Brushless motor

Abstract

Brushless motor, including: a stator including an annular stator core and first to twelfth teeth provided in a sequential order in the circumferential direction on an inner circumference of the stator core; a first to twelfth coil, each wound around the first to twelfth tooth and forming a delta circuit; and a rotor provided in a center of the stator, wherein the first to twelfth coils are designed such that the twelfth, first, sixth and seventh coils connected in series form a W phase, the eighth, ninth, second and third coils connected in series form a U-phase, the fourth, fifth, tenth and eleventh coils connected in series form a V-phase, adjacent coils of different phases are wound in an arrangement on the teeth in the same direction, adjacent coils of the same phase are wound in opposite directions, the W phase includes a first connecting wire (F1) connecting the first coil and the sixth coil, the U-phase includes a second connecting wire (F2) connecting the ninth coil and the second coil, the V-phase contains a third connecting wire (F3) connecting the fifth coil and the tenth coil the first to third connecting wires are arranged so that the coils do not cross each other and are arranged on an outer edge of one of the end faces in the axial direction of the stator core, the first and third connecting wires are arranged such that the wires partially overlap each other in an axial direction and are arranged at different positions in the axial direction, and the second connecting wire includes a bent part (F') extending in the axial direction from below the third connecting wire and to and above the first connecting wire.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to a brushless motor. 2. Description of the state of the art

[0002] Conventional motors are used as drive sources for various devices and products. For example, motors are used for office machines such as printers and copiers, various types of household electrical appliances, and power sources for vehicles such as motor vehicles and power-assisted bicycles. For increased durability and noise reduction, brushless motors are sometimes used as drive sources for moving parts with high operating frequency.

[0003] A brushless motor with an internal rotor is known. A stator is arranged around a rotor, and coils are wound around a plurality of stator teeth provided in the stator. Various methods for winding coils around a plurality of stator teeth are known. For example, a synchronous machine is disclosed in which the coils are delta-connected or star-connected (see document JP 2012 - 517 209 A).

[0004] Document JP 2006 - 197 674 A discloses a stator for a three-phase rotating electrical machine. Three unit coil groups are formed adjacently in a circumferential direction of a stator core by winding unit coils that establish three phase coils. The other documents JP 2010 - 183 662 A, JP 2002 - 101 596 A, and US 2011 / 0 234 031 A1 also deal with further structures and arrangements of stators for rotating electrical machines.

[0005] In one type of synchronous machine, a delta connection is achieved through a continuous wire connection. This continuous connection requires a large number of connecting wires that bridge stator teeth of the same phase, which are spaced apart from each other, and thus requires space for arranging the connecting wires and spare components such as busbars. Since the connecting wires do not contribute to generating a magnetic force in the stator, the number of connecting wires is preferably reduced as much as possible. SUMMARY OF THE INVENTION

[0006] The present invention addresses this problem, and its object is to provide a technology for implementing a brushless motor with a compact size and high torque through a new approach to the stator coils.

[0007] The problem is solved by a brushless motor having the features of the independent claim. The brushless motor comprises: a stator including an annular stator core and first to twelfth teeth provided in a circumferential direction in a sequential order on an inner circumference of the stator core; first to twelfth coils wound around the first to twelfth teeth, respectively, forming a delta connection; and a rotor provided at a center of the stator.The first to twelfth coils are configured such that the twelfth, first, sixth, and seventh coils are connected in series to form a W phase; the eighth, ninth, second, and third coils are connected in series to form a U phase; and the fourth, fifth, tenth, and eleventh coils are connected in series to form a V phase, with adjacent coils of different phases wound in the same direction in an array on the teeth, and adjacent coils of the same phase are wound in opposite directions. The W phase includes a first connecting wire connecting the first coil and the sixth coil. The U phase includes a second connecting wire connecting the ninth coil and the second coil. The V phase includes a third connecting wire connecting the fifth coil and the tenth coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] With reference to the accompanying drawings, which are given as examples and not as limitations, and in which like elements in several figures are given the same reference numerals, embodiments will now be described by way of example only, in which Fig. 1 is an entire perspective view of a brushless motor according to the first embodiment; Fig. 2 is a side view of the brushless motor according to the first embodiment; Fig. 3 is an exploded perspective view of the brushless motor according to the first embodiment; Fig. 4 is a plan view of the stator core; Fig. 5 is a perspective view of the stator; Fig. 6 schematically shows the delta connection of the stator according to the embodiment; and Fig. 7 schematically shows the delta connection of the stator according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The invention will now be described with reference to the preferred embodiments. These are not intended to limit the scope of the present invention, but rather to illustrate the invention by way of example.

