JP5763707B2 - Constant velocity joint boots - Google Patents

Description

  The present invention relates to a constant-velocity joint boot that constitutes an outer member of a constant-velocity joint and is attached to a cup portion having a non-cylindrical outer shape.

  A constant velocity joint used in an automobile or the like is mainly composed of an outer member and an inner member. The outer member has a bottomed cylindrical cup portion and a shaft portion that protrudes from the bottom portion of the cup portion. The inner member is fixed to the distal end portion of the driving force transmission shaft and is inserted into the cup portion of the outer member. A part of the driving force transmission shaft is covered with a constant velocity joint boot (hereinafter also simply referred to as a boot) from the tip of the cup portion. Specifically, the boot is formed of an elastomeric material such as a thermoplastic resin, and has a large-diameter annular portion that is externally fitted to the cup portion, a small-diameter annular portion that is externally fitted to the driving force transmission shaft, and a large-diameter annular portion. And an accordion portion provided in a freely stretchable manner between the small-diameter annular portion.

  Each of the large-diameter annular portion and the small-diameter annular portion is fastened and fixed by, for example, a metal band from its outer peripheral surface in a state of being fitted around the cup portion and the driving force transmission shaft. With this boot, grease for lubrication is sealed in the cup portion, and dust, water, and the like are prevented from entering the cup portion. Therefore, the outer member and the driving force transmission shaft and the boot need to be well sealed.

  In this constant velocity joint, for example, in order to reduce weight, a so-called meat steal may be provided with a recess extending along the axial direction on the outer wall of the cup portion of the outer member. That is, the outer shape of the cup portion is a non-cylindrical shape formed by the arc surface and the concave portion. In this case, the large-diameter annular portion of the boot that is externally fitted to the cup portion is set so that the inner wall corresponds to the shape of the outer wall of the cup portion while the outer shape is maintained in a cylindrical shape. That is, the thickness of the large-diameter annular portion varies depending on the outer shape of the cup portion. Specifically, the large-diameter annular portion includes a thin wall portion whose inner wall is formed in an arc shape along the arc surface of the cup portion, and a thick wall portion whose inner wall is formed in a convex shape along the recess portion of the cup portion. The thick part is thicker than the thin part.

  In addition, a seal portion protruding toward the axis is formed on the inner wall of the large-diameter annular portion so as to improve the sealing performance between the cup portion and the large-diameter annular portion. When the band is wound around the large-diameter annular portion, the convex inner wall of the thick wall portion presses the wall surface of the concave portion of the cup portion, and the arc-shaped inner wall of the thin wall portion presses the circular arc surface of the cup portion. Further, the seal portion is deformed so as to be crushed and is brought into close contact with the outer wall of the cup portion, thereby sealing between the boot and the cup portion.

  This type of seal part is generally set to the same protruding length regardless of whether it is a thin part or a thick part. On the other hand, in Patent Document 1, with the aim of further improving the sealing performance, the protruding length of the seal portion is reduced and the width of the seal portion is reduced from the bottom to the top of the convex inner wall in the thick portion. It has been proposed to widen.

  Further, in Patent Document 2, a seal portion having a larger protruding length than other portions is provided near the boundary between the thick portion and the thin portion of the large-diameter annular portion, and further, the seal portion of the seal portion is disposed near the boundary. A boot with ribs to prevent falling is described.

  These techniques are configured based on the assumption that the sealing performance is lowered because the contact pressure between the vicinity of the boundary between the thick portion and the thin portion and the cup portion is reduced. That is, by adopting the above-described configuration, the concern is that the sealing performance between the vicinity of the boundary and the cup portion is lowered.

Japanese Patent No. 4258329 Japanese Patent No. 4428080

  An automobile equipped with a constant velocity joint is assumed to be used within a wide temperature range such as −40 to 120 ° C., for example, but the sealability between the boot and the cup portion is particularly low at extremely low temperatures. You may not get enough. According to the inventor's earnest study, it was recognized that the grease slightly leaked between the thick portion and the concave portion. In particular, in the techniques described in Patent Documents 1 and 2, since the protruding length of the seal portion in the thick portion is smaller than that in other portions, there is a concern that this tendency becomes remarkable.

  It is recalled that the band tightening force is increased in order to improve the sealing performance. However, in this case, the amount of compressive deformation of the thick portion increases, and as a result, the repulsive force of the thick portion increases. For this reason, excessive tension | tensile_strength generate | occur | produces in a band and a band may lead to a fracture | rupture.

