WO2015079742A1 - Torque converter for automobile provided with lockup device, and method for welding impeller shell and front cover thereof - Google Patents

Abstract

　The present invention relates to a welded structure and a laser welding method for a bonded section of an impeller shell and a front cover in a torque converter for an automobile. An impeller shell (10) and a front cover (12) have a structure in which axial tubular protrusions (10-1A, 12-1A) thereof are engaged with each other in an axial direction, and the axial tubular protrusion (12-1A) positioned on the radially outer side and an opposing abutting surface are welded in a laser welded section (14) through the entire periphery. A laser welded section (11) extends from the radially outer peripheral surface into the space between the abutting surfaces, so as to partially penetrate into the axial tubular protrusion (10-1A) on the radially inner side (depth of penetration = d). A welding beam has a rectangular cross section. The shape of the welded section (11) is configured of a tack weld leaving a gap along the circumferential direction in a first stage and a final weld in the entire periphery in a second stage, and the tack welded section has a long, thin shape so that a part thereof remains in a solidified state during the final weld.

Description

Torque converter for automobile with lock-up device and method for welding impeller shell to front cover

The present invention relates to an automotive torque converter provided with a lock-up device, and more particularly to a welding structure and a welding method at a joint portion between an impeller shell and a front cover.

The torque converter is driven by internal hydraulic pressure and is engaged with a front cover facing surface via a clutch facing, and is connected to an input side and an output side. And a lock-up member for directly transmitting power to the impeller shell. The impeller shell is closed to the outside by welding the entire circumference of the front cover by arc welding or the like at the outer periphery. The lock-up member mechanically fastens the input / output of the torque converter in a vehicle speed range above a predetermined level. The lockup member is configured as a piston plate having a clutch facing attached to the front surface and fitted into the turbine hub so as to be movable in the axial direction. At the time of lockup, the pressure in the front chamber of the piston plate is released, and the piston plate moves forward by the pressure of the power transmission oil in the rear chamber, whereby the clutch facing on the front surface of the piston plate is pressed against the opposing surface of the front cover. In the high-speed range, the clutch facing is brought into contact with the cover by a high differential pressure before and after the piston plate, and in the low-speed range, the torque converter function is effective to some extent by relatively reducing the differential pressure. A so-called slip lock-up is performed in which the clutch facing is slid with respect to the front cover while interposing an oil film. And the annular part of the front cover which opposes a clutch facing is roughened from a viewpoint of the rapid wear suppression of the friction surface at the time of slip lock-up. See Patent Document 1 for slip lockup. For the welded structure between the front cover and the impeller shell, see Patent Documents 2-4. See Patent Document 5 for a torque converter with a lock-up mechanism.

JP 7-174208 A Japanese Patent Laid-Open No. 10-2398 JP 2002-147564 A JP 2006-509168 A Japanese Patent Publication No. 2013-87827

For stable slip lock-up, it is necessary to keep the oil film pressure between the clutch facing and the front cover constant. For this reason, the flatness of the portion of the front cover facing the clutch facing is important. However, it is necessary to weld the impeller shell and the front cover all around for sealing the inside, and the large heat input causes the front cover part facing the clutch facing to swell under thermal strain, There is a concern that the flatness is deteriorated, and the deterioration of flatness increases the fluctuation of the pressure of the oil film between the clutch facing and the front cover, thereby impairing the stable slip lock-up operation. In Patent Literature 2 and Patent Literature 3, the impeller shell and the front cover have an insertion structure between the cylindrical portions, and arc welding is performed in the cylindrical portion where stress concentration hardly occurs, and the impeller shell in this cylindrical portion is formed. The weld structure between the front cover and the front cover can be a countermeasure against the problems of deterioration of the flatness of the front cover surface facing the clutch fading and the flatness of the boss seat surface. I couldn't take complete measures against There was also a problem of interference with adjacent parts of the torque converter due to weld beads. Moreover, although patent document 4 shows adoption of the laser welding for joining of the plate-shaped front cover with respect to a cylindrical impeller shell, it is not more than that, and is not intended to solve the above-mentioned problem. Nor could it give suggestions for a solution.

The present invention solves such a conventional problem, and the desired flatness of the portion of the front cover facing the clutch facing is irrespective of the heat input during the welding of the impeller shell and the front cover. The purpose is to maintain.

According to the first aspect of the present invention, the impeller shell, the front cover welded to the impeller shell at the welded portion along the entire circumference of the outer peripheral portion, and the internal space formed by the impeller shell and the front cover A hydrodynamic power transmission device that is housed and includes an impeller, a turbine, and a stator, and is housed in the internal space, driven by internal hydraulic pressure, and engaged with the front cover facing surface via a clutch facing. A piston plate that directly transmits power to the output side and the output side, and the impeller shell and the front cover are each provided with an axial cylindrical protruding portion that is axially fitted to each other. Of the axial cylindrical protrusion located on the radially outer side of one of the front cover and the other of the front cover and the impeller shell A torque converter is a laser welding unit for welding the entire circumference of the surface is provided. Preferably, the laser welded portion extends so as to partially bite into the axial cylindrical protruding portion radially inward from the abutting surface, and the laser welding beam has a rectangular cross section, particularly, a vertically long shape on the abutting surface. It is preferably an elongated rectangular cross section extending in the direction along.

