JP5742089B2 - Power tools - Google Patents

Description

  The present invention relates to a power tool such as a brush cutter, a high branch pruner, and an electric tool, and more particularly to a power tool that transmits rotation of a drive source to a tool such as a rotary blade using a rotary shaft.

  In a power tool such as a brush cutter, an engine is generally used as a drive source. In a power tool using an engine, it is also a problem to reduce vibration. For example, as described in Patent Document 1, vibration generated in the engine is prevented from being transmitted to the handle via the operating rod. In this case, a shock absorber is inserted between the operating rod and the clutch case.

Japanese Utility Model Publication No. 7-11113

  The brush cutter described in the above-mentioned Patent Document 1 is a torsional vibration that occurs in a long power transmission shaft due to torque fluctuation, rotation speed fluctuation, load change of the rotary blade, etc. during acceleration or deceleration of the drive source. It does not have the effect of suppressing the occurrence. For example, when an obstacle comes into contact with the rotating blade and locks, an excessive torque is generated between the stopped driven shaft and the rotating drive shaft. For this reason, an excessive load is applied to the rotating shaft, the centrifugal clutch, the engine, and the like, which may lead to a shortened life of these components.

  The present invention has been made in view of the above problems, and suppresses and attenuates the generation of torsional vibration generated in a long power transmission shaft, thereby reducing vibration transmitted to the handle, and further, driving shaft and driven An object of the present invention is to provide a power tool that prevents an excessive load from being applied to a component by interrupting an excessive torque transmission with a shaft, thereby enabling a long life.

In order to achieve the above object, a power tool according to a first aspect of the present invention includes a drive unit that generates a rotational driving force, a hollow flange that is positioned between the drive unit and the work tool, rotational driving force of the driving unit from one end is input, a first rotating portion being rotatably supported in said rod portion, the rotational driving force inputted from the other end toward the working tool from a end outputting a rotatably a second rotating portion that is supported and the other end of the other end of the first rotating portion and the second rotating portion and linked to the dynamic force transmitted into the rod portion , when more than a predetermined value of torque is generated between the front Symbol the second rotating portion and the first rotating part, be deformed in the radial direction of the first rotating portion or the second rotation part Accordingly, and an elastic connecting portion for interrupting power transmission between the first rotating portion and the second rotating part, the bullet Any one of the connecting portion, the other end of the first rotating portion, and the other end of the second rotating portion has a non-circular cross-sectional shape in a cross section perpendicular to the rotation axis, and the elastic connecting portion is The elastic connecting portion, the other end of the first rotating portion, and the first are expanded and contracted in the axial direction according to an increase / decrease in torque between the first rotating portion and the second rotating portion. At least one of the other ends of the two rotating parts slides in the axial direction.

Further, the elastic connecting portion is fitted between the outer periphery of the other end of the first rotating portion and the outer periphery of the other end of the second rotating portion, respectively, in the normal driving direction of the working tool. the when a predetermined value or more torque is generated between the first rotating part and the second rotating part, preferably a coil spring that deformation as the inner diameter is increased.

  Furthermore, either the other end of the first rotating part or the other end of the second rotating part may be loosely inserted into the inner peripheral surface of the elastic connecting part.

  In addition, the flange portion has a dividing portion that divides the power tool into the drive portion side and the work tool side on the flange portion, and the elastic connecting portion is provided in the vicinity of the dividing portion, and the elastic portion The connecting portion may be loosely inserted into at least one of the first rotating portion or the second rotating portion.

Furthermore, it is preferable that a centrifugal clutch is provided between the driving unit and the first rotating unit, and the torque not less than the predetermined value is smaller than the maximum transmission torque that can be transmitted by the centrifugal clutch .

A power tool according to a second aspect of the present invention includes a drive unit that generates a rotational drive force, a hollow collar positioned between the drive unit and the work tool, and rotational drive of the drive unit from one end. Rotating in the flange, to which a force is input, and outputting a rotational driving force input from the other end toward the working tool from one end of the first rotating portion that is rotatably supported in the flange The second rotating part supported in a possible manner, the other end of the first rotating part, and the other end of the second rotating part are connected so as to be able to transmit power, and the first rotating part and the first rotating part are connected. When a torque greater than a predetermined value is generated between the first rotating unit and the second rotating unit, the first rotating unit and the second rotating unit are deformed in a radial direction of the first rotating unit or the second rotating unit. An elastic coupling portion that cuts off power transmission between the second rotary portion and the other end of the first rotary portion or the One of the other ends of the two rotating portions has at least one flat portion in a cross section perpendicular to the rotation axis, and the elastic connecting portion is the other end of the first rotating portion or the second rotation A torque that is fixed to the other end of the part and circumscribes the flat part and is greater than or equal to a predetermined value between the first rotating part and the second rotating part in the driving direction of the working tool. It is characterized by comprising a plate-like elastic member that deforms outward in the radial direction when this occurs .

Moreover, the said collar part has a division part which divides | segments the said power tool into the said drive part side and the said work tool side on the said collar part, and the said plate-shaped elastic member is provided in the division surface vicinity of the said division part. May be .

