EP2435682B1 - Electrically controlled carburettor - Google Patents

Description

Technical area

The present invention relates to an electrically controlled carburetor for gasoline engines with a venturi for sucking fuel from a fuel line opening into the air duct, which is connected to a fuel chamber and between the fuel chamber and the mouth in the venturi a fuel nozzle for adjusting a due to negative pressure in the venturi comprising fuel quantity sucked from the fuel chamber.

State of the art

Such a carburetor is for example from the DE 102 16 084 A1 known.

Conventional carburetors produce a fuel-air mixture by drawing in fuel and mixing with air. The amount of fuel supplied to the venturi is adjusted at the fuel nozzle in the fuel line. Due to growing demands, especially in special small engines, such as internal combustion engines for chainsaws, which are constantly changing angles to the horizontal, as well as the desire for flexible power adjustment results in the requirement to influence the production of fuel-air mixtures in gasoline engines quickly and flexibly. Even with engines for two-wheelers, for example, the goal of a lower pollutant production by flexible adjustment of the carburetor.

This task tries the DE 102 16 084 A1 to be solved in that the fuel nozzle is provided with a variable flow cross-section. To change the flow cross section, a piezoelectric actuator is proposed. Because of a short travel of such piezoelectric actuators, however, a translation element is needed, which makes the construction of such a carburetor consuming. In addition, the use of a translation element leads to a higher degree of inaccuracy and higher susceptibility.

The DE 102 42 816 A1 describes an electromagnetic valve in which flow channels are fluidly separated by current flow in a coil from one another by an anchor plate. With the anchor plate as the only moving part only small forces for opening and closing the valve are necessary.

DESCRIPTION OF THE INVENTION: Problem, Solution, Advantages

The object of the present invention is to provide a flexibly adaptable carburettor for gasoline engines, in particular for engine working devices, which overcomes the above-mentioned drawbacks of the prior art and has a simple, robust construction which allows constant long-term behavior.

This object is achieved on the basis of a gasifier according to claim 1. Advantageous embodiments and further developments of the invention are specified in the subclaims.

The invention includes the technical teaching that at least two Tesla diodes are inserted in series with the fuel nozzle, between which a chamber (hereinafter referred to as "pumping chamber") is located with a pump unit.

The invention takes advantage of the property of Tesla diodes to have a higher flow resistance in a direction hereinafter referred to as the "reverse direction" than a direction opposite to the reverse direction, hereinafter referred to as the "forward direction". The ratio of the pressure loss in both directions is expressed by the so-called "diodicity", which is a dimensionless number. Because of this asymmetric property, such a component is also referred to as a fluidic diode analogous to the diodes in electrical engineering.

The asymmetry of the flow resistance of a Tesla diode results from a loop-like arrangement of flow channels, wherein in the forward direction a liquid flowing through the Tesla diode fluid flows predominantly through straight channels, in the reverse direction, however, at least one curved channel must be traversed, whereby the flow resistance is increased. In addition, arises in at least one area in which a curved and a straight channel coincide, a backwater, which in turn increases the flow resistance in the reverse direction. The exact operation of a Tesla diode is known and should therefore not be discussed further here.

If the volume is lowered by the pump unit in the pumping chamber arranged between the two Tesla diodes, the pressure in it increases. Seen from the pumping chamber, a first Tesla diode is connected in the reverse direction, a second Tesla diode in the forward direction. Because of the lower flow resistance in the second Tesla diode, fluid from the chamber flows either completely or at least for the most part through the second Tesla diode.

If the pump unit moves in a pumping process in the opposite direction, so that a negative pressure arises in the chamber, fluid is sucked from the fuel line. Since the first Tesla diode in the forward direction is now present with regard to flowing into the pumping chamber, fuel flows either completely or at least for the most part through the first Tesla diode.

Thus, by the arrangement of a pumping chamber with a pumping unit, which are arranged between two arranged in the same direction of flow Tesla diodes, a simply constructed pumping device is achieved. This acts as a regulating unit, which efficiently and flexibly adapts the flow of fuel in the fuel line from the fuel nozzle to the mouth in the air funnel. Thus, with the invention, a flexibly adaptable carburetor is achieved, which can respond to external influences, such as tilting or pivoting of an engine working device, or internal influences, such as the lambda value in the exhaust gas, quickly and at the same time simple design.

