JP5614331B2 - Lawn mower - Google Patents

Description

  The present invention relates to a lawn mower that rotates a rotary blade to cut grass and grass.

  2. Description of the Related Art Conventionally, there is known a lawn mower in which a drive source is mounted on a main body and a rotating blade is rotated by power from the drive source to cut grass and grass (see, for example, Patent Document 1). In the lawn mower described in Patent Document 1, a motor is provided as a drive source, a rotary blade provided at the lower portion of the main body is driven to rotate by power from the motor, a rotary blade that rotates, and a fixed blade provided on the main body, Is cut across the turf.

Japanese Utility Model Publication No.59-59113

  In the above-mentioned lawn mower, when cutting a turf with a rotating blade and a fixed blade, if a hard foreign object (such as a pebble or a tree branch) is caught with the turf, a hard foreign object is sandwiched between the rotating blade and the fixed blade. Otherwise, the motor may be overloaded or the rotary blade or fixed blade may be damaged.

  The present invention has been made in view of these points, and an object of the present invention is to prevent the rotary blade from being damaged when a stone or the like is involved during lawn mowing.

In order to achieve the above object, a lawn mower according to the present invention provides:
A drive source for outputting power;
A rotary blade that is rotationally driven by power from the drive source;
A first shaft that transmits power from the drive source to the rotary blade, a shaft engaging portion, a second shaft that transmits power from the drive source to the rotary blade, and the first shaft A first gear mounted; and a second gear provided with a gear engaging portion that engages with the first gear and engages with the shaft engaging portion. A power transmission mechanism that disengages the shaft engagement portion and the gear engagement portion when a load greater than a predetermined load is applied to the gear and the second gear;
It is characterized by providing.

  The power transmission mechanism may be configured such that when a load greater than a predetermined load is applied to the first gear and the second gear, the second gear moves in the axial direction of the second shaft. The engagement between the shaft engaging portion and the gear engaging portion may be released.

  Further, the second gear may be formed hollow and the second shaft may be inserted therein.

The first shaft is one of an output shaft of the drive source and a rotation shaft of the rotary blade,
The second axis may be the other axis of the output axis and the rotation axis.

  Further, at least one of the shaft engaging portion and the gear engaging portion has a slope inclined with respect to the rotation direction of the second shaft, and the shaft engaging portion and the gear engagement on the slope. You may engage with the other of a part.

  The second gear may be biased in the axial direction of the second shaft.

The shaft engaging portion is formed in a convex shape that is substantially perpendicular to the second shaft,
The gear engaging portion extends in the axial direction of the second shaft from a gear portion in which a side surface of the second gear is formed in an uneven shape, and at least a part of the upper surface is a rotational direction of the second shaft. It may be formed in a spiral shape that becomes higher toward the surface, and a hollow with an upper surface protruding upward is formed at an end in the rotational direction, and the upper surface of the hollow may be engaged with the shaft engaging portion.

  The power transmission mechanism may further include a moving mechanism that moves the second gear in a direction opposite to a direction in which the second gear is urged in accordance with an operation by an operator.

Position detecting means for detecting the position of the second gear;
Informing means for informing the operator of the release of engagement between the shaft engaging portion and the gear engaging portion based on the detected position of the second gear;
May be further provided.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a rotary blade is damaged when a stone etc. are caught at the time of lawn mowing.

