JPH10231908A - Rolling element for toroidal type continuously variable transmission and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Problem] To prevent a decrease in hardness due to a rise in temperature of a rolling part,
Provided is a long-life rolling element for a toroidal-type continuously variable transmission, in which the depth of depression of a rolling surface is significantly reduced and the rolling life is further improved. When a rolling element is manufactured in a toroidal-type continuously variable transmission 1 using a plurality of metal rolling elements (input disk 5, output disk 9, and power roller 10) that come into contact with each other via a lubricating oil, a material is used. After rolling into the rolling element shape using steel for machine structural use, carburizing and quenching and tempering or carbonitriding and quenching and tempering, or after carburizing and nitrocarburizing and quenching and induction hardening and tempering, grinding the rolling surface After the working, the rolling surface is subjected to shot peening, and then the finish is performed. The rolling surface has a surface hardness of HV800 or more and a surface roughness of Ra0.
A rolling element of 1 μm or less is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

As a transmission used in a vehicle such as an automobile, an attempt has been made to adopt a continuously variable transmission instead of the conventional stepped transmission such as four-stage or five-stage. There are also some that have been put into practical use and marketed several years ago ("New Car Manual NISSAN March").
(Edited and published by Nissan Motor Co., Ltd., pages C-9 to C-48, January 1992).

Since the continuously variable transmission continuously changes gears, it has features such as improved fuel efficiency and power performance, and no shift shock. Depending on its structure, it has a belt type and a toroidal type. It is roughly divided into two.

Among them, a toroidal type continuously variable transmission is
As shown in FIG. 1, the toroidal-type continuously variable transmission 1 has a structure using a metal rolling element that contacts through a lubricating oil. It has input disks 5 and 5 that rotate integrally via a shaft 4 and output disks 9 and 9 that rotate an output shaft 8 via gears 6 and 7. The input disks 5 and 5 and the output disk 9 , 9 are provided between the power rollers 10, 10, 10, 10, and each power roller 10 has a structure supported by a support 12 via a ball bearing 11.

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 rotational speed of the input disk 5 and the output disk 9. The mechanism is such that power is transmitted from the input shaft 2 to the output shaft 8 while changing gears (Japanese Patent Laid-Open No. 1-229158).

In such a metal rolling element (5, 9, 10) of the toroidal type continuously variable transmission 1, a load is applied to the input disk 5 by the loading cam 3 in order to transmit torque. Therefore, when driven, a maximum of 4 GPa is applied between the input disk 5 and the power roller 10 and between the power roller 10 and the output disk 9.
In addition to the high contact pressure reaching to the extent, high shear stress is generated at a deep position inside the rolling element.

Therefore, in the conventional case, the surface hardness is ensured by subjecting the steel for machine structural use to a surface hardening treatment such as carburizing and quenching and tempering or carbonitriding and quenching and tempering to obtain a deep hardened layer. In some cases (for example, JP-A-7-71555). However, a high contact pressure is generated at the contact surfaces of the rolling elements such as the input disk 5, the output disk 9, and the power roller 10, and the heat generated by the spin sliding causes the temperature of the rolling element contact portion to rise, and the hardness to decrease. There is a problem in that it is easy to cause early peeling and breakage, and the rolling fatigue life is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is directed to a method of carburizing and quenching and tempering or carburizing and nitrocarburizing using steel for machine structural use as a material. After quenching, further subjected to induction hardening and tempering, after performing the grinding process of the rolling surface, performing shot peening on the rolling surface, and then performing the finishing process, without reducing the surface roughness of the rolling surface. The purpose of this invention is to provide a long-life rolling element for a toroidal-type continuously variable transmission with improved surface hardness, which prevents a decrease in hardness due to a rise in the temperature of the rolling section and further improves the rolling life. And

[0009]

According to a first aspect of the present invention, there is provided a rolling element for a toroidal-type continuously variable transmission, which comprises a plurality of metal rolling elements contacting via a lubricating oil. In the toroidal type continuously variable transmission used, the rolling surface is shot-peened after carburizing and quenching and tempering or carbonitriding and quenching and tempering, and the surface hardness of the rolling surface is HV800 or more. , Surface roughness is R
It is characterized by having a configuration of a 0.1 μm or less.

