Heat pump

Abstract

The invention relates to a heat pump for heating and cooling a building, having a refrigerant circuit (100) which contains a first heat exchanger (1), in particular a lamellar heat exchanger, a second heat exchanger (3), in particular a plate heat exchanger, an expansion element (5), and a reciprocating-piston compressor (2), the reciprocating-piston compressor (2) being situated between the first heat exchanger and the second heat exchanger and being configured to convey a refrigerant in the refrigerant circuit (100) and, in the process, to compress said refrigerant from a first pressure level to a second pressure level.

Description

[0001] heat pump

[0002] The present invention relates to a heat pump for heating and cooling a building with a refrigerant circuit comprising a first heat exchanger, a second heat exchanger, an expansion element and a reciprocating compressor.

[0003] Background of the invention

[0004] Heat pumps make it possible to use freely available energy from the environment to heat and / or cool a building, thus contributing to the reduction of CO2 emissions in the building sector. In particular, a heat pump can be used for both heating and cooling because the heat exchangers contained in the refrigerant circuit can function as both evaporators and condensers. For example, by reversing the flow direction of the refrigerant circuit, a heat exchanger that acts as a condenser in heating mode can function as an evaporator in cooling mode, and vice versa. This allows, for example, a secondary circuit of the corresponding heat exchanger to release heat to the building in heating mode and absorb heat from the building in cooling mode.

[0005] A refrigerant circuit in heat pumps of this type also includes a compressor designed to circulate refrigerant within the circuit and compress it from a lower to a higher pressure level. Positive displacement compressors are typically used, which compress the refrigerant in a closed working chamber either through rotary or translational motion. Typical rotary compressors are scroll, rotary piston, or screw compressors, while reciprocating compressors compress the refrigerant in at least one cylinder through the translational motion of at least one piston within that cylinder. Scroll compressors, which contain a stationary and an eccentrically rotating spiral, are frequently used in heat pumps of this type, particularly due to their low noise emissions.However, compared to reciprocating compressors, these exhibit lower efficiency at high pressures and are also less robust at high pressures and temperatures. Furthermore, vibrations occur, particularly at high speeds, due to the eccentrically rotating spiral.

[0006] Since current requirements for heat pumps, such as the provision of high flow temperatures to enable heating of existing buildings, and / or the use of climate-friendly refrigerants (e.g., CO2), necessitate a compressor with a high pressure ratio, the use of a reciprocating compressor could be advantageous in the future. Furthermore, reciprocating compressors are already widely used, for example, in the refrigeration circuits of air conditioning systems in motor vehicles, and are therefore a proven and cost-effective alternative to scroll compressors.

[0007] In this context, EP 0 447 027 Bl discloses a compressor for air conditioning systems in motor vehicles, comprising a housing in which a plurality of cylinders are arranged. Inlet and outlet valve plates for supplying and removing refrigerants to and from the cylinders are arranged on the end faces of the housing. The cylinders are arranged at equal intervals around a radius around the drive shaft, and a piston is slidably mounted in each cylinder, which is moved back and forth by means of a swashplate. The swashplate is rigidly connected to a drive shaft of the air conditioning compressor and arranged at an angle to it. The drive shaft is supported in the housing by means of radial needle bearings.

[0008] Due to the angular arrangement of the swashplate, for example, a piston on one side of the swashplate can move towards its top dead center to compress refrigerant (compression stroke), while at the same time a piston on the opposite side of the swashplate can move towards its bottom dead center to draw in refrigerant (suction stroke).

[0009] However, the angular arrangement of the swashplate also means that after every half revolution of the drive shaft, the bending moment and the resulting vertical bearing forces change direction. These changing bearing forces can lead to structural vibration, which is transmitted to the housing via the bearings and can cause undesirable vibrations in the compressor. Such vibration excitation must be avoided when using a reciprocating compressor in a heat pump in order to meet its requirements for low noise emissions.

[0010] One object of the present invention is to provide a heat pump that has improved efficiency and robustness without compromising comfort and noise emissions.

[0011] To solve the problems, the characteristics of independent claims are proposed. Advantageous variations can be found in dependent claims.

[0012] Disclosure of the invention

[0013] A heat pump according to the invention for heating and cooling a building has a refrigerant circuit in which a refrigerant circulates. The heat pump can, for example, be designed as an air-to-water heat pump with an outdoor unit and an indoor unit. Alternatively, the heat pump can, for example, be a brine-to-water heat pump. Any other type of heat pump is also possible.

[0014] The refrigerant circuit comprises a first heat exchanger, which can, for example, use ambient air as a heat source and heat sink, and a second heat exchanger, which can, for example, use the building's heating / cooling circuit as a heat source and heat sink. For heating the building (heating mode of the heat pump), the first heat exchanger can function as an evaporator and the second as a condenser; for cooling the building (cooling mode of the heat pump), the second heat exchanger can function as an evaporator and the first as a condenser. The first heat exchanger can be, in particular, a finned heat exchanger, which can be installed, for example, in the outdoor unit of the heat pump. The second heat exchanger can be, in particular, a plate heat exchanger, the secondary side of which can be connected to the building's heating / cooling circuit. Alternatively, the second heat exchanger can also be a finned heat exchanger.

[0015] Furthermore, the refrigerant circuit includes a reciprocating compressor, which is arranged between the first and second heat exchangers and is designed to circulate a refrigerant within the circuit, compressing it from a first pressure level to a second pressure level. The refrigerant circuit also includes an expansion element, which can be advantageously arranged between the second and first heat exchangers.

[0016] In heating mode, the reciprocating compressor of the heat pump can be located downstream of the first heat exchanger and upstream of the second heat exchanger, and the expansion element can be located downstream of the second heat exchanger and upstream of the first. In cooling mode, the refrigerant flow direction can be reversed, so that in this case the reciprocating compressor can be located downstream of the second heat exchanger and upstream of the first, and the expansion element can be located downstream of the first heat exchanger and upstream of the second. The expansion element can be any type of throttling element, in particular a thermostatic or electronic expansion valve.

