JP4244175B2 - Transmission shaft for brush cutter and method for manufacturing the same - Google Patents

Description

  The present invention relates to a transmission shaft that transmits the power of a prime mover to a blade in a brush cutter that cuts weeds by rotating the blade with the power of a prime mover such as a two-cycle engine.

  In the brush cutter, the prime mover is connected to the cutting blade via a transmission shaft, and the power generated by the prime mover is transmitted to the cutting blade via the transmission shaft to rotate the cutting blade (for example, Patent Document 1).

  The transmission shaft of such a brush cutter includes a transmission shaft main body and a connecting portion including a spline shaft or the like for connecting the transmission shaft provided at the end of the transmission shaft main body to another member. The transmission shaft main body is connected to the prime mover directly or via an intermediate member by this connecting portion, or is connected to the cutting blade directly or via an intermediate member by this connecting portion.

The transmission shaft of such a conventional brush cutter is, for example, joined to the end of a solid elongated rod-shaped transmission shaft main body by welding the above-mentioned connecting portion configured as a separate part, or a solid elongated rod. The end portion of the rod-shaped transmission shaft main body is directly machined to form a connecting portion there.
Japanese Utility Model Publication No. 7-5322

  However, the method of welding the connecting portion of the separate part to the transmission shaft main body is that the welding work is troublesome, and when the large torque acts on the transmission shaft, the welded portion breaks down due to insufficient strength of the welded portion. There is a risk that the power transmission shaft main body and the central axis of the connecting portion coincide with each other, and it is difficult to weld the shaft.

  Further, the method of machining the end portion of the transmission shaft main body and directly forming the connecting portion there is a problem that the processing is troublesome and takes time.

  In view of the above circumstances, the present invention provides a transmission shaft of a brush cutter and a method for manufacturing the same that can provide a connecting portion with a center axis aligned with the end of the transmission shaft body in a simple and short time with high accuracy. It is to provide.

In order to achieve the above object, the transmission shaft of the brush cutter according to the present invention,
A transmission shaft main body having a pipe-like end portion, a connecting portion for connecting to another member on one end side, and a fitting portion fitted into the pipe-like end portion on the other end side, the fitting portion having a cross section A joint body in which a non-circular rotation transmission portion and a locking portion having a smaller diameter than the portion located in the front of the insertion direction are formed,
The fitting portion of the joint body is fitted into the pipe-shaped end portion of the transmission shaft main body, and the rotation transmitting portion is in close contact with the inner surface of the pipe-shaped end portion so as not to rotate relative to the pipe-shaped end portion. The part which opposes a part protrudes toward this latching | locking part side, It is characterized by the above-mentioned.

  The rotation transmitting portion may have an outer diameter larger than an inner diameter of the pipe-shaped end portion, the rotation transmitting portion may be press-fitted into the pipe-shaped end portion, and an outer diameter may be equal to or less than the inner diameter of the pipe-shaped end portion. The rotation transmission portion is fitted into the pipe-shaped end portion, and the pipe-shaped end portion is pressed and deformed inward in the radial direction so as to be in close contact with the rotation transmission portion so as not to be relatively rotatable. good.

  The rotation transmission portion of the pipe-shaped end portion may be press-fitted and a widened portion extending radially outward may be reduced in diameter so that the outer diameter is equal to or less than the outer diameter of the intermediate portion of the transmission shaft main body. .

In order to achieve the above object, a method of manufacturing a transmission shaft of a brush cutter according to the present invention,
A transmission shaft main body having a pipe-shaped end portion, a connecting portion for connecting to another member on one end side, and a fitting portion fitted into the pipe-shaped end portion on the other end side, the fitting portion having a cross-section Using a non-circular rotation transmission portion and a joint body in which a locking portion having a smaller diameter than the portion located in the insertion direction front is formed,
The rotation transmission part of the joint body is fitted into the pipe-shaped end of the transmission shaft main body, and is brought into close contact with the inner surface of the pipe-shaped end so as not to be relatively rotatable.
A portion of the pipe-shaped end portion that faces the locking portion is protruded toward the locking portion.

