JP2008157291A - Bush cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear box to be stably used for a long time by improving supply of the grease to a bevel gear and restricting heat generation to prevent leakage of grease from a gear box and to prevent abrasion and seizure of gears. <P>SOLUTION: A gear box 23 comprises a driving bevel gear 34 fixed to a driving shaft 21, a driven bevel gear 37 engaged with the driving bevel gear 34 and fixed to an output shaft 38, a box main body 30 for housing the driving bevel gear 34 and the driven bevel gear 37, a first rolling bearing 33 rotatably supporting the driving bevel gear 34, and a second and a third rolling bearings 35 and 36 rotatably supporting both ends of the output shaft 38. A space capacity S surrounded by the box main body 30 and the first, the second and the third rolling bearings 33, 35 and 36 and to be filled with the lubricant is adjusted to be reduced by a large-diameter part 44 of the output shaft 38. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gear box, and more particularly, to a gear box that transmits power to an output shaft that is arranged in a vertical direction when in use, such as a brush cutter or a lawn mower.

  A brush cutter generally includes a drive shaft disposed inside a pipe-shaped operation rod, an output shaft provided with a cutting blade at a tip, and a bevel gear disposed between the drive shaft and the output shaft. The cutting blade is rotationally driven by the power transmitted from the drive shaft (see, for example, Patent Document 1). In the brush cutter described in Patent Document 1, a bearing structure of a brush cutter that lubricates a slide bearing that supports a bevel gear with grease enclosed in a gear box that houses the bevel gear is known.

  Further, in the brush cutter 100 shown in FIG. 10, in order to enable high-speed rotation, the main drive bevel gear 108 that rotates together with the drive shaft 106 and the output shaft 112 to which the driven bevel gear 111 is attached are freely rotatable by rolling bearings 107, 109, and 110. A bearing structure for supporting the motor is known.

The box body 102 of the brush cutter 100 includes a first tube portion 104 into which the operation rod 103 is fitted, and a second tube portion 105 formed integrally with the first tube portion 104. The drive shaft 106 disposed in the operation rod 103 is rotatably supported by a first rolling bearing 107 provided in the first cylindrical portion 104, and a main driving bevel gear 108 is fixed to the tip. The second and third rolling bearings 109 and 110 provided on the second cylindrical portion 105 support the output shaft 112 to which the driven bevel gear 111 is fixed in a vertical direction so that the output shaft 112 can rotate freely. The driven bevel gear 111 meshes with the main drive bevel gear 108 and is lubricated by the grease G enclosed in the box body 116. The third rolling bearing 110 is a sealed ball bearing with double-sided contact rubber seal, and leakage of the encapsulated grease G is prevented. A cutting blade 114 is fixed to the tip of the output shaft 112 by a fixture 115.
JP-A-2005-24009

By the way, in the brush cutter 100 as shown in FIG. 10, the box body 116 normally contains 70 to 100% of grease G of the space capacity of the box body 116, and the vibration is relatively large (not shown). A two-cycle gasoline engine or the like is mainly used as a drive source, and rotates at a high speed of about 9000 min ⁻¹ . For this reason, the main bevel gear 108 and the driven bevel gear 111 are vibrated with high speed rotation to generate frictional heat, and the pressure in the box body 116 increases.

  When the pressure in the box body 116 rises, the grease G enters the inside of the third rolling bearing 110, and when the inside of the box body 116 including the third rolling bearing 110 is filled with the grease G, the grease G flows out from the gear box 116. There was a problem to do. Further, since the grease G is softened by the heat generated by the stirring of the grease G, the grease G easily enters the third rolling bearing 110 and easily flows out to the outside.

  The outflow of the grease G may cause lubrication of the main driving bevel gear 108 and the driven bevel gear 111 and may cause wear of the gear, and in an extreme case, seizure may occur. Further, in order to suppress the outflow of the grease G, it is conceivable to reduce the amount of the grease G to be enclosed with respect to the space volume in the box body. In this case, the main driving bevel gear 108 and the driven bevel gear 111 are enclosed. This is not preferable because the frequency of contact with the applied grease G is reduced, the gear life is reduced, and the grease G needs to be sealed frequently.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to improve the supply of grease to the gear, suppress heat generation and prevent grease leakage from the gear box, and wear and wear of the gear. An object of the present invention is to provide a gear box that prevents sticking and the like and can be used stably over a long period of time.

