JP2014087511A - Washing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing machine in which reliability of a DC brushless motor has been enhanced.SOLUTION: A washing machine includes: a washing tub which accommodates laundry; an outer tub in which the washing tub is disposed; a DC brushless motor which rotationally drives the washing tub; and an inverter drive device which drives and controls the DC brushless motor. The washing machine has a dewatering process of centrifugally dewatering moisture contained in the laundry. The dewatering process has a plurality of dewatering steps of accelerating the washing tub gradually from a low rotation speed to a high rotation speed. When the rotation speed of the washing tub in a predetermined dewatering step is less than a rotation speed threshold value, and an electric current supplied to the DC brushless motor is more than an electric current threshold value, the DC brushless motor is determined to be overloaded.

Description

  The present invention relates to a washing machine having an inverter drive device.

  Motors that drive agitating blades and washing / dehydrating tubs in electric washing machines are required to be compatible with a variety of drive modes and to reduce operating noise and power consumption, so the use of DC brushless motors has increased. ing.

  A DC brushless motor basically has a three-phase winding consisting of U, V, and W on the stator, a permanent magnet such as neodymium is used for the magnetic pole of the rotor, and drive current is supplied to the three-phase winding by inverter control. It is the structure which supplies and drive | operates.

  Also, since the motor needs to manage the temperature of the winding, even in a DC brushless motor, the temperature of the winding is detected by the temperature detecting means, and the drive current is controlled so that the winding temperature does not rise abnormally. Has been done.

JP 2005-31570 A

  In the above prior art documents, when a DC brushless motor rises in temperature due to an overcurrent at the time of rotation restraint due to an overload or some trouble, the temperature of the winding is detected by a temperature protector provided in the stator core of the stator. Is disclosed to prevent the windings from being burned out.

  In the washing machine, after the washing operation and the rinsing operation, the washing tub is rotated at a high speed to centrifugally dehydrate water contained in the laundry. In this centrifugal dewatering process, if a drainage failure occurs due to a clogging of the drainage hose, the amount of drainage decreases, and if the amount of water dehydrated from the laundry exceeds the amount of drainage, it is dewatered between the washing tub and the outer tub. Fill with water containing enough detergent. This full water becomes a resistance that prevents rotation of the washing tub, and the dehydration rotation does not increase to the predetermined rotation speed.

  In addition, when the dehydrating liquid contains a large amount of detergent, the dehydrated water present between the washing tub and the outer tub is stirred by the rotation of the washing tub and foams. This foaming further impedes the rotation of the washing tub.

  In a washing machine that performs inverter drive control for dehydrating and driving a washing tub with a DC brushless motor, rotation of the DC brushless motor is detected by a rotation speed detection sensor. When the rotation speed sensor detects an increase in dehydration rotation due to poor drainage or foaming failure, the current supplied to the DC brushless motor is further increased to control the dehydration rotation to a predetermined rotation speed. For this reason, in the case of overload due to poor drainage or foaming, an increase in current supplied to the winding of the DC brushless motor becomes excessive, and the temperature of the winding rises and the winding is burned out.

  In the above-mentioned prior art document, the temperature of the winding is detected by a temperature protector to cut off the overcurrent. When detecting the temperature rise of a winding with a temperature protector, there is a temperature difference between the surface and the inside of the winding, and there is an error in the detection of the temperature protector. Not going. For this reason, although it does not lead to burning on the surface of the winding, the insulating coating is damaged in the inside, which may lead to a short circuit between the wires of the winding.

  On the other hand, if the detection temperature is lowered to prevent overheating with the temperature protector, the temperature protector will erroneously detect that the control current value to the motor is in an overcurrent state even when the DC brushless motor is operating normally. Operation control is not possible.

  Therefore, it is difficult to determine whether or not the DC brushless motor is in an overload state in the dehydration process by using only the temperature protector.

