JP2005344851A - Structure of seal, and spider joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a seal, which can show stable and sure sealing performance even if a shrink range of the seal scatters, and further to provide a spider joint. <P>SOLUTION: Lip portions are composed of two cylindrical axial lips 421, 422 alone (Radial lips are not provided.), which extend respectively by different lengths in the axial direction of a seal 4. In addition, a conical neck tilting surface portion 221 making an angle of 45° with respect to the axis is provided at a neck portion 22 of the spider 2. The two axial lips 421, 422 are brought into pressure contact with the conical neck tilting surface portion 221 from the axial direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a seal structure, and more particularly to a seal structure for a cross joint.

  For example, universal joints used in automobile drive shafts and steering devices require muddy water splashing from tires and muddy water splashing from the road surface. FIG. 13 is a front view (partially sectional view) showing the cross joint 1 as a main member constituting such a universal joint. In the figure, bearing cups 3 are mounted on the four raceways 21 of the cross shaft 2. The bearing cup 3 includes needle rollers 32 inside the cup 31, and the cup 31 is rotatable with respect to the raceway portion 21. A circumferential groove 3a is formed on the outer peripheral surface of the cup 31 (in addition, there is a type of cup without the circumferential groove 3a). A ring-shaped seal 4 is attached to the end of the bearing cup 3, thereby sealing the gap between the neck portion 23 of the cross shaft 2 and the cup 31.

  FIG. 14 is an enlarged view of the XIV portion of FIG. 13 (see Patent Documents 1 to 3, for example, for a similar structure). In the figure, the cross shaft 2 includes a neck portion 23 for pressing the seal 4 on the base side of the track portion 21. In the cross-sectional shape shown in the figure, the neck portion 23 has a straight portion 231 that is parallel to the central axis of the track portion 21 (three-dimensionally cylindrical), and a steep angle with respect to the straight portion 231 (for example, about 75). A neck slope portion 232 having a linear shape (in a three-dimensional conical shape) and a neck R portion 233 formed in an arc shape in the middle thereof. On the other hand, the seal 4 includes a metal ring body 41 that is press-fitted and fixed to the cup 31, and a rubber seal body 43 that is integrally formed with the metal ring body 41. Although the seal body 43 is shown in a free state, it is actually pressed against the cross shaft 2 and elastically deformed.

  The seal body 43 includes an axial lip 43 a pressed against the neck slope portion 232 and a radial lip 43 r pressed against the straight portion 231. In the case of this seal 4, the extending direction of the axial lip 43 a is, for example, about 25 degrees and the extending direction of the radial lip 43 r is, for example, about −40 degrees with respect to the central axis of the track portion 21.

In order to attach the cross shaft 2 to a yoke (not shown), after inserting the track portion 21 into the hole of the yoke, the bearing cup 3 (with the seal 4 press-fitted) is mounted on the track portion 21. Then, by fitting a retaining ring (not shown) in the circumferential groove 3a of the two bearing cups 3 at both ends of the single shaft, the cross joint 1 and one yoke are connected. The other yoke is connected in the same manner.
By connecting as described above, the bearing cup 3 is pushed to a predetermined axial position with respect to the cross shaft 2, and the axial lip 43 a is pressed against the neck inclined surface portion 232 by a predetermined tightening allowance. It is done. Further, the radial lip 43r is pressed against the straight portion 231 regardless of the fastening allowance. Thereby, a seal structure with mud water resistance is realized.

JP 2002-106594 A (pages 2 and 3, FIGS. 1 and 2) Japanese Utility Model Publication No. 53-88646 (Fig. 1) JP-A-11-223223 (pages 4-5, FIGS. 1-8)

  In the conventional cross shaft joint as described above, the relative axial position of the bearing cup 3 with respect to the cross shaft 2 is determined by the positional relationship with the yoke, and the tightening allowance of the seal 4 is determined. However, due to dimensional tolerances and assembly tolerances of each member, it is difficult to maintain the tightness of the seal 4 at a strictly constant value, and there are actually variations. Since the axial lip 43a is pressed against the steep neck slope portion 232, the way of hitting is considerably different even if the axial position is slightly changed. As a result, there is a problem that the muddy water resistance is not stable. On the other hand, as long as the radial lip 43r is pressed against the straight portion 231, the above-mentioned variation does not become a problem, but in the case of the maximum error, it may be pressed against the neck R portion 233. By pressing against the neck R portion 233, sufficient sealing performance cannot be obtained.