  According to the present invention, when the power tool generates a torque of a predetermined value or more between the first rotating part to which the rotational driving force is input and the second rotating part connected to be able to drive the work tool. In addition, since the elastic connecting part interrupts the power transmission between the first rotating part and the second rotating part, it is possible to suppress the overload from being applied to the components of the power tool and to extend the life of the power tool. Can be achieved.

1 is a perspective view of a brush cutter according to a first embodiment of the present invention. It is a principal part expanded sectional view of the brush cutter of FIG. It is an enlarged view of the spring part of FIG. It is the IV-IV sectional view taken on the line of FIG. It is a principal part expanded sectional view of the gear case part of the brush cutter of FIG. It is a figure corresponding to FIG. 3 which concerns on the modification of 1st Embodiment of this invention. It is sectional drawing of the part which the power shaft of the spring which concerns on 2nd Embodiment of this invention couple | bonds. It is sectional drawing of the part which the spring and driven shaft which concern on 2nd Embodiment of this invention couple | bond. It is sectional drawing in the state in which the torque more than predetermined was added between the spring which concerns on 2nd Embodiment of this invention, and a driven shaft. It is a disassembled perspective view of the coupling member which concerns on 3rd Embodiment of this invention. It is a front view of the cylindrical part of the coupling member of FIG. It is a perspective view which shows the state which assembled the coupling member of FIG. It is a perspective view in the state where torque more than predetermined was added between the coupling member of FIG. 10, and a power shaft. It is sectional drawing in the normal use state of the coupling member of FIG. 10 in an operating rod. FIG. 11 is a cross-sectional view of the coupling member of FIG. 10 in the operating rod in a state where a predetermined torque or more is applied between the coupling member and the power shaft. It is a perspective view of the brush cutter which concerns on 4th Embodiment of this invention. It is an expanded sectional view of the junction part part of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the brush cutter 1 (power tool) includes a hollow pipe-shaped operation rod 2 (a collar portion), and a cord-type rotary blade 3 (for work, for example) is provided at one end of the operation rod 2. Tool) is rotatably attached via the gear case 4. Further, the other end of the operation rod 2 is attached with a drive unit 5 in which an engine 10 that generates a rotational drive force for rotating the cord type rotary blade 3 is housed. The operation rod 2 is provided with an operation section 6 provided with a throttle lever for an operator to hold and adjust the rotation speed of the engine 10, a stop switch for stopping the engine 10 in operation, and the like. An operation handle 7 is provided in the center of the operation rod 2 for the operator to hold.

  As shown in FIG. 2, a centrifugal clutch mechanism 12 is attached to the crankshaft 11 of the engine 10 in the drive unit 5. The clutch drum 13 of the centrifugal clutch mechanism 12 is housed in a clutch case 8 that tapers toward the operation rod 2. A substantially cylindrical recess 14 is formed in the tapered portion of the clutch case 8, and the operating rod 2 is inserted through a rubber member 15 and a spacer 16 provided in the recess 14. A bearing 17 is attached to the end of the recess 14 on the clutch drum 13 side, and the bearing 17 is fixed to the clutch drum 13 and protrudes toward the operating rod 2 (step 1). (Rotating part) is supported rotatably. Further, a stepped columnar driven shaft 30 (second rotating portion) connected to a bevel gear mechanism housed in the gear case 4 is rotatably supported by the bush 18 in the operation rod 2.

  As shown in FIGS. 2 and 3, the power shaft 20 has an end 21 having a circular cross section that is smaller in diameter than the portion supported by the bearing 17 on the operating rod 2 side, and the driven shaft 30 has a bush 18 on the drive unit 5 side. And an end portion 31 having a circular cross section having a smaller diameter than that of the portion supported by. The end 21 of the power shaft 20 and the end 31 of the driven shaft 30 are opposed to each other in the operating rod 2 so as to face each other, and the power shaft 20, the driven shaft 30, the end 21 of the power shaft 20, and the end of the driven shaft 30. The part 31 is arrange | positioned so that it may become coaxial. Further, the diameter of the end portion 21 of the power shaft 20 and the end portion 31 of the driven shaft 30 are equal.

  As shown in FIGS. 3 and 4, a spring 40 (elastic connecting portion) is attached across the outer peripheral surface of the end portion 21 of the power shaft 20 and the outer peripheral surface of the end portion 31 of the driven shaft 30. The spring 40 is a cylindrical coil spring, and the inner diameter of the spring 40 is smaller than the outer diameter of the end portions 21 and 31. The end portion 21 of the power shaft 20 and the end portion 31 of the driven shaft 30 are press-fitted inside the spring 40, respectively, and the outer peripheral surface of the end portion 21 of the power shaft 20 and the end portion 31 of the driven shaft 30 A pressurizing force is generated between the peripheral surface. Further, the winding direction of the spring 40 is such that when the power shaft 20 and the driven shaft 30 are attached to the spring 40, the torque is spring when the power shaft 20 rotates in the normal rotation direction of the engine 10 with respect to the driven shaft 30. 40 is the direction in which the inner diameter of the spring 40 increases. As shown in FIG. 5, the driven shaft 30 has a corner 55 opposite to the side connected by the spring 40 and has a bevel gear 56 rotatably supported in the gear case 4. By being inserted into the rectangular hole portion, it is disposed so as to be relatively movable in the axial direction while maintaining the engagement state in the rotational direction with the bevel gear.

