DE3209378A1 - Venturi tube with variable cross-section - Google Patents

Abstract

The subject of the invention is a venturi tube (1) for controlling flows by varying its narrowest cross-section (10). The funnel comprises individual plates (12) which, when the cross-section is varied, slide over one another like scales as on a photographic diaphragm. The plates are swivel-mounted in the base plane (14) of the outlet funnel. In order to prevent secondary flows, the joints (59) between the plates must be sufficiently tight. This is achieved by means of a certain geometric shape of the large-surface joint walls (63/64). On the carburettor, with a venturi tube of this type a high degree of atomisation can be achieved over the entire output range and, with simultaneous control of the fuel feed (141), a constant mixing ratio, and thereby greater economy and cleaner exhaust gas. Throttle valve and compensating nozzles are not necessary. <IMAGE>

Description

State of the art.

The regulation of flows is generally done by a throttle valve, Gate valve or valve. The throttle valve in particular has the disadvantage that on its Rear side disturbing eddies can arise. Also occur in the carburetor with rigid Air funnel on the fuel nozzle at different speeds different air speeds on and thus (in quadratic relation to it) so different suppressions that the mixture becomes too lean at idle and too rich at full load. To compensate for this, additional correspondence facilities are required, but not always all of them Situations. Above all, step-free regulation is difficult to reach.

There is a version in which a piston or an Alembrane, through the differences between back pressure and flow pressure, a throttle slide and at the same time a conical nozzle needle moves, which in a The nozzle releases the required ring cross-section for the fuel flow. At this Execution, the slide changes the throttle cross-section up to the flow unfavorable Slot at no load position. A concentric arrangement of fuel nozzles is not possible here.

Concept of the invention The invention relates to an air funnel (1; 11) whose throttle point, if the cone characteristic remains, is enlarged or narrowed can be. The flow is restricted, but not disturbed. With the carburetor this has the advantage that in the, concentrically located at the narrowest point (10), Fuel nozzle (8), a constant air speed (resp. a constant negative pressure) is achieved. When changing the throttle cross-section (10) can simultaneously, by means of a longitudinally movable nozzle needle (9), the fuel nozzle cross-section can be changed so that the mixing ratio is constant at every load position remain.

There is a similar inventive idea in the constriction function Execution in patent no. 2263060 is based. In this case, a 1 is made from a piece of sheet metal manufacturable, double-conical clamping sleeve by longitudinal pressure of the inner cross-section narrowed like a waist. This is possible because the longitudinal slats are similar like an iris diaphragm in a camera, slide over each other. This simple sleeve is only used for fastening and contacting coaxial cables of different diameters. It is plastically deformed in the process and is not something that is constantly changing Suitable for air funnels.

Description: Fig. 1 shows the variable air funnel (i), such as it is built into a carburetor. It is one, in vertical section shown, oblique flow gasifier, in which the air according to the arrows of flows in at the top (2) and flows out horizontally (3). For the sake of simplicity, the Fuel supply drawn by means of an overflow control (4) known per se, whereby the constantly (at 5) inflowing fuel through a vertical pipe (6) again flows, the upper edge (7) of which determines the height of the level. The fuel nozzle (8th) is changed in cross-section by a nozzle needle (9) that can be moved in the longitudinal direction. Experience has shown that the most favorable point of the nozzle outlet (8) is shortly after narrowest cross section (10) of the air funnel (1; 11).

The air funnel (1; ii) is made up of several, one on top of the other, Lamellae (12) formed. These are pivotably mounted on the axes (13), which lie in the base plane (14) of the discharge funnel (1). In the enlarged section VII, the storage is again clear with the pivot point (13) in the plane (14) shown.

A spring (i5) keeps the bearing free of play and pushes at the same time the lamella (12) in the smallest load position, i.e. the narrowest cross-section (at 10). The speaking power is generated during operation by the air forces (dynamic pressure in the longitudinal direction and negative pressure towards the central axis) supported in the same direction.

