EP3511552B1 - Carburator for the combustion engine in a hand-held work device, combustion engine with a carburator and method for operating a combustion engine - Google Patents

Description

The invention relates to a carburetor for the internal combustion engine in a hand-held tool of the type specified in the preamble of claim 1, an internal combustion engine with a carburetor and a method for operating an internal combustion engine.

From the U.S. 4,909,211 A a carburetor with a carburetor roller is known. In order to detect the rotary position, a rotary position transmitter, not described in detail, is arranged at one end of the carburetor roller.

The DE 10 2013 009 668 A1 discloses an internal combustion engine having a starting device. The starting device comprises a guide surface that slides on a gate. As a result, a carburetor roller is moved in the axial direction and the free flow cross-section of an annular gap which is formed between a fuel opening and an adjusting needle held on the carburetor roller is thereby adjusted.

From the DE 103 26 313 A1 an internal combustion engine with a throttle element is known. On the throttle shaft of the throttle element, a stop is formed which, in the idle position, rests against a stop element and with this forms a switch which is actuated in the idle position of the throttle element.

The invention is based on the object of creating a carburetor of the generic type which has a simple structure and enables precise detection of at least one rotational position of the carburetor cylinder. Another object of the invention is to provide an internal combustion engine with a carburetor and a method for operating an internal combustion engine.

This object is achieved with regard to the carburetor for the internal combustion engine in a hand-held tool by a carburetor with the features of claim 1 solved. With regard to the internal combustion engine, the object is achieved by an internal combustion engine having the features of claim 13. With regard to the method, the object is achieved by a method having the features of claim 14.

It is provided that the detection device comprises a control contour and a detection means that interacts with the control contour and that the control contour is formed directly on the carburetor roller. The arrangement of the control contour on the carburetor cylinder allows tolerances between the position of the control contour and the position of the carburetor cylinder to be minimized. A control contour can be introduced into the carburetor cylinder in a simple manner during the manufacture of the carburetor cylinder. A control contour is a contour to be mechanically scanned, for example an elevation or depression on the outer circumference of the carburetor roller. A control contour can be easily produced by machining the carburetor roller. To detect the rotational position of the carburetor roller, it is advantageously provided that the control contour has different distances from the pivot axis of the carburetor roller in different circumferential sections of the carburetor roller, which are detected by the detection means. It is preferably provided that the detection means scans the control contour.

The detection device is designed to generate an electrical signal. The signal generated by the detection device can in particular be read out in an evaluation unit and can advantageously be used to control a fuel supply device. The evaluation unit can be, for example, a control unit of an internal combustion engine.

The control contour is preferably arranged directly on the carburetor roller. The control contour is arranged in particular on an upper side of the carburetor roller. The control contour is in particular formed in one piece with that part of the carburetor roller which has the at least one channel running transversely to the pivot axis. Thereby tolerances between the at least one channel and the control contour can be minimized.

The carburetor roller is advantageously designed in several parts. A first part of the carburetor roller advantageously has the control contour and a second part has the at least one channel. The first part and the second part are advantageously firmly connected to one another, in particular by welding, gluing or the like. The two parts are in particular connected to one another in a materially bonded manner. As a result, the control contour and the at least one channel can be easily produced. The at least two parts of the carburetor roller can advantageously consist of different materials. As a result, the control contour can be formed in a part from wear-resistant material, for example a plastic, and the at least one channel can be formed in a fuel-resistant material, for example metal or another plastic. The two parts can be precisely positioned to one another during production before the parts are firmly connected to one another, so that small tolerances can be maintained.

The control contour is advantageously arranged on the roller body. As a result, the control contour can be designed with a comparatively large distance from the pivot axis of the roller body. This minimizes tolerances when detecting the rotary position of the carburetor drum. The control contour is preferably arranged in the region of the roller body which has the largest diameter. The control contour is advantageously formed in the roller body of the carburetor roller. The roller body of the carburetor roller is designed in one piece in an advantageous design. In an advantageous alternative design, the roller body is made up of two parts that are firmly connected to one another.

The control contour preferably comprises at least one depression on the circumference of the carburetor roller. The control contour advantageously comprises at least one depression in the circumference of the roller body of the carburetor roller. In an advantageous embodiment, the control contour comprises a first depression which is assigned to the idle. Especially In a preferred embodiment, the control contour comprises a first recess, which is assigned to idling, and a second recess, which is assigned to full load. The idle position can therefore be determined via the control contour. The idling position and the full load position can be determined particularly advantageously via the control contour. The partial load range that exists between the idle position and the full load position can be determined by a signal that deviates from the idle position and the full load position. As a result, the position of all positions of the roller body that are important for controlling the internal combustion engine can be detected via two switching states of the detection device. The distinction between the idle position and the full load position can be achieved by different signals in the idle position and the full load position, for example by means of different depths for the idle position and the full load position. In a particularly preferred embodiment, the detection device detects the same signal in the idle position and the full load position, and the distinction between the idle position and the full load position is made using further information, in particular on the basis of a speed of the internal combustion engine.

