CN108223371B

CN108223371B - Screw compressor

Info

Publication number: CN108223371B
Application number: CN201711306826.0A
Authority: CN
Inventors: A.吉特-格尔克
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2016-12-22
Filing date: 2017-12-11
Publication date: 2020-02-21
Anticipated expiration: 2037-12-11
Also published as: CN108223371A; DE102016226118A1

Abstract

The invention relates to a screw compressor having a stator screw part, a rotor screw part which can be driven along a rail, and bases which are assigned to the stator screw part and the rotor screw part, respectively, and which delimit a pressure chamber in the axial direction with respect to the rail axis of the rotor screw part, which pressure chamber is delimited by the stator screw part and the rotor screw part in the radial direction with respect to the rail axis of the rotor screw part, characterized in that the rotor screw parts are arranged so as to be movable relative to the assigned bases. The base assigned to the rotor screw should therefore not follow the movement of the rotor screw along the track, which results in the base being integrated statically in the housing of the screw compressor and in particular of the screw compressor, as a result of which axially directed forces due to the pneumatic overpressure in the pressure chamber can be supported. This makes it possible to avoid complex measures for compensating the pressure acting axially on the trailing bottom of the rotor screw, for example by integrating a so-called intermediate pressure chamber.

Description

Screw compressor

Technical Field

The invention relates to a screw or scroll compressor, which can be used in particular as a coolant compressor for air conditioning of a motor vehicle.

Background

The screw compressor has in principle several advantages over compressors of other construction types, such as piston compressors, which make the screw compressor destined for use as a coolant compressor for air conditioners of motor vehicles. This makes the screw compressor, for example, relatively strong and efficient, and also inexpensive to manufacture. Furthermore, the screw compressor is designed with relatively small dimensions, in particular along the rotational axis of the drive shaft of the screw compressor, due to its radial direction of action when compressing the gas provided for this purpose.

Screw compressors (see for example US 2013/0115123 a1) essentially comprise one or more screw pairs which engage one inside the other in an eccentric arrangement and thus define a plurality of mutually independent, screw-shaped or sickle-shaped pressure chambers. During the relative movement of the screw elements (of each screw pair) along the rails, the pressure chamber is first open at its radially outer end to the low-pressure section of the screw compressor, so that the gas to be compressed can flow into the pressure chamber. Upon further relative movement of the screw elements, the individual pressure chambers, which are then closed, move on a helical path toward the central region, wherein the size of the pressure chambers decreases. Thereby, the gas enclosed in the pressure chamber is compressed according to the principle of squeezing. The central region of the screw element is usually connected with the high-pressure section of the screw compressor via an intermediate connection from the main valve, into which compressed gas is injected when the maximum compression pressure is reached as a result of the reduction in the size of the pressure chamber. The relative movement of the two screws (of each screw pair) is usually achieved by the driving of the (rotor) screw along the track, while the other (stator) screw is designed to be stationary.

In order to achieve the highest possible efficiency of the screw compressor, it is expedient for the rotor screw part and the stator screw part to be sealed off from one another as well as possible in the contact position. In this case, sealing the gap formed between the end edge of the spiral wall of the spiral element and the base of the associated mating spiral element is often problematic, since the compression of the gas in the compression space (Verdichtungstasche) generates a pressure at the higher pressure which presses the spiral elements apart from one another along the rail axis or longitudinal axis. Of course, the higher the compression ratio achieved by the screw compressor, the more serious the problems that arise. The problem therefore arises in particular in the case of the compression of coolants for air conditioners of motor vehicles, which are designed for the use of coolants, such as carbon dioxide (R744), which require a significantly higher system pressure than the conventional synthetic coolants used before (e.g. R134a, R1234yfF, R12). Furthermore, carbon dioxide as a coolant has a relatively small molecular size, as a result of which already in relatively small gaps significant leakage would be possible.

