Claims:We claim,
1. A position detecting apparatus (100) for an electric motor (200), said electric motor (200) having a housing (102) with a plurality of walls (102a), a rotating shaft (104) supported by said housing (102), and a rotor (106) disposed on said rotating shaft (104), said apparatus (100) comprising:
at least one magnetism generator (108) disposed towards periphery of said rotor (106); and
at least one sensor (110) being received in a sensor receiving portion defined in said wall (102a) of said housing (102),
wherein,
said magnetism generator (108) is adapted to emit magnetic field in at least one of radial direction and an axial direction of said rotor (106);
said sensor receiving portion being disposed in a position that allows said sensor (110) to detect leakage of magnetic field leaking out of said magnetism generator (108); and
said sensor (110) adapted to generate at least one rotor position signal representing the rotor position.

2. The apparatus (100) as claimed in claim 1, wherein said sensor (110) is mounted onto a circuit substrate (112) in such a manner that said sensor (110) is received in said sensor receiving portion with said circuit substrate (112) being attached to a rear wall (102ar) of said plurality of walls (102a), said sensor (110) is mounted in a plane perpendicular to said magnetic field emitted by said magnetism generator (108).

3. The apparatus (100) as claimed in claim 1, wherein said sensor (110) is at least one of a magnetic sensor, a magneto-resistive sensor, and a hall sensor.

4. The apparatus (100) as claimed in claim 1, wherein said sensor (110) includes a first surface (110a) facing said magnetism generator (108) and a second surface (110b) located opposite to said first surface (110a), said second surface (110b) is attached to said circuit substrate (112), said first surface (110a) of said sensor (110) includes a sensing element (114) disposed axially facing a mid-section of said magnetism generator (108).

5. The apparatus (100) as claimed in claim 1, wherein said periphery of said rotor (106) is made of a magnetic material, ferromagnetic material, and steel alloys.

6. The apparatus (100) as claimed in claim 1, wherein said magnetism generator (108) includes a plurality of permanent magnets, each of said permanent magnet includes a plurality of magnetic poles formed on a surface of said magnetism generator (108), wherein each of said magnetic pole forms a rotational position information means.

7. The apparatus (100) as claimed in claim 6, wherein said rotor (106) receives said plurality of permanent magnets such that said plurality of permanent magnets are embedded within a peripheral surface of said rotor (106).

8. The apparatus (100) as claimed in claim 7, wherein said rotor (106) receives said plurality of permanent magnets such that said plurality of permanent magnets extends axially to a predetermined distance beyond a rotor surface (106a) along an axis of rotation A.

9. A method (400) for detecting position of a rotor (106) in an electric motor (200), said electric motor (200) having a housing (102) with a plurality of walls (102a), a rotating shaft (104) supported by said housing (102), and said rotor (106) disposed on said rotating shaft (104), said method (400) comprising:
measuring, by at least one sensor (110), a magnetic field generated by a magnetism generator (108); and
outputting, by said sensor (110), a corresponding measurement signal representing a rotor position of said rotor (106),
wherein,
said magnetism generator (108) is adapted to emit magnetic field in at least one of radial direction and an axial direction of said rotor (106); and
said sensor (110) is received in a sensor receiving portion being disposed in a position that allows said sensor (110) to detect leakage of magnetic field leaking out of said magnetism generator (108).

10. The method (400) as claimed in claim 9, wherein said sensor (110) includes a first surface (110a) facing said magnetism generator (108) and a second surface (110b) located opposite to said first surface (110a), said second surface (110b) is attached to a circuit substrate (112), said first surface of said sensor (110) includes a sensing element (114) disposed axially facing a mid-portion of said magnetism generator (108).