The scanning of the control contour has an advantageous effect on an operating element, for example a throttle lever, via which the operator adjusts the carburetor roller. In order to keep the forces exerted by the detection device on the throttle lever as low as possible, it is advantageously provided that at least one recess has a base that delimits the recess in the radial direction. The bottom advantageously merges into the outer circumferential surface of the carburetor roller with a slope on at least one side lying in the circumferential direction. The forces exerted by the control contour on the detection means during the transition from the depression to the outer circumferential surface of the carburetor roller can be kept low via the incline. The inclination of the incline is advantageously chosen so that the rotational position of the carburetor roller can be detected with sufficient accuracy, but at the same time low forces from the incline be exercised on the throttle, which are advantageously not or hardly noticed by the operator. In a preferred embodiment, the bottom delimits the depression in a radially inner direction.

In an alternative design, it can be provided that the bottom of the recess merges with the incline into a curved surface segment. The surface segment is advantageously curved with one or more radii around the pivot axis of the roller body. The radii advantageously differ from the distance between the bottom of the recess and the pivot axis, so that the surface segment and the bottom of the recess are designed with different radii. A further switching state of the detection device can be achieved via the curved surface segment. In particular, this allows further rotational positions of the roller body to be recorded. The curved surface segment can be a surface segment whose radius is smaller than that of the outer circumferential surface of the carburetor roller in order to enable the arrangement in a smaller installation space. In an alternative configuration, the radius of the curved surface segment is greater than that of the outer circumferential surface. As a result, the accuracy of the detection of the rotational position of the roller body can be increased.

The bottom of the recess advantageously delimits the recess on the side lying radially inward relative to the pivot axis. In an advantageous embodiment, the detection means rests on the control contour radially outside the control contour in relation to the pivot axis. The detection means is advantageously spring-loaded radially inward by a return spring with respect to the pivot axis. The detection device advantageously comprises a switch which is actuated as a function of the position of the detection means. At least two switching states can be detected in a simple manner via a switch. An electrical signal generated by a switch can be further processed electronically in a simple manner, in particular by an electronic control device.

The detection means is preferably formed on a pivot lever which is mounted on the carburetor housing so as to be pivotable about a second pivot axis lying parallel to the pivot axis of the carburetor drum. In a particularly preferred embodiment, the pivot lever is connected to ground via the return spring. The return spring is therefore a contact spring, via which an electrical contact to ground is established. This results in a simple structure with few components. However, it can also be provided that different spring elements are used to establish the ground contact and to preload the pivot lever into its radially inner position.

A fuel valve is advantageously provided, via which fuel is fed into the intake duct. On the basis of the detection of at least one rotational position of the roller body, the fuel valve can be activated and the required amount of fuel can be precisely metered. For an internal combustion engine with a carburetor with a fuel valve, it is provided that the internal combustion engine has a control device which is connected to the detection device and the fuel valve for feeding fuel into the intake duct.

A method for operating an internal combustion engine advantageously provides that the control device controls the amount of fuel supplied as a function of the rotational position of the carburetor drum detected by the detection device. This enables precise metering of fuel, in particular if the entire amount of fuel supplied to the intake duct is metered via a single fuel valve. Provision can advantageously be made to influence the control of the ignition of the internal combustion engine by means of the detection of at least one rotational position of the carburetor drum.

Fig. 1

eine schematische perspektivische Darstellung eines Arbeitsgeräts,

Fig. 2

eine schematische Schnittdarstellung eines Verbrennungsmotors des Arbeitsgeräts aus Fig. 1,

Fig. 3

eine schematische Schnittdarstellung des Vergasers des Verbrennungsmotors aus Fig. 2,

Fig. 4

eine perspektivische Darstellung der Vergaserwalze des Vergasers aus Fig. 3,

Fig. 5

eine Seitenansicht der Vergaserwalze aus Fig. 4,

Fig. 6

eine Draufsicht auf die Vergaserwalze aus Fig. 5 in Richtung des Pfeils VI in Fig. 5,

Fig. 7

eine Seitenansicht der Vergaserwalze in Richtung des Pfeils VII in Fig. 5,

Fig. 8

eine schematische Draufsicht auf den Vergaser mit abgenommenem Deckel in Leerlaufstellung eines Ausführungsbeispiels der Vergaserwalze,

