JPH09294354A - Permanent-magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the demagnetized state of a permanent magnet to be monitored in real time and to make it possible to quickly respond to the abatement of generated torque. SOLUTION: A voltage detecting circuit 13 outputs a voltage signal Vd corresponding to the line-to-line voltage of the coil 2 of W phase. In this voltage signal Vd, a voltage induced in the coil 2 as a permanent-magnet rotor rotates is contained in a state of being superimposed in a power source voltage. A magnetic flux computing circuit 14 samples the voltage signal Vd during a period of time when the power source voltage is not impressed to the coil 2 of W phase, determines the levels of voltage constituents induced in the coil 2 as a permanent-magnet rotor rotates, based on the sampling signal and calculates the levels of the magnetic flux from the permanentmagnet rotor according to the difference in the determined levels. A comparing circuit 16 compares the data of the computed magnetic flux levels with an initial value or designated value stored in a memory 15 to output an alarm signal Sa. when the ratio of the data of the magnetic flux to the initial value (or the designated value) is less than a preset reduction ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet motor having a permanent magnet rotor arranged in a field space formed by a stator.

[0002]

In the permanent magnet motor, it is unavoidable that the permanent magnet is demagnetized with the lapse of time, and when such demagnetization progresses, the generated torque is reduced. It may lead to a loss of operation in some cases. Therefore, it is desirable to take some measures against demagnetization of the permanent magnet.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an effect such that the demagnetized state of a permanent magnet can be monitored in real time, and a decrease in generated torque can be quickly dealt with. It is to provide a permanent magnet motor.

[0004]

According to the first aspect of the present invention,
In a permanent magnet motor including a stator provided with a field coil and a permanent magnet rotor arranged in a field space of the stator, a voltage for detecting a voltage induced by the rotation of the permanent magnet rotor. Detecting means, calculating means for calculating the magnetic flux level from the permanent magnet rotor based on the detection output by the voltage detecting means, and outputting an alarm signal when the magnetic flux level obtained by the calculating means falls below a set level. And a comparison means for performing the comparison.

According to this structure, the detection output of the voltage detecting means, that is, the voltage induced by the rotation of the permanent magnet rotor shows a higher value as the magnetic flux level of the permanent magnet increases. The calculating means calculates the magnetic flux level from the permanent magnet based on the detection output as described above, and the comparing means outputs the alarm signal when the calculation result becomes equal to or lower than the set level. Therefore, the demagnetization state of the permanent magnet
It is possible to monitor in real time based on the above-mentioned alarm signal, which makes it possible to promptly deal with the situation where the generated torque is reduced beyond the limit.

In this case, the calculating means may be configured to calculate the magnetic flux level from the permanent magnet by utilizing the detection output of the voltage detecting means and the speed detecting means and the rotational speed information of the permanent magnet rotor. (Claim 2). According to this configuration, when the magnetic flux level is calculated by the calculating means, it is possible to cope with the phenomenon that the voltage induced by the rotation of the permanent magnet rotor increases as the rotation speed increases. The calculation accuracy of can be improved.

The voltage detecting means may be configured to detect the induced voltage of the coil (claim 3), and the voltage detecting means may be a search coil wound around the teeth of the stator, or A search coil wound with the coil can be used (claim 4).

The calculation of the magnetic flux level by the calculating means is
A configuration may be adopted in which the power supply voltage applied to the coil is zero or a period close to zero (claim 5). According to this configuration, when the magnetic flux level is calculated based on the output detected by the voltage detection means, the influence of the component based on the voltage applied to the coil can be ignored, and therefore the calculation process can be simplified.

Further, the application of the power supply voltage to the coil is stopped for a predetermined short time, and then the magnetic flux level is calculated by the calculating means during the period when the voltage application is stopped. Good (Claim 6). With this configuration, when the magnetic flux level is calculated based on the output detected by the voltage detecting means, the influence of the component based on the voltage applied to the coil can be ignored, and the calculation process can be simplified.

