JP4231802B2 - More blade - Google Patents

Description

  The present invention relates to a technique for reducing noise of a mower that projects a drive shaft into a mower casing, fixes a blade (cutting blade) to the drive shaft, and rotates the blade with power from a prime mover to perform a cutting operation. About.

  Conventionally, the drive shaft protrudes vertically into the mower casing from the upper surface of the mower casing that opens downward, the blade is fixed on the drive shaft in the mower casing, and the drive shaft is rotated by the power from the prime mover. Mowers that let you cut grass and other things are known. The blade in the mower is configured in a belt shape, and the drive shaft is fixed and rotated at the center to perform the cutting operation. A technique is known in which the mowing work can be performed satisfactorily and the cut grass can be efficiently conveyed rearward or laterally, and noise generated during rotation can be reduced (see, for example, Patent Document 1). . The blade of this technology is formed in a band shape, and both ends are bent forward in the rotational direction in a plan view, and further, the trailing edge at both ends of the blade is bent and formed to rise, It was the composition made into a wind-up piece.

JP 2003-189720 A

  However, with the conventional blade, the pressure at the time of rotation is particularly high at the leading edge and the bent portion of the wind-up piece as shown in the numerical calculation results shown in FIG. It shows that it becomes. Further, the flow velocity around the blade indicates that a separation vortex is generated in the wake of the blade as in the experimental result shown in FIG. This shows that the flow velocity is disturbed and causes noise. Therefore, the present invention aims to reduce noise during rotation by preventing the distribution of the high and low wind pressure portions and the high and low flow velocity portions around the blade from becoming unevenly large. It is.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  The blade (14) of the mower (14) according to claim 1, wherein the blade (14) is a mower blade (14) which is fixedly rotated so as to project radially from a vertical shaft (29) projecting into the mower casing (21). Has an opening (30) to the shaft (29) in the center, and extends from the mounting hole (30) to both sides in the diametrical direction with a predetermined width (D). The predetermined length (L) is a mounting portion (14a) extending in the horizontal direction, and both sides in the diametrical direction of the mounting portion (14a) are bent upward in a "<" shape so as to stand up (14b) And the bent portion (14d) of the valley fold of the rising portion (14b) is bent upward in a direction perpendicular to the radial direction, and the outer side of the rising portion (14b) is inclined with respect to the rotational direction. Then, a mountain-folded folding part (14e) toward the center (O) is formed, The wing portion (14c) is bent downward to form a wing portion (14c), the rising portion (14b) has a trapezoidal shape in plan view, and the wing portion (14c) has a divergent shape from the center in the radial direction toward the outside in plan view It is composed.

  According to a second aspect of the present invention, in the blade of the mower according to the first aspect, the wing portion (14c) is configured to have a curved surface with a lower front end edge in the rotational direction and a higher rear end edge, and rearward from the front side in the rotational direction in side view. And the maximum length in the rotational direction of the wing part (14c) is the wing length (B), and the height from the lowest part to the highest part of the wing part (14c) is the blade height. When (A) and the angle of the line connecting the lower end and the upper end with respect to the horizontal line is the warp angle (C), the warp angle (C) is an angle at which the value of tanC = A / B is 0.2 or less. Is.

According to claim 3, in the blade of the mower according to claim 1, the distance between the inner upper surface of the mower casing (21) and the upper end of the blade (14) with respect to the diameter (E) of the blade (14) ( The value of the ratio (H / E) of H) is such that the ratio (H / E) is in the range of 0.13 or more and 1 or less .

  According to a fourth aspect of the present invention, in the blade of the mower according to the first aspect, a notch (35) is provided on the center side of the rear end portion in the rotational direction of the wing portion (14c).

  According to a fifth aspect of the present invention, in the blade of the mower according to the first aspect, the cross-sectional shape of the rear end edge (33) constituting the rear side in the rotational direction of the wing portion (14c) is a curved surface.

