needle bearing

Abstract

Axial end portions (16) in the column portions (14) of the cage (12) are arranged on the outer diameter side, axial central portions (17) in the column portions (14) are arranged on the inner diameter side, the axial end portions (16) and the axial central portions (17) have pocket wall surfaces (18) facing the pockets (15), an inner diameter side region in the pocket wall surface (18) provided in the axial end portion (16) and an outer diameter side region in the pocket wall surface (18) provided in the axial central portion (17) constitute a repeating region (Rb) which repeats in the radial position, the repeating region (Rb) includes a roller guide surface which guides the needle-shaped roller (11), and intersects with a pitch circle (PCD) of the needle-shaped roller (11).

Description

Technical Field

[0001] This invention relates to rolling bearings, and more particularly to cages that retain the rollers. Background Technology

[0002] As rolling bearings comprising needle rollers and cages, stamped outer ring needle roller bearings, such as those described in Patent Documents 1 and 2, are known. The cage of Patent Document 1 is also called a straight-shaped cage because it extends straight from one axial end of the column to the other and the radial dimension of the entire column is equal to the radial thickness of the pair of rings. The cage of Patent Document 2 is also called a V-shaped cage because it positions the axial central portion of the column closer to the inner diameter than the axial end portions.

[0003] When the plate thickness is large, straight-shaped cages tend to exhibit significant flash and slump, thus limiting the plate thickness. Furthermore, to prevent the needle rollers from detaching from the cage, the cage's outer diameter is smaller than the needle roller's pitch circle (PCD). Consequently, the needle rollers are guided along the outer diameter side of the cage's column portion, contacting the corner of the column portion. Not only does this prevent oil film formation at the corners, but the corners also hinder oil film formation on the roller rolling surface. Additionally, the increased stress generated by the needle rollers pressing against the cage results in poor cage strength.

[0004] Next, through Figure 7 The longitudinal sectional view and front view show a conventional V-shaped cage. The V-shaped cage 112 is constructed from a thin sheet, which simultaneously increases the overall radial thickness of the cage, giving it an advantage over straight-shaped cages. The V-shaped cage 112 has a pair of axially separated rings 113, 113 and a plurality of pillars 114 connecting these rings 113 to each other. The steps between the axial end portions 116 and the axial central portion 117 of the pillars 114 are formed by roll forming. The pitch circle PCD of the needle roller 111 intersects with the axial end portions 116 corresponding to the radially outer section. The axial central portion 117 corresponding to the radially inner section is positioned closer to the inner diameter than the pitch circle PCD, preventing the needle roller 111 from falling radially inward from the pocket 115. According to the V-shaped cage, the needle roller is guided by the surface of the cage. As an advantage, the oil permeability is better than that of the straight-shaped cage mentioned above, and the stress generated on the cage due to the roller pressing the cage is less than that of the straight-shaped cage.

[0005] The stamped outer ring needle roller bearings of Patent Documents 1 and 2 are mainly used as rolling supports for rotating components in the drive system of engine vehicles.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 4310089

[0009] Patent Document 2: Japanese Patent No. 5668515 Summary of the Invention

[0010] Summary of the invention

[0011] The problem that the invention aims to solve

[0012] With the recent requirements for fuel-saving quantification leading to a shift from gasoline-powered engine vehicles to electric and hybrid vehicles, vehicle drive is being replaced by electric motor drive. Consequently, bearings in the rotating parts of the drive system are being used at faster speeds than previously possible.

[0013] Specifically, the needle roller 111 increases the force on the V-shaped cage 112 compared to the previous configuration. On the other hand, the needle roller 111 does not contact the axial central portion 117, which forms the inner diameter section, but is guided only by the axial end portions 116, which form the outer diameter section. Therefore, the roller guide surfaces that contact the needle roller 111 with the column portion 114 of the V-shaped cage 112 are limited to the axial end portions 116. This raises the following concerns.

[0014] First, there is a concern about the strength of the cage. The contact between the needle roller 111 and the column portion 114 of the V-shaped cage 112 is limited to the axial end portions 116, thus increasing the principal stress at the pocket corner R and deteriorating the durability of the V-shaped cage 112. (Refer to...) Figure 1 The pocket corner R is typically defined by the junction of the column portion 14 and the ring portion 13, and is cut into an arc shape. Because it is cut into an arc shape, the principal stress previously generated at the pocket corner R is mitigated. However, for the reasons mentioned above, the principal stress generated at the pocket corner R has become a new problem.

