JP2010226914A - Motor control apparatus, drum-type washing machine and method for controlling magnetization of permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control apparatus capable of suppressing unexpected magnetization or demagnetization, without in a permanent magnet arranged in a rotor during the operation of a motor. <P>SOLUTION: A magnetization-change suppressor 69 prevents demagnetization of the permanent magnet 9b arranged to the rotor 3 for the motor 1, because a magnetization-current command Id<SB>-</SB>com3 is output so that an exciting current Id is made to flow, at the same time, when the level of a torque current Iq exceeds a specified threshold, thus improving the operational efficiency of the motor 1. In this case, the magnetization-change suppressor 69 determines the magnetization-current command Id<SB>-</SB>com3 by Id<SB>-</SB>com3=(Iq-a)×b (for Iq>a) and increases the level of the exciting current Id to be superimposed, in response to the increase in the level of the torque current Iq. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor control device that controls a permanent magnet motor in which a permanent magnet having a low coercive force so that the amount of magnetization can be changed is arranged in a rotor, and detects a current flowing through the motor to perform vector control. The present invention also relates to a drum-type washing machine that includes a motor control device and rotates a drum by a permanent magnet motor to perform a washing operation, and a magnetization control method for the permanent magnet motor.

  In recent years, in washing machines, the rotational accuracy is improved by vector-controlling the motor and rotating the drums etc. by the direct drive method, thereby improving washing performance and reducing vibration and noise during operation. The structure which obtains is adopted. In such a configuration, when the drum is rotated at a high speed as in the dehydrating operation, a d-axis current that does not contribute to the torque output of the motor is applied to reduce the induced voltage generated in the stator winding. Field control is performed. However, in the field weakening control, the copper loss increases when the d-axis current is applied, so a reduction in drive efficiency is inevitable.

  On the other hand, in Japanese Patent Application No. 2008-266386, the applicant arranges a permanent magnet having a weak holding force on the rotor side of a 48-pole / 36-slot motor, and applies a large current to the stator winding for a moment. By demagnetizing the permanent magnet and reducing the magnetic flux of the permanent magnet to reduce the induced voltage generated in the motor, a technology has been proposed that enables high-speed operation without performing field-weakening control. An example of a permanent magnet motor having the above structure is disclosed in Patent Document 1.

JP 2006-280195 A

  However, if the amount of magnetization of the permanent magnet is changed as in the above application, depending on the structure of the motor, the permanent magnet may increase or decrease even when the q-axis current is applied to generate torque. understood. FIG. 10 shows an actual measurement result. It is assumed that the permanent magnet is magnetized in order to perform the washing operation in the washing machine, and the magnetizing level is 100% in the initial state. When the operation is started from this state, the maximum q-axis current flows, for example, about 6 A to 7 A when the motor is started, but the magnetized state of the permanent magnet is reduced to 91.8% by this maximum current. In the washing operation, the q-axis current when the motor is rotated at a constant speed is, for example, about 3A to 4A. However, since the magnetized state of the permanent magnet continues to decrease as described above, the operation efficiency decreases. End up.

Since high torque output is required during washing operation of the washing machine, it is desirable that the generated induced voltage is large. However, if the permanent magnet is demagnetized by applying the q-axis current, more q-axis current must be supplied. As a result, a desired torque output cannot be obtained, resulting in an increase in current consumption.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device that can suppress unintentional magnetization or demagnetization of a permanent magnet during operation of the motor, and the device. It is an object of the present invention to provide a magnetization control method for a drum type washing machine and a permanent magnet motor.

In order to achieve the above object, the motor control device according to claim 1 is directed to a permanent magnet motor in which a permanent magnet having a coercive force that is low enough to change the amount of magnetization is arranged on the rotor, and the motor is controlled. In which the current flowing through is detected and vector controlled,
Position detecting means for detecting the rotational position of the motor;
Magnetizing means for magnetizing or demagnetizing the permanent magnet according to the rotational position of the motor by adjusting the magnetization state of the permanent magnet by an armature reaction magnetic field;
When a q-axis current (torque current) is supplied to the motor winding in a state where the permanent magnet is magnetized by the magnetizing means, a period for superimposing the d-axis current (excitation current) is provided. Magnetization change suppression means for suppressing change in the magnetization state of the permanent magnet is provided.

