GB1584561A

GB1584561A - Braking of a capacitor motor in a washing machine

Info

Publication number: GB1584561A
Application number: GB26889/77A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-06-29
Filing date: 1977-06-27
Publication date: 1981-02-11
Also published as: SE432856B; FR2356759B1; FR2356759A1; SE7707253L; IT1085497B

Description

(54) BRAKING OF A CAPACITOR MOTOR IN A WASHING MACHINE (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company of Berlin and Munich, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may - be granted to us, and the method by which it is to be performed, to be particularly described in and by the following - statement: This invention relates to the braking of motors of washing machines having a drive arrangement comprising a single-phase capacitor motor, and is particularly but not exclusively concerned with wall-loading drum-type washing machines in which a further speed, lower than the washing speed, is provided for rotating the drum to a loading position.

In a known drive arrangement of this kind (German Patent Specification 1 956 272), having separate windings for the washing and spinning speeds, the further speed is obtained by supplying direct current to the motor winding for the spinning speed and supplying alternating current to the motor winding.for the washing speed, the main and auxiliary windings associated with the spinning speed being connected in series with a rectifier to a direct current source.

As is well known, a capacitor motor usually comprises a single-phase induction motor arranged to start as a 2-phase motor by connecting a capacitor in series with an auxiliary starting winding. The capacitor may be automatically disconnected when the motor is up to speed (capacitor -start motor) or it may be left permanently in circuit for power-factor improvement (capacitor start-and-run motor).

When loading the drum and removing the wash therefrom in wall-loading drum-type washing machines, the drum must be brought to a certain position in which a loading opening in a side wall registers with an opening in the casing of the machine, where the wash is introduced and removed.

In simple drum-type washing machines, this loading position is not readily reached when the machine stops, so that it is necessary to rotate the drum by hand into the loading position after the machine has stopped.

Automatic devices are known which, upon completion of the washing operation of a drum-type washing machine, enable the drum to be brought automatically into the loading position. For this purpose, in a wall-loading drum-type washing machine of the initially stated kind (German Utility Model 6,603,508), the drum is caused to turn more slowly than during the normal washing operation, by the drum motor being alternately switched on and off.

In yet another known drive for a drumtype washing machine (German Patent Specification 2,028,520) having different washing and spinning speeds and comprising a drive motor having a low-pole stator winding for the spinning speed and a highpole stator winding with an auxiliary phase for the washing speed, what is known as an inching speed is achieved by connecting, in parallel with the high-pole stator winding, a particular form of stator winding, acting as a brake winding, whih can be connected from the low-pole stator winding and has a greater number of poles than the number corresponding to the high-pole stator winding.

According to the present invention, there is provided a washing machine having a drum which is arranged to be loaded through a side wall thereof and a singlephase capacitor motor which is arranged to drive the drum, the stator of the motor having a symmetrical arrangement of a main winding and an auxiliary winding, with the capacitor of the motor in series with the auxiliary winding, the rotor of the motor being a wound rotor with axially extending conductors, and the washing machine hav ing a switching means which is operable effectively to connect said auxiliary winding in parallel with said main winding across the supply to the motor and to disconnect the capacitor, whereby to cause braking of the motor and the drum.

We have found that, in at least some embodiments of the invention, it has been possible to achieve hard braking of the wash drum to bring it to a stop and to hold it in a desired position by the use of relatively simple means and wlthout the provision of mechanical braking means. The required braking effect can be achieved in a surprisingly simple manner by simply shortcircuiting or switching off the capacitor whilst, at the same time, the main and auxiliary windings of the single-phase capacitor motor are connected in parallel to the single-phase supply.

Since in certain circumstances, e.g. when the wash drum is heavily loaded, braking of the wash drum is achieved very quickly, it is advantageous, for the purpose of bringing the drum into a loading position, to provide a switching means (short-circuiting device) which can be periodically switched on and off with a predetermined cycle so that, when the switching means is switched off, the motor is briefly accelerated in the usual operational manner and can then be braked again-when the switching means is switched on. Thus, by means of suitable timing impulses, the drum of the wall-loading machine can be slowed down from its running speed in the shortest possible manner to bring the loading opening in the wall of the drum into register with an opening in the top of the casing where the wash is introduced and removed.

To achieve substantial independence of variations in voltage and load; it is advantageous, when providing such timed switching on and off of the switching means, for the capacitor motor to attain an operating speed during unbraked operation, i.e. each time the switching means is switched off, which is higher than that corresponding to stalling torque. According to a further optional feature of the invention and for the purpose of achieving a still greater braking and holding action on the wash drum, the supply is connectible to the parallel arrangement comprising the main winding and the auxiliary winding, by way of a rectifier arrangement. To achieve this in a particularly simple manner, a single diode is provided in a connecting lead between a supply terminal and one end of the main winding.

