JP2003322231A - Rolling body for toroidal type continuously variable transmission and manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling body improving the transmitable torque of a toroidal type continuously variable transmission. <P>SOLUTION: This rolling body has an inner ring 42 having a bearing rolling face 42a and a traction face 42b and an outer ring 43 having a bearing rolling face 43a. The bearing rolling faces have an effectively hardened layer comprising a first composition including C of 0.6 to 1.2 wt.%, Si of less than 0.35 wt.%, Mn of 0.2 to 1.5 wt.% Cr of 0.8 to 1.40 wt.% and Mo of 0.15 to 0.35 wt.% and Fe as reminder and obligatory impurity. The traction face has an effectively hardened layer comprising a second composition including C of 0.6 to 1.2 wt.%, Si of 0.50 to 1.5 wt.%, Ni of 0.40 to 4.5 wt.%, Mn of 0.20 to 1.5 wt.%, Cr of 1.5 to 3.0 wt.%, Mo of 0.50 to 2.0 and Cr+Mo of 2.5 to 4.0 wt.% and Fe as reminder and obligatory impurity. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rolling element for a toroidal type continuously variable transmission and a method for manufacturing the same.

[0002]

2. Description of the Related Art The traction surface (disk rolling portion) of the inner ring of a power roller, which is a rolling element of a toroidal type continuously variable transmission, is used under a high surface pressure from a sub-high temperature to a WEC (white structure change). ) Type rolling fatigue peeling is exhibited.
On the other hand, the bearing rolling surfaces (bearing groove portions) of the inner ring and the outer ring exhibit hydrogen embrittlement type rolling fatigue peeling due to infiltration of hydrogen generated by oil decomposition or the like.

Therefore, the rolling contact fatigue strength, which is the limit surface pressure for ensuring a predetermined separation life on the traction surface and the bearing rolling surface, limits the amount of torque that can be transmitted by the toroidal type continuously variable transmission. .

Therefore, for example, Japanese Patent Laid-Open No. 2001-983
No. 43 publication, like gears and bearing rolling elements,
It relates to a member applied as a power transmission component requiring high surface fatigue strength, and discloses a high surface pressure resistant member suitable for use under a high surface pressure of about 100 to 300 ° C. and a manufacturing method thereof.

[0005]

However, the load tends to increase more and more due to further demands for higher engine output and smaller and lighter components. Therefore, there is a demand for further improvement in the amount of torque that can be transmitted by the toroidal-type continuously variable transmission.

The present invention has been made in order to solve the problems associated with the prior art described above, and an object of the present invention is to provide a rolling element capable of improving the transmittable torque of a toroidal type continuously variable transmission and a method of manufacturing the rolling element. And

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inner ring having a bearing rolling surface and a traction surface, which is arranged between an input side disc and an output side disc, and an outer ring having a bearing rolling surface. (EN) Provided is a rolling element for a toroidal type continuously variable transmission. More specifically, the bearing rolling surfaces of the inner ring and the outer ring have C: 0.6 to 1.2.
wt%, Si: less than 0.35 wt%, Mn: 0.20 to 1.
5 wt%, Cr: 0.8-1.40 wt%, Mo: 0.15
˜0.35 wt%, with an effective hardened layer composed of the first composition of balance Fe and unavoidable impurities. The depth of the effective hardened layer is more than twice the maximum shear stress generation depth due to Hertzian contact on the surface of the finished part. Then, in the vicinity of the surfaces of the bearing rolling surfaces of the inner ring and the outer ring, a concentrated portion of an element or compound having a hydrogen diffusion coefficient lower than that of the base is formed. On the other hand, the traction surface of the inner ring is C: 0.6 to 1.2 wt%, Si: 0.50 to 1.5
wt%, Ni: 0.40 to 4.5 wt%, Mn: 0.20
1.50 wt%, Cr: 1.5-3.0 wt%, Mo: 0.
50 to 2.0 and Cr + Mo: 2.5 to 4.0 wt% and an effective hardened layer composed of a second composition consisting of balance Fe and unavoidable impurities. The depth of the effective hardened layer is more than twice the maximum shear stress generation depth due to Hertzian contact on the surface of the finished part.

