Abstract:
A starter mechanism for an internal combustion engine for a motor-driven, manually-guided implement is provided. A clutch drum is rotatably mounted about a journal pin on a housing of the implement. The clutch drum is fixedly connected with a carrier of a ratchet for transfer of drive torque from the drum to the motor shaft. For the reversible engagement of the ratchet in a clutch member fixedly connected with the motor shaft, the ratchet has a pawl on the carrier that, with the aid of a guide element resting against a pawl pin, pivots during a starting process. On that side facing away from the carrier the pawl is spanned by an abutment element, at least in the region of its pivot axis.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a starter mechanism for an internal combustion engine, especially a rope or cord pull starter mechanism for a motor-driven, manually guided implement. 
     With one known starter mechanism for an internal combustion engine, a rope pull actuated clutch drum is rotatably disposed on a journal pin and acts upon a carrier of a ratchet. The ratchet serves for the transfer of a drive torque from the coupling drum to a motor shaft of the internal combustion engine. For this purpose, the ratchet is provided with a pivotable pawl on the carrier that is pivoted during the starting process with the aid of a sliding block type of guide that comprises a pawl pin on the pawl and a guide element that is embodied as a guide clamp; the pawl is reversibly engageable with a toothing of a coupling or clutch member. The clutch member is fixedly connected with the motor shaft, as a result of which the motor shaft is rotated. 
     The pawl is mounted with play, preferably taper bore mounted, on the carrier, so that during operation of the internal combustion engine axial play and tilting movements of the pawl cannot be precluded, as a result of which wear can occur on the pawl pin and on the guide clamp. 
     It is therefore an object of the present invention to improve a starter mechanism for internal combustion engines in such a way that the starter mechanism has a longer service life. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This object, and other objects and advantages of the present invention, will appear more clearly with the following specification in conjunction with the accompanying schematic drawings, in which: 
     FIG. 1 is an exploded view of one exemplary embodiment of an inventive starter mechanism; 
     FIG. 2 is a plan view of the starter mechanism of FIG. 1; 
     FIG. 3 is a cross-sectional view through the starter mechanism taken along the line III—III in FIG. 2; 
     FIG. 4 a  is a view of an abutment element of the starter mechanism; 
     FIG. 4 b  is a plan view of the abutment element of FIG. 4 a ; and 
     FIG. 4 c  is a view of the abutment element taken in the direction of the arrow IV in FIG. 4 b.    
    
    
     SUMMARY OF THE INVENTION 
     The starter mechanism of the present invention comprises: a clutch drum that is rotatably disposed about a journal pin; a carrier for a ratchet for transferring drive moment or torque on the clutch to the motor shaft of the engine, wherein the clutch drum is connected with the carrier; a pawl, as part of the ratchet, wherein the pawl is disposed on the carrier such that the pawl is pivotable about a pivot axis, wherein the pawl is reversibly engageable in a clutch member, and wherein the pawl is provided with a pawl pin; a guide element that rests against the pawl pin for a pivotable control of the pawl; and an abutment element that extends about a portion of the pawl from the side thereof that is remote from the carrier. 
     On that side on which it is not directly held and mounted on the carrier, the pawl is spanned on that side that faces away from the carrier by an abutment element, at least in the region of its pivot axis. Due to the fact that the abutment element preferably rests against the pawl, it forms an axial abutment relative to the pivot axis of the pawl. This improves the mounting of the pawl on the carrier; in particular, a tilting or canting of the pawl, for axial movement of the pawl, is thereby avoided during operation of the internal combustion engine. Wear of the pawl pin and the guide clamp or guide element is reduced. Disruptions in operation of the starter mechanism due to breaking or failure of the pawl pin or of the guide clamp are to a large extent precluded, whereby after failure of the pawl pin the pawl cannot escape from its guide means. Secondary damage to the starter mechanism is avoided. 
     The basic configuration of the abutment element is preferably such that it at least partially covers the pawl at its pivot axis, and thus the pawl is axially guided only in the region of its pivot axis and is secured against tilting. The abutment element is expediently positively or frictionally detachably fixed in position on the carrier, so that during operation of the internal combustion engine, with the exception of the pivoting of the pawl, no further relative movements of the abutment element relative to the pawl occur. Wear of the pawl due to rubbing against the abutment element is thereby minimized. The pawl is permanently guided and held on the carrier. 
     The abutment element is essentially flat and disk-shaped, and is preferably provided with a connecting tongue that is monolithically formed with the abutment element and preferably projects at an angle from the abutment element. The connecting tongue can be provided with a securement opening through which an appropriate securement element can be guided. The connecting tongue can nevertheless be formed in such a way that it can be positively, preferably in a positively clamping manner, mounted in an appropriate receiving means on the carrier. In this way, the abutment element can be easily pre-mounted on the carrier. 
