JP7767999B2 - Manufacturing method of a stator for a rotating electric machine - Google Patents

Description

This disclosure relates to a method for manufacturing a stator for a rotating electric machine.

A known method for manufacturing a stator for a rotating electric machine involves preparing a workpiece for a rotating electric machine, in which multiple coil pieces that form the stator coil are attached to a stator core, joining the tips of the multiple coil pieces at one axial end of the workpiece, impregnating the areas to be impregnated, including the joints (exposed conductor areas), with a liquid resin material, and then curing the liquid resin material to cover the joints with an insulating resin coating. In this type of manufacturing method, a proposed technique involves immersing the workpiece, with the joints facing downward, in a tank of liquid resin material (impregnating the areas to be impregnated with the liquid resin material), and then heating and curing the liquid resin material in a positive pressure environment to prevent voids from forming in the insulating coating (resin mold) due to the boiling of the curing agent.

Japanese Patent Application Laid-Open No. 2021-136787

However, the above-mentioned conventional techniques make it difficult to reduce cavities (caused by air accumulating below the workpiece) that can occur when the workpiece is immersed in a vat of liquid resin material. In particular, if the liquid resin material impregnation process is performed two or more times to ensure the thickness of the insulating coating, air is likely to accumulate below the workpiece when the workpiece is immersed in the vat of liquid resin material the second or subsequent time due to the uneven shape of the liquid resin material impregnated previously. Such cavities can cause voids in the insulating coating (resin mold) after curing.

Therefore, in one aspect, the present disclosure aims to reduce cavities within the liquid resin material at the impregnation target area that may occur when the workpiece is immersed in a tank of liquid resin material, while ensuring the thickness of the insulating coating.

In one aspect, a mounting step of mounting a plurality of coil pieces that form a stator coil on a stator core to form a workpiece;
a joining step of joining tip portions of one of the coil pieces and another of the coil pieces to each other at one axial end side of the workpiece after the attaching step;
a first impregnation step of impregnating a circular impregnation target portion including a joining portion between the tip portions of the workpiece with a liquid resin material after the joining step;
After the first impregnation step, a second impregnation step is performed in which the workpiece is immersed in a tank of a liquid resin material so that at least a portion of the impregnation target portion related to the first impregnation step is immersed.
a curing step of curing the liquid resin material impregnated into the impregnation target portion after the second impregnation step,
The second impregnation step includes moving the workpiece to form an inclined posture of the workpiece, in which a portion of the entire circumference of the portion to be impregnated is separated from the liquid surface of the liquid resin material in the tank, two or more times in such a manner that the circumferential position of the portion changes.

In one aspect, the present disclosure makes it possible to reduce cavities within the liquid resin material at the impregnation target area that may occur when the workpiece is immersed in a tank of liquid resin material, while ensuring the thickness of the insulating coating.

1 is a schematic flowchart illustrating an example of a method for manufacturing a stator for a rotating electric machine. FIG. 2 is a diagram schematically illustrating an entire workpiece for forming a stator for a rotating electric machine. 10 is a cross-sectional view taken along the axial direction of the workpiece in a state in which coil pieces are assembled to a stator core. FIG. FIG. FIG. 2 is a schematic cross-sectional view of a coil piece. 3 is an explanatory diagram of a joint portion, and corresponds to an enlarged view of part Q1 in FIG. 2. FIG. 2 is a diagram schematically illustrating a side view of a workpiece before it is immersed in a tank of liquid resin material. FIG. 2 is a diagram schematically illustrating a side view of a workpiece immersed in a tank of liquid resin material. FIG. 10 is a diagram schematically illustrating the state of the workpiece in a lifting process as viewed from the side. 10 is a side view schematically illustrating a state of a workpiece undergoing an outer diameter side resin hardening process in an outer diameter side resin hardening step. FIG. 10 is a side view schematically illustrating the workpiece in an upward orientation in a top-down inversion process after the outer diameter side resin hardening treatment. FIG. FIG. 10 is an explanatory diagram of a preferred rotation axis when turning the workpiece upside down. FIG. 10 is an explanatory diagram of a rotation shaft according to a comparative example. 10 is a side view schematically illustrating a state of a workpiece undergoing an upper surface resin curing process in an upper surface resin curing step. FIG. 10 is a side view schematically illustrating a state of a workpiece undergoing an inner diameter side resin hardening process in an inner diameter side resin hardening step. FIG. FIG. 10 is a side view schematically illustrating the state of the workpiece in a downward orientation immediately before being subjected to a second immersion step. FIG. 10 is a diagram schematically showing the workpiece in an upward position after the second insulating coating process is completed. FIG. 10 is a diagram schematically illustrating the state of the workpiece in a heating step as viewed from the side. FIG. 10 is an explanatory diagram of the effect of the heating process. FIG. 2 is a diagram schematically illustrating an example of a cooling structure. FIG. 10 is an explanatory diagram of a preferred method for the immersion step (step S208). FIG. 21 is an explanatory diagram of the effect of the method shown in FIG. 20 . FIG. 10 is an explanatory diagram of a problem that may occur in the immersion step according to the comparative example. FIG. 10 is an explanatory diagram of another inclined posture. FIG. 10 is an explanatory diagram of another inclined posture. FIG. 10 is an explanatory diagram of a preferred method for the immersion step (step S208) in the second insulating coating step. FIG. 10 is an explanatory diagram of a problem that may occur in the immersion step according to the comparative example. 10A and 10B are explanatory diagrams of preferred examples of eight types of inclined postures.

Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional proportions in the drawings are merely examples and are not intended to be limiting. Furthermore, shapes and other features in the drawings may be partially exaggerated for the sake of explanation.

The manufacturing method for a stator for a rotating electric machine described below can be applied to any stator for a rotating electric machine as long as it has a joint between the coil pieces at the coil end. Below, we will describe a suitable application example of a manufacturing method for a stator for a rotating electric machine that can function as a power source that generates propulsion force for a vehicle.

FIG. 1 is a schematic flowchart illustrating an example of a method for manufacturing a stator for a rotating electric machine. Note that FIG. 1 is a flowchart illustrating a general flow, and additional processes may be included at any stage. FIGS. 2 to 6 are explanatory diagrams of a workpiece W. FIG. 2 is a schematic diagram illustrating the entire workpiece W, which includes a stator core 112 and a stator coil 114 for forming a stator 10 for a rotating electric machine. FIG. 3 is a cross-sectional view along the axial direction of the workpiece W, with coil pieces 52 assembled to the stator core 112. FIG. 4 is a front view of one of the multiple coil pieces 52. FIG. 5 is a schematic cross-sectional view of the coil piece 52. FIG. 6 is an explanatory diagram of a joint 400, corresponding to an enlarged view of portion Q1 in FIG. 2. FIGS. 7 to 18 are explanatory diagrams of this manufacturing method, and FIGS. 7 to 11 and 13 to 18 are schematic side views illustrating the state of the workpiece W at each process. FIG. 12 is an explanatory diagram of a preferred rotation axis I1 for turning the workpiece W upside down. Figure 12 shows a schematic diagram of a workpiece gripping unit 1000, part of a manufacturing device. Figure 12A is an explanatory diagram of a rotation axis I2 according to a comparative example.

