WO2010131061A1

WO2010131061A1 - Hermetically closed compressor and related methods

Info

Publication number: WO2010131061A1
Application number: PCT/IB2009/005573
Authority: WO
Inventors: Harry Stenfoft Nissen
Original assignee: JENSEN, Söby, Stefan
Priority date: 2009-05-12
Filing date: 2009-05-12
Publication date: 2010-11-18

Abstract

Compressor for heat pumps and air conditioning- and refrigeration systems for vehicles and industrial cooling, having hermetic compressor and preferably being driven by electro motor. A preferred embodiment of the present invention would include at least one of each of the following objects not excluding other possible objects: block (1), crank (2), stator (3), rotor (4), input shaft (5), connecting rod (6), piston ball joint (7), piston (8), cap (9), intake tank (10), discharge chamber (11), discharge valve (12), intake valve (13), cap screw (14), wire coils (15), oil pump (16) and cylinder (17). The invention also includes refrigerants preferably having greenhouse effect below 10. The refrigerants would preferably be embodied in the cylinder (17), the intake tank (10), the discharge tank (11) and also pulsate through the intake valve (13) and the discharge valve (12). The resulting compressor is hermetic and electrically driven.

Description

Title

Hermetically closed compressor and related methods.

Technical Field

The invention relates to air conditioning and refrigeration systems, more specifically to compressors for heat pumps and air conditioning and refrigeration systems for industrial cooling and vehicles comprising hermetic technology.

Background Art

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. The applicant makes no admission that any reference constitutes prior art - they are merely assertions by their authors and the applicant reserves the right to contest the accuracy, pertinence and domain of the cited documents. None of the documents or references constitute an admission that they form part of the common general knowledge in the US or in any other country.

Refrigeration is defined as the process of cooling of bodies or fluids to temperatures lower than those available in the surroundings at a particular time and place. Various methods of producing low temperatures include: sensible cooling using a cold medium, endothermic mixing of substances, phase change processes, expansion of liquids, expansion of gases, thermoelectric method and magnetic method.

A compressor is the most important and often the costliest component of any vapour compression refrigeration system. The compressor has to draw the refrigerant vapour from the evaporator, so that the low pressure and temperature can be maintained at which the refrigerant and boil extracting heat from the refrigerated space. The compressor then has to raise the pressure of refrigerant to a level at which it can condense by rejecting heat to the cooling medium in the condenser. Compressors for air conditioning and refrigeration systems of various kinds contain refrigerants. Historically different refrigerants have been used. Ethyl ether is the first refrigerant to be used by Jacob Perkins in 1835. Alexander Twining proposes use of the ammonia and carbon dioxide in 1850. Charles Tellier tries dimethyl ether in 1864. Raoul Pictet uses sulphur dioxide in 1874. Linde builds ammonia system in 1877. Hydrocarbons and their mixtures are also tried around this time. Some problems are experienced when using these refrigerants. Ethers and ammonia are toxic. Hydrocarbons for instance are flammable. Ammonia for instance has poor material compatibility and for instance sulphur dioxide has problems concerning chemical stability. Also, all the mentioned early refrigerants have limited temperature range.

Compared to the early refrigerants, CFCs are non-toxic, nonflammable, chemically stable, compatible with the common materials and available for a wide refrigeration temperature range. However, in 1974, Rowland and Molina proposed a theory of ozone layer depletion due to CFCs released into the atmosphere. Subsequent studies confirm the ozone-depleting potential of CFCs and related substances. The Montreal protocol bans the use of ozone-depleting substances such as CFCs. This protocol was signed in 1987.

