JP2006322528A - Sealing device - Google Patents

Abstract

Provided is a sealing device capable of reducing sliding resistance at a lip portion and preventing oil leakage.
A lip portion having a substantially V-shaped cross section is provided in contact with an outer peripheral surface of a rod that reciprocates. Three annular projections 11, 12, and 13 are formed on the surface of the inner peripheral surface of the lip 6 on the outer side B of the lip tip 7. The protruding heights of the protrusions 11, 12, 13 are formed so as to increase in order from the lip tip 7 toward the outer side B.
[Selection] Figure 1

Description

  The present invention relates to a sealing device used for a reciprocating shaft.

It is provided between the inner peripheral surface of the casing and the outer peripheral surface of the shaft that reciprocates inside the casing, and has a seal lip portion that comes into contact with the outer peripheral surface of the shaft, and seals the sealing fluid so as not to leak to the outside. As a sealing device, for example, there is one as shown in Patent Document 1. This sealing device is an oil seal including an annular cored bar, a seal member having a seal lip portion, a spring ring, and a backup ring, and can be used for a rod of a power steering device in an automobile.
When the rod reciprocates in the axial direction by the operation of the power steering device, the seal lip portion of the sealing device is in sliding contact with the outer peripheral surface of the rod. In order to reduce the contact area, reduce the frictional resistance during the reciprocating movement of the rod, increase the durability, and suppress the occurrence of abnormal noise (squeal), A plurality of protrusions that are continuous in the circumferential direction are formed on the outer peripheral surface of the inner peripheral surface relative to the lip tip (top). That is, an oil pool is formed between the protrusions, and the rod reciprocates in the axial direction, whereby oil is supplied to the sliding contact portion of the lip portion to form a lubricating oil film, and the frictional resistance is reduced.
And as for the oil seal of patent document 1, although the axial direction width dimension of each projection part is set so large that it is far from a lip front-end | tip part, all the height dimensions are set to the same.

  Also, a plurality of protrusions are provided on the outer surface of the lip tip so as to form an oil film, and the height of the protrusion closest to the lip tip is large, and the adjacent protrusion on the outer side of this There is an oil seal whose height dimension is reduced (for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 11-141689 Japanese Utility Model Publication No. 4-124373

  When the oil seal described in Patent Documents 1 and 2 is used for a rod of a power steering device, the lip portion may sag over time (decrease in rigidity) depending on the usage environment (degraded oil, compatibility with oil, etc.). There is a problem that the fluid becomes larger and the sealing fluid leaks.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a sealing device that can reduce sliding resistance at the lip portion and can prevent leakage of sealing fluid over a long period of time. To do.

  In order to achieve the above object, a sealing device according to the present invention includes a substantially V-shaped lip portion that comes into contact with the outer peripheral surface of a reciprocating shaft and whose cross section narrows radially inward. In the sealing device for sealing so as not to leak, a plurality of protrusion heights increase in order from the lip tip to the outside on the outer surface of the lip tip than the lip tip. An annular protrusion is formed.

The present inventor conducted FEM analysis on the oil seal in order to investigate the cause of leakage of the sealing fluid in the conventional oil seal.
FIG. 7 shows the result of FEM analysis of a conventional oil seal corresponding to Patent Document 1 (provided with three protrusions), and FIG. FIG. 7B is a diagram showing the contact surface pressure by the lip portion 40 after the sag in the lip portion 40 is increased. It is. This is a result of analyzing the pressure of the sealing fluid as 1.2 MPa.

  In this figure, since the lip portion 40 does not sag at the beginning of use, as shown in FIG. 7A, the protrusion portion 42 sequentially from the lip tip portion 41 toward the outside (left side). , 43, 44 are reduced in surface pressure, and the lip portion 40 is in contact with the rod 45. Furthermore, the lip tip 41 can contact the rod 45 with contact pressure. As a result, the surface pressure can be secured also at the lip tip portion 41 (arrow 46 portion), and the sealing fluid can be sealed.

