JP2008095842A - Constant velocity joint boot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant velocity joint boot to be assembled while suppressing its deformation by improving the rigidity near its large diameter cylinder part. <P>SOLUTION: The constant velocity joint boot comprises the large diameter cylinder part 2, a small diameter cylinder part 3 arranged apart from the large diameter cylinder part 2 coaxially therewith and having a smaller diameter than the large diameter cylinder part 2, and an intermediate part 10 connecting the large diameter cylinder part 2 to the small diameter cylinder part 3. The intermediate part 10 consists of a flexible bellows portion 19 integrally connected to the small diameter cylinder part 3, and a rigid formation portion 11 integrally connected to the bellows portion 19 and the large diameter cylinder part 2. The rigid formation portion 11 has a diameter enlarged ranging from the bellows portion 19 toward the large diameter cylinder part 2. A plurality of steps 61 are formed stepwise on at least an outer peripheral face 101 of the rigid formation portion 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a constant velocity joint boot that covers a constant velocity joint used in a drive shaft of a vehicle.

  In a power transmission device such as a vehicle, driving force is transmitted from a transmission to driving wheels via a drive shaft including a shaft portion and a constant velocity joint. As shown in FIG. 10, the drive shaft has an inner member 8 made of a shaft, and joints 41 and 42 disposed on both sides of the inner member 8. One joint 41 is connected to a driving member such as a differential on the inboard side, and the other joint 42 is connected to a driven member such as a driving wheel on the outboard side.

  The joints 41 and 42 are, for example, of the ball type, and an inner member 8 in which a plurality of ball grooves 81 are formed at equal intervals in the circumferential direction, a ball 80 that rolls in the ball groove 81, and an inner member The outer member 7 accommodates the eight ball grooves 81 and the balls 80 in the cup portion 70. The joint 41 on the inboard side transmits rotational torque at a constant speed from the outer member 7 on the input side to the inner member 8 on the output side via the rollable ball 80. The constant velocity joint 42 on the outboard side transmits rotational torque at a constant velocity from the inner member 8 on the input side to the outer member 7 on the output side via a rollable ball 80. Both of the constant velocity joints 41 and 42 are covered with a bellows-structured boot 1 filled with grease, and are prevented from invading foreign substances from the outside, thereby maintaining a smooth rotation at a large angle.

  The constant velocity joint boot 1 includes a large-diameter cylindrical portion 2 held by the outer member 7 and a small-diameter cylindrical portion 3 having a smaller diameter than the large-diameter cylindrical portion 2 and held by the shaft portion 83 of the inner member 8. And a substantially frustoconical elastic bellows portion 19 that integrally connects the large-diameter cylindrical portion 2 and the small-diameter cylindrical portion 3. At the time of use, the bellows portion 19 is deformed according to a change in an angle (joint angle) formed by the outer member 7 and the inner member 8. For this reason, the boot 1 reliably seals the joints 41 and 42 by the deformation of the bellows portion 19 even when the joint angle increases.

  To assemble the drive shaft, first, the balls 80 are disposed in the ball grooves 81 at both ends of the inner member 8, and both ends thereof are inserted into the cup portion 70 of the outer member 7. Next, the small diameter cylindrical portion 3 of the boot 1 is fixed to the shaft portion 83 of the inner member 8 with a clamp 53. Further, the large-diameter cylindrical portion 2 of the boot 1 is fixed to the cup portion 70 of the outer member 7 with a clamp 52.

  When the drive shaft is assembled to the vehicle, as shown in FIG. 11, the vicinity of the center of the inner member 8 is gripped by the hand 85 and lifted. At both ends of the inner member 8, the outer member 7 is disposed via rotatable balls 80. For this reason, when the inner member 8 is lifted, the outer member 7 having a predetermined weight hangs downward from both ends of the inner member 8. At this time, the bellows portion 19 of the boot 1 may be deformed in the radial direction, and the boot 1 and the ball 80 inside the cup portion 70 of the outer member 7 may interfere with each other. Sometimes, as shown in FIG. 12, the ball 80 is detached from the outer member 7. In order to assemble the ball 80 into the outer member 7, the boot 1 is removed from the joints 41, 42, and the joints 41, 42 are disassembled, and then the inner member 8, the ball 80, and the outer member 7 are connected again. The joints 41 and 42 must be assembled to fix the boot 1 to the joints 41 and 42. Thus, when the ball 80 is detached from the outer member 7, it is necessary to disassemble and assemble the joints 41 and 42 again, which is troublesome.

