JP2000234658A - Power roller for toroidal continuously variable transmission and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen the usuful service life of a power roller by performing grinding super-finishing after quenching/tempering by performing hot gear rolling on a bearing groove part by using a ball or a roller after applying carburization or carbonitriding processing to a roughly worked raw material when manufacturing an inner race and an outer race of the power roller. SOLUTION: A toroidal continuously variable transmission continuously variably shifts rotation of an input disc by changing an inclination of a power roller interposed between input and output discs to be transmitted to the output disc. When manufacturing, for example, an outer race 7 of a power roller of this transmission, first of all, rough work is applied to carburization steel (Cr-Mo steel) as a material to obtain an outer race raw material 10 having a shape. Next, after applying carburization processing to this raw material 10, hot gear rolling is performed on a bearing groove part 7a by using a ball 11 having a diameter not less than a diameter of a bearing steel ball used for a power roller and not more than a radius of curvature of the bearing groove part 7a, and after quenching/tempering, the outer race 7 is completed by performing grinding super-finishing.

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 which is used in a vehicle such as an automobile or a rotary power source to transmit a rotational power by continuously changing the speed, and particularly to a toroidal type continuously variable transmission. The present invention relates to a method of manufacturing a power roller as a component for a step transmission, and a power roller for a toroidal-type continuously variable transmission manufactured by such a method.

[0002]

As shown in FIG. 1, the toroidal type continuously variable transmission is connected to a plurality of metal rolling elements, that is, an input shaft 1 and an output shaft 2 which are in contact with each other via lubricating oil. Input disk 3 and output disk 4, and a power roller 5 that transmits the rotation of the input disk 3 to the output disk 4 by rotating between the input and output disks 3 and 4. By changing the inclination of the power roller 5 as indicated by an arrow in the drawing, the contact position (radius) of the input / output disks 3, 4 with the power roller 5 is changed, and the rotation of the input disk 3 is steplessly changed. To the output disk 4.

The power roller 5 has an inner race 6 and an outer race 7, and between the inner race 6 and the outer race 7, bearing grooves 6a, 7a are provided on opposing surfaces, respectively. A bearing portion is formed by sandwiching steel balls 8, 8 as ball bearings in
The inner ring 6 rotating while contacting the input / output disks 3 and 4 is supported by the outer ring 7.

A material for such a metal rolling element (input / output disk and power roller) is AISI521
No. 00 steel (equivalent to high carbon chromium bearing steel SUJ2 specified in JIS G 4805) is an example of NASA Tech
nical note NASA ATN D-8362, and JP-A-7-71555 discloses that chromium molybdenum steel is used and carburized or carburized so that the effective hardened layer depth becomes 2.0 to 4.0 mm. It is disclosed that a nitriding treatment is performed.

The bearing portion of the power roller 5 receives a high load due to the pressing force between the disk and the power roller, and the inner ring 6 of the power roller rotates at a high speed, so that the bearing rolls under a high surface pressure and a high temperature. That is, the bearing portion of the power roller 5, that is, the bearing groove portion 6
There is a problem in that a and 7a are liable to cause peeling due to rolling fatigue, and it is a problem in the conventional toroidal type continuously variable transmission to prevent such peeling and improve the rolling fatigue life of the power roller. I was

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in a conventional toroidal-type continuously variable transmission,
Manufacture of power rollers for toroidal-type continuously variable transmissions that can prevent rolling fatigue separation in bearing grooves of power rollers used in toroidal-type continuously variable transmissions and can greatly improve the service life of power rollers It is an object of the present invention to provide a method and a power roller for a toroidal-type continuously variable transmission manufactured by such a method.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing a power roller for a toroidal-type continuously variable transmission, wherein an inner ring and an outer ring, and bearings formed on opposing surfaces of the inner and outer rings, respectively. Manufacturing the inner ring and / or outer ring of a power roller including a steel ball held in a groove and interposed between an input disk and an output disk of a toroidal-type continuously variable transmission and transmitting rotation of the input disk to the output disk. At this time, the material roughened into the shape of the inner ring and / or the outer ring is subjected to carburizing or carbonitriding, then the bearing groove portion is hot rolled using a ball or a roller, quenched and tempered, and then subjected to super-grinding. And a method for manufacturing a power roller for a toroidal-type continuously variable transmission. And a means for solving the problems.

