Multi-stage reciprocating compressor, pneumatic vehicle system and vehicle

Abstract

The invention relates to a multi-stage reciprocating compressor (10) for a pneumatic vehicle system (30), the multi-stage reciprocating compressor (10) comprising a crankcase (11), a plurality of compression cylinders (12a, 12b) radially arranged in the crankcase (11), wherein at least two compression cylinders (12a) of the plurality of compression cylinders (12a, 12b) form first stage compression cylinders (12a) configured to operate in a first compression stage and wherein a further compression cylinder (12b) of the plurality of compression cylinders (12a, 12b) forms a second stage compression cylinder (12b) configured to operate in a second compression stage, and a crankshaft (13) supported by the crankcase (11) and connected to pistons (15a, 15b) configured to reciprocate in the compression cylinders (12a, 12b) by rotation of the crankshaft (13), wherein the crankshaft (13) is connected to the pistons (15a, 15b) via a con rod assembly (16), the con rod assembly (16) comprising a main rod (17) extending between the crankshaft (13) and the piston (15b) reciprocating in the second stage compression cylinder (12b), and connecting rods (18) being connected to the main rod (17) in a movable manner and extending between the main rod (17) and the pistons (15a) reciprocating in the first stage compression cylinders (12a). Furthermore, the invention relates to a pneumatic vehicle system (30) and a vehicle (50).

Description

[0001] Hannover, 15.11.2024

[0002] IP, Copi, Reichenbach / sw 304922-WO-PCT EM 304922 MULTI-STAGE RECIPROCATING COMPRESSOR, PNEUMATIC VEHICLE SYSTEM AND VEHICLE

[0003] The present disclosure relates to a multi-stage reciprocating compressor for a pneumatic vehicle system. Furthermore, the present disclosure relates to a pneumatic vehicle system comprising such a multi-stage reciprocating compressor and a pneumatic consumer system. Furthermore, the present disclosure relates to a vehicle, in particular a commercial vehicle, with such a pneumatic vehicle system.

[0004] The multi-stage reciprocating compressor may comprise a crankcase and a plurality of compression cylinders radially arranged in the crankcase. At least two compression cylinders of the plurality of compression cylinders may form first stage compression cylinders configured to operate in a first compression stage. A further compression cylinder of the plurality of compression cylinders may form a second stage compression cylinder configured to operate in a second compression stage. The multi-stage reciprocating compressor may furthermore comprise a crankshaft supported by the crankcase and connected to pistons configured to reciprocate in the compression cylinders by rotation of the crankshaft.

[0005] Multi-stage reciprocating compressors of the afore-mentioned type are generally known. For instance, DE 10 2018 129 747 A1 discloses a reciprocating compressor of a compressed air supply system of a vehicle, having at least six cylinders arranged in a star configuration, of which a single cylinder is connected in series downstream of the other cylinders, which are connected in parallel and form a first pressure stage, wherein the single cylinder forms the second pressure stage. The cylinders following the cylinder of the second pressure stage in the direction of rotation of the drive shaft are offset by a gradually decreasing offset angle compared to the angular position of the cylinders in a symmetrical arrangement.

[0006] Furthermore, WO 2015 / 172144 A1 describes an oil-free compressor for a rail vehicle including a compressor housing, a first low pressure piston cylinder supported in the compressor housing, a second low pressure piston cylinder supported in the compressor housing, a first high pressure piston cylinder supported in the compressor housing, a second high pressure piston cylinder supported in the compressor housing, and a crankshaft assembly supported by the compressor housing and linked to pistons of the piston cylinders by respective connecting rods. The first and second low pressure piston cylinders and the first and second high pressure piston cylinders are positioned in an X-shaped configuration around an outer circumference of the compressor housing.

[0007] Although available multi-stage reciprocating compressors may already represent compact configurations and provide well-performing driving concepts to ensure accurate piston reciprocation, the technology still holds potential for further efficiency enhancement and refined compressor designs. In particular, the constructional complexity of multi-stage reciprocating compressors due to the plurality of pistons and cylinders is still high according to prior art concepts, and it may be desirable to provide improved compressor designs with reduced complexity and size. At the same time, it may be desirable to provide a compressor configuration which ensures a finely coordinated actuation of the individual pistons.

[0008] In view of the above, it is an object of the invention to provide a multi-stage reciprocating compressor with an enhanced reciprocation accuracy and a decreased constructional complexity for providing a compact and efficient compressor design. It is a further object of the present invention to provide an improved pneumatic vehicle system and a vehicle comprising such a pneumatic vehicle system.

[0009] Aspects and embodiments of the invention provide a multi-stage reciprocating compressor, a pneumatic vehicle system and a vehicle as indicated in the appended claims.

[0010] According to a first aspect of the present invention, there is provided a multi-stage reciprocating compressor for a pneumatic vehicle system, the multi-stage reciprocating compressor comprising:

[0011] - a crankcase;

[0012] - a plurality of compression cylinders radially arranged in the crankcase, wherein at least two compression cylinders of the plurality of compression cylinders form first stage compression cylinders configured to operate in a first compression stage and wherein a further compression cylinder of the plurality of compression cylinders forms a second stage compression cylinder configured to operate in a second compression stage; and

[0013] - a crankshaft supported by the crankcase and connected to pistons configured to reciprocate in the compression cylinders by rotation of the crankshaft; wherein the crankshaft is connected to the pistons via a con rod assembly, the con rod assembly comprising:

[0014] - a main rod extending between the crankshaft and the piston reciprocating in the second stage compression cylinder; and

[0015] - connecting rods being connected to the main rod in a movable manner and extending between the main rod and the pistons reciprocating in the first stage compression cylinders.

[0016] By providing a con rod assembly in which the pistons reciprocating in the first stage compression cylinders are connected to the crankshaft in an indirect manner via a main rod, a compact piston drive arrangement may be provided which ensures a finely coordinated actuation of the pistons reciprocating in the first and second stage compression cylinders. The interconnection of the main rod and the connecting rods leads to an efficient coupling of the piston movements in the compression cylinders, thus enabling a well-performing compressor operation. Furthermore, the complexity and size of the multi-stage reciprocating compressor may be significantly decreased, and the multi-stage reciprocating compressor may be easy to assemble since it is no longer required to accurately orient and connect each connecting rod with the crankshaft.

