needle roller bearings

Abstract

To provide a needle roller bearing capable of achieving a roller filling rate equal to that of a whole roller type needle roller bearing without causing the separation of needle rollers to pieces during assembly.SOLUTION: A needle roller bearing includes a plurality of needle rollers 2, and a holding tool 3 for preventing the falling of the needle rollers 2, the holding tool 3 having a pair of rim parts arranged on both axial sides, and a plurality of pillar parts 3b for connecting both radial outsides of the pair of rim parts to each other at a predetermined space in the peripheral direction, the pair of rim parts and the pillar parts 3b forming pockets to hold the needle rollers 2. The inner diameter face of the pillar part 3b is located on the outer diameter side further than the pitch circle diameter of the needle roller 2. An inter roller space rs between the needle rollers 2 on the pitch circle diameter of the needle roller 2 is smaller than a pocket space cs at a contact position between the pillar part 3b and the needle roller 2, and a surface roughness Ra of the outside face of the rim part is set to be 0.4 μm or lower.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to a needle roller bearing equipped with a needle roller holding jig, which prevents the needle rollers from coming apart during assembly as in a needle roller bearing with a cage, and which can achieve a roller filling rate equivalent to that of a full-complement needle roller bearing without a cage. [Background technology]

[0002] In order to increase the load capacity of needle roller bearings, it is necessary to increase the roller packing ratio.

[0003] However, in the case of conventional needle roller and cage bearings, the column portion of the cage is a constraint, so there is a natural limit to how much the roller packing rate can be increased.

[0004] On the other hand, in the case of a full complement needle roller bearing without a cage, although it is possible to increase the roller packing ratio, the needle rollers tend to come apart during assembly, which poses a problem in terms of ease of assembly.

[0005] Incidentally, Patent Document 1 discloses that in a needle roller bearing with a cage, the column portion of the cage is positioned on the outer diameter side of the pitch circle diameter (PCD) of the needle rollers, thereby reducing the column width of the column portion of the cage and increasing the roller filling rate.

[0006] However, needle roller bearings with cages generate thrust forces induced by roller skew, causing the outer surface of the cage to interfere with other components. In particular, when used in double rows to achieve high load capacity, the cages interfere with each other in the axial direction, requiring column strength.

[0007] Therefore, if the column width of the column portion of the cage is reduced to increase the roller packing ratio, as in Patent Document 1, there is a possibility that the column strength will be sacrificed.

[0008] Furthermore, in the needle roller bearing with cage disclosed in Patent Document 2, a restricting member such as a thrust washer is provided between the outer surface of the cage and other components to prevent a decrease in column strength and deformation of the cage.

[0009] However, when increasing the roller packing ratio or using needle roller bearings in double rows to increase the load capacity, if a restricting member such as a flange or thrust washer is provided on the outer surface of the cage to prevent wear and heat generation in the cage due to interference between the needle roller bearings, the restricting member will be extended in the axial direction by the thickness of the restricting member, which creates the problem of increasing the space in the axial direction.

[0010] Furthermore, Patent Document 3 discloses a full complement bearing in which a separator with self-lubricating properties is arranged, but the separator cannot hold the rollers, which causes problems with assembly. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 6613576 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-012699 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-219084 Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, this invention aims to provide a needle roller bearing equipped with a needle roller holding jig that prevents the needle rollers from coming apart during assembly, as is the case with needle roller bearings with cages, and that can achieve a roller filling rate equivalent to that of full-complement needle roller bearings that do not have cages. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the present invention provides a needle roller bearing comprising a plurality of needle rollers and a retaining jig to prevent the needle rollers from falling out, the retaining jig having a pair of rim portions arranged on both axial sides and a plurality of pillar portions connecting the radially outer diameter portions of the pair of rim portions at a predetermined interval in the circumferential direction, and the pair of rim portions and the plurality of pillar portions form pockets to hold the needle rollers, wherein the inner diameter surfaces of the pillar portions are located on the outer diameter side of the pitch circle diameter of the needle rollers, and the roller gap rs between the needle rollers on the pitch circle diameter of the needle rollers is narrower than the pocket gap cs formed between the pillar portions and the needle rollers at the contact positions between the pillar portions and the needle rollers.

