Radial-piston compressor

Abstract

The present invention relates to a radial piston compressor comprising a drive unit (1) and a compressor unit (2), wherein the compressor unit (2) comprises a drive shaft (21) with an eccentric (22), wherein at least one, preferably several, piston-working chamber combinations (23-23 ‴ʺʺ) extend radially from the drive shaft (21), wherein each piston-working chamber combination comprises a working chamber (231) and a piston (232) displaceable in the working chamber, wherein certain preferable combinations of number of pistons (V), number of pole pairs (3) of the electric motor and number (V) including the dimensions (M) of the screw connections (4) are selected, which are expected to improve the acoustic behavior of the overall system, and / or the excitation events per revolution from the various excitation components are different.

Description

[0001] The present invention relates to a radial piston compressor according to the preamble of claims 1 and 2.

[0002] A radial piston compressor is a fluid power component. In contrast to an axial piston pump, this type of compressor has at least one piston-working chamber combination arranged radially and perpendicular to the drive shaft. The piston's delivery or stroke motion is typically driven by an eccentric shaft. A radial piston compressor generally comprises several piston-working chamber combinations radiating outwards from the drive shaft, particularly the eccentric shaft, in a star-shaped pattern.

[0003] Radial piston compressors are used, for example, as radial piston compressors for refrigerants in air conditioning systems of motor vehicles, especially in electrically powered motor vehicles.

[0004] A piston-working chamber combination essentially comprises a working chamber, also called a cylinder, and a piston that moves up and down within the working chamber. The piston has a central geometric axis that coincides with the piston's direction of movement. In a radial piston compressor with an eccentric shaft, the piston has a contact surface on the side facing the eccentric shaft. The eccentric disk contacts this surface as the shaft rotates. The eccentric shaft has an axis of rotation around which it rotates. When the eccentric disk contacts the contact surface, the piston moves upwards, compressing the medium in the working chamber and thus increasing pressure and force.

[0005] From DE 10 2012 005 297 A1 a compressor unit or compressor with radially arranged pistons guided in cylinder bores, which are driven via an eccentric, has become known.

[0006] From DE 10 2010 030 239 A1 a method and a device for starting an electric motor became known.

[0007] Disadvantages have become known in connection with radial piston compressors.

[0008] In an electrically driven radial piston compressor, the selection of a suitable number of pistons depends not only on the desired delivery volume (piston stroke, piston diameter, number of pistons), but also on other component groups with a "multitude" of individual components.

[0009] These are determined by the geometry / design of the electric motor, for example, the number of coils / windings; the number of pole pairs; the number of magnets. For example, eight pole pairs, but they are always an even multiple of two.

[0010] Another component with numerous individual parts is the housing screw connection. The housing screw connection is designed to axially clamp the housing parts together, preventing refrigerant from escaping into the environment under all operating conditions and test requirements. It must therefore function as a seal. The required clamping force from the screw connection must be sufficient to counteract the pressure force that would otherwise push the housing apart. Ideally, the screw connections are positioned individually or in pairs along the angle bisector "between" the pistons or cylinders. In the example of a radial piston compressor with 7 pistons, 2 x 7 = 14 M6x100 screws are used to fulfill this function. Seven M8 screws would not achieve the required clamping force, while seven M10 screws would achieve the required clamping force but would significantly increase the radial installation space.The number of housing bolts is linked to the number of pistons / cylinders (equal to or a multiple of the number of pistons) and the number of pole pairs. As the name suggests, it is an even-numbered quantity.

[0011] It is therefore provided that the radial piston compressor comprises a number of pistons, the drive unit being designed as an electric machine comprising a number of pole pairs, and the radial piston compressor comprising a housing of at least two parts, the housing components of which are connected by a number of housing screws. Preferably, the radial piston compressor comprises a housing and a housing cover, which are connected to each other by the housing screws.

[0012] The piston-working chamber combinations and the number of poles of the electric machine are excitation components that influence the acoustic behavior of the radial piston compressor through excitation events such as pressure peaks in the working chamber, changes between the pole pairs, etc.

