WO2007068698A1 - Diagnostic device for heating element - Google Patents
Diagnostic device for heating element Download PDFInfo
- Publication number
- WO2007068698A1 WO2007068698A1 PCT/EP2006/069606 EP2006069606W WO2007068698A1 WO 2007068698 A1 WO2007068698 A1 WO 2007068698A1 EP 2006069606 W EP2006069606 W EP 2006069606W WO 2007068698 A1 WO2007068698 A1 WO 2007068698A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- heating element
- diagnostic device
- analogue
- temperature
- diagnostic
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B1/00—Details of electric heating devices
- H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
- H05B1/0227—Applications
- H05B1/0252—Domestic applications
Definitions
- the present invention relates to a diagnostic device for a heating element, intended to be used within a fluid or a body to be heated.
- Heating elements which are generally electrical resistances protected by appropriate materials, either insulating or not, are commonly used in the field of electrical household appliances or other types of apparatuses. Such heating elements are immersed in the container or in the closed environment to be heated and the output heat is used to heat both the fluid within the container and the material which either surrounds it or which is arranged near the heating element. Such elements, being highly cost-effective, are widely used in the industry, but are also subject to wear and must therefore be subjected to checks and to diagnostic processes to verify correct operation.
- the present invention relates to a diagnostic device for a heating element which overcomes the aforementioned drawbacks constructing a simple and reliable device which is inexpensive to manufacture, manage and maintain.
- a diagnostic device for a heating element which in accordance with claim 1 comprises a heating element comprising an electronic circuit, adapted to acquire and process electrical signals from the temperature sensors and send said electrical signals to a conditioning block, an analogue- digital conversion block adapted to transform the analogue temperature values into digital and a processor adapted to identify an exceeding condition of predetermined thresholds and to generate fault alarms.
- the mentioned objects are obtained by means of a diagnostic process for a heating element which according to claim 5 comprises the following steps:
- a diagnostic device and a process capable of detecting abnormal or failure conditions, in industrial or domestic applications in which a heating element is present for heating bodies or fluids.
- the device also performs the control and driving process of the heating element. The detection of operating conditions by the diagnostic device allows, according to the application and the needs, to generate alarms and/or perform targeted maintenance actions.
- the control is capable of easily identifying faulty operating conditions by only measuring the temperatures of the heating element and the body or the fluid to be heated, using two appropriate temperature sensors Tr and Tc and by knowing the heat provided QF(O to the heating element.
- the conditions detectable with the diagnostic device of the invention comprise: a) an inadequate thermal exchange between the heating element and the heated body, as for example the presence of lime scale on the surface of the heating element if the heated body is water; b) a correct operation with adequate thermal exchange; c) a faulty heating element or in protected conditions, such as for example the case of thermofuses inside the heating element or overheating protection devices; d) a fault in the control temperature measuring sensors.
- - Fig. 1 is a diagram of the system in which the device according to the present invention is employed;
- - Fig. 2 is a graph showing the operating curves of the device of the invention in various actual conditions;
- - Fig. 3 is a graph showing the operating curves of the device of the invention compared against curves showing the values detected during operation;
- FIG. 4 is a block diagram showing the operation of a control circuit of the device according to the invention.
- the diagnostic device uses some theoretic notions presented below.
- the system in which the heating element is used comprises a body or fluid to be heated 1 , for example water or air, two temperature sensors 4, 5, and a control system 3.
- Heating element 2 transforms a form of energy, either stored or received, preferably of electrical nature, into heat and is either placed in thermal contact with the body or submerged in the fluid to be heated.
- Control system 3 manages the amount of heat provided by heating element 2 and consequently has the information related to the amount of heat QF (t) involved.
- Tr(t)-Tc(t) temperature difference between heating element and body or fluid to be heated
- A surface of the heating element
- k thermal conduction coefficient through the surface of the heating element
- s length of the heat pathway.
- the detection of: one of more conditions such as an inadequate thermal exchange between the heating element and the heated body, a correct operation with adequate thermal exchange, a fault of the heating element or protective conditions of the same, a temperature measuring sensors fault, may be determined during the heating step of the heating element and in this case the heating dynamics may be obtained.
- ⁇ T(t) depend on the system being considered: e.g. on the type of heating element, on the type of fluid or body to be heated, on the masses involved.
- an experimental calibration of thresholds D A , DB, DC, described below is therefore necessary, establishing the following conditions:
- the thermal exchange conditions k are artificially degraded to the condition considered critical and the value of DB (insufficient thermal exchange threshold) is experimentally measured in such a condition; - the values of DB and Dc are set to prevent temperature measurement errors or loss of resolution of the temperature measurement from incorrectly identifying a type C fault condition.
