JPH08326862A - Rolling element for troidal type continuously variable transmission and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a rolling element productively and inexpensively for a troidal type continuously variable transmission excellent in remedy for rolling fatigue characteristics. CONSTITUTION: A steel as a rough material contains the following elements by weight percent: 0.50-0.80% C, 0.50-2.00% Mn, 0.040% or less P, and 0.040% or less S, and optionally 0.25-3.00% Si, 0.05-0.50% V, and 2.00% or less Cr, and Fe as a balance and impurities. The steel is deformed into a rolling-element- shape and subjected to high frequency wave quenching, so that a rolling element for a troidal type continuously variable transmission (an input disk 5, an output- disk 9, and a power roller 10) excellent in remedy for rolling fatigue characteristics can be manufactured with good productivity and at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toroidal type (rolling type) continuously variable transmission that can be used as a continuously variable transmission in vehicles such as automobiles and rotary power sources, and more particularly to a toroidal type continuously variable transmission. And a manufacturing method thereof.

[0002]

2. Description of the Related Art As a transmission, a gear type gear has been used in many directions and in a large amount from the past, and as a gear steel for forming a gear, carbon for mechanical structure established in JIS G 4051 to 4202. Among steels and alloy steels, for example, low alloy steels such as chromium steel SCr420 and chromium molybdenum steel SCM420 are used, and carburizing or nitriding is performed after forming such a mechanical structural steel into a gear shape. It has been used after surface hardening treatment such as.

However, since the conventional gear type stepped transmission is a stepwise shift, there is a drawback that a loss occurs in power transmission or a shift shock occurs.

On the other hand, since the continuously variable transmission has no shift shock and is excellent in power transmission, various practical applications have been studied, and it has been practically used in some passenger cars (see "New model manual"). NISSAN March ", edited by Nissan Motor Co., Ltd. January 1992, pages C-9 to C-48).

The continuously variable transmission is roughly classified into a belt drive system in which a belt and a pulley are combined and a traction drive system in which rolling elements are used. The former has already been used when the transmitted power is small. The toroidal type (rolling type) is one of the latter, and has a mechanism capable of coping with high horsepower, for example, as shown in FIG. 1, has a structure using a metal rolling element that contacts through lubricating oil. The toroidal type continuously variable transmission 1 includes an input shaft 2
Input disks 5 and 5 that rotate integrally via a loading cam 3 and a connecting shaft 4 connected to the input disk, and output disks 9 and 9 that rotate the output shaft 8 via gears 6 and 7 Power rollers 10, 10, 10, 1 between the disks 5, 5 and the output disks 9, 9.
0, each power roller 10 has a ball bearing 1
1 has a structure supported by the support 12 respectively.

In the toroidal type continuously variable transmission 1, the inclination of the power roller 10 sandwiched between the input disk 5 and the output disk 9 is changed to change the relative rotation speed of the input / output disks 5, 9. The mechanism is such that power is transmitted from the input shaft 2 to the output shaft 8 while shifting gears (Japanese Patent Laid-Open No. 1-229158, etc.).

In such a continuously variable transmission, in order to transmit a large amount of power, the rolling elements (input / output disks 5, 9, power roller 10) of the toroidal type continuously variable transmission 1 are
A material and a manufacturing method capable of obtaining high surface hardness and deep hardened layer depth which are excellent in rolling contact fatigue life under high surface pressure are required.

[0008]

However, in such a conventional rolling element for a toroidal type continuously variable transmission, a conventional carburizing steel is used in order to have a rolling fatigue life under a high surface pressure. Carburizing, quenching, and tempering treatments are performed for a long time (for example, JP-A-7-71555).
Therefore, there is a problem that productivity is very poor and cost is increased.

In the process of obtaining a deep hardened layer,
Since the grain boundary oxide layer grows deeply in the vicinity of the surface, there is a problem that cracks tend to occur starting from the grain boundary oxide layer.

On the other hand, when the hardened layer is shallow, it collapses due to high surface pressure and peeling occurs on the rolling surface. On the contrary, when the hardened layer is too deep, in the thin portion, Since the interior is hardened, there is a problem that cracks are likely to occur due to bending stress. Further, when the surface hardness is low, there is a problem that the rolling element surface may be deformed. Furthermore, the rolling elements are subject to heat generation due to friction and repetitive stress, so that there is a problem that they tend to soften.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to provide a rolling element for a toroidal type continuously variable transmission which is excellent in rolling fatigue life and a method for manufacturing the rolling element. The high frequency that prevents the occurrence of grain boundary oxidation due to carburization as in the past and prevents cracks starting from the grain boundary oxide layer and can obtain a deep hardened layer in a short time. By applying quenching and designing an alloy to prevent softening due to frictional heat, it is possible to provide rolling elements for toroidal type continuously variable transmission with excellent rolling fatigue characteristics with good productivity and at low cost. It is an object.

