Radial piston compressor
By optimizing the piston root chamfer and the number of combined pistons, motor pole pairs and housing threaded connections, the structural compactness and noise problems of radial piston compressors were solved, and a smaller radial structure and improved acoustic performance were achieved.
Patent Information
- Application Number
- CN202480012341.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-02-13
- Filing Date
- 2024-02-07
- Publication Date
- 2025-09-30
AI Technical Summary
When the number of pistons in existing radial piston compressors is increased to reduce the structural space, piston collisions are prone to occur, the guide length is insufficient, and the noise and acoustic performance are poor.
By optimizing the piston root chamfer angle to 360°/number of pistons/2, ensuring that adjacent piston chamfer surfaces are parallel, and combining the appropriate number of pistons, number of motor pole pairs, and number of housing threaded connections, the piston diameter and stroke ratio are optimized, reducing the risk of piston collision and improving acoustic performance.
A more compact radial structure design is achieved, which reduces the risk of piston collision, reduces noise and acoustic impact, and improves the system's acoustic performance and bearing service life.
Smart Images
Figure CN120731322A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a radial piston compressor according to the preamble of claim 1 . Background Art
[0002] A radial piston compressor is a fluid-processing component. Unlike axial piston pumps, at least one piston-working chamber combination is arranged radially and perpendicularly to the drive shaft. The piston's delivery or stroke motion is typically caused by an eccentric shaft. Typically, a radial piston compressor comprises multiple piston-working chamber combinations that extend radially 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 coolants in air-conditioning systems of motor vehicles, in particular also in electrically driven motor vehicles.
[0004] The piston-working chamber combination essentially consists of a working chamber (also called a cylinder) and a piston that moves up and down in the working chamber. The piston has a central geometric piston axis that coincides with the direction of its movement. In radial piston compressors with an eccentric shaft, the piston includes a contact surface on its side facing the eccentric shaft, against which the eccentric disc touches or rests during the rotation of the eccentric shaft. The eccentric shaft has an axis of rotation about which the eccentric shaft rotates. The contact of the eccentric disc with the contact surface causes the piston to move upward and to compress the medium located in the working chamber, resulting in an increase in pressure and force.
[0005] In particular when using radial piston compressors in motor vehicles, a compact design is advantageous.
[0006] If the radial installation space of a radial piston compressor is to be further reduced without reducing the delivery capacity, the number of pistons can be increased to, for example, seven. For the same delivery volume (e.g., with six pistons), the piston diameter can be reduced. As the number of pistons increases, collisions can occur at the points of closest contact between adjacent pistons.
[0007] In order to generate the most uniform delivery flow possible (with minimal pressure pulsations), a minimum number of five or more pistons should be sought. However, since the radial installation space of the entire radial piston compressor must be kept as small as possible, the diameter of the eccentric, through which the piston performs its stroke function, must also be kept as small as possible. This limitation, combined with the simultaneous demand for larger piston diameters or an increased number of pistons, is unattainable with pistons having a continuous outer diameter according to the prior art, as the pistons would collide with each other near bottom dead center.
[0008] Solutions known from the prior art use chamfers at the piston root to prevent collisions in the "critical position." However, the introduction of chamfers simultaneously reduces the guide length of the piston in the cylinder bore. To increase the guide length further, the piston and, accordingly, the cylinder bore must be enlarged, which in turn increases the radial installation space. Summary of the Invention
[0009] The present invention proceeds from this point and has the object of proposing an improved radial piston compressor, in particular a radial piston compressor which can be designed more compactly while maintaining the same or similar performance parameters.
[0010] According to the invention, this object is achieved by a radial piston compressor having the features of the characterizing portion of claim 1. Since each piston includes a piston root, each piston root is provided with at least one circumferential chamfer or two chamfers, wherein the chamfer or chamfers form a chamfer angle relative to the longitudinal axis of the piston, which is set so that the greatest possible guide length of the piston in the working chamber is achieved in the area of closest contact with the adjacent piston. Thus, an improved radial piston compressor, in particular a compact radial piston compressor, can be provided. The core of the concept is to provide the chamfers at the piston root with an "optimal" chamfer angle, which results in a uniform minimum distance in the area of closest contact with the adjacent pistons and thereby achieves the greatest possible guide length of the piston.
[0011] Further advantageous embodiments of the proposed invention result in particular from the features of the dependent claims. In principle, the subject matter or features of the various claims can be combined with one another in any manner.
