JP7064369B2 - Welding method and welding structure - Google Patents

Description

The present invention relates to a welding method and a welded structure.

The vehicle is equipped with a differential device such as a front differential or a rear differential that distributes the driving force output from the engine between the corresponding left and right driving wheels when turning or the like. Further, as another aspect of the differential device, there is also a center differential that distributes the driving force output from the engine between the front and rear driving wheels. The differential device includes a ring gear to which a driving force is transmitted and a differential case that is joined to the ring gear and rotates integrally with the ring gear. As a joining method between the ring gear and the differential case, a joining method by welding is adopted. For example, the ring gear and the differential case are joined by performing beam welding on the contact position between the ring gear made of steel and the differential case cast using cast iron.

A technique for improving the strength of the joint between the ring gear and the differential case has been proposed. For example, in Patent Document 1, a gap is formed between the welded surface on the gear side of the ring gear and the welded surface on the case side of the differential case, which makes it possible to absorb thermal deformation of the ring gear and reduce the residual stress of the weld bead. The differential device is disclosed. Such a differential device further has a cavity portion that releases welding gas generated during laser welding, and can suppress the occurrence of welding defects.

Further, in Patent Document 2, a stress concentration portion is provided in at least one of the ring gear and the differential case at a portion away from the inner end of the joint portion, and a differential device capable of relaxing the stress generated in the joint portion. The welded structure of is disclosed.

Japanese Unexamined Patent Publication No. 2013-18835 Japanese Unexamined Patent Publication No. 2016-65582

Here, when the ring gear and the differential case are joined by welding, the strength of the joined portion may decrease due to the elution of carbon contained in the constituent material of the ring gear or the differential case. More specifically, if the elution amount of iron during welding or the elution amount of carbon is larger than the elution amount of iron and filler wire, poor fusion and brittle structure are generated, and cracks and peeling of the joint are caused. May occur. Even if the target of joining is other than the ring gear and the differential case, the same joining failure may occur.

The present invention has been made in view of the above problems, and an object of the present invention is a new and improved welding capable of reducing the amount of carbon elution during welding and suppressing welding defects. The method and the welded structure are to be provided.

In order to solve the above problems, according to a certain viewpoint of the present invention, the first member and the second member having different carbon amounts are abutted against each other, a groove is formed, and energy is applied to the groove. This is a welding method for welding the first member and the second member, wherein the first member and the second member include a first facing surface and a second facing surface that are in contact with each other. The groove is in a state where the first facing surface is provided with a concave groove and the first facing surface and the second facing surface are in contact with each other. , The first thrust in the first member which has a symmetrical shape centered on the virtual extending surface of the first facing surface and the second facing surface and has a relatively large amount of carbon in the range where the groove is open. The first abutment portion and the second abutment portion are formed so that the volume of the abutment portion is smaller than the volume of the second abutment portion in the second member having a relatively small amount of carbon. A welding method is provided in which a first member and a second member are welded by applying energy toward the center of a groove formed by abutting the first facing surface and the second facing surface. Weld.

The area of the first facing surface may be smaller than the area of the second facing surface.

In a state where the first facing surface and the second facing surface are in contact with each other, the end portion of the first facing surface opposite to the groove side is the end of the second facing surface opposite to the groove side. It may be located on the groove side of the portion.

A concave groove may be provided on the first facing surface.

The first member may be cast iron and the second member may be steel.

The first member may be a differential case and the second member may be a ring gear.

Further, in order to solve the above problems, according to another viewpoint of the present invention, the first member and the second member having different carbon contents are abutted against each other and a groove is formed, and welded to the groove. A welded structure in which a first member and a second member are welded by applying a material and energy, the first member having a relatively large amount of carbon and the second member having a relatively small amount of carbon. A weld bead is formed in the joint portion by through welding , and has a concave groove on the first facing surface facing the second member of the first member in the weld bead forming portion, and is forward in the penetration direction of the joint portion. A welded structure is provided in which the position of the boundary between the weld bead and the second member on the side is located on the front side in the penetration direction with respect to the position of the boundary between the weld bead and the first member.

As described above, according to the present invention, the amount of carbon elution during welding can be reduced, and welding defects can be suppressed.