[0015] Secondly, there is a concern about wear. When the bearing is used at a higher speed, the product of the contact pressure and the sliding velocity (PV value) generated by the needle rollers 111 pressing against the column portion 114 of the V-shaped cage 112 increases. Furthermore, the contact length Lc between the needle rollers 111 and the V-shaped cage 112 is limited to the outer diameter section, thus increasing the contact pressure calculated by the pressing force F / contact length Lc. Therefore, there is a concern about premature wear of the column portion 114.

[0016] Third, there is a concern about the decrease in the load capacity of the needle roller bearing. To cope with the increased principal stress mentioned above, the width Ln of the ring 113 needs to be increased. When the width Ln of the ring 113 is obtained in a larger way, the axial dimension of the remaining pocket of the bearing, which is a limited circumferential dimension, decreases, and consequently the roller length of the needle roller 111 decreases, thus reducing the load capacity of the needle roller bearing, which is therefore disadvantageous.

[0017] The object of this invention is to provide a technology that can be advantageously used in high-speed rotating environments that have not been used until now.

[0018] Solution for solving the problem

[0019] For this purpose, the needle roller bearing of the present invention comprises: a cage having a pair of ring portions and a plurality of column portions each having both ends respectively coupled to the pair of ring portions, and pockets being formed between adjacent column portions in the circumferential direction; and needle rollers being held in the pockets. Furthermore, the axially extending end portions of the column portions are disposed on the outer diameter side, and the axially extending central portion of the column portions is disposed on the inner diameter side. The axially extending end portions and the axially extending central portion have pocket wall surfaces facing the pockets. The inner diameter side region of the pocket wall surface provided in the axially extending end portions and the outer diameter side region of the pocket wall surface provided in the axially extending central portion constitute repeating regions in a radial position. The repeating regions include roller guide surfaces for guiding the needle rollers.

[0020] According to the present invention described above, the roller guide surface is increased in length from one end of the column to the other. This reduces the principal stress generated at the pocket corner R, thereby improving the durability of the V-shaped cage. Furthermore, the contact surface pressure is also reduced compared to the past, thus suppressing the increase of the PV value even under high-speed rotation of the needle roller bearing and eliminating premature wear of the column. Moreover, since the principal stress at the pocket corner R can be reduced, it is not necessary to significantly increase the width of the ring. Therefore, by maintaining the same roller length as before, the load capacity of the needle roller bearing can be ensured. It should be noted that the roller guide surface refers to the surface in the pocket wall that contacts the rolling surface of the needle roller.

[0021] Because the needle rollers can make slight relative movement along the radial direction of the cage, the roller guide surface has a width dimension in the radial direction of the cage. The roller guide surface may coincide with the repeating region or may be smaller than the repeating region. In other words, the cage is allowed a slight eccentric movement from the pitch circle when all the needle rollers are in the neutral position. As one aspect of the invention, the repeating region of the pocket wall intersects the pitch circle of the needle rollers. According to the above aspect, the needle rollers can be guided in the tangential direction of the pitch circle, thus reducing contact surface pressure. As another aspect, the repeating region of the pocket wall may be offset towards the outer diameter side or towards the inner diameter side of the needle rollers' pitch circle.

[0022] The needle roller bearing of the present invention can be used with various outer rings. As a preferred aspect of the invention, the needle roller bearing further comprises a stamped outer ring forming the outer raceway surface for the rolling of the needle rollers. The stamped outer ring is not welded into a cylindrical shape, but rather formed into a cylindrical shape through deep drawing. As another aspect of the invention, the needle roller bearing further comprises a solid outer ring forming the outer raceway surface for the rolling of the needle rollers. The solid outer ring is formed by cutting. As yet another aspect of the invention, the needle roller bearing can also be a roller with a cage.

[0023] In another aspect of the invention, the cage includes a flange portion projecting from the outer axial edge of the ring towards the inner diameter side. According to the above aspect, the cage strength is increased and durability is improved. Alternatively, the axial dimension of the ring portion can be reduced, while the axial dimension of the pocket and the roller length of the needle roller can be increased, thereby increasing the load capacity.

