JPH0826900B2 - Boots for constant velocity joints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boot for a constant velocity joint.

[Prior Art] A constant velocity joint is generally used for a drive wheel axle of an automobile. As shown in FIG. 5, the boot 20 equipped in this type of constant velocity joint has an annular large-diameter fitting portion 21 and an annular small-diameter fitting portion 22 provided at both ends. The bellows portion 23 for absorbing the deformation of the boot 20 due to the swing of the driven shaft is provided between the spaces. Conventionally, chloroprene rubber was generally used as the material of the boot 20, but in recent years, thermoplastic elastomers such as polyester resins and polyolefin resins have been adopted as alternative materials for the purpose of maintenance-free, lightweight, high speed, etc. Have begun.

Further, in the boot made of a thermoplastic elastomer, the bellows portion 23 is formed so that the wall thickness thereof is substantially the same on the large diameter side and the small diameter side. Further, the height difference A between the peaks 23a and the valleys 23b of the bellows portion 23 is also formed to be substantially the same from the large diameter side to the small diameter side.
That is, the film length between the top of each crest 23a and the bottom of each valley 23b is formed to be substantially the same from the large diameter side to the small diameter side.

[Problems to be Solved by the Invention] The conventional boot 20 made of a thermoplastic elastomer has smaller flexibility than that of a boot 20 using chloroprene rubber as a material. Therefore, as shown in FIG. 6, the joint angle θ
When the driven shaft 24 is rotated to a position where the value of (the angle formed by the shaft center of the driven shaft 24 and the shaft center of the drive shaft (not shown)) increases, a specific portion on the large diameter side of the bellows portion 23. In the above, a so-called kink phenomenon occurs in which the boundary between the tension side and the compression side is bent. Therefore, as the driven shaft 24 swings, the same portion of the bellows portion 23 is repeatedly bent, and this portion is likely to be damaged early due to fatigue, which shortens the durability (life) of the boot 20. There is. The specific portion varies depending on the number of peaks that the bellows portion 23 has, and the large-diameter fitting portion is included in the peak.
Numbering 1, 2, 3, ... from the 21st side in order, the number 2 is when the number of mountains is 4 and the number 2 and 3 when the number of mountains is 5 and 6.
When the number of crests is 7, the kink phenomenon occurs in the crests of 2, 3, and 4.

The following can be considered as the cause of the kink phenomenon occurring at a specific position on the large diameter side. When the driven shaft 24 is rotated to a position where the value of the joint angle θ increases, the crests 23a on the tension side of the bellows part 23 (especially the crests 23a on the large diameter side) are fitted to the small diameter fitting part 22.
Moves greatly to the side. On the compression side, the valley on the large diameter side
The second valley 23b from the large-diameter fitting portion 21 of 23b first comes into contact with the driven shaft, and then the third valley 23b comes into contact with it, resulting in the state shown in FIG. 7 (b). FIG. 7 (b)
The force in the arrow direction acts on the valley 23b in accordance with the clockwise rotation of the. Therefore, in the state where the driven shaft 24 is arranged at a predetermined position, as shown in FIG. 7 (a), the second and third valleys are formed.
23b becomes parallel to the end face of the joint body 25, and the deformation becomes large. Then, stress concentration occurs at the boundary between the tension side and the compression side of the bellows portion 23, and the bellows portion 23 is bent at that portion.

The present invention has been made in view of the above problems, and an object thereof is to use a thermoplastic elastomer as a material for a boot even if the driven shaft is swung to a position where the joint angle has a large value. An object of the present invention is to provide a constant velocity joint boot capable of reliably preventing a kink phenomenon due to stress concentration from occurring at the boundary between the tension side and the compression side of the bellows part.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, an annular large-diameter side end portion attached to a joint body, an annular small-diameter side end portion attached to a driven shaft, and an intermediate portion therebetween. The provided bellows part is integrally formed with a thermoplastic elastomer, the number k of the peaks of the bellows part is 4 to 7, and each peak is provided with a number N starting from 1 in order from the large diameter side of the bellows part. When attached, the film length between at least one crest and the bottom of a valley with a number satisfying 2 ≦ N <(k + 1) / 2 is N ≧ (k +
All the numbers satisfying 1) / 2 were made shorter than the film length between the top of the peak and the bottom of the valley.

[Operation] In the boot of the present invention, when the driven shaft is swung to a position where the joint angle is large, the small-diameter side portion of the bellows, which is unlikely to cause the kink phenomenon, is greatly deformed, and the deformation of the boot is absorbed. The deformation of the large-diameter side portion of the bellows portion where the kink phenomenon easily occurs is small. Then, the difference in deformation degree between the tension side and the compression side in the large-diameter side portion of the bellows portion where the kink phenomenon is likely to occur becomes small, stress concentration at the boundary between the two is reduced, and the kink phenomenon is prevented from occurring.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 to 3, the boot 1 has an annular large-diameter side end 3 attached to a joint body 2 (shown in FIGS. 2 and 3) of a constant velocity joint, and an annular small diameter attached to a driven shaft 4. It is composed of a side end portion 5 and a bellows portion 6 provided therebetween. The boot 1 is made of a thermoplastic elastomer such as polyester resin or polyolefin resin,
The whole is integrally formed by a molding method such as blow molding, injection molding, or injection blow molding.

