JP2012154384A - Thrust roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep down rotational resistance, by preventing the side surface in an axial direction of a retainer 3b, and a thrust raceway surface 25, from coming into contact with or coming close to each other in a large area.SOLUTION: The retainer 3b is constituted by assembling both first and second retainer elements 5d and 6d, and both first and second round rings 12b and 15b are mutually made tilted. Then, the thickness of the retainer 3b in the axial direction is made the greatest at the inner end in the radial direction. When the retainer 3b is displaced in the axial direction, the side surface in the axial direction of the retainer 3b and the thrust raceway surface 25 come into contact with or come close to each other only at the inner end in the axial direction. By narrowing down an area of an oil film covering over between both surfaces, the rotational resistance due to shearing resistance of an oil film is reduced.

Description

  The present invention relates to an improvement of a thrust roller bearing (including a thrust needle bearing) used in a state where it is assembled to a rotating portion of a transmission of an automobile in order to support a thrust load applied to the rotating portion. Specifically, an oil film is formed between the axially opposite side surfaces of a cage that holds a plurality of rollers (including needles) in a freely rolling manner, and a thrust raceway surface on which the rolling surfaces of these rollers roll. By suppressing this, increase in dynamic torque based on the presence of the oil film is suppressed.

  For example, a thrust roller bearing as described in Patent Document 1 is attached to a rotating portion of a transmission or the like so as to support a thrust load applied to a rotating shaft or the like. As shown in FIG. 7, the thrust roller bearing 1 includes a plurality of rollers 2 arranged in a radial direction, a cage 3 that holds the rollers 2, and a pair of races that clamp the rollers 2 from both sides. 4a and 4b. This cage 3 is formed by combining first and second cage elements 5 and 6 each of which is U-shaped in cross section and formed into a ring shape as a whole in a hollow annular shape. As shown in FIG. The same number of pockets 7 as the roller 2 are arranged radially.

  The first cage element 5 is formed by subjecting a metal plate such as a steel plate to plastic working such as press working, and the first inner diameter side cylindrical portion 9 is formed on both inner and outer peripheral edges of the first annular portion 8. And the first outer diameter side cylindrical portion 10 are formed concentrically with each other. And the rectangular 1st through-hole 11 with long each in the radial direction for comprising each said pocket 7 and 7 is provided in the circumferential direction several places of the 1st ring part 8 among these. The second cage element 6 is also made by subjecting a metal plate such as a steel plate to plastic working such as press working. The cylindrical portion 13 and the second outer diameter side cylindrical portion 14 are formed concentrically with each other. And the rectangular 2nd through-hole 15 which is long in the radial direction for comprising each said pocket 7 and 7 is provided in the circumferential direction several places of the 2nd ring part 12 among these. The first and second retainer elements 5 and 6 each having such a configuration are arranged in a state where the first through holes 11 and the second through holes 15 are aligned with each other in the axial direction. The second outer diameter side cylindrical portion 14 is internally fitted on the inner diameter side of the first outer diameter side cylindrical portion 10, and the second inner diameter side cylindrical portion 13 is positioned on the outer diameter side of the first inner diameter side cylindrical portion 9. Are combined with the external fitting. And separation | separation is prevented by bending the front-end edge of this 1st internal diameter side cylindrical part 9 to radial direction outward.

  Each of the races 4a and 4b is formed in an annular shape from a metal plate having sufficient hardness, such as bearing steel or case-hardened steel. The inner peripheral edge of one of the races 4a generally called an inner ring (left side in FIG. 7) and the outer peripheral edge of the other race 4b generally called an outer ring (right side in FIG. 7) are short cylindrical. Flange 16a, 16b is formed. And among these, the plurality of tip portions of the flange 16a arranged on the radially inner side are bent radially outward, and the plurality of tip portions of the flange 16b arranged on the radially outer side are bent radially inward, respectively. The locking portions 17a and 17b are used. Then, the engaging parts 17a and 17b and the inner peripheral edge or the outer peripheral edge of the cage 3 are engaged with each other, and the components of the thrust roller bearing 1 are coupled to each other without separation.

