JP2010014219A - Sealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower torque based on fluid lubrication by thickening a fluid film in a sliding face in a sealing device having a seal lip. <P>SOLUTION: The sealing device has the seal lip slidably and closely contacted to the circumferential face of a counterpart member such as a shaft, and the seal lip has a sealed fluid side inclined face, an opposite sealed fluid side inclined face, and an intermediate face provided between both inclined faces. A positive screw part pushing back the sealed fluid by a pumping action during rotation is provided on the opposite sealed fluid side inclined face. A reverse screw part sucking the sealed fluid by pumping action during rotation is provided on the intermediate face. An annular groove is provided on the intermediate face to cross the reverse screw part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealing device, and more particularly to a sealing device having a sealing lip. The sealing device of the present invention is used, for example, in the field of automobiles or in the field of general-purpose machines.

  Generally, a sealing device having a seal lip is required to have a low torque so as to suppress sliding wear of the seal lip. As methods for reducing torque, reduction of the frictional force, such as reducing the tension by reducing the cross-section of the seal lip, changing the material, and modifying the surface (for example, fluororesin coating) has been studied. In order to reduce the torque, it is conceivable to reduce the torque based on fluid lubrication by increasing the thickness of the fluid film (oil film) on the sliding surface.

As a conventional technique, as shown in FIG. 4, screw portions 54 and 55 are provided on the sealing fluid side inclined surface 52 and the anti-sealing fluid side inclined surface 53 of the seal lip 51, respectively, and sealing is performed by a pumping action performed by the screw portions 54 and 55. A technique for pushing back the fluid to the sealed fluid side has been developed (see Patent Document 1).
Japanese Utility Model Publication No. 3-29768

  However, according to this prior art, the sealing fluid is pushed back to the sealing fluid side by the pumping action exerted by the screw portions 54 and 55, so that the sealing performance is improved, but the thickness of the fluid film on the sliding surface is thin. Therefore, it is impossible to realize a reduction in torque based on fluid lubrication.

Moreover, although the technique which provides an intermediate surface between a sealing fluid side slope and an anti-sealing fluid side slope is described in following patent document 2, this prior art provides a reverse thread part and an annular groove in an intermediate surface. is not.
JP 2003-254439 A

  In view of the above, an object of the present invention is to achieve a reduction in torque based on fluid lubrication by thickening a fluid film on a sliding surface as described above in a sealing device having a seal lip.

  In order to achieve the above object, a sealing device of the present invention has a seal lip that is slidably in close contact with a peripheral surface of a mating member such as a shaft, and the seal lip includes a sealed fluid side slope and an anti-sealing fluid side slope. And an intermediate surface provided between the two slopes, and a positive thread portion that pushes back the sealing fluid by a pumping action at the time of rotation is provided on the anti-sealing fluid side slope, and the intermediate surface is rotated at the time of rotation. A reverse screw portion that sucks the sealing fluid by the pumping action is provided, and an annular groove is provided on the intermediate surface so as to intersect the reverse screw portion.

  In the sealing device of the present invention having the above-described configuration, an intermediate surface is provided between the sealing fluid side inclined surface and the anti-sealing fluid side inclined surface of the seal lip, a reverse screw portion is provided on the intermediate surface, and an annular groove is further formed on the intermediate surface. Is provided so as to intersect the reverse screw portion. The intermediate surface is slidably in close contact with the peripheral surface of the mating member to form a sliding portion. The reverse thread part is a screw opposite to the normal thread part provided on the anti-seal fluid side slope, and the normal thread part pushes back the sealing fluid by the pumping action during rotation, whereas the reverse thread part Has the effect of sucking the sealing fluid by the pumping action during rotation. Therefore, the sealing fluid is positively introduced into the intermediate surface by the pumping action produced by the reverse threaded portion, a thick fluid film is formed, and a dynamic pressure is generated that floats the intermediate surface from the counterpart member.

  In addition, since the annular groove is provided on the intermediate surface so as to intersect the reverse threaded portion, the sealing fluid introduced to the intermediate surface by the pumping action of the reverse threaded portion tends to accumulate in the groove, and the sealing fluid is present on the intermediate surface. Retained. This makes it possible to supply the sealing fluid accumulated in the groove to the intermediate surface during start-up, stop, and low-speed rotation, where the fluid film tends to be thin, and achieve low torque in a wide range of rotation speeds. Is possible.

