EP0741990A2

EP0741990A2 - System for signalling the concentration of the salt used for the resins regeneration in a washing machine

Info

Publication number: EP0741990A2
Application number: EP96107207A
Authority: EP
Inventors: Valerio Aisa; Luigi Alluto; Gaetano Olivieri
Original assignee: Merloni Elettrodomestici SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 1995-05-09
Filing date: 1996-05-07
Publication date: 1996-11-13
Also published as: IT1279192B1; EP0741990A3; ITTO950361A1; ITTO950361A0

Abstract

A signal system is described of the salt concentration used for resin regeneration in a washing machine, specifically a household dishwasher incorporating a water softening device (DD) comprising

a compartment ( R ) for the resins used to reduce the degree of water hardness,
a compartment (S) for the salt required for regeneration of the resins that have lost their effectiveness following execution of softening steps,
means to determine salt availability in the relevant salt compartment (S),
means (L) to signal the need for salt filling when the level in the salt compartment (S) lowers down to a preset minimum level,

where the resin reactivating processes take place periodically in time, specifically with each wash cycle executed by the machine.

According to the invention, said means to determine salt availability comprise a sensing device (A,B,C,Q,MP) of the degree of water hardness from the mains and an electronic control unit (MP) for evaluating salt the consumption as a function of the degree of water hardness from the mains, said signal means (L) being activated, if necessary, by said control unit (MP) when the evaluated salt concentration reaches a defined threshold.

Description

The present invention relates to a signal system of the salt concentration used for resin regeneration in a washing machine, specifically a household dishwasher as per the preamble of Claim 1, and a method to control the salt level in a softening system for the water used in a washing machine as per the preamble of Claim 10.
It is known for washing machines, specifically household dishwashers, to incorporate a damping system of water hardness. In such systems the washing water from the mains is flown through a resin compartment to reduce its calcium contents that would inhibit the action of the washing agents and cause calcareous deposits.
Since after a certain volume of softened water said resins become exhausted, they have to be reactivated by letting a solution of water and sodium choride called brine flow through them. The calcium ions deposited on the resins are then replaced by the brine sodium ions and the resins will be ready again at each washing for a new softening step. To this purpose a regeneration process normally takes place during each wash cycle.
Therefore, the softening systems comprise a kitchen salt tank that needs periodic filling due to the salt consumption caused by the resin regeneration processes. Decalcifier or softener devices of the above type and their relevant regeneration method are known as such, so a detailed description is not required in this context. On principle, it will be enough to mention here that the higher the water hardness the faster the resins become exhausted. As a result, the quantity of salt consumed to reactivate the resins will also be higher. In other words, this means that salt consumption is directly proportional to the degree of water hardness used in the washing machine.
It is also known that the washing machines of the above type usually incorporate a device suitable to inform the user about exhaustion of the salt used for the resins regeneration. Such a signalling device usually comprises a warning light on the machine control board, whose lighting is caused by a proper float associated with the salt tank. Therefore, when said warning light illuminates the dishwasher user is warned that new salt should be added to avoid total exhaustion of the resins effectiveness to lower the hardness of the water to the machine, due to the non execution of a number of regeneration cycles .
The above warning light is usually enabled by the closing of a contact, normally "reed" type, caused by a magnet located on said float, which take a position depending on the brine density available in the salt tank. Therefore it is obvious that when salt concentration decreases, also the density of the water-salt mixture will decrease causing the float to change its height position till said magnet approaches the reed contact of the warning light signalling a lack of salt and lights it up.
However, some problems related to the above signal system determine a certain unreliability of the signal offered by the warning light.
In the practice, most times said warning is either performed in advance or delayed against the real needs. This is substantially due to a non-homogeneity of the fluid density in the salt tank and to a likely mechanical float jamming inside its housing chamber where it can slide. Such float jams are usually due to a likely friction in the float sliding area or to dirt particles in the salt, which may lock the float or still to the difficulties of accurate calibration of the float weight.
It is the object of this invention to overcome the above problems and provide in particular a washing machine incorporating a highly accurate, and low-cost signal system for the lack of the salt used for resin regeneration.
These objects are obtained according to this invention by the signal system of the salt concentration according to Claim 1 and following ones and by the control method of salt level according to Claim 14 and following ones.
Further characteristics and advantages of this invention will become apparent from the following detailed description and annexed drawings, which are supplied only by way of a non limiting example, where:

Fig. 1 shows a simplified block diagram of the control system for a washing machine embodiment according to the features of present invention, referred only to the part involving its signal device for salt lacking.
Fig. 2 shows schematically the relationship between the degree of water hardness (French degrees), the volume of water used for resins regeneration (centiliters) and the volume of softened water (liters). Such a relationship governs the evaluating system to enable the signal device in agreement with a possible different embodiment of this invention.

Referring to Fig. 1, DD indicates a water softener device as a whole, comprising a resin compartment R and a salt compartment S.
G shows schematically a float device, whose position changes according to the quantity of salt available in the compartment S.
The float device G can substantially be of the type mentioned at the beginning of this description, i.e. with a reed type contact actuated by a magnet on a proper float moving inside a chamber associated with the compartment S. However, the float G in the system object of this invention is used differently from the known state of the art, as better explained further on.
Reference number 2 indicates a pipe connecting the washing machine with the household water supply network; number 3 indicates a solenoid valve that manages the water supply to the machine. The pipe 2 is connected with a multipurpose device, not shown in the figure being known as such, comprising a socalled "air-breaker" (consult eg. Italian patent no. 1.238.419 in the name of the Applicant). From this complex device water flows through a pipe AL to the resins compartment R, to be softened. Viceversa, V shows a pipe to deliver the softened water, i.e. from the device DD to the washing tub of the machine, not shown in the figure.
AR indicates a pipe to deliver a determined volume of water collected in the above multipurpose device to the compartment S to obtain the brine required for the various resins regeneration cycles. To this purpose the pipe AR carries a solenoid valve E.V. whose opening lets a determined volume of water flow from said multipurpose device to the tank S, so that a corresponding amount of brine can flow from the compartment S to the resins compartment R, to reactivate resins effectiveness.
As mentioned, the device DD is based on a known concept and operation, so it will not be further described in detail.
MP indicates an electronic microcontroller making part of the machine control system. Such a microcontroller MP can for instance be a part of an either electronic or hybrid timer of the machine, i.e. of the device controlling the wash cycles to be executed by the machine on user's actuation.
The microcontroller MP has an adequate internal clock, indicated by CLOCK, permanent memory means indicated by ROM and nonvolatile read/write memory means, not shown.
According to the invention and as described later, illumination of the warning light L to signal a lack of salt is not controlled by the float device G as it is usual in the known state of the art, but it is controlled by the microcontroller MP.
The present invention is based in fact on the acknowledgement that the float signal system, as typical for the known state of the art, is reliable enough only to switch off the warning light after a salt filling of the compartment by the user, as in this case the thrust generated on the float is such to win likely frictions and is related, anyway, to a considerable salt concentration change not subject to a likely brine non-homogeneity status. Viceversa, as said, such a float system is often very inaccurate to indicate a lack of salt.
Therefore, it is the basic idea of the present invention to use only the reliability of the indication that salt level has been restored by the user and electronically manage the lighting process for the warning light, based on the measurements and elaboration by the microcontroller MP as a function of water hardness, of the wash cycles and consequently the number of resins regeneration cycles executed by the machine.
As said above, the washing machine object of the present invention has a control unit provided with a microcontroller, conveniently programmed according to the rules of the fuzzy logic. The permanent memory ROM associated with such a microcontroller has an adequate codified knowledge base, obtained through the experience of technical people and experimental investigations.
As it will be clarified, according to said knowledge base the microcontroller MP acknowledges the procedures of salt consumption as a function of the wash cycles and resin regeneration cycles, of the water hardness and of the characteristics of the machine hydraulic system.
To this purpose, information about the physical characteristics of the water for washing is available to the control unit through adequate measurement means
Specifically, the machine object of this invention is provided with a device to measure the resistivity of the water from the mains, which according to this invention is used to measure the degree of water hardness.
Such a device comprises two electrodes, shown in Fig. 1 by the letters A and B, consisting of electrically conductive elements inserted on the pipe 2 for water inlet from the mains supply.
Obviously, both electrodes A and B are electrically isolated to each other.
Connecting the electrode A to the positive pole of a direct voltage generator E (eg.E=5V) and earthing the electrode B (negative pole of the same voltage generator E) through a capacitor C of adequate capacity, since water in 2 is surely conductive, there will be a current flow from A to B proportional to the resistivity of the washing water.
Such a current flow feeds a charge transient of capacitor C and will stop when said transient endson its conclusion, i.e. when a voltage equal to the value of E is available at the terminals of capacitor C. The transient is generated by the microcontroller MP and its duration depends both on the capacity of capacitor C and resistivity value of the medium through which the charge current is flowing, i.e. the water from the mains.
Once a proper value of capacitor C (eg. C=1 microfarad) has been established, information about the resistivity of the washing water can be obtained by measuring the duration of the charge time of said capacitor C. Such a measurement is executed by the microcontroller MP, whose internal clock (CLOCK) is able to measure time with a good resolution (eg. 1 microsec resolution).
A digital input of microcontroller MP, indicated by INP in Fig. 1, is connected with the terminals of capacitor C, whereas one digital output, indicated by OUT, is used to pilot a transistor Q, which is used as a switch to control the transient and whose manifold is connected with the terminals of capacitor C.
Charging time of capacitor C is measured by the following operations of microcontroller MP:

fast discharge of capacitor C applying a short pulse (eg. 1 millisec) to the base of transistor Q through output OUT, so that it will saturate and shortcircuit to earth capacitor C;
start time count right when transistor Q - upon ending the discharge pulse of capacitor C - goes back to its lock state, letting the capacitor itself to start its charge ;
time count stop right when voltage at the capacitor terminals reaches the tripping threshold of digital input INP, whose value is typically equal to half the feed voltage of the microcontroller MP (i.e. E/2=2.5V);
the value reached by the time counter available inside MP upon count stop is the measurement result and is directly related to the intrinsic resistivity characteristics of the the washing fluid.

As it can be understood, the microcontroller MP conveniently programmed according to the fuzzy logic techniques and provided with an adequate knowlwdge base, is able to calculate water resistivity from the measurement of the charge time of said capacitor.
Similarly, the microcontroller is capable of calculating the degree of water hardness from the mains, which is easy to desume through the water resistivity value according to said knowledge base in fuzzy logic.
Therefore, as it can be realized, the electronic control system of the machine according to the present invention is able to know the degree of water hardness through the sensors A and B. Moreover, it appears also quite easy to insert in the ROM memory of the microcontroller MP any information derived from the experience related to typical salt consumption procedures as a function of wash cycles and regeneration cycles, of water hardness and of the characteristics of the machine hydraulic system (i.e. water volumes used during the various steps).
Therefore, according to the basic object of this invention, illumination of the warning light L occurs after a certain number of wash cycles (and consequently of resin regenerations) or, more in general, after the flowing through the resins of a determined volume of water of a given hardness degree. It should also be pointed out that according to this invention the cycle or volume count is strictly related to their number and degree of water hardeness.
Based on such an approach it should be emphasized that according to this invention the number of regeneration cycles or the volume of softened water is conveniently weighed, which means that the capability of each regeneration cycle to consume salt is strictly related to the degree of water hardness. Therefore, the higher the hardness the higher the weight abscribed to a given regeneration cycle in said count.
To said purpose, the nonvolatile ROM memory contains proper tables or algorythms, letting the microcontroller MP to evaluate salt consumption during each wash cycle as a function of the volume of softened water during said cycle and as a function of the value of water hardness detected by the sensor, which is obviously included in a preset range of values.
Thus, during each washing the microcontroller MP will update its own counter of the regeneration cycles or volumes of softened water through its nonvolatile read/write memory means.
From the above, it is obvious how according to the present invention the total number of cycles to be reached before indicating the salt exhaustion is automatically selected by the control system, considering the salt consumption capability of each cycle.
In order to adequately develop said counting function, it is necessary for the machine control system to detect when the user tops up the salt level in the relevant compartment S, so that the microcontroller MP may reset its internal counter for the regeneration cycles (or volumes of softened water) and start a new counting cycle.
To such a purpose, i.e. to have a suitable feedback at the time the salt level is restored by the user, the signal associated with the reed contact of the floating device G - practically reliable only when salt is introduced in the relevant compartment - can be conveniently used according to the present invention.
According to this invention, an important condition to comply with is represented by the fact that the "reed" position must be such to warrant the closing of the relevant contact also when the salt concentration is not very high. This because the reed contact according to the present invention simply provides for the "resetting" of the signal system and not informing the user on the need of restoring the salt level.
This can be obtained by selecting eg. the reed position to cause the contact closure already when only half the salt quantity required is available or anyway to warrant a contact closure even in the worst working conditions, i.e. with salt concentrations lower than the max one foreseen.
The operation of the washing machine according to the present invention is as follows.
