JP2021008899A - Transmission device - Google Patents

Abstract

To provide a transmission device for fixing a hub part of a ring gear to a flange part on the outer periphery of a transmission member via a weld zone, while reducing residual stress to occur around the weld zone of the flange part due to the thermal contraction of the weld zone.SOLUTION: In a lateral face sf1 of a flange part 3f provided on the outer periphery of a transmission member 3 in the radially outward direction, an annular groove Gf for reducing residual stress to occur around a weld zone 3w of the flange part 3f due to the mutually pulling force of the flange part 3f and the hub part Rb on the inner periphery of a ring gear R in association with the thermal contraction of the weld zone 3w is recessed in a position where the annular groove Gf and a positioning outer peripheral part A3 of the flange part 3f partly overlap with each other in view from a projection plane perpendicular to the rotation axis of a transmission case 3.SELECTED DRAWING: Figure 2

Description

The present invention includes a transmission device, particularly a rotatable transmission member having a radially outward flange portion on the outer circumference and a ring gear having a hub portion surrounding the flange portion on the inner circumference, and the outer circumference of the flange portion. The surface relates to a transmission device including at least a first outer peripheral portion that extends inward in the axial direction from one side surface of the flange portion in the axial direction and the inner peripheral surface of the hub portion is fitted and welded.

In the present invention and the present specification, the "axial direction" refers to the direction along the rotation axis of the transmission member (the first axis in the embodiment), and in particular, the "inward side in the axial direction from the side surface" refers to the side surface. Refers to the inner side of the flange portion having the side surface in the axial direction, that is, the wall thickness direction, and the "outer side in the axial direction than the side surface portion" refers to the side surface with the side surface portion as a reference. Refers to the outer side of the flange portion having the portion in the axial direction, that is, the wall thickness direction. Further, the "diameter direction" means a radial direction with the rotation axis of the transmission member as the central axis.

The transmission device is already known, for example, as disclosed in Patent Document 1 below.

Japanese Unexamined Patent Publication No. 2016-188657

In the transmission device of Patent Document 1, the welded portion between the first outer peripheral portion of the flange portion of the transmission member and the hub portion of the ring gear thermally expands at the time of welding and heat shrinks after the welding, so that the flange portion and the hub portion , The portions sandwiching the welded portion are pulled with a large force in the direction of approaching each other in the radial direction. In this case, the ring gear is configured to have high rigidity as a whole including the hub portion, and in order to maintain the original annular shape, the welded portion and the peripheral portion of the welded portion of the flange portion are particularly on the hub portion side. There is a tendency for relatively high residual stress to be generated in the portion due to strong tension.

Note that FIG. 4 shows an example of the distribution state of the residual stress obtained by the simulation analysis by a computer for the comparative example of the same type as the differential device. In this figure, the light ink portion indicates the portion where the residual stress is generated, and the darker the tone, the larger the residual stress.

The present invention has been proposed in view of the above, and an object of the present invention is to provide a transmission device capable of reducing the residual stress with a simple structure.

In order to achieve the above object, the present invention includes a rotatable transmission case having a radially outward flange portion on the outer circumference and a ring gear having a hub portion surrounding the flange portion on the inner circumference. The outer peripheral surface of the flange portion extends inward in the axial direction from the side surface on one side in the axial direction of the flange portion, and the inner peripheral surface of the hub portion is fitted and welded to the first outer peripheral surface. A positioning convex portion protruding from the inner peripheral surface of the hub portion on the other side in the axial direction from the first outer peripheral portion is fitted or press-fitted to position the hub portion and the flange portion in the radial direction and the axial direction. In a transmission device having at least an outer peripheral portion for positioning, the side surface of the flange portion has a force around the welded portion of the flange portion due to a force that pulls the flange portion and the hub portion with each other due to thermal shrinkage of the welded portion. First, the annular groove for reducing the residual stress generated in the transmission case is recessed at a position where the annular groove and the outer peripheral portion for positioning partially overlap when viewed from a projection plane orthogonal to the rotation axis of the transmission case. It is a feature of.

