EP3489481B1 - Manually operated work device - Google Patents

Description

The invention relates to a hand-held implement with an internal combustion engine of the type specified in the preamble of claim 1.

From the EP 2 607 642 A1 is a hand-held tool with an internal combustion engine and a fan wheel for conveying cooling air for the internal combustion engine is known. The fan wheel is arranged in a fan wheel housing. The internal combustion engine has an injection valve for supplying fuel. The injection valve is arranged in a cooling area, into which cooling air conveyed by the fan wheel flows via a connecting opening in the rear wall of the fan wheel housing.

Fan wheel housings are usually approximately spiral-shaped, the distance between the peripheral wall of the fan wheel housing and the axis of rotation of the fan wheel increasing in the direction of rotation of the fan wheel. At the end of the fan coil, an outlet opening is usually provided, through which cooling air flows from the fan wheel to the cylinder of the internal combustion engine. To cool a muffler of the internal combustion engine, it is known to subsequently conduct the cooling air, which has previously cooled the cylinder, to the muffler. Such a cooling air duct is, for example, from the DE 38 11 181 C2 forth.

The WO 2013/042535 A1 discloses a hand-held implement according to the preamble of claim 1 and shows in particular an internal combustion engine with a fan housing from which cooling air can flow through a cooling air inlet passage into a muffler housing. Cooling air also flows from the fan wheel to the engine through an engine cooling air duct formed by the fan housing and the cylinder housing.

The WO 2014/163078 A1 shows an implement with an internal combustion engine, a fan wheel housing and a silencer housing. A plate protrudes into the silencer housing.

The invention has for its object to provide a hand-held implement of the generic type, which has an advantageous structure and ensures good cooling.

This object is achieved by a hand-held implement with the features of claim 1.

It is provided to arrange a passage opening in the rear wall of the fan wheel housing facing the crankcase. The peripheral wall of the fan wheel housing has a first end and a second end. The two ends define an outlet opening for cooling air for the cylinder. The outlet opening extends in the direction of rotation of the fan wheel from the second end to the first end. The passage opening is arranged such that the angular distance between the first end and the passage opening measured in the direction of rotation from the first end is smaller than the angular distance between the passage opening and the second end measured in the direction of rotation from the passage opening. The angular distance is measured as a circumferential angle around the axis of rotation. The angular distance is measured in each case as the distance between one side of the circumferential boundary and one side of the passage opening. Accordingly, the distance to the center of the passage opening is not measured. The passage opening is an opening formed separately from the outlet opening and therefore represents an opening that is present in addition to the outlet opening. A cooling air flow flows through the passage opening to the outside of the crankcase and a separate cooling air flow to the cylinder of the internal combustion engine from the outlet opening. In other words, the cooling air that flows to the outside of the crankcase through the passage opening is not preheated by the waste heat from the cylinder, since it does not flow over the cylinder beforehand. This improves the cooling of the internal combustion engine.

The outlet opening extends in the direction of rotation of the fan wheel in the direction of rotation between the second end and the first end of the circumferential boundary. The air for cooling the cylinder emerges from the outlet opening. The fan wheel conveys cooling air both to the passage opening and to the outlet opening. The fan wheel is advantageously bladed on one side. However, it can also be provided that the fan wheel is provided with fan blades on both sides. The cooling air is advantageously sucked in from the ambient air via ventilation slots. The fan wheel housing designates in particular the space in which the fan wheel of the internal combustion engine is located.

The passage opening is closer in the circumferential direction to the first end of the circumferential boundary, that is to say in the direction of rotation at the beginning of the circumferential boundary, than to the second end of the circumferential boundary, that is to say in the direction of rotation at the end of the circumferential boundary. The passage opening is accordingly in the circumferential direction with respect to the direction of rotation of the fan wheel after the first end and before the second end of the circumferential limit. By arranging the additional passage opening closer to the first end of the circumferential limit, the total air volume conveyed by the fan wheel increases. If the passage opening is arranged closer to the second end of the circumferential boundary, it has been shown that this air is branched off from the cooling air flow and the amount of air conveyed to the cylinder is reduced accordingly. The inventive arrangement of the passage opening can accordingly provide additional cooling air without the cooling air conveyed through the outlet opening to the cylinder being markedly reduced. This improves, for example, the cooling of the entire internal combustion engine, namely the cylinder cooling and the cooling of the muffler space as well as the crankcase and the space in which the crankcase is arranged.

The angular distance between the first end and the passage opening measured in the direction of rotation from the first end is advantageously less than 120 °, in particular less than 90 °, preferably less than 60 °. Because the distance between the first end of the circumferential boundary and the passage opening is selected to be comparatively small, the influence of the amount of air conveyed through the passage opening on the amount of air conveyed through the outlet opening to the cylinder is negligible. This arrangement also results in an advantageous arrangement of the additional passage opening on the side of the crankcase, on which a muffler of the internal combustion engine is preferably also arranged.

The passage opening advantageously extends at least partially into the rear wall of the fan wheel housing. Due to the arrangement in the rear wall of the fan wheel housing, the direction vector, which indicates the main flow direction of the air flowing through the passage opening, has a direction component in the direction of the axis of rotation of the fan wheel and is in particular aligned parallel to the axis of rotation of the fan wheel.

The passage opening preferably extends at least partially into the circumferential boundary of the fan wheel housing. It can thereby be achieved that the direction vector, which indicates the main flow direction of the cooling air emerging through the passage opening, has at least one direction component in the radial direction to the axis of rotation of the fan wheel. In particular, the direction vector is oriented perpendicular to the axis of rotation of the fan wheel.

