DE102023103388A1 - Radial piston compressor - Google Patents

Abstract

The present invention relates to a radial piston compressor, comprising a drive device (1) and a compressor device (2), wherein the compressor device (2) comprises a drive shaft (21) with an eccentric (22), wherein at least one, preferably several, piston-working chamber combinations (25-25''''''') 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 the piston (232) comprises a longitudinal axis (A), which is characterized in particular in that each piston (232) comprises a piston foot (2321), wherein each piston foot (2321) is equipped with a circumferential chamfer (F) or two chamfers (F1, F2), wherein the chamfer (F) or the chamfers (F1, F2) have a chamfer angle (α or α1, α2) in relation to the longitudinal axis (A) of the piston (232), wherein the chamfer angle (α or α1, α2) is set up such that it enables the greatest possible guide length (L) of the piston (232) within the working space (231) in the area of closest contact with the adjacent piston, and/or certain preferred combinations of the number of pistons (V), the number of pole pairs (3) of the electric machine and the 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, and/or a suitable combination of the number of pistons (Z), diameter (D) and stroke (H) of the pistons (232) is selected, in which the exciting force component from the pressure curves of the compression processes represents an optimum.

Description

The present invention relates to a radial piston compressor according to the preamble of claim 1.

A radial piston compressor is an element of fluid technology. In this compressor, in contrast to an axial piston pump, at least one piston-working chamber combination is arranged radially and perpendicular to the drive shaft. The delivery or lifting movement of the piston is usually caused by an eccentric shaft. The radial piston compressor usually comprises several piston-working chamber combinations that extend in a star shape and radially from the drive shaft, in particular the eccentric shaft.

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

A piston-working chamber combination essentially comprises a working chamber, also called a cylinder, and a piston that is moved up and down in the working chamber. The piston has a central geometric piston axis that corresponds to the direction of displacement of the piston. In a radial piston compressor with an eccentric shaft, the piston has a contact surface on its side facing the eccentric shaft, onto which the eccentric disk strikes or rests during rotation of the eccentric shaft. The eccentric shaft has an axis of rotation around which the eccentric shaft is rotated. When the eccentric strikes the contact surface, the piston moves upwards and compresses a medium in the working chamber, thus increasing pressure and force.

A compact design is particularly advantageous when using radial piston compressors in motor vehicles.

If the radial installation space of the radial piston compressor is to be further reduced without reducing the delivery capacity, the number of pistons could be increased to 7, for example. With the same delivery volume (as with 6 pistons), the piston diameter can be reduced. As the number of pistons increases, a collision problem occurs at the point of closest contact between adjacent pistons.

To ensure that the flow rate is generated as evenly as possible - with minimal pressure pulsations - a piston count of at least five or more pistons is desirable. However, since the radial installation space of the entire radial piston compressor should remain as small as possible, the diameter of the eccentric through which the pistons perform their lifting function must also remain as small as possible. For a state-of-the-art piston with a continuous outer diameter, this restriction with the requirement for a larger piston diameter or an increase in the number of pistons cannot be implemented, since the pistons would then collide with one another in the position close to bottom dead center.

State-of-the-art solutions are known that counteract piston collision in the "critical position" by means of a chamfer on the piston base. However, the introduction of the chamfer simultaneously reduces the length of the piston guide in the cylinder bore. In order to increase the guide length again, the piston and therefore the cylinder bore would have to be enlarged, which in turn leads to an increase in the radial installation space.

This is where the present invention comes in and sets itself the task of proposing an improved radial piston compressor, in particular a radial piston compressor that can be designed more compactly with the same or similar performance data.

According to the invention, this object is achieved by a radial piston compressor with the characterizing features of claim 1. Because each piston comprises a piston base, each piston base is equipped with at least one circumferential bevel or two bevels, the bevel or bevels assuming a bevel angle in relation to the longitudinal axis of the piston, the bevel angle being set up in such a way that it enables the greatest possible guide length of the piston within the working space in the area of closest contact with the adjacent piston, an improved radial piston compressor, in particular a compact radial piston compressor, can be provided. The core of the idea is to provide the bevel on the piston base with an "optimal" bevel angle, which leads to a uniformly minimal distance in the area of closest contact between adjacent pistons and thereby enables the greatest possible guide length of the piston(s).

