JP2010043691A - Constant velocity universal joint and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant velocity universal joint capable of surely restraining reduction in the service life of a cutting tool even in intermittent hardened steel cutting, by reducing a burden imposed on the cutting tool when cutting a surface of a cage and an inner ring after a quenching process, and to provide a method for manufacturing the constant velocity universal joint. <P>SOLUTION: The cage 5 is provided by forming a decarbonization layer on a surface of a specific part and an unspecific part by carburization quenching. This decarbonization layer is cut and removed by using the cutting tool in the specific part (a ball interfering surface 23 of a pocket 7, a surface 22 interfering with the inner ring and a surface 21 interfering with an outer ring). The pocket 7 is formed in the cage 5 by press working. The cutting tool used when cutting the ball interference surface 23 of this pocket 7 and the cutting tool used when cutting and removing the decarbonization layer, are used in the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a constant velocity universal joint used in power transmission systems of automobiles and various industrial machines.

  Constant velocity universal joints are roughly classified into fixed type constant velocity universal joints that allow only angular displacement and sliding type constant velocity universal joints that allow angular displacement and axial displacement.

  The fixed type constant velocity universal joint is used, for example, in a steering shaft that transmits a rotational force of a steering wheel of an automobile to a wheel. On the other hand, the sliding type constant velocity universal joint is used for a drive shaft that transmits power from an engine to wheels. As a fixed type constant velocity universal joint, a Barfield type constant velocity universal joint (BJ) and an undercut free constant velocity universal joint (UJ) in which the maximum operating angle of the BJ is increased are widely known. In addition, as a sliding type constant velocity universal joint, a double offset type constant velocity universal joint (DOJ), a cross-clave type constant velocity universal joint (LJ), a tripod type constant velocity universal joint (TJ), etc. are widely known. It has been.

  FIG. 9 illustrates a double offset type constant velocity universal joint (DOJ) which is one of sliding type constant velocity universal joints. The constant velocity universal joint 101 includes an outer ring (outer joint member) 102 having an opening at one end, an inner ring (inner joint member) 103, a ball 104, and a cylindrical cage 105 as main parts. The inner ring 103, the ball 104, and the cage 105 are accommodated and arranged in the outer ring 102 and constitute an internal part 106.

  A plurality of track grooves 108 having a linear cross section are formed on the cylindrical inner peripheral surface of the outer ring 102 along the circumferential direction. A plurality of track grooves 109 having a linear cross section are formed on the outer spherical surface of the inner ring 103 along the circumferential direction. One ball 104 is interposed between the track groove 108 of the outer ring 102 and the track groove 109 of the inner ring 103, and these balls 104 are pockets 107 of the cage 105 disposed between the outer ring 102 and the inner ring 103. Is held by.

  A shaft 110 is inserted into the center hole 111 of the inner ring 103 and is spline-fitted. The shaft 110 is prevented from coming out of the center hole 111 in the axial direction by a circlip 112 interposed between the shaft 110 and the center hole 111 of the inner ring 103.

  The inner part 106 is prevented from coming out from the opening end 114 of the outer ring 102 in the axial direction by a circlip 113 fitted into the opening end 114 of the outer ring 102.

The cage 105 has a shape composed of a large-diameter portion 120 and a small-diameter portion 121 as shown in an enlarged view in FIG. Since the outer surface 120a of the large-diameter portion 120 contacts the cylindrical inner peripheral surface of the outer ring 102 to control the operation of the constant velocity universal joint 101, it is necessary to ensure strength. Therefore, only the outer surface 120a of the large-diameter portion 120 (the inner surface 122 is not processed) is subjected to quenching and cutting (hard processing) after soft processing (turning before quenching). On the other hand, the outer surface 121b and the inner surface 123 of the small diameter portion 121 are not processed after the soft processing (see Patent Document 1).
JP 2007-71394 A

  In the method of manufacturing a constant velocity universal joint disclosed in Patent Document 1, the outer surface 120a of the large-diameter portion 120 is not the entire cage, but the outer surface 120a of the large-diameter portion 120 that is cut after quenching when the cage is processed. Therefore, the number of times of cutting with a cutting tool (manual cutting tool, cutting machine, etc.) can be reduced. Therefore, it can suppress that the lifetime of a cutting tool falls.