The reason why the ball 80 is detached from the outer member 7 is considered to be that the portion close to the large-diameter cylindrical portion 2 of the bellows portion 19 of the boot 1 has a bellows shape, so that the rigidity is weak and the portion is easily deformed. As means for increasing the rigidity of the bellows portion 19 in the vicinity of the large-diameter cylindrical portion 2, conventionally, Patent Document 1 shows that a cylindrical rigidity forming portion is formed in the vicinity of the large-diameter cylindrical portion.
Japanese Utility Model Publication No. 1-69916

  However, in the technique of Patent Document 1, the rigid cylindrical portion has a cylindrical shape. There is a demand for further improving the rigidity by devising the shape of the rigid cylindrical portion to further increase the rigidity in the vicinity of the large-diameter cylindrical portion. This invention is made | formed in view of this situation, and makes it a subject to provide the boot for constant velocity joints which can raise the rigidity of large diameter cylinder part vicinity and can suppress the deformation | transformation at the time of an assembly | attachment.

Means and effects for solving the problems

  The constant velocity joint boot of the present invention includes a large-diameter cylindrical portion, a small-diameter cylindrical portion that is coaxially disposed apart from the large-diameter cylindrical portion, and has a smaller diameter than the large-diameter cylindrical portion, a large-diameter cylindrical portion, and a small-diameter cylindrical portion. A constant velocity joint boot comprising an intermediate portion, and an intermediate portion integrally connected to the bellows portion and the large-diameter cylindrical portion, and an elastic bellows portion integrally connected to the small-diameter cylindrical portion. The rigidity forming portion is expanded from the bellows portion toward the large-diameter cylindrical portion, and at least the outer peripheral surface of the rigidity forming portion has a plurality of steps in a stepped manner.

  According to the above configuration, the rigidity forming portion has a diameter that increases from the bellows portion toward the large-diameter cylindrical portion, and at least the outer peripheral surface of the rigidity forming portion has a plurality of stepped portions. A rigidity forming portion in which a plurality of step portions is formed in a staircase shape has higher rigidity than a cylindrical rigidity forming portion. For this reason, the rigidity in the vicinity of the large-diameter cylindrical portion can be increased. Therefore, even when the joint is lifted, the boot can be prevented from being deformed downward by the weight of the outer member, and the ball can be prevented from being detached from the outer member.

  As described above, according to the present invention, it is possible to provide a constant velocity joint boot that can increase the rigidity in the vicinity of the large-diameter cylindrical portion and suppress deformation during assembly.

  The rigidity forming portion in the vicinity of the large-diameter cylindrical portion in the constant velocity joint boot expands from the bellows portion toward the large-diameter cylindrical portion, and at least the outer peripheral surface of the rigid forming portion has a plurality of steps in a stepped manner. .

  The step part has a crest protruding in the radially outward direction and a trough recessed in the radially inward direction alternately, a side surface connecting the valley and the crest in the substantially axial direction, and a crest And an end face that connects the trough part in a substantially radial direction. The side surface of the stepped portion is preferably parallel to the axial direction of the stepped portion. In this case, the rigidity forming portion can exhibit excellent rigidity. Further, the side surface of the step portion may be inclined in a tapered shape with respect to the axial direction of the step portion. Also in this case, the rigidity that can withstand the weight of the outer member when lifting the joint can be exhibited. The end surface of the stepped portion is preferably parallel to the radial direction of the stepped portion. In this case, the rigidity forming portion can exhibit excellent rigidity. In addition, the end surface of the step portion may be inclined in a tapered shape with respect to the radial direction of the step portion. Also in this case, the rigidity that can withstand the weight of the outer member when lifting the joint can be exhibited.

  The step portion is formed on at least the outer peripheral surface of the rigidity forming portion, but the same step portion as the step portion of the outer peripheral surface may be formed on the inner peripheral surface of the rigidity forming portion.

