DE102020130779A1 - Feeding device and method for its operation - Google Patents

Abstract

The invention relates to a method for operating a supply device (10) for supplying a working fluid and a flushing fluid from their respective source (Q1, Q1) to a common destination, comprising a rotary feedthrough (12) in which the working fluid from a fixed tube (16) is fed into a coaxial tube (18) rotating about the common axial direction, the stationary tube (16), which tapers conically towards its outlet, protrudes into the rotating tube (18), which correspondingly widens conically towards its inlet, and an annular gap (24) existing radially between the tubes (16, 18) is fed with the flushing fluid. The invention is characterized in that the working fluid and the flushing fluid are supplied individually with volume flow control. The invention further relates to a corresponding supply device.

Description

field of invention

The invention relates to a method for operating a supply device for supplying a working fluid and a flushing fluid from their respective source to a common destination, comprising a rotary feedthrough in which the working fluid is fed from a fixed pipe into a coaxial pipe rotating about the common axial direction, The stationary tube, which tapers conically towards its outlet, projects into the rotating tube, which correspondingly widens conically towards its inlet, and an annular gap existing radially between the tubes is charged with the flushing fluid.

• - einem feststehenden Rohr, welches eingangsseitig mit einer mit der Arbeitsfluid-Quelle verbindbaren Arbeitsfluid-Zuleitung verbunden ist und sich zu seinem Ausgang hin konisch verjüngt, und
• - einem zu dem feststehenden Rohr koaxialen, um die gemeinsame Axialrichtung rotierbaren Rohr, welches sich zu seinem Eingang hin korrespondierend konisch erweitert und in welches das feststehende Rohr hineinragt,

wobei ein radial zwischen den Rohren bestehender, wenigstens abschnittsweise konischer Ringspalt mit einer mit der Spülfluid-Quelle verbindbaren Spülfluid-Zuleitung verbunden ist.The invention further relates to a supply device for supplying a working fluid and a flushing fluid from their respective source to a common destination, comprising a rotary union

• - A stationary tube which is connected on the input side to a working fluid supply line that can be connected to the working fluid source and tapers conically towards its output, and
• - a tube that is coaxial with the fixed tube and can be rotated about the common axial direction, which expands conically towards its entrance and into which the fixed tube projects,

an annular gap that is conical at least in sections and that exists radially between the tubes is connected to a flushing fluid supply line that can be connected to the flushing fluid source.

State of the art

Such methods and devices are known from DD 236 972 A1 .

In the field of industrial production of internal combustion engines, it is known to provide the inner surfaces of cylinder bores in crankcases with a coating in order to produce durable, low-friction running surfaces for the pistons moving in the cylinder bores. This coating is typically carried out as a plasma coating, with a rotating torch head of a plasma torch being pushed in the axial direction through the cylinder bore and in the process spraying the inner wall of the bore evenly with molten coating powder. During this process, a working fluid composed of a carrier gas and admixed coating powder, e.g. steel powder, is supplied to the torch head. The problem here is that the working fluid has to pass at some point from a stationary system comprising its source and supply line into the rotating system of the burner head. A so-called rotary feedthrough is typically provided for this transition. As an alternative to plasma coating, so-called laser coating is also known, in which coating powder is applied via a carrier liquid, ie the working fluid is a carrier liquid mixed with the coating powder.

From the DE 10 2016 112 470 A1 a rotary feedthrough is known in which a rotating tube connected to the burner head is coupled to a coaxial, fixed tube via a sealing gap in the shape of an annular disk between two radially protruding sealing flanges. An escape of working fluid is to be brought about by the sealing contact of the two flange surfaces with one another, for which purpose the sealing flanges are spring-loaded against one another. In practical implementation, however, sealing usually only succeeds to a limited extent. Powder entering the sealing gap causes severe abrasion here, so that such rotary feedthroughs are prone to malfunction and are wearing components that have to be replaced frequently in any case. The publication mentioned proposes flushing the sealing flange radially with a flushing gas, which is intended to quickly transport escaping working fluid and in particular its powder component, in order to prevent greater wear. Although this solution lengthens the service life of the rotary union, it does not prove to be completely satisfactory overall.