The Z direction is shown in Figure 2 and other figures. The Z direction corresponds to the up-down direction, with the Z1 side and Z2 side corresponding to the upper and lower sides, respectively. The Y direction is shown in Figure 3 and other figures. The Y direction corresponds to the radial direction, with the Y1 side corresponding to the radially outer side and the Y2 side corresponding to the radially inner side (the side closer to the central axis I of the stator core 112).

In the following description, unless otherwise specified, the axial direction refers to the direction in which the central axis I of the stator core 112 (= the central axis of the workpiece W) extends, and the radial direction refers to the radial direction centered on the central axis I. Therefore, the radially outer side refers to the side away from the central axis I, and the radially inner side refers to the side closer to the central axis I. Furthermore, the axially outer side refers to the side away from the axial center of the stator core 112, and the axially inner side refers to the side closer to the axial center of the stator core 112. Furthermore, the circumferential direction corresponds to the direction of rotation around the central axis I.

This manufacturing method first includes an attachment process (step S200) in which multiple coil pieces 52 that form the stator coil 114 are attached to the stator core 112 to form an assembly (hereinafter also referred to as the "workpiece W").

Here, the stator coil 114 includes a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter, when U, V, and W are not distinguished, they will be referred to as "phase coils"). The base end of each phase coil is connected to an input terminal (not shown), and the end of each phase coil is connected to the end of the other phase coil to form a neutral point. In other words, the stator coil 114 is star-connected. However, the connection mode of the stator coil 114 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coil 114 may be delta-connected instead of star-connected.

Each phase coil of the stator coil 114 is formed by connecting multiple coil pieces 52. The coil pieces 52 are in the form of segment coils (segment conductors) that divide the phase coil into units that are easy to assemble (for example, units that can be inserted into two slots 23). As shown in Figure 5, the coil pieces 52 are formed by coating a linear conductor (flat wire) 120 with a substantially rectangular cross section with an insulating film 130. Here, the linear conductor is formed from copper, as an example. However, in modified examples, the linear conductor may be formed from other conductive materials such as iron. The cross-sectional shape of the linear conductor may also be other than rectangular.

In the example shown in FIG. 4, one coil piece 52 may be formed into a generally U-shape having a pair of linear slot-receiving portions 50 and a bridge portion 54 connecting the pair of slot-receiving portions 50. The bridge portion 54 on the other axial side (upper side in FIG. 4) may be formed by circumferentially molding the state shown in FIG. 4. A coupling portion 40 is set at the end of the bridge portion 54 on the other axial side (upper side in FIG. 4) to couple with the coupling portion 40 of the bridge portion 54 of another coil piece 52. The coupling portion 40 is a portion where the insulating film 130 has been removed (i.e., a portion where the conductor portion related to the linear conductor is exposed).

When assembling the coil pieces 52 to the stator core 112, the pair of slot accommodating portions 50 are each inserted into the slots 23 between the teeth 22 (see Figure 3). In this case, the coil pieces 52 can be assembled, for example, in the axial direction.

In each slot 23, multiple slot-accommodating portions 50 of the coil pieces 52 shown in Figure 4 are inserted side by side in the radial direction. Therefore, multiple circumferentially extending bridge portions 54 are aligned radially at both axial ends of the stator core 112. The bridge portions 54 (and the connecting portions 40 that are part of them) form coil end portions 114A, which protrude axially outward from the axial end faces of the stator core 112.

The coil pieces 52 may be wound around the stator core 112, for example, in a lap winding configuration. In the example shown in FIG. 4, the lower transition portion 54 may have an offset portion 521B that is offset radially by one layer so that the coil pieces are spaced apart from each other. The upper transition portion 54 may also have a similar offset portion 521A.

Note that while Figures 2 to 5 show a stator core 112 and stator coil 114 with a specific structure, the structure of the stator core 112 and stator coil 114 is arbitrary as long as the stator coil 114 has a joint 40. Furthermore, the winding method of the stator coil 114 is also arbitrary, and may be a winding method other than the lap winding method described above, such as a wave winding method.

Next, this manufacturing method includes a joining process (step S202) in which the joint portions 40, which are the respective tip portions of one coil piece 52 and another coil piece 52, are joined together at one axial end of the workpiece W. The joint portions 40 may be overlapped, and the opposing sides may be joined together. Any method may be used to join the joint portions 40 together, but welding, for example, may be used. In this case, welding may be achieved by any method, such as laser welding or TIG welding. Figure 6 schematically shows a joint portion 400 including a welded portion 401 (jointed portion) formed on two joint portions 40 that are overlapped in the radial direction.

For example, if four or more coil pieces 52 are mounted in each slot 23 of the stator core 112 in a radially overlapping manner, the joining process may involve joining multiple pairs of adjacent joints 40 (tips) together in the radial direction.

The joining range of the joining portions 40 and the orientation of the joining portions 40 when joined (the orientation when overlapping) are optional. For example, in Figure 6, the joining portions 40 are shown standing upright in the vertical direction and overlapped radially, but they may be overlapped in an X-shaped crossing when viewed radially, or only the joining portions 40 may be overlapped radially in an oblique orientation. Furthermore, the joining portions 40 may be overlapped axially in an orientation extending radially.

The joining process may not only join the coil pieces 52 together, but may also join the coil pieces 52 to a bus bar or a terminal block (an output bus bar for connection to an inverter, not shown). Figure 2 shows a schematic representation of a neutral point bus bar 59 as an example of such a bus bar. The neutral point bus bar 59 is the bus bar that forms the neutral point described above.

In this embodiment, as an example, the joint 400 is provided on only one axial side of the stator core 112. Hereinafter, for the sake of distinction, the side of both axial sides of the stator core 112 (or both axial sides of the workpiece W) that has the joint 400 will also be referred to as the lead side. Note that in a modified example, the joint 400 may be provided on both axial sides of the stator core 112.

Next, in this manufacturing method, the workpiece W is set at the starting position (workpiece loading position) for the insulation coating process (step S204). At this time, the workpiece W may be set in a position where the lead side is facing up (i.e., the joint portion 400 is facing up). Hereinafter, this position where the lead side is facing up will also be referred to as the "upward position of the workpiece W."

Next, this manufacturing method includes an upside-down inversion process (step S206) in which the orientation of the workpiece W is inverted as the first step in the insulating coating process. That is, the workpiece W is inverted upside down so that the lead side is on the bottom (i.e., the joint 400 is on the bottom). Hereinafter, this orientation in which the lead side is on the bottom is also referred to as the "downward orientation of the workpiece W." The upside-down inversion of the orientation of the workpiece W may be achieved by a manufacturing device (not shown) (for example, an articulated robot with a hand that grasps the workpiece W).

