Seal mechanism having metal seal ring

Abstract

A sealing mechanism (1) for sealing an annular gap (4) between a housing (2) and a rotating shaft (3) is provided with a metal sealing ring (10). A first shaft sliding surface (15), a labyrinth seal forming surface (16), and a second shaft sliding surface (17) are formed on a circular inner circumferential surface (11) of a seal ring (10). The first shaft sliding surface and the second shaft sliding surface (15, 17) are pear-peel-shaped surfaces having a predetermined surface roughness. A labyrinth seal is formed between the labyrinth seal forming surface (16) and the circular outer peripheral surface (3a) of the rotating shaft (3). The first and second shaft sliding surfaces (15, 17) are formed to be pear-peel-shaped surfaces so that frictional resistance between the first and second shaft sliding surfaces (15, 17) and the rotating shaft (3) can be reduced, and wear and heat generation of the first and second shaft sliding surfaces (15, 17) can be suppressed. In addition, a sealing mechanism capable of preventing oil leakage in two directions in the axial direction can be obtained.

Description

Technical Field

[0001] The present invention relates to a sealing mechanism for sealing an annular gap between a relatively rotatable shaft and a housing. Background Art

[0002] As such a sealing mechanism, rubber products such as oil seals and gaskets are widely used. The rubber oil seal is installed on the housing side at the annular gap between the housing and the rotating shaft. The sealing lip of the oil seal is brought into contact with the outer peripheral surface of the rotating shaft to form a state of sealing the annular gap, thereby preventing the lubricating oil from leaking out of the housing through the annular gap. The contact force of the lip tip with respect to the outer peripheral surface of the rotating shaft is controlled by the pressure of the rubber oil seal body and the spring pressure of the spring arranged inside the oil seal.

[0003] The sealing mechanism including such a rubber oil seal has the following problems to be solved.

[0004] (1) Since the rubber seal lip is in contact with the outer peripheral surface of the metal rotating shaft, if the seal lip is worn or deteriorated, an appropriate contact state cannot be formed, resulting in oil leakage.

[0005] (2) To prevent oil leakage, there is a method of increasing the force (tension) of the oil seal in the circumferential direction. However, it is difficult to estimate the heat generation and wear amount of the oil seal caused by the contact force with the metal (rotating shaft), so it is also difficult to set the tension to an appropriate value.

[0006] (3) Frictional resistance is generated when the oil seal contacts the metal (rotating shaft), which generates heat at the contact point. This heat affects the product characteristics.

[0007] (4) Since the oil seal is in contact with the metal (rotating shaft), the metal is scratched, resulting in secondary oil leakage.

[0008] (5) Since a general oil seal requires a metal ring and a spring, it is particularly difficult to manufacture a product that is desired to be small and light.

[0009] (6) The oil leakage prevention portion (lip portion) of the oil seal can prevent oil leakage in one direction only, and the basic structure is not intended to prevent oil leakage in both directions.

[0010] Here, a sealing device having a sealing lip is proposed in Patent Document 1. In order to reduce the frictional force accompanying the sliding of the rubber sealing lip and suppress wear, the sealing device described in this document forms fine irregularities on the sliding surface of the sealing lip and supplies grease of a predetermined viscosity to the sliding surface.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: International Publication No. 2012 / 127895 Summary of the invention

[0014] The existing sealing mechanism with a rubber lip seal still has the problem of wear and heat generation of the sliding surface of the lip seal, which causes the sealing performance to deteriorate. In addition, the contact state of the lip seal with the rotating shaft is formed by the spring force, so it is not easy to form an appropriate contact state (sealing state). In addition, the wear and heat generation of the lip seal also change according to the contact state, so it is not easy to maintain the appropriate contact state (sealing state).

[0015] In view of the above-mentioned problems, an object of the present invention is to provide a sealing mechanism capable of eliminating the disadvantages of a sealing mechanism including a rubber oil seal.

[0016] In order to solve the above-mentioned problems, the present invention provides a sealing mechanism for sealing an annular gap between a relatively rotatable shaft and a housing, characterized in that:

[0017] The sealing mechanism comprises a metal sealing ring.

[0018] A first shaft sliding surface, a labyrinth seal forming surface and a second shaft sliding surface are formed on the inner circumferential surface of the sealing ring along the axial direction.

[0019] The first shaft sliding surface and the second shaft sliding surface are surfaces on which the outer peripheral surface of the shaft slides, and the first shaft sliding surface and the second shaft sliding surface are formed with a pear skin-like surface throughout the entire circumferential direction.

[0020] The labyrinth seal forming surface located between the first shaft sliding surface and the second shaft sliding surface has an annular concave portion and an annular convex portion that form a labyrinth seal with the outer peripheral surface of the shaft.

