JP2008032192A - Resin joint boot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint boot having improved durability by suppressing the buckling of a bellows at its ridges when rotated in a wide-angle buckled and deformed state. <P>SOLUTION: The joint boot for integrally connecting a large diameter cylinder 12 to a small diameter cylinder 14 comprises the bellows 16 which is composed of a plurality of alternately continuous valleys and ridges including a first valley 30-1, a first ridge 32-1, a second valley 30-2, a second ridge 32-2, and a third valley 30-3 sequentially from the large diameter cylinder 12. Thicknesses Ta1, Ta2 of the first and second ridges 32-1, 32-2 are set to be greater than thicknesses Ta3-Ta6 of the other ridges 32-3 to -6 and greater than thicknesses Tb-1 to Tb3 of the adjacent first-third valleys 32-1 to -3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bellows-shaped joint boot mainly used for a constant velocity joint of an automobile.

  The joint of drive shafts of automobiles and industrial machines has a bellows-like joint boot that can be appropriately expanded and contracted and bent to retain the enclosed grease or prevent the entry of dust and foreign objects. It is installed.

  Such a joint boot has a cylindrical bellows structure with a difference in diameter at both ends, a large-diameter cylindrical portion attached to a cylindrical outer case of a constant velocity joint, and a space between the large-diameter cylindrical portion. It consists of a small-diameter cylindrical part that is coaxially arranged and attached to the shaft, and a bellows part that integrally connects both, and is integrally molded by blow molding using an elastic material such as a thermoplastic elastomer resin (for example, , See Patent Documents 1 and 2 below).

  Such a joint boot, particularly a resin joint boot formed using a resin material that is less flexible than a rubber material, is described in Patent Document 3 below when rotated in a bent state at a wide angle. As described above, there is a case where a so-called kink phenomenon (buckling of the peak portion) occurs in which the peak portion of the bellows portion on the large diameter cylindrical portion side bends at the boundary portion between the bent inner side and the bent outer side.

  That is, as shown in FIG. 3, in the joint boot 100 assembled to the outer case 1 and the shaft 2, when the joint angle θ is rotated at a wide angle (for example, 54 °), the large diameter cylindrical portion 102 When the first first peak 104 and the second second peak 106 buckle at the boundary between the bent inner side (left side in FIG. 3) and the outer bent side (right side in FIG. 3) ( There is a phenomenon in which a bent portion indicated by reference numeral 110 occurs.

  Such buckling at the peak portion is particularly likely to occur when the outer shape of the bellows portion is made compact. If the outer shape of the bellows part is small, the step between the peak part and the valley part of the bellows part will be small in order to avoid interference with the shaft. is there. Such buckling is required to be suppressed in order to further improve the durability of the joint boot.

In Patent Document 4 below, the bellows part is composed of a portion near the large-diameter mounting portion, a portion near the small-diameter mounting portion, and a central portion therebetween, and at least one of the valley portion and the mountain portion of the bellows portion. It has been proposed that the relationship between the thicknesses of one of the thicknesses is such that the central portion ≧ the portion close to the large diameter mounting portion> the portion close to the small diameter mounting portion. However, in this document, when the joint boot is bent and deformed by making the rigidity of the central portion of the bellows portion larger than the portion near the large diameter mounting portion or the small diameter mounting portion, the small diameter mounting portion inside the bending In addition to restraining the extension of the small-diameter mounting part, the extension of the small-diameter mounting part prevents the part near the large-diameter mounting part from being crushed more than necessary. is not.
JP 2004-308671 A Japanese Utility Model Publication No. 6-87777 JP-A-4-165121 JP 2002-257152 A

  The present invention has been made in view of the above points, and is a joint boot excellent in durability by suppressing buckling at the peak portion of the bellows portion when rotated in a state bent and deformed at a wide angle. The purpose is to provide.

  The joint boot according to the present invention integrally connects the large-diameter tube portion, the small-diameter tube portion, and the large-diameter tube portion and the small-diameter tube portion. In a joint boot comprising a plurality of valleys including a first peak, a second valley, a second peak, and a third valley, and a bellows portion in which the peaks are alternately continuous, the first peak And the thickness of the second peak is greater than the thickness of the other peaks, and is set to be greater than the thickness of the adjacent first, second and third valleys. It has been done.

  Thus, by making the thickness of the 1st peak part and the 2nd peak part by the side of a large diameter cylinder part larger than the thickness of other peak parts, the rigidity of this 1st peak part and the 2nd peak part Therefore, buckling at the peak portion of the bellows portion when rotated in a state of bending deformation at a wide angle can be suppressed. Moreover, about the 1st-3rd trough part adjacent to these 1st peak part and 2nd peak part, it is desired as a joint boot by making thickness thinner than a 1st peak part and a 2nd peak part. While securing the bent shape, it is possible to effectively increase the thickness of the mountain where buckling is a problem.

