JP2000081043A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extremely extend the life of a rolling bearing by restraining a high vibration and also preventing the early peel off of a fixed race. SOLUTION: In a rolling bearing 1 with plural rolling bodies 4 arranged in the gap between a fixed race (outer race) 2 and a rotary race (inner race) 3 lubricated by a grease, the track surface center line average roughness of the fixed race 2 is σ1=0.04 to 0.08 μmRa, the track surface center line average roughness of a rotary race 3 is σ2=0.01 to 0.04 μmRa and the ratio of σ1/σ2 is in a range of 1 to 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease-lubricated rolling bearing, and more particularly to early rolling of a rolling bearing used for an auxiliary engine (alternator, electromagnetic clutch, intermediate pulley, car air compressor, water pump, etc.). It relates to prevention technology and vibration noise prevention technology.

[0002]

2. Description of the Related Art As an index relating to the life of a rolling bearing,
The concept of oil film parameter 表 す, which represents the degree of oil film formation that greatly affects the quality of lubrication, is used ("Rolling bearing engineering", Rolling bearing engineering editorial board, edited by Yokendo Showa 50)
Published the first edition on July 10, p178).

Λ = h _min / (hr ₁ ² + hr ₂ ² ) ^1/2 ≒ h _min /1.15(σ ₁₂ ² + σ _C ² ) ^1/2 (1) where h _min = minimum oil film thickness hr ₁ , hr ₂ = root mean square roughness of _two contact surfaces (the rolling contact surface between the bearing ring and the rolling element) σ ₁₂ = center line average roughness of the bearing ring (h ≒ 1.12R) σ _C = center of steel ball Line average roughness (h ≒ 1.12R) From equation (1), it is understood that the larger the value of the oil film parameter Λ, the thicker the oil film is formed and the longer the bearing life,
When さ れ ≦ 3, a so-called boundary lubrication state is established, and the bearing life is shortened. Therefore, conventionally, it is considered necessary to process the rolling contact surface between the bearing ring and the rolling element as smooth as possible to form an oil film sufficiently to extend the life of the bearing. I was

[0004] The same concept can be applied to a grease lubricated rolling bearing. Therefore, the raceway surface is machined to be as smooth as possible to increase the oil film parameter Λ and improve the raceway surface roughness. By doing so, oil film breakage is suppressed, and the occurrence of high vibration is suppressed.

In a grease lubricated rolling bearing,
Japanese Patent Publication No. 5-32602 discloses that 0.05 μm Ra <
The surface roughness of the steel ball <the surface roughness of the rolling surface, and by bringing the roughness of the steel ball closer to the rolling surface roughness, an oil film is formed between the rolling surfaces to improve lubricity and the temperature of the steel ball There is disclosed a technique for suppressing the rise, thereby preventing the early peeling of the steel ball surface and extending the life.

[0006] Patent Publication No. 2508178 discloses that
At least the outer ring raceway surface of each raceway surface of the outer ring / inner ring and the surface of the rolling element is 0.0005 mm or more in depth and 0.00
A large number of grooved recesses of not more than 08 mm, and a roughness of 0.08 μmRa separated by the grooved recesses and having the grooved recesses removed.
By forming with the following smooth portion, the sliding motion is suppressed, and the function of the oil reservoir is also acted as a secondary function in the groove-shaped concave portion to prevent metal adhesion in the smooth portion, thereby There has been disclosed a technique for preventing seizure of the bearing and obtaining sufficient bearing performance.

[0007]

In a bearing for an alternator, which is used under grease lubrication, high temperature, high vibration, and high load (approximately 4G to 20G by gravitational acceleration) due to high-speed rotation act simultaneously via a belt. Λ becomes small, and oil film formation tends to be difficult. For example, as shown in p.551 of the proceedings of the Japanese Society of Tribology Conference (Tokyo 1995-5), the average rotation slip ratio is increased to about 25 to 30%. There may be a problem that the load is applied to the fixed ring in which slippage is likely to occur, that is, the outer ring raceway is early separated to shorten the life of the bearing.

[0008] As a measure for preventing the early peeling of the fixed ring (bearing outer ring), "SAE Technical Paper: SAE
E950944 (Date February 27-March 2, 1995
1) to 14), the fatigue mechanism of alternator bearings is clarified, and slip is suppressed by changing the filled grease from E grease to M grease having a high damper effect. There is disclosed a technique for preventing metal contact by absorbing high vibration and high load, thereby preventing early peeling of a bearing.

However, the above-mentioned Japanese Patent Publication No. 5-32602.
In the technology disclosed in Japanese Patent Application Publication No.
<Surface roughness of steel ball> The surface roughness of the rolling surface is considered as the surface roughness, and by making the roughness of the steel ball close to the rolling surface roughness, an oil film is formed between the steel ball and the rolling surface to improve lubricity. By suppressing the temperature rise of the steel balls, the surface can be eliminated and the life of the steel balls can be extended, but the roughness of the steel balls is 0.05 μmR.
Since it is large as a, vibration is expected to increase, and the sound of the bearing becomes a problem.

