JP2020079630A - Cage for constant velocity universal joint, and constant velocity universal joint - Google Patents

Abstract

To improve the strength of a cage without impairing the function thereof as a constant velocity universal joint.SOLUTION: A cage 5 has a pocket 15 capable of holding a ball 4, the pocket 15 including an edge 16 which the ball 4 can contact, and a carburized, quenched and hardened layer HL formed over the whole periphery of the edge 16, the edge 16 including a pair of first side part 16a opposed to each other in the axial direction to contact the ball 4, and a pair of second side part 16b connecting one first side part 16a to the other. In this cage 5, a thickness t3 of the carburized, quenched and hardened layer HL at a boundary 18 between the first side part 16a and the second side part 16b is smaller than a thickness t2 of the carburized, quenched and hardened layer HL at the first side part 16a.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a cage for constant velocity universal joints applied to automobiles and various industrial machines, and a constant velocity universal joint including the cage.

  A general constant velocity universal joint has an outer ring with a track groove formed on the inner spherical surface, an inner ring with a track groove formed on the outer spherical surface, a plurality of balls that transmit torque via the track grooves, and retain the balls. And a cage (retainer) that operates (for example, see Patent Document 1).

  In order to meet the demand for improved fuel economy (vehicle weight reduction) in automobiles and various industrial machines, constant velocity universal joints are constantly required to be smaller and lighter. The most difficult issue in downsizing and weight reduction of constant velocity universal joints is to secure sufficient strength at high operating angles. In order to evaluate this strength, a high-angle strength test is performed on the constant velocity universal joint. The rating in this test is highly dependent on the strength of the cage. Therefore, in order to reduce the size and weight of the constant velocity universal joint, the strength of the cage must be increased.

  For example, in Patent Document 2, in order to realize high strength, the ductility and hardness obtained by subjecting steel having a carbon content of 0.3 to 0.5% to quenching and tempering become uniform throughout. A cage thus provided is disclosed. The Vickers hardness of the cage is Hv500 to 650 (see claims 1 and 3 of the same document).

JP, 2000-104749, A Japanese Patent No. 4708430

  However, the cage disclosed in Patent Document 2 has a low hardness of Hv500 to 650 in order to increase the strength of the entire cage. Therefore, the wear resistance of the portion (rolling surface) in contact with the ball in the pocket of the cage is reduced, and abnormal noise or vibration may occur during use due to wear.

  The present invention has been made in view of the above circumstances, and a technical object thereof is to improve the strength of a cage without impairing the function as a constant velocity universal joint.

  The present invention is for solving the above-mentioned problems, and in a cage for a constant velocity universal joint including a pocket capable of holding a ball, the pocket includes an edge portion to which the ball can contact and an entire edge portion. A carburized and quenched hardened layer formed over the circumference, wherein the edge portion is a pair of first side portions that face each other in the axial direction so as to contact the ball, and a pair that connects the first side portions to each other. A second side portion of the carburizing quench hardening layer at the boundary between the first side portion and the second side portion is more than the thickness of the carburizing quench hardening layer at the first side portion. It is also characterized by being thin.

  According to such a configuration, by making the thickness of the carburizing and quenching hardened layer at the boundary portion thinner than the thickness of the carburizing and quenching hardened layer at the first side portion, the hardness of the boundary portion is lower than the hardness of the first side portion. Can be lowered. If the hardness of the boundary is high, the boundary may serve as a starting point of damage in the above high-angle strength test. Therefore, by lowering the hardness of this boundary portion, the ductility can be increased and the strength of the cage as a whole can be improved. On the other hand, since the first side portion has a hardness higher than that of the boundary portion, it is possible to improve the strength of the cage without impairing the wear resistance of the first side portion, that is, the function of the constant velocity universal joint. become.

