EP3601800B1 - Multistage compressor - Google Patents

Description

The present invention relates to a multi-stage compressor. The invention also relates to a compressor with such a multistage compressor and an operating method for such a multistage compressor.

Multi-stage compressors or multi-stage compressors are well known and usually have at least one low-pressure stage and one high-pressure stage, the high-pressure stage being exposed to increased wear and thus often representing a weak point of such a multi-stage compressor.

Multi-stage compressors can, for example, have a plurality of piston-cylinder units, of which, for example, one piston-cylinder unit forms a high-pressure stage and a piston-cylinder unit forms a low-pressure stage. In the low-pressure stage, the gas to be compressed, for example air, is (pre-) compressed to a first pressure stage and then fed to the at least one second piston-cylinder unit, hence the high-pressure stage. Of course, there can be a charge air cooler in between.

From the DE 10 2014 213 391 A1 a piston compressor, in particular for supplying air to air suspension systems in motor vehicles, is known, which is designed as a multi-piston compressor with n> 2 cylinders in a star arrangement.

The disadvantage of the multistage compressors known from the prior art, however, is that the piston rings in particular in the high pressure stage wear out more quickly due to the higher load, so that failure of the multistage compressor can occur even if the low pressure stages are still working properly because of a worn high pressure stage.

The present invention is therefore concerned with the problem of specifying a multistage compressor which overcomes the disadvantages known from the prior art.

This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject of the dependent claims.

The present invention is based on the general idea of specifying a multi-stage compressor with at least one high pressure stage and with at least one low pressure stage, which is switched during operation in such a way that not only a single piston-cylinder unit constantly forms the high pressure stage, but the high pressure stage across all Piston-cylinder units migrate, which means that even wear and thus a longer service life can be achieved. For this purpose, a so-called "clocking" valve device is used which, depending on the switching position, relays the high pressure stage to a position for each cycle, that is to say assigns it to a subsequent piston-cylinder unit. The multi-stage compressor according to the invention has at least two pistons driven via a common crankshaft mounted in a crankcase, which are guided in associated cylinders of a respective piston-cylinder unit and which form the at least one high pressure stage or the at least one low pressure stage. Of course, a total of three or more piston-cylinder units can also be provided, one of which forms a high-pressure stage and the other two or more each form the upstream low-pressure stages. In addition, a line arrangement communicating with the individual cylinders is provided for supplying and removing air to and from the individual cylinders. According to the invention, the switchable valve device is arranged in this line arrangement, which valve device is designed in such a way that the high pressure stage depending on the switching position is assigned to different cylinders, wherein the at least one high pressure stage according to the invention moves one cylinder or a piston-cylinder unit on with each cylinder work cycle.

It is also conceivable to change the high pressure stage not every working cycle, but e.g. only every tenth working cycle. That is, over a time interval t, all piston-cylinder assemblies would still be loaded in the same way and therefore also worn. It is also conceivable to change the high pressure stage each time the compressor is started up / started again.

The valve device can be designed mechanically, electrically, pneumatically or in some other way. The embodiment of the multi-stage compressor according to the invention makes it possible to use piston-cylinder units with the same dimensions, whereas in contrast to multi-stage compressors known from the prior art, for example, a high-pressure stage is executed with a smaller volume. As a result of the dimensions that are now the same for the first time in the multistage compressor according to the invention, standard parts can be used, as a result of which the variety of parts and thus also the storage and logistics costs as well as the assembly costs can be reduced. Another advantage of the multistage compressor according to the invention is that the high-pressure stage can still provide highly compressed air, even if a piston-cylinder unit fails. This can be detected, for example, via appropriate sensors, whereupon a control of the multistage compressor no longer activates the damaged or no longer correctly working piston-cylinder unit and skips it. In the case of multistage compressors known from the prior art, failure of the high-pressure stage, for example, always leads to failure of the entire compressor.

In an advantageous development of the solution according to the invention, a pre-compression cooler is provided which is connected downstream of the at least one low-pressure stage and upstream of the at least one high-pressure stage. The thermal energy that is supplied to the air during compression can be withdrawn again via such a pre-compression cooler, whereby further compression is more easily possible. Of course, a high-compression cooler can also be connected downstream of the high-pressure stage, for example before the now highly compressed charge air is introduced into a pressure accumulator, as a result of which the storage capacity can be increased.