The bellows portion 6 has five ridges 6a and five valleys 6b. When the boot 1 is cut along a plane including its center line, the tops of the respective ridges 6a and the bottoms of the respective valleys 6b are substantially aligned with each other. It is formed such that the distance between the existing straight line passing through the bottom of each valley 6b and the top of each crest 6a increases toward the small-diameter side end 5 side. That is, the film length between the top of the peak 6a and the bottom of the valley 6b is formed so as to be closer to the small-diameter side end 5.

The boot 1 configured as described above is mounted between the joint body 2 and the driven shaft 4 in a compressed state on the small diameter side of the bellows portion 6 instead of the free state shown in FIG.

As described above, the boot 1 includes the joint body 2 and the driven shaft 4.
When the driven shaft 4 is rotated to a position where the joint angle θ has a large value (θ = 40 °), the bellows part 6 has a peak 6a and a valley 6b at the bottom. Since the film length between them is formed so as to be closer to the large-diameter side end portion 3, the bellows portion 6 is formed.
On the tensile side, unlike the conventional case shown by the chain line, the large-diameter side deformation is suppressed, and the small-diameter side that was in the compressed state expands, and most of the deformation on the entire tensile side is absorbed. Therefore, the deformation of the large diameter side portion is small.

On the other hand, on the compression side of the bellows portion 6, unlike the conventional case, the second and third valleys 6b close to the large-diameter side end portion 3 do not come into contact with the driven shaft 4 before the valleys 6b on the smaller diameter side, Third
As shown in the figure, when the valley 6b on the small diameter side is almost the same, the driven shaft 4
It comes into contact with. Therefore, each valley 6b of the bellows portion 6 receives a uniform pressing force from the driven shaft 4 and is close to the large diameter side end portion 2.
The force pressing the valley 6b downward in FIG. 3 does not act on the third and third valleys 6b. Therefore, unlike the conventional 2
The abnormal deformation such that the second and third valleys 6b are crushed is prevented, and the deformation on the compression side is reduced.

Therefore, at the second and third peaks 6a near the large-diameter side end portion 3 where the kink phenomenon is likely to occur, the degree of deformation between the tension side and the compression side is reduced, and the boundary between the tension side and the compression side is reduced. Stress concentration is reduced and the occurrence of the kink phenomenon is prevented.

The present invention is not limited to the above-described embodiment, and for example, instead of forming the film length between the tops of the peaks 6a and the bottoms of the valleys 6b of the bellows part 6 closer to the small-diameter side end 5, the fourth film is formed. As shown in the figure, the film length between the top of the peak 6a and the bottom of the valley 6b where the kink phenomenon is likely to occur is shorter than the film length between the top of the peak 6a and the bottom of the valley 6b on the smaller diameter side of the peak 6a. You may form.
Further, the number of the peaks 6a of the bellows portion 6 is not limited to 5, but may be 4 to 7. In that case, 1 for each mountain 6a in order from the large diameter side of the bellows part 6.
If the number N starting from is added, N is 2 ≦ N <(k +
1) The film length between the top of at least one peak 6a and the bottom of the valley 6b satisfying / 2 is calculated from the film length between the top of every th peak and the bottom of the valley satisfying N ≧ (k + 1) / 2. Form short. Here, k represents the number of peaks 6a included in the bellows portion 6.

[Effects of the Invention] As described in detail above, according to the present invention, stress concentration occurs at the boundary between the tension side and the compression side of the bellows portion of the boot even when the driven shaft is swung to the position where the joint angle has a large value. It is possible to reliably prevent the occurrence of a kink phenomenon caused by, and to prevent early fatigue of a specific portion of the bellows portion, thereby improving the durability of the boot.

[Brief description of drawings]

1 to 3 show an embodiment embodying the present invention.
The figure is a partially cutaway front view of the boot, FIG. 2 is a front view of the boot when the driven shaft is arranged at a position where the joint angle has a large value, FIG. 3 is its sectional view, and FIG. Partial front view of the boot, FIGS. 5 to 7 show a conventional example, FIG. 5 is a partially cutaway front view of the boot, and FIG. 6 is the boot when the driven shaft is arranged at a position where the joint angle has a large value. FIG. 7 (a) is a sectional view thereof, and FIG. 7 (b) is a partial sectional view showing the relationship between the bellows portion and the driven shaft during movement of the driven shaft at a position where the joint angle has a large value. It is a figure. 1 ... boots, 2 ... joint body, 3 ... large diameter side end, 4 ... driven shaft, 5 ... small diameter side end, 6 ... bellows,
6a ... mountain, 6b ... valley, θ ... joint angle.

Claims (1)

[Claims] 1. An annular large-diameter side end (3) attached to a joint body (2), an annular small-diameter side end (5) attached to a driven shaft (4), and a bellows provided therebetween. The part (6) is integrally formed of a thermoplastic elastomer, and the number k of the peaks (6a) of the bellows part (6) is set to 4 to 7, and each peak (6a) has a bellows part (6). When a number N starting from 1 is attached in order from the large diameter side, 2 ≦ N <(k + 1)
The film length between the top of at least one peak (6a) and the bottom of the valley (6b) satisfying / 2, the top and the valley of all peaks (6a) satisfying N ≧ (k + 1) / 2 A boot for a constant velocity joint, which is shorter than the film length between the bottoms of (6b).