[0013] Another object of the present invention is to propose an improved radial piston compressor, in particular a radial piston compressor which is designed to be quieter during operation with the same or similar performance data.

[0014] According to the invention, this problem is solved by a radial piston compressor with the characterizing features of claim 1. This is achieved by selecting certain preferable combinations of the number of pistons, the number of pole pairs of the electric motor, and the number and dimensions of the housing connections, which are expected to improve the acoustic behavior of the overall system. The core idea here is to define a suitable combination of the number of pistons, the number of housing connections, and the number of pole pairs that is favorable with regard to the acoustic effects or the acoustic radiation behavior of the entire compressor. It is provided that the housing connections are arranged individually or in pairs on the bisector of the angle between the piston axes.

[0015] What is new in particular is that certain preferred combinations of piston number, pole pair number of the electric motor and number including dimensions of the housing screws are defined, which are expected to improve the acoustic behavior of the overall system.

[0016] Alternatively or additionally, if the excitation events per revolution from the various excitation components are designed to be different, a radial piston compressor can be provided that is quieter during operation while offering the same or similar performance data. In other words, to avoid acoustic disturbances, the excitation events per revolution from the various excitation components (for example, pressure profiles with 7 pistons = 7 events per revolution; excitation from an electric drive - 8 pole pairs = 8 events per revolution) should be as different as possible.

[0017] This can reduce the acoustic impact (sound pressure level) of the overall system and thus improve the acoustic behavior of the vehicle.

[0018] Further advantageous embodiments of the proposed invention arise in particular from the features of the dependent claims. The subject matter or features of the various claims can, in principle, be combined with one another in any way.

[0019] In an advantageous embodiment of the invention, it can be provided that the radial piston compressor is an electrically driven radial piston compressor.

[0020] In a further advantageous embodiment of the invention, it can be provided that the drive device designed as an electric machine comprises a slot-pole pair combination, in particular permanent magnet excited, externally excited or self-excited electric motors.

[0021] In a further advantageous embodiment of the invention, it can be provided that the piston-working chamber combinations are arranged in an even distribution over the circumference of the radial piston compressor, in particular that evenly distributed pistons of the radial piston compressor are present.

[0022] In a further advantageous embodiment of the invention, it can be provided that the distance between the screws is as uniform as possible, in particular equal, as viewed on the circumference of the screw hole circle, in order to generate a uniform contact force on the surface seal (axially between the housing components).

[0023] In a further advantageous embodiment of the invention, it can be provided that the strength class of the screws (8.8; 10.9; 12.9 oa) can be varied.

[0024] In a further advantageous embodiment of the invention, it can be provided that the type of housing screw connection (screw head shape, screw shank, expansion screws, studs with nut...) can be varied.

[0025] In a further advantageous embodiment of the invention, it can be provided that the type and material of the magnets of the electric machine can be varied.

[0026] In a further advantageous embodiment of the invention, it can be provided that the electrical machine can optionally be designed as an asynchronous machine or a separately excited synchronous machine.

[0027] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying figures. These show Fig. 1 A radial piston compressor in a side sectional view; Fig. 1a A radial piston compressor in a sectional view; Fig. 2 A schematic representation of a radial piston compressor, illustrating the pistons with a larger diameter and small eccentric and the resulting collision; Figs. 3a to 3e A schematic representation of a radial piston compressor and details of a radial piston compressor, in particular the chamfer at the piston base; Fig. 4 Possible combinations of number of pistons, number of pole pairs of the electric motor and required number / dimension of housing connections; Fig. 5 Sensible combination variants with the number of pistons "5"; Fig. 6 Sensible combination variants with seven and eight pistons; Fig. 7 Sensible combination variants with nine pistons; Fig. 8 Cylinder pressure curve over cylinder volume - compression phases; Fig. 9 Pressure curve per piston; Fig. 10 Superimposed piston pressure curves of a five-piston radial piston compressor; Fig.Fig. 11 Resultant radial load from the superposition of the pressure profiles of 5 and 6 pistons; Fig. 12 Resultant radial force at an operating point for different numbers of pistons; Fig. 13 Principle diagram of eccentric bearing loads under different operating conditions.