  In addition, there is an overcurrent prevention control in which a current detection sensor detects a transition of a current supplied to the DC brushless motor in the dehydration process and interrupts the overcurrent. However, even in a normal dehydration process that does not reach overload without drainage failure or foaming disturbance, the supply current value to the DC brushless motor changes greatly from the start of dehydration to the end of dehydration, and the change is in the overload state. It is difficult to distinguish whether the product is normal or normal. Therefore, it is difficult to determine whether or not the DC brushless motor is in an overload state in the dehydration process using only the current detection sensor.

  Thus, it is difficult to determine an overload state only by temperature and current. Therefore, as a control for suppressing the burnout of the DC brushless motor, the set temperature of the temperature protector and the set current value of the current detection sensor are lowered. As a result, overloading during dehydration operation can be avoided, but on the other hand, since the set temperature and set current value are lowered, it stops even in dehydration operation that does not reach the overload state, and the frequency of stoppage increases, so the usability is impaired. Become.

  In view of the above problems, an object of the present invention is to provide a washing machine with improved reliability of a DC brushless motor.

  In order to achieve the above object, the present invention provides a laundry tub for storing laundry, an outer tub in which the laundry tub is placed, a DC brushless motor that rotationally drives the laundry tub, and drive control of the DC brushless motor. In the washing machine including the inverter driving device, and having a dehydration step of centrifugally dehydrating water contained in the laundry, the dehydration step includes a plurality of steps of accelerating the washing tub in stages from a low rotation speed to a high rotation speed. The DC brushless motor has a dehydration step, and when the rotation speed of the washing tub in a predetermined dehydration step is less than a rotation speed threshold value and the current supplied to the DC brushless motor exceeds the current threshold value, Determined to be overloaded.

  ADVANTAGE OF THE INVENTION According to this invention, the washing machine which improved the reliability of DC brushless motor can be provided.

It is related with the Example of this invention, and is a vertical side view of a washing-drying machine. It is related with the Example of this invention, and is a vertical side view of a drive device. FIG. 4 is a block diagram of a control device showing a basic drive circuit of a DC brushless motor, relating to an embodiment of the present invention. It is related with the other Example of this invention, and is a block diagram of the control apparatus which shows the basic drive circuit of DC brushless motor. It is a figure which shows the appropriate coil surface temperature change pattern of the DC brushless motor in the spin-drying | dehydration process which carries out centrifugal dehydration. It is a figure which shows the appropriate dehydration supply current change pattern supplied to DC brushless motor in the spin-drying | dehydration process which carries out centrifugal dehydration. It is a figure which shows the appropriate dehydration step change pattern of the washing tub in the dehydration process which carries out centrifugal dehydration. It is a figure which shows the coil surface temperature change pattern of the overload abnormal state of DC brushless motor in the spin-drying | dehydration process which carries out centrifugal dehydration. It is a figure which shows the dehydration supply current change pattern of the overload abnormal state supplied to the DC brushless motor in the dehydration process which performs centrifugal dehydration. It is a figure which shows the spin-drying | dehydration step change pattern of the overload abnormal state of DC brushless motor. It is a figure which shows the control flow which concerns on the Example of this invention and stops the overload driving | operation in a spin-drying | dehydration operation.

  First, along with FIG. 1, an outline of a washing and drying machine will be described based on an embodiment in which the present invention is applied to a washing and drying machine that performs a series of steps from washing to drying.

  This washing / drying machine has an outer frame 1, a corner plate 2 at the upper four corners, four suspension bars 3 attached to the corner plate 2, and an outer tub 4 supported by the suspension bar 3. Since the outer tub 4 is supported via a push spring 5 attached to the hanging rod 3, vibration of the outer tub 4 during washing and dehydration is absorbed and relaxed and is not easily transmitted to the outer frame 1. On the outside of the bottom of the outer tub 4, a metal base 6 for attaching a drive mechanism equipped with a motor is attached. The drive device 7 has a double rotation output shaft 71 that is an output shaft. The double-rotation output shaft 71 penetrates the bottom of the outer tub 4 and protrudes to the inside of the bottom of the outer tub 4, and is coupled to the bottom of the washing and dewatering tub 9 by screws.

