Hand-held working tool

• US 6,314,922 B1
• Filed: 07/23/1999
• Issued: 11/13/2001
• Est. Priority Date: 07/23/1998
• Status: Expired due to Fees

• Current Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Original Assignee: Andreas STIHL AG & Company KG (Stihl Holding AG & Company KG)
• Inventors: Stücke, Peter, Zimmermann, Helmut, Schliemann, Harald, Geyer, Werner, Schlossarczyk, Jörg, Stein, Gunter, Klimmek, Axel, Dürr, Bernhard, Nickel, Hans
• Primary Examiner(s): Wolfe, Willis R.
• Assistant Examiner(s): Benton, Jason
• Application Number:
  US09/360,107
• Time in Patent Office: 844 Days
• Field of Search: 123/41.56, 123/41.63, 123/41.65, 123/41.66, 123/41.7
• US Class Current: 123/41.65
• CPC Class Codes: B25F 5/008 Cooling means
• CPC Class Codes: B27B 17/00 Chain saws; Equipment therefor slotting or mortising machines equipped with chain cutters B27F5/06
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F02B 63/02 for hand-held tools
• CPC Class Codes: F02M 35/10013 Means upstream of the air filter; Connection to the ambient air
• CPC Class Codes: F02M 35/1017 Small engines, e.g. for handheld tools, or model engines; Single cylinder engines
• CPC Class Codes: F02M 35/10262 Flow guides, obstructions, deflectors or the like for generating a charge motion in the cylinder F02B31/00; for re-atomising condensed fuel or homogenising fuel-air mixture F02M29/00
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A hand-held working tool has a housing and an internal combustion engine arranged in the housing and comprising a crankshaft and an air filter. A tool is driven by the crankshaft of the internal combustion engine. A fan housing is attached to the engine housing and has an air inlet. A fan wheel is arranged in the fan housing and is driven by the crankshaft of the internal combustion engine to supply cooling air, sucked in through the air inlet, to the internal combustion engine. The fan housing has a bottom extending radially to the crankshaft. The bottom and a side of the fan wheel facing the bottom define a chamber in the fan housing. The bottom has a combustion air outlet. A combustion air channel is connected to the combustion air outlet and to the air filter. The combustion air outlet is axially supplying combustion air from the chamber through the combustion air channel into the air filter of internal combustion engine. The fan housing has a channel wall having a bottom portion connected to the face of the bottom remote from the fan wheel and covering the bottom partially to form a double-walled bottom. The end face portion of the combustion air channel is defined by the bottom and the bottom portion of the channel wall. In an alternative embodiment the combustion air channel is provided in a hollow beam of a support that supports the drive unit of the working tool.

Claims

1. A hand-held working tool comprising:

an engine housing (17);

an inter combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4), wherein said bottom (7) is positioned directly adjacent to said internal combustion engine (2) and said crankshaft (4), such that said fan housing (6) has a minimal axial depth;

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein said combustion air channel is provided at an end face portion (9s) of said fan housing (6), said combustion air channel (9, 9u, 9s) defined by said bottom (7) and said portion (8s).

2. A working tool according to claim 1, wherein said fan housing (6) has a circumferential wall (12) covering said fan wheel (5) in an axial direction of said fan housing (6), wherein said channel wall (8, 8u, 8s) has a tangential portion (8u) projecting tangentially past a periphery of said bottom (7) and projecting axially past said bottom (7) in a direction toward said circumferential wall (12), wherein said tangential portion (8u) of said channel wall (8, 8u, 8s) is connected to said circumferential wall (12) at a spacing such that said tangential portion (8u) and said circumferential wall (12) form a circumferential portion (9u) of said combustion air channel (9, 9u, 9s).

3. A working tool according to claim 2, wherein said end face portion (9s) of said combustion air channel (9) has a flow cross-section decreasing continuously in a flow direction of said combustion air and wherein said circumferential portion (9u) has a widened flow cross-section relative to said end face portion (9s).

4. A working tool according to claim 2, wherein said circumferential portion (9u) of said combustion air channel (9) forms the end of said combustion air channel connected to said air filter device (18, 19, 20).

5. A working tool according to claim 2, further comprising an elastic bellows (16), wherein said combustion air channel (9, 9u, 9s) has an end socket (14) connected to said fan housing (6) and wherein said air filter device (18, 19, 20) is connected to said end socket (14) by said elastic bellows (16) positioned adjacent to said internal combustion engine (2), wherein said elastic bellows (16) is attached to a circumferential edge (15) of said end socket (14) and bridges a vibration gap.

