JP2004301341A - Thrust roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thrust roller bearing capable of reducing differential slide caused on a rolling body face, reducing load capacity, and suppressing increase of rolling contact face pressure. <P>SOLUTION: This thrust roller bearing is provided with rollers 2 and a holder 3, which is a resin-made holder manufactured by injection molding. At least two rollers or more are held in each pocket of the holder, and crowning is formed on at least one roller. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The thrust roller bearing (including the thrust needle roller bearing) according to the present invention is installed on a rotating part of an electric component such as a transmission (manual and automatic), a transfer, or a compressor of an air conditioner for a vehicle, in particular. Used to support the thrust load applied to the part.

  As shown in FIG. 8, the thrust roller bearing 1 is made of a plurality of rollers 2 arranged radially and evenly in the circumferential direction, and is formed in a ring shape as a whole, and holds the plurality of rollers 2 in a freely rolling manner. It comprises a retainer 3 and a track ring that clamps the rollers 2 from both sides, that is, an outer ring 4 and an inner ring 5. The outer ring 4 and the inner ring 5 are each made of a metal plate having a sufficient hardness in a ring shape. The outer race 4 has a ring-shaped outer raceway surface 6, and the inner race 5 has a ring-shaped inner raceway surface 7.

  A thrust roller bearing is a bearing having various advantages such as a simple structure, high load capacity and high rigidity. In some cases, the bearing ring is not used, and only the retainer and the rollers are used. In this case, the shaft or housing, which is the rolling surface of the roller against the rolling surface of the roller, has a function equivalent to the bearing raceway surface such as roughness and hardness, and by using the shaft or the housing as the raceway surface, Eliminates the need for bearing rings, making it possible to reduce the size. In particular, a thrust needle roller bearing using a needle roller (needle roller) as a roller can reduce the cross-sectional height of the bearing, and is particularly suitable for a compact mechanical design.

  A main application in which a thrust needle roller bearing which is a typical example of the thrust roller bearing is used is a compressor of an air conditioner for an automobile. These compressors are of various types. For example, as shown in FIG. 5, a double swash plate type in which a piston 10 is reciprocated by a double-sided inclined plate 9 fixed to an input rotary shaft 8, and as shown in FIG. A single swash plate type in which a piston 14 is reciprocated via a rod 13 by a single-sided inclined plate 12 fixed to 11, and a rod 17 is mounted on a swash plate 16 variably mounted on an input rotary shaft 15 as shown in FIG. There is a variable capacity swash plate type in which the piston 18 is reciprocated via the shaft. In each case, a rolling bearing is incorporated in a rotating portion and used.

  As a specific example of the use of the bearing, in the case of the double swash plate type shown in FIG. 5, a needle roller bearing 19 with a cage and a thrust needle roller bearing 20 are used. The single swash plate type shown in FIG. 6 employs a needle needle roller bearing 21 and a needle roller thrust bearing 22. Further, the variable capacity swash plate type shown in FIG. 7 uses a needle roller bearing 23 with a cage and a thrust needle roller bearing 24. As described above, the thrust needle roller bearing has advantages such as a low sectional height and is used for compressors and the like, particularly for applications requiring space saving.

  In a general type of bearing (for example, a ball bearing), a differential slip occurs between the rolling element and the bearing ring. The differential slip of these bearings is basically based on the rolling element and the raceway. It depends on the peripheral speed difference in the contact surface of the wheel. That is, in the case of point contact with a ball bearing or the like, since the contact area is small, it can be said that these peripheral speed differences in the contact surface are small and the differential slip is small.

  However, the thrust roller bearing has a structure in which cylindrical rollers are arranged as rolling elements on a raceway having a flat raceway surface, and the roller and the raceway are in line contact with each other. It has a basic structure that coincides with the center of revolution of the roller. In this case, the peripheral speed on the rolling surface of the roller is the same speed, while the bearing ring that comes into rolling contact with the roller moves toward the outer radial direction from the rotation center of the bearing (in proportion to the rotation radius of the bearing ring). Then, the peripheral speed increases. Therefore, the peripheral speed difference between the roller and the bearing ring becomes maximum at both ends of the roller. Theoretically, pure rolling motion is performed only on the bearing pitch circle, and from the point on the roller pitch circle to both ends of the roller, the peripheral speed difference between the roller and the bearing ring increases, increasing differential slip. I do. This differential slip increases in proportion to the roller length.

  As described above, the differential sliding inside the bearing of the thrust roller bearing is more than that of other types of bearings, and the differential sliding between the roller and the bearing ring is a factor. In this case, the edge stress is easily generated, and the surface-starting type separation is easily generated at the edge of the rolling portion of the bearing ring.

