Stator for use in a brushless motor

A stator having a stator yoke, a first and second printed substrates, a plurality of drive coils and hall elements mounted on the first substrate, and a group of drive circuits mounted on the second substrate, wherein an end of the drive coil which is to be connected to the group of the drive circuits is directly connected to the second printed substrate.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a stator for use in a brushless 
motor. More particularly, the invention relates to a stator which is 
compact in size and decreases soldering steps thereby improving a yield 
rate. 
There has been known a conventional stator for use in a brushless motor 
shown in FIGS. 1A, 1B and 1C. More specifically, FIG. 1A is a front view 
of a conventional stator, FIG. 1B is a side view and FIG. 1C is a rear 
view of the stator. 
The conventional stator is provided with a stator yoke 1, a first printed 
substrate 2 which is fixedly mounted on a front surface of the stator yoke 
1 in such a manner that the substrate 2 faces a rotor of the motor, and a 
second printed substrate 3 which is fixedly mounted on a rear surface of 
the stator yoke 1. As shown in FIG. 1A, both a plurality of drive coils 4 
for rotating the rotor of the motor and a plurality of hall elements 5 for 
detecting a rotational position of the rotor are mounted on the first 
printed substrate 2 and electrically connected thereto. A group of drive 
circuits 6 is disposed on the second printed substrate 3 and electrically 
connected thereto. 
In the conventional stator shown in FIGS. 1A, 1B and 1C, six drive coils 4 
and three hall elements 5 are utilized thereby constituting a three-phase 
drive system. The first printed substrate 2 and second printed substrate 3 
are electrically connected to and communicated with each other through a 
plurality of copper wires 7. The copper wires 7 are insulated by a film 8 
at an edge portion of the stator. Both ends of each of the drive coils 4 
are connected to respective land portions 9 of the first printed substrate 
2. 
The conventional stator thus constructed necessitates eleven copper wires 7 
in total because three wires are required for the drive coils 4 and eight 
wires are required for the hall elements 8. These eleven wires 7 are 
gathered in one portion on the stator thereby raising a problem in that a 
large range is necessary to be provided both on the first and second 
printed substrates 2 and 3, so that the size of the stator would be 
disadvantageously increased. 
Moreover, many soldering steps are required for assembling the stator, for 
example, soldering steps for connecting the land portion 9 to a pattern of 
the first printed substrate 2, for connecting the pattern of the first 
printed substrate 2 to the copper wires 7, and for connecting the copper 
wires 7 to a pattern of the second printed substrate 3. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to eliminate the 
above-described problems accompanying a conventional stator. More 
specifically, an object of the invention is to provide a stator for use in 
a brushless motor in which copper wires are decreased in number and, 
therefore, soldering steps are decreased during the assembly process and, 
further, a stator can be made compact in size. 
Another object of the invention is to provide a stator in which a hall 
element does not interfere a drive coil thereby improving a yield rate. 
The foregoing and other objects have been achieved by the provision of a 
stator which, according to the invention, has a stator yoke, a first and 
second printed substrates, a plurality of drive coils and hall elements 
mounted on the first substrate, and a group of drive circuits mounted on 
the second substrate, wherein an end of the drive coil which is to be 
connected to the group of the drive circuits is directly connected to the 
second printed substrate not through the copper wires. By this 
arrangement, copper wires connecting the first printed substrate to the 
second printed substrate are decreased in number thereby achieving a 
stator which is compact in size. 
According to another aspect of the invention, the hall elements are 
positioned in a group of drive circuits. Such an arrangement is 
advantageous in that the copper wires can completely be eliminated and, 
further, the hall element does not interfere the drive coils so that a 
yield rate can be improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 2A, 2B and 2C show a stator of a brushless motor according to a first 
embodiment of the present invention. More specifically, FIG. 2A shows a 
front surface of a stator. FIG. 2B is a side view of the stator and FIG. 
2C shows a rear surface of the stator. 
As illustrated in FIGS. 2A, 2B and 2C, the stator is provided with a stator 
yoke 11, a first printed substrate 12, and a second printed substrate 13. 
The first printed substrate 12 is fixedly mounted on a front surface of 
the stator yoke 11 which surface faces a rotor of the brushless motor (not 
shown). A plurality of drive coils 4 and a plurality of hall elements 5 
are mounted on the first printed substrate 12 and electrically connected 
thereto. The second printed substrate 13 is fixedly mounted on a rear 
surface of the stator yoke 11. A group of the drive circuits 6 is disposed 
on the second printed substrate 13 and electrically connected thereto. 
The stator yoke 11 is made smaller in diameter than the first and second 
printed substrates 12 and 13. Due to this arrangement, a part 14 toward an 
outer periphery of the drive coils 4 does not contact the stator yoke 11. 
Therefore, part 14 of the drive coils 4 is not necessary to be subjected 
to an extra insulating treatment because it does not contact stator yoke 
11. However, in case that either the stator yoke 11 or the part 14 of the 
drive coils 4 is subjected with the insulating treatment, the stator yoke 
11 does not necessarily have to be made smaller. 
