JP2016020528A - Manufacturing method of planetary carrier, and planetary carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a planetary carrier and a planetary carrier, which can secure rigidity of stress concentration planned portions after hardening and meanwhile, suppressing heat treatment strain from occurring at portions where hardening is not required.SOLUTION: A planetary carrier [10] includes: welded parts [96] at which a plurality of steel components [30]-[36] are welded; and stress concentration planned portions [98] at which stress concentration is planned. A manufacturing method of the planetary carrier includes: a carburization step of performing carburization treatment on the planetary carrier [10]; an annealing step of cooling the carburized planetary carrier [10] at speed not generating martensitic transformation; and a hardening step of performing hardening using laser on the stress concentration planned portions of the cooled planetary carrier [10].SELECTED DRAWING: Figure 3

Description

  The present invention relates to a planetary carrier manufacturing method and a planetary carrier, and in particular, a planetary carrier including a welded portion in which a plurality of steel parts are welded, and a stress concentration planned portion where stress concentration is scheduled, and its It relates to a manufacturing method.

  2. Description of the Related Art Conventionally, a manufacturing method for manufacturing a workpiece including a welded portion subjected to welding made of steel parts is known (see, for example, Patent Document 1). The manufacturing method includes a step of carburizing the raw material of the workpiece, a step of slowly cooling the carburized raw material, and a step of induction hardening the cooled raw material. According to this manufacturing method, it is possible to homogenize the metal structure of the welded portion embrittled by welding of the workpiece, and to improve the strength of the workpiece. Moreover, a planetary carrier including a welded portion in which a plurality of parts are welded is known (see, for example, Patent Document 2). This planetary carrier is formed by welding parts including predetermined parts obtained by pressing a steel plate.

JP 2000-63952 A International Publication No. 2013/088880

  By the way, the planetary carrier described in Patent Document 2 described above has a complicated shape in which parts including a predetermined pressed part are welded to each other, and a device (for example, a vehicle, for example) mounted along with the complicated shape. There is a part where stress concentrates (stress concentration planned part) during operation of the automatic transmission. In the production of such a planetary carrier, when the production method described in Patent Document 1 is applied for the purpose of homogenizing the metal structure including the weld and improving the strength by heating / cooling treatment, the planetary carrier is produced. Induction hardening is performed.

  However, in the quenching by induction hardening described above, it is difficult to place the jig used for induction hardening (specifically, the induction coil) only at a place where quenching is necessary, and a relatively wide area in the parts to be quenched. Therefore, in addition to the stress-concentration-scheduled portion that needs to be quenched, there may be a situation where quenching is performed at a location that does not require quenching. For this reason, in said manufacturing method, heat processing distortion arises in a quenching unnecessary part, and there exists a possibility that the dimensional accuracy of a product may fall because warp, a wave | undulation, etc. generate | occur | produce in the manufactured planetary carrier.

  The present invention has been made in view of the above points, and a planetary carrier manufacturing method capable of suppressing the occurrence of heat treatment distortion in a portion that does not require quenching while ensuring the hardness of the portion where stress concentration is planned by quenching. And it aims at providing a planetary carrier.

  One aspect of the present invention is a planetary carrier that includes a welded portion (96) to which a plurality of steel parts (30) to (36) are welded, and a stress concentration planned portion (98) where stress concentration is planned. 10), a carburizing step for carburizing, a slow cooling step for cooling the planetary carrier (10) carburized in the carburizing step at a speed that does not cause martensitic transformation, and a cooling step in the slow cooling step. A planetary carrier (10) manufacturing method comprising: a quenching step of performing quenching using a laser on the planned stress concentration portion of the planetary carrier (10).

  Moreover, one aspect of the present invention is a planetary including a welded portion (96) where a plurality of steel parts (30) to (36) are welded, and a stress concentration planned portion (98) where stress concentration is planned. The carrier (10), wherein the crystal grains in the weld (96) have the same size as the crystal grains in a site different from the weld (96), and the stress concentration planned site (98) is: A planetary carrier (10) comprising a martensite composition.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the heat processing distortion in a quenching unnecessary location can be suppressed, ensuring the hardness of the stress concentration planned site | part by quenching.

