JP2011226623A - Rolling bearing for conveyance roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing for a conveyance roller, the bearing having reduced friction and reduced torque as well as superior durability by allowing a solid lubricant included in a resin cage to be easily transferred.SOLUTION: The rolling bearing includes an outer ring having an outer ring raceway on the inner circumference face, an inner ring having an inner ring raceway on the outer circumference face, a plurality of balls disposed between the outer ring raceway and the inner ring raceway, and an annular cage which is made of a synthetic resin and rotatably holds the plurality of balls. The cage is molded from a synthetic resin containing a solid lubricant, and has a bending elastic modulus of 600 to 2,000 MPa and a coefficient of dynamic friction of 0.2 or less.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing incorporating a resin cage containing a solid lubricant, and in particular, a rolling bearing for a conveying roller that is suitably used as a supporting roller for a film conveying roller that requires low torque and durability. It is about.

Films used for materials such as FPDs (flat panel displays) and solar cells can exhibit functions of light emission and power generation by laminating films of different materials, but the thickness of the film becomes thinner every day. Even those with a thickness of about several tens of μm have appeared.
Conventionally, the film 20 is supported and transported by a plurality of transport rollers 21 that are arranged in parallel to each other and rotate around the axis as shown in FIG. 7, but there is a bias in the thickness and length of the film 20. If it exists, sufficient ability cannot be exhibited at the time of lamination, which causes a product defect. Some of the conveying rollers 21 are driving rollers that apply a driving force to the film 20, and most of the remaining rollers are driven rollers. The driven roller is rotated by the frictional force with the moving film 20, and smoothly conveys the film 20, or changes the vertical angle of the film 20 by changing the relative position with the previous roller. Owed. Since the driven roller rotates only by the frictional force with the film 20, it is important that the traveling speed of the film 20 and the peripheral speed of the roller surface are the same. Therefore, the driven roller has a very small tangential force. Must rotate at. Accordingly, the conveyance roller bearing, which is the support bearing 22 of the conveyance roller 21 that conveys the film 20, is required to have low torque performance and durability that starts rotating with an extremely small moment and continues to rotate stably.

By the way, as a bearing for a film conveyance roller, a rolling bearing is generally used, and an example is shown in FIG. This is a deep groove ball bearing comprising an outer ring 4, an inner ring 2 and a corrugated cage 23. The corrugated cage 23 sandwiches the ball 5 with two press-molded parts, and is then inseparable by a caulking process. Ball bearings are the most common form of cage. The waveform holder 23 is formed so that the pocket 24 on the inner peripheral surface is formed into a spherical surface so as to follow the spherical surface of the ball 5, and is arranged so as to hold the ball 5. Due to the action of this spherical surface, the ball 5 does not fall off after caulking is completed, and a predetermined pitch dimension is maintained at equal intervals. Thus, the waveform holder 23 is not only excellent in mass productivity but also has high rigidity and is widely used. However, since the corrugated holder 23 is integrated and has a structure in which the pocket 24 is spherical and holds the ball 5, the ball 5 cannot freely move in the pocket 24. When the bearing starts to rotate, the ball 5 starts to rotate by receiving the frictional force from the cage, so the starting torque has to be increased. Further, the rotating cage receives a strong pressure from the balls 5 due to this pocket shape, and as a result, some of the balls 5 are pressed against the inner and outer ring races 1 and 3 and are released. Repeated. For this reason, there is a problem that the friction torque value also increases.

As prior art for improving this problem, Patent Documents 1 to 4 disclose inventions for improving the lubrication performance and low torque performance of rolling bearings.
In Patent Document 1, the bending elastic modulus of the resin cage is defined within a predetermined range, the occurrence of collision noise between the rolling element and the cage pocket is alleviated, and the increase in torque is suppressed by reducing the restraint between the cage and the rolling element. Resin cages are described.
In Patent Document 2, potassium titanate whisker is contained in a resin cage as a reinforcing agent to increase the cage deformation strength, and the lubrication performance is improved by the self-lubricating property of the potassium titanate whisker to reduce torque. Ball bearings are described.
In Patent Document 3, a clearance is formed between the bearing ring on the opposite side and the cage by providing the bearing ring guide surface of the resin cage only at one end, and it is easy for lubricant to enter the bearing from there. Thus, a rolling bearing that achieves low torque is described.
In Patent Document 4, by forming a strength reinforcing portion at the edge of the cage pocket, the twist of the cage during high-speed rotation is reduced, and the cage and the rolling element are prevented from sliding unnecessarily. A rolling bearing that suppresses the increase in torque is described.