As a solution to the above-mentioned problem, a double-row type bearing in which a roller length is shortened in order to reduce a relative sliding amount of a roller end face, or two rollers are put in one pocket of a retainer has been conventionally used. It is used. In addition, for the problem that a stress (edge load) is generated at the roller end, measures such as forming crowning on the roller are taken.
JP-A-9-14131

  Thrust roller bearings are required to be reduced in size due to demands for energy saving, space saving, weight reduction, and the like (reduction in friction loss). Therefore, bearing use conditions have become more severe in terms of load capacity. As described above, in the thrust roller bearing, the differential slip between the rollers and the races is a factor, so that the friction loss and wear on the contact surface are increased, and the oil film formation state on the contact surface is deteriorated, and the edge of the roller is deteriorated. In the portion, edge stress between the bearing ring and the bearing ring is likely to occur, and the surface-starting type peeling is likely to occur at the edge of the rolling portion of the bearing ring. In order to suppress differential slip, it is conceivable to simply shorten the roller length.However, since the contact area of the rollers is reduced, the contact surface pressure increases, in which case the contact surface pressure at the contact surface is increased. And the oil film formation state is deteriorated, and problems such as peeling on the outer diameter side of the roller occur.

  The bearing used in the compressor has a lubricating oil and refrigerant mixed inside the bearing, and the compression and expansion of the compressor causes repeated liquefaction and vaporization of the lubricating oil. There is a problem that the amount of oil decreases, and the state of forming an oil film is poor as compared with hydraulic oil lubrication of a general machine, causing a problem that the oil is separated at an early stage.

  In addition, from the viewpoint of environmental problems such as prevention of global warming, alternative refrigerants such as HCFC134a are used as refrigerants in compressors and the like for air conditioners. These alternative CFCs are said to have poor self-lubricating properties as compared with conventionally used refrigerants. Since it is mixed by dissolving with CFC substitute, the kinematic viscosity of the lubricating oil is reduced and the state of oil film formation of the bearing is extremely deteriorated, causing the bearing rolling elements and raceway to peel and wear. And the like, resulting in a short life.

  Although a method of improving the lubricating oil is conceivable, the selection range of the lubricating oil is limited due to the problem of compatibility with the refrigerant, and a drastic improvement in the oil film forming ability cannot be expected. Further, in the method of increasing the amount of lubricating oil in the refrigerant to improve the lubricity, there is a problem that the cooling capacity of the compressor is reduced due to a decrease in the amount of the refrigerant.

  Thrust needle roller bearings used in air conditioner compressors receive a thrust load offset from the center of rotation, rotate at a high speed of about 8000 rpm or higher, and are severe in terms of the rotation speed and load conditions. In addition, the number of failure phenomena indicating surface damage of bearings due to differential slip is increasing.

  SUMMARY OF THE INVENTION In view of the above-described circumstances, an object of the present invention is to reduce the differential slip, reduce frictional wear, and excel in anti-peeling life in a thrust roller bearing, and further suppress a decrease in load capacity and an increase in contact surface pressure. It is to provide a thrust roller bearing.

  In order to solve the above problems, the thrust roller bearing according to the present invention includes a roller and a retainer that retains the roller, wherein the retainer is a resin molded retainer manufactured by injection molding, A thrust roller bearing, wherein at least two or more rollers are held in each pocket, and crowning is formed on at least one of the rollers. In this configuration, a complicated pocket shape can be formed by using a resin-molded cage by injection molding for the cage including the pocket for accommodating the rollers. For this reason, a thrust roller bearing having excellent peel resistance can be obtained. Furthermore, the effect of reducing the differential slip caused by the double row rollers and the effect of reducing the differential slip by shortening the effective length of the rollers by adding a crowning shape are synergistic, and the edge portion in the crowning shape This has the effect of reducing the load on the device. At the same time, there is an effect of reducing the friction torque of the bearing.

  In the above thrust roller bearing, the diameter Da of the roller is Da ≦ 5 mm, and the ratio L / Da of the length L of the roller to the diameter Da can satisfy 1 ≦ L / Da ≦ 10. When L / Da <1, the roller length is shortened, the effective length of the roller is also shortened, the contact area of the roller is too small, and the contact surface pressure is increased. Is good. On the other hand, when 10 <L / Da, since the effective length of the roller is increased by increasing the roller length and the differential slip between the roller and the raceway surface is increased, L / Da ≦ 10 is set. That is, by setting the pressure in the above range, it is possible to suppress the differential slip while preventing the contact surface pressure from becoming excessive.

