JPH01182625A - Part of equal velocity joint for vehicle - Google Patents

Abstract

PURPOSE:To improve wear resistance and fatigue resistance as well by constituting a contact surface to be formed with a hardened layer composed of a sinter hardened layer and of a shot peening hardened layer by use of shots with high hardness values in the part of an equal velocity joint which comes in contact with a rotor. CONSTITUTION:A sinter hardened layer (a) is provided with a shot peening hardened layer (b) formed of shots with high hardness values. Owing to this constitution, the hardness and compression residual stresses in a contact section is increased as compared with those of one provided only with a sinter hardened layer (a). In addition, crystal grains are reduced in diameter. Both wear resistance and fatigue resistance in a contact surface with a rotor is thereby substantially improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to constant velocity joint parts for vehicles, and more specifically to parts that come into contact with rolling elements in Barfield type constant velocity joints, tripod type constant velocity joints, etc. - related to.

(Prior Art) For example, as shown in FIG. 7, a Barfield type constant velocity joint has an outer race 2 provided at one end of the rotating shaft l and an inner race provided at one end of the rotating shaft 3.
It consists of a pawl 6 which is held by a cage 5 and rolls between the pawl groove 2a of the outer race 2 and the pawl groove 4a of the inner race 4. For example, a tripod type constant velocity joint, as shown in FIG. , a tripod 12 attached to one end of the rotating shaft 11 so as to intersect with the axis thereof, and an inboard roller 14 attached to the tripod 12 via a needle roller bearing 13;
This constant velocity joint consists of a tulip 15 having a groove 16 in which this inboard roller 14 rolls.
), or the rolling elements such as the needle roller bearing 13 and the inboard roller 14 (Fig. 8) are subjected to high loads and transfer simultaneously, and therefore the outer race 2 and the inner race 4 (Fig. 7) come into contact with these rolling elements. Alternatively, the tripod 12, the inboard roller 14 itself, the tulip 15 (FIG. 8), etc. are required to have excellent wear resistance and high fatigue strength to withstand pitting, flaking, etc. Therefore, conventionally, chromium-molybdenum steel (JIS 90M420~44
The material was case hardened steel such as No. 0), which was carburized and quenched, and then finished by final grinding.

(Problems to be Solved by the Invention) However, according to the conventional constant velocity joint described above, as shown in FIG. Even if it is obtained, about 0.2 mm of the hardened layer (the shaded area in the figure) is removed by subsequent grinding, which not only reduces the surface hardness and deteriorates wear resistance, but also reduces the maximum shear stress. The area just below the surface (approximately 0.5 +
There was a problem in that the hardness of im) was substantially reduced, leading to a reduction in fatigue life. Particularly recently, vehicle engines have tended to have higher output and higher rotation speed due to the adoption of turbochargers, multiple valves, etc., and the load on the constant velocity joint in the drive system has become severe, which is a major cause of the above-mentioned problems. This posed the problem of having to deal with this by changing the material to a higher grade material or increasing the size of the parts.

There have been some attempts to apply a phosphoric acid film treatment to the contact surface (Japanese Patent Application Laid-open No. 58-200819) and a low-temperature sulfurization treatment (Japanese Patent Application Laid-Open No. 82-113918), but none of them have been found to be resistant. Although it is effective in improving seizure resistance, the effect of improving wear resistance and fatigue resistance is relatively small.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a constant velocity joint part that comes into contact with a rolling element, in which a carburized and hardened layer and a high-hardness shot grain are formed at least on the contact surface. It is characterized by having a structure having a hardened layer consisting of a shot peening hardened layer.

In the above invention, it is desirable to select shot grains having a hardness of 87,550 or higher to form the shot peening hardened layer. This is because not only the degree of stress is small, but also the application of compressive residual stress is insufficient. In addition, it is desirable to select shot particles with a small diameter of 0.02 to 0.5 cm (generally 0.6 cm or more); if the diameter is less than 0.02 am, the hardening depth is too shallow; This is because when it exceeds 0.51, the surface roughness becomes rough. The above hardness and particle size are met by using steel beads granulated by nitrogen gas atomization. The conditions for shot peening using such shredded grains are not particularly limited, but include, for example, a projection speed of 40 to 70 IIl/sec, a projection time of 1 to 2 m1n,
Coverage 200-300%, 7-high)
0.3 to 0.5 mm (7) Each condition can be selected.

Further, in the present invention, the hardened layer may have a structure in which an induction hardened layer is added in addition to the carburized hardened layer and the shot peened hardened layer formed of high hardness shot grains. In this case, the hardness and compressive residual stress of the surface layer portion will further increase.

Furthermore, in the present invention, the contact surface of the hardened layer may be finished to a mirror surface, or a molybdenum disulfide coating layer may be provided on the hardened layer.When finished to a mirror surface, fatigue resistance is improved and When a molybdenum sulfide coating layer is provided, initial conformability is improved.

