Patent Description:
The invention also relates to a household appliance including such compressor module.

Document <CIT> discloses a compressor module for a heat pump according to the preamble of claim <NUM>.

Document <CIT> discloses a compressor module for a heat pump in a household appliance, the compressor module including a compressor encased into a single casing with a motor driving the compressor, and an accumulator attached to the casing. The accumulator is connected upstream of the compressor inlet and is designed to provide phase separation between liquid and gaseous refrigerant for allowing only gaseous refrigerant to proceed to the compressor.

Document <CIT> discloses a heat pump in a household appliance including a compressor which includes two independently operable compressing chambers which may be connected in series or in parallel selectable by a distributor valve.

Document <CIT> discloses a compressor for a heat pump in a household appliance which comprises a rotating roller for compressing a gaseous phase of a refrigerant, wherein the roller is lubricated by means of a mixture of oil and refrigerant dissolved in the oil. The compressor includes an oil sump for receiving the mixture, and a rotatable agitating element at least partially submerged in the mixture for agitating the mixture.

Document <CIT> discloses a compressor in a heat pump in a household appliance and a heat transfer device associated to the compressor, the heat transfer device in particular being a heat tube partly wrapped around the compressor's casing and arranged so as to transfer heat from the compressor into a process air flow within the household appliance.

Document <CIT> discloses a household appliance having a heat pump with a compressor and means for preventing overheating of the compressor. These means provide heat transfer from the compressor into a process air flow within the household appliance.

In the present context a household appliance is an appliance determined for use in operating a private household to provide a specific and predetermined material purpose, or a plurality of such purposes. Examples of such household appliances include laundry care appliances such as a washing machine, a washer-dryer and a laundry drying appliance, a dishwasher, a cooling appliance such as a refrigerator and a freezer, a cooking appliance, and a climate control appliance.

A household appliance such as a laundry care appliance dedicated to drying laundry, a dishwasher, a cooling appliance, and a climate control appliance, may employ a heat pump on purpose of conveying heat from a location at a relatively low temperature to a location at a relatively high temperature, where the difference between the relatively low temperature and the relatively high temperature may be small and even approach zero. Such heat pump includes a heat sink for absorbing heat and a heat source for releasing heat, and a system for pumping heat from the heat sink to the heat source. Many types of heat pumps are known for application to such purpose, with the heat pump applying the inverse Rankine process by cyclically evaporating and condensing a working medium (usually termed a "refrigerant" as a result of its application in a cooling appliance) being the most widely used concurrently.

In the heat pump of the type applying the inverse Rankine cycle, the heat pumping system is composed of conduits for circulating the refrigerant in a closed circuit. The conduits include tubes for guiding the refrigerant, the heat sink and the heat source embodied as heat exchangers for transferring heat from or to the refrigerant, a compressor for compressing and driving the refrigerant through the conduits, and an expander for reducing an internal pressure of the refrigerant as it passes through. In operation of such heat pump, the refrigerant is compressed by the compressor in its gaseous phase, and then guided to the heat source. In the heat source the gaseous refrigerant condenses to its liquid phase whereby it releases heat. The liquid refrigerant then is guided to the expander for reducing its internal pressure, which incurs the refrigerant's partial evaporation into a two-phase mixture. This mixture is then guided to the heat sink where it evaporates fully into its gaseous phase by absorbing heat and is finally guided back to the compressor for being compressed again.

An accumulator that is a vessel providing an extra volume for the refrigerant is conventionally also included in the conduits and conventionally placed between the heat sink and the compressor and closely adjacent to the compressor to combine with the compressor to a compressor module, to allow adaptation of the overall amount of refrigerant present in the heat pump.

The heat pump's compressor is usually driven by an electric motor which is integrated into a single casing with the compressor. The refrigerant guided into the casing may be applied to provide cooling to the electric motor, whereby heat produced by operating the motor is transferred into the heat pump by further heating up the refrigerant. Thereby a compact and sealed compressor unit including both the compressor and the motor may be provided.

Properly operating the heat pump's compressor requires the refrigerant to be fully converted to its gaseous phase when entering the compressor. Otherwise, liquid refrigerant having entered the compressor may evaporate explosively during the compression process, and possibly damage the compressor thereby. Further, liquid refrigerant may dilute or even wash away the lubricant from metal surfaces in the compressor, thereby impair lubrication and possibly cause wear at metal surfaces. It is convenient therefore to design the heat sink for not only providing full evaporation of the refrigerant passing through, but also for overheating the refrigerant in its gaseous phase by a small amount to provide safety against liquid refrigerant to reach the compressor.

