JP3940991B2 - Toroidal continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a toroidal type continuously variable transmission used for a transmission of an automobile or the like.
[0002]
[Prior art]
Conventionally, for example, a toroidal continuously variable transmission as shown in FIGS. 3 and 4 is known as a transmission for an automobile.
The toroidal continuously variable transmission includes an input shaft 15 and an input side disk 2 and an output side disk 4 that are rotatably supported on the outer periphery of the input shaft 15 via needle bearings 16 and 16. . Further, the cam plate 10 is spline-engaged with the outer peripheral surface of the end portion (left end portion in FIG. 3) of the input shaft 15, and is prevented from moving in a direction away from the input side disk 2 by the flange portion 17. The cam plate 10 and the rollers 12 and 12 constitute a loading cam type pressing device 9 that rotates the input side disk 2 while pressing it toward the output side disk 4 based on the rotation of the input shaft 15. is doing.
An output gear 18 is coupled to the output side disk 4 by means of keys 19 and 19 so that the output side disk 4 and the output gear 18 rotate integrally. The output gear 18 and a gear (not shown) meshed with the output gear 18 constitute a power take-out means for taking out the rotation of the output side disk 4.
[0003]
The pivots 5 and 5 provided at both ends of the pair of trunnions 6 and 6 are swingable and displaceable in the axial direction (front and back direction in FIG. 3, left and right direction in FIG. 4) on the pair of support plates 20 and 20. It is supported. The pair of support plates 20 and 20 are formed in a plate shape having sufficient rigidity, and the circular holes 21 and 21 formed in the central portions of the support plates 20 and 20 are the inner surface of the casing 22 and the casing 22, respectively. By being externally fitted to support plates 24a and 24b fixed to the side surface of the cylinder case 23 provided in the inside, it is supported inside the casing 22 so as to be swingable and displaceable in the axial directions of the pivots 5 and 5. ing. In addition, circular support holes 25 and 25 are formed at both ends of each of the support plates 20 and 20, and the support holes 25 and 25 are respectively provided at both ends of the trunnions 6 and 6. The pivot shafts 5 and 5 are supported by radial needle bearings 27 and 27 having outer rings 26 and 26. With these configurations, the trunnions 6 and 6 are supported in the casing 22 so as to be swingable about the pivots 5 and 5 and to be displaced in the axial direction of the pivots 5 and 5.
[0004]
Displacement axes (trunnion central axes) 7 and 7 are supported in the circular holes 40 and 40 formed in the intermediate portions of the trunnions 6 and 6, respectively. Each displacement shaft 7 includes a support shaft portion 28 and a pivot shaft portion 29 that are parallel to each other and eccentric. Each support shaft portion 28 is swingably supported inside each circular hole 40 via a radial needle bearing 30. Further, the power roller 8 is rotatably supported on the outer peripheral portion of each pivot shaft portion 29 via a radial needle bearing 31. The power roller 8 has a traction surface 8 a that contacts the input side disk 2 and the output side disk 4, and rolls freely between the input side disk 2 and the output side disk 4 about the tilt axis O. Has been.
[0005]
The pair of displacement shafts 7 and 7 are arranged so as to be point-targeted positions (positions opposite to 180 degrees) with the input shaft 15 as the center. The directions in which the pivot shafts 29 and 29 of the displacement shafts 7 and 7 are eccentric with respect to the support shafts 28 and 28 are the same with respect to the rotational directions of the input side and output side disks 2 and 4. (The left and right direction in FIG. 4). Further, the axial directions of the respective pivot shaft portions 29, 29 are substantially orthogonal to the axial direction of the input shaft 15 (the left-right direction in FIG. 3 and the front-back direction in FIG. 4). Therefore, each power roller 8, 8 is supported with a slight displacement allowed in the axial direction of the input shaft 15. As a result, even if the power rollers 8 and 8 are slightly displaced in the axial direction of the input shaft 15 due to variations in the dimensional accuracy of the constituent parts or elastic deformation during power transmission, this displacement can be absorbed. Unreasonable force is not applied to each component.
