Starter device for an internal combustion engine and handheld work apparatus having an internal combustion engine and said starter device

Abstract

A starter device for an internal combustion engine has an entrainer for coupling to the engine. The entrainer and an actuator of the starter device are mounted rotatably about a rotational axis. A damper spring is arranged between and operatively connects the entrainer and the actuator to each other. The starter device has at least one stud, on whose outer periphery the damper spring is mounted. The damper spring is a hinge spring wound from a spring wire. The cross section of the spring wire is rounded on the inner side of the spring wire. At least a portion of the cross section runs linearly on the outer side of the spring wire.

Claims

1. A starter device for an internal combustion engine having a crankshaft and defining a rotational axis, the starter device comprising: an actuator configured to permit rotation to be imparted thereto to start said engine; an entrainer having at least one coupling unit for coupling to said crankshaft of said engine; said entrainer and said actuator being rotatably mounted about said rotational axis; a damper spring arranged between and operatively connecting said entrainer and said actuator to each other; at least one stud having an outer periphery; said damper spring being mounted on said outer periphery of said stud; said damper spring being a hinge spring wound from spring wire and said spring wire being wound to include a plurality of turns; said damper spring being tensioned when starting said internal combustion engine whereupon said damper spring becomes tight onto said stud; said damper spring defining a section plane containing said rotational axis; said spring wire having a cross section in said section plane; in said cross section, said spring wire having an axially measured width (e) and a radially measured thickness (d, g, h); in said cross section, said spring wire further having a radially inner-lying inner side and a radially outer-lying outer side; in said cross section, said inner side of said spring wire being a rounded inner side with said rounded inner side being in contact engagement with said outer periphery of said stud; at least a portion of said cross section running linearly at said outer side of said spring wire; and, said outer side of said spring wire lying exposed over at least half of said turns so as not to be in contact engagement with adjacent components.

2. The starter device of claim 1, wherein said inner side of said spring wire runs in a through radius (r).

3. The starter device of claim 2, wherein said radius (r) of said inner side is greater than half of said width (e).

4. The starter device of claim 1, wherein said at least a portion of said cross section extends over at least 30% of said width (e).

5. The starter device of claim 1, wherein said spring wire has transverse sides running transversely to said rotational axis and said at least a portion of said cross section runs linearly at said transverse sides.

6. The starter device of claim 5, wherein said spring wire has respective transitions whereat said outer side runs into corresponding ones of said transverse sides with a radius (s, t).

7. The starter device of claim 6, wherein said radius (s, t) of said transitions is less than one quarter of said width (e) of said spring wire.

8. The starter device of claim 1, wherein said thickness (d, g, h) is at least as large as said width (e) of said spring wire.

9. The starter device of claim 1, wherein said stud is a first stud configured to be part of said actuator; and, said starter device further comprises a second stud configured to be part of said entrainer and said second stud has an outer periphery; and, said actuator and said entrainer are mounted so as to cause the respective outer peripheries thereof to conjointly accommodate said damper spring thereon.

10. The starter device of claim 1, wherein said damper spring defines an essentially constant turns diameter (f).

11. The starter device of claim 1, wherein said damper spring has first and second end segments bent over inwardly; and, said damper spring is held on said actuator with said first end segment and held on said entrainer with said second end segment.

12. The starter device of claim 1, wherein said at least one of said studs has depressions formed in the outer periphery thereof.

13. The starter device of claim 1, wherein said coupling unit includes at least one pawl pivotally mounted on said entrainer and a cam contour fixedly mounted on said crankshaft so as to rotate therewith; and, said pawl and said cam contour are configured to coact to couple said starter device to said crankshaft.

14. The starter device of claim 1, wherein said actuator is a rope pulley which is configured so as to permit rotation to be manually imparted thereto with a pull rope.

