JPH0328189Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a boot for a universal joint that is attached to the universal joint for dust prevention and grease retention.
This invention is particularly suitable for boots such as constant-velocity joint boots used in automobiles, where there is a strong demand for improved durability from the viewpoint of maintenance-free maintenance.

<Prior Art> Here, explanation will be given by taking a constant velocity joint boot as an example, but the same applies to boots for other universal joints.

In recent years, as the living space of automobiles has expanded, the space occupied by the engine compartment has tended to become relatively smaller. Therefore, it is desirable that the boot attached to the constant velocity joint in the engine room be as small as possible without interfering with its function.

Therefore, recent boots have a large-diameter ring portion 1 fitted into the housing 11 of the shaft joint, a small-diameter ring portion 3 fitted onto the drive shaft (shaft portion) 13 of the universal joint, and a space between the two ring portions. As shown in FIGS. 4 and 5, the arrangement of the peaks and troughs of the bellows part is similar to that of the large-diameter ring part. Boots B are being adopted in which the first valley part v1, the first peak part m1, . . . are arranged in this order from the first side.

However, in such a boot, when the constant velocity joint (universal joint) crosses, on the contracting side, the first peak m1 is connected to the shoulder part 2 that connects with the first valley v1 of the large diameter ring part 1. , and the second mountain part m2 and are pressed, so that wear near the top of the first mountain part m1 is likely to be accelerated. This tendency is particularly noticeable in the case of boots assembled to modern constant velocity joints, in which the joint angle (intersection angle) α has been increased in order to reduce the minimum turning radius. At this time, the chamfered shape of the shoulder portion 2 is a curved surface, that is, R, and the size of the R is usually 2
It was ~3.5R.

In order to solve this problem, it is conceivable to make the outer diameter d2 of the first mountain part m1 larger than the outer diameter d1 of the shoulder part 2 of the large diameter ring part 1 (see the two-dot chain line in Fig. 4). However, increasing the diameter is not desirable because it goes against the above-mentioned request for smaller boots, increases the membrane length of the bellows part, and reduces deformation resistance due to grease centrifugal force during high-speed running, so-called swinging performance (especially Publication No. 1986-201166 (Patent application No. 59-56534)
(See No.).

An object of the present invention is to provide a boot for a universal joint that can solve the above problems.

<Means for Solving the Problems> In order to solve the above problems, the present inventor came up with a boot for a universal joint having the following configuration.

It consists of a large diameter ring part that is fitted into the housing of the universal joint, a small diameter ring part that is fitted into the shaft part of the universal shaft, and a bellows part that is interposed between both ring parts,
The arrangement of the peaks and valleys of the bellows part is from the large diameter ring part side to the first valley part, first peak part, etc. Diameter d1
and the outer diameter d2 of the first mountain part, d2/d1=0.9
The boot for a universal joint having a configuration having the relationship of ~1.1 is characterized in that the chamfered shape of the shoulder portion of the large diameter ring portion is a slope, and the slope is a flat surface.

<Example> An example of the present invention will be described below with reference to FIGS. 1 and 2. It should be noted that the same reference numerals are given to the previously described parts in the diagrams, and the explanation thereof will be omitted in whole or in part.

The boots that are the premise of this invention are the 4th to 5th boots mentioned above.
Similar to what is shown in the figure, the arrangement of the peaks and valleys of the bellows portion 5 is in the order of the first valley v1, the first peak m1, . . . from the large diameter ring portion 1 side.

Then, the outer diameter d1 of the shoulder portion 2 connected to the first valley portion v1 of the large diameter ring portion 1 is the outer diameter d2 of the first peak portion m1.
There is a relationship between d2/d1=0.9 and 1.1.
Here, if it is less than 0.9, that is, d2 is small, the membrane length of the bellows part 5 becomes short, the flexibility of the boot itself is reduced, and large stress tends to occur locally which reduces fatigue properties, which is undesirable. If it exceeds 1.1, as mentioned above, it is not desirable because it goes against the demand for smaller boots and reduces the ability to swing during high-speed driving.

In the boot having the above-described prerequisite configuration, the chamfered shape of the shoulder portion 2 of the large diameter ring portion 1 is a flat slope (cut surface) C. The size of this chamfer depends on the wall thickness of the large diameter ring portion 1, but usually,
2 to 6C. If it is less than 2C, it is difficult to achieve the effect of the present invention, that is, the effect of preventing the acceleration of wear at the top of the first mountain part m1, and if it exceeds 6C, the wall thickness from the shoulder part 2 to the bellows part 5 becomes too thin, and the When an impact force such as a flying stone is applied while driving,
This is undesirable as it tends to cause cracks.

