EP2931959A1

EP2931959A1 - Laundry washing machine with protection circuit

Info

Publication number: EP2931959A1
Application number: EP13818433.8A
Authority: EP
Inventors: Mauro Possanza
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2012-12-05
Filing date: 2013-12-04
Publication date: 2015-10-21
Also published as: ITTO20121049A1; WO2014087339A1; RU2015125023A

Abstract

A laundry washing machine comprising: a wash tub (10); a main hydraulic circuit (20) for supplying a wash fluid to said tub (10); a hydraulic drain circuit (.30) in fluidic communication with said tub (10) and comprising at least one drain pump (P) connected to a power supply unit (U) and adapted to promote an outflow of said wash fluid from said tub (10); an electric protection circuit (40) associated with said drain pump (P) and comprising at least one positive temperature coefficient thermistor (41) electrically connected in series to said drain pump (P) and configured for limiting a current (I) flowing in said drain pump (P) when a parameter indicative of faulty operation of said drain pump (P) exceeds a given threshold.

Description

LAUNDRY WASHING MACHINE WITH PROTECTION CIRCUIT

DESCRIPTION

[TECHNICAL FIELD]

The present invention relates to a laundry washing machine equipped with a protection circuit.

[PRIOR ART]

As is known, laundry washing machines, in particular washing and washing/drying machines, comprise a frame that supports a wash tub in which a drum rotates, in which drum the laundry items to be washed are placed.

The tub has an opening through which one can gain access to the drum and load laundry items into it.

Such machines also comprise a controlled hydraulic system that supplies water, appropriately mixed with detergents, for washing the laundry items.

Usually the presence of liquid in the tub is detected by means of a suitable sensor, e.g. a pressure switch, through which it is determined whether the liquid in the tub has reached a given level or not.

The information obtained through said sensor can be synthesized as "full state" or "empty state" with reference to the presence or absence of liquid in the tub.

After having been supplied to the tub and to the drum, the wash liquid, comprising water possibly mixed with detergents, may be either reused through a suitable recirculation system or made to flow out of the machine by means of a drain circuit.

The drain circuit typically consists of a drain pump, connected to the tub through a first intake duct, and an outflow duct, which allows the fluid that must be drained to flow out.

The electric control of the pump is provided through an electronic device of the TRIAC type, which acts as a switch to supply the necessary alternating power to the pump. One particularly important aspect concerns the prevention of pump overheating, which might even lead to the risk of a fire, and which may be caused by faulty working conditions of the pump itself; for example, a seized drain pump, i.e. a seized rotor of the motor included in the pump, will cause the motor to absorb more current than the nominal value, thus overheating and reaching very high temperatures that might cause severe damage both to its own structure and to the structure of other components of the washing machine; in particular, as aforesaid, it might even cause a fire.

A further condition of faulty operation of the drain pump may arise should the TRIAC drive device fail and enter into the so-called "diode mode", i.e. a mode in which a unidirectional short-circuit of the TRIAC occurs; the pump will in this case be supplied with a direct current component, since the pump is an inductive load; as a consequence, there will be an anomalous current flow, resulting in dangerous overheating of the pump itself.

In order to prevent the risk of an uncontrolled rise of the temperature of the pump and of a fire resulting therefrom, the pump generally incorporates a thermal protection device that will cut the pump supply current should overheating occur. However, this solution has the drawback that it provides "one-shot" operation, i.e. it cannot be reset. Therefore, after the thermal protector has tripped, it will at least be necessary to call a skilled technician to replace the whole pump.

Another solution currently available in the art uses electronic circuits characterized by complex hardware/software structures which, in addition to increasing the complexity of the washing machine manufacturing process, contribute to significantly increase the costs thereof.

[OBJECTS AND SUMMARY OF THE INVENTION]

It is one object of the present invention to provide a laundry washing machine equipped with a protection circuit adapted to prevent overheating of the drain pump in faulty conditions.

It is another object of the invention to provide a laundry washing machine in which the protection circuit adapted to prevent overheating of the drain pump operates in a reversible manner, i.e. it can return to standard operation without requiring the intervention of a skilled technician and/or the substitution of any components of the machine, as soon as the pump operates correctly again.

It is a further object of the invention to provide a laundry washing machine equipped with a protection circuit adapted to prevent overheating of the drain pump, the construction of which is simpler and more economical and requires no complex hardware/software structures.

These and other objects are substantially achieved through a laundry washing machine with a protection circuit as set out in the appended claims.

One idea at the basis of the present invention is to provide, in a laundry washing machine, a protection circuit associated with the drain pump, said protection circuit comprising at least one positive temperature coefficient thermistor electrically connected in series to said drain pump and configured for limiting the current flowing in said drain pump when a parameter indicative of faulty operation of said pump exceeds a given threshold.

