JP2004129551A - Bush cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bush cutter with which clamping force of a brake band on a clutch drum is adjusted. <P>SOLUTION: The bush cutter is equipped with a centrifugal clutch having the clutch drum on a power transmission route between an internal combustion engine and a reaping blade and a damping device for braking the rotation of the clutch drum. The damping device has the brake band arranged along the outer peripheral surface of the clutch drum and its release means. The release means has a first shake member which is urged to an initial position by a tension spring and is moved to a shake position by an operation lever. The brake band has one end connected to the first shake member, is clamped by he clutch drum when the first shake member exists at the initial position and is loosened when at the shake position, The damping device has an adjusting means for adjusting clamping force of the clutch drum by the brake band. The adjusting means has a base end position changing member to which the base end of the tension spring is connected and a screw which moves the base end position changing member in the direction to pull the tension spring or in the direction to loosen the tension spring. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a brush cutter for cutting grass and the like, and more particularly, to a power transmission path between an internal combustion engine and a cutting blade, a centrifugal clutch having a clutch drum, and rotation of the clutch drum when not working. And a braking device for braking to prevent power from the internal combustion engine from being transmitted to the cutting blade and to prevent idling.
[0002]
[Prior art]
2. Description of the Related Art As a mower driven by an internal combustion engine such as a small air-cooled two-stroke gasoline engine for mowing grass and the like, a mower having a braking device for controlling idling of a cutting blade has been conventionally known. For example, in a brush cutter described in Japanese Patent Application Laid-Open No. 11-196648, a centrifugal clutch having a clutch drum is provided in a power transmission path between an internal combustion engine and a cutting blade, and the rotation of the clutch drum is braked when not working. And a braking device for preventing the power from the internal combustion engine from being transmitted to the cutting blade and preventing the power from idling.
[0003]
The braking device includes a brake band disposed along a peripheral surface of the clutch drum, and a release unit for releasing the brake band. The release unit includes a swing member biased to an initial position by a spring. And an operating wire having one end connected to the swing member and the other end operatively connected to the brake operating lever. One end of the brake band is fixed to the housing, and the other end is connected to the swinging member. The swinging member operates against the spring force of the spring by operating the brake operation lever. It is pulled to swing from the initial position to the swing position, whereby the brake band moves from the tightened position to the relaxed position and is released.
[0004]
[Patent Document 1]
JP-A-11-196648 (pages 5-9, FIGS. 1-4)
[0005]
[Problems to be solved by the invention]
By the way, the rotation of the clutch drum is stopped by the tightening by the brake band. However, if the tightening is too loose, the clutch drum slips and rotates, and the idling of the cutting blade is braked within a predetermined time. If it is tightened too hard, it will cause a large reaction to the hands of the operator due to a sudden stop, and may cause abnormal noise due to collision between gears provided in the power transmission path, and related parts. May be damaged or the blade may be loosened. Therefore, it is desirable that the tightening force of the brake band on the clutch drum can be adjusted to an appropriate strength.
Therefore, an object of the present invention is to provide a brush cutter capable of adjusting a tightening force of a brake band on a clutch drum.
[0006]
[Means for Solving the Problems]
The object of the present invention is to provide a centrifugal clutch having a clutch drum in a power transmission path between an internal combustion engine and a cutting blade, and to brake the rotation of the clutch drum in order to prevent the cutting blade from idling when not working. The braking device has a brake band disposed along the outer peripheral surface of the clutch drum, and a releasing device for the brake band, and the releasing device is initially provided by a spring. A first swing member biased to a position and moved to a swing position by a brake operation lever, wherein the brake band has one end connected to the first swing member, Is a brush cutter that tightens the clutch drum when it is at the initial position, and is relaxed when it is at the swing position, wherein the braking device is configured to control the clutch drum by the brake band. Adjusting means for adjusting the urging force, the adjusting means includes a base end position changing member connected to a base end of the spring opposite to a side attached to the first swing member, And a screw for moving the base position changing member in a direction to pull or relax the spring.