[0010] Similarly, a rolling element for a toroidal type continuously variable transmission according to the present invention is a toroidal type using a plurality of metal rolling elements contacting via lubricating oil. In the continuously variable transmission, the rolling surface is shot peened after carburizing quenching or carbonitriding and quenching and further induction hardening and tempering using steel for machine structural use as a material, and the surface hardness of the rolling surface is HV800 or more, It is characterized in that the surface roughness is Ra 0.1 μm or less.

According to a third aspect of the present invention, there is provided a method for manufacturing a rolling element for a toroidal-type continuously variable transmission, wherein a plurality of metal rolling elements contacting via a lubricating oil are used. In manufacturing the rolling element in the toroidal-type continuously variable transmission, a carburizing quenching and tempering or a carbonitriding and quenching and tempering were performed after molding using steel for machine structural use as a material, and the rolling surface was ground. Later, the rolling surface is subjected to shot peening, and then subjected to finishing, so that the surface hardness of the rolling surface is HV800 or more and the surface roughness is R.
It is characterized by having a configuration of a 0.1 μm or less.

Similarly, a method of manufacturing a rolling element for a toroidal-type continuously variable transmission according to the present invention uses a plurality of metal rolling elements that come into contact with each other via lubricating oil. In manufacturing the rolling element in the toroidal-type continuously variable transmission, after carburizing quenching or carbonitriding quenching using a steel for machine structural use as a material, further subjected to induction hardening and tempering, after grinding the rolling surface The rolling surface is subjected to shot peening, and then subjected to a finishing process so that the rolling surface has a surface hardness of HV 800 or more and a surface roughness of R
It is characterized by having a configuration of a 0.1 μm or less.

[0013] In an embodiment of the method of manufacturing a rolling element for a toroidal-type continuously variable transmission according to the present invention, the average hardness during shot peening is HV700-800. In addition, by using shots having an average particle diameter of 0.6 mm or less, it is possible to suppress the decrease in hardness during rolling and to improve the rolling fatigue life without reducing the surface roughness of the rolling surface.

In the rolling element for a toroidal type continuously variable transmission and the method for manufacturing the same according to the present invention, the steel for machine structure is SC, which is carbon steel for machine structure stipulated by JIS.
And SNC, SNCM, SC which are alloy steels for machine structure
r, SCM, SMn, SMnC, etc. can be used,
If necessary, a material containing an appropriate additive element in an appropriate amount can be used.

In some cases, burnishing may be performed after the surface hardening treatment. In this burnishing process, the material is hardened by work hardening by pressing and rolling a ball or roller, and a maximum shear stress τ0 equivalent to the actual operation is generated in advance near the maximum shear stress depth Zo equivalent to the actual operation. Under such conditions (tool shape, pressing load, etc.), small plastic deformation and work-induced transformation of retained austenite occur near the position of the maximum shear stress depth Zo before actual operation, and the maximum shear stress depth Z
By strengthening the vicinity of the o position, it is possible to suppress a decrease in dimensional accuracy due to the depression of the rolling surface and to improve the rolling fatigue life.

[0016]