  In view of the conventional problems as described above, it is an object of the present invention to provide a seal structure and a cross joint that exhibits stable and reliable sealing performance even if there is variation in the tightening allowance of the seal.

The seal structure of the present invention has a ring shape as a whole, and the lip portion is positioned coaxially with the seal composed of only a plurality of cylindrical axial lips extending in the axial direction by different lengths. A conical surface, and a portion to be sealed that contacts the conical surface with the plurality of axial lips from the direction of the central axis.
In the sealing structure as described above, the plurality of cylindrical axial lips pressed against the conical surface from the central axis direction obtains a pressing force in the axial direction and the radial direction, and the sealing performance is ensured. . Such a seal structure has a small change in contact surface pressure distribution with respect to a change in seal tightening allowance.

The seal structure of the present invention is generally ring-shaped, has a seal having an axial lip extending substantially parallel to the axial direction, is positioned coaxially with the seal, and is approximately 45 with respect to the central axis. It may have a conical surface inclined at an angle, and a sealed portion that makes the axial lip contact the conical surface from the central axis direction.
In the sealing structure as described above, the axial lip pressed from the central axis direction against the conical surface inclined by approximately 45 degrees obtains a pressing force in the axial direction and the radial direction, and the sealing performance is ensured. . Such a seal structure has a small change in contact surface pressure distribution with respect to a change in seal tightening allowance.

Further, the cross shaft joint of the present invention includes a cross shaft in which a conical neck slope portion inclined at a predetermined angle with respect to the shaft of the track portion is formed on the base side of the track portion, and a bearing attached to the track portion. The cup and the bearing cup are mounted in a ring shape as a whole, and the lip portion that is brought into contact with the neck inclined surface portion from the central axis direction is composed of only a plurality of cylindrical axial lips extending in the axial direction. And a seal.
In the cross shaft joint as described above, a plurality of cylindrical axial lips pressed against the neck inclined surface from the central axis direction obtains a compressive force in the axial direction and the radial direction to ensure sealing performance. Is done. Such a cross joint has a small change in the contact surface pressure distribution with respect to a change in the tightening margin of the seal.

In addition, the cross joint of the present invention is attached to the cross section in which a conical neck inclined surface portion inclined approximately 45 degrees with respect to the axis of the track section is formed on the base side of the track section, and the track section. A bearing cup, and a seal that is attached to the bearing cup and has a ring shape as a whole, and a lip portion that comes into contact with the neck inclined surface portion from its central axis direction, and that includes an axial lip extending substantially parallel to the axial direction. It may be provided.
In the cross shaft joint as described above, the axial lip pressed from the central axis direction against the neck inclined surface inclined approximately 45 degrees obtains a pressing force in the axial direction and the radial direction, thereby ensuring the sealing performance. Is done. Such a cross joint has a small change in the contact surface pressure distribution with respect to a change in the tightening margin of the seal.

  According to the seal structure or the cross joint of the present invention, the change in the contact surface pressure distribution is small with respect to the change in the seal tightening allowance. Therefore, it is possible to provide a seal structure that exhibits stable and reliable sealing performance even if there is variation in the tightening allowance of the seal.

  FIG. 1 is a front view (partially sectional view) showing a cross joint 1 according to an embodiment of the present invention. The cross joint 1 is a main member constituting a universal joint used in, for example, a drive shaft and a steering device of an automobile. In the drawing, the cross shaft 2 composed of two axes in the X and Y2 directions has four track portions 21, and a bearing cup 3 is attached to each track portion 21. The bearing cup 3 includes needle rollers 32 inside the cup 31, and the cup 31 is rotatable with respect to the raceway portion 21. Moreover, the circumferential groove 3a is formed in the outer peripheral surface of the cup 3 of this example (There is also a type without the circumferential groove 3a). A ring-shaped seal 4 is attached to the end of the bearing cup 3 as a whole, thereby sealing the gap between the neck portion 22 of the cross shaft 2 and the cup 31, and muddy water and dust inside the cup 31. Is prevented from entering. Here, the track portion 21, the neck portion 22, the seal 4 and the bearing cup 3 are in a coaxial relationship with each other.