[0024] In one aspect of the invention, the cage is guided by rollers guided by needle rollers. In another aspect of the invention, the cage is guided by an outer ring guided by an outer raceway surface.

[0025] The radial height difference between the axial end portions and the axial center portion of the column is less than 1.0 times the radial wall thickness of the axial center portion. Therefore, a repeating region where the axial end portions and the axial center portion overlap radially in the column can be provided. As one aspect of the invention, the radial height difference between the axial end portions and the axial center portion of the column is within the range of 0.2 times to 0.8 times the radial wall thickness of the axial center portion. Thus, the upper limit of the aforementioned repeating region can be set to 80%, and the lower limit can be set to 20%.

[0026] Invention Effects

[0027] Thus, according to the present invention, compared with conventional needle roller bearings, the present invention can reduce the principal stress generated at the cage pocket corner R even under high-speed operation, thereby improving the cage durability. Furthermore, the PV value is reduced, and wear is lessened. Moreover, the load capacity of the needle roller bearing can be increased. Attached Figure Description

[0028] Figure 1 This is a front view of the cage as an embodiment of the present invention.

[0029] Figure 2 This is a longitudinal sectional view showing the cage and needle rollers of this embodiment.

[0030] Figure 3 This is a cross-sectional view showing the cage and needle rollers of this embodiment.

[0031] Figure 4 This is a longitudinal sectional view showing a stamped outer ring needle roller bearing having this embodiment.

[0032] Figure 5 This is a longitudinal sectional view showing a solid outer ring needle roller bearing having this embodiment.

[0033] Figure 6 This is a longitudinal sectional view showing the cage and needle rollers as a variation of this embodiment.

[0034] Figure 7 These are longitudinal sectional views and front views of the conventional cage and needle rollers. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 This is a front view of the cage according to one embodiment of the present invention, showing the state as viewed from the outer diameter side. Figure 2 This is a longitudinal sectional view showing the cage and needle rollers of this embodiment, with the section plane obtained by cutting the cage through a plane containing the axis of the cage being enlarged. Figure 3 This is a transverse sectional view showing the cage and needle rollers as described in this embodiment. The cage is cut through by a plane perpendicular to its axis, and the sections above and below the axis are enlarged for this view. It should be noted that, to avoid cluttering the drawings, in… Figure 2 From now on, the top or bottom pockets and pillars on the paper will be indicated, and the rest will be omitted from the illustration.

[0036] The needle roller bearing of this embodiment includes needle rollers (hereinafter simply referred to as rollers 11) and a cage 12. The roller length Lr of the roller 11 is within the range of 3 times or more and 10 times or less than the roller diameter φr (3φr≤Lr<10φr). The cage 12 has a pair of ring portions 13, 13 and a plurality of column portions 14 at both ends respectively engaged with the pair of ring portions 13, 13. The pair of ring portions 13, 13 extends circumferentially along the cage 12 and is arranged with a gap in the axial direction. The column portions 14 extend axially along the cage 12 and are arranged at equal intervals in the circumferential direction of the ring portions 13, thus dividing pockets 15 between adjacent column portions 14, 14 in the circumferential direction. The roller 11 is held in each pocket 15.

[0037] like Figure 1 As shown, the column portion 14 includes axially spaced end portions 16, 16 and axially spaced central portion 17. (As...) Figure 2 As shown, the two axial end portions 16, 16 are positioned on the outer diameter side when viewed from the axis O of the cage 12, while the axial central portion 17 is positioned on the inner diameter side close to the axis O. Therefore, the column portion 14 becomes a so-called V-shape. Thus, the cage 12 is also called a V-shaped cage.

[0038] Here, if the manufacturing method of the cage 12 is described, first, a strip steel plate is prepared. Next, the strip steel plate is roll-formed into a V-shaped cross-section. Next, pocket holes 15 are formed in the strip steel plate by blanking. Next, the strip steel plate is cut into a specified length. Next, the strip steel plate is rounded into a cylindrical shape and the ends are welded to each other. Next, grinding is performed.

