JP2010148484A - Engine-driven bush cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bush cutter suppressing torsion of a shaft caused by variation of rotational speed and reducing gear noise in contrast with conventional engine-driven bush cutter generating non-uniform rotation caused by acceleration of an engine by combustion-induced torque and deceleration by sliding resistance between a cylinder and a piston ring and pumping loss, etc., in compression of a fuel with a piston. <P>SOLUTION: The problems comprising generation of twisting oscillation of the shaft and gear noise can be solved by placing a circumferentially movable and power-transmitting elastic member in the inner part of a gear enclosed in a gear case, thereby decreasing a torsional spring constant of a power transmission part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention mainly relates to vibration of a brush cutter and reduction of gear noise.

  2. Description of the Related Art Conventionally, an engine brush cutter using an engine as a drive source has been used to cut grass on a flat ground, an inclined land, a mountain, and the like. An engine brush cutter connects a gear box that houses gears to one end of a long shaft, and attaches a cutting blade or nylon cord for cutting grass and branches to the lower end of a spindle housed in the gear box, and a fuel tank. The integrated engine housing is connected to the other end of the shaft, and the engine output is transmitted to the cutting blade via the shaft and the gear housed in the gear box to rotate the cutting blade or nylon cord. Things are used.

  The engine generates rotational torque by combustion and accelerates the rotation of the cutting blade, but tends to decelerate due to sliding resistance due to the cylinder and piston ring, or pumping loss when the fuel is compressed by the piston, In general, the rotational speed is not constant.

  On the other hand, since the tool attached to the tip has a certain amount of mass, when it rotates, inertia occurs, and the transmission of the driving force between the engine body and the cutting blade here is a torsion spring constant made of solid or hollow steel material. Since a long shaft with a long axis is used, rotational fluctuations occur in the tool and the engine, and when the shaft is twisted, the shaft is vibrated and the handle vibrates. In addition, since the object to be cut is grass or wood, intermittent cutting is performed, and torque fluctuation is larger than when cutting a predetermined material.

  From the above, it is easy to generate gear noise due to the meshing accuracy of the bevel gear arranged on the tip side and chattering due to rotation fluctuation, etc. These vibrations and noises make the operator uncomfortable and cause the work ability to decrease It becomes one of.

  With regard to these problems, a configuration in which a clutch is disposed on the output shaft portion of the engine and a configuration using a flexible shaft to lower the torsion spring constant of the shaft have been devised for reducing the vibration of the brush cutter.

JP 2003-88220 A

  In the engine brush cutter in Patent Document 1, a one-way clutch is mounted on a transmission path that transmits rotation from a crankshaft of an internal combustion engine to a cutting blade that rotates about a rotation axis, thereby transmitting torque when excessive torque is generated. Although it is configured to cut off, there is a problem that there is little effect of attenuating minute repetitive rotational fluctuations of the cutting blades when mowing the grass or rotational fluctuations caused by engine combustion and pumping loss.

  Further, in the case where a flexible shaft using wires is used, durability becomes a problem when the displacement and output are increased. In addition, since the gears are operated at a high speed, the small gear 7 and the large gear 8 with poor gear accuracy cannot be properly meshed with each other, and chattering occurs, so that noise is likely to deteriorate.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a brush cutter that suppresses torsion of a shaft due to rotational fluctuation and reduces gear noise.

  Of the inventions disclosed in the present application, typical features will be described as follows. According to one aspect of the present invention, a long shaft capable of transmitting a driving force, a cutting blade attached to one end of the shaft, and an engine as a drive source attached to the other end of the shaft; In the brush cutter having a gear device arranged on a transmission shaft for driving force from the engine to the cutting blade, the gear device comprises a rotatable drive shaft and a gear having an elastic material disposed on the inner diameter portion. The gear is movable in the circumferential direction with respect to the drive shaft, and transmits power to the drive shaft through the elastic material.

