Ball bearing

Abstract

To provide a ball bearing which can optimize the diameters of a plurality of balls with different sizes as a roller and which can contribute to reduction in rotation torque and increase in acceptable load.SOLUTION: A representative configuration of a ball bearing 100 includes: an outer ring 110; an inner ring 120; and a plurality of balls that roll between the outer ring and the inner ring. As the balls, balls with different diameters are regularly aligned. When a parameter γ representing an internal configuration of the bearing is indicated by the following formula: γ=(Da / PCD)*cosα (where Da is the diameter of the ball, PCD is a pitch circle diameter, and α is a contact angle), a maximum ball diameter difference ΔDa between a ball with the largest diameter (largest-diameter ball 132) and a ball with the smallest diameter (smallest-diameter ball 134) is within a range of (7.52×10-4γ+8.91×10-4)*Da≤ΔDa≤(6.43×10-3γ+7.62×10-3)*Da when γ≤0.09, and (-9.65×10-4γ+1.05×10-3)*Da≤ΔDa≤(-8.25×10-3γ+8.98×10-3)*Da when γ>0.09.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a ball bearing including an outer ring, an inner ring, and a plurality of balls that roll between the outer ring and the inner ring. [Background technology]

[0002] Conventionally, bearings for supporting shafts have been used in vehicles. For example, Patent Document 1 discloses a bearing comprising: "an outer ring having a raceway surface; an inner ring having a raceway surface; first rolling elements having a first diameter and disposed between the raceway surface of the outer ring and the raceway surface of the inner ring; second rolling elements having a second diameter smaller than the first diameter and disposed between the raceway surface of the outer ring and the raceway surface of the inner ring; and a cage for holding the first rolling elements and the second rolling elements, wherein when a load equal to or less than a first load is applied, the upper The document discloses a rolling bearing characterized in that the first rolling element contacts both the raceway surface of the outer ring and the raceway surface of the inner ring, while the second rolling element is spaced apart from both the raceway surface of the outer ring and the raceway surface of the inner ring, and both the first rolling element and the second rolling element contact both the raceway surface of the outer ring and the raceway surface of the inner ring when a load equal to or greater than a second load that is greater than the first load is applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-300133 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 states, "According to the present invention, when a load equal to or less than a first load is applied, the first rolling element contacts both the raceway surface of the outer ring and the raceway surface of the inner ring, while the second rolling element does not contact both the raceway surface of the outer ring and the raceway surface of the inner ring. Therefore, when a load equal to or less than a first load is applied, the number of rolling elements contacting the raceway surfaces of the inner and outer rings can be reduced by the number of second rolling elements. Therefore, when a load equal to or less than a first load is applied, the number of rolling elements, which are the source of generation of dynamic friction with the raceway surfaces of the inner and outer rings, is reduced, and therefore, in this state, the rotational torque can be significantly reduced."

[0005] However, Patent Document 1 only mentions that the diameter of the first ball is set larger than that of the second ball, and therefore does not consider at all the diameters of the two different sized balls, which leaves room for further improvement in this regard.

[0006] In view of these problems, the present invention aims to provide a ball bearing that can optimize the diameters of multiple balls of different sizes that serve as rolling elements, thereby contributing to reducing rotational torque and increasing allowable load. [Means for solving the problem]

[0007] In order to solve the above problems, a typical configuration of a ball bearing according to the present invention is a ball bearing comprising an outer ring, an inner ring, and a plurality of balls that roll between the outer ring and the inner ring, in which the balls have different diameters and are arranged regularly, and when the parameter γ that represents the internal structure of the bearing is expressed by the following formula, γ = (Da / PCD) cos α (where Da is the diameter of the balls, PCD is the pitch circle diameter, and α is the contact angle), the maximum diameter ball and the minimum diameter ball are The maximum ball diameter difference ΔDa for small diameter balls is characterized by the range (7.52×10-4γ+8.91×10-4)·Da≦ΔDa≦(6.43×10-3γ+7.62×10-3)·Da when γ≦0.09, and (-9.65×10-4γ+1.05×10-3)·Da≦ΔDa≦(-8.25×10-3γ+8.98×10-3)·Da when γ>0.09. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a ball bearing that can optimize the diameters of multiple balls of different sizes that serve as rolling elements, thereby contributing to reducing rotational torque and increasing allowable load. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating a first example of a ball bearing according to the present embodiment. [Figure 2] The setting of the diameter difference ΔDa between the maximum diameter ball and the minimum diameter ball will be described. [Figure 3] 4A and 4B are diagrams illustrating a second example of the ball bearing according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and, unless otherwise specified, do not limit the present invention. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0011] Figure 1 is a diagram illustrating a first example of a ball bearing according to the present embodiment. As shown in Figure 1(a), ball bearing 100 of the first example includes outer ring 110, inner ring 120, and multiple balls that roll between them. The multiple balls are made up of large diameter balls 132 and small diameter balls 134, which are balls of different diameters. Because ball bearing 100 of the first example uses balls of two different diameters, large diameter balls 132 are the "largest diameter balls" and small diameter balls 134 are the "smallest diameter balls."

