JP2009097716A - Differential gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential gear whose weight and parts count are reduced for reducing its cost, while achieving required durability. <P>SOLUTION: In the differential gear, a differential case includes: a first differential case on a side ranging from a pinion-shaft installation part on which a pinion shaft is installed, to a ring gear; and a second differential case on a side axially opposite to the side ranging from a pinion-shaft installation part on which the pinion shaft is installed, to the ring gear. The first differential case is integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging. The second differential case is also integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging. The first differential case and the second differential case are bonded to each other by welding. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ring gear that rotates upon input of a driving force from a drive source, a differential case that rotates integrally with the ring gear, a pinion shaft that is assembled to the differential case and rotates integrally with the differential case, and the pinion shaft. The present invention relates to a differential device that includes a pinion gear that is rotatably supported and a side gear that meshes with the pinion gear.

  Conventionally, in a vehicle such as an automobile, a driving force (torque) from an engine is applied to a ring gear, a differential case assembled to the ring gear, a pinion shaft assembled to the differential case, a pinion gear assembled to the pinion shaft, and teeth to the pinion gear. There are known differential devices that transmit via a mating side gear. The pinion shaft, the pinion gear, and the side gear are arranged inside the differential case.

  As a method of forming the differential case of such a differential device, the differential case is divided into a first differential case and a second differential case, a ring gear is integrally formed in the first differential case by forging, and a pinion shaft is assembled to the second differential case. A technique is known in which an assembly portion is integrally formed by forging, and a first differential case and a second differential case are assembled by a plurality of bolts (see Patent Document 1).

In a different method of forming the differential case of the differential device, the differential case is divided into a first differential case and a second differential case, the first differential case is formed by a press, and the second differential case having a pinion shaft assembly is formed by a cold roller. The Thereafter, the ring gear is molded separately, and the first differential case and the second differential case, and the second differential case and the ring gear are joined by welding (see Patent Document 2).
JP 2000-266162 A JP 2006-509172 A

  In the technique in which the first differential case and the second differential case are assembled by a plurality of bolts in Patent Document 1, torque from the ring gear is transmitted to the second differential case via a plurality of bolt assembly locations. For this reason, it is necessary to ensure the durability of the plurality of bolt assembly locations of the first differential case and the second differential case, and it is necessary to increase the thickness around the bolt assembly location. As a result, there is a problem that the differential case becomes heavy. In addition, since a plurality of bolts are required, there is a problem that the number of components of the differential case increases and the cost increases.

  On the other hand, in the forming method in Patent Document 2, a bolt is not used. For this reason, the above problem does not occur. However, the welded portion between the first differential case and the second differential case, and the welded portion between the second differential case and the ring gear are located in a region where the driving force from the engine is transmitted (region between the pinion shaft assembly portion and the ring gear). Therefore, there is a problem in that the welded portion having relatively low strength may crack during torque transmission, that is, the durability of the differential case is low.

  The present invention has been made to solve the above-mentioned problems, and while reducing the weight without fixing the first differential case and the second differential case with bolts, the number of parts is reduced, and the cost is reduced. It is an object of the present invention to provide a differential device that can realize desired durability.

  The present invention relates to a ring gear that rotates upon input of a driving force from a drive source, a differential case that rotates integrally with the ring gear, a pinion shaft that is assembled to the differential case and rotates integrally with the differential case, and the pinion shaft. In a differential device comprising a pinion gear rotatably supported and a side gear meshing with the pinion gear, the differential case includes a first differential case on the ring gear side from a pinion shaft assembly portion on which the pinion shaft is assembled, The pinion shaft is assembled to a second differential case opposite to the ring gear side from the pinion shaft assembly portion, and the first differential case has a low C content of less than 0.45%. Forged from carbon steel only, or It is integrally formed by forging and cutting, and the second differential case is also integrally formed by forging or forging and cutting only from a low carbon steel having a C content of less than 0.45%. The differential case is characterized in that the first differential case and the second differential case are joined by welding.

