Rolling-piston compressor for a motor vehicle

Abstract

The invention relates to a rolling-piston compressor (2) for a motor vehicle, comprising: a compressor housing (14) having a low-pressure-side inlet (58) and a high-pressure-side outlet (60); an electric-motor drive (4); and a compressor head (6) coupled to the electric-motor drive via a hollow shaft (34), wherein the hollow shaft (34) is axially open at both ends and is provided with radial bores (42), wherein the compressor head (6) comprises a compression chamber (46) and a high-pressure side (52) coupled to the outlet (60), wherein at least one compressor rotor (44a, 44b), eccentrically driven by the hollow shaft, is arranged in the compression chamber (46), wherein at least one spring-loaded separating slide (54a, 54b) for separating the compression chamber (46) into a suction chamber and a pressure chamber is pressed radially against the compressor rotor (44a, 44b), wherein the high-pressure side (52) is fluidically coupled to the low-pressure side (50) of the compressor housing (14) via the hollow shaft (34), and wherein a throttle element (80) is arranged between the high-pressure side (52) and the hollow shaft (34).

Description

[0001] Description

[0002] Rotary piston compressor for a motor vehicle

[0003] The invention relates to a positive displacement machine or a rotary compressor in the form of a rotary piston compressor for a motor vehicle, which is used in particular for the compression of refrigerant in a vehicle air conditioning system.

[0004] Motor vehicles are regularly equipped with air conditioning systems that use a refrigerant circuit to regulate the vehicle interior (passenger compartment), i.e., to cool and heat it. In electrically powered or plug-in hybrid vehicles, the air conditioning system can also be used to condition the vehicle battery (traction battery). These systems generally consist of a closed loop containing a refrigerant. The refrigerant, for example, R-744 (carbon dioxide, CO2), is heated at an evaporator and compressed by a refrigerant compressor. The refrigerant then releases the absorbed heat via a heat exchanger before being returned to the evaporator through an expansion valve.

[0005] In electrically or electromechanically driven refrigerant compressors, the compressor mechanism, the electric motor, and the motor electronics (control unit, ECU) are typically housed together in a single compressor casing. Part of the compressor casing is thus exposed to suction pressure (low-pressure side), and another part to discharge pressure (high-pressure side). The suction gas is also used to cool the electric motor and the electronics. So-called scroll compressors are generally used as refrigerant compressors in vehicle air conditioning systems to compress a refrigerant-oil mixture. The resulting gas-oil mixture is separated, with the separated gas being introduced into the air conditioning circuit, while the separated oil is typically circulated within the scroll compressor to lubricate moving parts.

[0006] So-called rolling piston compressors are generally not used for automotive applications, but only for stationary applications, such as cooling systems or heat pumps.

[0007] In rotary piston compressors, a cylindrical or piston-like compressor rotor rotates completely around an eccentric axis; therefore, rotary piston compressors are also called rotary or circulating compressors. A spring-loaded separating or shut-off valve (vane) is pressed radially against the outer circumference of the compressor rotor, dividing the compressor chamber into two separate chambers (suction and pressure chambers). When a gaseous refrigerant enters the compressor on the suction side (suction gas), it is forced against the separating valve by the compressor rotor, which rolls along the inner wall of the compressor chamber. The rotational movement reduces the volume of the pressure chamber, thus compressing the refrigerant. The separating valve, which moves back and forth with the rotation of the rotor, seals the suction side from the pressure side, eliminating the need for additional inlet valves (suction valves) for the compressor chamber.Rotary piston compressors thus achieve a high coefficient of performance and exhibit particularly low noise levels.

[0008] Rotary piston compressors in stationary applications typically feature a vertical hollow shaft with radial bores, one open end of which is immersed in an oil sump (oil pan) serving as the oil reservoir. The oil is drawn upwards through the hollow shaft and, with the aid of an internal oil slinger plate, continuously supplies the shaft bearings with oil. Another characteristic of such rotary piston compressors is that the compressor housing, particularly the oil sump, is under a uniform gas pressure. In other words, the compressor housing is under either high or medium pressure. Due to this uniform gas pressure inside the compressor housing, the end faces of the hollow shaft are at the same pressure level, so no pressure-induced axial force acts on the hollow shaft.

