JP2006038055A - Method of manufacturing impeller for fluid transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an impeller for a fluid transmission device while easily welding and temporarily fastening a retainer plate to a shell without giving distortion to the shell and the retainer plate. <P>SOLUTION: This method of manufacturing the impeller for the fluid transmission device comprises welding and temporarily fastening the annular retainer plate 2r to the inner face of the shell 2s for pressing the radial inner ends of a plurality of blades 2b annularly arranged on the inner face of the shell 2s and then brazing the blades 2b and the retainer plate 2r to the inner face of the shell 2s. The retainer plate 2r is laid on the inner face of the shell 2s which is irradiated at the side of the retainer plate 2r with a laser beam B1 to form a welding seam 46 between the retainer plate 2r and the shell 2s. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a plurality of blades are arranged in an annular shape on the inner surface of a bowl-shaped shell, and an annular retainer plate that holds the radially inner ends of these blades is temporarily fixed to the inner surface of the shell by welding. , A blade and a retainer plate are brazed to the inner surface of the shell, and after the brazing, a hub is welded to the center of the shell.

Such a manufacturing method of an impeller for a fluid transmission device is already known as disclosed in, for example, Patent Document 1 below.
JP 2003-214523 A

  Conventionally, in the manufacturing method of such an impeller for a fluid transmission device, spot welding or projection welding is usually performed to temporarily fix the retainer plate to the inner surface of the shell. The retainer plates need to be strongly pressed together, and the pressure may cause distortion in the shell and the retainer plate. In particular, during projection welding, the deformation of the protrusion formed on one of the opposing surfaces of the shell and the retainer plate spreads to the surroundings, and distortion is likely to occur.

  SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and manufacture of an impeller for a fluid transmission device that can easily temporarily fix the retainer plate to the shell by welding without causing distortion of the shell and the retainer plate. It aims to provide a method.

  In order to achieve the above object, according to the present invention, a plurality of blades are arranged in an annular shape on the inner surface of a bowl-shaped shell, and an annular retainer plate for holding the radially inner ends of the blades is welded to the inner surface of the shell. In the manufacturing method of the impeller for a fluid transmission device, the blade and the retainer plate are brazed to the inner surface of the shell after the temporary fixing, and the hub is welded to the center of the shell after the brazing. A first feature is that a weld seam is formed between the retainer plate and the shell by superimposing the retainer plate on the inner surface of the shell and irradiating a laser beam from the retainer plate side.

  According to the present invention, in addition to the first feature, the weld seam is formed in an annular shape so as to surround the hub, and the blade and the retainer plate are brazed to the inner surface of the shell outside the weld seam in the radial direction. This is the second feature.

  In addition to the first feature of the present invention, a cylindrical boss that protrudes toward the retainer plate and is welded to the hub is formed on the inner peripheral end of the shell, and the weld seam is formed in a spot shape. The third feature.

  The fluid transmission device corresponds to a torque converter T in an embodiment of the present invention described later, and the impeller corresponds to the pump impeller 2 and the turbine impeller 3.

  According to the first feature of the present invention, when forming a weld seam by laser welding between the two in order to temporarily fix the retainer plate to the shell, the flat opposing surfaces of the shell and the retainer plate are simply overlapped. Since it is not necessary to press both of them at the same time as in conventional spot welding or projection welding, it is possible not only to simplify the welding operation but also to avoid distortion in the shell and retainer plate. Can contribute to the improvement of quality and productivity.

  According to the second aspect of the present invention, when brazing the blade and the retainer plate to the shell, the molten brazing material is prevented from flowing out to the inner peripheral surface side of the shell by the annular temporary welding weld seam. Therefore, after brazing, when the shell and the hub are welded, the elution and mixing of the brazing material into the melted portion can be surely prevented, and the welding can be performed satisfactorily.