15. A handheld work apparatus comprising: an internal combustion engine having a crankshaft and defining a rotational axis; a starter device for said engine; said starter device including: an actuator configured to permit rotation to be imparted thereto to start said engine; and, an entrainer having at least one coupling unit for coupling to said crankshaft of said engine; said entrainer and said actuator being rotatably mounted about said rotational axis; a damper spring arranged between and operatively connecting said entrainer and said actuator to each other; said starter device further including at least one stud having an outer periphery; said damper spring being mounted on said outer periphery of said stud; said damper spring being a hinge spring wound from spring wire; said damper spring defining a section plane containing said rotational axis; said spring wire having a cross section in said section plane; in said cross section, said spring wire having an axially measured width (e) and a radially measured thickness (d, g, h); in said cross section, said spring wire further having a radially inner-lying inner side and a radially outer-lying outer side; in said cross section, said inner side of said spring wire being a rounded inner side; and, at least a portion of said cross section running linearly at said outer side of said spring wire.

16. A starter device for an internal combustion engine having a crankshaft and defining a rotational axis, the starter device comprising: an actuator configured to permit rotation to be imparted thereto to start said engine; an entrainer having at least one coupling unit for coupling to said crankshaft of said engine; said entrainer and said actuator being rotatably mounted about said rotational axis; a damper spring arranged between and operatively connecting said entrainer and said actuator to each other; at least one stud having an outer periphery; said damper spring being mounted on said outer periphery of said stud; said damper spring being a hinge spring wound from spring wire and said spring wire being wound to include a plurality of turns; said damper spring defining a section plane containing said rotational axis; said spring wire having a cross section in said section plane; in said section plane, said spring wire having an axially measured width (e) and a radially measured thickness (d, g, h); in said cross section, said spring wire further having a radially inner-lying inner side and a radially outer-lying outer side; said damper spring being mounted between said entrainer and said actuator so as to cause the outer diameter of said damper spring to be reduced when said actuator is actuated by an operator with said outer-lying outer side of said spring wire being exposed over at least half of said turns and lying at a spacing away from adjacent components; in said cross section, said inner side of said spring wire being a rounded inner side; and, at least a portion of said cross section running linearly at said outer side of said spring wire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the drawings wherein:

(2) FIG. 1 is a schematic side elevation view of a motor-driven chain saw;

(3) FIG. 2 is a schematic section view through the motor-driven chain saw of FIG. 1;

(4) FIG. 3 is an exploded representation of the starter device of the motor-driven chain saw of FIGS. 1 and 2;

(5) FIG. 4 is a perspective view of the starter device of FIG. 3;

(6) FIG. 5 is a schematic of the coupling means of the starter device of FIGS. 3 and 4;

(7) FIG. 6 is a schematic through the starter device;

(8) FIG. 7 is a schematic side elevation view of the studs of the starter device;

(9) FIG. 8 is a section view showing the cross section of the spring wire of the damper spring of the starter device; and,

(10) FIGS. 9 and 10 are schematics of embodiments of the cross section of the spring wire of the damper spring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(11) FIG. 1 shows a motor-driven chain saw as a work apparatus having a starter device. The motor-driven chain saw 1 is configured as a handheld, manually operated work apparatus and has a housing 2, on which a rear handle 3 and a bale handle 4 are mounted. The motor-driven chain saw 1 has a guide bar 5 on which a saw chain 6 is rotatingly driven. Projecting from the housing 2 is a starter handle 7 of a starter device 8 shown schematically in FIG. 2.

(12) As shown by FIG. 2, an internal combustion engine 10 is mounted in the housing 2 of the motor-driven chain saw 1. The internal combustion engine 10 is advantageously configured as a two-stroke engine or as a mixture-lubricated four-stroke engine. The internal combustion engine 10 has a cylinder 11, in which a piston 12 is reciprocatingly mounted. The piston 12 drives a crankshaft 13 rotatingly about a rotational axis 14. In the embodiment shown, a fan wheel 9 is mounted on the crankshaft 13 and serves for moving cooling air for the internal combustion engine 10. The starter device 8 is in engagement with the fan wheel 9 during the starting process, as is explained in greater detail below. On that side of the internal combustion engine 10, which faces away from the fan wheel 9, is disposed a centrifugal clutch 15, which, when a structurally pregiven rotational speed is exceeded, connects the crankshaft 13 in a rotationally secure manner to a drive sprocket 16. The drive sprocket 16 serves to drive the saw chain 6 (FIG. 1).

