JP2021112178A - Antivibration device of bush cutter - Google Patents

Abstract

To reduce vibration of a bush cutter including an engine at one end of an operation bar and a cutter at the other end.SOLUTION: A bush cutter is configured such that an engine is mounted by a holder fixed to an operation bar, at a height equal to a distance from the center of gravity of the engine to a crank shaft, and a lower part of the engine elastically supported by a bracket fixed to the operation bar, so as to generate an inertia force vector of the engine in the vertical direction.SELECTED DRAWING: Figure 2

Description

Detailed description of the invention

The present invention relates to a vibration isolator of a brush cutter provided with an engine and operating a handle left and right while rotating a cutter to mow weeds.

A brush cutter equipped with an engine and rotating a cutter to mow weeds operates left and right while holding the mass of the brush cutter with a belt on the shoulder and holding the handle provided on the operating rod with both hands. It is required to reduce the fatigue of the operator due to the vibration generated by the engine.

Therefore, the entire engine is covered with a tubular cover and the space between the cover and the engine is held by a vibration isolator to enable a large amount of elastic movement of the engine due to vibration and reduce the vibration transmitted to the operation rod. There is Patent Document 1. (The name is as described in the literature)

Further, there is Patent Document 2 below as an example in which a mount frame for mounting a prime mover is integrally fixed to a rear end portion of an operation paddle, and an elastic member for supporting the prime mover in a vibration-proof manner is provided on the mount frame. (The name is as described in the literature)

Japanese Unexamined Patent Publication No. 2013-21979 JP-A-2015-130831

The above-mentioned Patent Document 1 covers the entire engine with a cover and holds it by springs arranged vertically and horizontally between the cover and the cover so as to receive the vibration of the engine due to vibration. There were problems such as an increase in rigidity and external size, and an increase in mass associated therewith.

The above-mentioned Patent Document 2 is supported by a compression spring in the vertical and front-rear directions on the mount frame, but since the spring arrangement is only on one side, it cannot be supported in the upward and rear directions, so that effective cushioning is difficult to be performed. There was a problem that the vibration transmitted to the operating rod was not reduced even though the engine was swinging due to the spring.

In addition, all of the above prior art documents are technical ideas on how to arrange the buffer members in order to buffer the vibration from the engine, but measures based on the idea of simply arranging the buffer members. However, there is a problem that it is difficult to obtain an effective vibration reduction effect. It is because the expected vibration reduction effect by the cushioning member can be obtained by supporting the engine, which is the vibration source, with the most effective vibration reduction, but such a technical idea is not shown. .. Therefore, even if the cushioning member is used to obtain the cushioning effect of the cushioning member, a new vibration mode other than the mode to be reduced is generated, so that the engine is vibrating greatly but the large vibration reducing effect cannot be obtained. Therefore, the worker has been fatigued due to engine vibration.

The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for effectively reducing the vibration of the engine transmitted to the operating pad of the brush cutter with a simple configuration. It is to reduce the fatigue of the operator due to the vibration.

In order to achieve the above object, the anti-vibration device of the mowing machine according to the invention according to claim 1 of the present application includes a cutter provided at the front end of the operation paddle, an engine for driving the cutter at the rear end of the operation paddle, and a length of the operation paddle. In a mowing machine equipped with a handle operated by an operator in the middle of the direction, the engine is swingably attached to the operating paddle at the same height as the distance from the engine center of gravity to the crank shaft by a holder fixed to the operating paddle. It is characterized in that the lower part of the engine is elastically supported by the bracket so that the inertial force vector of the engine is generated in the vertical direction.

The invention according to claim 2 is characterized in that the line connecting the center of the engine mounting portion of the holder and the center of gravity of the engine is arranged at right angles to the cylinder center line.

The invention according to claim 3 is characterized in that the distance from the center of the engine mounting portion of the holder to the center of gravity of the engine is set larger than the distance from the center line of the cylinder to the center of gravity of the engine.

In the invention according to claim 4, the center of the cylinder of the engine is arranged upward through the center of the crankshaft, and the intake system device is located on one side of the crankshaft rotation direction with respect to the center of the cylinder and the exhaust system device is located on the other side. It is characterized by being equipped with.

The invention according to claim 5 is characterized in that the engine is attached to an engine mounting portion of a holder by an arm portion extending forward from a clutch case fixed to a crankcase.