  Further, the thickness of the carburizing and quenching hardened layer in the first side portion, since high dimensional accuracy is required, it is necessary to cut after quenching, than the thickness of the carburizing and quenching hardened layer in the second side portion. Becomes thinner. However, since the amount of scraping is small, the wear resistance of the first side is maintained.

  In the cage according to the present invention, the Vickers hardness on the surface of the boundary portion can be made lower than the Vickers hardness on the surface of the first side portion. Thereby, the strength of the cage can be improved without impairing the wear resistance of the first side portion.

  The Vickers hardness of the surface of the boundary portion is preferably Hv500 to 650. Thereby, the strength of the cage that can withstand the high-angle strength test can be secured.

  Since the constant velocity universal joint according to the present invention includes the cage having the above-mentioned features, it is possible to realize downsizing and weight saving without impairing its function.

  According to the present invention, the strength of the cage can be improved without impairing the function of the constant velocity universal joint.

It is a perspective view of a constant velocity universal joint concerning one embodiment of the present invention. It is a front view of a constant velocity universal joint. FIG. 3 is a sectional view taken along the line III-III of FIG. 2. It is a side view of a cage. It is a side view of the cage which expanded the A area|region of FIG. It is a flowchart which shows the manufacturing method of a cage. It is a side view of the cage after heat processing. It is a graph which shows the hardness distribution of the cage after heat processing. It is a side view of the cage in a pocket cutting process. It is a side view of the cage which expanded the B area|region of FIG. It is a side view of the cage in a pocket cutting process. It is a side view of the cage which expanded the C area|region of FIG.

  Hereinafter, modes for carrying out the present invention will be described with reference to the drawings. 1 to 12 show an embodiment of a constant velocity universal joint including a cage according to the present invention. 1 to 3 exemplify a fixed type constant velocity universal joint that allows only angular displacement between two axes.

  As shown in FIGS. 1 to 3, a constant velocity universal joint 1 includes an outer ring 2 as an outer joint member, an inner ring 3 as an inner joint member, a plurality of balls 4 for transmitting torque, and a ball 4. And a cage 5 (retainer) for holding.

  The outer ring 2 has a mouth portion 6 and a stem portion 7 protruding from the bottom wall of the mouth portion 6. The mouth portion 6 has a spherical inner spherical surface 8 inside thereof. The inner spherical surface 8 has a plurality of track grooves 9 formed in a curved shape. The plurality of track grooves 9 are formed at predetermined intervals in the circumferential direction of the outer ring 2. Each track groove 9 is formed along the axial direction X (see FIG. 3).

  The inner ring 3 has a center hole 10 and a spherical outer spherical surface 11. A shaft may be fitted in the central hole 10. A plurality of curved track grooves 12 are formed on the outer spherical surface 11. The plurality of track grooves 12 are formed at predetermined intervals in the circumferential direction of the inner ring 3. Each track groove 12 is formed along the axial direction X. Each track groove 12 is arranged so as to face the track groove 9 of the outer ring 2. As a result, the track groove 9 of the outer ring 2 and the track groove 12 of the inner ring 3 form a ball track that accommodates the ball 4.

  The ball 4 is housed in a ball track (track grooves 9 and 12) and transmits power between the outer ring 2 and the inner ring 3 while rolling within the range of the ball track. In the present embodiment, eight balls 4 are arranged in the constant velocity universal joint 1, but the number of the balls 4 is not limited to this example, and may be six, for example.

  As shown in FIGS. 1 to 5, the cage 5 is configured in an annular shape and is arranged in the space between the inner spherical surface 8 of the outer ring 2 and the outer spherical surface 11 of the inner ring 3. The cage 5 includes an outer spherical surface 13 and an inner spherical surface 14 each having a spherical shape, and a plurality of pockets 15 for holding the balls 4. As shown in FIG. 3, the outer spherical surface 13 is in contact with the inner spherical surface 8 of the outer ring 2. The cage 5 is made of carburizing steel such as chrome steel, chrome molybdenum steel, and nickel chrome molybdenum steel.