  In the above joint boot, when the thickness of the first valley portion, the second valley portion, and the third valley portion is set larger than the thickness of the other valley portions, the following effects are exhibited. That is, in general, this type of joint boot is manufactured by blow molding, and in the blow molding, the mountain portion is stretched more than the valley portion, so it is difficult to increase the thickness only in the mountain portion. Therefore, along with the first and second ridges, increasing the thickness of the first to third valleys adjacent to the first and second ridges can improve the moldability and lead to quality improvement.

  The present invention is particularly effective for a joint boot in which the outer diameter of the first peak portion is set smaller than the outer diameter of the large-diameter cylindrical portion. This is because the problem of buckling at the peak as described above is likely to occur in such a compact boot shape.

  Therefore, the large-diameter cylindrical portion includes a fixing groove for receiving a fastening member, and the fixing groove is connected to the bellows portion via a cylindrical connection portion having a right cylindrical shape. It is more effective against this. That is, as a connecting part that connects the fixing groove and the bellows part, there is a part protruding outward in a mountain shape (see FIG. 1 of the above-mentioned Patent Document 4). Even if the outer diameter of the portion is set smaller than the outer diameter of the large-diameter cylindrical portion, the outer diameter of the first peak portion can be increased by the extent that the connecting portion protrudes, and the compactness is inferior. On the other hand, in the case of a straight cylindrical connecting portion that does not have such a protruding shape, the bellows portion is extremely compact when the outer diameter of the first peak portion is set smaller than the outer diameter of the large-diameter cylindrical portion. Thus, the present invention is particularly effective for such a compact joint boot.

  Further, according to the present invention, the large-diameter cylindrical portion and the small-diameter cylindrical portion each include a fixing concave groove for receiving a fastening member, and the bellows portion side end of the fixing concave groove of the large-diameter cylindrical portion and the above-described This is particularly effective for joint boots in which the axial dimension between the fixing groove of the small diameter cylindrical portion and the bellows portion side end is set smaller than the inner diameter of the large diameter cylindrical portion. Thus, even when the axial dimension is short, it is difficult to secure the development length of each mountain portion (the length along the slope of the mountain from one valley bottom to the other valley bottom of each mountain). This is because it is difficult to absorb bending deformation.

  With the joint boot of the present invention, buckling at the peak portion of the bellows portion when rotating in a state of bending deformation at a wide angle can be suppressed, and durability can be improved.

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

  FIG. 1 is a half cross-sectional side view of a joint boot 10 according to the embodiment, and FIG. 2 is a half cross-sectional view of the joint boot 10. The joint boot 10 is a thermoplastic elastomer resin boot that is attached to a constant velocity joint of an automobile, and includes a large-diameter cylindrical portion 12 attached to the outer case 1, a small-diameter cylindrical portion 14 attached to the shaft 2, and both. It consists of the bellows part 16 connected integrally.

  The large-diameter cylindrical portion 12 has a short cylindrical shape that is fitted and fixed to the outer peripheral surface of the outer case 1, and the outer peripheral surface of the large-diameter cylindrical portion 12 is for receiving a ring-shaped fastening member 3. A fixing groove 18 extending in the circumferential direction is provided over the entire circumference. Further, on the inner peripheral surface, a seal protrusion 20 that fits in a seal groove (not shown) provided on the outer peripheral surface of the outer case 1 is provided over the entire periphery.

  The small diameter cylindrical portion 14 has a short cylindrical shape that is fitted and fixed to the outer peripheral surface of the shaft 2, and the outer peripheral surface of the small diameter cylindrical portion 14 has a circumferential direction for receiving the ring-shaped fastening member 4. An extending fixing groove 22 is provided over the entire circumference. Further, on the inner peripheral surface, a seal protrusion 24 is provided that fits into a seal groove (not shown) provided on the outer peripheral surface of the shaft 2. The small-diameter cylindrical portion 14 is disposed so as to be separated from the large-diameter cylindrical portion 12 and coaxially, that is, to have a common axis O.

  The bellows portion 16 is a bellows body having a circular cross section with a difference in diameter at both ends, and a grease filled space 26 is formed therein. The bellows portion 16 has a first valley portion 30-1, a first peak portion 32-1, a second valley portion 30-2, a second peak portion 32-2,. It consists of a plurality of troughs and crests where troughs and crests are alternately and continuously formed. The outer diameters of the crests and troughs are set so as to decrease sequentially from the large diameter cylindrical part 12 to the small diameter cylindrical part 14, respectively.