  The washing / dehydrating tub 9 is placed in the outer tub 4 and accommodates the laundry 33. The upper end of the double rotation output shaft 71 is fixed to the outer bottom portion of the washing / dehydrating tub 9 as a washing tub, and the washing / dehydrating tub 9 is supported by the double rotation output shaft 71 and rotates. An inner shaft 71 b of the double rotation output shaft 71 further penetrates the washing / dehydrating tub 9 and protrudes to the inside of the bottom of the washing / dehydrating tub 9. The agitating blade 10 is attached to the projecting inner shaft 71b, and the agitating blade 10 is installed in the washing and dewatering tub 9 so as to be rotatable left and right. An annular fluid balancer 11 is attached to the upper opening edge of the washing and dewatering tub 9.

  The base 6 is further provided with a drain electromagnetic valve 12 for connecting a water inlet to a drain outlet 4a opened at the bottom of the outer tub 4, and an electric blower fan 13 interposed in a dry air circulation air passage 18 described later. Install. A drainage hose 14 is connected to the outlet of the drainage electromagnetic valve 12 and led out of the machine. Further, a ground wire 15 is connected to the base 6 and led out of the machine.

The upper end opening of the outer tub 4 is covered with an outer tub cover 16 having an inner clothing input port 16a.
The inner clothing input port 16a is covered with an inner lid 17 so as to be freely opened and closed. An exhaust port 4 b is formed in the lower part of the side wall of the outer tub 4. On the side surface of the side wall, an ascending dehumidifying air passage 18a extending upward from the exhaust port 4b, and a descending air passage 18b that is folded back from the upper end of the ascending dehumidifying air passage 18a and extends downward and continues to the intake port of the electric blower fan 13 is provided. Is provided. Further, on the side surface of the side wall, there is provided a dry air circulation air passage 18 configured by an upward heating air passage 18 c that extends upward from the exhaust port of the electric blower fan 13 and bends along the upper surface of the outer tank cover 16.

  A metal cooling plate 19 for water cooling is installed in the ascending dehumidifying air passage 18a, and a humidity sensor 20 is installed under the descending air passage 18b. A heater 21 is installed at a portion of the ascending heating air passage 18c that is bent along the upper surface of the outer tub cover 16, and a hot air outlet 22 provided at the tip of the heater 21 penetrates the outer tub cover 16 to perform washing and washing. It installs so that it may open toward the inside of the dehydration tank 9.

  The upper end portion of the outer frame 1 is covered with a top cover 23 attached to the outer frame 1. The top cover 23 includes an outer clothing input port 23a. The outer clothing input port 23a of the top cover 23 is covered with an outer lid 24 that can be opened and closed. A control device 25 with an integrated operation panel is built in the front edge of the top cover 23. The control device 25 is connected to the drainage electromagnetic valve 12 and the drive device 7 via the wire harness 25a. A washing water supply electromagnetic valve 26, a cooling water supply electromagnetic valve 27, and a water receiving port 28 are built in the rear edge of the top cover 23. The water receiving port 28 is connected to a water supply hose (not shown) to receive water from a water tap (not shown), and the washing water supply electromagnetic valve 26 controls water supply from the water receiving port 28 to the washing water supply port 29. The cooling water supply electromagnetic valve 27 controls water supply from the water receiving port 28 to the cooling water supply port 30.

  The washing water supply port 29 is installed in the outer tub cover 16 via the flexible hose 31 so as to open toward the outer tub 4. The cooling water supply port 30 is installed so that the cooling water flows down from the upper end of the cooling plate 19 along the surface of the cooling plate 19. Since the outer tub 4 moves (vibrates) relative to the outer frame 1, flexible hoses 31 and 32 are interposed in the water channel between the water supply electromagnetic valves 26 and 27 and the water supply ports 29 and 30. Water injection from the water supply port 29 into the washing / dehydrating tub 9 is sprayed on the laundry 33 in the washing / dehydrating tub 9.

