JP2002010550A - Three-phase brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a motor to be downsized by unnecessitating a large current board for connecting the neutral points of each coil when stator coil are star- connected in a three-phase brushless DC motor in which many stator coils arrayed in the circumferential direction are star-connected. SOLUTION: A set of coils is formed by three neighboring stator-coils. One end of each stator coil that forms each coil set is connected to each other to form a neutral point, the other end is each connected to a different phase electrode, and the neutral point of each coil set is separated from each other. With regard to the three stator-coils of each coil group, the ends of the neutral point side are collected and bundled and it is sufficient to leave them pushed into between the neighboring stator coils. A ring-shaped wiring board is mounted along the stator coils at the one side of the axial direction of the stator so that the end of the opposite neutral point side of each coil can be connected to this wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase brushless DC motor having a star-connected three-phase stator coil.

[0002]

2. Description of the Related Art In a three-phase brushless DC motor,
When the stator coil wound around the magnetic pole of the stator core is star-connected (star-shaped connection) and when delta-connected (ring-shaped connection)
And sometimes. In the star connection, one end of three adjacent stator coils is connected to each other to serve as a neutral point, and the other end of each coil is connected to an electrode of a different phase.
The delta connection connects the stator coils between different phases without having a neutral point.

FIG. 8 is a side sectional view showing the structure of a conventional stator in a star connection, and FIG. 9 is a wiring diagram of a stator coil. In FIG. 8, reference numeral 1 denotes a motor case, and 2 denotes a stator fixed to the motor case 1. The stator 2 has a magnetic pole formed on an annular stator core 3 and a bobbin 5 around which a stator coil 4 is wound.
Reference numeral 6 denotes a rotor, on the outer peripheral surface of which a permanent magnet whose polarity changes in the circumferential direction is fixed. That is, this motor is an inner rotor type permanent magnet brushless DC motor.

There are 18 stator coils 4 which are connected, for example, as shown in FIG. That is, one end of six coils 4 of the same phase is connected to the neutral point N, and the other ends are connected to different phase electrodes U, V, W, respectively, so that adjacent coils 4 have different phases. FIG. 9A shows an in-phase coil 4 connected in parallel.
Conventionally, coils of each phase are connected in series as shown in FIG. Further, in FIG. 9A, there is also a configuration in which a plurality of coils 4 of the same phase are connected in series to form a plurality of coils (series-parallel composite connection).

Usually, a series connection shown in FIG. 9B is used for an application in which a sufficiently high power supply voltage can be used. For example, since a commercial power supply can be used for home electric appliances and the like, the series connection shown in FIG. On the other hand, when the power supply voltage is low, a parallel connection as shown in FIG. For example, it is difficult to increase the power supply voltage of an electric vehicle or the like using a battery as a power supply, so this parallel connection is used.

When the coils having the same phase are connected in parallel, the currents of all the coils connected in parallel flow to the neutral point N. Therefore, it is necessary to increase the diameter of the wiring at the neutral point N. Therefore, an annular large current substrate 7 is fixed to one side of the stator 2 in the axial direction, and one ends (neutral point N side) of all the coils 4 are connected to the large current substrate 7. Here, the large current substrate 7 is formed by attaching copper foil having a thickness of several 100 μm to both surfaces of an insulating resin substrate.

On the other side of the stator 2, another annular wiring board 8 is fixed, and the other end of each coil 4 is connected to an electrode of each phase provided on the wiring board 8. That is, the U, V, and W phase coils 4 are connected to the corresponding electrodes (U, V, W).

[0008]

In the case where the power supply voltage is low and a large current flows through the coil as described above, the neutral point N side is connected by an annular large current substrate 7 as shown in FIG. The current shunted by the parallel connection is again concentrated at the neutral point N, and the substrate 7 must be adapted to a large current. For this reason, it is necessary to increase the thickness of the copper foil attached to the front and back.