The passage opening extends partly into the rear wall and partly into the circumference of the fan wheel housing. The cooling air flow can be directed in the desired direction in a simple manner by suitably designing the proportions of the passage opening in the rear wall and in the peripheral limitation.

It can be provided that at least one additional guide element for guiding the cooling air flow to the cylinder adjoins the peripheral limitation of the fan wheel housing. The additional guide element projects in particular approximately in the direction of the first end or in the direction of the axis of rotation of the crankshaft. The additional guide element advantageously reduces the free flow cross section of the outlet opening.

An elevation projecting into the fan wheel housing is advantageously arranged on the rear side of the passage opening in the direction of rotation of the fan wheel. The increase reduces the flow cross section on the rear side of the passage opening in the direction of rotation of the fan wheel. As a result, the increase conducts cooling air in the manner of a flow guide element from the interior of the fan wheel housing through the passage opening. The increase in the amount of air flowing through the passage opening increases. The contour lying at the front in the direction of rotation advantageously corresponds to the increase in the circumferential profile of the passage opening. The contour of the elevation therefore corresponds to an extension of the peripheral wall of the passage opening. The contour of the elevation lying at the front in the direction of rotation advantageously merges seamlessly into the passage opening. In a particularly advantageous design, the contour of the elevation lying at the front in the flow direction is curved, in particular approximately in the shape of a blade.

In an advantageous embodiment, the internal combustion engine has a muffler, the muffler being arranged in a muffler room. The silencer room does not have to be a closed space within a housing of the implement, but rather denotes the area in which the silencer is arranged. The silencer chamber is advantageously partially open to the surroundings. The passage opening preferably connects the interior of the fan wheel housing to the silencer chamber. Direct cooling of the muffler can therefore be achieved via the passage opening. The cooling air used to cool the muffler is therefore not first used to cool the cylinder and only then directed to the exhaust muffler. The muffler is supplied with cooling air directly through the passage opening connecting the interior of the fan wheel housing with the muffler chamber. As a result, the cooling air directed to the muffler is not yet preheated by the cylinder, so that the muffler is cooled particularly effectively. The silencer is advantageously fixed to a boundary of the silencer space by means of at least one silencer screw. The at least one silencer screw is thermal due to the high heat input heavily burdened. The at least one silencer screw can be specifically cooled via the air flowing in through the passage opening. This reduces the loss of preload and prevents loosening of the silencer screw. In a particularly advantageous embodiment, the air flowing through the passage opening is directed to the at least one silencer screw by a suitable arrangement of the passage opening and / or by at least one cooling fin.

In a particularly advantageous embodiment, a section of the rear wall of the fan wheel housing delimits the interior of the fan wheel housing with one side and the silencer chamber with the opposite side. The passage opening is advantageously arranged in this section of the rear wall. The passage opening thereby connects the interior of the fan wheel housing directly to the muffler chamber, so that cooling air can pass directly from the fan wheel housing into the muffler chamber and cool the muffler. A space is expediently formed between the muffler and a wall of a motor housing of the working device, into which the cooling air flows from the passage opening. In a particularly preferred embodiment, the space between an operating medium tank, in particular an oil tank, and the silencer is formed. The wall of the motor housing is preferably a wall of the resource tank. The space runs in an advantageous design on the underside of the exhaust silencer. The underside of the muffler is the side that is arranged below in the usual storage position of the implement.

In order to achieve an improved cooling effect, it is advantageously provided that at least one cooling fin projects into the muffler space. In a particularly preferred design, at least one cooling fin is designed in such a way that it simultaneously stiffens the motor housing and thus increases the stability of the motor housing.

It has been shown that, particularly in the area where the cylinder is screwed to the crankcase, high temperatures can arise during operation, since this area of the cooling air flowing around the cylinder is often not adequately cooled. In an advantageous embodiment, the cylinder is fixed to the crankcase via at least one cylinder foot screw. The cylinder foot screw protrudes advantageously into a hole in the crankcase. The air flowing through the passage opening advantageously flows to a wall section of the crankcase adjacent to the bore. This improves cooling of the cylinder foot screw. In order to achieve a further improvement in the cooling of the cylinder foot screw, it is advantageously provided that the at least one cooling fin is arranged on the outside of the wall section of the crankcase adjoining the bore. Particularly good cooling is achieved in the area of the at least one cylinder foot screw. A further improvement in the cooling of the cylinder foot screw is achieved if a muffler plate is arranged between the cylinder and the muffler, which largely separates the muffler chamber from the cylinder. The muffler plate advantageously protrudes close to the wall of the muffler space and largely seals the muffler space from the cylinder in the area of the cylinder foot screws. This largely prevents air that has been preheated by the cylinder from entering the silencer chamber.

In an advantageous embodiment variant, at least one cooling fin is arranged parallel to the wall of the motor housing delimiting the intermediate space. In a preferred embodiment, the at least one cooling fin runs approximately horizontally in the storage position of the implement. Alternatively, it can also be provided that at least one cooling fin is arranged perpendicular to the wall of the motor housing that delimits the intermediate space. Alternatively, a combination of horizontal and vertical ribs can also be provided. The use of a cross rib, that is to say a plurality of intersecting ribs, can also advantageously be provided for cooling.

