JPH07217661A - Thrust ball bearing - Google Patents

Abstract

PURPOSE:To prevent damage to an inner ring raceway track, an outer ring raceway track and the rolling contact surface of a ball while suppressing an increase in rotational torque. CONSTITUTION:The cross-sectional form of raceway tracks 18a, 19a are formed into such composite curved surface that the radii of curvature R18a, R19a at the center part in the width direction are large and that the radii of curvature r18a, r19a on both sides in the width direction are small. At the time of supporting pure thrust load, the rolling contact surface of a ball 16 comes in contact with the center part with the large radius of curvature, so that small rotational torque is sufficient. When radial load is applied, the rolling contact surface comes in contact with the part with the small radius of curvature. As a result, the surface pressure of the contact part is lowered to prevent the damage of the contact part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The thrust ball bearing according to the present invention is used to support a thrust load applied to a power roller which constitutes a toroidal type continuously variable transmission, for example.

[0002]

2. Description of the Related Art The use of a toroidal type continuously variable transmission as schematically shown in FIGS. 4 to 5 has been studied as a transmission for automobiles or a transmission for various industrial machines. This toroidal type continuously variable transmission supports an input side disk 2 concentrically with an input shaft 1 and an output side disk at an end of an output shaft 3 as disclosed in Japanese Utility Model Laid-Open No. 62-71465. 4 is fixed. An inner surface of a casing accommodating the toroidal type continuously variable transmission, or a support bracket provided in the casing, has pivots 5 and 5 in a twisted position with respect to the input shaft 1 and the output shaft 3 as a center. Swing trunnions 6, 6 are provided.

The trunnions 6, 6 are provided with the pivots 5, 5 on the outer surfaces of both ends. Further, the base ends of the displacement shafts 7, 7 are supported on the central portions of the trunnions 6, 6, and the trunnions 6, 6 are swung about the pivot shafts 5, 5, so that the displacement shafts 7, The inclination angle of 7 can be freely adjusted. Power rollers 8, 8 are rotatably supported around displacement shafts 7, 7 supported by the trunnions 6, 6, respectively. The power rollers 8, 8 are sandwiched between the input side and output side disks 2, 4.

The inner surfaces 2a, 4a of the input-side and output-side disks 2, 4 facing each other have arcuate concave surfaces whose cross sections are substantially centered on the pivot shaft 5, respectively. The peripheral surfaces 8a, 8a of the power rollers 8, 8 formed on the spherical convex surface are in contact with the inner side surfaces 2a, 4a.

A loading cam type pressing device 9 is provided between the input shaft 1 and the input side disk 2, and the pressing device 9 causes the input side disk 2 to face the output side disk 4 and elastically moves. Pressing. This pressing device 9
Is a cam plate 10 that rotates together with the input shaft 1, and a retainer 11.
A plurality of (for example, four) rollers 12 held by
It is composed of 12 and. On one side surface (left side surface of FIGS. 4 to 5) of the cam plate 10, there is formed a cam surface 13 which is an uneven surface extending in the circumferential direction, and on the outer side surface of the input side disk 2 (FIGS. 4 to 5). A similar cam surface 14 is also formed on the right side surface of the. And the plurality of rollers 12, 12
Are arranged radially with respect to the center of the input shaft 1.

When the toroidal type continuously variable transmission constructed as described above is used, when the cam plate 10 rotates as the input shaft 1 rotates, the cam surface 13 causes the plurality of rollers 12, 1 to rotate.
2 is a cam surface 14 formed on the outer surface of the input side disk 2.
Is pressed by. As a result, the input side disk 2 is pressed by the plurality of power rollers 8 and at the same time, the input side disk 2 is input based on the engagement between the pair of cam surfaces 13 and 14 and the plurality of rollers 12 and 12. The side disc 2 rotates.
Then, the rotation of the input side disk 2 is transmitted to the output side disk 4 via the plurality of power rollers 8 and the output shaft 3 fixed to the output side disk 4 rotates.