[0012] In one advantageous embodiment of the present invention, the following can be provided: chamfer angle = 360° / number of pistons / 2. An advantageous solution for the length and angle of the piston root chamfer, i.e., the optimal chamfer angle at the piston root, results in "optimal chamfer angle = 360° / number of pistons / 2." If the optimal chamfer angle is achieved, the chamfered surfaces of adjacent pistons are parallel to one another at their narrowest point. This results in a safe and reliable piston while simultaneously minimizing radial installation space.
[0013] In a further advantageous embodiment of the invention, it can be provided that the longitudinal axes of the pistons lie in one plane.
[0014] In another advantageous embodiment of the invention, provision can be made for pistons / cylinders to be provided which are distributed uniformly over the circumference.
[0015] In a further advantageous embodiment of the invention, it can be provided that an additional edge rounding is provided at the transition from the piston root chamfer to the piston root.
[0016] The invention also relates to a radial piston compressor according to the preamble of claim 6 and / or 7.
[0017] Further disadvantages are known with respect to radial piston compressors.
[0018] In the case of electrically driven radial piston compressors, 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 the further component grouping with a “multiple” of individual components.
[0019] These are determined by the geometry / construction of the motor, e.g. the number of coils / windings, the number of pole pairs, the number of magnets. For example, 8 pole pairs, but always an even multiple of 2.
[0020] Another parameter with multiple individual components is the housing threaded connection. These connections are designed to axially clamp the housing components, depending on the design, together so that no refrigerant leaks into the environment under all operating conditions and test requirements. In other words, the housing threaded connection must fulfill its sealing function. The required contact force achieved by the threaded connection must be so high that it resists pressure forces that attempt to push the housing apart. Ideally, the threaded connections are positioned individually or in pairs on the angle bisector "between" the pistons or cylinders. For example, in a radial piston compressor with seven pistons, 2 x 7 = 14 M6 x 100 screws are used to meet this requirement. Seven M8 screws would not achieve the required contact force, while seven M10 screws would significantly increase the radial installation space. In other words, the number of housing threaded connections is related 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, this is an even number.
[0021] In other words, a radial piston compressor is provided that includes a certain number of pistons, wherein the drive is designed as an electric motor with a certain number of pole pairs, wherein the radial piston compressor includes an at least two-part housing, whose housing parts are connected by a certain number of housing screw connections. Preferably, the radial piston compressor includes a housing and a housing cover, which are connected to each other by means of the housing screw connections.
[0022] The piston-working chamber combination and the number of poles of the electric motor are excitation components which influence the acoustic properties of the radial piston compressor via excitation events (eg pressure peaks in the working chamber, transitions between pole pairs, etc.).
[0023] A further object of the present invention is to provide an improved radial piston compressor, in particular a radial piston compressor which is designed to be quieter during operation with identical or similar performance parameters.
[0024] According to the invention, this object is achieved by a radial piston compressor having the characterizing features of claims 6 and / or 7. This is achieved by selecting a preferred combination of properties, including the number of pistons, the number of motor pole pairs, and the number of screw connections in the housing, along with their dimensions, wherein these combinations are expected to improve the acoustic performance of the overall system. The core of the concept is to define suitable combinations of the number of pistons, the number of screw connections in the housing, and the number of pole pairs that are beneficial for the acoustics or sound radiation performance of the overall compressor.
[0025] The novelty lies in particular in defining preferred combinations of properties, including the number of pistons, the number of motor pole pairs and the number and dimensions of the screw connections of the housing, wherein these combinations are expected to improve the acoustic properties of the overall system.
[0026] Alternatively or additionally, provision can be made for the excitation events per revolution from the various excitation assemblies to be different, thereby providing a radial piston compressor that is designed to be quieter during operation while maintaining identical or similar performance parameters. In other words, to avoid acoustic anomalies, the excitation events per revolution from the various excitation assemblies (e.g., pressure curves with seven pistons = seven per revolution; excitation from an electric drive—eight pole pairs = eight per revolution) should be as different as possible.
[0027] As a result, the acoustic impact (sound pressure level) of the entire system can be reduced and the acoustic performance in the vehicle can thus be improved.
[0028] Further advantageous embodiments of the proposed invention result in particular from the features of the dependent claims. In principle, the subject matter or features of the various claims can be combined with one another in any manner.
[0029] In an advantageous embodiment of the invention, it can be provided that the radial piston compressor is an electrically driven radial piston compressor.
[0030] 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 a permanently excited motor, a separately excited motor or a self-excited motor.
[0031] 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, evenly distributed pistons of the radial piston compressor are present.
[0032] In a further advantageous embodiment of the invention, provision can be made for the housing screw connections to be arranged individually or in pairs on the angle bisector between the piston axes.
