EP3578817B1 - Compressor, heat pump or air conditioning system or refrigeration machine and method for compacting - Google Patents

Description

The invention relates to a compressor with a compression device with an inlet and an outlet and with an inlet-side collector and an outlet-side collector, the compression device being set up to convey a fluid from the inlet-side collector into the outlet-side collector. The invention also relates to a heat pump, air conditioning or refrigeration machine equipped with such a compressor, and a method for compressing a fluid. Devices and methods of this type can be used in particular for compressing a refrigerant which transports useful heat between an evaporator and a condenser in heat pumps, air conditioning systems or refrigerating machines.

From the US 7,082,785 B2 a generic compressor is known. The moving parts of this compressor require oil lubrication. This oil is therefore partly discharged together with the compressed refrigerant. This leads to the contamination of the following components, for example the evaporator or the condenser of a heat pump, air conditioning system or refrigeration machine. The known compressor therefore has an oil separator which separates the oil from the refrigerant and feeds it to a sump, where it can be used again to lubricate the compressor.

However, this known compressor has the disadvantage that the oil separation takes place before the compression. Thus, although the known compressor prevents the accumulation of Oil in the components of the heat pump, air conditioning or refrigeration machine. However, since the cleaned refrigerant is immediately contaminated again during the subsequent compression, contamination of subsequent components with oil is not reliably prevented. Pipes, condenser and evaporator can be contaminated with a permanent oil layer, which is established as a mass balance between the entry from the contaminated refrigerant and the discharge from the returning refrigerant. This oil film can lead to thermal resistance, so that the performance of the device equipped with the known compressor can decrease.

From the EP 0 066 221 A1 a compressor unit is known in which the compressed, oil-laden gas is passed over a sieve wire body in order to separate the entrained oil particles. The oil separated on the mesh of the sieve wire body collects at the bottom of the pressure chamber. To return the oil to the low-pressure side, a valve should be used which is controlled depending on the oil level in the pressure chamber.

The WO 02/42645 A1 discloses a compressor. The gas stream conveyed by this is fed to a lubricant separator. A branch duct connects to the lubricant separator, which leads back to the compressor and in which a control valve is arranged.

The EP 3 136 020 A1 shows a compressor and an oil separator. This oil separator has a return line which returns the oil to the compressor. A capillary tube is arranged in the return line as a flow limiter, which represents a flow resistance. The flow through the return line is not regulated depending on the oil level, so that the oil return worsens the efficiency.

From the EP 1 043 501 A2 a compressor is known which has an oil separator. The oil separator is provided with a return line which returns the oil to the compressor after the compressor has been switched off.

Proceeding from the prior art, the invention is therefore based on the object of specifying a compressor and a heat pump, air conditioning or refrigeration machine equipped therewith with improved performance.

The object is achieved according to the invention by a device according to claim 1, a heat pump or an air conditioning system or a refrigerating machine according to claim 10 and a method according to claim 11. Advantageous further developments of the invention can be found in the subclaims.

According to the invention, a compressor with at least one compression device is proposed, the compression device having at least one inlet and at least one outlet. The compression device can be, for example, a known screw compressor, a rotary piston compressor, a reciprocating piston compressor, a scroll compressor, a rotary vane compressor, a swash plate compressor or another known compression device. A fluid, in particular a refrigerant, is made available to this at the inlet at a comparatively low pressure and a low temperature. This is conveyed in the compression device and compressed in the process, so that it is released via the outlet of the compression device with a higher pressure and, in some cases, a higher temperature. The compression device usually has an oil supply. On the one hand, this oil is used for lubrication, ie to reduce friction and to protect the moving parts of the compression device against wear. In addition, the oil can also be used to seal the gap, so that the fluid to be compressed is undesirably transferred from the high pressure side to the low pressure side of the compression device is avoided or at least reduced.

The compressor according to the invention also has an inlet-side collector and an outlet-side collector. The collector in the sense of the present description is a delimited volume, for example part of the housing of the compressor or a separate reservoir. The fluid or refrigerant to be compressed is fed to the collector on the inlet side. The compression device sucks in the gas from the inlet-side collector, compresses it and feeds it via its outlet to the outlet-side collector. The collector on the outlet side is also a delimited, pressure-resistant volume, for example a housing part or a separate pressure accumulator in the line system of the device provided with the compressor. Pipelines can be connected to the outlet-side collector, which supply the downstream components with the pressurized fluid or refrigerant.

In some embodiments of the invention, the compression device and optionally also the associated drive means can be arranged in the inlet-side collector. In other embodiments of the invention, the compression device and optionally also the drive means required for this can be arranged in the outlet-side collector. This leads to the compression device and its drive means being washed around by the fluid or refrigerant flowing past and thereby cooled. In some embodiments of the invention, separate cooling by air or liquid can thereby be dispensed with.