According to a second aspect of the present invention, there is provided a method of manufacturing a power roller for a toroidal-type continuously variable transmission, wherein a radius of curvature of a ball or a roller is interposed between an inner ring and an outer ring. And the radius of curvature of the bearing groove formed on the opposing surfaces of the inner ring and the outer ring is equal to or less than the radius of curvature. In the manufacturing method according to claim 3, the material after the carburizing or carbonitriding It is characterized in that the bearing groove portion is hot-rolled after applying a carbon-proofing agent.

A power roller for a toroidal type continuously variable transmission according to a fourth aspect of the present invention is a power roller manufactured by the method according to any one of the first to third aspects, wherein the power roller has a bearing groove. Room temperature hardness in the range up to the maximum shear stress generation depth position of Hv780 or more,
In addition, the average crystal grain size is 10 or more, and the effective hardened layer depth is 3 times or more of the maximum shear stress generation depth. Such a structure in a power roller for a toroidal-type continuously variable transmission is employed. It is characterized in that it is a means for solving the above-mentioned conventional problem.

[0010]

The rolling contact fatigue peeling at the bearing portion of the power roller for a toroidal-type continuously variable transmission is often internal-origin type peeling starting from the vicinity of the maximum shear stress generation depth position inside the power roller. Has been confirmed. Therefore, in order to improve the rolling fatigue life of the power roller, it is necessary to positively improve the fatigue strength of the material not only on the surface but also in the vicinity of the position where the maximum shear stress occurs at the depth.

In the method for manufacturing a power roller for a toroidal-type continuously variable transmission according to the first aspect of the present invention, after performing carburizing or carbonitriding, the bearing groove is hot rolled using a ball or a roller. , Then quenching
Since tempering is performed and grinding super-finishing is performed, the principle of thermomechanical treatment causes refinement of austenite crystal grains, toughening of martensite, increase in compressive residual stress, optimization of fiber flow, etc. Dynamic fatigue strength and impact strength are improved.

Further, since the bearing groove is formed by hot rolling instead of forging after carburizing or carbonitriding, the bearing groove is formed not only in the vicinity of the surface but also in the vicinity of the internal maximum shear stress generation depth. Since a large compositional deformation occurs, the effect of improving the rolling fatigue strength and the impact strength can be obtained not only in the surface layer of the bearing groove but also in the vicinity of the position where the maximum shear stress is generated.

According to a second aspect of the present invention, there is provided a method of manufacturing a power roller for a toroidal-type continuously variable transmission, wherein the ball or roller used for hot rolling has a radius of curvature for a bearing. Since the steel ball having a radius of curvature equal to or larger than the radius of curvature of the steel ball and having a radius equal to or smaller than the radius of curvature of the bearing groove portion is used, the workability at the position where the maximum shear stress is generated becomes larger and more effective. At this time, if the radius of curvature of the ball or roller is less than the radius of curvature of the steel ball, the machining at the position where the maximum shear stress is generated and at a depth deeper than that is considered in consideration of the allowance for finishing after rolling. And the effect of improving rolling fatigue strength and toughness is reduced. On the other hand, if the radius of curvature of the ball or roller exceeds the radius of curvature of the bearing groove, the radius of curvature of the rolled bearing groove will exceed its finished dimension, so the grinding allowance during finishing must be large. Will have to be.

According to another aspect of the present invention, there is provided a method of manufacturing a power roller for a toroidal-type continuously variable transmission, wherein the bearing groove portion is hot-rotated in a state in which a carburizing agent has been applied to the carburized or carbonitrided material. Since hot rolling is performed, decarburization in the surface layer of the material is suppressed, the strength of the surface layer is improved, and grinding allowance during finishing is reduced. In the present invention, as the carbon preventive, a conventionally well-known one can be used.

According to a fourth aspect of the present invention, there is provided a power roller for a toroidal-type continuously variable transmission, the method comprising hot-rolling and quenching after carburizing or carbonitriding as described in the first to third aspects. The hardness at room temperature in the range up to the maximum shear stress generation depth position of the bearing groove is Hv 780 or more, the crystal grain size is 10 or more in average grain size number, and the effective hardened layer depth is Since the depth is at least three times the stress generation depth, the rolling fatigue strength and the impact strength in the vicinity of the position where the maximum shear stress is generated together with the surface layer are improved, and the rolling fatigue life is greatly improved.