[0010] The brushless motor according to one embodiment of the present invention includes an annular stator, and first to twelfth teeth provided in a circumferential direction in a sequential order on the inner circumference of the stator core. The brushless motor also includes first to twelfth coils wound around the first to twelfth teeth, respectively, forming a delta connection, and a rotor provided in the center of the stator. The first to twelfth windings are configured such that the twelfth, first, sixth, and seventh coils connected in series form a W phase. The eighth, ninth, second, and third coils connected in series form a U phase. The fourth, fifth, tenth, and eleventh coils connected in series form a V phase. Adjacent coils of different phases in the arrangement of the teeth are wound in the same direction, and adjacent coils of the same phase are wound in opposite directions.The W phase contains a first connecting wire (jumper wire) that connects the first and sixth coils. The U phase contains a second connecting wire that connects the ninth and second coils. The V phase contains a third connecting wire that connects the fifth and tenth coils.

[0011] According to the embodiment, the length of the connecting wires connecting spaced-apart coils is reduced. The end of the U-phase coil and the lead wire of the V-phase coil are led out from the adjacent coils, or the end of the V-phase coil and the lead wire of the W-phase coil are led out from the adjacent coils, or the end of the W-phase coil and the lead wire of the U-phase coil are led out from the adjacent coils, so that the lead wire and the end of the coils wound around teeth can be easily handled and the length of the wire connection is reduced. Accordingly, the number of coils that do not contribute to the generation of magnetic force is reduced, the coil resistance is reduced, and the space required for arranging the coils is reduced.

[0012] The first to third connecting wires are arranged so that the coils do not cross each other. This improves insulation reliability and contributes to reducing the thickness and size of the motor.

[0013] The first to third connecting wires may be arranged on the outer edge of one of the end faces in the axial direction of the stator core. The first and third connecting wires are arranged so that the wires partially overlap each other in the axial direction and are arranged at different positions in the axial direction. The second connecting wire includes a bent portion extending in the axial direction from below the third connecting wire to and above the first connecting wire. This ensures that the number of connecting wires overlapping each other in a plan view of the stator is at least one and contributes to reducing the thickness and size of the motor.

[0014] As additional embodiments of the present invention, optimal combinations of the above structural elements and embodiments of the invention in the form of components, manufacturing methods, and systems can also be implemented. According to this embodiment, a brushless motor with a compact size and high torque can be implemented.

[0015] With reference to the drawings, a description will be given of an embodiment of the present invention. Like reference numerals denote like elements, and a description will be omitted accordingly. The structure described below is only an example and does not limit the scope of the present invention. A description will be given below using an internal rotor brushless motor as an example. (First Embodiment)(The brushless motor)

[0016] Fig. 1 is an entire perspective view of the brushless motor according to the first embodiment. Fig. 2 is a side view of the brushless motor according to the first embodiment. Fig. 3 is an exploded perspective view of the brushless motor according to the first embodiment.

[0017] The brushless motor (hereinafter sometimes referred to as "motor") 10 according to the embodiment includes a columnar rotor 12 containing magnets, a stator 14 having a space for arranging the rotor 12 at its center, a front bell 16, a housing body 18, and a power supply 19.

