JP2007061031A - Vibration-absorbing joint and portable bush cutter equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration-absorbing joint capable of effectively suppressing torsional vibration of a transmission shaft and performing improvement of endurance, etc. <P>SOLUTION: The vibration-absorbing joint is constituted so as to transmit rotation of an output shaft (31) of an internal combustion engine (6), etc. to a transmission shaft (7) and absorb torsional vibration of the transmission shaft (7) by converting the torsional vibration to telescopic movement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vibration-absorbing joint that transmits rotation of a prime mover-side output shaft of a two-cycle internal combustion engine or the like to a transmission shaft, and absorbs torsional vibration of the transmission shaft, and a portable mowing provided with the same Related to the payment machine.

  FIG. 11 shows a conventional example of a portable brush cutter. In the illustrated example, the portable brush cutter 1 ′ is provided with a cutting blade mechanism section 3 including a circular saw blade-shaped cutting blade 4, a gear case (bevel gear unit) 19, a safety cover 5, and the like at the front end of the operation rod 2. At its rear end, with a centrifugal clutch provided with a recoil starter 8 and a fuel tank 9 as a prime mover for driving the cutting blade 4 via a transmission shaft 7 and a centrifugal clutch 33 housed in the operation rod 2 An internal combustion engine (small air-cooled two-cycle gasoline engine) 6 is attached.

  Further, a U-shaped handle 10 is attached near the central portion of the operation rod 2 for swinging the cutting blade mechanism unit 3 to the left and right and moving it up and down to perform the brushing operation. A left grip 11 and a right grip 12 are attached to both ends.

  In the portable brush cutter 1 ′ having such a configuration, the transmission shaft 7 is twisted due to torque fluctuation, rotation speed fluctuation, and load fluctuation applied to the cutting blade 4 during acceleration / deceleration of the internal combustion engine 6. Vibration occurs. More specifically, since the transmission shaft 7 is thin and long (for example, about 6 mm in diameter and about 1500 mm in length), if the engine speed fluctuation or the load on the cutting blade 4 increases, the transmission shaft 7 becomes considerably large. Twist (rotation delay) occurs. Further, when the load is suddenly reduced, the transmission shaft 7 causes a springback phenomenon, overruns in the rotational direction and twists. In this way, torque transmission, rotational speed fluctuation, load fluctuation, springback phenomenon, etc. during acceleration / deceleration of the engine cause the transmission shaft 7 to twist or return in the rotational direction and the opposite direction, resulting in torsional vibration.

  Then, the torsional vibration of the transmission shaft 7 propagates to the operator's hand through the operation rod 2 and the handle 10. Such vibration not only causes a decrease in operability and an increase in fatigue, but also may cause white wax etc. if the work takes a long time, and the anti-vibration measure for suppressing this vibration is the portable brush cutter. Has become an important issue.

  As one of the anti-vibration measures, for example, the following Patent Document 1 proposes that a joint member formed of anti-vibration rubber is interposed between the centrifugal clutch and the transmission shaft.

  Further, as another vibration isolation measure, Patent Document 2 below proposes that a one-way clutch be interposed between the centrifugal clutch and the transmission shaft.

  Furthermore, as another anti-vibration measure, it is considered that a torsion coil spring is interposed between the centrifugal clutch and the transmission shaft.

Japanese Utility Model Publication No. 56-53618 JP 2003-88220 A

  However, in the conventional anti-vibration measures using the joint member, the one-way clutch, or the torsion coil spring formed from the anti-vibration rubber, a temporary anti-vibration effect can be obtained, but the practicality is still insufficient. There wasn't.

  In particular, when a joint member formed of vibration-proof rubber is used, problems are likely to occur in the durability of the joint member of vibration-proof rubber, and even when a torsion coil spring is used, the torsional direction of the transmission shaft, Since the torsion coil spring is elastically deformed (twisted) indefinitely according to the torsion amount (twist angle), the torsion coil spring is easily damaged, and there is a problem in durability.