When the rotational speeds of the input shaft 1 and the output shaft 3 are changed, and when deceleration is first performed between the input shaft 1 and the output shaft 3, the trunnions 6, 6 centering on the pivot shafts 5, 5 are used.
As shown in FIG. 4, the peripheral surfaces 8a, 8a of the power rollers 8, 8 are moved toward the center of the inner side surface 2a of the input side disk 2 and the outer side of the inner side surface 4a of the output side disk 4. The displacement shafts 7, 7 are tilted so as to abut with and respectively.

On the other hand, when increasing the speed, the peripheral surfaces 8a, 8a of the power rollers 8, 8 are, as shown in FIG. 5, a portion near the outer periphery of the inner side surface 2a of the input side disk 2 and the output side disk. The displacement shafts 7, 7 are tilted so as to abut the center portion of the inner side surface 4a of the shaft 4. Each displacement axis 7,
If the inclination angle of 7 is set to an intermediate value between FIG. 4 and FIG. 5, an intermediate gear ratio can be obtained between the input shaft 1 and the output shaft 3.

FIGS. 4 to 5 show only the basic structure of the toroidal type continuously variable transmission, but a more specific structure such as a transmission for an automobile is also disclosed in, for example, Japanese Utility Model Application No. 61-87523.
As described in the microfilm of Japanese Utility Model Publication No. Sho 62-199557, various types are conventionally known.

By the way, during operation of the toroidal type continuously variable transmission as described above, the power rollers 8, 8 rotate at a high speed while receiving the thrust load from the input side disk 2 and the output side disk 4. Therefore, thrust ball bearings 15 are provided between the power rollers 8, 8 and the trunnions 6, 6 as shown in FIG.

The thrust ball bearing 15 has the power roller 8 having a function as an inner ring which is a second bearing ring, a plurality of balls 16 and 16, and a plurality of these balls 16 and 1.
It is composed of a cage 20 for rotatably holding 6 and an outer ring 17 which is a first bearing ring and has the same central axis α as the power roller 8. The power roller 8, balls 16, 16 and outer ring 17 are each made of bearing steel such as bearing steel or carburized steel, or ceramic. Further, an inner ring raceway 18, which is a second raceway, is provided on one surface (upper surface in FIG. 6) in the axial direction of the power roller 8 and the outer ring 1
An outer ring raceway 19, which is a first raceway, is formed at a portion of the shaft 7 on one side in the axial direction (the lower surface in FIG. 6) facing the inner ring raceway 18. Each of these trajectories 18, 19 has an arcuate cross section and is entirely annular. The rolling surfaces of the balls 16, 16 are in rolling contact with the inner ring raceway 18 and the outer ring raceway 19.

Further, the cage 20 has a main body 21 made of metal or synthetic resin in the shape of a circular ring. This subject 2
Circular pockets 22 and 22 are formed at equal intervals in the circumferential direction at the diametrical intermediate portion of 1, and these pockets 22 and 22 are formed.
22 holds the balls 16, 16 one by one so that they can roll. Further, the outer ring 17 is abutted against the inner side surface of each trunnion 6 via a spacer 23 also formed in a circular ring shape. During operation of the toroidal type continuously variable transmission, such thrust ball bearing 15 rotates at high speed while bearing the thrust load applied to each of the power rollers 8, 8. Reference numeral 24 is an oil supply hole for supplying lubricating oil to the thrust ball bearing 15.

By the way, the thrust ball bearing 15 incorporated in the above-described toroidal type continuously variable transmission is required to have the following functions. The rotational torque should be small in order to reduce the loss of power transmission between the input side disk 2 and the output side disk 4 (improve the transmission efficiency). To ensure sufficient durability, the rolling surfaces of the balls 16 and 16 as well as the inner ring raceway 18 and the outer ring raceway 19 should have a long life.