It is a figure which shows a mode that the lawn mower which concerns on embodiment of this invention was seen from the side. It is a figure which shows a mode that the lawn mower was seen from the bottom. It is a figure which shows a mode that the case cover of the main body was removed and the lawn mower was seen from the top. It is the figure which looked at the main body from the IV-IV direction in FIG. It is the figure seen from the VV direction in FIG. 3 when motive power is transmitted with a drive source and a rotary blade. It is the figure seen from the VV direction in FIG. 3 when transmission of the motive power of a drive source and a rotary blade is cancelled | released. It is a figure which shows the mode of an output shaft periphery when an output gearwheel and an output shaft are engaging. It is a figure which shows the mode of an output-shaft periphery when engagement with an output gearwheel and an output shaft is cancelled | released. It is a figure which shows the mode of an output-shaft periphery when the reset switch is pushed. It is a figure which shows the mode of an output shaft periphery when a reset switch is pushed in. It is a figure which shows an example of an alerting | reporting panel.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating a lawn mower 20 according to an embodiment of the present invention as viewed from the side, and FIG. 2 is a diagram illustrating a lawn mower 20 as viewed from below. The lawn mower 20 according to the embodiment is configured as a working machine that cuts turf grass, and as shown in the figure, the handle 22 held by the operator, the main body 30 to which a plurality of wheels are attached, and the rear of the main body 30 are attached. A grass collection bag 26.

  The handle 22 is attached to the rear upper surface of the main body 30 so as to be rotatable within a predetermined range. The handle 22 is provided with an operation switch 24 for the operator to operate the lawn mower 20 in the vicinity of the grip portion 23 that the operator grips.

  FIG. 3 schematically shows a state in which the case cover 32b of the main body 30 is removed and viewed from above, and FIG. 4 shows a state in which the main body 30 is viewed from the IV-IV direction in FIG. The main body 30 includes a casing 32 that forms an outer edge of the main body 30, a fan 34 that generates a flow of air to guide the turf grass, a cutting unit 40 that cuts the turf grass, and a height adjustment mechanism 36 that adjusts the height of cutting the turf grass. A power source 38 that outputs power, a power transmission mechanism 50 that transmits power from the drive source 38 to the fan 34 and the cutting unit 40, and a notification mechanism (not shown) that notifies the operator of the state of the power transmission mechanism 50. And).

  As shown in FIG. 4, the casing 32 includes a lower casing 32 a formed in a bowl shape with an opening at the bottom, and a case cover 32 b that covers the lower casing 32 a from above, and includes a fan 34, a cutting unit 40, and a drive source. 38, storing the power transmission mechanism 50; A handle 22 is attached to the upper rear side of the casing 32, and a grass collection bag 26 for collecting the cut grass is detachably attached to the rear side of the casing 32.

  The fan 34 is provided on the front side of the casing 32, and generates a flow of air rearward from an air outlet 33 a provided in the bottom of the casing 32. The fan 34 is disposed in the casing 32 so that the rotating shaft 34a thereof is substantially vertical, and is rotated by power from the drive source 38. When the fan 34 rotates, outside air is taken in through a gap provided on the side surface of the casing 32 or an air intake port (not shown) above the casing 32, and the taken-out outside air is volute 33 b of the casing 32 as the fan 34 rotates. It rotates along the wall surface (rotates counterclockwise in FIG. 3), is discharged from the blower port 33a at the center of the bottom of the casing 32 through the opening of the lower casing 32a and the fan guide 33c, and flows backward in the traveling direction. .

  The mowing unit 40 includes two fixed blades 41 and 42 fixed to the casing 32 and two rotary blades 43 and 44 that are rotated by power from the drive source 38, and constitutes a first cutting unit. The rotary blade 43 and the first fixed blade 41, and the second rotary blade 44 and the second fixed blade 42 constituting the second cutting portion are arranged side by side. The two fixed blades 41 and 42 are respectively fixed to fixed shafts 41 a and 42 a extending vertically downward from the casing 32, and two rotary blades 43 and 44 are provided so as to be in contact with the upper surfaces of the fixed blades 41 and 42. . The two fixed blades 41 and 42 have a plurality of blade portions 41b and 42b formed on the outer periphery. The two rotary blades 43 and 44 have a plurality of blade portions 43b and 44b, are configured in a cylindrical shape, and are fixedly supported by the fixed shafts 41a and 42a so that the fixed shafts 41a and 42a are inserted into the inner portions. It rotates integrally with the rotating shafts 43a, 44a. The two rotary blades 43 and 44 are rotated in opposite directions by the power from the drive source 38, and the outer peripheral ends (blade portions 43b and 44b) overlap at the center so that no mowing is left in the center of the lawn mower 20. It is formed to do. The two rotary blades 43 and 44 are urged toward the fixed blades 41 and 42 by an urging mechanism 46 such as a spring, respectively.