[0017] Generally, a reciprocating compressor, also referred to as a piston compressor, may be a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases, in particular air, at high pressure. A multi-stage reciprocating compressor may be a reciprocating compressor configured to compress gases stepwise to a desired pressure level. Multi-stage reciprocating compressors may use at least two cylinders in order to achieve a stepwise pressure increase. Multi-stage reciprocating compressors may present higher pressure output levels and increased efficiency compared to single-stage reciprocating compressors. The pneumatic vehicle system may be configured to provide and use compressed air in a vehicle. The pneumatic vehicle system may comprise at least one multi-stage reciprocating compressor and at least one pneumatic consumer system such as, for instance, a pneumatic braking system, an air suspension system or a sensor cleaning system. Optionally, the pneumatic vehicle system may comprise a processing unit such as an air dryer unit configured to dry the compressed air provided by the multi-stage reciprocating compressor. Furthermore, the pneumatic vehicle system may comprise a distribution system having, for instance, lines, valves, ports and / or buffers. A vehicle which may comprise such a pneumatic vehicle system may, for instance, be a motor vehicle of any type designed to transport people and / or cargo. In particular, the vehicle may be a commercial vehicle, i.e. a vehicle commercially used for carrying goods or fare-paying passengers. For instance, the commercial vehicle may be a truck or a bus.

[0018] As indicated above, the multi-stage reciprocating compressor comprises a crankcase. The crankcase may be a housing configured to at least partially encase the compression cylinders, the crankshaft, the pistons and the con rod assembly. The compression cylinders are radially arranged in the crankcase. In other words, the longitudinal center axes of the compression cylinders may be extended along spatial axes crossing in a common center to form a radial arrangement. Radial arrangements of the compression cylinders may include symmetrical and asymmetrical radial arrangements of the compression cylinders, meaning that a position angle may be equal or different between various cylinder combinations of adjacent compression cylinders. The pistons and the compression cylinders may be configured to provide oil free compression, thus increasing the service life of the multi-stage reciprocating compressor. Furthermore, the piston reciprocating in the second stage compression cylinder may comprise a diameter which is different to the diameters of the pistons reciprocating in the first stage compression cylinders, thus providing two-stage compression with high efficiency. With a con rod assembly in which the connecting rods supporting the pistons reciprocating in the first stage compression cylinders are attached to the main rod in a finely coordinated manner, the pistons reciprocating in the first stage compression cylinders and the piston reciprocating in the second stage compression cylinder may comprise the same strokes. Furthermore, the multi-stage reciprocating compressor comprises a crankshaft supported by the crankcase and connected to the pistons configured to reciprocate in the compression cylinders by rotation of the crankshaft, wherein the crankshaft is connected to the pistons via the con rod assembly. In particular, the crankshaft may be connected directly to the main rod of the con rod assembly and indirectly to the connecting rods which are connected to the main rod. By rotation of the crankshaft, the main rod may be driven by the crankshaft leading to a reciprocation of the piston connected to the main rod in the second stage compression cylinder. The main rod may be connected to the crankshaft in an eccentric manner, thus performing a reciprocating movement upon rotation of the crankshaft. The reciprocating movement may be transmitted to the piston reciprocating in the second stage compression cylinder and to the connecting rods being connected to the main rod in a movable manner. Hence, the connecting rods may transmit the reciprocating movement to the pistons reciprocating in the first stage compression cylinders, wherein the individual trajectory of the connecting rods may depend on their position and type of connection to the main rod. In conclusion, the rotation of the crankshaft may beneficially be converted to reciprocating movements of the pistons by interconnection of the main rod between the crankshaft and the connecting rods, thus providing an efficient coupling in order to reduce constructional complexity and to allow for a finely coordinated actuation of the pistons.

[0019] In accordance with the present disclosure, at least two compression cylinders of the plurality of compression cylinders form first stage compression cylinders configured to operate in a first compression stage. For instance, two, three, four, five, six or more compression cylinders may be arranged sequentially around the crankshaft and configured to compress a predefined air volume to a first pressure level. A further compression cylinder of the plurality of compression cylinders forms a second stage compression cylinder configured to operate in a second compression stage. The second stage compression cylinder may be arranged between two first stage compression cylinders indicated herein as the following and the preceding first stage compression cylinders. The second stage compression cylinder is configured to compress the air volume compressed to the first pressure level to a second pressure level which is higher than the first pressure level. In other words, the second stage compression cylinder may be connected in series downstream of the first stage compression cylinders.

[0020] According to an embodiment of the first aspect of the invention, the main rod may comprise a crank disc with openings for movable fixation of the connecting rods. In this way, a simple and compact construction with efficient motion transmission may be provided. Furthermore, the design allows for easy fixation of the connecting rods. The crank disc may be a disc-shaped extension of or attachment to the main rod which may be either formed integrally with the rod section or being attached to it by suitable mechanical fixation or bonding means. The connecting rods may, for instance, be attached to the crank disc using pins and / or bearings.

[0021] According to a refined embodiment, the main rod may comprise a center bore receiving the crankshaft, wherein the openings for movable fixation of the connecting rods are radially distributed around the center bore. Accordingly, the connecting rods may extend radially from the main rod in a mounted state of the connecting rods. This provides a further enhanced construction being simple and compact and providing efficient motion transmission. The openings and the center bore may form circular through-holes. The openings for movable fixation of the connecting rods may be spaced apart from the center bore. The opening centers of the openings may be arranged equidistantly or with an offset between at least two openings compared to an equidistant distribution, thus allowing to transmit suitable movements via the connecting rods to pistons reciprocating in symmetrically or asymmetrically arranged compression cylinders.

[0022] According to an embodiment of the first aspect of the invention, the main rod may comprise a pair of crank discs extending parallel to each other. Accordingly, the connecting rods may be fixed to both crank discs, thus providing an improved hold and stabilization of the movably fixed connecting rods. Furthermore, using a pair of crank discs may assist in providing accurate orientation and alignment of the movably fixed connecting rods. Preferably, the crank discs may comprise a congruent shape and orientation for facilitated attachment of the connecting rods. Preferably, both crank discs comprise openings for movable fixation of the connecting rods, wherein the openings are arranged opposite to each other for further facilitated attachment of the connecting rods.

[0023] According to an embodiment of the first aspect of the invention, at least one of the connecting rods may be connected to the main rod via a needle bearing. The needle bearing may provide a small-sized bearing with a high load capacity, being suitable for high rotation speeds and promoting overall compact arrangement of the con rod assembly. Preferably, all connecting rods may each be connected to the main rod via a needle bearing. For instance, the needle bearing may be inserted in the opening of a crank disc as explained above, or needle bearings may be inserted in opposite openings of two crank discs extending in parallel as described above. Hence, the connecting rods may be fixed to the main rod in a movable manner by using needle bearings which allows for accurate and smooth movement transmission between the main rod and the connecting rods.

