JP2011066960A - Rotor position detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a position of a rotor by a low-cost magnetic detection sensor to a permanent magnet motor, where a permanent magnet of which magnetic force is different partially is disposed in the rotor. <P>SOLUTION: When the permanent magnet motor 1 is composed by disposing two types of magnets having different magnetic force, namely a neodymium magnet 9a and an alnico magnet 9b, in the rotor 3, and when a speed-position detection unit 55 detects rotational speed of the permanent magnet motor 1 by three Hall sensors 68 (A, B, C), the speed-position detection unit detects the position of the rotor 3 based on the rotational speed. Then, when a speed-position correction unit 80 detects a boundary between the neodymium magnet 9a and the alnico magnet 9b from a change state of a sensor signal output by the Hall sensor 68, the speed-position correction unit corrects the rotational speed or the position of the rotor, which is detected by the speed-position detection unit 55. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting a rotor position in a permanent magnet motor in which a permanent magnet having a different magnetic force is disposed in a rotor among some of the plurality.

  In recent years, in washing machines, the combination of a direct drive type permanent magnet motor and a motor control device employing vector control has improved motor control accuracy and washing performance, while reducing power consumption and during washing operations. The effect of reducing vibration is obtained. In the conventional general control method, when the motor is rotated at a high speed in a dehydrating operation or the like, field weakening control is performed in which a d-axis current Id that does not contribute to torque is supplied to reduce the induced voltage of the motor. In this case, the copper loss is increased by constantly flowing a current that does not contribute to the torque in the dehydration operation, resulting in a decrease in efficiency.

  On the other hand, in the technique disclosed in Patent Document 1, a demagnetization phenomenon is caused irreversibly by causing a d-axis current to flow for a moment to a permanent magnet having a low coercive force, and the magnetic flux of the permanent magnet is reduced during dehydration operation. I try to decrease. As a result, the induced voltage generated in the motor winding during high-speed rotation is reduced, and high-speed operation is possible without constantly energizing the d-axis current.

JP 2009-118663 A

However, in order to drive and control the permanent magnet motor as described above, when using a Hall sensor that includes a Hall element that detects magnetic flux or an IC incorporating the Hall element as a position sensor that detects the rotor position, position detection The error may increase. As an example, FIG. 13 shows the relationship between the rotor position and the signal waveform output from each Hall sensor when three Hall sensors that output magnetic flux detection results as binary signals are arranged at an electrical angle interval of 60 degrees. Show.
Since the Hall sensor detects the magnetic flux of the permanent magnet, and the magnetic flux changes depending on the rotor position, the three binary signals change at different phases (60 degree intervals) according to the rotor position (see FIG. 13B). The rotor position and rotational speed can be detected from these signals.

However, as in Patent Document 1, when permanent magnets with greatly different generated magnetic fluxes (magnetic forces) are mixed and arranged, the relationship between the change in these magnetic fluxes and the change in the rotor position is the case of FIG. Different. In FIG. 14, the permanent magnet 101 arranged at the center is a low coercivity permanent magnet (Alnico magnet in Patent Document 1), and the permanent magnets 102 arranged on both sides of the permanent magnet 101 are both permanent magnets with high coercivity. It is a magnet (Neodymium magnet in Patent Document 1).
In this case, the boundary where the magnetic flux density is 0 between the two permanent magnets 102 is linear (three-dimensional planar), but the permanent magnet 101 and the permanent magnets 102 on both sides of the boundary are formed. In the meantime, the boundary is pushed from both sides, and has a curved shape bent to the permanent magnet 101 side (three-dimensionally, the boundary surface forms a curved surface at the upper end side and the lower end side).

  FIG. 15 shows the magnetic flux generated by the permanent magnet arranged in the rotor and the output pulse of the Hall sensor (A phase only). When the Hall sensor is related to a magnet having a stronger magnetic force than other magnets, the pulse width is changed in a direction in which the pulse width increases. On the contrary, when the Hall sensor is related to a magnet having a weaker magnetic force than other magnets, the pulse width is changed in a narrowing direction. When the pulse width changes temporarily as described above, an error occurs in position detection.

