Grass-cutting blade rotation direction switching mechanism, self-propelled grass cutter, and grass-cutting method

Abstract

To provide a rotation direction switching mechanism for a weeding blade which has a relatively simple structure but reduces noise during operation and is capable of reliably switching weeding blade rotation directions, a self-propelled grass mower, and a grass-mowing method.SOLUTION: In a self-propelled grass mower 1, a rotation direction switching mechanism 6 of weeding blade arranged between a prime mover 4 and a rotary weeding blade has: a first pulley which rotates by power from the prime mover and has a first receiving groove part and a second receiving groove part; an output shaft, a second pulley and a first gear which are provided for the same and integrally rotatable; a third pulley and a second gear which is coaxially provided for the same, is integrally rotatable with the same, and normally engages the first gear; a first belt wound around the first pulley and the second pulley; a second belt wound around the first pulley and the third pulley; and a tension imparting part of a switchable structure which imparts tension only to either the first belt or the second belt.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a grass cutting blade rotation direction switching mechanism, a self-propelled grass cutter, and a grass cutting method, and more particularly to a grass cutting blade rotation direction switching mechanism, a self-propelled grass cutter, and a grass cutting method, which have a relatively simple structure, reduce noise during operation, and can reliably switch the grass cutting blade rotation direction. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there have been mowers that cut grass by rotating a shaft, on the outer periphery of which a mowing blade is provided, in an up-cut direction or a down-cut direction relative to the direction of travel.

[0003] By the way, mowing with an up-cut blade produces a better finish than a down-cut blade, but there is a risk that the blade will throw pebbles in the direction of travel, and on the other hand, mowing with a down-cut blade has less of the aforementioned risks, but compared to an up-cut blade, grass that has not been cut before the blade reaches its lowest point may be pressed by the blade and fall to the ground, leaving it uncut. In other words, whether the blade rotates in the up-cut direction or the down-cut direction, each has its advantages and disadvantages.

[0004] In order to solve such problems, a grass cutting machine as described in Patent Document 1 has been proposed. The grass cutting machine described in Patent Document 1 includes a rotary drive grass cutter and a vehicle body on which the drive source and traveling device of the grass cutter are provided, and the grass cutter includes a cutter having a plurality of hammer knives on the outer periphery of a rotating shaft, and a power transmission device that can freely switch the rotation direction of the shaft to either a downcut direction or an upcut direction with respect to the traveling direction. According to this grass cutting machine, whether to downcut or upcut the grass can be freely changed depending on the working environment, and since the power transmission device is provided on the grass cutter side, it is said that switching operation and maintenance can be made easier than in the past, when the power transmission device is provided in a complicated part on the vehicle body side on which the drive source is mounted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-16332 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the power transmission device for the grass cutting machine described in Patent Document 1 includes a first power transmission device that can switch the rotation direction of the shaft to either a downcut direction or an upcut direction relative to the direction of travel, a second power transmission device that rotates the shaft only in the downcut direction relative to the direction of travel, and a third power transmission device that rotates the shaft only in the upcut direction relative to the direction of travel, and the patent only discloses a structure that is selectively used from among the first to third power transmission devices.

[0007] This structure is specifically disclosed in paragraphs 0028 to 0034 and Figures 7 to 12 of the specification, in which a first gear 361 having external teeth provided on shaft 33, the input shaft, directly meshes with a second gear 362 having external teeth provided on shaft 34, the output shaft, and the moved first gear 361 indirectly meshes with a fourth gear 364 having external teeth provided on shaft 34, and the first gear 361 and fourth gear 364 are connected via a third gear 363 having external teeth provided on shaft 37.

[0008] In other words, since it has a structure with three shafts and externally toothed gears on each shaft that mesh with each other, it produces a lot of noise when in operation, has a complex structure, and when changing the rotation direction, depending on the position of the gears, it may not be possible to perform a smooth switching operation, so it is difficult to say that the rotation direction of the grass cutting blade can be reliably changed.

[0009] The present invention has been devised in consideration of the above points, and has an object to provide a grass cutting blade rotation direction changing mechanism, a self-propelled grass cutter, and a grass cutting method that have a relatively simple structure, reduce noise during operation, and can reliably change the grass cutting blade rotation direction. [Means for solving the problem]

[0010] In order to achieve the above object, the mechanism for switching the rotation direction of a grass cutting blade of the present invention is equipped to a self-propelled grass cutter having a rotary grass cutting blade driven by a prime mover, and rotates when power is input from the prime mover. The mechanism comprises a first pulley having a first receiving groove portion that is continuous around the outer circumferential surface and a second receiving groove portion that is provided parallel to the first receiving groove portion, a second pulley having a third receiving groove portion that is continuous in shape and that is arranged so that the third receiving groove portion and the first receiving groove portion are positioned on approximately the same line, a third pulley having a fourth receiving groove portion that is continuous in shape and that is arranged so that the fourth receiving groove portion and the second receiving groove portion are positioned on approximately the same line, and a third pulley that is connected to the second pulley and is arranged so that it can rotate integrally with the second pulley. the second gear is disposed so as to be constantly in mesh with the first gear, is disposed coaxially with the third pulley and is disposed so as to be rotatable integrally with the third pulley; a first belt is wound around the first receiving groove portion and the third receiving groove portion and is structured to rotate freely on surfaces of the first receiving groove portion and the third receiving groove portion in an untensioned state; a second belt is wound around the second receiving groove portion and the fourth receiving groove portion and is structured to rotate freely on surfaces of the second receiving groove portion and the fourth receiving groove portion in an untensioned state; and a tension application portion which is structured to be able to apply tension to only one of the first belt or the second belt by switching.

[0011] Here, the grass cutting blade rotation direction switching mechanism of the present invention is equipped to a self-propelled grass cutter, and can be given the function of switching between an operation in which the output shaft rotates only in the upcut direction (hereinafter referred to as "upcut operation") and an operation in which the output shaft rotates only in the downcut direction (hereinafter referred to as "downcut operation") relative to the direction of travel of the self-propelled grass cutter.

[0012] With a self-propelled grass cutter of this structure, the operator can determine whether the direction of rotation of the grass cutting blade should be up-cut or down-cut depending on the working environment and the nature of the grass, and can freely select and switch between up-cut and down-cut operation based on that determination to perform grass cutting work in the most optimal operation. Note that an example of the "working environment" is information such as the terrain and season (whether the grass is young or dead), and an example of the "nature of the grass" is information such as the length of the grass, and the hardness and softness of the leaves and stems.

[0013] The function of each part of the grass cutting blade rotation direction switching mechanism of the present invention will be described. The above-mentioned first pulley receives power from the prime mover, and can transmit the power to the second pulley via the first belt, and can transmit the power to the third pulley via the second belt. Note that, for example, the first pulley may be connected to the output shaft of the prime mover, rotate following the rotation of the output shaft of the prime mover, and be provided so as to be able to input power from the prime mover, but is not limited thereto, and may be provided with a known power transmission structure such as a power belt or chain between the first pulley and the prime mover.