At this time, when the room temperature hardness is less than Hv780, and when the crystal grain size is coarse and the average grain size number is 1
When it is less than 0, the improvement range of the rolling fatigue life is small, and the effective hardened layer depth is 3 times the maximum shear stress generation depth.
If the ratio is less than twice, the rolling fatigue strength is lowered due to the decrease in yield strength due to the lack of the hardened layer, and the effect of improving the life by carburizing or carbonitriding and hot rolling and quenching cannot be sufficiently exhibited.

In the present invention, the effective hardened layer is H
v means a range of a cured layer having a hardness of 550 or more.

[0018]

According to the method of manufacturing a power roller for a toroidal-type continuously variable transmission according to the first aspect of the present invention, after carburizing or carbonitriding, the bearing groove is hot rolled and quenched. Therefore, the rolling fatigue strength and impact strength not only in the vicinity of the surface but also in the vicinity of the position where the maximum shear stress occurs below the surface can be improved, and the useful life of the power roller can be greatly improved. Excellent effect is brought.

Further, the method of manufacturing a power roller for a toroidal type continuously variable transmission according to the present invention is described in claim 2 as an embodiment.
In the manufacturing method according to the above, the bearing groove portion is hot rolled using a ball or a roller having a radius of curvature equal to or larger than the radius of curvature of the bearing steel ball and equal to or smaller than the radius of curvature of the bearing groove portion. The plastic deformation at the stress generating position can be made larger and more effective, and the effect of improving the service life can be made larger. Similarly, in the method for manufacturing a power roller according to claim 3 as an embodiment, After applying a carburizing agent to the carburized or carbonitrided material, hot rolling of the bearing groove is performed, so that decarburization in the surface layer of the material during hot rolling is suppressed, and the surface layer This leads to a further excellent effect that the reduction in strength can be prevented and the amount of grinding during finishing can be reduced.

The power roller for a toroidal-type continuously variable transmission according to claim 4 of the present invention is formed as described above, that is, after the carburizing or carbonitriding treatment, the bearing groove is formed by hot rolling, and then quenched and tempered. The hardness at room temperature in the range up to the maximum shear stress generation depth position of the bearing groove is Hv 780 or more, the grain size is 10 or more, and the effective hardened layer depth is the maximum shear stress generation depth. 3 times or more, it is possible to improve not only the surface layer portion but also the rolling fatigue strength and impact strength in the vicinity of the position where the maximum shear stress occurs,
This has an extremely excellent effect that the useful life can be greatly extended.

[0021]

EXAMPLES The present invention will be described below more specifically based on examples. In this embodiment, an example of manufacturing an outer ring of a power roller for a toroidal type continuously variable transmission will be described. However, an inner ring of a power roller can be manufactured by basically the same procedure. Inventive Example 1 First, an outer ring material 10 having a shape as shown in FIG. 2A was obtained by subjecting a steel for carburization (Cr-Mo steel) A shown in Table 1 to a roughing process. The material 10
Was carburized. Subsequently, as shown in FIG. 2B, using balls 11 having a radius of curvature equal to or larger than the radius of curvature of the bearing steel ball 8 used for the power roller and equal to or smaller than the radius of curvature of the bearing groove 7a described later. The bearing groove is hot rolled, quenched and tempered, and then super-finished by grinding and polishing to finish it to a predetermined size, and as shown in FIG. 2C, a toroidal type having a bearing groove 7a. An outer ring 7 of a power roller for a continuously variable transmission was obtained. When the bearing groove is rolled, a shallow groove may be formed in a corresponding position of the material 10 in advance.

FIG. 3 (a) shows the heat treatment conditions at this time. After carburizing at 1050 ° C. in an atmosphere of Rx gas and enriched gas, hot rolling of the bearing groove is performed to obtain Rx. After being kept at a quenching temperature by maintaining in a gas atmosphere, quenching in oil
Tempering was performed at 0 ° C. × 2 hours. At this time, the working ratio during hot rolling (the thickness reduction ratio before and after rolling) was about 30 to 40%.

