JP2003074545A - Designing method of ball bearing and ball bearing therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce bearing torque without decreasing supporting rigidity and a life caused by noises. SOLUTION: Dimensions for a ball diameter, a bearing outer diameter, and a bearing bore diameter are set so as to satisfy the following expression (1) when the ball diameter is set at DW, the bearing outer diameter is set at D, and the bearing bore diameter is set at d. 0.650<=DW/ (D-d)/2}<=0.750...(1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball bearing suitable as a bearing for a small motor used for a cooling fan, a motor for information equipment and the like.

[0002]

2. Description of the Related Art Normally, two deep groove ball bearings are used as a set for the above-mentioned ball bearings, and a pressing force is applied in the axial direction by a spring or a spacer to reduce vibration and maintain shaft rigidity. Preload is applied by Therefore, the balls and the raceways of the inner and outer races are in contact with each other at an angle.

In addition to the strength and rigidity of the bearing, the ball bearing for the above-mentioned applications has strict requirements for downsizing, high rotational accuracy, long acoustic life, low torque, and the like. On the other hand, in response to recent environmental problems, there has been a demand for energy saving of electric appliances, and for this reason, the demand for lower torque of bearings incorporated in electric appliances has become particularly severe. Bearing torque can be reduced by reducing the load acting on the bearing, especially by reducing the preload, by reducing the amount of lubricant (lubricating oil or grease) enclosed in the bearing, by the viscosity of the lubricating oil or by grease. The method of lowering the viscosity of the base oil and the method of using a soft grease can be mentioned.

[0004]

However, these methods have the following problems. If the preload is reduced by the above method, the supporting rigidity of the bearing may be reduced, abnormal vibration may occur, and the positioning accuracy may be reduced.
When the amount of the lubricant enclosed is reduced by the method described above, the lubrication state between the balls and the raceway surface is likely to be poor, and the acoustic life is likely to be shortened. If the viscosity of the lubricant is reduced by the method described in (1), the thickness of the oil film formed between the ball and the raceway surface becomes thin, and the lubrication state is likely to be poor, so that the acoustic life is likely to be shortened.

When a soft grease is used by the method described above, the grease tends to leak to the outside of the bearing unless the seal is of a contact type. If grease leaks, the lubrication state becomes poor, and the acoustic life tends to be shortened. When a contact type seal is used to prevent grease leakage while using soft grease, friction torque is generated by contact between the seal and the inner ring or the outer ring, and it is difficult to obtain the action of reducing the torque.

The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a method capable of reducing the torque of the bearing without lowering the supporting rigidity and the acoustic life. To do.

[0007]

In order to solve the above-mentioned problems, the present invention is as follows, where D _W is the diameter of the ball, D is the bearing outer diameter (diameter), and d is the bearing inner diameter (diameter). Provided is a ball bearing designing method characterized by setting these dimensions so as to satisfy the expression (1). 0.650 ≦ D _W /{(D−d)/2}≦0.750 (1) The present invention also defines the ball diameter as D _W , the bearing outer diameter as D, and the bearing inner diameter as d. And a ball bearing configured to satisfy the above formula (1).

As shown in FIG. 1, D _W / {(D-d) /
When 2} = 0.750, when the ball 1 is arranged at an intermediate position between the bearing inner diameter and the outer diameter, that is, when the diameter D _PW of the pitch circle P of the ball 1 is (D + d) / 2, the inner ring and The groove bottom thickness (thickness of the deepest portion) T of the outer raceway groove is 0.12.
It becomes 5 × {(D−d) / 2}. Where d = 4 mm
The 7 mm ball bearing is a bearing that is particularly required to reduce the torque, but if D _W /{(D−d)/2}=0.750, for example, when d = 4 mm and D = 7 mm In addition, the groove bottom thickness is very thin, T≈0.19 mm, and if it is further thinned, it becomes difficult to process the raceway groove. As a result, the machining accuracy of the raceway groove becomes insufficient, or it takes machining time to improve the machining accuracy, resulting in an increase in cost.

