JPH03199716A - Bearing part - Google Patents

Abstract

PURPOSE:To extend a fatigue life of a bearing by providing a surface hardening treated layer, in which depth of a peak in distribution of compression residual stress is set to the almost equal depth when a rolling unit is brought into contact, in a contact part with the rolling unit. CONSTITUTION:A cemented hardened layer 14 and a shot peening hardened layer 15 are compound-formed on a surface layer part of a bearing part 12, and a contact surface 13 with a rolling unit 11 is formed in a lapping finished skin. The cemented hardened layer 14 is set to a depth of about 1mm, and the shot peening hardened layer 15 is set to a depth of about 0.3mm. An internal quality of the shot peening layer is adjusted so as to provide distribution of compression residual stress in a similar figure to distribution S of shearing force generated when the rolling unit 11 is brought into contact with the contact surface 13. Thus, a life is extended by increasing fatigue strength in a region where fatigue destruction is easily generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to bearing parts that come into contact with rolling elements, such as races of pole bearings and races of constant velocity joints.

(Prior Art) For example, a Barfield type constant velocity joint, which is one of the constant velocity joints for a vehicle, has an outer race 2 attached to one end of one rotating shaft 1, as shown in FIG. The inner race 4 attached to one end of the other rotating shaft 3 and the raceway grooves 2a of both races 2.4 held by the cage 5
, 4a, and is separated from the rolling pole 6. In a visible constant velocity joint, the outer race 2 and inner race 4 are repeatedly subjected to high loads from the poles (rolling elements) 6, and their lifespan is mainly limited by pitting, flaking, etc. that occur on the raceway surface (contact surface). It is determined by the fatigue failure of For this reason, conventionally, at least the contact portion of each race 2, 4 with the pole 6 is subjected to surface hardening treatment such as carburizing and quenching, induction hardening, etc. to increase surface hardness and compressive residual stress, thereby improving fatigue resistance. Measures to improve the situation were widely implemented. However, according to these measures, there is a certain limit to the surface hardness and compressive residual stress that can be obtained, and there is a problem that the fatigue life cannot be extended as expected.

Therefore, JP-A-1-182825 reports the usefulness of performing shot peening using high hardness shot grains after carburizing and quenching. According to this measure, the surface hardness and compressive residual stress are increased, and the fatigue life is extended, compared to the measures of simply carburizing and quenching or induction hardening.

(Problem to be Solved by the Invention) However, recently, vehicle engines tend to have higher output and higher rotation speed, so the load on the above-mentioned constant velocity joint has also increased, and the above-mentioned carburizing and quenching and shot Even with the measures taken in combination with peening, there was still a problem in that it was difficult to ensure a sufficient fatigue life.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to provide a bearing component that has a longer fatigue life than ever before.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a surface hardening layer at least in the contact portion with the rolling element, and the peak depth of the compressive residual stress distribution of the surface hardening layer. It is characterized in that the depth is configured to substantially match the peak depth of the shear accommodation force distribution generated when the rolling element comes into contact with the rolling element.

Generally, when considering the contact between rolling elements and bearing parts, the distribution of shear force generated in the bearing parts is determined by the Hertzian contact pressure theory, as shown in FIG. A state where the peak stress value τ0 is reached in a region that is a predetermined distance Zo from the contact surface 13 of 12 (
Therefore, as a measure to extend the fatigue life of the bearing component 12, the peak depth Z of the shear adaptation force distribution
If the o area is not strengthened preferentially, the effect cannot be maximized.6 The present invention has been made with attention to this point, and at least the contact surface 13 with the rolling element 11 is strengthened. A surface hardening layer is provided on the surface layer including
The peak depth Zo of the shear adaptation force distribution is made to coincide with f. In this case, the peak depth Zo of the shear adaptation force distribution varies depending on the contact load P between the rolling elements 11 and the bearing component 12, the size of the contact ellipse, Young's modulus, etc. The depth Za is estimated and the internal quality of the surface hardened layer is changed accordingly.