[0012]

A rolling element for a toroidal type continuously variable transmission according to the present invention has, as described in claim 1, C: 0.50 to 0.80% by weight and Mn: 0. .50
~ 2.00 wt%, P: 0.040 wt% or less, S:
It is characterized in that it is made of steel containing 0.040% by weight or less and the balance Fe and impurities.

The rolling element for a toroidal type continuously variable transmission according to the present invention is formed from steel containing Si: 0.25 to 3.00% by weight, as described in claim 2. Or a steel containing V: 0.05 to 0.50 wt% in the steel as described in claim 3, As described in claim 5, the steel may be formed of steel containing Cr: 2.00% by weight or less, and as described in claim 5, any one of claims 1 to 4 In the rolling element for a toroidal type continuously variable transmission described in (1), a surface-hardened layer formed by induction hardening may be formed.

The method for manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 6, has C: 0.50 to 0.80% by weight, Mn: 0. Fifty
~ 2.00 wt%, P: 0.040 wt% or less, S:
It is characterized in that the steel is made of steel containing 0.040% by weight or less and the balance of Fe and impurities as a raw material, and is then subjected to induction hardening treatment after being formed into a rolling element shape.

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 7, Si: 0.25 to 0.25 in the steel.
A steel containing 3.00% by weight is used as a raw material to be formed into a rolling element, or a steel containing V: 0.05 to 0.50% by weight is used as described in claim 8. The material may be formed into a rolling element shape, or as described in claim 9, a steel containing Cr: 2.00% by weight or less may be formed into a rolling element shape. You can do it.

[0016]

The rolling element for a toroidal-type continuously variable transmission according to the present invention has a C: 0.
50 to 0.80 wt%, Mn: 0.50 to 2.00 wt%, P: 0.040 wt% or less, S: 0.040 wt%
The present invention is characterized in that it is formed of steel composed of the balance Fe and impurities including the following, and the method for producing a rolling element for a toroidal type continuously variable transmission according to the present invention is defined in claim 6. As noted, C: 0.50
0.80% by weight, Mn: 0.50 to 2.00% by weight,
P: 0.040% by weight or less, S: 0.040% by weight or less, characterized in that the steel is made of a balance Fe and impurities and is formed into a rolling element shape, and then induction hardening is performed. However, the action of each component and the reason for limiting the content thereof are as follows.

C: 0.50 to 0.80% by weight C (carbon) is an element which acts to make the strength of the rolling element sufficiently good, and particularly, the strength of the rolling element is sufficiently high after induction hardening. It is an essential element in order to keep it in good condition. And, in order to maintain the surface hardness after induction hardening, it is necessary to contain 0.50% by weight or more.

However, when the content of C exceeds the eutectoid point of 0.80% by weight in the Fe-C phase diagram, the surface hardness rather lowers, leading to deterioration of strength improvement. Moreover, not only does proeutectoid cementite generate and impair the toughness, but it also raises the material hardness in the raw material state, reduces machinability, and causes adverse effects such as deterioration of formability into rolling elements. Therefore, the upper limit of the C content is 0.80.
Weight%

Mn: 0.50 to 2.00% by weight Mn (manganese) acts as a deoxidizing agent / desulfurizing agent during the melting of steel, improves hot workability of steel, and has good hardenability. Since it is an element having a function of achieving such an effect, it is contained in an amount of 0.50% by weight or more in order to improve such hot workability and ensure good hardenability.

However, if it is contained excessively, the machinability of the material is deteriorated and the formability of the rolling element is deteriorated. Therefore, the upper limit of the Mn content is 2.0.
0% by weight.

P: 0.040% by weight or less P (phosphorus) lowers the toughness of steel, so it is limited to 0.040% by weight or less.

S: 0.040 wt% or less S (iodine) has the effect of reducing the workability and toughness of steel, so it is limited to 0.040 wt% or less.

Fe: Balance Fe (iron) is an element useful as a matrix component for inexpensively obtaining a rolling element having high strength and high toughness, and is therefore defined as the balance.

In the rolling element for a toroidal type continuously variable transmission and the manufacturing method thereof according to the present invention, steel may further contain the following components.

