WO2000029793A1

WO2000029793A1 - Piston compressor

Info

Publication number: WO2000029793A1
Application number: PCT/DE1999/003675
Authority: WO
Inventors: Horst Kruse
Original assignee: FKW HANNOVER Forschungszentrum für Kältetechnik und Wärmepumpen GmbH
Priority date: 1998-11-18
Filing date: 1999-11-18
Publication date: 2000-05-25
Also published as: DE19955554A1

Abstract

The invention relates to a piston compressor, comprising a compressor and an expansion part whose pistons are connected by a common driving unit. This enables the energy that is liberated when a coolant expands to be used for its compression.

Description

description

Piston compressor

The invention relates to a piston compressor, in particular for compressing a refrigerant according to the preamble of patent claim 1.

Piston compressors, for example axial piston machines are u. a. used to compress a refrigerant in car air conditioning systems. Another area of application for such compressors is in heat pump technology, which has recently come into competition with conventional heating systems for buildings.

So far, heat pump systems have often been operated with CFCs as work equipment. Because of the considerable global warming potential of such refrigerants, efforts are being made to replace them with natural substances. As of 2015, the CFC-containing refrigerants in the European Community should be replaced with non-toxic, non-flammable refrigerants with a low global warming potential. The natural substances represent a promising alternative to the CFC-containing tools.

In the article "Heat pump systems with C0 ₂ as a working fluid" (heat pump - September 1998) it is shown that CO2 appears to be particularly suitable as a working fluid for such heat pumps due to its environmental compatibility and an extraordinarily high volumetric cooling capacity. When heat is given off by CO2 heat pumps in the supercritical range, temperatures can be achieved which, at 60 ° to 90 ° Celsius, are significantly higher than those that can be achieved with conventional heat pumps. FIG. 1, to which reference is already made here, shows a theoretical refrigeration process of a compression refrigeration system in a pressure-enthalpy diagram. FIG. 2 shows a system diagram of a refrigeration system with which the ideal process shown in FIG. 1 can be carried out.

Accordingly, the refrigerant with the state indicated by the number 1 (pressure pι_, t = 0 ° C) is sucked in by the compressor 6 and isentropically compressed to state 2 (P2 _^ t = 140 ° C). The compressed, heated refrigerant is cooled in a heat exchanger 8 at constant pressure to a temperature of, for example, 30 ° C. (state 3) and then expanded isentropically to the pressure p in an expansion machine 10. As can be seen from FIG. 1, the refrigerant is in the wet steam area after expansion in the expansion machine 10 and has cooled to a temperature of, for example, -20 ° C. The heat exchange with the room to be air-conditioned then takes place in an evaporator 12, in which the refrigerant (CO2) is brought to the initial state identified by 1 by supplying heat.

In the event that a throttle valve is used for relaxation instead of the expansion machine 10, the state 4 'is set instead of the state 4, since the relaxation takes place in a throttle valve along an isenthalpic. The relaxation work obtained when using an expansion machine corresponds to the distance 4 4 'in FIG. 1. For energy optimization, efforts are therefore made to exploit the advantages of a work-expanding expansion of the refrigerant by means of suitable device-technical measures. In the field of refrigeration technology, there have already been some efforts to carry out compression and expansion in supercritical processes in a common machine unit. When using air as the refrigerant, for example, turbomachines are used in which 2 impellers are driven by a common shaft. The air is compressed by one impeller, while the other impeller relaxes.

In refrigeration processes using air as the refrigerant, multi-cell compressors are often also used, in which two sickle-shaped work spaces are formed in an oval housing, one of which acts as a compressor and the other as an expansion machine.

Because of the very high pressure difference that occurs in transcritical refrigeration processes, for example with the refrigerant CO2, the above-mentioned working machines are unsuitable, since the working spaces of the expansion and the compressor part cannot be reliably sealed against the high pressure differences.

The invention has for its object to provide a piston compressor by means of which compression is possible with a minimum of device technology and energy expenditure.

This object is achieved by a piston compressor with the features of claim 1.

By the measure, the piston compressor with a

Perform compression and an expansion part, wherein

Compressor pistons and pistons of the expansion part are operatively connected to a common drive, an extremely compact unit can be realized in which the mechanical work of the compressor pistons and the pistons of the expansion part can reduce the compression work compared to conventional solutions.

