JP6228056B2 - Lawn mower - Google Patents

Description

  The present invention relates to a technology of a rotary lawn mower having an improved housing for housing a cutter blade.

  The rotary lawn mower cuts the turf grass by rotating a cutter blade housed in a housing open at the bottom along the turf grass. In recent years, the housing of lawn mowers has been improved. As such a lawn mower technology, for example, Patent Document 1 is known.

  The lawn mower known in Patent Document 1 includes a housing that is open at the bottom, a rotary shaft that is positioned in the housing and extends in the vertical direction of the housing, and is rotatable about the rotary shaft. And a cutter blade housed in the housing. The cutter blade has a blade formed at the leading edge in the rotational direction and an air lift portion formed at the trailing edge in the rotational direction at both ends in the longitudinal direction. On the inner peripheral surface of the peripheral wall portion of the housing, a plurality of vertical convex portions and a plurality of concave portions are alternately formed in the circumferential direction.

  When the cutter blade rotates, a negative pressure is generated in the concave portion, thereby generating an air vortex. As a result, the wind speed on the inner peripheral surface of the peripheral wall portion of the housing is increased, and the effect of raising the turf grass is increased. Accordingly, even if the rotational speed of the cutter blade is lowered, the mowing performance can be ensured. By reducing the rotation speed, the noise of the lawn mower can be suppressed.

  However, from the viewpoint of improving the lawn mowing performance of the lawn mower, the rotation speed of the cutter blade may not be lowered. In order to further improve the lawn mowing performance of the lawn mower without changing the size of the housing, it is necessary to further increase the rotational speed of the cutter blade. When the rotational speed of the cutter blade cannot be lowered or needs to be increased, some noise countermeasure is required to suppress the noise of the lawn mower.

  Furthermore, the lawn mower known in Patent Document 1 increases the eddy current of the air in the housing, which is one of the factors that generate noise, and the eddy current of the noise source does not disappear.

Japanese Utility Model Publication No. 4-117535

  It is an object of the present invention to provide a lawn mower technology that can secure lawn mowing performance while suppressing noise eddy current generated in a housing to improve noise suppression performance.

According to the first aspect of the present invention, the housing that is open at the bottom, the rotary shaft that is located in the housing and extends in the up-down direction of the housing, and the rotary shaft that is rotatable about the rotary shaft as the rotation center. The cutter blade is an elongated member extending both in the horizontal direction with respect to the rotational axis, and both longitudinal ends of the cutter blade are arranged in the rotational direction. A blade formed on the front edge; and an air lift portion that generates a swirling flow and an ascending air flow while curving upward and rearward from the front edge, and the housing is based on the rotation center of the cutter blade. has a peripheral wall portion of the substantially circular shape in plan view cross section and, of among the inner peripheral surface of the peripheral wall portion, at a position facing the rotation locus of the air lift portions, the plurality over the entire circumference wings constant peak Formed by Ji, wings of said plurality of elongated ridge vertically projecting from the inner peripheral surface of the peripheral wall portion inwardly, or an elongated concave in the vertical recessed from the inner circumferential surface, said airlift formed inclined while curving in opposite to the bending direction of the parts, the scope of the respective wings is located within the rotational locus of the air lift portions, the range of the height of the respective wings, The height of the range of rotation trajectory of the air lift portion is set to be the same, and the pitch of the plurality of wing portions is formed smaller than the distance from the front upper end to the rear lower end of the wing portion. A lawn mower is provided.

  In the invention according to claim 1, a plurality of wing parts (diffusers) are formed over the entire circumference at a position on the inner peripheral surface of the substantially circular peripheral wall part of the housing that faces the rotation locus of the air lift part. Yes. The plurality of wing portions are formed in a vertically elongated ridge or recess, and are inclined to the opposite side with respect to the bending direction of the air lift portion.