[0009] In contrast, refrigerant compressors in vehicle air conditioning systems have a horizontally oriented shaft when installed. Furthermore, these refrigerant compressors do not have a traditional oil pan. Because the electric motor and electronics are cooled by the suction gas, the compressor housings of refrigerant compressors in motor vehicles also do not have a uniform gas pressure inside the housing.

[0010] The invention is based on the objective of providing a particularly suitable rotary piston compressor for a motor vehicle, especially for a vehicle air conditioning system. In particular, the oil supply or lubrication of the bearings and moving parts is to be ensured in the case of a horizontally oriented hollow shaft. Furthermore, it is to be ensured that both ends of the hollow shaft have the same pressure level, so that no resulting axial forces act on the hollow shaft.

[0011] The problem is solved according to the invention with the features of claim 1. Advantageous embodiments and further developments are the subject of the dependent claims.

[0012] The rotary piston compressor according to the invention is intended for, and suitable and configured for, a motor vehicle, in particular for a vehicle air conditioning system. The rotary piston compressor has a compressor housing with a low-pressure or suction-side inlet and a high-pressure or discharge-side outlet. An electric motor drive is arranged in the compressor housing, which drives a (rotary piston) compressor mechanism. During operation, the rotary piston compressor conveys or compresses a refrigerant, in particular R744.

[0013] The drive comprises an electric motor, in particular a brushless electric motor, which can be powered by motor or control electronics. The electric motor has a stator fixed to the housing and a rotor mounted to rotate or rotate relative to the stator. The stator is wound with a rotating field or stator winding, and the rotor is, for example, equipped with permanent magnet rotor magnets. The rotor is rigidly connected to a motor or drive shaft. The motor shaft is mounted to rotate or rotate within the compressor housing by means of shaft bearings. Preferably, the motor shaft is mounted by means of plain bearings.

[0014] The motor electronics are housed in a fluid- and pressure-tight separate electronics compartment within the compressor housing. Preferably, the inlet is oriented such that the incoming refrigerant flows along a housing wall of the electronics compartment, thus cooling it. The refrigerant also flows around the electric motor, so that in particular the energized or energizable rotating field or stator winding is cooled.

[0015] The motor shaft is coupled to a compressor head for drive purposes. The compressor head contains the compressor mechanism, which draws in the refrigerant from the low-pressure side, compresses it, and delivers it via a high-pressure side through the outlet of the compressor housing.

[0016] The motor shaft, which in the installed state is arranged particularly horizontally or lying down, is designed as a hollow shaft and will be referred to as such below. The hollow shaft is open axially at both ends, meaning that the hollow shaft has an axial bore which opens at its end face into a hollow shaft inlet facing the high-pressure side and into a hollow shaft outlet facing the low-pressure side. The hollow shaft also has a number of radial bores which are connected to the axial bore. The radial bores are preferably arranged at the level of the shaft bearings. The compressor head has the high-pressure side and a compressor chamber. The compressor mechanism is arranged in the compressor chamber. The compressor mechanism is, for example, designed as a single-stroke or multi-stroke unit and has at least one compressor rotor which is driven eccentrically by the hollow shaft.In the compressor chamber, a spring-loaded separating slide is also arranged to separate the compressor chamber into a suction chamber and a pressure chamber, which is pressed radially against the compressor rotor by means of a spring element, in particular by means of a compression or helical spring.

[0017] The high-pressure side is fluidically coupled to the low-pressure side of the compressor housing via the hollow shaft. According to the invention, a throttling element or throttle device is arranged between the high-pressure side and the hollow shaft, which reduces the fluid pressure from the high-pressure level to the low-pressure level. This ensures that the pressure level at the hollow shaft inlet is equal to the pressure level at the hollow shaft outlet. Thus, fluid recirculation from the high-pressure side via the hollow shaft to the low-pressure side is achieved without any axial forces acting on the hollow shaft. Therefore, no additional axial bearings for the hollow shaft are necessary. This results in a particularly suitable rotary piston compressor for motor vehicles.