In a further advantageous embodiment of the solution according to the invention, a high-pressure stage and three low-pressure stages are provided, as well as four pistons driven by a common crankshaft mounted in a crankcase, which are guided in associated cylinders in associated piston-cylinder assemblies and the one high-pressure stage and three Form low pressure stages. Such a compressor can be driven, for example, by an electric motor. Of course, alternative embodiments of the multistage compressor according to the invention can also be considered for this, for example with a total of five, six or more compressor stages, two of which function as high-pressure stages and the rest as low-pressure stages. Due to the fact that in the multistage compressor according to the invention all compressor stages, that is to say all piston-cylinder units, have the same dimensions, almost any scaling is possible. If, for example, a higher volume flow is required, the number or the volume of the compressor units can simply be increased.

The present invention is further based on the general idea of equipping a compressor, in particular an oil-free compressor, with an interconnection described in the previous paragraphs, whereby an intrinsically long-lived one and reliable functioning can be achieved, since the multistage compressor according to the invention not only wears less and is therefore more durable, but also theoretically can easily compensate for the failure of at least one pressure stage with appropriate detection devices and sensors and control devices.

The present invention is further based on the general idea of specifying an operating method of the multi-stage compressor described above, in which a switchable valve device is switched such that the high pressure stage is assigned to different cylinders depending on the switching position of the valve device, in particular that the at least one high pressure stage is assigned to each work cycle , that is, when an associated piston moves up and down in an associated piston-cylinder unit, one cylinder moves further. Here, too, it is conceivable not to change the high pressure stage every working cycle, but e.g. only every tenth working cycle. That is, over a time interval t, all piston-cylinder assemblies would still be loaded in the same way and therefore also worn. As a result of the continuous migration of the at least one high-pressure stage, the signs of wear that have hitherto only occurred in a single piston-cylinder unit forming the high-pressure stage can now be evenly distributed to all piston-cylinder units, which means that they wear less and thus a higher overall level for the compressor Life expectancy is reached.

Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures on the basis of the drawings.

It goes without saying that the features mentioned above and those yet to be explained below not only in the respectively specified combination, but can also be used in other combinations or on their own without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to the same or similar or functionally identical components.

Fig. 1

eine Schnittdarstellung durch einen erfindungsgemäßen mehrstufigen Verdichter ohne nähere Darstellung einer erfindungsgemäßen zugehörigen Ventileinrichtung,

Fig. 2

eine zugehörige Ventileinrichtung in einer ersten Schaltstellung,

Fig. 3

eine Darstellung wie in Fig. 2, bei einer Ventileinrichtung in einer zweiten Schaltstellung,

Fig. 4

eine mögliche Ausführungsform eines Ventilkörpers der Ventileinrichtung,

Fig. 5

ein oberes Teil des Ventilkörpers im Ansaugtakt,

Fig. 6

ein unteres Teil des Ventilkörpers im Ausstoßtakt.

Show, each schematically,

Fig. 1

a sectional view through a multistage compressor according to the invention without a detailed representation of an associated valve device according to the invention,

Fig. 2

an associated valve device in a first switching position,

Fig. 3

a representation as in Fig. 2 , with a valve device in a second switching position,

Fig. 4

a possible embodiment of a valve body of the valve device,

Fig. 5

an upper part of the valve body in the intake stroke,

Fig. 6

a lower part of the valve body in the exhaust stroke.

According to the Figs. 1 to 3 A multistage compressor 1 according to the invention has at least one high pressure stage 2 and at least one low pressure stage 3. According to the Fig. 2 the multi-stage compressor 1 according to the invention has a total of four pressure stages, one of which is a high pressure stage 2 and three as a Low pressure stages 3 are formed. Each pressure stage 2, 3 has its own piston-cylinder unit 4 with a cylinder 5 and a piston 6 mounted in it so as to be translationally adjustable, the pistons 6 via a common and in a crankcase 7 (cf. Fig. 1 ) mounted crankshaft 8 are driven. Also provided is a line arrangement 9 communicating with the individual cylinders 5 for supplying and removing air to and from the cylinders 5. In the line arrangement 9 (cf. in particular FIG Fig. 2 and 3 ) According to the invention, a switchable valve device 10 is arranged, which is designed in such a way that the high-pressure stage 2 is or is assigned to different cylinders 5 depending on the switching position of a valve body 11 of the valve device 10, in particular that the at least one high-pressure stage 2 for each working cycle of a piston 6 a cylinder 5 moves on. Alternatively, it is also conceivable not to change the high pressure stage 2 with every work cycle but, for example, only with every tenth work cycle. That is to say, over a time interval t, all piston-cylinder assemblies 4 would still be loaded in the same way and therefore also worn.