Next, this manufacturing method includes an immersion process (step S208) in which the workpiece W is immersed in a tank 600 of liquid resin material M0. FIG. 7 is a schematic side view of the workpiece W before it is immersed in the tank 600 of liquid resin material M0, and FIG. 8 is a schematic side view of the workpiece W immersed in the tank 600 of liquid resin material M0. In this embodiment, the liquid resin material M0 is preferably a resin material that hardens when heated and also hardens through a polymerization reaction when irradiated with ultraviolet light. Note that the tank 600 may have a circular shape in top view corresponding to the circular impregnation target area.

The immersion process is performed while the workpiece W remains in a downward position, so that the axial end (the lower end in the downward position) of the workpiece W to be impregnated is immersed in the liquid resin material M0 (i.e., positioned below the liquid surface of the liquid resin material M0). The impregnation target areas of the workpiece W are set at the portions of the multiple coil pieces 52 of the workpiece W. Specifically, the impregnation target areas of the workpiece W are the axial end (lead-side end) of the multiple coil pieces 52, including the joints 400. More specifically, the impregnation target areas of the workpiece W include the portions of each coil piece 52 of the workpiece W where the conductor (the conductor portion of the linear conductor) is exposed (the portion including the joints 400). When viewed in the axial direction, the impregnation target areas are annular about the central axis I, and include a portion of the coil end portion 114A (a portion on the axial end side).

In this embodiment, as described below, the immersion process is performed twice for one workpiece W. In this case, the portions of the workpiece W to be impregnated in each immersion process may be completely the same, or, as described below, may be partially different.

During the immersion process, the workpiece W may be kept immersed in a downward position for a certain period of time by a manufacturing device (not shown) (e.g., an articulated robot having a hand that grasps the workpiece W).

Next, this manufacturing method includes a lifting process (step S210) in which the workpiece W is lifted from the tank 600. The lifting of the workpiece W may be achieved by a manufacturing device (not shown) (for example, an articulated robot having a hand that grasps the workpiece W). Figure 9 schematically shows the workpiece W in a downward position after being lifted. After being lifted, the workpiece W in a downward position has the liquid resin material M0 (schematically shown by the hatched area M1 in Figure 9) impregnated in the impregnation target area at the axial end (the lower end in the downward position).

Next, this manufacturing method includes an outer diameter side resin curing process (an example of an irradiation process) (step S212) in which the liquid resin material M0 is cured on the side surface of the portion to be impregnated, with the workpiece W in a downward orientation after being pulled out of the tank 600. Hereinafter, the resin curing process performed in the outer diameter side resin curing process (step S212) will also be referred to as the "outer diameter side resin curing process" to distinguish it from the resin curing process performed in the upper surface resin curing process (step S216) described below.

In this embodiment, the outer diameter side resin curing process involves irradiating ultraviolet rays onto the side surface of the workpiece W in the region to be impregnated. Figure 9 schematically shows the state in which the outer diameter side resin curing process is being performed. Also, in Figure 9 (as well as Figure 10, etc., described below), the liquid resin material M0 impregnated into the workpiece W is schematically shown by the hatched area M1. In the example shown in Figure 10, the ultraviolet irradiation device 900 irradiates ultraviolet rays onto the radially outer side surface of the region to be impregnated of the workpiece W (see arrow R10). This hardens the radially outer portion (mainly the surface portion) of the liquid resin material M0 impregnated into the region to be impregnated of the workpiece W.

The ultraviolet irradiation device 900 preferably irradiates ultraviolet rays onto the radially outer side surface of the portion of the workpiece W to be impregnated along the entire circumference. This allows the liquid resin material M0 in the radially outer portion to be hardened along the entire circumference of the portion to be impregnated. In this case, the workpiece W may be rotated around the central axis I, or the ultraviolet irradiation device 900 may be rotated. Alternatively, multiple ultraviolet irradiation devices 900 may be distributed around the circumference of the workpiece W radially outside.

The ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is approximately perpendicular to the radially outer side of the portion of the workpiece W to be impregnated. In other words, the ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is located in an approximately horizontal plane. Here, "approximately" is a concept that includes an error of, for example, 10% or less. The ultraviolet irradiation device 900 is also preferably positioned relative to the workpiece W so that the optical axis 901 passes through the portion of the workpiece W to be impregnated, and more preferably, the optical axis 901 passes near the axial center of the portion of the workpiece W to be impregnated. In this case, the liquid resin material M0 in the radially outer portion of the portion of the workpiece W to be impregnated can be efficiently cured.

In this manner, according to this embodiment, the workpiece W maintains its downward orientation after being lifted from the tank 600, allowing the radially outer portion of the liquid resin material M0 impregnated into the impregnation target portion to harden. This reduces the potential inconvenience of inverting the workpiece W after being lifted from the tank 600 without performing the outer diameter side resin hardening process. Specifically, if the workpiece W is inverted in the next inversion step (step S214) without performing the outer diameter side resin hardening process, the liquid resin material M0 impregnated into the impregnation target portion of the workpiece W is likely to drip downward due to its own weight (see arrow R11 in Figure 11). In this case, the exposed area (area not covered by the resin material) of the side surface of the coil end portion 114A may be unnecessarily narrow. Insufficient exposed area of the side surface of the coil end portion 114A may reduce the cooling efficiency when a refrigerant (e.g., oil) is supplied to the side surface of the coil end portion 114A during operation of the rotating electric machine (as described below with reference to Figure 19). Furthermore, if the liquid resin material M0 on the radially outer side of the impregnation target portion drips downward, it may adhere to the axial end face (upper end face) of the stator core 112. In this case, the liquid resin material M0 adhering to the stator core 112 must be removed separately using a scraper or the like. In contrast, this embodiment can reduce such inconveniences as described above.

Next, this manufacturing method includes an upside-down inversion process (step S214) in which the orientation of the workpiece W is inverted upside down. That is, the workpiece W is inverted upside down from a downward orientation to an upward orientation. Figure 11 schematically shows the workpiece W inverted upside down to an upward orientation.

However, when the workpiece W is inverted upside down while impregnated with the liquid resin material M0, centrifugal force can easily cause the liquid resin material M0 to scatter. If the liquid resin material M0 scatters, material waste can result, and the thickness or coverage of the insulating coating covering the joint 400 of the coil end portion 114A may become insufficient. Furthermore, if the rotation speed of the workpiece W is reduced to reduce centrifugal force, the time required for the upside-down process increases, which tends to increase the cycle time (CT).

Therefore, in this embodiment, the workpiece W is preferably rotated around the rotation axis I1 in a horizontal plane passing through the area to be impregnated, as schematically shown by arrow R12 in Figure 12, thereby flipping it upside down from a downward position to an upward position. That is, the workpiece gripping unit 1000 flips the workpiece W upside down so that it rotates around the rotation axis I1 in a horizontal plane passing through the area to be impregnated. This effectively reduces the distance from the rotation axis I1 to the area to be impregnated (the radius that affects the centrifugal force), and even when the workpiece is flipped at a relatively high rotation speed, the centrifugal force does not become excessive (for example, no centrifugal force that would cause the liquid resin material M0 to splash is generated). In this way, it is possible to prevent the liquid resin material M0 from splashing from the workpiece W and to prevent an increase in CT.

