JP2008082410A - Lip reversal detection method - Google Patents

Abstract

Provided is a lip reversal detection method capable of simply and reliably detecting whether or not a lip has been reversed at the time of bearing assembly.
SOLUTION: The bearing rings 2 and 4 are arranged to face each other so as to be relatively rotatable, and a seal structure for sealing the inside of the bearing partitioned between the bearing rings from the outside of the bearing, and the seal structure includes a base end thereof. Is a lip reversal detection method for a bearing provided with a seal member 10a fixed to one bearing ring and having a lip at the tip thereof slidably positioned with respect to the other bearing ring. A step of pumping a predetermined gas into the inside of the bearing, and a step of measuring a pressure change inside the bearing when the gas leaks outside the bearing through the lip of the seal member in a state where the inside of the bearing is pressurized. And detecting the presence or absence of lip reversal by comparing the pressure change inside the bearing with a reference value.
[Selection] Figure 1

Description

  The present invention relates to a lip reversal detection method for detecting whether or not a lip of the seal structure is reversed particularly when the seal structure is assembled on a wheel (outboard) side.

  2. Description of the Related Art Conventionally, various bearing units are known for rotatably supporting a vehicle wheel (for example, a disc wheel) with respect to a vehicle body (for example, a suspension device (suspension)). As the bearing unit, there are a drive wheel and a driven wheel. FIG. 3 shows a bearing unit for the driven wheel as an example. The bearing unit is fixed on the vehicle body (inboard) side and is always kept in a non-rotating state. The bearing unit is provided facing the inside of the stationary wheel 2 and on the wheel (outboard) side. A rotating wheel (inner ring) 4 that is connected and rotates together with the wheels, and a plurality of rolling elements 6 and 8 that are rotatably incorporated in a double row (for example, two rows) between the stationary wheel 2 and the rotating wheel 4. ing. In addition, although balls are illustrated in the drawings as the rolling elements 6 and 8, a roller may be applied depending on the configuration and type of the bearing unit.

  The stationary ring (outer ring) 2 has a hollow cylindrical shape and is arranged so as to cover the outer periphery of the rotating wheel 4. The stationary ring 2 has a fixing flange 2 a that protrudes outward from the outer peripheral side. It is integrally molded. In this case, a stationary bolt 2 can be fixed to a suspension device (knuckle) (not shown) by inserting a fixing bolt (not shown) into the fixing hole 2b of the fixing flange 2a and fastening it to the vehicle body side. The rotating wheel (inner ring) 4 is provided with a substantially cylindrical hub (spindle) 12 that rotates together with, for example, a disc wheel (not shown) of an automobile, and the hub (spindle) 12 includes A hub flange 12a to which the disc wheel is fixed protrudes.

  The hub flange 12a extends outward (outward in the radial direction of the hub 12) beyond the stationary ring (outer ring) 2, and is arranged at predetermined intervals along the circumferential direction in the vicinity of the extended edge. A plurality of hub bolts 14 are provided. In this case, by inserting a plurality of hub bolts 14 into bolt holes (not shown) formed in the disc wheel and tightening with hub nuts (not shown), the disc wheel can be positioned and fixed with respect to the hub flange 12a. it can. At this time, positioning of the wheel in the radial direction is performed by the pilot portion 12p protruding from the wheel side of the hub 12.

  The hub (spindle) 12 is fitted with a ring-shaped rotating wheel structure 16 (parts constituting the rotating wheel (inner ring) 4 together with the hub 12) on the fitting surface 4m-1 on the vehicle body side. It has become. In this case, for example, in a state where the rolling elements 6 and 8 are held by the cage 18 between the stationary wheel 2 and the rotating wheel 4, the stepped portion 12 b formed on the fitting surface 4 m −1 of the rotating wheel component 16. And the caulking region 12c at the vehicle body side shaft end portion of the hub 12 is plastically deformed, and the caulking region 12c is caulked (closely adhered) along the peripheral end portion 16s of the rotating wheel constituting body 16. Thus, the rotating wheel component 16 can be fixed to the rotating wheel 4 (hub 12).