[0018] The front bell 16, which is a plate-shaped member, has a hole 16a formed in a central portion for a rotating shaft 20 to pass therethrough, and is provided with a recess 16b for holding a bearing 22 near the hole 16a. The front bell 16 supports part of the rotating shaft 20 of the rotor 12 via the bearing 22. The housing body 18 is a cylindrical member. A recess 18b for holding a bearing (not shown) is formed in the center of the base 18a. The housing body 18 supports the other part of the rotating shaft 20 of the rotor 12 via the bearing. According to the first embodiment, the front bell 16 and the housing body 18 constitute a housing member for accommodating the rotor 12 and the stator 14. (The stator)

[0019] The structure of the stator 14 will be described. Fig. 4 is a plan view of a stator core. Fig. 5 is a perspective view of the stator 14. Fig. Figure 4 shows the shape of the stator core only schematically, and details have been omitted.

[0020] A stator core 36 is a cylindrical (annular) member in which a plurality of plate-shaped stator yokes 38 are stacked. A total of 12 teeth T1 to T12 are provided circumferentially in a sequential order on the inner circumference of the stator yoke, facing the center.

[0021] An insulator 40 is attached to each of the teeth T1 to T12. Then, for each of the teeth T1 to T12, a conductor (copper wire) is wound around the insulator 40 to form the first coil C1 to the twelfth coil C12 (see Fig. 5). Then, the rotor 12 is placed in the center of the stator 14 completed by the above processes.

[0022] Fig. 6 shows schematically the delta connection of the stator 14 according to the embodiment.

[0023] With reference to Fig. 5 to 6 an exemplary description will be given of how the coils are wound. Fig. The exemplary wire connection structure shown in Figure 6 is achieved using a jet-type coil winding machine. The wire connection remains essentially unchanged even if the U-phase, V-phase, and W-phase are interchanged. A description will now be given of a case where the twelfth coil C12 is formed first.

[0024] As in Fig. As shown in Figure 6, the W phase is first formed by forming the twelfth coil C12 counterclockwise (CCW), forming the first coil C1 clockwise (CW), forming the sixth coil C6 clockwise via the first connecting wire F1, and forming the seventh coil C7 counterclockwise. The twelfth coil C12, the first coil C1, the sixth coil C6, and the seventh coil C7, connected in series in the order shown, form the W phase.

[0025] After the seventh coil C7 is formed, the eighth coil C8 is formed counterclockwise, the ninth coil C9 is formed clockwise, the second coil C2 is formed clockwise via the second connecting wire F2, and the third coil C3 is formed counterclockwise. The eighth coil C8, the ninth coil C9, the second coil C2, and the third coil C3, connected in series in the specified order, form the U phase.

[0026] After the third coil C3 is formed, the fourth coil C4 is formed counterclockwise, the fifth coil C5 is formed clockwise, the tenth coil C10 is formed clockwise via the third connecting wire F3, and the eleventh coil C11 is formed counterclockwise. The fourth coil C4, the fifth coil C5, the tenth coil C10, and the eleventh coil C11, connected in series in the specified order, form the V phase. Then, the lead wire L1 of the W-phase coil and the lead wire L2 of the V-phase coil are connected, forming a delta circuit.

[0027] The adjacent coils of different phases (W-phase and U-phase, U-phase and V-phase, V-phase and W-phase) are wound in the same direction, and the adjacent coils of the same phase are wound in opposite directions.

[0028] As a result, a delta connection connecting the first coil C1 to the twelfth coil C12 of the stator 14 according to the first embodiment is formed by continuous operation of the coil winding machine. The length of the connecting wires connecting coils spaced apart in the stator 14 is reduced compared to the prior art. Since the end of the U-phase coil and the lead wire of the V-phase coil are led out from the same tooth space between the adjacent coils, or the end of the V-phase coil and the lead wire of the W-phase coil are led out from the same tooth space between the adjacent coils, or the end of the W-phase coil and the lead wire of the U-phase coil are led out from the same tooth space between the adjacent coils, the lead wire and the end of the coils wound around the teeth can be easily handled, and the length of the wire connection is reduced.Accordingly, the number of coils that do not contribute to the generation of magnetic force is reduced, and the space required for arranging the coils is reduced. In other words, using a new approach to winding coils around the stator, a brushless motor with a compact size and high torque can be implemented.