Fig. 9

eine schematische perspektivische Darstellung von Schwenkhebel und Vergaserwalze in der Schaltstellung aus Fig. 8,

Fig. 10

eine Seitenansicht des Vergasers in der Stellung aus den Fig. 8 und 9,

Fig. 11

eine Draufsicht auf den Vergaser mit abgenommenem Deckel mit der Vergaserwalze aus Fig. 8 in Teillaststellung,

Fig. 12

eine perspektivische Darstellung von Schwenkhebel und Vergaserwalze in der Stellung aus Fig. 11,

Fig. 13

eine Seitenansicht des Vergasers in der Schaltstellung aus den Fig. 11 und 12,

Fig. 14

eine Draufsicht auf den Vergaser mit der Vergaserwalze aus den Fig. 4 bis 7 in Volllaststellung,

Fig. 15

eine schematische perspektivische Darstellung des Vergasers in der Stellung aus Fig. 14,

Fig. 16

ein Schaltbild der Erfassungseinrichtung und einer Steuereinrichtung des Verbrennungsmotors.

An exemplary embodiment of the invention is explained below with reference to the drawing. Show it:

Fig. 1

a schematic perspective illustration of an implement,

Fig. 2

a schematic sectional view of an internal combustion engine of the implement from FIG Fig. 1 ,

Fig. 3

a schematic sectional view of the carburetor of the internal combustion engine Fig. 2 ,

Fig. 4

a perspective view of the carburetor roller of the carburetor Fig. 3 ,

Fig. 5

a side view of the carburetor roller Fig. 4 ,

Fig. 6

a top view of the carburetor roller Fig. 5 in the direction of arrow VI in Fig. 5 ,

Fig. 7

a side view of the carburetor roller in the direction of arrow VII in Fig. 5 ,

Fig. 8

a schematic plan view of the carburetor with the cover removed in the idle position of an embodiment of the carburetor roller,

Fig. 9

a schematic perspective view of the pivot lever and carburetor roller in the switching position Fig. 8 ,

Fig. 10

a side view of the carburetor in the position from FIG Fig. 8 and 9 ,

Fig. 11

a top view of the carburetor with the cover removed with the carburetor roller Fig. 8 in partial load position,

Fig. 12

a perspective view of the pivot lever and carburetor roller in the position from Fig. 11 ,

Fig. 13

a side view of the carburetor in the switching position from the Fig. 11 and 12th ,

Fig. 14

a top view of the carburetor with the carburetor roller from the Figures 4 to 7 in full load position,

Fig. 15

a schematic perspective view of the carburetor in the position from Fig. 14 ,

Fig. 16

a circuit diagram of the detection device and a control device of the internal combustion engine.

Fig. 1 shows a brushcutter 37 as an exemplary embodiment of a hand-held tool. The brushcutter 37 has a housing 38 which is connected to a tool head 69 via a guide tube 39. A tool 40, in the exemplary embodiment a cutting knife, is mounted on the tool head 69 so as to be rotatable about an axis of rotation 44. The tool 40 is arranged in the housing 38, in Fig. 2 internal combustion engine 1 shown schematically. To start the internal combustion engine 1, a starter device is provided, the starter handle 43 of which protrudes from the housing 38, as Fig. 1 shows. To guide the brush cutter 1 during operation, handles 41 are provided which are fixed to the guide tube 39 via a bracket. At least one operating element 42 for controlling the internal combustion engine 1 is arranged on one of the handles 41.

Fig. 2 shows the structure of the internal combustion engine 1 schematically. In the exemplary embodiment, the internal combustion engine 1 is a two-stroke engine working with a flushing reservoir. Another design of the internal combustion engine 1, for example a design as However, a four-stroke engine, in particular as a mixture-lubricated four-stroke engine, can be advantageous. The internal combustion engine 1 has a cylinder 2 in which a combustion chamber 3 is formed. The combustion chamber 3 is delimited by a piston 5 mounted to and fro in the cylinder 2, which piston drives a crankshaft 7 rotatably mounted in a crankcase 4 via a connecting rod 6. The internal combustion engine 1 comprises an air filter 17, via which combustion air is sucked in during operation. The air filter 17 is connected to an air inlet 10 and a mixture inlet 11 on the cylinder 2 via an intake duct 26. Intake combustion air and fuel / air mixture flow in a flow direction 36 through the intake channel 26. The intake channel 26 is separated by a partition 31 into the first supply channel 8 for air and the second supply channel 9 for mixture. The combustion air is drawn in through a first supply duct 8, which is provided for supplying air, to at least one air inlet 10 on the cylinder 2. Combustion air is also drawn in via a second supply channel 9, which is provided for supplying the fuel / air mixture, to a mixture inlet 11. The internal combustion engine 1 has transfer passages 13 close to the outlet and transfer passages 14 close to the inlet, which open with transfer windows 15 at the cylinder bore. The overflow channels 13 and 14 connect in the area of in Fig. 2 The bottom dead center of the piston 5 shown is the interior of the crankcase 4 with the combustion chamber 3.