The above object of the present invention can be achieved by the following constitution.
(1) A main driving gear that is rotated by a driving shaft connected to a driving source, a driven gear that meshes with the main driving gear, a box main body that accommodates the main driving gear and the driven gear, and the box main body A first rolling bearing that supports the main driving gear; and second and third rolling bearings that support both ends of an output shaft that rotates with the driven gear with respect to the box main body, the box main body and the first rolling bearing A gear box in which a lubricant is enclosed in a space volume surrounded by the second and third rolling bearings,
The space volume is adjusted by at least one of the drive shaft, the output shaft, and the third rolling bearing.
(2) The output shaft has a large-diameter portion between the driven gear and the third rolling bearing that is larger in diameter than the outer diameter of the inner ring of the third rolling bearing (1). Gearbox as described in.
(3) The box body includes a first tube portion in which an outer ring of the first rolling bearing is fitted, and a second tube portion in which the outer ring of the third rolling bearing is fitted,
The gear box according to (1), wherein an upper end surface in the axial direction of the third rolling bearing protrudes above a connection position between the first cylindrical portion and the second cylindrical portion.
(4) The gear box according to (1), wherein the drive shaft extends toward the output shaft in an axial direction from a tip side contact position between the main driving gear and the driven gear.
(5) The gear box according to any one of (1) to (4), which is applied to any one of a brush cutter, a lawn mower, a power tool, and a concrete drill.

  According to the gear box of the present invention, the space volume surrounded by the box main body that accommodates the main driving gear and the driven gear and the first, second, and third rolling bearings has the drive shaft, the output shaft, and the third rolling bearing. Therefore, by reducing the volume of the space, the enclosed lubricant can be easily rotated around the gear to maintain good lubrication of the gear, thereby suppressing heat generation. Thus, it is possible to prevent the leakage of the lubricant from the gear box and to prevent the gear from being damaged, thereby extending the life of the gear box.

  Hereinafter, each embodiment in which a gearbox according to the present invention is applied to a brush cutter will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIG. 1, the brush cutter 10 is a drive source in which a drive shaft 21 (see FIG. 2) disposed inside a pipe-shaped operation rod 20 is disposed at an end of the operation rod 20. It is driven by a two-cycle gasoline engine 22 and rotates. The rotation of the drive shaft 21 is transmitted to the cutting blade 24 through the gear box 23. An operation handle 25 is disposed on the operation rod 20 so as to be orthogonal to the operation rod 20, and a protective cover 26 is fixed in the vicinity of the cutting blade 24, so that injuries caused by inadvertent contact with the cutting blade 24 are caused. It is preventing.

  As shown in FIG. 2, the box main body 30 constituting the gear box 23 is integrally formed integrally with a second cylindrical part 32 having a substantially bottomed cylindrical shape and a side surface of the second cylindrical part 32 obliquely upward. And the first tube portion 31. An operating rod 20 in which the drive shaft 21 is rotatably disposed is fitted in the first cylindrical portion 31. The main driving bevel gear (main driving gear) 34 fixed to the drive shaft 21 is rotatably supported by a first rolling bearing 33 in which an outer ring 33 a is fitted in the first cylindrical portion 31.

  An outer ring 35a of the second rolling bearing 35 is fitted into the upper portion of the second cylindrical portion 32, and an outer ring 36a of the third rolling bearing 36 is fitted into the lower portion thereof, and both ends of the output shaft 38 are connected to the second rolling bearing 35 and the second rolling bearing 35. A third rolling bearing 36 is rotatably supported by the second cylindrical portion 32. A driven bevel gear (driven gear) 37 that is disposed between the second rolling bearing 35 and the third rolling bearing 36 and meshes with the main driving bevel gear 34 is fixed to the output shaft 38. A cutting blade 24 sandwiched between fixtures 41 and 42 is fixed to one end of an output shaft 38 projecting downward from the third rolling bearing 36 by a bolt 43.

  Grease as a lubricant is enclosed in the space volume S surrounded by the box body 30 and the first, second, and third rolling bearings 33, 35, and 36. The first, second, and third rolling bearings 33, 35, and 36 are sealed ball bearings with rubber seals on both sides, and prevent leakage of grease sealed in the box body 30.

  Further, the output shaft 38 of the gear box 23 is formed with a large diameter portion 44 having a diameter D larger than the outer diameter of the inner ring 36b of the third rolling bearing 36 between the driven bevel gear 37 and the third rolling bearing 36. ing. That is, the large diameter portion 44 is adjusted so that the space volume S of the gear box 50 is smaller than the conventional one as shown in FIG.