[0012] In Figure 1(a), the balls are regularly arranged between the outer ring 110 and the inner ring 120, repeating "large diameter balls 132, small diameter balls 134, small diameter balls 134." However, this arrangement is merely an example and is not limited to this. The arrangement can be modified as appropriate, such as arranging one large diameter ball 132 and one small diameter ball 134 alternately, or arranging multiple large diameter balls 132 and multiple small diameter balls 134 alternately.

[0013] 1(b) is a diagram illustrating the relationship between the load and the number of balls in contact with the outer ring 110 or the inner ring 120. As shown in FIG. 1(b), in the ball bearing 100 of the first embodiment, when the load is light, only the large diameter balls 132 are in contact with the outer ring 110 or the inner ring 120. In other words, only the large diameter balls 132 bear the load. When the load increases, in addition to the large diameter balls 132, the small diameter balls 134 also come into contact with the outer ring 110 or the inner ring 120, and the load is borne by all the balls included in the load zone.

[0014] With the above configuration, only the large diameter balls 132 roll under low loads, and the small diameter balls 134 also begin to roll before the static rated load is reached. Because only the large diameter balls 132 roll under low loads, friction is low, and noise, heat generation, and rotational torque can be reduced. Furthermore, because the small diameter balls 134 also roll under high loads, the allowable load can be increased. For example, while ensuring a sufficient allowable load during acceleration, when a large torque is applied, rotational noise and rotational torque can be dramatically reduced during idling and cruising.

[0015] Figure 2 explains how to set the diameter difference ΔDa between the largest and smallest diameter balls. Figure 2(a) is a graph showing the upper limit of the diameter difference ΔDa. Figure 2(b) is a graph showing the lower limit of the diameter difference ΔDa. For the verification, we used a large number of model numbers of "single ball diameter" bearings (i.e., conventional bearings) with different ball diameters and numbers of balls.

[0016] In FIG. 2(a) and FIG. 2(b), the parameters are as follows: Da: diameter of the large ball ΔDa: Difference in diameter between the largest and smallest balls PCD: Pitch circle diameter α: Contact angle γ: Parameter that represents the internal structure of the ball bearing γ is expressed as in Equation 1. γ=(Da / PCD)·cosα …Equation 1

[0017] The upper limit value / Da of the ball diameter difference ΔDa and the lower limit value / Da of the ball diameter difference ΔDa, which are the vertical axes in Figure 2(a) and Figure 2(b), are both dimensionless elastic displacement amounts.

[0018] The graph of upper limit values ​​shown in Figure 2(a) determines the conditions under which the smallest diameter ball also bears the load when subjected to the maximum load (static load rating Cor). Therefore, the amount of elastic displacement when the bearing is subjected to static load rating Cor (when the ball surface pressure is 4.2 GPa) is calculated, and this is used as the upper limit value for the ball diameter difference ΔDa. The ball diameter difference ΔDa is then divided by the ball diameter Da to make it dimensionless, and the result is displayed on the vertical axis of the graph.

[0019] The graph of the lower limit shown in Figure 2(b) determines the condition under which the smallest diameter ball will also bear the load when subjected to the minimum load (Cor x 0.04). Cor x 0.04 is the minimum load required for rolling, and the elastic displacement of the ball when that load is applied is calculated and used as the lower limit of the ball diameter difference ΔDa. The ball diameter difference ΔDa is then divided by the ball diameter Da to make it dimensionless, which is then displayed on the vertical axis of the graph.

[0020] As shown in Figures 2(a) and 2(b), the approximate line of the plot of the elastic displacement slopes upward until γ = 0.09, and then slopes downward when γ exceeds 0.09. Therefore, the upper and lower limits of the ball diameter difference ΔDa are calculated using γ = 0.09 as the boundary.