The invention according to claim 6 is characterized in that the engine is elastically supported by a bracket fixed to an operating paddle below the clutch case fixed to the crankcase.

The invention according to claim 7 is characterized in that the engine is elastically supported in the vertical direction by rubber.

According to the invention according to claim 1 of the present application, since the vibration mode generated by the engine is set only in the vertical direction and the lower part of the engine center of gravity is elastically supported, the vibration isolation effect of the elastic material without generating a new vibration mode. Can be effectively obtained, so that the operator's fatigue due to engine vibration can be effectively reduced.

According to the invention according to claim 2, since the vibration mode in the front-rear direction does not occur due to the vibration in the vertical direction, the vibration-proof effect by the elastic material can be effectively obtained.

According to the third aspect of the present invention, since the load due to the vibration acting on the engine mounting portion of the operating rod can be reduced, the vibration transmitted to the operating rod can be reduced.

According to the invention of claim 4, since the position of the center of gravity of the engine in the left-right direction can be brought closer to the center of the crankshaft, the generation of a moment that causes the handle to swing left and right due to the vertical swing is suppressed, so that the engine is added to the handle. No new vibration is generated.

According to the invention of claim 5, the engine can be firmly and easily attached to the operating paddle.

According to the invention of claim 6, since the engine is supported by the clutch case, it is not necessary to change the crankcase, so that the implementation can be facilitated and the versatility of the engine body can be improved.

According to the invention according to claim 7, the vibration generated in the vertical direction can be buffered in both directions, the elastic material can be realized in a small size, and the damping effect can be obtained, so that an effective anti-vibration effect can be obtained.

It is external perspective view of the brush cutter which concerns on this invention. It is a vertical sectional view of the engine part in 1st Example. FIG. 2 is a sectional view taken along line III-III in FIG. FIG. 2 is a sectional view taken along line IV-IV in FIG. It is a perspective view which shows the other embodiment of the elastic material.

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

FIG. 1 is an external perspective view of the brush cutter 1 according to the present invention. The brush cutter 1 is provided with a cutter 3 at the front end and an engine 4 at the rear end of an operation paddle 2 extending in the front-rear direction, and a handle 5 operated by an operator in the middle. Reference numeral 6 denotes a housing for changing the angle of power, which is provided with a bevel gear inside and a cutter 3 is attached. As shown in the figure, the front-back direction, the left-right direction, and the up-down direction are defined with reference to the direction of the operator at the time of operation.

FIG. 2 shows a vertical cross-sectional view of the engine 4. The piston 12 arranged in the cylinder 11 reciprocates up and down to generate power from the crankshaft 13. A recoil type starting device 14 is provided at the rear end of the crankshaft 13, and a flywheel magnet toe 15 that also serves as a cooling fan is provided at the front end. A clutch case 17 is fixed to the front of the crankcase 16 to which the cylinder 11 is attached, which also serves as a cooling fan case. A shoe 18 of a centrifugal clutch is attached to the flywheel magnet toe 15, and a clutch drum 19 of the centrifugal clutch coaxial with the crankshaft 13 is supported by a boss 20 integrally fixed to a bearing 21 supported by a clutch case 17. The power of the crankshaft 13 is transmitted from the shoe 18 to the clutch drum 19 at a predetermined rotation speed. Further, a fuel tank 22 is integrally attached below the crankcase 16.

The drive shaft 24 provided inside the operation paddle 2 is supported by a bearing (not shown in this figure), and power is driven from the boss 20 by a spline 25 provided at the rear end portion. The crankshaft 13 and the drive shaft 24 are arranged coaxially. Then, the cutter 3 is rotated from the front end of the drive shaft 24 via the bevel gear in the housing 6 at the front end of the operation paddle 2.

As shown in FIG. 3, the holder 26 and the bracket 27 are divided at the center of the axis of the operation paddle 2 and are integrally firmly attached to and fixed to the operation paddle 2 by the bolt 28.

The holder 26 is provided with engine mounting portions 26a and 26a at both left and right ends, and the mounting pin 29 is supported by the mounting pin 29, and the mounting pin 29 is prevented from coming off by the washer 30 and the clip 31.

An arm portion 17a integrally formed from the clutch case 17 is attached to the attachment pin 29 so that the clutch case 17, that is, the engine 4 can swing around the center O of the attachment pin 29. Reference numeral 32 denotes a bush made of a self-lubricating material such as synthetic resin, which is press-fitted and fixed to the arm portion 17a and swings with the outer circumference of the pin 29. The arm portion 17a has a ten-shaped cross section to obtain light weight and high rigidity, but an I-shaped cross section may be used.