  A drum-type washing machine according to claim 5 includes the permanent magnet motor and the motor control device according to any one of claims 1 to 4, and the laundry is washed by a rotational driving force generated by the motor. The washing operation is performed by rotating the drum to be accommodated.

According to a sixth aspect of the present invention, there is provided a permanent magnet motor magnetizing control method, wherein a permanent magnet motor having a rotor having a coercive force having a low coercive force so that the amount of magnetization can be changed is controlled. To detect the current flowing through the
By detecting the rotational position of the motor and adjusting the magnetization state of the permanent magnet with an armature reaction magnetic field, the permanent magnet is magnetized according to the rotational position of the motor,
When a q-axis current (torque current) is supplied to the motor winding in a state where the permanent magnet is magnetized, the magnetizing level is lowered by providing a period in which the d-axis current (excitation current) is superimposed. It is characterized by suppressing.

According to the magnetization control method of the motor control device or the permanent magnet motor of the present invention, it is possible to suppress the change in the magnetization state of the permanent magnets arranged on the rotor, so that the permanent magnet motor can be driven with high efficiency.
According to the drum type washing machine of the present invention, the motor control device of the present invention is provided, and the drum is rotated by the rotational driving force generated by the permanent magnet motor to perform the washing operation with high efficiency, and the power consumption can be suppressed.

1 is a functional block diagram showing an electrical configuration of a motor control device according to a first embodiment of the present invention. (A) is a top view which shows the structure of the rotor of a permanent magnet motor, (b) is a perspective view which shows the same part. Longitudinal side view schematically showing the internal structure of the drum type washing and drying machine Diagram showing the configuration of the heat pump The figure which shows typically the state from which the position of the clothing accommodated in the drum changes at the time of washing operation. (A) Rotational speed and torque during washing operation, (b) Torque current Iq, (c) Motor magnetic flux amount The figure which shows the exciting current Id energized according to the value of the torque current Iq The figure which shows the improvement result of the demagnetization state shown in FIG. FIG. 1 equivalent view showing a second embodiment of the present invention. The figure explaining the problem of the prior art

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 2A is a plan view showing the configuration of the rotor of the permanent magnet motor 1 (outer rotor type brushless motor), and FIG. 2B is a partial perspective view. In addition, this permanent magnet motor 1 comprises a motor having the same characteristics as those disclosed in Patent Document 1 as an outer rotor type.

The permanent magnet motor 1 includes a stator 2 and a rotor 3 provided on the outer periphery thereof. The stator 2 includes a stator core 4 and a stator winding 5. The stator core 4 is formed by laminating and caulking a number of silicon steel plates, which are punched and formed of soft magnetic materials. Teeth portion 4b. The surface of the stator core 4 is covered with PET resin (mold resin), except for the outer peripheral surface (tip surface of each tooth portion 4b) that forms a gap with the inner peripheral surface of the rotor 3.
A plurality of mounting portions 6 made of this PET resin are integrally formed on the inner peripheral portion of the stator 2. These attachment portions 6 are provided with a plurality of screw holes 6a, and by fixing these attachment portions 6 to the stator 2, the stator 2 in this case is provided in the water tank 25 (see FIG. 3) of the drum type washing and drying machine 21. It is designed to be fixed to the back. The stator winding 5 consists of three phases and is wound around each tooth portion 4b.

  The rotor 3 has a configuration in which the frame 7, the rotor core 8, and the plurality of permanent magnets 9 are integrated with a mold resin (not shown). The frame 7 is formed into a flat bottomed cylindrical shape by pressing, for example, an iron plate that is a magnetic material. The rotor core 8 is configured by laminating and caulking a large number of silicon steel plates, which are soft magnetic materials punched and formed in a substantially annular shape, and is disposed on the inner peripheral portion of the frame 7. The inner peripheral surface of the rotor core 8 (the surface that faces the outer peripheral surface of the stator 2 (the outer peripheral surface of the stator core 4) and forms a gap between the stator 2) has a plurality of arcs extending inward. It is formed in a concavo-convex shape having a convex portion 8a.

