JP2008105626A - Double row rolling bearing unit for supporting wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain settling of an O-ring 18 while restraining increase of costs, realize a structure capable of securing a sealing performance of the O-ring 18 for a long time, and realize a structure capable of preventing swelling of the O-ring 18 when needed, and easily recognizing a fact that the O-ring 18 is protruded from a predetermined portion due to swelling. <P>SOLUTION: The O-ring 18 is made of hydrogenation nitrile rubber, and has cross-sectional diameter of 1.4 mm or less and crushing ratio of 15-45%. Oil of a same kind as base oil of grease filled in a bearing space 11 is applied to a portion of a cap 6, to which the O-ring 18 is mounted. Furthermore, color on a surface of the O-ring 18 is other than black, which is a color of the surface of the cap 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement of a double-row rolling bearing unit for supporting a wheel that rotatably supports a wheel of an automobile with respect to a suspension device. Specifically, while maintaining cost, double-row rolling for wheel support while maintaining the sealing performance by O-rings provided for preventing rainwater and other foreign matter from entering the bearing space where rolling elements are installed. This ensures the durability of the bearing unit.

  The wheel of the automobile is rotatably supported by the suspension device by a double row rolling bearing unit for supporting the wheel. As such a wheel-supporting double-row rolling bearing unit, those having various structures have been widely known as described in many publications such as Patent Documents 1 and 2, for example. FIG. 1 shows an example of such a conventionally known wheel-supporting double-row rolling bearing unit. The wheel-supporting double-row rolling bearing unit 1 includes an outer ring 2, a hub 3, a plurality of rolling elements 4 and 4, a seal ring 5, and a cap 6.

  Out of these, the outer ring 2 is provided with double-row outer ring raceways 7 and 7 on the inner peripheral surface and an outward flange-shaped mounting portion 8 on the outer peripheral surface. Further, the hub 3 has a flange 9 at the outer end in the axial direction of the outer peripheral surface, and also an intermediate portion or an inner end in the axial direction (the inner side with respect to the axial direction is the side closer to the center in the width direction when assembled to the automobile). (The right side of each figure. In this regard, the left side of each figure, which is outward in the width direction when assembled to the automobile, is said to be outside in the axial direction. The same applies throughout the present specification and claims.) Are provided with double-row inner ring raceways 10 and 10, respectively, and rotate together with the wheels in use. Further, a plurality of rolling elements 4 and 4 are provided between the outer ring raceways 7 and 7 and the inner ring raceways 10 and 10, respectively, so as to be freely rotatable for each row. The seal ring 5 is provided between the inner peripheral surface of the outer end portion of the outer ring 2 and the outer peripheral surface of the intermediate portion of the hub 3. Such a seal ring 5 closes the axially outer end side opening of the bearing space 11 in which the rolling elements 4 and 4 are installed between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the hub 3. . Furthermore, the cap 6 is fixed to the inner end of the outer ring 2 in the axial direction so as to close the opening on the inner end.

  When the wheel support double row rolling bearing unit 1 configured in this way is used, the mounting portion 8 is screwed and fixed to a knuckle that constitutes a suspension device, and the wheel is supported and fixed to the flange 9. In this state, the wheel is supported rotatably with respect to the knuckle. For example, when running in rainy weather, this wheel jumps up foreign matter such as muddy water from the road surface, but this foreign matter is blocked by the seal ring 5 and the cap 6 as long as it is in a general use state, and the bearing space 11 There is no entry inside. In the case of the structure shown in FIG. 1 described above or described in Patent Document 1, the metal plate is subjected to plastic working such as drawing to close the opening on the inner end side in the axial direction of the outer ring 2. A metal cap is used. On the other hand, Patent Document 2 describes a structure using a cap made of synthetic resin. A synthetic resin cap is often used when a rotational speed sensor for ABS control is incorporated in the cap.

