JP4081339B2 - Brush cutter - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a brush cutter for cutting grass and the like, and more specifically, a centrifugal clutch having a clutch drum in a power transmission path between an internal combustion engine and a cutting blade, and rotation of the clutch drum when not working. The present invention relates to a brush cutter that includes a braking device that brakes and prevents transmission of power from the internal combustion engine to the cutting blade to prevent idling.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a brush cutter for cutting grass or the like driven by an internal combustion engine such as a small air-cooled two-cycle gasoline engine has been known which has a braking device that controls idling of a cutting blade. For example, in a brush cutter described in Japanese Patent 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 in operation. And a braking device for preventing the motive power from the internal combustion engine from being transmitted to the cutting blade and causing idling.
[0003]
The braking device includes a brake band disposed along a circumferential surface of the clutch drum, and a release means for the brake band, and the release means includes a swing member biased to an initial position by a spring. An operation wire having one end connected to the swing member and the other end operatively connected to a brake operation lever. The brake band has one end fixed to the housing and the other end connected to the swing member, and the swing member resists 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 tightening position to the relaxed position and is released.
[0004]
[Patent Document 1]
JP-A-11-196648 (page 5-9, FIGS. 1 to 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 too tight and tightens too much, it will give a large reaction to the operator's hand due to a sudden stop, and an abnormal noise may occur due to a collision between gears provided in the power transmission path, etc. May be damaged, or the blade may be loosely attached. Therefore, it is desirable that the tightening force of the brake band against the clutch drum can be adjusted to an appropriate strength.
Accordingly, an object of the present invention is to provide a brush cutter capable of adjusting the tightening force of a brake band with respect to 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 the power transmission path between the internal combustion engine and the cutting blade, and to brake the rotation of the clutch drum in order to prevent the cutting blade from idling when not working. The brake device includes a brake band disposed along an outer peripheral surface of the clutch drum, and a release means for the brake band. The release means is initially set by a spring. A first rocking member that is biased to a position and is moved to a rocking position by a brake operation lever, and one end of the brake band is connected to the first rocking member; A brush cutter that tightens the clutch drum when in the initial position and relaxes when the clutch drum is in the swing position. Adjusting means for adjusting the applied force, the adjusting means comprising: a base end position changing member connected to a base end of the spring opposite to the side attached to the first swing member; It can be achieved by a brush cutter having a screw for moving the base end position changing member in a direction of pulling or relaxing the spring.
[0007]
In the present invention, the position of the base end of the spring is moved by moving the base end position changing member with the screw, and the magnitude of the biasing 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 so that the tightening force of the brake band against the clutch drum can be adjusted, 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 is loosened due to wear or the like after a long period of use, the tightening force can be easily adjusted and 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 the tip of the screw is the first arm. The base end of the spring is connected to the second arm portion, and the distance from the pivot to the point of action of the screw is greater than the distance from the pivot to the connection 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 connecting position of the spring, so that a larger dimension can be obtained by slightly moving the screw forward or backward. The spring can be expanded 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 action point of the second arm portion, and the screw of the screw is moved while the second swinging member swings. The surface of the second rocking member with which the tip abuts is arcuate. Therefore, the second rocking member can be smoothly swung by the forward or backward movement of the screw.
[0012]
DETAILED DESCRIPTION OF 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 is attached to an internal combustion engine 4 which is a small air-cooled two-cycle or four-cycle gasoline engine, an operating rod 6 extending forward from the internal combustion engine 4, and a tip of the operating 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 from the internal combustion engine 4 side, a crankshaft of the internal combustion engine 4, 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 along the 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]
In the power transmission path between the internal combustion engine 4 and the cutting blade 8, the centrifugal clutch 12 having a clutch drum 16 is provided. In addition, as shown in FIG. 2, the centrifugal clutch 12 prevents the cutting blade 8 from idling while the brush cutter 2 is not operated so as to improve safety when the brush cutter 2 is started. A braking device 18 is provided. The brake device 18 can be released by gripping the brake operation lever 20 shown in FIG. 1. When the operator releases the brake operation lever 20, the brake device 18 rotates the clutch drum 16. And the cutting blade 8 is prevented from rotating carelessly.
[0016]
As shown in FIG. 2, the braking device 18 includes a brake band 22 disposed 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. A tip end portion 28a of a tension spring 28 is connected to the first swing member 26, and is biased to an initial (braking) position shown in FIG. 2 by a tension force of the tension spring 28. The first swing member 26 is connected to the brake operation lever 20 via a cable 30, and the initial force is resisted against the spring force of the tension spring 28 by the operation of the brake operation lever 20. Move from position to swing position (not shown). Note that one end 30 a of the cable 30 is connected to a first attachment portion 26 b located radially outward from the pivot shaft 26 a of the first swing member 26.
[0017]
Further, one end 22a of the brake band 22 is connected to a second mounting portion 26c located radially outward from the pivot shaft 26a with a predetermined inner angle from the first mounting position 26b of the cable 30. Yes. The other end 22 b of the brake band 22 is locked to the housing 4 a of the main body 4 by a pin 4 b. The brake band 22 is fastened to the outer peripheral surface 16a of the clutch drum 16 when the first swing member 26 is in the initial position (the position shown in FIG. 2), and the brake operating lever 20 is operated. To move to the swing position and relax.
[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 proximal end position changing member 32 connected to a proximal end portion 28b opposite to the distal end portion 28a attached to the first swinging member 26 of the tension spring 28, and the proximal end. 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 against the clutch drum 16 is determined by the pulling force of the pulling spring 28 and is adjusted by the adjusting means 31. In the present embodiment, the base end position changing member 32 is a second swinging member 32 having a first arm portion 32a and a second arm portion 32b extending from the pivot 32c at a predetermined angle. More specifically, the second rocking member 32 includes the pivot 32c, the first arm portion 32a formed of a semicircular portion protruding radially outward from the pivot 32c, and the first arm portion. 32a and the second arm portion 32b extending radially outward with a predetermined inner angle 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 force) of the push screw 34 of the adjusting means 31 is angled with respect to the central axis (moment arm) of the first arm portion 32a extending radially outward from the pivot 32c. As is made, the push screw 34 and the first arm portion 32a are disposed at appropriate positions. The tip 34a of the screw 34 has a spherical shape and is in contact with the arcuate outer peripheral surface of the first arm portion 32a. The distance from the pivot 32 c to the force application point (the tip 34 a) of the push screw 34 is shorter than the distance from the pivot 32 c to the connection position of the tension spring 28.
[0020]
A concave portion (not shown) for receiving a tool for turning the push screw 34, for example, an appropriately shaped groove or hole, is formed on the top surface of the head screw 34 exposed to the outside from the housing 4a. Yes. Since the recess is a so-called “tamper proof”, it preferably has a shape other than the recess of the standard screw defined in JIS or the like. That is, the standard tool for turning these standard screws cannot be inserted, or is shaped so as to be idle even if it is inserted. A special tool that fits into the specially shaped recess is prepared. In order to prevent the push screw 34 from loosening due to vibration or the like during the operation of the brush cutter 2, a synthetic resin non-rotating nut member 36 made of an appropriate material having a polygonal outer shape is screwed into a self-tapping screw type. It extends through.
[0021]
The centrifugal clutch 12, the braking device 18, and the release means 24 of the brush cutter 2 according to the present embodiment operate as follows.
First, the operation from the already described braking state shown in FIG. 2 until the braking device 18 is released by the brake operation lever 20 will be described. When an operator grasps 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 the initial position shown in FIG. Rotate clockwise to a 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 is rotated. When an 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 biasing force of the tension spring 28, and the clutch drum 16 is moved to the brake band. Tightened by 22 and braked.
[0022]
FIG. 3 shows a state where the adjusting means has adjusted the tightening force by the brake band 22 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 in the recess of the push screw 34 and the push screw 34 is rotated. When it is desired to increase the tightening force of the brake band 22, the screw 34 is screwed forward. As a result, the first arm portion 32a of the second swing member 32 is pushed, whereby the second swing member 32 rotates clockwise, and accordingly, the proximal end of the tension spring 28 The position of the portion 28b is moved in the direction of further pulling the tension spring 28 by the second arm portion 32b . That is, the tension force applied to the first swing member 26 by the tension spring 28 increases, and the tightening force of the brake band 22 increases. Conversely, when it is desired 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 can be turned only by a special tool, improper operation can be prevented.
Further, since the rotation preventing 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 modifications are possible 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.
[0026]
For example, in the present embodiment, the base end position changing member 32 is configured as the second swing member 32, but the base end position changing member 32 moves the base end portion 28 b of the spring 28. If it can be made, it may be comprised other than a rocking | swiveling member. For example, it may be configured to linearly move as the push screw 34 moves forward or backward.
Furthermore, in this embodiment, the tip 34 a of the screw 34 is in contact with the outer peripheral surface of the base end position changing member 32, but the tip of the screw 34 is screwed into the base end position changing member 32. It may be made like.
[0027]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the brush cutter which can adjust the clamping force with respect to the clutch drum of a brake band can be provided.
[Brief description of the drawings]
FIG. 1 shows an entire brush cutter according to the present embodiment.
2 is a cross-sectional view of the internal combustion engine taken along line II-II shown in FIG. 1, showing a state in which the centrifugal clutch is braked by the 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 Braking device 20 Brake operation lever 22 Brake band 22a One end 24 Release means 26 First swing member 28 Spring 28a Side 28b base end 31 Adjusting means 32 Base end position changing member (second swinging member)
32a First arm portion 32b Second arm portion 32c Axis 34 Screw 34a Tip

