Drum-type washing machine

Abstract

 A washing machine comprising a tub (2), a drum (3) mounted for rotation in the tub (2) to receive laundry to be washed and a controller (20) for controlling rotation of the drum (3) is described. The washing machine has a position sensor for generating a signal indicative of when the rotational position of the drum (3) relative to the tub (2) corresponds to a predetermined rotational position so that the controller (20) controls rotation of the drum (3) in dependence on the signal received from the position sensor.

Description

[0001] The present invention relates to a washing machine comprising a tub, a drum mounted for rotation within the tub to receive laundry to be washed and a controller for controlling rotation of the drum. The invention also includes a method of controlling such a washing machine.

[0002] A drum type washing machine washes laundry contained in a drum by operating a drum motor to rotate the drum and agitate the laundry in detergent and water.

[0003] A conventional drum-type washing machine has a drum rotatably mounted within a tub. Water supplied to the tub enters the drum through holes located therein. However, as there is a gap between the inner circumference of the tub and the outer circumference of the drum, the water must first fill this before it enters the drum to wet laundry in the drum. It therefore takes a long time to uniformly wet laundry in the drum.

[0004] Lifting elements or paddles on the inner circumference of the drum extend in a longitudinal direction parallel to the axis of rotation of the drum. To agitate the laundry, the lifting elements lift laundry, as the drum rotates and causes it to drop under gravity when the laundry reaches the upper part of the drum, thereby washing the laundry.

[0005] Since a conventional drum type washing machine determines the rotation speed of the drum based on the weight of the laundry and then operates the drum based on this rotational speed, the laundry carried by the lifters may drop either before or after the laundry reaches the top position of the drum. Therefore, the laundry is not agitated as much in comparison to when the laundry is allowed to drop from the top of the drum, thereby reducing the washing effect and requiring a longer time to wash the laundry.

[0006] The present invention seeks to provide a system which overcomes or substantially alleviates the problems discussed above.

[0007] A drum type washing machine according to the present invention is characterised by a position sensor for generating a signal indicative of when the rotational position of the drum relative to the tub corresponds to a predetermined rotational position, the controller controlling rotation of the drum in dependent on the signal received from the position sensor.

[0008] In a preferred embodiment, the position sensor is operable to generate a signal when the rotational position of the drum relative to the tub corresponds to a first predetermined rotational position, to cause the controller to reduce the speed of the drum and, to main that signal until the rotational position of the drum relative to the tub corresponds to a second predetermined rotational position, to cause the controller to increase the speed of the drum.

[0009] The drum may include at least one lifting element and the drum includes a rotational position in which the or each lifting element is at top-dead centre during each revolution of the drum, the first predetermined rotational position corresponding to a position just before the, or one, lifting element has reached top-dead centre.

[0010] Preferably, the second predetermined rotational position corresponds to the rotational position of the drum when the, or one, lifting element is at top-dead centre.

[0011] In one embodiment, the controller is operable to cause the drum to stop for a predetermined length of time when it has reached the second predetermined position, before increasing the speed of the drum.

[0012] The washing machine may include a water inlet positioned above the drum, the controller being operable to initiate a flow of water through the inlet when the controller has stopped rotation of the drum for said predetermined length of time so that at least some of the water enters the drum through the lifting element at top-dead centre.

[0013] A method of controlling a washing machine according to the invention is characterised by the steps of:

(a) generating a signal indicative of the rotational position of the drum relative to the tub when it corresponds to a predetermined rotational position using a position sensor, and

(b) controlling rotation of the drum in dependence on the signal received from the position sensor.

[0014] The lifter may include a main body, incoming holes formed through the main body for receiving the supplied water, and spray holes formed through the main body for spraying the wash water into the drum.

[0015] In a preferred embodiment, the method includes the steps of:

(c) generating a signal when the rotational position of the drum relative to the tub corresponds to a first predetermined rotational position, to cause the controller to reduce the speed of the drum and,

(d) maintaining that signal until the rotational position of the drum relative to the tub corresponds to a second predetermined rotational position, to cause the controller to increase the speed of the drum.

[0016] Preferably, the method includes the further step of stopping rotation of the drum for a predetermined length of time when it has reached the second predetermined position and before increasing the speed of the drum.