By means of the braking circuit with an additional diode, we have found it possible, with simple means, to achieve such rapid "sudden" braking of the wash drum to bring it to a stop with the highest possible braking torque, that the drum can be brought into a required loading position directly from the washing speed. In certain conditions, the "sudden" braking of the wash drum from the full washing speed results in items of washing, that hang from and are entrained by the periphery of the drum being thrown back to the bottom of the drum. This ensures that at the moment when the drum is brought to a standstill, the centre of gravity of all the contents of the drum is exactly below the axis of the drum, and the drum is thereby prevented from swinging back from the required and previously occupied loading or parking position. The centre of gravity of the wash thus stabilizes the rotation of the drum without the need for using additional mechanical retaining means for the purpose.

Further simplification is achieved by connecting a short-circuiting device, acting as the switching means, in parallel with the capacitor, which short-circuiting device connects the auxiliary winding in parallel with the main winding to the supply source and at the same time short-circuits the capacitor.

The energy stored in the capacitor for operating purposes can be advantageously dissipated when the short-circuiting device is switched on by connecting the auxiliary winding in series with a resistor to the supply source by way of the short-circuiting device when the capacitor is short-circuited.

Good braking is achieved by the main winding and the auxiliary winding being symmetrically arranged. A good holding moment in the stopped condition is achieved, due to the fact that the rotor is a wound rotor, thereby having a specific pole formation, and that the rotor is an "unlimited" rotor - i.e. in which the conductors extend axially.

The invention will now be further exemplified, by reference to embodiments thereof illustrated diagrammatically in the drawings, in which: Figure 1 is a basic circuit diagram of a motor for use in driving a wash drum of a washing machine; Figure 2 shows plots of braking torque against speed (MBr = f(n)), for asymmetric- al arrangement (solid line), and for an asymmetrical arrangement (dash line), of a main winding and an auxiliary winding of the motor, as well as for a symmetrical arrangement with an additional diode (dashdot line); Figure 3 is a basic circuit diagram of a further motor, including an additional diode; and Figure 4 is a more detailed circuit diagram of a motor arrangement for bringing a wash drum to a loading position.

In the figures, like the reference numerals denote like or corresponding parts.

Figure 1 shows the basic circuit diagram for a capacitor motor provided for driving a wall-loading drum-type washing machine, and having a braking circuit comprising no diode. Connected in parallel with the singlephase supply (R, Mp) is a main winding 1 and a series arrangement comprising an auxiliary winding 2 and the operating capacitor 4. In parallel with the operating capacitor 4 is a series arrangement consisting of a short-circuit device 3, and a discharge resistor 5.

If, with the motor running, the shortcircuiting device 3 is closed, the auxiliary winding 2 is connected in parallel with the main winding 1 to the single-phase supply R, Mp by way of the resistor 5, and the operating capacitor 4 is short-circuited through the resistor 5. This causes the single-phase capacitor motor to be braked to a stop, with the main phase and the auxiliary phase being symmetrically arranged, and the loaded wash drum is thus brought to a stop.

Figure 2 shows the functional relationship between, on the one hand, the braking torque MBr and loading moment ML, shown on the abscissa of the coordinate system, and, on the other hand, the speed n of the braked single-phase condenser motor, shown on the ordinate, when the shortcircuiting device 3 is actuated and no diode is present (solid line and dash line). As can be seen from the plot, the best braking effect is naturally achieved when the main winding and the auxiliary winding are symmetrically arranged (w1 = W3), since the brake characteristic curve terminates at the origin. When the windings are asymmetrical!y arranged and a diode is not present (w #w3), the main and auxiliary windings cause braking to a speed n of zero as long as the braking moment ML at the motor S the holding moment MH. The best holding moment in the stopped condition is achieved with a symmetrical arrangement of the main winding and auxiliary winding, and with a wound rotor having axially extending conditions, as is the case with the embodiments of Figures 1 and 3.

If, as illustrated in Figure 3, a diode 6 is incorporated in one connecting lead between the single phase supply R M and the parallel arrangement consisting of the auxiliary winding 2 and the main winding 1, a braking characteristic curve is obtained that is substantially the same as the dash-dot line in Figure 2. A functional plot of this kind is notable for the fact that the characteristic curve runs through the origin and, in comparison with the two other characterising curves, indicates a considerably stronger braking action.

