Patent Publication Number: US-2011048464-A1

Title: Dishwasher and associated control method

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a dishwasher, in particular a domestic dishwasher, having a sequencing controller in which one or more washing programs for controlling at least one wash cycle for cleaning dishes are stored, having a washing chamber for receiving dishes during the wash cycle, and having a sorption drying device which has a sorption system with a reversibly dehydratable material. 
     In modern dishwashers the dishes, in particular dishes to be washed, are introduced into a washing chamber and cleaned therein with the aid of water in a washing process, which is also called a wash cycle, and then dried. The aim of this is to perform a wash cycle such that a predefined cleaning result and a predefined drying result are attained as efficiently as possible. This demands high overall efficiency, which preferably results from the cleaning efficiency and the drying efficiency. The cleaning efficiency corresponds in this case in particular to the ratio between the cleaning result achieved by means of a wash cycle and the effort required for this purpose, wherein the effort can include a number of dimensions, for example the energy requirement, the water requirement and/or the time requirement. The drying efficiency also corresponds in particular to the ratio between the drying result achieved by means of a wash cycle and the effort required for this purpose, wherein the effort can include a number of dimensions, for example the energy requirement, the water requirement and/or the time requirement here as well. 
     In modern dishwashers a sequencing controller is usually provided in which one or more washing programs for controlling a wash cycle for cleaning dishes are stored. The sequencing controller is embodied in such a way that it automatically controls a wash cycle in accordance with a washing program that typically is selected by an operator. In known dishwashers the water required for performing wash cycles can be received via a water feed device which can receive water from a water supply installed in a building, for example. 
     A washing program comprises a plurality of successive program steps for treating the dishes, the water in the water-conveying program steps being provided with detergents and/or additives as a function of the respective program step and being brought to a temperature that is favorable for the respective program step. In order to be able to provide the water intended for washing with the provided detergents and/or additives modern dishwashers typically include automatic metering devices. Dishwashers may also have a typically electrical heating device to bring the water provided for washing to the required temperatures. 
     For cleaning the dishes in this time sequence a typical washing program comprises in particular a pre-wash step, a cleaning step, an intermediate washing step and a rinsing step in which water impinges on the dishes in each case. However, washing programs may also be provided in which one or more of these program steps are suppressed. Washing programs are also possible in which one or more of these program steps are performed several times. A typical washing program also comprises a subsequent drying step for drying the cleaned dishes. 
     A pre-wash step is primarily used to remove coarser accumulations of dirt from the dishes. The purpose of a following cleaning step consists in completely removing dirt accumulations from the dishes. An intermediate washing step that is then performed is used in particular to remove detergent residues that adhere to the dishes. A subsequent rinsing step is provided in particular for avoiding marks on the dishes which could occur due to dissolved substances in the water, such as salt and/or limescale. Rinsing agent is added to the water during the rinsing step for this purpose. 
     In a dishwasher having what is known as self-drying, an additional function of the rinsing step is to prepare for the subsequent drying step. During the rinsing step the dishes are heated to a high temperature. In the final drying step drops of water adhering to the hot dishes evaporate and are deposited on the inside of the washing chamber owing to the lower temperature that prevails there. 
     In order to dry the dishes other known dishwashers have a sorption drying device which comprises a sorption system with a reversibly dehydratable material. The functional principle of a sorption drying device consists in steam, in exceptional cases a different absorbable medium, being absorbed during the drying step by the reversibly dehydratable material, which can, for example, be zeolite, the reversibly dehydratable material being heated in the process. An air flow, produced for example by a fan, is heated by the resultant heat and introduced into the washing chamber where it absorbs moisture and thus dries the dishes. 
     In a first type of sorption drying device a moist air flow is conducted out of the washing chamber in the respective drying step by means of the reversibly dehydratable material and releases its absorbed moisture therein, whereby heat is in turn liberated which the air flow at least partially absorbs. 
     In a second type of sorption drying device a moist air flow is conducted along a cooled condensation surface in the respective drying step, whereby it is dried. The condensation surface can, for example, be located in the washing chamber or outside of it in a tube, pipe or the like which conducts the air flow to the reversibly dehydratable material. The dried air flow is then led past the reversibly dehydratable material, and this heats it further. In the case of the second type the condensation surface can be cooled by a container, connected to the sorption system for the purpose of exchanging a medium which can be absorbed by the sorption system, being connected to the condensation surface in a heat-conducting manner. During the drying step it is provided that a medium which can be absorbed by the reversibly dehydratable material, for example water, evaporates or sublimates in the container. The resultant evaporative heat loss then cools the container and the condensation surface. The now gaseous medium is conducted to the reversibly dehydratable material and absorbed there, whereby the reversibly dehydratable material is heated, as already mentioned. 
     In both types the reversibly dehydratable material is then desorbed at the latest when its absorption capacity for steam (or another medium) is exhausted. The reversibly dehydratable material is heated for this purpose, with the result that the absorbed medium detaches from the reversibly dehydratable material. 
     The temperature to which the dishes are heated during the rinsing step can in many cases therefore be selected so as to be lower, or heating of the dishes during the rinsing step can be omitted completely. This results in a higher drying efficiency compared with a dishwasher without a sorption drying device. 
     A need for even more efficient domestic dishwashers has emerged against the background of increased energy and water costs, but also against the background of generally increased environmental awareness and changed lifestyles in large portions of the population. 