Although the present invention does not specify a method for providing the surface hardening layer, the hardness and compressive residual stress of the surface layer are increased by well-known carburizing and quenching or induction hardening, and then A method can be used in which topeening or roller processing is added to loosen the peak depth of the compressive residual stress distribution of the hardened surface layer to match the peak depth Zo of the shear conforming force distribution. When performing shot peening, the peak depth ZO of the compressive residual stress distribution can be changed by changing the hardness and particle size of the shot, or its projection speed, but according to experiments, the peak depth ZO of the compressive residual stress distribution Since there is a good correlation between the peak depth Zo of the residual stress distribution, it is desirable to control the peak depth Zo of the compressive residual stress distribution by changing the grain size of the sheet. Since the roughness of the finished surface also affects the shot peening, it is desirable to finish the contact surface 13 of the bearing component 12 that contacts the rolling elements by lapping to make the surface roughness as fine as possible.

(Function) In the bearing component configured as described above, the peak depth of the compressive residual stress distribution of the surface hardening treatment layer is made to almost match the peak depth of the shear stress generated when it comes into contact with the rolling elements. Therefore, the fatigue strength in areas where fatigue fracture is likely to occur can be increased as much as possible.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a bearing component 12 according to the present invention, in which a carburized hardened layer 14 and a shot peened hardened layer 15 are formed in a composite manner on the surface layer, and which contact surfaces of the rolling elements 11 are formed. 13 is considered to be the wrapping finished skin. The carburized and quenched layer 14 is formed by carburizing and quenching a machined product into the shape of a peelable product, and its depth is 1Ill16.
It is said that the degree of On the other hand, shot peening hardened layer 1
No. 5 is formed by projecting a highly hard shot onto the carburized and quenched layer 14, and its depth is approximately 0.5 mm.
It is said to be 3m long. As described in detail later, this shot peening hardened layer 15 has a compressive residual stress distribution similar to the shear force distribution S that occurs when the rolling elements 11 come into contact with the contact surface 13 of the bearing component 12. Its inner quality has been adjusted so that it has. By adjusting the compressive residual stress distribution of the shot peening hardened layer 15 in this way, the peak depth of the compressive residual stress distribution becomes equal to the peak depth ZO of the shear conforming force distribution, and this As a result, the fatigue strength in areas where fatigue fractures are likely to occur is increased as much as possible, and the resistance to fatigue fractures such as pitting and flaking is significantly increased.

Examples of the present invention will be described in more detail below.

Example 1 As a fatigue life test, it is assumed that the 20-1 type transfer fatigue test shown in Fig. 5.6 will be conducted, and JIS 90M420
A disk-shaped sample 16 with a diameter Bowm was prepared from the material, and first, it was carburized and quenched to form a carburized and quenched layer with a depth of about 1 mm on its outer periphery, and then its outer periphery was polished with a whetstone. Then, a shot with a hardness of about H Muff 501 and a grain size of about 0.8 cm was applied to the outer peripheral surface using air pressure. kg, nozzle diameter 8■.

Shot peening was performed under the conditions of 10 minutes of projection time, and finally, lapping was performed to finish the surface roughness of the outer peripheral surface to 0.1 Rz. It was subjected to a fatigue life test and a fatigue life test.

Example 2 Particle size 1.2 as shot in shot peening
Example sample A2 was completed in the same manner as in Example 1 except that a sample having a diameter of mm was selected, and was similarly subjected to a residual stress measurement test, a hardness test, and a fatigue life test.

Example 3 Particle size 1.8 as shot in shot peening
Example sample fI4A 2 was tested in the same manner as in Example 1 except that a sample of mm was selected, and it was also subjected to a residual stress measurement test, a hardness test, and a fatigue life test.

Comparative Example I A disk-shaped sample 16 (Fig. 5.6) with a diameter Has was prepared from a JIS 5CN420 material, and first, it was subjected to the same carburizing and quenching treatment as in Example 1, and a depth of approximately 1 mm was formed on the outer periphery. A carburized and quenched layer is formed, and then its outer peripheral surface is polished with a whetstone.
Finally, lapping is performed to reduce the surface roughness of the outer peripheral surface to 0.1
JLmRz was finished, and this was used as comparative sample B1 and subjected to a residual stress measurement test, a hardness test, and a fatigue life test, which will be described later.

Comparative Example 2 Particle size 0.3 as shot in shot peening
Comparative sample B2 was completed in the same manner as in Example 1, except that sample (2) was selected, and was similarly subjected to a residual stress measurement test, a hardness test, and a fatigue life test.