In the laser welding method embodying the first invention, the impeller shell and the front cover are fitted with the axial cylindrical projections in the axial direction, and the outer side in the radial direction at one of the impeller shell and the front cover. The opposed axial projection of the axial cylindrical projection, the impeller shell, and the other of the front cover are abutted against each other, a laser beam is applied to the abutment from the outer periphery, and laser welding is performed along the entire circumference between the abutment surfaces A laser weld is formed on the surface.

According to the second aspect of the present invention, the impeller shell, the front cover welded to the impeller shell at the welded portion along the entire outer periphery, and the impeller shell and the front cover are formed. A fluid-type power transmission device housed in an internal space and comprising an impeller, a turbine and a stator, and also housed in the internal space, driven by internal hydraulic pressure, and engaged with the front cover facing surface via a clutch facing A piston plate that directly transmits power between the input side and the output side, and the welded portion joins the impeller shell and the front cover at a plurality of locations spaced in the circumferential direction, and a circular shape. A welded part temporarily extending in the circumferential direction, an impeller shell and a front cover are all welded on the entire circumference including the welded part. A torque converter comprising a weld is provided.

In the welding method for obtaining the welded structure according to the second aspect of the invention, as the first stage welding process, the impeller shell and the front cover are welded at a plurality of locations spaced in the circumferential direction. As a second stage welding process, welding is performed so as to overlap with the portion temporarily fixed along the entire circumference along the joint portion between the impeller shell and the front cover, At the time of the second stage welding, welding is performed so that the solidified state of the molten metal is always maintained for each part temporarily secured in the first stage welding process. It is preferable that the molten metal extends along the circumferential direction at each welding point in the first stage welding process.

The adoption of laser welding in the first invention is a problem of deterioration in the flatness of the bearing surface of the boss nut and the friction material due to the fact that the stress concentration is difficult to occur due to the welding of the cylindrical portions as a result of the concentration of heat input. Will not occur. Therefore, the thermal strain after the welding process is reduced, and the waviness of the front cover surface that slides with the clutch facing can be reduced. Therefore, the desired slip lock-up operation can be performed, and the fuel consumption efficiency can be improved. Also, unlike arc welding, laser welding does not cause beading, so bead grinding was necessary because arc welding between the cylindrical parts of the impeller shell and the front cover could cause interference with adjacent components of the torque converter. It is possible to omit additional work such as this. A structure in which the laser weld part is partially penetrated into the axially protruding part inside the radius beyond the abutting part is advantageous in improving the shearing characteristics. Also, laser welding with a rectangular beam cross-section makes it possible to weld with the desired quality regardless of the inevitable position and width variations in the circumferential direction of the abutment surface between the impeller shell and the front cover by appropriate selection of the beam width. Bonding can be ensured. From the viewpoint of efficient use of laser energy, it is preferable that the laser beam has a vertically long rectangular cross section, and the vertically long direction of the rectangular cross section is the direction along the abutting surface. By adopting semiconductor welding as laser welding, it is possible to obtain even higher welding quality due to the uniformity of the beam intensity. In addition, by making the laser beam a rectangular cross section, it is possible to ensure a wide irradiation area that can cover the entire area of the abutting portion that changes within the allowable tolerance range while ensuring the desired beam intensity, and the impeller shell and the front cover It is possible to reliably weld the abutting portion.

According to the second invention, the welding of the outer peripheral portion of the impeller shell and the front cover is performed as a first stage by performing temporary fixing welding by welding at a plurality of locations spaced in the circumferential direction. As a stage, it is performed in two stages, that is, welding around the entire circumference. For this reason, the second stage welding, which is performed on each temporary welding part in the first stage, is performed so that the solidified state of the molten metal is always maintained partially in each part. In this case, the temporary fixing state can be maintained at each part in the above, so that the effect of the temporary fixing is not impaired, the final thermal strain after the completion of the second stage all-around welding is reduced, and the clutch facing and sliding are reduced. The undulation of the moving front cover surface can be reduced. Therefore, the desired slip lock-up operation can be performed, and the fuel consumption efficiency can be improved.

FIG. 1 is a sectional view of the torque converter. FIG. 2 is a partially enlarged view of FIG. 1, and is a detailed view of the facing portion between the clutch facing and the front cover in the lock-up mechanism of the torque converter, (a) when not locked up, and (b) low pressing. The slip lock-up state of force / high differential rotation and (c) show the slip lock-up state of high pressing force / low differential rotation, respectively. 3 is an enlarged cross-sectional view of a welded portion between the impeller shell and the front cover in FIG. FIG. 4 is an enlarged cross-sectional view of a conventional weld, similar to FIG. FIG. 5 is a partial schematic circumferential development showing a contact surface (before welding) between the impeller shell and the front cover. FIG. 6 is a schematic cross-sectional view of the abutment surface between the impeller shell and the front cover, and schematically shows a welding process using a rectangular cross-section laser. FIG. 7 is similar to FIG. 2, but shows another embodiment of the present invention. FIG. 8 is a cross-sectional view showing only the impeller shell and the front cover along the line VIII-VIII in FIG. 1, and shows the progress of the welding process immediately after the start of main welding after temporary welding. 9 (a) to 9 (e) are circumferential development views schematically showing the progress of the main welding process after one temporary fixing at the joint of the impeller shell and the front cover. FIG. 10 is a graph showing the flatness of the clutch facing engagement surface of the front cover after the completion of the main welding, where (a) shows the present invention and (b) shows the conventional one.

