DE102017120000A1 - Low-vibration multistage reciprocating compressor, in particular for rail vehicles - Google Patents

Abstract

The invention relates to a multistage reciprocating compressor, in particular for rail vehicles, having a low-pressure stage and at least one subsequent high-pressure stage for multistage compression of sucked air, for which a drive unit (1) drives a downstream compressor unit (2) to produce a rotational movement. 6) for accommodating a crankshaft (11) arranged cup-shaped low or high pressure cylinder (7a, 7b, 8a, 8b) for internal piston (12), wherein via the drive unit (1) driven crankshaft (11) has a rotational movement over a plurality of at least one crank arranged connecting rod (13) in a linear movement for each associated piston (11) for compressing the air, wherein an even number of low and high pressure cylinders (7a, 7b, 8a, 8b) in a star shape on the compressor housing (6) is arranged, wherein in each case a high-pressure cylinder (7a, 7b) a Niederdruckz ylinder (8a; 8b) facing on the same longitudinal axis (A or B), and each with a piston (12) provided with connecting rod (13) has its own offset (14a to 14d) of the crankshaft (11) is assigned.

Description

The invention relates to a multi-stage piston compressor, in particular for rail vehicles, with a low-pressure stage and at least one subsequent high-pressure stage for compressing intake air in multiple stages, wherein a drive unit for generating a rotational movement drives a downstream compressor unit which comprises a plurality of cup-shaped cylinders arranged on a compressor housing for accommodating a crankshaft for internal piston, wherein the driven via the drive unit crankshaft converts a rotational movement over a plurality of arranged on at least one crank connecting rod in a linear movement for each associated piston for compressing the air, further comprising an even number of low and high pressure cylinders in a star shape on the compressor housing is arranged.

The field of application of the invention extends primarily to vehicle construction, in particular rail vehicle construction. Rail vehicles are usually equipped with compressed air consumers, such as in particular a compressed air-operated brake, which makes a compressor required to generate the required compressed air. The reciprocating compressors of interest in the context of the present invention are usually designed in multiple stages and thus have a low-pressure stage and at least one subsequent high-pressure stage in order to bring the air drawn in from the environment through multistage compression to the desired pressure level.

Due to a further development of the electrical converter technology reciprocating compressors are increasingly used, the electric drive unit is operated speed controlled in order to generate the compressed air needs - ie with variable capacity. Thus, for example, in operating situations with low compressed air demand, the speed of the compressor and thus its sound radiation can be reduced to a minimum.

In addition, the use of reciprocating compressors in rail vehicle construction also offers a number of technical advantages over conventional rotary compressors. The introduction of oil-free reciprocating compressors has developed a trend away from rotary compressors and towards robust reciprocating compressors. However, the overlap of this trend with the trend towards variable speed compressed air generation causes new problems with regard to vibrations that occur, which can affect the ride comfort. For piston engines generate - caused by the oscillating masses on the crank mechanism - due to design inertial forces and moments, which can be compensated well depending on the selected design, at least in the 1st order. The size of the free mass forces and moments decreases correspondingly as the speed decreases.

Larger problems, however, occur with respect to vibration excitations, resulting from the compression forces, especially when using two-stage reciprocating compressors of interest here kind. Because the two-stage compaction generated in most types of reciprocating compressors a particularly uneven torque. This non-uniform torque from the compression acts as a pendulum moment about the compressor rotational axis and thus generates vibrations at the attachment points of the compressor, resulting in a deterioration of ride comfort. These compression-related nonuniform torques do not decrease with falling speed, but can even increase with appropriate mass distribution and cause resonances of the elastic attachment points are excited and even exaggerated at low speed. Experiments have shown that particularly harmful in these compression-related non-uniform torques shares 1 , Order, which act once by pressure peaks in one revolution.

From the well-known state of the art, designs of reciprocating compressors emerge in which the vibration behavior is greatly improved in the region of higher rotational speeds because the fraction of the first order is greatly reduced at the moments resulting from the compression forces. However, that's a moment 1 , Order still exists and affects at low speeds still harmful to the vibration behavior.