Japanese Patent Laid-Open No. 2004-084867 JP 09-133137 A JP 2009-068636 A JP 2007-056930 A

  However, the invention of Patent Document 1 is to reduce the collision sound while suppressing the torque increase, and is not intended to further reduce the torque. In addition, although the resin cage containing the solid lubricant is considered to contribute to the improvement of the lubrication performance of the rolling bearing, it is unclear how much the solid lubricant is transferred in the invention of Patent Document 2. In order to reduce the torque increase and fluctuation, stable solid lubricant transfer is required. Since it is used in a clean environment in the film conveyance field assumed by the present invention, the lubrication technique for supplying lubricating oil from the outside of the bearing described in Patent Document 3 cannot be carried out. Further, when the cage is deformed, there is a problem that the pocket of the cage and the ball are in local contact, or the sliding friction between the cage and the raceway is increased. However, the invention described in Patent Document 4 has functions and effects. It is limited at the time of high-speed rotation and does not act on the reduction of sliding friction between the race and the cage, and the effect of lowering the torque is not sufficient.

  The present invention provides a rolling roller bearing for a transport roller that can easily transfer a solid lubricant contained in a resin cage to a rolling element, reduce friction and torque, and has excellent durability. The purpose is to do.

In order to solve the above problems, the present invention provides an outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner ring raceway on an outer peripheral surface, and a plurality of balls provided between the outer ring raceway and the inner ring raceway. And an annular cage made of synthetic resin that holds the plurality of balls in a rollable manner, and supports the object to be conveyed by a plurality of rollers that are arranged in parallel to each other and rotate around the axis. In the rolling roller rolling bearing that sequentially conveys, the cage is molded from a synthetic resin containing a solid lubricant, has a flexural modulus of 600 to 2000 MPa, and a dynamic friction coefficient of 0.2 or less. And
Furthermore, when the outer diameter of the bearing is D, the inner diameter of the bearing is d, and the width of the bearing is t, the following equation is satisfied.
(D−d) /2/t≦1.07

In the present invention, in order to reduce the sliding friction between the cage, the race and the rolling element, the flexural modulus is 600 to 2000 MPa (ASTM standard D-790) and the dynamic friction coefficient is 0.2 or less (Suzuki / Matsuhara). A cage is made of a resin material containing a solid lubricant of a measured value by a type friction and wear tester, P = 0.05 to 0.3 N / mm ² , V = 0.5 to 1 m / s). is there.
In order to reduce the sliding friction between the cage and the races and rolling elements, the cage resin material must contain a solid lubricant, but basically the dynamic friction coefficient of the material must be less than a certain value. Small effect. Furthermore, in order for the solid lubricant to transfer to the mating material, the cage needs to slide with the mating material for a certain area and for a certain time. For this purpose, the resin material is required to be flexible. Even if the flexibility is too high, it may not be used as a structural component, or there may be a difficulty in durability. Considering the balance between lubricity and durability, the above-mentioned numerical values set the characteristics of the cage material appropriately.

  According to the present invention, the cage is molded from a synthetic resin containing a solid lubricant and has a flexural modulus of 600 to 2000 MPa and a dynamic friction coefficient of 0.2 or less. Since the cage slides appropriately, the solid lubricant contained in the resin cage is easily transferred to the rolling elements and the raceway. As a result, the friction and torque can be reduced, and sufficient durability can be provided.

It is sectional drawing which shows the structure of the rolling bearing which is 1st Embodiment of this invention. It is a front view of the crown type holder in FIG. It is an external view which shows the structure of a test apparatus. It is a graph which shows the change with time of a dynamic friction coefficient. It is a graph which shows the relationship between the dynamic friction coefficient of a test result, and a bending elastic modulus. It is a fragmentary sectional view which shows the structure of the rolling bearing which is 2nd Embodiment of this invention. It is explanatory drawing of the film conveying apparatus which uses a conveyance roller. It is explanatory drawing of a general deep groove ball bearing.