Consequences of ozone layer depletion include: skin cancer, cataracts, weakened immune systems and damage to DNA structures. Further negative consequences of ozone layer depletion are adverse effect on crop yield and adverse effect on terrestrial and aquatic ecosystems. CFCs are also considered to contribute significantly to global warming. CFCs can absorb a lot more long wave length energy than carbon dioxide, and therefore it has a environmentally negative impact on the greenhouse effect. Carbon dioxide on the other hand is non-toxic, it has a greenhouse effect as low as 1 and it does not deplete the ozone layer. Carbon dioxide is the reference refrigerant when measuring the greenhouse effect of refrigerants. This is why carbon dioxide has a greenhouse effect on 1.

Different approaches are relevant when attempting to decrease greenhouse effect and ozone layer depletion, meanwhile still enjoying the life quality enhancing qualities of air conditioning- and refrigeration systems of various kinds. One approach is to use natural refrigerants which do not harm the ozone layer and which only have a limited impact on the greenhouse effect. As mentioned earlier, carbon dioxide is one such refrigerant. The volumetric enthalpy is high when using carbon dioxide as refrigerant. Per displacement volume the volumetric enthalpy is high. This is because carbon dioxide has a high density. The density of carbon dioxide is approximately 7 times bigger than for instance the density of the refrigerant 134a. The need and will to solve the aforementioned issues is underlined by political initiatives which have been made recently. The EU played an important part in a project called the RACE project where both the automotive industry- and the cooling industry of the countries Denmark, United Kingdom, Sweden and Germany cooperated. Danfoss, Rover, Volvo and Volkswagen were the participating companies in the project which ended in 1997. In 2008 the EU decided that it will only be legal to use refrigerants having greenhouse effect below 10 in air-conditioning systems for buses and cars. This will be implemented between 2011 and 2013.

It is important that service personnel and passengers in cars cannot be endangered in case of system leakages or accidents. The security risks related to human use of carbon dioxide has been investigated by Rover and Daimler-Benz in the 1990s.

A very good approach in order to decrease the amount of refrigerants which are released in the environment is to use hermetic compressors in air conditioning- and refrigeration systems. Such compressors are used today in household refrigerators, residential air conditioners and in smaller commercial air conditioning and refrigeration units. They are, however, not used in heat pumps or in air conditioning- and refrigeration systems for vehicles and industrial cooling. Among the refrigerants having greenhouse effect below 10, carbon dioxide has previously been used in non-hermetic systems, e.g. on cargo ships for refrigeration purposes where the under critical carbon dioxide gas process was used. The use of this process decreased. One problem with this process is that it was unable to provide sufficient cooling in hot regions of the world. However, Prof Gustaf Lorenzen from Sintef in Trondheim, Norway has played an important part in the revival of the carbon dioxide compressor, especially in relation to the super critical carbon dioxide gas process. Further information is provided in Lorenzen (1994).

Drawbacks concerning background art

Apart from the environmental issues mentioned earlier, drawbacks concerning prior art include the fact that in non-hermetic systems there is leakage of refrigerant at the gaskets or elsewhere in the system. For instance there will be leakage at the intake valve and the discharge valve arrangements. Furthermore it is disadvantageous that compressors which are not hermetic need to be refilled. Carbon dioxide is a natural substance that plays an important role in many different processes in nature and in industry. Although carbon dioxide is odorless, non-flammable and non-toxic, it will increase the breathing rates of humans if concentrations rise above the natural level of atmospheric air. This risk may still exist for instance for service personnel refilling non-hermetic compressors e.g. in heat pumps or in air conditioning- and refrigeration systems related to industrial cooling and vehicles. Disclosure of the invention

It is the object of the present invention to provide an electrically driven hermetic compressor to be used in heat pumps and in air conditioning- and refrigeration systems for vehicles and industrial cooling. The invention consists of simple mechanics and advanced electronics. The resulting product is a mechatronics product. It is a combination of mechanics, fluid dynamic, thermodynamic and electronics. Thermodynamics is the study of energy interactions between systems and the effect of these interactions on the system properties. Generally speaking the intelligence is in the electronic, the power and the thermodynamics are in the mechanics in mechatronics products.

