AU627705B2 - Refrigerating unit for refrigerator - Google Patents

Abstract

In the refrigerating unit disclosed, a thermoelectric Peltier element (19) is used as a heat pump between a first heat-exchanger (20, 23, 24) inside a refrigerator (10) and a second heat-exchanger (18, 28, 29, 30, 31) on the outside of the rear wall (11) of the refrigerator. Both heat-exchangers have a metal block (20 or 18) connected in a heat-conducting manner, either directly or via a heat-conducting block (15), to the Peltier element (19). The supply of electrical energy to the feed circuit of the Peltier element (19) is automatically controlled by an electric circuit arrangement with a variable-resistance temperature probe. The refrigerating unit is characterized by low energy consumption, no perceptible current peaks on start-up, and a particularly long service life.

Description

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OPI DATE 01/08/89 APPLN. I D 27976 89 PCT WEAOJP DATE 31/08/3 '9 PCT NUMBER PCT/CH88/00228 INTERNATIONALE ANMELDUNG VEROFFENTLIGH AHDMVRRGUE

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INTERNATIONALE ZUSAMMENARBEIT AUF DEM GEBIET PATENTWESENS (PCT) (51) Internationale Patentkiassifikation 4 21/02 (11) Internationale Verbffentlichungsnummer: WO 89/ 06335 Al (43) Internationales Veriiffentlichungsdatum: 13. Juli 1989 (13.07.89) (21) Internationales Aktenzeichen: PCT/CH88/00228 (22) Internationales Anmieldedatumn: 27. Dezember 1988 (27.12.88) (81) Bestimmungsstaaten: AT (europdisches Patent), AU, BE (europiiisches Patent), BR, DE (europaisches Patent), DK, FI, FR (europdisches Patent), GB (europliisches Patent), IT (europdisches Patent), JP, KP, LU (europdisches Patent), NL (europaisches Patent), NO, SE (europaisches Patent), US.

Verbffentlicht Mil internationalem Recherclienbericht.

(31) Prioritiitsaktenzeichen: (32) Prioritaitsdatumn: (33) Prioritaitsland: 23/88-7 5. Januar 1988 (05.01.88) (71) Anmielder (ftir alle Bestimmungsstaaten ausser US): CHEMONORM AG [CH/CH]; H~hgaden/Elmerstrasse 6, CH-8852 Altendorf (CH).

(72) Erfinder; und Erfinder/Anmelder (nurfiir US) KCJNZLE, Virgil [CH/ CH]; Elmerstrasse 6, CH-8852 Altendorf (CH).

(74) Anwalt: SCHEIDEGGER, ZWICKY, WERNER CO.; Stampfenbachstliasse 48, Postfach, CH-8023 Ziurich (CH).

62 (54) Title: REFRIGERATING UNIHT FOR REFRIGERATOR (54) Bezeichnung: KOHLAGGREGAT FOR EINEN KLOHLSCHRANK (57) Abstract In the refrigerating unit disclosed, a thermoelectric 29 Peltier element (19) is used as a heat pump between a first heat-exchanger (20, 23, 24) inside a refrigerator (10) and a second heat-exchanger (18, 28, 29, 30, 3 1) on the outside of

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the rear wall (11) of the refrigerator. Both heat-exchangers have a metal block (20 or 18) connected in a heat-conducting manner, either directly or via a heat-conducting block to the Peltier element The supply of electrical en- 2 ergy to the feed circuit of the Peltier element (19) is automatically con' -oiled by an electric circuit arrangement with a variable-resistance temperature probe. The refrigerating unit is characterized by low energy consumption, no perceptible current peaks on start-up, and a particularly long service life.