[0033] In another advantageous embodiment of the invention, provision can be made for the distances between the screws, viewed over the circumference of the threaded hole circle, to be as uniform as possible, in particular identical, in order to produce a uniform contact force on the surface seal (in the axial direction between the housing parts).
[0034] In another advantageous embodiment of the invention, it can be provided that other combinations of the number of pistons, the number of pole pairs and / or the number of screws are used.
[0035] In a further advantageous embodiment of the invention, provision can be made for a threaded connection that deviates from the standard (M7 size or thread pitch) to be used.
[0036] In a further advantageous embodiment of the invention, provision can be made for the strength class of the screw (8.8, 10.9, 12.9, etc.) to be variable.
[0037] In a further advantageous embodiment of the invention, it can be provided that the type of screw connection of the housing (screw head shape, screw shank, expansion screw, spacing bolt with nut . . . ) can vary.
[0038] In a further advantageous embodiment of the invention, provision can be made for the type and material of the magnets of the electric machine to be variable.
[0039] In a further advantageous embodiment of the invention, provision can be made for the type of electric machine (optionally an asynchronous machine or a separately excited synchronous machine) to be variable.
[0040] The invention also relates to a radial piston compressor according to the preamble of claim 19 .
[0041] Further disadvantages are known with respect to radial piston compressors.
[0042] A further object of the present invention is to provide an improved radial piston compressor, in particular a radial piston compressor which is designed to be quieter during operation with identical or similar performance parameters.
[0043] According to the invention, this object is achieved by a radial piston compressor having the characterizing features of claim 19. According to the invention, suitable combinations of the number of pistons, piston diameter, and piston stroke are proposed in which the excitation force component of the pressure profile of the compression process is optimal. In other words, a specific preferred combination of the number of pistons, piston diameter, and piston stroke is specified that results in an optimal excitation function at the eccentric at a selected operating point. A specific stroke / diameter ratio and the associated number of pistons should be selected to match the compression process.
[0044] This reduces the acoustic impact of the entire system, in particular the sound pressure level, and thus contributes to improving the acoustic performance in the vehicle. This also results in, in particular, an increased bearing service life of the eccentric bearing and / or reduced torque fluctuations of the compressor and thus improved adjustability. BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Other features and advantages of the present invention will become apparent from the following description of preferred embodiments in conjunction with the accompanying drawings, in which:
[0046] Figure 1 A radial piston compressor is shown in side cross-sectional view;
[0047] Figure 1a A radial piston compressor is shown in cross-section;
[0048] Figure 2 A schematic diagram of a radial piston compressor is shown to illustrate a piston with a large diameter and a small eccentric and the resulting collision;
[0049] Figures 3a to 3e A schematic diagram showing a radial piston compressor and details of the radial piston compressor, in particular the chamfer at the piston root;
[0050] Figure 4 Shows possible combinations of number of pistons, number of motor pole pairs and required number / size of housing threaded connections;
[0051] Figure 5 A suitable combination variant is shown in which the number of pistons is "5";
[0052] Figure 6 Suitable combination variants with 7 and 8 pistons are shown;
[0053] Figure 7 A suitable combination variant with 9 pistons is shown;
[0054] Figure 8 The cylinder pressure curve relative to the cylinder volume is shown - compression phase;
[0055] Figure 9 shows the pressure variation curve for each piston;
[0056] Figure 10 shows the superimposed piston pressure variation curve of a five-piston radial piston compressor;
[0057] Figure 11 The radial load generated by the superposition of the pressure curves of 5 and 6 pistons is shown;
[0058] Figure 12The radial force generated at the operating point for different numbers of pistons is shown;
[0059] Figure 13 Schematic diagram showing the eccentric bearing load under different operating conditions.
[0060] The following reference numerals are used in the drawings:
[0061] A Piston axis
[0062] R Rotation axis
[0063] F Chamfer
[0064] F1 First chamfer
[0065] F2 Second chamfer
[0066] Α chamfer angle
[0067] Φ driving angle
[0068] L Guide length
[0069] Z Number of cylinders / number of pistons
[0070] V Number of threaded connections
[0071] P number of pole pairs
[0072] M thread connection size
[0073] D Piston diameter
[0074] H piston stroke
[0075] K Piston Collision
[0076] 1. Drive unit
[0077] 2 Compressor unit
[0078] 3-pole
[0079] 4 Threaded connection
[0080] 5. Housing
[0081] 6 Coupling element / pivoting section
[0082] 21 drive shaft
[0083] 22 eccentric wheel
[0084] 23-23″″ piston-working chamber combination
[0085] 41 screws
[0086] 42 through holes
[0087] 43 threaded holes
[0088] 51 Housing cover
[0089] 52 Main body shell
[0090] 231 working chamber (cylinder bore)
[0091] 232 Piston
[0092] 2321 Piston Root
[0093] 2322 Edge rounding DETAILED DESCRIPTION
[0094] It goes without saying that the features and details described in conjunction with the method also apply in conjunction with the device according to the invention, and vice versa, so that reference is always made to one another or can be made to one another with respect to the disclosure of the various aspects of the invention. Furthermore, the method according to the invention described, if necessary, can be implemented using the device according to the invention.
