JP2017198234A - Sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction of tensile force of a spring to prevent oil leakage over a long period in a sealing device including the spring which reinforces a contact pressure of a radial lip.SOLUTION: A sealing device 10 includes a radial lip 20 extending to a side where oil is enclosed. A recessed part 21, into which an annular spring 40 is fitted, is formed at an outer periphery of the radial lip 20. A tip end 22 which slidably contacts with an outer peripheral surface of a rotation shaft 50 is formed at an inner periphery of the radial lip 20. A swelling part 24 which contacts with the oil to swell and is formed by a rubber material is exposed in a position of the recessed part 21 which contacts with at least the spring 40 in a radial direction. The tip end 22 is formed by a rubber material different from the above-mentioned rubber material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealing device that prevents oil leakage, and more particularly, to a sealing device that includes a spring that reinforces the contact pressure of a radial lip.

In a sealing device provided with an elastic radial lip, the radial lip is pressed against the rotating shaft to generate an appropriate surface pressure distribution at the contact portion, thereby preventing oil as a sealing object from leaking out. However, when the sealing device is used for a long time, an appropriate surface pressure distribution may not be maintained because the elasticity of the radial lip is reduced or the sliding contact portion is worn.
Therefore, conventionally, as a sealing device that prevents oil leakage, a spring is attached to the outer diameter side of a radial lip formed of an elastic body such as rubber, and the force that presses the radial lip against the rotating shaft is reinforced. (For example, Patent Document 1).

  The sealing device described in Patent Document 1 seals a gap between a retainer, which is a housing assembled coaxially with each other, and a crankshaft, which is a rotating shaft, and a metal core (holding member) is provided on the housing side. While fitting and fixing, the inner periphery of the radial lip is in contact with the rotating shaft. The radial lip is formed of an elastic body such as rubber. An annular spring is fitted outside the radial lip in the radial direction to reinforce the force for pressing the radial lip against the rotating shaft.

No. 08-10711

  However, when the sealing device having the conventional structure is used for a long time in a high temperature environment exceeding 120 ° C., for example, the residual stress of the spring is removed by the temperature, so that the spring constant is lowered. In this case, since the force pressing the radial lip against the rotating shaft is reduced, the surface pressure at the contact portion between the radial lip and the rotating shaft is reduced, and there is a possibility that oil leaks out.

  The present invention provides a sealing device provided with a spring that reinforces the contact pressure of a radial lip, and prevents the leakage of oil over a long period of time even when used in a high-temperature environment, preventing a decrease in tension. It aims at providing the sealing device which can do.

  One form of this invention seals between the housing and the rotating shaft which penetrates the opening part provided in this housing, and seals which prevent that the oil enclosed inside the said housing leaks outside An apparatus comprising: a fixed portion fixed to the housing; and a radial lip formed of an elastic body extending from the fixed portion toward a side where the oil is sealed. On the outer periphery of the lip, a recess that opens radially outward is formed over the entire circumference, and an annular spring is fitted, and on the inner periphery, a tip edge that is in sliding contact with the outer peripheral surface of the rotating shaft is formed. And a swollen portion formed of a rubber material that swells in contact with the oil is exposed at least in a position in radial contact with the spring, and the tip edge is formed of the rubber material. Different rubber material It is characterized by being formed.

  In a sealing device provided with a spring that reinforces the contact pressure of the radial lip, even when used in a high-temperature environment, it is possible to prevent a decrease in tightening force and prevent oil leakage over a long period of time.

It is an axial sectional view of the sealing device which is one embodiment of the present invention. It is a conceptual diagram for demonstrating the change of the residual stress of a spring, and the dimensional change when a rubber material swells.

Embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an axial cross-sectional view showing an embodiment (hereinafter referred to as “this embodiment”) of a sealing device according to the present invention. The sealing device 10 is incorporated in a vehicle engine (not shown) and is fitted coaxially with the crankshaft 50.

  The sealing device 10 has an annular shape, and includes a metal core 12, a radial lip 20 and a grease lip 30 formed integrally with the core 12, and a spring 40. The central axis of the sealing device 10 is the same as the rotation axis of the crankshaft 50. In the following description, the direction of the central axis of the sealing device 10 is referred to as the axial direction, the direction orthogonal to the central axis is the radial direction, and the central axis The direction that goes around is called the circumferential direction.