Further, after the standard operation mode for applying a predetermined standard power supply voltage to the coil is provided, the magnetic flux level is calculated by the calculating means during the period in the standard operation mode. It may be configured (Claim 7). Also in this configuration, when the magnetic flux level is calculated based on the detection output of the voltage detecting means, the influence of the component based on the voltage applied to the coil can be made to be a constant level, so that the calculation process can be simplified. become.

In place of the voltage detecting means, a magnetic sensor for outputting a voltage signal of a level corresponding to the magnetic flux from the permanent magnet rotor is provided, and the calculating means is based on the detection output of the magnetic sensor. The magnetic flux level from the permanent magnet rotor may be calculated (claim 8). With this configuration, the magnetic flux level from the permanent magnet can be reliably detected regardless of the rotation speed of the permanent magnet rotor.

Further, after the calculating means is configured to calculate the magnetic flux level every time a set time has elapsed,
A storage means for sequentially storing and saving the calculation results of the calculation means may be provided (claim 9). According to this configuration, the demagnetized state of the permanent magnet can be confirmed based on the time-series stored data, so that it is possible to deal with the situation in which the generated torque declines beyond the limit in advance.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment in which the present invention is applied to an inverter-integrated brushless motor will now be described with reference to FIG.
This will be described with reference to FIG. Referring to FIG. 2 showing the overall schematic sectional structure, a brushless motor 1 which is a permanent magnet motor has a stator 3 provided with a field three-phase coil 2 for forming a rotating magnetic field arranged in a frame 4. The permanent magnet rotor 5 is arranged in the field space defined by the coil 2. In this case, the permanent magnet rotor 5 has a configuration in which the permanent magnet 7 magnetized to have even poles is arranged around the shaft 6. An inverter unit 8 is integrally attached to the outer surface of the frame 4, and the inverter unit 8 is connected to the coil 2
It is configured to be energized to.

In FIG. 1 showing the electrical structure, an inverter unit 8 includes a rectifier circuit section 10 for converting the output of a three-phase AC power source 9 into a direct current, an inverter main circuit 11 for chopping the direct current output, and A base control circuit 12 for on / off controlling the power transistors Tr1 to Tr6 in the inverter main circuit 11 is provided.

In this case, the inverter main circuit 11 is
The power transistors Tr1 to Tr6 are configured by three-phase bridge connection, and output terminals Pu, Pv for each phase,
Pw is connected to each power supply terminal of the star-connected coil 2.

The base control circuit 12 includes a CPU, and drives the inverter main circuit 11 by, for example, a sine wave pulse width modulation method in a state where a speed command is given from an operation circuit (not shown). The coil 2 is energized, and a variable speed operation of the brushless motor 1 is performed according to such energization. A position sensor such as a Hall element can be used to control the energization timing of the coil 2 as described above, but so-called sensorless driving using the induced voltage phase in the coil 2 of each phase is also possible.

The voltage detection circuit 13 corresponding to the voltage detection means in the present invention is for detecting the line voltage of the coil 2 of a predetermined phase, for example, between the output terminal Pw of the W phase and the ground terminal. The sampling resistors 13a and 13b are connected in series with each other, and the voltage signal Vd indicating the line voltage is output from the common connection point of the resistors 13a and 13b. In order to realize the voltage detection function by the voltage detection circuit 13 as described above, the inverter main circuit 11
The power line on the negative side of is connected to the ground terminal.

In this case, in the voltage signal Vd, the voltage induced in the coil 2 with the rotation of the permanent magnet rotor 5 appears in a state of being superimposed on the output voltage of the inverter unit 8. Specifically, when the coil 2 has a well-known two-phase simultaneous energization, the voltage signal Vd shown in FIG.
The waveform is as shown in FIG. In FIG. 3, when two phases are simultaneously energized, a period It during which no current flows in the W-phase coil 2 appears twice at intervals of about 60 ° in one cycle. By sampling Vd, the induced voltage of the W-phase coil 2 can be obtained.

