Abstract:
An internal combustion engine has a cylinder which has a cylinder longitudinal axis. The internal combustion engine has at least one cooling fin. In order to route the cable in a defined fashion so that the internal combustion engine can be arranged even in a constricted installation space, a cable retainer is provided which is arranged on at least one cooling fin of the internal combustion engine and which retains at least one cable. A cable retainer for securing at least one cable to an internal combustion engine has at least one receptacle for at least one cable and at least one means for positioning the cable retainer on the internal combustion engine.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The right of foreign priority is claimed under 35 U.S.C. §119(a) based on Federal Republic of Germany Application No. 10 2007 020 681.1, filed May 3, 2007, the entire contents of which, including the specification, drawings, claims and abstract, are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an internal combustion engine of the generic type specified in the preamble of claim  1 , and to a cable retainer for securing at least one cable to an internal combustion engine. 
     An internal combustion engine which has a cylinder and cooling ribs is known, for example, from U.S. Pat. No. 6,289,856 B1. Such internal combustion engines are used, for example, in hand-held tools such as power saws, cut-off grinders, clearing saws or the like, in order to drive the tool. 
     The ignition of the internal combustion engine is provided in known internal combustion engines by means of a sparkplug which is connected to an ignition module via an ignition cable. It is also possible to provide other cables, for example for controlling or for grounding. 
     In order to permit simple handling of hand-held tools it is desirable for the housing in which the internal combustion engine is arranged to be kept as small as possible. However, at the same time it is necessary to avoid damage to the cables. 
     In known internal combustion engines, cables of the ignition module are laid loosely. The cables are merely secured to one another by means of cable binders. As a result, the position of the cables relative to the internal combustion engine and also relative to a housing, for example the housing of a tool, is not fixed. The cables can move relative to the internal combustion engine during operation. Therefore, sufficient installation space must be made available for the cables to ensure that the cables cannot come to bear on adjacent components owing to their movement during operation since this could lead to wear. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of providing an internal combustion engine of the generic type which permits an internal combustion engine to be installed in a comparatively small housing. A further object of the invention is to provide a cable retainer for an internal combustion engine. 
     This object is achieved by means of an internal combustion engine having the features of claim  1 . In terms of the cable retainer, the object is achieved by means of a cable retainer having the features of claim  18 . 
     The cable retainer fixes the position of the at least one cable relative to the internal combustion engine. As a result, the cable can be routed right against the internal combustion engine. Owing to the defined position of the cable, cable wear can be avoided. As a result, the internal combustion engine can be installed even under constricted installation conditions. 
     The cable retainer is advantageously arranged on the cylinder of the internal combustion engine. The cable retainer advantageously has means for positioning the cable retainer on the internal combustion engine. This makes it possible to ensure that the cable retainer is placed in a defined position, which cannot be confused, on the internal combustion engine. The cable retainer is easily secured to the internal combustion engine if the cable retainer has at least one slot with which the cable retainer is plugged onto a cooling fin. The slot can have play here, in particular with respect to the cooling fin, in order to compensate tolerances of the internal combustion engine. The cable retainer advantageously has a first slot which receives a first cooling fin which is positioned, in particular, transversely with respect to the cylinder longitudinal axis. In particular, the cable retainer has a second slot which receives a second cooling fin which extends transversely with respect to the first cooling fin. The first slot advantageously extends approximately parallel to the cylinder longitudinal axis. Through the slot, the cable retainer is respectively secured in a perpendicular direction with respect to the corresponding cooling fin. As a result, the position of the cable retainer on the internal combustion engine is fixed even if the cable retainer can execute slight movements with respect to the internal combustion engine owing to tolerances and owing to play. These movements can be allowed since they do not affect the securing of the position of the cables with respect to the internal combustion engine. 
     The cable retainer advantageously has a receptacle in which at least one cable is retained. The receptacle is bounded, in particular, by at least two limbs, wherein at least one of the limbs is sprung. The sprung embodiment of at least one limb allows the cable to be pressed between the limbs and therefore easily mounted in the receptacle. The sprung embodiment of the limbs permits, in particular, clamping of the cable so that the cable cannot move in the receptacle, either in its longitudinal direction or transversely with respect to the receptacle. It is also possible, for example, to provide three or more limbs which are arranged, in particular, offset in the longitudinal direction of the cable and alternately on each side of the cable. 
