EP1244867B1 - Flow switch - Google Patents

Description

The invention relates to a flow switch according to the Preamble of claim 1.

The legal requirements for noise reduction and reduction of pollutant levels in the exhaust gases of internal combustion engines lead to increasingly complex exhaust systems. It arise exhaust systems with ever greater flow resistance. The increasing energy expenditure must be provided by the engine become. At the same time, the costs for these facilities. These are the demands of vehicle manufacturers after reduction of the cost, the weight, the Fuel consumption and the installation space compared.

To solve this conflict of objectives are increasingly funds for Control and steering of the exhaust gases through - depending on the operating point of the engine - different treatment devices used. The vast majority of technical solutions for material flow switching in exhaust systems concerns mechanical flaps and valves (cf. e.g. for mufflers: MTZ Motortechnische Zeitschrift 53 (1992) Issue 7/8; DE 19729666; EP 0902171; US 5821474; US 5801343; US 5744762; US 5739483; in connection with exhaust gas heat exchangers: DE 19817391 A1; DE 19715939 C1; DE 19817340 A1; for exhaust gas recirculation: DE 19637078 A1).

The advantage of these solutions is that the geometric Dimensions of the switching elements in a reasonable Ratio are related to the dimensions of the incoming and outgoing Piping and the entire plant.

However occur with use of such mechanical Switching elements and flaps following problems: The closer the switching element is arranged on the internal combustion engine to the higher are the temperatures to which the switching element is exposed. Metallic spring materials achieve 700 ° C its limit of use. Above these temperatures ceramic springs can be used. In appropriate Way, e.g. also higher quality bearing materials be used in ceramic. The materials to be used However, with increasing temperature resistance more and more expensive. For the rest, mechanical skill issues can arise; because exhaust systems are subject at the same time high mechanical requirements. It kick Vibrations with load up to 50 times the acceleration of gravity on, in addition, temperature change - in particular Thermal shock stresses.

• Zu große Spalte verursachen durch die radiale Bewegung zwischen Welle und Lager Klappergeräusche.
  Große Spalte setzen auch die Lebensdauer der Bauelemente herab.
• Undichtigkeiten infolge großer Lagerspalte oder zwischen Verschlußorgan und Gehäuse erzeugen Pfeifgeräusche.
• Zu kleine Spalte im Lager führen infolge Verschmutzung oder unterschiedlicher Wärmeausdehnung von Welle und Lager zu Verklemmungen, die die Öffnungs- und Schließbewegungen des Verschlußorgans behindern.

Incidentally, mechanical components, consisting of shaft and bearing, always require a defined clearance, which is generally greater in cold plant than in the warm operating condition. These columns cause the following problems:

• Too large gaps cause rattling noises due to the radial movement between shaft and bearing.
  Large gaps also reduce the life of the components.
• Leaks due to large bearing gaps or between closure member and housing generate whistling noises.
• Too small gaps in the bearing lead due to contamination or differential thermal expansion of shaft and bearing to jamming, which hinder the opening and closing movements of the closure member.

To solve these problems, it requires relatively more complex Constructions.

The above, with mechanical switching elements associated problems occur to a significant extent when using fluidic switching elements as a flow actuator not up. However arise, one wants the from A.W. Right, Fluidics, Springer-Verlag Berlin, Heidelberg, New York 1976, 244 p., Adhesive beam elements measured transferred to scale to exhaust systems, Switching elements that are much larger in size are as the actual system components to be switched or Treatment devices. So these elements are in the illustrated form for the intended use in exhaust systems unusable by motor vehicles.

DE 19709432 A1 and DE 19729563 A1 disclose in contrast, the use of generic Flow switch in connection with exhaust systems for motor vehicles. In each case, the exhaust gas flow is dependent on the operating point of the internal combustion engine different exhaust treatment devices be fed, with a active, externally controlled as well as passive, autonomous switching the switching element is described.