The oil lubrication and oil seal of the compression device have the effect that a small amount of oil is discharged from the compression device. This oil is then together with the pumped fluid in the outlet Collectors promoted. In order to prevent oil from contaminating downstream components together with the fluid, it is proposed according to the invention to arrange at least one filter element in the collector on the outlet side. The filter element is designed to at least partially absorb the oil from the fluid. In some embodiments of the invention, a plurality of filter elements can also be cascaded so that the fluid flows through them sequentially. In other embodiments of the invention, a plurality of filter elements can be arranged in parallel so that only a partial flow of the fluid flows through each filter element. The arrangement of the filter element according to the invention in the outlet-side collector saves the installation space required for a separate oil separator. In addition, operational reliability increases, since the installation of the oil separator or the filter element can no longer be forgotten during the final assembly of a heat pump or an air conditioning system.

The oil absorbed by the filter element is aggregated into larger drops in the filter element, which are then transported, driven by gravity, to a collection point in the outlet-side collector. In some embodiments of the invention, the collection point can be the lowest point of the outlet-side collector, so that the oil deposited on the walls of the outlet-side collector also collects there. In addition, a separate conveying device within the collector can be dispensed with in this way.

At least one return line, which is set up to feed the oil from the collection point to an oil sump and / or the compression device, starts at the collection point. In order to avoid or at least reduce an overflow of the fluid to be conveyed from the outlet-side collector into the inlet-side collector, at least one valve is located on or in the return line which the return line can be closed. Thus, the permeability of the return line can be controlled so that it is only opened when there is actually oil to return. This can increase the efficiency of the compressor according to the invention.

According to the invention, the valve is a float valve. A float valve has the advantage that it can work automatically without complex electronic controls. The float opens the valve when a predeterminable first oil level is reached and closes the valve when it falls below a predeterminable second oil level, so that the oil is reliably returned and pressure losses in the fluid to be conveyed are avoided.

The same effect can be achieved with a solenoid valve and / or a motor-driven valve. In this case, a sensor system can optionally be present which determines the amount of oil in the collection point and, when a predefinable amount is reached, opens the valve either for a predefinable time or until the oil level in the collection point falls below the level. In other embodiments, the valve can be opened as a function of time or volume flow by an electronic control or regulation system, for example after a certain operating time or after a certain amount of fluid conveyed.

According to the invention, the float valve also contains a spring which acts on the valve in the opening direction with a spring force. Such a spring can compensate for the force acting on the float due to the pressure difference between the outlet-side collector and the inlet-side collector, so that lower actuation forces that can be applied by a smaller float are sufficient to open the float valve. In addition, such a spring has the effect that when the compressor is switched off and thus when the Pressure difference between the inlet-side and the outlet-side collector, the float valve is opened by the spring, so that any oil remaining in the collection point is reliably discharged into an oil sump when the compressor is shut down.

In some embodiments of the invention, the spring may contain or consist of a shape memory alloy. A shape memory alloy allows a spring to be given two different shapes or lengths depending on the temperature. For this purpose, the shape memory alloy can be selected from NiTi, in particular 60NiTi, 56NiTi, CoNiAl, CuZn, CuZnAl, CuAlNi, FeNiAl, FeMnSi, ZnAuCu, AgCd with 44-49 at.% Cd, AuCd with 46.5-50 at.% Cd, CuAlNi 14-14.5 wt% Al and 3.0-4.5 wt% Ni, CuSn with about 15 at% Sn, CuZn with 38.5-41.5 wt% Zn, CuZnX (X = Si, Al, Sn), FePt with about 25 at.% Pt, MnCu with 5-35 at% Cu, FeMnSi, CoNiAl, CoNiGa, NiFeGa, TiNb, NiTi with about 55-60 wt% Ni, NiTiHf, NiTiPd and / or NiMnGa.

In some embodiments of the invention, the filter element can contain or consist of a coalescence separator. In other embodiments of the invention, the filter element can contain or consist of a mass force separator. In yet other embodiments of the invention, the filter element can contain both a coalescence separator and a mass force separator.

A coalescence separator contains at least one porous material through which the fluid can flow, the oil mist contained in the fluid being at least partially deposited on the inner surfaces of the pores or spaces contained in the porous filter material. This oil mist can then aggregate to form larger drops, which are subsequently driven out of the filter element by gravity or also supported by the fluid flow. For this purpose, the filter element can contain a fiber mat, a woven fabric, a knitted fabric or a nonwoven fabric. In other In embodiments of the invention, the filter element can contain or consist of a plurality of expanded metal grids, an open-pore foam or a bed or a spherical packing. The filter element can contain or consist of a metal, plastic or glass fibers. The surfaces of the materials forming the filter element can be oleophilic or oleophobic. In some embodiments, the filter element can hold back more than 90% of the oil in the mass flow passing through it.

