JP2002340122A - Toroidal type continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toroidal type continuously variable transmission having input disc and output disc with excellent fatigue strength and high reliability. SOLUTION: This toroidal type continuously variable transmission is provided with the input disc 1 and the output disc 2 arranged by being coaxially connected to an input shaft 3 rotatably supported. The toroidal type continuously variable transmission is characterized by forming a maximum residual compressive stress layer having a maximum residual compressive stress value of 0.2 GPa to 2.0 GPa in a depth <1.0 mm from a surface of at least one top part of the input disc 1 and the output disc 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toroidal type continuously variable transmission, and more particularly to a toroidal type continuously variable transmission used as an automatic transmission for an automobile.

[0002]

2. Description of the Related Art Conventionally, as a toroidal type continuously variable transmission 20, for example, the one shown in FIG. 1 is known. In a housing (not shown), an input disk 1 and an output disk 2 are arranged coaxially facing each other. An input shaft 3 is penetrated through a shaft portion of a toroidal transmission portion having the input disk 1 and the output disk 2. At one end of the input shaft 3, a loading cam 4 is provided.
The loading cam 4 has a structure for transmitting the power (rotational force) of the input shaft 3 to the input disk 1 via the cam roller 5.

The input disk 1 and the output disk 2 have substantially the same shape and are symmetrically arranged. Their opposing surfaces cooperate to form a toroid so that they are substantially semicircular when viewed in an axial cross section. Formed on the surface. In a toroidal cavity formed by the toroidal surfaces of the input disk 1 and the output disk 2, a pair of power roller bearings 6 and 7 for operation transmission are disposed in contact with the input disk 1 and the output disk 2. It has a structure.

The power roller bearing 6 includes a power roller 6a (corresponding to an inner ring constituting the power roller bearing 6) that rolls on the toroidal surfaces of the input disk 1 and the output disk 2, an outer ring 6b, and a plurality of rolling elements ( 6c). The other power roller bearing 7 includes a power roller 7a (corresponding to an inner ring constituting the power roller bearing 7) that rolls on the toroidal surfaces of the input disk 1 and the output disk 2, an outer ring 7b, and a plurality of rolling elements (steel balls) 7c. It is composed of

That is, the power roller 6a also serves as an inner ring which is a component of the power roller bearing 6,
The power roller 7a also serves as an inner ring that is a component of the power roller bearing 7. In this structure, the power roller 6a is rotatably connected to the trunnion 10 via the pivot 8, the outer ring 6b, and the plurality of rolling elements 6c, and is connected to the center of the toroidal surfaces of the input disk 1 and the output disk 2. The pivot shaft O is pivotally supported about the pivot axis O.

On the other hand, the power roller 7a has a pivot 9,
It is rotatably connected to the trunnion 11 via an outer ring 7b and a plurality of rolling elements (steel balls) 7c, and is rotatable about a pivot axis O which is a center of a toroidal surface of the input disk 1 and the output disk 2. It is tiltably supported. Lubricating oil having a large viscous frictional resistance is supplied to the contact surfaces of the input disk 1, the output disk 2, the power roller 6a, and the power roller 7a.
Is transmitted to the output disk 2 via the lubricating oil film and the power roller 6a and the power roller 7a.

The input disk 1 and the output disk 2 are independent of the input shaft 3 via the needle 12 (ie, are not directly affected by the power of the input shaft 3). The output disk 2 is provided with an output shaft 14 disposed in parallel with the input shaft 3 and rotatably supported by a housing (not shown) via an angular 13.

In the toroidal type continuously variable transmission 20, the power of the input shaft 3 is transmitted to the loading cam 4. When the loading cam 4 rotates due to the transmission of the power, the power due to the rotation is transmitted to the input disk 1 via the cam roller 5, and the input disk 1 rotates. Further, the power generated by the rotation of the input disk 1 is transmitted to the output disk 2 via the power roller 6a and the power roller 7a. Then, the output disk 2 rotates integrally with the output shaft 14.