Here, while the workpiece W is being turned upside down, the rotation axis I1 may be fixed or may be moved in a translational manner. For example, the rotation axis I1 may be moved upward while rotating the workpiece W. This allows the workpiece W to be turned upside down while being moved to the next process in a manner that prevents the liquid resin material M0 from scattering. This type of operation is suitable when the workpiece gripping unit 1000 is attached to the hand of an articulated robot.

The rotation axis I1 may be fixed in a constant positional relationship with respect to the workpiece W to be inverted during the inversion operation, or its positional relationship with respect to the workpiece W may change for only a portion of the inversion operation. For example, if the workpiece gripping unit 1000 is attached to the hand of an articulated robot, the positional relationship between the rotation axis I1 and the workpiece W may deviate from the positional relationship in which the rotation axis I1 passes through the area to be impregnated for only a portion of the inversion operation, such as the final stage of the inversion operation.

Furthermore, as described above, the rotation axis I1 preferably passes through the impregnation target area so as to reduce the radius associated with centrifugal force, but this is not limited to this. When the rotation radius of the axial center of the stator core 112 around the rotation axis I1 is taken as the reference radius, significant effects can be achieved if the rotation radius of the impregnation target area around the rotation axis I1 is equal to or less than the reference radius. For example, the rotation axis I1 may be set to pass between the axial center of the stator core 112 and the impregnation target area. Even in this case, the radius associated with centrifugal force (the rotation radius of the impregnation target area around the rotation axis) is smaller than in the comparative example (see Figure 12A) in which the rotation axis I2 is located on the opposite side of the impregnation target area and outside the workpiece W, so the above-mentioned effects can still be achieved. In the comparative example shown in Figure 12A, the workpiece W held by the loader hand 1200 is rotated around the rotation axis I2, which is located on the opposite side of the impregnation target area and outside the workpiece W. In this case, the radius r2 of the centrifugal force (the radius of rotation of the portion to be impregnated around the rotation axis I2) becomes relatively large (at least equal to or greater than the axial length of the stator core 112), which can easily lead to the above-mentioned problems, such as the liquid resin material M0 scattering.

Next, this manufacturing method includes a top surface resin curing process (an example of an irradiation process) (step S216) in which the liquid resin material M0 is cured on the top surface of the portion to be impregnated of the workpiece W that has been inverted into an upward position. Hereinafter, the resin curing process related to the top surface resin curing process will also be referred to as the "top surface resin curing process" to distinguish it from the outer diameter side resin curing process described above.

In this embodiment, the top surface resin curing process involves irradiating the top surface of the workpiece W in the region to be impregnated with ultraviolet light. Figure 13 schematically shows the state in which the top surface resin curing process is being performed. In the example shown in Figure 13, the ultraviolet light irradiation device 900 irradiates ultraviolet light onto the top surface of the workpiece W in the region to be impregnated with ultraviolet light (see arrow R13). This hardens the upper portion (mainly the upper surface portion) of the liquid resin material M0 that has impregnated the region to be impregnated with the workpiece W. Note that the ultraviolet light irradiation device 900 may be the same as the ultraviolet light irradiation device 900 used in the outer diameter side resin curing process described above, or it may be a different device.

The ultraviolet irradiation device 900 preferably irradiates ultraviolet rays onto the entire upper surface of the portion of the workpiece W to be impregnated. This allows the liquid resin material M0 in the upper portion to be hardened along the entire circumference of the portion to be impregnated. In this case, the workpiece W may be rotated around the central axis I, or the ultraviolet irradiation device 900 may be rotated. Alternatively, multiple ultraviolet irradiation devices 900 may be arranged circumferentially above the workpiece W.

The ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is approximately perpendicular to the top surface of the portion of the workpiece W to be impregnated. That is, the ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is located in an approximately vertical plane. Here, "approximately" is a concept that includes an error of, for example, 10% or less. The ultraviolet irradiation device 900 is also preferably positioned relative to the workpiece W so that the optical axis 901 passes through the portion of the workpiece W to be impregnated, and more preferably, is positioned relative to the workpiece W so that the optical axis 901 passes near the center of the radial range (range from the innermost diameter position to the outermost diameter position) of the portion of the workpiece W to be impregnated. In this case, the liquid resin material M0 in the upper portion of the portion of the workpiece W to be impregnated can be efficiently cured.

In this manner, according to this embodiment, the workpiece W is in an upward position, and the upper portion (axial end) of the liquid resin material M0 impregnated into the impregnation target portion is cured. This reduces the inconvenience that can occur when the top-surface resin curing process is performed on the workpiece W while it is in a downward position after being lifted from the tank 600 (i.e., when the top-surface resin curing process is performed simultaneously with the outer diameter side resin curing process described above). Specifically, if the resin curing process is performed on the underside of the impregnation target portion of the workpiece W while it is in a downward position after being lifted from the tank 600, the liquid resin material M0 impregnated into the impregnation target portion of the workpiece W may harden while dripping downward due to its own weight. In other words, the liquid resin material M0 may harden into an icicle-like shape. In contrast, according to this embodiment, the top-surface resin curing process is performed in an upward position as described above, thereby reducing such inconvenience.

Furthermore, according to this embodiment, by curing the upper portion (axial end) of the liquid resin material M0 impregnated into the impregnation target portion, a thin film of the liquid resin material M0 can be formed on the corner of the rectangular cross section of the joint 40 (see Figure 5; hereinafter referred to as the "joint edge 122"). That is, even on the joint edge 122, where the liquid resin material M0 is difficult to form due to the wettability around the coil pieces 52, a relatively thin film of the liquid resin material M0 can be formed. The joint edge 122 on which such a film of the liquid resin material M0 is formed has increased wettability due to the film. In this way, the wettability (wettability of the liquid resin material M0) of the joint edge 122 can be improved. As a result, the required thickness of the insulating coating (cured liquid resin material M0) on the joint edge 122 of the coil pieces 52 can be more easily achieved in the subsequent second dipping process (described below). In other words, the second dipping process can form a relatively thick film on the joint edge 122 using the film of liquid resin material M0 formed through the first dipping process as a base. This point will be explained again when explaining the second dipping process.

Next, this manufacturing method includes an inner diameter side resin curing process (an example of an irradiation process) (step S218) in which the liquid resin material M0 is cured on the radially inner side surface of the portion to be impregnated, with the workpiece W inverted into an upward position. Hereinafter, the resin curing process related to the inner diameter side resin curing process will also be referred to as the "inner diameter side resin curing process" to distinguish it from the outer diameter side resin curing process and top surface resin curing process described above.