  It is preferable that the inner peripheral surface of the rigid forming portion has a stepped portion having a small step formed on the outer peripheral surface of the rigid forming portion. That is, it is preferable that the step of the step formed on the inner peripheral surface of the rigidity forming portion is smaller than the step of the step formed on the outer peripheral surface of the rigidity forming portion. The level difference of the step portion refers to the distance between the peak portion and the valley portion of the step portion. Thus, when the step of the step formed on the inner peripheral surface of the rigid forming portion is small, the radial direction between the side surface of the step of the outer peripheral surface and the inner peripheral surface is larger than when the step is the same. The thickness increases, and the axial thickness between the end surface of the step on the outer peripheral surface and the inner peripheral surface increases. For this reason, the rigidity of the rigidity forming portion is further improved.

  A stepped portion may not be formed on the inner peripheral surface of the rigid forming portion. In this case, the inner peripheral surface of the rigidity forming portion linearly expands from the bellows portion toward the large-diameter cylindrical portion. Therefore, compared with the case where the step portion is formed on the inner peripheral surface, the radial thickness between the side surface of the step portion on the outer peripheral surface and the inner peripheral surface is further increased, and the end surface of the step portion on the outer peripheral surface is The axial thickness between the inner peripheral surface is increased. For this reason, the rigidity of the rigidity forming portion is further improved.

  The ratio (B / A) of the length (B) in the radial direction of the end surface to the radial thickness (A) of the side surface of the stepped portion should be small, for example, B / A is 0.5 to 2.0. Preferably there is. If it is less than 0.5, the rigidity forming portion may have a shape close to a cylindrical shape, and may be easily bent (see Comparative Example 2). If it exceeds 2.0, the length (B) of the end face is too long, and the end face may bend due to stress concentration, leading to deformation of the entire rigid forming portion.

  The number of steps in the step portion may be two or more, and the upper limit is preferably five. Even if there are too many stages, the improvement of the effect corresponding to it cannot be expected.

  The ratio (P / Q) of the axial length (P) of the rigidity forming portion to the axial length (Q) of the bellows portion is preferably 0.3 to 2.0. If it is less than 0.3, the vicinity of the large-diameter cylindrical portion may be easily bent, and if it exceeds 2.0, the bellows portion may be shortened, and the stretchability of the boot may be reduced.

  The thickness of the rigid forming portion is preferably equal to or greater than the thickness of the bellows portion. In this case, the rigidity of the rigidity forming portion is further improved.

  Moreover, it is preferable that the connection part with the rigidity formation part in a bellows part is formed in the radial direction, and the hollow part whose axial direction cross section is U-shaped groove shape is formed. When an external force is applied to the boot, the bellows portion can be easily compressed and expanded by the U-shaped depression, and the deformation of the rigid forming portion can be more effectively suppressed.

  The boot is made of a synthetic resin. For example, the boot is made of a thermoplastic elastomer resin such as TPE (polyester thermoplastic elastomer), TPO (polyolefin thermoplastic elastomer), or rubber by a known method such as blow molding or injection molding. Can be molded.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Example 1)
A constant velocity joint boot 1 according to an embodiment of the present invention includes a large-diameter tube portion 2 and a large-diameter tube that are coaxially disposed apart from the large-diameter tube portion 2 as shown in FIGS. A small-diameter cylindrical portion 3 having a smaller diameter than the portion 2 and a substantially frustoconical intermediate portion 10 connecting the large-diameter cylindrical portion 2 and the small-diameter cylindrical portion 3. The intermediate portion 10 includes a stretchable bellows portion 19 integrally connected to the small diameter cylindrical portion 3, and a rigidity forming portion 11 integrally connected to the bellows portion 19 and the large diameter cylindrical portion 2. The rigidity forming portion 11 is expanded from the bellows portion 19 toward the large-diameter cylindrical portion 2, and the outer peripheral surface 101 and the inner peripheral surface 102 of the rigidity forming portion 11 are stepped in a plurality of step portions 61, respectively. 62.