     One drawback of the known dishwashers fitted with a storage tank is that the dishwashers no longer satisfy the current requirement for efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a dishwasher which is equipped with a sorption drying device and which allows wash cycles to be performed more efficiently. 
     The object is achieved in the case of a dishwasher of the type mentioned in the introduction in that a water feed device is provided which has a hot water feed and a cold water feed, the hot water feed being provided for receiving hot water from an external hot water supply and the cold water feed being provided for receiving cold water from an external cold water supply, at least one program step being provided in at least one of the washing programs for washing dishes by using hot water from the hot water supply and at least one program step being provided for washing dishes using cold water from the cold water supply. 
     This program-step-specific supplying of cold or hot water makes it possible to reduce energy further and therefore increase energy efficiency. Since each program step of a selected and started dishwashing program is converted by the sequencing controller into a corresponding part-wash cycle of a wash cycle, cold or hot water is therefore supplied to the dishwasher in accordance with the specific part-wash cycle. The drying performance of the sorption drying device in the respective sorption process and its contribution to the drying cycle of the respective wash cycle, and/or the use of the waste heat which accumulates during the respective desorption process of the sorption drying device can therefore be improved for heating a washing tank volume of at least one part-wash cycle of the respective wash cycle. 
     Dishwashers, in particular domestic dishwashers, are typically operated at locations in which there is a hot water supply and a cold water supply. The temperature of the hot water of typically permanently installed hot water supplies can lie, for example, in a range from 40° C. to 70° C. By contrast, the temperature of the cold water of typical permanently installed cold water supplies lies in a range from 5° C. to 15° C. 
     A water feed device which has a hot water feed and a cold water feed allows a wash cycle for cleaning and/or drying dishes to be performed more efficiently. Thus, washing programs for controlling a wash cycle are accordingly possible which make provision for performing individual program steps by using hot water from an external hot water supply and performing other program steps using cold water from an external cold water supply. 
     In this way a significant increase in efficiency can be achieved compared with known dishwashers, as are predominantly common in Europe, which are provided for connection to a cold water supply only, and compared with known dishwashers, as are predominantly common in the North American region, which are provided for connection to a hot water supply only. 
     If, due to its nature, a program step requires the use of water at a high temperature, or this is at least desirable, hot water can be admitted from the external hot water supply for this program step. The hot water can be admitted before or during the respective program step in this case. 
     Admitting hot water for such a program step is in many cases more energy- and cost-efficient than admitting cold water. The reason for the increased cost efficiency lies in the fact that when hot water is admitted, the internal electrical energy requirement of the dishwasher for a wash cycle sinks significantly due to a reduced electrical energy requirement for heating the admitted water. This can lead to a significant reduction in domestic electricity costs. This saving is in many cases greater than the additional cost of generating the hot water in the external hot water supply. In this way increased efficiency can be achieved compared with a dishwasher which is provided for connection to a cold water supply only. 
     This applies in particular if the household has a modern condensing boiler heating system, a combined heat and power system or a district heating system. The cost advantage can be increased even further, however, if the household has a geothermal pump or a solar installation to generate the hot water. 
     Cold water may also be admitted from the external cold water supply for a program step in which the use of water having a high temperature produces no advantages or indeed brings disadvantages. The cold water can be admitted before or during the respective program step in this case as well. 
     Unlike in the case of a dishwasher which is provided for connection to a hot water supply only, drawbacks relating to washing technology which could occur due to an obligatory use of hot water in specific program steps can thus be avoided. Furthermore, partially admitting cold water from the external cold water supply enables the volume of hot water which has to be taken from the external hot water supply for a wash cycle to be reduced without substantial drawbacks with respect to the cleaning effect and/or the drying effect having to be accepted as a result. It can thus be ensured that there is a favorable ratio between the reduction in electrical energy for operation of an electrical heating device of the dishwasher and the additional overhead involved in providing a sufficient quantity of hot water by means of the external hot water supply. 
     The inventive dishwasher achieves said advantages in that at least one program step is provided in at least one of the washing programs for washing dishes by using hot water from the hot water supply and at least one program step is provided for washing dishes using cold water from the cold water supply. 
     In a program step for washing dishes the achievable cleaning effect depends on the temperature of the water used for washing. In many cases it is therefore desirable or even necessary to use water which has a higher temperature than water from a typical cold water supply. Using hot water in such a program step can therefore save a significant amount of energy, which energy would have to be expended when using cold water in order to heat it. 
     On the other hand, during desorption of the sorption system the reversibly dehydratable material is heated to very high temperatures, for example to 300° C. Part of the heat typically generated by means of an electrical heating device for this purpose is used to overcome the binding forces between the absorbed medium and the reversibly dehydratable material. The other part is available for further use in the form of waste heat, however. It is provided in this connection that the waste heat produced during desorption of the sorption system be used to heat at least the water required for a program step for washing dishes. In general there is a sufficient amount of waste heat available to also bring water at a lower temperature to a temperature required for a program step for washing dishes. This applies even in the case of program steps in which a higher temperature is required or desirable. Cold water from the cold water supply can therefore be used for at least one program step, without the necessity of heating it using a higher input of electrical energy. At the same time the amount of heat drawn from the hot water supply can thus be reduced without the cleaning result being noticeably compromised. 
     According to an advantageous development of the invention, in at least one program step for which cold water from the cold water supply is provided for washing dishes, the cold water is therefore heated by means of waste heat that is produced during desorption of the sorption system. 
