DESCRIPTION

Field of the Invention

The present invention generally relates to the technical field of control systems, and it particularly relates to a method for controlling a working device, such as a burner or the like.

Another object of the invention is a system, a computer program and a programmable logic unit for controlling such working device.

Background of the invention

The need of maintaining a constant level of a parameter inside a closed chamber of a working device is well known, as for example in plants that use burners or in refrigeration.

Different types of burners according to their functioning are well known, based on the periodic detection of temperature in the working chamber itself.

The single stage burner of on/off type is well known, namely a single supply stage burner, wherein the fuel mixture flow rate doesn't change during the functioning of the same.

Such well known systems have a low accuracy of the supplied temperature, this resulting in an excessive oscillation of temperature inside the chamber.

Multistage burners having two or more power stages are also widely known, namely capable of varying the supply flow rate, generally in terms of maximum flow rate/one or more partial flow rates/switching-off.

Such known systems, cheap and simple to implement, offer a limited temperature supply interval.

Finally, modulating burners are also well known, whose flow rate is variable in a continuous way between the 30% and 100% of the burner's thermal input.

Such known systems are too expensive, and require a high fuel consumption in order to vary the supplied temperature.

In the refrigeration and air-conditioning industry, the importance of keeping a constant temperature in a closed environment is also widely known.

In this regard, simple systems including a temperature detector, an expansion valve, reversible in the case of heat pumps, an evaporator, a condenser and a compressor activated above or below a certain temperature level, are often used.

Such known systems offer an imprecise and poorly controlled temperature supply.

Likewise, controlling the humidity rate in a closed environment is particularly important, for example in a room of a private house or of a museum or similar, wherein a particular attention to the humidity rate is necessary in order to preserve the artworks.

With reference to dehumidification, the use of air conditioning systems is known, comprising a circuit for the drainage or evaporation of the condensate, or dedicated devices.

Conversely, humidifiers suitable for supplying water sprays or water vapor through nozzles are well know.

Such known systems ensure the maintenance of the humidity rate in a closed environment in an imprecise and poorly controlled manner.

Summary of the invention

Object of the present invention is to overcome, at least partially, the drawbacks illustrated above, by providing a method for maintaining the value of a parameter in a closed chamber, this being relatively cost-effective.

Another object of the present invention is to provide a method that allows to obtain a supply interval of the value of a large parameter, so as to maintain the value of the same as constant as possible inside the closed chamber.

Another object of the present invention is to provide a method that offers a high level of accuracy if used in a system comprising a burner and an exchanger.

Another object of the present invention is to provide a method that allows the preservation of the components of the devices that use the same method from mechanical stress, in order to extend their lifetime.

Such objects, as well as others that will be clearer hereinafter, are fulfilled by a method and/or a system, and/or by a computer program and/or by a programmable logic unit according to what is herein described, shown and/or claimed.

The dependent claims define advantageous embodiments of the invention.

Brief description of the drawings

Further features and advantages of the present invention will become more evident by reading the detailed description of some preferred but not exclusive embodiments of the invention, illustrated as a non-limiting example, with the help of the annexed drawings wherein:

FIG. 1 shows the scheme of a first embodiment of the described method;

FIG. 2 shows the scheme of a second embodiment of the described method;

FIG. 3 is a schematic presentation of an example of a system 1 usable in the described method.

Detailed description of some preferred embodiments.

With reference to the above mentioned figures, it is here described a method for maintaining in a working chamber C the value of a parameter in a neighborhood of a set- point value L _Sp , as well as a system 1 usable in such method.

Such system 1 may comprise a working chamber C and at least one sensor MR for the detection of the value of the parameter of interest, positioned in the working chamber C.

Even though hereinafter we refer to a single sensor MR, it is understood that such system 1 may comprise multiple sensors, without departing from the scope of the invention defined in the appended claims.

The system 1 may also comprise a programmable logic unit UL operatively connected to the sensor MR for elaborating the detected values of the parameter of interest and a device D operating in a state A, on or off, for a time X and a state B, respectively off or on for a time Y.