  According to a sixth aspect of the present invention, in the blade of the mower according to the first aspect, the cross-sectional shape of the outer peripheral edge (34) constituting the outer peripheral portion of the blade (14) is a curved surface.

  As effects of the present invention, the following effects can be obtained.

  That is, the blade (14) of the mower fixed and rotated so as to project radially from the vertical shaft (29) projecting into the mower casing (21), The blade (14) opens a mounting hole (30) to the shaft (29) in the center, extends from the mounting hole (30) to both sides in the diametrical direction with a predetermined width (D), and the mounting hole (30). A predetermined length (L) from the center (O) is a mounting portion (14a) extending in the horizontal direction, and both sides of the mounting portion (14a) in the diametrical direction are bent upward in a “<” shape and started up. Forming a portion (14b), and the bent portion (14d) of the valley fold of the rising portion (14b) is bent upward in a direction perpendicular to the radial direction, and the outside of the rising portion (14b) is in the rotational direction The fold part (14e) of the mountain fold toward the center (O) The wing part (14c) is formed by bending downward and obliquely downward, the rising part (14b) has a trapezoidal shape in plan view, and the wing part (14c) is outward from the radial center in plan view. Since it has a divergent shape, it is possible to increase the work area to be blown by the rotation of the blade, and to improve the conveying performance of the cut grass. And noise can be reduced.

According to a second aspect of the present invention, the wing portion (14c) is configured to have a curved surface with a low front end edge in the rotational direction and a high rear end edge, and is gradually curved upward from the front side in the rotational direction in a side view. Shape, the maximum length in the rotational direction of the wing (14c) is the wing length (B), and the height from the lowest part to the highest part of the wing (14c) is the wing height (A). Assuming that the angle of the line connecting the lower end and the upper end is the warp angle (C), the warp angle (C) is an angle at which the value of tanC = A / B is 0.2 or less. The pressure generated by the rotational movement of the blade can be reduced, the generation of turbulent flow can be suppressed, and the noise can be reduced.
In addition, the interference pressure at the branch portion between the inner surface of the mower casing and the weed path is reduced, and the ambient noise can be reduced. In addition, separation of the blade suction surface was suppressed, turbulence in the wake was suppressed, and turbulent sound due to turbulent flow could be reduced.

The ratio (H / E) of the distance (H) between the inner upper surface of the mower casing (21) and the upper end of the blade (14) with respect to the diameter (E) of the blade (14). Since the ratio (H / E) is in the range of 0.13 or more and 1 or less , the pressure loss in the mower casing during blade rotation can be reduced. Moreover, the pressure generated by the rotational movement of the blade can reduce the interference pressure generated at the branching portion between the inner surface of the mower casing and the weed path, and the blowing performance can be improved.

  Since the notch (35) is provided on the center side of the rear end portion in the rotation direction of the wing portion (14c), noise can be reduced by providing the notch. The noise reduction effect can be increased as the cutout is greatly cut in the outer peripheral direction. Therefore, when a large air volume is desired, the cutout can be made small to improve the air blowing performance.

  Since the cross-sectional shape of the rear end edge (33) constituting the rear side in the rotation direction of the wing portion (14c) is configured as a curved surface as described in claim 5, peeling of the blade rear end edge is suppressed, The turbulent flow was suppressed, and the turbulent sound caused by the turbulent flow could be reduced.

  As described in claim 6, since the cross-sectional shape of the outer peripheral edge (34) constituting the outer peripheral portion of the blade (14) is configured as a curved surface, peeling of the blade outer peripheral edge is suppressed, and wake turbulence is suppressed, The turbulent sound caused by the turbulent flow could be reduced.

  Next, an embodiment in which the present invention is applied to a lawn mower which is an embodiment of a mower using blades will be described with reference to the drawings. FIG. 1 is an overall side view of a lawn mower to which the present invention is applied, and FIG. 2 is an overall plan view of the lawn mower.

