JP3460891B2 - Method of manufacturing rolling element for toroidal type continuously variable transmission - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rolling element for a toroidal type continuously variable transmission which is used for continuously variable transmission in a rotation transmission path.

[0002]

2. Description of the Related Art A toroidal type continuously variable transmission is, as shown in FIG. 1, for example, a metal rolling element, which is a metal rolling element that contacts through lubricating oil, as well as an input disk 1 and an output disk 2. The power roller 3, which is composed of the power roller 3 and sandwiched between the input disk 1 and the output disk 2, changes the inclination of the power roller 3, changes the relative rotational speed of the disks 1 and 2, and shifts the speed, thereby changing the input shaft 5 and the loading cam 6. The power input through the gears is changed by a continuously variable transmission mechanism having a parallel structure as shown in the figure, and then transmitted to the output shaft 8 via the gear 7.

The rolling elements of the toroidal type continuously variable transmission, that is, the disks 1 and 2 and the power roller 3 have a deep hardened layer excellent in rolling fatigue life under high surface pressure in order to transmit large power. Is required.

[0004]

However, in such a rolling element for a toroidal type continuously variable transmission, in order to obtain a deep hardened layer, a carburizing quenching and tempering treatment for a long time is performed on a steel for machine structure. (For example, Japanese Patent Laid-Open No. 7-
71555, etc.). Therefore, if the hardened layer is too deep in the thin portion, there is a problem that cracking due to bending stress is more likely to occur rather than peeling of surface fatigue due to rolling contact.

Further, in the process of obtaining a deep hardened layer by gas carburization, since the grain boundary oxide layer grows deep in the vicinity of the surface, cracks tend to occur from the grain boundary oxide layer as a starting point, and Since the processing time by gas carburization takes a long time, there is a problem that productivity is very poor and cost is increased.

On the other hand, since the rolling surface is subjected to a high surface pressure, if the hardness at the position of maximum shear stress is not sufficient, a depression due to plastic deformation will occur, torque transmission will not be performed, and peeling from the plastically deformed portion will occur. However, there is a problem in that

[0007]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to such conventional problems, and has excellent surface fatigue strength on rolling surfaces.
Further, the non-rolling surface is excellent in bending fatigue strength, and it is an object of the present invention to provide a novel method for manufacturing a rolling element for a toroidal type continuously variable transmission in consideration of surface fatigue strength and bending fatigue strength. .

[0008]

A method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention is, as described in claim 1, a disk which is a rolling element and a power which is a rolling element. In a toroidal type continuously variable transmission configured to make rolling contact with a roller through lubricating oil, mechanical structural steel is used as the material of the rolling element, and the rolling element is electrically connected so that it becomes a cathode When a jig of a conductive material is installed on a surface other than the surface with a clearance dmm and the glow discharge thickness is set to tmm, a carburizing step of d> 2t, and d ≦ 2
It is characterized in that the plasma high-concentration carburizing process is performed in the carburizing process of t, and then the quenching and tempering process is performed.

A method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention which achieves the same object is, as described in claim 2, a rolling element which is the same as a disk which is a rolling element. In a toroidal type continuously variable transmission configured to make rolling contact with a power roller via lubricating oil,
A steel for machine structural use is used as a material of the rolling element, and the rolling element is conductively connected so as to be a cathode, and a jig of a non-conductive material is installed at a clearance dmm other than the rolling surface, and the glow discharge thickness is tmm. In this case, the plasma high-concentration carburizing process is performed in the carburizing process of d> t and the carburizing process of d ≦ t, and then the quenching and tempering process is performed.

In an embodiment of the method for manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 3, shot peening is performed after quenching and tempering. You can also

As another embodiment of the above-described manufacturing method according to the present invention, as described in claim 4, the maximum shear stress generation depth generated inside the rolling element by surface contact is defined as Zst. In this case, the hardness is Hv780 or more and the effective hardened layer depth is 2Zst at the Zst position on the rolling surface.
Above 5Zst, the surface hardness is Hv on the non-rolling surface.
650 or more, effective hardened layer depth 0.3 mm or more 4Zst
It is desirable that the depth is less than or equal to the effective hardened layer depth of the rolling surface.