When the groove bottom becomes thin, the inner ring is used as an axis,
When fixing the outer ring to the housing by press fitting, the raceway groove is likely to be deformed into a shape according to the roundness of the shaft and housing, and when fixing by adhesion, the raceway groove is affected by the curing shrinkage of the adhesive. It becomes easy to receive. As a result, the rotation accuracy and acoustic characteristics of the bearing may deteriorate. From the above, in the present invention, D _W /{(D−d)/2}≦0.75
Set to 0. It is preferable to set D _PW = (D + d) / 2 so that the inner ring and the outer ring have the same groove bottom thickness so that only one of the groove bottom thicknesses does not become extremely thin, but the inner ring groove bottom thickness is extremely small. D _PW <(D + d) / 2 may be set within the range in which the thickness does not decrease. On the contrary, if D _PW > (D + d) / 2, the orbital radius of the ball becomes large and the torque of the bearing becomes high, which is not preferable.

On the other hand, when d = 4 mm to 7 mm and "D _W
/ {(D-d) / 2} "values are various values. From the results of the rotation test using a large number of ball bearing samples," D _W / {(D
“−D) / 2} ≧ 0.650”, then “D _W / {(D−
It was found that the torque was significantly smaller than in the case of d) / 2} <0.650 ”. This will be described in detail in the embodiment.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

[0012]

[Table 1]

First, regarding the deep groove ball bearings Nos. 1 to 11 shown in Table 1 above, the radial clearance: 16.5 μm, the radius of curvature of the raceway groove of the inner and outer rings: 0.56 × D _W (ball diameter), preload ( Axial load): In the case of 4.9 N, the maximum surface pressure acting between the raceway surface and the ball was determined. The result is calculated for each No. as D _W /{(D−d)/2}=0.750 and the number of balls Z is the minimum value, but the maximum surface pressure is “1”. This maximum surface pressure ratio is taken as the vertical axis, and "D _W / {(D-d)
/ 2} "values are plotted on the horizontal axis. FIG. 2 is a graph showing the relationship between the inner ring maximum surface pressure ratio and “D _W / {(D−d) / 2}”, and FIG. 3 is the outer ring maximum surface pressure ratio and “D _W /
It is a graph which shows the relationship with {(D-d) / 2}.

The deep groove ball bearings Nos. 1 to 11 in Table 1 are
The pitch circle diameter D _PW = (D + d) / 2, and the number of balls Z is a stress that elastically deforms the outer ring according to the ball diameter by a normal method (here, a preferable value is 1079 MPa or less).
I set it to the number that can be assembled. Next, shown in Table 1 above
For No. 1 to 11 deep groove ball bearings, radial clearance:
7.5 μm, radius of curvature of raceway groove of inner and outer rings: 0.56 × D
_W (ball diameter), preload (axial load): 4.9N, radial displacement is 0.1μ when a radial load is applied.
The radial stiffness (spring constant for radial displacement) at the position of m was determined. This result is D _W / for each No.
The ratio of {(D−d) / 2} = 0.750, where the number Z of balls is the minimum value, is defined as the radial rigidity is “1”, and this radial rigidity ratio is taken as the vertical axis, and “D _W / {(D-d) /
2} ”values are plotted on the horizontal axis. This graph is shown in FIG.

Next, the depths of Nos. 2, 4, 6, 8 and 9 in Table 1
For grooved ball bearings, actually manufacture the bearings and
Distance: 16.5 μm, radius of curvature of raceway groove of inner and outer rings: 0.5
6 x D _W(Ball diameter), preload (axial load): 4.9N
Then, rotate the inner ring for 5 minutes at a rotation speed of 1800 rpm.
After continuing rotation, the bearing dynamic torque at that time was measured. Na
Regarding the lubricant, the internal space volume of the bearing
Enclosed 10%.