Brief description of the drawings

Figure 1 shows an example of an embodiment of the present invention in the form of a compressor comprising hermetic compressor technology and being electrically driven. Figure 2 shows an example of a valve system for carbon dioxide compressors.

Best modes of carrying out the invention

The purpose here is to give an example of a possible embodiment of the present invention. It should be noticed that many other possible embodiments of the present invention can be made, however, one example of a possible embodiment of the present invention concerns, with reference to figure 1, a compressor comprising at least one block (1), at least one crank (2), at least one stator (3), at least one rotor (4), at least one input shaft (5), at least one connecting rod (6), at least one piston ball joint (7), at least one piston (8), at least one cap (9), at least one intake tank (10), at least one discharge chamber (11), at least one discharge valve (12), at least one intake valve (13), at least one cap screw (14), wire coils (15), at least one oil pump (16) and at least one cylinder (17). The invention also contains refrigerants, which are not included in figure 1. The refrigerant- or combination of refrigerants can be of any type of refrigerant. Preferably the refrigerant- or combination of refrigerants will have greenhouse effect below 10 and normally these would be embodied in the cylinder (17), the intake tank (10), the discharge tank (11) and also pulsate through the intake valve (13) and the discharge valve (12). The resulting compressor is hermetic and electrically driven. Figure 2 displays an example of the valve system according to figure 1, constituted by an intake valve (13), a discharge valve (12) and a cylinder (17). According to figure 1 a cylinder head is constituted by the cap screws (14), the cap (9), the intake tank (10), the discharge chamber (11), the intake valve (13) and the discharge valve (12). The aforementioned elements can be provided in a number of ways and positioned in relation to each other in a number of ways. One such way, not excluding other alternative ways, still referring to figure 1, would include a block (1) being fixedly attached to a cylinder (17). The cylinder (17) contains a piston (8), piston ball joint (7) and a connecting rod (6). The connecting rod (6) being movably attached to a crank (2), which is fixedly attached to the block (1). The input shaft (5) connects the crank (2) with the motor which consists of stator (3), rotor (4), input shaft (5), wire coils (15) and oil pump (16). Stator (3) and rotor (4) are symmetrically positioned around the input shaft (5). Fixedly attached to the motor and connected to the input shaft (5) an oil pump (16) or lubrication pump is provided. Fixedly connected to the stator (3) wire coils (15) are positioned. The motor may comprise an inverter.

It should be noticed that any compressor comprising hermetic compressor technology and being electrically driven, used in heat pumps and air conditioning and refrigeration systems for vehicles and industrial cooling, should be considered within the scope of the present invention. Compressors can be classified into different types. Generally it is common to distinguish between two main groups which are firstly positive displacement compressors and secondly roto dynamic compressors. Positive displacement compressors include for instance reciprocating compressors, rotary compressors, screw compressors and scroll compressors. Roto dynamic compressors include for instance centrifugal compressors and axial compressors. Other types of compressors concern: vertical two cylinder compressors; horizontal, single cylinder compressors; carbon dioxide compressors; oil free sulphur dioxide compressors; horizontal and double acting compressors. Further types of compressors include electric motor driven compressors; high-speed compressors which operate with rotation speeds of more than 500 rpm; diaphragm compressors; rotary vane mastery compressors and rolling piston compressors. New compressor types such as the linear piston compressor, the trochoidal compressor and the acoustic compressor are at various levels of development.

Hermetic compressor technology enables a compressor to avoid leakage of refrigerant from compressors. As an example of hermetic compressor technology the stuffing box can be mentioned. Also some compressors have hermetic compressor motor assembly contained in a welded steel case. Another part of what can be considered as constituting hermetic compressor technology concerns hermetic compressor-motor assemblies being contained in a casting with no penetration by a rotating shaft and with gasketed cover plates for access to key parts such as valves and connecting rods.