  In general, when the cutter blade rotates, air is separated from the rear end of the cutter blade in the rotation direction, and a vortex is generated. The vortex can cause noise. The vortex flows in the circumferential direction along the inner peripheral surface of the peripheral wall portion of the housing due to the centrifugal force generated by the rotation of the cutter blade.

  At this time, in the invention according to claim 1, the plurality of wings inclined to the opposite side, that is, the front upper side, with respect to the bending direction of the air lift part becomes an obstacle, and the vortex is disrupted and scattered. For this reason, the vortex is disturbed and becomes a smaller vortex or a more turbulent turbulence. Accordingly, the size of the vortex is reduced, and the kinetic energy of the vortex is reduced. As a result, it is possible to suppress noise due to the vortex generated by the separation of air from the rear end in the rotational direction of the cutter blade. That is, the noise suppression performance can be improved by suppressing the air vortex generated in the housing by the rotation of the cutter blade. In addition, the noise suppression performance can be improved regardless of the rotational speed of the cutter blade.

  Further, since the plurality of wing portions are inclined to the opposite side with respect to the bending direction of the air lift portion, the upward flow of the air sucked into the housing from the opened lower side of the housing is It can be guided upward by the wings. That is, it does not hinder upward flow. Therefore, the turfgrass growing on the turf can be erected by the upward flow and efficiently cut by the cutter blade. As a result, the lawn mower performance of the lawn mower can be ensured.

  Further, the plurality of wing portions are formed over the entire circumference of the inner peripheral surface of the peripheral wall portion of the housing. Moreover, the plurality of wing parts are elongated vertically and inclined in the circumferential direction. Therefore, the plurality of wing portions can serve as reinforcing ribs for reinforcing the substantially circular peripheral wall portion. Therefore, the rigidity of the peripheral wall can be increased.

It is a left view of the lawn mower which concerns on Example 1 of this invention. It is a top view of the lawn mower shown in FIG. It is sectional drawing of the housing and cutter blade which are shown by FIG. It is a bottom view of the lawn mower shown in FIG. It is a figure which shows the side surface structure of the cutter blade shown by FIG. 3, a plane structure, and the structure of an outer periphery part. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. It is the perspective view which looked at the housing and wing | blade part which were shown by FIG. 3 from the downward direction. It is sectional drawing which expanded the relationship between the housing shown in FIG. 3, a wing | blade part, and a cutter blade, and was seen from the top. It is the expanded view which looked at the relationship between the housing shown in FIG. 8, the wing | blade part, and the cutter blade from the inner side of the housing. It is the expanded sectional view which looked at the wing | blade part shown by FIG. 8 from the top. It is the figure which looked at the wing | blade part shown by FIG. 10 from the front end side. It is the expanded view which looked at the relationship between the housing of the lawn mower which concerns on Example 2 of this invention, a wing | blade part, and a cutter blade from the inner side of the housing. It is sectional drawing which looked at the relationship between the housing of the lawn mower which concerns on Example 3 of this invention, a wing | blade part, and a cutter blade from the top.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated below based on an accompanying drawing.

  The lawn mower according to the first embodiment will be described with reference to FIGS. “Front”, “Rear”, “Left”, “Right”, “Up”, “Down” follow the direction viewed from the operator, Fr is front, Rr is rear, Le is left, Ri is right , Up is the upper side, Dw is the lower side, and CL is the machine width center (machine width center line).

  As shown in FIGS. 1 and 2, the lawn mower 10 is a walking type self-propelled working machine for mowing turf grass, and includes a housing 11 and left and right front wheels 12, 12 provided at a front portion of the housing 11. The left and right rear wheels 13, 13 provided at the rear of the housing 11, the lawn mowing cutter blade 14 housed inside the center of the housing 11, and the engine 15 (power source provided at the top of the housing 11 15) and an operation handle 16 extending rearward from the housing 11. The power source 15 is not limited to an engine, and may be an electric motor, for example.