  A rectangular insertion hole 13 that penetrates the rotor core 8 in the axial direction (lamination direction of the silicon steel plates) is formed inside the plurality of convex portions 8a. The plurality of insertion holes 13 are annularly formed in the rotor core 8. It is an arranged configuration. The plurality of insertion holes 13 are composed of two types of insertion holes 13 a and 13 b having different short sides. The insertion holes 13 a and 13 b are arranged one by one along the circumferential direction of the rotor core 8. Alternatingly arranged.

The permanent magnet 9 is composed of a rectangular neodymium magnet 9a (high coercive force permanent magnet) inserted into the insertion hole 13a and a rectangular alnico magnet 9b (low coercive force permanent magnet) inserted into the insertion hole 13b. ing. In this case, the coercive force of the neodymium magnet 9a is about 900 kA / m, the coercive force of the alnico magnet 9b is about 100 kA / m, and the coercive force differs by about 9 times. That is, the permanent magnet 9 is composed of two types of permanent magnets 9a and 9b having different coercive forces, and these permanent magnets 9a and 9b are arranged in a ring shape and one by one in the rotor core 8.
The neodymium magnet 9a has a high coercive force, and the alnico magnet 9b has a low coercive force. The magnetizing amount of the alnico magnet 9b is increased when a magnetizing current is applied through the stator 2 as will be described later. On the basis that the amount of magnetization of the neodymium magnet 9a does not change with a current that can be changed, the former is referred to as high coercivity and the latter is referred to as low coercivity.

Each of these two types of permanent magnets 9a and 9b forms one magnetic pole, and the magnetization direction thereof is the radial direction of the permanent magnet motor 1 (from the outer periphery of the permanent magnet motor 1 to the stator 2 and the rotor 3). It is arrange | positioned along the direction toward the space | gap between. In this way, by arranging the two types of permanent magnets 9a and 9b alternately so that their magnetization directions are along the radial direction, the adjacent permanent magnets 9a and 9b have magnetic poles in opposite directions. A state (a state in which one N pole is on the inside and the other N pole is on the outside) is generated, and a magnetic path (magnetic flux) is generated between the neodymium magnet 9a and the alnico magnet 9b in the direction indicated by the arrow B, for example.
In addition, the arrow shown by the upper broken line is a magnetic flux passing through the rotor core 8. That is, a magnetic path passing through both the neodymium magnet 9a having a large coercive force and the alnico magnet 9b having a small coercive force is formed. The permanent magnet motor 1 has a 48 pole / 36 slot configuration, and 4 poles correspond to 3 slots (4 poles / 3 slots).

  Next, the structure of the drum type washing / drying machine 21 provided with the permanent magnet motor 1 configured as described above will be described. FIG. 3 is a longitudinal sectional side view schematically showing the internal configuration of the drum type washing / drying machine 21. The outer box 22 forming the outer shell of the drum-type washing / drying machine 21 has a laundry entrance / exit 23 opening in a circular shape on the front surface, and the laundry entrance / exit 23 is opened and closed by a door 24. ing. Inside the outer box 22, a bottomed cylindrical water tank 25 having a closed back surface is disposed, and the permanent magnet motor 1 (stator 2) is fixed to the center of the back surface of the water tank 25 by screwing. Has been.

  The rotating shaft 26 of the permanent magnet motor 1 has a rear end portion (right end portion in FIG. 3) fixed to the shaft mounting portion 10 of the permanent magnet motor 1 (rotor 3), and a front end portion (left side in FIG. 3). End) protrudes into the water tank 25. A bottomed cylindrical drum 27 whose rear surface is closed is fixed to the front end of the rotating shaft 26 so as to be coaxial with the water tank 25, and this drum 27 is driven by the permanent magnet motor 1. It rotates integrally with the rotor 3 and the rotating shaft 26. The drum 27 is provided with a plurality of flow holes 28 through which air and water can flow, and a plurality of baffles 29 for scraping and unraveling the laundry in the drum 27.

