Method for preventing early failure of ball groove of spherical constant velocity universal joint and constant velocity universal joint

Abstract

The invention relates to the technical field of universal joints, in particular to a method for preventing early failure of a ball groove of a spherical constant velocity universal joint and the constant velocity universal joint, which mainly comprises the following steps of: vulcanizing the surface of a steel ball of the spherical constant velocity universal joint to generate a FeS compound layer on the surface of the steel ball; the FeS compound layer on the surface of the steel ball is transferred to the bearing area of the ball groove making contact with the steel ball in the working process of the spherical constant velocity universal joint, and a FeS lubricating layer is formed on the bearing area of the ball groove under the extrusion and friction action of the steel ball and the ball groove. The FeS lubricating layer has very high binding force with the surface of the ball groove, has very high bearing capacity, and can effectively avoid adhesive wear and scratch between the steel ball and the bearing area of the ball groove, so that the constant velocity universal joint can directly bear normal high working load without passing through the running-in process at the initial working stage, and the service life of the constant velocity universal joint is prolonged. And abrasion and early failure of the fairway are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of universal joints, and in particular to a method for preventing early failure of a ball track of a spherical constant velocity universal joint and a constant velocity universal joint. Background Art

[0002] The parts of the ball-type constant velocity universal joint used for the constant velocity drive shaft of an automobile mainly include an outer star wheel with a plurality of equally distributed inner ball tracks, an inner star wheel with a plurality of equally distributed outer ball tracks, force transmission steel balls located between the outer ball tracks of the inner star wheel and the inner ball tracks of the outer star wheel with the same number as the ball tracks, and a retaining frame that holds the steel balls in the correct position.

[0003] The ball-type constant velocity universal joint transmits torque and motion through the contact force between the steel ball and the inner and outer star wheel ballways. The maximum contact stress between the steel ball and the ballway can reach 4GPa-6GPa. Therefore, the working condition of the contact point between the steel ball and the ballway is very harsh and it must operate normally under good lubrication conditions.

[0004] Normally, ball-type constant velocity joints require special grease for lubrication. Because the contact stress between the steel ball and the ballway is very high, the special grease for ball-type constant velocity joints must contain extreme pressure (EP) additives. Under the contact stress between the steel ball and the ballway, the extreme pressure additives form a very thin friction chemical reaction film on the surface of the steel ball and the ballway. This friction chemical reaction film prevents the metal surfaces of the steel ball and the ballway from directly contacting and squeezing, resulting in metal adhesion (or cold welding), thereby playing a role in lubrication and reducing friction.

[0005] However, the special grease for constant velocity joints has the following disadvantages:

[0006] (1) Extreme pressure additives need to undergo complex friction chemical reactions under the conditions of extrusion and friction between the steel ball and the ballway to generate a chemical reaction film of sufficient thickness and coverage that can bear the load on the contact surface. The process before the chemical reaction film is formed is the running-in process of the parts. During the running-in process, because the chemical reaction film has not yet been fully established, there is still direct contact between the metal surfaces of the steel ball and the ballway. If the contact stress between the steel ball and the ballway is too large, severe cold welding adhesion will occur between the steel ball and the ballway. Since the surface hardness of the ballway is generally 1HRC-3HRC lower than that of the steel ball, the adhesion between the steel ball and the ballway surface will cause severe scratches on the ballway surface, and due to the severe stress concentration on the scratched surface, the universal joint ballway will quickly produce contact fatigue peeling and lose its working ability.

[0007] (2) The speed of chemical reaction film formation depends on factors such as the reactivity of the extreme pressure additive and the initial microscopic morphology of the ballway surface. If an extreme pressure additive with higher reactivity is used, the speed of chemical reaction film formation can be increased, the running-in process of parts can be shortened, and early failure of the ballway due to heavy loads during the running-in process can be avoided. However, excessive reactivity of extreme pressure additives can lead to excessive corrosion and wear of metal parts, which can cause micropitting and peeling of the universal joint ballway during normal operation after running-in, resulting in failure.

[0008] (3) The extreme pressure additive has too high a reactivity, which can easily lead to premature failure of the thermoplastic elastomer (TPE) material of the universal joint sealing boot.