  The height adjusting mechanism 36 is configured so that the operator operates the height adjusting lever 36a provided on the upper surface of the casing 32 so that the height of the wheels 31a and 31b (the wheel 31a is increased) by the link mechanism 36b interlocked with the height adjusting lever 36a. , 31b and the casing 32) is changed, and the height for cutting turfgrass can be arbitrarily adjusted. The front wheel 31a and the rear wheel 31b are connected to the link mechanism 36b and operate in the same manner, thereby adjusting the cutting height while the rotary blades 43 and 44 are maintained parallel to the ground. It is possible.

  In the embodiment, the drive source 38 uses a periodic motor such as an induction motor or a synchronous motor. The drive source 38 is disposed substantially rearward of the center of the casing 32 so that the output shaft 39 is in the vertical direction, and outputs power according to the operation of the operation switch 24 by the operator.

  The power transmission mechanism 50 transmits the power output from the drive source 38 to the fan 34 and the rotary blades 43 and 44. 5 and 6 show the inside of the main body 30 as viewed from the direction VV in FIG. 5 shows a state in which power from the drive source 38 is transmitted to the rotary blades 43 and 44 by the power transmission mechanism 50. In FIG. 6, power from the drive source 38 by the power transmission mechanism 50 is shown. The state when the transmission of is canceled is shown. As shown in FIGS. 3 to 6, the power transmission mechanism 50 includes a first transmission gear 51 attached to a rotary shaft 43 a of the first rotary blade 43 and a rotary shaft of the rotary blade 44 of the second rotary blade. A second transmission gear 52 attached to 44a, a fan gear 53 attached to the rotating shaft 34a of the fan 34, an output gear 54 engaged with the output shaft 39 of the drive source 38, and the output gear 54 vertically downward. And a reset switch 59 for resetting the position of the output gear 54.

  The first transmission gear 51, the second transmission gear 52, and the fan gear 53 are directly fixed to the first rotary blade 43, the second rotary blade 44, and the rotary shafts 43a, 44a, and 34a of the fan 34, respectively. Yes. As shown in FIG. 3, the first transmission gear 51 engages with the output gear 54 and the second transmission gear 52, and the second transmission gear 52 engages with the first transmission gear 51. And the fan gear 53 is engaged. With such a configuration, any one of the first transmission gear 51, the second transmission gear 52, the fan gear 53, and the output gear 54 rotates in conjunction with each other. In the embodiment, the first transmission gear 51 and the second transmission gear 52 are designed to have more teeth than the fan gear 53 and the output gear 54, and when the power from the drive source 38 is transmitted, The power is decelerated and transmitted to the first rotary blade 43 and the second rotary blade 44, and the power is accelerated and transmitted from the first rotary blade 43 and the second rotary blade 44 to the fan 34. Is done.

  The output gear 54 has an insertion hole formed at the center thereof, and the output shaft 39 of the drive source 38 is inserted into the insertion hole. The output gear 54 is movable in the axial direction of the output shaft 39 of the drive source 38, and the output gear 54 is engaged with the first transmission gear 51 regardless of the position of the output gear 54 relative to the output shaft 39. The output gear 54 engages with two convex portions (shaft engaging portions) 39 a provided on the output shaft 39 of the drive source 38. The two convex portions 39a are configured by pins press-fitted into the output shaft 39. FIG. 7 shows an enlarged view around the output gear 54. FIG. 7 shows a state where the output shaft 39 and the output gear 54 are engaged. In the embodiment, when power is output from the drive source 38, the output shaft 39 rotates clockwise as viewed from above (in the direction of the arrow in FIG. 7). As shown in the figure, the output gear 54 includes a gear portion 55 having a gear formed on the outer peripheral surface, and an engaging portion extending from the gear portion 55 in the axial direction of the output shaft 39 (on the convex portion 39a side of the output shaft 39). (Gear engaging portion) 56 is provided, and the engaging portion 56 engages with a cylindrical convex portion 39 a that is convex on the side surface of the output shaft 39.

