Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F37/00—Details specific to washing machines covered by groups D06F21/00 - D06F25/00
  • D06F37/30—Driving arrangements 
  • D06F37/304—Arrangements or adaptations of electric motors

Definitions

• the invention relates to a laundry treatment device such as a washing machine, tumble dryer or washer dryer with a rotatably mounted drum with at least approximately a horizontal axis of rotation, and with a drive motor arranged on the drum shaft in the form of a permanent magnet-excited synchronous motor, the stator of which is provided with a winding which is supplied with current by a converter .
• a washing machine is already known from DE 38 19 651 A1, in which the washing drum is driven directly without using the usual intermediate drive (drive belt, pulley). In these drives, the rotor forms the rotary motion transmission part to the drum of the washing machine.
• DE 38 19 651 A1 proposes to use an asynchronous motor with a squirrel-cage rotor. Such an engine is characterized by a relatively quiet running, but it has the disadvantage that under the given conditions such. B. large air gap and multi-pole design with asynchronous machines good efficiencies are not possible. Especially with a frequently operated household appliance, however, there is a desire for an environmentally friendly, ie. H. energy-saving mode of operation.
• a motor according to the preamble of claim 1 is known from DE 43 41 832 A1. There, a motor that drives the drum is described, which is designed as an inverter-fed synchronous motor. No further details are given on the type of engine.
• Washing machines with directly driving motors are also known which are constructed as external rotor motors (DE 44 14 768 A1, DE 43 35 966 A1, EP 413 915 A1, EP 629 735 A2).
• the rotor can be manufactured as a deep-drawn part, as a plastic bell or in a composite construction.
• the solution is advantageous as a deep-drawn part, since the iron forms the magnetic yoke at the same time.
• This design is, among other things, a typical version of fan motors.
• collectorless DC motors are used.
• Their stator winding can either be designed as a conventional three-phase winding with a winding step over several stator teeth or as a single-pole winding with winding around a stator tooth.
• the current is reversed using power semiconductors. The individual are dependent on the rotor position
• CONFIRMATION COPY Strands of the stator winding are energized by an inverter so that the field of excitation rotates with the motor.
• this motor control only ever flows a current in two phases, which is used to generate moments, the third phase remaining de-energized.
• the current flow in the individual strings is block or trapezoidal.
• Hall sensors In electronically commutated direct current motors, Hall sensors, magnetic sensors or optical sensors are used to sense the rotor position.
• the attachment of such sensors and the associated signal lines is associated with additional costs.
• sensors and cables are prone to failure.
• Another disadvantage is that operation with field weakening is not readily possible with such self-guided permanent magnet excited motors.
• the large torque and speed spreads between washing and spinning operations required in washing machines normally cause large spreads in the motor current. Therefore switchable or tapped windings must be installed or the motor winding and the power semiconductors must be dimensioned for the largest possible current.
• Synchronous motors with sinusoidal current and controlled via a converter are already known as servo drives. They are used where precise positioning is required.
• the stator winding is designed as a classic three-phase winding, and the number of poles of the rotor and stator are identical.
• the three-phase winding is characterized by common and known winding techniques, but has the disadvantage that the copper volume is particularly large in the winding heads, which increases the manufacturing costs and increases the depth of the motor. The latter would reduce the drum volume in washing machines with a given housing depth.
• servo drives for controlled operation require very precise and expensive sensors to detect the rotor position
• the invention thus presents the problem of optimizing the motor in terms of energy consumption, noise development and costs in a laundry treatment machine of the type mentioned at the outset. According to the invention, this problem is solved by a laundry treatment appliance with the features specified in claim 1. Advantageous refinements and developments of the invention result from the following subclaims.
• the copper insert is less than with a classic three-phase winding, in particular the copper volume of the winding heads is significantly lower. This makes the entire drive smaller and more compact. Due to the lower copper volume, higher efficiency can be achieved with the same motor size due to lower copper losses.
• a control device which adjusts the output voltage of the frequency converter by regulating such that a minimal sinusoidal current is established as a function of the load torque. Sinusoidal currents make the motor run very quietly and reduce the losses caused by current harmonics. This is particularly the case if the output voltage is set in the form of a sinus-weighted pulse width modulation. Furthermore, the torque-dependent current control ensures optimum efficiency at every load point.