[0017] Additionally, the refrigerant circuit may include a directional control valve, which can be configured to reverse the flow direction of the refrigerant within the circuit, thus switching the heat pump from heating to cooling mode and vice versa. This directional control valve could, for example, be a 4 / 2-way valve.

[0018] The function of the refrigerant circuit described above, with the components mentioned, is known to experts and is therefore not explained in more detail here.

[0019] The reciprocating compressor comprises a drive shaft and at least two cylinders, each with at least one piston, arranged on a radius around the drive shaft offset from each other by 180° and extending parallel to it. Specifically, in a longitudinal section of the reciprocating compressor, the at least two cylinders are arranged opposite each other on both sides of the drive shaft, parallel to it and at an equal distance from it. The drive shaft is expediently supported in the reciprocating compressor by means of suitable bearings, e.g., plain bearings, roller bearings, needle bearings, etc.

[0020] The following refers to two cylinders arranged on a radius around the drive shaft, offset from each other by 180° and extending parallel to it, also referred to as "radially opposed cylinders". The at least two cylinders can advantageously have the same bore diameter and their pistons the same geometric shape. In particular, the pistons can have the same piston diameter and their piston crowns can be identically designed.

[0021] Furthermore, the reciprocating compressor includes at least one transmission device that translates a rotary motion of the drive shaft into a reciprocating motion of the pistons in the at least two cylinders, during which they travel the same piston stroke. In other words, the pistons in two radially opposite cylinders, driven by a transmission device, move the same amount in the same direction. The piston stroke (maximum piston travel between its two dead centers) of these pistons is also expediently identical.

[0022] Consequently, the same working stroke (intake or compression stroke) always occurs in these cylinders, and the pistons always assume the same axial position. Since the axial forces on the pistons act on the drive shaft with equal magnitude but opposite lever arms, no resulting bending moment occurs on the shaft. As a result, no vertically directed dynamic forces are generated at the drive shaft bearings, thus preventing or at least reducing vibrations and oscillation excitations emanating from the reciprocating compressor. This significantly reduces the noise emissions of the heat pump.

[0023] According to one embodiment, the at least one transmission device of the reciprocating compressor can move the pistons in the at least two cylinders for at least two stroke cycles per revolution of the drive shaft (double stroke). A stroke cycle can comprise an intake stroke and a compression stroke, whereby a piston can move from its top dead center to its bottom dead center during the intake stroke and from its bottom dead center to its top dead center during the compression stroke. The top dead center of a piston is defined here as the dead center at which a working chamber in a cylinder, in which the piston moves translationally, has its smallest volume. Accordingly, the bottom dead center of a piston is defined as the dead center at which the working chamber has its largest volume. The drive shaft can complete a rotational angle of 360° per revolution, and the at least two stroke cycles can occur uniformly across this angle of rotation.For example, in the case of two stroke cycles, a first intake stroke can occur within a range of 0° to 90° and a first compression stroke within a range of 90° to 180° rotational angle. A second intake stroke can then occur within a range of 180° to 270° and a second compression stroke within a range of 270° to 360° rotational angle. If a first intake or compression stroke occurs in one of the at least two radially opposite cylinders, the second intake or compression stroke can occur in the other, and vice versa.

[0024] This allows the refrigerant flow rate per drive shaft revolution to be doubled compared to a reciprocating compressor with a conventional swashplate, while maintaining the same number and geometric design of cylinders and pistons. This increases the efficiency of the heat pump, as the reciprocating compressor can, for example, operate at a lower speed, thereby reducing friction losses.

[0025] According to one embodiment, the number of cylinders in the reciprocating compressor and the number of stroke cycles per revolution of the drive shaft can be even. Two cylinders can be arranged radially opposite each other, each traveling the same piston stroke. The number of cylinders can range, for example, from two to twelve.

[0026] In particular, the number of cylinders in the reciprocating compressor can correspond to the number of strokes per revolution as an even multiple or an even subset of the number of strokes. An even multiple of the number of strokes is obtained by multiplying the number of strokes by an even number. Likewise, an even subset of the number of strokes is obtained by dividing the number of strokes by an even number. For example, if the reciprocating compressor's transmission provides two strokes per revolution of the drive shaft, the number of cylinders in the aforementioned range can be two, four, eight, or twelve.

[0027] According to one embodiment, the at least one transmission device of the reciprocating compressor can comprise at least one cam disk and at least two piston rods. Advantageously, the number of piston rods can equal the number of pistons. The at least one cam disk can extend radially essentially perpendicular to the drive shaft and, to realize the two stroke cycles of each piston, have a correspondingly shaped cam track on at least one of its surfaces. For example, the cam disk can have at least two radially opposite, e.g., cam-shaped projections on one surface, each adjacent to a corresponding recess. Any other shape of projection, e.g., trapezoidal, stepped, etc., is equally possible. By means of two opposing projections, two stroke cycles per revolution can be realized in each cylinder.To ensure that the pistons in the at least two cylinders travel the same distance, the shape of the at least two opposing protrusions and the adjacent depressions can be identical. A maximum point of each protrusion on the surface of the cam can correspond to the top dead center of a piston, and a minimum point of each depression can correspond to the bottom dead center. It is also possible for the cam to have a multitude of opposing protrusions. In particular, the number of stroke cycles, as described above, can be determined by the number of opposing protrusions.

[0028] Advantageously, the cam disc is connected to the drive shaft in such a way that it does not move relative to it. The cam disc can be rigidly connected to the drive shaft, for example, by being pressed into it. Alternatively, the cam disc can be connected to the drive shaft by means of a suitable positive-locking connection, such as a splined connection, or by any other suitable connection. It is also possible for the drive shaft and the at least one cam disc to be formed as a single piece.

[0029] The piston rods can be connected to the pistons at one side / end in a known manner, e.g., by means of piston pins, and at the opposite side / end to the at least one cam disk. The latter can be achieved in particular by means of rollers or sliding blocks that are attached to / in the piston rods and can interact with at least one surface of the at least one cam disk.