The DE 100 58 924 A1 discloses a multi-stage reciprocating compressor whose vibration behavior is not a moment 1 , Order includes more. In this case, two connecting rods are arranged on each crank of the crankshaft, which are assigned to opposite pistons, wherein adjacent cranks are arranged offset substantially 180 ° to each other. This results in a series arrangement of low and high pressure cylinders, the two opposite rows of cylinders form a kind of boxer arrangement. By this boxer-like arrangement of low and high pressure cylinders, however, an air-cooled construction, as is customary in rail vehicle construction, but no longer efficiently implemented. In addition, this special design for a multi-stage low-vibration compression requires at least six cylinders, which leads to a fairly high production cost.

The WO 2015/172144 A1 discloses a kind of star design for a multi-stage reciprocating compressor, which is described as particularly smooth running. The compressor housing is pentagonal in the basic cross section, wherein a lower side surface fastening means for attachment to a support structure. The other four side surfaces are each assigned a high or low pressure cylinder. This results in an unequal-axis cylinder arrangement, since each cylinder has its own longitudinal axis, which is at an angle offset to the longitudinal axes of the remaining cylinders.

Further, in this prior art design all connecting rods are on the same circumferential crank of the crankshaft. Thus, all four crank mechanisms of this multi-stage piston compressor form a circulating unbalance, which is difficult to compensate dynamically. In addition, results in the torque diagram, a remaining proportion 1 , Order. As already explained above, shares in particular deteriorate 1 , Order the vibration behavior and have a negative impact on the electric drive unit in the form of torsional vibrations and rotational irregularities. This results in the electric drive unit to an increased power consumption, harmonic components in the electric current and a reduced power factor with high thermal load of the electric drive unit.

In addition, the star design of this previously known multi-stage piston compressor in comparison to the prior art discussed with boxer design a fairly large height, so that this star-shaped multi-stage piston compressor is only partially suitable for underfloor installation in the rail vehicle.

It is the object of the present invention to provide a suitable for rail vehicle multi-stage piston compressor, which is characterized by a minimal vibration behavior, low height and easy cooling by air flow.

The object is achieved on the basis of a multi-stage reciprocating compressor according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims give advantageous developments of the invention.

The invention includes the technical teaching that in a multi-stage reciprocating compressor in star design each a low-pressure cylinder facing a high-pressure cylinder on the same longitudinal axis and each piston provided with a piston own crank of the crankshaft is assigned, which is so angularly offset to at least one adjacent Kröpfung arranged the crankshaft can be brought into a position in which one of the high pressure cylinders is in the top dead center position while the other high pressure cylinder is in the bottom dead center position and at the same time a low pressure cylinder is in the top dead center position while the other low pressure cylinder is in the bottom dead center position ,

So not all the pistons compress at the same time, but in each case the preferably two low-pressure pistons are offset by 180 ° and the two high-pressure pistons are offset by 180 ° relative to one another. The solution according to the invention results in a compression sequence which leads to the result that each event of a compression occurs twice with respect to one revolution of the entire compressor unit, the torque resulting from the gas forces being free of portions 1 , and 3rd order. This allows the operation of a multi-stage piston compressor in the range of lowest speeds without disturbing vibration peaks.

The existing in conventional reciprocating compressors rotational irregularities are even further enhanced by the electric drive unit, because the reaction of the drive unit to a load peak out of phase takes place at a time in which the torque requirement of the reciprocating compressor is lower. The resulting increased speed variations over one revolution can be up to ± 14% in conventional two-stage reciprocating compressors. So far, this effect can only be reduced by using large flywheel masses. By contrast, according to the invention strong reduction of the proportion 1 , Order in the load moment this effect is reduced. The rotational nonuniformity is reduced, so that the current consumption of the electric drive unit also decreases. Accordingly, the power factor increases considerably, so that conditions are reached that correspond to an approximately constant torque requirement (rated load conditions). This has the consequence that electric drive units no longer need to be oversized, but can be designed according to the power requirement of the reciprocating compressor.

These effects of the solution according to the invention form the precondition for the fact that preferably a synchronous reluctance motor can be used as the electric drive unit, in which the rotor has a fairly low mass. In addition, such a synchronous reluctance motor is operable even at low speeds with high torque. A variable speed can be regulated between 15 Hz and 80 Hz by means of an upstream inverter.

