JP2024074550A - Laminated core and method for repairing weld cracks therein - Google Patents

Abstract

[Problem] To provide a laminated core that makes it possible to repair weld cracks and eliminate or suppress scrapping. [Solution] A laminated core 1 includes a laminated core piece 3 in which a plurality of annular core pieces 7 are stacked, a first welded portion 5 in which the laminated core 3 is welded along the stacking direction, and a second welded portion 9 in which a weld crack 11 in the first welded portion 5 is welded by melting and solidifying a portion of the first welded portion 5. [Selected Figure] Figure 1

Description

This invention relates to a laminated core for electric motors and a method for repairing weld cracks.

Conventional laminated cores are made by stacking and welding multiple annular core pieces. In such laminated cores, welding is performed in the stacking direction, but cracks (weld cracks) can occur in the middle of the welds that are formed.

If cracks occur in the welds, the weld quality will not meet the standards and the laminated core will have to be scrapped.

In contrast, in the rotor manufacturing method of Patent Document 1, the welding head is inclined at a predetermined angle to the stacked surface of the core pieces, and the welding head is moved relative to the stacked core pieces.

This rotor manufacturing method can improve welding quality, but has the problem that if a weld crack occurs, the laminated core with the crack must be discarded.

Patent No. 6652190

The problem to be solved involves the disposal of laminated cores that contain weld cracks.

The present invention provides a laminated core comprising a laminated core piece formed by stacking a plurality of annular core pieces, a first welded portion in which the laminated core pieces are welded in the stacking direction, and a second welded portion in which a weld crack in the first welded portion is welded by melting and solidifying a portion of the first welded portion.

The present invention also provides a method for repairing weld cracks used in a laminated core, the method comprising a first welding step for forming the first welded portion, a confirmation step for checking for weld cracks in the first welded portion, and a second welding step for forming the second welded portion by welding along the weld cracks.

The present invention can eliminate or reduce the waste of laminated cores.

FIG. 1 is a perspective view of a laminated core according to an embodiment of the present invention. FIG. 2 is a plan view of the laminated core of FIG. FIG. 3(A) is an enlarged plan view showing a portion of a laminated core piece before welding, and FIG. 3(B) is an enlarged plan view showing a portion of a laminated core corresponding to FIG. 3(A) after welding. FIG. 4 is an enlarged side view of a portion of a laminated core including a weld crack. FIG. 5 is an enlarged side view showing the periphery of the weld crack in FIG. FIG. 6 is a side view showing the second welded portion. FIG. 7 is a cross-sectional view of the second weld of FIG. FIG. 8 is a process diagram showing a method for manufacturing a laminated core according to an embodiment. FIG. 9 is a table showing an example of various conditions for the first welding step and the second welding step in the manufacturing method of FIG.

The present invention achieves the objective of eliminating or reducing the need to scrap laminated cores by welding weld cracks in the first weld by melting and solidifying a portion of the first weld.

The laminated core 1 is composed of a laminated core piece 3, a first welded portion 5, and a second welded portion 9. The laminated core piece 3 is formed by stacking a number of annular core pieces 7. The first welded portion 5 welds the core pieces 7 of the laminated core piece 3 along the stacking direction. The second welded portion 9 welds the weld crack 11 of the first welded portion 5 by melting and solidifying a portion of the first welded portion 5.

The second weld 9 may be formed by melting and solidifying a portion of the first weld 5 including the weld crack 11 at a predetermined weld width W and weld depth D2 based on an approximation line 15 relative to the crack line 12 of the weld crack 11.

The weld crack repair method of the present invention includes a first welding process S1 for forming a first weld 5, a confirmation process S2 for checking for a weld crack 11 in the first weld 5, and a second welding process S4 for forming a second weld by welding along the weld crack 11.

The welding in the second welding step S4 may be performed by applying pressure in the stacking direction to the laminated core piece 3 that includes the weld crack 11 in the first welded portion 5.

The second welding process S4 may involve welding in which a portion of the first weld 5 including the weld crack 11 is melted and solidified at a predetermined weld width W and weld depth D2, based on an approximation line 15 relative to the crack line 12 of the weld crack 11.

The focal spot size of the second welding step S4 may be smaller than the focal spot size of the first welding step S1.

The second welding step S4 may be non-pulse welding.