A further object of the present invention is to provide a method of manufacturing the rolling element for a toroidal type continuously variable transmission described above. More specifically, by hot forging a cylindrical material having an outer peripheral portion composed of a second portion having the second composition and a core portion composed of the first portion having the first composition, and then machining it, The inner ring is manufactured.

[0009]

EFFECTS OF THE INVENTION Hydrogen-brittle type rolling contact fatigue strength of bearing rolling surfaces of inner and outer rings and W of traction surfaces of inner rings
It is possible to improve the EC type rolling contact fatigue strength. Therefore, the transmittable torque of the toroidal type continuously variable transmission can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a toroidal type continuously variable transmission according to an embodiment of the present invention has an input shaft 10, a pressing device 20, an input side disk 30, and a pair of trunnions 4.
0, an output side disk 50, and an output shaft 60.

The pressing device 20 includes a cam plate 21 and a retainer 22.
And a roller 23.

A pivot shaft 41 is attached to each trunnion 40. On the pivot shaft 41,
A power roller (rolling element) having an inner ring 42 and an outer ring 43 arranged between the input side disc 30 and the output side disc 50 is attached.

The outer ring 43 is fixed to the pivot shaft 41, and the inner ring 42 has a plurality of balls 44 constituting the bearing and the radial needle bearing 4.
It is rotatable about the axis via 5. Also, the inner ring 42
Is the rolling surface 3 of the input side and output side disks 30 and 50.
1, 51 are in contact with each other via lubricating oil.

Therefore, when the input shaft 10 rotates, the input side disk 30 is rotationally driven via the pressing device 20. The rotation of the input side disk 30 is performed by the input side disk 3
It is transmitted to the output side disk 50 having the rolling surface 51 that comes into contact with the inner ring 42 via the inner ring 42 that makes rolling contact with the zero rolling surface 31. As a result, the output shaft 60 rotates together with the output disk 50.

On the other hand, the trunnion 40 and the inner ring 42 are rotated about a rotation axis S indicated by a chain double-dashed line in the figure, and the contact position of the inner ring 42 with respect to the input side and output side disks 30, 50 is moved. As a result, the gear ratio can be changed steplessly.

FIG. 2 is a sectional view for explaining the structure of the inner race 42 and the outer race 43 which are the rolling elements according to the embodiment of the present invention.

In an actual use environment, the traction surface (disk rolling portion) 42b of the inner ring 42 is used under a high surface pressure, and the surface temperature is from a quasi high temperature to a high temperature (100 to 300).
Since the temperature rises to about 0 ° C.), WEC (white microstructure change) type rolling fatigue peeling is exhibited. On the other hand, the inner ring 42 and the outer ring 43
Bearing rolling surfaces (bearing groove) 42a, 43a
Exhibits hydrogen embrittlement type rolling fatigue delamination due to the external hydrogen generated by oil decomposition or the like infiltrating with rolling.

Therefore, in the present embodiment, the bearing rolling surfaces 42a and 43a of the inner ring 42 and the outer ring 43 are formed.
The hydrogen brittle type rolling fatigue strength and the WEC type rolling fatigue strength of the traction surface 42b of the inner ring 42 are improved.

More specifically, the bearing rolling surfaces 42a, 42a
3a is C: 0.6 to 1.2 wt%, Si: 0.35 wt%
Less than, Mn: 0.2 to 1.5 wt%, Cr: 0.8 to 1.
40% by weight, Mo: 0.15 to 0.35% by weight, and an effective hardening layer composed of the first composition consisting of balance Fe and unavoidable impurities.

The depth of the effective hardened layer is more than twice the maximum shear stress generation depth due to Hertzian contact on the surface of the finished part (after heat treatment and machining).

More specifically, C ensures the hardness after quenching. In order to secure a Vickers hardness of Hv550 or more, C of 0.6 wt% or more is preferable.
It is necessary to have a C content, more preferably 0.7 wt% or more.

This is because when the depth of the effective hardened layer having a Vickers hardness of Hv550 or more is less than twice the maximum shear stress generation depth due to the shear stress distribution generated inside due to Hertzian contact, rolling occurs. This is because a high plastic strain is generated inside and the rolling fatigue life is reduced.

