JP2008032052A - Thrust roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thrust roller bearing enabling an increase in the wear resistance and seizure resistance of a cage even under the environment of low viscosity oil. <P>SOLUTION: This thrust roller bearing 1 comprises a cage 3 formed of press-formed parts rollingly holding a plurality of rollers 2. A compound layer S having a nitride layer S1 and an oxide layer S2 is formed on the surface of the cage 3. The nitride layer S1 is formed dense. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a thrust roller bearing used in a rotation support portion of general industrial machines, automotive parts, machine tools, steel machines, and the like, and more particularly to a thrust roller bearing suitably used in a rotation support portion of a transmission of a vehicle or a torque converter. About.

  As a cage for a thrust roller bearing, a steel plate (SPCC, SPCE material, etc.), carbon steel, chromium molybdenum steel (SCM material), etc., subjected to nitriding treatment such as gas nitriding or salt bath nitriding is generally used. (For example, refer to Patent Document 1). By subjecting the cage to such nitriding treatment, a surface hardness of about Hv 350 to 600 cured from the base material is obtained, and excellent wear resistance characteristics are exhibited. Further, since the nitrogen compound generated on the surface has high temperature softening resistance, adhesion and welding are less likely to occur on the sliding surface, and seizure resistance is also improved.

JP 2001-90734 A (second page)

  In recent years, there are many needs for using low-viscosity oil to improve unit performance (low fuel consumption) in automobile transmissions, torque converters, etc., but under low-viscosity oil environments, the oil film formation on the bearing sliding surface is poor, Since this leads to a decrease in durability due to wear, further improvement in durability is required for the cage of the thrust roller bearing.

  In particular, thrust roller bearings differ from radial bearings in that the cage that holds the rollers moves greatly in the radial direction, so that there is a gap between the inner or outer circumferential surface of the cage and the mating member (inner ring, outer ring, housing, etc.). There is a problem that the amount of wear tends to be large and the wear resistance is poor.

  Also, the thrust roller bearings that are assembled in automobile transmissions and torque converters are integrated thrust roller bearings that are not separated from the cage that holds the race place, but are easy to assemble into the unit and easy to handle. Widely adopted. However, when the integrated thrust roller bearing is used in a position where the eccentricity between the support members of the inner ring and outer ring is large, for example, an excessive load (compression force) in the radial direction acts on the cage to hold it. There is a problem that the life of the vessel is reduced.

  The present invention has been made in order to eliminate such inconveniences, and its object is to provide a thrust roller bearing capable of improving the wear resistance and seizure resistance of a cage even in a low-viscosity oil environment. There is to do.

The above object of the present invention can be achieved by the following constitution.
(1) A thrust roller bearing comprising a cage made of a press-molded product that holds a plurality of rollers in a rollable manner, wherein a compound layer comprising a nitride layer and an oxide layer is formed on the surface of the cage, A thrust roller bearing characterized by a dense layer.
(2) Equipped with an outer ring and an inner ring, E1 is the amount of eccentricity between the outer ring support member and the inner ring support member, and W1 is a half of the inner bearing clearance between the outer ring and the cage. If the inner clearance of the inner circumferential side of the bearing is W2, W2 + W2>E1> (W1 + W2) / 2 is established in a state where the outer ring, the inner ring, and the cage are concentrically arranged ( A thrust roller bearing according to 1).
(3) According to (1) or (2), the outer ring and the inner ring are provided with locking portions that are locked to the cage at a plurality of positions in the circumferential direction or over the entire circumference. Thrust roller bearing.
(4) Equipped with an outer ring and inner ring equivalent member, where E2 is the amount of eccentricity between the outer ring support member and the inner ring equivalent member, and W1 is 1/2 of the inner clearance on the outer peripheral side bearing between the outer ring and the cage. The thrust roller bearing according to (1), wherein a relationship of W1>E1> (W1) / 2 is established in a state where the rollers are concentrically arranged.
(5) Equipped with an outer ring equivalent member and an inner ring, where E3 is the amount of eccentricity between the outer ring equivalent member and the inner ring support member, and W2 is ½ of the inner clearance on the inner peripheral side bearing between the inner ring and the cage. The thrust roller bearing according to (1), wherein a relationship of W2>E1> (W2) / 2 is established in a state where the cages are arranged concentrically.
(6) Equipped with an outer ring equivalent member and an inner ring equivalent member, where E4 is the amount of eccentricity between the outer ring equivalent member and the inner ring equivalent member, and 1/2 of the total radial clearance between the outer ring equivalent member or the inner ring equivalent member and the cage is The thrust roller bearing according to (1), wherein a relationship of W3>E4> (W3) / 2 is established when the outer ring equivalent member or the inner ring equivalent member and the cage are concentrically arranged. .