The programmable logic unit UL may for example be an electronic board or a PLC (Programmable logic controller), programmed or programmable through a proper computer program, and may act on the device D in order to control its operation.

It is understood that the logic unit UL may be operatively connected to or may include a data storage unit UM, cooperating with the same for elaborating and comparing the detected values, without departing from the scope of the invention defined in the appended claims.

The typology of a working device D is non-limiting for the present invention, as long as it includes at least one working chamber C and means acting on the latter in order to increase or decrease the value of the parameter of interest so that it tends to a set or settable a set-point value L _sp .

According to a preferred but not exclusive embodiment, the device D may be a single stage, two-stage or a multistage burner, such as a three-stage burner, for example being part of a boiler, of a dryer, of a blast furnace, of a metallurgical plant or a chemical plant.

In particular, in a multistage burner, one or more flames may be constantly active, while the lightning or the extinction of another flame may be adjusted respectively for a time X and a time Y.

In the case of a burner, the parameter of interest may be the temperature detected in a chamber of a combustion plant and state A is to be intended as the operating state on, while state B will be the operating state off.

It is understood that such method may be applied also in the presence of a heat exchanger, without departing from the scope of the invention defined in the appended claims.

Therefore, it is understood that the combustible flow rate, as well as its consumption, will be related to the variation of times X and Y, as well as to the system capacity to maintain a constant temperature inside the chamber, regardless of external climatic factors.

According to another example, the device D may be a compressor being part of a refrigeration or air-conditioning system for cold air supply.

In such case, the parameter of interest may be the temperature, and state A is to be intended as the operating state off, while state B is to be intended as the operating state on.

According to another example, the device D may be a compressor being part of an air conditioning system for hot air supply.

In such case, the parameter of interest may be the temperature, and state A is to be intended as the operating state on, while state B is to be intended as the operating state off.

Finally, according to another example, the device D may be a part of a humidifier or a dehumidifier.

In such case the parameter if interest may be the humidity rate and, in case of humidification, state A is to be intended as the operating state on, and state B as the operating state off.

On the contrary, in the event of dehumidification, state A is to be intended as the operating state off, while state B as the operating state on.

Preferably, times X and Y may be initially set or settable by a user on initial values Xo and Yo, each of these values, for example, equal to 5 or 10 seconds.

Suitably, the temperature inside the chamber may be detected at constant periodic time intervals, with a length according to the type of system 1 used, as well as to the necessity of a more or less rapid detection of the variation of the value of the parameter inside the chamber C.

For example, in the event of a burner D, with or without a heat exchanger, the detection period may be between 1 and 10 seconds.

Preferably, a prior check may be possible in order to control if the initial value L _mitiai of the parameter of interest inside the working chamber C, is a value contained in a working interval I working.

Such working interval I _working may comprise the set-point value L _s , and may be defined according to the use of the system, as well as its inertia.

The same working interval I _working may be settable by the user or it may be preset.

During an initial transitional step or during the operating state of the control logic unit, the device D may operate in the state A or in the state B so that, inside the working chamber C, an initial value Lmi _tiai of the parameter of interest contained in the working interval I _working is reached, situation in which the control logic unit may be activated.

During the transitional step or during the operating state of the control logic unit, such initial value Lmi _ti ai may be for example the last value detected by the sensors MR.

If the initial value Lmi _tiai of the parameter of interest is not contained in the working interval I _orking and is greater than the set-point value L _sp , the device D may be set in the operating state B on or off according to the above mentioned typology of device D. For example, in the event of a burner, be it a single stage, two-stage or a multistage burner possibly included in a boiler or a dryer, such operating state B may be off.

On the contrary, whenever the initial value Lmi _tiai of the parameter of interest is not contained in the working interval L _o sing and is lower than the set-point value L _sp , the device D may be set in an operating state A on or off according to the above mentioned typology of device D. For example, in the event of the above burner, be it a single stage, two-stage or a multistage burner possibly included in a boiler or a dryer, such operating state A may be on.

