A stator for use in a brushless motor

Abstract: A stator having a stator yoke (11), first and second printed substrates (12,13), a plurality of drive coils (4) and hall elements (5) mounted on the first substrate (12), and a group of drive circuits (6) mounted on the second substrate (13), wherein an end (17) of the drive coil which is to be connected to the group of the drive circuits (6) is directly connected to the second printed substrate (13).

Description: BACKGROUND OF THE INVENTION The present invention relates generally to a stator for use in a brushless motor having a rotor, comprising: a stator yoke; a first printed substrate fixedly mounted on a first surface of said yoke; means for driving said brushless motor; a second printed substrate on which said motor driving means is mounted, said second printed substrate being fixedly mounted on a second surface of said yoke; a plurality of drive coils mounted on said first printed substrate and electrically connected thereto; and means for detecting a rotational position of said rotor. Such a stator is known from EP-A-0 210 835. US-A-4 435 673 discloses another brushless motor. The known conventional stator for use in a brushless motor is shown in accompanying 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. 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, the stator can be made compact. According to the invention, the stator initially defined is characterized in that at least one of said printed substrates is provided with at least one notch through which an end of a respective one of the drive coils passes whereby said end is directly connected to said motor driving means. In one embodiment of the invention, there is provided a stator which has a stator yoke, a first and second printed substrates, a plurality of drive coils and hall elements rounded 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 connected to the second printed substrate directly and not through copper wires. By this arrangement, copper wires connecting the first printed substrate are decreased in number thereby achieving a stator which is compact in size. According to another embodiment 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 the yield rate can be improved. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Fig. 1A shows a front surface of a conventional stator. Fig. 1B is a side view of the stator shown in Fig. 1A. Fig. 1C shows a rear surface of the stator shown in Fig. 1B. Fig. 2A shows a front surface of a stator according to a first embodiment of the present invention. Fig. 2B is a side view of the stator shown in Fig. 2A. Fig. 2C shows a rear surface of the stator shown in Fig. 2B. Figs. 3A and 3B are other arrangements of notches according to the invention. Fig. 4 is a sectional view showing a brushless motor employing a stator according to a second embodiment of the present invention. Fig. 5 shows a rear surface of the stator shown in Fig. 4. 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. By this arrangement, a part 14 of the drive coils 4 does not contact the stator yoke 11 thereby being insulated therefrom. Therefore, the part 14 of the drive coils 4 is not necessary to be subjected to an extra insulating treatment. However, in case that either the stator yoke 11 or the part 14 of the drive coils 4 is subjected with an insulating treatment, the stator yoke 11 is not necessarily 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 would decrease 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 both to 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 shaped. 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 smaller 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 the 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 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, the yield rate is improved and, further, the motor can be made compact in size.

Claims: A stator for use in a brushless motor having a rotor, comprising: a stator yoke (11,24); a first printed substrate (12,23) fixedly mounted on a first surface of said yoke; means (6) for driving said brushless motor; a second printed substrate (13,31) on which said motor driving means is mounted, said second printed substrate (13,31) being fixedly mounted on a second surface of said yoke (11,24); a plurality of drive coils (4,25) mounted on said first printed substrate (12,23) and electrically connected thereto; and means (5) for detecting a rotational position of said rotor, characterized in that at least one of said printed substrates is provided with at least one notch (15,16), through which an end (17) of a respective one of the drive coils (4,25) passes whereby said end (17) is directly connected to said motor driving means (6). A stator according to claim 1, wherein the or each notch (15) is formed on an outer periphery of said first printed substrate (12,23). A stator according to claim 1 wherein the or each notch (15) is formed on an inner periphery of said first printed substrate (12,23). A stator according to any preceding claim wherein the or each notch (15,16) is semicircular. A stator according to any of claims 1 to 3 wherein the or each notch (15,16) is V-shaped. A stator according to any of claims 1 to 3 wherein the or each notch (15,16) is Y-shaped. A stator according to any preceding claim wherein said yoke (11,24) is smaller in diameter than said first printed substrate (12,23) whereby said end of each drive coil (4,25) does not contact said stator yoke (11,24). A stator according to any preceding claim wherein said detecting means is positioned apart from said drive coils (4,25) mounted on said first printed substrate (12,23). A stator according to any preceding claim wherein said detecting means is mounted on said second printed substrate (13,31). A stator according to claim 9, wherein said stator yoke (11,24) is provided with a through hole (32) at a portion corresponding to said detecting means. A stator according to any of claims 1 to 8 wherein said detecting means is buried into said second printed substrate (13,31). A stator according to any preceding claim wherein said detecting means comprises a plurality of hall elements (5,26). A stator according to claim 12, wherein six of said drive coils (4,25) and three of said hall elements (5,26) are provided thereby constituting a three-phase drive system. A stator according to any preceding claim, wherein the second printed substrate (13,31) carries land portions (18) for connection to respective ends (17) of said drive coils (4,25).

Inventors: ARAI KOJI C O AKAI ELECTRIC CO, KAKINOKI WATARU C O AKAI ELECT, MIYOSHI NORIAKI C O AKAI ELECT, ARAI, KOJI C/O AKAI ELECTRIC CO.,LTD., KAKINOKI, WATARU C/O AKAI ELECTRIC CO.,LTD., MIYOSHI, NORIAKI C/O AKAI ELECTRIC CO.,LTD.
Applicants: AKAI ELECTRIC, AKAI ELECTRIC CO., LTD.
Application year: 1988
Main classification: H02K29
IPC codes: H02K29