  The plurality of pockets 15 are formed at regular intervals in the circumferential direction of the cage 5 configured in an annular shape. The pocket 15 is a substantially rectangular opening. The pocket 15 holds the ball 4 by clearance fitting or press fitting. The pocket 15 has an edge portion 16 that divides the pocket 15 and a carburizing and quenching hardened layer HL formed over the entire circumference of the edge portion 16. As shown in FIGS. 4 and 5, the edge portion 16 has a pair of first side portions 16a that come into contact with the ball 4 and a pair of second side portions 16b that connect the pair of first side portions 16a to each other.

  The first side portion 16a is a linear portion that is orthogonal to the axial direction X. The pair of first side portions 16a are configured to face each other in the axial direction X. The first side portion 16a has a rolling surface 17 on which the ball 4 rolls while being in contact with the ball 4.

  The second side portion 16b is a curved portion that curves with a predetermined radius of curvature. The pair of second side portions 16b are configured to face each other in the circumferential direction of the cage 5. The distance between the pair of second side portions 16b is set to be larger than the diameter of the ball 4 so that a gap is formed between the pair of second side portions 16b and the ball 4 accommodated in the pocket 15.

  The carburizing and quenching hardened layer HL has different thicknesses at the first side portion 16a, the second side portion 16b, and the boundary portion 18 between the first side portion 16a and the second side portion 16b. That is, the thickness t1 of the carburizing and quenching hardened layer HL in the second side portion 16b is the thickest, and the thickness t2 of the carburizing and quenching hardened layer HL in the first side portion 16a is the next thickest. The thickness t3 of the hardened layer HL is the thinnest (see FIG. 5). Note that, in FIGS. 4 and 5, the carburizing and quenching hardened layer HL is shown by hatching in order to distinguish it from other portions (the same applies to FIGS. 7 and 9 to 12).

  The Vickers hardness of the rolling surface 17 in the first side portion 16a is preferably higher than Hv650, and more preferably Hv700 or higher. The Vickers hardness of the surface of the boundary portion 18 is the lowest and is preferably Hv500 to 650. Here, the surface (including the rolling surface 17) of the edge portion 16 (the first side portion 16a, the second side portion 16b, and the boundary portion 18) means the outer spherical surface between the outer spherical surface 13 and the inner spherical surface 14. A surface connecting 13 and the inner spherical surface 14.

  Next, a method for manufacturing the cage 5 having the above structure will be described. As shown in FIG. 6, this method includes a pipe cutting step S1, a press forming step S2, a turning step S3, a pocket forming step S4, a heat treatment step S5, a pocket cutting step S6, and a grinding step S7. Prepare

  In the pipe cutting step S1, the steel pipe is cut into a predetermined length to form an annular body as a base material of the cage 5. Then, a press molding step S2 is performed so that the outer peripheral surface and the inner peripheral surface of the annular body are formed into a spherical shape. Further, a turning step S3 is performed on the outer peripheral surface and the inner peripheral surface which are formed in a spherical shape. As a result, the outer spherical surface 13 and the inner spherical surface 14 of the cage 5 are formed in the annular body. At this point, the outer spherical surface 13 and the inner spherical surface 14 have no pockets 15 formed therein.

  Then, a pocket forming step S4 is performed to form the pocket 15 in the annular body. In the pocket forming step S4, a plurality of pockets 15 are penetratingly formed at predetermined intervals in the circumferential direction by punching the annular body. Then, the edge portion 16 of the pocket 15 is formed by shaving. In the pocket forming step S4, cutting allowances CMa and CMb are set in the pocket 15 in order to cut a part of the pocket 15 after the heat treatment step S5 (pocket cutting step S6). Hereinafter, the annular body after the pocket forming step S4 is referred to as a cage 5.