  In the embodiment, the engaging portion 56 includes two portions that are point-symmetric with respect to the rotation center of the output gear 54, and an upper surface (hereinafter referred to as an upper slope portion) 56 b of the engaging portion 56 is a gear portion 55 of the output gear 54. Is formed in a spiral slope gradually increasing clockwise from the top to the furthest head portion 56a, and is formed so as to gradually decrease clockwise from the top when the head portion 56a is exceeded. The The engaging portion 56 has a top surface (hereinafter referred to as a lower slope portion) 56c that is convex upward when viewed from the side at a clockwise end when viewed from above (an end in the rotational direction of the output shaft 39 of the drive source 38). Boring is performed, and the convex portion 39a of the output shaft 39 is positioned on the lower slope portion 56c of the hollowed portion, and the engaging portion 56 and the convex portion 39a of the output shaft 39 are engaged. Since the output gear 54 is urged vertically downward by the urging mechanism 58, the convex portion 39a of the output shaft 39 and the lower inclined surface portion 56c of the engaging portion 56 of the output gear 54 are loads less than a predetermined load. Is engaged, the output shaft 39 and the output gear 54 rotate together, and when a load greater than a predetermined load is applied, the convex portion 39a of the output shaft 39 moves down the lower slope portion 56c. Then, it moves clockwise (rotation direction) and the engagement between the output shaft 39 and the output gear 54 is released. When the convex portion 39a of the output shaft 39 moves clockwise beyond the lower inclined surface portion 56c, the output gear 54 is urged vertically downward by the urging mechanism 58. Therefore, as shown in FIG. Is moved vertically downward, and the output shaft 39 and the output gear 54 are not engaged even if the output shaft 39 is rotated thereafter, and the power is transmitted from the drive source 38 to the two rotary blades 43 and 44 and the fan 34. Not. Here, the engaging portion 56 of the output gear 54 is assumed when a normal lawn mowing operation is performed (for example, when a foreign object is not caught between the rotary blade and the fixed blade) by an experiment or the like. What is necessary is just to design so that engagement with the convex part 39a of the output shaft 39 may be cancelled | released when the load a little larger than load acts.

  The reset switch 59 is provided at a position corresponding to the tip of the output shaft 39 of the drive source 38 of the casing 32. The reset switch 59 is designed so that it can be pushed in the axial direction (vertically upward) of the output shaft 39, and when the engagement between the output shaft 39 and the output gear 54 is released, that is, the output gear 54. Is moving in the tip direction of the output shaft 39, the output gear 54 is moved upward in the vertical direction by pressing the reset switch 59. 9 and 10 show an enlarged view of the periphery of the output gear 54 when the reset switch 59 is pressed. When the engagement between the output shaft 39 and the output gear 54 is released (see FIG. 8), when the operator presses the reset switch 54, the output gear 54 moves upward in the vertical direction. The convex part 39a contacts the upper slope part 56b of the engaging part 56 of the output gear 54, and the convex part 39a of the output shaft 39 moves along the upper slope part 56b (see FIG. 9). Then, the convex portion 39a of the output shaft 39 moves to below the lower slope portion 56c of the engaging portion 56 of the output gear 54 (see FIG. 10), and in this state, the operator releases the reset switch 59, The output gear 54 moves vertically downward by the urging mechanism 58, and the engaging portion 56 of the output gear 54 and the convex portion 39a of the output shaft 39 are engaged (see FIG. 7). As described above, when the output shaft 39 and the output gear 54 are disengaged, the operator operates the reset switch 59 to reset the position of the output gear 54 so that the output shaft 39 and the output gear 54 are engaged. 54 again engages.