  According to the present invention, since the first differential case and the second differential case do not need to be fixed with bolts, the thickness of the first differential case and the second differential case can be reduced, and the weight of the differential case can be reduced. Can do. In addition, since the number of parts (volts) is reduced, the cost can be reduced. Furthermore, the ring gear side portion (including the ring gear) from the pinion shaft assembly portion is integrated as a first differential case by forging from forging only low carbon steel having a C content of less than 0.45%, or forging and cutting. The welded part between the first differential case and the second differential case is located outside the torque transmission area (the area between the pinion shaft assembly and the ring gear). Is prevented from being destroyed. In addition, since the first differential case having a C content of less than 0.45% and the second differential case having a C content of less than 0.45% are welded, the welded portion is hardened and cracks, etc. Defects are less likely to occur. Thereby, the differential apparatus which has desired durability can be provided.

  Preferably, the first differential case and the pinion shaft are caulked and fixed. This fixing method is extremely simple. In particular, the first differential case has high toughness because it is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of less than 0.45%. For this reason, even if the pinion shaft is caulked and fixed, the first differential case is not destroyed. In this case, the pinion shaft is also preferably formed only from a low carbon steel having a C content of less than 0.45%. In this case, since the pinion shaft has high toughness, the pinion shaft is not destroyed when the pinion shaft is caulked and fixed.

  For example, the first differential case is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of 0.10% to 0.40%. Similarly, for example, the second differential case is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of 0.10% to 0.40%.

  The above considerations are mainly made on carbon steel materials whose properties are generally determined by the amount of carbon. The present inventor further studied structural steel materials whose properties are affected by the amount of steel components other than carbon. As a result, it was found that such structural steel should be based on carbon equivalent instead of carbon content.

  The carbon equivalent is defined in JIS as follows.

Carbon equivalent = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14
Here, C is carbon amount (%), Mn is manganese amount (%), Si is silicon amount (%), Ni is nickel amount (%), Cr is chromium amount (%), Mo is molybdenum amount (%) , V is the amount of vanadium (%).

And if carbon steel material of the carbon amount of "0.45%" which is the threshold value which this inventor discovered initially is converted using the component data of general carbon steel materials (for example, S45C etc.), "0.60% It is equivalent to a structural steel material having a carbon equivalent of "", and it was actually confirmed that such substitution is possible in the present invention. (An example of S45C: C = 0.46, Mn = 0.72, Si = 0.18, Ni = 0.04, Cr = 0.11, V = 0.00: Carbon content = 0.46%, carbon Equivalent = 0.613%)
That is, the present invention includes a ring gear that rotates by receiving a driving force from a driving source, a differential case that rotates integrally with the ring gear, a pinion shaft that is assembled to the differential case and rotates integrally with the differential case, and the pinion In a differential device comprising a pinion gear rotatably supported on a shaft, and a side gear meshing with the pinion gear, the differential case includes a first differential case on the ring gear side from a pinion shaft assembly portion on which the pinion shaft is assembled. And a second differential case opposite to the ring gear side in the axial direction from the pinion shaft assembly portion to which the pinion shaft is assembled. The first differential case has a carbon equivalent of less than 0.60%. Forging from only one steel material Alternatively, it is integrally formed by forging and cutting, and the second differential case is also integrally formed by forging or forging and cutting only from the second steel material having a carbon equivalent of less than 0.60%. The differential case is characterized in that the first differential case and the second differential case are joined by welding.

  According to the present invention, since the first differential case and the second differential case do not need to be fixed with bolts, the thickness of the first differential case and the second differential case can be reduced, and the weight of the differential case can be reduced. Can do. In addition, since the number of parts (volts) is reduced, the cost can be reduced. Furthermore, the ring gear side portion (including the ring gear) from the pinion shaft assembly portion is integrally formed as a first differential case by forging from only the first steel material having a carbon equivalent of less than 0.60%, or by forging and cutting. Because the welded part between the first differential case and the second differential case is located outside the torque transmission area (the area between the pinion shaft assembly and the ring gear), the welded part with weak strength is destroyed during torque transmission. Is prevented. Further, since the first differential case made of the first steel material having a carbon equivalent of less than 0.60% and the second differential case made of the second steel material having a carbon equivalent of less than 0.60% are welded, the welded portion is hardened. Defects such as cracks are less likely to occur. Thereby, the differential apparatus which has desired durability can be provided.