The Applicant believes that in this manner it is possible to create a laundry washing machine in which the protection adapted to prevent overheating of the drain pump in faulty conditions is ensured in a simple, reliable and economically advantageous way. Preferably, the laundry washing machine according to the present invention also comprises an electric drive circuit acting upon said drain pump for adjusting the operation thereof.

Preferably, said drive circuit comprises a controlled switch adapted to selectively modulate the power supplied by said power supply unit to said drain pump, and a control module configured for controlling said controlled switch.

Preferably, said parameter indicative of faulty operation of said pump is represented by the current drawn by the pump itself.

Preferably, said given threshold is comprised between 250mA and 350mA.

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

Further features and advantages will become more apparent from the following detailed description of one preferred and non-limiting embodiment of the invention. Said description will refer to the annexed drawings, which are also provided merely as explanatory and non-limiting examples.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Figure 1 is a block diagram representative of a part of a laundry washing machine according to the present invention. Figure 2 is a block diagram of a circuit belonging to the laundry washing machine of Figure 1.

Figure 3 is a diagram representative of the operating characteristic of a circuit element used in the circuit of Figure 2.

Figure 4 schematically shows a sectional side view of a laundry washing machine according to the present invention, wherein some parts have been removed in order to highlight other parts.

The drawings show different aspects and embodiments of the present invention and, where appropriate, similar structures, components, materials and/or elements in the various drawings are designated by the same reference numerals.

[DETAILED DESCRIPTION OF THE INVENTION]

With reference to the annexed drawings, reference numeral 1 designates as a whole a laundry washing machine according to the present invention.

The laundry washing machine 1 is preferably a washing or washing/drying machine. By way of example, the laundry washing machine 1 may be a front-loading washing machine or, alternatively, a top-loading washing machine.

Preferably, the laundry washing machine 1 comprises a support structure 70 (Figure 4) having a substantially box-like shape, e.g. 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 side surface 75 and a second side surface (not shown), opposite to said first side surface 75.

Inside the support structure 70 a wash tub 10 is arranged, in which a drum 11 is rotatably mounted.

The tub 10 has a load opening, through which the laundry items to be washed can be inserted.

The load opening is closed by a door 12 (Figure 4). The door 12 may include a transparent porthole glass, which allows the user to see the internal portion of the drum 11 and the laundry loaded therein. In different embodiments, the door 12 is completely opaque and does not allow such observation.

The drum 11 is rotated by suitable actuating members, which are per se known and will not therefore be described herein in detail. When in use, the clothes to be washed are loaded into the drum 11.

A fluid is supplied into the tub 10 and into the drum 11, which fluid may comprise, depending on the specific wash step being carried out, either water only or water mixed with one or more detergents.

To this end, the laundry washing machine 1 comprises a main hydraulic circuit 20, which is schematically shown in Figure 1.

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

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

Preferably, the hydraulic drain circuit 30 also comprises a first duct 31 and a second duct 32.

The first duct 31 (or intake duct), also referred to as drain bellows, connects the tub 10 to an inlet of the drain pump P, whereas the second duct 32 (or delivery duct) connects an outlet of the drain pump P to a hydraulic drain network, to which the wash fluid can be sent at the end of a wash or rinse step.

The hydraulic drain circuit 30 is schematically shown in Figure 1 and partially depicted in Figure 4.

The drain pump P is connected to a power supply unit U (Figure 2), so as to be able to receive the electric energy required for its operation. In practice, the drain pump P comprises an electromechanical actuator (such as, for example, an electric motor), which, by appropriately rotating the so-called impeller of the pump itself, creates the desired fluid flow. The function of the connection between the drain pump P and the power supply unit U is therefore to ensure an appropriate power supply to the above- mentioned electromechanical actuator.

The power supply unit U may comprise the circuitry needed to take electric energy from a domestic or industrial network (not shown) and make it usable by the electromechanical actuator included in the drain pump P.

Preferably, the laundry washing machine 1 further comprises an electric drive circuit 50 which acts upon the drain pump P for adjusting the operation thereof.

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

The controlled switch 51 may be designed, for example, as a TRIAC (Triode for Alternating Current) or another equivalent circuit element.

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

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

When powered appropriately, the drain pump P promotes the outflow of the wash fluid from the tub 10, preferably via the first and second ducts 31, 32.

Advantageously, the laundry 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 positive temperature coefficient thermistor 41, also referred to as PTC (Positive Temperature Coefficient) thermistor.

In other words, the thermistor 41 is designed in a manner such that, as its temperature increases, its resistance increases significantly as well.

It must be pointed out that, in general, all the circuit elements having a resistive component tend to modify their own equivalent resistance as their temperature changes. Thermistors are however so designed as to amplify this phenomenon in a controlled manner, thus substantially differing from, for example, conventional resistors.

