Patent Application
20200102945
This application claims priority under 35 U.S.C. § 119(a) to Europe Application No. 18 198 034.3 filed Oct. 1, 2018, the disclosure of which is expressly incorporated by reference herein in its entirety.
The present invention relates to a refrigerant compressor comprising an electrical drive unit, a piston/cylinder unit which can be driven by the drive unit for the cyclical compression of refrigerant, and at least one sound-damping unit made of a thermoplastic, through which sound-damping unit refrigerant can flow and which sound-damping unit comprises at least one damping chamber, wherein the at least one sound-damping unit is connected to the piston/cylinder unit in order to enable an exchange of refrigerant between the sound-damping unit and piston/cylinder unit.
Hermetically encapsulated refrigerant compressors have been known for quite some time and are primarily used in refrigerators or refrigerated display cases. The refrigerant process as such has also been known for a long time. Refrigerant is thereby heated in an evaporator by an absorption of energy from the space being cooled and is ultimately overheated and pumped to a higher pressure level by the refrigerant compressor with a piston/cylinder unit, at which pressure level it emits heat via a condenser and is transported back into the evaporator again via a throttle valve in which a pressure reduction and the cooling of the refrigerant take place.
An intake of the (gaseous) refrigerant occurs via a suction tube coming directly from the evaporator during an intake cycle of the piston/cylinder unit. In known hermetically encapsulated refrigerant compressors, the suction tube normally leads to the hermetically encapsulated compressor housing—usually in the vicinity of an inlet of a suction muffler, from which location the refrigerant flows into and through the suction muffler to an intake valve of the piston/cylinder unit. That is, as viewed in the direction of flow, the suction muffler is located upstream of the piston/cylinder unit and primarily serves to keep the noise level of the refrigerant compressor as low as possible during the intake process.
Furthermore, a discharge muffler is usually located downstream of the piston/cylinder unit as viewed in the direction of flow, which discharge muffler serves to keep the noise level of the refrigerant compressor as low as possible during the outflow of the compressed refrigerant.
Possibilities for improving the efficiency of the refrigerant compressor can in particular be found in the reduction of the temperature of the refrigerant at the start of the compression process. Each reduction of the intake temperature of the refrigerant into the cylinder of the piston/cylinder unit causes a decrease in the technical work necessary for the compression process.
In known hermetically encapsulated refrigerant compressors, a marked heating of the refrigerant takes place on the refrigerant's path through the suction muffler to the piston/cylinder unit for design-related reasons. This can be attributed to the heating of the interior of the compressor housing, which heating primarily occurs as a result of the compressed refrigerant discharged in the discharge muffler. The compressed refrigerant discharged in the discharge muffler has temperatures of up to 180° C. and thus constitutes a significant heat source. This leads to a heating of the interior of the compressor housing and, as a further result, to a heat transfer to the refrigerant located in the suction muffler.
A heating of the interior of the compressor housing due to the compressed refrigerant in the discharge muffler is also undesirable in regard to motor cooling.
It is therefore an object of the invention to provide a refrigerant compressor which avoids the aforementioned disadvantages. Temperature increases in the interior of the compressor housing are to be reduced. In particular, the refrigerant temperature at the start of the compression process is to be kept as low as possible in order to increase the efficiency.
With a refrigerant compressor comprising an electrical drive unit, a piston/cylinder unit which can be driven by the drive unit for the cyclical compression of refrigerant, and at least one sound-damping unit made of a thermoplastic, through which sound-damping unit refrigerant can flow and which sound-damping unit comprises at least one damping chamber, wherein the at least one sound-damping unit is connected to the piston/cylinder unit in order to enable an exchange of refrigerant between the sound-damping unit and piston/cylinder unit, the object named at the outset is attained according to the invention in that the at least one sound-damping unit comprises at least in sections a functional surface, wherein the functional surface is embodied such that an emissivity of a section of the sound-damping unit comprising the functional surface is less than 0.7, preferably less than 0.5, particularly preferably less than 0.1.
The functional surface present at least in sections reduces the heat emission and/or heat absorption caused by radiation at the at least one sound-damping unit. Through the use of a functional surface, the at least one sound-damping unit exhibits a reduced emissivity in those regions in which the functional surface is present.
The emissivity of the at least one sound-damping unit indicates how much radiation the at least one sound-damping unit emits compared to an ideal radiant heater, a black body. That is, the at least one sound-damping unit exhibits in those regions in which the functional surface is present a reduced heat emission and/or heat absorption caused by radiation compared to surface sections without a functional surface. The temperature inside a compressor housing is thus reduced. This causes the refrigerant compressor according to the invention to exhibit a better efficiency.
The functional surface can be embodied either on an outer surface of the at least one sound-damping unit, wherein the outer surface is facing the interior of the compressor housing, or on an inner surface of the at least one sound-damping unit, wherein the inner surface is facing the interior of the at least one sound-damping unit, in particular the at least one damping chamber.