  FIG. 1 is a sectional view showing the structure of a rolling bearing according to the first embodiment of the present invention, and FIG. 2 is a front view of the crown type cage in FIG. The rolling bearing 10 according to this embodiment includes an outer ring 4 having an outer ring raceway 3 on an inner peripheral surface, an inner ring 2 having an inner ring raceway 1 on an outer peripheral surface, and a plurality of rollers provided between the outer ring raceway 3 and the inner ring raceway 1. And a synthetic resin annular crown-shaped machined cage 7 for holding the ball 5 in a freely rollable manner. The outer peripheral edges of the annular ring-shaped shield plates 6 and 6 are respectively engaged with the inner peripheral surfaces of both ends of the outer ring 4, and a gap is provided between the inner diameter of the shield plate 6 and the outer peripheral surface of the inner ring 2 facing each other. A cage 7 formed of a resin material containing a solid lubricant serves as an inner ring guide, and is provided with a pocket 8 that holds the balls 5 in a circumferentially arranged position so as to be able to roll, and has an opening at one end face. 9. The opening 9 has a snapping allowance so that the ball 5 that passes through the opening 9 and is stored in the pocket 8 does not fall off the cage 7.

When assembling such a rolling bearing 10, a predetermined number of balls 5 are equally arranged at a position between the inner ring raceway 1 and the outer ring raceway 3, a cage 7 is loaded from the bearing end face side, and all the balls 5 are placed in the pockets 8. Store. Further, a thin film (not shown) of grease or oil is applied to the balls 5 or raceways to lubricate the bearings, and then the shield plate 6 is loaded and sealed.
The rolling bearing 10 may be an angular bearing. In this case, the same assembly method as described above may be used, or the outer ring counter that is held integrally with the inner ring in a state in which the rolling element is put in a cage having a circular pocket that is not cut and is expanded by heating. You may load and assemble from the bore (outer ring mouth base taper part) side.
Examples of the material of the inner and outer rings 2, 4 and the ball 5 include SUJ2 and SUS440C, and the material of the shield plate 6 may be SPCC, SUS304, or a rubber molded product using them as a core metal.

  In the rolling bearing 10 of the present embodiment, the balls 5, the inner ring raceway 1 and the outer ring raceway 3 are lubricated by grease or oil applied with a thin film, and the bearing is in a rotatable state. The cage 7 rotates around the inner ring 2 as the bearing rotates. However, as shown in FIG. 1, the cage 7 is an inner ring guide, so that the outer diameter portion of the inner ring 2 and the inner diameter portion of the cage 7 are separated from each other. Rotates while sliding. Even if a thin film of lubricant is applied to the outer diameter portion of the inner ring 2, the grease (or oil) is peeled off by this sliding, and the inner diameter portion of the cage 7 and the outer diameter portion of the inner ring 2 slide in a dry state. Will move. At this time, the solid lubricant contained in the resin material of the cage 7 is detached from the cage 7 and transferred to the surface of the outer diameter portion of the inner ring 2 to be used for sliding lubrication between the cage 7 and the inner ring 2. The Thus, although the cage 7 and the inner ring 2 are sliding, since they are lubricated with the solid lubricant, a large frictional resistance is not generated, and the torque of the bearing rotation is not increased.

  Since the rolling bearing 10 is thin-film lubricated, the agitation resistance of grease (or oil) during rotation of the bearing is small, so that the torque of the bearing can be reduced. Lubricating with solid lubricants is a lubrication that does not involve agitation resistance that is always generated in wet lubrication, and the dynamic friction coefficient of the resin material directly affects the dynamic friction force. preferable. However, as a precondition, it is necessary that the solid lubricant is reliably transferred to the counterpart material (inner ring outer diameter portion in FIG. 1). For this reason, the dynamic friction coefficient and the flexural modulus are determined based on the grounds described later. It is necessary to select a resin material that is within the range. The smaller the flexural modulus is, the more flexible the cage 7 is, and the cage 7 slides over a wide area following the shape of the counterpart material, increasing the opportunity for transfer of the solid lubricant. As a result, the lubricity of the cage 7 is improved. However, the higher the flexibility is, the less rigid the structure is. Therefore, when the cage 7 receives a force from the ball 5, the cage 7 is deformed during rotation. The rotation of the bearing becomes unstable or the rotation cannot be started.