[0018] In this and the following, "axial" or "axial direction" refers in particular to a direction parallel (coaxial) to the axis of rotation of the electric motor, i.e., along a longitudinal direction of the hollow shaft. Similarly, in this and the following, "radial" or "radial direction" refers in particular to a direction oriented perpendicular (transverse) to the axis of rotation of the electric motor along a radius of the hollow shaft or the electric motor. In this and the following, "tangential" or "tangential direction" refers in particular to a direction along the circumference of the hollow shaft or the electric motor (circumferential direction, azimuthal direction), i.e., a direction perpendicular to both the axial and radial directions. In a preferred embodiment, the rotary piston compressor is oil-lubricated and has an integrated oil circuit for an oil. The term "oil" here is not to be understood as being limited to mineral oils.Alternatively, fully synthetic or semi-synthetic oil, silicone oil, or other oil-like fluids such as hydraulic fluid or lubricant can be used.

[0019] In this configuration, the high-pressure side features an oil reservoir which is fluidly coupled to the hollow shaft, or rather the end-face hollow shaft inlet, via the throttling element. In particular, an oil separator, for example a cyclone separator, is arranged on the high-pressure side, which separates the oil from the refrigerant and deposits it into the oil reservoir.

[0020] During operation of the refrigerant drive, or rotary compressor, the refrigerant is introduced into the compressor housing through the inlet. This area of ​​the compressor housing forms the suction or low-pressure side of the rotary compressor. Inside the compressor housing, the refrigerant is mixed with oil to form a refrigerant-oil mixture and drawn along the rotor and stator through an opening to the suction or low-pressure chamber of the compressor head. The compressor mechanism compresses the refrigerant-oil mixture, with the oil lubricating the at least one compressor rotor, thus reducing friction and consequently increasing efficiency. The oil also acts as a seal to prevent uncontrolled escape of the refrigerant from the pressure chamber to the suction chamber.

[0021] The compressed refrigerant-oil mixture is fed into a high-pressure chamber within the compressor housing, forming the high-pressure side. Within the oil separator, the refrigerant-oil mixture is set into rotation. Due to its increased inertia and mass, the heavier oil is drawn towards the walls of the oil separator and, under the influence of gravity (g), collected in an oil reservoir at the bottom of the separator. The refrigerant is discharged upwards or laterally through the outlet. The oil is then returned to the electric motor via an oil return line, which opens at the bottom or side of the oil reservoir, passing through the throttle element and the hollow shaft. Centrifugal force forces the oil, which is contained within the hollow shaft, out through the radial bores, thus lubricating the shaft's bearings.

[0022] This ensures reliable and safe oil return via the horizontal hollow shaft, without causing any axial stress on the shaft. This is achieved through internal oil return, where the oil is guided through various components in a controlled manner.

[0023] On the high-pressure side, i.e., after gas compression, an oil separator and an oil reservoir are arranged, preferably integrated into the compressor housing. A fluid connection exists from the oil reservoir via the throttle element to the hollow shaft inlet (hollow shaft inlet). The hollow shaft outlet (hollow shaft discharge) is open to the low-pressure side. The throttle element is mounted in this connection between the oil reservoir and the low-pressure side, operating at high pressure on the inlet side and at suction or low pressure on the outlet side. Specifically, a pressure-driven oil flow from the high-pressure side to the low-pressure side is achieved via the pressure differential at the throttle element, so that the separated oil from the high-pressure side or high-pressure chamber is directed through the throttle element to the hollow shaft.The oil flows through the hollow shaft (and the radial bores in the area of ​​the shaft bearings) to the low-pressure side, i.e., the housing section of the compressor casing that accommodates the electric motor. This creates a particularly advantageous oil circuit for a rotary piston compressor used in automotive applications.

[0024] In a practical and structurally simple design, the throttling element is designed as an orifice, in particular as an oil orifice.