In order to achieve favorable cooling air guidance, it is advantageously provided that at least one cooling fin on the wall of the motor housing delimiting the intermediate space is arranged. In a particularly preferred embodiment, the at least one cooling fin is arranged obliquely, in particular at an angle of 10 ° to 80 °, preferably at an angle of 20 ° to 70 °, on the wall of the motor housing.

The silencer chamber advantageously has a first transverse side, which is adjacent to the fan wheel housing, and a second transverse side, which is arranged opposite the first transverse side. It is advantageously provided that the at least one cooling fin extends up to the first transverse side. As a result, the motor housings are stiffened by the cooling fins. In a particularly preferred embodiment, the at least one cooling fin is molded onto the first transverse side. Good heat dissipation is thereby achieved in the transverse side of the muffler space and in particular also in the engine housing. The first and the second transverse side of the silencer chamber are advantageously molded onto the motor housing.

At least one cooling fin is advantageously arranged on the second transverse side of the silencer chamber. The at least one cooling fin on the second transverse side of the muffler space advantageously serves both for improved cooling and for guiding the cooling air emerging from the passage opening. It can also be provided that at least one cooling fin extends from the first to the second transverse side of the silencer chamber.

The distance between the circumferential boundary and the axis of rotation is advantageously smaller at the first end than at the second end. The circumferential limitation advantageously runs in a spiral in at least one section. In the subsection, the distance between the circumferential limit and the axis of rotation of the fan wheel advantageously increases in the direction of rotation of the fan wheel.

Fig. 1

eine perspektivische Darstellung eines handgeführten Arbeitsgeräts in einer Abstellposition,

Fig. 2

eine schematische Schnittdarstellung durch den Antriebsstrang des Arbeitsgeräts aus Fig. 1,

Fig. 3

eine ausschnittsweise Seitenansicht des Motorgehäuses des Arbeitsgeräts aus Fig. 1 mit Zylinder und Schalldämpfer, wobei ein Deckel des Lüfterradgehäuses abgenommen ist,

Fig. 4

eine Seitenansicht des Motorgehäuses entsprechend der Darstellung aus Fig. 3, wobei das Lüfterrad nicht dargestellt ist,

Fig. 5

eine ausschnittsweise perspektivische Darstellung des Motorgehäuses mit Blick in das Lüfterradgehäuse, wobei das Lüfterrad nicht dargestellt ist,

Fig. 6

eine ausschnittsweise Schnittdarstellung durch Motorgehäuse und Schalldämpfer,

Fig. 7

eine ausschnittsweise Schnittdarstellung durch das Motorgehäuse mit daran angeordnetem Lüfterrad entlang der Linie VII-VII in Fig. 6,

Fig. 8

eine Schnittdarstellung entsprechend Fig. 7, wobei das Lüfterrad nicht dargestellt ist,

Fig. 8a und 8b

Ausführungsvarianten in Darstellungen entsprechend Fig. 8,

Fig. 9

eine Seitenansicht in Richtung des Pfeils X in Fig. 3,

Fig. 10

eine perspektivische Darstellung des Schalldämpferraums, wobei der Schalldämpfer nicht dargestellt ist,

Fig. 11

eine perspektivische Schnittdarstellung durch den Schalldämpferraum und das Motorgehäuse,

Fig. 12

eine Schnittdarstellung durch den Schalldämpferraum,

Fig. 13

eine schematische ausschnittsweise Seitenansicht von der dem Lüfterrad abgewandten Querseite des Schalldämpferraums.

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

Fig. 1

1 shows a perspective illustration of a hand-held implement in a parking position,

Fig. 2

is a schematic sectional view through the drive train of the implement Fig. 1 ,

Fig. 3

a partial side view of the motor housing of the implement Fig. 1 with cylinder and muffler, whereby a cover of the fan wheel housing is removed,

Fig. 4

a side view of the motor housing according to the illustration Fig. 3 , the fan wheel is not shown,

Fig. 5

3 shows a cutaway perspective view of the motor housing with a view into the fan wheel housing, the fan wheel not being shown,

Fig. 6

a partial sectional view through the motor housing and silencer,

Fig. 7

a fragmentary sectional view through the motor housing with an attached fan wheel along the line VII-VII in Fig. 6 ,

Fig. 8

a sectional view accordingly Fig. 7 , the fan wheel is not shown,

8a and 8b

Design variants in representations accordingly Fig. 8 ,

Fig. 9

a side view in the direction of arrow X in Fig. 3 ,

Fig. 10

a perspective view of the muffler room, the muffler is not shown,

Fig. 11

3 shows a perspective sectional view through the silencer chamber and the motor housing,

Fig. 12

a sectional view through the silencer room,

Fig. 13

is a schematic partial side view of the transverse side of the silencer chamber facing away from the fan wheel.

Fig. 1 shows as an embodiment of a hand-held implement 1 a chainsaw. However, the implement can also be another hand-held, preferably hand-carried implement 1, such as a cut-off machine, a brush cutter, a blower or the like. The implement 1 has a motor housing 2 and a handle housing 3, which have several in Fig. 1 schematically illustrated anti-vibration elements 11 are interconnected. The working device has an internal combustion engine 9, which can be partially formed in one piece with the motor housing 2. The internal combustion engine 9 is used to drive a tool of the implement 1. The internal combustion engine is advantageously a two-stroke engine. In the exemplary embodiment, the tool is a saw chain 8, which is arranged all round on a guide rail 7 held on the motor housing 2.