At the time of shifting, the trunnion 10 and the trunnion 11 are moved by a small distance in the direction of the pivot axis O. That is, due to the axial movement of the trunnions 10 and 11, the intersection between the rotation axis of the power roller 6a and the power roller 7a and the axis of the input disk 1 and the output disk 2 slightly deviates. Then, the balance between the rotational peripheral speeds of the power rollers 6a and 7a and the rotational peripheral speed of the input disk 1 is broken, and the component of the rotational driving force of the input disk 1 causes the power roller 6a and the power roller 7a to rotate.
Tilt around the pivot axis O. Therefore, the power rollers 6a and 7a tilt on the curved surfaces of the input disk 1 and the output disk 2.

For this reason, the power rollers 6a and 7a tilt on the curved surfaces of the input disk 1 and the output disk 2, and as a result, the speed ratio changes and deceleration or acceleration is performed. As a toroidal-type continuously variable transmission having such a structure, for example, there is a conventional example disclosed in Japanese Utility Model Publication No. 2-49411.

The input disk, output disk, and power roller bearing as described above include "N
ASA Technical note NAS A
AISI, as described in TND-8362.
There is a conventional example using 52100 (JIS SUJ2, equivalent to high carbon chromium bearing steel).

Japanese Patent Application Laid-Open No. 7-71555 has been filed by the present applicant for applying a surface treatment such as carburizing or carbonitriding to an input disk, an output disk and a power roller bearing for the purpose of extending the durability life. Further, there are disclosed conventional examples such as Japanese Patent Application Laid-Open No. 9-79336, in which the amount of nitriding and retained austenite are limited to carbonitriding.

[0013]

In the above-described toroidal-type continuously variable transmission, the inner end face existing on the inner diameter side and the inner end face closer to the inner end face than the arcuate concave inner side face of the input disk or the output disk. The stress generated in the part is extremely high, and even if the fatigue strength in the disk rolling part is improved, cracks are formed from the inner end face and the inner peripheral face inner end present on the inner diameter side than the inner surface which is this arc-shaped concave surface. This may cause the disk to break.

As a countermeasure against this breakage, Japanese Patent Application Laid-Open No. 9-3248 discloses
42, the disc-shaped metal rolling element has a top portion and / or a hole portion fitted with the input / output shaft provided with a compressive residual stress layer extending from the surface to a depth of 1.0 mm or more; "To generate a residual compressive stress from the surface to a deep position to improve the fatigue strength.

However, when a residual compressive stress exists, a residual tensile stress exists near the residual compressive stress. This is a spontaneous occurrence for establishing the balance of the stress balance inside the material. This residual tensile stress, on the contrary, lowers the fatigue strength, rather than improving the fatigue strength.

The present invention has been made in view of the above circumstances, and has a depth of less than 1.0 mm from a surface of at least one top of an input disk and an output disk.
Provided is a toroidal-type continuously variable transmission having an input disk and an output disk having excellent fatigue strength and high reliability by forming a structure having a compressive residual stress layer having a maximum residual compressive stress value of 2.0 GPa. With the goal.

The present invention also provides an inner disk having an inner surface extending over at least one top of an input disk, an output disk and a top of a hole in which the input shaft is mounted, and having a depth of at least one third of the total height of the disk. A disk having a maximum residual compressive stress value of 0.2 GPa to 2.0 GPa at a depth of less than 1.0 mm to a depth of less than 1.0 mm. An object of the present invention is to provide a toroidal type continuously variable transmission having a disk.

[0018]

The first invention of the present application is directed to a toroidal type continuously variable transmission including an input disk and an output disk which are concentrically connected to an input shaft rotatably supported. A depth of less than 1.0 mm from the surface of at least one top of the input disk, the output disk,
A toroidal-type continuously variable transmission in which a compressive residual stress layer having a maximum residual compressive stress value of 0.2 GPa to 2.0 GPa is formed.