11. An elevator door control system (300) configured to open and close an opening (or space), said control system (300) provided in communication with an electric motor (200), said electric motor (200) comprising:
a housing (102);
a rotatable shaft (104) supported by said housing (102) for rotation;
a rotor (106) coupled to said rotatable shaft (104);
a rotational position detecting apparatus (100) disposed within said housing (102), said position detecting apparatus (100) includes:
at least one magnetism generator (108) disposed towards periphery of said rotor (106); and
at least one sensor (110) being received in a sensor receiving portion defined in said wall (102a) of said housing (102),
wherein,
said magnetism generator (108) is adapted to emit magnetic field in at least one of radial direction and an axial direction of said rotor (106);
said sensor receiving portion being disposed in a position that allows said sensor (110) to detect leakage of magnetic field leaking out of said magnetism generator (108) and generate at least one rotor position signal representing the rotor position; and
said control system (300) adapted to receive said rotor position.
, Description:
TECHNICAL FIELD
[001] The embodiments herein generally relate to electric motor, and more particularly, to a position detecting apparatus configured to detect a position of a rotor in an electric motor, and generate a rotor position signal representative of the rotor position. Further, the embodiments herein relate to a position detecting apparatus for use in an elevator door control system.
BACKGROUND
[002] Many electric motor applications require smooth rotation and/or accurate control. Brushless motors typically achieve this by using 3-phase sine-wave commutation and accurate rotor position detectors, usually in the form of an encoder or a resolver. The accurate rotor position detector ensures that the sine wave remains synchronized with the rotor, thus avoiding commutation-induced torque ripple. Methods presently used in the industry for accurately detecting rotor positions use encoders and resolvers which are known and employed in motor drives for many years. Encoders sense mechanical motion, and translate the sensed motion into electrical signals. Encoders in their simplest form have one output to determine shaft rotational speed or to measure a number of shaft revolutions. Other encoders have two outputs and can provide direction-of-rotation information as well as speed and number of revolutions. Still other encoders provide an index pulse, once per revolution, which indicates an absolute rotor position. However, rotary encoders are very susceptible to mechanical load and, accordingly, often fail or produce faulty rotor angular position values. In addition, encoder assembly is complex, as additional wiring is needed to be fitted to the machine, which is work-intensive and expensive. In addition, such rotary encoders always require maintenance which incurs additional cost.
[003] Resolvers, on the other hand, typically provide one signal period per revolution and are known to be highly tolerant of vibration and high temperatures. A typical use of this technology would include a resolver generating two signals, both a sine-wave signal and a cosine-wave signal, for each revolution. An advantage of using resolvers is that they provide absolute rotor position information, rather than incremental information as is typical with most encoders. A primary drawback, however, is that resolvers deliver increasingly poor performance at low speeds. Because of this limitation, the speed control range possible with resolvers is much smaller than with encoders. Accordingly, use of resolvers is typically limited to applications that do not require high quality motor control over a wide speed range.
[004] In another approach, for detecting the rotor position, the rotor may include a rotor position magnet connected to the rotor and configured to generate a magnetic sensor field for detecting the rotor position by a rotor position sensor. While this approach provides desired result, the size of the motor structure increases. Further additional components required for detection increases overall cost.
[005] Therefore, there exists a need for a position detecting apparatus configured to detect a rotor position. Further, there exists a need for a position detecting apparatus for an electric motor, which obviates the aforementioned drawbacks.
OBJECTS
[006] The principal object of the embodiments herein is to provide a position detecting apparatus configured to detect a position of a rotor in an electric motor.
[007] Another object of the embodiments herein is to provide a position detecting apparatus configured to detect a position of a rotor and generate a rotor position signal representative of the rotor position.
[008] Another object of the embodiments herein is to provide an electric motor in which it is possible to reduce the dimension of housing in a direction along a rotation center line of a rotor.
[009] Yet another object of the embodiments herein is to provide an electric motor having a rotor which includes a plurality of permanent magnets extending axially from a rotor surface along an axis of rotation.
[0010] Still another object of the embodiments herein is to provide an electric motor having a rotor which includes a plurality of permanent magnets configured to generate a useful magnetic field axially from a rotor surface along an axis of rotation.
[0011] Another object of the embodiments herein is to provide a method for detecting position of a rotor in an electric motor.
[0012] Still another object of the embodiments herein is to provide a position detecting apparatus which is inexpensive and easy to manufacture.
[0013] Yet another object of the embodiments herein is to provide a position detecting apparatus which can be used in small areas or in an area where space constraints exist.
[0014] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0015] The embodiments herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0016] FIG. 1a is a schematic view of a position detecting apparatus, according to an embodiment as disclosed herein;
[0017] FIG. 1b depicts a side view of a rotor of the position detecting apparatus, according to an embodiment as disclosed herein;
[0018] FIG. 2a depicts a front perspective view of an electric motor, according to an embodiment as disclosed herein;
[0019] FIG. 2b depicts a rear perspective view of an electric motor, according to an embodiment as disclosed herein;
[0020] FIG. 3 depicts an image of an elevator door coupled an electric motor, according to alternate embodiment as disclosed herein; and
[0021] FIG. 4 is a flowchart depicting a method for detecting position of a rotor in an electric motor, according to an embodiment as disclosed herein.