[0012]

According to the method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 1, the disk as the rolling element and the power roller as the rolling element are lubricated. In a toroidal type continuously variable transmission configured by rolling contact through oil, steel for machine structure is used as a material of the rolling element, and the rolling element is conductively connected so as to serve as a cathode and electrically conductive except for the rolling surface. When a jig of a flexible material is installed with a clearance of dmm and the glow discharge thickness is tmm, a high-concentration plasma carburizing process is performed in a carburizing process in which d> 2t and a carburizing process in which d ≦ 2t, followed by quenching and quenching. A toroidal type non-rolling device which is configured to be subjected to a dehumidification treatment, or as described in claim 2, in which a disk which is a rolling element and a power roller which is also a rolling element are in rolling contact with each other through lubricating oil. In a transmission, machine structural steel is used as a material for the rolling element, conductively connected so that the rolling element serves as a cathode, and a jig made of a non-conductive material is installed on a portion other than the rolling surface with a clearance dmm. Thickness is tm
When m is set, a high-concentration plasma carburizing process is performed in a carburizing process in which d> t and a carburizing process in which d ≦ t. After that, quenching and tempering treatment is performed. The reason why the plasma high-concentration carburizing process is performed will be described below.

The rolling elements (1, 2 ,, etc.) comprising the input disk 1, the output disk 2 and the power roller 3 shown in FIG.
3) are all steels for machine structure (as stipulated in JIS, JIS G 4501 to 4202 SC,
SNC, SNCM, SCr, SMn, SMnC, SAC
There is M etc. ) Is used as a material, and chromium steel (SCr) or chromium-molybdenum steel (SCM) having the chemical composition shown in Table 1 is used, and each part shape is machined.

[0014]

[Table 1]

The jig used for the high-concentration carburization of plasma uses a jig made of SUS309 as a jig made of a conductive material, and a jig made of ceramics as a jig made of a non-conductive material, as shown in FIG. As shown in B), a jig 11 having a shape surrounding the surfaces other than the rolling surfaces of the disks 1 and 2 and the power roller 3 is formed, and the negative electrode 13 is brought into contact with the cathode 13 through the conductor 12 so that Moving body (1, 2,
3) was set as a cathode.

Then, a jig made of SUS309 is used as the jig of such a conductive material, and a jig made of ceramics is used as the jig of the non-conductive material, and the rolling elements (1, 2, 3) are used as the cathode 13 Conductively connected to C3H8 gas as carburizing gas and H2, N2 as carrier gas
When the plasma high-concentration carburizing process was performed by changing the clearance dmm between the non-rolling surface of the rolling element and the jig using a mixed gas to which Ar gas was added, respectively, a jig made of a conductive material made of SUS309 was obtained. When used, as shown in FIG. 4, and when a jig made of non-conductive material made of ceramics was used, as shown in FIG. 5, the carburization limit curve was obtained by changing the gas pressure. (Note that
In FIG. 3, reference numerals 1a and 2a indicate the carburized hardened layers of the input disk 1 and the output disk 2, and reference numeral 3a indicates the carburized hardened layer of the power roller 3.)

This carburizing limit curve is defined by the glow discharge thickness tm.
Depending on m, when a conductive material jig (SUS309) is used, it is carburized when d> 2t, not carburized when d ≦ 2t, and when a non-conductive material jig (ceramics) is used. , D> t, and not d ≦ t.

That is, the carburization limit curve is 1 / g of the glow discharge thickness tmm for the jig (SUS309) made of a conductive material.
No. 2 shows the glow discharge thickness tmm for a jig (ceramics) made of a non-conductive material.
Is calculated as shown in FIG.

From this, the higher the gas pressure, the thinner the glow discharge thickness tmm, and as the carburizing gas, C ₃ H ₈ gas is mixed with H ₂ gas, N ₂ gas and Ar gas in the order of glow. The discharge thickness tmm becomes thicker.

