Screw compressor with direct oil return from oil separator into compression section

Abstract

A screw compressor (1) comprising: - a compression section (10) having an inlet (11) for drawing fluid into the compression section (10), an outlet (12) for discharging compressed fluid, a fixed disk (20) having a fixed screw portion (21) and a rotating disk (30) having a rotating screw portion (31), wherein the rotating disk (30) is rotatable relative to the fixed disk (20); - an oil separator (45) for separating oil from the compressed fluid and a direct oil return device (50) for directly returning oil from the oil separator (45) into the compression section (10), wherein the direct oil return device (50) has at least one through-port opening (59a, 59b). The direct oil return device (50) further comprises a discharge chamber (54) arranged between a first flow valve (53) and the through-port opening (59a, 59b) and a fluid return device (70) for returning fluid from the discharge chamber (54) into the compression section (10).

Description

Technical Field

[0001] The present invention relates to a screw compressor that uses a compression section to compress fluid, the compression section having an inlet for drawing fluid into the compression section, an outlet for discharging compressed fluid from the compression section, a fixed disc having a fixed screw portion, and a rotating disc having a rotating screw portion. Background Technology

[0002] Screw compressors are used, for example, in air conditioning systems, especially in air conditioning systems for motor vehicles. They are also used in heat pumps. Compared to other types of compressors, they excel in their particularly even, low-vibration, and quiet operation.

[0003] The compression section forms the core of a scroll compressor. Fluids, especially gases or gas mixtures, are compressed by the movement of a rotating disc relative to a stationary disc. For this purpose, the rotating and stationary spiral sections are nested within each other, forming compression chambers for the fluid between them. Regarding the stationary spiral section, each compression chamber, containing the fluid enclosed within it, moves from the outer region of the stationary spiral section to its center. Here, the space available for the fluid becomes increasingly smaller, and the fluid is compressed.

[0004] During operation, the fluid reaches its maximum pressure at the outlet of the compression section. The fluid enters the compression section at suction pressure and exits at a significantly higher outlet pressure.

[0005] The fluid, gradually compressed between the rotating and stationary discs, pushes them apart. Therefore, a lifting force acts on the rotating disc. The strength of this lifting force depends particularly on the suction pressure, the outlet pressure, and the geometry of the compression section. Generally, changes in outlet pressure have a more significant impact on the pressing pressure than changes in suction pressure.

[0006] To achieve high compression, the compression chamber, formed by the engagement of a fixed disc and a rotating disc, and moving towards the center, must be sufficiently sealed. To ensure the rotating disc is firmly and securely pressed against the fixed disc and no fluid escapes from the compression section, the rotating disc is loaded with a pressing pressure on its rear side, opposite the fixed disc. For this purpose, a pressing pressure chamber is provided on the rear side of the rotating disc. The pressing pressure compresses the rotating disc along the direction of the fixed disc.

[0007] The engagement between the rotating helix and the stationary disc, and the engagement between the stationary helix and the rotating disc, are responsible for friction during operation. Electric screw compressors typically operate in the speed range of 500 to 12000 min⁻¹. Here, high friction becomes apparent through reduced efficiency.

[0008] Oil is guided into the pressing pressure chamber to lubricate the rotating disc. Furthermore, an oil supply line can pass through the pressing pressure chamber and the rotating disc structure. Oil can also flow out from the pressing pressure chamber between the fixed disc and the rotating disc via the oil supply line.

[0009] The fluid discharged from a screw compressor should contain as little oil as possible. Excessive oil in the discharged fluid can negatively impact the efficiency of downstream components. For example, the efficiency of the refrigerant circuit may deteriorate as more oil is mixed in.

[0010] Typically, in a refrigerant circuit, the screw compressor is the only component within the circuit that requires oil to lubricate mechanically stressed parts. A refrigeration circuit can operate under various conditions, and its efficiency largely depends on these conditions. For example, excessive oil can wet the surfaces within a heat exchanger, thereby reducing the heat transfer coefficient. Consequently, the efficiency of the evaporator and condenser decreases. Therefore, the refrigerant circuit as a whole must operate at a higher pressure ratio to provide the required cooling capacity. Thus, excessive oil reduces overall efficiency and increases stress on the mechanical components within the screw compressor due to the increased pressure ratio.

[0011] Therefore, the compressed fluid is guided through the oil separator after the compression section. The oil separator at least partially separates the oil from the compressed fluid. The separated oil is guided back to the pressing pressure chamber via a (second) oil return device.

[0012] During operation of the screw compressor, the oil in the pressing chamber is subjected to pressing pressure. The opening of the oil supply line is located in the central region of the compressor passage of the rotating disc, which is constructed by the rotating helix portion on the rotating disc. Due to this positioning and the continuous mass flow of the mixture of oil and refrigerant from the high-pressure side, a pressing pressure at an intermediate pressure level appears in the pressing chamber. The pressing pressure squeezes the rotating disc along the direction of the fixed disc. The positioning in the intermediate region is primarily responsible for achieving the desired and sufficiently large pressing pressure. The pressing pressure is variable and depends on the operating pressure. This ensures a seal between the fixed disc and the rotating disc at all operating points and maintains friction as low as possible.

[0013] However, due to this positioning of the oil supply line opening, the radially outer area between the stationary and rotating discs is not optimally supplied with oil. This results in increased friction, reduced efficiency, and in some cases, a shorter lifespan for the screw compressor. Summary of the Invention

[0014] The objective of this invention is to create a screw compressor that enables more efficient operation and has higher reliability.

[0015] The above task is accomplished by a screw compressor for compressing fluids.

[0016] Screw compressors used for compressing fluids include:

[0017] Compression section, has

[0018] ● The inlet of the compression section, used to draw fluid into the compression section.

[0019] ● The outlet of the compression section is used to discharge the compressed fluid from the compression section.

[0020] ●A fixed disc with a fixed spiral section, and

[0021] ● A rotating disk having a rotating helical section, wherein the rotating disk can rotate relative to a fixed disk in the compression direction to convey fluid from the inlet of the compression section to the outlet of the compression section, and compress it thereon; and

[0022] Oil separator used to separate oil from compressed fluid;

[0023] The screw compressor has a direct oil return device for directly returning oil from the oil separator to the compression section, wherein the direct oil return device has at least one port opening.

[0024] The direct oil return system continuously returns oil from the oil separator to the compression section during operation. This reduces friction in the compression section. Thus, the direct oil return system enables more efficient operation of the screw compressor. Furthermore, wear in the compression section is reduced. This improves the reliability and service life of the screw compressor.

[0025] During operation, the oil separator is (at least substantially) loaded with outlet pressure. This invention utilizes the pressure difference between the oil separator and the fluid pressure at the inlet opening to directly and specifically redirect oil from the oil separator back into the compression section. A key advantage is that the oil flow via the direct oil return device is driven by the pressure ratio of the outlet pressure to the suction pressure. The amount of oil returned depends primarily on this pressure ratio. For example, at an inlet pressure of 3 bar and an outlet pressure of 15 bar, at a rotational speed of 600 min... -1 At that time, this quantity was the same as when the inlet pressure was 3 bar, the outlet pressure was 15 bar, but the rotation speed was 8500 min. -1 The time is the same.

[0026] The amount of oil returned by the direct oil return device is (at least substantially) independent of the screw compressor's rotational speed and (at least substantially) independent of the precise outlet pressure. Even at low speeds, the direct oil return device returns sufficient oil to the compression section. Therefore, the direct oil return device is suitable for lubricating the compression section of a screw compressor under various load conditions. In particular, it improves lubrication at low speeds.

[0027] Furthermore, the direct oil return device operates regardless of the pressing pressure. Even when the pressing pressure decreases, the direct oil return device will continue to return oil to the compression section as long as the outlet pressure remains sufficiently high.

[0028] Furthermore, oil is better retained in the screw compressor. The inlet region no longer needs to be supplied with oil that creeps from the pressure chamber into the compression section or guided through the external portion of the refrigerant circuit to the inlet of the compression unit. The external portion of the refrigerant circuit is understood as those areas in the refrigerant circuit located outside the screw compressor. The fluid after the oil separator contains less oil. Less oil is guided through the external portion of the refrigerant circuit. Typically, a higher proportion of oil in the fluid in the external portion of the refrigerant circuit is responsible for the poorer thermodynamic properties of the refrigerant-oil mixture. The proposed direct oil return device significantly reduces the oil circulation ratio (OCR) of the refrigerant circuit. The direct oil supply device accurately introduces oil into the inlet region of the compression unit. This improves the efficiency of the refrigerant circuit.

[0029] Especially at low speeds, in conventional screw compressors, there is an increased risk of low refrigerant mass flow through the external part of the refrigerant circuit, meaning that oil will be unintentionally retained in the external part of the refrigerant circuit.

[0030] Conversely, the proportion of oil available for lubrication within the screw compressor, particularly in the compression section, increases during operation. Active direct oil return systems reduce the total amount of oil required for screw compressor operation. This lowers costs and reduces the weight of the refrigerant circuit. As a result, for example, the efficiency of vehicles housing screw compressors increases.

[0031] The outlet of the compression unit is located at least substantially at the center of the fixed plate. In particular, the outlet of the compression unit can be precisely located at the center of the fixed plate.

[0032] The fixed helical section constructs a helical compressor passage (of the fixed disc) that extends from the outer end to the inner end of the fixed helical section. The inner end of the fixed helical section is located at its center. It is situated at the outlet opening of the fixed disc. The outlet of the compression section includes this outlet opening. In particular, this outlet opening can constitute the outlet of the compression section.

[0033] The fixing screw portion can be arranged on the fixing base surface of the fixing disk. The fixing screw portion can be formed by a wall that extends from the fixing base surface parallel to the central axis of the fixing disk and away from the fixing base surface. Preferably, the end face of the fixing screw portion facing away from the fixing base surface along the central axis is flat and constructed parallel to the fixing base surface.

[0034] The outlet opening may include a hole in the fixed base surface. In particular, the outlet opening may be configured as a hole in the fixed base surface.

[0035] Similarly, the rotating helical portion constructs a spiral compressor passage for the rotating disc, the spiral compressor passage extending from the outer end of the rotating helical portion to the inner end of the rotating helical portion. In this disclosure and claims, unless expressly stated otherwise and unless the context compels otherwise, the term "compressor passage" always refers only to the compressor passage of the fixed disc, without further supplementation.

[0036] The rotating helical portion can be arranged on the rotating base surface of the rotating disk. The rotating helical portion can be formed by a wall that extends parallel to the central axis of the rotating disk from the rotating base surface away from it. Preferably, the end face of the rotating helical portion facing away from the rotating base surface along the central axis (of the rotating disk) is flat and constructed parallel to the rotating base surface. The rotating base surface can be parallel to the fixed base surface.

[0037] The fixed helical part and the rotating helical part can each have exactly one helical arm.

[0038] The screw compressor has a winding mechanism for rotating a rotating disc relative to a fixed disc. During rotation, the rotating disc is eccentrically displaced relative to the fixed disc along an at least substantially circular track. Here, the central axis of the rotating disc preferably moves circularly about the central axis of the fixed disc. The central axis of the fixed disc may be perpendicular to a fixed base surface. It may extend through the center of the fixed disc and / or the center of the fixed screw portion. In particular, the center of the fixed screw portion may form the center of the fixed disc, and vice versa.

[0039] During operation (compressor operation), at least one compression chamber is constructed between the rotating spiral section and the stationary spiral section. The drawn-in fluid is enclosed in the compression chamber, compressed within the chamber, moves in the direction of the outlet opening of the stationary disc, and is ultimately squeezed into the outlet opening.