Similarly, in order to achieve the above object, the present invention comprises a case body, a rotatable transmission case having a flange portion protruding outward in the radial direction on the outer periphery of the case body, and a hub surrounding the flange portion. A ring gear having a portion on the inner circumference is provided, and the flange portion is offset on one side in the axial direction from the center of the case body, and the outer surface of the case body and the flange portion are arranged in the offset direction. An annular recess facing one side in the axial direction is formed between them, and the outer peripheral surface of the flange portion extends inward in the axial direction from the side surface of the flange portion facing one side in the axial direction. In a transmission device including at least a first outer peripheral portion to which the inner peripheral surface of the hub portion is fitted and welded, the flange portion and the hub portion are provided on the side surface of the flange portion due to heat shrinkage of the welded portion. An annular groove that reduces the residual stress generated around the welded portion of the flange portion due to the force of pulling each other is provided between the recess and the welded portion in the radial direction, shallower than the recess. Is the second feature.

Further, in the present invention, in addition to the first or second feature, the side surface of the flange portion includes a first side surface portion extending radially inward from the annular groove and a radial outward side from the annular groove. The first side surface portion has a second side surface portion extending in the axial direction, or the first side surface portion has an axial position that coincides with the second side surface portion, or the first side surface portion projects outward in the axial direction from the second side surface portion. The third feature is that.

According to the first feature, the outer peripheral surface of the flange portion of the transmission case extends inward in the axial direction from the side surface on one side in the axial direction of the flange portion, and the inner peripheral surface of the hub portion of the ring gear is fitted and welded. In a transmission device having a first outer peripheral portion to be formed and a positioning outer peripheral portion into which a positioning convex portion protruding from the inner peripheral surface of the hub portion on the other side in the axial direction from the first outer peripheral portion is fitted or press-fitted. On the side surface of the flange portion, an annular groove that reduces the residual stress generated around the welded portion of the flange portion due to the force that the flange portion and the hub portion pull each other due to the thermal shrinkage of the welded portion is formed on the rotation axis of the transmission case. The annular groove and the outer peripheral portion for positioning are recessed at a position where the annular groove and the outer peripheral portion for positioning partially overlap when viewed from the projection plane orthogonal to the annular groove, and the rigidity in the vicinity of the welded portion of the flange portion is appropriately weakened by this annular groove.

According to the second feature, the flange portion of the transmission case is offset on one side in the axial direction from the center of the case body, and an annular shape is formed between the outer surface of the case body and the flange portion in the offset direction. A recess is formed, and the first outer peripheral portion of the flange portion extends inward in the axial direction from the side surface of the flange portion facing one side in the axial direction, and the inner peripheral surface of the hub portion of the ring gear is fitted and welded. In the apparatus, an annular groove is formed on the side surface of the flange portion in the radial direction to reduce the residual stress generated around the welded portion of the flange portion due to the force of the flange portion and the hub portion pulling each other due to the thermal shrinkage of the welded portion. The recess is shallower than the recess between the recess and the welded portion, and the annular groove moderately weakens the rigidity of the flange portion in the vicinity of the welded portion.

As described above, according to the first and second features, the annular groove recessed in the specific portion of the side surface of the flange portion moderately weakens the rigidity in the vicinity of the welded portion of the flange portion, resulting in thermal shrinkage of the welded portion. Along with this, the residual stress generated around the welded portion of the flange portion can be effectively reduced by the force of the flange portion and the hub portion pulling each other, and as a result, the transmission member has a high residual stress at the flange portion. It is possible to effectively prevent the occurrence of delayed destruction.

Further, according to the third feature, the side surface of the flange portion has a first side surface portion extending radially inward from the annular groove and a second side surface portion extending radially outward from the annular groove. , The first side surface portion has the same axial position as the second side surface portion, or projects outward in the axial direction from the second side surface portion, so even if an annular groove is specially provided, the diameter is larger than that. Sufficient rigidity of the first side surface portion on the inner side in the direction can be secured. Therefore, the effect of reducing the residual stress by the special provision of the annular groove can be achieved without lowering the rigidity of the flange portion on the inner side in the radial direction from the annular groove.