When the thickness of the copper foil is increased, the heat capacity of the copper foil increases, and when soldering the ends of the coil 4, heat escapes to the copper foil to deteriorate solderability. The large current board 7 comes closer to the inner surface of the motor case 1 and the gap G (FIG. 8) between them becomes smaller. In particular, since the coil terminal usually protrudes in the thickness direction of the large current substrate 7, the gap between the terminal of the coil and the inner surface of the motor case is further reduced. When the gap G, that is, the creepage distance is reduced, a spark discharge easily occurs between the substrate 7 and the motor case 1. Therefore, the inner surface of the motor case must be sufficiently separated from the large current substrate 7 and the coil terminal. For this reason, the size of the motor case becomes large, which hinders downsizing of the motor.

The present invention has been made in view of such circumstances, and when a stator coil is star-connected,
It is an object of the present invention to provide a three-phase brushless DC motor that does not require a large-current board for connecting a neutral point of each coil and enables downsizing of the motor.

[0011]

According to the present invention, it is an object of the present invention to provide a three-phase brushless DC motor in which a number of stator coils arranged in a circumferential direction are star-connected, and one set of coils is formed by three adjacent stator coils. One end of a stator coil forming one coil set is connected to a neutral point and the other end is connected to a different phase electrode, and the neutral point of each coil set is separated from each other. Achieved by a brushless DC motor.

The three stator coils of each coil group may be assembled by binding the terminals on the neutral point side and binding them together and then pushing them between adjacent stator coils. In this way, the connection portions of the neutral points can be made extremely small to reduce the amount of protrusion from the stator. Also, wiring processing of the coil terminal is easy.

An annular wiring board is mounted on one side of the stator in the axial direction along the stator coil, and the terminal on the anti-neutral point side of each coil can be connected to this wiring board. In this case, the wiring processing of the coil can be facilitated, and the wiring processing portion can be reduced in size.

[0014]

FIG. 1 is a longitudinal sectional view of a wheel-in motor according to an embodiment of the present invention, FIG. 2 is a front view of a stator of the motor alone, FIG. 3 is a rear view thereof, and FIG.
FIG. 5 is an exploded perspective view for explaining a procedure of assembling the stator, FIG. 6 is an exploded perspective view showing a structure of a bobbin and a stopper, and FIG. 7 is a connection diagram of a stator coil. The wheel-in motor of this embodiment is incorporated in a vehicle wheel.

In FIG. 1, reference numeral 10 denotes a three-phase permanent magnet type brushless DC motor, which is housed in a motor case 12 which is divided into right and left parts. A special oil is put in the motor case 12, and the motor 10 is immersed in the oil to operate. The motor case 12 includes a right case half 12a fixed to a vehicle body (not shown) and a left case half 12b fixed to the right case half 12a in a liquid-tight manner.
With

An axle 14 is rotatably held by bearings 16 and 18 on the left case half 12b. The left end of the axle 14 projects from the left case half 12b, and the wheel 20 is mounted here. The wheel 20 is formed by a disc 20a and a rim 20b. A hub 22 is spline-coupled to the axle 14, and a disk 20a of the wheel 20 is bolted to the hub 22. Rim 20b
Is mounted with a tire (not shown).

An oil seal 24 is mounted between the left case half 12b and the boss of the hub 22 to prevent oil in the motor case 12 from leaking. Also hub 2
2, a brake drum portion 26 is formed integrally, and a brake shoe 30 is held on a pin 28 implanted in the left case half 12b. As a result, a well-known in-expandable drum brake that generates a braking force by pressing the brake shoe 30 against the drum portion 26 from the inside is formed.

The motor 10 is of an inner rotor type, and has a stator 32 fixed to the right case half 12a and a rotor 34 rotating inside the stator 32. The rotor 34 has a drum shape and houses a planetary gear type speed reducer 36 inside thereof. Both ends of a shaft (rotor shaft) 38 integral with the rotor 34 are supported by bearings 40 and 42 on the inner surface of the right case half 12a and the axle 14, respectively.