[0025] In a practical embodiment, the compressor head features a shaft cover (cover plate) located at the end face of the hollow shaft. Specifically, the shaft cover separates the suction pressure side, coupled via the hollow shaft, from the high pressure side or high pressure chamber within the compressor housing. The shaft cover has an axial bore and a radial bore opening into it. When the shaft cover is installed, the axial bore is located in a lower region (relative to a direction of gravity) of the high pressure side or the oil reservoir. The throttle element is positively engaged in the axial bore. The radial bore extends from the outlet side of the throttle element to the inlet side of the hollow shaft. In other words, the radial bore connects the throttle element to the hollow shaft.This allows for a structurally simple design of the compressor housing, thus simplifying the assembly of the rotary piston compressor.

[0026] In one possible design, the hollow shaft is supported by two bearing shields. In other words, a shaft bearing and a plain bearing are integrated into each bearing shield. The compressor chamber is formed between the bearing shields. In other words, the compressor chamber is axially bounded by the bearing shields. The bearing shields thus form the axial end walls of the compressor chamber. Specifically, the shaft cover is mounted on the end face of the A-side bearing shield. This results in a particularly compact and component-reduced design of the compressor head.

[0027] In a possible further development, the compressor mechanism is designed as a two-stage unit. For this purpose, two compressor rotors, arranged axially apart along the hollow shaft, are driven eccentrically within the compressor chamber, with a fixed partition between them. Correspondingly, two spring-loaded separating slides are provided, each pressing radially against one of the compressor rotors. The compressor chamber is thus divided into an upper suction chamber (i.e., arranged along the axial direction above the partition), an upper pressure chamber, a lower suction chamber (i.e., arranged along the axial direction below the partition), and a lower pressure chamber. The partition, for example, has an axial bore that connects the outlet of the upper pressure chamber to the inlet of the lower suction chamber. This creates a two-stroke compressor.This achieves improved smoothness of operation through reduced torque ripple and pressure pulsation per shaft revolution. Preferably, two identical (rotor) counterweights are used on the hollow shaft.

[0028] In an advantageous embodiment, the compressor housing comprises a compressor head-side housing section (compressor head housing) with the outlet and a drive-side housing section (drive housing) with the inlet, which are joined together at a housing interface. The compressor head, including the compressor mechanism and the high-pressure side, is housed in the outlet-side housing section, while the low-pressure side and the electric motor are housed in the inlet-side housing section. This provides a modular compressor system in which different electric motors and compressor mechanisms can be flexibly combined and interchangeable.

[0029] In a suitable further development, the housing interface is formed in particular by the drive-side (B-side) bearing shield. The bearing shield here forms at least a section of the compressor housing wall around its circumference. The bearing shield is specifically designed as a center plate. This results in a particularly suitable housing interface.

[0030] In a preferred embodiment, the inlet-side housing section comprises a motor compartment accommodating an electric motor and an electronics compartment accommodating motor electronics, which are fluid- and pressure-tightly separated from each other by an integrated housing partition, with the inlet and the hollow shaft being fluidically connected to the motor compartment. This results in a particularly efficient compressor housing design.

[0031] An embodiment of the invention is explained in more detail below with reference to a drawing. Figure 1 shows a schematic representation of a rotary piston compressor.

[0032] Fig. 2 shows a sectional view of the rotary piston compressor,

[0033] Fig. 3, Fig. 4 show a partial perspective exploded view of the rotary piston compressor.

[0034] Fig. 5 shows a schematic representation of a section of the oil return system of the rotary piston compressor, and

[0035] Fig. 6 shows a sectional view of the oil return.

[0036] Corresponding parts and sizes are always marked with the same reference symbols in all figures.

[0037] Figure 1 shows a schematic and simplified representation of a rotary piston compressor 2 according to the invention, which is installed, for example, as a refrigerant compressor in a refrigerant circuit (not shown in detail) of an air conditioning system of a motor vehicle. The refrigerant used is, for example, R744.

[0038] The modularly constructed electric refrigerant or rotary piston compressor 2 has an electric (electromotive) drive (drive module) 4 and a compressor head (compressor module) 6 coupled to it. A bearing plate (center plate) 8 is provided between the drive 4 and the compressor head 6 as a mechanical interface, by means of which the compressor head 6 is connected to the drive 4.