  The present invention solves this type of problem, can suppress the generation of excessive tension in the band, and has a good sealing property with a cup portion having a non-cylindrical outer shape even in a cold environment. An object of the present invention is to provide a constant velocity joint boot capable of exhibiting the above.

In order to achieve the above-mentioned object, the present invention constitutes an outer member of a constant velocity joint, and has an arc surface on an outer wall, and is recessed in a curved shape from the arc surface toward the axis and extending along the axial direction. A boot for a constant velocity joint having an annular portion that is fastened and fixed by a band in a state of being fitted around a cup portion formed with a concave portion,
The annular part has a thin part and a thick part set to be thicker than the thin part,
The inner wall of the thin-walled portion has an arc shape along the arc surface of the cup portion, and the inner wall of the thin-walled portion is deformably abutted against the arc-shaped surface, and the arc-shaped surface and the thin-walled portion A first seal portion that seals between is formed to project toward the axis of the annular portion,
The inner wall of the thick part has a convex shape along the concave part of the cup part, and the inner wall of the thick part is in contact with the wall surface of the concave part so as to be deformable. A second seal portion that seals between the two portions is formed protruding toward the axis of the annular portion,
The first seal portion and the second seal portion are connected to each other and circulate around the inner wall of the annular portion,
The protruding length of the second seal part is larger than that of the first seal part.

  When the ambient temperature of the boot is changed from room temperature to very low temperature, the boot contracts. According to the earnest study of the present inventors, knowledge has been obtained that the shrinkage rate is increased at the site where the wall thickness is large. That is, in the large-diameter annular portion, the thick-walled portion contracts greatly compared to the thin-walled portion. It is speculated that this is the reason why the sealing performance between the thick wall portion and the concave portion is lowered at an extremely low temperature.

  Therefore, in the present invention, the first seal portion is provided on the inner wall of the thin portion having a small thickness in the annular portion, and the second seal portion is provided on the inner wall of the thick portion having a large thickness. And the interference length of a thick part is enlarged compared with a thin part by making the protrusion length of a 2nd seal part larger than a 1st seal part. Here, the fastening allowance is a difference between the inner diameter of the annular portion before being fitted onto the cup portion and the outer diameter of the cup portion.

  For example, in a cold environment such as −40 ° C., the shrinkage ratio of the annular portion due to the temperature drop increases as the wall thickness increases. Therefore, the shrinkage rate is greater in the thick part than in the thin part. Thus, in the thick part where the shrinkage rate is large, the tightening margin is set large as described above. As a result, even if the thick portion contracts greatly in a cold environment, the gap between the thick portion and the concave portion of the cup portion can be satisfactorily sealed.

  A deformable first seal portion and a second seal portion are interposed between the annular portion and the cup portion. The second seal part has a larger amount of deformation than the first seal part because the protrusion length is larger. Therefore, even if the tightening margin of the thick part is increased as described above to improve the sealing performance between the thick part and the cup part, the second seal part is mostly deformed, and the thick part itself is Almost no compression deformation. That is, it is possible to suppress an increase in the amount of compressive deformation of the thick-walled portion due to the large deformation of the second seal portion.

  As a result, generation of excessive tension in the band can be suppressed. This is because the repulsive force that the band receives from the thick part is reduced.

  Furthermore, as described above, the difference between the amount of compressive deformation due to the tightening force of the band between the thick part and the thin part, that is, the difference in the repulsive force against the band can be suppressed. It becomes possible to press the whole part substantially uniformly. Thereby, it can suppress that the sealing performance of the vicinity of the boundary of a thick part and a thin part and a cup part falls.

  As described above, in this constant velocity joint boot, it is possible to maintain good sealing performance between the annular portion and the cup portion even in a cold environment while suppressing excessive tension from being generated in the band.

  Further, in this constant velocity joint boot, by reducing the protruding length of the first seal portion provided in the thin portion as described above, the formability of the constant velocity joint boot and the mounting property of the annular portion to the cup portion are achieved. Can be improved.

  In the constant velocity joint boot described above, it is preferable that the protruding length of the second seal portion increases as the thickness of the thick portion increases from the convex bottom to the top. That is, since the protrusion length of the second seal portion increases as the shrinkage rate increases in a cold environment, the sealing performance between the thick wall portion and the concave portion of the cup portion can be maintained better.

  In the case where the constant velocity joint boot is formed of an elastomeric material, it is possible to more effectively suppress a decrease in sealing performance in a cold environment. This is because the elastomeric material has a higher shrinkage rate due to a decrease in environmental temperature than, for example, rubber.

