JPH0247764Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> In the present invention, a bellows portion is formed between the large diameter ring portion and the small diameter ring portion, and the bellows portion is located at the first ridge counting from the large diameter. The present invention relates to improvements in the trough in a mechanical shaft joint boot (hereinafter abbreviated as "boot") made of an elastic polymer having a first trough formed between the large-diameter ring portion and the first trough. Such a boot is suitable for, for example, a constant velocity universal joint that connects a drive shaft and an axle of a passenger car. In this specification, the troughs and peaks are numbered (first, second, etc.) counting from the large diameter ring part side. <Prior art> As shown in FIG. 4, a conventional boot 1 for a constant velocity universal joint has a first peak 9 on a bellows portion 7 between a large diameter ring portion 3 and a small diameter ring portion 5. The diameter ring portion 3 was configured to be connected in a straight line. However, as passenger cars have become faster and the passenger spaces of smaller cars have become larger, engine compartments have become smaller. Therefore, the boot of the shaft coupling part is also required to have a small circumferential diameter of the first mountain part 9, that is, a small occupied space (including swingability), and a bellows between the large diameter ring part 3 and the small diameter ring part 5 is required. between the first mountain portion 9 and the large diameter ring portion 3 in the portion 7;
Boots 10 of the type provided with troughs 11 are being put on the market (see FIG. 5, Japanese Patent Laid-Open Publication No. 60-201166). Such boots 10 have general peaks (first, second, third peaks 9, 13, 17) and general valleys (first, second, third peaks 9, 13, 17).
Even if the diameters of the second and third troughs 11, 15, 19) are made smaller, the bellows portion 7 can have a predetermined film length, which satisfies the demand for smaller boots. However, in the boot 10 of the type shown in FIG. 5, there is a risk that damage leading to grease leakage etc. may occur earlier in the first mountain part 9 compared to the boot 1 of the type shown in FIG. 4, and there is a problem in durability. was discovered through research by the present inventors. As shown in FIG. 6, on the compression side, a first
The mountain portion 9 is pinched and crushed, that is,
It is thought that this is because a sharp bending collapse occurs and bending fatigue of the first mountain portion 9 is accelerated. Therefore, in order to prevent such crushing of the first mountain part, for example, the diameter of the first mountain part may be increased (see the above-mentioned Japanese Patent Application Laid-Open No. 60-201166), or the first mountain part as shown in FIG. Boots 20 in which a convex portion 27 is formed on the slope of the back surface of the boot (Utility Application filed in 1983-
No. 62410 (see Utility Model Application Publication No. 62-174122)). <Problems to be solved by the invention> The durability of such boots is certainly improved. Then, as shown in FIG. 8, when the axle 21 crosses, damage occurs on the compression side at the second trough that is pinched and crushed between the first trough 11 and the axle 21. (1st
(see table). Therefore, in a boot for a mechanical shaft joint having a specific configuration in which a convex portion is formed on the back slope portion of the first peak portion in order to prevent the bending fatigue of the first valley portion from accelerating, damage to the second valley portion 15 is prevented. The purpose is to further improve the durability of boots by suppressing the occurrence of such problems. <Means for Solving the Problem> The inventors of the present invention have made extensive studies to achieve the above object, and have come up with the following boots. The space between the large diameter ring part and the small diameter ring part is a bellows part, and the bellows part has a first valley part located between the large diameter ring part and the first peak part counted from the large diameter side. , at least the second trough portion and the first trough portion on the compression side are made of a polymeric elastic material and are subjected to the action of being sandwiched between the shaft and the joint housing during the cross-rotation movement of the boot, and at least the first trough portion is In the boot for a mechanical shaft joint having a configuration in which a convex portion is formed on the slope on the back side near the top of the part, the wall thickness of the slope part on at least one side of the first valley part is approximately the same as that of the remaining slope part. It is characterized by having a thinner wall than the other parts. <Description of Configuration> Hereinafter, an example of the boot of the present invention will be described based on the drawings. Conventional example (Fig. 5), comparative example (Fig. 7)
The same parts as in the boots are given the same reference numerals, and their explanation will be omitted. FIG. 1 is a half-sectional view of a boot 30 according to the present invention,
FIG. 2 is an enlarged sectional view of the vicinity of the first trough 11,
FIG. 3 is an X-ray perspective view when the boot 30 shown in FIG. 1 is attached to a mechanical shaft joint and subjected to cross movement. This boot 30 is different from the boot 20 shown in FIG.
7) and the general valley portions (second and third valley portions 15, 19). For example, as shown in FIG.
When the wall thickness A (the wall thicknesses of the other general peaks and general valleys are also the same) is 2.3 mm, the wall thickness B of the slope portions 29 and 31 on both sides of the first valley portion 11 is 2.0 mm. The ratio B/A between the two is preferably in the range of 0.95 to 0.75. 0.95
If it exceeds 0.75, the following effects will not be obtained, and if it is less than 0.75, problems will arise in the rigidity of the boot, which is not preferable. Furthermore, by making the slope parts 29 and 31 thinner, there is a danger that the swinging performance of the boot, especially the first mountain part 9, will be reduced; There was no difference in the swingability between the boot 30 of FIG. 1 and the boot 20 of FIG. 7, in which the slope portions 29 and 31 were made thinner. Such a thin wall portion may be provided only at one slope portion of the first valley portion 11, or the large diameter side slope portion 2
9 and the small diameter side slope portion 31 may have different degrees of thinness. The thickness of the bottom of the first valley portion 11 was set to the same thickness A as the other general portions. This is because if the bottom part is made thin, buckling deformation occurs at this part during cross motion, and bending fatigue tends to progress (see Fig. 2). Examples of the polymeric elastomer that is the molding material for the boots include synthetic rubbers such as NR, NBR, SBR, BR, and CR, TPEs such as urethane-based, vinyl-based, polyester-based, and olefin-based. <Functions and effects of the invention> As explained above, the boots of the invention have the first
In a boot for a mechanical shaft joint having a specific configuration in which a convex portion is formed on the slope portion on the back side of the mountain portion, since the slope portion of the first valley portion is configured to be thin, the mechanical shaft joint as shown in FIG. On the compression side during cross motion,
When the first trough and the axle sandwich the second trough, the thin sloped surface of the first trough becomes easier to bend due to the reaction force from the second trough. In other words, the surface pressure of the first valley with respect to the second valley is reduced. Therefore, the bending fatigue of the second valley portion on the compression side is reduced, and the progress of wear is also suppressed. In addition, since only the slope portion of the first valley portion is made thin, there is no danger that the swinging ability during the above-mentioned cross motion will deteriorate. Such boots were tested according to the test results (first
As shown in Table 1, the durability is improved compared to the boots shown in Figure 7. <Test Results> The boot 10 shown in Fig. 5 (conventional example), the boot 20 shown in Fig. 7 (comparative example), and the boot 30 shown in Fig.
Durability tests were conducted at 40°. The results were determined based on the total number of rotations (rotational speed x time) of the drive shaft at which the grease in the boot began to leak, and the results are shown in the durability test column of Table 1. Note that the average wall thickness of the general peaks and general valleys is 2.3 mm. From the results in Table 1, it can be seen that the boots of the present invention have approximately 1.5 times the durability of conventional products. In addition, considering that the boot according to the present invention used in the test has thin walls on both slopes of the first valley, the intersection angle of the axle with the drive shaft is set to 3 degrees,
The amount of expansion in the diameter of the first peak was measured when the drive shaft was rotated at a speed approximately eight times faster than in the above durability test. The results are shown in the column of high-speed whirlability test in Table 1. From the results of the high-speed swivel test shown in Table 1, even if the slope part of the first valley (not only both but also one) is thin, it has a negative effect on the swivel performance of the boots of the present invention. It turns out that it does not appear. 【table】

