COMPRESSOR, IN PARTICULAR REFRIGERANT COMPRESSOR, REFRIGERATION MACHINE, AND METHOD FOR PRODUCING A COMPRESSOR

Abstract

The present disclosure relates to a compressor having a low-pressure region and a high-pressure region, wherein a lubricant is provided in the low-pressure region in order to lubricate the compressor. A fluid is conveyed from the low-pressure region into the high-pressure region and compressed, wherein a portion of the lubricant with the fluid from the low-pressure region reaches the high-pressure region, and wherein a lubricant separator for separating the lubricant from the fluid/lubricant mixture in the high-pressure region is provided. A lubricant return channel for transporting the separated lubricant from the high-pressure region into the low-pressure region is provided.

Description

The present invention relates to a compressor according to the preamble of claim 1, a refrigeration machine according to the preamble of claim 10, and a method for producing a compressor according to the preamble of claim 11.

A compressor is a machine, in particular a fluid energy machine, which supplies mechanical work to an enclosed gas. Compressors are generally used to compress gases. They preferably increase the pressure and the density of the gas.

The compressor or the moving components of the compressor are generally lubricated by means of a lubricant, such as, for example, oil. In this instance, a mixing, in particular as an aerosol, of the fluid which is intended to be compressed and the lubricant is in most cases inevitable. The atomization of the lubricant may, for example, be brought about by components moved by the lubricant (cam/connecting rod, etcetera). The lubricant is distributed as a fluid lubricant aerosol in the fluid circuit, in particular in the high-pressure region HD and in the low-pressure region ND and is no longer available, for example, for lubricating compressor components. The lubricant reservoir may, where applicable become exhausted.

Assistance is provided in this instance by the separation of the lubricant from the fluid lubricant aerosol, in particular both in the HD region and in the ND region. Lubricant which is separated in the HD region must subsequently be returned to the ND region. However, this always means a fluidic “short-circuit” between HD and ND and consequently a loss/power loss for the compressor.

In order to overcome this problem, for example, DE102015224071 discloses a compressor which comprises a lubricant system for lubricating components of the compressor with a lubricant. The compressor has a low-pressure region, in particular in the form of a machine room, and a high-pressure region having a compressor output. During operation of the compressor, the lubricant in the low-pressure region comes into contact with the fluid so that a fluid mixture of fluid and lubricant is formed. Furthermore, the compressor comprises a compressor device for compressing the fluid mixture. In order to ensure a reliable recirculation of the lubricant in the compressor, the compressor comprises a lubricant return which fluidically connects the HD to the ND region and which enables a lubricant return. The lubricant return consequently represents a type of bypass of the compressor unit or the piston arrangement. A first lubricant return is to this end arranged in the high-pressure region and the second lubricant return is arranged in the low-pressure region. Both lubricant returns are fluidically connected to each other so as to be able to be controlled by means of a valve arrangement. The valve arrangement consequently controls the separation/connection of the high-pressure region from/to the low-pressure region of the compressor. The valve arrangement can adjust a throughflow cross section independently at least in accordance with a flow force. The flow force is produced by the fluid mixture flowing through the valve arrangement.

A disadvantage in the case of this solution for lubricant return from the high-pressure region into the low-pressure region which should in particular be mentioned is that many moving components are used so that a high wear, but also high production costs may be anticipated. Furthermore, the valve arrangement has to be adjusted, whereby in turn uncertainties may occur during operation. There is also the risk of the valve arrangement becoming clogged so that lubricant return actually no longer takes place. An uncontrolled pressure loss via the valve arrangement may also take place so that a large amount of fluid would flow back via the valve.

This is the starting point of the present invention and the object thereof is to provide an improved compressor, in particular to propose a compressor in which at least some, preferably all of the problems set out above can be overcome, but at least can be reduced. In particular, a compressor is intended to be proposed, wherein at least for the lubrication return from a small number of to no moving components at all are used, which requires a low or even no adjustment with regard to the lubricant return, and wherein a clogging of the lubricant return can be eliminated to the greatest possible extent.

According to the invention, this object is achieved with a compressor having the characterizing features of claim 1. As a result of the fact that the lubricant return channel comprises a fluid diode, for example, it is possible to dispense with a controlled or connected valve, where applicable a sensor system for determining the fluid present upstream of the valve and the required electronic control. In addition, no moving components are present, whereby a wear is in principle excluded. In an advantageous structural configuration, hardly any fluid, but primarily lubricant is allowed through from the high-pressure region to the low-pressure region. A risk of clogging as a result of particles is reduced by means of an open geometry. No adjustment of the fluid diode is also required in principle. Preferably, the blocking behavior is determined structurally by means of the length and/or the geometry of the throttle location, that is to say, of the fluid diode.