     A further advantage of using cold water from the cold water supply in a program step for washing dishes during which the sorption system is desorbed results from the fact that a lower temperature level is established in the washing chamber, at least at the start of desorption, when using cold water from the cold water supply than when using hot water from the hot water supply. As a result the water provided for washing can absorb more of the waste heat generated during desorption. If, for example, an air flow is provided which is conducted in a circuit from the sorption system into the washing chamber and from the washing chamber back to the sorption system, this air flow cools more intensely in the washing chamber and therefore has a lower temperature when it reaches the sorption system again. Overheating of the reversibly dehydratable material can thus be prevented. 
     According to a preferred development of the invention it is provided that the sorption drying device comprises an air conduction system for generating an air flow from the sorption system into the washing chamber, provision being made in at least one of the washing programs for the air flow to be generated during desorption of the sorption system in order thereby to heat cold water from the cold water supply provided for washing dishes by means of waste heat that is produced during desorption. In many cases an air conduction system of this kind is present for the purpose of generating an air flow in order to conduct relatively dry air into the washing chamber during the drying step to thus dry the dishes. Using this air conduction system, which can include a fan and tubes, pipes or the like, during desorption makes it possible to easily remove waste heat from the sorption system and to heat water contained in the washing chamber. This results in a simple constructional design of the dishwasher. 
     According to a preferred development of the invention it can be provided that at least one of the washing programs provides at least one cleaning step for washing dishes in which cold water from the cold water supply which has been heated by means of waste heat produced during desorption impinges on the dishes. A cleaning step is used to thoroughly clean the dishes. For this purpose it is necessary for water which is at a relatively high temperature to impinge on the dishes in order thereby to achieve a high thermal cleaning effect. Furthermore, detergent whose chemical cleaning effect is most effective at a higher temperature is generally added to the water. A temperature of about 50° to 70° C. is therefore typically provided for a cleaning step. By using desorption waste heat to heat cold water from the cold water supply a great saving in electrical energy can be achieved precisely here, since it is necessary to heat or re-heat the cold water from the cold water supply by way of the internal electrical heating device to a slight extent only or even not at all in order to bring it to a required setpoint temperature. The waste heat input into heating of the washing tank of the respective part-wash cycle to a desired setpoint temperature may already be sufficient in this case for it not to be necessary to use the appliance-internal heating device for additional re-heating and/or to remove thermal energy from the hot water supply. Owing to the relatively high heat requirement of the cleaning step a large portion of the waste heat liberated during desorption can therefore expediently be used to heat washing liquor during at least one part-wash cycle. The overall efficiency of the dishwasher is thus increased further. By using the desorption waste heat for the respective part-wash cycle, in particular the cleaning cycle of a wash cycle, the appliance-internal, electrical heating device in the liquid circulating system of the dishwasher can possibly even be dispensed with completely, i.e. omitted. 
     Additionally or independently hereof, it may sometimes be expedient if in particular a residual volume of hot water is drawn from the hot water supply to provide a certain washing tank volume for a part-wash cycle which requires the washing tank volume to be heated to a certain minimum temperature, if the waste heat from the respective desorption process is not sufficient for heating the washing liquor of the washing tank volume for the respective part-wash cycle to the desired setpoint temperature. Additionally or independently hereof, the washing liquor for the respective part-wash cycle can possibly also be re-heated using the appliance-internal heating device in the liquid circulating system of the dishwasher. 
     According to a preferred development of the invention at least one of the washing programs provides a pre-wash step for washing dishes in which hot water from the hot water supply impinges on the dishes in preparation for a cleaning step. The pre-wash step is used to remove coarser dirt accumulations from the dishes in order thereby to prepare for a cleaning step. In principle higher temperatures are not required for this purpose. However, the removal of coarser dirt can in many cases be accelerated by means of higher temperatures during the pre-wash step. The required cleaning effect of the pre-wash step can therefore be achieved in a shorter time. In this case the electrical energy requirement of the dishwasher can be reduced further through the use of hot water from the external hot water supply. 
     According to an advantageous development of the invention at least one of the washing programs provides an intermediate washing step for washing dishes in which hot water from the hot water supply impinges on the dishes to remove detergent from the dishes following a cleaning step. An intermediate washing step is used in particular to remove detergent residues that adhere to the dishes following a cleaning step. The desired effect of the intermediate washing step can also be achieved in a shorter time in this connection if water at a higher temperature is used. The electrical energy requirement of the dishwasher can be reduced further by using hot water from the external hot water supply. 
     According to an advantageous development of the invention at least one of the washing programs provides a rinsing step for washing dishes in which cold water from the cold water supply impinges on the dishes. A rinsing step is used in particular to avoid marks on the dishes which could occur due to dissolved substances in the water, such as salt and/or limescale. Rinsing agent is added to the water during the rinsing step for this purpose. In a dishwasher with a sorption drying device it is generally not necessary to heat the dishes to a higher temperature during the rinsing stage, but instead the waste heat is sufficient for the most part, or even on its own, during desorption of the sorption material of the sorption system. Cold water from the cold water supply can therefore be used without any problems, and in particular for the rinsing cycle effected by the respective rinsing step, without this having to be additionally heated or warmed using a higher input of electrical energy. At the same time the quantity of heat removed from the hot water supply can be reduced and an adequate drying result still achieved in a reasonable time. 