  FIG. 2 is an enlarged view of a portion II in FIG. In the drawing, the cross shaft 2 includes a neck portion 22 as a “sealed portion” for pressing the seal 4 on the base side of the track portion 21. The solid line indicates the shape of the neck portion 22 of the present embodiment, and the two-dot chain line indicates the shape of the conventional neck portion (FIG. 14). In the cross-sectional shape shown in the figure, the neck portion 22 has a neck slope portion 221 that is a straight line (conical surface inclined 45 degrees in three dimensions) inclined 45 degrees with respect to the central axis (X axis) of the track portion 21, The upper and lower ends are formed by neck R portions 222 and 223 formed in an arc shape. In addition, the straight part for making the seal | sticker 4 press-contact from the radial direction outer side like the past is not provided. Due to the absence of the straight portion, even if the neck slope portion 221 inclined 45 degrees as described above is provided, the dimensions of the entire neck portion 22 in the X and Y directions are within the conventional size range. In other words, by eliminating the conventional straight portion, it is possible to provide the neck slope portion 221 inclined by 45 degrees without changing the basic dimensions of the cross shaft 2.

  In the conventional neck portion 23 (FIG. 14), stress concentration occurs in the neck R portion 233, and cracks or deformation may occur in the neck portion. However, according to the neck portion 22 of the present embodiment, the neck R slope portion 221 inclined by 45 degrees, the neck R portion 223 approaches the loaded track portion 21 as compared with the prior art, and the Due to the increased curvature radius, the mechanical strength is greatly improved, and the occurrence of cracks and deformation can be prevented. In addition, the shape of the neck portion 22 is simpler than that of the prior art, and therefore processing is easy.

  On the other hand, the seal 4 includes a metal ring body 41 that is press-fitted into the cup 31 and fixed, and a rubber seal body 42 that is integrally formed with the metal ring body 41. Although the seal body 42 is shown in a free state, it is actually pressed against the cross shaft 2 and elastically deformed. 3, 4, 5, 6, 7, and 8 are drawings of the seal 4 alone, and are respectively a front view, a rear view, a side view, a sectional view taken along line VI-VI in FIG. 3, a front perspective view, and a rear side. FIG.

Referring to FIGS. 3 to 8, in FIG. 2, the sealing body 42 includes a first axial lip 421 that is pressed above the neck slope 221 and a second axial that is pressed below the neck slope 221. It has a lip 422 and a base 423 common to them. Each of the lips 421 and 422 has a cylindrical shape extending to the left with respect to the base portion 423 in parallel with the central axis of the track portion 21. Further, the first axial lip 421 extends longer than the second axial lip 422 so as to match the inclination of the neck slope 221. The seal body 42 is not provided with a conventional radial lip, and only the axial lips 421 and 422 constitute a lip portion of the seal.
On the other hand, the inner diameter D2 of the seal 4 satisfies D2> D1 in relation to the outer diameter D1 of the track portion 21. In addition, the gap ((D2-D1) / 2) is not very small but has a margin enough to be illustrated.
The other three raceways 21 are also provided with the same seal structure.

  In order to attach the cross shaft 2 to a yoke (not shown), after inserting the track portion 21 into the hole of the yoke, the bearing cup 3 (with the seal 4 press-fitted) is mounted on the track portion 21. Then, by fitting a retaining ring (not shown) into the circumferential grooves 3a of the two bearing cups 3 at both ends of one axis (for example, the X axis), the cross joint 1 and one yoke are connected. The other yoke is connected in the same manner. By connecting in this way, the bearing cup 3 is pushed to a predetermined axial position with respect to the cross shaft 2. When the bearing cup 3 is mounted on the raceway portion 21, the inner peripheral edge of the left end of the needle roller 32 of the entire circumference in FIG. 3 are “centered” to each other. At this time, since the inner diameter D2 of the seal 4 is larger than the outer diameter of the track portion 21 as described above, the second axial lip 422 secures a gap between the track portion 21 and does not interfere with the track portion 21. Further, since it does not interfere with the track portion 21, the internal pressure of the seal body 42 does not increase until the axial lips 421 and 422 come into contact with the neck inclined surface portion 221. Therefore, the attachment of the bearing cup 3 to the cross shaft 2 is easy.