The basic notion is that the flow resistance in one flow direction is less than in the opposite direction. This is intended to result in the flow receiving a preferred direction or the fluid flowing only in one direction. This is intended to be achieved by means of structures which in one direction enable a rather laminar flow, but in the opposite direction cause turbulence as a result of swirls and consequently increase the flow resistance. For each location inside such a valve, the flow resistance is very low in the direction of the output and very high in the direction of the input. This device is therefore also referred to as a “fluid diode”. Such a fluid diode is according to the invention operated as a connection or in the connection (lubricant return channel) of the high-pressure and low-pressure region of the refrigerant compressor in the blocking direction. That is to say, the fluid flowing from the high-pressure region into the low-pressure region is counteracted by a resistance which is dependent on the respective fluid and consequently on the respective material properties/physical properties. Consequently the lubricant is counteracted by a lower resistance than the refrigerant.

Other advantageous embodiments of the invention proposed will be appreciated in particular from the features of the dependent claims. The aspects of subject-matter or features of the various claims may in principle be freely combined with each other.

In an advantageous embodiment of the invention, there may be provision for the lubricant return channel to have a heart-shaped or offset-heart-shaped inner wall in order to form a fluid diode. Such a structure is advantageously suitable for configuring a fluid diode, in particular with the properties set out above.

In another advantageous embodiment of the invention, there may be provision for the lubricant return channel to be introduced into a metal sheet. The metal sheet may, for example, be integrated in a simple manner in the compressor, for example, as an intermediate sheet in the housing of the compressor.

In another advantageous embodiment of the invention, there may be provision for the lubricant return channel to be configured in a semi-circular manner. In this manner, for example, an integration in a circular-cylindrical housing can be carried out in a simple manner, wherein the input and output of the lubricant return channel can be arranged, for example, to be offset at 180° in the circumferential direction.

In another advantageous embodiment of the invention, there may be provision for the lubricant return channel to be formed in a planar partition face in a housing, a sealing face and/or in a seal of the compressor. In this manner, the lubricant return channel can advantageously be integrated in the compressor housing.

In another advantageous embodiment of the invention, there may be provision for the fluid to be a refrigerant, in particular supercritical CO2.

In another advantageous embodiment of the invention, there may be provision for the lubricant oil to be oil.

In another advantageous embodiment of the invention, there may be provision for the channel geometry which is significant for the fluid diode, in particular the configuration of the inner wall of the lubricant return channel, to have been produced by means of punching, etching or erosion. The above-mentioned measures are advantageous production methods for the configuration of the lubricant return channel.

In another advantageous embodiment of the invention, there may be provision for the lubricant return channel to have a fluid diode as a separate component and/or for the lubricant return channel to be at least partially in the form of a fluid diode.

Another object of the present invention is to provide an improved refrigeration machine.

According to the invention, this object is achieved with a refrigeration machine having the characterizing features of claim 10. Use can thereby be made of the advantages of the compressor according to the invention for a refrigeration machine, for example, an air-conditioning system in a motor vehicle.

Another object of the present invention is to provide an advantageous method for producing a compressor according to the invention.

This object is achieved according to the invention with a method for producing a compressor with the characterizing features of claim 11.

As a result of the fact that the channel geometry which is significant for the fluid diode, in particular the configuration of the inner wall of the lubricant return channel, has been produced by means of punching, etching or erosion, a method which is simple in technical production terms can be proposed.

Other features and advantages of the present invention will be appreciated with reference to the following description of preferred embodiments and the appended drawings, in which:

FIG. 1 shows a schematic illustration of a refrigeration machine having a compressor according to the invention;

FIG. 2 shows a fluid diode as a sectioned view;

FIG. 3a shows an exemplary surface structure of a fluid diode of a compressor according to the invention with an indicated movement profile of the fluid;

FIG. 3b shows an exemplary surface structure of a fluid diode of a compressor according to the invention with an indicated movement profile of the lubricant;

FIG. 4 shows a housing component of a compressor according to the invention with a milled fluid diode;

FIG. 5 shows a detail “X” according to FIG. 4;

FIG. 6 shows a portion of a housing for a compressor according to the invention (partition faces in the housing);

FIG. 7 shows a compressor according to the invention as a sectioned schematic illustration.