  The number of ridges is preferably 5 or more, more preferably 5 to 7, and in this embodiment, the bellows portion 16 includes the first ridge portion 32-1, the second ridge portion 32-2, and the third ridge portion. Six crests including a crest 32-3, a fourth crest 32-4, a fifth crest 32-5, and a sixth crest 32-6, a first trough 30-1, and a second trough 30 -2, 6th valley 6th valley shape consisting of 6th valley part with 3rd valley part 30-3, 4th valley part 30-4, 5th valley part 30-5, and 6th valley part 30-6. ing.

  In this embodiment, each peak part of the bellows part 16 is composed of two peak groups distinguished by the cross-sectional shape. That is, the mountain group 34 near the large-diameter cylindrical portion including the first mountain portion 32-1, the second mountain portion 32-2, and the third mountain portion 32-3, the fourth mountain portion 32-4, and the fifth mountain portion. It is comprised with the mountain group 36 near the small diameter cylinder part which consists of 32-5 and the 6th peak part 32-6. And in the mountain group 36 near a small diameter cylinder part, all the heights of the mountain parts 32-4 to 6 are formed lower than the mountain parts 32-1 to 3 in the mountain group 34 near the large diameter cylinder part. Has been. Moreover, in the mountain group 36 near the small diameter cylinder part, each mountain part 32-4 to 6 is laid on the small diameter cylinder part 14 side, that is, each mountain part 32-4 in the mountain group 36 near the small diameter cylinder part. The inclination angle with respect to the axis O of the large-diameter cylindrical portion 12 side slope of -6 is the inclination angle with respect to the axis O of the large-diameter cylindrical portion 12 side slope of each mountain portion 32-1 in the mountain group 34 near the large diameter cylindrical portion. Is set smaller than.

  In the present embodiment, the outer diameter D1 of the first peak portion 32-1 is set smaller than the outer diameter D0 of the large diameter cylindrical portion 12. Specifically, in the large-diameter cylindrical portion 12, the fixing groove 18 is connected to the bellows portion 16 via a cylindrical connecting portion 38 that surrounds the outer periphery of the distal end portion of the outer case 1 with a space. The cylindrical connecting portion 38 is formed in a right cylindrical shape having no overhanging portion on the radially outer side, and the first valley portion 30 of the bellows portion 16 via a vertical wall portion 40 that falls inward in the radial direction. -1. And the outer diameter D1 of the 1st peak part 32-1 is set small with respect to the outer diameter D0 of this cylindrical connection part 38. As shown in FIG.

  Further, the axial dimension L between the bellows portion side end 18A of the fixing concave groove 18 of the large diameter cylindrical portion 12 and the bellows portion side end 22A of the fixing concave groove 22 of the small diameter cylindrical portion 14 is the large diameter cylindrical portion. 12 is set smaller than the inner diameter D. Here, since both ends of the joint boot 10 are fixed by the fastening members 3 and 4 disposed in the fixing grooves 18 and 22, the axial dimension L is in a range that can be bent and deformed at the time of deformation.

  As described above, the joint boot 10 according to the present embodiment has a compact shape with respect to the outer shape of the bellows portion 16 and the axial dimension. Buckling is likely to occur where the peak portion 32-1 and the second peak portion 32-2 are bent at the boundary between the bent inner side and the bent outer side. In order to eliminate such buckling of the mountain portion, the thickness of each mountain valley is configured as follows in this embodiment.

  The thickness of the 1st peak part 32-1 and the 2nd peak part 32-2 is larger than the thickness of the other peak parts 32-3-6, and the adjacent 1st trough part 30-1, It is set to be larger than the thickness of the second valley portion 30-2 and the third valley portion 30-3. Moreover, the thickness of the 1st trough part 30-1, the 2nd trough part 30-2, and the 3rd trough part 30-3 is set larger than the thickness of the other trough parts 30-4-6. .

  Here, the thickness of the peak is the thickness in the normal direction at the peak (highest point) of the peak, and the thickness of the valley is the normal at the bottom (lowest point) of the valley. The wall thickness in the direction. Further, such a wall thickness setting can be realized by changing the wall thickness at each part in the axial direction when molding the parison and then blow molding it.

  In the present embodiment, more specifically, the thicknesses of the first to sixth peak portions 32-1 to 32-6 are Ta1 to Ta6, respectively, and the first to sixth valley portions 30-1 to 30-6 The wall thicknesses are set as Tb1 to Tb6, respectively, so as to satisfy the following expressions (1) to (3).