(57) Zusammenfassung Bei diesem Kfihlaggregat ist emn thermoelektrisches Peltier-Element (19) als Wiirmepumpe zwischen einem ersten Wiirmetauscher (20, 23, 24) im Innern eines Kohlschrankes (10) und einem zweiten Wdrmetauscher (18, 28, 29, 30, 31) an der Aussenseite der Rilckwand (11) des Ktihlschrankes verwendet. Die beiden Wiirmetauscher weisen je einen Metaliblock bzw. 18) auf, der uber einen Wilrmeleitblock (15) bzw. unmittelbar mit dem Peltier-Element (19) in wiirmeleitender Verbindung stehen. Zur automatischen Regelung der Zufuhr elektrischer Energie zumn Speisestromkreis des Peltier-Elementes (19) ist eine elekirische Schaltungsanbordniung mit einem als Temperaturfuhfler dienenden variablen Widerstand vorgesehen. Dieses Kiihlaggregat hat einen verhdltnismilssig geringen Energieverbrauch, keine fiilbaren Einschalt-Leistungsspitzen und eine ausgesprochen lange Lebensdauer.

/jz~iI v,.j REFRIGERATION UNIT FOR A REFRIGERATOR The present invention relates to a refrigeration unit for a refrigerator, in particular a small refrigerator.

The object of the invention is to attempt to provide a refrigerating unit which has no moving parts, is substantially maintenance-free, has a long service life, uses only comparatively little electric energy for its operation and does not have any cut-in power peaks.

According to the present invention there is provided a refrigerator with a refrigerating unit in which at least one thermoelectric Peltier element is in thermal connection between first and second metal blocks spaced by a wall of the refrigerator, said first metal block being in thermally conductive connection with a first heat e:changer located inside the refrigerator and equipped with convection gills and the second metal block being in thermally conductive connection 9 with at least one further heat exchanger located outside of the refrigerator and equipped with convection gills, wherein an electric feed circuit of the Peltier element is connected to an electric circuit arrangement for controlling a supply of :e electric energy in such a way that heat transfer from the said first heat exchanger to the said further heat exchanger by S"means of the Peltier element is made possible, wherein the ••go convection gills of each of said heat exchangers are provided on heat tubes, which heat tubes are mounted and held in respective bores formed in the first and second metal blocks.

Details of the invention and the advantages achieved with it are explained in more detail in the following description of a preferred exemplary embodiment, with reference to the associated drawinqs, in which:

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jz 2- Fig. 1 shows a horizontal section along the line 1-1 in Fig. 2 through a part of a refrigerator and a plan view of a refrigerating unit according to the invention, built onto the refrigerator; Fig. 2 shows a cross section along to the line 2-2 in Fig. 1, on a greater scale; Fig. 3 shows an electric circuit arrangement for automatically controlling the energy supply to the thermoelectric Peltier element of the refrigerating unit.

According to Figs. 1 and 2, a refrigerator 10 has a rear wall 11 and two side walls 12 and 13, which project backwards beyond the rear wall 11. The inside surfaces of the refrigerator 10 are covered with an insulating layer 14. A heat conducting block 15, consisting of metal, preferably an aluminum alloy, is flushfitted into a clearance 16 of the rear wall 11 and of the insulating layer 14 there. On this heat conducting block there is fastened by means of screws 17 a metal block 18 arranged on the rear of the refrigerator, to be precise with a thermoelectric Peltier element 19 inbetween, which is clamped by means of the screws 17 between the two metal blocks 15 and 18. The Peltier element 19 is a commercially available model, which is supplied for example by the North American company Melcor under the type designation 1.4/127.06L. It is of sandwich-like design and has between two highly thermally conductive but electrically insulating end plates, which 04ifTA W)l -3are in thermally conductive contact with the two blocks and 18, a plurality of pairs of semiconductor members, which internally are electrically connected in series and form the feed circuit of the Peltier element. Since such Peltier elements are, as mentioned, commercially available, there is no need foa an extensive description and graphic representation here.