[0017] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view of a drum type washing machine in accordance with the present invention;

Figure 2 is a perspective view of a lifter of the drum type washing machine in accordance with the present invention;

Figure 3 is a block diagram of the drum type washing machine in accordance with the present invention;

Figure 4 is a schematic view illustrating a water supplying operation of the drum type washing machine in accordance with the present invention;

Figure 5 is a schematic view illustrating a washing operation of the drum type washing machine in accordance with the present invention;

Figure 6 is a graph illustrating the relation between angle of rotation a drum and rotational speed of the drum of the drum type washing machine in accordance with the present invention; and

Figure 7 is a graph illustrating the relation between output signal of an encoder and rotational speed of the drum of the drum type washing machine in accordance with the present invention.

[0018] Referring to the drawings, there is shown in Figures 1 and 2 a drum type washing machine in accordance with the present invention comprising a housing 1 having a nearly cubic shape defining an external appearance, a tub 2 for containing water, a drum 3 rotatably installed in the tub 2 and provided with a plurality of holes 4 formed therethrough, and a drum motor 5 for rotating the drum 3 to wash laundry. The drum motor 5 includes a stator 5a and a rotor 5b.

[0019] Openings 2a and 3a are respectively formed through the front surfaces of the tub 2 and the drum 3 and a door 6 for opening and closing the openings 2a and 3a is hinged to a front surface of the housing 1.

[0020] A water supply pipe 7 for supplying water from the outside to the washing machine and a detergent container 8 for mixing a detergent with the water supplied through the water supply pipe 7 are installed in an upper part of the housing 1 and a drain pump 9 and a drain hose 10 for discharging the water to the outside of the housing 1 after the washing operation is completed are installed on a lower part of the housing 1.

[0021] The drum 3 and the tub 2 are upwardly inclined at a designated angle towards the front surface of the housing 1.

[0022] A plurality of lifters 11, 12 and 13 (Figure 5) are installed on the inner circumference of the drum 3 such that the lifters 11, 12 and 13 are spaced from each other by designated intervals. The lifters serve to lift the laundry loaded in the drum 3 together with the water to a designated height. The laundry then drops due to the rotation of the drum 3 thereby allowing the laundry to be washed.

[0023] As shown in Figure 2, the lifter 11 includes a main body 11a having a trapezoidal shape for defining an external appearance, a longitudinal inlet recess 11b formed through the upper surface of the main body 11a for receiving the supplied water, a plurality of spray holes 11c formed through the lower and side surfaces of the main body 11a for spraying the water into the drum 3 to wet the laundry, and connection holes 11d formed through the upper surface of the main body 11a for connecting the lifter 11 to the drum 3 using screws 11e.

[0024] When one of the lifters 11 is disposed under the water supply pipe 7, the majority of the water supplied through the water supply pipe 7 falls into the longitudinal inlet recess 11b and is supplied to the inside of the drum 3 through the spray holes 11c. The remainder of the water, which does not fall into the longitudinal inlet recess 11b, falls along the outer circumference of the drum 3 and fills the drum 3 from the bottom. As described above, the drum type washing machine consistent with the present invention sprays water directly from the upper part of the drum 3 thereby allowing the laundry contained in the drum 3 to be uniformly and rapidly wetted.

[0025] As shown in Figure 3, the drum type washing machine further comprises a controller 20 for controlling the overall operation including the water supply mode and the wash mode.

[0026] The controller 20 controls a motor driving unit 22 which drives the drum motor 5 based on input instructions from a user through an input unit 21, thereby transmitting the driving force of the drum motor 5 to the drum 3 and then rotating the drum 3 at a designated speed.

[0027] A speed sensor 23 senses the rotational speed of the drum motor 5 and supplies the sensed speed to the controller 20.

[0028] An encoder 24 senses the angle of rotation of the drum 3 and supplies the sensed angle to the controller 20. The encoder 24 is installed in the tub 2 such that the encoder 24 generates a designated pulse signal by means of a magnetic force generated from magnets (not shown) installed on the outside of the drum 3 when the drum 3 is rotated. A magnet having a comparatively large magnetic force, as compared to the other magnets installed on the drum 3, is installed at a predetermined standard position. Thus, the intensity of a standard pulse signal outputted from the encoder 24 by means of the comparatively large magnetic force of the above magnet is higher than the intensities of the pulse signals outputted from the encoder 24 by means of the magnetic force of the other magnets. Although, in this embodiment, the encoder outputs a plurality of standard pulse signals based on the standard position to respectively correspond to the plurality of lifters during one revolution of the drum, the encoder may output only one standard pulse signal, based on the standard position, to correspond to any one lifter of the plurality of lifters per one revolution of the drum.

[0029] Hereinafter, the operation of the drum type washing machine according to the present invention will be described in detail.