  In addition, when the first differential case made of the first steel material and the second differential case made of the second steel material are joined together by welding, the sum of the value of the hot crack sensitivity of the first steel material and the value of the hot crack sensitivity of the second steel material If it is 7 or less, generation | occurrence | production of a crack can be prevented more reliably. Here, the value of hot cracking sensitivity is calculated by the following equation.

Hot cracking susceptibility = 1000 × C (S + P + (Si / 25) + (Ni / 100)) / (3Mn + Cr + Mo + V)
Here, C is the carbon content (%), S is the sulfur content (%), P is the phosphorus content (%), Si is the silicon content (%), Ni is the nickel content (%), and Mn is the manganese content (%). Cr is the chromium content (%), Mo is the molybdenum content (%), and V is the vanadium content (%).

  FIG. 1 is a cross-sectional view of a differential apparatus according to an embodiment of the present invention.

  FIG. 2A is a cross-sectional view of the first material for illustrating a molding process of the first differential case of the differential device according to the embodiment of the present invention. FIG. 2B is a cross-sectional view of the preliminary first differential case for illustrating the molding process of the first differential case of the differential device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of the first differential case of the differential device according to the embodiment of the present invention. FIG. 4A is a cross-sectional view of the second material for illustrating a molding process of the second differential case of the differential device according to the embodiment of the present invention.

  FIG. 4B is a cross-sectional view of the preliminary second differential case for explaining the molding process of the second differential case of the differential device according to the embodiment of the present invention. FIG. 4C is a cross-sectional view of the second differential case of the differential device according to the exemplary embodiment of the present invention. FIG. 5A is a cross-sectional view of a third material for illustrating a step of forming a pinion shaft of the differential device according to one embodiment of the present invention. FIG. 5B is a cross-sectional view of the preliminary pinion shaft for explaining a step of forming the pinion shaft of the differential device according to the embodiment of the present invention. FIG. 6A is a cross-sectional view of the pinion shaft of the differential device according to one embodiment of the present invention. FIG. 6B is a plan view of the pinion shaft of the differential device according to the embodiment of the present invention.

  FIG. 7 is a cross-sectional view of an apparatus for caulking the first differential case and the pinion shaft. FIG. 8A is a plan view of a principal part of the pinion shaft assembly portion of the first differential case before the pinion shaft is caulked and fixed. FIG. 8B is a plan view of a main part of the pinion shaft assembly portion of the first differential case after the pinion shaft is caulked and fixed. FIG. 9 is a cross-sectional view for explaining a method of assembling the first differential case and the second differential case.

  First, the differential apparatus 1 will be described with reference to FIG. The differential case 2 of the differential device 1 includes a first differential case 2a and a second differential case 2b.

  The first differential case 2a is made of only low carbon steel (first steel material) having a C content of less than 0.45%, and has a first boss portion 13 extending in the axial direction at one end in the axial direction. A first through hole 15 is provided inside the first boss portion 13. A first gear chamber 17 having a larger diameter than the first through hole 15 communicates with the first through hole 15, and a pinion shaft assembly portion 10 for assembling the pinion shaft 3 is assembled in the first gear chamber 17. Communicate. A ring gear 9 that projects in the outer diameter direction about the axis X is provided. A fitting recess 11 for fitting the second differential case 2b is provided on the outer periphery of the other end in the axial direction.

  The second differential case 2b is also made of only a low carbon steel (second steel material) having a C content of less than 0.45%, and has a second boss portion 14 extending in the axial direction at the other end in the axial direction. . A second through hole 18 is provided inside the second boss portion 14. A second gear chamber 20 having a larger diameter than the second through hole 18 communicates with the second through hole 18. A fitting convex portion 12 for fitting the fitting concave portion 11 of the first differential case 2a is provided on the outer periphery of one end in the direction. The fitting concave portion 11 and the fitting convex portion 12 are joined by any one welding method of electron beam welding, laser welding, and resistance welding. Thus, the differential case 2 is configured.

  The content of C in the first steel material is, for example, 0.10% to 0.40%. Further, the C content of the second steel material is, for example, 0.10% to 0.40%.