Further advantageous embodiments of the proposed invention result in particular from the features of the subclaims. The objects or features of the various claims can in principle be combined with one another as desired.

In an advantageous embodiment of the invention, it can be provided that the bevel angle = 360°/number of pistons/2. An advantageous solution for the length and angle of the piston base chamfer, i.e. an optimal chamfer angle on the piston base, is <<Optimal chamfer angle = 360°/number of pistons/2>>. If an optimal chamfer angle is implemented, the surfaces of the chamfers of neighboring pistons - in the narrowest section - are parallel to each other. This results in reliable piston guidance with a small radial installation space.

In a further advantageous embodiment of the invention, it can be provided that the longitudinal axes of the pistons lie in one plane.

In a further advantageous embodiment of the invention, it can be provided that pistons/cylinders are evenly distributed around the circumference.

In a further advantageous embodiment of the invention, additional edge rounding can be provided at the transition from the piston base chamfer to the piston base.

The present invention further relates to a radial piston compressor according to the preamble of claim 6 and/or 7.

Further disadvantages have become known in connection with radial piston compression.

In an electrically driven radial piston compressor, the selection of a suitable number of pistons depends not only on the desired displacement volume (piston stroke, piston diameter, number of pistons), but also on other component groups with a “multiplicity” of individual components.

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

Another size with a large number of individual components is the housing screw connection. The housing screw connection is intended to axially clamp the design-related housing parts together so that no coolant is released into the environment under all operating conditions and test requirements. It must therefore fulfill a sealing function. The required contact force through the screw connection must be so great that it counteracts the pressure force that wants to push the housings apart. It makes sense to place the screw connections in the bisector "between" the pistons or cylinders, individually or in pairs. In the example of a radial piston compressor with 7 pistons, 2x7=14 M6x100 screws are arranged to fulfill the task. 7x M8 screws do not achieve the required contact force, 7x M10 screws do achieve the required contact force, but increase the radial installation space enormously. This means that the number of housing screw connections 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 size.

It is therefore provided that the radial piston compressor comprises a number of pistons, the drive device being designed as an electric machine comprising a number of pole pairs, the radial piston compressor comprising at least a two-part housing, the housing components of which are connected by a number of housing screw connections. The radial piston compressor preferably comprises a housing and a housing cover, which are connected to one another by the housing screw connections.

The piston-working chamber combinations and the number of poles of the electrical 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.

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

According to the invention, this object is achieved by a radial piston compressor with the characterizing features of claim 6 and/or 7. By selecting certain preferred combinations of the number of pistons, the number of pole pairs of the electric motor and the number including the dimensions of the housing screw connections, which are expected to improve the acoustic behavior of the overall system. The core of the idea here is to define a suitable combination of the number of pistons, the number of housing screw connections and the number of pole pairs that are favorable with regard to the acoustic effects or the acoustic radiation behavior of the entire compressor.

What is new in particular is that certain preferred combinations of the number of pistons, the number of pole pairs of the electric machine and the number including the dimensions of the housing screw connections are defined. which are expected to improve the acoustic behavior of the overall system.

Alternatively or additionally, it can be provided that the excitation events per revolution from the various excitation components are different, a radial piston compressor can be provided that is designed to be quieter during operation with the same or similar performance data. In other words, to avoid acoustic abnormalities, the excitation events per revolution from the various excitation components (for example, pressure curves with 7 pistons = 7x per revolution; excitation from electric drive - number of pole pairs 8 = 8x per revolution) should be as different as possible.

This can reduce the acoustic impact (sound pressure level) of the overall system and thus lead to improved acoustic behavior in the vehicle.

