EP4119782A1 - Fuel supply device and two-stroke engine having a fuel supply device - Google Patents

Abstract

A fuel supply device (20) has a base body (21) with an intake channel section (22) into which a main fuel opening (24) opens. A throttle valve (25) is provided for controlling the free flow cross section of the intake duct section (22), which is pivotably mounted about a pivot axis (45). The fuel supply device (20) has a partition section (27) which also runs at least upstream of the throttle valve (25) in the intake duct section (22) and which divides the intake duct section (22) into a mixture duct (18) into which the fuel opening (23, 24 ) supplies fuel, and shares an air duct (19). The partition section (27) has a recess (48) in which the throttle valve (25) lies at least partially in an end position (52). Upstream of the recess (48), the partition wall section (27) has a continuous mixture channel surface (41) facing the mixture channel (18), the lateral sections (54) adjoining the intake channel wall (56) and an area between the lateral sections (54) extending middle section (53). The lateral sections (54) have a tear-off edge (43) for the flow in the mixture channel (18) upstream of the throttle valve (25). The side (57) of the throttle flap (25) facing the mixture duct (18) in the end position (52) of the throttle flap (25) defines a reference plane (60) which moves the fuel supply device into a first area (71) in which the throttle flap ( 25) and divides a second region (72). The lateral sections (54) extend at least directly upstream of the recess (48) into the second region (72) of the fuel supply device.

Description

The invention relates to a fuel supply device of the type specified in the preamble of claim 1 and to a two-stroke engine with a fuel supply device.

From the DE 10 2005 003 559 A1 discloses a fuel supply device, namely a carburetor, in which the intake duct in the carburetor is divided into a mixture duct and an air duct. For this purpose, a partition section is provided in the carburetor. In order to avoid an uncontrolled leaning of the fuel/air mixture when the throttle flap is pivoted from the fully open position into a closed position, means are provided for dethrottling the mixture duct and/or for throttling the air duct. For this purpose, the dividing wall section can be slanted toward the throttle valve.

In particular, when the throttle valve is in the fully open position, fuel is to be prevented from spilling over into the air duct in such fuel supply devices, which are provided in particular for two-stroke engines working with a scavenging fluid.

The invention is based on the object of creating a fuel supply device of the generic type which is easy to produce and achieves good separation of the mixture channel and air channel in the second end position of the throttle valve.

For easy manufacture of the intake duct section and to enable a complete, defined closing of the throttle valve in the first end position, the intake duct section is usually machined in the region of the bearing points of the throttle shaft. The machining area usually extends beyond the bearing area of the throttle shaft in order to prevent the throttle valve from jamming and tilting in the areas in which the throttle valve protrudes close to the intake port wall, even if the manufacturing tolerances are unfavorable. A narrow connecting opening between the air duct and the mixture duct is formed in this area between the wall of the intake duct and the throttle valve. If the partition wall section protrudes into this area in order to close the connection opening, the partition wall section cannot be designed in one piece with the main body of the fuel supply device, since otherwise the machining of the intake port section in the area of the throttle shaft bearing is not possible as before. In the case of a separately formed partition wall section that is pushed into the base body of the fuel supply device, it must be ensured that the partition wall section projects as far as the throttle shaft and laterally up to the intake port wall, in order to enable good sealing and, on the other hand, that the movement of the throttle shaft is not impeded by the partition wall section will. This makes the production of the fuel supply device expensive.

It has now been shown that there is no need for a complex seal between the throttle shaft and the partition wall section running upstream of the throttle shaft and that good operating behavior can still be achieved if the lateral sections of the partition wall section are at least immediately upstream of the recess in which the throttle valve is in the end position lies, extend into the second region of the fuel supply device.

The two areas of the fuel supply device result when the fuel supply device is mentally divided into two parts by a plane at the reference plane. The throttle valve is arranged in the first area when it is in the end position is located. The end position of the throttle valve, in which the throttle valve lies at least partially in the recess, is the open end position of the throttle valve. In the end position, the throttle valve advantageously forms part of a partition that divides the intake channel into the mixture channel and the air channel. In the end position, the throttle valve advantageously largely frees up the flow cross section in the intake port. The throttle valve advantageously has a further, closed end position in which the throttle valve largely closes the flow cross section in the intake port.

Due to the fact that the lateral sections extend into the second area immediately upstream of the recess, the flow in the mixture channel in the area of the lateral sections is diverted away from the connecting openings formed between the partition wall section and the throttle valve. As a result, there is no need for a complex seal between the partition wall section and the throttle shaft, and a transfer of fuel into the air duct in the specified end position of the throttle valve can be largely avoided.

The middle section of the partition is hereinafter referred to as the middle section. The lateral sections of the partition are referred to below as lateral sections.