  When a torsional torque of a predetermined value or more is applied in the direction in which the inner diameter of the spring 40 increases, the inner diameter of the spring 40 increases, and the pressurization (frictional force) between the spring 40 and the end portions 21 and 31 decreases. Relative rotation between 40 and the end 21 and / or end 31 is possible. Note that the pressure applied to the spring 40 generates a sufficient frictional force between the spring 40 and the end portions 21 and 31 within the range of torsional torque generated in the spring 40 in a normal working state (slip occurs). There is no pressure). Further, the torsional torque not less than a predetermined value is smaller than the allowable torque of the centrifugal clutch mechanism 12. As shown in FIG. 6, an elastic body 45 that exhibits viscoelastic characteristics in the axial direction and torsional direction of rubber or the like may be attached between the end portion 21 of the power shaft 20 and the end portion 31 of the driven shaft 30. . In this case, the elastic body 45 is fixed to the facing surface of the end portion 21 (31) of either the end portion 21 or the end portion 31, and is pressed against the facing surface of the other end portion 31 (21).

  According to the brush cutter 1 configured as described above, sufficient pressure is generated between the end portion 21 of the power shaft 20 and the end portion 31 of the driven shaft 30 and the spring 40 in a normal working state. Therefore, the rotation of the crankshaft 11 of the engine 10 is transmitted to the power shaft 20, the spring 40, the driven shaft 30, and the bevel gear mechanism via the centrifugal clutch mechanism 12, and the rotary blade 3 rotates. When torque fluctuation occurs in the drive transmission system due to the contact of the rotary blade 3 with the grass or the like during acceleration or acceleration / deceleration of the engine speed, and the torsional vibration is generated between the driven shaft 30 and the power shaft 20, the spring 40 is It rotates in the direction in which the inner diameter is reduced or expanded, and is also displaced in the axial direction (when the inner diameter is reduced, it is displaced in the axial direction, and when the inner diameter is increased, it is displaced in the axial direction). The fluctuation component of the torque transmitted through the spring 40 is effectively caused by the torsional vibration of the spring 40 due to the buffering action of the spring 40 itself and the friction generated during the axial displacement between the spring 40 and the end portions 21 and 31. Can be suppressed and attenuated. Further, as shown in FIG. 6, when the elastic body 45 exhibiting viscoelastic characteristics is attached between the end portion 21 and the end portion 31, the elastic body 45 between the end portion 21 or the opposing surface of the end portion 31. And the elastic body 45 itself is twisted, so that a buffering action is generated, and the generation of torsional vibration can be suppressed and attenuated more effectively.

  On the other hand, when the rotation of the rotary blade 3 is suddenly stopped while the rotary blade 3 is rotating, for example, when grass or the like is entangled, the torque generated in the spring 40 is suddenly increased and the inner diameter of the spring 40 is increased. As a result, the pressurization between the spring 40 and the end portions 21 and 31 rapidly decreases, and when the increased torque exceeds a predetermined value, the relative rotation between the spring 40 and the end portion 21 and / or the end portion 31 occurs. Occurs. For this reason, transmission of the rotational torque of the engine 10 to the locked driven shaft 30 is cut off by the expansion of the spring 40, and the rotary blade 3, the bevel gear mechanism, the driven shaft 30, the power shaft 20, the centrifugal clutch mechanism 12, An excessive load is suppressed from being applied to the engine 10 or the like. In particular, since the torque causing the relative rotation is set to a torque lower than the allowable torque of the centrifugal clutch mechanism 12, it is possible to suppress applying a load to the centrifugal clutch mechanism 12. Therefore, the load applied to these components can be reduced, the wear and damage of the components can be prevented, the life can be extended, and the ease of use can be improved by reducing the frequency of maintenance.

  Next, 2nd Embodiment of this invention is described based on FIGS. 7-9. In this embodiment, the shapes of the cylindrical coil spring-like spring 40, the end portion 21 of the power shaft 20 having a circular cross section, and the end portion 31 of the driven shaft 30 having a circular cross section are changed. In addition, about the structure which has a function equivalent to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The spring 140 is wound in a coil shape, and the cross section perpendicular to the longitudinal direction of the spring 140 has a non-circular shape as shown in FIG. 7, and a parallel facing portion 141 facing the inside in parallel is formed. A rounded rectangle or a substantially oval shape composed of two parallel lines of equal length and two semicircles. As shown in FIG. 7, the end 121 of the power shaft 20 has a substantially regular octagonal cross section. Further, as shown in FIG. 8, the end 131 of the driven shaft 30 also has a substantially regular octagonal cross section. The shape of the cross section of the end 121 of the power shaft 20 is slightly smaller than the shape of the cross section of the end 131 of the driven shaft 30. The distance between the parallel opposite sides in the cross section of the end portion 121 of the power shaft 20 is slightly larger than the distance of the parallel facing portion 141 in the cross section of the spring 140, and the distance between the parallel opposite sides in the cross section of the end portion 131 of the driven shaft 30 is The distance is slightly smaller than the distance between the parallel opposing portions 141 in the cross section of the spring 140. In addition, the outermost diameter in the cross section of any end part 121 and 131 is also smaller than the diameter of the cross section of the power shaft 20 and the passive shaft 30.