[0030] For example, one or more rollers can be rotatably mounted on one end of each piston rod facing the cam, allowing them to roll on the cam's surface. The rolling of the piston rods on the cam can be initiated by rotating the drive shaft, resulting in an up-and-down or back-and-forth motion of the pistons following the cam track. It is also possible for the cam track to be mounted on two cams (e.g., as a cam and counter-cam track), with, for example, one of several rollers at the ends of the piston rods rolling on one cam and another roller rolling on the other.

[0031] Alternatively, the piston rods can, for example, include a pair of sliding blocks that can slide over opposing surfaces of a cam. In this case, the surfaces of the cam can be parallel to each other to form the cam track, and the pair of sliding blocks can, for example, enclose an outer circumference of the cam.

[0032] According to one embodiment, a first and a second piston can be arranged in each of the cylinders of the reciprocating compressor. A first transmission device can move the first piston and a second transmission device can move the second piston in each cylinder. The first and second pistons can be axially opposed to each other and have a predetermined distance from each other at top dead center or bottom dead center. In particular, the first transmission device can drive a number of first pistons corresponding to the number of cylinders, and the second transmission device can drive a number of second pistons corresponding to the number of cylinders. The transmission devices can be axially spaced from each other and mounted opposite each other on the drive shaft.

[0033] According to one embodiment, the first and second transmission devices of the reciprocating compressor can move the first and second pistons by the same amount of piston travel in opposite directions. In other words, the first and second pistons in one of the at least two cylinders can move towards or away from each other by the same amount, starting from their bottom dead center. In particular, the first and second transmission devices can be identical and have the same components (cams, piston rods, rollers / sliding blocks, etc. with the same geometry).

[0034] Due to the two counter-rotating pistons in the two axially opposed cylinders, the axial forces acting on the pistons, in addition to the vertically directed dynamic forces on the drive shaft bearings, also cancel each other out. As a result, no dynamic forces from the translational movement of all pistons affect the drive shaft bearings, further reducing vibrations of the reciprocating compressor.

[0035] According to one embodiment, at least one working chamber can be arranged in each cylinder of the reciprocating compressor. If the cylinders contain a first and a second piston, then, for example, a single working chamber can be located between the two pistons.

[0036] In this embodiment, the first and second transmission devices of the reciprocating compressor can move the first and second pistons in opposite directions to compress the refrigerant in the refrigerant circuit, thus reducing the distance between the two pistons. In other words, the first and second pistons in each cylinder can move synchronously towards each other from their bottom dead center and jointly compress the refrigerant in the working chamber. The first and second pistons of the reciprocating compressor can be arranged in their respective cylinders such that their piston crowns face each other. The common working chamber can be located inside the reciprocating compressor, and the pistons can move from the outside inwards to compress the refrigerant. For this purpose, the two transmission devices can be arranged on opposite end faces of the reciprocating compressor.

[0037] The first and second pistons can simultaneously reach their top dead center, and the compressed refrigerant in the working chamber can conveniently be expelled through a single outlet element. To draw refrigerant into the working chamber, the first and second transmission devices can move the first and second pistons synchronously from their top dead center to their bottom dead center. The refrigerant can also enter the working chamber, for example, through a single inlet element. The inlet and outlet elements can be valves, such as reed valves. Any other suitable valve type is also possible.

[0038] This embodiment allows for a particularly compact design of the reciprocating compressor, in which dynamically acting forces are almost completely balanced, resulting in no or only very slight vibrations. This increases the robustness and longevity of the heat pump. According to a further embodiment, it is also possible for each cylinder to contain a working chamber per piston. In this embodiment, the first piston can be arranged in a first working chamber and the second piston in a second working chamber of the cylinder. For this purpose, the cylinders can, for example, have at least one cylinder head plate by means of which the two working chambers in the cylinders can be formed. Separate inlet and outlet elements for each working chamber can be included / integrated in the at least one cylinder head plate.It is also possible that one inlet and one exhaust valve plate for the first and second working chambers of all cylinders are attached to the at least one cylinder head plate.

[0039] A working chamber per piston in a cylinder is particularly advantageous when the first and second pistons move synchronously away from each other from their bottom dead center. In this embodiment, the first and second transmission devices of the reciprocating compressor can move the first and second pistons in opposite directions to compress the refrigerant in the refrigeration circuit, thereby increasing the distance between the two pistons. The piston crowns of the first and second pistons can be facing away from each other.

[0040] In this case, the first and second working chambers of the cylinders can be located at a distance from each other at the two end faces of the reciprocating compressor and each be closed off to the outside by a cylinder head plate. The two transmission devices, on the other hand, can be arranged inside the reciprocating compressor and move the pistons synchronously from the inside to the outside to compress the refrigerant. Advantageously, the first and second transmission devices can be configured to separate the first and second working chambers of the cylinders from each other inside the reciprocating compressor. Each cylinder head plate can, in turn, include inlet and outlet elements to draw refrigerant, e.g., from a common inlet channel, into the individual working chambers and to discharge compressed refrigerant into a common outlet.

[0041] to push out the outlet channel.

[0042] Since the first and second pistons of each cylinder move in opposite directions in this embodiment as well, dynamically acting forces almost completely cancel each other out, and the reciprocating compressor causes no or very little vibration, which can improve the robustness and longevity of the heat pump.

[0043] According to one embodiment, the reciprocating compressor can comprise a housing that seals it hermetically or semi-hermetically. The drive shaft, the cylinders with the pistons, and the transmission device(s) can be at least partially arranged within the housing. The degree of hermetic sealing of the housing can be adapted to the boundary conditions of the heat pump. To seal the reciprocating compressor semi-hermetically, individual parts of the housing can be bolted together, for example, using suitable gaskets. For a hermetic seal, the individual parts of the housing can be welded together, for example. The drive shaft can be driven by a drive motor, in particular an electric motor. The drive motor can, in particular, be speed-controlled.