[0024] According to an embodiment of the first aspect of the invention, the main rod may be connected to the crankshaft via a roller bearing. The roller bearing may represent a compact bearing with a generally higher load capacity due to an increased contact area between rollers of the roller bearing and the crankshaft supported by the roller bearing. Hence, the higher mass and forces acting on the bearing connecting the main rod to the crankshaft may beneficially be balanced by the roller bearing.

[0025] Preferably, the roller bearing may be configured as a cylindrical roller bearing. With regard to the crankshaft supported in the crankcase, a ball bearing may be provided to enable a movable connection of the crankshaft and the crankcase, wherein the ball bearing may enable rotational and limited translational movements of the crankshaft in the crankcase.

[0026] According to an embodiment of the first aspect of the invention, the pistons reciprocating in the first stage compression cylinders may be formed integrally with the connecting rods, thus providing combined functional elements which are easy to assemble, robust and configured for high force transmission. For instance, each connection rod may comprise an elongated bar section with a fixation section configured to be connected to the main rod, wherein the bar section directly merges into a piston section which is opposite of the fixation section and which comprises a piston shape configured to reciprocate in a first stage compression cylinder. Preferably, the pistons may be configured to reciprocate in the cylinders with a limited allowable tilt, thus decreasing the complexity of the con rod assembly by allowing piston trajectories being only defined by the main rod movement and the movable fixation of the connecting rods to the main rod.

[0027] According to an embodiment of the first aspect of the invention, longitudinal center axes of the first stage compression cylinders may be arranged in a first stage plane and a longitudinal center axis of the second stage compression cylinder may be arranged in a second stage plane, wherein the first stage plane and the second stage plane coincide. In this way, a compact compression cylinder arrangement may be provided. In other words, the first and second stage compression cylinders may be arranged in the same plane.

[0028] According to a refined embodiment, the connecting rods may extend from the main rod in a main rod plane of the main rod, thus providing suitable rod adaptation for coincident stage planes. In this way, a compact con rod assembly may be provided, configured for high force transmission and comprising beneficial stability and endurance properties. More precisely, a main rod axis of the main rod and connecting rod axes of the connecting rods may extend in the same plane.

[0029] Furthermore, the movement of the main rod and the connecting rods may be performed in the same plane. The main rod axis may correspond to a longitudinal center axis of the main rod. The connecting rod axes may correspond to longitudinal center axes of the connecting rods.

[0030] According to a refined embodiment, the main rod may comprise a pair of crank discs arranged symmetrically to the main rod axis of the main rod, which provides a simple and robust implementation of an arrangement according to which the connecting rods extend from the main rod in the main rod plane of the main rod. By arranging a pair of crank discs symmetrically to the main rod axis, the connecting rods may be positioned and fixed between the crank discs, e.g. using openings in the crank discs. In this way, the connecting rod axes may be aligned automatically with the main rod axis. According to an embodiment of the first aspect of the invention, longitudinal center axes of the first stage compression cylinders are arranged in a first stage plane and a longitudinal center axis of the second stage compression cylinder is arranged in a second stage plane, wherein the first stage plane and the second stage plane are spaced apart from each other. In this way, improved stage separation may be provided, and a compact design may be achieved since a center to center distance between the main rod and the connecting rods can be decreased when using separated stage planes. Hence, reciprocating masses may be reduced which results in a balanced design, improved force transmission and well-performing compressor operation. In accordance with the embodiment, the first stage compression cylinders and the second stage compression cylinder may be axially offset from each other. Accordingly, the pistons reciprocating in the associated first and second compression cylinders may be axially offset from each other.

[0031] According to a refined embodiment, the connecting rods may extend in a connecting rod plane and the main rod may extend in a main rod plane, wherein the connecting rod plane and the main rod plane are spaced apart from each other, thus providing suitable rod adaptation for separate stage planes. The different rod planes may result in an axial offset between the main rod and the connecting rods which may correspond to a provided offset of the compression cylinders and pistons arranged in different stage planes.

[0032] According to a refined embodiment, the main rod may comprise a pair of crank discs unilaterally protruding from the main rod axis, which may allow for a simple and effective implementation of different rod planes. Accordingly, the connecting rods may be fixed between the crank discs with connecting rod axes extending in a plane spaced apart from the main rod axis. Using the refined embodiment, the crank discs may be designed independently of a center bore provided in the main rod for receiving the crankshaft. Hence, the distances from a crank disc center to openings for fixation of connecting rods may be decreased and a compact con rod assembly can be provided.

[0033] According to an embodiment of the first aspect of the invention, the multi-stage reciprocating compressor may comprise at least three first stage compression cylinders and one second stage compression cylinder, thus providing a high-performance arrangement resulting in a powerful multi-stage reciprocating compressor with a smooth operation. Preferably, the multi-stage reciprocating compressor may comprise at least four or at least five first stage compression cylinders and one second stage compression cylinder. In particular, the multi-stage reciprocating compressor may comprise exactly five first stage compression cylinders and one second stage compression cylinder, which may provide a powerful but still compact arrangement. Nevertheless, the invention may also apply to compression cylinder arrangements comprising more than five first stage compression cylinders and / or more than one second stage compression cylinder.

[0034] According to an embodiment of the first aspect of the invention, the crankshaft may be configured to rotate in a predefined rotation direction, wherein in accordance with the rotation direction of the crankshaft, a first stage compression cylinder following the second stage compression cylinder may be positioned at a first angle from the second stage compression cylinder and the second stage compression cylinder may be positioned at a second angle from a preceding first stage compression cylinder, wherein the second angle is larger by a predefined angle difference than the first angle. By using different position angles with regard to the preceding first stage compression cylinder and the following first stage compression cylinder, wherein the position angle between the preceding first stage compression cylinder and the second stage compression cylinder is larger than the position angle between the second stage compression cylinder and the following first stage compression cylinder, a load torque peak induced by the second stage compression cylinder can be shifted to an extended load torque peak gap between load torque peaks induced by the preceding first stage compression cylinder and the following first stage compression cylinder. Accordingly, superimposition of load torque induced by the preceding and following first stage compression cylinders with the load torque induced by the second stage compression cylinder may be reduced. In this way, overall load torque over time may be equalized, thus leading to less load torque variation, less vibration, smooth running and higher durability of the multi-stage reciprocating compressor. Upon closer inspection, the predefined rotation direction and the selected angles between the first stage compression cylinders preceding and following the second stage compression cylinder may have a significant impact on the time-related load torque profile of the multi-stage reciprocating compressor. Using a sophisticated cylinder arrangement as suggested herein, the operational behavior of the multi-stage reciprocating compressor may be optimized in a finely tuned manner.

