JPH0511345Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ratchet transmission for a recoil starter for starting an internal combustion engine.

BACKGROUND ART In general, a ratchet transmission device for a recoil starter has a ratchet wheel attached to the recoil starter, and a ratchet pawl eccentrically pivoted to the crankshaft inside a cooling fan attached to the tip of the crankshaft of an internal combustion engine. The pawl is detachably arranged on the ratchet wheel, and the manual rotational force of the recoil starter is transmitted to the crankshaft of the internal combustion engine via the ratchet pawl and the ratchet pawl to start the internal combustion engine. When the engine speed increases after starting the internal combustion engine, the ratchet pawl pivots due to centrifugal force and separates from the ratchet wheel, thereby releasing the driving connection between the recoil starter and the internal combustion engine. In such conventional devices, the ratchet pawl is constructed from an assembly consisting of a relatively large number of separate parts, such as a pawl member, a spring member, a spacer member, a bolt, a washer, and the like.

Problems to be Solved by the Invention In the conventional ratchet transmission device for recoil starters, the ratchet pawl is composed of an assembly of many parts, so it takes time and effort to process and assemble the parts, and the structure is poor. This is complicated, making it difficult to miniaturize the device, and when the device is damaged, many parts fly off, posing a great danger to workers.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a recoil starter ratchet transmission device that solves the problems of the prior art and is simple and convenient.

Means for Solving the Problems A ratchet transmission device for a recoil starter according to the present invention has a rotatable ratchet wheel and a ratchet pawl eccentrically attached to a cooling fan rotor fixed to the crankshaft of an internal combustion engine, The ratchet pawl is integrally formed with an engaging part that removably engages with the ratchet wheel and a long and thin rod-shaped spring part that biases the engaging part in the direction of engaging with the ratchet wheel, and the crankshaft rotates at high speed. At times, the action of centrifugal force causes the spring portion to curve into a circle connecting the inner ends of the blades of the cooling fan rotor.

Effects According to the configuration of the present invention, the engaging portion and the spring portion are configured as one integral part and can be assembled at the same time, and the number of parts and assembly man-hours can be significantly reduced.

Embodiments Next, the present invention will be described based on illustrated embodiments.

This embodiment is an example in which the present invention is applied to a portable power working machine such as a chainsaw. Fixed. The cooling fan rotor 2 has a large number of blades 4 integrally formed on a portion of its end surface 2' near the outer circumferential edge, and sucks air from the outside by rotation of the crankshaft 1 and the cooling fan rotor 2 due to the operation of the internal combustion engine. This system cools the internal combustion engine by forcing it to flow around the engine.

A recoil starter 5 is disposed close to and coaxially with the tip of the crankshaft 1. The recoil starter 5 has a drawstring 7 wound around a drum 6 biased by a spiral spring (not shown), and by pulling the drawstring 7, the drum 6 is rapidly rotated against the spring force of the spiral spring. , is configured to start the internal combustion engine as described below.

Crankshaft 1 of drum 6 of recoil starter 5
A ratchet wheel 8 is coaxially formed on the side end face, and the ratchet wheel 8 forms a pair of ratchet teeth 9 and 10 respectively projecting radially outward.

On the other hand, the cooling fan rotor 2 is provided with a pair of ratchet pawls 11 and 12 that can engage with the ratchet teeth 9 and 10 on the recoil starter side end surface 2'.
The ratchet pawls 11 and 12 are eccentrically disposed symmetrically with respect to the crankshaft 1 at positions radially inward of the rotor 2 from the blades 4 and diametrically opposed to each other.
The ratchet claws 11 and 12 are made of a wear-resistant and elastic synthetic resin material such as polyacetal or nylon resin, and have the same shape and dimensions. Therefore, only the structure of one ratchet pawl 11 will be described.

The ratchet pawl 11 has a shaft portion 15 integrally formed with one end portion 14 of the engaging portion 13.
is rotatably fitted into a hole 16 formed eccentrically from the attachment portion of the cooling fan rotor 2 to the crankshaft 1 . Furthermore, the one end portion 14 of the engaging portion 13
A flange portion 17 is integrally formed adjacent to the shaft portion 15, and the flange portion 17 is fixed in the axial direction by a washer member 18 which is fastened to the crankshaft 1 together with the cooling fan 2 by a nut 3. Retained immovably. With this configuration, the ratchet pawl 11 has the other end 19 of the engaging portion 13 connected to the ratchet wheel 8.
The engagement position (the position shown by the solid line in FIG. 2) where the other end 19 of the engaging portion 13 engages with the ratchet tooth 9 or 10 of the ratchet wheel 8 (the position shown by the solid line in FIG. 2)
It can be pivoted between a release position (shown in phantom in FIG. 2) and a release position.