However, as shown in FIG. 7B, when the lip of the lip portion 40 becomes large, the base end portion 47 side of the lip portion 40 is pressed radially inward by the pressure from the sealing fluid side and deformed, and the base end The inclined surface 47a of the portion 47 comes into contact with the rod 45, and the lip tip portion 41 acts in a direction in which the lip tip portion 41 is pushed outward in the radial direction, so that the contact pressure tends to decrease.
Therefore, as in Patent Document 1, when the protrusions on the inner peripheral surface of the lip part are all large at the same height dimension, or as in Patent Document 2, the height dimension of the protrusion part closest to the lip tip is the same. In the case of being large, as shown in FIG. 7B, when the lip of the lip 40 becomes large, the protrusion 42 closest to the lip tip 41 is high, so that the lip tip 41 side is lifted. As a result, the lip tip 41 floats away from the outer peripheral surface of the rod 45, and no surface pressure is obtained at the lip tip 41 (arrow 48), and the sealing fluid leaks to the outside. .

On the other hand, according to the sealing device of the present invention, the lip of the lip portion increases, and the surface on the outer side (first inclined surface) contacts the shaft in a wide range due to the pressure on the sealing fluid side. Even if it is in a state (solid contact state), since the height of the protrusion formed on the first inclined surface is formed so that the protruding height increases in order from the lip tip toward the outside, The first inclined surface can secure the contact pressure of the lip tip. For this reason, the state which the lip front-end | tip part contacted the outer peripheral surface of the axis | shaft can be maintained.
Furthermore, it is possible to prevent the lip tip portion from being lifted due to the projection portion on the side close to the lip tip portion being too high, and to prevent the lip tip portion from being lifted from the outer peripheral surface of the shaft. This can prevent the sealing fluid from leaking to the outside.
Further, since a plurality of annular protrusions are formed in the axial direction, an oil pool is formed between the protrusions, and the shaft reciprocates to supply oil to the sliding contact portion of the lip portion to form a lubricating oil film. be able to. Thereby, the contact resistance between a lip | rip part and a axis | shaft can be made small, durability can be improved, and generation | occurrence | production of abnormal noise can be suppressed.

Further, the protrusion has at least three stripes of a first protrusion, a second protrusion, and a third protrusion in order from the lip tip side, and the height dimension of the first protrusion is It is preferable that the height is 20 to 35 μm, the height of the second protrusion is 40 to 60 μm, and the height of the third protrusion is 90 to 110 μm.
According to this configuration, by setting the height dimension of each protrusion within the above range, it is possible to form an oil film without the protrusion being too low, and the protrusion is not too high, and the protrusion is the tip of the lip. By lifting the part side, it is possible to prevent the lip tip from floating from the outer peripheral surface of the shaft.

  The shaft is preferably a power steering rod of an automobile. As a result, in a power steering device that becomes a high temperature, high pressure environment, and an environment that frequently changes from low pressure to high pressure, leakage of the sealing fluid to the outside when the power steering rod reciprocates in the axial direction can be prevented. . Therefore, the sealing device is particularly suitable for a power steering device.

  According to the sealing device of the present invention, even if the lip portion sags, the lift of the lip tip portion can be suppressed, and the sealing fluid can be prevented from leaking to the outside for a long period of time.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an upper half portion of an embodiment of a sealing device according to the present invention. This sealing device can be used in a power steering device of an automobile, and is provided between an inner peripheral surface 20 of the casing of the device and an outer peripheral surface 10a of a power steering rod 10 that reciprocates in the axial direction inside the casing. Yes. And this sealing device seals sealing fluid between the side A and the exterior side B in which sealing fluid is accommodated so that sealing fluid may not leak to the exterior side B. The sealing device shown in FIG. 1 shows a free state before deformation, which is before being mounted on the power steering device.

The sealing device includes an annular cored bar 2 having an L-shaped cross section, a seal member 1 fixed to the cored bar 2, an annular spring ring 3, and an annular backup ring 4.
The cored bar 2 includes a cylindrical portion 14 and an annular plate portion 15 that is bent radially inward from one end of the cylindrical portion 14.
The sealing member 1 is made of an elastic member such as synthetic rubber, and includes a main body portion 16 fixed to the core metal 2 and a lip portion 6 extending from the main body portion 16 to the rod 10 side and to the sealing fluid side A. Have. The main body portion 16 has an outer peripheral portion 16a on the outer peripheral side of the cylindrical portion 14 of the core metal 2, and an inner peripheral portion 16b on the inner peripheral side, and further extends radially inward from the inner peripheral portion 16b. And a main portion 16c fixed to the annular plate portion 15 of the cored bar 2.

