AU689727B2

AU689727B2 - Drying stroke control method for washing machine

Info

Publication number: AU689727B2
Application number: AU67981/96A
Authority: AU
Inventors: Kwon Son
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 1995-10-02
Filing date: 1996-10-02
Publication date: 1998-04-02
Anticipated expiration: 2016-10-02
Also published as: KR970021442A; KR0161919B1; CN1152047A; JPH09131486A; AU6798196A; CN1098945C; TW305894B

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): LG Electronics Inc.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Drying stroke control method for washing machine The following statement is a full description of this invention, including the best method of performing it known to me/us:r o o o e a BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a washing machine and, more particularly, to a method of controlling the washing machine to sense its drying speed during a drying cycle.

Discussion of Related Art FIG. 1 illustrates a convent-".al washing machine. As illustrated in FIG. 1, a conventional washing machine includes a main body 1, a cover 2, an inner tub, namely, a washing tub 3, an outer tub 4, a plurality of supporting bars 5 which support the main body 1 and outer tub 4, a motor 6 installed on one side of the bottom of the outer tub 4, a speed sensor 7, a micro computer 8 for controlling the entire system, and a safety switch 9 for sensing the vibration of the outer tub 4.

As illustrated in FIG. 2, a control device of the washing machine includes a iconverter 11 for converting AC current into DC current, an inverter 12 for connecting power to the motor 6, a micro computer 8 for performing various control operations, an overcurrent protection circuit part 13, a gate driving circuit part 14 for driving a switching element of the inverter 12, a rotor position detecting circuit part 15 for detecting the positions Ha, Hb, Hc of the motor's rotor, a modulator/buffer circuit part 16 for modulating a PWMo output of the micro computer 8 and a gate driving signal Pgout, as a buffer, a safety switch 9 for sensing the vibration during the drying step, and a signal converting part As illustrated in FIG. 3, the safety switch 9 switches according to the displacement amount of a depending pivotal part of the safety switch 9 during the vibration of the outer tub 4 c'ue to the biased laundry. Here, the displacement amount dmin is the displacing width in accordance with the vibration amount generated between the depending pivotal part of the safety switch 9 and the outer tub 4. That is, if the displacement amount of the depending pivotal part of the safety switch 9 is below dmin, the drying operation is continuously performed even though outer tub 4 touches the depending pivotal part of the safety switch 9. In addition, when the displacement amount of the depending pivotal part of the safety switch 9 is above dmin, the drying operation is stopped once, and then the biased laundry is properly balanced to continuously perform the drying operation.

A drying operation of the thus-structured washing machine is as follows.

FIG. 4 is a flowchart of a conventional drying cycle controlling method for a washing machine. With reference to FIG. 4, in the conventional washing machine, if AC current is applied and thus the motor is driven for a predetermined period of time in step S101, the washing machine determines if the safety switch signal Ps is in the HIGH state in accordance with the vibration amount generated between the safety switch 9 and outer tub 4 in step S102 as shown in FIG. 5. At this time, the motor measures the rotor position detecting signals Ha, Hb, IHc in the control part 8 through the rotor position detecting circuit part 15. If the safety switch signal Ps is in the HIGH state, the motor detects the time T, in which the safety switch signal Ps maintains the HIGH level in step S103. If the .i measured time T, is shorter than a fixed time in step S104, as illustrated in FIG. 5, the 0 modulator/buffer circuit part 16 controls a PWMo duty which is previously input to thereby control the motor speed such as the fixed drying speed pattern in step S105. The drying 20 operation proceeds until the drying time is completed according to the controlled motor speed in step S106, the drying operation is completed if the motor's spare rotation end in """step S107.

FIG. 6, is a graph showing a drying speed pattern fixed during the control of the motor's PWMo duty according to the displacement amount of the safety switch after driving the motor during the drying operation.

However, such a conventional method of controlling the drying cycle of a washing machine has a problem that only the vibration of outer tub's upper part which is above the predetermined vibration displacement dmin can be sensed. In addition, if the left/right vibration or up/down vibration of the drying tub's lower part is severe, the vibration amount is not sensed. Therefore, there occurs a severe noise during the drying step. Accordingly, the supporting bar, inner/outer tubs and main body of the washing machine are worn away.