Since there are neither mechanically movable nor electrical components in the Tesla diodes, they have an extremely low susceptibility. They have no wearing parts and therefore retain a constant long-term behavior without wear. In addition, since there are no moving parts in the Tesla diodes, they have no leakage problems. If, in addition, a simply constructed pumping unit is used, the entire regulating unit and thus the erfindungsgemäBe carburetor high robustness and low susceptibility while maintaining constant long-term behavior. In addition, due to the lack of an opening threshold, a Tesla diode can be easily operated in the kHz range.

It is particularly advantageous if the Tesla diodes are introduced in the direction of flow from the fuel nozzle to the venturi in the reverse direction. In this case, the regulating unit pumps in the opposite direction to the fuel flow from the fuel nozzle to the mouth in the air funnel and thus has the function of a throttle unit. If the regulating unit fails, more fuel in the fuel line is delivered to the venturi than during operation of the regulating unit, i. the fuel-air mixture that is produced in the carburetor then gets fatter. Therefore, it is advantageous to adjust the fuel nozzle so that would be generated without the regulator in the vent a too rich fuel-air mixture. During normal operation of the carburetor according to the invention, the regulating unit empties the mixture to the desired mixing ratio. In case of failure of the regulating unit, the fuel-air mixture is then too fat instead of too lean, which does not damage the engine.

But it may also be advantageous to grease a lean fuel-air mixture through the regulating unit. In this case, the two Tesla diodes are arranged in the forward direction, thus supporting in operation the flow from the fuel nozzle to the mouth.

In a preferred embodiment, the pumping unit is a membrane element. This has a membrane which forms a portion of an inner wall of the pumping chamber. Periodic movement of the membrane periodically generates a volume change in the pumping chamber and thus periodically a pressure change in the pumping chamber. The membrane is moved, for example, electromechanically or via a piezoelectric element. Such membrane elements are robust elements that have low susceptibility and long life. Because of the very low weight of the membrane, it can be moved at very high frequencies.

Alternatively, it may be advantageous to use a pump unit having a pump piston. In this case, the piston takes over the task to reduce the volume in the pumping chamber periodically or increase.

Advantageously, the pump unit is controlled in a voltage-modulated manner. This has the advantage that you can work with digital signals. The modulation allows a stepless adjustment of the pump unit and thus a stepless regulation of the fuel flow in the fuel line.

It is particularly advantageous if the pump unit is controlled in pulse width modulation. This modulation is particularly easy to handle, with a simple control to effect a stepless adjustment of the pumping unit.

Furthermore, it may be advantageous for the pump unit to be regulated by a control which evaluates measured values of an exhaust gas lambda probe. The generated exhaust gas mixture is analyzed by a sensor and leads via the control to an adjustment correction for the amount of fuel to be supplied to the air funnel.

Advantageously, however, instead of or in addition, a number of other measured values can be supplied to the control, which activates the pump unit and thus adjusts the amount of fuel to be supplied to the air funnel.

Preferably, the Tesla diodes with gasoline fuel have a Diodizität between 1.1 and 3, in particular between 1.3 and 2.

The diodes of the Tesla diodes can be influenced as desired or required by the geometric design of the Tesla diodes in their manufacture. Thus, radii of curvature, angles and cross-sectional areas of the tracks of a Tesla diode are suitable for influencing the diodesicity. Also, the geometric design of the Tesla diodes is advantageously suitable to adjust the delivery characteristic of the regulating device targeted. Depending on how the flow rate, delivery pressure, dependence on the frequency of the pumping unit and similar parameters of the regulating device are desired or required, the Tesla diodes are designed accordingly or appropriate Tesla diodes are used for the regulating unit.

