ITTO20121049A1 - WASHING MACHINE WITH PROTECTION CIRCUIT - Google Patents

Description

â € œWASHING MACHINE WITH PROTECTIVE CIRCUITâ €

DESCRIPTION

[FIELD OF TECHNIQUE]

The present invention refers to a washing machine with protection circuit.

[ART NOTE]

As is known, washing machines, and in particular washing machines and washer-dryers, include a support frame, on which a washing tank is mounted in which a basket rotates, inside which the garments are arranged. that need to be washed.

The tank has an opening through which it is possible to access the basket and clothes can be placed inside the basket.

These machines also include a controlled hydraulic system, which supplies water, suitably mixed with detergents, so that the garments are subjected to the washing process.

Usually the condition of the presence of liquid in the tank is detected by means of a suitable sensor, for example a pressure switch, through which it is determined whether the liquid present in the tank reaches a given level or not.

The information obtained through this sensor can be summarized as â € œstate of fullnessâ € or â € œstate of emptyâ € with reference to the presence or absence of liquid in the tank.

The washing liquid, including water possibly mixed with detergents, after being supplied to the tank and basket, can be reused, through a suitable recirculation system, or it can be drained outside the machine by means of a drain circuit.

The drain circuit typically consists of a drain pump, connected to the tank via a first suction pipe, and a drain pipe, which allows the fluid to be eliminated to drain.

The electric driving of the pump takes place by means of an electronic device of the TRIAC type, which acts as a switch to supply the appropriate alternating power supply to the pump itself.

A particularly important aspect concerns the prevention of overheating of the pump, which can give rise to a risk of fire, caused by abnormal operating conditions of the pump; for example, a possible blockage of the drain pump, that is a block of the motor rotor which is part of the pump itself, causes the motor to absorb a current greater than the nominal value and overheat until it can reach extremely high temperatures such to cause serious damage both to its own structure and to that of the other parts of the washing machine; in particular, as mentioned, a fire can be triggered.

A further condition of anomalous functioning of the drain pump may occur in the event that the driving TRIAC should fail in the so-called “diode mode” failure mode, ie a mode in which a one-way short-circuit of the TRIAC is substantially realized; in this case the pump would be powered with a direct current component and, since the pump is an inductive load, an anomalous flow of current would consequently occur, with consequent dangerous overheating of the pump itself.

In order to prevent the risk of uncontrolled pump temperature increases and any subsequent fires, the pump generally integrates a thermo-protective device that cuts off the power supply to the pump in case of overheating. However, this solution has the drawback of having a â € œone-shotâ € type of operation, that is, it cannot be restored. Therefore, following the intervention of the thermo-protector, it is necessary to involve at least one specialized technician to replace the entire pump.

Another solution made available by the state of the art involves the use of electronic circuits characterized by complex hardware / software structures which, in addition to making the production of the washing machine more difficult, contribute to significantly increasing costs.

[OBJECTIVES AND SUMMARY OF THE INVENTION]

The purpose of the present invention is to provide a washing machine equipped with a protection circuit designed to prevent the drain pump from overheating in conditions of abnormal operation.

Another purpose of the invention is to provide a washing machine in which the protection circuit designed to prevent overheating of the drain pump operates in a reversible manner - that is, it can restore its standard operation without requiring the intervention of a specialized technician and / or the replacement of some component of the machine, once the pump returns to operate correctly.

Another object of the invention is to make available a washing machine equipped with a protection circuit designed to prevent overheating of the drain pump, which is simpler and cheaper to manufacture, and does not require complex hardware / software structures.

These and other purposes are substantially achieved by a washing machine with protection circuit according to what is described in the attached claims.

An idea underlying the invention provides for the provision, in a washing machine, of a protection circuit associated with the drain pump, said protection circuit comprising at least one thermistor with a positive temperature coefficient, electrically connected in series to said pump drain and configured to limit the current flowing in said drain pump, when a parameter indicative of abnormal operation of said pump exceeds a certain threshold.

The Applicant believes that, in this way, a washing machine can be made in which the protection suitable to prevent overheating of the drain pump in abnormal operating conditions is provided in a simple, reliable and economically advantageous manner.

Preferably, the washing machine according to the present invention further comprises an electric driving circuit active on said drain pump to regulate its operation.

Preferably, said driving circuit comprises a controlled switch, adapted to selectively modulate the electric power supply from said power supply unit to said drain pump, and a control module configured to control said controlled switch.

Preferably, said parameter indicative of an anomalous operation of said pump is represented by the current absorbed by the pump itself.

Preferably said determined threshold is comprised between 250mA and 350mA.

Preferably the washing machine according to the invention is provided with an electronic control board, comprising said thermistor and, even more preferably, also said driving circuit.

Further features and advantages will become more apparent from the detailed description of a preferred and non-exclusive embodiment of the invention. This description is provided hereafter with reference to the accompanying figures, which are also purely for illustrative and therefore non-limiting purposes.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Figure 1 shows a block diagram representative of a part of a washing machine according to the present invention.