6. A working tool according to claim 5, wherein said air filter device (18, 19, 20) comprises an air filter box (19) having a dirt chamber (21) and wherein said elastic bellows (16) is connected to said dirt chamber (21) of said air filter box (19).

7. A working tool according to claim 5, wherein said circumferential wall (12) has a cutout forming a cooling air outlet (22), wherein said end socket (14) is positioned adjacent to said cutout (22).

14. A working tool according to claim 1, wherein said fan wheel (5) has a radial wall (36) having a first face with a first vane arrangement (30) and a second face with a second vane arrangement (31), wherein said first vane arrangement (30) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10).

15. A working tool according to claim 14, wherein said first vane arrangement (31) has curved vanes having an axial length that is greater than an axial length of said radial vanes (34).

16. A working tool according to claim 14, wherein an axial height of said radial vanes (34) is at least one fourth of a spacing between said bottom (7) and said radial wall (36).

17. A working tool according to claim 14, wherein a central portion of said radial wall (36) is curved away from said bottom (7).

18. A working tool according to claim 14, wherein said first face of said radial wall (36) has an auxiliary axial blower vane arrangement (37) passing across said combustion air outlet (11).

19. A working tool according to claim 14, wherein said first face of said radial wall (36) is radially covered by a cover plate (40) fastened to said fan wheel (5), wherein said cover plate (40) has penetrations (38) and wherein between said cover plate (40) and said bottom (7) radially outwardly of said combustion air outlet (11) a non-dragging seal 39 of said chamber (10) is arranged.

20. A working tool according to claim 14, wherein said fan wheel (5) has at least one ignition solenoid (49) positioned at the periphery of said fan wheel 95), wherein said at least one ignition solenoid (49) is positioned within said second vane arrangement (30) and extends axially at least to said radial wall (36).

21. A working tool according to claim 14, wherein said radial vanes (34) of said second vane arrangement (30) have a cross-section increasing in a radial outward direction of said fan wheel (5) and are symmetrical to a radial axis (35) of said fan wheel.

31. A working tool according to claim 1, wherein said combustion air channel (9) branches substantially tangentially to a rotational direction (60) of said fan wheel (5) away from said fan housing (6) and extends linearly to said air filter device (18, 19, 20).

32. A working tool according to claim 31, wherein said combustion air channel (9) has a flow cross-section widening continuously in a flow direction of the combustion air, wherein an outlet cross-section of said combustion air channel (9) adjacent to said air filter device (18, 19, 20) is four to six times as large as an inlet cross-section of said combustion air channel (9).

33. A working tool according to claim 31, wherein said outlet opening (11) extends arc-shaped in said rotational direction (60) and has a rearward end (52) and a forward end (51) in said rotational direction (60), wherein said rearward end (52) is adjacent to a plane (28) of a lateral surface (55) of said combustion air channel (9) facing said crankshaft (4) and wherein said forward end (51) is positioned at a side of said crankshaft (4) opposite said combustion engine (2).

34. A working tool according to claim 33, wherein said combustion air channel (9) widens in said flow direction parallel to said housing bottom (7) and at said forward end (51) is flat in an axial direction of said crankshaft (4), wherein said double-walled bottom (54) has a spacing to said housing bottom (7) that increases within an angular distance of said arc-shaped outlet opening (11), wherein said spacing is preset according to a mounting space of a crankcase of said internal combustion engine (2) positioned adjacent to said housing bottom (7).

35. A working tool according to claim 31, wherein said combustion air channel (9) has an axial projection (57) projecting from said housing bottom (7) into said fan housing (6), said axial projection (57) having an end face extending parallel to a plane of said housing bottom (7).

36. A working tool according to claim 31, wherein said fan housing (6) has a circumferential wall (12) covering axially said fan wheel (5), wherein said channel wall (8) is connected at a location opposite a plane of said housing bottom (7) to said circumferential wall (12) of said fan housing (6).

37. A working tool according to claim 31, wherein a volume of an air filter box (19) of said air filter device is at least five times a displacement of said internal combustion engine (2).

8. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s);

said fan housing (6) further having a circumferential wall (12) covering said fan wheel (5) in an axial direction of said fan housing (6), wherein said channel wall (8, 8u, 8s) has a tangential portion (8u) projecting tangentially past a periphery of said bottom (7) and projecting axially past said bottom (7) in a direction toward said circumferential wall (12), wherein said tangential portion (8u) of said channel wall (8, 8u, 8s) is connected to said circumferential wall (12) at a spacing such that said tangential portion (8u) and said circumferential wall (12) form a circumferential portion (9u) of said combustion air channel (9, 9u, 9s).

9. A working tool according to claim 8, wherein said combustion air outlet (11) is located in said bottom (7), relative to said crankshaft (4), opposite said internal combustion engine (2).

10. A working tool according to claim 8, wherein a spacing of a radially outer edge of said combustion air outlet (11) to an axis of said crankshaft (4) is 0.5 to 1.4 times a radius of said fan wheel (5).

11. A working tool according to claim 8, wherein said combustion air outlet (11) has a main extension in a circumferential direction of said bottom (7).

12. A working tool according to claim 8, wherein said fan housing (6) is comprised of a base member, including said bottom (7) and said circumferential wall (12), and an end face member (46) comprising said bottom portion (8s) of said channel wall.

13. A working tool according to claim 8, wherein said fan housing (6) is a guide spiral opening toward said combustion engine (2).

22. A hand-held working tool comprising:

an engine housing (17);

a drive unit 50 including an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a support (13) to which said drive unit (50) is connected;

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a face (33) of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20) said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9) into said air filter device (18, 19, 20) of said internal combustion engine (2);

wherein said support (13) includes a hollow beam (13) and wherein said combustion air channel (9) extends inside said hollow beam (13).

23. A working tool according to claim 22, wherein said fan wheel (5) has a radial wall (36) having a first face with a first vane arrangement (30) and a second face with a second vane arrangement (31), wherein said first vane arrangement (30) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10).

24. A working tool according to claim 23, wherein said first vane arrangement (31) has curved vanes having an axial length that is greater than an axial length of said radial vanes (34).

25. A working tool according to claim 23, wherein an axial height of said radial vanes (34) is at least one fourth of a spacing between said bottom (7) and said radial wall (36).

26. A working tool according to claim 23, wherein a central portion of said radial wall (36) is curved away from said bottom (7).

27. A working tool according to claim 22, wherein said first face of said radial wall (36) has an auxiliary axial blower vane arrangement (37) passing across said combustion air outlet (11).

28. A working tool according to claim 22, wherein said first face of said radial wall (36) is radially covered by a cover plate (40) fastened to said fan wheel (5), wherein said cover plate (40) has penetrations (38) and wherein between said cover plate (40) and said bottom (7) radially outwardly of said combustion air outlet (11) a non-dragging seal 39 of said chamber (10) is arranged.

29. A working tool according to claim 22, wherein said fan wheel (5) has at least one ignition solenoid (49) positioned at the periphery of said fan wheel 95), wherein said at least one ignition solenoid (49) is positioned within said second vane arrangement (30) and extends axially at least to said radial wall (36).

30. A working tool according to claim 23, wherein said radial vanes (34) of said second vane arrangement (30) have a cross-section increasing in a radial direction toward an axis of said crankshaft (4) and are symmetrical to a radial axis (35) of said fan wheel (5).

38. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s);

said fan wheel (5) having a radial wall (36) having a first face with a first vane arrangement (3) and a second face with a second vane arrangement (31), wherein said first vane arrangement (3) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10), wherein said first face of said radial wall (36) is radially covered by a cover plate (4) fastened to said fan wheel (5), wherein said cover plate (4) has penetrations (38) and wherein between said cover plate (4) and said bottom (7) radially outwardly of said combustion air outlet (11) a non-dragging seal 39 of said chamber (10) is arranged.

39. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s);

said fan wheel (5) having a radial wall (36) having a first face with a first vane arrangement (3) and a second face with a second vane arrangement (31), wherein said first vane arrangement (3) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10), said fan wheel (5) having at least one ignition solenoid (49) positioned at the periphery of said fan wheel (5), wherein said at least one ignition solenoid (49) is positioned within said second vane arrangement (30) and extends axially at least to said radial wall (36).

40. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20), wherein said combustion air channel (9) branches substantially tangentially to a rotational direction (60) of said fan wheel (5) away from said fan housing (6) and extends linearly to said air filter device (18, 19, 20), and wherein said combustion air channel (9) has a flow cross-section widening continuously in a flow direction of the combustion air, wherein an outlet cross-section of said combustion air channel (9) adjacent to said air filter device (18, 19, 20) is four to six times as large as an inlet cross-section of said combustion air channel (9);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s).

41. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20)), wherein said combustion air channel (9) branches substantially tangentially to a rotational direction (60) of said fan wheel (5) away from said fan housing (6) and extends linearly to said air filter device (18, 19, 20), wherein said combustion air outlet (11) extends arc-shaped in said rotational direction (60) and has a rearward end (52) and a forward end (51) in said rotational direction (60), wherein said rearward end (52) is adjacent to a plane (28) of a lateral surface (55) of said combustion air channel (9) facing said crankshaft (4) and wherein said forward end (51) is positioned at a side of said crankshaft (4) opposite said combustion engine (2);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s).

42. A hand-held working tool comprising:

an engine housing (17);

an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20);

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a side of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20), wherein said combustion air channel (9) branches substantially tangentially to a rotational direction (60) of said fan wheel (5) away from said fan housing (6) and extends linearly to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9, 9u, 9s) into said air filter device (18, 19, 20) of said internal combustion engine (2);

said fan housing (6) having a channel wall (8, 8u, 8s) having a bottom portion (8s) connected to a face of said bottom (7) remote from said fan wheel (5) and covering said bottom (7) partially to form a double-walled bottom, wherein an end face portion (9s) of said combustion air channel (9, 9u, 9s) is defined by said bottom (7) and said bottom portion (8s), said fan housing (6) having a circumferential wall (12) covering axially said fan wheel (5), wherein said channel wall (8) is connected at a location opposite a plane of said housing bottom (7) to said circumferential wall (12) of said fan housing (6).

43. A hand-held working tool comprising:

an engine housing (17);

a drive unit (50) including an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20)

a support (13) to which said drive unit (50) is connected;

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a face (33) of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9) into said air filter device (18, 19, 20) of said internal combustion engine (2);

wherein said support (13) includes a hollow beam (13) and wherein said combustion air channel (9) extends inside said hollow beam (13);

said fan wheel (5) having a radial wall (36) having a first face with a first vane arrangement (3) and a second face with a second vane arrangement (31), wherein said first vane arrangement (3) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10), said first face of said radial wall (36) radially covered by a cover plate (40) fastened to said fan wheel (5), wherein said cover plate (4) has penetrations (38) and wherein between said cover plate (4) and said bottom (7) radially outwardly of said combustion air outlet (11) a non-dragging seal (39) of said chamber (10) is arranged.

44. A hand-held working tool comprising:

an engine housing (17);

a drive unit (50) including an internal combustion engine (2) arranged in said engine housing (17) and comprising a crankshaft (4) and an air filter device (18, 19, 20)

a support (13) to which said drive unit (50) is connected;

a tool (41) driven by said crankshaft (4) of said internal combustion engine (2);

a fan housing (6) attached to said engine housing (2) and having an air inlet;

a fan wheel (5) arranged in said fan housing (6);

said fan wheel (5) driven by said crankshaft (4) of said internal combustion engine (2) to supply cooling air, sucked in through said air inlet, to said internal combustion engine (2);

said fan housing (6) having a bottom (7) extending radially to said crankshaft (4);

said bottom (7) and a face (33) of said fan wheel (5) facing said bottom (7) defining a chamber (10) in said fan housing (6);

said bottom (7) having a combustion air outlet (11);

a combustion air channel (9, 9u, 9s) connecting said combustion air outlet (11) to said air filter device (18, 19, 20);

said combustion air outlet (11) axially supplying combustion air from said chamber (10) through said combustion air channel (9) into said air filter device (18, 19, 20) of said internal combustion engine (2);

wherein said support (13) includes a hollow beam (13) and wherein said combustion air channel (9) extends inside said hollow beam (13);

said fan wheel (5) having a radial wall (36) having a first face with a first vane arrangement (3) and a second face with a second vane arrangement (31), wherein said first vane arrangement (3) sucks in the cooling air for said internal combustion engine (2) and wherein said second vane arrangement faces said bottom (7) and has radial vanes (34) projecting into said chamber (10), said fan wheel (5) having at least one ignition solenoid (49) positioned at the periphery of said fan wheel (5), wherein said at least one ignition solenoid (49) is positioned within said second vane arrangement (30) and extends axially at least to said radial wall (36).