(13) FIG. 3 shows the assembly of the starter device 8 in detail. The starter device 8 comprises a rope pulley 18, which is rotatably mounted in the housing 2 and is coupled by a return spring 17 to the housing 2. The return spring 17 has an inner end 52, which is held on the pulley 18. The outer end of the return spring 17 is held on the housing 2. The rope pulley 18 has a groove 19 for receiving a pull rope. On the side which projects into the housing 2, on the rope pulley 18 is formed a receiving space 20 into which projects a stud 21. The receiving space 20 is delimited by a roughly cylindrical peripheral wall 51. The rope pulley 18 has a central opening 53, which receives a bearing shaft (not shown in FIG. 3).

(14) As shown in FIG. 8, a damper spring 23, configured as a hinge spring, is provided. A first end 26 of damper spring 23 is suspended from a wall portion 38. The wall portion 38 is disposed on the base of the receiving space 20. A second end 27 of the damper spring 23 is connected to an entrainer 24. Between the rope pulley 18 and the entrainer 24 is disposed a disc 22 having an outer diameter (a). The entrainer 24 has an opening 54, which likewise receives the bearing shaft. On the entrainer 24, on the side facing away from the damper spring 23, are provided two receptacles 28 for accommodating pawls 25. The pawls 25 are pivotably mounted on the entrainer 24. The damper spring 23 is disposed largely in the receiving space 20. The receiving space 20 is largely closed off by the entrainer 24. Penetration of dirt deposits into the receiving space 20 during operation can hence be largely avoided.

(15) FIG. 4 shows the arrangement of the pawls 25 on the entrainer 24 in detail. As shown by FIG. 4, a bearing shaft 32 projects through the entrainer 24. The entrainer 24 and the rope pulley 18 are rotatably mounted on the bearing shaft 32. The bearing shaft 32 is fixed on the housing 2. The pawls 25 have respective actuating lugs 35. In the region of their mounting, the pawls 25 are surrounded by wall portions 31 of the entrainer 24. Hence, the region of the mounting of the pawls 25 is protected from dirt. In addition, the wall portions 31 form a stop defining the outer pivoting position of the pawls 25. As shown also by FIG. 4, the housing 2 has, adjacent to the starter device 8, a multiplicity of cooling air openings 29. Via the cooling air openings 29, dirt deposits such as chips, dust or the like can also be sucked up during operation. Because of the peripheral wall 51, the starter device 8 is largely protected from dirt deposits. The peripheral wall 51 is supported by radially outward projecting reinforcing ribs 30.

(16) FIG. 5 shows the arrangement of the actuating lugs 35 on a spring clip 33 fixed onto the bearing shaft 32. In addition, a cam contour 34 of the fan wheel 9, with which the pawls 25 cooperate during the starter process, is shown schematically. When the starter rope is pulled, the entrainer 24 rotates, in FIG. 5, in the clockwise direction. The actuating lugs 35 thereby move outwards in the spring clip 33 held by friction on the bearing shaft 32. In this way, the pawls 25 are pivoted outward about their pivot axes 36. In the outwardly pivoted position, the free ends of the pawls 25 enter into engagement with the cam contour 34 and thereby couple the entrainer 24 in a rotationally secure manner to the fan wheel 9 and the crankshaft 13 so as to rotate therewith. When the starter rope is retracted due to the return spring 17, the entrainer 24 rotates in FIG. 5 anti-clockwise. The pawls 25 are thereby pivoted back into the position shown in FIG. 5 due to the actuating lugs 35 being directed inward in the spring clip 33.

(17) The assembly of the starter device 8 is shown in detail in FIG. 6. The bearing shaft 32 is fixed in the housing 2. The bearing shaft 32 can, for example, be injection molded onto the housing 2. The bearing shaft 32 includes a retaining bolt 40, which has a groove 55 for accommodating the spring clip 33. The rope pulley 18 has a lug 37, which engages in the inner end 52 of the return spring 17 and thereby provides a rotationally secure connection between the inner end 52 of the return spring and the rope pulley 18. In FIG. 6, a pull rope 43 is shown schematically in the groove 19 of the rope pulley 18. Advantageously, one end of the pull rope 43 is held fixedly on the rope pulley 18, and the other end is held on the starter handle 7 (FIG. 1).