  The rotation transmitting portion has an outer diameter larger than the inner diameter of the pipe-shaped end portion, and the rotation transmitting portion may be press-fitted into the pipe-shaped end portion, and the outer diameter is equal to or smaller than the inner diameter of the pipe-shaped end portion. The rotation transmitting portion may be fitted into the pipe-shaped end portion, and the pipe-shaped end portion may be pressed and deformed inward in the radial direction so as to be in close contact with the rotation transmitting portion so as not to allow relative rotation.

  The diameter of the widened portion of the pipe-shaped end portion that is press-fitted into the rotation transmission portion and expands outward in the radial direction may be reduced, and the outer diameter may be equal to or less than the outer diameter of the intermediate portion of the transmission shaft main body.

  Further, by using a die having an inner diameter substantially the same as the outer diameter of the intermediate portion of the transmission shaft main body, passing the expanded portion of the pipe-shaped end portion through the die, the outer portion of the expanded portion is removed. The diameter may be substantially the same as the outer diameter of the intermediate portion of the transmission shaft main body, and a portion of the pipe-shaped end facing the locking portion may be protruded toward the locking portion.

  According to the transmission shaft of the brush cutter and the manufacturing method thereof according to the present invention, as described above, the transmission shaft main body having the pipe-shaped end portion, and the connecting portion for connecting to the other member on the one end side, the other end side A fitting body having a fitting portion fitted into the pipe-shaped end portion, the fitting portion having a non-circular cross-sectional shape of the rotation transmitting portion and a locking portion having a smaller diameter than the portion positioned in the front in the fitting direction. The rotation transmitting portion is fitted into the pipe-shaped end portion of the transmission shaft main body so as to be in close contact with the inner surface of the pipe-shaped end portion so as not to be relatively rotatable, and the portion of the pipe-shaped end portion facing the locking portion is the engagement member. Since it protrudes toward the stop portion side, when manufacturing the prepared joint body, the fitting portion is inserted into the pipe-shaped end portion, and when the rotation transmitting portion is press-fitted, the pipe is simply piped thereafter. The part facing the locking part of the shape end is made to protrude toward the locking part Or, in case of simple insertion (insertion where the outer diameter of the rotation transmission part is less than the inner diameter of the pipe-shaped end and does not require a large pressure for fitting), the pipe-shaped end after swaging is inserted It is only necessary to reduce the diameter to make it closely contact the rotation transmission part and to project the part facing the locking part toward the locking part, and to form the connecting part by machining directly on the end of the conventional transmission shaft body Compared to the case where the connecting part of another part is joined to the end of the transmission shaft main body by welding or the like, it can be manufactured very easily and in a short time and at the same time, the rotation transmitting part can be Since it is fitted and attached in the part, the central axes of both can be easily matched with high accuracy.

  In particular, press the rotation transmission part into the pipe-shaped end and make the outer diameter of the pipe-shaped end expanded by press-fitting by diameter reduction using a die the same as the outer diameter of the intermediate part of the transmission shaft body. By doing so, it is very easy to achieve both uniformization of the outer diameter of the transmission shaft main body and prevention of disconnection of the connecting portion due to protrusion of the pipe-shaped end portion to the locking portion only by diameter reduction processing using the die. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a conceptual cross-sectional view showing a main part of a portable brush cutter provided with an embodiment of a transmission shaft of the present invention. The illustrated brush cutter includes an operation rod 1, a motor unit 2 indicated by an imaginary line, and a cutting blade unit 3.

  The operating rod 1 includes a pipe-shaped operating rod main body 4 and a transmission shaft 6 that is rotatably supported inside the operating rod main body 4 via a bearing 5. A bevel gear 7 connected to the transmission shaft 6 is rotatably supported at the distal end portion (cutting blade unit 3 side) of the operating rod 2, and the centrifugal clutch portion 8 is supported at the base end portion (prime unit 2 side). Is formed.