[0040] The suction region of the compressor passage consists of all areas of the compressor passage that are at least temporarily in direct fluid connection with the inlet of the compression section when the rotating disk revolves relative to the fixed disk in the compression direction. The outlet region of the compressor passage consists of all areas of the compressor passage that are at least temporarily in direct fluid connection with the outlet of the compression section when the rotating disk revolves relative to the fixed disk in the compression direction. The central region of the compressor passage consists of all areas of the compressor passage that are not in direct fluid connection with either the inlet or outlet of the compression section. These definitions apply not only to compressor passages with fixed disks but also to compressor passages with rotating disks.

[0041] In the context of this application, the innermost or first turn of a corresponding spiral portion refers to a region of the spiral portion that extends from the inner end of the spiral portion to the point where the spiral portion wraps around the center of the spiral portion once.

[0042] A 0° position angle is assigned to the inner end of the fixed screw. The position angle increases continuously along the extension of the fixed screw until it reaches the outer end of the fixed screw. The helix angle of the fixed screw is given by its outer end. Therefore, the helix angle corresponds to the maximum position angle of the fixed screw.

[0043] This is explained exemplarily with a fixed helix having two turns: the first turn of the fixed helix begins at a position angle of 0° with the inner end of the fixed helix and ends at a position angle of 360°. The second and outermost turn begins at a position angle of 360° and ends at the outer end of the fixed helix at a helix angle of 720°.

[0044] Accordingly, the position angle in the compressor passage is defined. The outer end of the spiral compressor passage is determined by the inlet opening of the compressor passage, which is formed between the outer end of the fixed spiral section and the inner starting point of the outermost ring of the fixed spiral section.

[0045] In the context of this application, the outer side of the corresponding helical region is the side of the helical region that is radially away from the center of the helical region. Correspondingly, the inner side of the helical region is the side of the helical region that is radially facing the center of the helical region.

[0046] The compression section can be constructed with compression chambers guided on the inner side and compression chambers guided on the outer side. The compression chambers guided on the inner side are formed on the outer side of the fixed helix and guided along the outer side of the fixed helix. The compression chambers guided on the outer side are formed on the outer side of the fixed helix and guided along the outer side of the fixed helix.

[0047] It should be emphasized that the definition of the compressor passage is independent of the definition of the compression chamber. In particular, the compression chamber does not necessarily need to be entirely located within the compressor passage of the fixed disc. For example, the compression chamber can be formed by contacting the outer end of the rotating helix with the outermost ring of the fixed helix. This seal closes and seals the compression chamber guided on the inner side. In this case, the newly formed compression chamber guided on the inner side can still (partially) be located outside the compressor passage of the fixed disc. Conversely, the compression chamber guided on the outer side is closed by contacting the outer side of the rotating helix with the outer end of the fixed helix. In this case, the newly formed compression chamber guided on the outer side is completely located within the compressor passage. It is guided at the outer side of the compressor passage. In other words, the outer side of the compressor passage is formed by the inner side of the fixed helix.

[0048] During operation, there is a suction pressure at the inlet of the compression section and an outlet pressure at the outlet of the compression section. The suction pressure during operation is preferably in the range of 1 bar to 7 bar. Alternatively or additionally, the outlet pressure during operation is in the range of 8 bar to 32 bar. The exact suction pressure and the exact outlet pressure may vary depending on the fluid used and the exact operating conditions.

[0049] During operation, the intake and outlet pressures can be determined by a system connected to the screw compressor through which the fluid compressed in the screw compressor flows. Such a system can be, for example, a heat exchanger in an air conditioning system.

[0050] The maximum outlet pressure of a screw compressor is determined by the geometry of the compression section and the corresponding suction pressure. Furthermore, the dead volume of the outlet opening (outlet bore) of the stationary disc also affects the maximum outlet pressure. Higher suction pressures result in higher maximum outlet pressures. At a given suction pressure, the maximum outlet pressure is determined by the compressibility of the fluid within the compression section, according to known fluid equations (e.g., the ideal gas equation or van der Waals equations). The actual outlet pressure is typically lower than the maximum outlet pressure.

[0051] The inlet of the compression section may include multiple sub-regions. In particular, the inlet may have a first inlet portion region and a second inlet portion region, through which fluid is supplied to the compression chamber guided radially inward, and through the second inlet portion region to the compression chamber guided radially outward. The portion regions may be spatially separated from each other, for example, located on two opposite sides in the radially outer region of the compression section.

[0052] The direct oil return system is used to directly return oil from the oil separator to the compression section. The direct oil return system extends directly from the oil separator to the compression section.

[0053] During operation, the oil is forced by pressure from the oil separator into the direct oil return unit. The oil flows through the direct oil return unit in the direction of oil flow and exits through the inlet of the direct oil return unit into the compression section. The oil thus returned is used to lubricate the compression section.

[0054] In a preferred embodiment of the invention, the inlet opening (of the direct oil return device) is arranged in the inlet region of the compression section, and is at least temporarily in direct fluid connection with the inlet of the compression section during operation. This ensures particularly good lubrication in the radially outer regions of both the moving and stationary spiral sections.

[0055] Based on the precise positioning of the port opening, it is feasible, for example, to temporarily sweep over and cover the port opening during operation by the rotating spiral section. In this case, the port opening is not directly fluidly connected to the inlet. It is also feasible that, during the complete rotation of the rotating disc, the port opening is directly fluidly connected to the inlet for a first time period, swept over by the rotating spiral section for a second time period, connected to the compression chamber for a third time period, and swept over again by the rotating spiral section for a fourth time period.

[0056] In a particularly preferred embodiment, the compression chamber (or any one of the compression chambers) never sweeps across the port opening.

[0057] Alternatively or additionally, it is particularly preferred that the rotating helical portion sweeps across the opening of the passage exactly once during the complete circumference of the rotating helical portion.

[0058] The inlet of the direct oil return device is preferably arranged in the fixed plate. This reduces complexity and simplifies the production of the direct oil return device. In particular, the inlet can be arranged entirely in the fixed base surface. Alternatively, the inlet can be arranged entirely or partially on the inner or outer side of the fixed spiral portion. This variation is more difficult to produce. Therefore, lubrication at the inner or outer side of the fixed spiral portion can be further improved.

[0059] In a particularly preferred embodiment, the inlet opening of the direct oil return device is arranged in the suction area of ​​the compressor passage (of the fixed screw section), and is at least temporarily in direct fluid connection with the inlet of the compression section during operation, and / or is arranged outside the compressor passage. When the inlet opening is arranged at the outer end of the compressor passage, a first portion of the inlet opening may be arranged in the compressor passage, and a second portion of the inlet opening may be arranged outside the compressor passage.

[0060] According to another aspect, the inlet opening of the direct oil return device is preferably arranged at a position angle within the range of γ-30° and γ+30°, where γ is the position angle of the outer end of the compressor passage. In this case, the inlet opening can also be arranged at a radial distance R from the center of the fixed plate. M，1 At, where R M，1 Located in (R I (γ)-B K ) and R I Within the range of (γ), where R I(γ) is the radial distance between the inner side of the fixed helix and the outer end of the compressor passage (i.e., the outer end of the fixed helix), and BK is the width of the compressor passage in the radial direction at the outer end of the compressor passage. In this case, the port opening is therefore arranged near the outer end (upstream end) of the compressor passage. Then, the end face of the rotating helix sweeps across the port opening at least once during the rotation. As a result, the oil escaping from the port opening is distributed particularly well. In particular, R M，1 It can be found in (R) I (γ)-B K / 2) and R I Within the range of (γ). The opening thus implemented particularly facilitates lubrication in the area of ​​the compression chamber guided from the outside.

[0061] Alternatively, the inlet opening of the direct oil return device is preferably located outside the fixed spiral section, at a position angle ranging from θ-30° to θ+30°, where θ = γ+180°. In this case, the inlet opening can also be located at a radial distance R from the center of the fixed disc. M，2 At, where R M，2 From R A (θ-360°) to R A (θ-360°)+B K Within the range, where R A (θ-360°) is the radial distance of the outer side of the fixed helix at the position angle θ-360°. In this embodiment, the port opening is therefore located outside the fixed helix and positioned relative to the center of the fixed helix at a position opposite to the outer end of the compressor passage. This results in particularly good distribution of oil escaping from the port opening. In particular, R... M，2 In R A (θ-360°) and R A (θ-360°)+B K Within a range of / 2. This type of opening in the port particularly facilitates lubrication in the area of ​​the compression chamber guided from the inside.

[0062] Particularly preferably, a plurality of through openings are constructed, wherein at least one of the plurality of through openings corresponds to a construction according to an embodiment of the penultimate aspect, and at least one of the plurality of through openings corresponds to a construction according to an embodiment of the last described aspect. Advantages apply accordingly.

[0063] In an advantageous embodiment of the invention, the direct oil return device includes a first flow valve. The first flow valve (viewed along the direction of oil flow in the direct oil return device) is preferably arranged between a first oil inlet and a port opening of the direct oil return device. However, typically, the first flow valve can also be arranged directly at the first oil inlet or the port opening. The first flow valve can be constructed, in particular, by the first oil inlet and / or the second port opening itself. The first flow valve reduces the mass flow rate of the oil (possibly carrying dissolved liquids) which is returned through the direct oil return device.

[0064] The first flow valve is particularly preferably implemented as a throttle valve.

[0065] In this application, a throttle valve should preferably be understood as an element that generates a pressure differential between the valve inlet and outlet. It can be particularly preferably an uncontrolled throttle valve. For example, it can be an orifice or a nozzle. This allows for simple, cost-effective, and reliable implementation.

[0066] The first flow valve is configured to reduce the mass flow rate of oil (along with any fluids that may be dissolved therein) from the oil separator. In this way, the pressure in the direct oil return device downstream of the first flow valve (e.g., the intermediate pressure described below and / or the inlet pressure described below) can be affected in a simple manner.

[0067] In a particularly preferred embodiment, the direct oil return device includes a first flow valve and an exhaust chamber, which (viewed along a predetermined flow direction of the oil in the direct oil return device) is arranged between the first flow valve and the inlet opening of the direct oil return device. In other words, the exhaust chamber is located downstream of the first flow valve and upstream of the inlet opening.

[0068] The direct oil return unit continuously extracts oil from the oil separator during operation and stores excess oil in the discharge chamber, located inside the screw compressor. By continuously removing oil from the oil separator, for example at or near the bottom of the separator, and actively storing the oil temporarily, the efficiency of the separation process is maximized. The amount of oil leaving the compressor and reaching the external refrigerant circuit is minimized.

[0069] As mentioned earlier, especially at low speeds, there is an increased risk due to the low refrigerant mass flow rate: oil discharged from the screw compressor to the external portion of the refrigerant circuit will unintentionally remain there. Even in this case, oil from the discharge chamber continues to ensure the oil supply to the screw compressor until the system is back in equilibrium. If I subsequently change the operating point to a high load point, the oil previously trapped in the external portion of the refrigerant circuit will be brought back to the screw compressor along with the high-mass flow of refrigerant, and will be collected and temporarily stored there again. Thus, the system will adjust itself: absorbing or releasing oil as needed.