  In the present invention, the protruding length of the second seal portion provided in the thick portion is made larger than the first seal portion provided in the thin portion in the annular portion of the constant velocity joint boot. Thereby, the tightening allowance in the annular portion can be set according to the thickness of the annular portion. As a result, even in a cold environment, it is possible to satisfactorily seal the gap between the cup portion and the annular portion having a non-cylindrical outer diameter without causing excessive tension in the band.

It is a disassembled perspective view of the tripod type | mold constant velocity joint with which the boot for constant velocity joints concerning this embodiment is mounted | worn. It is a principal part expansion perspective view of the boot for constant velocity joints shown in FIG. It is a schematic front view from the large diameter annular part side of the boot for constant velocity joints shown in FIG.

  Hereinafter, preferred embodiments of a constant velocity joint boot (hereinafter also simply referred to as a boot) according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an exploded perspective view of a triport type constant velocity joint 12 to which a boot 10 according to the present embodiment is attached. In FIG. 1, the inner member constituting the constant velocity joint 12 is omitted.

  First, the constant velocity joint 12 will be described. The constant velocity joint 12 includes an outer member 16 and an inner member (all not shown) inserted into a bottomed hole formed in the outer member 16.

  The outer member 16 includes a long shaft portion 18 and a cup portion 20 provided at a tip portion of the shaft portion 18. A differential gear (not shown) is connected to the shaft portion 18, and the rotational driving force of the differential gear is transmitted to the drive shaft 22 via the cup portion 20 and the inner member.

  Three track grooves (not shown) extending along the axial direction of the outer member 16 and spaced apart from each other by 120 ° are formed on the inner wall of the cup portion 20. In addition, the outer wall of the cup portion 20 has three arcuate surfaces 24a to 24c, a concave shape that is curved from the arcuate surfaces 24a to 24c toward the axis, and along the axial direction (the direction of the arrow X in FIG. 1). The three recessed parts 26a-26c which extend in this way are formed.

  The arc surfaces 24a to 24c are provided on the outer wall of the portion where the track groove is provided on the inner wall. In other words, the arc surfaces 24a to 24c are provided at regular intervals, and the recesses 26a to 26c are provided between the arc surfaces 24a to 24c, respectively. Thus, by providing the concave portions 26a to 26c, the cup portion 20 can be reduced in weight as so-called meat stealing. That is, the outer shape of the cup portion 20 is a non-cylindrical shape formed by the arc surfaces 24a to 24c and the concave portions 26a to 26c.

  Further, arc-shaped step portions 28 a to 28 c are formed on the outer wall on the opening side of the cup portion 20. The concave portions 26a to 26c extend in the axial direction (X direction) of the cup portion 20 so as to cross the arc-shaped step portions 28a to 28c. For this reason, the arc-shaped step portions 28a to 28c are divided into three portions at positions where the concave portions 26a to 26c cross.

  The large-diameter annular portion 30 (annular portion) of the boot 10 is fitted on the arc-shaped step portions 28a to 28c and the concave portions 26a to 26c. On the other hand, the small-diameter annular portion 31 of the boot 10 is fitted on the end portion of the drive shaft 22. The boot 10 is attached to the constant velocity joint 12 by winding a band (not shown) from the outer peripheral surface of each of the large-diameter annular portion 30 and the small-diameter annular portion 31.

  That is, the boot 10 is formed of an elastomer material, and the large-diameter annular portion 30 is provided at one end and the small-diameter annular portion 31 is provided at the other end. Further, a bellows portion 32 is provided between the large-diameter annular portion 30 and the small-diameter annular portion 31 so as to be stretchable. Therefore, by attaching the boot 10 to the constant velocity joint 12 as described above, the portion extending from the opening side of the outer member 16 to the end of the drive shaft 22 can be surrounded by the bellows portion 32 of the boot 10. Thereby, in the boot 10, grease for lubrication can be enclosed in the cup portion 20, and dust, water, and the like can be prevented from entering the cup portion 20.

  Here, while the principal part expansion perspective view of the boot 10 is shown in FIG. 2, the schematic front view from the large diameter annular part 30 side of the boot 10 is shown in FIG. As shown in FIGS. 2 and 3, the large-diameter annular portion 30 has an outer wall formed in a cylindrical shape and an inner wall formed in a shape corresponding to the shape of the outer walls of the arc-shaped step portions 28 a to 28 c of the cup portion 20. Has been.