[0014] The second pulley rotates by applying tension to the first belt by switching the tension applying unit, and the connected output shaft can be rotated integrally. At this time, the rotation direction of the second pulley and the rotation direction of the output shaft are the same, and the output shaft rotates only in the up-cut direction, and the output shaft can operate the rotary grass cutting blade directly or indirectly connected to it in up-cut operation. Furthermore, at this time, no tension is applied to the second belt, and the second belt rotates freely relative to the first and third pulleys, so as not to impede the rotation of the output shaft in the up-cut direction.

[0015] The third pulley rotates by applying tension to the second belt by switching the tension applying unit, and the second gear rotates integrally with the third pulley in the same direction. The first gear, which is always engaged with the second gear, rotates in the opposite direction to the second gear, and the output shaft to which the first gear is connected rotates in the opposite direction to the rotation direction of the third pulley. At this time, the rotation direction of the third pulley and the rotation direction of the output shaft are opposite, so that the output shaft rotates only in the downcut direction, and the output shaft can operate the rotary grass cutting blade directly or indirectly connected to it in the downcut direction. Furthermore, at this time, no tension is applied to the first belt, and the first belt rotates idly relative to the first pulley and the second pulley, so as not to hinder the rotation of the output shaft in the downcut direction.

[0016] In the specification and claims of this application, the aforementioned "down cut" refers to a direction of rotation of the rotary grass cutting blade in which the rotation direction of the rotary grass cutting blade is the same as the rotation direction of the travel means such as wheels of the self-propelled grass cutting machine when moving forward. Also, the aforementioned "up cut" refers to a direction of rotation of the rotary grass cutting blade in which the rotation direction of the rotary grass cutting blade is opposite to the rotation direction of the travel means such as wheels of the self-propelled grass cutting machine when moving forward.

[0017] In the specification and claims of the present application, the above-mentioned "first belt" and "second belt" are preferably V-belts, but are not limited thereto and may be flat belts, for example. A V-belt or flat belt can protect the machine by slipping when the grass cutting blade is subjected to an impact or excessive stress. With regard to the above-mentioned "first belt" and "second belt," "spinning freely" on the surfaces of the first to fourth receiving grooves in an untensioned state includes not only a case where the belt spins completely freely, but also a case where the belt rotates slightly due to frictional force, and can be said to "slide on the surfaces of the receiving grooves."

[0018] In the specification and claims of this application, an example of a configuration in which "the output shaft and the rotary grass cutting blade are directly connected" is a structure in which the output shaft is directly connected to the rotating shaft of the grass cutting blade, and an example of a configuration in which "the output shaft and the rotary grass cutting blade are indirectly connected" is a configuration in which a power transmission structure such as a combination of multiple gears, a combination of sprockets and chains, or a combination of pulleys and belts is arranged between the output shaft and the grass cutting blade.

[0019] In this way, the grass cutting blade rotation direction switching mechanism of the present invention has a simple structure with fewer parts and does not require high levels of processing and assembly precision, compared to the grass cutting blade rotation direction switching mechanism for the grass cutting machine described in Patent Document 1. This makes it possible to simplify the manufacturing process, reduce manufacturing costs, and make the entire grass cutting blade rotation direction switching mechanism lighter.

[0020] Furthermore, the grass cutting blade rotation direction switching mechanism of the present invention has only the aforementioned first and second gears, and is not structured so that numerous externally toothed gears provided on each of the three shafts mesh together. Therefore, compared to the grass cutting blade rotation direction switching mechanism for the grass cutting machine described in Patent Document 1, noise levels during operation are reduced, and because the switching operation is performed by applying tension to the belt, the grass cutting blade rotation direction can be switched reliably and smoothly.

[0021] In addition, when the tension application unit has a first arm unit having a tension pulley at its tip that can contact the first belt, a second arm unit having a tension pulley at its tip that can contact the second belt, a base shaft unit that connects the bases of the first arm unit and the second arm unit so that they can rotate coaxially, and an operating unit that can operate only one of the selected first arm unit or second arm unit, the structural parts related to the tension application unit can be made compact.

[0022] Furthermore, if the first and second belts are V-belts and the first, second, third and fourth receiving grooves are V-shaped in cross section, the large contact area and wedge action resulting from the shape of the V-belt will generate stronger friction than a flat belt of the same width, resulting in less slippage and greater transmission capacity. Furthermore, if the blade is subjected to an impact or excessive stress, the V-belt will slip, protecting the motor and other mechanical parts.

[0023] In order to achieve the above object, the self-propelled grass cutter of the present invention comprises a main body having a travelling means, a prime mover mounted on the main body, a rotary grass cutting blade arranged in a position where work can be performed in the direction of travel of the main body and driven by power from the prime mover, a first pulley arranged between the grass cutting blade and the prime mover, rotated by input of power from the prime mover, and including a first receiving groove portion that is continuous around the outer circumferential surface and a second receiving groove portion that is provided parallel to the first receiving groove portion, a second pulley including a third receiving groove portion that is continuous in shape and that runs around the outer circumferential surface and that is arranged so that the third receiving groove portion and the first receiving groove portion are positioned on approximately the same line, a third pulley including a fourth receiving groove portion that is continuous in shape and that runs around the outer circumferential surface and that is arranged so that the fourth receiving groove portion and the second receiving groove portion are positioned on approximately the same line, and a third pulley connected to the second pulley. the second pulley is rotated integrally with the output shaft; a first gear attached to the output shaft and rotatable integrally with the output shaft; a second gear arranged so as to be constantly in mesh with the first gear, arranged coaxially with the third pulley and rotatable integrally with the third pulley; a first belt wound around the first receiving groove portion and the third receiving groove portion and structured to rotate freely on the surfaces of the first receiving groove portion and the third receiving groove portion when no tension is applied; a second belt wound around the second receiving groove portion and the fourth receiving groove portion and structured to rotate freely on the surfaces of the second receiving groove portion and the fourth receiving groove portion when no tension is applied; and a grass cutting blade rotation direction switching mechanism having a tension application portion structured to apply tension to only one of the first belt or the second belt by switching.

[0024] Here, the self-propelled grass cutter of the present invention is equipped with the above-mentioned main body, prime mover, rotary grass cutter blade, and grass cutter blade rotation direction switching mechanism, and is therefore capable of self-propelling to perform grass cutting work and switching between up-cut operation and down-cut operation. In other words, the operator can determine whether the grass cutter blade should rotate in the down-cut or up-cut direction depending on the work environment and the nature of the grass, and can freely select and switch between up-cut operation and down-cut operation based on that determination to perform grass cutting work in the optimal operating mode.