[Brief explanation of the drawing]

The figure shows a boot for a mechanical shaft coupling, Fig. 1 is a half-sectional view showing an example of the boot of the present invention, Fig. 2 is an enlarged sectional view of the vicinity of the first valley, and Fig. 3 is a cross-sectional view of the drive shaft. FIG. 4 is a half-sectional view of the conventional boot in which the first peak is directly connected to the large diameter ring, and FIG. 5 is a half-sectional view of the conventional boot shown in FIG. A half-sectional view of a type of boot in which a first trough is formed between the first peak and the large-diameter ring.
FIG. 7 is a half-sectional view of the boot which is an improved product by the applicant, and FIG. 8 is an X-ray perspective view of the boot of FIG. 7 during movement across the drive shaft. be. 3...Large diameter ring part, 5...Small diameter ring part, 7
... Bellows section, 9 ... First peak, 11 ... First valley, 15 ... Second valley, 30 ... (For mechanical shaft coupling) Boot.

Claims (1)

[Scope of Claim for Utility Model Registration] A bellows portion is defined between the large diameter ring portion and the small diameter ring portion, and the bellows portion is between the large diameter ring portion and the first ridge counted from the large diameter side. The first trough is located in the boot, and at least the second trough and the first trough are sandwiched between the shaft and the joint housing on the compression side during the boot cross-rotation movement. In the boot for a mechanical shaft coupling having a configuration in which a convex portion is formed on the slope on the back side near the top of the first ridge, the wall thickness of the slope on at least one side of the first trough is A boot for a mechanical shaft coupling, characterized in that the wall thickness is thinner than that of the general part including the remaining slope part.