  In the thrust roller bearing 1 configured as described above, for example, as shown in FIG. 7, a flange 16 b formed on the outer peripheral edge of a race 4 b called an outer ring is formed on a holding portion 19 that is a circular recess formed in a casing 18. It is mounted on the rotating part where thrust load is generated while it is fitted inside. In this state, the right surface of the race 4b contacts the back surface 19a of the holding portion 19, and the left surface of the other race 4a contacts the end surface 20a of the mating member 20. As a result, the mating member 20 is rotatably supported with respect to the casing 18 and a thrust load acting between the members 20 and 18 is supported. In addition, the back surface 19a or the end surface 20a may be a track surface, and one or both of the races 4a and 4b may be omitted.

  Further, Patent Document 1 discloses a thrust roller bearing 1a having a structure as shown in FIG. 9 for the purpose of reducing dynamic torque and preventing abnormal wear of the cage. The cage 3a constituting the improved type thrust roller bearing 1a is also formed by combining the first and second cage elements 5a and 6a in a hollow annular shape, and the same number of pockets 7a as the rollers 2a are provided in the cage 3a. It is arranged in a radial pattern with respect to the center. Further, with respect to the radial direction of the cage 3a, both end surfaces 21, 21 of the rollers 2a in the axial direction are partially spherical convex surfaces having a center of curvature on the central axis of each roller 2a. 21 is protruded most in the axial direction at each central portion.

  In the case of the cage 3a constituting the improved type thrust roller bearing 1a, both first and second cage elements 5a and 6a formed on the first and second cage elements 5a and 6a to constitute the pockets 7a. The through holes 11a and 15a are formed in the radially outer portions of the first and second circular ring portions 8a and 12a, respectively. In particular, the second through hole 15a is open to the outer peripheral edge of the second annular portion 12a. And in the state which each roller 2a hold | maintained in each said pocket 7a displaced to the outermost side regarding the radial direction of the said holder | retainer 3a, the center part of the end surface 21 of the outer-diameter side among each said end surface 21 and 21, and the said The inner peripheral surface of the second outer diameter side cylindrical portion 14a of the second cage element 6a abuts on the abutting portion 22 indicated by a small broken-line circle in FIG. 9B. Since the sliding speed V of the center portion corresponding to the contact portion 22 is low, the PV value at the contact portion 22 portion is kept low, and the center portion of the end surface 21 on the outer diameter side and the second outer diameter side Wear of the contact portion with the inner peripheral surface of the cylindrical portion 14a is suppressed to a slight level.

  The conventional thrust roller bearings 1 and 1a incorporating the retainers 3 and 3a formed by combining the first and second retainer elements 5, 5a, 6, and 6a have the structure shown in FIG. Even in the structure shown in FIG. 4, the outer surfaces of the first and second circular ring portions 8, 8a, 12, 12a and the pair of thrust raceway surfaces 23a, 23b face each other over a wide area. Positioning of the cages 3 and 3a in the axial direction is achieved by so-called roller guides which are achieved by engaging the inner peripheral edges of the pockets 7 and 7a with the rolling surfaces of the rollers 2 and 2a, and the both circles. If the outer surfaces of the ring portions 8, 8a, 12, 12a and the thrust raceway surfaces 23a, 23b are always sufficiently separated from each other, no particular problem occurs.

  However, it may be difficult to always keep the above surfaces sufficiently separated depending on conditions such as the diameters of the rollers 2 and 2a. The reason for this is as follows. In order to achieve the axial position of the cages 3 and 3a by roller guidance, the inner diameter of the pockets 7 and 7a and the rolling surfaces of the rollers 2 and 2a are set to the maximum diameter of the rollers 2 and 2a. It is necessary to engage at some distance away from each other on opposite sides. Accordingly, the distance between the first and second annular portions 8, 8a, 12, 12a needs to be separated to some extent. On the other hand, the inner peripheral edges of the pockets 7 and 7a do not hinder the rotation of the rollers 2 and 2a, and the inner peripheral edges of the pockets 7 and 7a are on the rolling surfaces of the rollers 2 and 2a. In order to prevent the adhering lubricating oil from being scraped excessively, it is necessary to interpose a certain amount of gap between the inner peripheral edge and the rolling surface. Based on the existence of this gap, it is inevitable that the cages 3 and 3a are displaced in the axial direction with respect to the rollers 2 and 2a.