  In the present embodiment, the inner ring guide retainer 7 is shown, but even if the retainer 7 is an outer ring guide, the action of solid lubrication is the same, and an increase in rotational torque can be suppressed. Furthermore, in the case of a rolling element guide cage, sliding between the thin film lubricated portion on the rolling element and the cage pocket facing surface occurs. Therefore, by using the resin cage of the present invention, low torque is achieved. There is an effect in making.

Next, two rolling tests, a dynamic friction torque test and a durability test, were performed on the rolling bearing having the same configuration as described above.
The dynamic friction torque test and the durability test both use the same type of test apparatus, and FIG. 3 is an external view showing the structure of the test apparatus. The two test bearings 31 and 31 are arranged coaxially in a state in which a bearing inner ring is loaded on a shaft 30 which is a horizontal axis, and a bearing outer ring is fitted to a bearing holder 32. Preload load (axial load) is applied. Since the test bearing 31 has friction, when the bearing inner ring is rotated by the rotational movement of the shaft 30, the bearing outer ring rotates. The yarn is stretched 34 from the middle point of the outer ring of the two test bearings 31 arranged in the tangential direction and the end thereof is connected to the force gauge 35. Measure the tangential force (tangential load) around. The test bearing 31 is compared by substituting the tangential force value for the bearing torque value. The test bearing 31 is a pair of identical specification bearings (inner diameter 60 mm), and the measured value is halved to be one bearing.
The dynamic friction torque test was performed at an inner ring rotational speed of 70 min ⁻¹ , and the durability test was performed at an inner ring rotational speed of 420 min ⁻¹ (atmospheric pressure, normal temperature). FIG. 4 shows an example of measuring the tangential force. Since the tangential force value has a swing width, the median value and the swing width amount are set as representative values of the bearing torque.

The test results are shown in Table 1. As test bearings, ten types of bearings were prepared, which were different in the resin material of the cage and had the same specifications, thin film lubrication amount, and the like. The resin material of the cage in the test bearing is a commercially available non-oriented compression molding material, and a cage is manufactured by machining a round bar or cylindrical material. The retainer is a crown-type grind retainer having a pocket opening of the same type as that in FIG. 2, and the pocket is an inner ring guide retainer having the same cross section in the radial direction. The resin material of the cage is pure PTFE test bearing # 1, # 2-5 is PTFE blended with reinforcing fiber or reinforcing material (PI: polyimide), and # 1-5 is solid lubricated with PTFE as the base resin It is an agent. # 6 is a blend of fluorine resin (solid lubricant) in polypropylene, # 7 and 8 are blends of polyamide 6, MoS ₂ (solid lubricant) in polyamide 66, # 9 is PTFE (polyether ether ketone and PTFE (solid lubricant) Solid lubricant) is blended, and # 10 is a blend of polyethylene terephthalate and solid lubricant.

In Table 1, the median value of the tangential force 30 minutes after the rotation test and the runout amount, the median value after 12 hours, and the total number of revolutions of the durability test are described.
In the dynamic friction torque test, the test bearing # 4 does not rotate, the test bearings # 5, 7 and 8 have an abnormally high median tangential force after 30 minutes, the test bearing # 9 has a large deflection width, and the test bearing # No endurance test was conducted on 10 because the median value for 12 hours was significantly increased. As a result of the durability test, the cage of test bearing # 1 was damaged, but all of test bearings # 2, 3, and 6 reached the target 5 × 10 7 revolutions. Based on the above, it was determined that the test bearings # 2, 3, and 6 were suitable for the rolling bearings for the transport rollers from the low torque performance and durability performance.
The pure PTFE cage of test bearing # 1 is damaged due to PTFE being worn out and shed. The reason why the result of NG in the dynamic friction torque test is thought to be that the cage of the test bearing is too soft as a structure, or that the solid lubricant is not sufficiently transferred.