[0021] In the sealing mechanism of the present invention, a shaft sliding surface (a first shaft sliding surface and a second shaft sliding surface) is formed on the inner peripheral surface of a metal sealing ring, so that the shaft sliding surface is formed into a pear-skin-like surface with a predetermined surface roughness. By forming the shaft sliding surface into a pear-skin-like surface, the friction resistance between the shaft sliding surface and the shaft can be reduced, thereby suppressing the wear and heat generation of the shaft sliding surface. In addition, unlike a rubber oil seal, there is no need to assemble a metal ring or a spring component for making a lip seal contact the outer peripheral surface of the shaft inside, so it is also easy to achieve compactness and lightness.

[0022] In addition, regarding the sealing mechanism of the present invention, when microscopically observed, the shaft sliding surface formed into a pear-skin surface becomes a tiny oil accumulation portion, and therefore also functions as an oil leakage prevention portion. A labyrinth seal is formed between the labyrinth seal forming surface located between the shaft sliding surfaces and the outer peripheral surface of the shaft. The labyrinth seal and the oil leakage prevention function of the shaft sliding surfaces formed into pear-skin surfaces on both sides can prevent oil leakage in both directions of the axial direction.

[0023] Here, the sealing mechanism of the present invention further comprises a mounting ring mounted on the sealing ring and located between the sealing ring and the housing. Preferably, the mounting ring is formed of a material that can be elastically deformed or can be expanded and contracted. Due to the elastic displacement or expansion and contraction of the mounting ring, errors such as dimensional errors, assembly errors, or alignment errors of the shaft, housing, and sealing ring can be absorbed. In addition, the change in the gap between the sealing ring and the shaft during rotation or the influence of eccentricity can be alleviated.

[0024] In addition, the pear-skin surface formed on the shaft sliding surface can be formed to have a surface roughness of about 3 μm to 15 μm with a maximum height Ry. In this case, the gap size between the shaft sliding surface of the metal seal ring and the outer peripheral surface of the shaft can be set to 5 μm to 15 μm.

[0025] Effects of the Invention

[0026] In the sealing mechanism of the present invention, the shaft sliding surface (first shaft sliding surface, second shaft sliding surface) formed on the inner peripheral surface of the metal sealing ring is formed into a pear-skin-like surface, and a labyrinth seal is arranged between the shaft sliding surfaces. Thus, wear and heat generation of the shaft sliding surface can be suppressed, and oil leakage in two directions of the axial direction can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic half-sectional view showing an example of a sealing mechanism to which the present invention is applied.

[0028] Figure 2 It is shown Figure 1 An illustration of the main parts of the sealing mechanism. DETAILED DESCRIPTION

[0029] The following is a description of an embodiment of the sealing mechanism according to the present invention with reference to the accompanying drawings. Figure 1 , 2As shown, the sealing mechanism 1 involved in the embodiment is a mechanism for sealing the annular gap 4 formed between the housing 2 and the rotating shaft 3. The sealing mechanism 1 includes: a metal sealing ring 10; and a rubber or resin mounting ring 20, which is coaxially mounted on the outer periphery of the sealing ring 10 and formed in an annular shape. The mounting ring 20 is arranged between the sealing ring 10 and the housing 2. The sealing ring 10 is mounted on the housing 2 by means of the mounting ring 20. In addition, for the sealing ring 10, for example, steel materials such as SS material (general structural rolled steel), SC material (carbon steel for mechanical structure), SCr material (chrome steel), SCM material (chrome-molybdenum steel), SNC material (nickel-chrome steel), and SNCM material (nickel-chrome-molybdenum steel) are used.

[0030] The seal ring 10 is a ring having a rectangular cross section, and includes a circular inner peripheral surface 11, a circular outer peripheral surface 12, an inner end surface 13 formed in a circular shape facing the inside of the circular gap 4, and an outer end surface 14 formed in a circular shape on the opposite side. A first shaft sliding surface 15, a labyrinth seal forming surface 16, and a second shaft sliding surface 17 are formed in the circular inner peripheral surface 11 in order from the inner end surface 13 side toward the outer end surface 14 along the direction of the axis 1a.

[0031] The first shaft sliding surface 15 and the second shaft sliding surface 17 are circular inner circumferential surfaces on which the circular outer circumferential surface 3a of the rotating shaft 3 can slide. The first shaft sliding surface 15 is a circular inner circumferential surface having a certain width in the direction of the axis 1a relative to the inner end surface 13, and the second shaft sliding surface 17 is a circular inner circumferential surface having a certain width in the direction of the axis 1a relative to the outer end surface 14. The first shaft sliding surface and the second shaft sliding surface 15 and 17 are pear-skin-like surfaces with a predetermined surface roughness.