  1 and 2, the lawn mower has an engine 13 mounted on a body 12 having a pair of left and right front wheels 10 and 10 and a pair of left and right rear wheels 11 and 11. The rear wheels 11 and 11 and the blade 14 installed on the main body 12 are rotationally driven to extend a loop-shaped handle 15 upward and backward from the rear portion of the main body 12. Various driving operations can be performed. A walking type lawn mower is thus constructed.

  The main body 12 of the lawn mower is configured to have a shape with the ridged face down, and is disposed on the upper portion of the mower casing 21 opened at the lower side. The front wheel support portion 22 is continuously provided on the front side of the mower casing, and A traveling mission case 24 is continuously formed at the rear portion of the casing 21. The front wheel support portion 22 supports the left and right front wheels 10 and 10 so as to freely rotate. The traveling mission case 24 supports the left and right rear wheels 11 and 11, and the left and right rear wheels 11 and 11 are supported. The traveling transmission case 24 is configured to be rotationally driven by a traveling transmission mechanism built in the traveling transmission case 24.

  The front wheels 10 and 10 and the rear wheels 11 and 11 are provided so that their relative positions can be changed and adjusted in the vertical direction with respect to the main body, and the front wheels 10 and 10 and the rear wheels 11 are adjusted as necessary. -By changing the vertical position of 11, the ground height of the main body 12 and the blade 14 installed thereon can be adjusted, and the cutting height can be changed by changing this height.

  The output shaft 19 of the engine 13 projects downward from the approximate center of the mower casing 21, and power is transmitted from the output shaft 19 to a traveling transmission mechanism of the traveling mission case 24 via a gear and a traveling output shaft 16 (not shown). The rear wheels 11 and 11 are driven to rotate when the travel clutch provided in the travel transmission mechanism is ON. It is connected to a travel clutch operating lever 17 installed in the shape portion via an operation wire 18, and is turned on and off by swinging the travel clutch operating lever 17 in the front-rear direction, so that it can run and stop. It has become.

  Moreover, the weed path 25 for discharging the cut grass cut back from the left and right side rear portions inside the mower casing 21 to the rear is formed. As shown in FIG. 3, a branch portion between the horizontal surface 21 a on the inner surface that is the back side of the upper surface of the mower casing 21 and the inner side surface of the weed path 25 is a tongue portion 26. That is, the tongue 26 indicates a step or an opening formed between the inner surface of the mower casing 21 that covers the upper portion of the blade 14 and the weed path 25, and the mower casing 21 and the weed path 25. The portion where the flow of the wind changes is the tongue 26. A grass collection bag 20 is detachably attached to a discharge port at the end of the weed path 25. Thus, the grass that has been cut by the blade 14 and driven to the weed path 25 is collected by the grass collection bag 20. The blade 14 is fixed below the output shaft 19 on a drive shaft 29 rotatably supported via a bearing, and turns on / off a clutch interposed between the output shaft 19 and the drive shaft 29. Therefore, power transmission can be turned on and off. The clutch is connected to a work clutch operation lever 23 so that the work clutch can be turned ON / OFF by operating the clutch operation lever 23.

  Thus, by operating the work clutch operating lever 23 to the ON side, the rotation of the engine 13 is transmitted from the output shaft 19 to the blade 14 and rotated. Further, by rotating the traveling clutch operating lever 17 to the ON side, power is transmitted to the rear wheel 11 to drive the rear wheel 11 and advance the main body 12. The grass is cut by this forward movement and the rotation of the blade 14, and the cut grass is put into the grass collection bag 20 from the weed path 25. In the present embodiment, one blade 14 is housed in the mower casing 21, but a plurality of blades 14 may be disposed. Moreover, although the weed path 25 is provided on one side of the left and right, it can also be provided at the center of the left and right or at the top.

