JP2015132334A - Boot for constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a stick slip sound generated from a bellows part of a boot when a constant velocity universal joint rotates while taking an operation angle.SOLUTION: In a boot 2 for a constant velocity universal joint having a bellows shape in which a crest 12 and a trough 14 alternately appear, linear protrusions 18 which do not intersect with each other on one slope 16a/16b, and intersect with each other between mutually-opposing slopes 16a, 16b are formed at the slopes 16a, 16b, respectively, which oppose each other with at least one trough 14 sandwiched therebetween, and the protrusions 18 point-contact with each other when the opposing slopes 16a, 16b approximate each other. Furthermore, water on the slopes can be discharged by utilizing a groove 18a between the protrusion 18 and the protrusion 18.

Description

  The present invention relates to a constant velocity universal joint boot.

  Constant velocity universal joints are used in the power transmission systems of automobiles and various industrial machines. They are roughly divided into fixed constant velocity universal joints and sliding constant velocity universal joints. Not only displacement but also axial displacement (plunging) is possible. A drive shaft used for transmitting power from an automobile engine to drive wheels is composed of an intermediate shaft, fixed constant velocity universal joints and sliding constant velocity universal joints attached to both ends thereof.

  These constant velocity universal joints are generally used with boots attached in order to prevent leakage of lubricant such as grease filled therein and to prevent foreign matter from entering from the outside. A constant velocity universal joint boot generally includes a large-diameter end that covers the open end of the outer joint member of the constant-velocity universal joint, a small-diameter end that fits the intermediate shaft extending from the inner joint member, a large-diameter end, and a small-diameter It is comprised by the bellows part which connects an edge part. Such a bellows type boot follows the behavior when the constant velocity universal joint rotates with the operating angle taken, or in the case of a sliding type, it rotates while sliding in the axial direction. Can be expanded and contracted flexibly (see, for example, Patent Document 1).

  Conventionally, rubber boots such as chloroprene rubber have been used as boots for constant velocity universal joints, but resin boots using thermoplastic elastomers that are superior to rubber boots are now widely used. It has become to. However, when the constant velocity universal joint boot rotates with the constant velocity universal joint at a high operating angle, the bellows part repeatedly bends and stretches, causing a so-called stick-slip and a rubbing sound (abrasion sound). There are things to do. In particular, when the constant-velocity universal joint rotates with a constant operating angle, the resin boot makes contact with the inclined surfaces of the bellows portions pressed strongly against each other and repeats the operation of separating them. Likely to happen. In particular, when the surface of the resin boot is wet with water, a large rubbing sound may be generated.

  As a countermeasure against such scratching noise, in Patent Document 1, a plurality of raised portions (see FIG. 3 of Patent Document 1) or concave portions (see also FIG. 8) are formed on one or both of the inclined surfaces of the bellows portion facing each other across the valley. ) Is proposed.

  When the constant velocity universal joint rotates, it becomes only point contact at the raised part, it does not rub against each other, the adhesion force resulting from the water film between the slopes is reduced, and unnecessary noise generation is prevented. There is a statement to the effect. Furthermore, since the slopes do not come into surface contact with each other, the moisture present on the slope in the form of a film with a thickness exceeding the nanoscale range shows good lubricating performance, and the wear rate is minimal by sliding on the slope where the ridges face each other. (See paragraphs 0010 and 0011 of Patent Document 1).

  Even when multiple recesses are provided, the opposing slopes do not rub against each other during rotation of the constant velocity universal joint, reducing the adhesion force resulting from the water film between the slopes and reducing unpleasant noise. It is said that As in the case of the raised portion, there is a description that the lubrication performance of water between the slopes is improved, the wear rate on the slope is minimized, and the service life of the bellows-like boot is extended (paragraph 0016 of Patent Document 1). 0017).

  Patent Document 2 proposes providing a grid-like convex portion on at least one of a pair of slopes facing each other across the valley of the bellows portion (see FIG. 1 of Patent Document 1). Even if the inclined surfaces approach each other, the grid-like convex portions hit each other, so that the contact area is reduced and the generation of scratching noise is suppressed. In addition, since water can be held in the concave portions other than the lattice-shaped convex portions, it is possible to reliably suppress the rubbing noise and to secure a long duration in which the rubbing noise does not occur (see paragraph 0033 of Patent Document 2).

