JP4288760B2 - Power roller bearing for toroidal-type continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a toroidal type continuously variable transmission used in a speed change mechanism of, for example, an automobile, and more particularly to improvement of a power roller bearing.
[0002]
[Prior art]
A toroidal continuously variable transmission used in a transmission mechanism of an automobile or the like transmits the rotation of the input disk to the output disk via a power roller that can be tilted between the input disk and the output disk. The input disk is pressed toward the output disk by a pressing mechanism. The power roller has a traction portion that contacts the input disk and the output disk, and is rotatably supported by the trunnion by a power roller bearing. The power roller is tiltable about the trunnion axis between the input disk and the output disk. By changing the tilt angle of the power roller, the rotation of the input disk is transmitted to the output disk at a desired gear ratio. Like to do.
[0003]
The power roller bearing includes an inner ring provided on the power roller side, an outer ring provided to face and separate from the inner ring, and a plurality of rolling spheres provided to freely roll between the raceway grooves of the inner ring and the outer ring. ing. These rolling spheres reduce the resistance when the inner ring and the outer ring rotate relative to each other by transmitting the thrust load acting on the inner ring from the power roller to the outer ring and rolling along the raceway groove. I have to.
[0004]
The configuration of such a power roller bearing is almost the same as that of a thrust ball bearing, except for a power roller having an inner ring. Conventionally, a thrust ball bearing has been used to support a rotating shaft on which a thrust force (axial load) acts. Therefore, it has been studied to divert bearing parts designed for existing thrust ball bearings to power roller bearings.
[0005]
However, the power roller bearings for toroidal type continuously variable transmissions have completely different functions from the inner ring than the conventional general thrust ball bearings. As a result, the load distribution acting on the inner ring itself, the inner ring and the outer ring Since the contact behavior of the rolling elements interposed between the inner ring and the outer ring is significantly different from that of a general thrust ball bearing, improvement in consideration of the difference is indispensable.
[0006]
For example, the inner ring of a general thrust ball bearing functions as a shaft support member, but the power roller that rotates integrally with the inner ring of the power roller bearing functions as a power transmission member that transmits rotation from the input disk to the output disk. This corresponds to a transmission gear in a gear type multi-stage transmission. Since such a power roller rotates at a high speed under a strong pressing force from the input disk or the output disk, the heat roller generates a large amount of heat, and the heat generated by the power roller heats the inner ring and the rolling element. Therefore, as the lubricating oil supplied between the inner ring and the outer ring, it is essential to use a high-viscosity traction oil developed in consideration of power transmission.
[0007]
In addition, the traction portions of the power roller that come into contact with the input disk and the output disk are positioned 180 degrees apart from each other on the outer periphery of the power roller, and the strong pressing force from the input disk and the output disk is the opposite position (traction section). It acts intensively as a radial load. Therefore, a very high contact surface pressure is generated in the traction portion that contacts the input disk and the output disk.
[0008]
For example, a general bearing is used at a contact surface pressure of 2 to 3 Gpa or less, whereas a power roller bearing used in a toroidal-type continuously variable transmission for a vehicle is in contact even at a normal reduction ratio. The surface pressure is 2.5 to 3.5 Gpa, and the contact surface pressure may reach 4 Gpa at the time of maximum deceleration.
[0009]
Further, the strong pressing force from the input disk and the output disk acts as a radial load intensively on the traction portion of the power roller, thereby causing the power roller and the inner ring to undergo a compressive deformation in the radial direction. Since the inner ring warps due to this compression deformation, it becomes almost impossible to evenly distribute the thrust load acting on the inner ring from the power roller to all the rolling elements interposed between the inner ring and the outer ring. That is, the thrust load acts intensively on some of the rolling elements that are 180 degrees apart from each other, resulting in variations in the contact surface pressure of the rolling elements with respect to the raceway grooves. The track groove rolls with extremely high contact pressure.
[0010]
Therefore, the traction part that contacts the input disk and output disk, and the raceway grooves of the inner ring and outer ring that contact the rolling elements are made of a material in order to prevent a decrease in the service life due to high contact surface pressure acting locally. In addition, special considerations regarding surface hardness, surface roughness, etc. are indispensable.