- DA and Dc therefore depend on the temperature measurement system. The detection of these conditions is implemented by means of a diagnostic device, by measuring the temperatures in consecutive moments in time ti and t. 2 and evaluating the variation of ⁇ T in such consecutive moments in time.
- the discrete derivative D is determined and corresponds to:
- Sensors 4, 5 preferably of the NTC or thermocouple type, transform the physical amount temperature into an electrical signal; the subsequent conditioning block 7 of the signal has the function of amplifying and conducting the electrical signal within the range of electrical voltages that the board can recognise.
- the analogue-digital conversion block 8 allows to transform the analogue temperature values into digital form and render them processable according to the sequence described above to identify one of the conditions.
- the information for the generation of alarms by means of block 10 are thus available at microprocessor 9 and, if the diagnostic and control system are integrated, the microprocessor system also manages the driving of heating element by means of block 11.
- control and diagnostic functions are advantageously integrated in a single device because of device cost and implementation simplicity.
- the diagnostic device may also be separated from the control system which manages the power of the heating element, but in this case it must be interfaced with the latter to receive information on the activation status of the heating element.
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- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
A diagnostic device for a heating element for electrical household appliances comprises an electronic circuit (6) for acquiring and processing electrical signals from the temperature sensors (4, 5), and sending these electrical signals to a conditioning block (7) and to an analogue-digital conversion block (8) which transforms the temperature values from analogue to digital. The process identifies an exceeding condition of predetermined thresholds ((DA, DB, DC) and generates fault alarm signals.
Description
Diagnostic device for heating element
* ** *** ** *
Field of the invention The present invention relates to a diagnostic device for a heating element, intended to be used within a fluid or a body to be heated. State of the art
Heating elements, which are generally electrical resistances protected by appropriate materials, either insulating or not, are commonly used in the field of electrical household appliances or other types of apparatuses. Such heating elements are immersed in the container or in the closed environment to be heated and the output heat is used to heat both the fluid within the container and the material which either surrounds it or which is arranged near the heating element. Such elements, being highly cost-effective, are widely used in the industry, but are also subject to wear and must therefore be subjected to checks and to diagnostic processes to verify correct operation. A problem which often occurs in domestic environments in relation to heating elements in washing machines or dishwashers is the deposit of lime scale on the outside of the heating element with subsequent increasing reduction of the conductivity of the external wall of the element, which is in contact with the water to be heated, due to the increasing accumulation of lime scale, in the case of very hard water. This phenomenon becomes gradually more severe until irreversible damage to the heating element, which must be replaced, occurs. Various attempts have been made in the past to solve such drawbacks by developing diagnostic systems to be applied to the heating element and capable of detecting faults of various kind.
The need is therefore felt to overcome such drawbacks in this type of heating elements by means of diagnostic systems which detect the correct operation during its working life. Summary of the invention
The present invention relates to a diagnostic device for a heating element which overcomes the aforementioned drawbacks constructing a simple and reliable
device which is inexpensive to manufacture, manage and maintain. These objects of the present invention are obtained, according to a first aspect of the invention, by means of a diagnostic device for a heating element which in accordance with claim 1 comprises a heating element comprising an electronic circuit, adapted to acquire and process electrical signals from the temperature sensors and send said electrical signals to a conditioning block, an analogue- digital conversion block adapted to transform the analogue temperature values into digital and a processor adapted to identify an exceeding condition of predetermined thresholds and to generate fault alarms. According to a further aspect of the invention, the mentioned objects are obtained by means of a diagnostic process for a heating element which according to claim 5 comprises the following steps:
- definition of threshold values (DA, D8, Dc),
- detection of temperatures of a heating element and of a body or fluid in subsequent moments in time (ti. t2 ),
- calculation of the temperature variations in subsequent moments in time,
- calculation of the discreet derivative D = (ΔTfø) - ΔT(ti))/(t2- ti),
- output of an alarm signal for a condition in which a value of DA < D <DB or DC < D <DA or D < DC occurs. In virtue of the defining features of the invention, there are provided a diagnostic device and a process capable of detecting abnormal or failure conditions, in industrial or domestic applications in which a heating element is present for heating bodies or fluids. The device also performs the control and driving process of the heating element. The detection of operating conditions by the diagnostic device allows, according to the application and the needs, to generate alarms and/or perform targeted maintenance actions.
The control is capable of easily identifying faulty operating conditions by only measuring the temperatures of the heating element and the body or the fluid to be heated, using two appropriate temperature sensors Tr and Tc and by knowing the heat provided QF(O to the heating element. The conditions detectable with the diagnostic device of the invention comprise:
a) an inadequate thermal exchange between the heating element and the heated body, as for example the presence of lime scale on the surface of the heating element if the heated body is water; b) a correct operation with adequate thermal exchange; c) a faulty heating element or in protected conditions, such as for example the case of thermofuses inside the heating element or overheating protection devices; d) a fault in the control temperature measuring sensors.