Further advantageous embodiments of the proposed invention result in particular from the features of the subclaims. The objects or features of the various claims can in principle be combined with one another as desired.

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

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 permanently excited, separately excited or self-excited electric motors.

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

In a further advantageous embodiment of the invention, it can be provided that the housing screw connections are arranged individually or in pairs in the bisector between the piston axes.

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

In a further advantageous embodiment of the invention, it can be provided that further combinations of number of pistons, number of pole pairs and/or number of screws are used.

In a further advantageous embodiment of the invention, it can be provided that screw connections deviating from the standard (size M7, or thread pitch) are used.

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 or others) can be varied.

In a further advantageous embodiment of the invention, it can be provided that the type of housing screw connection (screw head shape, screw shaft, expansion screws, stud bolts with nuts...) can be varied.

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.

In a further advantageous embodiment of the invention, it can be provided that the type of electrical machine (optionally also asynchronous machine or separately excited synchronous machine)

The present invention further relates to a radial piston compressor according to the preamble of claim 19.

Further disadvantages have become known in connection with radial piston compression.

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

According to the invention, this object is achieved by a radial piston compressor with the characterizing features of claim 19. According to the invention, a suitable combination of the number of pistons, diameter and stroke of the piston is proposed, in which the exciting force component from the pressure curves of the compression processes represents an optimum. In other words, it is provided that certain preferable combinations of the number of pistons, diameter This piston and the stroke of the piston should lead to an optimal excitation function on the eccentric at selected operating points. A specific stroke/diameter ratio with the corresponding number of pistons should be selected, adapted to the compression process.

This reduces the acoustic impact, particularly the sound pressure level, of the entire system and thus contributes to improved acoustic behavior in the vehicle. In particular, this also results in a longer service life of the eccentric bearing and/or lower torque fluctuations of the compressor and thus better controllability.

• 1 ein Radialkolbenverdichter in einer seitlichen geschnittenen Ansicht;
• 1a ein Radialkolbenverdichter in einer geschnittenen Ansicht;
• 2 eine schematische Darstellung eines Radialkolbenverdichters, zur Darstellung der Kolben mit größerem Durchmesser und kleinem Exzenter und der hieraus resultierenden Kollision;
• 3a bis 3e eine schematische Darstellung eines Radialkolbenverdichters und Details eines Radialkolbenverdichters, insbesondere Fase am Kolbenfuß;
• 4 mögliche Kombinationen von Kolbenanzahl, Polpaarzahl der E-Maschine und erforderliche Anzahl/Dimension an Gehäuseverschraubungen;
• 5 sinnvolle Kombinationsvarianten mit der Kolbenanzahl „5“;
• 6 sinnvolle Kombinationsvarianten mit sieben und acht Kolben;
• 7 sinnvolle Kombinationsvarianten mit neun Kolben;
• 8 Zylinderdruckverlauf über Zylindervolumen - Verdichtungsphasen,
• 9 Druckverlauf je Kolben;
• 10 überlagerte Kolbendruckverläufe eines Fünf-Kolben Radialkolbenkompressors;
• 11 resultierende Radiallast aus der Überlagerung der Druckverläufe von 5 und 6 Kolben;
• 12 resultierende Radialkraft in einem Betriebspunkt für verschiedene Kolbenzahlen;
• 13 Prinzip-Darstellung Exzenterlagerlasten bei verschiedenen Betriebsbedingungen.

Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings.

• 1 a radial piston compressor in a side sectional view;
• 1a a radial piston compressor in a sectional view;
• 2 a schematic representation of a radial piston compressor, showing the pistons with larger diameter and small eccentric and the resulting collision;
• 3a to 3e a schematic representation of a radial piston compressor and details of a radial piston compressor, in particular chamfer on the piston base;
• 4 possible combinations of number of pistons, number of pole pairs of the electric machine and required number/dimension of housing screw connections;
• 5 useful combination variants with the number of pistons “5”;
• 6 sensible combination variants with seven and eight pistons;
• 7 sensible combination variants with nine pistons;
• 8 Cylinder pressure curve over cylinder volume - compression phases,
• 9 Pressure curve per piston;
• 10 superimposed piston pressure curves of a five-piston radial piston compressor;
• 11 resulting radial load from the superposition of the pressure curves of 5 and 6 pistons;
• 12 resulting radial force at an operating point for different numbers of pistons;
• 13 Principle representation of eccentric bearing loads under different operating conditions.