  As shown in FIG. 2, the lawn mower 10 cuts turf grass in the housing 11 by rotating the cutter blade 14 in the clockwise direction (arrow Ra direction) by the engine 15 in a plan view. An air flow (a swirling flow of swirling air) as indicated by an arrow Rb is generated, and the swirling flow allows the turf grass mowed by the cutter blade 14 to be sent to the mowed grass storage body 22 (see FIG. 1) for storage. it can. Hereinafter, turf grass mowed by the cutter blade 14 is referred to as “cut grass”.

  As shown in FIG. 3, the housing 11 is a housing in which only a lower end surface (a surface facing the grass ground Gr shown in FIG. 1) is completely opened, so-called a lower portion is opened. The housing 11 also serves as a fuselage, and is integrally assembled by overlapping the engine 15 on the upper surface and bolting. The engine 15 has an output shaft 15a extending from the lower end toward the lower grass field Gr and into the housing 11. The output shaft 15 a is a rotation shaft that is located in the housing 11 and extends in the vertical direction of the housing 11. As a result, the output shaft 15a is substantially perpendicular to the horizontal lawn Gr (ground).

  As shown in FIGS. 3 and 4, the cutter blade 14 is attached to the output shaft 15 a via the clutch 17 in the housing 11. By driving the cutter blade 14 by the engine 15, the cutter blade 14 can rotate around the output shaft 15 a (rotating shaft 15 a) in the housing 11.

  FIG. 5A shows a configuration in which the cutter blade 14 shown in FIG. 3 is viewed from the side. FIG. 5B shows a configuration of the cutter blade 14 shown in FIG. FIG. 5C is a perspective view of a part of the cutter blade 14 shown in FIG. 5B as viewed from the outer peripheral edge 45 side with the rotation shaft 15a as the rotation center. FIG. 5D shows an end face of the cutter blade 14 shown in FIG. 5C as viewed from the direction of the arrow d (the outer peripheral edge 45 side).

  As shown in FIGS. 5A to 5D, the cutter blade 14 is an elongated member having a substantially flat plate shape in plan view, extending in both the horizontal direction with respect to the rotation shaft 15a. Both ends 41, 41 in the longitudinal direction of the cutter blade 14 are a pair of blades 43, 43 formed on the front edge 42 in the rotation direction Ra of the cutter blade 14, and the rear upper side (in the direction of the arrow Rd). ) And a pair of air lift portions 44, 44 extending in a curved manner. Hereinafter, the “arrow Rd direction” is referred to as “the bending direction Rd of the air lift portion 44”. The air lift portions 44 and 44 are portions for generating a swirling flow of air and an updraft when the cutter blade 14 rotates in the rotation direction Ra, and are formed integrally with the cutter blade 14.

  Details of the housing 11 will be described below. As shown in FIGS. 2 to 4, the housing 11 has a scroll portion 11 d for moving the turf grass mowed by the cutter blade 14 to the mowed grass carrying-out passage 21 while making the swirl movement with the swirling wind. A spiral member in a plan view, that is, a spiral casing (spiral case, scroll case).

  More specifically, as shown in FIG. 4, in the bagging mode, the scroll portion 11d moves the turf grass mowed by the cutter blade 14 in the housing 11 in the direction of the arrow Rc (the turning direction Rc) while moving the arrow. It is directed to the cut grass transport passage 21 like Rb.

  As shown in FIGS. 3, 4, and 6, the housing 11 includes a top plate 11 a, an outer cylinder part 11 b, an inner cylinder part 11 c, a scroll part 11 d, and a cut grass transport passage 21. The top plate 11 a is a substantially circular plate that is closing the upper end of the housing 11 and is substantially horizontal in plan view. The outer cylinder portion 11b is a cylindrical member that extends downward from the outer edge of the top plate 11a around the output shaft 15a. That is, the outer cylinder portion 11b is a peripheral wall portion having a substantially circular cross section in plan view with respect to the axis SC of the output shaft 15a (the rotation center SC of the cutter blade 14). Hereinafter, the outer cylinder portion 11b is appropriately rephrased as “the peripheral wall portion 11b”. The inner cylinder portion 11c is a cylindrical member extending downward from the inner edge of the top plate 11a around the output shaft 15a, and is configured to have a smaller diameter than the outer cylinder portion 11b.