[0009] With the continuous development of electric vehicles, the torque load on constant velocity joints continues to increase, and the number of early failure cases of constant velocity joints caused by poor running-in is also increasing. Therefore, appropriate technical methods are needed to avoid this situation.

[0010] One method that has been used is to deposit a phosphate lubricating film with friction reduction and lubrication on the surface of the universal joint ball track through a phosphating surface treatment process. However, the load-bearing and wear-resistance capacity of the phosphate lubricating film can generally only reach 1GPa-2GPa, which cannot withstand the high load of the constant velocity joint, and therefore cannot eliminate the early failure problems such as ball track scratches that occur during the running-in process of the constant velocity joint. Summary of the invention

[0011] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a method for preventing premature failure of the ball track of a spherical constant velocity universal joint and a constant velocity universal joint that will not cause abrasion, wear and premature failure of the ball track.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] The present invention provides a method for preventing the early failure of a ballway of a ball type constant velocity universal joint. The surface of a steel ball of the ball type constant velocity universal joint is vulcanized to generate an FeS compound layer on the surface of the steel ball. The FeS compound layer on the surface of the steel ball is transferred to the bearing area of ​​the ballway in contact with the steel ball during the operation of the ball type constant velocity universal joint. Under the extrusion and friction between the steel ball and the ballway, an FeS lubricating layer is formed on the bearing area of ​​the ballway.

[0014] Preferably, the process for vulcanizing the surface of the steel ball is low temperature vapor deposition.

[0015] Preferably, the processing temperature of the low temperature vapor deposition is lower than 200°C.

[0016] Preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 3 micrometers to 50 micrometers.

[0017] Preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 5 micrometers to 10 micrometers.

[0018] Preferably, the surface hardness of the steel ball is greater than 60HRC, the surface roughness of the steel ball is less than Ra0.05 micrometer, the surface hardness of the bearing area of ​​the ballway is greater than 58HRC, and the surface roughness of the bearing area of ​​the ballway is less than Ra1.0 micrometer.

[0019] The present invention also provides a constant velocity universal joint, comprising an outer star wheel, an inner star wheel, a ballway, a retaining frame arranged between the outer star wheel and the inner star wheel, and a steel ball arranged on the retaining frame, the ballway comprising an inner ballway arranged on the outer star wheel and an outer ballway arranged on the inner star wheel, the steel ball is located between the inner ballway and the outer ballway, the surface of the steel ball is vulcanized to form a FeS compound layer, the FeS compound layer on the surface of the steel ball is transferred to the bearing area of ​​the ballway in contact with the steel ball during the operation of the constant velocity universal joint, and a FeS lubricating layer is formed on the bearing area of ​​the ballway under the extrusion and friction between the steel ball and the ballway.

[0020] Preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 3 micrometers to 50 micrometers.

[0021] Preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 5 micrometers to 10 micrometers.

[0022] Preferably, the surface hardness of the steel ball is greater than 60HRC, the surface roughness of the steel ball is less than Ra0.05 micrometer, the surface hardness of the bearing area of ​​the ballway is greater than 58HRC, and the surface roughness of the bearing area of ​​the ballway is less than Ra1.0 micrometer.

[0023] Compared with the prior art, the present invention has significant improvements:

[0024] The present invention generates an FeS compound layer by performing a sulfurization treatment on the surface of a steel ball. Based on the characteristics of FeS being relatively soft and easy to shear and flow, the FeS compound layer is quickly transferred from the surface of the steel ball to the bearing area of ​​the ballway in contact with the steel ball during the operation of the spherical constant velocity universal joint, and forms a dense FeS lubricating layer on the bearing area of ​​the ballway under the extrusion and friction between the steel ball and the ballway. The FeS lubricating layer has a high bonding force with the surface of the ballway and a high bearing capacity, and can effectively avoid adhesive wear and abrasion between the steel ball and the bearing area of ​​the ballway, thereby enabling the constant velocity universal joint to directly bear a normal high working load without going through a running-in process at the initial stage of operation, and will not cause abrasion wear and early failure of the ballway. At the same time, the FeS lubricating layer produced by the transfer of the FeS compound layer on the surface of the steel ball on the bearing area of ​​the ballway surface has excellent durability. During the entire working life of the constant velocity joint, it can always maintain the lubrication and protection of the bearing area of ​​the ballway surface, and effectively isolate the contact and chemical reaction between the active substances in the constant velocity joint grease and the metal material on the ballway surface, avoiding the erosion of the bearing area of ​​the ballway surface by chemical active substances, greatly improving the durability of the constant velocity joint. In addition, since the FeS lubricating layer has a lower friction coefficient, the constant velocity joint using a steel ball with a surface sulfurized layer (FeS compound layer) has a higher transmission efficiency. The bench test shows that the temperature rise of the universal joint surface caused by the friction between the internal parts can be reduced by 15℃-20℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 2 is a cross-sectional schematic diagram of a constant velocity universal joint according to an embodiment of the present invention.

[0026] The reference numerals are described as follows:

[0027] 1 Alien Wheel

[0028] 2 Inner Star Wheel

[0029] 3 Cage

[0030] 4 Steel Balls DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0032] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0035] Sulfur and metal compounds such as FeS (ferrous sulfide) have good extreme pressure lubrication effects. The FeS film formed by the extreme pressure additive containing active sulfur elements on the surface of steel materials has a high load-bearing capacity and a small friction coefficient. In order to eliminate the problems of ballway abrasion and early failure in the running-in process of the ball constant velocity universal joint, the present invention proposes to use FeS film for lubrication, and conducts in-depth research on the application of FeS film on the parts of the constant velocity universal joint. In the research of the present invention, one way to try to use FeS film for lubrication is to perform a sulfurization treatment on the entire working surface of the outer star wheel of the ball constant velocity universal joint to produce a sulfurized layer, the main component of which is FeS. However, it was found during the test that due to the large area of ​​the working surface of the outer star wheel part, the amount of active S components remaining in the sulfurized layer that did not combine with Fe to produce FeS was large. These active S components caused the thermoplastic elastomer (TPE) material of the universal joint sealing sleeve to fail prematurely, and the grease of the universal joint was lost due to the rupture of the sleeve, which would cause the early failure of the universal joint. On this basis, the present invention proposes a method of performing a sulfurization treatment on the surface of the steel ball of the spherical constant velocity joint to produce a FeS sulfurized layer, so as to achieve the purpose of eliminating the ball track abrasion and early failure problems of the spherical constant velocity joint by utilizing the lubricating effect of the FeS film.

[0036] Specifically, an embodiment of the present invention provides a method for preventing the early failure of the ball track of a spherical constant velocity joint. The method for preventing the early failure of the ball track of a spherical constant velocity joint in this embodiment is to perform a vulcanization treatment on the surface of a steel ball of a spherical constant velocity joint to generate a FeS compound layer on the surface of the steel ball, and the FeS compound layer is a FeS sulfurized layer with FeS as the main component. In this embodiment, the steel ball body of the spherical constant velocity joint is a conventional force-transmitting steel ball made of high-carbon chromium bearing steel, such as China's GCr15, Germany's 100Cr6, Japan's SUJ2, and the United States' SAE52100. The thickness of the FeS compound layer generated on the surface of the steel ball is in the micron level. Performing a vulcanization treatment on the surface of the steel ball to generate a FeS compound layer will not cause a decrease in the hardness of the steel ball body material. The FeS compound layer is firmly bonded to the surface of the steel ball, but because FeS is relatively soft and easy to shear flow, the FeS compound layer on the surface of the steel ball will quickly transfer to the bearing area of ​​the ballway (the inner ballway on the outer star wheel and the outer ballway on the inner star wheel) that contacts the steel ball (i.e., the area where the ballway surface contacts the steel ball) during the operation of the ball constant velocity joint, and form a dense FeS lubricating layer on the bearing area of ​​the ballway under the extrusion and friction between the steel ball and the ballway. The FeS lubricating layer has a high bonding force with the surface of the ballway and has a high load-bearing capacity, which can effectively avoid adhesive wear and abrasion between the steel ball and the bearing area of ​​the ballway. As a result, the ball constant velocity joint can directly withstand normal high working loads without going through the initial running-in process, and will not cause abrasion wear and early failure of the ballway.

