The present invention relates to a washing machine wherein the belt breakage or the belt slippage is detected during the washing/drying process and relates to the operation method thereof.

In washing machines, the power transmission to the drum from the motor is realized by means of direct drive systems or belt-pulley systems. In the direct drive systems, the drum speed and the motor speed are the same since the power transmission is performed directly. However, in the belt-pulley systems, the motor pulley and the drum pulley are generally chosen in different sizes to achieve price optimization. The power transmission is realized by means of the belt between said two pulleys and the drum speed is controlled based on the data received from the motor. In cases where the belt between the two pulleys slips since the drum is overloaded or as a result of a piece of laundry stuck between the door glass and the bellows, or when the user does not notice the belt slippage, resulting in breakage of the belt, the motor rotates but the drum does not rotate. Thus, the washing machine cannot perform its function.

In the state of the art Japanese Patent Application No. JP07031041, a washer/dryer is disclosed, wherein the breakage of the belt is detected by detecting changes in the drive motor speed by means of the speed sensor in the motor. In this document, when a change in the motor speed is detected, the motor is stopped and the user is informed that there is a problem in the belt by means of the audio warning system.

In the state of the art European Patent Application No. EP1521880, a dryer is disclosed, comprising a movable transmission element connected to the belt rotating the drum, wherein the breakage of the belt or changes in the length of the belt is/are detected by means of a sensor.

The aim of the present invention is the realization of a washing machine wherein the slippage or breakage of the belt in the belt-pulley system can be detected. In the washing machine of the present invention, the slippage of the belt over the pulley or the complete breakage of the belt is determined by detecting the balance between the speed and RPM measurements of the motor and the drum.

The washing machine of the present invention comprises a sensor unit which measures the speed and/or the RPM of the drum and a speed sensor which measures the speed and/or RPM of the motor.

The speed sensor can be a tachogenerator, a hall sensor or an encoder.

In another embodiment of the present invention, the motor speed can be determined by means of the control unit which processes the signal frequency of the stator current of the motor in addition to the data received from the sensor.

In an embodiment of the present invention, the sensor unit comprises at least one magnet which is disposed in at least one baffle and a reed switch which is placed on the tub and which is triggered by the magnetic field created by the magnet.

In the preferred embodiments of the present invention, for example, three baffles separated at 120-degree intervals on the circumference the drum, one magnet in each thereof and the reed switch on the tub can be used to measure the speed of the drum more precisely. Thereby, the speed of the drum can be more accurately measured by means of the signal generated at 120 degree angles.

In another embodiment of the present invention, the magnet can be disposed directly in the drum at a position outside the baffles.

In another embodiment of the present invention, the sensor unit is composed of a light source and a light sensor. In this embodiment, the light source or the light sensor is placed onto the tub at a position between the rear side of the pulley and the tub. For example, when the light source is placed onto the tub, a light sensor is positioned on the body so as to face the light source and detect the light coming from the light source through the gaps between the arms of the pulley during the rotation of the pulley. Thereby, the rotational speed of the drum is determined by means of the sensor detecting the light passing through the gaps between the arms of the pulley during the rotation of the pulley. In an embodiment of the present invention, the light source comprises at least one LED.

In an embodiment of the present invention, the control unit informs the user by means of an audio warning or a text warning upon detecting a failure related to belt breakage or slippage.

By means of the present invention, a washing machine is realized, wherein the breakage or slippage of the belt is detected based on the differences between the RPM or speed of the motor and the drum.

The washing machine realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

Figure 1 - is the front view of the washing machine in an embodiment of the present invention.

Figure 2 - is the front perspective view of a section of the body in an embodiment of the present invention wherein the washing machine comprises a magnet disposed in the baffle and a reed switch disposed in the tub.

Figure 3 - is the perspective view of the rear section of the tub wherein the pulley and the motor are positioned in an embodiment of the washing machine of the present invention.

Figure 4 - is the perspective view of the tub and the motor of the washing machine in the embodiment of the present invention wherein the sensor unit comprises a light source.

Figure 5 - is the perspective view of a section of the body comprising the light source in the embodiment in Figure 4 of the washing machine of the present invention.

The elements illustrated in the figures are numbered as follows:

1. Washing machine

2. Body

3. Tub 4. Drum

5. Motor

6. Baffle

7. Pulley

8. Belt

9. Control unit

10. Magnet

11. Sensor unit

12. Reed switch

13. Light source

14. Light sensor

15. Speed sensor

The washing machine (1) comprises a body (2); a tub (3) which is disposed in the body (2); a drum (4) which is disposed in the tub (3) and wherein the laundry is loaded; at least one baffle (6) which tumbles the laundry in the drum (4); a motor (5) which enables the drum (4) to be rotated; a speed sensor (15) which measures the speed and the RPM of the motor (5); a pulley (7) which transmits the movement of the motor (5) to the drum (4); and a belt (8) which is connected to the motor (5) at one part and to the pulley (7) at the other part.

