[0001] The present invention refers to a method for verifying the laundry load conditions
in a washing and/or drying machine and to a machine using said method.
[0002] It is known that washing and/or drying machines can include in their washing program
one or more spinning cycles, i.e. phases of drum rotation gradually bringing the drum
to a much higher speed than that normally foreseen during the actual washing cycles;
in some types of machine, the drum can reach a speed up to 1100 rpm.
[0003] However, due to special requirements and applications, an increasing interest has
recently developed for spin speeds in the order of 1400 rpm, i.e. by far higher than
the one mentioned above. In view of this requirement, manufacturers have to face the
problem of adapting their present production of washing machines reaching 1100 rpm
speed to the new requirements, i.e. 1400 rpm speed.
[0004] If on one hand the motor and its relevant control system can be adapted in a relatively
simple way to reach 1400 rpm, on the other hand this is rather more complex from a
mechanical standpoint. As a matter of fact, it is clear that the mechanical stresses
the machine is submitted to at 1100 rpm are by far lower than the ones a machine with
the same structure has to withstand when reaching 1400 rpm, specially under severe
and/or out-of-balance load conditions. In particular, to the purpose of this description
a severe load defines a quantity of laundry in the drum approaching the maximum quantity
of laundry the machine can wash, whereas an out-of-balance load defines an irregular
distribution of the laundry inside the drum, which may cause significant oscillations
and mechanical damages to the machine during high speed rotation.
[0005] By way of example, according to practical tests carried out on conventional structured
machines with 5-kg drum capacity, it has been ascertained that a rotating speed over
1100 rpm may cause damages to the drum containing the laundry; drum failures typically
occur already at 1200 rpm speed and 500 to 800 gram unbalance with loads over 80%
the drum capacity (i.e. over 4 kg).
[0006] Said problem can obviously be solved by changing the mechanical structure of the
machine, e.g.. by strengthening the drums and relevant hubs, but this would involve
very high investments for the remaking of complete production lines.
[0007] Accordingly, it is the object of the present invention to provide a control method
for a machine of the above type, that allows to solve the above problem in a low-cost
manner and with no substantial changes to the mechanical structure of the machine;
accordingly, it is the main object of the present invention to indicate a control
method through which it is possible to verify whether the laundry load contained in
the drum of a washing machine exceeds a predetermined mass and is out of balance,
thus allowing the machine drum to reach speeds over 1100 rpm only if there are no
such dangerous conditions for the mechanical structure of the machine. Therefore,
it is the object of the present invention to let a normally structured machine reach
high spin speeds only under balanced load conditions, i.e. without any risk of mechanical
failures.
[0008] To this purpose, it is the object of the present invention to provide a method for
controlling the load in a washing and/or drying machine and a machine implementing
such a method, incorporating the characteristics of the annexed claims.
[0009] Further characteristics and advantages of the present invention will be apparent
from the following description and annexed drawings, which are supplied only as an
explanatory and non limiting example, wherein :
- Fig. 1 shows a simplified block diagram of a section of the machine control circuit
implementing the method according to the present invention;
- Figs 2 to 5 show graphically some explanatory curves of the rotating speed analysis
of the machine shown in Fig. 1, based on the method according to the present invention;
- Fig. 6 shows the block diagram of a section of the control logic circuit of the machine
shown in Fig. 1, implementing the method according to the present invention.
- Fig. 7 shows the block diagram of another section of the control logic circuit of
the machine shown in Fig. 1, implementing the method according to the present invention.
[0010] The present invention will be further described with reference to a laundry washing
machine equipped with all known elements for its operation; in particular said machine
is assumed to have a standard mechanical structure, i.e. reaching a spin speed around
1100 rpm and a 5 kg capacity drum; however, said machine is equipped with a motor
having a control system, in particular an electronic digital control system, which
allows the drum to reach a rotating speed up to 1400 rpm.
[0011] Fig. 1 shows the simplified block diagram of a section of the machine control circuit
implementing the method according to the present invention. In this figure M is the
washing-machine motor generating the drum rotation in a known manner, by means of
belts and pulleys; D is an electronic digital control module for the motor M; MP is
an electronic microcontroller comprising a counter or internal clock, indicated with
CLOCK, with associated permanent memory means, named ROM, and read-and-write memory
means named RAM; in the embodiment shown by way of example said microcontroller MP
is the one already available in the digital module D for motor M control.