[0035] The pistons are configured to reciprocate in the compression cylinders by rotation of the crankshaft. The piston movement of a piston reciprocating in a compression cylinder may cause an increasing and decreasing load torque curve at the drive of the crankshaft. As the compression cylinders may be arranged in an asymmetrical manner, the rotation of the crankshaft may result in different temporal load torque curves depending on the rotation direction. Preferably, the multi-stage reciprocating compressor may be operated with the crankshaft rotating in a predefined rotation direction in which the first stage compression cylinder following the second stage compression cylinder is positioned at a first angle from the second stage compression cylinder and the second stage compression cylinder is positioned at a second angle from a preceding first stage compression cylinder, wherein the second angle is larger by a predefined angle difference than the first angle. In this way, a load torque peak induced by the second stage compression cylinder may be beneficially shifted to an extended load torque peak gap between load torque peaks induced by the preceding first stage compression cylinder and the following first stage compression cylinder.

[0036] As indicated above, in accordance with the rotation direction of the crankshaft, the first stage compression cylinder following the second stage compression cylinder may be positioned at a first angle from the second stage compression cylinder. For instance, the longitudinal center axis of the following first stage compression cylinder and the longitudinal center axis of the second stage compression cylinder may form the first angle. Furthermore, the second stage compression cylinder is positioned at a second angle from a preceding first stage compression cylinder. For instance, the longitudinal center axis of the second stage compression cylinder and the longitudinal center axis of the preceding first stage compression cylinder may form the second angle. In accordance with the described embodiment, the second angle may be larger by a predefined angle difference than the first angle. In other words, a circular arc between the second stage compression cylinder and the preceding first stage compression cylinder may be larger than a circular arc between the following first stage compression cylinder and the second stage compression cylinder.

[0037] Accordingly, an extended load torque peak gap is created between a first load torque peak induced by the preceding first stage compression cylinder and a second load torque peak induced by the following first stage compression cylinders, wherein the extended load torque peak gap may reduce superimposition of the load torque induced by the preceding and following first stage compression cylinder with the load torque induced by the second stage compression cylinder, thus decreasing overall load torque. In this way, the overall load torque level and temporal load torque distribution of the drive of the multi-stage reciprocating compressor may be equalized, leading to a smooth operation of the multi-stage reciprocating compressor with less vibration and sound emission. Furthermore, the lifetime of the multi-stage reciprocating compressor may be extended due to reduced load torque variation exposure.

[0038] For instance, the predefined angle difference may be at least 20°, in particular at least 30°. More specifically, the second angle between the preceding first stage cylinder and the second stage cylinder may be at least 20° larger than the first angle between the following first stage compression cylinder and the second stage compression cylinder. According to a non-limiting example, the predefined angle difference may be 30°. With a cylinder arrangement comprising a predefined angle difference of at least 20°, the load torque curve may be efficiently equalized with a sufficient gap between the preceding first stage compression cylinder and the second stage compression cylinder, while preventing an unnecessary excessive gap between the second stage compression cylinder and the following first stage compression cylinder due to the smaller first angle.

[0039] For instance, the first angle may be an angle between 58° and 62°. Preferably, the first angle may be 60°. A first angle between 58° and 62°, in particular a first angle of 60°, may be an advantageous first angle to ensure that the overall load torque does not drop too low between a load torque peak induced by the second stage compression cylinder and a load torque peak induced by the following first stage compression cylinder. In this way, the load torque variation overtime may be efficiently reduced. Preferably, the first angle may be an angle between 58° and 62°, in particular a first angle of 60°, if the multi-stage reciprocating compressor comprises five first stage compression cylinders and one second stage compression cylinder. In this way, a first angle of 60° may comply with an equivalent angle of a corresponding symmetrical arrangement of the six compression cylinders, thus promoting a smooth running of the multi-stage reciprocating compressor.

[0040] For instance, the second angle may be an angle between 88° and 92°. Preferably, the second angle may be 90°. A second angle between 88° and 92°, in particular a second angle of 90°, may be an advantageous second angle to ensure that an extended offset is provided between the preceding first stage compression cylinder and the second stage compression cylinder for temporally shifting the load torque peak induced by the second stage compression cylinder to an extended load torque peak gap, thus improving equalization of the overall load torque overtime.

[0041] For instance, the multi-stage reciprocating compressor may comprise at least five first stage compression cylinders and one second stage compression cylinder.

[0042] Preferably, the multi-stage reciprocating compressor may comprise five first stage compression cylinders and one second stage compression cylinder. In this way, a high-performance compression cylinder arrangement may be provided, the compression cylinder arrangement being associated with improved load torque equalization over time but still being based on a simple construction with enough space to arrange the compression cylinders in an asymmetrical manner.

[0043] Nevertheless, the described embodiment may also apply to compression cylinder arrangements comprising more than five first stage compression cylinders or more than one second stage compression cylinder.

[0044] For instance, in accordance with the rotation direction, at least two adjacent first stage compression cylinders may be positioned with a specific position angle from one another, the specific position angle being defined by an offset angle compared to a corresponding regular position angle of a symmetrical radial arrangement of the compression cylinders. Due to the asymmetrical arrangement of the first stage compression cylinders following and preceding the second stage compression cylinder, it may be advantageous to arrange the first stage compression cylinders independently of symmetrical aspects in order to achieve an improved performance and an equalized load torque behavior. The embodiment may beneficially be combined with a compression cylinder arrangement of five first stage compression cylinders and one second stage compression cylinder. For instance, a regular position angle of a symmetrical radial arrangement of six compression cylinders in total may equate to a position angle of 60° between adjacent compression cylinders. Here, for instance, a specific position angle between two adjacent first stage compression cylinders may be 55°, corresponding to an offset angle of 5° compared to the regular position angle. According to a further example, a specific position angle between two adjacent first stage compression cylinders may be 50°, corresponding to an offset angle of 10° compared to the regular position angle. According to a further example, a specific position angle between two adjacent first stage compression cylinders may be 45°, corresponding to an offset angle of 15° compared to the regular position angle. According to a non-limiting example, in which the first stage compression cylinders may be numbered from 1 to 5 in accordance with the rotation direction of the crankshaft starting with the first stage compression cylinder following the second stage compression cylinder and ending with the first stage compression cylinder preceding the second stage compression cylinder, a specific position angle between the first and second first stage compression cylinders may be 50°, resulting in an offset angle of 10°. Furthermore, a specific position angle between the second and third first stage compression cylinders may be 50°, resulting in an offset angle of 10°. Furthermore, a specific position angle between the third and fourth first stage compression cylinders may be 55°, resulting in an offset angle of 5°. Furthermore, a specific position angle between the fourth and fifth first stage compression cylinders may be 55°, resulting in an offset angle of 5°. Preferably, a regular position angle may be present between the second stage compression cylinder and the following first stage compression cylinder.