In this embodiment, the inner diameter side resin curing process includes irradiating ultraviolet rays onto the radially inner side surface of the portion of the workpiece W to be impregnated. Figure 14 schematically shows the state in which the inner diameter side resin curing process is being performed. In the example shown in Figure 14, the ultraviolet irradiation device 900 irradiates ultraviolet rays onto the radially inner side surface of the portion of the workpiece W to be impregnated (see arrow R14). This hardens the radially inner portion (mainly the surface portion) of the liquid resin material M0 that has impregnated the portion of the workpiece W to be impregnated. Note that the ultraviolet irradiation device 900 may be the same as the ultraviolet irradiation device 900 used in the upper surface resin curing process described above.

The ultraviolet irradiation device 900 preferably irradiates ultraviolet rays onto the radially inner side surface of the portion of the workpiece W to be impregnated along the entire circumference. This allows the liquid resin material M0 in the radially inner portion to be hardened along the entire circumference of the portion to be impregnated. In this case, the inner diameter side resin hardening process may be performed sequentially in parallel with the top surface resin hardening process. Specifically, the top surface resin hardening process and the inner diameter side resin hardening process may be performed together for each divided circumferential range of the entire circumference of the portion to be impregnated of the workpiece W. Alternatively, the inner diameter side resin hardening process may be performed before the top surface resin hardening process. In this case, the inner diameter side resin hardening process may be performed simultaneously with or before the outer diameter side resin hardening process.

The ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is approximately perpendicular to the radially inner side surface of the portion of the workpiece W to be impregnated. In other words, the ultraviolet irradiation device 900 is preferably positioned relative to the workpiece W so that the optical axis 901 is located in an approximately vertical plane. Here, "approximately" is a concept that includes an error of, for example, 10% or less. The ultraviolet irradiation device 900 is also preferably positioned relative to the workpiece W so that the optical axis 901 passes through the portion of the workpiece W to be impregnated, and more preferably, the optical axis 901 passes near the axial center of the portion of the workpiece W to be impregnated. In this case, the liquid resin material M0 in the upper portion of the portion of the workpiece W to be impregnated can be efficiently cured.

However, depending on the size of the ultraviolet irradiation device 900 and the space radially inside the workpiece W, the ultraviolet irradiation device 900 may be positioned relative to the workpiece W so that the optical axis 901 intersects obliquely with the radially inside side surface of the portion of the workpiece W to be impregnated, as shown in FIG. 14. In this case, one of the inner diameter side resin curing process and the upper surface resin curing process may serve as the other.

Once the inner diameter side resin hardening process (step S218) is completed, the insulation coating process for that cycle is complete.

Next, in this manufacturing method, it is determined whether the insulation coating process has been performed on one workpiece W a predetermined number of times (in this embodiment, for example, twice) (step S220). This determination may be made manually or by image processing, etc. If the determination result is "YES," the process proceeds to the next step; otherwise, steps S206 to S218 are similarly performed to perform the second insulation coating process. Figure 15 schematically shows the workpiece W that has been turned upside down in step S206 and placed in a downward position during the second insulation coating process. The workpiece W then undergoes a second immersion process, etc.

The second insulation coating process may be exactly the same as the first insulation coating process. In this case, for example, the control of the manufacturing equipment can be simplified.

However, the second insulating coating process preferably differs from the first insulating coating process in at least the dipping step. Specifically, the dipping step in the second insulating coating process reduces the area to be impregnated compared to the dipping step in the first insulating coating process. That is, the area to be impregnated in the second dipping process may be a portion of the area to be impregnated in the first dipping process (a portion on the axial end side). In this case, the area to be impregnated in the second dipping process may be a minimum area that includes the joint edge 122 of the coil piece 52. This allows an insulating coating (cured product of the liquid resin material M0) with the required functionality to be efficiently formed using a relatively small (e.g., minimum) amount of liquid resin material M0.

Figure 15 shows a schematic diagram of the range Q15 containing the impregnation target portion for the second insulation coating process, relative to the range (hatched area M1) of the liquid resin material M0 impregnated into the workpiece W in the first insulation coating process.

In this manner, in this embodiment, the insulating coating process is performed multiple times (twice in this embodiment, as an example). This makes it possible to ensure the required thickness of the insulating coating (cured liquid resin material M0) on the joint edge 122 of the coil piece 52.

Specifically, Figure 16 schematically shows the workpiece W in an upward position after the second insulation coating process has been completed. Figure 16 also shows the range of liquid resin material M0 formed in the first insulation coating process (hatched area M1), as well as the range of liquid resin material M0 formed in the second insulation coating process (hatched area M2). For ease of explanation, Figure 16 (as well as Figure 18, etc., described below) only shows the axial end of the coil end portion 114A of the stator coil 114 in a simplified diagram.

In the first insulating coating process, a thin film of liquid resin material M0 can be formed on the joint edge 122 of the coil piece 52, as shown schematically in the hatched area M1. In this case, the thickness of the thin film of liquid resin material M0 on the joint edge 122 is significantly smaller than the required thickness of the insulating coating (cured liquid resin material M0) due to the low wettability of the joint edge 122 (i.e., the wettability of the corners of the linear conductor). However, even if the thin film of liquid resin material M0 on the joint edge 122 is relatively thin, it can increase the wettability of the joint edge 122 to the liquid resin material M0. Therefore, during the dipping step in the second insulating coating process, the liquid resin material M0 on the joint edge 122 is more likely to adhere. That is, in the second insulating coating process, a further film of liquid resin material M0 can be formed with a relatively large thickness on the joint edge 122 of the coil piece 52, as shown schematically in the hatched area M2. In this way, it is possible to ensure the necessary thickness of insulating coating (cured liquid resin material M0) even for the joint edge 122 of the coil piece 52, which has low wettability.

Once the second insulating coating process is completed, the manufacturing method includes a heating process (an example of a curing process) (step S222) in which the workpiece W is heated so that the liquid resin material M0 is cured throughout the workpiece W. This heating process has the function of completely curing the portions of the liquid resin material M0 that have not been cured in the various resin curing processes described above (e.g., the portions inside the surface). The heating method used in the heating process is arbitrary and may be achieved, for example, by placing the workpiece W in a furnace. The liquid resin material M0 impregnated into the impregnation portions, including the portions of the workpiece W to be impregnated, is heated and completely cured. This forms an insulating coating of the liquid resin material M0 on the stator coil 114.

The orientation of the workpiece W during the heating process is arbitrary, but is preferably downward-facing, as shown schematically in Figure 17. Note that Figure 17 also shows a schematic diagram of multiple workpieces W being placed side by side in a downward-facing orientation and undergoing the heating process. Note that Figure 17 also shows a workpiece gripping unit 1001, part of the manufacturing equipment, clamping multiple workpieces W, but the workpieces W may also be supported on a table with the end face of the stator core 112 abutting the top surface of the table (not shown). Also, as an example, Figure 17 shows heat being radiated from below the workpiece W (see arrow R17), but the direction of heat radiation is arbitrary.

