Oil seal structure

Abstract

To provide an oil seal structure that enables the detection of abnormal conditions. [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, and a sensing plate 51 fixed to a part of the dust cover 50 so as to rotate together with the rotating shaft 30, wherein the sensing plate 51 is thermally deformed so as to come into contact with a member that rotates relative to the sensing plate 51 by receiving frictional heat from the sliding of the side lip 45 through the 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 used in a power transmission device of a vehicle may be submerged when traveling on a river or a muddy road. In an end-face contact type oil seal structure having mud resistance, two rotating members forming a sealed gap may move relative to each other in the axial direction. The generation of a gap between the lip and the thrust surface due to relative movement significantly degrades the seal performance. To solve this problem, in the oil seal structure of Patent Document 1, when the lip is displaced in the axial direction, the thrust surface moves relative to the axial direction so as to cancel out the displacement. Thereby, the contact between the two rotating members is maintained and the seal performance is suitably ensured.

Prior Art Documents

Patent Documents

[0003]

Patent Document

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 problem is an oil seal structure comprising: an oil seal that seals the gap between a rotating shaft inserted through 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, wherein the oil seal has a lip fixed to the housing so as to slide against the dust cover having an annular shape along the outer circumferential surface; and a sensing plate to which a part of the dust cover is fixed so as to rotate together with the rotating shaft, wherein the sensing plate is thermally deformed so as to come into contact with a member that rotates relative to the sensing plate by receiving frictional heat from the sliding of the lip through the heat conduction of 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 sensing plate by heat conduction from the dust cover. The sensing plate, deformed by the frictional heat, comes into contact with a component that rotates relative to the sensing plate. This contact between the component and the sensing plate generates vibrations and abnormal noises to the outside. As a result, abnormalities such as excessive frictional heat can be detected as vibrations and abnormal noises. [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 sensing 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. [Figure 4] Figure 4(A) is a cross-sectional view showing an example of a modified sensing plate, and Figure 4(B) is a cross-sectional view showing another example of a modified sensing plate. [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 includes a sensing plate 51. The sensing plate 51 has a strip shape extending in the axial direction D1. The sensing 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. The sensing plate 51 is spaced apart from the support member 41. The distance between the sensing 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 towards the outside of the oil seal structure 10.

[0018] The base end portion 51E of the sensing 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 sensing plate 51 is aligned with the outer circumferential covering portion 50B of the dust cover 50. Methods for fixing the sensing plate 51 include adhesive bonding, welding, and fitting. When the rotating shaft 30 rotates, the sensing 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 sensing plate 51 is heated to a temperature above a predetermined detection temperature.

[0019] The constituent material of the sensing plate 51 may be a bimetal formed by laminating two types of metals. The two types of metals have mutually different coefficients of thermal expansion at the detection temperature. When the constituent material of the sensing plate 51 is a bimetal, the side surface of the sensing 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 sensing plate 51 may be a shape memory alloy that recovers its shape at or above the detection temperature. The constituent material of the sensing plate 51, the shape of the sensing plate 51, and the arrangement of the sensing plate 51 are configured such that the sensing plate 51 contacts the support member 41 due to thermal deformation at or above the detection temperature.

[0020] As shown in FIG. 2(A), the sensing plate 51 is fixed to a part of the outer peripheral covering portion 50B in the circumferential direction of the rotation axis 30. The sensing plate 51 is arranged on the outer peripheral covering portion 50B such that the side surface facing the rotation axis 30 is disposed substantially parallel to the tangential direction on the outer peripheral surface 31S of the rotation axis 30. Note that the sensing plates 51 may be equally arranged along the circumferential direction of the rotation axis 30. The sensing plates 51 equally arranged in the circumferential direction match the center of gravity of the plurality of sensing plates 51 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 sensing plate 51 facing the outer peripheral covering portion 50B is fixed to the outer peripheral covering portion 50B. The tip end portion 51F of the side surface of the sensing plate 51 facing the outer peripheral covering portion 50B is not fixed to the outer peripheral covering portion 50B and is separated from the inner peripheral surface of the outer peripheral covering portion 50B. The sensing plate 51 with only the base end portion 51E fixed is easily bent so as to move the tip end portion 51F away from the inner peripheral surface of the outer peripheral covering portion 50B and closer to the support member 41.

[0022] Note that, a portion of the sensing 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 shaft 30 toward the axial direction D1. In this case, the side surface of the sensing 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. In the tip portion 51F deformed to be twisted, it may be configured to rotate from a portion close to the outer peripheral covering portion 50B toward a portion far from it. That is, the tip portion 51F deformed to be twisted may have an inclination such that it gradually approaches the support member 41 while rotating together with the rotation shaft 30.

