JP2015102120A - Sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ozone resistance of a seal part of a sealing device.SOLUTION: A sealing device 10 comprises: a core grid 11 having a cylinder part 12 fixed to a pinion shaft housing part 41, and an annular part 13 extending in an inner radial direction from one end in an axial direction of the cylinder part 12; and a seal part 14 made of an elastic material. The seal part 14 has: an adhesion part 15 adhered to the core grid 11; a spring part 17 extending toward one side in an axial direction as it goes in the inner radial direction from an end on an inner radial side of the adhesion part 15, and extending toward the other side in the axial direction as it goes in the inner radial direction; and a lip part 18 extending toward the other side in the axial direction from the spring part 17, and enlarged in diameter to come into contact with an outer periphery of a pinion shaft 20. A tip corner part 18e of the lip part 18 in the axial direction is formed into an almost arc-like cross sectional shape.

Description

  The present invention relates to a sealing device for sealing an annular space between a cylindrical inner shaft housing portion and an inner shaft rotatably disposed in the inner shaft housing portion.

  The rack and pinion mechanism of an automobile includes a pinion shaft and a bottomed cylindrical pinion shaft housing portion that houses a part of the pinion shaft. Then, an annular space between the pinion shaft and the pinion shaft housing portion is sealed in the opening formed on the steering wheel side (that is, the upper side) of the pinion shaft housing portion to prevent entry of muddy water and dust from the outside. A sealing device is provided.

  A conventional sealing device 110 used for a rack and pinion mechanism is constituted by a core metal 111 and a seal portion 114 as shown in FIG. The cored bar 111 is composed of a cylindrical part 112 and an annular part 113 that extends radially inward from the upper end of the cylindrical part 112. The seal portion 114 is made of an elastic material such as nitrile rubber. In the illustrated example, the seal portion 114 includes an adhesive portion 115, a spring portion 117, and a lip portion 118. The bonding portion 115 is vulcanized and bonded to the core metal 111. The spring portion 117 extends downward in the axial direction from the radially inner end of the bonding portion 115 toward the radially inward direction, and then extends upward in the axial direction toward the radially inward direction. . The lip portion 118 extends upward in the axial direction from the spring portion 117 and is in contact with the outer periphery of the pinion shaft 120.

  The lip portion 118 includes a main lip 118a having a triangular cross section (tapered shape) on the axially distal end side (upper side) in the radial direction and an auxiliary lip 118b on the axially proximal end side (lower side) in the radial direction. ing. As shown in FIG. 6, the taper surface 118t on the front end side in the axial direction of the main lip 118a is formed by cutting a burr B generated during vulcanization molding of the seal portion 114 along a one-dot chain line in the drawing.

  The sealing device 110 is formed so that the innermost inner diameter in an unloaded state is smaller than the diameter of the pinion shaft 120. For this reason, when the sealing device 110 is disposed in the annular space S between the pinion shaft 120 and the pinion shaft accommodating portion 141, the main lip 118 a and the auxiliary lip 118 b abut against the outer periphery of the pinion shaft 120, and the spring portion 117. And the lip part 118 is expanded in diameter. Thereby, the spring part 117 and the lip part 118 can urge the pinion shaft 120 in the radially inward direction to seal the annular space S and follow the eccentricity of the pinion shaft 120.

  However, when the sealing device 110 is disposed in the annular space S, the spring portion 117 and the lip portion 118 are expanded in diameter, so that tensile stress is always generated in the circumferential direction in the spring portion 117 and the lip portion 118. It becomes a state. In particular, as shown in FIG. 5, the tip 118 c in the axial direction of the lip 118 is greatly expanded in diameter as compared with the other portions of the spring 117 and the lip 118, so that a larger tensile stress is generated. In the lip portion 118, the corner portion on the radially inner side of the main lip 118a is always in contact with the pinion shaft 120. Therefore, ozone cracks do not occur here, but the tip end corner portions 118e and 118f in the axial direction of the lip portion 118 Ozone cracks occur early along the radial direction due to a large tensile stress. For this reason, the seal part 114 of the sealing device 110 did not have a desired ozone resistance.