  Further, in the above thrust roller bearing, the rollers are arranged as two rows of rollers housed in the pocket, and all of the two rows of rollers can be crowned rollers. According to this configuration, the non-contact portion with the race is greatly increased in the roller with the double row crowning as compared with the roller with the single row crowning having the same total roller length. Therefore, the contact surface pressure is higher than that of a two-row straight roller having the same roller length. However, although the contact surface pressure is increased, the differential slip is reduced by the rollers with the two-row crowning, and the damage of the surface starting type can be largely suppressed. As a result, the durability of the thrust roller bearing can be improved, and the life can be extended.

  In the above thrust roller bearing, the two rollers with crowning can be the same rollers. According to this configuration, the thrust roller bearing can be formed by one type of roller with crowning.

  The present invention has the following effects. (1) Since it is a resin molded cage by injection molding, a cage having a complicated shape can be easily formed. The double-row rollers have an effect of reducing differential slip, and an effect of forming crowning to reduce the effective length of the rollers to reduce differential slip. (2) In the above thrust roller bearing, the contact surface pressure is reduced by satisfying 1 ≦ L / Da ≦ 10, where the roller diameter Da ≦ 5 mm and the ratio L / Da of the roller length L to the diameter Da satisfies 1 ≦ L / Da ≦ 10. Differential slip can be reduced without becoming excessive. (3) Furthermore, the rollers are arranged as two rows of rollers that are stored in two pockets, and by making all of the two rows of rollers with crowning rollers, the contact surface pressure increases but the differential slip is reduced. In addition, it is possible to greatly suppress the damage of the surface starting type. As a result, the durability can be improved and the life can be extended. (4) In the above-mentioned thrust roller bearing, by making the two rollers with crowning the same roller, a thrust roller bearing can be formed by one kind of roller with crowning.

  Hereinafter, embodiments of the present invention will be described. In the following description, unless otherwise specified, the cage is a resin molded cage by injection molding. FIG. 4A is a diagram showing a shape of the roller 2a in which crowning is formed. A crowning having a length a is formed at both ends of the roller 2a having a roller length L. By forming the crowning on the rollers, it is possible to reduce the load on the edge portion (reduce the edge stress) and reduce the effective length of the roller (the straight portion b), thereby reducing the differential slip.

  FIG. 4B shows a configuration in which both end faces of the rollers are spherical. With this configuration, the edge stress due to the contact with the inner end surface of the pocket in the pocket surface of the cage is reduced, and the interference between the end surfaces of the rollers and the interference between the roller end surface and the cage pocket portion are reduced. Skew can be reduced. Further, the friction torque generated due to the skew of the rollers can be reduced. Usually, ± 50% of the roller diameter Da is adopted as the spherical shape.

  FIG. 4C shows a configuration that does not employ a crowning shape, that is, a straight roller, unlike the configuration of FIG. 4A. When the crowning shape is not adopted, the length of the straight portion of the roller can be increased, and the contact surface pressure can be reduced particularly under the condition that the inclination of the rolling surface does not occur. In the present invention, the straight rollers are used in at least one row on the outer diameter side of the innermost roller row of the rollers arranged in multiple rows. The materials for these rollers are usually bearing steel having a surface hardness of HRC 60 to 65.

  FIG. 1A shows an embodiment according to the first embodiment of the present invention, in which each pocket of a cage having one row of pockets is provided with two rows of rollers 2a having crownings formed at both ends in the radial direction. This is a thrust roller bearing in which a crowning is accommodated. FIG. 1 (b) shows a form according to a second embodiment of the present invention, wherein the cage has two rows of pockets, and a thrust roller bearing holding one roller having a crowning formed in each pocket. It is. FIG. 1 (c) shows an embodiment according to the seventh aspect of the present invention, wherein the number of at least one row of rollers located on the outer diameter side is more than the number of rows located on the outer diameter side of the innermost row of rollers. This figure shows thrust roller bearings having the same number or more, and it is possible to make the load capacity of the roller row located in the outer diameter direction larger than that of the inner row.

  A life test was performed using the thrust roller bearing having the configuration of the invention described above. That is, by the above means, the reduction of differential slip at the roller end face and the reduction of stress concentration near the roller end reduce friction loss and wear inside the bearing, and can improve the peeling life of the rolling part edge. The effect was verified by a life test.