[0011]
From such a background, the applicant of the present application forms rolling elements with medium carbon steel or high carbon steel in order to improve durability against local action of contact surface pressure and improve bearing life, and carburizing. A technique for adjusting the hardness and strength of the surface of the rolling element by nitriding, quenching and tempering has been proposed (see Japanese Patent Application Laid-Open No. 7-208568). Further, the applicant of the present invention applied the grinding finishing process after performing the carburizing process on the input disk and the output disk, the power roller, the inner ring, etc., or performing the grinding finishing process after performing the carbonitriding process. Proposed a technique for adjusting the hardness and effective hardened layer depth of the member to appropriate values (2 mm or more and 4 mm or less) that can withstand the effect of local contact surface pressure.
[0012]
[Problems to be solved by the invention]
However, a special traction oil is used as the lubricating oil supplied between the inner ring and the outer ring, and the hardness, effective hardened layer depth, surface roughness of the power roller and inner ring and rolling element are selected by material selection and surface treatment. It is not enough to implement appropriate optimization. That is, since power transmission is the original purpose of the power roller bearing, it is important to reduce the dynamic torque loss in the bearing as much as possible and improve the torque transmission efficiency. For example, depending on the setting of the raceway grooves and the rolling elements of the inner ring and the outer ring, the dynamic torque loss in the bearing may increase, which may cause a problem of a decrease in torque transmission efficiency. Even if the surface hardness or effective hardened layer depth of the power roller or inner ring described above is adjusted, sometimes the edge of the raceway groove or the rolling element is damaged early, or the contact surface between the raceway groove and the rolling element is damaged. In some cases, this may cause a problem that the bearing life is reduced.
[0013]
As described above, when a thrust ball bearing is used as a power roller bearing, a radial force called a traction force is applied to the power roller, so that the surface pressure or PV value (P: maximum surface pressure) in the direction along the raceway groove of the power roller. , V: spin slip velocity) distribution occurs. However, since the thrust ball bearing is not originally designed to apply a radial force, a portion having a high surface pressure or a portion having a high PV value is locally generated in the raceway groove of the power roller. Normally, a thrust ball bearing is used at about 5000 rpm, whereas a power roller bearing may have a rotational speed of 10,000 rpm or more at the maximum speed change gear ratio (when the vehicle is traveling at high speed). That is, the influence of the increase in PV value is large during high-speed rotation.
[0014]
When the PV value is high, heat generation is large, which may cause damage to the raceway groove due to local oil film breakage or deterioration of the traction oil. If the heat generation is remarkably large, the molecular structure of the traction oil, which is a synthetic oil, is decomposed, leading to deterioration of the traction coefficient and the safety factor against gross slip. Moreover, since it becomes difficult to secure a predetermined oil film in terms of lubricity, it causes early detachment of the traction portion and the power roller bearing.
[0015]
Further, since the backup portion of the outer ring of the power roller bearing may not be uniform (the trunnion is deformed), there are places where the load is large and small in the circumferential direction of the bearing. If the load becomes uneven in this way, the behavior of slipping becomes complicated, and the slipping speed changes while the power roller inner ring makes one round. Since this inner ring is traction driven with the input disk or the output disk, the heat generated at the contact point is transmitted to the power roller bearing, so it is more likely to generate heat. In addition, if the surface pressure is locally increased, the life is naturally reduced.
[0016]
Therefore, an object of the present invention is to suppress the excessive increase in the maximum surface pressure and PV value in the raceway groove, to improve durability, and toroidal type that allows the traction oil to exhibit a predetermined function. The object is to provide a power roller bearing for a step transmission.
[0017]
[Means for Solving the Problems]
In order to solve the problems peculiar to the power roller bearing described above, the present inventor has earnestly studied about the increase / decrease in dynamic torque loss and the correlation with the bearing life with respect to various design data related to the components constituting the power roller bearing. Research has shown that the contact angle of the rolling elements has a significant effect on the maximum surface pressure P and PV values, and that the life of the power roller bearing can be greatly extended by maintaining the contact angle at an appropriate level. I started. In other words, by setting the optimal contact angle for a power roller to which thrust force and radial force are applied simultaneously, the surface pressure and PV value increase that occur locally, so-called heat generation, can be suppressed, so the bearing life and traction drive performance To prevent the decline.
[0018]
When the relationship between the PV value according to the contact angle and the maximum value of the surface pressure was determined, the result shown in FIG. 4 was obtained in the case of a bearing to which only a thrust load is applied. That is, in the case of only the thrust load, since the distribution of the maximum value of the PV value and the surface pressure does not occur in the raceway groove, the PV value (PVmax) hardly changes and the change of the surface pressure (Pmax) due to the contact angle is observed. It is only done.