In the case of a thrust ball bearing, in order to satisfy the above conditions, the radius of curvature of the cross section of the inner ring raceway 18 and the outer ring raceway 19 is increased so that the rolling surface of the ball and the inner ring raceway 1
8 and the outer ring raceway 19 to narrow the contact width, balls 16, 16
It is necessary to reduce the rolling resistance of. On the contrary,
In order to satisfy the above condition, the radius of curvature of the cross section of the inner ring raceway 18 and the outer ring raceway 19 (which is larger than the radius of the balls 16, 16) is made small so that the rolling surface and the inner ring raceway 18 and the outer ring raceway 19 are connected to each other. It is necessary to widen the contact width of the inner ring raceway and the inner raceway raceway 18 and the outer raceway raceway 19 to reduce the contact surface pressure.

As described above, the thrust ball bearing 15 has conflicting requirements. For this reason, conventionally, the radii of curvature of the inner ring raceway 18 and the outer ring raceway 19 are regulated so as to ensure practically satisfactory durability and also practically satisfactory transmission efficiency. More specifically, as shown in FIG. 7, for example, the radius of curvature r ₁₈ of the cross section of the inner ring raceway 18 formed on one side in the axial direction of the power roller 8 and the outer ring raceway 19 formed on one side in the axial direction of the outer ring 17 are described. The curvature radius r _{19 of the} cross section is set to an appropriate single curved surface (curved surface whose curvature does not change in the middle) which is equal to each other.

[0016]

However, in the case of a thrust ball bearing which is actually incorporated in a toroidal type continuously variable transmission to support the power roller 8, the inner ring raceway 18 and the outer ring raceway 19 have a single curved surface. In this case, it was confirmed by experiments that sufficient durability (according to the design value) may not always be obtained, and it was found that the main cause of this is the radial load applied to the power roller 8.

That is, a toroidal type continuously variable transmission, in particular, a so-called half toroidal type 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. In the case of, in operation, the power roller 8 is subjected to a complicated force (load) to which not only the thrust load but also the radial load is applied. Such a radial load is caused by the traction force between the disks 2 and 4 and the power roller 8, the trunnion 6 supporting the power roller 8 tilting due to a change in the gear ratio, or the assembling accuracy of each component. Or it is caused by an unbalanced load based on its own weight. In addition, the direction in which the unbalanced load associated with such a radial load is generated and the magnitude of the unbalanced load are varied depending on the gear ratio, the rotation speed, and the like.

The radial load based on such an unbalanced load is
Much smaller than thrust load (1/10 or less)
However, the power roller 8 forming the thrust ball bearing 15 and the outer ring 17 are relatively displaced in the diametrical direction. In other words, conventional thrust ball bearings were designed on the premise of bearing a pure thrust load (not including a radial load).
The power roller 8 and the outer ring 17 are relatively displaced so that they cannot be ignored. When the power roller 8 rotates while bearing a large thrust load while the power roller 8 and the outer ring 17 are relatively displaced in this manner, the balls 16, 16 make a complicated motion different from the original motion of the thrust ball bearing. do.
In this case, not only rolling friction but also sliding friction is added to the frictional state between the rolling surfaces of the balls 16 and 16 and the inner ring raceway 18 and the outer ring raceway 19.

As a result, a part of the inner ring raceway 18 and the outer ring raceway 19, that is, a state in which a radial load is applied, the balls 1
Damage such as flaking is likely to occur at the portion where the rolling surfaces of 6 and 16 come into contact (the portion that is diametrically displaced from the center in the width direction of each race), and the durability of the thrust ball bearing 15 is impaired. In particular, the outer ring 17 is formed to be thinner than the power roller 8 in order to reduce the size and weight of the toroidal type continuously variable transmission, and it is not always possible to secure sufficient rigidity, so that the durability tends to be insufficient. .