[0039] The bearing shield 8 forms an intermediate wall between a drive housing 10 and a compressor head housing 12. The bearing shield 8, the drive housing 10, and the compressor head housing 12 form a compressor housing 14 of the rotary piston compressor 2. The compressor head 6 is connected to the drive 4, for example, by means of circumferentially distributed flange connections extending in an axial direction A of the rotary piston compressor 2 (joined, bolted).

[0040] A compressor-side housing section of the drive housing 10 is designed as a motor housing or motor compartment 16 for accommodating an electric motor 18 and is closed on one side by an integrated housing partition 20 to an electronics compartment (electronics housing) 24, which is provided with a housing cover 22 and contains motor electronics (electronics) that control the electric motor 18 (not shown in detail), and on the other side by the bearing shield 8. The drive housing 10 has a connection section 20 in the area of ​​the electronics housing 16 for electrically connecting the electronics 18 to the vehicle's electrical system.

[0041] The electric motor 18, which is primarily brushless, has a housing-mounted or stationary stator 26 equipped with a rotating field winding 28 (Fig. 2). The rotating field winding 28 is connected to the electronics via vias 30 (Fig. 2) through the (housing) partition 20. The electric motor 18 also has a rotor 32, which is rigidly connected to a drive or motor shaft 34. The motor shaft 34 is designed as a hollow shaft and will be referred to as such below.

[0042] In this and the following, "axial" or "axial direction A" refers in particular to a direction parallel (coaxial) to the axis of rotation of the electric motor 18, i.e., along the longitudinal direction of the rotary piston compressor 2. Similarly, in this and the following, "radial" or "radial direction R" refers in particular to a direction oriented perpendicular (transverse) to the axis of rotation of the electric motor 18 along a radius of the electric motor 18. In this and the following, "tangential" or "tangential direction" refers in particular to a direction along the circumference of the electric motor (circumferential direction, azimuthal direction), i.e., a direction perpendicular to both the axial and radial directions. In the figures, the direction of gravity (gravitational direction) is denoted by g and shown as an example.

[0043] The hollow shaft 34 has a central axial bore 36, which opens at the shaft end or face into a compressor head-side (hollow shaft) inlet 38 and an electric motor-side (hollow shaft) outlet 40. The hollow shaft 34 also has a number of axially distributed radial bores 42 (Fig. 2). Only one bore 42 is shown in the illustrations. The bores 42 extend through the hollow shaft 34 from the bore 36 along a radial direction R and are open towards the outer circumference of the hollow shaft 34.

[0044] The compressor head 6 has a (rolling piston) compressor mechanism. In the exemplary embodiment, the compressor mechanism is particularly designed as a two-stage mechanism, wherein two compressor rotors 44a, 44b are eccentrically connected to the hollow shaft 34. The compressor rotors 44a, 44b, which are designed, for example, as pistons or rollers (rolling piston), are arranged in a compressor chamber 46. A housing-fixed partition 48 is arranged between the compressor rotors 44a, 44b, which divides the compressor chamber 46 into an upper working chamber 46a – facing a low-pressure side 50 – and a lower working chamber 46b – facing a high-pressure side 52. In the working chambers 46a, 46b, one of the compressor rotors 44a, 44b and one spring-loaded separating slide (wing) 54a, 54b are arranged to separate the working chambers 46a, 46b into a suction chamber and a pressure chamber.The separating slides 54a, 54b are pressed radially against the respective compressor rotors 44a, 44b by means of a spring element 55, in particular by means of a compression or helical spring. The working chamber 46a is fluidically connected to the motor compartment 16, which forms the low-pressure side 50 of the compressor housing 14, and to the working chamber 46b. The working chamber 46b is similarly fluidly connected to the working chamber 46a and to a high-pressure chamber 56, which forms the high-pressure side 52 of the compressor housing 14.

[0045] The rotary piston compressor 2 has a (refrigerant) inlet or (refrigerant) supply 58 for connection to the refrigerant circuit and a (refrigerant) outlet 60. The inlet 58 is integrally formed in a region of the drive housing 10 facing the electronics compartment 24. The outlet 60 is integrally formed on the base of a compressor head housing 12. When connected, the inlet 58, which is connected to the motor compartment 18, forms the low-pressure or suction side 50 (suction gas side), and the outlet 60, which is connected to the high-pressure chamber 56, forms the high-pressure or pump side (pump side) of the rotary piston compressor 2. The construction of the rotary piston compressor 2 is explained in more detail below with reference to Figures 2 to 4.