  Further, the gear device has an intermediate member press-fitted into the drive shaft with a predetermined pressure input, an inner packet portion that includes the intermediate member, and a gear that engages with the intermediate member and rotates coaxially with the drive shaft. The predetermined pressure input causes the drive shaft and the intermediate member to rotate relative to each other when a load is generated between the drive shaft and the intermediate member, and the inner part includes a convex portion, and the intermediate member includes the drive shaft. It is preferable that a protrusion that can contact the protrusion in the circumferential direction is provided by relative rotation of the gear and the gear.

The intermediate member includes a protrusion that overlaps the protrusion of the inner packet portion in the radial direction,
It is preferable that the elastic material is inserted between the protruding portion and the convex portion in the circumferential direction.

  Moreover, it is preferable that the said elastic material is comprised so that it may contact | abut each of the said protrusion part and the said inner packet part by a curved surface.

  Further, it is preferable that the elastic material is arranged in a state of being compressed and deformed in the inner packet part, and holds the rotation center axis of the gear and the axis of the drive shaft on substantially the same axis.

  The gear device is configured to transmit a driving force by meshing the first gear portion on the engine side with the second gear portion on the cutting blade side, and the elastic member includes the first gear portion. It is desirable that both the second gear portion and the second gear portion are provided.

According to the first aspect of the present invention, a long shaft capable of transmitting a driving force, a cutting blade attached to one end of the shaft, and an engine as a drive source attached to the other end of the shaft. When,
A brush cutter having a gear device disposed on a transmission shaft for driving force from the engine to the cutting blade, wherein the gear device includes a rotatable drive shaft and a gear having an elastic member disposed on an inner diameter portion. With
The gear moves in the circumferential direction with respect to the drive shaft, and transmits power to the drive shaft via the elastic material, thereby torsion of the shaft due to the difference between the rotational fluctuation of the engine and the inertia moment of the cutting blade attached to the tip It is possible to suppress vibrations that occur and torque fluctuations that are transmitted to the shaft when an impact is applied to the cutting blade. In addition, gear sound generated by gear meshing is absorbed by the elastic material and backlash is increased in a pseudo manner, so that the meshing excitation force can be reduced and vibration from the gear to the cutting blade can be suppressed. It becomes.

  According to a second aspect of the present invention, the gear device has an intermediate member press-fitted into the drive shaft with a predetermined pressure input, an inner packet portion containing the intermediate member, and is engaged with the intermediate member to engage the drive shaft. And the predetermined pressure input causes relative rotation between the drive shaft and the intermediate member when a load is generated between the drive shaft and the intermediate member, and The portion includes a convex portion, and the intermediate member is provided with a projecting portion capable of contacting the convex portion in the circumferential direction by relative rotation between the driving shaft and the gear, whereby the driving shaft and the gear The transmission of the rotational force can be cut off. Even when an excessive impact or the like is generated between the drive shaft and the gear, the intermediate member can be prevented from being damaged by the relative rotation of the drive shaft and the intermediate member.

  According to a third aspect of the present invention, the intermediate member includes a projecting portion that overlaps the convex portion of the inner packet portion in the radial direction, and the elastic member is disposed between the projecting portion and the convex portion in a circumferential direction. By being inserted, when a load occurs, the elastic material can be deformed to absorb the load. Furthermore, damage to the elastic material can be prevented by the protrusion and the projecting portion coming into contact with each other after the protruding portion and the inner packet portion absorb the load through the elastic material.

  According to the invention of claim 4, the elastic material is configured to come into contact with the projecting portion and the inside of the inner packet portion with curved surfaces, so that the contact surface is small when the load relating to impact or the like is small. If the spring constant of the elastic material is small and easily absorbs the impact, and the load due to the impact is large, the contact surface becomes large and the spring constant of the elastic material becomes large. Is possible. Further, by forming the contact portion of the elastic material in a curved surface, for example, a gap is formed in the vicinity of the contact portion with the wall surface. Since the gap serves as a escape place when the elastic material is pressed and deformed, the elastic material can be easily deformed to absorb the load when a load is generated. Furthermore, according to the load when the elastic material comes into contact with the protruding portion and the inside of the inner packet portion, the convex portion and the protruding portion can come into contact after the protruding portion and the inner packet portion come into contact with the elastic material.