[0070] During operation, the oil separator is (at least substantially) loaded at the outlet pressure. This results in a high solubility of the fluid in the liquid oil within the oil separator. A first flow valve reduces the mass flow rate of the oil (along with any fluid that may be dissolved therein) from the oil separator. This helps to set the intermediate pressure in the vent chamber below the outlet pressure. This also reduces the solubility of the fluid in the oil. Downstream of the first flow valve, the oil may become supersaturated. In the vent chamber, the supersaturated portion of the fluid present in the oil can be (at least partially) separated from the oil in a controlled manner. This reduces the risk of uncontrolled and intense bubble formation of the fluid in the oil downstream of the vent chamber. If the supersaturated portion of the fluid is completely separated from the oil, the fluid in the oil is at most exactly the amount of fluid that could dissolve in the oil under given conditions in equilibrium (the saturated portion of the fluid in the oil).

[0071] The first fluid connection of the direct oil return device extends from the oil separator to the vent chamber. A first flow valve may be arranged in this first fluid connection. The second fluid connection of the direct oil return device leads from the vent chamber to the inlet opening.

[0072] The screw compressor is preferably configured such that the intermediate pressure in the discharge chamber (during operation) is in the range of 0.2 bar to 6 bar higher than the suction pressure (of the compression section or the screw compressor), and very preferably in the range of 0.3 bar to 5 bar higher than the suction pressure. The precise intermediate pressure can be influenced, for example, by a first throttle valve and / or by a fluid return device, as described further below.

[0073] This ensures that sufficient oil is selected from the inlet opening of the direct oil return device. Furthermore, it ensures that no fluid flows through the direct oil return device in the opposite direction to the oil flow. Excessive pressure drop between the intermediate pressure and the suction pressure can cause excessive oil to flow from the exhaust chamber into the compression section.

[0074] Alternatively or additionally, the screw compressor is preferably configured such that the intermediate pressure in the exhaust chamber is at least 106% of the intake pressure during operation.

[0075] Here, the absolute value of the suction pressure may differ for different operating conditions, and the absolute value of the intermediate pressure may also differ for different operating conditions. The ratio between the intermediate pressure and the suction pressure may also differ for different operating conditions. However, for all (as specified) operating conditions, this ratio should be at least 1.06.

[0076] Particularly preferred, the exhaust chamber has a depth of 30cm 3 Up to 150cm 3 Within a range, and most preferably within 50cm 3 Up to 90cm 3 The volume is within a certain range. Thus, on average, the oil remains in the exhaust chamber long enough for at least a majority of the supersaturated portion of the fluid to evaporate during this period. On the other hand, the intermediate chamber is so compact that it requires less space and can be easily integrated together.

[0077] In a highly preferred embodiment, the direct oil return device includes a second flow valve arranged downstream of the vent chamber (viewed along the flow direction of the oil in the direct oil return device). Specifically, the second flow valve can be arranged in the second fluid connection, i.e., downstream of the vent chamber and upstream of the inlet opening of the direct oil return device. In particular, the second flow valve can be configured as a throttle valve. As previously defined, a throttle valve can be, for example, an orifice or a nozzle. The second flow valve can be integrally formed with the inlet opening and / or oil inlet of the second fluid connection at the vent chamber. The second flow valve is used to limit the mass flow rate of oil from the vent chamber. Thus, the inlet pressure of the oil at the inlet opening can be influenced in a simple and reliable manner.

[0078] If the direct oil return device has multiple port openings, the direct oil return device (with respect to the direction of oil flow in the direct oil return device) preferably branches downstream of the exhaust chamber. Therefore, only one suction chamber is needed for multiple port openings. This simplifies the structure and manufacture of the screw compressor and reduces its cost. Multiple second fluid connections can also be drawn directly from the exhaust chamber.

[0079] It is highly advantageous if the direct oil return device (or second fluid connection) is a downstream branch of the second flow valve. Therefore, only a common second flow valve is needed for multiple port openings of the same direct oil return device. This further reduces structural and manufacturing costs. Furthermore, the same port pressure exists (at least substantially) at the multiple port openings.

[0080] Alternatively, different second flow valves can be installed for different port openings among the multiple port openings. Therefore, the port pressure can be set differently for different port openings.

[0081] In a particularly preferred embodiment, the screw compressor has a fluid return device that allows fluid to enter the compression section from the exhaust chamber. In this way, fluid that separates from the oil in the outlet chamber can be returned to the fluid circuit.

[0082] The inlet of the fluid return device is preferably arranged in the compressor passage of the fixed plate. For example, the inlet can be constructed as a hole in the fixed base surface. At least a portion of the fluid return device can be constructed in the fixed plate. This reduces complexity and manufacturing costs.

[0083] The inlet of the fluid return device is preferably located in the central region of the compressor passage (of the fixed disc). This ensures that no fluid can flow out from the inlet of the fluid return device upstream of the compression section inlet. Simultaneously, it ensures that the inlet of the fluid return device is not in direct fluid contact with the outlet opening of the fixed screw section. This ensures the high efficiency and effectiveness of the screw compressor.

[0084] The fluid return device may include a check valve. The check valve prevents fluid from flowing from the compression chamber through the inlet opening of the fluid return device into the exhaust chamber. Alternatively or additionally, the fluid return device may include a flow valve. This simplifies the process of selectively setting the intermediate pressure in the exhaust chamber to a level higher than the average pressure of the fluid (in the compressor passage) at the inlet opening of the fluid return device.

[0085] In another embodiment, the fluid can flow (at least substantially) unimpeded between the exhaust chamber and the opening of the second fluid connection port. That is, the second fluid return device has neither a check valve nor a flow valve. Therefore, the intermediate pressure in the suction chamber is particularly directly affected by the time average value of the fluid at the opening of the fluid return device.

[0086] According to another aspect, the inlet opening of the fluid return device is very preferably arranged in a location in the compressor passage where the average value of the fluid pressure in the compressor passage during operation is in the range of 104% to 170% of the suction pressure, and in an improved embodiment, in the range of 105% to 150%.

[0087] If we neglect the mass flow rate of the returned oil and fluid in an idealized observation, then the intermediate pressure in the exhaust chamber is precisely the time-averaged pressure of the fluid at the inlet opening of the fluid return device. In reality, due to the mass flow rate of the returned oil and fluid, the operating intermediate pressure is higher than the time-averaged pressure of the fluid at the inlet opening of the fluid return device. This pressure differential is responsible for the flow of fluid from the exhaust chamber through the fluid return device to the compression section. The pressure differential is maintained by supplying fresh oil from the oil separator, along with the fluid dissolved therein, into the exhaust chamber. However, the intermediate pressure is decisively influenced by the time-averaged pressure of the fluid at the inlet opening of the fluid return device.

[0088] The ratio between the time-averaged fluid at the inlet opening of the fluid return device and the suction pressure depends essentially on the geometry of the compression section and the precise location of the inlet opening of the fluid return device in the compressor passage. Even under different operating conditions, it remains essentially constant at a given location of the inlet opening. On the other hand, this ratio can be selectively controlled by moving the location of the inlet opening. Therefore, the described embodiment is a particularly simple, reliable method for selectively influencing intermediate pressures and applicable to a wide variety of operating conditions.

[0089] Here, the absolute value of the suction pressure may differ for different operating conditions, and the absolute value of its time-averaged value may also differ for different operating conditions. The ratio between the suction pressure and the time-averaged pressure of the fluid at the inlet opening of the fluid return device may also differ for different operating conditions. However, this ratio should be within the mentioned range for all (as specified) operating conditions.

[0090] The described ratio setting is responsible for the favorable intermediate pressure in the exhaust chamber, such as in one of the advantageous embodiments described elsewhere. The intermediate pressure is high enough that sufficient oil flows from the exhaust chamber to the opening of (at least one) port of the direct oil return device, from there exits and reaches the compression section. On the other hand, the intermediate pressure is low enough that no excess oil flows out of the exhaust chamber, and at least a majority of the fluid dissolved in the oil supplied to the exhaust chamber separates from the oil.

[0091] The ratio of the time-averaged fluid pressure at the port opening (in the compressor passage) to the suction pressure can be determined, for example, by calculating and / or measuring the average pressure of the fluid in the compressor passage at the port opening location over a circle, given a suction pressure. This determination can also be achieved by measuring and / or calculating the average compression ratio of the fluid in the compressor passage at the port opening of the fluid return device over a circle.

[0092] When calculating the average value of the fluid pressure at the inlet opening of the fluid return device over time, the time range (or the range of the surrounding angle) during which the inlet opening of the fluid return device is closed by the rotating helix can be ignored.

[0093] The absolute value of the suction pressure may differ for different operating conditions. The absolute value of the average fluid pressure over time at the inlet opening of the fluid return device may also differ for different operating conditions. The ratio between the suction pressure and the average pressure over time may also differ for different operating conditions. However, for all (as specified) operating conditions, the average pressure over time should be within the range of 104% to 170% of the suction pressure in the corresponding operating condition, and in the improved version, within the range of 105% to 150% of the suction pressure in the corresponding operating condition.

[0094] Preferably, the fluid inlet is located outside the outlet region of the compressor passage. This ensures that the inlet of the fluid return device is never loaded with fluid at the outlet pressure. In an improved embodiment, the inlet is arranged in the compressor passage such that it is never in direct fluid contact with the final stage compression chamber. Otherwise, undesirable high intermediate pressures may occur in the exhaust chamber.

[0095] According to another aspect, the inlet of the fluid return device is very preferably arranged at a position angle ε in the compressor passage, wherein ε is in the range of γ-300° to γ, and wherein γ is the position angle of the outer end of the compressor passage.

[0096] Very preferably, the inlet of the fluid return device is arranged at a position angle ε1 in the compressor passage, where ε1 is in the range of γ-300° to γ-180°. The inlet opening can be arranged such that it is swept only by the compression chamber guided on the outside, and is closed exactly once each time it is surrounded by the rotating helical portion. For example, in this case, the sum of the distance of the inlet opening from the outside of the compressor passage at this position angle and the width of the inlet opening in the radial direction can be less than the width of the spiral arm of the rotating helical portion in the radial direction at the corresponding position angle of the rotating helical portion.

[0097] Alternatively, the inlet of the fluid return device is very preferably arranged at a position angle ε2 in the compressor passage, where ε2 is in the range from γ-120° to γ. The inlet opening can be arranged such that it is swept only by the compression chamber guided on the inside, and is closed exactly once each time by the rotating helical portion. For example, in this case, the sum of the distance of the inlet opening from the inside of the compressor passage at this position angle and the width of the inlet opening in the radial direction can be less than the width of the spiral arm of the rotating helical portion in the radial direction at the corresponding position angle of the rotating helical portion.

[0098] Particularly preferably, the inlet opening of the fluid return device is positioned such that a total of 130° of its 360° rotation around the rotating disc is directly fluidly connected to the inlet (suction pressure) of the compression section. Alternatively or additionally, the inlet opening of the fluid return device is closed by the rotating helix portion for a total of 130° of the 360° rotation around the rotating disc each time. Thus, the average and intermediate pressures of the fluid at the inlet opening of the fluid return device become sufficiently high to efficiently deliver oil from the exhaust chamber to the compression section.

[0099] According to another aspect, the screw compressor is very preferably configured such that, during operation, the intermediate pressure is at least 0.1 bar higher over time than the average pressure of the fluid (in the compressor passage) at the inlet opening of the fluid return device. Due to the pressure difference, the fluid released in the exhaust chamber flows back to the compression section through the fluid return device.