Another advantage of this solution is that the device complexity is comparatively low due to the common components of the compressor and the expansion part compared to the known solutions with separate compressors and expansion machines.

The concept according to the invention can be implemented particularly advantageously in a piston compressor with a crank mechanism and in a piston compressor with an axial piston design. In principle, the operative connection of the compressor and expansion pistons according to the invention can also be used with other piston compressor designs via the common drive.

When a crank mechanism is used, a common crankshaft is connected to both the compression piston and the expansion piston, so that the work gained during the expansion of the medium (refrigerant) can be used to compress the medium in the piston compressor.

It is particularly advantageous if the expansion part is designed with a slot control in which the inlet and outlet openings are opened and closed by the movement of the expansion piston.

The piston compressor is of particularly simple construction if the medium to be expanded is fed from a high-pressure connection into the associated expansion space through the expansion piston. The expansion piston can be designed with the same diameter as the compressor piston or as a stepped piston.

In the crank drive concept, it is preferred to connect the pistons to a common crankshaft using connecting rods. The outlay in terms of device technology in the implementation of this variant is minimal if the cylinder bores are formed at least in the area of the connecting rod head with essentially identical dimensions, so that the motor housing can be produced in a simple manner and there is a possibility of retrofitting.

In an alternative, preferred embodiment, the piston compressor is designed in an axial piston design, the expansion and compression pistons being biased against a common lifting disc, the

Angle of attack determines the piston stroke.

In this variant in the axial piston design, it is particularly preferred if the compressor pistons and the pistons of the expansion part act on the front or rear of the lifting disk, so that the lifting disk is loaded on both sides. Because of this symmetrical arrangement, there is a certain balance of forces between the effective piston forces, so that the mounting of the movable components is considerably simplified.

The regulation of the compression capacity depending on the parameters of the refrigeration process is particularly simple if the piston compressor is designed as a swash plate machine or as a swash plate machine, the capacity regulation being able to be carried out by adjusting the swash plate or the swash plate. In a particularly preferred embodiment, the compressor and the expansion part are designed symmetrically to one another, so that the same cylinders are formed in both sections. To reduce the geometric volume in the expansion part, some cylinders in this area are designed as idle cylinders, which do not contribute to the expansion of the refrigerant.

A variant preferred by the applicant provides that the compressor and the expansion part are each designed with 4 cylinders, 2 cylinders of the expansion part being designed as idle cylinders.

In this variant, it is particularly preferred if these idle cylinders are blocked off from the input and output connections via an intermediate plate, the geometric volume of the expansion part being changeable by exchanging the intermediate plate.

The inlet and outlet control to the expansion part and to the compressor takes place on the expansion side via a rotary valve-like control disk and on the compressor side via conventional inlet and outlet valve arrangements.

The piston compressor according to the invention is particularly well suited for a cycle with CO2 as the refrigerant. In principle, however, other refrigerants can also be used.

Because of the higher density of the refrigerant present at the high-pressure connection of the expansion part and the resulting low volume flow (compared to the volume flow of the refrigerant drawn in by the compressor), the geometric volume of the expansion part is made smaller than that of the compression part. This can be achieved, for example, by suitable design of the cylinder diameter or by a different number of cylinders in the expansion and in the compressor part.

Other advantageous developments of the invention are the subject of the further subclaims.

Preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

1 shows a transcritical cooling process in a p / h diagram;

FIG. 2 shows a system diagram for carrying out a cooling process according to FIG. 1;

FIG. 3 shows a section through a first exemplary embodiment of a piston compressor as an axial piston unit;

FIG. 4 shows a sectional view through an expansion control disk of the axial piston unit from FIG. 3;

Figure 5 shows an embodiment of a piston compressor with crank mechanism and

Figure 6 shows a variant of the embodiment shown in Figure 4.

The invention will first be explained with reference to a piston compressor in an axial piston design. Such a piston compressor is referred to below as an axial piston unit 14. In the axial piston unit 14 shown in FIG. ter 6 and the expansion machine 10 from Figure 2 combined into a compact unit.

The axial piston unit 14 according to the invention has a housing with an expansion cylinder block 16 and a compressor cylinder block 18, which are closed at the end by an expansion cylinder head 20 and a compressor cylinder head 22, respectively.

