JPH0237287Y2 - - Google Patents

Description

[Detailed Description of the Invention] 1. Purpose of the Invention (a) Field of Industrial Application The present invention relates to a flexible boot with a vent hole that is attached to a constant velocity joint used in, for example, a drive shaft of an automobile.

(B) Prior Art A flexible boot seals and retains grease used for lubricating a constant velocity joint, and prevents dust, water, etc. from entering the joint from the outside. As shown in FIG. 4, the flexible boot 1 is made up of a large-diameter mounting portion 2, a small-diameter mounting portion 3, and a bellows portion 4 located between them. The large diameter side mounting portion 2 is a joint outer ring 5.
In addition, the small diameter side mounting part 3 is connected to the shaft, that is, the shaft 6.
and are each further tightened and fixed by a coupling band or boot band 7. Constant velocity joints generate heat when fixed, reaching temperatures of approximately 50 to 80 degrees Celsius, and the ambient temperature rises due to radiant heat from the engine, which can reach a maximum of 130 degrees Celsius or more.
As a result, the temperature inside the flexible boot also increases.
Temperatures may exceed 100℃. When the temperature inside the flexible boot rises, the internal pressure also rises, and this internal pressure causes the flexible boot to expand and cause damage due to interference with surrounding components, or if the temperature rise is rapid, the bellows part may burst.

In addition, materials such as rubber and resin used in flexible boots have gas permeability, and the larger the pressure difference between the inside and outside of the flexible boot and the higher the temperature, the more gas permeates. Therefore, when the internal pressure of the flexible boot increases due to the heat generated by the joint, air passes through the bellows portion and escapes from the inside to the outside.
The amount of permeation (escape) varies depending on the temperature, pressure, and time the internal pressure has been rising. When the constant velocity joint stops rotating, the temperature inside the flexible boot decreases, and air permeates from the outside to the inside, contrary to when the boot is in operation. However, because the temperature of the flexible boot is low, the amount of air passing through (escaping) is the same as above. It takes a considerable amount of time for a large amount of air to enter compared to the time required for it to escape. Therefore, as the temperature decreases after the special speed joint stops rotating, negative pressure is generated within the boot over time. This negative pressure corresponds to the amount obtained by subtracting the amount of air permeated due to the temperature drop from the amount of air permeated due to the temperature increase. When this negative pressure reaches a negative pressure that causes a dent in the flexible boot, the flexible boot will dent in the crest of the bellows portion, as shown in FIG. Therefore, when the constant velocity joint, that is, the shaft, starts to rotate again, the flexible boot rotates in a recessed state, and when the operating angle is reached (Fig. 6), the aforementioned flexible boot is inserted between the shaft 6 and the joint outer ring 5. A problem arises in that they bite into the dented part and damage it. As a means to prevent damage to the flexible boot due to pressure increase inside these joints, a ventilation groove 8 or a small hole, that is, a vent hole 9, which communicates between the inside and outside of the flexible boot is provided, or the ventilation groove 8 and the vent hole 9 are used together to function as a breather. There is something that has this.

(C) Problems with the Prior Art The constant velocity joint boot shown in FIG. 7 is a flexible boot with a vent hole, which has an axial groove 8 on the inner surface of the small-diameter fitting portion to communicate between the inside and outside of the boot. However, since the small-diameter fitting portion is fixed to the shaft by the boot band 7, the cross-sectional shape of the ventilation groove changes depending on the shape of the boot band 7 and the magnitude of the tightening force. In general, the cross-sectional shape is such that even when the boot band is tightened, it maintains a size that allows sufficient communication between the inside and outside, but if the boot band tightening force is small, there will be little change in the groove cross section, and grease leakage will increase. . Furthermore, if the tightening force is large, the groove will close and the breather function will be lost.

A flexible boot with a vent hole for a constant velocity joint shown in FIG. 8 has a small hole 9 in a small diameter cylindrical portion to allow communication between the inside and outside of the boot. However, when a flexible boot has an operating angle on its bellows surface, large tensile stress and compressive stress are repeatedly applied during rotation. Therefore, the small diameter cylindrical part is short,
If the small hole is close to the curved portion extending from the cylindrical portion to the first peak, stress concentration occurs in the peripheral portion of the small hole due to the notch effect, leading to breakage. Furthermore, even if no damage occurs, the small holes are deformed and a stable breather function cannot be maintained.

In addition, in order to place the small hole in a position where no stress is applied to the periphery of the small hole, the cylindrical part must be made long, and as a result, the installation space for the flexible boot must be larger than necessary. There is a problem.

The constant velocity joint boot shown in FIG. 9 has a subchamber 10 at the end on the small diameter side, communicates the constant velocity joint part and the subchamber with a groove 8 provided on the small diameter inner surface, and further connects the subchamber and the outside with the subchamber 10. The chambers are communicated with each other through a small hole 9 provided in the chamber.

As shown in Figure 7, the groove on the small diameter inner surface does not deform because it is not tightened by the connecting band, and the small hole provided in the subchamber is not affected by the deformation of the flexible boot, so it exhibits a stable breather function. There is no problem of breakage from the small hole. However, compared to a general boot, the boot becomes extremely large due to the provision of the sub-chamber, and there is a problem in that a large installation space is required. This is a particularly important issue since flexible boots used in automobiles are required to be compact.

(d) Problems with the invention The present invention is a flexible flexible motor with a vent hole that maintains a stable breather function, prevents the strength from decreasing due to the vent hole, and prevents an increase in space due to the provision of the vent hole. The purpose is to provide boots.

