DE2023715A1 - Controlled drive device for the laundry drum of a washing machine - Google Patents

Description

Dr. T. Hi ^ 'i

8 HOndmn 2 May 14, 1970

Kaufingeratr. 8, T # L24027e

Company INDUSTRIE A.ZANUSSI S.poA.

Viale Montereale 8
Pordenone / Italy

Controlled drive device of the laundry drum one

Washing machine α

The invention relates to a drive device for the laundry drum a washing machine, by means of which the same can be set in rotation at a controlled speed.

As is known, a drive device for washing machines essentially comprises two characteristic parts: the motor and the speed controller β

AC motors, especially three-phase motors, used after the direct current motors, which probably for various reasons and ins- especially due to their greater suppleness and adaptability a very fine and precise speed control would be preferable, cannot be used because of the possibility that the humidity

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speed of the room in which they are placed, short circuits and consequently causes very high currents: through which the rectifier elements, via which the motors are fed, can be seriously damaged or at least the controllability can be prevented.

Usually those "with wave trains" and those "with partial phase suppression" are used as speed controllers »The

The former are based on the presence of a group of electronic Components with controlled opening (silicon rectifier diodes, thyratron, etc.), which are controlled in such a way that the Feeding of the motor is interrupted when the motor speed exceeds a predetermined value and that the feed is restored at any moment when the engine speed drops below this predetermined value. The latter Speed controllers are based on the presence of a group of electronic components with controlled opening, the be controlled in such a way that the supply of the motor is suppressed for a certain part of each half-wave of the supply voltage

P and is resumed for the remaining part of the half-wave, the time ratio of these two parts automatically changing depending on the speed of the controlled motor is.

Both speed controllers mentioned have the disadvantage that they cause strong radio frequency interference, which affects the steep tension fronts that arise at the moment of the transition from the phase of interruption of the supply to the phase of releasing the supply. These disturbances are always and definitely undesirable, but in the case of

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■ Drive motors for washing machines are particularly harmful because they are of direct interest to the users of the machines «It is probably possible to eliminate the malfunctions mentioned or at least to such an extent that they are negligible, but this must be appropriate filters with large dimensions which make the devices bulky and expensive.

The object of the invention is to create a device for controlled drive of the laundry drum of a washing machine, which is able to use the parts of the DC motors, without having to accept their disadvantages and in which the speed control is carried out in such a way that none excessive radio frequency interference.

The invention solves the problem posed by means of a device, the one through a transformer of the kind with constant Electricity fed DC motor and a rectifier device comprises, the opening of the rectifier elements of the latter being controlled by a control device, which is synchronized with the zero crossings of the AC supply voltage Gives opening impulses as long as the speed of the motor is smaller than a predetermined value, while it is exceeded when exceeded this predetermined speed value no opening pulses gives more.

The special combination of the drive device according to the invention forming elements has numerous advantages. The use of a direct current motor (preferably with separate excitation, so that the generated starting torques are limited and the use of a tachometer generator for speed

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determination is avoided) allows a finer and linear Speed control. The presence of a transformer of the Type with constant current (i.e. a transformer

of the kind used for electric welding maui approx

machines used / ^ allows the currents through the controlled rectifier elements in the event of a short circuit of the motor to limit and thus the harmful consequences for this controlled Avoid rectifier elements. Finally, the use of a control device that is suitable the opening times of the controlled rectifier elements coincide with the zero crossings of the alternating supply voltage (and which can therefore iverden defined as a control device "with suppression of whole half-waves") the occurrence steep tension fronts at the moment of transition from a state of suppression to a state of release, thereby eliminating the aforementioned radio frequency interference which occur in the control devices with wave trains and with partial phase suppression "

ψ Further characteristics and advantages of the device according to the invention emerge from the following detailed description of a preferred embodiment. This description refers to the drawing in which:

Fig.l shows the exact circuit diagram of the preferred embodiment

represents the game of the drive device according to the invention and the

Figures 2-7 are graphs showing the time course illustrate some of the signals that are particularly important for the operation of the device according to FIG.