The center O of the pin 29 is the center of the mounting portion of the engine 4, and the engine 4 can swing around the center O. The center O is set to a height h from the axis center of the drive shaft 24, and h has the same dimension as the distance from the crankshaft 13 center of the engine center of gravity indicated by G. That is, the line connecting the center O of the engine mounting portion and the center of gravity G of the engine is parallel to the crankshaft 13 and is arranged at right angles to the cylinder center line P.

Here, the distance from the engine mounting portion center O of the holder to the engine center of gravity G is set larger than the distance from the cylinder center line P to the center of gravity G.

A seal 33 is mounted between the clutch case 17 and the rear end of the operating rod 2 to prevent water and dust from entering the bearing 21. The seal 33 has a lip shape and has a lip shape to reduce the resistance to deformation while obtaining the ability to follow the operation paddle 2 due to the swing of the engine 4.

The bracket 27 is extended downward and rearward, and elastically supports the stay portion 17b of the clutch case 17 by vertically sandwiching the stay portion 17b of the clutch case 17 below the engine with elastic members 35 and 36 made of rubber. The amount of deformation of the elastic members 35 and 36 at the time of attachment is set by tightening the bolt 38 and the nut 39 via the spacer 37. 40 is a washer. The bracket 27 has a U-shaped cross section and has sufficient strength and rigidity to support the mass of the engine 4.

As shown in FIG. 4, the center of the cylinder 11 is arranged upward through the center of the crankshaft 13, and the air cleaner 45 and the carburetor 46, which are intake system devices, are insulators on one side of the crankshaft rotation direction with respect to the cylinder center P. It is attached via 47, and a muffler 48, which is an exhaust system device, is provided on the other side. Therefore, the position of the center of gravity G in the left-right direction is set to be close to the center P of the cylinder 11 due to the balance of the masses of the intake system device and the exhaust system device. Further, since the fuel tank 22 has a shape that is thinned in the vertical direction and extended in the horizontal direction to obtain a required capacity, the influence on the change in the vertical position of the center of gravity G due to the change in the amount of fuel is reduced. There is. The elastic members 35 and 36 are arranged directly below the center of gravity G.

Next, the operation of the vibration isolator having the above configuration will be described.

In an engine, the inertial force due to the reciprocating mass of the reciprocating mass part such as a piston or connecting rod acts as a vibration source to generate vibration, but it is known that the inertial force of the generated engine can be set in the vector direction by the crank balance. .. Therefore, if the vibration generated by the engine is set to be in the vertical direction only, the engine 4 vibrates in only one mode of vibrating in the vertical direction around the center O of the engine mounting portion.

At this time, since the engine is elastically supported below the engine 4, only the compression action in the vertical direction acts on the elastic materials 35 and 36. Therefore, the vibration transmission rate can be lowered by setting the elastic materials 35 and 36 to have a resonance frequency lower than the normal rotation speed of the engine, so that the vibration transmitted to the bracket 27 can be sufficiently lowered. The vibration transmitted to 5 can be effectively reduced.

Further, since the line connecting the center O of the engine mounting portion and the engine center of gravity G is parallel to the crankshaft 13 and arranged at right angles to the cylinder center line P, it is arranged in the front-rear direction as the engine 4 swings in the vertical direction. Since no vibration is generated, a new vibration mode is not generated.

Since the distance from the center O of the engine mounting part of the holder to the center of gravity G of the engine is larger than the distance from the center line P of the cylinder to the center of gravity G, the load applied to the engine mounting part due to the inertial force is reduced to reduce the vibration transmitted to the operating rod. Can be made smaller. Further, since the elastic materials 35 and 36 are arranged below the center of gravity G, the load applied to the engine mounting portion can be reduced, but the elastic materials 35 and 36 are arranged from directly below the engine center of gravity G on the cylinder center line P side. Is desirable.

