Patent Publication Number: US-7721698-B2

Title: Starter of small engine

Description:
BACKGROUND 
   This invention relates to an ignition system for small engines which may give sufficient horse power to a horse power spring for engine rotation, by providing a torque limiter with the current ignition systems. 
   Generally, a small engine ignition system has a drive gear which connects to a tubular cam having a nail engaging to a centrifugal latchet of a pulley fixed to the engine crankshaft with a horse power spring. This drive gear is rotated manually or by an electric motor to store energy in the horse power spring, when the energy exceeds the start resistance, the sudden release of the horse power spring starts the engine. 
   SUMMARY 
   Problems Resolved by the Invention 
   If the energy exceeding the start resistance is then stored in the horse power spring, the engine may be rotated by the horsepower of the horse power spring. 
   However, the start resistance of the engine is at its highest when the piston is at near the top dead center, and at its lowest when the piston is at near the bottom dead center; thus, the start resistance of the engine is unstable. Before enough horsepower is given to the horse power spring and/or sufficient energy is stored, the engine may start to rotate. In this case, the engine may not surely start. 
   This invention will solve the problems above and the purpose of the invention is to provide an ignition system for small engines that will enable the engine to surely start by giving enough horsepower to the horse power spring, regardless of the resistance. 
   Means to Resolve the Problem 
   In order to solve these problems, the invention defined as claim  1  is comprised of; the inside of the starter motor, a cylindrical cam having a cam nail which engages with a pulley centrifugal latchet fixed on the engine crank shaft, and a drive gear connecting to the cylindrical cam via a horse power spring located on the same axis; 
   a stopper being arranged near a cam plate which is integrally formed with the pulley, and having an engageable engaging with the end part behind the rotation direction of the cam plate depressed area; 
   urging means supporting the stopper in movable manner to an engaging position where the engaging engages with the depressed area and to an avoidance position for avoiding the cam plate rim, and normally urging to move the stopper to the avoidance position, on the other hand enabling the stopper to move the engaging position from outside, and urging not to move the stopper to the avoidance position until a sufficient rotation load is added to the cam plate at the engaging position. 
   The Ignition system for small engines as defined in claim  2  is comprised of; the first spring supporting the stopper in a swinging manner to the spindle provided in the starter case, and, around the spindle on both sides of the stopper, urging the stopper to swing to the avoidance position; 
   the second spring urging the stopper to swing to the engaging position; 
   enabling to move the stopper to the engaging position by pulling the second spring from the outside. 
   The ignition system for small engines as defined in claim  3  is comprised of; operation means which pulls the second spring from outside enabling operation of the start button of the engine self starter motor. 
   The invention defined as claim  4  is comprised of; a long hole being provided in the stopper and a spindle provided in the starter being engaged with the long hole so as to retract the stopper from the engaging position and move to the avoidance position. 
   EFFECTS OF THIS INVENTION 
   According to the invention defined in claim  1 , since the start resistance of the engine and rotational resistance due to a stopper are added to the cam plate during ignition of the engine, sufficient energy is stored in the horse power spring due to the drive gear rotation. Since the engine is rotated releasing sufficient energy, the engine can surely tart. 
   According to the invention defined in claim  2 , the stopper quickly moves between an avoidance position and an engaging position with the first and second springs. The movement operation is also easy. 
   According to the invention defined in claim  3 , the stopper movement and self starter motor start can be performed by single operation. This makes for an efficient operational system. 
   According to the invention defined in claim  4 , the stopper may smoothly retract from the engaging position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a front view of the starter of the present invention; 
       FIG. 2  shows a vertical cross-section drawing of the starter; 
       FIG. 3(   a ) and ( b ) show the front view of the small-diameter gear and cross-section drawing of a-a line respectively; 
       FIG. 4(   a ) and ( b ) show the front view of small-diameter gear and cross-section drawing on b-b line respectively; 
       FIG. 5  is a cross-section diagram which shows nails of small-diameter gear and large-diameter ear engages with each other; 
       FIG. 6  is a cross-section diagram which shows nails of small-diameter gear and large-diameter gear do not engage with each other; 
       FIG. 7  is a vertical cross-section diagram of the starter during recoil start; 
       FIG. 8  is an illustration viewed from the front which shows the status where the stopper is at the avoidance position against the cam plate; 
       FIG. 9(   a ) and ( b ) show operation function of the limiter button and the motor start button; 
       FIG. 10  is an illustration which shows the stopper is moving to the engaging position; 
       FIG. 11  is an illustration whish shows the stopper in the engaging position; 
       FIG. 12  is an illustration which shows the stopper is pushed out from the engaging position and retracts; and 
       FIG. 13  is a simplified illustration which shows another example of the cam plate and the stopper. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   Hereinafter, embodiments of the present invention will be described with reference to the drawings. In  FIG. 1  and  FIG. 2 , the ignition system for small engines is a combination of a recoil starter towing the starter rope  2  which is wound around the rope reel  1  and an electric self starter motor  3 , the pulley  5  fixed to the engine crank shaft is installed on one side of the starter case  4 , a spindle  6  is formed on the same axis of the pulley  5  in the starter case  4  and a cylindrical cam  7  engageable with the pulley  5  and a drive gear  8  which connects to the cylindrical  7  via a horse power spring  11  (spiral spring) are arranged in a freely rotating manner. 