  The end 121 of the power shaft 20 is press-fitted into the inner periphery of the spring 140 and the end 131 of the driven shaft 30 is loosely inserted into the inner periphery of the spring 140 with slight play (not shown). The winding direction of the spring 140 is such that when the power shaft 20 and the driven shaft 30 are attached to the spring 140, the torque is spring when the power shaft 20 rotates in the normal rotation direction of the engine 10 with respect to the driven shaft 30. When applied to 140, the inner diameter of the spring 140 is increased.

  When a torsional torque of a predetermined value or more is applied in the direction in which the inner diameter of the spring 140 increases, the inner diameter of the spring 140 increases as shown in FIG. 9, and the distance between the parallel facing portions 141 in the cross section of the spring 140 is the end of the driven shaft 30. It becomes larger than the outermost diameter of the part 131, and the relative rotation of the spring 140 and the driven shaft 30 becomes possible. Note that, within the range of torsional torque generated in the spring 140 in a normal working state, the distance of the parallel facing portion 141 in the cross section of the spring 140 is the outermost diameter of the end portion 121 of the power shaft 20 and the end portion 131 of the driven shaft 30. The spring 140 is applied with a pressure that does not become larger (a pressure that does not cause relative rotation). Further, the torsional torque not less than a predetermined value is smaller than the allowable torque of the centrifugal clutch mechanism 12. Note that the cross-sectional shapes of the end portions 121 and 131 are not limited to a substantially regular octagon, and any cross-sectional shape having at least one pair of parallel opposite sides that can come into contact with the parallel facing portion 141 of the spring 140, for example, a regular hexagon. Various polygonal shapes such as a rectangular shape and a rectangular shape, a rounded rectangular shape, and the like may be used. In addition, the parallel facing portion 141 of the spring 140 may be a non-circular shape and may have another cross-sectional shape as long as the end portions 121 and 131 are in contact with each other and can transmit power. For example, the opposite side has a curvature. It may have an oval shape or a shape recessed inside.

  According to the brush cutter 1 configured as described above, in a normal working state, the parallel facing portion 141 of the spring 140 is connected to the end portion 121 of the power shaft 20 and / or the driven shaft 30 as shown in FIGS. Therefore, the rotation of the crankshaft 11 of the engine 10 is transmitted to the power shaft 20, the spring 140, the driven shaft 30, and the bevel gear mechanism via the centrifugal clutch mechanism 12, The rotary blade 3 rotates. When torque fluctuation occurs in the drive transmission system due to contact of the rotary blade 3 during work with the grass or the like and acceleration / deceleration of the engine speed, and torsional vibration is generated between the driven shaft 30 and the power shaft 20, the spring 140 is It rotates in the direction in which the inner diameter is reduced or expanded, and is also displaced in the axial direction (when the inner diameter is reduced, it is displaced in the axial direction, and when the inner diameter is increased, it is displaced in the axial direction). For this reason, when torsional vibration is generated, it occurs when the spring 140 is buffered and axially displaced between the spring 140, the end 121, and the end 131 (when the inner diameter of the spring 140 contracts and contacts the end 131). By friction, the spring 140 can effectively suppress and dampen the generation of torsional vibration. When the elastic body 45 is attached between the end portion 121 and the end portion 131, the elastic body 45 is pressed between the end portion 121 or the opposing surface of the end portion 131 and the elastic body 45 itself is twisted. Thus, a buffering action is generated, and the generation of torsional vibration can be suppressed and attenuated more effectively.

  On the other hand, when the rotary blade 3 is rotating, for example, when grass or the like is entangled and the rotation of the rotary blade 3 is suddenly stopped, the torque generated in the spring 140 is suddenly increased and the inner diameter of the spring 140 is expanded. As a result, as shown in FIG. 9, the distance between the parallel facing portions 141 in the cross section of the spring 140 becomes larger than the outermost diameter of the end portion 131 of the driven shaft 30, and the spring 140 rotates with respect to the driven shaft 130. For this reason, the transmission of the rotational torque of the engine 10 to the locked driven shaft 30 is blocked by the expansion of the spring 140, and the rotary blade 3, the bevel gear mechanism, the driven shaft 30, the power shaft 20, the centrifugal clutch mechanism 12, An excessive load is suppressed from being applied to the engine 10 or the like. In particular, since the torque causing the relative rotation is set to a torque lower than the allowable torque of the centrifugal clutch mechanism 12, it is possible to suppress applying a load to the centrifugal clutch mechanism 12. Therefore, the load applied to these components can be reduced, the wear and damage of the components can be prevented, the life can be extended, and the ease of use can be improved by reducing the frequency of maintenance.

