JP3638303B2 - Thrust ball bearing for half toroidal type continuously variable transmission - Google Patents

Description

[0001]
[Industrial application fields]
The thrust ball bearing half toroidal type continuously variable transmission according to the present invention is utilized to support the thrust load applied to the power rollers constituting the toroidal type continuously variable transmission.
[0002]
[Prior art]
The use of a toroidal continuously variable transmission as schematically shown in FIGS. 4 to 5 has been studied as a transmission for automobiles or various industrial machines. This toroidal-type continuously variable transmission supports an input side disk 2 concentrically with the input shaft 1 as disclosed in, for example, Japanese Utility Model Publication No. 62-71465, and an output side disk at the end of the output shaft 3. 4 is fixed. The inner surface of the casing containing the toroidal-type continuously variable transmission, or the support bracket provided in the casing, is centered on the pivot shafts 5 and 5 that are twisted with respect to the input shaft 1 and the output shaft 3. Swing trunnions 6 and 6 are provided.
[0003]
Each trunnion 6, 6 is provided with the pivots 5, 5 on the outer side surfaces of both ends. Further, by supporting the base ends of the displacement shafts 7 and 7 at the center of the trunnions 6 and 6, and by swinging the trunnions 6 and 6 around the pivot shafts 5 and 5, 7 tilt angle can be adjusted freely. Power rollers 8 and 8 are rotatably supported around the displacement shafts 7 and 7 supported by the trunnions 6 and 6, respectively. The power rollers 8 and 8 are sandwiched between the input side and output side disks 2 and 4.
[0004]
Inner side surfaces 2a and 4a of the input side and output side discs 2 and 4 facing each other have a substantially arcuate concave surface with the cross-sectional shape being substantially centered on the pivot 5. And the peripheral surfaces 8a and 8a of each power roller 8 and 8 formed in the spherical convex surface are made to contact | abut to the said inner surface 2a and 4a.
[0005]
A loading cam type pressing device 9 is provided between the input shaft 1 and the input side disc 2, and the pressing device 9 elastically presses the input side disc 2 toward the output side disc 4. Yes. The pressing device 9 includes a cam plate 10 that rotates together with the input shaft 1 and a plurality of (for example, four) rollers 12 and 12 held by a cage 11. A cam surface 13 that is a concavo-convex surface in the circumferential direction is formed on one side surface (the left side surface in FIGS. 4 to 5) of the cam plate 10, and the outer surface of the input side disk 2 (in FIGS. 4 to 5). A similar cam surface 14 is also formed on the right side surface). The plurality of rollers 12 and 12 are arranged radially with respect to the center of the input shaft 1.
[0006]
When the toroidal-type continuously variable transmission configured as described above is used, when the cam plate 10 rotates with the rotation of the input shaft 1, the plurality of rollers 12, 12 are moved by the cam surface 13 to the input side disk 2. It is pressed by the cam surface 14 formed on the outer surface. As a result, the input side disk 2 is pressed against the plurality of power rollers 8, 8, and at the same time, based on the engagement between the pair of cam surfaces 13, 14 and the plurality of rollers 12, 12, the input disk 2 is pressed. The side disk 2 rotates. Then, the rotation of the input side disk 2 is transmitted to the output side disk 4 through the plurality of power rollers 8, 8, and the output shaft 3 fixed to the output side disk 4 rotates.
[0007]
When the rotational speed of the input shaft 1 and the output shaft 3 is changed, and when the deceleration is first performed between the input shaft 1 and the output shaft 3, the trunnions 6 and 6 are swung around the pivot shafts 5 and 5. As shown in FIG. 4, the peripheral surfaces 8a and 8a of the power rollers 8 and 8 are respectively formed on a portion near the center of the inner surface 2a of the input side disk 2 and a portion near the outer periphery of the inner surface 4a of the output side disk 4. The displacement shafts 7 and 7 are inclined so as to contact each other.
[0008]
On the contrary, when the speed is increased, the peripheral surfaces 8a and 8a of the power rollers 8 and 8 are located near the outer periphery of the inner surface 2a of the input side disk 2 and the inner side of the output side disk 4 as shown in FIG. The displacement shafts 7 and 7 are inclined so as to abut against the center portion of the side surface 4a. If the inclination angles of the displacement shafts 7 and 7 are set intermediate between those shown in FIGS. 4 and 5, an intermediate speed ratio can be obtained between the input shaft 1 and the output shaft 3.