The rolling element for a toroidal type continuously variable transmission according to the present invention is a toroidal type continuously variable transmission using a plurality of metal rolling elements that come into contact with each other through lubricating oil. In the invention of claim 1, the rolling surface is shot-peened after carburizing and quenching and tempering or carbonitriding and quenching and tempering using steel for machine structural use as a material.
In the invention described in the above, the rolling surface is subjected to shot peening after carburizing quenching or carbonitriding quenching and further induction hardening and tempering after using steel for machine structural use as a material,
Each of the rolling elements has a surface hardness of HV800 or more and a surface roughness of Ra0.1 μm or less. Further, the rolling element for a toroidal type continuously variable transmission according to the present invention is characterized in that: The manufacturing method according to claim 3, wherein the rolling element is manufactured in a toroidal-type continuously variable transmission using a plurality of metal rolling elements that are in contact with each other via a lubricating oil. And then subjected to carburizing and quenching and tempering or carbonitriding and quenching and tempering, and in the invention according to claim 4, after forming by using steel for machine structural use as a material, further carburizing and quenching and quenching and quenching are further performed. After quenching and tempering, each of the rolling surfaces is subjected to grinding and then shot peening is performed on the rolling surfaces, and then the surface is subjected to finishing to reduce the surface hardness of the rolling surfaces to HV. 00 or more, the surface roughness Ra0.1
It is characterized in that it is set to be equal to or less than μm. The reason for such a configuration will be described together with the operation.

The rolling elements such as the input disk 5, the output disk 9, and the power roller 10 of the toroidal type continuously variable transmission 1 illustrated in FIG. 1 rotate at a high speed while receiving a high load. When rotating at a high speed under a high load, the rolling part generates heat due to spin sliding and the temperature rises, so that the hardness of the rolling part is reduced (softened) by the heat.
However, when the contact surface is depressed, it is easy to cause early peeling or breakage, and the rolling fatigue life is reduced.

For example, the toroidal type continuously variable transmission 1 shown in FIG.
When the temperature of the lubricating oil is 100 ° C., the temperature of the lubricating oil that has passed through the rolling part is about 30 ° C. higher than before the inflow. 1
There is a description that the temperature has increased to about 30 ° C. (Japanese Patent Laid-Open No. 7-208568).

On the other hand, shot peening generally improves the fatigue strength by crushing the abnormal layer (softened layer) on the outermost surface of the carburized steel, and can be expected to improve the fatigue strength by increasing the compressive residual stress. There are examples of application to a continuously variable transmission (JP-A-7-07155, JP-A-7-208568, etc.).

Further, by the shot peening, the retained austenite undergoes work-induced transformation into martensite, so that the surface hardness is 15 to 130 with respect to the hardness before working.
It is known to improve by about
(The Japan Institute of Metals, The Iron and Steel Institute of Japan, p. 226) Carburizing or carbonitriding steel for machine structural use and, if necessary, further induction hardening, and then performing shot peening to achieve a surface hardness of HV800 or more. it can.

The improvement in rolling contact fatigue strength increases as the tempering softening resistance increases. Therefore, the surface hardness is improved when shot peening is performed as compared with the case where shot peening is not performed. The tempering hardness at 300 ° C. is also improved.

However, when shot peening is performed, the surface becomes rough under the influence of shot marks, so that metal contact is likely to occur, and the rolling fatigue strength is rather reduced.

For example, as a description of the surface roughness of a rolling element for a traction drive continuously variable transmission, reference can be made to the proceedings of the Tribology Conference of the Japan Society of Tribology, (Nagoya 1993-11), pp. 657-660. There are literature.

According to this document, a driving roller serving as a rolling element is disclosed in a test method and a test condition in consideration of a high surface pressure, a high peripheral speed, and a high temperature, which appear in a half toroidal type traction drive continuously variable transmission for an automobile. There is a description that the influence of metal contact is small when the average surface roughness of the driven roller is set to Ra 0.08 μm or less.

Therefore, in order to reduce the influence of metal contact in order to improve the rolling fatigue strength, the average surface roughness of the rolling element must be R
a is desirably 0.1 μm or less.

On the other hand, since the depth of the processed layer by shot peening is shallow, if processing such as cutting is performed after shot peening, this layer is lost, and the effect of improving the surface hardness is reduced.

Therefore, after performing surface hardening treatment such as carburizing quenching or carbonitriding quenching, or carburizing quenching or carbonitriding quenching followed by induction hardening, grinding is performed in advance, and shot peening is performed after securing dimensional accuracy. By applying and then finishing such as wrapping,
A surface roughness Ra of 0.1 μm or less can be achieved.