A mass force separator is based on a mechanical structure that leads to flow deflection. The flow can be deflected in such a way that the oil mist is at least partially deposited on the structures used for deflection, aggregated there to form larger drops and then fed to the collection point driven by gravity. The inertial force separator can thus contain or consist of at least one baffle plate and / or a cyclone and / or a pipe bend.

A coalescence separator can contain at least one first layer and at least one second layer, the first layer being selected from a fleece and / or a porous shaped body with a first pore size and the second layer being selected from a fleece or a shaped body with a second pore size or a perforated material layer. The second pore size can be larger than the first pore size, so that the separation on the one hand and the transport of the oil droplets by gravity and / or capillary forces on the other hand takes place in spatially separate layers of the coalescence separator. A perforated material layer can contain a metal or plastic and be provided with regular or irregular holes. In some embodiments of the invention, such a material layer can furthermore have fluid channels which reliably discharge the oil discharged from the first layer into the collection point.

In some embodiments of the invention, the coalescence separator can also contain a third layer, which in turn is selected from a fleece or a molded body with the second pore size or a perforated material layer. If perforated material layers are used for the first and third layers of the coalescence separator, the bores can be offset from one another in the direction of flow of the fluid, so that the path length of the flow in the second layer is increased and the oil separation is thereby improved. In other embodiments of the invention, the bores can be arranged one above the other in the direction of flow and in this way offer a lower flow resistance to the flow of the fluid.

In some embodiments of the invention, the compressor according to the invention can have a housing which is divided by at least one partition wall into at least two partial volumes, one partial volume forming the inlet-side collector and the other partial volume forming the outlet-side collector. This does not exclude the fact that there are further partition walls which separate further partial volumes, for example to form an oil sump or an electrical connection box or to accommodate drive means or control electronics for the at least one compression device and / or the valve.

• Figur 1 einen erfindungsgemäßen Verdichter gemäß einer ersten Ausführungsform.
• Figur 2 zeigt einen erfindungsgemäßen Verdichter gemäß einer zweiten Ausführungsform.
• Figur 3 zeigt einen Querschnitt durch einen Koaleszenzabscheider gemäß einer ersten Ausführungsform.
• Figur 4 zeigt den Querschnitt durch einen Koaleszenzabscheider gemäß einer zweiten Ausführungsform.
• Figur 5 erläutert die Funktionsweise einer ersten Ausführungsform eines Ventils.
• Figur 6 zeigt eine zweite Ausführungsform eines Ventils in geschlossener Stellung.
• Figur 7 zeigt eine zweite Ausführungsform eines Ventils in geöffneter Stellung.
• Figur 8 erläutert die Funktionsweise einer dritten Ausführungsform eines Ventils.
• Figur 9 erläutert die Funktionsweise einer vierten Ausführungsform eines Ventils.

The invention is to be explained in more detail below without restricting the general inventive concept. It shows

• Figure 1 a compressor according to the invention according to a first embodiment.
• Figure 2 shows a compressor according to the invention according to a second embodiment.
• Figure 3 shows a cross section through a coalescence separator according to a first embodiment.
• Figure 4 shows the cross section through a coalescence separator according to a second embodiment.
• Figure 5 explains the functioning of a first embodiment of a valve.
• Figure 6 shows a second embodiment of a valve in the closed position.
• Figure 7 shows a second embodiment of a valve in the open position.
• Figure 8 explains the functioning of a third embodiment of a valve.
• Figure 9 explains the functioning of a fourth embodiment of a valve.

Figure 1 shows a first embodiment of a compressor according to the invention in section. The compressor 1 contains a housing 3, which can be made of metal or plastic, for example. The housing 3 can be manufactured, for example, as a cast or deep-drawn part from a steel or aluminum sheet. In the exemplary embodiment shown, the housing 3 has an approximately round base area and thus an approximately cylindrical appearance overall. Furthermore, the housing has a mounting flange 37 in the bottom area, with which the housing can be fastened in a vehicle, aircraft or a building. The invention is not restricted to this form of housing.

In the interior of the housing 3 there is a partition 35 which divides the interior of the housing 3 into two partial volumes. In the illustrated embodiment, a forms The partial volume forms the inlet-side collector 31 and the other partial volume forms the outlet-side collector 32. The fluid to be compressed, for example a refrigerant, enters the inlet-side collector 31 via a first connection piece 311. An optional baffle plate 312 can be located in front of the first connection piece 311 in order to direct and control the flow of the entering fluid. The fluid is conveyed by the compression device 2 from the collector 31 on the inlet side. Here, the pressure and / or the temperature of the fluid can increase and the volume can be reduced.