     According to an advantageous alternative development of the invention, in addition hereto or independently hereof, at least one washing program can provide a rinsing step for washing dishes in which hot water from the hot water supply impinges on the dishes. In a dishwasher with a sorption drying device a drying step can be accelerated if the dishes are heated during the preceding rinsing step. Hot water which has a temperature, for example, of 60° C. to 75° C. can be used during the rinsing step for this purpose. In this case it is advantageous to use hot water from the hot water supply for the rinsing step since this also ensures that the thermal energy drawn from the hot water supply is beneficially used. A large saving in electrical energy may also be achieved here since in many cases the hot water from the hot water supply does not have to be re-heated at all, and in other cases only to a slight extent, by means of the electrical heating device in the dishwasher in order to reach the desired temperature. Overall, a program of this kind can have a much shorter running time than a program in which unheated cold water from the cold water supply is used during the rinsing cycle, but consumes slightly more energy which is drawn from the hot water supply. It is therefore beneficial to store both programs in the sequencing controller of the dishwasher so that the operator can select one of the programs as required. 
     According to an advantageous development of the invention a free flow path can be associated with the hot water feed device and/or the cold water feed device. The free flow path or paths can be arranged in the storage tank, for example. The free flow paths prevent water from being sucked back in the direction of the hot water supply or cold water supply, which could occur with a temporary vacuum resulting from dynamic processes. In this way in particular an inadequate water level in the storage tank and/or washing chamber can be avoided. 
     According to a preferred development of the invention the hot water feed can comprise a hot water valve and the cold water feed can comprise a cold water valve, it being possible to control the hot water valve and the cold water valve independently of each other by way of the sequencing controller. Consequently it is easily possible to carry out the admission of hot water from the hot water supply as provided by the washing program, and the admission of cold water from the cold water supply as provided by the washing program. In particular an external device for controlling water admission can be dispensed with. 
     According to a beneficial development of the invention it is provided that the hot water valve is arranged at an upstream end of a hot water hose and is embodied in such a way that it can be secured to a connecting piece of the external hot water supply, and/or that the cold water valve is arranged at an upstream end of a cold water hose and is embodied in such a way that it can be secured to a connecting piece of the external cold water supply. For this purpose the hot water valve and/or the cold water valve can for example comprise connection threads which correspond with threads of domestic faucets. Valves of this kind can be embodied in particular as aquastop valves. 
     The arrangement of the hot water valve and/or the cold water valve at the upstream end of the water feed device has the advantage that virtually no leaking water can escape from the dishwasher, even in the case of damage, as long as the valves are closed. If the valves are embodied in such a way that they close when they are not activated, leaking water is prevented in almost all cases from escaping from a dishwasher that is switched off. In order also to prevent leaking water escaping from a dishwasher that is switched on, a leaking water sensor for detecting leaking water can be associated with the sequencing controller so that the sequencing controller can close the valves in the event of leaking water occurring during operation of the dishwasher. 
     According to a preferred development of the invention it is provided that a downstream end of the hot water hose and a downstream end of the cold water hose are in each case connected in a liquid-conducting manner by way of a link to a feed hose which is connected to a connecting piece, fixed to the housing, of the dishwasher. Such an embodiment of the water feed device is simple in terms of construction and in many cases significantly reduces the overall hose length required, in particular if the connection points of the external hot water supply and the external cold water supply are located further away from the installation location of the dishwasher as in this case two longer hoses running in parallel can be omitted. 
     The invention also relates to a method for controlling at least one wash cycle for cleaning dishes by means of one or more washing programs which are stored in the sequencing controller of a dishwasher, in particular a domestic dishwasher, the dishwasher having a washing chamber for receiving dishes to be cleaned during the wash cycle and a sorption drying device which includes a sorption system with a reversibly dehydratable material, the method being characterized in that in at least one of the washing programs hot water from an external hot water supply is used by at least one program step for washing dishes, and cold water from the cold water supply is used by at least one program step for washing dishes. 
     Other embodiments and developments of the invention are recited in the subclaims. The advantageous embodiments and developments mentioned above and/or recited in the claims can be used individually or else in any desired combination with one another in the inventive dishwasher. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, its embodiments and developments and their advantages are explained hereinafter with reference to drawings, in which: 
         FIG. 1  shows a schematic three-dimensional diagram of an advantageous exemplary embodiment of an inventive dishwasher, 
         FIG. 2  shows a block diagram of the dishwasher from  FIG. 1 , 
         FIG. 3  shows an operating diagram of a first washing program of the dishwasher from  FIG. 2 , 
         FIG. 4  shows an operating diagram of a second washing program of the dishwasher from  FIG. 2 , 
         FIG. 5  shows a block diagram of a further advantageous exemplary embodiment of an inventive dishwasher, 
         FIG. 6  shows an operating diagram of a first washing program of the dishwasher from  FIG. 5 , 
         FIG. 7  shows an operating diagram of a second washing program of the dishwasher from  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
     Mutually corresponding parts are provided with the same reference signs in the following figures. Only the components of a dishwasher that are necessary for an understanding of the invention are described and provided with reference signs. It is to be understood that the inventive dishwasher can comprise additional parts and assemblies. 
       FIG. 1  shows a schematic three-dimensional diagram of an advantageous exemplary embodiment of an inventive dishwasher  1 . This comprises a washing chamber  2  which can be sealed by a door  3 , thereby producing a washing cell for washing dishes. The washing chamber  2  is arranged inside a housing  4  of the dishwasher  1  having standard dimensions. Thus, the housing  4  can, for example, have a width of 45 cm or 60 cm, thereby allowing the dishwasher  1  to be integrated in a standard run of kitchen units having a corresponding installation recess. In particular the housing  4  may also be omitted so that the dishwasher is embodied to be more easily fitted into recesses such as kitchen cupboards, for example. 