The central section and the lateral sections are sections of a continuous mixture channel surface of the partition section facing the mixture channel and are located upstream of the recess. The mixture channel area is therefore not interrupted. This allows fuel to flow freely from the center section to the side sections. The lateral sections and the central section are sections of the surface of the partition section along which the mixture can flow in the second end position of the throttle valve, ie the mixture channel surface. Upstream of the throttle valve, the lateral sections form a separation edge for the flow in the mixture channel. This directs the flow from the middle Section to the lateral sections and from there via the connection openings formed in the partition section between the throttle valve, the intake port wall and the partition section. Due to this design, the flow in the mixture channel advantageously does not flow through the connection openings into the air channel but flows past the connection openings and remains in the mixture channel. The connection openings extend between the throttle valve, the partition wall and the intake port wall. The connection openings have a substantially triangular shape, with one side of the triangle being curved.

The flow flowing in the mixture channel is guided via the throttle valve and does not impinge on the end face of the throttle valve in the lateral sections. As a result, the flow in the mixture channel can be guided well via the connection openings. Preferably, the mixture channel area in the lateral sections in the direction of flow does not decrease in relation to the reference area but runs parallel to the reference plane or increases in relation to the reference plane. As a result, mixture flowing along the mixture channel surface in the lateral sections is conducted away via the connection openings.

In a particularly preferred embodiment, the middle section lies at least partially in the first area. As a result, the flow in the mixture channel in the second end position of the throttle valve flows at least partially against the end face of the throttle valve. If the throttle valve is pivoted out of the fully open position, the proportion of the end face of the throttle valve against which the mixture in the mixture channel flows increases continuously. Due to the fact that the end face is also subjected to flow in the second end position of the throttle valve, the change in flow when the throttle valve is opened is comparatively small, so that a disruption in mixture formation due to suddenly changing pressure conditions at the fuel opening, in particular at a main fuel opening, is avoided . Mixture that flows onto the end face of the throttle valve is due to the curvature of the Front side of the throttle at least partially passed in the direction of the lateral sections and from there over the connecting openings.

Advantageously, the middle section, at least immediately upstream of the recess, is at least in one area at a distance of at least 50% of the thickness of the throttle valve, in particular at least 80% of the thickness of the throttle valve, from the reference plane. Advantageously, the central section is at a smaller distance from a partition plane of the partition immediately upstream of the cutout for the throttle valve over a length that corresponds to at least 30%, advantageously at least 50%, of the diameter of the throttle valve than the lateral sections. The length of the middle section is measured parallel to the longitudinal center axis of the intake port section.

As a result, the flow in the mixture channel can be influenced in such a way that no mixture or only very small amounts of mixture can enter the air channel via the connecting openings and at the same time disturbances in mixture formation when the throttle valve is opened from the second end position are avoided. In a particularly preferred embodiment, the central section is at a smaller distance from the plane of the partition wall over its entire length than the lateral sections. As a result, a comparatively large flow cross section can also be provided in the mixture channel. The lateral sections advantageously have an overall width of at least 5 mm, in particular at least 7 mm. The overall width of the lateral sections is the sum of the individual widths of the two lateral sections. The overall width is measured perpendicularly to the longitudinal center axis of the intake port section.

Advantageously, the lateral sections have a total width of at least 50% of the smallest width of the mixture channel surface of the partition section, in particular at least 70% of the smallest width of the mixture channel surface of the partition section.

The overall width and the smallest width are measured perpendicularly to the longitudinal center axis.

The middle section advantageously has a width which is at least 30%, advantageously at least 50%, of the smallest width of the mixture channel surface of the partition section. The width of the lateral sections and the middle section are measured perpendicularly to the longitudinal center axis and on the surface of the mixture channel.

The lateral sections preferably run at an angle to the reference plane, at least immediately upstream of the tear-off edge. The lateral sections can run inclined in a sectional plane perpendicular to the longitudinal center axis to the reference plane. Alternatively or additionally, it is preferably provided that the lateral sections run inclined in a sectional plane that contains the longitudinal center axis of the intake port section and that runs perpendicular to the pivot axis of the throttle valve, preferably rising in the direction of flow relative to the reference plane. This allows mixture in the mixture passage to be effectively guided away from the communication port. The lateral sections are designed in particular in the form of ramps.

In an advantageous embodiment, it is provided that the tear-off edge extends over the entire width of the mixture channel surface of the partition section. In an alternative advantageous design, it can be provided that the mixture channel surface merges into the bottom of the recess for the throttle valve. A transition without a tear-off edge can be provided in this area.

In an advantageous embodiment, the middle section is formed by a recess in the partition section. The depression preferably runs concavely in a sectional plane perpendicular to the longitudinal center axis of the intake port section. However, a different course of the depression can also be advantageous. In an advantageous embodiment, the bottom of the recess runs parallel to the longitudinal center axis of the intake port section. The course parallel to the longitudinal center axis of the intake port section is provided in particular in a sectional plane perpendicular to the pivot axis of the throttle valve and parallel to the longitudinal center axis of the intake port section. In particular, it can be provided that the indentation forms a section of the recess for the throttle valve.