  For this reason, when the ratio of the axial displacement amount of the cages 3 and 3a to the diameter of the rollers 2 and 2a is increased due to the small diameter of the rollers 2 and 2a, It becomes difficult to set the axial position by roller guidance. Specifically, any one of the axial side surfaces of the cages 3 and 3a is in contact with or close to any thrust track surface, and the axial position of the cages 3 and 3a The raceway surface is controlled by the thrust raceway surface. And even when the both surfaces come into contact with each other, even when they are close to each other, when an oil film is formed between the opposing surfaces, the cages 3 and 3a rotate based on the shear resistance of the oil film. The resistance (dynamic torque) to doing becomes large. As a result, the resistance against the revolving motion of the rollers 2, 2a increases, and the rotational resistance (dynamic torque) of the thrust roller bearings 1, 1a increases. In particular, when the two surfaces are brought into contact or close to each other over a wide area, the shear resistance of the oil film existing between the two surfaces increases, and the degree to which the rotational resistance of the thrust roller bearings 1 and 1a increases becomes significant.

Japanese Patent Laying-Open No. 2005-164023

  In view of the circumstances as described above, the present invention can prevent the axial side surface of the cage and the thrust raceway surface from contacting or approaching each other over a wide area, and the rotation of the thrust roller bearing incorporating the cage. It was invented to realize a structure that can keep resistance low.

The thrust roller bearing of the present invention includes a cage and a plurality of rollers, similarly to the conventionally known thrust roller bearing.
In particular, in the thrust roller bearing of the present invention, a part of the radial direction of the first and second annular parts is projected in the axial direction with respect to the remaining part. The remaining portion and the pair of thrust raceway surfaces on which the rolling surfaces of the respective rollers are in rolling contact with each other are separated so as not to form an oil film between the surfaces facing each other in the axial direction.

  When implementing such a thrust roller bearing of the present invention, for example, as in the invention described in claim 2, the first and second annular portions are opposite to each other with respect to the central axis of each roller. The thickness dimension in the axial direction of the cage is made larger at one end in the radial direction than at the other end in the radial direction. Then, both the axial side surfaces of the cage and the thrust raceway surfaces are opposed to each other in the axial direction even when the cage is displaced in the axial direction with respect to the rollers except for one end in the radial direction. More than the extent that an oil film is not formed between the surfaces to be performed.

  In the case of carrying out the invention described in claim 2, preferably, as in the invention described in claim 3, each roller is a cylindrical roller, and the thickness dimension in the axial direction of the cage is set to an inner diameter. The diameter is gradually decreased from the side end toward the outer diameter side end. Then, both the axial side surfaces of the cage and the thrust raceway surfaces are opposed to each other in the axial direction even when the cage is displaced in the axial direction with respect to the rollers except for the inner diameter side end portions. The distance between the two surfaces is more than the oil film is not formed. Along with this, the width dimension in the circumferential direction of each pocket is gradually reduced from the outer diameter side end portion toward the inner diameter side end portion, and the rolling surface of each roller and the circumferential side edge of each pocket, Is substantially uniform with respect to the radial direction (except for a notch or the like formed in the radial intermediate portion in order to distribute the lubricating oil).