  According to the thrust roller bearing of the present invention, a compound layer including a nitride layer and an oxide layer is formed on the surface of the cage, and the nitride layer is a dense layer. Therefore, the wear resistance of the cage is improved even in a low-viscosity oil environment. Seizure resistance can be improved.

Hereinafter, an embodiment of a thrust roller bearing according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view of an essential part for explaining an embodiment of a thrust roller bearing according to the present invention, FIG. 2 is a schematic view for explaining a compound layer formed on the surface of the cage, and FIG. 3 is a cage. Fig. 4 is an explanatory diagram for explaining the inner clearance of the outer bearing, the inner clearance of the inner bearing of the cage, and the amount of eccentricity, Fig. 4 is an explanatory diagram for explaining a locking portion provided on the inner ring and the outer ring, and Fig. 5 FIG. 6 is a schematic perspective view for explaining the Fabry type friction and wear tester, FIG. 6 is a graph showing the relationship between the temporal change of the oxide layer thickness of the compound layer and the friction coefficient, and FIG. 7 is a description of the Ogoshi type wear tester. FIG. 8 is a graph showing the relationship between the thickness of the dense nitrided layer of the compound layer and the amount of wear.

  As shown in FIG. 1, the thrust roller bearing 1 of the present embodiment has a plurality of rollers (for example, cylindrical rollers, needle rollers, etc.) 2 arranged in a radial direction, and a plurality of rollers formed in an annular shape as a whole. A cage 3 that holds the roller 2 in a rollable manner, and an outer ring 4 and an inner ring 5 that clamp the cage 3 from both sides in the axial direction are provided.

  The cage 3 has a structure in which metal plates, each of which is substantially U-shaped in cross section and press-formed as a whole in an annular shape, are combined in the middle, and the same number of pockets 10 as the rollers 2 are arranged in the radial direction. .

  The outer ring 4 and the inner ring 5 are each formed in an annular shape by a metal plate having sufficient hardness, and one outer ring 4 has an annular outer ring race part 6 and an outer peripheral edge of the outer ring race part 6 all around the circumference. A cylindrical outer flange 7 formed over the inner ring 5. The other inner ring 5 includes an annular inner ring race part 8 and an inner side formed on the inner periphery of the inner ring race part 8 over the entire circumference. And a flange 9.

  Further, an outer locking portion (locking portion) 11 is formed at the distal end edge of the outer flange 7 of the outer ring 4, and the outer locking portion 11 is provided by bending the entire circumference of the outer flange 7. (See FIG. 4 (a)). Then, the engagement between the outer locking portion 11 and the outer peripheral edge of the cage 3 prevents separation of the cage 3 and the outer ring 4. Further, an inner locking portion (locking portion) 12 is formed at the leading edge of the inner flange 9 of the inner ring 5, and the inner locking portion 12 is provided by bending over the entire circumference of the inner flange 9. (See FIG. 4 (a)). Further, the engagement between the inner locking portion 12 and the inner peripheral edge of the cage 3 prevents separation of the cage 3 and the inner ring 5. In the present embodiment, the outer locking portion 11 (inner locking portion 12) is provided by bending over the entire circumference of the outer flange 7 (inner flange 9). 7 (inner flange 9) may be provided by extrusion so as to be scattered at a plurality of locations in the circumferential direction (see FIG. 4 (b)), and may extend to a plurality of locations in the circumferential direction. May be provided by bending (see FIG. 4C). Similarly, the inner locking portion 12 is also provided by bending or extruding at the entire circumference of the inner flange 9 or at a plurality of locations in the circumferential direction. Furthermore, the combination of the outer side latching | locking part 11 and the inner side latching | locking part 12 is free.