[0095] The terms used herein are only used to describe specific embodiments and should not limit the present disclosure. As used herein, the singular forms "a", "an" and "the" should also include the plural forms, unless the context clearly indicates otherwise. It is also clear that when the expression "having" is used in this specification, it indicates the presence of the mentioned features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations. As used herein, the expression "and / or" includes any and all combinations of one or more associated, listed elements.
[0096] First reference Figure 1 and Figure 1a .
[0097] Figure 1 A radial piston compressor with a piston design is shown, in particular a compact embodiment of a radial piston compressor with six pistons 232 for use with the refrigerant CO 2 . A coupling element 6 , also called a pivoting section, can be provided between the eccentric bearing outer diameter and the piston root.
[0098] The radial piston compressor mainly comprises a drive unit 1 and a compressor unit 2 .
[0099] The drive device 1 may be an electric motor, for example.
[0100] The compressor device 2 comprises a drive shaft 21 with an eccentric 22 and 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.
[0101] The piston-working chamber combination 23 essentially comprises a working chamber 231 (also referred to as a cylinder) and a piston 232 that moves up and down in the working chamber 231. The piston 232 has a central geometric piston axis A, which coincides with the direction of movement of the piston 232. In radial piston compressors with eccentric shafts 21, 22, the piston 232 includes a contact surface on the side facing the eccentric shaft, against which the eccentric disc 22 contacts or rests during rotation of the eccentric shaft. The eccentric shaft has an axis of rotation R, about which the eccentric shaft rotates. The contact of the eccentric disc with the contact surface causes the piston to move upward and compress the medium located in the working chamber 231, thereby increasing the pressure and force.
[0102] Next, especially the reference Figure 2 .
[0103] Figure 2 It is schematically shown that a piston collision K may occur when two adjacent pistons are at or near bottom dead center and appropriate preventive measures are not taken.
[0104] Below, special reference Figures 3a to 3e .
[0105] The piston 232 used here has a piston root 2321, that is, the area of the piston 232 that faces the drive shaft 21. The piston root 2321 is provided 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, relative to the longitudinal axis K of the piston. Accordingly, the first chamfer F1 forms a chamfer angle α1 relative to the piston axis A, and in the case of two chamfers, the second chamfer F2 forms a chamfer angle α2 relative to the piston axis.
[0106] In the case of a circumferential chamfer, a conical piston root is essentially obtained. Here, the chamfer angle is correspondingly referred to as the chamfer angle α. In the case of two chamfers, two surfaces arranged at corresponding angles are essentially obtained.
[0107] The chamfer itself is preferably designed as a plane. The chamfer angles α1 and α2 are preferably identical, so that reference is made below to the chamfer angle α as a representative example.
[0108] According to the present invention, an optimal chamfer angle α is provided at the piston root 2321 , which enables the largest possible guide length L of the piston in the cylinder bore 231 in the area of closest contact between adjacent pistons 232 .
[0109] The guide length L of the piston 232 is the section or the length of the piston 232 over which it can be guided in the working chamber.
[0110] The optimal solution for the length and angle of the piston root chamfers F1 and F2, or the optimal chamfer angle α at the piston root 2321, results in "optimal chamfer angle α = 360° / number of pistons / 2." The number of pistons corresponds to the number of pistons arranged side by side in the circumferential direction of the radial piston compressor. If the optimal chamfer angle α is achieved, the surfaces of the chamfers F1 and F2 of adjacent pistons are parallel to each other in their narrowest sections. This ensures safe and reliable piston guidance while minimizing radial installation space.
[0111] Figure 3 shows some examples for this purpose, in particular Figure 3a and Figure 3b The diagram shows a piston root 2321 with a small chamfer F1 or F2 and a large guide length. Figure 3c and Figure 3d It is shown that the piston root has a large chamfer F1 or F2 which is designed so large that no collision occurs, but at the same time reduces the guide length while maintaining the same overall piston length.