The stator (3), the rotor (4), the intake shaft (5), the oil pump (16) or lubrication pump, and the wire coils (15) constitute a motor. Different kinds of motors and engines may be used in relation to the present invention. Preferably, an electro motor such as for instance a permanent magnet motor may be used not excluding other alternative motors and engines. These motors may be for instance AC motors or DC motors. Both AC and DC motors can be used not excluding other types. AC will typically be used for heat pumps and air conditioning- and refrigeration systems for industrial cooling, whereas DC motors preferably will be used for air conditioning- and refrigeration systems for vehicles. The motor may have variable rotation speed and inverter.

The refrigerant used in the compressor can be any type of refrigerant. Preferably the refrigerant used in the compressor has greenhouse effect below 10, not excluding other refrigerants. I'm very relevant refrigerant to use would be carbon dioxide. The block (1) may have any geometric shape.

One preferred shape of the block (1) is double curved, since this shape reduces noise.

Generally rotating masses are masses which only rotate and oscillating masses are masses which go forth and back along a line. The crank (2) may have a crankshaft which may rotate when the compressor is functioning. Piston (8) and connecting rod (6) constitute oscillating masses when the compressor is functioning. Preferably, the rotating masses, such as a crankshaft, and oscillating masses, such as the piston (8) and the connecting rod (6), may be balanced.

The oil pump (16) or lubrication pump is preferably a positive volume displacement pump. It may also concern traditional lubricant pumps such as pick up pumps, but more relevant lubrication pumps concern positive volume displacement pumps since when using these pumps the volume displacement is not dependent upon rotation speed. The term positive volume displacement pumps should be understood as including all types such as piston pumps, gear pumps, gerrotor pumps etc, not excluding other types of pumps. The stator (3) may preferably be made of iron sheets. These iron sheets may for instance be 0,5mm thick.

The present invention may be provided in various ways and any type of material such as metals may be used for the manufacture.

According to figure 1 a cylinder head is constituted by the cap screws (14), the cap (9), the intake tank (10), the discharge chamber (11), the intake valve (13) and the discharge valve (12).

The aforementioned elements can be provided following a number of methods and positioned in relation to each other in different ways. One such way, not excluding other alternative ways, still referring to figure 1, would include a number of steps in order to provide a compressor. Preferably the following objects would be provided: at least one block (1), at least one crank (2), at least one stator (3), at least one rotor (4), at least one input shaft (5), at least one connecting rod (6), at least one piston ball joint (7), at least one piston (8), at least one cap (9), at least one intake tank (10), at least one discharge chamber (11), at least one discharge valve (12), at least one intake valve (13), at least one cap screw (14), wire coils (15), at least one oil pump (16) and at least one cylinder (17). Refrigerants will also be provided, which are not included in figure 1. The refrigerant- or combination of refrigerants can be provided in the form of any type of refrigerant. Preferably the refrigerant- or combination of refrigerants will have greenhouse effect below 10 and normally these would be embodied in the cylinder (17), the intake tank (10), the discharge tank (11) and also pulsate through the intake valve (13) and the discharge valve (12). The resulting compressor is hermetic and electrically driven. Preferably the connecting rod (6) may be connected to at least one journal gearing. Preferably there may be no metallic contact between the connecting rod (6) and journal gearing thereby enabling prolonged lifetime.