  Next, a specific configuration of the driving device 7 will be described with reference to FIG. The driving device 7 has a DC brushless motor 72. The DC brushless motor 72 has a stator 72a and a winding 72b applied to the stator 72a. The winding 72b is provided with a U / V / W three-phase winding and supplies a drive current with an electrical angle of 180 degrees. The drive device 7 has a structure in which the rotation of the DC brushless motor 72 is transmitted to the speed reduction mechanism 74 via the clutch mechanism, and is connected to the double rotation output shaft 71 from the speed reduction mechanism 74.

  The speed reduction mechanism 74 accommodates a planetary gear unit supported by a bearing in a speed reduction mechanism case 74a, and an outer input shaft 74c and an outer output shaft 71a of the double rotation output shaft 71 from the outer case 74b of the planetary gear unit. To derive. Then, the planetary gear shaft in the planetary gear unit 74d is led out as the inner input shaft 74e inside the outer input shaft 74c, and the inner output shaft 71b of the double rotation output shaft 71 is led out from the outer planetary gear. The speed reduction mechanism case 74 a is attached to an attachment base 75 for attachment to the base 6.

  In the DC brushless motor 72, a rotor 72c having a neodymium (Nd) magnet that is a rare earth magnet as a magnetic pole is attached to an inner input shaft 74e in the speed reduction mechanism 74. The stator 72a provided with the winding 72b is attached to the speed reduction mechanism case 74a in the speed reduction mechanism 74 via the stator case. The Hall IC magnetic sensor 72d detects the rotational position of the magnetic pole attached to the rotor 72c and is used to measure the rotational speed of the rotor 72c.

  The clutch mechanism includes a slider that engages with a serration formed on the outer periphery of the outer input shaft 74c in the speed reduction mechanism 74 and slides in the axial direction. Then, the clutch lever 73b is swung by the electric operating device 73a attached to the attachment base 75, thereby sliding the slider to intermittently engage the outer input shaft 74c and the rotor 72c. is there. Incidentally, when the slider engages with the rotor 72c, the rotation of the rotor 72c is transmitted to both the outer input shaft 74c and the inner input shaft 74e, and when the engagement between the slider and the rotor 72 is released, the rotor 72c. Is transmitted only to the inner input shaft 74e.

  FIG. 3 is a block circuit diagram of a basic drive control device for a DC brushless motor in this embodiment. The basic drive control device includes a power supply 80, a power switch 81, a filter circuit 82, a rectifier circuit 83, an inverter drive circuit 84, a microcomputer 85, and a drive circuit 86. Furthermore, the basic drive control device is provided in the current detectors 87U, 87V, 87W, the current detection circuit 88, and the DC brushless motor 72, and has a Hall IC magnetic sensor 72d (rotation speed detection means). The current detectors 87U, 87V, 87W detect currents supplied to the phase windings U, V, W of the DC brushless motor 72. The detected detection signal is provided to the microcomputer 85 via the current detection circuit 88 and processed. When the power source 80 is connected to AC 100 V and the power switch 81 is turned ON, a power source current is supplied to the drive circuit 86. The supplied power supply current passes through a filter circuit 82 that cuts power line noise and airwave noise, is converted from AC to DC by a rectifier circuit 83, and is supplied to an inverter drive circuit 84 and a drive circuit 86.

  The inverter drive circuit 84 has an IGBT element circuit and supplies a direct current to each phase winding U, V, W of the DC brushless motor 72. The microcomputer 85 controls the operation of the DC brushless motor 72 by controlling the inverter drive circuit 84. Further, when controlling the rotation of the DC brushless motor 72, the rotational speed of the rotor 72c is detected by the magnetic sensor 72d of the Hall IC which is a rotational speed detecting means, and the detection signal is taken into the microcomputer 85 to control the speed of the DC brushless motor 72. Do.