  As shown in FIG. 3A, the stepped portion 61 of the outer peripheral surface 101 of the rigidity forming portion 11 is formed by alternately repeating a ridge portion M projecting radially outward and a valley portion V recessed in the radially inward direction. And a side surface 611 that connects the valley portion V and the peak portion M in the axial direction, and an end surface 612 that connects the peak portion M and the valley portion V in the radial direction. The side surface 611 of the step portion 61 is parallel to the axial direction of the step portion 61, and the end surface 612 of the step portion 61 is parallel to the radial direction of the step portion 61. The angle formed between the side surface 611 and the end surface 612 in the peak portion M is a right angle, and the angle formed between the end surface 612 and the side surface 611 in the valley portion V is also a right angle.

  The ratio (B / A) of the radial length (B) of the end surface 612 to the radial thickness (A) of the side surface 611 of the outer peripheral surface 101 is 1.39.

  In the stepped portion 62 of the inner peripheral surface 102 of the rigidity forming portion 11, a peak portion m projecting radially outward and a trough portion v recessed in the radially inner direction are alternately repeated. Side surface 621 that connects the first and second portions in the substantially axial direction, and an end surface 622 that connects the peak portion m and the valley portion v in the substantially radial direction. The side surface 621 is inclined with respect to the axial direction of the stepped portion 62 on the side where the rigidity forming portion 11 is expanded. The end surface 622 is inclined with respect to the radial direction of the stepped portion 62 toward the side where the rigidity forming portion 11 is expanded.

  The distance between the peak portion m and the valley portion v of the step portion 62 on the inner peripheral surface 102 of the rigidity forming portion 11, that is, the step height h of the step portion 62 is the peak portion M and the valley portion V of the step portion 61 of the outer peripheral surface 51. Is smaller than the distance H, ie, the step H.

The thickness D of the thinnest portion of the rigidity forming portion 11 is approximately the same as the thickness d of the bellows portion 19.
The number of the step portions 61 on the outer peripheral surface 101 of the rigidity forming portion 11 and the number of the step portions 62 on the inner peripheral surface 102 are four. As shown in FIG. 1, the bellows portion 19 has a crest portion X and a trough portion Y repeated, and has a right-upward inclined surface 191 and a left-upward inclined surface 192 that connect between them in a triangular shape.

  The connection part with the rigid formation part 11 in the bellows part 19 forms the hollow part 18 whose hollow axial cross section is U-shaped groove shape in the radial direction. The ratio (P / Q) of the axial length P of the rigidity forming portion 11 to the axial length Q of the bellows portion 19 is 0.5.

  The boot 1 is made of a synthetic resin and is formed by blow molding using a thermoplastic elastomer resin such as TPE (polyester thermoplastic elastomer) or TPO (polyolefin thermoplastic elastomer).

  As shown in FIGS. 2 and 10, the boot 1 covers joints 41 and 42 that connect the inner member 8 and the outer member 7. The large-diameter cylindrical portion 2 of the boot 1 is fitted into the cup portion 70 of the outer member 7 of the joints 41 and 42, and the small-diameter cylindrical portion 3 is fitted into the shaft portion 83 of the inner member 8. Then, ring-shaped clamps 52 and 53 are caulked and fastened to the outer peripheral surfaces 22 and 32 of the large diameter cylindrical portion 2 and the small diameter cylindrical portion 3.

  The constant velocity joint boot 1, as shown in FIG. 10, covers the joint portions 41, 42 between the inner member 8 and the outer member 7 formed of a shaft, thereby preventing leakage of grease inside the boot. And prevent water and dust from entering inside. The cup portion 70 of the outer member 7 is brought into elastic contact with the inner peripheral surface 21 of the large-diameter cylindrical portion 2 of the boot 1 and fixed by the fastening force of the clamp 52 from the outer peripheral surface side. Further, the small diameter cylindrical portion 3 is fixed to the shaft portion 83 of the inner member 8. The end portion 84 of the inner member 8 is coaxially inserted into the cup portion 70 of the outer member 7. A plurality of balls 80 are interposed in the circumferential direction between the end portion 84 of the inner member 8 and the cup portion 70 of the outer member 7 so that the inner member 8 and the outer member 7 can swing freely. It is connected. The rotational torque is transmitted at a constant speed from the driving member of the outer member 7 and the inner member 8 to the driven member of the inner member 8 and the outer member 7.