A

Kolbenachse

R

Drehachse

F

Fase

F1

erste Fase

F2

zweite Fase

α

Fasenwinkel

φ

Antriebswinkel AW

L

Führungslänge

Z

Zylinderanzahl / Kolbenanzahl

V

Anzahl an Verschraubungen

P

Anzahl Polpaare

M

Dimension der Verschraubung

D

Kolbendurchmesser

H

Kolbenhub

K

Kolbenkollision

1

Antriebseinrichtung

2

Verdichtungseinrichtung

3

Pol

4

Verschraubung

5

Gehäuse

6

Koppelglied / Schwenksegment

21

Antriebswelle

22

Exzenter

25-25''''

Kolben-Arbeitsraum-Kombinationen

41

Schraube

42

Durchgangsbohrung

43

Gewindebohrung

51

Gehäusedeckel

52

Rumpfgehäuse

231

Arbeitsraum (Zylinderbohrung)

232

Kolben

2321

Kolbenfuß

2322

Kantenverrundung

The following reference symbols are used in the figures:

A

Piston axis

R

Rotation axis

F

chamfer

F1

first phase

F2

second phase

α

Chamfer angle

φ

Drive angle AW

L

Guide length

Z

Number of cylinders / number of pistons

V

Number of screw connections

P

Number of pole pairs

M

Dimension of the screw connection

D

Piston diameter

H

Piston stroke

K

Piston collision

1

Drive system

2

Compaction device

3

pole

4

Screw connection

5

Housing

6

Coupling link / swivel segment

21

Drive shaft

22

eccentric

25-25''''

Piston-working chamber combinations

41

screw

42

Through hole

43

Threaded hole

51

Housing cover

52

Fuselage housing

231

Working space (cylinder bore)

232

Pistons

2321

Piston foot

2322

Edge rounding

Features and details that are described in connection with a method naturally also apply in connection with the device according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other. In addition, a method according to the invention that may be described can be carried out with the device according to the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of the recited features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.

First, the 1 and 1a reference is made.

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 swivel segments - can be provided between the eccentric bearing outer diameter and the piston base.

A radial piston compressor essentially comprises a drive device 1 and a compression device 2.

The drive device 1 can, for example, be an electric motor.

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

A piston-working chamber combination 23 essentially comprises a working chamber 231, also called a cylinder, and a piston 232, which is moved up and down in the working chamber 231. The piston 232 has a central geometric piston axis A, which corresponds to 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, onto which the eccentric disk 22 strikes or rests during rotation of the eccentric shaft. The eccentric shaft has an axis of rotation R, about which the eccentric shaft is rotated. When the eccentric strikes the contact surface, the piston moves upwards and a medium in the working chamber 231 is compressed, thus increasing pressure and force.

In the following, particular attention is drawn to the 2 reference is made.

In the 2 It is schematically shown that a piston collision K can occur if two adjacent pistons are at a lower low point or in the vicinity of the lower low point and no suitable measures are taken against this.

In the following, particular attention is drawn to the 3a to 3e reference is made.

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 assume or assume an angle, hereinafter referred to as chamfer angle α, to the longitudinal axis K of the piston. Accordingly, the first chamfer F1 assumes a chamfer angle α ₁ and the second chamfer F2 - in the case of two chamfers - a chamfer angle α ₂ to the piston axis A.

In the case of a circumferential chamfer, the result is essentially a conical piston base. The chamfer angle is referred to here as chamfer angle α. In the case of two chamfers, the result is essentially two surfaces set at the corresponding angle.