An important problem with such flow switches is the stability of the respective switching state. to Maintaining stable switching states becomes regular requires a circulation flow, which in the known technical solutions by a concave impact surface, DE 19729563, or a recess in the wedge between the two Outputs, A.W. Right, p. 92, is generated. These Recess or concave annular surface is opposite to the arranged narrowest flow cross-section. In the narrowest Flow cross-section occur but the largest flow rates on. These high flow rates lead in conjunction with the described Devices and their arrangement to large flow losses in the control room. They cause large back pressures in the Exhaust system. High back pressures are not desirable because they have a performance-reducing effect. Besides, these are Solutions not very space saving.

Also TESAR V. "Large Scale Fluidic Valves for the Flow control "measure - control - regulate, Vol. 26 (1983) 4 pp. 189 ff as well as J. Loll and K. Thomas - Control - regulate, Bd. 26 (1983) 4 p. 186 ff describe Flow switch, which is essentially the Coanda effect as a wall effect and use the vortex effect. These too Switching elements are available with up to 1000 mm length comparable pipe dimensions, for use in car exhaust systems too large.

The Coanda effect as adhesive flow along curved walls is used in numerous other patents: US 5435489; US 5577294; US 5957413; US 5438429; US 5658141.

Against the background of the disadvantages set out above The prior art is the subject of the present invention the task is based, in particular for exhaust systems of motor vehicles suitable flow switch develop, the no outward guided waves operated closure elements and thus no sealed Bearings for such waves requires only comparatively low flow losses produced, if possible precise switching point enables bistable switching states, caused a small mechanical manufacturing effort and acceptable geometric dimensions compared to Entire facility allows. Especially preferred is the Flow switch either as externally controlled Device as well as autonomous, out of itself acting switching element can be executed.

According to the invention this object is achieved by a Flow switch with the features of claim 1. The Flow switch according to the present invention comprises thus an inflow channel, a Coanda tulip, at least two outlet channels and a displacement body. Of the Displacer is in the field of Coanda tulip arranged. The displacer has an inflow surface on, which is downstream of a jacket in the flow direction; According to the invention, the position is at least the inflow area changeable in the flow direction.

The inventively provided Lageveränderbarkeit the Flow surface of the displacer in the flow direction favors in conjunction with the other features of the switching element according to the invention the reproducibility of Switching point, i. she strongly supports that Switching element as precisely as possible at a certain, predetermined switching point of a first switching state switches a second switching state. this applies regardless of whether the flow switch as passive Switching element or as active, externally controlled Switching element (s.u.) Is executed.

A first preferred embodiment of the invention is characterized This is characterized by the fact that only the Anströmplatte with the Flow surface is variable in position, whereas the remaining components of the displacer stationary are arranged; This results in a special low construction costs. This construction is not absolutely; Rather, for example, together with the Anströmplatte also a part of the jacket of the displacer or the entire jacket in the flow direction be variable in position.

As for the geometric shape of the inflow, so exists here a design width. So the inflow area even, more or less convex or more or less concave. Especially It should be emphasized that the invention Flow switch with level design of the inflow surface sufficiently good switching results for most applications supplies. In this way, flow switch can be particularly inexpensive according to the present invention produce.

The latter applies even more if the jacket is cylindrical is executed. In this construction results in the rest a clearly defined tear-off edge in the area of the transition from the inflow surface to the lateral surface, which in turn is favorable in terms of switching behavior.

The inflow channel can be designed as a simple cylindrical tube to which the Coanda tulip immediately adjoins. However, it is particularly preferred as cylindrical Pipe with an additional conical extension followed by a preferably cylindrical channel section educated. The Coanda tulip closes at this Embodiment of the invention advantageously to those cylindrical channel section on.