  Alternatively, as in the invention described in claim 4, each of the rollers is a cylindrical roller, and the thickness dimension in the axial direction of the cage is gradually reduced from the outer diameter side end to the inner diameter side end. Then, both the axial side surfaces of the cage and the thrust raceway surfaces are opposed to each other in the axial direction even when the cage is displaced in the axial direction with respect to each of the rollers except for the outer diameter side end portion. More than the extent that an oil film is not formed between the surfaces to be performed. At the same time, the width dimension in the circumferential direction of each pocket is gradually reduced from the inner diameter side end portion toward the outer diameter side end portion, and the rolling surface of each roller and the circumferential side edge of each pocket, Is substantially uniform in the radial direction.

  Further, when the thrust roller bearing of the present invention as described above is implemented, for example, as in the invention described in claim 5, the radial intermediate portions of the first and second annular portions are arranged on the cage. It is dented inward in the thickness direction with respect to the axial direction, and the thickness dimension with respect to the axial direction of the cage is made smaller at the radial intermediate portion than at both radial end portions. Further, both the axial side surfaces of the cage and the thrust raceway surfaces are excluded from both ends in the radial direction, and the cages are opposed to each other in the axial direction even when the cage is displaced in the axial direction with respect to the rollers. The distance between the two surfaces is more than the oil film is not formed.

  In the case of the thrust roller bearing of the present invention configured as described above, it is possible to prevent the axial side surface of the cage and the thrust raceway surface from coming into contact or approaching each other over a wide area. For this reason, even when an oil film is formed between these two surfaces, the area of this oil film can be suppressed, and the shear resistance based on this oil film can be kept low, and the rotational resistance of the thrust roller bearing incorporating the cage Can be kept low.

The fragmentary sectional view (A) which shows the 1st example of an embodiment of the invention, and the aa sectional view (B) of (A) shown in the state where a roller was removed. The fragmentary sectional view which shows the state combined with the race. Sectional drawing (A) which shows the 2nd example of embodiment of this invention, and bb sectional drawing (B) of (A) shown in the state which excluded the roller. The fragmentary sectional view which shows the state combined with the race. Sectional drawing (A) which shows the 3rd example of embodiment of this invention, and cc sectional drawing (B) of (A) shown in the state except a roller. The fragmentary sectional view which shows the state combined with the race. The fragmentary sectional view which shows the 1st example of a conventional structure. The partial side view which took out the holder | retainer and was seen from the axial direction. Partial sectional drawing (A) which shows the 2nd example of a conventional structure, and dd sectional drawing (B) of (A).

[First example of embodiment]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1 to 3. The feature of the present invention, including this example, is that when the shape of the cage constituting the thrust roller bearing is devised, the axial side surface of this cage and the race surface are in contact with or in close proximity to each other. However, the increase in rotational resistance of the cage is also suppressed. Since the structure and operation of the other parts are the same as those of the second example of the conventional structure shown in FIG. 9, the description of the equivalent parts will be omitted or simplified, and the following description will focus on the features of this example. To do.

  The cage 3b of this example is also formed by combining first and second cage elements 5b and 6b, which are formed in a ring shape as a whole, in a hollow annular shape. In particular, in the case of this example, the height (axial dimension) of the first and second inner diameter side cylindrical portions 9a and 13a formed on the inner peripheral edge portions of both the cage elements 5b and 6b is also set to the same value. It is made larger than the height of the first and second outer diameter side cylindrical portions 10a, 14b formed at the peripheral edge. Each of these cylindrical portions 9a, 13a, 10a, and 14b has a cylindrical shape having a constant diameter in the axial direction, and the second outer diameter side cylinder is formed on the inner diameter side of the first outer diameter side cylindrical portion 10a. The portion 14b is internally fitted, and the second inner diameter side cylindrical portion 13a is combined with the outer diameter side of the first inner diameter side cylindrical portion 9a. And the front-end | tip edge of said 1st internal diameter side cylindrical part 9a is bend | folded to radial direction outward, and the isolation | separation prevention of both said retainer elements 5b and 6b is aimed at.