, It is advantageous if the Tesla diodes are designed so that the Reynolds number in the Tesla diodes is well below the critical Reynolds number of 2300. "Clear" here is a Reynolds number of less than 2000, in particular less than 1200, preferably less than 500 to understand. This has the advantage that the fuel flows through the Tesla diodes with a laminar flow. This results in a good-natured behavior of the Tesla diodes, where "good-natured" is understood to mean a continuous property profile which does not show abrupt changes in the flow resistance of the Tesla diodes as a function of the flow velocity. This supports a stepless regulation of the fuel flow.

The advantageous Reynolds numbers can be achieved preferably by a small size of the Tesla diodes, with an advantageous cross section of the channels in the Tesla diode between 0.05 mm ² and 1 mm ² , in particular between 0.1 mm ² and 0.5 mm ² ,

Advantageously, the chamber and / or the Tesla diodes are formed as a depression of a plate. This plate may for example be a metal plate. This has the advantage that the chamber and / or the Tesla diodes can be produced by conventional surface treatment methods. These can advantageously be methods such as spark erosion, lasers, etching, but also milling. Whether a more delicate machining method, such as etching, or rather a rough machining method, such as milling, comes into question, depends mainly on the size of the carburetor.

Particularly advantageous is the production of the Tesla diodes by embossing by means of micro-embossing dies. This method allows a precise and cost-effective production.

A cover-like completion of the chamber and / or the Tesla diodes is advantageously formed by a further plate which closes cavities of the chamber and / or the Tesla diodes from above.

This construction of two plates has the advantage that already by two easy to manufacture plates, a substantial part of the regulating unit is present. Two plates can be easily integrated into a conventional carburettor housing. Thus, the present invention also has the advantage that existing manufacturing processes for conventional carburetor only need to be changed slightly or even existing carburetor can be retrofitted.

Brief description of the drawings

• Fig. 1 ein Schaltbild eines erfindungsgemäßen Vergasers,
• Fig. 2 ein Makrofoto einer Tesla-Diode,
• Fig. 3 eine perspektivische Explosionsansicht einer Reguliereinheit des erfindungsgemäßen Vergasers,
• Fig. 4 eine perspektivische Ansicht der Reguliereinheit aus Fig. 3 im zusammengebauten Zustand, und
• Fig. 5 eine perspektivische schematische Ansicht eines ursprünglich herkömmlichen Vergasers mit eingebauter Reguliereinheit gemäß Figuren 3 und 4.

Further advantageous embodiments and further developments of the carburetor according to the invention are explained in more detail below with reference to embodiments in conjunction with the drawings. In a purely schematic representation:

• Fig. 1 a circuit diagram of a carburetor according to the invention,
• Fig. 2 a macro photo of a Tesla diode,
• Fig. 3 an exploded perspective view of a regulating unit of the carburetor according to the invention,
• Fig. 4 a perspective view of the regulating unit Fig. 3 in the assembled state, and
• Fig. 5 a perspective schematic view of an originally conventional carburettor with built-in regulating unit according to FIGS. 3 and 4 ,

Best way to carry out the invention

Fig. 1 The carburettor has a fuel line 2, which extends from a fuel chamber (not shown) via a fuel nozzle 3 to a venturi 4, where it exits at an orifice 5. In the fuel line 2, a first Tesla diode 6 and a second Tesla diode 7 are introduced. Both Tesla diodes 6, 7 are arranged in the reverse direction in this embodiment, which is in Fig. 1 represented by the corresponding orientation of the switching symbol. Between the Tesla diodes 6, 7 a below called "pumping chamber" chamber 8 is arranged, which is in fluid communication with the Tesla diodes 6, 7 via the fuel line 2. With the pumping chamber 8 in operative connection is a membrane element 9 as a pump unit, which has a membrane 10 which is movable via an actuating element 11. This in Fig. 1 shown schematically as a spring element Control element 11 is a piezoelectric element in this embodiment. Alternatively, the membrane 10 may be electromagnetically driven. The tesla diodes 6, 7, the pumping chamber 8 and the pumping unit 9 together form a regulating unit 30.

