1. Field of the Invention
The present invention relates to an engine starter which starts an internal combustion engine by using an ultra-compact direct current motor, and more particularly to an electric engine starter which can remove a conventional recoil driving unit from its body and arrange a battery for driving the motor, outside there, hence to realize downsizing because of the most efficient arrangement of the components and to extremely decrease fatigues at each operation of various working machine.
2. Description of the Related Art
At the present, an engine starter which starts a compact air-cooled gasoline engine mounted on a popular portable machine such as a shearing machine and a chain saw generally includes a recoil driving unit, a follower connected to a crank shaft of an engine through an switching means such as a centrifugal clutch, and a shock absorbing/pressure accumulating unit including a spring, arranged between the driving unit and the follower for absorbing the driving power of the driving unit and accumulating the pressure under the follower. The recoil driving unit has a recoiling reel with a recoil rope wound there and a recoiling spring arranged between the recoiling reel and a casing, the internal and external ends of the recoiling spring being respectively fixed to the recoiling reel and the casing. The recoiling reel is rotated only in one direction by drawing the recoil rope, the recoiling spring is wound up to accumulate a spring power, and when the recoil rope is released in this state, the accumulated power of the recoiling spring is released to wind back the recoiling reel automatically.
The above recoil driving unit requires a drawing operation for drawing the recoil rope every time of starting the engine. The drawing operation of the recoil rope has to be done so quickly and widely that a person having little power or an elderly person cannot start the engine only by one drawing operation. Thus, there have been a lot of proposals to make the engine start easy through the drawing operation of the recoil rope and they are in a practical use, but the troublesome operation of the drawing operation itself still remains. On the other hand, a progress in the recent compact electric motor and battery is remarkable and in spite of being downsized, they come to have the larger capacity. Taking this situation into account, an electric engine starter is reviewed which can start an engine quickly and easily by a switching operation, in order to avoid the troublesome operationality of the above recoiling starter, and its development is desired.
A compact electric engine starter of this kind includes the engine starter of old disclosed in, for example, Japanese Utility Model Application Laid-Open (JP-U) No. 63-110672 (patent document 1). This starter includes a direct current motor which is driven by the power of a battery, a spring which is wound up through the operation of a spring barrel drum by a warm gear fixed to an output shaft of the motor, an output rotation shaft to which the lateral end of the spring is fixed, a rotation shaft of the engine connected to the output rotation shaft through a one-direction clutch, a rotation lever which stops the rotation of the output rotation shaft or releases the stop, an interlock electric switch which operates to turn on only at a stage of releasing the rotation stop of the output rotation shaft by the lever, and an armature current controller which drives the motor at a time of turning off the electric switch, winds up the spring while keeping the rotation also when the rotation speed of the motor is beyond the set rotation speed, and stops the rotation of the motor by the power off when the rotation speed falls down below the set rotation speed at a time of finishing the winding up of the spring. A speed reducing gear may be interposed between the warm gear and a gear formed around the outer periphery of the spring barrel drum.
By way of example, Japanese Patent No. 2573340 (patent document 2) discloses a spring-driven starter which accommodates into a single frame a battery, a direct current electric motor driven by the electric power of the battery, a controller which controls the stop of the operation of the motor, a reduction gear mechanism of high reduction gear ratio which transmits the power of the motor, a spring-driven power accumulating unit or which is driven by the reduction gear mechanism, and a driving power transmitter which transmits the power of the accumulating unit to the crank shaft one-sidedly. The reduction gear mechanism of high reduction gear ratio includes a planetary reduction gear of the first stage to be driven by the direct current electric motor, which is arranged on the other axis line parallel to the crank shaft, and a reduction gear of the second stage which is formed by meshing a driven gear integrated with the outer periphery of the spring power accumulating room of the accumulating unit, with a driving gear provided on the output shaft of the planetary reduction gear.
For example, in JP-U No. 2-13171, a spring barrel drum is pivoted rotatably in one direction through a supporting system of the planetary reduction gear arranged at the opposite side of the crankshaft of the engine. The rotation speed of the spring barrel drum is reduced by the planetary reduction gear connected through a pair of reduction spur gears composed of a small gear and a large gear fixed to the output shaft of the direct current electric motor arranged within the housing. One-way rotation at this time is performed by the mesh of a ratchet claw and a tooth portion provided on the outer peripheral portion of the spring barrel drum. A start ratchet wheel and a start ratchet claw are arranged on the side of the crankshaft of the spring barrel drum and when the mesh is released, the ratchet wheel becomes rotatable. A starter ratchet wheel is built in the start ratchet wheel and the starter ratchet wheel is engaged in a centrifugal clutch claw provided in the crankshaft.