[0032] The labyrinth seal forming surface 16 between the first shaft sliding surface and the second shaft sliding surface 15 and 17 is formed with: two annular recesses 18a and 18b; and an annular convex portion 19, which is located between the annular recesses 18a and 18b. The annular recesses 18a and 18b are recesses with a rectangular cross section of a certain width and a certain depth, and are open to the inner circumference (rotating shaft side). The annular convex portion 19 formed between the annular recesses 18a and 18b is a convex portion with a rectangular cross section of a certain width and a certain height, and a predetermined gap is formed between the inner circumference of the annular convex portion 19 and the circular outer circumference 3a of the rotating shaft 3. A labyrinth seal is formed between the annular recesses 18a and 18b and the annular convex portion 19 and the circular outer circumference 3a of the rotating shaft 3. In addition, the structure of the labyrinth seal forming surface 16, that is, the number, width, and height (depth) of the annular concave portions and the annular convex portions are not limited to the embodiment.

[0033] The circular inner circumferential surface 11 of the seal ring 10 and the circular outer circumferential surface 3a of the rotating shaft 3 are subjected to surface treatments such as nitriding, high-frequency quenching, carburizing, and coating to increase the surface hardness. In addition, after the surface treatment is performed to increase the surface hardness, the circular inner circumferential surface 11 of the seal ring 10 is subjected to a pear skin-like surface processing. The pear skin-like surface is formed, for example, by shot peening. Here, according to the rotation conditions, the outer circumferential surface portion of the circular outer circumferential surface 3a of the rotating shaft 3 that is opposite to the seal ring 10 is also formed into a pear skin-like surface. The pear skin-like surface formed on the first shaft sliding surface and the second shaft sliding surface 15, 17 of the seal ring 10 can be formed into a surface with a surface roughness of about 3μm to 15μm in maximum height Ry. In this case, the gap size between the first shaft sliding surface, the second shaft sliding surface 15, 17 and the circular outer circumferential surface 3a of the rotating shaft 3 can be formed into 5μm to 15μm.

[0034] Next, the metal seal ring 10 of the above structure is installed on the housing 2 by means of the mounting ring 20. The mounting ring 20 is a component made of a rubber material or a resin material, and can be elastically deformed or expanded. The mounting ring 20 includes: a cylindrical portion 21 of a certain thickness; and an annular end portion 22 of a certain thickness, which is bent at a right angle from one end of the cylindrical portion 21 and extends radially inward. The cylindrical portion 21 is sandwiched between the circular inner peripheral surface 2a of the housing 2 and the circular outer peripheral surface 12 of the seal ring 10 in the radial direction, and the annular end portion 22 is sandwiched between the annular inner peripheral end surface 2b of the housing 2 and the inner end surface 13 of the seal ring 10 in the axial direction.

[0035] Errors such as dimensional errors, assembly errors, and alignment errors occur in the housing 2, the rotating shaft 3, and the seal ring 10. In addition, when the rotating shaft 3 rotates, the gap size between the seal ring 10 and the rotating shaft 3 may change, the rotating shaft 3 may become eccentric, etc. If the metal seal ring 10 is mounted on the circular inner peripheral surface 2a of the housing 2 via the rubber or resin mounting ring 20, the above errors are absorbed by the elastic deformation or expansion and contraction of the mounting ring 20, and the influence of the gap size change, eccentricity, etc. is alleviated.

[0036] According to the sealing mechanism 1 including the metal seal ring 10 of this example, as described below, the problems of the conventional sealing mechanism including the rubber oil seal can be solved.

[0037] (1) Since the rubber oil seal is in contact with the outer peripheral surface of the metal rotating shaft, if the rubber oil seal is worn or deteriorated, oil leakage occurs.

[0038] In contrast, the sealing mechanism 1 of this example forms the first and second shaft sliding surfaces 15 and 17 of the metal seal ring 10 subjected to high hardness surface treatment into a pear-skin-like surface, thereby preventing the wear of the first and second shaft sliding surfaces 15 and 17. When the pear-skin-like surface is observed microscopically, it becomes a tiny oil reservoir, thus having the function of preventing oil leakage. Due to the running-in of the contact between metals, the deterioration of the rubber oil seal will not occur.

[0039] (2) To prevent oil leakage, there is a method of increasing the force (tension) of the oil seal in the circumferential direction. However, it is difficult to estimate the heat generation and wear amount of the oil seal caused by the contact force with the metal (rotating shaft), so it is also difficult to set the tension to an appropriate value.

[0040] In contrast, the sealing mechanism 1 of this example does not require control based on a force (tension) that is stretched in the circumferential direction as in an oil seal, and therefore has the advantage of being able to easily estimate the amount of heat generation and wear.