It is a block diagram of the system carrying the planetary carrier which is one Example of this invention. It is a disassembled perspective view of the planetary carrier of a present Example. It is a block diagram of the apparatus which heat-processes the planetary carrier of a present Example. It is the figure showing the mode of the structure of the welding part before and behind carburizing and slow cooling of the planetary carrier of a present Example. It is the enlarged view showing the mode of the structure of the welding part after carburizing and slow cooling of the planetary carrier of a present Example. It is the figure showing the location which performs laser hardening of the planetary carrier of a present Example. It is a figure for demonstrating the effect by the heat processing of the planetary carrier of a present Example.

  Hereinafter, a planetary carrier manufacturing method and a specific embodiment of a planetary carrier according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a system 12 on which a planetary carrier 10 according to an embodiment of the present invention is mounted. FIG. 2 is an exploded perspective view of the planetary carrier 10 of the present embodiment. A system 12 on which the planetary carrier 10 of this embodiment is mounted is an automatic transmission including a planetary gear mechanism 14 mounted on a vehicle. Hereinafter, the system 12 is referred to as an automatic transmission 12. The automatic transmission 12 changes the gear position when the power output from the vehicle-mounted engine is transmitted to the drive wheels.

  The planetary gear mechanism 14 includes two sun gears 16, 18, a ring gear 20, a plurality of short pinion gears 22, a plurality of long pinion gears 24, and a planetary carrier 10. The sun gears 16 and 18 are external gears. The ring gear 20 is an internal gear fixed to the output shaft of the automatic transmission 12. Each short pinion gear 22 meshes with the sun gear 16. Each long pinion gear 24 meshes with the sun gear 18 and the short pinion gear 22 and meshes with the ring gear 20.

  The planetary carrier 10 holds a plurality of short pinion gears 22 and a plurality of long pinion gears 24 so as to rotate and revolve freely, and is supported by a transmission case 28 via a one-way clutch 26. The planetary carrier 10 is composed of four parts: a first carrier member 30, a second carrier member 32, a center plate 34, and an annular member 36. Each part of the planetary carrier 10 is a steel part formed of a metal of a steel material. As this steel material, it is preferable to use a low carbon steel or a low carbon alloy steel having a carbon content of 0.35 mass% or less from the viewpoint of processing surface such as press formability and bendability and cost.

  The first carrier member 30 includes a flat plate-like first shaft support portion 40 and a plurality (three in FIG. 2) of first leg portions 42. The first shaft support portion 40 supports one end of a plurality of short pinion shafts 41 inserted through the short pinion gear 22 and one end of a plurality of long pinion shafts 43 inserted through the long pinion gears 24, respectively. It is. The first leg portion 42 is a leg extending from the first shaft support portion 40. The 1st leg part 42 is arrange | positioned at predetermined intervals in the circumferential direction.

  The first shaft support portion 40 is provided with a center hole 44 at the center and shaft holes 46 and 48 around the center hole 44. The input shaft 49 and the sun gears 16 and 18 of the automatic transmission 12 are inserted through the center hole 44. The short pinion shaft 41 is inserted into the shaft hole 46. The long pinion shaft 43 is inserted into the shaft hole 48. A plurality of shaft holes 46 and shaft holes 48 are alternately provided around the center hole 44.

  The first leg portion 42 has a base portion 50 and a free end portion 52. The base portion 50 is a portion that extends in the axial direction from the outer periphery of the first shaft support portion 40. The free end portion 52 is a portion extending radially outward from the axial tip of the base portion 50. The distal end of the free end portion 52 in the radial direction is formed in an arc shape so as to have a predetermined radius of curvature.

  The second carrier member 32 has a second shaft support portion 54 and a plurality (three in FIG. 2) of second leg portions 56. The second shaft support portion 54 is a part that supports the other end of the short pinion shaft 41 described above and the other end of the long pinion shaft 43 described above. The second leg portion 56 is a leg extending from the second shaft support portion 54. The 2nd leg part 56 is arrange | positioned at predetermined intervals in the circumferential direction.

