FR2658671A1 - DRUM DRIVE SYSTEM OF A WASHING MACHINE. - Google Patents

Abstract

a) Drum drive system of a washing machine. b) the system comprises a universal motor (M), a controlled power switch (4), as well as a tachometer sensor (8) and a safety device (7) against high temperature, connected to an input of a regulation and control circuit (6) which closes or opens a switch (4) according to the signals sent to it by the cadencer (9) and the tachometer detector (8) and which therefore stops the engine if, after its start, a period of time greater than a predetermined period elapses without the signal sent by the tachometer (8) arriving. c) The invention increases the operational safety of a washing machine.

Description

DRUM DRIVE SYSTEM OF A WASHING MACHINE

  The present invention relates to a drum drive system of a washing machine having a programmable sequencer (timer). More specifically, the invention relates to a drive system comprising an engine

universal electric.

  Training systems have been proposed and

  alternatively powered by AC power and controlled by phase control. In these systems, the

  safety devices (typically

  bimetallic breakers) to meet the requirements of safety standards, particularly with regard to so-called rotor tests

stopped and stopped timer.

  In the stopped rotor test (which simulates for example the breaking of a bearing), the intensity passing in the motor increases suddenly and the safety device intervenes as soon as the intensity

exceeds a predetermined threshold.

  In the stopped timer test (which simulates a situation in which the drive electric motor runs indefinitely), the safety device intervenes, after a longer period,

  as soon as the temperature exceeds a predetermined limit

  completed. In known systems, described above, the nominal characteristics of the safety device are sometimes extremely critical: the same safety device must be able to intervene reliably and accurately when a certain threshold of intensity is reached and / or when a certain temperature limit is reached, but these two conditions are not always easily combined. In fact, the behavior of such safety devices is generally extremely accurate when they have to

  intervene following an increase in temperature

  However, it is much less precise when they have to intervene as a result of an increase in intensity. In the systems of the prior art, with a universal motor used with an alternating current and a

  controlled by phase adjustment, usually

  a triac The triac and the safety device

  are electrically connected in series with the motor.

  The triac is controlled by a regulation and control circuit whose input is connected to a tachometer detector (typically a dynamo)

associated with the engine.

  These systems of the prior art generally do not have protection against damage to the power switch (the triac) or a short circuit of this switch and / or with respect to damage to the tachometer detector or a

short circuit of this detector.

  The object of the present invention is to provide a drum drive system of a washing machine in which the nominal characteristics of the safety device are less critical and in which it is also possible to stop the engine in case of damage to the tachometer or short-circuit detector of this detector, possibly also in case of damage to the power switch

  or short circuit this switch.

  These and other objects are achieved by means of a drum drive system of a washing machine comprising a sequencing device or programmable timer, characterized in that it comprises in combination: a voltage supply continuous, a universal electric drive motor, a controlled power switch interposed between the power supply and the electric motor, a safety device for stopping the engine when its temperature exceeds a predetermined value, a tachometric detector associated with the engine, and means which form a control and control circuit and which are adapted to drive the power switch in a circuit-off mode in a predetermined manner according to the signals supplied by the timer and the tachometer detector, when receiving the from the timer a control signal to start the engine, the safety device being connected n series with the tachometer detector, the safety device and the tachometer detector being connected in series with an input of the control and control circuit means, the control and control circuit means being arranged to open the controlled switch and stopping the electric motor accordingly if, after receiving a command signal to start the engine, a period of time greater than a predetermined period has elapsed without the signal supplied by the detector

  tachometer is detected at its input.

  Other features and advantages of the invention will become apparent from the

  following detailed description, referring to the following

  attached drawing, provided only by way of non-limiting example. The attached drawing is a partial block diagram of a drive system according to the invention. In the diagram, a full-wave rectifying circuit of known type, for example of the Graetz bridge type, is designated by the reference 1 L input of the rectifier circuit is expected to be connected to the network

  AC distribution system.

  A safety fuse 2 whose operation will be explained later is connected to the input of the

rectifier circuit 1.

  A capacitor 3 of small capacity (for example, 3 SF) is connected to the output of the rectifier circuit 1, and in practice its only role is

  to filter the high frequency components.

  A universal electric drive motor of the drum (not shown) of the washing machine is designated by the mark M The motor is connected to the output of the rectifier circuit 1 in series with a controlled power switch, designated by the reference 4 Ce last is for example a MOS power switch or a transistor

bipolar IGBT insulated gate.