From another technical field, namely from the field of transporting aggressive gases, it is known from the generic document mentioned at the outset to realize a conical transition between the stationary and the rotating pipe instead of a radially projecting sealing flange. The fixed tube is injection molded towards its outlet, ie conically tapered, and protrudes into the correspondingly widening, rotating tube, resulting in a conical annular gap as the sealing gap. Due to the flow conditions at this transition between the stationary and the rotating system, it is already highly improbable that the aggressive transport gas will penetrate through the conical sealing gap against the main flow direction to the outside. In order to reliably prevent this and the associated damage to a lip seal sealing the bearing of the rotating tube, the publication cited proposes enclosing said transition region and coating the housing with a cushion gas under a predetermined overpressure cken, which forms a gas cushion axially between the conical sealing gap and the lip seal, which prevents contact between the aggressive transport gas and the lip seal. The disadvantage here, however, is that the transport gas is diluted in a way that cannot be precisely predicted by cushion gas penetrating the sealing gap, the degree of dilution depending on the overpressure in the housing, the width of the sealing gap and the flow rate and speed of the transport gas. It is true that the publication mentioned proposes selecting a carrier gas of the transport gas as the flushing or cushion gas; nevertheless, the exact composition of the transport gas behind the rotary union remains undefined, particularly with regard to the ratio of carrier gas to additives. Even if all adjustable parameters are set in anticipation of the dilution, in particular the pressure at which the flushing gas is supplied, the resulting composition of the transport gas would change over time, especially with increasing mechanical wear on the rotary feedthrough and a corresponding increase in the annular gap. Exactly adopting the known arrangement for supplying the working fluid to a plasma torch is therefore out of the question. The coating result depends in a highly sensitive manner on the total amount and the exact composition of the working fluid consisting of carrier gas and coating powder.

task

It is the object of the present invention to develop a generic device and a generic method in such a way that they are suitable for precision applications such as charging a plasma torch, in particular for coating cylinder running surfaces in crankcases for internal combustion engines.

Presentation of the invention

This object is achieved in connection with the features of the preamble of claim 1 in that the working fluid and the flushing fluid are supplied individually with volume flow control.

The object is further achieved in connection with the features of the preamble of claim 8 in that the two supply lines are each equipped with a volume flow controller which is set up to regulate material flows through the supply lines individually during operation and with the respective volume flow as the controlled variable.

Preferred embodiments of the invention are the subject of the dependent claims.

The basic idea of the invention, based on a mechanical design of the rotary union largely corresponding to that of the generic publication, is to ensure through suitable control that the composition of the fluid arriving at the outlet of the rotary union or at the inlet of downstream components, such as in particular a burner head is always available in the exact amount and composition required. For this purpose, both the supply of the working fluid and the supply of the flushing fluid are individually regulated in terms of volume flow, with these regulations not only being matched to one another with regard to the total volume flow but also in particular with regard to their quantity relation. However, there are different levels to be distinguished here. The focus of the invention is to enable the stated goal. This is done—initially without being restricted to specific default values—by the flushing fluid and working fluid being supplied in a volume-flow-controlled manner or by corresponding volume-flow regulators being provided in the supply lines. The specific setting up of said regulation or controller, namely the specification of a suitable total volume and the specification of the relation of its components, takes place at a higher level of controller programming. Its specific design is therefore a preferred, but not mandatory, part of the present invention.

Advantageously, it is provided that the volume flow control uses the pressure in the respective supply line between the respective source and the rotary leadthrough as a manipulated variable. In the context of the device according to the invention, this means that the volume flow controllers are set up to carry out the regulation by varying the pressure in the respective supply line between the respective source and the rotary union, thereby monitoring the resulting volume flow and deviations of the actual from the target volume flow feedback control of the pressure. The pressure in the supply lines has proven to be a technical parameter that can be influenced easily and very quickly, with an almost instantaneous effect on the “volume flow” control variable.

As mentioned, the preferred application of the invention is in the field of plasma coating of cylinder running surfaces in a crankcase for an internal combustion engine. In such a case, the rotating tube is usually part of or connected to a torch head of a plasma torch and is the working fluid a carrier gas mixed with a powder, preferably with a coating powder, particularly preferably with a steel powder. In these cases in particular, it has proven advantageous if the flushing fluid is also a gas, namely a flushing gas, and—particularly preferably—the carrier gas is chemically identical to the flushing gas. Particularly preferably, the working fluid in front of the rotary union then has a slightly too large proportion of powder or a slightly too small proportion of carrier gas, so that the "missing" carrier gas can be supplied as flushing gas in the area of the rotary union via the annular gap between the two tubes - and precisely the amount needed to provide the optimal amount and composition at the burner head. In the case of laser coating, which is also considered to be an advantageous application, the stationary tube can be connected to a laser coating head or be part of one, with a liquid—preferably chemically identical—being used as the carrier or flushing fluid.