[0112] Figure 3e The chamfer angle α relative to the longitudinal axis K of the piston 232 is shown.
[0113] It is further preferably provided that the longitudinal axes of the pistons, ie the piston axes A of the pistons, lie in a plane.
[0114] It is also preferably provided that piston / cylinder, ie piston-working chamber, combinations are provided which are distributed uniformly over the circumference, ie the angles between adjacent piston axes A are always the same.
[0115] A small installation space requirement is also preferably provided, which does not result in a risk of collisions between adjacent pistons.
[0116] Preferably, an additional edge rounding 2322 may be provided at the transition from the piston root chamfer F1 or F2 to the piston root 2321 .
[0117] Preferably, the size of the individual piston diameters / cylinder bore diameters, the number of pistons and / or the length of the chamfer at the piston root can be varied.
[0118] In the case of an offset of the piston axis A, different chamfer lengths can also be provided on both sides at the piston root, in particular when the cylinder bores are staggered so that the axes do not intersect or the opposing cylinders are not on the same axis, or when the piston root 2321 has a chamfer in a section along the eccentric axis that is different from the chamfer in the cross section.
[0119] Next reference Figures 4 to 7 .
[0120] For the basic characteristics of radial piston compressors, please refer to Figure 1 and Figure 1a and related descriptions.
[0121] The radial piston compressor comprises a drive device 1 designed as an electric motor having a corresponding number of poles 3, also referred to as the pole number. Typically, two poles are combined to form a pole pair. Furthermore, the radial piston compressor comprises a threaded connection 4. This threaded connection typically comprises a screw 41, a through-hole 42, and a corresponding threaded hole 43, into which the screw 41 can be inserted or screwed. The at least two-part housing 5 of the radial piston compressor is connected to one another via the threaded connection 4. Preferably, the housing comprises a housing cover 51 and a main housing 52, which are connected to one another via the threaded connection 4.
[0122] Depending on the design, the screwed housing connections 4 should axially clamp the housing components 51, 52 against each other so that no refrigerant leaks into the environment under all operating conditions and test requirements. In other words, the screwed housing connections must fulfill their sealing function. The required contact force achieved by the screwed connections 4 must be so high that it resists pressure forces that attempt to push the housing components 51, 52 apart. The screwed connections 4 are preferably positioned individually or in pairs on the angle bisector "between" the pistons or cylinders (i.e., the piston-working chamber combinations 23).
[0123] The radial piston compressor also has a certain number of piston-working chamber combinations 23 , and accordingly a corresponding number of pistons 232 and working chambers 231 .
[0124] Additionally or alternatively, it can be provided here that the radial piston compressor forms excitation components via the piston-working chamber combination 23 and the poles 3 of the electric motor, which are characterized by excitation events (e.g. pressure peaks in the working chamber 231 and transitions between the pole pairs 3) which influence the acoustic properties of the radial piston compressor.
[0125] Next, especially in Figures 4 to 7 In the list and description of advantageous combinations of the number of cylinders Z, the number of pole pairs P, the number of housing screw connections V and the dimension M. In principle, for the "acoustic" criterion, variants are preferred in which the "least common multiple (kgV)" is as large as possible.
[0126] The lowest common multiple (kgV) is the product of the number of pistons or cylinders Z and the number of pole pairs P of the drive in the form of an electric motor, especially if it is a prime number. In the case of 6 screws and 8 pole pairs, the lowest common multiple (kgV) is 24 (4×6=24 and 3×8=24), not 6×8=48.
[0127] On the other hand, some of these variants have a large number of components (pistons; pole pairs) and are therefore not preferred with regard to production costs.
[0128] Figure 4 One design path shows a possible combination of the number of pistons Z, the number of pole pairs P of the drive device designed as an electric motor, and the required number V and size M of the screw connections 4 of the housing. The forces that the screw connections must withstand are largely influenced by their inner diameter Di or the resulting pressure surface. The number of pistons Z is influenced by the required stroke volume HVol and the radial installation space. The number of magnets or pole pairs P varies depending on the requirements. A larger number of pole pairs P results in less "ripple," meaning lower locking torque, but this also means higher costs.
[0129] Figure 5 The purpose is to show that for a number of pole pairs P = 8 (combination "1") and a low number of components, an acceptable "least common multiple (kgV)" of 40 can be achieved. For P = 12 pole pairs (combination "2"), the "least common multiple (kgV)" is 60.