Figure 3 shows, merely by way of example, one possible characteristic Temperature- Current curve of a positive temperature coefficient thermistor. Indicatively, when the current flowing in the component exceeds values of the order of 250 mA - 300 mA, the resistance takes significantly high values and the current flowing through the thermistor decreases accordingly. It should however be noted that positive temperature coefficient thermistors may have characteristic curves that, while still describing a tight and clear relationship between temperature increase and current decrease, show a different trend than shown in Figure 3.

The thermistor 41 is electrically connected in series to the drain pump P; the thermistor 41 may be arranged either upstream or downstream of the pump P. The thermistor 41 is configured for limiting, in certain circumstances, the current I flowing in the pump P, supplied by the power supply unit U.

In particular, the thermistor 41 limits said current I when a parameter indicative of faulty operation of the pump P exceeds a given threshold. Advantageously, said parameter indicative of faulty operation consists of the current I flowing in the drain pump P, and is correlated to the temperature of the thermistor 41.

In this manner, if the drain pump P seizes, the temperature of the thermistor 41 will increase considerably; since also its resistance will increase accordingly, it will thus limit the current absorption by the pump P, thereby preventing overheating and any damage possibly arising therefrom.

In one embodiment, the above-mentioned given threshold is comprised between 250mA and 350mA.

In practice, the thermistor 41 is so sized as to have a negligible resistance compared to the equivalent resistance of the drain pump P when the latter is operating correctly in normal conditions, and draws a current I of approx. 200 mA. Thus, as long as no problems, faults or malfunctions arise, such as, for example, seizure of the rotor of the pump P, the thermistor 41 will by no means affect the operation of the pump P.

Should the rotor of the pump P seize, the current I drawn by the pump P will increase by about 50% (e.g. up to a value in the range of 300-350 mA). This will cause an increase in the temperature of the thermistor 41, which, in the light of the above explanation, will increase its own electric resistance accordingly. In this situation, therefore, there will be a substantial intervention of the thermistor 41 , which will limit the current I drawn by the pump P, thereby preventing it from overheating.

One particularly advantageous aspect related to the use of the thermistor 41 concerns the fact that, following its intervention, the thermistor 41 can go back to normal operation as soon as its temperature returns below the critical intervention values. In other words, the protection action exerted by the thermistor 41 is not self-destroying (unlike the so-called "fuses", for example), but is simply due to a reversible variation of the operating condition of the thermistor 41.

Preferably, the laundry washing machine 1 is equipped with an electronic control board 60. Preferably, at least the thermistor 40 is a part of said electronic control board 60.

In the preferred embodiment, the electronic board 60 includes the drive circuit 50, in particular the controlled switch 51 and the control module 52.

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

The invention offers significant advantages.

First of all, the solution of the present invention allows to prevent, in a simple and reliable manner, the drain pump from overheating in faulty operating conditions.

Another advantage is given by the fact that the protection circuit adapted to prevent overheating of the drain pump operates in a reversible manner, i.e. it can return to standard operation without requiring the intervention of a skilled technician and/or the substitution of any components of the machine, as soon as the pump operates correctly again.

Another advantage is that the protection circuit of the laundry washing machine according to the invention is characterized by simplicity and low cost of construction, and requires no complex hardware/software structure.

A further advantage is that the protection circuit of the present invention can come into action in any situation wherein the current absorbed by the drain pump becomes excessive, regardless of the cause of the fault or malfunction.

Claims

A laundry washing machine comprising:

- a wash tub (10);

- a main hydraulic circuit (20) for supplying a wash liquid to said tub (10);

- a hydraulic drain circuit (30) in fluidic communication with said tub (10) and comprising at least one drain pump (P) connected to a power supply unit (U) and adapted to promote an outflow of said wash fluid from said tub (10);

- an electric protection circuit (40) associated with said drain pump (P) and comprising at least one positive temperature coefficient thermistor (41) electrically connected in series to said drain pump (P) and configured for limiting a current flowing in said drain pump (P) when a parameter indicative of faulty operation of said drain pump (P) exceeds a given threshold.

A laundry washing machine (1) according to claim 1, further comprising an electric drive circuit (50) acting upon said drain pump (P) for adjusting the operation thereof.

A laundry washing machine (1) according to claim 3, wherein said drive circuit (50) comprises a controlled switch (51) adapted to selectively modulate the power supplied by said power supply unit (U) to said drain pump (P), and a control module (52) configured for controlling said controlled switch (51).

A laundry washing machine (1) according to any one of the preceding claims, wherein said parameter indicative of faulty operation of said pump (P) is representative of a current drawn by said pump (P).

A laundry washing machine (1) according to any one of the preceding claims, wherein said given threshold is comprised between 250mA and 350mA.

A laundry 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).

A laundry washing machine (1) according to claim 6 when dependent on claim 2 or 3, wherein said drive circuit (50), and particularly said controlled switch (51) and said control module (52), are parts of said electronic control board (60).