At this time, the carburizing treatment time is set to the material 2
Depending on the size and composition of the steel, the desired hardness, the carburizing depth, etc., it can be selected in the range of about 5 to 22 hours. Further, the quenching temperature is similarly set to 800 to 8
The holding time for soaking at 60 ° C. can be about 1 to 60 minutes.

With respect to the outer ring 7 thus obtained,
A rolling fatigue test was performed using a laboratory test apparatus, and a contact pressure of 4.0 was obtained.
The rolling fatigue life under the conditions of GPa and a rotation speed of 4000 rpm was evaluated. Furthermore, for the outer ring 7 manufactured using the same steel type under the same conditions, the effective effect layer depth (Hv550 or more) after rolling (before finishing), the decarburized layer depth by hot rolling, and the effective after finishing. The hardness and the crystal grain size at the depth of the effective layer and the maximum shear stress generation depth Zo position (Zo = 0.3 mm under the rolling fatigue test conditions) were examined. Table 2 shows the results.

The rolling fatigue life in Table 2 is shown as a ratio when the fatigue life of the outer race according to Comparative Example 1 (conventional example) described later is set to 1. Inventive Example 2 Outer ring 7 of a power roller for a toroidal-type continuously variable transmission using carburizing steel B shown in Table 1 under exactly the same conditions as in Inventive Example 1.
Was manufactured, and the same measurement and evaluation of rolling contact fatigue life were performed. The carburizing steel B is obtained by adding a small amount of Al and N to the carburizing steel A in order to further refine the crystal grains. These results are also shown in Table 2. Invention Example 3 As in Invention Example 1, carburizing steel (Cr-Mo) shown in Table 1 was used.
Outer ring material 1 having the shape shown in FIG.
After rough processing to 0, the material 10 was carburized under the conditions shown in FIG. After being quenched once in oil, the surface of the raw material 10 was subjected to a carbon prevention treatment by applying Thermocoat Super (trade name: manufactured by Thermal Co., Ltd.) as a carbon prevention agent. Then, FIG.
After heating to 1050 ° C. in an Rx gas atmosphere as shown in (b), hot rolling is performed under the same conditions as in Invention Example 1 shown in FIG. 2 (b) to form a bearing groove,
After quenching and tempering, it was worked to a predetermined size by grinding and superfinishing to obtain an outer ring 7 of a power roller for a toroidal type continuously variable transmission having a bearing groove 7a as shown in FIG. 2 (c).

With respect to the outer ring 7 thus obtained,
The same measurement and evaluation of rolling fatigue life were performed. These results are also shown in Table 2. Invention Example 4 As in Invention Example 1, the carburizing steel (Cr-Mo) shown in Table 1 was used.
Outer ring material 1 having the shape shown in FIG.
After roughing to 0, the material 10 is subjected to a carburizing process under the conditions shown in FIG. 3 (c), and then hot-rolled to form a bearing groove portion in the same manner as in each of the above invention examples. The outer ring 7 of a power roller for a toroidal type continuously variable transmission was manufactured by molding, quenching / tempering, grinding and superfinishing. Table 2 also shows the results of the same measurement and the evaluation of the rolling fatigue life of the obtained outer ring 7. Comparative Example 1 Using carburizing steel (Cr-Mo steel) A shown in Table 1 as a material,
Rough processing was performed to obtain an outer race material 12 having a shape close to the final shape of the outer race, as shown in FIG. And the material 1
2 is carburized under the conditions shown in FIG. 5, quenched in oil, tempered at 170 ° C. for 2 hours, and then ground and super-finished to a predetermined size in the same manner as in each of the above invention examples. Then, as shown in FIG. 4 (b), an outer ring 13 of a power roller for a toroidal type continuously variable transmission having a bearing groove 13a was obtained.

The outer ring 13 thus obtained is
The same measurement as that of the above-mentioned invention example was performed, and the rolling fatigue life was evaluated by the same rolling fatigue test. These results are also shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

As is evident from the results in Table 2, the outer race 7 according to Invention Examples 1 to 3 manufactured by hot rolling the bearing groove after carburizing treatment and performing quenching and tempering treatment has a The composition deformation at the internal position based on rolling works effectively, and the effective effect layer having a hardness of Hv550 or more is deep, and the hardness and the grain size at the position where the maximum shear stress occurs are reduced. Therefore, it was confirmed that the rolling fatigue life was improved as compared with the comparative example (conventional example). In particular, the steel B for carburization containing Al and N, which are crystal grain refining elements, was used as the material steel. In the case of Inventive Example 2 used as the above, the effect of greatly improving the rolling fatigue life by refining the crystal grains was recognized. In addition, in the case of Inventive Example 3 in which carbon prevention treatment was performed prior to hot rolling, it was confirmed that decarburization during rolling was reduced.