A water supply valve 30 is connected to the water tank 25, and water is supplied into the water tank 25 when the water supply valve 30 is opened. Further, a drain hose 32 having a drain valve 31 is connected to the water tank 25, and when the drain valve 31 is opened, water in the water tank 25 is discharged.
A ventilation duct 33 extending in the front-rear direction is provided below the water tank 25. A front end portion of the ventilation duct 33 is connected to the water tank 25 via the front duct 34, and a rear end portion is connected to the water tank 25 via the rear duct 35. A blower fan 36 is provided at the rear end of the ventilation duct 33, and the air in the water tank 25 is blown from the front duct 34 into the ventilation duct 33 by the blowing action of the blower fan 36 as indicated by an arrow. And is returned to the water tank 25 through the rear duct 35.

  An evaporator 37 is disposed on the front end side inside the ventilation duct 33, and a condenser 38 is disposed on the rear end side. The evaporator 37 and the condenser 38 constitute a heat pump 41 together with the compressor 39 and the throttle valve 40 (see FIG. 4), and the air flowing in the ventilation duct 33 is dehumidified by the evaporator 37 and heated by the condenser 38. And is circulated in the water tank 25. The throttle valve 40 is formed of an expansion valve and has an opening degree adjusting function.

  An operation panel 42 is provided on the front surface of the outer box 22 above the door 24. The operation panel 42 is provided with a plurality of operation switches (not shown) for setting a driving course and the like. ing. The operation panel 42 is composed mainly of a microcomputer and is connected to a control circuit unit (not shown) that controls the overall operation of the drum type washing and drying machine 21. The control circuit unit is connected via the operation panel 42. In accordance with the set contents, various operation courses are executed while controlling the driving of the permanent magnet motor 1, the water supply valve 30, the drain valve 31, the compressor 39, the throttle valve 40, and the like. Although not shown, the compressor motor constituting the compressor 39 also employs the same configuration as that of the permanent magnet motor 1.

  FIG. 1 is a block diagram showing the configuration of a motor control device 50 that vector-controls the rotation of the permanent magnet motor 1. The compressor motor is also controlled by the same configuration. In the vector control, the current flowing through the armature winding is separated into the magnetic flux direction of the permanent magnet, which is a field, and the direction orthogonal thereto, and these are adjusted independently to control the magnetic flux and the generated torque. For the current control, a current value represented by a coordinate system rotating with the rotor of the motor 1, that is, a so-called dq coordinate system, is used. The d axis is a magnetic flux direction created by a permanent magnet attached to the rotor, and the q axis is The direction is orthogonal to the d-axis. The q-axis current Iq that is the q-axis component of the current flowing through the winding is a component that generates rotational torque (torque component current), and the d-axis current Id that is the d-axis component is a component that generates magnetic flux (excitation or Magnetization component current).

  The current sensor 51 (U, V, W) is a sensor that detects currents Iu, Iv, Iw flowing in the phases (U phase, V phase, W phase) of the motor 1. In place of the current sensor 51 (current detecting means), three shunt resistors are arranged between the lower arm side switching element constituting the inverter circuit 52 (driving means) and the ground, and the terminal voltages thereof are set. A configuration may be adopted in which the currents Iu, Iv, and Iw are detected on the basis of them.

  The currents Iu, Iv, Iw detected by the current sensor 51 are converted into two-phase currents Iα, Iβ by the uvw / dq coordinate converter 53 when A / D converted by an A / D converter (not shown), Further, it is converted into a d-axis current Id and a q-axis current Iq. α and β are coordinate axes of a biaxial coordinate system fixed to the stator of the motor 1. For the calculation of the coordinate conversion here, the estimated rotational position of the rotor (estimated value of the phase difference between the α axis and the d axis) θ estimated by the speed / position estimating unit (position detecting means) 54 is used. Further, the rotational speed (angular speed) ω of the motor 1 estimated by the speed / position estimation unit 54 is output.

The speed / position estimation unit 54 estimates the angular speed ω of the motor 1 and the rotational position θ of the rotor as described above, and the d-axis inductance Ld of the armature winding, which is the circuit constant (motor constant) of the motor 1. , Q-axis inductance Lq, winding resistance value R, and d-axis current Id, q-axis current Iq, and d-axis output voltage command value Vd are input.
The speed / position estimation unit 54 estimates the rotational speed ω of the motor 1 using the d-axis motor voltage equation of formula (1).
Vd = R · Id + ω · Lq · Iq (1)
Further, the angular velocity ω is integrated by the integrator 55, and the integration result is output as the rotational position estimated value θ.