  However, in the above case, since the portion whose hardness has been improved by the quenching process (HRC of 60 or more) is cut with a cutting tool, in particular, in the case of intermittent cutting with a pocket such as a cage, it is possible to perform a single cutting. The burden on the cutting tool increases, leading to a reduction in the life of the cutting tool. It is known that the inner ring 103 is also cut by quenching the outer spherical surface, but in this case as well, the burden imposed on the cutting tool by one cutting is large, leading to a reduction in the life of the cutting tool.

  The present invention has been made in view of the above circumstances, and reduces the burden on the cutting tool when cutting the surface of the cage and the inner ring after the quenching treatment, so that the cutting tool can be cut even in intermittent quenching steel cutting. An object of the present invention is to provide a constant velocity universal joint and a method for manufacturing the same that can surely suppress a decrease in life.

  In order to solve the above problems, a constant velocity universal joint according to the present invention includes an outer joint member having an opening in at least one, an inner joint member disposed inside the outer joint member, the outer joint member, and the inner joint member. A cage having a plurality of pockets formed in a circumferential direction, and being held in the cage in a state of being accommodated in the pocket, between the outer joint member and the inner joint member. In the constant velocity universal joint including a ball that enables torque transmission, at least one of the inner joint member or the cage has a decarburized layer by quenching treatment only on a surface of a non-specific part.

  Further, in order to solve the above-mentioned problems, a method for manufacturing a constant velocity universal joint devised by the present applicant includes an outer joint member having an opening on at least one side, and an inner joint member arranged inside the outer joint member. A cage that is disposed between the outer joint member and the inner joint member and has a plurality of pockets formed in a circumferential direction, and is held in the cage while being accommodated in the pocket, and the outer joint member, In a constant velocity universal joint provided with a ball that enables torque transmission with the inner joint member, after quenching the inner joint member and the cage, at least one of the inner joint member or the cage Is characterized in that a decarburized layer is formed on the surface of the specific part and the non-specific part by the quenching process, and thereafter only the specific part of the decarburized layer is cut and removed.

  In the constant velocity universal joint and the manufacturing method thereof according to the present invention described above, the “specific part” means an interference surface with other joint constituent members. For example, in the case of an inner ring, the interference surface with the cage and the ball In the case of the cage, the interference surface with the ball in the pocket and the interference surface with the outer ring and the inner ring. In addition, the “non-specific part” refers to a part excluding the specific part already described, that is, a part excluding an interference surface with another joint constituent member. Furthermore, specific and non-specific sites in the cage refer to the respective outer and inner surfaces. A decarburized layer is formed in both the specific part and the non-specific part.

  In the case of the constant velocity universal joint and the manufacturing method thereof according to the present invention described above, the decarburized layer formed on the surface of the specific part and the non-specific part of the inner joint member and the cage by the quenching process is then cut in the grinding process for the specific part. It is removed and the decarburized layer remains only in the non-specific part. In this case, in the inner joint member or the cage, the decarburized layer having a low carbon content (in other words, low hardness) does not remain on the interference surface (specific part) with the other joint component member, and the lower layer of the decarburized layer. Therefore, a portion (in other words, a portion with improved hardness) exposed to the carbon and having a high carbon content is exposed. Therefore, in the inner joint member or the cage, it is possible to ensure the wear resistance of the interference surface (specific part) with other joint constituent members. In addition, since the hardness of the decarburized layer is lower than the hardness of the conventional inner joint member and cage surface subjected to quenching treatment, the burden on the cutting tool (manual cutting tool or cutting machine) by a single cutting is small. Become.

  The carbon content of the decarburized layer is desirably 0.4 wt% or more and less than 0.8 wt%.

  When the carbon content of the decarburized layer is less than 0.4% by weight, the hardness of the decarburized layer is low, and the dimensional accuracy in the cutting process decreases. When the carbon content of the decarburized layer is 0.8% by weight or more, the decarburized layer is too hard, and when the decarburized layer is removed by cutting, the burden on the cutting tool is increased by a single cutting.

  In addition, the thickness of the decarburized layer needs to be a thickness that can be removed by cutting after quenching. Specifically, it is desirable to set it to 0.05 mm or more and less than 0.15.