The engine 4 is arranged so that the cylinder center P is arranged upward through the crankshaft center and the intake system device is provided on one side of the crankshaft rotation direction with respect to the cylinder P center and the exhaust system device is provided on the other side. Since the center of gravity G can be located close to the center P of the cylinder 11, the rotational moment in the left-right direction generated from the center of gravity G to the operating rod 2 by the inertial force can be reduced. Therefore, vibration that causes the operation rod 2 to swing left and right is not generated, and only the compression action in the vertical direction acts on the elastic members 35 and 36. Therefore, the left and right handles from the operation rod as shown in FIG. Even if the asymmetrical handles have different lengths, the vibration strength does not differ between the left and right handles. Further, as shown in FIG. 3, since the center of gravity G fits within the width of the arm portion 17a, the swing around the center O of the engine mounting portion can be smoothly operated.

Since the elastic materials 35 and 36 are sandwiched from above and below as rubber, vibration-proof support that suppresses the amplitude while obtaining a damping effect against vibrations in both the upper and lower directions can be obtained. Since the elastic material 35 supports the mass of the engine, it may have the same characteristics as or different from 36. Further, as shown in FIG. 5, when the end face of the elastic material has a chrysanthemum-shaped uneven shape, the initial deformation can be softened and the resonance frequency can be lowered, so that the vibration transmission rate can be lowered and the spring constant can be made non-linear. The runout can be suppressed to a small value even with a strong external force, and excessive bending with respect to the drive shaft 24 can be suppressed. The chrysanthemum shape may be formed not only on one side but also on both end faces.

The fuel tank 22 has a shape that is thinned in the vertical direction and extended in the horizontal direction so that the change in the vertical position of the center of gravity G due to a change in the amount of fuel is small, but the height h of the center O of the engine mounting portion is set. May be set to the center of gravity G between the state where the fuel amount is full and the state where the fuel amount is close to the sky, and the effect of the present invention is not impaired by the change in the position of the center of gravity due to the change in the fuel amount.

The line connecting the center O of the engine mounting portion and the engine center of gravity G is parallel to the crankshaft 13 and preferably arranged at right angles to the cylinder center line P. Even if the line connecting G cannot always be parallel to the crankshaft 13 and perpendicular to the cylinder center line P, the technical idea does not differ from the present invention.

Although the two-handed handle brush cutter has been described in the above embodiment, the present invention can be applied to a loop handle brush cutter, a grip handle brush cutter, and a backpack type brush cutter, and the engine is the same regardless of the two-cycle or four-cycle engine. The action effect can be obtained.

1 Mowing machine 2 Operation rod 4 Engine 5 Handle 11 Cylinder 12 Piston 13 Crankshaft 15 Flywheel Magneto 16 Crankcase 17 Clutch case 19 Clutch drum 20 Boss 22 Fuel tank 24 Drive shaft 26 Holder 27 Bracket 29 Mounting pin 35, 36 Elastic Material 45 Air cleaner 48 Muffler O Engine mounting center G Engine center of gravity P Crankcase center line h Height from driveshaft center to engine mounting center

Claims (7)

In a reaper equipped with a cutter provided at the front end of the operating paddle, an engine for driving the cutter at the rear end of the operating paddle, and a handle operated by an operator in the middle of the longitudinal direction of the operating paddle, a holder fixed to the operating paddle The engine is mounted swingably at the same height as the distance from the engine center of gravity to the crank shaft, and the lower part of the engine is elastically supported by the bracket fixed to the operation paddle so that the inertial force vector of the engine is generated in the vertical direction. Anti-vibration device for paddles. The vibration isolator for a brush cutter according to claim 1, wherein a line connecting the center of the engine mounting portion of the holder and the center of gravity of the engine is arranged at a right angle to the center line of the cylinder. The anti-vibration device for a mowing machine according to claim 1, wherein the distance from the center of the engine mounting portion of the holder to the center of gravity of the engine is set larger than the distance from the center line of the cylinder to the center of gravity of the engine. The engine is characterized in that the center of the cylinder is arranged upward through the center of the crankshaft, and the intake system device is provided on one side of the crankshaft rotation direction with respect to the center of the cylinder and the exhaust system device is provided on the other side. The anti-vibration device for the brush cutter according to claim 1. The vibration isolator for a brush cutter according to claim 1, wherein the engine is attached to an engine mounting portion of a holder by an arm portion extending forward from a clutch case fixed to a crankcase. The vibration isolator for a brush cutter according to claim 1, wherein the engine is elastically supported by a bracket fixed to an operating paddle below the clutch case fixed to the crankcase. The vibration isolator for a brush cutter according to claim 6, wherein the engine is elastically supported in the vertical direction by rubber.

Images