The shot at the time of shot peening uses a material having an average hardness of HV 700 to 800 and an average particle size of 0.6 mm or less to obtain a surface roughness Ra.
0.1 μm or less, but the average hardness is HV700
If the average particle diameter exceeds 0.6 mm, it is difficult to achieve a surface roughness Ra of 0.1 μm or less.

Therefore, in the present invention, steel for machine structural use is used as a material, carburizing and quenching and tempering or carbonitriding and quenching and tempering are performed, and after the rolling surface is ground, shot rolling is performed on the rolling surface. After finishing, or after carburizing or carbonitriding and quenching, it is further subjected to induction hardening and tempering, and after the grinding of the rolling surface, the rolling surface is subjected to shot peening, followed by finishing. By setting the surface hardness of the rolling surface to HV800 or more and the surface roughness to Ra0.1 μm or less, metal contact on the rolling contact surface is prevented, and the softening resistance is excellent even under high load and high rotation. The decrease is suppressed, the amount of depression after contact is reduced, and the peeling life is improved.

[0030]

According to the present invention, the rolling element for a toroidal type continuously variable transmission according to the present invention is a toroidal type continuously variable transmission using a plurality of metal rolling elements which are in contact with each other via lubricating oil. In the invention according to the invention, steel for machine structure is used as a material, and the rolling surface is subjected to shot peening after carburizing quenching and tempering or carbonitriding quenching and tempering, and the invention according to claim 2 uses the steel for machine structure as a material. After carburizing quenching or carbonitriding and quenching, and after induction hardening and tempering, the rolling surface is subjected to shot peening, and the rolling surface has a surface hardness of HV800 or more and a surface roughness of Ra0.1 μm or less. , Which prevents metal contact on the rolling contact surface, has excellent softening resistance even under high load and high rotation, suppresses hardness reduction, and reduces the amount of depression after contact , It becomes possible to increase the flaking life, markedly excellent effect that it is possible to further improved so the toroidal type continuously variable transmission rolling element rolling fatigue life is provided.

[0031] Even when the carburizing and quenching and tempering or carbonitriding and quenching and tempering as described in claim 1 is employed, or after the carburizing and quenching and quenching and quenching and quenching as described in claim 2, In addition, even when induction hardening and tempering are adopted, the rolling elements for toroidal type continuously variable transmissions have further improved rolling fatigue life in each case, taking advantage of the features of each quenching method. A significant effect of being able to do so.

Further, in the method of manufacturing a rolling element for a toroidal type continuously variable transmission according to the present invention, the rolling element is preferably used in a toroidal type continuously variable transmission using a plurality of metal rolling elements which come into contact with each other via lubricating oil. In manufacturing the steel according to the third aspect of the present invention, the material is formed by using steel for machine structural use and then carburized and quenched and tempered or carbonitrided and quenched and tempered. After being formed using steel for machine structural use, after carburizing and quenching and carbonitriding and quenching, it is further subjected to induction hardening and tempering, and after each of the rolling surfaces is ground, the rolling surfaces are shot-peened and then finished. And the surface hardness of the rolling surface is HV800 or more, and the surface roughness is Ra0.1.
Since it is set to be not more than μm, a remarkable effect that it is possible to manufacture a rolling element for a toroidal-type continuously variable transmission having a further improved rolling fatigue life as described in claim 1 or 2. Is brought.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, a case where the present invention is applied to the toroidal type continuously variable transmission 1 shown in FIG. 1 will be described. As described above, the toroidal-type continuously variable transmission 1 shown in FIG. 1 includes the input disk 5, the output disk 9 and the power roller 10, which are metal rolling elements, as one set. It is composed of a set or a plurality of sets (two sets in this embodiment).

In the input disk 5, output disk 9 and power roller 10 which are the metal rolling elements,
As the material, SCM420H and SCM440H, which are steels for machine structure as shown in Tables 1 and 2, were used.