According to a preferred but not exclusive embodiment of the invention, the control logic unit may carry out several steps of the process, as shown in FIGs. 1 and 2.

First of all, there may be a detection step, carried out by the sensor MR, of the value of the parameter in a first instant of time ti so as to define a first comparison value LI. For example, in the above mentioned event of a burner, be it a single stage, two-stage or a multistage burner and possibly included in a boiler or a dryer, such parameter may be the temperature.

Subsequently, a second detection may be carried out by the same or another sensor MR of the value of the parameter in a second instant of time so as to define a second comparison value L2.

It is understood that LI and L2 may be detected by the same or by two or more different sensors MR, without departing from the scope of the invention defined in the appended claims.

Subsequently, a comparison between the comparison value L2 and the set-point value L _Sp may occur, so as to determine if L2 it is equal, greater or lower than L _sp .

In particular, if L2 is equal to the set-point value L _sp , the device D is not going to undergo changes on his operating state, thus remaining in its operating state on or off, in which it was before the detection.

On the contrary, if L2 is greater or lower than L _sp , there may be a comparison between the comparison values LI and L2, so as to determine if L2 is greater or lower than the first one.

After the above mentioned steps, if the comparison value L2 is substantially lower than the set-point value L _sp and substantially equal or lower than the value LI, an increase of the working time X may occur, of a predetermined or settable value N, otherwise, a decrease of the working time Y of the same predetermined or settable value N.

It is understood that the increase of time X or the decrease of time Y may depend on the characteristics of the system and on the monitored parameter. Anyways, such variation may allow the parameter of interest to tend to the set-point value L _sp .

For example, in the event of a burner, be it a single stage, two-stage or a multistage burner possibly included in a boiler or a dryer, if the above mentioned comparison indicates the need of a bigger supply of heat in the chamber C, the switch on time of the value N will increase, otherwise the switch off time Y will decrease of the same value N.

Afterwards, a value L3 may be detected in an instant time t ₃ , which may be compared with the value L2 during a comparison step.

If the value L3 is greater than the value L2, there will be no change in the times X and Y.

For example, still in the above mentioned event of a burner, be it a single stage, two- stage or a multistage burner possibly included in a boiler or a dryer, if the above mentioned comparison indicates that the heat supplied in the chamber C is sufficient to increase the working temperature, the system will continue to remain in the operating state on for a time X + N and in the operating state off for a time Y, otherwise in the operating state off for a time Y - N and in the operating state on for a time X.

On the other hand, if the value L3 was lower or equal to value L2, the result will be the decrease of time Y or the increase of time X of value N, depending on what happened in the above mentioned step.

Always considering the above mentioned example of a burner, if the above mentioned comparison indicates that the heat supplied into the chamber C is not sufficient to increase the working temperature, the system may decrease the switch off time or it may increase the switch on time of the burner, for example of a quantity equal to the one in which the switch on time increased or decreased.

It is understood that different values of increase or decrease N may be provided, for example equal to 0,5 seconds and 1 second, depending on the difference, respectively for example of 0,5° and 2° occurring at two by two between the values LI, L2, L3 periodically and subsequently detected, without departing from the scope of the invention defined in the appended claims.

It is also clear that the time instants ti, t _å , t3 correspond to instants defined within a certain period of time.

Therefore, the detected values LI, L2, L3 may coincide with the value of the beginning of the period, with the value of the end of the period, with the maximum, minimum or average value within the elapsed period.

On the contrary, if the comparison value L2 is substantially greater than the set-point value L _Sp and substantially equal or greater than the value LI, an increase of the working time Y of a predetermined or settable value N, or a decrease of the working time X of the same predetermined or settable value N may occur.

Always considering the above mentioned example of a burner, if the above mentioned comparison indicates the need of a lower supply of heat inside the chamber C, the switch-on time may decrease, or the switch-off time of value N may increase.

Subsequently, if the value L3 is lower than value L2, there will be no variation to the time Y.

