WO2011025321A1

WO2011025321A1 - Control method of laundry machine

Info

Publication number: WO2011025321A1
Application number: PCT/KR2010/005817
Authority: WO
Inventors: Jae Hyuk Jang; Bon Kwon Koo
Original assignee: Lg Electronics Inc.
Priority date: 2009-08-27
Filing date: 2010-08-27
Publication date: 2011-03-03
Also published as: EP2470710A4; EP2470710A1; US20120151685A1; EP2470710B1

Abstract

The patent application discloses a control method of a laundry machine provided with a balancer. The method includes a balancing step of at least one time for rotating a drum (30) at a constant speed for a predetermined time by decelerating the drum (30) if the drum (30) is accelerated at a predetermined RPM or more. The balancing step is performed after a rotation speed of the drum (30) passes through a transient region of the laundry machine (100).

Description

CONTROL METHOD OF LAUNDRY MACHINE

The present invention relates to a control method of a laundry machine.

In general, a laundry machine may include washing, rinsing and spinning cycles. Here, the spinning cycle includes a rotating step of rotating a drum provided in such a laundry machine at the highest RPM. Because of the step, the spinning cycle would generate noise and vibration quite a lot, which is required to be solved in the art the prevent invention pertains to.

Accordingly, the present invention is directed to a control method of a laundry machine.

An object of the present invention is to provide a control method of a laundry machine which can solve the above problem.

To solve the problems, an object of the present invention is to provide a control method of a laundry machine provided with a balancer includes a balancing step of at least one time for rotating a drum at a constant speed for a predetermined time by decelerating the drum if the drum is accelerated at a predetermined RPM or more, the balancing step performed after a rotation speed of the drum passes through a transient region of the laundry machine.

According to the control method of the present invention, noise of the laundry machine can be reduced remarkably when the spinning cycle is carried out.

The accompanying drawings, which are included to provide further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principle of the disclosure.

In the drawings:

FIG. 1 is a schematic view illustrating a laundry machine to which a control method according to the first embodiment of the present invention is applied;

FIG. 2 is an exploded perspective view illustrating a laundry machine to which a control method according to the second embodiment of the present invention is applied;

FIG. 3 is a coupled sectional view of FIG. 2;

FIG. 4 is a graph illustrating variation in rotation speed of a drum in a control method of a spinning cycle of a laundry machine according to the first embodiment of the present invention;

FIG. 5 is a graph illustrating variation in rotation speed of a drum in a control method of a spinning cycle of a laundry machine according to the second embodiment of the present invention;

Fig. 6 is a graph showing a relation of mass vs. a natural frequency. ; and

Fig. 7 is a graph illustrating vibration characteristics of the laundry machine of FIG. 3.

As follows, an exemplary embodiment of the present invention will be described in reference to the accompanying drawings. First of all, a laundry machine a control method according to an embodiment of the present invention can be applied to will be descried and the control method according to an embodiment of the present invention will be described after that.

In reference to FIG. 1, a laundry machine 100 includes a cabinet 10 configured to define an exterior appearance thereof, a tub 20 mounted in the cabinet 10 to hold wash water therein and a drum 30 rotatably provided in the tub 20.

The cabinet 10 defines the exterior appearance of the laundry machine 100 and configuration elements which will be described later may be mounted in the cabinet 10. A door 11 is coupled to a front of the cabinet 10 and a user may open the door 11 to load laundry items including clothes, beddings, cloth items and the like (hereinafter, ‘laundry’) into the cabinet 10.

The tub 20 configured to hold wash water therein may be provided in the cabinet 10 and the drum configured to receive the laundry therein may be rotatale within the tub 20. In this case, a plurality of lifters 31 may be provided in the drum 30 to lift and drop the laundry during the rotation of the drum 30.

The tub 20 may be supported by a spring 50 provided above the tub 20. Here, a motor 40 is mounted to a rear surface of the tub 20 to rotate the drum 30. That is, the motor 40 is provided in a rear wall of the tub 20 and it rotates the drum 30. When vibration is generated in the drum 30 rotated by the motor 40, the tub 20 provided in the laundry machine according to this embodiment may be vibrated in communication with the drum 30. When the drum 30 is rotated, the vibration generated in the drum 30 and the tub 20 may be absorbed by a damper 60 provided below the tub 20.

As shown in FIG. 1, the tub 20 and the drum 30 may be provided in parallel to a base of the cabinet 10 or tilted downward although not shown in the drawing. As the user loads the laundry into the drum 30, it is advantageous that the front portions of the tub 20 and the drum 30 should be tilted upward.

To suppress the vibration of the drum in a spinning cycle that the drum is rotated, specially, at a high speed, a balancer 70 is provided in a front surface and/or rear surface to balance the drum and the balancer 70 will be described in detail later.

According to a laundry machine according to an embodiment, the tub may be fixedly supported to the cabinet or it may be supplied to the cabinet by a flexible supporting structure such as a suspension unit which will be described later. Also, the supporting of the tub may be between the supporting of the suspension unit and the completely fixed supporting.

That is, the tub may be flexibly supported by the suspension unit which will be described later or it may be complete-fixedly supported to be movable more rigidly. Although not shown in the drawings, the cabinet may not be provided unlike embodiments which will be described later. For example, in case of a built-in type laundry machine, a predetermined space in which the built-in type laundry machine will be installed may be formed by a wall structure and the like, instead of the cabinet. In other words, the built-in type laundry machine may not include a cabinet configured to define an exterior appearance thereof independently.