  At this time, a predetermined preload is applied to the bearing unit, and in this state, the rolling elements 6 and 8 are formed on opposite surfaces of the stationary wheel 2 and the rotating wheel 4 at a predetermined contact angle. The two rows of raceway grooves (stationary raceway groove 2s, rotary raceway groove 4s) are rotatably incorporated. The stationary raceway groove 2s is formed continuously in the circumferential direction along the inner peripheral surface of the stationary wheel 2 (the surface facing the rotary wheel 4), and the rotary raceway groove 4s is formed on the outer periphery of the rotary wheel 4. It is formed to face the stationary track groove 2s along the surface (the surface facing the stationary ring 2). In this case, an action line (not shown) connecting the two contact points is perpendicular to each raceway groove 2s, 4s and passes through the center of each rolling element 6, 8 to one point (action point) on the center line of the bearing unit. ) This constitutes a rear combination (DB) bearing.

  In such a configuration, all of the force acting on the wheel during traveling of the vehicle is transmitted from the disk wheel to the suspension device through the bearing unit. At that time, various loads (radial loads) are applied to the bearing unit. , Axial load, moment load, etc.). However, since the bearing unit is a back combination (DB) bearing as described above, high rigidity is maintained with respect to various loads.

  Further, in the bearing unit as described above, a seal structure for sealing the inside of the bearing unit is constructed between the stationary ring (outer ring) 2 and the rotating ring (inner ring) 4. As an example of the seal structure, the bearing unit shown in FIG. 3 is provided with a seal member for sealing the wheel (outboard) side and a seal member for sealing the vehicle body (inboard) side. . Thereby, the inside of the bearing partitioned between the stationary wheel 2 and the rotating wheel 4 can be sealed from the outside of the bearing.

  In this case, a cover 10b is provided as a sealing member on the inboard side. The cover 10b has a disk shape that seals the inside of the bearing on the vehicle body side from the outside of the bearing, and the base end thereof is fixed to the fixing surface 2m-1 of the stationary wheel 2 on the vehicle body side. On the other hand, a lip seal 10a is provided as a seal member on the outboard side. The base end of the lip seal 10a is fixed to the stationary surface 2m-2 on the wheel side of the stationary wheel 2, and the distal end thereof is slidably positioned with respect to the seal sliding surface 4m-2 of the rotating wheel 4. . The seal sliding surface 4m-2 is continuous along the circumferential direction (the rotating direction of the rotating wheel 4) in the root portion of the hub flange 12a (the portion that transitions from the outer peripheral surface of the hub 12 to the side surface of the hub flange 12a). Is formed.

  Here, FIG. 4A shows a configuration example of the lip seal 10a. The lip seal 10a is configured by adding a sealing material 22 to the outer peripheral surface of the mandrel 20, and at its tip, three lips Ls slidably in contact with the seal sliding surface 4m-2 of the rotating wheel 4. , Lm and Lg are provided. In this case, each lip Ls, Lm, Lg has a continuous annular shape along the circumferential direction (rotating direction of the rotating wheel 4), and is always in sliding contact with the seal sliding surface 4m-2. As a result, while the stationary ring (outer ring) 2 and the rotating ring (inner ring) 4 rotate relative to each other and in a stationary state, leakage of lubricant (for example, grease, oil) to the outside of the bearing and foreign matter ( For example, muddy water and dust) can be prevented from entering at the same time.

  More specifically, the mandrel 20 of the lip seal 10a includes a hollow cylindrical portion 20a fitted into the fixed surface 2m-2 of the stationary ring 2, and a seal slide between the hollow cylindrical portion 20a and the hub 12 (rotating wheel 4). It is comprised from the cyclic | annular bending part 20b bent in the substantially S shape toward the moving surface 4m-2. In this case, before the lip seal 10a is fixed to the fixed surface 2m-2 of the stationary wheel 2, the outer diameter of the hollow cylindrical portion 20a is set slightly larger than the inner diameter of the fixed surface 2m-2. For this reason, the hollow cylindrical portion 20a is fitted into the fixed surface 2m-2 of the stationary ring 2 with an interference fit.

  The sealing material 22 is added to the outer peripheral surface of the annular bent portion 20b (the surface facing the seal sliding surface 4m-2). In this case, before the lip seal 10a is fixed to the fixed surface 2m-2 of the stationary ring 2, the outer diameter of the sealing material 22 added to the outer peripheral surface of the S-shaped transition portion 20c of the annular bent portion 20b is fixed. It is set slightly larger than the inner diameter of the surface 2m-2. In this case, when the hollow cylindrical portion 20a is fitted into the fixed surface 2m-2, the sealing material 22 added to the S-shaped transition portion 20c is elastic between the S-shaped transition portion 20c and the fixed surface 2m-2. Is pressed into contact with the fixed surface 2m-2, thereby further improving the sealing performance. For example, an elastic material such as rubber or elastomer may be applied as the sealing material 22. Further, as a method of adding the sealing material 22 to the annular bent portion 20b, it may be added by, for example, baking or an adhesive.