The mixture inlet 11 and the air inlet 10 are controlled by the piston skirt of the piston 5. The internal combustion engine 1 of the embodiment is a slot-type engine. The mixture inlet 11 is connected to the interior of the crankcase 4 in the area of the top dead center of the piston 5. The air inlet 10 opens into a region of the piston 5 in which a piston pocket 12 of the piston 5 moves. The piston pocket 12 connects the air inlet 10 in the area of the top dead center of the piston 5 with the overflow windows 15 of the overflow channels 13 near the outlet and the overflow channels 14 remote from the outlet. The illustration in FIG Fig. 2 is only schematic. A carburetor 18 is provided for supplying fuel. The carburetor 18 has a carburetor roller 20. The carburetor roller 20 is rotatably mounted to control the amount of combustion air supplied. In the carburetor drum 20, a first channel 34 is formed, which forms an air channel section, and a second channel 33, which forms a mixture channel section. Alternatively, it can also be provided that only one mixture duct section is provided in the carburetor roller 20.

During operation of the internal combustion engine 1, during the upward stroke of the piston 5, the fuel / air mixture is sucked from the second supply channel 9 via the mixture inlet 11 into the interior of the crankcase 4. As soon as the piston pockets 12 connect the at least one air inlet 10 to the overflow windows 15, fuel-free or low-fuel combustion air is sucked from the first supply duct 8 through the overflow windows 15 into the overflow ducts 13 and 14. The fuel / air mixture in the interior of the crankcase 4 is compressed in the interior of the crankcase 4 during the subsequent downward stroke, that is, the movement of the piston 5 from the combustion chamber 3 in the direction of the crankcase 4. As soon as the transfer windows 15 are opened by the piston 5 moving downwards, fuel-free or low-fuel air initially flows out of the transfer windows 15 into the combustion chamber 3. The low-fuel or fuel-free combustion air flushes exhaust gases from the previous engine cycle out of the combustion chamber 3 through an outlet 16 from the combustion chamber 3 out. Fresh mixture then flows from the interior of the crankcase 4 into the combustion chamber 3. During the subsequent upward stroke of the piston, the mixture is compressed in the combustion chamber 3 and ignited and burned in the region of the top dead center of the piston 5. As a result of the combustion, the piston 5 is accelerated again in the direction of the crankcase 4. As soon as the transfer windows 15 open, upstream air first flows from the transfer channels 13 and 14 and then fresh mixture flows from the interior of the crankcase 4 via the transfer channels 13 and 14 into the combustion chamber 3.

Fig. 3 shows the structure of the carburetor 18 in detail. The carburetor 18 has a carburetor housing 19 which is closed by a cover 21. In the carburetor housing 19, the carburetor roller 20 is mounted pivotably about a pivot axis 35. An actuating lever 23 is fixed to the carburetor drum 20, on which the operating element 42 ( Fig. 1 ) of the implement is effective. The operating element 42 is advantageously connected to an actuating pin 24 fixed on the actuating lever 23 via a Bowden cable or another transmission element. If the operator actuates the operating element 42, the carburetor drum 20 swivels in the carburetor housing 19 about the swivel axis 35.

How Fig. 3 9, the channels 33 and 34 in the carburetor roller 20 are separated by a partition wall section 32 which lies flush in the partition wall 31. A fuel opening 28, which opens into the second channel 33 of the carburetor roller 20, is provided for the supply of fuel. In the exemplary embodiment, the fuel opening 28 is connected to a fuel chamber 30 via a fuel valve 27. The fuel valve 27 is preferably designed as an electromagnetic valve and controls the entire amount of fuel supplied into the channel 33 via the fuel opening 28. The fuel opening 28 is advantageously the only fuel opening opening into the carburetor cylinder 20. The fuel valve 27 is activated by a control device 45. To detect the rotational position of the carburetor roller 20, a switch 22 is provided in the exemplary embodiment, which is shown in FIG Fig. 3 is shown schematically and its structure is explained in more detail below. The switch 22 is connected to the control device 45.