The following reference numerals are used in the drawings:

• • V Compressor
  • G Gas cooler
  • E Expansion valve
  • D Evaporator
  • S Lubricant, in particular oil
  • F Fluid, in particular refrigerant
  • 1 Low-pressure region
  • 2 High-pressure region
  • 3 Lubricant return channel
  • 4 Compressor housing
  • 5 Electric motor (drive)
  • 11 Lubricant reservoir
  • 12 Low-pressure input
  • 13 Piston cover with inlet valve
  • 14 Piston
  • 15 Eccentric shaft
  • 16 Cylinder housing
  • 17 Working space
  • 21 Lubricant separator
  • 22 High-pressure output
  • 23 Outlet valve
  • 24 Channel
  • 31 Fluid diode
  • 32 Seal/sealing ring
  • 41 Portion of the compressor housing
  • 42 Portion of the compressor housing

Reference will first be made to FIG. 1.

A compressor V according to the invention, in particular a refrigerant compressor, is, for example, part of a refrigeration machine, such as, for example, an air-conditioning system. Such a refrigeration machine generally comprises in addition to the compressor V a gas cooler G, an expansion valve E and an evaporator D. The above-mentioned components are fluidically connected to each other, that is to say, a fluid F, such as preferably a cooling fluid, is compressed in the compressor V, reaches via the high-pressure output 22 of the compressor V the gas cooler G and travels from the gas cooler G to the expansion valve E and from there into the evaporator D. From the evaporator D, the fluid is again introduced via the low-pressure input 12 of the compressor V. Such a refrigeration machine is sufficiently known to the person skilled in the art so that no additional explanation is required in this instance.

The compressor V may, for example, be a piston compressor, in particular an axial piston compressor, radial piston compressor or scroll compressor.

The compressor has a low-pressure region 1 and a high-pressure region 2. In the compressor V, in particular in the low-pressure region 1 thereof, a lubricant S, such as, for example, oil, is used to lubricate the movable components of the low-pressure region 1.

The low-pressure region 1 of the compressor V comprises, for example, a low-pressure input 12 for the fluid or the refrigerant for supplying to the compressor. The compressor V further comprises in particular a driving electric machine 5 or a shaft for connecting an external drive. The compressor which is shown, for example, in FIG. 7 comprises two housing portions 41, 42. A cylinder housing 16 forms a cylinder in which pistons 14 are movably arranged. These pistons 14 can be driven by an eccentric shaft. The cylinders and consequently also the pistons 14 which can be moved therein extend radially or are arranged radially with respect to the eccentric shaft. A cover with an inlet valve 13, the pistons 14 and the cylinders form the working space 17 or the compression space. Fluid is drawn from the low-pressure region 1 via the inlet valves, compressed in the working space 17 and discharged by the outlet valves 23 into a channel 24 and consequently into the high-pressure region of the compressor. The condensed or compressed fluid may contain lubricant S which can be separated, for example, at edges or when the flow direction of the fluid is changed. This generally also takes place in a lubricant separator 21. The lubricant separator 21 does not have to be a separate component. Instead, any geometry in which lubricant can be separated, for example, at edges or redirected portions, may in principle be considered as a lubricant separator 21, in particular geometries for flow redirection or changing the flow speed, etcetera. The separated lubricant S then accumulates in the channel 24. The compressed fluid can be guided via a high-pressure connection 22 from the compressor to the additional components of the refrigerant circuit. Preferably, a lubricant separator 21 is arranged upstream of the high-pressure connection 22 so that the fluid can be directed via the lubricant separator 21 and the high-pressure output from the compressor. In order to be able to guide the lubricant S from the high-pressure region 2 into the low-pressure region 1 of the compressor, at least one lubricant return channel 3 is provided. Such a lubricant return channel 3 may be in the form of a fluid diode 31 or have such a fluid diode 31 as a separate component, as indicated in FIG. 7. A plurality of fluid diodes 31 may also be arranged in the lubricant return channel 3 in order to achieve the desired properties. A lubricant return channel 3 may also be formed between two housing portions of the compressor V, for example, also formed in a seal. Such a seal 32 is, for example, arranged or formed between a portion of the compressor housing 42 and the cylinder housing 16, as shown in FIGS. 6 and 7. In the seal 32, for example, the geometry of the fluid diode is formed. In the installed state, the seal 32 forms with the adjacent components, such as, for example, the housing portion 42 and the cylinder housing 16, the lubricant return channel 3.