  When the thickness of the decarburized layer is less than 0.05 mm, it is difficult to reduce the tool burden due to cutting, and it becomes difficult to obtain the intended function and effect of the present invention. Moreover, since the thickness of the decarburized layer remaining in the non-specific part (part excluding the specific part that is the interference surface) is low, it is difficult to sufficiently improve the strength of the inner joint member and the surface of the cage. Further, when the thickness of the decarburized layer is 0.15 mm or more, the decarburized layer cannot be completely removed by cutting, and the inner joint member or cage has a hardness on the interference surface (specific part) with other joint constituent members. A low decarburized layer may remain. This makes it difficult for the inner joint member or cage to sufficiently maintain the wear resistance of the interference surface with other joint constituent members.

  It is preferable that the cage is formed by press forming, then a decarburized layer is formed on the surface of the specific part and the non-specific part by quenching, and then only the specific part of the decarburized layer is removed by cutting.

  The pocket can be formed by pressing or milling, but when the pocket is formed by pressing, a decarburized layer is formed on the rough sheared surface, resulting in grain boundary embrittlement due to a low coal layer on the surface (particles). It is possible to reduce the fact that the arrangement balance between them is lost and the material formed by the particles becomes brittle. Thereby, the strength of the inner joint member and the cage can be improved.

  The cage cuts the ball interference surface of the pocket formed by pressing, and then forms a decarburized layer on the surface of the specific part and non-specific part by the quenching process, and then cuts the ball interference surface of the pocket It is preferable that the decarburized layer formed on the ball interference surface of the pocket is removed by cutting with the same cutting tool used in the above.

  It is not necessary to use a cutting tool with a high cutting force (capability of cutting a hard object) used in the cutting of the interference surface with the ball (hereinafter referred to as the ball interference surface) performed after the pocket formation. This is because the ball interference surface of the pocket is not hardened by the quenching process and can be easily cut even with a cutting tool having a low cutting force. Here, cutting processing after the conventional quenching process will be described. Conventionally, after the quenching process, the cutting tool used in the grinding process for cutting the surface of the specific part and the non-specific part of the cage is the pocket ball before the quenching process. It was necessary to use a tool having a higher cutting force than the cutting tool used for cutting the interference surface. This is different from the cutting tool used for cutting the ball interference surface of the pocket before quenching, and the cutting tool used for grinding the surface of specific and non-specific parts of the cage after quenching. Means you have to use.

  However, since the hardness of the decarburized layer of the present invention is lower than the surface of the conventional cage that has been quenched, the same cutting tool as that used for cutting the ball interference surface of the pocket that has not been hardened by the quenching process is used. It can be removed by cutting with a tool. In this case, since it is not necessary to change the cutting tool, the amount of the cutting tool used can be reduced, thereby reducing the equipment cost or the tool cost.

  The number of balls is not particularly limited, but may be eight, for example. When the number of balls is eight, the operation and effect of the present invention can be obtained more easily than when the number of balls is six. The reason for this will be described.

  When the number of balls is eight, it is necessary to form eight pockets for holding the balls. When the number of balls is six, it is necessary to form six pockets for holding the balls. In other words, when the number of balls is eight, the number of pockets that must be formed increases and the surface of the cage must be cut intermittently when the number of balls is eight. The number of times increases, and the burden on the cutting tool increases. This leads to a reduction in the life of the cutting tool. Therefore, as described above, the operation and effect of the decarburized layer according to the present invention is easier when the number of balls is eight than when the number of balls is six.

  As the quenching treatment, carburizing and quenching in which only the surface of the component is hardened by carburizing and the core portion is not quenched, or all-hardening quenching in which the entire component including the core portion is cured can be employed.

  Further, in the constant velocity universal joint and the manufacturing method thereof according to the present invention, the inner joint member and the cage form a decarburized layer on the surface of the specific part and the non-specific part by quenching, and the decarburized layer is the above-mentioned for the specific part. It is removed by cutting after the quenching process, and a decarburized layer remains in the non-specific part. Since the hardness of this decarburized layer is lower than the outer surface of conventional inner joint members and cages that have been hardened, the burden on the cutting tool during one cutting is significantly smaller than that of conventional products. Become. Therefore, it can suppress reliably that the lifetime of a cutting tool falls. Moreover, since the hardness of the decarburized layer is lower than that of the outer surface of the conventional inner joint member or cage that has been hardened by quenching, it can be easily removed by a cutting tool. Therefore, the time required for processing the inner joint member and the cage can be reduced.