[0007]
In the present invention, the position of the base end of the spring is moved by moving the base position changing member with the screw, and the magnitude of the urging force of the spring acting on the first swing member is adjusted. Thus, the tightening force of the brake band connected to the swing member is adjusted.
[0008]
In the present invention, since the adjusting means is provided to adjust the tightening force of the brake band with respect to the clutch drum, the rotation of the clutch drum is braked with a desired braking force and within a desired stop time. can do. Further, when the brake band becomes loose due to wear or the like after long-term use, the tightening force can be easily adjusted, and the brake band can always be operated with an appropriate tightening force.
[0009]
In an embodiment of the present invention, the base end position changing member is a second swinging member having a first arm portion and a second arm portion extending from a pivot, and a tip of the screw is the first arm portion. And the proximal end of the spring is connected to the second arm portion, and the distance from the pivot to the point of application of the screw is greater than the distance from the pivot to the connecting position of the spring. short.
[0010]
In this embodiment, the distance from the pivot to the point of application of the screw is shorter than the distance from the pivot to the coupling position of the spring, so that a slightly larger advance or retreat of the screw will result in a larger dimension. In addition, the spring can be extended and contracted, and the tightening force of the brake band can be easily adjusted.
[0011]
In another embodiment of the present invention, the tip of the screw is in contact with the point of action of the second arm portion, and the screw of the screw is swung while the second swing member swings. The surface of the second swinging member with which the tip abuts has an arc shape. Therefore, the second swing member can be smoothly swung by the forward or backward movement of the screw.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a brush cutter according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows the entire brush cutter according to the present embodiment.
As shown in FIG. 1, the brush cutter 2 includes a small air-cooled two-cycle or four-cycle gasoline engine, an internal combustion engine 4, an operation rod 6 extending forward from the internal combustion engine 4, and a front end of the operation rod 6. And a handle portion 10 attached to an intermediate portion of the operation rod 6.
[0013]
A power transmission path from the internal combustion engine 4 to the cutting blade 8 is not shown, but a crankshaft of the internal combustion engine 4 from the internal combustion engine 4 side, a centrifugal clutch 12 for transmitting rotation of the crankshaft, The output shaft 14 extends from the centrifugal clutch 12 into the operation rod 6, and the cutting blade 8 is connected to the output shaft 14 via the gear chamber 7.
[0014]
FIG. 2 is a cross-sectional view of the internal combustion engine taken along line II-II shown in FIG. 1 and shows a state where the clutch drum of the centrifugal clutch is braked by the braking device.
[0015]
The centrifugal clutch 12 having a clutch drum 16 is provided in a power transmission path between the internal combustion engine 4 and the cutting blade 8. As shown in FIG. 2, the centrifugal clutch 12 is provided to prevent the idler of the cutting blade 8 while the work is not performed in order to improve the safety at the time of starting the brush cutter 2. Braking device 18 is provided. The brake device 18 can be released by grasping the brake operation lever 20 shown in FIG. 1. When the operator releases his / her hand from the brake operation lever 20, the brake device 18 rotates the clutch drum 16. To prevent the cutting blade 8 from rotating carelessly.
[0016]
As shown in FIG. 2, the braking device 18 has a brake band 22 arranged along the outer peripheral surface 16 a of the clutch drum 16, and release means 24 for the brake band 22. The release means 24 has a first swing member 26. The distal end portion 28a of a tension spring 28 is connected to the first swing member 26, and is biased by the tension force of the tension spring 28 to an initial (braking) position shown in FIG. Further, the first swing member 26 is connected to the brake operation lever 20 via a cable 30, and by operating the brake operation lever 20, the first swing member 26 resists the spring force of the tension spring 28, and From the position to the swing position (not shown). One end 30a of the cable 30 is connected to a first attachment point 26b located radially outward from a pivot 26a of the first swing member 26.
[0017]
Further, one end 22a of the brake band 22 is connected to a second mounting point 26c located radially outward from the pivot shaft 26a at a predetermined inner angle from the first mounting position 26b of the cable 30. I have. The other end 22b of the brake band 22 is locked to a housing 4a of the main body 4 by a pin 4b. When the first swing member 26 is at the initial position (the position shown in FIG. 2), the brake band 22 is tightened to the outer peripheral surface 16a of the clutch drum 16, and the brake operating lever 20 is operated. Thereby, it is moved to the swing position and relaxed.