  Regardless of whether a cap made of metal or synthetic resin is used, it is difficult to bring the fitting surface between the cap and the outer ring into close contact with the entire circumference without any gaps. For example, in the case of the metal cap 6 shown in FIG. 1, the fitting cylinder portion 12 formed in the outer diameter portion of the outer surface in the axial direction is fitted into the inner end portion of the outer ring 2 with an interference fit. Yes. If the outer peripheral surface of the fitting cylinder portion 12 is a highly accurate cylindrical surface, the water tightness of the fitting portion with the outer ring 2 can be maintained. However, actually, when the cap 6 is plastically processed, the fitting is performed. Fine irregularities are likely to be formed on the outer peripheral surface of the combined cylinder portion 12, and it is difficult to keep the water tightness of the fitting portion high. Also, in the case of a synthetic resin cap, a fitting surface or a contact surface with the outer ring is also formed due to deformation called shrinkage caused by the cooling and shrinkage of the synthetic resin during the synthetic resin injection molding. It is difficult to finish accurately. For this reason, it is difficult to reliably prevent foreign matter from entering the bearing space if the operating conditions become severe simply by fitting the cap to the outer ring.

  In view of such circumstances, for example, as described in Patent Document 2, it is conceivable to hold an O-ring between the outer ring and the cap and maintain water tightness between the outer ring and the cap. Have been implemented in part. FIG. 2 shows an example of a seal structure using an O-ring 18 described in Patent Document 2. In the case of this conventional structure, the cap 6a is composed of a synthetic resin main body 14 and a metal plate sleeve 15. Among them, the main body 14 incorporates a rotational speed sensor 16 for ABS control. The sleeve 15 has an L-shaped cross section and is formed in an annular shape as a whole, and is embedded in a portion near the outer periphery of the main body 14 when the main body 14 is injection-molded. When the cap 6 a closes the axially inner end opening of the outer ring 2, the front half of the sleeve 15 is fitted into the outer ring 2 with an interference fit. In this state, the O-ring 18 mounted in the locking groove 17 formed on the outer surface outer peripheral portion of the main body 14 is elastic between the axial inner end surface of the outer ring 2 and the bottom surface of the locking groove 17. And the space between the outer ring 2 and the cap 6a is sealed.

  FIG. 2 shows a structure in which the sealing performance between the synthetic resin cap 6a and the outer ring 2 is improved by the O-ring 18, but the structure shown in FIGS. Thereby, the sealing performance between the cap 6 and the outer ring 2 can be improved. In this case, a step portion 19 is provided over the entire circumference at a continuous portion between the inner end surface and the inner peripheral surface in the axial direction of the outer ring 2. Then, the O-ring 18 is elastically compressed between the side surface and the inner peripheral surface of the step portion 19 and the outer peripheral surface of the fitting cylinder portion 12 and the outer surface of the flange portion 20 constituting the cap 6 ( Crush).

  For example, as shown in FIGS. 2 to 4 described above, the O-ring 18 used in the structure for sealing between the outer ring 2 and the caps 6a and 6 is conventionally made of NBR (nitrile rubber), which is an oil-resistant rubber. Was used. However, in the case of the N-ring O-ring 18, when the diameter (wire diameter) of the cross section is small, the OBR 18 is likely to sag as the temperature rises (a phenomenon in which elasticity becomes poor due to deterioration). That is, in the case of a double-row rolling bearing unit for supporting a wheel incorporating the O-ring 18, the temperature rises to over 100 ° C. due to its own heat generation or heat received from an attached brake part during driving of the automobile. There is. The O-ring 18 is used for a long period of time under such high temperature conditions, but the crushing rate of the O-ring 18 {= (wire diameter in free state−wire diameter in assembled state) / free If the wire diameter in the state is large, the above-mentioned sag is likely to occur.