Longitudinal sectional view of a main part showing a differential device according to an embodiment of the present invention. Two-part enlarged cross-sectional view of FIG. FIG. 2 Corresponding sectional view showing the residual stress distribution of the differential case in the completed cooling state after welding, which was obtained by simulation analysis by a computer. FIG. 3 Corresponding sectional view showing a comparative example

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, in FIG. 1, a difference in which power from a power source (for example, an in-vehicle engine) (not shown) is distributed and transmitted to axles S1 and S2 as a pair of output shafts in a transmission case MC of a vehicle (for example, an automobile). The moving device 10 is housed. The differential device 10 is an example of a transmission device, and in the present embodiment, the differential device 10 includes a metal differential case 3 and a differential gear mechanism 20 built in the differential case 3.

The differential case 3 is a hollow case body 3c in which the differential gear mechanism 20 is housed, and first and second bearings that are integrally connected to the right side and left side of the case body 3c and lined up on the first axis X1. The bosses 3b1 and 3b2 and an annular flange portion 3f integrally formed on the outer peripheral portion of the case body 3c in the outward direction in the radial direction are provided. The case body 3c is formed in a substantially spherical shape, and the inner surface 3ci thereof is formed in a spherical shape around the center O of the differential case 3.

Then, the first and second bearing bosses 3b1, 3b2 are rotatably supported by the mission case MC around the first axis X1 via the bearings 13 and 14 on the outer peripheral side of the bosses 3b1, 3b2. The left and right axles S1 and S2 are rotatably fitted and supported on the inner peripheral surfaces of the first and second bearing bosses 3b1 and 3b2, respectively.

It should be noted that one of the fitting surfaces of the bearing bosses 3b1 and 3b2 and the axles S1 and S2 can exert a screw pumping action of feeding the lubricating oil in the transmission case MC into the differential case 3 as it rotates relative to the other side. Spiral grooves 15 and 16 are provided.

The inner peripheral portion of the ring gear R, that is, the hub portion Rb, is fixed to the flange portion 3f of the differential case 3 by a fixing means that combines welding and press fitting (or fitting) as described later. Further, the flange portion 3f of the illustrated example is offset from the center O of the case body 3c to one side in the axial direction (that is, the first bearing boss 3b1 side), and the outer surface of the case body 3c and the flange portion 3f are arranged in the offset direction. An annular recess 32 facing one side in the axial direction is formed between the two.

The ring gear R is integrally formed with a short cylindrical rim portion Ra having a helical gear (oblique tooth) -shaped tooth portion Rag on the outer circumference and a narrower axial width than the rim portion Ra on the inner peripheral side of the rim portion Ra. It has a series of hubs Rb, and the tooth portion Rag meshes with a drive gear 50 which is an output portion of a transmission connected to a power source.

Then, the rotational driving force from the drive gear 50 is transmitted to the case body 3c of the differential case 3 via the ring gear R and the flange portion 3f. In FIG. 1, the tooth portion Rag is displayed in cross section along the tooth muscle in order to simplify the display.

The differential gear mechanism 20 is rotatably connected to a pinion shaft 21 arranged on the second axis X2 orthogonal to the first axis X1 at the center O of the case body 3c and supported by the case body 3c, and the pinion shaft 21. A pair of supported pinion gears 22 and 22 and left and right side gears 23 and 23 that mesh with each pinion gear 22 and are rotatable around the first axis X1 are provided. The side gears 23 and 23 function as output gears of the differential gear mechanism 20, and the inner end portions of the left and right axles S1 and S2 are spline-fitted on the inner peripheral surfaces of the side gears 23 and 23. ..

The back surfaces of the pinion gear 22 and the side gear 23 are rotatably supported on the spherical inner surface 3ci of the case body 3c via the pinion gear washer Wp and the side gear washer Ws, respectively (or directly without the washer). At least the pinion gear support surface and the side gear support surface of the inner surface 3ci of the case body 3c are machined by a processing device such as a lathe through a work window H described later after casting the differential case 3.

The pinion shaft 21 is inserted and held in a pair of pinion shaft support holes 3ch formed at the outer peripheral end of the case body 3c and extending on the second axis X2. Further, a retaining pin 17 penetrating across one end of the pinion shaft 21 is inserted (for example, press-fitted) into the case body 3c, and the retaining pin 17 separates the pinion shaft 21 from the pinion shaft support hole 3ch. Is blocked.