  Further, when a current is passed through the stator coil when the magnetic fluxes of the permanent magnets are different, the magnetic flux generated by the coil affects the Hall sensor, and the position detection error tends to be further expanded. That is, since the Hall sensor detects the magnetic flux leakage from the magnet, the magnetic field acting on the magnet from the stator side acts in the direction to demagnetize or increase the magnet's main magnetic flux. Thus, the amount of magnetic flux leakage acting on the Hall sensor also changes. For example, when the magnetic field on the stator acts in a direction in which the main magnetic flux of the magnet is greatly increased, the direction of the leakage flux itself may be reversed and the pulse signal may be partially reversed. Then, a large error occurs in the detected rotor position and rotational speed. When motor control is performed based on the detection result, noise is generated due to a sudden change in current or the motor stops due to step-out. There is a fear.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately detect a rotor position using a low-cost magnetic detection sensor for a permanent magnet motor in which a permanent magnet having a partially different magnetic force is arranged on a rotor. The object is to provide a rotor position detecting device.

In order to solve the above-described problem, the rotor position detection device according to claim 1 is a detection target of a permanent magnet motor including a permanent magnet having a different magnetic force in a part of the plurality of permanent magnets arranged in the rotor.
When detecting the rotational speed of the permanent magnet motor using a plurality of magnetic detection sensors, speed / position detecting means for detecting the position of the rotor based on the rotational speed;
When the boundary of the permanent magnets having different magnetic forces among the plurality of permanent magnets is detected from the change state of the sensor signal output by the magnetic detection sensor, the rotational speed detected by the speed / position detection means or the rotor And correction means for correcting the position.

  According to the rotor position detecting device of claim 1, when detecting a rotor position of a permanent magnet motor, in which a permanent magnet having a partially different magnetic force is disposed on the rotor, by a magnetic detection sensor, a boundary between the magnets having different magnetic forces. Even if distortion occurs, the correction means corrects the rotational speed or rotor position of the permanent magnet motor detected by the speed / position detection means, so that the rotor position can be obtained accurately.

The flowchart which shows the process which is one Example and correct | amends a speed and a position Flow chart showing speed and position detection processing Timing chart showing signal waveforms when all magnets have the same magnetic force Fig. 3 equivalent when some magnets have different magnetic forces Timing chart showing the case where the signal pulse width of the Hall sensor is greatly expanded The figure which shows the case where the hall sensor which detects falsely depends on the rotation direction of the rotor Block diagram showing the configuration of the motor controller The top view which shows the structure of the rotor of a permanent magnet motor The figure which shows the arrangement state of Hall sensor Longitudinal side view schematically showing the internal structure of the drum type washing and drying machine Diagram showing the configuration of the heat pump Diagram showing the washing machine operation sequence FIG. 3 is a partial equivalent diagram illustrating the prior art. The figure explaining the state where the boundary from which magnetic flux density becomes 0 changes when the magnetic force of the magnet arrange | positioned at a rotor differs. The figure which shows the magnetic flux which the permanent magnet arrange | positioned at a rotor generate | occur | produces, and the output pulse of an A-phase Hall sensor

  Hereinafter, an embodiment will be described with reference to FIGS. FIG. 8 is a plan view showing the configuration of the rotor of the permanent magnet motor 1 (outer rotor type brushless motor). 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 a large number of punched and formed soft magnetic bodies of silicon steel plates, and has an annular yoke portion 4a and a large number of teeth portions 4b projecting radially from the outer periphery of the yoke portion 4a. is doing. The surface of the stator core 4 is covered with PET resin (mold resin) except for the front end surface of each tooth portion 4b.

  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 each attachment portion 6 with screws, the stator 2 in this case is provided in the water tank 25 (see FIG. 10) of the drum type washing and drying machine 21. 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 body. 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 an uneven shape having a convex portion (magnetic pole tip) 8a.

  A rectangular insertion hole 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, and the plurality of insertion holes are annularly arranged in the rotor core 8. ing. The permanent magnet 9 is composed of a rectangular neodymium magnet 9a (high coercive force permanent magnet) inserted into the insertion hole and a rectangular alnico magnet 9b (low coercive force permanent magnet) which is also rectangular. 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. There are a total of 48 permanent magnets 9, of which 6 are alnico magnets 9 b and 42 are neodymium magnets 9 a.