  For the life test, a roller diameter: φ3 mm, bearing ring inner diameter: φ65 mm, bearing ring outer diameter: φ85 mm bearing was used, test temperature: 60 to 80 ° C., load: 1000 kgf, rotation speed: 5000 rpm, lubricating oil: spindle oil VG2 (Oil film parameter, lambda: 0.101). The test results are shown in Table 1 together with Comparative Examples (using a standard roller and a thrust needle roller bearing using a standard cage). The life was expressed as 10% life of 10 test bearings. The roller length was 7.8 mm for one row and 3.8 mm × 2 for two rows, and the crowning amount (drop amount) was 5 to 15 μm. In the life determination, the point in time at which any member of the bearing peeled was defined as the life.

  From the results in Table 1, assuming that the life of sample 1 (standard bearing), which is the first comparative example, is 1, the number of crowning rollers (single-row rollers) of sample 2, which is a two-row roller specification, is 2.5 times that of sample 1. Certain sample 3 has a life of 4.9 times that of sample 1, whereas sample 4 of the first embodiment, in which crowning is formed in two rows, has a life of 7.5 times that of sample 1. As a result, the life was significantly improved as compared with Samples 1 and 2. Moreover, no peeling occurred at the time after the test. In addition, the current consumption of the motor during the test was 3.9 A, which was the lowest in Sample 4, as compared with the other samples, indicating that the torque of the bearing was low, and that the friction loss inside the bearing was reduced. I understand.

  According to the above results, thrust roller bearings with two or more rows of return rollers and crowning formed on the rollers have reduced friction loss and wear, and improved the surface-starting type separation life generated at the rolling trace edge, It is clear that there is an effect of preventing separation occurring at the roller outer diameter.

  Next, Table 2 shows test results obtained by using rollers in which two rows of crownings were formed and by changing the effective length and the end face shape of the rollers. By providing two or more rows of pockets in the radial direction of the retainer (second embodiment, sample 5), interference between the rollers is prevented, roller retainability by the retainer is improved, and roller skew is reduced. As a result, the friction loss and wear are reduced, and the peel life is improved (the life ratio of 10% life is 1.5).

  When two or more return rollers have a crowning shape on the inner diameter side row and a crowning shape on the outer diameter side row smaller than the inner diameter side row (third embodiment, sample 6), and only the outer diameter side row has straight rollers. In the case of the fourth embodiment (sample 7), by suppressing the contact surface pressure of the rollers of the outer diameter side row rather than the inner diameter side row, it is possible to prevent the roller outer diameter peeling and the raceway outer diameter side peeling. It is clear from the test results that the life is improved.

  The roller length of the inner diameter side row was shortened, and the roller length of the outer diameter side row was longer than that of the inner diameter side row (fifth embodiment, sample 8, in this case, with respect to the two row rollers of the other embodiments). In this case, the rollers in the inner diameter side row are shorter and the rollers in the outer diameter side row are longer.) In addition to preventing the peeling off, the differential slip of the rollers in the inner diameter side row was reduced, and the life was improved (the life ratio of 10% life was 1.7). Also, from these results, it is possible to increase the load capacity on the outer diameter side by setting the number of rollers (number of pockets) in the circumferential direction of the outer diameter side row to be equal to or greater than the number of rollers in the inner diameter side row. However, it is clear that a similar effect is obtained (FIG. 1 (c)).

  Further, by making the roller end faces spherical (the sixth and seventh embodiments, samples 9 and 10), interference between the end faces of the rollers and interference between the roller end faces and the cage pockets are reduced, and the life is improved (10). The life ratio of the% life to 1.3, 1.6) was remarkable. In addition, since the motor current consumption is lower than those of the samples 4 and 5, it is clear that there is an effect of reducing friction such as skew of the rollers and reducing the torque of the bearing. In each of Examples 1 to 7 (Samples 4 to 10), the current consumption of the motor tends to be lower than that of the comparative example, and the friction loss inside the bearing is small and the torque of the bearing is low. Is shown.

  FIG. 2 shows an embodiment relating to the shape of the cage according to the present invention. FIG. 2 is a view showing a first embodiment of the present invention in which a resin molding retainer by injection molding used in the present invention is used and needle rollers are used as rollers. In this embodiment, the cage 3 can be formed in a complicated pocket shape by injection molding. As shown in FIG. 2B, two pockets (two rows) are held in each pocket, and a projection is provided at a central portion to prevent the rollers from falling. As shown in FIG. 2C, the cage 3 can hold the rollers 2 by the protrusions. Since the resin molding retainer can perform complicated molding efficiently and at low cost, for example, by forming a complicated shape, lubricating oil can be easily supplied to the roller edge portion and the like. At this time, as shown in the above figure, when all the rollers in the two rows are crowned rollers, the effect of the complicated shape provided on the resin molding retainer can be easily enhanced.