  The second shaft support portion 54 has a flat plate-like base portion 58 and a cylindrical tubular portion 60 that extends from the outer periphery of the base portion 58. A center hole 62 is provided at the center of the base portion 58 of the second shaft support portion 54, and shaft holes 64 and 66 are provided around the center hole 62. The input shaft 49 of the automatic transmission 12 is inserted through the center hole 62. The short pinion shaft 41 is inserted into the shaft hole 64. The long pinion shaft 43 is inserted into the shaft hole 66. A plurality of shaft holes 64 and shaft holes 66 are alternately provided around the center hole 62. The second shaft support portion 54 also functions as a clutch hub. A spline 70 is formed on the outer peripheral surface of the cylindrical portion 60 to which the friction plate 68 constituting the clutch is fitted.

  The second leg portion 56 has a base portion 72 and a free end portion 74. The base portion 72 is a portion extending in the axial direction from the outer periphery of the second shaft support portion 54, that is, the tubular portion 60. Further, the free end portion 74 is a portion extending radially outward from the axial tip of the base portion 72. The radially outer tip of the free end 74 is formed in an arc shape so as to have the same radius of curvature as the radially outer tip of the free end 52 of the first leg 42 of the first carrier member 30.

  The center plate 34 is formed by pressing a metal as a material. The center plate 34 has a center hole 76, a plurality of long pinion gear insertion portions 78, and a plurality of shaft holes 80. The input shaft 49 and the sun gear 16 of the automatic transmission 12 are inserted through the center hole 76. The long pinion gear insertion part 78 is a part that is cut away from the central hole 76. The long pinion gear 24 is inserted into the long pinion gear insertion portion 78. The short pinion shaft 41 is inserted into the shaft hole 80. The long pinion gear insertion portion 78 may be a through hole. Further, the center plate 34 may have a second pinion shaft insertion portion that is cut out and is continuous with the center hole 76 instead of the shaft hole 80.

  The center plate 34 is formed in an arc shape so as to have the same radius of curvature as the radially outer end of the free end portion 52 of the first leg portion 42 and the free end portion 74 of the second leg portion 56. The center plate 34 has notches 82 and 84. The notches 82 and 84 are portions where the main body of the center plate 34 is notched, and a plurality of notches 82 and 84 are provided. The circumferential width of each notch 82 is determined such that one free end 52 of the first leg 42 of the first carrier member 30 is accommodated. The circumferential width of each notch 84 is determined so that one free end 74 of the second leg 56 of the second carrier member 32 is accommodated.

  The annular member 36 is formed by forging. The annular member 36 functions as both an inner race of the one-way clutch of the automatic transmission 12 and a brake hub of the brake of the automatic transmission 12. That is, the annular member 36 has a cylindrical inner race portion 86 and a cylindrical brake hub portion 88. The inner race part 86 and the brake hub part 88 are connected in series in the axial direction. The brake hub portion 88 is a portion where splines are formed on the outer periphery. A friction plate 90 constituting a brake is fitted into the brake hub portion 88.

  The brake hub portion 88 of the annular member 36 is provided with an abutting end surface 92 and an annular projecting portion 94. The abutting end surface 92 protrudes from the inner peripheral surface of the cylindrical brake hub portion 88 toward the axial center, thereby allowing the free end portion 52 of the first leg portion 42 of the first carrier member 30 and the second carrier member. This is a portion that forms a surface with which the free end portion 74 of the 32 second leg portion 56 and the center plate 34 abut. The annular protrusion 94 is a portion that protrudes in the axial direction from the radially outer end of the contact end surface 92. The radius of curvature of the inner peripheral surface of the annular protrusion 94 is such that the free end 52 of the first leg 42 of the first carrier member 30, the free end 74 of the second leg 56 of the second carrier member 32, and the center plate. 34 is set to be slightly larger than the radius of curvature of the radially outer end of 34.

  Next, the manufacturing method of the planetary carrier 10 of a present Example is demonstrated.