The implement 1 comprises a rear handle 4 and a grip tube 6 for guiding the implement 1 during operation. In the exemplary embodiment, the rear handle 4 and the handle tube 6 are part of the handle housing 3 and are thus vibration-decoupled from the internal combustion engine 9 via the anti-vibration elements 11. A gas lever 5 is pivotally mounted on the rear handle 4. The implement 1 also has two operating agent tanks, namely a fuel tank 10 and an oil tank 48. In the exemplary embodiment, the fuel tank 10 is formed on the handle housing 3. The oil tank 48 is formed on the motor housing 2. The internal combustion engine 9 has a silencer 12. The silencer 12 is advantageously arranged on the side of the implement 1 facing away from the rear handle 4.

Fig. 1 shows the implement 1 in a parking position 75. In the parking position 75, the implement 1 is on a flat, horizontally aligned storage surface 76 with a bottom provided for parking the implement or parking feet provided for this purpose. The parking position 75 is a stable position of the implement 1, in the rear handle 4 and handle tube 6 are easily accessible to the operator. The implement 1 has a starter device 21 for starting the internal combustion engine 9. In the exemplary embodiment, the starter device 21 is designed as a manual pull starter. An electrically operated starter device 21 can also be advantageous.

Fig. 2 shows the drive unit of the implement 1 in detail. The internal combustion engine 9 comprises a cylinder 13 and a crankcase 14. In the cylinder 13, a piston 15 is mounted reciprocally. The piston 15 drives, via a connecting rod 16, a crankshaft 17 which is rotatably mounted in the crankcase 14 about an axis of rotation 18. The crankshaft 17 is connected via a centrifugal clutch 19 to a drive pinion 20 which drives the saw chain 8. A fan wheel 22 is also connected in a rotationally fixed manner to the crankshaft 17. The starter device 21 acts on the crankshaft 17.

In the exemplary embodiment, the centrifugal clutch 19 and the drive pinion 20 are arranged on one side of the crankcase 14 and the fan wheel 22 and the starter device 21 on the opposite side of the crankcase 14.

To cool the internal combustion engine 9, cooling air is conveyed by the fan wheel 22 during operation. Fig. 3 shows the design of the cooling air flow in detail. How Fig. 3 shows, the fan wheel 22 is arranged in a fan wheel housing 23. The fan wheel housing 23 is of one of those in Fig. 3 crankcase 14, not shown ( Fig. 2 ) facing rear wall 25 and a circumferential limit 26 limited. In addition, a cover hood, not shown, advantageously covers the fan wheel housing 23. The cover advantageously has ventilation slots for cooling air drawn in by the fan wheel 22. The peripheral limitation 26 is advantageously designed as a peripheral wall. The fan wheel 22 is driven in a direction of rotation 24 during operation. In the exemplary embodiment, the direction of rotation 24 runs in the in FIG Fig. 3 shown view in the viewing direction parallel to the axis of rotation 18 and from the fan wheel 22 to the crankcase 14 counterclockwise. The circumferential limit 26 has a first end 27 and a second end 28. The circumferential limit 26 extends from the first end 27 in the direction of rotation 24 to the second end 28 advantageously largely without interruption. However, it can also be provided that the peripheral boundary 26 between the first end 27 and the second end 28 is interrupted or composed of several sections. An outlet opening 29 is formed in the direction of rotation 24 from the second end 28 to the first end 27. The outlet opening 29 is delimited by the first end 27 and the second end 28. No section of the circumferential boundary 26 is advantageously arranged in the outlet opening 29, so that the outlet opening 29 is not interrupted by the circumferential boundary 26.

During operation, cooling air conveyed by the fan wheel 22 flows through the outlet opening 29 to the cylinder 13 of the internal combustion engine 9. The cylinder 13 has a multiplicity of cylinder cooling fins 38, which in the exemplary embodiment run obliquely to a cylinder longitudinal axis 74. The cooling air flows from the outlet opening 29 to the cylinder 13 approximately in the direction of arrows 61 which in FIG Fig. 3 are shown schematically. Part of the cooling air can advantageously flow from the cylinder 13 to an upper side 73 of the muffler 12. The upper side 73 of the muffler 12 is the side which, in the storage position 75, lies away from the storage surface 76.

The peripheral boundary 26 and the rear wall 25 of the fan wheel housing 23 delimit an interior 41 of the fan wheel housing 23. The fan wheel is in the interior 41 22 arranged. The outlet opening 29 leads from the interior 41. The circumferential boundary 26 extends at least in a partial section 49 in a spiral around the axis of rotation 18 of the crankshaft 17 ( Fig. 2 ). In the exemplary embodiment, the spiral section 49 extends in the direction of rotation 24 from the first end 27 to an area 50. In the exemplary embodiment, the section 49 extends over a circumferential angle about the axis of rotation 18 of somewhat more than 90 °. In the section 49, the distance between the circumferential boundary 26 and the axis of rotation 18 increases. At the first end 27, the circumferential boundary 26 is at a distance a from the axis of rotation 18. At region 50, the circumferential boundary 26 is at a distance b from the axis of rotation 18. The distance b in region 50 is advantageously greater than the distance a in section 49.