[Laminated core]
Fig. 1 is a perspective view of a laminated core according to an embodiment of the present invention. Fig. 2 is a plan view of the laminated core of Fig. 1. Fig. 3(A) is an enlarged plan view of a portion of a laminated core piece before welding, and Fig. 3(B) is an enlarged plan view of a portion of a laminated core piece corresponding to Fig. 3(A) after welding.

The laminated core 1 of this embodiment is a stator core used on the stator side of an electric motor or generator. This laminated core 1 is formed by laminating a plurality of annular core pieces 7 into a laminated core piece 3, and welding the core pieces 7 together with a plurality of first welds 5. The plurality of first welds 5 are arranged at intervals on the outer periphery of the laminated core piece 3. The core pieces 7 are made of electromagnetic steel plates.

The laminated core 1 can also be formed and used for a rotor core. In this case, the welded portion can be formed on the inner circumference of the rotor core.

Each first weld 5 is formed along the stacking direction of the laminated core piece 3. Note that the first weld 5 does not need to be strictly aligned with the stacking direction as long as both ends are separated in the stacking direction. The stacking direction refers to the axial direction along the axis of the laminated core 1. In the following, the circumferential direction refers to the extension direction around the axis of the laminated core 1, and the radial direction refers to the direction along the diameter of the laminated core 1.

The welding locations and number of the first welds 5 are not limited, but in the embodiment, the first welds 5 are formed in six recesses 8 (see FIG. 3(A)) spaced 60° apart in the circumferential direction. Before welding the laminated core pieces 3, as shown in FIG. 3(A), welding protrusions 8a are formed in the recesses 8 continuously in the stacking direction. As shown in FIG. 3(B), the first welds 5 are formed by welding, which melts and solidifies the protrusions 8a of the laminated core pieces 3.

The weld width B of the first weld 5 is the dimension of the first weld 5 in the circumferential direction of the laminated core piece 3, and the weld depth D1 is the dimension of the first weld 5 from the bottom of the recess 8 in the radial direction of the laminated core piece 3.

The laminated core 1 of this embodiment has a second welded portion 9, which will be described later, in which the weld crack 11 of the first welded portion 5 is welded.

Figure 4 is an enlarged side view of a portion of the laminated core 1, including the weld crack 11. Figure 5 is an enlarged side view showing the area around the weld crack 11 in Figure 4.

Before the second welded portion 9 is formed, the first welded portion 5 has a weld crack 11, which divides the first welded portion 5. In this embodiment, the weld crack 11 is a transverse crack oriented in the circumferential direction. This weld crack 11 creates a gap 13 between adjacent core pieces 7 of the laminated core piece 3.

Even if the weld crack 11 is a transverse crack, it may not cause a gap 13 between adjacent core pieces 7. Also, the weld crack 11 may not divide the welded portion 5 and may be merely a crack. Weld cracks 11 that divide the welded portion 5 may have a gap between the divided parts of the welded portion 5, may be linear with almost no gap, or may be a combination of these.

The orientation of the weld crack 11 refers to the orientation of the approximation line 15 of the weld crack 11, which will be described later. The weld crack 11 may be a vertical crack oriented in the axial direction or a diagonal crack oriented in a direction inclined with respect to both the axial and circumferential directions.

Figure 6 is a side view of the second welded portion 9. Figure 7 is a cross-sectional view of the second welded portion 9 of Figure 6.

The second welded portion 9 is formed by welding the weld crack 11 of the first welded portion 5 by melting and solidifying a portion of the first welded portion 5. Therefore, the weld crack 11 of the laminated core 1 is repaired by the second welded portion 9, and scrap is eliminated or suppressed. Since the second welded portion 9 is formed by melting and solidifying a portion of the first welded portion 5, it is integrated with the first welded portion 5 to suppress a decrease in strength, etc.

In this embodiment, the second weld 9 is formed along the weld crack 11, and is formed by melting and solidifying a portion of the first weld 5 at a predetermined weld width W and weld depth D2. The formation of the second weld 9 along the weld crack 11 refers to the formation along the direction of the weld crack 11 or the formation following the weld crack 11.

In this embodiment, the second weld 9 is aligned with the orientation of the weld crack 11 and is formed following an approximation line 15 relative to the crack line 12 of the weld crack 11. Therefore, the second weld 9 is linear with a weld width W and weld depth D2 based on the approximation line 15. Therefore, in this embodiment, the second weld 9 does not have a shape following the weld crack 11, and the reduction in strength after repairing the weld crack 11 is more reliably suppressed.

