JP6006937B2 - Brushless motor and method for manufacturing brushless motor - Google Patents

Description

  The present invention relates to a connection structure of a brushless motor, and in particular, a metal conductive member (bus bar) conventionally used for terminal connection of each slot winding is omitted to reduce the number of parts and the motor size. It relates to a brushless motor.

  In the Y-connection type three-phase brushless motor, after the stator winding, the starting and ending lines of each slot winding are the neutral point where one end of each phase winding is connected together and the other end of each phase winding. Connected to each side. Conventionally, a connection unit (bus bar unit) using a metal conductive member called a bus bar has been used for the connection of each phase winding. FIG. 7 is an explanatory diagram showing the configuration of the bus bar unit. As shown in FIG. 7, the bus bar unit 50 includes a phase-specific bus bar 51 (51U, 51V, 51W) for each phase, a neutral ring bus bar 52 for neutral points, and a synthetic resin bus bar body (insulation). Member) 53. Each bus bar 51 and 52 is insert-molded in a bus bar body 53 made of synthetic resin. The bus bar unit 50 is attached to the stator end of the motor, and the ends of the phase windings are connected to the bus bars 51 and 52, respectively. The bus bar unit 50 is housed in a motor housing or the like together with the stator in a state where terminals of the respective phase windings are connected.

Japanese Patent Laid-Open No. 6-233383

  However, such a bus bar has a problem that it takes a long processing time because a terminal piece for connection is formed by bending after punching a metal plate by pressing. Moreover, since each bus bar is similar in size and shape, parts management is complicated, and there is a risk of defective products due to wrong parts. Further, the bus bar unit itself is composed of four bus bars and an insulating member, so that the number of parts is large, and the configuration in which they are integrally formed requires a large number of processing steps and a high manufacturing cost. In addition, if the bus bar is bent even a little during insert molding, the bus bar could not be set properly in the mold, and there was a problem that extra work time was required. Further, when the bus bar is set in the mold, the mold is heated, so that workability is poor, and there are problems in terms of work environment and manufacturing cost.

  Furthermore, it is necessary to increase the thickness of the bus bar to withstand the molding pressure, and it is necessary to secure an insulation gap between the bus bars. there were. In addition, the bus bar unit has a structure in which the bus bar and the insulator are laminated, and accordingly, the axial length is required. The use of the bus bar increases the axial length of the motor. In this respect, there has been a problem that it is contrary to the demand for miniaturized products.

  An object of the present invention is to enable a coil terminal of a stator winding to be connected without using a connection unit in a brushless motor, thereby reducing the number of parts, reducing the number of processing steps, and reducing the motor size. There is.

The brushless motor of the present invention is a brushless motor comprising a stator having a plurality of phase field coils, and a rotor rotatably disposed inside the stator. A stator core in which a plurality of teeth extending radially inward are formed along the circumferential direction, an insulator made of an insulating material attached to the stator core, and the coil wound around the insulator, together with the insulator A first connection terminal connected to one end of the coil, a second connection terminal connected to the other end of the coil, and a radially inner end of the insulator. and the guide member, connecting the first connection that connects all of the respective first connecting terminals, to each other as in-phase of the second connecting terminal, for each phase Possess a second connection of the plurality of provided, a second connecting terminal, the disposed between the first connection terminal, wherein the first connection is to connect the first connecting terminals adjacent to each other, Wiring is performed via the guide member provided between the first connection terminals and disposed on the radially inner end side .

  In the present invention, the insulator attached to the stator core is provided with a first connection terminal to which one end side of the coil is connected and a second connection terminal to which the other end side of the coil is connected. Since the same phase among the second connection terminals is connected by the second connection in one connection, a connection unit (bus bar unit) is not required for the connection of the end of the stator winding, The number of parts and the number of processing steps can be reduced. Further, since the space for the bus bar unit is not required in the motor, the axial dimension can be shortened, and the motor can be reduced in size.

  In the brushless motor, the stator may be formed by a split core. That is, even if the stator core is divided for each tooth in order to improve the space factor of the stator winding to each tooth, a connection unit (bus bar unit) is connected to the end of the stator winding. Is eliminated, and the number of parts and the number of processing steps can be reduced. Further, the stator may be formed by mounting the insulator and forming a split core in which the coil is wound around the insulator and connecting a plurality of the cores in an annular shape.