     In order to permit simple mounting of the cable in the cable retainer even under restricted spatial conditions, there is provision for the receptacle to be accessible via a longitudinal opening which is bounded by at least two limbs, wherein at least one limb has, adjacent to the longitudinal opening, an insertion slope which extends inclined with respect to the longitudinal direction of the cable. Owing to the inclined arrangement of the insertion slope, the cable can be arranged on the receptacle in an oblique position with respect to the longitudinal direction of the receptacle and can be mounted from an oblique orientation in the receptacle. The oblique mounting permits the cable to be arranged in the receptacle even if only very small spring travel values of the limbs are possible, for example owing to the comparatively small possible overall size of the cable retainer. 
     In order to permit the largest possible spring travel of the limbs there is provision that a slot extends adjacent to the bottom area of the receptacle, wherein the side walls of the slot are inclined with respect to one another by an angle which opens toward the internal combustion engine. As a result, the entire side wall of the slot can be moved together with the limb which is arranged thereon. As a result, the possible spring travel can be made larger without adversely affecting the stability of the cable retainer. 
     There is provision for at least one cable to be held clamped in the receptacle. The receptacle advantageously has a lower section and an upper section between which a constriction is arranged, wherein a cable which closes off the lower section of the receptacle is held clamped in the upper section. In particular, at least one cable which is retained in the receptacle by the cable in the upper section is arranged in the lower section. The diameter of the cable in the lower section is advantageously smaller than the diameter of the cable in the upper section. As a result, the position can easily be secured, the position of a plurality of cables being advantageously secured at the same time. 
     In order to define on which cooling fins the cable retainer will be mounted there is provision for the cable retainer to have a stop which is adjacent to a third cooling fin, with the third cooling fin being made lower than at least one adjacent cooling fin. Owing to the stop it is not possible to arrange the cable retainer next to a cooling fin which is made higher than the third cooling fin. In this context, the stop does not have to bear against the third cooling fin. The height at which the stop extends is between the height of the third cooling fin and the height of the adjacent, relatively high cooling fin. As a result, the position of the cable retainer on the internal combustion engine is fixed. Incorrect mounting is avoided. 
     Means for securing the cable retainer to the internal combustion engine are advantageously provided. The securing means secure the cable retainer which is plugged onto the internal combustion engine. The internal combustion engine advantageously has an ignition module, and the cable retainer is arranged adjacent to the ignition module, wherein at least one cable which is retained by the cable retainer is connected to the ignition module. This makes it possible to ensure that the cables which are made to lead away from the ignition module are led past the internal combustion engine in a defined fashion. The ignition module is advantageously fixed to at least one screw boss of the internal combustion engine via an insulating element. The insulating element advantageously insulates the ignition module thermally from the internal combustion engine. The insulating element expediently secures the cable retainer to the internal combustion engine. The insulating element must, in any case, be fixed to the internal combustion engine. Since the insulating element is used to secure the cable retainer, no additional components are required. No additional mounting steps are necessary. As a result, the cable retainer is secured to the internal combustion engine in a simple and reliable way. 
     A simple configuration is obtained if the cable retainer has a bearing web, wherein the cable retainer is plugged onto the internal combustion engine in an insertion direction, and wherein the insulating element secures the bearing web in the insertion direction of the cable retainer. As a result, the cable retainer is secured counter to the insertion direction in a simple way and without additional components. 
     In order to fix the direction in which the cables are routed, there is provision for the insulating element to have at least one stop for the connection of a cable which is retained in the cable retainer. 
     For a cable retainer for securing at least one cable to an internal combustion engine there is provision for the cable retainer to have at least one receptacle for at least one cable, and at least one means for positioning the cable retainer on the internal combustion engine. As a result, the cable retainer can easily ensure the relative position of the cable with respect to the internal combustion engine. 