In an advantageous embodiment variant, the lateral sections run in a radius in a section perpendicular to the longitudinal center axis of the intake port section. The radius connects to the intake port wall and is at least 2 mm, in particular at least 3 mm. Compared to known designs, the radius with which the partition wall section merges into the intake port wall is significantly increased as a result. This increased radius is already sufficient to direct the flow away from the connection openings.

In an advantageous design, the lateral sections adjoin the middle section on both sides. In an alternative advantageous design, it can be provided that further sections, which can be located in the first area or in the second area of the fuel supply device, extend between the lateral sections and the middle section.

A choke element is advantageously arranged upstream of the partition section. The choke element is preferably a choke flap. In the open position of the choke flap and the second end position of the throttle flap, the choke flap, partition wall section and throttle flap advantageously form an approximately continuous partition wall between the mixture duct and the air duct.

The partition wall section is particularly advantageously designed in one piece with the base body of the fuel supply device. As a result, an uninterrupted transition between the mixture channel surface of the partition wall section and the intake channel wall can be produced in a simple manner. The molding of the partition wall section to the body also allows for easy manufacture. Due to the increased lateral sections of the mixture channel area, a mixture can largely be avoided from the mixture channel passing through the connecting openings formed between the intake channel wall, partition wall section and throttle valve into the air channel. At the same time, a sufficiently long surface can be made available for machining the area of the intake port section in which the throttle valve is mounted. This results in the fuel supply device being easy to manufacture and also in advantageous properties during operation.

The fuel supply device is preferably used with a two-stroke engine, in particular with a two-stroke engine working with a scavenging receiver. The air duct section of the fuel supply device preferably forms part of an air duct of the two-stroke engine, which is used to supply fuel-free air for pre-storage in overflow ducts of the two-stroke engine. The mixture channel section forms part of a mixture channel of the two-stroke engine, with which the mixture is advantageously fed into the crankcase interior of the two-stroke engine.

An independent inventive idea lies in the design of the middle section of the mixture channel area.

From the DE 10 2005 003 559 A1 it is known to provide the partition wall section upstream of the throttle with a flattening. As a result, the end face of the throttle valve which is at the front in the direction of flow is flown to even when the throttle valve is fully open.

Starting from the DE 10 2005 003 559 A1 It is another object of the invention to provide a fuel supply device with good performance.

This object is achieved by a fuel supply device having the features of claim 16.

Due to the fact that the middle section of the mixture channel surface is located at least directly upstream of the recess in the first region, the flow is directed against the end face of the throttle valve that is upstream in the direction of flow when the throttle valve is open. As a result, the flow conditions change less strongly when the throttle valve is closed slightly from the fully open position on the front side of the throttle valve. As a result, uncontrolled leaning of the mixture when closing the throttle valve can be avoided. Because the lateral portions are in the reference plane or in the second region, mixture is directed across the connection openings and not towards the connection openings. As a result, the proportion of mixture that passes into the air duct when the throttle valve is closed and when the throttle valve is opened can be reduced compared to known designs.

The lateral sections are particularly preferably located at least directly upstream of the recess in the second area, so that the mixture flowing in the mixture channel is routed via the connection openings.

The fuel supply device is provided in particular in a two-stroke engine, preferably in the two-stroke engine in a hand-held, advantageously a hand-held working device. The fuel supply device is in particular a carburetor.

Fig. 1

eine schematische Darstellung eines mit Spülvorlage arbeitenden Zweitaktmotors,

Fig. 2

eine schematische Schnittdarstellung durch eine erfindungsgemäße Kraftstoffzuführeinrichtung,

Fig. 3

eine ausschnittsweise schematische Schnittdarstellung entlang der Linie III-III in Fig. 2,

Fig. 3a

eine ausschnittsweise vergrößerte Darstellung des Bereichs der Verbindungsöffnungen aus Fig. 3,

Fig. 4

eine ausschnittsweise schematische Schnittdarstellung entlang der Linie IV-IV in Fig. 2,

Fig. 5

eine ausschnittsweise schematische Schnittdarstellung entlang der Linie V-V in Fig. 2,

Fig. 6

eine ausschnittsweise schematische Ansicht in Richtung des Pfeils VI in Fig. 2,

Fig. 7 und Fig. 8

schematische perspektivische Längsschnittdarstellungen durch die Kraftstoffzuführeinrichtung aus Fig. 2,

Fig. 9

eine ausschnittsweise Schnittdarstellung einer Ausführungsvariante der Kraftstoffzuführeinrichtung,

Fig. 10

eine ausschnittweise Ansicht in Richtung des Pfeils X in Fig. 9,

Fig. 11

die Darstellung aus Fig. 9 ohne Drosselklappe, Chokeklappe, Drosselwelle und Chokewelle,

Fig. 12

eine ausschnittsweise Ansicht in Richtung des Pfeils XII in Fig. 11.