(Example 2)
In the constant velocity joint boot of this example, as shown in FIG. 4, the stepped portion 61 of the outer peripheral surface 101 of the rigidity forming portion 12 protrudes radially outward from the first embodiment, and the side surface 611 of the stepped portion 61 is the shaft. Inclined with respect to direction. The end surface 612 of the step portion 61 is parallel to the radial direction. Others are the same as in the first embodiment.

(Comparative Example 1)
In the boot of this comparative example, as shown in FIG. 5, the rigidity forming portion 15 has a flange shape extending from the bellows portion 19 toward the large-diameter cylindrical portion 2, and step portions are provided on the outer peripheral surface 101 and the inner peripheral surface 102 thereof. Absent. Other points are the same as in the first embodiment.

(Comparative Example 2)
As shown in FIG. 6, the boot of this comparative example is different from the first embodiment in that the rigidity forming portion 16 is entirely cylindrical. The diameter of the rigidity forming portion 16 is larger than the bellows portion 19 and smaller than the large diameter cylindrical portion 2. Other points are the same as in the first embodiment.

(Comparative Example 3)
The boot of this comparative example is different from the first embodiment in that the rigidity forming portion 17 has a bellows shape as shown in FIG. The rigidity forming portion 17 has a shape in which the valley portion W and the mountain portion N are repeated twice. A trough portion 180 is formed at the connecting portion between the rigidity forming portion 17 and the bellows portion 18. Other points are the same as in the first embodiment.

(Evaluation)
The following physical properties of the boots of Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated.
(Bending torque) The torque required to bend the rigid forming portion of the boot was measured. The required torque was evaluated in 4 stages. ◎ is very large, ○ is large, Δ is medium, and x indicates a case where the rigid forming portion can be bent with a small torque.
(Fatigue) An experiment was conducted in which the rigid forming portion of the boot was left at a predetermined angle in a state where the boot was bent at a predetermined angle. The stress change was measured before and after the experiment, and the endurance time when the stress change was below a predetermined amount was determined. The case where the endurance time was not less than the predetermined time was marked with ◯, and the case where the durability time was less than the predetermined time was marked with x.
(Interference) As shown in FIG. 10, the large-diameter cylindrical portion 2 of the boot 1 is fixed to the cup portion 70 of the outer member 7 using a clamp 52, and the small-diameter cylindrical portion 3 is fixed to the shaft portion 83 of the inner member 8. It was fixed using a clamp 53. Thereby, the boot 1 was assembled | attached to joint 41,42 which consists of the cup part 70, the ball | bowl 80, and the edge part 84 of the inner member 8. FIG. In this state, it was examined whether or not the boot interferes with the ball and the outer member when the inner member 8 is lifted. The case where it did not interfere with the outer member or the ball was indicated as ◯, and the case where it interfered was indicated as x.

  Judging comprehensively from the above measurement results, the overall characteristics of the boots were evaluated with ◎ (best), ○ (good), Δ (normal), and × (poor). The evaluation results are shown in Table 1.

  From the table, Examples 1 and 2 gave good results for any physical property evaluation. On the other hand, in Comparative Examples 1 to 3, the bending torque was small, and the rigidity of the rigidity forming portion was low.

  From the above evaluations, it was found that Examples 1 and 2 have a shape in which the rigidity of the rigidity forming portion is high and is not easily deformed by an external force. The reason is that the rigid forming portions of Examples 1 and 2 have a plurality of stepped steps, which is higher than the flange shape of Comparative Example 1, the cylindrical shape of Comparative Example 2, and the bellows shape of Comparative Example 3. It is thought that rigidity was obtained.

  Moreover, in Example 1, the boot is produced by blow molding. For this reason, the inner peripheral surface of the boot is difficult to be formed into the same shape as the outer peripheral surface, and tends to have a gentler slope than the outer peripheral surface. Therefore, in the first embodiment, as shown in FIG. 3B, the inner peripheral surface 102 of the rigidity forming portion 11 includes an end surface 622 inclined with respect to the radial direction and a side surface 621 inclined with respect to the axial direction. Will have. The level difference h of the stepped portion 62 formed on the inner peripheral surface 102 of the rigidity forming portion 11 is smaller than the level difference H of the stepped portion 61 formed on the outer peripheral surface 101. For this reason, compared with the case where both the level | step differences H and h are the same (dotted line in FIG.3 (b)), radial thickness L1 between the side surface 611 of the step part 61 of the outer peripheral surface 101 and the inner peripheral surface 102 is shown. And the axial thickness L2 between the end surface 612 of the stepped portion 61 of the outer peripheral surface 101 and the inner peripheral surface 102 is increased. This is also considered to be a factor for improving the rigidity of the rigidity forming portion 11.