[0025] The operation of each part of the self-propelled grass cutter will now be described. The main body serves as a base on which the travel means, the prime mover, the rotary grass cutting blade, and the grass cutting blade rotation direction switching mechanism are attached or mounted. The main body can be self-propelled by having the travel means. The prime mover can supply power to the travel means and the rotary grass cutting blade. The grass cutting blade can be rotated by power from the prime mover via the grass cutting blade rotation direction switching mechanism.

[0026] The operation of each part of the above-mentioned grass cutting blade rotation direction switching mechanism will be described below. The first pulley described above receives power from a prime mover, and can transmit the power to the second pulley via the first belt, and can transmit the power to the third pulley via the second belt.

[0027] The second pulley rotates by applying tension to the first belt by switching the tension applying unit, and the connected output shaft can be rotated integrally. At this time, the rotation direction of the second pulley and the rotation direction of the output shaft are the same, and the output shaft rotates only in the up-cut direction, and the output shaft can operate the rotary grass cutting blade directly or indirectly connected to it in up-cut operation. Furthermore, at this time, no tension is applied to the second belt, and the second belt rotates freely relative to the first and third pulleys, so as not to impede the rotation of the output shaft in the up-cut direction.

[0028] The third pulley rotates by applying tension to the second belt by switching the tension applying unit, and the second gear rotates integrally with the third pulley in the same direction. The first gear, which is always engaged with the second gear, rotates in the opposite direction to the second gear, and the output shaft to which the first gear is connected rotates in the opposite direction to the rotation direction of the third pulley. At this time, the rotation direction of the third pulley and the rotation direction of the output shaft are opposite, so that the output shaft rotates only in the downcut direction, and the output shaft can operate the rotary grass cutting blade directly or indirectly connected to it in the downcut direction. Furthermore, at this time, no tension is applied to the first belt, and the first belt rotates idly relative to the first pulley and the second pulley, so as not to hinder the rotation of the output shaft in the downcut direction.

[0029] In the specification and claims of this application, the aforementioned "main body" is not particularly limited in shape or structure as long as it can be equipped with at least a traveling means, a prime mover, a rotary grass cutting blade, and a grass cutting blade rotation direction switching mechanism. Also, in the specification and claims of this application, the aforementioned "prime mover" is preferably an engine or a motor, but is not limited thereto and may be other known power means.

[0030] Thus, the above-mentioned grass cutting blade rotation direction switching mechanism has a simple structure with fewer parts and does not require high processing and assembly precision compared to the grass cutting blade rotation direction switching mechanism according to the invention described in Patent Document 1, and the self-propelled grass cutter of the present invention employing this mechanism can simplify the manufacturing process, reduce manufacturing costs, and reduce the weight of the entire grass cutting blade rotation direction switching mechanism. Furthermore, the above-mentioned grass cutting blade rotation direction switching mechanism only has the first gear and the second gear, and does not have a structure in which multiple external gears provided for each of the three shafts mesh with each other, so the self-propelled grass cutter of the present invention employing this mechanism produces less noise during operation compared to the grass cutting machine described in Patent Document 1, and is structured to perform switching operation by applying tension to the belt, so that the grass cutting blade rotation direction can be reliably and smoothly switched.

[0031] In order to achieve the above object, the grass cutting method of the present invention includes a main body having a travel means, a prime mover mounted on the main body, a rotary grass cutting blade disposed in a position where it is operable in the direction of travel of the main body and driven by power from the prime mover, a first pulley disposed between the grass cutting blade and the prime mover, rotated by input of power from the prime mover, and including a first receiving groove portion which is continuous around the outer circumferential surface and a second receiving groove portion which is provided in parallel to the first receiving groove portion, a third receiving groove portion which is continuous in shape and which is continuous around the outer circumferential surface, a second pulley including a fourth receiving groove portion having a continuous shape going around an outer circumferential surface thereof and disposed so that the fourth receiving groove portion and the second receiving groove portion are positioned on substantially the same line; an output shaft connected to the second pulley and arranged so as to be rotatable integrally with the second pulley; a first gear attached to the output shaft and arranged so as to be rotatable integrally with the output shaft; a second gear disposed on the shaft and rotatable integrally with the third pulley; a first belt wound around the first receiving groove and the third receiving groove and configured to idle on the surfaces of the first receiving groove and the third receiving groove when tension is not applied; a second belt wound around the second receiving groove and the fourth receiving groove and configured to idle on the surfaces of the second receiving groove and the fourth receiving groove when tension is not applied; and a tension adjusting device capable of applying tension to only one of the first belt and the second belt by switching. The system uses a self-propelled grass cutter having a structure including a blade rotation direction switching mechanism having a tension application unit having a tension application structure, and appropriately switches between a first operating step in which tension is applied only to the first belt by the tension application unit, causing the rotary grass cutter blade to rotate only in the upcut direction relative to the traveling direction of the self-propelled grass cutter, and a second operating step in which tension is applied only to the second belt by the tension application unit, causing the rotary grass cutter blade to rotate only in the downcut direction relative to the traveling direction of the self-propelled grass cutter.

[0032] According to the grass-cutting method of the present invention, by using the self-propelled grass cutter described above, grass cutting work can be performed by switching between a first operating step in which the rotary grass cutter blade rotates only in an up-cut direction relative to the traveling direction of the self-propelled grass cutter, and a second operating step in which the rotary grass cutter blade can rotate only in a down-cut direction relative to the traveling direction of the self-propelled grass cutter, and when switching between operating steps, the rotation direction of the grass cutter blade can be switched with greater reliability than with conventional self-propelled grass cutters.

[0033] In addition, according to the grass cutting method of the present invention, by using the self-propelled grass cutter described above, noise during operation is reduced compared to the grass cutting machine described in Patent Document 1, and since the structure performs switching operations by applying tension to the belt, the rotation direction of the grass cutting blade can be switched reliably and smoothly. Effect of the Invention

[0034] According to the grass cutting blade rotation direction switching mechanism, the self-propelled grass cutter, and the grass cutting method of the present invention, noise during operation is reduced and the grass cutting blade rotation direction can be reliably switched while being of a relatively simple structure. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is an oblique view of the self-propelled grass mower of the present invention seen from above, where (a) is an oblique view showing the left side and rear of the self-propelled grass mower when viewed from the rear of the body toward the front, and (b) is an oblique view showing the right side and rear of the self-propelled grass mower when viewed from the same direction. [Diagram 2] 2 is a perspective view showing the right side and front of the self-propelled grass mower shown in FIG. 1 as viewed from the rear of the machine body toward the front. [Diagram 3] 2 is an enlarged view showing the right side of the front part of the body of the self-propelled grass cutter shown in FIG. 1. [Figure 4] FIG. 2 is a plan view of the grass cutting blade and its rotation direction switching mechanism. [Diagram 5]Regarding the first operation of the grass cutting blade and rotation direction switching mechanism shown in Figure 4, (a) is an oblique view showing the left side side toward the front when viewed from the rear of the machine body, and (b) is an oblique view showing the right side side toward the front when viewed from the rear of the machine body. [Figure 6] Regarding the second operation of the grass cutting blade and rotation direction switching mechanism shown in Figure 4, (a) is an oblique view showing the left side side toward the front when viewed from the rear of the machine body, and (b) is an oblique view showing the right side side toward the front when viewed from the rear of the machine body. [Figure 7] 2 is an enlarged view showing a handle portion of the self-propelled grass cutter shown in FIG. 1. [Figure 8] 5A and 5B illustrate the arrangement of each component during the first and second operations, where FIG. 5A is a schematic diagram of the first operation shown in FIG. 5, and FIG. 6B is a schematic diagram of the second operation shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The embodiment of the present invention will be described in more detail with reference to Figures 1 to 8. The reference symbols in each drawing are given within the scope of reducing complexity and facilitating understanding, and the same reference symbols may be given to only some of the equivalent parts. The reference symbols associated with the arrows shown in Figures 1 to 7 indicate directions for explanation, with the reference symbol F meaning "forward", B meaning "rearward", R meaning "rightward", L meaning "leftward", U meaning "upward", and D meaning "downward".