The spring can be used as a compression, tension, torsion or bending spring (the latter also as a leaf spring), depending on how space is available.

By moving the lever (16) the slats (12) are moved outwards pivoted so that the air funnel expands at the throttle cross-section (10), like is shown in FIG. The lamellar parts forming the inlet funnel (11) (17) disappear behind the housing cover (18). At the same time, through a transmission system (not shown here) the nozzle needle (9) in the direction of the arrow (19) withdrawn, whereby the annular nozzle opening (8) is enlarged. Around To ensure the same mixing ratio for all positions, it is beneficial to when the tip of the nozzle needle (9) is somewhat convex. The one behind the Back pressure (20) which forms lamellae pushes the lamellae in the direction of the idle position. It is fed through the gap (21), which is directed against the air flow. It Only clean air gets in here, as the concentrically located mixture cone (22) has not yet spread to the wall at this point.

In Fig. 3, the section I - I (from Fig. 1) is shown. He shows i.e. the face of the inlet funnel <11) in the position of the lowest load.

Fig. 4 shows the section V - V (from Fig. 2) in the full load position, that is with maximum air cross-section (23).

Fig. 5 illustrates the adjustment mechanism in section II-II (from Fig. 1) so with the narrowest cross section (24). The lamellae (25) are close together. The outer edge of each lamella is provided with a nose (26) which is in a Groove (27) of the adjusting ring (28) engages. By the action of the spring (ins) lies they play one-sided without play. The adjusting lever (16) belongs to the adjusting ring is operated by the accelerator pedal. From Fig. 6, which corresponds to the section VI - VI (in Fig. 2), you can see how to adjust the lever (16) by the angle (29) the adjusting ring (28) rotates by the same angle (29), and the Groove (27) moves the nose (26) from the lamella (25) into the outer position. the inner contact edge (30) of the lamella migrates in the radial direction <31) away from the center (32) without the gap (33) between the individual Slats changed significantly. In the opposite direction of movement there would be one Theoretically, cross-section reduction down to zero is possible.

If the movement (31) were perpendicular to the lamella plane (34), so the air gap (33) would enlarge on the way to the outside or in the On the way inwards, decrease to the point of collision and no more movement allow.

The useful movement of the edge (30) is in the radial direction (31), i.e. from or to the center point, that is, at an angle a (35) to the perpendicular Move. This angle 0 <(35) comprises half a division. In the representation 8 slats are drawn. The pitch angle from slat to slat 360 ° 360 ° is 8 or n, if "n" is the number of lamellas. Has half the division accordingly an angle (35) of 360 ° 180 ° α = 2n = n. To the required direction of movement (31) the pivot axis (56) must be at right angles, that is, the Angle (37) between axis (36) and slat plane (34) 1800 must also be the size C ñ ~~ have, since the corresponding legs are perpendicular to each other.

However, the air gap (33) between the lamellas widens at this angle O (when the cross-section is enlarged by a few tenths of a millimeter. That is - relative to the growing total cross-section - meaningless, but canal largely avoided by increasing the angle CX slightly by the amount "z" will. So it is α = (180 + z) ° n where the addition æt 'from case to case is to be determined.

Fig. 7 shows the lamella pack with base plate (38) on which the lamellae are stored, seen from the inlet side, according to section I - I (in Fig. 1), but without the housing and adjusting ring. In the upper part of the figure are three lamellas (39) completely drawn. Then two slats follow to the right of it (40) in section II - II (as in the functional drawing in FIG. 6). Below is c one lamella (4i) in section III - III, and in the lower area there are two Lamellae completely omitted, so that only the base plate (38) with the bearing edges (42) (see also section IV - IV in Fig. 1) can be seen, as well as the guide grooves (43), which prevent the slats from shifting sideways. As you can see it went the axes (36), identical to the bearing edges, at the angles already mentioned «To the lamella planes and intersect in their extension at an intersection (44), which is approximately behind the center of the visible lamella surface (45), as can be seen in the upper lamellae.