  When the brush cutter 10 starts the two-cycle gasoline engine 22 and rotates the drive shaft 21, the rotation is transmitted to the output shaft 38 through the main driving bevel gear 34 and the driven bevel gear 37 to rotate the cutting blade 24. At this time, the grease sealed in the space volume S of the box body 30 lubricates the main driving bevel gear 34, the driven bevel gear 37, the first, second, and third rolling bearings 33, 35, and 36.

  Here, in this embodiment, even if the amount of grease filled is smaller than that in the conventional structure of FIG. 10, the grease accumulated below is raised by the large diameter portion 44 and can be sufficiently adhered to the main driving bevel gear 34. . Further, the grease is supplied to a driven bevel gear 37 that meshes with the main driving bevel gear 34 (in the direction of arrow A), and lubricates the meshing surfaces of the main driving bevel gear 34 and the driven bevel gear 37. In addition, the grease that has lubricated the driven bevel gear 37 flows down in the direction of arrow B in the drawing, accumulates again on the upper surface of the slinger 44, flows in the direction of arrow C, and is supplied to the main drive bevel gear 34.

  As described above, according to the gear box 23 of the present embodiment, the space volume S of the gear box 23 is reduced by the large diameter portion 44 of the output shaft 38, so that it is compared with a gear box having a large space volume. Thus, the grease is easily supplied to the main driving bevel gear 34 and the driven bevel gear 37 and can be sufficiently lubricated, and the temperature rise is suppressed. Accordingly, grease leakage from the gear box 23 is prevented, and wear of the bevel gears 34 and 37 is prevented, so that the gear box 23 can be used stably over a long period of time.

  In addition, the shape of the large diameter part of an output shaft is not limited to this, As shown in FIG. 3, it can deform | transform into various shapes. The large-diameter portion 44a shown in FIG. 3A has a shoulder 45a having a tapered shape, thereby increasing the diameter D of the large-diameter portion 44a while avoiding interference with the main driving bevel gear 34, thereby effectively increasing the space volume. S is narrowed. The large-diameter portion 44b shown in FIG. 3 (b) is formed by tapering the entire large-diameter portion to facilitate processing. The large-diameter portion 44c shown in FIG. 3 (c) is a large-diameter portion. In order to avoid interference with the main driving bevel gear 34, the upper portion of the shaft is made a small diameter. Further, in the large diameter portion 44d shown in FIG. 3 (d), a shoulder portion 45b is notched in an arc shape so as to avoid interference with the main driving bevel gear 34. That is, any of the large-diameter portions 44a, 44b, 44c, and 44d has a shape that maximizes the diameter D while avoiding interference with the main driving bevel gear 34, thereby effectively reducing the space volume S of the gear box 50. It is narrowed to.

(Second Embodiment)
Next, a gear box according to a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

  As shown in FIG. 4, the gear box 60 of the second embodiment is formed such that the height H of the second cylindrical portion 32 of the box body 61 is low. Accordingly, the third rolling bearing 36 is disposed such that the upper end surface 62 in the axial direction protrudes above the connection position JP between the first cylindrical portion 31 and the second cylindrical portion 32. That is, the third rolling bearing 36 is disposed closer to the main driving bevel gear 34 than the third rolling bearing 36 of the gear box 23 of the first embodiment, so that the space volume S of the gear box 60 is effective. Therefore, the grease is easily supplied to the bevel gears 34 and 37.

As shown in FIG. 4, in the first cylindrical portion 31 of the box body 61, in the vicinity of the connection position JP with the second cylindrical portion 32, below the lower fitting position with the outer ring 33 a of the first rolling bearing 33. A horizontal plane is formed. As a result, the space volume S of the gear box 60 is more effectively narrowed, and the second cylindrical portion 32 can further secure a fitting surface with the outer ring 36a of the third rolling bearing 36, so that the outer ring 36a and the box The occurrence of fretting wear and creep with the main body 61 can be suppressed, and the third rolling bearing 36 can be prevented from coming off.
Since other configurations and effects are the same as those of the first embodiment, description thereof will be omitted.