FIG. 1 shows a torque converter according to an embodiment of the present invention in a cross section along an axial line. Reference numeral 10 denotes an impeller shell, and a front cover 12 (press plate of a steel plate made of the same material as the impeller shell 10) is applied to the impeller shell 10. As will be described later, the molded product) is joined by the laser welded portion 11 around the entire periphery, and an internal space sealed from the outside is formed. The fluid type power transmission device 13 and the lockup device 14 are accommodated in the internal space. As is well known, the fluid type power transmission device 13 includes an impeller 15, a turbine 16, and a stator 17 as basic components. The turbine 16 is fixed to a turbine support plate 19 on the hub 18, and the hub 18 forms a spline 18-1 on the inner peripheral surface. On the other hand, as is well known, an input shaft (not shown) of the transmission is inserted from the left side of FIG. 1 into the sleeve 20 fixed to the inner peripheral side of the impeller shell 10, and the tip of the input shaft is the spline 18-1 of the hub 18. Fitted. As is well known, the lock-up device 14 includes a driven plate 22 that is an output side rotating member (clamped to the hub 18 by a rivet 24 together with the turbine support plate 19), a drive plate 26 that is an input side rotating member, A plurality of circumferentially separated damper springs 28 that elastically connect the driven plate 22 and the drive plate 26 in the circumferential direction as is well known, and an equalizer plate 29 that is an intermediate member that is moved together with the damper springs 28. It consists of. Further, the drive plate 26 is fixed by a rivet 31 to a piston plate 30 that can slide on the hub 18. A clutch facing (friction material) 32 is installed on the outer peripheral surface of the piston plate 30 so as to face the front cover 12 in a minute gap. In addition to the outer damper spring 28, a damper spring 33 is also provided on the inner peripheral side. Like the outer damper spring 28, the inner damper spring 33 also connects the driven plate 22 and the drive plate 26 in the circumferential direction. It is elastically connected and functions to suppress rotational fluctuation in a higher elastic region than the buffer region by the spring 28. A boss nut 34 is fixed to the outer surface of the front cover 12 by welding (arc welding). As is well known, a rotating plate 35 that rotates integrally with the output shaft of the engine is connected and fixed to the boss nut 34 with bolts 36. . In FIG. 2, the annular portion 12 </ b> A on the surface of the front cover 12 facing the clutch facing 32 is a rough surface.

The above configuration is well known as a torque converter, and the rotation of the output shaft of the engine is transmitted from the rotating plate 35 to the impeller 15 via the front cover 12 and the impeller shell 10, and from the impeller 15 from the turbine 16 and the turbine 16. The rotational torque is transmitted to the input shaft of the transmission (not shown) via the hub 18 by the flow of oil circulated to the impeller 15 via the stator 17. Further, at the time of lock-up, the piston plate 30 is moved to the front cover 12 side by the differential pressure across the front, and the clutch facing 32 is frictionally engaged with the opposing surface of the front cover 12 so that the engine output side and the transmission input side are directly connected. . Further, the inner and outer damper springs 28 and 33 allow the relative rotation of the driven plate 22 and the drive plate 26 according to the rotation fluctuation, and the outer peripheral damper spring 28 having a small elastic modulus when the relative rotation is small. A vibration absorbing function is achieved by each of the high elastic modulus inner damper springs 33 when the rotation increases. The configuration and operation of the spring damper including the inner and outer damper springs 28 and 33 are substantially the same as those disclosed in Patent Document 6.

Next, the lock-up operation between the clutch facing 32 and the front cover 12 facing the clutch facing 32 in the lock-up mechanism will be described in more detail with reference to FIG. The portion facing the cover 12 is partially enlarged and shown in FIG. 2A, and the clutch facing 32 is made of a special paper having a good friction characteristic, and the piston facing the front cover 12 of the piston plate 30 is used. The plate 30 is fixed in an annular shape on the surface. The surface 30-1 of the piston plate 30 to which the clutch facing 32 is fixed is somewhat so that the inner peripheral side is retracted from the outer peripheral side with respect to the surface of the front cover 12 perpendicular to the torque converter center line C (FIG. 1). Inclined. Therefore, the clutch facing 32 fixed to the surface 30-1 of the piston plate 30 also exhibits the same inclination with respect to the front cover facing surface. Therefore, in the non-lock-up state in which the clutch facing 32 is separated from the facing surface of the front cover 12, the size of the gap S between the front cover 12 and the clutch facing 32 is smaller on the outer peripheral side and larger on the inner peripheral side. . A portion 12A facing the clutch facing 32 on the surface of the front cover is roughened.