In each cylinder block 16, 18, more than 1 cylinders 24a, b, c, d and 25a, b, c, d are distributed evenly on the circumference, two cylinders (24a, 25a; 24b, 25b, ...) are formed coaxially in the expansion cylinder block 16 and in the compressor cylinder block 18. In the sectional view according to FIG. 3, only two of the four cylinders in each cylinder block 16, 18 are shown; in the illustration according to FIG. 3, the two other cylinders in each case are arranged in the central plane running through the central axis 26 perpendicular to the drawing planes.

A compressor piston 28a, b, c, d is guided in each of the four compressor cylinders 25a, b, c, d, while an expansion piston 30a, b, c, d is axially displaceable in each of the expansion cylinders 24a, b, c, d is arranged.

Each piston 28, 30 carries on its piston-bottom end section piston rings 32 for sealing the respective cylinder chamber 34 from a drive chamber 35 delimited by the two cylinder blocks 16, 18. Depending on the piston stroke, the piston foot-side sections of the pistons 28, 30 dip into this drive chamber 35 a.

The expansion cylinder block 16 and the compressor cylinder block 18 are penetrated by an axial bore 36, in which a drive shaft 38 out. The lower end section 40 of the drive shaft 38 in FIG. 3 is radially set back and led out of the housing via a sealing arrangement 42 and connected to a drive motor. The drive shaft 38 has a swivel bearing 48 for a swash plate 50 between two bearing sections 44, 46 which are radially enlarged relative to the end section 40 and whose angle of inclination α can be changed with respect to the central axis 26. The swash plate 50 is rotatably connected to the drive shaft 38.

The bearing of the swash plate 50 and the structure of the pivot bearing is not explicitly shown in the illustration according to FIG. 3, since these components are sufficiently known from the prior art.

The end support of the drive shaft 38 takes place via two axial bearings 52 which are supported on the end faces of the cylinder blocks 16 and 18 and on the end face of the radially expanded pivot bearing section 48 of the drive shaft 38.

The pistons 28, 30 are each supported by a hydrostatic sliding shoe 54, 56 on the adjacent large surface of the swash plate 50. Each slide shoe 54, 56 has a spherical body 58 which rests with a flat section on the swash plate 50 and is guided with its spherical section in a slide shoe bearing receptacle 60, so that the slide shoe 56 is always flat on the adjacent one during the wobble movement of the swash plate 50 Large area of the swash plate 50 is present.

The bearing seats 60 of the piston pairs in the axial direction 28a, 30a; 28b, 30b, ... are each connected to one another via a connecting element 62. A suction channel 64 and a pressure channel 66 are formed in the compressor cylinder head 22, via which the suction ports and the pressure ports of the compressor cylinders 25 are connected to one another.

An intermediate plate 68 is arranged between the compressor cylinder head 22 and the compressor cylinder block 18. For each cylinder 25, this has a suction bore 70 and a pressure bore 72, which on the one hand open into the suction channel 64 or in the pressure channel 66 and on the other hand into the cylinder spaces 34.

In the parting plane between the intermediate plate 68 and the compressor cylinder head 18, a suction valve 74 is formed, which is designed in a conventional manner as a check valve. The opening stroke of the suction valve 74 is limited by a suction stroke catcher 76. Correspondingly, a pressure valve 78 is formed in the parting plane between the compressor cylinder head 22 and the intermediate plate 68, the opening stroke of which is limited by a pressure stroke catcher 80.

The valves 74, 78 are designed in such a way that they only permit a refrigerant flow in one direction (suction stroke, pressure stroke) and prevent the backflow in the opposite direction.

This construction of the compressor part in the axial piston design (swash plate pump) is known per se from the prior art, so that further explanations are unnecessary.

On the expansion machine side, an intermediate plate 82 is likewise arranged between the expansion cylinder head 20 and the expansion cylinder 16, which is similar to the previously described exemplary embodiment for two of the four cylinders (24a, 24b) each have an inlet bore 84 and an outlet bore 86.

For the reasons mentioned at the outset, the geometric volume of the expansion machine 10 must be designed to be smaller than the geometric volume for the compressor 6. In order to achieve this, the two cylinders (24c, 24d), not shown, which are arranged perpendicular to the plane of the drawing, are called idle cylinders performed that do not participate in the expansion of the refrigerant. That these cylinders do not reduce the enthalpy of CO2 through expansion work.