[0039] In the present embodiment, the axially opposite end portions 16, 16 and the axially central portion 17 are not completely offset in the radial direction of the cage 12, and the radial positions partially overlap. In such an overlapping region Rb, it contacts the rolling surface of the roller 11. Figure 2 In, the overlapping region Rb is indicated by the dotted hatching. The inner diameter edge of the overlapping region Rb becomes the inner diameter surface 16d of the axially opposite end portions 16. The outer diameter edge of the overlapping region Rb becomes the outer diameter surface 17c of the axially central portion 17. That is, the overlapping region Rb of the present embodiment is a roller guide surface.

[0040] In the present embodiment, in order to obtain the overlapping region Rb, the height difference between the outer diameter section and the inner diameter section of the column portion 14, that is, the radial height difference Rd between the outer diameter surface 16c of the axially opposite end portions 16 and the outer diameter surface 17c of the axially central portion 17 is smaller than the plate thickness Tp of the axially central portion 17 (Rd < Tp). More preferably, the radial height difference Rd is within the range of 0.2 times or more and 0.8 times or less of the plate thickness Tp (0.2Tp ≤ Rd ≤ 0.8Tp). Thereby, it is possible to obtain the thinning of the plate thickness Tp, which is the first advantage of the V-shaped cage, and the increase in the radial thickness dimension of the cage 12. In addition, as the second advantage of the V-shaped cage, since the roller 11 is guided by the planar overlapping region Rb, lubricating oil is supplied when the roller rolling surface contacts the overlapping region Rb that becomes the roller guide surface, and the oil permeability of the needle roller bearing is improved. Moreover, the pitch circle PCD overlaps with the overlapping region Rb, so the contact surface pressure decreases when the roller rolling surface contacts the overlapping region Rb that becomes the roller guide surface. It should be noted that when the height difference is small (Rd < 0.2Tp), the overlapping rate exceeds 80%, and it is difficult to obtain the advantages of the V-shaped cage. On the contrary, when the height difference is large (0.8Tp < Rd), the overlapping region Rb decreases (the overlapping rate is less than 20%), and the pitch circle PCD may deviate from the overlapping region. The plate thickness Tp is the plate thickness of the ring portion 13, or the plate thickness of the axially opposite end portions 16, or the plate thickness of the axially central portion 17. These plate thicknesses are substantially equal.

[0041] In the present embodiment, the radial height difference Rd = 0.2Tp, and the overlapping rate of the overlapping region Rb is 80% of the plate thickness Tp.

[0042] Furthermore, in this embodiment, the inner diameter side region of the pocket wall 18 belonging to the axial end portions 16 and the outer diameter side region of the pocket wall 18 belonging to the axial central portion 17 include the repeating region Rb, which serves as the roller guide surface.

[0043] Reference Figure 3 In the pocket walls 18, the circumferential spacing of the parallel column portions 14 is greatest at the outer diameter edges of the axial end portions 16, and the spacing of the axial central portions 17 is smallest at the inner diameter edges. This pocket clearance Gp is ​​less than 97% of the roller diameter φr. Thus, the roller 11 is held in the pocket 15, preventing it from falling off towards the inner diameter side due to impacts during operation.

[0044] As a side note, the pocket clearance Gp is ​​preferably 90% to 97% of the roller diameter φr. When the pocket clearance Gp is ​​less than 90% of the roller diameter φr, the pitch circle PCD may detach from the repeating region Rb towards the outer diameter side. When it exceeds 97%, the roller may detach from the cage due to impacts during operation, etc.

[0045] Reference Figure 4 The cage 12 is fitted onto the shell outer ring 21. The shell outer ring 21 is formed into a cylindrical shape by bending a flat circular plate through deep drawing or other processes. It has a cylindrical portion 22 and a pair of flange portions 23 and 24. The flange portions 23 and 24 are inwardly projecting flanges formed at both axial ends of the cylindrical portion 22, and the inner diameter of the flange portions 23 and 24 is smaller than the outer diameter of the cage 12. The cage 12 is positioned between the flange portions 23 and 24. The flange portions 23 and 24 abut against the annular portion 13 of the cage 12 in the axial direction, restricting the axial movement of the cage 12 between the flange portions 23 and 24. Thus, the cage 12 is inseparably fitted into the shell outer ring 21. It should be noted that the wall thickness of the flange portion 24 is thinner than the wall thickness of the flange portion 23.