Exemplary embodiments of the invention are explained below with reference to the drawing. Show it:

1

a schematic representation of a two-stroke engine working with scavenging,

2

a schematic sectional view through a fuel supply device according to the invention,

3

a partial schematic sectional view along the line III-III in 2 ,

Figure 3a

shows a partially enlarged view of the area of the connection openings 3 ,

4

a partial schematic sectional view along the line IV-IV in 2 ,

figure 5

a partial schematic sectional view along the line VV in 2 ,

6

a partial schematic view in the direction of arrow VI in 2 ,

7 and 8

schematic perspective longitudinal sectional views through the fuel supply device 2 ,

9

a partial sectional view of an embodiment variant of the fuel supply device,

10

a fragmentary view in the direction of the arrow X in 9 ,

11

the representation 9 without throttle valve, choke valve, throttle shaft and choke shaft,

12

a partial view in the direction of arrow XII in 11 .

1 shows a two-stroke engine 1 schematically. The two-stroke engine 1 can advantageously be provided as a drive motor in a working device, in particular in a hand-held working device, for example a chain saw, a cut-off grinder, a blower, a brush cutter, a lawnmower or the like. The two-stroke engine 1 has a cylinder 2 in which a combustion chamber 3 is formed. In the cylinder 2, a piston 5 is mounted to go back and forth. Via a connecting rod 6 , the piston 5 drives a crankshaft 7 , which is mounted rotatably about an axis of rotation 8 in a crankcase interior 9 . The crankcase interior 9 is formed in a crankcase 4 and is separated from the combustion chamber 3 by the piston 5 . An outlet opening 15 for exhaust gases leads out of the combustion chamber 3 . A spark plug 32 protrudes into the combustion chamber 3.

A mixture channel 18 with a mixture inlet 10 opens on the cylinder 2 . The mixture inlet 10 opens into the crankcase interior 9 and is fluidically connected to the crankcase interior 9 in the region of top dead center of the piston 5 . The piston 5 preferably has at least one piston pocket 14 . The two-stroke engine 1 has overflow channels 12 which fluidly connect the crankcase interior 9 to the combustion chamber 3 in the region of the bottom dead center of the piston 5 . The overflow channels 12 open out with overflow windows 13 on the cylinder bore.

The two-stroke engine 1 comprises an air duct 19 which opens out with an air inlet 11 at the cylinder bore of the cylinder 2 . In the area of the bottom dead center of the piston 5, the air inlet 11 is located in the area of the piston pocket 14 and connects the air duct 19 with the overflow windows 13 of the overflow ducts 12. Four overflow ducts 12 are provided in the exemplary embodiment, of which the sectional view in FIG 1 two are visible. A different number and/or a different shape of overflow channels 12 can also be advantageous. The overflow channels 12 connect the crankcase interior 9 in the area of bottom dead center 5 to the combustion chamber 3, so that the fuel/air mixture flows out of the crankcase interior 9 can flow into the combustion chamber 3 via the overflow channels 12 . The overflow windows 13 are controlled by the piston 5 and open towards the combustion chamber 3 in the region of the bottom dead center of the piston 5 .

The combustion air is drawn in via an air filter 37 . The air filter 37 has filter material 39 which separates a clean room 38 of the air filter 37 from the environment. The mixture channel 18 and the air channel 19 are connected to the clean room 38 . Air is sucked in via an intake duct 16 which opens out at the clean room 38 of the air filter 37 . The intake channel 16 is divided into the air channel 19 and the mixture channel 18 by a partition wall 17 over at least part of its length.

A fuel supply device 20 is provided for supplying fuel. The fuel supply device 20 has a base body 21. In the base body 21, an intake channel section 22 of the intake channel 16 is formed. The fuel supply device 20 can be a carburetor, which supplies fuel as a function of the negative pressure prevailing in the intake channel section 22 . In a preferred embodiment variant, the fuel supply device 20 is a membrane carburettor. In an alternative preferred embodiment, it is provided that the fuel supply device 20 comprises a fuel valve which is opened and closed by a controller of the two-stroke engine 1 . The fuel valve is in particular an electromagnetic valve, preferably a normally open valve or a normally closed valve. The fuel metered by the fuel valve is advantageously fed into the intake duct section 22 due to the negative pressure prevailing in the intake duct section 22 .