     A schematically illustrated water feed device  5  is arranged at the back of the dishwasher  1 . This comprises a hot water feed  6 ,  7  and a cold water feed  8 ,  9 , the hot water feed  6 ,  7  being provided for admitting hot water from an external hot water supply WH and the cold water feed  8 ,  9  being provided for admitting cold water from an external cold water supply KH. 
     The hot water feed  6 ,  7  comprises a controllable hot water valve  6  and the cold water feed  8 ,  9  a controllable cold water valve  8 . The hot water valve  6  and the cold water valve  8  are basically identical in terms of construction. Both valves  6 ,  8  can, by way of example, be embodied as solenoid valves. The intake sides of the valves  6 ,  8  are each embodied such that they can be secured to connecting pieces WH, KH of a conventional domestic water supply, for example to faucets WH, KH. The connection can in each case be made by means of a screw connection, a snap-fit connection or the like. Such valves  6 ,  8  are designed in particular as water stop or aquastop valves  6 ,  8 . These are advantageously closed when they are not activated, so that when it is switched off the dishwasher  1  is disconnected from the water supply. Leaking water can thus be prevented from escaping from the switched-off dishwasher  1  in the event of a fault. 
     In accordance with the intended purpose, the intake side of the hot water valve  6  is connected to a hot water faucet WH and the intake side of the cold water valve  8  is connected to a cold water faucet KH. The output side of the hot water valve  6  is connected to a hot water hose  7  and the output side of the cold water valve  8  to a cold water hose  9 , the downstream ends of the hot water hose  7  and the cold water hose  9  being connected to an intake side of a link  10 . A common feed hose  11  for hot water and cold water connects to the output side of the link and is in turn connected to a connecting piece  12  on the housing  4  of the dishwasher  1 . By means of the water feed device  5  it is consequently possible to conduct hot water from an external hot water supply WH and/or cold water from an external cold water supply KH into the interior of the dishwasher  1  in an individually controlled manner in each case. Obviously it is also possible to provide the common link  10  in or on the appliance as an attachment or fixture so that the hot water hose  7  and the cold water hose  9  are led up to the dishwasher  1 . 
     The hot water hose  7 , the cold water hose  9  and/or the common feed hose  11  can be embodied as safety hoses with an inner water-conveying pressure hose and an outer sheathing hose, it being possible to provide a respective leaking water channel between pressure hose and sheathing hose for removing leaking water that may potentially occur. The link  10  can be designed in such a way that the leaking water channels of the hot water hose  7 , the cold water hose  9  and the common feed hose  11  are interconnected, so leaking water which occurs in the region of the water feed device  5  during operation of the dishwasher is conveyed via the connecting piece  12  fixed to the housing and into the interior of the dishwasher  1 . Here it can be detected by a leaking water sensor (not shown), so appropriate measures, for instance closing the hot water valve  6  and cold water valve  8 , can be taken by the dishwasher&#39;s sequencing controller. 
     Provided downstream of the connecting piece  12  fixed to the housing is a free flow path  13 . The free flow path  13  is what is known as a pipe interrupter which is used to prevent water from the dishwasher  1  being sucked back if a vacuum occurs in the external water supply due to dynamic processes. In particular this prevents water which has already been used and may be adulterated with dirt, detergents and/or cleaning aids, from being able to pass back into the building-side water supply. 
     The dishwasher  1  also comprises means (not shown in  FIG. 1 ) which connect the free flow path  13  to the washing chamber  2  in such a way that it can be filled with cold water from the cold water supply KH and/or with hot water from the hot water supply WH. 
     A pump well  16  is provided in the lower region of the washing chamber  2  in which a circulating pump is beneficially provided for circulating water in the washing chamber  2  during a wash cycle. The circulating pump can have a heating device for heating the water contained in the washing chamber  2 , for example an instantaneous water heater. A pump for pumping out water, for example at the end of a wash cycle, may also be provided in the pump well  16 . The various pump functions can also be handled by a single pump in conjunction with switchable valves, however. The pump well  16  is usually connected to a waste water connecting piece  17  via means (which are not shown) in such a way that water from the washing chamber  2  can be pumped via a waste water hose  18  connected to the waste water connecting piece  17  into a waste water device A, for example a waste water pipe A, installed in the building. 
     The dishwasher  1  also comprises a sequencing controller  19  for controlling the sequence of a washing program. Various washing programs which can be selected by an operator can be stored in the sequencing controller  19 . The sequencing controller  19  is arranged inside the door  3  of the washing chamber  2 , though it could also be arranged at another location in the dishwasher  1 . The dishwasher  1  also comprises a sorption drying device  20  which is arranged on a side wall of the washing chamber, here in the exemplary embodiment in particular between the washing chamber  2  and the housing  4 . Alternatively, however, most of the components of the sorption drying device  20 , such as its fan assembly or fan  25 , its sorption system  30 , in particular sorption column, are housed in a base assembly under the washing chamber. 
       FIG. 2  shows an operating diagram of the dishwasher from  FIG. 1 . The hot water valve  6  and the cold water valve  8  are each connected to the sequencing controller  19  in such a way that both can be activated individually or specifically. A feed  21  for charging the washing chamber  2  with water from the feed device  5  is arranged downstream of the free flow path  13 . It is therefore possible to fill the washing chamber  2  with hot water and/or cold water via the link  10 , the free flow path  13  and the feed  21  as a function of the selected washing program. 