  Further, in the case of the present embodiment, the distance between parallel opposite sides in the cross section of the end portion 131 of the driven shaft 30 is slightly smaller than the parallel facing portion 141 in the cross section of the spring 140. Therefore, when the driven shaft 30 is assembled to the spring 140, the driven shaft 30 is inserted into the spring 140 by aligning the positions so that the opposite sides of the end 131 of the driven shaft 30 are parallel to the parallel opposed portion 141 of the spring. Just do it. For this reason, the assembling work can be easily performed, and the manufacturing cost can be reduced and the maintainability can be improved.

  Not limited to the above-described configuration, if the spring 140 has a non-circular cross-section, and either the end on the power shaft side or the end on the driven shaft side has a non-circular cross-section, it can rotate without requiring press-fitting. Therefore, assembly work is facilitated, and manufacturing costs can be reduced and maintainability can be improved. In addition, the end 121 of the power shaft 120 is press-fitted into the inner periphery of the spring 140 so as to be inserted, but a locking portion that performs relative rotation and retaining of the end 121 and the spring 140 during forward rotation is provided. The end 121 or the inner wall of the operation rod 2 may be provided.

  The relationship between the spring 140 and the end 131 of the driven shaft 30 and the end 121 of the power shaft 20 described above is such that the end 121 of the power shaft 20 is loosely inserted into the inner periphery of the spring 140 with slight play. The end 131 of the shaft 30 may be press-fitted into and inserted into the inner periphery of the spring 140. In this case, the same effect as described above can be obtained.

  Next, 3rd Embodiment of this invention is described based on FIGS. 10-15. In this embodiment, a coupling member 240 is used instead of the coiled springs 40 and 140 of the first and second embodiments. In addition, about the structure which has a function equivalent to 1st and 2nd embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 10, the coupling member 240 (elastic connecting portion) is composed of a cylindrical portion 241 and a leaf spring portion 245. The cylindrical portion 241 is formed with a first notch portion 242 and a second notch portion 243 that extend in parallel with the shaft 250 from one end portion. As shown in FIG. 11, the wall surface (shaft side wall surface) 242a on the shaft 250 side and the wall surface (edge side wall surface) 242b on the side away from the shaft 250 are formed in a plane parallel to the shaft 250 of the first notch 242. Opposite parallel. Further, the shaft side wall surface 243a formed in a planar shape parallel to the shaft 250 of the second notch 243 is formed so as to be located on the same plane as the shaft side wall surface 242a of the first notch 242. . The edge side wall surface 243b formed in a planar shape parallel to the shaft 250 of the second notch 243 is inclined by a predetermined angle α with respect to the shaft side wall surface 243a, and the edge side wall surface of the first notch 242 Connect to 242b. Therefore, the distance between the shaft side wall surface 242a and the edge side wall surface 242b of the first notch 242 is smaller than the distance between the shaft side wall surface 243a and the edge side wall surface 243b of the second notch 243.

  The leaf spring portion 245 is a rectangular metal plate made of, for example, spring steel or the like, and has a thickness substantially equal to the distance between the shaft side wall surface 242a and the edge side wall surface 242b of the first cutout portion 242. Further, the leaf spring portion 245 has a length substantially equal to the length of the notches 242 and 243 in the direction of the shaft 250 in the axial direction in FIG. 10, and the first notch portion 242 in the left-right direction in FIG. The shaft side wall surface 242a of the second notch 243 has a length reaching the shaft side wall surface 243a.

  As shown in FIGS. 12 and 14, the leaf spring portion 245 is fixed by being sandwiched between the shaft side wall surface 242 a and the edge side wall surface 242 b in the first cutout portion 242 of the cylindrical portion 241. The coupling member 240 is configured by being assembled to the cylindrical portion 241 so as to close the internal space of the cylindrical portion 241 toward the portion 243. Since the leaf spring portion 245 is fixed by the first cutout portion 242 and the second cutout portion 243 side is a free end, the radial direction of the coupling member 240 (the second cutout portion 242 of the cylindrical portion 241 It can be elastically deformed in the direction of the edge side wall surface 243b).

  As shown in FIG. 12, a coupling member 240 is fixed to the end of the driven shaft 30 on the side opposite to the rotary blade 3. The driven shaft 30 is fixed to the end of the coupling member 240 opposite to the side where the plate spring portion 245 is provided so that the driven shaft 30 and the coupling member 240 are coaxial. Then, the end portion 221 of the power shaft 20 is loosely inserted into the space formed inside the leaf spring portion 245 and the cylindrical portion 241 from the end portion of the coupling member 240 on the leaf spring portion 245 side. The end portion 221 of the power shaft 20 is formed with a flat surface 221a (flat portion). When the brush cutter 1 is assembled, the flat portion 221a of the end portion 221 of the power shaft 20 is a plate as shown in FIG. The spring portion 245 is opposed to the spring portion 245 with a slight play (not shown), and the power shaft 20, the driven shaft 30, and the coupling member 240 are arranged to be coaxial. When the power shaft 20 rotates with respect to the coupling member 240, the flat surface 221a contacts the leaf spring portion 245, and the leaf spring portion 245 is moved radially outward (in the direction of the edge side wall surface 243b of the second notch portion 242). Deform.