  In the differential case 2, a pinion shaft 3 that rotates integrally with the differential case 2, pinion gears 21 and 22 that are rotatably supported by the pinion shaft 3, and a pinion gear thrust washer that is attached between the pinion gears 21 and 22 and the differential case 2. 25, 26, side gears 23, 24 meshing with the pinion gears 21, 22, and side gear thrust washers 27, 28 attached between the side gears 23, 24 and the differential case 2 are arranged. The C content of the steel material constituting the pinion shaft is also, for example, 0.10% to 0.40%.

  Next, a method for forming the first differential case 2a will be described with reference to FIGS. 2A to 3.

  First, as shown in FIG. 2A, a low carbon steel (eg, SCM420, S35C, etc.) having a cylindrical shape and a C content of less than 0.45% (preferably 0.10% to 0.40%). A preliminary first differential case 42a as shown in FIG. 2B is formed from one material 40 by plastic deformation by hot forging.

  As shown in FIG. 2B, the preliminary first differential case 42a has a first boss portion 13 extending in the axial direction at one end in the axial direction. A preliminary first through hole 43 is formed inside the first boss portion 13. A spare first gear chamber 47 having a larger diameter than the spare first through hole 43 communicates with the spare first through hole 43. In addition, a spare ring gear 49 that protrudes in the outer diameter direction about the axis X is formed. A pre-fitting recess 41 is formed on the outer periphery of the other end in the axial direction.

  As shown in FIG. 3, the preliminary first through hole 43 of the preliminary first differential case 42 a is finished with an inner diameter, and the first lubricating groove 16 is cut to form the first through hole 15. The first preliminary gear chamber 47 is cut into the first gear chamber 17 according to the shapes of the pinion gear thrust washers 25 and 26 and the side gear thrust washer 27. Further, the pinion shaft assembly portion 10 is cut between the outer periphery of the other end of the auxiliary first differential case 42 a in the axial direction and the first gear chamber 17. Then, the caulking recess 10 a is cut at the outer diameter direction end of the pinion shaft assembly 10. The preliminary ring gear 49 and the preliminary fitting recess 41 are cut into required shapes to become the ring gear 9 and the fitting recess 11, respectively.

  The preliminary first differential case 42a after the cutting is subjected to carburizing and quenching. This increases the hardness.

  As a result, the first differential case 2a having a desired hardness with no material breaks in the region from the ring gear 9 to the pinion shaft assembly portion 10 as the torque transmission region is completed as an integrally formed product by forging as a whole.

  Next, a method for forming the second differential case 2b will be described with reference to FIGS. 4A to 4C.

  First, as shown in FIG. 4A, a low carbon steel (for example, SCM420, S35C, etc.) having a cylindrical shape and a C content of less than 0.45% (preferably 0.10% to 0.40%). A spare second differential case 52b as shown in FIG. 4B is formed from the two materials 50 by plastic deformation by hot forging.

  As shown in FIG. 4B, the spare second differential case 52b has a second boss portion 14 extending in the axial direction at one end in the axial direction. A spare second through hole 53 is formed in the second boss portion 14. The spare second through hole 53 communicates with a spare second gear chamber 57 having a diameter larger than that of the spare second through hole 53. A pre-fitting convex portion 52 is formed on the outer periphery of the other end in the axial direction.

  As shown in FIG. 4C, the spare second through hole 53 of the spare second differential case 52 b is finished with an inner diameter, and the second lubricating groove 19 is cut to become the second through hole 18. The second auxiliary gear chamber 57 is cut into the second gear chamber 20 according to the shape of the pinion gear thrust washers 25 and 26 and the side gear thrust washer 28. Further, the preliminary fitting convex portion 52 is cut into a required shape to become the fitting convex portion 12.

  As described above, the second differential case 2b having a desired hardness is completed as an integrally formed product by forging as a whole. The second differential case 2b is not carburized and quenched because the required hardness is lower than that of the first differential case 2a.

  Next, a method for forming the pinion shaft 3 will be described with reference to FIGS. 5A to 6B.