In order to generate the axial pressing force between the screws of the screw pair of the screw compressor, which is as ideal as possible and is dependent on the operating load, it is known to provide what is known as an intermediate pressure chamber, which is connected in a fluid-conducting manner to one or more pressure chambers by means of one or more intermediate pressure channels. The one or more intermediate pressure ducts have a relatively small opening cross section, so that they act as a throttle for the gas flowing between the pressure chamber and the intermediate pressure chamber. As a result of the fluid-conducting connection to the pressure chamber or pressure chambers, an intermediate pressure is set in the intermediate pressure chamber, which intermediate pressure is between the suction pressure and the compression end pressure and fluctuates significantly less than the pressure of the gas or gaseous coolant in the pressure chamber due to the throttling effect of the intermediate pressure channel. The intermediate pressure in the intermediate pressure chamber acts on the base of the screw elements of the screw pair and thereby presses the base axially against the associated counter-screw element.

DE 102013200807 a1 discloses a screw compressor in which a rotor screw is connected to an inner ring of a wobble slider mechanism, wherein the inner ring is also rotatably mounted on the eccentric end of the drive shaft. The inner ring is also connected to the fixed outer ring by a plurality of pendulums. The wobble mechanism ensures that the rotating drive, via the drive shaft, only causes a movement of the rotor screw along the track, but not also a rotation thereof relative to the stator screw.

Disclosure of Invention

The object of the present invention is to provide a screw compressor which, despite a simple and therefore inexpensive design, ensures a good sealing of the pressure chamber defined by the screw element and the associated bottom.

The object is achieved according to the invention by a screw compressor having a stator screw part, a rotor screw part which can be driven along a rail, and bases which are assigned to the stator screw part and the rotor screw part, respectively, wherein the bases delimit a pressure chamber in the axial direction with respect to the rail axis of the rotor screw part, which pressure chamber is delimited by the stator screw part and the rotor screw part in the radial direction with respect to the rail axis of the rotor screw part, according to which the rotor screw parts are arranged so as to be movable relative to the assigned bases. Advantageous design solutions of the screw compressor according to the invention result from the following description of the invention.

According to the invention, the screw compressor has a stator screw part, a rotor screw part which can be driven along a track, and bases which are assigned to the stator screw part and the rotor screw part, respectively, wherein the bases at least partially, preferably completely, delimit a pressure chamber in the axial direction relative to the track axis of the rotor screw part (about which the rotor screw part can be moved along the track), which pressure chamber is delimited by the screw part in the radial direction relative to the track axis of the rotor screw part. It is provided that the rotor helix is arranged so as to be movable relative to the base associated therewith. The base part should therefore not follow the movement of the rotor screw along the rail, which results in the base part being integrated statically in the housing of the screw compressor and in particular of the screw compressor, as a result of which the support for axial forces, which occur as a result of the pneumatic overpressure in the pressure chamber, can be achieved in an advantageous manner. In particular, it can be provided that as far as possible only the rotor screw part can perform an orbital movement, while the stator screw part and the two bases associated with the screw part are integrated in a stationary manner in the screw compressor. In this way, an overpressure in the pressure chamber of the screw compressor substantially does not lead to forces acting axially on the rotor screws, whereby the sealing of the screws can be achieved in a simple manner, which is required in the screw compressor according to the invention for both screws and even with respect to both bottoms. In the case of the screw compressor according to the invention, therefore, the complex constructional measures for compensating the pressure forces acting on the base which follows the orbiting movement of the rotor screw, which would otherwise lead to a lack of tightness of the screw compressor, can be dispensed with, and in particular the integration of a so-called intermediate pressure chamber can be dispensed with, as a result of which the constructional design for the screw compressor according to the invention can be made more complex and therefore the production costs can also be kept relatively low. The screw compressor according to the invention is furthermore characterized in that the mass moving along the rail is relatively small, which can advantageously influence the efficiency and/or the acoustic operating performance of the screw compressor. The design of the screw compressor according to the invention also has the advantage of relatively low friction losses and, in particular, further, relatively high efficiency.

In a preferred embodiment of the screw compressor according to the invention, it can be provided that the base of the rotor screw is connected to the stator screw and/or to the base of the stator screw in a non-movable manner (at a distance or preferably directly), at least in the axial direction relative to the rail axis. In this way, a particularly advantageous support of the pressure forces in the axial direction relative to the rail axis, which occur as a result of the pneumatic overpressure in the pressure chamber, can be achieved. A particularly advantageous support can be achieved if the two bases and thus the components to which pressure is applied directly in the axial direction relative to the rail axis are connected directly to one another, for example by means of bolts.