In an alternative embodiment it can be provided that a control needle protrudes into the fuel opening 28 to control the amount of fuel supplied and the size of an annular gap formed between the control needle and the fuel opening changes as a function of the rotational position of the carburetor roller 20. To change the size of the annular gap, it is known to provide a ramp between the carburetor housing 19 and the carburetor roller 20, via which the carburetor roller 20 is moved in the direction of the pivot axis 35 during a pivoting movement about the pivot axis 35.

The Figures 4 to 6 show the design of the carburetor roller 20 in detail. The carburetor roller 20 has a roller body 54 on which an outer peripheral surface 60 is formed. The outer circumferential surface 60 is the region of the carburetor roller 20 which has the largest diameter. A roller shaft 61 with a reduced diameter is advantageously fixed on the roller body 54. The roller body 54 is advantageously designed in one piece with the roller shaft 61. In an alternative design, however, a multi-part design, in particular a design made up of a plurality of parts that are firmly and non-detachably connected to one another, can also be advantageous. The roller shaft 61 has an engagement contour 75 on which the actuating lever 23 ( Fig. 2 ) must be fixed in a rotationally fixed manner. The roller shaft 61 and the roller body 54 are preferably of essentially cylindrical design, the pivot axis 35 forming the longitudinal center axis of the roller body 54 and the roller shaft 61. How Fig. 4 also shows, the channels 33 and 34 are formed as through openings through the roller body 54 running transversely to the pivot axis 35. The roller body has an upper side 25 from which the roller shaft 61 extends. The top 25 is the end face of the roller body 54 facing the roller shaft 61.

On the side of the roller body 54 which is adjacent to the roller shaft 61, the roller body 54 has a control contour 57 on its outer circumference. The control contour 57 is used to detect the rotational position of the carburetor cylinder 20 and actuates the switch 22 ( Fig. 3 ). The control contour 57 is preferably formed by at least one recess 47 or 48. In particular, the control contour 57 is formed by two depressions 47 and 48. The control contour 57 is preferably formed by two depressions 47 and 48 as well as a region of the outer circumferential surface 60 lying between the depressions 47 and 48. Instead of the outer circumferential surface 60, the area lying between the depressions 47 and 48 can also be formed by a further contour. The further contour is in particular a surface curved around the pivot axis 35, which extends at a different distance from the pivot axis 35 than the outer circumferential surface 60. In the exemplary embodiment, the control contour 57 to extends to the top 25. The recesses 47 and 48 are open to the top 25. In an alternative embodiment, the control contour 57 can also be at a distance from the top 25.

How Fig. 5 shows, the roller body 54 has an adjusting contour 64 on the end face facing away from the roller shaft 61. The adjusting contour 64 can be provided in order to change the position of the carburetor roller 20 in the direction of the pivot axis 35 as a function of the rotary position of the carburetor roller 20, for example, to increase the amount of fuel supplied via a fuel opening 28 ( Fig. 3 ) to adjust the protruding needle. In the exemplary embodiment, the adjusting contour 64 is of no importance, since the fuel quantity supplied via the fuel opening 28 is adjusted via the fuel valve 27.

Fig. 6 shows the design of the recesses 47 and 48 in detail. Both depressions 47 and 48 have a base 58 lying radially on the inside with respect to the pivot axis 35. The ends of the depressions 47 and 48 lying in the circumferential direction go into the FIG Fig. 6 The embodiment shown in each case on one side with a slope 79, 80 over into the outer circumferential surface 60. In an alternative design, instead of the depressions 47 and 48, elevations can be provided. The elevations preferably merge into the outer circumferential surface 60 with bevels.

How Fig. 7 shows, a groove 63 running in the circumferential direction is provided on the channel 33. The channel 33 is preferably a mixture channel for guiding the fuel / air mixture. The mixture is preferably formed in the roller body 54 by supplying fuel into the mixture channel. The groove 63 serves to open the mixture duct slightly even in the idling position of the carburetor drum 20.

In the exemplary embodiment, the roller body 54 is formed in one piece. In the Figures 5 and 7th a further advantageous design variant is shown schematically, in which the roller body is constructed from two parts 54a and 54b connected to one another.

The parts 54a and 54b are advantageously firmly, in particular permanently connected to one another. However, a detachable connection of the two parts 54a and 54b, for example a screw connection, can also be advantageous. The part 54a is cylindrical and has the channels 33 and 34. The part 54a is advantageously made of media-resistant plastic or metal. In the exemplary embodiment, the part 54b is designed as a flat disk and has the control contour 57. The part 54b is advantageously made of plastic. The material of the part 54b is advantageously matched to the material of the pivot lever 49 in such a way that there are low frictional forces between the control contour 57 and the pivot lever 49. The parts 54a and 54b are adjusted to one another in particular before the fixed, in particular materially bonded connection with one another, so that small tolerances arise between the control contour 57 and the channels 33 and 34. Alternatively, the position of the parts 54a and 54b with respect to one another can also be determined structurally, for example by means of a stop or the like.