Si: 0.25 to 3.00% by weight Si (silicon) is an element which acts as a deoxidizing agent during steel melting, and at the same time increases the temper softening resistance of steel. In order to fully exert such actions and effects, it is necessary to contain 0.25% by weight or more. However, even if it is contained excessively, not only the effect is saturated, but also it causes problems such as impairing forgeability and machinability, so the upper limit of the Si content is preferably 3.00% by weight. As described in the items 2 and 7, it is possible to make the steel contain Si: 0.25 to 3.00% by weight.

V: 0.05 to 0.50 wt% V (vanadium) is an element that has the effect of refining the crystal grain boundaries of steel and contributes to the improvement of strength and toughness, and at the same time, rolling fatigue. Since it is an element effective in preventing the phenomenon that destruction occurs in a short life, it is necessary to contain 0.05% by weight or more in order to obtain such actions and effects. However, even if excessively contained, the effect is saturated, so the upper limit of the V content is preferably 0.50% by weight, and as described in claims 3 and 8, V:
The content may be 0.05 to 0.50% by weight.

Cr: 2.00% by weight or less Cr (chromium) has the effect of improving the hardenability of steel and increasing the resistance to temper softening. Therefore, it is necessary to incorporate Cr having such an effect. You can also However, even if it is contained excessively, the effect is saturated, so the upper limit of the Cr content is preferably 2.00% by weight.
As described in (1), steel may contain Cr: 2.00% by weight or less.

In the rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 5,
It is assumed that a hardened layer is formed by induction hardening treatment, and in the method for manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 6,
The steel with the above composition is formed into a rolling element shape and then induction hardening is performed. The dielectric (coil) shape, power, frequency, heating rate, heating temperature, and heating time in this induction hardening treatment are used. , The cooling method and the cooling agent, and the subsequent tempering method can be appropriately selected.

Thus, by rolling the alloy by preventing induction of intergranular oxidation due to carburizing treatment and applying induction hardening capable of obtaining a deep hardened layer in a short time to prevent softening due to frictional heat. A rolling element for a toroidal type continuously variable transmission having excellent fatigue characteristics can be provided with high productivity and at low cost.

[0030]

EXAMPLES Examples shown in Table 1 were used for producing a metal rolling element including an input disk 5, an output disk 9 and a power roller 10 which are components of the toroidal continuously variable transmission 1 having the structure shown in FIG. Steel having the chemical composition shown in 4 was used as a raw material.

Then, using the steel of Example 4 as a raw material, each rolling element shape was machined and molded, and at the same time, a roller pitching test piece shape used for a rolling fatigue life test was machined and molded. .

Next, each rolling element shaped article and roller pitching test piece shaped article were subjected to induction hardening under the induction hardening conditions shown in Table 3, followed by tempering treatment at 170 ° C. for 2 hours and polishing. Finished.

Under the induction hardening conditions shown in Table 3, the disk A surface is the back surface and the hole surface side of the input disk 5 and the output disk 9 shown in FIG. 2, and the disk B surface is the same as the figure. 2 is the surface on the rolling surface side. Further, the surface of the power roller A is a surface on the back surface and the hole surface side of the power roller 10 shown in FIG. 3, and the surface of the power roller B is a surface on the rolling surface side in FIG. Then, in induction hardening, first, heating and quenching was performed with a coil having a shape matching the A surface (back surface and hole surface), and then, the B surface (rolling surface) was hardened. . When quenching the B side, it was cooled sufficiently so that the A side was not annealed by the conduction heat of the induction heating.

After the induction hardening / tempering treatment was carried out in this manner, the hardness distribution in the cross section of the disks 5 and 9 was measured, and the results shown in FIG. 4 were obtained. In this case, the measurement position is in the direction of the arrow in FIG. 4, and the relationship between the distance from the surface and the hardness in the direction of the arrow is shown in FIG.
It was shown to.

The surface hardness (HV) of the disks 5 and 9 after the induction hardening / tempering treatment and the effective hardened layer depth (mm) shown in () are the results shown in FIG. Similarly, the surface hardness (HV) of the power roller 10 and the effective hardened layer depth (mm) shown in ().
Was the result shown in FIG.

Then, in the same manner as in the case of using the steel of Example 4, the steels of Examples 1 to 3 and 5 to 7 and Comparative Examples 2 to 9 were used as raw materials and machined into respective rolling element shapes. In addition to being molded, it was molded into a roller pitching test piece shape by mechanical processing, induction hardening was carried out under the induction hardening conditions shown in Table 3, and then tempering treatment was carried out at 170 ° C. for 2 hours, and finish processing by polishing was carried out. .