The speed reducer 36 includes a ring gear 36a fixed to the inner surface of the left case half 12b, a sun gear 36b formed on the rotor shaft 38, and a plurality of planetary gears 36c meshing with the ring gear 36a and the sun gear 36b. have. A planet gear shaft 36d holding the planet gear 36c is fixed to a disk 14a integrally formed with the axle 14. As a result, the rotation of the rotor 34 is transmitted from the sun gear 36b to the planet gear 36c, and the planet gear 36c rotates around the sun gear 36b inside the ring gear 36a.
Therefore, the rotation of the rotor 34 is decelerated and transmitted to the axle 14.

The rotor 34 is press-fitted and fixed to an outer periphery of an aluminum drum 34a by press-fitting an annular magnet bush 34b formed by laminating thin sheets of electromagnetic steel slope.
A plurality of (for example, 12) plate-like permanent magnets 36c are fixed at predetermined intervals to 6b. These permanent magnets 36c are magnetized so that the polarity alternates in the circumferential direction. The permanent magnet 36c is preferably a magnet having a high magnetic flux density, for example, a neodymium / iron / boron magnet.

Next, the stator 32 will be described. Stator 3
The second stator core 44 is of a split type, in which an annular stator inner 46 and an annular stator outer 48 are fitted. Here, the stator inner 46 and the stator outer 48 are formed by laminating thin electromagnetic steel plates. As shown in FIG. 5, the stator inner 46 has a structure in which a number (for example, 18) of magnetic poles 50 projecting radially outward are connected in an annular shape on the inner diameter side. The stator outer 48 is annular as shown in FIG. 5, and can be fitted to the outer peripheral end of the magnetic pole 50 of the stator inner 46.

Before fitting the stator outer 48 to the stator inner 46, as shown in FIG.
2 is attached to each magnetic pole 50. After the bobbin 52 is mounted in this manner, the stator outer 48 is shrink-fitted and press-fitted as shown in FIG. Here, the bobbin 52 will be described.

The bobbin 52 is made of an insulating resin and is formed in a square thread shape as shown in FIG. That is, the flanges 56 and 58 are formed at both ends of the rectangular tube portion 54 fitted to the magnetic pole 50. One of the flanges 58, that is, the magnetic pole 5
A locking claw 60 is formed integrally with the flange 58 disposed on the outer peripheral end side of the stator core 46 so as to protrude from the magnetic pole 50 in the outer diameter direction along the upper surface or the lower surface of the stator core 46.

A guide groove 62 (FIG. 6) is formed in the bobbin 52 along the inside of the rectangular tube portion 56 facing the locking claw 60. A metal stopper 64 is provided in the guide groove 62.
Can be inserted. The stopper 64 is L as shown in FIG.
It is made of a metal plate bent in a letter shape, and its tip side 64 a can be inserted into the guide groove 62. This tip side 64a
A claw-shaped protrusion 64b is formed on each of the left and right edges.
These projections 64b bite into the guide groove 62 when the distal end side 64a is inserted into the guide groove 62, and prevent the stopper 64 from dropping off.

An appropriate number of convex portions 66 (FIG. 6) are formed on the inner surface of the rectangular cylindrical portion 54 of the bobbin 52. When the bobbin 52 is mounted on the magnetic pole 50, these convex portions 66
0, and has a function of firmly fixing the bobbin 52 to the magnetic pole 50.

The stator 32 is assembled as follows.
First, the stator coil 68 is wound around the bobbin 52. The stator coil 68 is formed by winding an enamel wire having a property of being fused by the heat generated by the coil 68 itself (self-fusing property). The bobbin 52 around which the stator coil 68 is wound is positioned such that the locking claw 60 is positioned on one surface (the lower surface in FIG. 5) of the stator inner 46.
Attach to 0. At this time, the locking claw 60 protrudes outward from the outer peripheral end of the magnetic pole 50 (step in FIG. 5).

Next, the stator outer 48 is mounted. That is, the stator outer 48 is moved axially (downward) from the plane (upper surface in FIG. 5) opposite to the plane of the stator inner 46 where the locking claws 60 of the bobbin 52 mounted on the magnetic pole 50 are located. The inner peripheral surface of the outer 48 is
0 and press-fitted to the outer peripheral end (step of FIG. 5). At this time, shrink fitting may be used. If the stator outer 48 is correctly fitted to the stator inner 46, the fitting portions 70 (see FIG. 4) of the both will come into contact with the locking claws 60 of the bobbin 52 and be positioned.