[0028] The following reference symbols are used in the illustrations: A Piston axis R Rotation axis F Chamfer F1 First chamfer F2 Second chamfer α Chamfer angle ϕ Drive angle AW L Guide length ZZ Number of cylinders / Number of pistons V Number of screw connections PA Number of pole pairs MD Dimension of screw connection D piston diameter H piston stroke Piston collision 1 Drive unit 2 Compression unit 3 Pole 4 Screw connection 5 Housing 6 Coupling element / Swivel segment 21 Drive shaft 22 Eccentric 23-23ʺʺ Piston-working chamber combinations 41 Screw 42 Through hole 43 Threaded hole 51 Housing cover 52 Body housing 231Working space (cylinder bore) 232Piston 2321 Piston foot 2322 Edge rounding

[0029] Features and details described in connection with a method naturally also apply to the device according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always makes or can make reciprocal reference. Furthermore, any described method according to the invention can be carried out with the device according to the invention.

[0030] The terminology used herein serves only to describe certain embodiments and is not intended to limit the disclosure. As used herein, the singular forms "a" and "the" shall also include the plural forms unless the context otherwise makes clear. It shall also be clear that the expressions "indicates" and / or "indicating," when used in this description, specify the presence of the aforementioned features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the expression "and / or" includes any and all combinations of one or more of the associated, listed elements.

[0031] The following descriptions include some items that are not part of the present invention. These are described for the sake of completeness and serve in particular to improve understanding of the technical context. The actual invention relates in particular to the following in connection with the Figures 4 to 7 described embodiments.

[0032] First, attention will be drawn to the Figs. 1 and 1a Reference made to.

[0033] Figure 1 Figure 1 shows a radial piston compressor with piston designs, in particular a compact embodiment of a radial piston compressor, with six pistons 232 for use with the refrigerant CO2. Coupling elements 6 – also called pivot segments – can be provided between the eccentric bearing outer diameter and the piston base.

[0034] A radial piston compressor essentially comprises a drive unit 1 and a compression unit 2.

[0035] The drive unit 1 could, for example, be an electric motor.

[0036] The compression device 2 comprises a drive shaft 21 with an eccentric 22, as well as piston-working chamber combinations 23-23ʺʺ arranged radially around the drive shaft. The drive shaft 21 with the eccentric 22 can also be referred to as an eccentric shaft.

[0037] A piston-working chamber combination 23 essentially comprises a working chamber 231, also called a cylinder, and a piston 232, which moves up and down within the working chamber 231. The piston 232 has a central geometric axis A, which coincides with the direction of displacement of the piston 232. In a radial piston compressor with an eccentric shaft 21, 22, the piston 232 has a contact surface on its side facing the eccentric shaft, against which the eccentric disk 22 strikes or rests during the rotation of the eccentric shaft. The eccentric shaft has an axis of rotation R about which it rotates. When the eccentric disk strikes the contact surface, the piston moves upwards, compressing the medium in the working chamber 231 and thus increasing the pressure and force.

[0038] The following section will focus in particular on the Fig. 2 Reference made to.

[0039] In the Fig. 2The schematic diagram shows that a piston collision K can occur if two adjacent pistons are located at or near a lower low point and no suitable measures are taken to prevent this.

[0040] The following section will focus in particular on the Figs. 3a to 3e Reference made to.

[0041] The pistons 232 used here have a piston base 2321, i.e., a region of the piston 232 facing the drive shaft 21. The piston base 2321 is equipped with a circumferential chamfer F or two chamfers, in particular a first chamfer F1 and a second chamfer F2, which form an angle, hereinafter referred to as chamfer angle α, with the longitudinal axis K of the piston. Accordingly, the first chamfer F1 forms a chamfer angle α1 and the second chamfer F2 – in the case of two chamfers – a chamfer angle α2 with respect to the piston axis A.

[0042] In the case of a circumferential chamfer, the resulting piston base is essentially conical. The chamfer angle is accordingly denoted as chamfer angle α. In the case of two chamfers, the result is essentially two surfaces angled accordingly.

