Radial piston compressor

Abstract

The invention relates to a radial piston compressor comprising a compressor unit (2) and a drive unit (1) for driving the compressor unit (2), wherein the compressor unit (2) comprises at least one, preferably a plurality of piston / working chamber combinations (21, 22), arranged radially around an eccentric shaft (23, 24), wherein each piston / working chamber combination (21, 22) comprises a working chamber (21) with a piston (22) moveably accommodated therein, wherein the piston (22) is driven by the eccentric shaft (23, 24), wherein the eccentric shaft (23, 24) is rotatably mounted in the radial piston compressor by at least three bearings, preferably three bearings (3, 4, 5).

Description

[0001] Radial piston compressor

[0002] The invention relates to a radial piston compressor according to the preamble of claim 1.

[0003] A radial piston compressor is a fluid power component. Unlike an axial piston compressor, this type of compressor has at least one piston-working chamber combination arranged radially and perpendicular to the drive shaft. A radial piston compressor can also be referred to as a compressor based on the radial piston principle.

[0004] The piston's displacement or reciprocating motion is usually driven by an eccentric. Therefore, the drive shaft can also be referred to as an eccentric shaft. Radial piston compressors typically comprise several piston-working chamber combinations that extend radially and in a star pattern from the drive shaft or eccentric shaft.

[0005] A piston-working chamber combination essentially comprises a working chamber, also called a cylinder, and a piston that moves up and down within the working chamber. The piston has a central geometric piston axis that coincides with the piston's direction of displacement. In a radial piston compressor with an eccentric shaft, the piston has a contact surface on its side facing the eccentric shaft, against which the eccentric disc impacts or rests during rotation of the eccentric shaft. The eccentric shaft has an axis of rotation about which the eccentric shaft is rotated. When the eccentric impacts the contact surface, the piston moves upwards, compressing a medium in the working chamber.

[0006] Radial piston compressors are used, for example, to compress coolant in motor vehicle air conditioning systems, especially in electrically powered vehicles. A coolant such as CO2 can be used as the compressed medium. However, other media or coolants are also conceivable.

[0007] During one revolution, the refrigerant is drawn in, compressed, and expelled again. This periodic process exhibits a uniform phase shift between the cylinders, which depends on the number of cylinders. The pressure created in the cylinder acts via the piston surface on the eccentric pin, thus exciting the eccentric shaft. The superposition of the forces of all cylinders involved in the compression process produces the resulting force on the eccentric shaft. The eccentric shaft, in turn, in conjunction with the bearings and the surrounding housing, represents a vibratory system. This system is excited to bending vibrations as a result of the periodically acting compression pressures.

[0008] In the system described here, bending vibrations have a particularly detrimental effect on the acoustic behavior, since the static force equilibrium is no longer maintained in the resonance range. Resonances occur when the natural frequency of the oscillating system coincides with the excitation frequency.

[0009] 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 which has improved acoustic behavior.

[0010] According to the invention, this object is achieved by a radial piston compressor with the characterizing features of claim 1. This is achieved by the eccentric shaft being rotatably mounted in the radial piston compressor by at least three bearings, preferably three bearings. In other words, to improve the acoustic behavior of the radial piston compressor, it is advisable to influence the system so that resonances can be less pronounced by carefully selecting the number of bearings, bearing position, and / or bearing stiffness.

[0011] Further advantageous embodiments of the proposed invention emerge in particular from the features of the subclaims. The subject matter and features of the various claims can, in principle, be combined with one another in any desired way.

[0012] In an advantageous embodiment of the invention, the radial piston compressor can comprise a drive housing, a compressor housing, and a compressor housing cover. In principle, the housing of the radial piston compressor can have additional components or, in principle, be designed in only two parts. However, with the three-part division outlined here, the positions of the individual bearings lend themselves to a preferred embodiment of the invention, particularly since they are easily accessible in the individual housing parts and can be easily assembled and disassembled, for example, for maintenance purposes.

[0013] In a further advantageous embodiment of the invention, the first bearing can be accommodated in the compressor housing cover, the second bearing in the compressor housing, and the third bearing in the drive housing. This indicates a preferred positioning of the bearings with regard to the available housing components. As already outlined above, the bearings can be easily mounted and removed from the individual housing components.

[0014] In a further advantageous embodiment of the invention, the first bearing and the second bearing can be accommodated in the compressor housing, and the third bearing in the drive housing. This indicates a preferred positioning of the bearings with regard to the available housing components. As already outlined above, the bearings can be easily mounted and removed from the individual housing components.

[0015] In a further advantageous embodiment of the invention, it can be provided that the shaft has a vibration node due to the three bearing points and their arrangement, wherein this vibration node is arranged in its axial position close to the location of a load introduction.

