JP2008190693A - Gear box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear box stably usable for a long period by preventing the pressure in the gear box body from rising to prevent a grease from flowing out of the gear box for preventing gears from being worn and seized. <P>SOLUTION: This gear box 23 comprises a driving bevel gear 34 secured to a drive shaft 21, a driven bevel gear 37 meshed with the driving bevel gear 34 and secured to an output shaft 38, the box body 30 for containing the driving bevel gear 34 and the driven bevel gear 37, a first rolling bearing 33 rotatably supporting the driving bevel gear 34, and second and third rolling bearings 35, 36 rotatably supporting both ends of the output shaft 38. The first rolling bearing 33 is an opening bearing without a seal. <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 gear box 116 of the brush cutter 100 shown in FIG. 6, 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 rolling bearings 107, 109, A bearing structure that is rotatably supported by 110 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 102. For the first rolling bearing 107, a double-sided contact rubber seal or a sealed ball bearing with a metal shield plate is used, and for the third rolling bearing 110, a sealed ball bearing with a double-sided contact rubber seal is used. 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. 6, the box body 102 normally contains 70 to 100% of the grease G of the space capacity of the box body 102, 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 driving 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 102 increases.

  Therefore, when the pressure in the box body 102 increases, the grease G enters the inside of the third rolling bearing 110, and when the inside of the box body 102 including the third rolling bearing 110 is filled with the grease G, the grease G There has been a problem that a phenomenon of flowing out of 102 at a time occurs. 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.

The present invention has been made in view of the above-described problems, and its purpose is to prevent an increase in pressure in the gear box body, to prevent grease from flowing out of the gear box, and to wear and seize gears. An object of the present invention is to provide a gear box that 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 gear box comprising: 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 body;
The gear box, wherein the first rolling bearing is an open type bearing without a seal.
(2) The gear box according to (1), wherein the first rolling bearing includes at least three rolling elements, and a space for air bleeding is provided between the adjacent rolling elements.

  According to the gear box of the present invention, the first rolling bearing that supports the main driving gear with respect to the box body is an open type bearing without a seal, so that even if heat is generated in the box body, the box body The internal pressure is prevented from rising, the outflow of grease from the gear box is suppressed, the gear is prevented from being worn or seized, and can be used stably over a long period of time.

  Hereinafter, an 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.

  As shown in FIG. 1, in the brush cutter 10 of the present embodiment, a drive shaft 21 (see FIG. 2) disposed inside a pipe-shaped operation rod 20 is disposed at the end of the operation rod 20. It is driven and rotated by a two-cycle gasoline engine 22 as a driving source. 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. Here, the third rolling bearing 36 uses a sealed ball bearing with a double-sided contact rubber seal, while the first and second rolling bearings 33 and 35 use an open type bearing without a seal. The two rolling bearings 33 and 35 are lubricated by grease that lubricates the bevel gears 34 and 37.

  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.

  Further, heat is generated in the gear box main body 30 due to heat generation of the main driving bevel gear 34 and the driven bevel gear 37, stirring of grease, and the like, and the pressure in the gear box main body 30 is going to increase. However, the open first rolling bearing 33 is open. As a result, the pressure inside the gear box body 30 is prevented from being increased. As a result, it is possible to prevent a phenomenon in which the grease flows out to the outside at once due to the pressure increase in the gear box body 30 as in the prior art.

  In addition, as shown in FIG. 2, by reducing the number of rolling elements 33c of the first rolling bearing 33 to at least three and minimizing the number of rolling elements 33c as much as possible, the outer ring has a cross-sectional area through which air can pass. The space obtained by subtracting the cross-sectional areas of the rolling elements 33c and the cage 33d from the cross-sectional area between the inner ring 33b and the inner ring 33b can be increased.

  Therefore, according to the gear box 23 of the present embodiment, the first rolling bearing 33 that supports the main driving bevel gear 34 with respect to the box body 30 is an open type bearing without a seal, so that heat is generated in the gear box body 30. Even if it occurs, the pressure rise in the gear box body 30 is prevented, the outflow of grease from the gear box body 30 is suppressed, and the grease can be sufficiently supplied to the bevel gears 34 and 37, so that the bevel gears 34 and 37 are worn. It can be used stably over a long period of time by preventing seizure or the like.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
In the said embodiment, although the 1st rolling bearing was made into the deep groove ball bearing, it is not limited to this, Any of an angular ball bearing, a cylindrical roller bearing, and a needle roller bearing may be sufficient.
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. Further, the second rolling bearing 35 may be a sealed ball bearing with rubber seals on both sides.

(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 23 'as shown in FIG. In this gear box 23 ', instead of using the first rolling bearing as an open type bearing to release air from the gear box, a hole 50 having a diameter of 1 mm is provided in the upper portion of the gear box body 30 to enable air removal. For this reason, the first rolling bearing 107 is a bearing with a double-sided contact rubber seal as in the prior art, and the other configuration is the same as that of the above embodiment.

The third rolling bearing 36 is a sealed ball bearing with a seal having an outer diameter of 32 mm, an inner diameter of 12 mm, a width of 10 mm, and a contact rubber seal having no air holes on both sides. Lithium soap is increased inside the bearing. About 0.35 g of mineral oil-based grease (Shell Albany Grease S2 manufactured by Showa Shell Sekiyu KK) was sealed.

  The evaluation test was performed using a brush cutter (Example) in which the gear box 50 shown in FIG. 4 was incorporated and a brush cutter (Comparative Example) in which the conventional gear box shown in FIG. 6 was incorporated.

Further, in both the example and the comparative example, as shown in FIG. 5, the brush cutter 10 is fixed in a cage 95 made of angle steel 93 and expanded metal 94 with a nylon string 96 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. In Example 1, 100% (13.5 g) of the static space volume of the gear box was compared. In Example 1, about 80% (10.8 g) in the space volume ratio was sealed in the gear box, and in Comparative Example 2, about 50% (6.8 g) in the space volume ratio was sealed in the gear box. The test results are shown in Table 1 together with the test results of the comparative example.

  As shown in Table 1, in Example 1, there was no grease leakage after the 30-hour test, and no discoloration of the grease was observed. On the other hand, in the tests of Comparative Examples 1 and 2, although the amount of grease filling was smaller than that in Example 1, there was a grease leakage amount of 4 g or more at 12 hours and 15 hours of operation, and the discoloration of grease was also observed. It was. Therefore, it was confirmed that by removing the air from the gearbox, there was no grease leakage and the life of the grease was extended.

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 one Embodiment in FIG. It is sectional drawing of the 1st rolling bearing in FIG. It is a longitudinal cross-sectional view of the test gearbox for confirming the effect of this invention. 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 Drive shaft 22 2-cycle gasoline engine (drive source)
23 gear box 30 box main body 31 first cylinder part 32 second cylinder part 33 first rolling bearing 34 main driving bevel gear 35 second rolling bearing 36 third rolling bearing 37 driven bevel gear 38 output shaft S space volume

Claims (2)

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 that accommodates the main driving gear and the driven gear, and the main driving gear with respect to the box main body And a second rolling bearing that supports both ends of an output shaft that rotates with the driven gear with respect to the box body, and a gear box comprising:
The gear box, wherein the first rolling bearing is an open type bearing without a seal.   2. The gear box according to claim 1, wherein the first rolling bearing includes at least three rolling elements, and a space for air bleeding is provided between the adjacent rolling elements.

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