The chamfer as such 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 a chamfer angle α.

According to the invention, an optimal chamfer angle α is provided on the piston base 2321, which allows the greatest possible guide length L of the piston within the cylinder bore 231 in the region of the closest contact between adjacent pistons 232.

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.

The best solution for the length and angle of the piston base chamfer F1, F2, i.e. an optimal chamfer angle α on the piston base 2321, is <<Optimal chamfer angle α = 360°/number of pistons/2>>. The number of pistons is the number of pistons of the radial piston compressor arranged next to each other in the circumferential direction. 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 narrowest section. This results in reliable piston guidance with a small radial installation space.

In the 3 Some examples are given, in particular 3a and 3b show representations with a small chamfer F1 or F2 on the piston base 2321 with the longer guide length and 3c and 3d show the larger chamfer F1 or F2 at the piston base, which is designed so large that no collision occurs, but at the same time reduces the guide length with the same total piston length.

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

It is further preferably provided that the longitudinal axes of the pistons, i.e. their piston axes A, lie in one plane.

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

Furthermore, preferably small installation space requirements are provided, which causes the risk of collision between adjacent pistons.

Preferably, additional edge roundings 2322 can be provided at the transition of the piston base chamfer F1 or F2 to the piston base 2321.

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

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

The following refers to the 4 to 7 reference is made.

Regarding the basic characteristics of the radial piston compressor, it can be 1 and 1a and the relevant description.

A radial piston compressor comprises a drive device 1 designed as an electric machine with a corresponding number of poles 3, i.e. a number of poles. Two poles are usually combined to form pole pairs. The radial piston compressor also comprises screw connections 4. The screw connections generally comprise a screw 41, a through hole 42 and a corresponding threaded hole 43 into which the screw 41 can be pushed through or screwed. A housing 5 of the radial piston compressor, which is made up of at least two parts, is connected to one another via the screw connection 4. The housing preferably comprises a housing cover 51 and a body housing 52, which are connected to one another via the screw connections 4.

The housing screw connection 4 is intended to axially clamp the design-related housing parts 51, 52 together so that no coolant is released into the environment under all operating conditions and test requirements. It must therefore fulfill a sealing function. The required contact force through the screw connection 4 must be so great that it counteracts the pressure force that tries to push the housing parts 51, 52 apart. It makes sense to place the screw connections 4 in the bisector "between" the pistons or cylinders, i.e. the piston-working chamber combinations 23, individually or in pairs.

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.

Additionally or alternatively, it can be provided here 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.

Below, especially in the 4 to 7 , advantageous combinations of number of cylinders Z, number P of pole pairs, number V and dimensions M of housing screw connections are listed and explained. Basically, for the criterion "acoustics", variants in which the "kgV" is as large as possible are to be preferred.

The LCM is the product of the number of pistons or cylinders Z and the number P of pole pairs of the drive device designed as an electric machine, especially for prime numbers. With 6 screws and 8 pole pairs, the least common multiple (LCM) is not 6x8=48 but 24 (4×6=24 and 3×8=24).

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.

In the 4 possible combinations of number of pistons Z, number of pole pairs P of the drive device designed as an electric machine and required number V or dimension M of housing screw connections 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 number of pistons Z can be influenced by the required displacement 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" and therefore smaller/less cogging torque, but is more expensive.

In the 5 It is to be shown that with the number of pole pairs P=8 (combination “1”) an acceptable “kgV” of 40 can be achieved with a small number of components. With P=12 pole pairs (combination “2”) the “kgV” is 60.

The 6 is intended to show that with seven pistons each of the selected pole pair numbers P (8, 10, 12) can achieve a large "kgV". With eight pistons only the combination of 10 pole pairs is still acceptable. With pole pair number P=12 the result is a "kgV" of 24, ie every second revolution of the compressor would result in a "simultaneous" excitation from the piston drive and the electric machine, which would lead to "poor" acoustics.