Fig. 8 shows the carburetor housing 19 with the carburetor roller 20 in a top view without cover 21 (see Fig. 3 ). As a result, the carburetor roller 20 and the switch 22 are visible. A pivot lever 49 is advantageously mounted on the carburetor housing 19 so as to be pivotable about a pivot axis 62 of the pivot lever 49. The pivot axis 62 of the pivot lever 49 is arranged at a distance c from the pivot axis 35 of the carburetor roller 20. The distance c is advantageously greater than the distance b between the outer circumferential surface 60 and the pivot axis 35 of the carburetor roller 20. The pivot axis 62 of the pivot lever 49 is therefore outside the roller body 20. The pivot axis 62 of the pivot lever 49 is preferably aligned parallel to the pivot axis 35 of the carburetor roller 20. The pivot lever 49 advantageously has a nose which rests on the carburetor roller 20 and which forms a detection means 56 for detecting the rotational position of the carburetor roller 20. The detection means 56 together with the control contour 57 forms a detection device 55 for detecting the rotational position of the carburetor drum 20. As in FIG Fig. 8 Shown with a dashed line, the pivot lever 49 can have a recess 72 adjacent to the detection means 56 which avoids contact of this region of the pivot lever 49 with the outer circumferential surface 60.

In the idling position of the carburetor roller 20 shown, the detection means 56 rests on the bottom 58 of the first depression 47. The base 58 has a distance a from the pivot axis 35 of the carburetor roller 20 which is smaller than the distance b from the outer circumferential surface 60 to the pivot axis 35 of the carburetor roller 20. The pivot lever 49 is pretensioned in the direction of the position of the detection means 56 which is located radially inward in relation to the pivot axis 35 of the carburetor roller 20. The bias of the pivot lever 49 is in Fig. 8 indicated by an arrow 71. The preload of the pivot lever 49 can be adjusted by a return spring 70 ( Fig. 14 ), which is part of the switch 22. Alternatively, the preload can also be applied by a spring element separate from the switch 22. However, it can also be provided that the preload is applied in the direction of arrow 71 by a separate spring element. Due to the bias, the detection means 56 rests on the bottom 58 of the recess 47.

A contact pin 51, which forms the switch 22 with the spring 50, is advantageously fixed on the pivot lever 49. In the switching position shown, the contact pin 51 is at a distance d from the spring 50, which is designed as a contact spring. The contact pin 51 is therefore not connected to the spring 50 in an electrically conductive manner. The switch 22 is open. The spring 50 rests against a contact 53 of a diode 52 which is connected to the control device 45.

As the Figures 9 and 10 show, the contact pin 51 protrudes from the pivot lever 49 advantageously parallel to the pivot axis 35 upwards.

Fig. 10 shows an embodiment of a carburetor with a carburetor roller 20 in the idle position. The idle position relates to the operation of the internal combustion engine 1 in idle, i.e. when the internal combustion engine 1 is running without a user accelerating, for example by means of an operating element 42 ( Fig. 1 ).How Fig. 10 shows is the first feed channel 8 is completely closed in the idling position of the carburetor roller 20. In the second feed channel 9 for mixture, a small flow cross section is released via the groove 63. This allows a small amount of combustion air to flow through the second supply duct 9 and fuel from the fuel opening 28 ( Fig. 2 ) take with you.

If the carburetor roller 20 is rotated in the direction of the arrow 68, for example by pressing the operating element 42 ( Fig. 1 ) like a gas lever, the roller body 20 reaches the into the Figures 11 to 13 Part load position shown. The detection means 56 slides from the floor 58 over the incline 79 onto the outer circumferential surface 60. The inclination of the incline 79 adjusts the forces exerted by the pivot lever 49 on the carburetor roller 20 and thus on the operating element 42 during the transition from the idle position to the partial load position. Due to the inclination of the incline 80 of the recess 48, the forces exerted by the pivot lever 49 on the carburetor drum 20 and thus on the operating element 42 are set during the transition from the full load position to the part load position. The inclination of the bevels 79 and 80 is advantageously chosen so that the forces exerted by the pivot lever 49 on the carburetor roller 20 are as small as possible. While the detection means 56 is on a slope 79, 80, the switching state of the switch 22 is not defined. In order to be able to determine the rotational position of the carburetor roller 20 with a low tolerance, the bevels 79 and 80 are advantageously short in the circumferential direction. The recesses 47 and 48 can, as in Fig. 6 shown, on the side over which the pivot lever 49 does not move from the partial load position to the idle position or full load position, each have a slope 59 or 81. The depressions 47, 48 can, however, also be designed without an incline on this side, as in FIG Fig. 8 is shown.