After the steel material subjected to the normalizing treatment after hot forging is machined into a part shape, the SCM420H is subjected to carburizing, quenching and tempering under the surface hardening treatment conditions shown in FIGS. 2 and 3, or to FIGS. Carbonitriding and quenching and tempering under the conditions shown in the surface hardening treatment or plasma carburizing and quenching and tempering under the conditions shown in FIG. 6 were performed.

Further, the SCM440H was subjected to induction hardening and tempering after carburizing and quenching under the surface hardening conditions shown in FIG. 7, or to induction hardening and tempering after carbonitriding and quenching under the surface hardening conditions shown in FIG.

In case of carburizing quenching and tempering, carbonitriding and quenching and tempering, and plasma carburizing and quenching and tempering under the surface hardening treatment conditions shown in FIGS. 2 to 6, secondary quenching was carried out in order to make the network carbide spherical. .

After the surface hardening treatment was performed under each condition, the rolling surface and the like were ground and finished to a predetermined size and shape. Thereafter, using an air nozzle type shot peening machine, a round cut wire having an average particle size of 0.3 to 0.8 mm and a hardness of HV 700 to 800 also shown in Tables 1 and 2 was used as a shot, and an arc height of 0 was used. Shot peening was performed at .48 mmA and a coverage of 300% or more.

Thereafter, the rolling surfaces were finished by lapping to produce input disks 5, output disks 9 and power rollers 10.

Next, in order to confirm the quality of the input disk 5, output disk 9 and power roller 10 produced, the surface roughness of the rolling surface was measured, and the hardness at room temperature was measured with a Vickers hardness meter. went. Further, in order to know the softening resistance at a high temperature, the hardness after tempering at 300 ° C. for 3 hours was also measured.

Next, these rolling elements were assembled as shown in FIG. 1 to form a toroidal type continuously variable transmission 1, and a durability test was conducted under the test conditions shown in Table 3, and the depth of depression after the durability test was performed. Was measured.

Tables 1 and 2 show the results of these measurements.
Shown in

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

As is clear from Tables 1 and 2, as shown in Examples 1 to 5 of the present invention, after the carburizing and quenching and tempering or the carbonitriding and quenching and tempering, By setting the surface hardness of the surface to HV800 or more and the surface roughness to Ra0.1 μm or less, metal contact on the rolling contact surface is prevented, and the depth of depression of the rolling surface even after 100 hours of the durability test has been completed. Has been confirmed to be small, whereby the occurrence of peeling is greatly reduced and the rolling fatigue life can be improved.

As shown in Examples 6 and 7, the rolling surface is shot-peened after plasma carburizing, quenching and tempering, and the rolling surface has a surface hardness of HV 800 or more and a surface roughness of 0.1 μm or less. Even if it is assumed to be, it can be made as excellent as the one that has been subjected to shot peening after carburizing and quenching and tempering and carbonitriding and quenching and tempering and has a predetermined hardness and roughness, It has been confirmed that the carburizing time can be significantly reduced due to the treatment.

Further, as shown in Examples 8 and 9, induction hardening and tempering are further performed after carburizing quenching or carbonitriding and quenching, and the rolling surface is subjected to grinding and then shot peening. Also, the depth of depression and life of the rolling surface are as excellent as those obtained by performing carburizing and quenching and tempering or carbonitriding and quenching and tempering, and performing grinding of the rolling surface and then performing shot peening on the rolling surface. It was confirmed that the carburizing time could be significantly reduced.

On the other hand, when shot peening was not performed as shown in Comparative Examples 1 to 4, since the surface hardness at room temperature was low, the tempering hardness at 300 ° C. was low. The rolling surface had a large amount of depression, and peeling occurred in a short time.

Further, as shown in Comparative Examples 5 to 7, when the shot size is excessive even after shot peening, the hardness at room temperature and the tempering hardness at 300 ° C. are large. Even if the rolling surface has a surface roughness of Ra0.
Exceeding 1 μm and causing metal contact on the rolling contact surface, so the surface temperature rises greatly, so the amount of depression is larger than that of the same shot peened, and peeling occurs in a short time Had become.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view illustrating the structure of a toroidal (rolling) continuously variable transmission.