The 7 is intended to show that a large "kgV" can be achieved with nine pistons and a pole pair number of P=8 or 10. However, this combination also requires a high number of components for the overall system.

According to the invention, it is provided here that certain preferable combinations of the number of pistons or cylinders Z, the number of pole pairs P of the electric machine and the 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.

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

This makes it possible to provide a radial piston compressor that is designed to be quieter during operation with the same or similar performance data. In other words, to avoid acoustic abnormalities, the excitation events per revolution from the various excitation components (for example, pressure curves with seven pistons = 7x per revolution; excitation from an electric drive - number of pole pairs 8 = 8x per revolution) should be as different as possible.

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

It is preferably an electrically driven radial piston compressor, i.e. the drive device is designed as an electrical machine.

It is preferably an electrical machine with a slot-pole pair combination of either permanently excited, separately excited or self-excited electric motors.

Preferably, evenly distributed pistons or piston-working chamber combinations are provided for the radial piston compressor.

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

Preferably, a distance as equal as possible, preferably the same distance, seen on the circumference of the screw hole circle, is provided between the screws 41 in order to generate a uniform contact pressure on the surface seal, in particular axially between the housing components 51, 52.

In particular, variations or further combinations of the number of pistons Z, the number of pole pairs P and/or the number of screws V are conceivable.

In particular, screw connections 4 that deviate from the standard, in particular size M7, or thread pitch, are conceivable.

In particular, variations with regard to the strength class of the screws 41, for example strength class 8.8; 10.9; 12.9 or others, are conceivable.

In particular, variations with regard to the type of housing screw connection 4, in particular screw head shape, screw shaft, expansion screws, stud bolts with nuts, etc., are conceivable.

Variations in the type and material of the magnets of the electric motor are conceivable.

Variations in the type of electrical machine are conceivable, in particular either an asynchronous machine or a separately excited synchronous machine.

The following refers to the 8 to 13d reference is made.

Regarding the basic characteristics of the radial piston compressor, it can be 1 and 1a and the relevant description.

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

In the 8 a cylinder pressure curve over the cylinder volume, in particular compression phases, is shown schematically. In an electrically driven radial piston compressor, the selection of a suitable number of pistons Z depends not only on the desired delivery volume, in particular piston stroke H, piston diameter D, number of pistons Z, but also on its force excitation in interaction over the individual compressor stroke processes. Each stroke movement of a radial piston compressor follows the two-stroke principle, which includes the intake phase, compression phase, discharge phase and expansion phase.

In the 9 a pressure curve is shown for each piston. During the compression phase, ejection phase and expansion phase, a pressure force acts on the piston, which can be represented as a cylinder pressure curve ZD over time or the angle/drive angle AW or the cylinder volume ZV of the compression process.

In the 10 Superimposed piston pressure curves of a 5-piston radial compressor are shown schematically. Similar to the excitation function of an internal combustion engine, the cylinder pressure curves ZD are superimposed, which leads to an exciting force component F on the eccentric 22 of the radial piston compressor.

In the 11 a resulting real load from the superposition of the pressure curves of five and six pistons 232 is shown schematically. With one cylinder 231 there is a permanent pulse once per revolution. With two cylinders there is a pulse twice per revolution, etc. The optimal way to excite the system would be a superposition of pulses which, due to their length, shape and number of the exciting radial force components, form exactly a constant total force without superimposed amplitude. The number of pistons must therefore be selected so that the compression processes of the individual pistons do not overlap but also do not overlap. However, since no matter what combination is used, depending on the pressure level there can always be an overlap or no overlap of the pressure curves, the resulting force amplitude is crucial for exciting the system. If you use small pistons with lower surface pressure forces for the same compressor displacement, you need a larger number of pistons. This in turn results in smaller resulting force amplitudes.

In the 12 a resulting radial force F is shown schematically at an operating point for different numbers of pistons (numbers on the curves). Certain combinations of number of pistons 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. In 12 For example, a minimum of the exciting amplitude is shown for a combination of seven pistons, 16 mm piston diameter D and a stroke H of 8 mm. Despite a higher number of pistons, this minimum system excitation is not achieved by the system with 8 pistons.