Conveniently the compressor requires lubrication by oil which is stored in its casing. The oil is selected for proper lubrication at operating temperatures as well as for interaction with refrigerants that the compressor is rated to be operated with. The interaction between oil and refrigerant is determined by the pressure and by the refrigerant's solubility in the oil, which by itself is temperature-dependent in that the lower the temperature of the oil, the higher the solubility. Further, the higher the refrigerant's temperature, the lower its kinematic viscosity.

In a heat pump in a household appliance, the refrigerant used may by a fluorinated hydrocarbon such as the compound commonly known as R134a or a mixture of compounds commonly known as R407C, or a hydrocarbon such as propane and also known as R290, or propene also known as propylene and as R1270, or isobutane also known as R600a. In the case of use of a flammable refrigerant such as R290, R600a and R1270, safety regulations may require or recommend use of a specifically limited amount per heat pump such as an amount not exceeding <NUM>. In such case the amount of refrigerant dissolved in the oil, and thus inefficient in the thermodynamic process, may be considerable.

Presently there is a need for further improvement of the heat pump and its constituents, particularly for applying the refrigerant more efficiently to the thermodynamic process.

Therefore, it is an object of the invention to provide an improved compressor module for a heat pump in a household appliance, and a household appliance including such compressor module.

On purpose of solving this object the present invention provides a compressor module of the generic type defined in the generic part of the respective independent claim attached which also includes the features of the characterizing part of said independent claim. The present invention also provides a household appliance including such compressor module as defined in the respective independent claim attached.

Preferred embodiments of the invention are defined in dependent claims attached as well as in the subsequent disclosure. Such preferred embodiments may be applied in mutual combinations insofar as possible under technical considerations to any extent, even if not specified herein explicitly.

Accordingly the present invention provides, as a solution to the problem as defined above, compressor module for a heat pump in a household appliance, including a compressor for compressing a circulating refrigerant, a motor for driving said compressor, a casing enclosing said compressor and said motor, an inlet guide for guiding the refrigerant to said compressor and an outlet guide for guiding the refrigerant from said compressor, wherein a heat exchanger is provided for transferring heat from said outlet guide to said inlet guide. Further, said casing is part of said outlet guide, said heat exchanger includes said casing, and said inlet guide includes a tube coil wound around and contacting said casing, said tube coil included in said heat exchanger.

Likewise, the invention provides a household appliance including a heat pump and a compressor module including a compressor, wherein said compressor module is a compressor module according to the invention as defined in the preceding paragraph or a preferred embodiment thereof.

In the present context the term "module" applies to a combination of functionally linked components without implying that such components must be connected to each other such as to form a constructional unit.

Advantages of the invention include that specific heating is provided for the refrigerant about to enter the compressor, thereby alleviating from concern related to drops of liquid refrigerant entering the compressor. Such heating is provided by coupling heat, that is, a part of the total heat available, from refrigerant exiting the compressor back to refrigerant entering the compressor. Thereby heat generated in the compressor which is heat generated by compressing the refrigerant as well as excess heat produced in the motor driving the compressor is utilized in a novel way. Heating the refrigerant upon entering the compressor may also incur transfer of heat to oil applied for lubricating the compressor, thereby heating the oil and reducing the amount of refrigerant dissolved in the oil.

According to the invention, the casing is applied to transfer heat from the compressed refrigerant to the refrigerant about to enter the compressor. This is particularly useful as applied to a compressor module with a casing made of steel which is proper for providing heat transfer.

According to the invention, the tube coil may be provided by any means and may be provided by coiling stock tube material around the casing.

Principally the invention may be applied to any compressor for application in any household appliance. In particular, the household appliance may be a laundry care machine such as a laundry dryer or a washer-dryer, or a dishwasher, or a cooling appliance such as a refrigerator or a freezer, or a heating appliance such as a water heater or a climatization device, all equipped with a heat pump for drying, cooling, or heating purposes.

In a preferred embodiment of the invention said tube coil is a shell arranged around said casing and partitioned into a helicoidal path for the refrigerant by a helicoidal wall arranged between said shell and said casing. Even more preferred, said compressor and said motor are stacked along a vertical direction in said casing and said tube coil is arranged nearest to said motor. Thereby the heat transferred to the refrigerant about to enter the compressor is excess heat of the motor. Further the additional shell may contribute to damping the motor's operational sound, thereby assisting to reduce noise produced by operating the compressor module.

In a further preferred embodiment of the invention said heat exchanger is configured for storing a predetermined amount of refrigerant. Thereby the heat exchanger adopts a function which is conventionally provided by an accumulator. The invention may thus dispense from applying a separate accumulator, thereby saving expense of material and money.