  On the other hand, in order to ensure the sealing performance between the outer ring 2 and the caps 6a, 6, the crushing amount of the O-ring 18 (the wire diameter in the free state-the wire diameter in the assembled state) is It is necessary to secure the degree. If the absolute value of this crushing amount is small, the contact surface pressure between the surface of the O-ring 18 and the mating surface is sufficiently secured over the entire circumference (regardless of the unevenness of the surface that presses the O-ring 18, It is difficult to ensure a sufficient surface pressure over the entire circumference), and it is difficult to sufficiently secure the sealing performance between the outer ring 2 and the caps 6a and 6. Therefore, when a large (thick) wire diameter is used as the O-ring 18, the crushing rate can be kept small. However, when a small (thin) wire diameter is used, the crushing rate is increased. Need arises. Generally, the recommended value for the crushing rate of the O-ring is 8 to 30%. However, when the usage conditions become severe, even if the usage is within this range, the higher the crushing rate, the more sag occurs. It becomes easy. In particular, when an O-ring having a small wire diameter is used, there is a possibility that a large crushing rate exceeding the above range may be adopted. In such a case, the above-described sag is more likely to occur.

  In consideration of the above circumstances, by using a large wire diameter as the O-ring 18, if the crushing rate is kept low while securing the crushing amount, the O-ring 18 can be prevented from being sag. However, cases where the diameter of the O-ring 18 cannot be increased due to the following reasons are increasing. That is, in recent years, in order to reduce the weight of the double-row rolling bearing unit for wheel support, which is an unsprung load, for the purpose of improving the running performance of an automobile centering on the ride comfort and running stability, this double-row rolling for wheel support is used. The components of the bearing unit tend to be thin. In any structure shown in FIGS. 2 to 4, when the thickness of the outer ring 2 is reduced and the radial width of the inner end surface in the axial direction of the outer ring 2 is reduced, the O-ring 18 is used. It is necessary to use a small wire diameter.

  In order to prevent the sag of the O-ring 18 regardless of use in a high temperature environment, the O-ring 18 with a small wire diameter is used as a rubber material constituting the O-ring 18. It is also possible to use acrylic rubber (AKM), fluorine rubber (FCM), or the like. Since these AKM and FCM have heat resistance superior to that of the NBR, the settling can be suppressed even under the use conditions as described above. However, the AKM and FCM are not only inferior in mechanical properties such as elasticity and strength compared with the NBR, but are also expensive, so that the double-row rolling bearing unit for supporting a wheel incorporating the O-ring 18 is used. It is not preferable from the viewpoint of reducing the manufacturing cost. In consideration of these matters, it is conceivable that the O-ring 18 is made of hydrogenated nitrile rubber (H-NBR) which is stabilized by replacing the unsaturated bond portion of NBR with hydrogen. . However, H-NBR is not as expensive as the above-mentioned AKM or FCM, but it is more expensive than NBR, so simply replacing the N-ring O-ring with H-NBR made the O-ring 18 incorporated. From the viewpoint of reducing the manufacturing cost of the wheel-supporting double row rolling bearing unit, it is also not preferable.

  Further, in the case of the NBR O-ring 18 that has been generally used from the past, there is a possibility that a problem may occur due to swelling (volume expansion) due to oil. That is, in the installation site of the O-ring 18, the rust prevention of the metal cap 6 and the sleeve 15, and the work of fitting the fitting cylinder portion 12 and the sleeve 15 of the cap 6 into the outer ring 2 by interference fitting. It is necessary to apply some oil to make it easier. Although it is conceivable to apply grease filling the bearing space 11, it is difficult to automatically apply grease having extremely high viscosity. For this reason, conventionally, rust preventive oil has been applied to the cap 6 and the sleeve 15. However, when rust preventive oil is applied to the cap 6 and the sleeve 15 with which the O-ring 18 comes into contact, there arises a problem that the O ring 18 is swollen by the rust preventive oil. That is, since the NBR constituting the O-ring 18 is polar, it has a property that it is strong (does not swell) with mineral oil, which is a non-polar oil, but is weak (swells) with antirust oil, which is a polar oil. For this reason, when antirust oil is applied to the cap 6 and the sleeve 15, the O-ring 18 in contact with the cap 6 and the sleeve 15 swells. As a result of this swelling, the diameter (peripheral length) and wire diameter of the entire ring increase, and it may not be possible to fit in a predetermined portion where the O-ring 18 is to be mounted, such as the locking groove 17 or the step portion 19. There is sex. When the O-ring 18 does not fit completely, the O-ring 18 is illegally deformed and adversely affects the sealing performance between the outer ring 2 and the caps 6 and 6a. In a particularly remarkable case, the O-ring 18 may protrude from the predetermined portion, and the O-ring 18 may hardly be used for securing the sealing performance between the outer ring 2 and the caps 6 and 6a at the protruding portion. There is also.