  Moreover, you may provide the guide member in which the said 1st and 2nd connection is wound around in the said stator. In this case, the guide member may be erected on the insulator. In addition, the guide member is provided with a coil hooking portion around which the first and second connections are wound, and the coil hooking portion is provided with a stepped return that regulates the movement of the first and second connections. A part may be formed.

  Further, one of the second connection terminals of each phase may be provided with a connection protrusion for electrical connection with the outside. By providing the connection protrusions, electrical connection with the outside can be easily performed, and the number of motor assembly steps can be reduced.

On the other hand, the brushless motor manufacturing method of the present invention includes a stator core in which a plurality of teeth extending radially inward are formed along a circumferential direction, an insulator made of an insulating material attached to the stator core, and the insulator A method of manufacturing a brushless motor, comprising: a stator including a wound multi-phase field coil; and a rotor rotatably disposed inside the stator. A neutral point connection step for connecting all the first connection terminals to which one end side of the coil is formed and the second connection terminal formed on the insulator and connected to the other end side of the coil. It has a phase connection step of connecting objects together, respectively, to the phase connection step and the neutral point connection step sequentially using the same wire Subsequently, after the neutral point connection step and each phase connection step, the conductive wire is connected to the first connection for connecting all the first connection terminals, and a plurality of in-phase ones are connected to each other. A cutting process for cutting the second connection is performed .

  In the present invention, the insulator attached to the stator core is provided with a first connection terminal to which one end side of the coil is connected and a second connection terminal to which the other end side of the coil is connected. Since a neutral point connection process for connecting by 1 connection and each phase connection process for connecting the same phase among the second connection terminals by the second connection are provided, a connection unit (bus bar unit) is provided. Without using it, the end of the stator winding can be easily connected, and the number of parts and the number of processing steps can be reduced. Further, since the space for the bus bar unit is not required in the motor, the axial dimension can be shortened, and the motor can be reduced in size.

In the method of manufacturing the brushless motor, after the cutting step, a fusing step is performed in which the first connection and the first connection terminal, and the second connection and the second connection terminal are joined by fusing. You may do it.

  Furthermore, the stator may be formed by a split core. That is, the stator core is divided for each of the teeth, the insulator is mounted, and a split core is formed by winding the coil around the insulator, and a plurality of the cores are connected in a ring to form the stator. You may do it.

  In addition, the stator is provided with a guide member formed of an insulating material, and in the neutral point connection step and each phase connection step, the terminals are connected while the conductor wire is wound around the guide member. May be. In this case, the guide member is provided with a coil latching portion around which the conducting wire is wound, and the coil latching portion is formed with a stepped return portion for restricting movement of the conducting wire, You may hang around the said coil latching part, engaging with the said return part.

  According to the brushless motor of the present invention, the insulator attached to the stator core is provided with the first connection terminal to which one end of the coil is connected and the second connection terminal to which the other end of the coil is connected, and each first connection terminal Since the first connection and the second connection terminals of the same phase are connected by the second connection, the end of the stator winding can be connected without using a connection unit. Become. Accordingly, the number of parts and the number of processing steps can be reduced, and the space for the bus bar unit in the motor becomes unnecessary, so the axial dimension can be shortened and the motor can be downsized. Is possible.

  According to the brushless motor manufacturing method of the present invention, the insulator attached to the stator core is provided with the first connection terminal to which one end of the coil is connected and the second connection terminal to which the other end of the coil is connected. Since the neutral point connection process for connecting the connection terminals by the first connection and the respective phase connection processes for connecting the same phase among the second connection terminals by the second connection are provided. Without using it, the end of the stator winding can be connected. Accordingly, the number of parts and the number of processing steps can be reduced, and the space for the bus bar unit in the motor becomes unnecessary, so the axial dimension can be shortened and the motor can be downsized. Is possible.