[0012] In the ROM memory, the programs for handling the motor M in the various phases are
codified, according to the different machine cycles, which can be selected by the
user through proper control elements (e.g. electromechanical timer and/or selection
keys). Module D controls motor M operation - in particular through microcontroller
MP and associated ROM memory - based on the signals received by the above control
elements and other machine components, such as a pressure switch, control keys, a
speedometer dynamo, etc.
[0013] T indicates a device capable of generating a signal representative of the rotating
speed reached by the drum during machine operation, and consequently by motor M; in
the figure T is shown as a speedometer dynamo but other similar devices can obviously
be used for the purpose of measuring the motor and consequently the drum rotating
speed (e.g. a magnetic reed type sensor).
[0014] According to the invention, a suitable program in the ROM permanent memory of the
microcontroller MP allows the microcontroller itself to decide whether the laundry
load and/or its eventual out-of-balance extent should be considered dangerous for
the mechanical structure of the machine in view of the spin speed to be reached; such
decisions are taken by the microcontroller MP based on the data representative of
the drum speed detected by speedometer T, and on the time required to reach given
speed thresholds, detected by the speedometer T and the counter CLOCK.
[0015] In particular, according to the present invention, the control system of the motor
M verifies during the high speed spinning phase and before reaching 1200 rpm (assumed
as the threshold of a likely critical speed), whether the laundry load is either severe
or out of balance. As mentioned above, to the purpose of the present invention severe
load defines a quantity of laundry in the drum assumed to be potentially dangerous
in view of an out-of-balance condition, e.g. over 80% drum capacity (over 4 kg in
the example); whereas out-of-balance load defines an irregular weight arrangement
of the laundry inside the drum, which could in fact getting the whole machine "out
of balance" during the spinning cycles: in the embodiment shown by way of example
this situation is assumed to be a critical one in case of 500 to 800 gram load unbalance.
[0016] According to the present invention, since motor M and drum characteristics are known,
the entity of the laundry load is determined by measuring the time required to reach
900 rpm speed (hereafter called V2) from 150 rpm speed (hereafter called V1); said
measurements is made by microcontroller MP through speedometer T and the counter CLOCK.
More specifically, it has been ascertained, based on practical tests, that if the
time required for speed V1 to reach speed V2 is below a predetermined time TR of eight
seconds, the laundry load is assumed not to be a severe one and consequently a non
critical one: in this instance, after measuring speed V2, the microcontroller MP can
give release to reach a maximum spinning speed of 1400 rpm apart from an eventual
unbalance. Viceversa, if the time interval from V1 to V2 is higher than the predetermined
time TR, then the load is a severe one, and potentially critical for the mechanical
structure of the machine due to unbalance.
[0017] Therefore, if the laundry load is detected to be a severe one, its out-of-balance
condition will be verified according to the invention; if no unbalance is detected
(or in case of a fair non-critical unbalance, i.e. such not to jeopardize the machine
from a mechanical standpoint), then the spinning speed can reach 1400 rpm.
[0018] Viceversa, if an out-of-balance condition over the established limit is detected,
then microprocessor MP will provide for the necessary correction and decrease the
maximum spinning speed to a lower value, e.g. only 1000 rpm, which is low enough to
avoid jeopardizing the machine from a mechanical standpoint.
[0019] According to the invention, unbalance is detected by verifying the degree of the
so-called over-elongation, i.e. a laundry load inertia entraining the drum at a higher
rotating speed (VM) than a predetermined speed (VR). Also in this case, according
to practical tests, it has been ascertained that the over-elongation entity is representative
of the laundry distribution quality inside the drum.
[0020] According to the present invention, the verification of the over-elongation and consequently
of the laundry distribution inside the drum, takes place as follows.
[0021] During speed rise, the microcontroller MP detects the speed reached by the motor
M through the speedometer T, starting from 150 rpm for a predetermined time measured
by the counter CLOCK (e.g. 40 secs); maximum speed VM reached during this time is
temporarily stored in the RAM memory associated with the microcontroller MP (typically,
the maximum speed is reached about 10-15 secs after exceeding 150 rpm). Said maximum
speed VM, stored in the volatile RAM memory, is compared with the predetermined speed
VR in the permanent ROM memory of the microcontroller MP; the predetermined speed
VR can be for example equal to 1000 rpm.
[0022] The difference between the predetermined speed VR and the detected maximum speed
VM indicates the over-elongation entity. As mentioned, practical tests have indicated
that within certain limits, the over-elongation is higher under very good load balance
conditions; viceversa, no over-elongation or just a minimum over-elongation or the
detection of a speed VM lower than the speed VR within predetermined time (40 secs)
indicates an out-of-balance laundry load: as a matter of fact, it is evident how at
high speeds an irregular laundry distribution in the drum may determine a braking
effect.