Generally when using compressors of the positive displacement type, compression is achieved by trapping a refrigerant vapour into an enclosed space and then reducing its volume. Since a fixed amount of refrigerant is trapped each time, its pressure rises as its volume is reduced. When the refrigerant pressure inside the compressor rises to the level of condensing pressure, then the refrigerant is expelled from the enclosed space and a fresh charge of refrigerant is drawn in and the cycle continues. A preferred way of functioning of the invention could be the following: By means of the electro motor constituted by the stator (3), the rotor (4), the intake shaft (5), the wire coils (15) and oil pump (16), the piston (8) is brought to move back and forth in the cylinder (17). As the piston (8) nears the bottom of its stroke within the cylinder (17), the intake valve (13) opens and the refrigerant vapor enters. As the piston (8) rises, the increased pressure closes the intake valve (13). Then as the piston nears the top of its stroke, the discharge valve (12) opens thereby permitting the refrigerant vapor at the higher pressure to exit. When the refrigerant in the intake tank (10) evaporates it creates a cooling effect. The suction pressure in the intake tank (10) is lower than the high-pressure or delivery pressure in the discharge chamber (11). As a result of this process a cooling effect is occurring in relation to the intake tank (10) and a heating effect is taking place in relation to the discharge chamber (11). Preferably the process is reversible. Effect is measured in joules/time in seconds. In relation to air conditioning- and refrigeration systems, effect is called enthalpy and it is measured in kilojoules per kilogram circulated cooling amount. Flow work is the work done when a fluid enters or leaves a control volume. The specific flow work is the product of pressure and specific volume. Enthalpy of a system is equal to the internal energy of the system plus flow work. Preferred processes to function with the invention are the under critical carbon dioxide gas process and particularly the supercritical carbon dioxide gas process possibly in the plasma area not excluding other relevant processes preferably combined with refrigerants having greenhouse effect below 10.

Various methods relate to the present invention such as: applying a hermetic and electrically driven compressor in a vehicle; applying a hermetic and electrically driven compressor in a heat pump; applying a hermetic and electrically driven compressor in relation to industrial cooling. Preferable methods, still referring to figure 1 , not excluding other steps or combinations thereof, for providing the compressor for various applications such as heat pumps and air conditioning- and refrigeration systems related to industrial cooling and vehicles, can include the following steps of: fixedly attaching a block (1) to a cylinder (17); providing the cylinder (17) such that the piston (8) contained in the cylinder (17) can move back and forth in the cylinder touching at least one surface of said cylinder; movably attaching a piston ball joint (7) to a piston (8); movably attaching a piston ball joint (7) and a connecting rod (6); movably attaching the connecting rod (6) to a crank (2); fixedly attaching a crank (2) to a block (1); providing the input shaft (5) such that it connects the crank (2) with the motor which are provided including a stator (3), a rotor (4), an input shaft (5), wire coils (15) and an oil pump (16); symmetrically positioning stator (3) and rotor (4) around the input shaft (5); fixedly attaching to the motor and connected to the input shaft (5) an oil pump (16) or lubrication pump; fixedly attaching wire coils (15) to the stator (3); providing any type of refrigerant; providing hermetic compressor technology such that the resulting compressor is hermetic.

Further methods and steps may concern: providing the compressor motor with variable rotation speed and an inverter; providing the refrigerant such that it has greenhouse effect below 10; providing the motor such that it is a permanent magnet motor; providing the block (1) such that it has double curved shape preferably reducing noise; providing the rotating masses of the crankshaft and the oscillating masses of the piston (8) and the connecting rod (6) such that both masses are balanced with each other; providing the lubrication pump (16) of the positive volume displacement type; providing more than one cylinder; providing the motor such that it is an AC motor; providing the motor such that it is a DC motor; providing the stator using iron sheets preferably of 0.5 mm thickness each. For applications in vehicles preferably at least one compressor is positioned in the motor body of a vehicle. The motor of the compressor is using high- voltage power. From the battery or the motor of the vehicle comes 12 V or 24 V DC power which enters the cable throughput, via said cable throughput it enters the motor of the compressor. If a permanent magnet motor is provided in the motor of the compressor, this motor inverts the DC to magnetic fields which drive the motor and thereby the compression through the piston (8). The battery and the generator of the vehicle deliver DC power. The wire coils (15) or cables will preferably be provided through the cable house of the vehicle, which is typical for hermetic compressors. The cables can be put through the cable house in the vehicle without isolating the cable throughput. Each phase is isolated independently. Typically, three phases will be needed in order to deliver as big an effect as it is needed for vehicles. Preferably the compressor will contain an engine being from 1-5 kW. Another relevant application for the present invention is heat pumps. A heat pump is a machine or device which moves heat from one location (the 'source') to another location (the 'sink' or 'heat sink¹) using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink. A common example is reversible-cycle heat pumps for providing thermal comfort. Heat pumps can also operate in reverse, providing heat. Heat pumps can be thought of as a heat engine which is operating in reverse. One common type of heat pump works by exploiting the physical properties of a refrigerant. In heating, ventilation, and air conditioning applications, a heat pump normally refers to a vapour compression refrigeration device that includes a reversing valve and optimised heat exchangers, so that the direction of heat flow may be reversed. Most commonly, heat pumps draw heat from the air or from the ground. For heat pump applications 110 V in the US and 380 V in EU will be provided for the compressor, either one phased or three phased power. Cooling is provided on the side of the intake tank and heating is provided on the side of the discharge chamber and this can be exploited in order to provide both cooling and heating. Another application for the present invention includes industrial cooling which concerns air conditioning and refrigeration processes in relation to any type of industrial process such as manufacturing including pharmaceutical processes excluding warehouses and other types of commercial refrigeration. Industrial applicability