[0018]
Further, the braking device 18 has adjusting means 31 for adjusting the tightening force of the clutch drum by the brake band 22. The adjusting means 31 includes a base position changing member 32 connected to a base end 28b of the tension spring 28 opposite to the front end 28a attached to the first swing member 26; And a push screw 34 for moving the position changing member 32 in a direction in which the tension spring 28 is pulled or relaxed. The tightening force of the brake band 22 on the clutch drum 16 is determined by the tensile force of the tension spring 28, and is adjusted by the adjusting means 31. In the present embodiment, the base position changing member 32 is a second swinging member 32 having a first arm portion 32a and a second arm portion 32b extending at a predetermined angle from the pivot 32c. More specifically, the second swing member 32 includes the pivot 32c, the first arm portion 32a formed of a semicircular portion projecting radially outward from the pivot 32c, and the first arm portion. And a second arm portion 32b extending radially outward at a predetermined inner angle from the second arm portion 32a and having a length from the pivot 32c longer than the first arm portion 32a. The proximal end 28b of the tension spring 28 is connected to the distal end of the second arm portion 32b.
[0019]
The longitudinal axis (line of action) of the set screw 34 of the adjusting means 31 is at an angle with respect to the central axis (arm of moment) of the first arm portion 32a extending radially outward from the pivot 32c. As described above, the push screw 34 and the first arm portion 32a are arranged at appropriate positions. The tip 34a of the screw 34 has a spherical shape and is in contact with the arc-shaped outer peripheral surface of the first arm portion 32a. The distance from the pivot 32c to the point of application of the force of the push screw 34 (the tip 34a) is shorter than the distance from the pivot 32c to the connection position of the extension spring 28.
[0020]
A concave portion (not shown) for receiving a tool for turning the push screw 34, for example, a groove or a hole of an appropriate shape is formed on the top surface of the head of the push screw 34 exposed from the housing 4 a. I have. The recess preferably has a shape other than the recess of a standard screw defined in JIS or the like because of the so-called “tamper proof”. That is, the standard tool for turning these standard screws cannot be inserted, or has such a shape that it can run idle even if inserted. A special tool that fits into the special shaped recess is prepared. In order to prevent the push screw 34 from being loosened due to vibration or the like during operation of the bush cutter 2, a synthetic resin detent nut member 36 of a suitable polygonal outer shape is screwed in a self-tapping screw type. It extends through the joint.
[0021]
The centrifugal clutch 12, the braking device 18, and the releasing means 24 of the brush cutter 2 according to the present embodiment operate as follows.
First, the operation from the braking state shown in FIG. 2 already described until the braking device 18 is released by the brake operating lever 20 will be described. When the operator grips the brake operation lever 20, the cable 30 is pulled, whereby the first swing member 26 is pulled against the pulling force of the tension spring 28, and from the initial position shown in FIG. Rotate clockwise to swing position (not shown). Thereby, the brake band 22 is relaxed, the rotation of the clutch drum 16 is allowed, the rotation of the internal combustion engine 4 is transmitted through the power transmission path, and the cutting blade 8 rotates. When the operator releases the brake operation lever 20, the first swing member 26 is pulled back from the swing position to the initial position by the urging force of the tension spring 28, and the clutch drum 16 is moved to the brake band. It is tightened and braked by 22.
[0022]
FIG. 3 shows a state in which the tightening force of the brake band 22 is adjusted by the adjusting means so as to be stronger than the state shown in FIG.
[0023]
The adjusting means 31 will be described with reference to FIGS. The special tool is fitted into the recess of the push screw 34 and the push screw 34 is rotated. If it is desired to increase the tightening force of the brake band 22, the screw 34 is screwed forward. As a result, the first swing arm portion 32a of the second swing member 32 is pushed, whereby the second swing member 32 rotates clockwise, and accordingly, the tension spring 28 The position of the base end portion 28b is moved by the second swing arm portion 32b in a direction to further pull the tension spring 28. That is, the tension force of the tension spring 28 on the first swing member 26 increases, and the tightening force of the brake band 22 increases. In order to make the tightening force of the brake band 22 smaller, the screw 34 can be retracted.