According to the technique disclosed in Japanese Patent Publication No. 2508178, the outer raceway surface is formed to a depth of 0.0005 mm.
A large number of groove-shaped recesses of not less than 0.0008 mm and a roughness of 0.0
By forming with a smooth portion of 8 μmRa or less, the sliding motion is suppressed, so that the effect of extending the life of the fixed wheel can be expected. However, regarding sound, since the optimal rotating wheel surface roughness is unknown, it is necessary to solve the problem. Has not been reached.

Therefore, the present invention is directed to a grease lubricated rolling bearing in order to suppress the slip caused by high vibration and make the damper effect more effective in the rolling fatigue life, with reference to FIG. The grease can be accumulated on the stationary wheel where frequent peeling occurs, and in particular, the raceway surface should be rough enough to hold grease additives etc. in order to obtain an oil retaining effect on the raceway, and the rotating wheel (1) To provide a rolling bearing in which the raceway surface roughness is made smoother than that of the fixed wheel in order to suppress bearing vibration, whereby high vibration can be suppressed and the fixed wheel can be prevented from being separated early. With the goal.

[0012]

In order to achieve the above object, a rolling bearing according to the present invention is used in which a plurality of rolling elements are arranged between a fixed wheel and a rotating wheel to be grease-lubricated. , The center line average roughness σ ₁ of the fixed wheel raceway surface is set to 0.04 to 0.08 μmRa, preferably 0.04 to 0.08 μmRa.
4 to 0.06 μm Ra, the center line average roughness σ ₂ of the rotating wheel raceway surface to 0.01 to 0.04 μm Ra, and σ ₁
The ratio of / σ ₂ is in the range of 1 to 8, preferably 1 to 6.

In this case, the center line average roughness σ of the rolling element surface
Regarding _C , in order to prevent an acoustic problem, it is processed more accurately than the raceway, and σ _C = 0.002 to 0.010 μmR
It is preferable to set the range of a.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory cross-sectional view illustrating a rolling bearing according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a grease additive reservoir in a fixed wheel raceway groove of the embodiment, and FIG. 3 is a schematic diagram of a grease additive reservoir in a fixed ring raceway groove of a comparative example.

In FIG. 1, reference numeral 1 denotes a deep groove ball bearing for rotating an inner ring. In this bearing 1, an outer ring 2 is fixed to a housing 8, and an inner ring 3 is fitted around a shaft 7. A number of rolling elements 4 held by a retainer 5 are disposed between the outer ring 2 and the inner ring 3, and a seal member 6 is provided between the outer ring 2 and the inner ring 3 on both sides of the retainer 5. 6
Is installed. E grease is sealed in a space surrounded by the seal members 6 and 6. Then, the inner ring 3 also rotates with the rotation of the shaft 7, and the vibration and vibration caused by the rotation
The load acts on the load zone of the outer ring 2 from the shaft 7 via the inner ring 3 and the rolling elements 4.

In this embodiment, the outer ring (fixed)
Ring) 2 center line average roughness σ of the raceway surface ₁From 0.04 to 0.
08 μmRa, center line average of the raceway surface of the inner ring (rotating wheel) 3
Roughness σ_TwoIs 0.01 to 0.04 μm Ra, and σ
₁/ Σ_TwoIs in the range of 1 to 8 (hereinafter referred to as “condition 1”).
That. ).

As described above, in this embodiment, the raceway is formed so that grease can accumulate on the raceway surface of the fixed wheel, which is likely to be chipped early under high temperature, high vibration and high load (about 4 G to 20 G) due to high speed rotation. The surface roughness is reduced to prevent premature chipping.On the other hand, the raceway surface of the rotating wheel is made lower than the raceway surface roughness of the fixed wheel to suppress bearing vibration. The life is extended.

Next, the life tests of the rolling bearing of the embodiment satisfying “condition 1” and the rolling bearing of the comparative example not satisfying “condition 1” will be described. As a testing machine, "N
SK Technical Journal No. 656 (1993), page 2 "every predetermined time (for example, every 9 seconds)
A bench rapid acceleration / deceleration tester that switches between 9000 rpm and 18000 rpm was used. In both the embodiment and the comparative example, JIS No. 6303 is used for the test bearing, the bearing clearance is 10 to 15 μm, the load condition is P (load load) / C (dynamic load rating) = 0.10, and the test is performed. The temperature is 80
° C constant, and E grease was used as the enclosed grease.
Further, the calculated life of the bearing at this time is 1350 hours,
Therefore, the test termination time was set to 1500 hours. The test was interrupted when the vibration increased five times the initial vibration, and the presence or absence of peeling was confirmed. The number of tests was n = 10.