The Figures 11 to 13 show the arrangement with the carburetor roller 20 in the partial load position. Like in particular the Fig. 11 and Fig. 12 show, the depressions 47 and 48 also extend in the embodiment according to FIGS Figures 11 to 13 up to the top 25. The part load position refers to the operation of the internal combustion engine 1 in part load, i.e. when the internal combustion engine 1 is running and a user accelerates, for example by means of an operating element 42 ( Fig. 1 ). When the operating element 42 is completely depressed, a full throttle position is present. In a partial load position, the carburetor roller 20 is between the idle position and the full throttle position. How Fig. 13 shows, the first feed channel 8 and the second feed channel 9 are partially open in the partial load position. The detection means 56, in the exemplary embodiment the nose of the pivot lever 49, has moved out of the first recess 47 along the slope 79 during the rotary movement of the carburetor roller 20 and is now in contact with the outer circumferential surface 60. The detection device 56 lies at the distance b from the pivot axis 35, that is to say it has been moved radially outward with respect to the pivot axis 35. As a result, the pivot lever 49 was pivoted about the pivot axis 62. The contact pin 51 has moved accordingly about the pivot axis 62 and is now in contact with the spring 50. The switch 22 formed by the contact pin 51 and the spring 50 is closed. The contact pin 51 is connected in an electrically conductive manner to the contact 53 of the diode 52 via the spring 50. As a result, the control device 45 receives a signal which indicates that the carburetor roller 20 is in a partial load position. How Fig. 13 shows, the first feed channel 8 and the second feed channel 9 are partially open in the partial load position.

The Fig. 14 and 15th show the arrangement in full throttle position. The full throttle position relates to the operation of the internal combustion engine 1 at full throttle, i.e. an operating state in which the internal combustion engine 1 is running and a user accelerates and, for example, completely depresses the control element 42 ( Fig. 1 In the full throttle position, the detection means 56 rests on the bottom 58 of the second recess 48. As a result, the pivot lever 49 has pivoted back about the pivot axis 62. The pivot lever 49 is reset due to an in Fig. 14 return spring 70 shown. The return spring 70 is connected to the contact pin 51 in every position of the pivot lever 49. The ground contact is established via the return spring 70. The contact pin 51 is not contacted by the spring 50 in the pivoted-back position of the pivot lever 49 (corresponding to FIG Fig. 8 ). The switch 22 is open.

In the in the Fig. 14 and 15th The full throttle position shown, the cross-sections of the first feed channel 8 and the second feed channel 9 are completely open. In the full throttle position, the cross-sections of the first feed channel 8 and the second feed channel 9 are advantageously not reduced by the carburetor roller 20.

In the figures, two slightly different designs of the depressions 47 and 48 and of the spring 50 are shown. In the embodiment according to the Fig. 8 and 11 the recesses 47 and 48 only have a bevel 79, 80 on the sides, via which the actuating means 56 comes when adjusting from the idle position to the part-load position and when adjusting from the part-load position to the full-load position. On the opposite side, the wall is rounded and steep, so that the actuating means 56 on the side facing away from the other recess 47, 48 cannot emerge from the recesses 47 and 48. This is usually prevented in any case by means of corresponding stops on the carburetor roller 20, which set the idle position and the full load position.

How Fig. 6 shows, the recesses 47 and 48 can have a different geometry. The recesses 47 and 48 can, however, also have an identical geometry and can be arranged in mirror symmetry, such as Fig. 8 shows. In the case of depressions 47 and 48 with different geometries, for example, one of the depressions 47, 48 can be designed deeper, longer, more rounded or angular than the other of the depressions 47, 48. It can also be provided that the bevels 59, 79, 80 and / or 81 are designed differently. For example, a bevel 79, 80 can be designed as a bevel, and the contour arranged at the other end of the recess 47, 48 can be designed as a sharp edge. Other geometries such as radii can also be advantageous. The depressions 47 and 48 can, for example, alternatively or additionally have different depths. These different configurations can be used by the detection device 55 to detect the different positions. The different trainings can also be used in order to be able to identify unambiguous positions of the carburetor roller 20 during manufacture. To detect the various switch positions, an alternative position detection can alternatively be used for at least one switch position, for example a lever in combination with a potentiometer.