  A stabilizing diode 5 is connected in

parallel with the motor.

  The power switch 4 is controlled by a regulation and control circuit generally designated by the reference numeral 6. This circuit comprises an input 6 connected in series with a safety device 7 and a tachometric detector 8 associated with the motor M The safety device 7 is, for example, a bimetallic switch As a variant, it could consist of a varistor with a coefficient of

positive temperature.

  The detector 8 is, for example, a tachogenerator. The regulation and control circuit 6 comprises another input 6b connected to the programmable sequencer (timer) 9 (of known type) of the

washing machine.

  The control control circuit 6 is designed so that, when it receives, from the timer 9, a control signal to start the motor M, it controls the power switch

  4 in circuit-off mode in a predetermined manner.

  function of the signals sent to it by the timer 9 and the tachometer detector 8. For this purpose, the control and control circuit comprises, for example, an integrated circuit

  of known type, for example a TDA circuit 1085.

  According to the invention, the regulation circuit

  and control also includes a temporary circuit

  control printer designated by 11 in the drawing In operation, this circuit opens the power switch 4, and thus stops the motor M, if, after receiving a control signal to start the engine, a period of time greater than a predetermined period (for example 1 second) has elapsed without the signal from the tachometer detector 8 having appeared at the input 6a. The safety timer circuit 11, which can be easily formed with the aid of an operational amplifier Drotè 2 e in fact the system in case of damage to the tachometer detector 8 (for example rupture of the magnet) or in case short circuit

this detector.

  It is interesting to note that, in the system described above, the protection in case of stopping the motor M is provided not by the safety device 7 (as was the case elsewhere in the systems of the prior art), but thanks to the circuit 11 and the tachometer detector 8 Accordingly, in the system according to the invention, the safety device 7 is intended to intervene only if the engine temperature is too high, and the nominal characteristics of the device

are absolutely more critical.

  The safety device 7 also protects

  the system if the connection to the tachograph detector

metric is broken.

  With regard to the fuse 2, however, it can be seen that it intervenes to protect the system in the event of damage to the regulation and control circuit 6 or in the event of a short circuit of

the power switch 4.

  The system according to the invention has

many advantages.

  First, as already indicated, the nominal characteristics of the thermal device

  security are much less critical.

  Another advantage lies in the fact that it is not necessary for the electric drive motor to be oversized with respect to

its operating conditions.

  Other advantages lie in the fact that the form factor of the current flowing in the motor is very close to 1, which translates into a

reduced heat dissipation.

  In the system shown, the universal motor operates with direct current, which also brings advantages from the point of view of the

on / off.

  Other advantages lie in the fact that the engine operating noise in particular can be reduced and in that the brooms

  can be made to last longer.

  Naturally, the principle of the invention remaining the same, one can vary widely the embodiments and construction details with respect to those described and illustrated only by way of non-limiting examples, without departing

  hence the object of the present invention.

REV E N D I CA T IO N S

  1 Drum driving system of one

  washing machine having a sequencing device

  programmable circuit or timer (9), characterized in that it comprises, in combination: a DC voltage supply (1), a universal electric drive motor (M), a controlled power switch (4) interposed between voltage supply (1) and the electric motor (M), a safety device (7) for stopping the motor (M) when its temperature exceeds a predetermined value, a tachometric detector (8) associated with the motor (M) , and means (6) which form a control and control circuit and which are adapted to drive the power switch (4) in off-circuit mode in a predetermined manner according to the signals provided by the timer (9) and the tachometric detector (8), when they receive from the timer (9) a control signal for starting the engine, the safety device (7) being connected in series with the tachometer detector (8), the device security and the tachometric detector (8) being connected in series with an input (6a) of the control and control circuit means (6), the control circuit means (6)

  and control being arranged to open

  switch (4) and stop the electric motor (M) accordingly if, after receiving a control signal to start the engine, a

  period of time greater than a pre-

  minus the signal supplied by the tachometer detector (8) is detected at its input (6a). 2 System according to claim 1, wherein the DC voltage supply comprises a rectifier circuit (1) whose input is intended to be connected to the power supply of the AC mains, characterized in that a fuse of safety device (2) is connected to the input of the rectifier circuit (1) to break the connection between the rectifier circuit and the network if the current passing through it exceeds one

predetermined value.

  3 System according to claim 1 or claim 2, characterized in that the safety device (7) is a switch

thermal bimetallic.

  4 System according to claim 1 or claim 2, characterized in that the safety device consists of a varistor

  with a positive temperature coefficient.