JPH04271251A - Position detector for motor - Google Patents

Abstract

PURPOSE:To get high accuracy in rotation by FG pulses by omitting the magnetic pole detector such as a Hall element, etc., which is the problem in thinning in materializing the thinned motor structure. CONSTITUTION:The FG coil 1 of a position sensor is arranged on a sensor sheet 6, and the PS coil 2 of a reference position sensor, which becomes a reference signal, is arranged at the position, where the pattern of the FG coil 1 of the position sensor is vacant, so that it may not overlap the FG pattern 1, whereby the thickness of the sensor sheet 6 can be minimized. Moreover, when fixing this sensor sheet 6 to the coil 3 of the motor, the magnetic position signal can be gotten by arranging it in the place where it has the phase difference of 30 deg. with the voltage induced by the motor coil 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic pole position sensor for a control brushless motor, and more particularly to detecting the position based on the induced voltage of a coil disposed within the motor without using a Hall element or the like.

0002

2. Description of the Related Art Conventionally, a magnetic pole position detector such as a Hall element has been used on the stator side as a reference signal for controlling the drive winding current of a brushless motor for a VTR. but,
As motors become thinner, it has become difficult to secure a place to mount thick items such as Hall elements. Therefore,
A Hall sensorless drive system has been developed that detects the motor's back electromotive force and uses it as a magnetic pole position signal. This is disclosed in JP-A-52-80414 and JP-A-52-80415.

0003

Problems to be Solved by the Invention Since the above-mentioned prior art Hall element has a thickness of about 2 mm, it is difficult to make the motor thinner. In addition, in the above-mentioned conventional technology, for example, in the case of a three-phase, eight-pole motor, the zero crosses of the three-phase induced voltage occur 24 times in one rotation, so by electrically processing the positions of these zero crosses, 24 Pulse signals can be obtained, but since current is applied to the coil while the motor is driving, the mechanical position and the position that can be detected electrically change depending on the magnitude of the applied current, so the motor rotates with high positional accuracy. It is difficult to do so, and the applications for which it can be used are limited. In addition, when the magnetic pole position signal is created from the induced voltage, the phase of the magnetic pole position signal that is really needed is 30 degrees in electrical angle.
Since the phase is shifted, it is necessary to shift the phase of the current applied to the motor. Normally, this phase correction is designed using a phase correction filter, but when the motor rotation speed changes (when used at variable speed), the constant of the filter must be changed, so it is not used for variable speed applications. Can not.

The purpose of the present invention is to realize a motor with a thickness of 5 mm or less and a value including rotational unevenness and rotational drift of 0.1% or less, by omitting the Hall element having a thickness of about 2 mm. By using a printed coil type position detector, the motor can be made thinner and the position detection accuracy can be increased.

Another method of position detection is to use an FG coil of a position sensor composed of a sheet coil to perform mechanical positioning and to suppress a decrease in position accuracy.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a magnetic pole position is determined by circuit processing using a sensor sheet in which an FG coil as a position sensor and a PS coil as a reference position sensor are arranged on a single thin sheet. The purpose is to obtain a signal equivalent to the signal. In addition, the pattern of the FG coil of the position sensor is set to 1/1 of the magnetization pitch of the permanent magnet so that the third harmonic of the permanent magnet can be detected.
It is set at a pitch of 3. Furthermore, the PS coil of the reference position sensor is provided between the FG coil of the position sensor,
The sensor patterns are arranged so that they do not overlap. Furthermore, in order to simplify circuit processing, the mounting phase of the FG coil is shifted by 30 electrical degrees with respect to the phase of the motor coil. Currently, this sensor sheet can be made with a thickness of 0.1 mm or less by etching a copper foil on a base film and overlaying a protective film as an oxidation-preventing and protective film.

[0007]

[Effect] The third harmonic component, which is included in a large amount in the induced voltage,
By extracting the harmonics using the FG coil of the position sensor, a signal with an electrical angle of 60 degrees can be obtained. Further, the PS coil of the reference position sensor can obtain a signal of 180 electrical degrees. Therefore, this FG signal is used as a clock for a ring counter constructed from a flip-flop circuit.
Further, by inputting the PS signal as data, a continuous magnetic pole position signal can be obtained.

[0008]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 13.