The magnetizing control unit (magnetizing means) 59 outputs a magnetizing current command Id_com2 when increasing or decreasing magnetizing according to the operation of the washing machine. Id_com2 takes a positive value when magnetizing and a negative value when demagnetizing. Further, based on the energization command position θ when the rotor is rotating, the energization command is output twice for each electrical angle 360 for a period of several ms to several tens of ms.
The magnetizing control unit 59 outputs a magnetizing current command Id_com2 for magnetizing the alnico magnet 9b, determined based on the phase θ and the rotational speed ω, to the changeover switch 60. One of commands Id_com1, Id_com2, and Id_com3 described later is selected and output to the current control unit 61 as a d-axis current command value Id_ref. Further, when the difference between the rotational speed command value ω_ref given from the outside and the rotational speed ω is obtained by the subtractor 62, the difference is proportionally integrated by the proportional integrator (PI) 63, and the q-axis current command value Iq_ref is calculated. Is output to the current control unit 61.

  In the current control unit 61, the subtractors 64d and 64q obtain the differences between the d-axis current command value Id_ref and the q-axis current command value Iq_ref and the d-axis current Id and the q-axis current Iq, respectively, and the difference is proportional integrator 65d. , 65q, the proportional integral operation is performed. Then, the result of the proportional integration calculation is output to the dq / uvw coordinate converter 66 as output voltage command values Vd and Vq expressed in the dq coordinate system. In the dq / uvw coordinate converter 66, the voltage command values Vd and Vq are converted into values expressed in the α-β coordinate system, and further converted into respective phase voltage command values Vu, Vv and Vw. The magnetic pole position θ described later is also used for calculation of coordinate conversion in the dq / uvw coordinate converter 66.

  The phase voltage command values Vu, Vv, and Vw are input to the power converter 67, and a pulse drive modulated gate drive signal for supplying a voltage that matches the command value is formed. The inverter circuit 52 is configured by connecting switching elements such as IGBTs in a three-phase bridge, and is supplied with a DC voltage from a DC power supply circuit (not shown). The gate drive signal formed by the power converter 67 is given to the gates of the switching elements constituting the inverter circuit 52, and thereby PWM-modulated three-phase alternating current that matches the phase voltage command values Vu, Vv, Vw. A voltage is generated and applied to the winding 5 of the motor 1.

  In the above configuration, the current controller 61 performs feedback control by proportional integral (PI) calculation, and the d-axis current Id and the q-axis current Iq coincide with the d-axis current command value Id_ref and the q-axis current command value Iq_ref, respectively. To be controlled. The estimated angular velocity value ω as a result of the control is fed back to the subtractor 62, and the proportional integrator 63 converges the deviation Δω to zero by the proportional integration calculation. As a result, the rotational speed ω becomes equal to the command value ωref.

The demagnetization suppression unit (magnetization change suppression means) 69 increases the number of permanent magnets 9 arranged in the rotor 3 of the motor 1 according to the value of the q-axis current Iq output from the uvw / dq coordinate converter 53. In order to prevent the magnetic level from decreasing, a magnetizing current command Id_com3 is generated and output to the changeover switch 60. The changeover control of the changeover switch 60 is performed by a microcomputer that controls the entire washing machine 21 (for example, generates and outputs the rotation speed command value ω_ref).
In the above configuration, the motor control device 50 plus the permanent magnet motor 1 constitutes the motor control system 70. The parts excluding the inverter circuit 52 and the PWM forming unit 62 are functions realized by software of a microcomputer constituting the motor control device 50.

  Next, the operation of the drum type washing / drying machine (hereinafter simply referred to as a washing machine) 21 provided with the permanent magnet motor 1 will be described. When the motor controller 50 energizes the stator winding 5 via the inverter circuit 52, an external magnetic field (magnetic field generated by the current flowing through the stator winding 5) due to the armature reaction acts on the permanent magnets 9 a and 9 b of the rotor 3. To come. Of these permanent magnets 9 a and 9 b, the magnetization state of the alnico magnet 9 b having a small coercive force is demagnetized or increased by an external magnetic field due to this armature reaction, whereby the magnetic flux interlinking with the stator winding 5. The amount (linkage magnetic flux amount) can be increased or decreased. Therefore, in the present embodiment, the motor control device 50 controls the energization of the stator winding 5 to switch the magnetization state of the alnico magnet 9b for each operation process (washing process, dehydration process, drying process). . Here, the operation content in each operation process will be described in order.