(Function) In the constant velocity joint part for vehicles having the above structure, by providing a shot peening hardened layer formed of high-hardness shot grains, the contact portion is harder than when a carburized and hardened layer is simply provided. The grain size increases as well as the compressive residual stress and the grain size decreases.

(Example) The present invention will be explained in detail below.

"Support 1" JIS 420 steel is used as the material, and the inner race 4 of the Barfield type constant velocity joint (Fig. 7) and the tripod 12 of the tripod type constant velocity joint (Fig. 8) are formed by forging and machining. The contact surface with each rolling element is carburized, quenched and tempered (950℃
5 hours→150'OX 2 hours), the surface of the contact surface was ground to a depth of 0.2 mm, and then shot peened to obtain actual survey A1. Shot peening is performed using nitrogen gas atomization method to reduce the particle size to 0.3mm.
The test was conducted using steel beads with a hardness of about 550 mm, a projection speed of 50 m/see, a projection time of 10 min, a coverage of 20 oz or more, and an arc high of 0.3 tam. As shown in FIG. 1, the contact surface of the constant velocity joint part thus obtained has a carburized and hardened layer a with a depth of about 1 m and a carbon layer with a depth of about 0.51 m.

A composite topeened hardened layer was formed.

After performing the same processing and carburizing quenching and tempering treatment as in Example 1, induction hardening treatment was performed, then grinding was performed, and shot peening was further performed in the same manner as in Example 1 to obtain the actual survey A2. Ta. Induction hardening has a plate voltage of 10KV, a plate current of 22A, and a grid current of 5.4
A. The heating time was 3.5 seconds, the rotation speed was 10 orpm, and the cooling time was 15 seconds. As shown in FIG. 2, the contact surface of the constant velocity joint component thus obtained has a carburized and quenched layer a with a depth of approximately 0.0.
Approximately 1.5mm with a 5mm thick shot peening layer
A deep induction hardened layer C was formed in combination.

For the above-mentioned product A2, the contact surface is further emery #
The sample was polished with a polishing powder of 400 to 1,000 and was also polished with a puff to obtain an actual survey A3 having a mirror contact surface. The amount of surface removal due to this polishing is about 2go+, and the texture of the contact surface is the same as the texture shown in FIG. 2 above.

Using the same material as in Example 1, the same carburizing and quenching and tempering treatment and grinding were performed to obtain a comparative amount B1 having only a carburized and quenched layer.

Next day 11 The above-mentioned measurements Al, A2, A3 and comparison Bl were subjected to a hardness test and a surface roughness test, and the constant velocity joint (Fig. 7) was completed and released on the market. It was subjected to a bench durability test simulating the conditions of use.

Inner lace was used for the hardness test and bench durability test, and both inner lace and tripod were used for the surface roughness test.

As a result of the hardness test, as shown in Figure 3, the hardness of the actual survey A1 increased in the depth range of approximately 0.5 mm from the surface compared to the comparative amount Bl, indicating that the effect of short peening was It's appearing. In addition, the conducted survey A2 is the conducted survey A1 at the outermost surface part.
Although the hardness is only slightly increased compared to the surface, it maintains a higher hardness level than the surveyed A1 and comparative B1 from the surface to a depth of about 1.5 mm, and the hardening depth is increased by induction hardening. It is clear that the intensity has increased.

Furthermore, as shown in the table below, the results of the surface roughness test showed that for both inner lace and tripod, the surface roughness of the actual survey A1 was significantly improved compared to the comparative B1, and the one-plane accuracy was superior. Ta. Moreover, the surface roughness of the mirror-finished survey A3 is naturally significantly improved compared to the former two.

On the other hand, as a result of the bench durability test, as shown in FIG.
It became clear that the cumulative failure rate was significantly lower and the flaking life was significantly improved in both cases. In addition, in a comparison of the actual surveys of the present invention, the flaking life of the actual survey A3, in which the contact surface was finished to a mirror surface, was significantly improved compared to the other actual surveys A1 and A2.

Next, a description will be given of an example conducted to examine the influence of shot peening conditions and molybdenum disulfide coating.

"Mitate 1" Using the same material as in Example 1 above, the same carburizing, quenching and tempering treatment and grinding were performed to obtain the inner race of the Barfield type constant velocity joint, and this was coated with zero grain size by nitrogen gas atomization method. .2mm, using steel beads with a hardness of about Hma580, and a projection speed of 5E1m/s.
ec, projection time 150 sec + coverage 20 (
Shot peening was performed under conditions of H or higher and an arc height of 0° and 33 mm to obtain actual survey A4.

"Support 1" The above-mentioned sample A4 was roughly coated with molybdenum disulfide to obtain sample A5.

"Support 1" The same material as in Example 1 was used, and the same carburizing, quenching, tempering and grinding were carried out to obtain the inner race of the Barfield type constant velocity joint. .2+a+*, using steel beads with hardness of approximately H muff 20, arc height is 0.
．． Shot peening was performed under the same conditions as in Example 5 except that the thickness was 33 mm, and actual survey A6 was obtained.