When the shear stress distributed in the depth direction due to Hertzian contact in rolling exceeds the yield point of the material, plastic deformation of the material locally occurs, which leads to shortening of the life. The yield point of the material is approximately 1 / Vickers hardness Hv of each part.
It is supposed to be 6. Since the present embodiment has a Vickers hardness of Hv 550 or higher, it is possible to prevent the rolling fatigue life from decreasing due to high plastic strain inside due to rolling.

On the other hand, a C content of 1.1% wt or more, in particular,
A C content of 1.2 wt% or more increases the amount of retained austenite after quenching, resulting in insufficient hardness.

Therefore, the C content is preferably
0.6 to 1.2 wt%, more preferably 0.7 to 1.
It is 1 wt%.

Si is a deoxidizing agent at the time of melting steel, and improves hardenability and reduces workability. In the present embodiment, since the hardenability can be sufficiently secured by the separately contained Cr and Mo, the Si content is preferably less than the necessary minimum of 0.35 wt%.

Mn, like Si, is a deoxidizing agent during steel melting. In order to improve hardenability, preferably,
Mn content of 0.20 wt% or more, more preferably,
A Mn content of 0.31 wt% or more is required. on the other hand,
Mn content over 1.31 wt%, especially 1.50 wt%
If the Mn content exceeds 1, it causes excessive hardening, lowers the workability, and prolongs the transformation end time by the annealing treatment.

Therefore, the Mn content is preferably
0.2-1.5 wt%, more preferably 0.31-
It is 1.31 wt%.

Cr improves toughness, hardenability and temper softening resistance. To obtain this effect, the Cr content is preferably 0.8 wt% or more, more preferably
A Cr content of 1.0 wt% or more is required. On the other hand, 1.
A Cr content of more than 25 wt%, especially a Cr content of more than 1.40 wt% reduces the hydrogen embrittlement type delamination life.

Therefore, the Cr content is preferably
0.8-1.40 wt%, more preferably 0.85-
1.40 wt%, particularly preferably 1.0-1.25 wt%
Is.

Mo, like Si and Cr, has the function of improving hardenability. In order to obtain this effect, a Mo content of 0.15 wt% or more is preferable, and a Mo content of 0.20 wt% or more is more preferable. On the other hand, a Mo content of more than 0.30 wt%, especially a Mo content of more than 0.35 wt% reduces the hydrogen embrittlement type delamination life.

Therefore, the Mo content is preferably
0.15-0.35 wt%, more preferably 0.20
Is about 0.30 wt%.

In the vicinity of the surfaces of the bearing rolling surfaces 42a, 43a of the inner ring 42 and the outer ring 43, concentrated portions of elements or compounds having a hydrogen diffusion coefficient lower than that of the base are formed. Since the concentrated portion forms a hydrogen barrier layer, hydrogen generated by decomposition of hydrocarbons or mixed water during rolling or sliding is prevented from entering the inner ring 42 and the outer ring 43.

The concentrated portion can be formed, for example, by concentrating an element or compound having a face-centered cubic structure. The element of the face-centered cubic structure is nickel or copper, for example.
Nickel or copper film formation accompanied by formation of thickened parts
For example, electroplating, electroless plating, or strike plating can be applied.

The thickness of the thickened portion is, for example, 50 nm.
That is all. In this case, like the coating, it is possible to sufficiently suppress hydrogen invasion into the substrate, and it is possible to maintain the excellent performance of the concentrated portion, which is the hydrogen blocking layer, for a long period of time.

Further, after forming a coating film containing the same element or compound as the main component on the contact surface, the coating component is permeated and diffused into the base material by rolling contact or sliding contact with the mating member to form a base material. It is possible to form a concentrated portion of an element or compound having a hydrogen diffusion coefficient lower than that of the material. In this case, it is possible to form a hydrogen barrier layer that is relatively inexpensive and simple but reliably suppresses the intrusion of hydrogen into the interior and suppresses hydrogen brittle short-life exfoliation.

Next, the traction surface 42b of the inner ring 42 will be described in detail.