  In such a lip seal 10a, the three lips Ls, Lm, and Lg are integrally formed with the seal material 22, and the sliding contact positions of the rotating wheel 4 with respect to the seal sliding surface 4m-2 are different from each other. More specifically, the side lip Ls is in sliding contact with the outer diameter of the seal sliding surface 4m-2 in a state of being directed toward the wheel side, while the grease lip Lg is in a state of being directed toward the vehicle body. It is in sliding contact with the inner surface of the seal sliding surface 4m-2. The main lip Lm is positioned between the side lip Ls and the grease lip Lg. The main lip Lm extends toward the wheel (outboard) side, and its inner diameter side is in the radial direction with respect to the seal sliding surface 4m-2. Is in sliding contact. In this case, the side lip Ls and the main lip Lm prevent foreign matters from entering the bearing, and the grease lip Lg prevents the lubricant from leaking.

  When assembling the bearing unit as described above, after the rolling elements 6 and 8 held by the cage 18 are mounted on the stationary ring (outer ring) 2, the lip seal 10a is fixed to the outboard side. In this state, it is combined with the hub (spindle) 12. At this time, each lip Ls, Lm, Lg of the lip seal 10a is fed in sliding contact with the seal sliding surface 4m-2 of the rotating wheel (inner ring) 4 and positioned in a state as shown in FIG. 4 (a). The

  By the way, during the bearing assembly process as described above, for example, if a misalignment occurs between the stationary wheel 2 and the rotating wheel 4, the main lip Lm facing the wheel (outboard) side is moved in the direction of the arrow t ( In some cases, the image is inverted as shown in FIG. In this case, in a state where the main lip Lm is inverted, the sealability on the outboard side of the bearing is deteriorated, so that foreign matters easily enter the bearing from here. For this reason, it becomes difficult to maintain the inside of the bearing in a certain sealed state over a long period of time, and as a result, the bearing may be deteriorated early. Note that the side lip Ls and the grease lip Lg have no fear of inversion depending on their directions.

  Therefore, as a measure for solving such an adverse effect, for example, in the conventional example of Patent Document 1, as shown in FIG. 4B, between the seal sliding surface 4m-2 and the wheel-side rotation track groove 4s. A technique has been proposed in which an annular taper portion 24 is continuously provided in this area. In this case, the taper portion 24 constitutes a truncated cone having a tapered shape (decreasing in diameter) from the seal sliding surface 4m-2 toward the rotating raceway groove 4s on the wheel side, and is the portion with the smallest diameter ( The outer diameter of the portion adjacent to the rotating raceway groove 4s is set smaller than the inner diameter of the main lip Lm. Thus, the main lip Lm is prevented from being reversed when the bearing is assembled.

  However, the technique of Patent Document 1 has the following problems. That is, in the bearing unit, since the seal structure on the outboard side is required to have high waterproof durability, the lip Ls, Lm, Lg of the lip seal 10a and the seal sliding surface 4m-2 of the rotating wheel 4 are used. “Squeeze” is set relatively large. For this reason, even if the taper portion 24 is provided between the seal sliding surface 4m-2 and the wheel-side rotating raceway groove 4s, it is difficult to reliably prevent the lips Ls, Lm, and Lg from being reversed.

  In this case, it is preferable to confirm whether or not each lip Ls, Lm, Lg is inverted. In particular, the main lip Lm is interposed between the side lip Ls and the grease lip Lg and visually confirmed from the outside. It is placed in a difficult place. For this reason, it cannot be confirmed whether or not the main lip Lm is inverted during the assembly of the bearing. In addition, since the main lip Lm is a lip that forms the basis of the seal structure, it is difficult to maintain the sealing function constant in a state where the main lip Lm is inverted.