  In FIG. 8, A to F are attached to the positions where the alnico magnets 9b are arranged, and five neodymium magnets 9a arranged between A and B, neodymium magnets arranged between B and C. Nine 9a, five neodymium magnets 9a arranged between C and D, nine neodymium magnets 9a arranged between D and E, and neodymium magnet 9a arranged between E and F There are nine neodymium magnets 9a disposed between F and A. In this arrangement, the average value of the induced voltages generated for the same phase is set to the same value to suppress the generation of cogging torque. The permanent magnet motor 1 has a 48 pole / 36 slot configuration, and 4 poles correspond to 3 slots (4 poles / 3 slots).

In the case of the magnet arrangement shown in FIG. 8, the boundary between the Alnico magnet 9b in A to F and the neodymium magnet 9a located on both sides thereof is a boundary where the magnetic flux becomes “0” in the circumferential direction as shown in FIG. This is the position where distortion occurs.
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.

  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. 10 is a longitudinal side view schematically showing the internal configuration of the drum type washing and 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. 10) fixed to the shaft mounting portion 10 of the permanent magnet motor 1 (rotor 3), and a front end portion (left side in FIG. 10). The end of the projection 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. 11), 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 may adopt the same configuration as that of the permanent magnet motor 1.

  FIG. 7 is a block diagram showing the configuration of the 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, the estimated rotational position of the rotor estimated by the speed / position estimation unit 54 (estimated value of the phase difference between the α axis and the d axis) θ_est, or the speed / position detection unit 55 Any one of the rotational position detection values θ_ho detected and output via the speed / position correction unit 80 is selected by the changeover switch 56 and is output. The rotational speed (angular speed) ω_est of the motor 1 estimated by the speed / position estimation unit 54 and the rotational speed ω_ho detected by the speed / position detection unit 55 and output via the speed / position correction unit 80 are The rotation speed ω is output by being selected by the changeover switch 57 interlocked with the changeover switch 56.

  The speed / position correction unit 80 performs a correction process by comparing the motor rotation speed ω_h detected by the speed / position detection unit 55 and the electrical angle θ_h with the previously detected value, and the corrected motor rotation speed ω_ho Output as angle θ_ho. In addition, a washing machine sequence signal is received from a control circuit unit that manages the operation of the entire washing machine, and whether or not to perform correction is switched depending on the sequence state.

The magnetization control unit 58 (magnetization control means) outputs a magnetization current command Id_com2 for magnetizing the alnico magnet 9b, determined based on the phase θ and the rotational speed ω, to the adder 59. 59 outputs the result obtained by adding the field weakening current command Id_com1 output as necessary to the magnetizing current command Id_com2 to the current control unit 60 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 61, the difference is proportionally integrated by the proportional integrator 62, and current control is performed as the q-axis current command value Iq_ref. Is output to the unit 60.
Id_com2 takes a positive value when the magnet is increased and a negative value when the magnet is demagnetized. Then, based on the energization command position θref (internally set) when the rotor 3 is rotating, an energization command is output twice for each electrical angle 360 for a period of several ms to several tens of ms. That is, the three alnico magnets 9b are magnetized in two portions.

  In the current controller 60, the subtractors 63d and 63q 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 64d. 64q. The result of the proportional integration calculation is output to the dq / uvw coordinate converter 65 as output voltage command values Vd and Vq expressed in the dq coordinate system. In the dq / uvw coordinate converter 65, the voltage command values Vd and Vq are converted into values expressed in the α-β coordinate system, and then converted into respective phase voltage command values Vu, Vv and Vw. Note that the rotational position θ is also used for calculation of coordinate conversion in the dq / uvw coordinate converter 65.

  The phase voltage command values Vu, Vv, and Vw are input to the power converter 66, 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 conversion unit 66 is applied to the gate of each switching element that constitutes the inverter circuit 52, and thereby PWM-modulated three-phase alternating current that matches each phase voltage command value Vu, Vv, Vw. A voltage is generated and applied to the winding 5 of the motor 1.

  In the above configuration, the current controller 60 performs feedback control by proportional integral (PI) calculation, and the d-axis current Id and the q-axis current Iq respectively match the d-axis current command value Id_ref and the q-axis current command value Iq_ref. To be controlled. The estimated angular velocity value ω as the control result is fed back to the subtractor 61, and the proportional integrator 62 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 speed / position estimation unit 54 (speed / position estimation means) estimates the angular velocity ω of the motor 1 and the rotational position θ of the rotor, respectively, and d of the armature winding that is the circuit constant (motor constant) of the motor 1. Each value of the shaft inductance Ld, the q-axis inductance Lq, and the winding resistance value R is stored, and the d-axis current Id, the q-axis current Iq, and the d-axis output voltage command value Vd are input. The speed / position estimation unit 54 estimates the rotational speed ω_est of the motor 1 using the d-axis motor voltage equation of formula (1).
Vd = R · Id−ω_est · Lq · Iq (1)
Further, the angular velocity ω_est is integrated by the integrator 67, and the integration result is output as the rotational position estimated value θ_est.