The voltage signal Vd from the voltage detection circuit 13
The magnetic flux calculation circuit 14 (corresponding to the calculation means in the present invention) which receives the voltage samples the voltage signal Vd in the above period It based on the control signal from the base control circuit 12. In this case, the sampling target may be the peak value of the voltage signal Vd, but may be the average value or the effective value.

Then, the magnetic flux calculation circuit 14 determines the level of the voltage component induced in the coil 2 as the permanent magnet rotor 5 rotates based on the sampling signal, and the magnetic flux operation circuit 14 determines whether the level of the determination is permanent. The magnetic flux level from the magnet rotor 5 is calculated. The calculation of the magnetic flux level as described above is performed by utilizing the characteristic that the voltage induced by the rotation of the permanent magnet rotor 5 is higher as the magnetic flux level from the permanent magnet 7 is higher. is there.

The magnetic flux calculation circuit 14 calculates the magnetic flux level as described above for a set time (for example, 500 to 100).
It is configured to be performed every time (0 hours) has elapsed, and the calculation result is sequentially stored and stored in the memory 15 (corresponding to the storage means in the present invention).

In the memory 15, in addition to the calculation data by the magnetic flux calculation circuit 14 as described above, the permanent magnet rotor 5 is also included.
The initial value of the magnetic flux level from or the preset specified value is stored.

The comparison circuit 16 (corresponding to the comparison means in the present invention) which receives the magnetic flux level data calculated by the magnetic flux calculation circuit 14 and the magnetic flux level data and the initial value (or designated value) stored in the memory 15 When the ratio of the magnetic flux level data to the initial value (or specified value) is less than or equal to the preset decrease ratio, the alarm signal S
It is configured to output a.

The warning circuit 17 is configured to notify, through a display means such as a light emitting diode, that the permanent magnet 7 is in a demagnetized state exceeding the limit when the warning signal Sa is output. ing.

The alarm signal Sa is also supplied to the base control circuit 12 in the inverter unit 8, and the base control circuit 12 supplies a current to the coil 2, for example, when the alarm signal Sa is received. Is increased to increase the torque generated by the brushless motor 1. It should be noted that if the generated torque becomes insufficient even by such control, control for stopping the energization of the coil 2 may be performed.

In short, according to the configuration of this embodiment described above, the magnetic flux level from the permanent magnet 7 calculated by the magnetic flux calculation circuit 14 is set to the set level (initial value (or specified value)).
On the other hand, the warning signal Sa is output when it becomes less than or equal to a level obtained by multiplying a preset reduction ratio), and the fact is notified through the warning circuit 17. By such notification, it becomes possible to monitor the demagnetization state of the permanent magnet 7 in real time, whereby it is possible to promptly deal with the state in which the torque generated by the brushless motor 1 is reduced beyond the limit. Specifically, in this embodiment, the alarm signal Sa
Is output, the control is performed by increasing the torque generated by the brushless motor 1 on the inverter unit 8 side.

In this case, in this embodiment, the magnetic flux calculation circuit 1
Since the calculation of the magnetic flux level by 4 is performed on the basis of the voltage signal Vd output when the power supply voltage applied to the coil 2 is zero or at a level close to zero, at the time of the above calculation, The influence of the component based on the applied voltage to the coil 2 can be ignored, and the calculation process can be simplified.

Furthermore, in this embodiment, the magnetic flux level is calculated by the magnetic flux calculation circuit 14 every time the set time (500 to 1000 hours) elapses, and the calculation result is sequentially stored in the memory 15. It has characteristics. According to this structure, the demagnetized state of the permanent magnet 7 is stored in the memory 15
Since it can be confirmed based on the stored data, that is, the time-series stored data, it is possible to deal in advance with the situation where the torque generated by the brushless motor 1 declines beyond the limit.