[0014] In this way, in this invention, the inner diameter surface of the column portion is positioned on the outer diameter side of the pitch circle diameter of the needle roller, and the roller gap rs between the needle rollers on the pitch circle diameter of the needle roller is narrower than the pocket gap cs formed between the column portion and the needle roller at the contact point between the column portion and the needle roller.Therefore, even if the needle roller skews during operation, adjacent needle rollers will come into contact with each other before the needle rollers and the column portion come into contact.

[0015] Therefore, in the needle roller bearing of the present invention, the roller packing ratio can be increased, making it possible to achieve a high load capacity.

[0016] However, as the load capacity of bearings increases, the induced thrust load generated by roller skew also increases, which means that the outer surface of the rim of the holding jig comes into strong contact with other parts, and this is expected to cause wear and heat on the outer surface of the rim.

[0017] For this reason, while the surface roughness Ra (arithmetic mean roughness) of a generally well-machined surface is 6.3 μm, in this invention, the surface roughness Ra of the outer surface of the rim is set to 1.6 μm or less in order to avoid wear and heat generation on the outer surface of the rim.

[0018] Furthermore, when using the needle roller bearings of the present invention in multiple rows, the outer side surfaces of the rim portions interfere with each other, and an induced thrust load corresponding to the number of bearing rows acts on the outer side surfaces of the rim portions. As a result, the possibility of wear and heat generation on the outer side surfaces of the rim portions further increases.

[0019] Therefore, when using the needle roller bearings of the present invention in multiple rows, in order to further improve reliability, it is necessary to set the surface roughness Ra of the outer side surface of the rim portion to 0.4 μm or less.

[0020] In the present invention, the surface roughness Ra refers to the arithmetic mean roughness defined in JIS B 0601:1990.

[0021] Next, in the needle roller bearing of the present invention, if the rim portion of the holding jig is inclined such that the inner diameter end extends outward in the axial direction, the induced thrust generated by the roller skew is received by the rim portion of the holding jig, and the load point position moves radially inward. When the load point position moves radially inward, the moment load applied to the column portion increases, so the possibility of strength reduction of the holding jig increases.

[0022] Therefore, in the present invention, the angle of the rim portion with respect to the outer diameter surface of the holding member should be set to 90° or less so that the rim portion of the holding jig does not extend outward in the axial direction, and the moment load applied to the column portion should be reduced. On the other hand, if the rim portion of the holding jig tilts too much toward the needle roller side, that is, inward in the axial direction, the needle roller and the rim portion interfere with each other, so it is also necessary to set the lower limit value of the tilting angle inward in the axial direction.

[0023] The lower limit value of the tilting angle of this rim portion inward in the axial direction can be defined by the following formula 1. W1 < Tsinθ + Lcosθ ··· Formula 1

[0024] In Formula 1, W1 is the length from the pocket to the outer side surface of the rim portion, T is the plate thickness of the rim portion, L is the length from the inner diameter end of the rim portion to the inner diameter surface of the column portion, and θ is the angle of the rim portion with respect to the outer diameter surface of the holding jig.

[0025] Therefore, in this invention, the rim portion of the holding jig needs to satisfy the following Equation 2. θ ≤ 90° and W1 < Tsinθ + Lcosθ ··· Equation 2

[0026] In addition, in this invention, the induced thrust generated by the roller skew is received by the rim portion, and since the width surface of the rim portion contacts other members, if the length of the rim portion is not sufficiently ensured, the possibility of strength reduction of the holding jig increases. Therefore, in order to improve the strength of the holding jig, the relationship between the length L of the rim portion, the roller Diameter D a needs to satisfy the following equation. 0.78 ≤ (Lsinθ + W2) / Da < 1 Here, W2 is the length from the outer diameter surface of the holding jig to the outer diameter end of the rim portion.

