JP5680452B2 - Heat treatment method, outer joint member, and tripod type constant velocity universal joint - Google Patents

Description

  The present invention relates to a heat treatment method, an outer joint member, and a tripod type constant velocity universal joint.

  Constant velocity universal joints used in power transmission devices such as automobiles and various industrial machines include tripod type constant velocity universal joints using trunnions as inner joint members. For example, as shown in FIG. 18, the tripod type constant velocity universal joint includes an outer joint member 1, a trunnion 2 as an inner joint member, and a torque transmission member (roller member) 3.

  The outer joint member 1 includes a cup-shaped mouth portion 4 opened at one end, and three track grooves 6 extending in the axial direction are formed on the inner peripheral surface of the mouth portion 4. Roller guide surfaces (roller contact surfaces) 7 and 7 are formed on the side walls of each track groove 6 facing each other in the circumferential direction.

  The trunnion 2 includes a boss 8 and a leg shaft 9. The boss 8 is formed with a spline or serration hole 11 which is coupled to a shaft (not shown) so as to be able to transmit torque. The leg shaft 9 protrudes in the radial direction from the circumferentially divided position of the boss 8.

  The torque transmission member 3 includes a roller 12 made of a ring-shaped body whose outer diameter surface 13 is a convex spherical surface, and a ring 15 that is fitted into the roller 12 via a plurality of rollers 16. That is, the roller 12 and the ring 15 are unitized via a plurality of rollers 16, and these constitute a roller assembly. In this case, the roller 12 can be called an outer roller, and the ring 15 can be called an inner roller.

  By the way, the outer joint member 1 includes a mouth portion 4 having a track groove 6 and a stem portion (not shown) protruding from the bottom wall of the mouth portion 4. Further, the inner diameter surface of the mouse portion 4 has a three-valve corollary shape in which small inner diameter portions 7b and large inner diameter portions 7c that appear alternately in the circumferential direction are connected by a roller guide surface 7a. That is, in the outer joint member 1, track grooves 6 including a roller guide surface 7a facing in the circumferential direction and a large inner diameter portion 7c provided between the roller guide surfaces 7a and 7a are formed at three locations on the inner periphery. Is.

  In general, the roller guide surface 7a of the outer joint member 1 is subjected to thermosetting treatment. There is induction hardening as the thermosetting treatment, and induction hardening includes a one-shot (one-shot) hardening method (Patent Document 1) in which heat treatment is performed at a fixed position, and moving hardening in which the coil and the outer joint member move relatively. It is broadly divided into the input method (Patent Document 2).

  As shown in FIG. 13, the one-shot quenching uses a high-frequency heating device including a high-frequency induction heating coil 17 having heating portions 17 a, 17 a, and 17 a that are respectively fitted into the three track grooves 6 of the outer joint member 1. For this reason, the roller guide surface 7a can be heated and cooled at once over the entire region in the joint axial direction. In Patent Document 1, a non-conductive ferrite core is attached to the induction coil in order not to form a hardened layer on the inner surface of the large inner diameter portion 7c. For this reason, by using such a high-frequency heating device, the hardened layer S can be formed only on the surface of the roller guide surface 7a as shown in FIG.

  In the moving quenching method, a high-frequency heating apparatus shown in FIGS. 15 to 17 is used. The high-frequency heating apparatus includes a coil 18 wound in a three-leaf clover shape and a cooling jacket 19 attached to the coil 18. The coil 18 includes substantially triangular heating portions 18a, 18a, 18a disposed at a pitch of about 120 ° along the circumferential direction. The heating unit 18a includes curved portions 20a and 20a facing the roller guide surface 7a, and a linear portion 20b facing the large inner diameter portion 7c. The shape of the cooling jacket 19 is a three-leaf clover shape similar to the coil 18.

  In this moving quenching method, the coil 18 and the cooling jacket 19 are moved in the mouth portion 4 of the outer joint member 1 along the axial direction. Along with this movement, the heating surface (the roller guide surface 7a and the large inner diameter portion 7c) is heated, and this heating surface is rapidly cooled by the cooling water ejected from the cooling jacket 19 following this heating. For this reason, as shown in FIG. 17, the roller guide surface 7a and the large inner diameter portion 7c are heat-cured to form a cured layer S.

Japanese Patent Publication No. 61-34481 Japanese Utility Model Publication No. 3-26335

  In a general one-shot (one-shot) quenching method, since heating is performed at a time and cooling is performed at a time, there is a demerit that distortion is likely to occur in a thin portion or the like. On the other hand, the moving quenching has the effect of stabilizing the generated strain and making the quench hardened layer depth uniform.