According to a second aspect of the present invention, there is provided a toroidal type continuously variable transmission having an input disk and an output disk concentrically connected to an input shaft rotatably supported. 0.2 GPa to at least one top and the top of the hole in which the input shaft is mounted, at least in the range of the inner diameter surface over a depth of 1/3 of the total disk height and less than 1.0 mm from the surface,
A toroidal-type continuously variable transmission in which a compressive residual stress layer having a maximum residual compressive stress value of 2.0 GPa is formed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The toroidal type continuously variable transmission according to the present invention will be described below in more detail. FIG. 2 shows a disk which is a main part of the toroidal type continuously variable transmission of the present invention. The disk is subjected to a heat treatment, or an inner end surface (top) 31 and an inner end surface inner end portion (a hole in which the input shaft is mounted) which are present on the inner diameter side with respect to the inner surface which is an arc-shaped concave surface of the disk. By performing shot peening on the inner diameter surface and the inner diameter surface at a predetermined depth from the top) 32,
A residual stress layer is formed. Here, this residual stress layer mainly consists of residual stress of compression, and this compressive residual stress layer is a layer extending from the surface (top) to a depth of less than 1.0 mm. In the present invention, the depth at which the compressive residual stress layer is formed on the inner diameter surface is set to at least a range covering (１ ／) H of the total height H of the disk following the top.

As described above, the reason why the residual compressive stress layer improves the fatigue strength is as follows. In the case of receiving a rolling stress and a bending stress at the same time as in a toroidal continuously variable transmission, a crack may be generated starting from a non-metallic inclusion or the like existing in the stress field, leading to a crack. For this reason, measures have been taken to reduce the amount of non-metallic inclusions that serve as starting points, and to use a material with reduced large non-metallic inclusions in terms of size.

However, with the increase in the output of the toroidal type continuously variable transmission, sufficient fatigue strength may not be obtained only by controlling nonmetallic inclusions at the top portion of the disk and the portion closer to the inner peripheral surface. There is now. For this reason, measures have been taken to add a residual compressive stress layer by a method such as heat treatment or shot peening to reduce the effectiveness of tensile stress generated in the disk.

FIG. 3 shows the stress distribution from the surface of the top of the disk in Example 4 and Comparative Examples 2 and 3 in Table 1 when the carbonitriding and hardening conditions of the present invention were applied. Since the top portion and the inner diameter surface of the disk are used without being ground after the heat treatment, the stress distribution shown in FIG. 3 exists on the top portion and the inner diameter surface of the finished disk as they are.

However, as shown in FIG. 3, the residual stress layer has a maximum residual compressive stress value that increases as the depth of the compressive stress layer increases, and a total amount of residual compressive stress existing inside the disk. Becomes larger. This means that the maximum residual tensile stress value existing inside the disk increases and the total value of the residual tensile stress increases. This residual tensile stress, combined with externally applied stress, increases the effective value of the tensile stress.

On the disk traction surface of the toroidal type continuously variable transmission, a normal contact surface pressure (for example, 2G) of a rolling bearing is applied.
Since a contact surface pressure (for example, about 4 GPa) larger than the pressure (approximately Pa) is applied, a large bending stress occurs at least on the top and the inner diameter surface of the hole. For this reason, it is necessary to increase and deepen the maximum compressive stress value (increase the total compression energy), but it is necessary to reduce the effective value of the subsequent tensile stress on the core side.

When the residual compressive stress layer is at least 1.0 mm from the surface, the existence of the residual tensile stress cannot be ignored.
Decreases the fatigue strength of the disc. In addition, 1.
Since tensile stress generated by external stress is relatively high up to about 0 mm, in the present invention, the residual compressive stress layer is set to a range of less than 1.0 mm from the surface, and the maximum residual compressive stress of the compressive residual stress layer in this range is set. Is 0.2 GPa
２．０2.0 GPa. If the residual compressive stress is less than 0.2 GPa, the effect of improving the fatigue strength is not seen, and if the residual compressive stress exceeds 2.0 GPa, the range of the residual compressive stress layer extends 1.0 mm or more from the surface and the residual compressive stress This is because the residual tensile stress generated at the same time as the occurrence of becomes large, and the fatigue strength is reduced (the effect is opposite). Further, in order to further reduce the effective tensile value, it is desirable that the residual compressive stress value at 1.0 mm from the surface exceeds 0 GPa, and it is more preferable that at least the residual compressive stress be present up to 0.8 mm from the surface. In order to increase the total compression energy and increase the external bending stress resistance, and to surely lower the effective tensile value, the residual compression stress value at this position should be set to 0 GP.
a.