Next, the lock-up operation according to the present invention will be described. Before the lock-up, as shown in FIG. 2A, the piston plate 30 is positioned away from the facing surface of the front cover 12, and the piston plate 30 is Although it is rotating, the differential rotation with the front cover 12 is large. In order to shift to the lockup region, when a differential pressure is applied to the piston plate 30 in the front-rear direction, the piston plate 30 is slid toward the front cover 12. At this time, since the pressure applied to the piston plate 30 is still small, the piston plate 30 is lightly pressed through the oil film against the rough surface portion 12A on the opposed inner surface of the front cover 12 while maintaining the posture. Then, the piston shifts to the slip lock-up state due to the difference between the low rotational speed of the piston plate 30 and the large rotational speed of the front cover 12, but because of the inclination of the surface 30-1 of the piston plate 30, As shown in FIG. 2B, the contact mainly occurs at the outer peripheral portion of the clutch facing 32 while the facing surface slips. The slip lock-up state at this time is a slip lock-up under a low pressing force and high differential rotation. In slip lock-up, power transmission by a lock-up clutch is also performed, but the power transmission function by a torque converter is still effective, and power transmission occurs in the presence of both. Since the annular region 12A of the front cover 12 that comes into contact with the clutch facing 32 has a rough surface, the oil film between the clutch facing 32 and the front cover 12 can be satisfactorily cut and a good slip can be obtained. You can get a lockup.

As the rotational speed of the piston plate 30 increases due to the transition to the slip lock-up region, and the pressure of the power transmission oil applied to the piston plate 30 increases, the slip lock-up region under high pressing force and low differential rotation to go into. At this time, since the piston plate 30 is deformed starting from the contact surface of the front cover 12 via the clutch facing 32, the center of the piston plate 30 is deformed to the front cover side as shown in FIG. The surface 30-1 of the piston plate 30 (the surface of the clutch facing 32) eliminates the initial inclination shown in (a) and (b). Rather, the inner peripheral side of the clutch facing 32 is rough on the surface of the front cover 12. It mainly hits the surface area 12A. Even at this time, the annular region 12A of the front cover 12 that is in contact with the clutch facing 32 has a rough surface, so that the oil film between the clutch facing 32 and the front cover 12 can be cut well. And good slip lockup can be obtained. Then, when the pressing force further increases and the differential rotation between the lockup piston and the front cover completely disappears, the operation shifts to a complete lockup operation.

Next, the configuration of the welded portion 11 by laser welding between the impeller shell 10 and the front cover 12 will be described. As will be described later, the welded portion 11 is composed of temporary fixing welding in the first stage and all-around welding (main welding) in the second stage thereafter. As shown in FIGS. 1 to 3, the welded portion 11 includes an impeller shell 10 on the front cover 12 side that forms the cylindrical portion 10-1, and the front cover 12 also includes the impeller shell 10 side that forms the cylindrical portion 12-1. . As shown in an enlarged view in FIG. 3, the tip of the cylindrical portion 10-1 of the impeller shell 10 forms an inner cylindrical protruding portion 10-1 </ b> A whose thickness is removed on the outer diameter side. The distal end of the cylindrical portion 12-1 forms an outer cylindrical protruding portion 12-1A that is stripped on the inner diameter side, and the inner cylindrical protruding portion 10-1A of the impeller shell 10 and the outer cylindrical shape of the front cover 12. The protrusions 12-1A are axially fitted to each other, and in this embodiment, the laser beam is applied to the abutting surface of the outer cylindrical protrusion 12-1A with respect to the cylindrical part 10-1 of the impeller shell 10 as described later. Irradiation forms the weld 11.

FIG. 4 schematically shows a welding structure in Patent Documents 2 and 3 having an axial fitting structure between the impeller shell and the front cover. In this case, the welding method is an arc from the shape of the melted portion. The welded portion 111 is located on the abutting surface of the outer cylindrical protruding portion 112-1A of the front cover with respect to the cylindrical portion 10-1 of the impeller shell, and the outer surface has a structure in which the bead 111A is raised. . Further, the arc welded portion 111 remains on the outer surface of the inner cylindrical protrusion 110-1A, and a structure that penetrates (penetrates) into the inner cylindrical protrusion 110-1A is not seen. The problem with the welded part 111 by this conventional arc welding is that the flatness of the part of the front cover 12 (FIG. 2) facing the clutch facing 32 is deteriorated due to heat input during welding. That is, in the arc welding, heat input to the adjacent portion of the welded portion is large, and thermal distortion is generated in the front cover 12 at the portion facing the clutch facing 32. This thermal strain, particularly the surface facing the clutch facing 32, is generated. At 12A, the flatness of the front cover 12 deteriorates. The deterioration of the flatness of the surface 12A adversely affects the above-described slip lock-up control in which the clutch facing 32 is slid with respect to the surface of the front cover 12 facing the lock-up control, particularly when the lock-up control is started. That is, the presence of the undulation on the front cover surface 12A increases the pressure fluctuation of the oil film due to the so-called wedge effect, and the desired slip lock-up control cannot be performed. Further, the deteriorated flatness of the front cover 12 at the portion facing the clutch facing 32 is caused by the sliding resistance with the clutch facing 32 (the gap between the clutch facing and the front cover 12 facing portion cannot be increased so much). In order to increase the frictional force of the clutch phasing 32, a material having a high yield strength is required. Moreover, the large heat input to the part adjacent to the welded part by arc welding also deteriorates the flatness of the seating surface 34A of the boss nut 34 (the mounting surface of the rotating plate 35 in FIG. 1). Accordingly, in consideration of thermal strain during welding, the expected processing of the seat surface 34A of the boss nut 34 (the seat surface 34A of the boss nut 34 is cut into a taper shape in accordance with the assumed thermal strain, and the seat surface 34A is formed by thermal strain. It is necessary to perform a process for correcting so as to be parallel. Further, there is a problem of buffering to adjacent components of the torque converter due to the weld bead. That is, in the case of arc welding, a weld bead 111A is inevitably generated as shown in FIG. 4, and the swell of the weld bead 111A is likely to interfere with external parts (the interference line is schematically indicated by L). ) In order not to exceed the interference line L, a cutting process for removing the raised portion of the weld bead 111A is required as a post-process.