In an additional preferred embodiment of the invention said casing includes an oil for lubricating said compressor. It is natural that such lubricating oil is in contact with the refrigerant to be or being compressed, whereby a proper amount of refrigerant will dissolve in the oil. By raising the temperature of refrigerant entering the compressor the refrigerant's solubility in the oil will decrease, thereby releasing refrigerant from dissolution in the oil and making it effective in the thermodynamic process that it is dedicated to.

In yet another preferred embodiment of the invention said compressor is one of a reciprocating piston compressor, a rolling piston compressor, and a scroll compressor, the two latter types of compressors defining types of rotary compressors.

In yet a further preferred embodiment of the invention said heat pump includes a refrigerant selected from the group consisting of R134a, R407C, R290, R1270, and R600a. More preferred said refrigerant is one of R290, R1270, and R600a, and included in said heat pump at an amount not exceeding <NUM>. Thereby the household appliance may be operated in accordance with conventional safety regulations limiting the use of flammable refrigerants in a household appliance.

In yet an additional preferred embodiment of the invention the household appliance implementing the invention or one of its preferred embodiments is embodied as an appliance for drying household items such as pieces of laundry and dishes. In other words, the household appliance may be embodied as a laundry drying appliance or a dishwashing appliance. More preferred the household appliance is embodied as an appliance for drying pieces of laundry.

Preferred embodiments of the invention are now explained in detail with reference to the Figures of the attached drawing. These Figures show and exhibit as follows:.

As shown in detail in <FIG> and <FIG>, a compressor module <NUM> for a heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in a household appliance <NUM> (see <FIG> as explained below) includes a compressor <NUM> for compressing a refrigerant circulating through heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, a motor <NUM> for driving compressor <NUM>, a casing <NUM> enclosing compressor <NUM> and motor <NUM>, an inlet guide <NUM> for guiding the refrigerant to compressor <NUM> and an outlet guide <NUM>, <NUM> for guiding the refrigerant from compressor <NUM>. Compressor <NUM> in accordance with usual practice releases the compressed refrigerant into casing <NUM> for freely flowing and thereby cooling motor <NUM>. Thereby casing <NUM> itself forms part of outlet guide <NUM>, <NUM>. A heat exchanger <NUM> is provided for transferring heat from said outlet guide <NUM>, <NUM> to said inlet guide <NUM>.

<FIG> shows heat exchanger <NUM> as a component separate from casing <NUM>, not at least to fully exhibit the principle underlying provision of heat exchanger <NUM> which does not form part of the present invention. An embodiment of heat exchanger <NUM> according to the present invention is described below with reference to <FIG>.

Electric leads <NUM> are provided for connecting to motor <NUM>, leads <NUM> insulatingly guided through lid <NUM> provided for and closing casing <NUM>.

Compressor module <NUM> is arranged for compressor <NUM> being associated to heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM> configured for operating based on the inverse Rankine cycle and comprising a refrigerant circuit <NUM> closed in itself for circulating a working medium or refrigerant to be condensed and evaporated cyclically, a heat source <NUM> which is another heat exchanger for releasing heat from the refrigerant to another medium by condensing the refrigerant, an expander <NUM> embodied as a capillary for reducing an internal pressure of the refrigerant to have it cool down and evaporate partly, a heat sink <NUM> which is also another heat exchanger for absorbing heat from another medium into the refrigerant, thereby fully evaporate it, and finally compressor <NUM> dedicated to compressing the gaseous refrigerant and driving it through refrigerant circuit <NUM>. Of course, inlet guide <NUM> and outlet guide <NUM>, <NUM> are sections of refrigerant circuit <NUM>. A condensate collector <NUM> is connected to heat sink <NUM> for collecting condensate which has formed by the cooling action of heat sink <NUM>, for example by cooling a process air flow <NUM> with entrained humidity, the humidity condensing to water which precipitates in heat sink <NUM> and is collected in condensate collector <NUM> for disposal.

Casing <NUM> includes an oil <NUM> collected in a sump formed by a lower part of casing <NUM> as seen along vertical direction <NUM> for lubricating compressor <NUM>. Oil <NUM> is in contact with the refrigerant to be or being compressed, whereby a proper amount of refrigerant will dissolve in oil <NUM>. By raising the temperature of refrigerant entering compressor <NUM> by heat exchanger <NUM> the refrigerant's solubility in oil <NUM> will decrease, thereby releasing refrigerant from dissolution in oil <NUM> and making it effective in the thermodynamic process that it is dedicated to.