It is sectional drawing which shows the structural example of the differential apparatus to which the welding structure which concerns on embodiment of this invention can be applied. It is sectional drawing which shows the joint structure of the differential case and the ring gear which concerns on the same embodiment. It is sectional drawing which shows the joint part before welding of the differential case and the ring gear which concerns on the same embodiment. It is explanatory drawing which shows the welding process of the differential case and the ring gear which concerns on this embodiment. It is sectional drawing which shows the joint part before welding of the differential case and the ring gear which concerns on the conventional welding method. It is sectional drawing which shows the joint part before welding of the differential case and the ring gear which concerns on the 1st application example of the same embodiment. It is sectional drawing which shows the joint part before welding of the differential case and the ring gear which concerns on the 2nd application example of the same embodiment. It is sectional drawing which shows the joint part before welding of the differential case and the ring gear which concerns on the 3rd application example of the same embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<1. Application example of welded structure>
First, a configuration example of a differential device to which the welded structure according to the embodiment of the present invention can be applied will be described. FIG. 1 is a cross-sectional view showing an example of the configuration of the differential device 10. FIG. 1 shows a cross section including a rotation axis A of the differential case 20 and the ring gear 30, and a rotation axis B of the pinion bevel gear 50. The differential device 10 is used, for example, as a differential gear device that is assembled in a transmission device of a vehicle and distributes a driving force output from an internal combustion engine to the left and right drive wheels.

The differential device 10 includes a differential case 20, a ring gear 30, a pinion shaft 40, pinion bevel gears 50 and 55, and side bevel gears 60 and 65. The differential case 20 as the first member is supported in a housing (not shown) so as to be rotatable about the rotation axis A. The ring gear 30 as the second member has an opening 38 fitted with the tubular portion 21 of the differential case 20. The ring gear 30 fitted to the differential case 20 by fitting the opening 38 to the tubular portion 21 until the second abutting portion 300 of the ring gear 30 abuts on the first abutting portion 200 of the differential case 20. It is press-fitted.

The differential case 20 and the ring gear 30 are joined by welding the first abutting portion 200 and the second abutting portion 300. A weld bead W is formed at the joint between the ring gear 30 and the differential case 20. The welded structure according to the present embodiment is applied to the joint structure between the differential case 20 and the ring gear 30.

The tooth surface 30a of the ring gear 30 meshes with the tooth surface of a pinion gear integrally provided on a propeller shaft (not shown), and the driving force from the internal combustion engine is transmitted to the ring gear 30 via the propeller shaft. As a result, the differential case 20 is rotationally driven around the rotation axis A by the driving force from the internal combustion engine.

The differential case 20 supports a pinion shaft 40 having a rotation axis B along a direction orthogonal to the rotation axis A. The pinion shaft 40 is inserted into the shaft support hole 24 provided in the differential case 20. Pin insertion holes 22a and 22b are formed in the differential case 20, and pin insertion holes 40a are formed in the pinion shaft 40. The retaining pin 80 is press-fitted so as to penetrate the pin insertion holes 22a, 22b, 40a, and the pinion shaft 40 is prevented from coming off from the differential case 20. As the retaining pin 80, for example, a compatible pin having a C-shaped cross section can be used.

A pair of pinion bevel gears 50 and 55 are supported on the pinion shaft 40 so as to be rotatable around the pinion shaft 40. The pair of pinion bevel gears 50 and 55 are arranged on both sides of the rotation axis A. The pair of pinion bevel gears 50 and 55 rotate about the rotation axis B orthogonal to the rotation axis A, respectively.

In the differential device 10 shown in FIG. 1, a pair of pinion bevel gears 50 and 55 are supported by one pinion shaft 40, but a pinion shaft may be provided for each pinion bevel gear 50 and 55. .. In such a case, two or more sets of pinion bevel gears and pinion shafts may be provided.

The tooth surfaces 50a and 55a of the pair of pinion bevel gears 50 and 55 mesh with the tooth surfaces 60a and 65a of the pair of left and right side bevel gears 60 and 65, respectively. A drive shaft (axle drive shaft) (not shown) that rotationally drives the left drive wheel is spline-fitted to the side bevel gear 60 on the left side in the figure, and the right drive wheel is fitted to the side bevel gear 65 on the right side in the figure. A drive shaft (axle drive shaft) (not shown) that drives the rotation is spline-fitted. The left and right drive shafts are rotatably supported by drive shaft support holes 70 and 74 provided in the differential case 20.