[0024]
According to the present embodiment, since the screw 34 cannot be turned unless it is a special tool, improper operation can be prevented.
Further, since the detent nut member 36 is provided, it is possible to prevent the set screw 34 from being loosened due to vibration or the like.
[0025]
The present invention is not limited to the above embodiments, and various changes can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say, there is.
[0026]
For example, in the present embodiment, the base position changing member 32 is configured as the second swinging member 32, but the base position changing member 32 moves the base end portion 28 b of the spring 28. If it can be made, it may be constituted by other than the swinging member. For example, the push screw 34 may be configured to move linearly with the advance or retreat of the push screw 34.
Further, in the present embodiment, the distal end 34a of the screw 34 is in contact with the outer peripheral surface of the proximal position changing member 32, but the distal end of the screw 34 is screwed to the proximal position changing member 32. It may be so.
[0027]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the brush cutter which can adjust the fastening force with respect to a clutch drum of a brake band can be provided.
[Brief description of the drawings]
FIG. 1 shows the entire brush cutter according to the present embodiment.
2 is a cross-sectional view of the internal combustion engine taken along a line II-II shown in FIG. 1 and shows a state where the centrifugal clutch is braked by a braking device.
FIG. 3 shows a state in which the tightening force of the brake band is adjusted by the adjusting means.
[Explanation of symbols]
2 Brush cutter 4 Internal combustion engine 8 Cutting blade 12 Centrifugal clutch 16 Clutch drum 16a Outer peripheral surface 18 Brake device 20 Brake operating lever 22 Brake band 22a One end 24 Release means 26 First swing member 28 Spring 28a Mounted side 28b Base end 31 Adjusting means 32 Base end position changing member (second swing member)
32a first arm portion 32b second arm portion 32c pivot 34 screw 34a tip

Claims (3)

A centrifugal clutch (12) having a clutch drum (16) in a power transmission path between the internal combustion engine (4) and the cutting blade (8), and a centrifugal clutch (8) for preventing idling of the cutting blade (8) during non-operation. A braking device (18) for braking the rotation of the clutch drum (16), wherein the braking device (18) is arranged along the outer peripheral surface (16a) of the clutch drum (16). A band (22) and a release means (24) for the brake band (22). The release means (24) is urged to an initial position by a spring (28), and has a brake operation lever ( 20) has a first rocking member (26) that moves to a rocking position by the brake band (22). One end (22a) of the brake band (22) is connected to the first rocking member (26); When the swing member (26) is at the initial position Serial tightening the clutch drum (16), also when in the swinging position is a brush cutter that is relaxed (2),
The braking device (18) has adjusting means (31) for adjusting the tightening force of the clutch drum (16) by the brake band (22), and the adjusting means (31) includes the spring ( 28) a base position changing member (32) to which a base end (28b) opposite to the side (28a) attached to the first swing member (26) is connected, and the base position changing member A brush (34) for moving the spring (28) in a direction in which the spring (28) is pulled or relaxed. The proximal end position changing member is a second swing member (32) having a first arm portion (32a) and a second arm portion (32b) extending from a pivot (32c), and a distal end of the screw (34). 34a) acts on the first arm portion (32a), and the proximal end (28b) of the spring (28) is connected to the second arm portion (32b), and is connected to the pivot (32c). 2. The brush cutter according to claim 1, wherein a distance from a point of application of the screw (34) is shorter than a distance from the pivot (32 c) to a connection position of the spring (28). The tip (34a) of the screw (34) is in contact with the point of action of the second arm portion (32b), and the screw (34) is rotated while the second rocking member (32) rocks. The brush cutter according to claim 1, wherein a surface of the second swinging member (32) with which the tip (34 a) abuts has an arc shape.

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