On the other hand, a comparative example obtained by subjecting a material 12 having a shape close to the final shape of the outer ring and having a bearing groove portion to a carburizing treatment in advance and then finishing without hot rolling. Although the depth of the effective effect layer does not change, the hardness at the position where the maximum shear stress occurs is low, and the crystal grain size at the position is coarse. The rolling fatigue life was found to be inferior.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the structure and principle of a toroidal type continuously variable transmission.

FIG. 2A is an explanatory sectional view showing a shape of a material used in a method of manufacturing a power roller for a toroidal-type continuously variable transmission according to the present invention. (B) It is explanatory drawing which shows the situation of the hot rolling of the bearing groove part in the manufacturing method of the power roller for toroidal type continuously variable transmissions concerning this invention. (C) It is sectional explanatory drawing which shows the completion state of the outer ring by the manufacturing method of the power roller for toroidal type continuously variable transmissions concerning this invention.

FIG. 3 (a) is an explanatory view showing an example of heat treatment conditions applied to a method of manufacturing a power roller for a toroidal type continuously variable transmission according to the present invention. (B) It is explanatory drawing which shows the other example of the heat processing conditions applied to the manufacturing method of the power roller for toroidal type continuously variable transmissions concerning this invention. (C) It is explanatory drawing which shows another example of the heat processing conditions applied to the manufacturing method of the power roller for toroidal type continuously variable transmissions concerning this invention.

FIG. 4A is an explanatory sectional view showing a shape of a material used in a conventional method of manufacturing a power roller for a toroidal-type continuously variable transmission. (B) It is sectional explanatory drawing which shows the completion state of the outer ring by the conventional manufacturing method of the power roller for toroidal type continuously variable transmissions.

FIG. 5 is an explanatory view showing heat treatment conditions according to a conventional manufacturing method of a power roller for a toroidal type continuously variable transmission.

[Explanation of symbols]

 Reference Signs List 3 input disk 4 output disk 5 power roller 6 inner ring 7 outer ring 6a, 7a bearing groove 8 steel ball 10 material 11 ball

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3J051 BA03 BB01 BC03 BD02 BE09 CB04 EC03 EC07 EC08 FA02 4K028 AA01 AA03 AB06 4K042 AA25 DA01 DA02 DA06

Claims (4)

[Claims] An inner ring and an outer ring, and steel balls held in bearing grooves formed on opposing surfaces of the inner ring and the outer ring, respectively, and are interposed between input and output disks of a toroidal type continuously variable transmission. And / or the inner race of the power roller for transmitting the rotation of the input disk to the output disk.
Or, when manufacturing the outer ring, after subjecting the material roughly processed into the shape of the inner ring and / or the outer ring to carburizing or carbonitriding, hot rolling the bearing groove portion using a ball or a roller, followed by quenching and tempering. A method of manufacturing a power roller for a toroidal-type continuously variable transmission, comprising performing grinding super finishing. 2. The method according to claim 1, wherein the radius of curvature of the ball or the roller is not less than the radius of curvature of the steel ball interposed between the inner ring and the outer ring, and not more than the radius of curvature of the bearing groove formed on the opposing surfaces of the inner ring and the outer ring. The method for manufacturing a power roller for a toroidal-type continuously variable transmission according to claim 1. 3. The toroidal-type continuously variable transmission according to claim 1 or 2, wherein a hot rolling of the bearing groove is performed after applying a carburizing agent to the material after the carburizing or carbonitriding treatment. Of manufacturing power rollers for presses. 4. A power roller manufactured by the method according to claim 1, wherein a normal temperature hardness in a range up to a maximum shear stress generation depth position of a bearing groove portion is Hv780 or more, A power roller for a toroidal type continuously variable transmission, wherein the average crystal grain size is 10 or more, and the effective hardened layer depth is 3 times or more the maximum shear stress generation depth.