In reference to FIGS. 2 and 3, a tub 12 provided in the laundry machine is fixedly supported to a cabinet. The tub 12 includes a tub front 100 configured to define a front part of the tub and a tub rear 120 configured to define a rear part of the tub. The tub front 100 and the tub rear 120 are assembled to each other by screws, to form a predetermined space big enough to accommodate the drum. The tub rear 120 has an opening formed in a rear portion thereof and an inner circumference of the rear portion composing the tub rear 120 is connected with an outer circumference of a rear gasket 250. The tub back 130 has a through-hole formed in a center thereof to pass a shaft to pass there through. The rear gasket 250 is made of a flexible material not to transmit the vibration of the tub back 130 to the tub rear 120.

The tub rear 120 has a rear surface 128 and the rear surface 128, the tub back 130 and the rear gasket 250 may define a rear wall of the tub. The rear gasket 250 is connectedly sealed with the tub back 130 and the tub rear 120, such that the wash water held in the tub may not leak. The tub back 130 is vibrated together with the drum during the rotation of the drum. At this time, the tub back 130 is distant from the tub rear 120 enough not to interfere with the tub rear. Since the rear gasket 250 is made of the flexible material, the tub back 130 is allowed to relative-move, without interference of the tub rear 120. The rear gasket 250 may include a corrugated portion 252 extendible to a predetermined length to allow the relative-motion of the tub back 130.

A foreign substance preventing member 200 configured to prevent foreign substances from drawn between the tub and the drum may be connected to a front portion of the tub front 100. The foreign substance preventing member 200 is made of a flexible material and it is fixed to the tub front 100. Here, the foreign substance preventing member 200 may be made of the flexible material identical to the material composing the rear gasket 250. Hereinafter, the foreign substance preventing member 200 will be referenced to as‘front gasket’.

The drum 32 includes a drum front 300, a drum center and a drum back 340.

Balancers

310 and 330 may be installed in front and rear parts of the drum, respectively. The drum back 340 is connected with a spider 350 and the spider 350 is connected with the shaft 351. The drum 32 is rotated in the tub 12 by a torque transmitted via the shaft 351.

The shaft 351 is directly connected with a motor 170, passing through the tub back 130. Specifically, a rotor 174 composing the motor 170 is directly connected with the shaft 351. a bearing housing 400 is secured to a rear portion of the tub back 130 and the bearing housing 400 rotatably supports the shaft, located between the motor 170 and the tub back 130.

A stator 172 composing the motor 170 is secured to the bearing housing 400 and the rotor 174 is located surrounding the stator 172. As mentioned above, the rotor 174 is directly connected with the shaft 351. Here, the motor 170 is an outer rotor type motor and it is directly connected with the shaft 351.

The bearing housing 400 is supported via a suspension unit with respect to a cabinet base 600. The suspension unit 180 includes three perpendicular supporters and two oblique supporters configured to support the bearing housing 400 obliquely with respect to a forward and rearward direction.

The suspension unit 180 may includes a first cylinder spring 520, a second cylinder spring 510, a third cylinder spring 500, a first cylinder damper 540 and a second cylinder damper 530.

The first cylinder spring 520 is connected between a first suspension bracket 450 and the cabinet base 600. The second cylinder spring 510 is connected between a suspension bracket 440 and the cabinet base 600.

The third cylinder spring 500 is directly connected between the bearing housing 400 and the cabinet base 600.

The first cylinder damper 540 is inclinedly installed between the first suspension bracket 450 and a rear portion of the cabinet base. The second cylinder damper 530 is inclinedly installed between the second suspension bracket 440 and a rear portion of the cabinet base 600.

The cylinder springs 520, 510 and 500 of the suspension unit 180 may be elastically connected to the cabinet base 600 enough to allow a forward/rearward and rightward/leftward movement of the drum, not connected to the cabinet base 600 fixedly. That is, they are elastically supported by the base 600 to allow the drum to be rotated to a predetermined angle in forward/rearward and rightward/leftward directions with respect to the connected portion.

The perpendicular ones of the suspension unit may be configured to suspend the vibration of the drum elastically and the oblique ones may be configured to dampen the vibration. That is, in a vibration system including a spring and damping means, the perpendicular ones are employed as spring and the oblique ones are employed as damping means.

The tub front 100 and the tub rear 120 are fixedly secured to the cabinet 110 and the vibration of the drum 32 is suspendedly supported by the suspension unit 180. The supporting structure of the tub 12 and the drum 32 may be called‘separated’substantially, such that the tub 12 may not be vibrated even when the drum 32 is vibrated.

The bearing housing 400 and the suspension brackets may be connected with each other by first and second weights 431 and 430.

In case the

drum

30 and 32 is rotated after the laundry 1 is loaded in the

drum

30 and 32 of the laundry machine according to the above embodiments, quite severe noise and vibration may be generated according to the position of the laundry 1. For example, when the

drum

30 and 32 is rotated in a state of the laundry not distributed in the

drum

30 and 32 uniformly (hereinafter,‘unbalanced rotation’), much noise and vibration may be generated. Especially, if the

drum

30 and 32 is rotated at a high speed to spin the laundry, the noise and vibration may be problematic.

Because of that, the laundry machine may include

balancer

70, 310 and 330 to prevent the noise and vibration generated by the unbalanced rotation of the

drum

30 and 32. The

balancer

70, 310 and 330 may be provided in a front or rear portion, or in both of the portions of the

drum

30 and 32.