  According to the invention of claim 5, since the elastic material is arranged in a state of being compressed and deformed in the inner packet part, the rotation center axis of the gear and the axis of the drive shaft are held on substantially the same axis. Is possible.

  According to a sixth aspect of the present invention, the gear device transmits driving force by meshing the first gear portion on the engine side and the second gear portion on the cutting blade side, and the elastic member Is provided in both the first gear portion and the second gear portion, so that the torsional vibration generated in the shaft can be suppressed before being transmitted from the engine to the gear device via the shaft.

  FIG. 1 is an external view of an engine brush cutter. As shown in FIG. 1, the engine 1 is provided with a scissor 2 into which a shaft for transmitting a driving force is rotatably inserted, and the scissor 2 has an engine brush cutter near the middle. And a gear case 5 containing a small gear 7 and a large gear 8 for changing the angle of the driving force at the opposite end to the engine 1 and decelerating, A driving force is transmitted to the cutting blade 4 through the gear case 5.

  FIG. 2 is a cross-sectional view of the gear case 5 for explaining a power transmission path in the vicinity of the gear case 5 according to the first embodiment of the present invention. 3-7 is some examples which show 1st embodiment, and is sectional drawing of the elastic body vicinity of FIG.

  2 and 3, a shaft 6 connected to an output shaft (not shown) of the engine 1 and rotatably supported and having an end formed by a spline or the like, and a small gear 7 having an inner diameter formed by a spline or the like. The power is transmitted by meshing the gears, and the power is transmitted to the drive shaft 11 by the meshing of the small gear 7 (first gear portion) and the large gear 8 (second gear portion). A concave portion in which the elastic body 10 is disposed is provided on the inner periphery of the large gear 8, and a concave portion is also provided on the inner periphery of the drive shaft 11 disposed in the center of the large gear 8. The large gear 8 and the drive shaft 11 are disposed at positions that enter the radial direction. Further, a lid 9 is provided on the inner diameter portion of the large gear 8 to prevent the elastic body 10 from falling off.

  Further, the small gear 7 has a recess formed in the inner periphery thereof, like the large gear 8, and an elastic body 20 is disposed. As an embodiment related to the elastic body 20 on the small gear side, the system for the large gear 8 shown in FIGS. 3 to 7 can be applied respectively, but the end of the shaft 6 used in a general brush cutter Since the shape is rectangular, it is desirable to use the embodiment shown in FIG. 5, and it is possible to arrange the elastic body 20 without requiring special processing. Further, the elastic body 20 is fixed by being sandwiched between the lids 19 and 21 to prevent the elastic body 20 from falling off from both sides.

  The elastic bodies 10 and 20 are disposed at positions that are sufficiently movable in the rotational direction. The cutting blade 4 is fixed to the drive shaft 11 on the side opposite to the large gear 8. Further, as shown in FIGS. 4 to 7, the number, size, shape, material, and the like of the elastic member 10 can be changed in a timely manner according to use conditions.

  Next, the operation of the first embodiment of the present invention will be described.

  The operator operates the throttle lever provided on the handle 3 while holding the handle 3 of the engine 1 in the starting state, whereby the rotation speed of the engine 1 increases to the use rotation speed, and the driving force transmission path The driving force is transmitted to the shaft 6 inserted in the flange 2 through a clutch (not shown) provided in the middle of the gear, and is arranged on the inner diameters of the small gear 7, the large gear 8, and the large gear 8 included in the gear device 5. The driving force is transmitted to the provided elastic member 10, the elastic member 10 rotates the driving force 11, and the cutting blade attached to the driving shaft 11 rotates to perform a cutting operation.

  According to such a configuration, by disposing the elastic material 10 in the large gear 8, the power from the shaft 6 is transmitted to the small gear 7 and the large gear 8, but the power from the shaft 6 is elastic. 10 and 20 to be transmitted to the output shaft 11, elasticity is generated in the circumferential direction, and even if shocking torque is generated, it is absorbed by the elastic materials 10 and 20, and stable torque transmission to the cutting blade 4 is achieved. It can be carried out. Furthermore, even when a hard material to be cut such as wood collides with the cutting blade 4 and the rotation of the cutting blade 4 fluctuates, fluctuations in torque to the shaft 6 are alleviated by the effects of the elastic members 10 and 20. The elastic members 10 and 20 can be configured to have a great damping effect by being disposed at positions that are sufficiently movable in the rotational direction.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a cross-sectional view of the vicinity of the elastic body of the gear case 5 corresponding to FIGS. 3 to 7 of the first embodiment, showing the second embodiment.