In the 13a to 13d Eccentric bearing loads are plotted under different operating conditions and piston numbers. In the 13a to 13d the load on the eccentric drive is shown at different speeds, pressure ratios and numbers of pistons. The basis for this is the same displacement of the compressor varies over the number of pistons and the piston diameter D with the same stroke H. It is clearly visible that from seven pistons onwards there is a significant reduction in the radial loads on the eccentric compared to the variants with five or six pistons. The exciting forces and their amplitudes drop significantly, which leads to better NVH behavior. (noticeable and audible vibration behavior) and thus to greater acceptance by the end customer. A radial piston compressor with at least seven pistons, ideally eight or nine pistons, represents a system with favorable excitation in this case.

Furthermore, the bearing load on the eccentric drive is reduced due to the lower amplitudes. This enables either the installation of a smaller bearing or a longer service life of the eccentric bearing.

Particularly at low pressure ratios, it is clear that seven pistons represent an optimum due to the favorable overlap of the cylinder pressure curves. This favors the operation of the compressor at a low pressure ratio, since purely mechanically a resulting low torque fluctuation can be expected. Due to the low torque fluctuation of the compressor, the electric machine has better control options and is stimulated less.

According to the invention, it is intended to propose a suitable combination of number of pistons Z, piston diameter D and stroke H of the piston, in which the exciting force component from the pressure curves of the compression processes represents an optimum. In other words, it is intended that certain preferred combinations of number of pistons Z, piston diameter and stroke H of the piston 232 should lead to an optimal excitation function on the eccentric 22 at selected operating points. A specific stroke/diameter ratio H/D with the associated number of pistons Z should be selected, adapted to the compression process.

This reduces the acoustic effects, particularly the sound pressure level, of the entire system and thus contributes to improved acoustic behavior in the vehicle. In particular, this also results in a longer bearing life of the eccentric or a bearing arranged on the eccentric disk, particularly a roller bearing, and/or lower torque fluctuations of the compressor and thus better controllability.

The radial piston compressor is preferably an electrically driven radial piston compressor in two-stroke operation. An electric machine is preferably used as the drive device. Furthermore, evenly distributed pistons 232 are preferably provided for the radial piston compressor.

Furthermore, further combinations of number of pistons/diameter to number of pistons are preferably conceivable. Refrigerants other than CO2 are also conceivable as a fluid for the radial piston compressor.

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

Claims (24)