The pair of side bevel gears 60 and 65 rotate about the rotation axis A common to the differential case 20 by the driving force of the internal combustion engine transmitted via the ring gear 30, the differential case 20 and the pinion bevel gears 50 and 55. The differential case 20, the ring gear 30, the side bevel gears 60 and 65, and the drive shaft (axle drive shaft) (not shown) are all rotatable around the rotation axis A. Further, the pinion bevel gears 50 and 55 can rotate about the rotation axis B and revolve around the rotation axis A. The differential case 20, the side bevel gears 60 and 65, the pinion bevel gears 50 and 55 and the side bevel gears 60 and 65 are respectively rotatable relative to each other.

When the driving force is transmitted from the internal combustion engine to the ring gear 30, the differential case 20 rotates about the rotation axis A, and the pair of pinion bevel gears 50 and 55 supported by the pinion shaft 40 fixed to the differential case 20 also. It revolves around the axis of rotation A. When there is no difference in rotation between the left and right drive wheels (when the vehicle goes straight, etc.), the differential device 10 evenly transmits the driving force to the pair of left and right side bevel gears 60 and 65. At this time, since the rotation speeds of the pair of left and right side bevel gears 60 and 65 are equal, the pinion bevel gears 50 and 55 revolve around the rotation axis A without rotating around the rotation axis B.

On the other hand, when there is a difference in rotation between the left and right drive wheels (such as when the vehicle is turning), the differential device 10 appropriately distributes the driving force to the pair of left and right side bevel gears 60 and 65. For example, when the vehicle turns to the left and the rotation speed of the right drive wheel is higher than that of the left drive wheel, the side bevel gear 65 fitted with the drive shaft of the right drive wheel rotates faster than the differential case 20. The side bevel gear 60 to which the drive shaft of the left drive wheel is fitted tries to rotate slower than the differential case 20. At this time, the pinion bevel gears 50 and 55 revolve around the rotation axis A and rotate around the rotation axis B, and the difference in the rotation speeds of the left and right drive wheels is absorbed.

When the differential device 10 is a center differential that distributes the driving force to the front and rear drive shafts, the side bevel gears 60 and 65 are fitted to the front drive shaft or the rear drive shaft, respectively.

<2. Welded structure>
As a welding structure according to the present embodiment, a joint structure between the differential case 20 and the ring gear 30 will be described. FIG. 2 is a cross-sectional view showing a joint structure between the differential case 20 and the ring gear 30, and shows an enlarged region X surrounded by the alternate long and short dash line in FIG. The left-right direction in FIG. 2 indicates the axial direction of the rotation axis A of the differential device 10. In FIG. 2, the member on the left side shows the differential case 20, and the member on the right side shows the ring gear 30. The vertical direction in FIG. 2 indicates the radial direction of the differential case 20 or the ring gear 30. In FIG. 2, the upper side shows the outer peripheral side of the differential case 20 or the ring gear 30, and the lower side shows the inner peripheral side of the differential case 20 or the ring gear 30.

It should be noted that FIGS. 3 to 8 shown below are all shown as diagrams corresponding to FIG. 2.

In the welded structure according to the present embodiment, a weld bead W is formed on the outer peripheral side of the joint portion across the differential case 20 and the ring gear 30 so that a part of the groove G is not exposed. That is, the weld bead W is formed so that undercut does not occur. On the inner peripheral side of the joint portion, the weld bead W is formed so as to penetrate the first abutting portion 200 and the second abutting portion 300.

In the welded structure according to the present embodiment, the position W1 of the boundary between the weld bead W and the differential case 20 on the inner peripheral side of the joint portion is located on the outer peripheral side of the position W2 of the boundary between the weld bead W and the ring gear 30. .. As will be described later, of the first abutting portion 200 of the differential case 20 and the second abutting portion 300 of the ring gear 30 that are abutted against each other, the inner peripheral side end portion of the first facing surface 220 is the first. This is because it is arranged on the outer peripheral side of the inner peripheral side end portion of the facing surface 320 of 2. As a result, the volume of the melted portion of the differential case 20 that is melted during welding is smaller than the volume of the ring gear 30 that is melted during melting. That is, the differential case 20 and the ring gear 30 are joined so that the volume of the molten portion of the differential case 20 is smaller than that of the conventional one.