(18) The stud 21 of the rope pulley 18 has an inner region 46, which is journalled on the bearing shaft 32, and an outer region 49, on whose outer periphery the damper spring 23 is mounted. The outer region 49 has an outer diameter (c), which in the embodiment shown corresponds to the outer diameter (a) of the disc 22 (FIG. 3). In the embodiment shown, the inner region 46 of the stud 21 has a shoulder 48, on which the disc 22 is mounted.

(19) The entrainer 24 has a stud 42, which projects in the direction of the rope pulley 18. The stud 42 has an outer region 50, on whose outer periphery the damper spring 23 is mounted. The stud 42 has an inner region 47, which serves for the rotatable mounting of the entrainer 24 on the bearing shaft 32. Also, the inner region 47 of stud 42 lies with its end against the inner region 46 of the stud 21 adjacent to the outer periphery of the bearing shaft 32 in the embodiment shown. The stud 42 can also bear against the disc 22, which for its part bears against the stud 21 of the rope pulley 18. The bearing contact can here be provided against the inner regions (47, 46) or the outer regions (49, 50). As FIG. 6 also shows, the stud 42 has a wall portion 39, on which the second end 27 of the damper spring 23 is hooked into. The outer region 50 of the stud 42 has an outer diameter (b). Advantageously, the outer diameter (b) roughly corresponds to the outer diameter (c) of the outer region 49 of the stud 21 and to the outer diameter (a) of the disc 22 (FIG. 3).

(20) The damper spring 23 has a radially inner side 56 referred to the rotational axis 14. This inner side 56 lies facing the studs 21 and 42. The damper spring 23 also has radially outermost outer side 57, which lies facing the peripheral wall 51 of the receiving space 20. As shown by FIG. 6, the cross section of the spring wire of the damper spring 23 is configured such that it is rounded off on the inner side 56. On the outer side 57, the cross section has a straight region. The damper spring 23 has a coil diameter (f), which corresponds to the outer diameter of the damper spring 23.

(21) In FIG. 6, the fan wheel 9 is also shown schematically. The fan wheel 9 has a rim 41, which is of roughly cylindrical configuration, which, between the peripheral wall 51 and the entrainer 24, engages in the receiving space 20, and on the inner side of which is configured the cam contour 34.

(22) During the starting operation, the damper spring 23 is tensioned when the pull rope 43 is pulled. The inner side 56 of the damper spring 23 can here be pulled as far as it will go onto the studs 21 and 42. If the damper spring 23 is pulled to the limit, then, upon further pulling on the pull rope 43, the tensile force is transmitted to the crankshaft 13 directly via the coupling device formed by the pawls 25 and the cam contour 34. If the damper spring 23 is not pulled to the limit, then the force of the damper spring 23 and the force applied to the pull rope 43 by the operator act jointly on the crankshaft 13.

(23) For the avoidance of dirt deposits, the studs 21 and 42 have, on their outer side, a multiplicity of depressions (44, 45), as shown schematically in FIG. 7. The depressions (44, 45) can be configured, for instance, as grooves running parallel to the rotational axis 14.