[0100] Alternatively or additionally, the screw compressor is very preferably configured such that the intermediate pressure during operation is less than 2 bar higher over time than the average pressure of the fluid (in the compressor passage) at the inlet opening of the fluid return device. If the intermediate pressure is too high, a small amount of fluid dissolved in the oil will be converted back to the gas phase in the discharge chamber. Furthermore, excessively high intermediate pressure will cause excessive oil flow from the discharge chamber to the inlet opening of the direct oil return device. As previously explained, the intermediate pressure and the difference between the intermediate pressure and the average pressure of the fluid at the inlet opening of the fluid return device can be simply and specifically influenced by accurately positioning that inlet opening.

[0101] For example, the intermediate pressure during operation can be in the range of 0.2 bar to 1.5 bar higher over time than the average pressure of the fluid (in the compressor passage) at the location of the fluid return device inlet opening.

[0102] Very preferably, the inlet of the fluid return device is arranged in the exhaust chamber above the oil inlet of the second fluid connection of the direct oil return device. Therefore, only the separated fluid flows into the fluid return device; correspondingly, the liquid oil flows into the second fluid connection of the direct oil return device. In this sense, "above" means that the inlet of the fluid return device opens into the exhaust chamber in front of (i.e., above) the oil inlet of the second fluid connection of the direct oil return device when viewed in the direction of gravity, when the screw compressor is in the desired operating position relative to the direction of gravity. In particular, the inlet of the fluid return device can be arranged at the upper end of the exhaust chamber and / or the inlet of the second fluid connection of the direct oil return device can be arranged at the lower end of the exhaust chamber.

[0103] The desired operating position can be defined, for example, by fixing the central axis of the helical part to be at least substantially perpendicular to the direction of gravity.

[0104] In a preferred embodiment, the screw compressor has an outlet pressure chamber, through which the oil separator is directly fluidly connected to the outlet of the compression section. The outlet pressure chamber is directly fluidly connected to the compression section. The oil separator is directly fluidly connected to the outlet pressure chamber, and therefore directly fluidly connected to the outlet of the compression section via the outlet pressure chamber. The outlet pressure chamber serves as a buffer chamber for the discharged fluid. It smooths the outlet pressure.

[0105] In a particularly preferred improvement, the exhaust chamber is constructed radially outside and surrounds the outlet pressure chamber. The exhaust chamber has a generally hollow cylindrical shape, with the outlet pressure chamber coaxially arranged at the center of the exhaust chamber. This allows for a very compact structure.

[0106] The screw compressor preferably includes a pressing pressure chamber that is loaded with a pressing pressure during compression operation, wherein the pressing pressure presses the rotating disc against the fixed disc during operation.

[0107] The pressing pressure chamber is located outside the direct oil return device. The pressing pressure chamber is not part of the direct oil return device. Oil returned by the direct oil return device does not pass through the internal space of the pressing pressure chamber; it is loaded with pressing pressure during operation. Functionally, the direct oil return device "bypasses" the internal space of the pressing pressure chamber.

[0108] The direct oil return device is spatially separate from the pressing pressure chamber. It is separate from the pressing pressure chamber.

[0109] In particular, the exhaust chamber may be attached to the pressing pressure chamber structure when necessary, i.e., constructed separately. For example, viewed parallel to the central axis, the pressing pressure chamber may be arranged on the side of the rotating disc opposite to the rotating disc. Conversely, viewed parallel to the central axis, the exhaust chamber may be arranged on the side of the fixed disc opposite to the rotating disc.

[0110] The screw compressor particularly preferably includes a second oil return device for returning oil from the oil separator to the pressing pressure chamber.

[0111] Oil is supplied to the pressing pressure chamber using a second oil return device. This second oil return device can be used to apply pressure to the pressing pressure chamber. The back side of the rotating disc opposite the fixed disc can form part of the boundary of the pressing pressure chamber. Preferably, the second oil return device leads directly from the oil separator to the pressing pressure chamber. This results in low complexity and allows the screw compressor to be manufactured simply and cost-effectively.

[0112] In a highly advantageous embodiment of the invention, the second oil return device includes a flow valve. The flow valve affects the effectiveness of the second oil return device. In particular, it affects the amount of oil flowing into the pressing pressure chamber through the second oil return device. Thus, the flow valve helps to coordinate and set the correct pressing pressure in the pressing pressure chamber.

[0113] The flow valve of the second oil return device is particularly preferably implemented as a throttle valve. Thus, the coordination of the pressing pressure is significantly facilitated by the second oil return device (and, if necessary, the return connection, see below). This improves the efficiency of the screw compressor compared to embodiments without a throttle valve in the second oil return device.

[0114] The second oil return device is constructed at least partially separately from the direct oil return device (the first oil return device). The second oil return device and the direct oil return device may share a common initial region. In this case, the direct oil return device branches off from the second oil return device, with this branch located upstream of the pressure chamber when viewed along the direction of oil flow from the second oil return device. Particularly preferably, this branch is located upstream of the flow valve of the second oil return device when viewed along the direction of oil flow from the second oil return device. The common initial region begins with a common oil inlet leading to the oil separator.

[0115] In a highly preferred embodiment of the invention, the direct oil return device has a first oil inlet leading to an oil separator, and the second oil return device has a second oil inlet leading to an oil separator. The second oil inlet is different from the first oil inlet. The second oil inlet is constructed separately from the first oil inlet. In particular, the second oil inlet may be spatially spaced from the first oil inlet.

[0116] In the improved design, in the event of an oil shortage, the second oil return device takes precedence over the direct oil return device. If the amount of liquid oil in the oil separator is lower than a preset value, the oil flow through the direct oil return device is reduced compared to the oil flow through the second oil return device, and / or the oil flow through the direct oil return device stops completely.

[0117] In this state, less oil is introduced into the compression section or no oil is introduced into the compression section via the direct oil return device. Therefore, friction in the compression section increases and efficiency decreases. However, the pressing chamber continues to supply oil. The time-limited lack of lubrication can be temporarily compensated by the oil located in the exhaust chamber. Therefore, the rotating disc is further lubricated at least from its rear side. Furthermore, if necessary, the components of the rotating mechanism located in the pressing chamber continue to be lubricated. Additionally, the pressing pressure in the pressing chamber can be maintained more easily. Thus, the screw compressor at least maintains its functional capacity. A certain level of lubrication in the compression section can be maintained, for example, by oil that peristalts from the pressing chamber through the rotating disc into the compression section, by oil flowing from the pressing chamber into the compression section via the reference connection described further below, and / or by oil guided by the drawn-in fluid.

[0118] In a highly preferred embodiment, the first oil inlet is arranged above the second oil inlet. In this sense, "above" means that when the screw compressor is positioned in the desired operating position relative to the direction of gravity, the first oil inlet, viewed along the direction of gravity, leads to the oil separator before (i.e., above) the second oil inlet. In other words, the first oil inlet in the oil separator opens above the second oil inlet. In particular, the second oil inlet can be arranged at the lower end of the oil reservoir in the oil separator. If the oil level in the oil separator drops from its normal level, in this arrangement, only the first oil inlet dries out first.

[0119] Alternatively or additionally, the screw compressor may have a valve mechanism that automatically reduces or stops the oil flow via a direct oil return device when the amount of liquid oil in the oil separator falls below a preset value. The valve mechanism may have one or more valves. If the second oil return device and the direct oil return device share a common initial area, a branch valve may be constructed, for example, at the junction of the direct and second oil return devices. The valve mechanism may include a level sensor that detects when the amount of liquid oil in the oil separator falls below a preset value.

[0120] Alternatively or additionally, the direct oil return device is very preferably constructed completely separately from the second oil return device. This means that the direct oil return device is never directly connected to the second oil return device in any location (and vice versa). In particular, in this case, the two do not share a common initial area. In this sense, the second oil return device and the direct oil return device are not directly fluidly connected. Of course, this does not preclude the first oil inlet of the direct oil return device and the second oil inlet of the second oil return device from being directly (but indirectly) fluidly connected to each other via the internal space of the heat exchanger.

[0121] The screw compressor particularly preferably has a reference opening arranged in the compression section and a reference connection that constructs a fluid connection between the pressing pressure chamber and the reference opening. The reference connection can be configured to influence the pressing pressure by means of a reference pressure present at the reference opening during operation.

[0122] The reference opening can be constructed in the rotating base plane of the compressor channel of the rotating disk or in the fixed base plane of the compressor channel of the fixed disk.

[0123] Very preferably, the reference opening is constructed in the rotating base plane within the compressor passage of the rotating disk, and the reference connection extends through the rotating disk. This allows for a very easy and cost-effective implementation of the reference connection.

[0124] The pressing pressure is directly affected by the reference pressure. At a given location of the reference opening in the compressor passage, the reference pressure strongly depends on the suction pressure and may also depend on the outlet pressure. In this respect, the difference between the pressing pressure and the suction pressure itself matches the operating state of the screw compressor. Therefore, complex, external, fragile, and expensive pressing pressure control is unnecessary. In particular, an active variable adjustable pressure control valve is not required to set and control the pressing pressure. Pressure balance occurs in the pressing chamber through the combined action of the reference return connection and the reference opening. Through the targeted design and coordination of the reference return connection and the reference opening, especially the accurate positioning of the reference opening in the corresponding compressor passage, automatic setting of different, separately desired pressing pressures for different operating states of the screw compressor is achieved. Accordingly, for different operating states, the pressing pressure that presses the rotating disc onto the fixed disc is coordinated with the lifting force acting on the rotating disc under the corresponding operating state. This improves the efficiency and reliability of the screw compressor.

[0125] The reference connection may include a flow valve. In particular, the flow valve may be configured as a non-regulating throttle valve. This allows the pressing pressure to be additionally affected. The flow valve also helps to prevent pressure differentials during the rotation of the rotating disc from acting unbufferedly in the pressing pressure chamber.

[0126] Oil from the pressing chamber is preferably guided between the fixed disc and the rotating disc via a reference connection. In this case, in addition to the direct oil return device, the screw compressor also has an "indirect oil return device," which indirectly and only indirectly returns oil from the oil separator to the compression section via the internal space of the pressing chamber. The indirect oil return device includes a second oil return device and a reference connection. This indirect oil return device is certainly not a direct oil return device in the sense of this disclosure.

[0127] In a very preferred embodiment of the invention, the screw compressor has two compression chambers, wherein a reference opening is arranged in the compressor passage (of a fixed disc or a rotating disc) such that, during compression operation, the reference opening is in direct fluid connection with the last stage compression chamber for a first portion of the time required for the rotating disc to rotate, and in direct fluid connection with the penultimate stage compression chamber for another portion of the time required for the rotation. Here, the first and second portions together do not necessarily determine the total time required for the cycle. Instead, there may be other portions.

[0128] This targeted positioning of the reference opening ensures that the high-pressure area of ​​the screw compressor also affects the pressing pressure, and that the pressing pressure during compression operation remains sufficiently high in every operating state, so that the pressing pressure acting on the rotating disc is sufficiently greater than the lifting force. Thus, in every operating state, the rotating disc is sealed against the stationary disc during compression.

[0129] The final stage compression chamber is characterized in that the fluid in the final stage compression chamber is at least partially guided to the outlet opening during compression operation, within the annulus of the rotating disc. The penultimate stage compression chamber is characterized in that the fluid in the penultimate stage compression chamber is at least partially guided to the outlet opening during compression operation, within the next annulus of the rotating disc.

[0130] For further explanation, details, and implementation possibilities regarding reference return connections and reference openings, particularly reference openings in compressor passages of fixed disks, refer to publications DE 10 2017 125 968 A1 and WO 2019 / 092024 A1. The disclosures contained therein apply appropriately and aptly to reference openings in compressor passages of rotating disks.