  The present invention has been made to solve the conventional problems as described above. The object of the present invention is to sufficiently suppress torsional vibration of the transmission shaft and improve durability and the like. An object of the present invention is to provide a vibration absorbing joint that can be used and a portable brush cutter having the same.

  In order to achieve the above-mentioned object, the vibration absorbing joint according to the present invention basically transmits the rotation of the output shaft of the prime mover to the transmission shaft, and converts the torsional vibration of the transmission shaft to the expansion and contraction motion of the compression coil spring. It is converted and absorbed.

  In a preferred specific embodiment, a movable sleeve provided with spline male teeth that are slidably fitted along a rotation axis on the spline male teeth provided on the transmission shaft, and a rotating sleeve integrally with the output shaft. A cylindrical coupling body in which the movable sleeve is slidably inserted, and a compression coil spring that is compressed between the movable sleeve and a locking portion provided in the cylindrical coupling body, The movable sleeve and the cylindrical coupling body are provided with conversion means for converting torsional vibration of the transmission shaft into expansion and contraction motion of the compression coil spring.

  Preferably, the conversion means includes a protrusion or pin provided on the movable sleeve and a groove or window provided on the cylindrical coupling body, and the protrusion or pin is in sliding contact with the groove or window. And an inclined side portion inclined at a predetermined angle with respect to the rotation axis.

  In this case, the groove or window is preferably formed in a triangular shape, and the apex corner portion and both bottom corner portions formed by the inclined side portions are the locking portions of the protrusions or pins, respectively.

  In another preferred specific aspect, the movable sleeve provided with the spline male teeth that are slidably fitted along the rotation axis to the spline male teeth provided on the transmission shaft, and the movable sleeve is slidable. A cylindrical body that is fitted in, a compression coil spring that is compressed between the movable sleeve and a locking portion that is provided in the cylindrical body, and the output shaft that is integrally rotated. A rotation transmission shaft that is inserted into the cylindrical body and locked to move in the direction of the rotation axis so as to prevent the movement of the movable sleeve due to the urging force of the compression coil spring, and the movable sleeve The rotation transmission shaft is provided with conversion means for converting torsional vibration of the transmission shaft into expansion and contraction motion of the compression coil spring.

  Preferably, the converting means is provided with a concave section and a convex section having a triangular section or a trapezoidal shape having an inclined surface section inclined at a predetermined angle with respect to the rotation axis, provided on the contact side of the movable sleeve and the rotation transmission shaft. It consists of parts.

  In this case, the cylindrical body and the movable sleeve are provided with a locking portion for restricting the movement of the movable sleeve in the direction in which the compression coil spring is compressed.

  On the other hand, the portable brush cutter according to the present invention is provided with a cutting blade mechanism portion including a cutting blade and a gear box at the front end of the operating rod, and the cutting blade is provided in the operating rod at the rear end of the operating rod. A prime mover for driving via the transmission shaft is attached, and the vibration absorbing joint is interposed between the output shaft of the prime mover and the transmission shaft.

  In addition, another one of the portable brush cutters according to the present invention is provided with a cutting blade mechanism portion including a cutting blade and a gear box at the front end of the operating rod, and the cutting blade is provided at the rear end of the operating rod. An internal combustion engine with a centrifugal clutch for driving through a transmission shaft built in the operation rod is attached, and the vibration absorbing joint is interposed between the centrifugal clutch and the transmission shaft. The vibration absorbing joint is integrated as a boss portion with a movable sleeve provided with a spline female tooth that is slidably fitted along a rotation axis with a spline male tooth provided on the transmission shaft, and a drum of the centrifugal clutch. A cylindrical coupling body in which the movable sleeve is slidably fitted, and a compression coil spring that is compressed between the movable sleeve and a locking portion provided in the cylindrical coupling body; The movable sleeve and the tube The connecting body, converting means for converting the torsional vibration of the transmission shaft to the expansion and contraction of said compression coil spring is characterized by being provided.