  The current detection circuit 88 that captures the current detection signals of the current detectors 87U, 87V, and 87W includes a current input capture circuit and an integration circuit. The current input capturing circuit captures detection currents of the current detectors 87U, 87V, and 87W, respectively. The current detection signals of the current detectors 87U, 87V, 87W are taken into a current input taking circuit in a short time unit, averaged by an integrating circuit, and calculated by the microcomputer 85.

  4 is a block circuit of the basic drive control device for the DC brushless motor shown in FIG. 4 in place of providing the current detectors 87U, 87V, 87W shown in FIG. A triac 89, which is a semiconductor switching element, interposed between the inverter drive circuit 84 is provided so as to be interposed between the filter circuit 82 and the rectifier circuit 83. Others are the same as those in the embodiment shown in FIG.

  In the embodiment shown in FIG. 4, the load current supplied from the rectifier circuit 83 to the inverter drive circuit 84 is detected. This load current detection detects the current supplied to the DC brushless motor 72. Since the current detectors 87U, 87V, and 87W are not required, the circuit is simpler than the circuit shown in FIG.

  Further, the triac 89 is turned off when the microcomputer 85 determines that the DC brushless motor 72 is overloaded based on the rotational speed value and current value of the DC brushless motor 72, and the power supply to the DC brushless motor 72 is stopped to damage the DC brushless motor 72. Protect.

  Next, the dehydration operation will be described. FIG. 5 shows changes in rotational speed, motor supply current value, and motor temperature during the dehydration of the DC brushless motor for driving the washing tub. FIG. 5 (FIG. 5C) is a diagram showing an increase in the dehydration rotation due to the dehydration operation time. In this way, by increasing the dehydration rotation step by step from the step S1 to the constant speed rotation of S7, the moisture contained in the laundry 33 is gradually dehydrated, so that the foaming phenomenon at the time of dehydration can be avoided. Come out.

  5 (FIG. 5B) shows a change in the value of the current supplied to the DC brushless motor from step S1 to S7 described in FIG. 5 (FIG. 5C). 5 (FIG. 5A) shows the change in the motor coil surface temperature of the DC brushless motor from step S1 to S7 described in FIG. 5 (FIG. 5C). It is the measurement data when the room temperature is 23 ° C. These experimental values shown in FIG. 5 (FIGS. 5-A to 5-C) are states during operation of the DC brushless motor, and are related to the dehydration time.

  The dehydration operation takes about 5 minutes from the start of the dehydration operation to the end of the dehydration operation. The DC brushless motor is controlled by the basic drive controller so that the washing and dewatering tub 9 is accelerated stepwise from the low rotation speed dehydration step to the high rotation speed dehydration step and the dehydration rotation is changed. S1, S2, S3, S4, S5, and S6 change so as to increase in steps in a short time, and the total time of S1, S2, S3, S4, S5, and S6 is almost half of the dehydration operation time (2. 5 minutes), the maximum dewatering rotation S7 of the remaining dewatering operation time is kept constant at about 750 RPM. At the end of the dewatering operation, reverse braking 90 is applied to decelerate the inertial rotation speed of dewatering.

  A standard operation mode in which the dehydration pattern normally changes from S1 to S7 is provided in the microcomputer 40 as a standard dehydration step change pattern 750 RPM. Based on the standard dehydration step change pattern 750 RPM, the DC brushless motor is controlled for dehydration operation by the basic drive controller of the DC brushless motor. In this control, the rotation speed of the DC brushless motor is detected by the rotation speed detecting means (Hall IC 72d) so that the rotation of the DC brushless motor follows the standard dehydration step change pattern 750 RPM.

  As shown in FIG. 5 (FIG. 5B), at the start of the dehydration operation, the supply current value to the DC brushless motor 72 suddenly increases temporarily, so that the motor coil surface temperature rises accordingly (FIG. 5 (FIG. 5B)). 5A)). At the time of moving from the dehydration step S1 to S2, the supply current value rapidly increases to about 6.5 A, and the motor coil surface temperature rapidly increases to 92 ° C. and immediately decreases. After that, the supply current value to the DC brushless motor 72 is temporarily increased even when the speed is increased stepwise as S3, S4, S5, S6, and S7. Therefore, the motor coil surface temperature is temporarily increased when the current increases. Temperature rise is observed. In S7, it changes at a substantially constant high rotational speed, the supply current value is constant at 3.2A, and the motor coil surface temperature also remains constant at about 70 ° C.