[0044] In one embodiment, the drive motor can be located within the housing between the first and second working chambers of the cylinders. For example, the drive motor can be arranged between the first and second transmission devices if these separate the working chambers inside the reciprocating compressor and move the pistons from the inside to the outside to compress the refrigerant. If the two transmission devices are located at the end faces of the reciprocating compressor and the pistons have a reverse direction of action, the first and second working chambers inside the reciprocating compressor can each be provided with a separate cylinder head plate, between which the drive motor can be arranged.

[0045] If the drive motor is located inside the housing, one or more inlet ports, through which refrigerant is drawn into the cylinder working chambers, can be arranged adjacent to the drive motor so that heat can be transferred from it to the refrigerant. It is also possible for one or more outlet ports, through which compressed refrigerant exits the reciprocating compressor, to be arranged adjacent to the drive motor.

[0046] The inlet and / or outlet channels can also be adjacent to the two transmission units to transfer additional heat to the refrigerant, for example, through their mechanical friction. In this way, the refrigerant temperature can be raised by waste heat from the drive motor and the transmission units, thus further increasing the efficiency of the heat pump. In particular, the additional heat input from the drive motor and the transmission unit can reduce superheating in the heat exchanger acting as an evaporator, thereby increasing its efficiency.

[0047] In summary, the use of the described reciprocating compressor, whose dynamic forces are almost balanced due to the arrangement of its pistons, enables improved efficiency and robustness of the entire heat pump. Additionally, it makes it possible to meet the requirements for comfort and noise emissions of the heat pump. Brief description of the figures

[0048] Figure 1 schematically shows a refrigerant circuit of a heat pump for heating and cooling a building according to an embodiment of the invention.

[0049] Figures 2a and 2b show schematic representations of a reciprocating compressor of a heat pump not according to the invention and of a reciprocating compressor that can be used in an embodiment of the heat pump according to the invention.

[0050] Figure 3 schematically shows a principle representation of another reciprocating compressor that can be used in an embodiment of the heat pump according to the invention.

[0051] Figures 4a to 4c schematically show specific embodiments of the reciprocating compressor from Figure 3.

[0052] Figures 5a and 5b show further embodiments of reciprocating compressors that can be used in an embodiment of the heat pump according to the invention.

[0053] Detailed description of preferred embodiments

[0054] Exemplary embodiments of the present invention are described in detail below with reference to exemplary figures. The features of the exemplary embodiments can be combined in whole or in part, and the present invention is not limited to the described exemplary embodiments. In the figures, identical or comparable elements are provided with the same reference numerals, so that a repeated description of the elements is omitted unless necessary.

[0055] Figure 1 schematically shows a refrigerant circuit 100 of a heat pump for heating and cooling a building according to an embodiment of the invention.

[0056] The refrigerant circuit 100 shown contains a first heat exchanger 1, a compressor 2, which is designed as a reciprocating compressor 2, a 4 / 2-way valve 6, a second heat exchanger 3, a refrigerant receiver 4, and an expansion valve 5.

[0057] The individual components of the refrigerant circuit 100 are connected by refrigerant lines (not specified in detail). Solid arrows indicate the flow direction in the refrigerant circuit 100 for heating the building (heating mode of the heat pump), and dashed arrows indicate the flow direction for cooling the building (cooling mode of the heat pump). In heating mode, the first heat exchanger 1 acts as an evaporator and the second heat exchanger 3 as a condenser. In cooling mode, the functions of the first and second heat exchangers 1 and 3 are reversed.

[0058] A pressure sensor 1.1 and a temperature sensor 1.2 are arranged between the first heat exchanger 1 and the compressor 2. Downstream of the compressor 2, a further temperature sensor 2.1, a further pressure sensor 2.2, and a high-pressure safety switch 2.3 are arranged. The illustrated temperature and pressure sensors 1.1 to 2.3 can be used in a known manner for controlling and monitoring the expansion valve 5 and the compressor 2 during the heating and cooling operation of the heat pump.

[0059] The two heat exchangers 1 and 3 shown can each utilize a different heat source or heat sink during heating and cooling operation of the heat pump. The first heat exchanger 1 can use ambient air as both a heat source and a heat sink and can therefore be designed as a finned heat exchanger. The second heat exchanger s can use the building's heating / cooling circuit as both a heat source and a heat sink and is therefore designed as a plate heat exchanger and connected on its secondary side to a supply line (VL) and a return line (RL) of the heating / cooling circuit. However, the second heat exchanger 3 can also be designed as a finned heat exchanger and use air inside the building as both a heat source and a heat sink.

[0060] In heating mode, the heat pump's gaseous refrigerant flows along the solid arrows from the first heat exchanger 1, where it has absorbed heat from the ambient air, through the 4 / 2-way valve 6, to the compressor 2. The 4 / 2-way valve 6 has two different positions, the corresponding flow paths of which are indicated by two solid and two dashed lines. In heating mode, the 4 / 2-way valve 6 is in a position where the refrigerant flows through it along both solid paths.

[0061] In compressor 2, the refrigerant is compressed from a first pressure level to a second pressure level and flows as hot gas from compressor 2 through the 4 / 2-way valve 6 into the second heat exchanger 3. Figures 2b to 5b describe embodiments of the reciprocating compressor 2 used here in detail. This compressor is characterized in particular by its smooth operation due to a balanced force and moment distribution of its moving components. This significantly reduces noise emissions from the heat pump.

[0062] In the second heat exchanger, the refrigerant is liquefied, thereby transferring the heat absorbed in the first heat exchanger 1 to the building's heating / cooling circuit (see arrows VL, RL, indicating the flow and return of the heating / cooling circuit). The condensed refrigerant then flows from the second heat exchanger 3 into the refrigerant receiver 4 and from there to the expansion valve 5. The refrigerant receiver 4 uses gravity to separate the liquid phase of the two-phase refrigerant exiting the second heat exchanger 3 from the gaseous phase, ensuring that only liquid refrigerant enters the expansion valve 5. The expansion valve 5 then reduces the pressure of the liquid refrigerant to an outlet pressure, allowing it to revert to a gaseous state in the first heat exchanger 1 and absorb heat in the process.