JP 2004-293791 A JP 2012-237332 A

  In the conventional technique described in Patent Document 1, when the constant velocity universal joint has a high operating angle, deformation of the bellows portion becomes large, and the slopes facing each other across the valley strongly press each other. As a result, the portion of the slope where the ridge or recess is formed, except for the ridge or recess, comes into strong contact with the other slope, eventually increasing the contact area between the slopes and preventing the generation of scratching noise. Effect is reduced. In the case of a configuration in which a plurality of recesses are provided, the surface contact is made on the surface of the slope other than the recesses, and therefore the stick-slip suppression effect cannot be expected as much as the configuration in which the bulging portions are provided. Rather, it is proposed to suppress stick-slip by sliding the slopes using the lubricating action of the water film.

  In the conventional technique described in Patent Document 2, when the water that can be held in the concave portion formed by the lattice-shaped convex portion exceeds the limit, the water overflows on the convex portion, so that the effect of suppressing the scratching sound is reduced. To do. Moreover, the water in the concave portion formed by the lattice-shaped convex portions is difficult to be discharged due to the action of the surface tension, and tends to remain indefinitely.

  Accordingly, an object of the present invention is to eliminate the above-mentioned problems of the prior art and to further suppress the scratching sound generated from the bellows portion of the boot when the constant velocity universal joint rotates in a state where the operating angle is taken. is there.

  The present invention has solved the problem by providing linear protrusions extending in directions intersecting each other on the inclined surfaces of the bellows part facing each other across the valley.

  The constant velocity universal joint boot according to the present invention is a bellows-shaped constant velocity universal joint boot in which peaks and valleys alternately appear in the axial direction. Each of the inclined surfaces facing each other across at least one valley Then, by providing linear protrusions that do not intersect each other and that intersect each other between the slopes facing each other, the protrusions come into point contact when the facing slopes approach each other. In addition, it has a function of discharging water on the slope using a groove between the protrusions.

  According to the present invention, when the constant velocity universal joint rotates with an operating angle, when the bellows part is bent and the slopes facing each other across the valley approach each other, the linear protrusions provided on the slope face each other. Will come into point contact at the intersection. Accordingly, the contact area is remarkably reduced as compared with the case where the inclined surfaces are in contact with each other, and the occurrence of stick-slip, and hence the rubbing noise associated therewith, can be further suppressed or prevented.

  Further, since the linear protrusions do not intersect on each slope, the groove between the protrusions constitutes a drainage mechanism, and acts to quickly discharge water adhering to the bellows portion surface. As a result, the action of suppressing or preventing the generation of scratching sound is further promoted. According to the knowledge of the present inventor, it is preferable that water does not intervene in order to prevent fretting noise, and if water adhering to the surface of the bellows portion is quickly discharged, even if the slope approaches, water does not intervene. There is no difference in the coefficient of friction, and this is effective in suppressing the occurrence of stick-slip and hence scratching noise.

(A) is a front view of a boot for a constant velocity universal joint, and (B) is a schematic view of the fifth mountain and the fourth mountain from the small diameter end portion side of (A). It is a front view of the slope which shows the example of two types of radial protrusion, Comprising: (A) shows a linear protrusion, (B) shows a curved protrusion. It is a partial expanded sectional view of a slope. It is sectional drawing of protrusion, Comprising: (A) is a rectangle, (B) is a trapezoid, (C) is a triangle, (D) shows the example of a semicircle. It is a longitudinal cross-sectional view which shows the example of the constant velocity universal joint equipped with boots.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the constant velocity universal joint to which the constant velocity universal joint boot is attached will be briefly described. Various constant velocity universal joints have been developed and used, but here the configuration of the constant velocity universal joint itself is not directly related to the invention of the present application, so it is necessary from the viewpoint of the subject to which the constant velocity universal joint boot is to be mounted. Keep it to a minimum.

  The constant velocity universal joint 20 illustrated in FIG. 5 is an undercut-free constant velocity universal joint among fixed constant velocity universal joints, and includes an inner joint member 22, an outer joint member 32, a plurality of balls 30, and the like. The cage 40 is formed as a main component.