  As indicated by the arrows in FIG. 13, when the power shaft 20 rotates counterclockwise with respect to the coupling member 240 and a torsional torque of a predetermined value or more is generated between the power shaft 20 and the coupling member 240, The leaf spring portion 245 is deformed in the direction of the edge side wall surface 243b so that the surface 221a can get over the leaf spring portion 245, and the power shaft 20 and the coupling member 240 are relatively rotated. It should be noted that a pressure is applied so that the leaf spring portion 245 is deformed and relative rotation between the power shaft 20 and the coupling member 240 does not occur within a range of torsional torque generated in the coupling member 240 in a normal working state. Part 245 is provided. Further, the torsional torque not less than a predetermined value is smaller than the allowable torque of the centrifugal clutch mechanism 12.

  According to the brush cutter 1 configured in this manner, in a normal working state, the leaf spring portion 245 of the coupling member 240 is deformed outward in the radial direction of the coupling member 240 as shown in FIG. Since the relative rotation between the ring member 240 and the power shaft 20 does not occur, the rotation of the crankshaft 11 of the engine 10 is performed via the centrifugal clutch mechanism 12 to the power shaft 20, the coupling member 240, the driven shaft 30, and the bevel gear mechanism. The rotary blade 3 rotates. Torque fluctuations occur in the drive transmission system due to contact of the rotary blade 3 with the grass or the like during the operation or acceleration / deceleration of the engine speed, and torsional vibration is generated between the driven shaft 30 and the power shaft 20 that move together with the coupling member 240. When this occurs, the flat surface 221a of the end 221 of the power shaft 20 deforms the leaf spring portion 245. The leaf spring portion 245 and the flat surface 221a are effectively caused by the buffering force acting in the direction of the rotation axis of the end portion 221 and the friction generated between the flat surface 221a and the leaf spring portion 245 when the leaf spring portion 245 is deformed. Generation of torsional vibration can be suppressed and attenuated. In addition, by using a material having viscoelastic characteristics for the leaf spring portion 245, it is also possible to exert a vibration damping effect.

  On the other hand, if the rotation of the rotary blade 3 suddenly stops while the rotary blade 3 is rotating, for example, when grass or the like is entangled, the torque generated between the coupling member 240 and the power shaft 20 rises rapidly and the leaf spring portion 245. Is deformed radially outward. As a result, as shown in FIG. 15, the flat surface 221 a of the end 221 of the power shaft 20 gets over the leaf spring portion 245, and the power shaft 20 rotates in the direction of the arrow with respect to the coupling member 240. For this reason, transmission of the rotational torque of the engine 10 to the locked driven shaft 30 is blocked by the deformation of the leaf spring portion 245 of the coupling member 240, and the rotary blade 3, the bevel gear mechanism, the driven shaft 30, and the power shaft 20. Further, an excessive load is suppressed from being applied to the centrifugal clutch mechanism 12, the engine 10, and the like. In particular, since the torque causing the relative rotation is set to a torque lower than the allowable torque of the centrifugal clutch mechanism 12, it is possible to suppress applying a load to the centrifugal clutch mechanism 12. Therefore, the load applied to these components can be reduced, the wear and damage of the components can be prevented, the life can be extended, and the ease of use can be improved by reducing the frequency of maintenance.

  Furthermore, in the case of this embodiment, the flat surface 221a of the end 221 of the power shaft 20 faces the leaf spring 245 of the coupling member 240 with a slight play. Therefore, the assembly of the power shaft 20 and the coupling member 240 fixed to the driven shaft 30 is performed by aligning the positions so that the flat surface 221a of the end 221 of the power shaft 20 and the leaf spring portion 245 are parallel to each other. The end 221 of the power shaft 20 may be inserted into the cylindrical portion 241 of the ring member 240. For this reason, the assembling work can be easily performed, and the manufacturing cost can be reduced and the maintainability can be improved.

  As described above, the coupling member 240 and the driven shaft 30 are fixed, and not only the power shaft 20 is assembled to the coupling member 240 but also the coupling member 240 and the power shaft 20 are fixed and the driven shaft 30 is fixed. A flat surface may be formed on the end portion 231 and assembled to the coupling member 240. In this case, the same effect as described above can be obtained.

  In any of the above-described embodiments, the operation rod 2 is configured by a single hollow pipe, and the power shaft 20 and the driven shaft 30 are connected by the springs 40 and 140 or the coupling member 240 on the engine 10 side. Alternatively, the configuration of the fourth embodiment of the present invention described with reference to FIGS. 16 and 17 may be employed. In addition, about the structure which has a function equivalent to 1st-3rd embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 16, the operation rod 302 of the brush cutter 1 is configured by attaching a first pipe 303 and a second pipe 304 to a joint portion 305. The first pipe 303 has one end attached to the drive unit 5 and the other end attached to the joint 305. One end of the second pipe 304 is attached to the gear case 4, and the other end is detachably attached to the joint 305 by a pin 309.