Therefore, in performing the plasma high-concentration carburizing treatment on the rolling elements, SUS3, which is a conductive material, is used as a jig.
In the case of using 09 or the like, a carburizing process that satisfies d> 2t and d ≦ 2t is adopted, and when using insulating ceramics which is a non-conductive material as a jig, d> t and d ≦ t By adopting the carburizing process, different hardened layer thickness can be obtained on the rolling surface and the non-rolling surface, so it is desirable to perform such plasma high concentration carburizing treatment and then quench and temper treatment. Is, for example, when the depth of maximum shear stress generated inside the rolling element due to surface contact is Zst, as described in claim 4,
At the Zst position on the rolling surface, the hardness is Hv780 or more,
The effective hardened layer depth is 2Zst or more and 5Zst or less, the surface hardness of the non-rolling surface is Hv650 or more, and the effective hardened layer depth is 0.3mm or more and 4Zst or less (that is, the effective hardened layer depth of the rolling surface is Of less than 80% of the upper limit value of 5Zst) and shallower than the effective hardened layer depth of the rolling surface, the rolling element has excellent surface fatigue strength on the rolling surface and bending fatigue strength on the non-rolling surface. Will be obtained.

In the carburizing step in which the clearance with the jig is d> 2t, it is preferable that 50 mm ≧ d because the processing capacity decreases if the clearance dmm is too large.

Then, as described in claim 3,
By applying shot peening after quenching and tempering treatment, high residual stress is added, bending fatigue strength is further improved, crack occurrence rate is further reduced, and rolling fatigue life is further improved. Becomes

In the method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, by performing the plasma high-concentration carburizing and tempering treatments as described above,
When the depth of maximum shear stress generated inside the rolling element due to surface contact is Zst, the hardness is Hv780 or more and the effective hardened layer depth is 2Zst at the Zst position on the rolling surface.
Above 5Zst, the surface hardness is Hv on the non-rolling surface.
650 or more, effective hardened layer depth 0.3 mm or more, 4Zs
It is desirable that the depth is not more than t and is shallower than the effective hardened layer depth of the rolling surface, but the reason for limiting in this way will be described.

Hertzian stress distribution at the rolling element contact portion and 1/6
The Vickers hardness distribution is shown in FIG. The plastic deformation of the rolling element is the critical shear stress of the material (1/6 of the Vickers hardness).
Degree) is below the maximum shear stress.

For example, under the durability conditions shown in Table 2, that is, the contact surface pressure (Pmax) of 3.8 GPa, when the conventional gas carburizing quenching and tempering treatment is applied to the steel for machine structure, the maximum shear stress position (Zst Position: 0.8m from the surface
Since the carbide does not precipitate at the position (m position), Hv780
Does not meet. As a result, a portion where the 1/6 Vickers hardness is lower than the shear stress is generated, so that a depression due to plastic deformation occurs.

In order to prevent depression due to plastic deformation, the hardness is Hv near the maximum shear stress position (Zst position).
780 or more is required, and it is obtained by precipitating a carbide by a high-concentration carburizing treatment. However, if the hardness at the Zst position exceeds Hv950, the area ratio of carbides is 50%.
Since more than area% will be precipitated, during quenching,
It is preferable that the upper limit of the hardness at the Zst position is Hv950 or less because quench cracking is likely to occur.

Since peeling due to rolling fatigue occurs in an effective hardened layer that is less than twice the Zst, the effective hardened layer depth must be at least twice the Zst.

Further, in the thin portion, if the hardened layer is too deep, the bending fatigue strength decreases, so the effective hardened layer depth at the rolling surface was set to a maximum of 5 Zst.

On the other hand, on the non-rolling surface, it is necessary to prevent the surface depression at the contact portion with parts other than the rolling elements. If the surface hardness is less than Hv650, the depression will occur. Therefore, the hardness is Hv650 or more. It is necessary to form an effective hardened layer depth of 0.3 mm or more. However, the surface hardness is Hv950
If it exceeds, the carbides will be deposited in an area ratio of 50 area% or more, so that quenching cracks easily occur during quenching. Therefore, the upper limit of the hardness is preferably Hv950 or less. Further, in the thin portion, if the hardened layer is too deep, the bending fatigue strength decreases, so the effective hardened layer depth on the non-rolling surface was set to 4Zst.

Therefore, with such a structure, the surface fatigue strength and the rolling fatigue strength are improved on the rolling surface, and the bending fatigue strength is improved on the non-rolling surface, so that the durability is improved. Good rolling elements can be obtained.

[0031]

EXAMPLES Examples of the present invention and comparative examples are shown in Tables 3 to 3.
It will be described below together with Table 44.