  Further, according to the third aspect of the present invention, when brazing the blade and the retainer plate 3r to the shell, the molten brazing material passes between the shell and the retainer plate around the spot-like weld seam. Even if this occurs, the outer peripheral surface of the boss of the shell does not reach the inner peripheral surface of the boss. Therefore, a spot-like weld seam is sufficient for temporarily retaining the retainer plate, and the efficiency of the temporary securing work can be improved. Then, at the time of welding between the boss and the hub of the next shell, it is possible to reliably prevent the elution and mixing of the brazing material into the molten portion, so that the welding can be performed satisfactorily.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  1 is a longitudinal sectional side view of an upper half portion of a torque converter according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, FIG. 3 is a sectional view taken along line 3-3 of FIG. FIG. 5 is a sectional view taken along the line 5-5 of FIG. 1, FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5, FIG. 7 is an explanatory diagram of the manufacturing process of the turbine impeller, and FIG. FIG. 9 is a view corresponding to FIG. 3 showing a modification of the impeller, and FIG. 9 is a view corresponding to FIG. 6 showing a modification of the turbine impeller.

  First, in FIG. 1, a torque converter T as a fluid transmission device includes a pump impeller 2, a turbine impeller 3 opposed to the pump impeller 2, and a stator impeller 4 disposed between the inner peripheral portions thereof. Between these three impellers 2, 3 and 4, a circulation circuit 6 for power transmission by the working oil is defined.

  A transmission cover 5 that covers the outer surface of the turbine impeller 3 is integrally connected to the pump impeller 2 by welding. A starting ring gear 7 is welded to the outer peripheral surface of the transmission cover 5, and a drive plate 8 coupled to the crankshaft 1 of the engine is fixed to the ring gear 7 with bolts 9. A thrust needle bearing 17 is interposed between the hub 3 h of the turbine impeller 3 and the transmission cover 5.

  An output shaft 10 arranged coaxially with the crankshaft 1 is disposed at the center of the torque converter T. The output shaft 10 is spline-fitted to the hub 3h of the turbine impeller 3 and is connected to the hub 5a of the transmission cover 5. A bearing bush 16 is rotatably supported on the inner peripheral surface. The output shaft 10 becomes the main shaft of the multi-stage transmission.

  A cylindrical stator shaft 12 for supporting the hub 4h of the stator impeller 4 via a free wheel 11 is disposed on the outer periphery of the output shaft 10, and the relative rotation between the output shaft 10 and the stator shaft 12 is arranged. A bearing bush 15 that allows The outer end portion of the stator shaft 12 is supported by the transmission case 14 so as not to rotate.

  Thrust needle bearings 18 and 18 'are interposed between the hub 4h of the stator impeller 4 and the hubs 2h and 3h of the pump impeller 2 and the turbine impeller 3 opposed to the hub 4h.

  Further, on the outer periphery of the stator shaft 12, an auxiliary machine drive shaft 20 connected to the hub 2 h of the pump impeller 2 is disposed so as to be relatively rotatable, and hydraulic oil is supplied to the torque converter T by the auxiliary machine drive shaft 20. The oil pump 21 is driven.

  The turbine impeller 3 and the transmission cover 5 define a clutch chamber 22 therebetween, and accommodates a lockup clutch L that can be directly connected between the turbine impeller 3 and the transmission cover 5. The clutch piston 25 that forms the main body of the lockup clutch L is disposed so as to partition the clutch chamber 22 into an inner chamber 22a on the turbine impeller 3 side and an outer chamber 22b on the transmission cover 5 side. The clutch piston 25 is provided with a friction lining 25a facing the inner side surface of the transmission cover 5 on the outer peripheral side wall, and is separated from the connection position where the friction lining 25a is pressed against the inner side surface of the transmission cover 5 and the inner wall. It is slidably supported on the outer peripheral surface of the hub 3h of the turbine impeller 3 so that it can move in the axial direction between the unconnected positions.

  The clutch chamber 22 is also provided with a torque damper D that buffers the clutch piston 25 and the turbine impeller 3.

  A first oil passage 30 communicating with the outer chamber 22 b of the clutch chamber 22 through the lateral hole 26 and the thrust needle bearing 17 is provided at the center of the output shaft 10. A second oil passage 31 is defined between the auxiliary drive shaft 20 and the stator shaft 12 and communicates with the inner periphery of the circulation circuit 6 via the thrust needle bearings 18 and 18 'and the free wheel 11. The first oil passage 30 and the second oil passage 31 are alternately connected to the discharge side of the oil pump 21 and the oil reservoir 33 by a lock-up control valve 32.