The present invention creates a number of advantages. Generally, hermetic compressor systems have longer lifetime and a much lower level of service is needed. Regardless of the application hermetic systems will work in 20,000-30,000 hours and sometimes 50,000-60,000 hours. The present invention comprises few mechanical parts which secures that no undue use of material and thereby natural resources is made. Due to the high density- and volumetric pressure of the refrigerant, carbon dioxide compressors generally have smaller pistons than other compressors. Therefore the weight of these compressors is normally lower and they are normally cheaper. The present invention facilitates a reduction of the quantity of mechanical components needed in the compressor, which in turn improves the reliability of the compressor. In order to clarify this, it can be mentioned that, when the compressor consists of fewer components there are fewer components which can fail, and therefore the risk of breakdown of the compressor is reduced. An additional advantage of the present invention is that in a possible embodiment of the present invention, journal bearings may be used in all bearing surfaces, which makes it possible to prevent compressor constructions where there is contact between metallic surfaces. The resulting advantage is a longer life of the compressor. One exception from this benefit could be the piston ball bearing or the piston ball joint, but in this bearing, movement is minimal and therefore abrasion and risk of reduced lifetime of the compressor, is minimal.

When applying the present invention in relation to heat pumps it is beneficial that when using one of the refrigerants having a greenhouse effect below 10, namely carbon dioxide, it is possible to heat water up to a temperature of 90⁰C since heat sink effect occurs when using carbon dioxide as a refrigerant. This occurs since the main part of the enthalpy is created in the gas phase and not in the liquid phase, when using carbon dioxide as a refrigerant. When chemical refrigerants are used instead, it is only possible to achieve heating of water to a temperature level of around 50°C. One of the refrigerants having a greenhouse effect below 10, namely carbon dioxide has a greenhouse effect as low as 1 , which was also mentioned previously. Generally carbon dioxide compressors can be scrapped without huge cost of reusing the refrigerant. In comparison with non- hermetic compressors containing natural refrigerants, a hermetic compressor secures that no refrigerant is spread in the environment in the lifetime of the compressor. Since the invented compressor is hermetic there is no leakage and it will not need to be refilled with additional refrigerant during its lifetime, which is environmentally beneficial, especially in relation to the greenhouse effect. Also, service costs related to refilling, are saved for the user. For the service personnel the risk related to carbon dioxide refrigerant of increased breathing rates if concentrations rise above the natural level of atmospheric air, which might happen in case of leakage, is avoided with hermetic compressors since no risk of leakage exists.