The traction surface 42b has a C: 0.6-
1.2 wt%, Si: 0.50 to 1.5 wt%, Ni: 0.
40 to 4.5 wt%, Mn: 0.20 to 1.50 wt%, C
r: 1.5 to 3.0 wt%, Mo: 0.50 to 2.0 wt%
And Cr + Mo: 2.5-4.0 wt%, balance F
It has an effective hardening layer composed of a second composition consisting of e and inevitable impurities.

The depth of the effective hardened layer is more than twice the maximum shear stress generation depth due to Hertzian contact on the surface of the finished part (after heat treatment and machining).

That is, since the inner ring 42 is composed of the first part having the first composition and the second part having the second composition, it is easy to produce.

More specifically, C ensures the hardness after quenching. In order to secure a Vickers hardness of Hv550 or more, a C content of 0.6 wt% or more,
More preferably, a C content of 0.7 wt% or more is required. On the other hand, a C content of 1.1% wt or more, particularly 1.2
A C content of wt% or more increases the amount of retained austenite after quenching, resulting in insufficient hardness.

Therefore, the C content is preferably
0.6 to 1.2 wt%, more preferably 0.7 to 1.
It is 1 wt%. In this case, as described above, it is possible to prevent the rolling fatigue life from decreasing.

Incidentally, it is preferable that the C concentration continuously decreases in the direction from the traction surface 42b to the inside at a right angle. In this case, since the hardness decreases in the depth direction, residual compression is applied near the traction surface 42b. Therefore, the bending fatigue strength against the pressing load on the traction surface 42b increases, and the pressing load limit can be improved. The concentration gradient of C can be formed by a diffusion process of C from the inner ring surface by, for example, carburizing or carbonitriding quenching.

Si is a deoxidizing agent when steel is melted, and improves hardenability and temper softening resistance. Furthermore, Si
Are required to maintain the fatigue strength of the matrix from sub-high temperature to high temperature. To obtain these effects,
Preferably, a Si content of more than 0.50 wt% is required, and more preferably, a Si content of 0.52 wt% or more is required. On the other hand, Si content exceeding 1.24 wt%, especially,
A Si content exceeding 1.50 wt% causes excessive hardening and reduces workability.

Therefore, the Si content is preferably
0.50 to 1.50 wt%, more preferably 0.52
˜1.24 wt%.

Ni improves the fatigue strength, toughness and hardenability of the matrix. In order to obtain these effects, a Ni content of 0.40 wt% or more is preferable, and a Ni content of 0.61 wt% or more is more preferable. On the other hand, the Ni content exceeding 3.55 wt%, especially 4.50
Ni content above wt% causes excessive hardening,
It reduces workability and increases cost.

Therefore, the Ni content is preferably
0.40 to 4.50 wt%, more preferably 0.61
˜3.55 wt%.

Like Si, Mn is a deoxidizing agent during steel melting, and improves hardenability. In order to obtain this effect, the Mn content of 0.20 wt% or more is preferable, and the Mn content of 0.31 wt% or more is more preferable. On the other hand, a Mn content of more than 1.31 wt%, especially a Mn content of more than 1.50 wt% causes excessive hardening, lowers workability, and prolongs the transformation end time by the annealing treatment.

Therefore, the Mn content is preferably
0.20 to 1.50 wt%, more preferably 0.31
Is about 1.31 wt%.

Cr improves toughness and hardenability,
In addition, C introduced during steel melting or carburizing
To form M23C6 type carbide. The M23C6 type carbide has an extremely fine average grain size of 1 μm or less, is difficult to be a stress concentration source, and is dispersed and precipitated in the crystal grains of martensite or bainite. To do. In other words, the M23C6 type carbide improves the WEC type rolling contact fatigue strength from sub-high temperature to high temperature.

In order to obtain these effects, a Cr content of 1.50 wt% or more is preferable, and a Cr content of 1.61 wt% or more is more preferable. On the other hand, Cr content exceeding 2.59 wt%, especially 3.0 wt
If the Cr content exceeds%, a large amount of coarse carbide is precipitated and the WEC type rolling contact fatigue strength is reduced.

