A ROTOR POSITION DETECTING APPARATUS FOR A BRUSHLESS MOTOR

Abstract: The present invention is related to a rotor position detecting apparatus for a brushless motor enclosed in a housing. The apparatus comprises a plurality of light reflecting members attached to the surface of a rotor of the motor in the rotor axis of symmetry; a plurality of light non-reflecting members attached to the surface of the rotor of the motor being alternately with the light reflecting members; a pair of transmitting and receiving optical fibers positioned for one end thereof to face the surface of the rotor in the housing; and, a pair of light emitting and photoelectric converting elements respectively positioned to face the other end of the pair of transmitting and receiving optical fibers.

Description: DESCRIPTION A ROTOR POSITION DETECTING APPARATUS FOR A BRUSHLESS MOTOR Technical Field The present invention is related to a rotor position detecting apparatus for a brushless motor, and particularly to a rotor position detecting apparatus for a compressor which is embodied by a brushless motor. Background Art In a refrigerator, an air conditioner or the like, a compressor, which is used-for changing the condition of fluid, for example refrigerant, is generally embodied by an A.C induction motor. Furthermore, the compressor used in the appliance is tightly enclosed with housings welded together in order to prevent decreasing the pressure therein. In the housing, a motor is connected with a piston (in a reciprocating compressor) . A connector, which is mounted in the body of the housing, has several terminals electrically connected to each of the phase windings of the motor. Upon each of the phase voltages being applied to the terminals, the axis of the motor starts to rotate, thereby reciprocating the piston connected to the axis into a cylinder. In the manner described above, refrigerant intakes into the cylinder and then is compressed. The closed compressor is required to normally operate under the condition of maximum 130 C and several tens Psi, and to endure in oil and refrigerant. Compared with an A.C motor, a brushless motor has low noise level and low power consumption, and may be driven as continuously varying the rotating speed. Considering the advantages, a closed compressor embodied by a brushless motor has been continuously developed. The brushless motor is activated by alternatingly flowing currents with different phases to each other into each of the phase windings. Accordingly, means for detecting the polarity of a rotor are essential to the brushless motor. A pair of light emitting and receiving elements are typically used for detecting the polarity-of the rotor. However, there is a problem in that it is impossible to place the elements in the housing of the closed compressor which has the condition of high temperature and high pressure, because the elements are normally made of semiconducting material. Furthermore, there is another problem in that the sealing of the compressor is damaged, because the signal lines of the elements are drawn out of the housing. Considering the problems, a system using a winding induced voltage, instead of detection by the elements, has been developed. However, the system has a problem in that means for detecting the winding induced ..voltage, filter means and means for starting the compressor are additionally required, and in that it is not applicable to the brushless motor. Disclosure of Invention It is an object of the present invention to provide a rotor position detecting apparatus required for driving a brushless motor. It is another object of the present invention to provide a rotor position detecting apparatus using a photoelectric conversion system to increase the detection ability in a brushless motor. It is another object of the present invention to provide a rotor position detecting apparatus constructed with simple configuration without damaging the sealing of a closed compressor embodied by a brushless motor. According to the present invention, there is provided a rotor position detecting apparatus for a brushless motor enclosed- in a housing. The apparatus comprises a plurality of light reflecting members attached to the surface of a rotor of the motor in the rotor axis of symmetry; a plurality of light non-reflecting members attached to the surface of the rotor of the motor being alternately with the light reflecting members; a pair of transmitting and receiving optical fibers positioned for one end thereof to face the surface of the rotor in the housing; and, a pair of light emitting and photoelectric converting elements for respectively positioned to face the other end of the pair of transmitting and receiving optical fibers. Brief Description of the Drawings The present invention will now be described in detail with reference to the accompanying drawings: in which, Fig. 1 is a plane view of a compressor, to which an apparatus of the present invention is applied, in condition of removing a cover thereof; Fig. 2 is a circuit diagram for explaining a rotor position detecting method according to the present invention; and, Figs. 3 A to D are cross-sectional views of a connector for phase voltage supply and optical fibers, in which A is a cross- sectional view of a connector, B is a cross-sectionally exploded view of a connector, C is a cross-sectional view of a connector in condition connected with optical fibers, and D is a right side view of a connector. Best Mode for Carrying out the Invention As a preferred embodiment employing a rotor position detecting apparatus according to the present invention, a closed compressor will now be described in detail. Referring to Fig. 1, the numeral 1 denotes a housing for tightly enclosing the compressor. Field cores 2 wound with coil 21, as a stator, are annularly fixed to the housing 1, and a rotor 3 is provided to rotatably be secure in the middle of the field cores 2. In the preferred embodiment, it will be explained that the compressor is embodied by a bipolar two- phase brushless motor, -I but the number of poles and phase windings of the motor may be properly increased. A control system for driving the brushless motor has been already disclosed in U.S patent No. 4,472,664 by the inventor of the present invention. Therefore, a further description will be omitted in the specification. Two light reflecting members 31 are attached to the upper surface of the rotor 3 in the rotor axis of symmetry. Two light non-reflecting members 32 are also attached to the upper surface of the rotor 3 being alternately with the light reflecting members 31. For example, the two light reflecting members 31 may be attached to the N-poles of the rotor 3, and the two light non-reflecting members 32 may be attached to the S-poles thereof. It is possible to arrange the light reflecting and non-reflecting members 31 and 32 opposite to the above arrangement. The number of the light reflecting and non-reflecting members 31 and 32 may be properly increased according to the number of poles and phase windings of the rotor 3. The light reflecting and non-reflecting members 31 and 32 may be also attached to the cylindrical surface of the rotor 3. A pair of optical fibers 41 and 42 for respectively transmitting and receiving light are positioned for the one end thereof to face toward the upper surface of the rotor 3, to which the light reflecting and non-reflecting members 31 and 32 are attached. A numeral 7 denotes a connector which has terminals 71 electrically connected to the phase windings 21 and ground line. The connector 7 also has a hole for guiding the pair of optical fibers 41 and 42 in the middle thereof. The pair of optical fibers 41 and 42 may be drawn out of the housing 1 through the hole, and positioned for the other end thereof to face toward a pair of light emitting and photoelectric elements 8 and 5. However, when the pair of optical fibers 41 and 42 is directly drawn out of the housing 1, the compressor can not be sealed to a satisfactory extent. Accordingly, it is desirable for the internal optical fibers of the housing 1 to face the external optical fibers of the housing 1 through the medium of a transparent window. Further details will be described later referring to Figs. 3A to 3D. Referring to Figs. 3A to 3D, sealing members 72 are provided in the spaces between terminals 71 and connector 7 to prevent decreasing pressure in the compressor. The guide holes 75 and 78 are formed in the middle of the connector 7. The diameter of hole 75 facing inward to housing 1 is smaller than that of hole 78 facing outward to housing 1. The other end of the- internal pair of optical fibers 41 and 42 is fitted into the hole 75. The transparent window 76 is inserted into the hole 78. A connecting member 77, which subsequently is tightly fitted into the hole 74, has a hole 78 for. guiding the one end of the external pair of optical fibers 411 and 421. The other end of the pair of external optical fibers 411 and 421 is positioned to face the pair of light emitting and photoelectric elements 8 and 5. By arranging the apparatus in the manner described above, the decrease of the pressure in the compressor can be effectively prevented. A motor drive control portion 6 is provided in the external of the housing 1. The motor drive control portion 6 supplies the phase voltages with the terminals 71 connected with the phase windings 21. In the apparatus described above, the light generated by the light emitting element 8 is delivered by the optical fibers 41 and 411, and reaches the upper surface of the rotor 3, to which the light reflecting and non-reflecting members 31 and 32 are attached. The light thus reached is reflected, and then delivered through the optical fibers 42 and 421 only when the light reflecting members 31 are placed under the end the optical fibers 41 and 42. The delivered light is converted into a corresponding electric signal through the photoelectric element 5, and is provided to the motor drive control portion 6. Based on whether the electrical signal from the photoelectric element 5 is input or not, the motor drive control portion 6 detects the kind of pole of the rotor 3, thereby providing the phase windings 21 with the voltages having different phases with each other. The light emitting diode 8 may be used as a light emitting element 8, A photo transistor may be used as a photoelectric converting element. Industrial Applicability As described above, a rotor position detecting apparatus according to the present invention is applied to a brushless motor, particularly to a closed compressor embodied by a brushless motor ' in a refrigerator or an air conditioner, thereby increasing not only the detecting ability but also the sealing of the closed compressor.