  This invention is made | formed in view of such a problem, and it aims at improving the ozone resistance of the sealing part of a sealing device.

The present invention for achieving the above object
A sealing device for sealing an annular space between a cylindrical inner shaft housing portion and an inner shaft rotatably disposed in the inner shaft housing portion,
A cored bar having a cylindrical part fixed to the inner shaft accommodating part, and an annular part extending radially inward from one axial end of the cylindrical part;
From the bonded portion bonded to the core metal and the radially inner end of the bonded portion, it extends toward one side in the axial direction as it goes in the radial direction, and then toward the other axial direction as it goes in the radial direction. An elastic material having a spring portion extending toward the outside and a lip portion extending from the spring portion toward the other in the axial direction and contacting the outer periphery of the inner shaft by being expanded in diameter. A prepared seal part,
The lip portion is characterized in that a tip corner portion in an axial direction is formed in a substantially arc shape in cross section.

  In the sealing device of the present invention, the lip portion is formed such that the tip end corner portion in the axial direction has a substantially arc-shaped cross section. For this reason, the tensile stress which arises in the front-end | tip corner | angular part of the said axial direction can be disperse | distributed, and it can prevent that an ozone crack generate | occur | produces in the front-end | tip corner | angular part of the said axial direction early along a radial direction. For this reason, the ozone resistance of a seal part can be improved.

The lip portion includes a seal lip that abuts the outer periphery of the inner shaft at an axial tip portion, and the seal lip has a tapered surface on the axial tip side. It is preferable that the taper has a two-step taper that is continuous with the tip surface in the direction.
In this case, as compared with the case where the taper surface on the axial front end side of the seal lip is a one-step taper, the front end corner in the axial direction is increased by one and the obtuse angle becomes larger. Concentration of tensile stress can be suppressed.

  According to the sealing device of the present invention, the ozone resistance of the seal portion can be improved.

It is sectional explanatory drawing of the rack and pinion mechanism of the steering device of a motor vehicle. It is a section explanatory view of the sealing device concerning the embodiment of the present invention. It is expansion sectional explanatory drawing which shows the formation method of a two-step taper surface. It is a section explanatory view of the modification of the sealing device of the present invention. It is sectional explanatory drawing of the conventional sealing device. It is expansion sectional explanatory drawing which shows the formation method of a one-step taper surface.

Hereinafter, a sealing device 10 according to an embodiment of the present invention used for a rack and pinion mechanism 1 of an automobile steering device will be described with reference to the drawings.
FIG. 1 is an explanatory cross-sectional view showing a rack and pinion mechanism 1 in which a sealing device 10 is disposed.

  The rack and pinion mechanism 1 includes a pinion shaft 20 and a bottomed cylindrical pinion shaft housing portion 41 (a portion of the housing 40) that houses a part of the pinion shaft 20. A sealing device 10 that seals the annular space S between the pinion shaft accommodating portion 41 and the pinion shaft 20 is provided in an opening 41 a formed on the steering wheel (not shown) side of the pinion shaft accommodating portion 41. It is fitted. The sealing device 10 prevents muddy water and dust from entering the annular space S through the opening 41a from the outside.

FIG. 2 is an explanatory cross-sectional view in which one side portion of the transverse cross section of the sealing device 10 in FIG. 1 is enlarged.
The sealing device 10 has a configuration in which an annular seal portion 14 made of an elastic material such as nitrile rubber is vulcanized and bonded to a core metal 11 having an annular shape and an L-shaped cross section.
The core metal 11 is formed to have a diameter slightly smaller than the inner diameter of the pinion shaft housing portion 41, and a cylindrical portion 12 fixed to the inner peripheral surface of the pinion shaft housing portion 41, and the axial direction of the cylindrical portion 12 And an annular portion 13 extending from the upper end, which is one end, along the radially inward direction of the cylindrical portion 12.