In Fig. 3 a coordinate system with axes x and y is also shown. In the side view shown, looking parallel to the axis of rotation 18 of the crankshaft 17 ( Fig. 2 ) the origin of the coordinate system lies on the axis of rotation 18. The y-axis extends in the direction from the axis of rotation 18 to the second end 27. The x-axis is arranged at right angles thereto. The x-axis is aligned in such a way that the positive x-axis coincides with the positive y-axis after pivoting through 90 ° counterclockwise. The axes x and y divide the implement 1 into four sectors I, II, III and IV. Sector I is delimited by the positive y-axis and the negative x-axis, sector II by the negative x-axis and the negative y-axis, sector III from the positive x-axis and the negative y-axis and sector IV from the positive x-axis and the positive y-axis. The outlet opening 29 extends at least partially, in the exemplary embodiment completely in the fourth sector IV. The second end 28 of the circumferential boundary 26 is arranged in the fourth sector IV in the exemplary embodiment. The spiral section 49 of the circumferential boundary 26 extends in the first sector I. In the exemplary embodiment, the section 49 extends into the second sector II. It can also be provided that the spiral section 49 extends into the third sector III or up to the second End 28 extends. The silencer 12 is advantageously arranged in the first sector I. The oil tank 49 extends in the first sector I and in the second sector II. In Fig. 3 a tank cap 47 of the oil tank 48 is also shown.

How Fig. 3 shows, an ignition module 44 is arranged in the third sector III, which is connected via an ignition cable 45 to a spark plug 46 projecting into a combustion chamber of the internal combustion engine 9. The fan wheel 22 carries in Fig. 3 Magnets, not shown, which induce the ignition voltage for the spark plug 46 in the ignition module 44.

The second end 28 has the axis of rotation 18 of the crankshaft 17 ( Fig. 2 ) a distance c that is greater than the distance a and also greater than the distance b. It can be provided that the distance c is the greatest distance between the circumferential boundary 26 and the axis of rotation 18. In the exemplary embodiment, however, the circumferential limitation 26 in the area of the ignition module 44 is at an even greater distance from the axis of rotation 18, since in this area the flow cross section in the fan wheel housing 23 is reduced due to the ignition module 44. The rear wall 25 is advantageously closed except for one or more passage openings for cooling air, which will be described in more detail below. In the Fig. 3 shown, formed in the rear wall 25 receiving opening 58 for an anti-vibration element 11 is advantageously closed by the anti-vibration element.

How Fig. 3 shows, the rear wall 25 has a passage opening 30. The passage opening 30 is formed separately from the outlet opening 29. Additional cooling air is conducted to the silencer 12 through the passage opening 30. The passage opening 30 is an additional opening for cooling air. The muffler 12 is arranged in a muffler chamber 32, into which the passage opening 30 opens.

On the side 79 (based on the direction of rotation 24 behind the passage opening 30 ( Fig. 4 ) an opening 31 is advantageously arranged in the passage opening 30. The increase 31 points in the in Fig. 3 shown side view has an approximately triangular cross-section.

How Fig. 3 also shows, adjoins the peripheral boundary 26 at the second end 28, a partition 57, which one in Fig. 3 Intake chamber, not shown, of the internal combustion engine 9 is separated from the cylinder 13. An air filter and the fuel supply are advantageously arranged in the intake chamber. The fuel can advantageously be supplied via a carburetor arranged in the intake space or via a fuel valve. The fuel valve can also be arranged in the intake chamber. For cooling the intake space and / or for cooling a fuel valve, in Fig. 3 a cooling air opening 77 shown in dashed lines may be provided in the rear wall 25. The cooling air opening 77 is advantageously arranged in the third sector III and / or fourth sector IV, that is to say it is located significantly closer to the second end 28 than to the first end 27.

Fig. 4 shows the side view of the motor housing 2 Fig. 3 in sections and without the fan wheel 22 arranged in the fan wheel housing 23 Fig. 4 shows, the first end 27 has an angular distance a from the passage opening 30. The angular distance a is measured in the direction of rotation 24 starting from the first end 27 to the front side 78 of the passage opening 30 in the direction of rotation 24. The angular distance α is advantageously less than 120 °, in particular less than 90 °, preferably less than 60 °. In the exemplary embodiment, the angular distance α is less than 50 °. The angular distance β between the passage opening 30 and the second end 28, measured in the direction of rotation 24 starting from the passage opening 30, is significantly larger than the angular distance α. The angular distance β is measured from the side 79 of the passage opening 30 at the back in the direction of rotation to the second end 28 of the circumferential limit 26. The angular distance β is advantageously more than 90 °, in particular more than 180 °. In the exemplary embodiment, the angular distance β is more than 210 °. How Fig. 4 also shows, the elevation 31 is arranged adjacent to the rear side 79 of the passage opening 30. In Fig. 4 An air duct 54 arranged in the fan wheel housing 23 is also shown, which will be described in more detail below.

How Fig. 4 schematically shows with a dashed line, in an advantageous embodiment, a portion of the circumferential boundary 26 can be formed by a guide element 83 which projects into the fan wheel housing 23. The guide element 83 projects in particular approximately in the direction of the axis of rotation 18 of the crankshaft 17 or in the direction of the first end 27. The guide element 83 reduces the free flow cross section of the outlet opening 29. The second end 28 ′ of the circumferential boundary 26 is formed on the guide element 83. In this embodiment variant, the outlet opening 29 extends in the direction of rotation from the second end 28 ′ to the first end 27.