  By the way, considering the function of the joint, there is no problem as long as at least the roller guide surface 7a is provided with a hardened layer. However, if moving quenching is performed, as shown in FIG. 16, the roller guide surface 7a and the large inner diameter portion 7c are heat-cured to form the hardened layer S.

  A boot band fastening groove 5 is formed on the outer periphery of the outer joint member 1, and the thickness of this portion is thin. For this reason, in this thin part, the hardened layer S may come off to the outer peripheral side, and this part may become weak in strength. For this reason, there existed a demerit that the freedom degree of design, such as it becoming difficult to miniaturize a joint, was restricted.

  Therefore, in view of such circumstances, the present invention is a heat treatment method that can form an outer joint member of a tripod type constant velocity universal joint that is excellent in strength without forming a hardened layer in a large inner diameter portion by induction hardening of induction hardening. The present invention intends to provide an outer joint member and a tripod type constant velocity universal joint configured by such a heat treatment method.

In the heat treatment method of the present invention, three track grooves extending in the axial direction are provided on the inner periphery, and guide surfaces facing each other are provided on the inner side wall of each track groove, thereby forming a large inner diameter portion provided between the two guide surfaces. The outer joint member of the tripod type constant velocity universal joint having a trunnion having three leg shafts and the leg shaft of the trunnion being in direct sliding contact with the guide surface of the outer joint member. As the induction heating coil moves relatively in the axial direction, the outer joint member is heated by moving and quenching in order to heat the guide surface sequentially and to rapidly cool the heated area of the guide surface with a cooling fluid following this heating. The high frequency induction heating coil includes three heating portions arranged at equal intervals along the circumferential direction, and is a heat treatment method for forming a hardened layer on the guide surface of the high frequency induction heating coil. surface facing the large diameter portion To form a recessed portion in the circumferential direction central portion, to the recessed portion forms a flat-plate, by fitting the ferromagnetic core as a magnetic line blocking member that blocks magnetic force lines generated in the high-frequency induction heating coil A portion for suppressing the heating of the large inner diameter portion is provided, and the boot mounting portion corresponding range at least in the central portion in the circumferential direction in the large inner diameter portion of the outer joint member is defined as an unbaked portion.

  According to the heat treatment method of the present invention, the hardened layer is formed on the guide surface without forming a hardened layer in the boot mounting portion corresponding range at least in the circumferential central portion of the large inner diameter portion of the outer joint member by induction hardening by induction hardening. Can be formed.

  The part that suppresses the heating of the large inner diameter portion is a magnetic field line blocking body that blocks the magnetic field lines generated in the high frequency induction heating coil. It is composed of a ferromagnetic core to be fitted. The ferromagnetic core is made of, for example, silicon steel.

  In the high frequency induction heating coil in which a portion close to the large inner diameter portion is retracted, the boot mounting portion corresponding range at least in the center in the circumferential direction in the large inner diameter portion of the outer joint member may be set as an unbaked portion.

  As described above, in the case where the high frequency induction heating coil retracts the portion close to the large inner diameter portion, at least the boot mounting portion corresponding range in the central portion in the circumferential direction in the large inner diameter portion is not heated in this heat treatment and is not baked. Part.

  In addition, on the outer diameter side of the guide surface of the outer joint member, a flange portion extending in a direction approaching so as to form a substantially right angle to the guide surface is provided, and at least the boot mounting portion corresponding range in the large inner diameter portion is set to the non-heating portion. There may be an unbaked part.

  Thus, by providing the collar portion, at least the boot mounting portion corresponding range in the large inner diameter portion is not heated in this heat treatment, and becomes an unbaked portion. Moreover, it is preferable to form a hardened layer on the inner surface of the buttocks.

  In each of the heat treatment methods, the outer joint member may have a small inner diameter portion formed between the large inner diameter portions, and a hardened layer may be formed on the small inner diameter portion by the moving quenching. Further, the entire inner diameter portion of the outer joint member may be an unbaked portion.

  On the back side of the large inner diameter portion of the outer joint member, a boot mounting groove or the like is not formed on the outer diameter surface of the outer joint member. For this reason, an unbaked part can be prevented from being provided on the joint back side of the large inner diameter part of the outer joint member. Further, a hardened layer may be provided only on the guide surface on the inner diameter side of the outer joint member.