Here, the ring gear 30 is made of, for example, steel. Further, the differential case 20 is formed of, for example, cast iron. The amount of carbon per unit volume contained in cast iron is higher than the amount of carbon per unit volume contained in steel. As will be described later, in the welded structure according to the present embodiment in which the volume of the melted portion of the differential case 20 melted at the time of welding is smaller than that of the conventional one, the amount of carbon elution at the time of welding is reduced. In particular, in the welded structure according to the present embodiment, the amount of carbon elution during welding is effectively reduced as compared with the case where the volume of the molten portion of the ring gear 30 that is melted during welding is made smaller than before.

On the other hand, in the welded structure according to the present embodiment, it is not essential to change the position of the inner peripheral side end portion of the second facing surface 320 of the ring gear 30 from the conventional position. Therefore, the amount of carbon elution is reduced without significantly reducing the width (diametrical length) of the joint portion.

<3. Welding method>
Up to this point, a configuration example of a differential device to which the welded structure according to the present embodiment can be applied and a joint structure of the differential case 20 and the ring gear 30 has been described. Hereinafter, the welding method according to this embodiment will be described by taking as an example a method of joining the ring gear 30 and the differential case 20.

(3-1. Shape of differential case and ring gear)
The shapes of the differential case 20 and the ring gear 30 to be welded to each other will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a joint portion of the differential case 20 and the ring gear 30 before welding.

The differential case 20 and the ring gear 30 have a first abutting portion 200 and a second abutting portion 300, which are abutted against each other, respectively. Part or all of the first abutting portion 200 is thermally affected during welding and melted. Part or all of the second abutting portion 300 is thermally affected during welding and melted.

The first abutting portion 200 of the differential case 20 has an inclined portion 210 and a first facing surface 220 in order from the outer peripheral side in a portion facing the ring gear 30. The first facing surface 220 is a plane on a plane orthogonal to the rotation axis A of the differential case 20. The inclined portion 210 is formed as a surface that separates from the ring gear 30 as it moves away from the first facing surface 220 toward the outer peripheral side. A first space forming recess 230 is formed on the inner peripheral side of the first facing surface 220. The first space forming recess 230 is formed as a concave step recessed in the axial direction from the first facing surface 220.

The second abutting portion 300 of the ring gear 30 has an inclined portion 310 and a second facing surface 320 in order from the outer peripheral side in a portion facing the differential case 20. The second facing surface 320 is a plane on a plane orthogonal to the rotation axis A of the ring gear 30. The inclined portion 310 is formed as a surface that separates from the differential case 20 as it moves away from the second facing surface 320 toward the outer peripheral side. The inclined portion 310 is formed symmetrically with the inclined portion 210 about the virtual extending surface C of the first facing surface 220 and the second facing surface 320 that are in contact with each other. A second space forming recess 330 is formed on the inner peripheral side of the second facing surface 320. The second space forming recess 330 is formed as a concave step recessed in the axial direction from the second facing surface 320.

In a state where the ring gear 30 is fitted to the differential case 20 and the second facing surface 320 of the ring gear 30 is press-fitted until it comes into contact with the first facing surface 220 of the differential case 20, the inclined portion 210 of the differential case 20 and the ring gear 30 are inclined. The groove G is formed by the portion 310. Here, since the inclined portion 210 of the differential case 20 and the inclined portion 310 of the ring gear 30 are formed in a symmetrical shape about the virtual extending surface C, the groove G has a symmetrical shape about the virtual extending surface C. Become.

Further, the first space forming recess 230 and the second space forming recess 330 formed in the differential case 20 and the ring gear 30 are provided on the inner peripheral side of the first abutting portion 200 and the second abutting portion 300, respectively. The space portion 400 is formed.

In the welding method according to the present embodiment, the inner peripheral side of the first facing surface 220 of the differential case 20 is in contact with the first facing surface 220 of the differential case 20 and the second facing surface 320 of the ring gear 30. The end portion is located on the groove G side of the inner peripheral side end portion of the second facing surface 320 of the ring gear 30. That is, the area of the first facing surface 220 is smaller than the area of the second facing surface 320. Therefore, the volume of the first abutting portion 200 of the differential case 20 in the range where the groove G is open is smaller than the volume of the second abutting portion 300 of the ring gear 30 in the range where the groove G is open. , The first abutting portion 200 and the second abutting portion 300 are formed.