The approximation line 15 may be a straight line connecting the start and end of the weld crack 11, or it may be an approximation line or an approximation curve obtained by regression analysis or the like. If the weld crack 11 has a gap at the start or end, the approximation line 15 may be a straight line connecting any part between the edges of the gap in the stacking direction as the start or end. In this case, it is preferable to use one of the edges as the start or end.

The weld width W is the circumferential dimension above the crack line 12 of the weld crack 11, and the weld depth D2 is the dimension of the second weld 9 from the bottom of the recess 8 in the radial direction of the laminated core piece 3.
This weld depth D2 is preferably greater than the weld depth D1 of the first weld portion 5.

The weld width W of the second weld 9 is the width where the largest peak is included in the approximation line 15. In this embodiment, the weld width W is set smaller than the weld width B of the first weld 5. However, the weld width W may be larger than the weld width B. The weld width W of the second weld 9 can be set to any degree of smallness as long as the weld crack 11 can be welded.

The weld length L of the second welded portion 9 is set to be smaller than the weld width B of the first welded portion 5. However, the weld length L of the second welded portion 9 can be set arbitrarily, and may be set to be larger than the weld width B of the first welded portion 5. Note that the weld length L is the dimension in the direction in which the second welded portion 9 is oriented, and in the embodiment, it refers to the circumferential dimension of the second welded portion 9.

[Disposal and repair of weld cracks]
8 is a process diagram showing a manufacturing method of a laminated core 1 to which the weld crack repair method according to Example 1 is applied. In the manufacturing method of this example, the process after welding is performed on a laminated core piece 3 in which a plurality of core pieces 7 are laminated.

In the first welding step S1, a first weld 5 is formed on the outer periphery of the laminated core piece 3. This welds the core pieces 7 of the laminated core piece 3 along the lamination direction (see Figures 1 and 2).

When welding, multiple core pieces 7 are stacked as laminated core pieces 3 on an alignment jig (not shown), and the laminated core 3 is pressed to a specified thickness on the alignment jig.

Next, welding is performed on the laminated core 3 in a pressurized state using a torch such as a fiber laser welding machine to form the first weld 5.

The laminated core 1 thus completed is checked for weld cracks 11 using camera images in confirmation process S2. Laminated cores 1 that do not have weld cracks 11 are subjected to the next process S3, and laminated cores 1 in which weld cracks 11 are found are not discarded but are instead subjected to the second welding process S4.

In the second welding process S4, the second weld 9 is formed by welding along the weld crack 11. Welding along the weld crack 11 refers to welding along the direction of the weld crack 11 or welding that follows the weld crack 11.

In the second welding process S4 of this embodiment, a portion of the first weld 5 including the weld crack 11 is melted and solidified at a welding width W and welding depth D2 based on an approximation line 15 relative to the crack line 12 of the weld crack 11. For example, the torch is moved with the center of focus aligned with the approximation line 15. This simplifies the welding operation.

In this embodiment, the approximation line 15 is an approximation straight line, and the torch is moved linearly along the approximation straight line. The approximation line 15 can also be an approximation curve depending on the occurrence state of the weld crack 11. In this case, the torch is moved in a curved line along the approximation curve.

In this welding, the welding width W is set to the width at which the largest peak falls on the approximation line 15, and the welding conditions such as welding power, welding speed, focal spot size, and number of reciprocations (number of overlaps) are set so that the welding depth D2 exceeds the welding depth D1 of the first welded portion 5, or the cross-sectional area of the second welded portion 9 exceeds the cross-sectional area of the first welded portion 5. The crack line 12 of the weld crack 11 has a zigzag shape in the circumferential and axial directions, but this is not a problem because it also melts in the axial direction when the torch moves in the circumferential direction. Note that the welding conditions may be set so that the welding depth D2 falls below the welding depth D1 of the first welded portion 5, or the cross-sectional area of the second welded portion 9 falls below the cross-sectional area of the first welded portion 5.

Once a weld crack 11 occurs, the cause of the crack (stress, etc.) at the crack location may be reset. In this case, the weld crack 11 can be reliably repaired by the second welded portion 9 with the stress, etc., removed by the weld crack 11.

Therefore, in this embodiment, even if a weld crack 11 occurs in the first welded portion 5, the weld crack 11 can be repaired by welding using the second welded portion 9, eliminating or reducing the need to discard the laminated core 1.