Then, the rotational driving force transmitted from the drive gear 50 to the case body 3c of the differential case 3 via the ring gear R is distributed and transmitted to the pair of axles S1 and S2 via the differential gear mechanism 20 while allowing differential rotation. Will be done. Since the differential function of the differential gear mechanism 20 is well known in the past, the description thereof will be omitted.

Further, as shown by the dotted line in FIG. 1, the differential case 3 has a pair of work windows H on the side wall of the case body 3c on the other side in the axial direction (that is, the second bearing boss 3b2 side) from the flange portion 3f. The pair of work windows H are symmetrically arranged and formed on both sides of a virtual plane including the first and second axes X1 and X2. Each work window H is a window for allowing machining on the inner surface 3ci of the case body 3c and assembling the differential gear mechanism 20 into the case body 3c, and is formed in a sufficiently large shape suitable for the purpose. To.

Next, an example of a structure in which the hub portion Rb of the ring gear R is fixed to the flange portion 3f of the differential case 3 will be described with reference to FIG.

The outer peripheral surface of the flange portion 3f extends inward in the axial direction from the first side surface sf1 on one side in the axial direction of the flange portion 3f (that is, the first bearing boss 3b1 side), and is a welded portion on the inner circumference of the hub portion Rb. A first outer peripheral portion A1 to which B1 is fitted and welded, and a second outer peripheral portion A2 adjacent to the axial inner end of the first outer peripheral portion A1 are provided. An annular cavity portion 30 having a rectangular cross section is formed between the second outer peripheral portion A2 and the opposite surface of the cavity forming portion B2 recessed in the inner circumference of the hub portion Rb. The fitting of the first outer peripheral portion A1 and the welded portion B1 before welding may be light press-fitting or may be fitting without play.

The hollow portion 30 faces the inner end in the axial direction of the welded portion 3w between the first outer peripheral portion A1 and the hub portion Rb (more specifically, the welded portion B1). Then, the cavity portion 30 is formed so as to expand at least outward side in the radial direction (also inward side in the embodiment) with respect to the welded portion 3w. The hollow portion 30 can be used as a degassing means for smoothly discharging the gas generated in the welded portion 3w to the outside. Although the second outer peripheral portion A2 in the illustrated example is lowered by one step inward in the radial direction from the first outer peripheral portion A1, it may be continuous with the first outer peripheral portion A1.

Further, the outer peripheral surface of the flange portion 3f has a positioning outer peripheral portion A3 on the other side in the axial direction (that is, the second bearing boss 3b2 side) from the cavity portion 30, and the positioning outer peripheral portion A3 is the second outer peripheral portion. The portion A2 is formed in a stepped shape that descends inward in the radial direction from the inner end in the axial direction. Then, the positioning convex portion B3 projecting inward in the radial direction is engaged with the outer peripheral portion A3 for positioning with the inner circumference of the hub portion Rb. By the engagement, the hub portion Rb is positioned radially and axially with respect to the flange portion 3f, respectively.

For the positioning, the positioning outer peripheral portion A3 includes a radial positioning surface A3r for axially press-fitting the inner peripheral surface B3i of the positioning convex portion B3 so as to position the hub portion Rb in the radial direction with respect to the flange portion 3f. It has an axial positioning surface A3a of the positioning convex portion B3 that abuts the side surface B3s on the first outer peripheral portion A1 side so as to position the hub portion Rb in the axial direction with respect to the flange portion 3f. The relationship between the radial positioning surface A3r and the inner peripheral surface B3i of the positioning convex portion B3 may be a loose fitting instead of the above press fitting.

The axial positioning surface A3a extends radially inward from the axial inner end of the second outer peripheral portion A2 on a virtual plane orthogonal to the first axis X1. Then, the radial inner end portion of the axial positioning surface A3a smoothly continues to the radial positioning surface A3r via the rounded surface. Further, the radial positioning surface A3r is formed in a cylindrical surface shape around the first axis X1 and is continuous with the second side surface sf2 on the other side in the axial direction (that is, the second bearing boss 3b2 side) of the flange portion 3f. ..