[0131] The screw compressor may have a suction pressure chamber that is fluidly connected to the inlet of the compression section. In particular, the suction pressure chamber may be directly fluidly connected to the inlet of the compression section. The suction pressure chamber is loaded during operation to draw pressure.

[0132] The screw compressor may have a suction connection. The suction connection may be connected to the inlet fluid of the compression section via the suction pressure chamber.

[0133] The screw compressor may have an outlet connection. This outlet connection may be fluidly connected to an oil separator. Preferably, the oil separator outlet connection (which is directly fluidly connected to the outlet connection) for the fluid in the oil separator is arranged above the first oil inlet of the direct oil return device (and possibly the second oil inlet of a second oil return device). In this sense, "above" means that when the screw compressor is in its desired operating position relative to gravity, the oil separator outlet opening in the oil separator is arranged in front of (i.e., above) the first oil inlet when viewed along the direction of gravity.

[0134] In an improved embodiment of the invention, the outlet of the compression section includes a check device. This may include, for example, a check valve and / or a check damper. The check unit prevents the compressed fluid (opposite to the desired flow direction) from flowing back through the outlet of the compression section. Otherwise, if the outlet pressure in the outlet pressure chamber is higher than the pressure at the center of the fixed helix, fluid from the outlet pressure chamber may flow back through the outlet of the compression section.

[0135] Check devices can (functionally and / or spatially) form the (downstream) end of a compression section.

[0136] Because the check valve is part of the outlet of the compression section, the oil separator is fluidly connected to the outlet of the compression section even when the check valve is closed. If the outlet pressure chamber is constructed between the outlet of the compression section and the oil separator, then when the check valve is closed, the outlet pressure chamber, as understood in this application, is also directly fluidly connected to the outlet of the compression section.

[0137] The outlet pressure chamber, pressing pressure chamber, rotating disc, fixed disc, return connection, and reference return connection are particularly preferably arranged in the suction pressure chamber. Thus, all these components are reliably sealed by the suction pressure chamber. In this case, the suction connection and outlet connection can be arranged at the suction pressure chamber, wherein the outlet connection is fluidly connected to the oil separator in a pressure-sealed manner.

[0138] In an improved embodiment of the invention, the fixed helix has at least 1.25 turns. This corresponds to a helix angle of at least 450° for the fixed helix. This ensures sufficient maximum compression for common applications of the screw compressor.

[0139] Alternatively and / or additionally, the fixed helix portion preferably has a maximum of 2.5 turns. This corresponds to a maximum helix angle of 900° for the fixed helix portion. This keeps the screw compressor compact, lightweight, and suitable for production.

[0140] Particularly preferably, the fixed helix has two turns, wherein the reference opening in the compressor passage (leading to the pressing pressure chamber) is arranged at a position angle of at least 315° and a maximum of 435° with respect to the inner end of the fixed helix, and most preferably at least 345° and a maximum of 405°. This arrangement has proven to be particularly practical.

[0141] If the second return connection has multiple through-holes and / or is provided with multiple second return connections each having at least one through-hole, then each through-hole can be implemented independently according to any of the foregoing embodiments and modifications. Advantages apply accordingly. Thus, for example, all through-holes can be implemented in the same way, i.e., a first subset of all through-holes is constructed according to the first embodiment, and a second portion of all through-holes is implemented according to the second embodiment, or all through-holes can be implemented differently.

[0142] The screw compressor preferably has an electric motor to drive the rotating disc. Integrating the electric motor into the screw compressor allows it to operate with particular precision and efficiency. The operation of the electric motor can be precisely coordinated with the specific screw compressor. In particular, the drive of the screw compressor does not depend on the operating status of other external units. The electric motor is very preferably located within the suction chamber. In a particularly preferred improvement, the screw compressor is an electric screw compressor with an integrated inverter.

[0143] Alternatively and / or additionally, the screw compressor may also have a force transmission device for driving the rotor via an external drive unit. The external drive unit may be, for example, an internal combustion engine. The force transmission device may have a clutch (e.g., an electromagnetic clutch).

[0144] Alternatively, spiral compressors can also be used, for example, in heat pump systems. This is particularly important for the air conditioning systems of electric vehicles and / or full hybrid vehicles.

[0145] The present invention also relates to an air conditioning unit having a spiral compressor according to the invention. In particular, it can be an air conditioning unit for motor vehicles.

[0146] The implementation possibilities and advantages described for the screw compressor apply accordingly to this system. Attached Figure Description

[0147] The invention will now be explained with reference to embodiments and the accompanying drawings. All features described and / or illustrated herein, either alone or in any combination, form the subject matter of the invention, equally independent of their summary in the claims or their reverse reference.

[0148] in:

[0149] Figure 1A longitudinal section of a first embodiment of a screw compressor according to the present invention is schematically shown;

[0150] Figure 2 schematically shown Figure 1 The screw compressor's compression section, oil separator, and direct oil return device for directly returning oil from the oil separator to the compression section;

[0151] Figure 3 schematically shown Figure 1 The cross-section of the compression section has two inlet openings for direct oil return devices and an inlet opening for a fluid return device for returning refrigerant from the exhaust chamber of the direct oil return devices, wherein all these inlet openings are arranged in the fixed disk of the fixed helix portion of the compression section, and wherein only the rotating helix portion is visible from the rotating disk of the compression section.

[0152] Figure 4 The direction is schematically shown. Figure 3 A top view of a modified fixed plate of a screw compressor, used to accurately explain the preferred arrangement of the inlet openings of the direct oil return device.

[0153] Figure 5 The longitudinal section of the compression section, outlet pressure chamber, oil separator, and direct oil return device for directly returning oil from the oil separator to the compression section is schematically shown in a second embodiment of the screw compressor according to the invention.

[0154] Figure 6 schematically shown Figure 5 The cross section at point A of the midsection; and

[0155] Figure 7 The direction is schematically shown. Figure 3 Top view of the fixed disk in the middle. Figure 7 Used to explain the advantageous location of the inlet opening for the fluid return device. Detailed Implementation

[0156] exist Figure 1 The image schematically illustrates a first embodiment of a screw compressor 1 for compressing fluids according to the invention in longitudinal section. The fluid is, for example, a refrigerant or a refrigerant mixture in a refrigerant circuit.

[0157] The screw compressor 1 includes a compression section 10 having an inlet 11, a fixed disc 20, a rotating disc 30, and an outlet 12. An outlet pressure chamber 40 is directly connected to the outlet 12. In this embodiment, the outlet 12 includes a check valve 13 that prevents compressed refrigerant from flowing back from the outlet pressure chamber 40 into the compression section 10. The check valve 13 is exemplarily shown here as a check valve and forms the downstream end of the compression section 10.

[0158] Viewed along the refrigerant flow direction (during operation), the oil separator 45 is directly connected to the outlet pressure chamber 40. Therefore, the oil separator 45 is directly fluidly connected to the outlet pressure chamber 40, and via the outlet pressure chamber 40 is directly fluidly connected to the outlet 12 of the compression section 10.

[0159] The screw compressor 1 includes a housing 90 having a suction connection 91 and an outlet connection 92.

[0160] The suction connection 91 is directly fluidly connected to the inlet 11 of the compression section 10 via the suction pressure chamber 93. During operation, refrigerant is drawn from the external refrigerant circuit through the suction connection 91.

[0161] The outlet connection 92 is directly fluidly connected to the oil separator outlet opening 46 of the oil separator 45. During operation, the compressed refrigerant is discharged into the external refrigerant circuit via the outlet connection 92.

[0162] During operation, suction pressure exists in suction pressure chamber 93 and inlet 11 of the compression section. Suction pressure can, for example, range from 0.7 bar to 9 bar. During operation, outlet pressure greater than the suction pressure exists in outlet pressure chamber 40, oil separator 45, and outlet connection 92. Outlet pressure can, for example, range from 6 bar to 32 bar. Suction and outlet pressures depend particularly on the refrigerant used and the operating conditions of the external refrigerant circuit.

[0163] Figure 1 The suction pressure chamber 93 is shown only schematically. The suction pressure chamber 93 preferably surrounds at least the pressing pressure chamber 80 in a jacket-like manner. That is, the suction pressure chamber 93 extends completely around the pressing pressure chamber 80 along the circumferential direction (relative to the central axis). Alternatively or additionally, the suction pressure chamber 93 may surround at least a portion of the compression section 10 in a jacket-like manner. That is, the suction pressure chamber 93 extends completely around the aforementioned portion of the compression section 10 along the circumferential direction (relative to the central axis). The aforementioned portion of the compression section 10 may face the pressing pressure chamber 80, particularly when viewed along the central axis.

[0164] The suction pressure chamber 93 may be constructed, for example, at least substantially cylinder-shaped around the pressing pressure chamber 80 and / or at least a portion of the compression section 10 on one side of the pressing pressure chamber 80.

[0165] The fixed plate 20 faces the outlet pressure chamber 40, while the rotating plate 30 faces the pressing pressure chamber 80.

[0166] against Figure 3 The cross section is located at Figure 1 or Figure 2The spiral portion extends between the rotating disk 30 and the fixed disk 20, and parallel to the fixed base surface 22 of the fixed disk 20. A fixed spiral portion 21 with 2.25 turns is arranged on the fixed base surface 22. Correspondingly, the outer end 25 of the fixed spiral portion 21 is arranged at a helix angle of 810° with the inner end 24 of the fixed spiral portion 21.

[0167] Figure 4 This is a simplified top view of the fixed plate 20. For simplicity, the rotating spiral part 31 is... Figure 4 The modified version with two turns is shown in the middle. Correspondingly, the outer end 25 of the fixing screw 21 is arranged at a helix angle of 720° with the inner end 24 of the fixing screw 21. In other aspects, Figure 3 and Figure 4 The structure and function of the fixed disk 20 are the same, and the same reference numerals are used for the same components.

[0168] Back Figure 3 Due to the cross-section, only the rotating spiral portion 31 is visible from the rotating disk 30. This rotating spiral portion 31 is arranged on the rotating base surface 32 of the rotating disk 30. Figure 3 Not shown in the image, but see [link / reference]. Figure 5 The rotating helical part 31 has (as shown in the image) Figure 3 (Implementation scheme of fixed spiral part 21) 2.25 turns.

[0169] The fixed disk 20 and the rotating disk 30 are nested together. During (compression) operation, the rotating disk 30 is subjected to the pressing pressure in the pressing pressure chamber 80 (see...). Figure 1 The screw is pressed against the fixed plate 20. As a result, on the one hand, the end face of the rotating screw 31 facing away from the rotating base 32 is sealed against the fixed base 22, and on the other hand, the end face of the fixed screw 21 facing away from the fixed base 22 is sealed against the rotating base 32.

[0170] The fixed base surface 22, the fixed spiral part 21, the rotating base surface 32, and the rotating spiral part 31 thereby define a plurality of compression chambers 14a, 14b, and 14c.

[0171] exist Figure 3 In the position shown by the rotating disc 30 or rotating spiral section 31, the last stage compression chamber 14c and the two compression chambers 14a and 14b of the penultimate stage are defined in the compressor passage 26 constructed between the turns of the fixed spiral section 21, wherein the last stage compression chamber 14c includes two sub-regions that pass through the narrow gap between the fixed spiral section 21 and the rotating spiral section 31. Figure 3 (Invisible to each other) fluidly connected.