Therefore, the Cr content is preferably
1.50 to 3.0 wt%, more preferably 1.
61 to 2.59 wt%.

Mo improves toughness and hardenability,
In addition, C introduced during steel melting or carburizing
And by forming M23C6 type carbide,
Similarly, it improves the WEC type rolling contact fatigue strength from sub-high temperature to high temperature.

For the stable precipitation of M23C6 type carbides, a Mo content of more than 0.50 wt% is preferable, and a Mo content of more than 0.75 wt% is more preferable. On the other hand, a Mo content exceeding 1.25 wt%, especially a Mo content exceeding 2.0 wt% reduces machinability.

Therefore, the Mo content is preferably
0.50 to 2.0 wt%, more preferably 0.75
It is 1.25 wt%.

It should be noted that the Cr + Mo content is set to an appropriate WEC.
2.5 wt% or more is preferable for precipitating M23C6 type carbide required for obtaining the die rolling fatigue strength. On the other hand, when the Cr + Mo content exceeds 4.0 wt%, the M23C6 type carbide is not stably precipitated. Therefore, the Cr + Mo content is preferably 2.5 to 4.
It is 0 wt%.

The first portion having the first composition and the second portion having the second composition are in a metallurgically bonded state, and the composition is continuous in the vicinity of the interface between the first portion and the second portion. Is preferably changed to.

In this case, since the inner ring 42 has a rigidity equivalent to that of an integrated product manufactured from the same steel type, the deformation thereof can be suppressed to the minimum with respect to the pressing load applied to the inner ring 42.

In addition, the second composition, compared to the first composition,
It contains many expensive elements such as Ni, Cr and Mo. On the other hand, what requires the second composition? It is only a portion along the ridgeline of the traction surface 42b of the inner ring 42. Therefore,
In order to reduce the material cost, the interface between the first portion and the second portion is preferably formed along the ridgeline of the traction surface 42b.

As described above, in the present embodiment,
The hydrogen embrittlement type rolling contact fatigue strength of the inner ring and outer ring bearing rolling surfaces and the WEC type rolling contact fatigue strength of the inner ring traction surface are improved. Therefore, the transmittable torque of the toroidal type continuously variable transmission can be improved.

Next, a method of manufacturing the rolling element for the toroidal type continuously variable transmission according to the embodiment of the present invention will be described.

As shown in FIG. 3, the manufacturing method includes a covering step, a first roughing step, a hot forging step, a second roughing step, a heat treatment step, a finishing step, and a concentrated portion forming step. Have.

In the coating step, a material having a different composition (the second portion having the second composition) is formed on the surface layer of the base material (the surface of the first portion having the first composition) of the workpiece to be the rolling element. ) Is clad. The different layer boundaries are metallurgically bonded. The workpiece is an intermediate processed product in which a steelmaking product (continuously cast round bar material) is stretched by plastic working so that the outer diameter approaches the material diameter before hot forging. Further, the coating of materials having different compositions is not limited to the clad method, and for example, a PPW (plasma powder spraying) method can be applied.

In the first roughing process, the workpiece is
In a shape with a length and outer diameter suitable for the hot forging process,
Machined.

In the hot forging step, the work piece is preformed by plastic working at a high temperature using a die.

In the second roughing process, the workpiece is
The shape of the final product is approximated by cutting.

In the heat treatment step, the work piece is carburized, quenched and tempered. More specifically, as shown in FIG. 4, the workpiece is heated at 950 ° C. for 10 to 20 hours, kept at 850 ° C. for 1 hour, cooled at 60 ° C. in oil, and heated at 840 ° C. for 1 hour. Heating, cooling in oil at 60 ° C,
And, it is kept warm at 170 ° C. for 2 hours. In carburization, a C concentration gradient is formed by the diffusion process of C from the surface.

If necessary, nitriding can be performed simultaneously during carburization. The nitrogen that has penetrated into the inside can stabilize a predetermined amount of austenite (soft layer) after quenching and can remain in the surface layer. This plays the role of a cushion against foreign matter biting during rolling fatigue, and thus can prevent the life from being shortened.