  The gear 8 has an inner packet part 15 that encloses the intermediate member 12, and a drive shaft 11 that rotates coaxially with the gear 8 is press-fitted into the intermediate member 12 with a predetermined pressure input. Here, the predetermined pressure input is adjusted to such an extent that relative rotation between the rotating shaft 11 and the intermediate member 12 occurs when a load is generated between the rotating shaft 11 and the intermediate member 12. The inner packet part 15 includes a convex part 14, and the intermediate member 12 is provided with a protruding part 16 that overlaps the convex part 14 in the radial direction by relative rotation between the rotary shaft 11 and the large gear 8. An elastic material 10 is included between the protruding portion 16 of the intermediate member 12 and the convex portion 14 of the large gear 8. Further, the intermediate member 12 is formed with a protruding portion 13 and is disposed at a position where it can contact the convex portion 14. Further, the elastic material 10 is arranged in a state of being compressed and deformed in the inner packet part 15.

  Next, the operation of the second embodiment of the present invention will be described.

  Driving force is transmitted to the shaft 6, and the force is transmitted to the projecting portion 16 via the small gear 7, the large gear 8 included in the gear device 5, and the elastic member 10 disposed in the internal portion of the large gear 8, By rotating the intermediate member 12 and rotating the drive shaft 11 connected by pressure input, the cutting blade attached to the drive shaft 11 rotates and performs a cutting operation.

  According to such a configuration, the gear device 5 has the intermediate member press-fitted into the drive shaft with a predetermined pressure input, and the inner packet portion that encloses the intermediate member, and engages with the intermediate member 12 to drive the drive shaft 11. The predetermined pressure input causes relative rotation between the drive shaft 11 and the intermediate member 12 when a load is generated between the drive shaft 11 and the intermediate member 12. The inner packet part 15 includes a convex part 14, and the intermediate member 12 is provided with a protruding part 13 that can contact the convex part 14 in the circumferential direction by relative rotation of the drive shaft 11 and the large gear 8. By doing so, transmission of rotational force between the drive shaft 11 and the large gear 8 can be blocked.

  Further, the drive shaft 11 is configured such that relative rotation between the drive shaft 11 and the intermediate member 12 occurs when a predetermined load or more is generated between the drive shaft 11 and the intermediate member 12 as the predetermined pressure input. Even when an excessive impact or the like is generated between the drive shaft 11 and the large gear 8, the drive shaft 11 and the intermediate member 12 rotate relative to each other, so that damage to the intermediate member 12 can be suppressed.

  Further, the intermediate member 12 has a protrusion 16 having a wall surface that intersects the rotation direction, and the elastic member 10 is inserted between the protrusion 14 and the protrusion 16 of the inner packet part 15. When the transmission torque is increased, the elastic member 10 is deformed, and the load generated between the intermediate member 12 press-fitted into the drive shaft 11 and the large gear 8 can be absorbed. Further, even if excessive torque is generated, the elastic member 10 is prevented from being excessively deformed by the projection 13 of the intermediate member 12 and the convex portion 14 of the large gear 8 coming into contact with each other at a predetermined angle. 10 breakage can be prevented.

  In addition, since the elastic material 10 is configured to come into contact with the protruding portion 16 and the inner packet portion 15 with curved surfaces, the elastic material 10 has a small contact surface in a state where the load related to impact or the like is small. The spring constant of the elastic material 10 becomes small and it is easy to absorb the impact, and when the load due to the impact is large, the contact surface becomes large and the spring constant of the elastic material 10 becomes large. It becomes possible. Further, since the contact portion of the elastic member 10 is formed in a curved surface, for example, a gap is formed in the vicinity of the contact portion with the protruding portion 16. Since this gap serves as a refuge when the elastic material 10 is pressed and deformed, the elastic material 10 can be easily deformed to absorb the load when a load is generated. Further, after the elastic member 10 absorbs the impact through the elastic member 10 according to the load when the elastic member 10 contacts the protrusion 16 and the inner packet part 15, The protrusion 13 can come into contact.