  The mutually opposing guide surfaces of the outer joint member may be parallel flat surfaces. By setting in this way, even if the operating angle is taken and the center of the outer joint member and the center of the trunnion are eccentric, this eccentricity can be absorbed. In particular, the flat surface preferably has a guide surface width that allows for an increase in leg shaft cross-sectional width when the operating angle is taken and the center of the outer joint member and the center of the trunnion are eccentric.

  The outer joint member of the tripod type constant velocity universal joint is processed by the heat treatment method.

  The tripod type constant velocity universal joint of the present invention uses an outer joint member processed by the heat treatment method.

  In the heat treatment method of the present invention, a hardened layer can be formed on the guide surface without forming a hardened layer at least in the boot mounting portion corresponding range at the center portion in the circumferential direction in the large inner diameter portion of the outer joint member. For this reason, the intensity | strength of the opening part of an outer joint member is securable. Moreover, since it is moving quenching, distortion is less likely to occur and the depth of the quenched and hardened layer can be made uniform.

  If the magnetic field blocker is composed of a ferromagnetic core, the unbaked portion can be formed stably. The ferromagnetic core can be made of, for example, silicon steel and can be mounted on the high-frequency induction heating coil at a relatively low cost without using a special (special) material. In addition, in the case of using a high frequency induction heating coil in which a portion close to the large inner diameter portion is retracted, the ferromagnetic core constituting the magnetic force line blocker can be omitted, and the configuration of the high frequency induction heating device is simplified and the cost is reduced. Can be achieved. Further, when the outer joint member has the flange portion, the unfired portion in the large inner diameter portion can be stably formed.

  Even if the outer diameter of the outer joint member is the unbaked part, or the non-baked part is not provided on the inner side of the large inner diameter part, the hardened layer is provided only on the guide surface. The hardened layer can be formed in the optimum range without impairing the function as the outer joint member.

  Since the outer joint member of the tripod type constant velocity universal joint of the present invention is processed by the heat treatment method, it is stable in strength and excellent in durability. By the way, by making the guide surfaces facing each other into parallel flat surfaces, it is possible to obtain a stable operating angle.

  Since the tripod type constant velocity universal joint of the present invention uses the outer joint member treated by the heat treatment method, it becomes a high quality tripod type constant velocity universal joint excellent in durability, and further, downsizing of the joint, etc. The degree of design freedom increases. In the case where the leg shaft of the trunnion is in direct sliding contact with the guide surface of the outer joint member, such as the first tripod type constant velocity universal joint, the rollers and needle rollers as the torque transmission member can be omitted, and the number of parts can be reduced. Can be reduced, and assemblability can be improved and costs can be reduced. Even in the second tripod type constant velocity universal joint, the number of parts can be relatively reduced.

It is sectional drawing which shows the relationship between the high frequency induction heating coil and outer joint member which are used for the heat processing method which shows embodiment of this invention. It is a perspective view of the said high frequency induction heating coil. It is a top view of the said high frequency induction heating coil. It is a cross-sectional view of a tripod type constant velocity universal joint showing a comparative example. It is a longitudinal cross-sectional perspective view of the outer joint member of the said tripod type constant velocity universal joint. It is principal part sectional drawing which shows other embodiment of an outer joint member. It is a top view of other high frequency induction heating coils. It is principal part sectional drawing of the tripod type | mold constant velocity universal joint of this invention. It is a longitudinal cross-sectional view of the tripod type constant velocity universal joint shown in the said FIG. It is a longitudinal cross-sectional view of the state where the tripod type constant velocity universal joint shown in FIG. It is a cross-sectional view of the outer joint member of the tripod type constant velocity universal joint shown in FIG. The trunnion of the tripod type constant velocity universal joint shown in the said FIG. 8 is shown, (a) is a cross-sectional view, (b) is a top view of a leg axis | shaft. It is a perspective view of the heat-heating process state by the one-shot hardening method. It is principal part sectional drawing of the heat-heating process state by the one-shot hardening method. It is a perspective view of the high frequency induction heating coil and outer joint member by the conventional moving hardening method. It is a perspective view of the heat-heating process state by the conventional moving quenching method. It is principal part sectional drawing of the heat-heating process state by the conventional moving quenching method. It is a cross-sectional view of a tripod type constant velocity universal joint using an outer joint member formed by a conventional heat treatment method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a main part of an outer joint member that is heat-cured by the heat treatment method according to the present invention. The outer joint member is a tripod type constant velocity free as shown in FIG. 4 showing a comparative example. Used for joints. The tripod type constant velocity universal joint includes an outer joint member 21 and a trunnion 22 as an inner joint member.