   The cam plate  12  is integrally formed on the periphery of pulley  5 . 
   The cam  7  is arranged on the pulley  5  side of the drive gear  8 , and the cam nail  10  formed on the cam  7  is arranged oppositely to latch with the centrifugal latchet  9  provided on the side surface of pulley  5 . The centrifugal latchet  9  is urged to always latch with the cam  7  with a spring. Consequently, similarly to the patent publication  1  mentioned earlier, when the cam  7  rotates in one direction, a pulley  5  also rotates since the centrifugal latchet  9  and the cam nail  10  engage with each other, and when the cam  7  rotates in the opposite direction, the cam idles so that the pulley  5  does not rotate. When rotation of the pulley  5  rotates the engine, and the rotation of the engine rotates the pulley  5 , the centrifugal latchet  9  rotates in the direction that unlatches the centrifugal latchet  9  from the cam nail  10  due to centrifugal force, so that rotation transfer with the cam  7  of the engine is blocked. 
   A cyclic depressed area  13  is formed on the cam  7  side of the gear of drive gear  8  and the horse power spring  11  is arranged in the cyclic depressed area  13 . One end of horse power spring  11  latches onto the drive gear  8  and the other end of the horse power spring  11  latches onto the cam  7 . Thus, when the drive gear  8  rotates, the horse power spring  11  is wound and the rotary force is stored in the horse power spring  11 , and when sufficient horsepower is stored, the cam  7  starts to rotate. The nails  14  and  15  are formed on the side surface of the opposite side of cam  7  of the drive gear  8 . 
   The recoil start and the motor start are structured so as to rotate the drive gear  8 . 
   The rotation transfer mechanism with its recoil start works in the follow manner; the rope reel  1  is supported in a freely rotating manner at the opposite side of the cam  7  on the spindle  6  of the drive gear  8 . The rope groove  16  is formed on the periphery of the rope reel  1 , and the disk area  17  is formed on the inner periphery. The starter rope  2  is wound in the rope groove  16 , one end of the starter cord  2   a  is pulled outside of the starter case  4  and end of a base side is fixed at the rope reel  1  being pulled outside of the bottom hole (not shown) of the groove  16  to prevent it from coming off. By pulling the one end of the starter cord  2   a , the starter rope  2  is pulled out from the rope reel  1  and the rope reel  1  rotates and drives around a reel spindle  6 . In the disc store  17 , a disk  19  which is equipped with the latchet nail  15  attaching and detaching to the latchet nail  14  of the drive gear  8  is provided in a movable manner, and is urged to always engage with the ratchet nail  14  of the drive gear with a compressive spring  18 . The disk  19  is provided in a movable manner along a cylindrical part  1   a  of inner periphery of the rope reel  1 . 
   Next, the mechanism of rotation transfer to the drive gear  8  with the self starter motor  3  is composed of two reducing gears. That is, the first reducing gear  23  is meshed and connected to the gear  2  of the self starter motor  3  (driven by a battery) output shaft  21 , the second reducing gear  24  is meshed and connected to small-diameter gear  23   a  of the fist reducing gear  23 , and the second reducing gear  24  meshes with the periphery gear  25 . The second reducing gear  24  meshing with the drive gear  8  is divided into the small-diameter gear  24   a  and large-diameter gear  24   b , and both gears are supported in a freely rotating manner on the common rotation axis  26 . The small-diameter  24   a  meshes with the drive gear  8 , and the large-diameter gear  24   b  meshes with the small-diameter gear  23   a  of the reducing gear  23 . The large-diameter gear  24   b  moves along the rotation axis  26  and is arranged in a detachable manner to the small-diameter  24   a.    