Such an abrasion causes many troubles which reduce the duration of the washing machine.

Moreover, if the washing tub is suddenly biased toward the part in which there is no safety switch, the sensing operation becomes more difficult. Therefore, the washing machine may be severely damaged and a safety accident may occur to the user.

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a method of controlling a drying step of a washing machine that substantially reduces one or more of the problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method of controlling a drying step of a washing machine.

O Additional features and advantages of the invention will be set forth in the ilescription which follows, and in part Oa II L~ ~Al~l 1 1 11 i J 1. P'I 1.1 .7 4 will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawngs.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for controlling a drying step of a washing machine of the invention includes the steps of: initializing a maximum acceleration, minimum acceleration, acceleration variation and rotation amount of a motor by a PWM, duty in case of driving the motor; determining if the motor drives at substantially constant speed for a predetermined period of time tl; measuring an amount of speed decrease if the predetermined period of time for driving the motor does not elapse.

and then comparing it with a maximum allowable decrease; measuring the maximum acceleration, minimum acceleration, and rotation amount if the predetermined time for 15 driving motor elapses, and then determining if a washing tub rotates one revolution; (e) :comparing the acceleration variation with the maximum acceleration if the washing tub rotates i one revolution; determining if the motor is driven for a predetermined period of time if the acceleration variation is greater than the maximum acceleration; and comparing the acceleration

S

variation with the maximum allowable a:eleation if the predetermined time for driving the mctor elapses.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to crovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the drawings.

In the drawings: SFIG. 1 illustrates a structure of a conventional washing machine; FIG. 2 is a detailed circuit diagram of the inner washing machine controlling device; FIG. 3 illustrates the operation state of a safety switch of FIG. 1; FIG. 4 is a flowchart of a conventional drying cycle controlling method of a washing machine; FIG. 5 illustrates a resoective oar: wavefor m uring :he drying operation of the conventional washing machine; FIG. 6 is a graph showing a drying speed pattern of the conventional washing machine; FIG. 7 illustrates a construction of the washing machine of the invention; FIG. 8 is a detailed circuit diagram of te'e inner sontrl device of the washing machine of FI3. 7; FIG. 9 illustrates various vibration states occurring due to biased laundry during the rotation of the washing tub; FIG. 10 is a flowchart showing the drying step controlling method of a washing machine of the invention; FIG. 11 is a respective part waveform during the drying 0..15 step of the washing machine of the invention; FIG. 12a is a graph showing the speed vibration due to the vibration of the washing tub generated by the biased laundry in case that the drying time is t<tl; FIG. 12b is a graph showing the speed vibration due to 20 the vibration of the washing tub generated by the biased laundry in case that the drying time t>tl; and FIG. 13 is a graph of a drying speed control pattern of a e washing machine of the invention.

CCC.

-8- DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

As illustrated in FIG. 7, the washing machine of the invention includes a main body 1, a cover 2, an inner tub, namely, a washing tub 3, an outer tub 4, a plurality of supporting bars 5 which support the main body 1 and outer tub 4, a motor 6 installed on one side of the bottom of the outer tub 4, a speed sensor 7 for analyzing the speed data sensed from the rotor position detecting signal and for sensing the vibration amount, and a micro computer 8 for controlling the entire system.

As illustrated in FIG. 8, the control device of the washing machine includes a eeo converter 11 for converting AC current into DC current, an inverter 12 for controlling power which is applied to the motor 6, a micro computer 8 for performing various controls, an overcurrent protection circuit part 13 for detecting an overcurrent and providing circuit ."•protection, a gate driving circuit part 14 for driving a switching element of the inverter 12, a rotor position detecting part 15 for detecting the positions Ha, Hb, He of the rotor of the motor 6, and a modulator/buffer circuit part 16 for modulating a PWMo output of the micro computer 8 and a gate driving signal Pgout, as a buffer.

In addition, various vibrations occurring due to the biased laundry during the rotation of the washing tub, such as a right/left vibration of upper part, a right/left vibration gee of lower part, an up/down vibration, and a right/left vibration, are illustrated in FIG. 9.

A drying operation of the thus-structured present invention will be described below.