FIG. 3 shows the structure of a motor equipped with the sensor sheet 6 of the present invention. As for the configuration, stator case 2
A permanent magnet 24 is attached to a back yoke 25 that is arranged on a shaft 20 that is free to rotate via a bearing 26. It consists of a yoke 21.

FIG. 4 shows the structure of a motor having a structure similar to that of FIG. The difference from FIG. 3 is that the sensor sheet 6 is attached to a surface of the coil 3 far from the permanent magnet 24. The effects of the present invention can be obtained in either structure.

FIG. 1 shows a three-phase motor with eight poles and six coils as an example of the pattern of the sensor for detecting the position of a motor according to the present invention. The configuration has 12 FG coils 1 of the position sensor on one side of the sensor sheet 6.
Four PS coils 2 of four reference position sensors are arranged between the FG coil and the FG coil of the position sensor, so that the respective coils do not overlap. This is because the sensor sheet 6 is made thin. Further, the three-phase coil arranged in the stator of the motor is composed of two sets of a U-phase coil 3U, a V-phase coil 3V, and a W-phase coil 3W, as shown by dotted lines. As shown in the figure, the FG coil 1 of the position sensor and the PS coil 2 of the reference position sensor have a configuration in which the straight line portion of the FG coil and the straight line portion of the PS coil are parallel and close to each other. Further, the positional relationship between the sensor sheet 6 and the motor coil is as shown in the figure. That is, the arrangement is such that the phase difference between the induced voltage of the motor coil and the induced voltage generated in the FG coil is 30 degrees in electrical angle. In the embodiment of the present invention, an 8-pole permanent magnet was used, so 30 degrees in electrical angle corresponds to 7.5 degrees when converted to mechanical angle. Further, N and S shown in the figure correspond to the magnetic pole positions of the permanent magnets arranged in the rotor of the motor, and are shown overlappingly. In other words, 8
Since they are poles, they are arranged at a pitch of 45 degrees. Figure 2 is Figure 1
This figure similarly shows the pattern of the position detector of the present invention, and the difference from FIG. 1 is the pattern of the PS coil 2 of the reference position sensor. In Figure 1, the FG coil of the position sensor and the PS coil of the reference position sensor are arranged on one side of one sensor sheet, so the PS coil of the reference position sensor must be arranged so that the coils do not overlap. The coil must be wound in short intervals, but since both sides of the sensor sheet 6 are used in FIG. 2, the PS coil of the reference position sensor can be wound in full intervals, making effective use of the magnetic flux of the permanent magnet 24. Can be done.

FIG. 5 shows one sheet 3 as shown in FIG.
2 is a cross-sectional view of a sensor sheet 6 in which an FG coil 1 of a position sensor and a PS coil 2 of a reference position sensor are arranged on one side of the sensor sheet 0. Further, FIG. 6 shows a sheet 30 in which the PS coil 2 of the reference position sensor and the FG coil 1 of the position sensor are formed on separate surfaces as shown in FIG. 2. Further, although not shown in FIG. 7, the sensor sheet 6 is constructed by stacking separately prepared PS coil 2 of the reference position sensor and FG coil 1 of the position sensor on two sheets 30. Although the protective film corresponding to the protective film is omitted in the present invention, it is attached on top of the coil if necessary. Although not shown, it is also possible to create a motor coil on one sheet coil, create an FG coil and a PS coil on another sheet coil, and combine them into one sheet by thermocompression bonding.