The

balancer

70, 310 and 330 is mounted to the

drum

30 and 32 to reduce the unbalance. Because of that, the

balancer

70, 310 and 330 may have a movable gravity center. The balancers are mounted to the

drum

30 and 32 to reduce the unbalance. Because of that, the balancer may have a movable gravity center. For example, the balancer may include movable bodies having a predetermined weight located therein and a passage the movable bodies move along. If the balancers may be ball balancers, the

balancer

70, 310 and 330 may include

balls

72, 312 and 332 having a predetermined weight located therein and a passage the ball moves along. That is, the

balancer

70, 310 and 330 includes

balls

72, 312 and 332 having a predetermined weight located therein and a passage the ball moves along.

More specifically, the balls are rotated by the friction generated during the rotation of the

drum

30 and 32 and they are not kept unmovable in the drum when the drum is rotated. Because of that, the balls are rotated at a different speed from the rotation speed of the drum. Here, the laundry which generates the unbalance may be rotated at the almost same speed as the speed of the drum because of the friction generated by the close contact with an inner circumferential surface of the drum and the lifters provided in the inner circumferential surface. As a result, the rotation speed of the laundry is different from that of the balls. The rotation speed of the laundry is higher than that of the balls during an initial rotation stage in which the drum is rotated at a relatively low speed, specifically, a rotation angle speed of the laundry is higher. In addition, a phase difference between the balls and the laundry, which is a phase difference with respect to a rotation center of the drum, may changes continuously.

Hence, when the rotation speed of the drum is getting higher, the balls may be in close contact with an outer circumferential surface of the passage by the centrifugal force. At the same time, the balls are aligned at a predetermined position having approximately 90˚ to 180˚ of the phase difference with respect to the laundry. If the rotation speed of the drum is a predetermined value or more, the centrifugal force is getting larger and the friction generated between the outer circumferential surface and the balls is a predetermined value or more and the balls may be rotated at the same speed as the drum. at this time, the balls are rotated at the same speed as the drum, with maintaining the position having the 90˚ to 180˚, preferably, approximately 180˚ of the phase difference with respect to the laundry. In this specification of the present invention, the rotation of the balls at the predetermined positions as mentioned above may be expressed as‘unbalance corresponding position’or ‘balancing’.

As a result, in case load is concentrated on a predetermined portion of the drum inside by the laundry, the ball located in the

balancer

70, 310 and 330 may move to an unbalance corresponding position to reduce the unbalance.

Hereinafter, control methods of the aforementioned laundry machines will be described. The laundry machine generally includes a washing cycle, a rinsing cycle, and a spinning cycle. In the control method according to the present invention, the spinning cycle will mainly be described with reference to the accompanying drawings.

FIG. 4 is a graph illustrating variation in RPM of the drum based on the passage of time in the control method of the spinning cycle according to the present invention. In FIG. 4, a horizontal axis represents time, and a vertical axis represents variation of the rotation speed of the

drum

30, 32, i.e., revolutions per minute (RPM).

Referring to FIG. 4, the control method of the spinning cycle according to the present invention includes a laundry distributing step S100 and a spinning step S200.

The laundry distributing step S100 serves to rotate the drum at a relatively low speed and uniformly distribute the laundry inside the drum. The spinning step S200 serves to remove water of the laundry by rotating the drum at a relatively high speed. However, it is to be understood that the laundry distributing step and the spinning step are classified based on their main functions and are not limited to their main functions. For example, even in the laundry distributing step, water may be removed from the laundry by rotation of the drum.

In this control method, the laundry distributing step S100 includes a wet laundry sensing step S110, a laundry disentangling step S130, and an eccentricity sensing step S150. The spinning step S200 includes a transient region passing step S210 and an accelerating step S230. Hereinafter, each step will be described in detail.

If the rinsing cycle ends, the laundry inside the

drum

30, 32 is wetted by water. The control part initially senses the amount of laundry inside the

drum

30, 32, i.e., the amount of wet laundry if the spinning cycle starts (S110).

The reason why that the control part senses the amount of wet laundry is that weight of laundry containing water is different from that of dry laundry even though the control part initially senses the amount of laundry, which is not wet, i.e., the amount of dry laundry. The sensed amount of wet laundry may be used as a factor that determines an allowable condition for accelerating the

drum

30, 32 at the transient region passing step S210, which will be described later, or determines to again carry out the laundry distributing step by decelerating the

drum

30, 32 through an eccentricity condition at the transient region passing step S210.

In this control method, the amount of wet laundry inside the

drum

30, 32 is sensed when the

drum

30, 32 is rotated at a constant speed for a predetermined time and then decelerated after being accelerated at a first rotation speed RPM 1, for example, 100RPM to 110RPM. When the

drum

30, 32 is decelerated, braking power is used. Specifically, the amount of wet laundry is sensed using a rotation rate for an acceleration period when driving

motors

40 and 170 rotating the

drum

30, 32 are accelerated, a rotation rate for a deceleration period when the driving

motors

40 and 170 are decelerated, a DC power of the applied motor, etc.

In the mean time, after sensing the amount of wet laundry, the control part carries out the laundry disentangling step to distribute the laundry inside the drum 30, 32 (S130).

The laundry disentangling step is to uniformly distribute the laundry inside the

drum

30, 32, thereby preventing an eccentricity rate of the

drum

30, 32 from being increased by concentration of the laundry on a specific region inside the

drum

30, 32. This is because that noise and vibration may be increased when RPM of the drum 32 is increased if the eccentricity rate is increased. The laundry disentangling step is carried out until the drum 32 is accelerated in one direction with a predetermined inclination to reach the rotation speed of the eccentricity sensing step, which will be described later.