  The cored bar 12 is formed by pressing a cold rolled steel plate such as SPCC. The shape of the cross section in the axial direction of the cored bar 12 is L-shaped, a cylindrical cylindrical portion 13 formed in the axial direction, and a flange portion 14 extending radially inward from one axial end of the cylindrical portion 13; Are integrally formed.

The radial lip 20 extends substantially in the axial direction in the same direction as the cylindrical portion 13 with the inner diameter side of the flange portion 14 as a base.
In the vicinity of the distal end of the radial lip 20, a recess 21 is formed on the outer diameter side so as to have an axial cross section that opens radially outward. A tapered surface a and a tapered surface b that are inclined in opposite directions are formed coaxially on the inner diameter side, and a tip edge 22 is formed over the entire circumference at a portion where the tapered surface a and the tapered surface b intersect. . In the axial cross section, the leading edge 22 of the radial lip 20 is pointed radially inward.
The recess 21 and the tip edge 22 are formed at substantially the same position in the axial direction.

An annular spring 40 is fitted in the recess 21. The spring 40 is manufactured by plastic working a spring stainless steel wire (SUS304WPB) or the like, and is formed in a spiral shape along the circumferential direction thereof. Thereby, it can extend with elasticity in the circumferential direction.
A spring locking portion 23 is formed at the distal end of the radial lip 20. The spring locking portion 23 is formed in the radial direction on the side closer to the tip of the radial lip 20 than the recess 21. The outer diameter dimension is larger than the diameter dimension (average value of the outer diameter dimension and the inner diameter dimension) of the spring 40, and when the spring 40 is attached to the recess 21, the spring 40 does not easily fall off. Yes.

  A swollen portion 24 is formed at the position of the concave portion 21 of the radial lip 20. The swelling part 24 is formed of a rubber material of ethylene propylene rubber (EPDM). Symbols in parentheses are JIS symbols (hereinafter the same). The swollen portion 24 has a crescent shape in which an axial cross-section is convex inward in the radial direction, and is formed in a uniform cross-sectional shape over the entire circumference. The radially outer surface of the swollen portion 24 forms a recess 21, and the axial cross section is formed with a curvature substantially equal to the outer diameter of the spring 40 in the axial cross section.

  The radial lip 20 is formed of an elastic body such as nitrile rubber (NBR) at a portion other than the swelling portion 24, the bending portion 25 extending in the axial direction from the inner diameter side of the flange portion 14, and the diameter of the swelling portion 24. A sliding contact portion 26 formed inward in the direction and a spring locking portion 23 are provided. Each part is formed in a uniform cross-sectional shape over the entire circumference. In the following description, portions of the radial lip 20 that are formed of nitrile rubber (referred to as the bending portion 25, the sliding contact portion 26, and the spring locking portion 23) may be referred to as “other elastic portions E”.

  The grease lip 30 extends in the substantially axial direction opposite to the radial lip 20 with the inner diameter side of the flange portion 14 as a base. Like the radial lip 20, the grease lip 30 is formed of an elastic body such as nitrile rubber.

The radial lip 20 and the grease lip 30 are formed by vulcanization molding of a rubber material with a high-temperature mold in a state where the core metal 12 is molded.
At the time of molding, ethylene propylene rubber forming the swelling portion 24 and nitrile rubber forming the other elastic portion E excluding the swelling portion 24 are simultaneously inserted into the mold. Since the ethylene propylene rubber and the nitrile rubber are vulcanized and bonded to each other by heat at the time of molding, the radial lip 20 can be formed in a form in which the swelling portion 24 and the other elastic portion E are integrated.
In the sealing device 10, the outer periphery of the cylindrical portion 13 and one side surface in the axial direction of the flange portion 14 are formed so as to be simultaneously covered with nitrile rubber when the radial lip 20 and the grease lip 30 are formed.

  Thus, in the portion where the concave portion 21 is formed, the swelling portion 24 formed of ethylene propylene rubber is exposed on the outer diameter side of the radial lip 20.

The outer periphery of the sealing device 10 is fitted into an opening of a retainer 51 (housing) attached to the engine block in an interference fit state. In FIG. 1, the left side of the drawing is the inside of the engine, and the radial lip 20 is incorporated in a direction extending toward the inside of the engine in which engine oil is sealed, with the inner diameter side of the flange portion 14 as a base. .
Between the inner periphery of the opening and the outer periphery of the cylindrical portion 13, nitrile rubber, which is an elastic body, is assembled in a state compressed in the radial direction. Thereby, the outflow of engine oil from the fitting portion between the retainer 51 and the sealing device 10 is prevented.