[0043] The chamfer itself is preferably designed as a flat surface. The chamfer angles α1 and α2 are preferably equal, so that in the following, reference is made to one chamfer angle α as a representative example.

[0044] An optimal chamfer angle α is provided at the piston base 2321, which allows the greatest possible guide length L of the piston within the cylinder bore 231 in the area of ​​closest contact between adjacent pistons 232.

[0045] The guide length L of the piston 232 is the section or length of the piston 232 with which the piston can be guided in the working space.

[0046] The best solution for the length and angle of the piston base chamfer F1, F2, i.e., an optimal chamfer angle α at the piston base 2321, is given by: "Optimal chamfer angle α = 360° / number of pistons / 2". The number of pistons is the number of pistons arranged next to each other in the circumferential direction of the radial piston compressor. If an optimal chamfer angle α is implemented, the surfaces of the chamfers F1, F2 of adjacent pistons are parallel to each other in the closest cross-section. This results in reliable piston guidance while simultaneously requiring a small radial installation space.

[0047] In the Fig. 3 Some examples are given here, in particular Figs. 3a and 3b The illustrations show a small chamfer F1 or F2 at the piston base 2321 with the larger guide length and Fig. 3c and 3d The larger chamfer F1 or F2 at the piston base is designed to be so large that no collision occurs, while simultaneously reducing the guide length for the same overall piston length.

[0048] In the Fig. 3e A chamfer angle α is shown in relation to the longitudinal axis K of a piston 232.

[0049] It is also preferably provided that the longitudinal axes of the pistons, i.e. their piston axes A, lie in a plane.

[0050] It is also preferably provided that pistons / cylinders, i.e., piston-working chamber combinations, are provided that are evenly distributed around the circumference, i.e., that the angle between adjacent piston axes A is the same for all.

[0051] Furthermore, preferably small installation space requirements are provided, which does not create a risk of collision between adjacent pistons.

[0052] Preferably, additional edge rounding 2322 can be provided at the transition of the piston foot chamfer F1 or F2 to the piston foot 2321.

[0053] Preferably, the size of the respective piston diameters / cylinder bore diameters, number of pistons and / or chamfer length at the piston base can vary.

[0054] Different chamfer lengths can also be provided on the piston base 2321 on both sides when the piston axis A is offset, in particular when the cylinder bores are offset such that the axes do not intersect or the opposing cylinders do not lie on one axis, or when the piston base 2321 has a different chamfer in section along the eccentric axis than in cross-section.

[0055] The following refers to the Figures 4 to 7 Reference made to.

[0056] Regarding the fundamental characteristics of the radial piston compressor, reference can be made to the following: Figs. 1 and 1a as well as the relevant description.

[0057] A radial piston compressor comprises a drive unit 1 designed as an electric machine with a corresponding number of poles 3, i.e., a pole count. Two poles are usually grouped together to form pole pairs. The radial piston compressor also includes screw connections 4. These screw connections typically comprise a screw 41, a through-hole 42, and a corresponding threaded hole 43 into which the screw 41 can be inserted or screwed. A housing 5 of the radial piston compressor, consisting of at least two parts, is connected via the screw connections 4. Preferably, the housing comprises a housing cover 51 and a body housing 52, which are connected to each other via the screw connections 4.

[0058] The housing screw connection 4 is intended to axially clamp the housing parts 51, 52 together, so that no refrigerant is released into the environment under all operating conditions and test requirements. It must therefore fulfill a sealing function. The required clamping force exerted by the screw connection 4 must be sufficient to counteract the pressure force that would otherwise force the housing parts 51, 52 apart. The screw connections 4 are advantageously positioned individually or in pairs along the angle bisector "between" the pistons or cylinders, i.e., the piston-working chamber combinations 23.

[0059] The radial piston compressor also has a number of piston-working chamber combinations 23, and accordingly a corresponding number of pistons 232 or working chambers 231.

[0060] Additionally or alternatively, it can be provided that the radial piston compressor forms excitation components through the piston-working chamber combinations 23 and the poles 3 of the electric machine, wherein the excitation components are characterized by excitation events such as pressure peaks in the working chamber 231 and a change between the pole pairs 3, which have an influence on the acoustic behavior of the radial piston compressor.