  The prime mover unit 2 is attached to the base end side of the operation rod 1 via a centrifugal clutch portion 8. The prime mover unit 2 accommodates a prime mover (not shown) that generates rotational force such as a two-cycle engine.

  The cutting blade unit 3 is attached to the distal end side of the operation rod 1. The cutting blade unit 3 includes a case 9, a cutting blade support shaft 10 rotatably supported in the case 9, a bevel gear 11 fixed to the base end side of the cutting blade support shaft 10, and a distal end side. The bevel gear 11 is meshed with the bevel gear 7 connected to the transmission shaft.

  Next, the transmission shaft 6 will be described in more detail. The transmission shaft 6 is composed of a transmission shaft main body 20 made of a long and narrow pipe of 1.5 m whose inner diameter and outer diameter are uniform in the axial direction, and joint bodies 21 attached to both ends of the transmission shaft main body 20. . Since the joint body 21 attached to both ends of the transmission shaft main body 20 and its attachment mode are the same, the joint body 21 on the cutting blade unit 3 side of the transmission shaft main body 2 and its attachment will be described below.

  2A is a view showing the end 20a of the transmission shaft main body 20 on the cutting blade unit 3 side and the joint body 21, and FIG. 2B is a right side view of the fitting portion 23 in FIG. 2A. As shown in the figure, the transmission shaft main body 20 is made of a metal pipe having an outer diameter of 8 mm and an inner diameter of 6 mm and having a uniform cross-sectional shape in the axial direction, and the end portion 20a is naturally pipe-shaped. On the other hand, the joint body 21 is fitted into the connecting portion 22 for connecting the transmission shaft main body 20 to the bevel gear 7 which is another member, and the pipe-shaped end portion 20a of the transmission shaft main body, and is connected to the pipe-shaped end portion 20a. It is comprised by the insertion part 23 to which it adheres. The fitting portion 23 includes a rotation transmitting portion 24 having a non-circular cross section, a locking portion 25 having a smaller diameter than the outer diameter of the rotation transmitting portion 24 located on the coupling portion 22 side of the rotation transmitting portion 24, and a rotation transmitting portion. A leading end guide portion 26 located on the leading end side of 24 (the side opposite to the connecting portion 22) is formed.

  In addition, as a metal pipe which comprises the said transmission shaft main body 20, the pipe made from steel and the pipe made from carbon steel for machine structures can be used conveniently. Also, the joint body 21 can be suitably made of metal, and further, alloy steel. Further, it is desirable that the surface of the rotation transmission portion 24 of the joint body is subjected to carburizing and quenching.

  The connecting portion 22 is constituted by a spline shaft in which a male spline that is engaged with a female spline formed on the shaft of the bevel gear 7 and transmits rotation to the bevel gear 7 is formed, and the rotation transmitting portion 24 is formed on the circumferential surface. It is comprised by the knurl part provided with the parallel knurl which has many protrusions extended in the axial direction in parallel with each other formed.

  The outer diameter of the connecting portion (male spline shaft) 22 is 7.9 mm. The rotation transmission portion (knurl portion) 24 is press-fitted into the pipe-shaped end portion 20a of the transmission shaft body, and the outer diameter thereof is 6.3 to 6.4 mm, which is larger than the inner diameter 6 mm of the pipe-shaped end portion 20a. The outer diameter of the locking portion 24 is 5.5 mm, which is smaller than the outer diameter of the rotation transmitting portion 24, and the outer diameter of the tip guide portion 25 is 6 mm, which is the same as the inner diameter of the pipe-shaped end portion 20a.

  Next, a method of fixing the joint body 21 to the pipe-shaped end 20a of the transmission shaft main body and providing the connecting portion 22 at the end of the transmission shaft main body 20 will be described.

