 compares with the standard heat treatment product, and nitrocarburizing treatment product No.5, No.6 have also improved more than 20%.Can think that this is because nitrogen enters and forms the cause of compressive residual stress in skin section to the surface.

In sum, product No.1～No.3 of the present invention has nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category more than 11 grades by miniaturization, and has an an amount of retained austenite amount, surface hardness with appropriateness, therefore the area ratio height of spheroidization carbide, can improve rolling fatigue life, the fracture fatigue strength of common dependence load type.

(embodiment 2)

Use JIS specification SUJ2 to make to peel off, the scoring test sheet.Test film is of a size of external diameter φ 40mm * wide L12mm.The manufacture process of each test bearing is as described below.

Test bearing No.1 (embodiment of the invention 1): in the nitrocarburizing treatment temperature is that 850 ℃, endurance are to carry out nitrocarburizing under 150 minutes the condition to handle.Nitrocarburizing is handled in the environment of the mixed gas of RX gas and ammonia and is carried out.Then,, carry out primary quenching, then carried out secondary quenching in 20 minutes, carry out tempering in 90 minutes with 180 ℃ then with 800 ℃ of heating that are lower than the nitrocarburizing treatment temperature since 850 ℃ nitrocarburizing treatment temperature according to heat treatment cycle curve shown in Figure 6.

Test bearing No.2 (comparative example 1): carry out standard heat treatment.That is, in the RX gaseous environment, after heating with 840 ℃ heating-up temperatures, endurance of 20 minutes, quench, carry out tempering in 90 minutes with 180 ℃ then.

Test bearing No.3 (comparative example 2): in the nitrocarburizing treatment temperature is that 850 ℃, endurance are to carry out nitrocarburizing under 150 minutes the condition to handle.Nitrocarburizing is handled in the environment of the mixed gas of RX gas and ammonia and is carried out.Then, quench since 850 ℃, then carry out tempering in 90 minutes with 180 ℃.

Table 4 is represented material investigation result, spalling test result and the scoring test result with the test film No.1～No.3 of above-mentioned manufacture method making.

Table 4:

No.	Austinite grain size (JIS)	Retained austenite amount (%)	Nitrogen content (%)	Surface hardness (HV)	The area ratio of spheroidization carbide (%)	Peel off strength ratio	The scratch strength ratio	Remarks
										1	12	21	0.30	770	13.0	1.8	1.7	Embodiment 1
2	9	7	0	740	7.8	1	1	Comparative example 1
									3	8	29	0.31	760	9.5	1.4	1.5	Comparative example 2

Below spalling test method and scoring test method are described.Carry out with the method identical for the material investigation result with embodiment 1.

(1) spalling test: under the test conditions shown in the table 5, the standard heat treatment product of the JIS specification SUJ2 that surface roughness is more coarse is the object test film, when the rolling of test film and object test film is contacted, be determined at the area ratio that peels off (the fine aggregate of peeling off) that produces on the test film, obtain peeling off intensity.For peeling off strength ratio, No.2 is made as 1 with the standard heat treatment product, and the result of each test bearing is represented with the inverse of ratio.

Table 5:

The spalling test condition

Testing machine	Two cylinder type testing machines
		Test film	φ 40 straight line surfaces roughness (Rt) 0.2 μ m
The object test film	φ 40 * R60 surface roughness (Rt) 3.0 μ m (SUJ2 system)
		Interface pressure	Pmax 2.3Gpa
Lubricant oil	Turbine oil VG46
		Object test film rotational speed	2000rpm (experiment slice driven rolling)
The total load number of times	4.8×10 5Inferior

(2) scoring test: under the test conditions shown in the table 6, with test film and object test film all is the form of the combination of identical material, make the test film contact of rolling each other, at the rotating speed that only makes test film during with the certain proportion speedup, the mutual relative rotational of test film of the moment that the sound that sends is bigger than a certain value is made as scratch intensity.For the scratch strength ratio, No.2 is made as 1 with the standard heat treatment product, and the result of each test bearing is represented with the form of ratio.

Table 6:

The scoring test condition

Testing machine	Two cylinder type testing machines
		Test film	φ 40 * R60 surface roughness (Rt) 3.0 μ m
The object test film	φ 40 * R60 surface roughness (Rt) 3.0 μ m
		Interface pressure	Pmax 2.1GPa
Lubricant oil	Turbine oil VG46
		Object test film rotational speed	Begin to increase in per 30 seconds 100rpm from 200rpm
The test film rotational speed	200rpm

Test result shown in the following his-and-hers watches 4 describes.

(1) spalling test: No.2 compares with the standard heat treatment product, and product No.1 of the present invention has the intensity of peeling off more than 1.5 times, compares basic identical with nitrocarburizing treatment product No.3 or improvement is arranged slightly.Can think that this is owing to have nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category more than 11 grades by miniaturization, and has an an amount of retained austenite amount, surface hardness with appropriateness, the area ratio height of spheroidization carbide, therefore, toughness improves, and the generation of freedom from cracking and the resistivity of development are improved.

(2) scoring test: No.2 compares with the standard heat treatment product, and product No.1 of the present invention has the scratch intensity more than 1.5 times, compares basic identical with nitrocarburizing treatment product No.3 or improvement is arranged slightly.Can think that this is owing to have nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category more than 11 grades by miniaturization, and has an an amount of retained austenite amount, surface hardness with appropriateness, the area ratio height of spheroidization carbide, therefore, can suppress the top layer and under big sliding condition, produce plastic flow, improve sintering resistance.

In sum, in spalling test and scoring test, product No.1 of the present invention is good than in the past bearing material.In addition, also can improve poor lubrication and produce to each other at roller and to disturb or can not successfully control roller position and crooked caused surface failure life-span of producing roller.

Product of the present invention has nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category more than 11 grades by miniaturization, and has an an amount of retained austenite amount, surface hardness with appropriateness, the area ratio height of spheroidization carbide, therefore, very big to the resistivity of the generation of freedom from cracking and development, the generation of the surface checking that surface heat that produces in the time of can suppressing slippage and tangential force are caused.

(embodiment 3)

Use JIS specification SUJ2 material (Cr of the Mn-1.5 weight % of the Si-0.4 weight % of the C-0.25 weight % of 1.0 weight %) to carry out mensuration, the mensuration of (2) crystal size, (3) pendulum impact test, the mensuration of (4) failure stress values, the test of (5) rolling contact fatigue of (1) hydrogen amount.Its result is illustrated in the table 7.