(24) The damper spring 23 is wound from spring wire 58. FIG. 8 shows the cross section of the spring wire 58 of the damper spring 23 in detail. FIG. 8 here shows a section through the spring wire in a plane containing the rotational axis 14. In this section plane, the cross section of the spring wire 58 has a thickness (d), which is measured perpendicular to the rotational axis 14 (FIG. 5), and a width (e), which is measured parallel to the rotational axis 14. On the inner side 56, the cross section of the spring wire 58 runs in a radius (r) which is greater than half the width (e). Hence the cross section of the spring wire 58 on the inner side 56 is flatter compared with a damper spring of circular cross section. On its outer side 57, the spring wire 58 has a portion 61, in which the cross section runs straight. The damper spring 23 is accordingly configured flattened on its outer side 57. The straight portion 61 here extends over at least 30% of the width (e). In the embodiment shown, the straight portion 61 extends over approximately half the width (e). In the straight portion 61, the outer side 57 here runs parallel to the rotational axis 14. The spring wire 58 has transverse sides 59 and 60, which run roughly perpendicular to the rotational axis 14 (FIG. 6). The transverse sides 59 and 60 connect the inner side 56 to the outer side 57. In the embodiment shown, the transverse sides 59 and 60 are configured in mirror symmetry to each other. The transverse sides 59 and 60 have respective straight portions 62. The straight portion 62 advantageously extends over more than 30%, in particular over at least 50% of the thickness (d). The transverse sides 59 and 60 each extend over at a radius (s) into the outer side 57. The radius (s) is markedly less than the radius (r) and can measure, for instance, 60%, in particular roughly 50% of the radius (r). The radius (s) is here advantageously less than half the width (e), in particular less than 30% of the width (e).

(25) FIG. 9 shows an embodiment of a damper spring 63 having a spring wire 68, which is intended for use in a starter device 8. The configuration of the damper spring 63 substantially corresponds to that of the damper spring 23. The spring wire 68 has an inner side 66 and an outer side 67. On its inner side 66, the spring wire 68 runs with a radius (r). Also in the embodiment of FIG. 9, the radius (r) is greater than half the width (e) of the spring wire 68. The width (e) of the spring wire 68 here corresponds to the width (e) of the spring wire 58 from FIG. 8. The spring wire 68 has a thickness (g) which is less than the thickness (d) of the spring wire 58. The thickness (g) roughly corresponds to the width (e). On its outer side 67, the spring wire 68 has a straight portion 71, which extends over at least 30%, in particular over at least 50% of the width (e). In the embodiment shown, the straight portion 71 extends over more than 70% of the width (e). The outer side 67 passes with a radius (t) into transverse sides 69 and 70 of the spring wire 68. The radius (t) is markedly less than the radius (s) of the spring wire 58. The radius (t) advantageously measures less than 20%, in particular less than 15% of the width (e).

(26) FIG. 10 shows an embodiment of a damper spring 73, which has a spring wire 78 and which is intended for use in a starter device 8. The spring wire 78 has an inner side 76 and an outer side 77, and transverse sides 79 and 80. The outer side 77 is configured in accordance with the outer side 57 of the spring wire 58 and has a straight portion 61, which passes with respective radii (s) into the transverse sides 79 and 80. The transverse sides 79 and 80 have respective straight portions 82, which run perpendicular to the rotational axis 14 (FIG. 6). The straight portion 82 advantageously extends over more than 30% of the thickness (g), in the embodiment shown, over roughly 50% of the thickness (g). The thickness (g) roughly corresponds to the width (e).

(27) The damper spring 73 occupies the same structural space as a damper spring whose spring wire has a circular cross section of diameter corresponding to the width (e) or the thickness (g). In relation to such a damper spring of circular cross section, the spring wire 78 has however a larger section modulus against bending due to the material accumulation on the outer side 77. Due to the radius (r), which is greater than half the width (e), a flatter course of the rounding on the inner side 76 is additionally obtained. The damper spring 63 has, in relation to the damper spring 73, an increased section modulus against bending, and hence a higher spring constant due to the smaller radius (t) and the larger width of the straight portion 71.

(28) The damper spring 23 too has a larger spring constant than the damper spring 73 due to the larger thickness (d). A desired spring constant can be set by an appropriate configuration of the cross-sectional form of the spring wire (58, 68, 78). Since the inner side (56, 66, 76) is of rounded-off configuration, the susceptibility to the formation of dirt on the inner side is reduced. As a result of the straight portions (62, 82) on the transverse sides (59, 60, 69, 70, 79, 80), adjacent coils, when they come to bear one against another, are in mutual contact not only linearly, but over a larger area. This prevents adjacent coils from sliding one over the other.

(29) It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.