  Therefore, combined with the action of the reverse screw portion and the annular groove, it is possible to realize a reduction in torque based on fluid lubrication.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross section of a main part of a sealing device (oil seal) 1 according to an embodiment of the present invention. FIG. 2A shows an enlarged part of FIG. The sealing device 1 according to this embodiment is a one-way rotating seal in which a shaft that is a sliding counterpart member rotates in one direction on the circumference, and is configured as follows.

  That is, first, the rubber-like elastic body 3 adhered (vulcanized and bonded) to the metal ring 2 is slidable on the peripheral surface of the shaft (the other member, not shown) together with the outer peripheral seal portion 4 and the dust lip 5. An intimate seal lip 6 is provided, and a seal fluid side A slope (sealing fluid side slope) 7 and an anti-sealing fluid side (atmosphere side) B slope (anti-sealing fluid) are provided at the tip sliding portion of the seal lip 6. Side slopes) 8 are provided, and an intermediate surface (flat surface) 9 is provided between the slopes 7 and 8. The intermediate surface 9 is formed in a cylindrical surface shape, and is slidably in close contact with the peripheral surface of the shaft when the shaft is inserted.

  The anti-sealing fluid side inclined surface 8 is provided with a positive thread portion 10 that has an action of pushing the sealing fluid back to the sealing fluid side A by a pumping action during shaft rotation. The positive screw portion 10 is composed of a spiral projection group provided on the circumference and is drawn assuming projections having a triangular cross section in the figure, but the shape is not particularly limited. The direction of the spiral is set so as to incline toward the front in the rotational direction (sliding direction) C of the shaft from the end portion on the anti-sealing fluid side B to the end portion on the sealing fluid side A.

  The intermediate surface 9 is provided with a reverse screw portion 11 that has an action of sucking the sealing fluid from the sealing fluid side A by a pumping action during shaft rotation. The reverse thread portion 11 is composed of a spiral groove group provided in a large number on the circumference, and is opposite to the normal thread portion 10, that is, the direction of the spiral is changed from the end of the sealed fluid side A to the anti-sealed fluid side. The direction is set to be inclined toward the front in the rotational direction C of the shaft toward the end of B. The shape of the groove is not particularly limited.

Similarly, an annular groove 12 is provided on the intermediate surface 9 so as to intersect the reverse screw portion 11. As the name suggests, the annular groove 12 is provided endlessly over the entire circumference, and has a constant width w ₂ (FIG. 2A) over the entire circumference. The cross-sectional shape of the annular groove 12 is not particularly limited, and a triangular groove having a triangular cross section (FIG. 2B), a tapered groove having a trapezoidal cross section (FIG. 2C), or a round bottom groove having a circular arc cross section (FIG. D)).

In the sealing device 1 having the above configuration, the intermediate surface 9 is slidably in contact with the peripheral surface of the shaft with a predetermined axial width w ₁ between the sealing fluid side inclined surface 7 and the anti-sealing fluid side inclined surface 8 of the seal lip 6. Since the seal lip 6 is provided, sliding wear is suppressed and the contact state with the shaft is stabilized. In addition, since the reverse screw portion 11 is provided on the intermediate surface 9 to suck in the sealing fluid by the pumping action at the time of rotating the shaft, the sealing fluid is applied to the intermediate surface 9 by the pumping action played by the reverse screw portion 11. Is actively introduced, a thick fluid film is formed, and a dynamic pressure is generated to float the intermediate surface 9 from the peripheral surface of the shaft.

  In addition to this, since the annular groove 12 is provided in the intermediate surface 9 so as to intersect the reverse threaded portion 11, the sealing fluid introduced into the intermediate surface 9 by the pumping action of the reverse threaded portion 11 is in this annular shape. It is easy to collect in the groove 12, and the sealing fluid is easily held on the intermediate surface 9. Therefore, it is possible to supply the sealing fluid accumulated in the annular groove 12 to the intermediate surface 9 even when the shaft is in a state where the fluid film is likely to be thinned, when the shaft is started, when stopped, and when rotating at a low speed. Low torque can be realized in the region.

  The sealing fluid flowing out from the intermediate surface 9 toward the anti-sealing fluid side inclined surface 8 is pushed back by the pumping action performed by the positive screw portion 10 provided on the anti-sealing fluid side inclined surface 8, so that it moves to the anti-sealing fluid side B. There is no leakage. In order to fulfill this sealing action, the pumping force of the forward screw portion 10 is set to be larger than the pumping force of the reverse screw portion 11.