Table 7:

Test portion	A	B	C	D	E	F	Nitrocarburizing treatment product in the past	The normal quenching product
									The secondary quenching temperature (℃)	780 1)	800	815	830	850	870	-	-
Hydrogen amount (ppm)	-	0.37	0.40	0.38	0.42	0.40	0.72	0.38
									Crystal size (JIS)	-	12	11.5	11	10	10	10	10
Pendulum type impact value (J/cm 2)	-	6.65	6.40	6.30	6.20	6.30	5.33	6.70
									Failure stress values (MPa)	-	2840	2780	2650	2650	2700	2330	2770
Rolling fatigue life is than (L 10)	-	5.4	4.2	3.5	2.9	2.8	3.1	1

1) current because of not estimating under hardening

The manufacture process of each test portion is as described below.

Test portion A～D (example of the present invention): the temperature that nitrocarburizing is handled is that 850 ℃, endurance are 150 minutes.Environment is the mixed gas of RX gas and ammonia.According to heat treatment cycle curve shown in Figure 6, carry out primary quenching since 850 ℃ nitrocarburizing treatment temperature, then be heated to 780 ℃～830 ℃ temperature provinces that are lower than the nitrocarburizing treatment temperature and carry out secondary quenching.But, the secondary quenching temperature is that 780 ℃ test portion A is not because of having as subjects under hardening.

Test portion E, F (comparative example): nitrocarburizing is handled with the process identical with the present invention's example A～D and is carried out, and secondary quenching carries out under 850 ℃ more than 850 ℃ the nitrocarburizing treatment temperature～870 ℃ temperature.

Nitrocarburizing treatment product (comparative example) in the past: the temperature that nitrocarburizing is handled is that 850 ℃, endurance are 150 minutes.Environment is the mixed gas of RX gas and ammonia.Begin directly to quench from the nitrocarburizing treatment temperature, do not carry out secondary quenching.

Normal quenching product (comparative example): do not carry out nitrocarburizing and handle, quench after being heated to 850 ℃.Do not carry out secondary quenching.

Below test method is described.

(1) mensuration of hydrogen amount

For the hydrogen amount, the DH-103 type hydrogen analytical equipment that utilizes LECO company to produce is analyzed the non-dispersive hydrogen amount in the steel.Do not measure diffusivity hydrogen amount.The specification of the DH-103 type hydrogen analytical equipment that this LECO company produces is as described below.

Analyst coverage: 0.01～50.00ppm

Analysis precision: ± 0.1ppm or ± 3%H (the big persons among both)

Sensitivity for analysis: 0.01ppm

Detection mode: thermal conductivity method

Test portion weight and size: 10mg～35mg (maximum: diameter 12mm * length 100mm)

Furnace temp scope: 50 ℃～1100 ℃

Reagent: anhydrone Mg (ClO ₄) ₂, ascarite NaOH

Carrier gas is a nitrogen, gasometry feed gas (Japanese: be hydrogen ガ ス De one ジ Application グ ガ ス), each gas all be purity more than 99.99%, pressure is 40psi (2.8kgf/cm ²).

The summary of determination step is as described below.Be inserted in the above-mentioned hydrogen analytical equipment corresponding each sample collector of test portion that the sample collector that use is special-purpose is taked.Inner diffusivity hydrogen imports to thermal conductivity detectors by the nitrogen carrier gas.This diffusivity hydrogen is not measured in the present embodiment.Then, from sample collector, take out test portion, in resistance-heated furnace, heat, non-dispersive hydrogen is imported in the thermal conductivity detectors by the nitrogen carrier gas.In thermal conductivity detectors, measure thermal conductivity, thereby try to achieve non-dispersive hydrogen amount.

(2) mensuration of crystal size

The mensuration of crystal size is carried out based on the austinite grain size test method of the steel of JIS G 0551.

(3) pendulum impact test

Pendulum impact test is carried out based on the pendulum impact test method of the metallic material of JIS Z 2242.Test film uses the U font notched specimen (JIS3 test film) shown in the JIS Z 2202.

(4) mensuration of failure stress values

Figure 17 is the figure of the test film of expression static pressure breakdown strength test (mensuration of failure stress values).Along the P direction imposed load among the figure, measure the load till extremely destroying.Then, the breaking load that the obtains stressometer formula by following bent beam is converted into stress value.In addition, test film is not limited to test film shown in Figure 17, also can use the test film of other shapes.

The fiber stress of the nonreentrant surface of the test film of Figure 17 is made as σ ₁, the fiber stress on recessed surface is made as σ ₂, σ then ₁And σ ₂Try to achieve (Machine tool engineering Bian list A4 woven material mechanics A4-40 by following formula).At this, N represents to comprise the axle power of the axle of circular test film in interior cross section, and A represents cross-section area, e ₁The expression outer radius, e ₂The expression inside radius.In addition, κ is the section factor of bent beam.

σ ₁＝(N/A)+{M/(Aρ ₀)}[1+e1/{κ(ρ ₀+e ₁)}]

σ ₂＝(N/A)+{M/(Aρ ₀)}[1-e2/{κ(ρ ₀-e ₂)}]

$\mathrm{\κ}=-(1/A)\underset{A}{\∫}\{\mathrm{\η}/({\mathrm{\ρ}}_0+\mathrm{\η})\}\mathrm{dA}$

(5) rolling fatigue life

The test conditions of rolling fatigue life test is as shown in table 8.In addition, Figure 18 is the skeleton diagram of rolling fatigue life testing machine.Figure 18 (a) is a plan view, and Figure 18 (b) is a side view.Shown in Figure 18 (a) and Figure 18 (b), rolling fatigue life test film 121 is driven by head roll 111, rotates contiguously with ball 113.Ball 113 is balls of 3/4 inch, by guide roller 112 guiding, while and rolling fatigue life test film 121 between apply high surface pressure and roll.

Table 8:

Test film	φ 12 * L22 cylinder test sheet
		The test number	10
The object steel ball	3/4 inch (19.05mm)
		Interface pressure	5.88GPa
Loading speed	46240cpm
		Lubricant oil	Turbine oil VG68 pump circulation fuel feeding

Test result shown in the following his-and-hers watches 7 describes.

(1) hydrogen amount

The nitrocarburizing treatment product in the past of only having carried out the nitrocarburizing processing is the so very high value of 0.72ppm.Can think that this is because the ammonia (NH that contains in the environment that nitrocarburizing is handled ₃) decompose and hydrogen enters into the cause of steel.Yet the hydrogen amount of test portion B～D is 0.37～0.40ppm, reduces about half.This hydrogen amount and normal quenching product are basic identical.