In order to bring about this so-called idle stroke, axial grooves 88 (dash-dotted in FIG. 3) are formed in the cylinders 24c, d (perpendicular to the plane of the drawing), via which the associated cylinder space 34 is connected to the drive space 35.

Furthermore, the intermediate plate 82 in the area of these cylinders 24c, 24d (not shown) has no inlet or. Outlet bores so that the refrigerant cannot enter the cylinder space 34. A pressure equalization takes place between the cylinder spaces 34 and the drive space 35 via the axial groove 88, so that practically no opposing forces are applied to the swash plate 50 through these cylinders 24c, 24d.

The upper end section of the drive shaft 38 in FIG. 3 dips with a fastening pin 90 into a receiving bore of the expansion cylinder head 20. On this mounting pin 90 a control disk 92 is rotatably fixed, via which the intake and exhaust control of the two cylinders 24a, 24b takes place. Expansion cylinder and control disc can also be on the drive side find, then the compressor unit is arranged on the opposite side.

As explained in more detail below, a connection between the inlet bore 84 and a high-pressure duct 94 in the expansion cylinder head 20 or a connection between the outlet bore 86 and a low-pressure duct 96 can be opened or closed via the control disk 92.

The structure of this control disc can be seen in FIG. 4, which shows a section along the line A-A in FIG. 3.

Accordingly, the control disk 92 has an approximately semicircular control slot 94 which is formed coaxially with the fastening pin 90. Depending on the rotational position of the control disk 92, the outlet bores 86 assigned to the cylinders 24a or 24b can be opened or closed via this control slot 94.

The control of the inlet bores 84 takes place via an inlet window 100 which opens towards the peripheral edge of the control disk 92 and via which a connection can be established with the high-pressure channel 94 surrounding the outer periphery of the control disk 92 and the inlet bore 84.

The relative arrangement of the radially outer inlet window 100 and the arcuate control slot 98 with respect to one another and to the inlet and outlet bores 84, 86 is selected such that the refrigerant to be expanded is introduced into an expansion cylinder (24b) via the inlet window 100 and the inlet bore 84 , while the relaxed working fluid in the other expansion cylinder 24 a, via the outlet bore 86, the control slot 98 practically without counter pressure to the evaporator. to be led. In a transition phase (see FIG. 4), both expansion cylinders 24a, 24b can also be shut off by the control disk 92 with respect to the high-pressure duct 94 and the low-pressure duct 96.

For a better understanding, the essential functions of the axial piston unit 14 according to the invention are again explained below.

The drive shaft 38 is rotated by a suitable drive motor. The swash plate 50 set to the desired angle α is connected in a rotationally fixed manner to the drive shaft 38, so that the four compressor pistons 28a, b, c, d are driven in the axial direction due to the rotating movement of the swash plate 50. FIG. 3 shows a state in which the piston 25a has reached its top dead center (TDC) and the opposite compressor piston 28b has accordingly reached its bottom dead center (TDC). The two compressor pistons (not shown) arranged perpendicular to the plane of the drawing are in intermediate positions. That is, with a further rotation of the swash plate 50 with respect to the position shown in FIG. 3, the compression piston 28b in the compression cylinder 25b is moved downward, so that the refrigerant located in the cylinder space 34 compresses and into the pressure channel 66 via the pressure valve 78 that opens in the direction of pressure build-up flows in. Due to the fluid pressure, the suction valve 74 is closed, so that the connection to the suction channel 64 is shut off.

At the same time, the other compressor piston 25a moves upwards in the illustration according to FIG. 3, so that the associated pressure valve 78 is in its closed position and the suction valve 74 is opened due to the negative pressure in the cylinder space 34 (or the pressure in the suction channel 64). The refrigerant can then from The suction channel 64 flows into the cylinder space 34 via the suction bore 70. As already mentioned, the other two compressor pistons are in intermediate positions so that the refrigerant is compressed or sucked in accordingly.

The compressed refrigerant is led to the heat exchanger 8 via a connecting line connected to the pressure channel 66.

The refrigerant compressed to high pressure and cooled in the heat exchanger 8 is introduced into the high-pressure duct 94 of the expansion machine via a corresponding pressure line. The filling of the two cylinder spaces 34 of the expansion machine is controlled by the control disk 92, which is non-rotatably connected to the drive shaft 38.