  As shown in FIG. 1, the thrust roller bearing 1 configured as described above includes an outer ring race portion 6 of the outer ring 4 supported by a housing (outer ring support member) 13, and an inner ring race portion 8 and an inner flange of the inner ring 5. 9 is supported by the step portion 17 of the shaft (inner ring support member) 16.

  In this embodiment, as shown in FIGS. 1 and 3, the eccentricity between the axis O1 of the housing 13 that is the outer ring support member and the axis O2 of the shaft 16 that is the inner ring support member is E1, and the outer ring 4 When the outer circumferential bearing internal clearance C1 between the outer ring 4 and the cage 3 is W1, and the inner circumferential bearing internal clearance C2 between the inner ring 5 and the cage 3 is 1/2, the outer ring 4, the inner ring 5, In a state where the cages 3 are concentrically arranged, a relationship of W1 + W2> E1> (W1 + W2) / 2 is established. In this case, when W1 + W2> E1, the thrust roller bearing 1 is assembled so that the radial compressive force does not act on the cage. On the other hand, when E1> (W1 + W2) / 2, the thrust roller bearing 1 is assembled so that a radial compressive force acts on the cage.

Further, in this embodiment, the retainer 3 after press molding is subjected to nitriding (soft nitriding or pure nitriding) treatment, and a nitride layer S1 and an oxide layer S2 are formed on the surface of the retainer 3 as shown in FIG. Is formed, and the nitride layer S1 is a dense layer. That is, the compound layer S formed on the diffusion layer A and the base layer B on the surface of the cage 3 is composed of an ε phase (Fe ₂ N, Fe ₃ N), a ν ′ phase (Fe ₄ N), iron carbonitride. The nitrided dense layer S1 is composed of iron oxide mainly composed of a small amount of Fe ₃ O ₄ , and is located on the surface of the base material B, which is an iron-based substrate. It has a two-layer structure composed of 60% oxide layer S2.

  The oxide layer S2 has good initial conformability and functions as a sump of lubricating oil, has an effective effect on protecting the oil film and prevents seizure. However, when the oxide layer S2 exceeds a certain thickness, the surface becomes rough, and an oil film may not be uniformly formed even when oil is applied on the surface, and the roughness may remain. In this case, the initial wear amount increases, and the abrasion powder peeled off thereby causes indentation on the rolling surfaces or rolling elements of the inner ring and outer ring of the bearing, and causes abrasion or digging. These accelerate the oil shortage and the lubrication condition deteriorates, and the cage is seized. Moreover, the problem that dimensional accuracy also worsens arises. If the extra porous layer near the surface is removed beforehand by mechanical means, such a problem can be improved, but in this case, the cost increases.

  On the contrary, when the thickness of the oxide layer S2 is small, the effect of oil film protection is not sufficient, so the cage and the rolling surface or rolling element of the inner ring or outer ring are in direct contact with each other to generate heat and easily wear. As a result of damage and seizure, the cage may have a short life.

Therefore, the present inventors conducted the following experiment to clarify the appropriate thickness of the oxide layer S2. That is, a test pin 25 of a test body subjected to gas nitriding is attached to a rotating device 27 through a shear pin 26 using a Fabry-Le Valy type friction and wear tester as shown in FIG. sandwiching a pair of V-block 28, 28 is opposed by performing nitriding is rotated at a rotational speed 300 min ^-1 while applying a load F, were compared with the wear resistance of the test pin 25.

