Abstract:
A heater apparatus divides a heater capacity (heater wire), connects the divided heater wire portions to each other outside the a heat insulating layer, changes a connection mode irrespective of which of a 100 V system or a 200 V system is used as a supply voltage, and thereby suppresses a heater temperature to within a safe range even in a continuous current conduction mode, and uses a common heater and suppress management cost. Furthermore, since the heater wire portions are connected to each other outside the heat insulating layer for the heater embedded in the heat insulating layer of a refrigerator, the heater apparatus is capable of reducing production loss due to misconnections and using a common heater.

Description:
TECHNICAL FIELD 
     The present invention relates to a heater apparatus used for an electric apparatus such as a refrigerator. 
     BACKGROUND ART 
     A refrigerator is generally constructed of an inner box formed through vacuum molding, metal outer walls outside the inner box, wall surfaces surrounding three sides of a storeroom of the refrigerator with a urethane foam heat insulator injected and made to foam in a space formed between the inner box and the metal outer wall, and a door provided in an opening of the storeroom in a freely openable/closable manner with its interior also filled with a urethane foam heat insulator. 
     Furthermore, many electrical components such as various temperature sensors for detecting temperatures of various storerooms provided in the refrigerator and detecting completion of defrosting, a fan that blows air to the respective storerooms, a damper for adjusting the amount of cold air blow are arranged in the refrigerator and these electrical components are connected to a control substrate set up outside the refrigerator via lead wires. 
     Furthermore, the refrigerator uses heaters for temperature compensation inside the refrigerator, for prevention of condensation, for prevention of freezing, for defrosting or the like (e.g., see Patent Literature 1). These heaters are connected to the control substrate outside the refrigerator via lead wires in a heat insulating layer. Furthermore, the condensation prevention heater and storeroom temperature compensation heater are arranged on the urethane heat insulating layer side from the standpoint of securing an accommodation volume and safety such as preventing the heaters from contacting people. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Utility Model Laid-Open No. 61-203285 
     SUMMARY OF INVENTION 
     Technical Problem 
     Since a supply voltage of a refrigerator varies depending on its destination (country), heaters specific to their respective supply voltages are used, but heaters are preferably standardized using same exterior parts so as to cover a broader range of destinations. 
     Furthermore, condensation prevention heaters and storeroom temperature compensation heaters are preferably standardized so that the same heaters can be used for different models of refrigerators in order to reduce management cost and eliminate production loss due to misconnections among different models caused by providing different types of heaters for different models of refrigerators. 
     In the case of a refrigerator, it is difficult to replace a heater arranged in a heat insulating layer after urethane foaming. Therefore, if heaters are misconnected, the heaters are totally wasted and production loss is great. For example, a temperature compensation heater for a vegetable room, a freezing prevention heater of a water supply tank and a condensation prevention heater on the mating surface of the refrigerator door are attached before urethane foaming, but once urethane of the cabinet or door is foamed, it is difficult to extract the heaters unless the cabinet or door is destroyed. 
     Furthermore, an identical heater is preferably used commonly for heaters for temperature compensation, freezing prevention, condensation prevention or the like, but since the heating value differs depending on the use, to realize standardization, it is necessary to assume a current conduction time and a current interruption time as one cycle, adjust the current conduction rate which is the ratio of the current conduction time in the one cycle through an adjustment mechanism and adjust the heating value of the heater. However, should the current conduction rate adjustment mechanism of the heater fail, the current may be continuously applied to the heater and exceed its safe temperature range. 
     Therefore, a heater to be shared is intended for extremely limited use. A freezing prevention heater for a water supply tank or a condensation prevention heater for the refrigerator door in particular has a small heater size and it is impossible to suppress the wattage density of heater wires (referring to a value obtained by dividing the heater capacity (wattage) by the heater surface area, that is, wattage per unit area or value obtained by dividing the heater capacity (wattage) by the length of the heater wire) to within a safe range. 
     Furthermore, a heater may be shared using a voltage divider circuit or using a transformer to transform its voltage as described in Patent Literature 1, but these methods not only result in high cost but also require extra space for installation of the transformer or the like, which becomes a demerit. 
     In view of the above-described problems, it is an object of the present invention to provide a heater apparatus capable of sharing a heater in an electric apparatus such as a refrigerator. 
     Solution to Problem 
     In order to attain the above described object, the present invention provides a heater apparatus provided with a heater including a heater wire that is incorporated in an exterior member, wherein the heater wire of the heater is divided into a plurality of heater wires and the divided heater wire portions are connected together outside the exterior member according to a supply voltage. 