  First, in the washing process, the control circuit unit of the washing machine 21 opens the water supply valve 30 to supply water into the water tank 25, and then rotates the drum 27 to perform washing. In this washing process, since the laundry containing water is scraped up by the baffle 29, it is necessary to rotate the drum 27 with high torque, but the rotation speed may be low. Therefore, the motor control device 50 controls energization of the stator winding 5 by the inverter circuit 52 so that the magnetization state of the alnico magnet 9b is increased. As a result, the amount of magnetic flux acting on the stator winding 5 is increased (the magnetic force is strong), so that the drum 27 can be rotated at a high torque and a low speed.

  Next, in the dehydration step, the control circuit unit dehydrates moisture contained in the laundry by opening the drain valve 31 to discharge the water in the water tank 25 and then rotating the drum 27 at a high speed. In this dewatering step, it is necessary to rotate the drum 27 at a high speed in order to improve the dewatering efficiency, but the torque may be small. Therefore, the motor control device 50 controls energization of the stator winding 5 by the inverter circuit 52 so that the magnetization state of the alnico magnet 9b is demagnetized. Thereby, since the amount of magnetic flux acting on the stator winding 5 is reduced (the magnetic force is weak), the drum 27 can be rotated at a low torque and a high speed.

  Finally, in the drying process, the control circuit unit dries the laundry by driving the blower fan 36 and the heat pump 41 and rotating the drum 27. In this drying process, the motor control device 50 controls the energization of the stator winding 5 by the inverter circuit 52 so that the magnetization state of the alnico magnet 9b is increased in preparation for the next washing process. As a result, the amount of magnetic flux acting on the stator winding 5 can be increased, and the drum 27 can be easily rotated at high torque and low speed in the next washing step.

  As described above, in the washing operation, a large torque is required to rotate the clothes containing water. FIG. 5 schematically shows a state in which the position of the clothes housed in the drum 27 changes during the washing operation. When the drum 27 is rotated, the largest torque is obtained when the internal garment starts from the lowest position shown in FIG. 5A and is lifted by the baffle 29 to the state shown in FIG. 5B. Is required. Further, when the rotational speed of the drum 27 reaches the steady rotational speed (assuming 50 rpm), the operation is continued for a certain period of time with the rotational speed being maintained, but since the clothing continues to rotate at the steady rotational speed, the load torque is Small compared to startup. That is, the largest torque is generated in the washing operation when the motor 1 starts to move from the stopped state to the state shown in FIG.

  FIG. 6 shows (a) rotational speed and torque during washing operation, (b) torque current Iq and exciting current Id, and (c) magnetic flux amount of motor 1: induced voltage constant (induced voltage value per unit rotational speed). Show the relationship. As indicated by a broken line in FIG. 6A, a large torque is generated at the time of starting in the forward direction and at the time of starting in the reverse direction, and the amount of torque current Iq increases accordingly. Here, if only the torque current Iq flows at about 6 to 7 A at the time of startup, the Alnico magnet 9b is demagnetized according to the increase / decrease magnetic characteristics of FIG. descend.

Therefore, in this embodiment, the exciting current Id is energized as shown in (b) at the timing when the torque current Iq is energized greatly when the motor 1 is started. For this reason, the magnetization change suppressing unit 69 generates and outputs a magnetization current command Id_com3. FIG. 7 shows the characteristics of the exciting current Id that is energized according to the value of the torque current Iq in this case. The magnetization change suppression unit 69 determines the magnetization current command Id_com3 by the following equation.
Id_com3 = (Iq−a) × b (where Iq> a) (2)
a and b are constants, and in this embodiment, for example, a = 3 and b = 1 are set. If Iq ≦ a, Id_com3 = 0. Note that the number of constants a and b to be set may be selected based on the result of actual measurement according to the individual design.