The dependent claims refer to preferred embodiments of the invention.
List of figures Other objects and advantages of the present invention will be apparent in the light of the following detailed description of non-limitative embodiments of the invention, in relation to the following figures in which:
- Fig. 1 is a diagram of the system in which the device according to the present invention is employed; - Fig. 2 is a graph showing the operating curves of the device of the invention in various actual conditions;
- Fig. 3 is a graph showing the operating curves of the device of the invention compared against curves showing the values detected during operation;
- Fig. 4 is a block diagram showing the operation of a control circuit of the device according to the invention.
Detailed description of a preferred embodiment of the invention With particular reference to the figures, the diagnostic device according to the invention uses some theoretic notions presented below. In Fig. 1 , the system in which the heating element is used comprises a body or fluid to be heated 1 , for example water or air, two temperature sensors 4, 5, and a control system 3. Heating element 2 transforms a form of energy, either stored or received, preferably of electrical nature, into heat and is either placed in thermal contact with the body or submerged in the fluid to be heated. Control system 3 manages the amount of heat provided by heating element 2 and consequently has the information related to the amount of heat QF (t) involved.
This provided heat QF (t) will be transmitted by conduction, and therefore by means of the continuous contact between one molecule and an another of the
heating element until the surface, which separates heating element 2 from environment 1 in which it is immersed, is encountered. Through the surface, it then flows towards the heated body or fluid. The conduction transfer equation is
Fourier's law: Qc (t)= (ΔT(t) A-k)/s where:
Qc (t) = conducted heat flow;
T(t)= Tr(t)-Tc(t) = temperature difference between heating element and body or fluid to be heated; A = surface of the heating element; k = thermal conduction coefficient through the surface of the heating element; s = length of the heat pathway.
From this relation, it is deduced that given equal heat flow provided by Qc(t), the lower the thermal exchange coefficient k, the higher the ΔT(t) = Tr-Tc. Therefore: if the quantity of heat Qc(t) is known and value ΔT(t) is measured, information on the quality of thermal exchange k may be obtained.
The detection of: one of more conditions such as an inadequate thermal exchange between the heating element and the heated body, a correct operation with adequate thermal exchange, a fault of the heating element or protective conditions of the same, a temperature measuring sensors fault, may be determined during the heating step of the heating element and in this case the heating dynamics may be obtained.
In this case, the amount of heat is preferably provided in constant manner to the heating element, therefore the rate with which ΔT(Ϊ)= Tr(t)-Tc(t) varies depends only on the thermal exchange quality represented by the value of parameter k.
The situation is described by the following time trend, which represents the trend of variables ΔT(t) temperature difference, Qc (t) conducted heat flow, and QF (t) provided or generated heat within the heating element. No heat is provided in the initial condition and therefore the relation Qc(t)=QF(t)=0 applies.
Considering Fourier's law, it follows that ΔT(t)=0;
When heat QF* is provided to the heating element, the subsequent trend of measured ΔT(t) allows to determine the conditions indicated above according to the following table:
The variations in ΔT(t) depend on the system being considered: e.g. on the type of heating element, on the type of fluid or body to be heated, on the masses involved. In order to establish the abnormality conditions shown by curves A, C, D in figure 3, an experimental calibration of thresholds DA, DB, DC, described below is therefore necessary, establishing the following conditions:
- the system is operated in conditions of normality;
- the thermal exchange conditions k are artificially degraded to the condition considered critical and the value of DB (insufficient thermal exchange threshold) is experimentally measured in such a condition; - the values of DB and Dc are set to prevent temperature measurement errors or loss of resolution of the temperature measurement from incorrectly identifying a type C fault condition. DA and Dc therefore depend on the temperature measurement system. The detection of these conditions is implemented by means of a diagnostic device, by measuring the temperatures in consecutive moments in time ti and t.2 and
evaluating the variation of ΔT in such consecutive moments in time.
If the heat provided to the heating element is QF, the discrete derivative D is determined and corresponds to:
D = (ΔT(t2) - ΔT(t1))/(t2_ ti) which represents the slope of ΔT in the interval t 2 - t-i, the trends of which are shown in figure 3:
If D > D8 condition B occurs)
If DA < D <DB condition A occurs)
If Dc < D <DA condition C occurs) If D < Dc condition D occurs).
An embodiment of the diagnostic device and of the associated control device is described hereinafter with reference to Fig. 4.
An electronic board 6, preferably comprising a microcontroller 7, acquires the electrical signals from temperature sensors 4, 5 and processes them. Sensors 4, 5 preferably of the NTC or thermocouple type, transform the physical amount temperature into an electrical signal; the subsequent conditioning block 7 of the signal has the function of amplifying and conducting the electrical signal within the range of electrical voltages that the board can recognise. Subsequently, the analogue-digital conversion block 8 allows to transform the analogue temperature values into digital form and render them processable according to the sequence described above to identify one of the conditions. The information for the generation of alarms by means of block 10 are thus available at microprocessor 9 and, if the diagnostic and control system are integrated, the microprocessor system also manages the driving of heating element by means of block 11.