[0046] The cylindrical portion 22 surrounds the outer periphery of the cage 12, forming the outer raceway surface 22w for the roller 11 to roll. Furthermore, the roller 11 is prevented from falling off from the pocket 15 to the outer diameter side by stamping the outer ring 21.

[0047] Will Figure 4 The embodiment shown is called a stamped outer ring needle roller bearing. A shaft (not shown) passes through the center hole of the cage 12. The outer circumferential surface of the shaft forms the inner raceway surface for the rollers 11 to roll.

[0048] Figure 3In the diagram, the cage 12 is shown tilted upwards towards the paper surface (U) when viewed from the pitch circle (PCD). The uppermost roller 11 falls downwards towards the paper surface (D), and is held between its circumferential sides by its axially oriented central portions 17, 17, separated by pockets 15. The cage 12 is roller-guided and does not contact the outer or inner raceway surfaces. Alternatively, although not shown, the cage 12 may be outer-ring-guided and not contact the inner raceway surface. Alternatively, although not shown, the cage 12 may be inner-ring-guided or shaft-guided and not contact the outer raceway surface.

[0049] like Figure 3 As shown, at the most biased locations (top and bottom) of the cage 12, the pitch circle PCD intersects the repeating region Rb. Furthermore, although not shown, even at locations of less bias in the cage 12, the pitch circle PCD intersects the repeating region Rb. Even in the neutral position of the cage 12, the pitch circle PCD intersects the repeating region Rb.

[0050] Figure 3 In the diagram, the rotation direction T and the revolution direction B of roller 11 are indicated by arrows. The rolling surface of each roller 11 is in contact with at least the repeating region Rb on the side of the revolution direction B.

[0051] for Figure 2 The needle roller bearing shown in this embodiment and Figure 7 A comparative experiment was conducted on the needle roller bearing with a conventional V-cage. The comparative experiment was based on FEM analysis using the finite element method. The radial height difference Rd = 0.4Tp (60% repeatability) of the V-cage of this embodiment is different from that of the conventional V-cage, which has a repeatability of 0%. All conditions except the shape of the cage are the same. The pitch circle PCD of the rollers is 18 mm, and the load is 100 N.

[0052] The results of the comparative experiment show that in the V-shaped cage of this embodiment, the maximum principal stress generated at the pocket corner R is 253.76 [MPa]. In contrast, in the conventional V-shaped cage, the maximum principal stress generated at the pocket corner R is 375.25 [MPa]. That is, it can be seen that if the principal stress generated at the pocket corner R of the conventional cage is set to 1, then the maximum principal stress generated at the pocket corner R of the cage 12 of this embodiment is 1. Figure 1 The principal stress generated is 0.68. It can be seen that the V-shaped cage 12 of this embodiment has greater strength than the conventional V-shaped cage.

[0053] Therefore, while keeping the axial dimension of the cage 12 the same as before, the axial width of the ring 13 can be reduced, and the axial length of the column 14, pocket 15 and roller 11 can be increased at the same time, thereby increasing the load capacity of the needle roller bearing.

[0054] Furthermore, according to the retainer 12 of this embodiment, such as Figure 2 As shown, the length of the repeating region Rb, which serves as the roller guide surface, extends across approximately the entire column 14, thus being longer than... Figure 7 The contact length 2Lc shown in the previous diagram is larger. Therefore, the contact surface pressure of the roller guide surface is reduced compared to the previous method, the PV value decreases, and thus the wear resistance is improved compared to the previous method.

[0055] Thus, the cage of this embodiment is superior in strength, wear resistance and load capacity compared with the conventional V-shaped cage.

[0056] Next, another embodiment of the present invention will be described. Figure 5 This is a longitudinal sectional view illustrating another embodiment of the present invention. Regarding this other embodiment, structures identical to those in the foregoing embodiment are labeled with the same reference numerals and their descriptions are omitted; the different structures are described below. This other embodiment is a solid outer ring needle roller bearing, incorporating the aforementioned... Figure 4 The stamped outer ring 21 shown is replaced with a solid outer ring 31.

[0057] The solid outer ring 31 has a cylindrical portion 32 and flange portions 33 protruding from both ends of the cylindrical portion toward the inner diameter side. The solid outer ring 31 is formed by cutting a metal blank, and its wall thickness is thicker than that of the aforementioned stamped outer ring 21.