  The scroll portion 11d is a substantially annular space that is surrounded by the top plate 11a, the outer tube portion 11b, and the inner tube portion 11c. The scroll portion 11d is formed in an inverted U-shaped cross section (see FIG. 6) that is downward when viewed from the side, and is a passage through which the cut grass turns, and the cut grass carry-out passage while the cut grass turns. It is comprised so that it may head for 21. That is, the scroll portion 11 d is continuous with the passage opening 23 of the cut grass carrying-out passage 21.

  As shown in FIGS. 3 and 4, the cut grass carrying-out passage 21 is a member that extends in the tangential direction of the outer cylinder portion 11 b from the outer cylinder portion 11 b toward the rear (more specifically, rear upper side). The cut grass transport passage 21 has a passage opening 23 facing the housing 11 at the front end, and a cut grass storage body 22 (see FIG. 1) such as a glass bag can be attached to the rear end. The cut grass is sent to the cut grass carry-out passage 21 while turning around the output shaft 15 a inside the housing 11.

  As is clear from the above description, the direction in which the cut grass carrying-out passage 21 extends from the outer cylinder portion 11 b matches the rotation direction Ra of the cutter blade 14. In other words, the cut grass carrying-out passage 21 extends in the tangential direction of the rotation locus of the cutter blade 14. The passage opening 23 of the cut grass carrying-out passage 21 is open in the rotation direction Ra of the cutter blade 14.

  As shown in FIGS. 3 and 4, a shutter 30 is disposed on the inner peripheral surface of the housing 11, that is, the inner peripheral surface 11e of the outer cylinder portion 11b. The shutter 30 includes a turntable 31 that is rotatably attached to the top plate 11 a inside the housing 11, and a shutter main body 32 that is attached to the outer edge of the turntable 31. The shutter main body 32 can be turned about the axis SC of the output shaft 15a. The shutter main body 32 can open and close the passage opening 23 of the cut grass carrying-out passage 21 and adjust the opening.

  By operating the operation lever 33, (1) the bagging mode in which the shutter main body 32 is fully opened and the cut grass is stored in the cut grass storage body 22 shown in FIG. 1, and (2) the shutter main body 32 is fully closed. Thus, it is possible to switch appropriately between a mulching mode in which the cut grass is discharged below the housing 11 and (3) an intermediate mode between the bagging mode and the mulching mode in which the shutter body 32 is set to an arbitrary opening degree.

  As shown in FIGS. 3, 4, and 7, the position 11 f in the inner peripheral surface 11 e of the peripheral wall portion 11 b that faces the rotation locus 46 (see FIG. 8) of the air lift portions 44, 44, that is, the opposite surface. A plurality of wing parts 50 (diffusers 50) are formed over the entire circumference at the position 11f. Hereinafter, the position 11f facing the rotation locus 46 of the air lift part 44 is appropriately rephrased as the “opposing position 11f”.

  As shown in FIGS. 7 to 9, the plurality of wing parts 50 are vertically elongated strips protruding inward from the inner peripheral surface 11e of the peripheral wall part 11b, and the air lift parts 44, It is inclined to the opposite side (arrow Re direction) with respect to the bending direction Rd of 44. Hereinafter, the “arrow Re direction” is appropriately rephrased as “the inclination direction Re of the wing part 50”.

  More specifically, as shown in FIGS. 10 and 11, the plurality of wing parts 50 swell from the inner peripheral surface 11e of the outer cylinder part 11b toward the rotation center SC of the cutter blade 14 (see FIG. 7). I'm out. The amount of swelling of the plurality of wing parts 50 is preferably the thickness of the outer cylinder part 11b in consideration of the ease of production, but is not limited to this.