Subsequently, the control part senses eccentricity of the drum (S150).

If the laundry inside the

drum

30, 32 is not distributed uniformly but concentrated on a predetermined region, the eccentricity rate is increased, whereby noise and vibration may be caused when the RPM of the

drum

30, 32 is increased. Accordingly, the control part determines whether to accelerate the drum by sensing the eccentricity rate of the drum.

Eccentricity sensing is carried out using the difference in acceleration when the drum is rotated. Namely, when the drum is rotated, the difference in acceleration between the case where the drum is rotated downwardly along gravity and the case where the drum is rotated upwardly contrary to gravity occurs depending on an eccentricity level. The control part measures this difference in acceleration by using a speed sensor such as a hole sensor provided in the driving

motors

40 and 170, thereby sensing the eccentricity rate. Accordingly, if the eccentricity rate is sensed, the laundry inside the drum sticks to an inner wall of the drum without dropping even though the drum is rotated. In this case, the drum is rotated in the range of 100 RPM to 110 RPM, approximately.

When the sensed eccentricity rate of the drum from a predetermined amount of wet laundry is more than a reference eccentricity rate, vibration and noise of the drum may be increased remarkably if the drum is accelerated at high speed. For this reason, it may be difficult to accelerate the drum. Accordingly, the control part can store data having a reference eccentricity rate previously determined to allow acceleration depending on the amount of wet laundry, in the form of table. As a result, the control part can determine whether to accelerate the drum by applying the sensed amount of wet laundry and the sensed eccentricity rate to the table. In other words, if the eccentricity rate depending on the sensed amount of wet laundry is more than the reference eccentricity rate, the eccentricity rate is too great, whereby the drum cannot be accelerated. Accordingly, the wet laundry sensing step, the laundry disentangling step, and the eccentricity sensing step, as described above, are repeated.

In the mean time, the wet laundry sensing step, the laundry disentangling step, and the eccentricity sensing step can be repeated until the sensed eccentricity rate satisfies a value of the reference eccentricity rate or less. However, if something is wrong with the laundry machine, or if the laundry inside the drum is entangled extremely, the sensed eccentricity rate does not satisfy the value of the reference eccentricity rate or less, whereby the wet laundry sensing step, the laundry disentangling step, and the eccentricity sensing step can be repeated continuously. Accordingly, it is preferable that the control part stops rotation of the drum and reports to the user that the spinning cycle has not ended normally if the drum is not accelerated for a predetermined time, for example, 20minutes to 30minutes, after the spinning cycle starts.

If the eccentricity rate depending on the sensed amount of wet laundry is the reference eccentricity rate or less, it satisfies the condition for allowing acceleration. Accordingly, the transient region passing step S210 is carried out.

In this case, the transient region can be defined as a predetermined RPM band that includes one or more resonant frequencies. In the transient region, resonance occurs depending on the system of the laundry machine. If the system of the laundry machine is determined, the transient region has natural vibration characteristics generated depending on the determined system of the laundry machine. The transient region is varied depending on the system of the laundry machine, and, for example, is in the range of 200rpm to 270rpm in the laundry machine according to the first embodiment and in the range of 200rpm to 350rpm in the laundry machine according to the second embodiment.

Fig. 6 illustrates a graph showing a relation of mass vs. a natural frequency. It is assumed that, in vibration systems of two laundry machines, the two laundry machines have mass of m0 and m1 respectively and maximum holding laundry amounts are △m, respectively. Then, the transition regions of the two laundry machines can be determined taking △nf0 and △nf1 into account, respectively. In this instance, amounts of water contained in the laundry will not be taken into account, for the time being.

In the meantime, referring to Fig. 6, the laundry machine with smaller mass m1 has a range of the transition region greater than the laundry machine with greater mass m0. That is, the range of the transition region having variation of the laundry amount taken into account becomes the greater as the mass of the vibration system becomes the smaller.

The ranges of the transition regions will be reviewed on the related art laundry machine and the laundry machine of the embodiment.

The related art laundry machine has a structure in which vibration is transmitted from the drum to the tub as it is, causing the tub to vibrate. Therefore, in taking the vibration of the related art laundry machine into account, the tub is indispensible. However, in general, the tub has, not only a weight of its own, but also substantial weights at a front, a rear or a circumferential surface thereof for balancing. Accordingly, the related art laundry machine has great mass of the vibration system.

Opposite to this, in the laundry machine of the embodiment, since the tub, not only has no weight, but also is separated from the drum in view of a supporting structure, the tub may not be put into account in consideration of the vibration of the drum. Therefore, the laundry machine of the embodiment may have relatively small mass of the vibration system.

Then, referring to Fig. 6, the related art laundry machine has mass m0 and the laundry machine of the embodiment has mass m1, leading the laundry machine of the embodiment to have a greater transition region, at the end.

Moreover, if the amounts of water contained in the laundry are taken into account simply, △m in Fig. 6 will become greater, making a range difference of the transition regions even greater. And, since, in the related art laundry machine, the water drops into the tub from the drum even if the water escapes from the laundry as the drum rotates, an amount of water mass reduction come from the spinning is small. Since the laundry machine of the embodiment has the tub and the drum separated from each other in view of vibration, the water escaped from the drum influences the vibration of the drum, instantly. That is, the influence of a mass change of the water in the laundry is greater in the laundry machine of the embodiment than the related art laundry machine.