  At the end of the dehydration operation, the supply current increases momentarily due to reverse braking 90. Since the supply current instantaneously becomes about 7.6 A, the motor coil surface temperature reaches 110 ° C. and immediately drops. The allowable temperature limit of the motor coil is 115 ° C., and since the temperature reaching 110 ° C. is an instantaneous value, there is no thermal damage to the motor coil.

  Needless to say, in the dehydration operation, the washing tub is rotated at a high speed, and the washing water contained in the laundry 33 is centrifugally dehydrated. When the dehydration pattern of the washing tub is rapidly increased, the amount of washing water dehydrated from the laundry 33 increases rapidly, and does not drain beyond the drainage capacity of the drainage hose, and the dehydrating liquid is between the washing tub and the outer tub. Accumulate. This accumulated water becomes a resistance that prevents the rotation of the washing tub and the dehydration rotation of the washing tub does not increase. Therefore, the dehydration operation is controlled so as to gradually accelerate the washing tub during dehydration.

  At the time of the dehydration steps S1 and S2, the amount of the washing liquid contained in the laundry 33 is 4-5 times the weight of the clothes. Since the washing tub into which the heavy laundry 33 is placed is rotated, the supply current to the DC brushless motor 72 increases as shown in FIG. 5 (FIG. 5B) at the time of S1 and S2. Along with the transition of dehydration, the amount of washing liquid contained in the laundry 33 decreases and the load of the DC brushless motor becomes lighter. Therefore, the supply current does not increase for the increase in the dehydration pattern of the washing tub, and the supply current is half (about 3.2 A) of the dehydration step S1 (about 120 RPM) in the dehydration step S7 (about 750 RPM). It is falling. Although the temperature rise of the DC brushless motor tends to depend on the cumulative supply time of the supply current, since the supply current of S7 is much smaller than S1, the motor coil surface temperature is maintained at about 70 ° C.

  Thus, when the normal dehydration operation is performed in accordance with the dehydration pattern 750PRM, the dehydration process is not overloaded due to foaming or imbalance, and the current supply to the DC brushless motor also becomes the dehydration supply current change pattern. The temperature is within the allowable temperature rise without causing thermal damage to the motor coil.

  Now, rotation inhibition of the washing tub due to foaming during the dehydration operation will be described with reference to FIG. FIG. 6 shows the overload operation due to foaming in terms of the rotational speed of the DC brushless motor, the motor supply current value, and the motor temperature change.

  If foaming or poor drainage occurs during the dehydration operation, the dehydration rotation will not increase. This is because foamed foam or washing water is filled between the washing tub and the outer tub and becomes a resistance that hinders the rotation of the washing tub, and the DC brushless motor is overloaded. For this reason, dehydration rotation does not increase.

  As shown in FIG. 6 (FIG. 6C), when foaming occurs at the time of the dehydration step S3a, the rotation speed does not increase due to the rotational resistance of the washing tub, and the rotation speed does not increase as in the normal dehydration step S3b91. That is, foaming occurs due to poor drainage. However, in the dehydration step S1 where the primary resonance point (100 RPM or less) is present even if there is poor drainage, since the rotational speed at the time of dehydration is low from the laundry 33, the dehydrating liquid is not dehydrated by centrifugal force, and thus foaming does not occur.

  Now, since the moisture contained in the laundry 33 is dehydrated by the dewatering centrifugal force from the region around the dehydration step S2 where the dewatering amount increases, the dehydrated liquid amount increases and foaming starts, and the dehydration step S3 is started. As the rotational speed of a certain secondary resonance point (180 RPM to 220 RPM) approaches, the amount of dehydrated liquid further increases and foaming increases. In the normal dehydration process, the amount of water contained in the laundry 33 decreases as the dehydration proceeds after the dehydration step S4, and the amount of water dehydrated from the laundry 33 decreases.