  The motor 1 is provided with three (A, B, C) position sensors: Hall sensors (magnetic detection sensors) 68 configured using Hall ICs, and position signals output by these Hall sensors 68. Ha, Hb, and Hc are given to the speed / position detection unit 55. The speed / position detection unit 55 calculates and outputs the rotational position detection value θ_h and the rotational speed detection value ω_h based on the position signals Ha, Hb, and Hc.

FIG. 9 shows the arrangement state of the hall sensor 68. A terminal block 81 is provided so as to protrude above the rotor 3 from above the tooth portion 4 b in the stator 2, and the hall sensor 68 is disposed above the permanent magnet 9. And it arrange | positions so that it may become the space | interval equivalent to 60 electrical degrees between Hall sensors 68A and 68B, and between 68B and 68C, respectively.
In the above configuration, the motor control device 50 plus the permanent magnet motor 1 constitutes the motor control system 70. Further, the speed / position detection unit 55, the hall sensor 68, and the speed / position correction unit 80 constitute a rotor position detection device 82. The parts excluding the inverter circuit 52 and the power conversion unit 66 are functions realized by software of a microcomputer constituting the motor control device 50.

Next, the operation of the drum type washer / dryer 21 provided with the motor control system 70 will be described. When the control circuit unit energizes the stator winding 5 by the inverter circuit 52 via the magnetization control unit 58, an external magnetic field (a magnetic field generated by a current flowing through the stator winding 5) due to the armature reaction is permanently applied to the rotor 3. It acts on the magnets 9a and 9b. The magnetization state of the alnico magnet 9b having a small coercive force is demagnetized or increased by the external magnetic field, and as a result, the amount of magnetic flux interlinked with the stator winding 5 (interlinkage magnetic flux amount) is increased or decreased.
In the washing operation, the control circuit unit 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 case, 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 large (the magnetic force is strong), so that the drum 27 has characteristics suitable for rotating at high torque and low speed.

  In the dehydration operation, the control circuit unit opens the drain valve 31 to discharge the water in the water tank 25, and then rotates the drum 27 at a high speed to dehydrate water contained in the laundry. In this case, the magnetization state of the alnico magnet 9b is demagnetized. As a result, the amount of magnetic flux acting on the stator winding 5 is reduced (the magnetic force is weak), so that the drum 27 has characteristics suitable for rotating at low torque and high speed. Finally, in the drying operation, the control circuit unit drives the blower fan 36 and the heat pump 41 and rotates the drum 27 to dry the laundry. In this case, the magnetized state of the alnico magnet 9b is increased in preparation for the next washing operation.

  Next, the operation of the present embodiment will be described with reference to FIGS. First, assuming that the permanent magnets 9 arranged on the rotor 3 are all neodymium magnets 9a (which is a configuration of a general permanent magnet motor), processing in the case of performing rotor position detection will be described. When the rotor 3 rotates as shown in FIG. 3, the Hall sensor 68 outputs three binary (low: L, high: H) pulses with a 60-degree phase difference accordingly (FIG. 3 (a), ( b)). These correspond to the position signals Ha, Hb, Hc shown in FIG.

  The speed / position detection unit 55 includes an encoder 55E inside, and encodes and outputs, for example, the hole number (3 bits) shown in the figure according to the L and H patterns of these three pulses (FIG. 3). (See (c)). For example, if the signal level of each phase of A / B / C of the Hall sensor 68 is a combination of L / H / H, the number 0 is output, and each time the combination of signal levels is changed, the Hall number is 1, Cycles through 3, 7, 6, 4, 0, 1, 3,.