[0030] When a user puts washing instructions into the input unit 21 as shown in Figure 4, the controller 20 controls the motor driving unit 22 to drive the drum motor 5 so that the one of the lifters 11 is disposed under the water supply pipe 7. That is, the controller 20 controls the angle of the drum 3 based on the standard pulse signal outputted from the encoder 24. Subsequently, when the water is supplied to the inside of the drum through the water supply pipe 7 it falls into the longitudinal inlet recess 11b of the lifter 1 and is sprayed into the drum 3 through the spray holes 11c.

[0031] When the washing machine is operated in the wash mode as shown in Figure 5, the drum 3 is rotated in the clockwise direction (R) and the lifter reaches a predetermined position (B). Then the rotational speed of the drum 3 is suddenly decreased.

[0032] As shown in Figures 6 and 7 when the rotation of the drum 3 is started from the condition that the lifter 11 is disposed at a start position (A), the controller 20 operates the drum 3 at a first rotational speed (S1). Here, the encoder 24 outputs a pulse signal having a low intensity (M2). When the lifter 11 reaches the predetermined position (B), i.e. the angle of rotation of the drum 3 is a first predetermined angle (P1), the encoder 24 outputs a standard pulse signal having a high intensity (M1) and then the controller 20 reduces the rotational speed of the drum 3. When the drum 3 is rotated so that the lifter 11 reaches a top position (C) the rotational speed of the drum 3 has reduced from the first rotational speed (S1) to a second rotational speed (S2) which is lower than the first rotational speed (S1). The rotational speed of laundry (L) carried by the lifter 11 is now reduced and laundry (L) drops in the gravitational direction (F) from the top position (C), which deviates from the predetermined position (B) by a designated angle (a). Then, while the lifter 11 passes through the top position (C), the controller 20 increases the rotational speed of the drum 3 to the first rotational speed (S1) and maintains the first rotational speed of the drum 3 to the first rotational speed (S1) and maintains the first rotational speed (S1) of the drum 3.

[0033] Whenever the subsequent lifter 12 or 13 reaches the predetermined position (B), that is, the angle of rotation of the drum 3 reaches a second predetermined angle (P2) or a third predetermined angle (P3), the rotational speed of the drum 3 is decreased to the second rotational speed (S2). When the lifter 12 or 13 passes through the top position (C), the rotational speed of the drum 3 is increased to the first rotational speed (S1) and maintained at the first rotational speed (S1). Whenever the drum 3 turns one revolution, the above described process is repeated.

[0034] Similarly, when the drum 3 is rotated in the counter-clockwise direction and the lifter 11 reaches a predetermined position before the top position (C) by a designated angle, the controller 20 decreases the rotational speed of the drum 3 and allows the laundry carried by the lifter 11 to drop from the top position (C).

[0035] As described above, the drum of the washing machine may be rotated alternately in the clockwise and counter-clockwise directions during the wash mode, and whenever a lifter reaches the top position, the laundry carried by the lifter is allowed to fall by the force of gravity, thereby maximising falling power.

[0036] Although an embodiment of the invention has been shown and described, it will be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles of the invention, the scope of which is defined in the claims and their equivalents and the foregoing description should be regarded as a description of a preferred embodiment only.

Claims

1. A washing machine comprising a tub, a drum mounted for rotation in the tub to receive laundry to be washed and a controller for controlling rotation of the drum, characterised by a position sensor for generating a signal indicative of when the rotational position of the drum relative to the tub corresponds to a predetermined rotational position, the controller controlling rotation of the drum in dependence on the signal received from the position sensor.

2. A washing machine according to claim 1, wherein the position sensor is operable to generate a signal when the rotational position of the drum relative to the tub corresponds to a first predetermined rotational position, to cause the controller to reduce the speed of the drum and, to maintain that signal until the rotational position of the drum relative to the tub corresponds to a second predetermined rotational position, to cause the controller to increase the speed of the drum.

3. A washing machine according to claim 2, wherein the drum includes at least one lifting element and the drum includes a rotational position in which the or each lifting element is at top-dead centre during each revolution of the drum, the first predetermined rotational position corresponding to a position just before the, or one, lifting element has reached top-dead centre.

4. A washing machine according to claim 3, wherein the second predetermined rotational position corresponds to the rotational position of the drum when the, or one, lifting element is at top-dead centre.

5. A washing machine according to any preceding claim, wherein the controller is operable to cause the drum to stop for a predetermined length of time when it has reached the second predetermined position, before increasing the speed of the drum.

6. A washing machine according to claim 1, wherein the washing machine includes at least one lifting element and the drum includes a rotational position at which the lifting element is at top-dead centre during each revolution of the drum, the position sensor being operable to generate a signal indicative of when the, or one, lifting element has reached top-dead centre so that the controller stops rotation of the drum for a predetermined length of time.