  FIG. 3 is a view showing a form of the reference example, in which a box-shaped iron plate press retainer formed by press molding or the like is used as a retainer, and needle rollers are used as rollers. In this embodiment, the cage can be produced at low cost by press molding. As shown in FIG. 3 (c), two members 3a and 3b press-formed from an iron plate are assembled into a box shape such that two rollers 2 are sandwiched in one pocket. Can be Since the width of the pocket is smaller than the diameter of the roller, the cage 3 can hold the roller 2.

  When the dimensions of the rollers used in the needle roller bearing in the examples of FIGS. 2 and 3 are a roller diameter Da and a roller length L, the dimensions are defined as Da ≦ 5 mm and 1 ≦ L / Da ≦ 10. Is preferred. That is, when L / Da <1, the roller length is reduced, the effective length of the roller is also reduced, and the contact area of the roller is reduced, so that the contact surface pressure increases. In this case, there is a problem that a contact surface pressure on the contact surface is increased, an oil film formation state is deteriorated, and a problem such as peeling is generated on the outer diameter side of the roller. On the other hand, when 10 <L / Da, as the roller length increases, the effective length of the roller also increases, and the differential slip between the roller and the raceway surface increases. At the edge portion of the roller, edge stress is likely to be generated between the roller and the bearing ring, and there is a problem that surface-starting type separation occurs at the edge of the rolling portion of the bearing ring.

(A) is a top view of the upper half of the thrust roller bearing holding two rows of rollers in one pocket of the cage according to the first embodiment of the present invention, and (b) is the second embodiment of the present invention. It is a top view of the upper half of the thrust roller bearing which has one roller in each of two rows of pockets of a cage concerning an example, and (c) is a cage concerning a 7th invention of the present invention. FIG. 10 is a plan view of an upper half of a thrust roller bearing in which one roller is held in each of the two rows of pockets and the number of rollers on the outer diameter side is larger than that on the inner diameter side. (A) is a plan view of a thrust needle roller bearing using a resin-molded retainer as a retainer according to the first embodiment of the present invention, and (b) is an enlarged view of a portion A in (a). (C) is a cross-sectional view taken along the line BB in FIG. (A) is a plan view of a thrust needle roller bearing using a box-shaped iron plate press retainer as a retainer according to a reference example, and (b) is a cross-sectional view taken along the line CC in (a) of FIG. (C) is an enlarged view of the pocket portion in FIG. (B). (A) is explanatory drawing of the time when the crowning which concerns on this invention was formed, (b) is the time which formed the crowning which concerns on the 6th and 7th Example of this invention, and has a spherical surface at an end surface. It is an explanatory view of a roller at which a portion is formed, and (c) is an explanatory view of a roller at which only a straight portion is formed according to a fourth embodiment of the present invention. It is a longitudinal section showing the compressor of a double swash plate type for air conditioners. It is a longitudinal section showing a single swash plate type compressor for air conditioners. It is a longitudinal section showing the variable capacity single swash plate type compressor for air conditioners. (A) is a longitudinal sectional view showing a thrust roller bearing according to a conventional embodiment, and (b) is a plan view of the upper half of a roller 2 and a retainer 3 in (a).

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 Thrust roller bearing, 2 rollers, 2a Crown formed, 2b Crown formed, spherical roller formed on end face, 2c Roller formed only straight part, 3 cage, 3a upper part of cage , 3b Cage lower part, 4 outer ring, 5 inner ring, 6 outer ring raceway surface, 7 inner ring raceway surface, 8 input rotary shaft, 9 double-sided inclined plate, 10 piston, 11 input rotary shaft, 12 single-sided inclined plate, 13 rod, 14 Piston, 15 input rotating shaft, 16 swash plate, 17 rod, 18 piston, 19 needle roller bearing with cage, 20 thrust needle roller bearing, 21 shell needle roller bearing, 22 thrust needle roller bearing, 23 holding Needle roller bearings, 24 thrust needle roller bearings, 25 crowning.

Claims (4)

In a thrust roller bearing including a roller and a cage for holding the roller,
The retainer is a resin molded retainer manufactured by injection molding,
A thrust roller bearing, wherein at least two or more rollers are held in each pocket of the cage, and a crowning is formed on the at least one roller.   2. The thrust according to claim 1, wherein the diameter Da of the roller is Da≤5 mm, and a ratio L / Da of the length L of the roller to the diameter Da satisfies 1≤L / Da≤10. Roller bearing.   The thrust roller bearing according to claim 1, wherein the rollers are arranged as two rows of rollers accommodated in the pocket, and all of the two rows of rollers are crowned rollers.   The thrust roller bearing according to claim 3, wherein the two rollers with crowning are the same rollers.

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