Because above-mentioned hydrogen amount reduces, the embrittlement that can alleviate the caused steel of solid solution of hydrogen.That is, because the minimizing of hydrogen amount, the pendulum type impact value of the test portion B～D of example of the present invention obtains very big improvement.

(2) crystal size

For crystal size, when the temperature of quench when the secondary quenching temperature is handled than nitrocarburizing (primary quenching) is low, when being test portion B～D, the crystal size grade of austenite crystal is 11～12, by miniaturization significantly.The crystal size grade of the austenite crystal of test portion E, F, nitrocarburizing treatment product in the past and normal quenching product is 10, is the crystal grain thicker than the test portion B～D of the present invention example.

(3) pendulum impact test

According to table 7, the pendulum type impact value of nitrocarburizing treatment product in the past is 5.33J/cm ², and the pendulum type impact value of the test portion B～D of example of the present invention is 6.30～6.65J/cm ², be than higher value.Wherein, also show the low then high tendency of pendulum type impact value of secondary quenching temperature.The pendulum type impact value of normal quenching product is 6.70J/cm ²

(4) mensuration of failure stress values

Above-mentioned failure stress values is equivalent to anti-rupture strength.According to table 7, the failure stress values of nitrocarburizing treatment product in the past is 2330MPa.Compare with nitrocarburizing treatment product in the past, the failure stress values of test portion B～D is 2650～2840Mpa, is improved value.The failure stress values of normal quenching product is 2770Mpa, can be estimated as: the anti-rupture strength that obtains improveing of test portion B～D and the miniaturization of austenite crystal grain mainly are because the reduction of hydrogeneous rate is caused.

(5) rolling contact fatigue test

According to table 7, the normal quenching product is not because skin section has nitrogen-enriched layer, thus rolling fatigue life L ₁₀Minimum.The rolling fatigue life of nitrocarburizing treatment product in the past is 3.1 times of normal quenching product.The rolling fatigue life of test portion B～D significantly improves than nitrocarburizing treatment product in the past.Test portion E of the present invention, F and nitrocarburizing treatment product in the past are basic identical.

In sum, the hydrogeneous rate of the test portion B～D of example of the present invention descends, and austinite grain size is changed into more than 11 grades by fine, and pendulum type impact value, anti-rupture strength and rolling fatigue life also improve.

(embodiment 4)

Below embodiment 4 is described.Following X material, Y material and Z material are carried out a series of test.Heat treatment is used JIS specification SUJ2 material (Cr of the Mn-1.5 weight % of the Si-0.4 weight % of the C-0.25 weight % of 1.0 weight %) with raw material, and X material～Z material is identical.The manufacture process of X material～Z material is as described below.

(X material: comparative example): only carry out normal quenching (not carrying out nitrocarburizing handles)

(Y material: comparative example): after nitrocarburizing is handled, directly quench (nitrocarburizing is in the past quenched).The temperature that nitrocarburizing is handled is 845 ℃, and the endurance is 150 minutes.The environment that nitrocarburizing is handled is RX gas+ammonia.

(Z material: example of the present invention): the Bearing Steel of having implemented the heat treatment cycle curve of Fig. 6.The temperature that nitrocarburizing is handled is 845 ℃, and the endurance is 150 minutes.The environment that nitrocarburizing is handled is RX gas+ammonia.Final quenching temperature is 800 ℃.

(1) rolling fatigue life

As mentioned above, test conditions and the testing apparatus such as the table 8 and shown in Figure 16 of rolling fatigue life test.This rolling fatigue life test result is as shown in table 9.

Table 9:

Material	Life-span (load number of times)		L 10The ratio
				L 10(×10 4Inferior)	L 10(×10 4Inferior)
	The X material	8017				18648	1.0
The Y material			24656	33974	3.1
	The Z material	43244				69031	5.4

According to table 9, the L of the Y material of comparative example ₁₀Life-span (life-span of a breakage in 10 test films) is 3.1 times of the X material of only having implemented normal quenching that are similarly comparative example, thereby the effect that has played life-saving is handled in nitrocarburizing as can be known.Yet the Z material of example of the present invention is 1.74 times of Y material, is 5.4 times of X material, shows the long lifetime.Can think that the main cause of this improvement is the miniaturization of microstructure.

(2) pendulum impact test

U font notched specimen is used in pendulum impact test, is undertaken by the above-mentioned method based on JIS Z 2242.Test result is as shown in table 10.

Table 10:

Material	Pendulum type impact value (J/cm 2)	The ratio of impact value
			The X material	6.7	1.0
The Y material	5.3	0.8
			The Z material	6.7	1.0

Carried out X material (comparative example) height of the pendulum type impact value of the Y material (comparative example) that nitrocarburizing handles, but the Z material obtains and the essentially identical value of X material unlike normal quenching.

(3) the static test that destroys toughness value

Figure 19 is the static figure that destroys the test film of toughness test of expression.After the notch part of this test film is provided with the crack of about 1mm in advance, apply the static load that three-point bending causes, try to achieve breaking load P.Destroy toughness value (K _IcValue) use following (I) formula to calculate.In addition, test result is as shown in table 11.

$K_{\mathrm{Ic}}=(\mathrm{PL}\sqrt{a}/{\mathrm{BW}}^2)\{5.8-9.2(a/W)+43.6{(a/W)}^2-{73.5(a/W)}^3+77.5{(a/W)}^4\}---\left(I\right)$

Table 11:

Because the be full of cracks degree of depth that is provided with in advance is greater than the nitrogen-enriched layer degree of depth, therefore, the X material of comparative example does not have different with the Y material.But the Z material of example of the present invention can obtain about 1.2 times value of comparative example.

(4) static pressure breakdown strength test (mensuration of failure stress values)

As mentioned above, static pressure breakdown strength test film uses shape shown in Figure 17.Among the figure,, carry out the test of static pressure breakdown strength along P direction imposed load.Test result is as shown in table 12.

Table 12:

Material	The test number	Static pressure breakdown strength (Kgf)	The ratio of static pressure breakdown strength
				The X material	3	4200	1.00
The Y material	3	3500	0.84
				The Z material	3	4300	1.03

The Y material that carries out the nitrocarburizing processing is the value lower slightly than the X material of normal quenching.But the static pressure breakdown strength of Z material of the present invention obtains and the essentially identical level of X material than Y material height.