Therefore, it is desired to develop a technology that can easily and reliably detect whether or not each lip Ls, Lm, and Lg has been reversed at the time of bearing assembly, but such technology is currently known. It is not done.
Japanese Patent No. 3640786

  The present invention has been made to solve such problems, and its purpose is to detect lip reversal that can be detected easily and reliably without visually confirming whether or not the lip has been reversed during the assembly of the bearing. It is to provide a method.

  In order to achieve such an object, the present invention includes a bearing ring disposed so as to be relatively rotatable and a seal structure for sealing the bearing interior defined by the bearing rings from the outside of the bearing. Is a lip reversal detection method for a bearing provided with a seal member whose base end is fixed to one bearing ring and whose tip lip is slidably positioned with respect to the other bearing ring. The pressure change inside the bearing when the gas leaks to the outside of the bearing through the lip of the seal member in the state of pressurizing the inside of the bearing and pressurizing the inside of the bearing and the inside of the bearing being pressurized. A step of measuring, and a step of detecting the presence or absence of lip inversion by comparing the pressure change in the bearing with a reference value.

  In the present invention, the lip of the seal member is formed with a gas passage for facilitating gas leakage through the lip to the outside of the bearing. In this case, one of the track rings is a stationary wheel that is fixed to the vehicle body side and is maintained in a non-rotating state at all times, and the other track ring is provided facing the stationary wheel and connected to the wheel side to be a wheel. The seal member is provided on the wheel side between the stationary wheel and the rotating wheel.

  According to the present invention, it is possible to realize a lip reversal detection method capable of easily and reliably detecting whether or not a lip has been reversed at the time of bearing assembly.

  Hereinafter, a lip inversion detection method according to an embodiment of the present invention will be described with reference to the accompanying drawings. As bearings applicable to the lip reversal detection method of the present embodiment, there are various bearing units for driving wheels and driven wheels of a vehicle. Here, as an example, the bearings for the driven wheels shown in FIG. Assume a bearing unit. Since the configuration of the bearing unit has already been described in detail, the description thereof is omitted.

  FIG. 1 shows a configuration example of a detection apparatus applied to the seal function detection method according to the present embodiment. The detection device includes a detection housing 26 mounted so as to seal the vehicle body side of the stationary wheel 2 and a pump 30 for pumping a predetermined gas (for example, air or other gas). A gas introduction port 26 a is formed in the detection housing 26, and a pump 30 is connected to the detection housing 26 via a pressure feed line 28.

  In such a detection device, the detection housing 26 is mounted so as to seal the vehicle body side of the stationary wheel 2 before attaching the vehicle body (inboard) side cover 10b. Thereby, the gas pumped from the pump 30 through the pumping conduit 28 is introduced into the detection housing 26 through the inlet 26a. Note that the pressure of the gas introduced into the detection housing 26 is measured by the pressure gauge 32.

  At this time, the gas introduced into the detection housing 26 is pumped into the bearing partitioned by the stationary ring (outer ring) 2 and the rotating ring (inner ring) 4, so that the inside of the bearing reaches a predetermined pressure value. Pressurized. Here, as shown in FIG. 4 (a), in the lip seal 10a that seals the wheel (outboard) side, the side lip Ls and the main lip Lm are intruded by foreign matter (for example, muddy water, dust) into the bearing. In order to prevent this, it is in sliding contact with the seal sliding surface 4m-2 in a state facing the wheel side (leakage direction), and the grease lip Lg is in a state facing the vehicle body side (direction of entry) It is in sliding contact with the seal sliding surface 4m-2.

  In this state, when the inside of the bearing is pressurized to 6 atmospheres, for example, if the leakage pressure of each lip Ls, Lm, Lg of the lip seal 10a is about 1 atmosphere, the residual pressure is about 5 atmospheres. . That is, when each lip Ls, Lm, Lg is in normal sliding contact with the seal sliding surface 4m-2, the pressure value inside the bearing measured by the pressure gauge 32 is about 5 atm. . In the following description, the pressure value inside the bearing at this time (about 5 atmospheres) is used as a reference value.

  On the other hand, when each lip Ls, Lm, Lg is not normally in sliding contact with the seal sliding surface 4m-2, each lip Ls, Lm, Lg and the seal sliding surface 4m-2 The “interference” between the points is partially reduced or partially eliminated. Such a state is caused by, for example, a misalignment between the stationary wheel 2 and the rotating wheel 4 during the bearing assembly process, but, for example, the main lip Lm is reversed in the direction of the arrow t (FIG. 4A). There is a case. In this case, when the pressure value inside the bearing is measured by the pressure gauge 32 and the measured value is compared with the above-described reference value (about 5 atm), the pressure value inside the bearing is the leakage pressure from the main lip Lm. Due to the effect, the result is below the standard value. Therefore, based on this result, it can be detected that the main lip Lm is inverted.