In the present specification, the "first abutting portion 200 in the range where the groove G is open" is parallel to the inclined portion 210, the first facing surface 220, and the outer peripheral surface of the differential case 20 in the differential case 20. It is a portion existing in the region S1 surrounded by the virtual surface D1 and the virtual surface E1 parallel to the first facing surface 220. The virtual surface D1 passes through the inner peripheral side end portion located on the inner peripheral side of the inner peripheral side end portion of the first facing surface 220 and the inner peripheral side end portion of the second facing surface 320, and the outer peripheral surface of the differential case 20. It is a virtual plane parallel to. The virtual surface E1 is a virtual surface that passes through the boundary between the inclined portion 210 and the outer peripheral surface of the differential case 20 and is parallel to the first facing surface 220.

Further, the "second abutting portion 300 in the range where the groove G is open" is a virtual surface D2 of the ring gear 30, which is parallel to the inclined portion 310, the second facing surface 320, and the outer peripheral surface of the ring gear 30. And a portion existing in the region S2 surrounded by the virtual surface E2 parallel to the second facing surface 320. The virtual surface D2 passes through the inner peripheral side end portion located on the inner peripheral side of the inner peripheral side end portion of the first facing surface 220 and the inner peripheral side end portion of the second facing surface 320, and the outer peripheral surface of the ring gear 30. It is a virtual plane parallel to. The virtual surface E2 is a virtual surface that passes through the boundary between the inclined portion 310 and the outer peripheral surface of the ring gear 30 and is parallel to the second facing surface 320.

Both the virtual surface D1 and the virtual surface D2 are the inner peripheral side end portions located closer to the inner peripheral side of the inner peripheral side end portion of the first facing surface 220 and the inner peripheral side end portion of the second facing surface 320. It is a surface on the same virtual surface that passes through. That is, when the groove G has a symmetrical shape with respect to the virtual extension surface C, the area of the region S1 and the area of the region S2 shown in FIG. 3 are equal to each other.

However, in the welding method according to the present embodiment, the inner peripheral side end portion of the first facing surface 220 of the differential case 20 is closer to the groove G side than the inner peripheral side end portion of the second facing surface 320 of the ring gear 30. The volume of the first abutment portion 200 in the open range of the groove G present in the region S to be located is the volume of the second abutment portion 300 in the open range of the groove G present in the region S2. It is smaller than the volume.

(3-2. Welding process)
The welding process of the differential case 20 and the ring gear 30 will be described with reference to FIG. FIG. 4 is an explanatory diagram showing a welding process between the differential case 20 and the ring gear 30.

First, the opening 38 of the ring gear 30 is fitted to the tubular portion 21 of the differential case 20. The ring gear 30 fitted to the differential case 20 is press-fitted until the second abutting portion 300 of the ring gear 30 comes into contact with the first abutting portion 200 of the differential case 20. More specifically, the second facing surface 320 of the second abutting portion 300 is press-fitted until it comes into contact with the first facing surface 220 of the first abutting portion 200. At this time, a part of the second facing surface 320 does not come into contact with the first facing surface 220.

When the second facing surface 320 comes into contact with the first facing surface 220, the groove G is formed by the inclined portion 210 of the differential case 20 and the inclined portion 310 of the ring gear 30. Since the inclined portion 210 of the differential case 20 and the inclined portion 310 of the ring gear 30 are formed symmetrically with respect to the virtual extending surface C, the groove G has a symmetrical shape with respect to the virtual extending surface C. Further, the space portion 400 is formed on the inner peripheral side of the first facing surface 220 and the second facing surface 320 by the first space forming recess 230 and the second space forming recess 330.

When joining the differential case 20 and the ring gear 30, the welding material 94 is supplied to the groove G, and energy 92 is applied toward the center of the groove G. For example, while the filler wire or the like is supplied to the groove G, a laser, an electron beam, or the like is irradiated from the outer peripheral side toward the center of the groove G. The applied energy 92 melts the welding material 94, the first abutting portion 200 of the differential case 20, and the second abutting portion 300 of the ring gear 30, to generate molten metal. At this time, energy 92 is applied so that the molten metal reaches the space 400, and through welding is performed.