A throttle flap 25 is arranged in the intake duct section 22 . The throttle flap 25 is advantageously pivoted with a throttle shaft 35 . The throttle flap 25 has a diameter m. In the exemplary embodiment, the partition wall 17 has a partition wall section 27 upstream of the throttle shaft 35 and a partition wall section 28 downstream of the throttle shaft 35. The intake channel section 22 has a longitudinal center axis 29 . The longitudinal central axis 29 is the axis that connects the geometric centers of the intake channel section 22 to one another on the upstream and downstream end faces of the base body 21 . During operation, the combustion air and the fuel/air mixture flow in the intake channel 16 essentially in a flow direction 30 from the air filter 37 to the cylinder 2. In the case of back pulsations, a flow in the opposite direction can also take place. The partition wall 17 divides the intake channel 16 into the mixture channel 18 and the air channel 19. A main fuel opening 23 and several auxiliary fuel openings 24 open into the mixture channel 18 in the fuel supply device 20. The main fuel opening 23 is arranged in the area of a venturi section 31.

2 shows the fuel supply device 20 schematically in detail in longitudinal section. The throttle valve 25 is pivoted about a pivot axis 45 with the throttle shaft 35 . how 2 shows, a choke valve 26 is arranged in the intake channel section 22 upstream of the throttle valve 25 in relation to the direction of flow 30 . The choke flap 26 is pivoted about a pivot axis 46 with a choke shaft 36 . In the exemplary embodiment, the longitudinal center axis 29 of the intake duct section 22 intersects the pivot axes 45 and 46. However, it can also be provided that the pivot axes 45 and 46 are offset in the intake duct section 22 with respect to the longitudinal center axis 29 and do not intersect the longitudinal center axis 29. The main fuel opening 23 is formed on a main fuel nozzle 40 shown in the sectional view in FIG 2 is shown partially cut.

The intake duct section 22 has a center plane 50 . The center plane 50 contains the longitudinal center axis 29 of the intake port section 22 and runs parallel to the pivot axes 45 and 46. In the exemplary embodiment, the pivot axes 45 and 46 lie in the center plane 50.

2 shows the choke flap 26 in its fully open end position. In this end position, a section of the choke flap 26 protrudes into a recess 49 in the partition section 27. The partition section 27 has a mixture channel surface 41. The mixture channel surface 41 of the partition section 27 is the surface that delimits the mixture channel 18 in the illustrated end positions of the throttle valve 25 and choke valve 26 . The partition section 27 has an air duct surface 42 which delimits the air duct 19 in the illustrated end positions of the throttle flap 25 and choke flap 26 . In the exemplary embodiment, the air duct surface 42 runs flat and approximately parallel to the center plane 50. In the exemplary embodiment, the choke flap 26 lies parallel to the center plane 50 in its fully open position.

The throttle flap 25 can be pivoted between a first end position 51, shown with a dashed line, and the second end position 52, shown with a solid line. In the first end position 21, the throttle flap 25 largely closes the flow cross section in the intake channel section 22. The first end position 51 preferably corresponds to the position of the throttle valve 25 when idling. In the first end position 51, the throttle flap 25 is arranged completely downstream of the partition section 27 in the exemplary embodiment. In the second distortion 52, the throttle valve 25 largely frees the flow cross section in the intake channel section 22. In the second end position 52 , the throttle valve 25 encloses an angle α with the center plane 50 . An upstream face 58 of the throttle flap 25 is on the side of the center plane 50 on which the mixture channel 18 runs. The end face 62 of the throttle flap 25 lying downstream lies on the side of the central plane 50 on which the air duct 19 runs. The angle α, which the throttle valve 25 forms with the center plane 50, can also be 0°. A slight inclination of the throttle flap 25 in the opposite direction in its second end position 52 can also be provided.

The partition wall section 27 has a recess 48 on its side facing the mixture channel 18, into which the throttle flap 25 in its second end position 52 at least partially protrudes. The partition section 27 and the throttle valve 25 overlap in the second end position 52, so that the partition section 27 is not arranged completely upstream of the throttle valve 25 in the second end position 52. The partition wall portion 27 is located entirely upstream of the throttle shaft 35 . In the exemplary embodiment, the dividing wall section 27 has a depression 47 on its side facing the mixture channel 18 . Because of the depression 47 , the mixture flowing in the mixture channel section 18 flows against the end face 58 of the throttle valve 25 lying counter to the direction of flow 30 . In the exemplary embodiment, the recess 47 has a base 59 which runs parallel to the longitudinal center axis 29 in particular. In the exemplary embodiment shown, the bottom 59 of the depression 47 runs through the longitudinal center axis 29 closer to the air duct 19 than the end face 58 in the longitudinal section shown.

In the exemplary embodiment, the throttle valve 25 protrudes with a peripheral region over its entire thickness d from the recess 48. However, it can also be provided that the end face 58 in the second end position 52 only extends over part of the thickness d of the throttle valve 25 from the recess 48 in the mixture channel 18 protrudes. Throttle flap 25 advantageously protrudes in a peripheral region by at least 50%, in particular by at least 80% of its thickness d out of recess 48.