For gas nitriding, pure nitriding with an atmosphere gas of N ₂ + NH ₃ was used, and the processing temperature was 560 ° C. Regarding the compound layer S formed on the test pin 25 and the V block 28, the thickness of the dense nitride layer S1 is fixed to 5 μm, and the thickness of the oxide layer S2 is set to five types of 0 μm, 0.1 μm, 2 μm, 4 μm, and 5 μm. Changed and went. The test oil was turbine oil and the friction speed was 0.15 m / s. The result of the experiment is shown in FIG.

  As is clear from FIG. 6, when the thickness of the oxide layer S2 is less than 0.1 μm, the effect of oil film protection cannot be expected, and the friction coefficient μ suddenly increased and seizure occurred in a short time. When the thickness of the oxide layer S2 is in the range of 0.1 μm or more and less than 5 μm (preferably 0.1 μm or more and less than 2 μm), the seizure resistance is greatly improved.

  Thereafter, as the thickness of the oxide layer S2 is increased, it acts as a sump of lubricating oil, so that the seizure time is extended and the seizure resistance is improved, but the initial wear amount is increased. Therefore, the occurrence of a small amount of initial wear (an increase in the friction coefficient μ near the elapsed time of 15 sec) as shown in the graphs of the thickness 2 μm and 4 μm of the oxide layer S2 in FIG. However, when the thickness of the oxide layer S2 is 5 μm or more, a large amount of initial wear occurs and there is no initial conformability effect, and the wear powder deteriorates the lubrication conditions and causes seizure in a short time. Accordingly, the upper limit of the thickness of the oxide layer S2 is set to less than 5 μm.

  That is, the seizure resistance characteristic of the compound layer S depends on the thickness of the oxide layer S2, and the seizure resistance is achieved by setting the thickness of the oxide layer S2 to 0.1 μm or more and less than 5 μm (preferably 0.1 μm or more and less than 2 μm). It can be said that it has favorable characteristics and can be suitably used as a cage for a thrust roller bearing having severe use conditions.

  The present inventors further conducted the following experiment to clarify the appropriate thickness of the dense nitride layer S1. That is, a plate-shaped SPCC fixed test piece 30 subjected to gas nitriding is applied to a SUJ2 annular rotating test piece 31 and a load F is applied using an Ogoshi type abrasion tester as shown in FIG. Then, the rotation test was performed while pressing, and the wear resistance of the fixed test piece 30 was compared.

For the gas nitriding of the fixed test piece 30, pure nitriding in which the atmosphere gas was N ₂ 20% + NH ₃ 80% was used, and the processing temperature was 560 ° C. As the compound layer S formed by nitriding in this way, a layer in which the thickness of the oxide layer S was kept constant at 5 μm and the thickness of the dense nitrided layer S1 was variously used was used. The rotating test piece 31 was used by quenching SUJ2 material at 840 ° C and tempering at 170 ° C. The test conditions were unlubricated (dry), surface pressure: 0.2 to 4 kg / mm ² , friction speed: 2.6 m / s, friction distance (sliding distance): 400 m. The result of the experiment is shown in FIG.

  As is apparent from FIG. 8, the wear amount is very large when the thickness of the nitrided dense layer S1 is less than 3 μm. On the other hand, the wear amount is suppressed when the thickness of the dense nitride layer S1 is 3 μm or more. This is because when the dense nitride layer S1 is as thin as less than 3 μm, the nitride layer is not uniform, and as a result, uneven nitriding occurs. In this way, if there is a part where the nitrided dense layer is not partially formed due to uneven nitriding, the SPCC substrate will make a true contact with the rolling surface of the inner ring or outer ring or the bearing steel of the rolling element, and the sliding contact will occur. The cage becomes unusable early. Therefore, in the case of a nitrided cage in which the thickness of the nitrided dense layer S1 in the compound layer S is less than 3 μm, the wear resistance characteristics cannot be sufficiently expected.