Further, the bottom surface of the outer ring 43 is supported by the adjacent components. Therefore, by transmitting the pressing load applied to the inner ring 42, the outer ring 43
The stress generated in the inner ring 42 is not higher than that in the inner ring 42.

Therefore, for example, by including C: 0.95 to 1.1 wt% in the melting stage of the steelmaking product, the necessary pressing load limit can be secured.
That is, since carburization (carbonitriding) can be omitted in the heat treatment step, productivity and cost are improved.

In the finishing step, the workpiece is
Finished within the tolerance of the shape of the final product, mainly by grinding.

In the concentrated portion forming step, the workpiece is
For example, nickel plating is performed to form a plated layer of several μ, and a finished product is obtained.

Next, another method of manufacturing the rolling element for a toroidal type continuously variable transmission according to the embodiment of the present invention will be described.

The manufacturing method, as shown in FIG.
It has a roughing process, a diffusion bonding process, a hot forging process, a second roughing process, a heat treatment process, a finishing process, and a concentrated portion forming process.

In the first roughing process, the workpiece to be the rolling element (inner ring) is machined into a shape having a length and an outer diameter suitable for the hot forging process. The work piece is an intermediate processed product made of a columnar material having an outer peripheral portion having a second portion having the second composition and a core portion having the first portion having the first composition.

In the diffusion bonding process, the workpiece is heated (1000 to 1050 ° C.). Therefore, the second composition and the first composition mutually diffuse at the interface between the outer peripheral portion and the core portion, and a strong metallurgical bonding state is obtained.

In the first roughing process, the workpiece is
In a shape with a length and outer diameter suitable for the hot forging process,
Machined.

In the hot forging step, the work piece is preformed by plastic working at a high temperature using a die. At this time, the second portion having the second composition of the outer peripheral portion is projected to the inner ring traction surface by the plastic deformation in the mold. That is, the productivity of the inner ring can be improved.

Since the second roughing process to the concentrated portion forming process are generally the same as those described above, the description thereof will not be repeated.

Next, the durability of the rolling element according to the embodiment of the present invention will be described.

FIG. 6 is a table for explaining the material specifications applied to the durability test, and FIG. 7 is the W related to the material specifications of FIG.
It is a chart showing the evaluation results of EC type rolling fatigue life and hydrogen embrittlement type peeling life.

The material specifications will be described in detail. As shown in FIG. 6, the composition, the heat treatment conditions, and the presence or absence of the formation of the nickel plating layer (concentrated portion) are combined and changed.
Types (A to I) were prepared. In the material specification A, the nickel plating layer is not formed. Material specification I is C
It is a high carbon steel with a content of 1.05 wt% and it is possible to ensure a suitable hardness, so the applied heat treatment does not include carburizing.

To evaluate the WEC type rolling contact fatigue life, a thrust type rotary contact test apparatus 100 shown in FIG. 8 was used.

The thrust type rotary contact test apparatus 100 includes a casing 101, a rotating shaft 103, a lubricating oil 104 housed in the casing 101, a driving device (not shown) for rotating the rotating shaft 103, and a vibration sensor. (Not shown). The housing 101 holds the lower surface of the sample 142 on the inner bottom surface. The rotating shaft 103 is a steel ball 1 which is a mating material of the sample 142.
A predetermined pressing force is applied to the upper surface of the sample 142 via 44. The vibration sensor detects the time until peeling (flaking).

The sample 142 had a circular shape (φ60 × 5 m).
m). Three steel balls 144 are arranged, the diameter is 9.53 mm (3/8 inch), and the PCD is 38.
mm. The lubricating oil is traction oil at 100 ° C. The thrust load is set so that the Hertzian stress is 6.17 GPa. The rotation speed is 2000 rpm. The rolling fatigue life was defined as the time until the peeling detected by the vibration sensor.

The evaluation of the hydrogen embrittlement type peeling life is shown in FIG.
The bearing rolling fatigue test apparatus 200 shown in FIG.