The throttle valve 25 has a side 57 facing the mixture channel 18 . Side 57 is a flat side of throttle valve 25. Mixture flows along side 57 in second end position 52 of throttle valve 25 during operation. The side 57 delimits the mixture channel 18 in the second end position 52. The side 57 of the throttle valve 25 forms an in 2 drawn reference plane 60. At the in 2 In the illustrated position of the fuel supply device 20, the reference plane 60, i.e. also the side 57 of the throttle valve 25 facing the mixture channel 18, is arranged horizontally, and the fuel opening 23 ( 1 ) is arranged above the partition wall section 27 . In this position of the fuel supply device 20 the middle section 53 of the mixture channel surface 41 runs below the reference plane 60.

The reference plane 60 divides the fuel supply device into two areas, namely a first area 71 and a second area 72. In the first area 71, the throttle flap 25 is arranged in its second end position 52. In the exemplary embodiment, the partition wall section 27 runs in the first area 71. The main fuel nozzle 40 is arranged in the second area 72 in the exemplary embodiment. The air duct 19 advantageously runs in the first area 71.

The middle section 53 has a distance e measured perpendicularly to the reference plane 60 at the edge of the recess 48 to the reference plane 60 . The distance e is advantageously at least 50%, in particular at least 80%, of the thickness d of the throttle valve 25. In a preferred embodiment, the distance e corresponds at least to the thickness d. In the exemplary embodiment, the distance e is greater than the thickness d.

The dividing wall 17 has a dividing wall plane 63 which runs in the middle of the dividing wall 17 . The partition plane 63 advantageously runs parallel to the center plane 50. In the exemplary embodiment, the partition plane 63 coincides with the center plane 50. The middle section 53 ( 3 ), which is shown in 2 runs through the sectional plane has a smallest distance f measured perpendicularly to the partition plane 63 to the partition plane 63 . In the exemplary embodiment, the distance f is over the entire length 1 of the middle section 53 (measured parallel to the longitudinal center axis 29 3 ) is less than a distance g between the lateral sections 54 and the partition plane 63. Advantageously, the central section 53 has a distance f from the partition plane 63 over a length 1 immediately upstream of the recess 48 for the throttle valve 25, which is smaller than a distance g between the lateral Sections 54 to the partition plane 63 is. The length 1 advantageously corresponds to at least 30%, in particular at least 50%, of the diameter m of the throttle valve 25.

The distance g of the lateral sections 54 to the partition plane 63 changes in the exemplary embodiment in the direction of flow 30, such as 2 indicates. The lateral sections 54 accordingly do not run parallel to the partition plane 63. The smallest distance f of the central section 53 from the partition plane 63 is constant in the flow direction 30 in the exemplary embodiment. The smallest distance f is in each case the smallest distance between the middle section 53 and the partition plane 63 in each cross section perpendicular to the longitudinal center axis 29.

3 shows the configuration of the partition wall section 27 in detail. The recess 47 extends from the side of the partition wall section 27 facing the choke shaft 36 to the throttle valve 25 in its second end position 52. The recess 47 has a width c on the side facing the throttle valve 25, which is measured perpendicularly to the longitudinal center axis 29. The width c is measured at the mixture channel surface 41 . The width c is advantageously at least 30%, in particular at least 50% of the smallest width b, measured in the same direction, of the mixture channel surface 41 of the partition section 27. The smallest width b of the mixture channel surface is on the mixture channel surface 41 from one suction channel wall 56 to the opposite and perpendicular to the longitudinal center axis 29 measured. In the exemplary embodiment, the smallest width b runs in the region of the Venturi section 31. The depression 47 has a length 1 which is advantageously at least 30%, in particular at least 50%, of the diameter m of the throttle flap 25. amounts to. The length 1 is measured on the longitudinal center axis 29 in a plan view of the center plane 50 .

The recess 47 forms a central section 53 of the mixture channel surface 41. Between the intake channel wall 56 and the central section 53, lateral sections 54 extend on both sides of the central section 53. In the exemplary embodiment, the lateral sections 54 directly adjoin the central section 53. However, it can also be provided that further areas are arranged between the lateral sections 54 and the central section 53 . The lateral sections 54 connect directly and without interruption to the intake port wall 54 .