On the other hand, the axial lips 421 and 422 receive a force F that is pushed back in the normal direction of the neck slope portion 221 at the contact portion with the neck slope portion 221. This force F includes an axial component Fa that becomes the pressing force of the seal 4 in the axial direction and a radial component Fr that becomes the pressing force of the seal 4 in the radial direction, and the magnitude of Fa (the magnitude of F) × cos 45 °) is basically the same as the size of Fr (the size of F × sin 45 °). Accordingly, each of the axial lips 421 and 422 not only exhibits a sealing action in the axial direction but also exhibits a similar sealing action in the radial direction, and the lip itself is an axial lip extending in the axial direction. However, in the relationship with the neck slope 221, the sealing action equivalent to that of the radial lip is also exhibited.
Further, since the extending direction of each of the axial lips 421 and 422 is parallel to the axial direction, the conventional axial lip 43a (FIG. 14) that extends at a predetermined angle (about 25 degrees) with respect to the axial direction. In contrast, it is considered that the contact surface pressure distribution is less likely to change even if the tightening allowance of the seal 4 varies, thereby contributing to stabilization of the seal performance.

  Next, the contact pressure distribution of the seal by FEM analysis will be described. In addition, the inventors confirmed that the result of the FEM analysis for the contact surface pressure distribution was not significantly different from the actually measured value. Therefore, it can be said that the result of the FEM analysis represents the actual contact surface pressure distribution almost accurately. FIG. 9 is a graph showing an outline of the result of examining the contact surface pressure distribution of the seal 4 while changing the tightening allowance. In this example, the interference is (a) is the smallest, increases in the following order, and (g) is the largest. The contact width in the figure is, for example, the width of the contact surface between the first axial lip 421 and the neck slope portion 221 in the inner and outer directions along the surface of the neck slope portion 221. The left side of each distribution is the atmosphere side (above the first axial lip 421 in FIG. 2), and the right side is the grease side (below the first axial lip 421).

  As shown in the figure, the smaller the interference is, the more the distribution becomes a sharp peak. As the interference increases, the contact width increases and the peak value of the contact pressure decreases. Here, the left and right widths of the distribution centered on the peak are a and b as shown, and the value of a / (a + b) corresponding to (a) to (g) in FIG. The graph of FIG. 10 shows the outline of the change represented by a continuous solid line. In the figure, the horizontal line is a / (a + b) = 0.5. As shown in the figure, a / (a + b) of each plot point is smaller than 0.5, and even if the interference is changed, the value of a / (a + b) does not change much.

  Basically, the seal surface has such a characteristic that the fluid is pushed out from a gentle surface pressure distribution to a steep one. Therefore, the value of a / (a + b) is an index indicating the sealing performance. That is, when a / (a + b) is smaller than 0.5 as described above, a characteristic of pushing out grease from the grease side to the atmosphere side occurs, and good sealing performance can be ensured. On the contrary, when a / (a + b) is larger than 0.5, the characteristic is that the fluid (water or the like) is sucked from the outside, and the sealing performance is not ensured.

As described above, according to the seal structure of the present embodiment, even if the tightening allowance changes, the value of a / (a + b) does not change so much and is smaller than 0.5, so the change in the tightening allowance is almost not changed. Stable sealing performance can be ensured without being affected.
Therefore, it is possible to provide a seal structure and a cross shaft joint that exhibit stable and reliable mud water resistance performance even if there is variation in the tightening allowance of the seal 4.
It should be noted that the inclination angle of the neck inclined surface portion 221 is most excellent in the case of 45 degrees shown here from the viewpoint of the stability of the sealing performance (a / (a + b)) with respect to the change in the tightening allowance. Confirmed by However, for practical purposes, even if it is not exactly 45 degrees, it is sufficient if it is about 45 degrees, and if it is within ± 10 degrees, the effect of stabilizing the sealing performance can be obtained accordingly. Not what you want.