[0029] The first connecting wire F1 to the third connecting wire F3 according to the embodiment are arranged so that the lines do not cross each other. This prevents contact between the connecting wires, improves insulation reliability, and contributes to reducing the thickness and size of the motor. To describe this in more detail, the first to third connecting wires F1 to F3 are as shown in Fig. 5, the first connecting wire F1 and the third connecting wire F3 are arranged on one of the end surfaces of the stator core 36 in the axial direction Ax in an arc shape around an outer edge 14a of the insulator. The first connecting wire F1 and the third connecting wire F3 partially overlap each other in the axial direction Ax and are arranged at different positions in the axial direction. The second connecting wire F2 includes a bent part F' extending in the axial direction from below the third connecting wire F3 and to and above the first connecting wire F1. This ensures that the number of connecting wires overlapping each other in a plan view of the stator is 2 or less, and contributes to reducing the thickness and size of the motor.

[0030] The rear surface (outer peripheral surface) of each insulator 40 is provided with a locking part 40a to control the movement of the connecting wires. This fixes the connecting wires at the desired positions. Of particular importance is that the second connecting wire F2 according to the embodiment is firmly fixed at the desired position because it is held in a taut state by being supported in different directions by the two locking parts 40a before and after the bent part F'. (Second embodiment)

[0031] Fig. Figure 7 shows a schematic diagram of the delta connection of the stator according to a second embodiment. The exemplary connection structure shown in Fig. 7 is achieved using a flyer-type coil winding machine. A description will now be given of a case where the twelfth coil C12 is formed first. Those features similar to the features of the first embodiment will not be described.

[0032] As in Fig. 7, first the W phase is formed by forming the twelfth coil C12 counterclockwise (CCW), forming the first coil C1 clockwise (CW), over the first connecting wire F1' which is connected next to one of the end faces of the stator (to the top of Fig. 7), the sixth coil C6 is formed clockwise, and the seventh coil C7 is formed counterclockwise. The twelfth coil C12, the first coil C1, the sixth coil C6, and the seventh coil C7, connected in series in the specified order, form the W phase.

[0033] After the formation of the seventh coil C7, the eighth coil C8 is formed counterclockwise, the ninth coil C9 is formed clockwise, over the second connecting wire F2', which is next to the other end face of the stator (to the bottom of Fig. 7), the second coil C2 is formed clockwise, and the third coil C3 is formed counterclockwise. The eighth coil C8, the ninth coil C9, the second coil C2, and the third coil C3, connected in series in the specified order, form the U phase.

[0034] After the third coil C3 is formed, the fourth coil C4 is formed counterclockwise, the fifth coil C5 is formed clockwise, and the tenth coil C10 is formed clockwise via the third connecting wire F3' extending from one end face of the stator to the other end face. The fourth coil C4, the fifth coil C5, the tenth coil C10, and the eleventh coil C11 are formed counterclockwise. The fourth coil C4, the fifth coil C5, the tenth coil C10, and the eleventh coil C11, connected in series in the order shown, form the V phase. Then, the lead wire L1 of the W-phase coil and the lead wire L2 of the V-phase coil are connected, forming a delta circuit.

[0035] The same advantages as those obtained in the first embodiment are also obtained by using a flyer type coil winding machine.