  In the subsequent heat treatment step S5, the pocket 15 (edge 16) of the cage 5 is carburized and quenched. Carburizing and quenching is a heat treatment in which carbon is infiltrated/diffused from the surface of a low carbon material, and then quenching is performed. In the case of steel, the vicinity of the surface with high carbon concentration is hard and has compressive residual stress, and the inside with low carbon concentration is low carbon martensite with high toughness. By the heat treatment step S5, the carburized and hardened layer HL having an increased hardness is formed on the edge portion 16 of the pocket 15. As shown in FIG. 7, the carburizing and quenching hardened layer HL before execution of the pocket cutting step S6 described later has a uniform thickness t1 (effective hardened layer depth: generally) over the entire circumference of the edge portion 16 of the pocket 15. Hv513 or more).

  In the present embodiment, the carburizing and quenching treatment includes carbonitriding and quenching treatment, and the carburizing and quenching hardening layer HL includes a carbonitriding and quenching hardening layer formed by carbonitriding and quenching processing.

  FIG. 8 shows the hardness distribution of the pocket 15 after the carburizing and quenching treatment. In FIG. 8, the distance from the surface of the edge portion 16 of the pocket 15 is shown as the depth of the carburized and quenched hardened layer HL on the horizontal axis, and the hardness of the carburized and quenched hardened layer HL is shown on the vertical axis. As shown in FIG. 8, the carburizing and quenching hardened layer HL has the highest hardness (indicated by symbol Hv1) on the surface of the edge portion 16, and the hardness decreases as the depth from the surface increases.

  In the pocket cutting step S6, the boundary portion 18 is cut so as to reduce the hardness of the boundary portion 18 of the edge portion 16. Further, in the pocket cutting step S6, the first side portion 16a is cut in order to hold the ball 4 in a predetermined clearance and interference. Hereinafter, the pocket cutting step S6 will be described in detail.

  In the pocket cutting step S6, the cutting margins CMa and CMb set on the edge portion 16 of the pocket 15 are removed by a cutting tool. As shown in FIGS. 9 and 10, the cutting margins CMa and CMb are a first cutting margin CMa set on the first side portion 16 a of the edge portion 16 and a second cutting margin CMb set on the boundary portion 18. including. The second cutting margin CMb is set to be larger than the first cutting margin CMa. In this specification, cutting the carburized and hardened layer HL after the heat treatment step S5 (after hardening) is referred to as "hardened steel cutting". In FIGS. 9 and 10, in order to distinguish between the cutting allowances CMa, CMb and the carburizing and quenching hardened layer HL, hatching different from the carburizing quenching hardened layer HL is attached to the cutting allowances CMa, CMb and displayed. (The same applies to FIGS. 11 and 12).

  11 and 12 show the cage 5 with the second cutting margin CMb removed in the pocket cutting step S6. By removing the second cutting margin CMb by cutting the hardened steel, the boundary portion 18 is formed between the first side portion 16a and the second side portion 16b.

  As shown in FIGS. 11 and 12, the first cutting margin CMa remains on the first side portion 16a of the cage 5. In the pocket cutting step S6, the first cutting margin CMa is removed by quenching steel cutting. As a result, the rolling surface 17 is formed on the pair of first side portions 16a.

  In the first side portion 16a, the thickness t2 of the carburized and hardened layer HL becomes smaller than the thickness t1 before cutting by removing the first cutting margin CMa. Further, as shown in FIG. 8, the hardness of the rolling contact surface 17 becomes the hardness Hv2 at the depth position D1 corresponding to the first cutting margin CMa from the surface of the edge portion 16 before the pocket cutting step S6. Therefore, the hardness Hv2 of the rolling surface 17 is lower than the hardness Hv1 of the surface of the second side portion 16b.