  The outer joint member 21 has a cup-shaped mouth portion 24 opened at one end and a shaft portion (stem portion) 25 protruding from the bottom wall of the mouth portion 24. A track groove 26 extending in the axial direction is formed at a position equally divided in three directions. The mouse portion 24 has a non-cylindrical shape in which a large diameter portion 24a and a small diameter portion 24b appear alternately when viewed in a cross section. That is, the mouse portion 24 is formed with the large-diameter portion 24a and the small-diameter portion 24b, whereby the three track grooves 26 extending in the axial direction are formed on the inner peripheral surface thereof.

  Guide surfaces 27 are formed on the side walls of each track groove 26 facing in the circumferential direction. The inner diameter surface has a three-valve corollary shape in which small inner diameter portions 45 and large inner diameter portions 46 that appear alternately in the circumferential direction are connected by a guide surface 27. That is, the outer joint member 21 is formed with the track groove 6 composed of the guide surface 27 facing in the circumferential direction and the large inner diameter portion 46 provided between the guide surfaces 27, 27 at three locations on the inner periphery. is there.

  The trunnion 22 includes a boss 28 and a leg shaft 29. The boss 28 is formed with a spline or serration hole 31 that is coupled to a shaft (not shown) so as to be able to transmit torque. The leg shaft 29 protrudes in the radial direction from the circumferentially divided position of the boss 28.

  The roller 23 is a ring-shaped body having an outer diameter surface 23a that is a convex spherical surface and an inner diameter surface 23b that is a cylindrical surface. That is, the outer diameter surface of the leg shaft 29 is a cylindrical surface, the inner diameter surface 23b of the roller 23 is a cylindrical surface in accordance with this, and the cross-sectional shape of the guide surface 27 is a concave curved surface. The outer diameter surface 23a is a convex spherical surface.

  By the way, the opening of the outer joint member 21 is sealed by a boot (not shown). The boot includes a large-diameter portion, a small-diameter portion, and a bellows portion that connects the large-diameter portion and the small-diameter portion. Further, as shown in FIG. 5, a boot mounting portion 44 having a concave groove 43 is formed on the opening side of the outer diameter surface of the outer joint member 21. A large diameter portion of the boot is externally fitted to the boot mounting portion 44, and the large diameter portion of the boot is mounted on the boot mounting portion 44 of the outer joint member 21 by tightening the large diameter portion with a boot band. . As described above, a shaft is connected to the trunnion 22, and a boot mounting portion having a concave groove is also formed on the shaft. Then, the small diameter portion of the boot is fitted on the boot mounting portion of the shaft, and the small diameter portion of the boot is mounted on the boot mounting portion of the shaft by tightening the small diameter portion with a boot band.

  The trunnion 22 is subjected to heat treatment, and this heat treatment is performed by carburizing quenching and tempering or carbonitriding quenching and tempering. Carburizing and quenching is a method in which carbon is infiltrated / diffused from the surface of a low carbon material and then quenched. Carbonitriding and quenching is a method in which carbon and nitrogen are diffused and hardened, whereas carburizing and quenching is a method of diffusing carbon and nitrogen, especially surface hardening of free-cutting steel (SUM), low carbon steel, SPCC materials, etc. Applied to improving fatigue strength. Compared with carburizing and quenching, the processing temperature is low, dimensional change and distortion are generally small, and it can be used in many precision parts.

  The outer diameter surface of the leg shaft 29 of the trunnion 22 is finished by grinding or hardened steel cutting. Grinding is to grind the surface of a workpiece with grindstone particles (abrasive grains), smooth the surface, and perform precision finishing. Also, hardened steel cutting is simply cutting, and since cutting is usually performed in the state of raw material, it was called hardened steel cutting in order to clarify that the cutting was after heat treatment (after quenching). . Since cutting is performed after quenching, the heat treatment deformation of the material can be removed in this cutting process. Further, the grinding oil cutting does not require a grinding oil agent that is normally required for grinding, enabling dry processing, and reducing the load on the environment.

  The heat treatment may be induction hardening. Induction hardening is a hardening method that applies the principle of heating a conductive object by placing a portion necessary for hardening in a coil through which high-frequency current flows and generating Joule heat by electromagnetic induction. Induction hardening can perform partial quenching, increase fatigue strength, improve wear resistance, use carbon steel that is cheap in material, and easily adjust the quenching conditions and adjust the effective depth, etc. There are advantages.