  In the vibration-absorbing joint according to the present invention configured as described above, torque fluctuation and rotation speed fluctuation during acceleration / deceleration of the engine, and further, torsional vibration of the transmission shaft caused by load fluctuation or springback to the transmission shaft, etc. However, since the built-in compression coil spring is expanded and contracted, the torsional vibration of the transmission shaft can be effectively suppressed.

  Therefore, in the portable brush cutter provided with the vibration absorbing joint, it is possible to reduce and suppress unpleasant vibration that propagates to the operator's hand through the operating rod and the handle.

  Moreover, since the compression coil spring is used, durability etc. can be improved compared with the case where the coupling and the torsion coil spring which were shape | molded with the anti-vibration rubber | gum are used.

Hereinafter, embodiments of the vibration absorbing joint of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a main part of a portable brush cutter to which a first embodiment of a vibration absorbing joint according to the present invention is applied.

  The illustrated portable brush cutter 1A has substantially the same overall configuration as the portable brush cutter 1 ′ shown in FIG. 11 described above, and has a cutting blade mechanism including a cutting blade 4 and a gear box 19 at the front end of the operation rod 2. An internal combustion engine 6 with a centrifugal clutch 33 (compact air cooling 2 for driving the cutting blade 4 via a transmission shaft 7 housed in the operation rod 2 at the rear end of the operation rod 3. A cycle gasoline engine) is attached via a fixture 23, and the vibration absorbing joint 30A of the present embodiment is interposed between the centrifugal clutch 33 and the transmission shaft 7.

  More specifically, a centrifugal clutch 33 is connected to an output shaft (crankshaft) 31 of the internal combustion engine 6 via a cooling fan 32. The centrifugal clutch 33 is not shown in detail, but a clutch arm 33b rotated by the output shaft 31, a shoe 33c provided at the tip of the clutch arm 33b, and the shoe 33c are frictionally engaged. Thus, a clutch drum 33a that rotates integrally with the output shaft pull is provided.

  The vibration absorbing joint 30A includes a movable sleeve 45 provided with spline female teeth 45a slidably fitted to the spline male teeth 7a provided on the transmission shaft 7 along the rotation axis O, and the clutch drum 33a. And a cylindrical coupling body 35 and a compression coil spring 40 that are integrally coupled to each other as a boss portion.

  The cylindrical connecting body 35 is rotatably supported in the fixture 23 via a bearing 26, and a bearing locking cylinder 36 is fitted on the outer periphery of the cylindrical portion 35a. The movable sleeve 45 is fitted on one end side of the circumference (the transmission shaft 7 side) so as to be slidable in the rotational axis O and the rotational direction.

  The compression coil spring 40 is contracted between the movable sleeve 45 and a locking portion 35b provided on the other end side (the clutch drum 33a side) of the cylindrical coupling body 35. A ring-shaped spacer 52 is provided between the compression coil spring 40 and the movable sleeve 45 for adjusting the set load of the compression coil spring 40 and as a wear resistant material.

  The movable sleeve 45 and the cylindrical connecting body 35 are provided with conversion means for converting torsional vibration of the transmission shaft 7 into expansion and contraction motion of the compression coil spring 40.

  As can be understood by referring to FIGS. 2 to 5 in addition to FIG. 1, the converting means is formed in the movable sleeve 45 (from the formed holes 49, 49) in a radial direction with both ends protruding. And a pin 50 (possible to be a protrusion) provided in the tube, and an isosceles triangle-shaped window 37 (possible to a groove) provided in the cylindrical coupling body 35. 37 has inclined side portions 37a and 37b (see FIG. 2) inclined by a predetermined angle θa (here, 45 °) with respect to the rotation axis O, with which the pin 50 is slidably contacted. The apex angle portion 37c and the bottom corner portions 37d, 37e, which are aligned with the rotation axis O formed by the side portions 37a, 37b and face the front end side of the operating rod 2, are respectively engaged with the locking portions of the pin 50. It has become.

  In the vibration absorbing joint 30A of the present embodiment configured as described above, the engine 6 (the output shaft 31) and the transmission shaft 7 are shown in FIGS. Thus, the pin 50 is positioned at the apex angle portion 37c of the window 37, and the compression length of the compression coil spring 40 at this time is La.