The inner joint member 22 has a plurality of arc-shaped ball grooves 26 extending in the axial direction formed at equal intervals in the circumferential direction on the spherical outer peripheral surface 24 thereof.
The inner joint member 22 has a spline hole 28 in the shaft center portion, and the spline hole 28 is connected to a drive shaft (or a driven shaft), here, the spline shaft of the shaft 50 so as to transmit torque.

The outer joint member 32 has a mouth portion 32a and a stem portion 38 that are integral with each other, and the mouth portion 32a opens at the end opposite to the stem portion 38 and has a cup shape.
A plurality of arc-shaped ball grooves 36 extending in the axial direction are formed at equal intervals in the circumferential direction on the spherical inner peripheral surface 34 of the mouse portion 32a.
The outer joint member 32 is a spline shaft formed in the stem portion 38 and is connected to a spline hole on the wheel bearing side so that torque can be transmitted.

  A ball 30 is incorporated between the ball groove 26 of the inner joint member 22 and the ball groove 36 of the outer joint member 32 that form a pair.

Each ball 30 is accommodated in a pocket formed at a predetermined interval in the circumferential direction of the cage 40, and all the balls 30 are held on the same plane by the cage 40.
The cage 40 has a spherical inner peripheral surface and a spherical outer peripheral surface, and is interposed between the spherical outer peripheral surface 24 of the inner joint member 22 and the spherical inner peripheral surface 34 of the outer joint member 32. Contact.

  The ball groove 36 of the outer joint member 32 has a straight shape parallel to the axis of the outer joint member 32 on the opening end side of the outer joint member 32, thereby eliminating the undercut of the ball groove 36. Similarly, the ball groove 26 of the inner joint member 22 has a straight shape parallel to the axis of the inner joint member 22 on the back side of the outer joint member 32. In this manner, when the constant velocity universal joint 20 takes an operating angle, the position where the shaft 50 interferes with the opening end of the outer joint member 32 is moved to the outer diameter side to increase the operating angle. . Since the degree of bending of the boot increases as the operating angle increases, the inclined surfaces tend to push each other and tend to generate scratching noise.

  The inside of the outer joint member 32 is filled with a lubricant, and the spherical surfaces of the ball 40 and the ball grooves 26 and 36, the ball 30 and the cage 40, and the inner joint member 22, the outer joint member 32, and the cage 40. Lubricate the contact area. Then, in order to prevent leakage of the lubricant sealed inside the joint and to prevent entry of foreign matter from the outside, the bellows-like boot 2 is mounted between the outer joint member 32 and the shaft 50, and the outer side The opening of the joint member 32 is closed.

  Next, the boot 2 will be described with reference to FIG. In FIG. 1, the parallel oblique lines are not cross-sectional views, but schematically show linear protrusions 18 described later.

  The boot 2 illustrated in FIG. 1 is a rotating body having a generally hollow conical trapezoidal shape. From the left to the right in FIG. 1A, the large-diameter end 4, the bellows 10, and the small-diameter end 6 Consists of. The large-diameter end portion 4 and the small-diameter end portion 6 are mounting portions, both of which are cylindrical and have band grooves 8 formed on the outer periphery thereof. The large-diameter end 4 is put on the opening end of the outer joint member 32 and fastened with a boot band, and the small-diameter end 6 is fitted on the shaft 50 and fastened with the boot band (see FIG. 5).

  As the material of the boot 2, a thermoplastic polyester elastomer having a type D durometer hardness of 35 or more and 53 or less as defined in JIS K 6253 and blended with an additive for preventing scratching sound is preferable. For example, with respect to 100 parts by weight of the polyester block copolymer, “HO (RO) × H” (R: a functional group obtained by removing 2 hydrogen from a hydrocarbon compound having 1 to 6 carbon atoms, x: an integer of 1 to 1000) A thermoplastic polyester elastomer containing 0.01 to 1.5 parts by weight of the compound represented by the formula is preferred.