  Further, as shown in FIGS. 7 to 9, the plurality of wing portions 50 are inclined while being curved upward in the rotational direction Ra of the cutter blade 14. That is, the plurality of wing parts 50 are formed in a substantially crescent shape that is curved so as to protrude downward in the rotation direction Ra of the cutter blade 14 when viewed from the rotation center SC of the cutter blade 14.

  As shown in FIG. 8, the tip 51 in the inner circumferential direction of each wing part 50 is close to the rotation locus 46 of the air lift part 44 with a minute gap Cr.

  As shown in FIG. 9, the range Hi of each wing portion 50 is located within the range Hb of the rotation locus 46 of the air lift portion 44. The height of the range Hi of each wing part 50 is set to be the same or larger than the height of the range Hb of the rotation locus 46 of the air lift part 44.

  As shown in FIG. 9, the plurality of wing parts 50 are arranged at a constant pitch Pi in the circumferential direction of the inner peripheral surface 11e of the outer cylinder part 11b. The pitch Pi is more preferably smaller than the distance Li from the front upper end 52 to the rear lower end 53 of the wing portion 50. Here, the front upper end 52 is the position of the front upper end in the rotation direction Ra of the cutter blade 14 in the wing portion 50.

  Next, the operation of the above configuration will be described. As shown in FIGS. 7 to 9, a position 11 f (opposing position) facing the rotation locus 46 of the air lift parts 44, 44 in the inner peripheral surface 11 e of the peripheral wall part 11 b having a substantially circular cross section in a plan view of the housing 11. In 11f), a plurality of wing portions 50 are formed over the entire circumference. The plurality of wing parts 50 are formed in a vertically elongated ridge, and are inclined to the opposite side Re to the bending direction Rd of the air lift parts 44, 44, that is, the front upper side Re.

  In general, when the cutter blade 14 rotates, air is separated from the rear end of the cutter blade 14 in the rotation direction, and a vortex is generated. The vortex can cause noise. The vortex flows in the circumferential direction along the inner peripheral surface 11 e of the peripheral wall portion 11 b of the housing 11 due to the centrifugal force generated by the rotation of the cutter blade 14.

  At this time, in the first embodiment, the plurality of wing portions 50 inclined to the opposite side Re with respect to the bending direction Rd of the air lift portions 44, 44 become obstacles, and the vortex flow fs (see FIG. 10) is collapsed. Scatter. For this reason, the vortex flow fs is disturbed to become a smaller vortex or a more turbulent turbulence. Therefore, the magnitude of the vortex flow fs is reduced, and the kinetic energy of the vortex flow fs is reduced. As a result, the air is separated from the rear end of the cutter blade 14 in the rotation direction, so that noise caused by the generated vortex can be suppressed. That is, it is possible to improve the noise suppression performance by suppressing the air vortex generated in the housing 11 by the rotation of the cutter blade 14. Moreover, the noise suppression performance can be improved regardless of the rotational speed of the cutter blade 14.

  Further, since the plurality of wing portions 50 are inclined to the opposite side Re with respect to the bending direction Rd of the air lift portions 44, 44, the air sucked into the housing 11 from the lower side where the housing 11 is opened. Can be guided upward by the plurality of wing portions 50. That is, it does not hinder upward flow. Therefore, the turfgrass growing on the turf ground Gr can be erected by the updraft and efficiently cut by the cutter blade 14. As a result, the lawn mowing performance of the lawn mower 10 can be ensured.

  Further, the plurality of wing parts 50 are formed over the entire circumference of the inner peripheral surface 11 e of the peripheral wall part 11 b of the housing 11. Moreover, the plurality of wing portions 50 are elongated vertically and inclined in the circumferential direction. Therefore, the plurality of wing parts 50 can serve as reinforcing ribs for reinforcing the substantially circular peripheral wall part 11b. Accordingly, the rigidity of the peripheral wall portion 11b can be increased.