     According to the above-described configuration, the heater wire of the heater (heater capacity) is divided and the divided heater wire portions are connected together outside the exterior member, and it is thereby possible to change the heater wire connection mode according to a supply voltage specification to change a heating value of the heater, and thereby suppress the heater temperature to within a safe range even in continuous current conduction mode. Therefore, it is possible to use a common heater when the supply voltage specification is any one of a 100 V system (100 V to 127 V) and a 200 V system (200 V to 240 V) and suppress management cost. Furthermore, since a common heater can be used for both supply voltage specifications, it is possible to eliminate the necessity for destroying the exterior member due to misconnections of the heaters and reduce production loss. 
     The exterior member includes all kinds of electric apparatus incorporating a heater. The present invention is preferably applicable to an exterior member which has an embedded heater that cannot be removed without destruction in particular. For example, the present invention is preferably applicable to an electric apparatus in which a heater is embedded in an exterior member made up of a urethane heat insulating layer. Examples of such an electric apparatus include refrigerators, hot carpets and floor heating appliances. 
     Furthermore, examples of the method of changing the mode in which the heater wires are connected outside the exterior member according to the supply voltage specification include parallel connection or series connection of the divided heater wire portions. For example, the divided heater wire portions may be connected each other in parallel in the case of a power supply voltage 100 V system and the divided heater wire portions may be connected each other in series in the case of a 200 V system to thereby suppress heating values of the respective heater wires. 
     As an aspect of external connection between the heater wires, a control substrate that controls the heater is used. That is, a wiring pattern constituting part of the electric circuit of the heater is formed on the control substrate and the heater wires are connected together in parallel or in series using this wiring pattern. 
     As a preferred embodiment, a first control substrate having a wiring pattern in which heater wires are connected in parallel and a second control substrate having a wiring pattern in which heater wires are connected in series may be prepared, and the choice of which control substrate to use may be determined according to the supply voltage specification. 
     In the heater apparatus in which heater wires are connected in parallel, the first control substrate that drives and controls the heater is provided outside the exterior member, a wiring pattern for connecting a plurality of heater wires in parallel is formed on the first control substrate, end lead wires connected to both ends of the heater wire and an intermediate lead wire for connecting the divided heater wire portions outside the heater are led out of the exterior member, and also connected to a connection section of the first control substrate and the divided heater wire portions are connected each other in parallel. 
     In the heater apparatus in which heater wires are connected in series, the second control substrate that drives and controls the heater is provided outside the exterior member, a wiring pattern for connecting a plurality of heater wires in series is formed on the second control substrate, end lead wires connected to both ends of the heater wire and an intermediate lead wire for connecting the divided heater wire portions outside the heater are led out of the exterior member, and also connected to a connection section of the second control substrate and the divided heater wire portions are connected in series. 
     Connecting the heater on the first control substrate or the second control substrate in this way provides an advantage that the heater connection mode is automatically determined if a predetermined control substrate (first control substrate or second control substrate) is prepared and lead wires from the heater are attached thereto without being aware of (managing) whether a heater circuit connected is connected in parallel or in series during production/assembly. 
     Furthermore, in the heater apparatus in which the heater wires are connected in parallel and the heater apparatus in which the heater wires are connected in series, a change section that changes the current conduction rate of the heater is provided outside the exterior member and the heating value of the heater is adjusted through the change section. 
     Irrespective of whether the supply voltage is, for example, a specification of 100 V to 127 V (100 V system) or a specification of 200 V to 240 V (200 V system), the heating value can be adjusted within these ranges by the change section changing the current conduction rate of the heater. 
     In particular, the heater apparatus in the above configuration can be assembled into a refrigerator provided with a heat insulating box that includes a heat insulating layer of urethane foam or the like filling a space formed of an inner box and an outer wall and uses the interior of the inner box as a storeroom. That is, the heater apparatus is applicable to a refrigerator in which the heater of the heater apparatus is embedded in a heat insulating layer and divided heater wire portions are connected together outside the heat insulating layer according to a supply voltage. 
     It is thereby possible to make connections according to the power supply voltage specification outside the heat insulating layer by switching the control substrate even after urethane foaming and suppress production loss. 