In order to accumulate or store this lubricant S in the compressor V, in particular in the low-pressure region 1, the low-pressure region 1 may be provided with a lubricant reservoir 11.

During the compression of the fluid F which is intended to be compressed, a portion of the lubricant together with the fluid F reaches the high-pressure region 2. In order to separate the lubricant S from the fluid/lubricant mixture, a lubricant separator 21 may be provided. In principle, lubricant S in the compressor V may be separated at any redirection or cross sectional change of the fluid lubricant mixture.

In order to transport the lubricant S from the high-pressure region 2 back into the low-pressure region 1, a lubricant return channel 3 is provided between the high-pressure region 2, in particular the lubricant separator 3 in the high-pressure region, and the low-pressure region 1, in particular the lubricant reservoir 11 in the low-pressure region. The compressor V may be provided with a compressor housing 4 for receiving or forming the above-mentioned components.

According to the invention, there is provision for the lubricant return channel 3 to comprise a fluid diode 31. In principle, the fluid diode 31 comprises a geometry which provides counter to a flowing medium a resistance to throughflow which differs in accordance with the direction. A fluid diode is also known under the name Tesla valve. In other words, the lubricant return channel 3 is at least partially configured to be media-selective, or in the form of a media-selective throttle, that is to say, differences in the material properties are used, whereby the in particular gaseous fluid F, preferably refrigerant, and the in particular liquid lubricant S, are subjected to different flow resistances when passing through the lubricant return channel 3 from the high-pressure region 2 to the low-pressure region 1. There is in particular a high resistance for the fluid F, in particular for the gaseous fluid, whereby little fluid F reaches the low-pressure region 1 from the high-pressure region 2 via the lubricant return channel. The fluid F is preferably a refrigerant, such as, for example, supercritical CO2. Compared with the fluid F, the lubricant S, which in particular after the separator 3 is present in liquid form, is subjected to a lower flow resistance when passing through the fluid diode 31.

Examples of fluid diodes or flow paths are illustrated in FIGS. 2, 3a, and 3b.

The fluid guide 31 or the portion of the lubricant return channel 3 which is in the form of a fluid diode may in particular be characterized by the following details.

For the selective construction of the flow resistance, a lubricant return channel 3 is, for example, introduced into a metal sheet. The flow guide is carried out in particular with a non-constant cross section and preferably has a repetitive base contour along any development curve. The fluid F, in particular the refrigerant, and the lubricant S are thus forced into a meandering main flow with circulating secondary flows.

The lubricant return channel 3 has a similar geometry to the “Tesla valve” or fluid diode and is operated in this instance so to speak in the “blocking direction”, whereby in particular a high resistance is produced in the flow direction from the high-pressure region 2 to the low-pressure region 1. In addition, differences in the material properties are used. The material properties or the different physical properties may, for example, be density, viscosity or compressibility. These different physical properties require with a specific pressure drop a different configuration of flow properties such as flow speed and degree of turbulence for the respective medium.

The gaseous fluid F, in particular the refrigerant, is significantly redirected in the fluid diode 31, it passes in particular more powerfully into the “contour corners” of the portion of the lubricant return channel 3 in the form of a fluid diode 31. The kinetic energy of the fluid F, in particular the gaseous fluid, is partially dissipated during the redirection. In particular, the degree of turbulence in the gas flow is greater, whereby a higher flow resistance results. The gaseous fluid F has a high speed, which is in particular a result of the density. An expanding gas has significantly higher flow speeds.

The lubricant S which is present in a liquid state is not so significantly redirected as the gaseous fluid F present, in particular the gaseous refrigerant. It can pass the fluid diode 31, in particular the contour of the fluid diode at a virtually constant speed and with a lower degree of turbulence. Consequently, the flow resistance acting here is smaller.

For example, a heart-shaped, in a particularly preferred manner an offset-heart-shaped structure may be considered as embodiments of the fluid diode 31 or an embodiment of the inner wall of the lubricant return channels 3. However, other forms of the contour are conceivable and in principle are known as “fluid diodes”. The length of the lubricant return channel 3 is preferably a matter of individual configuration. In principle, any number of such units may be connected in series. The lubricant return channel 3 per se may be constructed with different geometries, in particular as a semi-circle (cf., for example, FIGS. 4 and 5). The lubricant return channel 3, in particular the portion which is in the form of a fluid diode 31, may also be in the form of a fold or other arrangement, in particular as a result of the respective spatial relationships in the compressor.