DETAILED DESCRIPTION
[0022] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0023] The embodiments herein achieve a position detecting apparatus configured to detect a position of a rotor in an electric motor. Further, the embodiments herein achieve the position detecting apparatus configured to detect a position of a rotor and generate a rotor position signal representative of the rotor position. Furthermore, the embodiments herein achieve an electric motor in which it is possible to reduce the dimension of housing in a direction along a rotation center line of a rotor. Moreover, the embodiments herein achieve the electric motor having a rotor which includes a plurality of permanent magnets extending axially from a rotor surface along an axis of rotation. Additionally, the embodiments herein achieve the electric motor having a rotor which includes a plurality of permanent magnets configured to generate a useful magnetic field axially from a rotor surface along an axis of rotation. Also, the embodiments herein achieve a method for detecting position of a rotor in an electric motor. Referring now to the drawings, and more particularly to Figs. 1 through 4, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0024] FIG. 1a is a schematic view of a position detecting apparatus, according to an embodiment as disclosed herein. FIG. 1b depicts a side view of a rotor of the position detecting apparatus, according to an embodiment as disclosed herein. In an embodiment, the electric motor (200) generally includes a housing (102), a plurality of walls (102a), a rotating shaft (104), a rotor (106), a position detection apparatus (100), a magnetism generator (108), at least one sensor (110), and a circuit substrate (112).
[0025] The position detecting apparatus (100) is provided in the electric motor (200) which includes the housing (102) adapted to enclose all components of the position detecting apparatus (100). The housing (102) is formed by combining a plurality of walls (102a). The plurality of walls (102a) includes a front wall (102af), an opposite rear wall (102ar), and at least one side wall (not shown). Further, the housing (102) includes a circular front opening (not shown) provided in the front wall (102af), and circular rear opening (not shown) provided in the rear wall (102ar) as shown in FIGS. 2a and 2b. A first bearing (not shown) is attached to the front opening and a second bearing (not shown) is attached to the rear opening. The rotating shaft (104) is rotatably supported by the housing (102) via the first and second bearings. The rotor (106) is mounted on the rotating shaft (104). The rotor (106) includes a rotor iron core (not shown) fixed to the rotating shaft (106) and at least one magnetism generator (108) embedded in an outer circumferential portion of the rotor iron core. In an embodiment, the outer circumferential portion of the rotor (106) may be made-up of magnetic material such as, ferromagnetic material, and steel alloys. The rotor (106) rotates integrally with the rotating shaft (104). Further, the rotating shaft (104) includes a first end portion (104a) and a second end portion (104b) which are disposed in the circular front opening (not shown) provided in the front wall (102af), and the circular rear opening (not shown) provided in the rear wall (102ar) of the housing (102). The first end portion (104a) penetrates the first bearing and protrudes outside of the housing (102) in the front, while the second end portion (104b) is held by the second bearing within the rear opening.
[0026] The position detecting apparatus (100) further includes the magnetism generator (108). The magnetism generator (108) is disposed towards a peripheral surface (106p) of the rotor (106). In an embodiment, the magnetism generator (108) includes a plurality of permanent magnets. Each of the permanent magnet includes a plurality of magnetic poles (N-S) formed on a surface of said magnetism generator (108). In an embodiment, the magnetic pole forms a rotational position information means thereby enabling the position detecting apparatus (100) to detect or measure the position of the rotor (106). The magnetism generator (108) is adapted to emit magnetic field in at least one of radial direction and an axial direction of the rotor (106). In an embodiment, the rotor (106) is configured to receive the plurality of permanent magnets such that the plurality of permanent magnets are embedded within the peripheral surface of the rotor (106). The rotor (106) is configured to receive the plurality of permanent magnets such that the plurality of permanent magnets extends axially to a predetermined distance beyond a rotor surface (106a) along an axis of rotation A of the rotor (106). The extension of the plurality of permanent magnets facilitate in accurate detection of position of the rotor (106). The magnetism generator (108) is formed by integrating two permanent magnets. The two permanent magnets are magnetized in mutually opposite directions in the axial direction of the rotating shaft (104) i.e. the N pole of one permanent magnet and the S pole of the other permanent magnet face the magnetic sensor (110).