Ta1 = Ta2> Ta3 = Ta4 = Ta5 = Ta6 (1)
Ta1 = Ta2> Tb1 = Tb2 = Tb3 (2)
Tb1 = Tb2 = Tb3> Tb4 = Tb5 = Tb6 (3)

  Thus, thickness Ta1, Ta2 of the 1st peak part 32-1 and the 2nd peak part 32-2 by the side of the large diameter cylinder part 12 is made thicker than thickness Ta3-6 of other peak parts 32-3-6. Since it was made large, the rigidity of the 1st peak part 32-1 and the 2nd peak part 32-2 becomes high, and buckling at the time of rotating in the state bent and deformed to the wide angle can be suppressed. Moreover, about 1st-3rd trough part 30-1-3 adjacent to these, other performance is impaired by not increasing the thickness as much as the 1st peak part 32-1 and the 2nd peak part 32-2. In addition, the above buckling can be effectively eliminated while ensuring good moldability during blow molding.

  A joint boot according to an example having the above-described configuration was manufactured and a durability test was performed. In this embodiment, the inner diameter D of the large-diameter cylindrical portion is 86 mm, the outer diameter D0 of the large-diameter cylindrical portion is 94 mm, the outer diameter D1 of the first peak portion is 92, and the fixing concave groove for the large-diameter cylindrical portion and the small-diameter cylindrical portion is fixed. The axial dimension L was set to 82 mm, and the thickness of each peak and valley was set as follows, and a joint boot was produced by blow molding using a thermoplastic polyester elastomer resin.

Ta1 = Ta2 = 1.4mm
Tb1 = Tb2 = Tb3 = 1.2 mm
Ta3 = Ta4 = Ta5 = Ta6 = Tb4 = Tb5 = Tb6 = 1.1 mm

  For comparison, a joint boot of a comparative example was manufactured in the same manner as in the example except that the thickness of all the peaks and valleys was 1.1 mm.

  The obtained joint boots of Examples and Comparative Examples were assembled to constant velocity joints, respectively, and a fixed angle rotation durability test was performed at an ambient temperature = 25 ° C. and a joint angle θ = 54 °. As a result, in the joint boot of the comparative example, buckling occurred in the first peak and the second peak as shown in FIG. 3, whereas in the joint boot of the example, the first peak and the second peak. The part was not buckled and was excellent in durability.

It is a half section half side view of the joint boot concerning the embodiment of the present invention. It is a half sectional view of the joint boot. It is a figure which shows the state which the joint boot is buckling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Joint boot 12 ... Large diameter cylinder part 14 ... Small diameter cylinder part 16 ... Bellows part 18 ... Groove for fixation of a large diameter cylinder part, 18A ... Bellows part side end 22 ... Concave groove for fixation of a small diameter cylinder part, 22A ... Bellow part side end 30-1 ... 1st trough part 30-2 ... 2nd trough part 30-3 ... 3rd trough part 30-4-6 ... Other trough parts 32-1 ... 1st peak part 32-2 ... 2nd peak part 32-3-6 ... Other peak part 38 ... Cylindrical connection part 3, 4 ... Fastening member D ... Inner diameter D0 of large diameter cylindrical part ... Outer diameter D1 of large diameter cylindrical part ... 1st peak part Outside diameter L: Axial dimension between the large diameter cylindrical portion and the small diameter cylindrical portion fixing groove

Claims (6)

A large-diameter cylindrical portion, a small-diameter cylindrical portion, and the large-diameter cylindrical portion and the small-diameter cylindrical portion are integrally connected. The first valley portion, the first peak portion, and the second valley are sequentially connected from the large-diameter cylindrical portion side. In a joint boot comprising a plurality of valley parts including a part, a second mountain part and a third valley part, and a bellows part in which the mountain parts are alternately continuous,
The wall thicknesses of the first peak part and the second peak part are larger than the thicknesses of the other peak parts, and the thicknesses of the adjacent first valley part, second valley part, and third valley part are large. Joint boots characterized by being set larger than.   The joint boot according to claim 1, wherein the thicknesses of the first valley portion, the second valley portion, and the third valley portion are set larger than the thicknesses of the other valley portions.   The joint boot according to claim 1 or 2, wherein an outer diameter of the first peak portion is set smaller than an outer diameter of the large-diameter cylindrical portion.   The said large diameter cylinder part is provided with the ditch | groove for fixation for receiving a clamping member, and this ditch | groove for fixation is connected with the said bellows part via the cylindrical connection part of a right cylindrical shape. Joint boots.   The large-diameter cylindrical portion and the small-diameter cylindrical portion are each provided with a fixing groove for receiving a fastening member, and for fixing the small-diameter cylindrical portion to the bellows side end of the fixing concave groove of the large-diameter cylindrical portion. The joint boot according to any one of claims 1 to 4, wherein an axial dimension between the concave bellows portion side end is set smaller than an inner diameter of the large-diameter cylindrical portion. The joint boot according to any one of claims 1 to 5, wherein the bellows portion has a shape of six peaks and six valleys including six peaks and six valleys.

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