  In the present embodiment, when the planetary carrier 10 is manufactured, the first carrier member 30, the second carrier member 32, the center plate 34, and the annular member 36 that constitute the planetary carrier 10 are prepared. The first shaft support portion 40 of the first carrier member 30 and the base portion 50 of the first leg portion 42 are inserted into the radially inner side of the annular member 36 from the opening on the brake hub portion 88 side of the annular member 36, and the first The free end portion 52 of the one leg portion 42 is brought into contact with the contact end surface 92 of the annular member 36.

  Next, the center plate 34 is inserted from the opening of the annular member 36 on the brake hub portion 88 side, and the free end portion 52 of the first leg portion 42 of the first carrier member 30 is inserted into the notch portion 82 of the center plate 34. The center plate 34 is disposed so that the radially outer end of the center plate 34 abuts against the abutting end surface 92 so as to be accommodated. Further, the second carrier member 32 is inserted from the opening on the brake hub portion 88 side of the annular member 36, and the second carrier member 32 is inserted into the notch portion of the center plate 34 with the free end portion 74 of the second leg portion 56. 84, and the free end portion 74 is disposed so as to contact the contact end surface 92 of the annular member 36.

  As described above, after the first carrier member 30, the second carrier member 32, and the center plate 34 are assembled to the annular member 36, the annular member 36 annularly extends from one axial direction along the inner peripheral surface of the annular protrusion 94. Weld. When such welding is performed, each first leg portion 42 of the first carrier member 30, each second leg portion 56 of the second carrier member 32, and the center plate 34 are on the inner peripheral side of the annular protrusion 94 of the annular member 36. Fixed to. Therefore, according to the structure of the planetary carrier 10 of the present embodiment, the first carrier member 30, the second carrier member 32, and the first leg member 42 and the second leg portion 56 are not directly welded to the center plate 34. Since the center plate 34 can be collectively welded to the annular member 36, accurate welding can be realized while reducing the number of welding steps.

  In the present embodiment, as described above, the planetary carrier 10 is configured by welding the four parts of the first carrier member 30, the second carrier member 32, the center plate 34, and the annular member 36. Next, as will be described in detail later, the planetary carrier 10 is heat-treated.

  Next, with respect to the planetary carrier 10 that has been heat-treated, the center hole 44 formed in the first shaft support portion 40 of the first carrier member 30 and the second shaft support portion 54 of the second carrier member 32 are formed. The short pinion gear 22 and the long pinion gear 24 are disposed through the center hole 62 formed.

  The short pinion shafts 41 are inserted into the short pinion gears 22, the shaft holes 46 of the first shaft support portion 40, the shaft holes 80 of the center plate 34, and the shaft holes 64 of the second shaft support portion 54. Is done. The short pinion gear 22 is rotatably supported by the planetary carrier 10 by fixing both ends of the short pinion shaft 41 in the axial direction by, for example, caulking. The long pinion shafts 43 are inserted into the long pinion gears 24 and the shaft holes 48 of the first shaft support portion 40 and the shaft holes 66 of the second shaft support portion 54. The long pinion gear 24 is rotatably supported by the planetary carrier 10 by fixing both ends of the long pinion shaft 43 in the axial direction by caulking, for example.

  FIG. 3 shows a configuration diagram of an apparatus 100 for performing a heat treatment on the planetary carrier 10 of the present embodiment. FIG. 4 is a diagram showing the structure of the welded portion of the planetary carrier 10 of this example before and after carburizing and slow cooling. 4A shows before carburizing and slow cooling, and FIG. 4B shows after carburizing and slow cooling. FIG. 5: shows the enlarged view showing the mode of the structure | tissue after carburizing and slow cooling of the planetary carrier 10 of a present Example. FIG. 5 (A) shows a photograph showing the cross-sectional structure of the surface layer portion, and FIG. 5 (B) shows a photograph showing the internal cross-section. FIG. 6 is a diagram showing the places where the planetary carrier 10 of this embodiment is subjected to laser hardening. Moreover, FIG. 7 shows the figure for demonstrating the effect by the heat processing of the planetary carrier 10 of a present Example. In addition, in FIG. 7, the figure showing the relationship between the distance from the surface and Vickers hardness of the planetary carrier 10 is shown. In FIG. 7, the relationship when the heat treatment including all of the carburizing process, the slow cooling process, and the quenching process using a laser is performed in this embodiment is C1, and the carburizing process and the slow cooling process are performed. In this case, the relationship is C2, and the relationship before the heat treatment of this embodiment is C3.