  Further, in the inner joint member or cage, a specific portion, that is, an interference surface with another joint component member (for example, an inner joint member, an outer spherical surface that interferes with the cage, an interference surface with the ball, or a cage) The surface that interferes with the ball in the pocket, and the surface that interferes with the outer ring and the inner ring), the decarburized layer formed by the quenching process is cut and removed, and the portion hardened by the quenching process is exposed under the decarburized layer. . Therefore, it is possible to ensure wear resistance of the inner joint member and the interference surface of the cage.

  Embodiments of the present invention will be described below with reference to the accompanying drawings (FIGS. 1 to 8).

  FIG. 8 shows a constant velocity universal joint to which the present invention is applied. This constant velocity universal joint 1 is called an undercut free type constant velocity universal joint (UJ) which is one of fixed type constant velocity universal joints. However, the embodiment of the present invention is not limited to UJ, and can also be applied to DOJ (see FIG. 9).

  The constant velocity universal joint 1 includes an outer ring 2 (outer joint member) having an opening at one end, an inner ring 3 (inner joint member), a ball 4 and a cage 5 as main parts. An inner ring 3, a ball 4, and a cage 5 are housed and arranged in the outer ring 2 to constitute an internal component 6.

  On the inner spherical surface of the outer ring 2, eight track grooves 8 having a cross-sectional shape in which the opening side is linear and the anti-opening side is curved are formed at equal intervals in the circumferential direction. Further, on the outer spherical surface of the inner ring 3, eight track grooves 9 having a cross-sectional shape in which the opening side is curved and the non-opening side is linear are formed at equal intervals in the circumferential direction. One ball 4 is interposed between the track groove 8 of the outer ring 2 and the track groove 9 of the inner ring 3, and the balls 4 (total of eight balls) are arranged between the outer ring 2 and the inner ring 3. The cage 5 is held by eight pockets 7 formed in the circumferential direction.

  A shaft 10 is inserted into the center hole 11 of the inner ring 3 and is splined. The shaft 10 has a circlip 14 interposed between a concave groove 13 formed in a tip side portion thereof and a tapered surface 12 formed in a portion opposite to the opening of the center hole 11 of the inner ring 3. It is prevented from coming out of the central hole 11 in the axial direction.

  Below, the point which becomes the characteristic of this invention is described.

  2A shows a cross-sectional view of the cage 5, and FIG. 2B shows a vertical cross-sectional view of the cage 5. The cage 5 is formed of case-hardened low carbon steel (Scr415), and the surface (outer spherical surface) of a part (specific part) that interferes with other joint constituent members and a part (non-specific part) that does not interfere with other joint constituent members. The surface constituting the outer shape of the cage 5 including 21, the surface 23 interfering with the ball 4 in the pocket 7 and the surface constituting the inner shape of the cage 5 including the inner spherical surface 22) are hardened by heat treatment (carburizing and quenching). By this carburizing and quenching, a decarburized layer is formed on the surface of the cage 5, and as shown on the left side of the drawing in FIG. 3, the decarburized layer (dotted line portion in the drawing) from the surface side (lower side of the drawing), the hardened carburized layer ( The cross-hatched portion in the figure and the core (hatched portion in the figure) have a three-layer structure that is continuous in this order. The carbon content of the decarburized layer is desirably 0.4% by weight or more and less than 0.8% by weight. FIG. 6B is a graph showing the relationship between the depth (mm) and hardness (Hv: Beakers hardness) of each layer.

  As shown in the process diagram of FIG. 6 (A), the above-mentioned carburizing and quenching is first quenching for 130 minutes under the conditions of 950 ° C. and CP (carbon potential: the amount of atmospheric carbon in the carburizing furnace) = 1.3. And then quenching for 100 minutes under the conditions of 950 ° C. and CP = 0.8, further quenching for 30 minutes under the conditions of 850 ° C. and CP = 0.5, and then cooling with oil quenching. Do. By this carburizing and quenching, the decarburized layer is formed on the surface of the specific part and the non-specific part of the cage 5, and the part up to 0.1 mm or less is removed from the surface side as shown in the graph of FIG. It becomes a charcoal layer, and a portion from 0.1 mm to 0.6 mm becomes a carburized layer, and 0.6 mm or more becomes a core portion. For comparison with the carburizing and quenching process diagram according to the present embodiment shown in FIG. 6A, FIG. 7A shows a conventional carburizing and quenching process diagram. Moreover, in order to compare with the graph of FIG. 6 (B) which showed the relationship between the depth (mm) and hardness (Hv) of the layer formed in the cage 5 after carburizing and quenching according to the present embodiment, FIG. ) Shows the relationship between the depth (mm) and hardness (Hv) of the layer (carburized layer, core) formed in the cage after conventional carburizing and quenching.