  Based on the equation (2), if the torque current Iq flows, for example, at a peak of 6 A, the magnetization change suppression unit 69 outputs a magnetization current command Id_com3 so that the excitation current Id flows at 3 A simultaneously. Thereby, it is avoided that the induced voltage of the motor 1 falls like the thick broken line shown in (c). Similarly, when the motor 1 rotates in reverse, the magnetizing current command Id_com3 may be output with the polarity reversed.

  FIG. 8 shows a simulation result indicating that the demagnetization state shown in FIG. 10 is improved as a result of the magnetization change suppression unit 69 outputting the magnetization current command Id_com3 to suppress the demagnetization of the permanent magnet 9b. It is. Thus, it can be seen that the induced voltage ratio that has been reduced to 91.8% can be suppressed to 97.0% as shown by the one-dot chain line. Also, in the case where the dehydration operation is performed in a state where the permanent magnet 9b is demagnetized, if an unintentional magnetization is generated during the operation, the magnetization current command Id_com3 has a pattern shown in FIG. 6B. By outputting in reverse polarity, it is possible to superimpose the excitation current Id and act in the demagnetization direction to suppress the magnetization.

  As described above, there are two advantages of suppressing the demagnetization by superimposing the excitation current Id by the magnetic current command Id_com3 without remagnetizing the permanent magnet 9b demagnetized during the operation in another process. . One of them is that, if energization by remagnetization is frequently performed during washing operation, noise is generated each time, and the product quality as a washing machine is impaired. The other is that a large current flows through the switching element of the inverter circuit 52 during magnetization, so that the durability of the switching element is not deteriorated and the life is maintained. In this embodiment, it is assumed that the maximum value of the current that flows to drive the motor 1 is about 8 A and the current that flows to magnetize the alnico magnet 9 b is about 20 A.

  As described above, according to the present embodiment, when the level of the torque current Iq exceeds the predetermined threshold, the magnetization change suppression unit 69 outputs the magnetization current command Id_com3 so that the excitation current Id flows simultaneously. It is possible to improve the operation efficiency of the motor 1 by preventing the permanent magnet 9b disposed on the rotor 3 of the motor 1 from demagnetizing (that is, suppressing the change of the magnetized state). In this case, since the magnetization change suppression unit 69 determines the magnetization current command Id_com3 from the equation (2), the level of the excitation current Id to be superimposed is increased as the level of the torque current Iq increases. Can do.

  Since the drum type washing / drying machine 21 includes the motor control system 70 including the permanent magnet motor 1 and the motor control device 50, and the drum 27 is rotated by the permanent magnet motor 1, the washing operation is performed. It is possible to prevent the alnico magnet 9b of the motor 1 from being demagnetized during operation or the like, thereby preventing a decrease in operating efficiency. Then, when starting the washing or rinsing operation, the magnetization change suppressing unit 69 superimposes the excitation current Id when the maximum value of the q-axis current Iq at the start of the motor 1 exceeds a predetermined value. Can be detected during a period when the probability of demagnetization of the alnico magnet 9b is high.

(Second embodiment)
FIG. 9 shows a second embodiment of the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the motor control device 71 in the second embodiment, a position sensor (position detection means) 72 (u, v, w) including, for example, a Hall IC is disposed in the motor 1, and the speed in the configuration of the first embodiment. The position estimation unit 54 is replaced with a speed position detection unit (position detection means) 73. The motor 1 and the motor control device 71 constitute a motor control system 74.
The speed position detector 73 detects the rotational speed ω and the rotational position θ of the motor 1 based on the position signals Hu, Hv, Hw given from the position sensor 72. Other functions and effects are the same as those in the first embodiment.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
The demagnetization may be suppressed by superimposing the excitation current Id even when the level of the torque current Iq is increased due to a sudden load fluctuation, even in an originally steady operation state, not limited to when the motor is started.
The determination of the magnetizing current command Id_com3 is not limited to the equation (2). For example, the output characteristics may follow a curve formula.
Further, the magnetizing current command Id_com3 is not necessarily determined based on the value of the torque current Iq, and may be set to a fixed value. Furthermore, the timing for outputting the magnetizing current command Id_com3 may also be fixed within the period for outputting the torque current Iq.