If the air funnel 4 is traversed by air, which is in Fig. 1 is shown with an arrow 15, formed at a constriction 16 of the venturi 4 as Venturi nozzle, a negative pressure .DELTA.P, which is sucked in the fuel line 2 befindlicher fuel via the mouth 5 in the venturi 4, as shown schematically by arrow 17. Via an actuator 18 on the fuel nozzle 3, the fuel flow (in Fig. 1 represented by arrow 31) from the control chamber to the mouth 5. In this case, the fuel nozzle 3 is set so that the resulting in the air horn 4 fuel-air mixture, which is the engine (not shown) is supplied, for a normal operation of the engine is too rich.

By a periodic activation of the membrane element 9, an overpressure and underpressure are periodically generated in the pumping chamber by an up and down movement (represented by a double arrow 12). The dashed line represents the diaphragm 10 in the presence of a negative pressure, the solid line in the presence of an overpressure. The periodic volume change, in conjunction with the diodes of the Tesla diodes 6, 7 to a pumping action of the regulating unit 30. This pumping action is opposed to the flow 31 in the fuel line 2, whereby the regulating unit 30 acts as a throttle unit in this embodiment. In this embodiment, the diodeicity of both Tesla diodes is 1.5.

The membrane element 9 is operated in a pulse-width-modulated manner, so that a change in the pumping action of the membrane element 9 is possible simply and effectively using a digital control. In the simplest case, the oscillation frequency of the diaphragm 10 can be changed by changing an applied voltage frequency.

Fig. 2 shows a representation of the first Tesla diode 6. On the left is a first recess 19 can be seen, with the fuel line from the fuel nozzle comes, is connected (not shown). On the right, the pumping chamber 8 can be seen, which lies in the reverse direction behind the Tesla diode 6. The fuel line 2 between the first recess 19 and the Tesla diode 6 and between the Tesla diode 6 and the pumping chamber 8 is in this embodiment directly in the tracks 20, 21 of the Tesla diode over. The curved track 20 and the straight track 21 are formed and open into each other so that when flow of the Tesla diode 6 in the reverse direction (in the drawing from left to right) due to the geometric conditions and the resulting flow conditions, a high flow resistance results.

In this example, the first recess 19, pump chamber 8, fuel line 2 and curved track 20, and straight track 21 of the throttle unit 30 are introduced into a metal plate by embossing by means of a micro-embossing die. The width of the webs 20, 21 is about 600 microns.

In a second embodiment ( Fig. 3-5 ), the first recess 19, pumping chamber 8, fuel line 2 and curved, and first and second Tesla diode 6, 7 of the regulating unit 30 are introduced into a first metal plate 22 by spark erosion. The diameter of the pumping chamber 8 is in this case about 3 mm, the dimensions of the other elements of the regulating unit 30 behave with respect to the pumping chamber 8 approximately as in the Fig. 3 shown. In the first metal plate 22, the first and second Tesla diodes 6, 7 are formed substantially parallel to each other. They are connected to each other via the pumping chamber 8. This results in a U-shaped course, which has a space-saving design of the regulating unit 30 result. At a free end of the first Tesla diode 6, a first recess 19 is inserted into the metal plate, at a free end of the second Tesla diode 7, a second recess 23 is introduced, which penetrates the first metal plate 22. Can be screwed to the first metal plate 22, a second metal plate 24 which forms a cover of the tracks 20, 21 of the Tesla diodes 6, 7 and the fuel line 2. In the second metal plate 24, a hole 25 is inserted, which forms a connection to the first recess 19 of the first metal plate 22. Thus, the regulating unit 30 is externally connected to a Fuel line 2 connected. The second metal plate 24 further has an opening 26 which extends the pumping chamber 8 upwards. In the opening 26, the membrane element 9 is used, wherein the membrane element 9 in this embodiment has an electrical connector 27, via which the membrane element 9 is easily and reversibly connected to a corresponding mating connector, for example, to a high frequency source.

The second recess 23 is connected via the fuel line 2 to the mouth 5 in the venturi 4 (see correspondingly Fig. 1 ).