  First, the knurled portion 24 that is the rotation transmitting portion of the joint body 21 is press-fitted into the pipe-shaped end portion 20a of the transmission shaft main body. At that time, the locking portion 25 is also press-fitted so as to be positioned in the pipe-shaped end portion 20a. In this press-fitting, a tip guide portion 26 having an outer diameter equal to the inner diameter of the pipe-shaped end portion 20a is first fitted into the pipe-shaped end portion 20a, whereby the pipe-shaped end portion 20a, that is, the transmission shaft main body 20, the knurled portion 24, and the like. Since the knurled portion 24 is press-fitted from this state, the center axes of the two are matched with high accuracy. Due to the press-fitting, the knurled portion 24 comes into close contact with the inner surface of the pipe-shaped end portion 20a, and both cannot be relatively rotated around the central axis.

  When press-fitting as described above, the outer diameter of the knurled portion 24 is larger than the inner diameter of the pipe-shaped end portion 20a, and the surface of the knurled portion 24 is carburized and hardened and has a higher hardness than the pipe-shaped end portion 20a. As shown in FIG. 3 showing the press-fitted state, the portion where the knurled portion 24 of the pipe-shaped end portion 20a is press-fitted expands radially outward, and the outer diameter of the portion is 8.2 to 8.3 mm. become.

  By the way, after connecting portions 22 are attached to both ends of the transmission shaft main body 20 to complete the transmission shaft 6, the transmission shaft 6 is inserted into a bearing 5 provided inside the operation rod main body 4 and into the operation rod main body 4. Be placed. Further, the transmission shaft main body 20 has an outer diameter of 8 mm and a length of 1.5 m which is very long and thin, and rotates at a high speed of 8000 to 12000 rpm. Therefore, vibration and vibration during rotation are large, so the inner diameter of the bearing 5 is the transmission shaft main body. The bearing is designed to have an inner diameter substantially equal to the outer diameter of 20 and with almost no gap. Therefore, if the pipe-shaped end portion 20 a is expanded radially outward as described above, the completed transmission shaft 6 cannot be inserted into the bearing 5.

  Therefore, after press-fitting the knurled portion 24, as shown in FIG. 3, a die 27 having an inner diameter of 8 mm is used, and the pipe-shaped end portion 20a expanded inside the die 27 is passed in the direction of arrow A by drawing or extruding. The portion expanded by press-fitting the end portion 20a is squeezed to reduce the diameter, and the outer diameter of the portion is also 8 mm, which is the same as the outer diameter of the intermediate portion of the transmission shaft body 20 (the portion excluding the pipe-shaped end portion). At the same time, by reducing the diameter of the die 27, the portion facing the locking portion 25 of the pipe-shaped end portion 20a, that is, the portion located outside the locking portion 25 is simultaneously locked. It protrudes inward in the radial direction toward 25 and enters the locking portion 25. This state is shown in FIG.

  In the transmission shaft 6 manufactured as described above, the knurled portion 24 is press-fitted into the pipe-shaped end portion 20a and then pressed from the outside by a diameter reducing process, so that the inner surfaces of the knurled portion 24 and the pipe-shaped end portion 20a Is securely engaged, can withstand a large rotational torque, and a locking portion 25 having a diameter smaller than that of the knurling portion 24 is formed next to the knurling portion 24, and a pipe is connected to the locking portion 25. Since the projecting end portion 20a protrudes and enters, sufficient strength against the disconnection of the joint body 21 due to the tensile force in the axial direction is sufficiently secured. That is, it has a sufficient strength against both rotation and slipping. Moreover, in manufacturing, it is only necessary to press-fit the fitting portion 23 of the joint body 21 into the pipe-shaped end portion 20a and then pass it through the die 27, so that the manufacturing is extremely simple, in a short time, and at low cost. In addition, since both are assembled by press fitting, the central axes of both can be easily matched with high accuracy. In particular, the method using the die 27 is extremely advantageous because the diameter can be reduced and the removal prevented at the same time and the relative rotation can be reliably prevented only by passing the die 27.

  In the above embodiment, the diameter 27 and the protrusion to the locking portion 25 are performed by passing the die 27. However, the diameter reduction and the protrusion to the locking portion 25 are not limited to this, and various types are possible. It can be done by a method. For example, the widened portion of the pipe-shaped end portion 20a is struck from the outside in the radial direction by the swaging method, thereby reducing the diameter of the entire widened portion and fixing the portion facing the locking portion 25 to the locking portion 25. You may make it protrude and enter.