In the embodiment of <FIG>, casing <NUM> is part of said outlet guide <NUM>, <NUM> as well as in <FIG>. According to <FIG> heat exchanger <NUM> includes casing <NUM> by inlet guide <NUM> including a tube coil <NUM>, <NUM> wound around and contacting casing <NUM>, tube coil <NUM>, <NUM> included in said heat exchanger <NUM>. Tube coil <NUM>, <NUM> may of course be made be winding tube stock around casing <NUM> and forming a coil. It may be more appropriate in terms of enabling proper heat transfer to provide tube coil <NUM>, <NUM> as a shell <NUM> arranged around casing <NUM> and partitioned into a helicoidal path for the refrigerant by a helicoidal wall <NUM> arranged between shell <NUM> and casing <NUM>.

As a simplification of the embodiment of <FIG>, helicoidal wall <NUM> may possibly dispensed with, thus providing a simple shell <NUM> around a respective part of casing <NUM> and appropriately closed in itself except for inlet and outlet.

Further, compressor <NUM> and said motor <NUM> are stacked along vertical direction <NUM> in casing <NUM> and tube coil <NUM>, <NUM> is arranged nearest to said motor <NUM>. The term "vertical direction" refers to a convenient mode of mounting casing <NUM> as a vertically upright cylinder but does not imply any requirement to mount casing <NUM> in any specific direction. As a particular case may require, casing <NUM> may be mounted in an appliance with its cylinder upright, that is vertically aligned, horizontally aligned or angled to the vertical as well as to the horizontal. Yet, by arranging heat exchanger <NUM> as close as possible to motor <NUM> heat exchanger <NUM> may contribute advantageously to providing cooling to motor <NUM> and assisting in damping thermal loads and extending lifetime. In addition, heat exchanger <NUM> may contribute to damping operational noise generated by motor <NUM>.

Heat exchanger <NUM> is configured for storing a predetermined amount of refrigerant. Thereby heat exchanger <NUM> assumes a function of an accumulator, dispensing from adding a specific accumulator to heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Compressor <NUM> may be one of a reciprocating piston compressor or a rotary compressor such as a rolling piston compressor and a scroll compressor.

<FIG> shows a household appliance <NUM> including heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and a compressor module <NUM> as in <FIG> and <FIG> and including a compressor <NUM>. Household appliance <NUM> includes a treatment chamber <NUM> for drying household items <NUM>, <NUM> (see <FIG> as explained below) and a control unit <NUM> which controls operation and interfaces to a user. Under control of control unit <NUM> a process air flow <NUM> is generated in process air guide <NUM> by process air blower <NUM> to penetrate treatment chamber <NUM> for drying household items <NUM>, <NUM>. Sensors <NUM> whereof two examples are shown as placed in heat source <NUM> are connected to control unit <NUM> for providing process relevant data.

Heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM> includes a refrigerant that may be selected from the group consisting of R134a, R407C, R290, R1270, and R600a. Specifically the refrigerant is one of R290, R1270, and R600a, and included in heat pump <NUM>, <NUM>, <NUM>, <NUM>, <NUM> at an amount not exceeding <NUM> as required or suggested by pertinent safety regulations for household appliances <NUM> incorporating flammable refrigerants.

As shown in <FIG>, household appliance <NUM> may be embodied as an appliance for drying pieces of laundry <NUM>, or washing and drying pieces of laundry <NUM>. In that case drying chamber <NUM> includes a drum <NUM> for receiving the pieces of laundry to be dried, drum <NUM> rotatable reversibly in two directions as shown by double arrow <NUM>. Paddles <NUM> server for agitating and tumbling pieces of laundry <NUM> during a drying process.

As shown in <FIG>, household appliance <NUM> may also be embodied as an appliance whose treatment chamber has a cabinet <NUM> for cleaning and drying dishes <NUM>. The cabinet <NUM> has a rack <NUM> for disposing dishes <NUM> for cleaning and drying, and a spray arm <NUM> (or rather, a plurality thereof) for spraying cleaning fluid onto dishes <NUM>.

Claim 1:
A compressor module (<NUM>) for a heat pump (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in a household appliance (<NUM>), including a compressor (<NUM>) for compressing a circulating refrigerant, a motor (<NUM>) for driving said compressor (<NUM>), a casing (<NUM>) enclosing said compressor (<NUM>) and said motor (<NUM>), an inlet guide (<NUM>) for guiding the refrigerant to said compressor (<NUM>) and an outlet guide (<NUM>, <NUM>) for guiding the refrigerant from said compressor (<NUM>), wherein a heat exchanger (<NUM>) is provided for transferring heat from said outlet guide (<NUM>, <NUM>) to said inlet guide (<NUM>), characterized in that
said casing (<NUM>) is part of said outlet guide (<NUM>, <NUM>), and wherein said heat exchanger (<NUM>) includes said casing (<NUM>); and
said inlet guide (<NUM>) includes a tube coil (<NUM>, <NUM>) wound around and contacting said casing (<NUM>), said tube coil (<NUM>, <NUM>) included in said heat exchanger (<NUM>).