  Next, the blade 14 of the present invention will be described. 3 is a perspective view of the mower casing as viewed from below, FIG. 4 is a plan view of the blade, FIG. 5 is a front view of the blade, FIG. 6 is a side view of the blade, FIG. 7 is a perspective view of the blade, and FIG. It is a figure which shows the pressure state. As shown in FIGS. 3, 4, and 5, the blade 14 has an attachment hole 30 for attachment to the drive shaft 29 disposed on the extension of the output shaft 19 in the center, and has a predetermined width D from the attachment hole 30. Extending in the diameter direction (both sides), the predetermined length L from the center O extends in the horizontal direction as a length matching the width of the mounting seat 27 to form a mounting portion 14a. A plurality of mounting holes 31 are opened in the mounting portion 14a. In this embodiment, two openings are provided on both sides. However, in the case where a plurality of blades are arranged, the blades protrude in the radial direction at equal angles.

  On the outside (both sides in the diametrical direction) of the mounting portion 14a, a rising portion 14b having the same width as the mounting portion 14a is formed by bending upward in a “<” shape. The bent portion (valley fold line) 14d is perpendicular to the radial direction (tangential direction). A wing portion 14c is formed on the outside (both sides in the radial direction) of the rising portion 14b by bending obliquely downward. The raised portion 14b has a trapezoidal shape in plan view, and the outer side forms a bent portion (mountain folding line) 14e toward the oblique center in the rotational direction.

  The wing portion 14c has a divergent shape from the center in the radial direction toward the outside in a plan view. In this embodiment, the outer periphery is formed in an arc shape, but it may be a straight line or a polygonal shape. That is, it can be configured in a sector shape, a trapezoidal shape, or a triangular shape. In this embodiment, the wing part 14c is configured as a forward wing so that the front end edge 32 is in front of the extension direction of the extension line of the attachment part 14a of the blade 14. The front edge 32 can be configured to have a sharp cross section as a rising portion 14b, that is, a blade portion extending linearly outward from the base portion of the wing portion 14c. However, it is also possible to use a retreating wing in which the rear edge 33 is arranged so as to be behind the extension line of the attachment portion 14a of the blade 14 in the rotation direction.

  Thus, by making the wing portion 14c have a divergent shape, the work area of the blade can be increased, and when the rotational speed is constant, a larger air volume than the banded blade can be obtained at the same warp angle. It is possible to improve the discharge efficiency of cut grass.

  Further, the wing portion 14c has a smaller warp angle than the conventional one. That is, as shown in FIGS. 6 and 8, the wing portion 14 c is configured as a curved surface having a low front end edge in the rotational direction and a high rear end edge. That is, in the side view, the shape is gradually curved upward from the front side in the rotational direction. In FIG. 8, the maximum length in the rotational direction of the wing part 14c is a wing length (chord length) B, and the wing part 14c. If the height from the lowest part to the highest part is the blade height A, the angle of the line connecting the lower end and the upper end with respect to the horizontal line is the warp angle C (the camber warp angle), and the blade height A is blown Or a certain amount of height is necessary because it must be housed in the mower casing 21. Therefore, the blade length (B) is changed. At this time, the warp angle C is expressed as tanC = A / B. In the present invention, the A / B value is configured to be 0.2 or less.

  With this configuration, the pressure applied to the surface of the blade 14c generated by the rotational movement of the blade 14 can be reduced as compared with the conventional case. In other words, conventionally, since a large camber is used, the pressure applied during rotation is large, but in the present invention, the wind can be smoothly released and the pressure can be reduced. Specifically, in the prior art, a large pressure was generated at the bent portion on the upper surface side as shown in FIG. 14, but in the present invention, a high portion appears on the front portion in the rotational direction of the upper surface as shown in FIG. As in the prior art, a large pressure is not generated, and the negative pressure distribution is not disturbed. Therefore, noise can also be reduced.

  And since the pressure concerning this braid | blade 14 is lowered | hung compared with the past, the tongue part 21a inside mower casing 21 and interference pressure are reduced, and ambient noise can be reduced. In addition, negative pressure is generated on the lower surface of the blade 14, but the wing portion 14c has a long and smooth warp, so that separation is suppressed and wake turbulence is also suppressed. This is caused by this turbulence. Turbulent sound can also be reduced, and noise can also be reduced. Furthermore, as shown in FIG. 9, the time waveform of the surface pressure of the blade 14 configured in this way is formed by periodically changing sharp peaks and valleys in the conventional waveform indicated by a thin solid line. The blade 14 of the present invention approaches the shape of a sine curve (sin waveform) as shown by a thick solid line, suppresses high-order frequency components of pressure fluctuations, and reduces noise in a frequency band that is easily felt by humans. Can do it.