     As a method of assembling a heater apparatus into a refrigerator, a method is provided for a refrigerator provided with a heat insulating box that includes a heat insulating layer of urethane foam or the like filling a space formed of an inner box and an outer wall and uses the interior of the inner box as a storeroom, including embedding a heater having a plurality of divided heater wire portions in the heat insulating layer, causing end lead wires connected to both ends of the heater wire and an intermediate lead wire that connects the divided heater wire portions to be led out of the heat insulating layer, connecting the lead wires to a connection section of a control substrate that controls the heater and connecting the heater wires in parallel or in series in a wiring pattern formed on the control substrate. 
     By dividing the heater capacity (heater wire) and changing connections according to a supply voltage specification in this way, it is possible to use a common heater for both supply voltages of a 100 V system and a 200 V system, suppress management cost and reduce production loss due to misconnections. 
     Advantageous Effects of Invention 
     As described above, according to the present invention, the heater capacity (heater wire) is divided and the divided heater wire portions are connected together outside the heater, and it is thereby possible to change the connection mode according to a supply voltage and suppress the heater temperature to within a safe range even in continuous current conduction mode. Therefore, it is possible to use a common heater for any supply voltage specification and suppress management cost, and since heater wires are connected together outside the heater, it is possible to reduce production loss due to misconnections. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view illustrating an aluminum foil heater of a refrigerator. 
         FIG. 2  is a diagram illustrating two heater wires connected in series in a control substrate. 
         FIG. 3  is a diagram illustrating two heater wires connected in series in a control substrate. 
         FIG. 4  is a cross-sectional view of a refrigerator illustrating various heater connections. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment in which a heater apparatus according to the present invention is applied to a refrigerator will be described with reference to the accompanying drawings. As shown in  FIG. 4 , a refrigerator is constructed of a cabinet  1  and a door  2 . In the cabinet  1 , a space is formed between an inner box  3  formed through vacuum molding and a metal outer wall  4  as an outer box arranged so as to surround the outside of the inner box  3 , a urethane foam heat insulator that is made to foam by chemical reaction is injected into this space and the urethane foam heat insulator is made to foam and a foamed heat insulating layer  5  is formed in and filling the space. As a result, a storeroom  6  having insulating wall surfaces that surround the three sides is formed inside the inner box  3 . 
     As shown in  FIG. 4 , the storeroom  6  in the present embodiment is made up of three rooms; a cold room on a top row, a freezing room on a middle row and a vegetable room on a bottom row. An opening  7  of the storeroom  6  is covered with the door  2 , provided in a freely openable/closable manner, which is formed in the same way as described above and the interior of which is filled with a foamed urethane heat insulator. 
     Furthermore, many electrical components are arranged in the storeroom  6  such as various temperature sensors that detect a temperature of each part of the storeroom  6  and detect completion of defrosting, a fan  9  that blows cold air into the storeroom  6  and a damper  10  for adjusting the amount of cold air blow. These electrical components are connected to a control substrate  12  via lead wires (not shown). The electrical components output a signal to the control substrate  12  or are driven and controlled by a command from the control substrate  12 . 
     A compressor  11  that constitutes a refrigerant cycle is arranged in a space formed on the rear side of a vegetable room  17  and on the rear side of and outside the heat insulating layer  5  of the cabinet  1 . An electrical component box  33  is provided in this space and the control substrate  12  is accommodated in this electrical component box  33 . 
     Furthermore, a freezing prevention heater  15  of a water supply tank  14  is embedded in a partition  13  between the cold room and the freezing room on the urethane foam heat insulating layer side. Furthermore, a temperature compensation heater  18  is embedded on the heat insulating layer side of the vegetable room  17  on the bottom row. These freezing prevention heater  15  and temperature compensation heater  18  are embedded in the heat insulating layer  5  when the cabinet  1  is formed and designed not to be removable after the heat insulating layer is molded. Therefore, in this embodiment, the foamed heat insulating layer  5  can be illustrated as an exterior member in which the heater  18  is embedded, and without the destruction of which the heater  18  cannot be extracted. A defrosting heater  32  for defrosting a refrigerant cycle evaporator is arranged below the evaporator in the cooling room on the rear side of the vegetable room. 
       FIG. 1  is an example of the temperature compensation heater. This heater  18  is a plane heater made up of heater wires  22  and  23  arranged on a metal foil  21  in a predetermined pattern at a predetermined wattage density. The heater wires  22  and  23  are formed by coating the circumference of a nichrome wire coil with an insulator of PVC (polyvinyl chloride) or the like and arranged in a predetermined pattern such as a serpentine pattern. 