  As a modification, when molding is performed by injection molding or the like, it is possible to mold the inner peripheral surface 102 of the rigidity forming portion 13 into the same shape as the outer peripheral surface 101 as shown in FIG. In this case, the radial thickness L1 between the side surface 611 of the stepped portion 61 of the outer peripheral surface 101 and the inner peripheral surface 102 is substantially the same as the thickness d of the bellows portion 19, and the stepped portion 61 of the outer peripheral surface 101. The thickness L2 in the axial direction between the end surface 612 and the inner peripheral surface 102 is also approximately the same as the thickness d of the bellows portion 19. Even in this case, since the rigidity forming portion 13 has a stepped shape, the section modulus is higher than that of the cylindrical shape. Therefore, the rigidity forming portion 13 exhibits high rigidity, is difficult to be deformed when lifted, and can suppress interference with the ball and the outer member.

  As another modified example, as shown in FIG. 9, a staircase-shaped stepped portion 61 is formed on the outer peripheral surface 101 of the rigidity forming portion 14, and the inner peripheral surface 102 has no stepped portion. It can be set as the inclined surface 63 inclined linearly toward the large diameter cylindrical part 2. In this case, the radial thickness L1 between the side surface 611 of the stepped portion 61 of the outer peripheral surface 101 and the inner peripheral surface 102 is larger than that of the first embodiment, and the stepped portion 61 of the outer peripheral surface 101 is increased. The axial thickness L2 between the end surface 612 and the inner peripheral surface 102 is increased. For this reason, higher rigidity than Example 1 is obtained.

1 is a cross-sectional view of a constant velocity joint boot of Example 1. FIG. It is sectional drawing of the state which assembled | attached the boot to the constant velocity joint in Example 1. FIG. FIG. 3 is a cross-sectional explanatory view of a rigidity forming portion of Example 1. 6 is a cross-sectional view of a constant velocity joint boot of Example 2. FIG. 3 is a cross-sectional view of a constant velocity joint boot of Comparative Example 1. FIG. 6 is a cross-sectional view of a constant velocity joint boot of Comparative Example 2. FIG. 10 is a cross-sectional view of a constant velocity joint boot of Comparative Example 3. FIG. It is sectional explanatory drawing of the rigid formation part of a modification. It is sectional explanatory drawing of the rigid formation part of another modification. It is sectional drawing of a drive shaft. It is explanatory drawing which shows a problem when the drive shaft of a prior art example is lifted. It is explanatory drawing which shows a problem when the drive shaft of a prior art example is lifted.

Explanation of symbols

1: boot, 2: large diameter cylindrical portion, 3: small diameter cylindrical portion, 41, 42: joint, 7: outer member, 8: inner member, 11, 12, 13, 14: rigidity forming portion, 18: depression Part: 19: bellows part, 61, 62: step part, 70: cup part, 80: ball, 81, ball groove, 101: outer peripheral face, 102: inner peripheral face, 611, 621: side face, 612, 622: end face

Claims (2)

A large-diameter cylindrical portion, a small-diameter cylindrical portion that is coaxially disposed apart from the large-diameter cylindrical portion, and has a smaller diameter than the large-diameter cylindrical portion, and an intermediate portion that connects the large-diameter cylindrical portion and the small-diameter cylindrical portion. A constant velocity joint boot comprising:
The intermediate portion is composed of a stretchable bellows portion integrally connected to the small diameter cylindrical portion, and a rigidity forming portion integrally connected to the bellows portion and the large diameter cylindrical portion,
The rigidity forming portion has a diameter that increases from the bellows portion toward the large-diameter cylindrical portion, and at least an outer peripheral surface of the rigidity forming portion has a plurality of stepped portions in a step shape. Joint boots.   2. The constant velocity joint boot according to claim 1, wherein an inner peripheral surface of the rigidity forming portion has a step portion having a small step difference formed on the outer peripheral surface of the rigidity forming portion.

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