  On the other hand, when the engine speed becomes equal to or higher than a predetermined speed (for example, 3200 rpm) and the centrifugal clutch 33 enters a clutch-in state (connected state), the rotation of the output shaft 31 causes the centrifugal clutch 33 (clutch The drum 33 a) → the window 37 of the cylindrical coupling body 35 → the pin 50 → the movable sleeve 45 → the transmission shaft 7 is sequentially transmitted, and the transmission shaft 7 is rotated in the same direction as the output shaft 31.

  Thereafter, as the engine speed increases, the transmission shaft 7 is twisted (rotation delay). When this twist (rotation delay) occurs, the pin 50 is pulled up so as to slide on the window 37 (inclined side portion 37a) according to the twist (rotation delay) angle, and the movable sleeve 45 rotates. It is moved in a direction along the axis O, that is, in a direction in which the compression coil spring 40 is compressed.

  When the engine speed further increases and the torsional (rotation delay) angle of the transmission shaft 7 reaches a predetermined angle (for example, 3 °), the pin 50 becomes the bottom corner portion of the window 37 on the inclined side portion 37a side. It reaches 37e and is locked. Therefore, when the torsion angle of the transmission shaft 7 is equal to or greater than the predetermined angle, as shown in FIG. 5, the compression coil spring 40 is rotated from the no-load state shown in FIG. Further compressed by the moving distance α in the direction along the axis O, the length becomes Lb, the compression coil spring 40 is not further compressed, and the cylindrical coupling body 35 and the movable sleeve 45 are substantially separated. Directly connected.

  On the other hand, when the load is suddenly reduced from the drive rotation state, the transmission shaft 7 causes a springback phenomenon, overruns in the rotation direction and twists. Also at this time, the pin 50 is pulled up so as to slide on the window 37 (the inclined side portion 37b), and the movable sleeve 45 is in a direction along the rotation axis O, that is, in a direction in which the compression coil spring 40 is compressed. It is moved to the bottom corner 37d.

  As described above, in the vibration absorbing joint 30A of the present embodiment, torque fluctuation and rotation speed fluctuation during acceleration / deceleration, and torsional vibration of the transmission shaft 7 caused by load fluctuation, springback phenomenon, etc. Since the spring 40 is absorbed and expanded, the torsional vibration of the transmission shaft 7 can be effectively suppressed.

  Therefore, in the portable brush cutter 1A provided with the vibration absorbing joint 30A, it is possible to effectively reduce and suppress unpleasant vibrations that propagate to the operator's hand through the operation rod 2 and the handle 10.

  Moreover, since the compression coil spring 40 is used, durability etc. can be improved compared with the case where the coupling and the torsion coil spring which were shape | molded with the anti-vibration rubber | gum are used.

  FIG. 6 is a cross-sectional view showing a main part of a portable brush cutter to which the second embodiment of the vibration absorbing joint according to the present invention is applied.

  The illustrated portable brush cutter 1B has substantially the same overall configuration as the aforementioned portable brush cutter 1A of the first embodiment, but differs in the configuration of the vibration absorbing joint.

  That is, the vibration-absorbing joint 30B of the second embodiment is slidably fitted to the cylindrical coupling body 65 integrally coupled as a boss portion to the clutch drum 33a and the spline male teeth 7a provided on the transmission shaft 7. A movable sleeve 80 provided with a spline female tooth 80a to be mated is provided in the cylindrical portion 86, and the movable sleeve 80 is slidably inserted in the rotational axis O and the rotational direction and is press-fitted into the operation rod 2. Rotates integrally with the output shaft 31 and the compression coil spring 90 that is compressed between the cylindrical body 75, the movable sleeve 80 large-diameter recess 83 and the locking portion 76 provided in the cylindrical body 75. It is inserted into the cylindrical body 75 and locked by a locking ring 77 so as to prevent the movable sleeve 80 from moving to the output shaft pulling side by the urging force of the compression coil spring 90. Rotation transmission shaft Including 0 and, the. A ring-shaped spacer 92 is interposed between the compression coil spring 90 and the movable sleeve 80 for adjusting the set load of the compression coil spring 90 and as a wear resistant material.