On the end of the heat conducting block 15 inside the refrigerator 10 there is fastened a further metal block 20.by means of screws 21, so that the blocks 15 and are in good thermally conductive connection. The metal block 20 has a bore 22, in which an end portion of a so-called heat tube 23 is seated, which is provided moreover with a relatively large number of convection gills 24. The heat tube 23 consists in a known way of an evacuated copper tube, closed at both ends, which is filled with saturated steam of high-purity water and is provided on its cylindrical inside surfaces with a liner acting as a wick (Fig. Heat tubes of this type are likewise commercially available and are manufactured for example by the company Furukawa Electric Co. Ltd., Tokyo (Japan), and marketed under the type designation SB 100. The metal block 20, the heat tube 23 and the gills 24 together form a first heat exchanger, which is arranged inside the refrigerator The metal block 18, already mentioned, on the rear of the refrigerator 10 has two parallel bores 26 and 27, in each of which there is seated an end portion of a •'f *1iI: i

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-4 heat tube 28 and 29, respectively. These two heat tubes 28 and 29 are of the same design as the heat tube 23 described above and are likewise provided with a relatively large number of convection gills 30 and 31, respectively. The metal block 18 and the heat tubes 28 and 29 with their gills 30 and 31 together form a second heat exchanger, which is located on the outside of the rear wall 11 of the refrigerator.

On the top of the m. tal block 18 there is fastened by means of screws 32 (Fig. 2) a housing 33, which contains an electric circuit arrangement for automatically controlling the supply of electric energy to the feed circuit, already mentioned, of the Peltier element 19. In Fig. 3, the electric circuit arrangement is represented diagrammatically and denoted generally by 34.

The electric circuit arrangement 34 has an electronic voltage comparator 35 with two inputs 36 and 37 as well as an output 38. To the positive input 36 there is applied.a constant reference voltage U 1 which is generated by means of a bridge rectifier 39, smoothed by two capacitors 40, 41 and a resistor 42, stabilized to a constant value Uo by means of a voltage stabilizer 43 and reduced to the desired value U, with the aid of a voltage divider 44, 45. The bridge rectifier 39 has two connection terminals 46 and 47, which are to be connected to the alternating current system via a not represented transformer.

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4i ii ii 1> At the negative input 37 of the voltage comparator 35 is the pick-off of a second voltage divider 48, 49, which reduces the stabilized voltage Ug to a variable value U 2 This second voltage divider consists 5 of anadjustable fixed resistor 48 and a variable resistor 49, which has a pronounced negative temperature coefficient (NTC) and serves as temperature sensor.

According to Fig. 2, the heat conducting block 15 is provided with a bore 50 for receiving the variable resistor 49, which is in connection with two connection terminals 51, 52 of the circuit arrangement, 34. A capacitor 53 serves for the suppression of transient fluctuations in the variable voltage U 2 The output 38 of the voltage comparator 35 is connected via a protective resistor 54 to the control input 55 of an electronic FET switch 56, which is looped into the feed circuit of the Peltier element 19. The circuit arrangement 34 has two terminals 57 and 58 for the connection of the Peltier element 19. With turnedon switch 56, the feeding of the Peltier element 19 directly with the unstabilized voltage from the bridge rectifier 39 takes place. Between the two connection terminals 57 and 58 for the Peltier element 19 there is a series circuit comprising a light-emitting diode 59 and an associated series resistor 60. Between the output 38 of the voltage comparator 35 and the positivepole of the unstabilized voltage of the bridge rectifier 39 there is a pull-up resistor 61, and with the aid of a zener diode S- 6 62 it is ensured that the voltage U 3 at the output 38 of the comparator 35 and at the control input 55 of the electronic switch 56 can in no way assume an inadmissibly high value. Between the positive input 36 and the output 38 of the voltage comparator 35 there is a series connection comprising a resistor 63 and a diode 64, in order to effect a positive feedback whenever the voltage U. exceeds the voltage U,.

The operating principle of the refrigerating unit described is briefly as follows: It is assumed that an alternating voltage of, for example, 10 volts, is applied to the terminals 46 and 47.