The jacket of the displacer is preferably in essentially cylindrical. At specific Switching tasks, however, the jacket can also special forms have, for example, by being conical or barrel-like is trained. The displacer is preferred dimensioned and arranged so that the inflow surface inside the Coanda Tulip or in an upstream arranged for this cylindrical channel section is. The jacket is preferably in the extension area the Coanda tulip; he extends in this case completely or partially within the Coanda tulip. The Outlet passages are preferably arranged concentrically and provided with catching spaces in their flow cross-section larger than the actual outlet channels are formed. The outer outlet channel closes expediently immediately to the Coanda tulip.

Depending on the switching task, the displacement body is or at least partially formed as a hollow body. Of the simplest and thus most cost-effective construction is a level Inflow area, which in the flow direction is a cylindrical Pipe section is arranged downstream as a jacket. For the Fulfillment of the simplest switching tasks is not even a downstream termination required.

• Die Anströmfläche kann eben, konkav oder konvex geformt sein.
• Der Durchmesser der Anströmfläche kann wahlweise größer, kleiner oder gleich dem äußeren Umfang des Mantels gewählt werden.
• Der äußere Umfang der Anströmfläche kann eine Fase und/oder eine Kante oder einen Grenzschichtzaun aufweisen, scharfkantig oder abgerundet sein. Die Anordnung von Unterbrechungen, Zacken oder beliebige Unregelmäßigkeiten sind möglich.
• Der Mantel kann als Zylinder, Kegel, faßartig oder wellig ausgebildet sein.
• Der stromabwärts gerichtete Abschluß des Verdrängerkörpers kann entfallen (s.o.), oder als im wesentlichen ebene Scheibe, als Halbkugel oder als sonstiges geeignetes Strömungsprofil ausgebildet sein.
• Bei bestimmten geometrischen Anforderungen an den Einbauraum kann das System aus Coanda-Tulpe, Verdrängerkörper, Zuströmkanal und Auslaßkanälen von der koaxialen, axialsymmetrischen Form abweichen. In diesem Sinne kommt beispielsweise zur besonders flachen Ausführung des Schaltelements eine zweidimensionale Gestaltung mit einer ebenen Umströmung des Verdrängungskörpers in Betracht.

However, if you want to set the switching point even under unfavorable conditions to a well-defined mass flow, the following additional measures are applicable according to the invention:

• The inflow surface may be flat, concave or convex.
• The diameter of the inflow surface can be chosen to be larger, smaller or equal to the outer circumference of the shell.
• The outer circumference of the inflow surface may have a chamfer and / or an edge or a boundary layer fence, be sharp-edged or rounded. The arrangement of interruptions, spikes or any irregularities are possible.
• The jacket can be designed as a cylinder, cone, barrel-like or wavy.
• The downstream completion of the displacer may be omitted (see above), or be formed as a substantially flat disc, as a hemisphere or other suitable flow profile.
• For certain geometric requirements on the installation space, the system of Coanda tulip, displacer, inflow and outlet channels may differ from the coaxial, axially symmetric shape. In this sense, for example, the particularly flat design of the switching element is a two-dimensional design with a flat flow around the displacement body into consideration.

The operation of the invention is as follows:

The handling of the solution according to the invention can done two ways: either works the flow switch out of oneself, passively, autonomously, or the Switching is done externally by an active, manual and / or control engineering initiated arbitrarily.

Is desired in a process that, for example, below a predetermined value for the gas velocity, the Mass flow or the volume flow through the flow Pipe 1 and passed above the switching point in tube 2 is, then the autonomous shift task is advantageous.

Depending on the specification of the switching point of the invention Displacer in a defined position within the Coanda tulip arranged. The location depends on the concrete process parameters and the flow guidance in the System off. Experiments have shown that depending on the process a definable switching window exists, the by usually two axial position positions of the flat inflow surface inside the Coanda tulip and / or the inflow pipe is limited and by the additional described above Measures can be postponed. The limits show up by unstable flow conditions, which are by a mutual turning of the flow in the represent one or the other switching direction. Outside These limits are not switched.