  The rotation transmission shaft 70 includes a large-diameter portion 72 and a spline shaft portion 74 provided with spline male teeth 74a fitted to the spline female teeth 65a provided on the cylindrical coupling body 65. The transmission shaft 70 and the movable sleeve 80 are provided with conversion means for converting torsional vibration of the transmission shaft 7 into expansion and contraction motion of the compression coil spring 90.

  As can be understood with reference to FIGS. 7 and 9, the conversion means is provided in the large diameter portion 82 of the movable sleeve 80 and the large diameter portion 72 of the rotation transmission shaft 70 which are brought into contact with each other. It consists of a triangular or trapezoidal convex part 73 and a concave part 83 having inclined surface parts 73a, 73b, 83a, 83b inclined at the same angle θb (here 45 °) with respect to the rotational axis O.

  Further, a cylindrical body locking portion 76 and a movable sleeve locking portion (for limiting the movement of the movable sleeve 80 in the direction in which the compression coil spring 90 is compressed) to the cylindrical body 75 and the movable sleeve 80 ( A stepped portion 87 is provided.

  Also in the vibration absorbing joint 30B of the second embodiment configured as described above, as in the first embodiment, the engine 6 (output shaft 31) and the transmission shaft 7 are not rotated. 6 and 9A, the convex portion 73 (inclined surface portions 73a and 73b) and the concave portion 83 (inclined surface portions 83a and 83b) are fitted and brought into contact with each other, and the separation distance therebetween. β is 0.

  On the other hand, when the engine speed becomes equal to or higher than a predetermined speed (for example, 3200 rpm) and the centrifugal clutch 33 enters a clutch-in state (connected state), the rotation of the output shaft 31 causes the centrifugal clutch 33 (clutch Drum 33 a) → the cylindrical connecting body 65 → the rotation transmission shaft 70 (convex portion 73) → the movable sleeve 80 (concave portion) → the transmission shaft 7, and the transmission shaft 7 is the same as the output shaft 31. It can be rotated in the direction.

  Thereafter, as the engine speed increases, the transmission shaft 7 is twisted (rotation delay). When this twist (rotation delay) occurs, the inclined surface portions 73a and 73b of the protrusion 73 are inclined according to the twist (rotation delay) angle, as shown in FIG. 9B. Sliding on the surface portions 83a and 83b, the rotation transmission shaft 70 pushes the movable sleeve 80 against the urging force of the compression coil spring 90 along the rotation axis O, and the convex portions 73 (inclined surface portions 73a and 73b). ) And the concave portions (inclined surface portions 83a and 83b) are separated (the separation distance β is, for example, 1.0 mm).

  When the engine speed further increases and the twist (rotation delay) angle of the transmission shaft 7 becomes a predetermined angle (for example, 5 °) or more, as shown in FIG. 5 mm, the movable sleeve locking portion (stepped portion) 87 is contacted and locked to the cylindrical body locking portion 76, and the compression coil spring 90 is not further compressed, and the rotation transmission shaft 70 and the movable The sleeve 80 is substantially directly connected.

  On the other hand, when the load is suddenly reduced from the drive rotation state, the transmission shaft 7 causes a springback phenomenon, overruns in the rotation direction and twists. Also at this time, the inclined surface portions 73 a and 73 b of the convex portion 73 slide on the inclined surface portions 83 a and 83 b of the concave portion 83, and the rotation transmission shaft 70 uses the movable sleeve 80 as an urging force of the compression coil spring 90. The projection 73 (inclined surface portions 73a and 73b) and the concave portion (inclined surface portions 83a and 83b) are separated from each other by pushing along the rotation axis O.