In this example and the comparative example, the heat treatment pattern was carried out by any of (1) and (2) shown in FIG. 7 and (3) (4) (5) (6) shown in FIG. 8 as a comparative example. Then, quenching treatment was performed.

Specifically, as shown in the table, Example 1
According to the above, after the rolling element is manufactured using SCM420,
A jig made of a conductive material made of SUS309 is installed in the non-rolling portion with a clearance d = 12 mm, and according to the heat treatment pattern shown in (1) of FIG. 7, C ₃ H ₈ + H ₂ mixed gas, gas pressure 2 Torr, glow discharge D = at thickness tmm
The high concentration plasma carburizing process of the first step was performed under the condition of 0.8 t, and then d = 2.4 at a C ₃ H ₈ + Ar mixed gas, a gas pressure of 2 Torr, and a glow discharge thickness tmm.
The plasma high concentration carburizing process of the second step was performed under the condition of t.

Further, in Examples 2 to 73, the plasma high-concentration carburizing process was performed under the conditions shown in the table in the same manner as in Example 1.

As a comparative example, a conventional gas carburizing process (Comparative Examples 1 and 2), a plasma high-concentration carburizing process without a jig (Comparative Example 3), and A jig made of a conductive material made of SUS309 was installed on the rolling surface with a clearance d = 12 mm, and according to the heat treatment pattern shown in (1) of FIG. 7, in the first step, a mixed gas of C ₃ H ₈ + H ₂ and a gas pressure of 2 Torr were used. After the plasma high-concentration carburizing treatment under the condition that d = 2.5t at the glow discharge thickness tmm, in the second step, a C ₃ H ₈ + Ar mixed gas,
D at gas pressure 2 Torr and glow discharge thickness tmm
The case where the plasma high-concentration carburizing process is performed under the condition of = 11.4 t (Comparative Example 6) is shown as an example.

In Comparative Examples 7 to 22, the plasma high concentration carburizing process was performed under the conditions shown in the table in the same manner as in Comparative Example 6.

A tempering treatment was applied to the test pieces that had been subjected to the quenching treatment after the plasma high-concentration carburization, and some of the test pieces had a coverage of 300% and an arc height of 0.5 m.
Shot peening of mA was performed.

After that, only the rolling surface was finished and a durability test was conducted.

The durability test was carried out under the conditions shown in Table 2 using a physical durability tester having the same structure as that shown in FIG. The same material is used for the disk and power roller that have undergone the durability test,
A heat treatment pattern was used.

[0040]

[Table 2]

The area ratio of precipitated carbides at the maximum shear stress position (Zst position) on the rolling surface of the disk and power roller subjected to carburizing and tempering according to the present invention and comparative examples, the hardness, and the effective hardened layer depth ( E.C.D.) and surface hardness on non-rolling surface, effective hardened layer depth (E.C.D.), grain boundary oxide layer depth and durability test results are shown in Tables 3 to 38.

As is clear from the results shown in the table, the high-concentration plasma carburizing and tempering product obtained by the manufacturing method of the present invention has a longer life than the comparative product.
The reasons for this are as follows: (1) The plasma carburized product does not generate a grain boundary oxide layer, which is likely to be a starting point of cracks, because it is processed in a vacuum, so that the bending fatigue strength is improved and the crack generation rate is lowered.

(2) Since the thin portion does not harden to the inside, the bending fatigue strength is improved, the incidence of cracking is reduced, and the effective hardened layer is deep on the rolling surface and excellent in rolling fatigue characteristics. Therefore, the life is improved.

(3) Hv 780 or higher is obtained at the maximum stress shearing position (Zst position), and the hardness is improved, so that it does not sink even under high surface pressure and the rolling fatigue life is improved.

(4) By performing shot peening after the plasma high-concentration carburizing treatment, a high residual stress is added, so that the bending fatigue strength is improved, the crack occurrence rate is reduced, and the rolling fatigue life is also increased. improves.

On the other hand, (5) When trying to obtain a deep hardened layer by gas carburization, it takes a long time and the grain boundary oxide layer grows, so that cracks originating from the grain boundary oxide layer start from the edges. It grows and cracks easily.

(6) When plasma high-concentration carburization is performed without using a jig, cracks are likely to occur because the inside of the thin-walled portion is hardened as in gas carburization.