  It is conceivable that the sealing device 1 according to the embodiment described above is added / changed as follows.

  In the above-described embodiment, the reverse screw portion 11 is formed from the boundary portion 13 between the intermediate surface 9 and the sealed fluid side inclined surface 7 to the boundary portion between the intermediate surface 9 and the anti-sealed fluid side inclined surface 8 as shown in FIG. 14, but instead of this, as shown in FIG. 2E, the reverse screw portion 11 does not reach the boundary portion 14 between the intermediate surface 9 and the anti-sealed fluid side inclined surface 8. And a belt-like screw-free region 15 is set between the reverse screw portion 11 and the boundary portion 14 so as to be in close contact with the peripheral surface of the shaft over the entire circumference. By setting the screw-free region 15 over the entire circumference in this way, the screw-free region 15 acts as a seal dam, so that it is possible to prevent the so-called stationary leakage from occurring when the shaft rotation is stopped. There is.

The intermediate surface 9 is parallel to the central axis (not shown) of the sealing device 1 which is an annular body, or the inclination angle with respect to the central axis of the sealing device 1 is the sealing fluid side inclined surface 7 and the anti-sealing fluid. It is set smaller than the side slope 8. Therefore, as an aspect of the intermediate surface 9, in the mounted state (when the shaft is inserted),
(1) As shown in FIG. 3A, a cylindrical surface parallel to the central axis of the sealing device 1,
(2) As shown in FIG. 3B, the anti-sealing fluid side B has an inclined surface shape (conical surface shape) having an angle θ ₁ (the inner diameter dimension extends from the sealing fluid side A to the anti-sealing fluid side B. To expand)
(3) As shown in FIG. 3 (C), an inclined surface (conical surface) having an angle θ ₂ on the sealing fluid side A (inner diameter dimension from the anti-sealing fluid side B to the sealing fluid side A To expand)
There are three types, and any of them is included in the present invention.

  Of these, (3) has the following effects.

That is, in the above (3), since the intermediate surface 9 has an inclined surface shape having an angle θ ₂ on the sealing fluid side A, the sliding of the seal lip 6 is between the anti-sealing fluid side inclined surface 8 and the intermediate surface 9. On the other hand, this line is formed by the pumping action by the normal screw portion 10 provided on the anti-sealing fluid side inclined surface 8 and the reverse screw portion provided on the intermediate surface 9. This is also the site where the sealing fluid is most collected by the pumping action by 11. Therefore, since the sliding of the seal lip 6 is performed at the site where the sealing fluid is most collected, the fluid film formed on the sliding portion is thicker than (1) or (2), and the lower Torque is realized.

The magnitude of the inclination angle θ ₂ of the intermediate surface 9 toward the sealed fluid side A in the mounted state is preferably 0 <θ ₂ ≦ 25 degrees, and more preferably 0.1 ≦ θ ₂ ≦ 20 degrees. Moreover, about the magnitude | size of inclination-angle (theta) ₁ of the intermediate surface 9 to the anti-sealing fluid side B in a mounting state, 0 <= theta ₁ <= 25 degree | times is suitable.

Sectional drawing of the principal part of the sealing device which concerns on the Example of this invention. (A) is a partially enlarged view of FIG. 1, (B), (C) and (D) are cross-sectional views of the annular groove, and is a cross-sectional view taken along the line DD in (A), and (E) is the reverse screw portion. Diagram showing another shape example (A) (B) and (C) are explanatory diagrams of the inclination angle of the intermediate surface Cross section of the main part of the oil seal according to the conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing device 2 Metal ring 3 Rubber-like elastic body 4 Peripheral seal part 5 Dustrip 6 Seal lip 7 Sealing fluid side slope 8 Anti-sealing fluid side slope 9 Middle surface 10 Positive thread part 11 Reverse thread part 12 Annular groove 13, 14 boundary Part 15 Screw-free area

Claims (1)

It has a seal lip that is slidably in close contact with the peripheral surface of a mating member such as a shaft,
The seal lip has a sealing fluid side slope and an anti-sealing fluid side slope and an intermediate surface provided between the slopes,
Provided on the anti-sealing fluid side slope is a positive thread portion that acts to push back the sealing fluid by a pumping action during rotation,
Provided on the intermediate surface is a reverse screw portion that acts to suck in a sealing fluid by a pumping action during rotation,
Furthermore, a sealing device characterized in that an annular groove is provided on the intermediate surface so as to intersect the reverse thread portion.

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