The increase 31 shows how Fig. 4 shows, seen in the direction of view parallel to the axis of rotation 18 of the crankshaft 17 an approximately triangular shape. Fig. 5 shows the design of the elevation 31 in detail. The elevation 31 has a contour 63 located at the front in the direction of rotation 24. The contour 63 advantageously corresponds to the circumferential course of the passage opening 30 and preferably merges into the circumferential wall of the passage opening 30. The contour 63 is designed as a flow guiding element which branches off part of the cooling air conveyed by the fan wheel 22. The increase 31 can advantageously extend over up to 50% of the free flow cross-section between the circumferential limit 26 and the fan wheel 22 at the passage opening 30. In an advantageous embodiment, the width of the increase decreases with increasing distance from the rear wall 25 of the fan wheel housing 23. The increase 31 is therefore narrower with increasing distance from the rear wall 25. In an advantageous embodiment, the elevation has an approximately triangular shape in the viewing direction approximately in the circumferential direction and approximately parallel to the circumferential boundary 26 at the passage opening 30. When looking in the parking position 75 ( Fig. 1 ) vertically downward an approximately triangular shape of the elevation 31.

How Fig. 5 also shows, the air guiding component 54 extends predominantly in the fourth sector IV and extends into the third sector III. How Fig. 5 shows, an air inlet opening 55 is formed on the air guide component 54, via which combustion air is branched off from a region of the interior 41 of the fan wheel housing 23, in FIG which the air has little pollution. The clean combustion air is guided into the intake space (not shown) via the air duct 54. The combustion air is then supplied with fuel for the operation of the internal combustion engine during operation. In the exemplary embodiment, the air duct 54 projects through the outlet opening 29 and thereby reduces the free flow cross section of the outlet opening 29.

Like the sectional view in Fig. 6 shows, the passage opening 30 opens into the muffler chamber 32. The muffler 12 has an underside 80 which, in the storage position 75 ( Fig. 1 ) is the area of the muffler 12 that has the smallest distance from the storage surface 76. A gap 35 is formed between the underside 80 and the motor housing 2. The intermediate space 35 is delimited by a wall 34 of the motor housing 2. In the exemplary embodiment, the wall 34 is a wall of the oil tank 48. A cooling fin 51 can be seen through the passage opening 30 and is described in more detail below.

How Fig. 7 shows, the cooling air exits from the interior 41 of the fan housing 32 through the passage opening 30 in a flow direction schematically indicated by an arrow 62 into the silencer chamber 32. The muffler 12 is adjacent to its underside 80 ( Fig. 6 ) on mounting domes 59 of the motor housing 2 ( Fig. 7 ) screwed. For this purpose, in Fig. 9 shown muffler screws 82 screwed into the mounting dome 59. In the exemplary embodiment, the fastening domes 59 are arranged in the intermediate space 35. How Fig. 7 also shows, the silencer chamber 32 is delimited by a first transverse side 39 and a second transverse side 40. The first transverse side 39 lies adjacent to the fan wheel housing 23. The second transverse side 40 lies on the opposite side, that is to say adjacent to that in FIG Fig. 7 not shown guide rail 7 ( Fig. 1 ). The transverse sides 39 and 40 run on the opposite longitudinal sides of the implement 1. In the exemplary embodiment, the transverse sides 39 and 40 are part of the engine housing 2. The transverse sides 39 and 40 of the muffler chamber 32 are advantageously formed on the crankcase 14 and extend as an extension of the transverse sides of the crankcase 14.

The fastening domes 59 are fixed on the transverse sides 39 and 40 of the silencer chamber 32. The fastening domes 59 and the silencer screws 82 are cooled by the air flowing into the silencer chamber 32 through the passage opening 30.

How Fig. 7 also shows, the crankcase 14 has a wall section 56 which delimits the silencer chamber 32. The wall section 56 simultaneously delimits the crankcase interior 81. The cylinder 13 ( Fig. 2 ) is fixed to the crankcase 14 by means of cylinder foot screws 37 which are screwed into bores 36 of the crankcase 14. In Fig. 7 three of the four cylinder foot screws 37 are shown. At least one cooling fin 51 is preferably arranged on the outside of the wall section 56 delimiting the silencer chamber 32. The at least one cooling fin 51 is advantageously formed on the wall section 56. The at least one cooling fin 51 is particularly advantageously arranged adjacent to a bore 36. Improved cooling of the cylinder foot screws 37 is thereby achieved. The cooling fin 51 preferably projects into the muffler space 32. In the exemplary embodiment, the cooling fin 51 extends up to the transverse side 40 and is at a distance from the transverse side 39. The stability of the motor housing 2 is simultaneously increased via the cooling fin 41.

The Fig. 7 and 8th also show the design of the passage opening 30 in detail. In the exemplary embodiment, the passage opening 30 extends both into the rear wall 25 and into the circumferential boundary 26. As a result, the cooling air flows out of the interior 41 in a direction oblique to the axis of rotation 18 into the muffler chamber 32. The vector of the flow direction accordingly has both directional components parallel to the axis of rotation 18 and directional components perpendicular to the axis of rotation 18. This orientation of the direction of flow allows both the cylinder foot screws 37 and the muffler screws 82 to be well cooled by the cooling air flowing into the muffler chamber 32.

The 8a and 8b show alternative designs of the passage opening. Fig. 8a shows a passage opening 64 which extends exclusively into the rear wall 25. In this configuration, the cooling air flows in the direction of an arrow 65 approximately parallel to the axis of rotation 18 into the muffler chamber 32. The arrow 65, which corresponds to the vector of the main flow direction, has no or only very small directional components perpendicular to the axis of rotation 18.