[0009]
4 to 5 show only the basic structure of the toroidal-type continuously variable transmission, but a more specific structure as an automobile transmission or the like is also disclosed in, for example, Japanese Utility Model Application No. 61-87523 (Japanese Utility Model Application No. 62-62). As described in the microfilm of No. 1995557), various types are conventionally known.
[0010]
By the way, when the toroidal type continuously variable transmission as described above is operated, the power rollers 8 and 8 rotate at high speed while receiving a thrust load from the input side disk 2 and the output side disk 4. Therefore, a thrust ball bearing 15 is provided between the power rollers 8 and 8 and the trunnions 6 and 6 as shown in FIG.
[0011]
The thrust ball bearing 15 is configured to hold the power roller 8 having a function as an inner ring which is a second race ring, a plurality of balls 16 and 16, and the plurality of balls 16 and 16 so as to roll freely. The cage 20 includes an outer ring 17 which is the first race ring and has the same central axis α as that of the power roller 8. The power roller 8, balls 16, 16 and outer ring 17 are made of bearing steel, bearing steel such as carburized steel, or ceramic, respectively. Further, the inner ring raceway 18 as the second raceway is opposed to the one side surface (upper surface in FIG. 6) of the power roller 8 and the inner ring raceway 18 is opposed to the inner ring raceway 18 on the one side surface (lower surface in FIG. 6) of the outer ring 17. An outer ring raceway 19 that is a first raceway is formed in each part. Each of the tracks 18 and 19 has an arc shape in cross section and an annular shape as a whole. The rolling surfaces of the balls 16, 16 are in rolling contact with the inner ring raceway 18 and the outer ring raceway 19.
[0012]
The cage 20 has a main body 21 made of a metal or a synthetic resin in a ring shape. Circular pockets 22 and 22 are formed at circumferentially equally spaced positions in the diameter direction intermediate portion of the main body 21, and the balls 16 and 16 can be rolled one by one in the pockets 22 and 22, respectively. keeping. Further, the outer ring 17 is abutted against the inner side surface of each trunnion 6 via a spacer 23 also formed in an annular shape. During operation of the toroidal-type continuously variable transmission, such a thrust ball bearing 15 rotates at high speed while supporting a thrust load applied to each of the power rollers 8 and 8. Reference numeral 24 denotes an oil supply hole for supplying lubricating oil to the thrust ball bearing 15.
[0013]
Incidentally, the thrust ball bearing 15 incorporated in the toroidal type continuously variable transmission as described above is required to have the following functions (1) and (2).
(1) In order to reduce the loss of power transmission between the input side disk 2 and the output side disk 4 (to improve transmission efficiency), the rotational torque must be small.
(2) Extend the life of the rolling surfaces of the balls 16, 16 and the inner ring raceway 18 and the outer ring raceway 19 in order to ensure sufficient durability.
[0014]
In the case of a thrust ball bearing, in order to satisfy the condition (1), the curvature radii of the cross-sectional shapes of the inner ring raceway 18 and the outer ring raceway 19 are increased, and the ball rolling surfaces, the inner ring raceway 18 and the outer ring raceway are increased. It is necessary to reduce the contact width with the ball 19 and reduce the rolling resistance of the balls 16 and 16. On the other hand, in order to satisfy the condition (2), the radius of curvature of the cross-sectional shape of the inner ring raceway 18 and the outer ring raceway 19 (larger than the radius of the balls 16, 16) is reduced to reduce the rolling surface. It is necessary to widen the contact width between the inner ring raceway 18 and the outer ring raceway 19 and lower the contact surface pressure between the rolling surface and the inner ring raceway 18 and the outer ring raceway 19.
[0015]
Thus, the thrust ball bearing 15 has conflicting requirements. For this reason, conventionally, the radius of curvature of the cross-sectional shapes of the inner ring raceway 18 and the outer ring raceway 19 is regulated to such a degree that the transmission efficiency can be ensured to the extent that it can be practically satisfied while ensuring the durability that is practically satisfactory. It was. More specifically, for example, as shown in FIG. 7, the curvature radius r ₁₈ of the cross-sectional shape of the inner ring raceway 18 formed on one axial surface of the power roller 8 and the outer ring raceway 19 formed on one axial side surface of the outer ring 17. An appropriate single curved surface (a curved surface whose curvature does not change on the way) equal to each other is used as the curvature radius r ₁₉ of the cross-sectional shape.
