Abstract:
According to an aspect of the present invention, there is provided a recoil starter including: a base plate that has a bearing portion formed therein; a rotary shaft that is supported by the bearing portion so as to pass through the base plate; a rope reel that is rotatably supported at one side of the base plate; a recoil rope that is wound around the rope reel; a recoil spiral spring that urges the rope reel to rewind the recoil rope; a damper spring that has one end connected to the rotary shaft and the other end connected to the rope reel; and a clutch mechanism that is disposed on an end of the rotary shaft at the other side of the base plate and that transfer a rotational force to an engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The entire disclosure of Japanese Patent Application No. 2007-277592 filed on Oct. 25, 2007 including specification, claims, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    An aspect of the present invention relates to a recoil starker in which a rope reel is rotated by pulling a recoil rope wound therearound, and a rotation force of the rope reel is transferred to a clutch mechanism to start an engine via a damper spring. 
         [0004]    2. Background Art 
         [0005]    Generally, a speed adjustment unit equipped with a throttle lever is mounted on the pipe handle of a soil and vegetation management machine, such as a string trimmer, a rotary tiller, a rice transplanter or a lawn mower, and the rotation speed of an engine is controlled by adjusting the pulling amount of the throttle lever. For example, for a string trimmer, a throttle adjustment unit is mounted near a grip on a pipe handle to control the rotation speed of an engine. This throttle adjustment unit is so designed that an engine, such as a gasoline engine, is mounted on one end of a pipe handle, and a rotary blade to be driven by the engine is provided on the other end via a drive shaft fitted into the pipe handle. 
         [0006]    A recoil starter for starting the engine can be provided on the pipe handle. A related-art recoil starter have a structure in which a rope reel and a cam member that serves as a clutch mechanism are elastically connected through a coil-shaped. damper spring located therebetween, and in which the rotation force of the rope reel accumulated by pulling a recoil rope is transferred to the cam member via the damper spring. The rotational force transferred to the cam member can then be transferred to, and used to start, the engine (see, for example, JP-2006-132519-A). 
         [0007]    According to the structure of the related-art recoil starter, a shaft portion is integrally formed with the starter case, and the rope reel and the bearing of the cylindrical cam member (around which the damper spring is wound) are rotatably supported on the shaft portion. Since the shaft portion is formed short, the shaft can not support the rope reel and the cam member along the entire lengths, and merely holds them along only one side. Further, while the starter case is secured to the crankcase of the engine, the shaft portion is not stably provided because it is located away from the crankcase. In addition, since the rope reel and the cylindrical cam member are arranged on the shaft portion of the starter case, high rigidity is required for the starter case to ensure smooth rotations. 
         [0008]    When simply move the shaft portion from the starter case side to the crankcase side, the recoil reel is positioned at the distal end of the shaft portion protrude from the crankcase. Between the recoil reel and the cam member that is to be positioned at the proximal end of the shaft portion, the damper spring is disposed. Since the damper spring is formed in a coil shape and requires a certain length, the rope reel is positioned at a distance from the crankcase. Therefore, the shaft and the supporting structure for the shaft must be formed rigidly. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention resolves these shortcomings, and one objective of the invention is to provide a recoil starter that can reduce the operating load imposed on a rope reel, and that can ensure a steady smooth operation. 
         [0010]    According to an aspect of the present invention, there is provided a recoil starter including: a base plate that has a bearing portion formed therein; a rotary shaft that is supported by the bearing portion so as to pass through the base plate; a rope reel that is rotatably supported at one side of the base plate; a recoil rope that is wound around the rope reel; a recoil spiral spring that urges the rope reel to rewind the recoil rope; a damper spring that has one end connected to the rotary shaft and the other end connected to the rope reel; and a clutch mechanism that is disposed on an end of the rotary shaft at the other side of the base plate and that transfer a rotational force to an engine. 
         [0011]    The base plate may include a partition wall that covers an opening of on a crankcase. 
         [0012]    The base plate may be disposed to cover an opening formed on a case of the engine. 