Advantages of the Invention

[0027] As described above, the needle roller bearing according to this invention positions the inner diameter surface of the column portion on the outer diameter side of the pitch circle diameter of the needle rollers, and makes the roller clearance rs between the needle rollers on the pitch circle diameter of the needle rollers narrower than the pocket clearance cs formed between the column portion and the needle rollers at the contact position between the column portion and the needle rollers. Therefore, even if the needle rollers skew during operation, adjacent needle rollers contact each other before the needle rollers and the column portion contact each other.

[0028] For this reason, the load on the column portion is small, the width of the column portion can be made thinner, and the needle rollers can be arranged in a total roller state on the pitch circle diameter. For example, it is also possible to increase the roller filling rate to 80 - 100% or less, preferably 93 - 100% or less.

[0029] In addition, in this invention, by setting the surface roughness Ra of the outer surface of the rim portion to 1.6 μm or less, the occurrence of wear and heat generation on the outer surface of the rim portion is avoided.

[0030] Furthermore, by setting the surface roughness Ra of the outer surface of the rim to 0.4 μm or less, the possibility of wear and heat generation on the outer surface of the rim can be avoided even if an induced thrust load equal to the number of bearing rows acts on the outer surface of the rim. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a perspective view of a needle roller bearing according to an embodiment of the present invention; [Figure 2] FIG. 2 is a side view of the needle roller bearing of FIG. 1. [Figure 3] 2 is a cross-sectional view of the needle roller bearing of FIG. 1 taken along a plane perpendicular to the axis. [Figure 4] 2 is an enlarged view showing the relationship between a post portion and needle rollers of the needle roller bearing according to the embodiment of the present invention. FIG. [Figure 5] 3 is a partially enlarged view showing the relationship between needle rollers and a rim portion of the needle roller bearing according to the embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0033] As shown in Figures 1 to 3, the needle roller bearing 1 of the present invention comprises a plurality of needle rollers 2 and a retaining jig 3 for preventing the needle rollers 2 from falling off, and a resin sleeve 4 is fitted onto the inner diameter side of the circumferentially arranged needle rollers 2 to prevent the needle rollers 2 from coming apart during assembly.

[0034] The holding jig 3 has a pair of rim portions 3a arranged on both axial sides, and a plurality of pillar portions 3b connecting the radially outer portions of the pair of rim portions 3a at predetermined intervals in the circumferential direction, and the pair of rim portions 3a and the plurality of pillar portions 3b form a plurality of pockets that hold the needle rollers 2.

[0035] The inner diameter surface of the column portion 3b is located on the outer diameter side of the pitch circle diameter (PCD) of the needle rollers 2 arranged in the circumferential direction.

[0036] In the present invention, as shown in FIG. 4, the roller gap rs formed between two needle rollers on the pitch circle diameter is set to be narrower than the pocket gap cs formed between the column portion 3b and the needle roller at the contact position between the column portion and the needle roller, that is, rs < cs.

[0037] The roller gap rs is the gap formed between adjacent needle rollers when the needle rollers 2 are evenly arranged on the pitch circle diameter, and can be obtained by dividing the value obtained by subtracting the total length of the diameters D of the needle rollers 2 from the circumferential length of the pitch circle diameter by the total number of the needle rollers 2.

[0038] The pocket gap cs is the distance from the contact point of the column portion 3b to the contact point of the needle roller at the contact position between the needle roller 2 and the column portion 3b, and can be obtained by taking half of the length obtained by subtracting the diameter of the needle roller 2 at the contact position between the needle roller 2 and the column portion 3b from the column distance at the contact position between the needle roller 2 and the column portion 3b in a state where the needle rollers 2 are evenly arranged on the pitch circle diameter.

[0039] As described above, when the roller gap rs is set to be narrower than the pocket gap cs, even if the needle roller 2 skews during operation, adjacent needle rollers 2 contact each other before the needle roller 2 and the column portion 3b contact, so that the load on the column portion 3b can be reduced. Therefore, it becomes possible to narrow the column width of the column portion 3b and arrange the needle rollers 2 to a total roller state on the pitch circle diameter. For example, it is also possible to increase the roller filling rate to 80 to 100% or less, preferably 93 to 100% or less.