[0037] At the same time, the FeS lubricating layer produced by the transfer of the FeS compound layer on the surface of the steel ball on the bearing area of ​​the ballway surface has excellent durability. During the entire working life of the ball constant velocity joint, it can always maintain the lubrication and protection of the bearing area of ​​the ballway surface, and effectively isolate the contact and chemical reaction between the active substances in the grease of the ball constant velocity joint and the metal material on the ballway surface, avoiding the erosion of the bearing area of ​​the ballway surface by chemical active substances, greatly improving the durability of the ball constant velocity joint. In addition, since the FeS lubricating layer has a lower friction coefficient, the ball constant velocity joint using a steel ball with a surface sulfurized layer (FeS compound layer) has a higher transmission efficiency. The bench test shows that the temperature rise of the universal joint surface caused by the friction between the internal parts can be reduced by 15℃-20℃.

[0038] Since the total surface area of ​​the steel ball is much smaller than the working surface area of ​​the inner or outer star wheel, a FeS compound layer is generated on the surface of the steel ball, which will result in a very small amount of active S components remaining in the sulfurized layer. During multiple repeated tests, no adverse effects of the active S components on the thermoplastic elastomer (TPE) material of the universal joint sealing sleeve were found.

[0039] In the method for preventing the early failure of the ball track of the ball type constant velocity universal joint of this embodiment, preferably, the process of vulcanizing the surface of the steel ball is low temperature vapor deposition. In order to prevent the hardness of the steel ball body material from decreasing during the sulfurization process, preferably, the processing temperature of the low temperature vapor deposition is lower than 200°C. A preferred low temperature vapor deposition method with a processing temperature lower than 200°C is the glow ion discharge deposition method. Of course, other low temperature vapor deposition methods with a processing temperature lower than 200°C can also be used.

[0040] In the method for preventing early failure of the ball track of a spherical constant velocity universal joint of this embodiment, preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 3 microns to 50 microns. More preferably, the thickness of the FeS compound layer formed on the surface of the steel ball is 5 microns to 10 microns.

[0041] In the method for preventing premature failure of the ball track of a ball type constant velocity universal joint of the present embodiment, in order to ensure the function of the FeS compound layer, preferably, the surface hardness of the steel ball is greater than 60HRC, the surface roughness of the steel ball is less than Ra0.05 microns, the surface hardness of the bearing area of ​​the ball track is greater than 58HRC, and the surface roughness of the bearing area of ​​the ball track is less than Ra1.0 microns.

[0042] The method for preventing premature failure of the ball track of a spherical constant velocity joint of the present embodiment can be used for a fixed constant velocity joint at the hub end of a vehicle transmission shaft or a mobile constant velocity joint at the transmission end of a vehicle transmission shaft. Using the method for preventing premature failure of the ball track of a spherical constant velocity joint of the present embodiment, all steel balls in the constant velocity joint are vulcanized steel balls with a surface vulcanization treatment to form a FeS compound layer.

[0043] The embodiment of the present invention also provides a constant velocity universal joint. Figure 1 The constant velocity universal joint of this embodiment includes an outer star wheel 1, an inner star wheel 2, a ball track, a retaining frame 3 arranged between the outer star wheel 1 and the inner star wheel 2, and a steel ball 4 arranged on the retaining frame 3. The ball track includes an inner ball track arranged on the outer star wheel 1 and an outer ball track arranged on the inner star wheel 2. The steel ball 4 is located between the inner ball track and the outer ball track. The number of steel balls 4, the inner ball track and the outer ball track is the same and is arranged one by one.

[0044] In the constant velocity joint of the present embodiment, the surface of the steel ball 4 is subjected to a sulfurization treatment to generate a FeS compound layer, and the FeS compound layer is a FeS sulfurized layer with FeS as the main component. Preferably, the process of sulfurizing the surface of the steel ball is low-temperature vapor deposition. In order to prevent the hardness of the steel ball body material from decreasing during the sulfurization process, preferably, the processing temperature of the low-temperature vapor deposition is lower than 200°C. A preferred low-temperature vapor deposition method with a processing temperature lower than 200°C is a glow ion discharge deposition method. Of course, other low-temperature vapor deposition methods with a processing temperature lower than 200°C can also be used.