[0041] (3) Frictional resistance is generated when the oil seal contacts the metal (rotating shaft), which causes heat to be generated at the contact part, affecting the product characteristics.

[0042] In contrast, in the sealing mechanism 1 of the present example, the first shaft sliding surface and the second shaft sliding surface 15, 17 of the metal sealing ring 10 are formed into pear-skin-like surfaces, thereby reducing the frictional resistance between the first shaft sliding surface, the second shaft sliding surface 15, 17 and the rotating shaft 3, enabling smooth movement and suppressing heat generation of the sliding part.

[0043] (4) Since the oil seal is in contact with the metal (rotating shaft), scratches are formed on the metal, causing secondary oil leakage. The tip of the oil seal lip is in line contact with the rotating shaft, causing "scratches".

[0044] In contrast, in the sealing mechanism 1 of the present example, when assembling the metal sealing ring 10, lubricating oil (grease is applied) is supplied between the metal sealing ring 10 and the circular outer peripheral surface 3a of the rotating shaft 3, thereby preventing the occurrence of "initial wear" and "scars" caused by the running-in between the metals.

[0045] Furthermore, the first and second shaft sliding surfaces 15 and 17 of the metal seal ring 10 are pear-skin-like surfaces and are in point contact with the circular outer peripheral surface 3a of the rotating shaft 3, thereby suppressing the occurrence of "scratches" associated with sliding.

[0046] (5) For general oil seals, a mold is required to manufacture the rubber part, and it is not easy to change the size. In particular, since the metal ring and spring component are assembled inside the oil seal, it is not easy to achieve miniaturization, and it is difficult to manufacture a product that is expected to be small and lightweight.

[0047] In contrast, the sealing mechanism 1 of this example uses a metal seal ring 10. The metal seal ring 10 has no internally assembled parts and is therefore less likely to be restricted in size. Therefore, it is more advantageous in achieving miniaturization than a rubber seal ring.

[0048] (6) The oil leakage prevention portion (lip portion) of the oil seal can prevent oil leakage in one direction only, and the basic structure is not intended to prevent oil leakage in two directions.

[0049] In contrast, in the sealing mechanism 1 of the present example, the first and second shaft sliding surfaces 15 and 17 having pear-skin-like surfaces are in point contact with the circular outer peripheral surface 3a of the rotating shaft 3, and there is no directionality in the oil leakage prevention function, so oil leakage in both axial directions can be prevented.

Claims

1. A sealing mechanism for sealing an annular gap between a relatively rotatable shaft and a housing, characterized in that: The sealing mechanism comprises a metal sealing ring. A first shaft sliding surface, a labyrinth seal forming surface and a second shaft sliding surface are formed on the inner circumferential surface of the sealing ring along the axial direction. The first shaft sliding surface and the second shaft sliding surface are surfaces on which the outer circumferential surface of the shaft slides, and a pear-skin-like surface is formed on the first shaft sliding surface and the second shaft sliding surface over the entire circumferential direction. The labyrinth seal forming surface located between the first shaft sliding surface and the second shaft sliding surface includes an annular concave portion and an annular convex portion that form a labyrinth seal with the outer peripheral surface of the shaft.

2. The sealing mechanism according to claim 1, characterized in that: The sealing mechanism further comprises a mounting ring mounted on the sealing ring and located between the sealing ring and the housing. The mounting ring is formed of an elastically deformable material or a stretchable material.

3. The sealing mechanism according to claim 2, characterized in that: The mounting ring is a rubber ring or a resin ring and includes: a portion sandwiched between the seal ring and the housing in a radial direction; and a portion sandwiched between the seal ring and the housing in an axial direction.

4. The sealing mechanism according to claim 1, characterized in that: The pear-skin-like surface is a surface having a surface roughness with a maximum height Ry of about 3 μm to 15 μm.

5. The sealing mechanism according to claim 3, characterized in that: The gap size between the first shaft sliding surface, the second shaft sliding surface and the outer peripheral surface of the shaft is 5 μm to 15 μm.

6. The sealing mechanism according to claim 1, characterized in that: The sealing mechanism further comprises a mounting ring mounted on the sealing ring and located between the sealing ring and the housing. The mounting ring is formed of a rubber material or a resin material that is elastically deformable or stretchable. The mounting ring includes: a portion sandwiched between the seal ring and the housing in a radial direction; and a portion sandwiched between the seal ring and the housing in an axial direction. The pear-skin-like surface is a surface with a surface roughness of 3 μm to 15 μm with a maximum height Ry. The gap size between the first shaft sliding surface, the second shaft sliding surface and the outer peripheral surface of the shaft is 5 μm to 15 μm.

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