Figure 4 show a circuit diagram for obtaining what is called the parking position (loading position) in the case of a wallloading machine. One terminal of the single-phase capacitor motor, constituted by its main winding 1 and the series arrangement, arranged parallel thereto and consisting of the auxiliary winding 2 and the operating capacitor 3, is connectible, through a contact 92 of a relay 9, to one phase Mp of the single-phase supply source R, M and its other terminal is connectible, through a diode 6, a parking button 8 and a second contact 91 of the relay 9, to the other phase R of said supply source. The relay 9 is a component of the programme-selection circuitry of the washing machine and serves to prepare the braking-parking-operating position and, for example, after completion of a washing or spinning run, to connect the braking-parking circuit to the single-phase supply source. Provided for obtaining the actual parking position is a further relay 7, one contact 72 of which closes a short-circuit for the diode 6, while its other contact 73 in series with a contact 93 of the relay 9 is connected in parallel with the operating capacitor 3. A parallel arrangement consisting of a position-indicating or sensing device 10 and the relay 7 in series therewith, is branched off between the parking button 8 and the diode 6, and the other end of this parallel arrangement is connected to the pole Mp, of the single phase supply. A further contact 71 of the relay 7, with self-holding action, is connected in parallel with the position-indicating device 10.

As soon as the braking-parking-operation has been selected by means of the programme-selection circuitry (not illustrated in detail), and relay 9 is energised to close the contacts 91 and 92 and 93, the relay 7 is energised by depressing the parking button 8, provided for example on the front face of the washing machine casing, as soon as the position-indicating device 10 closes. This happens when the loading opening in the wash drum has approached to within a certain angular distance (e.g. 5 - 10 degrees) of the associated loading opening in the top of the washing machine casing. The position-indicating device 10 consists, for example, of a magnet secured to a pulley of the washing drum, and of a corresponding receiver (e.g. reed contact) which can be influenced by a magnet and is fixedly secured with the machine. When the relay 7 is energized, the contact 72 opens and brings the diode 6 in series with the main winding 1 and with the auxiliary winding 2, which is immediately in parallel with the main winding after the capacitor 3 has been shortcircuited by the closure of contact 73. The single phase capacitor motor is "suddenly" braked, and the opening in the wash drum is brought into the upper operating position in register with the opening in the casing.

Braking occurs in so sudden a manner that over-running of the opening in the wash drum beyond the associated loading opening in the casing, as well as swing-back from this position, are reliably avoided. With the aid of the closed contact 71 with self-holding action, the braking-parking-operating position is maintained as long as the parking button is depressed, irrespective of any change in the condition of the positionindicating device 10 during the braking operation.

WHAT WE CLAIM IS: 1. A washing machine having a drum which is arranged to be loaded through a side wall thereof and a single-phase capacitor motor which is arranged to drive the drum, the stator of the motor having a symmetrical arrangement of a main winding and an auxiliary winding, with the capacitor of the motor in series with the auxiliary winding, the rotor of the motor being a wound rotor with axially extending conductors, and the washing machine having a switching means which is operable effectively to connect said auxiliary winding in parallel with said main winding across the supply to the motor and to disconnect the capacitor, whereby to cause braking of the motor and the drum.

2. A washing machine according to claim 1, wherein the motor is arranged to drive the drum at a washing speed and also at a further speed lower than the washing speed for rotating the drum until it reaches a loading position in which the drum can be loaded.

3. A washing machine according to claim 2, wherein said switching means is arranged to be switched periodically on and off with a predetermined cycle, whereby to achieve said further speed.

4. A washing machine according to claim 3, wherein said cycle is so chosen that, during unbraked operation, the motor reaches a speed greater than that corresponding to stalling torque.

5. A washing machine according to any one of the preceding claims, wherein, during braked operation, said main and auxiliary windings are connectd to the supply via rectifier means.

6. A washing machine according to claim 5, wherein said rectifier means comprises a single diode between a supply terminal and one end of the main winding.

7. A washing machine according to any one of the preceding claims, wherein said switching means is operative effectively to disconnect the capacitor by connecting a discharge resistor across the terminals thereof.

8. A washing machine according to claim 7, wherein said switching means is operative effectively to connect the auxiliary winding in parallel with the main winding via said discharge resistor.

9. A washing machine provided with a capacitor motor, substantially as hereinbefore described with reference to Figure 1, 3 or 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. over-running of the opening in the wash drum beyond the associated loading opening in the casing, as well as swing-back from this position, are reliably avoided. With the aid of the closed contact 71 with self-holding action, the braking-parking-operating position is maintained as long as the parking button is depressed, irrespective of any change in the condition of the positionindicating device 10 during the braking operation. WHAT WE CLAIM IS:

1. A washing machine having a drum which is arranged to be loaded through a side wall thereof and a single-phase capacitor motor which is arranged to drive the drum, the stator of the motor having a symmetrical arrangement of a main winding and an auxiliary winding, with the capacitor of the motor in series with the auxiliary winding, the rotor of the motor being a wound rotor with axially extending conductors, and the washing machine having a switching means which is operable effectively to connect said auxiliary winding in parallel with said main winding across the supply to the motor and to disconnect the capacitor, whereby to cause braking of the motor and the drum.