     A circulating pump  22  embodied as a heat pump is arranged in the pump well  16  of the washing chamber  2  and is connected to a spray system  23  arranged in the interior of the washing chamber  2 . It is hereby possible for water to impinge on dishes arranged in the washing chamber  2  during a wash cycle in order to clean them. Also arranged in the pump well is a drain pump  24  which allows water that is no longer required to be pumped out. Both the heating function and the pumping function in the heat pump can be individually controlled by the sequencing controller  19 . The sequencing controller  19  is also connected to the drain pump  24  for the purpose of controlling the latter. Obviously it is also possible as an alternative to provide an electrical heating device, separate from the circulating pump, in the liquid circulating system of the dishwasher. 
     The sorption drying device  20  has an air conduction system  25 ,  26 ,  28  which comprises a fan  25 , a suction-side air pipe  26  and a pressure-side air pipe  28 . The fan  25  is connected by way of the suction-side air pipe  26  to an air outlet  27  of the washing chamber  2  and by way of the pressure-side air pipe  28  to an air inlet  29  of the washing chamber  2 . 
     During a drying step of a washing program an air flow LS can thus be generated which is led through a sorption system  30  arranged in the pressure-side air pipe  28 . The sorption system  30  could also be arranged in the suction-side air pipe  26 . It contains a reversibly dehydratable material  31  which, during the drying step, absorbs moisture in the air flow LS coming from the washing chamber  2 . The air flow LS is dried hereby and when it is conveyed back into the washing chamber can absorb more moisture, and this leads to drying of the dishes in the washing chamber. 
     In order to enable the sorption system to be desorbed, a preferably electrical heating device  32  is provided which has a heating element which is arranged in the air conduction system  25 ,  26 ,  28  for the purpose of heating the sorption system  30 . In this connection the reversibly dehydratable material is heated to very high temperatures, for example to  300 ° C. Part of the heat typically generated by means of the electrical heating device  32  for this purpose is used to overcome the binding forces between the absorbed medium and the reversibly dehydratable material  31 . The other part, however, is introduced into the washing chamber  2  with the air flow LS in the form of waste heat. It is provided in this case that the waste heat resulting during desorption of the sorption system be used to heat at least the water required for a part-wash cycle initiated by a program step for washing dishes. 
     The water feed device  5 , the heat pump  22 , the drain pump  24 , the sorption drying device  20  and other devices of the dishwasher  1  that are not described further here are controlled as a function of a selected washing program which is stored in the sequencing controller  19 . The dishwasher  1  is provided with at least one washing program which can be selected specifically for efficient use of hot water from the hot water supply WH and cold water from the cold water supply KH. In particular this means that cold water is specifically supplied for a part-wash cycle for which cold water is sufficient or required and hot water is specifically supplied for a part-wash cycle for which hot water is required. 
       FIG. 3  shows an operating diagram in order to explain the operation of the inventive dishwasher  1  in  FIGS. 1 and 2 . For this purpose the sequence of a washing program SP is shown which is provided for controlling an execution sequence of a wash cycle in such a way that efficient use of hot water from the hot water supply WH and of cold water from the cold water supply KH is ensured. 
       FIG. 3  shows the curves SWV, SKV, BGE and BHZ on a common time axis t, the curves indicating switching and operating states of components of the dishwasher  1  on the vertical axis Z. 
     The curve SWV represents the switching state of the hot water valve  6  of the dishwasher  1 . Furthermore, the curve SKV shows the switching state of the cold water valve  8  of the dishwasher  1 . The switching state “0” corresponds to a closed valve  6 ,  8  in each case, the switching state “1” to an open valve  6 ,  8 . The curve BGE, moreover, illustrates the operating state of the fan  25 , the OFF state being symbolized by “0” and the ON state by “1”. Finally, the curve BHZ shows the operating state of the heating device  32  of the sorption drying device  20 . The OFF state is identified by “0” and the ON state by “1” here as well. 
       FIG. 3  shows by way of example a washing program SP which for washing dishes using water comprises in the given sequence: a pre-wash step VS, a cleaning step RS, an intermediate wash step ZS and a rinsing step KS. These program steps are implemented in corresponding liquid-conveying part-wash cycles, i.e. each program step of a selected dishwasher program is accompanied by a part-wash cycle. This is followed by a drying step TS for drying the cleaned dishes in a drying cycle. Part-wash cycles can therefore be liquid-conveying part-wash cycles and drying cycles. One or more of these steps could be suspended in other examples. Examples would also be possible in which one or more steps are run through several times. Moreover, desorption DS of the sorption system  30  is provided which is coordinated in time with the programs steps already mentioned. 
     The pre-wash step VS performed first is used to remove coarser dirt accumulations from the dishes in order thus to prepare for the cleaning step RS. The hot water valve  6  is opened for this purpose at the start of the pre-wash step VS, so hot water from the hot water supply WH passes via the feed  21  into the washing chamber  2 . If the washing chamber  2  is charged with a volume of hot water from the hot water supply WH sufficient for the pre-wash step VS, the hot water valve  6  is closed again. The hot water is circulated for a predefined time in the washing chamber  2  by means of the heat pump  22 , usually without—in exceptional cases with—activation of its heating device in order for hot water at a desired setpoint temperature to impinge on the dishes thereby. The now contaminated hot water is then pumped out by means of the drain pump  24 . 