[0172] exist Figure 3The left side shows a vector diagram representing the encirclement angle 103 of the rotating disk 30 (and therefore the rotating helical portion 31) and its encirclement direction or compression direction 100. When the encirclement position 103 of the rotating disk 30 in the vector diagram is exactly at an encirclement angle 101 of 0°, the rotating disk 30 begins a new encirclement. Then, the outer side of the rotating helical portion 31 just contacts the outer end 25 of the fixed helical portion 21, and here closes the compression chamber of the penultimate stage 14b guided on the outer side. At the same time, the outer end 34 of the rotating helical portion 31 contacts the outermost outer ring of the fixed helical portion 21, and here closes the compression chamber of the penultimate stage 14a guided on the inner side. Figure 3 In the middle, the rotating disk 30 has moved further along the compression direction 100 from the 0° encirclement angle 101 to the 45° encirclement position 103. From Figure 3 Starting from there, the rotating disc 30 continues to rotate around the center of the fixed spiral part 21 along the compression direction 100.

[0173] When the rotating disk 30 from Figure 3 When it starts to rotate 270° relative to the fixed disk 20 along the compression direction 100, it reaches the 0° rotation position and its current rotation ends. Figure 3 Most of the refrigerant in the final stage compression chamber 14c is guided to the outlet opening 28 in the fixed base surface 22, and thus to the outlet 12 of the compression section 10. The outlet opening 28 is located at the center of the fixed plate 20 or the fixed spiral section 21.

[0174] The screw compressor 1 has a direct oil return device 50 for returning oil from the oil separator 45 back to the compression section 10.

[0175] More precisely, the direct oil return device 50 extends from the first oil inlet 51 in the oil separator 54 to two through openings 59a, 59b in the fixed base surface 22 of the fixed disk 20. In operation, the direct oil return device 50 injects oil from the oil separator 45 directly between the fixed disk 20 and the rotating disk 30 through the through openings 59a, 59b.

[0176] exist Figure 1 In the embodiment shown, the direct oil return device 50, viewed along the oil flow direction, includes a first oil inlet 51, a first fluid connection 52 having a first throttle valve 53, an exhaust chamber 54, a second fluid connection 56 having a second throttle valve 57 and a branch 58, and two additional port openings 59a and 59b.

[0177] During operation, the outlet pressure exists within the internal space of the oil separator 45. In the oil separator 45, the refrigerant rises, while the liquid oil accumulates in the lower half of the separator. In this way, the refrigerant and oil are separated from each other. Due to the high outlet pressure, the liquid oil exhibits increased solubility for the refrigerant and contains a certain proportion of dissolved refrigerant.

[0178] The first oil inlet 51 is located in the lower half of the internal space of the oil separator 45, while the oil separator outlet opening is located at the upper end of the internal space of the oil separator 45. Liquid oil is forced from the oil separator 45 through the first oil inlet 51 into the first fluid connection 52 by the outlet pressure.

[0179] In the first fluid connection 52 of the direct oil return device 50, the oil flows through a first throttle valve 53. The first throttle valve 53 can be configured as a non-regulating throttle valve. For example, the first throttle valve 53 can be implemented as an orifice or nozzle. The first throttle valve 53 reduces the mass flow rate of the oil. The oil then flows further into the exhaust chamber 54. By affecting the mass flow rate of the oil, the intermediate pressure in the exhaust chamber 54 can be affected. Due to the pressure drop, the solubility of the refrigerant in the oil decreases. After the first throttle valve 53, the oil can become supersaturated with refrigerant. The supersaturated portion of the refrigerant can evaporate in the exhaust chamber 54. The liquid oil collects in the lower region of the exhaust chamber 54, and the refrigerant collects in the upper region of the exhaust chamber 54. The exhaust chamber 54 can be considered as an auxiliary oil separator for both the direct oil return device 50 and the fluid return device 70.

[0180] In the lower region of the exhaust chamber 54, for example, at the bottom region of the exhaust chamber 54, an oil inlet 55 of the second fluid connection 56 of the direct oil return device 50 is arranged. Due to the intermediate pressure present in the exhaust chamber 54, liquid oil is forced from the exhaust chamber 54 into the second fluid connection 56 through the oil inlet 55.

[0181] The second fluid connection 56 has a second throttle valve 57, which limits the mass flow rate of oil escaping from the exhaust chamber. This also prevents an undesirable sharp drop in the intermediate pressure in the exhaust chamber 54. The second throttle valve 57 can also be implemented as a non-regulating throttle valve, such as an orifice or nozzle.

[0182] Downstream of the second throttle valve 57, the second fluid connection 56 branches into two arms at branch 58. The two arms are guided at least partially through the fixed disc 20. They terminate respectively in one of the through openings 59a and 59b arranged in the fixed base surface 22.

[0183] Each port opening 59a, 59b is arranged in the inlet region of the compression section 10, and is in direct fluid contact with the inlet 11 of the compression section 10 at least temporarily during operation. Thus, oil escaping from the port openings 59a, 59b is entrained by the absorbed refrigerant and subsequently sealed together with the refrigerant in the newly formed compression chambers. Because the port openings 59a, 59b are located in the inlet region of the compression section 10, the radially outer engagement area of ​​the fixed helix 21 and the rotating helix 31 is also prominently lubricated.

[0184] Furthermore, during each revolution of the rotating disc 30, all openings 59a and 59b are swept by the rotating spiral portion 31 at least once. This ensures proper distribution of the supplied oil. Oil selected from the openings 59a and 59b is applied by the rotating spiral portion 31. Figure 4 As can be seen from the example, during each rotation, the opening 59a of the passage is swept by the outer end 34 of the rotating spiral part 31.

[0185] The following will refer to Figure 4 The particularly preferred positioning of the openings 59a and 59b will be discussed in more detail.

[0186] Compression chambers 14a, 14b, 14c (see also) are located in the compression section 10 formed between the fixed disk 20 and the rotating disk 30. Figure 3 In the process, the refrigerant is delivered to the center of the fixed spiral section 21, where it is compressed by reducing the volume of the compression chambers 14a, 14b, and 14c until the refrigerant reaches the outlet pressure. Subsequently, the refrigerant is delivered to the oil separator 45 through outlet 12 and outlet pressure chamber 40. In this example, outlet 12 includes an outlet opening 28 located at the center of the fixed disc 20 and a check valve 13.

[0187] Here, the oil is also transported along with the refrigerant and eventually reaches the oil separator 45. There, the oil is separated from the refrigerant and can be used for a new cycle in the direct oil return device 50. The oil-free, compressed refrigerant at the outlet pressure is drawn out from there through the oil separator outlet opening 46 and the outlet connection 92 from the screw compressor 1.

[0188] according to Figure 4 The location where the inlet openings 59a and 59b of the direct oil return device can be preferably arranged will now be explained.

[0189] The 0° position angle is determined by the inner end 24 of the fixed screw portion 21. It should be noted that the terminating flange 24a of the inner end 24 is not important in determining the 0° position angle. Because... Figure 4The fixed helix 21 has two turns, so its outer end 25 is arranged at a position angle or helix angle of 720°. Accordingly, the inlet opening of the compressor passage 26, which extends between the outer end 25 and the beginning of the outer turn of the fixed helix 21 at a position angle of 360°, is located at a position angle of 720°.

[0190] Figure 4 A preferred first region A is shown, illustrating the arrangement of the inlet openings for the direct oil return device 50. M，1 .

[0191] exist Figure 4 In this context, γ is the position angle of the outer end 25 of the fixed screw section 21. Correspondingly, γ is also the position angle of the outer end of the compressor passage 26. At position angle γ, the inner side of the fixed screw section 21 has a distance R from the center of the fixed screw section 21 in the radial direction. I (γ). Meanwhile, the inlet opening of the compressor passage 26 of the fixed disk 20 has a width B in the radial direction at the position angle. K Width B here K As B K =R I (γ)-R A (γ-360°) is derived, where R A (γ-360°) is the distance to the outside of the fixed spiral part 21 at the position angle corresponding to γ-360°.

[0192] Area A, First Zone M，1 The position angle extends from position angle γ-30° to γ+30° in the circumferential direction, and from R in the radial direction. I (γ)-B K / 2 extends to R I (γ). This means that the first region A M，1 Arranged at the inlet opening of the compressor passage 26, or more precisely, on the radially outer half of the compressor passage 26 within the angular range of that position or its hypothetical continuation.

[0193] exist Figure 4 In the middle, the opening 59a is located in the first region A. M，1 In the middle, more precisely, exactly at the position angle γ = 720° and near the outer side of the compressor passage 26, that is, for example, at a radial distance R from the center of the fixed screw section 21. I (γ)-B K / 10. The opening 59a is closed only once per revolution of the rotating helical portion 31. In the illustrated embodiment, this opening 59a is not directly connected to the compression chamber 14b guided on the inner side. The opening 59a ensures lubrication of the outer side of the compression chamber in a particularly advantageous manner. Figure 3 In the middle, the compression chamber 14a is guided on the outside.

[0194] Figure 4 A preferred second region A is also shown, illustrating the arrangement of the port openings for the direct oil return device 50. M，2 In this example, the opening 59b is located in the second region A. M，2 middle.

[0195] Second Area A M，2 Extending radially outside the fixed helix 21 around the position angle θ, where θ = γ + 180°. Second region A M，2 Extending in the circumferential direction from position angle θ-30° to position angle θ+30°, and in the radial direction from R A (θ-360°) extends to R A (θ-360°)+B K / 2. Therefore, the second region A M，2 Located outside the compressor passage 26 of the fixed plate 20, more precisely on the side opposite to the inlet opening of the compressor passage 26. Here, R A (θ-360°) is the radial distance on the outside of the fixed spiral part 21 at the position angle θ-360°=γ-180°.

[0196] exist Figure 4 In the middle, the opening 59b is located in the second region A. M，2 More precisely, it is located at a position angle θ = 900° and is close to the outermost ring of the fixed screw portion 21, i.e., having a radial distance R from the center of the fixed screw portion 21. A (θ)+B K / 10. The inlet opening 59b ensures lubrication of the compression chamber guided on the inner side in a particularly advantageous manner. Figure 3 In the middle, the compression chamber 14b is guided on the inner side.

[0197] exist Figure 3 In the middle, the inlet openings 59a and 59b of the direct oil return device 50 are also as described in reference. Figure 4 Positioned as described.

[0198] The screw compressor 1 also includes a fluid return device 70 for returning refrigerant from the discharge chamber 54 back to the compression unit. The fluid inlet 71 of the fluid return device 70 is located in the upper region of the discharge chamber 54. Thus, no liquid oil flows from the discharge chamber 54 into the fluid return device 70.

[0199] The fluid return device 70 extends through the fixed plate 20. The port opening 72a of the fluid return device 70 is arranged in the compressor passage 26 of the fixed plate 20 (see...). Figure 3 and Figure 5Here, the inlet opening 72a is located in the inlet area of ​​the compressor passage 26, but is sometimes swept across by the enclosed compression chamber. Figure 3 In this embodiment, the penultimate stage compression chamber 14b sweeps directly across the outlet opening 72a. Therefore, the time-averaged refrigerant pressure in the compressor passage 26 at outlet opening 72a is higher than the suction pressure. In this embodiment, during specified operation, the intermediate pressure in the discharge chamber 54 is higher than the time-averaged refrigerant pressure in the compressor passage 26 at outlet opening 72a, more precisely—depending on the exact operating conditions—in the range of 0.2 bar to 1.5 bar. The pressure differential with the outlet pressure forces liquid oil out of the discharge chamber into the second fluid connection 56 and out of the outlet openings 59a, 59b of the direct oil return device 50.

