Oil seal structure

Abstract

To provide an oil seal structure that enhances the durability of the oil seal structure. [Solution] The oil seal 40 includes a side lip 45 fixed to the housing 20 so as to slide against the dust cover 50 and having an annular shape along the outer peripheral surface 31S, the side lip 45 having a gap S between an inner space S1 and an outer space S2 in a radial direction R1 relative to the side lip 45 at the sliding contact portion within the dust cover 50, and a plate 51 fixed to a part of the dust cover 50 in the outer space S2, configured to deform into a fin shape by receiving frictional heat due to the sliding of the side lip 45 through heat conduction of the dust cover 50.

Description

Technical Field

[0001] The present invention relates to an oil seal structure including an oil seal and a dust cover.

Background Art

[0002] An oil seal structure for suppressing the intrusion of foreign matter from the outside into the gap between an outer member and an inner member is known. When the periphery of the oil seal comes into contact with a fluid such as water and the pressure around the oil seal decreases, the gap between the oil seal and the rotating shaft expands due to the deformation of the oil seal so as to allow foreign matter to enter the space surrounding the lip. To solve this problem, in the oil seal structure described in Patent Document 1, the gaps of the first inclined surface and the second inclined surface leading to the space surrounding the lip are inclined so as to move radially outward as they go toward one side in the axial direction. Then, when the inner member rotates with respect to the outer member, the centrifugal force acting on the space surrounding the lip generates a fluid from the space toward the outside, suppressing the intrusion of foreign matter from the outside.

Prior Art Documents

Patent Documents

[0003] [[ID=Z3]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the temperature at the tip of the lip rises due to a change in the sliding state or the like, the function of the lip for suppressing the intrusion of foreign matter deteriorates. Therefore, there is still room for improvement in the above-described oil seal structure.

Means for Solving the Problems

[0005] An oil seal to solve the above problems comprises an oil seal that seals the gap between a rotating shaft inserted into a housing and the housing, and a dust cover fixed to the outer circumferential surface of the rotating shaft so as to rotate together with the rotating shaft and covering the oil seal, wherein the oil seal has an annular shape along the outer circumferential surface and is fixed to the housing so as to slide against the dust cover, and the side lip divides the gap into an inner and outer side in the radial direction of the rotating shaft relative to the side lip at the sliding contact portion within the dust cover, and a plate fixed to a part of the dust cover in the outer space and configured to deform into a fin shape by receiving frictional heat due to the sliding of the side lip through the heat conduction of the dust cover, and the plate is configured to form a negative pressure in the outer space as the fin-shaped plate rotates together with the dust cover. [Effects of the Invention]

[0006] According to the present invention, frictional heat generated by the sliding of the lip is transmitted to the plate by heat conduction through the dust cover. The plate, which deforms due to the frictional heat, creates negative pressure in the outer space covered by the dust cover. The negative pressure acting on the outer space draws lubricant from the inner space toward the sliding contact area and expels foreign matter that has entered the inner space to the outside of the outer space. This increases the durability of the oil seal structure. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a partial cross-sectional view showing a part of the oil seal structure. [Figure 2] Figure 2(A) is a plan view showing the dust cover and plate, and Figure 2(B) is a cross-sectional view of Figure 2(A) along line BB. [Figure 3] Figure 3 is a partial cross-sectional view showing the operation of the oil seal structure. [Modes for carrying out the invention]

[0008] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a partial cross-sectional view showing a part of the oil seal structure 10, and shows a portion above the center line in a cross-section that includes the center line of the rotating shaft 30.

[0009] As shown in Figure 1, the interior of the housing 20 houses a portion of the rotating shaft 30 extending in the axial direction D1, and electrical equipment connected to the rotating shaft 30. The rotating shaft 30 is inserted into the interior of the housing 20 through an opening 20H along the axial direction D1.

[0010] The oil seal structure 10 comprises an oil seal 40 and a dust cover 50. The oil seal 40 seals the gap S between the housing 20 and the rotating shaft 30. The dust cover 50 is fixed to the rotating shaft 30 so as to rotate together with the rotating shaft 30 and covers the oil seal 40 in the gap S.

[0011] The dust cover 50 comprises a sliding contact portion 50A and an outer peripheral covering portion 50B. The sliding contact portion 50A is the bottom wall of the dust cover 50, which has a bottomed cylindrical shape. The sliding contact portion 50A has a disc shape that extends in the radial direction R1 of the rotating shaft 30, and the rotating shaft 30 is inserted through it. The sliding contact portion 50A is located on the opposite side of the oil seal 40 in the axial direction D1 and covers the oil seal 40 in the axial direction D1. The sliding contact portion 50A is fixed to the stepped portion on the outer peripheral surface 31S of the rotating shaft 30, which has a two-stage cylindrical shape.