7. A washing machine according to claim 5 or claim 6, including a water inlet positioned above the drum, the controller being operable to initiate a flow of water through the inlet when the controller has stopped rotation of the drum for said predetermined length of time so that at least some of the water enters the drum through the lifting element at top-dead centre.

8. A method of controlling a washing machine comprising a tub, a drum mounted for rotation in the tub to receive laundry to be washed and a controller for controlling rotation of the drum, characterised by the steps of:

(a) generating a signal indicative of the rotational position of the drum relative to the tub when it corresponds to a predetermined rotational position using a position sensor, and

(b) controlling rotation of the drum in dependence on the signal received from the position sensor.

9. A method according to claim 8, wherein step (a) includes the steps of:

(c) generating a signal when the rotational position of the drum relative to the tub corresponds to a first predetermined rotational position, to cause the controller to reduce the speed of the drum and,

(d) maintaining that signal until the rotational position of the drum relative to the tub corresponds to a second predetermined rotational position, to cause the controller to increase the speed of the drum.

10. A method according to claim 9, including the step of stopping rotation of the drum for a predetermined length of time when it has reached the second predetermined position and before increasing the speed of the drum.

11. A drum type washing machine comprising a drum, an angle sensing device which senses the angle of rotation of the drum, a drum motor rotating the drum, a motor driving unit driving the drum motor, and a controller controlling water supply operations and washing operations based on the angle of rotation of the drum sensed by the angle sensing device.

12. The drum type washing machine according to claim 11 comprising at least one lifter wherein the at least one lifter supplies wash water to the inside of the drum and wherein the controller recognizes the position of the at least one lifter using the angle sensing device and thereby controls the rotational position of the drum such that the drum can receive the wash water from the at least one lifter.

13. The drum type washing machine according to claim 12 wherein the at least one lifter includes a main body, incoming holes formed through the main body for receiving the supplied wash water and spray holes formed through the main body for spraying the wash water into the drum.

14. The drum type washing machine according to claim 11 comprising at least one lifter, wherein the at least one lifter carries laundry loaded in the drum and wherein the controller recognizes the position of the laundry carried by the at least one lifter using the angle sensing device and thereby controls the rotational speed of the drum.

15. The drum type washing machine according to claim 14 wherein the controller decreases the rotational speed of the drum before the laundry reaches a top position so that the laundry falls from the top position.

16. The drum type washing machine according to claim 12 wherein the angle sensing device is an encoder outputting different pulse signals based on the rotational position of the drum, and the encoder outputs a standard pulse signal when the drum is in a predetermined standard position and outputs another pulse signal when the drum is not in the predetermined standard position.

17. The drum type washing machine according to claim 16 wherein the standard pulse signal has a higher intensity than that of another pulse signal.

18. The drum type washing machine according to claim 14 wherein the angle sensing device is an encoder outputting different pulse signals based on the rotational position of the drum and the encoder outputs a standard pulse signal when the drum is in a predetermined standard position and outputs another pulse signal when the drum is not in the predetermined standard position.

19. The drum type washing machine according to claim 18 wherein the standard pulse signal has a higher intensity than that of another pulse signal.

20. A drum type washing machine comprising a rotary drum, a motor rotating the rotary drum, a motor driving unit driving the motor, at least one lifter lifting laundry and supplying wash water to the inside of the drum, a sensing device which detects the position of the lifter and a controller that places the lifter at a first predetermined position to supply the wash water to the inside of the drum, and reduces the rotational speed of the drum when the lifter rotated along the rotational direction of the drum reaches a second predetermined position.

21. The drum type washing machine according to claim 20 wherein the lifter includes a main body, incoming holes formed through the main body for receiving the supplied wash water and spray holes formed through the main body for spraying the wash water into the drum.

22. The drum type washing machine according to claim 20 wherein the sensing device is an encoder outputting different pulse signals based on the rotational position of the drum corresponding to the position of the lifter and the encoder outputs a standard pulse signal when the drum is in a predetermined standard position and outputs another pulse signal having a lower intensity than that of the standard pulse signal when the drum is not in the predetermined standard position.

23. The drum type washing machine according to claim 22 wherein the first determined position is a top position of the drum having the highest level in the drum and the second determined position is a position of a level lower than that of the top position.

24. A drum type washing machine comprising a drum, means for sensing the angle of rotation of the drum, a drum motor for rotating the drum, means for driving the drum motor and means for controlling water supply operations and washing operations based on the angle of rotation of the drum sensed by the angle sensing means.

Drawing