  First, as shown in FIG. 5A, a third material that is a low carbon steel (for example, SCM415) having a cylindrical shape and a C content of less than 0.45% (preferably 0.10% to 0.40%). From 60, a preliminary pinion shaft 63 as shown in FIG. 5B is formed by plastic deformation by cold forging.

  As shown in FIG. 5B, the spare pinion shaft 63 is smaller in diameter than the third material 60 and is longer in the axial direction. A lubrication plane 3c is provided at a location facing the pinion gear hole 21a of the pinion gear 21, and a lubrication plane 3e is provided at a location facing the pinion gear hole 22a of the pinion gear 22.

  Subsequently, in order to increase the hardness, the preliminary pinion shaft 63 is carburized and quenched. Thereafter, as shown in FIGS. 6A and 6B, pinion shaft recesses 3a and 3b are formed by cutting at both ends in the axial direction. Moreover, the outer periphery of the both ends of an axial direction is machined (the carburizing quenching part of the both ends of the axial direction of the pinion shaft 3 is removed). Thus, the pinion shaft 3 having a desired shape and hardness is formed.

  Next, a caulking device 30 for assembling the pinion shaft 3 to the first differential case 2a will be described with reference to FIG. The caulking device 30 includes a support base 31 on which the first differential case 2a is placed at the center thereof. The support base 31 is supported by a support column 32. The caulking device 30 includes an upper caulking punch 33 and a lower caulking punch 34 for caulking both end portions of the pinion shaft 3 to the pinion shaft assembly portion 10 of the first differential case 2a. A spring 35 is provided around the support column 32, and the support base 31 is positioned substantially in the middle of the support column 32 by the elastic force of the spring 35.

  A method for assembling the differential device 1 will be described with reference to FIGS.

  As shown in FIG. 7, the side gear 23 to which the side gear thrust washer 27 is attached on the opposite tooth side is placed on the rotation axis X of the first differential case 2a so that the tooth shape side of the side gear 23 faces the center Y of the differential case. Is done.

  Next, the differential case rotating shaft is arranged such that the pinion gear 21 with the pinion gear thrust washer 25 attached on the side opposite to the tooth profile and the pinion gear 22 with the pinion gear thrust washer 26 attached on the side opposite the tooth form mesh with the side gear 23, respectively. It arrange | positions so that it may mutually oppose about X. At this time, the pinion gear holes 21a and 22a of the pinion gears 21 and 22, the pinion shaft assembly portion 10 of the first differential case 2a, and the holes of the pinion gear thrust washers 25 and 26 are aligned on the same straight line.

  Subsequently, the pinion shaft 3 passes through the pinion shaft assembly portion 10, the hole of the pinion gear thrust washer 25, and the pinion gear hole 21a formed in the pinion gear 21, and is inserted to the rotation axis X of the first differential case 2a. Further, the pinion gear hole 22 a of the pinion gear 22 that is symmetrical with respect to the rotation axis X, the hole of the thrust washer 26 for the pinion gear, and the pinion shaft assembly 10 are guided. Then, the pinion shaft 3 is positioned at a predetermined position of the first differential case 2a. At this time, as shown in FIG. 8A, both end portions of the pinion shaft 3 are only in contact with the pinion shaft assembly portion 10 of the first differential case 2a, and the pinion shaft 3 is movable with respect to the first differential case 2a. .

  As described above, the first differential case 2 a in which the pinion gears 21 and 22, the pinion gear thrust washers 25 and 26, the side gear 23, and the pinion shaft 3 are positioned inside is placed on the support base 31 of the caulking device 30. The At this time, one end of the pinion shaft 3 in the axial direction is supported by the lower crimping punch 34 so that the pinion shaft 3 does not fall out of the first differential case 2a.

  Subsequently, the upper caulking punch 33 provided above the support base 31 is lowered. The support base 31 is located at a substantially intermediate portion of the support column 32 by the elastic force of the spring 35 provided around the support column 32 of the support table 31. However, when the tip of the upper caulking punch 33 presses the pinion shaft recess 3 a of the pinion shaft 3, the first differential case 2 a and the support base 31 placed on the support base 31 are lowered while the spring 35 is contracted.