[0027] The position detecting apparatus (100) further includes the sensor (110) which is disposed in a sensor receiving portion defined in the wall (102a) of the housing (102). The sensor (110) is at least a magnetic sensor (110). The sensor receiving portion is formed such that the sensor (110) is adjacently located near the magnetism generator (108) with a predefined gap defined between them. In an embodiment, the sensor (110) is mounted onto the circuit substrate (112). The circuit substrate (112) is attached to the rear wall (102ar) of the plurality of walls (102a). In an embodiment, the circuit substrate (112) is a printed circuit board (PCB). The sensor (110) is mounted in a plane perpendicular to the magnetic field emitted by the magnetism generator (108). The sensor (110) includes a first surface (110a) which is configured to face the magnetism generator (108) and a second surface (110b) located opposite to said first surface (110a). The second surface (110b) is attached to the circuit substrate (112). The first surface (110a) of the sensor (110) includes a sensing element (114). In an embodiment sensing element (114) is disposed axially facing a mid-section of the magnetism generator (108) as shown in FIG. 1b. In an embodiment, the sensor (110) is at least one of a magnetic sensor, a magneto-resistive sensor, and a hall sensor. The sensor (110) is configured to detect a leakage of magnetic field leaking out of the magnetism generator (108) and generate at least one rotor position signal representing the rotor position.
[0028] In an embodiment, the rotor (106) may include at least one recess (not shown) defined towards its peripheral surface (106p). The magnetism generator (108) may is disposed in the recess. The magnetism generator (108) is fixed in the recess by an adhesive. As, the magnetism generator (108) is provided in the recess, the magnetic sensor (110) can be arranged close to an end face (106a) of the rotor (106), and the overall axial dimension of the housing (102) can be reduced.
[0029] In an embodiment, the position detecting apparatus (100) mainly includes the magnetism generator (108), the circuit substrate (112), and includes the sensor (110). Further, the position detecting apparatus (100) may include a control unit (not shown) to control the rotation of the motor (200) based on the detected rotor position signal.
[0030] FIG. 3 depicts an image of an elevator door coupled an electric motor (200), according to an embodiment as disclosed herein. In an alternate embodiment, the position detecting apparatus (100) is provided in communication with an elevator door system (300), which typically includes an elevator car (not shown) and elevator car doors (304) (hereafter described as elevator door or door in this description) which are driven into open and closed positions by the electric motor (200) (hereafter described as motor in this description) and a first toothed belt (302) (as shown in FIG. 3) which rotates a drive roller (not shown). The elevator doors (304) typically are coupled to hoistway doors (not shown) by means of a coupling device (not shown) and pull the hoistway doors into open and closed positions. Further, the motor (200) is supplied with electrical energy by connection to a power supply unit (not shown). A motor micro-controller (not shown) is provided in communication with the motor (200) and the magnetic sensor (110). The micro-controller is adapted to receive input from the position detecting apparatus (100) and commands to move the elevator doors (304) by generating velocity command signal (not shown). Further, the micro-controller is provided with a means (not shown) for communicating with the elevator controller (not shown).
[0031] In alternate embodiment, the electric motor (200) generally includes a housing (102), a rotating shaft (104), a rotor (106), a position detection apparatus (100), a magnetism generator (108), at least one sensor (110), and a circuit substrate (112). The magnetism generator (108) is disposed towards a peripheral surface (106p) of the rotor (106). The magnetism generator (108) is adapted to emit magnetic field in at least one of radial direction and an axial direction of the rotor (106). The sensor (110) to configured to detect a leakage of magnetic field leaking out of the magnetism generator (108) and generate at least one rotor position signal representing the rotor position. Thus, the position detection apparatus (100) transmits the rotor position signal to the elevator controller. Thereby the elevator controller is adapted to control the position of the door (304).
[0032] FIG. 4 is a flowchart depicting a method for detecting position of a rotor in an electric motor, according to an embodiment as disclosed herein. A method (400) for detecting position of a rotor (106) in an electric motor (200) is disclosed. The method includes measuring, by at least one sensor (110), a magnetic field generated by a magnetism generator (108) (at step 402). Further, the method includes outputting, by said sensor (110), a corresponding measurement signal representing a rotor position of said rotor (106) (at step 404).
[0033] The advantages provided by the embodiments herein include accurate position detection of a rotor, better control of elevator door operation, and accurate control on speed and position of elevator door.
[0034] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.