[0020] For the life of the thrust ball bearing is prevented from being reduced on the basis of such reasons described above, the radius of the balls 16, 16 to reduce the above-mentioned radius of curvature _{r 18, r 19 (D 16} /
It is possible to bring it closer to 2). In this way, each radius of curvature r
_{When 18} and r ₁₉ are reduced, the contact area between the rolling surfaces of the balls 16 and 16 and the raceways 18 and 19 is increased, and the contact surface pressure is reduced. At the same time, when the power roller 8 receives a radial load, relative displacement of the power roller 8 and the outer ring 17 in the diametrical direction is prevented (the displacement amount is reduced), and the bearing life is extended (durability is improved). Can be improved).

[0021] However, when simply having a small radius of curvature r ₁₉ of the cross section of radius of curvature r ₁₈ and the outer ring raceway 19 of the section of the inner ring raceway 18, the rolling resistance of these two trajectories 18 and 19 and balls 16, 16 increases Then, the rotational torque of the thrust ball bearing increases. As a result, the force required for the rotation of the power roller 8 increases, which causes the performance of various devices such as a toroidal type continuously variable transmission incorporating a thrust ball bearing to deteriorate, which is not preferable. The thrust ball bearing of the present invention was invented in view of such circumstances.

[0022]

The thrust ball bearing of the present invention is formed on the first bearing ring and one axial surface of the first bearing ring, similarly to the conventionally known thrust ball bearings. A first orbit having an arcuate cross section and an annular shape as a whole, a second orbital ring arranged concentrically with the first orbital ring, and the first orbital on one side in the axial direction of the second orbital ring A second orbit with a circular cross section formed in a portion facing the orbit and an annular shape as a whole, and a plurality of balls having their respective rolling surfaces in contact with the first and second orbits. I have it.

In particular, in the thrust ball bearing of the present invention, the radius of curvature of the cross section of at least one of the first raceway and the second raceway is set so that both sides in the widthwise direction of the raceway are centered in the widthwise central portion. I have made it small.

[0024]

In the thrust ball bearing of the present invention configured as described above, it is possible to improve durability while suppressing an increase in rotational torque.

That is, when the radial load is not received (or the radial load is small enough to be ignored) and the relative displacement in the diametrical direction does not occur between the first bearing ring and the second bearing ring. The rolling surfaces of the plurality of balls contact the widthwise central portions of the first and second tracks. Since the radius of curvature of the center of each raceway in the width direction is relatively large, the contact width between the rolling surface and each raceway is narrow, the rolling resistance of the balls is reduced, and the rotational torque of the thrust ball bearing is reduced.

Further, when a radial load is applied and the first bearing ring and the second bearing ring are displaced relative to each other in the diametrical direction, the rolling surfaces of a plurality of balls are on the respective raceways and on one side in the width direction of the raceways. Abut on the part that is closer. Since the radius of curvature of this portion is small, the contact width between the rolling surface and the raceway becomes wide, and the contact surface pressure between the rolling surface and the raceway becomes low. As a result,
Even when a radial load is applied, the stress applied to the track does not become excessive, and the durability of the thrust ball bearing including the track can be improved.

[0027]

1 and 2 show a first embodiment of the present invention. The thrust ball bearing of the present embodiment is characterized in that the inner ring raceway 18a and the outer ring raceway 19 are designed to extend the life of the power roller 8A and the outer ring 17a while suppressing an increase in the rotational torque.
The point is that the cross-sectional shape of a is devised, and other configurations and operations are the same as those of the conventionally known thrust ball bearings, such as those incorporated in the above-described toroidal type continuously variable transmission. Therefore, overlapping description will be omitted and the description will focus on the characteristic part of the present invention.

Each of the outer raceway 19a, which is the first raceway, and the inner raceway 18a, which is the second raceway, is not a single curved surface, but is formed by smoothly connecting a plurality of curved surfaces having different radii of curvature. There is. That is, the above two orbits 19a, 1
The cross-sectional shape of 8a has a radius of curvature R _19a in the central portion in the width direction,
Larger R _18a , radius of curvature r _19a , r on both sides in the width direction
_18a is made small (R _19a > r _19a , R _18a > r _18a ).