  On the other hand, even when the thickness of the nitrided dense layer S1 exceeds 20 μm, an increase in the amount of wear is observed. That is, the surface hardness of the nitrided dense layer S1 is 7 to 18 μm and shows the highest hardness. When the thickness is further increased, the highest hardness position is shifted to the inside, and the surface hardness is reduced. When the thickness of the layer S1 exceeds 20 μm, a remarkable decrease in surface hardness is observed. That is, if the nitrided dense layer S1 is simply thicker, it cannot be said that the wear resistance is improved, and the decrease in the hardness of the dense layer due to the excessive thickness causes breakage or tearing of the cage. Therefore, it can be said that the thickness of the nitrided dense layer S1 of the nitriding cage needs to be 20 μm or less.

  These results can be said not only when the thickness of the oxide layer S2 is limited to 5 μm but also when the thickness of the oxide layer S2 is changed. That is, the wear resistance of the compound layer S depends on the thickness of the dense nitride layer S1, and the nitrided layer having excellent wear resistance is obtained by setting the thickness of the dense nitride layer S1 to 3 to 20 μm, preferably 7 to 18 μm. A cage can be provided.

  As described above, according to the thrust roller bearing 1 of the present embodiment, the compound layer S including the nitrided dense layer S1 and the oxide layer S2 is formed on the surface of the cage 3, and the nitrided dense layer S1 has a thickness of 3 μm. The wear resistance and seizure resistance of the cage 3 can be improved because the thickness of the oxide layer S2 is controlled within the range of 0.1 μm or more and less than 5 μm. As a result, it is an integrated type even in a low-viscosity oil environment (for example, 40 cSt or less at 40 ° C., 10 cSt or less at 100 ° C.) or in an environment where excessive radial load (compression force) acts on the cage 3. This thrust roller bearing can be employed, and can be suitably applied to a rotation support portion of an automobile transmission or a torque converter.

As a first modification of the present embodiment, as shown in FIG. 9, the thrust roller bearing 1 includes an outer ring race portion 6 and an outer flange 7 of an outer ring 4 supported by a support recess 14 of a housing 13, and an inner ring. Five inner ring race portions 8 may be supported by the inner ring support member 40.
Also in this case, the amount of eccentricity between the housing 13 as the outer ring support member and the inner ring support member 40 is E1, and 1/2 of the outer bearing inner clearance C1 between the outer ring 4 and the cage 3 is W1, and the inner ring 5 is held. Assuming that W2 is 1/2 of the inner clearance C2 on the inner peripheral side with the cage 3, the relationship of W1 + W2>E1> (W1 + W2) / 2 is established with the outer ring 4, the inner ring 5 and the cage 3 being concentrically arranged. Is configured to do.

As a second modification of the present embodiment, as shown in FIG. 10, the present invention may be applied to a thrust roller bearing 1a that does not include an inner ring. The thrust roller bearing 1a is equivalent to an outer ring 4 and an inner ring. A cage 3 holding a plurality of rollers 2 is interposed between the member 41 and the member 41. The outer race 4 and the outer flange 7 of the outer ring 4 are supported by the support recess 14 of the housing 13.
In this case, assuming that the eccentric amount of the housing 13 which is the outer ring support member and the inner ring equivalent member 41 is E2 (see FIG. 3), and ½ of the inner clearance of the outer peripheral side bearing between the outer ring 4 and the cage 3 is W1. In a state where the outer ring 4 and the cage 3 are arranged concentrically, the relationship of W1>E2> (W1) / 2 is established.

As a third modification of the present embodiment, as shown in FIG. 11, the present invention may be applied to a thrust roller bearing 1b that does not include an outer ring. In this thrust roller bearing 1 b, a cage 3 holding a plurality of rollers 2 is interposed between the outer ring equivalent member 42 and the inner ring 5. The inner race portion 8 and the inner flange 9 of the inner race 5 are supported by the step portion 17 of the shaft 16.
In this case, the amount of eccentricity between the outer ring equivalent member 42 and the shaft 16 serving as the inner ring support member is E3 (see FIG. 3), and ½ of the inner clearance of the inner ring side bearing between the inner ring 5 and the cage 3 is W2. In a state where the inner ring 5 and the cage 3 are concentrically arranged, a relationship of W2>E3> (W2) / 2 is established.