[0063] To reverse the refrigerant circuit 100, the 4 / 2-way valve 6 can be switched to a second position, in which the refrigerant flows through it along the paths indicated by the dashed lines. The 4 / 2-way valve also assumes this position in the cooling mode of the heat pump, in which the second heat exchanger 3 operates as an evaporator and the first heat exchanger 1 as a condenser.

[0064] In cooling mode, the heat pump's gaseous refrigerant flows along the dashed arrows from the second heat exchanger 3, where it has absorbed heat from the building's heating / cooling system, via the 4 / 2-way valve 6, to the reciprocating compressor 2. In the compressor, the refrigerant is compressed and then flows as hot gas via the 4 / 2-way valve 6 into the first heat exchanger 1, where it liquefies and releases the heat absorbed in the second heat exchanger 3 to the ambient air. The liquid refrigerant then flows to the expansion valve 5, where it is expanded to the outlet pressure, allowing it to return to a gaseous state in the second heat exchanger 3 and absorb heat again. The refrigerant receiver 4 is located downstream of the expansion valve 5 in this case and is therefore inactive.Therefore, in this case, sufficient subcooling of the refrigerant in the first heat exchanger 1 must be ensured in order to supply liquid refrigerant to the expansion valve 5. Figures 2a and 2b schematically show a principle representation of a reciprocating compressor of a heat pump not according to the invention and of a reciprocating compressor that can be used in an embodiment of the heat pump according to the invention.

[0065] In particular, Figure 2a shows a schematic representation of a swashplate reciprocating compressor 2', which in this case has two pistons 26 arranged in cylinders (not shown) offset by 180° crank angle on a radius around a drive shaft 20 (radially opposite pistons and cylinders). The pistons 26 are each connected via a piston rod 25 to a swashplate 24', which in turn is connected to the drive shaft 20. The swashplate 24' extends perpendicular to the drive shaft, forming two lever arms 24a', 24b'. The drive shaft 20 is supported in a fixed bearing 29a and a floating bearing 29b and is driven by a drive motor 250.

[0066] By means of the swashplate 24', a rotational movement of the drive shaft 20 with the angle of rotation O is converted into a translational movement x of the pistons 26. One of the two pistons 26 moves from its top dead center (TDC) towards its bottom dead center (BDC) (positive x-direction) to draw in refrigerant and is accelerated with an acceleration x. The intake movement x of piston 26 is opposed by an intake force Fintake and a weight force m ■ x of piston 26. The other piston 26 is at its bottom dead center (BDC) and moves towards its top dead center (TDC) (negative x-direction) to compress and expel the refrigerant. This piston 26 is accelerated with an acceleration -x. The extension movement -x of piston 26 is opposed by an extension force Fextension and a weight force m - x of piston 26.The forces acting on the pistons 26, fan suction and fan thrust, result in a dynamically varying axial force FA.H, which is absorbed by the fixed bearing 29 and depends on the direction of movement of the pistons 26. These forces also cause F. a n suck,

[0067] Faustrieb via the lever arms 24a', 24b' of the swashplate 24' a bending moment Mßiegung on the drive shaft 20, which opposes vertical bearing forces F v , F B , V at the two bearings 29. In this process, one direction of these vertical bearing forces FA.V, F changes. B , VThis occurs every 180° rotation angle, i.e., with every half turn of the drive shaft 20, since the pistons 26 change their direction at each rotation angle. This periodic change in the direction of force generates a structural vibration, which is transmitted via the bearings 29a, 29b to a housing (not shown here) of the reciprocating compressor 2' and thus generates a vibration excitation that can lead to undesirable noise emissions from the heat pump.

[0068] In contrast, Figure 2b shows a schematic representation of a reciprocating compressor 2, which can be used in an embodiment of the heat pump according to the invention.

[0069] The reciprocating compressor 2 shown here differs from the one shown in Figure 2a in that it contains a cam disk 24 instead of a swashplate 24'. This cam disk is designed such that it converts a rotary motion of the drive shaft 20 with the angle of rotation O via the piston rods 25 into a translational motion x of the pistons 26 such that they travel the same piston stroke x. Consequently, the two pistons 26 always assume the same axial position x.

[0070] In this case, both pistons 26 are at their top dead center (TDC) and move synchronously towards their bottom dead center (BDC) (positive x-direction) to draw in refrigerant. Thus, both pistons 26 perform an intake stroke during half a revolution of the drive shaft 20, whereas in the swashplate reciprocating compressor 2' shown in Figure 2a, one piston 26 performs an intake stroke and the other a compression stroke. The intake movement x of the two pistons 26 of the reciprocating compressor 2 shown in Figure 2b is each subjected to a suction force F. an Suction and a weight force m ■ x of the respective piston 26 oppose it. If the pistons 26 both move from their bottom dead center (BDC) towards their top dead center (TDC) in the subsequent compression stroke, a thrust force Ffausschub and a weight force m ■ x of the respective piston 26 oppose them (not shown). The forces F acting on the pistons 26 an suction, Fau Thrust, in turn, has a dynamically changing force in the axial direction F. A h This is also absorbed by the fixed bearing 29. However, since the piston forces F intake and F exhaust act on the drive shaft 20 with lever arms 24a and 24b of the piston disk 24 of equal magnitude but acting in opposite directions, due to the design of the piston disk, no resultant bending moment occurs at the drive shaft 20 (Mbending = 0). Consequently, no vertically directed dynamic forces (FA V=FB) arise. V =0) at the bearings 29 of the drive shaft 20, which can prevent or at least reduce vibrations and oscillation excitations emanating from the reciprocating compressor 2.

[0071] Figure 3 schematically shows a principle representation of another reciprocating compressor that can be used in an embodiment of the heat pump according to the invention.