However, during the heating process, if the assembly is in an upward position, the liquid resin material M0 that is still in the process of hardening and not yet completely hardened may drip downward onto the stator core 112 due to its own weight (see arrow R16 in Figure 16). In this case, the liquid resin material M0 that has adhered to the stator core 112 must be removed separately using a scraper or similar tool.

In contrast, in the downward position, even if the partially cured liquid resin material M0 moves downward under its own weight before it is completely cured, it will not reach the stator core 112. Furthermore, the portions of the liquid resin material M0 cured during the outer diameter side resin curing process, the upper surface resin curing process, and the inner diameter side resin curing process (see the C-shaped area 1800 when viewed from the same direction in Figure 18) function as a "bottom lid," reducing the possibility of dripping liquid resin material M0 becoming icicle-like. Figure 18 shows the downward movement of the partially cured liquid resin material M0, as schematically indicated by arrow R19. This downward movement of the partially cured liquid resin material M0 is blocked by the portions of the liquid resin material M0 cured during the outer diameter side resin curing process, the upper surface resin curing process, and the inner diameter side resin curing process. This prevents problems that can occur when the heating process is performed in the downward position.

In this way, according to this embodiment, the heating process is performed in a downward position, preventing the liquid resin material M0 from dripping onto the stator core 112, while the "bottom lid" function of the portions of the liquid resin material M0 that have hardened during the outer diameter side resin hardening process, upper surface resin hardening process, and inner diameter side resin hardening process reduces the amount of liquid resin material M0 that drips downward and hardens into icicle-like shapes.

In order to effectively enhance this "bottom cover" function, it is desirable to perform all of the outer diameter side resin hardening process, upper surface resin hardening process, and inner diameter side resin hardening process, but it is also possible to omit only the outer diameter side resin hardening process and/or the inner diameter side resin hardening process.

Furthermore, with this manufacturing method, one heating step is performed for every two insulating coating steps, as described above, which reduces energy consumption (and the associated carbon dioxide emissions) compared to when a heating step is performed for each insulating coating step. Therefore, with this manufacturing method, the thickness of the insulating coating of the liquid resin material M0 can be efficiently increased.

Furthermore, when a heating process is performed after each insulating coating process, a discontinuous boundary (layer separation) forms between the insulating coating of liquid resin material M0 formed the first time and the insulating coating of liquid resin material M0 formed the second time. However, this manufacturing method eliminates this boundary, increasing the strength of the insulating coating of liquid resin material M0 as a whole. In other words, with this manufacturing method, the viscosity of the liquid resin material M0 impregnated twice decreases during the heating process, forming a single layer, eliminating discontinuous boundaries (layer separation) within the insulating coating and improving strength.

Next, with reference to Figure 19, we will explain a cooling structure suitable for a rotating electric machine 1 incorporating a rotating electric machine stator 10 manufactured using this manufacturing method.

Figure 19 is a diagram showing an example of a cooling structure, and is a diagram showing a portion of the cross-sectional structure of the rotating electric machine 1.

In the example shown in FIG. 19, oil is supplied from the radially outer and radially inner sides to the coil end portions 114A at both axial ends of the stator coil 114. Specifically, oil supplied to the case internal oil passage 60 of the case 2 (see arrow R20A) is supplied to the radially outer side of the coil end portion 114A via an oil hole 62 that penetrates radially inward (see arrow R20). Note that the oil hole 62 may be positioned vertically upward to promote dripping of oil due to gravity. Furthermore, oil supplied to the axial oil passage 64 of the rotor shaft 112A (see arrow R21A) is supplied to the radially inner side of the coil end portion 114A via an oil hole 66 that penetrates radially outward (see arrow R21).

According to this manufacturing method, as described above, an insulating coating of liquid resin material M0 is applied to the coil end portions 114A of the stator coil 114. The portions of the stator coil 114 that are coated with the insulating coating of liquid resin material M0 have lower thermal conductivity than portions that are not (i.e., portions where the insulating film 130 is the surface). Therefore, if the exposed area of the radially outer side surface of the coil end portion 114A that is not covered with the insulating coating of liquid resin material M0 becomes unnecessarily narrow, the cooling performance of the oil from the oil hole 62 described above may be unnecessarily reduced. Similarly, if the exposed area of the radially inner side surface of the coil end portion 114A that is not covered with the insulating coating of liquid resin material M0 becomes unnecessarily narrow, the cooling performance of the oil from the oil hole 66 described above may be unnecessarily reduced.

In this regard, with this manufacturing method, as described above, the radially outer portion of the liquid resin material M0 impregnated into the impregnation target portion by the outer diameter side resin curing process is cured while facing downward. Therefore, even if the workpiece W is then turned upward, the radially outer liquid resin material M0 will not drip downward. This reduces the possibility of the exposed area of the radially outer side surface of the coil end portion 114A that is not covered by the insulating coating of the liquid resin material M0 becoming unnecessarily narrow. As a result, the cooling performance of the coil end portion 114A by the oil from the oil hole 62 described above can be effectively improved.

In the above-described embodiment, the inner diameter side resin curing process is performed on the workpiece W in an upward position. However, like the outer diameter side resin curing process, it may also be performed on the workpiece W in a downward position. In this case, the inner diameter side resin curing process may be performed simultaneously in parallel with the outer diameter side resin curing process. In this case, the radially inner portion of the liquid resin material M0 impregnated into the impregnation target portion by the inner diameter side resin curing process is cured while remaining in a downward position. Therefore, even if the workpiece W is then in an upward position, the liquid resin material M0 on the radially inner side will not drip downward. This reduces the possibility of unnecessary narrowing of the exposed area of the radially inner side surface of the coil end portion 114A that is not covered by the insulating coating of the liquid resin material M0. As a result, the cooling performance of the coil end portion 114A by the oil from the oil hole 66 described above can be effectively improved.

Next, with reference to Figure 20 onwards, we will explain further preferred configurations for the above-mentioned manufacturing method.

Figure 20 is an explanatory diagram of a preferred method for the immersion process (step S208). Figure 20 schematically shows a portion of the workpiece W together with the tank 600 at the start of the immersion process in the first insulating coating process. Figure 21 is an explanatory diagram of the effect of the method shown in Figure 20, and schematically shows the state in which part Q20 in Figure 20 has entered the liquid resin material M0 in the tank 600. Figure 22 is an explanatory diagram of an inconvenience that may occur in the immersion process according to a comparative example. Figures 23 and 24 are explanatory diagrams of other tilted positions.

In the immersion process, the workpiece W is preferably immersed in the liquid resin material M0 in the tank 600 in an inclined position. An inclined position refers to a position of the workpiece W in which, when a perpendicular line I3 to the liquid surface of the liquid resin material M0 in the tank 600 is used as a reference, the angle α (see Figure 20) formed by the axial direction of the stator core 112 with respect to the perpendicular line I3 is different from 0 degrees. The angle α is arbitrary and may be, for example, 5 degrees or greater. Hereinafter, for comparison, the position of the workpiece W in which angle α = 0 is also referred to as the upright position.