  Thus, in the engine idling or extremely low speed operation region, the lockup control valve 32 connects the first oil passage 30 to the discharge side of the oil pump 21 as shown in FIG. Is connected to the oil reservoir 33 by an electronic control unit (not shown). Therefore, when the output torque of the crankshaft 1 of the engine is transmitted to the drive plate 8, the transmission cover 5, and the pump impeller 2 to rotate and drive the oil pump 21, the discharge operation of the oil pump 21 is performed. The oil sequentially flows from the lock-up control valve 32 to the circulation circuit 6 through the first oil passage 30, the lateral hole 26 and the thrust needle bearing 17, the outer chamber 22 b of the clutch chamber 22, and the inner chamber 22 a to fill the circuit 6. Thereafter, the thrust needle bearings 18, 18 ′ and the free wheel 11 are sequentially moved to the second oil passage 31, and returned to the oil reservoir 33 from the lockup control valve 32.

  Thus, in the clutch chamber 22, the outer chamber 22b has a higher pressure than the inner chamber 22a due to the flow of the working oil as described above, and the clutch piston 25 is pulled away from the inner wall of the transmission cover 5 due to the pressure difference. Since it is pressed, the lock-up clutch L is in a disconnected state and allows relative rotation of the pump impeller 2 and the turbine impeller 3. Therefore, when the pump impeller 2 is rotationally driven from the crankshaft 1, the working oil that fills the circulation circuit 6 circulates in the circulation circuit 6 as indicated by the arrow, thereby reducing the rotational torque of the pump impeller 3 to the turbine blade. This is transmitted to the car 3 to drive the output shaft 10.

  At this time, if a torque amplifying action is generated between the pump impeller 2 and the turbine impeller 3, the accompanying reaction force is borne by the stator impeller 4, and the stator impeller 4 is caused by the locking action of the freewheel 11. Fixed.

  When the torque amplification operation is finished, the stator impeller 4 rotates in the same direction together with the pump impeller 2 and the turbine impeller 3 while idling the free wheel 11 due to the reversal of the torque direction received by the stator impeller 4.

  When the torque converter T enters such a coupling state, the lockup control valve 32 is switched by the electronic control unit. As a result, the oil discharged from the oil pump 21 flows into the circulation circuit 6 from the lock-up control valve 32 through the second oil passage 31 and fills the circuit 6, contrary to the previous time, and then the clutch chamber 22. The inner chamber 22a is filled to fill the inner chamber 22a. On the other hand, the outer chamber 22b of the clutch chamber 22 is opened to the oil sump 33 via the first oil passage 30 and the lockup control valve 32. Therefore, in the clutch chamber 22, the inner chamber 22a is more than the outer chamber 22b. Due to the pressure difference, the clutch piston 25 is pressed to the transmission cover 5 side, the friction lining 25a is pressed against the inner wall of the transmission cover 5, and the lockup clutch L is connected. Then, since the rotational torque transmitted from the crankshaft 1 to the pump impeller 2 is mechanically transmitted to the turbine impeller 3 via the torque damper D, the pump impeller 2 and the turbine impeller 3 are in a directly connected state. Thus, the output torque of the crankshaft 1 can be efficiently transmitted to the output shaft 10 and fuel consumption can be reduced.

  Now, the configuration of the pump impeller 2 and the manufacturing method thereof will be described with reference to FIGS.

  The pump impeller 2 is brazed to the inner surface of the shell-like and annular shell 2s, the shell 2s, a plurality of blades 2b, 2b... Brazed to a fixed position on the inner surface of the shell 2s. Are fitted to the inner peripheral surfaces of the annular retainer plate 2r that holds the radially inner ends of the blades 2b, 2b..., The core 2c that connects the intermediate portions of all the blades 2b, 2b, and the shell 2s and the retainer plate 2r. The hub 2h is joined to each other via an annular welding seam 40 formed by laser welding.

  A plurality of positioning recesses 41, 41,... Arranged in the circumferential direction are formed in the shell 2s, and positioning protrusions 42 formed at the inner ends in the radial direction of the blades 2b are engaged with the recesses 41, respectively.

