Seal structure using oil seal

Abstract

A seal structure according to the present invention comprises an oil seal (4) that forms a seal between a rotary shaft (2) and a housing (3). Spiral grooves (22), which are lathe machining marks, remain on the outer peripheral surface (20) of the rotary shaft (2). First and second inner peripheral surface regions (47, 48) are disposed so that a pumping force (leakage prevention effect) due to the first inner peripheral surface region (47) provided with a rightwardly-twisted protrusion (47a) or the second inner peripheral surface region (48) provided with a leftwardlytwisted protrusion (48a), is larger than a pumping force (leakage promotion effect) brought about by the spiral grooves (22) that are the lathe processing marks remaining on the outer peripheral surface of the rotary shaft (2), even if the rotary shaft (2) rotates in either direction. It is possible to achieve a seal structure having a superior leakage prevention effect without using plunge grinding or the like in the machining of the rotary shaft.

Description

Seal structure using oil seal

[0001] The present invention relates to a seal structure that uses an oil seal made of elastic rubber to seal between a rotating shaft and a fixed member, and more specifically to a seal structure that can provide a sufficient sealing effect even if cutting marks such as spiral lathe marks remain on the outer peripheral surface of the rotating shaft, which is the sliding surface of the oil seal.

[0002] A seal structure using an elastic rubber oil seal is known as a seal for a rotating shaft. As proposed in Patent Documents 1 and 2, a type of oil seal is known in which a helical protrusion (helix) or groove extending obliquely to the axial direction is formed on the inner surface of the seal lip of the oil seal. The helical protrusion or groove increases the pumping force, which is the basis for the function of drawing a fluid (liquid or grease) into the device to be sealed. The helical protrusions or grooves are arranged in equal proportions, with the helical protrusions or grooves inclined toward one side of the axial direction and the helical protrusions or grooves inclined toward the opposite side, so that a pumping force that draws the fluid into the device is generated whether the rotating shaft rotates forward or backward.

[0003] Utility Model Registration No. 2583861 Utility Model Registration No. 2602575

[0004] Here, care has traditionally been taken to avoid leaving a machining pattern (cutting mark pattern) with a lead on the outer circumferential surface of the rotating shaft on which the seal lip of the oil seal slides. If a spiral-shaped machining pattern twisted in a specific direction remains on the outer circumferential surface of the rotating shaft, depending on the direction of rotation of the rotating shaft, the spiral machining pattern can generate a pumping force that moves the fluid toward the outside of the device (the atmosphere side), which promotes oil leakage and reduces the sealing effect of the oil seal. For this reason, surface finishing processes such as plunge grinding have traditionally been used to prevent spiral cutting marks from remaining on the outer circumferential surface of the rotating shaft on which the oil seal slides.

[0005] The object of the present invention is to provide a seal structure using an oil seal that can maintain good sealing effect even on a rotating shaft that has lead cutting marks such as lathe machining marks.

[0006] In order to solve the above problems, the present invention provides a seal structure using an oil seal made of elastic rubber that seals between a rotating shaft and a fixed-side member, wherein right-handed or left-handed spiral cutting marks remain on the outer peripheral surface of the rotating shaft, and the oil seal has a seal lip that is slidably pressed against the outer peripheral surface of the rotating shaft, and the seal lip has an inner peripheral surface region on which a plurality of protrusions or grooves are formed for generating a first pumping force that moves a fluid toward a sealed object that is one side in the axial direction of the rotating shaft, and the inner peripheral surface region comprises at least one of a first inner peripheral surface region and a second inner peripheral surface region, and the first inner peripheral surface region has protrusions or grooves that extend in a direction inclined to one side with respect to the axial direction so that the first pumping force is generated when the rotating shaft rotates clockwise, and the second inner peripheral surface region has protrusions or grooves that extend in a direction inclined to the other side with respect to the axial direction so that the first pumping force is generated when the rotating shaft rotates counterclockwise, When the rotating shaft rotates, the pumping force that moves the fluid toward the atmosphere, which is the other side of the axial direction, that is generated by the cutting marks is defined as a second pumping force, and the magnitude of the first pumping force generated by the first inner circumferential surface region or the second inner circumferential surface region is greater than the second pumping force.

[0007] If a second pumping force (leak promotion effect) is generated by cutting marks when the rotating shaft rotates clockwise, the formation range of the first inner circumferential surface region that generates the first pumping force (leak suppression effect) when the rotating shaft rotates clockwise is set so that the first pumping force is greater than the second pumping force. Conversely, if a second pumping force (leak promotion effect) is generated by cutting marks when the rotating shaft rotates counterclockwise, the formation range of the second inner circumferential surface region that generates the first pumping force (leak suppression effect) when the rotating shaft rotates counterclockwise is set.

