ES2362691T3 - AN IMPROVED DRYER. - Google Patents

Abstract

A domestic dryer (1), comprising: - a rotating drum (2) having an interior drying volume (200) to receive a wash load (100) for drying, said interior drying volume having a portion (201) of air inlet, through which a flow (20) of air enters said internal drying volume, and a part (202) of air outlet, through which said air flow leaves said volume of internal drying; - heating means (5) for heating said air flow before said air flow passes through said air inlet part; - first means (6A) sensor to detect the temperature (TH) of said air flow in said air inlet part; and - second means (6B) sensor for detecting the temperature (TA) of said air flow in said air outlet part; and - a control system (7) for controlling the operation of the dryer (1); characterized in that said control system comprises at least a first control loop (51) for regulating the temperature (TH) of said air flow in said air inlet portion (201), and a second control loop (52) for regulating the temperature (TA) of said air flow in said air outlet part (202), said first control loop and said second control loop operating together to control said heating means (5).

Description

The present invention relates to a domestic dryer that has improved yields in terms of drying cycle efficiency, energy consumption and safety. Household dryers are very popular today.

As is widely known, these appliances generally comprise a rotating drum that defines an interior drying volume to receive a wash load to be dried.

The rotating drum is driven by an electric motor to flip the wash load during the drying cycle.

The dryers can be of the ventilated type, in which an air flow is extracted from the outside of the appliance during the drying cycle. The air flow is heated by a heating element and is forced to pass through the drying volume to remove moisture from the wash load. Then, the moist exhaust air is expelled out.

In condenser type dryers, on the other hand, the air flow follows a closed path that is completely inside the appliance. After being heated, the air flow passes through the drying volume and is circulated to a condenser for dehumidification. Then, the air flow is transported to the heating element to be reheated.

In both cases described, the circulation of the mentioned air flow is ensured by a fan.

The available dryers generally comprise a control system, which regulates the operation of the dryer and directs the drying cycle.

In general, the control system regulates the flow rate of the air flow through the drying volume and the temperature of the heating medium to achieve the desired temperature levels and ensure safety.

An example of these known control systems is described in US Pat. 4231166.

Unfortunately, traditional control systems provide relatively poor yields in terms of drying efficiency and energy consumption, since they are mainly focused on achieving certain predefined levels of heating or flow energy, which are established based on the User settings

Important environmental factors that influence the efficiency of the drying cycle, such as the actual conditions of the wash load, the operating conditions of the dryer (for example, the possible presence of lint obstructions) are not properly taken into account. , etc.

Other simpler control methods make use of hysteresis control, for which the heater is located in the air channel and is controlled therein by means of a temperature sensing element, and is turned on when the feedback temperature is below a predefined threshold, and off when it is above a second predefined threshold, in order not to exceed the safety temperature limit for the air channel. According to this control strategy, the temperature inside the air channel varies with a “sawtooth” profile. As a consequence, the average temperature within the air channel is higher than the average temperature in the drying chamber, and the latter is also forced to fall during the drying cycle due to continuous interruptions of heater energy.

This behavior is particularly critical in the final phase of drying, when maximum energy must be provided to the washed clothes to obtain high quality drying yields.

It follows that the average temperature of the drying chamber is not optimized, because it is relatively low and remains below a value that could be reached when the heater is controlled, in a more stable manner, near the highest allowed temperature limit. in the air channel (preferably below a safety temperature threshold). Therefore, this hysteresis control strategy results in inefficient energy consumption, which is derived from a longer drying process (time) executed at a lower temperature, compared to a drying cycle when the heater temperature it is kept closer to the temperature of the predetermined upper temperature limit (preferably below a safety temperature threshold), without being controlled in an oscillating (predominant) manner, as is the case with on-off or hysteresis control.

Therefore, the main purpose of the present invention is to provide a domestic dryer, which allows the above-mentioned drawbacks to be overcome.

Within this purpose, it is an object of the present invention to provide a domestic dryer in which the control system is capable of offering improved yields in terms of efficiency of the drying cycle, reduction of drying time, reduction of energy consumption and control robustness.

It is also an object of the present invention to provide a domestic dryer that is easy to manufacture on an industrial level, at competitive costs.