In Fig. 8 is a single lamella in four views and a section drawn. The part of the lamella (46) which forms the inlet funnel has two spherically curved surfaces (-47 and 48), their spherical centers (44 and 49) at the same time the points of intersection (44 and 49 from FIG. 7) of the pivot axes (36) are. The respectively exposed edge (50) of the lamellar part (46) lies in the direction of movement, so at right angles to the pivot axis (36). In the middle of the bearing edge (5i) is located a web (52) which comes to rest in the guide groove (43 in FIG. 7).

The spring (15) already mentioned in Fig. 1 is drawn in again, with their support (53) and their direction of force (54).

The axle bearing can be done in a variety of ways. In Fig. 9 is a journal bearing (55) is shown as a further example.

In Fig. 10, a six-part disk pack is in the full load position shown in perspective, for clarification with the bearing journals mentioned in FIG (55). The two front slats have been removed so that the one shown above Lamella (56) the Wa I dfläche of the sealing gap (57) over its entire length u see is.

In order to keep undesired secondary currents as small as possible, the gaps between the slats on the one hand and the slats and the housing on the other be very tight and very deep.

In Fig. 11 the plate pack is cut just in front of the base plane, in which the pivot axes (55) lie. In Fig. 12 only the inlet side is in the middle load position to see, with the lamellar parts (58) behind them, drawn in dashed lines of the discharge funnel. It can be seen in both images, like the enlarged one Depth of the gaps (59) is achieved by protruding edges (60 or 61). By the edge (60), which is protruding on the inside and has a rounded shape, is achieved at the same time that the exit funnel despite its low number of lamellas is shaped to an approximate circular cone towards the outlet end.

This approximate circular shape extends at a low load position all over the cone.

Because when the slats are inclined, their edge angles are mutually different change, the walls of the columns (59) must be in full load position, as drawn in Fig. 11, gape outwards under a iiicl (62) so that they are in the idle position parallel lie.

Fig. 13 shows two complete lamellas 1 seen from the front side, in throttle position; Fig. I4 shows it in full load position. You can see how Slide the lamellar walls (67 and 64) of the inlet funnel over one another. the Edge (65; strokes over the surface (64) during its adjustment path the possibility of even the finest gap differences through appropriate profiling to compensate for the surface (64).

FIG. 15 shows the two lamellas from their rear side, that is to say from the outside seen. The dome-shaped ones opposite one another in the air gaps (66) Wall surfaces between the slats (67 and 68) on the one hand and between the slats (67) and the housing (70) (with spherical cap 69) on the other hand, have their spherical centers lie exactly in the intersection points (44 and 49) of the pivot axes (36) and are thus Part of both intersecting axes. As a result, the gap width remains with everyone The position of the lamellas is the same because the ball rotates around its central axis the periphery of the sphere remains immovable. The gap can therefore be kept very narrow will.

Fig. I6 shows a carburetor design in which the adjustment of the lamellas is not carried out by a rotatable ring (28), but by a Plate (71) which is moved in the longitudinal direction (72). To simplify it is in the horizontal section only one lamella (73) is shown. It is stored in the recesses (74) one Plate (75) (see cross section) which is attached to the housing (77) by means of screws (76) is. Here, too, a spring (78) compensates for play and returns it to the no-load position.

The adjustment plate (71) is attached to a bracket via guide rods (79) (80) moved out. With this movement (72) is once the lamella (73) over their Lever arm <8i) moved towards full load and at the same time the nozzle needle (82) by means of Federdruc1.c (83) in the corresponding open position.

The mixture can be changed to "lean" or "rich" via a 1 adjusting screw (85) secured with nut (84). The mixture change but can also be done during operation by means of a lever (86) if the The thread of the adjusting screw is correspondingly steep and its backup by the Nut (87) against the lever (ore 6) is guaranteed.