[0046] The hollow shaft 34, which in the installed state is arranged in a horizontal or lying position, is in this embodiment rotatably or perpendicularly mounted in the compressor housing 14 by means of three shaft bearings 62. Alternatively, the hollow shaft 34 can also be mounted with only two shaft bearings 62.

[0047] The shaft bearings 62 are each designed as plain bearings. One shaft bearing 62 is arranged in a bearing seat 64 connected to the motor compartment 16, which is integrally formed on the housing base or on the intermediate wall 20 of the drive housing 10. The second shaft bearing 62 is received in the bearing shield 8 that delimits the working chamber 46a. The third shaft bearing 62 is arranged in a bearing shield 66 that separates the working chamber 46b from the high-pressure chamber 56.

[0048] The bearing shields 8 and 66 are sealed against the engine compartment 16 and the high-pressure chamber 56, respectively, by means of sealing plates 68 and 70 arranged at their end faces. The sealing plate 68 seals the bearing shield 8 axially and radially.

[0049] The high-pressure-side sealing plate 70, also referred to below as the shaft cover, has a central, trough-shaped receptacle 72 into which the hollow shaft 38 and the section of the bearing shield 66 forming the shaft bearing 62 engage, at least partially. The receptacle 72 is radially sealed against the section of the bearing shield 66 forming the shaft bearing 62 by means of a sealing ring (not specified in detail). The receptacle 72 is connected to a radial bore 74, which opens into an axial bore 76 in the shaft cover 70. The axial bore 76 extends along an integrally formed nozzle 78 of the shaft cover 70. A throttling element 80, for example in the form of an oil orifice, is arranged in the axial bore 76. The nozzle 78 is inserted into a corresponding receptacle in the compressor head housing 12 and radially sealed against it.An inlet of the throttle element 80 or the axial bore 76 opens into a radial bore 82 of the compressor head housing 12, the bore 82 being connected to an oil reservoir 84 of the compressor head housing 12.

[0050] A separating disc 86 is installed in the high-pressure chamber 56, or high-pressure side 52, which is radially sealed against the inner walls of the compressor head housing 12. The separating disc 86 divides the high-pressure side 52 into the high-pressure chamber 56 (high-pressure pulsation chamber), which acts as a pulsation chamber, and the oil reservoir 84. A bore is provided in the separating disc 86, in which an oil separator 88 is inserted. The bore, or rather the oil separator 88, is coupled to the outlet of the compressor chamber 46, the outlet 60, and to the oil reservoir 84. The compressed oil-refrigerant mixture is introduced into the oil separator 88, whereby the oil is separated or collected in the oil reservoir 84, and the refrigerant is expelled from the compressor housing 14 via the outlet 60. The oil separator 88, for example, is designed as a cyclone separator.

[0051] As can be seen relatively clearly in connection with Fig. 3, the hollow shaft 34 has an eccentric cam as an eccentric 90 at the level of the compressor rotors 44a, 44b, onto which one of the compressor rotors 44a, 44b is pressed.

[0052] The compressor mechanism is composed of two compressor plates 92a, 92b and the partition 48 in a sandwich configuration, which are axially stacked between the bearing shields 8, 66 in the compressor head housing 12. Each of the approximately annular compressor plates 92a, 92b has a radial recess as a (bearing) seat for the respective separating slide 54a, 54b or for the respective spring element 55, and a central recess as a working chamber 46a, 46b in which the respective compressor rotor 44a, 44b is seated. A balancing device is provided to compensate for the imbalance generated by the eccentric cams 90 and compressor rotors 44a, 44b. In the illustrated embodiment, the balancing device is implemented by two counterweights 94, which are rigidly connected to the hollow shaft 34 and are arranged on both sides of the rotor 32.

[0053] During compressor operation, the refrigerant is drawn into the motor compartment 16 through the inlet 58. The refrigerant flows along the partition 20, allowing the motor electronics to be cooled through this partition. Furthermore, the refrigerant flows around and cools the rotating field winding 28 of the stator 26.