At the portion where the energy 92 is applied, the molten metal is cooled and solidified, and the weld bead W is formed. The weld bead W is formed over the entire circumference of the joint portion between the differential case 20 and the ring gear 30.

Although the case where the welding material 94 is used is shown here, the welding material may not be used when welding is possible without using the welding material 94.

Here, FIG. 5 is a cross-sectional view showing a joint portion of the conventional differential case 120 and the ring gear 130 before welding. In the differential case 120 and the ring gear 130 shown in FIG. 5, the width (diameter length) of the first facing surface 220 and the second facing surface 320 are equal, and the position of the inner peripheral side end portion of the first facing surface 220 is equal. And the position of the inner peripheral side end portion of the second facing surface 320 coincide with each other.

In such a configuration, both the virtual surface D1 defining the region S1 defining the volume of the first abutting portion 200 and the virtual surface D2 defining the region S2 defining the volume of the second abutting portion 300 are both. It is a surface on a virtual surface that passes through the inner peripheral side end portion of the first facing surface 220 and the inner peripheral side end portion of the second facing surface 320. Since the first facing surface 220 and the second facing surface 320 are flat surfaces without concave grooves or the like, the areas of the first facing surface 220 and the second facing surface 320 are the same. Further, the volume of the first abutting portion 200 in the range where the groove G existing in the region S1 is open is equal to the volume of the second abutting portion 300 in the range where the groove G existing in the region S2 is open. ..

In the conventional differential case 120 and ring gear 130 configured as described above, the volume of the melted portion of the differential case 20 melted at the time of welding is substantially equal to the volume of the melted portion of the ring gear 30 melted at the time of welding. At this time, the position W1 of the boundary between the weld bead W and the differential case 20 formed in the space portion 400 is substantially the same in the radial direction which is the penetration direction between the position W2 of the boundary between the weld bead W and the ring gear 30 and the weld bead W. Located in position.

On the other hand, in the differential case 20 and the ring gear 30 according to the present embodiment shown in FIG. 3, the inner peripheral side end portion of the first facing surface 220 is located on the groove G side from the inner peripheral side end portion of the second facing surface 320. do. In such a configuration, the volume of the first abutting portion 200 existing in the region S1 is smaller than the volume of the second abutting portion 300 existing in the region S2. That is, the volume of the melted portion of the differential case 20 that is melted at the time of welding can be made smaller than before.

Since the amount of carbon per unit volume contained in cast iron, which is the material of the differential case 20, is larger than the amount of carbon per unit volume contained in the steel, which is the material of the ring gear 30, the welding method according to the present embodiment uses the differential case 20. The amount of carbon elution during welding with the ring gear 30 is effectively reduced. Further, in the welding method according to the present embodiment, it is not essential to change the radial length of the second facing surface 320 of the ring gear 30 from the conventional method. Therefore, the amount of carbon elution is reduced without significantly reducing the joint surface between the differential case 20 and the ring gear 30.

<4. Effect>
According to the welding method between the differential case 20 and the ring gear 30 according to the present embodiment, the inner peripheral side end portion of the first facing surface 220 of the differential case 20 is from the inner peripheral side end portion of the second facing surface 320 of the ring gear 30. The first abutting portion 200 of the differential case 20 and the second abutting portion 300 of the ring gear 30 are formed so as to be located on the groove G side. Therefore, the volume of the melted portion of the differential case 20 that is melted during welding is smaller than the volume of the melted portion of the ring gear 30 that is melted during welding.

The amount of carbon per unit volume contained in cast iron, which is the material of the differential case 20, is larger than the amount of carbon per unit volume contained in the steel, which is the material of the ring gear 30. Therefore, the welding method according to the present embodiment can effectively reduce the amount of carbon elution during welding as compared with the case where the volume of the molten portion of the ring gear 30 is smaller than the volume of the molten portion of the differential case 20. Further, since it is not necessary to change the position of the inner peripheral side end portion of the second facing surface 320 of the ring gear 30, the amount of carbon elution can be reduced without significantly reducing the joint surface between the differential case 20 and the ring gear 30. Can be reduced.

By reducing the amount of carbon elution, poor fusion of the joint and the formation of brittle structure are suppressed, so that cracking and peeling of the joint are suppressed and the formation of blow holes and pits at the joint is suppressed. .. Therefore, the strength of the joint is improved.