In the position of the control disk 92 shown in FIG. 3, the connection between the high-pressure duct 94 and the expansion cylinder 24b is opened, while the cylinder space 34 of the other expansion cylinder 24a is connected to the low-pressure duct 96 via the control slot 98. By means of the compressed gas, the expansion piston 30b is pressed against the inclined surface of the swash plate 50 via the slide shoe 58, so that a torque is exerted on the swash plate 50 - or more precisely on the drive shaft 38 - via a force component directed parallel to the inclined surface plane. That is, the rotation of the drive shaft 38 is supported by the compressed gas, so that the drive power of the motor for the compressor can be designed to be lower than is the case with conventional devices.

In the exemplary embodiment shown, the sliding shoes are the pistons 28, 30 arranged coaxially to one another the expansion machine 10 and the compressor 6 connected to one another via the connecting element 62, so that a reliable contact with the inclined surface is always guaranteed.

As already mentioned at the beginning, the two idle cylinders, not shown, do not contribute to the expansion of the refrigerant. However, the pistons 30c, d (not shown) which are guided in these idling cylinders are likewise connected to the corresponding compressor pistons 28c, d in the manner shown. This construction has the advantage that the pistons of the idle cylinders act as guide elements. Due to the reduced bearing forces, the service life of the axial piston unit is extended considerably compared to conventional solutions with swash plates loaded on one side, so that no premature wear is to be feared even under high pressure conditions.

In the exemplary embodiment shown in FIG. 3, the axial piston unit 14 is designed with a swash plate 50. Of course, this concept according to the invention can also be realized with other constructions, for example in a swashplate construction.

In the exemplary embodiment described above, the control disk 92 with the expansion unit was arranged on the end section of the drive shaft 38; in deviation from this, the expansion unit could also be arranged on the drive side on the drive shaft 38, so that the compression unit is designed accordingly at the other end section.

Preliminary tests showed that the power control is particularly advantageous in terms of energy by varying the swashplate angle, so that the efficiency of the Axial piston unit can be further increased. For simple applications, however, it is sufficient if the swash plate (swash plate) is set at a predetermined angle α to the drive shaft 38.

FIGS. 5 and 6 show exemplary embodiments of a piston compressor 108, in which the compressor and expansion pistons are connected to one another via a crank mechanism 110. The basic structure of the piston compressor 108 shown in FIG. 5 corresponds to that of a compressor, so that a detailed description of the basic components can be dispensed with.

The piston compressor 108 shown has a crankcase 112 in which a crankshaft 114 is mounted via shaft bearings 116, 118. The left frontal cover of the crankcase 112 is provided by a housing cover 120. The right end section of the crankshaft 114 in FIG. 5 passes through an end cover 122, the freely projecting end section 124 being able to be coupled to an output shaft of a drive motor, not shown. To seal the crankcase 112, shaft seals 116 are provided in the bearing area of the crankshaft 114.

An end plate 128 forms the foot-side end section of the crankcase 112. A cylinder block 130 is flanged to the upper side of the crankcase 112, in which the expansion and compression part of the piston compressor 108 according to the invention is formed. For this purpose, two connecting rods 132, 134 are mounted on the crankshaft 114, the connecting rod eye of which is connected to an expansion piston 136 or a compressor piston 138. With regard to the mounting, the sealing and the construction of the crankshaft 114 and the connection of the connecting rods 132, 134 to the crankshaft 114 and to the pistons 136 or 138 should be referred to the existing literature on compressors or internal combustion engines.

The two pistons 136, 138 are guided in cylinders 140 and 142 of the cylinder block 130. These cylinders 140, 142 are delimited on the end face by a cylinder head 144. A cylinder head gasket 145 is formed between the cylinder head 144 and the cylinder block 130. In this inlet and outlet channels 146, 148 are formed with the associated - not shown - inlet and outlet valves for the compressor cylinder 142.