[0016] In a further advantageous embodiment of the invention, the bearings can be designed as plain or rolling bearings, in particular as cylindrical roller bearings or ball bearings. Such bearing types exhibit advantageous bearing rigidity.

[0017] In a further advantageous embodiment of the invention, one of the bearings can be designed as an axial bearing. Accordingly, the axial bearing can be used to axially fix the eccentric shaft.

[0018] In a further advantageous embodiment of the invention, the bearings can be held in the housing by pressing. This type of bearing fixation is well suited for industrial series production.

[0019] In a further advantageous embodiment of the invention, it can be provided that the eccentric shaft is guided axially by a retaining ring. This advantageously results in the bearings not having to absorb any axial forces. Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the accompanying drawings.

[0020] Fig. 1 shows a first bending mode of a shaft with external double bearing;

[0021] Fig. 2 shows a first bending mode of a shaft with triple support and vibration nodes close to the location of the excitation;

[0022] Fig. 3 shows an eccentric shaft of a radial piston compressor according to the invention in a side sectional view;

[0023] Fig. 4 shows an embodiment of a radial piston compressor according to the invention in a side sectional view;

[0024] Fig. 5 shows a further embodiment of a radial piston compressor according to the invention in a side sectional view;

[0025] Fig. 6 shows a further embodiment of a radial piston compressor according to the invention in a side sectional view;

[0026] Fig. 7 is a sectional plan view of a radial piston compressor according to the invention.

[0027] The following reference symbols are used in the figures:

[0028] S vibration node

[0029] 0 Location of excitation, load introduction

[0030] G deflection shape

[0031] D axis of rotation

[0032] 1 drive device

[0033] 2 compressor unit

[0034] 3 first camp

[0035] 4 second camp

[0036] 5 third camp

[0037] 11 Drive housing

[0038] 12 Rotor

[0039] 21 Workspace

[0040] 22 pistons

[0041] 23 Drive shaft

[0042] 24 Eccentric disc 25 Compressor housing, cylinder housing

[0043] 26 Compressor housing cover

[0044] 27 eccentric bearings

[0045] 28 Transmission element

[0046] 29 Piston guide ring

[0047] 30 retaining ring

[0048] 231 first section

[0049] 232 second section

[0050] Features and details 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 always made to each other. Furthermore, a method according to the invention that may be described can be carried out with the device according to the invention.

[0051] 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" and "an" and "the" are intended to include the plural forms 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.

[0052] First, reference is made to Fig. 1.

[0053] Fig. 1 schematically illustrates a first bending mode G of an eccentric shaft 23 with external double bearings. This is intended to illustrate, in particular, that in a conventional bearing system with two bearings 3, 4 at the beginning and end of the shaft 23, a first bending mode G of the shaft develops, which has vibration nodes S exclusively at or outside the bearing points 3, 4. As shown in Fig. 1, the arrangement illustrated here has two vibration nodes S.

[0054] Vibration mode and vibration node are terms from (mechanical) vibration theory and machine dynamics. The vibration mode or vibration mode describes the form / formation of a natural frequency of an elastic structure. In addition to bending vibration modes, there are torsional vibration modes, in which the shaft oscillates around the axis of rotation, and mixed modes.

[0055] When such a system is excited, a very dominant resonance develops, which in turn leads to poor NVH behavior of the entire system. NVH (Noise Vibration Harshness) is generally used to describe the acoustic behavior.

[0056] To significantly shift this mode into non-critical excitation ranges, the shaft stiffness, bearing stiffness, and housing stiffness would have to be significantly increased. Due to the space constraints and the compressor's peripherals, this is only possible to a limited extent.

[0057] As previously described, the problem lies in the severity of bending vibration resonances, which severely impair the acoustic behavior. The extent to which a system's resonance can be excited depends largely on the factors of excitation frequency, excitation amplitude, system damping, excitation location, and / or vibration mode. The first four factors are difficult to influence due to the nature of the system.

[0058] According to the invention, the eccentric shaft is supported by at least three bearings, preferably three bearings, in the radial piston compressor. In other words, by carefully selecting the number, position, and / or stiffness of the bearings, the vibration shape is influenced so that the vibration node is located as close as possible to the excitation location.

[0059] For this purpose, Fig. 2 shows, for example, a first bending vibration shape G of a shaft 23 with triple bearings and vibration node S close to the location of the excitation 0. In the theoretical case that the vibration node S and the location of the excitation 0 coincide exactly, no resonance would develop. For practical reasons, such as the installation space and the resulting limited choice of arrangement of the bearing points or the cylinder arrangement or the stroke (height / deflection of the eccentric), the person skilled in the art endeavors to design the compressor in such a way that the vibration node S is as close as possible to the location of the excitation or the location of the force introduction. As can be seen, the shaft 23 here comprises a first bearing 3, a second bearing 4 and a third bearing 5. The location of the force introduction 0 or the location of the excitation 0 is shown schematically as a point and represents the forces acting on the shaft 23.