[0072] In particular, Figure 3 shows a reciprocating compressor 2 which contains two of the reciprocating piston units 220 shown in Figure 2, which are axially opposed to each other. Both reciprocating piston units 220 are arranged on a drive shaft 20, which is supported in a fixed bearing 29a and a floating bearing 29b and is driven by a drive motor 250.

[0073] The two piston units 220 are arranged opposite each other on the drive shaft 20 such that their pistons 26 and cylinders 28 (see Figure 5a) are opposite each other, with the opposing pistons 26 and cylinders 28 having a common central axis 26a (axially opposite pistons 26 and cylinders 28). The piston crowns of axially opposite pistons 26, which are not further specified, face each other.

[0074] In both piston units 220 shown, the pistons 26 are at their top dead center (TDC) and move towards their bottom dead center (BDC) to draw in refrigerant. In other words, both the radially and axially opposite pistons 26 perform the same working stroke, namely a suction stroke. During this stroke, the pistons 26 of the left piston unit 220 move in the positive Xi direction and experience an acceleration x. lt while the pistons 26 of the right-hand piston unit 220 move in the positive X2 direction and experience an acceleration x2. In other words, the pistons 26 of the two piston units 220 move synchronously outwards away from each other during an intake stroke and synchronously inwards towards each other during a compression stroke.

[0075] With regard to the vertical bearing forces FA.V, FB, VThe same applies to both piston units 220 as to the one shown in Figure 2, namely a cancellation of the same by the cancellation of the bending moment Mbending due to the opposing lever arms 24a, 24b with which the piston forces act on the drive shaft 20.

[0076] By using two opposing piston units 220 as described above, the dynamically changing axial force components of axially opposed pistons 26 cancel each other out. In other words, it follows from the described axially opposed arrangement of the piston units 220 that the resulting axial bearing force F is also hThe equation is zero. Therefore, no dynamic forces from the translational movement of all pistons 26 affect the bearings 29 of the drive shaft 20, and consequently, none affect the housing of the reciprocating compressor 2. As a result, no vibrations are generated by the compressor, and the noise emissions of the heat pump can be significantly reduced. Figures 4a to 4c schematically show specific embodiments of the reciprocating compressor from Figure 3.

[0077] Figure 4a shows a reciprocating compressor 2 with a housing 21 in which two axially opposed reciprocating piston units 220 are arranged according to the schematic diagram in Figure 3. Each reciprocating piston unit 220 comprises a transmission device 240, which is rigidly connected to the drive shaft 20. The transmission devices 240 of the two reciprocating piston units 220 are identical.

[0078] The drive shaft 20 is supported in the housing 21 by bearings 29 and protrudes from one side of the housing 21 so that it can be connected to a drive motor 250 located outside the housing 21. The two bearings 29 are each located in opposite end faces of the housing 21. In this case, each piston unit 220 contains four pistons 26, each of which moves back and forth in a corresponding cylinder 28. The cylinders 28 extend in the housing 21 parallel to the drive shaft 20, and in each cylinder 28, two pistons 26 from axially opposite piston units 220 are arranged, with their piston heads (not specified) facing each other. The pistons 26 have piston rings (not specified) which seal a working chamber in the cylinder 28 between the piston heads.

[0079] The four cylinders 28 are arranged around the drive shaft 20 on a radius R. In other words, a central axis of the cylinders 28 lies on a circumference with radius R, which has the drive shaft 20 as its center point (indicated by the double arrows labeled R). Two cylinders are arranged on the circumference at 180° intervals. These are subsequently referred to as radially opposite cylinders 28. In this example, the pistons 26 in two visible, opposite cylinders 28 are at top dead center (TDC), while the pistons of two other radially opposite cylinders, of which only one is visible, are at bottom dead center (BDC).

[0080] The translation device 240 of each of the two reciprocating piston units 220 is, according to the principle shown in Figure 3, designed to translate a rotary movement of the drive shaft 20 into a reciprocating movement of the pistons 26 in the two radially opposite cylinders in such a way that they travel the same piston path.

[0081] Each of the two transmission devices 240 in Figure 4a comprises a first cam disk 24a and a second cam disk 24b, which are arranged axially spaced apart from each other on the drive shaft 20 and extend substantially perpendicular to it. The first cam disk 24a has a larger diameter than the second cam disk 24b. The first cam disk 24a abuts the bearing 29 in the end face of the housing 21, and a cam track 24u of the first cam disk 24a is located on a surface of the first cam disk 24a facing away from the bearing 29. The second cam disk 24b is located opposite the cam track 24u of the first cam disk 24a on the drive shaft 20 and also has a cam track 24o on a surface facing it, which forms a counter-cam track to the cam track 24u of the first cam disk 24a.

[0082] Each transmission device 240 also has four piston rods 25, each of which is connected at one end to the associated piston 26 by means of a piston pin (not specified in detail) and has two rollers 23 at the opposite end, of which a radially outer roller rolls on the cam track 24u of the first cam disk 24a and a radially inner roller rolls on the cam track 24o of the second cam disk 24b. The outer roller is mounted in a recess within the piston rod 25, and the inner roller is mounted on a side of the piston rod 25 facing the drive shaft 20.

[0083] The rolling motion of the piston rods 25 on the two cam discs 24a, 24b can be initiated by a rotation of the drive shaft 20, resulting in a reciprocating motion of the pistons following the two cam tracks 24u, 24o. The cam tracks 24u, 24o on the first and second cam discs 24a, 24b can be designed such that each piston 26 performs two stroke cycles per revolution of the drive shaft 20 (double stroke). In other words, each piston 26 can draw in and compress refrigerant twice per drive shaft revolution, with an axial force being transmitted in the corresponding direction from the cam discs 24a, 24b via the rollers 23 to the piston rods 25 with the pistons 26. The drive shaft 20 can complete a rotation angle θ of 360° per revolution, and the two stroke cycles can be uniform across this rotation angle θ.For example, a first intake stroke can occur within a range of 0° to 90° and a first compression stroke within a range of 90° to 180° rotational angle. A second intake stroke can then occur within a range of 180° to 270° and a second compression stroke within a range of 270° to 360° rotational angle.