  Specifically, the large-diameter annular portion 30 has three thin portions 34 whose inner walls are formed in an arc shape along the arc surfaces 24a to 24c, and 3 whose inner walls are formed in a convex shape along the recess portions 26a to 26c. And a thick portion 36. The thick portion 36 is set to be thicker than the thin portion 34 because the thick portion 36 protrudes in a convex shape. Further, the inner wall of the thick portion 36 has a shape that gently bulges (curves) toward the top that is intermediate between the adjacent thin portions 34 so as to correspond to the curved shape of the recesses 26a to 26c. There is no. For this reason, the thickness of the thick portion 36 is maximized at the top, and decreases toward the skirt portion close to the thin portion 34.

  Two first seal portions 38 arranged in parallel are formed on the inner wall of the thin wall portion 34 so as to protrude toward the axis of the large-diameter annular portion 30. The first seal portion 38 contacts the arcuate surfaces 24a to 24c in a deformable manner, and seals between the arcuate surfaces 24a to 24c and the thin portion 34.

  Two second seal portions 40 arranged in parallel are formed on the inner wall of the thick portion 36 so as to protrude toward the axis of the large-diameter annular portion 30. The second seal portion 40 abuts deformably against the wall surfaces of the recesses 26 a to 26 c and seals between the recesses 26 a to 26 c and the thick portion 36.

  The first seal portion 38 and the second seal portion 40 are connected to each other in the circumferential direction, and thereby, two seal portions that circulate around the inner wall of the large-diameter annular portion 30 are configured.

  Further, the protruding lengths of the first seal portion 38 and the second seal portion 40 are set to increase as the thickness of the large-diameter annular portion 30 increases. Therefore, the protruding length of the second seal portion 40 is set to be larger than that of the first seal portion 38. Further, the protruding length of the second seal portion 40 is set so as to increase as the thickness of the thick portion 36 increases from the skirt portion to the top portion of the thick portion 36.

  As shown in FIG. 3, for example, when the radius r of the large-diameter annular portion 30 is about 38 mm, the protruding length L1 of the first seal portion 38 may be set to about 0.7 mm. At this time, the protrusion length of the second seal portion 40 may be set such that the minimum protrusion length L2 is about 1.0 mm and the maximum protrusion length L3 is about 1.7 mm.

  The boot 10 according to the present embodiment is basically configured as described above. Next, the function and effect will be described.

  As described above, in the boot 10, the large-diameter annular portion 30 is fitted on the cup portion 20. At this time, the thick portion 36 enters the concave portions 26a to 26c, and the thin portion 34 covers the arc-shaped step portions 28a to 28c. That is, the first seal portion 38 is seated on the arc-shaped step portions 28a to 28c, while the second seal portion 40 is seated on the recess portions 26a to 26c. Further, the small-diameter annular portion 31 is fitted on the end portion of the drive shaft 22. After this external fitting, bands (not shown) are wound around the outer peripheral surfaces of the large-diameter annular portion 30 and the small-diameter annular portion 31.

  The large-diameter annular portion 30 is pressed toward the cup portion 20 by this winding. As a result, the first seal portion 38 and the second seal portion 40 are deformed so as to be crushed.

  In the present embodiment, the protruding length of the second seal portion 40 provided in the thick portion 36 is made larger than the protruding length of the first seal portion 38 provided in the thin portion 34. That is, the tightening margin of the thick portion 36 is larger than that of the thin portion 34. Here, the tightening allowance is a difference between the inner diameter of the large-diameter annular portion 30 before being externally fitted to the cup portion 20 and the outer diameter of the cup portion 20.

  Each of the first seal portion 38 and the second seal portion 40 is deformable, and the second seal portion 40 has a larger amount of deformation than the first seal portion 38 because the protrusion length is larger. Therefore, even if the tightening allowance of the thick portion 36 is increased as described above, when the band tightening force is applied, the second seal portion 40 is greatly deformed, and the thick portion 36 itself is almost compressed and deformed. Not. For this reason, it can suppress that the amount of compressive deformation of the thick part 36 increases. As a result, generation of excessive tension in the band can be suppressed.

  The constant velocity joint 12 (see FIG. 1) to which the boot 10 is attached is mounted on an automobile. The car may be driven in cold regions. In some cases, it is assumed that the environmental temperature reaches an extremely low temperature of −40 ° C.

  When the boot 10 is used in such a cold environment, the boot 10 contracts. Here, since the boot 10 is formed of an elastomer-based material, for example, the shrinkage rate when the ambient temperature decreases is likely to be larger than that of the constant velocity joint 12 formed of metal or the like. Further, the shrinkage rate is larger in the thick portion 36 having a larger thickness than the thin portion 34 having a small thickness in the large-diameter annular portion 30.