It is sectional drawing which shows the structure of the brushless motor 1 which is Example 1 of this invention. It is a perspective view which shows the structure of the stator used for the brushless motor of FIG. It is explanatory drawing which shows the state of the coil terminal connection of the stator in the brushless motor of FIG. It is explanatory drawing which shows the structure of a guide pole. It is explanatory drawing which shows the structure of a connection terminal. It is explanatory drawing which shows the state of the coil terminal connection in the motor which is Example 2 of this invention. It is explanatory drawing which shows the structure of a bus-bar unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a configuration of a brushless motor 1 that is Embodiment 1 of the present invention, and FIG. 2 is a perspective view showing a configuration of a stator (stator) 2 used in the brushless motor of FIG. As shown in FIG. 1, a brushless motor 1 (hereinafter abbreviated as “motor 1”) includes a stator 2 on the outside and a rotor (rotor) 3 on the inside, and a plurality of phases (main parts) are disposed on a tooth portion (not shown) of the stator 2. In the embodiment, it is an inner rotor type brushless motor provided with a field coil provided with three-phase windings, and is used as a drive source for an oil pump or the like of an automobile.

  The stator 2 includes a stator core 4 formed by laminating electromagnetic steel plates, and a field coil 5 (hereinafter abbreviated as a coil 5) wound around the stator core 4. An insulator 6 made of synthetic resin is attached to the stator core 4, and a coil 5 is wound on the outside of the insulator 6 in the tooth portion. The stator 2 of the motor 1 has a so-called split core type configuration, and as shown in FIG. 2, a plurality of split cores 7 around which the coil 5 is wound are connected in a ring shape. By adopting such a split core structure, it is possible to wind a field coil in advance on the teeth portion before connecting each split core 7 in an annular shape, and the space of the stator winding can be increased. The rate is improved, the motor efficiency is improved, and the number of man-hours required for winding can be reduced. Further, the field coil of the brushless motor 1 of this embodiment is composed of three phases of U phase, V phase, and W phase, and each phase has three sets in order in the circumferential direction, U → V → W → U. It is wound around nine teeth portions so as to be arranged in the order of V → W → U → V → W.

  As described above, since a field coil is wound around each divided core 7 in advance, a pair of end portions (start and end lines) 5a and 5b of the coil 5 of each divided core 7 is connected to the insulator 6. Are connected (temporarily fixed) to the connection terminal 8 (first connection terminal) and the connection terminal 9 (second connection terminal) formed by insert molding. A part (9u, 9v, 9w) of the connection terminal 9 includes an external connection protrusion 10 extending in the axial direction, and the external connection protrusion 10 is connected to the circuit board 11. Since the insulator 6 is provided with such external connection terminals (9u, 9v, 9w), electrical connection with the circuit board 11 can be easily performed. The stator 2 is accommodated in a motor case 12 formed of synthetic resin, and a case cover 13 and an end bracket 14 are attached to both ends thereof. The circuit board 11 is disposed in the motor case 12 so as to be covered with the case cover 13. Reference numeral 20 denotes a connector integrally formed with the motor case 12 in order to electrically connect the brushless motor 1 and the vehicle body side harness.

  A rotor 3 is inserted inside the stator 2. The rotor 3 has a shaft 15 serving as a motor rotation shaft. The shaft 15 is rotatably supported by a ball bearing 16 attached to the end bracket 14. An oil seal 17 is attached to the end bracket 14, and the shaft 15 is in sliding contact with the oil seal 17. A rotor core 18 formed by laminating electromagnetic steel plates is fixed to the shaft 15. On the outer periphery of the rotor core 18, an excitation multi-pole magnet 19 (in this embodiment, a 6-pole magnet) is attached. Thus, the brushless motor 1 according to the present embodiment is configured as a 6-pole 9-tooth portion (slot) motor.

  Here, in the conventional brushless motor, a bus bar unit as shown in FIG. 7 is used for the terminal connection of the coil 5 and electrical connection to the circuit board, and it is accommodated in the X portion of FIG. However, there are cases where the size of the X portion is small due to the component specifications, and the bus bar unit cannot be disposed there. In the case of such specifications, the bus bar unit must be arranged on the opposite side (end bracket 14 side), and a long wiring and a space for it are required between the bus bar unit and the circuit board. Further, the allowable dimension in the axial direction is small, and the space for providing the bus bar unit itself may not be twisted.