That is, the radii of curvature R _19a , r _19a , R _18a ,
Of r _18a, each track 19a, the width-direction central portion the radius of curvature R _19a in 18a, R _18a are the same values as in the conventional thrust ball bearing or contrast is made larger than the value The radius of curvature r of the cross section of each of the tracks 19a, 18a.
_19a, r _18a is closer to one-half (radius) of the outer diameter D ₁₆ of the R _19a, balls from R _18a 16.

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 corresponding portions have the same radius of curvature), but they may be different. When different, the radius of curvature of the outer ring raceway 19a is set to the inner ring raceway 18a.
It is preferably smaller than the radius of curvature of a. this is,
Since the thickness of the outer ring 17a is smaller than that of the power roller 8A, the rigidity of the outer ring 17a cannot always be sufficiently secured, and the life of the outer ring raceway 19a tends to be shorter than the life of the inner ring raceway 18a. Is.

Incidentally, it is appropriate to regulate the relationship between these respective dimensions as follows, for example. R _19a −r _19a = (0.01 to 0.2) D ₁₆ R _18a −r _18a = (0.01 to 0.2) D ₁₆

In the case of the thrust ball bearing of the present invention configured as described above, it is possible to improve durability while suppressing an increase in rotational torque.

That is, the power roller 8A receives no radial load (or the radial load is small enough to be ignored).
When the diametrical relative displacement does not occur between the outer ring 17a and the outer ring 17a, the rolling surfaces of the plurality of balls 16, 16 are, as shown in FIG. 1, central portions in the width direction of the outer ring raceway 19a and the inner ring raceway 18a. Abut. As described above, each track 19a, the radius of curvature R _19a in the widthwise central portion of 18a, since R _18a is relatively large, the rolling surface and the raceway 19a, the contact width between 18a l
Becomes narrower.

Therefore, 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 type 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 the raceways 19a and 18a increases, but the contact state between these rolling surfaces and the raceways 19a and 18a is close to a pure rolling contact. Therefore, sliding friction hardly occurs. Therefore, even if the maximum value P _max becomes large, the rolling surface and each track 1
The durability of 9a and 18a does not deteriorate so much as to be a practical problem.

When a radial load is applied and the power roller 8A and the outer ring 17a are relatively displaced in the diametrical direction,
As shown in FIG. 2, the rolling surfaces of the balls 16, 16 are
These orbits 19a and 18a are respectively added to these orbits 19a and 1a.
8a abuts on one side in the width direction. Since the radii of curvature r _19a and r _{18a in} this portion are small, the contact width L between the rolling surface and both raceways 19a and 18a becomes wide, and the contact surface pressure between the rolling surface and the raceways 19a and 18a becomes large. the maximum value _P'max is low (<P _max). As a result, even when a radial load is applied, the rolling surface and each track 19a,
The stress applied to 18a does not become excessive, and the durability of the thrust ball bearing including these rolling surfaces and raceways 19a, 18a can be improved.

That is, when the power roller 8A and the outer ring 17a are displaced relative to each other in the diametrical direction as described above, not only the rolling friction but also the sliding friction at the contact portion between the rolling surface and these raceways 19a and 18a. However, in the case of the thrust ball bearing of the present invention, the amount of elastic deformation of the outer ring raceway 19a and the inner ring raceway 18a decreases as the maximum value of the contact surface pressure decreases. As a result, the stress strain repeatedly applied to the outer ring raceway 19a and the inner ring raceway 18a due to the use of the thrust ball bearing is reduced, and the life of the power roller 8A and the outer ring 17a including the outer ring raceway 19a and the inner ring raceway 18a can be extended.