In contrast, in this embodiment, the abutment surface is welded by laser welding instead of arc welding. That is, in FIG. 3, the inner cylindrical protrusion 10-1A of the impeller shell 10 and the outer cylindrical protrusion 12-1A of the front cover 12 are fitted to each other in the axial direction, so that the cylindrical portion 10 of the impeller shell 10 is fitted. The abutting surface of the outer cylindrical projecting portion 12-1A with respect to -1 constitutes a welded portion 11 by laser welding. The welded portion 11 extends not only inwardly between the abutting surfaces, but also extends partially into the radially inner cylindrical projecting portion 10-1A. The laser weld 11 is partially penetrated through the inner cylindrical protrusion 10-1A. Laser welding has a high penetration density of the welding beam due to its high energy density, such penetration welding can be realized, and shear strength can be guaranteed. Further, by reducing the plate thickness on the front cover side (thickness of the outer cylindrical protrusion 12-1A of the front cover 12) and securing a large welding area, it is possible to improve the shear strength. Further, the impeller shell 10 and the front cover 12 have a press-fit structure (the inner cylindrical projecting portion 10-1A of the impeller shell 10 and the outer cylindrical projecting portion 12-1A of the front cover 12 are press-fitted structure), so that the welding gap Becomes very narrow, and it becomes a countermeasure against welding defects such as voids. Instead of the front cover tip (outer cylindrical protrusion 12-1A) having an abutting structure against the impeller shell as in the illustrated embodiment, the impeller shell tip has an abutting structure against the front cover (outer cylindrical shape). It is also possible that the projecting portion is the impeller shell 10 side and the inner cylindrical projecting portion is the front cover 12 side).

In laser welding, since the energy density is high, the beam can concentrate heat on the welded part (butting part), and there is little heat input to the part other than the welded part (heat input to the front cover 12 side), Since the flatness of the front cover 12 with respect to the clutch facing 32 is maintained, the sliding resistance with the clutch facing 32 is kept small, and the clutch facing 32 does not require a large proof strength (the clutch facing 32). Cost reduction). In addition, since the flatness of the seating surface 34A of the boss nut 34 can be maintained, it is possible to omit the prospective processing step for the seating surface of the boss nut 34 (the mounting surface of the rotating plate 35), which was necessary in the case of arc welding. Yes (reduction of processing costs). In addition, in laser welding, there is almost no swell of the weld bead (maintained to be flush with the welded portion), so even if the weld bead is left as it is, the interference bead L with respect to the outer part is not shown. As shown in FIG. 3, there is a margin, and there is no concern that this will be exceeded (there is no need for the cutting of the bead portion, which is necessary for arc welding, and this reduces the processing cost).