FIG. 2 is an explanatory view showing surface hardening conditions by gas carburizing, quenching and tempering employed in an embodiment of the present invention.

FIG. 3 is an explanatory view showing conditions of surface hardening treatment by gas carburizing, quenching and tempering employed in Examples and Comparative Examples of the present invention.

FIG. 4 is an explanatory view showing conditions of surface hardening treatment by gas carbonitriding, quenching and tempering employed in an example of the present invention.

FIG. 5 is an explanatory view showing conditions of surface hardening treatment by gas carbonitriding, quenching and tempering employed in Examples and Comparative Examples of the present invention.

FIG. 6 is an explanatory view showing conditions of surface hardening treatment by plasma carburizing, quenching and tempering employed in Examples and Comparative Examples of the present invention.

FIG. 7 is an explanatory view showing conditions of surface hardening treatment by induction hardening and tempering after gas carburization adopted in Examples and Comparative Examples of the present invention.

FIG. 8 is an explanatory view showing surface hardening conditions by induction hardening and tempering after gas carbonitriding employed in Examples and Comparative Examples of the present invention.

[Description of Signs] 1 Toroidal (rolling) continuously variable transmission 5 Input disk (rolling element) 9 Output disk (rolling element) 10 Power roller (rolling element)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoichi Watanabe Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa

Claims (5)

[Claims] 1. A toroidal-type continuously variable transmission using a plurality of metal rolling elements that come into contact with each other via a lubricating oil, wherein the rolling is performed after carburizing and quenching and tempering or carbonitriding and quenching and tempering using steel for machine structural use as a material. A rolling element for a toroidal-type continuously variable transmission, characterized in that the running surface is subjected to shot peening, the surface hardness of the rolling surface is HV800 or more, and the surface roughness is Ra 0.1 μm or less. 2. A toroidal-type continuously variable transmission using a plurality of metal rolling elements that are in contact with each other via a lubricating oil, wherein the steel for machine structural use is used as a material, and after carburizing or nitrocarburizing, further induction hardening and tempering are performed. After the shot surface is subjected to shot peening, the surface hardness of the rolling surface is HV
A rolling element for a toroidal-type continuously variable transmission, wherein the rolling element has a surface roughness of not less than 800 and a surface roughness Ra of not more than 0.1 μm. 3. A toroidal-type continuously variable transmission using a plurality of metal rolling elements that come into contact with each other through a lubricating oil, when manufacturing the rolling elements, forming the steel using mechanical structural steel as a material, and then carburizing the steel. After quenching and tempering or carbonitriding and quenching and tempering, the rolling surface is subjected to grinding, and then shot peening is performed on the rolling surface, followed by finishing, and the surface hardness of the rolling surface is HV800 or more. A method for manufacturing a rolling element for a toroidal-type continuously variable transmission, wherein the surface roughness is set to Ra 0.1 μm or less. 4. A method for manufacturing a rolling element in a toroidal-type continuously variable transmission using a plurality of metal rolling elements that are in contact with each other via lubricating oil, using carburizing and quenching or carburizing using steel for machine structural use as a material. After the nitriding and quenching, induction hardening and tempering are further performed, and after the rolling surface is ground, the rolling surface is shot-peened, and then the finishing is performed, and the rolling surface has a surface hardness of HV800 or more. A method for manufacturing a rolling element for a toroidal-type continuously variable transmission, wherein the roughness is set to Ra 0.1 μm or less. 5. A shot having an average hardness of 700 to 800 HV and an average particle diameter of 0.6 mm or less during shot peening, to suppress a decrease in hardness during rolling and to reduce a surface roughness of a rolling surface. The method for manufacturing a rolling element for a toroidal-type continuously variable transmission according to claim 4 or 5, wherein the rolling fatigue life is improved without causing the rolling fatigue life.