EP0563751B1 - Dispositif pour capter et contrÔler la formation de givre sur l'évaporateur d'un réfrigérateur - Google Patents

Dispositif pour capter et contrÔler la formation de givre sur l'évaporateur d'un réfrigérateur Download PDF

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Publication number
EP0563751B1
EP0563751B1 EP93104737A EP93104737A EP0563751B1 EP 0563751 B1 EP0563751 B1 EP 0563751B1 EP 93104737 A EP93104737 A EP 93104737A EP 93104737 A EP93104737 A EP 93104737A EP 0563751 B1 EP0563751 B1 EP 0563751B1
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EP
European Patent Office
Prior art keywords
evaporator
frost
flat elements
refrigerator
sensing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP93104737A
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German (de)
English (en)
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EP0563751A1 (fr
Inventor
Daniele c/o Whirlpool Europe S.r.l. Turetta
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Whirlpool Europe BV
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Whirlpool Europe BV
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Publication date
Application filed by Whirlpool Europe BV filed Critical Whirlpool Europe BV
Publication of EP0563751A1 publication Critical patent/EP0563751A1/fr
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Publication of EP0563751B1 publication Critical patent/EP0563751B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/02—Detecting the presence of frost or condensate

Definitions

  • This invention relates to a device for sensing and controlling frost formation on the evaporator of a refrigerator, of the type specified in the pre-characterising portion of appended claim 1.
  • frost forms on the evaporator during the use of the refrigerator. This is due to the condensation of moisture on the evaporator (which has a temperature considerably lower than any other part of the refrigerator), this moisture being present in the compartment by having penetrated into it following the opening of its door. The frost is also due to condensation of the moisture which is released naturally by the food placed in the refrigerator for its preservation.
  • Said defrosting is effected in various ways.
  • the evaporator may be defrosted automatically after a fixed period of operation of the usual refrigeration circuit of the refrigerator (or of the known compressor of this circuit).
  • this method of defrosting does not take account of whether it is really necessary to remove frost from the evaporator at that time, hence defrosting may take place when there is no real need for it (with obvious disadvantages in terms of refrigerator operation).
  • a device for sensing the presence of frost on the evaporator and using capacitive sensing means is known from the above mentioned US-A- 4347709, these sensing means either activating or not activating the heating element associated with the evaporator (while at the same time interrupting the operation of the refrigeration circuit of which this latter forms part).
  • This device is based on the use of the evaporator itself as one plate of the capacitor. Due to the earth connection of the evaporator through the compressor, and due to the related instability of the signal caused by the variation vs. time of the earth potential, said device does not allow accurate measurement of the frost thickness on the evaporator, and is able to sense only whether a layer is present on a given portion of it. Consequently, operation of the heating element associated with the evaporator, based on the sensing of frost on it, may sometimes be unnecessary, so negatively affecting the performance of the refrigerator.
  • An object of the present invention is to provide a device for sensing the presence of frost on the evaporator by which this latter is defrosted only if it is covered with a layer of frost to the extent of changing its heat transfer characteristics.
  • a further object is to provide a device of the aforesaid type which is of low implementation cost and which enables the evaporator defrosting process to be optimized.
  • a further object of the invention is to provide a device for evaluating the thickness of frost on an evaporator which is of simple construction, of reliable use and operation, and is able to activate the heating element associated with the evaporator only when on the surface of this latter there is a quantity of frost present such as to change its heat transfer characteristics.
  • a known finned evaporator is indicated overall by 1 and comprises parallel fins 2 with opposing surfaces 2A and 2B. On the surface 2A of a first of two adjacent fins and on the facing surface 2B of the second there are arranged two flat elements 4 and 5 connected to electrical lines 6 and 7.
  • insulating elements 10 and 11 Between the elements and the corresponding fins there are interposed flat electrically insulating elements 10 and 11. These insulating elements have high thermal conductivity and are formed for example of mica, alumina or similar materials. These elements are associated with the faces 4A and 5A of the elements 4 and 5, while the surfaces 4B and 5B of these latter face each other.
  • the electrical lines 6 and 7 terminate in an operating and control circuit 12 for powering the capacitor 8 (defining a capacitive frost sensor) and for powering (or not powering) a usual defrosting resistance element (or other equivalent heating element) associated with the evaporator 1.