The bearing rolling fatigue test apparatus 200 includes the housing 20.
1, the plate 202, the rotary shaft 203, and the rotary shaft 20.
Drive device for rotating inner ring 42 together with 3 (not shown)
And a lubricating oil 204 and a vibration sensor (not shown). The plate 202 holds the lower surface of the outer ring 43. The rotating shaft 203 contacts the upper surface of the inner ring 42 with a predetermined pressing force. Lubricating oil 204 passes through plate 202 to inner ring 4
It is supplied inside 2. The vibration sensor detects the time until the bearing rolling surfaces 42a and 43a are separated.
A plurality of balls 44 are provided between the inner ring 42 and the outer ring 43.
Are arranged.

The lubricating oil 204 is a traction oil at 120 ° C., and the lubricating oil supply rate is 3 L / min. The pressing force applied by the rotating shaft 203 is the bearing rolling surfaces 42a, 43.
It is set so that the maximum contact surface pressure at a is 3.6 GPa. The rotation speed is 6000 rpm. The rolling fatigue life was defined as the time until the peeling detected by the vibration sensor.

FIG. 10 is a chart showing the results of the box durability test of rolling elements according to the embodiment of the present invention.

The test pieces 1 and 2 according to the embodiment are applied by combining the material specifications for each part. More specifically, the inner ring of the test piece 1 is formed by clad a material of material specification C with a material of material specification B. The outer ring of the test piece 1 is formed using a material of material specification B.

Further, the inner ring of the test piece 2 is obtained by clad the material of material specification C with the material of material specification B,
It is formed. The outer ring of the test piece 2 is formed using a material of material specification I.

On the other hand, in the test pieces 3 to 11 according to the comparative example, the single material specifications A to I are applied to all parts, respectively.

In the box durability test, the test pieces 1 to 11 are the time until peeling in the case where the lubricating conditions are the same and the gear ratio is 1: 1 and continuous operation is performed at a constant input torque.
The durability was evaluated. The lubricating oil is traction oil at 110 ° C.

The test pieces 1 and 2 according to the embodiment are shown in FIG.
As shown in, the value (618, 63
4 hours), while the test pieces 3 to 1 according to the comparative example are shown.
1 has shown the value less than 400 (94-352 hours).

Further, the peeling sites in the test pieces 1 and 2 according to the embodiment were all inner ring traction surfaces, and the peeling mode was the WEC type. FIG. 11 (a)
[FIG. 4] is an example of a structure photograph of a cross section in the rolling direction in the vicinity of a WEB type peeling portion.

The peeled portions in the test pieces 3 to 11 according to the comparative example are the outer ring bearing rolling surface and the inner ring traction surface, and they are mixed. Further, when the peeling portion was the outer ring bearing rolling surface, the peeling mode was hydrogen embrittlement type, and when the peeling portion was the inner ring traction surface, the peeling mode was WEB type. FIG. 11B is an example of a microstructure photograph of a cross section in the rolling direction in the vicinity of the hydrogen embrittlement type peeling portion.

That is, the WEB type peeling was observed in the sample having a relatively long life. On the other hand, hydrogen embrittlement type exfoliation was observed in the sample having a relatively short life.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a toroidal type continuously variable transmission according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a configuration of a rolling element for a toroidal type continuously variable transmission according to an embodiment of the present invention.

FIG. 3 is a flowchart for explaining a method for manufacturing a rolling element for a toroidal type continuously variable transmission according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining the heat treatment shown in FIG.

FIG. 5 is a flowchart for explaining another method of manufacturing the rolling element for a toroidal type continuously variable transmission according to the embodiment of the present invention.

FIG. 6 is a table for explaining material specifications applied to a durability test of a rolling element for a toroidal type continuously variable transmission according to an embodiment of the present invention.

7 is a chart showing the evaluation results of WEC type rolling contact fatigue life and hydrogen embrittlement type peeling life according to the material specifications of FIG.

FIG. 8 is a cross-sectional view for explaining a thrust type rotary contact test apparatus applied to evaluation of WEC type rolling contact fatigue life.

FIG. 9 is a cross-sectional view for explaining a thrust type rotary contact test apparatus applied for evaluation of hydrogen embrittlement type peeling life.

FIG. 10 is a chart showing the results of a box durability test of rolling elements for a toroidal type continuously variable transmission according to an embodiment of the present invention.