     It is expedient to embody the connecting tongue with surfaces that are angled off toward one another, preferably providing a U-shaped configuration in cross-section, so that the connecting tongue is appropriately resistant to bending. Pursuant to one particularly preferred embodiment, the connecting tongue is bent out of the peripheral edge of the abutment element. The configuration of the abutment element itself is elliptical or rhombic. In the mounted state of the starter mechanism, the abutment element is preferably—when viewed in the axial direction of the pivot axis of the pawl—disposed between the pawl and the guide element or guide clamp. 
     It can be expedient to dispose two or more pawls on the carrier of the starter mechanism, whereby the configuration of the abutment element is such that it at least partially spans or extends about all of the pawls. The abutment element is provided with an opening, preferably a central circular opening, with which it surrounds an axial end of the journal pin with play, such axial end preferably having the shape of a collar stud. The abutment element is advantageously formed by being stamped and shaped from a metal plate, preferably from a steel plate. 
     Further specific features of the present invention will be described in detail subsequently. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings in detail, FIG. 1 shows a starter mechanism  1  for the manual starting of an internal combustion engine  2 , for example for a motor-driven, manually guided implement, such as a blower, a power chain saw, or a brush cutter or trimmer. The starter mechanism  1 , as is also shown in the cross-sectional view of FIG. 3 taken along the line III—III in FIG. 2, is accommodated in a housing  19 . In the illustrated embodiment, the housing  19  is illustrated as a cover of an engine housing, with the cover surrounding the starter mechanism  1  in a cup-shaped manner with radial spacing. In the illustrated embodiment, the cover is monolithically formed in a light-weight construction, and has a correspondingly thin wall. 
     Projecting from a planar, circular inner wall  20  of the cover is a pivot or journal pin  3 , the interior of which is hollow (see FIG.  3 ). The journal pin  3  is formed of the same material as the cover, for example polymeric material or lightweight metal. It has a cylindrical shape, whereby when viewed in a longitudinal cross-section, it tapers in a stepped manner. The free axial end  17  of the pin  3  is provided with a reduced diameter section  21 , so that the axial end  17  is embodied in the manner of a collar stud. The cover of the housing  19  is fixed in position on the motor housing with the aid of three threaded bolts  22 , which are disposed approximately equidistantly from one another and relative to the longitudinal axis  23  of the journal pin  3 . The threaded bolts  22  extend approximately parallel to the longitudinal axis  23  of the pin  3 , and in the direction of extension of the pin  3  project out of the cover. In the cover, the journal pin  3  is surrounded by a helical spring  24 , one end of which is connected to the rim of the housing. The helical spring  24  serves as a retraction spring for a coupling or clutch drum  4  that is slide-mounted on the journal pin  3 . The clutch drum  4  is provided with a non-illustrated pin for the connection of an inner-housing end  25  of the spring  24 . Wound onto the clutch drum  4  is a cable or cord  26  (see FIG.  2 ), the free end of which projects out of the housing, and on the free end of which is fastened a handle  27  in the form of a T-shaped grip. By pulling the cord  25  via the handle  27 , the clutch drum  4  is rotated about the journal pin  3  in the direction of rotation D. The clutch drum  4  is monolithically formed with a carrier  5  of a ratchet  6 ; the cup-shaped carrier  5  surrounds the journal pin  3 . The ratchet  6  is provided with a pawl  9  that is mounted in the carrier  5  so as to be pivotable about a pivot axis  8 . 
     As FIG. 1 shows, the pawl  9  has a cylindrical widened portion  28  about its pivot axis  8 . Via an axial end  29  of the widened portion  28 , the pawl  9  is taper bore mounted in a bearing block or support element  30  of the carrier  5 . Over its entire axial length, the widened portion  28  is additionally radially surrounded with a slight spacing, and guided, by half shells  44 , 44 ′ that have the shape of a segment of a cylinder and extend in the axial direction of the support element  30 , which is monolithically formed with the carrier  5 . The clutch drum  4  is mounted on the journal pin  3  over its entire axial length. The pawl  9  carries a pawl pin  11 , which projects outwardly in a direction opposite to the direction of extension of the widened portion  28 . Threaded into an axial thread  31  on the axial end  17  of the journal pin  3  is a threaded bolt  32 , in the head of which is provided a peripheral recess  45  (see also FIG.  3 ). A further peripheral recess  45 ′ is provided at the axial end  17  of the journal pin  3 . In the mounted state of the threaded bolt  32 , the recesses  45 , 45 ′ form an annular groove  33 . Disposed in the annular groove  33  as a guide clamp is a guide element  12  that is made of spring steel wire and that in the state of rest of the clutch drum  4  extends around the pawl pin  11  via its free leg  34 . The guide element  12  has a hairpin shaped bend  35  in which the pawl pin  11  is disposed. Between the guide element  12  and the support element  30  of the carrier  5 , there is disposed an abutment element  14  that preferably slidingly comes to rest on that side  13  of the pawl  9  that faces away from the carrier. Relative to the pivot axis  8 , the abutment element  14  forms an axial abutment. In this connection, in the vicinity of its pivot axis  8 , the pawl  9  is covered in a crescent-shaped manner. 