The compression device 2 conveys the fluid into the outlet-side collector 32. There, the compressed fluid can be fed to a subsequent use via a second connection piece 322 and can be used, for example, to drive a machine tool, a heat pump, an air conditioning system or a refrigeration machine.

The compression device 2 has at least one inlet 21 and at least one outlet 22. The inlet 21 withdraws the fluid from the inlet-side collector 31. The outlet 22 is connected to the outlet-side collector 32 via an opening 352 in the partition 35. It should be pointed out that the pipe sockets shown in the drawing as inlet 21 and outlet 22 are only to be understood as examples. In other embodiments of the invention, the pipelines can be shorter or longer. In some embodiments of the invention, pipelines can also be omitted completely, for example if the partition 35 is at the same time part of the housing of the compression device 2.

The compression device 2 itself can be a scroll compressor, a Roots compressor, a reciprocating piston compressor, a rotary vane compressor or a rotary piston compressor or any other compression device known per se contain. The invention does not teach the use of a specific compression device 2 as a solution principle. Therefore, the compression device 2 is in Figure 1 also shown only schematically. Details of the construction are familiar to the person skilled in the art.

Drive means 25 are available to provide the mechanical drive power of the compression device 2. In some embodiments of the invention, this can be an electric motor. This can be controlled in a manner known per se with connection contacts, switches and motor protection devices (not shown).

It should be pointed out that in some embodiments of the invention, the compression device can also be operated with a plurality of drive means 25. In the same way, several compression devices 2 can also be present in the housing 3, which either convey the fluid in series in order to achieve a higher final pressure, or which convey the fluid in parallel in order to increase the flow rate. A plurality of compression devices 2 can be operated with a single electric drive device 25 or, in turn, a plurality of drive devices 25 are available to drive the plurality of compression devices 2.

The compression device 2 is usually provided with an oil supply. On the one hand, the oil serves to lubricate the moving parts of the compression device and thus to reduce wear and friction. In addition, the compression device 2 can also be oil-sealed, ie production-related gaps in the compression space are sealed by the oil film forming in this gap in order to enable or at least optimize the operation of the compression device.

The oil required to operate the compression device 2 is collected in an oil sump 36 at the bottom of the housing 3. From there the oil is withdrawn via an oil pump (not shown) and fed to the compression device 2. Excess oil can be discharged from the compression device 2 via corresponding flushing openings and then collected again in the sump 36.

Due to the functioning of the compression device 2 as an oil-lubricated and optionally also oil-sealed machine, some of the oil is undesirably expelled with the fluid to be pumped and reaches the outlet-side collector 32 there. In order to avoid that this oil reaches the outlet-side collector 32 together with the fluid flow via the leaves the second connection piece 322, it is proposed according to the invention to arrange a filter element 4 in the outlet-side collector 32. The filter element 4 can contain or consist of a coalescence separator and / or a mass force separator. Embodiments of a coalescence separator are described below with reference to FIG Figures 3 and 4 explained in more detail.

The filter element 4 is set up and intended to feed the oil to the collecting point 325 driven by gravity and / or by capillary forces when the compressor 1 is in operation. As soon as a predeterminable amount of oil has collected there, it is fed via a valve 6 to a return line 5, which returns the oil from the collection point 325 to the oil sump 36. In this way, the fluid emerging from the second connecting piece 322 contains no or a smaller amount of the oil, as a result of which the contamination of the following components is reduced or avoided. In the case of a heat pump, an air conditioning system or a refrigeration machine, this can increase the output and / or the efficiency.

Based on Figure 2 a second embodiment of the invention is explained. Also Figure 2 represents a section through a compressor according to the invention. Identical components of the invention are provided with the same reference symbols, so that the following description is limited to the essential differences.

How out Figure 2 As can be seen, the filter element 4 does not surround the opening 352 and thus the inlet side of the outlet-side collector, but the filter element 4 is arranged in front of the second connection piece 322. Oil conveyed with the fluid can thus be deposited on the surfaces of the collector and drain from there into the collecting point 325 driven by gravity. Any oil still remaining is then removed by the filter element 4 immediately before the fluid flow leaves the second connection piece 322 and from there likewise fed to the collection point 325. In this case too, the filter element 4 can be a coalescence separator and / or a mass force separator. The simplest form of a mass force separator can be a baffle plate, which deflects the flow in such a way that the oil mist adheres to the baffle plate due to its inertia and runs off into the collecting point 25 driven by gravity. A coalescer can be used as described above in connection with Figure 1 be constructed as described.