[0023] Therefore, according to the invention, if the time from V1 to V2 is higher than TR
(8 secs), the microcontroller MP verifies the presence of a predetermined over-elongation
value, calculating the difference between VM and VR; if over-elongation is lower than
a predetermined value, or if there is no over-elongation, then the microcontroller
itself assumes an out-of-balance load condition: this means that there is a condition
of severe and out-of-balance load, i.e. surely a critical and dangerous condition
such to cause drum failures or damages to the machine structure; in this case the
final spin speed is lowered to 1000 rpm, i.e. a value low enough not to jeopardize
the machine from a mechanical standpoint. On the contrary, if over-elongation is higher
than a predetermined value representative of a good load balance, the microcontroller
MP will enable 1400 rpm final spin speed since due to its correct balance there is
no mechanical risk for the machine also in the event of a severe load. Figs. 2-5 show
by way of example some curves representative of the analysis of the rotating speed
of the machine motor according to the method object of the present invention. In said
graphs the axis of the abscissas indicates time, whereas the axis of the ordinates
indicates the value of the rotating speed of the drum and, consequently, of the washing-machine
motor. The graph in Fig. 2 shows an ideal operating condition of the machine according
to the present invention. As it can be noted, in fact, in this case time T1 -T2 required
from speed V1 (150 rpm) to V2 (900 rpm) is below 8 secs, i.e. below the predetermined
time TR, indicating the presence of a non severe load, so that the machine is enabled
to reach its maximum spin speed MC (1400 rpm). In any case, the graph also indicates
an over-elongation, since the maximum speed VM that has been reached, e.g. 1080 rpm,
is higher than the predetermined 1000 rpm speed VR. Such an over-elongation of 80
rpm - which is higher than a predetermined threshold SS - indicates a balanced load,
so that Fig. 2 shows a situation under ideal load conditions.
[0024] The graph in Fig. 3 also shows a very good operating condition of the machine according
to the present invention. As it can be seen, in this case time T1-T2 required from
speed V1 to speed V2 is higher than 8 secs, i.e. higher than TR, indicating a severe
load condition; therefore the microcontroller MP has to verify unbalance through the
measurement of over-elongation. As it can be seen from the graph in Fig. 3, such an
over-elongation is due to the fact that the maximum speed VM is higher than the predetermined
speed VR. Such an over-elongation higher than the predetermined threshold SS indicates
a good balanced load: thus, the machine has a severe but good balanced load and can
be enabled to reach its maximum spin speed MC without any risk from a mechanical standpoint.
[0025] The graph in Fig. 4 indicates a non ideal but still acceptable operating condition
of the machine according to the present invention. As it can be seen, time T1-T2 required
from speed V1 to speed V2 is lower than TR, indicating a non severe load; thus, the
machine is enabled to reach 1400 rpm spin speed. The graph also shows an over-elongation
under threshold SS (as it can be seen the maximum speed VM is slightly over the predetermined
speed VR). Such a minimum over-elongation indicates an out-of-balance load; however,
such an out-of-balance but non severe load condition is not critical for the machine
mechanical structure, so that the motor can reach 1400 rpm spir. speed (MC): operating
vibrations are acceptable because they are not dangerous for the machine mechanical
structure.
[0026] Finally, the graph in Fig. 5 shows a non acceptable operating condition of the machine,
according to the present invention. As it can be seen, time T1-T2 required from speed
V1 to reach speed V2 is higher than TR, indicating a severe load; in this case the
out-of-balance load needs to be verified by measuring its over-elongation. According
to the graph in Fig. 5 there is a minimum over-elongation, below the predetermined
threshold SS, since the maximum speed VM reached by the motor is slightly higher than
the predetermined speed VR. This lack of over-elongation indicates as said an out-of-balance
load, so that the situation shown in Fig. 5 is assumed highly critical for the machine
mechanics due to the presence of a sever out-of-balance load; therefore the control
system will decrease the spin speed to a predetermined value below MC, which is low
enough not to jeopardize the machine from a mechanical standpoint.