  Further, the flow velocity around the blade 14 can be made smooth. That is, as shown in FIG. 10 of the present invention and FIG. 16 of the prior art, there is no fast flow portion at the rear of the upper surface of the blade 14, and the area of the slow flow portion is small. Therefore, by reducing the warp angle as in the present invention, the flow velocity is less disturbed and the noise can be reduced.

  Further, the rear edge 33 of the wing portion 14c is formed into a curved surface. That is, the cross-sectional shape of the rear end edge 33 is formed in an arc shape as shown in FIG. This arc shape may be a semicircle or a semi-oval. As a reference example, a wedge shape (pointed shape) can also be used as shown in FIG. The upper and lower centers of the wedge shape may be eccentric upward or downward, and the inclined surface may be a curved surface. Moreover, as shown in FIG. 13, it can also be set as a loose curve shape (ship bottom shape). This curve may be upside down. That is, when cut at right angles to the blade plane, the air flow was disturbed and caused noise, so by forming the rear edge in a chamfered or curved shape, the flow of wind became smooth, Noise can be reduced.

  Moreover, the outer peripheral edge 34 of the wing | blade part 14c is comprised in the curved surface. That is, the cross-sectional shape of the outer peripheral edge 34 is also formed in an arc shape as described above, but this arc shape may be a semicircular shape or a semi-oval shape. As a reference example, a wedge shape (pointed shape) can also be used as shown in FIG. Moreover, as shown in FIG. 13, it can also be made into ship bottom shape. Thus, when cut at right angles to the blade plane, the air flow was disturbed and caused noise, so by forming the rear end circle chamfered or curved, the flow of wind became smooth, Noise can be reduced.

  Further, a notch 35 is provided on the center side (drive shaft side) of the rear end portion in the rotational direction of the blade 14. That is, a notch 35 is formed on the rotation base side of the rear edge 33 of the wing portion 14c. Specifically, as shown in FIG. 4, the base end of the notch 35 on the rotation base side is located near the rear end edge in the rotation direction of the bent portion 14e. The notch direction toward the outer peripheral side has the same width as the mounting portion 14a and extends a predetermined length parallel to the front edge 32 to the outer periphery. Then, it extends forward from the rear end edge 33 at a predetermined length from the bent portion 14e in the right-angle direction, thereby forming a notch space. That is, the base side of the rear end edge 33 is cut out in a triangular shape. However, the shape of the notch is not limited to a sector shape or a polygonal shape, and the notch 35 is provided at the rear portion in the rotational direction on the base side of the wing portion 14c.

  By providing the notches in this way, noise can be reduced. The noise reduction effect becomes greater as the cutout 35 is cut out in the outer circumferential direction. Therefore, when it is desired to obtain a large air volume, the notch 35 is configured to be small to improve the blowing performance. Therefore, the size of the notch 35 is determined in consideration of the balance between noise reduction and air volume.

  Further, if the distance between the inner upper surface of the mower casing 21 and the upper end of the blade 14 is too small, the wind generated by the rotation of the blade 14 has a lower conveying ability due to the resistance of the inner surface of the mower casing 21. Also, turbulence increases and noise increases due to interference with the tongue 26. Conversely, if the distance between the inner upper surface of the mower casing 21 and the upper end of the blade 14 is increased, the noise is reduced, but the casing becomes larger, and if it is too large, the conveying ability to the grass collection bag 20 is reduced.