Claims (2)

The centrifugal clutch (12) having a clutch drum (16) in the power transmission path between the internal combustion engine (4) and the cutting blade (8), and for preventing the cutting blade (8) from idling when not working, A brake device (18) for braking the rotation of the clutch drum (16), and the brake device (18) is a brake disposed along the outer peripheral surface (16a) of the clutch drum (16). And a release means (24) for the brake band (22). The release means (24) is biased to an initial position by a spring (28), and a brake operating lever ( 20), the brake band (22) has one end (22a) connected to the first swing member (26), and is moved to the swing position. When the swing member (26) is in 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 an 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 end 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 end position changing member A screw (34) for moving (32) in a direction to pull or relax the spring (28) ;
The base end position changing member is a second swinging member (32) having a first arm portion (32a) and a second arm portion (32b) extending from the pivot (32c), and the tip end of the screw (34) ( 34a) acts on the first arm portion (32a), also wherein the proximal end of the spring (28) (28 b) is connected to said second arm portion (32 b), the pivot (32c) The brush cutter is characterized in that the distance from the operating point of the screw (34) is shorter than the distance from the pivot (32c) to the connecting position of the spring (28). The tip (34a) of the screw (34) is in contact with the operating point of the second arm portion (32b), and the screw (34) is moved while the second swinging member (32) is swinging. The brush cutter according to claim 1 , wherein a surface of the second rocking member (32) with which the tip (34a) contacts has an arc shape.

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