  The lip portion 6 of the seal member 1 is formed to extend from the inner peripheral side portion of the main body portion 16 (main portion 16c). And the front end side from the base end part 17 of the lip | rip part 6 following the main part 16c can be slidably contacted with the outer peripheral surface 10a of the rod 10. FIG. The seal member 1 is vulcanized and bonded to the core metal 2.

The spring ring 3 is a so-called garter spring, and is provided in the circumferential groove 18 on the outer peripheral side surface of the lip portion 6. The spring ring 3 fastens the lip 6 in the radially inward direction.
The backup ring 4 is made of resin and prevents the lip portion 6 from being reversed when the sealing fluid becomes high pressure. The backup ring 4 is configured by an inner peripheral surface of the main body portion 16 of the seal member 1, an inner peripheral surface of the base end portion 17 of the lip 6 portion, and a side surface on the radially inner side of the annular plate portion 15 of the core metal 2. It is mounted in the recess.

  As shown in FIG. 2, the inner peripheral surface 6 a of the lip portion 6 of the seal member 1 has a first inclined surface 8 that is reduced in diameter toward the distal end side (right side) of the lip portion 6, and the first inclined surface. The second inclined surface 9 having a diameter increasing toward the tip side (right side) of the lip portion 6 is formed continuously from the minimum diameter portion of the lip portion 6, and the first inclined surface 8 and the second inclined surface 9 The minimum diameter portion (top portion) between the two is the lip tip portion 7. The surface on the outer side B from the lip tip 7 is a first inclined surface 8, and the sealing fluid side A is a second inclined surface 9 from the lip tip 7. The first inclined surface 8 and the second inclined surface 9 are both straight toward the lip tip 7 in the cross section (cut surface including the center line) in FIG. That is, the cross-sectional shape of the lip portion 6 is substantially V-shaped, which becomes thinner inward in the radial direction (the axial width dimension becomes smaller).

  In the first inclined surface 8 of the inner peripheral surface 6a of the lip portion 6, a plurality of annular (continuous in the circumferential direction) protrusions are formed. In FIG. 2, three protrusions 11 and 12 are formed. , 13 are formed. That is, as shown in FIGS. 2 and 3, the first protrusion 11, the second protrusion 12, and the third protrusion 13 are formed in order from the lip tip 7 side. And these protrusion parts 11, 12, and 13 are arrange | positioned so that each may become parallel along the 1st inclined surface 8 at equal intervals. Furthermore, these are formed so that the protruding height increases in order from the lip tip 7 toward the outer side B.

  Specifically, the height dimension h1 of the first protrusion 11 closest to the lip tip 7 is smaller than the height dimensions h2 and h3 of the second and third protrusions 12 and 13, and the intermediate dimension The height dimension h2 of the second protrusion 12 is smaller than the height dimension h3 of the third protrusion 13 (h1 <h2 <h3). The height dimension h1 of the first protrusion 11 is 20 to 35 μm, and the height dimension h2 of the second protrusion 12 adjacent to the outer side B is 40 to 60 μm. The height dimension h3 of the third protrusion 13 adjacent to the outer side B of the lens is 90 to 110 μm, and the height is set in three stages. The height dimension is a dimension from the first inclined surface 8 to the topmost portion of the protrusion.

If the heights of these protrusions 11, 12, 13 are less than the above lower limit values, the protrusions 11, 12, 13 are too low, and the outer peripheral surface 10 a of the rod 10 and the sliding contact surface portion of the first inclined surface 8 In this case, it is difficult to form an oil film between them, and when the rod 10 reciprocates, the frictional resistance becomes large and noise may be generated or the durability of the lip portion 6 may be reduced.
If the height dimension exceeds the upper limit, the heights of the protrusions 11, 12, and 13 are too high. In particular, the protrusion 11 lifts the lip tip 7 side, and the lip tip 7 is the outer periphery of the rod 10. There is a risk of floating from the surface 10a.

  The projections 11, 12, and 13 will be described in more detail. The arc shape can be an arc having the same radius in all the protrusions 11, 12, and 13. In this case, the center position of the arc of each protrusion is sequentially shifted in the direction orthogonal to the first inclined surface 8, and the center position of the first protrusion 11 is the most distant position from the first inclined surface 8 (first A deep position from the inclined surface 8 into the lip portion 6). That is, in the three protrusions 11, 12, and 13, the distance from the first inclined surface 8 to the center position of each arc-shaped protrusion is gradually decreased from the lip tip 7 toward the outer side B. (E1> e2> e3). Thereby, the protrusion height of the projections 11, 12 and 13 can be increased as the distance from the lip tip 7 increases.