  Further, when the tip of the upper caulking punch 33 is press-fitted into the pinion shaft recess 3a and the tip of the lower caulking punch 34 is press-fitted into the pinion shaft recess 3b, as shown in FIG. 8B, the upper caulking punch 33 and Due to the lower caulking punch 34, the pinion shaft recesses 3a and 3b are plastically deformed into the assembly recess 10a of the pinion shaft assembly 10 of the first differential case 2a. That is, caulking is performed. Here, since the carburizing and quenching portions at both ends in the axial direction of the pinion shaft 3 are removed in advance by cutting, cracks and the like are generated even if the pinion shaft recesses 3a and 3b are plastically deformed in the assembly recess 10a. There is no.

  When the caulking process is completed, the upper caulking punch 33 is raised, and the first differential case 2a and the support base 31 placed on the support base 31 are returned to the substantially intermediate portion of the support column 32 by the restoring force of the spring 35. . Thereby, the caulking fixing of the first differential case 2a and the pinion shaft 3 is completed.

  Next, as shown in FIG. 9, the side gear 24 to which the side gear thrust washer 28 is attached on the opposite tooth side is placed so as to mesh with the pinion gears 21 and 22.

  And the fitting recessed part 11 of the 1st differential case 2a and the fitting convex part 12 of the 2nd differential case 2b are fitted. Thereafter, the fitting concave portion 11 and the fitting convex portion 12 are melt-bonded by electron beam welding, and the assembly of the differential case 2 of the differential device 1 is completed.

  According to the differential case 2 as described above, since it is not necessary to fix the first differential case 2a and the second differential case 2b with bolts, the thickness of the first differential case 2a and the second differential case 2b can be reduced. The weight of the differential case 2 can be reduced. In addition, since the number of parts (volts) is reduced, the cost can be reduced. Further, the ring gear 9 side portion (including the ring gear 9) from the pinion shaft assembly portion 10 is integrally formed by forging only from a low carbon steel having a C content of less than 0.45% as the first differential case 2a. Since the welded portion between the first differential case 2a and the second differential case 2b is located outside the torque transmission region (the region between the pinion shaft assembly 10 and the ring gear 9), the welded portion having low strength during torque transmission Is prevented from being destroyed. Further, since the first differential case 2a having a C content of less than 0.45% and the second differential case 2b having a C content of less than 0.45% are welded, the welded portion is hardened and cracks occur. Defects such as these are less likely to occur. Thereby, the differential apparatus 1 which has desired durability can be provided.

  Further, the first differential case 2a and the pinion shaft 3 can be fixed very easily by caulking and fixing the first differential case 2a and the pinion shaft 3. In particular, since the first differential case 2a is integrally formed by forging as a whole from only low carbon steel having a C content of less than 0.45%, it has high toughness. For this reason, even if the pinion shaft 3 is caulked and fixed, the first differential case 2a is not destroyed.

  Furthermore, the pinion shaft 3 is also formed only from a low carbon steel having a C content of less than 0.45%. Thereby, since the toughness of the pinion shaft 3 is also high, the pinion shaft 3 is not broken when the pinion shaft 3 is caulked and fixed.

  In the above embodiment, the first differential case 2a and the second differential case 2b are formed by hot forging, but may be cold forging or warm forging.

  Further, as an example of melting and joining the first differential case 2a and the second differential case 2b, joining by electron beam welding has been described. However, even if other melting welding such as laser welding or resistance welding is used. Good.

  In addition, the fitting recess 11 is formed in the first differential case 2a and the fitting protrusion 12 is formed in the second differential case 2b, and positioning is performed during welding, but the fitting protrusion 11 is formed in the first differential case 2a. A part may be shape | molded and a fitting recessed part may be shape | molded by the 2nd differential case 2b, and positioning may be performed.

  Further, in the above-described embodiment, the both ends of the pinion shaft 3 are plastically deformed toward the first differential case 2a, thereby being caulked and fixed. However, the first differential case 2a may be caulked and fixed by plastically deforming both ends of the pinion shaft 3.