• the number of magnetic poles differs in a characteristic manner from the number of stator poles.
• a ratio of rotor poles to stator poles of 2 to 3 or 4 to 3 is favorable. Only in these two cases does the vectorial addition of the voltages of a phase induced in the individual pole windings result in a maximum and an optimum in efficiency.
• stator poles With a pole ratio of 4 to 3, the use of about 30 stator poles is favorable in order to cover the required speed range from 0 to 2000 1 / min.
• the selected number of poles guarantees a safe start-up with externally controlled operation, a low torque ripple and a large speed spread.
• control device for regulating the motor current is based on a mathematical model of the motor and if the current is applied to the winding strands without the use of rotary sensors. Since the motor current and the voltage on the motor can be recorded in the frequency converter itself, no sensors are required on the motor.
• the mathematical model can be calibrated as required or continuously.
• the motor-specific parameters such as winding resistance, motor inductance and constant of the induced voltage can be determined using the current sensors and the microprocessor control in the frequency converter and the mathematical model can be adapted based on the measured values.
• the main advantage of the laundry treatment device designed according to the invention results from the possibility of dimensioning the number of turns of the stator windings in such a way that the amount of the induced voltage or the magnet wheel voltage for high speeds is greater than the maximum output voltage of the frequency converter.
• Such a winding design enables a field weakening operation of the synchronous motor in the higher speed range.
• the advantage of this winding design is a significant reduction in the motor current in washing mode. It can be chosen such that the motor can be operated with the same current in the washing and spinning mode. Because of the lower motor current, smaller and more cost-effective power semiconductors can therefore be used. In addition, the losses in the power semiconductors are reduced, which means that the overall efficiency of the motor and power electronics is higher than that of comparable ones
• field weakening can also be used to achieve good efficiencies at high speeds even with multi-pole, permanently excited synchronous motors, since the magnetic loss as a result of the field weakening is reduced.
• Collectorless DC motors can only be operated with extensive field weakening, since the position of the rotor position encoder would then have to be changed or the commutation times would have to be shifted computationally.
• a field weakening operation is not known for servo drives for the aforementioned reasons.
• FIG. 1 shows a section through a washing machine constructed according to the invention as
• FIG. 4 shows a single sheet of a stator (16) of the drive motor (10)
• Figure 5 shows a permanent magnetic rotor (15) in perspective
• FIG. 6 is a block diagram of the structure of the controlled drive with three-phase
• FIG. 7 is a block diagram of the structure of the sensorless controlled drive with three-phase synchronous motor
• the washing machine shown in Figure 1 has a housing (1) in which a tub (2) is suspended on springs (4) so that it can move. To dampen the vibrations, it is supported against the housing base (1a) by friction dampers (5).
• a drum (6) for holding laundry (not shown) is rotatably mounted in the tub (2) in a known manner.
• Drum (6), tub (2) and the housing front wall (1a) have corresponding openings through which the laundry can be filled into the drum (6).
• the openings can be opened through a front wall (1a) arranged door (7) are closed.
• the door (7) is locked by an electromagnetic locking device (8).
• the door lock is only shown schematically in the drawing.
• an electromagnetic closure device (8) itself is sufficiently known from the above-mentioned DE-OS 16 10 247 or from DE 34 23 083 C2 and is therefore not described in more detail.
• a control panel not shown
• a rotary selector switch 9
• the washing programs include a wash cycle and a subsequent rinse cycle, during which the laundry is spun several times.
• the washing speed for household washing machines is between 20 and 60 min-1, the spin speed should be as high as possible, especially during the last spin at the end of the wash cycle. It is limited by the resilience of the vibrating tub (2) - suspension (3; 4) - drive motor (10) - drum (6) system, the limits are currently around 1600 min-1.
• FIG. 2 shows a partial section through the rear area of a tub (2), a drum (6) and its drive motor (10).
• a four-armed bearing cross (11) shown in FIG. 3 is provided on an edge attachment (2a), which is formed by the jacket (2b) of the tub (2) and an edge of its base (2c) ) attached.
• a bearing hub (12) In the center of this bearing cross (11) is a bearing hub (12) into which two radial roller bearings (13a, b) are inserted. These roller bearings (13a, b) in turn serve for rotatably receiving a drive shaft (14) which is connected to the drum base (6a) in a rotationally fixed manner.
• the rear end (14a) of the drive shaft (14) protrudes from the bearing hub (12).
