JP2666272B2 - Brushless motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a brushless motor suitable for use in a tape recorder (TR) or a video tape recorder (VTR) requiring a small size, high precision and high resolution. Things. SUMMARY OF THE INVENTION According to the present invention, a signal recording unit is provided on a rotor side, and a signal detector is provided on a stator side. In a brushless motor adapted to perform position control, the signal recording unit is formed by irradiating a film whose reflectance changes by irradiating a laser beam with a laser beam and writing pits for detecting the number of rotations and the rotation position. As a result, the brushless motor can be made smaller and more accurate. [Related Art] In a brushless motor used for a tape recorder, a video tape recorder, or the like, a signal recording unit is generally provided on a rotor side, while a signal detector is provided on a stator side.
The signal detector detects a signal recorded in the signal recording unit to control the number of rotations and the rotational position. [Problems to be Solved by the Invention] By the way, conventionally, magnetism is used as a signal recording unit,
As shown in FIG. 12, the N and S poles are alternately magnetized on the outer periphery of the rotor 1 to form the signal recording unit 2, while the stator 3 has a Hall element 4 as a rotational position detector and a rotational speed detector. A magnetoresistive element 5 is mounted as a detector, and the Hall element 4 and the magnetoresistive element 5 detect a magnetic force as a signal generated from the signal recording unit 2 to control a rotational position and a rotational speed. Widely used. However, such a brushless motor using a magnet as the signal recording unit 2 has the following problems. (1) Two Hall elements 4 as position detectors are required for two-phase energization, and three Hall elements 4 are required for three-phase energization, which increases the number of components. (2) The Hall element 4 as a position detector must be arranged on the stator 3 with a predetermined positional relationship with respect to the magnet as the signal recording section 2, but as the size of the motor or the rotor is reduced, the arrangement space becomes larger. Gone
As shown in FIG. 12, a case arises in which the coil must be arranged in the coil 6. (3) The smaller the size of the motor or the rotor, the smaller the allowable amount of displacement of the detectors such as the Hall element 4 and the magnetoresistive element 5 (the position of the detector is determined by the angle). It becomes difficult. (4) When a brushless motor is used as a capstan motor, the number of revolutions is very low (60 rpm), so a number of revolutions per revolution is required. Only about 520 pulses of φ36 rotor have been commercialized. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems and to provide a small and highly accurate motor. [Means for Solving the Problems] While a signal recording unit is provided on the rotor side, a signal detector is provided on the stator side, and the signal recorded on the signal recording unit is detected by the signal detector, and the number of rotations and the number of rotations are determined. In a brushless motor adapted to control the position, a film whose reflectance changes by irradiating a laser beam is provided on an outer peripheral portion of the rotor, and the laser beam is rotated by a motor via a rotary encoder while the laser beam is being rotated. The signal recording section was provided by providing pits for detecting the number of revolutions and / or detecting the rotational position by hitting. [Operation] A signal recording unit for controlling the number of rotations and the rotation position is formed by writing a pit for detecting the rotation position and the number of rotations by applying a laser beam to a film whose reflectivity changes by irradiation with the laser beam. Therefore, a larger number of signals (data) can be recorded than those using a magnet as a signal recording unit (magnets can be magnetized only in units of 200 microns at present, but pits can be recorded in units of 10 microns). Recording and reading are possible), and pits can be written with a laser beam while rotating the rotor with a motor via a rotary encoder. This has the effect of deteriorating the detection accuracy of rotor runout and core runout. Since the state is canceled, a highly accurate detection pattern can be created. Embodiment Next, a brushless motor according to the present invention will be described with reference to FIGS. In FIG. 1, reference numerals 11 and 12 denote a rotor and a stator constituting a brushless motor. The rotor 11 is provided with a driving magnet unit 13 and a signal record 14 for controlling the rotation position and the number of rotations. The stator 12 is provided with a drive coil 15 and a signal detector (rotation detector) 16 for detecting a signal recorded in the signal recording unit 14. The signal recording unit 14 includes, as shown in FIG.
A film 17 whose reflectivity is changed by irradiation of a laser beam is provided on the outer periphery of the laser beam 11, and a laser beam is applied to the film 17 so that pits 18.
.. 19 are formed. In the embodiment shown in the drawings, the film 17 is formed of a so-called silver salt, and the rotor 11 is sandwiched between a polyvinyl chloride base material 20 and a protective layer 21 of polycarbonate resin.
A laser beam is applied through the protective layer 21 and the portion to which the laser beam is applied is partially melted to lower the reflectivity and the pits 18 for detecting the rotational speed are provided.
And pits 19... 19 for detecting the rotational position are written. FIG. 3 shows a method (apparatus) for writing the pits 18... 18 and 19... 19, in which the rotor 11 for writing the pits is connected to a motor 23 via a rotary encoder 22 and rotated. The output of the rotary encoder 22 is frequency-divided by a frequency divider 24, and pits 18... 18 for detecting the required number of pulses are written on the silver salt film 17.