Chamfered surfaces are provided at both ends of the inner peripheral surface B3i of the positioning convex portion B3 in the axial direction, and a gap is formed between each chamfered surface and the outer peripheral portion A3 for the positioning surface.

Further, on the first side surface sr1 of the hub portion Rb on one side in the axial direction (that is, the side of the first bearing boss 3b1), an annular groove Gr recessed shallowly inward in the axial direction is provided. The depth of the annular groove Gr is set to a depth that hardly reduces the rigidity for maintaining the annular shape of the hub portion Rb.

By the way, on the first side surface sf1 of the flange portion 3f on one side in the axial direction (that is, the first bearing boss 3b1 side), the flange portion 3f and the hub portion Rb are pulled together by the heat shrinkage of the welded portion 3w. The annular groove Gf that reduces the residual stress generated in the welded portion 3w of 3f and its peripheral portion is a part of the annular groove Gf and the outer peripheral portion A3 for positioning when viewed from the projection plane orthogonal to the first axis X1 of the differential case 3. It is recessed at the overlapping position.

The annular groove Gf is recessed between the annular recess 32 and the welded portion 3w in the radial direction at a depth shallower than the recess 32 and at a depth shallower than the axial length of the welded portion 3w. ..

Further, the first side surface sf1 of the flange portion 3f has a first side surface portion sf11 extending radially inward from the annular groove Gf and a second side surface portion sf12 extending radially outward from the annular groove Gf. There is. The first side surface portion sf11 is formed so as to coincide with the second side surface portion sf12 in the axial direction as shown in the illustrated example, or to project outward in the axial direction from the second side surface portion sf12. To.

Next, the operation of the first embodiment will be described.

The differential case 3 is cast and molded from a metal material (for example, aluminum, aluminum alloy, cast iron, etc.), and after casting, predetermined portions of the inner and outer surfaces of the differential case 3 (for example, the inner surface 3ci of the case body 3c, the bearing boss 3b1, The inner and outer circumferences of 3b2, the flange portion 3f, the pinion shaft support hole 3ch, etc.) are machined.

Each element of the differential gear mechanism 20 is incorporated into the machined differential case 3 through the work window H, and the ring gear R in which the tooth portion Rag is formed in advance with respect to the flange portion 3f of the differential case 3 is formed. The inner peripheral portion of the hub portion Rb is joined by both press fitting and welding.

Next, the coupling work of the ring gear R will be described. First, the welded portion B1 of the hub portion Rb of the ring gear R is fitted to the first outer peripheral portion A1 of the flange portion 3f, and the inner peripheral surface B3i of the positioning convex portion B3 of the hub portion Rb is the diameter of the third outer peripheral portion A3. It is press-fitted into the directional positioning surface A3r, and the inner side surface B3s of the positioning convex portion B3 is brought into contact with the axial positioning surface A3a of the third outer peripheral portion A3. As a result, the hub portion Rb is positioned in the radial direction and the axial direction with respect to the flange portion 3f.

After that, the fitting portion between the welded portion B1 of the hub portion Rb and the first outer peripheral portion A1 of the flange portion 3f is welded. For example, as shown by a chain line in FIG. 2, this welding operation is performed from the welding laser torch T toward the outer end of the fitting portion between the first outer peripheral portion A1 of the flange portion 3f and the welded portion B1 of the hub portion Rb. The laser is irradiated, and the irradiated portion is gradually moved over the entire circumference of the outer end of the fitting portion.

Thus, the inner peripheral portion of the hub portion Rb of the ring gear R is firmly coupled to the flange portion 3f of the differential case 3 at a fixed position by using press fitting and welding together.

By the way, FIG. 4 shows a comparative example having no technical feature (annular groove Gf) of the present invention. In this case, the flange portion 3f in the differential case 3 as a transmission case (transmission member) and the welded portion 3w between the hub portion Rb of the ring gear R are thermally expanded during welding, and the flange portion 3f is thermally contracted after the welding. And the portion of the hub portion Rb that sandwiches the welded portion 3w is pulled with a large force in the radial direction so as to approach each other, as shown by the white arrows in FIG.