• a permanent magnet rotor (15) designed as an external rotor is attached to it and thus drives the drum (6) directly.
• the stator (16) of the drive motor (10) is attached to the bearing cross (11).
• FIG. 4 shows the sheet metal section of an individual stator sheet (17a).
• the individual sheets (17a) have attachment eyes for attaching the stator laminated core (17) to the bearing cross, which are arranged on the inner circumferential surface and are provided with through holes (19). Fastening screws (not shown) are guided through these bores (19) and screwed into threaded bores (26) on the bearing cross (11).
• the bores (26) are arranged concentrically with the bearing hub (12). Their free ends have contact surfaces (20) for an end face of the stator core (17).
• the stator lamination stack (17) is centered by means of radially designed stiffening ribs (21).
• the rotor (15) consists of a pot-shaped deep-drawn part or an aluminum injection molded part (15a) with a hollow cylinder section (15b), which contains an annular iron yoke (22) and the permanent magnets (23) attached to it as rotor poles (see also FIG. 5). Furthermore, the rotor (15) has a hub (24) which is positively connected to the free end (14a) of the drive shaft (14) by means of a screw bolt (25) and a serration (not shown) and thus non-rotatably.
• the drive motor is designed as a permanent magnet three-phase synchronous motor.
• a three-strand single-pole winding (tooth winding) is accommodated in the stator (16), the strands being connected in a star connection (see FIGS. 5, 6).
• the windings of the teeth (27) of one strand are connected in series.
• the drive motor is thus constructed as a modular permanent magnet machine.
• the pole ratio of rotor poles (23) to stator poles (27) is 4 to 3 with a number of 30 stator poles (27).
• Figure 5 shows a block diagram of the structure of the controlled drive with three-phase synchronous motor (10).
• the speed of the motor (10) is a function of the program set with the rotary selection switch (9, see FIG. 1)) as a setpoint by the program control
• the aforementioned variables are adjusted via the frequency converter (104).
• the mains voltage is first converted into a DC voltage using a rectifier (105) and smoothed using an intermediate circuit capacitor (106).
• the DC voltage is converted by a three-phase inverter (107) which is connected on the output side to the stator winding (18). Since the DC link voltage is constant, the voltage at the motor (10) is set using pulse width modulation. The effective value of the voltage can be changed over the pulse width.
• a pulse pattern is selected by means of which sinusoidal currents form in the stator winding (18) of the motor (10). One speaks therefore of a sinus-weighted pulse width modulation. The sinusoidal currents cause the motor (10) to run very quietly and reduce the losses caused by current harmonics.
• the inverter (107) is assigned a microprocessor control MC (108) in which a control R (109) and a valve control V ⁇ 1 0) are integrated.
• the control signals for the transistors of the inverter (107) are calculated on the basis of the respective rotor position in order to set the optimal orientation and strength of the rotating field at all times and thus to ensure a sufficient torque on the rotor (15). Because of the sinusoidal current supply to the synchronous motor (10) and the torque-dependent current control, continuous and accurate rotor position detection is required. Resolvers or analog Hall generators (111) can be used for this. Hall sensors (111) should be preferred because of their low cost.
• FIG. 6 shows a block diagram of the structure of a control system in which sensors for rotor position detection can be dispensed with.
• the rotor position In the case of sensorless control of the synchronous motor (10) with continuous, in particular with sinusoidal current supply, the rotor position must be calculated by the microprocessor control MC (108). This is done on the basis of a mathematical model M (113) of the motor (10) stored in the control, in which the characteristic motor parameters such as winding resistance, motor inductance and induced voltage must be known.
• the motor currents (I1 2) and the motor voltage U_ w are continuously measured vectorially, ie according to the magnitude and phase position, the currents being measured with the sensors and the voltage being known on the basis of the pulse pattern generated by the valve control V (110).
• the respective operating point of the motor (10) can thus be determined precisely and the motor (10) can be operated with the minimum current required for the load torque. Since the motor current and the voltage on the motor (10) can be recorded in the frequency converter (104) itself, no further sensors on the motor (10) are required.
• the parameters of the mathematical model M (113) are adjusted either as required or continuously. Such a calibration may be necessary if the motor-specific parameters (winding resistance, motor inductance and induced voltage) change during operation as the motor (10) heats up.
• the winding resistance and induced voltage in particular are highly temperature-dependent variables.
• Switch-on frequencies of 0.1 to 1 Hz are typical. In conjunction with the high number of poles of the motor (10), this guarantees a safe and smooth start even under load.