[0045] For instance, at least two pairs of adjacent first stage compression cylinders may comprise different offset angles. For instance, as illustrated with the non-limiting example above, a specific position angle between a first pair of adjacent first stage compression cylinders may be 55°, corresponding to an offset angle of 5°, and a specific position angle between a second pair of adjacent first stage compression cylinders may be 50°, corresponding to an offset angle of 10°. Against technical expectation, a slightly irregular arrangement of the first stage compression cylinders between the first stage compression cylinder following the second stage compression cylinder and the first stage compression cylinder preceding the second stage cylinder may further promote load torque equalization overtime, thus achieving less load torque variation in a compression cycle.

[0046] For instance, an offset angle of at least one pair of adjacent first stage compression cylinders may be smaller than an offset angle of at least one following pair of adjacent first stage compression cylinders. In other words, in accordance with the rotation direction, the first stage compression cylinders may show decreasing offset angles between each other. For instance, as illustrated with the non-limiting example above, a specific position angle between the second and third first stage compression cylinders may be 50°, resulting in an offset angle of 10°, and a specific position angle between the third and fourth first stage compression cylinders may be 55°, resulting in an offset angle of 5°. According to the refined embodiment, it may be optional but not necessary that the offset angle decreases with every following pair of adjacent first stage compression cylinders. For instance, as illustrated with the nonlimiting example above, a following pair of adjacent first stage compression cylinders may comprise the same offset angle or a smaller offset angle than a preceding pair of adjacent first stage compression cylinders. Decreasing offset angles from the first stage compression cylinder following the second stage compression cylinder to the first stage compression cylinder preceding the second stage compression cylinder may have a further improved effect on load torque equalization overtime.

[0047] For instance, based on the position of the second stage compression cylinder, in the rotation direction of the crankshaft, the first stage compression cylinders may be positioned at reference angles of 60°, 110°, 160°, 215° and 270° from the second stage compression cylinder. The suggested compression cylinder distribution may provide an optimized arrangement of six compression cylinders in order to achieve the intended load torque equalization overtime.

[0048] According to a second aspect of the invention, there is provided a pneumatic vehicle system comprising a multi-stage reciprocating compressor according to any aspect or embodiment disclosed herein and a pneumatic consumer system connected to the multi-stage reciprocating compressor. Due to the enhanced multi-stage reciprocating compressor which may supply compressed air with high efficiency, smooth operation and low noise emission, a beneficially improved pneumatic vehicle system may be provided. Furthermore, since the suggested multi-stage reciprocating compressor comprises an improved compressor design with reduced complexity and size, it may be easily assembled and implemented in a pneumatic vehicle system without requiring large installation space. The pneumatic vehicle system may be configured to provide and use compressed air in a vehicle. The pneumatic vehicle system may comprise at least one pneumatic consumer system such as, for instance, a pneumatic braking system, an air suspension system and / or a sensor cleaning system. Optionally, the pneumatic vehicle system may comprise a processing unit such as an air dryer configured to dry the compressed air provided by the multi-stage reciprocating compressor. Furthermore, the pneumatic vehicle system may comprise a distribution system having, for instance, lines, valves, ports and / or buffers.

[0049] According to a third aspect of the invention, there is provided a vehicle, in particular a commercial vehicle, with a pneumatic vehicle system according to the second aspect of the invention. The vehicle comprising the described pneumatic vehicle system may represent a vehicle with improved operation performance due to the highly efficient multi-stage reciprocating compressor comprised by the pneumatic vehicle system. The vehicle may be a motor vehicle of any type designed to transport people and / or cargo. In particular, the vehicle may be a commercial vehicle, i.e. a vehicle commercially used for carrying goods or fare-paying passengers. For instance, the commercial vehicle may be a truck or a bus. For commercial vehicles, the advantage of an improved pneumatic vehicle system may, due to the presence of pneumatic consumers with high consumption, significantly increase the operating efficiency of the vehicle. Hence, the present invention may be beneficially applicable to commercial vehicles.

[0050] The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, which will be further outlined with reference to the appended drawings. The drawings are not necessarily to scale. Some features could be exaggerated or minimized to show details of particular components.

[0051] Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.

[0052] Fig. 1 shows a sectional front view of a multi-stage reciprocating compressor according to a first embodiment.

[0053] Fig. 2 depicts a sectional side view of the multi-stage reciprocating compressor according to the first embodiment.

[0054] Figs. 3 and 4 provide a perspective front view and a side view of a main rod of a con rod assembly of the multi-stage reciprocating compressor according to the first embodiment.

[0055] Figs. 5 and 6 provide a front view and a side view of a connecting rod of the con rod assembly of the multi-stage reciprocating compressor according to the first embodiment.

[0056] Fig. 7a shows a sectional front view of the multi-stage reciprocating compressor according to the first embodiment with indicated first and second angles and specific position angles.

[0057] Fig. 7b shows the sectional front view of the multi-stage reciprocating compressor according to Fig. 7a with indicated reference angles. Fig. 8 depicts a sectional side view of a multi-stage reciprocating compressor according to a second embodiment.

[0058] Figs. 9 and 10 provide sectional front views of the multi-stage reciprocating compressor according to the second embodiment in two different planes.

[0059] Figs. 11 and 12 show a front view and a side view of a main rod of a con rod assembly of the multi-stage reciprocating compressor according to the second embodiment.

[0060] Fig. 13 schematically depicts a vehicle with a pneumatic vehicle system comprising a multi-stage reciprocating compressor.

[0061] Figs. 1 and 2 illustrate a multi-stage reciprocating compressor 10 according to a first embodiment. The multi-stage reciprocating compressor 10 may, for instance, be implemented in a pneumatic vehicle system 30 as illustrated in Fig. 13. The multi-stage reciprocating compressor 10 comprises a crankcase 11. According to the depicted first embodiment, the multi-stage reciprocating compressor 10 comprises a plurality of compression cylinders 12a, 12b radially arranged in the crankcase 11. Here, five compression cylinders 12a of the plurality of compression cylinders 12a, 12b form first stage compression cylinders 12a configured to operate in a first compression stage in order to compress a defined air volume to a first pressure level. A further compression cylinder 12b of the plurality of compression cylinders 12a, 12b forms a second stage compression cylinder 12b configured to operate in a second compression stage in order to compress the defined air volume to a higher second pressure level.

