JPS6274564A - Vibration isolator for handy power tool - Google Patents

Abstract

PURPOSE:To obtain a vibration isolator for a disc grinder or the like while is excellent in manipulatability, by coupling a drive section to which a grindstone or the like is attached, with a motor section, and by coupling the drive shafts with each other by means of a universal joint. CONSTITUTION:A motor section 5 to which a handle section 6 is secured is fixed by means of screws to a drive section 10 through the intermediary of a resilient member 8 to which stationary plates 7, 9 are bonded. Further, the drive shaft 14 of the motor section 5 is coupled with the drive shaft 19 of the drive section 10 through the intermediary of a key joint 17 by means of two cross joints 16, 18. Thus, the mass M2 of the handle section becomes larger, the mass M2 being such as M2 M1 where M1 is the mass of the grindstone, and therefore, M' in the following equation: M'=M1.M2/M1+M2, becomes larger. Accordingly, the inherent frequency W' in the following equation: W'=(K/M')<1/2>, may be made lower even if the spring constant K is made larger. That is, even if the one having a high hardness or a large spring constant K is used as a resilient member, vibration damping may be made satisfactory and the manipulatability may be also made satisfactory. Further, due to the provision of the universal joint no problem is caused in the operation of the drive section even if the resilient member 8 is deformed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a vibration isolator for hand-held power tools, and particularly to a vibration isolator suitable for disc grinders and the like.

[Background of the invention]

In conventional hand-held power tools such as disc grinders, the part to which the grindstone etc. is attached (hereinafter referred to as the drive part)
and electricity or a part that uses electricity as a power source (hereinafter referred to as the motor part) to form a main body, and an elastic body such as rubber is provided between this main body and the part that moves it. Therefore, a vibration isolator was used to isolate the vibrations transmitted from the main body to the handle. However, in this case, in order to improve the anti-vibration effect, the above-mentioned elastic body must be made softer, and as a result, the overall operation becomes softer, causing the steering wheel to wobble, resulting in poor operability. .

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, prevent harmful imaging that occurs when using the tool without increasing the weight of the tool, and provide a vibration-proofing system for hand-held power tools that has excellent operability. We are in the process of providing equipment.

[Summary of the invention]

The present invention provides a hand-held power tool that has a drive section to which a cutter such as a grindstone is attached, a motor section having a power source, and a handle section for hand-held operation. In the pre-audience, the driving part and the motor part are connected via an elastic body, and the driving power shaft is provided in the driving part and drives the cutter, and the driving power shaft is provided in the motor part and drives the cutting tool. It is characterized in that the motor part that transmits power to the shaft and the power shaft are connected by universal joints at all valves, thereby achieving the intended purpose.

First, the present invention will be explained in detail.

FIG. 5 is a diagram illustrating the principle of a vibration damping system for a conventional hand-held power tool. In the figure, 1 indicates a vibrating body having a mass M, which corresponds to a grindstone. 2 digits IJIt view M, the handle part, 3 is a spring with a spring constant, 4 is a damper with a damping coefficient C, vibrating body 1
A spring 3 and a damper 4 are connected in parallel between the handle portion 2 and the handle portion 2 . The spring 3 and damper 4 correspond to elastic bodies such as rubber.

The force F that excites the vibrating body 1 is as follows: F is the quality of unbalance existing in a rotating body such as a grindstone, ffi is the door, Mir is the distance between the center of rotation of the grindstone and the point where the unbalance exists, and ω is the rotation frequency. = employment・r・ω′・・・・・・・−・−・・−・−
・−・・−・・−・(1). Vibrating body 1 generates excitation force F
When the handle is shaken by 7Jl+, this vibration is transmitted to the handle portion 2 through the spring 3 and the damper 4, and the handle 2 vibrates. At this time, assuming that the amplitude of the handle portion 2 is X, the vibration damping performance is good if the ratio X/@*r between X and the unbalance amount mt is small.

The vibration ratio X/771·r is given by the following equation as a function of the rotational frequency ω.

That frequency again! The ￥f property is approximately as shown in Figure 6. That is, this figure shows the frequency characteristic of X7m-r, with the horizontal axis representing the rotational frequency ω and the vertical axis represented by X/7yL-r. From the figure, if X7m-r becomes smaller than the value A when ω is small, then
iit of vibrating body 1! This means that l is attenuated and transmitted to the handle 2.

In Figure 6, when the rotation frequency is gradually increased,
The frequency at which −r is equal to the value indicated by A in the figure is (2)
At about 1.4 times the natural frequency ω obtained from the formula, the vibration is attenuated in the region B where the rotational frequency is higher than ω. When the damping coefficient C is small like rubber, the natural frequency ω is approximately determined by the following equation. If the natural frequency at this time is ω', then Mr + Mx.

Conventionally, since the mass Ml of the wheel is considerably smaller than the mass M of the vibrating body, that is, the grindstone, the quality −J is determined from equation (4).
F) where iM' is small, (from formula 31, in order to lower the natural frequency ω', the spring constant Ktl must be made smaller, so the elastic body becomes softer and it becomes difficult to operate the handle. If we try to lower the natural frequency ω' by increasing the quality fM of the handle, the overall mass (1'
4 + Mx) becomes dog-like.

In the present invention, the mass M+ and the mass Vb are made equal (7) without changing the overall quality ffi (Ml +Ml). The purpose is to lower the frequency ω' and reduce the temperature by ℃.For example, M
If l = 10, M'' = 1, λf2 is 0.91, and if Ml = 6, M = 5, M' = 2.7.
3, and comparing the ω' of both with the same K, the latter is about 171 and 7 of the former. Furthermore, when K is compared with the same ω', the latter is about three times as hard as the former, which means that the latter can be made into a spring that is about three times harder.