  In the present embodiment, as described above, when the planetary carrier 10 having the welded portion in which the four parts of the first carrier member 30, the second carrier member 32, the center plate 34, and the annular member 36 are welded is manufactured. Thereafter, the planetary carrier 10 is heat-treated. Hereinafter, the welded portion of the planetary carrier 10 is referred to as a welded portion 96. Specifically, carburizing treatment, slow cooling treatment, and quenching treatment are performed in this order on the planetary carrier 10 having the welded portion 96. According to such heat treatment, the surface hardness can be increased while ensuring the toughness of the welded portion 96 of the planetary carrier 10 having the welded portion 96.

  In this embodiment, the apparatus 100 for performing a heat treatment on the planetary carrier 10 includes a heating chamber 102, a carburizing chamber 104, a slow cooling chamber 106, and a quenching chamber 108. In the heating chamber 102, a process for heating the planetary carrier 10 having the welded portion 96 is performed. In the carburizing chamber 104, a carburizing process for carburizing the planetary carrier 10 heated in the heating chamber 102 is performed. In the slow cooling chamber 106, a slow cooling process for gradually cooling the planetary carrier 10 carburized in the carburizing chamber 104 is performed. In the quenching chamber 108, a quenching process is performed in which the planetary carrier 10 that has been slowly cooled in the slow cooling chamber 106 is quenched.

  The heat treatment in the heating chamber 102 is a step of heating the planetary carrier 10 having the welded portion 96 to a temperature not lower than the austenitizing temperature (for example, 930 ° C.). A plurality of planetary carriers 10 having welds 96 are carried into the heating chamber 102 collectively. In the heating chamber 102, the plurality of planetary carriers 10 are heated together.

  Carburizing treatment in the carburizing chamber 104 is performed by supplying carburizing gas into the carburizing chamber 104 in a state where the atmosphere in the carburizing chamber 104 is reduced to a pressure lower than atmospheric pressure, and carburizing the planetary carrier 10 (that is, vacuum carburizing). ). A plurality of heated planetary carriers 10 are carried together into the carburizing chamber 104. In the carburizing chamber 104, the plurality of planetary carriers 10 are carburized together.

  In this carburizing process, a hydrocarbon-based gas (for example, methane, propane, ethylene, acetylene, etc.) is used as the carburizing gas. When such carburization is performed, active carbon generated by decomposition when the carburizing gas comes into contact with the surface of the carburizing treatment object becomes a carbide on the surface of the carburizing treatment object and is stored in the carburizing treatment object. The carbide is decomposed, and the stored carbon is dissolved in the matrix and diffused toward the inside.

  According to the carburization described above, carbon can be infiltrated into almost the entire surface of the planetary carrier 10 to form a carburized layer on the surface layer portion thereof. The carbon concentration of the carburized layer is higher than the carbon concentration of the base material (that is, the planetary carrier 10 before carburizing). In addition, it is desirable that the carbon concentration of the carburized layer is 0.75% by mass or less in order to prevent the carbide from being deposited on the 90 ° edge portion to be carburized.

  Moreover, since the said carburizing process is performed after the several components 30-36 which comprise the planetary carrier 10 are welded, unlike the structure in which a carburizing process is performed before welding, each of the components 30-36 are before carburizing. It is not necessary to apply a carbon-proof treatment to the welded part, and the process can be simplified. Further, since the above carburizing treatment is vacuum carburizing, the oxygen concentration in the atmosphere in the carburizing chamber 104 can be kept low, so that grain boundary oxidation of the carburized layer can be prevented.

  Moreover, according to said vacuum carburizing, since the carburizing process with respect to the planetary carrier 10 can be performed using a relatively small amount of carburizing gas, the carburizing process can be performed efficiently. Further, according to the above vacuum carburizing, it is not necessary to perform the heat treatment for a long time, so that the processing time can be shortened and the energy consumption can be reduced, and the cost and size of the carburizing equipment can be reduced. Can be achieved. Instead of depressurizing the atmosphere in the carburizing chamber 104 as described above, the carburizing chamber 104 may be filled with nitrogen gas or an inert gas to keep the oxygen concentration in the atmosphere low.