[0062] Furthermore, the multi-stage reciprocating compressor 10 comprises a crankshaft 13 as shown in Fig. 2. The crankshaft 13 is movably supported by the crankcase 11 via a ball bearing 23. Furthermore, the crankshaft 13 is connected to pistons 15a, 15b forming a piston assembly 14. The pistons 15a, 15b are configured to reciprocate in the compression cylinders 12a, 12b by rotation of the crankshaft 13, wherein first pistons 15a are configured to reciprocate in the first stage compression cylinders 12a and a second piston 15b is configured to reciprocate in the second stage compression cylinder 12b. The crankshaft 13 may be configured to rotate in a predefined rotation direction RD as illustrated in Fig. 1. For easier reference, the first stage compression cylinders 12a are numbered from 12-I to 12-V in Fig. 1 in accordance with the predefined rotation direction RD.

[0063] As illustrated in Fig. 2, the first stage compression cylinders 12 comprise longitudinal center axes L-1 being arranged in a first stage plane P-1 and the second stage compression cylinder 12b comprises a longitudinal center axis L-2 being arranged in a second stage plane P-2, wherein according to the first embodiment, the first stage plane P-1 and the second stage plane P-2 coincide, i.e., the first stage plane P-1 and the second stage plane P-2 are aligned with each other. In other words, the first stage compression cylinders 12a and the second stage plane cylinder 12b are arranged in a same plane.

[0064] As further apparent from Figs. 1 and 2, the crankshaft 13 is connected to the pistons 15a, 15b via a con rod assembly 16. The con rod assembly 16 may be connected to the crankshaft 13 via a cylindrical roller bearing 24 as depicted in Fig. 2. The con rod assembly 16 comprises a main rod 17 extending between the crankshaft 13 and the piston 15b reciprocating in the second stage compression cylinder 12b. Furthermore, the con rod assembly 16 comprises connecting rods 18 being connected to the main rod 17 in a movable manner and extending between the main rod 17 and the pistons 15a reciprocating in the first stage compression cylinders 12a. In this way, a very compact and efficient coupling of the pistons 15a, 15b may be provided. According to the first embodiment depicted in Figs. 1 and 2, the main rod 17 and the connecting rods 18 extend in a main rod plane PM of the main rod 17, thus providing suitable rod adaptation for coincident stage planes P-1, P-2 and forming a compact con rod assembly 16 with beneficial stability properties.

[0065] Figs. 3 and 4 each show an isolated representation of the main rod 17. As depicted, the main rod 17 comprises a pair of crank discs 19 extending parallel to each other and comprising openings 20 for movable fixation of the connecting rods 18. The movable fixation may be implemented via bearings. For instance and as illustrated in Fig. 1, needle bearings 22 may be used to movably attach the connecting rods 18 to the main rod 17. The main rod 17 comprises a center bore 25 configured to receive the crankshaft 13. The openings 20 are radially distributed around the center bore 25 for efficient motion transmission. The connecting rods 18 may be arranged between the crank discs 19 in the plane of a main rod axis MA. As apparent from Fig. 4, the pair of crank discs 19 is arranged symmetrically to a main rod axis MP of the main rod 17 for providing a simple implementation which allows automatic alignment of the connecting rods 18 with the main rod axis MA.

[0066] Figs. 5 and 6 each show an isolated representation of a connecting rod 18. The connecting rod 18 comprises an aperture 21 for movable fixation to the main rod 17 via a bearing and it comprises a piston 15a configured to reciprocate in a first stage compression cylinder 12a. As depicted, the piston 15a is formed integrally with the connecting rod 18, thus facilitating the assembly of the multi-stage reciprocating compressor 10.

[0067] Fig. 7a provides an additional view of the multi-stage reciprocating compressor 10 represented in Fig. 1 with indicated first and second angles and specific position angles. Fig. 7b provides an additional view of the multi-stage reciprocating compressor 10 represented in Fig. 1 with indicated reference angles. In accordance with the rotation direction RD of the crankshaft 13, the first stage compression cylinder 12a following the second stage compression cylinder 12b, indicated as first stage compression cylinder 12-1 in Figs. 7a and 7b, is positioned at a first angle a1 from the second stage compression cylinder 12b. Furthermore, the second stage compression cylinder 12b is positioned at a second angle a2 from the preceding first stage compression cylinder 12a, indicated as a first stage compression cylinder 12-V in Figs. 7a and 7b. As apparent from Figs. 7a and 7b, the second angle a2 is larger by a predefined angle difference Aa than the first angle a1.

[0068] With a larger second angle a2 between the preceding first stage compression cylinder 12a and the second stage compression cylinder 12b, a load torque peak induced by the second stage compression cylinder 12b may beneficially be shifted to an extended load torque peak gap between load torque peaks induced by the preceding and following first stage compression cylinders 12a. In conclusion, load torque variation over time may be reduced, leading to less vibration, smooth running and higher durability of the multi-stage reciprocating compressor 10.

[0069] The first angle a1 and the second angle a2 may be defined by the longitudinal center axes L-1 of the first stage compression cylinders 12a and the longitudinal center axis L-2 of the second stage compression cylinder 12b. According to the example provided in Figs. 7a and 7b, the first angle a1 may be an angle of approximately 60°, in particular exactly 60°, and the second angle a2 may be an angle of approximately 90°, in particular exactly 90°. Consequently, the predefined angle difference may be approximately 30°, in particular exactly 30°, thus providing a sufficient load torque peak gap and preventing an unnecessary excessive gap between the second stage compression cylinder 12b and the following first stage compression cylinder 12a positioned to each other under a smaller first angle a1. Furthermore, the suggested first angle a1 and second angle a2 may promote a smooth running of the multi-stage reciprocating compressor 10.