  Further, the first differential case 2a and the second differential case 2b are made of low carbon steel having a C content of less than 0.45% in order to avoid defects such as the welded portion being hardened and cracked. Although it is one of the important features of the invention, the C content is preferably 0.10% to 0.40% from the viewpoint of preventing hardening of the welded portion. Further, from the viewpoint of preventing hardening of the welded portion, it is particularly preferably 0.10% to 0.35%.

  The above explanation is mainly made on carbon steel materials whose properties are generally determined by the amount of carbon. The present inventor further studied structural steel materials whose properties are affected by the amount of steel components other than carbon. As a result, it was found that such structural steel should be based on carbon equivalent instead of carbon content.

  The carbon equivalent is defined in JIS as follows.

Carbon equivalent = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14
Here, C is carbon amount (%), Mn is manganese amount (%), Si is silicon amount (%), Ni is nickel amount (%), Cr is chromium amount (%), Mo is molybdenum amount (%) , V is the amount of vanadium (%).

And if carbon steel material of the carbon amount of "0.45%" which is the threshold value which this inventor discovered initially is converted using the component data of general carbon steel materials (for example, S45C etc.), "0.60% It is equivalent to a structural steel material having a carbon equivalent of "", and it was actually confirmed that such substitution is possible in the present invention. (An example of S45C: C = 0.46, Mn = 0.72, Si = 0.18, Ni = 0.04, Cr = 0.11, V = 0.00: Carbon content = 0.46%, carbon Equivalent = 0.613%)
That is, in contrast to the above-described embodiment, a steel material having a carbon equivalent of less than 0.60% can be used instead of the low carbon steel having a C content of less than 0.45%.

  Even in this case, since the first differential case 2a and the second differential case 2b do not need to be fixed with bolts, the thickness of the first differential case 2a and the second differential case 2b can be reduced, and the weight of the differential case 2 can be reduced. Can be achieved. In addition, since the number of parts (volts) is reduced, the cost can be reduced. Further, the ring gear 9 side portion (including the ring gear 9) from the pinion shaft assembly portion 10 is forged only from the first steel material having a carbon equivalent of less than 0.60% as the first differential case 2a, or forging and cutting, Since the welded portion between the first differential case 2a and the second differential case 2b is located outside the torque transmission region (the region between the pinion shaft assembly 10 and the ring gear 9), torque transmission is performed. Sometimes the weak welds are prevented from being destroyed. Further, since the first differential case 2a made of the first steel material having a carbon equivalent of less than 0.60% and the second differential case 2b made of the second steel material having a carbon equivalent of less than 0.60% are welded, Defects such as hardening and cracking are less likely to occur. Thereby, the differential apparatus which has desired durability can be provided.

  In addition, when the 1st steel material and the 2nd steel material are joined by fusion welding, when the sum of the value of the high temperature crack sensitivity of the 1st steel material and the value of the high temperature crack sensitivity of the 2nd steel material is 7 or less, Occurrence can be prevented more reliably. Here, the value of hot cracking sensitivity is calculated by the following equation.

Hot cracking susceptibility = 1000 × C (S + P + (Si / 25) + (Ni / 100)) / (3Mn + Cr + Mo + V)
Here, C is the carbon content (%), S is the sulfur content (%), P is the phosphorus content (%), Si is the silicon content (%), Ni is the nickel content (%), and Mn is the manganese content (%). Cr is the chromium content (%), Mo is the molybdenum content (%), and V is the vanadium content (%).

  In FIG. 10, the data of the steel material which this inventor actually examined are shown. In the table, Ceq is carbon equivalent, and HCS is hot cracking sensitive. And the evaluation result at the time of using each steel material shown by FIG. 10 as the 1st differential case 2a and the 2nd differential case 2b in the said embodiment is shown in FIG.

  As shown in FIG. 11, the suitability of steel materials to be melt-bonded was determined with a carbon amount of 0.45% to a carbon equivalent of 0.60% as a threshold value. It has also been found that when the sum of the hot cracking susceptibility values of the two steel materials to be joined is 7 or less, the occurrence of cracking is more reliably prevented.

  Needless to say, when selecting a steel material, its workability is also taken into account (a steel material with poor workability that makes it difficult to perform desired processing is not used).