In this case, too, the collecting point 25 can represent the lowest point of the outlet-side collector 32, so that the oil is collected there without further measures, such as pumps, and is supplied to the sump 36 via the valve 6 and the return line 5.

Both embodiments have in common that the valve 6 remains closed until a sufficient amount of the oil has accumulated in the collection point 325. This avoids that the fluid is in an undesirable manner from the outlet-side collector 32, which under comparatively high pressure, flows back into the inlet-side collector 31, which is under comparatively low pressure. Such a backflow would return part of the fluid compressed and conveyed by the compression device 2, so that this would have to be conveyed again. This reduces the efficiency of the compressor. The invention avoids this disadvantage through the valve 6, which closes the return line 5 until a sufficient amount of oil has been collected in the collection point 325. The valve 6 then opens briefly in order to transfer the oil via the return line 5 into the sump 36. This is done on the one hand by gravity. On the other hand, the pressure difference between the outlet-side and inlet-side collectors also helps to pump the oil through the return line. When the oil level falls below a predeterminable level in the collection point 325, the valve 6 closes. For this purpose, the valve 6 can be, for example, a shape memory valve. The valve can thus be activated as a function of the measured oil level in the collection point 325. According to the invention, the valve 6 is a float valve. Such a float valve is described below with reference to Figure 5 explained in more detail.

Based on Figures 3 and 4 two embodiments of a coalescence separator are shown in section. Figure 3 shows a section through a coalescence separator 4, which, for example, as in FIG Figure 1 shown above the opening 352 in the outlet-side collector 32 can be arranged. The coalescence separator contains a first layer 41 and at least one second layer 42 Figure 3 also an optional third layer 43, which can also be omitted in other embodiments.

The first layer 41 represents the actual filter layer, which is used for oil separation. This can for example consist of a plurality of fibers, which for example as a fleece, knitted fabric, knitted fabric or braid are joined together so that pores form between adjacent fibers. In other embodiments of the invention, the first layer 41 can contain a porous shaped body, for example an open-cell foam. In yet other embodiments of the invention, the second layer 42 can contain a metal or an alloy, for example in the form of an expanded metal grid or a stack of expanded metal grids or perforated plates. In some embodiments of the invention, the first layer 41 can also contain a plurality of different layers, for example a nonwoven layer which is surrounded on one or both sides by a knitted fabric or a porous shaped body which is embedded in a nonwoven. The person skilled in the art will recognize a large number of possible embodiments here. Fibers or molded bodies can consist of a metal or an alloy, glass or plastic. Fibers, perforated sheets or expanded metal grids can be provided with an oleophobic or oleophilic coating.

The first layer 41 represents the actual filter element. This means that when the fluid passes through the first layer 41, the fluid penetrates the layer 41 almost unchanged, but the oil mist contained therein is at least partially bound to the inner surfaces of the porous body of the first layer 41 becomes. The oil film bound in this way can grow into larger droplets in the pores of the first layer 41, which then drain out of the coalescence separator 4 either in the first layer or via the adjacent second and / or third layers 42 and 43, driven by gravity.

The second layer 42 and the optional third layer 43 can be used to transport the oil into the collection point 325 as described above. For this purpose, the second layer 42 and / or the third layer 43 can have a similar structure to the first layer 41, the pore size or the The pore size distribution can be selected to be larger than the mean pore size or pore size distribution of the first layer 41. In this way, the functions of separation and transport can be spatially separated from one another.

In other embodiments of the invention, the second layer 42 and the optional third layer 43 can also only serve to mechanically stabilize the first layer 41. For this purpose, the second and / or third layer can contain a perforated material layer, for example a metal or an alloy in the form of a sheet metal or a plastic, which are each provided with bores 425 and 435. In some embodiments of the invention, the pores 425 in the second layer 42 and the pores 435 in the third layer 43 can be arranged offset from one another in such a way that they are not arranged one above the other in the flow direction of the fluid. This extends the mean path covered by the fluid in the first layer 41, so that the separation can be improved. In other embodiments of the invention, the bores can also be arranged one above the other in order to reduce the flow resistance.

Based on Figure 4 a second embodiment of a coalescence separator is explained in more detail. The same components of the invention are provided with the same reference numerals, so that the following description is limited to the essential differences of the invention. The main difference is the design of the bores 435 in the third layer 43. These are designed in such a way that an overhang 431 is punched out of the third layer 43, so that on the one hand there is a gap as an opening 435 and on the other hand a remainder of the punched material layer as an overhang 431 is above the opening. This prevents constituents of the first layer 41 from being carried out of the opening 435 by the flow of the fluid. Furthermore, it is avoided that large oil droplets detaching from the wall of the second collector get into the first layer 41 penetrate. Rather, these can run over the protrusion 431 on the outside of the third layer 43.