Furthermore, it may be provided that the base associated with the stator screw part and/or the base associated with the rotor screw part forms a section of the housing of the screw compressor. In this case, it can also be provided in particular that the side of the bases which is remote from the associated screw element is the outer side of the housing or of the screw compressor. Such a screw compressor according to the invention can be distinguished by a particularly compact design and thus only a relatively small installation space.

In order to achieve the best possible sealing of the screw part with respect to the base and thus also of the screw compressor according to the invention as a whole, it can be provided that the rotor screw part and the stator screw part are arranged as free of play as possible in the axial direction between the bases. Due to the static integration of the two bottoms in the screw compressor which is achieved according to the invention, the smallest possible gap, which is largely independent of the pressure relationship in the pressure chamber, can be adjusted in a structurally relatively simple manner by adapting the components which connect the bottoms to one another. However, due to manufacturing tolerances, it is generally not possible to achieve the greatest degree of play-free. Furthermore, the thermally dependent differential expansion of the components of the screw compressor during operation, by which the distance of the bases from one another and the distance of the bases from the screw elements can be changed, must be taken into account if necessary. In order to ensure the best possible sealing of the screw part against the base at any time during operation of the screw compressor according to the invention, therefore, additional measures should preferably be taken which ensure the most gapless possible arrangement of the screw part between the bases at any time, for example also during thermally relevant expansions, but at the same time keep the friction losses due to the relative movement of the base with respect to the screw part as low as possible. For this purpose, it may be provided that the rotor and/or stator screw part is flexible and in particular elastic at least in the axial direction relative to the rail axis. For this purpose, it can be provided that the spiral wall of the rotor spiral and/or the spiral wall of the stator spiral itself is at least partially made of a flexible or preferably elastic material, for example an elastomer or a thermoplastic. Alternatively or additionally, one or more separate sealing elements may also be integrated, which are arranged at least axially movably on the base body of the respective screw element forming the screw wall and which are supported on the base body, for example by means of one or more prestressed spring elements, and are thus loaded onto the adjoining base part.

In a further preferred embodiment of the screw compressor according to the invention, it can be provided that the rotational axis of the drive for the rotor screw is arranged radially offset with respect to the track axis. In this way, a design for the base assigned to the rotor screw, which is as free of through-holes as possible and in particular can also be designed as one piece, can be advantageously achieved, which is advantageous with regard to the sealing of the pressure chamber and/or the support of the axial pressure.

It can also be provided that the rotor screw is connected to a guide part which surrounds the rotor screw at least partially on the outer circumference side and which forms a rotational stop for the rotor screw. The rotation stop ensures that the process of generating the orbital movement of the rotor screw by the drive is independent of the relative rotation of the rotor screw with respect to the stator screw. It is sufficient for the function of the guide to be achieved that the guide extends on the outer circumferential side of the rotor screw only in relatively small sections (for example in sections rotated by a maximum of 180 °, a maximum of 120 ° or a maximum of 90 ° relative to the orbit axis of the rotor screw). The relatively small guide elements can also play an advantageous role in terms of the mass size moving along the rail and in terms of the friction losses and thus in terms of the efficiency and acoustic operating conditions of the screw compressor according to the invention. In this case, it can also be advantageously provided that the guide elements are arranged only on the outer circumference of the rotor screw, so that the entire inner region of the rotor screw, in which the rotor screw interacts with the stator screw to delimit the pressure chamber, can be covered axially by the associated base, which in turn can be advantageous with regard to sealing of the pressure chamber and/or support of the axial pressure.

The preferably provided guide element of the screw compressor according to the invention can also preferably be used to transmit an orbital drive movement to the rotor screw, which drive movement is generated by a central drive (i.e. the rotational axis of the drive is arranged coaxially to the orbital axis) or preferably by a non-central drive (i.e. the rotational axis of the drive is arranged radially offset to the orbital axis), so that additional transmission elements can be dispensed with, which is advantageous in terms of achieving as little mass of the orbital movement as possible and in terms of as little friction losses as possible.