The float system G is calibrated to detect the introduction of a determined quantity of salt by the user. Therefore, to switch off the warning light L, if lighted, the user has to introduce in the compartment S a quantity of salt at least capable of opening the reed contact, thus resetting the control device of the warning light L.
Thus, the opening of the reed contact associated with the float will also inform the microcotroller MP that the user has at least introduced a certain quantity of salt. Then the microcontroller will reset said internal counter of the regeneration cycles.
Then the microcontroller MP starts a new cycle counting after the salt introduction in the compartment S.
As metioned, such a counting is executed by detecting the degree of water hardness for each cycle. Thus, the microcontroller MP based on the data codified in its memory will evaluate the capability of salt consumption of each cycle during the relevant regeneration process. Thus, in a certain sense, the microcontroller operates a "ponderated average" of resins regeneration till a preset limit value based on the experience and codified in the microcontroller storage is reached, according to which in the compartment S no more salt is available.
In other words, in the machine according to this invention the salt lack is not physically detected but is deduced by the microcontroller MP according to the data obtained through investigations based on measurements and experience. The microprocessor MP is then able to calculate a "virtual" salt level inside the relevant compartment S washing by washing; when such a virtual level goes down to a preset minimum value, the microcontroller itself will control illumination of the warning light L.
At this point, the user is warned to introduce new salt in the compartment S, so that a new resetting of the microcontroller counter MP, switching-off of the warning light L and starting a new count as described above will take place.
As previously mentioned, to ensure the correct operation the signal system of the machine according to the present invention invention requires the user to introduce at least a certain quantity of salt in the compartment S, below which the signal that salt is lacking could be wrong.
It should be pointed out, anyway, that in the practice it never happens for the user to introduce small quantities of salt in the compartment, in particular if he is made aware of this through proper advice in the instructions for use. Also such a risk can be minimized by conveniently calibrating the float system G.
Anyway, should the reed contact not open up in case of a minimum filling of salt, the control device MP will keep the warning light L continuously illuminated having received no signal of salt level filling by the user. In case of likely operation errors, with the reed contact never closing nor opening, the resin regeneration cycles will be normally executed by the machine provided the user fills the salt compartment. However, the persisting illumination of the warning light L will at any rate advise the user to call for technical assistance. The warning light L illuminated all time will warn the technical man of a local trouble, i.e. the reed contact of the float system G not operating properly or likely interruption, or stil a wiring shortcircuit of the two wires transferring the signal from the reed contact to the control logic MP.
For simplicity's sake it was previously referred to an example of application according to this invention, with all wash cycles requiring consumption of a fixed volume of water. However, this invention can also be conveniently applied in those machines provided with a plurality of wash programs using different volumes of water according to the specific needs, i.e. where any program may require more or less water to be softened in respect to other programs.
Also in this case the total number of regeneration cycles to be reached before salt exhaustion is signaled is automatically selected by the machine control system, considering how the inlet procedures of the water to be softened - managed by a suitable level sensor (such as a pressure switch or turbine metering device) have been made during the various wash cycles.
In this case, according to this invention, the nonvolatile storage ROM of the microcontroller MP contains suitable tables or algorythm enabling the microcontroller MP to know for each type of wash cycle being selected the relevant volume of softened water and relevant consumption of regeneration salt as a function of the value of water hardness.
This invention is also particularly convenient for application in washing machines whose resin regeneration cycles may have different procedures, i.e. with variable volumes of regeneration water, managed by a solenoid valve as a function of water hardness.
As a matter of fact and as already mentioned above, according to this invention the count of regeneration cycles can be optionally replaced by the count of the volume of water used for the regeneration, should such a quantity change according to water hardness and/or to the selected wash cycle.