Under above reason, though the related art laundry machine has the transition region of about 200 ~ 270rpm, A start RPM of the transient region of the laundry machine according to this embodiment may be similar to a start RPM of the transient region of the conventional laundry machine. An end RPM of the transient region of the laundry machine according to this embodiment may increase more than a RPM calculated by adding a value of approximately 30% of the start RPM to the start RPM. For example, the transient region finishes at an RPM calculated by adding a value of approximately 80% of the start RPM to the start RPM. According to this embodiment, the transient region may include a RPM band of approximately 200 to 350 rpm.

In the meantime, by reducing intensity of the vibration of the drum, unbalance may be reduced. For this, even laundry spreading is performed for spreading the laundry in the drum as far as possible before the rotation speed of the drum enters into the transition region.

In a case, a balancer is used, a method may be put into account, in which the rotation speed of the drum passes through the transition region while movable bodies provided in the balancer are positioned on an opposite side of an unbalance of the laundry. In this instance, it is preferable that the movable bodies are positioned at exact opposite of the unbalance in middle of the transition region.

However, as described above, the transient region of the laundry machine according to this embodiment is relatively wide in comparison to that of the conventional laundry machine. Because of that, even if the laundry even-spreading step or ball balancing is implemented in a RPM band lower than the transient region, the laundry might be in disorder or balancing might be failed with the drum speed passing the transient region.

As a result, balancing may be implemented at least one time in the laundry machine according to this embodiment before and while the drum speed passing the transient region. Here, the balancing may be defined as rotation of the drum at a constant-speed for a predetermined time period. Such the balancing allows the movable body of the balancer to the opposite positions of the laundry, only to reduce the unbalance amount. By extension, the effect of the laundry even-spreading. Eventually, the balancing is implemented while the drum speed passing the transient region and the noise and vibration generated by the expansion of the transient region may be prevented.

Here, when the balancing is implemented before the drum speed passing the transient region, the balancing may be implemented in a different RPM band from the RPM of the conventional laundry machine. For example, if the transient region starts at 200 RPM, the balancing is implemented in the RPM band lower than approximately 150 RPM. Since the conventional laundry machine has a relatively less wide transient region, it is not so difficult for the drum speed to pass the transient region even with the balancing implemented at the RPM lower than approximately 150 RPM. However, the laundry machine according to this embodiment has the relatively wide expanded transient region as described above. if the balancing is implemented at the such the low RPM like in the conventional laundry machine, the positions of the movable bodies might be in disorder by the balancing implemented with the drum speed passing the transient region. Because of that, the laundry machine according to this embodiment may increase the balancing RPM in comparison to the conventional balancing RPM, when the balancing is implemented before the drum speed enters the transient region. That is, if the start RPM of the transient region is determined, the balancing is implemented in a RPM band higher than a RPM calculated by subtracting a value of approximately 25% of the start RPM from the start RPM. For example, the start RPM of the transient region is approximately 200 RPM, the balancing may be implemented in a RPM band higher than 150RPm lower than 200 RPM.

Moreover, the unbalance amount may be measured during the balancing. That is, the control method may further include a step to measure the unbalance amount during the balancing and to compare the measured unbalance amount with an allowable unbalance amount allowing the acceleration of the drum speed. If the measured unbalance amount is less than the allowable unbalance amount, the drum speed is accelerated after the balancing to be out of the transient region. In contrast, if the measured unbalance amount is the allowable unbalance amount or more, the laundry even-spreading step may be re-implemented. in this case, the allowable unbalance amount may be different from an allowable unbalance amount allowing the initial accelerating.

In other words, when the rotation speed of the

drum

30, 32 passes through the transient region, resonance occurs in the laundry machine, whereby noise and vibration of the laundry machine may be increased remarkably. Noise and vibration in the laundry machine may cause the user to feel displeasure. Moreover, such noise and vibration may disturb acceleration of the drum. Preferably, when the rotation speed of the drum passes through the transient region, if the drum 32 is accelerated by appropriately controlling an acceleration inclination, noise and vibration should be maintained within a minimum range.

In the mean time, the eccentricity rate of the

drum

30, 32 may be increased either as the

drum

30, 32 is accelerated while the rotation speed of the drum is passing through the transient region, or by unexpected impact, which is externally caused. If the eccentricity rate of the

drum

30, 32 becomes greater than a predetermined value, noise is increased remarkably, whereby it is difficult to accelerate the drum continuously. Accordingly, when the rotation speed of the drum passes through the transient region, the control part needs to continuously sense the eccentricity rate of the

drum

30, 32.

Also, a vibration sensor may be provided in the drum of the laundry machine, so that the control part may sense vibration of the drum when the rotation speed of the drum passes through the transient region. In particular, in the aforementioned laundry machine where the tub is separated from vibration of the drum, since the tub is fixed and the drum is only vibrated, it is necessary to sense vibration of the drum to prevent the drum being in contact with the tub. If the vibration and/or eccentricity rate of the

drum

30, 32 as sensed at the transient region passing step becomes greater than the predetermined value, the control part repeats the wet laundry sensing step, the laundry disentangling step and the eccentricity sensing step by decelerating the

drum

30, 32.

Subsequently to the transient region passing step, the control part carries out the accelerating step S230.

In this embodiment, the accelerating step S230 includes a first accelerating step S236 for accelerating the

drum

30, 32 to reach a first target RPM, a balancing step S237 for carrying out balancing by decelerating the drum to reach a predetermined RPM, and a second accelerating step S238 for accelerating the

drum

30, 32 to reach a second target RPM.

The control part removes water by increasing the rotation speed of the

drum

30, 32 to reach the first target RPM (S236). In this case, the first target RPM is set equally to the second target RPM of the second accelerating step but its duration is set to be shorter than that of the second target RPM.