[0130] Figure 6 The purpose is to show that for the case of 7 pistons, each of the selected numbers of pole pairs P (8, 10, 12) results in a large "least common multiple (kgV)". For the case of 8 pistons, only the combination with 10 pole pairs is still acceptable. For the case of the number of pole pairs P = 12, the "least common multiple (kgV)" is 24, that is, for every 2 revolutions of the compressor, the piston drive and the motor are "simultaneously" excited, which would lead to "unfavorable" acoustic effects.
[0131] Figure 7 The purpose is to show that a large “lowest common multiple (kgV)” can be achieved for 9 pistons and a number of pole pairs P=8 or 10. However, this combination also depends on the large number of components used for the entire system.
[0132] According to the invention, it is provided here that certain preferred combinations of the number of pistons or cylinders Z, the number of pole pairs P of the motor and the number V of screw connections of the housing together with the dimension M are selected, wherein these combinations are expected to improve the acoustic properties of the overall system.
[0133] Alternatively or additionally, provision can be made for the excitation events per revolution from the various excitation components to be different.
[0134] This makes it possible to provide a radial piston compressor that is designed to operate even quieter with identical or similar performance data. In other words, to avoid acoustic anomalies, the excitation events per revolution from the various excitation components (e.g., pressure curve with 7 pistons = 7 per revolution; excitation from the electric drive—8 pole pairs = 8 per revolution) should be as different as possible.
[0135] The radial piston compressor described here has, in particular, the following features.
[0136] Preferably, this is an electrically driven radial piston compressor, ie the drive is designed as an electric motor.
[0137] Preferably, it is an electric machine having a slot-pole pair combination, optionally a permanently excited motor, a separately excited motor or a self-excited motor.
[0138] Preferably, uniformly distributed pistons or piston-working chamber combinations are provided for radial piston compressors.
[0139] Preferably, the screw housing connections 4 are arranged individually or in pairs on the angular bisector between the piston axes A.
[0140] Preferably, the distances between the screws 41 , viewed over the circumference of the threaded hole circle, are as identical as possible, preferably identical, in order to generate a uniform contact force on the face seal, in particular in the axial direction between the housing components 51 , 52 .
[0141] In particular, variations or other combinations of the number of pistons Z, the number of pole pairs P and / or the number of screws V are conceivable.
[0142] In particular, threaded connections 4 deviating from the standard, in particular M7 size or thread pitch, are conceivable.
[0143] In particular, variations in the strength class of the screw 41 are conceivable, for example strength class 8.8, 10.9, 12.9, etc.
[0144] In particular, variations are conceivable with regard to the type of the housing screw connection 4 , in particular the shape of the screw head, the screw shank, an expansion screw, a spacer bolt with a nut, etc.
[0145] Variations in the type and material of the magnets of the electric machine are conceivable.
[0146] Variations in the type of electric motor are conceivable, in particular asynchronous motors or separately excited synchronous motors are also conceivable as an alternative.
[0147] Next reference Figures 8 to 13 d.
[0148] For the basic characteristics of radial piston compressors, please refer to Figure 1 and Figure 1a and related descriptions.
[0149] The radial piston compressor outlined here is characterized in particular in that it has a number of pistons 232 , wherein the pistons 232 have a piston diameter D and a piston stroke H.
[0150] Figure 8 The diagram schematically illustrates the cylinder pressure curve over the cylinder volume, specifically during the compression phase. In electrically driven radial piston compressors, the selection of the appropriate number of pistons Z depends not only on the desired delivery volume, specifically the piston stroke H, the piston diameter D, and the number of pistons Z, but also on the force excitation that interacts during the individual compression strokes. Each stroke motion in a radial piston compressor follows the two-stroke principle, consisting of an intake phase, a compression phase, an exhaust phase, and an expansion phase.
[0151] Figure 9 The pressure curve for each piston is shown. During the compression phase, exhaust phase and expansion phase, the pressure acts on the piston, which can be represented as a cylinder pressure curve ZD over time or angle / drive angle AW or cylinder volume ZV of the compression process.
[0152] Figure 10 The superimposed piston pressure curves of a five-piston radial compressor are schematically shown. Analogously to the excitation function of an internal combustion engine, the individual cylinder pressure curves ZD are superimposed, which results in an excitation force component F on the eccentric 22 of the radial piston compressor.
[0153] Figure 11 The actual load resulting from the superposition of the pressure curves of 5 and 6 pistons 232 is shown schematically. For one cylinder 231, one continuous pulse is generated per revolution. For two cylinders, two pulses are generated per revolution, and so on. Optimal for the excitation of the system is the superposition of pulses, which, due to their length, shape, and number of radial excitation force components, just form a constant total force without superimposed amplitudes. Therefore, the number of pistons should be selected so that the compression processes of the individual pistons are neither superimposed nor overlapped. However, since overlapping and non-overlapping of the pressure curves always occur depending on the pressure position in either combination, the resulting force amplitude plays a decisive role in the excitation of the system. If smaller pistons with lower surface pressure are used for the same stroke volume of the compressor, a larger number of pistons is required. This in turn results in a smaller force amplitude.