On the lateral sections 54, the mixture channel surface 41 ends upstream of the recess 48 at a tear-off edge 43. The tear-off edge 43 delimits the recess 48. In the middle section 53, the recess 47 extends partially into the area of the throttle valve 25. The length 1 of the recess 47 corresponds the length of the region of central section 53, which is lower than lateral sections 54 in relation to reference plane 60. In the exemplary embodiment, recess 47 extends to the upstream side of mixture channel surface 41, facing choke flap 26. Mixture channel surface 41 is included the in the in 3 The sectional view shown shows a top view of the side of the partition wall 17 facing the mixture channel 18 when the throttle valve 25 and choke valve 26 are in the open end position 41 considered.

how 2 shows, the mixture channel 18 and the air channel 19 are connected in the illustrated second end position 52 of the throttle valve 25 via connecting openings 55. The connection openings 55 are located downstream of the partition section 27 between the throttle valve 25 and the intake port wall 56. In the area of the connection openings 55, the intake port wall 56 is advantageously machined to prevent the throttle valve 25 from jamming when opening and closing. The design of the connection openings 55 is also shown in the enlarged view in FIG Figure 3a shown.

how 3 also shows the throttle flap 25 with a fastener 33 on the throttle shaft 35 and the choke flap 26 with a fastener 34 on the choke shaft 36. The fasteners 33 and 34 are preferably screws. 4 shows the end face 58 of the throttle valve 25 in the area of the recess 47. As the illustration makes clear, the mixture in the mixture channel 18 flows against the end face 58. As the Figures 4 to 6 show, the depression 47 runs concavely in longitudinal sections perpendicular to the longitudinal central axis 29 of the intake port 16 .

In 6 the course of the lateral sections 54 and the middle section 53 is visible. The lateral sections 54 each end at a tear-off edge 43. The middle section 53 extends over the width c, which is advantageously at least 30%, in particular at least 50%, of the smallest width b of the mixture channel surface 41. The lateral sections 54 have a width _a1 or a width a2. The widths a ₁ and a ₂ of the two lateral sections 54 can be the same size or different sizes. The lateral sections 54 have an overall width a which is the sum of the widths a ₁ and a ₂ . The overall width a is advantageously at least 5 mm. The overall width a is advantageously at least 50%, in particular at least 70%, of the smallest width b of the mixture channel surface 41. The throttle valve 25 has a thickness d, which is advantageously 0.5 mm to 3 mm.

As the Figures 7 and 8 show, the lateral sections 54 are flat in the area arranged upstream of the throttle valve 25 . The tear-off edge 43 is located approximately at the same height as the side 57 of the throttle valve 25 facing the mixture channel 18. The tear-off edge 43 is therefore advantageously located in the reference plane 60.

The lateral sections 54 run in the reference plane 60 (see Figures 6 to 8 ). 8 also shows the design of the tear-off edge 43 on the central section 53 at a distance from the longitudinal central axis 29.

In the embodiment after 9 a depression 47 is also provided on the partition wall section 27 . The same reference symbols designate in all exemplary embodiments corresponding elements. Elements that are not described in detail for an exemplary embodiment are advantageously designed in accordance with one of the other exemplary embodiments.

The recess 47 is in the embodiment according to 9 formed less deep than in the previous embodiment. The tear-off edge 43 extends continuously over the entire width of the mixture channel surface 41. The lateral sections 54 extend, as in particular 11 12, upstream of the trailing edge 43 in the second region 72. The main fuel nozzle 40 and the lateral sections 54 are advantageously arranged on the same side of the reference plane 60. The main fuel nozzle 40 and the lateral sections 54 are advantageously arranged in the second region 72 . The lateral sections 54 are designed as guide elements 44 . The lateral sections 54 run in the direction of flow 30 inclined to the reference plane 60. As a result, the mixture of the in 3 shown connection openings 55 passed away. The guide elements 44 are advantageously designed as ramps. In the exemplary embodiment, the lateral sections 54 run approximately parallel to the longitudinal central axis 29 and to the central plane 50. In the exemplary embodiment, the guide elements 44 run inclined at an angle β to the reference plane 60, which corresponds to the angle α. The angle β between the guide elements 44 and the reference plane 60 is advantageously at least 5°, in particular at least 10°: It can also be provided that the guide elements 44 rise in the flow direction 30 . A curved course of the guide elements 44 can also be advantageous. The guide elements 44 advantageously extend over a length h in the first region 72, which is at least 3 mm, in particular at least 5 mm.

The guide elements 44 are also in 12 shown.

In all of the exemplary embodiments, the partition wall section 27 is preferably formed in one piece with the base body 21 of the fuel supply device 20 . The partition wall section 27 and the base body 21 are advantageously designed as a one-piece cast part.

The fuel supply device 20 is advantageously a carburetor, in particular a membrane carburetor. Metering fuel via an electromagnetic valve can also be advantageous.