  The notification mechanism includes a position detection sensor 62 that detects the position of the output gear 54, and a notification panel 64 that indicates whether or not power is transmitted by the power transmission mechanism 50 to the operator. As shown in FIG. 5 and FIG. 6, the position detection sensor 62 is fixed to the casing 32 on the side surface of the output shaft 39, and outputs a signal regarding whether or not the output gear 54 is in a position to engage with the output shaft 39. Output to the notification panel 64. The notification panel 64 notifies the operator of information according to whether or not power is transmitted by the power transmission mechanism 50, that is, whether or not the output shaft 39 and the output gear 54 are engaged. For example, a panel as shown in FIG. 11 is provided on the upper surface of the casing 32 so that the operator can visually check the lawn during the lawn mowing work. It can be turned on when the gear 54 is engaged, and can be turned off when the engagement between the output shaft 39 and the output gear 54 is released.

  Next, operation | movement of the lawn mower 20 of embodiment comprised in this way is demonstrated. When an operator connects a power cable (not shown) to an external power source and operates the operation switch 24, power is output from the drive source 38, and the output power is transmitted via the power transmission mechanism 50, so that two rotary blades 43 and 44 and the fan 34 rotate. As a result, turf and grass are sandwiched between the two rotary blades 43 and 44 and the fixed blades 41 and 42 and cut, and air flows backward from the air blowing port 33a at the front bottom of the casing 32 to collect the cut turf grass. Collected in grass bag 28. Then, when the operator pushes the handle 22 to move the lawn mower 20, the turfgrass at the site where the lawn mower 20 has moved is cut off. In the lawn mower 20 of the embodiment, the rotary blades 43 and 44 and the fixed blades 41 and 42 are provided as the mowing unit 40, so that the lawn can be cut even if the rotary blades 43 and 44 have a low rotational speed. By simply pressing the lawn mower 20 in accordance with the walking speed, the lawn can be cut efficiently. Moreover, since the two rotary blades 43 and 44 are arranged horizontally, the lawn mower 20 can obtain a wide cutting area without enlarging one rotary blade. Furthermore, since the two rotary blades 43 and 44 are provided so that the blade portions 43b and 44b overlap at the center, it is possible to obtain a beautiful finished surface with no uncut residue.

  When the mowing operation is performed by the lawn mower 20, hard foreign matters such as pebbles and branches are caught between the fixed blades 41 and 42 and the rotary blades 43 and 44, so that the drive source 38 and the rotary blades 43 and 44 When a large load is applied to the output shaft 44, the engagement of the output shaft 39 of the drive source 38 with the output gear 54 is released, and the output gear 54 is moved downward in the vertical direction by the urging force from the urging mechanism 58. The movement of the power from the drive source 38 to the rotary blades 43 and 44 and the fan 34 is stopped. Thereby, it is possible to prevent the rotary blades 43 and 44 and the fixed blades 41 and 42 from being damaged, and it is possible to prevent an excessive load from acting on the drive source 38. Further, when the transmission of power by the power transmission mechanism 50 is released in this way, the notification panel 64 notifies the operator to that effect. As a result, the operator can easily and immediately recognize that the transmission of power by the power transmission mechanism 50 has been released. For example, the power cable is disconnected from the external power source and the fixed blades 41 and 42 and the rotary blade For example, it is possible to take measures such as removing the foreign matter caught in 43 and 44.

  Furthermore, when mowing again, the operator presses the reset switch 59 to move the output gear 54 to the drive source 38 side (vertically upward) against the urging force of the urging mechanism 58. As shown in FIGS. 8 to 10 and FIG. 7, since the output shaft 39 of the drive source 38 and the output gear 54 are engaged again, the operator can easily reset the state of the power transmission mechanism 50, that is, Lawn mowing work can be performed in a state where power from the drive source 38 is transmitted to the two rotary blades 43 and 44 and the fan 34.