     Alternatively, cold water from the cold water supply KH could be used for all or some of the pre-wash step VS. This would lead to an energy saving, although the pre-wash time usually has to be extended compared with the above case of pre-washing with drawing of hot water in order to achieve a predetermined cleaning effect. 
     The cleaning step RS which is then performed serves to thoroughly clean the dishes. Desorption of the sorption system  30  is performed at the same time in order to remove water that has accumulated on the reversibly dehydratable material  31  in a drying step of a wash cycle performed previously. Firstly the fan  25  and secondly the heating device  32  of the sorption drying device  20  is switched on for this purpose. This produces the air flow LS which conveys waste heat of the desorption DS into the washing chamber. The fan  25  and the heating device  32  are typically then switched off when the reversibly dehydratable material  31  is substantially liberated of absorbed water. This point in time can be reached before the termination of the cleaning step RS. 
     During the cleaning step RS it is usually necessary for water to impinge on the dishes, the water having a comparatively high temperature in order to achieve a high thermal cleaning effect. Furthermore, detergent is generally added to the water, the chemical cleaning effect of said detergent being best at higher temperatures. A setpoint temperature of about 50° C. to 70° C. is therefore typically provided for a cleaning step RS. Owing to the waste heat introduced into the washing chamber  2  by the air flow LS, this temperature can be reached without any problems without switching on the instantaneous water heater arranged in the pump well  16 , even if water at a lower temperature is introduced into the washing chamber  2  at the start of the cleaning step. It is therefore provided to perform the cleaning step RS using cold water from the cold water supply KH. The cold water valve  8  is temporarily opened at the start of the cleaning step RS for this purpose. The cold water introduced into the washing chamber  2  is accordingly circulated for a predefined time with the aid of the circulating pump  22 . The cold water is increasingly heated by means of the waste heat of the desorption DS in the process, so the temperature desired for the cleaning step is reached. 
     The cleaning step RS can be performed particularly efficiently in this way. It is therefore possible to achieve a big saving in electrical energy here since the cold water from the cold water supply KH does not usually have to be re-heated at all, and in rare cases only to a slight extent, by the electrical heat pump  22  of the dishwasher  1  in order to reach the desired temperature. Furthermore, it is not necessary to draw thermal energy from the hot water supply WH. 
     A further advantage of using cold water from the cold water supply KH during the cleaning step RS results from the fact that, at least at the start of the desorption DS, a lower temperature level is established in the washing chamber  2  when using cold water from the cold water supply KH than when using hot water from the hot water supply WH. Consequently more waste heat which is generated during the desorption DS can be absorbed by the water provided for washing. The air flow LS which is conducted in a circuit from the sorption system  30  into the washing chamber  2  and from the washing chamber  2  back to the sorption system  30  therefore cools more intensely in the washing chamber  2  and therefore is at a lower temperature when it reaches the sorption system  30  again. Overheating of the reversibly dehydratable material  31  can therefore be prevented. 
     The appliance-internal heating device for heating the washing liquor can be omitted altogether where appropriate if the waste heat from the respective desorption process of the sorption drying device and/or the heat energy of the volume of hot water supplied from the external hot water supply is sufficient for heating the washing tank volume required for the respective part-wash cycle to a certain setpoint temperature. 
     To conclude the cleaning step RS the now contaminated hot water is pumped out (in a manner not shown) by means of the drain pump  24 . 
     By contrast, the intermediate washing step ZS that is now performed in order to remove detergent from the dishes following the cleaning step RS provides charging the washing chamber  2  with hot water from the hot water supply WH in order for hot water to be able to impinge on the dishes. For this purpose the hot water valve  6  is firstly opened until the washing chamber  2  is charged with a volume of hot water sufficient for the intermediate washing step ZS. This hot water is circulated for a predefined time by means of the circulating pump  22 , it usually being possible for switching-on of its heating device, or more generally put, of the heating device of the liquid circulating system, to be omitted. The now contaminated hot water is then pumped out by means of the drain pump  24 . 
     Alternatively, cold water from the cold water supply KH could be used for all or some of the intermediate washing step ZS. This would lead to an energy saving, although the intermediate wash time usually has to be extended to achieve a predetermined cleaning effect. 
     The rinsing step KS that now follows serves in particular to avoid marks on the dishes which could occur due to dissolved substances in the water, such as salt and/or limescale. Rinse aid is added to the water during the rinsing step KS for this purpose. In the case of a dishwasher  1  with a sorption drying device  20  it is generally not necessary to heat the dishes to a higher temperature during the rinsing step KS because the dishes can be dried solely by means of the sorption effect of the sorption material in the sorption system  30 . Cold water from the cold water supply KH can therefore be used without any problems, without it having to be heated by means of the heating device of the circulating pump  22  using a higher input of electrical energy. At the same time the quantity of heat drawn from the hot water supply WH can therefore be reduced and an adequate drying result still be attained in a reasonable time. 
     Therefore the cold water valve  8  is firstly opened in the rinsing step KS until the washing chamber  2  is charged with a volume of cold water sufficient for the rinsing step KS. This cold water is circulated for a predefined time by means of the circulating pump  22 , it usually being possible for switching-on of its associated heating device to be omitted. The now contaminated water is pumped out by means of the drain pump  24  at the end of the rinsing step KS. 