The impregnation target portion of the workpiece W is formed by the coil pieces 52, bus bars, etc., but may have a flat portion extending perpendicular to the central axis I. Such a flat portion is formed by a portion of the coil pieces 52, a portion of the neutral bus bar 59, etc. Such a flat portion is likely to cause air to accumulate below the workpiece W when the workpiece W is immersed in an upright position in a tank 600 of liquid resin material M0. Figure 22 schematically shows air (air bubbles) B22 that accumulate below the workpiece W when the workpiece W is immersed in an upright position in a tank 600 of liquid resin material M0. If such air B22 adheres to the bottom of the workpiece W and the end surface of the impregnation target portion of the workpiece W is covered with the liquid resin material M0, a cavity will form within the liquid resin material M0, which may cause voids in the insulating coating (resin mold) after the liquid resin material M0 hardens.

In contrast, when the workpiece W is immersed in a tank 600 of liquid resin material M0 in an inclined position as shown in FIG. 20, air (air bubbles) B21 below the workpiece W rises along the inclined flat portion 591 (in FIG. 21, the flat portion 591 of the neutral bus bar 59), as schematically shown by arrow R21 in FIG. 21. In other words, it is possible to reduce or eliminate air that may accumulate below the workpiece W. In this way, the method shown in FIG. 20 makes it possible to reduce or eliminate cavities within the liquid resin material M0 in the impregnation target portion that may occur when the workpiece W is immersed in the tank 600 of liquid resin material M0. As a result, it is possible to reduce or eliminate voids that may occur in the insulating coating (resin mold) after curing.

Here, the inclined posture shown in Figure 21 causes the air bubble B21 to rise radially outward, but for example, as shown in Figure 23, an inclined posture may be set that causes the air bubble B23 to rise radially inward (see arrow R23). Alternatively, as shown in Figure 24, an inclined posture may be set that causes the air bubble B24 to rise in the circumferential direction (see arrow R24).

In this way, the highest circumferential position of the workpiece W in an inclined position may be appropriately determined so that the bubbles can easily rise, depending on the position and shape of the flat portion. In this case, the highest circumferential position of the workpiece W in an inclined position may be set, for example, so that the length of the flat portion along which the bubbles rise (the distance traveled by the bubbles) is shortened. Specifically, if the flat portion has a longitudinal direction and a lateral direction, the inclined position of the workpiece W may be determined so that the angle of the flat portion relative to the liquid surface of the liquid resin material M0 along the lateral direction is greater than the angle along the longitudinal direction. In this case, since the bubbles rise along the lateral direction, the length of the flat portion along which the bubbles rise (the distance traveled by the bubbles) can be shortened. In other words, an inclined position that makes it easy for the bubbles to escape can be achieved.

In the immersion process using the method shown in Figure 20, the workpiece W is preferably changed from an inclined position to an upright position after the flat portion reaches below the liquid surface of the liquid resin material M0 in the tank 600. In other words, the final position of the workpiece W in the immersion process is preferably an upright position. In this case, the immersion depth of the workpiece W is approximately the same at each position in the circumferential direction (i.e., the area where the insulating coating of the liquid resin material M0 is formed is approximately the same at each position in the circumferential direction), making product management easier.

When the immersion depth of the workpiece W during the immersion process is made approximately the same at each circumferential position in this manner, the inclined posture may be set so that the flat portions are immersed before other circumferential positions (so that they reach below the liquid surface first) to prevent the immersion depth from becoming unnecessarily large. In this case, even if the inclined posture is changed to an upright posture once most of the flat portions are immersed, the immersion depth is less likely to become large, which is advantageous. For example, the inclined posture shown in Figure 23 is more advantageous than the inclined posture shown in Figure 21 in that the immersion depth is less likely to become large. Therefore, an inclined posture may be adopted in which the circumferential range in which the neutral point busbar 59 having the flat portion 591 extends is lower than the other circumferential ranges.

Note that the method shown in Figure 20 is preferably implemented in each immersion process when the insulating coating process is performed multiple times on a single workpiece W, but may be implemented in only some of the immersion processes.

Figure 25 is an explanatory diagram of a preferred method for the immersion process (step S208) in the second insulation coating process. Figure 25 schematically shows a portion of the workpiece W in an inclined position during the immersion process in the second insulation coating process, along with the tank 600. Figure 26 is an explanatory diagram of a disadvantage that may occur in the immersion process in a comparative example.

In the following description of the second insulation coating process, unless otherwise specified, the impregnation target portion of the workpiece W refers to the impregnation target portion involved in the immersion process in the second insulation coating process. In addition, hereinafter, the immersion process in the first insulation coating process (an example of the first impregnation process) will also be referred to as the "first immersion process," and the immersion process in the second insulation coating process (an example of the second impregnation process) will also be referred to as the "second immersion process."

In the second immersion step, the workpiece W is preferably partially immersed in the liquid resin material M0 in the tank 600 in two or more inclined positions before being fully immersed. An inclined position refers to a position of the workpiece W in which the angle α (see FIG. 20) described above is significantly greater than 0. The angle α in the second immersion step is arbitrary, but may be greater than the angle α described above with reference to FIG. 20. Two or more inclined positions can be formed by moving the workpiece W.

Two or more types of inclined postures include postures in which the angle α is the same but the highest circumferential position of the workpiece W is different. In other words, in each inclined posture, only a portion of the workpiece W to be impregnated (a portion of the circumference) is above the liquid surface of the liquid resin material M0 in the tank 600, but the circumferential position of this portion changes depending on the type of inclined posture. In a modified example, the two or more types of inclined postures may have different angles α.

However, when the insulating coating process is performed in two or more stages to ensure the thickness of the insulating coating (for example, the thickness of the insulating coating on the joint edge 122), as in this manufacturing method, when the workpiece W is immersed in the tank M0 of liquid resin material 600 for the second or subsequent time, air tends to accumulate below the workpiece W due to the uneven shape of the liquid resin material impregnated previously (i.e., the unevenness of the axial end surface of the workpiece W). Furthermore, because the liquid resin material M0 is not breathable, the liquid resin material M0 impregnated previously prevents the air from escaping. Such cavities can cause voids in the insulating coating (resin mold) after hardening.

Figure 26 shows a schematic of air (air bubbles) B26 accumulating below the workpiece W due to the uneven shape of the liquid resin material M0 previously impregnated. If this air B26 adheres to the bottom of the workpiece W and the end surface of the portion of the workpiece W to be impregnated is covered with liquid resin material M0, this will create cavities within the liquid resin material M0, as in the case described above with reference to Figure 22, and may cause voids in the insulating coating (resin mold) after the liquid resin material M0 hardens.