  In reducing the diameter of the expanded portion expanded by the press-fitting, the diameter can be reduced to the same diameter as the outer diameter of the intermediate portion of the transmission shaft main body 20 or a smaller diameter. The diameter is not limited to the exact same diameter, but includes a diameter that can be regarded as substantially the same diameter.

  Next, another embodiment will be described. In the above-described method, when the knurled portion 24, which is a rotation transmission portion of the joint body, is fitted into the pipe-shaped end portion 20a, the outer diameter of the knurled portion 24 is made to be larger than the inner diameter of the pipe-shaped end portion 20a. However, this insertion is not necessarily limited to press-fitting, but is performed by simple insertion in which the outer diameter of the knurled portion 24 is equal to or smaller than the inner diameter of the pipe-shaped end portion 20a, and the fitting is performed without applying pressure. You can also.

  In this case, for example, as shown in FIG. 5, the outer diameter of the knurled portion 24 in which parallel knurls are formed on the peripheral surface is set to 6 mm, which is the same as the inner diameter of the pipe-shaped end portion 20 a, and the outer diameter of the locking portion 25 is set. The joint body 21 having the same configuration as the above-described joint body 21 is used except that the outer diameter of the knurled portion 24 is 5.5 mm, the outer diameter of the tip guide portion 26 is 5.7 mm. The knurled part 24 formed in such a size is simply fitted into the pipe-shaped end part 20a, and then the part where the knurled part 24 and the locking part 25 are located inside the pipe-shaped end part 20a is swaging. By hitting from the outside by the method, the inner surface of the pipe-like end portion 20a is firmly brought into close contact with the knurled portion 24, and the two portions are made relatively unrotatable around the central axis and are opposed to the locking portion 25. Projecting into the locking portion 25. As a result, as in the case of the press-fitting described above, it is possible to reliably prevent relative rotation and prevent slipping. However, the outer diameter of the pipe-shaped end 20a is slightly smaller than 8 mm by swaging, but if it is 8 mm or less, the subsequent insertion of the operating rod to the bearing 5 can be performed without any problem, and there is no problem.

  In this embodiment, the connecting portion 22 is constituted by a male spline shaft. However, the connecting portion 22 may be any member as long as it can be connected to other members so as to be able to transmit rotation. It may be a serration shaft which is a kind of shaft, or may be a prismatic shaft having a square cross section or a screw member.

  Further, in this embodiment, the rotation transmission part 24 is constituted by a parallel knurling part, but this rotation transmission part 24 has a non-circular cross section and is fitted (press-fit) into the pipe-shaped end 20a of the transmission shaft main body. Alternatively, it may be of any shape as long as it has a shape in which the pipe-shaped end portion 20a is in close contact with the inner surface of the pipe-shaped end portion 20a and cannot be rotated relative to the central axis.

  Moreover, in this embodiment, although the small diameter latching | locking part 25 is formed in the connection part 22 side of the knurl part 24, it is not necessarily required, For example, you may form in the center of a knurl part. Furthermore, the engaging portion 25 has a smaller diameter than the outer diameter of the portion located in the insertion direction front (right side in FIG. 2) of the engaging portion 25 in the fitting portion inserted into the pipe-shaped end portion 20a. Any material may be used as long as it is formed to be.

  Moreover, in the said embodiment, although the pipe is used as the transmission shaft main body 20, the transmission shaft main body 20 should just be a pipe shape at least, for example, only the edge part of a solid rod is formed in a pipe shape. It is also possible to use what is present.

  In the above embodiment, a disc-shaped round blade is used as the cutting blade. However, the cutting blade may be any blade that can cut weeds and the like by rotating. It may be composed of one or two string-like nylon cords having one end connected to the tip of the shaft 10.