Therefore, the present invention provides a domestic dryer according to the following claim 1.

In its most general definition, the domestic dryer according to the present invention comprises a control system that is provided with at least a first control loop and a second control loop, which are capable of operating together for the purpose of control the operation of said heating means.

This dual loop control of the dryer's heating medium ensures that heating energy and adequate safety levels are obtained, and at the same time, achieving high drying cycle efficiency and significant savings in terms of consumption of energy

Another object of the present invention is to provide a dryer in which the heater is controlled by means of a PI (proportional / integral) control, causing the difference between the average temperature of the air channel and the average temperature of the drying chamber (with or without clothes washed inside) be minimized.

Additional features and advantages of the domestic dryer according to the present invention will become apparent from the following description of the preferred embodiments, taken together with the drawings, in which:

Fig. 1 represents a schematic diagram of the domestic dryer according to the present invention in a ventilated type configuration; Fig. 2 represents a schematic diagram of the domestic dryer according to the present invention in a condensation type configuration; Fig. 3 represents a schematic diagram of a control system in the domestic dryer according to the present invention, in a first embodiment; and Fig. 4 represents a schematic diagram of a control system in the domestic dryer according to the present invention, in a second embodiment.

Referring now to the drawings, the present invention relates to a domestic dryer 1, which comprises a rotary drum 2 which is preferably driven by an electric motor 3.

Rotary drum 2 defines an interior drying volume 200 to receive a wash load 100 for drying.

The drying volume 200 comprises a part 201 in the air inlet, through which an air flow 20 can enter the drying volume 200, and an air outlet part 202, through which the flow 20 of air leaves the volume 200 of drying after having passed through it.

In the embodiment of Figure 1, the dryer 1 is structured as a ventilated dryer. The air flow 20 is therefore extracted directly from the outside of the dryer 1, and is blown back into the external environment, after having passed through the drying volume 200. Before entering the drying volume 200, the air flow 20 is heated by the heating means 5, such as an electric heater.

As an alternative (figure 2), dryer 1 can be configured as a condenser dryer. In this case, the air flow 20 follows a substantially closed loop, which is inside the dryer. After having passed through the drying volume 200, the air flow 20 is directed through the condenser means 9 for dehumidification and then directed again to the heating means 5.

The correct circulation of the air flow 20 is ensured by properly positioned air ducts (not shown) and by a fan 8.

The dryer 1 comprises a first sensor means 6A and a second sensor means 6B for detecting respectively the temperature TH of the air flow 20 in the air inlet part 201 and the temperature TA in the air outlet part 202.

It should be noted that the temperature TH substantially coincides with the temperature of the heating medium 5, while the temperature TA is substantially the actual temperature of the wash load 100.

Preferably, the sensor means 6A-6B comprises temperature sensors that are capable of providing signals indicative of the detected temperatures, eg, thermocouples. Of course, temperature sensors of different type can be used.

The dryer 1 comprises a control system 7, which, in general terms, can be defined as the complete set of control arrangements used to control the dryer 1, in particular to direct the drying cycle of the dryer 1.

In this regard, the term "drying cycle" means the sequence of steps needed to perform drying operations of the wash load 100.

The control system 7 preferably comprises a control unit 70, which controls the operating drying cycle of the dryer 1 by sending appropriate command signals 71 to the heating means 5, the motor 3 and the fan 8, and which receives from the means 6A-6B signal sensors 61 that are indicative of the temperature of the air flow 20 respectively in the air inlet and outlet parts 201, 202.

The control system 7 also comprises a plurality of control loops, which preferably involve the control unit 70 in its physical implementation, as will be more evident in the following.

In particular, the control system 7 comprises a first control loop 51 (Figures 3, 4) to regulate the temperature TH of the air flow 20 in the air inlet portion 201, and a second control loop 52 to regulate the temperature TA of the air flow 20 in the air outlet part 202.

The control loops 51 and 52 are configured to be able to work together to control the operation of the heating means 5.

Preferably, the first control loop 51 receives at the input a first feedback signal YTH from the first sensor means 6A, the signal YTH being indicative of the temperature TH.