[0045] In the present embodiment, the steel ball body of the ball type constant velocity universal joint is a conventional force transmission steel ball, and the material is high carbon chromium bearing steel, such as China's GCr15, Germany's 100Cr6, Japan's SUJ2, and the United States' SAE52100. The thickness of the FeS compound layer generated on the surface of the steel ball is micron-level. The FeS compound layer is vulcanized on the surface of the steel ball to generate the FeS compound layer, which will not cause the hardness of the steel ball body material to decrease. The FeS compound layer is firmly combined with the surface of the steel ball, but because FeS has the characteristics of being soft and easy to shear flow, the FeS compound layer on the surface of the steel ball 4 will quickly transfer to the bearing area (i.e., the area where the surface of the ball track contacts the steel ball 4) of the ball track (the inner ball track on the outer star wheel 1 and the outer ball track on the inner star wheel 2) in the working process of the constant velocity universal joint, and form a dense FeS lubricating layer on the bearing area of ​​the ball track under the extrusion and friction between the steel ball 4 and the ball track. The FeS lubricating layer has a high bonding force with the surface of the ballway and has a high load-bearing capacity, which can effectively avoid adhesive wear and abrasion between the steel ball 4 and the bearing area of ​​the ballway. Therefore, the constant velocity joint of this embodiment using the steel ball 4 with a surface sulfurized layer (FeS compound layer) can directly withstand the normal high working load without going through the initial running-in process, and will not cause abrasion wear and early failure of the ballway.

[0046] At the same time, the FeS lubricating layer produced by the transfer of the FeS compound layer on the surface of the steel ball 4 on the bearing area of ​​the ballway surface has excellent durability. During the entire working life of the constant velocity joint, it can always maintain the lubrication and protection of the bearing area of ​​the ballway surface, and effectively isolate the contact and chemical reaction between the active substances in the constant velocity joint grease and the metal material on the ballway surface, avoiding the erosion of the bearing area of ​​the ballway surface by chemical active substances, greatly improving the durability of the constant velocity joint. In addition, since the FeS lubricating layer has a lower friction coefficient, the constant velocity joint using the steel ball 4 with a surface sulfurized layer (FeS compound layer) has a higher transmission efficiency. The bench test shows that the temperature rise of the universal joint surface caused by the friction between the internal parts can be reduced by 15℃-20℃.

[0047] Since the total surface area of ​​the steel ball 4 is much smaller than the working surface area of ​​the inner star wheel 2 or the outer star wheel 1, an FeS compound layer is generated on the surface of the steel ball 4, which will result in a very small amount of active S components remaining in the sulfurized layer. During multiple repeated tests, no adverse effects of the active S components on the thermoplastic elastomer (TPE) material of the universal joint sealing sleeve were found.

[0048] In the constant velocity universal joint of this embodiment, preferably, the thickness of the FeS compound layer formed on the surface of the steel ball 4 is 3 micrometers to 50 micrometers. Preferably, the thickness of the FeS compound layer formed on the surface of the steel ball 4 is 5 micrometers to 10 micrometers.

[0049] In the constant velocity joint of this embodiment, in order to ensure the function of the FeS compound layer, preferably, the surface hardness of the steel ball 4 is greater than 60HRC, the surface roughness of the steel ball 4 is less than Ra0.05 microns, the surface hardness of the bearing area of ​​the ball track is greater than 58HRC, and the surface roughness of the bearing area of ​​the ball track is less than Ra1.0 microns.

[0050] The constant velocity joint of this embodiment can be used for a fixed constant velocity joint at the hub end of a vehicle transmission shaft or a mobile constant velocity joint at the transmission end of a vehicle transmission shaft. All the steel balls 4 in the constant velocity joint of this embodiment are vulcanized steel balls with a FeS compound layer formed on the surface by vulcanization treatment.