  At the boundary portion 18, by removing the second cutting margin CMb, the thickness t3 of the carburizing and quenching hardened layer HL becomes thinner than the thickness t2 of the carburizing and quenching hardened layer HL on the rolling surface 17. Further, as shown in FIG. 8, the hardness of the surface of the boundary portion 18 is the hardness Hv3 at the depth position D2 corresponding to the second cutting margin CMb from the surface of the edge portion 16 before the pocket cutting step S6. Since the second cutting margin CMb is larger than the first cutting margin CMa, the hardness Hv3 of the surface of the boundary portion 18 is lower than the hardness Hv2 of the rolling surface 17.

  Finally, in the grinding step S7, the outer spherical surface 13 and the inner spherical surface 14 of the cage 5 are ground by a grinding tool.

  According to the cage 5 of the constant velocity universal joint 1 according to the present embodiment described above, the thickness t3 of the carburizing and quenching hardened layer HL at the boundary portion 18 between the first side portion 16a and the second side portion 16b in the pocket 15 is set. Is made thinner than the thickness t2 of the carburized and hardened layer HL of the first side portion 16a, the hardness of the boundary portion 18 can be made lower than the hardness of the first side portion 16a. When the hardness of the boundary portion 18 is high, the boundary portion 18 can be a starting point of damage when the high-angle strength test of the constant velocity universal joint 1 is performed. Therefore, it is possible to improve the strength of the cage 5 as a whole by reducing the hardness of the boundary portion 18 to enhance the ductility and suppressing the crack sensitivity. As a result, the same strength can be obtained even if the thickness of the cage 5 is reduced, and the size and weight of the cage 5 can be reduced.

  On the other hand, with respect to the first side portion 16a, the hardness of the rolling contact surface 17 is set to the boundary by setting the first cutting margin CMa of the first side portion 16a to be smaller than the second cutting margin CMb of the boundary portion 18 and cutting the hardened steel. The hardness can be higher than that of the portion 18. Therefore, the strength of the cage 5 can be improved without impairing the wear resistance of the first side portion 16a (rolling surface 17), that is, the function of the constant velocity universal joint 1.

  It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and is not limited to the above-described operational effects. The present invention can be variously modified without departing from the scope of the present invention.

  The present invention can be applied to all constant velocity universal joints provided with a cage. Examples of the constant velocity universal joint include a barfield type (Rzeppa type), a fixed undercut-free type, a sliding double offset type, and a cross groove type.

  In the above embodiment, an example in which the rolling surface 17 and the boundary portion 18 are formed in the pocket 15 of the cage 5 by performing the hardened steel cutting in the pocket cutting step S6 has been shown, but the present invention is limited to this aspect. It is not something that will be done. For example, the rolling surface 17 and the boundary portion 18 may be formed by grinding without cutting the hardened steel.

1 constant velocity universal joint 4 ball 5 cage 15 pocket 16 edge portion 16a first side portion 16b second side portion 18 boundary portion HL carburizing and quenching hardened layer X axial direction

Claims (5)

In a cage for constant velocity universal joints equipped with pockets that can hold balls,
The pocket includes an edge portion with which the ball can come into contact, and a carburizing quench hardening layer formed over the entire circumference of the edge portion,
The edge portion includes a pair of first side portions that face each other in the axial direction so as to contact the ball, and a pair of second side portions that connect the first side portions to each other,
A constant velocity characterized in that the thickness of the carburized and quenched hardened layer at the boundary between the first side portion and the second side portion is smaller than the thickness of the carburized and quenched hardened layer at the first side portion. Universal joint cage.   The cage for a constant velocity universal joint according to claim 1, wherein the thickness of the carburized and quenched hardened layer at the first side portion is smaller than the thickness of the carburized and quenched hardened layer at the second side portion. ..   The cage for a constant velocity universal joint according to claim 1 or 2, wherein a Vickers hardness on a surface of the boundary portion is lower than a Vickers hardness on a surface of the first side portion.   The cage for constant velocity universal joint according to claim 3, wherein Vickers hardness of the surface of the boundary portion is Hv500 to 650. A constant velocity universal joint comprising the cage for constant velocity universal joint according to claim 1.

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