It is sectional drawing of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the 1st raw material for demonstrating the formation process of the 1st differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the preliminary | backup 1st differential case for demonstrating the formation process of the 1st differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the 1st differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the 2nd raw material for demonstrating the formation process of the 2nd differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the preliminary | backup 2nd differential case for demonstrating the formation process of the 2nd differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the 2nd differential case of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the 3rd material for demonstrating the formation process of the pinion shaft of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the preliminary | backup pinion shaft for demonstrating the formation process of the pinion shaft of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the pinion shaft of the differential apparatus which concerns on one embodiment of this invention. It is a top view of the pinion shaft of the differential apparatus which concerns on one embodiment of this invention. It is sectional drawing of the apparatus which caulks a 1st differential case and a pinion shaft. It is a principal part top view of the pinion shaft assembly | attachment part of a 1st differential case before caulking and fixing a pinion shaft. It is a principal part top view of the pinion shaft assembly | attachment part of a 1st differential case after caulking and fixing a pinion shaft. It is sectional drawing for demonstrating the method to assemble | attach a 1st differential case and a 2nd differential case. The table | surface which shows the data of the steel materials which this inventor actually examined. The table | surface which shows the evaluation result as a steel material for fusion welding about the steel materials of FIG.

Claims (8)

A ring gear (9) that rotates upon input of a driving force from a driving source;
A differential case (2) rotating integrally with the ring gear (9);
A pinion shaft (3) assembled to the differential case (2) and rotating integrally with the differential case (2);
Pinion gears (21, 22) rotatably supported on the pinion shaft (3);
Side gears (23, 24) meshing with the pinion gears (21, 22);
In a differential device equipped with
The differential case (2)
A first differential case (2a) on the ring gear (9) side from a pinion shaft assembly (10) to which the pinion shaft (3) is assembled;
A second differential case (2b) on the opposite side in the axial direction from the ring gear (9) side from the pinion shaft assembly (10) to which the pinion shaft (3) is assembled;
Consists of
The first differential case (2a) is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of less than 0.45%.
The second differential case (2b) is also integrally formed by forging or forging and cutting from a low carbon steel having a C content of less than 0.45%.
The differential device, wherein the first differential case (2a) and the second differential case (2b) are joined by welding. The differential apparatus according to claim 1, wherein the first differential case (2a) and the pinion shaft (3) are fixed by caulking. The differential device according to claim 2, wherein the pinion shaft (3) is also formed only from a low carbon steel having a C content of less than 0.45%. The first differential case (2a) is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of 0.10% to 0.40%. The differential device according to claim 1. The second differential case (2b) is integrally formed by forging or forging and cutting only from a low carbon steel having a C content of 0.10% to 0.40%. The differential device according to claim 1. A ring gear (9) that rotates upon input of a driving force from a driving source;
A differential case (2) rotating integrally with the ring gear (9);
A pinion shaft (3) assembled to the differential case (2) and rotating integrally with the differential case (2);
Pinion gears (21, 22) rotatably supported on the pinion shaft (3);
Side gears (23, 24) meshing with the pinion gears (21, 22);
In a differential device equipped with
The differential case (2)
A first differential case (2a) on the ring gear (9) side from a pinion shaft assembly (10) to which the pinion shaft (3) is assembled;
A second differential case (2b) on the opposite side in the axial direction from the ring gear (9) side from the pinion shaft assembly (10) to which the pinion shaft (3) is assembled;
Consists of
The first differential case (2a) is integrally formed by forging or forging and cutting only from the first steel material having a carbon equivalent of less than 0.60%.
The second differential case (2b) is also integrally formed by forging or forging and cutting only from the second steel material having a carbon equivalent of less than 0.60%.
The differential device, wherein the first differential case (2a) and the second differential case (2b) are joined by welding. The first steel material and the second steel material are selected so that the sum of the value of the hot cracking susceptibility of the first steel material and the value of the hot cracking susceptibility of the second steel material is 7 or less. A melt-bonded product having a high-strength portion as described in 1. The differential device according to claim 6 or 7, wherein the first differential case (2a) and the pinion shaft (3) are fixed by caulking.

Images