     The cable retainer advantageously has a first slot and a second slot for plugging the cable retainer onto at least one cooling fin of the internal combustion engine. As a result, the cable retainer can easily be arranged on the internal combustion engine. The slots secure the position of the cable retainer relative to the internal combustion engine. At the same time, the slots can have play with respect to the cooling fins of the internal combustion engine in order to compensate tolerances, for example fabrication tolerances of the internal combustion engine. The slots advantageously extend transversely, and in particular approximately perpendicularly, with respect to one another, in a plane which extends perpendicularly with respect to the insertion direction. As a result the slots fix the position of the cable retainer in two directions which are transverse, in particular perpendicular, with respect to one another. 
     There is provision for a slot to extend adjacent to the bottom area of the receptacle, wherein the side walls of the slot are inclined with respect to one another in the insertion direction by an angle, wherein the angle opens toward the plug-in opening of the slot. The receptacle is advantageously bounded by two limbs, wherein at least one of the limbs is embodied in a sprung fashion. 
     In order to make the cable retainer easy to manufacture and low in weight there is provision for the cable retainer to be composed of plastic. The cable retainer is advantageously made of polyamide. As a result, sufficient heat resistance of the cable retainer is provided. The cable retainer is expediently embodied in one piece. 
     Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying Figures of drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is explained in the text which follows with reference to the drawing, in which: 
         FIG. 1  shows a schematic longitudinal section through a power saw, 
         FIG. 2  shows the cylinder of the internal combustion engine of the power saw from  FIG. 1  in a side view, 
         FIG. 3  shows a side view of the cylinder in the direction of the arrow III in  FIG. 2 , 
         FIG. 4  shows the detail IV in  FIG. 3  in an enlarged illustration, 
         FIG. 5  shows the detail V from  FIG. 2  in an enlarged illustration, 
         FIG. 6  shows a detail of a section along the line VI-VI in  FIG. 3 , 
         FIG. 7  shows a detail through a plan view of the cylinder in the direction of the arrow VII in  FIG. 2 , 
         FIG. 8  shows a perspective illustration of a detail of the cylinder with a cable retainer arranged thereon, 
         FIG. 9  shows the insulating element of the internal combustion engine in a side view, 
         FIG. 10  shows a perspective illustration of the insulating element, 
         FIG. 11  shows a side view of the cable retainer, 
         FIG. 12  shows a side view of the cable retainer in the direction of the arrow XII in  FIG. 11 , 
         FIG. 13  shows a side view of the cable retainer in the direction of the arrow XIII in  FIG. 12 , 
         FIG. 14  shows a plan view of the cable retainer in the direction of the arrow XIV in  FIG. 12 , and 
         FIG. 15  and  FIG. 16  show perspective illustrations of the cable and retainer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a power saw as an exemplary embodiment of a portable, hand-held tool. The invention can also be used with other hand-held tools such as, for example, cut-off grinders, clearing saws or the like. Use in internal combustion engines may also be possible for other purposes of use. The power saw  1  has a housing  2  to which a rear handle  3  is secured. A throttle lever  4  and a throttle lever lockout  5  are pivotably mounted on the rear handle  3 . The throttle lever  4  is used to start an internal combustion engine  8  which is arranged in the housing  2 . The internal combustion engine  8  is embodied as a single-cylinder engine. The internal combustion engine  8  is, in particular, a two-stroke engine, advantageously a two-stroke engine which operates with a scavenging gas shield. The internal combustion engine  8  can, however, also be a four-stroke engine, in particular a mixture-lubricated four-stroke engine. The internal combustion engine  8  has a cylinder  9  in which a combustion chamber  10  is formed. A sparkplug  16  projects into the combustion chamber  10 . 
     The internal combustion engine  8  is connected to a carburetor  7  which is controlled by the throttle lever  4 . An air filter  6  is secured to the carburetor  7 . The internal combustion engine  8  sucks in fuel and combustion air via the air filter  6  and the carburetor  7  during operation. An exhaust gas silencer  11  is arranged at the outlet of the cylinder  9 . The power saw  1  has a guide rail  12  which guides a saw chain  13 . The saw chain  13  is driven by the internal combustion engine  8  so that it runs around the guide rail  12 . To do this, the internal combustion engine  8  has a crankshaft  40  which is driven in rotation around a crankshaft axis  14 . 