  In the lawn mower 20 of the embodiment described above, the output gear 54 that engages with the transmission gears 51 and 52 connected to the two rotary blades 43 and 44 has the convex portion 39 a provided on the output shaft 39 of the drive source 38. , And when a large load is applied to the transmission gears 51 and 52 of the rotary blades 43 and 44 and the output gear 54 of the output shaft 39, the engagement between the convex portion 39a of the output shaft 39 and the output gear 54 is released. Therefore, it is possible to prevent the rotary blades 43 and 44 from being damaged when a foreign object is caught in the lawn mower 20 and to prevent an excessive load from acting on the drive source 38. .

  In the lawn mower 20 described above, the convex portion 39a is formed on the output shaft 39, and the output gear 54 having the engaging portion 56 into which the output shaft 39 is inserted and engaged with the convex portion 39a is provided. The gear 54 is formed integrally with the output shaft 39, and a transmission gear 51 is formed so that a convex portion is formed on the rotary shaft 43a of the first rotary blade 43 and an engaging portion is engaged with the convex portion of the rotary shaft 43a. May be formed. In this case, when a large load acts on the first rotary blade 43 and the drive source 38, the engagement between the transmission gear 51 and the rotary shaft 43 a of the rotary blade 43 is released, and the drive source 38 and the two rotary blades 43. , 44 and the fan 38 are released, and the same effects as in the embodiment can be obtained.

  In the lawn mower 20 described above, the output gear 54 is attached to the output shaft 39 of the drive source 38 and the transmission gear 51 is attached to the rotary shaft 43a of the rotary blade 43. It is sufficient that gears corresponding to the transmission gear 51 and the output gear 54 are attached to the first shaft and the second shaft for transmitting the power, and the power of the output shaft 39 of the drive source 38 and the rotary shaft 43a of the rotary blade 43 is transmitted. When another shaft is interposed in the transmission, gears corresponding to the transmission gear 51 and the output gear 54 may be attached to the other shaft.

  In the lawn mower 20 described above, a convex portion 39 a that is convex in a columnar shape is formed on the side surface of the output shaft 39, and this convex portion 39 a engages with the lower slope portion 56 b of the engaging portion 56 of the output gear 54. However, only one of the convex portion 39a of the output shaft 39 and the engaging portion 56 needs to be in contact with and engaged with the other on the inclined surface. For example, the convex portion 39a of the output shaft 39 has a quadrangular prism shape. May be formed.

  In the lawn mower 20 described above, the engaging portion 56 of the output gear 54 is formed in a spiral shape in which the upper inclined surface portion 56b becomes higher toward the rotational direction of the output shaft 39 of the drive source 38 up to the top of the head 56a. The top 56 a is formed so as to become lower toward the rotation direction of the output shaft 39, but all of the upper inclined surface portion 56 b may be formed to increase toward the rotation direction of the output shaft 39. .

  In the lawn mower 20 described above, the engaging portion 56 of the output gear 54 is composed of two parts that are point-symmetric with respect to the rotation center. However, the engagement part 56 may be composed of one part or point-symmetric with respect to the rotation center. It may consist of three or more parts. In addition, the convex part 39a of the output shaft 39 should just be formed by the number of parts which comprise the engaging part 56 of the output gear 54. FIG.

  In the lawn mower 20 described above, the urging mechanism 58 that urges the output gear 54 vertically downward and the reset switch 59 that resets the state of the power transmission mechanism 50 are provided. The switch 59 may not be provided.

  The lawn mower 20 described above includes a notification mechanism that notifies the operator of the state of the power transmission mechanism 50 based on the position of the output gear 54 detected by the position detection sensor 62. However, the notification mechanism is a power transmission mechanism. Any information may be used as long as it notifies the state of 50, and information may be provided based on information other than the position of the output gear 54. For example, when the output gear 54 is in a position where it engages with the output shaft 39, a power line that mechanically supplies power to the notification panel 64 is connected, and when the output gear 54 is in a position where it does not engage with the output shaft 39. The connection of the power line that mechanically supplies power to the notification panel 64 may be released. In addition, the notification mechanism may indirectly detect the state of the power transmission mechanism 50 from, for example, information related to the load state of the drive source 38. For example, when the drive source 38 is driven, a load smaller than a predetermined load is detected. Is output, it can be determined that the output gear 54 and the output shaft 39 are disengaged. Further, such a notification mechanism may not be provided.