Of course, the radiant emission and absorption are equal at a given wavelength. That is, in addition to a reduced heat emission, the functional surface also leads to a reduced heat absorption.
It would be conceivable that the at least one sound-damping unit is produced by an injection-molding method. A production method of this type is characterized by the particular cost-efficiency thereof.
Furthermore, it would be conceivable that the functional surface is polished in order to achieve a particularly low emissivity.
According to the invention, it is provided that the at least one sound-damping unit or at least one of the sound-damping units is embodied as a discharge muffler arranged downstream of the piston/cylinder unit in the direction of flow.
Since the at least one discharge muffler is arranged downstream of the piston/cylinder unit in the direction of flow, preferably inside of the compressor housing, the functional surface must exhibit a low emissivity. This is especially true because the refrigerant enters the at least one discharge muffler after the piston/cylinder unit with a high temperature due to the compression and heats the discharge muffler accordingly. The functional surface is in this case preferably embodied on the inner surface facing the interior of the discharge muffler and results in an improved efficiency of the refrigerant compressor according to the invention, since temperature increases in the interior of the compressor housing are reduced because the heat radiation by the refrigerant is essentially reflected back into the interior of the discharge muffler by the functional surface.
On the discharge muffler, the functional surface can of course also be embodied on the outer surface of the discharge muffler facing the interior of the compressor housing, and can thereby result in an improved efficiency of the refrigerant compressor according to the invention.
It would be conceivable that additional parts of the refrigerant compressor according to the invention are also provided with a similar functional surface having low emissivity, such as parts of the piston/cylinder unit, for example.
In the refrigerant compressor according to the invention, it is preferably provided that the thermoplastic comprises additives, for example, aluminum and/or chromium.
In elaborate tests, it was determined that, under some circumstances, it can be sufficient to add additives to the thermoplastic in order to achieve the formation of a functional surface with an appropriately low emissivity and absorptivity of the at least one sound-damping unit. That is, in such a case, the functional surface is at least partially embodied by a surface section of a solid material of the at least one sound-damping unit, and no additional coating is necessary (although such a coating is also not excluded). It would also be possible that the additives are only present in regions of the solid material of the sound-damping unit that are close to the surface.
In other words, with a refrigerant compressor comprising an electrical drive unit, a piston/cylinder unit which can be driven by the drive unit for the cyclical compression of refrigerant, and at least one sound-damping unit made of a thermoplastic, through which unit refrigerant can flow and which unit comprises at least one damping chamber, wherein the at least one sound-damping unit is connected to the piston/cylinder unit in order to enable an exchange of refrigerant between the sound-damping unit and piston/cylinder unit, the object named at the outset is attained according to the invention in that the thermoplastic comprises additives, such as aluminum and/or chromium, for example, wherein the heat emission of a sound-damping unit made of thermoplastic with additives is reduced compared to a sound-damping unit made of thermoplastic without additives.
The heat emission and heat absorption can also be reduced if the surface of the solid material of the at least one sound-damping unit composed of thermoplastic is polished.
It would be conceivable that the functional surface is only formed by the polishing. That is, the functional surface is in this case formed even if the thermoplastic does not comprise any additives.
Preferably, in the refrigerant compressor according to the invention, it is provided that the functional surface is embodied as a metallic layer. A metallic layer as a functional surface is characterized by a low emission coefficient, especially if the metallic layer is polished.
However, it would also be conceivable that the functional surface is embodied as a non-metallic layer, preferably as a ceramic layer with a low emission coefficient.
In a preferred embodiment of the refrigerant compressor according to the invention, it is provided that the at least one sound-damping unit is completely covered by the metallic layer. In this manner, the temperature inside of the compressor housing is significantly reduced, since the heat absorption and heat dissipation of the at least one sound-damping unit are reduced.
A covering of the at least one sound-damping unit with the metallic layer is particularly easy and cost-effective to produce.
Of course, the metallic layer can also be arranged on the inner surface facing the interior of the at least one sound-damping unit.
In a preferred embodiment of the refrigerant compressor according to the invention, it is provided that the metallic layer contains chromium and/or aluminum. Both chromium and aluminum exhibit, particularly with a polished surface, low emissivities and absorptivities, for which reason they are exceptionally well-suited to be constituents of the metallic layer.
It would be conceivable that the layer containing chromium and/or aluminum exhibits an emissivity between 0.1 and 0.02 in a polished state.
It would furthermore be conceivable that the metallic layer comprises further constituents in addition to chromium and/or aluminum.
In the refrigerant compressor according to the invention, it is preferably provided that the metallic layer is embodied as a metallic film. The metallic layer in the form of a metallic film is characterized by a particularly good reduction in heat emission and heat absorption and is easy to apply.