[0200] The intermediate pressure in exhaust chamber 54 is particularly affected by the following factors:

[0201] -The oil, along with the entrained refrigerant, flows through the first fluid connection 52 and into the exhaust chamber 54 at its outlet pressure and mass flow rate.

[0202] - The time average of the pressures at the inlet openings 59a and 59b and the corresponding mass flow rate of the oil leaving the exhaust chamber 54 via the second fluid connection 56, and

[0203] - The time average pressure of the refrigerant in the compressor passage 26 at the inlet opening 72a and the corresponding mass flow rate of the refrigerant leaving the exhaust chamber 54 through the fluid return device 70.

[0204] The driving force is the outlet pressure in the oil separator 45.

[0205] In this implementation, the intermediate pressure (or the time-averaged intermediate pressure without changing operating conditions) is in the range of 0.3 bar to 5 bar above the suction pressure during operation. During operation, when the suction pressure is 1 bar, the intermediate pressure is at least 0.3 bar higher than the suction pressure, i.e., absolutely within 1.3 bar, and at most 1.9 bar higher, i.e., absolutely within 1.9 bar. During operation, when the suction pressure is 7 bar, the intermediate pressure is at most 4.2 bar higher than the suction pressure, i.e., within 11.2 bar. Of course, the intermediate pressure is still significantly lower than the outlet pressure, which in this case is 32 bar. When the suction pressure is 5 bar, the intermediate pressure is in the range of 0.6 bar to 3.5 bar above the suction pressure. These values ​​are examples. The exact intermediate pressure depends on the exact operating conditions, and also on the outlet pressure, for example. The exact pressure ratio may also depend on the refrigerant used.

[0206] In other words, during operation, the intermediate pressure is in the range of 1.3 bar (minimum intermediate pressure) and 11.2 bar (maximum intermediate pressure).

[0207] The following is based on Figure 7 Explain the advantageous positions of the inlet openings 72a and 72b for the fluid return device 70.

[0208] Generally, the openings 72a and 72b of the fluid return device 70 in the compressor passage 26 are preferably arranged at a position angle (of the compressor passage 26), which is within ε min =γ-300° and ε max = γ, where γ is the position angle of the outer end of the compressor channel.

[0209] Figure 7 Two particularly preferred regions A are shown, illustrating the arrangement of the port openings 72a, 72b for the fluid return device 70 in the compressor passage 26. M，3 and A M，4 .

[0210] A region A for arranging the opening 72a of the passageway. M，3 By means of the following definition, the opening 72a of the fluid return device 70 located therein is arranged at a position angle ε1, which is within ε min =γ-300° to ε max，1 Within the range of γ-180°, the opening 72a is further arranged such that it is swept only by the compression chamber 14b guided on the outside and swept exactly once each time around the rotating helical portion 31. For example, Figure 3 , Figure 4 and Figure 7 The inlet opening 72a of the fluid return device 70 is arranged in the compressor passage 26 at a position angle ε1 = γ - 248°. Furthermore, the inlet opening 72a is located on the outside of the compressor passage 26 at this position angle. Thus, in this embodiment, the inlet opening 72a is only swept by the compression chamber 14b guided on the outside. The inlet opening 72a is never in direct fluid contact with one of the compression chambers 14a guided on the inside.

[0211] More precisely, in this embodiment, the inlet opening 72a of the fluid return device 70 is closed by the rotating helix 31 within an angle of 0° to 20°. When the angle of 20° is reached, the compression chamber 14b guided on the outside begins to sweep across the inlet opening 72a. Within an angle of 20° to 270°, the inlet opening 72a is in fluid connection with the compression chamber 14a guided on the outside. Figure 3 In the case of the 90° surround angle shown, the inlet opening 72a of the fluid return device 70 is directly fluidly connected to the compression chamber 14b guided on the outside, for example, on its entire surface. Within the surround angle range of 270° to 360°, the rotating helix 31 closes the inlet opening 72a again.

[0212] At a 20° encirclement angle, the pressure of the refrigerant in the outer-guided compression chamber 14b, which is fluidly connected to the inlet opening 72a, is already slightly higher than the suction pressure. This is because the compression chamber 14b was closed shortly before at a 0° encirclement angle (reference numeral 101), and has narrowed slightly up to a 20° encirclement angle.

[0213] For the following example, assume the suction pressure is 3 bar. Then, at an angle of 20°, the refrigerant pressure in the compressor chamber 14b is, for example, 3.08 bar. In this example, the refrigerant pressure in the compressor chamber 14b continuously increases to 4.76 bar up to an angle of 270°. Here, the time-averaged refrigerant pressure in the compressor passage 26 at the port opening 72a is 3.76 bar, which is therefore 0.76 bar higher than the suction pressure of 3 bar. This is a non-limiting example for a specific operating condition.

[0214] Thus, according to Figure 3 In the embodiment, the time average value of the refrigerant pressure in the compressor passage 26 located at the port opening 72a of the fluid return device 70 is...

[0215] ●At a suction pressure of 1 bar, it is 126% of that suction pressure.

[0216] ●At a suction pressure of 3 bar, it is 125% of that suction pressure.

[0217] ●At a suction pressure of 5 bar, it is 124% of that suction pressure, and

[0218] ● When the suction pressure is 7 bar, it is 123% of that suction pressure.

[0219] In a modified embodiment (not shown), when the inlet opening 72a of the fluid return device 70 is in region A M，3 When the fluid returns to the position angle ε1=γ-295°, the time average pressure of the refrigerant in the compressor passage 26 at the position of the inlet opening 72a of the fluid return device 70 depends on the operating conditions, for example, in the range of 138% to 142% of the corresponding suction pressure.

[0220] In a modified embodiment (not shown), when the inlet opening 72a of the fluid return device 70 is in region A M，3 When the fluid returns to the position angle ε1=γ-190°, the time average pressure of the refrigerant in the compressor passage 26 at the position of the inlet opening 72a of the fluid return device 70 depends on the operating conditions, for example, in the range of 107% to 109% of the corresponding suction pressure.

[0221] Another area A used for arranging the opening 72b′ M，4 By the following limitation, the opening 72b of the fluid return device 70 located therein is arranged at a position angle ε2, which is within ε min，2 =γ-120 to ε max Within the range of γ, the opening 72b is further arranged such that it is swept only by the compression chamber 14a guided on the inside and swept exactly once per revolution by the rotating spiral 31.

[0222] exist Figure 7 The example shown is for region A with a position angle ε2 = γ - 68°. M，4 The location of the through opening 72b. The through opening 72b is further arranged at this location angle ε2 on the inner side of the compressor passage 26. Thus, the through opening 72b is only swept by the compression chamber 14a guided on the inner side. Therefore, the through opening 72b is never in direct fluid contact with one of the compression chambers 14b guided on the outer side. The through opening 72b can be replaced by or added to... Figure 7 Another port opening 72a of the fluid return device 70 shown is constructed.

[0223] When compression chambers 14a and 14b are closed, the position angle of the inner compression chamber 14b is offset by +180° relative to the position angle of the outer compression chamber 14a. Since the position angle of the port opening 72b is also offset by +180° relative to each of the port openings 72a, the pressure conditions at the port opening 72b develop similarly to those at the port opening 72a during the circumferential process.

[0224] In an embodiment not shown, the port opening of the fluid return device 70 can, for example, be arranged from ε max，1 to ε min，2 At the position angle within the range. Such an opening can be arranged at this position angle in the central region of the compressor passage 26, such that it is completely closed twice by the rotating helix 31 in each turn, and alternately fluidly connected to the inner-guided compression chamber 14a and the outer-guided compression chamber 14b. Thus, the average pressure of the refrigerant at this opening is between the average pressure of the refrigerant in the outer-guided compression chamber 14b of the compressor passage 26 at this position angle and the average pressure of the refrigerant in the inner-guided compression chamber 14b of the compressor passage 26 at this position angle. As mentioned elsewhere, the time period during which the opening is completely closed by the rotating helix 31 can be disregarded for the calculation of the average pressure of the refrigerant at the opening.

[0225] The screw compressor 1 also has a second oil return device 82. The second oil return device 82 returns oil from the oil separator 45 back to the pressing pressure chamber 80. It includes a second oil inlet 81 located in the oil separator 45 and a throttle valve 83 arranged between the second oil inlet and the pressing pressure chamber 80 in the second oil return device 82.

[0226] During operation, oil is forced into the second oil return device 82 through the second oil inlet 81 by the outlet pressure present in the oil separator 45. The oil pressure is reduced by the throttle valve 83. The pressure drop in the throttle valve 83 affects the pressing pressure.

[0227] Pressing the oil in the pressure chamber 80 helps lubricate the rotating disc 30. In addition, a small portion of the oil can creep through the rotating disc 30 into the interior of the compression section 10.

[0228] Figure 1 The screw compressor 1 shown also includes a reference connection 84 between the internal space of the pressing pressure chamber 80 and a reference opening 86. The reference opening 86 is arranged in the rotating base surface 32 of the rotating disk 30, more specifically in the compressor passage of the rotating disk 30. The reference connection 84 affects the pressing pressure in the pressing pressure chamber 80 according to the operating state of the screw compressor 1. The reference connection 84 is guided from the pressing pressure chamber 80 through the rotating disk 30 to the reference opening 86 in the rotating base surface 32.

[0229] Viewed radially, the reference opening 86 of the reference connection 84 is positioned further inward than the through openings 59a and 59b of the direct oil return device 50. Figure 3 The reference opening 86 of the reference connection 84 is located in the outlet region of the compressor passage of the rotating disc 30. Therefore, the reference connection 84 does not contribute, or only slightly contributes, to the lubrication of the radially outer regions of the stationary helix 21 and the rotating helix 31. The reference opening 86 is not arranged in the inlet region of the compressor passage of the rotating disc 30. Therefore, during the operation of the screw compressor 1, no direct fluid connection is formed between the inlet 11 of the compression section 10 and the reference opening 86.

[0230] Optionally, reference connection 84 includes a throttle valve 85. The throttle valve 85 helps to regulate the pressing pressure.

[0231] The second oil inlet 81 of the second oil return device 82 is located in the bottom region of the oil separator 45. Specifically, this second oil inlet is located below the first oil inlet 51 of the direct oil return device 50. If the oil level in the oil separator 45 drops below the level of the first oil inlet 51 during operation, the first oil inlet 51 dries out and stops supplying oil. However, the second oil inlet 81 continues to be supplied with oil. The oil supply from the second oil return device thus takes precedence over the oil supply from the direct oil return device 50. This ensures that the pressing pressure is maintained even in the event of an oil shortage. A certain level of lubrication in the compression section 10 is maintained by the oil that peristally travels through the rotating disc 30 externally and by the oil that returns from the external refrigerant circuit to the inlet 11 reaching the compression section 10. Additionally, oil from the pressing pressure chamber 80 can be supplied to the compression section 10 via the reference connection 84, especially when the oil level in the pressing pressure chamber is very high.

[0232] The screw compressor 1 also includes an electric motor and an inverter (not shown) for the electric motor. The screw compressor 1 can be integrated into the refrigerant circuit of a vehicle. The screw compressor 1 can be installed, for example, in an electric vehicle or a hybrid vehicle.