Therefore, when the experiment is performed using the blade 14 of the present invention while changing the relationship between the distance between the inner upper surface of the mower casing 21 and the upper end of the blade 14 and the noise, the result is as shown in FIG. As a result, when the distance between the inner upper surface of the mower casing 21 and the upper end of the blade is changed using a conventional belt-shaped blade, the noise decreases as the distance becomes narrower, as shown by a thin solid line. became. However, when the divergent forward blade of the present invention is used, the optimum interval is 45 mm, but when the blade of the present invention is used, a peak appears around 35 mm. That is, noise can be significantly reduced in the range of 26 mm to 42 mm. In other words, the relationship between the blade diameter (cutting width) E and the distance H, that is, the value of H / E is 0.13 or more and 1 or less, and noise can be reduced.

  The blade of the present invention is particularly useful as a cutting blade of a mower, and can be used in a mowing machine in which a blade is disposed in a casing and the grass is conveyed backward while cutting weeds and the like.

1 is an overall side view of a lawn mower to which the present invention is applied. Similarly, Lonemore overall plan view. The perspective view which looked at the more casing from the lower part. The top view of a braid | blade. The front view of a braid | blade. Side view of the blade. The perspective view of a braid | blade. The figure which shows the pressure state at the time of rotation. The figure which shows the change of the surface pressure of a braid | blade. The figure which shows the flow velocity around a braid | blade. Sectional drawing which made the blade rear end edge semicircular. Sectional drawing which made the blade rear end edge wedge shape. Sectional drawing which made the blade rear end edge into ship bottom shape. The figure which shows the relationship between the distance of a braid | blade upper end and a mower casing inner surface, and a noise level. The figure which shows the pressure state at the time of rotation of the conventional blade. The figure which shows the change of the surface pressure of the conventional blade.

Explanation of symbols

21 More casing 29 Shaft 14 Blade 33 Rear edge 34 Outer peripheral edge 35 Notch

Claims (6)

  A mower blade (14) which is fixed and rotated so as to project radially from a vertical shaft (29) projecting into the mower casing (21), the blade (14) going to the shaft (29) The mounting hole (30) is opened in the center, extends from the mounting hole (30) to both sides in the diameter direction with a predetermined width (D), and has a predetermined length (from the center (O) of the mounting hole (30) ( L) is a mounting portion (14a) extending in the horizontal direction, and both sides in the diameter direction of the mounting portion (14a) are bent upward in a “<” shape to form a rising portion (14b). A raised portion (14d) of the raised portion (14b) is bent upward in a direction perpendicular to the radial direction, and the outside of the raised portion (14b) is inclined with respect to the rotational direction, and the center (O) Form a mountain-folded folding part (14e) toward Forming a portion (14c), the rising portion (14b) having a trapezoidal shape in plan view, and the wing portion (14c) having a divergent shape from the center in the radial direction toward the outside in the plan view. More mower blades.   The blade of the mower according to claim 1, wherein the wing portion (14c) is formed in a curved surface having a low front end edge in the rotational direction and a high rear end edge, and gradually upward from the front side in the rotational direction toward the rear side in a side view. A curved shape, the maximum length in the rotational direction of the wing part (14c) is the wing length (B), the height from the lowest part to the highest part of the wing part (14c) is the wing height (A), and the horizontal line Where the angle of the line connecting the lower end and the upper end is the warp angle (C), the warp angle (C) is the angle at which the value of tanC = A / B is 0.2 or less. blade. 2. The blade of the mower according to claim 1, wherein the ratio (H) of the distance (H) between the inner upper surface of the mower casing (21) and the upper end of the blade (14) to the diameter (E) of the blade (14). / E), the ratio (H / E) is in the range of 0.13 or more and 1 or less .   The mower blade according to claim 1, wherein a notch (35) is provided on a center side of a rear end portion in the rotation direction of the wing portion (14c).   The mower blade according to claim 1, wherein the cross-sectional shape of the rear end edge (33) constituting the rear side in the rotational direction of the wing portion (14c) is a curved surface.   2. The mower blade according to claim 1, wherein the outer peripheral edge (34) constituting the outer peripheral portion of the blade (14) has a curved cross-sectional shape.