If an overhang as described above is found in the product inspection, the double-row rolling bearing unit for supporting the wheel can be discarded or reassembled. However, in the case of the conventional structure using the NBR O-ring 18, the following is performed. For these reasons, it was difficult to find the above protrusion. That is, NBR is black unless a dye is added, and the N-ring O-ring 18 is considered to have good performance when it is black without adding a dye. When a dye is added to the NBR O-ring 18, the settling characteristics at a high temperature deteriorate due to the mixing of the SiO ₂ component accompanying the addition of the dye. On the other hand, out of the caps 6 and 6a that close the axial inner end opening of the outer ring 2, the metal cap 6 is usually black (chassis black) electrodeposited to prevent the cap from being noticeable. It is. The synthetic resin cap 6a is also made of a black synthetic resin mixed with a black pigment to prevent fading. For this reason, the caps 6 and 6a and the O-ring 18 have almost the same color, and even if the O-ring 18 protrudes from the predetermined portion, the fact of this protrusion is obtained by an industrial method (by a short visual observation). It is difficult to find.

JP 2000-198304 A JP-A-9-171030

In view of the circumstances as described above, the present invention suppresses the increase in cost and suppresses the sag of the O-ring to ensure the sealing performance of the O-ring over a long period of time, and incorporates the O-ring. The invention was invented to realize a structure capable of sufficiently ensuring the durability of the wheel-supporting double-row rolling bearing unit.
In addition, the present invention prevents the O-ring from swelling, if necessary, and if the O-ring protrudes from a predetermined portion set for securing the sealing property due to swelling or the like. The purpose is to realize a structure that can easily confirm the facts.

The double-row rolling bearing unit for wheel support of the present invention includes an outer ring, a hub, a plurality of rolling elements, a seal ring, a cap, and an O-ring, as in the conventional structure described above.
Of these, the outer ring is provided with a double row outer ring raceway on the inner peripheral surface, and does not rotate while being supported by the suspension device in use.
In addition, the hub is provided with a flange for supporting and fixing the wheel at the axial outer end of the outer peripheral surface, and a double-row inner ring raceway is also provided at the intermediate part or the axial inner end. Rotate with.
In addition, a plurality of rolling elements are provided between the outer ring raceways and the inner ring raceways so as to be freely rollable for each row.
The seal ring closes the axially outer end side opening of the bearing space in which the rolling elements are installed between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub.
The cap is fixed to the inner end of the outer ring in the axial direction so as to close the opening on the inner end.
Furthermore, the O-ring is provided over the entire circumference in a state of being elastically compressed between the outer ring and the cap.

In particular, in the double-row rolling bearing unit for supporting a wheel of the present invention, the O-ring is made of hydrogenated nitrile rubber (H-NBR), the cross-sectional diameter is 1.4 mm or less, the outer ring and the cap The crushing rate, which is the ratio of the amount of elastic deformation accompanying the sandwiching between and the original size, is 15 to 45%.
Further, when implementing the present invention as described above, preferably, as described in claim 2, grease is enclosed in the bearing space, and a portion of the cap where the O-ring is mounted is provided with the grease. Apply the same type of oil as the base oil.
In carrying out the present invention, the material of the cap is not particularly limited. For example, as described in claim 3, at least a portion of the cap that compresses the O-ring between the outer ring and the cap. And made of black synthetic resin.
Alternatively, as described in claim 4, the cap is made of metal, and the portion visible from the outside in a state of being fixed to the axially inner end opening of the outer ring is colored black.
And when implementing the invention described in the third to fourth aspects, preferably, as described in the fifth aspect, the color of the surface of the O-ring is the color of the cap such as red. , Other than black.