Further, since the radii of curvature of the cross sections of the outer ring raceway 19a and the inner ring raceway 18a are smaller on both sides in the width direction, the balls 16, 16 are less likely to be displaced in the radial direction with respect to these raceways 19a, 18a. As a result, the outer ring raceway 1
An eccentric load based on the displacement of the balls 16, 16 is less likely to be applied to the inner race 9a and the inner raceway 18a, so that the life of the power roller 8A and the outer race 17 can be extended.

That is, the power roller 8A and the outer ring 17a
When and are relatively displaced in the radial direction, an eccentric load having a magnitude corresponding to the displacement amount is easily applied to the abutting portion between the rolling surfaces of the balls 16 and 16 and the inner ring raceway 18a and the outer ring raceway 19a. Become. On the other hand, in the case of the thrust ball bearing of the present invention, since the displacement amount can be suppressed to a small amount, the unbalanced load can be reduced and the life of the thrust ball bearing can be extended.

Next, FIG. 3 shows a second embodiment of the present invention. In the case of the present embodiment, only the outer ring raceway 19a is configured by smoothly connecting 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 radius of curvature r _{19a at} both sides in the width direction is smaller than the radius of curvature R _{19a at the} center in the width direction. On the other hand, the inner ring raceway 18 formed on the power roller 8A
Is a single curved surface having a relatively large radius of curvature in the cross section (R ₁₈ ≈R _19a ).

In the case of this embodiment, the durability of the outer ring 17a is improved by devising the cross-sectional shape of the outer ring raceway 19a of the outer ring 17a, which has a low rigidity and is more susceptible to the durability than the power roller 8 due to vibration. It is intended to improve the sex. In the case of the present embodiment, the durability improvement effect is slightly inferior to the case of the first embodiment described above, but the durability can be sufficiently improved when compared with the conventional thrust ball bearing.
Moreover, since the inner ring raceway 18 can be easily processed, it is possible to obtain a thrust ball bearing exhibiting practically sufficient performance without increasing the manufacturing cost.

In the case of each of the above embodiments, each track 1
Curvature radii r _19a , r on both sides in the width direction of 9a, 18a
_Although a single curved surface having _18a is formed, both side portions thereof may be formed as a compound curved surface in which arcs having two or more kinds of radii of curvature are continuous. In this case, it is preferable that the radius of curvature becomes smaller toward the edge in the width direction. The cross sections of the tracks 19a and 18a may have an arc shape in which at least one of the widthwise central portion and both sides in the widthwise direction is a continuous arc. Also, the outer ring raceway 19a and the inner ring raceway 18a
At least one of them may have an arc shape whose cross section is a series of several arcs.

[0042]

Since the thrust ball bearing of the present invention is constructed and operates as described above, it is possible to prevent an increase in rotational torque and improve durability and reliability.

[Brief description of 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 applied.

FIG. 2 is a sectional view similar to FIG. 1, showing a state in which 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 a basic configuration of a toroidal type continuously variable transmission incorporating a thrust ball bearing in a state at maximum deceleration.

FIG. 5 is a side view showing the same state at maximum acceleration.

FIG. 6 is a sectional view of a thrust ball bearing and a lubrication device portion thereof.

FIG. 7 is a sectional view showing only a thrust ball bearing.

[Explanation 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 Axis 6 Trunnion 7 Displacement Axis 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 (1)

[Claims] 1. A first orbital ring, a first orbital ring which is formed on one side in the axial direction of the first orbital ring, has an arcuate cross section, and has an annular shape as a whole, and is concentric with the first orbital ring. And a second raceway having a circular ring-shaped cross section formed in a portion facing the first raceway on one side in the axial direction of the second raceway and a second raceway. , In a thrust ball bearing having a plurality of balls each rolling surface of which is in contact with both the first and second raceways, at least one of the first raceway and the second raceway A thrust ball bearing characterized in that the radius of curvature of the cross section of the raceway is made smaller on both sides in the width direction than in the center portion in the width direction of the raceway.