  As described above, according to the present embodiment, by measuring the leakage pressure of each lip Ls, Lm, Lg, it is simple and without visually confirming whether each lip Ls, Lm, Lg is inverted during the bearing assembly. It can be detected reliably. In this case, in particular, the main lip Lm is interposed between the side lip Ls and the grease lip Lg and cannot be visually confirmed from the outside, but only by measuring the leakage pressure of each lip Ls, Lm, Lg. Whether or not the main lip Lm is reversed can be detected easily and reliably without visually confirming from the outside. As a result, the sealing function of the bearing unit incorporating the seal structure can be maintained constant, and as a result, the quality of the finished product can be improved.

  By the way, for example, when the main lip Lm is reversed in the direction of the arrow t (FIG. 4 (a)), when the inverted portion is strongly pressed against the seal sliding surface 4m-2, the main lip Lm passes through the main lip Lm and the bearing outside It may be difficult for the gas to flow to. In this case, the other lips Ls and Lg that are not reversed are pressed and deformed along the seal sliding surface 4m-2 at the time of assembling the bearing, and the pressing force on the seal sliding surface 4m-2 is increased. At this time, a sealed space 10v (FIG. 2A) is formed between the main lip Lm and the grease lip Lg, in which gas is difficult to leak.

  In this case, the pressure resistance of the grease lip Lg is increased, so that it may be difficult to accurately detect whether the main lip Lm is reversed by the lip reversal detection method of the above-described embodiment. Therefore, as a method for solving such a problem, each lip Ls, Lm, Lg of the seal member (seal structure) is provided with a gas passage for facilitating gas leakage through the lips Ls, Lm, Lg to the outside of the bearing. It is preferable to form.

  Here, as the gas passage, for example, as shown in FIG. 2A, a part of the main lip Lm may be cut out to form a slit-like or concave gas passage 22k. In this case, the gas passage 22k may be formed at one place with respect to the main lip Lm, or may be formed at a plurality of places. When the gas passages 22k are formed at a plurality of locations, they may be arranged at regular intervals along the main lip Lm or may be arranged at irregular intervals. Note that the size and shape of the gas passage 22k are not particularly limited because, for example, the size and shape of the main lip Lm, or the pressing amount of the inverted portion against the seal sliding surface 4m-2 are arbitrarily set. I do not.

  Thus, by forming the gas passage 22k in the main lip Lm, when the main lip Lm is reversed, for example, as shown in FIG. Even when pressed strongly, gas can be easily leaked from the sealed space 10v between the main lip Lm and the grease lip Lg through the gas passage 22k. As a result, it is possible to suppress an increase in the pressure resistance of the grease lip Lg. As a result, it is possible to accurately detect whether or not the main lip Lm is reversed by the lip reversal detection method of the above-described embodiment.

  In the above-described embodiment, the presence or absence of inversion of the main lip Lm is detected by measuring the leakage pressure of each lip Ls, Lm, Lg. As another alternative embodiment, for example, each lip The presence or absence of inversion of the main lip Lm may be detected by measuring the change in the volume surrounded by Ls, Lm, Lg and the seal sliding surface 4m-2 (hereinafter referred to as the seal volume).

  In such a detection method, as shown in FIG. 1, gas is pumped from the pump 30 into the detection housing 26 to pressurize the inside of the bearing. Then, the seal volume inside the bearing (hereinafter referred to as a reference value) is calculated from the pressure rise at this time. Here, the stationary wheel (outer ring) 2, the rotating wheel (inner ring) 4, the rolling elements 6, 8, and the cage 18 are machined with high precision in order to maintain the bearing performance constant. There is little variation. Therefore, the pressure increase value inside the bearing and the volume inside the bearing have a corresponding relationship, and the volume can be calculated from the pressure increase value.