In this case, the ring gear R is configured to have high rigidity as a whole including the hub portion Rb on the inner peripheral side, and is intended to maintain the original annular shape. Therefore, the welded portion 3w and the flange portion 3f are particularly welded. The peripheral portion of the portion 3w is strongly pulled toward the hub portion Rb side, and a relatively high residual stress tends to be generated in the portion (see the residual stress distribution in FIG. 4).

On the other hand, according to the present embodiment, on the first side surface sf1 of the flange portion 3f, the welded portion of the flange portion 3f is subjected to a force in which the flange portion 3f and the hub portion Rb are mutually pulled by the heat shrinkage of the welded portion 3w. An annular groove Gf for reducing residual stress generated in 3w and its peripheral portion is recessed. In this case, the annular groove Gf is located at a position where the annular groove Gf and the positioning outer peripheral portion A3 partially overlap when viewed from the projection plane orthogonal to the first axis X1 of the differential case 3, and the annular recess 32 and the annular recess 32 in the radial direction. The depth is set to be between the welded portion 3w, shallower than the recess 32, and shallower than the axial length tw of the welded portion 3w.

Therefore, since the rigidity of the peripheral portion of the welded portion 3w of the flange portion 3f can be appropriately weakened by the special provision of the annular groove Gr, as is clear from FIG. 3, the flange portion 3f, which was remarkable in the comparative example, It is possible to reduce the residual stress generated in the welded portion 3w and its peripheral portion. As a result, the differential case 3 can effectively prevent the occurrence of delayed fracture due to the increase in residual stress in the flange portion 3f, particularly in the peripheral portion of the welded portion 3w.

Further, the first side surface sf1 of the flange portion 3f has a first side surface portion sf11 extending radially inward from the annular groove Gf and a second side surface portion sf12 extending radially outward from the annular groove Gf. In particular, the first side surface portion sf11 is formed so that the position in the axial direction coincides with the second side surface portion sf12, or, although not shown, the first side surface portion sf11 projects outward in the axial direction from the second side surface portion sf12. To. Therefore, even if the annular groove Gf is specially provided, the rigidity of the first side surface portion sf11 on the inner side in the radial direction can be sufficiently secured. Therefore, the rigidity of the flange portion 3f on the inner side in the radial direction from the annular groove Gf can be sufficiently secured. It is possible to achieve the effect of reducing the residual stress by specially installing the annular groove Gf without lowering.

Further, in the present embodiment, the annular groove Gf and the recess 32 are formed as substantially separate recesses in the first side surface portion sf11. On the other hand, for example, it is conceivable to form the recess 32 and the annular groove Gf as one continuous recess without providing the first side surface portion sf11, but the first side surface portion sf11 is provided as in the embodiment. Therefore, even if the recess 32 is formed for weight reduction, the rigidity of the flange portion 3f can be sufficiently secured by the first side surface portion sf11.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various design changes can be made without departing from the gist thereof.

For example, in the above embodiment, the differential device 10 as a transmission device is implemented as a vehicle differential device, particularly as a differential device between the left and right drive wheels. However, in the present invention, the differential device 10 is used. It may be implemented as a differential between the front and rear drive wheels, or it may be implemented as a differential in various mechanical devices other than vehicles.

Further, the present invention may be applied to a transmission device other than a differential device (for example, a speed reducer, a speed increase device, a transmission device, etc.), in which case a rotating case or a rotating member responsible for torque transmission of the transmission device is transmitted. It becomes a case or a transmission member.

Further, in the above embodiment, the tooth portion Rag of the ring gear R is used as a helical gear, but the ring gear of the present invention has a tooth shape that receives a thrust load in the direction along the first axis X1 by meshing with the drive gear 50. It may be another gear (for example, bevel gear, hypoid gear, etc.). Alternatively, a tooth-shaped gear (for example, a spur gear) that does not receive the thrust load due to meshing with the drive gear 50 may be used.

Further, in the above embodiment, the flange portion 3f of the differential case 3 is coupled with the hub portion Rb of the ring gear R in which the tooth portion Rag is formed in advance, but the ring gear R before the tooth portion Rag is formed is shown. The tooth portion Rag may be formed and processed after being coupled to the hub portion Rb.