[0054] To lubricate the shaft bearings 62, a lubricant or oil (e.g., PAG or POE) is added to the refrigerant within the motor compartment 16 or on the low-pressure side 50 of the compressor housing 14. The fluid flow delivered by the rotary piston compressor 2 is thus a mixture of the gaseous refrigerant and the liquid, droplet-shaped oil.

[0055] The refrigerant-oil mixture is drawn into the suction chamber of the working chamber 46a through corresponding openings in the bearing shield 8 and compressed by the compressor rotor 44a. The compressed refrigerant-oil mixture is then introduced into the suction chamber of the working chamber 46b, where it is further compressed by the compressor rotor 44b. The oil also lubricates the two separating slides 54a and 54b, thus reducing friction and consequently increasing efficiency. The oil also seals the suction and pressure chambers, which are separated by the separating slides 54a and 54b, to prevent uncontrolled escape through these slides. After this two-stage compression, the compressed refrigerant-oil mixture 96 (Fig. 5) is introduced into the high-pressure chamber 56, or the high-pressure side 52, of the compressor housing 14.

[0056] The oil 98 is separated from the refrigerant by the oil separator 88. The refrigerant 100 is expelled via the outlet 60, whereby the oil 98 is collected in the oil reservoir 84 and conveyed back to the low-pressure side 50 for the lubrication of the shaft bearings 62 via an oil return system, which is explained in more detail below with reference to Figs. 5 and 6.

[0057] Figures 5 and 6 show the oil return system according to the invention for a hollow shaft 34 arranged horizontally or in a horizontal position. The oil return system, or rather the flow path of the returned oil, is shown schematically in Figure 6 by means of arrows.

[0058] In the operating condition shown in Fig. 5, the oil reservoir 84 is at least partially filled with the separated oil 96. Due to the pressure difference between the high-pressure side 52 and the low-pressure side 50, the oil 96 flows through the bore 82 to the inlet of the throttle element 80. The bore 82 is located at the bottom of the oil reservoir 84 with respect to the direction of gravity g.

[0059] The throttling element 80 is designed to reduce the (static) high pressure of the oil 96 to the low pressure level of the low-pressure side 50. In other words, the fluid pressure of the oil 96 is reduced from the high-pressure level to the low-pressure level by the throttling element 80, which is arranged between the high-pressure side 52 and the hollow shaft 34, so that no axial forces act on the hollow shaft 34 during the return flow. The oil 96, now at low pressure, is then guided through the radial bore 74 into the receptacle 72 and enters the hollow shaft inlet 38.

[0060] The oil 96 flows axially through the bore 36 to the hollow shaft outlet 40. The radial bores 42 are arranged at the level of the shaft bearings 62, so that the oil 96 is flung out of the bore 36 through the bores 42 by centrifugal force, thus lubricating the shaft bearings 62. The excess oil 96 exits at the hollow shaft outlet 40 into the engine compartment 16 or into the low-pressure side 50, and is mixed again with the refrigerant. The claimed invention is not limited to the embodiments described above. Rather, other variants of the invention can also be derived by a person skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention.Furthermore, all individual features described in connection with the various embodiments can also be combined in other ways within the scope of the disclosed claims without leaving the subject matter of the claimed invention.