[0037] [Self-propelled grass cutter 1] The self-propelled grass cutter 1 will be described with reference to Figures 1 to 8. The self-propelled grass cutter 1 comprises a main body 2, a travel means 3, a prime mover 4, a rotary grass cutter blade 5 (hereinafter referred to as the "grass cutter blade 5"), a grass cutter blade rotation direction switching mechanism 6 (hereinafter referred to as the "rotation direction switching mechanism 6"), a grass cutter blade cover 55, and a grass cutter blade side power transmission unit 7 (see Figures 1 to 3). Each part will be described in detail below.

[0038] (Main body 2) The main body 2 has a frame 20 , an operating handle 21 , and a step 22 . The frame 20 is formed from a rigid material (metal material in this embodiment) and is disposed from the center to the rear of the aircraft.

[0039] The operating handle 21 is a two-handed operating rod that is approximately V-shaped in plan view, with the tip, which serves as the grip of the work vehicle, extending rearward of the machine body and the base end attached to the frame 20 and supported so as to be able to be raised and lowered in the vertical direction of the machine body. The operating handle 21 of this embodiment is provided with a first side clutch lever that turns the machine to the right when gripped, a second side clutch lever that turns the machine to the left when gripped, a traveling clutch lever that makes the machine travel when lifted, a throttle lever that adjusts the RPM of the prime mover 4, a grass cutting blade clutch lever that rotates the grass cutting blade 5 when lifted, a handle position left-right adjustment lever that can change the handle position left-right when gripped, and a handle position up-down adjustment lever that can change the handle position up-down when gripped (see Figs. 1 to 3 and 7).

[0040] The operating handle 21 is provided with a plate 210 that spans between the left and right operating rods, and a rotation direction switching lever 211 is provided on the plate 210. The rotation direction switching lever 211 can be moved along a roughly U-shaped lever guide groove 212 formed in the plate 210, and can operate a tension adding section, which will be described later, via a cable (not shown) connected to the base end of the rotation direction switching lever 211. The lever guide groove 212 can be switched to upcut operation when placed in the right groove in Fig. 7, and to downcut operation when placed in the left groove.

[0041] The step 22 is a plate disposed at the rear of the frame 20, and has a structure capable of withstanding a load sufficient to allow a worker to stand on it (see FIGS. 1 and 2).

[0042] (Traveling means section 3) The traveling means section 3 has a pair of left and right rear traveling structures 31 arranged below the main body section 2, and a pair of left and right front traveling structures 32 arranged in front of the main body section 2 (see FIGS. 1 and 2).

[0043] The rear running structure 31 is a track-type running structure, and is arranged on the left and right sides of the body with the frame 201 in between. The rear running structure 31 has a pair of front and rear rollers 311 arranged on the ground side, sprockets 312 arranged above each roller, and tracks 313 wrapped around the sprockets 312 and the front and rear rollers 311. The sprockets 312 are driven by power supplied from the prime mover 4. The rear running structures 31 on the left and right sides of the body are each substantially the same structure (see Figures 1 and 2).

[0044] The front running structure 32 has a support frame 321 and running wheels 322. The support frame 321 has a base portion attached to the front of the frame 20, and has a pair of left and right arm portions whose tips extend forward of the machine body, and the arm portions are supported so that they can be raised and lowered in the vertical direction of the machine body. The running wheels 322 are attached to the arms of the support frame 321 near their tips, and a pair of wheels are provided on the left and right (see Figures 1 to 3).

[0045] (Prime mover 4) The prime mover 4 is disposed behind the frame 20 and is an engine in this embodiment. The prime mover 4 supplies power to the rear traveling structure 31 via a power transmission structure (not shown), and also supplies power to the grass cutting blade 5 via a rotation direction switching mechanism 6 (see FIGS. 1 to 3).

[0046] (Mowing blade 5) The grass cutting blade 5 has an attachment base 51, a cutting blade 52, and a grass cutting blade rotation shaft 53 (see FIGS. 3 to 6). The mounting base 51 is cylindrical and has a base end to which a grass-cutting blade rotating shaft 53 is connected so as to be rotatable. A plurality of mounting portions 54 for the cutting blades 52 are provided on the circumferential surface of the mounting base 51, and the cutting blades are attached to the mounting portions 54 (see Figures 3 to 6. Note that the cutting blades 52 are omitted in Figure 4).

[0047] Cutting blade 52 is generally Y-shaped, with each branched tip piece being a blade portion formed on both sides, and a base piece being a portion attached to mounting part 54. Cutting blade 52 has its shaft portion attached to mounting base 51 via mounting part 54 in such a manner that the blade portion is generally parallel to the rotation axis of mounting base 51 (see Figs. 3, 5 to 6).

[0048] The cutting blades 52 are provided at a predetermined angle apart such that their axes coincide with the radius of a circle in an end view of the mounting base 51, and in this embodiment, a total of three are provided, one for every 120 degrees (see Figs. 3, 5 and 6). Furthermore, the mounting base 51 is attached such that, with the cutting blades 52 attached, the lower end of the rotation trajectory of the tip of the cutting blade 52 and the lower edge of the grass cutting blade cover 55 (in other words, the edge of the opening portion provided below) approximately coincide with each other (see Fig. 3).

[0049] (Grass cutting blade cover 55) The grass-cutting blade cover 55 is provided in a shape that covers the top, front, rear, and sides of the grass-cutting blade 5, has a structure that opens downward, and is disposed in front of the main body 2.

[0050] (Rotation direction switching mechanism 6) The rotation direction switching mechanism 6 is positioned at the front of the frame 20, between the prime mover 4 and the grass cutting blade 5 (see Figure 1(b) and Figures 2-3), and has a first pulley 61, a second pulley 62, a third pulley 63, an output shaft 64, a first gear 65, a second gear 66, a first belt 67, a second belt 68, and a tension application section 69 (see Figures 4-6 and 8).