  As shown in FIG. 17, in the operating rod 302, a first driven shaft 330 that is rotatably supported in the first pipe 303 and a second driven shaft 335 that is rotatably supported in the second pipe 304. And is housed. The structure on the drive unit 5 side of the first driven shaft 330 is the same as the structure on the drive unit 5 side of the driven shaft 30 in any of the first to third embodiments described above, and the first to third embodiments described above. It attaches with respect to the drive part 5 using the structure demonstrated in either. On the other hand, the first driven shaft 330 protrudes from the end of the first pipe 303 into the joint 305 fixed to the first pipe 303 on the joint 305 side, and is rotatably supported by the bush 318. And the end part 331 by the side of the junction part 305 of the 1st driven shaft 330 is comprised by the substantially regular octagonal cross section similarly to the edge part 121 of the power shaft of 2nd Embodiment mentioned above. In this case, the first driven shaft 330 also corresponds to the first rotating unit.

  The end of the second driven shaft 335 on the rotary blade 3 side is configured in the same manner as the driven shaft 30 in any of the first to third embodiments described above, and is the same as in the case of the first to third embodiments described above. To the drive unit 5. The structure of the second driven shaft 335 on the rotary blade 3 side is the same as the structure of the driven shaft 30 on the rotary blade 3 side in any of the first to third embodiments described above, and the first to third embodiments described above. As in either case, the bevel gear mechanism in the gear case 4 is connected. On the other hand, the second driven shaft 335 protrudes from the end of the second pipe 304 on the rotary blade 3 side and protrudes into the joint 305 fixed to the second pipe 304 with the pin 309. The end 336 of the second driven shaft 335 on the joint 305 side has a substantially regular octagonal cross section similar to the end 131 of the driven shaft 130 of the second embodiment described above. In this case, the second driven shaft 335 also corresponds to the second rotating unit.

  The end portion 331 of the first driven shaft 330 and the end portion 336 of the second driven shaft 335 are coil springs having a rounded rectangular cross section in the joint portion 305 as in the spring 140 of the second embodiment described above. It is connected by a second spring 340 (elastic connecting part). In this case, the end 331 of the first driven shaft 330 is press-fitted into the inner periphery of the second spring 340 and the end 336 of the second driven shaft 335 is slightly inserted inside the second spring 340. It is loosely inserted (not shown). The winding direction of the second spring 340 is such that the first driven shaft 330 is connected to the engine 10 with respect to the second driven shaft 335 when the first driven shaft 330 and the second driven shaft 335 are attached to the second spring 340. When torque is applied to the second spring 340 when rotating in the rotation direction during the forward rotation, the inner diameter of the second spring 340 is increased. The characteristics in the state where the other second spring 340, the first driven shaft 330, and the second driven shaft 335 are assembled are the same as those in the second embodiment.

  According to the brush cutter 1 configured in this manner, the torsion is performed between the first driven shaft 330, the second spring 340, and the second driven shaft 335 in the joint portion 305 as in the second embodiment. It has the effect of reducing vibrations and the effect of protecting components by cutting off power transmission when a torque exceeding a predetermined value is generated. In the case of this embodiment, torsional vibration can be reduced and power transmission can be interrupted at both ends of the first driven shaft 330. For this reason, not only the vibration reduction effect is further improved, but also power transmission can be interrupted more reliably, and the brush cutter 1 having a longer life can be provided by protecting the components.

  Further, when the second pipe 304 is pulled out by removing the pin 309 from the joint portion 305, the end 336 of the second driven shaft 335 is also pulled out from the spring 340 at the same time, so that the long operation rod 302 can be easily divided. . In addition, the divided operation rod 302 is assembled such that the parallel opposite side of the end 336 on the joint 305 side of the second driven shaft 335 is parallel to the parallel opposing portion (not shown) of the second spring 340. The second pipe 304 can be easily inserted by simply inserting the second pipe 304 into the joint 305 and fixing it with the pin 309. For this reason, the maintainability of the brush cutter 1 is further improved, and storage and carrying can be easily performed.

  The assembling relationship between the second spring 340 and the end 331 of the first driven shaft 330 and the end 336 of the second driven shaft 335 is such that the end 331 of the first driven shaft 330 is connected to the second spring 340. The inner periphery may be loosely inserted with slight play, and the end 336 of the second driven shaft 335 may be press-fitted into the inner periphery of the second spring 340, and in this case, the same effect as described above can be obtained. be able to.

  Further, the second spring 340, the end 331 of the first driven shaft 330, and the end 336 of the second driven shaft 335 are the same as those of the second embodiment. It may be replaced with a configuration. In this case, the 1st driven shaft 330 or the 2nd driven shaft 335 is fixed to the 2nd coupling member similar to the coupling member 240 of 3rd Embodiment, and the edge part 336 of the 2nd driven shaft 335 which formed the flat surface. Alternatively, the end 331 of the first driven shaft 330 is loosely inserted into the second coupling member. In this case, the same effect as described above can be obtained.

  Moreover, the both ends of the 1st driven shaft 330, the power shaft 20, and the 2nd driven shaft 335 may be connected using the same structure (For example, the structure using the springs 140 and 340 similar to 2nd Embodiment). The power shaft 20 and the second driven shaft 335 may be connected using different configurations (for example, the power shaft 20 and the second driven shaft 335 may be connected to each other), and the power shaft 20 and the first driven shaft 330 may be integrated or directly connected. There may be.