  As shown in the process diagram of FIG. 6A and the process diagram of FIG. 7A, the difference between the carburizing and quenching of the present embodiment and the conventional carburizing and quenching is the CP at the time of quenching at 850 ° C. for 30 minutes. (Invention: CP = 0.5, conventional: CP = 0.8).

  Next, the manufacturing process of the cage 5 will be described with reference to the flowchart of FIG.

First, an outer surface and an inner surface of the short cylindrical hardened, low carbon steel (SCr415) was turned, the inner spherical surface 22 formed with an outer spherical surface 21, as shown in step (A), a steel Q ₁ ( Turning process).

And punching the steel Q ₁ by a pressing machine to form the eight pockets 7, as shown in step (b), the steel Q ₂ (pressing process).

Next, the ball interference surface 23 of the pocket 7 of the steel material Q ₂ is cut to form the steel material Q ₃ as shown in the step (c) (shaving step or milling step).

If carburizing and quenching the steel material Q _3, the cage 5 comprises a surface (outer spherical surface 21 of the specific portion and the non-specific sites is an interference surface between the other joint component (a site that does not interfere with the other joint components) A decarburization layer is formed on the surface forming the outer shape of the cage 5, the inner spherical surface 22 and the surface forming the inner shape of the cage 5 including the ball interference surface 23 of the pocket 7, as shown on the left side of FIG. from the surface side decarburized layers, cured carburized layer, the core portion is a continuous three-layer structure in this order, which, as shown in step (d), the steel Q ₄ (heat treatment step by carburizing and quenching).

Further, the decarburized layer formed on the surface of the steel material Q ₄ is removed by cutting with a cutting tool (manual cutting tool or cutting machine) to obtain a steel material Q ₅ (grinding step) as shown in the step (e).

Finally, the ball interference surface 23 of the pocket 7 of the steel Q ₅ and recut (decarburized layer is removed), and steel Q ₆ as shown in step (f) to complete the cage 5 (finishing step). Since the decarburized layer has a lower hardness than the surface of the conventional cage that has been quenched, it can be easily removed by cutting.

  In the present embodiment, in the cage 5, a decarburized layer is formed on the surface of the specific part and the non-specific part, so that the specific part (the surface 22 that interferes with the ball interference surface 23 and the inner ring 3 of the pocket 7 and the surface that interferes with the outer ring 2) When cutting and grinding 21), it is possible to significantly reduce the load applied to the cutting tool by one cutting. As a result, it is possible to greatly suppress a reduction in the life of the cutting tool. The reason for this is that, conventionally, the surface of the cage whose hardness is increased by the quenching process is cut, but in this embodiment, the surface having a decarburized layer whose hardness after the quenching process is lower than that of the conventional is cut. is there.

  Cutting of specific portions of the cage 5 (the ball interference surface 23 of the pocket 7 and the surface 22 that interferes with the inner ring 3 and the surface 21 that interferes with the outer ring 2) has been conventionally hardened by quenching after carburizing and quenching as described above. This is done by cutting a decarburized layer whose hardness is lower than that of the outer spherical surface and inner spherical surface of the cage. As a result, the workability of the cage 5 can be improved.

  In addition, after forming the decarburized layer on the surface of the cage 5, the decarburized layer has an interference surface with another joint component that is a specific portion, that is, a surface that interferes with the ball interference surface 23 of the pocket 7 and the inner ring 3. 22, in order to cut and remove the surface 21 that interferes with the outer ring 2, a decarburized layer is formed on a specific portion of the cage 5 (the ball interference surface 23 of the pocket 7 and the surface 22 that interferes with the inner ring 3, the surface 21 that interferes with the outer ring 2). The carburized layer located in the lower layer of the decarburized layer and hardened by carburizing and quenching is exposed. That is, in the cage 5, the non-specific part (the surface excluding the ball interference surface 23 of the pocket 7 and the surface 22 that interferes with the inner ring 3 and the surface 21 that interferes with the outer ring 2) has a decarburized layer. (The ball interference surface 23 of the pocket 7, the surface 22 that interferes with the inner ring 3, and the surface 21 that interferes with the outer ring 2) have no decarburized layer with low hardness. Therefore, in the cage 5, it is possible to ensure wear resistance of specific parts (the ball interference surface 23 of the pocket 7, the surface 22 that interferes with the inner ring 3, and the surface 21 that interferes with the outer ring 2).