[0060] Reference is made below to Figs. 3 to 6, which relate to embodiments of radial piston compressors according to the invention. In particular, the design of the radial piston compressor was adjusted so that the third bearing point, particularly with the associated adjusted stiffnesses of the bearings, shaft, and housing parts, leads to the described effect.

[0061] In Fig. 3, a cut-out eccentric shaft 23, 24 with a rotor 12 of a radial piston compressor according to the invention is shown.

[0062] The eccentric shaft 23, 24 essentially comprises a drive shaft 23 and an eccentric disc 24. An eccentric bearing 27, such as a needle bearing, can be mounted on the eccentric disc 24.

[0063] It can also be seen that a bearing 3, 4, 5, in particular a ball bearing, is mounted at three different axial positions of the eccentric shaft 23, 24, in particular a first bearing 3 in the region of one end of the eccentric shaft, a second bearing 4 approximately in the middle of the eccentric shaft and a third bearing 5 at the other end of the eccentric shaft. It can be seen in particular that the second bearing 4 is arranged between the eccentric disc 24 and the rotor 12. Furthermore, it can be seen that this results in a bearing arrangement of the shaft 23 in which the eccentric disc 24 is arranged in the axial direction between two bearings, the bearings 3 and 4. The bending vibration shape G (shown in dashed lines) of the shaft 23 according to Fig. 3 has a vibration node S due to the three bearing points 3, 4, 5 and their arrangement. This vibration node S is arranged in its axial position, in particular on the rotation axis D of the shaft 23, close to the location of the load introduction 0.

[0064] In Fig. 4, an embodiment of a radial piston compressor according to the invention is shown in a lateral sectional view. A radial piston compressor comprises, in addition to the eccentric shaft 23, 24, essentially a

[0065] Drive unit 1 and a compressor unit 2.

[0066] The drive device 1 essentially comprises a drive housing 11 and a rotor 12. A stator is not shown here for reasons of clarity. The drive device 1 is therefore preferably designed as an electric motor.

[0067] The compressor unit 2 essentially comprises at least one, preferably several, piston-working chamber combinations 21, 22, which are arranged around the eccentric shaft 23, 24. The piston-working chamber combinations 21, 22 preferably extend radially from the eccentric shaft 23, 24. The piston-working chamber combinations 21, 22 are arranged in a compressor housing 25, also called a cylinder housing, or it can be provided that the working chamber(s) 21 are formed, at least partially, from the compressor housing 25. It is further provided that the compressor housing 25 is equipped on one side with a compressor housing cover 26. The compressor housing cover 26 can be removed, for example, for maintenance purposes and / or form part of the working chamber(s) 21. In the axial direction, the following sequence of housing components results: compressor housing cover 26, compressor housing 25, drive housing 11., whereby in the design according to Fig.4 The compressor housing 25 does not extend to the outer surface of the compressor. The housing components can be connected detachably using screws. The housing of the radial piston compressor can be formed from the drive housing 11, the compressor housing 25, and the compressor housing cover 26.

[0068] The piston-working chamber combination as such comprises a working chamber 21 and a piston 22 slidably received in the working chamber 21. By displacing the piston 22 in the working chamber 21, the fluid contained in the working chamber 21, such as a refrigerant, in particular CO2, can be compressed.

[0069] The drive device 1 causes the drive shaft 23 to rotate, causing the eccentric disc 24 to strike the piston 22, in particular the piston crown. As a result, the piston 22 is displaced away from the eccentric shaft within the working chamber 21. The piston(s) 22 are therefore driven by the eccentric shaft. A piston guide ring 29 can also be provided, which can come into contact with the piston(s) 22 and can push the piston 22 back towards the eccentric shaft 23, 24. As already indicated above, the eccentric disc 24 can be equipped with an eccentric bearing 27. The piston 22, in particular the piston crown, can also be equipped with a transmission element 28. The transmission element 28 can be made of a different material than, for example, the piston 22, for example of plastic or, in particular, metal alloys, which is designed for the frequently recurring contacts with the eccentric disc 24 orEccentric bearing 27, is advantageously suitable.

[0070] Other components, such as valves, channels, etc., are not described in detail here. However, the operating principle of a radial piston compressor is well known to those skilled in the art.

[0071] As already outlined above, the invention provides that the eccentric shaft is mounted in the radial piston compressor by at least three bearings, preferably three bearings 3, 4, 5.

[0072] Figure 4 shows an embodiment of the radial piston compressor according to the invention, whose eccentric shaft 23, 24 is mounted in the radial piston compressor by means of three bearings 3, 4, 5. Here, the first bearing 3 is accommodated in the compressor housing cover 26, the second bearing 4 in the compressor housing 25, and the third bearing 5 in the drive housing 11.