(Third embodiment)
Next, a gear box according to a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

As shown in FIG. 5, the gear box 70 of the third embodiment differs from the gear box 23 of the first embodiment in the shape of the fixture 71 that holds the cutting blade 24. The fixture 71 is formed such that the length L of the small-diameter cylindrical portion 72 that contacts the inner ring 36b of the third rolling bearing 36 is long. Accordingly, the third rolling bearing 36 is positioned above the main drive bevel gear 34 as compared with the gear box 23 of the first embodiment, and the axial upper end surface 62 is connected to the first cylindrical portion 31 and the first cylindrical portion 31. It is arranged so as to protrude above the connection position JP with the two cylindrical portions 32, and the outer peripheral surface of the outer ring is also partially exposed. Therefore, the space volume S of the gear box 70 is effectively reduced, and the grease is easily supplied to the bevel gears 34 and 37.
Since other configurations and effects are the same as those of the first embodiment, description thereof will be omitted.

(Fourth embodiment)
Next, a gear box according to a fourth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

As shown in FIG. 6, the third rolling bearing 81 incorporated in the gear box 80 of the fourth embodiment is a bearing with a special dimension having a width W larger than the width of the rolling bearing defined by the JIS standard. In particular, in the present embodiment, the width W of the third rolling bearing 80 is set to be larger than the radial sectional dimension {(outer diameter−inner diameter) / 2}. Thereby, the axial upper end surface 62 of the third rolling bearing 81 is disposed so as to protrude above the connection position JP between the first cylindrical portion 31 and the second cylindrical portion 32. Accordingly, since the axial end portion 62 of the third rolling bearing 81 is disposed at a position close to the main driving bevel gear 34, the space volume S of the gear box 80 is effectively reduced, and the grease is supplied to the bevel gears 34 and 37. Is easily done.
Since other configurations and effects are the same as those of the first embodiment, description thereof will be omitted.

(Fifth embodiment)
Next, a gear box according to a fifth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the part equivalent to the said embodiment, and description is abbreviate | omitted or simplified.

In the gear box 90 of the fifth embodiment, the drive shaft 91 extends to the output shaft side in the axial direction from the tip side contact position P between the main driving bevel gear 34 and the driven bevel gear 37. As a result, the space volume S of the gear box 90 is narrowed by the drive shaft 91, and the supply of grease to the bevel gears 34 and 37 is facilitated. It should be noted that not only the drive shaft 91 but also the drive shaft 21 and the main driving bevel gear 34 may be arranged close to the output shaft 38. In this case, the space volume S of the gear box 90 can be further reduced. .
Since other configurations and effects are the same as those of the first embodiment, description thereof will be omitted.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. Further, the above-described embodiments can be appropriately combined within a practicable range.
For example, in the above embodiment, the gearbox of the present invention has been described as applied to a brush cutter, but the present invention is not limited to this, and the output shaft of the lawn mower, power tool, concrete drill, etc. is longitudinal. It can be applied to a gear box arranged in the above, and has the same effect.
Further, the main drive and driven gear of the present invention are not limited to the main drive and driven bevel gear of the present embodiment, but may have other gear configurations.

(Evaluation test)
In order to confirm the effect of the present invention, an evaluation test was performed using a brush cutter incorporating a gear box 50 to which the slinger 51 shown in FIG. It was. In addition, the same code | symbol is attached | subjected about the part equivalent to 1st Embodiment of the gear box 50, and description is abbreviate | omitted or simplified.

  As shown in FIG. 8, in the gear box 50, a resin slinger 51 is disposed on the third rolling bearing 36 and around the output shaft 38 so as not to rotate. The slinger 51 is arranged so as to be as close as possible within a range in which the slinger 51 is partially fitted to the second cylindrical portion 32 and does not contact the main drive bevel gear 34. Thus, the slinger 51 has a smaller space volume S surrounded by the box body 30 and the first, second, and third rolling bearings 33, 35, and 36 than the conventional one shown in FIG. It is adjusted.

  The third rolling bearing is a sealed ball bearing with an outer diameter of 32 mm, an inner diameter of 12 mm, a width of 10 mm, and a contact rubber seal without air holes attached on both sides, and lithium soap is used as a thickener inside the bearing. About 0.4 g of mineral oil-based grease (Shell Albania Grease S2 manufactured by Showa Shell Sekiyu KK) was sealed.

  The evaluation test was performed using a brush cutter (Example) incorporating the gear box 50 shown in FIG. 8 and a brush cutter (Comparative Example) incorporating the conventional gear box shown in FIG.