In this case, the nonvolatile memory MP contains suitable tables or algorythms indicating to the microcontroller M P the opening time for the solenoid valve E.V. of Fig. 1 with reference to each value supplied by the water hardness sensor and included in a preset range of values, provided to control water inlet for regeneration purposes. Obviously, an exact volume of the the water used will correspond to a given opening time of the solenoid valve E.V.
In this frame, therefore, according to this invention, the control unit is able to relate the values of water hardness, of the volume of regeneration water and of the volume of softened water to obtain the signal that salt is lacking. Such an application of the invention is shown as a diagram in Fig. 2, indicating on the abscissa axis the volumes of softened water (liters), on the ordinate axis the possible values of water hardness (French degrees, dHF) and on the horizontal arrows the volumes of water (centiliters) used for resins regeneration and the relevant activation times of solenoid valve E.V. for regeneration water control. Obviously, these examplifying data are related to the max capacity of the salt compartment or, in the case described above, to the quantity of salt required to cause the warning light L to switch out.
As it will be noticed, for instance, when the water hardness from the mains equals 60 dHF, which is a very high hardness value, each regeneration will take place with 190 cc of water, namely 40 secs opening of the solenoid valve E.V. In this case, illumination of the warning light is enabled by the microcontroller after about 740 liters of water have been softened.
Viceversa, when water hardness from the mains equals 10 dHF, which is a relatively low hardness value, each regeneration will take place with 30 cc of water, namely 3 secs opening of the solenoid valve E.V. In this case illumination of the warning light is enabled by the microcontroller after nearly 3000 liters of water will have been softened.
From the above description it will be apparent how through a proper programming the microcontroller MP will be able to evaluate salt consumption exactly and enable the relevant signal with extreme accuracy.
The characteristics of the present invention and its relevant advantages appear obvious from the above description.
Specifically, they are represented in that the signal system object of this invention offers an increased accuracy in respect to the known state of the art. According to this invention, there is practically no longer a need for a physical detecting system of the salt consumption but an accurate evaluation of it is required to obviate to the problems of the known state of the art, which can derive from a lack of homogeneity of the fluid density in the salt tank, from a likely mechanical jamming of the float and from calibration difficulties related to the float weight.
It is obvious that a number of changes to the washing-machine described by way of example are possible to the expert of the art, and it is also obvious that in the practical actuation of this invention the components described above can be replaced by other elements technically equivalent.
For instance, according to a more sophisticated embodiment than described above by way of example, there is also the opportunity of providing sensing means for salt concentration or hardness of the water exiting the DD device so as to transfer more information to the microcontroller MP. Such sensing means can in fact be obtained with other means similar to the ones indicated by A and B. In fact, codification of proper data and fuzzy rules in the ROM memory associated with the microcontroller will let the latter to derive the degree of salt concentration or its hardness from the water resistivity.
The microcontroller MP can then relate with the information previously mentioned (water hardness and/or volume of softened water and/or volume of water used for regeneration) also the value of salt concentration or hardness of the water exiting from the device DD. Thus, the microcontroller MP is able to determine very precisely and economically (low cost incidence of complementary electrodes A and B) through a proper knowledge base codified in the ROM memory means when salt is lacking in the compartment S.
Previously, in the instance described by way of example, it has already been mentioned that the float system G practically has the sole function of informing the control logic MP about salt filling in the tank S.
However, it is obvious that such information can also be differently transferred to the microcontroller MP, eg. through a proper control element actuated by the user. Using the capability of the control system with microprocessor it would also be possible to provide that said information is given by the user through a specific operating sequence on some control devices usually available on the machine, such as pressing two or more keys simultaneously.