  The slow cooling treatment in the slow cooling chamber 106 is a step of cooling (slow cooling) the planetary carrier 10 after carburizing in the carburizing chamber 104 at a cooling rate slower than the rate at which the steel material undergoes martensitic transformation. A plurality of carburized planetary carriers 10 are carried together into the slow cooling chamber 106. In the slow cooling chamber 106, the plurality of planetary carriers 10 are gradually cooled. This slow cooling treatment is performed to a temperature below the temperature at which the tissue transformation is completed by the cooling. When such slow cooling is performed, the structure of the welded portion 96 of the planetary carrier 10 having a relatively low toughness transformed into a bainite structure or martensite structure in which the crystal grains are coarsened by welding has a toughness in which the crystal grains are refined. Modified to a relatively high ferrite-pearlite structure.

  Note that the welded portion 96 is a portion where the molten metal is solidified by welding, and the portion around the molten metal is transformed into a bainite structure in which crystal grains are enlarged due to the influence of welding heat (so-called Welding heat affected zone).

  Therefore, according to such slow cooling, it is possible to prevent the planetary carrier 10 after carburizing from undergoing martensitic transformation. Further, the coarsened bainite structure or martensite structure crystal grains (see FIG. 4) of the welded portion 96 generated by welding are refined as shown in FIG. 5, and the size of the crystal grains is defined as the welded portion 96. Since the ferrite-pearlite structure having the same size as the crystal grains in different parts can be obtained, the weakness of the structure due to the coarsening of the crystal grains of the welded portion 96 can be eliminated, and the toughness of the planetary carrier 10 can be reduced. The strength of the planetary carrier 10 can be increased.

  The quenching chamber 108 accommodates a laser device 110 that can irradiate a laser having a high density energy in an arbitrary position and direction. Planetary carrier 10 after slow cooling in slow cooling chamber 106 is carried into quenching chamber 108 one by one. The quenching process in the quenching chamber 108 is a process of quenching the planetary carrier 10 after slow cooling in the slow cooling chamber 106 one by one using a laser irradiated by the laser device 110. This quenching process is performed on the planetary carrier 10 where stress is expected to concentrate during operation (for example, the first carrier member 30 formed by bending a press material in an arc shape as shown in FIG. 6). Or the like near the root of the first leg portion 42 cut out in the following; hereinafter referred to as a stress concentration planned portion 98). In addition to the portion cut out in the above-mentioned arc shape, the stress concentration planned portion includes a bent portion such as a base of the first leg portion 42, which is bent by a press material. Then, a quenching process using a laser may be performed.

  When such quenching is performed, only the stress concentration planned portion 98 irradiated by laser irradiation is heated to a temperature equal to or higher than the austenitizing temperature, and the stress concentration planned portion 98 is rapidly cooled by stopping the laser irradiation. The Since the temperature of the part that has not been quenched hardly changes before and after the laser irradiation is stopped (for example, at room temperature), the local heat that has been quenched is rapidly transferred to the part that has not been quenched. The stress concentration planned portion 98 is cooled at a speed higher than the speed at which the martensitic transformation is performed.

  According to the quenching using the laser, the planetary carrier 10 can be locally quenched, and the structure of the stress concentration planned portion 98 can be transformed to include the martensite composition. The hardness (fatigue strength) of 98 can be improved. Specifically, as shown in FIG. 7, at least in a region within a distance of 0.3 mm from the surface, stress that has been subjected to heat treatment including all of carburizing treatment, slow cooling treatment, and quenching treatment by laser irradiation. Compared to the surface of the planned concentration site 98 and the vicinity of the surface, compared with the one just subjected to the carburizing process and the slow cooling process that are not quenched by laser irradiation, or the one before the heat treatment is performed. High hardness can be achieved. Therefore, the planetary carrier 10 (specifically, the parts 30, 32, 34, and 36 constituting the planetary carrier 10) can be used without using another method for increasing the strength such as increasing the plate thickness. The carrier 10 can be made light and compact and usable up to a high torque range.