[0051] <First pulley 61> The first pulley 61 has a first receiving groove portion 611 and a second receiving groove portion 612, and is connected to the output shaft (not shown) of the prime mover 4 so as to be rotatable when power from the prime mover 4 is input (in other words, the structure is such that the power from the prime mover 4 is transmitted to the first pulley 61 via the output shaft). The first receiving groove 611 is a continuous groove that runs around the outer circumferential surface of the first pulley 61 and has a V-shape in cross section (see Figs. 4 and 8), and is provided on the prime mover 4 side of the first pulley 61. The second receiving groove 612 is a continuous groove that runs around the outer circumferential surface of the first pulley 61 and has a V-shape in cross section (see Figs. 4 and 8), and is provided in parallel to the first receiving groove 611 at a predetermined distance, at a position on the first pulley 61 opposite the prime mover 4.

[0052] <Second pulley 62> The second pulley 62 has a third receiving groove 621 which is a continuous groove that is V-shaped in cross section and goes around the outer circumferential surface (see Figs. 4 and 8). The second pulley 62 is connected to the output shaft 64 in an arrangement in which the third receiving groove 621 and the first receiving groove 11 are positioned on approximately the same line. The second pulley 62 is connected to the output shaft 64 so as to be rotatable integrally therewith. In this embodiment, the second pulley 62 is connected to the end of the output shaft 64 on the motor 4 side.

[0053] <Third pulley 63> The third pulley 63 has a fourth receiving groove 631 which is a continuous groove that is V-shaped in cross section and goes around the outer circumferential surface (see Figs. 4 and 8). The third pulley 63 is disposed so that the fourth receiving groove 631 and the second receiving groove 612 are positioned on substantially the same line. In this embodiment, the third pulley 63 is connected to a short rotating shaft 632 disposed in parallel with the output shaft 64. The third pulley 63 is connected to an end of the rotating shaft 632 on the motor 4 side in such a manner that the third pulley 63 can rotate integrally with the rotating shaft 632.

[0054] <Output shaft 64> The output shaft 64 is a rod of a predetermined length, and the second pulley 62 is connected to the end of the output shaft 64 on the prime mover 4 side, and the fifth pulley 71 (described later) is connected to the other end of the output shaft 64. A first gear 65 is attached to the axial middle of the output shaft 64 (see FIGS. 4 and 8).

[0055] <First Gear 65> The first gear 65 is a gear having external teeth on its outer periphery, and is provided so as to be rotatable integrally with the output shaft 64 (see FIGS. 4 to 6 and 8).

[0056] <Second Gear 66> The second gear 66 is a gear having external teeth on its outer circumference, and is disposed so as to constantly mesh with the first gear 65, and is attached to the end of the connecting shaft 632 on the side opposite to the third pulley 63 (in other words, the second gear 66 is disposed coaxially with the third pulley 63). The second gear 66 is configured to be rotatable integrally with the third pulley 63 via the connecting shaft 632 (see FIGS. 4 to 6 and 8).

[0057] <First Belt 67> The first belt 67 is wound around the first receiving groove portion 611 and the third receiving groove portion 621 (see Figures 4 to 6 and 8) and is structured to rotate freely on the surfaces of the first receiving groove portion 611 and the third receiving groove portion 621 when no tension is applied. In this embodiment, the first belt 67 is a V-belt.

[0058] <Second Belt 68> The second belt 68 is wound around the second receiving groove portion 612 and the fourth receiving groove portion 631 (see Figures 4 to 6 and 8) and is structured to rotate freely on the surfaces of the second receiving groove portion 612 and the fourth receiving groove portion 631 when no tension is applied. In this embodiment, the second belt 68 is a V-belt.

[0059] <Tension adding part 69> The tension applying unit 69 is structured so as to be switchable to apply tension to only one of the first belt 67 and the second belt 68. In this embodiment, the tension applying unit 69 has a first arm portion 691, a second arm portion 692, a base portion 693, and an operating portion 694, and is disposed below the first belt 67 and the second belt 68 (FIGS. 5 to 6 and 8).

[0060] The first arm portion 691 has a predetermined length, has a tension pulley at its tip that can contact the first belt 67, and has its base connected to the base shaft portion 693. The second arm portion 692 has a predetermined length, has a tension pulley at its tip that can contact the second belt 68, and has its base connected to the base shaft portion 693.

[0061] The base shaft portion 693 has a structure that rotatably connects the base portions of the first arm portion 691 and the second arm portion 692 on the same axis. The operation portion 694 is connected via a wire (not shown) to a rotation direction switching lever 211 provided near the operation handle 21, and is provided so as to be able to operate only one of the selected first arm portion 691 or second arm portion 692 by operating the rotation direction switching lever 211.

[0062] <Grass cutting blade side power transmission part 7> The blade-side power transmission section 7 has a fifth pulley 71, a sixth pulley 72, a third belt 73, and a tension applying section 74 (FIGS. 4 to 6).

[0063] The fifth pulley 71 is connected to the other end side of the output shaft 64. The fifth pulley 71 has a fifth receiving groove portion (reference numeral omitted) which is a continuous groove that is V-shaped in cross section and runs around the outer circumferential surface.

[0064] The sixth pulley 72 has a sixth receiving groove (reference number omitted) which is a continuous groove that is V-shaped in cross section and goes around the outer circumferential surface. The sixth pulley 72 is disposed so that the sixth receiving groove and the fifth receiving groove are positioned on substantially the same line, and is connected to an end of the grass cutting blade rotating shaft 53 in such a manner that the sixth pulley 72 can rotate integrally with the grass cutting blade rotating shaft 53.

[0065] The third belt 73 is wound around the fifth receiving groove portion and the sixth receiving groove portion, and in this embodiment, the third belt 73 is a V-belt.

[0066] The tension applying portion 74 is configured to be able to apply tension to the third belt 73 by switching. In this embodiment, the tension applying portion 74 has a first arm portion 741, a second arm portion 743, and a base shaft portion 745.

[0067] First arm portion 741 has a predetermined length, has a tension pulley 742 provided at its tip, and has its base connected to base shaft portion 745. Tension pulley 742 is structured to be able to come into contact with the upper surface of the upper portion of third belt 73 in the wound state, and first arm portion 741 is structured to apply tension by coming into contact with the upper surface of the upper portion of third belt 73 and pushing it down.

[0068] Second arm portion 743 has a predetermined length, a tension pulley 744 is provided at its tip, and its base is connected to base shaft portion 745. Tension pulley 744 is structured to be able to come into contact with the lower surface of the lower part of third belt 73 in the wound state, and second arm portion 743 is structured to apply tension by coming into contact with the lower surface of the lower part of third belt 73 and pushing it up.

[0069] The base shaft portion 745 connects the base portions of the first arm portion 741 and the second arm portion 743 so that they can rotate coaxially, and is configured to enable the first arm portion 741 and the second arm portion 743 to simultaneously clamp the third belt 73 from above and below.