[0154] Figure 12 The radial force F generated at the operating point is shown schematically for different numbers of pistons (numbers on the curve). A specific combination of number of pistons and stroke / bore ratio leads to an almost complete cancellation of the excitation amplitude at the selected operating point due to shape, length and number. Figure 12 For example, it is shown that the excitation amplitude is minimum for a combination of 7 pistons, a piston diameter D of 16 mm and a stroke H of 8 mm. Despite the higher number of pistons, a system with 8 pistons cannot achieve this minimum system excitation.
[0155] Figure 13 a to Figure 13 d Plot of the eccentric bearing load under different operating conditions and number of pistons. Figure 13 a to Figure 13 d shows the loads acting on the eccentric drive at different speeds, pressure ratios, and numbers of pistons. This is based on the fact that, at the same stroke H, the same stroke volume of the compressor varies with the number of pistons and piston diameter D. It can be clearly seen that, starting with seven pistons, the radial loads acting on the eccentric are significantly reduced compared to variants with five or six pistons. The excitation forces and their amplitudes are drastically reduced, which leads to improved NVH (perceptible and audible vibration) performance and, therefore, increased end-customer acceptance. In this case, a radial piston compressor with at least seven pistons, and advantageously eight or nine pistons, represents a system with favorable excitation.
[0156] Furthermore, due to the lower amplitude, the bearing loads on the eccentric drive are reduced. This allows for the installation of smaller bearings or increases the service life of the eccentric bearings.
[0157] Seven pistons have proven to be optimal, particularly at low pressure ratios, as the individual cylinder pressure curves are advantageously superimposed. This facilitates compressor operation at low pressure ratios, as the resulting torque fluctuations are expected to be lower from a purely mechanical perspective. Due to the low torque fluctuations in the compressor, the motor has improved control capabilities and is driven less strongly.
[0158] According to the present invention, suitable combinations of the number of pistons Z, piston diameter D, and piston stroke H are proposed in which the excitation force component of the pressure curve of the compression process is optimized. In other words, a specific preferred combination of the number of pistons Z, piston diameter, and stroke H of the piston 232 is specified to produce an optimal excitation function at the eccentric 22 at the selected operating point. A specific stroke / diameter ratio H / D and the associated number of pistons Z should be selected to match the compression process.
[0159] This reduces the acoustic impact of the entire system, in particular the sound pressure level, and thus contributes to improving the acoustic performance in the vehicle. This also results in, in particular, an increased bearing service life of the eccentric or the bearings arranged on the eccentric disk (in particular roller bearings), and / or reduced torque fluctuations in the compressor, thus improving adjustability.
[0160] Preferably, the radial piston compressor is an electrically driven radial piston compressor with a two-stroke operation. Preferably, an electric motor is used as the drive device. In addition, preferably, the radial piston compressor is provided with uniformly distributed pistons 232.
[0161] Furthermore, other combinations of the number of pistons / diameter and the number of pistons are preferably conceivable. In addition to CO 2 , other refrigerants are also conceivable as fluid for the radial piston compressor.
[0162] A preferred field of application of the radial piston compressor proposed here is in the field of air conditioning systems in motor vehicles. Accordingly, the radial piston compressor is preferably provided for compressing refrigerants or fluids, such as CO 2 . However, other purposes of use or fluids are also conceivable.
Claims
1. A radial piston compressor comprising: a drive unit (1) and a compressor unit (2), The compressor device (2) comprises a drive shaft (21) having an eccentric (22), At least one piston-working chamber combination, preferably a plurality of piston-working chamber combinations (23-23"""') extending radially from the drive shaft (21), Each piston-working chamber combination comprises a working chamber (231) and a piston (232) movable in the working chamber, the piston (232) having a longitudinal axis (A). It is characterized by: Each piston (232) comprises a piston root (2321), each piston root (2321) is provided with a surrounding chamfer (F) or two chamfers (F1, F2), The surrounding chamfer (F) or the two chamfers (F1, F2) form a chamfer angle (α or α1, α2) relative to the longitudinal axis (A) of the piston (232), and the chamfer angle (α or α1, α2) is set so that in the area of closest contact with the adjacent piston, the chamfer angle can achieve the maximum possible guide length (L) of the piston (232) in the working chamber (231).