While the compressor part with the compressor cylinder 142, the compressor piston 138 and the inlet and outlet channels 146, 148 and the inlet and outlet valves (not shown) corresponds to the aforementioned state of the art, the expansion part is designed in a different construction with slot control. For this purpose, in the exemplary embodiment shown in FIG. 5, the expansion piston 136 is designed as a stepped piston, the diameter of the piston base in the connection area to the connecting rod 132 corresponding approximately to the diameter of the compressor piston 138. The section of the expansion piston 136 adjoining the piston foot is reduced radially to an expansion section 150, so that the geometric volume of the expansion part is also less than that of the compression part, as in the exemplary embodiment described above.

The expansion section 150 of the expansion piston 136 is sealingly guided in an expansion cylinder 152 projecting upwards (illustration according to FIG. 5). A high-pressure connection 154 and a low-pressure connection 156 are formed in the peripheral wall of the expansion cylinder 152, via which the medium to be expanded, for example as CO2 can be introduced into the expansion cylinder 152 or can be removed therefrom.

According to FIG. 5, an inner bore 158 is formed in the expansion piston 136, which opens on the one hand in the end face and on the other hand in the peripheral wall of the expansion section 150 of the expansion piston 136. Accordingly, the inner bore 158 is made with an approximately axially extending part and an approximately obliquely extending part in the radial direction, the latter opening in the region of the high-pressure connection 154.

A few piston rings 160 are arranged on the outer circumference of the expansion section 150, so that the high-pressure connection 154 is sealed off from the low-pressure connection 156.

In the illustration according to FIG. 5, the expansion piston 136 is at its top dead center. The geometry of the inner bore 158 is selected such that, in the area of the top dead center, the high-pressure connection 154 is connected via the inner bore 158 to the expansion space 162 delimited by the expansion cylinder 152 and the expansion piston 136. As a result, the expansion space 162 is filled with the high-pressure refrigerant. During the subsequent downward movement of the expansion piston 136, the high-pressure connection 154 is controlled by the peripheral edge of the inner bore 158 and the refrigerant located in the expansion space 162 is expanded. After a predetermined piston stroke, the low-pressure connection 156 is opened by the control edge 164 formed by the peripheral edge of the end face, so that the expanded refrigerant can escape through the low-pressure connection 156. On the subsequent return of the expansion piston 136 to the top dead center, the low-pressure connection 156 is first closed and the remaining refrigerant in expansion space 162 is compressed. After a predetermined stroke, the high-pressure connection 154 is opened by the circumferential edge of the inner bore 158, so that high-pressure refrigerant is fed into the expansion space 162 - the cycle begins again.

The basic structure of such an expansion machine with slot control can already be found in the printed publication Dr. R. Doll, Prof. F. X. Eder "Novel expansion machine for generating low temperatures"; Refrigeration technology; 16th year; Issue 1/1964 known, so that with regard to the thermodynamic processes during this expansion process reference is made to this reference.

The energy released during the expansion of the refrigerant is used according to the invention in addition to driving the crankshaft 114, so that the entire compression work does not have to be applied via the drive coupled to the crankshaft 114.

In the exemplary embodiment described above, the expansion piston 136 is designed as a stepped piston, although considerable expenditure is required to guide the radially reduced expansion section 150.

FIG. 6 shows an exemplary embodiment in which the outlay in terms of device technology is reduced in comparison with the previously described solution in that the expansion piston 136 is designed without a step and preferably essentially with the same dimensions as the compression piston 138. In such an embodiment, the expansion cylinder 140 and the compressor cylinder 142 are - apart from the slot control of the expansion part and the valve control of the compressor - partly - identically constructed. As a result, the cylinder head 144 can be made much simpler than in the exemplary embodiment described above, since it essentially only has to accommodate the intake and exhaust control for the compression cylinder 142. In the exemplary embodiment shown in FIG. 6, the geometric volume of the expansion part can be reduced in that the expansion piston 136 is designed with a slightly smaller diameter than the compressor piston 138.

Of course, the piston compressor 108 can also be designed with more than two cylinders, it being possible in principle for all piston compressor types with a crank mechanism to be used. The geometric volume of the expansion part and the compressor part can then be determined, as in the exemplary embodiments described at the outset, by the number of cylinders in the compression or expansion part.

The expansion part of the piston compressor can thus be formed by modifying the cylinder block 130 or the cylinder head 144. The expansion cylinder (s) can be identical or can be designed with different configurations.

Otherwise, the exemplary embodiment shown in FIG. 6 corresponds to that from FIG. 5, so that further explanations are unnecessary.