As a modification of the protrusion, although not shown, the radii of the protrusions 11, 12, and 13 having an arcuate cross section may increase in order from the lip tip 7 toward the outer side B. In this case, the distance from the 1st inclined surface 8 to the center position of each projection part made into circular arc shape can be made equal.
With these configurations, the axial width dimension of the protrusions 11, 12, 13 (the width dimension in the direction along the inclination of the first inclined surface 8) increases in order from the lip tip 7 toward the outer side B. As a result, the protrusion on the lip tip 7 side is reduced, the sag of the lip 6 is increased, and the contact pressure that increases on the base end 17 side of the lip 6 is dispersed on the lip tip 7 side of the lip 6. Is done.

Next, FIG. 4 shows the result of the FEM analysis in the sealing device shown in FIG. 1 with the pressure on the sealing fluid side A being 1.2 MPa, and FIG. It is the figure which showed the contact surface pressure with respect to the rod 10 of the lip | rip part 6 of the initial stage of use before it becomes large, FIG.4 (b) is the contact by the lip | rip part 6 after the sag in the lip | rip part 6 became large. It is the figure which showed the surface pressure.
As shown in FIG. 4 (a), at the initial stage of use, the surface pressure at the projections 11, 12, and 13 increases in order from the lip tip 7 toward the external side B (left side), and the lip 6 has the rod 10 However, compared with the conventional one (see FIG. 7A), the surface pressure at each part is made uniform, and the surface pressure can be dispersed. That is, a large contact pressure is not generated locally, and a good contact state is obtained. Further, the lip tip 7 is in contact with the rod 10 with contact pressure, and the surface pressure can be secured also at the lip tip 7 (arrow 22), and the sealing fluid can be sealed.

  Next, as shown in FIG. 4B, since the base end 17 side of the lip portion 6 is deformed radially inward when the lip portion 6 becomes large, pressure is applied to the sealed fluid side A. As a result, the inclined surface 17a on the base end portion 17 side of the lip portion 6 is also in contact with the outer peripheral surface 10a of the rod 10 and a surface pressure is generated. And since the protrusion height of the three protrusion parts 11, 12, and 13 is made to become high in order toward the outer side B from the lip front-end | tip part 7, it is the 1st among the three protrusion parts 11, 12, and 13 The largest surface pressure is generated in the three protrusions 13 and the smallest surface pressure is generated in the first protrusion 11. Further, the lip tip 7 also has a contact pressure to the rod 10 and a surface pressure is secured between the lip tip 7 and the rod 10 (arrow 21). Thereby, it turns out that the sealing performance between the sealing fluid side A and the external side B can be maintained.

Next, Table 1 shows the result of the leakage test of the sealing device shown in FIG. For comparison, the protrusion heights h of the three protrusions 42, 43, 44 as shown in FIG. 5 are all 100 μm and the same (conventional example), and 3 as shown in FIG. A similar test was also performed on the one in which the protrusion heights of the protrusions 52, 53, and 54 of the strip gradually decreased from the lip tip 41 toward the outside (comparative example). That is, in the comparative example of FIG. 6, the height of the protrusion is h4 = 100 μm, h5 = 50 μm, and h6 = 30 μm from the lip tip 52 side, contrary to the embodiment.
The test condition is that 10 sealing devices are tested, and when the rod 10 is moved in the axial direction, the sealing fluid side A is pressurized from 0 MPa to 10.3 MPa, and the reciprocating cycle of the rod 10 is (maximum) 120,000 times. It was. The oil temperature and the shaft temperature are set to 135 ° C., and vibration (impact) in a direction orthogonal to the axial direction is applied to the rod 10 along the actual machine (power steering device). In all cases, used power steering oil was used as a sealing fluid.