Claims

Signal system of the salt concentration used for resin regeneration in a washing machine, specifically a household dishwasher having a water softening device (DD) comprising
- a container (R) for the resins used to reduce the degree of water hardness (resins)

- a container (S) for the salt required for the regeneration of the resins that have lost their effectiveness following the execution of softening steps,

- means to determine the salt availability in the salt compartment (S),

- means (L) to signal the need for salt filling when the level in the salt compartment (S) lowers down to a preset minimum level,
where the resin reactivating processes take place periodically in time, in particular with each wash cycle executed by the machine, characterized in that said means to determine the salt availability comprise a sensing device (A,B,C,Q,MP) of the hardness degree of water coming from the mains and an electronic control unit (MP) fit to evaluate the salt consumption in a function of the hardness degree of water from the mains, said signal means (L) being activated, if necessary, by said control unit (MP) when the evaluated salt concentration reaches a defined threshold.
System according to Claim 1, characterized in that the control unit (MP) is associated with nonvolatile memory means (ROM), containing codified experimental data representing the quantity of salt consumed during each resins regeneration cycle, in function of the values of water hardness detected by said sensor (A,B,C,Q,MP) and comprised in a preset range of values and in function of the procedures used for the regeneration processes.
System according to Claim 1, characterized in that the control unit (MP) is associated with nonvolatile memory means (ROM), containing codified experimental data representing the quantity of salt consumed during each resins regeneration cycle, in function of the values of water hardness detected by said sensor (A,B,C,Q,MP) and comprised in a preset range of values and in function of the volumes of softened water.
System according to Claim 1, characterized in that the control unit (MP) is associated with nonvolatile memory means (ROM), containing codified experimental data representing the quantity of salt consumed during each resins regeneration cycle, in function of the values of water hardness detected by said sensor (A,B,C,Q,MP) and comprised in a preset range of values and in function of the volumes of water used for the regeneration processes.
System according to Claims 3 and 4, characterized in that said nonvolatile memory means (ROM) contain codified experimental data representing the quantity of salt consumed during each resins regeneration cycle, in function of the values of water hardness detected by said sensor (A,B,C,Q,MP) and comprised in a preset range of values in function of the volumes of softened water and as a function of the volumes of water used for regeneration processes.
System according to at least one of the previous Claims, characterized in that said control unit comprises nonvolatile read/write memory means, within which counters are stored and updated of the wash-cycles and/or regeneration processes and/or of the volumes of softened water and/or of the volumes of regeneration water and/or of the quantities of salt consumption during each regeneration cycle.
System according to at least one of the previous Claims, characterized in that said sensor comprises detecting means for the resistivity degree of water, wherefrom the control unit (MP) can detect the degree of water hardness, said means for the resistivity degree detection comprising two electrodes (A,B) in contact with the water from the mains and a microcontroller (MP), which is associated with nonvolatile memory means (ROM) containing codified experimental data to indicate the degree of water hardness in function of its resistivity degree.
System according to at least one of the previous Claims, characterized in that sensing means are provided for the salt concentration or the hardness of water exiting the resin compartment(R).
System according to at least one of the previous Claims, characterized in that control means (G) are provided to inform the control unit that salt filling in the relevant container (S) has occurred.
Method to control salt concentration in a water softening system used in a wahing machine, said system comprising a resin, container and a salt tank, where said resins have to be periodically submitted to a regeneration process through a water and salt solution, characterized in that the salt consumption value, i.e. its concentration in the relevant tank, is evaluated by a control unit (MP) in time and updated on occasion of each wash cycle in function of the hardness value of water from the mains.
Method according to the previous Claim, characterized in that signal means are enabled upon reaching a preset concentration or salt consumption value.
Method according to Claim 10, characterized in that a new evaluating cycle of salt consumption or concentration start when the control unit (MP) receives a message indicating that at least a preset quantity of new salt has been introduced in the relevant tank.
A method according to the previous Claim, characterized in that the salt consumption and/or concentration is evaluated in function of both the water hardness and number and/or modes used for the execution of the wash cycles or regeneration processes.
Method according to Claim 13, characterized in that the evaluation of salt consumption and/or concentration is executed in function of the volume of softened water during each wash cycle and of the degree of water hardness.
Method according to Claims 16 and 17, characterized in that the evaluation and/or concentration of the salt is executed in function of the water hardness degree, the quantity of water used for each regeneration process and the quantity of softned water.