Claims: CLAIMS 1. A rotor position detecting apparatus for a brushless motor, wherein said brushless motor includes a closed housing, said apparatus further comprising: a plurality of light reflecting members attached to the surface of a rotor of said motor in the rotor axis of symmetry; a plurality of light non-reflecting members attached to the surface of the rotor of said motor being alternately with said light reflecting members; a pair of transmitting and receiving optical fibers positioned for one end thereof to face the surface of said rotor in said housing; and, a pair of light emitting and photoelectric converting elements respectively positioned to face the other end of said pair of transmitting and receiving optical fibers. 2. A rotor position detecting apparatus, as set forth in Claim 1, wherein said plurality of light reflecting and non- reflecting members are attached to the upper surface of said rotor. 3. A rotor position detecting apparatus, as set forth in Claim 1, wherein said plurality of light reflecting and non- reflecting members are attached to the cylindrical surface of said rotor. 4. A rotor position detecting apparatus, as set forth in Claim 2 or Claim 3, said apparatus further comprising: a connector mounted to the body of said housing, said connector comprising a plurality of terminals connected to phase windings of said rotor, and a hole for guiding said pair of transmitting and receiving optical fibers in the middle thereof . 5. A rotor position detecting apparatus, as set forth in Claim 4, said apparatus further comprising a transparent window inserted into said hole of said connector. 6. A rotor position detecting apparatus, as set forth in Claim 5, wherein said ,<pair of transmitting and receiving optical fibers are divided into two centering said transparent window.

Inventors: JUNG YEONG CHUN, JUNG, YEONG, CHUN
Applicants: JUNG YEONG CHUN, SAMSUNG ELECTRONICS CO LTD, JUNG, YEONG, CHUN, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1993
Main classification: H02K29
IPC codes: H02K29