  In the case where the hardening process is performed by induction hardening and tempering, a hardened layer is formed at least on a portion (outer diameter surface of the leg shaft 29) that is in contact with the leg shaft root 10 and the roller 23. For this reason, the part which omits the site | part which contacts the leg shaft root 10 and the roller 23 is a forging skin.

  A hardened layer S (see FIG. 1) is formed on the inner diameter surface of the mouth portion 24 of the outer joint member 21. In this case, an unbaked portion 50 is formed in the large inner diameter portion 46. In the illustrated example, the unbaked portion 50 is not the entire large inner diameter portion 46, but the hardened layer S is formed at the circumferential end portion.

  For the formation of the hardened layer S, a high-frequency heating device 52 having a high-frequency induction heating coil 51 shown in FIGS. 2 and 3 is used. The high frequency induction heating coil 51 includes three substantially triangular heating parts 51A, 51B, 51C arranged in a three-leaf clover shape. Each of the heating parts 51A, 51B, 51C has curved parts 53, 53 facing the guide surface 27 and a straight part 54 facing the large inner diameter part 46.

  In addition, a concave portion 55 is provided in the central portion of the surface facing the large inner diameter portion of the linear portion 54, and a magnetic field line blocking body A including a ferromagnetic core 56 is disposed in the concave portion 55. In this case, the recessed portion 55 is a rectangular recessed portion, and a flat plate-shaped ferromagnetic core 56 is fitted into the recessed portion 55. The length L in the longitudinal direction of the ferromagnetic core 56 is set shorter than the length L1 in the longitudinal direction of the recessed portion 55, and the length W in the short direction of the ferromagnetic core 56 is the length in the short direction of the recessed portion 55. Is set substantially the same as the length W1. For this reason, the upper surfaces of the heating parts 51A, 51B, 51C and the upper surface of the ferromagnetic core 56 are arranged on the same plane, and the lower surfaces of the heating parts 51A, 51B, 51C and the lower surface of the ferromagnetic core 56 are on the same plane. Placed on top. In addition, gaps 60 are formed between the side surface of the recessed portion 55 and the side surface corresponding to the ferromagnetic core 56. The thickness T of the ferromagnetic core 56 is set to be larger than the depth T1 of the recessed portion 55, and the outer surface 56a of the ferromagnetic core 56 is formed on the straight portion 54 of the heating unit 51A (51B, 51C). It protrudes slightly toward the large inner diameter portion from the outer surface (large inner diameter portion facing surface) 54a.

  Although not shown, a cooling jacket as shown in FIG. 15 or the like is attached below the high-frequency induction heating coil 51. The cooling jacket is composed of a cooling pipe through which cooling water flows, and its shape substantially coincides with the shape of the high-frequency induction heating coil 51.

  A high-frequency current is passed through the high-frequency induction heating coil 51 from a high-frequency power supply (not shown). At this time, the high-frequency current flows in the order of the heating unit 51A → the heating unit 51B → the heating unit 51C. In this way, an induced electromotive force is generated by the electromagnetic induction action when the high-frequency current flows. Due to this electromagnetic induction action, Joule heat is generated, and the guide surface 27 and the like of the outer joint member 21 can be heated.

  For this reason, the high frequency induction heating coil 51 is sequentially moved from the opening side of the mouse part to the back side of the mouse part. Thereby, the guide surface 27 and the like are heated from the opening side to the back side. Further, the cooling jacket moves with the movement of the high-frequency induction heating coil 51, and cooling fluid (cooling water) is jetted from the cooling jacket to the heating portion of the outer joint member 21 to be cooled. That is, the guide surface 27 and the like are sequentially heated in accordance with the relative movement of the high-frequency induction heating coil 51, and the heating part is rapidly cooled by the cooling fluid following that, so that induction hardening is performed.

  By the way, since each of the heating parts 51A, 51B, 51C of the high frequency induction heating coil 51 is provided with a ferromagnetic core 56, the high frequency induction heating coil 51 generates the ferromagnetic core 56. Magnetic field lines will be cut off. In other words, the ferromagnetic core is made of a material having a high magnetic permeability and is attached to the coil so as to concentrate the magnetic field lines on the work and thereby enhance the power. On the other hand, the ferromagnetic core is used to block the magnetic field lines and prevent unintended heating. For this reason, as in the present invention, if the inner surface of the outer joint member 21 of the tripod type constant velocity universal joint is used for the heat curing process, the unfired portion 50 can be added to the large inner diameter portion 46 which is impossible with the conventional moving firing. Can be provided. Therefore, as shown in FIG. 1, an unbaked portion 50 in which the hardened layer S is not formed is formed in the large inner diameter portion 46 facing the ferromagnetic core 56.