  The bellows portion 10 connects the large-diameter end portion 4 and the small-diameter end portion 6, and peaks 12 and valleys 14 appear alternately in the axial direction. FIG. 1A shows an example having six peaks 12, but the number is arbitrary. Six mountains 12 are arranged in order from the large-diameter end 4 side, first mountain 12-1, second mountain 12-2, third mountain 12-3, fourth mountain 12-4, fifth mountain 12-5, It will be called the sixth mountain 12-6. However, when it is not necessary to distinguish, it may be simply referred to as a mountain 12.

  Similarly, for the valley 14, the first valley 14-1, the second valley 14-2, the third valley 14-3, the fourth valley 14-4, and the fifth valley 14-in order from the large diameter end 4 side. Let's call it 5. However, when it is not necessary to distinguish, it may be simply referred to as valley 14.

Each mountain 12 is composed of a pair of inclined surfaces 16 sandwiching the top (outer peripheral end). In other words, a pair of slopes 16 face each other across each valley 14. Of the slope 16, the slope on the large diameter end 4 side is referred to as slope 16a, and the slope on the small diameter end 6 side is referred to as slope 16b. Again, when it is not necessary to distinguish, it may be simply referred to as the slope 16.
Although illustration is omitted, a groove may be provided over the entire circumference at the top of the crest 12 or the bottom of the trough 14 for easy bending of the bellows portion 10 or for convenience of molding.

  In the illustrated embodiment, in the central three valleys, that is, the second valley 14-2, the third valley 14-3, and the fourth valley 14-4, a pair of inclined surfaces 16a and 16b facing each other across the valley 14 are provided. In each case, a linear protrusion 18 is provided. As shown by parallel oblique lines in FIG. 1, the protrusion 18 is inclined with respect to the rotational axis of the boot 2.

  As shown in the figure, in the case of the boot 2 having the bellows portion 10 composed of six ridges 12, when the constant velocity universal joint rotates in a state of taking an operating angle, the bellows portion 10 is bent and the small diameter end portion 6 is bent. It is known that the second fifth mountain 12-5, the third fourth mountain 12-4, and the fourth third mountain 12-3 are greatly deformed. And the slope 16 which comprises the 2nd valley 14-2, the 3rd valley 14-3, and the 4th valley 14-4 each contacts, and it is easy to raise | generate a stick slip. Therefore, linear protrusions 18 are provided on the slope 16 constituting these three valleys 14-2, 14-3, 14-4. As a result, when the slopes 16a and 16b facing each other across the valley approach each other, the protrusions 18 come into point contact at the intersecting portion, so that the generation of scratching sound is more reliable than when the slopes are in surface contact. Can be suppressed.

Of course, you may provide the linear protrusion 18 also in the slope 16a, 16b which comprises the 1st trough 14-1 and / or the 5th trough 14-5 of both ends.
In short, it is necessary to provide the protrusion 18 at a site where the generation of scratching noise is a concern in consideration of the usage environment and usage conditions of the constant velocity universal joint.

  The plurality of protrusions 18 are provided radially so as not to cross each other. Each protrusion 18 may be linear (FIG. 2A) or curved (FIG. 2B). In addition to a curve as shown in FIG. 2B, a waveform or a zigzag shape may be used.

  As shown in FIG. 3, a groove 18 a is formed between the protrusion 18 and the protrusion 18. The groove 18a is preferably open toward the outer diameter side of the inclined surface 16 from the surface of drainage. 1 and 2, the protrusion 18 is shown to reach the outer peripheral end of the slope 16. The outer peripheral end of the slope 16 is nothing but the top of the mountain 12, but normally there is no other party to rub against the outer peripheral surface of the top of the mountain 12, so the projection 18, the groove 18 a, It is not necessary to provide even the outer peripheral surface of the top. Rather, considering the strength and durability of the boot 2, it is preferable that the groove 18 a ends before the top of the mountain 12. For this purpose, for example, the groove 18a may gradually become shallower toward the outer diameter side of the slope 16 and disappear before the outer peripheral end. When the groove 18a becomes shallow, it means that the height of the protrusion 18 becomes low. In that sense, the height of the protrusion 18 need not be uniform over the entire length of the protrusion 18.