Since in the inventive solution can be largely dispensed with additional centrifugal masses, except for unbalance compensation, the rotor of the synchronous reluctance motor can be mounted directly on the crankshaft end of the compressor unit and the stator of the motor directly to the compressor housing. This creates a particularly compact design.

According to a further improvement of the invention in terms of compactness measure is proposed that the longitudinal axes of low and high pressure cylinders in a star shape at an angle α to the horizontal H of 25 ° +/- 10 ° are arranged. As a result, a space-saving arrangement of the multi-stage piston compressor in the underfloor area of a rail vehicle is possible, in which the installation situation is limited in particular with regard to the installation height. The arrangement of the cylinder in the specified angular range ensures a largely flat design of the multi-stage piston compressor. Preferably, the high-pressure cylinders are below the horizontal H and the low pressure cylinders above the horizontal H positioned. In this arrangement, condensate, which can form in unfavorable conditions in the high-pressure stage, run on the cylinder wall. In addition, the heat generated by the low-pressure cylinders can rise upwards and be dissipated. In a preferred four-cylinder embodiment of the compressor unit, two high-pressure cylinders and two low-pressure cylinders are used.

According to a further measure improving the invention, it is proposed that the connecting rods and / or the pistons of the high-pressure stage are made of a material, preferably metal, which has a higher specific weight compared to the connecting rods and / or the pistons of the low-pressure stage. In addition, the connecting rods of the low-pressure stage can be made longer than the connecting rods of the high-pressure stage and the center of gravity of the connecting rod of the low-pressure side should be closer to the piston than the center of gravity of the connecting rod of the high-pressure stage. The connecting rods of the low-pressure stage are preferably at least 1.1 times longer than the connecting rods of the high-pressure stage. Overall, results from these constructive measures a low-vibration mass distribution.

If, however, a slight mass balance of the crank mechanisms, for example, to remedy imbalances, be required, it is sufficient that additional masses are attached to the relevant connecting rod. As a result, the mass balance does not need to be made on the crankshaft.

By the measures described above, the crank mechanisms of the two-stage compressor unit can be carried out such that the proportion of 1 , Order in torque chart a value of less than 10% of the proportion of 2 , Order is. Since the multi-stage reciprocating compressor according to the invention only generates vibrations in higher orders insofar, a relatively stiff bearing can be used on a support structure of the vehicle, which nevertheless offers sufficient vibration isolation.

The star-shaped cylinder arrangement of the multi-stage piston compressor according to the invention provides the prerequisite for the fact that all cylinders can be supplied with cooling air by an axial fan. A wind shadow situation is thus avoided. In this case, there is the plane through which two adjacent cylinders - in particular high and low pressure cylinder - go, perpendicular to the flow direction of the cooling air generated by the axial fan. If required, additional air baffles can be arranged on the compressor housing, which guide the cooling air uniformly in the direction of the ribs of the cylinders.

• 1 zeigt eine perspektivische Außenansicht eines mehrstufigen Kolbenkompressors in 4-Zylinderbauform,
• 2 zeigt eine stirnseitige Ansicht des mehrstufigen Kolbenkompressors nach 1,
• 3 zeigt eine teilweise aufgebrochene Draufsicht des mehrstufigen Kolbenkompressors nach 1,
• 4 zeigt eine perspektivische Darstellung einer Kurbelwelle der Verdichtereinheit dieses Kolbenkompressors,
• 5 zeigt eine grafische Darstellung des Momentenverlaufs an der Kurbelwelle, und
• 6 zeigt eine Fourier-Analyse der Lastmomente aus der grafischen Darstellung gemäß 5.

Further measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS.