If and for as long as the temperature inside the refrigerator 10 exceeds a value, of for example which can be chosen in certain limits by means of the adjustable resistor 48, the variable resistor 49 serving as temperature sensor has a relatively high resistance value, so that the variable voltage Ui at the negative input 37 of the voltage comparator 35 exceeds the constant reference voltage U, at the positive input 36. At the control input 55 of the electronic switch 56 there is then consequently a positive voltage U 3 by which the switch 56 is forced into its conductive state. As a result, the feed circuit of the Peltier element 19 is closed and the latter causes heat to pump from the heat exchanger 20, 23, 24 inside the refrigerator to the heat exchanger 18, 28, 29, 30, 31 on the outside of the rear wall 11 of the refrigerator. This offects a heat 7 C 4 ftt i 9- 7 transfer from inside the refrigerator to outside and a lowering of the temperature inside the refrigerator. In parallel with the feed circuit of the Peltier element 19, the light-emitting diode 59 is also switched on, in order to indicate visually the activated state of the refrigerating unit.

With dropping temperature in the refrigerator, the resistance value of the variable resistor 49, serving as temperature sensor, becomes smaller, which has as a consequence a. corresponding reduction in the variable voltage U 2 at the negative input 37 of the voltage comparator 35. If the variable voltage U 2 drops below the value of the reference voltage Ul, the voltage U 3 at the control input 55 of the electronic switch 56 suddenly becomes approximately equal to zero. As a result, the switch 56 is forced into its non-conductive or blocking state and thus the feed circuit of the Peltier element 19 is interrupted. The refrigerating unit is then in an inactive state, which is indicated visually by extinguishing of the light-emitting diode 59, On renewed rising of the temperature inside the refrigerator, the cycle described is repeated. It is thus a so-called two-point control, which allows the j temperature inside the refrigerator to be kept constant to approximately 0.15*C. The cutting-in and cuttingout of the feed circuit of the Peltier element 19 happens virtually without any loss, without excessive power peaks during cutting-in.

8 -8- Depending on the temperature difference of the two heat exchangers insid and outside, the refrigerating capacity of the refrigerating unit is in the range from to 30 watts. With corresponding adjustment of the adjustable resistor 48, it is possible to lower the temperature inside the refrigerator to about 2*C when the outside temperature is in the range of the usual domestic temperature, The refrigerating unit described needs no maintenance and has an extremely long service life of the order of 150,000 hours or more.

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Claims (4)

1. A refrigerator with a refrigerating unit in which at least one thermoelectric Peltier element i in thermal connection between first and second metal blocks spaced by a wall of the refrigerator, said first metal block being in thermally conductive connection with a first heat exchanger located inside the refrigerator and equipped with convection gills and the second metal block being in thermally conductive connection with at least one further heat exchanger located outside of the refrigerator and equipped with convection gills, wherein an electric feed circuit of the Peltier element is connected to an electric circuit arrangement for controlling a supply of electric energy in such a way that heat transfer from the said first heat exchanger to the said further heat exchanger by means of the Peltier element is made possible, wherein the convection gills of each of said heat exchangers are provided on heat tubes, which heat tubes are mounted and held in respective bores formed in the first and second metal blocks.

2. A refrigerator according to claim 1, wherein said first metal block passes through said refrigerator wall and comprises two interconnected separate block parts, one of them being held in a through-passage formed in said refrigerator wall and forming a support for all other parts of the refrigerating unit.

3. A refrigerator according to claim 1 or 2, characterised in that the electric circuit arrangement has an electronic voltage comparator with two inputs, at the one input of which there is a constant voltage and at the other input of which there is a variable voltage, which can be influenced by the member serving as temperature sensor, and in that an output of the voltage comparator is connected to the control input of an electronic switch, which is looped into the feed circuit of the Peltier element. 10

4. A refrigerator according to any one of claims 1 to 3, wherein the bores in said metal blocks extend parallel to said refrigerator wall and are spaced from said wall at a distance such that one side of each of the conVection gills provided on the heat tubes is located proximate to said refrigerator wall. A refrigerator substantially as herein described with reference to and as illustrated in the accompanying drawings. Dated this 16th day of June, 1992. CHEMONORM AG By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. :l l ok **4 *i