[0051] The method for preventing the early failure of the ballway of the ball type constant velocity joint according to the embodiment of the present invention and the use effect of the constant velocity joint according to the embodiment of the present invention were tested and verified. On the constant velocity joint life tester, the constant velocity joints in different states were subjected to high load life tests without running-in. The test results are shown in Table 1 below. Among them, the test pieces of Test 1 and Test 2 are constant velocity joints using conventional steel balls in the prior art, and the test piece of Test 3 is a constant velocity joint according to the embodiment of the present invention using a vulcanized steel ball whose surface is vulcanized to form a FeS compound layer. From the comparison of the test results, it can be seen that the constant velocity joint according to the embodiment of the present invention using a vulcanized steel ball whose surface is vulcanized to form a FeS compound layer will not cause abrasion and early failure of the ballway and can work normally.

[0052] Table 1 Test verification results

[0053]

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preventing premature failure of a ball track of a ball type constant velocity universal joint, characterized in that: The surface of the steel ball of the ball type constant velocity joint is vulcanized to generate an FeS compound layer on the surface of the steel ball. The FeS compound layer on the surface of the steel ball is transferred to the load-bearing area of ​​the ball track in contact with the steel ball during the operation of the ball type constant velocity joint, and a FeS lubricating layer is formed on the load-bearing area of ​​the ball track under the extrusion and friction between the steel ball and the ball track.

2. The method for preventing premature failure of a ball track of a ball type constant velocity universal joint according to claim 1, characterized in that: The process for vulcanizing the surface of the steel ball is low-temperature vapor deposition.

3. The method for preventing premature failure of a ball track of a ball type constant velocity universal joint according to claim 2, characterized in that: The processing temperature of the low temperature vapor deposition is lower than 200°C.

4. The method for preventing premature failure of a ball track of a ball type constant velocity universal joint according to claim 1, characterized in that: The thickness of the FeS compound layer generated on the surface of the steel ball is 3 microns to 50 microns.

5. The method for preventing premature failure of a ball track of a ball type constant velocity universal joint according to claim 4, characterized in that: The thickness of the FeS compound layer generated on the surface of the steel ball is 5 microns to 10 microns.

6. The method for preventing premature failure of a ball track of a ball type constant velocity universal joint according to claim 1, characterized in that: The surface hardness of the steel ball is greater than 60HRC, the surface roughness of the steel ball is less than Ra0.05 micrometer, the surface hardness of the bearing area of ​​the ballway is greater than 58HRC, and the surface roughness of the bearing area of ​​the ballway is less than Ra1.0 micrometer.

7. A constant velocity universal joint, comprising an outer star wheel (1), an inner star wheel (2), a ball track, a retaining frame (3) arranged between the outer star wheel (1) and the inner star wheel (2), and a steel ball (4) arranged on the retaining frame (3), wherein the ball track comprises an inner ball track arranged on the outer star wheel (1) and an outer ball track arranged on the inner star wheel (2), and the steel ball (4) is located between the inner ball track and the outer ball track, characterized in that: The surface of the steel ball (4) is subjected to a sulfurization treatment to generate an FeS compound layer. The FeS compound layer on the surface of the steel ball (4) is transferred to the bearing area of ​​the ball track in contact with the steel ball (4) during the operation of the constant velocity universal joint, and the FeS lubricating layer is formed on the bearing area of ​​the ball track under the extrusion and friction between the steel ball (4) and the ball track.

8. The constant velocity universal joint according to claim 1, characterized in that: The thickness of the FeS compound layer generated on the surface of the steel ball (4) is 3 micrometers to 50 micrometers.

9. The constant velocity universal joint according to claim 8, characterized in that: The thickness of the FeS compound layer generated on the surface of the steel ball (4) is 5 micrometers to 10 micrometers.

10. The constant velocity universal joint according to claim 1, characterized in that: The surface hardness of the steel ball (4) is greater than 60HRC, the surface roughness of the steel ball (4) is less than Ra0.05 micrometer, the surface hardness of the bearing area of ​​the ballway is greater than 58HRC, and the surface roughness of the bearing area of ​​the ballway is less than Ra1.0 micrometer.

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