In more detail, at the accelerating step, the drum is accelerated at a relatively high speed to reach a desired RPM, whereby water is removed from the laundry. If the drum is accelerated, water is removed from the laundry by a centrifugal force. Moreover, a water discharge level is varied depending on kinds of the laundry. In other words, water is easily removed from soft clothes such as knit, whereas water is not easily removed from clothes such as jean. Accordingly, as a water discharge level is varied depending on the laundry, variation in eccentricity occurs. In particular, since water is almost removed from clothes such as knit at the first accelerating step, variation in eccentricity becomes greater than that of the second accelerating step, which will be described later.

However, the balls of the balancer are moved more actively at a lower speed than a higher speed, especially are moved at a constant speed more actively than at acceleration. Accordingly, as the drum is accelerated at a relatively high speed at the accelerating step, if there is any change in eccentricity due to water discharge, the balls of the balancer fail to actively move to the eccentricity corresponding position. For this reason, the

drum

30, 32 is rotated at a high speed in a state that the balls of the balancer are not moved to the eccentricity corresponding position, whereby noise due to eccentricity is increased remarkably. As a result, since variation in eccentricity due to water discharge is not compensated appropriately at the first accelerating step, noise may be increased. Accordingly, it is preferable that the first target RPM duration at the first accelerating step is shorter than the second target RPM duration at the second accelerating step. Moreover, as shown in FIG. 4, at the first accelerating step S236, the drum is decelerated directly after reaching the first target RPM, whereby the balancing step S237 can be carried out.

In this case, the first target RPM and/or its duration are determined as follows.

The first target RPM and/or its duration at the first accelerating step can be set to reach a noise reference level which is previously set at the second accelerating step subsequently to the first accelerating step. In other words, the noise reference level of the laundry machine can be set based on the spinning cycle where the drum is spun at a maximum speed. In the control method according to this embodiment, the noise reference level of the laundry machine is set based on the noise of the second target RPM at the second accelerating step.

It is supposed that the amount of washing water (hereinafter, referred to as‘water content’) remaining in the laundry is more than a predetermined value when the drum is accelerated to reach the second target RPM at the second accelerating step. In this case, if the drum is rotated by the water content, noise may occur in the range that exceeds the noise reference level which is previously set. Accordingly, at the first accelerating step, water contained in the laundry should be reduced to reach a predetermined value or more. In other words, in order to reduce noise occurring at the second accelerating step to reach a value of the noise reference level or less, water should be removed from the laundry at the first accelerating step.

Finally, at the first accelerating step, a value of the first target RPM and/or constant speed rotation duration of the first target RPM can be varied to control the water content (or water discharge) at the first accelerating step.

The water content that can reduce the noise occurring at the second accelerating step to reach the value of the noise reference level or less can be controlled appropriately depending on capacity of the drum and the tub in the laundry machine, the amount of laundry, and the amount of washing water. For example, in this embodiment, after the first accelerating step is carried out, the first target RPM and/or its constant speed rotation duration can be determined such that the water content becomes 40% to 60% or less of weight of the laundry loaded into the drum. Alternatively, the first target RPM and/or its constant speed rotation duration can be determined such that the water discharge level at the first accelerating step is equal to or greater than that at the second accelerating step. For example, in this embodiment, the first target RPM can be set in the range of 1100RPM to 1300RPM, approximately, and can be maintained for 80seconds to 100seconds, approximately. Preferably, the first target RPM can be maintained in the range of 1200RPM for 90seconds. In this way, if the water content or water discharge level at the first accelerating step is set, average noise at the second accelerating step can be reduced to reach a predetermined value or less, for example, 55DB or less when the second accelerating step is carried out by balancing.

Subsequently, the control part carries out the balancing step S237 by decelerating the drum to reach the second rotation speed RPM 2. In this case, the second rotation speed is set to be greater than the transient region of the laundry machine. The lower the RPM of the

drum

30, 32 is, the better balancing is carried out. However, if the RPM of the

drum

30, 32 is lowered than the transient region for balancing, noise and vibration may be generated by resonance. Accordingly, the balancing is preferably carried out at RPM more than the transient region. Accordingly, in this control method, the second rotation speed can be set in the range of 350RPM to 400RPM.

At the first accelerating step S236, variation in eccentricity due to water discharge can be compensated by the balancing step S237. In other words, since the balls are located to correspond to the varied eccentricity at the balancing step, noise can be reduced when the drum is accelerated at the second accelerating step. In particular, since water is almost removed from the laundry, which is made of a material to easily remove water therefrom, at the first accelerating step, the laundry, which is made of a material to be relatively difficult to remove water therefrom, remain at the second accelerating step. Accordingly, variation in eccentricity due to water discharge at the second accelerating step may not be greater than that at the first accelerating step. Finally, when the drum is accelerated at a constant rotation speed at the second accelerating step by the balancer subjected to balancing at the balancing step, noise can be minimized.

In the mean time, FIG. 5 is a graph illustrating a control method of a spinning cycle of a laundry machine according to the second embodiment of the present invention. In this embodiment, the first target RPM is different from the second target RPM. Hereinafter, the control method will be described based on the difference between the first target RPM and the second target RPM.