Figure 9 is a diagram showing an example of the conditions for the first welding step S1 and the second welding step S4 in the manufacturing method of Figure 8. The first welding and second welding in the diagram refer to welding by the first welding step S1 and the second welding step S4, respectively.

The welding power and focal spot size of the second welding process S4 are smaller than those of the first welding process S1. This allows for precise corrections. It is also possible for the welding power and focal spot size of the second welding process S4 to be equal to or larger than those of the first welding process S1.

The welding speed of the second welding process S4 is faster than the welding speed of the first welding process S1. This prevents sudden melting and allows precise correction. The welding speed is the speed at which the focal point moves. The welding speed of the second welding process S4 can be the same as or slower than the welding speed of the first welding process S1.

In the second welding process S4, the welding power is lower than in the first welding process S1, so spattering can be suppressed. In addition, if the welding power is low, the oscillator can be made cheaper.

The focal spot size in the second welding process can be made relatively smaller than the focal spot size in the first welding process S1 because the crack line 12 of the weld crack 11 is thin and becomes even thinner due to the application of pressure.

The lower limit of the pressure applied to the laminated core pieces 3 in the first welding process S1 is the load at which the gaps between the core pieces 7 become smaller. However, the upper limit is the load at which the core pieces 7 do not deform or break due to the pressure.

The lower limit of the pressure applied to the laminated core pieces 3 in the second welding process S4 is the load at which the gap 13 between the layers caused by the weld cracks 11 becomes smaller. This load is greater than the lower limit in the first welding process S1. The upper limit of the load in the second welding process S4 is the load at which the core pieces 7 do not deform or break, just like the upper limit in the first welding process S1.

In addition, the first welding step S1 involves pulse welding, whereas the second welding step S4 involves non-pulse welding. By using non-pulse welding in the second welding step S4, the generation of spatter can be suppressed.

However, the second welding step S4 can also be pulse welding. The first welding step S1 can also be non-pulse welding.

In addition, in the second welding process S4, the second welding is performed by multiple overlap welding, which can compensate for the reduction in the welding depth D2 and cross-sectional area of the second welded portion 9 while suppressing spatter. In the embodiment, for example, a total of eight welding passes are performed with four round trips. However, if the second welding process S4 is performed at high output, etc., there is no need to perform round trips.

After the correction in the second welding process S5, the confirmation process S2 may be carried out again on the laminated core 1. Checking for weld cracks 11 after the correction can be carried out in the same manner as the confirmation process S2 after the first welding process S1. Therefore, the laminated core 1 after the correction can be re-introduced upstream of the line for the confirmation process S2.

1 Laminated core 3 Laminated core piece 5 First welded portion 7 Core piece 9 Second welded portion 11 Weld crack 12 Crack line 15 Approximation line S1 First welding step S2 Confirmation step S4 Second welding step

Claims (7)

a laminated core piece formed by laminating a plurality of annular core pieces;
a first welded portion formed by welding the laminated core pieces together along a lamination direction;
a second welded portion formed by welding a weld crack of the first welded portion by melting and solidifying a portion of the first welded portion;
A laminated core with 2. The laminated core of claim 1,
The second welded portion is formed by melting and solidifying the portion of the first welded portion at a predetermined weld width and weld depth based on an approximation line of the weld crack.
Laminated core. A method for repairing weld cracks used in the laminated core of claim 1, comprising the steps of:
a first welding step of forming the first welded portion;
a confirmation step of confirming a weld crack in the first weld portion;
A second welding process of forming the second welded portion by welding along the weld crack;
A method for repairing weld cracks comprising the steps of: The weld crack repair method of claim 3,
The welding in the second welding step is performed by applying pressure to the laminated core piece including the weld crack in the first weld portion in a lamination direction.
How to repair weld cracks. The method for repairing a weld crack according to claim 3 or 4,
The second welding step is to perform welding in which the portion of the first weld including the weld crack is melted and solidified at a predetermined weld width and weld depth based on an approximation line of the weld crack.
How to repair weld cracks. The method for repairing a weld crack according to claim 3 or 4,
The focal spot size of the second welding step is smaller than the focal spot size of the first welding step.
How to repair weld cracks. The method for repairing a weld crack according to claim 3 or 4,
The second welding step performs the welding without pulse.
How to repair weld cracks.

Images