As a fourth modification of the present embodiment, as shown in FIGS. 12 and 13, the present invention may be applied to thrust roller bearings 1c and 1d that are not provided with both an outer ring and an inner ring. As shown in FIG. 12, the thrust roller bearing 1 c includes a cage 3 that holds a plurality of rollers 2 between a housing (outer ring equivalent member) 13 and an inner ring equivalent member 41. The outer peripheral surface of the cage 3 is loosely supported by the inner peripheral surface of the support recess 14 of the housing 13.
In this case, the amount of eccentricity between the housing 13 corresponding to the outer ring and the inner ring corresponding member 41 is E4 (see FIG. 3), and 1 is the total radial clearance between the inner peripheral surface of the housing 13 and the outer peripheral surface of the cage 3. Assuming that / 2 is W3, the relationship of W3>E4> (W3) / 2 is established in a state where the housing 13 and the cage 3 are concentrically arranged.

In the thrust roller bearing 1d, as shown in FIG. 13, a cage 3 holding a plurality of rollers 2 is interposed between an outer ring equivalent member 42 and a step portion 17 of a shaft (inner ring equivalent member) 16. . The inner peripheral surface of the cage 3 is loosely supported by the outer peripheral surface of the step portion 17 of the shaft 16.
In this case, the amount of eccentricity between the outer ring equivalent member 42 and the shaft 16 that is the inner ring equivalent member is E4, and 1 / of the total radial clearance between the outer peripheral surface of the step portion 17 of the shaft 16 and the inner peripheral surface of the cage 3. When 2 is W3, the relationship of W3>E4> (W3) / 2 is established in a state where the shaft 16 and the cage 3 are arranged concentrically.

In addition, this invention is not limited to what was illustrated to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in this embodiment, the cylindrical roller 2 is held by the cage 3 having a structure in which two metal plates having a substantially U-shaped cross section are combined in the middle. 14, the axial end surface 2 b of the roller 2 a is formed into a spherical convex surface so that the center portion of the axial end surface 2 b on the outer peripheral side of the roller 2 a comes into contact with the outer peripheral inner peripheral surface of the cage 3. You may comprise. In this case, even when the roller 2a is displaced radially outward of the cage 3 by centrifugal force, the axial end surface 2b on the outer circumferential side of the roller 2a and the outer circumferential inner circumferential surface of the cage 3 rub against each other. Since the PV value of the part can be kept low, wear of the rubbing part can be suppressed.
In the present embodiment, the cage 3 has a structure in which two metal plates are press-molded and combined in the middle. Instead, as shown in FIG. The cage 3a configured by press-molding a plate may be used.

  Below, each test performed in order to confirm the effect of the thrust roller bearing of this invention is demonstrated.

(Durability test)
In this test, an integral thrust roller bearing having substantially the same structure as that in FIG. 1 in which the inner and outer rings and the cage are not separated is used, and as shown in FIG. 16, an outer ring support member 50 and an inner ring support member for supporting the inner and outer rings. A durability test of the cage was performed by setting a large eccentric amount so as to generate a radial load on the cage. In the nitriding treatment of the cage, a compound layer composed of a dense nitride layer and an oxide layer was formed on the cage surface as two kinds of parameters of tuftride / NV nitriding. And about the thing which changed the thickness of the nitrided dense layer and the oxide layer variously, the amount of wear of the inner and outer peripheral surfaces of the cage after the rated life L10 (= 40 hours) was confirmed.

  In this test, since an excessive radial load is applied to the inner and outer peripheral surfaces of the cage, the outer peripheral edge of the cage may break due to accelerated wear (see FIG. 17). In this case, the test time until breakage was confirmed. The lubricating oil used in the test was a low viscosity oil having a kinematic viscosity at 100 ° C. of 5.0 cSt. The results are shown in Table 1.