Further, the ratchet pawl 11 is integrally formed with an elongated rod-shaped spring portion 20 extending from the one end portion 14 substantially parallel to the engaging portion 13. When the rotor 2 is at rest, the outer end of the spring portion 20 is in contact with the inner end 21 of the blade 4 of the cooling fan rotor 2, and the resulting elastic force of the synthetic resin material of the spring portion 20 causes the entire ratchet pawl 11 to be It is biased toward the engagement position with the ratchet teeth 9,10.

With the above configuration, when the internal combustion engine is stopped,
The ratchet pawls 11 and 1 are moved by the biasing force of the spring portion 20.
2 is in the engagement position with the ratchet teeth 9,10. When starting an internal combustion engine, when the pull string 7 of the recoil starter 5 is pulled to rotate the drum 6, the rotational force is transmitted to the crankshaft via the ratchet wheel 8, ratchet teeth 9, 10, ratchet pawls 11 and 12, and cooling fan rotor 2. The signal is transmitted to the shaft 1, rotates the crankshaft 1, and starts the internal combustion engine. When the pull string 7 of the recoil starter 5 is released, it is wound back onto the drum 6 by the force of the spiral spring and returns to its original state. When the internal combustion engine is started, the crankshaft 1 rotates at high speed, so that the ratchet pawls 11 and 12 overcome the biasing force of the spring portion 20 due to the centrifugal force acting on them, and rotate in the radial direction about the respective shaft portion 15. Pivoting outwards instantaneously, the respective engagement part 13 disengages from the ratchet teeth 9 and 10 of the ratchet wheel 8 and moves into the said release position. At this time, the spring portions 20 of the ratchet pawls 11 and 12 bend into a circle connecting the inner ends 21 of the blades 4 of the cooling fan rotor 2, as shown by chain lines in FIG. A spring force is stored to return the pawls to the engagement position, and when the internal combustion engine stops, the ratchet pawls 11 and 12 are returned to the engagement position again, and the respective engaging portions 13 are engaged with the ratchet teeth 9 and the ratchet teeth 9 of the ratchet wheel 8. 10. In this way, the ratchet wheel 8 and the ratchet pawl 1
1 and 12 constitute a ratchet transmission device that transmits the rotational starting force of the recoil starter 5 to the internal combustion engine.

Effects of the invention As explained above, the ratchet claw of the invention has
Since the engaging part and the spring part are integrally formed as one part from synthetic resin material, the number of parts of the device is greatly reduced, the structure is simplified and lightened, and the assembly work is simplified. In addition, when the crankshaft rotates at high speed, the elongated rod-shaped spring part formed integrally with the ratchet pawl curves into a circle connecting the inner ends of each blade of the cooling fan rotor due to the action of centrifugal force. Since the elongated rod-shaped spring portion is safely supported at the inner end of each blade of the cooling fan rotor even when the crankshaft rotates at high speed, it effectively prevents accidents such as breakage.
If the ratchet pawl is made of a synthetic resin material or the like, the self-lubricating property of the material itself can improve the operational stability.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part of an embodiment in which the present invention is applied to a portable power working machine, FIG. 2 is a cross-sectional view taken along the - arrow in FIG. FIG. 3 is a side view of the ratchet pawl of FIG. 1... Crankshaft, 5... Recoil starter,
8... Ratchet wheel, 11, 12... Ratchet pawl, 13
...Engagement part, 20...Spring part.

Claims (1)

[Scope of utility model registration request] It has a rotatable ratchet wheel and a ratchet pawl eccentrically attached to a cooling fan rotor fixed to a crankshaft of an internal combustion engine, and an engaging portion that removably engages with the ratchet pawl on the ratchet pawl. An elongated rod-shaped spring portion that urges the engaging portion in a direction to engage the ratchet wheel is integrally formed, and the spring portion is moved toward the cooling fan rotor by the action of centrifugal force when the crankshaft rotates at high speed. A ratchet transmission device for a recoil starter characterized by bending the inner ends of each blade into a circle connecting them.