[0084] This allows the refrigerant delivery rate per drive shaft revolution to be doubled compared to a swashplate compressor 2', while maintaining the same number and geometric design of cylinders 28 and pistons 26. In this way, the efficiency of the heat pump can be increased, as the reciprocating compressor 2 can, for example, be operated at a lower speed, thereby reducing friction losses.

[0085] To realize the two stroke cycles of each piston 26, the cam tracks 24o, 24u on the first and second cam disks 24a, 24b can be designed accordingly. In this case, the first cam disk 24a has two opposing plateau-shaped elevations 24h, at the maximum point of which a piston 26 is moved to its top dead center (TDC) via the rollers 23 and the piston rod 25.

[0086] Each of the plateau-shaped elevations 24h is bordered by a depression 241, at the minimum point of which a piston 26 is moved to its bottom dead center. The two elevations and depressions are symmetrically distributed over the circumference of the first cam disk 24a, so that the pistons 26 complete two uniform stroke cycles over the rotation angle O of the drive shaft.

[0087] In this arrangement, each cylinder 28 has a single working chamber into which refrigerant is drawn in via the valve 27 by a movement of the two axially opposed pistons 26 from their top dead center (TDC) towards their bottom dead center (BDC). Subsequently, by a reverse movement of the opposing pistons 26, the drawn-in refrigerant is compressed in the working chamber and expelled again via the valve 27. In particular, each working chamber can also have at least one inlet valve (not shown) and at least one outlet valve (not shown). The inlet and outlet valves can be positioned between the working chamber of each cylinder 28 and the valve 27. The at least one inlet valve can be arranged downstream of the valve 27 when refrigerant is drawn into the working chamber. Conversely, the at least one outlet valve can be arranged upstream of the valve 27 when refrigerant is expelled.

[0088] The reciprocating compressor 2 shown in Figure 4b differs from that in Figure 4a only in the design of the transmission device 240. This device comprises only one cam disk 24, which has two parallel cam tracks (primary and secondary) on two opposing outer surfaces. Two rollers 23 run on these tracks, both of which are mounted along a central axis of the piston rod 25 at its end furthest from the piston 26. The rollers 23 are spaced apart from each other in the axial direction of the piston rod 25, and the cam disk 24 is arranged between them. The cam tracks are arranged on an outer circumference of the cam disk 24 and are designed such that the pistons 26 complete two stroke cycles per drive shaft revolution.

[0089] The reciprocating compressor 2 shown in Figure 4c differs from those in Figures 4a and 4b only in the design of the transmission device 240.

[0090] This also comprises only one piston disk 24, which is similar to the one in Figure 4b and, analogously, has two parallel cam tracks 24o, 24u on opposite surfaces, forming a cam track 24o and a counter-cam track 24u. The cam tracks 24o, 24u are again arranged on an outer circumference of the cam disk 24, but instead of rollers 23, a pair of sliding blocks 23a is attached to the piston rod 25. Similar to the rollers 23 in Figure 4b, the two sliding blocks 23a are arranged axially spaced apart from each other in a recess in the piston rod 25 at an end of the piston rod 25 facing away from the piston 26. The cam disk 24 is located between the two sliding blocks 23a, so that they slide together over the cam track 24o and the counter-cam track 24u. Their contour is designed in such a way that the pistons perform two stroke cycles per drive shaft revolution.

[0091] Figures 5a and 5b show further embodiments of reciprocating compressors 2 that can be used in an embodiment of the heat pump according to the invention.

[0092] The reciprocating compressor shown in Figure 5a differs essentially from that in Figure 4c in that the drive motor 250 is arranged inside the housing between the two axially opposed reciprocating piston units 220. In this case, the drive shaft 20 no longer protrudes from the housing 21, but is enclosed by it. The housing 21 can be designed to be semi-hermetic or hermetically sealed. The ends of the drive shaft 20 serve to accommodate the cam discs 24 of the transmission device 240, and the bearings 29 of the drive shaft are arranged directly next to the drive motor 250.

[0093] By positioning the drive motor 250 between the two piston units 220, each piston 26 is assigned a separate working chamber in the cylinder 28. Specifically, a first working chamber is assigned to the cylinders 28 located on the left side of the drive motor 250, and a second working chamber is assigned to the cylinders 28 located on the right side of the drive motor. For this purpose, the cylinders 28 on both sides of the drive motor 250 are each closed by a cylinder head plate 28a. In this plate, inlet valves 27a and outlet valves 27b are installed for supplying and removing refrigerant to and from the cylinders 28. Adjacent to the inlet and outlet valves 27a and 27b in the cylinder head plate 28a are bores through which the refrigerant to be drawn in and discharged flows.Furthermore, the cylinder head plates 28a accommodate the bearings 29 arranged next to the drive motor 250.

[0094] The refrigerant to be drawn in is supplied to the reciprocating compressor 2 via a radial bore 27aa in the housing. From there, the refrigerant flows via the drive motor 250 or adjacent to it to the corresponding bores in the cylinder head plates 28a and through these via the inlet valve 27a into the cylinders 28, which are in the intake stroke.

[0095] Since the refrigerant being drawn in flows over the drive motor 250, it can absorb heat from it, thus raising the refrigerant's temperature even before it is compressed. Simultaneously, the incoming refrigerant provides cooling for the drive motor.

[0096] The drawn-in refrigerant can subsequently be compressed in the working chamber of the cylinders 28 and, at the end of the compression stroke, discharged via the exhaust valves 27b and the corresponding channels in the cylinder head plates 28 into a manifold 27ba. From there, the refrigerant flows to a further radial bore 27bb in the housing 21 and exits the reciprocating compressor through this bore. The manifold 27ba is arranged as a bore in the housing 21 adjacent to the drive motor compartment 21a, so that the exiting refrigerant can also absorb heat from the drive motor 250, thereby increasing the efficiency of the heat pump.