FIG. 11 is a graph showing the result of FEM analysis performed on the seal of the conventional example (FIG. 14) in the same manner for comparison. The tightening margins (a) to (e) are the same as the tightening margins (a) to (e) in FIG. When the value of a / (a + b) of each distribution (each tightening allowance) in FIG. 11 is plotted, it becomes as shown in FIG. 12, and the change of the value of a / (a + b) with respect to the allowance is large. Moreover, since the value of a / (a + b) may be smaller than 0.5 or larger than 0.5 depending on the tightening allowance, the sealing performance is clearly unstable. For the tightening allowances (A) and (B) larger than 0.5, the sealing performance is not ensured as described above. Further, it is known that the sealing performance is not good when the contact pressure is significantly reduced as in (e) and there is a peak on the right side in addition to the peak value on the left side. Therefore, in the conventional example, the sealing performance is ensured only at the tightening allowances (c) and (d).
On the other hand, in this embodiment, the sealing performance can be ensured at all the tightening allowances shown in FIGS. Further, when the fastening allowances (A) to (E) are compared with the conventional example, the present embodiment has a small contact width. Therefore, the frictional resistance is small, the drag torque of the lip is reduced as compared with the prior art, and it contributes to the reduction in the torque of the rotation of the bearing cup 3.

In the above embodiment, the extending direction of the axial lips 421 and 422 is parallel to the axial direction, but may not be strictly parallel. For example, when the parallel is 0 degree, it is 0 ± 10 degrees. May be.
Further, the number of the axial lips 421 and 422 is not limited to two. If necessary, three or more may be provided, and conversely, there may be one.
Moreover, the seal structure of the said embodiment is applicable not only to a cross shaft coupling but to the various seal structures which produce a motion in an axial direction.

It is a front view (partial sectional view) showing a cross joint according to one embodiment of the present invention. It is an enlarged view of the II section of FIG. It is a front view of the seal | sticker single-piece | unit in the cross shaft coupling of FIG. It is a rear view of the said seal | sticker. It is a side view of the said seal | sticker. It is the VI-VI sectional view taken on the line of the said seal | sticker in FIG. It is a perspective view of the front side of the said seal | sticker. It is a perspective view of the back side of the said seal | sticker. It is a graph which shows the outline of the result of having investigated the contact surface pressure distribution of the said seal | sticker, changing tightening allowance. The values of a / (a + b) corresponding to (a) to (g) of FIG. 9 are plotted corresponding to the interference, and the outline of the change is represented by a continuous solid line. It is a graph which shows the outline of the result of having investigated the contact surface pressure distribution, changing the fastening margin about the conventional seal | sticker. The values of a / (a + b) corresponding to (a) to (e) in FIG. 11 are plotted corresponding to the interference, and the outline of the change is represented by a continuous solid line. It is a front view (partial sectional view) showing a conventional cross shaft joint. It is an enlarged view of the XIV part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cross shaft joint 2 Cross shaft 3 Bearing cup 4 Seal 21 Track part 22 Neck part (sealed part)
221 Neck slope (conical surface)
421 1st axial lip 422 2nd axial lip

Claims (4)

A seal having a ring shape as a whole, and a lip portion consisting only of a plurality of cylindrical axial lips extending in the axial direction by different lengths;
A sealing structure comprising: a conical surface positioned coaxially with the seal; and a sealed portion that contacts the conical surface with the plurality of axial lips from a central axis direction. A seal having an axial lip that is generally ring-shaped and extends substantially parallel to the axial direction;
A conical surface that is positioned coaxially with the seal and that is inclined at approximately 45 degrees with respect to the central axis, and a sealed portion that contacts the axial lip with the conical surface from the direction of the central axis. Characteristic seal structure. A cruciform shaft in which a conical neck slope portion inclined at a predetermined angle with respect to the axis of the track portion is formed on the base side of the track portion;
A bearing cup attached to the track portion;
A seal that is attached to the bearing cup and has a ring shape as a whole, and a lip portion that is brought into contact with the neck inclined surface portion from the central axial direction thereof is composed of only a plurality of cylindrical axial lips extending in the axial direction. A cross joint with a featured feature. A cruciform shaft in which a conical neck slope portion inclined at about 45 degrees with respect to the axis of the track portion is formed on the base side of the track portion;
A bearing cup attached to the track portion;
A seal that is attached to the bearing cup and has a ring shape as a whole, and a lip portion that comes into contact with the neck inclined surface portion from the central axis direction, is formed of an axial lip extending substantially parallel to the axial direction. Cross shaft coupling characterized by.

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