00 9ÖU / 1 3 β9 -4-

As can be seen from the circuit diagram of Fig.1, is a DC collector motor 2 with external excitation (either with permanent magnets or with field winding) in a branch of a bridge 1 switched on, a resistor in each of the other three branches 3, 4, 5 is · In points 6 and 7, bridge 1 is from Output of a bridge rectifier 8 fed, which two Diodes 9 and 10 and two silicon controlled rectifier diodes 11 and 12 includes. The two points 13 and I4 of the bridge rectifier: judge's 8 are with points 6 and 7 of bridge 1 and more among each other via a further diode 64 (which prevents the controlled silicon rectifier diodes from being caused by the delayed by the inductive load formed by the motor 2) connected, while the other two points 15 and 16 of the bridge rectifier connected to the secondary winding 17 of a transformer 18 of the type with constant current are whose primary winding I9 via terminals 20 and 21 is fed with normal Metz AC voltage. A changeover switch 22 mats it, a choice between 5 different taps the secondary winding 17 of the transformer and thus the input voltage of the bridge rectifier 8 between five to change different values.

The controlled silicon rectifier diodes 11 and 12 of the rectifier bridge 8 are controlled by a regulator which is suitable for supplying them with opening pulses synchronized with the AC mains voltage until the back EMF of the motor 2 exceeds a predetermined value. This regulator comprises a rectifier 23> consisting of a bridge circuit of four diodes 24 > 25, 26 and 27, the points 28 and 29 of which are connected to the Metz terminals 20 and 21, respectively, while the others

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the two points 30 and 31 are connected to one another by the series connection of a resistor 32 and a Zener diode 33 and by the series connection of two resistors 34 and 35.

The point 36 between the resistor 32 and the Zener diode 33 is directly connected to the connection point 37 of the anode of the diode 38 and the anode of the silicon controlled rectifier diode 39. The cathode of the diode. 38 is connected to the point 31 of the rectifier 23 via a capacitor 40, while the cathode of the controlled silicon rectifier diode 39 via a resistor 41 to the control electrode of the controlled silicon rectifier diode 11, via a resistor 42 to the control electrode of the controlled silicon rectifier diode 12 and is connected to the point 13 of the bridge rectifier 8 via the series connection of the resistor 41 and a further resistor 43 and via a series connection of the resistor 42 and a further resistor 44. As a result, both the resistors 41 and 42 to each other, as

W the resistors 43 and 44 are also equal to one another.

The control electrode of the controlled silicon rectifier diode 39 is connected to the emitter of an n-p-n transistor 45, its collector to line 47 via a resistor 46 connected to the cathode of the diode 38 with the corresponding Plate of capacitor 40 connects '' The base of transistor 45 is in turn connected to the collector of an n-p-n transistor 38 connected, which collector also has a Resistor 49 is connected to line 47. The emitter of the transistor 48, however, is directly connected to a line 50

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connected, which connects the other plate of the capacitor 40 to the point ßl of the rectifier 23, while the base of the transistor 48 is connected to the line 50 via a resistor 35 «

The base of the transistor 48 is also through a Zener diode 51 connected to the collector of a transistor 52, the emitter of which is connected directly to the line 50 and whose collector is connected to line 47 via a resistor 53. The base of transistor 52 is through a Capacitor 54 'with the collector and via a diode 55 connected to the emitter of the same transistor 52 and is also directly at a node 56, which is connected via a Wi-

Point

derstand 58 with a / 57 of bridge 1 and via a selector switch 60 and the selected one of the five resistors 59 to

V ■

59 is connected to line 47. The line 50 is finally directly connected to the fourth corner point 6l of the bridge 1.

The device shown in Fig.l has the following mode of operation.

The alternating voltage V applied to terminals 20-21 (Figo 2) is turned into a pulsating voltage by the rectifier 23

V (Figo 3) transformed, velche at the corner points 30 and 3I of the Rectifier bridge 23 and thus also at the ends of the resistor 35 »although it has a different amplitude. To the At the ends of the Zener diode 33, on the other hand, a voltage is formed

V from, as shown in Fig.4, which voltage is above the diode 38 charges the capacitor 40, whereby it is connected to it Ends a constant voltage V- (Figo 5) is maintained.