[0021] In FIG. 2(a), the approximate line when γ≦0.09 is expressed as Equation 2. y=(6.43×10-3γ+7.62×10-3)·Da…Formula 2 In FIG. 2(b), the approximate line when γ≦0.09 is expressed as Equation 3. y=(7.52×10-4γ+8.91×10-4)·Da…Formula 3 From these facts, when γ≦0.09, the “maximum ball diameter difference ΔDa between the maximum diameter ball and the minimum diameter ball” falls within the following range. (7.52×10-4γ+8.91×10-4)·Da≦ΔDa≦(6.43×10-3γ+7.62×10-3)·Da

[0022] In FIG. 2(a), the approximate line when γ>0.09 is expressed as Equation 4. y=(-8.25×10-3γ+8.98×10-3)·Da…Formula 4 In FIG. 2(b), the approximate line when γ>0.09 is expressed as Equation 5. y=(-9.65×10-4γ+1.05×10-3)·Da…Formula 5 From these facts, when γ>0.09, the "maximum ball diameter difference ΔDa between the maximum diameter ball and the minimum diameter ball" falls within the following range. (-9.65×10-4γ+1.05×10-3)·Da≦ΔDa≦(-8.25×10-3γ+8.98×10-3)·Da

[0023] As explained above, in this embodiment, it is possible to appropriately set "ΔDa, the time period during which only the large-diameter balls 132 roll under low loads and the small-diameter balls 134 also begin to support the load before the maximum load (static load rating Cor) is received." In other words, it is possible to optimize the diameters of the multiple balls of different sizes that serve as rolling elements. This contributes to the aforementioned effects, such as reducing rotational torque and increasing allowable load.

[0024] The extent to which the ball diameter difference ΔDa should be within the above range, i.e., the extent to which the small diameter balls 134 must also come into contact when subjected to a load, can be set appropriately based on the load range required for the bearing.

[0025] 3 is a diagram illustrating a second example of the ball bearing according to the present embodiment. In the ball bearing 100a of the second example, components common to the ball bearing 100 of the first example are given the same reference numerals and will not be described.

[0026] 3(a), the ball bearing 100a of the second embodiment includes large diameter balls 132 and small diameter balls 134, which are balls with different diameters, as well as medium diameter balls 136. Medium diameter balls 136 have a smaller diameter than large diameter balls 132 and a larger diameter than small diameter balls 134.

[0027] In Figure 3(a), the balls are regularly arranged between the outer ring 110 and the inner ring 120, repeating the sequence of "large diameter balls 132, small diameter balls 134, medium diameter balls 136, small diameter balls 134, large diameter balls 132." However, this arrangement is merely an example and is not limited to this. The arrangement and number of the large diameter balls 132, small diameter balls 134, and medium diameter balls 136 can be changed as appropriate.

[0028] FIG. 3(b) is a diagram illustrating the relationship between the load and the number of balls in contact with the outer ring 110 or the inner ring 120. As shown in FIG. 3(b), in the ball bearing 100a of the second embodiment, only the large-diameter balls 132 bear the load while the load is light. As the load increases, the medium-diameter balls 136 also bear the load in addition to the large-diameter balls 132. As the load increases further, the small-diameter balls 134 also bear the load in addition to the large-diameter balls 132 and medium-diameter balls 136. Therefore, it can be seen that the same effect as the ball bearing 100 of the first embodiment can be obtained even if the number of balls with different diameters is increased.

[0029] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Industrial Applicability]

[0030] The present invention can be used as a ball bearing including an outer ring, an inner ring, and a plurality of balls that roll between the outer ring and the inner ring. [Explanation of symbols]

[0031] 100...ball bearing, 100a...ball bearing, 110...outer ring, 120...inner ring, 132...large diameter ball, 134...small diameter ball, 136...medium diameter ball,

Claims

[Claim 1] A ball bearing comprising an outer ring, an inner ring, and a plurality of balls rolling between the outer ring and the inner ring, The balls are arranged in a regular pattern with different diameters, When the parameter γ representing the internal structure of the bearing is expressed by the following equation, γ=(Da / PCD)・cosα (where Da is the diameter of the ball, PCD is the pitch circle diameter, and α is the contact angle). The maximum difference in ball diameter ΔDa between the largest diameter ball and the smallest diameter ball is When γ≦0.09, (7.52×10-4γ+8.91×10-4)・Da≦ΔDa≦(6.43×10-3γ+7.62×10-3)・Da, When γ>0.09, (-9.65×10-4γ+1.05×10-3)・Da≦ΔDa≦(-8.25×10-3γ+8.98×10-3)・Da, A ball bearing characterized in that the range is

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