The volume flow control according to the invention also provides the basis for a further advantage that is particularly noteworthy. In a particular embodiment of the invention, a wear alarm is output in the event that one of the assigned manipulated variable values deviates from a stored reference value by more than a predetermined tolerance after adjusting predetermined volume flow values through the supply lines. In other words, the manipulated variable required to set the desired volume flow in one or both of the feed lines, in particular the pressure required for this, itself is used as an indicator for the state of the system, in particular the rotary feedthrough. In a given state of the rotary feedthrough, certain manipulated variables applied to the feed lines, in particular pressures, lead to the desired volume flows. If there is now a change in the system status, for example due to increased wear on the rotary union, in particular an enlargement of the annular gap, this is noticeable in that, in order to achieve the same volume flow through the working fluid and/or flushing fluid supply line, a different manipulated variable value is required there , in particular a different pressure, is required (and of course set within the scope of the regulation according to the invention). This change in manipulated variable required to achieve the control specifications can be recognized and quantified by the system by comparing the actually set manipulated variables with stored manipulated variable reference values representing a "normal" system state. If this deviation from the reference value exceeds a specified tolerance, this is an indicator that an unacceptable change in the state of the system, in particular excessive wear on the rotary union, has occurred. Other damage to the system can of course have similar consequences; however, wear and tear in the area of the rotary union is by far the most likely damage. In the preferred embodiment, the detected excessive change in the manipulated variable leads to the issuance of a warning, in particular a wear warning, which enables the system operator to carry out maintenance work in good time, for example replacing the mechanics of the rotary union, before the damage is so great that the specified volume flows are not can be adjusted more precisely, which would have a negative effect on the coating result.

With regard to the specific mechanics of the rotary leadthrough, it is preferably provided that the rotatable tube, which rotates during operation, is mounted in a housing block in which the stationary tube is fixed, with a bearing gap merging into the annular gap, and the flushing fluid supply line passes through the housing block up to this bearing gap . In other words, the entire rotary feedthrough is arranged in a housing block which, firmly connected to it, holds the stationary tube. At the same time, the rotatable/rotating tube is mounted in the same housing block. The bearing gap forms the boundary between the housing block and the rotatable/rotating tube. The (conical) annular gap forms the boundary between the widening entrance of the rotatable/rotating tube and the tapered exit of the fixed tube. Both gaps are fluidly connected to one another, so that the flushing fluid does not have to be introduced directly into the annular gap, but can be introduced into the bearing gap with significantly less mechanical effort and can be guided from there into the annular gap. The flushing fluid feed line preferably ends in a feed point that is located axially between the transition from the bearing gap to the annular gap on the one hand and a rotary seal with which the rotatable/rotating tube is sealed against the housing block on the other. This ensures that all flushing fluid introduced into the bearing gap is also routed to the annular gap and cannot escape in any other way. This also ensures that the volumetric flow regulated in the flushing fluid supply line actually corresponds to the flushing fluid or additional carrier gas quantity mixed with the working fluid in the rotary feedthrough.

The flushing fluid is preferably introduced into the bearing gap by means of a diffuser which projects into the bearing gap and is preferably designed as the end of the flushing fluid supply line. The diffuser can be designed as a hollow cylinder and cover the entire circumference of the rotatable/rotating tube res encompass, so that on the one hand an introduction of the flushing fluid distributed over the circumference is ensured and on the other hand a simple line in the form of a coupling tube, which penetrates the housing block and only contacts the diffuser locally, can be used. The diffuser can be designed, for example, as a metal foam cuff or a cuff made of a knitted or knitted wire.

The transition from the bearing gap to the annular gap is preferably formed by a transition gap in the shape of an annular disk. With this geometry, acute angles are avoided, so that the production of the individual rotary union parts is particularly easy and the individual elements are robust against damage.