The magnetization control unit 59 may also have a function as a magnetization change suppressing unit.
The high holding force permanent magnet and the low holding force permanent magnet are not limited to the neodymium magnet 9a and the alnico magnet 9b, respectively, and may be appropriately selected from materials made of materials capable of obtaining an appropriate holding force. Further, when desired output characteristics can be satisfied by increasing or decreasing the low holding force permanent magnet, the high holding force permanent magnet is not necessarily required.
You may apply to the permanent magnet motor of the structure currently disclosed by patent document 1. FIG.
The present invention is not limited to the washing / drying machine 21 or the washing machine having no drying function, and uses a permanent magnet motor having a low holding power permanent magnet in the rotor, and changes the output characteristics of the motor according to the load fluctuation state. This is applicable to any device that is desirable.

  In the drawings, 1 is a permanent magnet motor, 3 is a rotor, 9a is a neodymium magnet (high coercivity permanent magnet), 9b is an alnico magnet (low coercivity permanent magnet), 21 is a drum type washer / dryer, 27 is a drum, 50 is Motor controller 54, speed / position estimating unit (position detecting unit), 59 magnetizing control unit (magnetizing unit), 69 magnetizing change suppressing unit (magnetizing change suppressing unit), 70 motor control system, Reference numeral 71 denotes a motor control device, 73 denotes a speed position detection unit (position detection means), and 74 denotes a motor control system.

Claims (9)

In a motor control device that controls a permanent magnet motor in which a permanent magnet having a low coercive force such that the amount of magnetization can be changed is arranged in a rotor, and detects a current flowing in the motor to perform vector control,
Position detecting means for detecting the rotational position of the motor;
Magnetizing means for magnetizing or demagnetizing the permanent magnet according to the rotational position of the motor by adjusting the magnetization state of the permanent magnet by an armature reaction magnetic field;
When a q-axis current (torque current) is supplied to the motor winding in a state where the permanent magnet is magnetized by the magnetizing means, a period for superimposing the d-axis current (excitation current) is provided. A motor control apparatus comprising: a magnetization change suppressing unit that suppresses a change in the magnetization state of the permanent magnet.   The motor control apparatus according to claim 1, wherein the magnetization change suppressing unit determines a d-axis current to be superimposed on the q-axis current based on a value of the q-axis current.   The motor control apparatus according to claim 1, wherein the magnetization change suppression unit superimposes the d-axis current during a period in which the q-axis current exceeds a predetermined threshold. The magnetization change suppressing means calculates a d-axis current Id superimposed on the q-axis current Iq by the following formula (where a and b are positive real numbers):
Id = 0 [when Iq ≦ a]
Id = (Iq−a) × b [when Iq> a]
4. The motor control device according to claim 3, wherein the motor control device is determined by: The permanent magnet motor;
A drum-type laundry comprising: the motor control device according to any one of claims 1 to 4, wherein a washing operation is performed by rotating a drum containing laundry by a rotational driving force generated by the motor. Machine. A permanent magnet motor in which a permanent magnet having a low coercive force so that the amount of magnetization can be changed is arranged in the rotor, and a vector control is performed by detecting a current flowing through the motor,
By detecting the rotational position of the motor and adjusting the magnetization state of the permanent magnet with an armature reaction magnetic field, the permanent magnet is magnetized according to the rotational position of the motor,
When a q-axis current (torque current) is supplied to the motor winding while the permanent magnet is magnetized, the permanent magnet is magnetized by providing a period in which the d-axis current (excitation current) is superimposed. A method for controlling the magnetization of a permanent magnet motor, characterized by suppressing the change of the permanent magnet motor.   The magnetization control method for a permanent magnet motor according to claim 6, wherein a d-axis current superimposed on the q-axis current is determined based on a value of the q-axis current.   The magnetization control method for a permanent magnet motor according to claim 6 or 7, wherein the d-axis current is superimposed in a period in which the q-axis current exceeds a predetermined threshold. The d-axis current Id superimposed on the q-axis current Iq is expressed by the following formula (where a and b are positive real numbers):
Id = 0 [when Iq ≦ a]
Id = (Iq−a) × b [when Iq> a]
9. The method for controlling magnetization of a permanent magnet motor according to claim 8, wherein:

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