[0008] In the present invention, regardless of the direction of rotation of the rotating shaft, the magnitude of the first pumping force that moves the fluid toward the sealed side between the seal lip of the oil seal and the rotating shaft is greater than the second pumping force that moves the fluid toward the atmosphere. In other words, the effect of suppressing leakage of oil, etc. by the first or second inner circumferential surface region of the seal lip is greater than the effect of promoting leakage by cutting marks left on the outer circumferential surface of the rotating shaft, so a good sealing state is maintained regardless of the direction of rotation of the rotating shaft.

[0009] For example, on the inner circumferential surface of the seal lip of an oil seal, first and second inner circumferential surface regions are alternately arranged along the circumferential direction. In this case, in the case of a rotating shaft without lathe machining marks, the first and second inner circumferential surface regions are evenly arranged. In contrast, in the case of a rotating shaft with cutting marks such as lathe machining marks, which is the subject of the present invention, the formation ratio of the first and second inner circumferential surface regions is changed depending on the twist direction (inclination direction) of the cutting marks. When the rotating shaft rotates clockwise, if the cutting marks generate a second pumping force (leak promotion effect), the formation area of ​​the first inner circumferential surface region that generates the first pumping force (leak suppression effect) is increased. Conversely, when the rotating shaft rotates counterclockwise, if the cutting marks generate a second pumping force (leak promotion effect), the formation area of ​​the second inner circumferential surface region that generates the first pumping force (leak suppression effect) is increased.

[0010] Here, for example, only the first inner circumferential surface region may be disposed as the inner circumferential surface region, in which case the leakage prevention effect of the first inner circumferential surface region is utilized when the rotating shaft rotates clockwise, and the leakage prevention effect of the cutting marks is utilized when the rotating shaft rotates counterclockwise.

[0011] In the present invention, regardless of the direction of rotation of the rotating shaft, the leakage prevention effect of the first inner circumferential surface region or the second inner circumferential surface region is greater than the leakage promotion effect of the cutting marks remaining on the outer circumferential surface of the rotating shaft. Therefore, a seal structure with excellent leakage prevention effect can be realized without using expensive plunge grinding or the like to machine the rotating shaft.

[0012] 1A is an explanatory diagram showing an example of a seal structure using an oil seal to which the present invention is applied, (B) is an explanatory diagram showing first and second inner circumferential surface regions formed on the inner circumferential surface of a seal lip, and (C) is an explanatory diagram showing spiral grooves (cutting marks) remaining on the outer circumferential surface of a rotating shaft. (A) is an explanatory diagram showing a case where the first and second inner circumferential surface regions are formed evenly in the circumferential direction on the inner circumferential surface of the seal lip of the oil seal, (B) is an explanatory diagram showing a case where the first inner circumferential surface region is larger than the second inner circumferential surface region, (C) is an explanatory diagram showing a case where the second inner circumferential surface region is larger than the first inner circumferential surface region, and (D) is an explanatory diagram showing a case where only the first inner circumferential surface region is formed.

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a seal structure using an oil seal to which the present invention is applied will be described with reference to the drawings.

[0014] 1(A) is an explanatory diagram showing a half-longitudinal cross section of a seal structure according to this embodiment, with the oil seal shown in solid lines and the rotating shaft and housing, which is a stationary member, shown in dashed lines. As shown in this figure, in a rotating machine 1 such as a motor or a reducer, an annular gap between a rotating shaft 2 and a housing 3, which is a stationary member supporting the rotating shaft 2, is sealed by an elastic rubber oil seal 4. The oil seal 4 prevents fluids such as oil and grease from leaking from an interior 5 of the machine (the sealed side) to an exterior 6 of the machine (the atmosphere side), and also prevents foreign matter such as dust from entering the interior 5 of the machine from the exterior 6 of the machine.

[0015] The oil seal 4 includes an annular body 42 made of elastic rubber reinforced by a metal reinforcing ring 41. The outer annular portion of the annular body 42 to which the metal reinforcing ring 41 is attached forms a fitting portion 43 that is press-fitted and fixed to the inner circumferential surface of the housing 3. A seal lip 45 and a dust lip 46 that protrude radially inward are formed on the inner annular portion of the annular body 42. The seal lip 45 is pressed radially inward by an annular coil spring 44, and a lip tip portion 45a that protrudes radially inward is slidably pressed against the outer circumferential surface 20 of the rotating shaft 2. The dust lip 46 is formed on the side of the seal lip 45 facing the outside 6 of the machine (the atmosphere side).