  In the lawn mower 20 described above, a motor is used as the drive source 38, but instead of or in addition to this, an internal combustion engine such as an engine that outputs power using hydrocarbons such as gasoline as fuel may be used.

  In the embodiment described above, the present invention has been described by applying it to the lawn mower 20 that includes two rotary blades and two fixed blades and is blown by a fan from the front bottom of the casing to the rear. The present invention can be applied to any type of lawn mower, and is not limited to the type of lawn mower described in the embodiment.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment at all, and it cannot be overemphasized that various changes can be made within the range which does not deviate from the summary of this invention. .

20 Lawn mower 22 Handle 23 Grasping part 24 Operation switch 26 Grass collecting bag 30 Body 31a, 31b Wheel 32 Casing 32a Lower casing 32b Case cover 33 Blower 34 Fan 36 Height adjustment mechanism 38 Drive source 40 Cutting parts 41, 42 Fixed blade 43, 44 Rotary blades 43a, 44a Rotating shaft 50 Power transmission mechanism 51, 52 Transmission gear 53 Fan gear 54 Output gear 55 Gear portion 56 Engagement portion 56a Top portion 56b Upper slope portion 56c Lower slope portion 62 Position detection sensor 64 Notification panel

Claims (9)

A drive source for outputting power;
A rotary blade that is rotationally driven by power from the drive source;
A first shaft that transmits power from the drive source to the rotary blade, a shaft engaging portion, a second shaft that transmits power from the drive source to the rotary blade, and the first shaft A first gear mounted; and a second gear provided with a gear engaging portion that engages with the first gear and engages with the shaft engaging portion. A power transmission mechanism that disengages the shaft engagement portion and the gear engagement portion when a load greater than a predetermined load is applied to the gear and the second gear;
A lawn mower characterized by comprising: In the power transmission mechanism, when a load greater than a predetermined load is applied to the first gear and the second gear, the second gear moves in the axial direction of the second shaft, and The engagement between the shaft engaging portion and the gear engaging portion is released.
The lawn mower according to claim 1. The second gear is hollow and the second shaft is inserted;
The lawn mower according to claim 2. The first shaft is one of an output shaft of the drive source and a rotation shaft of the rotary blade,
The second axis is the other axis of the output axis and the rotation axis.
The lawn mower according to claim 2 or 3, characterized in that. At least one of the shaft engaging portion and the gear engaging portion has a slope inclined with respect to the rotation direction of the second shaft, and the shaft engaging portion and the gear engaging portion on the slope Engaging the other of the
The lawnmower according to any one of claims 2 to 4, wherein the lawn mower is provided. The second gear is biased in the axial direction of the second shaft;
The lawn mower according to any one of claims 2 to 5, wherein The shaft engaging portion is formed in a convex shape that is substantially perpendicular to the second shaft,
The gear engaging portion extends in the axial direction of the second shaft from a gear portion in which a side surface of the second gear is formed in an uneven shape, and at least a part of the upper surface is a rotational direction of the second shaft. Formed in a spiral shape that becomes higher as it goes toward the end, and is formed with a hollow with an upper surface protruding upward at an end in the rotational direction, and engages with the shaft engaging portion on the upper surface of the hollow.
The lawn mower according to claim 6. The power transmission mechanism further includes a moving mechanism that moves the second gear in a direction opposite to a direction in which the second gear is urged in accordance with an operation by an operator.
The lawn mower according to claim 6 or 7, characterized by the above. Position detecting means for detecting the position of the second gear;
Informing means for informing the operator of the release of engagement between the shaft engaging portion and the gear engaging portion based on the detected position of the second gear;
The lawn mower according to any one of claims 2 to 8, further comprising:

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