The double-row rolling bearing unit for supporting a wheel of the present invention suppresses the increase in cost and suppresses the sag of the O-ring to ensure the sealing performance of the O-ring over a long period of time, and incorporates the O-ring. The durability of the double-row rolling bearing unit for wheel support can be sufficiently secured.
That is, since a large value such as 15 to 45% is adopted as the crushing rate, even if a thin O-ring having a wire diameter of 1.4 mm or less is used, a sufficient amount of elastic deformation is secured, and this Ensuring sufficient contact pressure over the entire circumference of the surface of the O-ring and the mating surface (to ensure the necessary surface pressure over the entire circumference regardless of the irregularities of the surface that presses the O-ring ) And since the O-ring is made of H-NBR, even if the crushing rate is increased, it is possible to suppress the sag over a long period of time and to sufficiently ensure the sealing performance by the O-ring over a long period of time.
If the crushing rate is less than 15% (if the O-ring wire diameter can be set to a value exceeding 1.4 mm), the O-ring material is less expensive than H-NBR. Even with NBR, the required sag resistance can be ensured, so that the necessity of adopting the present invention is reduced. On the other hand, if the crushing ratio exceeds 45%, the sag cannot be sufficiently suppressed even if the material of the O-ring is H-NBR.

  H-NBR is an expensive material compared to NBR, but the O-ring built into the double row rolling bearing unit for wheel support of the present invention has a thin wire diameter of 1.4 mm or less, so the amount of material used is small. Cost increase based on material costs is minimized. On the other hand, when a thick O-ring having a wire diameter exceeding 1.4 mm is used, the required amount of crushing can be ensured even if the crushing rate is kept low. Therefore, an N-ring O-ring may be used without using the present invention under conditions where such a thick O-ring (wire diameter exceeding 1.4 mm) can be used.

Further, as in the invention described in claim 2, the same kind of oil (mineral oil or synthetic oil) as the base oil of the grease sealed in the bearing space is applied to the portion of the cap where the O-ring is mounted. In this case, the swelling of the O-ring can be prevented. For this reason, it is possible to prevent the O-ring from protruding from a predetermined portion due to deformation due to swelling, and to sufficiently ensure the sealing performance by the O-ring. Since the base oil of grease has a moderately high viscosity at room temperature, it is difficult to dry even if it is not polar, and can exhibit rust prevention performance. For this reason, if the base oil is also used as a rust preventive oil for the cap, it is possible to prevent the O ring from swelling even when the base oil adheres to the O ring while preventing the cap from being rusted.
Further, as in the invention described in claim 5, if the color of the surface of the O-ring is made other than black which is the color of the cover, the O-ring is set to ensure sealing properties due to swelling or the like. Even when it protrudes from the predetermined portion, the fact of the protrusion can be easily confirmed.

  The features of the double-row rolling bearing unit for wheel support of the present invention are the material, wire diameter, crushing rate, and color of the O-ring that seals between the cap that closes the opening on the inner end side in the axial direction of the outer ring and the outer ring. The point is to devise. The structure shown in the drawings is the same as the conventional structure or the previously considered structure shown in FIGS.

An experiment conducted in the process of making the present invention will be described. In the experiment, the material, color, crushing rate, and wire diameter of the O-ring 18 incorporated in the structure shown in FIGS. 3 to 4 are varied as shown in Table 1 below, and each of these elements affects the sealing performance. The effect was sought.

  As shown in Table 1, an O-ring 18 made of NBR or H-NBR and having a wire diameter of 1.3 to 1.5 mm when not used is shown in FIG. In addition, the inner peripheral surface and the outer peripheral surface of the fitting tube portion 12 constituting the cap 6 and the outer surface of the flange portion 20 were compressed elastically. The crushing rate was changed in the range of 9 to 35%. After holding at 120 ° C. for 360 hours and further holding at 130 ° C. for 3 hours, 50 kPa of compressed air is fed into the bearing space 11 to check whether there is leakage (air leak) from the portion where the O-ring 18 is installed. Inspected. When there was no leakage, it was set as OK, and when it was set as NG, it was described in the column of the sealing performance of Table 1 above.