The test conditions are as follows.
Bearing size: inner diameter φ55mm x outer diameter φ85mm x width 6mm
Load: 0.5Ca (Ca: Dynamic load rating (N))
Bearing rotation speed: 4000 min ⁻¹
Lubricating oil: ATF (kinematic viscosity at 100 ° C .: 5.0 cSt)
Test oil temperature: 120 ° C
Eccentricity: 0.6 mm
Cage nitriding treatment: Tuftride / NV nitriding

As is clear from Table 1, when the thickness of the dense nitrided layer of the cage is less than 3 μm and the thickness of the oxide layer is less than 0.1 μm, the wear of the cage proceeds abnormally and is retained in a short time. The vessel was broken. Moreover, even if the thickness of the dense nitride layer is 3 μm or more. When the thickness of the oxide layer exceeded 5 μm, although the cage was not broken, abnormal wear was observed. Abnormal wear was also observed when the nitrided dense layer thickness exceeded 20 μm and the oxide layer thickness was 5 μm or more.
On the other hand, when the thickness of the dense nitride layer is in the range of 3 μm or more and 20 μm or less, and the thickness of the oxide layer is in the range of 0.1 μm or more and less than 5 μm, no breakage and abnormal wear of the cage are observed. Results were obtained. In particular, in the range where the thickness of the oxide layer is 0.1 μm or more and less than 2 μm, more stable wear resistance was obtained.

(Seizure resistance test)
In this test, a thrust roller bearing having substantially the same structure as that shown in FIG. 12 having no inner and outer rings was used, and the test rotation speed was set to 5 times the allowable rotation speed of the bearing, and the seizure resistance test of the cage was performed. In the nitriding treatment of the cage, a compound layer composed of a dense nitride layer and an oxide layer was formed on the cage surface as two kinds of parameters of tuftride / NV nitriding. And about the thing which changed the thickness of the dense nitride layer and the oxide layer, the amount of wear on the inner and outer diameter surfaces of the cage after the rated life L10 (= 100 hours) was confirmed.

  In this test, the thrust roller bearing is rotated at 5 times the permissible rotation speed of the bearing, so that the cage may be seized. In this case, the time until seizure occurred was confirmed. The lubricating oil used in the test was a low-viscosity oil having a kinematic viscosity at 100 ° C. of 5.0 cSt. The results are shown in Table 2.

The test conditions are as follows.
Bearing size: Inner diameter 40 mm x Outer diameter 60 mm x Roller diameter 2 mm
Load: 0.2Ca (Ca: Dynamic load rating (N))
Bearing rotation speed: 30000 min ⁻¹ (bearing allowable rotation speed: 6000 min ⁻¹ )
Lubricating oil: ATF (kinematic viscosity at 100 ° C .: 5.0 cSt)
Test oil temperature: 120 ° C
Cage nitriding treatment: Tuftride / NV nitriding

As is clear from Table 2, when the thickness of the dense nitrided layer of the cage is less than 3 μm and more than 20 μm, abnormal wear was observed in the cage. In addition, when the thickness of the oxide layer was less than 0.1 μm and abnormal 5 μm, seizure occurred in the cage.
In contrast, when the thickness of the dense nitride layer is 3 μm or more and 20 μm or less, abnormal wear is not observed in the cage, and when the thickness of the oxide layer is 0.1 μm or more and less than 5 μm, the cage is baked. There was no occurrence of sticky marks. In particular, effective wear resistance was obtained when the thickness of the oxide layer was in the range of 0.1 μm or more and less than 2 μm.