Usually, the chamfered shape of the shoulder portion is set to a size corresponding to or slightly larger than the radius when the conventional chamfered shape of the shoulder is made into a curved surface, and the chamfered angle β is set to 30 to 60°.

These boots are molded by blowing, injection blowing, injection, etc. using an elastic polymer as a molding material. Polymer elastomer materials include NR, NBR,
Examples include rubber materials such as SBR, BR, and CR, and thermoplastic elastomers such as urethane-based, vinyl-based, polyester-based, and olefin-based elastomers.

Next, how to use the above boots will be explained.

In the same manner as described above, when assembled to a constant velocity joint boot, that is, when mounted on an actual vehicle, the drive shaft 1
3 makes a cross movement as in the past, but during the cross movement, the wall thickness at the shoulder part 2 of the large diameter ring part 1 is thinner than in the past, so the flexibility of the shape of the bellows part increases. It is difficult to generate large stress locally on the bellows part. In addition, since the chamfered shape of the shoulder portion 2 is a flat slope C, the first peak m1 is located between the shoulder portion 2 and the second peak m2 on the contraction side of the bellows portion, as in the conventional case. Even if it is pinched and pressed, the contact portion of the first mountain portion m1 with the shoulder portion 2 slides on the flat slope C formed on the shoulder portion 2, and the surface pressure is dispersed (see Fig. 2). These two factors combine to prevent the acceleration of wear on the first mountain portion m1.

<Actions and effects of the invention> As described above, the boot for a universal joint of the invention has the following features:
The arrangement of the peaks and valleys of the bellows part is in the order of the first valley, the first peak, and so on from the large-diameter ring side, and the arrangement of the peaks and valleys of the bellows part is in the order of the first valley, the first peak, and so on. Between the outer diameter d1 and the outer diameter d2 of the first peak, d2/d1=
A boot for a universal joint having a relationship of 0.9 to 1.1, characterized in that the shoulder chamfered shape of the large diameter ring part is a flat slope,
It has the following actions and effects.

When mounted on an actual vehicle, the drive shaft makes a cross movement as before, but during the cross movement, the wall thickness at the shoulder of the large diameter ring is thinner than before, so the shape of the bellows part can be freely shaped. This increases the elasticity of the bellows, making it difficult for local stress to occur in the bellows portion, which reduces fatigue resistance. In addition, since the chamfered shape of the shoulder part is a flat slope, the first peak part on the contraction side of the bellows part is
Even if it is pinched and pressed between the shoulder part and the second mountain part,
The contact portion of the first mountain portion with the shoulder portion slides on the slope formed on the shoulder portion, and surface pressure is dispersed. Both of these factors work together to prevent accelerated wear of the first mountain portion. Therefore, the durability of the boots is improved and it becomes easier to meet maintenance-free requirements.

By the way, in the boots having the basic configuration shown in Fig. 1, a durability test was conducted under the following conditions with the chamfered shape of the shoulder part as a flat slope C or a curved surface R as shown in the example shown in Fig. 3. The results are shown below. In both cases, it can be seen that the slope with a flat chamfered shape has improved durability compared to the curved surface.

Conditions: Maximum crossing angle 40° Rotation speed 300rpm Atmosphere temperature Room temperature

[Brief explanation of drawings]

Fig. 1 is a half-sectional view showing an example of the boot of the present invention, Fig. 2 is a partial X-ray perspective view of the boot shown in Fig. 1 during cross-driving motion, and Fig. 3 shows the results of a durability test of the boot. FIG. 4 is a half-sectional view showing an example of a conventional boot, and FIG. 5 is a partial X-ray perspective view of the boot shown in FIG. 4 during movement across the drive shaft. DESCRIPTION OF SYMBOLS 1... Large diameter ring part, 2... Large diameter ring part shoulder part, 5... Bellows part, 11... Housing, 13...
...Shaft part (drive shaft), m1...First mountain part, m2...
Second peak, v1...first valley, C...flat slope, R...curved surface.

Claims (1)

[Scope of Claim for Utility Model Registration] From a large diameter ring part fitted into the housing of the universal joint, a small diameter ring part fitted into the shaft part of the flexible shaft, and a bellows part interposed between the two ring parts. The arrangement of the peaks and valleys of the bellows part is in the order of the first valley, the first peak, etc. from the large diameter ring part side, and is connected to the first valley of the large diameter ring part. The boot for a universal joint is configured such that an outer diameter d1 of the shoulder of the large diameter ring portion has a relationship of d2/d1=0.9 to 1.1 with an outer diameter d2 of the first mountain portion, the shoulder of the large diameter ring portion A boot for a universal joint, characterized in that the chamfered shape of the portion is a slope, and the slope is a flat surface.