Preferably, the lubricant return channel 3 is constructed in planar partition faces in the housing, a sealing face and/or in a seal 32 of the compressor V. Such a configuration can be integrated in the compressor in a structurally simple manner and requires little structural space. Such a configuration is illustrated in particular in FIG. 6.

The channel geometry which is significant for the fluid diode, in particular the configuration of the inner wall, can be produced in planar partition faces by means of punching, etching or erosion.

The number of repetitions of the base contour of the inner wall of the lubricant return channel 3, in particular the fluid diode 31, and the height of the contour or the sheet thickness may be adapted to the requirements of the respective throttle function.

In this instance, features and details which are described in connection with a method also naturally apply in connection with the apparatus according to the invention, and vice versa, so that with respect to the disclosure relating to the individual aspects of the invention, mutual reference is or can always be made. Furthermore, where applicable a described method according to the invention can be carried out with the apparatus according to the invention.

The terminology used herein serves only to describe specific embodiments and should not limit the disclosure. As used herein, the singular forms “a/an” and “the” are also intended to include the plural forms unless the context otherwise clearly identifies this. It will additionally be clear that the terms “has” and/or “having” when used in this description specify the presence of the mentioned features, whole numbers, steps, operations, elements and/or components but do not exclude the presence or the addition of one or more other features, whole numbers, steps, operations, elements, components and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.

For example, a refrigerant can be considered to be a fluid which is intended to be compressed. In this regard, the compressor may preferably be in the form of a refrigerant compressor.

Claims

1. A compressor comprising:

a low-pressure region;

a high-pressure region;

a lubricant provided in the low-pressure region configured to lubricate the compressor;

a fluid configured to be conveyed from the low-pressure region into the high-pressure region and compressed, wherein a portion of the lubricant with the fluid from the low-pressure region is configured to reach the high-pressure region;

a lubricant separator for separating the lubricant from the fluid in the high-pressure region; and

a lubricant return channel for transporting the separated lubricant from the high-pressure region into the low-pressure region wherein the lubricant return channel includes a fluid diode.

2. The compressor of claim 1, wherein the lubricant return channel includes a heart-shaped or offset-heart-shaped inner wall in order to form the fluid diode.

3. The compressor of claim 1, wherein the lubricant return channel is introduced into a metal sheet.

4. The compressor of claim 1, wherein the lubricant return channel is shaped in a semi-circular manner.

5. The compressor of claim 1, wherein the lubricant return channel is formed in a planar partition face in a housing, a sealing face, and/or in a seal of the compressor.

6. The compressor of claim 1, wherein the fluid (F) is a refrigerant, in particular supercritical CO2.

7. The compressor of claim 1, wherein the lubricant (S) is oil.

8. The compressor of claim 1, wherein a configuration of an inner wall of the lubricant return channel, is produced by means of punching, etching or erosion.

9. The compressor of claim 1, wherein the lubricant return channel includes the fluid diode (31) as a separate component.

10. A refrigeration machine comprising: a compressor, a gas cooler, an expansion valve and an evaporator, which are fluidically connected to each other, wherein the compressor includes:

a low-pressure region;

a high-pressure region;

a lubricant provided in the low-pressure region configured to lubricate the compressor;

a fluid configured to be conveyed from the low-pressure region into the high-pressure region and compressed, wherein a portion of the lubricant with the fluid from the low-pressure region is configured to reach the high-pressure region;

a lubricant separator for separating the lubricant from the fluid in the high-pressure region; and

a lubricant return channel for transporting the separated lubricant from the high-pressure region into the low-pressure region wherein the lubricant return channel includes a fluid diode.

11. A method for producing a compressor:

punching, etching or eroding an inner wall of a lubricant return channel of the compressor comprising: a low-pressure region; a high-pressure region; a lubricant provided in the low-pressure region configured to lubricate the compressor; a fluid configured to be conveyed from the low-pressure region into the high-pressure region and compressed, wherein a portion of the lubricant with the fluid from the low-pressure region is configured to reach the high-pressure region; a lubricant separator for separating the lubricant from the fluid in the high-pressure region.

12. The compressor of claim 1, wherein the lubricant return channel is at least partially in the form of a fluid diode.