[0061] Reference symbol list

[0062] 2 rotary piston compressors

[0063] 4 Drive

[0064] 6 compressor head

[0065] 8 Storage sign

[0066] 10 drive housings

[0067] 12 compressor head housings

[0068] 14 compressor housings

[0069] 16 Engine compartment

[0070] 18 Electric motor

[0071] 20 Housing partition

[0072] 22 Case covers

[0073] 24 Electronic compartment

[0074] stator

[0075] 28 Rotating field winding

[0076] 30 Through-hole plating

[0077] 32 Rotor

[0078] 34 Hollow shaft

[0079] 36 bore

[0080] 38 Hollow shaft intake

[0081] 40 Hollow shaft outlet

[0082] 42 bore

[0083] 44a, 44b Compressor rotor

[0084] 46 Compressor chamber

[0085] 46a, 46b Chamber of Labour

[0086] 48 Partition wall

[0087] 50 Low-pressure side

[0088] 52 High-pressure side

[0089] 54a, 54b Separating slide

[0090] 55 Spring element

[0091] 56 High-pressure chamber

[0092] 58 Entry 60 Exit

[0093] 62 shaft bearings

[0094] 64 bearing seat

[0095] 66 Storage sign

[0096] 68, 70 Shaft cover, sealing plate

[0097] 72 recording

[0098] 74 radial bore

[0099] 76 Axial bore

[0100] 78 Stutzen

[0101] 80 Throttle element

[0102] 82 bore

[0103] 84 Oil reservoir

[0104] 86 Cutting disc

[0105] 88 oil separators

[0106] 90 cam, eccentric

[0107] 92a, 92b compressor plate

[0108] 94 Counterweight

[0109] 96 Cold medium oil mixed

[0110] 98 Oil

[0111] 100 refrigerants

[0112] A Axial direction

[0113] R Radial direction g Gravitational direction

Claims

Claims 1. Rotary piston compressor (2) for a motor vehicle, comprising a compressor housing (14) with a low-pressure inlet (58) and a high-pressure outlet (60) as well as with an electric motor drive (4) and with a compressor head (6) coupled thereto via a hollow shaft (34), - wherein the hollow shaft (34) is axially open on both sides and provided with radial bores (42), - wherein the compressor head (6) has a compressor chamber (46) and a high-pressure side (52) coupled to the outlet (60), - wherein at least one compressor rotor (44a, 44b) driven eccentrically by the hollow shaft is arranged in the compressor chamber (46), - wherein at least one spring-loaded separating slide (54a, 54b) is pressed radially against the compressor rotor (44a, 44b) to separate the compressor chamber (46) into a suction chamber and a pressure chamber, - wherein the high-pressure side (52) is fluidically coupled to the low-pressure side (50) of the compressor housing (14) via the hollow shaft (34), and - wherein a throttle element (80) is arranged between the high-pressure side (52) and the hollow shaft (34).

2. Rotary piston compressor (2) according to claim 1 , characterized in that the high pressure side (52) has an oil reservoir (84) which is fluidly connected to the hollow shaft (34) via the throttle element (80).

3. Rotary piston compressor (2) according to claim 1 or 2, characterized in that the high pressure side (52) has an oil separator (88).

4. Rotary piston compressor (2) according to one of claims 1 to 3, characterized in that the throttling element (80) is designed as an oil orifice.

5. Rotary piston compressor (2) according to one of claims 1 to 4, characterized in that the compressor head (6) has a shaft cover (70) which is arranged at the end face of the hollow shaft (34), wherein the throttle element (80) is inserted into the shaft cover (70), and wherein a radial bore (74) connects the throttle element (80) to the hollow shaft (34).

6. Rotary piston compressor (2) according to one of claims 1 to 5, characterized in that the hollow shaft (34) is supported by two bearing shields (8, 66), wherein the compressor chamber (46) is formed between the bearing shields (8, 66).

7. Rotary piston compressor (2) according to one of claims 1 to 6, characterized in that two compressor rotors (44a, 44b) axially spaced along the hollow shaft (34) are driven eccentrically in the compressor chamber (46), wherein a fixed partition (48) is arranged between the compressor rotors (44a, 44b).

8. Rotary piston compressor (2) according to one of claims 1 to 7, characterized in that the compressor housing (14) has a compressor head-side housing part (12) with the outlet (60) and a drive-side housing part (10) with the inlet (58), which are joined together at a housing interface.

9. Rotary piston compressor (2) according to claim 8, characterized in that the housing interface is formed by the drive-side bearing shield (8).

10. Rotary piston compressor (2) according to claim 8 or 9, characterized in that the drive-side housing part (10) has a motor compartment (16) accommodating an electric motor (18) and an electronics compartment (24) accommodating motor electronics, which are separated from each other by an integrated housing partition (20) in a fluid- and pressure-tight manner, wherein the inlet (58) and the hollow shaft (34) are fluidically connected to the motor compartment (16).

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