[0016]
[Problems to be solved by the invention]
However, in the case of a thrust ball bearing that is actually incorporated in a toroidal-type continuously variable transmission and supports the power roller 8, the inner ring raceway 18 and the outer ring raceway 19 are not necessarily sufficient if they are formed as a single curved surface (design). It was confirmed by experiment that there was a possibility that durability could not be obtained (as valued), and it was found that the main cause of this was due to the radial load applied to the power roller 8.
[0017]
That is, in the case of a so-called half-toroidal continuously variable transmission in which the cross-sectional shape of the inner side surfaces 2a, 4a of both the input side and output side disks 2, 4 is a quarter arc shape, During operation, the power roller 8 is subjected to a complex force (load) in addition to a thrust load and a radial load. Such a radial load may be caused by the traction force applied to the contact portion between the disks 2, 4 and the power roller 8, the trunnion 6 supporting the power roller 8 may be inclined as the gear ratio is changed, It is generated by the unbalanced load based on the assembly accuracy of the member or its own weight. In addition, the direction in which such an unbalanced load associated with the radial load is generated and the magnitude of the uneven load vary depending on the gear ratio, the rotational speed, and the like.
[0018]
The radial load based on such an unbalanced load is much smaller than the thrust load (1/10 or less), but the relative displacement of the power roller 8 constituting the thrust ball bearing 15 and the outer ring 17 in the diametrical direction. I will let you. In other words, the conventional thrust ball bearings for half-toroidal continuously variable transmissions were designed on the premise of supporting pure thrust loads (not including radial loads), so only received relatively small radial loads. Thus, the power roller 8 and the outer ring 17 are relatively displaced so as not to be ignored. When the power roller 8 rotates while supporting a large thrust load while the power roller 8 and the outer ring 17 are relatively displaced in this way, the balls 16 and 16 are complicated movements different from the original movements of the thrust ball bearings. do. In this case, not only rolling friction but also sliding friction is added to the friction state between the rolling surfaces of the balls 16 and 16 and the inner ring raceway 18 and the outer ring raceway 19.
[0019]
As a result, a part of the inner ring raceway 18 and the outer ring raceway 19, that is, a portion where the rolling surfaces of the balls 16 and 16 are in contact with each other in a state of receiving a radial load (displacement in the diametrical direction from the center in the width direction of each raceway And the like, and the durability of the thrust ball bearing 15 is impaired. In particular, the outer ring 17 is formed thinner than the power roller 8 in order to reduce the size and weight of the half- toroidal continuously variable transmission, and sufficient rigidity cannot be ensured. Become.
[0020]
For the life of the thrust ball bearing is prevented from being reduced on the basis of such reasons described above, the radius (D _16/2) of the ball 16, 16 by reducing the above-described radius of curvature r _18, r ₁₉ It can be considered to approach. When such a decrease the respective radii of curvature r _18, r _19, the contact area between the rolling surface and the respective track 18, 19 of the balls 16, 16 becomes wider, the contact surface pressure is reduced. At the same time, when the power roller 8 receives a radial load, the power roller 8 and the outer ring 17 are prevented from being displaced relative to each other in the diameter direction (the amount of displacement is reduced), and the bearing life is extended (durability is increased). Can be improved).
[0021]
However, when simply having a small radius of curvature r ₁₉ of the cross-sectional shape of radius of curvature r ₁₈ and the outer ring raceway 19 of the cross-sectional shape of the inner ring raceway 18, the rolling resistance of these two trajectories 18 and 19 and balls 16, 16 is increased As a result, the rotational torque of the thrust ball bearing increases. As a result, the force required for the rotation of the power roller 8 is increased, which causes a decrease in the performance of the half-toroidal continuously variable transmission incorporating a thrust ball bearing . The thrust ball bearing for a half toroidal type continuously variable transmission of the present invention has been invented in view of such circumstances.
[0022]
[Means for solving the problems]
The thrust ball bearing for the half toroidal type continuously variable transmission of the present invention is configured to rotatably support the power roller sandwiched between the inner side surface of the input side disk and the inner side surface of the output side disc on the inner side surface of the trunnion. It is provided between the power roller and the trunnion, and is used in a state where a radial load smaller than the thrust load acts in addition to the thrust load applied to the power roller.