  As shown in Table 1, in the conventional example, three of the ten leaks occurred, and the leak occurred when the reciprocating motion was between 69,000 times and 105,000 times. Further, in the comparative example, leakage occurred in 6 pieces, and the leakage occurred in 550,000 times to 101,000 times. That is, in the conventional example, particularly the comparative example, as the lip portion 40 becomes larger, the protrusions 42 and 52 close to the lip tip portion 41 lift the lip tip portion 41 side, and the lip tip portion 41 rises. Leakage is likely to occur. On the other hand, in the example, even if 120,000 times were reached, it was found that there was no leakage in all 10 pieces, and the lip tip 7 maintained the contact pressure against the rod 10.

As described above, according to the sealing device according to the above embodiment provided between the inner peripheral surface 20 of the casing of the power steering device and the outer peripheral surface 10a of the power steering rod 10 that reciprocally moves in the axial direction, There are the following effects.
The protrusions 11, 12, and 13 have sufficient height dimensions h1, h2, and h3, and an appropriate dimensional relationship (h1 <h2 <h3) is set so that the protrusion height of the first protrusion 11 on the lip tip 7 side is set. By making it the lowest, it is possible to prevent the lip tip portion 7 from floating from the outer peripheral surface 10a of the rod 10 even if the lip portion 6 becomes large after a long period of use at the beginning of use, An appropriate contact surface pressure sufficient to seal the sealing fluid at the lip tip 7 can be ensured. And it can prevent that the sealing fluid leaks to the external side B.

  Furthermore, since the three protrusions 11, 12, and 13 are formed in the axial direction at the sliding contact portion of the first inclined surface 8 of the lip portion 6, an oil pool is formed between these protrusions 11, 12, and 13. As the rod 10 reciprocates, oil can be supplied to the sliding contact portion of the lip portion 6 to form a lubricating oil film. Thereby, contact resistance can be made small, durability of a sealing device can be improved, and generation | occurrence | production of abnormal noise can also be suppressed.

In addition, the sealing device of the present invention is not limited to the illustrated form, and may be of other forms within the scope of the present invention. For example, the projecting portion is the first projecting portion 11 in order from the lip tip 7 side. It is sufficient that at least three strips of the second projection portion 12 and the third projection portion 13 are formed. The projection portions are four or more, and these projection portions are directed from the lip tip portion 7 toward the outer side B. The protruding height may be increased in order.
Further, the cross-sectional shape of the protrusions 11, 12, and 13 may be other than an arc shape, and may be a triangle, a trapezoid, or the like.
Furthermore, the intervals between the protrusions may not be equal, and the intervals may be gradually widened or sequentially narrowed.

It is a longitudinal section showing one embodiment of a sealing device concerning the present invention. It is sectional drawing of a lip | rip part. It is an expanded sectional view explaining the projection part formed in the lip | rip part. It is a figure explaining the contact surface pressure in the lip | rip part of the sealing device of this invention, (a) is an initial stage of use before the lip part sag becomes large, (b) is a lip part sag. It is after it grows up. It is sectional drawing of the lip | rip part of the sealing device used as a prior art example. It is sectional drawing of the lip | rip part of the sealing device used as a comparative example. It is a figure explaining the contact surface pressure in the lip | rip part of the sealing device of a prior art example, (a) is an initial stage of use before the lip part sag becomes large, (b) is a lip part sag. It is after it grows up.

Explanation of symbols

6 Lip part 6a Inner peripheral surface 7 Lip tip part 8 First inclined surface 9 Second inclined surface 10 Rod 10a Outer peripheral surface 11 First protrusion 12 Second protrusion 13 Third protrusion A Sealing fluid side B External side h1 First Height dimension of 1 projection part h2 Height dimension of 2nd projection part h3 Height dimension of 3rd projection part

Claims (3)

  A sealing device comprising a substantially V-shaped lip portion that comes into contact with an outer peripheral surface of a reciprocating shaft and whose cross section narrows radially inward, and seals sealing fluid so as not to leak to the outside. A plurality of annular protrusions whose protrusion heights increase in order from the lip tip to the outside are formed on the outer surface of the lip tip than the lip tip. Sealing device.   The protrusion has at least three stripes of a first protrusion, a second protrusion, and a third protrusion in order from the lip tip side, and the height of the first protrusion is 20 to 20 mm. 2. The sealing device according to claim 1, wherein the second protrusion has a height of 40 to 60 μm, and the third protrusion has a height of 90 to 110 μm.   The sealing device according to claim 1, wherein the shaft is a power steering rod of an automobile.

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