The second control loop 52, on the other hand, preferably receives at the input a second feedback signal YTA from the second sensor means 6B, the signal YTA being indicative of the temperature TA.

In practice, the control system 7 controls the operation of the heating means 5 by means of two concurrent loops 51 and 52, which operate based on different feedback signals.

The control loop 51 operates on the basis of a first feedback signal YTH that is indicative of the temperature TH substantially coinciding with the temperature of the heating means 5. In its control action, the first control loop 51 therefore takes into account control parameters that depend substantially on the operating conditions of the heating means 5 and / or related safety requirements.

The control loop 52, on the other hand, operates on the basis of a second feedback signal YTA indicative of the temperature TA that substantially coincides with the actual temperature of the wash load 100. In its control action, the second control loop 52 is therefore influenced by different control parameters that depend substantially on the actual state of the wash load 100 or other environmental conditions, such as for example the actual level of lint obstruction. in the exit part 202.

The control loops 51 and 52 may be arranged according to different configurations, and may comprise one

or more logical blocks such as adders, controllers, switches and the like.

Said logic blocks can be hardware implemented as self-sustaining devices or as circuits / boards of the control unit 70.

Alternatively, these logical blocks can be implemented as software programs, modules or routines that are executed by a suitable process unit, for example by a microprocessor (not shown) of the control unit 70.

According to a first embodiment of the present invention, which is shown in Figure 3, the control loops 51 and 52 may be arranged according to a cascade configuration, in which the control loop 51 is positioned downstream with respect to the loop 52 of control.

In this case, the control loops 51 and 52 are mutually nested, and can interact with each other to control the heating means 5.

According to this embodiment of the present invention, the first control loop 51 receives at the input a first reference signal YR1 which is provided by the second control loop 52.

The reference signal YR1 may be indicative of the desired temperature for the heating means 5. For example, the reference signal YR1 can express the temperature profile to be followed by the heating means 5 during a certain interval of the drying cycle.

The first loop 51 advantageously functions as a retroactive loop, and therefore comprises a first controller 511 that receives at the input a first error signal YE1 obtained from a first adder 512 which calculates the difference between the first reference signal YR1 and the first YTH feedback signal.

The controller 511 provides at the output a first control signal YH1 to regulate the operation of the heating means 5, which (from a logical point of view) can be represented as a logic block that receives the control signal YH1 at the input and which provides at the output a temperature value TH, which is detected by the first means 6A sensor that provides the feedback YTH signal.

The wash load 100 can in turn be modeled as a logic block that receives a temperature value TH at the input and provides a temperature value TA at the output, which is detected by the second sensor means 6B that provides the YTA signal Feedback

The second control loop 52 receives a second reference signal YR2 at the input, which may be indicative of a desired temperature for the wash load 100. As an example, the YR2 signal can be represented by a predefined temperature profile for the wash load 100 that is selected by the control unit 7 based on a manual selection operated by the user or that depends on other environmental conditions, such such as the presence of lint obstructions in the exit part 202.

The second control loop 52 preferably comprises a second controller 521 that receives at the input a second error signal YE2 that is obtained from the difference between the second reference signal YR2 and the second feedback signal YTA, a difference that is advantageously calculated by means of an adder 522.

The second controller 521 generates at the output the first reference signal YR1 for the first control loop 51.

It should be noted how the first integer control loop 51 can be modeled as a logic block that receives the first reference signal YR1 at the input and provides at the output a temperature value TA for the wash load 100.

Thanks to the described cascade configuration, the first control loop 51 retroactively regulates the operation of the heating means 5 based on the first reference signal YR1, which is in turn generated by the second base control loop 52 to a second reference YR2 signal that can be generated based on the conditions of the wash load and / or the surrounding conditions.

In this way, the regulation of the heating means 5 can easily take into account additional external factors that are not strictly linked to the operation of the heating means itself or with safety reasons.

According to a further embodiment of the present invention, shown in Figure 4, the control loops 51 and 52 may be arranged according to a parallel configuration. In this case, each control loop 51 and 52 operates in a substantially independent manner and is selectively activated based on the signals that are indicative of the operating state of the dryer 1.

For example, during the start of the drying cycle, the first control loop 51 can be activated in order to quickly bring the heating medium to full operation and quickly reach a certain temperature level TH in the inlet part 201.