It is necessary to weld the joint portion between the impeller shell 10 and the front cover 12 over the entire circumference because it is necessary to enclose the hydraulic oil therein. A gap remaining between the opposed surfaces of the impeller shell 10 to be welded and the front cover 12 (in FIG. 3, the outer cylindrical protruding portion 12-1A of the cylindrical portion 12-1 of the front cover 12 and the impeller shell 10 opposed thereto). The gap between the cylindrical part 10-1) is on the order of 0.2 mm on average, but the gap size variation and gap position variation within the allowable range, as well as the position of the laser welder Considering each tolerance of deviation, flatness, and axial perpendicularity, the range melted by the heat conduction from the direct irradiation sites on both sides of the range is directly covered by the laser beam so as to cover all of them. It is necessary for ensuring the welding quality that the added total range is about 0.6 mm. FIG. 5 schematically shows a gap between the abutment surfaces of the impeller shell 10 and the front cover 12 developed in the circumferential direction, and a gap between the abutment surfaces between the impeller shell 10 and the front cover 12 (joint). G is not constant in the circumferential direction but varies within a certain range, and the position of the abutting surface is also not constant, and the welding beam generated from the laser torch has a desired welding quality in the gap of this variation range. It is necessary to be able to obtain Therefore, in the embodiment of the present invention, a rectangular beam spot shape is employed so as to cover the variation range of the abutting surface in the circumferential direction. As for a laser beam having a rectangular cross section, for example, a YAG laser is described in Japanese Patent Application Laid-Open No. 2011-18823. Is preferable. As such a semiconductor laser, for example, an L1 type laser welding apparatus (output 4 kW) manufactured by Enshu Corporation can be used. That is, even in a semiconductor laser, the cross section of the laser beam obtained by the laser transmitter is a circular cross section, but when passing through a beam shape converter having an optical fiber core having a vertically long rectangular cross section covered with a clad, the core and the clad By repeating total reflection at the interface, the laser beam cross section can be converted into a vertically long rectangular cross section. That is, in FIG. 6, a laser beam having such a vertically long rectangular cross section obtained by a beam shape converter (not shown) is indicated by 40, and the laser beam 40 having a vertically long rectangular cross section is condensed by a condenser lens 42. Then, the abutting surface between the impeller shell 10 and the front cover 12 is irradiated (a laser beam at the irradiation position is indicated by 40A), and the laser welded portion 11 shown in FIGS. 1 to 3 can be obtained. In FIG. 5, the positional relationship with respect to the gap G between the abutting surfaces between the impeller shell 10 having a vertically long rectangular cross section of the laser beam and the front cover 12 is shown, and the direction of the vertically long L in the vertically long rectangular cross section of the laser beam 40 is between the abutting surfaces. The positional relationship is along the gap G. This positional relationship is important for efficient use of the laser energy of the rectangular cross section. That is, the longitudinal rectangular cross section of the laser beam 40 by the above-described L1 type laser welding apparatus is an extremely narrow shape of 1.6 mm × 0.4 mm, and each point of the welded portion in the welding direction (circumferential direction) is assumed. The laser beam 40 is arranged so that the substantially longest time (substantially maximum of the total amount of irradiation laser energy received at that point) of the laser beam 40 in the longitudinal rectangular section of the laser beam 40 is along the abutting portion. This is because it can be obtained. The formation of the molten metal between the abutting surfaces is performed by a combination of melting by direct application of the laser beam and melting by conduction heat from the melting portion. In other words, in the range in which the portion melted by the heat conduction effect is added to the vertical length L in the vertical rectangular cross-sectional shape of the laser beam 40 (in the case of the above-described L1 type laser welding apparatus, the range is about 0.5 mm in the vertical direction). Welding can be performed. The trajectories of the upper and lower edges of the welding range obtained by adding the heating part by the heat transfer to the direct heating part by the laser beam are indicated by imaginary lines M ₁ and M ₂ . As described above, the position and size of the gap G between the abutting surfaces vary along the circumferential direction, but the gap G is located inside the trajectories M ₁ and M ₂ over the entire circumference. The longitudinal length L in the rectangular cross section of the laser beam 40 is selected, and thereby, complete sealing welding between the abutting surfaces between the impeller shell 10 and the front cover 12 is possible over the entire circumference.

Due to the strong penetrating force of the laser beam, the welded portion 11 exceeds the abutting surface of the outer cylindrical protruding portion 12-1A of the front cover 12 with respect to the cylindrical portion 10-1 of the impeller shell, as shown in FIG. -1 partially bites into the inner cylindrical protrusion 10-1A of the impeller shell 10 (penetration depth = d), and high strength against shearing can be obtained.

FIG. 7 shows a modified embodiment in which a second laser weld 44 is provided in addition to the laser weld 11 shown in FIGS. The second laser welded portion 44 is also provided on the entire circumference, is spaced apart from the laser welded portion 11 in the axial direction, penetrates the outer cylindrical protruding portion 12-1A from the outer periphery of the front cover 12, and the impeller shell 10 The inner cylindrical protrusion 10-1A is slightly bitten. In this embodiment, a higher strength against shearing can be obtained by providing the welds at two locations.

In the present embodiment, the laser weld 11 is formed in the same manner as in the prior art, but is performed in two stages, temporarily and permanently. Hereinafter, the two-stage welding will be described. In the first stage of temporary fixing, local welding (temporary fixing) is performed on the impeller shell 10 at, for example, three locations where the front cover 12 is separated in the circumferential direction. 8 is a cross-sectional view of the abutting portion of the outer cylindrical protrusion 12-1A of the front cover 12 with respect to the cylindrical portion 10-1 of the impeller shell 10 (the impeller shell 10 and the front along the line VIII-VIII in FIG. 1). A cross-sectional view of the cover 12) is shown. As described with reference to FIG. 3, the cylindrical portion 10-1 of the impeller shell 10 and the cylindrical portion 12-1 of the front cover 12 during welding are an inner cylindrical protruding portion 10-1A and an outer cylindrical protruding portion 12-1A. Are inserted into each other, and laser welding is performed at the abutting portion of the outer cylindrical protruding portion 12-1A of the cylindrical portion 12-1 of the front cover 12 with respect to the cylindrical portion 10-1 of the impeller shell 10. In FIG. 8, the temporary fixing welded portion is indicated by Wp, and the laser beam 40 is applied to the abutting portion G of the impeller shell 10 and the front cover 12 as shown in FIG. . In this embodiment, as shown in FIG. 8, the temporary fixing welds Wp are performed at three locations at equal intervals of 120 degrees in the circumferential direction. Moreover, the partial expansion | deployment shape in the circumferential direction of a welding part is shown in FIG. In FIG. 9, the seam G (the abutting portion of the outer cylindrical protruding portion 12-1A of the front cover 12 with respect to the cylindrical portion 10-1 of the impeller shell 10) at the time of welding between the impeller shell 10 and the front cover 12 is originally The gap is not constant in the circumferential direction, and its position varies, but is represented by a straight line for convenience of explanation. The welded portion Wp for temporary fixing extends elongated along the seam G when the impeller shell 10 and the front cover 12 are welded. Conventionally, temporary fixing has been performed, but the shape of the conventional temporary fixing welded portion is a dot shape as indicated by Wp ′. In the present invention, the temporary fixing welded portion Wp is aligned along the joint G. The difference is that it is elongated in the circumferential direction. Such a shape of the temporarily welded portion Wp is useful for preventing the impeller shell 10 and the front cover 12 from moving relative to each other at the temporarily fixed portion during the main welding, thereby losing the effect of temporary fixing.