FIG. 8 shows P of the reference position sensor explained above.
The configuration of a waveform processing circuit using an S coil 2 and an FG coil 1 of a position sensor is shown. First, the circuit configuration will be explained. Timer 7 consisting of an oscillator, ring counter 8A, PS coil 2 of reference position sensor, and FG coil 1 of position sensor
waveform shaping circuits 12P and 12F, counter 9, monomulti 13, ring counter 8B, and ring counters 8A and 8
It is composed of a switch 10 for switching the B signal, a motor control IC 11 in which speed control and an inverter circuit are integrated into one chip, and a motor coil 3. 9 shows a circuit of the ring counter 8B shown in FIG. 8, which is composed of flip-flop circuits 14, 15, and 16. FIG. 10 shows a timing chart of waveform processing of the FG sensor and PS sensor. In the case of a three-phase motor, the induced voltage in the coil has a sine wave distribution with a phase difference of 120 degrees, as shown in FIG. For such an induced voltage, the maximum torque can be obtained by applying current as shown in the figure at the timing of the W phase, U phase, and V phase. Further, the PS coil 2 of the reference position sensor described above is shifted in phase by 30 electrical degrees with respect to the phase of the induced voltage of the W-phase coil 3W, so that the illustrated PS signal is obtained. Also, FG
The signal is FG to detect the third harmonic in the same phase as the PS signal.
The signals will be as shown. The PS and FG signals generated by the PS coil 2 of the reference position sensor and the FG coil 1 of the position sensor are processed by the waveform shaping circuit 12P shown in FIG.
, 12F to obtain a PS waveform shaped signal and an FG waveform shaped signal. However, the PS waveform shaping circuit 12P uses a comparator with hysteresis to shape the waveform, resulting in a signal that is temporally delayed from the FG signal. Further, as for the FG waveform shaping signal, the monomulti 13 generates an FG edge signal using the rising and falling edges of the FG waveform shaping signal. By inputting this to the ring counter 8B of FIG. 9 described earlier, the output signals of Q1 to Q3 can be obtained. control IC
(For example, HA13440MP commercially available from Hitachi) allows the current waveform shown in FIG. 10 to flow through the motor coil with waveforms Q1 to Q3.

Next, starting the motor will be explained using FIGS. 8 and 11 to 13. Timer 7 (HA
17555, etc.), a clock pulse corresponding to a speed command as shown in FIG. 13 is output to the ring counter 8A. The pattern shown in FIG. 13 is arbitrarily determined depending on the load and inertia of the motor. ring counter 8A
Since it is constituted by the circuit shown in FIG. 9, it is possible to obtain waveforms similar to those of Q1 to Q3 shown in FIG. 10. At startup, since the rotational speed is low, the signal output from the waveform shaping circuit 12P to the counter 9 has a low frequency, so the switching signal of the counter 9 is selected from the synchronizing signals QA to QC and input to the control IC. The speed of the motor thereby increases. Next, when the speed of the motor reaches the switching speed, the frequency of the pulses input to the counter 9 becomes the switching frequency, and the switch 10 selects Q3 from Q1 and sends a signal to the control IC. This increases the motor speed to the specified rotational speed. The situation is shown in FIG. The "H" portion of the synchronization signal and creation signal indicates the time when that signal is selected. Further, FIG. 12 shows a case where the switching is not performed at the speed of the motor, but after a certain period of time. In this case as well, when the synchronization signal and the creation signal are "H", it indicates the time when that signal is selected.

According to the embodiment of the present invention, the FG coil of the position sensor and the PS coil of the reference position sensor are fabricated on a single thin sheet for the motor position detector, thereby making it possible to reduce the thickness of the motor structure. be. This makes it possible to reduce the price of the sensor. Further, by winding the PS coil at full pitch with respect to the FG coil, there is an effect that the sensitivity of the sensor can be improved. In addition, a position sensor F is used to detect the speed and position of the motor.
Since the signal from the G coil is used, highly accurate phase control is possible. Furthermore, in low-frequency synchronous startup, by selecting an acceleration pattern based on the load inertia of the motor, smooth startup without step-out can be achieved.

[0016] By arranging the sensor sheet that constitutes the FG coil of the position sensor and the PS coil of the reference position sensor between the coil and the permanent magnet, the third harmonic can be effectively absorbed by the magnetic field distribution containing a large amount of the third harmonic. can be detected.

Further, the FG coil 1 of the position sensor is arranged on the sensor sheet 6, and the FG coil 1 of the position sensor is arranged on the sensor sheet 6.
By arranging the PS coil 2 of the reference position sensor, which serves as a reference signal, in the vacant part of the pattern so as not to overlap the FG pattern 1, the thickness of the sensor sheet 6 can be minimized. Further, when the sensor sheet 6 is fixed to the coil 3 of the motor, a magnetic pole position signal can be obtained by placing it at a position having a phase difference of 30 degrees from the induced voltage of the motor coil 3.

[0018]

According to the present invention, in order to realize a motor with a thickness of 5 mm or less, the Hall element having a thickness of about 2 mm is omitted and a printed coil type position detector is used to reduce the thickness of the motor. This has the effect of increasing the accuracy of position detection.

Furthermore, since the FG coil of the position sensor composed of a sheet coil is used for position detection, the positioning can be performed mechanically with respect to the motor coil, which has the effect of improving positional accuracy.