The control and diagnostic functions are advantageously integrated in a single device because of device cost and implementation simplicity. The diagnostic device may also be separated from the control system which manages the power of the heating element, but in this case it must be interfaced with the latter to receive information on the activation status of the heating element.
Claims
1. A diagnostic device for heating element (2) comprising an electronic circuit (6), adapted to acquire and process electrical signals from the temperature sensors (4, 5) and to send said electrical signals to a conditioning block (7), an analogue- digital conversion block (8) adapted to transform the temperature values from analogue to digital and a processor adapted to identify an exceeding condition of predetermined thresholds (DA, DB, DC) and to generate fault alarms.
2. A diagnostic device according to claim 1 , wherein the electronic circuit comprises a microcontroller (7).
3. A diagnostic device according to claim 1 or 2, wherein said sensors (4, 5) are of the NTC or thermocouple type.
4. A diagnostic device according to claim 1 , wherein management and driving means (11) of the heating element are provided.
5. A diagnostic method for a heating element by means of the heating device according to claim 1 , comprising the following steps:
- definition of threshold values (DA, DB, DC),
- detection of the temperatures of a heating element and of a body or fluid in consecutive moments in time (tι. t2),
- calculation of the temperature variations in such consecutive moments in time, - calculation of the discrete derivative D = (ΔT(t2) - ΔT(t-ι))/(t 2 - ti),
- output of an alarm signal for a condition in which a value of DA < D <DB or Dc < D <DA or D < DC occurs.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITRM2005A000623 | 2005-12-13 | ||
| ITRM20050623 ITRM20050623A1 (en) | 2005-12-13 | 2005-12-13 | DIAGNOSTIC DEVICE FOR HEATING ELEMENT. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2007068698A1 true WO2007068698A1 (en) | 2007-06-21 |
Family
ID=37895899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/EP2006/069606 WO2007068698A1 (en) | 2005-12-13 | 2006-12-12 | Diagnostic device for heating element |
Country Status (2)
| Country | Link |
|---|---|
| IT (1) | ITRM20050623A1 (en) |
| WO (1) | WO2007068698A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102016116598B3 (en) * | 2016-09-06 | 2017-11-16 | Miele & Cie. Kg | Method and computer program for heating control of a household appliance via virtual temperature and corresponding household appliance |
| DE102023203443A1 (en) | 2023-04-17 | 2024-10-17 | BSH Hausgeräte GmbH | laundry care device with a control system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4192992A (en) * | 1978-06-29 | 1980-03-11 | Kolene Corporation | Electric heating assembly for a fused bath |
| US4405855A (en) * | 1979-04-20 | 1983-09-20 | Ferrofil A/S | Method and apparatus for regulating the temperature of a heating element in a water heater |
| DE4244553A1 (en) * | 1992-07-09 | 1994-01-13 | Samsung Electronics Co Ltd | Unit to prevent overheating in washing machine with boiling cycle - has two thermistors for registering heating device temp. and washing water temp. respectively |
| EP0977008A2 (en) * | 1998-07-28 | 2000-02-02 | Dr. W. Kolb AG | Method and device for detecting the thickness of a deposition layer |
-
2005
- 2005-12-13 IT ITRM20050623 patent/ITRM20050623A1/en unknown
-
2006
- 2006-12-12 WO PCT/EP2006/069606 patent/WO2007068698A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4192992A (en) * | 1978-06-29 | 1980-03-11 | Kolene Corporation | Electric heating assembly for a fused bath |
| US4405855A (en) * | 1979-04-20 | 1983-09-20 | Ferrofil A/S | Method and apparatus for regulating the temperature of a heating element in a water heater |
| DE4244553A1 (en) * | 1992-07-09 | 1994-01-13 | Samsung Electronics Co Ltd | Unit to prevent overheating in washing machine with boiling cycle - has two thermistors for registering heating device temp. and washing water temp. respectively |
| EP0977008A2 (en) * | 1998-07-28 | 2000-02-02 | Dr. W. Kolb AG | Method and device for detecting the thickness of a deposition layer |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102016116598B3 (en) * | 2016-09-06 | 2017-11-16 | Miele & Cie. Kg | Method and computer program for heating control of a household appliance via virtual temperature and corresponding household appliance |
| DE102023203443A1 (en) | 2023-04-17 | 2024-10-17 | BSH Hausgeräte GmbH | laundry care device with a control system |
Also Published As
| Publication number | Publication date |
|---|---|
| ITRM20050623A1 (en) | 2007-06-14 |
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