Next, the stopper 64 is mounted (step in FIG. 5). The stopper 64 is fitted into the guide groove 62 of the bobbin 52 along the surface (the upper surface in FIG. 5) of the stator outer 48 on the side opposite to the locking claw 60. The protrusion 64b of the stopper 64 bites into the inner surface of the guide groove 62,
The stopper 64 is prevented from being detached. At this time, the stopper 64 is engaged with the fitting portion 70 between the stator inner 46 and the stator outer 48.
It is fixed at the position crossing the top. As a result, the fitting portion 70
Are sandwiched between the locking claws 60 and the stoppers 64 to prevent the stator outer 48 from falling off the stator inner 46 in the axial direction.

A wiring board 72 is further mounted on the stator 32 thus assembled (step of FIG. 5). The wiring substrate 72 is annular as shown in FIGS. 2 and 5, and has seven locking holes 74 that are wide in the circumferential direction near the outer periphery (FIG. 2). The stopper 64 is
The stoppers 64 are not mounted on the bobbins 52 at positions corresponding to the locking holes 74, and the other eleven bobbins 52 are not mounted.

The wiring board 72 is provided with a stopper 64
Is mounted on the stopper 64 such that the upright portion 64c (see FIG. 6) of the first member enters. The upright portion 64c of the stopper 64 projects through the locking hole 74 of the wiring board 72,
By mounting the solder on the protruding end, the wiring board 72 can be fixed to the stopper 64.

The stator coil 68 is excited by three-phase alternating current, and three stator coils 68 circumferentially adjacent to each other have U, V, W having a phase difference of 120 ° in electrical angle from each other.
Phase currents are supplied in sequence. The stator coil 68 is shown in FIG.
Star connection as shown in That is, the three adjacent stator coils 68 form one coil set, and the coils 68 forming each coil set have one end coupled to each other to become the neutral point N. Here, the neutral points of the different coil sets are separated from each other.

The other ends of the coils 68 forming each coil set are connected to U, V, W phase electrodes U, V, W, respectively. As shown in FIG. 2, U, V, W
Annular bus bar 76 (76U, 76V, 7
6W) are soldered and riveted, and these bus bars 76 are provided with cutout grooves 78 (78U, 78V, 7V) provided on the outer periphery of the wiring board 72 through the inner layer circuit of the wiring board 72.
8W). In FIG. 2, an inner layer circuit connecting the bus bar 76 and the notch groove 78 is simplified and shown by a broken line.

The three adjacent stator coils 68 constitute one set, and one end of each of the three coils 68 has a notch groove 78 (78U, 78V, 7V) near each coil 68.
8W) and soldered. The other ends of the set of three coils 68 are assembled as shown in FIG. 3 and soldered together. This soldered portion is covered with an insulating material 80 and is pressed between two adjacent coils 68 (FIG. 3).

The ends of the coil 68 assembled and covered with the insulating material 80 are introduced directly from the bobbin 52 into the collecting portion (inside the insulating material 80) in FIG. In this case, there is a problem that the end of the coil 68 is easily unraveled from the bobbin 52 and the coil 68 is easily loosened.

In order to solve this problem, a pair of notches 82 and 84 and an eave portion 86 located between the notches 82 and 84 are preferably provided on the flange 58 as shown in FIG. . In this case, the end of the coil 68 is passed from one notch 82 under the eaves 86 to the other notch 84.
Lead to. In this way, the eaves 86 and the notches 82,
84 ensures that the end of the coil 68 is held. As a result, the coil 68 does not loosen even when severe vibration is applied.

The wiring board 72 is integrally formed with wiring terminals 88 and 90 for a temperature sensor (not shown). In this embodiment, a temperature sensor such as a thermistor for detecting the temperature of the stator 32 is attached, and the leads of the temperature sensor are connected to these terminals 88 and 90.