FIG. 11A is an example of a microstructure photograph of a rolling direction cross section near the WEB type peeling portion, and FIG. 11B is an example of a microstructure photograph of a rolling direction cross section near the hydrogen embrittlement type peeling portion.

[Explanation of symbols]

10 ... Input shaft, 20 ... Pressing device, 21 ... cam plate, 22 ... a cage, 23 ... Laura, 30 ... Input side disk, 31 ... rolling surface, 40 ... trunnion, 41 ... Pivot shaft, 42 ... inner ring, 42a ... Bearing rolling surface (bearing groove), 42b ... Traction surface (disk rolling portion), 43 ... the outer ring, 43a ... Bearing rolling surface (bearing groove portion), 44 ... ball, 45 ... Radial needle bearing, 50 ... Output side disk, 51 ... rolling surface, 60 ... Output shaft, 100 ... Thrust type rotary contact test device, 101 ... housing, 103 ... rotation axis, 104 ... Lubricating oil, 142 ... Sample, 144 ... steel balls, 200 ... Bearing rolling fatigue test device, 201 ... housing, 202 ... plate, 203 ... rotary axis, 204 ... Lubricating oil, S ... Rotation axis.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Noriko Uchiyama             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Shino Kino             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F-term (reference) 3J051 AA03 BA03 BB02 BD02 BE09                       CB06 EC08 ED16                 4E087 BA17 BA26 CA11 CB01 DB01                       DB15 DB22 DB24 HA15 HA82

Claims (7)

[Claims] 1. A rolling element for a toroidal type continuously variable transmission, which is arranged between an input side disk and an output side disk and has an inner ring having a bearing rolling surface and a traction surface and an outer ring having a bearing rolling surface. The bearing rolling surface is C: 0.6 to 1.2 wt%, Si: less than 0.35 wt%, M
n: 0.20 to 1.5 wt%, Cr: 0.8 to 1.40 wt
%, Mo: 0.15 to 0.35 wt%, and has an effective hardened layer composed of the first composition consisting of the balance Fe and unavoidable impurities, and the depth of the effective hardened layer at the surface of the finished part is A concentrated portion of an element or compound having a shearing stress generation depth of at least twice due to Hertzian contact and having a hydrogen diffusion coefficient lower than that of the matrix is formed near the surface, and the traction surface has a C: 0.6-1.2 wt%, Si: 0.50-1.5 wt
%, Ni: 0.40 to 4.5 wt%, Mn: 0.20
1.50 wt%, Cr: 1.5-3.0 wt%, Mo: 0.
50-2.0 and Cr + Mo: 2.5-4.0 wt% and an effective hardened layer composed of a second composition consisting of balance Fe and inevitable impurities, and the depth of the effective hardened layer is completed. A rolling element for a toroidal type continuously variable transmission, characterized in that the depth of maximum shear stress due to Hertzian contact on the surface of a component is twice or more. 2. The inner ring has a first composition having the first composition.
The toroidal type continuously variable transmission rolling element according to claim 1, comprising a part and a second part having the second composition. 3. The first part and the second part are in a metallurgical joining state, and the composition continuously changes in the vicinity of the interface between the first part and the second part. The rolling element for a toroidal type continuously variable transmission according to claim 2. 4. The inner ring according to claim 2, wherein an interface between the first portion and the second portion is formed along a ridgeline of the traction surface. Rolling element for toroidal type continuously variable transmission. 5. The toroidal type according to claim 1, wherein the C concentration in the direction from the traction surface of the inner ring to the inside at a right angle is continuously decreased. Rolling element for continuously variable transmission. 6. The outer ring comprises C: 0.95 to 1.1 wt%
The rolling element for a toroidal type continuously variable transmission according to any one of claims 1 to 5, further comprising: 7. A method for manufacturing a rolling element for a toroidal-type continuously variable transmission according to claim 1, wherein
It is possible to manufacture an inner ring by hot forging a columnar material having an outer peripheral portion including a second portion having a composition and a core portion including a first portion having a first composition, and then machining the same. A method of manufacturing a rolling element for a toroidal type continuously variable transmission, which is characterized.