[0058] The outer diameter of the ring portion 13, which corresponds to the outer diameter of the cage 12, is smaller than the inner diameter of the flange portion 33. They are assembled such that the axial positions of the pair of ring portions 13 overlap with the axial positions of the pair of flange portions 33. The inner circumferential surface of the cylindrical portion 32 forms the outer raceway surface 32w, on which the roller 11 rolls. Figure 5 In the embodiment shown, the pitch circle PCD of the roller 11 is located on the outer diameter side of the cage 12, corresponding to the repeating region (see reference). Figure 2 The repeating regions Rb) do not intersect.

[0059] Figure 5 The other embodiment shown also excels in strength, wear resistance, and load capacity compared to the conventional V-shaped cage.

[0060] Next, another embodiment of the present invention will be described. Figure 6 This is a longitudinal sectional view illustrating yet another embodiment of the present invention. Regarding this yet another embodiment, structures identical to those in the foregoing embodiments are labeled with the same reference numerals and their descriptions are omitted; the different structures are described below. In this yet another embodiment, a roller with a cage is inserted into a hole in a housing (not shown). The inner circumferential surface of the hole in the housing forms the outer raceway surface for the roller 11 to roll.

[0061] Flange portions 19 are formed at both axial ends of the cage 12. The flange portion 19 engages with the outer axial edge of the ring portion 13 and protrudes inward.

[0062] Figure 6 The alternative embodiment shown also demonstrates superior strength, wear resistance, and load capacity compared to conventional V-shaped cages. Furthermore, Figure 6 The cage 12 shown has a flange 19, which strengthens the ring 13 and increases the strength of the pocket corner R. Therefore, the roller length of the roller 11 can be increased by lengthening the column 14, or the roller diameter of the roller 11 can be increased by widening the circumferential spacing between the columns 14, 14, which helps to increase the load capacity of the needle roller bearing.

[0063] The embodiments of the present invention have been described above with reference to the accompanying drawings; however, the present invention is not limited to the structures of the illustrated embodiments. Various modifications and variations can be applied to the illustrated embodiments within the same or equivalent scope as the present invention. For example, a portion of the structure can be extracted from one of the above embodiments, and another portion of the structure can be extracted from another of the above embodiments, and these extracted structures can be combined.

[0064] Symbol explanation:

[0065] 11 Roller, 12 Cage, 13 Ring, 14 Column, 15 Pocket, 16 Axial end portions, 17 Axial central portion, 18 Pocket wall, 21 Stamped outer ring, 31 Solid outer ring.

Claims

1. A needle roller bearing, wherein, The needle roller bearing has the following features: A retainer having a pair of ring portions and a plurality of posts at both ends respectively engaged with the pair of ring portions, and pockets being formed between adjacent posts in the circumferential direction; and The needle roller, which remains in the pocket, The two axial ends of the column are disposed on the outer diameter side, and the central axial portion of the column is disposed on the inner diameter side. The two axial ends and the central axial portion have pocket wall surfaces facing the pocket. The inner diameter side region of the pocket wall surface located at both ends of the axial direction and the outer diameter side region of the pocket wall surface located at the central part of the axial direction constitute repeating regions that are repeated in the radial direction. The repeating region includes a roller guide surface that guides the needle rollers. The roller guide surface extends continuously from one end of the column to the other end. The radial height difference between the two axial ends and the central axial portion is within the range of more than 0.2 times and less than 0.8 times the radial wall thickness of the central axial portion.

2. The needle roller bearing according to claim 1, wherein, The repeating region intersects with the pitch circle of the needle roller.

3. The needle roller bearing according to claim 1 or 2, wherein, The needle roller bearing also includes a stamped outer ring that forms an outer raceway surface for the rolling of the needle rollers.

4. The needle roller bearing according to claim 1 or 2, wherein, The needle roller bearing also has a solid outer ring that forms the outer raceway surface for the rolling of the needle rollers.

5. The needle roller bearing according to claim 1 or 2, wherein, The ring portion includes a flange portion that protrudes from the two ends of the column portion toward the inner diameter side.

6. The needle roller bearing according to claim 1 or 2, wherein, The cage is guided by rollers that are guided by needle rollers.

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