The above-explained limits become to switch used. Within the two boundary layers, the fluid flows along the Coanda tulip radially outward. Except for Borders, the flow is axially aligned. By the Inflow channel flows the undivided exhaust gas flow to the Flow switch too. In a first switching position For example, if the inflow surface is in the plane, from the approach of the Coanda tulip to the cylindrical one Channel section is formed. The flow splits, Forms a ring flow, the inside immediately at the Outer edge of Anströmplatte detaches, in the outer Area at the Coanda tulip and in the outer Outlet channel is derived. Downstream of the displacer creates a vortex zone extending from the wake to extends into the inner outlet channel and the inner Outlet channel closes fluidically. In a second switching position is the inflow surface upstream of the position of the first shift position, and although in the cylindrical channel section of the inflow channel. The Flow forms immediately behind the outer edge of the Anströmplatte on the circumference of the lateral surface a separation vortices, but the current is forced to turn back on to apply the lateral surface of the displacer. The Flow aligns axially and now dissolves in the outer Area from the Coanda tulip. The flow is now from the Displacer guided so that they are also in the wake the displacement body applies and through the inner outlet channel is derived. In the wake of the Coanda tulip forms a circumferential ring vortex, the outer outlet channel fluidically closes.

The circuit of the flow is inventively initiated the following operations:

The autonomous solutions:

A first autonomous solution uses equilibrium between the force of acting on the inflow surface Dynamic pressure and one on the movable Anströmplatte acting spring, preferably inside the Displacer is arranged.

At low exhaust gas mass flow is for example the flat inflow surface in a first switching position within the cylindrical channel section. The flow attaches to the lateral surface of the displacer and is due to the inventive shape of the displacement supplied to the internal outlet channel. With rising Exhaust gas mass flow increases the back pressure on the inflow. The inflow area shifts in the direction of flow against the restoring force of the spring until the second switching point at the base of the Coanda tulip is reached. The current is no longer attached to the cylindrical outer surface of the displacer, but at the Coanda tulip and passes through the outer outlet channel. Another switching area is located inside the Coanda tulip. He is through the second one described above Border marked. The inflow is initially so arranged the flow along the Coanda tulip in the outer flow channel is derived. One increases now the mass flow, then the back pressure and the Run-on surface moves downstream over the second Boundary line. It comes to the envelope of the flow. she lays back to the displacer.

Another autonomous solution uses thermal expansion solid, liquid or gaseous medium, the for example, in the interior of the displacer for Movement of the inflow surface are arranged. Here results a temperature-dependent switching of the flow switch.

In an externally controlled solution, for example, a external pressure or vacuum sensor with the interior of the Displacer connected. Through the interaction of Back pressure, internal pressure, a possibly provided spring element and external pressure sensor can be the inflow depending on Position your wish. Also the shift of complete displacement is possible.

The advantages of the solution according to the invention are that both autonomous and externally controlled versions possible and the diverse conditions of use can be covered.

Autonomous solutions are especially for use in Semi-active mufflers of interest, if at one low exhaust gas mass flow a first flow path and at higher exhaust gas mass flow a second flow path or Both flow paths are to be preferred.

Figur 1

eine erste bevorzugte Ausführungsform eines Strömungsschalters nach der vorliegenden Erfindung in Schaltzustand 1,

Figur 2

den Strömungsschalter gemäß Fig. 1 in Schaltzustand 2 und

Figur 3

eine zweite bevorzugte Ausführungsform eines Strömungsschalters nach der vorliegenden Erfindung.

With reference to the accompanying drawings, the present invention will be explained in more detail below with reference to two embodiments. It shows

FIG. 1

a first preferred embodiment of a flow switch according to the present invention in switching state 1,

FIG. 2

the flow switch of FIG. 1 in switching state 2 and

FIG. 3

A second preferred embodiment of a flow switch according to the present invention.