The seal part 14 includes an adhesive part 15, a spring part 17, and a lip part 18.
The bonding portion 15 is vulcanized and bonded to the outer surface of the core metal 11 (the outer peripheral surface of the cylindrical portion 12 and the upper surface of the ring portion 13), and is formed in an L-shaped cross section substantially the same shape as the core metal 11. Has been. Further, as shown in FIG. 2, the bonding portion 15 extends to the tip surface of the cylindrical portion 12 of the core metal 11 and is also vulcanized and bonded to the tip surface. Further, the bonding portion 15 extends to the inner surface (lower surface) of the annular portion 13 at the distal end portion of the annular portion 13 of the core metal 11. It is vulcanized and bonded to the tip of the side.

  The spring portion 17 extends obliquely downward in the axial direction of the cylindrical portion 12 of the core metal 11 from the radially inner end of the bonding portion 15 toward the radially inward direction, and smoothly in the radially inward direction along the way. It has a U-shaped cross section by curving and then extending obliquely upward in the axial direction as it goes inward. The distal end portion of the spring portion 17 is located below the annular portion 13 in the axial direction.

  The lip portion 18 is formed to be continuous with the distal end portion of the spring portion 17 inward in the radial direction of the distal end portion of the spring portion 17. The lip portion 18 extends upward in the axial direction. The tip end portion 18 c of the lip portion 18 is located on the outer side in the axial direction than the annular portion 13. A main lip 18a and an auxiliary lip 18b are formed on the inner side of the lip portion 18 in the radial direction.

  The main lip 18a is a convex portion having a substantially triangular cross section that protrudes in the radially inward direction on the tip end side of the lip portion 18 in the axial direction. The auxiliary lip 18b protrudes downward in the axial direction toward the radially inward direction on the lower side of the lip portion 18 in the axial direction. On the upper side in the axial direction of the auxiliary lip 18b, a belly contact portion 18s that suppresses extreme deformation of the auxiliary lip 18b in the radially outward direction is formed so as to protrude in the radially inward direction. The main lip 18a protrudes inward from the auxiliary lip 18b.

  On the radially outer side of the lip portion 18, an annular groove 18 u having a substantially arc-shaped cross section into which a garter spring 19 for urging the main lip 18 a in the radially inward direction is fitted at substantially the same axial position as the main lip 18 a. Is formed. A guide portion 18d is formed at the tip of the lip portion 18 in the axial direction so as to protrude from the main lip 18a in the radially outward direction and constitute a part of the annular groove 18u.

  A radially outer corner 18e at the tip of the lip 18 in the axial direction is formed in a substantially arc shape in cross section. In addition, the other corner | angular part of the radial direction outer side of the lip | rip part 18 is also formed in the cross-sectional arc shape. The taper surface 18t on the tip end side in the axial direction of the main lip 18a has a two-step taper, a first taper surface 18p inclined by about 45 degrees with respect to the radial direction, and a first taper surface with respect to the radial direction. The second tapered surface 18q is inclined more acutely than 18p. The first taper surface 18p is continuous with the second taper surface 18q, and the second taper surface 18q is continuous with the tip surface 18h.

  FIG. 3 is an enlarged cross-sectional explanatory view showing a method for forming the two-step tapered surface 18t. The two-step taper surface 18t is formed in advance by forming the second taper surface 18q by vulcanization, and the first taper surface 18p is formed by cutting the burr B generated at the time of vulcanization along the one-dot chain line in the figure. Is done. The tip end face 18h, the second tapered face 18q, and the first tapered face 18p of the lip part 18 form two corners 18f and 18g at the tip in the axial direction.

  The sealing device 10 is formed so that the dimension that can be deformed in the radial direction by being disposed in the annular space S is sufficiently larger than the assumed maximum eccentricity of the pinion shaft 20. As shown in FIG. 2, when the sealing device 10 is fitted into the pinion shaft accommodating portion 41, the diameter of the spring portion 17 and the lip portion 18 is expanded. At this time, the lip portion tip portion 18c provided with the main lip 18a among the spring portion 17 and the lip portion 18 is expanded to the largest extent. Further, the garter spring 19 is in a state of being expanded outward in the radial direction from the natural state. The main lip 18a and the auxiliary lip 18b are pressed against the outer peripheral surface of the pinion shaft 20 by the urging force of the spring portion 17, the lip portion 18 and the garter spring 19 in the radially inward direction.