  • the circuit 12 is therefore able to alter the state of the resistance element 13 (to cause it to operate or remain at rest by powering it or not).
  • the circuit 12 evaluates the capacitance of the capacitor 8, said capacitance varying with the deposition of frost on the evaporator 1.
  • the frost replaces the air which forms the dielectric of the capacitor 8 between the faces 4B and 5B of its elements or plates 4, 5 during the initial stage of use of the refrigerator or following defrosting of the evaporator.
  • the capacitor 8 can be formed as shown in Figure 3. In this, parts corresponding to those of Figures 1 and 2 are indicated by the same reference numerals.
  • the plates 4 and 5 of the capacitor 8 are not located on adjacent consecutive fins 2 but on two alternate fins, between which there is a fin without flat elements.
  • the plates are positioned on those faces of the corresponding fins which face the intermediate fin.
  • the intermediate fin forms part of the dielectric of the capacitor 8 and its presence results in a reduction in the capacitance bf the electrical capacitor.
  • FIG. 6 in which parts corresponding to those of the already described figures are indicated by the same reference numerals, shows the electrical operating and control circuit 12 for the heating element or resistance element 13 and for powering the capacitor 8.
  • the capacitor is connected to a usual oscillator circuit 30 which powers it and which is itself connected to a frequency/voltage converted member 31 connected to a unit 32 for controlling the defrosting or heating element 13.
  • the capacitor 8 is connected in parallel with a second capacitor 36 for increasing the total capacitance measurable by the circuit 12.
  • the converter 31 is also connected to earth at 38 and to a power line (not shown) by which power also reaches the capacitor 8.
  • the unit 32 is connected to this converter and comprises a comparator 39 with its inverting input 40 connected to the converter 31, its non-inverting input 41 connected to a current divider 42 and its output 43 to the base 44 of a transistor 45 via a resistor 46.
  • the transistor emitter 47 is connected to earth at 48 and the collector 50 is connected to a relay 51 (powered by said power line) operating on a movable contactor 52 for closing fixed contacts 54 in the power line 55 to the resistance element 13.
  • frost similar to ice
  • the frost has a dielectric value much higher than the air present between the plates 2 of the capacitor 8 at the commencement of use of the refrigerator or after its evaporator has been defrosted.
  • this latter increases considerably as the layer of frost on the evaporator increases and the frost deposits between the capacitor plates.
  • the capacitance variation is measured continuously by the circuit 12 in the illustrated example.
  • a signal V A from the capacitor 8 is fed to the oscillator (which at the same time feeds the capacitor) 30. This latter feeds a signal of determined frequency to the converter 31.
  • the comparator compares the signal V B with a reference signal V R defined (adjustably) by the voltage divider 42 and corresponding to a layer of frost on the evaporator 1 of an extent which does not (or only negligibly) affect the heat transfer characteristics of the evaporator.
  • the comparator When the signal V B exceeds the signal V R , the comparator generates a signal V C which reaches the base 44 of the transistor 45, which becomes saturated. In this manner the relay 51 is connected to earth and can act on the contactor 52 to close its contacts 54. In this manner the resistance element 13 becomes powered and can begin to defrost the evaporator. This powering lasts for a predetermined time sufficient to obtain the required defrosting.
  • the unit 32 forms part of a member which controls the refrigerator operation, preferably of microprocessor type.
  • the unit 32 can be provided with an electrical branch 50 (shown dashed in Figure 6) which connects it to the refrigerator control member and along which the signal V C reaching the transistor 45 is fed.
  • an electrical branch 50 shown dashed in Figure 6 which connects it to the refrigerator control member and along which the signal V C reaching the transistor 45 is fed.
  • the conductive means can' be used for determining when the evaporator defrosting is complete. This is achieved via the means used for evaluating the frost formation.
  • said means generally evaluate the presence of frost on the evaporator and act on the heating element in the sense of activating it (to defrost the evaporator) or to halt its operation (to hence halt defrosting when said means sense the absence of frost on said evaporator).
  • the alteration in the state of the heating element is effected on the basis of the measurement of frost on the evaporator by the use of said conductive means.
  • This measurement can be discrete (ie when the frost has been measured the conductive means can be deactivated by the control means) or continuous (said conductive means then sensing the variation in the frost layer on the evaporator, to halt evaporator defrosting when the layer on it has been reduced to the extent of not affecting heat transfer between the evaporator and the environment in which it is contained).

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Defrosting Systems (AREA)

Claims (9)