(5) timeliness size changing rate

With continuing temperature is that 130 ℃, endurance are that the measurement result of 500 hours timeliness size changing rates under the condition is illustrated in the table 13 with surface hardness, retained austenite amount (the 0.1mm degree of depth).

Table 13:

Material	The test number	Surface hardness (HRC)	Residual γ amount (volume %)	Size changing rate (* 10 -5)	The ratio of size changing rate *)
						The X material	3	62.5	8.8	18	1.0
The Y material	3	63.6	30.5	35	1.9
						The Z material	3	60.0	11.8	22	1.2

*: the smaller the better

Compare with the size changing rate of the more Y material of retained austenite amount, the Z material of example of the present invention can be suppressed at it below 1/2nd.

(6) foreign matter is sneaked into the life test under lubricating

Use ball bearing 6206, the rolling fatigue life that the foreign matter of sneaking into established amount standard foreign matter is sneaked under lubricating is estimated.Test conditions is as shown in table 14, and test result is as shown in Table 15.

Table 14:

Load	Fr＝6.86kN
		Interface pressure	Pmax＝3.2Gpa
Rotational speed	2000rpm
		Lubricated	Turbo machine	56 oil bath fuel feeding
The foreign matter amount	0.4g/1000cc
		Foreign matter	Particle diameter 100～180 μ m, hardness Hv800

Table 15:

Material	L 10Life-span (h)	L 10The ratio in life-span
			The X material	20.0	1.0
The Y material	50.2	2.5
			The Z material	45.8	2.3

The Y material of having implemented nitrocarburizing processing in the past is about 2.5 times of X material, and the Z material of example of the present invention is about 2.3 times of X material, can obtain the long lifetime.Though it is few that the Z material of example of the present invention and the Y material of comparative example are compared retained austenite and since nitrogen enter influence with the microstructure of miniaturization, can obtain the above long lifetime of Y material.

From The above results as can be known, the Z material of example of the present invention, promptly the bearing part by heat treatment method manufacturing of the present invention can satisfy the requirement that this three aspect of reduction of the raising of the long lifetime of the rolling fatigue life that is difficult to realize, rupture strength, timeliness size changing rate is handled in the past nitrocarburizing simultaneously.

(embodiment 5)

Use standard heat treatment, nitrocarburizing processing and these three kinds of heat treatment methods of heat treatment of the present invention to make roller, roll shaft and the roller of rolling bearing for rocker arm.Standard heat treatment herein, nitrocarburizing handle and following heat treatment method is represented in heat treatment of the present invention.

Standard heat treatment: in the RX gaseous environment, after heating with 840 ℃ heating-up temperatures, endurance of 20 minutes, quench, carry out tempering in 90 minutes with 180 ℃ then.

Nitrocarburizing is handled: in the environment of the mixed gas of RX gas and ammonia, be after 850 ℃, endurance are to heat under 150 minutes the condition, to quench since 850 ℃ temperature in temperature, then carry out tempering in 90 minutes with 180 ℃.

Heat treatment of the present invention: in the nitrocarburizing treatment temperature is that 850 ℃, endurance are to carry out nitrocarburizing under 150 minutes the condition to handle.Nitrocarburizing is handled in the environment of the mixed gas of RX gas and ammonia and is carried out.Then,, carry out primary quenching, then carried out secondary quenching in 20 minutes, carry out tempering in 90 minutes with 180 ℃ then with 800 ℃ of heating that are lower than the nitrocarburizing treatment temperature since 850 ℃ nitrocarburizing treatment temperature according to heat treatment cycle curve shown in Figure 6.

The material of the member that obtains by these heat treatment methods is shown in table 16.

Table 16:

Heat treatment method	Austinite grain size (JIS)	Retained austenite amount (volume %)	Nitrogen content (quality %)
				Standard heat treatment	9	7	0
Nitrocarburizing is handled	8	29	0.31
				Heat treatment of the present invention	12	21	0.30

Below the material investigation method is described.

(1) austinite grain size: the mensuration of austinite grain size is carried out based on the austinite grain size test method of steel among the JIS G 0551.

(2) retained austenite amount: the mensuration of retained austenite amount during by X-ray diffraction relatively the diffracted intensity of martensite α (211) and retained austenite γ (220) carry out.The value at the 50 μ m places, top layer of rolling surface after the retained austenite amount employing grinding.

(3) nitrogen content: the mensuration of nitrogen content uses EPMA to carry out.The value at the 50 μ m places, top layer of rolling surface after the nitrogen content employing grinding.

Test result shown in the following his-and-hers watches 16 describes.

(1) austinite grain size: the crystal size grade of heat-treated member of the present invention is 12, by miniaturization significantly.The crystal size grade that member is handled in standard heat treatment member and nitrocarburizing is 9 and 8, is the austenite crystal grain thicker than the present invention heat-treated member.

(2) retained austenite amount: the retained austenite amount of heat-treated member of the present invention is 21 volume %, has the austenite of appropriateness.The retained austenite amount of standard heat treatment member is 7 volume %, lacks than heat-treated member of the present invention.The retained austenite amount that member is handled in nitrocarburizing is 29 volume %, and is more than heat-treated member of the present invention.Hence one can see that, and the retained austenite amount of heat-treated member of the present invention is in the standard heat treatment member and nitrocarburizing is handled between the member.

(3) nitrogen content: the nitrogen content of heat-treated member of the present invention is 0.30%.The standard heat treatment member is not handled owing to not carrying out nitrocarburizing, so nitrogen content is 0%.The nitrogen content that member is handled in nitrocarburizing is 0.31%.Handle the nitrogen content of member with nitrocarburizing and compare, the nitrogen content of heat-treated member of the present invention is low slightly.Can think that this is to carry out Qa cause because heat treatment of the present invention is handled the back in nitrocarburizing to be lower than 800 ℃ of nitrocarburizing treatment temperature.

Then, roller, roll shaft and the roller that uses above-mentioned three kinds of heat treatment method manufacturings made up with various compound modes make rolling bearing for rocker arm, obtain test portion 1～test portion 11.Wherein, the sectional view of the structure (size) of expression test portion 1～test portion 6 as shown in figure 20, the sectional view of the structure (size) of expression test portion 7～test portion 11 is as shown in figure 21.As shown in figure 20, in test portion 1～test portion 6, the width of roller 4 and roller 3 is 6.9mm, and the width of roll shaft 2 is 17.3mm.On the other hand, as shown in figure 21, in test portion 7～test portion 11, the width of roller 4 and roller 3 is 5.5mm, and the width of roll shaft 2 is 15.9mm.That is, test portion 7～test portion 11 is than test portion 1～test portion 6 compactnesss about 20%.