  A lawn mower according to Embodiment 2 will be described with reference to FIG. FIG. 12 corresponds to FIG. 9 of the first embodiment. The lawn mower 10A of the second embodiment is characterized in that the plurality of wing parts 50 of the first embodiment shown in FIG. 9 are changed to the plurality of wing parts 50A shown in FIG. 12, and other configurations are implemented. Since it is the same structure as Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  More specifically, the plurality of wing portions 50A have a flat configuration inclined “without bending” in the rotation direction Ra of the cutter blade 14 and upward, that is, in the inclination direction Re. According to the second embodiment, the same operation and effect as the first embodiment are exhibited.

  A lawnmower according to Example 3 will be described with reference to FIG. FIG. 13 corresponds to FIG. 10 of the first embodiment. The lawnmower 10B according to the second embodiment is characterized in that the plurality of wing parts 50 according to the first embodiment shown in FIG. 10 are changed to the plurality of wing parts 50B shown in FIG. Since it is the same structure as Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  More specifically, the plurality of wing parts 50B (only one is shown in the figure) are vertically elongated strips recessed from the inner peripheral surface 11e of the peripheral wall part 11b, and the air lift parts 44, 44 are provided. It is inclined to the opposite side with respect to the bending direction Rd (see FIG. 9). More specifically, the plurality of wing parts 50B are recessed radially outward from the inner peripheral surface 11e of the outer cylinder part 11b, and the other configurations are the same as in the first embodiment. According to the third embodiment, the same operation and effect as the first embodiment are exhibited.

  The working machines 10, 10A, and 10B of the present invention are suitable for use in a walking lawnmower.

DESCRIPTION OF SYMBOLS 10 Lawn mower 10A Lawn mower 10B Lawn mower 11 Housing 11a Top plate 11b Perimeter wall part (outer cylinder part)
11c Inner cylinder part 11e Inner peripheral surface 11f Position facing the rotation locus of the air lift part 14 Cutter blade 15 Engine 15a Rotating shaft (output shaft)
41 End in longitudinal direction 42 Leading edge in rotational direction 43 Blade 44 Air lift part 45 Outer peripheral edge 46 Rotation locus of air lift part 50 Wing part 50A Wing part 50B Wing part Gr Turf Ra Ra Rotating direction of cutter blade Rd Bending direction of air lifting part Re Inclination direction of wing

Claims (1)

A housing that is open at the bottom, a rotating shaft that is positioned in the housing and extends in the vertical direction of the housing, and a cutter blade that is housed in the housing so as to be rotatable about the rotating shaft. In the lawn mower,
The cutter blade is an elongated member extending both in the horizontal direction with respect to the rotation axis;
Both end portions of the cutter blade in the longitudinal direction have blades formed at the leading edge in the rotational direction, and air lift portions that extend from the front edge while curving upward and generate a swirling flow and an updraft. And
The housing has a peripheral wall portion having a substantially circular cross section in plan view with respect to the rotation center of the cutter blade,
In the inner peripheral surface of the peripheral wall portion, a plurality of wing portions are formed at a constant pitch over the entire circumference at a position facing the rotation trajectory of the air lift portion.
The plurality of wing portions are vertically elongated ridges projecting inwardly from the inner peripheral surface of the peripheral wall portion, or vertically elongated ridges recessed from the inner peripheral surface, and in the bending direction of the air lift portion. In contrast, it is tilted while curving on the opposite side,
The range of each wing portion is located within the range of the rotation locus of the air lift portion, and the height of the range of each wing portion is set to be the same as the height of the range of rotation locus of the air lift portion. The lawn mower is characterized in that the pitch of the plurality of wing parts is smaller than the distance from the front upper end to the rear lower end of the wing parts.

Images