[0016] The inner circumferential surface of the seal lip 45 has an inclined inner circumferential surface portion 45b that is inclined radially outward from the lip tip 45a toward the dust lip 46, and the inclined inner circumferential surface portion 45b has an inner circumferential surface region in which a plurality of protrusions or grooves are formed for generating a first pumping force that moves the fluid toward the inside of the machine 5 (the side to be sealed), which is one side in the direction of the axis 21 of the rotating shaft 2. In this example, as shown in Figures 1(A) and 1(B), first inner circumferential surface regions 47 and second inner circumferential surface regions 48 are alternately formed along the circumferential direction of the inclined inner circumferential surface portion 45b of the seal lip 45 so that a first pumping force that moves the fluid toward the inside of the machine 5 (the side to be sealed) is generated between the seal lip 45 of the oil seal 4 and the rotating shaft 2 regardless of whether the rotating shaft 2 rotates clockwise or counterclockwise. The first inner peripheral surface region 47 is a region in which a plurality of first protrusions 47a (hereinafter referred to as right-handed twist protrusions 47a) extending spirally in a direction inclined to one side with respect to the axis 21 are formed at equal intervals in the circumferential direction. The second inner peripheral surface region 48 is a region in which a plurality of second protrusions 48a (hereinafter referred to as left-handed twist protrusions 48a) extending spirally in a direction inclined in the opposite direction with respect to the axis 21 are formed at equal intervals in the circumferential direction.

[0017] The dust lip 46 also has protrusions formed on its inner peripheral surface, an inclined inner peripheral surface portion 46a that is inclined radially outward toward the seal lip 45. As shown in FIG. 1A , multiple pairs of protrusions 49a, 49b are formed at equal angular intervals along the circumferential direction, extending in a direction inclined toward one side and the other at the same angle relative to the axis 21. Each pair of protrusions 49a, 49b is inclined toward each other toward the seal lip 45. The protrusions 49a, 49b on the dust lip 46 prevent the space between the seal lip 45 and the dust lip 46 from becoming negatively pressurized. Furthermore, foreign matter such as dust that has entered the space between the dust lip 46 and the seal lip 45 from the outside is discharged to the outside 6 (the atmosphere).

[0018] On the other hand, a spiral groove 22 (a lathe machining mark) remains on the outer peripheral surface 20 of the rotating shaft 2. As shown in Figure 1(C) , the spiral groove 22, which is a lathe machining mark, remains on the outer peripheral surface 20 of the rotating shaft 2 on which the oil seal 4 slides. For example, the surface roughness of the outer peripheral surface 20 of the rotating shaft 2 is 0.05 mm to 0.001 mm in terms of maximum peak height Sp (maximum value of the height from the average plane of the surface).

[0019] The seal structure of this example is configured to obtain a sufficient sealing effect regardless of the direction of rotation of the rotating shaft 2 by utilizing the right-handed twist protrusions 47 a and the left-handed twist protrusions 48 a formed on the seal lip 45 of the oil seal 4 and the spiral grooves 22 (lathe machining marks) remaining on the outer peripheral surface of the rotating shaft 2.

[0020] That is, a spiral groove 22, which is a right-handed or left-handed spiral cutting mark, remains on the outer peripheral surface 20 of the rotating shaft 2. A first inner peripheral surface region 47 and a second inner peripheral surface region 48 are arranged on the inclined inner peripheral surface portion 45b of the seal lip 45 of the oil seal 4. A right-handed helical protrusion 47a is formed on the first inner peripheral surface region 47, extending in a direction inclined to one side with respect to the direction of the axis 21, so that a first pumping force is generated when the rotating shaft 2 rotates clockwise. A left-handed helical protrusion 48a is formed on the second inner peripheral surface region 48, extending in a direction inclined to the other side with respect to the direction of the axis 21, so that a first pumping force is generated when the rotating shaft 2 rotates counterclockwise.

[0021] When the rotating shaft 2 rotates, the pumping force that moves the fluid toward the outside 6 of the machine (the atmosphere side) and is generated by the spiral groove 22 (lathe processing marks) on the outer circumferential surface 20 of the rotating shaft 2 is referred to as the second pumping force. In this example, the magnitude of the first pumping force generated by the first inner circumferential surface region 47 (right-handed helical protrusion 47 a) or the second inner circumferential surface region 48 (left-handed helical protrusion 48 a) is set to be greater than the second pumping force generated by the spiral groove 22.

[0022] If the spiral groove 22, which is a cutting mark, generates a second pumping force (leakage promotion effect) when the rotating shaft 2 rotates clockwise, the formation range of the first inner circumferential surface region 47 (right-handed twist protrusions 47 a) that generates the first pumping force (leakage suppression effect) when the rotating shaft 2 rotates clockwise is set so that the first pumping force is greater than the second pumping force. Conversely, if the spiral groove 22, which is a cutting mark, generates the second pumping force (leakage promotion effect) when the rotating shaft 2 rotates counterclockwise, the formation range of the second inner circumferential surface region 48 (left-handed twist protrusions 48 a) that generates the first pumping force (leakage suppression effect) when the rotating shaft 2 rotates counterclockwise is set.