[0040] Here, the roller filling rate is the ratio of the total sum of the diameters Da of the needle rollers 2 arranged on the pitch circle diameter to the circumferential length of the pitch circle diameter of the needle roller, and the roller filling rate becomes 100% in a state where the needle rollers 2 are arranged without gaps on the pitch circle diameter.

[0041] In the present invention, the inner diameter surface of the column portion 3b butSince the holding jig 3 is provided on the outer diameter side of the pitch circle diameter, the holding jig 3 acts as an outer diameter guide, and the strength and rigidity of the holding jig 3 can be maintained at a high level.

[0042] As shown in FIGS. 3 and 4, the column portion 3b has both side surfaces that are tapered from the inner diameter side toward the outer diameter side. In other words, the width of the column portion 3b on the outer diameter side is wider than the width of the column portion 3b on the inner diameter side, thereby increasing the cross-sectional area of ​​the column portion 3b and ensuring the strength of the column portion 3b.

[0043] The holding jig 3 is made of resin or steel plate. The side surfaces of the pillar portions 3b of the holding jig 3 may be tapered by milling, but from the viewpoint of cost, the tapered shape may be formed by pressing the surfaces in post-processing after pressing.

[0044] As described above, even when equipped with a retaining jig 3, the needle roller bearing 1 of the present invention is capable of increasing the roller filling rate to 80 to 100%, preferably 93 to 100%, making it suitable for applications requiring multiple rows of rollers or high-precision rotation.

[0045] In the needle roller bearing 1 of this invention, as the load capacity of the bearing increases, the induced thrust load generated by roller skew also increases, and it is therefore expected that the outer surface of the rim portion 3a of the holding jig 3 will come into strong contact with other components, causing wear and heat generation on the outer surface of the rim portion 3a.

[0046] For this reason, while the surface roughness Ra (arithmetic mean roughness) of a typical well-machined finished surface is 6.3 μm, in this invention, the surface roughness Ra of the outer surface of the rim portion 3a is set to 1.6 μm or less in order to avoid wear and heat generation on the outer surface of the rim portion 3a.

[0047] Furthermore, when the needle roller bearing of this invention is used in a double row configuration, the outer surfaces of the rim portions 3a interfere with each other, and an induced thrust load equal to the number of bearing rows acts on the outer surface of the rim portion 3a, further increasing the possibility of wear and heat generation on the outer surface of the rim portion 3a.

[0048] Therefore, when the needle roller bearing 1 of the present invention is used in multiple rows, in order to further improve reliability, it is necessary to set the surface roughness Ra of the outer surface of the rim portion 3a to 0.4 μm or less.

[0049] In the present invention, the surface roughness Ra refers to the arithmetic mean roughness defined in JIS B 0601:1990.

[0050] Next, in the needle roller bearing 1 of the present invention, when the rim portion 3a of the holding jig 3 is inclined such that the inner diameter end spreads outward in the axial direction, as shown in FIG. 5, the induced thrust generated by the roller skew is received by the rim portion 3a of the holding jig 3, and the load point position thereof moves radially inward. When the load point position moves radially inward, the moment load applied to the column portion 3b increases, so the possibility of strength reduction of the holding jig 3 increases.

[0051] Therefore, in the present invention, the angle of the rim portion 3a with respect to the outer diameter surface of the holding jig 3 is set to 90° or less so that the rim portion 3a of the holding jig 3 does not spread outward in the axial direction, and the moment load applied to the column portion 3b must be reduced. On the other hand, if the rim portion 3a of the holding jig 3 tilts too much toward the needle roller 2 side, that is, inward in the axial direction, the needle roller 2 and the rim portion 3a interfere with each other, so it is also necessary to set the lower limit value of the tilting angle inward in the axial direction.