By coupling the expansion part according to the invention to the compressor of a refrigerant system, the heat output of the heat pump can be significantly improved compared to conventional solutions, so that this construction according to the invention can be used particularly well in heat pump systems with CO2 as the refrigerant For example, can replace conventional boilers for central heating systems with radiators.

Another application could be in a motor vehicle air conditioning system, since in these systems the recooling temperature in the air-cooled gas cooler is relatively high. The cooling capacity can be significantly improved compared to conventional solutions with an expansion valve, since the recoverable work can be used to increase the coefficient of performance due to the high recooling temperatures at the gas cooler. The applicant reserves the right to direct its own subordinate claim to this use.

Disclosed is a piston compressor with a compressor and an expansion part, the pistons of which are connected via a common drive unit. With this construction, the energy released during the expansion of a refrigerant can be used to compress it.

Claims

Expectations

1. Piston compressor, in particular for compressing a refrigerant, with at least one compressor piston (28, 138) which is guided in a compression cylinder (18, 142) and is driven by a drive, characterized in that the drive (50, 114) with an expansion piston (30, 136) of an expansion part of the piston compressor (108) cooperates, so that the work gained during the expansion can be used at least in part to drive the compressor piston (28, 138).

2. Piston compressor according to claim 1, wherein the drive is a crank drive (114), and the expansion piston (138) during its piston stroke high pressure and low pressure connections (154, 156) on or controls for the medium to be expanded or expanded .

3. Piston compressor according to claim 2, wherein the expansion piston (136) has an inner bore (158) through which the high-pressure connection (154) can be connected to a cylinder space (162).

4. Piston compressor according to claim 2 or 3, wherein the expansion piston (136) is a stepped piston, the portion with a larger diameter is guided in a cylinder (140), the dimensions of which correspond approximately to that of the compression cylinder (142), and that the portion (150 ) with a smaller diameter is guided in an expansion cylinder (152) arranged coaxially to the cylinder (140).

5. Piston compressor according to one of claims 2 to 4, wherein the crank mechanism has a crankshaft (114) which is connected to the pistons (136, 138) by means of connecting rods (132, 134).

6. Piston compressor according to claim 1, wherein the piston machine is designed in an axial piston design, in which at least one compressor piston (28) is driven via a lifting disc (50), the stroke of which depends on the position of the lifting disc (50), on which the Expansion piston (30) of the expansion part is supported.

7. Piston compressor according to claim 6, wherein the expansion pistons (30) of the expansion part on the remote from the compressor pistons (28) rear side of the lifting plate (50) are arranged and guided in an expansion cylinder block (16), the refrigerant inlet and outlet controls Expansion cylinder (24) of the expansion cylinder block (16) via a control disc (92).

8. Piston compressor according to claim 6 or 7, wherein the lifting plate is a swash plate of a swash plate machine or a swash plate (50) of a swash plate machine.

9. Piston compressor according to claim 8, wherein the geometric volume of the expansion part is less than that of the compressor (10).

10. Piston compressor according to claim 8 or 9, wherein each compressor cylinder (25) is assigned an expansion cylinder (24).

11. Piston compressor according to claim 10, wherein a part of the expansion cylinder (25) is designed as an idle cylinder and thus does not contribute to the enthalpy decrease in the refrigerant.

12. Piston compressor according to claims 7 and 11, wherein the connection between the idle cylinders of the expansion part and the control disc (92) is blocked by an intermediate plate (82).

13. Piston compressor according to claim 10 and 11, wherein four compressor cylinders (25) are arranged coaxially with one expansion cylinder (24), two expansion cylinders being designed as idle cylinders.

14. Piston compressor according to one of the preceding claims, wherein each compressor cylinder (25) has inlet and outlet valves (74, 78).

15. Piston compressor according to one of the claims 10 to 14, characterized in that the pistons (28, 30) via sliding shoes (58) are supported on the lifting disc (50), the sliding shoes (58) of the compressor piston (28) with those of the associated expansion piston (30) are connected via a connecting element (62).

16. Piston compressor according to one of the preceding claims, wherein the bore diameter of the expansion cylinder (24, 152) is smaller than the diameter of the compressor cylinder (25, 142).

17. Piston compressor according to one of the preceding claims, wherein the refrigerant is CO2.