  The current rotor position and the rotational direction of the rotor can be detected by these hole numbers and their changes. FIG. 3E shows the rotor position that changes stepwise in response to the change in the hole number. When the hall number is 0, the rotor position, that is, the detection angle of the hall sensor 68 is set to −150 degrees. Next, the speed / position detector 55 measures the interval time at which the hole number changes with a counter or the like, converts the time into a speed, and calculates the rotor speed ω_h. The calculated result is the hall sensor detection motor speed (see FIG. 3D), and the value is updated each time the hall number changes. Note that FIG. 3D shows a discontinuous line in the sense of showing the transition of the detection speed, but of course, if the rotation speed of the motor 1 is constant, it becomes a continuous straight line.

Then, by integrating the detected motor speed, a Hall sensor detection angle based on the speed is calculated (indicated by a straight line rising upward in FIG. 3E). The motor current is controlled based on the detected angle. For this reason, the current waveform is sinusoidal as shown in FIG. 3 (f) (U phase only), and since the current does not change rapidly, the noise during motor driving is reduced.
When driving the permanent magnet motor 1, when the motor 1 is started by forced commutation, the rotational position and speed detected by the speed / position detection unit 55 are used until the rotational speed reaches, for example, 30 rpm, and thereafter The switches 56 and 57 are switched so as to perform position sensorless control using the rotational position and speed estimated by the speed / position estimation unit 54.

  FIG. 2 is a flowchart showing the position detection process. This process is executed at a cycle of 1 ms, for example. When acquiring the hole number (step S1), the speed / position detection unit 55 determines whether or not the hole number has changed from the previous value (step S2). If there is no change (NO), the hole number changes. A counter (interval measurement counter) for measuring the interval to be incremented is incremented (step S8). Then, the rotational speed (angular speed ω) of the motor 1 is calculated from the value of the counter, and the motor position (electrical angle) is calculated by integrating the speed (step S9).

On the other hand, if the hole number has changed from the previous value in step S2 (YES), the motor speed determined at that time is stored as the previous value (step S3). When the motor speed is newly calculated from the value of the interval measurement counter (step S4), the interval measurement counter is cleared to zero (step S5). Subsequently, when the motor position for each electrical angle of 60 degrees is calculated from the current hole number and the previous hole number (step S6), the mechanical angle is calculated from the motor position (step S7).
In the configuration of the permanent magnet motor 1 of the present embodiment, the electrical angle of 360 degrees corresponds to a mechanical angle of (360/24 =) 15 degrees, so the electrical angle of 60 degrees is further 1/6 of the mechanical angle. Corresponds to 5 degrees. Therefore, the mechanical angle can be obtained by accumulating the values.

  Next, as shown in FIG. 8, the rotor position detection process when permanent magnets having different magnetic fluxes are mixed will be described. Here, it is assumed that the pulse waveform of the signal based on the magnetic flux detected by the C-phase Hall sensor 68C is deviated as shown by the portion surrounded by the broken line in FIG. However, the deviation in this case does not correspond to the configuration of the rotor 3 shown in FIG. 8, and shows a case where the deviation is caused in the direction in which the pulse width expands due to the presence of a permanent magnet having a stronger magnetic force than other permanent magnets.

  Due to the above deviation, the timing at which the hole number changes from 3 to 7 is earlier than in the normal case (see FIG. 4C), and an error occurs in the detection angle (see FIG. 4E). The Hall sensor speed is detected at a value higher than the actual speed (see FIG. 4D). Then, the current waveform energized to the stator winding 5 of the permanent magnet motor 1 changes abruptly as shown by the broken line in FIG. Therefore, in order to correct such an error, the following processing is performed.

  FIG. 1 is a flowchart showing a process of correcting the speed and position, and is executed following the process of FIG. 2 executed at a cycle of 1 msec. First, similarly to step S2, it is determined whether or not the hole number has changed (step S11), and the subsequent processing is executed only when the hole number has changed (YES). It is determined whether or not the rotation direction of the motor 1 is the normal rotation direction from the change state of the hall number (step S12). In each case of the normal rotation (YES) and reverse (NO), the value of the correction number measurement counter described later is Then, it is determined whether or not the number of corrections determined in advance according to the structure of the rotor has been reached (steps S13 and S14).