  Further, according to the quenching using the laser, quenching is not performed on the portions that do not require quenching other than the stress concentration planned portion 98, so that it is possible to suppress the occurrence of heat treatment distortion due to quenching at the portions that do not require quenching. The dimensional accuracy of the planetary carrier 10 can be increased.

  Further, according to quenching using a laser, the stress concentration planned portion 98 is easily heated, so that the heating time can be shortened. Further, since laser irradiation can be performed using refraction by a mirror or the like, it is a method suitable for quenching the planetary carrier 10 having a complicated shape composed of four parts. Further, as described above, since the hardness (fatigue strength) of the stress concentration planned portion 98 can be improved, the hardness can be improved even if the carbon concentration of the steel material as the base material is kept low. . For this reason, it is possible to prevent the workability from being impaired due to the high carbon concentration of the base material, and to prevent weld cracking during welding due to the high carbon concentration of the base material. it can.

  In the above embodiment, the welded portion 96 corresponds to the “welded portion” described in the claims, and the stress concentration planned portion 98 corresponds to the “stress concentration planned portion” described in the claims. ing.

  By the way, in the above-described embodiment, the holes formed in the four parts 30 to 36 constituting the planetary carrier 10 are formed before the parts 30 to 36 are assembled to constitute the planetary carrier 10. . However, the present invention is not limited to this, and each hole 30 may be formed after the parts 30 to 36 in which holes are not formed are assembled to form the planetary carrier 10.

  Moreover, in said Example, the planetary carrier 10 is comprised from the four components 30-36 welded mutually. However, the present invention is not limited to this, as long as they are welded to each other, and the planetary carrier 10 may be composed of two or more parts.

  In the above-described embodiment, the planetary carrier 10 is not formed by welding a member for reinforcing the strength as a rib. However, the present invention is not limited to this, and may be applied to what is welded as another rib to the planetary carrier 10 for the purpose of partially reinforcing the strength. In such a modification, the welded portion between the rib added by welding and the planetary carrier 10 is modified in the carburizing process. Therefore, the planetary carrier 10 having high rigidity and strength can be easily realized by the addition by welding of the ribs.

  Furthermore, said Example does not include the process of performing a chilling process between a carburizing process and a quenching process. However, the present invention is not limited to this, and may include a step of performing a chilling process between the carburizing step and the quenching step. The chilling process is a process that uses the laser device 110 to melt only the surface for a short time with a larger energy than during quenching.

  Generally, a part punched from a steel plate by pressing has a shear surface and a fracture surface at the cut surface, and there are shear lines extending in the pressing direction, and the material is torn at the fracture surface. A lot of minute cracks exist. Then, starting from these streaks and minute cracks, there is a risk that large cracks or the like may occur when stress is concentrated. On the other hand, when the chilling treatment is performed, a smooth surface can be formed without the streaks and minute cracks on the cut surface, thereby improving the strength of the cut surface. Can do. Moreover, since the chilling process is performed using the same equipment as the equipment used in the quenching process, if the chilling process is performed before the quenching process, transportation of parts and the like is not necessary. Since it is not necessary to provide a separate facility without impairing productivity, the strength of the cut surface can be improved without causing an increase in cost.

  In addition, the following is further disclosed regarding the above Example.

  [1] For a planetary carrier (10) including a welded portion (96) in which a plurality of steel parts (30) to (36) are welded and a stress concentration planned portion (98) where stress concentration is planned. A carburizing step for carburizing, a slow cooling step for cooling the planetary carrier (10) carburized in the carburizing step at a speed that does not cause martensitic transformation, and the planetary carrier cooled in the slow cooling step. (10) The manufacturing method of a planetary carrier (10) provided with the hardening process which quenches using the laser with respect to the said stress concentration plan site | part.

  According to the configuration described in [1] above, the surface hardness of the planetary carrier can be increased by carburizing treatment, and the coarsened crystal grains of the welded portion can be refined by slow cooling treatment to improve its toughness. Moreover, generation | occurrence | production of the heat processing distortion in a quenching unnecessary location can be suppressed, ensuring the hardness of the stress concentration planned site | part by quenching.