  As is clear from Table 1 above, which shows the results of the experiment conducted as described above, if an O-ring 18 made of H-NBR is used, a thin O-ring 18 having a wire diameter of 1.4 mm or less is 15% or more. Even when used at a large crushing ratio, sufficient sealing performance can be secured. Incidentally, the thermal aging of the rubber constituting the O-ring 18 proceeds from the surface of the O-ring 18 because oxygen in the air is involved. Since the surface area ratio (surface area / volume of the O-ring) increases as the O-ring 18 has a smaller wire diameter, the settling progresses faster. Further, as the crushing rate is larger, the stress applied to the rubber constituting the O-ring 18 in use is increased, so that the sag progresses faster. As a result, in the case of the O-ring 18 made from NBR, the wire diameter was 1.4 mm or less and the sealing performance was poor (NG) (air leak occurred), but in the case of the O-ring 18 made from H-NBR The seal performance remained good (OK) even when the wire diameter was 1.4 mm or less (no air leak occurred). From this, it was confirmed that H-NBR had better sag resistance performance than NBR. The fact that H-NBR has better sag resistance than NBR is also evident from a comparison of the difference in wire diameter before and after the test (sag amount).

  Further, as is obvious from comparison between Comparative Example 1 and Comparative Example 4, in the case of the NBR O-ring 18, the red one is clearly easier to set than the black one. On the other hand, as is apparent from a comparison between Examples 1 to 3 and Examples 4 to 6, in the case of the O-ring 18 made of H-NBR, the red case is almost the same as the black case. The sag resistance can be secured. If the O-ring 18 is made of red H-NBR and this O-ring 18 is combined with the black cap 6, even if the O-ring 18 protrudes from a predetermined portion for some reason, the fact that it protrudes Can be easily confirmed visually.

Sectional drawing which shows an example of a conventional structure. Sectional drawing which shows the 1st example of the structure used as the object of this invention. Sectional drawing which shows the 2nd example. The A section enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel support double row rolling bearing unit 2 Outer ring 3 Hub 4 Rolling body 5 Seal ring 6, 6a Cap 7 Outer ring raceway 8 Mounting part 9 Flange 10 Inner ring raceway 11 Bearing space 12 Fitting cylinder part 14 Main body 15 Sleeve 16 Rotational speed sensor 17 Locking groove 18 O-ring 19 Step part 20 Gutter part

Claims (5)

  A double row outer ring raceway is provided on the inner peripheral surface, and an outer ring that does not rotate when supported by the suspension device in use and a flange for supporting and fixing the wheel on the outer end in the axial direction of the outer peripheral surface are also provided in the middle. A plurality of inner ring raceways are provided at inner end portions in the axial direction, and a plurality of hubs that rotate together with the wheels in use and between each of the inner ring raceways and the outer ring raceways in each row. A rolling element provided so as to be freely rollable, and a seal ring for closing an axially outer end side opening of a bearing space in which each of the rolling elements is installed between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub; A cap fixed to the inner end in the axial direction of the outer ring in a state of closing the opening on the inner end side, and a state of being elastically compressed between the outer ring and the cap over the entire circumference. In a double-row rolling bearing unit for supporting wheels provided with an O-ring provided The O-ring is made of hydrogenated nitrile rubber, has a cross-sectional diameter of 1.4 mm or less, and is a crush that is a ratio of the amount of elastic deformation caused by being sandwiched between the outer ring and the cap to the original size. A double-row rolling bearing unit for supporting a wheel, characterized in that the rate is 15 to 45%.   2. The double row rolling for wheel support according to claim 1, wherein grease is sealed in the bearing space, and the same kind of oil as the base oil of the grease is applied to a portion of the cap where the O-ring is mounted. Bearing unit.   The double row rolling bearing unit for wheel support according to any one of claims 1 to 2, wherein at least a portion of the cap that compresses the O-ring with the outer ring is made of a black synthetic resin. .   The wheel according to any one of claims 1 to 2, wherein the cap is made of metal, and a portion that is visible from the outside in a state in which the opening on the inner end side in the axial direction of the outer ring is closed is colored black. Double row rolling bearing unit for support.   The double-row rolling bearing unit for wheel support according to any one of claims 3 to 4, wherein the color of the surface of the O-ring is other than black.

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