  Therefore, in the motor 1 according to the present invention, instead of a bus bar using a copper plate, each coil terminal is electrically connected using a coil, thereby eliminating the bus bar unit and reducing the size and cost of the motor. Yes. FIG. 3 is an explanatory diagram showing a state of coil terminal connection in the stator 2 of the motor 1. In the stator 2, the connection terminals 8 and 9 are continuously connected (temporary wiring) without interruption by the terminal connection 21 (conductive wire) in the manner of one-stroke writing, and the common connection (first wire) for the neutral point is used. Connection) and each phase connection (second connection), and a three-phase Y connection is realized. Since current for three phases flows through the terminal connection 21, a conductive wire having a cross-sectional area three times that of the coil 5 is used (for example, the terminal connection 21 with respect to the coil 5: φ0.5 mm). : Maximum φ1.5mm).

  First, in order to form a common connection, the terminal connection 21 is skipped from the connection terminal 8a by one along the circumferential direction, and the connection terminals 8b to 8i (first connection terminals) are numbered 1 in FIG. Hook in the order of ~ 9 (neutral point connection process). The terminal connection 21 is performed while appropriately rotating the stator 2 in the circumferential direction while moving the nozzle of the winding machine in the radial direction. In this case, when the terminal connection 21 is hooked between the adjacent connection terminals 8 (for example, 8a and 8b), an insulating material erected on the inner end side of the insulator 6 (for example, made of the same synthetic resin as the insulator 6). The connection terminal 8 (8a, 8b) is connected once by drawing the terminal connection 21 to the inner diameter side through a guide pole (guide member) 22 composed of This is because if the terminals of adjacent phases are connected (temporary wiring) without passing through the guide pole 22, the terminal connection 21 may come into contact with other terminals between the terminals, and this connection is also caused during fusing. This is to hinder the work.

  FIG. 4 is an explanatory diagram showing the configuration of the guide pole 22. The guide pole 22 is formed integrally with the insulator 6 from a synthetic resin. As shown in FIG. 4A, the outer periphery of the guide pole 22 has a coil retaining portion 23 with a part of the outer diameter cut away. Is provided. A stepped return portion 23 a is formed at the upper end of the coil retaining portion 23. As shown in FIG. 4 (b), the terminal connection 21 is wound around the coil hooking portion 23 with tension applied. At that time, the terminal connection 21 is engaged with the return portion 23a and is prevented from coming off. It is held by the guide pole 22 in the form of a ring.

  In this way, the terminal connection 21 is reliably held by the guide pole 22 by the return portion 23a while preventing insulation between the wiring and the terminal by the guide pole 22 and ensuring insulation, thereby improving product reliability. . Further, since the guide pole 22 can be formed integrally with the insulator 6, the number of parts and the number of assembly steps are not increased. In FIG. 3, the terminal connection 21 is shown in a form not in contact with the guide pole 22 in order to show the route of the terminal connection 21 in an easy-to-understand manner. Thus, the terminal connection 21 is hung around the guide pole 22.

  In this way, the connection terminals 8b to 8i are connected (temporary wiring) by the terminal connection 21 to form a common connection, and then the remaining connection terminals 9u, 9v, 9w, 9a to 9f (second connection terminals). To connect each phase (temporary wiring) (each phase connection process). Here, the wiring is performed in the order of U phase (numbers 10 to 12 in FIG. 3) → V phase (same as 13 to 15) → W phase (same as 16 to 18). That is, after the terminal connection 21 is hung up to the connection terminal 8i, the terminal connection 21 is hung around the adjacent connection terminal 9u through the guide pole 22. Then, five terminals are skipped from the connection terminals 9u (step by three cores by a winding machine) and hooked on the connection terminals 9a and 9b which are other U-phase terminals. Thereby, the U-phase connection terminals 9 are connected (temporary wiring). Next, the terminal connection 21 is routed around the V-phase connection terminal 9c from the connection terminal 9b through the guide pole 22, and, like the U-phase, the terminals are skipped by five to obtain another V-phase. Hook on the connection terminals 9v, 9d. As a result, the V-phase connection terminals 9 are connected (temporary wiring). Further, the terminal connection 21 is routed around the W-phase connection terminal 9e from the connection terminal 9d via the guide pole 22, and the terminals are skipped by five as described above to the other W-phase connection terminals 9f and 9w. The W-phase connection terminals 9 are connected (temporary wiring) by hooking.