In the first embodiment, the magnetic flux calculation circuit 14, the memory 15, the comparison circuit 16 and the warning circuit 17 are also provided.
Base control circuit 1 configured to include the function of
It is possible to implement it by using the program of 2.
When such a configuration is adopted, the overall configuration can be greatly simplified.

In the first embodiment, the magnetic flux calculation circuit 1 is changed from the base control circuit 12 on the inverter unit 8 side.
4 is set so that the rotation speed information of the permanent magnet rotor 5 is given, and then the magnetic flux calculation circuit 14 outputs the rotation speed information from the voltage detection circuit 13 when the rotation speed information indicates the set speed. The magnetic flux level may be calculated based on the voltage signal Vd.

According to this configuration, when the magnetic flux level is calculated by the magnetic flux calculation circuit 14, the level of the voltage signal Vd from the voltage detection circuit 13 increases as the rotation speed of the permanent magnet rotor 5 increases. Since the influence of the phenomenon can be removed, it is possible to improve the calculation accuracy of the magnetic flux level. In this case, in order to obtain the rotation speed information of the permanent magnet rotor 5, a rotation speed detecting means for directly detecting the rotation speed may be separately provided.

Further, during the control period by the inverter unit 8, after setting the period for stopping the application of the power supply voltage to the coil 2 for a predetermined short time, the magnetic flux level is calculated by the magnetic flux calculation circuit 14 by applying the voltage. Voltage signal V from the voltage detection circuit 13 during the period in which the
The configuration may be performed based on d.

With such a configuration, the coil 2 is operated when the magnetic flux level is calculated by the magnetic flux calculation circuit 14.
The influence of the component on the basis of the applied voltage can be ignored, and the arithmetic processing can be simplified.

Further, during the control period by the inverter unit 8, a standard operation mode in which a predetermined standard power supply voltage is applied to the coil 2 is set and the magnetic flux level is calculated by the magnetic flux calculation circuit 14 in the standard operation. The configuration may be performed during the period in the mode. Also with this configuration, when the magnetic flux level is calculated by the magnetic flux calculation circuit 14, the influence of the component based on the voltage applied to the coil 2 can be set to a constant level, so that the calculation process can be simplified.

In the first embodiment described above, the magnetic flux level is calculated based on the induced voltage of the coil 2. However, as shown in FIG. 4 showing the second embodiment of the present invention, the teeth 3a of the stator 3 are By the wound search coil 18,
The voltage induced by the rotation of the permanent magnet rotor 5 may be detected, and the magnetic flux level may be calculated based on the detected output. In this case, the search coil 1
8 may be wound together with the coil 2, or a plurality of search coils 18 may be provided.

Further, as shown in FIG. 5 showing the third embodiment of the present invention, instead of the voltage detection circuit 13 in the first embodiment, a gap between the stator 3 and the permanent magnet rotor 5 is provided.
A magnetic sensor 19 (for example, a Hall element) that outputs a voltage signal at a level corresponding to the magnetic flux from the permanent magnet 7 may be arranged, and the voltage signal from the magnetic sensor 19 may be used for calculation by the magnetic flux calculation circuit 14. According to this configuration, there is an advantage that the magnetic flux level from the permanent magnet 7 can be reliably detected regardless of the rotation speed of the permanent magnet rotor 5.

FIG. 6 shows a fourth embodiment of the present invention, and only the parts different from the first embodiment will be described below. The temperature sensor 20 is provided at a position where the temperature of the permanent magnet rotor 5 can be indirectly detected, and the detection output thereof is given to the comparison circuit 16 '. The comparison circuit 16 'stores the magnetic flux level data calculated by the magnetic flux calculation circuit 14 in the memory 15 when the temperatures of the permanent magnet rotor 5 and the motor indicated by the detection output of the temperature sensor 20 suddenly rise. It is configured to perform an alarm signal output operation by comparing with an initial value or a designated value (these values are corrected by the temperature rise amount). According to this configuration, it is possible to accurately check the demagnetization state under the situation where the demagnetization of the permanent magnet 7 is likely to proceed.