[0070] As apparent from Fig. 7a, adjacent first stage compression cylinders 12a are positioned with specific position angles β1, β2, β3, β4 from one another. The specific position angles [31, [32, [33, [34 indicate angles being defined by an offset angle A[3 compared to a corresponding regular position angle [31’ of a symmetrical radial arrangement of the compression cylinders 12a, 12b. For transparency reasons, only the regular position angle β1' between the adjacent compression cylinders 12-I and 12-II and the corresponding offset angle Δβ have been illustrated in Fig. 7a. In accordance with the depicted arrangement of six compression cylinders 12a, 12b, regular position angles (31 ’ providing a symmetrical radial arrangement would correspond to angles of 60° between adjacent first stage compression cylinders 12a. Since an asymmetrical arrangement is provided according to the depicted embodiment, specific position angles [31, |32, (33, (34 have been applied resulting in individual offset angles A[3 compared to the regular position angles (31’.

[0071] According to the embodiment illustrated in Figs. 7a and 7b, a specific position angle β1 between the first first stage compression cylinder 12-I and the second first stage compression cylinder 12-II may be 50°, resulting in an offset angle Δβ of 10°.

[0072] Furthermore, a specific position angle β2 between the second first stage compression cylinder 12-II and the third first stage compression cylinder 12-III may be 50°, resulting in an offset angle Δβ of 10°. Furthermore, a specific position angle β3 between the third first stage compression cylinder 12-III and fourth first stage compression cylinder 12-IV may be 55°, resulting in an offset angle Δβ of 5°.

[0073] Furthermore, a specific position angle β4 between the fourth first stage compression cylinder 12-IV and fifth first stage compression cylinder 12-V may be 55°, resulting in an offset angle Δβ of 5°.

[0074] According to the illustrated first embodiment and the specific position angles β1, β2, β3, β4 of the first stage compression cylinders 12a described above, the pairs of adjacent first stage compression cylinders 12-I / 12-II, 12-II / 12-III comprise different offset angles Δβ compared to the pairs of adjacent first stage compression cylinders 12-III / 12-IV and 12-IV / 12-V, which comprise smaller offset angles Δβ. A slightly irregular arrangement of the first stage compression cylinders 12a between the first stage compression cylinder 12a following the second stage compression cylinder 12b and the first stage compression cylinder 12a preceding the second stage compression cylinder 12b may further reduce load torque variation in a compression cycle. As a supplement to the angles illustrated in Fig. 7a, Fig. 7b illustrates reference angles y1, y2, y3, Y4, Y§ of the first stage compression cylinders 12a referring to a position of the second stage compression cylinder 12b. The reference angles Y1, Y2, y3, y4, Y5areindicated in the rotation direction RD of the crankshaft 13. According to the example provided in Figs. 7a and 7b, the reference angles γ1, γ2, γ3, γ4, γ5 are γ1 = 60° for the first first stage compression cylinder 12-I, γ2 = 110° for the second first stage compression cylinder 12-II, γ3 = 160° for the third first stage compression cylinder 12-III, γ4 = 215° for the fourth first stage compression cylinder 12-IV and γ5 = 270° for the fifth first stage compression cylinder 12-V. In this way, an optimized high-performance arrangement of six compression cylinders 12a, 12b showing the above-mentioned beneficial effects on load torque distribution over time may be provided.

[0075] Figs. 8, 9 and 10 illustrate a multi-stage reciprocating compressor 10 according to a second embodiment. Generally, the multi-stage reciprocating compressor 10 according to the second embodiment may comprise a similar structure and operating principle compared to the multi-stage reciprocating compressor 10 according to the first embodiment. For instance, the depicted angles α1, α2 between the following and preceding first stage compression cylinders 15a and the second stage compression cylinder 15a as well as the depicted specific position angles β1, β2, β3, β4 may correspond to the according angles α1, α2 and specific position angles β1, β2, β3, β4 shown in Fig. 7a. In contrast to the first embodiment and as apparent in the side view of Fig. 8 and the sectional views in Figs. 9 and 10, the longitudinal center axes L-1 of the first stage compression cylinders 12 are arranged in a first stage plane P-1 and the longitudinal center axis L-2 of the second stage compression cylinder 12b is arranged in a second stage plane P-2, wherein the first stage plane P-1 and the second stage plane P-2 are spaced apart from each other. Furthermore, the connecting rods 18 extend in a connecting rod plane PC and the main rod 17 extends in a main rod plane PM. According to the second embodiment depicted in Figs. 8 to 10, the connecting rod plane PC and the main rod plane PM are spaced apart from each other. Fig. 9 shows a first sectional view in the second stage plane P-2 and Fig. 10 shows a second sectional view in the first stage plane P-1. By spatial stage plane division, an efficient operation and a compact size of the multi-stage reciprocating compressor 10 may be achieved, since a center to center distance between the main rod 17 and the connecting rods 18 can be decreased.

[0076] Figs. 11 and 12 each show an isolated representation of the main rod 17. As depicted, the main rod 17 comprises a pair of crank discs 19 with openings 20 for movable fixation of the connecting rods 18 via bearings as, for instance, needle bearings 22 as illustrated in Fig. 1. In contrast to the main rod 17 depicted in Figs. 3 and 4, the main rod 17 illustrated in Figs. 11 and 12 comprises a pair of crank discs 19 unilaterally protruding from the main rod 17, such that the connecting rods 18 may be fixed between the crank discs 19 in a connecting rod plane PC spaced apart from the main rod axis MA and a main rod plane PM, thus providing an offset between the main rod 17 and the connecting rods 18 for reciprocating pistons 15a, 15b in the compression cylinders 12a, 12b being axially offset from each other.

[0077] Fig. 13 provides a schematic view of a vehicle 50 comprising a pneumatic vehicle system 30 with a multi-stage reciprocating compressor 10 and pneumatic consumer systems 36. As depicted, the vehicle 50 is configured as a commercial vehicle 50’, here as a truck-and-trailer combination with a towing vehicle 51 and a trailer 52. The pneumatic vehicle system 30 according to the depicted embodiment comprises the multi-stage reciprocating compressor 10, an air dryer 31 configured to dry the compressed air supplied by the multi-stage reciprocating compressor 10, supply lines 32, a buffer 33, a first pneumatic consumer system 36 configured as a pneumatic braking system 34 and a second pneumatic consumer system 36 configured as an air suspension system 35. Further devices such as e.g. valves, ports or filters may form part of the pneumatic vehicle system 30 without being depicted in the drawings. With the pneumatic vehicle system 30 comprising a multi-stage reciprocating compressor 10 according to any of the aspects or embodiments described above, high-performance operation of the vehicle 50 may be achieved. List of reference numerals (part of the application):

[0078] 10 multi-stage reciprocating compressor

[0079] 11 crankcase

[0080] 12a first stage compression cylinder

[0081] 12b second stage compression cylinder

[0082] 12-1 first first stage compression cylinder

[0083] 12-11 second first stage compression cylinder 12-111 third first stage compression cylinder