Such a residual compressive stress layer can be obtained by carburizing or carbonitriding the disk. In addition, shot peening can be selectively performed on a portion requiring a residual compressive stress layer.

[0028]

Embodiments of the present invention will be described below. The basic configuration of the colloidal-type continuously variable transmission according to the present invention is the same as that of FIG. Next, a method for manufacturing an input disk, an output disk, and a power roller will be described.

The heat treatment shown in FIG. 4 is performed on the input disk, the output disk, and the power roller made of SCM420H, a structural steel specified in JIS G 4052. First, carbonitriding is performed under the following conditions. (Carburizing treatment conditions) Atmosphere gas: Rx gas and etch gas + ammonia Carbonitriding temperature: Select in the range of 900 to 960 ° C. Carbonitriding time: 10 to 50 hours Cold), and then heat-treated under the following conditions. (Heat treatment conditions) Quenching: 820 to 860 ° C. × 1 hour, oil quenching, tempering: 180 ° C. × 2 hours Next, those subjected to shot peening are arc-shaped concave surfaces of the input disk and the output disk. Inner end face (top) present on the inner diameter side from the inner side face and inner end face inner end portion (the inner diameter face of the hole in which the input shaft is mounted and a depth less than 1.0 mm from the top: from the top Shot peening was applied to at least the depth range up to 1 / 3H). Subsequently, grinding and finishing (after polishing, super finishing) were performed to complete the disk.

Disks with different heat treatment conditions and shot peening conditions were manufactured, and two disks of each lot were selected, and one-third of the total height H of the disk following the top of the disk and the top in the inner peripheral surface was selected. The residual stress was measured at the position of H. Since the residual stress at (1/3) H of the inner peripheral surface is almost equal to the residual stress and the distribution at the top, it should be represented by the measured value at the top. I also understood.

Therefore, the residual compressive stress values and distributions in Table 1 below are represented at the tops, and the values are shown. This stress value is applied at least to the top portion. To further improve the bending resistance of the disk, it is preferable that (1)
/ 3) It was also confirmed that it is preferable to perform the treatment up to the region up to H (although it may extend over the entire length).

The residual stress was measured every 0.1 mm from the surface to a depth of 1.5 mm. The surface of each of the disks had compressive stress, and the disks having a tensile stress at a certain depth obtained a tensile stress at a deeper position. Thus, the average value of the stress values obtained from the disks having the residual stress layers shown in Table 1 below is shown.

[0033]

[Table 1]

Next, a toroidal continuously variable transmission was manufactured, and a life test was performed under the following conditions. Input shaft rotation speed: 4000 min ^-1 Input torque: 480 Nm Oil used: Synthetic lubricating oil Supply temperature: 130 ° C. The test was performed until fatigue cracks occurred in either the input disk or the output disk. However,
The test was discontinued if it did not break for more than 300 hours. Table 2 below shows the life test results.

[0035]

[Table 2]

As is apparent from the test results, the residual compressive stress in the range of the present invention is generated at the tops of the input disk and the output disk which are arc-shaped concave surfaces and the inner peripheral surface near the inner end, so that the fatigue strength is reduced. High-quality disk can be obtained.

On the other hand, in Comparative Example 1, the residual stress of the residual compressive stress layer was as small as −0.1 GPa or less.
The output disk was damaged in as little as two hours.
Observation of the fracture surface after the test revealed that the starting point of the crack was near the surface.