The lamellas, which in the versions shown so far are made of cast, pressure or pressed metal are made, can also be stamped and embossed from sheet metal. Sheet metal parts are generally cheaper. However, if the sharp edges are in the If the discharge funnel is a nuisance, a bevel is necessary.

This bevel is not necessary if you only have four slats (88) is used as shown in Figs. 17 and 18, but using the square Cross-section must be accepted. The carburetor could, for example, be inserted directly into the already square one Intake the intake duct (89) of a two-stroke cylinder (90). The nozzle tube (91) should also have a square shape at its end.

In the horizontal section VIII - VIII, that is to say in FIG. 17, there is a different one Variant of the lamella bearing shown. The storage (92) of the lamella (88) is housed in the same housing part (93) on which the cover (94) is located, which is separated from the lamella (88) by a narrow air slot (95). the The return spring (95) must be made strong, as it is directed against the dynamic pressure is and is not supported by this, as in the previously shown construction.

Fig. 18 shows only the central part. It is in view IX at the top left - IX (Fig. 17), and the lamellas (97) according to X - X are shown at the bottom right cut. This means that the bearing edges (98) are visible at the bottom right of the housing and the groove (99) in which the raised sheet metal web (100) of the lamella is guided to prevent it from shifting sideways. Otherwise the function is the same as in Fig. 16.

In Fig. 19, the lamella (88) is in three views and a section shown with the adjustment lever (101) of the bearing edge (102), the Federaufiage (103) and the guide tab (10, Fig. 20 also shows the associated Blank before the bending process The exhaust gas law requires a Exact mixture composition in the idling position 'around the CO content so small as possible to keep. This means that there may still be a throttle valve in kind of the choke is required to a parallel idle system to be kept away from all unpredictable leaks, especially at the funnel outlet.

One possibility of bypassing this shutter is shown in FIG. 21 Drawn in 2 sectional views. It's a variation that has only three lamellae (104) for simplification. However, it changes in the process the cross-section at the narrowest point (105) when expanding from a circular one (106) into an approximately triangular shape (107). A larger number of lamellas brings approximation to the usual circular shape, however, requires greater accuracy. Another simplification is that the lamella pack is in the air filter housing (108) is housed. It eliminates the case and the air gap between Lamellas and housing. There is only the base plate (109) available on the also the float housing (not shown here) with the fuel nozzle (mio) mounted will. The function is similar to that shown in FIG. About two externally operated An adjusting ring (112) is raised, which is pressed against the lever (113) the lamella (104) presses and thus the lamella mounted in the pivot axis (114) moved into the full load position (115). The nozzle needle (116) is (to save space) horizontally movable and is activated by the two rams via a fork lever (117) (111) involved. The fork lever is rotated by 90 ° and therefore with a shortened Horizontal lever arm (imid) drawn. The dynamic pressure pushes the lamellas (10l-g) inwards and towards the base plate (109). A lash adjuster spring (119) acts in its direction of force (120) im same sense. the The other arrows shown show the direction of movement during the adjustment process after full load.

The special feature of this design is that the pivot axes (114) of the lamellas (104) are not located outside the air funnel (121), but rather are shifted so far inwards that their intersection points (122) are just within of the air funnel (121). Each lamella has an "outer" bearing (123) - as Edge or spherical -which is supported in the pan (124) of the base plate, and a ttinnerest 'bearing (125) which is spherical and located in the Supports the interior of the neighboring lamella (126).

The ball point of intersection lies at the point of intersection (12g) of the pivot axes.

This arrangement creates a closed inner cone envelope, which is circular in the idle position and fixed to the centrally located one The fuel nozzle tube (110). At the exit end is just a very narrow and deep one Air gap (122) between the lamellas and the conical extension (128) of the intake duct (129). This limits the secondary air flow to a minimum.