(7) SUS3 is provided between the clearance dmm from the jig on the non-rolling surface and the glow discharge thickness tmm.
With a jig made of a conductive material such as 09, d> 2t, d ≦ 2t
In the case of carburizing treatment which does not have two steps of d> t and d ≦ t with a jig of non-conductive material such as ceramics,
Since the inside of the thin portion is hardened, cracks are likely to occur.

(8) When a jig made of a conductive material such as SUS309 is used as the jig, a carburizing step of d> 2t only,
Alternatively, when a jig made of a non-conductive material such as ceramics is used for the jig, the carburizing step only for d> t causes the inside of the thin portion to be hardened, so that cracks are likely to occur.

(9) When a jig made of a conductive material such as SUS309 is used, a carburizing step of d≤2t only,
Alternatively, when a jig made of a non-conductive material such as ceramics is used as the jig, the non-rolling surface is not carburized in the carburizing step only for d ≦ t, so that the contact surface with parts other than the rolling elements is deformed, It peels off.

(10) When the carburizing time is short and the effective hardened layer depth of the rolling surface does not satisfy 2Zst, spalling separation occurs from the rolling surface at an early stage.

(11) The hardness near the maximum shear stress position is H
If v780 is not satisfied, the rolling surface is dented due to plastic deformation and peeling occurs.

On the other hand, according to the plasma high-concentration carburizing treatment of the present invention, the treatment time is about 1/3 of that of the conventional method.
It is shortened to 1/4, and a significant cost reduction is possible.

From the above, according to the present invention, it is possible to significantly reduce the cracks that occur in thin-walled portions other than the rolling surface, and to process rolling elements with a long life in a short time. It has become possible to obtain rolling elements that can cope with pressure.

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

[Table 5]

[0058]

[Table 6]

[0059]

[Table 7]

[0060]

[Table 8]

[0061]

[Table 9]

[0062]

[Table 10]

[0063]

[Table 11]

[0064]

[Table 12]

[0065]

[Table 13]

[0066]

[Table 14]

[0067]

[Table 15]

[0068]

[Table 16]

[0069]

[Table 17]

[0070]

[Table 18]

[0071]

[Table 19]

[0072]

[Table 20]

[0073]

[Table 21]

[0074]

[Table 22]

[0075]

[Table 23]

[0076]

[Table 24]

[0077]

[Table 25]

[0078]

[Table 26]

[0079]

[Table 27]

[0080]

[Table 28]

[0081]

[Table 29]

[0082]

[Table 30]

[0083]

[Table 31]

[0084]

[Table 32]

[0085]

[Table 33]

[0086]

[Table 34]

[0087]

[Table 35]

[0088]

[Table 36]

[0089]

[Table 37]

[0090]

[Table 38]

[0091]

According to the method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 1, the disk as the rolling element and the power roller as the rolling element are lubricated. In a toroidal type continuously variable transmission configured by rolling contact through oil, steel for machine structure is used as a material of the rolling element, and the rolling element is conductively connected so as to serve as a cathode and electrically conductive except for the rolling surface. When a jig of a flexible material is installed with a clearance of dmm and the glow discharge thickness is tmm, a high-concentration plasma carburizing process is performed in a carburizing process in which d> 2t and a carburizing process in which d ≦ 2t, followed by quenching and quenching. Or to carry out a dehumidification process, or as described in claim 2,
A steel for machine structural use is used as a material of the rolling element, and the rolling element is conductively connected so as to be a cathode, and a jig of a non-conductive material is installed at a clearance dmm other than the rolling surface, and the glow discharge thickness is tmm. , The plasma carburizing process is performed in the carburizing process with d> t and the carburizing process with d ≦ t, and then the quenching and tempering process is performed. Therefore, the effective carburizing depth of the non-rolling surface Can be made shallower than the rolling surface, and has excellent surface fatigue strength and rolling fatigue strength on the rolling surface as well as excellent bending fatigue strength on the non-rolling surface. It is possible to produce a remarkably excellent effect.

Then, as described in claim 3,
By performing shot peening after quenching and tempering treatment, it becomes possible to further improve the bending fatigue strength, and it is possible to further improve the rolling fatigue life, which is a more excellent effect. Be done.