Claims (18)

Fuel supply device for supplying fuel to a two-stroke engine (1) with a base body (21) in which an intake duct section (22) is formed, with at least one fuel opening (23, 24) which opens into the intake duct section (22), with a throttle valve (25) for controlling the free flow cross-section of the intake port section (22), which is mounted pivotably about a pivot axis (45), with a partition section (27) which also runs at least upstream of the throttle valve (25) in the intake port section (22) and which Intake duct section (22) into a mixture duct (18), into which the fuel opening (23, 24) supplies fuel, and an air duct (19), the partition section (27) having a recess (48) in which the throttle valve (25 ) lies at least partially in an end position (52), the partition wall section (27) upstream of the recess (48) having a continuous mixture channel surface (41) facing the mixture channel (18) which lateral sections (54) adjoining the intake port wall (56) and a central section (53) running between the lateral sections (54), the lateral sections (54) upstream of the throttle valve (25) having a tear-off edge (43) for the flow in the mixture channel (18), the side (57) of the throttle valve (25) facing the mixture channel (18) being in the end position (52) of the throttle valve (25), in which the throttle valve (25) is at least partially in the recess ( 48), a reference plane (60) is defined, which divides the fuel supply device into a first area (71), in which the throttle valve (25) is arranged, and a second area (72), characterized in that the lateral sections ( 54) at least extend immediately upstream of the recess (48) into the second region (72) of the fuel supply device. Fuel supply device according to claim 1,
characterized in that the mixture channel area (41) in the middle section (53) lies at least partially in the first region (71). Fuel supply device according to claim 2,
characterized in that the middle section (53) at least immediately upstream of the recess (48) has a distance (e) of at least 50% of the thickness (d) of the throttle valve (25), in particular of at least 80% of the thickness ( d) the throttle valve (25) to the reference plane (60). Fuel supply device according to one of claims 1 to 3,
characterized in that the middle section (53) immediately upstream of the recess (48) for the throttle valve (25) over a length (1) which is at least 30% of a diameter (m) of the throttle valve (25) has a distance (f ) to a dividing wall plane (63) running in the middle of the dividing wall (17) which is less than a distance (g) of the lateral sections (54) to the dividing wall plane (63), the length (1) being parallel to the longitudinal central axis (29) of the intake duct section (22) is measured. Fuel supply device according to claim 4,
characterized in that the central section (53) has a smaller distance (f) to the partition plane (63) over its entire length (1) than the lateral sections (54). Fuel supply device according to one of claims 1 to 5,
characterized in that the lateral sections (54) have an overall width (a) of at least 5 mm, in particular at least 7 mm, the total width (a) being measured perpendicularly to the longitudinal central axis (29) of the intake channel section (22). Fuel supply device according to one of claims 1 to 6,
characterized in that the lateral sections (54) have a total width (a) of at least 50% of the smallest width (b) of the mixture channel area (41) of the partition section (27), in particular at least 70% of the smallest width (b) of the mixture channel area (41 ) of the partition wall section (27), the total width (a) and the smallest width (b) being measured perpendicularly to the longitudinal central axis (29). Fuel supply device according to one of claims 1 to 7,
characterized in that the central section (53) has a width (c) which is at least 30%, preferably at least 50%, of the smallest width (b) of the mixture channel surface (41) of the partition wall section (27), the width (c) is measured perpendicularly to the longitudinal central axis (29). Fuel supply device according to one of claims 1 to 8,
characterized in that the lateral sections (54) extend inclined to the reference plane (60) at least immediately upstream of the tear-off edge (43). Fuel supply device according to one of claims 1 to 9,
characterized in that the tear-off edge (43) extends over the entire width of the mixture channel surface (41) of the partition section (27). Fuel supply device according to one of claims 1 to 10,
characterized in that the central portion (53) by a recess (47) of the partition section (27) is formed, which in a sectional plane perpendicular to the longitudinal center axis (29) of the intake port section (22) is in particular concave. Fuel supply device according to one of claims 1 to 11,
characterized in that the bottom (58) of the depression (47) runs parallel to the longitudinal central axis (29) of the intake channel section (22). Fuel supply device according to one of claims 1 to 12,
characterized in that the lateral sections (54) adjoin the central section (53) on both sides. Fuel supply device according to one of claims 1 to 13,
characterized in that a choke element is arranged upstream of the partition wall section (27). Fuel supply device according to one of claims 1 to 14,
characterized in that the partition wall section (27) is formed in one piece with the base body (21) of the fuel supply device (20), in particular is produced with the base body (21) as a one-piece cast part. Fuel supply device according to one of claims 1 to 15 or according to the preamble of claim 1,
characterized in that the middle section (53) of the mixture channel surface (41) lies at least immediately upstream of the recess (48) in the first region (71) and that the lateral sections (54) are in the reference plane (60) or in the second region (72) lie. Fuel supply device according to one of claims 1 to 16,
characterized in that the lateral portions (54) are at least immediately upstream of the recess (48) in the second region (72). A two-stroke engine having a fuel supply device according to any one of claims 1 to 17.

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