[0006]
A thrust rolling bearing 32 such as a thrust ball bearing is arranged between the outer surface of each of the power rollers 8 and 8 and the inner surface of the intermediate portion of each of the trunnions 6 and 6 in order from the outer surface of the power rollers 8 and 8. , 32 and thrust bearings 34, 34 such as thrust needle bearings for supporting a thrust load applied to the outer rings 33, 33 of the respective thrust rolling bearings 32, 32 are provided. In this case, the outer surfaces of the power rollers 8 and 8 form inner rings of the thrust rolling bearings 32 and 32. The thrust rolling bearings 32 and 32 allow the power rollers 8 and 8 to rotate while supporting a load in the thrust direction (vertical direction in the figure) applied to the power rollers 8 and 8. Further, the thrust bearings 34 and 34 support the thrust load applied to the outer rings 33 and 33 of the thrust rolling bearings 32 and 32 from the power rollers 8 and 8 while supporting the pivot shafts 29 and 29 and the outer rings 33 and 33. Swings about the support shafts 28 and 28.
[0007]
Further, driving rods 35 and 35 are respectively coupled to one end portions (the left end portion in FIG. 4) of the trunnions 6 and 6, and a driving piston 36 is fixed to the outer peripheral surface of the intermediate portion of each driving rod 35 and 35. Has been. The drive pistons 36 and 36 are oil-tightly fitted in drive cylinders 37 and 37 provided in the cylinder case 23, respectively. Further, a pair of rolling bearings 39, 39 are provided between the support wall 38 provided in the casing 22 and the input shaft 15, and the input shaft 15 is rotatably supported in the casing 22.
[0008]
In the toroidal type continuously variable transmission configured as described above, the rotation of the input shaft 15 is transmitted to the input side disk 2 via the pressing device 9. Then, the rotation of the input side disk 2 is transmitted to the output side disk 4 via the pair of power rollers 8 and 8, and the rotation of the output side disk 4 is taken out from the output gear 18.
When changing the rotational speed ratio between the input shaft 15 and the output gear 18, the pair of drive pistons 36, 36 are displaced in opposite directions. Then, as the drive pistons 36 and 36 are displaced, the pair of trunnions 6 and 6 are displaced in the opposite directions. For example, in FIG. 4, the lower power roller 8 is displaced to the right in the figure, and the upper power roller 8 is displaced to the left in the figure. As a result, the tangential force acting on the contact portions between the peripheral surfaces (traction surfaces) 8a and 8a of the power rollers 8 and 8 and the inner surfaces 2a and 4a of the input side disk 2 and the output side disk 4 is as follows. The direction changes. As the direction of the force changes, the trunnions 6 and 6 swing in directions opposite to each other in FIG. 3 about the pivots 5 and 5 pivotally supported by the support plates 20 and 20. As a result, the contact position between the peripheral surfaces 8a and 8a of the power rollers 8 and 8 and the inner surfaces 2a and 4a changes, and the rotational speed ratio between the input shaft 15 and the output gear 18 changes.
[0009]
When the power rollers 8 and 8 are displaced in the axial direction of the input shaft 15 as a result of elastic deformation of the constituent parts during power transmission, the displacement shafts 7 and 7 pivotally supporting the power rollers 8 and 8 are used. However, it swings slightly around the support shafts 28 and 28. As a result of this oscillation, the outer surfaces of the outer rings 33, 33 of the thrust rolling bearings 32, 32 and the inner surfaces of the trunnions 6, 6 are relatively displaced. Since the thrust bearings 34 and 34 exist between the outer surface and the inner surface, the force required for this relative displacement is small. Therefore, as described above, the force for changing the inclination angle of each displacement shaft 7, 7 can be small.