In contrast, when the workpiece W is immersed in a tank M0 of liquid resin material 600 in an inclined position as shown in Figure 25, the liquid resin material M0 is more likely to penetrate into the recesses 70, as shown schematically by arrow R25 in Figure 25. In other words, it is possible to reduce or eliminate air that may accumulate below the workpiece W due to the recesses 70. In this way, the method shown in Figure 25 makes it possible to reduce or eliminate cavities within the liquid resin material M0 at the impregnation target portion that may occur when the workpiece W is immersed in a tank M0 of liquid resin material 600. As a result, it is possible to reduce or eliminate voids that may occur in the insulating coating (resin mold) after hardening.

Here, the unevenness on the axial end surface of the workpiece W that can cause the above-mentioned voids (the uneven shape of the liquid resin material M0 applied to the workpiece W in the first dipping process) is likely to occur when four or more coil pieces 52 are attached to each slot 23 of the stator core 112 in a radially overlapping manner. In this case, when two radially adjacent joints 40 are considered as one pair and multiple pairs are joined radially in the joining process described above, recesses 70 (see Figure 25) that are recessed axially inward are likely to form between multiple pairs of joints 400 in the radial direction. Note that while Figure 25 shows one recess 70 between two pairs of joints 400 in the radial direction, when three or more pairs are joined, two or more recesses 70 will be formed. The recesses 70 basically extend around the entire circumferential direction of the workpiece W.

In this regard, if, in the second immersion process, the workpiece W is partially immersed in the liquid resin material M0 in the tank 600 in two or more tilted positions before being completely immersed, the liquid resin material M0 in the tank 600 can enter the recesses 70 at each circumferential position in the manner shown in Figure 25. In particular, if the recesses 70 are continuous in the circumferential direction, air within the recesses 70 in a circumferential range that enters the liquid resin material M0 in the tank 600 in one tilted position can escape to the outside of the liquid resin material M0 through recesses 70 in another circumferential range that is located above the liquid resin material M0. In other words, air within a recess 70 that is below the liquid surface can escape to the outside through other recesses 70 that are above the liquid surface.

The more types of tilt attitudes (two or more) that are applied to one workpiece W during the second immersion process, the greater the reduction in the amount of air that can remain in the recesses 70 at each circumferential position. On the other hand, the more types of tilt attitudes (two or more), the greater the disadvantage in terms of CT.

Therefore, the number of two or more types of tilt postures applied to one workpiece W in the second immersion process is preferably three or more, and may be, for example, eight, as described below with reference to Figure 27.

Figure 27 is an explanatory diagram of eight preferred examples of tilt postures. Figure 27 shows a schematic top view of the workpiece W, with the workpiece W divided equally into eight circumferential ranges SC1 to SC8. In this case, the eight circumferential ranges SC1 to SC8 are set at equal intervals.

In this case, the eight tilted positions include a first tilted position in which the circumferential range SC1 of the workpiece W is most immersed in the liquid resin material M0 in the tank 600 (i.e., located furthest below the liquid surface), a second tilted position in which the circumferential range SC2 of the workpiece W is most immersed in the liquid resin material M0 in the tank 600, and third to eighth tilted positions corresponding to similar positions SC3 to SC8.

The eight tilt positions may be formed in any order. For example, the first to eighth tilt positions may be formed in clockwise order in FIG. 27 . In this case, the air inside the recess 70 can be expelled clockwise in the circumferential direction. Note that in this case, although the air inside the recess 70 cannot be expelled circumferentially in the eighth tilt position, it is possible to minimize the air inside the recess 70 by, for example, increasing the angle α. Note that, for example, if the configuration of the recess 70 in the circumferential range in which the neutral point bus bar 59 is arranged is different from other circumferential ranges, the circumferential range SC8 for the eighth tilt position may be set to coincide with the circumferential range in which the neutral point bus bar 59 is arranged.

By changing the tilt position so that each of the eight circumferential ranges SC1 to SC8 is immersed in equal circumferential ranges, the area and thickness of the insulating coating formed by the liquid resin material M0 becomes uniform along the circumferential direction, making product management easier.

In the second immersion process using the method shown in Figure 27, the workpiece W may be tilted to the eighth tilted position and then changed from that tilted position to an upright position. In this case, the area and thickness of the insulating coating formed by the liquid resin material M0 will be approximately the same at each circumferential position, making product management easier.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the claims. It is also possible to combine all or several of the components of the above-described embodiments.

For example, in the above-described embodiment, the outer diameter side resin hardening process is preferably performed, but the inner diameter side resin hardening process may be performed instead of the outer diameter side resin hardening process.
In addition, in the above-described embodiment, instead of the first immersion process, a process of impregnating the target portion of the workpiece W with the liquid resin material M0 by dripping the liquid resin material M0 onto the target portion of the workpiece W (an example of another first impregnation process) may be performed.

40: Joint (tip), 52: Coil piece, 112: Stator core, 114: Stator coil, 70: Recess, 600: Tank, W: Workpiece, M0: Liquid resin material

Claims (6)

a mounting step of mounting a plurality of coil pieces that form a stator coil on a stator core to form a workpiece;
a joining step of joining tip portions of one of the coil pieces and another of the coil pieces to each other at one axial end side of the workpiece after the attaching step;
a first impregnation step of impregnating a circular impregnation target portion including a joining portion between the tip portions of the workpiece with a liquid resin material after the joining step;
After the first impregnation step, a second impregnation step is performed in which the workpiece is immersed in a tank of a liquid resin material so that at least a portion of the impregnation target portion related to the first impregnation step is immersed.
a curing step of curing the liquid resin material impregnated into the impregnation target portion after the second impregnation step,
The second impregnation process includes moving the workpiece to form an inclined posture of the workpiece two or more times, in which a portion of the entire circumference of the impregnation target portion is separated from the liquid surface of the liquid resin material in the tank, in such a manner that the circumferential position of the portion changes. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein the second impregnation process forms the inclined posture two or more times so that the circumferential positions of the portion are spaced at equal intervals along the circumferential direction. The method for manufacturing a stator for a rotating electric machine according to claim 1 or 2, wherein the second impregnation process forms the inclined posture three or more times such that each circumferential portion of the impregnation target portion is immersed in the liquid resin material in the vat at least once. The liquid resin material has the property of being hardened by irradiation with ultraviolet light,
4. The method for manufacturing a stator for a rotating electric machine according to claim 1, further comprising an irradiation step of irradiating the portion to be impregnated with ultraviolet light after the first impregnation step and before the second impregnation step. Four or more of the coil pieces in the workpiece are mounted in each slot of the stator core in a radially overlapping manner,
5. The method for manufacturing a stator for a rotating electric machine according to claim 1, wherein the joining step joins a plurality of pairs of two radially adjacent tip portions together in the radial direction. The method for manufacturing a stator for a rotating electric machine according to claim 5, wherein the liquid resin material in the workpiece immediately before the second impregnation step has recesses between the pairs of tip ends in the radial direction that are recessed axially inward.