The stator 32 thus assembled is
As shown in FIG. 1, the right case half 12 of the motor case 12
It is fixed inside a. That is, the bolt 32 is passed through three bolt holes 48a (FIGS. 2, 3, and 5) provided in the stator outer 48, and the bolt 32 is screwed into the right case half 12a to fix the stator 32. In FIG. 1, reference numeral 94 denotes a wiring plug mounted in a liquid-tight manner on the right case half 12a. The wiring passing through the wiring plug 94 is connected to the bus bar 76 (76U, 76V, 76B) of the wiring board 72.
W) terminals and temperature sensor terminals 88 and 9
Connected to 0.

Reference numeral 96 denotes an angle sensor attached to the right case half 12a. On the back surface of the drum 34a of the rotor 34 (the surface opposite to the speed reducer 36), a convex portion 98 is provided so as to correspond to every other angular position of the permanent magnet 34c. The rotor 3 is detected by detecting
4 is determined.

According to the three-phase brushless DC motor 10, a controller (not shown) determines the rotation angle of the rotor 34 based on the output of the angle sensor 96, and U, V, W corresponding to the rotation angle. Vary the phase current. As a result, the rotor 34 rotates. The drive torque is changed by, for example, performing phase shift control on the U, V, and W phase currents.

[0040]

As described above, according to the first aspect of the present invention, one set of coils is formed by three adjacent stator coils, and one end of each of the stator coils is connected to each other to serve as a neutral point. By connecting the other ends to different phase electrodes, the neutral points of each coil set are separated from each other, so that a large current board for connecting the neutral points of the different coil sets is unnecessary. Become. Therefore, the inner surface of the motor case is brought closer to the stator coil, and the size of the motor case can be reduced. Therefore, the outer dimensions of the motor can be reduced.

In this case, if the terminals on the neutral point side of the coils forming each coil set are assembled and this assembly is pushed into the gap between the adjacent stator coils, the operation is simple. The motor can be further miniaturized by reducing the amount of protrusion of the portion from the stator (claim 2).
In addition, if an annular wiring board is attached to one side of the stator and the anti-neutral side terminal of each coil is connected to this wiring board to allow each phase current to flow through each coil, coil wiring processing is easy. In addition, the wiring processing portion can be reduced in size, which is suitable for downsizing the motor.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

FIG. 2 is a front view of a stator of the motor alone.

FIG. 3 is a rear view of the same.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is an exploded perspective view showing a procedure for assembling the stator.

FIG. 6 is a perspective view showing a bobbin and a stopper.

FIG. 7 is a wiring diagram of a stator coil.

FIG. 8 is a side sectional view showing the structure of a conventional stator.

FIG. 9 is a wiring diagram of a stator coil.

[Explanation of symbols]

 10 Three-phase brushless DC motor 12 Motor case 32 Stator 34 Rotor 50 Magnetic pole 52 Bobbin 68 Stator coil 72 Wiring board N Neutral point U, V, W phase electrode

Continued on the front page F term (reference) 5H019 AA08 AA09 BB01 BB04 BB12 BB17 CC03 DD01 DD10 EE09 EE10 EE14 5H603 AA03 AA09 BB01 BB07 BB09 BB10 BB12 CA01 CA05 CB04 CB13 CB18 CB19 CC11 CC17 CC01 CC01 CC01 CC01 CC01 CC05 CC01 QB14 5H621 BB10 GA01 GA04 GB10 GB14

Claims (3)

[Claims] 1. A three-phase brushless DC motor in which a number of stator coils arranged in a circumferential direction are star-connected, wherein a set of three adjacent stator coils forms one set of coils, and each of the set of stator coils forms a coil set. A three-phase brushless DC motor, wherein one end is connected to each other to form a neutral point, while the other end is connected to different phase electrodes, and the neutral points of each coil set are separated from each other. 2. The three-phase brushless DC motor according to claim 1, wherein one end on the neutral point side of three stator coils forming each coil set is assembled and accommodated in a gap between adjacent stator coils. 3. An annular wiring board is mounted on one side of the stator in the axial direction along the stator coil, and a terminal on the anti-neutral point side of each coil is connected to the wiring board. 2, three-phase brushless DC motor.