In the case of the screw compressor according to the invention, a drive having an electric drive motor can be provided in a preferred manner, since this drive can also be used to set the required power of the screw compressor in a particularly simple manner. In contrast to the mechanically driven screw compressor according to the invention, for example, the integration of a clutch for power regulation can be dispensed with. Such a power regulation may be required or at least desirable, for example, when the screw compressor according to the invention is preferably used as a coolant compressor of a motor vehicle air conditioner, in order to keep the energy consumption for the screw compressor and thus also the fuel consumption of the motor vehicle internal combustion engine, which directly or indirectly supplies the energy for operating the screw compressor, as low as possible. Furthermore, such motor-driven screw compressors can also be used in motor vehicles with partially or fully electrified drive trains (independently of the operation of the internal combustion engine which may be present).

Due to the advantageous support of the axial pressure achieved by the design of the screw compressor according to the invention and thus due to the good sealability of the pressure chambers, the screw compressor according to the invention is also advantageously suitable for generating relatively high pressure ratios, for example at least 15, preferably at least 25. This screw compressor is therefore also suitable, in particular, as a coolant compressor for air conditioners of motor vehicles, in which a coolant is used, which, for example, carbon dioxide (R744), requires a correspondingly high system pressure in order to ensure the functionality of the air conditioner. A design can be provided for the screw compressor according to the invention, whereby a correspondingly high system pressure can be achieved.

In this case, it can also be provided that the screw compressor according to the invention is designed as a stage and thus has only one screw pair consisting of a stator screw and a rotor screw. Although the entire compression ratio must therefore be achieved by means of the sealing stages, which places correspondingly high demands on the sealing stages, in particular on the thermal load of the sealing stages and on the tightness between the stator and rotor screws, at the same time low complexity and a small installation space of the screw compressor can be maintained, as a result of which the screw compressor can be produced relatively inexpensively and can be used advantageously. A multistage compressor according to the invention is likewise possible.

The appearances of the indefinite articles "a" or "an" in particular in the claims and in the specification generally set forth the claims are not to be construed as numerical words. Accordingly, a component embodied accordingly is to be understood as meaning that the component is present at least once and may be present multiple times.

Drawings

The invention will be further elucidated with reference to the embodiments shown in the drawings. In the drawings, simplified respectively:

fig. 1 shows an exploded perspective view of a screw compressor according to the present invention; and is

Fig. 2 shows a three-dimensional, partially transparent view of a screw compressor.

Detailed Description

The screw compressor shown in fig. 1 comprises a multi-part housing, in which a double-walled stator screw 10 is integrated in a non-movable manner. The stator screw 10 is in one piece and is thus connected completely without play to a flat, substantially circular housing section 14 of the first housing part 12, wherein this housing section 14 forms a base 14 associated with the stator screw 10, a pressure chamber is arranged between the stator screw 10 and a rotor screw 18 which is embedded eccentrically in the stator screw 10 relative to the rail axis 16, and is delimited by the stator screw 10 and the rotor screw 18 in a radial direction relative to the rail axis 16, by which pressure chamber is delimited in one of the axial directions relative to the rail axis 16. The stator spiral 10 is also surrounded by a circular, circumferential limiting wall 42, which is likewise of one piece design and is thus connected without gaps to the flat housing section 14 of the first housing part 12. The first housing part 14 also comprises a housing section 20 in the form of a jacket which surrounds the stator spiral 10 and the limiting wall 42 on the circumferential side (completely). Integrated in the housing portion 20 is an interface 24 for the (for example two in the exemplary embodiment shown) supply channels 22 leading into the delimiting wall 42, through which the gas to be compressed can be supplied to the pressure chamber.

The housing also comprises a second housing part 26, which likewise has a planar housing section 28, which housing section 28 is approximately circular-segment-shaped. The housing section 28 is provided with a base 28 assigned to the rotor screw 18, by means of which base 28 a pressure chamber is delimited in the other axial direction with respect to the track axis 16. The second housing part 26 is also provided with a housing section 30 in the shape of a jacket. In the installed state of the screw compressor (see fig. 2), the two

housing parts

12, 26 are directly connected to one another by means of a not shown connecting element, such as a screw, the housing-shaped

housing sections

20, 30 of the two

housing parts

12, 26 being supported opposite one another.