The pits 19... 19 for detecting the rotational position detect the magnetic pole by a Hall element provided on the magnet surface of the rotor 11 and are written on the film 17 according to the magnetic pole. 25 is a magnetic detector, 26 is a control device, 27 is a laser light source, and 28 is a modulator. 4 to 6 show the signal detector 16 and its circuit diagram. The light of an LED (light emitting diode) 29 is applied to the signal recording unit 14 through a lens 30, and the reflected light from the signal recording unit 14 is applied to a lens 31. The pits 18 ... 18 for detecting the rotational speed and the pits 19 ... 19 for detecting the rotational position are read by the phototransistor 32 and received by the phototransistor 32. The brushless motor of the embodiment is configured as described above, and the rotor 11 is connected to the motor via the rotary encoder 22.
While rotating at 23, the pits 18 ... 18 for detecting the rotational speed and the pits 19 ... 19 for detecting the rotational position are written on the film 17 made of silver halide, so that the rotor 11 assembled as a brushless motor is rotated. Elements that deteriorate the detection accuracy, such as the runout and center runout of the rotor 11 when reading the pits 18 ... 18, 19 ... 19, are canceled, and the accurate rotation speed or This makes it possible to control the rotational position. 7 and 8 show another embodiment of the signal detector 16. In the embodiment shown in FIG. 7, the light of the LED 29 is applied to the signal recording unit 14 through the half mirror 33 and the lens 34, and the signal recording unit 14 is turned on. The reflected light from the lens passes through the lens 34, is reflected by the half mirror 33, is received by the phototransistor 35, and reads the signal recorded on the signal recording surface 14. In the embodiment shown in FIG. 8, the light of the LED 29 is applied to the signal recording surface 14 by the optical fiber 36, and the light applied to the signal recording surface 14 is received by the phototransistor 35 through the optical fiber 36. 9 to 11 show other examples of the pit pattern, and FIG. 9 shows a developed view of the pit pattern of the previous embodiment. The pit pattern in FIG. 10 is the signal recording surface of the rotor 11.
14 shows a case where addresses are assigned over the entire circumference of 14 and the absolute value of the rotation angle is detected by writing the value. FIG. 11 shows that the change in the torque ripple of the motor is written in advance in the pit 37 on the signal recording surface of the rotor 11 so that the current of the motor can be corrected according to the rotation angle, and the characteristics of each motor can be adjusted. By writing data including variations on the signal recording surface in pits, variations in motor characteristics can be reduced. In the embodiment shown in the drawings, a silver salt film is used as the film 17 whose reflectivity changes by irradiation with a laser beam, and a method of applying a laser beam to lower the reflectivity of the portion is adopted. , The reflectivity may be increased by changing the state of the crystal. The light source of the signal detector is not limited to the LED. [Effects of the Invention] As described above, in the present invention, a signal recording portion is formed by irradiating a laser beam on a film whose reflectance changes by irradiating a laser beam and providing pits for detecting the number of rotations and the rotational position. Therefore, the following effects are obtained. (1) Since the pit can be written to a size of about 6 μm, a high pulse of 9400 / revolution can be obtained with a φ36 rotor, and the resolution and accuracy of the rotation speed detection can be improved. In addition, since 83 pit rows can be written per 1 mm width, angle information, triripple information and performance variation information for each motor can be written in addition to rotation speed detection and position detection to improve motor characteristics. it can. (2) Since the reading of the pits for detecting the number of rotations and the pits for detecting the rotational position written in the signal recording section can be centrally performed at one place using the signal detector of the optical system,
The installation space for the signal detector is minimized, and the size of the brushless motor can be reduced. (3) By writing pits while rotating the rotor by a motor via a rotary encoder, elements that deteriorate detection accuracy such as surface runout and core runout of the rotor are cancelled, so that high accuracy is achieved. A pit pattern can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a rotor and a stator of a brushless motor according to the present invention, FIG. 2 is an enlarged perspective view of a part of a signal recording unit, and FIG. FIGS. 4 and 5 are side views of the signal detector, FIG. 5 is a plan view of the same, FIG. 6 is a circuit diagram of the signal detector, and FIGS. 7 and 8 are side views showing other examples of the signal detector. 9 and 11 are developed views showing examples of pit patterns, and FIG. 12 is a perspective view of a rotor and a stator of a conventional brushless motor. 11 ... rotor, 12 ... stator, 13 ... drive magnet part, 14 ... signal recording part, 15 ... drive coil, 16 ... signal detector, 17 ... film whose reflectance changes by laser beam, 18 pits for detecting rotation speed, 19 pits for detecting position.

Claims (1)

(57) [Claims] While a signal recording unit is provided on the rotor side, a signal detector is provided on the stator side, and the signal detector detects a signal recorded in the signal recording unit to control the number of rotations and the rotational position. In a brushless motor, a film whose reflectance changes by irradiating a laser beam is provided on an outer peripheral portion of a rotor, and a laser beam is applied to the film while rotating the rotor by a motor via a rotary encoder, and the number of rotations and rotation positions are determined. A brushless motor, wherein the signal recording section is formed by providing detection pits.