  Further, the first driven shaft 330 and / or the second driven shaft 335 may be a flexible shaft having flexibility. In this case, when the torsional vibration occurs, the flexible shaft itself absorbs the displacement of the torsional vibration, so that the vibration damping effect can be further improved. This is particularly effective when a flexible shaft is combined when the coupling member 240 as in the third embodiment is used.

  The present invention is not limited to application to the brush cutter 1 in which the drive unit 5 and the rotary blade 3 are provided at both ends of the operation rods 2 and 302 as in the first to fourth embodiments described above. For example, the present invention can also be applied to a power tool that transmits power via a drive shaft such as a backpack-type brush cutter or a pole saw or a cultivator other than the brush cutter. For example, in the case of a backpack type brush cutter using a flexible cover in which a flexible shaft removably connected to a clutch cover and an operating rod in which the engine 10 is accommodated at one end is inserted, What is necessary is just to apply the structure of 2nd or 3rd Embodiment to the connection part with a driven shaft, and to apply the structure of 2nd or 3rd Embodiment also to the connection part of a flexible shaft and a drive part. In this way, the flexible cover can be easily attached to and detached from the operation cover and the clutch cover, and at the same time, when an excessive torque is generated, the power transmission can be interrupted to protect the components.

DESCRIPTION OF SYMBOLS 1 Brush cutter 2 Operating rod 3 Rotary blade 5 Drive part 7 Operation handle 8 Clutch case 12 Centrifugal clutch mechanism 13 Clutch drum 17 Bearing 20 Power shaft 21, 121 Power shaft end 30 Drive shaft 31, 131 Drive shaft end 40 140 spring

Claims (7)

A driving unit for generating a rotational driving force;
A hollow collar positioned between the drive unit and the work tool;
A first rotating unit that receives rotational driving force of the driving unit from one end and is rotatably supported in the flange;
A second rotating part that is rotatably supported in the flange, and outputs a rotational driving force input from the other end toward the working tool from one end;
The other end of the first rotating part and the other end of the second rotating part are connected so as to be able to transmit power, and a torque greater than or equal to a predetermined value between the first rotating part and the second rotating part. Is generated, the power transmission between the first rotating part and the second rotating part is interrupted by deformation in the radial direction of the first rotating part or the second rotating part. An elastic coupling,
With
Any one of the elastic coupling part, the other end of the first rotating part, and the other end of the second rotating part has a non-circular cross-sectional shape in a cross section perpendicular to the rotation axis ,
The elastic connecting portion expands and contracts in the axial direction according to an increase or decrease in torque between the first rotating portion and the second rotating portion, so that the elastic connecting portion and the first rotating portion At least one of the other end and the other end of the second rotating portion slides in the axial direction.
Dynamic force tool you, characterized in that. The elastic connecting portions are respectively fitted between the outer periphery of the other end of the first rotating portion and the outer periphery of the other end of the second rotating portion, and in the normal driving direction of the working tool, A coil spring that is deformed so that the inner diameter is widened when a torque of a predetermined value or more is generated between the first rotating part and the second rotating part;
The power tool according to claim 1. Either the other end of the first rotating part or the other end of the second rotating part is loosely inserted into the inner peripheral surface of the elastic connecting part.
The power tool according to claim 1 or 2 , characterized by the above. The collar part has a dividing part which divides the power tool on the collar part into the driving part side and the working tool side,
The elastic connecting portion is provided in the vicinity of the divided portion, and the elastic connecting portion is loosely inserted into at least one of the first rotating portion or the second rotating portion.
The power tool according to any one of claims 1 to 3, wherein: A centrifugal clutch is provided between the driving unit and the first rotating unit,
The torque equal to or greater than the predetermined value is smaller than the maximum transmission torque that can be transmitted by the centrifugal clutch.
The power tool according to any one of claims 1 to 4 , wherein: A driving unit for generating a rotational driving force;
A hollow collar positioned between the drive unit and the work tool;
A first rotating unit that receives rotational driving force of the driving unit from one end and is rotatably supported in the flange;
A second rotating part that is rotatably supported in the flange, and outputs a rotational driving force input from the other end toward the working tool from one end;
The other end of the first rotating part and the other end of the second rotating part are connected so as to be able to transmit power, and a torque greater than or equal to a predetermined value between the first rotating part and the second rotating part. Is generated, the power transmission between the first rotating part and the second rotating part is interrupted by deformation in the radial direction of the first rotating part or the second rotating part. An elastic coupling,
With
One of the other end of the first rotating part or the other end of the second rotating part has at least one flat part in a cross section perpendicular to the rotation axis,
The elastic connecting portion is fixed to the other end of the first rotating portion or the other end of the second rotating portion, circumscribes the flat portion, and in the driving direction of the work tool, A plate-like elastic member that deforms outward in the radial direction when a torque greater than or equal to a predetermined value is generated between the first rotating part and the second rotating part;
A power tool characterized by that. The collar part has a dividing part which divides the power tool on the collar part into the driving part side and the working tool side,
The plate-like elastic member is provided in the vicinity of the dividing surface of the dividing portion;
The power tool according to claim 6 .

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