The rolling bearings used in this test were two types of bearing steel, and the surface hardness of the outer and inner rings was HRC 58-63.
The amount of retained austenite is 0 to 15%, the surface hardness of the rolling element is HRC 62 to 64, and the center line average roughness σ _{C of the} rolling element surface
Was set to 0.005 μmRa.

In the calculation of the oil film parameter Λ,
The minimum oil film thickness h _min was calculated by using the Cheng's formula shown in “Rolling Bearing Engineering”, edited by the Rolling Bearing Engineering Editing Committee: Ykendo, 1st Edition, July 10, 1975, p178. . In addition, since the center line average roughness is generally used for the surface roughness of the bearing, Λ = h shown in the above equation (1).
Λ was calculated using _{min /} 1.15 (σ ₁₂ ² + σ _C ² ) ^1/2 .

Table 1 shows the test results.

[0022]

[Table 1]

In the first to sixth embodiments, peeling was not observed even when the number reached 10 out of 10 and reached 1000 hours. This is because, as shown in FIG. 2, even in a region where Λ is 3 or less, peeling frequently occurs in a fixed wheel (outer ring).
It is considered that the grease pool was formed on the surface, and the damping effect of the thickener and the additive was increased, so that the oil film holding ability was improved. Further, when the slip occurs, the slip is easily controlled when the surface roughness is in the range of “condition 1”, so that the slip rate decreases.

In Embodiments 7 to 10, since Λ was small, metal contact was easy and 1/10 to 2
/ 10 pieces, about 900 hours, the outer ring (fixed ring) surface was cut off. As a result of observing the outer raceway surface where the peeling occurred, it was crushed to such an extent that the polished eyes disappeared, and traces of metal contact could be confirmed. However, as compared with the peeling life of Comparative Examples 1 to 10 described later, the life is 2 to 10
About twice as long.

On the other hand, in Comparative Examples 1 to 4, the level of the surface roughness of the normal ball bearing raceway surface is usually finished or super-finished, but the oil film parameter Λ is improved to suppress metal contact. Considered. However, in an environment where high temperatures and high vibrations act, as typified by engine accessory bearings, slip and metal contact are likely to occur. Therefore, simply improving the surface roughness alone is shown in FIG. As described above, almost no damping effect due to the effect of grease accumulation can be expected, and therefore, the early removal of the outer ring cannot be prevented. As a result, in Comparative Examples 1 to 4, peeling occurred at 125, 131, 325, and 317 hours, respectively, which was １ ／ or less of the calculated life.

In Comparative Examples 5 to 8, and 10, only the fixed wheel satisfies “condition 1”, but the surface roughness σ _{2 of the} rotating wheel, which significantly affects the increase in bearing vibration, is 0.1 mm.
Since the “condition 1” was not satisfied with the value of not less than 05 μmRa, 5, 7, 8, 10 out of the 10 tests were 5 times the initial vibration, respectively.
The test was stopped twice or more. As a result of examining the bearings whose test was stopped at the vibration level, the surface roughness was extremely deteriorated.

For Comparative Example 9, the surface roughness σ of the fixed wheel
₁ or 0.10 μm Ra, which is larger than “Condition 1”, the initial vibration level is higher than the other tests, and the grease reservoir is provided. However, since Λ is smaller than 1, Metal contact becomes the whole load zone, 5
In 12 hours, the surface origin of the outer ring was broken.

[0028]

As is apparent from the above description, according to the present invention, it is possible to suppress high vibration and to prevent the fixed wheel from being separated at an early stage. The effect that the length can be greatly extended is obtained.

In this case, the center line roughness σ ₁ of the fixed wheel raceway surface is set to 0.04 to 0.08 μmRa, preferably 0.04 to 0.08 μmRa.
The life of the rolling bearing can be reduced by setting 0.06 μm Ra, the center line roughness σ ₂ of the rotating wheel raceway surface to 0.01 to 0.04 μm Ra, and the ratio of σ ₁ / σ ₂ to 1 to 6. It can be extended further.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view for explaining a rolling bearing as an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram of a grease additive reservoir in a fixed ring raceway surface groove of the embodiment.

FIG. 3 is a schematic diagram of a grease additive reservoir in a fixed ring raceway surface groove of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rolling bearing 2 ... Outer ring (fixed ring) 3 ... Inner ring (rotating shaft) 4 ... Rolling element 5 ... Cage 6 ... Sealing member 7 ... Shaft 8 ... Housing 9 ... Acceleration pickup

Claims (1)

[Claims] In a rolling bearing used by arranging a plurality of rolling elements between a fixed wheel and a rotating wheel to be lubricated with grease, the center line average roughness of the fixed wheel raceway surface is set to σ ₁ = 0.04 to
0.08 μmRa, the center line average roughness of the rotating wheel raceway surface is represented by σ
₂ = 0.01 to 0.04 μm Ra, and σ ₁ / σ
A rolling bearing, wherein the ratio of ₂ is in the range of 1 to 8.