Notches 15 and 16 are formed on an outer periphery both of the first 
printed substrate 12 and the second printed substrate 13 so that the part 
14 of the drive coils 4 does not protrude from the outer periphery of the 
first and second printed substrates 12 and 13. Such an arrangement 
decreases a possibility that the part 14 of the drive coils 4 may be 
broken during the assembly process of the stator. Further, since a 
position of the part 14 of the drive coil 4 can be fixed with respect to 
both the first and second substrates 12 and 13, the stator can be 
assembled with high efficiency. 
In FIGS. 2A and 2C, the notches 15 and 16 are semicircular in shape. 
However, the notches may be V-shaped or Y-shaped as shown in FIGS. 3A and 
3B, respectively. These arrangements of the notches 15 and 16 are 
advantageous in that the efficiency of the assembly of the stator is 
further improved because the fixed position of the part 14 of the drive 
coil 4 is defined more accurately. Further, the notches 15 and 16 may be 
formed at an inner peripheral portion of the first and second printed 
substrates 12 and 13, respectively. 
A land portion 18 is formed on the second printed substrate 13 mounting the 
drive circuits at a surrounding of the notch 16, which land portion is 
connected to an end 17 of the drive coil 4 so that the end 17 is directly 
connected to the drive circuits mounted on the second substrate 13. Such a 
structure advantageously decreases the connection in number between the 
land portion 18 and the end 17 of the drive coil 4 to be connected to the 
drive circuits. Further, soldering steps during the assembly for soldering 
the end 17 of the drive coil 4 relative to the conventional structure can 
be decreased. 
Furthermore, merely eight copper wires 7 for the hall elements are required 
for connecting between the first printed substrate 12 and the second 
printed substrate 13 owing to the direct connection of the end 17 of the 
drive coil 4 to the drive circuits. Therefore, the first and second 
printed substrates 12 and 13 can be made small in size due to the decrease 
of the range for disposing the copper wires 7. 
FIGS. 4 and 5 show a stator assembled in a brushless motor according to a 
second embodiment of the present invention. More specifically, FIG. 4 is a 
cross sectional view showing a stator which is actually assembled in a 
brushless motor and FIG. 5 shows a rear surface of the stator. 
The brushless motor is provided with a drive magnet 21 which is polarized 
alternately by S and N in the circumference direction thereof, a magnet 
yoke 22 mounting thereon the drive magnet 21, and a pulley 27 coupling 
thereto the magnet yoke 22. The pulley 27 is firmly fitted to a rotational 
shaft 28 which is rotatable with respect to a housing 30 through a bearing 
29, so that the magnet 21, the magnet yoke 22 and the pulley 27 act as a 
rotor of the motor. 
The motor is further provided with a stator yoke 24, a first printed 
substrate 23 mounted on a front surface of the stator yoke 24, which front 
surface faces the rotor, and a second printed substrate 31 mounted on a 
rear surface of the stator yoke 24. The stator yoke 24, the first printed 
substrate 23 and the second printed substrate 31 are fixedly mounted on 
the housing 30 so that they act as a stator of the motor. As shown in 
FIGS. 4 and 5, a plurality of drive coils 25 are mounted on the first 
printed substrate 23 and electrically connected thereto, and a plurality 
of hall elements 26 for detecting a rotational position of the rotor of 
the motor are mounted on the second printed substrate 31. The stator yoke 
24 is provided with through holes 32 on a position corresponding to the 
respective hall elements 26 mounted on the second printed substrate. The 
magnetic flux of the magnet 21 is applied to the hall elements 26 through 
the respective through holes 32. 
FIG. 5 shows a rear surface of the stator viewing from an upper side of the 
rotational shaft 28. Although it is not illustrated in FIG. 5, the through 
hole 32 is positioned under each of the hall elements 26. 
In the stator of the brushless motor thus structured according to the 
second embodiment of the present invention, no copper wire for the hall 
elements is required since the hall elements are directly mounted on the 
second printed substrate 31. Further, the hall elements 26 and the 
respective drive coils 25 do not interfere each other since they are 
mounted on the separate printed substrates. 
Moreover, a group of drive circuits for driving the motor can be mounted on 
the second printed substrate 31. This provision eliminates whole copper 
wires for connecting the two printed substrates, so that the motor can be 
advantageously made compact in size. 
In the second embodiment of the invention described above, the hall 
elements are mounted on the second printed substrate 31. However, the hall 
elements may be buried into the second printed substrate. In such an 
arrangement, the magnetic flux to the hall elements can be increased 
thereby improving a detecting sensitivity of the rotational position of 
the rotor. 
As described above, according to the present invention, an end of the drive 
coil to be connected to the drive circuits side is directly connected to a 
printed substrate mounting thereon drive circuits. Therefore, copper wires 
connecting a first printed substrate mounting drive coils to a second 
printed substrate mounting thereon the drive circuits can be effectively 
decreased. By such a structure, both of the printed substrates can be made 
compact and, further, soldering steps are advantageously decreased. 
In another aspect of the present invention, hall elements are mounted 
directly on the second printed substrate. Under such a structure, a range 
of a land portion can be increased, a difficulty that an end terminal and 
a terminal of the hall elements may be short-circuited can be eliminated, 
and a shape and a winding number of the drive coil can be freely arranged 
Accordingly, a yield rate is improved and, further, the motor can be made 
compact in size.