[0010]
[Problems to be solved by the invention]
As described above, the toroidal type continuously variable transmission transmits power by the power roller 8 sandwiched between the input side disk 2 and the output side disk 4. Since it is a traction drive between 4 and the power roller 8, it is necessary to give a big pressing force. Since the power roller 8 is pressed at two points on the input side and the output side, high stress is generated on the thrust bearing 34 side of the inner diameter portion of the power rollers 8 and 8 forming the inner rings of the thrust rolling bearings 32 and 32.
[0011]
For this reason, Japanese Patent Laid-Open No. 2001-289297 discloses a configuration for closing the front surface of the power roller 8 (the surface opposite to the outer ring 33) in order to make such stress low. Thus, if the opening of the through hole of the power roller 8 through which the pivot shaft 29 penetrates is blocked, the deformation of the inner diameter portion of the power roller 8 can be suppressed, so that the inner diameter portion of the power rollers 8 and 8 is on the thrust bearing 34 side. It is possible to suppress the stress generated in.
[0012]
In the configuration in which the front surface of the power roller 8 (the surface opposite to the outer ring 33) is closed as disclosed in Japanese Patent Laid-Open No. 2001-289297, the inner diameter of the power rollers 8 and 8 increases as the thickness t of the closed portion increases. However, the capacity of the needle bearing 31 that supports the power roller 8 is reduced. This is because the capacity of the needle bearing 31 is determined by the length of the roller.
[0013]
As described above, in the configuration in which the front surface of the power roller 8 is closed, the stress generated on the thrust bearing 34 side of the inner diameter portion of the power rollers 8 and 8 can be kept low, while the capacity of the needle bearing 31 is reduced. There is a risk that peeling of the needle may occur.
[0014]
The present invention has been made paying attention to the above circumstances, and provides a toroidal type continuously variable transmission that can suppress the stress generated in the inner diameter portion of the power roller while reducing the capacity of the needle bearing. The purpose is to do.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides an input shaft to which rotational force is input, an input side disk coupled to the input shaft and rotating integrally with the input shaft, and rotatably supported by the input shaft. Output side disk, and a rotational speed of the input side disk is set to a predetermined speed ratio on the output side disk via a power roller provided to be tiltable between the input side disk and the output side disk. The power roller is rotatably supported by a central shaft of a trunnion provided between the input side disk and the output side disk via a needle bearing and provided between the trunnion. In the toroidal continuously variable transmission that forms an inner ring of a rolling bearing, and the power roller has a bottom plate portion that closes an opening of the inner hole through which the central shaft of the trunnion is inserted. The diameter of the bore of over La and D _0, the total height of the power rollers and H, when the wall thickness of the bottom plate portion and a ^{t, 0 <t 2 / [} D 0 · (H-t)] ≦ 0.2 is established.
Therefore, according to the said structure, the stress which generate | occur | produces in the internal diameter part of a power roller can be restrained low, preventing the fall of the capacity | capacitance of a needle bearing.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The feature of the present invention lies in the improvement of the structure of the power roller, and the other configurations and operations are the same as the conventional configurations and operations described above. Therefore, only the features of the present invention will be described below. Reference is made to the other portions, and the same reference numerals as those in FIGS. 3 and 4 are given, and detailed description thereof will be omitted.
[0017]
FIG. 1 shows an embodiment of the present invention. As illustrated, in this embodiment, the support shaft portion 28 of the displacement shaft 7 and the outer ring 33 in the conventional configuration shown in FIGS. 3 and 4 are integrally formed. Further, the power roller 8 has a bottom plate portion 50 that closes an opening of the inner hole through which the pivot shaft portion 29 is inserted.
[0018]
The stress σ _t generated on the thrust bearing 34 side of the inner diameter portion of the power roller 8 increases as the inner diameter D ₀ of the power roller 8 increases. Conversely, as the thicker the wall thickness t of the bottom plate portion 50, the stress sigma _t decreases. Therefore, the following formula (1) is established.