Due to the only partially circular design of the planar housing section 28, the second housing part 26 forms a cut-out section (Ausschnitt)32 which has the shape of a circular arc extending through approximately 120 ° around the rail axis 16. Within this cut-out section 32, a guide 34 is arranged, which likewise has the shape of a circular arc extending about 120 ° around the rail axis 16 and is connected fixedly and in particular integrally to a section of the adjoining rotor spiral 18, in particular to a section at the radially outer end of the rotor spiral 18. The guide element 34 is located axially next to the rotor helix (with reference to the rail axis 16) and radially outside the rotor helix 18 (with reference to the rail axis 16), so that the entire helical inner volume delimited by the rotor helix 18 is covered only (on the respective side) by the base 28 associated with the rotor helix 18 and not also by the guide element 34.

The function of the guide elements 34 is to guide the orbital movement of the rotor screw 18, which is produced by means of a drive, not shown, and to prevent (to a large extent) a rotation of the rotor screw 18 relative to the stator screw 10, as a result of which a torsion-resistant effect is achieved. For this purpose, the guide element 34 is designed with a plurality of cylindrical guide recesses 36, into which cylindrical guide pins 38 of the first housing part 12 engage. The guide pin 38 extends from a further housing section 40, the further housing section 40 being provided in a section of the first housing part 12 which is arranged above the cutout section 32 of the second housing part 26, and the further housing section 40 connecting the edge section of the shell-shaped housing section 20 at this point to the section of the delimiting wall 42 of the first housing part 12 at this point in a substantially parallel orientation relative to the planar housing section 14 and thus forming a bearing and guide surface for the guide 34. The diameter of the guide grooves 36 (which is dimensioned identically for all guide grooves 36) is significantly larger than the diameter of the guide pins 38 (which is dimensioned identically for all guide pins 38). The orbital movement of the guide element 34 and thus of the rotor screw 18 can be guided by the sliding of the guide pin 38 on the circumferential surface of the guide groove 36.

Another function of the guide 34 is to act as an orbital motion transmitter that transmits the orbital motion applied to it by means of a drive, not shown, to the rotor screw 18.

The orbiting movement of the rotor screw 18 relative to the stator screw 10 results in a known manner in that the pressure chambers are moved on the helically shaped orbit in the direction of the central section of the stator screw 10 and are thereby increasingly smaller, whereby the partial amounts of gas or the partial amounts of oil-gas mixture contained in the pressure chambers are increasingly compressed. When the oil/gas mixture is compressed in this way, oil is mixed into the gas before or at the start of the compression, in order to lubricate the contact surfaces, which are formed in particular between the stator screw 10 and the rotor screw 18, by means of the oil, whereby relatively low friction losses can be achieved. If the individual pressure chambers reach the central section of the stator screw 10, a compressed partial quantity of gas or a partial quantity of oil-gas mixture is discharged via three discharge openings, which are integrated in the base 14 associated with the stator screw 10 in the present exemplary embodiment. In this case, the compressed gas or oil-gas mixture is discharged from the pressure chamber as ideally as possible in a pressure-dependent manner by means of an autonomously pressure-controlled valve 44 (non-return valve) associated with the discharge opening.

The ejection of the compressed gas or oil-gas mixture through the outlet opening can also take place in a high-pressure chamber (not shown) formed, for example, by a housing, from which the compressed gas is centrally discharged. If the oil-gas mixture is already compressed or compressed in the pressure chamber, an oil separator (not shown), for example designed as a centrifugal separator, can also be integrated in the high-pressure chamber, by means of which oil is separated from the gas as completely as possible and reused (i.e. oil is reintroduced into the gas which still needs to be compressed).