     No provision is made for charging the washing chamber  2  with water during the final drying step TS. Instead the now cleaned dishes are dried in that the fan  25  is switched on and consequently the air flow LS generated. The air flow absorbs moisture in the washing chamber  2 , which moisture is then deposited in the reversibly dehydratable material  31 . 
       FIG. 4  shows a further washing program SSP which for washing dishes using water comprises in the given sequence: a pre-wash step VS, a cleaning step RS, an intermediate washing step ZS and a rinsing step KS′. A drying step TS′ for drying the cleaned dishes and which concludes the wash cycle follows in this case as well. The washing program SSP is a quick-wash program SSP with a reduced running time, the reduction being brought about by a rinsing step KS′ which is modified with respect to the washing program SP in  FIG. 3 , and a shortened drying step TS′. 
     In contrast to the above-described washing program SP, hot water from the hot water supply WH is used here during the rinsing step, so the dishes are heated. Evaporation of drops of water adhering to the hot dishes is consequently accelerated in the following drying step TS′, so that a predetermined drying result can be achieved in a shorter time. 
     Using hot water from the hot water supply WH for the rinsing step KS′ also ensures that the heat energy drawn from the hot water supply WH is meaningfully used. A high reduction in electrical energy may also be achieved here, since in many cases the hot water from the hot water supply WH does not have to be reheated at all by the electrical heating device of the liquid circulating system of the dishwasher  1 , and in other cases to only a slight extent, in order to reach the temperature required for the rinsing step KS′. 
       FIG. 5  shows a block diagram of a further exemplary embodiment of an inventive dishwasher. This has a modified sorption drying device  20 ′. In contrast to the exemplary embodiment described above, the sorption system  30  is arranged in such a way that the air flow LS does not flow through it but around it. A container  33  is also provided which is connected to the sorption system  30  in order to exchange a medium that can be absorbed by the sorption system  30 . Moreover, the container  33  is connected in a heat-conducting manner to a condensation surface  35 , the surface being arranged in the washing chamber. It could also be arranged in the air conduction system  25 ,  26 ,  28 , however. Container  33  and sorption system  30  are connected by way of a valve  36  which is controlled by the sequencing controller  19  as a function of the washing program selected in a particular case. 
       FIG. 6  shows a washing program SP′ for the dishwasher  1  in  FIG. 5 . It substantially corresponds to the washing program SP of  FIG. 2 , although the additionally illustrated curve SVE shows the switching state of valve  36 . At the start of desorption during the cleaning step RS, the valve  36  is accordingly opened. As a result the medium  34  desorbed by the reversibly dehydratable material  31  arrives in the container  33  where it liquefies and therefore gives off heat to the condensation surface  35 . The condensation surface  35  gives off at least some of this heat to the water in the washing chamber  2 . At the same time, as in the previous exemplary embodiment, heat is introduced by means of the air flow LS into the washing chamber, so the cold water from the cold water supply KH contained therein is heated. At the conclusion of desorption the valve  36  is closed, with the result that the absorbable medium  34  is enclosed in the container  33 . 
     The valve  36  is opened again during the drying step TS. The absorbable medium  34  evaporates as a result, so the condensation surface  35  is cooled, and this promotes condensation of steam in the washing chamber resulting in an improved drying effect. 
       FIG. 7  shows a quick-wash program SSP′ for the dishwasher of  FIG. 5  which substantially corresponds to the quick-wash program SSP of  FIG. 4 . The switching state SVE of the valve  36  is also shown, however. 
     According to an advantageous exemplary embodiment the invention relates to a dishwasher, in particular a domestic dishwasher, having an adsorption drying system which is combined with an external hot water supply, in particular a hot water solar supply, and a cold water supply, i.e. a bithermal water supply device. These two water supplies can be activated separately using a respective aquastop valve. The hot water supply is provided for drawing hot water from an external hot water supply device, in particular for drawing hot, inexpensive solar water from a hot water supply system operated wholly or partly by means of a thermal solar installation. The other water supply is provided for cold water from the mains. Both water supplies may be individually selected via a dishwasher controller. 
     The dishwasher is equipped with an adsorption drying system, programs specifically configured for this being stored in the control unit. If the customer selects a special function the machine can respond specifically thereto. 
     In particular a washing program having a normal program running time, i.e. a normal program, can be provided in which hot water from a solar-operated or solar-assisted hot water supply system is used for pre-washing and intermediate washing. By contrast, cold water from a cold water supply is preferably used for cleaning in said washing program in order to protect the sorption material, in particular zeolite, of the sorption system. Owing to the drying system a higher temperature is not required during rinsing in order to achieve a very good drying effect with a normal running time. Cold water from a cold water supply is therefore used for rinsing. 
     Additionally or independently hereof, a program with a reduced running time may be provided in which, in contrast to the above described program, hot water from a solar installation is used for the rinsing cycle. If the user selects this fast program there is a significant reduction in the drying time, with the drying effect remaining the same compared with the normal program because now the intrinsic-heat drying of the dishes can also be used. 
     An initial temperature level that is as low as possible is produced owing to the use of cold water during the desorption phase. This leads to the technical materials used in the adsorption drying system being sparingly treated. The inexpensive hot water from the hot water solar installation can be used again after the desorption phase. This results in a higher start to the temperature level during rinsing, and therefore to a shorter drying time. 
     Overall this results in effective use of the hot water, in an energy saving and material conservation in the adsorption drying system in conjunction with hot water admission, in particular from a hot water solar installation.