• the number of turns of the stator winding (18) is dimensioned such that at higher speeds the magnet wheel voltage and the induced voltage of the synchronous motor (10) are higher than the output voltage or the intermediate circuit voltage of the frequency converter (104). This design enables operation with field weakening at higher speeds. The field weakening enables the motor (10) to operate at approximately the same motor current in two operating points with different speeds and different moments, such as washing and spinning operation.
• field weakening is to be understood as a weakening of the field generated by the permanent magnets (23) of the rotor (15) in the air gap by a field generated in the stator (16) with a corresponding strength and phase position.
• the magnet wheel voltage and motor current are not in phase, but the phase current leads the magnet wheel voltage.
• the angle between the stator flooding and the rotor field becomes greater than 90 ° (electrical) when the field is weakened.
• the current has a negative stator longitudinal current component which is opposite to the rotor field.
• the phase current can be broken down vectorially into a force-forming and a field-forming component, the force-forming component being in phase with the magnet wheel voltage and the field-forming component being directed towards the rotor field and weakening it.
• the torque-forming component of the current in the transverse axis and the stator longitudinal current component can be set separately from one another with the aid of the current sensors (103a, b), which detect the phase current in at least two phases.
• the drive can also be operated in the field weakening area with minimal current and optimum efficiency. Sensing and regulating the motor current is advantageous in operation with field weakening, since if the longitudinal stator current component is too large, the magnets can be irreversibly weakened by the field generated by the stator flooding.
• the rotor position or the position of the rotor field is calculated with the aid of the measured phase currents and with the mathematical model M (113) of the motor (10).
• the rotor position can therefore only be determined as long as the motor (10) is energized.
• the frequency and amplitude of the rotating field specified by the frequency converter (104) is continuously reduced until standstill is reached.
• the outlet can also be unguided or de-energized.
• the drive described further enables reversing without or with only a slight reversing pause.
• washing machines which have a drive belt as an intermediate drive, this is not readily possible.
• universal motors are usually used as the drive, which run out uncontrolled or braked. After the engine has been switched off, the laundry drum will coast down or swing out. To avoid increased wear and noise from the drive belt, wait until the washing drum has come to a standstill after switching it off and then on again until the motor is switched on again.
• These downtimes for washing machines with drive belts are typically 2 to 4 seconds. The elimination of these hitherto usual and necessary breaks in reversing operation results in shorter washing times in the direct drive described here.
• a further advantageous embodiment of a laundry treatment device has a device for evaluating the voltage induced by the rotor (15) during the runout.
• the current speed can be inferred from this voltage.
• a voltage is induced in the stator winding (18) of the motor (10).
• the height and frequency are proportional to the rotor speed.
• the induced voltage can be used to sense the drum rotation.
• the induced voltage can be used to operate the lock.
• a state-dependent, secure locking (8) of the door (7) is possible in a simple manner without the use of additional speed sensors.
• Such an application is generally possible in washing machines with permanent magnet excited rotors and is therefore not limited to the embodiment according to the invention.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Control Of Motors That Do Not Use Commutators (AREA)
• Control Of Washing Machine And Dryer (AREA)
• Control Of Ac Motors In General (AREA)
• Treatment Of Fiber Materials (AREA)
• Rolls And Other Rotary Bodies (AREA)
• Main Body Construction Of Washing Machines And Laundry Dryers (AREA)
• Permanent Magnet Type Synchronous Machine (AREA)
• Control Of Multiple Motors (AREA)
• Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)

Applications Claiming Priority (3)

Publications (3)

Family

ID=7820597

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (45)

Family Cites Families (31)

• 1998
  • 1998-02-17 DE DE59804137T patent/DE59804137D1/de not_active Expired - Lifetime
  • 1998-02-17 AT AT98906957T patent/ATE217655T1/de active
  • 1998-02-17 EP EP98906957A patent/EP0960231B2/fr not_active Expired - Lifetime
  • 1998-02-17 JP JP53537798A patent/JP2001511674A/ja active Pending
  • 1998-02-17 DE DE19806258A patent/DE19806258A1/de not_active Withdrawn
  • 1998-02-17 WO PCT/EP1998/000902 patent/WO1998036123A2/fr not_active Ceased
  • 1998-02-17 US US09/367,378 patent/US6341507B1/en not_active Expired - Lifetime
  • 1998-02-17 KR KR10-1999-7004953A patent/KR100436152B1/ko not_active Expired - Fee Related
  • 1998-02-17 ES ES98906957T patent/ES2176972T3/es not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events