  When the load of the DC brushless motor increases due to the rotational resistance due to foaming and the dewatering pattern does not rise, the basic drive controller of the DC brushless motor increases the supply current to the DC brushless motor so as to follow the dewatering pattern (see FIG. 6 (FIG. 6B)). However, the rotational resistance of the DC brushless motor does not increase even if the supply current is increased due to the rotational resistance accompanying the progress of foaming, and the basic drive controller of the DC brushless motor further increases the supply current to increase the dehydration rotation. I do. With this increase in supply current, the supply current reaches about 15 (A) level, and the motor coil surface temperature rapidly increases to 220 ° C. as shown in FIG. 6 (FIG. 6A). The supply current reaching 15 (A) is defined as an overload supply current.

  Thus, when foaming occurs in the dehydrating operation and an overcurrent flows, the basic drive control device of the DC brushless motor performs forced stop control of the DC brushless motor in order to prevent motor burnout due to a rise in motor coil temperature. This stop control will be described along the dehydration control flow of FIG.

  This dehydration control flow shows the control from the end of the dehydration step S2 to S3. This control can be performed from the start of dehydration to the end of dehydration, but foaming is likely to occur around the region where the dehydration step S2 is passed (about 200 rpm).

  First, in step 100, whether or not the dehydration step S2 shown in FIG. If the dehydration step S2 is passed, the determination in step 300 is made. In step 300, a determination is made by comparing the actual operating rotational speed in the dewatering step S3 shown in FIG. 6C with the dewatering pattern threshold 90 in the dewatering step S3. The dehydration pattern threshold value 90 is indicated by a one-dot chain line 90 in FIG. 6 (FIG. 6C). A chain line S3b91 shown in the figure is the normal dehydration in the dehydration step S3. The dehydration pattern threshold 90 is set lower than the dehydration pattern S3b91 and higher than the rotation speed of the secondary resonance point.

  In step 300, when the rotational speed of actual operation in the dehydration step S3 is equal to or lower than the dehydration pattern threshold value 90 and a predetermined time has elapsed, the rotational speed of actual operation is determined to be equal to or lower than the dehydration pattern threshold value 90. If the predetermined time does not elapse even if the dehydration pattern threshold is 90 or less, the dehydration pattern threshold is not determined to be 90 or less.

  If it is determined in step 300 that the actual rotation speed is equal to or lower than the dehydration pattern threshold value 90, the determination in step 400 is immediately performed. In step 400, the actual supply current in the dehydration step S3 is compared with the supply current threshold 92 in the dehydration step S3. The supply current threshold value 92 is indicated by a one-dot chain line 92 in FIG. 6 (FIG. 6B). A chain line 93 shown in the figure is a normal dehydration supply current. The supply current threshold 92 is set higher than the normal dehydration supply current and lower than the overload supply current 94 (about 15 A).

  In step 400, when the actual supply current in the dehydration step S3 exceeds the supply current threshold 92 and a predetermined time has elapsed, it is determined that the DC brushless motor is overloaded, and overload dehydration is stopped (step 500). Even if the actual supply current exceeds the supply current threshold 92, it is not determined that the load is overloaded unless a predetermined time (about 60 seconds) elapses.

  If it is not determined in step 300 that the actual dehydration rotation speed is equal to or less than the dehydration rotation threshold value, dehydration is continued in step 600, and the determination by the step 300 is sequentially performed while dehydration is continued. If it is not determined at step 400 to be overloaded, dehydration is continued at step 600.

  In this way, if the rotational speed during actual operation is less than the dehydration pattern threshold and the actual supply current is greater than the supply current threshold due to foaming during the dehydration operation, it is determined that the load is overloaded and the dehydration operation is stopped. Therefore, thermal damage of the DC brushless motor can be prevented.