  [2] The method for manufacturing the planetary carrier (10) according to the above [1], wherein the carburizing treatment is a vacuum carburizing treatment.

  According to the configuration described in [2] above, grain boundary oxidation of the carburized layer can be prevented, and cost reduction and downsizing of the carburizing equipment can be achieved.

  [3] In the method for producing a planetary carrier (10) according to [1] or [2] above, in the slow cooling step, the structure of the welded portion (96) is the same as the portion excluding the welded portion (96). A method for producing a planetary carrier (10) having a ferrite-pearlite structure.

  [4] In the method for manufacturing the planetary carrier (10) according to any one of [1] to [3], the steel parts (30) to (36) are press parts obtained by pressing a steel plate. A method for producing a planetary carrier (10).

  [5] In the planetary carrier (10) manufacturing method according to any one of [1] to [4], the stress concentration planned portion (98) is a planetary carrier (98) which is a portion cut out in an arc shape. 10) The manufacturing method.

  [6] A planetary carrier (10) including a welded portion (96) in which a plurality of steel parts (30) to (36) are welded and a stress concentration planned portion (98) where stress concentration is planned. The crystal grains in the welded portion (96) have the same size as the crystal grains in a portion different from the welded portion (96), and the stress concentration planned portion (98) has a planetary structure including a martensite composition. Carrier (10).

  According to the configuration described in [6] above, since the crystal grains of the welded portion coarsened by the carburizing process are refined, the toughness of the welded portion can be improved. Moreover, since the stress concentration part contains a martensite composition, the hardness of the stress concentration part can be improved.

  [7] The planetary carrier (10) of the planetary carrier (10) according to the above [6], wherein the structure of the welded part (96) is a ferrite-pearlite structure in the same manner as the part excluding the welded part (96).

  [8] The planetary carrier (10) according to the above [6] or [7], wherein the steel parts (30) to (36) are press parts obtained by pressing a steel plate.

  [9] The planetary carrier (10) according to any one of the above [6] to [8], wherein the stress concentration planned part (98) is a part cut out in an arc shape.

DESCRIPTION OF SYMBOLS 10 Planetary carrier 12 Automatic transmission 14 Planetary gear mechanism 30 1st carrier member 32 2nd carrier member 34 Center plate 36 Ring member 96 Welding part 98 Stress concentration plan part

Claims (9)

A carburizing step of performing a carburizing process on a planetary carrier including a welded portion where a plurality of steel parts are welded and a stress concentration planned portion where stress concentration is planned;
A slow cooling step of cooling the planetary carrier that has been carburized in the carburizing step at a rate that does not cause martensitic transformation;
A quenching step of quenching using a laser for the stress concentration planned portion of the planetary carrier cooled in the slow cooling step;
A method for producing a planetary carrier, comprising:   The planetary carrier manufacturing method according to claim 1, wherein the carburizing process is a process of vacuum carburizing.   3. The method for producing a planetary carrier according to claim 1, wherein in the slow cooling step, the structure of the welded portion is a ferrite-pearlite structure in the same manner as the portion excluding the welded portion.   The planetary carrier manufacturing method according to any one of claims 1 to 3, wherein the steel part is a press part obtained by pressing a steel plate.   The method for producing a planetary carrier according to any one of claims 1 to 4, wherein the stress concentration planned portion is a portion cut out in an arc shape. A planetary carrier including a welded portion where a plurality of steel parts are welded and a stress concentration planned portion where stress concentration is planned,
The crystal grains in the weld have the same size as the crystal grains in a portion different from the weld,
The site where stress concentration is planned includes a martensite composition.   The planetary carrier according to claim 6, wherein the structure of the welded portion is a ferrite-pearlite structure in the same manner as the portion excluding the welded portion.   The planetary carrier according to claim 6 or 7, wherein the steel part is a press part obtained by pressing a steel plate.   The planetary carrier according to any one of claims 6 to 8, wherein the stress concentration planned portion is a portion cut out in an arc shape.