[0023]
The thrust ball bearing for a half toroidal type continuously variable transmission according to the present invention used in such a state has a thickness dimension in the axial direction that is abutted against the inner surface of the trunnion via a spacer, and is the same as that of the power roller. An outer ring smaller than a thickness dimension in the axial direction, an outer ring raceway having an arcuate cross-sectional shape formed on the axial inner side surface of the outer ring, and the power roller disposed concentrically with the outer ring The inner ring raceway, which is formed in a portion facing the outer ring raceway on the outer surface in the axial direction, has an arcuate cross section and a ring shape as a whole, and the respective rolling surfaces abut against the outer ring raceway and the inner ring raceway. A plurality of balls. The radius of curvature of the cross-sectional shape of at least the outer ring raceway between the outer ring raceway and the inner ring raceway is made smaller on both sides in the width direction than the central portion in the width direction of the raceway in a range equal to or larger than the radius of each ball .
[0024]
[Action]
In the case of the thrust ball bearing for a half-toroidal continuously variable transmission according to the present invention configured as described above, durability can be improved while suppressing an increase in rotational torque.
[0025]
That is, when the radial load is not received (or the radial load is small enough to be ignored) and no relative displacement in the diametrical direction occurs between the outer ring and the power roller , the rolling surfaces of the balls are The outer ring raceway and the inner ring raceway are in contact with the center in the width direction. Since the radius of curvature of the cross-sectional shape at the center in the width direction of each track is relatively large, the contact width between the rolling surface and each track is narrow, the ball rolling resistance is reduced, and it is for half-toroidal continuously variable transmissions. The rotational torque of the thrust ball bearing is reduced.
[0026]
In addition, when a radial load is applied and the outer ring and the power roller are relatively displaced in the diametrical direction, the rolling surfaces of a plurality of balls come into contact with each of the tracks at a portion close to one side in the width direction of the track. At least for the outer ring raceway, since the radius of curvature of the cross-sectional shape of this portion is small, the contact width between the rolling surface and the outer ring raceway is widened, and the contact surface pressure between the rolling surface and the outer ring raceway is reduced. . As a result, even when a radial load is applied, the stress applied to the outer ring raceway does not become excessive, and the durability of the thrust ball bearing for a half toroidal type continuously variable transmission including the outer ring raceway can be improved.
[0027]
【Example】
1 and 2 show a first embodiment of the present invention corresponding to claims 1 to 3 . The thrust ball bearing for the half toroidal type continuously variable transmission according to the present embodiment is characterized by the cross sections of the inner ring raceway 18a and the outer ring raceway 19a in order to extend the life of the power roller 8A and the outer ring 17a while suppressing an increase in rotational torque. The other features and functions are the same as the conventional thrust ball bearings for half-toroidal continuously variable transmissions , such as those incorporated in the above-described toroidal continuously variable transmissions. It is. Therefore, the description which overlaps is abbreviate | omitted and it demonstrates centering on the characteristic part of this invention.
[0028]
Each of the outer ring raceway 19a and the inner ring raceway 18a is not a single curved surface, but is configured by smoothly continuing a plurality of curved surfaces having different curvature radii. In other words, the cross-sectional shapes of both the tracks 19a and 18a are such that the radii of curvature R _19a and R _18a at the central portion in the width direction are large and the radii of curvature r _19a and r _18a at both sides in the width direction are small (R _19a > r _{19a 18a} > _r18a ).
[0029]
That is, of the radii of curvature R _19a , r _19a , R _18a , r _18a , the radii of curvature R _19a , R _{18a at the} center in the width direction of the tracks _19a , _18a are the thrusts for the conventional half-toroidal continuously variable transmission. The radius of curvature r _19a , r _18a of both side portions in the width direction of the cross-sectional shape of each of the raceways 19a, 18a is the same as that of the ball bearing or larger than that value. It is closer to one half (radius) of the outer diameter D ₁₆ of the ball 16 than _19a and R _18a .
[0030]
The cross-sectional shape of the outer ring raceway 19a and the cross-sectional shape of the inner ring raceway 18a may be the same (the radius of curvature of the corresponding part is the same), but may be different. When making it different, it is preferable to make the curvature radius of the cross-sectional shape of the outer ring raceway 19a smaller than the curvature radius of the cross-sectional shape of the inner ring raceway 18a. This is because the outer ring 17a has a thickness smaller than that of the power roller 8A, and the outer ring 17a cannot always have sufficient rigidity, and the life of the outer ring raceway 19a is shorter than the life of the inner ring raceway 18a. This is because there is a tendency.
[0031]
It is appropriate that the relationship between these dimensions is regulated as follows, for example.
R _19a -r _19a = (0.01-0.2) D ₁₆
R _18a -r _18a = (0.01 to 0.2) D ₁₆
[0032]
In the case of the thrust ball bearing for a half-toroidal continuously variable transmission according to the present invention configured as described above, durability can be improved while suppressing an increase in rotational torque.