  On the other hand, the retainer plate 2r is arranged so that the positioning projections 42 of all the blades 2b, 2b... Further, the retainer plate 2r is provided with positioning notches 43, 43... For engaging the blades 2b.

  Each blade 2b is formed with a positioning projection 44 at an edge facing the core 2c, and a positioning hole 45 with which the positioning projection 44 engages is formed in the core 2c.

  When brazing the shell 2s, the blades 2b, 2b... And the retainer plate 2r to the shell 2s, first, as shown in FIG. 4 (A), the blades 2b, 2b. 2r is set, and the outer surface near the inner peripheral end of the retainer plate 2r is irradiated with the laser beam B1 from the laser welding torch W1 while rotating the shell 2s and the retainer plate 2r around the axis thereof. An annular weld seam 46 is formed such that the penetration reaches the wall of the shell 2s from the outer surface of the retainer plate 2r and surrounds the hub 2h. The retainer plate 2r is temporarily fixed to the shell 2s by the weld seam 46.

  After this temporary fixing, as shown in FIG. 4B, the molten brazing material 47 is infiltrated between the shell 2s and the blades 2b, 2b... And the retainer plate 2r on the outer peripheral side of the annular weld seam 46. , Braze. As a result, the blades 2b, 2b... Are firmly joined to the shell 2s together with the retainer plate 2r. At this time, the molten brazing material 47 is reliably prevented from flowing out to the inner peripheral end side of the shell 2 s and the retainer plate 2 r by the annular welding seam 46.

  By the way, when the welding seam 46 is formed by laser welding, the flat opposing surfaces of the shell 2s and the retainer plate 2r may be simply overlapped, and both 2s and 2r are used as in conventional spot welding or projection welding. Therefore, it is possible not only to simplify the welding operation but also to prevent the shell 2s and the retainer plate 2r from being distorted. Moreover, since the weld seam 46 starts from the retainer plate 2r and ends in the wall of the shell 2s, the weld mark does not appear on the outer surface of the shell 2s, and the appearance can be improved.

  After the brazing, the retainer plate 2r and the inner peripheral surface of the shell 2s are simultaneously cut to form a fitting hole 48 that fits to the outer peripheral surface of the hub 2h. Then, after the outer peripheral surface of the hub 2h is fitted into the fitting hole 48, as shown in FIG. 4C, the shell 2s, the retainer plate 2r, and the hub 2h are rotated around the axis thereof. By irradiating the laser beam B2 from the laser welding torch W2 toward the fitting portion between the shell 2s and the retainer plate 2r and the hub 2h from the outside, the penetration is caused from one axial end to the other end of the fitting portion. An annular weld seam 40 is formed. Accordingly, the annular weld seam 40 is formed in the fitting portion over the entire length of the fitting depth, whereby the shell 2s, the retainer plate 2r, and the hub 2h are liquid-tight and firm. Be joined.

  As described above, the brazing material 47 in which the blades 2b, 2b... And the retainer plate 2r are joined to the shell 2s is prevented from flowing out toward the fitting hole 48 by the annular temporary welding weld seam 46. During laser welding of the fitting portion, elution and mixing of the brazing material 47 into the melted portion can be surely prevented, so that a good welding seam 40 is formed, and the shell 2s, retainer plate 2r and hub 2h are formed. Bonding strength can be increased.

  Further, according to laser welding, since the annular weld seams 40 and 46 can be formed with relatively little heat input, thermal distortion of the shell 2s can be avoided, and no spatter is generated. There is no need to perform the removal work. Therefore, the quality and productivity of the pump impeller 2 can be greatly improved.

  Further, the annular welding seam 40 is formed so that the penetration by the laser beam B2 reaches from the axial end to the other end of the fitting portion of the shell 2s and the retainer plate 2r and the hub 2h. An annular discoloration is formed on the other end of the plate, that is, on the outer surface of the retainer plate 2r, and anyone can easily and reliably determine whether or not laser welding is good simply by visual inspection for the presence or absence of the discoloration. Can contribute to high quality assurance.

  For joining between the shell 2s and the hub 2h, as shown in FIG. 8, an annular welding seam 140 by TIG or MIG welding can be formed.

  Next, a configuration of the turbine impeller 3 and a manufacturing method thereof will be described with reference to FIGS.