Further details and advantages of the invention result from the following specific description and the drawings.

character list

• 1 eine schematische Darstellung des Herzstücks einer erfindungsgemäßen Zuführvorrichtung.

It shows:

• 1 a schematic representation of the heart of a feeding device according to the invention.

Detailed Description of Preferred Embodiments

Without restricting the generality, the invention is to be illustrated below using an exemplary embodiment from the preferred area of application of the invention, namely the area of plasma coating, in particular of cylinder running surfaces of crankcases for internal combustion engines.

1 shows in a highly schematic representation the heart of a feeding device 10 according to the invention, namely its rotary feedthrough 12. The further periphery for the construction of the feeding device 10 is shown in 1 shown only symbolically. The rotary feedthrough 12 includes a housing block 14 in which a stationary tube 16 is fixed, for example screwed. Furthermore, a rotatable tube 18 that rotates during operation is rotatably mounted in the housing block by means of the bearings 20 . The bearing gap 22 is in 1 shown clearly exaggerated.

The rotatable/rotating tube 18 is arranged coaxially to the stationary tube 16 and overlaps it axially in some areas. In particular, the rotatable/rotating tube 18 in the overlap area has a section-wise conical widening of its inner diameter, whereas the stationary tube 16 has a corresponding conical narrowing of its outer diameter in the overlap area. The result is an annular gap 24 that is conical in sections and, in the embodiment shown, also has a cylindrical section. This annular gap forms the sealing gap between the fixed tube 16 and the rotatable/rotating tube 18 and is 1 shown clearly exaggerated. In the illustrated embodiment, the annular gap merges into the previously explained bearing gap 22 between the rotatable/rotating tube 18 and the housing block 14 by means of a transition gap 26 in the form of an annular disk.

The bearing gap 22 is in gas-conducting connection via an annular diffuser 28 with a coupling tube 31 of the flushing gas supply line 30 passing through the housing block 14 . Rinsing gas supplied via the rinsing gas supply line 30 can thus, distributed by means of the diffuser 28, penetrate into the bearing gap 22 and reach the lumen of the tubes 16, 18 via the transition gap 26 and the annular gap 24. In order to prevent flushing gas, which was supplied to the bearing gap 22, from escaping via the bearings 20, a rotary seal 32 is arranged axially between the diffuser 28 and the bearings 20, which seals the bearing gap in a gas-tight manner.

The free end of the rotatable/rotating tube 18 is connected to a plasma torch head, not shown. The free end of the fixed tube 16 is connected to a working fluid supply line 34, which is only indicated symbolically.

Working fluid, in particular a carrier gas mixed with coating powder, can be supplied from a corresponding source Q1 via the working fluid supply line 34 . Purge gas can be supplied from a corresponding source Q2 via the purge gas feed line 30 . Those skilled in the art will understand that the sources Q1, Q2, in particular the working fluid source Q1, are not limited to being designed as a simple reservoir, but rather have a complex structure and can include, for example, a mixing device for different fluid components.

An essential component of the present invention is that the supply lines 30, 34 each run via a separate controller ctrl V1 or ctrl V2, which are designed as volume flow controllers for the fluid being pumped in each case. The fluid streams can thus be conveyed from the sources Q1, Q2 to the rotary feedthrough 12 in a volume-flow-controlled manner.

The fluid flow available at the outlet of the rotatable/rotating tube, and consequently at the plasma burner head, therefore corresponds to the sum of the individual fluid flow-controlled partial fluids flows and can always be precisely adapted to the desired specifications in terms of size and composition. Even signs of wear in the area of the annular gap 24 between the tubes 16, 18, which can lead to a change in pressure conditions within the rotary union, do not result in a variation in the size or composition of the fluid provided at the plasma burner head, so that the result of a strongly parameter-dependent plasma coating remains completely unaffected.

Conversely, monitoring of the manipulated variables specifically varied for volume flow control, in particular the respective pressure, can be used to detect irregularities, in particular wear, in the individual flow paths.

Of course, the embodiments discussed in the specific description and shown in the figures only represent illustrative exemplary embodiments of the present invention. In the light of the present disclosure, a wide range of possible variations is available to those skilled in the art. In particular, the invention is not limited to application in the field of plasma coating, i. H. for feeding plasma burners, is still limited to the use of gaseous or gaseous working and/or rinsing fluids.