Then, the second control loop 52 may be enabled and the first control loop 51 may be excluded, to control the operation of the heating means 5 based on the temperature TA of the wash load 100, that is, based on Different factors such as wash load conditions and / or surrounding conditions.

The first control loop 51 can be enabled again if the operating conditions of the dryer 1 so require, for example in case the temperature TH exceeds predefined safety levels.

According to this additional embodiment of the present invention, the first control loop 51 receives at the input a third reference signal YR3, which can be advantageously indicative of the desired temperature profile for the heating means 5, when the first control loop 51 It is active.

The first control loop 51 also comprises a third controller 513 that receives at the input a third error signal YE3, which is obtained from an adder 514 that calculates the difference between the third reference signal YR3 and the first feedback signal YTH that It comes from the first half 6A sensor.

The controller 513 generates at the output a second control signal YH2 to regulate the operation of the heating means 5.

The second control loop 52 receives a fourth reference signal YR4 at the input, which may instead be indicative of the desired temperature for the wash load 100.

The second control loop 52 advantageously comprises a fourth controller 523 that receives at the input a fourth error signal YE4, which is obtained from adder 524 which calculates the difference between the reference signal YR4 and the second feedback signal YTA coming from the Second half 6B sensor.

In addition, the controller 523 generates at the output a third control signal YH3 to regulate the operation of the heating means 5.

For the activation / exclusion of the control loops 51 and 52, a switch means 555 is provided, which receives the control signals YH2 and YH3 at the input, and selects which control signal has to be enabled to control the means 5 of heating.

As mentioned above, such selection works advantageously based on the IS signals that are indicative of the operating state of the dryer 1. For example, said IS signals may be alarm signals that come from additional sensors (not shown) or from the means 6A and / or 6B sensors. Alternatively, the IS signals may be command signals generated by the control unit 70.

According to a preferred control method, when the temperature in the inlet part 201 (the air channel) rises above a first predefined temperature threshold THR1, which is above a safety temperature limit TS, the heater 5 It is energized only if the fan 8 is energized (rotated), in a synchronized manner.

In some dryer constructions the fan 8 is mounted on the axis of the rotating drum, and is rotated together with the motor 3 of the drum. With these constructions and under the conditions described, the heater is energized in synchronism with the drum and with the fan 8.

In another case, the heater 5 can be activated only when the measurable air flow (by means of known measuring tools) in the inlet part 201 is above a predetermined air flow threshold ATH. For example, the air flow threshold ATH corresponds to the reduced air flow achieved when the rotational direction of the drum is reversed.

This control method prevents the temperature in the air channel 201, especially around the heater 5, from rising above the safety thresholds TS, but still maintaining the temperature at an acceptable level, without sudden drops.

In other cases, when the temperature of the air channel is above a first threshold THR1 of predefined temperature, the energy delivered by the heater can be controlled in order to be reduced or temporarily interrupted, in order to reduce the magnitude of the temperature oscillation in the air channel 20 and in order to reduce the drying time (maintaining a higher temperature in the air channel 20) and, as a consequence, reduce the energy consumption.

When the temperature is below the first predetermined temperature threshold, synchronized activation is not required, because the air channel temperature is far enough from the safety temperature limit, and machine safety is not at risk.

The dryer 1 according to the present invention fully allows the achievement of the intended purposes and objects.

Thanks to the presence of two concurrent control loops 51, the drying cycle can be run also taking into account the actual conditions of the wash load and other additional environmental conditions. The possibility of incurring over-drying or under-drying conditions of the wash load is therefore drastically reduced, and the dryer 1 can operate more efficiently, with lower energy consumption and a reduced drying time.

The adoption of retroactive control loops ensures a remarkable robustness of control, with a high level of safety.

Additionally, it has been shown how control loops 51 and 52 can operate with dryer 1 in a ventilated or condensing configuration, without the need for additional hardware / software resources.

The dryer 1 has a simple structure, which has proved easy to manufacture at an industrial level, at competitive costs, since standard hardware components can be used or relatively simple software procedures can be adopted.