[0019]
On the other hand, in the case of a bearing to which a thrust load and a radial load are applied, the result shown in FIG. 5 was obtained. That is, when a thrust load and a radial load are applied, the distribution of the maximum value of the PV value and the surface pressure is generated in the raceway groove. Therefore, the local maximum value of the PV value has a contact angle of 90 degrees (corresponding to a thrust bearing). ) Shows a tendency to increase as it approaches. The maximum value (Pmax) of the surface pressure tends to have a maximum value near a contact angle of 85 degrees and a minimum value near 65 degrees.
[0020]
From FIG. 5, by setting the contact angle in the range of 50 degrees to 80 degrees, the local increase in PV value is suppressed, and the maximum value (Pmax) of the surface pressure is the case of the thrust bearing (θ = 90 °). ), And the durability is increased. More preferably, if the contact angle is set from 60 degrees to 70 degrees, this effect becomes more remarkable, and the durability can be further enhanced. 4 and 5 show values when the engine is operated with an input torque of 340 Nm and a gear ratio of 0.5, but the same tendency as in FIGS. 4 and 5 was observed when operated under other conditions. .
[0021]
Therefore, the power roller bearing of the present invention for achieving the above object is provided with an inner ring provided on the side of the power roller and having a raceway groove, a raceway groove provided at a position corresponding to the raceway groove of the inner ring and spaced from the inner ring. From the viewpoint of having the outer ring having the rolling element accommodated between the raceway grooves of the inner ring and the outer ring, and suppressing the above-mentioned maximum surface pressure and PV value low, the contact angle of the rolling element with respect to the respective raceway groove is set. It is characterized by a range of 50 degrees to 80 degrees. More preferably, the contact angle is set in a range of 60 degrees to 70 degrees.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
The half toroidal continuously variable transmission shown in FIG. 1 has an input shaft 1 that rotates integrally with a drive source including an engine and the like. An input disk 2 and an output disk 3 are provided on the input shaft 1 so as to be separated from each other in the axial direction of the input shaft 1. There is a cam plate 4 on the back of the input disk 2. Cam plate 4 is splined to the input shaft 1, rotates together with the input shaft 1. A cam roller 5 is provided between the cam plate 4 and the input disk 2.
[0023]
The input disk 2 is pressed toward the output disk 3 by a loading cam type pressing mechanism 6 including a cam roller 5. The output disk 3 is rotatably supported on the input shaft 1. For example, the rotated body 7 such as a gear can rotate integrally with the output disk 3.
[0024]
A trunnion 8 is provided between the input disk 2 and the output disk 3. The trunnion 8 can tilt in the direction indicated by the arrow Q in FIG. A displacement shaft 10 is provided on the trunnion 8. A power roller 11 is supported on the displacement shaft 10 so as to be rotatable around the axis O of the displacement shaft 10. The power roller 11 has a traction portion 11 a that makes rolling contact with the input disk 2 and the output disk 3. The power roller 11 can change the inclination in the Q direction between the input disk 2 and the output disk 3 with the trunnion shaft 9 as the center according to the gear ratio of both.
[0025]
The power roller 11 is supported by a power roller bearing 20 so as to be rotatable about the axis O. The power roller bearing 20 supports the thrust roller and the radial load applied to the power roller 11 and supports the power roller 11 so that the power roller 11 can smoothly rotate around the axis O. Yes. The power roller bearing 20 is interposed between an inner ring 21 formed on a part of the power roller 11, an outer ring 22 provided on the trunnion 8 side and facing the inner ring 21, and between the inner ring 21 and the outer ring 22. For example, a plurality of rolling spheres 23 such as steel balls are provided.
[0026]
As shown in FIG. 2, raceway grooves 31 and 32 are formed in the inner ring 21 and the outer ring 22 at positions corresponding to each other. The rolling sphere 23 is accommodated between the raceway grooves 31 and 32. These rolling spheres 23 are held by an annular cage 33 provided between the inner ring 21 and the outer ring 22. Although the inner ring 21 in the illustrated example is formed on a part of the power roller 11, the inner ring 21 may be formed separately from the power roller 11.