Further, carburizing steel (SCM420H steel) having the composition of Comparative Example 1 was used as a raw material to be formed into a rolling element shape and a roller pitching test piece shape, followed by carburizing and diffusion hardening for 40 hours and finishing by polishing. Processed.

For the rolling elements of Examples 1 to 7 and Comparative Examples 1 to 9 thus obtained, the surface hardness (HV) after the surface hardening treatment, the surface tempering hardness after tempering at 300 ° C. for 1 hour, Maximum shear stress generation position (0.8mm below the surface)
When the hardness, the internal hardness and the effective hardened layer depth were examined, the results shown in Tables 4 and 5 were obtained.

Further, as shown in FIG. 7, the small roller 21
The small roller 21a and the large roller 21 of the roller pitching test piece 21 having a
A roller pitching test was performed under the conditions shown in Table 6 by applying a load to 1 to measure the life until surface peeling occurred. The results are shown in the column of roller pitching test life in Table 8.

Further, each rolling element was assembled in the unit shown in FIG. 1 and an actual machine durability test was conducted under the conditions shown in Table 7,
The life until surface peeling occurred was measured. The results are shown in the column of the actual test life in Table 8.

Further, in order to evaluate the workability of each rolling element, a turning test was conducted under the turning test conditions shown in Table 9, and the results of the machinability characteristics shown in Table 10 were obtained.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

[Table 6]

[0048]

[Table 7]

[0049]

[Table 8]

[0050]

[Table 9]

[0051]

[Table 10]

As shown in Tables 4 and 5, Examples 1 to 1
The internal hardness of No. 7 is about HV1 in Examples 1 to 3 as compared with the internal hardness of Comparative Example 1 (made of carburizing steel).
00, and in Examples 4 to 7 are all about the same or even higher than HV50, which is low. That is, the hardness on the surface is large and the hardness on the inside is moderately soft, and the life characteristics are good as shown in Table 8 and the machinability as shown in Table 10. Was also good.

On the other hand, in the case of Comparative Example 2, since the C content in the steel was too small, the surface, as shown in Table 5,
The hardness of the interior and tempering at 300 ° C. is low, and although the machinability is good as shown in Table 10,
As shown in Table 8, the life characteristics were inferior.

Further, in the case of Comparative Example 3, since the C content in the steel is too large, the hardness characteristics are good as shown in Table 5 and the life characteristics are good as shown in Table 8. However, as shown in Table 10, the machinability was inferior, and the latheability was reduced by about 35%, which caused a problem in mass production.

Furthermore, in the case of Comparative Example 4, since the Si content was too small, the tempering hardness at 300 ° C. was low as shown in Table 5, and the durable life was shortened as shown in Table 8. It was

In the case of Comparative Example 5, since the Si content is too large, the hardness characteristics and the life characteristics are good, but
As shown in Table 10, the machinability is poor,
Since the turning property was reduced by about 30%, there was a problem in terms of mass production.

Further, in the case of Comparative Example 6, since the Mn content was too small, the effective hardened layer depth was slightly shallow as shown in Table 5, and the durability life was inferior as shown in Table 8. Was becoming.

Further, in the case of Comparative Example 7, since the Mn content is too large, the hardness characteristics and the life characteristics are excellent, but as shown in Table 10, the machinability is inferior. The turning property was reduced by about 25%, which was a problem in terms of mass productivity.

Furthermore, in the case of Comparative Example 8, the V content was too small, so there was no problem in terms of hardness, but since the prior austenite grain size was as large as JIS Gc 5.0, as shown in Table 8. The life characteristics were deteriorated.

Furthermore, in the case of Comparative Example 9, since the V content is too large, the hardness and the durable life are good, but the material cost is increased by about 30%, so that the characteristics corresponding to the increase in cost are obtained. There was a problem when trying to get.

In this way, induction hardening capable of obtaining a deep hardened layer in a short time is applied, and even with induction hardening, the hardened layer pattern, the hardness of each part, and the hardened layer depth are the same as those of the carburized and hardened product. Since the alloy design is such that the same or better quality can be obtained, it is possible to obtain good results that the roller pitting test life and the actual machine life are significantly improved compared to the long-time carburized and hardened product. It was

The heat treatment cost can be reduced by about 1/3 to 1/4 as compared with the conventional carburized and quenched product, and the heat treatment cost can be reduced by about 30% as compared with the carburized and induction hardened product. Met.

[0063]

As described in claim 1, the rolling element for a toroidal type continuously variable transmission according to the present invention has C: 0.
50 to 0.80 wt%, Mn: 0.50 to 2.00 wt%, P: 0.040 wt% or less, S: 0.040 wt%
To provide a rolling element for a toroidal type continuously variable transmission, which has excellent rolling contact fatigue characteristics, at a low cost with high productivity, because it is configured to be formed of steel containing the balance Fe and impurities. It is possible to obtain a remarkably excellent effect.