Reference List

10

feeding device

12

rotary joint

14

housing block

16

fixed pipe

18

rotatable/rotating tube

20

warehouse

22

bearing gap

24

annular gap

26

transition gap

28

diffuser

30

flushing fluid supply line

31

Coupling tube from 30

32

rotary seal

34

working fluid supply line

Q1

working fluid source

Q2

flushing fluid source

ctrlV1

volumetric flow controller

ctrlV2

volumetric flow controller

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• DD 236972 A1 [0003]
• DE 102016112470 A1 [0005]

Claims (15)

Method for operating a supply device (10) for supplying a working fluid and a flushing fluid from their respective source (Q1, Q1) to a common destination, comprising a rotary union (12) in which the working fluid flows from a fixed pipe (16) into a coaxial and a tube (18) rotating about the common axial direction is fed in, the stationary tube (16) tapering conically towards its outlet protruding into the rotating tube (18) which correspondingly widens conically towards its inlet and a radially between the tubes ( 16, 18) existing annular gap (24) is charged with the flushing gas, characterized in that the working fluid and the flushing fluid are supplied individually with volume flow control. procedure after claim 1 , characterized in that the volume flow control uses the pressure in the respective supply line (30, 34) between the respective source (Q1, Q2) and the rotary leadthrough (12) as a manipulated variable. Method according to one of the preceding claims, characterized in that a wear alarm is output in the event that after the adjustment of specified volume flow values through the supply lines (30, 34) one of the associated manipulated variable values deviates from a specified reference value by more than a specified tolerance. Procedure according to one of Claims 1 until 3 , characterized in that the working fluid is a carrier gas mixed with a powder. procedure after claim 4 , characterized in that the carrier gas is chemically identical to the flushing fluid consisting of a flushing gas. Method according to one of the preceding claims, characterized in that the rotating tube (18) is part of a burner head of a plasma burner or is connected to one. procedure after claim 6 , characterized in that the plasma torch is used for the plasma coating of cylinder running surfaces in a crankcase for an internal combustion engine. Supply device (10) for supplying a working fluid and a flushing fluid from their respective source (Q1, Q2) to a common destination, comprising a rotary union (12) with - a fixed pipe (16) which is connected on the input side to a working fluid source ( Q1) connectable working fluid supply line (34) and tapers conically towards its outlet, and - a tube (18) coaxial with the stationary tube (16) and rotatable about the common axial direction, which correspondingly conical towards its inlet widened and into which the fixed tube (16) protrudes, with an annular gap (24) existing radially between the tubes (16, 18) being conical at least in sections and connected to a flushing fluid supply line (30) which can be connected to the flushing fluid source (Q2). is characterized in that the two supply lines (30, 34) are each fitted with a volume flow regulator (ctrl V1, ctrl V2) which is set up to release material during operation to regulate flows through the supply lines (30, 34) individually and with the respective volume flow as the controlled variable. feeding device claim 8 , characterized in that the volume flow controllers (ctrl V1, ctrl V2) are set up to carry out the control with the pressure in the respective supply line (30, 34) as the correcting variable. Feeding device according to one of Claims 8 until 9 , characterized in that the rotatable tube (18) is mounted in a housing block (14), in which the stationary tube (16) is fixed, with a bearing gap (22) merging into the annular gap (24) and the flushing fluid supply line ( 30) penetrates the housing block up to this bearing gap (22). feeding device claim 10 , characterized in that the end of the flushing fluid supply line (30) is designed as a diffuser (28) projecting into the bearing gap (22). Feeding device according to one of Claims 10 until 11 , characterized in that the flushing fluid supply line (30) ends at a feed point which is located axially between the transition from the bearing gap (22) to the annular gap (24) on the one hand and a rotary seal (32) with which the rotatable tube (18) is counteracted the housing block (14) is sealed, on the other hand. Feeding device according to one of Claims 10 until 12 , characterized in that the transition from the bearing gap (22) to the annular gap (24) is formed by an annular disc-shaped transition gap (26). Feeding device according to one of Claims 8 until 13 , characterized in that the rotatable tube (18) is part of a burner head fes of or connected to a plasma torch. Feeding device according to one of Claims 8 until 13 , characterized in that the rotatable tube (18) is part of a laser coating head or connected to such.

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