  In the present embodiment, the thickness of the decarburized layer is 0.1 mm as shown in the graph of FIG. The thickness of the decarburized layer is preferably 0.05 mm or more and less than 0.15 mm. When the thickness of the decarburized layer is less than 0.05 mm, the tool burden due to cutting is hardly reduced, and the effect is low. On the other hand, when the thickness of the decarburized layer is 0.15 mm or more, the decarburized layer is too thick, and the decarburized layer cannot be completely cut and removed in the grinding process after carburizing and quenching. 23 and a surface 22 that interferes with the inner ring 3 and a surface 21) that interferes with the outer ring 2 may leave a decarburized layer with low hardness. Therefore, in the cage 5, it is difficult to sufficiently secure the wear resistance of specific portions (the ball interference surface 23 of the pocket 7 and the surface 22 that interferes with the inner ring 3 and the surface 21 that interferes with the outer ring 2).

  And in this embodiment, the cutting tool used when cutting the ball interference surface 23 of the pocket 7 of the cage 5 before the quenching process, and the specific portion of the cage 5 (the ball interference surface 23 and the inner ring 3) after carburizing and quenching. The same cutting tool is used when cutting and removing the decarburized layer formed on the interfering surface 22 and the outer ring 2 interfering surface 21). In this case, it is not necessary to change the cutting tool, and the amount of the cutting tool used can be reduced, so that the equipment cost or the tool cost can be reduced.

  The carbon content of the decarburized layer is desirably 0.4 wt% or more and less than 0.8 wt%, but if the carbon content of the decarburized layer is less than 0.4 wt%, the hardness of the decarburized layer Is low and the dimensional accuracy may be reduced. In addition, when the carbon content of the decarburized layer is 0.8% by weight or more, the carbon content is too high, and when the decarburized layer is removed by cutting, an excessive load is applied to the cutting tool. The intended effect of the present invention cannot be obtained.

  Next, the manufacturing method of the inner ring 3 will be described. However, the description of the overlapping part with the manufacturing method of the cage 5 described so far and the description of the operation and effect thereof are omitted or simplified.

  FIG. 4A shows a front view of the inner ring 3, and FIG. 4B shows a longitudinal sectional view of the inner ring 3. As with the cage 5 (see FIG. 2), the inner ring 3 forms a decarburized layer on the surface of the specific part and the non-specific part by carburizing and quenching, and as shown on the left side of the drawing in FIG. A three-layer structure in which a middle dotted line portion), a carburized layer (cross-hatched portion in the figure), and a core portion (hatched portion in the figure) are successively arranged.

  The quenching process for forming the decarburized layer described above is the same as the case of carburizing and quenching the surface of the specific part and the non-specific part of the cage 5, and is performed according to the procedure shown in the process diagram of FIG.

  Since the decarburized layer formed on the outer spherical surface 25 of the inner ring 3 is lower in hardness than the outer spherical surface of the conventional inner ring that has been quenched, it is easy to cut. Therefore, when the outer spherical surface 25 of the inner ring 3 and the surface 9 (track groove) interfering with the ball 4 are cut and removed after carburizing and quenching, the burden applied to the cutting tool by one cutting is significantly reduced compared to the conventional case. Therefore, it can suppress reliably that the lifetime of a cutting tool falls. Moreover, since the decarburized layer is easy to cut, the workability of the inner ring 3 can be improved.

  In the present embodiment, the heat treatment of the cage 5 and the inner ring 3 is carburized and quenched, but the present invention can also be implemented by fully hardening and quenching in which the core of the component is quenched. In this case, as shown on the right side of the drawing of FIG. 3 (in the case of the surface of the specific part and non-specific part of the cage 5) and on the right side of FIG. 5 (in the case of the surface of the specific part and non-specific part of the inner ring 3) A decarburized layer (dotted line portion in the figure) and a hardened layer (scattered dot pattern portion in the figure) are sequentially arranged from the side.