Based on Figure 5 a first embodiment of a valve 6 is explained in more detail. The valve 6 is seated in a housing 62, which has an approximately cylindrical basic shape and, starting from the bottom of the collecting point 325, projects through the partition 35 into the first collector 31. At the end of the housing 62 there is a cone 625 which can be sealed with a likewise cone-shaped, complementarily shaped sealing element 615.

The sealing element 615 is attached to a float 61. In some embodiments of the invention, the sealing element 615 and the float 61 can be manufactured in one piece, for example from a plastic material.

On the upper wall of the housing 3 there is a guide rod 63, which is also approximately perpendicular to the partition 35 and protrudes into the housing 62 parallel to the axis of symmetry of the latter. For this purpose, the guide rod 63 is attached with its first end 631 to the wall of the housing 3, for example by soldering or welding. The second, opposite end 632 projects freely into the housing 62. The float 61 is provided with a central bore into which the guide rod 63 engages so that the float can be moved up and down along the guide rod 63.

If oil now collects in the collecting point 325, it runs into the interior of the housing 62 at the lowest point of the collecting point 325. There the outlet is initially closed by the sealing element 615, which rests in the cone 625. As the oil level rises, the float 61 receives increasingly more buoyancy until it slides upwards along the guide rod 63 and releases the sealing element 615. In this case the oil can pass through the lower one Opening 64 of the housing 62 run off. After the oil level has fallen sufficiently low, the float 61 lowers so that the sealing element 615 can close the opening 64 again.

On the one hand, the weight of the float acts on the float 61, which moves the float 61 downward and thus the sealing element 615 into the closed position. This is counteracted by the buoyancy force of the oil collecting in the housing 62 and the collecting point 325. However, when the device is in operation, another force, which results from the pressure difference and which also holds the sealing element 615 in the closed position, acts on the float. This force results from the pressure difference between the inlet-side collector 31 and the outlet-side collector 32. Since the pressure generated by the compression device prevails in the outlet-side collector 32, the float 61 is additionally subjected to this pressure or through the opening 64 into the cone 625 sucked in. Depending on the pressure difference made available by the compression device 2, the float 61 must therefore have considerable buoyancy forces in order to still open against the pressure difference. According to the invention, a spring 65 is therefore arranged below the float 61, which presses the sealing element 615 out of the cone 625 and at least partially compensates for the force caused by the pressure difference.

This feature has several advantages. On the one hand, the float 61 can be made smaller, since the oil now only has to apply the force to overcome the friction of the guide rod 63 and its own weight. The force on the float 61 caused by the pressure difference is at least partially or predominantly compensated for by the spring. On the other hand, the spring 65 can be designed in such a way that it lifts the float 61 when the compression device 2 is switched off and after the Pressure difference increases, so that regardless of the respective filling level in the collection point 325, the oil in any case drains into the sump 36 when the compressor according to the invention is taken out of operation.

In the illustrated embodiment, the spring 65 is shown below the sealing element 615. This is only to be understood as an example. Of course, the spring can also act at other points on the float 61, for example as a tension spring along the guide rod 63 or as a compression spring in the housing 62, the spring being able to act at the transition from the housing 62 to the cone 625.

Based on Figures 6 and 7 a second embodiment of a valve 6 is explained in more detail. It shows Fig. 6 the valve in the closed position and Fig. 7 shows the valve in the open position. The same components of the invention are provided with the same reference symbols, so that the following description is limited to the essential differences.

The second embodiment of the invention also uses a spring 65 which is set up to move the float 61 with the sealing element 615 arranged thereon into the open position. In contrast to the in Fig. 5 As shown in the first embodiment, the spring 65 contains a shape memory alloy or consists of such an alloy. Such a shape memory alloy is a special metal that can exist in two different crystal structures. The shape change of the spring is based on the temperature-dependent change in the crystal structure. In the illustrated embodiment, the spring 65 has the in Fig. 6 shown, comparatively small longitudinal extent. At a lower temperature, the spring takes the in Fig. 7 Shown shape with greater longitudinal extent.

If the compressor according to the invention is put out of operation, the housing 3 cools down with all of the components contained therein. This leads to the fact that the spring 65 the in Fig. 7 position shown. As a result, the sealing element 615 is pressed out of the cone 625 and the opening 64 is released. In this way, oil located in the collecting point 325 reliably drains into the sump 36 when the compressor 1 is shut down.