In the sealing device 10 according to the embodiment of the present invention, the lip portion 18 has a radially outer corner portion 18e at the axial tip in the axial tip portion 18c that is the largest expanded diameter of the spring portion 17 and the lip portion 18. The cross section is formed in a substantially arc shape. Therefore, it is possible to disperse the tensile stress that has been concentrated on the outer diameter corner portion 118e in the past. The main lip 18a has a taper surface 18t on the tip end side in the axial direction, and the taper surface 18t is a two-step taper continuous with the tip end surface 18h in the axial direction. For this reason, as compared with the conventional example (in the case of FIG. 6) in which the taper surface 118t on the axial front end side is a one-step taper continuous with the front end surface 118h, the radially inner corners 18f and 18g are increased by one. Since it becomes a larger obtuse angle, it can suppress that a tensile stress concentrates on the said corner | angular parts 18f and 18g.
For this reason, it is possible to prevent ozone cracks from occurring at an early stage along the radial direction in the axial tip corners 18e, 18f, 18g. Thereby, the ozone resistance of the seal part 14 can be improved.

  In the sealing device 10 of the present invention, the time until the occurrence of ozone cracking is longer than that of the conventional example shown in FIGS. 5 and 6 is that the amount of eccentricity is 0.2 mm TIR, the ozone concentration is 50 ± 5 pphm, and the temperature is: It has been demonstrated in an ozone resistance evaluation test using HNBR (hydrogenated nitrile rubber) as the material of the seal portion 14 under the condition of 40 ± 2 ° C.

[Modification]
The sealing device of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, as shown in FIG. 4, instead of making the taper surface 18t of the main lip 18a into a two-step taper, a one-step taper and a radially inner corner 18f formed by the tip surface 18h and the one-step taper 18t are substantially circular in cross section. It may be formed in an arc shape. Further, in the above-described embodiment, the tip end corner portions 18f and 18g in the axial direction may be formed in a substantially arc shape in cross section. Further, the sealing device 10 described above can be applied not only to the rack and pinion mechanism 1 but also to other mechanisms in which the inner shaft can be eccentric with respect to the cylindrical inner shaft housing portion.

  10: sealing device, 11: cored bar, 12: cylindrical part, 13: ring part, 14: seal part, 15: adhesive part, 17: spring part, 18: lip part, 18a: main lip (seal lip), 18e: Diameter outer corner (tip corner), 18f: Diameter inner corner (tip corner), 18g: Diameter inner corner (tip corner), 18h: Tip surface, 18t: Tapered surface, 20: Pinion shaft (Inner shaft), 41: pinion shaft housing portion (inner shaft housing portion), S: annular space

Claims (2)

A sealing device for sealing an annular space between a cylindrical inner shaft housing portion and an inner shaft rotatably disposed in the inner shaft housing portion,
A cored bar having a cylindrical part fixed to the inner shaft accommodating part, and an annular part extending radially inward from one axial end of the cylindrical part;
From the bonded portion bonded to the core metal and the radially inner end of the bonded portion, it extends toward one side in the axial direction as it goes in the radial direction, and then toward the other axial direction as it goes in the radial direction. An elastic material having a spring portion extending toward the outside and a lip portion extending from the spring portion toward the other in the axial direction and contacting the outer periphery of the inner shaft by being expanded in diameter. A prepared seal part,
The said lip | rip part has the front-end | tip corner | angular part of the axial direction formed in the cross-sectional arc shape substantially, The sealing device characterized by the above-mentioned.   The lip portion includes a seal lip that abuts the outer periphery of the inner shaft at an axial tip portion, and the seal lip has a tapered surface on the axial tip side. The sealing device according to claim 1, wherein the sealing device has a two-step taper continuous with the distal end surface in the direction.

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