Figure 2 shows a block diagram of a circuit forming part of the washing machine of Figure 1.

Figure 3 shows a diagram representative of the operating characteristic of a circuit element employed in the circuit of Figure 2.

Figure 4 schematically shows a sectional side view of a washing machine according to the present invention, in which some parts have been eliminated to better highlight others.

The figures illustrate different aspects and embodiments of the present invention and, where appropriate, similar structures, components, materials and / or elements in different figures are indicated by the same reference numerals.

[DETAILED DESCRIPTION OF THE INVENTION]

With reference to the accompanying figures, 1 indicates as a whole a washing machine according to the present invention.

Washing machine 1 is preferably a washing machine or washer dryer.

By way of example, the washing machine 1 can be a front loading washing machine or alternatively a top loading washing machine.

Preferably the washing machine 1 comprises a support structure 70 (Figure 4) having a substantially box-like shape, for example substantially parallelepiped.

The support structure 70 has a base surface 71, a top surface 72, a front surface 73, a bottom surface 74, and a first lateral surface 75 and a second lateral surface (not shown) opposite said first lateral surface 75.

Inside the support structure 70 there is a washing tank 10, in which a basket 11 is rotatably mounted.

The tank 10 has a loading opening, through which the items to be washed can be inserted.

The loading opening is closed by a door 12 (Figure 4). The door 12 can comprise a transparent porthole, which allows the user to observe the internal portion of the basket 11 and the items inserted therein. In various embodiments, the door 12 is entirely opaque and does not allow such observation.

The basket 11 is moved in rotation by suitable actuator members, known per se and therefore not described in detail below.

In use, the garments to be washed are arranged inside the drum 11.

A fluid is dispensed into the tank 10 and the basket 11 which, depending on the single washing phase that is performed, can only comprise water, or water mixed with one or more detergent substances.

For this purpose, the washing machine 1 comprises a main hydraulic circuit 20, schematically shown in Figure 1.

Said main hydraulic circuit 20 is known per se and will not therefore be described in further detail.

The washing machine 1 further comprises a hydraulic discharge circuit 30; the latter is in fluid communication with the tank 10 and comprises at least one drain pump P.

Preferably, the discharge hydraulic circuit 30 also comprises a first conduit 31 and a second conduit 32.

The first duct 31 (or intake duct), also called discharge bellows, connects the tank 10 to an inlet of the drain pump P, while the second duct 32 (or delivery) connects an outlet of the drain pump P with a hydraulic disposal network, to which the washing fluid can be sent at the end of a washing or rinsing phase.

The drain hydraulic circuit 30 is schematically shown in figure 1, and partially shown in figure 4.

The drain pump P is connected to an electric power supply unit U (Figure 2), so that it can receive the electricity necessary for its operation. In practice, the discharge pump P comprises an electromechanical actuator (such as an electric motor) which, by imparting a suitable rotation movement to the so-called impeller of the pump itself, causes the desired fluid flow. The connection between the drain pump P and the electric power supply unit U therefore has the purpose of allowing a suitable power supply of the aforementioned electromechanical actuator.

The electric power supply unit U can include the circuitry necessary to draw electricity from a domestic or industrial network (not shown) and make it usable by the electromechanical actuator which is part of the drain pump P.

Preferably, the washing machine 1 further comprises an electric piloting circuit 50 active on the drain pump P to regulate its operation.

In particular, the electric driving circuit 50 can comprise a controlled switch 51 and a control module 52.

The controlled switch 51 can be realized, for example, as a TRIAC (Triode for Alternating Current) or other equivalent circuit element.

The control module 52 comprises the circuitry necessary to supply the controlled switch 51 with control signals, such as for example switching commands, so that the drain pump P can operate in the desired manner.

By way of example, the command module 52 can comprise a microprocessor and a connection interface towards the controlled switch 51.

When properly fed, the drain pump P therefore promotes the outflow of the washing fluid from the tank 10, preferably through the first and second conduits 31, 32.

Advantageously, the washing machine 1 further comprises an electric protection circuit 40 associated with the drain pump P.

The protection circuit 40 comprises, and preferably consists of, at least one thermistor 41 with a positive temperature coefficient, also known as a PTC (Positive Temperature Coefficient) thermistor.

In other words, thermistor 41 is designed in such a way that, as its temperature increases, its resistance also increases significantly.

It should be noted that, in general, all the circuit elements having a resistive component tend to modify their equivalent resistance as the temperature at which they are found varies. However, thermistors are made in such a way as to amplify this phenomenon in a controlled manner and therefore differ substantially, for example, from conventional resistors.

Figure 3 shows, purely by way of example, a possible Temperature-Current characteristic curve of a thermistor with a positive temperature coefficient. As an indication, when the current flowing in the component exceeds values in the order of 250 mA - 300 mA, the resistance assumes significantly high values and the current flowing through the thermistor decreases correspondingly. However, it should be noted that positive temperature coefficient thermistors can have characteristic curves which, while describing a close and evident relationship between the increase in temperature and the decrease in current, have a different trend from that shown in Figure 3.