For example, still considering the above mentioned burner, if the above mentioned comparison indicates that the heat supplied into the chamber C is sufficient to decrease the working temperature, the system will remain in the operating state on for the time X - N and off for the time Y, otherwise it will remain in the operating state off for the time Y + N and on for the time X.

On the other hand, if the value L3 is equal or greater than the value L2, a decrease of time Y or an increase of time X of the value N will occur, depending on what happened in the above mentioned step.

Always considering the above mentioned example of a burner, if the above mentioned comparison indicates that the heat supplied into the chamber C increases its working temperature, the system may increase the switch-off time, or it may decrease the switch-on time of the burner, for example of an equal quantity to the one in which the switch-on time decreased.

The above mentioned steps may occur consecutively or iteratively.

Thanks to what mentioned above, it may be possible to bring the value of the parameter of interest as close as possible to the set-point value with a high level of accuracy, preserving at the same time the components of the system from mechanical stress, so as to extend their duration over time.

I ndeed, the present invention does not have predefined working cycles, but it adjusts the switch-off and switch-on time of the system to the need, so as to maximize the lifetime of the system itself.

Moreover, the system of the present invention is particularly advantageous in the event of single stage, two-stage and multistage burners, for example being part of a dryer or boiler.

Thanks to the present invention it is possible indeed to obtain the performances of a modulating burner in terms of accuracy and constancy of the produced temperature, but now using a single stage, two-stage and multistage burner, thus very cheap and long lasting thanks to the reduced presence of precision mechanics. According to a second preferred but not exclusive embodiment of the invention particularly shown in FIG. 2, it may be possible to establish an initial working condition such that the sum of the times X and Y is greater than a predefined minimum value Z.

Such value Z, which is initially set by the user, may prevent the excessive stress of the mechanical components of the device D involved in the switch-off and switch-on of the same.

For example, in the event of a burner, the value Z may be equal to 10 or 20 seconds, accordingly to the thermal inertia of the masses to be heated inside the working chamber C and depending on the presence or absence of an exchanger.

In particular, Xo and Yo may be equal to a value Z/2.

According to this example, after the above mentioned comparison betweenLl, L2 and L3, a verification step may occur if the sum of the times X and Y is greater than the minimum value Z.

If the verification step gives a negative result, the step of increase of the time X and the comparison step between the second and the third values L2, L3 progressively detected, may iteratively occur at constant periodic time intervals until the same verification step gives a positive result, namely when the sum of the times X, Y is greater than the minimum value

Z.

If the verification step gives a positive result, the time decrease step Y may subsequently occur.

Conversely, after the comparison step between LI and L2, if the value L2 is greater than the set-point value L _s and equal or greater than the value LI, the step of increase of the time Y may occur.

Afterwards, the detection step of value L3 in an instant of time may occur, which, if equal or greater than value L2, may take to the verification step if the sum of the times X, Y is greater than the minimum value Z.

If the verification step gives a negative result, the step of increase of the time Y and the comparison step between values L2 and L3 may iteratively occur at subsequent constant periodic time intervals, until the same verification step gives a positive result, namely the sum of the value of times X, Y is greater than the minimum value Z.

If the verification step gives a positive result, the step of decrease of the time X may subsequently occur.

It is understood that if the value L2 is substantially equal to the set-point value L _s or lower than the set-point value L _sp and greater than the value LI, or if L2 is substantially equal to the set-point value L _sp and lower than the value LI, the control logic unit will not change the value of times X and Y.

According to a preferred but not exclusive embodiment of the invention, if the value L3 is substantially lower or equal to the set-point value L _s and greater than the value L2 , or if L3 is substantially greater than the set-point value L _sp and lower than the value L2, the control logic unit will not change the value of times X and Y.

From what described above, it is clear that the invention reaches the intended purposes.

The invention is susceptible to numerous modifications and changes. All the details may be replaced by other technically equivalent elements, and the materials may be different depending on requirements, without departing from the scope of the invention defined in the appended claims.