Further, in the welding method between the differential case 20 and the ring gear 30 according to the present embodiment, the first abutting portion 200 and the second abutting portion 200 and the second abutting portion 200 are formed so that the groove G is formed in a target shape centering on the virtual extending surface C. The abutting portion 300 is abutted and welded around the virtual extending surface C. Therefore, it is possible to prevent the formed weld bead W from being biased toward either the differential case 20 or the ring gear 30. Therefore, on the outer peripheral side of the joint portion, the weld bead W is formed so as to straddle the differential case 20 and the ring gear 30 and cover the groove G, and the occurrence of undercut is suppressed.

Further, in the welded structure of the differential case 20 and the ring gear 30 according to the present embodiment, since the amount of carbon elution during welding is reduced, cracking or peeling of the joint portion between the differential case 20 and the ring gear 30 is suppressed and the joint is joined. The generation of blow holes and pits in the section is suppressed. Further, in the welded structure of the differential case 20 and the ring gear 30 according to the present embodiment, the occurrence of undercut is suppressed on the outer peripheral side of the joint portion. Therefore, welding defects can be suppressed and the joint strength can be improved.

<5. Application example>
Although the welding method according to the present embodiment and one embodiment of the welded structure have been described above, the welding method according to the present embodiment can be applied in various ways. Hereinafter, application examples of the welding method will be described.

(5-1. First application example)
FIG. 6 is a cross-sectional view showing the shape of the joint portion of the differential case 20 and the ring gear 30 before welding in the first application example. In the above embodiment, the first facing surface 220 of the differential case 20 is formed of a flat surface. The first application example is different from the above embodiment in that the first facing surface 220 has a concave groove 240.

In the first application example, the area of the first facing surface 220 is smaller than the area of the second facing surface 320, as in the above embodiment. Further, for the volume of the first abutting portion 200 existing in the region S1, the volume of the concave groove 240 is added to the volume difference between the second abutting portion 300 and the first abutting portion 200 in the above embodiment. By the volume, it is smaller than the volume of the second abutting portion 300 existing in the region S2.

Also in the welding method according to the first application example, the volume of the melted portion of the differential case 20 melted at the time of welding is smaller than the volume of the melted portion of the ring gear 30 melted at the time of welding. Therefore, the amount of carbon elution during welding is effectively reduced, and the same effect as the welding method according to the above embodiment can be obtained.

(5-2. Second application example)
FIG. 7 is a cross-sectional view showing the shape of the joint portion of the differential case 20 and the ring gear 30 before welding in the second application example. In the above embodiment, the inner peripheral side end portion of the first facing surface 220 is arranged on the groove G side of the inner peripheral side end portion of the second facing surface 320. The second application example is different from the above embodiment in that the position of the inner peripheral side end portion of the first facing surface 220 and the position of the inner peripheral side end portion of the second facing surface 320 coincide with each other.

In the second application example, the virtual surface D1 defining the region S1 defining the volume of the first abutting portion 200 and the virtual surface D2 defining the region S2 defining the volume of the second abutting portion 300. Is a surface on a virtual surface that passes through both the inner peripheral side end portion of the first facing surface 220 and the inner peripheral side end portion of the second facing surface 320. In the second application example, the first facing surface 220 has a concave groove 240. Therefore, the positions of the outer peripheral side end portion and the inner peripheral side end portion of the first facing surface 220 coincide with the positions of the outer peripheral side end portion and the inner peripheral side end portion of the second facing surface 320. Nevertheless, the area of the first facing surface 220 is smaller than the area of the second facing surface 320. Further, the volume of the first abutting portion 200 existing in the region S1 is smaller than the volume of the second abutting portion 300 existing in the region S2 by the volume of the concave groove 240.

Also in the welding method according to the second application example, the volume of the melted portion of the differential case 20 melted at the time of welding is smaller than the volume of the melted portion of the ring gear 30 melted at the time of welding. Therefore, the amount of carbon elution during welding is effectively reduced, and the same effect as the welding method according to the above embodiment can be obtained.