• 1 shows an external perspective view of a multi-stage piston compressor in 4-cylinder design,
• 2 shows an end view of the multi-stage piston compressor after 1 .
• 3 shows a partially broken plan view of the multi-stage piston compressor after 1 .
• 4 shows a perspective view of a crankshaft of the compressor unit of this reciprocating compressor,
• 5 shows a graphical representation of the torque curve on the crankshaft, and
• 6 shows a Fourier analysis of the load moments from the graph according to 5 ,

To 1 consists of the multi-stage piston compressor essentially of a drive unit 1 , which is designed here as a synchronous electrical reluctance motor. The drive unit 1 generates a rotational movement to drive a compressor unit directly flanged thereto 2 , which has a low-pressure stage and a subsequent high-pressure stage for multi-stage compression of air sucked from the environment. For the Cooling of the heat generated during compression work is ensured by a cooler unit 3 with end face on the compressor unit 2 positioned axial fan 4 , The multi-stage piston compressor is about elastic fasteners 5a at the compressor unit 2 as well as fasteners 5b on the electric drive unit 1 attached to a - not shown - support structure of a vehicle.

The compressor unit 2 has a compressor housing 6 on which star shaped several cup-shaped larger low pressure cylinder 8a (exemplary) as well as smaller high-pressure cylinders 7a and 7b are arranged. This is a multi-stage reciprocating compressor in 4-cylinder design.

From the in 2 apparent end view is the invention star-shaped arrangement of high-pressure cylinder 7a . 7b in combination with the low-pressure cylinders 8a . 8b on the compressor housing 6 out. Accordingly stands on a longitudinal axis A a high pressure cylinder 7a a low-pressure cylinder 8b across from. On the other longitudinal axis B is a high pressure cylinder 7b a low-pressure cylinder 8a across from. The longitudinal axes A and B of low and high pressure cylinders 7a . 7b . 8a . 8b are star-shaped with an angle α to the horizontal H arranged from here 25 °. The two low pressure cylinders 8a and 8b of the 4 Cylinder arrangement are above the horizontal H arranged, whereas the two high pressure cylinder 7a and 7b below the horizontal H are arranged.

The compressor housing 6 has a hexagonal base cross-section, wherein both the left-side low-pressure cylinder 8a and the left-side high-pressure cylinder 7a at mutually adjacent side surfaces 9a and 9a ' of the compressor housing 6 are arranged. Opposite are mirror-symmetrical to this the right-side low pressure cylinder 8b and the right side high pressure cylinder 7b on adjacent side surfaces 9b such as 9b ' arranged. A different bottom side surface 10 serves the arrangement of - not shown - fastener 5a on the hexagonal compressor housing 6 ,

According to 3 serves the compressor housing 6 the compressor unit 2 the accommodation of a crankshaft 11 for driving the different each from pistons 12 . 12 ' and connecting rods 13 . 13 ' (exemplary) existing crank drives the high and low pressure stage.

To 4 is at the crankshaft 11 Each crankshaft has its own crank 14a to 14d associated, which with respect to the adjacent crank, for example 14a to 14b to an angle β are arranged at an angle of 30 ° to each other. This angular offset exists between all adjacent cranks 14a to 14d , This is the crankshaft 11 in a position, in which each of the four pistons 12 (exemplary) simultaneously assumes the bottom dead center position.

From the in 5 illustrated torque curve in the range of the angle of rotation γ one turn is the moment M _G from gas forces, the moment M _m from inertial forces as well as the sum moment M _s from mass and gas forces. The compression sequence of the two-stage reciprocating compressor is inventively chosen so that each event occurs twice within a revolution, and so the proportion 1 , Order in torque chart against 0 goes.

As from the Fourier analysis of the load torque 6 the proportion is 1 , order 0 , the amount 2 , order 27 Nm, the proportion 3 , order 0 and the share 4 , order 15 Nm.

The invention is not limited to the embodiment described above. There are also modifications thereof are conceivable, which fall within the scope of the following claims. For example, it is also possible that a design with more than 4 cylinders, for example with 6 or 8 cylinders, is used.