[0070] [Method of mowing] The mowing method according to this embodiment uses the above-described self-propelled mower 1, and is performed by an operator appropriately switching between the first operation and the second operation depending on the working situation, etc.

[0071] <First Operation> The operator operates the operating unit 694 using the rotation direction switching lever 211 to apply tension only to the first belt 67 with the first arm portion 691 of the tension applying unit 69 (see FIG. 4), and rotates the grass cutting blade rotating shaft 53 of the grass cutting blade 5 only in the up-cut direction relative to the traveling direction of the self-propelled grass cutter 1 (FIG. 8(a)). This allows grass to be cut in the up-cut direction by rotating the cutting blade 52 attached to the mounting base 51.

[0072] <Second Operation> The operator operates the operation unit 694 using the switching unit operation lever, and applies tension only to the second belt 68 with the second arm portion 692 of the tension application unit 69 (see FIG. 5), causing the grass cutting blade rotating shaft 53 of the grass cutting blade 5 to rotate only in the downcut direction relative to the traveling direction of the self-propelled grass cutter 1 (FIG. 8(b)). This allows grass to be cut in the downcut direction by rotating the cutting blade 52 attached to the mounting base 51.

[0073] According to the above-mentioned grass cutting method, grass cutting work can be performed by selectively switching between a first operating phase (Figure 8(a)) in which the grass cutting blade 5 rotates only in an upcut direction relative to the traveling direction of the self-propelled grass cutter 1, and a second operating phase (Figure 8(b)) in which the grass cutting blade 5 can rotate only in a downcut direction relative to the traveling direction of the self-propelled grass cutter 1, and in addition, when switching between operating phases, the rotation direction of the grass cutting blade can be switched with greater reliability than the grass cutting machine described in Patent Document 1.

[0074] In addition, according to the grass cutting method of the present invention, by using the self-propelled grass cutter 1, noise during operation is reduced compared to the grass cutting machine described in Patent Document 1, and since the structure performs switching operations by applying tension to the belt, the rotation direction of the grass cutting blade can be switched reliably and smoothly.

[0075] (effect) The operation of each part of the self-propelled grass cutter 1 when carrying out the above-mentioned grass cutting method will now be described in further detail.

[0076] By including the main body 2 and the like described above, the self-propelled grass cutter 1 can self-propel and perform grass cutting work, and can switch between a first operation in which the grass cutting blade 5 rotates only in the up-cut rotation direction UC relative to the traveling direction of the self-propelled grass cutter 1, and a second operation in which the grass cutting blade 5 rotates only in the down-cut rotation direction DC (see FIG. 3). In other words, the operator can determine whether the rotation direction of the grass cutting blade 5 should be up-cut or down-cut depending on the work environment and the nature of the grass, and can freely select and switch between the first operation and the second operation based on that determination to perform grass cutting work in the optimal operation.

[0077] The main body 2 has a frame 20, which serves as a mounting base for each section. Also, the step 22 allows the operator to get on while standing. Furthermore, the main body 2 has the above-mentioned operating handle 21, which allows the operator to control the traveling direction of the self-propelled grass cutter 1 and to operate each section of the machine. In addition, the operating handle 21 is provided with a rotation direction switching lever 211, which allows the operator to switch between the first operation and the second operation at his or her fingertips.

[0078] More specifically, when the rotation direction switching lever 211 is inserted into the right groove in Fig. 7 along the lever guide groove 212, the first arm portion 691 of the tension applying portion 69 moves upward via the operating portion 694, and tension is applied only to the first belt 67 (see Figs. 4 and 8(a)). As a result, the output shaft 64 rotates only in the up-cut direction relative to the traveling direction of the self-propelled grass cutter 1, and the grass cutter blade rotating shaft 53 rotates only in the up-cut direction relative to the traveling direction of the self-propelled grass cutter 1 via the grass cutter blade side power transmission portion 7 to which the output shaft 64 is connected (Fig. 8(a)). In other words, grass cutting work can be performed in the first operation (up-cut operation) by rotating the grass cutter blade 5 (more specifically, the cutting blade 52 attached to the mounting base 51).

[0079] When the rotation direction switching lever 211 is inserted into the left groove in Fig. 7 along the lever guide groove 212, the second arm portion 692 of the tension applying portion 69 moves upward via the operating portion 694, and tension is applied only to the second belt 68 (see Figs. 5 and 8(b)). As a result, the output shaft 64 rotates only in the downcut direction relative to the traveling direction of the self-propelled grass cutter 1, and the grass cutter blade rotating shaft 53 rotates only in the downcut direction relative to the traveling direction of the self-propelled grass cutter 1 via the grass cutter blade side power transmission portion 7 to which the output shaft 64 is connected (Fig. 8(b)). In other words, grass cutting work can be performed in the second operation (downcut operation) by rotating the grass cutter blade 5 (more specifically, the cutting blade 52 attached to the mounting base 51).

[0080] When moving the machine body or performing grass cutting work, the traveling means unit 3 has good travelability on rough roads and uneven ground because the rear traveling structure unit 31 has a track-type traveling structure, and also has good stability when working on slopes. When changing direction, the rear traveling structure unit 31 can be quickly turned on the spot by locking one of the axles, so it has good maneuverability and operability. The prime mover 4 supplies power to the rear traveling structure unit 31 and the grass cutting blade 5 (via the rotation direction switching mechanism 6) through the power transmission structure.

[0081] The grass cutting blade 5 has the above-mentioned structure, and is able to cut grass in the direction of travel of the machine with a width approximately the same as that of the machine body. Also, the grass cutting blade cover 55 has the above-mentioned structure, and prevents grass immediately after being cut by the grass cutting blade 5 and dirt and stones kicked up by the grass cutting blade 5 from flying up, and guides them toward the bottom of the machine body. This increases the safety of workers and those around the machine body and suppresses contamination.

[0082] The function of each part of the rotation direction switching mechanism 6 will be described. The first pulley 61 is connected to the output shaft of the prime mover 4 and rotates following the rotation of the output shaft of the prime mover 4, and receives the power from the prime mover 4. The power input from the prime mover 4 is then transmitted to the second pulley 62 via the first belt 67, and to the third pulley 63 via the second belt 68.

[0083] The second pulley 62 rotates by applying tension to the first belt 67 through the first arm 691 by switching the tension applying unit 69, and rotates the output shaft 64 integrally. At this time, the rotation direction of the second pulley 62 and the rotation direction of the output shaft 64 are the same, and the second pulley 62 rotates only in the up-cut UC direction, and the output shaft 64 operates the grass cutting blade 5 connected via the grass cutting blade side power transmission unit 7 in up-cut operation. At this time, no tension is applied to the second belt 68, and the second belt 68 rotates idly relative to the first pulley 61 and the third pulley 63 so as to slip, so that the third pulley 63 and the second belt 68 do not hinder the rotation of the output shaft 64 in the up-cut direction (see Figures 3, 5, and 8(a)).