Then, by following method test portion 1～test portion 11 is peeled off life test.Figure 22 is the plan view that the major component of life test apparatus is peeled off in expression, and Figure 23 is the sectional view along the XXIII-XXIII line of Figure 22.As Figure 22 and shown in Figure 23, with the form configuration rolling bearing for rocker arm 50 that the head roll 101 of peeling off life test apparatus contacts with roller 4, stationary roller shaft 2.Then, applying under the state of radial load to rolling bearing for rocker arm 50, making head roll 101, thereby making roller 4 rotations along the rotation of the direction of arrow among Figure 22 from the head roll 101 of peeling off life test apparatus.Measure the time (life-span) that any generation in roller 4, roll shaft 2 and the roller 3 is peeled off.In addition, the load that applies to rolling bearing for rocker arm 50 from head roll 101 is 2.58kN, and the rotational speed of roller 4 is 7000r/min.In addition, the lubricant oil between roller and roller and the roll shaft uses the engine lubricating oil of 10W-30, and the temperature of lubricant oil is 100 ℃.

The combination of member and each test portion peels off the life-span shown in table 17 and table 18 in each test portion.Product of the present invention is test portion 6, test portion 9, test portion 10 and test portion 11.In addition, the life-span of peeling off of each test portion is that 1 o'clock ratio form is represented with life-span of peeling off of test portion 1.

Table 17:

Test portion No.	1	2	3	4	5	6
							The width of test portion (mm)	6.9
Outer ring (roller)	Standard heat treatment			Nitrocarburizing is handled	Standard heat treatment	Heat treatment of the present invention
							Roller (rolling element)	Standard heat treatment	Nitrocarburizing is handled			Heat treatment of the present invention
Inner ring (roll shaft)	Standard heat treatment		Nitrocarburizing is handled		Heat treatment of the present invention
							Load load	2.58kN
Damaged member	Axle, roller	Axle	Axle	Axle	Axle	Axle
							Peel off the life-span	1	1.3	1.7	1.9	2.8	3.5

Table 18:

Test portion No.	7	8	9	10	11
						The width of test portion (mm)	5.5
Outer ring (roller)	Standard heat treatment	Nitrocarburizing is handled
						Roller (rolling element)	Nitrocarburizing is handled		Heat treatment of the present invention	Nitrocarburizing is handled	Heat treatment of the present invention
Inner ring (roll shaft)	Nitrocarburizing is handled			Heat treatment of the present invention
						Load load	2.58kN
Damaged member	The outer ring	Axle	Axle	Axle	Axle
						Peel off the life-span	0.8	1.1	1.2	1.5	1.7

Shown in table 17, all to carry out the life-span of peeling off of the heat treated test portion 6 of the present invention are 3.5 times of test portion 1 that whole members all carried out standard heat treatment to the whole members of pair roller, roll shaft and roller as can be known.In addition, shown in table 18, even as can be known with the bearing compactness time, pair roller and roll shaft carry out that nitrocarburizing is handled, life-span of peeling off that roller is carried out the heat treated test portion 9 of the present invention also is 1.2 times of test portion 1.In addition, pair roller and roller carry out that nitrocarburizing is handled as can be known, life-span of peeling off that roll shaft is carried out the heat treated test portion 10 of the present invention is 1.5 times of test portion 1.Moreover pair roller carries out that nitrocarburizing is handled as can be known, life-span of peeling off that roller and roll shaft are carried out the heat treated test portion 11 of the present invention is 1.7 times of test portion 1.From above result as can be known, all have nitrogen-enriched layer by making roller, roll shaft and roller, and at least one member in roll shaft and the roller is carried out heat treatment of the present invention, can realize the compactness of bearing, and can suppress the reduction in life-span.

(embodiment 6)

Use JIS specification SUJ2 to make the bearing of rolling contact fatigue test usefulness.Bearing is the needle bearing of the full dress roller-type that uses on rocking arm.Inner ring is of a size of internal diameter φ 10mm * external diameter φ 14.64mm * wide L15mm, and the outer ring is of a size of internal diameter φ 18.64mm * external diameter φ 24mm * wide L7mm.Roller is of a size of external diameter φ 2mm * long L6.8mm, uses 26, constitutes the full dress roller-type that does not use retainer.The basic dynamic rated load of this bearing is 8.6kN, and basic static rated load is 12.9kN.

The manufacture process of the inner ring of each test bearing is as described below.

Test bearing No.1 (example 1 of the present invention): the high frequency heat that makes the hardened layer pattern become the pattern shown in Figure 11 (b) is handled.

Test bearing No.2,3 (example 2,3 of the present invention): carry out the heat treatment of the operation of heating curve H1 shown in Figure 14.In addition, the high frequency heat that makes the hardened layer pattern become the pattern shown in Figure 11 (b) is handled.

Test bearing No.4 (comparative example 1): the high frequency heat that makes the hardened layer pattern become pattern shown in Figure 10 is handled.

Test bearing No.5 (comparative example 2): carry out the heat treatment of the operation of heating curve H1 shown in Figure 14.In addition, the high frequency heat that makes the hardened layer pattern become pattern shown in Figure 10 is handled.

Standard heat treatment product (quenching, tempering) is used in the outer ring of each test bearing.The manufacture process of the roller of each test bearing is as described below.

Test bearing No.1,4: standard heat treatment product (quenching, tempering)

Test bearing No.2,3,5: nitrocarburizing treatment product

The material investigation result and the functional evaluation test result of the inner ring of the test bearing of making of above-mentioned manufacture method are shown in table 19.

Table 19:

No.	Austinite grain size (JIS)	Retained austenite amount (volume %)	Nitrogen content (quality %)	Surface hardness (HV)	The area ratio of spheroidization carbide (%)	The hardened layer pattern	Static rupture strength ratio	The fracture fatigue ratio	The rolling fatigue life ratio	Remarks
											1	11	10	0	760	10.2	Figure 11 (b)	1.7	2.4	1.2	Example 1 of the present invention
2	12	20	0.12	780	13.6	Figure 11 (b)	1.6	3.2	3.2	Example 2 of the present invention
											3	12	35	0.28	770	13.0	Figure 11 (b)	1.6	3.3	3.5	Example 3 of the present invention
4	9	8	0	740	8.9	Figure 10	1	1	1	Comparative example 1
											5	9	29	0.31	760	9.6	Figure 10	0.9	1.2	2.9	Comparative example 2

Below material investigation method and functional evaluation test method are described.