Figures 1 and 2 show that as a hybrid switching element executed flow switch, consisting of a Inflow channel 1 with conical extension 2 and cylindrical channel section 3, to which the Coanda tulip 5 and an outer outlet channel 11 with trap 13th connect. The inner outlet channel 12 with trap 14th is located downstream of the displacer 6.

The displacement body 6 has a front side on a Anströmplatte 25 arranged flat inflow 7 with outer edge 15, a cylindrical shell 8, a Caster 9 and designed as a spring actuator 10, which is supported inside the displacer 6, on. The Anströmplatte 25 is in the flow direction slidably guided, by means of the central Guide rod 26. The inflow channel 1 comprises a conical Extension 2 and another cylindrical channel section Third

In Figure 1, the flat inflow surface 7 is in Area of the approach 4 of Coanda tulip 5 to the cylindrical channel section 3. In Figure 2 is the plane Inflow surface 7 due to the on the inflow acting low dynamic pressure, the one from FIG. 1 reduced mass flow results, contrary to Flow direction in the cylindrical channel section. 3 moved into it.

In a first embodiment, the switching task therein, at low mass flow rate, the exhaust gas to pass through an inner outlet channel 12. At large Mass flow should be the exhaust gas through the ring cross-section between outer outlet channel 11 and inner outlet channel 12th be derived.

The spring as adjusting device 10 is located in the Initial situation with low exhaust gas mass flow 20 in a defined bias state. The flat inflow surface 7 is in the cylindrical channel section 3rd positioned. The exhaust gas mass flow 20 is divided at the plane leading surface 7, triggers at the outer edge 15, forms a small detachment vertebra 16, but allows that the fluid again to the cylindrical surface 8th of the displacer 6 applies. On the inner surface of the Coanda tulip 5 triggers the exhaust gas mass flow 20 and forms a rotating vortex area 17, which is the flow stabilized and the inner trap 14 and the inner Outlet channel 12 leads. Increases with increasing mass flow the dynamic pressure on the flat inflow surface 7. The plane Run-on surface 7 shifts axially in the flow direction. In switching point 2, the flat inflow surface 7 is in Range of approach 4 of the Coanda tulip 5. The shape of the Flow changes and now forms according to FIG. The exhaust gas mass flow 20 no longer settles on the lateral surface 8 of the displacer 6 at. It is behind the caster 9 a large vortex area 18, which of the Edge 15 extends to the inner catching space 14 and the internal outlet channel 12 fluidically closes. On the outer circumference, the exhaust gas mass flow sets 20 at the Coanda Tulip 5 forms one stable ring flow 19, which over the outer trap 13th and the outer outlet channel 11 is derived.

Is required that in switching point 2, a part of the exhaust gas continues to flow through the inner outlet channel 12, If you extend the inner trap 14 so that a part of Ring flow 19 through the inner outlet 12th is derived.

In a further embodiment, Figure 3, is instead of the spring element 10, a bellows compensator 22nd arranged between the inflow surface 7 and lateral surface 8. Of the complete displacement body 6 forms a closed Hollow body, which is filled with a fluid. The thermal expansion of the trapped fluid adds Temperature increase to shift the flat inflow surface 7. Depending on the temperature of the exhaust gas, the size of the Back pressure on the inflow surface 7 and the spring stiffness of the corrugated pipe 22 can be so more autonomous Create switching combinations.

The variation possibilities for the change of position of the Anströmfläche 7 are no limits.

If you want to control the system externally, you connect in addition the pressure-tight closed displacement body 6 according to Figure 3 via a connecting line 21 with a external pressure-actuated actuator 23. The location of Anströmfläche 7 can be so pneumatic or hydraulic by increasing or decreasing the internal pressure change.