The above sample A6 was roughly coated with molybdenum disulfide to obtain sample A7.

The same material as in Example 1 was used, and the same carburizing, quenching, tempering, and grinding processes were used to obtain the inner race of the Barfield type constant velocity joint, which was then subjected to a water atomization process to obtain a particle diameter of 0. .1 (am, hardness approximately Hv 4
Use 50 steel beads and set the arc height to 0.25.
Shot peening was performed under the same conditions as in Example 5 except that the amount was set to mm to obtain a comparative amount B2.

Comparative amount B2 was further coated with molybdenum disulfide to obtain comparative amount B3.

The same material as in Example 1 was used, and the same carburizing, quenching, tempering and grinding processes were carried out to obtain the inner race of the Barfield type constant velocity joint, which was then coated with a grain size of 0.005 by water atomization. 2mm, hardness approximately Hv 45
Using 0.0 steel beads, the arc height is 0.17m.
Shot peening was performed under the same conditions as in Example 5 except that m was used to obtain a comparative amount B4.

No. 1" Comparative amount B5 was obtained by roughly coating molybdenum disulfide on comparative amount B4.

The above-mentioned measurements A4 to A7 and comparative quantities B2 to B5 were subjected to a residual stress measurement test, and a constant velocity joint (Fig. 7) was completed to simulate the conditions of use in the market. It was subjected to a bench durability test. For reference, the comparative amount 1 was also used in each test.

As a result of the residual stress measurement test, as shown in Figure 5, the comparative quantities B2 and B4, which were subjected to shot peening using shot grains of general-purpose hardness, had a higher compressive residual strength than the comparative quantity B1, which was not subjected to shot peening. Although the stress increases, shot peening was performed using shot grains with high hardness A4. It was found that the increase rate was small compared to A6, and the influence of the hardness of the shot grains was large. It should be noted that if grinding burn occurs with the comparative amount B1, tensile residual stress will occur at the outermost surface as shown by the dotted line in the figure, and it can be understood that grinding must be performed with sufficient care.

Figure 6 shows the results of a one-machine durability test. The test was repeated 3 times, pitching (general)
The results are listed as is, and the average values for wear depth are listed.

In the same figure, the white frames indicate the measurements carried out without molybdenum disulfide coating, A4 and A6, and the comparative quantity B2. B4
The total frame of the white frame and the black frame indicates the results of the survey conducted with molybdenum disulfide coating A5. From the results shown in No. 61N, which shows the results of A7 and comparative quantities B3 and B5, respectively, the actual measurements A4 to A7 of the present invention are the conventional comparative quantity Bl without shot peening, and low hardness shot grains. It was found that the number of repetitions until pitching occurred was about 2 to 3 times that of comparative quantities B2 to B5, which were subjected to shot peening, and that the fatigue resistance was excellent. It was also found that when molybdenum disulfide coating was applied, fatigue resistance was improved regardless of the amount of the example and the comparative product. Furthermore, regarding wear resistance, although the number of repetitions until pitting occurs is large, the amount of wear in Examples A4 to A7 of the present invention tends to be rather small, indicating that they are excellent in wear resistance. Do you get it.

(Effects of the Invention) As explained above in detail, according to the constant velocity joint component for a vehicle according to the present invention, the wear resistance and fatigue resistance of the contact surface with the rolling element can be significantly improved. This has the effect of improving durability and reliability without changing the material or increasing the size of parts.

[Brief explanation of the drawing]

Figures 1 and 2 are tissue diagrams of the surface of the constant velocity joint parts of the present invention with the rolling elements, and Figure 3 is a graph showing the surface hardness distribution of the wooden constant velocity joint parts in comparison with a comparative product. Figure 4 is a graph showing the bench durability test results of this constant velocity joint part in comparison with a comparative product. Figure 5 is a graph showing the surface residual stress distribution of this constant velocity joint part in comparison with a comparative product. Figure 6 is a graph showing the bench durability test results similar to Figure 4.
8 and 8 are partial sectional views of a constant velocity joint to which the present invention is applied, and FIG. 9 is a graph showing the surface hardness distribution of a conventional constant velocity joint component. 2... Outer lace, 4... Inner lace 6.
...Paul, 12...Tripod 13...
Needle roller bearing 14... Inboard roller, 15... Tulip a... Carburized hardened layer, b... Shot peening hardened layer, C... Induction hardened layer Fig. 1 hardened layer '' C- Induction hardening layer Fig. 2 Fig. 3 Distance from surface H (mm) Fig. 4 Fig. 5

Claims (1)

[Claims] (1) In constant velocity joint parts that contact rolling elements,
A constant velocity joint component for a vehicle, which has a hardened layer comprising a carburized hardened layer and a shot peened hardened layer formed of high hardness shot grains on at least its contact surface.