  In the heat treatment method of the present invention, the hardened layer S can be formed on the guide surfaces 27 and 27 without forming the hardened layer S on the large inner diameter portion 46 of the outer joint member 21. For this reason, the intensity | strength of the opening part of the outer joint member 21 is securable. Moreover, since it is moving quenching, distortion is less likely to occur and the depth of the quenched and hardened layer can be made uniform.

  If the magnetic field blocker A is composed of the ferromagnetic core 56, the unbaked portion 50 can be formed stably. The ferromagnetic core 56 can be made of, for example, silicon steel and can be attached to the high-frequency induction heating coil 51 at a relatively low cost without using a special (special) material.

Since the outer joint member 21 in which the hardened layer S is formed in this way is processed by the heat treatment method, the outer joint member 21 is stable in strength and excellent in durability. Further, the outer joint member 21 formed in this way can assemble a tripod type constant velocity universal joint as shown in FIG. Therefore, the preparative Ripodo type constant velocity universal joint, since use of the outer joint member being processed by the heat treatment method, it is high-quality tripod type constant velocity universal joint having excellent durability, moreover, the joint small The degree of freedom of design such as conversion is increased. In addition, the number of parts can be relatively reduced as a whole of the constant velocity universal joint.

  By heat-treating the trunnion 2 by carburizing / quenching / tempering or carbonitriding / quenching / tempering, the wear resistance of the trunnion 2 is improved and a tripod type constant velocity universal joint having excellent durability is obtained. Further, heat treatment can be performed by induction hardening, and in this case, at least a portion that contacts the guide shafts 27 and 27 of the leg shaft root 10 and the outer joint member 21 can be achieved, and cost reduction can be achieved.

  By the way, in the said embodiment, although the unbaked part 50 was formed along the axial direction in the center part of the circumferential direction of the large inner diameter part 46, the whole large inner diameter part 46 is made into the unbaked part 50. Alternatively, the unbaked portion 50 may not be provided on the joint inner side of the large inner diameter portion 46. That is, in the large inner diameter portion 46, the hardened layer S may be provided on the opening (inlet portion) side corresponding to the boot mounting portion 44 and the joint back side excluding the portion at the position for regular use. This is because even if a hardened layer is provided on the joint inner side of the large inner diameter portion 46, the influence on the strength is small. Further, the hardened layer S may or may not be provided for the small inner diameter portion 45, and the hardened layer S may be provided only on the guide surface 27. For this reason, the hardened layer S can be formed in an optimum range without impairing the function as the outer joint member 21.

  Next, FIG. 6 shows another embodiment of the outer joint member 21. In this case, the outer joint member 21 approaches the outer diameter side of the guide surface 27 so as to be substantially perpendicular to the guide surface 27. A flange 61 extending in the direction is provided. The inner surface of the large inner diameter portion 46 is an unbaked portion 50. The hardened layer S is also provided on the inner surface of the flange 61. This is because the roller 23 interferes with the flange portion 61, and hence the cured layer S is provided on the flange portion 61. Also in this case, the hardened layer S may be provided on the large inner diameter portion 46 on the opening (inlet portion) side corresponding to the boot mounting portion 44 and the joint back side excluding the portion at the position for regular use. .

  Even in the outer joint member 21 shown in FIG. 6, the hardened layer S can be formed using the high-frequency heating device shown in FIGS. For this reason, since the outer joint member 21 in which such a hardened layer S is formed is processed by the heat treatment method, it becomes stable in strength and has excellent durability. In the case having the flange portion 61, the unbaked portion 50 in the large inner diameter portion 46 can be stably formed. Even a tripod type constant velocity universal joint using the outer joint member 21 formed in this way is a high quality tripod type constant velocity universal joint having excellent durability.