In an embodiment of the rolling element for a toroidal type continuously variable transmission according to the present invention, as described in claim 2, Si: 0.25 to 3.00 wt% is contained in steel. By being made of steel containing
It is possible to improve the resistance to temper softening and to prevent a decrease in surface hardness after tempering. As described in claim 3, V: 0.05 to 0.
The strength and the toughness can be further improved and the rolling contact fatigue characteristics can be further improved by forming the steel containing 50% by weight. As stated, C in steel
It is possible to improve the hardenability and increase the temper softening resistance by forming the steel containing r: 2.00% by weight or less. As described above, by forming a hardened layer by induction hardening treatment, it is possible to provide a rolling element for a toroidal type continuously variable transmission having good rolling fatigue characteristics at a low cost, which is extremely excellent. The effect is brought.

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 6, C: 0.50 to 0.80% by weight, Mn: 0. Fifty
~ 2.00 wt%, P: 0.040 wt% or less, S:
0.040 wt% or less, further containing Si: 0.25 to 3.00 wt% in the steel as described in claim 7, and V in the steel as described in claim 8. : 0.05
˜0.50 wt%, Cr: 2.00 wt% or less in the steel as described in claim 9, and the remaining Fe and impurities are used as a raw material to form a rolling element shape and then induction hardening. Since the treatment is performed, a remarkably excellent effect that a rolling element for a toroidal type continuously variable transmission having excellent rolling contact fatigue characteristics can be manufactured with good productivity and at low cost is brought about.

[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 view showing induction hardening surfaces (A surface, B surface) of an input disk and an output disk.

[Fig. 3] Induction hardening surface of power roller (A surface, B surface)
FIG.

FIG. 4 is a graph illustrating the relationship between hardness and the distance from the surface of the input / output disk after induction hardening.

FIG. 5 is an explanatory diagram showing the surface hardness and the effective hardened layer depth (in parentheses) of the input / output disc after induction hardening.

FIG. 6 is an explanatory diagram showing the surface hardness and effective hardened layer depth (in parentheses) of the power roller after induction hardening.

FIG. 7 is an explanatory diagram showing an outline of a roller pitching test.

[Explanation of symbols]

 1 Toroidal type continuously variable transmission 2 Input shaft 5 Input disc 8 Output shaft 9 Output disc 10 Power roller

Front Page Continuation (72) Inventor Shinji Fushimi 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Takashi Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. ( 72) Inventor Shun Umegaki, 2nd Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor, Kimio Tani, 2nd Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (9)

[Claims] 1. C: 0.50 to 0.80% by weight, Mn:
0.5 to 2.00% by weight, P: 0.040% by weight or less, S: 0.040% by weight or less, and a toroidal type alloy characterized by being formed of steel composed of the balance Fe and impurities. Rolling element for gearbox. 2. Si: 0.25 to 3.00% by weight in steel
The rolling element for a toroidal-type continuously variable transmission according to claim 1, wherein the rolling element is formed of steel containing. 3. The rolling element for a toroidal type continuously variable transmission according to claim 1, wherein the rolling element is a steel containing V: 0.05 to 0.50% by weight. 4. The steel according to claim 1, wherein the steel is formed of steel containing Cr: 2.00% by weight or less.
The rolling element for a toroidal type continuously variable transmission according to any one of 1. 5. The toroidal type continuously variable transmission rolling element according to claim 1, wherein a hardened layer is formed by induction hardening treatment. 6. C: 0.50 to 0.80% by weight, Mn:
0.50 to 2.00% by weight, P: 0.040% by weight or less, S: 0.040% by weight or less, and the remaining Fe and impurities are used as a raw material to form a rolling element shape and then induction hardening treatment. A method for manufacturing a rolling element for a toroidal-type continuously variable transmission, which comprises: 7. Si: 0.25 to 3.00% by weight in steel
The method for manufacturing a rolling element for a toroidal-type continuously variable transmission according to claim 6, characterized in that the steel containing the is formed into a rolling element shape. 8. The toroidal type continuously variable transmission according to claim 6, wherein the steel containing V: 0.05 to 0.50 wt% is formed into a rolling element. For manufacturing rolling elements for automobiles. 9. The toroidal type continuously variable transmission according to claim 6, wherein a steel containing Cr: 2.00% by weight or less is used as a raw material and is formed into a rolling element shape. For manufacturing rolling elements for automobiles.