  Here, the “number of times to be corrected” is, for example, a value obtained by doubling the number of magnets on the minority side with respect to the number of permanent magnets having different magnetic forces among the permanent magnets arranged on the rotor. For the rotor 3 of the present embodiment, the number “6” of the minor-number side alnico magnets 9b is doubled to “12”. That is, this corresponds to the fact that the rotor 3 makes one round in each of the forward rotation direction and the reverse rotation direction and passes through the positions A to F of the alnico magnet 9b shown in FIG. As shown in FIG. 15, the number of alnico magnets 9b is doubled for both the rising and falling sides of the output signal pulse in accordance with the change in the magnetic flux waveform detected by the Hall sensor 68. This is because a deviation occurs. FIG. 4 shows a case where a deviation occurs only on one side of the signal pulse for the sake of simplicity.

  In steps S13 and S14, if the value of the correction number measurement counter has reached the number to be corrected (NO), the process proceeds to steps S15 and S16, respectively. It is determined whether or not the position has already been corrected in the process. If the position has already been corrected (YES), the process proceeds to step S19 described later. If the position has not been corrected (NO), the process of FIG. 1 is terminated (CONTINUE).

  Further, the reason why the forward rotation and the reverse rotation are divided is that the Hall sensors that cause erroneous detection differ depending on the rotation direction of the motor. This phenomenon will be described with reference to FIG. FIG. 6 shows three-phase signal pulse waveforms output when the motor rotates forward and when it reverses. However, in this case, the arrangement of the Hall sensors A, B, and C is different from the case shown in FIG. 9, and the C-phase Hall sensor is located at the center. Further, in order to clarify the change of the waveform, the pulse waveform is partially inverted as described above.

  That is, when the rotor rotates in the forward rotation direction (right direction in the figure) as shown in FIG. 6A, partial inversion occurs in the A-phase signal pulse arranged at the right end in the figure. When the rotor rotates in the reverse direction (left direction in the figure) as shown in FIG. 6B, partial inversion occurs in the B-phase signal pulse arranged at the left end in the figure. Thus, when a plurality of hall sensors are arranged, the sensors arranged on both ends are greatly affected.

  Refer to FIG. 1 again. If the value of the correction number measurement counter has not reached the number to be corrected in either step S13 or S14 (YES), the process proceeds to step S17, and the change of the hole number corresponds to the forward rotation direction and the reverse direction. It is determined whether or not the order has changed. If the order is the same (YES), the process proceeds to step S18. If the order is not satisfied (NO), the process proceeds to step S19.

  Here, the case where (NO) is determined in step S17 will be described with reference to FIG. FIG. 5 shows a case where the signal pulse width of the C phase is changed so as to expand more greatly. In the case of normal forward rotation, the hole number “1” is next to “3”, but the number “1” continued as a result of the C-phase signal pulse falling significantly changing beyond the electrical angle of 60 degrees. Later, an abnormal level combination is made (HLH), and the error E is encoded by the encoder 55E. Even in such a case, the process proceeds to step S19 to perform correction.

  In step S18, it is determined whether or not a false detection as shown in FIG. 4 has occurred. That is, the motor speed ω_h calculated in step S4 is compared with a threshold value obtained by multiplying the previous value ω_h_d1 stored in step S3 by a predetermined ratio, and the calculated motor speed has changed to the threshold value or lower than the threshold value. Determine whether it has changed. If none of the cases apply (NO), it is determined that no erroneous detection has occurred, and no correction is performed. On the other hand, if any of the cases applies (YES), it is determined that the detected ω_h is not detected by the actual rotor position / speed, but is caused by the Hall sensor detection error caused by the influence of the magnet having different magnetic force. To do. That is, it is determined that an erroneous detection as shown in FIG. 4 has occurred (in this case, calculated motor speed ≧ threshold), the process proceeds to step S19 and correction is performed.

  In step S19, instead of the motor speed calculated in step S4, the previous value stored in step S3 is used for the calculation process, and the hall sensor speed ω_h employed this time is rewritten to the previous value ω_h_d1. Correction is performed by integrating the speed to obtain the rotor position (step S20). By correcting the Hall sensor detection angle using this ω_h_d1, the angle detection error can be reduced, the motor current can be controlled without abrupt changes, and no noise due to erroneous detection due to the influence of magnets with different magnetic forces does not occur. .

  Subsequently, the current hole number and the previous hole number ("7" and "3" in the case of FIG. 4) are stored, and the motor mechanical angle obtained in step S7 is also stored (step S21). Then, the rotation direction of the motor 1 is determined in the same manner as in step S12 (step S22), and the same determination as in steps S15 and S16 is performed for each of forward rotation (YES) and reverse rotation (NO) (steps S23 and S24). ). Then, if “YES” is determined for each, the normal rotation and inversion correction count measurement counters are incremented (steps S25 and S26).