  By the way, each heating part 51A, 51B, 51C of the high frequency induction heating coil 51 of the high frequency heating device is formed with a recessed part 55 facing the large inner diameter part 46. That is, the high-frequency induction heating coil 51 is configured such that a portion close to the large inner diameter portion 46 is retracted. For this reason, heating of the large inner diameter portion 46 can be avoided without arranging the magnetic field line blocker A composed of the ferromagnetic core 56 or the like. Therefore, as shown in FIG. 7, the high-frequency induction heating coil 51 can have the large inner diameter portion 46 as the unfired portion 50 even if the ferromagnetic core 56 is omitted. Thus, the ferromagnetic core 56 etc. which comprise the magnetic force line blocker A etc. can be omitted, and simplification of the structure of the high frequency induction heating device and cost reduction can be achieved.

  Next, FIG. 8 shows a tripod type constant velocity universal joint according to the present invention. In this case, the tripod type constant velocity universal joint is composed of the outer joint member 21 and the trunnion 22 without the roller 23. The The guide surfaces 27 and 27 facing each other are parallel flat surfaces. The outer diameter surface of the leg shaft 29 is a convex curved surface, and is inserted into the track groove 26 to serve as a torque transmission portion. That is, the leg shaft 29 of the trunnion 22 is in sliding contact with the guide surfaces 27 and 27 of the outer joint member 21 directly. On the other hand, in the tripod type constant velocity universal joint shown in FIG. 4, the roller 23 is fitted on the leg shaft 29 of the trunnion 22, and the leg shaft 29 is fitted on the guide surfaces 27, 27 of the outer joint member 21. It was in sliding contact indirectly.

  In this case, as shown in FIGS. 12A and 12B, the leg axis on the surface S2 including the intersection O1 of the leg axis pitch circle P and the leg axis central axis A1 and perpendicular to the leg axis central axis A1. When the radius of curvature of the outer diameter surface is R1, and the radius of curvature of the outer surface of the leg shaft on the surface S1 including the leg axis A1 and perpendicular to the joint center line L is R2, R1 ≦ R2.

  When the operating angle θ is taken as shown in FIG. 10 from the state where the operating angle is not taken as shown in FIG. 9, the trunnion center O is eccentric with respect to the center line L (joint center line) of the outer joint member 21. It becomes an eccentric state at e. Accordingly, the guide surface length W1 and the guide surface width W2 (see FIG. 11) of the guide surfaces 27 and 27 are set in consideration of the amount of increase in the leg shaft cross-sectional width in an eccentric state.

  In the tripod type constant velocity universal joint shown in FIG. 8 and the like, the leg shaft 29 of the trunnion 22 serves as a torque transmission portion. Etc.) is not required. For this reason, the total number of parts can be reduced, the assemblability can be improved, and the cost can be reduced.

  By setting R1 ≦ R2, the surface pressure on the guide surfaces 27 and 27 can be relaxed, and the durability and NVH characteristics can be improved.

  By making the guide surfaces 27, 27 facing each other of the outer joint member 21 parallel flat surfaces, the operating angle is taken and the trunnion center O is decentered with respect to the center line L of the outer joint member 21. Even if it exists, this eccentricity can be absorbed. In particular, as a flat surface, a guide surface length that allows for an increase in leg shaft cross-sectional width in a state where the center line L (joint center line) of the outer joint member 21 and the trunnion center O are decentered by taking an operating angle, and It preferably has a width.

  That is, if the guide surfaces 27 and 27 are curved surfaces, when the operating angle θ is taken, the eccentricity cannot be absorbed in a state where the center line L of the outer joint member 21 and the trunnion center O are eccentric. However, this eccentricity can be absorbed by making the guide surfaces 27, 27 flat. Further, as described above, as the width dimension (guide surface width) of the guide surfaces 27, 27, it is possible to absorb the eccentricity stably by considering the increase amount of the leg shaft cross-sectional width.

  By finishing the outer diameter surface of the leg shaft 29 of the trunnion 22 by grinding or hardened steel cutting, it is possible to smoothly contact the guide surfaces 27 and 27 and to exhibit a stable torque transmission function. In particular, hardened steel cutting is superior in terms of the environment because it does not require a grinding fluid necessary for grinding.

  Moreover, since it is good also as a forging skin except the site | part which contacts the guide surfaces 27 and 27 of the leg axis | shaft 29, the turning process of these site | parts can be reduced and reduction of processing cost can be aimed at.

  Also in the outer joint member 21 of such a tripod type constant velocity universal joint, a high-frequency induction heating coil 51 provided with a high-frequency induction heating coil 51 in which the magnetic field line shield A (ferromagnetic core 56) shown in FIGS. Even if it is a heating device, even if it is a high frequency heating device provided with the high frequency induction heating coil 51 which does not have the magnetic force line blocker A (ferromagnetic core 56) as shown in FIG. The inner diameter portion 46 can be the unbaked portion 50.