         [0013]    According to such a configuration, a bearing is mounted on a partition wall that closes a side opening in an engine crankcase, and a clutch mechanism is provided on the crankcase end of a rotary shaft that passes through the bearing, while a rope reel is provided on the opposite end of the rotary shaft and a damper spring is positioned outside the rope reel. Since the clutch mechanism on which a load is imposed during transferring a rotational force to the engine and the rope reel on which a load is imposed by the withdrawal of the recoil rope are positioned at either end of the bearing, the effective load on the bearing can be reduced, and a steady, smooth operation can be obtained. In addition, a special strength is not required for the starter case that covers the recoil starter. 
         [0014]    The recoil spiral spring may be disposed between the base plate and the rope reel. 
         [0015]    According to such a configuration, since a recoil spiral spring is located between the partition wall and the rope reel, after the recoil rope has been pulled out to start the engine, the rope is automatically rewound on the rope reel by the recoil spiral spring, and the damper spring having a larger axial length as compared with the recoil spring is disposed on the opposite side of the rope reel. This arrangement permits the rope reel to be positioned nearer the bearing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Embodiments may be described in detail with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a general cross-sectional view of an engine starting apparatus according to an embodiment of the present invention; 
           [0018]      FIG. 2  is a cross-sectional view of a recoil starter according to the embodiment in the normal (in active) state; 
           [0019]      FIG. 3  is a cross-sectional view of the recoil starter in the started state; and 
           [0020]      FIG. 4  is a cross-sectional view of a recoil starter according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0021]    An engine A is shown in  FIG. 1 . In the engine A, a cylinder  1  that accommodates a piston  2  so that the piston  2  is freely reciprocatable within the cylinder  1  is provided. The piston  2  is connected to one end of a connecting rod  3  via a piston pin  2   a . The other end of the connecting rod  2  is connected to a crankshaft  4  that is arranged within a crankcase  6 . In the crankcase  6 , a flywheel  5  is provided. The crankshaft  4  is rotatably supported by the flywheel  5  at one end of the crankshaft  4 . At the other end of the crankshaft  4 , a crankshaft pin  4   a  is provided so as to be engageable with a recoil starter B, which will be described below. 
         [0022]    A starter case  7  that covers the recoil starter B is provided at an opening formed in the crankcase  6  of the engine A. As illustrated in detail in  FIG. 2 , a partition wall  8  is formed to close the opening of the crankcase  6 . A cylindrical bearing  10  is formed to project from the center of the partition wall  8  toward the opposite side of the crankcase  6 . A rotary shaft  11  is provided to pass through and to be rotatably supported by the bearing  10 . 
         [0023]    A rope reel  14  having a U-shaped groove  13  on which the recoil rope  12  is wound is rotatably supported around the outer face of the bearing  10 . One end of the recoil rope  12  is led outside the starter case  7 , while the other end is fixed to the rope reel  14 . A recoil spiral spring  15  is arranged between the rope reel  14  and the partition wall  8 . When the rope reel  14  has been rotated forward by pulling the recoil rope  12  and the recoil rope  12  is released, the recoil spiral spring  15  drives the rope reel  14  in reverse to rewind the recoil rope  12 . To accomplish this, the inner end of the recoil spiral spring  15  is fixed to the partition wall  8 , and the outer end is fixed to the rope reel  14 . Thus, as the recoil rope  12  is pulled and the rope reel  14  is rotated, rotational force is accumulated by the recoil spiral spring  15 , and when the recoil rope  12  is released, the rope reel  14  is rotated in reverse by the accumulated rotational force of the recoil spiral spring  15 , and the recoil rope  12  is rewound on the rope reel  14 . 
         [0024]    A winding drum  17  is continuously formed with the rotary shaft  11  at the end away from the crankcase  6 . A damper spring  16  shaped like a coil spring is wound on the winding drum  17 . The base portion of the winding drum  17  is embedded within a recessed portion  19  that is formed in the side face of the rope reel  14 , on the inner wall side of the U-shaped groove  13 . One end  16   a  of the damper spring  16  is secured to the distal end of the winding drum  17 , while an end  16   b  is secured to the rope reel  14 . 