[0023] In this example, first inner circumferential surface regions 47 and second inner circumferential surface regions 48 are alternately arranged along the circumferential direction of the inner circumferential surface of the seal lip 45. In this case, in the case of a rotating shaft 2 without a spiral groove 22 (lathe machining marks), the first and second inner circumferential surface regions 47, 48 are evenly arranged at equal angular intervals, as shown in FIG. 2A . In contrast, in the case of a rotating shaft 2 with a spiral groove 22 (lathe machining marks), the formation ratio of the first and second inner circumferential surface regions 47, 48 can be changed depending on the twist direction of the spiral groove 22 (lathe machining marks). If the spiral groove 22 (lathe machining marks) generates a second pumping force (leakage promotion effect) when the rotating shaft 2 rotates clockwise, for example, as shown in FIG. 2B , the formation area of ​​the first inner circumferential surface region 47 that generates a first pumping force (leakage suppression effect) upon clockwise rotation is increased. Conversely, if the second pumping force (leakage promotion effect) is generated by the spiral groove 22 (lathe machining marks) when the rotating shaft 2 rotates counterclockwise, the formation area of ​​the second inner surface region 48 that generates the first pumping force (leakage suppression effect) when the rotating shaft 2 rotates counterclockwise is increased, as shown in Figure 2 (C).

[0024] Here, as the inner circumferential surface region, only the first inner circumferential surface region 47 (right-handed twist protrusions 47 a) or only the second inner circumferential surface region 48 (left-handed twist protrusions 48 a) may be disposed. For example, as shown in FIG. 2(D), only the first inner circumferential surface region 47 (right-handed twist protrusions 47 a) may be disposed. In this case, when the rotating shaft 2 rotates clockwise, the leakage prevention effect of the first inner circumferential surface region 47 (right-handed twist protrusions 47 a) is utilized, and when the rotating shaft 2 rotates counterclockwise, the leakage prevention effect of the spiral grooves 22 (lathe processing marks) of the rotating shaft 2 is utilized.

[0025] As described above, in the seal structure of this example, regardless of the direction in which the rotating shaft 2 rotates, the leakage prevention effect of the right-handed twist protrusions 47a and the left-handed twist protrusions 48a is set to be greater than the leakage promotion effect of the cutting marks remaining on the outer peripheral surface of the rotating shaft 2. Therefore, a seal structure with excellent leakage prevention effect can be achieved without using expensive plunge grinding or the like to process the rotating shaft 2.

Claims

1. A seal structure using an oil seal made of elastic rubber to seal between a rotating shaft and a fixed-side member, wherein right-handed or left-handed spiral cutting marks remain on the outer peripheral surface of the rotating shaft, and the oil seal has a seal lip that is slidably pressed against the outer peripheral surface of the rotating shaft, and the seal lip has an inner peripheral surface region on which a plurality of protrusions or grooves are formed to generate a first pumping force that moves a fluid toward a sealed object, which is one side of the axial direction of the rotating shaft, and the inner peripheral surface region comprises at least one of a first inner peripheral surface region and a second inner peripheral surface region, and the first inner peripheral surface region has protrusions or grooves that extend in a direction inclined to one side with respect to the axial direction so as to generate the first pumping force when the rotating shaft rotates clockwise, and the second inner peripheral surface region has protrusions or grooves that extend in a direction inclined to the other side with respect to the axial direction so as to generate the first pumping force when the rotating shaft rotates counterclockwise, When the rotating shaft rotates, a pumping force that moves the fluid toward the atmosphere, which is the other side of the axial direction, generated by the cutting marks is defined as a second pumping force, and the magnitude of the first pumping force generated by the first inner circumferential surface region or the second inner circumferential surface region is greater than the second pumping force.

2. A seal structure according to claim 1, comprising both the first inner peripheral surface region and the second inner peripheral surface region, and wherein the first inner peripheral surface region and the second inner peripheral surface region are formed alternately in the circumferential direction on the inner peripheral surface of the seal lip.

3. A seal structure according to claim 1, wherein the roughness of the outer peripheral surface of the rotating shaft is 0.05 mm to 0.001 mm in maximum peak height.

4. A seal structure as described in claim 1, wherein the inner circumferential surface area is provided only with a first inner circumferential surface area, and the twist direction of the cutting marks is a direction in which a pumping force that moves the fluid toward the sealed object is generated by the cutting marks when the rotating shaft rotates counterclockwise.

5. A seal structure as described in claim 1, wherein the inner peripheral surface region is provided only with a second inner peripheral surface region, and the twist direction of the cutting marks is a direction in which a pumping force that moves the fluid toward the sealed object is generated by the cutting marks when the rotating shaft rotates clockwise.

Images