     The heater wires  22  and  23  are divided by two at an intermediate position and configured of a first heater wire  22  and a second heater wire  23 . The first heater wire  22  and the second heater wire  23  divide the capacity of the heater  18  by half. These heater wires  22  and  23 , and the divided portions of both heater wires are connected to lead wires  24 ,  25  and  26  and hermetically sealed with an insulating member  27 . As shown in  FIG. 2  and  FIG. 3 , these lead wires  24 ,  25  and  26  are connected to a connection section  31  of the control substrate  12  that controls the heater  18 . The three lead wires  24 ,  25  and  26  are bundled to a central part of the heater  18  so as to facilitate connections with the control substrate  12 . 
     The metal foil  21  is an aluminum foil and bonded to the heater wires  22  and  23  by means of a pressure sensitive adhesive double coated tape or adhesion. It goes without saying that a silicon heater may also be used instead of the aluminum foil heater. The heater  18  is constructed of the metal foil  21  and the heater wires  22  and  23 . Therefore, the metal foil  21  does not correspond to the exterior member of the present invention in the present embodiment. 
     A wire harness having a connector at a distal end thereof can be used for the lead wires  24 ,  25  and  26 . The connector can be detachably connected to the connection section  31  of the control substrate  12 . 
     Such a wire diameter of the lead wires  24 ,  25  and  26  is adopted that allows a sufficient current to flow irrespective of which of a 100 V system supply voltage of 100 V to 127 V or a 200 V system supply voltage of 200 V to 240 V is used. Since the lead wires  24 ,  25  and  26  may obstruct the flow of the urethane foam that forms the heat insulating layer and may form voids (hollow parts), the lead wires  24 ,  25  and  26  are made to creep the urethane heat insulator side of the inner box as much as possible. A wire harness having a connector at a distal end thereof can be used for the lead wires  24 ,  25  and  26  to improve the wiring operation. The distal end connector of this wire harness is connected to the connector provided in the connection section  31  of the control substrate  12  outside the box. 
     The control substrate  12  is arranged outside the heat insulating layer  5  of the cabinet  1 . In the present embodiment, as shown in  FIG. 4 , the electrical component box  33  is arranged in the space formed on the rear side of and outside the vegetable room and the control substrate  12  is placed in this electrical component box. A wiring pattern for connecting bipartite portions of the heater wire  18  in parallel or in series is formed on the control substrate  12  as shown in  FIG. 2  and  FIG. 3 . The connection section  31  of the control substrate  12  has a connector to allow connections with the lead wires. Furthermore, a heater drive circuit  30  and a power supply circuit (not shown) are connected to the control substrate  12 . 
     The control substrate  12  provides a wiring pattern that differs from one supply voltage specification to another. For example, the control substrate  12  provides a first control substrate  12   a  (see  FIG. 3 ) having a wiring pattern in which heater wires are connected in parallel and a second control substrate  12   b  (see  FIG. 2 ) having a wiring pattern in which heater wires are connected in series. 
       FIG. 2  shows the wiring pattern of the control substrate  12   b  used when the supply voltage in the destination of the refrigerator is 200 V to 240 V (200 V system) in which the two heater wires are connected in series.  FIG. 3  shows the wiring pattern of the control substrate  12   a  used when the supply voltage in the destination of the refrigerator is 100 V to 127 V (100 V system) in which the two heater wires are connected in parallel. Which of the control substrate  12   a  or  12   b  to use may be determined according to the supply voltage specification. 
     A wiring pattern for connecting a plurality of heater wires in parallel is formed on the first control substrate  12   a  as shown in  FIG. 3 , the end lead wires  24  and  26  connected to both ends of the heater wire and the intermediate lead wire  25  for connecting the divided heater wire portions outside the heater are connected to the connection section  31  of the first control substrate  12   a , and the divided heater wire portions are connected in parallel. The first control substrate  12   a  is used for a supply voltage 100 V to 127 V (100 V system). 
     A wiring pattern for connecting a plurality of heater wires in series is formed on the second control substrate  12   b  as shown in  FIG. 2 , the end lead wires  24  and  26  connected to both ends of the heater wire and the intermediate lead wire  25  for connecting the divided heater wire portions outside the heater are connected to the connection section  31  of the second control substrate, and the divided heater wire portions are connected in series. The second control substrate  12   b  is used for a supply voltage 200 V to 240 V (200 V system). 