Fig. 16 shows schematically a circuit diagram of the arrangement. The control device 45 is connected to a short circuit button 67 via a line 72. The control device 45 advantageously has a microprocessor. The short circuit button 67 is to be actuated by the operator and can also be designed as a switch. The short circuit button 67 is used to switch the ignition of the internal combustion engine 1 ( Fig. 2 ) short-circuit and thereby switch off the internal combustion engine 1. The control device 45 is connected via a further line 73 to a connection 66 for a diagnostic device, the fuel valve 27 as well as the diode 52 and the switch 22. The connection 66 for diagnosis, the fuel valve 27 and the switch 22 are advantageously connected in parallel. The switch 22 is opened or closed depending on the position of the control contour 57. In Fig. 16 the movement of the control contour 57 is indicated schematically by an arrow 65.

In the exemplary embodiment, it is provided that the switch 22 is open in the idling state and in the full load state and is closed in the intermediate partial load state. It is provided that the control device 45 controls the amount of fuel supplied via the fuel valve 27 as a function of the rotational position of the carburetor drum 20 determined by the detection device 55. In the exemplary embodiment, the detection device 55 is formed by the switch 22, the detection means 56, the control contour 57 and the diode 52.

In an alternative embodiment, it can be provided that the detection means 56, when the carburetor cylinder 20 is in a rotational position between the idling position and the full load position, is not located on the outer circumferential surface 60 of the carburetor cylinder 20 on the carburetor cylinder 20, but on a curved surface whose radius around the pivot axis 35 of the carburetor roller 20 differs from that of the outer circumferential surface 60, which is therefore closer to the pivot axis 35 of the carburetor roller 20 or further away from the pivot axis 35.

Further advantageous designs result from any combination of the exemplary embodiments described.

Claims (14)

1. Carburettor for the internal combustion engine in a hand-guided working implement, with a carburettor housing (19) wherein, in the carburettor housing (19), a carburettor roller (20) is rotatably mounted around a swivel axis (35), wherein the carburettor roller (20) has a roller body (54), wherein the roller body (54) has at least one channel (33, 34) running transversely to the swivel axis (35) and forming a suction channel section, wherein a detection device (55) is provided to detect at least one rotary position of the carburettor roller (20), wherein the detection device (55) is designed to generate an electrical signal, characterised in that the detection device (55) includes a control contour (57) and detection means (56) acting in conjunction with the control contour (57), and that the control contour (57) is formed on the carburettor roller (20).
2. Carburettor according to claim 1,
   characterised in that the control contour (57) is located on the roller body (54).
3. Carburettor according to claim 2,
   characterised in that the control contour (57) is located in the area of the roller body (54) which has the greatest diameter.
4. Carburettor according to any of claims 1 to 3,
   characterised in that the control contour (57) includes at least one recess (47, 48) on the circumference of the carburettor roller (20).
5. Carburettor according to claim 4,
   characterised in that the control contour (57) includes a first recess (47), which is assigned to idling and that the control contour (57) includes a second recess (48), which is assigned to full load.
6. Carburettor according to claim 4 or 5,
   characterised in that the recess or recesses (47, 48) has or have a base (58) bounding the recess (47, 48) in the radial direction which, on at least one side of the recess (47, 48) lying in the circumferential direction, merges with a bevel (59, 79, 80, 81) into the outer circumferential surface (60) of the carburettor roller (20).
7. Carburettor according to any of claims 1 to 6,
   characterised in that the detection means (56), relative to the swivel axis (35), make contact with the control contour (57) radially outside the control contour (57).
8. Carburettor according to any of claims 1 to 7,
   characterised in that the detection means (56), relative to the swivel axis (35), are spring-loaded inwards by a return spring (70).
9. Carburettor according to any of claims 1 to 8,
   characterised in that the detection device (55) includes a switch (22) which is actuated depending on the position of the detection means (56).
10. Carburettor according to any of claims 1 to 9,
    characterised in that the detection means (56) are formed on a swivel lever (49) which is pivotably mounted on the carburettor housing (19) around a second swivel axis (58) lying parallel to the swivel axis (35) of the carburettor roller (20).
11. Carburettor according to claim 10,
    characterised in that the swivel lever (49) is connected to earth via the return spring (70).
12. Carburettor according to any of claims 1 to 11,
    characterised in that there is provided a fuel valve (27), through which the fuel is fed into the channel (33) of the carburettor roller (20).
13. Internal combustion engine with a carburettor according to claim 12,
    wherein the internal combustion engine has a control unit (45) which is connected to the detection device (55) and the fuel valve (27) to feed fuel into the suction channel section.
14. Method of operating an internal combustion engine according to claim 13, wherein the control unit (45) controls the amount of fuel supplied on the basis of the rotary position of the carburettor roller (20) detected by the detection device (55).

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