  Moreover, in the thick part 36, it changes so that thickness may become large toward a top part from a skirt part. Therefore, in the thick portion 36, the contraction rate of the top portion is larger than that of the skirt portion.

  For the above reasons, particularly the top of the thick portion 36 contracts in a direction away from the recesses 26a to 26c. At this time, the second seal portion 40 expands due to an elastic action.

  In the present embodiment, the protruding length of the second seal portion 40 is made larger than that of the first seal portion 38, and the protruding length of the second seal portion 40 is also changed as described above. It is made to change along the circumferential direction corresponding to. That is, in the second seal portion 40, the tightening margin is set to increase in accordance with the shrinkage rate increasing from the skirt portion to the top portion of the convex thick portion 36.

  Therefore, even if the thick part 36 contracts greatly as compared with the thin part 34, the second seal part 40 has a large tightening margin (or amount of compressive deformation), so that the bottom part and the top part of the thick part 36 contract. It is possible to expand in accordance with the amount. For this reason, it is avoided that the 2nd seal part 40 leaves | separates from recessed part 26a-26c. That is, the state where the entire second seal portion 40 is seated in the recesses 26a to 26c is maintained. For the reasons as described above, the sealing performance between the thick portion 36 and the recesses 26a to 26c can be maintained satisfactorily.

  Needless to say, the first seal portion 38 is also stretched by an elastic action and maintained in a state of being seated on the arc-shaped step portions 28a to 28c.

  Further, as described above, since it is possible to suppress the difference in the amount of compressive deformation caused by the band tightening force between the thick part 36 and the thin part 34, that is, the difference in the repulsive force with respect to the band, On the other hand, the entire large-diameter annular portion 30 can be pressed substantially uniformly. As a result, it is possible to suppress the deterioration of the sealing performance between the cup portion 20 and the vicinity of the boundary between the thick portion 36 and the thin portion 34.

  As described above, in this constant velocity joint boot 10, the sealing performance between the large-diameter annular portion 30 and the cup portion 20 can be satisfactorily maintained even in a cold environment while preventing excessive tension from being generated in the band. Is possible.

  In the constant velocity joint boot 10, the protruding length of the first seal portion 38 is set smaller than that of the second seal portion 40. Thereby, the moldability of the constant velocity joint boot 10 and the mountability of the large-diameter annular portion 30 to the cup portion 20 can be improved.

  The present invention is not particularly limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  For example, in the above embodiment, the thickness provided in the large-diameter annular portion 30 according to the shape of the outer wall of the cup portion 20 in which the three arcuate surfaces 24a to 24c and the three concave portions 26a to 26c are formed. The number of each of the meat part 36 and the thin part 34 was three. However, these numbers are not limited to three, and can be set to arbitrary numbers.

DESCRIPTION OF SYMBOLS 10 ... Constant velocity joint boot 12 ... Constant velocity joint 16 ... Outer member 18 ... Shaft part 20 ... Cup part 22 ... Drive shaft 24a-24c ... Arc surface 26a-26c ... Recessed part 28a-28c ... Arc-shaped step part 30 ... Large Diameter annular part 31 ... Small diameter annular part 32 ... Bellows part 34 ... Thin part 36 ... Thick part 38 ... First seal part 40 ... Second seal part

Claims (3)

The outer member of the constant velocity joint is configured, and is externally fitted to a cup portion in which an arc surface is formed on the outer wall, and a concave portion that is concavely curved from the arc surface toward the axial center and extends along the axial direction. A constant velocity joint boot having an annular portion that is fastened and fastened by a band in a state of being
The annular part has a thin part and a thick part set to be thicker than the thin part,
The inner wall of the thin-walled portion has an arc shape along the arc surface of the cup portion, and the inner wall of the thin-walled portion is deformably abutted against the arc-shaped surface, and the arc-shaped surface and the thin-walled portion A first seal portion that seals between is formed to project toward the axis of the annular portion,
The inner wall of the thick part has a convex shape along the concave part of the cup part, and the inner wall of the thick part is in contact with the wall surface of the concave part so as to be deformable. A second seal portion that seals between the two portions is formed protruding toward the axis of the annular portion,
The first seal portion and the second seal portion are connected to each other and circulate around the inner wall of the annular portion,
The boot for a constant velocity joint, wherein the protruding length of the second seal portion is larger than that of the first seal portion.   2. The constant velocity joint boot according to claim 1, wherein the protruding length of the second seal portion increases as the thickness of the thick portion increases from the bottom of the convex shape toward the top. Constant velocity joint boots.   3. The constant velocity joint boot according to claim 1, wherein the constant velocity joint boot is formed of an elastomeric material.

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