In Comparative Example 2, the residual compressive stress layer extends 1.0 mm or more from the surface, and the residual tensile stress is generated inside, so that the fatigue strength is reduced. Comparative Example 3
In the above, the maximum residual compressive stress value is -0.2 Gpa or less, and the residual compressive stress layer extends 1.0 mm or more from the surface, and a large residual tensile stress is generated inside. It has fallen.

As described above, a certain degree of residual compressive stress (due to the difference in martensite initiation temperature between the surface and the core) is applied to the surface layer by the carbonitriding (the same applies to carburizing). The maximum residual compressive stress can be further increased and deepened by selectively performing the process on the inner diameter surface.

In the present invention, the maximum residual stress value from the surface to 1.0 mm satisfies the range of -0.2 to 2.0 GPa, and the residual stress at the depth of 1.0 mm exceeds 0 GPA. Those that have residual compressive stresses to a depth of at least 0.8 mm will have a longer life (in comparison with Examples 4 and 5) than those that do not, since they certainly lower the effective tensile value.

[0041]

As described above in detail, according to the present invention, at least one top of the input disk and the output disk and the inner surface of the hole in which the input shaft is mounted and 1.0 m from the top.
A toroidal having an input disk and an output disk with excellent fatigue strength by having a structure in which a compressive residual stress layer having a residual compressive stress of 0.2 GPa to 2.0 GPa is formed at a depth of less than m Type continuously variable transmission.

According to the present invention, at least one top of the input disk and the output disk and at least one third of the total height of the disk following the top of the hole in which the input shaft is mounted.
1.0 mm from the surface in the range of the inner diameter surface over the depth of
By having a structure in which a compressive residual stress layer having a maximum residual compressive stress value of 0.2 GPa to 2.0 GPa was formed at a depth of less than 2, an input disk and an output disk with excellent fatigue strength and high reliability were obtained. A toroidal-type continuously variable transmission can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a toroidal type continuously variable transmission.

FIG. 2 is an explanatory view of a disk which is a component of the toroidal type continuously variable transmission according to the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a depth from a surface of a residual compressive stress layer and a stress in a disk which is a component of the toroidal-type continuously variable transmission.

FIG. 4 is a characteristic diagram showing a relationship between time and temperature when heat-treating an input disk, an output disk, and a power roller in the toroidal-type continuously variable transmission according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Input disk, 2 ... Output disk, 3 ... Input shaft, 4 ... Loading cam, 5 ... Cam roller, 6, 7 ... Power roller bearing, 6a, 7a ... Power roller, 6b, 7b ... Outer ring, 6c, 7c ... Rolling Moving body (steel ball), 9: pivot, 10, 11: trunnion, 12: needle, 13: angular bearing 14: output shaft, 20: toroidal type continuously variable transmission, 31: inner end face (top), 32: inner circumference Near the end of the plane.

Claims (4)

[Claims] 1. A toroidal-type continuously variable transmission having an input disk and an output disk concentrically connected to a rotatably supported input shaft, wherein the input disk and the output disk have at least one top portion. 0.2 GPa to 2. Depth less than 1.0 mm from the surface.
A toroidal-type continuously variable transmission, wherein a compressive residual stress layer having a maximum residual compressive stress value of 0 GPa is formed. 2. A toroidal-type continuously variable transmission having an input disk and an output disk concentrically connected to an input shaft rotatably supported, wherein at least one top of the input disk and the output disk is provided. 0.2 GPa to 2.0 GP at a depth of less than 1.0 mm from the surface and at a depth of less than 1.0 mm from the surface at least one third of the total height of the disk following the top of the hole in which the input shaft is mounted.
A toroidal-type continuously variable transmission, wherein a compressive residual stress layer having a maximum residual compressive stress value of GPa is formed. 3. The toroidal type continuously variable transmission according to claim 1, wherein a residual compressive stress value at 1.0 mm from a surface of the compressive residual stress layer exceeds 0 GPa. Machine. 4. The toroidal-type continuously variable transmission according to claim 1, wherein a residual compressive stress value at 0.8 mm from the surface of the compressive residual stress layer is formed to be 0 GPa or less. Machine.