Further, in the above-described embodiment, laser welding is used for welding between the flange portion 3f and the hub portion Rb, but in the present invention, another welding method (for example, electron beam welding or the like) may be used.

A1 ・ ・ ・ ・ ・ First outer peripheral part A3 ・ ・ ・ ・ ・ Positioning outer peripheral part B3 ・ ・ ・ ・ ・ Positioning convex part Gf ・ ・ ・ ・ ・ Ring groove R ・ ・ ・ ・ ・ ・ Ring gear Rb ・ ・ ・ ・ ・ ・・ Hub portion sf1 ・ ・ ・ ・ First side surface sf11, sf12 as a side surface on one side in the axial direction of the flange portion ・ ・ ・ ・ First and second side surface portions X1 ・ ・ ・ ・ ・ First axis 3 as a rotation axis・ ・ ・ ・ Diff case 3c as a transmission case ・ ・ ・ ・ ・ Case body 3f ・ ・ ・ ・ ・ Flange part 3w ・ ・ ・ ・ ・ Welded part 10 ・ ・ ・ ・ ・ Differential device 32 as a transmission device・ ・ Dent

Claims (3)

A ring gear (R) having a rotatable transmission case (3) having a radially outward flange portion (3f) on the outer circumference and a hub portion (Rb) surrounding the flange portion (3f) on the inner circumference. The outer peripheral surface of the flange portion (3f) extends inward in the axial direction from the side surface (sf1) on one side in the axial direction of the flange portion (3f), and is inside the hub portion (Rb). A first outer peripheral portion (A1) to which the peripheral surfaces are fitted and welded, and a positioning convex portion protruding from the inner peripheral surface of the hub portion (Rb) on the other side in the axial direction from the first outer peripheral portion (A1). In a transmission device in which (B3) is fitted or press-fitted, the hub portion (Rb) and the flange portion (3f) have at least a positioning outer peripheral portion (A3) for positioning each other in the radial and axial directions.
On the side surface (sf1) of the flange portion (3f), the flange portion (3f) and the hub portion (Rb) are pulled against each other due to heat shrinkage of the welded portion (3w). The annular groove (Gf) that reduces the residual stress generated around the welded portion (3w) of 3f) is the annular groove (Gf) when viewed from the projection plane orthogonal to the rotation axis (X1) of the transmission case (3). A transmission device characterized in that the positioning peripheral portion (A3) and the positioning outer peripheral portion (A3) are recessed at a position where they partially overlap. A rotatable transmission case (3) having a case body (3c) and a flange portion (3f) projecting outward in the radial direction on the outer circumference of the case body (3c), and the flange portion (3f). A ring gear (R) having a surrounding hub portion (Rb) on the inner circumference is provided, and the flange portion (3f) is offset on one side in the axial direction from the center (O) of the case body (3c). An annular recess (32) facing one side in the axial direction is formed between the outer surface of the case body (3c) and the flange portion (3f) in the offset direction, and the flange portion (3c) is formed. The outer peripheral surface of the 3f) extends inward in the axial direction from the side surface (sf1) of the flange portion (3f) facing one side in the axial direction, and the inner peripheral surface of the hub portion (Rb) is fitted. In the transmission device including at least the first outer peripheral portion (A1) to be welded,
On the side surface (sf1) of the flange portion (3f), the flange portion (3f) and the hub portion (Rb) are pulled against each other due to heat shrinkage of the welded portion (3w). An annular groove (Gf) that reduces residual stress generated around the welded portion (3w) of 3f) is formed between the recess (32) and the welded portion (3w) in the radial direction from the recess (32). A transmission device characterized by being shallowly recessed. The side surface (sf1) of the flange portion (3f) has a first side surface portion (sf11) extending radially inward from the annular groove (Gf) and a radial outward side from the annular groove (Gf). It has a second side surface portion (sf12) that extends and
The first side surface portion (sf11) has an axial position that coincides with the second side surface portion (sf12), or the first side surface portion (sf11) projects outward in the axial direction from the second side surface portion (sf12). The transmission device according to claim 1 or 2, characterized in that.