   On the side surface, facing the small-diameter gear  24   a  and the large-diameter gear  24   b  each other, three engaging nails  27  and  28  are formed respectively. As shown in  FIGS. 3  ( a ), ( b ) and  FIGS. 4  ( a ), ( b ), one side of the circumferential direction of each engaging nail ( 27 ) and ( 28 ) is inclined and the other side is formed vertically against the side surface. As shown in  FIG. 5 , when engaging nails  27  and  28  rotate in the same direction, they engage each of their vertical surfaces and both gears rotate, and when the engaging nails rotate in the opposite direction, as shown in  FIG. 6 , each inclined surface abuts, not engages, and either of the gears idles. The compressive spring  29  is arranged between the starter case  4  and large-diameter gear  24   b , the large-diameter is pressed toward the small-diameter gear  24   a  by the compressive spring  29 , and the side surface of the large-diameter gear  24   b  and the small-diameter gear  24   a  is urged to contact to each other. 
   As shown in  FIG. 7  and  FIG. 8 , the cam plate  12  which is integrally formed with the pulley  5  is comprised of having a depressed area  30  formed on the rim of the disk, and the stopper  31  is arranged near the cam plate  12 . The stopper  31  is an elongated plate-like body, has an engageable engaging  31   a  at the end  32  (engaging end) behind the rotation direction of the cam plate  12  depressed area  30 , a long hole  33  is also created at the center of the stopper  31 , and the spindle  39  provided in the ignition case  4  engages with the long hole  33 . 
   The stopper  31  may swing around the spindle  39 , an engaging pin  34  is provided on both sides of the stopper  31  of the starter case, and the stopper  31  may swing until the stopper  31  engages with the pin  34 . That is, the stopper  31  is supported in a swinging manner to the avoidance position (the position shown in  FIG. 8 ) where the engaging  31   a  avoids the rim of the cam plate  12  and the engaging position (the position shown in  FIG. 8 ) where the engaging  31   a  engages with the engaging end  32  of the cam plate. 
   On the both sides of the stopper  31 , the first spring  35  which urges the stopper  31  to swing to the avoidance position and the second spring  36  which urges the stopper  31  to swing to the engaging position are arranged. The stopper  31  is urged to move to the avoidance position where the engaging  31   a  does not engage with the engaging end  32  of the cam plate  12  with the first spring  35 . 
   The end of the first spring  35  is fixed to the starter case  4 , and the second spring  36  end is installed in the limiter button  38  (operation means) installed outside of the wall  37  of the starter case  4  via the wire  43 . The limiter button  38  is installed detachably from the wall  37 , pulling the limiter button  38  pull the second spring  36 , and the stopper  31  may swing to the engaging position against the first spring  35 . 
   Next, the third spring  40  (urging means) is arranged at the end of the opposite side of the engaging  31   a  of the spindle  39  and the stopper  31 . Thus, within the area where the both ends of the long hole  33  engages with the spindle  39 , the stopper  31  is arranged in a movable manner to the position where the engaging  31   a  engages with the engaging end  32  of the cam plate, and the retracting position (the position shown in  FIG. 12 ) where the engaging  31   a  retracts from the engaging position and the engaging is released. The retracting is performed with the stopper engaged with the cam plate when sufficient rotation resistance is added to the cam plate and the cam plate cannot bear the load, and the stopper moves to the avoidance position with the first spring. 
   The limiter button  38 , as shown in  FIG. 9  ( a ), has a guard  42  on one side of the cylindrical part  41  and one end of the wire  43  is fixed to the cylindrical part. Inside the cylindrical part  41 , the axis  45  of the start button  44  for the self starter motor is fitted in a swinging manner. Hence, according to the switch button structure, conditions can be divided into four categories; when the limiter button  38  and the motor starter button  44  are pulled (as shown in  FIG. 9(   a )), or when only the limiter button  38  is pulled (as shown in  FIG. 9(   b )), or when neither of the limiter button  38  nor the motor starter button  44  is pulled (as shown in  FIG. 8) . 
   Next, operation function of the ignition system with the said structure is explained. 
   When the engine is started with the self starter motor  3 , as shown in  FIG. 9  ( a ), the limiter button  38  and the motor start button  44  are pulled. With the operation of the motor start button, as shown in  FIG. 2 , electricity is supplied from a battery to the self starter motor  3 , and the rotary force is transmitted to the large-diameter gear  24   b  of the second reducing gear  24  from the gear  22  fixed on the output shaft  21  through the first reducing gear  23 . Since the large-diameter gear  24   b  is pressed against the small-diameter  24   a  with a compressive spring  29  and when the large-diameter gear  24   b  rotates, in the direction shown in  FIG. 2 , engaging nails of the small-diameter gear  24   a  and the large-diameter gear  24   b  engage with each other; hence, the small-diameter gear  24   a  rotates, the rotary force is transmitted to the drive gear  8  and the drive gear  8  rotates. When the drive gear  8  rotates, the load to the cam  7  becomes large since the rotation resistance increases due to the engine start resistance, the horse power spring  11  is wound and fasten. Since the engine rotation resistance is small at first, when a sufficient amount of energy is stored in the horse power spring  11 , the cam rotates and the cam plate  12  integrally formed with the pulley  5  rotates via the centrifugal latchet  9 . 