Claims (22)

1. A flow switch comprising an afflux channel (1), a coanda bell (5), at least two outlet channels (11 and 12) and a displacing piece (6) arranged in the region of the coanda bell (5) and comprising a flow-impinged face (7) and a shell (8),
      characterized in that
      the position of the flow-impinged face (7) can be adjusted in the direction of flow.
2. The flow switch according to claim 1,
      characterized in that
      the flow-impinged face (7) is connected with an actuating device (10).
3. The flow switch according to claim 2,
      characterized in that
      the actuating device (10) is configured as a spring element or a thermal expansion element.
4. The flow switch according to any of the claims 1 to 3,
      characterized in that
      a corrugated pipe type compensator (22) is arranged between the flow-impinged face (7) and the shell (8) in such a manner that the displacing piece (6) forms a closed, hermetically sealed hollow piece filled with a fluid (24).
5. The flow switch according to claim 4,
      characterized in that
      the closed, hermetically sealed displacing piece (6) is connected through a connecting conduit (21) with an actuating member (22) which is operated by a pressurized medium.
6. The flow switch according to any of the claims 1 to 5,
      characterized in that
      the displacing piece (6) is arranged so as to be movable.
7. The flow switch according to any of the claims 1 to 6,
      characterized in that
      the outlet channels (11, 12) are arranged concentrically to each other and are each provided with a conical or cylindrical collecting space (13, 14).
8. The flow switch according to claim 7,
      characterized in that
      the exterior collecting space (13) adjoins the coanda bell (5) with a radially outward offset.
9. The flow switch according to claim 7 or claim 8,
      characterized in that
      the inner outlet channel (12) is arranged at a distance behind and downstream of the displacing piece (6).
10. The flow switch according to any of the claims 1 to 9,
       characterized in that
       the displacing piece (6) has a ball-shaped or planar trailing portion (9) at the end which is oriented downstream.
11. The flow switch according to any of the claims 1 to 10,
       characterized in that
       the shell (8) of the displacing piece (6) is configured so as to be substantially cylindrical and is preferably arranged in the flaring portion of the coanda bell (5).
12. The flow switch according to any of the claims 1 to 11,
       characterized in that
       the displacing piece (6) is configured as a hollow piece.
13. The flow switch according to any of the claims 1 to 12,
       characterized in that
       the flow-impinged face (7) of the displacing piece (6) is configured so as to be substantially planar and is preferably arranged within the coanda bell (5).
14. The flow switch according to any of the claims 1 to 13,
       characterized in that
       the exterior rim of the flow-impinged face (7) is larger or smaller than or equal to the outer diameter of the shell (8).
15. The flow switch according to any of the claims 1 to 14,
       characterized in that
       the shell (8) is configured so as to be conical, barrel-shaped or corrugated.
16. The flow switch according to any of the claims 1 to 15,
       characterized in that
       the flow-impinged face (7) of the displacing piece (6) is configured so as to be planar, concave or convex.
17. The flow switch according to any of the claims 1 to 16,
       characterized in that
       the flow-impinged face (7) in the region of the joint (4) of the coanda bell (5) is arranged at the afflux channel (1) or a cylindrical channel section (3) of the afflux channel (1) or within the coanda bell (5).
18. The flow switch according to any of the claims 1 to 17,
       characterized in that
       the exterior rim of the flow-impinged face (7) is sharp-edged, cut-off, rounded, configured so as to have gaps or provided with a stall fence or with irregular elevations and/or depressions.
19. The flow switch according to any of the claims 1 to 18,
       characterized in that
       openings are arranged in the flow-impinged face (7) and/or in the shell (8), which connect the interior space of the displacing piece (6) with the main flow.
20. The flow switch according to claim 19,
       characterized in that
       the openings in the displacing piece (6) or in the coanda bell (5) are connected via connecting conduits with a further fluid-containing pressure source.
21. The flow switch according to claim 20,
       characterized in that
       the additional pressure source is either an upstream or downstream section of the channel profile itself or is a pressurized container or vacuum container.
22. The flow switch according to any of the claims 1 to 21,
       characterized in that
       the system comprised of coanda bell (5), displacing piece (6), afflux channel (1) and outlet channels (11, 12) is configured so as to be not concentrical.

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