[0084] The third pulley 63 rotates when the second arm 692 applies tension to the second belt 68 by switching the tension applying unit 69, and the second gear 66 rotates integrally with the third pulley 63 in the same direction. The first gear 65, which is constantly meshed with the second gear 66, rotates in the opposite direction to the second gear 66, and the output shaft 64 to which the first gear 65 is connected rotates in the opposite direction to the rotation direction of the third pulley 63. At this time, the rotation direction of the third pulley 63 and the rotation direction of the output shaft 64 are opposite, so the output shaft 64 rotates only in the downcut direction DC, and the output shaft 64 operates the grass cutting blade 5, which is connected via the grass cutting blade side power transmission unit 7, in downcut operation. At this time, no tension is applied to the first belt 67, and the first belt 67 rotates freely relative to the first pulley 61 and the second pulley 62, so that the first pulley 61 and the first belt 67 do not hinder the rotation of the output shaft 64 in the down-cut direction (see Figures 3, 6, and 8(b)).

[0085] In this way, the rotation direction switching mechanism 6 has a simple structure with fewer parts and does not require high levels of machining and assembly precision compared to the rotation direction switching mechanism for the grass cutting blade in the grass cutting machine described in Patent Document 1, which makes it possible to simplify the manufacturing process, reduce manufacturing costs, and make the entire rotation direction switching mechanism lighter.

[0086] Furthermore, the rotation direction switching mechanism 6 only has the aforementioned first gear 65 and second gear 66, and is not structured so that a large number of externally toothed gears provided on each of the three shafts mesh together. As a result, noise levels during operation are reduced compared to the grass cutting blade rotation direction switching mechanism for the grass cutting machine described in Patent Document 1, and the structure performs the switching operation by applying tension to the first belt 67 or the second belt 68, making it possible to reliably and smoothly switch the grass cutting blade rotation direction.

[0087] In addition, in this embodiment, the tension application part 69 has a structure consisting of a first arm part 691, a second arm part 692, a base shaft part 693, and an operating part 694, so that the structural parts related to the tension application part 69 are compactly arranged.

[0088] Furthermore, in this embodiment, the first belt 67 and the second belt 68 are V-belts, and the first receiving groove 611, the second receiving groove 621, the third receiving groove 612, and the fourth receiving groove 631 are V-shaped in cross section, so that the large contact area and wedge action resulting from the shape of the V-belt generate stronger frictional forces compared to flat belts of the same width, resulting in less slippage and greater transmission capacity. Furthermore, because it is a V-belt, it can protect mechanical parts such as the prime mover 4 by slipping when the grass cutting blade 5 is subjected to an impact or excessive stress.

[0089] In this embodiment, the grass cutting blade 5 has the above-mentioned structure, but is not limited thereto, and may be, for example, a structure that protrudes a certain width in both directions, or in either direction, relative to the traveling direction of the machine body, and various modified forms of the shape and mounting form of the cutting blade are not excluded. Also, the grass cutting blade 5 is not excluded from being disposed at the rear of the machine body. Furthermore, in this embodiment, the cutting blade is substantially Y-shaped, but is not limited thereto, and may be, for example, L-shaped, T-shaped, or various other forms.

[0090] In this embodiment, the operating handle 21 has the above-mentioned structure, but is not limited thereto, and may be, for example, a T-shaped handle or a steering wheel type. Also, the operating means provided on the operating handle 21 may be partially or entirely disposed in a location other than the operating handle.

[0091] In this embodiment, the running means unit 3 is a combination of a driving rear running structure unit 31 (track-type running structure) and a driven front running structure unit 32 (wheels), but is not limited to this. For example, the rear running structure unit may be an independent running wheel, or may be an all-wheel drive type, and various modified forms are not excluded.

[0092] In this embodiment, a grass cutting blade cover 55 is provided for the grass cutting blade 5, but this is not limited to this, and a grass cutting blade cover 55 may not be provided, and the shape of the grass cutting blade cover 55 does not exclude various modified forms.

[0093] In order to evaluate the self-propelled grass cutter 1 equipped with the rotation direction switching mechanism 6 described in this embodiment, a measurement test was carried out under the following conditions.

[0094] (Test Method) In this test, the comparison objects described below were tested under the conditions described below, and the sound pressure was measured when the grass cutting blade clutch lever, which rotates the grass cutting blade, was in the OFF state, and when the grass cutting blade clutch lever was in the ON state.Furthermore, the sound pressure when the grass cutting blade clutch lever was in the ON state was measured in upcut operation (abbreviated as "upcut" in the table) and downcut operation (abbreviated as "downcut" in the table). (targets for comparison) The comparison subjects are the grass cutting machine described in Patent Document 1 and the self-propelled grass cutting machine 1 described in this embodiment. (Measurement conditions) Regarding the grass cutting machine described in Patent Document 1 and the self-propelled grass cutting machine 1 described in this embodiment, (1) On the lawn on the east side of the headquarters, start the engine and put it at full throttle. (2) Measure the sound pressure at the worker's ears with a sound level meter. (3) After switching to up-cut operation using the rotation direction switching mechanism, the grass cutting blade clutch lever that rotates the grass cutting blade is turned on, and the sound pressure at the operator's ear is measured. (4) After the measurement in (3), turn the grass cutting blade clutch lever to OFF, switch to down-cut operation using the rotation direction switching mechanism, then turn the grass cutting blade clutch lever to ON and measure the sound pressure at the operator's ear. The trip was conducted under the following conditions.

[0095] [Table 1]

[0096] [Table 2]

[0097] (Consideration) As can be seen from Tables 1 and 2, compared to the grass cutting machine described in Patent Document 1, the self-propelled grass cutting machine 1 equipped with a rotation direction switching mechanism 6 was confirmed to have clearly suppressed sound pressure and sound pressure rise value in both up-cut operation and down-cut operation. Furthermore, when the grass cutting machine described in Patent Document 1 tried to switch between up-cut operation and down-cut operation 100 times, the gear did not engage smoothly (i.e., switching failed) 12 times. On the other hand, when the self-propelled grass cutting machine 1 described in this embodiment tried to switch between up-cut operation and down-cut operation 100 times, the switching failed 0 times.

[0098] In this way, the self-propelled grass cutter 1 and the rotation direction switching mechanism 6 provided therewith described in this embodiment have the above-mentioned configuration and function based thereon, and while having a relatively simple structure, they reduce noise during operation and can reliably switch the grass cutting blade rotation direction. The same can be said about the grass cutting method using the self-propelled grass cutter 1.