(1) austinite grain size

The mensuration of austinite grain size is carried out based on the austinite grain size test method of steel among the JIS G 0551.The value at the 50 μ m places, top layer of rolling surface central part after the austinite grain size employing grinding.

(2) retained austenite amount

The mensuration of retained austenite amount during by X-ray diffraction relatively the diffracted intensity of martensite α (211) and retained austenite γ (220) carry out.The value at the 50 μ m places, top layer of rolling surface central part after the retained austenite amount employing grinding.

(3) nitrogen content

The mensuration of nitrogen content uses EPMA to carry out.The value at the 50 μ m places, top layer of rolling surface central part after the nitrogen content employing grinding.

(4) surface hardness

The surface hardness of rolling surface central part after the mensuration grinding.This mensuration uses Vickers hardness tester (1kgf) to carry out.

(5) area ratio of spheroidization carbide

The area ratio of spheroidization carbide corrodes the back, observes with optical microscope (400 times) and measure by using picric acid alcohol solution (picral).The value at the 50 μ m places, top layer of rolling surface central part after the area ratio employing grinding of spheroidization carbide.

(6) static fracture strength test

The inner ring of service test bearing with monomer form Amsler tester imposed load, carries out static fracture strength test.

(7) fracture Stromeyer test

The inner ring of service test bearing, Stromeyer test ruptures under the test conditions shown in the table 3.

(8) rolling fatigue life

Rolling fatigue life uses testing apparatus shown in Figure 16, carries out under the test conditions shown in the table 2.Testing apparatus shown in Figure 16 is the rotary-type testing apparatus in outer ring.As shown in figure 16, rollably dispose a plurality of needle-like rollers 53 (3) being contained between inner ring 52 (2) on the testing machine and the outer ring 54 (4), this outer ring 54 is rotated with fixing speed under the situation that is applied radial load by member 55,56, carry out the rolling contact fatigue test thus.

In addition, in table 19, the result of rolling fatigue life test, static fracture strength test and fracture Stromeyer test is made as 1 with the value of standard heat treatment product No.4, and the result of each test bearing is represented with the form of ratio.

Test result shown in the following his-and-hers watches 1 describes.

(1) austinite grain size

The crystal size grade of product No.1 of the present invention～3 is 11～12, by miniaturization significantly.Standard heat treatment product and nitrocarburizing treatment product No.4,5 crystal size grade are 9, are the austenite crystal grains thicker than the present invention product.

(2) retained austenite amount

Product No.2 of the present invention, 3 retained austenite amount are 20～35 volume %, have the austenite of appropriateness in these test portions.

(3) nitrogen content

Product No.2 of the present invention, 3 nitrogen content are 0.12～0.28 quality %, contain nitrogen.

(4) surface hardness

Product No.2 of the present invention, 3 surface hardness are HV770～780.

(5) area ratio of spheroidization carbide

The area ratio of product No.2 of the present invention, 3 spheroidization carbide is 13.0～13.6%.

(6) static fracture strength test

The static rupture strength of product No.1 of the present invention～3 is improved frequently than product No.4,5 height.Can think that this is because when to the bearing imposed load, with all be that the inner ring (product of the present invention) of hardened layer is compared from the external surface to the aperture surface shown in Figure 11 (a) and (b), the intensity of the inner ring (comparative product) that is mixed with hardened layer and unhardened layer shown in Figure 10 is less, easily deformable, therefore, the central part at aperture surface can produce bigger tensile stress.

(7) fracture Stromeyer test

No.4 compares with comparative product, and the fracture fatigue strength of product No.1 of the present invention has improved more than 2 times.In addition, No.5 compares with comparative product, and product No.2 of the present invention, 3 fracture fatigue strength have also improved about 3 times.Can think that this is because when to the bearing imposed load, with all be that the inner ring (product of the present invention) of hardened layer is compared from the external surface to the aperture surface shown in Figure 11 (a) and (b), the intensity of the inner ring (comparative product) that is mixed with hardened layer and unhardened layer shown in Figure 10 is less, easily deformable, therefore, can produce the cause of bigger tensile stress at the central part of aperture surface.

(8) rolling fatigue life test

No.4 compares with comparative product, and the rolling fatigue life of product No.1 of the present invention has obtained improving slightly.In addition, No.5 compares with comparative product, and product No.2 of the present invention, 3 rolling fatigue life have also obtained improving slightly.Compare with test portion No.1,4, test portion No.2,3,5 the preferable reason of rolling fatigue life are to be nitrogen-enriched layer.Can think that the principal element that nitrogen-enriched layer influences rolling fatigue life has area ratio of retained austenite amount, nitrogen content, spheroidization carbide etc.

In sum, by as product No.1 of the present invention～3, adopt the hardened layer pattern shown in Figure 11 (a) and (b), all form hardened layer to aperture surface, can improve static rupture strength, fracture fatigue strength from the rolling surface skin section of inner ring external diameter.In addition, if as product No.2 of the present invention, 3, has nitrogen-enriched layer in skin section, the austenite crystallization is become grain size category to surpass 10 grades by miniaturization, and has an an amount of retained austenite amount, have the appropriateness surface hardness, the area ratio height of spheroidization carbide, then can improve common dependence load type rolling fatigue life, the fracture fatigue strength.

Should be known in that top disclosed example and embodiment only are illustrations, do not limit the present invention.Scope of the present invention is not limited to above-mentioned explanation, and by claims explanations, and the meaning that is equal to claim and all changes in the claim scope are included in the scope of the present invention.

Industrial utilizability:

The present invention can be applied in the employed rolling bearing for rocker arm of rocking arm that opens and closes for intake valve or air bleeding valve to car engine especially effectively.

Claims (33)

1, a kind of rolling bearing for rocker arm (50), comprise: with the camshaft (6) of engine roll the outer ring (4) that contact, be positioned at the inboard of described outer ring (4) and be fixed on the inner ring (2) on the rocking arm (1) and be folded in described outer ring (4) and described inner ring (2) between a plurality of rolling elements (3), it is characterized in that

At least one member in described outer ring (4), described inner ring (2) and the described rolling element (3) has nitrogen-enriched layer, and the grain size category of the austenite crystal grain of this member is in surpassing 10 grades scope, and surface hardness Hv is more than 653.

2, rolling bearing for rocker arm as claimed in claim 1 (50) is characterized in that, described surface hardness Hv is more than 720 and below 800.