[0023] Further, a portion of the sensing 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 toward the axial direction D1. In this case, the side surface of the sensing plate 51 facing the outer peripheral covering portion 50B is easily bent so as to keep the inclination with respect to the radial direction R1 such that it separates from the outer peripheral covering portion 50B as it separates from the fixed portion in the circumferential direction of the rotation shaft 30, toward the axial direction D1. Also in this case, the tip portion 51F bent to be inclined with respect to the radial direction R1 may have an inclination such that it gradually approaches the support member 41 while rotating together with the rotation shaft 30.

[0024] As shown in FIG. 3, when the rotation shaft 30 continues to rotate, the sensing plate 51 continuously receiving frictional heat is heated to a temperature higher than the detected temperature, and is deformed into a shape with greater bending and twisting than before the temperature rise. The deformed sensing plate 51 rotates while contacting the support member 41.

[0025] According to the above embodiment, the following effects can be obtained. (1) Contact between the deformed sensing plate 51 and the support member 41 generates vibrations and abnormal noises to the outside through the rotation of the sensing plate 51. This signals to the outside that the sensing plate 51 is above the detection temperature, and consequently, that the frictional heat generated by the sliding of the side lip 45 is above a predetermined amount. As a result, abnormalities such as excessive frictional heat are detected as vibrations and abnormal noises. Therefore, it is possible to alert drivers and service personnel to operating conditions that reduce the durability of the oil seal structure 10 and to predict the deterioration of the function of the oil seal structure 10.

[0026] (2) The sensing plate 51 remains positioned between the outer peripheral covering portion 50B and the support member 41 in the outer space S2. Therefore, compared to the case where the sensing plate 51 is positioned radially R1 inward from the support member 41, foreign matter that enters the gap S is more easily discharged from the gap S toward the outside of the oil seal structure 10.

[0027] (3) Contact between the sensing plate 51 and the support member 41 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 sensing plate 51 and the support member 41 utilizes the heat of the dust cover 50 to vaporize water and other substances on the support member 41 through heat conduction from the sensing plate 51. This enhances the cooling effect of the dust cover 50 and suppresses the deterioration of the function of the side lip 45 due to frictional heat.

[0028] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0029] As shown in Figure 4(A), the tip 51F of the sensing plate 51 may have a projection 51T that protrudes toward the support member 41. The projection 51T may have a columnar shape that extends tangentially on the outer circumferential surface 31S of the rotating shaft 30. The tangentially extending projection 51T suppresses bending and twisting due to frictional force acting on the tip 51F. The projection 51T may be one or more hemispherical bodies that make point contact with the support member 41.

[0030] As shown in Figure 4(B), the tip portion 51F of the sensing plate 51 may be provided with a sliding portion 51M. The sliding portion 51M is more slippery against the support member 41 than the sensing plate 51. The sliding portion 51M may be a molded member bonded to the sensing plate 51, or a surface treatment layer applied to the surface of the sensing plate 51.

[0031] The sensing plate 51 may be positioned inside the radial R1 relative to the support member 41. In this case, the sensing plate 51 is configured to bend outward in the radial R1 so that its tip portion 51F moves closer to the core member 42 when the temperature is above the detection temperature. The deformed sensing plate 51 may then come into contact with the core member 42.

[0032] The member that the sensing plate 51 contacts due to deformation is not limited to the support member 41, but may be changed to a member that rotates relative to the dust cover 50, such as the core member 42 or the housing 20. The member that contacts the deformed sensing plate 51 may have a surface treatment applied to the surface that contacts the sensing plate 51 to make the sensing plate 51 slide more easily. [Explanation of symbols]

[0033] S...Gap, R1...Radial direction, 10...Oil seal structure, 20...Housing, 30...Rotation shaft, 31S...Outer surface, 40...Oil seal, 45...Side lip, 50...Dust cover, 51...Sensing 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, An oil seal structure comprising, The oil seal comprises a lip fixed to the housing so as to slide against the dust cover and having an annular shape along its outer circumferential surface. A sensing plate having a portion of the dust cover fixed so as to rotate together with the rotation axis, wherein the sensing plate is thermally deformed so as to come into contact with a member that rotates relative to the sensing plate by receiving frictional heat from the sliding of the lip through the heat conduction of the dust cover. An oil seal structure characterized by the following features.

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