2. Structure of the invention (a) Means for solving the problem The invention consists of a small diameter cylindrical part of a flexible boot,
A small protrusion that goes around the circumference of the flexible boot is provided on the cylindrical part side of the R portion extending from the small diameter side to the first peak, and a vent hole is provided on the small diameter side of the small protrusion,
In addition, the outer entrance of the cylindrical portion of the vent hole is housed within the small diameter shaft fitting device.

(B) Effect Since the vent hole part is located in the small diameter shaft fitting device fitted to the shaft, in other words, this cylindrical part is fixed to the shaft, so it is not subject to deformation or stress during rotation. . Further, when the operating angle is increased, the stress and strain on the bellows portion of the flexible boot have a distribution as shown in FIG. 3B. This is because stress is concentrated in the recesses formed by the aforementioned small protrusions. Therefore, stress and strain applied to the vent hole portion can be reduced as much as possible.

(C) Embodiment As shown in FIG. 1, the present invention also includes a portion of the small diameter side cylindrical portion 12 of the flexible boot and a portion of the R portion, that is, the curved portion that continues from the small diameter side to the first peak of the bellows portion. A small annular protrusion 11 is provided that goes around the circumference of the flexible boot, and a vent hole 9 is provided at a position closer to the small diameter side than the small protrusion, that is, at a position away from the bellows part, and an outer opening of the vent hole is provided. It is provided within the small diameter shaft fitting range (portion L in FIG. 1) on the outer surface of the small diameter side cylindrical portion. As mentioned above, the small protrusion 11 is connected to the small diameter side cylindrical portion 1.
It is important that the groove be present on the surface of 2 and also extend to the curved part from the small diameter side cylindrical part to the first mountain.

In the embodiment shown in FIG.
An annular recess 13 was provided in the recess 0, and an outer opening of the vent hole 9 was opened in the recess to clarify the processing position of the vent hole.

The aforementioned small diameter cylindrical portion 12 refers to a cylindrical portion on the outer peripheral surface of the small diameter attachment portion 3 that extends toward the bellows portion side from the recess into which the coupling band 7 is fitted.

The small diameter side mounting part 3 of the vent hole 9 is connected to the shaft 6.
Since it is fixed in the area where it fits with the small diameter shaft, that is, the small diameter shaft fitting area L, it is not subjected to deformation or stress during rotation. If the vent hole 9 protrudes from L, there will be no effect. Further, as shown in FIG. 6, the stress state of the bellows part when the operating angle is set is as shown in FIG. 10B for the conventional device, and as shown in FIG. 3B for the device of the present invention. The vertical axis shows the stress, and the horizontal axis shows the position on the flexible boot.
As will be seen, in the present invention, due to the presence of the annular protrusion 11, stress is concentrated in the recess 14 between the annular protrusion and the first peak of the flexible boot. Therefore, stress and strain applied to the vent hole 9 portion are reduced as much as possible. A vent hole 9 exists between the position l _p and the position l _x , and the stress acting there is very small.

3 Effects of the invention As described above, according to the invention, since the vent hole part is fixed to the shaft, deformation of the vent hole can be prevented, and a small protrusion that goes around the circumference of the flexible boot is provided. This prevents the stress and strain of the bellows portion from acting on the periphery of the vent hole, thereby maintaining a stable breather function and preventing damage due to stress concentration on the periphery of the vent hole. Furthermore, since stress and strain can be prevented from acting on the cylindrical portion side by the small protrusions, an unnecessarily long cylindrical portion is unnecessary, and a compact flexible boot can be designed.

[Brief explanation of the drawing]

Figures 1 and 2 are partial sectional views of the small-diameter end of a flexible boot according to the present invention, and Figures 3A and 3B are partial cross-sectional views of the small-diameter end of a flexible boot according to the present invention, respectively. FIG. 4 is a cross-sectional view of a conventional flexible boot attached to a constant velocity joint when not in operation, and FIGS. 5 and 6 are diagrams and graphs showing the corresponding stress. 7, 8, and 9 are schematic cross-sectional views of a part of a conventional flexible boot with a vent hole, and FIGS. 10A and 10B are schematic cross-sectional views of a small diameter end of a conventional flexible boot, respectively. 1 is a schematic diagram showing positions and corresponding stresses; 1... Flexible boot, 2... Large diameter side mounting part, 3... Small diameter side mounting part, 4... Bellows part, 5...
Joint outer ring, 6...shaft, 7...coupling band, 8...ventilation groove, 9...vent hole, 10
... subchamber, 11 ... small projection, 12 ... small diameter side cylindrical portion, 13 ... recess, 14 ... recess.

Claims (1)

[Scope of utility model registration request] Fix the large diameter side mounting part 2 to the joint outer ring 5,
In a flexible boot with a vent hole for a constant velocity joint, in which the small diameter side mounting part 3 is fixed to a shaft 6 fixed to the inner ring of the joint, and the inside and the outside are communicated to provide a breather function, the cylinder of the small diameter side mounting part A small annular protrusion 11 is provided that covers a part of the part 12 and a part of the curved part extending from the cylindrical part to the first peak of the bellows part of the flexible boot, and goes around the circumference of the flexible boot. A flexible boot with a vent hole, characterized in that a vent hole 9 having an outer opening is provided on the small diameter side of the small protrusion, and the outer opening of the vent hole is located within the shaft fitting range L on the small diameter side.