  In the present invention, the fitting portion 23 is provided with a small-diameter locking portion 25, and the pipe-like end portion 20a protrudes into the locking portion 25 to prevent it from coming off. The knurled portion 24 is formed as a knurled knurl formed by intersecting two kinds of protrusions extending obliquely with respect to the axial direction on the peripheral surface as shown in FIG. The outer diameter of the knurled portion 24 is made equal to or smaller than the inner diameter of the pipe-shaped end portion 20a, and the knurled portion 24 is simply fitted into the pipe-shaped end portion 20a, and then the pipe-shaped end portion 20a is swung or the like. It is possible to employ a method in which the inner surface of the pipe-shaped end portion 20a is brought into close contact with the twill knurl and bites in from the radially outer side toward the inner side. As a result, relative rotation prevention and retaining can be achieved at the same time.

Schematic cross section showing an example of a brush cutter (A) is a figure which shows the transmission shaft main body in one Embodiment of the transmission shaft of this invention isolate | separated from a coupling body, (b) is a right view of the insertion part of the coupling body in (a). The figure which shows the state which press-fit the fitting part of the coupling body to the edge part of a transmission shaft main body. The figure which shows the state which diameter-reduced the edge part of the transmission shaft main body expanded by the press fit of the insertion part. The figure which isolate | separates and shows the transmission shaft main body and coupling body in other embodiment of this invention. The figure which shows the coupling body which formed the Aya eyes knurl as an insertion part

Explanation of symbols

1 Operation rod 2 Motor unit 3 Cutting blade unit 5 Bearing 6 Transmission shaft 7 Separate member (bevel gear)
DESCRIPTION OF SYMBOLS 12 Cutting blade 20 Transmission shaft main body 20a Pipe-shaped edge part 21 Joint body 22 Connection part 23 Insertion part 24 Rotation transmission part 25 Locking part 27 Dies

Claims (3)

A transmission shaft main body having a pipe-like end portion, a connecting portion for connecting to another member on one end side, and a fitting portion fitted into the pipe-like end portion on the other end side, the fitting portion having a cross section A joint body in which a non-circular rotation transmission portion and a locking portion having a smaller diameter than the portion located in the front of the insertion direction are formed,
The outer diameter of the rotation transmitting portion is larger than the inner diameter of the pipe shaped end, with the rotation transmission portion is press - fit into the tubular end portion in close contact relative rotation impossible with the inner surface of the pipe shaped end, portion in which the locking portion is opposed to the locking portion of being fitted into the tubular end portion the pipe-shaped end protrudes toward the locking portion,
The rotation transmission part of the pipe-shaped end part is press-fitted and the widened part that has expanded radially outward is reduced in diameter so that the outer diameter is equal to or less than the outer diameter of the intermediate part of the transmission shaft main body . Brush shaft transmission shaft characterized by A transmission shaft main body having a pipe-like end portion, a connecting portion for connecting to another member on one end side, and a fitting portion fitted into the pipe-like end portion on the other end side, the fitting portion having a cross section Using a non-circular rotation transmission portion and a joint body in which a locking portion having a smaller diameter than the portion located in the insertion direction front is formed,
The outer diameter of the rotation transmitting portion is larger than the inner diameter of the pipe shaped end, Rutotomoni the rotation transmitting unit by entering pressure to the tubular end portion is adhered to non-rotatingly on the inner surface of the pipe shaped end , The engaging portion is inserted into the pipe-shaped end portion, and the portion of the pipe-shaped end portion that faces the engaging portion is protruded toward the engaging portion side ,
Wherein to Rukoto to not more than the outside diameter of the intermediate portion of the transmission shaft body the outer diameter of the expanded portion of the rotation transmitting portion is spread radially outwardly is press-fitted in the tubular end portion with diameter reduction A method of manufacturing a transmission shaft of a brush cutter. By using a die having an inner diameter substantially the same as the outer diameter of the intermediate portion of the transmission shaft main body, the outer diameter of the expanded portion is reduced by passing the expanded portion of the pipe-shaped end portion through the die. claim 2, wherein the projecting the portion facing to the engaging portion of the pipe-shaped ends as well as substantially equal to the outer diameter of the intermediate portion of the transmission shaft body toward the locking portion Method of transmission shaft of brush cutter.

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