σ _t Ｑ Qt ⁿ / [D ₀ ^m · (H−t) ^h ] (1)
Here, Q is a constant, n, m, and k are constants of 1 or more, respectively, and H is the total height of the power roller 8.
[0019]
Further, the capacity C of the needle bearing 31 inserted into the inner diameter portion (inner hole) of the power roller 8 is expressed by the following formula (2).
C ∝ Lw ^α · Z ^β · Dw ^γ (2)
Here, Lw is the length of the roller of the needle bearing 31, Z is the number of rollers, Dw is the diameter of the roller, and α, β, and γ are constants.
[0020]
Therefore, from the formula (2), the capacity C of the needle bearing 31 increases as the roller diameter increases and the roller length increases. Therefore, in order to increase the Lw, it is necessary to increase the (H-t), In order to increase the Dw, it is necessary to increase the D _0. Also, increasing the D _0, it is possible to increase also Z.
[0021]
From the above, C ∝ [D ₀ ^B · (H−t) ^C ] / t ^A (3) where the following expression (3) holds.
Here, A, B, and C are constants.
[0022]
The graph of FIG. 2 shows the influence of t ² / [D ₀ · (H−t)] on the stress σ _t and the change in the capacity of the needle bearing 31. As can be seen from this figure, by satisfying the following expression (4), the allowable limit of the tensile stress σ _T generated in the inner diameter portion of the power roller 8 and the allowable limit of the needle bearing 31 are not exceeded.
0 <t ² / [D ₀ · (H−t)] ≦ 0.2 (4)
[0023]
In this case, 0 is when t = 0, and there is no bottom plate portion 50, and the inner hole of the power roller 8 is a completely through hole. It can be seen from the graph of FIG. 2 that the stress is reliably reduced by providing the bottom plate portion 50 (by closing one end opening of the inner hole of the power roller 8). However, as the range to be closed becomes wider, the stress decreases, so σ _S / σ _T increases (σ _S is the fatigue limit of the material), and the life of the needle bearing 31 decreases. Therefore, by limiting t ² / [D ₀ · (H−t)] on the horizontal axis in the graph of FIG. 2 to a range where the life extension of the bearing 31 is large and smaller than 0.2, that is, the equation (4) ), The stress of the power roller 8 can be kept below the fatigue limit, and the life of the needle bearing 31 in the power roller 8 can be ensured long.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress the stress generated in the inner diameter portion of the power roller to a low level while preventing a decrease in the capacity of the needle bearing.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a toroidal continuously variable transmission according to an embodiment of the present invention.
FIG. 2 is a graph showing the influence of t ² / [D ₀ · (Ht)] on the stress σ _t and the change in capacity of the needle bearing.
FIG. 3 is a cross-sectional view of a main part of a conventional toroidal continuously variable transmission.
4 is a cross-sectional view taken along line XX of FIG.
[Explanation of symbols]
6 Trunnion 7 Displacement axis (center axis)
8 Power roller 31 Needle bearing 33 Thrust bearing 50 Bottom plate

Claims (1)

An input shaft that is coupled to the input shaft and rotates integrally with the input shaft; and an output disk that is rotatably supported by the input shaft. Is transmitted to the output side disk at a predetermined speed ratio via a power roller provided so as to be tiltable between the input side disk and the output side disk. A center shaft of a trunnion provided between the disc and the output side disc is rotatably supported via a needle bearing, and forms an inner ring of a rolling bearing provided between the trunnion and power. In the toroidal continuously variable transmission, the roller has a bottom plate portion that closes the opening of the inner hole through which the central shaft of the trunnion is inserted.
When the diameter of the bore of the power roller and D _0, the total height of the power rollers and H, the thickness of the bottom plate portion was t,
0 <t ² / [D ₀ · (H−t)] ≦ 0.2
A toroidal-type continuously variable transmission characterized by

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