[0061] The following, especially in the Figs. 4 to 7 Advantageous combinations of cylinder number Z, number of pole pairs P, number of V, and dimensions M of housing connections are listed and explained. Generally, for the "acoustics" criterion, variants with the highest possible "least common multiple" (LCM) are preferred.

[0062] The least common multiple (LCM) is calculated as the product of the number of pistons or cylinders (Z) and the number (P) of pole pairs in the drive unit designed as an electric machine, particularly when prime numbers are involved. For 6 screws and 8 pole pairs, the LCM is not 6 x 8 = 48 but 24 (4 x 6 = 24 and 3 x 8 = 24).

[0063] On the other hand, some of these variants have a large number of components (pistons; pole pairs) and are therefore not preferable in terms of manufacturing costs.

[0064] In the Fig. 4Possible combinations of piston number Z, pole pair number P of the drive unit designed as an electric machine, and the required number V or dimension M of housing screws 4 are shown in a design path. The forces to be withstood by the screw connection are significantly influenced by its inner diameter Di or the resulting pressurized area. The piston number Z can be influenced by the required stroke volume HVol and the radial installation space. The number of magnets or pole pairs P varies according to requirements, whereby a larger number of pole pairs P means less ripple, i.e., lower cogging torque, but is more expensive.

[0065] In the Fig. 5 It should be shown that with a pole pair number P=8 (combination "1"), an acceptable LCM of 40 can be achieved with a small number of components. With P=12 pole pairs (combination "2"), the LCM is 60.

[0066] The Fig. 6 This is intended to show that with seven pistons, each of the selected pole pair numbers P (8, 10, 12) achieves a large LCM (least common multiple). With eight pistons, only the combination of 10 pole pairs is acceptable. With a pole pair number P=12, an LCM of 24 results, meaning that every second revolution of the compressor would result in simultaneous excitation from the piston drive and the electric motor, which would lead to poor acoustics.

[0067] The Fig. 7 This is intended to demonstrate that a large LCM (least common multiple) is achieved with nine pistons and a pole pair number of P=8 or 10. However, this combination also necessitates a large number of components for the overall system.

[0068] According to the invention, it is provided that certain preferable combinations of piston number or cylinder number Z, pole pair number P of the electric motor and number V including the dimensions M of the housing screw connections are selected, which are expected to improve the acoustic behavior of the overall system.

[0069] Alternatively or additionally, it can be provided that the excitation events per revolution are different from the various excitation components.

[0070] This allows for the provision of a radial piston compressor that is quieter during operation while offering the same or similar performance data. In other words, to avoid acoustic disturbances, the excitation events per revolution from the various excitation components (for example, pressure profiles with seven pistons = 7 times per revolution; excitation from an electric drive - 8 pole pairs = 8 times per revolution) should be as different as possible.

[0071] The radial piston compressor described here is characterized in particular by the following features.

[0072] It is preferably an electrically driven radial piston compressor, i.e., the drive unit is designed as an electric machine.

[0073] It is preferably an electric machine with a slot-pole pair combination, optionally permanently excited, separately excited or self-excited electric motors.

[0074] Preferably, uniformly distributed pistons or piston-working chamber combinations are provided for the radial piston compressor.

[0075] Preferably, the housing screw connections 4 are arranged individually or in pairs in the angle bisector between the piston axes A.

[0076] Preferably, the screws 41 are spaced as evenly as possible, preferably with equal spacing, on the circumference of the screw hole circle, in order to generate a uniform contact force on the surface seal, in particular axially between the housing components 51, 52.

[0077] In particular, variations or further combinations of piston number Z, pole pair number P and / or screw number V are conceivable.

[0078] In particular, screw connections that deviate from the norm, especially size M7, or thread pitch, are conceivable.

[0079] In particular, variations regarding the strength class of the screws 41 are conceivable, for example strength class 8.8; 10.9; 12.9 etc.