       FIG. 2  shows the cylinder  9  of the internal combustion engine  8 . The internal combustion engine  8  is embodied as a scavenging gas shield two-stroke engine and has an air inlet  22  for scavenging gas shield air and a mixture inlet  23  for a fuel/air mixture. A plurality of cooling fins  32  are arranged on the cylinder  9 . In this context, cooling fins  32  are provided which protrude perpendicularly with respect to the cylinder longitudinal axis  31  and cooling fins  32  are provided which extend parallel to the cylinder longitudinal axis  31 . A different orientation of the cooling fins  32  may also be advantageous. 
     As is shown in  FIGS. 2 and 3 , an ignition module  19  is secured to the cylinder  9  by means of two fastening screws  25 . The ignition module  19  has a yoke  20  which is embodied as a laminated core and which ends at the outer circumference of a fan wheel  15  which is shown schematically in  FIGS. 2 and 3 . The fan wheel  15  is secured to the crankshaft  40  and is driven in rotation about the crankshaft axis  14 . Ignition magnets (not shown) which induce a voltage in a coil of the ignition module  19  are arranged on the fan wheel  15 . This voltage is used to ignite the internal combustion engine  8 . In addition, the voltage can also be used to supply energy to further components of the power saw  1 . 
     An ignition cable  18  is provided for supplying power to the sparkplug  16 , said ignition cable  18  connecting the ignition module  19  to a sparkplug connector  17 . The sparkplug connector  17  is removeably plugged onto the sparkplug  16  and it supplies the sparkplug  16  with ignition energy. As is shown in particular by  FIG. 3 , a grounding cable  26  is secured to the yoke  20  by means of a connection  29 . Furthermore, a connecting plug  28 , which connects a control cable  27  to the ignition module  19 , is plugged onto the ignition module  19 . The ignition cable  18 , the grounding cable  26  and the control cable  27  are secured to the cylinder  9  using a common cable retainer  30 . 
     As is shown by  FIG. 2 , an insulating element  21 , which insulates the ignition module  19  thermally from the cylinder  9  of the internal combustion engine  8 , is arranged between the ignition module and the internal combustion engine  8 . 
     As is shown by  FIG. 4 , the insulating element  21  has a stop  59  for the connection  29  of the grounding cable  26 . In the exemplary embodiment, the connection  29  is embodied as a pinch connector. The connection  29  bears against the stop  59 . This ensures that the grounding cable  26  is firstly guided away from the fastening screw  25 , approximately perpendicularly with respect to the cylinder longitudinal axis  31 , in the direction of the exhaust gas silencer  11  of the internal combustion engine  8 . The control cable  27  is also guided away from the connecting plug  28  in this direction. Both cables  26  and  27  are then routed in a loop to the cable retainer  30 . 
     As is shown by  FIGS. 5 and 6 , the cable retainer  30  can be plugged onto a first cooling fin  33  of a cylinder  9  in an insertion direction  70 . The first cooling fin  33  extends perpendicularly with respect to the cylinder longitudinal axis  31  and forms the head fin which faces away from the crank casing of the internal combustion engine  8 . The cable retainer  30  has a bearing web  41  which extends in the direction of the ignition module  19 . The bearing web  41  is retained by the insulating element  21  on the cylinder  9  in the insertion direction  70 . The bearing web  41  is located between the insulating element  21  and the cylinder  9 . As a result, the cable retainer  30  cannot slip counter to the insertion direction  70  of the first cooling fin  33 . The insulating element  21  has a positioning pin  42  which is arranged above a cooling fin  32  of the cylinder  9  and which secures the position of the insulating element  21 . 