The washing machine (1) of the present invention comprises a sensor unit (11) which calculates the speed of the drum (4); and a control unit (9) which detects the slippage of the belt (8) by comparing the speed and RPM data of the motor (5) received from the speed sensor (15) with the speed data of the drum (4) received from the sensor unit (11) based on the rotation rate of the motor (5), or which detects the breakage of the belt (8) by detecting that the drum (4) does not rotate while the motor (5) is rotating.

In the washing machine (1) of the present invention, the power generated by the motor (5) for rotating the drum (4) is transmitted to the drum (4) by means of the belt (8). The belt (8) is connected to the drum (7) by means of the pulley (7) and to the motor (5) by means of a shaft at the rear section of the tub (3). The speed of the motor (5) is detected by means of the speed sensor (15). The sensor unit (11) measures the instantaneous velocity of the drum (4). The rotation rate of the motor (5) refers to the ratio between the RPM of the motor (5) and the RPM of the drum (4). The rotation rate between the motor (5) and the drum (4) is included in the operating conditions/programs predetermined by the producer. For example, in a washing machine (1) wherein the motor (5) rotation rate is 10, the drum (4) is expected to reach 40 RPM when the motor (5) reaches 400 RPM. Using said rotation rate, the control unit (9) detects the slippage of the belt (8) by checking if the drum (4) rotates with the expected RPM. Furthermore, the control unit (9) detects the breakage of the belt (8) by determining that the energy of the motor (5) is not transmitted to the drum (4) if the speed of the drum (4) detected by the sensor unit (11) is zero while the speed of the motor (5) received from the speed sensor (15) is greater than zero.

In an embodiment of the present invention, the washing machine (1) comprises the sensor unit (11) having at least one magnet (10) which is disposed into at least one baffle (6) and a reed switch (12) which is disposed on the tub (3) and which is triggered by the magnetic field created by the magnet (10) for measuring the speed of the drum (4). In this embodiment, the magnet (10) in the baffle (6) triggers the reed switch (12) on the tub (3) as the drum (4) rotates and thus, the instantaneous speed of the drum (4) can be measured (Figure 2).

In another embodiment of the present invention, the washing machine (1) comprises a sensor unit (11) having at least one magnet (10) which is disposed onto the pulley (7) rotating as coupled with the drum (4) and a reed switch (12) which is disposed at the rear section of the tub (3) accommodating the motor (5) and the pulley (7). Thereby, the speed of the drum (4) is measured by means of the magnet (10) which creates a magnetic field as the pulley (7) rotates and the reed switch (12) which is triggered by the magnet (10) (Figure 3).

In another embodiment of the present invention, the washing machine (1) comprises a light source (13) which is positioned between the tub (3) and the pulley (7) in the tub (3) and a light sensor (14) which is disposed on the body (2), facing the light source (13) or a light sensor (14) which is positioned between the tub (3) and the pulley (7) in the tub (3) and a light source (13) which is disposed on the body (2), facing the light sensor (14). In this embodiment, during the rotation of the pulley (7), the light source (13) sends light through the gaps between the arms of the pulley (7), and the light sensor (14) measures the speed of the drum (4) by detecting the light (Figure 4).

In an embodiment of the present invention, the control unit (9) warns the user if the speed of the motor (5) is greater than zero when the speed of the drum (4) is zero or if the motor (5) rotation rate between the RPM of the drum (4) and the RPM of the motor (5) deviates from the values predetermined by producer. Thus, the unnecessary operation of the washing machine (1) as power cannot be transmitted from the motor (5) to the drum (4) is avoided or the breakage of the belt (8) is prevented if the pulley (7) continues to rotate in case of a belt (8) slippage.

In the washing machine (1) of the present invention, the breakage of the belt (8) or the slippage thereof from the pulley (7) is detected via the steps of:

- Determining the speed and the RPM of the motor (5) and measuring the speed of the drum (4) by means of the sensor unit (11),

- Calculating the RPM of the drum (4) by means of the control unit (9) using the RPM of the motor (5) and the motor (5) rotation rate which is the ratio between the RPM of the motor (5) and the RPM of the drum (4) predetermined by the producer,

- Deciding by the control unit (9) that the belt (8) is slipped from the pulley (7) or broken when the RPM of the drum (4) differs from the value calculated by the control unit (9).

In the operation method of the washing machine (1) of the present invention, the control unit (9) decides that the belt (8) is broken if the speed of the drum (4) is zero when the speed of the motor (5) is greater than zero. If the speed of the drum (4) is greater than zero, the control unit (9) checks the motor (5) conversion rate between the RPM of the motor (5) and the RPM of the drum (4) predetermined by the producer. If said ratio differs from the motor (5) rotation rate predetermined by the producer, the control unit (9) decides that the belt (8) is slipped from the pulley (7) and the motor (5) cannot transmit the required power to the drum (4) properly.

By means of the present invention, in the washing machines (1) which operate with the belt (8)-pulley (7) system, the user is warned in case the belt (8) slips from the pulley (7) or is broken and the unnecessary operation of the washing machine (1) is prevented.