As shown, the valve 44 can be designed as a finger valve (fingerlift) or as a flap valve (lamellengenventil), for which purpose the valve comprises a spring plate or a spring lug (Federlasche)46, which is fastened by one end, for example by means of a (not shown) screw, on the outside of the base 14 associated with the stator screw 10 or on the outside of the housing section 14 of the first housing part 12 forming the base 14, while the free ends of the spring lug 46 are arranged one above the other in each case with the associated outlet opening and close off the outlet opening in the unloaded state of the spring lug 46. When an overpressure occurs in the interior of the pressure chamber, which is in fluid connection with the outlet opening, in comparison with the pressure on the outside of the valve 44, the valve 44 opens, wherein the free end of the spring lug 46 is elastically deflected. The external overpressure conversely causes the free end of spring lug 46 to press increasingly against the section of bottom 14 surrounding the outlet opening, as a result of which valve 44 reliably closes the outlet opening.

The design of the screw compressor according to the invention, by which the pressure forces, which are caused by the overpressure in the pressure chambers and are oriented in the axial direction with respect to the rail axis 16, can be supported in an advantageous manner by the

base

14, 28 designed as a housing section, can be realized in a static integration of the base 28 in the screw compressor owing to the arrangement of the base 28 associated with the rotor screw 18 in a relatively movable manner with respect to the rotor screw 18, without axially oriented pressure forces acting on the rotor screw 18 or on the unit formed by the rotor screw 18 and the guide 34 (at the relevant level). A good sealing of the gap formed between the

screw elements

10, 18 and the

base

14, 28 can thus be achieved in a structurally relatively simple manner, since the pressure-dependent width of this gap can be avoided simply and reliably by suitable dimensioning of the connecting

housing parts

12, 26 and thus of the connecting pieces connecting the

base

14, 28, as would occur in screw compressors of the type described according to the prior art without costly compensation measures (for example integration of a so-called intermediate pressure chamber).

List of reference numerals

10 stator spiral

12 first housing part

14 bottom of the planar housing section/stator spiral of the first housing part

16 track axis

18 rotor screw

20 housing section in the shape of a jacket of a first housing part

22 input channel

24 interface of input channel

26 second shell part

28 bottom of the planar housing section/rotor screw of the second housing part

30 housing section in the shape of a jacket of the second housing part

32 intercepting section of the second housing part

34 guide member

36 guide groove of guide member

38 guide pin

40 further housing section of the first housing part

42 delimiting wall

44 valve

46 spring lifting lug of valve

Claims

1. Screw compressor with a stator screw (10), a rotor screw (18) which can be driven along a track and a base (14, 28) which is assigned to the stator screw (10) and the rotor screw (18), respectively, wherein the base (14, 28) defines a pressure chamber in the axial direction relative to the track axis (16) of the rotor screw (18), which pressure chamber is defined by the stator screw (10) and the rotor screw (18) in the radial direction relative to the track axis (16) of the rotor screw (18), characterized in that the rotor screw (18) is arranged so as to be movable relative to the assigned base (28), wherein the rotor screw (18) is connected to a guide (34) which surrounds the rotor screw at least partially on the outer circumferential side, the guide (34) forming a twist stop for the rotor screw (18), wherein the guide (34) has the shape of a circular arc extending up to 180 ° around the track axis (16) and is fixedly connected to a section of the rotor screw (18) at the radially outer end of the rotor screw (18).

2. Screw compressor according to claim 1, characterised in that the rotor screw (18) and the stator screw (10) are arranged as free as possible of play between the bottoms (14, 28) in the axial direction relative to the rail axis (16).

3. Screw compressor according to claim 1, characterised in that the rotor screw (18) and/or the stator screw (10) are designed to be flexible at least in the axial direction with respect to the rail axis (16).

4. Screw compressor according to claim 1, characterised in that the rotor screw (18) and/or the stator screw (10) are designed to be elastic at least in the axial direction with respect to the rail axis (16).

5. Screw compressor according to claim 1, characterised in that the base (28) of the rotor screw (18) is connected immovably to the stator screw (10) and/or to the base (14) associated with the stator screw (10), at least in the axial direction relative to the rail axis (16).

6. Screw compressor according to claim 1, characterised in that the base (14) associated with the stator screw (10) and/or the base (28) associated with the rotor screw (18) constitutes a section of the housing of the screw compressor.

7. Screw compressor according to claim 1, characterised in that the rotational axis of the drive for the rotor screw (18) is arranged radially offset with respect to the rail axis (16).

8. Screw compressor according to claim 1, characterised in that the drive for the rotor screw (18) acts on the guide (34).