  For this reason, the tripod type constant velocity universal joint shown in FIG. 8 becomes a high quality tripod type constant velocity universal joint excellent in durability, and the degree of design freedom such as downsizing of the joint is increased.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, as the material of the ferromagnetic core 56, other than silicon steel, Ceramics such as mild steel and ferrite may be used. R1 and R2 can be arbitrarily changed in a range satisfying R1 ≦ R2, but the ratio R1 / R2 is set to about 0.05 to 1.00 on the guide surfaces 27 and 27. This is preferable for reducing the applied surface pressure.

21 outer joint member 22 trunnion 23 roller 23a outer diameter surface 23b inner diameter surface 26 track groove 27 guide surface 45 small inner diameter portion 46 large inner diameter portion 50 unbaked portion 51 high frequency induction heating coil 55 recessed portion 56 ferromagnetic core 61 flange A Magnetic field line shield S Hardened layer

Claims (12)

An outer joint member in which three track grooves extending in the axial direction are provided on the inner periphery, and guide surfaces facing each other are provided on the inner wall of each track groove, and a large inner diameter portion provided between the two guide surfaces is formed; A trunnion having three leg shafts, and the high frequency induction heating coil is relative to the outer joint member of a tripod type constant velocity universal joint in which the leg shaft of the trunnion is in direct sliding contact with the guide surface of the outer joint member. A hardened layer is formed on the guide surface of the outer joint member by moving quenching in which the guide surface is sequentially heated as it moves in the axial direction , and the heated area of the guide surface is rapidly cooled with a cooling fluid following this heating. A heat treatment method for forming,
The high-frequency induction heating coil includes three heating units arranged at equal intervals along the circumferential direction.
A concave portion is formed in the central portion in the circumferential direction of the surface facing the large inner diameter portion of the high-frequency induction heating coil, and a magnetic force line that forms a flat plate shape in the concave portion and blocks magnetic lines generated in the high-frequency induction heating coil. By fitting a ferromagnetic core as a blocking body, a portion that suppresses heating of the large inner diameter portion is provided, and the boot mounting portion corresponding range at least in the circumferential central portion of the large inner diameter portion of the outer joint member is defined as an unbaked portion. A heat treatment method characterized by: The heat treatment method according to claim 1 , wherein the ferromagnetic core is made of silicon steel. A heat treatment method for forming a hardened layer on the guide surface of the outer joint member by moving quenching in which the high frequency induction heating coil moves relatively in the axial direction with respect to the outer joint member,
The high frequency induction heating coil in which a portion close to the large inner diameter portion is retracted, wherein the boot mounting portion corresponding range at least in the center in the circumferential direction of the large inner diameter portion of the outer joint member is an unbaked portion. 2. The heat treatment method according to 1. A heat treatment method for forming a hardened layer on the guide surface of the outer joint member by moving quenching in which the high frequency induction heating coil moves relatively in the axial direction with respect to the outer joint member,
Provided on the outer diameter side of the guide surface of the outer joint member is a flange that extends in a direction approaching the guide surface so as to be substantially perpendicular to the guide surface, and at least the boot mounting portion corresponding range in the large inner diameter portion is a non-heating portion. The heat treatment method according to any one of claims 1 to 3 , wherein an unbaked portion is formed. The heat treatment method according to claim 4 , wherein a hardened layer is formed on the inner surface of the collar portion. The outer joint member small-inner-diameter portion is formed between the large-diameter portion, this small diameter portion, any one of claims 1 to 5, characterized in that to form a cured layer at said mobile quenching 1 The heat treatment method according to item. The heat treatment method according to any one of claims 1 to 6 , wherein an entire inner diameter portion of the outer joint member is an unbaked portion. The heat treatment method according to any one of claims 1 to 6 , wherein an unbaked portion is not provided on the joint inner side of the large inner diameter portion of the outer joint member. The heat treatment method according to any one of claims 1 to 6, wherein a hardened layer is provided only on the guide surface on the inner diameter side of the outer joint member. The heat treatment method according to any one of claims 1 to 9 , wherein the guide surfaces facing each other of the outer joint member are parallel flat surfaces. Claim 1 outer joint member of the tripod type constant velocity joint, characterized in that processed by the heat treatment method according to any one of claims 10. Claim 1 tripod type constant velocity universal joint, characterized in that the application of the outer joint member processed by the heat treatment method according to any one of claims 10.

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