The main welding is started from an appropriate position in the circumferential direction. In FIG. 8, in the case of laser beam welding, the welding beam 40 is circumferentially along the joint between the impeller shell 10 and the front cover 12 as indicated by an arrow f. It can be seen that the main welding Wr is started by moving it. FIGS. 9A, 9B, 9C, 9D, and 9E schematically show the formation process of the main welded portion Wr along the entire circumference along the seam G developed in the circumferential direction. Through 9 (a) to (e), the white portion in the welded portion is the molten portion and the shaded portion is the solidified portion. FIG. 9 (a) shows one temporarily welded portion, and shows a state where the main welding has not yet been performed. In FIG. 9B, the main weld Wr is located in front of the temporarily welded portion Wp. However, at the position (c) where the main weld has advanced a little, the tip of the main weld Wr is the tip of the temporarily welded portion Wp. At this time, the tip of the temporarily welded portion Wp is completely melted by heat from the main welded portion Wr (represented by white lines), but the temporary welded portion Wp is melted as a whole. In other words, the front portion of the temporarily welded portion Wp remains in a solidified state (oblique line). The main welding further proceeds in (d), and the overlap with the lower temporary welding portion Wp is increased, but the front portion of the temporary welding portion Wp is still in a solid state, while in (c) The temporarily fixed portion (the portion first overlapping with the main welding) once melted returns to the solidified state (shaded line) together with the main welding portion. And in (e), the welding arc of this welding part has completely passed through one temporary fixing weld Wp, and the temporary fixing weld Wp is in a molten state (outlined) at the front side portion, but it is downstream. The re-coagulated part in the side part is further expanded. Accordingly, the fixed state (temporarily fixed state) between the impeller shell 10 and the front cover 12 at the site fixed by the temporarily fixed weld Wp in FIG. 9A is the same as that of the main welding of (b)-(e). Maintained throughout the process. As described above, in the present invention, by temporarily elongating the temporarily welded portion Wp along the seam G at the time of welding, a part of each part that has been temporarily fixed in the first stage welding regardless of the progress of the main welding is partially included. Since it is always in a solidified state, the relative position between the impeller shell 10 and the front cover 12 remains fixed at the temporary fixing weld, and the temporary fixing effect can be maintained. On the other hand, in the case of temporary fixing by conventional spot welding, the temporary fixing weld (Wp ′ in FIG. 9A) is completely melted by the heat of the main welding, and the impeller shell 10 and Since the relative position with respect to the front cover 12 is free, the temporary fixing effect disappears at the site, and the temporary fixing effect is weakened. FIG. 10 shows the measurement results of the flatness of the clutch facing facing surface (12A in FIG. 2) of the front cover after the main welding by the temporary welding method of the present invention and the conventional temporary welding method. Temporary fixing parts are three in the circumferential direction, 0 degrees, 120 degrees and 240 degrees, and the measured flatness is displayed as a displacement amount in the plus or minus direction with respect to the reference value (zero point). It can be seen that the temporary fixing method (a) of the present invention improves the flatness (swelling reduction) in comparison with the conventional temporary fixing method (b). Thereby, the pressure fluctuation in the oil film between the clutch facing 32 and the front cover 12 in the slip lock-up is suppressed, and the slip lock-up under the slip lock-up that causes the clutch facing 32 and the front cover 12 to slide through the oil film is good. Power transmission can be ensured. In addition, secondary processing after assembly of the torque converter for reducing thermal strain can be eliminated or minimized.

In the present embodiment, the welded portion is composed of two stages, that is, temporary fixing between the impeller shell 10 and the front cover 12 and final fixing, in particular, the temporary fixing welding portion Wp is elongated in the circumferential direction, and temporary fixing welding is performed during final fixing welding. The welding method that always maintains a part in a solidified state is not limited to laser welding, and the effects described in relation to FIGS. The effect according to can be produced.

10 ... Impeller shell
10-1 ... Cylinder part of impeller shell 10-1
10-1A ... Inner cylindrical projection 11 ... Laser weld 12 ... Front cover
12-1… The cylindrical part of the front cover
12-1A ... Outer cylindrical projection 13 ... Fluid power transmission unit 14 ... Lock-up unit 15 ... Impeller 16 ... Turbine 17 ... Stator 22 ... Driven plate (output side rotating member)
26 ... Drive plate (input side rotating member)
28 ... Damper spring 29 ... Equalizer plate (intermediate member)
30 ... Piston plate 30
32 ... Clutch facing 34 ... Boss nut 34A ... Boss nut seat 35 ... Rotating plate 40 ... Laser beam 42 ... Condensing lens 44 ... Second laser weld
M ₁ , M ₂ ... Laser welding range upper and lower edge trajectory Wp ... Temporary fixing weld Wr ... Main weld

Claims (16)