[0033]
That is, when the radial load is not received (or the radial load is small enough to be ignored) and no relative displacement in the diametrical direction occurs between the power roller 8A and the outer ring 17a, the rolling surfaces of the balls 16, 16 As shown in FIG. 1, the outer ring raceway 19a and the inner ring raceway 18a are in contact with the center in the width direction. As described above, the curvature radii R _19a and R _18a of the cross-sectional shape at the center in the width direction of the tracks _19a and _18a are relatively large, so the contact width l between the rolling surface and the tracks 19a and 18a is narrow. .
[0034]
Accordingly, the rolling resistance of the balls 16 and 16 is reduced, and the rotational torque of the thrust ball bearing 15 is reduced. As a result, the transmission efficiency of the toroidal continuously variable transmission incorporating this thrust ball bearing 15 is sufficiently high. At this time, the maximum value P _max of the contact surface pressure between the rolling surface and each of the tracks 19a, 18a increases, but the contact state between these rolling surfaces and each of the tracks 19a, 18a is a state close to a pure rolling contact. Thus, there is almost no sliding friction. Therefore, even if the maximum value P _max is increased, the durability of the rolling surfaces and the tracks 19a and 18a is not lowered to a practical level.
[0035]
When a radial load is applied and the power roller 8A and the outer ring 17a are relatively displaced in the diametrical direction, the rolling surfaces of the plurality of balls 16, 16 are brought into contact with the tracks 19a, 18a as shown in FIG. These abutments are brought into contact with each of the tracks 19a and 18a at a portion close to one side in the width direction. Since the curvature radii r _19a and r _18a of the cross-sectional shape of this portion are small, the contact width L between the rolling surface and both the tracks 19a and 18a is widened, and the contact between the rolling surface and each track 19a and 18a is increased. maximum value _P'max of surface pressure is low (<P _max). As a result, even when a radial load is applied, the stress applied to the rolling surface and each of the tracks 19a, 18a does not become excessive, and the half toroidal type continuously variable transmission including these rolling surfaces and the tracks 19a, 18a. The durability of thrust ball bearings for machines can be improved.
[0036]
That is, when the power roller 8A and the outer ring 17a are relatively displaced in the diametrical direction as described above, not only rolling friction but also sliding friction acts on the contact portion between the rolling surface and both the tracks 19a and 18a. However, in the case of the thrust ball bearing for a half toroidal type continuously variable transmission according to the present invention, the amount of elastic deformation of the outer ring raceway 19a and the inner ring raceway 18a is reduced by the amount that the maximum value of the contact surface pressure is reduced. As a result, stress strain repeatedly applied to the outer ring raceway 19a and the inner ring raceway 18a with the use of the thrust ball bearing for the half toroidal type continuously variable transmission is reduced, and the power roller 8A including the outer ring raceway 19a and the inner ring raceway 18a The life of the outer ring 17a can be extended.
[0037]
Further, since the curvature radii of the cross-sectional shapes of the outer ring raceway 19a and the inner ring raceway 18a are smaller on both sides in the width direction, the balls 16 and 16 are less likely to be displaced in the radial direction with respect to the respective raceways 19a and 18a. As a result, it is difficult to apply an uneven load due to the displacement of the balls 16 and 16 to the outer ring raceway 19a and the inner ring raceway 18a, and the life of the power roller 8A and the outer ring 17 can be extended.
[0038]
That is, when the power roller 8A and the outer ring 17a are relatively displaced in the radial direction, an uneven load having a magnitude corresponding to the amount of displacement is caused by the rolling surfaces of the balls 16, 16, the inner ring track 18a and the outer ring track. It becomes easy to join a contact part with 19a. When the thrust ball bearing half toroidal type continuously variable transmission of the present invention for this, for suppressing small the amount of displacement, to reduce the above unbalanced load, thrust ball for half toroidal type continuously variable transmission The life of the bearing can be extended.
[0039]
Next, FIG. 3 shows a second embodiment of the present invention corresponding to claim 1 only . In the case of the present embodiment, only the outer ring raceway 19a is configured by smoothly continuing curved surfaces having different curvatures instead of a single curved surface. That is, the cross-sectional shape of the outer ring raceway 19a is a compound curved surface in which the curvature radii _{r19a at} both side portions in the width direction are smaller than the curvature radius _{R19a at the} center portion in the width direction. On the other hand, the inner ring raceway 18 formed on the power roller 8A has a single curved surface having a relatively large radius of curvature R ₁₈ (R ₁₈ ≈R _19a ).