  In a state where the cage elements 5b and 6b are combined to form the cage 3b, the distance between the first and second annular portions 8b and 12b constituting the cage elements 5b and 6b is equal to the inner diameter. It gradually decreases from the side toward the outer diameter side. That is, the thickness dimension in the axial direction of the cage 3b is larger at the inner diameter side end than at the outer diameter side end. In order to hold the roller 2a (cylindrical roller) whose diameter of the rolling surface does not change in such a cage 3b so as to be freely rollable (with a reduced skew), the both circular rings The shape of each of the first and second through holes 11b and 15b for forming the pocket 7b formed in the portions 8b and 12b is tapered such that the width in the circumferential direction increases in the radial direction. The shape is a vertically long isosceles trapezoid. By making the shape of each of the first and second through holes 11b and 15b in this way, the circumferential side edge of each pocket 7b and each of the respective pockets 7b regardless of the inclination of the two annular portions 8b and 12b. The distance between the roller 2a and the rolling surface is made substantially uniform in the radial direction {to such an extent that the posture of each roller 2a is stabilized (skew can be prevented)}. In addition, a notch for circulating lubricating oil is formed in the radial direction intermediate part of each of the through holes 11b and 15b, and the width dimension in the circumferential direction of each of the through holes 11b and 15b is determined in the radial direction intermediate part. , Can be larger than both ends.

  In the case of the thrust roller bearing 1b of this example, with the rollers 2a incorporated in the pockets 7b of the cage 3b as described above, the rolling surfaces of these rollers 2a are as shown in FIG. Then, the thrust raceway surface 25 which is the axial side surface of the thrust trace 24 is brought into rolling contact. The thrust raceway surfaces 25 are provided in a pair with the rollers 2a interposed therebetween. The distance between the thrust raceway surfaces 25 is determined by the axial dimension (thickness) of the inner diameter side end of the cage 3b. Is also big. Accordingly, the cage 3b is in a state of being rotatably arranged between the two thrust raceway surfaces 25.

  The axial position of the cage 3b is slightly displaced based on the presence of a pocket gap between both circumferential edges of the pockets 7b and the rolling surfaces of the rollers 2a. As a result of the displacement, the inner diameter side end portion of the axial side surface of the cage 3b comes into contact with or is in close proximity to any thrust track surface 25, and an oil film is formed between the two surfaces. There is a possibility that it is formed in a state of being stretched over. Even when the oil film is formed in this way, in the portion excluding the inner diameter side end portion, the both surfaces are sufficiently separated so as not to form an oil film that is stretched between the two surfaces. Therefore, even when an oil film is formed between the axial side surface of the cage 3b and the thrust raceway surface 25, the area of the oil film can be suppressed, and the shear resistance based on the oil film can be suppressed to a low level. The rotational resistance of the thrust roller bearing 1b can be kept low.

Particularly in the case of this example, even if the oil film is formed, the diameter of the oil film may be small. Therefore, the increase in the rotational resistance of the thrust roller bearing 1b based on this oil film can be suppressed sufficiently low for the following two reasons (1) and (2).
(1) The relative displacement speed between a pair of surfaces facing each other across the oil film can be kept low. The oil film shear resistance that contributes to the rotational resistance increases remarkably as the relative displacement speed increases. Accordingly, reducing the diameter of the oil film so that the oil film is not formed on the inner end portion in the radial direction of the cage 3b and keeping the relative displacement speed low can reduce the shear resistance, and thus the rotation resistance. Can greatly contribute to the reduction of
(2) Since the diameter of the portion where the shear resistance is generated can be reduced, the arm length of the moment based on the shear resistance can be shortened, and the increase in the rotational resistance based on the moment can be suppressed.

[Second Example of Embodiment]
3 to 4 show a second example of an embodiment of the present invention corresponding to claims 1, 2, and 4. FIG. In the case of this example, contrary to the case of the first example of the above-described embodiment, both first and second inner diameters formed on the inner peripheral edge of the first and second cage elements 5c and 6c. The heights of the side cylindrical portions 9b and 13b are made smaller than the heights of the first and second outer diameter side cylindrical portions 10b and 14c formed on the outer peripheral edge. Therefore, in a state where the both cage elements 5c and 6c are combined to form a cage 3c, the distance between the first and second both annular portions 8c and 12c constituting both the cage elements 5c and 6c is as follows. It gradually increases from the inner diameter side toward the outer diameter side. That is, the thickness dimension in the axial direction of the cage 3c is smaller at the inner diameter side end than at the outer diameter side end. Further, the shape of the first and second through holes 11c and 15c constituting the pocket 7c formed in the both annular portions 8c and 12c is a direction in which the width in the circumferential direction becomes smaller as it goes radially outward. The taper shape is inclined in the direction.