  Therefore, when the motor 1 makes one rotation at a mechanical angle in the forward direction and the reverse direction, the respective correction count measurement counters are equal to or greater than the “number of corrections”, and therefore, it is determined (NO) in steps S13 and S14. The determinations at steps S15 and S16 are made. If the hole number of the mechanical angle has been corrected (YES), the process proceeds to step S19 and the correction is similarly performed.

  It is assumed that the series of position and speed detection processes described above and their correction processes are applied when the washing machine is actually operated. FIG. 12 shows an operation sequence of the washing machine. First, before water supply is started, for example, the drum 27 is rotated at a predetermined acceleration, and the integrated value of the q-axis current sampled during the period is evaluated. The weight sensing to be measured (weight detection processing) is performed. Subsequently, the washing operation, the dehydrating operation, and the rinsing operation are repeated (then, the drying operation is performed according to the user's selection).

Then, while the first weight sensing operation is performed, the speed / position correction unit 80 performs a series of processes in FIG. 2 to determine and store the position to be corrected. When the weight sensing operation is performed by rotating the drum 27 only in one direction, it is sufficient to perform only one rotation in the reverse direction after the operation is completed. In the subsequent washing operation or the like, since “NO” is determined in steps S13 and S14, the stored rotational position (steps S15 and S16: YES) is operated using the correction values obtained in steps S19 and S20. To do.
Then, since the load is heavy and the motor current increases, correction is performed at the determined correction position at the time of washing operation, so when a large current is applied, the current does not change abruptly and noise is not generated and stable. Driving is possible. Further, since the error between the speed detection and the angle detection is reduced, the followability of the motor speed control becomes good, and the washing performance as a washing machine is improved.

As described above, according to the present embodiment, when the permanent magnet motor 1 is configured by arranging the two types of magnets having different magnetic forces, the neodymium magnet 9a and the alnico magnet 9b, on the rotor 3, the speed / position detection is performed. When the rotational speed of the permanent magnet motor 1 is detected using the three hall sensors 68 (A, B, C), the unit 55 detects the position of the rotor 3 based on the rotational speed. When the speed / position correction unit 80 detects the boundary between the neodymium magnet 9a and the alnico magnet 9b from the change state of the sensor signal output by the hall sensor 68, the rotational speed detected by the speed / position detection unit 55 or The rotor position was corrected.
Therefore, even when the sensor signal output from the hall sensor 68 is deviated due to the magnetic force difference between the neodymium magnet 9a and the alnico magnet 9b, an accurate rotor position can be obtained by correction. When the permanent magnet motor 1 is driven and controlled via the inverter circuit 52 based on the rotor position, it is possible to avoid the occurrence of noise due to a sudden change in the energization current and to prevent the permanent magnet motor 1 from stepping out.

  Further, the speed / position correction unit 80 stores the position of the boundary detected during rotation of the permanent magnet motor 1, and thereafter performs correction when the stored boundary is exceeded, so that correction processing can be performed more easily. Can do. Then, the speed / position correction unit 80 monitors the time during which the pulse interval of the sensor signal output from the Hall sensor 68 changes when the permanent magnet motor 1 is rotated when the boundary is exceeded, by using a counter. Since correction is performed when the time exceeds the allowable range, it can be reliably detected that the output state of the sensor signal has changed.

Further, the speed / position correction unit 80 changes the Hall sensor 68 to be corrected according to the rotation direction of the permanent magnet motor 1. That is, when the three hall sensors 68 (A, B, C) are arranged, the hall sensors 68 (A, C) located at both ends are easily affected by the magnetic change, and the hall sensors 68 (A, C) are in the rotational direction of the rotor 3. Since it differs depending on the situation, the correction can be performed appropriately.
In addition, the speed / position correction unit 80 performs correction even when the combination of the level changes of the sensor signals output from the three hall sensors 68 is an abnormal pattern combination. Even when the difference in the magnetic force is large and the deviation width of the sensor signal pulse becomes large, the correction can be performed.