[0027] Always by way of example, Fig. 6 shows a block diagram of a section of the logic
circuit for the machine shown in Fig. 1 and in particular a program, by way of example,
contained in the microprocessor MP for the implementation of the method according
to the invention. In this program block 100 is the starting block yielding control
to block 101, in line with the start of a gradual spinning phase reaching final 1400
rpm speed; block 101 transfers control to block 102, which is a test block; said block
102 measures the drum rotating speed; if said speed reaches 150 rpm (V1) control is
transferred to the subsequent block 103; in the negative, control returns to block
102 itself.
[0028] Block 103 starts counting time T (point T1) and yields control to the subsequent
block 104, which is a test block.
[0029] Block 104 takes a new measurement of the drum rotating speed; if said speed reaches
900 rpm (V2), then control goes on to the subsequent block 105; in the negative, it
returns to block 104.
[0030] Block 105 stops time T count (point T2) and transfers control to the subsequent block
106: block 106 is a test block comparing the time T (or if preferred T2-T1 difference)
with the stored time TR equal to 8 secs; if the time T (or T1-T2 difference) is below
TR, then the control goes over to block 107; block 107 enables 1400 rpm spin and at
the end of it control goes over to block 108, which is the end-of-operation block.
[0031] If time T (or T1-T2 difference) on block 106 is higher than TR, control is yielded
to block 109, which is a test block and verifies the unbalance by controlling over-elongation
as described above; if there is no out-of-balance condition, control is yielded to
block 107 to enable 1400 rpm spin, then the program ends on block 108. If, on the
contrary, there is an out-of-balance condition, control goes over to subsequent block
110.
[0032] Block 110 enables a decreased spin sequence, e.g. 1000 rpm, i.e. a speed low enough
to avoid jeopardizing the machine from a mechanical standpoint.
[0033] The program will then end on block 108.
[0034] Fig. 7 shows the block diagram of a logic circuit section controlling the machine
shown in
[0035] Fig. 1, related to out-of-balance control, i.e. the phase substantially occurring
on block 109 of the previous figure.
[0036] In said Fig. 7 block 201 indicates program start (which substantially coincides with
block 101 of Fig. 6); control is yielded to block 202, which is a test block; said
block 202 measures the drum rotating speed, if the speed reaches 150 rpm control goes
over to subsequent block 203, whereas in the negative it goes back to block 202.
[0037] Block 203 starts counting a time TT and yields control to subsequent block 204; block
204 measures the drum rotating speed and stores the detected speed value in the RAM
memory of the microcontroller MP. Control is then yielded to block 205, which verifies
if time TT has reached 40 secs; in the affirmative, control goes over to subsequent
block 206, whereas in the negative it will return to block 204 for a new measurement
of the drum rotating speed; if the new speed value is higher than the previously stored
one, then the new value will replace the previously stored one in the RAM memory.
Practically, blocks 204 and 205 detect drum speed on a cyclic base to reach the maximum
speed value VM within the predetermined 40 secs stored in RAM memory.
[0038] Block 206 is a block comparing the maximum speed value VM stored in RAM memory with
a maximum reference speed value VR for the predetermined 40 secs. If speed VM is higher
than speed VR there will be an over-elongation indicating a balanced load condition,
provided it exceeds a predetermined threshold (SS); on the contrary, if over-elongation
is below the predetermined threshold (or no over-elongation) it means an out-of-balance
load. Thus, according to the condition detected on block 206, the control system will
either enable or inhibit 1400 rpm spin (practically as described with reference to
blocks 109-107-108 or 109-110-108 of Fig. 6).
[0039] The characteristics of the method object of the present invention as well as its
advantages are apparent from the given description.
[0040] Exhaustive testing has indicated how the present invention allows achievement of
the intended purposes, i.e. a simple and low-cost method for a washing and/or drying
machine to operate at high spin speed through a simple test method of the laundry
load conditions, without any substantial changes to the machine mechanical structure
and no risks for it.
[0041] It is obvious that many changes, adaptations, integrations and modifications - without
prejudice to the protective claims of the present invention - are possible to the
method and the machine described by way of non limiting example, without departing
from the novelty spirit of the innovative solution, and it is also clear that in practical
actuation of the invention the components may often differ in form and size from the
ones described and may be replaced with technical equivalent elements.
[0042] As an example, it is evident that, upon detecting any critical conditions as shown
in Fig. 5, the control system may be designed to incorporate a correction phase for
the out-of-balance condition instead of enabling a decreased spin speed: this can
be easily achieved through the program stored in the ROM memory associated with microcontroller
MP; e.g. if a severe out-of-balance condition is detected, the microcontroller MP
can stop the speed increase run, execute a re-balancing load step and attempt a new
spinning cycle to reach the maximum 1400 rpm speed; this could take place even several
times.