  In the case of the structure of this example as described above, when the cage 3c is displaced in the axial direction based on the presence of the pocket gap, the outer diameter side end of the side surface in the axial direction of the cage 3c and the race 24 The thrust raceway surface 25 abuts or approaches. In the case of such a structure of this example, when an oil film is formed between the axial side surface of the retainer 3c and the thrust raceway surface 25, the diameter of the oil film is equal to that of the first embodiment described above. It becomes larger than the case of the example. Therefore, the structure of this example is inferior in the rotational resistance reduction effect of the thrust roller bearing 1c as compared with the structure of the first example, but the rotational resistance is sufficiently reduced as compared with the conventional structure shown in FIG. it can.

[Third example of embodiment]
5 to 6 show a third example of the embodiment of the invention corresponding to claims 1 and 5. In the case of the structure of this example, the first and second circular ring portions 8d and 12d constituting the first and second cage elements 5d and 6d are arranged in the axial direction of the cage 3d. Recessed toward the inside in the thickness direction. And the thickness dimension regarding the axial direction of this cage | basket 3d is made smaller than the radial direction both ends by the radial direction intermediate part. Accordingly, in a state where the thrust roller bearing 1d is assembled, both the axial side surfaces of the cage 3d and the thrust raceway surface 25 of the race 24 are excluded from the both ends in the radial direction. Even in a state of being displaced in the axial direction, they are separated more than the extent that no oil film is formed between them.

  In the case of such a structure of this example, the axial side surface of the cage 3d and the thrust raceway surface 25 can contact or approach at two positions of the radially inner end portion and the outer end portion. Therefore, from the viewpoint of reducing the rotational resistance of the thrust roller bearing 1d, the first example of the embodiment described above is of course disadvantageous compared to the case of the second example of the embodiment described above. However, since both the circular ring portions 8d and 12d are parallel to each other except the radial intermediate portion, the shapes of the first and second through holes 11d and 15d for forming each pocket 7d are simplified. However, the posture of each roller 2a held in each pocket 7d can be stabilized.

  Since the present invention aims to reduce the rotational resistance (dynamic torque) of the thrust roller bearing, at least the end surface on the outer diameter side in the radial direction of the cage is a partially spherical convex surface as a roller used in the implementation. It is preferable to use one. However, the present invention can also be implemented by a thrust roller bearing incorporating a roller having a flat axial end surface as shown in FIG.

1, 1a, 1b, 1c, 1d Thrust roller bearing 2, 2a Roller 3, 3a, 3b, 3c, 3d Cage 4a, 4b Race 5, 5a, 5b, 5c, 5d First cage element 6, 6a, 6b , 6c, 6d Second cage element 7, 7a, 7b, 7c, 7d Pocket 8, 8a, 8b, 8c, 8d First annular portion 9, 9a, 9b First inner diameter side cylindrical portion 10, 10a, 10b First One outer diameter side cylindrical part 11, 11a, 11b, 11c, 11d First through hole 12, 12a, 12b, 12c, 12d Second annular part 13, 13a, 13b Second inner diameter side cylindrical part 14, 14a, 14b, 14c Second outer diameter side cylindrical portion 15, 15a, 15b, 15c, 15d Second through hole 16a, 16b Flange 17a, 17b Locking portion 18 Casing 19 Holding portion 19a Back surface 20 Mating member 20a End surface 21 End 22 abutting portion 23a, 23b thrust raceway surface 24 thrust race 25 thrust raceways

Claims (5)