It is principal part sectional drawing for demonstrating one Embodiment of the thrust roller bearing which concerns on this invention. It is a schematic diagram for demonstrating the compound layer formed on the surface of a holder | retainer. It is explanatory drawing for demonstrating the outer peripheral side bearing internal clearance of a holder | retainer, the inner peripheral side bearing internal clearance of a retainer, and eccentricity. It is explanatory drawing for demonstrating the latching | locking part provided in an inner ring | wheel and an outer ring | wheel. It is a schematic perspective view for demonstrating a Fabry type friction abrasion tester. It is a graph which shows the relationship between the time change of the oxide layer thickness of a compound layer, and a friction coefficient. It is a schematic explanatory drawing for demonstrating an Ogoshi type abrasion tester. It is a graph which shows the relationship between the thickness of the nitrided dense layer of a compound layer, and the amount of wear. It is principal part sectional drawing for demonstrating the 1st modification of the thrust roller bearing which concerns on this invention. It is principal part sectional drawing for demonstrating the 2nd modification of the thrust roller bearing which concerns on this invention. It is principal part sectional drawing for demonstrating the 3rd modification of the thrust roller bearing which concerns on this invention. It is principal part sectional drawing for demonstrating the 4th modification of the thrust roller bearing which concerns on this invention. FIG. 13 is a cross-sectional view of a principal part showing another example of assembly of the thrust roller bearing of FIG. 12. It is principal part sectional drawing which shows the modification of the retainer of a thrust roller bearing. It is principal part sectional drawing which shows the other modification of the holder | retainer of a thrust roller bearing. It is explanatory drawing for demonstrating the example of the load of the radial direction with respect to a holder | retainer. (A) is a perspective view of the cage before breaking, and (b) is a perspective view of the cage after breaking.

Explanation of symbols

1, 1a, 1b, 1c, 1d Thrust roller bearing 2 Roller 3 Cage 4 Outer ring 5 Inner ring 6 Outer race part 7 Outer flange 8 Inner race part 9 Inner flange 10 Pocket 11 Outer locking part (locking part)
12 Inside formation part (locking part)
13 Housing (Outer ring support member)
14 Support recess 16 Shaft (Inner ring support member)
17 Step 40 Inner ring support member 41 Inner ring equivalent member 42 Outer ring equivalent member S Compound layer S1 Nitride layer (dense nitride layer)
S2 oxide layer

Claims (6)

A thrust roller bearing including a cage made of a press-formed product that holds a plurality of rollers in a rollable manner,
A thrust roller bearing, wherein a compound layer including a nitride layer and an oxide layer is formed on a surface of the cage, and the nitride layer is a dense layer.   An outer ring and an inner ring, wherein E1 is the amount of eccentricity between the outer ring support member and the inner ring support member, and W1 is a half of the internal clearance on the outer peripheral side of the outer ring and the cage. When 1/2 of the internal clearance on the inner peripheral side of the cage is W2, the relationship of W1 + W2> E1> (W1 + W2) / 2 is established in a state where the outer ring, the inner ring, and the cage are arranged concentrically. The thrust roller bearing according to claim 1.   The thrust roller bearing according to claim 1 or 2, wherein the outer ring and the inner ring are provided with locking portions that are locked to the cage at a plurality of positions in the circumferential direction or over the entire circumference. .   An outer ring and an inner ring equivalent member, where E2 is the amount of eccentricity between the outer ring support member and the inner ring equivalent member, and W1 is a half of the inner clearance of the outer peripheral side bearing between the outer ring and the cage. The thrust roller bearing according to claim 1, wherein a relationship of W1> E1> (W1) / 2 is established in a state where the cages are concentrically arranged.   An outer ring equivalent member and an inner ring, the amount of eccentricity of the outer ring equivalent member and the support member of the inner ring is E3, and ½ of the inner clearance of the inner ring side bearing between the inner ring and the cage is W2, The thrust roller bearing according to claim 1, wherein a relationship of W2> E1> (W2) / 2 is established in a state where the inner ring and the cage are concentrically arranged.   The outer ring equivalent member and the inner ring equivalent member are provided, and the eccentric amount of the outer ring equivalent member and the inner ring equivalent member is E4, and 1 / of the total radial clearance between the outer ring equivalent member or the inner ring equivalent member and the cage 2. The relationship of W3> E4> (W3) / 2 is established when the outer ring equivalent member or the inner ring equivalent member and the cage are concentrically arranged, where 2 is W3. Thrust roller bearing.

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