  The arrangement and orientation of the projections 18 are set so that the projection 18 of one slope 16a and the projection 18 of the other slope 16b intersect the slopes 16a and 16b facing each other across the valley 14. For example, the protrusion 18 on one inclined surface 16a may be formed in a spiral shape inclined in the clockwise direction, and the protrusion 18 on the other inclined surface 16b may be formed in a spiral shape inclined in the counterclockwise direction. By doing so, when the constant velocity universal joint rotates at an operating angle and the bellows part 10 bends and the inclined surfaces 16a and 16b come into contact with each other, the protrusion 18 on one inclined surface 16a and the other inclined surface 16b. That is, the protrusions 18 make point contact at the intersection. In addition, the drainage function is maintained because the grooves 18a between the protrusions 18 on the slopes 16a and 16b are not blocked.

Since the linear protrusions 18 provided on the slopes 16a and 16b do not intersect each other on the same slope, even if the bellows part 10 is splashed with water, it can be easily along the groove 18a between the protrusions 18 and 18. To be discharged. In this way, since it is difficult for water to intervene between the slopes 16a and 16b facing each other, the generation of scratching noise is effectively suppressed.

The interval (pitch) between the protrusion 18 and the protrusion 18 is set so that the surface portions (16) other than the protrusion 18 do not come into contact with each other when the inclined surfaces 16a and 16b facing each other due to the bending of the bellows portion 10 are in contact with each other. As a specific example, as shown in FIG. 3, the interval L between the protrusions 18 provided on one slope 16 is preferably 2 mm or more and 5 mm or less. When the distance L between the protrusions 18 is smaller than 2 mm, the number of the protrusions 18 increases and the contact area between the protrusions 18 of the slope 16 facing each other increases, and the effect of preventing scratching sound decreases. Further, when the interval L between the protrusions 18 exceeds 5 mm, when the constant velocity universal joint rotates with a high operating angle, the bellows portion 10 is bent and the inclined surfaces 16a and 16b facing each other strongly press each other. The surface portion between the protrusion 18 and the protrusion 18 may be deformed and brought into contact, and the effect of preventing scratching noise may be reduced.

Note that the pitch of the protrusions 18 is not necessarily equal. Further, a plurality of protrusions 18 may be arranged at a predetermined pitch, such as two or three.

The height H of the protrusion 18 from the inclined surface 16 is preferably 0.2 mm or more and 0.5 mm or less. Within this range, the slopes 16a, 16b facing each other make point contact at the intersection of the protrusions 18, and the noise can be prevented by reducing the contact area. When the height H of the protrusion 18 is lower than 0.2 mm, when the constant velocity universal joint is rotated with a high operating angle, the bellows portion 10 is bent and the slopes 16a and 16b facing each other strongly press each other. In such a case, the surface portion (16) between the protrusion 18 and the protrusion 18 may come into contact, and the effect of preventing scratching noise may be reduced. Moreover, when the height H of the protrusion 18 exceeds 0.5 mm, there is a concern that the moldability of the boot 2 and the boot performance are deteriorated.

The width W of the protrusion 18 is preferably 0.5 mm or more and 1 mm or less. If the width W of the projection 18 is smaller than 0.5 mm, the projection 18 deforms without being able to withstand the contact force, and the surface portion (16) between the projection 18 and the projection 18 comes into contact. The prevention effect may be reduced. On the other hand, if the width W of the protrusions 18 exceeds 1 mm, the contact area between the protrusions 18 increases, and the effect of preventing scratching sound is reduced.

Although the cross-sectional shape of the protrusion 18 is not particularly limited, if a specific example is given, a rectangle (FIG. 4A), a trapezoid (FIG. 4B), a triangle (FIG. 4C), a semicircle, or an ellipse (FIG. 4D). As can be seen from FIG. 3, the width W of the projection 18 means the width of the base of the projection 18 regardless of the cross-sectional shape. As for the top of the protrusion 18, the smaller the radius of curvature, the smaller the contact area when the protrusions 18 intersect each other, which is preferable in terms of measures against scratching noise. However, if strength and durability are taken into consideration, a circular cross section is relatively more advantageous than a triangular cross section.