This measurement result is D _W /
The ratio of {(D-d) / 2} = 0.750, where the number Z of balls is the minimum value, and the bearing dynamic torque is "1" is calculated, and this torque ratio is taken as the vertical axis, and "D _W / {(D-d) / 2} "
The values are summarized in a graph with the horizontal axis. This graph is shown in FIG. From the graphs of Figs. 2 and 3, the maximum surface pressure and "D _W /
{(D−d) / 2} ”has a substantially linear relationship with“ D
It can be seen that the smaller the _W / {(D-d) / 2} ", the larger the maximum surface pressure. From the graph of FIG. 4, “D _W /
It can be seen that the radial rigidity is hardly changed in the range of {(D-d) / 2} "of 0.400 to 0.750.
From the graph of FIG. 5, the bearing dynamic torque is “D _W / {(D−
The larger "d) / 2}" is, the smaller it is, and "D _W / {(D
-D) / 2} ≧ 0.650 ”, then“ D _W / {(D
It can be seen that the torque is significantly smaller than in the case of −d) / 2} <0.650 ”.

On the other hand, as described above, D _W / {(D-d)
/2}=0.750, for example, d = 4 mm, D
= 7 mm, the groove bottom thickness becomes very thin, T≈0.19 mm, and if it is thinner than this, it becomes difficult to process the raceway groove, and the rotational accuracy and acoustic characteristics of the bearing may deteriorate. From the above, 0.650 ≦ D _W / {(D−d)
It can be seen that by setting /2}≦0.750, the torque of the bearing can be reduced without lowering the support rigidity and the acoustic life.

From the values of the outer diameter D, the inner diameter d, and the ball diameter D _W of the ball bearing described in the known document, "D _W / {(D-
d) / 2} "was calculated, and as shown in Table 2 below," D _W / {(D-d) / 2} "was 0.400-0.
It was within the range of 635.

[0019]

[Table 2]

That is, according to the ball bearing obtained by the designing method of the present invention, the ball diameter can be made larger and the number of balls can be made smaller than that of the conventional ball bearing. can do.

[0021]

As described above, according to the designing method of the present invention, the torque of the bearing can be reduced without lowering the support rigidity and the acoustic life. Further, since the ball diameter can be increased and the number of balls can be reduced, the effect of shortening the assembly time of the bearing can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the present invention.

FIG. 2 is a diagram showing the results obtained in the embodiment,
The maximum wheel surface pressure ratio is taken as the vertical axis, and "D _W/ {(D-d) /
2} ”value is plotted on the horizontal axis.

FIG. 3 is a diagram showing the results obtained in the embodiment,
The maximum wheel surface pressure ratio is taken as the vertical axis, and "D _W/ {(D-d) /
2} ”value is plotted on the horizontal axis.

FIG. 4 is a diagram showing the results obtained in the embodiment,
The radial rigidity ratio is plotted on the vertical axis, and "D _W/ {(D-d) /
2} ”value is plotted on the horizontal axis.

FIG. 5 is a graph showing results obtained in the embodiment, in which the vertical axis represents the torque ratio and the horizontal axis represents the “D _W / {(D−d) / 2}” value.

[Explanation of symbols]

1 Ball D _W Ball diameter D Bearing outer diameter d Bearing inner diameter P Ball pitch circle T Groove bottom thickness of raceway groove

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiromitsu Muraki             1-5-50 Kumei, Kugenuma, Fujisawa-shi, Kanagawa             Within NSK Ltd. F term (reference) 3J101 AA02 AA62 FA01 FA15 FA31                       FA60 GA29 GA53

Claims (2)

[Claims] 1. A ball bearing characterized in that these dimensions are set so that the following formula (1) is satisfied, where D _{W is} the diameter of the ball, D is the outer diameter of the bearing, and d is the inner diameter of the bearing. Design method. 0.650 ≦ D _W /{(D-d)/2}≦0.750 (1) 2. A ball bearing configured to satisfy the following formula (1), where D _{W is} the diameter of the ball, D is the outer diameter of the bearing, and d is the inner diameter of the bearing. 0.650 ≦ D _W /{(D-d)/2}≦0.750 (1)