  As described above, in the vibration absorbing joint 30B of the second embodiment, as in the first embodiment, the transmission shaft 7 caused by torque fluctuations and rotation speed fluctuations during acceleration / deceleration, load fluctuations, springback phenomenon, and the like. The torsional vibration of the transmission shaft 7 is absorbed by the expansion and contraction of the built-in compression coil spring 90, so that the torsional vibration of the transmission shaft 7 can be effectively suppressed.

  Therefore, even in the portable brush cutter 1B provided with the vibration absorbing joint 30B, it is possible to effectively reduce and suppress unpleasant vibrations that propagate to the operator's hand through the operation rod 2 and the handle 10.

  Moreover, since the compression coil spring 90 is used, durability etc. can be improved compared with the case where the coupling and the torsion coil spring which were shape | molded with the vibration proof rubber were used.

  In the second embodiment, the inclination angle θb of the inclined surface portions 73a, 73b, 83a, 83b with respect to the rotation axis O is 45 °, but this inclination angle θb is increased (for example, FIG. 8). And 60 ° as shown in FIG. 10), the torsional (rotational delay) angle of the transmission shaft 7 capable of absorbing torsional vibration is increased (for example, 5 ° to 2 ° to 3 °). 6 °).

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be used without departing from the spirit of the invention described in the claims. It can be changed.

Sectional drawing which shows the principal part of the portable brush cutter to which 1st embodiment of the vibration absorption coupling which concerns on this invention was applied. Sectional drawing with which it uses for description of the cylindrical connection body shown by FIG. 1, and the window formed in it. III-III arrow sectional drawing of FIG. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 1. Sectional drawing with which it uses for operation | movement description of the vibration-absorbing coupling shown by FIG. Sectional drawing which shows the principal part of the portable brush cutter to which 2nd embodiment of the vibration absorption coupling which concerns on this invention was applied. The figure which shows the rotation transmission shaft and movable sleeve which are shown by FIG. The figure which shows the other example of a rotation transmission shaft and a movable sleeve. Sectional drawing with which it uses for description of operation | movement of the vibrational absorption joint shown by FIG. Sectional drawing with which the operation | movement description of a vibrational absorption joint at the time of using the other example of the rotation transmission shaft shown in FIG. 8 and a movable sleeve is used. The perspective view which shows an example of the conventional portable brush cutter.

Explanation of symbols

1A, 1B Portable brush cutter 2 Operating rod 3 Cutting blade mechanism 4 Cutting blade 6 Internal combustion engine (prime mover)
7 Transmission shaft 7a Spline male teeth 19 Gear box 30A, 30B Vibration absorbing joint 31 Output shaft 33 Centrifugal clutch 33a Clutch drum 35 Cylindrical coupling body 35b Locking portion 37 Groove or window (conversion means)
37a, 37b Inclined side (locking part)
37c Vertical corner (locking part)
40 Compression coil spring 45 Movable sleeve 45a Spline female teeth 50 Projection or pin (conversion means)
70 Rotation transmission shaft 73 Convex part (conversion means)
73a, 73b Inclined surface portion 75 Cylindrical body 76 Locking portion 80 Movable sleeve 80a Spline female teeth 83 Concavity (conversion means)
83a, 83b Inclined surface portion 87 Locking portion 90 Compression coil springs θa, θb Inclination angle (predetermined angle)
O rotation axis

Claims (9)