  Here, for example, when the main lip Lm is reversed in the direction of the arrow t (FIG. 4A), the “interference” between the main lip Lm and the seal sliding surface 4m-2 is partially reduced. It will be in a state of being lost. At this time, the pressure resistance of the inverted portion of the main lip Lm decreases, and the gas easily flows through the inverted portion, so that the pressure value inside the bearing changes (decreases). In this case, the seal volume inside the bearing is changed (decreased) compared to the reference value. Therefore, based on this result, it can be detected that the main lip Lm is inverted.

  As described above, according to another embodiment, by measuring the change in the seal volume, it is possible to easily and reliably detect whether or not each lip Ls, Lm, Lg has been reversed during the assembly of the bearing. Can do. Since the other effects are the same as those of the above-described embodiment, the description thereof is omitted.

  By the way, for example, when the main lip Lm is inverted, if the inverted portion is strongly pressed against the seal sliding surface 4m-2, the gas may not easily flow to the outside of the bearing through the main lip Lm. In addition, the other lips Ls and Lg that are not reversed increase the tension on the seal sliding surface 4m-2. At this time, a sealed space 10v (FIG. 2A) is formed between the main lip Lm and the grease lip Lg, in which gas is difficult to leak.

  In this case, the volume of only the sealed space 10v is added to the seal volume, but the sealed space 10v originally has a small volume and a large amount of lubricant. For this reason, the change in the volume of the sealed space 10v is small, and it may be difficult to accurately detect whether the main lip Lm is reversed. Therefore, as a method for solving such a problem, a gas passage 22k for facilitating gas leakage to the outside of the bearing through each lip Ls, Lm, Lg of each lip Ls, Lm, Lg of the seal member (seal structure). (FIGS. 2A and 2B) are preferably formed. Note that the gas passage 22k may have the same configuration as that of the above-described embodiment, and a detailed description thereof will be omitted.

  As described above, by forming the gas passage 22k in the main lip Lm as in the above-described embodiment (FIG. 2 (a)), when the main lip Lm is reversed, the reversing portion is sealed and slid. Even when strongly pressed against the surface 4m-2 (FIG. 2B), the gas can be easily leaked from the sealed space 10v between the main lip Lm and the grease lip Lg through the gas passage 22k. . In this case, in addition to the sealed space 10v, the space volume surrounded by the side lip Ls, the main lip Lm, and the seal sliding surface 4m-2 can be added to the seal volume, so each lip Ls, Lm, Lg The volume change accompanying the leakage pressure increases. As a result, it is possible to accurately detect whether the main lip Lm is reversed based on the volume change.

Sectional drawing which shows the apparatus structure applied to the sealing function detection method which concerns on one embodiment of this invention. (a) is a partial cross-sectional view showing a configuration example of the seal structure on the outboard side shown in FIG. 1, (b) is a partial cross-sectional view showing a state in which the lip of the seal structure of FIG. . Sectional drawing which shows the structural example of the bearing unit for driven wheels. (a) is a figure which shows the structural example of the conventional seal structure by the side of a wheel, (b) is a figure which shows the structure of the prior art for aiming at the inversion prevention of a main lip.

Explanation of symbols

2 Stationary wheel (outer ring)
4 Rotating wheel (inner ring)
6,8 Rolling element 10a Lip seal (seal member)
10v sealed space
Ls, Lm, Lg Lip

Claims (3)

It is equipped with a bearing ring that is arranged so as to be capable of relative rotation and a seal structure for sealing the inside of the bearing partitioned between the bearing rings from the outside of the bearing, and the base end of the seal structure is fixed to one of the bearing rings. And a lip reversal detection method for a bearing provided with a seal member whose tip lip is slidably positioned with respect to the other raceway ring,
A step of pumping a predetermined gas into the bearing and pressurizing the bearing;
Measuring the pressure change inside the bearing when gas leaks out of the bearing through the lip of the seal member in a state where the inside of the bearing is pressurized;
And a step of detecting the presence or absence of lip reversal by comparing the pressure change inside the bearing with a reference value.   2. The lip reversal detection method according to claim 1, wherein a gas passage is formed in the lip of the seal member so that gas can easily leak through the lip to the outside of the bearing.   One of the track rings is a stationary wheel that is fixed to the vehicle body side and is maintained in a non-rotating state at all times. The other track ring is provided facing the stationary wheel and connected to the wheel side to rotate together with the wheel. The lip reversal detection method according to claim 1, wherein the lip reversal detection method is a rotating wheel, and the seal member is provided on a wheel side between the stationary wheel and the rotating wheel.

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