   With the operation of the limiter button  38 , in addition to the engine start resistance, rotation resistance of the cam plate  12  with the stopper  31  is also added to the cam. That is, by pulling the limiter button  38 , as shown in  FIG. 10 , spring power of the second spring  36  becomes larger than that of the first spring  35 , and the stopper is urged to swing toward the right rotation direction of the figure. In this situation, after the self starter motor start button is turned on as stated above, as stated above, when the cam plate  12  rotates and the depressed area  30  passes through the stopper  31 , the stopper  31  quickly swings to the engaging position as shown in  FIG. 11  through the status as shown in  FIG. 10 , and the engaging  31   a  of the tip end of the stopper  31  with the engaging  32  behind the depressed area  30  of the cam plate  12 ; hence, the cam plate  12  stops since the rotation resistance due to the stopper  31  is added. The engine rotation also stops. This stop position is at the compression top dead center of the piston, and the position almost matches with the position where the rotation resistance is at maximum when the air-fuel mixture is compressed. 
   Since the self starter motor  3  continues rotating, the drive gear  8  also continues rotating and the horse power spring  11  is more strongly wound and fastened; hence, the rotary force from the cam to the cam plate  12  increases. When the energy stored in the horse power spring  11  exceeds the rotation resistance against the cam plate  12 , which is the sum of the engine rotation resistance and rotation deterrent force, the stopper  31  cannot resist the load, and, as shown in  FIG. 12 , the stopper retracts against the spring power of the spring  40  and moves to the initial position as shown in  FIG. 8  by being swung by the first spring  35 . When the stopper  31  comes off from the cam plate  12 , the energy stored in the horse power spring is released suddenly, the cam  7 , the cam plate  12  and the pulley  5  rotate, and the engine connected to the pulley  5  starts to rotate at high speed. 
   When the drive gear  8  rotates as described above, in the rotation direction, as shown in  FIG. 2  and  FIG. 5 , each inclined surface of the latchet nail  14  of the drive gear  8  and the latchet nail  15  of the disk  19  of the rope reel  1  contact, the nails override against the compressive spring  18 , the nails do not engage and are separated; rotary force of the drive gear  8  is not transmitted to the rope reel  1 . 
   Next, when the engine is started with the recoil start, as shown in  FIG. 9  ( b ), only the limiter button  38  is pulled, a starter rope  1  is dragged to rotate the rope reel  1 . As shown in  FIG. 7 , since the latchet nail  15  of the disk  19  and the latchet nail  14  of the drive gear  8  are urged to engage with each other with the compressive spring  18 , the drive gear  8  rotates. When the drive gear  8  rotates, as described above, energy is stored in the horse power spring  11 , the energy is then released suddenly, the cam  7 , the cam plate  12 , and the pulley  5  rotate, simultaneously, the engine connected to the pulley  5  rotates at high speed and starts to run. 
   When the engine starts with the recoil start, the drive gear  8  rotates, this rotation is transmitted to the small-diameter gear  24   a  of the second reducing gear  24 ; hence the small-diameter gear  24   a  rotates. However, in the case of this rotation direction, as shown in  FIG. 5  and  FIG. 7 , each inclined surface of the engaging nails  27  and  28  of the small-diameter gear  24   a  and large-diameter gear  24   b  contact and override, so that the nails  27  and  26  cannot engage with each other. Because of the reduction rate, since the torque which rotates the large-diameter gear  24   b  is greater than the spring power of the compressive spring  29 , the large-diameter gear  24   b  is locked and moves on a rotation axis  26  to secede from the small-diameter gear  24   a  against the compressive spring  29 ; hence, only the small-diameter  24   a  idles and the rotary force of the drive gear  8  is not transmitted to the large-diameter gear  24   b.    
   As stated above, to start the engine, the start resistance and rotation resistance due to the stopper  31  are added to the cam plate  12 ; hence energy is sufficiently stored due to the rotation of the drive gear  8  in the horse power spring  11 , which surely start the engine. 
   The self starter motor start or the recoil start is selectively performed in the above example. However, this invention is not limited to the examples. Either start method can be applied. 
   The stopper adding the rotation resistance to the cam plate is not limited to the mentioned above. For example, the structure, a spring  41  engages a spherical shape to the depressed area  42  of the cam plate  12 , may be applied.