[0052] The lower limit value of the tilting angle θ of the rim portion 3a inward in the axial direction can be defined by the following formula 1. W1 < Tsinθ + Lcosθ ··· Formula 1

[0053] In Formula 1, W1 is the length from the pocket to the outer surface of the rim portion 3a, T is the width of the rim portion 3a, L is the length from the inner diameter end of the rim portion 3a to the inner diameter surface of the column portion 3b, and θ is the angle of the rim portion 3a with respect to the outer diameter surface of the holding jig 3.

[0054] Therefore, in the present invention, the rim portion 3a of the holding jig 3 needs to satisfy the following formula 2. θ ≤ 90° and W1 < Tsinθ + Lcosθ ··· Formula 2

[0055] Furthermore, in this invention, the induced thrust generated by roller skew is received by the rim portion 3a, and the outer surface of the rim portion 3a comes into contact with other components, so if the length of the rim portion 3a is not sufficiently secured, there is a high possibility that the strength of the holding jig 3 will decrease.

[0056] For this reason, in an evaluation test in which the width surface of the holding jig 3 comes into strong contact with other components, the length L of the rim portion 3a of the holding jig 3 was varied to check the state of damage to the holding jig 3. The evaluation results of the state of damage to the holding jig 3 are shown in Table 1. W2 is the length from the outer diameter surface of the holding jig 3 to the outer diameter end of the rim portion 3a.

[0057] [Table 1]

[0058] When (Lsinθ+W2) / Da≦0.77, damage was observed in the rim portion 3a of the holding jig 3, but when (Lsinθ+W2) / Da≧0.78, no damage was observed in the rim portion 3a of the holding jig 3. Therefore, by setting the length L of the rim portion 3a of the holding jig 3 to a predetermined dimension, damage to the rim portion 3a of the holding member 3 can be suppressed.

[0059] Therefore, in order to improve the strength of the holding jig 3, the length L of the rim portion 3a and the rollers of the needle rollers 2 Diameter D The relationship with a needs to be specified as follows: (Lsinθ+W2) / Da≧0.78 Equation 3

[0060] Furthermore, in order to avoid a decrease in the strength of the holding jig 3 due to contact of the holding jig 3 with the shaft 4 and the housing 5 during operation, the following formula must be satisfied. (Lsinθ+W2) / Da<1 Equation 4

[0061] From formulas 3 and 4, in order to suppress a decrease in strength of the rim portion 3a of the holding jig 3, the following formula 5 must be satisfied. 0.78≦(Lsinθ+W2) / Da<1...Equation 5

[0062] The present invention is not limited to the above-described embodiments, and can of course be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0063] 1: Bearing 2: Needle roller 3: Holding jig 3a: Rim 3b: Pillar part 4: Resin sleeve cs: Pocket gap rs: Roller clearance

Claims

1. A needle roller bearing is provided which comprises a plurality of needle rollers and a retaining jig for preventing the needle rollers from falling off, the retaining jig having a pair of rim portions arranged on both axial sides and a plurality of column portions connecting radially outer portions of the pair of rim portions at predetermined intervals in the circumferential direction, and the pair of rim portions and the plurality of column portions form pockets for holding the needle rollers, the inner diameter surfaces of the column portions being located on the outer diameter side of the pitch circle diameter of the needle rollers, and the roller gaps rs between the needle rollers on the pitch circle diameter of the needle rollers are located on the outer diameter side of the column portions at the contact positions of the needle rollers, A needle roller bearing having a roller filling rate of 80 to 100%, wherein the surface roughness Ra of the outer surface of the rim portion is set to 1.6 μm or less and is narrower than the pocket gap cs formed between the needle rollers, and the length L of the rim portion of the holding jig and the roller diameter Da of the needle rollers satisfy the following relational expression: 0.78≦(Lsinθ+W 2 ) / Da<1 where W 2 is the length from the outer diameter surface of the holding jig to the outer diameter end of the rim portion, and θ is the angle of inclination of the rim portion inward in the axial direction.

2. 2. The needle roller bearing according to claim 1, wherein the surface roughness Ra of the outer surface of the rim portion is set to 0.4 μm or less.

Images