[0233] Figure 5 A longitudinal section is shown of the compression section 10, outlet pressure chamber 40, oil separator 45, and direct oil return device 50 for directly returning oil from the oil separator 45 to the compression section 10 according to a second embodiment of the screw compressor according to the invention. The remaining components of the screw compressor are not shown. Unless otherwise stated, the screw compressor and its components correspond to... Figure 1 The structure and functional principle of the screw compressor 1 are described. The same reference numerals are used for the same components.

[0234] Figure 6 It shows in Figure 5 The cross section at point A in the diagram.

[0235] Figure 5 and Figure 6 The diagram shows an exhaust chamber 54 constructed radially (perpendicular to the central axis of the fixed disk 20) ​​outside and surrounding the outlet pressure chamber 40. The exhaust chamber 54 has a (at least substantially) hollow cylindrical basic shape. The outlet pressure chamber 40 has a (at least substantially) cylindrical basic shape. The outlet pressure chamber 40 and the exhaust chamber 54 are arranged coaxially. The hollow cylindrical peripheral wall 41 of the outlet pressure chamber 40 separates the outlet pressure chamber 40 and the exhaust chamber 45 from each other. In this way, otherwise unused space surrounding the peripheral wall 41 is used advantageously.

[0236] The outlet pressure chamber 40 is directly fluidly connected to the oil separator 45 through the opening 42. Figure 1Similarly, a check device may optionally be constructed at the outlet 11 of the compression unit 10 (not shown).

[0237] The described implementation with direct oil return device 50 allows for particularly efficient operation and high reliability.

[0238] Reference symbol list:

[0239] 1. Screw compressor

[0240] 10 Compression Section

[0241] 11 (Entrance of the compressed section)

[0242] 12 (Exit of the compression section)

[0243] 13 Check device

[0244] Compression chambers 14a, 14b, and 14c

[0245] 20 fixed plates

[0246] 21 Fixed spiral part

[0247] 22 Fixed base surface

[0248] 24 (Inner end of the fixed spiral part)

[0249] 25 (outer end of the fixed spiral part)

[0250] 26 (Fixed panel) Compressor channel

[0251] 28 (Fixed disc) outlet opening

[0252] 30 Rotating discs

[0253] 31. Rotating spiral section

[0254] 32. Around the base surface

[0255] 34 (Outer end of the rotating helix)

[0256] 40. Outlet pressure chamber

[0257] 41 Zhou Bi

[0258] 42 Opening

[0259] 45 Oil separator

[0260] 46. ​​Oil separator outlet opening

[0261] 50 Direct Oil Return Unit

[0262] 51 First Oil Inlet

[0263] 52 First fluid connection

[0264] 53 First flow valve (throttle valve)

[0265] 54 Exhaust Chamber

[0266] 55 Oil Inlet

[0267] 56 Second fluid connection

[0268] 57 Second flow valve (throttle valve)

[0269] 58 branches

[0270] 59a, 59b (Direct oil return device) inlet openings

[0271] 70 Fluid return device

[0272] 71 Fluid inlet

[0273] 72a, 72b (fluid return device) port openings

[0274] 80 Press the pressure chamber

[0275] 81 Second Oil Inlet

[0276] 83 Flow valve (throttle valve)

[0277] 84 Reference Links

[0278] 85 Flow valve (throttle valve)

[0279] 86 Reference opening

[0280] 90 housing

[0281] 91. Suction connection part

[0282] 92. Export Connection Section

[0283] 93 Suction pressure chamber

[0284] A M，1 A M，2 A M，3 A M，4 area

[0285] ε1, ε2, ε min , ε max Position angle

[0286] ε 1，max , ε 2，min Position angle

[0287] γ is the position angle of the outer end of the compressor channel.

[0288] θ position angle

[0289] R I (γ) Radial distance of the inner side of the fixed spiral section at the outer end of the compressor passage

[0290] B K The width of the compressor passage in the radial direction at the outer end of the compressor passage.

[0291] R A (θ-360°) Radial distance of the outer side of the fixed helix at the position angle θ-360°

Claims

1. A screw compressor (1) for compressing fluids, comprising: The compressed section (10) has the following characteristics: • The inlet (11) of the compression section (10) is used to draw the fluid into the compression section (10), wherein a suction pressure exists at the inlet (11) during operation. • The outlet (12) of the compression section (10) is used to discharge the compressed fluid from the compression section (10), wherein the screw compressor (1) has an outlet pressure chamber (40). • A fixed disk (20) with a fixed helical portion (21), wherein the fixed disk (20) has a fixed helical portion (21) arranged on a fixed base surface (22) of the fixed disk (20) and forming a helical compressor channel (26) of the fixed disk (20), and • A rotating disk (30) with a rotating spiral section (31), wherein the rotating disk (30) is rotatable relative to the fixed disk (20) in the compression direction (100) so as to convey the fluid from the inlet (11) of the compression section (10) to the outlet (12) of the compression section (10) and compress it thereon; • Pressing pressure chamber (80), which is loaded with pressing pressure during compression operation, wherein the rotating disk (30) presses against the fixed disk (20) by the pressing pressure; and An oil separator (45) is used to separate oil from the compressed fluid; The screw compressor (1) additionally includes a direct oil return device (50) for directly returning oil from the oil separator (45) to the compression section (10), wherein the direct oil return device (50) has at least one port opening (59a, 59b). The direct oil return device (50) includes a first flow valve (53). The direct oil return device (50) includes an exhaust chamber (54) disposed between the first flow valve (53) and the inlet openings (59a, 59b) of the direct oil return device (50), wherein the exhaust chamber is disposed downstream of the first flow valve and upstream of the inlet openings, and The screw compressor (1) additionally includes a fluid return device (70) for returning fluid from the exhaust chamber (54) back to the compression section (10). The oil separator (45) is separate from the outlet pressure chamber (40), located within the screw compressor (1), and directly fluidly connected to the outlet (12) of the compression section (10) via the outlet pressure chamber (40). The screw compressor (1) has an additional oil return device (82) for returning oil from the oil separator (45) to the pressing pressure chamber (80), wherein the additional oil return device (82) connects directly from the oil separator (45) to the pressing pressure chamber (80), and The inlet opening (72a) of the fluid return device (70) is arranged in the central region of the compressor passage (26) of the fixed disk (20), wherein the central region of the compressor passage (26) consists of all the regions of the compressor passage (26) that are not directly fluidly connected to the inlet (11) of the compression section (10) or the outlet (12) of the compression section (10).

2. The screw compressor (1) according to claim 1, characterized in that, The inlet openings (59a, 59b) of the direct oil return device (50) are arranged in the fixed plate (20).

3. The screw compressor (1) according to claim 2, characterized in that, The inlet openings (59a, 59b) of the direct oil return device (50) are arranged in the suction area of ​​the compressor passage (26), and during operation they are at least temporarily in direct fluid connection with the inlet (11) of the compression section (10) and / or arranged outside the compressor passage (26).

4. The screw compressor (1) according to claim 1 or 2, characterized in that, The inlet openings (59a, 59b) of the direct oil return device (50) Alternatively, it can be positioned at an angle within the range of γ-30° and γ+30°, where γ is the position angle of the outer end of the compressor passage (26), and at a radial distance R from the center of the fixed disk (20). M,1 At, where R M,1 In (R) I (γ)-B K ) and R I Within the range of (γ), where R I (γ) is the radial distance from the center of the fixed spiral part (21) at the outer end of the compressor channel (26) on the inner side of the fixed spiral part (21), and B K It is the width of the compressor passage (26) in the radial direction at the outer end of the compressor passage (26). Alternatively, it can be positioned outside the fixed spiral section (21) at an angle ranging from θ-30° to θ+30°, and at a radial distance R from the center of the fixed disk (20). M,2 At, where θ = γ + 180° and R M,2 In R A (θ-360°) to R A (θ-360°)+B K Within the range, where R A (θ-360°) is the radial distance from the outside of the fixed helical part (21) to the center of the fixed helical part (21) at the position angle θ-360°.

5. The screw compressor (1) according to claim 1 or 2, wherein, During compression operation, at least one compression chamber (14a, 14b, 14c) is constructed between the rotating spiral section (31) and the fixed spiral section (21), characterized in that the at least one through-hole (59a, 59b) is not swept by any compression chamber (14a, 14b, 14c) at any point in time.

6. The screw compressor (1) according to claim 1 or 2, characterized in that, The direct oil return device (50) includes a second flow valve (57) arranged after the exhaust chamber (54).

7. The screw compressor (1) according to claim 1 or 2, characterized in that, The screw compressor (1) is configured such that during compression operation, the intermediate pressure in the exhaust chamber (54) is within the range of 0.2 bar to 0.6 bar above the suction pressure of the compression section (10).

8. The screw compressor (1) according to claim 1 or 2, characterized in that, The exhaust chamber (54) is constructed radially outside the outlet pressure chamber (40) and surrounds the outlet pressure chamber (40).

9. The screw compressor (1) according to claim 1 or 2, characterized in that, In the event of a lack of oil, the additional oil return device (82) takes precedence over the direct oil return device (50).

10. The screw compressor (1) according to claim 1 or 2, characterized in that, The direct oil return device (50) has a first oil inlet (51) leading to the oil separator (45), and the additional oil return device (82) has a second oil inlet (81) leading to the oil separator (45), wherein the first oil inlet (51) is arranged above the second oil inlet (81).

11. The screw compressor (1) according to claim 1 or 2, characterized in that, The screw compressor (1) has a reference opening (86) and a reference connection (84) arranged in the compression section (10), the reference connection forming a fluid connection between the pressing pressure chamber (80) and the reference opening (86) to influence the pressing pressure according to a reference pressure present at the reference opening (86) during operation.

12. The screw compressor (1) according to claim 1 or 2, characterized in that, The exhaust chamber (54) has a depth of 30cm 3 Up to 150cm 3 Volume within the specified range.

13. The screw compressor (1) according to claim 1 or 2, characterized in that, The inlet opening of the fluid return device (70) is located in the compressor passage (26) at a position where the average pressure of the fluid in the compressor passage (26) during operation is in the range of 104% to 170% of the suction pressure.

14. The screw compressor (1) according to claim 13, characterized in that, The inlet opening of the fluid return device (70) is located in the compressor passage (26) at a position where the average pressure of the fluid in the compressor passage (26) during operation is in the range of 105% to 150% of the suction pressure.

15. The screw compressor (1) according to claim 1 or 2, characterized in that, The screw compressor (1) is configured such that, during operation, the intermediate pressure in the exhaust chamber is in the range of 0.2 bar to 1.5 bar higher over time than the average pressure of the fluid at the location of the inlet opening of the fluid return device (70).

16. The screw compressor (1) according to claim 15, characterized in that, The intermediate pressure in the exhaust chamber is at least 106% of the intake pressure during operation.

17. The screw compressor (1) according to claim 1 or 2, characterized in that, The screw compressor (1) is configured such that the direct oil return device (50) continuously extracts oil from the oil separator (45) and stores excess oil in the exhaust chamber (54) during operation.

18. The screw compressor (1) according to claim 1 or 2, characterized in that, The first fluid connection (52) of the direct oil return device (50) extends from the oil separator (45) to the exhaust chamber (54), and the second fluid connection (56) of the direct oil return device (50) extends from the exhaust chamber (54) to the at least one port opening (59a, 59b). The inlet (71) of the fluid return device (70) is arranged in the exhaust chamber (54) above the oil inlet (55) of the second fluid connection (56), so that during operation only the separated fluid flows into the fluid return device (70) and the liquid oil flows into the second fluid connection (56) of the direct oil return device (50).

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