  A method of forming a decarburized layer by full hardening and quenching as described above will be described with reference to FIG. First, using low carbon steel (S48C) as a raw material, it is quenched for 50 minutes under the conditions of 880 ° C. and CP = 0.5, and then for 30 minutes under the conditions of 830 ° C. and CP = 0. Furthermore, it cools by oil quenching for 2 minutes on 50 degreeC conditions, and then cools after performing tempering for 120 minutes on 160 degreeC conditions.

  In the present embodiment, the number of the balls 4 is eight, but may be six. However, when the number of balls 4 is eight as in the present embodiment, the number of pockets 7 (8) that must be formed in the cage 5 is the cage when the number of balls 4 is six. 5 is larger than the number of pockets 7 (6) that must be formed. In this case, the number of times that the surface of the cage 5 has to be cut intermittently increases and the burden on the cutting tool increases, leading to a reduction in the life of the cutting tool. Therefore, when the number of balls 4 is eight, the operation and effect when the present invention is applied can be obtained more easily than when the number of balls 4 is six.

  As described above, since the constant velocity universal joint of the present embodiment forms a decarburized layer by quenching treatment on the inner ring 3 and the cage 5, the turning of the inner ring 3 and the cage 5 has a surface having a decarburized layer with low hardness. It is possible by cutting. In this case, a burden applied to the cutting tool by one cutting is smaller than that of the conventional constant velocity universal joint. Therefore, the life of the cutting tool can be extended.

  Further, in the decarburized layer, an interference surface with another joint component which is a specific part (in the inner ring 3, an outer spherical surface 25 that interferes with the cage 5, a surface 9 that interferes with the ball 4, and a pocket 7 in the cage 5) Hardened by carburizing and quenching of the decarburized layer lower layer in a specific part (interference surface) to remove the portions formed on the surface 23 that interferes with the ball 4, the surface 22 that interferes with the inner ring 3, and the surface 21 that interferes with the outer ring 2. The exposed carburized layer can be exposed. That is, the non-specific part (the surface of the part excluding the outer spherical surface 25 and the surface 9 that interferes with the ball 4) in the inner ring 3 and the non-specific part (the surface 22 that interferes with the ball interference surface 23 of the pocket 7 and the inner ring 3), The part excluding the surface 21 that interferes with the outer ring 2 is in a state having a decarburized layer, the specific part in the inner ring 3 (the surface 9 that interferes with the outer spherical surface 25 and the ball 4 of the inner ring 3), and the specific part in the cage 5 ( The interference surface 23 of the pocket 7, the surface 22 that interferes with the inner ring 3, and the surface 21 that interferes with the outer ring 2 can be made to have no decarburized layer. Therefore, in the inner ring 3 and the cage 5, an interference surface that is a specific part (in the inner ring 3, the surface 9 that interferes with the outer spherical surface 25 and the ball 4, and in the cage 5, it interferes with the ball interference surface 23 of the pocket 7 and the inner ring 3. Wear resistance of the surface including the surface 22 and the surface 21) that interferes with the outer ring 2 can be ensured.

  The embodiments of the present invention have been described above. However, the embodiments of the present invention are not limited to those described here, and can be appropriately changed within the scope not departing from the technical idea described in the claims. Is possible.

  For example, the present invention can also be applied to the case where two or more pockets have the same shape (except when all pockets have the same shape). In this case, the cage column strength (strength between the pockets) can be improved as compared with the case where all the pockets have the same shape. This is because the column cross-sectional area of the cage can be increased as compared with the case where all the pockets have the same shape.

  When the cage is cut after carburizing and quenching, the cage end surface is cut, and the spherical surface (outer spherical surface / inner spherical surface) or the inner side surface of the pocket is cut with reference to this end surface, thereby producing a highly accurate cage. . The reason for this is that the current standard is the cage end surface after quenching, and the irregularities on the cage surface are large. However, as described above, the position accuracy is improved by cutting the cage end surface and determining the reference surface. Thereby, when mass-producing a cage, the dimensional variation between cages can be suppressed.