The ratchet wheel is integrated with the outer periphery of the spring barrel drum and the ratchet wheel of small diameter is engaged in the upper end portion of the spring barrel drum. A rotation shaft fixed to the ratchet wheel of small diameter is designed to remove a manual crank externally. During the ordinal operation of the engine, the manual crank is not inserted and the ratchet wheel of small diameter runs idle. When failing in start and trying to rewind the spring, the manual crank is inserted into the rotation shaft of the ratchet wheel of small diameter, to rotate the spring barrel drum and accumulate the pressure in the spring. At an engine start time, the above start ratchet is operated, an energy accumulated in the spring is released to rotate the starter ratchet wheel, thereby to crank and start the engine.
A starter, for example, in Japanese Patent Application Laid-Open (JP-A) No. 2002-285940 interposes a shock absorbing/pressure accumulating means on the way of the power transmission system between a driving unit and a follower. The driving unit is an electric motor as its driving source and a reduction mechanism is formed by a warm jointly fixed to the output rotation shaft of the electric motor and a warm wheel provided on the outer periphery of the spring barrel drum. The above structure is actually the same as that of the above JP-U No. 63-110672. A recoil driving unit is provided on the driving side, separately from the electric motor, and the recoil driving unit includes a rope reel with a recoil rope wound there, which reel is rotated by drawing the recoil rope, a recoiling spring which rotates the rope reel inversely so as to wind up the recoil rope, and a recoiling ratchet mechanism which transmits the rotation of the rope reel to the shock absorbing/pressure accumulating means. The spring barrel drum is designed to rotate only in one direction by a one-way clutch. Owing to this structure, the starter of the JP-A No. 2002-285940 may be referred to as only the combination of the above JP-U No. 63-110672 and the well-known recoil mechanism.
According to the engine starter of the above JP-U No. 63-110672, since the warm gear directly connected to the electric motor is engaged in the warm wheel formed on the outer periphery of the spring barrel drum, hence to rotate the spring barrel drum in one direction, the spring barrel drum is not rotated inversely, but in this power transmission mechanism due to the engagement of the warm gear and the warm wheel, the output axis direction of the electric motor and the rotation driving shaft of the spring barrel drum cross at right angle, and thus for the sake of design, efficiency is poor (about 60%) and the downsizing is limited. According to the engine starter in the JP-U No. 63-110672, when the battery is dead and the electric motor gets out of order, the engine starter itself cannot be operated.
According to the Japanese Patent No. 2573340, on the other hand, the reduction gear mechanism of high reduction gear ratio is arranged between the electric motor and the spring barrel drum, the capacity of motor and the capacity of battery are respectively reduced to less than 1/10 and 1/6 in the cell starter method, and even when a compact battery is mounted, it would not lose a practical use. The reduction ratio of the reduction gear mechanism of high reduction gear ratio is set to remarkable degrees of 1/250 to 1/300. Therefore, it naturally takes a lot of time to rotate the spring barrel drum enough to accumulate a necessary pressure in the spring. In this engine starter, an automatic winding controller of spiral spring is provided, the power accumulating operation of the power accumulating spring is automatically performed by a control circuit of this controller in every starting operation, and the power supply to the motor is stopped by detecting a timer or the winding up of the spring, thereby reducing the waiting time of restart. As a result, the whole device becomes complicated, naturally its maintenance becomes troublesome, and accordingly the cost becomes expensive. Needless to say, the battery is built the device within, and the whole device upsizes so much.
According to the JP-U No. 2-13171, when the electric motor breaks down, the manual crank is operated to rotate the spring barrel drum through the ratchet wheel of small diameter, the spring is rewound to have the accumulated power, the starting ratchet is operated after removing the manual crank, to release the energy accumulated in the spring, hence to rotate the starter ratchet wheel and start the engine. However, during the rotation of the engine, the ratchet wheel of small diameter runs idle. In the JP-U No. 2-13171, since the respective axes of the electric motor, the spring barrel drum, the ratchet wheel of small diameter, and the ratchet claw are in parallel with each other, this extremely limits the downsizing of the engine starter.
In the JP-A No. 2002-285940, since the spring barrel drum is manually driven through the recoil driving mechanism in an emergency, the whole device comes to include the electric motor and its reduction mechanism in addition to the conventional recoiling engine starter, and further, since the reduction mechanism is composed of the warm gear and the warm wheel of the spring barrel drum, the electric motor shaft and the supporting shaft of the spring barrel drum cross at right angle, and therefore, it is difficult to downsize the whole device similarly to the JP-U No. 63-110672.