2. The radial piston compressor according to claim 1, characterized in that The chamfer angle (α1 or α2) is equal to 360° / the number of pistons (Z) / 2.
3. Radial piston compressor according to at least one of the preceding claims, characterized in that The longitudinal axis (A) of each piston (232) lies in a plane.
4. 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 on the circumference.
5. Radial piston compressor according to at least one of the preceding claims, characterized in that An additional edge rounding (2322) is provided at the transition from the chamfer (F) to the piston root (2321).
6. Radial piston compressor according to at least one of the preceding claims or according to the preamble of claim 1, wherein: The radial piston compressor includes a certain number (V) of pistons (232), The drive device (1) is designed as an electric motor comprising a certain number of pole pairs (3). The radial piston compressor comprises at least a two-part housing (51, 52), the housing parts of which are connected by a number of threaded connections (4). It is characterized by: Certain preferred combinations of the number of pistons (V), the number of motor pole pairs (3) and the number of threaded connections (4) (V) together with the dimensions (M) are selected, wherein these combinations are expected to improve the acoustic performance of the overall system.
7. Radial piston compressor according to at least one of the preceding claims or according to the preamble of claim 1, wherein: The radial piston compressor comprises an excitation component formed by a piston-working chamber combination (23) and a pole pair (3) of an electric motor, wherein the excitation component is characterized by excitation events, such as pressure peaks in the working chamber (231) and transitions between pole pairs (3), which influence the acoustic properties of the radial piston compressor. It is characterized by: The excitation events per revolution from each of the different excitation components are different.
8. 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.
9. Radial piston compressor according to at least one of the preceding claims, characterized in that The drive device (1) is designed as an electric motor and comprises a slot-pole pair combination, in particular a permanently excited motor, a separately excited motor or a self-excited motor.
10. Radial piston compressor according to at least one of the preceding claims, characterized in that The piston-working chamber combinations (23) are arranged uniformly distributed over the circumference of the radial piston compressor; in particular, uniformly distributed pistons (232) of the radial piston compressor are present.
11. Radial piston compressor according to at least one of the preceding claims, characterized in that The threaded connections (4) are arranged individually or in pairs on the angle bisector between the piston axes (A).
12. Radial piston compressor according to at least one of the preceding claims, characterized in that The distances between the threaded connections (4) viewed on the circumference of the threaded hole circle are as uniform as possible, in particular identical, in order to generate a uniform contact force on the face seal, in particular in the axial direction between the housing components.
13. Radial piston compressor according to at least one of the preceding claims, characterized in that Other combinations of the number of pistons (Z), number of pole pairs (P), and / or number of threaded connections (V) are used.
14. Radial piston compressor according to at least one of the preceding claims, characterized in that Use of threaded connections (4) that deviate from the standard, in particular size 7 or thread pitch.
15. Radial piston compressor according to at least one of the preceding claims, characterized in that The strength grade of the screw (41), in particular the strength grades 8.8, 10.9, 12.9 etc., can vary.
16. Radial piston compressor according to at least one of the preceding claims, characterized in that The type of threaded connection, in particular the shape of the screw head, the screw shank, expansion screw, spacer bolt with nut, etc., may vary.
17. Radial piston compressor according to at least one of the preceding claims, characterized in that The type and material of the motor's magnets can vary.
18. Radial piston compressor according to at least one of the preceding claims, characterized in that The type of electric machine can vary; in particular, the electric machine can be designed alternatively as an asynchronous machine or as a separately excited synchronous machine.
19. Radial piston compressor according to at least one of the preceding claims or according to the preamble of claim 1, wherein: The radial piston compressor has a certain number (Z) of pistons (232), The piston (232) has a piston diameter (D), The piston (232) has a piston stroke, It is characterized by: Suitable combinations of the number of pistons (Z), the piston (232) diameter (D), and the piston stroke (H) are selected in which the excitation force component of the pressure curve from the compression process is optimal.
20. 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 operating in a two-stroke manner.
21. Radial piston compressor according to at least one of the preceding claims, characterized in that An electric motor is used as the driving device.
22. Radial piston compressor according to at least one of the preceding claims, characterized in that Uniformly distributed pistons (232) are provided for the radial piston compressor.
23. Radial piston compressor according to at least one of the preceding claims, characterized in that Other combinations of number of pistons / diameter (Z / D) and number of pistons (Z) are contemplated.
24. Radial piston compressor according to at least one of the preceding claims, characterized in that Other refrigerants than CO 2 are conceivable as fluid for the radial piston compressor.