Test Results Figure 2 shows the measurement results of residual stress. From this, comparative sample B1, which was not subjected to shot peening, obtained only a small amount of compressive residual stress, whereas example sample Al-A3 and comparative sample B2, which were subjected to shot peening, obtained very large compressive residual stress. It is clear that shot peening has a very effective effect on increasing compressive residual stress. In addition, in shot peened products, a peak of the compressive residual stress distribution is observed at the part that penetrates from the surface to the inside, but the depth of the peak shifts to the inside as the shot with a larger particle size is used. (Bl <Al <A2<
A3), Figure 3 shows the peak depth 0 of this compressive residual stress distribution arranged by the Sitt particle size d, and a close correlation is recognized between the two, and from this, it can be seen that the compressive residual stress distribution It can be seen that the peak depth 0th can be changed by changing the grain size d of the shot.

FIG. 4 shows the results of the hardness test. From this, it can be seen that the hardness of the surface layer of the example samples At to A3 and comparative sample B2, which were subjected to shot peening, is greater than that of comparative sample B, which was not subjected to shot peening. It is clear that shot peening is extremely effective in increasing the hardness of the surface layer. In addition, the peak depth of the hardness distribution of each sample corresponds to the peak depth of the compressive residual stress distribution (Fig. 2) mentioned above, and the larger the grain size selected as shot, the more it migrates to the inside. There is.

The fatigue life test was conducted on each sample 16 as shown in Figure 5.6.
A driving roller 17 of the same diameter (Eihm) is pressed under a predetermined load and rotated while supplying lubricating oil between the two rollers. ) was sought. Here, the test conditions are 30 rotations.
0Orpm, surface pressure 44Bkg/12. The slip rate is 0%,
Further, machine oil #1O was used as a lubricating oil. The shear stress distribution generated in sample 16 under these test conditions is as shown in FIG. 7, and the peak depth Zo is 0.0831.
It is 1m.

FIG. 8 shows the results of a fatigue life test conducted under the above conditions. From this, the fatigue life of Example Samples A, ~A3, and Comparative Sample B2, which were subjected to shot peening, was extended compared to Comparative Sample B1, which was not subjected to shot peening, indicating that shot peening is effective in extending fatigue life. is clear. In addition, in those subjected to shot peening, Example samples A and -A were compared to Comparative sample B2.
3 has a longer fatigue life, especially example test I.
That of 4A2 is the longest. These comparative samples B
2 and Example Samples A and -A3 are the difference in shot particle size, that is, the peak depth δ0 of compressive residual stress (third
), and the above result is that the peak depth δ0 of this compressive residual stress is the same as the peak depth Z of the shear accommodation force mentioned above.
o (0,083mm), the closer (BI<
AI < A3 < A2 ) This indicates that the fatigue life is extended.

(Effects of the Invention) As described above in detail, according to the bearing component according to the present invention, the peak depth of the compressive residual stress distribution of the surface hardened layer is adjusted to the depth that occurs when it comes into contact with the rolling elements. Since the peak depth of the shear accommodation force is made to coincide with X -, the fatigue strength in the area where fatigue fracture is likely to occur is increased as much as possible, and the effect of significantly improving the fatigue life can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing the state of the surface layer of the bearing component according to the present invention, and FIG. 2 is a graph showing the residual stress distribution of the surface layer of the present bearing component in comparison with a comparative example. , Figure 3 is
Figure 2 is a graph showing the peak depth of compressive residual stress organized by shot particle size; Figure 4 is a graph showing the hardness distribution of the surface layer of this bearing component in comparison with a comparative example; Figure 6 and Figure 6 are schematic diagrams showing the fatigue life test method, Figure 7 is a graph showing the shear stress distribution in the fatigue life test, and Figure 8 is a comparison of the fatigue life of this bearing component with a comparative example. The graph shown in FIG. 9 is a sectional view showing an example of application of a bearing component to a constant velocity joint. 11... Rolling element 12... Bearing parts 13... Contact surface 14... Carburized and hardened layer 15... Shot peened hardened layer (and 2 others) Figure 1 Distance of surface rudder (mm) ) Fig. Surface force) (mm) Fig. 4 Fig. 4 Depth from the surface (mm) Fig. 8 Fig. 9

Claims (1)

[Claims] (1) A surface-hardened layer is provided at least in the contact portion with the rolling element, and the peak depth of the compressive residual stress distribution of the surface-hardened layer is the peak depth of the shear stress distribution that occurs when it comes into contact with the rolling element. A bearing part characterized by having substantially the same depth.