[0084] 12-IV fourth first stage compression cylinder 12-V fifth first stage compression cylinder

[0085] 13 crankshaft

[0086] 14 piston assembly

[0087] 15a piston first stage compression cylinder 15b piston second stage compression cylinder 16 con rod assembly

[0088] 17 main rod

[0089] 18 connecting rod

[0090] 19 crank disc

[0091] 20 opening

[0092] 21 aperture

[0093] 22 needle bearing

[0094] 23 ball bearing

[0095] 24 roller bearing

[0096] 25 center bore

[0097] 30 pneumatic vehicle system

[0098] 31 air dryer

[0099] 32 supply line

[0100] 33 buffer

[0101] 34 pneumatic braking system

[0102] 35 air suspension system

[0103] 36 pneumatic consumer system

[0104] 50 vehicle

[0105] 50’ commercial vehicle 51 towing vehicle

[0106] 52 trailer

[0107] L-1 longitudinal center axis first stage compression cylinder L-2 longitudinal center axis second stage compression cylinder MA main rod axis

[0108] P-1 first stage plane

[0109] P-2 second stage plane

[0110] PC rod plane connecting rod

[0111] PM rod plane main rod

[0112] RD rotation direction

[0113] a1 first angle

[0114] a2 second angle

[0115] β1 first specific position angle

[0116] 1 ’ first regular position angle

[0117] β2 second specific position angle

[0118] β3 third specific position angle

[0119] β4 fourth specific position angle

[0120] Δα predefined angle difference

[0121] Δβ offset angle

Claims

Patent claims:

1. A multi-stage reciprocating compressor (10) for a pneumatic vehicle system (30), the multi-stage reciprocating compressor (10) comprising:- a crankcase (11);- a plurality of compression cylinders (12a, 12b) radially arranged in the crankcase (11), wherein at least two compression cylinders (12a) of the plurality of compression cylinders (12a, 12b) form first stage compression cylinders (12a) configured to operate in a first compression stage and wherein a further compression cylinder (12b) of the plurality of compression cylinders (12a, 12b) forms a second stage compression cylinder (12b) configured to operate in a second compression stage; and- a crankshaft (13) supported by the crankcase (11) and connected to pistons (15a, 15b) configured to reciprocate in the compression cylinders (12a, 12b) by rotation of the crankshaft (13);wherein the crankshaft (13) is connected to the pistons (15a, 15b) via a con rod assembly (16), the con rod assembly (16) comprising:- a main rod (17) extending between the crankshaft (13) and the piston (15b) reciprocating in the second stage compression cylinder (12b); and- connecting rods (18) being connected to the main rod (17) in a movable manner and extending between the main rod (17) and the pistons (15a) reciprocating in the first stage compression cylinders (12a).

2. The multi-stage reciprocating compressor (10) according to claim 1, wherein the main rod (17) comprises a crank disc (19) with openings (20) for movable fixation of the connecting rods (18).

3. The multi-stage reciprocating compressor (10) according to claim 2, wherein the main rod (17) comprises a center bore (25) receiving the crankshaft (13) and wherein the openings (20) are radially distributed around the center bore (25).

4. The multi-stage reciprocating compressor (10) according to claim 2 or 3, wherein the main rod (17) comprises a pair of crank discs (19) extending parallel to each other.

5. The multi-stage reciprocating compressor (10) according to any of the preceding claims, wherein at least one of the connecting rods (18) is connected to the main rod (17) via a needle bearing (22).

6. The multi-stage reciprocating compressor (10) according to any of the preceding claims, wherein the main rod (17) is connected to the crankshaft (13) via a roller bearing (24).

7. The multi-stage reciprocating compressor (10) according to any of the preceding claims, wherein the pistons (15a) reciprocating in the first stage compression cylinders (12a) are formed integrally with the connecting rods (18).

8. The multi-stage reciprocating compressor (10) according to any of the preceding claims, wherein longitudinal center axes (L-1) of the first stage compression cylinders (12a) are arranged in a first stage plane (P-1) and a longitudinal center axis (L-2) of the second stage compression cylinder (12b) is arranged in a second stage plane (P-2), wherein the first stage plane (P-1) and the second stage plane (P-2) coincide.

9. The multi-stage reciprocating compressor (10) according to claim 8, wherein the connecting rods (18) extend from the main rod (17) in a main rod plane (PM) of the main rod (17).

10. The multi-stage reciprocating compressor (10) according to claim 9, wherein the main rod (17) comprises a pair of crank discs (19) arranged symmetrically to a main rod axis (MP) of the main rod (17).

11. The multi-stage reciprocating compressor (10) according to any one of claims 1 to 7, wherein longitudinal center axes (L-1) of the first stage compression cylinders (12a) are arranged in a first stage plane (P-1) and a longitudinal center axis (L-2) of the second stage compression cylinder (12b) is arranged in a second stage plane (P-2), wherein the first stage plane (P-1) and the second stage plane (P-2) are spaced apart from each other.

12. The multi-stage reciprocating compressor (10) according to claim 11, wherein the connecting rods (18) extend in a connecting rod plane (PC) and the main rod (17) extends in a main rod plane (PM) and wherein the connecting rod plane (PC) and the main rod plane (PM) are spaced apart from each other.

13. The multi-stage reciprocating compressor (10) according to claim 12, wherein the main rod (17) comprises a pair of crank discs (19) unilaterally protruding from the main rod (17).

14. The multi-stage reciprocating compressor (10) according to any preceding claim, wherein the multi-stage reciprocating compressor (10) comprises at least three first stage compression cylinders (12a) and one second stage compression cylinder (12b).

15. The multi-stage reciprocating compressor (10) according to any preceding claim, wherein the crankshaft (13) is configured to rotate in a predefined rotation direction (RD) and wherein in accordance with the rotation direction of the crankshaft (13), a first stage compression cylinder (12a) following the second stage compression cylinder (12b) is positioned at a first angle (α2) from the second stage compression cylinder (12b) and the second stage compression cylinder (12b) is positioned at a second angle (α2) from a preceding first stage compression cylinder (12a), wherein the second angle (α2) is larger by a predefined angle difference (Δα) than the first angle (α1).

16. A pneumatic vehicle system (30) comprising a multi-stage reciprocating compressor (10) according to any preceding claim and a pneumatic consumer system (36) connected to the multi-stage reciprocating compressor (10).

17. A vehicle (50), in particular a commercial vehicle (50’), with a pneumatic vehicle system (30) according to claim 16.

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