[0040]
In the case of the present embodiment, the durability of the outer ring 17a can be improved by devising the cross-sectional shape of the outer ring raceway 19a of the outer ring 17a which has low rigidity and is susceptible to adverse effects on durability compared to the power roller 8 due to vibration. It is intended. In the case of this embodiment, the durability improvement effect is slightly inferior to that of the first embodiment described above, but it is sufficiently durable when compared with the conventional thrust ball bearing for a half-toroidal continuously variable transmission. To improve performance. In addition, since processing of the inner ring raceway 18 is facilitated, a thrust ball bearing for a half-toroidal continuously variable transmission that exhibits practically sufficient performance can be obtained without excessively increasing production costs.
[0041]
In the case of each of the above-described embodiments, the both sides in the width direction of each of the tracks 19a and 18a are formed as a single curved surface having the curvature radii r _19a and r _18a. It can also be set as the compound curved surface which the circular arc which has. In this case, it is preferable that the radius of curvature becomes smaller toward the edge in the width direction. The cross-sectional shape of the tracks 19a and 18a may be an arc shape in which at least one of the center portion in the width direction and both sides in the width direction is formed of a series of several arcs. Further, at least one of the outer ring raceway 19a and the inner ring raceway 18a may have an arc shape in which the cross-sectional shape is a series of several arcs.
[0042]
【The invention's effect】
Since the thrust ball bearing for a half toroidal type continuously variable transmission according to the present invention is configured and operates as described above, an increase in rotational torque can be prevented, and durability and reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a half sectional view showing a first embodiment of the present invention in a state where only a thrust load is received.
FIG. 2 is a cross-sectional view similar to FIG. 1, showing a state where a radial load is applied to the power roller.
FIG. 3 is a view similar to FIG. 1, showing a second embodiment of the present invention.
FIG. 4 is a side view showing the basic configuration of a half- toroidal continuously variable transmission incorporating a thrust ball bearing in the state of maximum deceleration.
FIG. 5 is a side view showing the state of the maximum speed increase.
FIG. 6 is a cross-sectional view of a thrust ball bearing and a lubricating device portion thereof.
FIG. 7 is a sectional view showing only a thrust ball bearing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input shaft 2 Input side disk 2a Inner side surface 3 Output shaft 4 Output side disk 4a Inner side surface 5 Pivot 6 Trunnion 7 Displacement shaft 8, 8A Power roller 8a Circumferential surface 9 Pressing device 10 Cam plate 11 Cage 12 Roller 13, 14 Cam Surface 15 Thrust ball bearing 16 Ball 17, 17a Outer ring 18, 18a Inner ring raceway 19, 19a Outer ring raceway 20 Cage 21 Main body 22 Pocket 23 Spacer 24 Oil supply hole

Claims (3)

In order to rotatably support the power roller sandwiched between the inner surface of the input side disk and the inner side surface of the output side disk on the inner surface of the trunnion, this power roller is provided between the power roller and the trunnion. A thrust ball bearing for a half toroidal type continuously variable transmission that is used in a state in which a radial load smaller than the thrust load is applied in addition to the thrust load applied to the inner surface of the trunnion via a spacer. The applied outer ring has a smaller axial dimension than the axial dimension of the power roller and the axially inner side surface of the outer ring. The outer ring raceway and the cross-sectional shape formed in the portion facing the outer raceway on the axially outer side surface of the power roller arranged concentrically with the outer race have an arc shape. A circular ring-shaped inner ring raceway and a plurality of balls whose respective rolling surfaces are in contact with the outer ring raceway and the inner ring raceway, and at least the curvature of the cross-sectional shape of the outer ring raceway between the outer ring raceway and the inner ring raceway. A thrust ball bearing for a half-toroidal continuously variable transmission, the radius of which is smaller than the radius of each ball and smaller on both sides in the width direction than the center in the width direction of the track. 2. The thrust ball bearing for a half toroidal continuously variable transmission according to claim 1, wherein the curvature radii of the cross-sectional shapes of the outer ring raceway and the inner ring raceway are made smaller on both sides in the width direction than in the center portion in the width direction of each raceway. The thrust ball bearing for a half-toroidal continuously variable transmission according to claim 2, wherein a radius of curvature of the cross-sectional shape of the outer ring raceway is smaller than a radius of curvature of the cross-sectional shape of the inner ring raceway.

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