If the compressor is now put into operation, the fluid is compressed by the compression device 2 and heated in the process. The heated fluid initially flows partially back through the collection point 325, the cone 625 and the opening 64 into the inlet-side collector 31. The flow of the heated fluid on the spring 65 leads to the heating of the spring 65. This pulls together and takes the in Fig. 6 shown, shortened form. As a result, the float 61 is lowered and the sealing element 615 is guided into the cone 625. This closes the opening 64 so that the flow of the heated fluid at the spring 65 comes to a standstill. The compressor 1 is now in normal operation, in which the fluid is conveyed from the inlet-side collector 31 into the outlet-side collector 32 and leaves it through the second connection piece 322.

Oil carried along by the fluid during regular operation is at least partially separated in the filter element 4, as described above, and fed to the collection point 325. The spring 65 is in thermal contact with the inlet-side collector 31 and can therefore give off thermal energy to the uncompressed, comparatively cold fluid. At the same time, the float 61 is moved upwards by the buoyancy forces generated by the oil in the collecting point 325. After a sufficiently long operating time, this ultimately leads to the float 61 returning to the in Fig. 7 assumes the open position shown, in which it slides up on the guide rod 63 and the opening 64 is free.

The oil in the collection point 325 can now flow off into the sump 36 via the opening 64 and an optional return line. The valve 6 then closes again, as described above for the initial start-up.

Based on Fig. 8 a third embodiment of a valve 6 is described. The valve 6 according to the third embodiment in turn has an opening 64 which can be closed by a sealing element 615. The sealing element 615 is located at the end of a push rod 73. The push rod 73 is moved up and down by electrical drive means 7 so that the sealing element 615 can be moved from the open to the closed position and from the closed to the open position.

The electric drive means 7 can contain, for example, a magnetic coil which, when current flows, generates a magnetic field which attracts a ferromagnetic push rod 73 and thus opens the valve 6. In other embodiments, the electric drive means 7 can contain a motor, for example a stepping motor or a linear motor. Such a motor can move the push rod 73, for example via a spindle drive, and thus open the sealing element 615.

For opening and closing the sealing element 615 there is an electronic control or regulation (not shown). This is supplied with an actual value of the oil level in the collection point 625, which is recorded by a sensor system. If it is recognized that the actual value exceeds a predefinable setpoint value, a corresponding control signal can be output to the drive means 7.

In the exemplary embodiment shown, the sensor system comprises a lower limit switch 731 and an upper limit switch 732. The limit switches 731 and 732 are actuated by a float 61, which has a through hole through which the push rod 73 is guided, so that the float 61 slides up and down along the push rod 73.

If the float 61 is in the lower position, it rests with its own weight on the lower limit switch 731. The control or regulating device can thus be reported that there is no or only a small amount of oil in the collection point 325. When the oil level in the collecting point 325 rises, the float 61 floats on the oil until it reaches the upper limit switch 732. If this limit switch is actuated, the control or regulating device gives the electrical drive means 7 the signal to open the sealing element 615 in the cone 625.

As the oil drains from the collection point 325, the float 61 sinks again until it actuates the lower limit switch 731. From this, the control or regulating device generates a signal to close the electrical drive means 7, so that the opening 64 is closed again and an undesired overflow of the compressed fluid from the outlet-side collector 32 into the inlet-side collector 31 is avoided.

In addition to this basic functionality, the control or regulating device can take on other functions, for example a safety shutdown of the compressor 1 can take place if the float 61 does not reach the limit switch 731 after a predetermined opening time of the valve 6.

It should be pointed out that the combination of the limit switches 731 and 732 with a float 61 is only to be understood as an example. In other embodiments of the invention, other types of Sensors can be used to measure the level of the collecting point 325, for example inductive, capacitive or optical sensors. In still other embodiments of the invention, sensors based on an electrical resistance measurement can be used. In these cases, a float 61 can also be dispensed with in some embodiments of the invention.

Figure 9 explains the functioning of a fourth embodiment of a valve. The same components of the invention are provided with the same reference symbols, so that the following description is limited to the essential differences. The fourth embodiment is similar to the second embodiment, which is based on FIG Figures 6 and 7 was explained.

The fourth embodiment uses a longer return line 5 than the second embodiment, which returns the oil deep into the inlet-side collector 31. The spring 65, which can contain a shape memory alloy or can consist of it, is arranged at the end of the return line 5 and thus also in the inlet-side collector 31. The spring can produce a higher spring force when it is relatively cold and produce a lower spring force when it is relatively warm. Since the spring 65 in the fourth embodiment is exposed to lower temperatures on average, the spring force is higher on average. The spring 65 acts on the sealing element 615 via a push rod 66, the push rod 66 being guided within the return line 5.