Claims (15)

1. A domestic dryer (1), comprising: - a rotating drum (2) having an internal drying volume (200) to receive a wash load (100) for drying, said internal drying volume having an air inlet part (201), through which an air flow (20) enters said internal drying volume, and an air outlet part (202), through which said air flow leaves said internal drying volume; - heating means (5) for heating said air flow before said air flow passes through said air inlet part; - first medium (6A) sensor to detect the temperature (TH) of said air flow in said air inlet part; and -second means (6B) sensor for detecting the temperature (TA) of said air flow in said air outlet part; and -a control system (7) to control the operation of the dryer (1); characterized in that said control system comprises at least a first control loop (51) for regulating the temperature (TH) of said air flow in said air inlet portion (201), and a second control loop (52) for regulating the temperature (TA) of said air flow in said air outlet part (202), said first control loop and said second control loop operating together to control said heating means (5).

2.

A domestic dryer according to claim 1, characterized in that said first control loop receives at the input a first feedback signal (YTH) indicative of the temperature (TH) of said air flow in said air inlet portion, said said proportion being provided first feedback signal by said first sensor means.

3.

A domestic dryer according to claims 1 or 2, characterized in that said second control loop receives a second temperature feedback signal (YTA) at the input (TA) of said air flow in said air outlet portion, said said second feedback signal provided by said second sensor means.

Four.

A domestic dryer according to one or more of the previous claims, characterized in that said first control loop and said second control loop are arranged according to a cascade configuration, said first control loop being positioned downstream with respect to said second control loop .

5.

A domestic dryer according to claim 4, characterized in that said first control loop receives a first reference signal (YR1) at the input, said first control loop comprising a first controller (511) that receives a first signal (YE1) at the input ) error, which is obtained from the difference between said first reference signal (YR1) and said first feedback signal (YTH), said first controller generating at the output a first control signal (YH1) to control said heating means .

6.

A domestic dryer according to claim 5, characterized in that said second control loop receives a second reference signal (YR2) at the input, said second control loop comprising a second controller (521) that receives a second signal (YE2) at the input ) error, which is obtained from the difference between said second reference signal (YR2) and said second feedback signal (YTA), said second controller generating at the output said first reference signal (YR1).

7.

A domestic dryer according to one or more of claims 1 to 3, characterized in that said first control loop and said second control loop are arranged according to a parallel configuration.

8.

A domestic dryer according to claim 7, characterized in that said first control loop or said second control loop is selectively activated based on the signals (IS) that are indicative of the operating state of said dryer.

9.

A domestic dryer according to claim 8, characterized in that said first control loop receives at the input a third reference signal (YR3), said first control loop comprising a third controller (513) that receives at the input a third signal (YE3 ) error, which is obtained from the difference between said third reference signal (YR3) and said first feedback signal (YTH), said third controller at the output generating a second control signal (YH2) to control said heating means .

10.

A domestic dryer according to claims 8 or 9, characterized in that said second control loop receives at the input a fourth reference signal (YR4), said second control loop comprising a fourth controller (523) that receives at the input a fourth signal (YE4) error, which is obtained from the difference between said fourth reference signal (YR4) and said second feedback signal (YTA), said fourth controller generating at the output a third control signal (YH3) to control said means heating

eleven.

A domestic dryer according to claims 9 and 10, characterized in that a switch means (555) receives at the input said second control signal (YH2) and said third control signal (YH3), said switch means selecting said first signal (YH1) of control or said second control signal (YH2) to regulate the

5 operation of said heating means.

12.

A domestic dryer according to claim 11, characterized in that said switch means selects said second control signal (YH2) or said third control signal (YH3) based on the signals (IS) that are indicative of the operating state of said dryer.

13.

A domestic dryer according to one or more of claims 1 to 12, characterized in that it is of the condensation type or the ventilated type.

14.

Method for controlling the domestic dryer of any of the preceding claims, comprising

10 15 also a fan (8), wherein the heating means (5) is energized only when the temperature in the inlet part (201) rises above a first threshold (THR1) of predefined temperature. 15. Method for controlling the domestic dryer of any of the preceding claims, comprising furthermore a fan (8), wherein the heater (5) is energized only when an air flow in the inlet part (201) is above a predetermined air flow threshold (ATH).