  Each has a ring-shaped retainer in which a plurality of radially extending pockets are provided at a plurality of locations in the circumferential direction, and a plurality of rollers provided in a freely rollable manner in each of these pockets. The two cage elements are overlapped in the axial direction. Of these, the first cage element is formed by circumferentially arranging the first through holes that are long in the radial direction to form the pockets. A first annular portion provided at a plurality of locations in the direction, a first inner diameter side cylindrical portion formed at the inner peripheral edge of the first annular portion, and a first outer portion formed at the outer peripheral edge of the first annular portion. A radial cylindrical portion, and the second retainer element is configured to form each pocket with a second through hole that is long in the radial direction and the first through hole in the circumferential direction. A second annular portion provided at the same pitch, a second inner diameter side cylindrical portion formed on the inner peripheral edge of the second annular portion, And a second outer diameter side cylindrical portion formed on the outer peripheral edge of the second annular ring portion, and the first and second cage elements are the first through holes and the respective first holes. In a state where the two through holes are aligned with each other in the axial direction, the second outer diameter side cylindrical portion is fitted inside the first outer diameter side cylindrical portion, and the second outer diameter side cylindrical portion is externally fitted. In a thrust roller bearing in which the second inner diameter side cylindrical portion is fitted on the radial side, a part of the radial direction of the first and second circular ring portions is the same in the axial direction with respect to the remaining portion. By projecting, the remaining portion and the pair of thrust raceway surfaces on which the rolling surfaces of the respective rollers are in rolling contact with each other are separated more than an oil film is not formed between the surfaces facing each other in the axial direction. A thrust roller bearing characterized by   By inclining the first and second annular portions in opposite directions with respect to the central axis of each roller, the thickness dimension in the axial direction of the cage can be set at one radial end and the other radial end. Even when the cage is displaced in the axial direction with respect to each of the rollers, except for one end in the radial direction, both axial side surfaces of the cage and both thrust raceway surfaces are made larger than the portion. 2. The thrust roller bearing according to claim 1, wherein the thrust roller bearings are separated so as not to form an oil film between surfaces facing each other in the axial direction.   Each of the rollers is a cylindrical roller, and the thickness dimension in the axial direction of the cage is gradually decreased from the inner diameter side end portion toward the outer diameter side end portion, and both the axial side surfaces of the cage and the cage Except for the inner diameter side end portions, both thrust raceway surfaces exceed the extent that no oil film is formed between the surfaces facing each other in the axial direction even when the cage is displaced in the axial direction with respect to each roller. The width dimension in the circumferential direction of each pocket is gradually decreased from the outer diameter side end to the inner diameter side end, and the rolling surface of each roller and the circumference of each pocket The thrust roller bearing according to claim 2, wherein the distance from the direction side edge is substantially uniform in the radial direction.   Each of the rollers is a cylindrical roller, and the thickness dimension in the axial direction of the cage is gradually decreased from the outer diameter side end portion toward the inner diameter side end portion. Except for the outer diameter side end, both thrust raceway surfaces are above the extent that an oil film is not formed between the surfaces facing each other in the axial direction even when the cage is displaced in the axial direction with respect to each roller. And the width dimension in the circumferential direction of each pocket gradually decreases from the inner diameter side end portion toward the outer diameter side end portion, and the rolling surface of each roller and the circle of each pocket The thrust roller bearing according to claim 2, wherein the distance from the circumferential side edge is substantially uniform in the radial direction.   By denting the radial intermediate portions of the first and second circular ring portions inward in the thickness direction with respect to the axial direction of the cage, the thickness dimension with respect to the axial direction of the cage is set in the radial direction. The cage is displaced in the axial direction with respect to each of the rollers except that both the axial side surfaces of the cage and the thrust raceway surfaces of the cage are made smaller than both ends in the radial direction at the intermediate portion. 2. The thrust roller bearing according to claim 1, wherein the thrust roller bearings are spaced apart to an extent that an oil film is not formed between the surfaces facing each other in the axial direction even in a state where the two are opposed to each other.

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