     The abutment element  14  can be seen in detail in a perspective view in FIGS. 1 and 4 a , as well as in plan in FIGS. 2 and 4 b . The abutment element is cut or stamped and formed from sheet metal, preferably from a steel plate, by bending out a connecting tongue  15  from the peripheral edge  16  of the abutment element. As can be seen from FIG. 4 c , the connecting tongue  15  is bent approximately at right angles toward the support element  30  of the carrier  5  relative to the elliptical, disk-shaped main body  36  of the abutment element  14 . When viewed in cross-section, the connecting tongue  15  is provided with surfaces  37 ,  37 ′,  37 ″ that are angled off toward one another and that in the illustrated embodiment provide a U-shaped cross-sectional course of the connecting tongue. The connecting tongue  15  engages in a receiving recess  38  in the support element  30  in a manner preferably free of play or in a slightly clamping manner. This effects a fixed, positively releasable connection of the abutment element  14  with the carrier  5 . 
     The abutment element  14  has an approximately central opening  18 , the diameter  39  of which is approximately half as great as the greatest length  40  of the main body  36  of the abutment element. By means of the opening  18 , the abutment element  14  extends about the preferably collar stud like axial end  17  of the journal pin  3  with play. In the illustrated embodiment, the main body  36  of the abutment element  14  has an approximately symmetrical shape, so that it is thereby possible to cover two pawls  9  in the region of the pivot axis  8 . It can be expedient to provide the starter mechanism  1  with more than two pawls. In accordance therewith, it is expedient to embody the main body  36  of the abutment element  14  in such a way that all of the pawls are covered on that side  13  thereof that faces away from the carrier  5 . It can also be expedient to dispose the abutment element  14  on the support element  30  of the carrier  5  in such a way that a play remains between the main body  36  and the respective side  13  of the pawl  9 . 
     Upon actuation of the starter mechanism  1 , it is provided that the pawl  9  reversibly engages in a coupling or clutch member  10  (see FIG.  1 ). The clutch member  10  is fixedly connected with the motor shaft  7  of the internal combustion engine  2 . In the embodiment of FIGS. 1 and 2, the clutch member  10  is a clutch cup  41  that is provided with a toothing  42  on its inner wall. In the assembled state of the starter mechanism  1 , the toothing  42  of the clutch cup  41  engages in the cup-shaped carrier  5 . 
     When the clutch drum  4  is rotated by pulling on the cord  26  via the handle  27 , it takes along the carrier  5  and the support element  30 . In so doing, the support element  30  of the ratchet  6  rotates about the journal pin  3 , while the guide element initially maintains its position, since it is frictionally or positively connected with the threaded bolt  32  and thereby with the journal pin  3 . With the aid of the abutment element  14 , the pawl  9  is secured against axial displacement, vibration and counter tilting about its pivot axis  8 . The pawl pin  11  of the pawl  9  migrates outwardly into the bend  35  of the guide element  12  in the direction toward the end of the bend, as a result of which the pawl  9  pivots radially outwardly. In this radially outwardly pivoted position, the pawl  9  takes along the guide element  12 , which then rotates against the frictional resistance in the annular groove  33  of the threaded bolt  32  about the longitudinal axis  23  of the journal pin  3 . During further rotation of the clutch drum  4 , and hence of the ratchet  6 , in the direction of the arrow D (see FIG. 2) the pawl  9  remains in its pivoted-out position and in so doing engages in a tooth base  43  of the toothing  42 . This rotates the clutch cup  41  and hence the motor shaft  7  that is to be driven. If the internal combustion engine  2  is started and achieves the prescribed speed, the toothing  42  of the clutch cup  41  overtakes the ratchet  6 , whereby the pawl  9  is again pivoted back into the position shown in FIG.  2 . 
     The specification incorporates by reference the disclosure of German priority document 201 13 012.2 filed Aug. 4, 2001. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.