In the embodiment according to Fig. 8b a passage opening 66 is provided which extends exclusively in the circumferential boundary 26. The cooling air flows through this passage opening 66 in the direction of an arrow 67, which is approximately perpendicular to the axis of rotation 18. The arrow 67 is the vector of the main flow direction and has no or only very small directional components parallel to the axis of rotation 18. By changing the position of the passage opening 30, 64, 66, the main flow direction of the cooling air exiting into the silencer chamber 32 can be changed. In a particularly advantageous embodiment, the passage opening 30, 64 extends at least partially into the rear wall 25, so that the muffler 12 is cooled over its entire width in the region of its underside 80.

Fig. 9 shows the arrangement of the muffler 12 in the muffler room 32. How Fig. 9 shows, the gap 35 is formed between the bottom 80 and the wall 34 of the oil tank 48. The muffler 12 largely fills the muffler space 32 between the transverse sides 39 and 40, so that an approximately uniform gap is formed around the muffler 12, through which the cooling air can flow.

How Fig. 10 shows, a silencer plate 68 is fixed to the cylinder 13. The muffler plate 68 has an opening 70 which is arranged at an outlet 71 of the cylinder 30. The exhaust gases of the internal combustion engine 9 pass through the opening 70 from the cylinder 13 into the muffler 12 ( Fig. 9 ) out. The muffler plate 68 has a plurality of stiffening beads 69 to increase the stability. How Fig. 10 shows, the muffler plate 68 protrudes laterally up to the transverse sides 39 and 40. A passage of cooling air from cylinder 13 directly to underside 80 ( Fig. 9 ) of the silencer 12 is largely avoided. The underside 80 of the muffler 12 is cooled by cooling air, which passes directly through the passage opening 30 from the interior 41 of the muffler housing 23 into the muffler chamber 32. The underside 80 of the muffler 12 is therefore cooled with cooling air which has not been previously heated by the cylinder 13. The cylinder 13 and the underside 80 of the muffler 12 are cooled by separate cooling air flows.

In Fig. 10 the partition 57 to the suction space is also shown. How Fig. 10 also shows, the fastening dome 59, which is held on the wall 34 and the transverse side 39 of the muffler chamber 32, has a cooling fin 60 with which it is supported on the wall 34. The in Fig. 10 Fastening dome 59, not shown, on the transverse side 40 is provided with a cooling fin 60 in a corresponding manner. On the one hand, this increases the stability of the connection of the fastening dome 59 and, on the other hand, improves the cooling of the fastening dome 59. How Fig. 10 also shows, further cooling fins 53 are provided on the transverse side 39. The cooling fins 53 are guided along the outside of the circumferential boundary 26 and the rear wall 25 of the fan housing 22 and improve the cooling on the transverse side 39. The longitudinal direction of the cooling fins 53 runs approximately parallel to the axis of rotation 18. The cooling fins 53 project from the rear of the rear wall 25 and the circumferential limit 26 in the silencer chamber 32.

Fig. 11 shows the arrangement of the cooling fins 51 on the transverse side 40 and the arrangement of the cooling fins 53 on the opposite transverse side 39 Fig. 11 also shows, the passage opening 30 is arranged in a section 33 of the rear wall 25, which delimits the interior 41 of the fan wheel housing 23 with one side 42 and the silencer chamber 32 with the opposite side 43. The air thereby flows out of the interior 41 through the section 33 the rear wall 25 directly into the silencer chamber 32.

How Fig. 12 shows, the motor housing 2 has a parting plane 72. In the exemplary embodiment, two cooling fins 51 are provided. The cooling fin 51 arranged adjacent to the wall 34 extends approximately to the parting plane 72. The cooling fin 51 further away from the wall 34 is shorter and in the exemplary embodiment does not extend to the parting plane 72. In the exemplary embodiment, the cooling fins 53 are comparatively short and end at a distance from the parting plane 72. However, cooling fins 53 ′ which are shown schematically can also be provided, which extend further in the direction of the transverse side 40, preferably up to approximately at the parting plane 72.

Fig. 13 shows a side view of the transverse side 40 as seen from the opposite transverse side 39. How Fig. 13 shows, the cooling fins 51 protrude close to the mounting dome 59 of the silencer 12. Fig. 13 also shows the cooling fin 60 on the fastening dome 59 on the second transverse side 40 Fig. 13 also shows, the wall 34 can also carry further cooling fins 52 which in Fig. 13 are shown schematically. The cooling fins 52 protrude from the wall 34 into the muffler chamber 32. The cooling fins 52 are preferably inclined to the wall 34 at an angle of less than 90 °. The inclination of the cooling fins 52 is advantageously provided such that the cooling fins 52 have a smaller distance from the wall section 56 of the crankcase 41 with increasing distance from the wall 34.

In the exemplary embodiment, the cooling fins 51 run parallel to the wall 34 of the muffler chamber 32, while the cylinder cooling fins 38 run inclined thereto. This is particularly true in Fig. 6 recognizable. The cooling fins 51, which are integrally formed on the crankcase 14, accordingly do not run parallel to the cylinder cooling fins 38.

Because the wall 34 carries the fastening domes 59 for the muffler 12, the fastening domes 59 are well cooled via the cooling air flow emerging through the passage opening 30. In the exemplary embodiment, the cooling fins 51, 52, 53, 53 ' formed as elongated ribs. However, cruciform or differently shaped cooling fins can also be advantageous.