     As is also shown in  FIG. 6 , the cable retainer  30  has a projection  37  which constitutes a stop. The projection  37  bears against the upper side of a third cooling fin  35 . However, it is also possible to provide for the projection  37  to be at a distance from the upper side of the third cooling fin  35 . The third cooling fin  35  is lower than an adjacent second cooling fin  35  onto which the cable retainer  30  is plugged. The side of the projection  37  which faces the cooling fins is arranged at a level between the upper side of the third cooling fin  35  and the upper side of the second cooling fin  34 . The second cooling fin  34  is also shown in  FIG. 7 . The projection  37  ensures that the plugging on of the cable retainer  30  onto the cylinder  9  can only occur adjacent to the low third cooling fin  35 . 
       FIG. 6  also shows the arrangement of the cables  18 ,  26  and  27  on the cable retainer  30 . The cable retainer  30  has a receptacle  39  in whose lower area the grounding cable  26  and control cable  27  are arranged one next to the other. The receptacle  39  has a longitudinal opening  67  through which the cables  26 ,  27 ,  18  can be plugged into the receptacle  39 . The ignition cable  18  is arranged on the side of the cables  26  and  27  facing the longitudinal opening  67 . The ignition cable  18  has a diameter which is significantly greater than the diameter b of the grounding cable  26  and than the diameter c of the control cable  27 . The ignition cable  18  is retained clamped in the receptacle  39 . The longitudinal opening  67  is therefore closed by the ignition cable  18  so that the cables  26  and  27  are secured in the receptacle  39  by the ignition cable  18 . The diameters b and c of the grounding cable  26  and control cable  27  are advantageously of approximately the same size. 
     As is shown by  FIG. 6 , the cable retainer  30  has a first slot  38  which extends perpendicularly with respect to the cylinder longitudinal axis  31  and which is plugged onto the first cooling fin  33 . 
     As is shown by  FIG. 7 , the cable retainer  30  has a second slot  36  which extends perpendicularly with respect to the first slot  38  and parallel to the cylinder longitudinal axis  31 . The second slot  36  is plugged onto a second cooling fin  34 . The cable retainer  30  is advantageously plugged onto the cooling fins  33  and  34  with play so that tolerances can be compensated. The two cooling fins  33  and  34  secure the cable retainer  30  in the parallel and perpendicular directions with respect to the cylinder longitudinal axis  31 . Parallel to the insertion direction  70  the cable retainer  30  is secured by the insulating element  21 . As a result, the cable retainer  30  is securely retained on the cylinder  9  in all three spatial directions. 
       FIG. 8  shows the arrangement of the bearing web  41  of the cable retainer  30  adjacent to an upper screw boss  52  at which the ignition module  19  is screwed tight to the cylinder  9 . The screw boss  52  has a round external diameter. The bearing web  41  has, in the exemplary embodiment, a bearing surface  53  which is of curved design and which is seated on the outside of the screw boss  52 . However, there may also be a distance between the bearing face  53  and the screw boss  52 . As is shown schematically by  FIG. 8 , the positioning pin  42  of the insulating element  21  is adjacent to the screw boss  52  and adjacent to the bearing web  41 . 
     The  FIGS. 9 and 10  show the configuration of the insulating element  21 . The insulating element  21  has a bearing face  54  for bearing against the upper screw boss  52  and a bearing face  55  for bearing against the lower screw boss  24 . The lower screw boss  24  is shown in  FIG. 2 . The bearing face  54  is partially surrounded by a wall  60  on which the stop  59  is formed. The bearing face  54  has a bore  56  for a fastening screw  25  and the bearing face  55  has a bore  57  for a fastening screw  25 . The ignition module  19  is screwed to the cylinder  9  using the two fastening screws  25 . The area of the insulating element  21  which extends between the two bearing faces  54  and  55  is arranged offset with respect to the cylinder  9 . As a result, a shoulder  62  is formed adjacent to the bearing face  54 , and a shoulder  63  is arranged adjacent to the bearing face  55 . The positioning pin  42  is arranged on the bearing face  54 , and a further positioning pin  61  is arranged on the bearing face  55 , adjacent to the shoulders  62  and  63 , respectively. The positioning pins  42  and  61  serve to pre-position the insulating element  21  on the cylinder  9  during assembly of the internal combustion engine. The bearing face  54  secures the bearing web  41  of the cable retainer  30  to the cylinder  9 . 