Furthermore, the structure of the motor can be simplified by using the magnetic flux of the main permanent magnet without using a dedicated magnet for the sensor.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram showing a position detector according to an embodiment of the present invention.

FIG. 2 is a pattern diagram of a position detector showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view when the position detector of the present invention is arranged on a motor.

FIG. 4 is a cross-sectional view when the position detector of the present invention is arranged on a motor.

FIG. 5 is a cross-sectional view showing the configuration of a sensor sheet.

FIG. 6 is a cross-sectional view showing the configuration of a sensor sheet.

FIG. 7 is a cross-sectional view showing the configuration of a sensor sheet.

FIG. 8: Waveform processing circuit.

FIG. 9 is a circuit diagram configuring the ring counter shown in FIG. 8.

FIG. 10 is a timing chart of waveform processing of the FG sensor and PS sensor.

FIG. 11 is a timing chart when switching from synchronous startup.

FIG. 12 is a timing chart when switching from synchronous startup.

FIG. 13 is a pattern diagram showing an acceleration pattern during synchronous startup.

[Explanation of symbols]

1...FG coil, 2...PS coil, 3...motor coil,
6...Sensor sheet, 7...Timer, 8...Ring counter,
9...Counter, 10...Switch, 11...Control I
C, 12... Waveform shaping circuit, 13... Mono multi, 14-1
6...Flip-flop circuit, 20...Shaft, 21...Yoke, 23...Rotor, 24...Permanent magnet, 25...Back yoke, 26...Bearing, 27...Case, 30...Seat.

Claims (13)

[Claims] Claim 1: In a motor equipped with a position and reference position sensor and a permanent magnet, an FG coil of the position sensor and a PS coil of the reference position sensor are configured on the same substrate, and
A motor position detector characterized in that this board is placed between the stator and rotor of the motor. 2. The FG coil which is the position sensor according to claim 1 has a coil pattern having a pitch that is 1/3 of the magnetized pitch of the permanent magnet, and the PS coil which is the reference position sensor is used as the position sensor. A motor position detector characterized in that the motor position detector is arranged closely between the FG patterns. 3. The PS coil of the reference position sensor and the FG coil of the position sensor according to claim 1 are arranged such that the PS coil of the reference position sensor is arranged on one side of one sheet, and the FG coil of the position sensor is arranged on the other side. A motor position detector characterized in that it is arranged on the surface of the motor. 4. A sensor sheet made from the FG coil of the position sensor and the PS coil of the reference position sensor according to claim 1 is arranged between a motor coil and a permanent magnet, and the FG coil is set at an electrical angle with respect to the motor coil. A motor position detector characterized in that the motor position detector is arranged at a 30 degree offset. 5. The motor position detector according to claim 4, wherein the sensor sheet is arranged on the surface of the coil near the permanent magnet. 6. In a brushless motor equipped with a position and reference position sensor, the brushless motor is controlled by using an FG pulse obtained from an FG coil of the position sensor based on a PS pulse obtained from a PS coil of the reference position sensor. A motor position detector characterized in that it generates a magnetic pole position signal. [Claim 7] The brushless motor according to claim 6 is created based on signals obtained from the FG coil and the PS coil after the rotation speed reaches a certain value by using low frequency synchronous starting when starting the motor. A motor position detector characterized by switching to a magnetic pole position signal. 8. The brushless motor according to claim 6 uses low frequency synchronous startup when starting the motor, and after a certain period of time has elapsed, a magnetic pole position signal is generated based on signals obtained from the FG coil and the PS coil. A motor position detector characterized by switching to. 9. A motor position detector, wherein the low frequency synchronous start operation pattern according to claim 7 changes the acceleration frequency depending on the load condition of the motor. 10. A motor position detector, wherein the FG coil of the position sensor and the PS coil of the reference position sensor according to claim 1 are formed on one sheet by etching. 11. The FG coil of the position sensor and the PS coil of the reference position sensor according to claim 1 are made separately from at least two sheets and made into one sensor sheet by thermal compression or the like. motor position detector. 12. A position detector for a motor, characterized in that the ratio of the motor coil according to claim 1, the FG coil of the position sensor, and the PS coil of the reference position sensor is 3:6:2. 13. A motor position detector characterized in that the FG coil of the position sensor according to claim 1, the PS coil of the reference position sensor, and the motor coil are formed into one sheet coil.