Further, as described in claim 4,
When the depth of maximum shearing stress generated inside the rolling element due to surface contact is Zst after the plasma high-concentration carburizing and tempering as described above is performed, the hardness at the Zst position on the rolling surface Is Hv780 or more, the effective hardened layer depth is 2 Zst or more and 5 Zst or less, and on the non-rolling surface, the surface hardness is Hv650 or more and the effective hardened layer depth is 0.
By making it 3 mm or more and 4 Zst or less and shallower than the effective hardened layer depth of the rolling surface, it has excellent surface fatigue strength and rolling fatigue strength on the rolling surface and bending on the non-rolling surface. It is possible to more reliably manufacture a rolling element for a toroidal type continuously variable transmission that is excellent in fatigue strength.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing a basic configuration of a toroidal type continuously variable transmission.

FIG. 2 is an explanatory diagram showing the relationship between the distance from the surface and shear stress or hardness.

FIG. 3 is a cross-sectional explanatory view showing the shapes of jigs arranged in proximity to a rolling element made of a disc ((A) in the figure) and a rolling element made of a power roller ((B) in the figure).

FIG. 4 is an explanatory diagram illustrating the relationship between clearance and gas pressure when SUS309, which is a conductive material, is used for the jig.

FIG. 5 is an explanatory diagram exemplifying a relationship between clearance and gas pressure when ceramics, which is a non-conductive material, is used for the jig.

FIG. 6 is an explanatory diagram illustrating the relationship between gas pressure and glow discharge thickness.

FIG. 7 is an explanatory diagram showing heat treatment heat patterns (1) and (2) of the present invention.

FIG. 8: Conventional heat treatment heat patterns (3) (4)
It is explanatory drawing which shows (5) and (6).

[Explanation of symbols]

1 Input disc (rolling element) 1a Carburizing layer of input disc 2 Output disc (rolling element) 2a Carburizing layer of output disc 3 Power rollers (rolling elements) 3a Carburizing layer of power roller

Front page continued (72) Inventor Shun Umegaki Nissan Motor Co., Ltd. 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa (56) References JP-A-6-159463 (JP, A) JP-A-63-297866 (JP, A) JP 6-212396 (JP, A) Actual development 1-87153 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16H 13/00-15 / 56 C21D 1/06 C21D 9/00-9/44 C21D 9/50 C23C 8/00-12/02

Claims (4)

(57) [Claims] 1. A toroidal type continuously variable transmission configured by rolling contact between a disk that is a rolling element and a power roller that is also a rolling element through a lubricating oil, and a mechanical structural steel as a material of the rolling element. , The conductive material is connected so that the rolling element becomes the cathode, and a jig made of a conductive material other than the rolling surface is installed with a clearance of dmm, and the glow discharge thickness is t.
mm, a carburizing step in which d> 2t, and d ≦ 2t
The method of manufacturing a rolling element for a toroidal-type continuously variable transmission, which comprises performing a high-concentration plasma carburizing process in a carburizing process, which is followed by a quenching and tempering process. 2. A toroidal type continuously variable transmission configured by rolling contact between a disk that is a rolling element and a power roller that is also a rolling element through lubricating oil, wherein a mechanical structural steel is used as a material of the rolling element. Carburizing so that d> t when the glow discharge thickness is set to tmm and a jig of non-conductive material is installed on the part other than the rolling surface with a clearance of dmm. A process for producing a rolling element for a toroidal-type continuously variable transmission, which comprises performing a plasma high-concentration carburizing process in a step and a carburizing process with d ≦ t, and then performing a quenching and tempering process. 3. The method for producing a rolling element for a toroidal type continuously variable transmission according to claim 1, wherein shot peening is performed after the quenching and tempering treatment. 4. When the depth of maximum shear stress generated inside the rolling element due to surface contact is Zst, the hardness is Hv780 or more and the effective hardened layer depth is 2Zst or more at the Zst position on the rolling surface. 5Zst or less, on non-rolling surface,
Surface hardness Hv 650 or more, effective hardened layer depth 0.3m
The method for manufacturing a rolling element for a toroidal type continuously variable transmission according to any one of claims 1 to 3, wherein the rolling element is made to be m or more and 4Zst or less and shallower than the effective hardened layer depth of the rolling surface. .