It is a flowchart explaining the preparation process of the cage shown in FIG. (A) is a cross-sectional view of the cage shown in FIG. (B) is a longitudinal cross-sectional view of the cage shown in FIG. FIG. 9 is a cross-sectional view illustrating a state after quenching treatment on the outer spherical surface of the cage shown in FIG. (A) is a front view of the inner ring shown in FIG. FIG. 9B is a longitudinal sectional view of the inner ring shown in FIG. It is sectional drawing explaining the state after a hardening process in the outer spherical surface of the inner ring | wheel shown in FIG. (A) is process drawing explaining the process of carburizing and quenching performed when producing the cage and inner ring shown in FIG. (B) is a graph showing the relationship between the depth and hardness of each layer formed by carburizing and quenching in the cage and inner ring shown in FIG. FIG. 9C is a process diagram for explaining a process of full hardening and quenching performed when the cage and the inner ring shown in FIG. 8 are manufactured. (A) is process drawing explaining the process of carburizing and quenching performed when producing the cage and inner ring shown in FIG. (B) is a graph showing the relationship between the depth and hardness of each layer formed by carburizing and quenching in the cage and inner ring shown in FIG. 9. It is sectional drawing of the constant velocity universal joint (UJ) to which this invention is applied. It is sectional drawing of the conventional constant velocity universal joint (DOJ). It is a longitudinal cross-sectional view of the cage shown in FIG.

Explanation of symbols

1 Fixed type constant velocity universal joint (UJ)
2 Outer ring (outer joint member)
3 Inner ring (inner joint member)
4 ball 5 cage 7 pocket 21 outer spherical surface (cage)
22 inner spherical surface (cage)
23 Ball interference surface (pocket)
25 Outer spherical surface (inner ring)

Claims (12)

An outer joint member having an opening in at least one; an inner joint member disposed inside the outer joint member; and an outer joint member disposed between the outer joint member and the inner joint member. In a constant velocity universal joint comprising a formed cage and a ball held in the cage in a state of being accommodated in the pocket and enabling torque transmission between the outer joint member and the inner joint member ,
At least one of the inner joint member or the cage has a decarburized layer by quenching treatment only on the surface of the non-specific part.   The constant velocity universal joint according to claim 1, wherein the carbon content of the decarburized layer is 0.4 wt% or more and less than 0.8 wt%.   The constant velocity universal joint according to claim 1 or 2, wherein the thickness of the decarburized layer is 0.05 mm or more and less than 0.15 mm.   The constant velocity universal joint according to any one of claims 1 to 3, wherein the number of the balls is eight.   The constant-velocity universal joint according to any one of claims 1 to 4, wherein the decarburized layer is quenched by carburizing quenching or full hardening quenching. An outer joint member having an opening in at least one; an inner joint member disposed inside the outer joint member; and an outer joint member disposed between the outer joint member and the inner joint member. In a constant velocity universal joint comprising a formed cage and a ball held in the cage in a state of being accommodated in the pocket and enabling torque transmission between the outer joint member and the inner joint member ,
After quenching the inner joint member and the cage, at least one of the inner joint member or the cage forms a decarburized layer on the surface of the specific part and the non-specific part by the quenching process, and then the debonding is performed. A method for manufacturing a constant velocity universal joint, wherein only a specific portion of a coal layer is cut and removed.   The method for manufacturing a constant velocity universal joint according to claim 6, wherein the carbon content of the decarburized layer is 0.4 wt% or more and less than 0.8 wt%.   The method for manufacturing a constant velocity universal joint according to claim 6 or 7, wherein a thickness of the decarburized layer is 0.05 mm or more and less than 0.15 mm.   The cage forms the pockets by press working, forms a decarburized layer on the surface of the specific part and the non-specific part by the quenching process, and then cuts and removes only the specific part of the decarburized layer. The manufacturing method of the constant velocity universal joint as described in any one of these.   After forming the pocket by press working, the cage cuts the ball interference surface of the pocket, then forms a decarburized layer on the surface of the specific part and the non-specific part by the quenching process, and then the pocket The method for manufacturing a constant velocity universal joint according to any one of claims 6 to 9, wherein the decarburized layer is cut and removed with the same cutting tool as the cutting tool obtained by cutting the ball interference surface.   The method for manufacturing a constant velocity universal joint according to any one of claims 6 to 10, wherein the number of balls is eight.   The method for manufacturing a constant velocity universal joint according to any one of claims 6 to 11, wherein the quenching is carburized quenching or fully cured quenching.

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