3, rolling bearing for rocker arm as claimed in claim 1 (50), it is characterized in that, described rocking arm (1) rotation is installed on the running shaft (5) that is positioned between a described square end portion (1b) and the described the opposing party end (1a) freely, the switching of a described square end portion (1b) and described engine end (9a) butt of valve (9), described rocking arm (1) has two forked inner ring supporting portions (14) in described the opposing party end (1a), described inner ring (2) is fixed on this two forked inner ring supporting portion (14).

4, rolling bearing for rocker arm as claimed in claim 1 (50) is characterized in that, this rolling bearing for rocker arm (50) is located between the square end portion (1b) and the opposing party end (1a) of described rocking arm (1),

Described inner ring (2) is fixed in the inner ring hole between two sidewalls (1c) that are in described rocking arm (1), one square end portion (1b) of described rocking arm (1) and end (9a) butt of the switching of described engine with valve (9), the opposing party end (1a) of described rocking arm (1) and pivot butt.

5, rolling bearing for rocker arm as claimed in claim 1 (50), it is characterized in that, described rocking arm (1) has rocking arm body (11) and transmits continuous motion stem (16) from the stress of described camshaft (6), described rocking arm body (11) rotates and is installed in freely in the square end portion (11b) and the running shaft (5) between the opposing party end (11a) that is positioned at described rocking arm body (11), a described square end portion (11b) of described rocking arm body (11) and end (9a) butt of the switching of described engine with valve (9), one square end portion (16b) butt of described the opposing party end (11a) of described rocking arm body (11) and described continuous motion stem (16), described inner ring (2) is fixed on the opposing party end (16a) of described continuous motion stem (16).

6, rolling bearing for rocker arm as claimed in claim 1 (50) is characterized in that, this rolling bearing for rocker arm (50) is the needle bearing of full dress roller form.

7, a kind of rolling bearing for rocker arm (50) comprising: being fixed on being used between the valve (9) that is located in engine and the cam (6) regulates inner ring (2) on the rocking arm (1) of air-breathing, exhaust; Be positioned at the foreign side of described inner ring (2) and the outer ring (4) that contacts with described cam (6); And be positioned at a plurality of rolling elements (3) between described outer ring (4) and the inner ring (2), it is characterized in that,

At least one member in described outer ring (4), inner ring (2) and the rolling element (3) has nitrogen-enriched layer, the grain size category of the austenite crystal grain in this nitrogen-enriched layer and is in the scope of 11 volume %～25 volume % in the skin section of the rolling surface of retained austenite amount after grinding of described nitrogen-enriched layer in surpassing 10 grades scope.

8, rolling bearing for rocker arm as claimed in claim 7 (50) is characterized in that, is in the scope of 0.1 weight %～0.7 weight % in the skin section of the rolling surface of the nitrogen content of described nitrogen-enriched layer after grinding.

9, rolling bearing for rocker arm as claimed in claim 7 (50), it is characterized in that, described rocking arm (1) rotation is supported on the running shaft (5) that is positioned between one square end portion (1a) and the opposing party end (1b) freely, a described square end portion (1a) has two forked inner ring supporting portions (14), described inner ring (2) is fixed on this two forked inner ring supporting portion (14), end (9a) butt of described the opposing party end (1b) and the valve (9) of described engine.

10, rolling bearing for rocker arm as claimed in claim 7 (50), it is characterized in that, end (9a) butt of the one square end portion (1b) of described rocking arm (1) and the valve (9) of described engine, be combined with pivot in described the opposing party end (1a), described inner ring (2) is fixed on the inner ring of relative two sidewalls (1c) between the square end portion (1b) that is in described rocking arm (1) and the opposing party end (1a) with in the hole.

11, rolling bearing for rocker arm as claimed in claim 7 (50), it is characterized in that; rocking arm (1) rotation is supported on the running shaft (5) that is positioned between one square end portion (11b) and the opposing party end (11a) freely; end (9a) butt of the valve (9) of this square end portion (11b) and described engine; described the opposing party end (11a) and square end portion (16b) butt of transmission; the inner ring (2) of described rolling bearing for rocker arm (50) is fixed on the opposing party end (16a) of described continuous motion stem, and its outer ring (4) contact with described cam (6) from the continuous motion stem (16) of the stress of described camshaft (6).

12, rolling bearing for rocker arm as claimed in claim 7 (50) is characterized in that, described rolling bearing for rocker arm is the needle bearing of full dress roller form.

13, a kind of rolling bearing for rocker arm (50), comprise: with the camshaft (6) of engine roll the outer ring (4) that contact, be positioned at the inboard of described outer ring (4) and be fixed on the inner ring (2) on the rocking arm (1) and be folded in described outer ring (4) and described inner ring (2) between a plurality of rolling elements (3), it is characterized in that

Described outer ring (4), described inner ring (2) and described rolling element (3) all have nitrogen-enriched layer,

The grain size category of the austenite crystal grain of the described nitrogen-enriched layer of at least one member in described inner ring and the described rolling element is in surpassing 10 grades scope, and the retained austenite amount of described member is more than the 11 volume % and below the 25 volume %, and the nitrogen content of described member is more than the 0.1 quality % and below the 0.7 quality %.

14, rolling bearing for rocker arm as claimed in claim 13 (50), it is characterized in that, described rocking arm (1) is installed on the pitman arm shaft (5) that is positioned between a square end portion (1b) and the opposing party end (1a), the switching of a described square end portion (1b) and described engine end (9a) butt of valve (9), described rocking arm (1) has two forked inner ring supporting portions (14) in described the opposing party end (1a), described inner ring (2) is fixed on this two forked inner ring supporting portion (14).

15, rolling bearing for rocker arm as claimed in claim 13 (50) is characterized in that, this rolling bearing for rocker arm (50) is located between the square end portion (1b) and the opposing party end (1a) of described rocking arm,

Described inner ring (2) is fixed in the inner ring hole between two sidewalls (1c) that are in described rocking arm, one square end portion (1b) of described rocking arm (1) and end (9a) butt of the switching of described engine with valve (9), the opposing party end (1a) of described rocking arm (1) and pivot butt.

16, rolling bearing for rocker arm as claimed in claim 13 (50), it is characterized in that, described rocking arm (1) has rocking arm body (11) and transmits continuous motion stem (16) from the stress of described camshaft (6), described rocking arm body (11) is installed in the square end portion (11b) and the pitman arm shaft (5) between the opposing party end (11a) that is positioned at described rocking arm body (11), a described square end portion (11b) of described rocking arm body (11) and end (9a) butt of the switching of described engine with valve (9), one square end portion (16b) butt of described the opposing party end (11a) of described rocking arm body (11) and described continuous motion stem (16), described inner ring (2) is fixed on the opposing party end (16a) of described continuous motion stem (16).