  After provisional wiring of the common connection and each phase connection as shown in FIG. 3, the terminal connection 21 wired with one stroke is cut to separate the common connection and each phase connection (cutting step). In the motor 1, they are individually separated by the A to C parts (CUT (A) to CUT (C)) of FIG. 3. In this case, in part A, the common connection N (first connection) for the neutral point is disconnected from each phase connection (second connection, here, the U-phase connection Lu). Further, the U phase connection line Lu and the V phase connection line Lv are separated from the B part, and the V phase connection line Lv and the W phase connection line Lw are separated from the C part. As a result, the terminals connected by the conventional bus bar are connected to the common connection N (solid line) and the respective phase connections Lu (one-dot chain line), Lv (two-dot chain line), Lw (long broken line) (provisional). Wiring).

  After disconnecting the common connection and each phase connection, the terminal connection 21 is electrically joined to the connection terminals 8 and 9 by fusing (fusing process). FIG. 5 is an explanatory diagram showing the configuration of the connection terminals 8 and 9. The connection terminals 8 and 9 are provided with a coil retaining piece 24, and a coil housing connection portion 26 is formed between the coil retaining piece 24 and the connection terminal main body 25. Both end portions 5a of the coil 5 and the terminal connection 21 are wired (temporary wiring) in the coil housing connection portion 26, and are fused and welded together with the coil retaining piece 24 (broken line → solid line in FIG. 1). For the coil 5 and the terminal connection 21, a conductive wire coated with enamel is used. The enamel coating melts during fusing, and the coils 5, 21 and the connection terminals 8, 9 are electrically connected. .

  As described above, in the motor 1 of the present invention, the terminal connection 21 is used instead of the bus bar, and this is continuously connected (provisional wiring) to the connection terminals 8 and 9 in the manner of one-stroke writing. Since it is separated into the common connection N and the respective phase connections Lu, Lv, Lw, a connection unit is not required for the connection of the end of the stator winding, and the number of parts and the number of processing steps can be reduced. . Further, since the space for the bus bar unit is not required in the motor, the axial dimension can be shortened, and the motor can be reduced in size. In particular, parts such as automobile oil pumps that are arranged with strict specifications in a narrow space can be designed to meet a wide range of design needs by increasing the degree of freedom in design by reducing the axial dimensions. Become.

  Next, as a second embodiment of the present invention, a configuration that facilitates the cutting of terminal connections will be described. FIG. 6 is an explanatory diagram illustrating a state of coil terminal connection in a motor that is Embodiment 2 of the present invention. In the following embodiments, the same members and portions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 6, in the stator 31 according to the second embodiment of the present invention, a part of the terminal connection 21 is hung on a guide pin 32 erected on the die of the winding machine and routed outside the stator. Has been. The portion that is wound around the guide pin 32 is a boundary portion between the common connection and each phase connection, and the terminal connection 21 is connected at portions A to C (CUT (A) to CUT (C)) in FIG. By cutting, the common connection N and the respective phase connections Lu, Lv, Lw can be separated. That is, in the stator 31, portions corresponding to the portions A to C in FIG. 3 are hung around the guide pins 32 and drawn outward. In this way, by cutting the cut portion out of the stator, the cutting work is easier than in the case where the terminal connection 21 is cut in the stator as shown in FIG. . In addition, it is possible to reduce cutting errors that cause other lines to be cut during the cutting operation, thereby suppressing the occurrence of defective products and improving product reliability.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, the present invention can be applied regardless of the core shape as long as the motor has two terminals (start line and end line) of each slot winding on one end side of the stator. Therefore, in the above-described embodiment, an example in which the present invention is applied to a brushless motor using a split core type stator is shown, but the present invention can also be applied to a motor of a type using an integral core. In the above-described embodiment, it has been described that the guide pole 22 is made of synthetic resin. However, since tension is applied to the guide pole 22 when the terminal connection 21 is hung, a metal is provided in the pole for reinforcement. A pin may be inserted. Furthermore, although the example which applied this invention to the three-phase brushless motor was shown in the above-mentioned Example, it is not limited to this, This invention can be widely applied to the brushless motor which consists of multiple phases.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Stator core 5 Field coil 5a, 5b End part 6 Insulator 7 Split core 8 Connection terminal (1st connection terminal)
8a to 8i connection terminal 9 connection terminal (second connection terminal)
9u, 9v, 9w, 9a to 9f Connection terminal 10 External connection protrusion 11 Circuit board 12 Motor case 13 Case cover 14 End bracket 15 Shaft 16 Ball bearing 17 Oil seal 18 Rotor core 19 Magnet 20 Connector 21 Terminal connection 22 Guide pole (guide member) )
23 Coil latching part 23a Return part 24 Coil latching piece 25 Connection terminal main body 26 Coil housing connection part 31 Stator 32 Guide pin 50 Bus bar unit 51 Phase-specific bus bar 52 Mid-point ring bus bar 53 Bus bar body N Common connection (first connection)
Lu U-phase connection (second connection)
Lv V-phase connection (second connection)
Lw W phase connection (second connection)