         [0025]    Furthermore, a clutch mechanism  18  for transferring a rotational force is provided on the rotary shaft  11  at the end of the crankcase  6  side. Part of the rotary shaft  11  projects outward, to the crankcase  6 , and a sleeve  20  is fixed to the outer wall of the projected portion. In addition, a screw spline  21  is attached to the outer wall of the sleeve  20 , and a cam  23  having a plurality of pawls  22  is fitted on the screw spline  21 . A friction spring  24  is attached to the cam  23  by compression bonding, and the rotation of the friction spring  24  is regulated by a guide  25  arranged on the starter case  7 . Thus, in a normal (inactive) state, the friction spring  24  is positioned at the left of the screw spline  21  as shown in  FIG. 3 . But when rotation of the rotary shaft  11  has begun, and the rope reel  14  is rotating as the recoil rope  12  is being pulled, the screw spline  21  and the cam  23  are fitted together, and the cam  23  is moved to the right. As a result, a pawl  22  on the cam  23  engages a crank pin  4   a  as shown in  FIG. 2 . It should be noted that for this arrangement, a washer  31  is fixed to the distal end of the rotary shaft  11  by a bolt  30 , and that a return spring  26 , located between the washer  31  and the cam  23 , applies a constant pressure to impel the cam  23  to the left. Further, an oil seal  28  is disposed in a recessed portion  27 , which is formed in the partition wall  8  near the rear face of the base of the bearing  10 , so that water, mud and dust, for example, will not enter the clutch mechanism  18 , or electric and electronic parts in the engine A, through an open space between the partition wall  8  and the rotary shaft  11 . 
         [0026]    The operation of the recoil starter B having this arrangement will now be described. 
         [0027]    At first, by pulling the recoil rope  12 , rotation of the rope reel  14  is started. While the recoil spiral spring  15  is wound, a rotational force of the rope reel  14  is transferred to the rotary shaft  11  via the damper spring  16  and to the cam  23 . In the initial state, the cam  23  is not rotated when the rotational force is transferred, since the friction spring  24  holds the cam  23  as shown in  FIG. 3 . As the recoil rope  12  continues to be pulled, the damper spring  16  is further wound in consonance with the rotation of the rope reel  14 , and the rotary shaft  11  begins to rotate against the rotational resistance of the friction spring  24  by the force accumulated in the damper spring  16 . Thereafter, as the rotary shaft  11  is rotated, the cam  23  is moved toward the engine A along the guide  25  and the screw spline  21  and is engaged with a crank pin  4   a , as shown in  FIG. 2 . Subsequently, as the rotation of the rope reel  14  continues, the movement of the cam  23  toward the engine A is regulated by the washer  31 , and the cam  23  begins to rotate with the rope reel  14 , thereby rotating the crank pin  4   a . The crank pin  4   a  and the crankshaft  4  are rotated, thereby reciprocating the piston  2  within the cylinder  1  through the connecting rod  3  and starting the engine A. 
         [0028]    When the engine A has been started and the recoil rope  12  has been released, the recoil spiral spring  15  rewinds the recoil rope by rotating the rope reel  14  in reverse, while the cam  23  is returned to the position shown in  FIG. 3 . 
         [0029]    According to this recoil starter B arrangement, the partition wall  8  is provided so as to close the opening of the crankcase  6 , the bearing  10  is formed on the partition wall  8 , and the rotary shaft  11  is provided to pass through the bearing  10 . Here, the clutch mechanism i 8  is provided on the rotary shaft  11  at the side facing the engine A, and the rope reel  14  is arranged at the other side while the damper spring  16  is located further outside of the rope reel  14 . Accordingly, the clutch mechanism  18  on which a load is imposed during transferring a rotational force and the rope reel  14  on which a load is imposed by pulling the recoil rope  12 , are arranged at either side of the bearing  10 . Therefore, a load imposed on the bearing  10  is minimized, and a steady and smooth operation can be ensured. 
         [0030]    Furthermore, as a starter case  7  covering the recoil starter B, a special rigidity is not required. 
         [0031]    In addition, the recoil spiral spring  15  is located between the partition wall  8  and the rope reel  14 , and the damper spring  16  having a larger axial length as compared with the recoil spiral spring  15  is located on the side opposite (outside) the rope reel  14 . Therefore, the rope reel  14  can be located nearer the bearing  10 . 
         [0032]    The damper spring  16  is not limited to the above described example, i.e., a coil spring, and may be formed like a spiral spring, as shown in  FIG. 4 . In this case, an end  16   a  of a damper spring  16  is secured to the distal end of a winding drum  17  of a rotary shaft  11 , and the other end  16   b  is secured to a rope reel  14 . It should be noted that the same reference numerals as used in  FIGS. 1 to 3  are employed to denote corresponding components in  FIG. 4 .