The thermistor 41 is electrically connected in series to the drain pump P; the thermistor 41 can be arranged both upstream and downstream of the pump P itself.

Thermistor 41 is configured to limit, under certain circumstances, the current I flowing into pump P, supplied by the power supply unit U.

In particular, the thermistor 41 limits this current I when a parameter indicative of an anomalous operation of the pump P exceeds a certain threshold. Conveniently, this parameter indicative of the anomalous operation is constituted by the current I which flows in the discharge pump P and is correlated to the temperature of the thermistor 41.

In this way, if the drain pump P were to stop, the thermistor 41 would considerably increase its temperature and, by correspondingly increasing its resistance, it would limit the current absorption by the pump P, thus preventing overheating and related damage.

In one embodiment, the determined threshold mentioned above is between 250mA and 350mA.

In practice, the thermistor 41 is sized in such a way as to have a negligible resistance compared to the equivalent resistance of the drain pump P when the latter operates correctly under normal conditions, and absorbs a current I of the order of 200 mA. In this way, as long as there are no problems, failures or malfunctions, such as blocking of the rotor of the pump P, the thermistor 41 does not affect in any way the operation of the pump P itself.

From the moment in which the rotor of pump P remains blocked, the current I absorbed by pump P itself increases by approximately 50% (for example up to a value in the order of 300-350 mA). This causes an increase in the temperature of the thermistor 41 which, in the light of the above, correspondingly increases its own electrical resistance. In this situation there is therefore a substantial intervention of the thermistor 41 which limits the current I absorbed by the pump P and prevents its overheating.

A particularly advantageous aspect linked to the use of the thermistor 41 concerns the fact that, following its own intervention, the thermistor 41 can return to operating in standard conditions, as soon as the temperature at which it is found falls below the critical values of intervention. In other words, the protective action exerted by the thermistor 41 is not self-destructive (as for example occurs, however, for the so-called â € œfusesâ €), but is simply due to a reversible change in the condition of work in which the thermistor 41 is brought to operate.

Preferably the washing machine 1 is provided with an electronic control board 60.

Preferably at least the thermistor 40 is part of said electronic control board 60.

In the preferred embodiment, the driving circuit 50, and in particular the controlled switch 51 and the control module 52 are part of the electronic board 60.

The solution in which the thermistor 40 is mounted on the board 60 is particularly advantageous in terms of simplicity of construction, in particular with respect to the solutions in which the thermal protection element is mounted directly on the drain pump.

The invention achieves important advantages.

First of all, the solution object of the present invention allows to prevent in a simple and reliable way the overheating of the drain pump in conditions of anomalous operation.

Another advantage is found considering that the protection circuit designed to prevent overheating of the drain pump operates in a reversible way - that is, it can restore its standard operation without requiring the intervention of a specialized technician and / or replacement. of some component of the machine, once the pump returns to operate correctly.

Another advantage consists in the fact that the protection circuit of the washing machine according to the invention is characterized by simplicity and economy of realization, and does not require complex hardware / software structures.

A further advantage concerns the fact that the protection object of the present invention is able to intervene in any situation in which the current absorption by the drain pump becomes excessive, regardless of the cause that may have caused the failure or malfunction. .

Claims (7)

CLAIMS 1. Washing machine comprising: - a washing tank (10); - a main hydraulic circuit (20) for supplying a washing fluid to said tank (10); - a hydraulic discharge circuit (30) in fluid communication with said tank (10) and comprising at least one discharge pump (P), connected to an electric power supply unit (U) and adapted to promote a flow of said discharge fluid washing from said tank (10); - an electrical protection circuit (40) associated with said discharge pump (P) and comprising at least one thermistor (41) with a positive temperature coefficient, electrically connected in series to said discharge pump (P) and configured to limit a current which flows into said discharge pump (P) when a parameter indicative of an anomalous operation of said discharge pump (P) exceeds a certain threshold. 2. Washing machine (1) according to claim 1 further comprising an electric piloting circuit (50) active on said drain pump (P) to regulate its operation. 3. Washing machine (1) according to claim 3 wherein said piloting circuit (50) comprises a controlled switch (51), adapted to selectively modulate the electric power supply from said power supply unit (U) to said pump (P) drain, and a control module (52) configured to control said controlled switch (51). Washing machine (1) according to any one of the preceding claims, in which said parameter indicative of an anomalous operation of said pump (P) is representative of a current absorbed by said pump (P). 5. Washing machine (1) according to any one of the preceding claims in which said determined threshold is comprised between 250mA and 350mA. 6. Washing machine (1) according to any one of the preceding claims further comprising an electronic control board (60), the latter including at least said thermistor (41). Washing machine (1) according to claim 6 when dependent on claim 2 or 3 in which said driving circuit (50), and in particular said controlled switch (51) and said control module (52) are part of said electronic board control (60).