The inner periphery of the radial lip 20 is in contact with the outer peripheral surface of the crankshaft 50 penetrating the opening over the entire periphery. Before the sealing device 10 is attached, the inner diameter dimension of the radial lip 20 is smaller than the outer diameter dimension of the crankshaft 50. 1/2 of this dimensional difference (diameter dimension) is called interference δ1 of radial lip 20. In FIG. 1, in order to show a state in which the radial lip 20 has an interference δ1, the radial lip 20 is shown in a form overlapping the sliding contact portion 26.
When the sealing device 10 is fitted to the crankshaft 50, the swelled portion 24 and the other elastic portion E are integrally expanded by the interference δ1 while the bent portion 25 is bent in the radial direction.
At this time, since the radial dimension of the radial lip 20 is elastically expanded, the radial lip 20 tends to shrink to the diameter dimension in the free state. The radial lip 20 is pressed radially inward against the outer periphery of the crankshaft 50 by the force to be contracted, and an appropriate surface pressure distribution is obtained at the contact portion between the outer periphery of the crankshaft 50 and the tip edge 22. Has occurred. The force when the radial lip 20 is pressed against the outer periphery of the crankshaft 50 is referred to as “tightening force”.

The spring 40 is fitted on the outer side of the recess 21 coaxially with the sealing device 10. When the sealing device 10 is fitted to the crankshaft 50, the diameter dimension Lo of the bottom of the recess 21 is larger than the inner diameter dimension of the spring 40 in the free state. Thereby, the spring 40 is mounted in a state where the circumferential length is elastically extended. For this reason, since the radial lip 20 is urged radially inward by the force of the circumferential length of the spring 40 to contract, the radial lip 20 is pressed against the outer periphery of the crankshaft 50 with a stronger force. Thus, a larger surface pressure distribution is generated at the contact portion between the outer periphery of the crankshaft 50 and the tip edge 22.
In this way, the radial force generated by the elastic force of the rubber forming the radial lip 20 (hereinafter referred to as “rubber component of the compressive force”) and the elastic force of the spring 40 (hereinafter referred to as “spring component of the compressive force”) The lip 20 is pressed against the outer periphery of the crankshaft 50.

  The inner diameter dimension of the grease lip 30 is slightly larger than the outer diameter dimension of the crankshaft 50. The grease lip 30 forms a labyrinth with the outer peripheral surface of the crankshaft 50 and prevents muddy water and dust from reaching the radial lip 20 directly.

Next, the operation of the sealing device 10 in this embodiment will be described with reference to FIG.
When the engine is continuously used in a high load state, the temperature of the engine body rises, so that the temperature of the sealing device 10 rises. Thus, by being exposed to a high temperature, the residual stress at the time of plastic working is relaxed in the spring 40, and the spring constant in the circumferential direction is lowered.
If it is assumed that the diameter dimension of the recess 21 into which the spring 40 is fitted is constant before and after being exposed to a high temperature, the diameter of the spring 40 in the free state will be restored as the spring constant decreases. The elastic force is reduced. In this case, the surface pressure of the contact portion where the outer periphery of the crankshaft 50 and the tip edge 22 contact each other is reduced.

In the sealing device 10 of the present embodiment, the concave portion 21 in which the spring 40 is mounted is provided with a swelling portion 24 using ethylene propylene rubber as a rubber material, and the swelling portion 24 is exposed radially outward. Yes.
Since the radial lip 20 is incorporated toward the inside of the engine, the engine oil reaches the swelling portion 24 when the engine is operated.
Engine oil is a mineral oil-based lubricating oil and can easily penetrate into ethylene propylene rubber (EPDM). For this reason, in the swelling part 24, rubber material swells and the dimension L1 of radial direction increases.

  The swollen portion 24 has an axial cross section projecting radially inward, and an outer peripheral surface thereof is in contact with the spring 40 in the radial direction. As the dimension L1 in the radial direction of the swollen portion 24 increases, the inner circumference of the spring 40 is pushed outward in the radial direction to expand the diameter. For this reason, the elastic force which tries to restore | restore to the diameter dimension in the free state of the spring 40 rises. As a result, the spring component of the tension force can be increased, so that the tension force of the radial lip 20 can be increased.