As illustrated in FIG. 10, in the washing machine of the invention, if the AC is applied and the motor starts to drive in step 5201, a predetermined signal PWM 0 is output through a micro processor 8 as illustrated in FIG. 11. The motor is controlled in a fixed

I

drying speed pattern by controlling the PWMo duty output from the micro processor 8 in step S202. Then, Rmax (maximum speed), Rmin (minimum speed), AR (speed variation), and ER (accumulated rotation amount) are initialized as in step S203. iHere, the motor measures the rotor position detecting signals Ha, Hb, Hc in the microprocessor 8 through the rotor position detecting part 15 as illustrated in FIG. 11.

After determining if the constant speed section of the early motor driving period exceeds the predetermined period of time tl, in step S204, the speed variation (AR=ARmax-ARmin) is measured in step S205 when the one exceeds the other. Then, it is determined that the measured speed variation is greater or the same as the maximum allowable variation (fixed value) in step S206. If the measured speed variation is greater than the maximum allowable variation (fixed value), a bias of the laundry is determined to be excessive so that the motor is stopped in step S207. After adjusting the bias of the laundry in the washing tub, the motor is operated again in step S208. If the measured 15 speed variation is smaller than the maximum allowable variation (fixed value), the operation goes to the previous step S202.

Here, the equation of the speed vibration due to the laundry bias is modelled as follows: RPM(t) RPM,,g(t) K x sin (27rt/T) R,,g a x t Kp x sin (2Tt/Tf) (1) (RPMvg: average speed, R,,g initial value average speed, Kp: speed vibration proportional constant-laundry bias proportional constant, a basic acceleration, T,: vibration cycle 1/RPM,vg) That is, if t tl, AR RPM(tn) RPM(tm) a (tn tm) K x {sin (2n7t/T) sin (2Trt/T)} (2) Additionally, if t tl, RPM(t) dRMP(t)/dt a Kpx sin (2xt/T) x cos (2tt/T,) AR' RPM(tn)' RPM(tm)' Kp x sin (2rt/T) {cos (2xt/T) sin (27rt/T)} (3) ThTe above equation refers to FIGS. 12a and 12b.

If the motor driving initial constant speed section does not exceed the predetermined period of time tl (t tl), in order to measure the vibration amount of the washing tub regardless of the acceleration/deceleration or constant speed, every rotation of the washing tub, namely, the maximum acceleration (R'max), minimum acceleration (R'min) and rotation amount ER in the cycle T are measured in step S209.

It is noted that the speed variation AR is proportional to the vibration amount, a 0, in constant speed section. However, in case of the acceleration/deceleration, that is, in case of a o 0, AR includes a so that it is impossible to measure only the vibration amount.

Accordingly, for measuring the vibration amount in any case of the constant speed, acceleration or deceleration, if the acceleration variation AR' is measured by way of equation it is possible to obtain information proportional to the pure vibration amount without being affected by the basic acceleration a.

By determining if the rotation amount ER is for one rotation in step S210, the acceleration variation AR' and the maximum allowable acceleration variation AR'max (fixed value) are compared with each other in step S211. The maximum allowable acceleration variation AR'max is an experimental value which includes acceleration variation in the predetermined section. If the measured at tleration variation is smaller than the maximum allowable acceleration variation (fixed value), the bias of the laundry is determined to be excessive, so that the motoi is stopped in step S207. And then the bias of the laundry is adjusted and the motor is driven again in step S2U8. If the measured acceleration variation is greater than the maximum allowable acceleration variation (fixed value), it is determined if the predetermined period of time t2 elapses in step S212. If the predetermined period rf time t2 does not elapse, the operation returns to the step S202.

If the predetermined period of time t2 elapses and the acceleration variation AR' is greater than R'max in step S213, the vibration amount becomes greater. Therefore, the final drying speed is accelerated at fast speed R3 in step S215 to weaken the vibration 11 amount as illustrated in FIG. 13. The drying operation proceeds until the drying time is completed in step S218, and if the remaining rotation ends, the drying step is completed in step S219.

If the acceleration variation AR' is sinaller than R'max, it is compared with R'min.