An impeller shell, a front cover that is welded to the impeller shell at a welded portion along the entire outer circumference, and an impeller, a turbine, and a stator that are accommodated in an internal space formed by the impeller shell and the front cover In the same manner, the fluid type power transmission device is housed in the internal space, driven by the internal hydraulic pressure, and engaged with the front cover facing surface via the clutch facing to directly transmit power between the input side and the output side. A piston plate, and the impeller shell and the front cover are each provided with an axial cylindrical protrusion that is axially fitted to each other, and the welded portion is radially outward of one of the impeller shell and the front cover. The abutting surfaces of the axial cylindrical protrusion, the impeller shell, and the other of the front cover are welded all around. Torque converter is over laser welding unit. 2. The torque converter according to claim 1, wherein the laser welded portion extends so as to partially bite into the axial cylindrical protruding portion radially inward from the abutting surface. 3. The torque converter according to claim 1, wherein the weld is a laser weld with a laser having a rectangular cross section. 4. The invention according to claim 1, further comprising a second laser welding portion extending in the entire circumference at a portion spaced in the axial direction from the welding portion, and the second laser welding in the radial direction. The torque extends so as to penetrate the axial cylindrical projection on the radially inner side through the cylindrical projection on the radially outer side from the outer surface of the axial cylindrical projection on the radially outer side. converter. The invention according to any one of claims 1 to 4, wherein the abutting surfaces of the impeller shell and the front cover have temporary welding portions by laser welding at a plurality of locations spaced in the circumferential direction. The torque converter in which the temporarily welded portion is integrally melted with the welded portion along the entire circumference from the outside. 6. The torque converter according to claim 5, wherein the temporarily welded portion extends in a circumferential direction. It is a laser welding method for obtaining the laser welding part of Claim 1, Comprising: An impeller shell and a front cover fit the axial direction cylindrical protrusion part in an axial direction, and between an impeller shell and a front cover, On the other hand, the axially cylindrical projecting portion located on the radially outer side, the impeller shell, and the other surface of the front cover are abutted against each other, a laser beam is applied to the abutting portion from the outer periphery, and laser welding is performed along the entire circumference A laser welding method in which a laser weld is formed between the abutting surfaces. 8. The laser welding method according to claim 7, wherein the laser welding is performed so that the laser welding portion extends beyond the abutting surface and partially bites into the axial cylindrical protruding portion on the radially inner side. 9. The laser welding beam according to claim 7 or 8, wherein the laser welding beam has a rectangular cross-sectional shape, and a beam can be formed on the abutting surface regardless of the gap between the abutting surfaces in any part of the circumference. Laser welding method in which the width is set. 10. The laser welding method according to claim 9, wherein the rectangular cross section of the laser welding beam has a vertically long shape, and the vertically long rectangular cross section extends in a direction along the abutting surface. The invention according to any one of claims 7 to 10, wherein a laser beam is applied from the outer periphery at a portion spaced in the axial direction from the welded portion, and is radially outward from the outer surface of the axial cylindrical protruding portion on the radially outer side. Laser welding method for forming a second weld that penetrates through the cylindrical protrusion and partially digs into the radially inner axial protrusion. The invention according to any one of claims 7 to 11, wherein the impeller shell and the front cover are arranged in a circumferential direction as a first stage welding process prior to the formation of the laser welded portion along the entire circumference. A temporary fixing weld is formed by applying a laser beam from the outer periphery to the abutting portion at a plurality of intervals, and as a subsequent second-stage welding process, the laser welding portion along the entire periphery is formed. A laser welding method in which the solidified state of the molten metal is always maintained partially for each temporarily welded portion obtained in the first stage welding process during the second stage welding. 13. The welding method according to claim 12, wherein the molten metal extends along the circumferential direction at each welding point in the first stage welding process. An impeller shell, a front cover that is welded to the impeller shell at a welded portion along the entire outer circumference, and an impeller, a turbine, and a stator that are accommodated in an internal space formed by the impeller shell and the front cover In the same manner, the fluid type power transmission device is housed in the internal space, driven by the internal hydraulic pressure, and engaged with the front cover facing surface via the clutch facing to directly transmit power between the input side and the output side. A piston plate, wherein the welded portion joins the impeller shell and the front cover at a plurality of locations spaced apart in the circumferential direction, and extends temporarily in the circumferential direction; and the impeller shell; A torque converter comprising a front cover and an all-around welded portion that welds the entire circumference including the temporarily welded portion. An impeller shell, a front cover welded along the entire circumference of the outer periphery of the impeller shell, and a fluid that is housed in an internal space formed by the impeller shell and the front cover and includes an impeller, a turbine, and a stator And a piston plate that is housed in the internal space and is driven by internal hydraulic pressure, is engaged with the front cover facing surface via a clutch facing, and directly transmits power between the input side and the output side. A circumferential welding method for an outer peripheral portion of an impeller shell and a front cover in a torque converter comprising the impeller shell and the front cover as a first stage welding step, wherein the impeller shell and the front cover are spaced apart in the circumferential direction. Temporary fixing is performed by welding at the location of the impeller shell as the second stage welding process The part temporarily fixed along the entire circumference along the joint with the front cover was welded so as to overlap with this, and in the second stage welding, it was temporarily fixed in the first stage welding process. A welding method characterized in that the welding is performed so that the solidified state of the molten metal is always maintained partially in each part. 16. The welding method according to claim 15, wherein the molten metal extends along the circumferential direction at each welding point in the first stage welding process.

Images