[0099] The terms and expressions used in the present specification and claims are merely explanatory and not limiting, and are not intended to exclude terms and expressions equivalent to the features described in the present specification and claims and parts thereof. It goes without saying that various modifications are possible within the scope of the technical idea of ​​the present invention. Furthermore, the terms first, second, etc. do not mean rank or importance, but are used to distinguish one element from another element. [Explanation of symbols]

[0100] 1 Self-propelled grass cutter 2 Main unit 20 Frames 21 Operating handle 210 Plate 211 Rotation direction change lever 212 Lever guide groove 22 Steps 3. Traveling means section 31 Rear running structure 311 Wheel 312 Sprocket 313 Tracks 32 Front running structure 321 Support Frame 322 Running Wheel 4. Prime Mover 41 Power transmission structure 5 Grass cutting blade 51 Mounting base 52 Cutting blade 53 Grass cutting blade rotating shaft 54 Mounting part 55 Grass cutting blade cover 6 Rotation direction switching mechanism 61 First pulley 611 First receiving groove 612 Second receiving groove 62 No. 2 pulley 621 Third receiving groove 63 3rd pulley 631 4th receiving groove 632 Rotating shaft 64 Output shaft 65 1st Gear 66 2nd Gear 67 First Belt 68 Second Belt 69 Tensioner 691 First Arm 692 Second Arm 693 Base part 694 Operation section 7. Power transmission part on the grass cutting blade side 71 5th pulley 72 6th pulley 73 3rd Belt 74 Tensioner 741 First Arm 741 Tension pulley 743 Second Arm 744 Tension pulley 745 Base part 745 UC Up cut rotation direction DC Down Cut Rotation Direction

Claims

1. The device is equipped on a self-propelled grass cutter having a rotary grass cutting blade driven by a prime mover, a first pulley that rotates by receiving power from the prime mover and has a first receiving groove that is continuous around an outer circumferential surface and a second receiving groove that is provided in parallel to the first receiving groove; a second pulley having a third receiving groove portion that is a continuous shape around an outer circumferential surface thereof, the third receiving groove portion and the first receiving groove portion being disposed so as to be positioned on substantially the same line; a third pulley having a fourth receiving groove portion that is a continuous shape that goes around an outer circumferential surface thereof, the fourth receiving groove portion and the second receiving groove portion being disposed so as to be positioned on substantially the same line; an output shaft connected to the second pulley and rotatable integrally with the second pulley; a first gear attached to the output shaft so as to be rotatable integrally with the output shaft; a second gear disposed so as to be constantly in mesh with the first gear, and disposed coaxially with the third pulley so as to be rotatable integrally with the third pulley; a first belt that is wound around the first receiving groove and the third receiving groove and that rotates idly on the surfaces of the first receiving groove and the third receiving groove when no tension is applied; a second belt that is wound around the second receiving groove and the fourth receiving groove and that rotates idly on the surfaces of the second receiving groove and the fourth receiving groove when no tension is applied; a tension applying unit having a structure capable of applying tension to only one of the first belt and the second belt by switching; Mechanism for switching the rotation direction of the grass cutting blade.

2. The tension applying unit has a first arm unit having a tension pulley at its tip that can come into contact with the first belt, a second arm unit having a tension pulley at its tip that can come into contact with the second belt, a base shaft unit that connects bases of the first arm unit and the second arm unit so as to be rotatable on the same axis, and an operation unit that can operate only one of the first arm unit or the second arm unit selected. The grass cutting blade rotation direction switching mechanism according to claim 1.

3. The first belt and the second belt are V-belts, and the first receiving groove portion, the second receiving groove portion, the third receiving groove portion, and the fourth receiving groove portion are V-shaped grooves in cross section. The grass cutting blade rotation direction switching mechanism according to claim 1 or 2.

4. A main body having a traveling means; A prime mover mounted on the main body; A rotary grass cutting blade is disposed at a position where the grass cutting blade can work in the moving direction of the main body and is driven by the power from the prime mover; a first pulley arranged between the grass cutting blade and the prime mover, rotated by input of power from the prime mover, and including a first receiving groove portion that is continuous around the outer circumferential surface and a second receiving groove portion that is provided in parallel to the first receiving groove portion; a second pulley including a third receiving groove portion that is continuous in shape and that is arranged so that the third receiving groove portion and the first receiving groove portion are positioned on approximately the same line; a third pulley including a fourth receiving groove portion that is continuous in shape and that is arranged so that the fourth receiving groove portion and the second receiving groove portion are positioned on approximately the same line; an output shaft that is connected to the second pulley and arranged so as to be rotatable integrally with the second pulley; the first gear being fixed to the first pulley; a second gear being disposed so as to be constantly in mesh with the first gear, and being disposed coaxially with the third pulley so as to be rotatable integrally with the third pulley; a first belt being wound around the first receiving groove portion and the third receiving groove portion and configured to rotate idly on surfaces of the first receiving groove portion and the third receiving groove portion when tension is not applied; a second belt being wound around the second receiving groove portion and the fourth receiving groove portion and configured to rotate idly on surfaces of the second receiving groove portion and the fourth receiving groove portion when tension is not applied; and a grass cutting blade rotation direction switching mechanism having a tension application portion configured to apply tension to only one of the first belt and the second belt by switching. Self-propelled lawn mower.

5. A main body having a traveling means; A prime mover mounted on the main body; A rotary grass cutting blade is disposed at a position where the grass cutting blade can work in the moving direction of the main body and is driven by the power from the prime mover; a first pulley arranged between the grass cutting blade and the prime mover, rotated by receiving power from the prime mover, and including a first receiving groove portion which is continuous around the outer circumferential surface and a second receiving groove portion which is provided in parallel to the first receiving groove portion; a second pulley including a third receiving groove portion which is continuous around the outer circumferential surface and which is disposed so that the third receiving groove portion and the first receiving groove portion are positioned on substantially the same line; a third pulley including a fourth receiving groove portion which is continuous around the outer circumferential surface and which is disposed so that the fourth receiving groove portion and the second receiving groove portion are positioned on substantially the same line; an output shaft which is connected to the second pulley and provided so as to be rotatable integrally with the second pulley; a second gear arranged so as to be constantly in mesh with the first gear, arranged coaxially with the third pulley and rotatable integrally with the third pulley; a first belt wound around the first receiving groove and the third receiving groove and configured to rotate idly on surfaces of the first receiving groove and the third receiving groove when tension is not applied; a second belt wound around the second receiving groove and the fourth receiving groove and configured to rotate idly on surfaces of the second receiving groove and the fourth receiving groove when tension is not applied; and a grass-cutting blade rotation direction switching mechanism having a tension application part configured to apply tension to only one of the first belt and the second belt by switching, a first operating step of applying tension only to the first belt by the tension applying unit and rotating the rotary grass cutting blade only in an up-cut direction relative to a traveling direction of the self-propelled grass cutter; A second operating step of applying tension only to the second belt by the tension applying unit and rotating the rotary grass cutting blade only in a downcut direction relative to the traveling direction of the self-propelled grass cutter; Switch between the following as appropriate. How to mow.

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