[0012] The outer peripheral covering portion 50B is the peripheral wall of the dust cover 50, which has a bottomed cylindrical shape. The outer peripheral covering portion 50B has a cylindrical shape that extends in the axial direction D1 from the sliding contact portion 50A. The outer peripheral covering portion 50B is positioned to cover the oil seal 40 on the outside in the radial direction R1 relative to the oil seal 40, and covers the oil seal 40 in the radial direction R1 over an overlap width d along the axial direction D1. The oil seal 40 and the dust cover 50 are separated by a labyrinthine gap S that bends from the radial direction R1 to the axial direction D1. As a result, the oil seal structure 10 prevents foreign matter from entering the housing 20 from the outside to the inside.

[0013] The oil seal 40 comprises a support member 41, a core member 42, a sealing member 43, and a side lip 45. The support member 41 and the core member 42 are fixed to the housing 20 and support the sealing member 43 and the side lip 45.

[0014] The support member 41 has an annular shape through which the rotating shaft 30 is inserted and is fixed to the housing 20 so as to fit into the housing 20 along the axial direction D1. The core member 42 has an annular shape through which the rotating shaft 30 is inserted and is located on the opposite side of the axial direction D1 from the support member 41. The core member 42 is fixed to the support member 41 so as to protrude inward from the support member 41 in the radial direction R1.

[0015] The sealing member 43 has an annular shape through which the rotating shaft 30 is inserted, and is sandwiched between the housing 20 and the support member 41 in an axial direction D1, thereby sealing the space between the housing 20 and the support member 41. The tip of the sealing member 43 is provided with a sealing portion 47 and a dust lip 44. The sealing member 43 is fixed to the support member 41 such that the sealing portion 47 and the dust lip 44 slide against the outer circumferential surface 31S via oil. The sealing portion 47 has a tongue shape that contacts the outer circumferential surface 31S over the entire circumference of the rotating shaft 30, suppressing the intrusion of moisture and other substances into the housing 20 from the gap S. The dust lip 44 has a tongue shape that contacts the outer circumferential surface 31S over the entire circumference of the rotating shaft 30, suppressing the intrusion of foreign matter into the housing 20 from the gap S.

[0016] The side lip 45 has an annular shape that follows the outer circumferential surface 31S of the rotating shaft 30. The side lip 45 has a tongue-shaped extension that extends from the core member 42 toward the sliding contact portion 50A of the dust cover 50 along the entire circumference of the rotating shaft 30. The side lip 45 is fixed to the core member 42 such that the tip portion 46 of the side lip 45 slides against the sliding contact portion 50A of the dust cover 50. The sliding contact portion 46T of the dust cover 50 where the side lip 45 slides is divided by a gap S in the radial direction R1 into an inner space S1 and an outer space S2 in the radial direction R1. The side lip 45 prevents foreign matter from entering from the outer space S2 toward the inner space S1.

[0017] The oil seal structure 10 comprises a plurality of plates 51. Each plate 51 has a strip shape extending in the axial direction D1. Each plate 51 is located near the boundary between the outside of the oil seal structure 10 and the outer space S2, and is positioned between the outer peripheral covering portion 50B and the support member 41 in the outer space S2. Each plate 51 is spaced apart from the support member 41. The distance between each plate 51 and the support member 41 allows the centrifugal force acting on the gap S to expel any foreign matter that has entered the gap S out of the gap S towards the outside of the oil seal structure 10.

[0018] The base end portion 51E of the plate 51 in the axial direction D1 is fixed to the inner circumferential surface of the outer circumferential covering portion 50B of the dust cover 50 so that the plate 51 is aligned with the outer circumferential covering portion 50B of the dust cover 50. Methods for fixing the plate 51 include adhesive bonding, welding, and fitting. When the rotating shaft 30 rotates, the plate 51 receives frictional heat from the sliding of the side lip 45 through heat conduction from the dust cover 50. As a result, the plate 51 is heated to a temperature above a predetermined deformation temperature.

[0019] The constituent material of the plate 51 may be a bimetal formed by bonding two types of metals. The two types of metals have different coefficients of thermal expansion from each other at the deformation temperature. When the constituent material of the plate 51 is a bimetal, the side surface of the plate 51 facing the outer peripheral covering portion 50B is composed of a different type of metal from the side surface facing the outer space S2. The constituent material of the plate 51 may be a shape memory alloy that restores its shape at or above the deformation temperature. Note that the constituent material of the plate 51, the shape of the plate 51, and the arrangement of the plate 51 are configured so that the plate 51 does not contact other members such as the support member 41 due to deformation at or above the deformation temperature.

[0020] As shown in FIG. 2(A), the plurality of plates 51 may be equally arranged in the circumferential direction of the rotation axis 30. The plates 51 equally arranged in the circumferential direction make the center of gravity of the plurality of plates 51 coincide with the center of the rotation axis 30, thereby stabilizing the rotation of the dust cover 50.

[0021] As shown in FIGS. 2(A) and 2(B), the base end portion 51E of the side surface of the plate 51 facing the outer peripheral covering portion 50B is fixed to the outer peripheral covering portion 50B at a part of the side surface in the axial direction D1 and at a part of the side surface in the circumferential direction of the rotation axis 30. The tip end portion of the side surface of the plate 51 facing the outer peripheral covering portion 50B is not fixed to the outer peripheral covering portion 50B over the entire axial direction D1 and the entire circumferential direction of the rotation axis 30.