[0073] Fig. 5 shows an embodiment of the radial piston compressor according to the invention, the eccentric shaft 23, 24 of which is mounted in the radial piston compressor by means of three bearings 3, 4, 5. Provision is made here for the first bearing 3 and the second bearing 4 to be accommodated in the compressor housing 25 and the cylinder housing 25, respectively, and for the third bearing 5 to be accommodated in the drive housing 11. The bearings 3 and 4 are thus arranged axially along the shaft 23 on both sides of the piston 22 and on both sides of the working chamber 21, respectively. In this way, the bearings 3 and 4 are arranged axially very close to the point of load introduction 0 and can optimally support the shaft 23. The housing of the radial piston compressor can be formed from the drive housing 11, the compressor housing 25, and the compressor housing cover 26.

[0074] Fig. 6 shows an embodiment of the radial piston compressor according to the invention, the eccentric shaft 23, 24 of which is mounted in the radial piston compressor by means of three bearings 3, 4, 5. It is provided here that the first bearing 3 and the second bearing 4 are accommodated in the compressor housing 25, and the third bearing 5 is accommodated in the drive housing 11. It is further provided that the eccentric shaft 23, 24 is designed in multiple parts in the axial direction. Essentially, it can have a first axial section 231 and at least one second section 232, preferably only one second section 232. In this regard, the eccentric shaft can also be referred to as a built-up eccentric shaft. The housing of the radial piston compressor can be formed from the drive housing 11, the compressor housing 25, and the compressor housing cover 26. As shown in Fig.As shown in Figure 6, the compressor housing 25 in this embodiment of the radial piston compressor extends to its outer surface or outer casing surface. Figure 6 also shows that the eccentric shaft is axially guided by a retaining ring 30. This advantageously means that the bearings do not have to absorb any axial forces.

[0075] In Fig. 7, a radial piston compressor according to the invention is shown in a sectional plan view, in particular to illustrate the arrangement of a plurality of, in this case six, piston-working chamber combinations 21, 22. For reasons of clarity, only one piston-working chamber combination is provided with the reference numerals 21, 22.

[0076] The radial piston compressor according to the invention can further be characterized by the following features.

[0077] It can preferably be provided that the bearings 3, 4, 5 are designed as plain or rolling bearings, in particular as cylindrical roller bearings or ball bearings.

[0078] It can preferably be provided that one of the bearings 3, 4, 5 is designed as an axial bearing.

[0079] It can preferably be provided that the bearings 3, 4, 5 are received in the housing 11, 25, 26 by means of pressing.

[0080] It may preferably be provided that the eccentric shaft can be axially guided by a retaining ring 30. Bearings 3, 4, and 5 therefore do not have to absorb any axial forces.

Claims

Claims 1. Radial piston compressor, comprising - a compressor unit (2) and a drive device (1) for driving the compressor unit (2), wherein - the compressor unit (2) comprises at least one, preferably a plurality of piston-working chamber combinations (21, 22) which are arranged radially around an eccentric shaft (23, 24), wherein - each piston-working chamber combination (21, 22) comprises a working chamber (21) with a piston (22) slidably received therein, wherein the piston (22) is driven by the eccentric shaft (23, 24), characterized in that the eccentric shaft (23, 24) is rotatably mounted in the radial piston compressor by at least three bearings, preferably three bearings (3, 4, 5).

2. Radial piston compressor according to claim 1, characterized in that the radial piston compressor comprises a drive housing (11), a compressor housing (25) and a compressor housing cover (26).

3. Radial piston compressor according to at least one of the preceding claims, characterized in that the first bearing (3) is accommodated in the compressor housing cover (26), the second bearing (4) in the compressor housing (25) and the third bearing (5) in the drive housing (11).

4. Radial piston compressor according to at least one of the preceding claims, characterized in that the first bearing (3) and the second bearing (4) are accommodated in the compressor housing (25) and the third bearing (5) is accommodated in the drive housing (11).

5. Radial piston compressor according to at least one of the preceding claims, characterized in that the shaft (23) has a vibration node (S) due to the three bearing points (3, 4, 5) and their arrangement, this vibration node (S) being arranged in its axial position close to the location of a load introduction (0).

6. Radial piston compressor according to at least one of the preceding claims, characterized in that the bearings (3, 4, 5) are designed as plain or rolling bearings, in particular as cylindrical roller bearings or ball bearings. Radial piston compressor according to at least one of the preceding claims, characterized in that a single bearing (3, 4, or 5) is designed as an axial bearing. Radial piston compressor according to at least one of the preceding claims, characterized in that the bearings (3, 4, 5) are accommodated in the housing by pressing. Radial piston compressor according to at least one of the preceding claims, characterized in that the eccentric shaft is axially guided by a retaining ring (30).

Images