There are also the longitudinal butt joints (130) between the slats split narrow and deep air. This increased tightness is mainly due to idling available and only required there. When adjusting to full load, they roll the inner circumferential surfaces (131) of the outlet cone on the curved outer surfaces (13g) of the cone attachment (128). The flat piece of the lamella already mentioned in FIG. 6 (133) is also at the already mentioned angle (134) to the pivot axis (114).

By shifting the pivot axes inwards, the inlet funnel becomes to the rosette (155) (in this case hexagonal). The rosette parts of the As already mentioned, lamellae are interconnected by spherical cap surfaces sealed against each other. But this seal is of minor importance. The rosette is only used for calming down the air inflow. One The lamellas are only tight from the nozzle tube (110) to the cone attachment (128) necessary. A tight contact of the lamellas on the nozzle pipe is achieved by that in the idle position between the tappet (111) and adjusting ring (112) there is enough play (136) is left. There is also play between the tappet and the horizontal lever (118) (137) left so that the nozzle needle to be lifted by means of the vertical lever arm (138) (116) by the pressure of the spring <139) with its shoulder (1ls0) the inlet of the Fuel (141) closes. If the play (137) between the tappet and lever is smaller is than the play (136) between the plunger and the adjusting ring1 when accelerating the Fuel nozzle opened earlier than the vent, causing temporary emaciation is avoided when accelerating.

Due to the shape of the nozzle needle tip (142) and the readjustment by means of an adjusting nut (144) secured by a spring (143) the mixing ratio remain the same in all positions. This will save fuel as well a cleaner exhaust gas composition is also achieved.

The mixture of idling can be fixed and variable beyond the usual Nozzles are formed and guided past the nozzle needle (in6) to the suction shaft.

Claims (9)

Claims: 1.) / Air funnel with variable cross-section, especially for carburetors, in which the cross-section change, while maintaining the funnel characteristic, takes place in such a way that, in the longitudinal direction, Slide the lamellas (12; 25) over one another like scales like a photo diaphragm, thereby characterized in that each lamella is mounted pivotably about an axis (13; 36), which is located in the base plane (14) of the discharge funnel (1) and in 180 at an angle (37) of von80 = n + Z) to the lamella plane (34), where "n" is the number of lamellas and 'z "is a, depending on the respective construction Surcharge. 2.) air funnel according to claim 1, characterized in that each Lamella (12; 17) at the same time the outer surface of the outlet funnel (i) and inlet funnel (11) forms. 3.) Air funnel according to claim i and 2, characterized in that on the inlet funnel the air gaps (66) between the lamellas (63 and 64) on the one hand and the lamellae (63; 64) and the housing (70) on the other hand, due to their curved Shape, can be very narrow in any position, the walls of these columns being spherical caps (67; 68; 69), the centers of which are at the intersections (44; 49) of the associated Pivot axes (36) lie. 4.) air funnel according to claim 1 to 3, characterized in that the lamellas at their joints (59) by a protruding edge (60 or 61) are widened in such a way that the air gaps between them are enlarged by their Deep, forming a great resistance to undesirable side currents. 5.) air funnel according to claim 4, characterized in that the protruding edge (60) is rounded on the inside, whereby, despite the multi-faceted Type, a. at least in the throttle position, approximately circular discharge cone arises. 6.) air funnel according to claim 1 to 5, characterized in that it can also be used for media other than air. 7.) air funnel according to claim 1 to 6, characterized in that the lamella through spring force (15) play-free in its axis and also in its Starting position (with carburettor: throttle position) is held. 8.) air funnel according to claim 1 to 7, characterized in that when used as a mixing chamber, e.g. with a carburetor, an adjustable nozzle (8) for the fuel or the like. Is also changed in the corresponding ratio. 9.) air funnel according to claim 1 to 8, characterized in that the pivot axes (114) of the slats (i04) are within the area formed by them Air funnel (121) cut, and the storage (123, 125) of these axes once takes place outside on the housing base plate and once inside on the neighboring lamella, whereby a better seal at the funnel outlet is possible.