  The rotation of the output shaft (31) of the prime mover (6) is transmitted to the transmission shaft (7), and the torsional vibration of the transmission shaft (7) is converted into the expansion and contraction motion of the compression coil springs (40, 90) and absorbed. A vibration-absorbing joint characterized by that.   A movable sleeve (45) provided with a spline female tooth (45a) slidably fitted along a rotation axis (O) to a spline male tooth (7a) provided on the transmission shaft (7); A cylindrical coupling body (35) in which the movable sleeve (45) is slidably fitted and rotated together with the output shaft (31), and the movable sleeve (45) and the cylindrical coupling body. The compression coil spring (40) that is compressed between the locking portion (35b) provided in (35), and the movable sleeve (45) and the tubular connector (35), The vibration-absorbing joint according to claim 1, further comprising conversion means (50, 37) for converting torsional vibration of the transmission shaft (7) into expansion and contraction motion of the compression coil spring (40).   The conversion means includes a protrusion or pin (50) provided on the movable sleeve (45) and a groove or window (37) provided on the cylindrical connector (35). (37) has inclined side portions (37a, 37b) inclined by a predetermined angle (θa) with respect to the rotation axis (O), with which the protrusion or pin (50) is brought into sliding contact. The vibration-absorbing joint according to claim 2.   The groove or window (37) has a triangular shape, and the apex and bottom corners formed by the inclined side portions (37a, 37b) are the locking portions (37c) of the protrusion or pin (50), respectively. 37d, 37e), The vibration-absorbing joint according to claim 3.   A movable sleeve (80) provided with a spline female tooth (80a) slidably fitted along a rotation axis (O) to a spline male tooth (7a) provided on the transmission shaft (7); Between the cylindrical body (75) in which the movable sleeve (80) is slidably fitted, and between the movable sleeve (80) and the locking portion (76) provided on the cylindrical body (75). The compression coil spring (90) that has been mounted and the output shaft (31) are rotated together, and the movement of the movable sleeve (80) due to the urging force of the compression coil spring (90) is prevented. A rotation transmission shaft (70) inserted into the cylindrical body (75) and locked in movement in the direction of the rotation axis (O), the movable sleeve (80) and the rotation The torsional vibration of the transmission shaft (7) is applied to the transmission shaft (70). Vibration absorbing joint according to claim 1, characterized in that conversion means for converting the expansion and contraction movement of the coil spring (90) (83,73) is provided.   The conversion means is provided on the contact side of the movable sleeve (80) and the rotation transmission shaft (70), and is an inclined surface portion (83a) inclined at a predetermined angle (θb) with respect to the rotation axis (O). 83b, 73a, 73b), comprising a concave section (83) and a convex section (73) having a triangular or trapezoidal cross section.   Locking portions (76, 87) for restricting movement of the movable sleeve (80) in the direction of compressing the compression coil spring (90) to the cylindrical body (75) and the movable sleeve (80). The vibration-absorbing joint according to claim 5 or 6, wherein: is provided. A cutting blade mechanism (3) including a cutting blade (4) and a gear box (19) is provided at the front end of the operating rod (2), and the cutting blade (4) is provided at the rear end of the operating rod (2). A portable brush cutter (1A, 1B) to which is attached a prime mover (6) for driving through a transmission shaft (7) incorporated in the operating rod (2),
The vibration absorbing joint (30A, 30B) according to any one of claims 1 to 7 is interposed between the output shaft (31) of the prime mover (6) and the transmission shaft (7). A portable brush cutter characterized by that. A cutting blade mechanism (3) including a cutting blade (4) and a gear box (19) is provided at the front end of the operating rod (2), and the cutting blade (4) is provided at the rear end of the operating rod (2). Is mounted with an internal combustion engine (6) with a centrifugal clutch (33) for driving through a transmission shaft (7) incorporated in the operating rod (2), and the centrifugal clutch (33) and the transmission shaft ( 7) is a portable brush cutter (1A) in which the vibration absorbing joint (30A) according to claim 1 is interposed,
The vibration absorbing joint (30A) is provided with a spline female tooth (45a) that is slidably fitted along a rotation axis (O) to a spline male tooth (7a) provided on the transmission shaft (7). The movable sleeve (45) and the cylindrical coupling body (35), which is integrally provided as a boss portion on the drum (33a) of the centrifugal clutch (33) and in which the movable sleeve (45) is slidably fitted. ) And a compression coil spring (40) that is compressed between the movable sleeve (45) and a locking portion (35b) provided on the cylindrical coupling body (35), and the movable sleeve (45) and the cylindrical coupling body (35) are provided with conversion means (50, 37) for converting torsional vibration of the transmission shaft (7) into expansion and contraction motion of the compression coil spring (40). A portable brush cutter.

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