The pulsating course of the voltage at the ends of the resistor 35 implies that the transistor 48 at each

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Zero crossing of this voltage is blocked in order to become conductive again immediately afterwards. The blocking of transistor 48 causes the voltage to rise at point 02 and consequently the transition of transistor 45 into the conductive state. This state lasts only a very short time, because as soon as the voltage at the ends of the resistor 35 assumes a value different from j ^ Iull, the transistor 48 returns to the conductive state, the potential of the point 62 being lowered and thus the transistor 45 is blocked. The collector-emitter output current of transistor 45 thus has a pulse-shaped profile, a pulse being generated when the supply voltage taken from terminals 20-21 is passed through.

These pulses, which are synchronized with the supply voltage, cause the controlled silicon rectifier diode 39 to open and consequently also to open the controlled silicon rectifier diodes 11 and 12 Current flow to the bridge 1 and consequently the supply of the motor 2 "This current flow lasts as long as the controlled silicon rectifier diodes 11 and 12 are open and thus for the entire half-wave of the supply voltage. The strength of this supply current and thus the rated speed of the motor depends on the position of the switch 22 from · and expedient construction of the transformer secondary winding L8 and in particular its \ ~ J, the feed stream can be held in such a way that the starting torque of the motor is kept low and the controlled Siliciumgleich-

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judge diodes 11 and 12 are not damaged.

If the processes were to continue unrestrictedly in the manner described, i.e. in particular the transistor 48 would at locked every zero crossing of the supply voltage of the device then became the controlled silicon rectifier diodes 11 and 12 are triggered at each zero crossing of the voltage and the result is a continuous succession of half-waves of pulsating current with double frequency and in * phase with the voltage at terminals 20 and 21 to motor 2, which would thus be fed permanently. This is actually the case as long as than the speed of the engine does not exceed a predetermined limit value.

As long as the speed of the motor is low (or »lower is than said predetermined limit value) is also the back EMF generated is small, so that part of the caused by the constant voltage V passes through the selected one of the resistors

IV
59 - 59 and the current flowing to the node 56 flows to the base of the transistor 52 (the resistor 58 and the capacitor 54 serve as a smoothing filter for the reactive component caused by the inductance of the motor 2), so that this transistor is conductive and the potential of the point is set below the value necessary for the discharge of the Zener diode 51.

In this state, the part of the device which makes the comparison between the fixed reference voltage V and the from the back EMF and thus the engine speed dependent signal carries out the operation of the remaining part of the device not affected and in particular the operation

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the pulse generator comprising the transistor 48 and the does not affect the amplifier comprising transistor 45, so that each time the supply voltage passes through zero an impulse is emitted, consequently get from the equi-directional gap 8 to bridge 1 continuously pulsing whole half waves Current to supply the motor,

However, if the engine speed is the said predetermined Limit value (which an appropriate selection of the

IV
, Resistors 59 - 59), where the becomes the node

56 passing current is passed almost completely through the resistor 58 (the capacitor 54 continues to absorb the reactive component of this current), so that the transistor 52 is blocked or is only permeable to a limited extent that the potential of the point 63 is above the threshold value of the Zener- diode 51 increases, and thus the supply of such a current to the base of transistor 48 causes that the same also at the zero crossing by the delivered by the rectifier 23 pulsating voltage upstream to the ends of the resistor 35 W handenen clamping voltage in the conducting state remains "Venn Thus, the engine speed is greater than the predetermined limit value, the mullet passages of the supply voltage no longer cause the blocking of the transistor 48, so that the transistor 45 is also non-conductive and the controlled silicon rectifier diode 39 does not supply any opening pulses. The controlled silicon rectifier diodes 11 and 12 thus remain blocked and consequently the supply of the motor 2 is prevented.

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This state lasts as long as the speed of the motor falls again below the specified upper limit value. In At this moment the base of the transistor 52 rises supplied current back to a value sufficient to the Transfer the transistor into the conductive state, whereby the potential of the point 63 below the threshold value of the Zener diode 51 goes down. With the following transition of the supply voltage The transistor 48 is blocked and thus the original one Condition restored.