According to the Fig. 2 the valve device 10 is shown in a suction position in which the low-pressure stages 3 suck in air from the crankcase 7 via the valve body 11 of the valve device 10. The suction can optionally also take place directly from the ambient air or an intermediate filter. Likewise, air that has already been pre-compressed in a previous work cycle and cooled via the pre-compression cooler 12 is sucked in and fed via the valve body 11 to the valve device 10 of the high-pressure stage 2, i.e. the piston-cylinder unit 4 shown above on the left. In a next working cycle, when the valve body 11 of the valve device 10 is then rotated clockwise, the high-pressure stage 2 would move from top left to top right and, in the same way, the low-pressure stages 3 would move by one piston-cylinder unit 4 in or against each other clockwise be twisted. Of course, other movements of the valve body 11 are also conceivable, for example translational movements.

If you look at the Fig. 3 , so you can see an exhaust cycle there, in which the now pre-compressed air from the three low-pressure stages 3 is fed to the first pre-compression cooler 12 via the valve body 11 of the valve device 10. Likewise, in the high-pressure stage 2, highly compressed charge air is fed via the valve body 11 of the valve device 10, for example to a second high-compression cooler 13 and / or finally to a pressure accumulator 14. By turning the valve body 11 clockwise or in the opposite direction, the valve device 10 according to the invention and the associated line arrangement 9 move the respective high pressure stage 2 over the individual piston-cylinder units 4, whereby the wear phenomena that increasingly occur in the high pressure stage 2 evenly occur all piston-cylinder units 4 can be distributed and as a result of which the life expectancy of the multistage compressor 1 according to the invention increases significantly.

According to the Fig. 2 For the sake of clarity, only the inlet lines of the line arrangement 9 into the respective piston-cylinder units 4 are shown, while according to FIG Fig. 3 only the outlet lines are shown. Of course, however, the line arrangement 9 always has one inlet and one outlet line to and from the respective piston-cylinder unit 4.

In the in the Fig. 2 and 3 The compressor 1 shown is provided with a total of three low-pressure stages 3 and only a single high-pressure stage 2, it being understood that further low-pressure stages 3 or high-pressure stages 2 can also be provided.

The multistage compressor 1 according to the invention is operated, in which the switchable valve device 10 is switched in such a way that the high pressure stage 2 is assigned to different cylinders 5, i.e. different piston-cylinder units 4, depending on the switching position, so that the at least one high pressure stage 2 at Each work cycle of the piston 6 or with each switching cycle of the valve device 10 a cylinder 5 or a piston-cylinder unit 4 moves on. Alternatively, it is also conceivable to change the high pressure stage 2 not every working cycle, but e.g. only every tenth working cycle. That is, over a time interval t, all piston-cylinder units 4 would still be loaded in the same way and the increased wear and tear caused by high-pressure stage 2 could be transferred evenly to all piston-cylinder units 4. The multistage compressor 1 according to the invention also has the great advantage that, for example, if a single low-pressure stage 3 fails, this can be switched off by detection, for example by means of a corresponding control device, so that the multistage compressor 1 according to the invention can also be used if one or more low-pressure stages 3 fail or high-pressure stage 2 continues to function, since high-pressure stage 2 is not only linked to a single piston-cylinder unit 4 or at least to a fixed piston-cylinder unit.

The valve device 10 has according to FIG Fig. 4 a rotatable cylindrical valve body 11 with an upper part 17 and a lower part 18 and can be pneumatically, electrically or hydraulically switchable. In this case, different inlets 15 or outlets 16 are arranged in the valve body 11 on its lateral surface, which can also change their inlet function or outlet function depending on the switching position. Of course, the inputs 15 and the outputs 16 can also be interchanged.