Further, means for detecting the level of the load current flowing through the coil 2 is provided, and when the current level detected by this means becomes excessive, the comparison circuit 1 as described above is provided.
Even if the comparison operation by 6'is performed, the demagnetization status of the permanent magnet can be accurately checked.

The present invention is not limited to the above embodiment, and the following modifications and expansions are possible.
For example, in a free-running state of the permanent magnet rotor 5 after the coil 2 is cut off, the magnetic flux level is calculated based on the voltage induced in the coil 2 when the rotation speed reaches a predetermined value. can do. Not only the brushless motor but also other permanent magnet motors such as a step motor can be applied.

[0040]

According to the present invention, as apparent from the above description, the magnetic flux level from the permanent magnet rotor is calculated based on the voltage induced by the rotation of the permanent magnet rotor, and the calculation is performed in this way. Since the alarm signal is output when the generated magnetic flux level falls below the set level, it is possible to monitor the demagnetization state of the permanent magnets in real time, and it is possible to quickly deal with the decrease in generated torque. Can be played.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view.

FIG. 3 is a waveform diagram of a coil line voltage.

FIG. 4 is a schematic cross-sectional view of a main part showing a second embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of essential parts showing a third embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1 showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 is a brushless motor (permanent magnet motor), 2 is a coil, 3 is a stator, 5 is a permanent magnet rotor, 7 is a permanent magnet, 13 is a voltage detection circuit (voltage detection means), 14 is a magnetic flux calculation circuit (calculation means), 15 is a memory (storage means), 1
Reference numerals 6 and 16 'are comparison circuits (comparison means), 18 is a search coil, and 19 is a magnetic sensor.

Claims (9)

[Claims] 1. A permanent magnet motor comprising a stator provided with a field coil and a permanent magnet rotor arranged in a field space of the stator, the permanent magnet motor being induced by rotation of the permanent magnet rotor. Voltage detecting means for detecting the voltage, calculating means for calculating the magnetic flux level from the permanent magnet rotor based on the detection output by the voltage detecting means, and when the magnetic flux level obtained by the calculating means is below a set level A permanent magnet motor, comprising: a comparison means for outputting an alarm signal to the. 2. The calculating means is configured to calculate the magnetic flux level from the permanent magnet by utilizing the detection output of the voltage detecting means and the rotational speed information of the permanent magnet rotor. The permanent magnet motor according to claim 1. 3. The permanent magnet motor according to claim 1, wherein the voltage detecting means is configured to detect an induced voltage of the coil. 4. The voltage detecting means comprises a search coil wound around a tooth of the stator, or a search coil wound together with the coil. 2. The permanent magnet motor according to 2. 5. The calculation of the magnetic flux level by the calculating means is configured to be performed during a period in which the power supply voltage applied to the coil is zero or a level close to zero. 4. The permanent magnet motor according to any one of 4 above. 6. The application of the power supply voltage to the coil is stopped for a predetermined short time, and the calculation of the magnetic flux level by the calculating means is performed during the period when the voltage application is stopped. The permanent magnet motor according to any one of claims 1 to 4, characterized in that: 7. A standard operation mode for applying a predetermined standard power supply voltage to the coil, wherein the calculation of the magnetic flux level by the calculation means is performed during a period in the standard operation mode state. The permanent magnet motor according to any one of claims 1 to 4, wherein the permanent magnet motor is provided. 8. A magnetic sensor that outputs a voltage signal of a level according to the magnetic flux from the permanent magnet rotor is provided in place of the voltage detection means, and the computing means is based on the detection output of the magnetic sensor. The permanent magnet motor according to claim 1, wherein the permanent magnet motor is configured to calculate a magnetic flux level from the permanent magnet rotor. 9. The calculating means is configured to calculate the magnetic flux level each time a set time has elapsed, and is provided with storage means for sequentially storing and storing the calculation results of the calculating means. Claims 1 to 8
The permanent magnet motor according to any one of 1.