Since the oil cools on its way through the return line 5, the fourth embodiment avoids the problem that the valve 64 is immediately closed by the sealing element 615 when the spring 65 comes into contact with the hot, draining oil and thereby the spring force decreases. This ensures that the collection point is completely emptied.

Of course, the invention is not limited to the embodiments shown. The above description is therefore not to be regarded as restrictive but rather as explanatory. The following claims are to be understood in such a way that a named feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Insofar as the claims and the above description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without defining a hierarchy.

Claims (15)

1. Compressor (1) comprising a compression device (2) having an inlet (21) and an outlet (22) and having an inlet-side collector (31) and an outlet-side collector (32), the compression device (2) being designed to deliver a fluid from the inlet-side collector (31) into the outlet-side collector (32),
   the outlet-side collector (32) also containing a filter element (4), which is designed to at least partially receive oil from the fluid and transport it to a collection point (325) in the outlet-side collector (32), the inlet-side collector (31) and the outlet-side collector (32) being further connected to one another via a return line (5), which starts at the collection point (325) and can be closed by a valve (6), the valve being designed to open when oil is present in the outlet-side collector (32) for being returned into the inlet-side collector (31),
   characterized in that
   the valve (6) is a float valve and the float valve contains a spring (65), which applies a spring force to the valve in the opening direction.
2. Compressor according to claim 1, characterized in that the spring (65) acts on the valve via a push rod (66).
3. Compressor according to claim 2, characterized in that the spring contains or consists of a shape memory alloy.
4. Compressor according to claim 3, characterized in that the shape memory alloy is selected from 60NiTi, 56NiTi, CoNiAl, CuZn, CuZnAI, CuAlNi, FeNiAl, FeMnSi, ZnAuCu, AgCd with 44-49 at.% Cd, AuCd with 46.5-50 at.% Cd, CuAINi with 14-14.5 wt% Al and 3.0-4.5 wt% Ni, CuSn with about 15 at% Sn, CuZn with 38.5-41.5 wt% Zn, CuZnX with X = Si, Al, Sn, FePt with about 25 at.% Pt, MnCu with 5-35 at.% Cu, FeMnSi, CoNiAl, CoNiGa, NiFeGa, TiNb, NiTi with about 55-60 wt% Ni, NiTiHf, NiTiPd and/or NiMnGa.
5. Compressor according to any of claims 1 to 3, characterized in that the collecting point (325) is located at the lowest point of the outlet-side collector (32).
6. Compressor according to any of claims 1 to 5, characterized in that the filter element (4) contains or consists of a coalescence separator and/or a mass force separator.
7. Compressor according to claim 6, characterized in that the coalescence separator comprises at least one first layer (41) and at least one second layer (42), the first layer being selected from a nonwoven fabric and/or a porous shaped body with a first pore size and the second layer being selected from a nonwoven fabric or a shaped body with a second pore size or a perforated material layer.
8. Compressor according to claim 7, characterized in that the coalescence separator further contains a third layer (43) which is selected from a nonwoven fabric or a shaped body with a second pore size or a perforated material layer.
9. Compressor according to any of claims 1 to 8, characterized in that it comprises a housing (3), which is divided into at least two partial volumes by at least one partition (35), one partial volume forming the inlet-side collector (31) and the other partial volume forming the outlet-side collector (32).
10. Heat pump or air conditioning system or refrigeration machine with at least one compressor according to any of claims 1 to 9.
11. Method for compressing a fluid, in which the fluid is supplied via an inlet-side collector (31) to the inlet (21) of a compression device (2) and flows via the outlet (22) of the compression device (2) into an outlet-side collector (32), at least some of the oil from the fluid being supplied to a filter element (4), which is arranged in the outlet-side collector (32), the oil from the filter element (2) being supplied in a gravity-driven fashion to a collection point (325) in the outlet-side collector (32) from where it reaches the inlet-side collector (31) via a return line (5) closable by a valve (6), the valve being opened when oil is present in the outlet-side collector (32) for being returned to the inlet-side collector (31),
    characterized in that
    the valve (6) is a float valve and a spring force is applied to the float valve in the opening direction.
12. Method according to claim 11, characterized in that the valve (6) is closed in a first operating state and is open in a second operating state.
13. Method according to any of claims 11 or 12, characterized in that the quantity of oil in the collection point (325) is determined and, when a predeterminable quantity is reached, the valve (6) opens until the oil level in the collection point (325) falls below a certain value.
14. Method according to any of claims 11 to 13, characterized in that the filter element (4) contains or consists of a coalescence separator and/or a mass force separator.
15. Method according to any of claims 11 to 14, characterized in that the spring force acts on the valve (6) via a push rod (66).

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