[0036] As described above, in the brushless motor according to the embodiment, the number and length of the connecting coils, which do not contribute to the motor characteristic, are reduced. As a result, the motor performance is improved due to the reduced resistance in the winding (the coil). Since the steps required for winding the coils are identical from phase to phase, the fluctuation in the winding resistance between phases is reduced, and the motor performance is stabilized. Since the total number of connecting wires adjacent to the respective end faces of the stator can be reduced to two or less, the space required for wire connection and for arranging connecting wires is reduced, thus reducing the size of the motor as a whole. Furthermore, the entire coils can be formed by continuous wires, eliminating the need for wasted wires for handling the lead and the end.Since the lead wire of any given phase is aligned with the end of another phase, the wire connection between the wound coils is facilitated. By using the novel winding structure of the embodiment, the coils wound around the respective teeth do not come loose, allowing a high-quality motor to be constructed without loose wires. The brushless motor according to the embodiment can be designed with a desired wire connection structure without the need for busbars or a complicated connection mechanism.

[0037] A description will now be given of the specification of a brushless motor in which the embodiment can be suitably used. The outer diameter of the brushless motor according to the embodiment is about 30 to 140 mm, and preferably about 35 to 85 mm. The number of grooves (teeth) of the stator is, for example, 12. Preferably, the number of magnets is 10 or 14. The magnetic force (energy product) at the main surface of the magnet is 8 MGOe or more, preferably 10 MGOe or more, and more preferably 30 MGOe or more. Further, the diameter of the rotor is preferably 20 to 70 mm.

Claims

[1] Brushless motor, comprising: a stator including an annular stator core and first to twelfth teeth provided in a circumferential direction in a sequential order on an inner circumference of the stator core; a first to twelfth coil, each wound around the first to twelfth tooth and forming a delta circuit; and a rotor provided in a center of the stator, wherein the first to twelfth coils are designed such that the twelfth, first, sixth and seventh coils connected in series form a W phase, the eighth, ninth, second and third coils connected in series form a U-phase, the fourth, fifth, tenth and eleventh coils connected in series form a V-phase, adjacent coils of different phases are wound in an arrangement on the teeth in the same direction, adjacent coils of the same phase are wound in opposite directions, the W phase includes a first connecting wire (F1) connecting the first coil and the sixth coil, the U-phase includes a second connecting wire (F2) connecting the ninth coil and the second coil, the V-phase contains a third connecting wire (F3) connecting the fifth coil and the tenth coil the first to third connecting wires are arranged so that the coils do not cross each other and are arranged on an outer edge of one of the end faces in the axial direction of the stator core, the first and third connecting wires are arranged such that the wires partially overlap each other in an axial direction and are arranged at different positions in the axial direction, and the second connecting wire includes a bent part (F') extending in the axial direction from below the third connecting wire and to and above the first connecting wire. [2] Brushless motor according to claim 1, wherein the first connecting wire is arranged in a region between the twelfth coil and the first coil to between the sixth coil and the seventh coil, the second connecting wire is arranged in a region between the eighth coil and the ninth coil and between the second coil and the third coil, the third connecting wire is arranged in a region between the fourth coil and the fifth coil and between the tenth coil and the eleventh coil, a W-phase line and one end of the V-phase are drawn out from a space between two adjacent coils and are connected to each other at one of the end faces of the stator core in the axial direction, a V-phase line and an end of the U-phase are drawn out from a space between two adjacent coils and are connected to each other at one of the end faces of the stator core in the axial direction, a U-phase line and an end of the W-phase are drawn out from a space between two adjacent coils and are connected to each other at one of the end faces of the stator core in the axial direction, and the bent part is arranged between the first coil and the twelfth coil. [3] Brushless motor according to claim 1 or 2, wherein the first to third connecting wires are arranged along a first circumference, and the line and the end of the W phase, the line and the end of the V phase and the line and the end of the U phase are arranged along a second circumference having a different diameter than the first circumference. [4] Brushless motor according to one of claims 1-3, wherein the stator core is a cylindrical core with an annular portion in the form of a body, and the first to twelfth coils and the first to third connecting wires are connected in series.

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