The cross-sectional shape of the bottom of the groove 18a between the protrusion 18 and the protrusion 18 may be a flat surface as shown in FIG. 4, or may be a concave arc (not shown), for example. In addition, in combination with the cross-sectional shape of the protrusion 18 in FIG. 4D, the cross-sectional shape of the slope 16 can be a waveform like a sine curve. The radius of curvature increases and the degree to which water is retained by surface tension decreases.

  The effects of the above-described embodiment can be summarized as follows.

  The constant velocity universal joint boot 2 of the embodiment is an accordion-shaped constant velocity universal joint boot in which peaks 12 and valleys 14 appear alternately in the axial direction, and includes slopes 16a and 16b facing each other across at least one valley 14. Each is provided with linear protrusions 18 that do not intersect each other on the same slope 16 but intersect each other between the slopes 16 a and 16 b facing each other across the valley 14. When the slopes 16 a and 16 b facing each other across the valley 14 approach each other, the protrusions 18 come into contact with each other, and point contact is made at the intersection of the protrusion 18 and the protrusion 18. Therefore, the contact area is remarkably reduced as compared with the case where the slopes 16a and 16b are in surface contact with each other, and stick-slip and thus the generation of scratching noise is suppressed.

By making the protrusion 18 radially extending from the inner diameter side to the outer diameter side, the groove 18a between the protrusion 18 and the protrusion 18 is used to adhere to the bellows portion 10 by the action of centrifugal force accompanying the rotation of the constant velocity universal joint. The action which drains the drained water is obtained (drainage action). That is, the groove 18a between the protrusion 18 and the protrusion 18 constitutes a drainage mechanism. In this case, a spiral shape may be used in addition to the radial shape. Further, each protrusion 18 is not limited to a linear shape, and may be a curved shape.

Adjacent protrusions 18 and grooves 18a between the protrusions 18 are open toward the outer diameter side of the boot 2, so that the water adhering to the bellows part 10 due to the centrifugal force associated with the rotation of the constant velocity universal joint. Is discharged quickly, and the drainage action is promoted.
In this case, the groove 18a between the protrusion 18 and the protrusion 18 extends to the outer peripheral end portion of the inclined surface 16 and is opened there, and becomes shallower toward the outer diameter side of the inclined surface, and the groove 18a is formed in front of the outer peripheral end portion. It also includes those that have disappeared. Since the height (outer diameter) of the mountain 12 varies depending on the position of the boot 2 in the axial direction, the height (outer diameter) of the slope 16 also differs, and the slopes 16a and 16b facing each other across the valley 14 are exactly the same height. There are few cases where it becomes the outer diameter. Therefore, on the high (large diameter) side of the slopes 16a and 16b facing each other, the slope on the other side may not come into contact with the other side in the vicinity of the outer peripheral end portion. It is not necessary to extend to the outer peripheral end (the top of the mountain 12).

By adopting a thermoplastic polyester elastomer as the material of the boot 2, it is possible to contribute from the material side in order to suppress the generation of scratching noise.

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the embodiments shown and described herein, and various modifications are made without departing from the scope of the claims. It goes without saying that it can be implemented.

2 Boot 4 Large-diameter end 6 Small-diameter end 8 Band groove 10 Bellows 12 Mountain 14 Valley 16 Slope 16a Slope on the large-diameter end side 16b Slope on the small-diameter end side 18 Projection 18a Groove 20 between projections, etc. Quick joint 22 Inner joint member 24 Spherical outer peripheral surface 26 Ball groove 28 Spline hole 30 Ball 32 Outer joint member 32a Mouse part 34 Spherical inner peripheral surface 36 Ball groove 38 Stem part 40 Cage 50 Shaft

Claims (4)

  In the bellows-shaped constant velocity universal joint boot in which peaks and valleys appear alternately in the axial direction, the slopes facing each other across at least one valley do not cross each other within one slope, and the one A boot for a constant velocity universal joint provided with linear protrusions intersecting each other between slopes facing each other across a valley. The boot for a constant velocity universal joint according to claim 1, wherein the linear protrusions extend radially from the inner diameter side to the outer diameter side. The boot for a constant velocity universal joint according to claim 1 or 2, wherein the linear protrusion is open toward the outer diameter side. The boot for a constant velocity universal joint according to claim 1, 2, or 3, comprising a thermoplastic polyester series elastomer.

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