Since the vibration amount is intermediate if the acceleration variation is greater than R'min, the final drying speed is set into intermediate speed R2 in step S216. The drying operation is proceeded until the drying time is completed in step S218, and if the remaining rotation ends, the drying step is completed in step S219.

If the acceleration variation is smaller than the maximum allowable acceleration variation R'max, it is compared with R'min. Since the vibration amount is small if the acceleration variation is smaller than R'min, the final drying speed is set into slow speed R1 in step S217. The drying operation is proceeded until the drying time is compl,"'.O in step S218, and if the remaining rotation ends, the drying step is completed in step As described above, the method of controlling the drying operation of the washing machine controls the drying speed of the washing tub in order to reduce the noise due to the vibration and prevent the malfunction of the washing machine, thereby elongating the duration of the washing machine.

It will be apparent to those skilled in the art that various modifications and variations can be made in the method for controlling the drying operation of the washing machine of 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.

Claims

12- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method of controlling the drying operation of a washing machine, comprising the steps of: initializing a maximum acceleration, minimum acceleration, acceleration variation and rotation amount of a motor by a PWM,, duty for driving the motor; determining if said motor drives at substantially constant speed for a predetermined period of time tl; measuring an amount of speed decrease if the predetermined period of time for driving said motor does not elapse, and then comparing it with a maximum allowable decrease: measuring the maximum acceleration, minimum acceleration, and rotation amount if said predetermined time for driving motor elapses, and then determining if a washim, tub rotates one revolution; 15 comparing the acceleration variation with said maximum acceleration if said washing tub rotates one revolution; determining if said motor is driven for a predetermined period of time if said acceleration variation is greater than said maximum acceleration; and comparing said acceleration variation with said i r 6 *o «F~ -13- maximum allowable acceleration if said predetermined time for driving said motor elapses. 2. The method as claimed in claim 1, wherein said step comprises the steps of: stopping said motor if said speed decrease amount is greater than the maximum allowable decrease amount to adjust the bias of laundry by a user; and continuously drying said laundry if said speed decrease amount is smaller than said maximum allowable decrease amount. iO 3. The method as claimed in claim 1, wherein said step 0* comprises the step of stopping said motor if said acceleration variation is greater than the maximum acceleration amount to adjust the bias of laundry by a user. 4. The method as claimed in claim 1, wherein said step ccmprises the step of continuously drying said laundry if said predetermined period of time for driving said motor does not elapse. The method as claimed in claim 1, wherein said step comprises the step of accelerating said drying speed if said acceleration variation is greater than said maximum 1r Wi 1 k1 ,l bl P) '1 1

14- allowable acceleration, and then completing said drying step. 6. The method as claimed in claim 1, wherein said step comprises the step of averaging said drying speed if said acceleration variation is less than said maximum allowable acceleration but greater than a min mum allowable acceleration, and then completing said drying step. 7. The method as claimed in claim 1, wherein said step comprises the step of slowing said drying speed if said acceleration variation is smaller than said maximum allowable acceleration variation, and then completing said drying step. 8. The method as claimed in claim 1, wherein a basic acceleration speed is measured if said predetermined period of time for driving said motor elapses. 15 9. A method substantially as hereinbefore described with reference to the drawings. S oe S. S S S S 0 5 55 DATED this 27th day of January 1998 LG ELECTRONICS INC. By its Patent Attorneys DAVIES COLLISON CAVE N S-1 F1 ~TFS Abstract of Disclosure A method of controlling the drying operation of a washing machine, is provided including the steps of: initializing a maximum acceleration, minimum acceleration, acceleration variation and rotation amount of a motor by a PMW, duty in case of driving the motor; determining if the motor drives for a predetermined period of time tl; measuring an amount of speed decrease if the predetermined period of time for driving the motor does not elapse, and then comparing it with a 10 maximum allowable decrease; measuring the maximum acceleration, minimum acceleration, and rotation amount if the predetermined time for driving motor elapses, and then determining if a washing tub rotates one revolution; (e) comparing the acceleration variation with the maximum acceleration if the washing tub rotates one revolution; (f) determining if the motor is driven for a predetermined period 0 of time if the acceleration variation is greater than the maximum acceleration; and comparing the acceleration variation with the maximum allowable acceleration if the predetermined time for driving the motor elapses. I