The present invention was made based on the results of such studies, and
This makes it possible to obtain a hand-held power tool with good operability using a hard elastic body without increasing the mass of the tool.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a front view of a disc grinder showing an embodiment of the hand-held power tool of the present invention, FIG. 2 is a plan view similarly seen from above, and FIG. FIG. 4 is a perspective view of the universal joint shown in FIG. 3.

In FIGS. 1 and 2, electricity, compressed air, or the like is used as a power source in the five motor section. Reference numeral 6 denotes a handle portion, which is fixed to the motor portion 5 with screws or the like. 7 is M fixed plate,
One surface is fixed to the motor section 5 with screws or the like, and the other surface is bonded to the elastic body 8. Reference numeral 9 denotes a fixing plate, one surface of which is bonded to the elastic body 8, and the other surface of which is fixed to the drive unit 10 with screws or the like. Reference numeral 10 denotes a drive unit, which is a part to which a grindstone is attached. Reference numeral 11 denotes a grindstone, which is attached to a rotating shaft provided in the drive section 10. An arm 12 is fixed to the motor section 5. 13 is an auxiliary handle attached to the tip of the arm 12. 14 is the motor section 5
15 is a bearing of the power shaft 14, 16 is a cross joint, 17 is a key joint or spline joint, 18 is a cross joint, 19 is a power shaft of the drive part, 20 is a bearing of the power shaft 19 is a part. be. Power shaft 14 of the motor section and power shaft 1 of the drive section
9 are connected by a universal joint consisting of two cross joints 16 and 18 and a key joint (or spline joint) 17.

In Figures 1 to 3, by fixing the motor part i and the handle part without using an elastic body in the middle, the mass of the handle part increases and becomes close to the mass of the drive part, and equivalently (
In Equation 31 (4), M in % Ms is obtained, so even if a hard elastic body with a large spring constant aK is used, it is possible to lower the natural frequency ω', and a soft elastic body such as rubber can be used. The natural frequency ω' of the vibration isolating device in this embodiment can be set to 1/1.4 or less, based on the frequency ω at which the steering wheel becomes difficult to operate.

In other words, it is possible to obtain a vibration isolator that has a hard elastic body, provides good operability of the tool, and has good vibration damping.

Furthermore, as shown in FIGS. 1 to 4, the use of a universal joint for power transmission between the motor section and the drive section can expand the operating performance of the tool. For example, even if the elastic body 8 is deformed and the relative position between the motor section 5 and the drive section 10 changes, the power of the motor section 5 can be transmitted to the drive section without any problem.

FIG. 7 is a diagram showing a universal joint according to another embodiment.

In this figure, 21 and 22 are the ends of the power shafts 14 and 19, and 23 and 24 are the ends. The concave portions 25a and 25b provided in A21 and 22 are convex portions provided in the intermediate transmission portion 26, and are formed at right angles to each other. Since this universal joint operates by coupling the concave portions 23 and 24 with the convex portions 25a and 25b, the rotational power of the motor portion 50 can be transmitted to the drive portion power shaft 19 through the power shaft 14 and the intermediate transmission portion 26.

Even when this universal joint is used, as in the case of the universal joint shown in Figs. 3 and 4, power can be reliably transmitted even if the relative positions of the motor section and the drive section change due to deformation of the elastic body 8. can be done.

〔Effect of the invention〕

According to the present invention, in the vibration isolating device for a hand-held power tool,
It is possible to obtain a hand-held power tool that prevents harmful imaging that occurs during tool operation without increasing the weight of the tool, and has excellent operability.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the vibration isolating device for a hand-held power tool of the present invention, FIG. 2 is a plan view similarly seen from above, and FIG.
The figure is a sectional view taken along the line C-C in Figure 2, Figure 4 is a perspective view of the power transmission section in Figure 3, Figure 5 is a principle diagram of the vibration isolation system for hand-held power tools, and Figure 6 is the A frequency characteristic diagram of X7m-r in the vibration system shown in the figure, and FIG. 7 is a perspective view of the main part of another embodiment of the present invention. 5...Motor part, 6--Handle part, 8--Elastic body, 10--Driving part, 11--Whetstone, 14--Power shaft, 16.18--Cross joint, 19- Power shaft, 21.2
2--Power shaft tip, 26--Intermediate transmission section. >1 figure 21 fang 3 figure 40 Sakae 5 prisoner middle mouth 1'

Claims (1)

[Scope of Claims] 1. A hand-held power tool having a drive section to which a cutter such as a grindstone is attached, a motor section having a power source, and a handle section for hand-held operation, wherein the motor section and the handle section are connected to each other. The driving portion and the motor portion are fixed to each other, and the driving portion and the motor portion are coupled via an elastic body, and a driving power shaft provided in the driving portion for driving the cutter, and a driving power shaft provided in the motor portion for driving the cutter. A vibration isolating device for a hand-held power tool, characterized in that a motor part that transmits power to the power shaft is connected to the power shaft via a universal joint. 2. The elastic body is configured such that the natural frequency of the vibration generated in the handle section is ω' due to the excitation force based on the motor section power source and the drive section, and When the vibration frequency of the vibration generated in the handle part due to force is ω, ω′/ω<1/1
．． The vibration isolating device for a hand-held power tool according to claim 1, which is an elastic body having a spring constant of 4.