A further benefit is that when applying the present invention in vehicles, the air conditioning and refrigeration system will last the lifetime of the vehicle without costing the user anything in service costs etc. Also it is advantageous that the present invention makes flexible cables redundant since the new compressor would be able to be positioned in the motor body of a vehicle instead of being positioned on the motor as in the previous systems. In previous systems it was necessary to use flexible cables. By applying the present invention it is not necessary to use flexible cables. There are no movements between compressor and heat exchanger. As a consequence thereof there is no need for flexible cables. Since the electro motor of the compressor may have variable rotation speed, a further advantage of the present invention is that the effect can be adapted to the size of the vehicle. An important advantage with the present invention is that the compressor can be embodied anywhere in the vehicle for instance in order to minimize noise emission to the passenger compartment. This opportunity, which is facilitated by the present invention, also makes it possible to optimize the weight distribution for the vehicle. Furthermore the present invention makes it possible to have engine output refrigeration to glove box, centre console and rear seat refrigerator for instance in luxury vehicles without the addition of a second refrigeration system over and above the motor vehicle air conditioning (MVAC) system.

A further advantage with the present invention is that it is able to facilitate that no sudden impact on engine torque takes place in vehicles with relatively small torque.

References

Lorenzen, G., 1994, Revival of carbon dioxide as a refrigerant. International Journal of Refrigeration, 17(5), pp 292-301

Claims

1. A compressor for heat pumps and air conditioning- and refrigeration systems related to industrial cooling and vehicles comprising hermetic compressor technology, carbon dioxide refrigerant and being electrically driven .

2. The compressor according to claim 1 characterised by being driven by a motor with variable rotation speed and inverter.

3. The compressor according to claim 1-2 comprising any type of refrigerant having greenhouse effect below 10.

4. The compressor according to any of the preceding claims characterised by being driven by a permanent magnet motor.

5. The compressor according to any of the preceding claims characterised by having double curved block shape.

6. The compressor according to any of the preceding claims characterised by having rotating masses of crankshaft and oscillating masses of the piston and the connecting rod, being balanced.

7. The compressor according to any of the preceding claims comprising lubrication pump being of the positive displacement type.

8. The compressor according to any of the preceding claims characterised by having at least one cylinder.

9. The compressor according to any of the preceding claims characterised by being driven by an AC motor.

10. The compressor according to preceding claims 1-9 characterised by being driven by a DC motor.

11. The compressor according to any of the preceding claims characterised by the stator being made of iron sheets.

12. Method in relation to air conditioning and refrigeration comprising the step of applying a hermetic and electrically driven compressor containing carbon dioxide refrigerant in a vehicle.

13. Method in relation to air conditioning and refrigeration comprising the step of applying a hermetic and electrically driven compressor containing carbon dioxide refrigerant in a heat pump.

14. Method in relation to air conditioning and refrigeration comprising the steps of applying a hermetic and electrically driven compressor containing carbon dioxide refrigerant in relation to industrial cooling.

15. Method of providing a compressor for heat pumps and air conditioning- and refrigeration systems related to industrial cooling and vehicles comprising the steps of: providing a compressor; providing said compressor with hermetic compressor technology; providing carbon dioxide refrigerant; providing said compressor with electrical motor.

16. Method according to claim 15 comprising a further step of providing the compressor with a motor having variable rotation speed and inverter.

17. Method according to claim 15 - 16, comprising a further step of providing the refrigerant in the form of any type of refrigerant having greenhouse effect below 10.

18. Method according to claim 15- 17, comprising a further step of providing the motor as a permanent magnet motor.

19. Method according to claim 15- 18, comprising a further step of providing a double curved block shape.

20. Method according to claim 15- 19, comprising a further step of balancing the rotating masses of the crankshaft and the oscillating masses of the piston and the connecting rod.

21. Method according to claim 15- 20, comprising a further step of providing a lubrication pump being of the positive volume displacement type.

22. Method according to claim 15- 21, comprising a further step of providing at least one cylinder.

23. Method according to claim 15- 22, comprising a further step of providing an AC motor.

24. Method according to claim 15- 22, comprising a further step of providing a DC motor.

25. Method according to claim 15- 24, comprising a further step of providing the stator by the use of iron sheets.