  FIG. 5 shows the results of the tests arranged for the dynamic friction coefficient and the flexural modulus of the cage resin material. It can be seen that when the roller bearings determined to be suitable for the conveyance roller rolling bearings are divided into regions with ◯ and NG with x, the regions are separated by thick lines in the figure. That is, low torque performance and durability performance are satisfied by using a resin material having a dynamic friction coefficient of 0.2 or less and a flexural modulus of 600 to 2000 MPa for the cage. In particular, a resin material having a flexural modulus of 900 MPa or more can be said to be more preferable because the cage rigidity can be secured.

  Next, FIG. 6 is a partial sectional view showing the structure of a rolling bearing according to the second embodiment of the present invention. The rolling bearing 10 of the present embodiment is substantially the same as the rolling bearing of the first embodiment, except that the bearing dimensions are limited. The transport roller rolling bearing 10 has a structure that satisfies (D−d) /2/t≦1.07, where D is the outer diameter of the bearing, d is the inner diameter of the bearing, and t is the width of the bearing. . A bearing for a film transport roller is required to have a low torque performance, but is rarely required to have a large load capacity. On the other hand, since the footprint of the equipment is required, a bearing called a thin bearing having a small thickness but not a large load capacity is often used. These are classified into the 08 series and 09 series in the bearing diameter series. Since these bearings have a small cross-sectional area with respect to the diameter of the ball 5, the built-in cage 7 is also subject to dimensional restrictions.

As can be seen from FIG. 6, the space allowed for the cage 7 is very small, and the cage 7 is placed on the inner ring side opposite to the fitting portion of the shield plate 6 so as not to interfere with the shield plate 6. It is necessary to install it. When the ball guide structure is adopted for the cage 7, the cage 7 comes closer to the region where the cross-sectional area is narrowed by the shield plate 6, so that there is a possibility that the shield plate 6 and the cage 7 come into contact with each other. This is not preferable. Accordingly, the cage 7 of the thin bearing has to be a bearing ring guide (inner ring guide in the figure). Since the bearing ring guide retainer 7 always slides with the outer ring 4 or the inner ring 2, it is necessary to use a resin retainer in which the sliding resistance is reduced as much as possible. That is, it can be said that the resin cage of the present invention is suitable for a bearing for a film transport roller in which a thin bearing is often used.
In the case of a 08,09 series bearing (with an inner diameter of 100 mm or less), when the ratio of the sectional height dimension (Dd) / 2 of the bearing and the width dimension t is taken, the maximum value is 1.07. All bearings that satisfy the conditions are thin-walled bearings.

  The roller bearing for the transport roller of the present invention can be suitably applied to the support shaft of the film transport roller.

DESCRIPTION OF SYMBOLS 1 Inner ring track 2 Inner ring 3 Outer ring track 4 Outer ring 5 Ball 6 Shield plate 7 Holder 8 Pocket 9 Opening portion 10 Rolling bearing 20 Film 21 Transport roller 22 Support bearing 23 Waveform holder 24 Pocket 30 Shaft 31 Test bearing 32 Outer ring holder 33 Preload Spring 34 Thread 35 Force gauge

Claims (2)

  An outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner ring raceway on an outer peripheral surface, a plurality of balls provided between the outer ring raceway and the inner ring raceway, and the plurality of balls can be freely rolled. In a rolling bearing for a conveyance roller, comprising a synthetic resin annular retainer for holding, and supporting the object to be conveyed by a plurality of rollers that are arranged in parallel to each other and rotate around an axis, respectively, and sequentially convey the object to be conveyed. The container is formed from a synthetic resin containing a solid lubricant, has a flexural modulus of 600 to 2000 MPa, and further has a dynamic friction coefficient of 0.2 or less. The rolling roller bearing according to claim 1, wherein the outer diameter of the bearing is D, the inner diameter of the bearing is d, and the width of the bearing is t.
(D−d) /2/t≦1.07

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