FIG. 2 is a conceptual diagram for explaining a tendency when the residual stress of the spring 40 decreases with time and a tendency that the dimension L1 increases with time when the swelling portion 24 swells in a high temperature environment.
As shown in FIG. 2, in a high temperature environment, the residual stress of the spring 40 is greatly reduced in the initial stage and thereafter converges to a constant value. For this reason, in the present embodiment, the elastic force to be restored to the diameter dimension in the free state of the spring 40 is greatly reduced in the initial stage and then converges to a constant value.
On the other hand, the dimension L1 in the radial direction of the swollen portion 24 increases significantly at the initial stage when it comes into contact with the engine oil, and then converges to a constant value. For this reason, the diameter dimension of the spring 40 increases greatly at the initial stage of starting the engine, and then converges to a constant value. As a result, the elastic force to restore the diameter of the spring 40 in the free state greatly increases in the initial stage, and then converges to a certain value.
That is, the decrease in the spring component of the tension force due to the decrease in the residual stress of the spring 40 and the increase in the spring component of the tension force due to the swelling of the rubber are complementary to each other. Even in this case, the spring component of the tension does not decrease.

  On the other hand, the elastic part E other than the swelling part 24 is formed of a nitrile rubber having high resistance to mineral oils such as engine oil, so that the elasticity is hardly lowered or worn. . For this reason, even if it is a case where it exposes to a high temperature environment, the rubber component of tension | tensile_strength does not fall.

  As a result, even when exposed to a high temperature environment, the change in the tension force of the radial lip 20 can be reduced, so that the contact portion where the outer periphery of the crankshaft 50 and the tip edge 22 are in contact is moderate. Surface pressure distribution can be maintained.

  As described above, in the present embodiment, even when the sealing device 10 including the spring 40 that reinforces the contact pressure of the radial lip 20 is used in a high temperature environment, a decrease in the tension force is prevented, Engine oil leakage can be prevented for a long time.

In the present embodiment, ethylene propylene rubber is used as the rubber material for forming the swelling portion 24, and nitrile rubber is used as the rubber material for forming the other elastic portion E excluding the swelling portion 24. And it is not limited to this.
In the case where the oil to be sealed is a mineral oil, the material of the swelling portion 24 may be a rubber material that can easily penetrate mineral oil such as styrene butadiene rubber (SBR). The same effect can be obtained.
The rubber material forming the elastic part E other than the swelling part 24 includes hydrogenated nitrile rubber (HNBR), fluorine rubber (FKM), acrylic rubber (ACM) having resistance to mineral oil. Etc. can be used as appropriate.

In the sealing device 10 used for sealing glycol-based hydraulic oil such as brake oil, glycol materials such as nitrile rubber (NBR) and acrylic rubber (ACM) are used as the rubber material forming the swelling portion 24. It is possible to use a rubber material that can easily penetrate the system oil.
In the case of sealing glycol-based hydraulic oil, the rubber material forming the elastic portion E other than the swelling portion 24 is chloroprene rubber (CR), styrene having resistance to glycol-based oil. Butadiene rubber (SBR), ethylene propylene rubber (EPDM), and the like can be used as appropriate.

  The sealing device according to the present invention can be used for an engine, a rotating part of an automobile such as a transmission, a roll support part of a steel rolling mill, etc., and can maintain a good sealing performance over a long period of time.

10: Sealing device, 12: Metal core, 13: Cylindrical part, 14: Flange part, 20: Radial lip, 21: Recessed part, 22: Tip edge, 23: Spring locking part, 24: Swelling part, 25: Deflection part , 26: sliding contact portion, 30: grease lip, 40: spring, 50: crankshaft, 51: retainer

Claims (3)

A sealing device that seals between a housing and a rotating shaft that passes through an opening provided in the housing, and prevents oil enclosed inside the housing from leaking outside,
A fixing portion fixed to the housing; and a radial lip formed of an elastic body extending from the fixing portion toward a side where the oil is sealed.
On the outer periphery of the radial lip, a recess that opens radially outward is formed over the entire circumference and an annular spring is fitted, and on the inner periphery, a tip edge that is in sliding contact with the outer peripheral surface of the rotating shaft is formed. Formed,
In the concave portion, a swelling portion formed of a rubber material that swells in contact with the oil is exposed at least at a position in radial contact with the spring,
The tip end edge is formed of a rubber material different from the rubber material.   The sealing device according to claim 1, wherein the oil is a mineral oil-based lubricating oil, and the swelling portion is formed of ethylene propylene rubber.   The sealing device according to claim 1, wherein the oil is glycol-based hydraulic oil, and the swelling portion is formed of nitrile rubber.

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