     Furthermore, a change section  29  that changes a current conduction rate of the heater is provided for each of the first control substrate  12   a  and the second control substrate  12   b  and this change section  29  adjusts the heating value of the heater. The change section  29  is constructed of a general microcomputer made up of a CPU, RAM and ROM, and controls the drive circuit  30  so as to change the current conduction rate of the heater. The current conduction rate of the heater is changed by adjusting the current conduction time. For example, a 20% drive is achieved by repeating two seconds ON/eight seconds OFF in a 10-second cycle. Furthermore, the drive is changed to a 70% drive by repeating seven seconds ON/three seconds OFF in a 10-second cycle. The current conduction rate is changed by sequence control in the change section  29 . Therefore, the current conduction rate is controlled at a heater current conduction rate specific to each control substrate  12 . The freezing prevention heater  15  also has a configuration similar to that of the temperature compensation heater  18 . 
     In the above configuration, the freezing prevention heater  15  and the temperature compensation heater  18  are embedded in the heat insulating layer  5  as the exterior member during foaming and molding of the cabinet  1 . In this case, the end lead wires  24  and  26  connected to both ends of the heaters  15  and  18 , and the intermediate lead wire  25  connecting the divided heater wire portions are led out of the heat insulating layer  5 . 
     Next, these lead wires  24 ,  25  and  26  are connected to the connection section of the control substrate  12   a  or  12   b  that controls the heaters  15  and  18 , and the heater wires are connected in parallel or in series through the wiring pattern formed on the control substrates  12   a  and  12   b.    
     For example, in the case of a supply voltage 100 V to 127 V (100 V system), the first control substrate  12   a  is used and the heater wires  22  and  23  are connected in parallel as shown in  FIG. 3 . In this case, a total resistance value R of the heater is expressed as (1/R)=(1/R 1 )+(1/R 2 ), where resistances of the heater wires  22  and  23  are R 1  and R 2  respectively. When R 1 =R 2 =10 KΩ, for example, 1/R= 1/10+ 1/10= 2/10, therefore R=5 KΩ. When the supply voltage is 100 V, a total current value Ic is Ic=100 V/5 KΩ=0.02 ampere (A). Wattage is 100 V×0.02 A=2 W. 
     In the case of a supply voltage 200 V to 240 V (200 V system), the second control substrate  12   b  is used, the heater wires are used in series connection as shown in  FIG. 2 . In this case, a total resistance value R of the heater is expressed as R=R 1 +R 2 , where resistances of the heater wires  22  and  23  are assumed to be R 1  and R 2  respectively. Similarly when R 1 =R 2 =10 KΩ as described above, the total resistance value R is R=10+10=20 KΩ. When the supply voltage is 200 V, the total current value Ic is Ic=200 V/20 KΩ=0.01 ampere (A). Wattage is 200 V×0.01 A=2 W. 
     If the heater wires  22  and  23  are connected in parallel at a 200 V system supply voltage, the total resistance value R is 1/R= 1/10+ 1/10= 2/10, therefore R=5 KΩ, whereas if the supply voltage is 200 V, the total current value I is I=200 V/5 KΩ=0.04 ampere (A). Therefore, wattage (W) is 200 V×0.04 A=8 W. 
     By dividing the heater capacity (heater wire) and changing between series connection and parallel connection according to the supply voltage specification in this way, it is possible to use a common heater, for example, for both supply voltages of the 100 V system and 200 V system, suppress management cost and reduce production loss due to misconnections. 
     The present invention is not limited to the above embodiment, and it goes without saying that a number of modifications or alterations can be made without departing from the scope of the present invention. For example, the above embodiment has described the connections of the freezing prevention heater  15  and the temperature compensation heater  18  of the refrigerator, but the present invention is not limited to these, and as descried above, the present invention is also applicable to heater apparatuses of other electric apparatuses such as a hot carpet and floor heating appliances. Examples of the exterior member in this case may include a heat insulating member of a hot carpet or floor heating appliances. 
     REFERENCE SIGNS LIST 
     
         
           1  Cabinet 
           2  Door 
           3  Inner box 
           4  Metal outer wall 
           5  Heat insulating layer 
           6  Storeroom 
           7  Opening 
           9  Fan 
           10  Damper 
           11  Compressor 
           12  Control substrate 
           13  Partition 
           15  Freezing prevention heater 
           18  Temperature compensation heater 
           21  Metal foil 
           22 ,  23  Heater wire 
           24 ,  25 ,  26  Lead wire 
           29  Change section 
           30  Drive circuit 
           31  Connection section