  The turbine impeller 3 is braided and annular shell 3s, a plurality of blades 3b, 3b... Brazed to a fixed position on the inner surface of the shell 3s, and braided on the inner surface of the shell 3s. , 3b... Retainer plate 3 r that holds the inner end in the radial direction, core 3 c that connects the intermediate portions of all blades 3 b, 3 b, and the inner peripheral surface of shell 3 s are formed by laser welding. The structure of the pump impeller 2 is the same as that of the pump impeller 2 in that the hub 3h is joined via an annular welded seam 40. The shell 3s of the turbine impeller 3 is the same as the shell 2s of the pump impeller 2. In contrast, the cylindrical boss 49 protruding inward in the axial direction of the turbine impeller 3 is bent in advance at its inner peripheral end so as to ensure a sufficient fitting depth with the hub 3h. Completion It is.

  The positioning structure of the shell 3s, the blades 3b, 3b... And the retainer plate 3r in the turbine impeller 3 is the same as that of the pump impeller 2, and therefore, in the drawing, there is a portion corresponding to the pump impeller 2 in the figure. , The same reference numerals are given, and the description of the positioning structure is omitted.

  When brazing the shell 3s, the blades 3b, 3b... And the retainer plate 3r to the shell 3s, first, as shown in FIG. 7A, the blades 3b, 3b. 3r is set, and the outer surface near the inner peripheral end of the retainer plate 3r is irradiated with the laser beam B1 from the laser welding torch W1 while rotating the shell 3s and the retainer plate 3r around the axis thereof. A plurality of spot-like welded seams 46 ′, 46 ′,... Reaching the inside of the shell 3s from the outer surface of the retainer plate 3r. The retainer plate 3r is temporarily fixed to the shell 3s by the plurality of spot-like welded seams 46 ', 46'.

  After this temporary fixing, as shown in FIG. 7B, brazing is performed by infiltrating the molten brazing material 47 between the shell 3s and the blades 3b, 3b... And the retainer plate 3r. As a result, the blades 3b, 3b... Are firmly joined to the shell 3s together with the retainer plate 3r.

  At the time of brazing, the molten brazing material 47 bypasses the periphery of each spot-like weld seam 46 'between the shell 3s and the retainer plate 3r, and reaches the inner peripheral end of the retainer plate 3r. Can be brazed to the shell 3s up to the inner peripheral end thereof, and the brazing strength can be increased. Therefore, the thickness of the retainer plate 3r can be reduced and the weight thereof can be reduced. Moreover, since the molten brazing material 47 that has reached the outer peripheral surface of the boss 49 by bypassing the periphery of each spot-like weld seam 46 ′ cannot climb the outer peripheral surface of the boss 49, the inner peripheral surface of the boss 49 Never reach. Therefore, the weld seams 46 ', 46',... For temporary fixing of the retainer plate 3r are sufficient as spot-like ones, and the efficiency of temporary fixing work can be improved.

  Also in this case, when the spot-like weld seams 46 ', 46',... Are formed by laser welding, the flat opposing surfaces of the shell 3s and the retainer plate 3r are simply overlapped, so that the welding operation is simple. In addition, it is possible to avoid distortion in the shell 3s and the retainer plate 3r. Moreover, since each weld seam 46 'starts from the retainer plate 3r and ends within the wall of the shell 3s, the weld mark does not appear on the outer surface of the shell 3s, and the appearance can be improved.

  After the brazing, as shown in FIG. 7C, after the boss 49 of the shell 3s is fitted to the outer peripheral surface of the hub 3h, the shell 3s, the retainer plate 3r and the hub 3h are rotated around the axis. However, by irradiating the laser beam B2 from the laser welding torch W2 from the outside of the shell 3s toward the fitting portion of the boss 49 and the hub 3h, the penetration reaches from one end of the fitting portion in the axial direction to the other end. That is, an annular weld seam 40 is formed over the entire length of the fitting depth. The annular weld seam 40 joins the shell 3s and the hub 3h in a liquid-tight and firm manner.