Fig. 5 shows a perspective view of a third embodiment in which the regulating unit 30 of the second embodiment ( 3 and 4 ) is integrated in a conventional housing 28 of a carburetor 1. Except for a slight increase in the thickness of the carburetor 1 through the first metal plate 22 and the second metal plate 24, only the pump element 9, which in this embodiment is a piston element, can be seen from the outside. Otherwise, the same supply lines and connections as in a conventional carburetor can be seen, which need not be described here in detail.

The features disclosed in the foregoing description, the claims and the drawing, both individually and in any combination, as claimed in the appended claims, for the realization of the invention in its various forms of importance. In particular, the design and arrangement of the Tesla diodes can be varied over a wide range. Thus, a plurality of Tesla diodes can be arranged in series or in parallel to cause some effects on desired delivery characteristics of the regulating unit. For this purpose, a plurality of curved tracks in a Tesla diode can be arranged one behind the other. It may also be advantageous in the context of the invention to provide a plurality of regulating units, of which at least one first performs a throttle function and at least one second represents a Anfetteinheit. In this case, the throttle unit cause the leaning of the fuel-air mixture in normal operation, whereas the Anfetteinheit, for example, as a choke temporarily performs a targeted enrichment.

LIST OF REFERENCE NUMBERS

1

carburettor

2

fuel line

3

fuel nozzle

4

venturi

5

muzzle

6

first Tesla diode

7

second Tesla diode

8th

pumping chamber

9

pump unit

10

membrane

11

actuator

12

Double arrow (for periodic membrane movement)

15

Arrow (for airflow)

16

narrowing

17

arrow

18

actuator

19

first recess

20

curved track

21

straight course

22

first plate

23

second recess

24

second plate

25

Through Hole

26

opening

27

electrical plug connection

28

casing

30

regulating

31

flow direction

Claims (12)

1. An electrically actuated carburettor (1) for petrol engines with a venturi (4) for sucking in fuel from a fuel line (2) terminating in the venturi (4), which is connected to a fuel chamber and between fuel chamber and orifice (5) in the venturi (4) comprises a fuel nozzle (3) for adjusting a fuel quantity that can be sucked in from the fuel chamber due to vacuum in the venturi (4), characterized in that in series connection with the fuel nozzle (3) at least two Tesla diodes (6, 7) are provided, between which a pumping chamber (8) with a pumping unit (9) is located.
2. The carburettor according to claim 1, characterized in that the Tesla diodes (6, 7) in the path from the fuel nozzle (3) to the venturi (4) are introduced in the blocking direction, so that a control unit (30) comprising the Tesla diodes (6, 7), the pumping chamber (8) and the pumping unit (9) has the function of a throttling unit.
3. The carburettor according to claim 1 or 2, characterized in that the pumping unit (9) is a membrane element.
4. The carburettor according to claim 1 or 2, characterized in that the pumping unit (9) has a pumping piston.
5. The carburettor according to one or more of the preceding claims, characterized in that the pumping unit (9) is activated in a voltage-modulated manner.
6. The carburettor according to claim 5, characterized in that the pumping unit (9) is activated in a pulse width modulated manner.
7. The carburettor according to one or more of the preceding claims, characterized in that the pumping unit (9) is regulated on the basis of measured values, such as in particular an exhaust gas lambda value.
8. The carburettor according to one or more of the preceding claims, characterized in that the Tesla diodes (6, 7) with petrol as fuel have a diodicity between 1.1 and 3, in particular between 1.3 and 2.
9. The carburettor according to one or more of the preceding claims, characterized in that the Reynolds number in the Tesla diodes (6, 7) is clearly below the critical Reynolds number of 2,300.
10. The carburettor according to one or more of the preceding claims, characterized in that the Tesla diodes (6, 7) and the pumping chamber (8) are introduced into at least one of two plates (22, 24) and the other plate (24, 22) serves as lid.
11. The carburettor according to claim 10, characterized in that the Tesla diodes (6, 7) and the pumping chamber (8) are introduced through surface machining such as spark erosion, laser treatment, milling, etching, stamping, in particular with micro-stamping dies.
12. The carburettor according to one or more of the preceding claims, characterized in that a carburettor comprises at least one first control unit (30) as throttling unit and at least one further control unit (30) as enrichment unit.

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