[0097] The reciprocating compressor 2 shown in Figure 4b differs from that in Figure 4a only in that the two reciprocating piston units 220 are arranged facing away from each other on the drive shaft 20. In particular, the piston crowns of the first and second pistons are, in this case, facing away from each other and from the drive motor 250, and the cylinder head plates 28a are arranged adjacent to the end faces of the housing 21. As a result, the flow paths for the refrigerant to be drawn in and discharged are arranged differently in the housing 21 of the reciprocating compressor 2.

[0098] The refrigerant to be drawn in is also supplied to the reciprocating compressor 2 via the radial bore 27aa. From there, it flows via the drive motor 250 and the transmission device 240 to the outer cylinder head plates 28a with the inlet valves 27a. In this configuration, the refrigerant to be drawn in can absorb heat from both the drive motor and the transmission device, which can be generated, for example, by friction on / in it, before it enters the cylinder. This can lead to a significant temperature increase of the refrigerant before compression.

[0099] The compressed refrigerant to be discharged flows through the outlet valves 27b in the cylinder head plates 28 into a manifold 27ba and from there out of the compressor 2 via the further radial bore 27bb. The manifold 27ba is also arranged as a bore in the housing 21 adjacent to the drive motor compartment 21a, so that the outgoing refrigerant can also absorb heat from the drive motor 250, thereby further increasing the efficiency of the heat pump. An arrangement of the reciprocating piston units 220 facing away from each other on the drive shaft 20, in which, in particular, the piston crowns of the first and second pistons 26 face away from each other, is not limited to an embodiment of the reciprocating compressor 2 in which the drive motor 250 is arranged in the housing 21, but can also be used in a reciprocating compressor 2 according to Figures 4a to 4c.

Claims

REQUIREMENTS 1. Heat pump for heating and cooling a building with a refrigerant circuit (100) comprising a first heat exchanger (1), in particular a finned heat exchanger, a second heat exchanger (3), in particular a plate heat exchanger, an expansion element (5) and a reciprocating compressor (2), wherein the reciprocating compressor (2) is arranged between the first heat exchanger and the second heat exchanger and is configured to circulate a refrigerant in the refrigerant circuit (100) and thereby compress it from a first pressure level to a second pressure level, and wherein the reciprocating compressor (2) comprises the following: - a drive shaft (20); - at least two cylinders (28) each with at least one piston (26), arranged on a radius around the drive shaft (20) offset from each other by 180° and extending parallel to the drive shaft (20); and - at least one translation device (240) which is designed to translate a rotary movement of the drive shaft (20) into a reciprocating movement of the pistons (26) in the at least two cylinders (28), in which the pistons travel the same piston path.

2. Heat pump according to claim 1, wherein the at least one transmission device (240) of the reciprocating compressor (2) is configured to move the pistons (26) in the at least two cylinders (28) for at least two stroke cycles per revolution of the drive shaft (20).

3. Heat pump according to claim 2, wherein a number of cylinders (28) of the reciprocating compressor (2) and a number of stroke cycles per revolution of the drive shaft (20) are even, and two cylinders (26) are arranged on the The radius around the drive shaft (20) is offset from each other by 180°.

4. Heat pump according to claim 3, wherein the number of cylinders (28) of the reciprocating compressor corresponds to the number of stroke cycles, an even multiple or an even subset of the number of stroke cycles.

5. Heat pump according to at least one of the preceding claims, wherein the at least one translation device (240) of the reciprocating compressor (2) comprises at least one cam disk (24) and at least two piston rods (25).

6. Heat pump according to claim 5, wherein the at least one cam disk (24) of the reciprocating compressor (2) is connected to the at least two piston rods (25) by means of rollers (23) or sliding blocks (23a).

7. Heat pump according to at least one of the preceding claims, wherein a first and a second piston (26) are arranged in each of the cylinders (28) of the reciprocating compressor (2), and a first transmission device (240) is configured to move the first piston (26) and a second transmission device (240) is configured to move the second piston (26).

8. Heat pump according to at least one of the preceding claims, wherein at least one working chamber is arranged in each cylinder (28) of the reciprocating compressor (2).

9. Heat pump according to claim 7 or 8, wherein the first and second transmission device (240) of the reciprocating compressor (2) are configured to move the first and second pistons (26) by an equal piston travel in opposite directions.

10. Heat pump according to at least one of claims 7 to 9, wherein a working chamber per piston (26) is arranged in each cylinder of the reciprocating compressor (2).

11. Heat pump according to at least one of claims 7 to 10, wherein the first and second translation device (240) of the reciprocating compressor (2) are configured to move the first and second pistons (26) in opposite directions for the compression of the refrigerant in the refrigerant circuit (100) such that the distance between the two pistons (26) is reduced.

12. Heat pump according to at least one of claims 7 to 11, wherein the first and second pistons (26) of the reciprocating compressor (2) are arranged in the cylinder (28) such that their piston heads face each other.

13. Heat pump according to at least one of claims 7 to 12, wherein the first piston (26) is arranged in a first working chamber and the second piston (26) is arranged in a second working chamber of the cylinder (28); and wherein the reciprocating compressor (2) has a drive motor (250) arranged between the first working chamber and the second working chamber.

14. Heat pump according to claim 10 and claim 13, wherein the first and second pistons (26) are arranged in the first and second working chamber of the cylinder (28) such that their piston heads are facing away from each other.

15. Heat pump according to claim 14, wherein the first and second translation device (240) of the reciprocating compressor (2) are configured to move the first and second pistons (26) in opposite directions for the compression of the refrigerant in the refrigeration circuit such that the distance between the two pistons (26) increases.

16. Heat pump according to at least one of the preceding claims, wherein the reciprocating compressor (2) comprises a housing (21) that seals it hermetically or semi-hermetically.

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