  As described above, the brazing material 47 obtained by joining the retainer plate 3r to the shell 3s is blocked by the outer peripheral surface of the boss 49 of the shell 3s and does not reach the inner peripheral surface of the boss 49. At the time of laser welding, it is possible to reliably prevent elution and mixing of the brazing material 47 into the melted portion. Therefore, in this case as well, a good welding seam 40 is formed, and the boss 49 of the shell 3s and the hub 3h are joined. Strength can be increased.

  Further, since the boss 49 of the shell 3s sufficiently increases the axial fitting length with the hub 3h, the depth of the weld seam 40 is sufficiently increased even though the shell 3s is relatively thin. It is possible to secure the connection between the shell 3s and the hub 3h.

  Of course, in this turbine impeller 3 as well, when the spot-like weld seams 46 ', 46'... And the annular weld seam 40 are formed by laser welding, heat input is relatively small, so that thermal distortion of the shell 3s is avoided. In addition, since no spatter is generated, there is no need to perform spatter removal work. Accordingly, the quality and productivity of the turbine impeller 3 can be greatly improved.

  Further, the annular welding seam 40 is formed so that the penetration by the laser beam B2 reaches from the axial end to the other end of the fitting portion between the boss of the shell 3s and the hub 3h. An annular discoloration portion is formed on the other end of the portion, that is, the outer surface of the retainer plate 3r, and anyone can easily and reliably determine whether the laser welding is good or not simply by visual inspection for the presence or absence of the discoloration portion. Can contribute to high quality assurance.

  For joining between the shell 3s and the hub 3h, as shown in FIG. 9, an annular welding seam 140 can be formed by TIG or MIG welding.

  The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention. The structure of the pump impeller 2 of the above embodiment can also be adopted for a turbine impeller, and the structure of the turbine impeller 3 of the above embodiment can also be adopted for a pump impeller. The present invention can also be applied to a fluid coupling pump impeller and a turbine impeller.

The upper half longitudinal section side view of the torque converter concerning the example of the present invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. Manufacturing process explanatory drawing of a pump impeller. FIG. 5 is a sectional view taken along line 5-5 in FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG. Manufacturing process explanatory drawing of a turbine impeller. The corresponding figure with Drawing 3 showing the modification of a pump impeller. FIG. 7 is a view corresponding to FIG. 6 showing a modification of the turbine impeller.

Explanation of symbols

B1 ... Laser beam T ... Fluid transmission device (torque converter)
2. Impeller (pump impeller)
2b ... blade 2h ... hub 2r ... retainer plate 2s ... shell 3 ... impeller (turbine impeller)
3b ... Blade 3h ... Hub 3r ... Retainer plate 3s ... Shell 46, 46 '... Welding seam 49 ... Boss

Claims (3)

A plurality of blades (2b, 3b) are arranged in an annular shape on the inner surface of the bowl-shaped shell (2s, 3s), and annular retainer plates (2r, 3r) for pressing the radially inner ends of these blades (2b, 3b). ) Is temporarily fixed to the inner surface of the shell (2s, 3s) by welding, and after the temporary fixing, the blade (2b, 3b) and the retainer plate (2r, 3r) are brazed to the inner surface of the shell (2s, 3s), In the manufacturing method of the impeller for a fluid transmission device, in which the hub (2h, 3h) is welded to the center of the shell (2s, 3s) after the brazing,
The retainer plates (2r, 3r) are superposed on the inner surfaces of the shells (2s, 3s) and irradiated with the laser beam (B1) from the retainer plates (2r, 3r) side. A method for manufacturing an impeller for a fluid transmission device, wherein a weld seam (46, 46 ') is formed between shells (2s, 3s). In the manufacturing method of the impeller for fluid transmission devices of Claim 1,
The weld seam (46) is formed in an annular shape so as to surround the hub (2h), and the blade (2b) and the retainer plate (2r) are placed on the shell (2s) radially outward of the weld seam (46). A method of manufacturing an impeller for a fluid transmission device, wherein the inner surface is brazed. In the manufacturing method of the impeller for fluid transmission devices of Claim 1,
A cylindrical boss (49) welded to the hub (3h) is formed on the inner peripheral end of the shell (3s) so as to protrude toward the retainer plate (3r), and the weld seam (46 ') is formed in a spot shape. A method of manufacturing an impeller for a fluid transmission device.

Images