According to the Fig. 5 an upper part 17 of the valve body 11 is shown in a suction position in which the low-pressure stages 3 suck in air from the crankcase 7 or from the environment, in particular via a filter device. Air is sucked in via three inlets 15a. The sucked-in air is fed via the outputs 16a assigned to the inputs 15a to the piston-cylinder assemblies 4 designed as low-pressure stages 3 and, after the compression cycle, to the pre-compression cooler 12. The term “pre-compression cooler 12” refers to the cooling after the low-pressure compression and before the high-pressure compression. Likewise, air that has already been pre-compressed in a previous work cycle and cooled by the pre-compression cooler 12 is sucked in via the inlet 15b and via the valve body 11 of the valve device 10 and the outlet 16b of the high-pressure stage 2 assigned to the inlet 15b, i.e. the piston-cylinder shown at the top left -Aggregate 4 supplied.

If you look at the Fig. 6 , so you can see a lower part 18 of the valve body 11 during an exhaust stroke that runs simultaneously with the intake stroke of the upper part 17 and in which the now pre-compressed air from the three low-pressure stages 3 via the inputs 15a and the associated outputs 16a of the valve body 11 of the valve device 10 is fed to the first pre-compression cooler 12. Likewise, in the high-pressure stage 2, highly compressed charge air is supplied via the inlet 15b of the valve body 11 of the valve device 10 and the associated outlet 16b, for example to a second high-compression cooler 13 and / or finally to a pressure accumulator 14. By turning the valve body 11 clockwise or in the opposite direction, the valve device 10 according to the invention and the associated line arrangement 9 move the respective high pressure stage 2 over the individual piston-cylinder units 4, whereby the wear phenomena that increasingly occur in the high pressure stage 2 evenly occur all piston-cylinder units 4 can be distributed and as a result of which the life expectancy of the multistage compressor 1 according to the invention increases significantly.

The two parts 17, 18 can be rotated relative to one another or together. The intake stroke is controlled via the lower part 17. The exhaust stroke via the upper part 18, or vice versa. Both parts 17, 18 move simultaneously clockwise or counter-clockwise in order to enable precise timing with a robust construction at the same time. However, there is no connection between the channels or millings between the upper part 17 and the lower part 18.

The crankshaft 8 and thus the multistage compressor 1 can be driven, for example, by an electric motor (not shown).

Claims (8)

1. Multistage compressor (1),

   - with at least one high-pressure stage (2) and at least one low-pressure stage (3),

   - with at least two pistons (6) which are driven via a common crankshaft (8) mounted in a crankcase (7), and which are guided in associated cylinders (5), and which form the at least one high-pressure stage (2) and the at least one low-pressure stage (3),

   - with a line arrangement (9) which communicates with the individual cylinders (5) for supplying and discharging air to and from the cylinders (5),

   - wherein in the line arrangement (9) a switchable valve device (10) is arranged, which is configured such that the at least one high-pressure stage (2) is associated with different cylinders (5) according to a switching position of the valve device (10),
   characterised in that
   the at least one high-pressure stage (2) moves one cylinder (5) further with each cylinder operating cycle or each switching position.
2. Compressor according to claim 1,
   characterised in that
   during a time interval t each of the piston-cylinder units (4) is configured for a same number of cylinder operating cycles as a high-pressure stage (2) or as a low-pressure stage (3).
3. Compressor according to any of the preceding claims,
   characterised in that
   a pre-compression cooler (12) is arranged downstream of the at least one low-pressure stage (3) and upstream of the at least one high-pressure stage (2).
4. Compressor according to any of the preceding claims,
   characterised in that
   the valve device (10) has a rotatable cylindrical valve body (11).
5. Compressor according to any of claims 1 to 4,
   characterised in that
   the valve device (10) is switchable pneumatically, electrically or hydraulically.
6. Compressor according to any of claims 1 to 5,
   characterised in that

   - one high-pressure stage (2) and three low-pressure stages (3) are provided,

   - four pistons (6) driven by a common crankshaft (8) mounted in a crankcase (7), which pistons are guided in associated cylinders (5), form the one high-pressure stage (2) and the three low-pressure stages (3).
7. Pressuriser (19), in particular an oil-free pressuriser, with a multi-stage compressor (1) according to any of the preceding claims.
8. Operating method of a multi-stage compressor (1) according to any of claims 1 to 5, wherein the switchable valve device (10) is switched such that the at least one high-pressure stage (2) depending on the switching position of the valve device (10) is assigned respectively to different cylinders (5), in particular the at least one high-pressure stage (2) moves one cylinder (5) further with each cylinder operating cycle.

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