[0022] Note that the portion of the plate 51 fixed to the outer peripheral covering portion 50B may be configured to gradually narrow the width in the circumferential direction of the rotation axis 30 toward the axial direction D1. In this case, the side surface of the plate 51 facing the outer peripheral covering portion 50B gradually separates from the outer peripheral covering portion 50B toward the axial direction D1, and is easily twisted so as to change the inclination with respect to the axial direction D1 and the radial direction R1 toward the axial direction D1.

[0023] Further, the portion of the plate 51 fixed to the outer peripheral covering portion 50B may be configured to keep the width in the circumferential direction of the rotation shaft 30 constant in the axial direction D1. In this case, the side surface of the plate 51 facing the outer peripheral covering portion 50B is more likely to bend so as to maintain an inclination with respect to the radial direction R1 such that it moves away from the outer peripheral covering portion 50B as it moves away from the portion fixed in the circumferential direction of the rotation shaft 30, in the axial direction D1.

[0024] As shown in FIG. 3, as the rotation shaft 30 continues to rotate, the plate 51 that continues to receive frictional heat is heated to a temperature above the deformation temperature and deformed into a fin shape with more twist and bend than before the temperature rise. The plate 51 deformed into a fin shape functions as an axial fan, a centrifugal fan, or a sirocco fan, and forms a larger negative pressure in the outer space S2 than before the thermal deformation.

[0025] According to the above embodiment, the following effects can be obtained. (1) The negative pressure formed by the plate 51 draws the lubricant G from the inner space S1 toward the sliding contact portion 46T, and re-lubricates the sliding of the side lip 45 with respect to the sliding contact portion 50A. As a result, the temperature of the sliding contact portion 46T, and thus the temperature of the plate 51, is lowered, and the plate 51 returns to its original shape. Therefore, self-recovery of the plate 51 by re-lubrication is realized, and the durability of the oil seal structure 10 is improved.

[0026] (2) The negative pressure formed by the plate 51 draws back foreign matter from the inner space S1 toward the outer space S2. And since the shape recovery of the plate 51 due to the drawing of the lubricant G discharges the foreign matter in the outer space S2, the durability of the oil seal structure 10 is also improved thereby.

[0027] Note that the above embodiment can be implemented with the following modifications. The above embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0028] The plate 51 may come into contact with other members due to deformation above the deformation temperature. The plate 51 may come into contact with other members as the amount of deformation gradually increases above the deformation temperature. The other members are members that rotate relative to the dust cover 50, such as the support member 41, the core member 42, and the housing 20.

[0029] Contact between the plate 51, which rotates with the rotating shaft 30, and other components generates contact noise and vibration. The occurrence of contact noise and vibration signals to the outside that the plate 51 has undergone thermal deformation, and consequently, that excessive friction is occurring in the side lip 45. Therefore, contact between the plate 51 and other components allows the driver and service personnel to be alerted to operating conditions that reduce the durability of the oil seal structure 10, and to foresee a decrease in the function of the oil seal structure 10. In other words, the fin-shaped plate 51 may be configured to rotate with the dust cover 50 and come into contact with other components that rotate relative to the rotating shaft 30, thereby providing an abnormality detection function in the oil seal structure 10.

[0030] • Contact between the plate 51, which rotates with the rotating shaft 30, and other components increases the surface area for cooling the dust cover 50. For example, when used in an environment where the area around the oil seal structure 10 may come into contact with water, the contact between the plate 51 and other components utilizes the heat of the dust cover 50 to vaporize water in the housing 20 and support member 41 through heat conduction of the plate 51. This enhances the cooling effect of the dust cover 50 and suppresses the deterioration of the function of the side lip 45. [Explanation of Symbols]

[0031] S...Gap, R1...Radial direction, S1...Inner space, S2...Outer space, 10...Oil seal structure, 20...Housing, 30...Rotating shaft, 31S...Outer surface, 40...Oil seal, 45...Side lip, 46T...Sliding contact area, 50...Dust cover, 51...Plate

Claims

[Claim 1] An oil seal that seals the gap between the rotating shaft inserted into the housing and the housing, A dust cover is fixed to the outer surface of the rotating shaft so as to rotate together with the rotating shaft and covers the oil seal, An oil seal structure comprising, The oil seal is a side lip fixed to the housing so as to slide against the dust cover and having an annular shape along the outer circumferential surface, the side lip comprising a sliding contact portion within the dust cover that divides the gap into an inner space and an outer space in the radial direction of the rotation axis relative to the side lip, A plate is fixed to a part of the dust cover in the outer space and is configured to deform into a fin shape by receiving frictional heat from the sliding of the side lip through the heat conduction of the dust cover, wherein the fin-shaped plate is configured to rotate together with the dust cover to form a negative pressure in the outer space. An oil seal structure characterized by the following features.

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