In both the example and the comparative example, as shown in FIG. 9, the brush cutter 10 is fixed with a nylon string 96 in a cage 95 made of angle steel 93 and expanded metal 94, and cut by a two-cycle gasoline engine 22. The blade 24 was continuously rotated. In all the tests, the ambient temperature was room temperature, the weight of the grease leaked from the gear box was measured after the cutting blade 24 was continuously rotated at a rotation speed of 8000 min ⁻¹ for a maximum of 30 hours, and whether or not the grease was colored. Was visually evaluated.

  Duplexes EP No. 2 (manufactured by Kyodo Yushi Co., Ltd.) was used for gear lubrication of the gear box, and 50% and 80% of the space volume ratio was enclosed in the gear box. In addition, the space volume of the gear box of an Example is about 2.3 cc less than the space volume of the gear box of a comparative example, and this is equivalent to about 2.1 g in grease weight. For the examples, two sets of gearboxes each filled with 50% and 80% grease in space volume ratio were prepared, and the test was performed twice, for a total of four times. The test results are shown in Table 1 together with the test results of the comparative example.

  As shown in Table 1, according to the test results of the four times of the examples, the amount of grease leakage after the test for 30 hours was a very small amount of 0.07 g or less, and it was a level with no problem. In addition, no discoloration of the grease was observed, indicating that the grease was sufficiently supplied to the bevel gear and good lubrication was performed. On the other hand, in the test of the comparative example, the grease leakage amount of 4 g or more was observed at the operation time of 12 hours and 15 hours, and discoloration of the grease was observed, so the test was stopped. Therefore, it was confirmed that the life of the grease was extended by adjusting the space volume of the gear box smaller than before.

1 is an overall perspective view of a brush cutter to which a gear box of the present invention is applied. It is a longitudinal cross-sectional view of the gear box of 1st Embodiment in FIG. It is a principal part side view of the modification of the output shaft in FIG. It is a longitudinal cross-sectional view of the gear box of 2nd Embodiment. It is a longitudinal cross-sectional view of the gear box of 3rd Embodiment. It is a longitudinal cross-sectional view of the gear box of 4th Embodiment. It is a longitudinal cross-sectional view of the gear box of 5th Embodiment. It is a longitudinal cross-sectional view of the gear box of 6th Embodiment. It is a schematic block diagram of the brush cutter testing device. It is a longitudinal cross-sectional view of a brush cutter having a conventional gear box.

Explanation of symbols

10 Brush cutter 21, 91 Drive shaft 22 2-cycle gasoline engine (drive source)
23, 50, 60, 70, 80, 90 Gear box 30, 61 Box body 31 First cylinder part 32 Second cylinder part 33 First rolling bearing 34 Main bevel gear 35 Second rolling bearing 36, 81 Third rolling bearing 36b Inner ring 37 Driven bevel gear 38 Output shaft 44, 44a, 44b, 44c, 44d Large diameter portion 62 Axial upper end surface JP Connection position S between first and second cylinder portions S Space volume

The present invention relates to a brush cutter .

The present invention has been made in view of the above-described problems, and an object of the present invention is to improve the supply of grease to the gear, suppress heat generation and prevent grease leakage from the gear box, and wear and wear of the gear. An object of the present invention is to provide a brush cutter that prevents sticking and the like and can be used stably over a long period of time.

The above object of the present invention can be achieved by the following constitution.
(1) a drive shaft connected to the drive source ;
A main driving bevel gear that rotates together with the drive shaft,
And the driven bevel gear to the main motion bevel gear meshing,
A bottomed cylindrical gear box body housing said main driving bevel gear and the driven bevel gear,
An output shaft for rotating the disc-shaped cutting blade at a point rotated together with the driven bevel gear in position of the center axis, protruding from the gear box casing in a bottomed cylindrical space of the gear box body,
A cylindrical portion having a cylindrical space communicating with the bottomed cylindrical space of the gear box body, and extending along the drive shaft disposed in the cylindrical space;
The main driving bevel gear so that it can rotate in a bottomed cylindrical space of the gear box body, a first ball bearing for supporting the rotation of the main drive bevel gear in position to close the ends of the gear box body side of the tubular portion When,
A second ball bearing that supports rotation of the output shaft at a bottom-side position in the bottomed cylindrical space of the gear box body;
A third ball bearing with seal that supports the rotation of the output shaft in cooperation with the second ball bearing at a position that closes the opening in the bottomed cylindrical space of the gear box body ;
A pair of fixtures inserted between the third ball bearing and the output shaft projecting outward of the gear box body with the cutting blade interposed therebetween;
A fixture for fixing the fixture to the output shaft so that the fixture on the third ball bearing side contacts the inner ring of the third ball bearing;
With
The fixture on the third ball bearing side includes a small-diameter cylindrical portion that protrudes toward the third ball bearing and a tip of which abuts against an inner ring of the third ball bearing, and a protruding length of the small-diameter cylindrical portion. Is set to a predetermined length to reduce the bottomed cylindrical space inside the first ball bearing, the second ball bearing, and the third ball bearing of the gear box body, and the reduced bottomed cylindrical space bush cutter lubricant, characterized in Tei Rukoto sealed in.