FIGS. 6 and J show the course of signals 1 and V, for example. at the output of transistor 45 or between the

14th

Rectifier bridge S and bridge 1 are present when the condition of the excessive speed of the motor has such a duration that only one of the transistors 45 generated in synchronism with the zero crossings of the supply voltage of the device. Impulse is suppressed. The voltage gradient shown in FIG. 7 at the fourth half-wave corresponds to the vert of the counter-EIIK of the motor when the supply voltage is> iull. From the figures mentioned it can be seen that the beginning and the end of the suppression phases of the supply of the motor are caused by the zero passages of the supply voltage, so that only whole half-waves and not parts of the same are suppressed and the various transitions from one State in the other are not accompanied by undesirable tension fronts. In the case of the control device described, no radio frequency interference can therefore be seen. The Vei- a "DC motor, made possible by the presence of oj.ios tra.islorm'ators with constant-lead current (like the transformer 18), allows at the same time

00980/1389

an extremely fine and linear speed control within one very large area.

It should be noted that the device shown in Fig.l only represents an exemplary embodiment and that numerous variants are possible within the scope of the invention, so could, for example the through the amplifier to the transistor 45 and through the controlled silicon rectifier diode 39 formed part without further be replaced by a monostable multivibrator and an amplifier without affecting the general The way the device works changes.

The motor to be controlled could also be a not separately excited, but, for example, be a main circuit DC motor, in which case the signal proportional to its speed is not more could be removed with the help of a bridge 1 and an integrator (resistor 58 and capacitor 54), soudera the use of a tachometer generator would be required. K This is one of the reasons why a DC motor with external excitation for use in the drive device according to the invention is most suitable, especially in view of the fact that the device for the drive . the washing drum of a washing machine is intended. Further reasons for using a separately excited DC motor are the limitation of starting torques, the possibility of using them of permanent magnets, the non-susceptibility to disturbances, .which the AC supply voltage directly to the Lead engine, etc.

1369

Claims (7)

Claims \ Λ °) Device for the controlled drive of the laundry drum of a washing machine, characterized by a DC motor (2) fed via a transformer (l8) of the type with constant current and by a rectifier device (8) whose rectifier elements (9 * 10,11 , 12) are opened in a controlled manner by a control device, which is suitable for delivering opening pulses synchronized with the liull passages of the AC supply voltage as long as the motor speed is lower than a predetermined value and to interrupt this output of pulses when this predetermined speed value is exceeded. 2. Apparatus according to claim 1, characterized in that the control device comprises a pulse generator which is suitable to generate an im- the pulse dispense, said input signal / sum of a pulsating signal which is connected to the AC supply voltage in phase and double the frequency has the same, and a signal is the amplitude of which is only different from IJuIl, \; f the rotational speed of the Mobors greater than the predetermined value. 3, device according to claim 2, characterized in that The pulse generator is controlled by a silicon rectifier diode via an amplifier (39) controls which the control electrode)! the controlled one present in the rectifier device (8) Equatorial element (11, 12) feeds. 009847/1369 4. Apparatus according to claim 2, characterized in that the pulse generator controls a monostable multivibrator, the output of which is connected to the control electrodes via an amplifier controlled rectifier elements (11, 12) present in the rectifier device (8). 5. Device according to claims 2-4 »characterized in that that the signal whose amplitude only differs from rJull is when the engine speed exceeds the predetermined ".tfert, consists of the discharge current of a Zener diode, at the ends of which there is a voltage which is the difference between one of the Engine speed dependent signal and a fixed reference signal 6. Apparatus according to claim 5> characterized in that the direct current motor (2) is externally excited (in particular by means of a permanent magnet or a field winding) and that the The signal dependent on the engine speed is picked up at the corner points of a bridge (l), which in one branch connects the engine (2) contains. 7. Apparatus according to claim 6, characterized in that for smoothing the removed at the corner points of the bridge (l) Signal a filter (54 * 58) is provided « -14- BAO 009847/13 89 Blank page