LIST OF REFERENCE NUMBERS

1

drive unit

2

compressor unit

3

cooler unit

4

Axial

5

fastener

6

compressor housing

7

High pressure cylinder

8th

Low-pressure cylinder

9

lateral side surface

10

lower side surface

11

crankshaft

12

piston

13

pleuel

14

cranking

A

first longitudinal axis

B

second longitudinal axis

H

horizontal

α

Horizontal angle

β

offset angle

γ

Angular position crankshaft

M

torque

f

frequency

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10058924 A1 [0007]
• WO 2015/172144 A1 [0008]

Claims (12)

Multi-stage reciprocating compressor, in particular for rail vehicles, with a low-pressure stage and at least one subsequent high-pressure stage for compressing sucked air in multiple stages, for which a drive unit (1) for generating a rotary movement drives a downstream compressor unit (2), which several to a compressor housing (6) for housing a cup-shaped low or high pressure cylinder (7a, 7b, 8a, 8b) arranged for crankshaft (11) for internal pistons (12), wherein via the drive unit (1) driven crankshaft (11) arranged a rotational movement over a plurality of at least one crank Connecting rod (13) in a linear movement for each associated piston (11) for compressing the air, wherein an even number of low and high pressure cylinders (7a, 7b, 8a, 8b) is arranged in a star shape on the compressor housing (6), characterized in that - one high-pressure cylinder (7a, 7b) in each case corresponds to a low-pressure cylinder ends (8a; 8b) facing on the same longitudinal axis (A or B), and - each with a piston (12) provided connecting rod (13) own crank (14a to 14d) of the crankshaft (11) is assigned, which is so angularly offset from at least one adjacent Cranking (14a to 14d) is arranged, that - the crankshaft (11) is brought into a position in which one of the high pressure cylinder (7a, 7b) is in the top dead center position, while the other high pressure cylinder (7b, 7a) in the lower Is dead center position with a low pressure cylinder (8a; 8b) being in the top dead center position while the other low pressure cylinder (8b; 8a) is in the bottom dead center position. Multi-stage piston compressor after Claim 1 , characterized in that the longitudinal axes (A; B) of low and high pressure cylinders (7a, 7b, 8a, 8b) are arranged in a star shape at an angle (a) to the horizontal (H) of 25 ° ± 10 °. Multi-stage piston compressor after Claim 1 or2, characterized in that the low pressure cylinder (8a, 8b) above the horizontal (H) and the high pressure cylinder (7a, 7b) below the horizontal (H) are arranged. Multi-stage piston compressor after Claim 2 or 3 , characterized in that a four-cylinder embodiment of the compressor unit (2) consists of two low-pressure cylinders (8a, 8b) and two high-pressure cylinders (7a, 7b). Multi-stage piston compressor after Claim 1 , characterized in that the drive unit (1) is designed as a synchronous electrical reluctance motor. Multi-stage piston compressor after Claim 1 , characterized in that the connecting rods (13 ') and / or the pistons (12') of the high pressure stage are made of a material which has a higher specific gravity relative to the connecting rods (13) and / or the pistons (12) of the low pressure stage , Multi-stage piston compressor after Claim 1 , characterized in that the connecting rods (13) of the low-pressure stage are designed to be longer than the connecting rods (13 ') of the high-pressure stage. Multi-stage piston compressor after Claim 7 , characterized in that the center of gravity of the connecting rod (13) of the low-pressure stage is closer to the piston than the center of gravity of the connecting rod (13 ') of the high-pressure stage. Multi-stage piston compressor after Claim 1 , characterized in that a mass balance of the crank mechanisms via only at at least one connecting rod (13, 13 ') attachable additional masses takes place. Multi-stage reciprocating compressor according to one of the preceding claims, characterized in that each of the piston (12) and connecting rod (13) existing crank mechanism of the two-stage compressor unit (2) is designed such that the proportion of the 1st order in the torque diagram has a value of less than 10 % of the 2nd order share. Multi-stage piston compressor according to one of the preceding claims, characterized in that the compressor housing (6) has a hexagonal basic cross-section. Multi-stage piston compressor after Claim 11 characterized in that in a four-cylinder embodiment of the compressor unit (2) a low-pressure cylinder (8a; 8b) and a high-pressure cylinder (7a; 7b) on mutually adjacent side surfaces (9a, 9a ', 9b, 9b') of the hexagonal compressor housing (6) are arranged, wherein at least one of these different lower side surface (10) fastening means (5a) of the compressor unit (2) are arranged.

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