[0080] In particular, variations regarding the type of housing screw connection 4, especially screw head shape, screw shank, expansion screws, studs with nut, etc., are conceivable.

[0081] Variations in the type and material of the magnets in the electric machine are conceivable.

[0082] Variations regarding the type of electrical machine are conceivable, in particular optionally an asynchronous machine or a separately excited synchronous machine.

[0083] Reference is made below to Figures 8 to 13d.

[0084] Regarding the fundamental characteristics of the radial piston compressor, reference can be made to the following: Figs. 1 and 1a as well as the relevant description.

[0085] The radial piston compressor outlined here is characterized in particular by the fact that the radial piston compressor has a number of pistons 232, wherein the pistons 232 have a piston diameter D, and wherein the pistons have a piston stroke H.

[0086] In the Fig. 8 The figure schematically depicts a cylinder pressure curve versus cylinder volume, particularly compression phases. In an electrically driven radial piston compressor, the selection of a suitable number of pistons Z depends not only on the desired delivery volume, especially piston stroke H, piston diameter D, and number of pistons Z, but also on the force excitations in their interaction across the individual compressor strokes. Each stroke of a radial piston compressor follows the two-stroke principle, which includes the intake phase, compression phase, exhaust phase, and expansion phase.

[0087] In the Fig. 9A pressure curve for each piston is shown. During the compression, exhaust, and expansion phases, a pressure force acts on the piston, which can be represented as a cylinder pressure curve ZD over time, at the angle / drive angle AW, or at the cylinder volume ZV of the compression process.

[0088] In the Fig. 10 The superimposed piston pressure profiles of a 5-piston radial compressor are shown schematically. Similar to the excitation function of an internal combustion engine, the cylinder pressure profiles ZD are superimposed, resulting in an excitation force component F on the eccentric 22 of the radial piston compressor.

[0089] In the Fig. 11A resulting real load from the superposition of the pressure profiles of five and six pistons 232 is schematically represented. With one cylinder 231, there is a continuous impulse once per revolution. With two cylinders, there is a impulse twice per revolution, and so on. Optimally for exciting the system, the impulses would be superimposed in such a way that, due to their length, shape, and number, the exciting radial force components form exactly a constant total force without any superimposed amplitude. Therefore, the number of pistons must be chosen such that the compression processes of the individual pistons neither superimpose nor overlap. However, since, regardless of the combination, depending on the pressure level, there can always be an overlap or a lack of overlap of the pressure profiles, the resulting force amplitude is crucial for exciting the system.If smaller pistons with lower surface pressure forces are used for the same compressor displacement volume, a larger number of pistons are required. These, in turn, result in smaller force amplitudes.

[0090] In the Fig. 12 The resulting radial force F at an operating point for different numbers of pistons (numbers on the curves) is shown schematically. Certain combinations of piston number and stroke / bore ratio lead to an almost complete cancellation of the exciting amplitude at selected operating points due to the shape, length, and number of pistons. Fig. 12 For example, a minimum excitation amplitude is shown for a combination of seven pistons, a piston diameter D of 16 mm, and a stroke H of 8 mm. Despite a higher number of pistons, this minimum system excitation is not achieved by the system with eight pistons.

[0091] Figures 13a to 13d show eccentric bearing loads under different operating conditions and numbers of pistons. These figures illustrate the load on the eccentric drive at different speeds, pressure ratios, and numbers of pistons. The basis for this is the same compressor displacement volume, varied by the number of pistons and the piston diameter D, with the same stroke H. It is clearly evident that with seven or more pistons, there is a significant reduction in the radial loads on the eccentric compared to the variants with five or six pistons. The excitation forces and their amplitudes decrease considerably, resulting in improved NVH (noise, vibration, and harshness) and thus greater acceptance by the end customer. In this case, a radial piston compressor with at least seven pistons, and ideally eight or nine, represents a system with favorable excitation characteristics.

[0092] Furthermore, the lower amplitudes reduce the bearing load on the eccentric drive. This allows either the installation of a smaller bearing or a longer service life for the eccentric bearing.