  1. Dispositif de détection et de maítrise de la formation de givre sur l'évaporateur (1) d'un réfrigérateur, comprenant un élément de chauffage (13) associé à l'évaporateur pour son dégivrage, un dispositif alimenté électriquement (8) destiné à créer un signal électrique (VA) qui varie avec la présence de givre sur l'évaporateur, un dispositif d'activation et destiné à alimenter le dispositif à alimentation électrique (8), et un dispositif de commande et de comparaison (12) destiné à comparer ledit signal (VA) à un signal électrique prédéterminé de référence (VR) qui correspond à une étendue prédéterminée du givre sur l'évaporateur, le dispositif de commande et de comparaison (12) agissant sur l'élément de chauffage (13) d'après cette comparaison, et le dispositif à alimentation électrique (8) comprenant au moins deux éléments plats (4, 5) qui sont supportés par l'évaporateur, connectés électriquement au dispositif de commande et de comparaison (12) et isolés électriquement de l'évaporateur, caractérisé en ce que les éléments plats (4, 5) délimitent les plaques d'un condensateur (8).
  2. Dispositif selon la revendication 1, caractérisé en ce que les deux éléments plats (4, 5) sont associés à des ailettes consécutives adjacentes (2) de l'évaporateur (1), les éléments plats (4, 5) étant associés aux faces opposées (2A, 2B) des ailettes consécutives adjacentes (2).
  3. Dispositif selon la revendication 2, caractérisé en ce que des éléments isolés électriquement (10, 11) de conductibilité thermique élevée sont placés entre les éléments plats (4, 5) et les ailettes (2) qui les supportent.
  4. Dispositif selon la revendication 1, caractérisé en ce que les deux éléments plats (4, 5) sont placés sur des ailettes (2) de l'évaporateur (1) qui alternent, et une ailette intermédiaire supplémentaire (2) est disposée entre les éléments plats (4, 5).
  5. Dispositif selon la revendication 1, caractérisé en ce que le dispositif de commande et de comparaison (12) comporte au moins une unité de commande (32) qui comprend au moins un organe de comparaison (39) auquel est transmis le signal de référence (VR), et un premier dispositif de commutation (45) connecté dans la ligne qui alimente le dispositif (51) de commande du second dispositif de commutation (52) connecté à la ligne (55) d'alimentation de l'élément de chauffage (13).
  6. Dispositif selon la revendication 5, caractérisé en ce que le premier dispositif de commutation est formé d'au moins un commutateur statique (45).
  7. Dispositif selon la revendication 5, caractérisé en ce que le dispositif de commande est un relais (51).
  8. Dispositif selon la revendication 5, caractérisé en ce que le second dispositif de commutation est un contacteur mobile (52).
  9. Application d'un dispositif selon l'une quelconque des revendications précédentes à la détection et à la maítrise de la formation du givre sur l'évaporateur d'un réfrigérateur.
EP93104737A 1992-03-31 1993-03-23 Dispositif pour capter et contrÔler la formation de givre sur l'évaporateur d'un réfrigérateur Expired - Lifetime EP0563751B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI920769A IT1255045B (it) 1992-03-31 1992-03-31 Metodo e dispositivo per rilevare e controllare la formazione di brina su un evaporatore di un refrigeratore
ITMI920769 1992-03-31

Publications (2)

Publication Number Publication Date
EP0563751A1 EP0563751A1 (fr) 1993-10-06
EP0563751B1 true EP0563751B1 (fr) 1998-06-03

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP93104737A Expired - Lifetime EP0563751B1 (fr) 1992-03-31 1993-03-23 Dispositif pour capter et contrÔler la formation de givre sur l'évaporateur d'un réfrigérateur

Country Status (3)

Country Link
EP (1) EP0563751B1 (fr)
DE (1) DE69318878T2 (fr)
IT (1) IT1255045B (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69426567T2 (de) * 1994-11-17 2001-06-21 Whirlpool Europ Vorrichtung zur Feststellung von Eis auf einem Kühlgerät-Verdampfer
IT240417Y1 (it) * 1996-01-30 2001-04-02 Whirlpool Europ S R L Dispositivo per rilevare la formazione di brina e per eliminarlaper riscaldamento particolarmente per evaporatori di frigoriferi
DE10221903A1 (de) * 2002-05-16 2003-12-04 Bsh Bosch Siemens Hausgeraete Gefriergerät mit Abtauanzeige
US7836710B2 (en) 2002-05-16 2010-11-23 Bsh Bosch Und Siemens Hausgeraete Gmbh Freezer with defrosting indicator
WO2008009701A1 (fr) * 2006-07-18 2008-01-24 Arcelik Anonim Sirketi Dispositif de refroidissement
US9562757B2 (en) 2009-10-02 2017-02-07 The Controls Group, Inc. Removal of an accumulated frozen substance from a cooling unit
ITUD20130108A1 (it) 2013-08-13 2015-02-14 New Technology Consultants N T C Dispositivo di controllo del funzionamento di uno scambiatore di calore, scambiatore di calore comprendente detto dispositivo e relativo procedimento di controllo
DE102014221317A1 (de) * 2014-10-21 2016-04-21 BSH Hausgeräte GmbH Haushaltskältegerät mit einem Reiferkennungssensor, welcher zur Erfassung einer Reifbildung an einem Verdampfer einer Kälteerzeugungsvorrichtung des Haushaltskältegeräts ausgebildet ist
CN110749151A (zh) * 2019-10-16 2020-02-04 长虹美菱股份有限公司 一种冰箱化霜控制方法及冰箱

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4347709A (en) * 1981-01-19 1982-09-07 Honeywell Inc. Demand defrost sensor
US4732009A (en) * 1986-06-26 1988-03-22 Whirlpool Corporation Refrigerator compartment and method for accurately controlled temperature

Also Published As

Publication number Publication date
EP0563751A1 (fr) 1993-10-06
ITMI920769A1 (it) 1993-10-01
ITMI920769A0 (it) 1992-03-31
IT1255045B (it) 1995-10-17
DE69318878D1 (de) 1998-07-09
DE69318878T2 (de) 1998-10-22

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