Radial piston compressor, comprising - a drive device (1) and a compressor device (2), wherein - the compressor device (2) comprises a drive shaft (21) with an eccentric (22), wherein - at least one, preferably several, piston-working chamber combinations (23-25''''''') extend radially from the drive shaft (21), wherein - each piston-working chamber combination comprises a working chamber (231) and a piston (232) which can be displaced in the working chamber, wherein the piston (232) comprises a longitudinal axis (A), characterized in that - each piston (232) comprises a piston foot (2321), wherein each piston foot (2321) is equipped with a circumferential chamfer (F) or two chamfers (F1, F2), wherein - the circumferential chamfer (F) or the chamfers (F1, F2) have a chamfer angle (α or α ₁ , α ₂ ) with respect to the longitudinal axis (A) of the piston (232), wherein the chamfer angle (α or α ₁ , α ₂ ) is arranged such that it enables the greatest possible guide length (L) of the piston (232) within the working space (231) in the region of closest contact with the adjacent piston. Radial piston compressor according to Claim 1 , characterized in that the chamfer angle (α ₁ or α ₂ ) = 360°/number of pistons (Z) / 2. Radial piston compressor according to at least one of the preceding claims, characterized in that the longitudinal axes (A) of the pistons (232) lie in one plane. Radial piston compressor according to at least one of the preceding claims, characterized in that pistons/cylinders (231, 232) are provided which are evenly distributed over the circumference. Radial piston compressor according to at least one of the preceding claims, characterized in that additional edge rounding ings (2322) are provided at the transition of the chamfer (F) to the piston base (2321). Radial piston compressor according to at least one of the preceding claims or the preamble of Claim 1 , wherein - the radial piston compressor comprises a number (V) of pistons (232), wherein - the drive device (1) is designed as an electric machine, comprising a number of pole pairs (3), wherein - the radial piston compressor comprises an at least two-part housing (51, 52), the housing components of which are connected by a number of screw connections (4), characterized in that certain preferable combinations of the number of pistons (V), the number of pole pairs (3) of the electric machine and the 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. Radial piston compressor according to at least one of the preceding claims or the preamble of Claim 1 , wherein - the radial piston compressor forms excitation components through the piston-working chamber combinations (23) and the pole pairs (3) of the electrical 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, characterized in that the excitation events per revolution are different from the various excitation components. Radial piston compressor according to at least one of the preceding claims, characterized in that the radial piston compressor is an electrically driven radial piston compressor. Radial piston compressor according to at least one of the preceding claims, characterized in that the drive device (1) designed as an electric machine comprises a slot-pole pair combination, in particular it is a permanently excited, separately excited or self-excited electric motor. Radial piston compressor according to at least one of the preceding claims, characterized in that the piston-working chamber combinations (23) are arranged evenly distributed over the circumference of the radial piston compressor, in particular evenly distributed pistons (232) of the radial piston compressor are present. Radial piston compressor according to at least one of the preceding claims, characterized in that the arrangement of the screw connections (4) is provided individually or in pairs in the bisector between the piston axes (A). Radial piston compressor according to at least one of the preceding claims, characterized in that a distance as equal as possible, in particular equal, is provided between the screw connections (4) as seen on the circumference of the screw hole circle, in order to generate a uniform contact pressure on the surface seal, in particular axially between the housing components. Radial piston compressor according to at least one of the preceding claims, characterized in that further combinations of number of pistons (Z), number of pole pairs (P) and/or number (V) of screw connections (V) are used. Radial piston compressor according to at least one of the preceding claims, characterized in that screw connections (4) deviating from the standard, in particular size 7, or thread pitch, are used. Radial piston compressor according to at least one of the preceding claims, characterized in that the strength class of the screws (41), in particular strength class 8.8; 10.9; 12.9 or similar, can be varied. Radial piston compressor according to at least one of the preceding claims, characterized in that the type of screw connection, in particular screw head shape, screw shaft, expansion screws, stud bolts with nuts, etc., can be varied. Radial piston compressor according to at least one of the preceding claims, characterized in that the type and material of the magnets of the electric machine can vary. Radial piston compressor according to at least one of the preceding claims, characterized in that the type of electrical machine can vary, in particular the electrical machine can be designed either as an asynchronous machine or a separately excited synchronous machine. Radial piston compressor according to at least one of the preceding claims or the preamble of Claim 1 , wherein - the radial piston compressor has a number (Z) of pistons (232), wherein - the pistons (232) have a piston diameter (D), wherein - the pistons (232) have a piston stroke, characterized in that a suitable combination of number of pistons (Z), diameter (D) and stroke (H) of the pistons (232) is selected, in which the exciting force component from the pressure curves of the compression processes represents an optimum. Radial piston compressor according to at least one of the preceding claims, characterized in that the radial piston compressor is an electrically driven radial piston compressor in two-stroke operation. Radial piston compressor according to at least one of the preceding claims, characterized in that an electric machine is used as the drive device. Radial piston compressor according to at least one of the preceding claims, characterized in that evenly distributed pistons (232) are provided for the radial piston compressor. Radial piston compressor according to at least one of the preceding claims, characterized in that further combinations of number of pistons/diameter (Z/D) to number of pistons (Z) are conceivable. Radial piston compressor according to at least one of the preceding claims, characterized in that other refrigerants than CO2 are conceivable as fluid for the radial piston compressor.

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