Referring to FIG. 5, the first target RPM at the first accelerating step S236 is different from the second target RPM at the second accelerating step S268. Moreover, the first target RPM at the first accelerating step S236 may be smaller than the second target RPM at the second accelerating step S268. In the aforementioned embodiment of FIG. 4, since the first target RPM is set equally to the second target RPM, noise due to variation in eccentricity at the first accelerating step may be increased to reach a predetermined value or more. Since such a noise during the spinning cycle may cause the user to feel displeasure, it is necessary to reduce noise at the first accelerating step. In order to reduce noise at the first accelerating step, the first target RPM is set differently from the second target RPM. Preferably, the first target RPM is set to be lower than the second target RPM. As the first target RPM is set to be lower than the second target RPM, noise at the spinning step can be reduced.

In the mean time, the first target RPM of the first accelerating step can be set to reach a noise reference level which is previously set at the second accelerating step subsequently to the first accelerating step. In other words, the noise reference level of the laundry machine can be set based on the spinning cycle where the drum is spun at a maximum speed. In the control method according to this embodiment, the noise reference level of the laundry machine is set based on the noise of the second target RPM at the second accelerating step.

It is supposed that the water content remaining in the laundry is more than a predetermined value when the drum is accelerated to reach the second target RPM at the second accelerating step. In this case, if the drum is rotated by the water content, noise may occur in the range that exceeds the noise reference level which is previously set. Accordingly, at the first accelerating step, water contained in the laundry should be reduced to reach a predetermined value or more. In other words, in order to reduce noise occurring at the second accelerating step to reach a value of the noise reference level or less, water should be removed from the laundry at the first accelerating step.

The water content that can reduce the noise occurring at the second accelerating step to reach the value of the noise reference level or less can be controlled appropriately depending on capacity of the drum and the tub in the laundry machine, the amount of laundry, and the amount of washing water. For example, in this embodiment, after the first accelerating step is carried out, the first target RPM and/or its constant speed rotation duration can be determined such that the water content becomes 40% to 60% or less of weight of the laundry loaded into the drum. Alternatively, the first target RPM and/or its constant speed rotation duration can be determined such that the water discharge level at the first accelerating step is equal to or greater than that at the second accelerating step. In this way, if the water content or water discharge level is set, average noise at the second accelerating step can be reduced to reach a predetermined value or less, for example, 55DB or less when the second accelerating step is carried out by balancing.

Subsequently to the balancing step S237, the control part carries out water discharge by accelerating the drum to reach the second target RPM (S238). In this case, the second target RPM may be set previously by the control part, or may be carried out by input of the user.

In the mean time, the balancing step S237 at the first and second accelerating steps can be carried out depending on the value of the second target RPM. In other words, if the value of the second target RPM set previously by the control part or set by input of the user is greater than a predetermined value, the balancing step is carried out. If the value of the second target RPM set previously by the control part or set by input of the user is a predetermined value or less, the balancing step may not be carried out. The predetermined value is variable, and for example, is set in the range of 1200RPM, approximately, in this embodiment.

In the mean time, the control method of the laundry machine according to this embodiment may further include a balancing step S232 before the first accelerating step S236. The balancing step serves to move the balls of the balancer to move to the eccentricity corresponding position before the drum is accelerated at a relatively high speed at the first accelerating step. Accordingly, noise that may occur at the first accelerating step can be reduced in a predetermined range.

In the mean time, a control method of a laundry machine according to the related art includes an‘intermediate spinning’step for removing water by accelerating the drum at RPM lower than the target RPM several times, before the accelerating step. If water is contained between the drum and the tub, it may cause noise and vibration when the drum is accelerated, especially it may disturb rotation of the drum when the drum is rotated at a high speed at the accelerating step. In this respect, in the control method of the laundry machine according to the related art, the intermediate spinning step has been required necessarily.

However, in the laundry machine according the second embodiment of the present invention, since it is important to prevent the tub from being in contact with the drum, the distance between the tub and the drum becomes greater than that according to the related art. As a result, in the laundry machine according to the second embodiment of the present invention, as the distance between the tub and the drum becomes greater than that according to the related art, noise due to water contained the tub may be reduced when the drum is rotated. Moreover, water contained in the tub does not disturb rotation of the drum. Accordingly, the control method of the laundry machine according to the second embodiment of the present invention may omit the intermediate spinning step, whereby the time required for the spinning cycle can be reduced.

First, vibration characteristics of the laundry machine according to the embodiment of the present invention will now be described with reference to Fig. 7.

As the rotation speed of the drum is increased, a region (hereinafter, referred to as“transient vibration region”) where irregular transient vibration with high amplitude occurs is generated. The transient vibration region irregularly occurs with high amplitude before vibration is transited to a steady-state vibration region (hereinafter, referred to as “steady-state region”), and has vibration characteristics determined if a vibration system (laundry machine) is designed. Though the transient vibration region is different according to the type of the laundry machine, transient vibration occurs approximately in the range of 200rpm to 270rpm. It is regarded that transient vibration is caused by resonance. Accordingly, it is necessary to design the balancer by considering effective balancing at the transient vibration region.

In the mean time, as described above, in the laundry machine according to the embodiment of the present invention, the vibration source, i.e., the motor and the drum connected with the motor are connected with the tub 12 through the rear gasket 250. Accordingly, vibration occurring in the drum is little forwarded to the tub, and the drum is supported by a damping means and the suspension unit 180 via a bearing housing 400. As a result, the tub 12 can directly be fixed to a cabinet 110 without any damping means.