In the brush cutter according to the present invention, the space surrounded by the box main body that accommodates the main driving gear and the driven gear and the first, second, and third ball bearings is reduced. Therefore, the lubricant enclosed in the space is used as the gear. Easy to rotate and maintain good gear lubrication, thereby suppressing heat generation and preventing lubricant leakage from the gearbox, and preventing gear damage and extending the life of the gearbox Can do.

The above object of the present invention can be achieved by the following constitution.
(1) a drive shaft connected to the drive source;
A primary bevel gear that rotates with the drive shaft;
A driven bevel gear meshing with the main drive bevel gear;
A bottomed cylindrical gear box body that houses the main bevel gear and the driven bevel gear;
An output shaft that rotates together with the driven bevel gear at a position of a central axis in a bottomed cylindrical space of the gear box body, and rotates a disk-shaped cutting blade at a position protruding from the gear box body;
A cylindrical portion having a cylindrical space communicating with the bottomed cylindrical space of the gear box body, and extending along the drive shaft disposed in the cylindrical space;
A first ball bearing that supports rotation of the main driving bevel gear at a position that closes an end of the cylindrical portion on the gear box main body side so that the main driving bevel gear can rotate in a bottomed cylindrical space of the gear box main body; ,
A second ball bearing that supports rotation of the output shaft at a bottom-side position in the bottomed cylindrical space of the gear box body;
A third ball bearing with seal that supports the rotation of the output shaft in cooperation with the second ball bearing at a position that closes the opening in the bottomed cylindrical space of the gear box body;
A pair of fixtures inserted between the third ball bearing and the output shaft projecting outward of the gear box body with the cutting blade interposed therebetween;
A fixture for fixing the fixture to the output shaft so that the fixture on the third ball bearing side contacts the inner ring of the third ball bearing;
With
Lubricant is enclosed in the bottomed cylindrical space,
The fixture on the third ball bearing side includes a small-diameter cylindrical portion that protrudes toward the third ball bearing and a tip of which abuts against an inner ring of the third ball bearing, and a protruding length of the small-diameter cylindrical portion. Is arranged inside the first ball bearing, the second ball bearing, and the third ball bearing of the gear box body so that the lubricant collected below the bottomed cylindrical space can adhere to at least the main driving bevel gear. brush cutter, characterized in that it is set to a length that causes reduction of a bottomed cylindrical space.

Claims (5)

A main driving gear rotated by a driving shaft connected to a driving source, a driven gear meshing with the main driving gear, a box main body containing the main driving gear and the driven gear, and the main driving gear with respect to the box main body A first rolling bearing that supports the box body, and second and third rolling bearings that support both ends of the output shaft that rotates with the driven gear relative to the box body, the box body and the first and second rolling bearings. And a gear box in which a lubricant is enclosed in a space volume surrounded by the third rolling bearing,
The space volume is adjusted by at least one of the drive shaft, the output shaft, and the third rolling bearing.   The said output shaft has a large diameter part larger diameter than the outer diameter of the inner ring | wheel of a said 3rd rolling bearing between the said driven gear and the said 3rd rolling bearing. Gear box. The box body has a first tube portion in which an outer ring of the first rolling bearing is fitted, and a second tube portion in which an outer ring of the third rolling bearing is fitted,
2. The gear box according to claim 1, wherein an upper end surface in the axial direction of the third rolling bearing protrudes upward from a connection position between the first cylindrical portion and the second cylindrical portion.   2. The gear box according to claim 1, wherein the drive shaft extends toward the output shaft in an axial direction from a tip side contact position between the main driving gear and the driven gear.   The gearbox according to any one of claims 1 to 4, wherein the gearbox is applied to any one of a brush cutter, a lawn mower, a power tool, and a concrete drill.

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