  This thermal damage prevention shutdown is determined when the actual rotational speed is less than the dehydration pattern threshold and the actual supply current is greater than the supply current threshold, so the conventional method using a temperature protector or current detection sensor is used. In comparison, the determination becomes more accurate. For this reason, compared with the conventional system, unnecessary operation stop that does not reach an overload can be suppressed, so that usability is improved.

  When the overload dehydration is stopped in Step 500, the predetermined amount 502 is supplied to the washing and dewatering tub 9 501 and the stirring blade 10 is stirred (Step 503) to eliminate the bubbles between the washing tub 9 and the outer tub 4. Do. After draining (step 504), the DC brushless motor 72 is driven again to restart the dehydration operation. The restarted dehydration operation is performed in the same manner as the above-described dehydration operation.

  The overload determination due to foaming is performed around the region where the dehydration step S2 is passed, that is, in a region where the rotational speed is higher than the location of the secondary resonance point, and is not performed in other regions of the rotational speed, thereby controlling the dehydration operation. Can be easy.

  In addition, by setting the dehydration pattern threshold value in the vicinity of the secondary resonance point including the secondary resonance point (rotation region slightly lower than the secondary resonance point to a slightly higher rotation region), it can cope with overload caused by foaming. it can.

  That is, due to an overload in which light foaming overlaps, the process proceeds to step 400 after it is determined in step 300 that the actual rotational speed is equal to or less than the dehydration pattern threshold. Since foaming is mild, there is little rotational resistance due to foaming. For this reason, before the supply current to the DC brushless motor is determined to be greater than or equal to the supply current threshold in step 400, the rotation speed exceeds the dehydration pattern threshold by increasing the supply current to the DC brushless motor, and the secondary resonance point is exceeded. Will pass. By passing through the secondary resonance point, an overload due to imbalance is reduced, and the suspension of the dehydration operation is avoided, so the frequency of the operation stop is reduced and the usability is improved.

DESCRIPTION OF SYMBOLS 9 ... Washing / dehydration tank 4 ... Outer tank 72 ... DC brushless motor 84 ... Inverter drive circuit 900 ... Dehydration step change pattern 910 ... Dehydration supply current change pattern 90 ... Dehydration pattern threshold 92 ... Supply current threshold

Claims (5)

Included in the laundry, comprising: a washing tub for storing laundry; an outer tub in which the washing tub is placed; a DC brushless motor that rotationally drives the washing tub; and an inverter driving device that drives and controls the DC brushless motor In a washing machine having a dehydration process of centrifugally dehydrating
The dehydration step includes a plurality of dehydration steps for accelerating the washing tub in stages from a low rotation speed to a high rotation speed.
Determining that the DC brushless motor is overloaded when the rotational speed of the washing tub in a predetermined dehydrating step is below a rotational speed threshold and the current supplied to the DC brushless motor exceeds a current threshold; A washing machine featuring. Included in the laundry, comprising: a washing tub for storing laundry; an outer tub in which the washing tub is placed; a DC brushless motor that rotationally drives the washing tub; and an inverter driving device that drives and controls the DC brushless motor In a washing machine having a dehydration process of centrifugally dehydrating
The dehydration step includes a plurality of dehydration steps for accelerating the washing tub in stages from a low rotation speed to a high rotation speed.
Washing characterized in that the DC brushless motor is stopped when the rotational speed of the washing tub in a predetermined dehydration step is lower than a rotational speed threshold and the current supplied to the DC brushless motor exceeds the current threshold. Machine. The washing machine according to claim 2,
A washing machine, wherein after the DC brushless motor is stopped, water is supplied to the washing tub, bubbles are placed between the washing tub and the outer tub, and then the DC brushless motor is driven again. The washing machine according to any one of claims 1 to 3,
The washing machine, wherein the DC brushless motor is stopped when the rotation speed threshold value is below a predetermined time and exceeds the current threshold value for a predetermined time. The washing machine according to any one of claims 1 to 3,
The washing machine according to claim 1, wherein the rotation speed threshold is lower than a dehydration pattern of the rotation speed of the washing tub in the dehydration step and higher than a secondary resonance point of the washing tub.