As a result of studies of the inventor of the present invention, vibration characteristics not observed generally have been found in the laundry machine according to the present invention. According to the general laundry machine, vibration (displacement) becomes steady after passing through the transient vibration region. However, in the laundry machine according to the embodiment of the present invention, a region (hereinafter, referred to as“irregular vibration”) where vibration becomes steady after passing through the transient vibration region and again becomes great may be generated. For example, if the maximum drum displacement or more generated in an RPM band lower than the transient region or the maximum drum displacement or more of steady state step in a RPM band higher than the transient region is generated, it is determined that irregular vibration is generated. Alternatively, if an average drum displacement in the transient region, +20% to -20% of the average drum displacement in the transient region or 1/3 or more of the maximum drum displacement in the natural frequency of the transient region are generated, it may be determined that the irregular vibration is generated.

However, as a result of the studies, irregular vibration has occurred in a RPM band higher than the transient region, for example has occurred at a region (hereinafter, referred to as“irregular vibration region”) in the range of 350 rpm to 1000rpm, approximately. Irregular vibration may be generated due to use of the balancer, the damping system, and the rear gasket. Accordingly, in this laundry machine, it is necessary to design the balancer by considering the irregular vibration region as well as the transient vibration region.

For example, the balancer is provide with a ball balancer, it is preferable that the structure of the balancer, i.e., the size of the ball, the number of balls, a shape of the race, viscosity of oil, and a filling level of oil are selected by considering the irregular vibration region as well as the transient vibration region. When considering the transient vibration region and/or the irregular vibration region, especially considering the irregular vibration region, the ball balancer has a greater diameter of 255.8mm and a smaller diameter of 249.2. A space of the race, in which the ball is contained, has a sectional area of 411.93mm². The number of balls is 14 at the front and the rear, respectively, and the ball has a size of 19.05mm. Silicon based oil such as Poly Dimethylsiloxane (PDMS) is used as the oil. Preferably, oil has viscosity of 300CS at a room temperature, and has a filling level of 350cc.

In addition to the structure of the balancer, in view of control, it is preferable that the irregular vibration region as well as the transient vibration region is considered. For example, to prevent the irregular vibration, if the irregular vibration region is determined, the balancing may be implemented at least one time before, while and after the drum speed passes the irregular vibration region. Here, if the rotation speed of the drum is relatively high, the balancing of the balancer may not be implemented properly and the balancing may be implemented with decreasing the rotation speed of the drum. however, if the rotation speed of the drum is decreased to be lower than the transient region to implement the balancing, it has to pass the transient region again. In decreasing the rotation speed of the drum to implement the balancing, the decreased rotation speed may be higher than the transient region.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

According to the aforementioned control method of the present invention, noise of the laundry machine can be reduced remarkably when the spinning cycle is carried out.

Claims

A control method of a laundry machine provided with a balancer, the control method comprising:

a balancing step of at least one time for rotating a drum at a constant speed for a predetermined time by decelerating the drum if the drum is accelerated at a predetermined RPM or more, the balancing step performed after a rotation speed of the drum passes through a transient region of the laundry machine.
The control method as claimed in claim 1, wherein accelerating step includes a first accelerating step for accelerating the drum to reach a first target RPM, a balancing step for carrying out balancing by decelerating the drum, and a second accelerating step for accelerating the drum to reach a second target RPM.
The control method as claimed in claim 2, wherein the first target RPM is set equally to the second target RPM.
The control method as claimed in claim 3, wherein first target RPM duration of the first accelerating step is shorter than second target RPM duration of the second accelerating step.
The control method as claimed in claim 3, wherein the balancing step is carried out by decelerating the drum immediately after the drum reaches the first target RPM at the first accelerating step.
The control method as claimed in claim 3, wherein, after the first accelerating step is carried out, the first target RPM and its duration are determined such that a water content becomes 40% to 60% or less of a weight of laundry loaded into the drum.
The control method as claimed in claim 3, wherein the first target RPM and its duration are determined such that water discharge at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 3, wherein the first target RPM and its duration are determined such that water discharge at the first accelerating step is substantially equal to that at the second accelerating step.
The control method as claimed in claim 3, wherein maximum noise at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 3, wherein average noise at the second accelerating step is substantially 55DB or less.
The control method as claimed in claim 2, wherein the first target RPM is different from the second target RPM.
The control method as claimed in claim 11, wherein the first target RPM is lower than the second target RPM.
The control method as claimed in claim 12, wherein, after the first accelerating step is carried out, the first target RPM and its duration are determined such that a water content becomes 40% to 60% or less of a weight of laundry loaded into the drum.
The control method as claimed in claim 12, wherein the first target RPM and its duration are determined such that water discharge at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 12, wherein the first target RPM and its duration are determined such that water discharge at the first accelerating step is substantially equal to that at the second accelerating step.
The control method as claimed in claim 12, wherein maximum noise at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 12, wherein average noise at the second accelerating step is substantially 55DB or less.
The control method as claimed in claim 2, wherein water discharge at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 2, wherein maximum noise at the first accelerating step is greater than that at the second accelerating step.
The control method as claimed in claim 2, wherein average noise at the second accelerating step is substantially 55DB or less.
The control method as claimed in claim 1, wherein the balancing step is carried out to compensate for variation in eccentricity due to water discharge of laundry at the accelerating step.
The control method as claimed in claim 1, wherein the laundry machine comprises a driving unit comprising a shaft connected to a drum, a bearing housing to rotatably support the shaft, and a motor to rotate the shaft, and a suspension assembly is connected to the driving unit.
The control method as claimed in claim 1, wherein the laundry machine comprises a rear gasket for sealing to prevent washing water from leaking from a space between a driving unit and a tub, and enabling the driving unit movable relative to the tub.
The control method as claimed in claim 1, wherein a tub is supported rigidly more than a drum being supported by a suspension assembly.