     The  FIGS. 11 to 16  show the cable retainer  30 . As is shown by  FIG. 11 , the receptacle  39  has an upper section  43  for the ignition cable  18  and a lower section  44  for the grounding cable  26  and the control cable  27  (see also  FIG. 6 ). The two sections  43  and  44  are separated from one another by a constriction  45 . The constriction  45  allows the grounding cable  26  and the control cable  27  to be clipped into the lower section  44 . The receptacle  39  is bounded by an outer limb  46 , positioned facing away from the cylinder  9 , and an inner limb  47  arranged adjacent to the cylinder  9 . The second slot  36  is positioned adjacent to the bottom area  64  of the receptacle  39 . As is shown by  FIG. 11 , the side walls of the second slot  36  are inclined with respect to one another and enclose an angle α with one another which may be, for example, 0.5° to 4°. The angle α is advantageously approximately 2°. The angle α opens here onto the side facing the inner limb  47  and the cylinder  9 . Owing to the inclined side wall of the slot  36 , the inner limb  47  is embodied so as to be moveable even if the cable retainer  30  is arranged on a first cooling fin  33 . As is shown by  FIG. 6 , a gap, which becomes larger toward the internal combustion engine  8  is formed between the cable retainer  30  and the first cooling fin  33 . This permits a sprung movement of the inner limb  47 . As a result, the ignition cable  18  can be clipped into the cable retainer  30  and is retained clamped in the cable retainer  30 . In order to permit the cable retainer  30  to be installed adjacent to a housing wall the cable retainer  30  has an outer slope  48  which faces a housing wall of the housing  2 . The profile of the housing  2  adjacent to the cable retainer  30  is shown schematically in  FIG. 2 . 
     As is shown in  FIG. 12 , the second limb  46  has, on its upper side, an insertion slope  49  whose function will be explained in the text which follows. As is shown in  FIG. 11 , an insertion slope  50  is provided on the inner limb  47  lying opposite. In  FIG. 12  the profile of the bottom area  64  of the receptacle  39  is also shown schematically. As is shown in  FIG. 12 , the bottom area  64  extends in a slightly inclined fashion so that the longitudinal direction  68  of the cables  18 ,  26  and  27  which are retained in the cable retainer  30  is also inclined with respect to the first cooling fin  33 . 
     The profile of the insertion slopes  49  and  50  can be seen in particular in  FIG. 15 . The insertion slope  49  is provided on the side of the cables  18 ,  26 ,  27 , said insertion slope  49  being connected to the ignition module  19 , while the insertion slope  50  is arranged on the opposite side, that is to say at the exit of the cables from the cable retainer  30 . 
     As is shown in  FIG. 14 , the insertion slopes  49  and  50  are embodied in such a way that an ignition cable  18  (shown by dashed lines in  FIG. 14 ) can be fitted obliquely onto the longitudinal opening  67 . The ignition cable  18  can be arranged in the cable retainer  30  by means of a pulling movement. Assembly is facilitated by the insertion slopes  49  and  50 . During assembly, the ignition cable  18  is turned at the position shown by dashed lines in  FIG. 14  until the longitudinal direction of the cable coincides with the longitudinal direction  68  of the cable which is shown by dot dashed lines in  FIG. 14 . As a result, the cable retainer can be short in design. There is no need for long spring arms of the limbs  46 ,  47 . 
     In order to permit the cable retainer  30  to be plugged on, the first slot  38  has the plug-in opening  65  which is shown in  FIG. 13 . The second slot  36  has the plug-in opening  66  which is shown in  FIG. 14 . In order to facilitate assembly and at the same time to retain the ignition cable in the receptacle  39 , the bevel  51  which is shown in  FIG. 15  is provided on the inner limb  47 , adjacent to the longitudinal opening  67  of the receptacle  39 . 
     As is shown in particular by  FIG. 16 , the first slot  38  and the second slot  36  together form an essentially T-shaped groove depression. As a result, the cable retainer  30  can easily be plugged onto cooling fins of the cylinder  9 . 
     The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description only. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible and/or would be apparent in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and that the claims encompass all embodiments of the invention, including the disclosed embodiments and their equivalents.