  Further, since the elastic member 10 is disposed in a state of being compressed and deformed in the inner packet part 15, the rotation center axis of the large gear 8 and the axis of the drive shaft 11 are held on substantially the same axis. .

  The gear case 5 includes elastic members 10 and 20 for both the small gear 7 and the large gear 8 in transmission of driving force by meshing between the small gear 7 on the engine side and the large gear 8 on the cutting blade 4 side. Thus, the torsional vibration generated in the shaft can be suppressed before being transmitted from the engine to the gear device via the shaft.

As mentioned above, although demonstrated based on embodiment which shows this invention, this invention is not limited to the above-mentioned form, A various change is possible within the range which does not deviate from the meaning. For example, in the present embodiment, the configuration using an engine as a drive source has been described, but the present invention can also be applied to a tool driven by an electric motor. Further, although the two elastic bodies 10 and 20 are arranged on the transmission shaft, they may be arranged on either the large gear 8 or the small gear 7, and the torsional vibration of the shaft or the impact applied to the cutting blade. Has the effect of suppressing the transmission to the shaft.

1 is an external view of an engine brush cutter according to the present invention. It is sectional drawing of the gear case vicinity of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing which shows the modification of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing which shows the modification of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing which shows the modification of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing which shows the modification of the engine brush cutter which concerns on 1st embodiment of this invention. It is gear part sectional drawing of the engine brush cutter which concerns on the 2nd embodiment of this invention.

Explanation of symbols

  1 is an engine, 2 is a rod, 3 is a handle, 4 is a cutting blade, 5 is a gear case, 6 is a shaft, 7 is a small gear, 8 is a large gear, 9 is a lid, 10 is an elastic material, 11 is an output shaft, 12 Is an intermediate member, 13 is a protruding portion, 14 is a convex portion of the intermediate member, 15 is an inner packet portion of the intermediate member, and 16 is a protruding portion of the intermediate member.

Claims (6)

A long shaft capable of transmitting driving force;
A cutting blade attached to one end of the shaft;
An engine as a drive source attached to the other end of the shaft;
A brush cutter having a gear device disposed on a transmission shaft of driving force from the engine to the cutting blade,
The gear device includes a rotatable drive shaft and a gear in which an elastic material is disposed on an inner diameter portion,
An engine brush cutter characterized in that a gear moves in a circumferential direction with respect to a drive shaft, and transmits power to the drive shaft via the elastic material. The gear device is
An intermediate member press-fitted into the drive shaft with a predetermined pressure input;
Having an inner packet part that encloses the intermediate member, and having a gear that engages with the intermediate member and rotates coaxially with the drive shaft;
The predetermined pressure input causes a relative rotation between the drive shaft and the intermediate member when a load is generated between the drive shaft and the intermediate member,
The inner packet part includes a convex part, and the intermediate member is provided with a projecting part capable of contacting the convex part in a circumferential direction by relative rotation of the drive shaft and the gear. Item 1. An engine brush cutter according to Item 1. The intermediate member includes a protruding portion that overlaps the convex portion of the inner packet portion in a radial direction,
The engine brush cutter according to claim 2, wherein the elastic member is inserted between circumferential directions of the protruding portion and the protruding portion.   4. The engine brush cutter according to claim 2, wherein the elastic member is configured to come into contact with the protruding portion and the inside of the inner packet portion with curved surfaces. 5.   The elastic material is disposed in a state of being compressed and deformed in the inner packet part, and holds the rotation center axis of the gear and the axis of the drive shaft on substantially the same axis. The engine brush cutter according to any one of claims 2 to 4. The gear device is configured to transmit a driving force by meshing the first gear portion on the engine side and the second gear portion on the cutting blade side,
The engine brush cutter according to any one of claims 1 to 5, wherein the elastic material is provided in both the first gear portion and the second gear portion.

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