The passage opening 30 enables largely separate cooling air flows for the cylinder 13 and the muffler 12, in particular for the underside 80 of the muffler 12. This improves the cooling of the muffler 12. Because the passage opening 30 is only a small circumferential distance from the first end 27 of the circumferential boundary 26, the passage opening 30 does not result in a reduction in the amount of air conveyed through the outlet opening 29, but rather increases the total amount of air conveyed by the fan wheel 22.

The passage opening 30 is advantageously significantly smaller than the outlet opening 29. The flow cross section of the passage opening 30 is preferably less than 50%, in particular less than 30% of the outlet opening 29. The flow cross section of the passage opening 30 is advantageously less than 16 cm ² , in particular less than 9 cm ² . The passage opening 30 can have a circular or elliptical cross section. Another cross-sectional shape for the passage opening 30, in particular a rectangular cross-sectional shape or a cross-sectional shape similar to a rectangular cross-sectional shape, can, however, be advantageous.

Claims (15)

1. Hand-guided working implement with an internal combustion engine (9) and with a fan impeller (22) for conveying cooling air for the internal combustion engine (9), wherein the internal combustion engine (9) has a cylinder (13) and a crankcase (14), wherein the fan impeller (22) is located in an impeller housing (23) and driven to rotate in a direction of rotation (24) by the internal combustion engine (9), wherein the impeller housing (23) has a rear wall (25) facing the crankcase (14) of the internal combustion engine (9) and a circumferential boundary (26), wherein the circumferential boundary (26) has a first end (27) and a second end (28, 28'), wherein the first end (27) and the second end (28, 28') bound a discharge opening (29) for cooling air to be conveyed to the cylinder (13), wherein the discharge opening (29) extends in the direction of rotation (24) from the second end (28, 28') to the first end (27), wherein the impeller housing (23) is provided with an additional through-opening (30, 64, 66), through which the cooling air flows from the impeller housing (23) to the outside of the crankcase (14), wherein the angular distance (α) between the first end (27) and the through-opening (30, 64, 66), as measured in the direction of rotation (24) from the first end (27), is less than the angular distance (β) between the through-opening (30, 64, 66) and the second end (28, 28'), as measured in the direction of rotation (24) from the through-opening (30, 64, 66), wherein the angular distance (α, β) is in each case measured as a circumferential angle about the axis of rotation (18), characterised in that the through-opening (30, 64, 66) at least partially extends into the rear wall (25) of the impeller housing (23).
2. Working implement according to claim 1,
   characterised in that the angular distance (α) between the first end (27) and the through-opening (30, 64, 66), as measured in the direction of rotation (24) from the first end (27), is less than 120°.
3. Working implement according to claim 1 or 2,
   characterised in that the through-opening (30, 66) at least partially extends into the circumferential boundary (26) of the impeller housing (23).
4. Working implement according to any of claims 1 to 3,
   characterised in that an elevation (31) extending into the impeller housing (23) is located on the side (79) of the through-opening (30, 64, 66) which is at the rear in the direction of rotation (24) of the fan impeller (22).
5. Working implement according to any of claims 1 to 4,
   characterised in that the internal combustion engine (9) has a silencer (12), wherein the silencer (12) is located in a silencer chamber (32) and wherein the through-opening (30, 64, 66) connects the interior of the impeller housing (23) to the silencer chamber (32).
6. Working implement according to claim 5,
   characterised in that a section (33) of a wall of the impeller housing (23) bounds with one side (42) the interior (41) of the impeller housing (23) and with the opposite side (43) the silencer chamber (32), wherein the through-opening (30, 64, 66) is located in said section (33) of the wall of the impeller housing (23).
7. Working implement according to claim 5 or 6,
   characterised in that a gap (35), into which cooling air flows from the through-opening (30, 64, 66), is formed between the silencer (12) and a wall (34) of an engine housing (2) of the working implement.
8. Working implement according to any of claims 5 to 7,
   characterised in that at least one cooling fin (51, 52, 53) projecting into the silencer chamber (32) is provided.
9. Working implement according to claim 8,
   characterised in that the cylinder (13) is fixed to the crankcase (14) by at least one cylinder base screw (37), wherein the cylinder base screw (37) extends into a bore (36) in the crankcase (14), and in that the at least one cooling fin (51) is located at the outside of the wall section (56) of the crankcase (14) which adjoins the bore (36).
10. Working implement according to claim 8 or 9,
    characterised in that the at least one cooling fin (51) extends parallel to the wall (34) of the engine housing (2) which bounds the gap (35).
11. Working implement according to any of claims 8 to 10,
    characterised in that the at least one cooling fin (52) is located at the wall (34) of the engine housing (2) which bounds the gap (35).
12. Working implement according to any of claims 8 to 11,
    characterised in that the silencer chamber (32) has a first transverse side (39), which is adjacent to the impeller housing (23), in that the silencer chamber (32) has a second transverse side (40), which is located opposite the first transverse side (39), and in that the at least one cooling fin (51, 52) extends to the first transverse side (39).
13. Working implement according to any of claims 1 to 12,
    characterised in that the at least one cooling fin (53) is located on the second transverse side (40) of the silencer chamber (32).
14. Working implement according to any of claims 1 to 13,
    characterised in that the distance (a, c) of the circumferential boundary (26) from the axis of rotation (18) is smaller at the first end (27) than at the second end (28, 28').
15. Working implement according to any of claims 1 to 14,
    characterised in that the circumferential boundary (26) is helical in at least a subsection (49), wherein the distance (a, c) of the circumferential boundary (26) from the axis of rotation (18) of the impeller (22) increases in the subsection (49) in the direction of rotation (24) of the impeller (22).

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