[0093] Especially at low pressure ratios, it becomes apparent that seven pistons represent an optimum due to the favorable superposition of the cylinder pressure profiles. This favors compressor operation at low pressure ratios, as purely mechanically, a low torque fluctuation can be expected. The electric motor, due to the low torque fluctuation of the compressor, has better control capabilities and is driven less intensely.

[0094] It is evident that a suitable combination of piston number Z, piston diameter D, and piston stroke H is described, in which the excitation force component from the pressure profiles of the compression processes represents an optimum. In other words, it is intended that certain preferred combinations of piston number Z, piston diameter, and stroke H of piston 232 should lead to an optimal excitation function at the eccentric 22 at selected operating points. A specific stroke / diameter ratio H / D with a corresponding piston number Z should be selected, adapted to the compression process.

[0095] This results in a reduction of the overall system's acoustic impact, particularly the sound pressure level, and thus contributes to improved acoustic performance in the vehicle. It also leads, in particular, to a longer bearing life for the eccentric or any bearing mounted on the eccentric disc, especially roller bearings, and / or reduced torque fluctuations of the compressor, resulting in better controllability.

[0096] Preferably, the radial piston compressor is an electrically driven radial piston compressor operating in two-stroke mode. An electric motor is preferably used as the drive unit. Equally spaced pistons 232 are also preferably provided for the radial piston compressor.

[0097] Furthermore, other combinations of piston number / diameter to piston number are preferably conceivable. Refrigerants other than CO2 are also conceivable as fluids for the radial piston compressor.

[0098] A preferred application for the radial piston compressors proposed here is in the field of air conditioning systems in motor vehicles. Accordingly, the radial piston compressor is preferably designed to compress a refrigerant or fluid, such as CO2. However, other applications and fluids are also conceivable.

Claims

1. A radial piston compressor comprising a drive unit (1) and a compressor unit (2), wherein the compressor unit (2) comprises a drive shaft (21) with an eccentric (22), wherein several piston-working chamber combinations (23-23‴ʺʺ) extend radially from the drive shaft (21), wherein each piston-working chamber combination comprises a working chamber (231) and a piston (232) displaceable in the working chamber, the piston (232) comprising a longitudinal axis (A), wherein the radial piston compressor comprises a number (V) of pistons (232), wherein the drive unit (1) is designed as an electric machine comprising a number of pole pairs (3), wherein the radial piston compressor comprises a housing (51, 52) of at least two parts, the housing components of which are connected by a number of screw connections (4). characterized by the fact thatcertain preferable combinations of piston number (V), pole pair number (3) of the electric machine and number (V) including dimensions (M) of the screw connections (4) are selected which are expected to improve the acoustic behavior of the overall system, wherein the arrangement of the screw connections (4) is provided individually or in pairs in the angle bisector between the piston axes (A).

2. Radial piston compressor according to at least one of the preceding claims, characterized by the fact that The radial piston compressor is an electrically driven radial piston compressor, particularly in two-stroke operation, whereby in particular the electric machine can optionally be designed as an asynchronous machine or a separately excited synchronous machine.

3. Radial piston compressor according to at least one of the preceding claims, characterized by the fact thatthe drive device designed as an electric machine (1) comprises a slot-pole pair combination, in particular a permanently excited, separately excited or self-excited electric motor.

4. Radial piston compressor according to at least one of the preceding claims, characterized by the fact that the piston-working chamber combinations (23) are arranged in a uniform distribution over the circumference of the radial piston compressor, in particular uniformly distributed pistons (232) of the radial piston compressor are present.

5. Radial piston compressor according to at least one of the preceding claims, characterized by the fact that An equal distance between the screw connections (4), viewed on the circumference of the screw hole circle, is provided in order to generate a uniform contact force on the surface seal, in particular axially between the housing components.

6. Radial piston compressor according to at least one of the preceding claims, characterized by the fact thatthe strength class of the screws (41), in particular strength class 8.8; 10.9; 12.9 oa, can be varied.

7. Radial piston compressor according to at least one of the preceding claims, characterized by the fact that The type of screw connection, in particular screw head shape, screw shank, expansion screws, studs with nut, etc., can be varied.

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