17, a kind of rolling bearing for rocker arm (50), comprise: with the camshaft (6) of engine roll the outer ring (4) that contact, be positioned at the inboard of described outer ring (4) and be fixed on the inner ring (2) on the rocking arm (1) and be folded in described outer ring (4) and described inner ring (2) between a plurality of rolling elements (3), it is characterized in that

At least one member in described outer ring (4), described inner ring (2) and the described rolling element (3) has nitrogen-enriched layer, the grain size category of austenite crystal grain of member with described nitrogen-enriched layer is in surpassing 10 grades scope, and the area ratio of spheroidization carbide of member with described nitrogen-enriched layer is more than 10%.

18, rolling bearing for rocker arm as claimed in claim 17 (50) is characterized in that, the area ratio of spheroidization carbide of member with described nitrogen-enriched layer is more than 10% and below 25%.

19, rolling bearing for rocker arm as claimed in claim 17 (50), it is characterized in that, described rocking arm (1) rotation is installed on the running shaft (5) that is positioned between a described square end portion (1b) and the described the opposing party end (1a) freely, the switching of a described square end portion (1b) and described engine end (9a) butt of valve (9), described rocking arm (1) has two forked inner ring supporting portions (14) in described the opposing party end (1a), described inner ring (2) is fixed on this two forked inner ring supporting portion (14).

20, rolling bearing for rocker arm as claimed in claim 17 (50) is characterized in that, this rolling bearing for rocker arm (50) is located between the square end portion (1b) and the opposing party end (1a) of described rocking arm (1),

Described inner ring (2) is fixed in the inner ring hole between two sidewalls (1c) that are in described rocking arm (1), one square end portion (1b) of described rocking arm (1) and end (9a) butt of the switching of described engine with valve (9), the opposing party end (1a) of described rocking arm (1) and pivot butt.

21, rolling bearing for rocker arm as claimed in claim 17 (50), it is characterized in that, described rocking arm (1) has rocking arm body (11) and transmits continuous motion stem (16) from the stress of described camshaft (6), described rocking arm body (11) rotates and is installed in freely in the square end portion (11b) and the running shaft (5) between the opposing party end (11a) that is positioned at described rocking arm body (11), a described square end portion (11b) of described rocking arm body (11) and end (9a) butt of the switching of described engine with valve (9), one square end portion (16b) butt of described the opposing party end (11a) of described rocking arm body (11) and described continuous motion stem (16), described inner ring (2) is fixed on the opposing party end (16a) of described continuous motion stem (16).

22, rolling bearing for rocker arm as claimed in claim 17 (50) is characterized in that, this rolling bearing for rocker arm (50) is the needle bearing of full dress roller form.

23, a kind of rolling bearing for rocker arm (50), comprise: the inner ring (2) of the inboard that roll the outer ring (4) that contacts with the camshaft (6) of engine, is positioned at described outer ring (4) and be folded in described outer ring (4) and described inner ring (2) between a plurality of rolling elements (3), it is characterized in that

Described inner ring (2) is made of the steel that contains the carbon more than the 0.50 quality %, drum with hollow, end face has the hardness that HV200 is above and HV300 is following, and upwards has hardened layer (2a) in the surperficial whole footpath to aperture surface (2c) of the rolling surface of the described inner ring (2) that rolls from described rotor (3).

24, rolling bearing for rocker arm as claimed in claim 23 (50), it is characterized in that, the grain size category of the austenite crystal grain of the rolling surface skin section of described inner ring (2) is in surpassing 10 grades scope, and the grain size category of described austenite crystal grain is the value at the 501 μ m places, top layer of rolling surface after the grinding.

25, rolling bearing for rocker arm as claimed in claim 23 (50) is characterized in that, described inner ring (2) has nitrogen-enriched layer in skin section.

26, rolling bearing for rocker arm as claimed in claim 25 (50), it is characterized in that, the retained austenite amount of the rolling surface skin section of described inner ring (2) is more than 11 volume % and in the scope below the 40 volume %, the value at the 50 μ m places, top layer that described retained austenite amount is a rolling surface after the grinding.

27, rolling bearing for rocker arm as claimed in claim 25 (50) is characterized in that, the nitrogen content of described nitrogen-enriched layer is more than 0.1 quality % and in the scope below the 0.7 quality %, and described nitrogen content is the value at the 50 μ m places, top layer of rolling surface after the grinding.

28, rolling bearing for rocker arm as claimed in claim 25 (50) is characterized in that, the surface hardness of the rolling surface of described inner ring (2) is more than HV653.

29, rolling bearing for rocker arm as claimed in claim 25 (50), it is characterized in that, the area ratio of the spheroidization carbide of the nitrogen-enriched layer of the rolling surface skin section of described inner ring (2) is more than 10%, and the area ratio of described spheroidization carbide is the value at the 50 μ m places, top layer of rolling surface after the grinding.

30, rolling bearing for rocker arm as claimed in claim 23 (50), it is characterized in that, described rocking arm (1) is installed on the pitman arm shaft (5) that is positioned between a square end portion (1b) and the opposing party end (1a), described square end portion (1a) at described rocking arm (5) is provided with two forked inner ring supporting portions (14), the switching of described the opposing party end (1b) and described engine is with end (9a) butt of valve (9), and described inner ring (2) is fixed on the described two forked inner ring supporting portions (14).

31, rolling bearing for rocker arm as claimed in claim 23 (50), it is characterized in that, one square end portion (1a) of described rocking arm (1) and pivot butt, described rolling bearing (50) is located between the described square end portion (1a) and the opposing party end (1b) of described rocking arm (1), the switching of described the opposing party end (1b) and described engine end (9a) butt of valve (9).

32, rolling bearing for rocker arm as claimed in claim 23 (50), it is characterized in that, described rocking arm (1) is installed on the pitman arm shaft (5) that is positioned between a square end portion (11a) and the opposing party end (11b), a described square end portion (11a) of described rocking arm (1) and square end portion (16b) butt of transmission from the continuous motion stem (16) of the power of described camshaft (6), the switching of described the opposing party end (11b) and described engine end (9a) butt of valve (9), described rolling bearing (50) is located on the opposing party end (16a) of described continuous motion stem (16).

33, rolling bearing for rocker arm as claimed in claim 23 (50) is characterized in that, described rolling bearing is the needle bearing of full dress roller form.

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