The alnico magnet 9b disposed in the rotor 3 is a permanent magnet having a coercive force that is low enough to change the amount of magnetization, and the magnetization controller 58 detects the rotor detected by the speed / position detector 55. Since at least a part of the alnico magnet 9b is magnetized according to the position, the characteristics of the permanent magnet motor 1 can be applied to high torque output and low speed rotation by changing the magnetization state of the alnico magnet 9b. It can be changed to apply to low torque output and high speed rotation.
In addition, the washing / drying machine 21 includes the motor control system 70 and rotates the drum 27 by the rotational driving force generated by the permanent magnet motor 1 to perform the washing operation, so that the operation control can be stabilized. Then, by changing the characteristics of the permanent magnet motor 1 as described above, it is possible to perform the operation with high efficiency by adapting the characteristics suitable for the washing operation and the characteristics suitable for the dehydration operation, and the power consumption can be reduced.

  Further, when the washing / drying machine 21 performs a weight sensing operation for detecting the weight of the laundry at the start of operation, the speed / position correction unit 80 of the motor control device 50 performs the weight sensing operation. Alternatively, the boundary is detected before water supply is started in the drum 27, and the boundary position is stored. Therefore, since the boundary detection process is completed before the washing operation in which the water supply to the drum 27 is started and the load becomes heavy, the correction can be performed at the detected position when the washing operation is performed. Therefore, during an operation period in which a relatively large current is applied, sudden changes in the current value based on the position detection error and generation of noise can be avoided, and the operation can be performed stably.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
For example, even the same permanent magnet may have different characteristics (magnetic force) in the manufacturing process. Even when such manufacturing variations occur, the position detection can be accurately performed by performing the correction of the present invention.
The arrangement ratio of the neodymium magnets 9a and alnico magnets 9b may be appropriately changed according to the individual design.
The low coercive force permanent magnet is not limited to an alnico magnet, but may be another samarium / cobalt magnet, for example. Further, the high coercivity permanent magnet is not limited to the neodymium magnet.

There may be three or more types of permanent magnets having different magnetic forces.
The speed / position estimation unit 54 and the magnetization control unit 58 may be provided as necessary.
As for the correction, only the rotor position may be corrected without correcting the rotational speed.
The number of hall sensors 68 may be two or four or more.
The magnetic detection sensor is not limited to a hall sensor, and may be any sensor that outputs a signal according to the result of detecting magnetism.
The present invention is not limited to a washing machine, and can be applied to any permanent magnet motor in which a part of the magnet on the rotor side has a different magnetic force is to be detected or controlled.

  In the drawings, 1 is a permanent magnet motor, 3 is a rotor, 9a is a neodymium magnet, 9b is an alnico magnet (low coercive force permanent magnet), 21 is a drum type washer / dryer, 50 is a motor controller, 52 is an inverter circuit, 55 Is a speed / position detection unit (speed / position detection unit), 58 is a magnetization control unit (magnetization control unit), 68 is a Hall sensor (magnetic detection sensor), 80 is a speed / position correction unit (correction unit), and 82. Indicates a rotor position detection device.

Claims (5)

In a part of a plurality of permanent magnets arranged on the rotor, a permanent magnet motor including a permanent magnet having a different magnetic force is to be detected.
When detecting the rotational speed of the permanent magnet motor using a plurality of magnetic detection sensors, speed / position detecting means for detecting the position of the rotor based on the rotational speed;
When the boundary of the permanent magnets having different magnetic forces among the plurality of permanent magnets is detected from the change state of the sensor signal output by the magnetic detection sensor, the rotational speed detected by the speed / position detection means or the rotor A rotor position detection apparatus comprising: a correction unit that corrects the position.   2. The rotor position detecting device according to claim 1, wherein the correcting means stores the position of the boundary detected during rotation of the permanent magnet motor, and thereafter performs correction when the stored boundary is exceeded.   The correction means monitors when the pulse interval of the sensor signal output from the magnetic detection sensor changes when the boundary is exceeded, and corrects when the change time exceeds an allowable range. The rotor position detecting device according to claim 1 or 2.   4. The rotor position detection device according to claim 1, wherein the correction unit changes a magnetic detection sensor to be corrected in accordance with a rotation direction of the permanent magnet motor. 5.   5. The correction unit according to claim 1, wherein the correction unit performs correction even when a combination of level changes of the sensor signals output from the plurality of magnetic detection sensors is an abnormal pattern combination. The rotor position detection apparatus in any one.

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