(5-3. Third application example)
FIG. 8 is a cross-sectional view showing the shape of the joint portion of the differential case 20 and the ring gear 30 before welding in the third application example. In the above embodiment, the inner peripheral side end portion of the first facing surface 220 is arranged on the groove G side of the inner peripheral side end portion of the second facing surface 320. The third application example is different from the above embodiment in that the inner peripheral side end portion of the second facing surface 320 is located on the groove G side of the inner peripheral side end portion of the first facing surface 220. ..

In the third application example, the virtual surface D1 defining the region S1 defining the volume of the first abutting portion 200 and the virtual surface D2 defining the region S2 defining the volume of the second abutting portion 300. Is a surface on a virtual surface passing through the inner peripheral side end portion of the first facing surface 220. In the third application example, the first facing surface 220 has a concave groove 240. At this time, the inner peripheral side end portion of the first facing surface 220 is set so that the volume of the first abutting portion 200 existing in the region S1 is smaller than the volume of the second abutting portion 300 existing in the region S2. The position, the position of the inner peripheral side end portion of the second facing surface 320, and the size of the concave groove 240 are determined.

Also in the welding method according to the third application example, the volume of the melted portion of the differential case 20 melted at the time of welding is smaller than the volume of the melted portion of the ring gear 30 melted at the time of welding. Therefore, the amount of carbon elution during welding is effectively reduced, and the same effect as the welding method according to the above embodiment can be obtained.

<6. Summary>
Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of the art to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

For example, in the above embodiment, the second facing surface 320 of the ring gear 30 is configured to be a flat surface, but the present invention is not limited to this example. For example, as long as the volume of the first abutting portion 200 of the differential case 20 is smaller than the volume of the second abutting portion 300 of the ring gear 30, even if the second facing surface 320 of the ring gear 30 is provided with a concave groove. good.

Further, in the above embodiment, an example in which the welding method of the present invention is applied to a differential device has been described, but the present invention is not limited to such an example. The welding method according to the present invention can be applied to other structures as long as it is a welding method in which a plurality of members having different carbon contents are abutted against each other and welded.

10 Differential device 20 Diff case 30 Ring gear 92 Energy 94 Welding material 200 First abutment part 210 Inclined part 220 First facing surface 230 First space forming recess 240 Concave groove 300 Second abutment part 310 Inclined part 320 Second facing surface 330 Second space forming recess 400 Space part C Virtual extension surface D1, D2 Virtual surface E1, E2 Virtual surface G Groove W Welding bead W1, W2 Boundary position

Claims (6)

The first member and the second member having different carbon amounts are abutted against each other to form a groove, and energy is applied to the groove to weld the first member and the second member. It ’s a welding method.
The first member and the second member have a first abutting portion and a second abutting portion including a first facing surface and a second facing surface that are in contact with each other.
A concave groove is provided on the first facing surface.
In a state where the first facing surface and the second facing surface are in contact with each other, the groove has a symmetrical shape about the virtual extending surface of the first facing surface and the second facing surface. In the range where the groove is open, the volume of the first abutting portion in the first member having a relatively large amount of carbon is the volume of the second member having a relatively small amount of carbon. The first abutting portion and the second abutting portion are formed so as to be smaller than the volume of the second abutting portion in the above.
The first member and the second member are welded by applying the energy toward the center of the groove formed by abutting the first facing surface and the second facing surface. ,
Welding method. The welding method according to claim 1, wherein the area of the first facing surface is smaller than the area of the second facing surface. In a state where the first facing surface and the second facing surface are in contact with each other, the end portion of the first facing surface on the side opposite to the groove side is the first on the side opposite to the groove side. The welding method according to claim 1 or 2, which is located on the groove side of the end of the facing surface of 2. The welding method according to any one of claims 1 to 3 , wherein the first member is cast iron and the second member is steel. The welding method according to any one of claims 1 to 3 , wherein the first member is a differential case and the second member is a ring gear. The first member and the second member having different carbon amounts were abutted against each other to form a groove, and energy was applied to the groove to weld the first member and the second member. It is a welded structure
A weld bead is formed by through welding at the joint portion of the first member having a relatively large amount of carbon and the second member having a relatively small amount of carbon.
The first member of the first member at the weld bead forming portion has a concave groove on the first facing surface facing the second member.
The position of the boundary between the weld bead and the second member on the front side in the penetration direction of the joint portion is located on the front side in the penetration direction with respect to the position of the boundary between the weld bead and the first member. Welded structure.

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