Claims (10)

A brushless motor comprising a stator having a plurality of phase field coils, and a rotor rotatably disposed inside the stator,
The stator is
A stator core having a plurality of teeth extending radially inward along the circumferential direction;
An insulator made of an insulating material attached to the stator core;
The coil wound around the insulator;
A first connection terminal that is formed on the radially outer end side of the insulator and connected to one end of the coil; a second connection terminal connected to the other end of the coil;
A guide member formed on a radially inner end side of the insulator;
A first connection for connecting all the first connection terminals;
A plurality of second connections provided for each phase, connecting the same phase among the second connection terminals, and
The second connection terminal is disposed between the first connection terminals,
The first connection is wired via the guide member provided between the first connection terminals and disposed on the radially inner end side so as to connect the adjacent first connection terminals. Brushless motor. The brushless motor according to claim 1,
The stator is
A brushless motor, wherein the stator core is divided for each of the teeth, the insulator is mounted, and a plurality of divided cores in which the coil is wound around the insulator are connected in an annular shape. The brushless motor according to claim 1 or 2,
The brushless motor, wherein the guide member is erected on the insulator. The brushless motor according to any one of claims 1 to 3,
The guide member has a coil latching portion around which the first and second connections are wound,
The brushless motor, wherein the coil latching portion has a stepped return portion that restricts movement of the first and second connections. In the brushless motor according to any one of claims 1 to 4,
One of the second connection terminals of each phase has a connection projection for electrical connection with the outside. A stator core in which a plurality of teeth extending radially inward are formed along the circumferential direction, an insulator made of an insulating material attached to the stator core, and a multi-phase field magnet wound around the insulator A stator comprising a coil;
A rotorlessly disposed rotor inside the stator, and a method of manufacturing a brushless motor,
A neutral point connection step of connecting all the first connection terminals formed on the insulator and connected to one end of the coil; and
Each phase connection step of connecting the same phase among the second connection terminals formed on the insulator and connected to the other end side of the coil, and
The neutral point connection step and each phase connection step are sequentially performed using the same conductor,
After the neutral point connection step and each phase connection step, the conductive wire is cut into a first connection for connecting all the first connection terminals and a plurality of second connections for connecting in-phase ones to each other. The manufacturing method of the brushless motor characterized by implementing the cutting process to perform. In the manufacturing method of the brushless motor according to claim 6 ,
After the cutting step, a brushless motor characterized by performing a fusing step of joining the first connection and the first connection terminal, and the second connection and the second connection terminal by fusing. Manufacturing method. In the manufacturing method of the brushless motor according to claim 6 or 7,
The stator is
A brushless motor characterized in that the stator core is divided for each of the teeth, the insulator is mounted, and a plurality of divided cores in which the coil is wound around the insulator are connected in a ring shape. Production method. In the manufacturing method of the brushless motor according to claim 6 or 7,
The stator has a guide member formed of an insulating material,
In the neutral point connecting step and each phase connecting step, the terminals are connected to each other while a conducting wire is wound around the guide member. In the manufacturing method of the brushless motor according to claim 9,
The guide member includes a coil latch portion around which the conducting wire is wound,
The coil latching portion has a stepped return portion that regulates movement of the conducting wire,
The method of manufacturing a brushless motor, wherein the conductive wire is wound around the coil hooking portion in a state of being engaged with the return portion.

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