[0027]
The rotation of the input disk 2 is transmitted to the output disk 3 through the rotational movement of the power roller 11. That is, the input disk 2, the output disk 3, and the power roller 11 are configured to perform traction drive using high-viscosity traction oil that is synthetic oil. The traction oil is supplied between the inner ring 21 and the outer ring 22 and functions as a lubricating oil.
[0028]
The contact angle θ (shown in FIG. 2) of the rolling sphere 23 with respect to the raceway grooves 31 and 32 is set in the range of 60 degrees to 80 degrees for the reason described above. That is, when a thrust load and a radial load are applied as in the power roller bearing 20, the distribution of the maximum value Pmax and the PV value of the surface pressure is generated in the raceway grooves 31 and 32, and as shown in FIG. The local maximum value of the PV value tends to increase as the contact angle approaches 90 degrees (that is, a thrust bearing). The maximum value of the surface pressure tends to have a maximum value near a contact angle of 85 degrees and a minimum value near 65 degrees.
[0029]
Here, by setting the contact angle θ in the range of 50 degrees to 80 degrees, a local increase in the PV value is suppressed, and the maximum value Pmax of the surface pressure is more than in the case of the thrust bearing (θ = 90 °). Can be reduced, and durability is increased. Preferably, if the contact angle θ is set from 60 degrees to 70 degrees, the Pmax can be used in the vicinity of the minimum value (330 kgf / mm ² or less) in the region where the PVmax is sufficiently low. Will be able to.
[0030]
The contact angle θ referred to in this specification is an angle formed by a line segment L1 connecting the centers of the rolling spheres 23 and a line segment L2 connecting the contact points C1 and C2 of the rolling spheres 23 with the inner ring 21 and the outer ring 22. . In the embodiment, the contact C2 of the outer ring 22 is closer to the axis O than the contact C1 of the inner ring 21. In the reference example shown in FIG. 3 , the contact angle θ is set in the same range as in the above embodiment in the power roller bearing 20 where the contact C1 of the inner ring 21 is closer to the axis O than the contact C2 of the outer ring 22.
[0031]
In carrying out the present invention, it goes without saying that the elements constituting the present invention such as the input disk, the output disk, the power roller, the inner ring and the outer ring, and the dimensions and specific shapes of the rolling elements can be modified as appropriate. Yes. In the above embodiment, the single cavity type half toroidal continuously variable transmission has been described. However, the present invention can also be applied to a double cavity type half toroidal continuously variable transmission.
[0032]
【The invention's effect】
According to the present invention, in the actual use state of the toroidal type continuously variable transmission, that is, in the case where the traction drive is performed with not only the thrust load but also the radial load applied to the power roller, excessive surface pressure and PV value As a result, it is possible to suppress the local rise of the traction oil, thereby suppressing heat generation, allowing the traction oil to exhibit a predetermined function, and improving the durability life.
[Brief description of the drawings]
FIG. 1 is a sectional view of a half-toroidal continuously variable transmission showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a power roller bearing portion taken along line II-II in FIG.
FIG. 3 is a cross-sectional view of a power roller bearing portion showing a reference example .
FIG. 4 is a diagram showing a relationship between a contact angle and a maximum surface pressure P and PV value when only a thrust load is applied to the bearing.
FIG. 5 is a diagram showing the relationship between the contact angle and the maximum surface pressure P and PV value when a thrust load and a radial load are applied to the bearing.
[Explanation of symbols]
2 ... Input disk 3 ... Output disk 8 ... Trunnion 11 ... Power roller 20 ... Power roller bearing 21 ... Inner ring 22 ... Outer ring 23 ... Rolling sphere (rolling body)
31, 32 ... raceway groove

Claims (2)

A power roller bearing that rotatably supports the power roller of a toroidal continuously variable transmission that has a power roller that can be tilted between an input disk and an output disk and that performs traction drive using traction oil. And
An inner ring provided on the power roller side and having a raceway groove;
An outer ring that is provided to be spaced apart from the inner ring and has a raceway groove at a position corresponding to the raceway groove of the inner ring;
Having rolling elements housed between the raceway grooves of the inner ring and the outer ring,
The contact point between the outer ring and the rolling element is located closer to the axis of the bearing than the contact point between the inner ring and the rolling element; and
A power roller bearing for a toroidal-type continuously variable transmission, wherein a contact angle of the rolling element with respect to each raceway groove is in a range of 50 to 80 degrees.   2. A power roller bearing for a toroidal continuously variable transmission according to claim 1, wherein the contact angle is in the range of 60 to 70 degrees.

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