In the refrigerant compressor according to the invention, it is preferably provided that the at least one sound-damping unit can be obtained by back injection-molding the metallic film; that is, the metallic film is back injection-molded with the thermoplastic. In this case, the film is first supplied to an injection mold. Then, the thermoplastic is injected into the injection mold, wherein the thermoplastic and the film are bonded. It is advantageous that the back injection-molding can be fully automated, and that no adhesive at all is required for the bonding between the thermoplastic and the film.
In a preferred embodiment of the refrigerant compressor according to the invention, it is provided that the metallic layer is spread onto and/or painted onto and/or glued onto and/or galvanized onto the at least one sound-damping unit. With the spreading-on and/or painting-on and/or gluing-on and/or galvanizing, the metallic layer is applied on the at least one sound-damping unit in a simple manner. These types of application are characterized by simple handling and good cost-efficiency.
Galvanizing in particular can be easily automated, and the coating produced by galvanizing is characterized by low costs as well as rapid producibility.
Preferably, in the refrigerant compressor according to the invention, it is provided that the at least one sound-damping unit or one of the sound-damping units is embodied as a suction muffler arranged upstream of the piston/cylinder unit in the direction of flow.
Since the at least one suction muffler is arranged inside of the compressor housing upstream of the cylinder/piston unit in the direction of flow, the functional surface must exhibit a low absorptivity. This is true because, otherwise, the refrigerant inside of the suction muffler will be heated as a result of the high temperatures that are present inside of the compressor housing—among other things due to the compressed refrigerant discharged in the pressure tube. In this case, the functional surface is thus preferably embodied on the outer surface of the suction muffler facing the interior of the compressor housing and results in an improved efficiency of the refrigerant compressor according to the invention, since the temperature of the refrigerant inside of the suction muffler is not increased by a higher temperature inside of the compressor housing because the heat radiation is essentially reflected back into the compressor housing by the functional surface.
On the suction muffler, the functional surface can of course also be embodied on the inner surface facing the interior of the suction muffler, and can thereby result in an improved efficiency of the refrigerant compressor according to the invention.
The invention will now be explained in greater detail with the aid of exemplary embodiments. The drawings are by way of example and are intended to demonstrate, but in no way restrict or exclusively describe, the inventive concept.
In this matter:
The at least one sound-damping unit 4 can be a suction muffler 6 and/or a discharge muffler 7. The suction muffler 6 is arranged upstream of the piston/cylinder unit 3 in the direction of flow of the refrigerant, whereas the discharge muffler 7 is located downstream of the piston/cylinder unit 3 in the direction of flow of the refrigerant.
On the path between the entry of the refrigerant into the compressor housing 8 and the intake valve of the piston/cylinder unit 3, there occurs, as mentioned previously, an undesired heating of the refrigerant. This can be attributed to the heating of the interior of the compressor housing 8, which occurs, among other things, as a result of the compressed refrigerant discharged in the discharge muffler 7. The compressed refrigerant discharged in the discharge muffler 7 thereby occasionally has temperatures of up to 180° C. and thus constitutes a significant heat source. This leads to a heating of the interior of the compressor housing 8 and, as a further result, to a heat transfer to the refrigerant located in the suction muffler 6.
For this reason, both the suction muffler 6 illustrated in
The metallic layer 5 preferably contains aluminum and, particularly preferably, is embodied as a film that is applied to the suction muffler 6. The metallic layer 5 on the suction muffler 6 is polished in the exemplary embodiment illustrated, for which reason it has a particularly well-reflecting surface. The metallic layer 5 thus has a lower absorptivity, which is why the refrigerant inside of the suction muffler 6 is hardly heated, or not heated at all, as a result of the higher temperatures that can prevail in the interior of the compressor housing 8.
The metallic layer 5 preferably contains aluminum and, particularly preferably, is embodied as a film that is applied to the discharge muffler 7. The metallic layer 5 on the discharge muffler 7 is polished in the exemplary embodiment illustrated, for which reason it has a particularly well-reflecting surface. The metallic layer 5 thus has a lower emissivity, which is why the high temperature of the compressed refrigerant is hardly transferred, or not transferred at all, to the interior of the compressor housing 8. That is, the metallic layer 5 on the at least one discharge muffler 7 reduces or prevents a heat emission.
Of course, additional parts of the refrigerant compressor 1 according to the invention, such as parts of the piston/cylinder unit 3 and various tubes, for example, can also be provided with a functional surface 11, in particular with a metallic layer 5.
Via the refrigerant compressor 1 according to the invention, temperature increases in the interior of the compressor housing 8 are thus reduced, whereby in particular the refrigerant temperature at the start of the compression process, and therefore necessarily also during the intake into the cylinder of the piston/cylinder unit 3, is kept as low as possible. This causes the refrigerant compressor 1 according to the invention to exhibit a better efficiency compared to a known refrigerant compressor 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18198034.3 | Oct 2018 | EP | regional |