[0043] The same may be foreseen to solve non-critical conditions, however troublesome as
shown in Fig. 4.
[0044] Moreover, it is also clear that the method used to detect unbalance as described
herein - based on over-elongation measurement - may also be profitably used separately
from time measurement from 150 to 900 rpm. Storage possibility for microcontroller
MP of a considerable quantity of data based on experience in an extremely compact
format in ROM permanent memory, which can be processed even using low-cost devices
(4 and 8 bit limited process capacity microcontrollers), allows development of the
over-elongation based method also for an exact determination of out-of-balance extent.
Thus, it is also obvious that other techniques are available for automatic load verification,
i.e. the quantity of laundry in the washing-machine drum; reference is made e.g. to
the Italian Patent Application for Industrial Invention no. TO93A000798 in the name
of the same Applicant describing and commenting several techniques for automatic load
information, among which: method of the analysis of the duration time and number of
the fluid level restorations in the washing tub, controlled by a first-level pressure
switch; power measurement method (associated with torque) absorbed by the washing-machine
motor to start the drum containing the laundry; measurement method for the energy
required to switch over from a given inertial state as defined by a determined speed
of the washing-machine drum to another inertial state, defined by a different drum
speed.
1. A method for verifying the laundry load conditions in a washing and/or drying machine
comprising a drum containing the laundry, rotated by a motor (M), wherein a high spin
speed (MC) is gradually reached during an operation phase, characterized in that the
load balance conditions are verified by testing the over-elongation, i.e. the laundry
load inertia entraining the drum at a rotating speed (VM) higher than a predetermined
theoretic speed threshold (VR).
2. A method according to Claim 1, characterized in that the load balance conditions are
verified by measuring the maximum speed (VM) reached by the motor (M) or by the machine
drum during a predetermined time interval (40 secs) and comparing said maximum speed
(VM) with a predetermined maximum theoric speed (VR) for said time interval.
3. A method according to Claim 1, characterized in that the over-elongation extent is
obtained by the difference between the predetermined maximum theoric speed (VR) and
the measured maximum speed (VM).
4. A method according to Claims 1 or 2 or 3, characterized in that a balanced load condition
is reached when there is an over-elongation exceeding a predetermined threshold (SS)
and an out-of-balance load condition is gathered when there is an over-elongation
below a predetermined threshold (SS).
5. A method according to Claim 1, characterized in that the load entity is verified before
reaching said high spin speed (MC), and. if the load exceeds a predetermined mass,
also the load balance conditions are verified, and that, in order to avoid any risks
for the machine mechanical structure, the achievement of the maximum spin speed (1400
rpm) is inhibited if a load exceeding said predetermined mass and an out-of-balance
condition are detected.
6. A method according to Claim 4, characterized in that the laundry load entity is determined
by comparing against a reference value (TR) the time (T2-T1) required for passing
from a first predetermined speed (V1) to a second predetermined speed (V2) during
the gradual spin speed increase.
7. A method, according to the previous Claim, characterized in that when said time (T2-T1)
is higher than the reference value (TR), then the laundry load is assumed to be a
severe one, i.e. higher than said predetermined mass.
8. A method according to one or more of the previous Claims, characterized in that when
the load is higher than said predetermined mass and an out-of-balance condition of
said higher load exceeds a predetermined threshold, then the achievement of the maximum
spin speed (1400 rpm) is inhibited and/or corrective actions are foreseen, such as
at least an attempt to restore the load balance or the spinning at a lower speed (1000
rpm), which is low enough not to jeopardize the machine from a mechanical standpoint.
9. A method according to one or more of the previous Claims, characterized in that when
a non severe load and a balanced condition of said load is detected, the motor (M)
is enabled to reach the maximum spin speed (1400 rpm).
10. A method according to one or more of the previous Claims, characterized in that when
a non severe load and an unbalanced condition of said load is detected, the motor
(M) is equally enabled to reach the maximum spin speed (1400 rpm).
11. Laundry washing and/or drying machine, comprising all known operation elements, including
a drum rotated by a motor (M), a device (T) generating a signal representative of
the achieved motor (M) or drum speed and an electronic control device (D,MP), which
implements the methods according to one or more of the previous claims.
12. Laundry washing and/or drying machine according to the previous Claim, characterized
in that said electronic control device comprises a microcontroller (MP) to which permanent
memory means (ROM) and read-and-write memory means (RAM) are associated.