JPS6033636B2 - electric hammer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric hammer, and more particularly to an electric hammer that reduces vibrations caused by inertial unbalanced force.

Figure 1 shows the structure of a conventional single-cylinder reciprocating electric hammer.The rotation of a motor 1 is transmitted to a crank pin 4 via a gear 3 fixed to a crankshaft 2. Rotate in the direction. This rotation of the crank pin 4 is transmitted to a piston 7 attached to the cone rod 5 via a piston pin 6, and the piston 7 reciprocates within the cylinder case 8. A striker 9 is interposed between the piston 7 and the cylinder case 8, and when the piston 7 moves in the direction of the arrow, the air between the striker 9 and the piston 7 is compressed, thereby pushing the striker 9. and hit the end face of bull point 10. Bull Point 1 River hits, for example, concrete 11, crushes the concrete 11, and then bounces back. On the other hand, Striker 9
is the rebound from the end face of the pull point 10 and the piston 7
It returns to its original position with the suction caused by the return stroke, and the same movement is repeated.

FIG. 2 shows details of the piston-crank mechanism portion of the electric hammer shown in FIG. 1, and parts with the same reference numerals as in FIG. 1 are the same parts.

A rotating balancing bell 12 is attached to the center of the crankshaft 2, and a crank pin 4 is mounted on the rotating balancing weight 12.
is fixed. It is the pull point impact reaction force and the piston compression reaction force that contribute to the vibration of the electric hammer under actual load as shown in FIGS. 1 and 2, and the influence of the inertial unbalanced force is the main factor.

However, the main cause of vibration when no load is applied is inertial unbalanced force. Although no-load vibration is specifically specified, it is an important element in increasing the commercial value of electric hammers.
The piston-crank mechanism of the secondary electric hammer shown in FIG. 2 is shown in FIG. 3 as a lumped mass system. The equivalent weight WP of the piston 7 and the equivalent weight W2 of the crank mechanism are expressed by the following equations.

WP=WPo+WcP W2=Wc20W2.

In the above formula, WPo: Weight of piston 7 WcP: Equivalent weight of cone rod 5 on the piston side Wc2:
Equivalent weight of the cone rod 5 on the crank side W2o: Weight of the crank mechanism Subsequently, the unit weight Wc of the cone rod 5 is Wc=WcP+Wc2 WcP・a! Wc2・b a: Length from the crank pin 4 to the center of gravity G of the cone rod 5 alone b: Length from the piston 7 to the center of gravity of the cone rod 5 alone Also, modified moment of inertia J to make it a concentrated mass system is J=Wc(k2-a・b)/g In the above equation, g is the gravitational acceleration and k is the cone.

The radius of rotation of the moment of inertia around G of only the head 5,
IG: What is the crank angle of the moment of inertia around the center of gravity G of a single cone rod? , if the rotation angle is a, then Sm=pSm8 r P=t . COS8 = P's centering = -p's 2 COS and Sina p: Ratio of crank radius to length of cone rod 5 r: Crank radius w: Rotational angular velocity L: Length of cone rod 5 Inertial unbalance at this time The force U is U=IP1120IB={(WP+W2)r-WBRB}W2ei8/g+W
PL(iA1■2)ei○/g The inertial unbalanced force referred to here refers to a force that acts in the same direction and perpendicular direction to the piston operating direction.

IP: Inertia force acting on the piston 7 12: Inertia force acting on the crank mechanism IB: Inertia force acting on the rotating balancing weight R8: Length of the arm of the rotating balancing weight and inertial unbalance torque M is M: -K[rWPL(mecos(80J)-gu n(8
10)}/g 1 pCOS8 {r's WPbin (80○) 10◇(WP
L20gL)}/gcos] In the conventional electric hammer shown in FIGS. 1 and 2, the weight W of the rotating counterweight 12 is
The inertial unbalanced force is reduced by changing B or the radius rB of the balance wheel weight.

Typical methods for reducing the inertial unbalanced force mentioned above are:
There are rotating weight balance methods, half balance methods, overbalance methods, etc. The adjustment methods for these methods and the inertial forces in each direction after adjustment are as follows.

,M〒(Wpノg)r2oj28/2--Sin8
No413Sin38-4)-J.

2.2Sin28.2 In the conventional balancing system, as described above, a large inertial unbalanced force remains in the direction where balance is achieved and not.

For example, in the case of a rotational weight balance system, a large inertial unbalance force remains in the direction of piston movement, and vibrations in the piston direction become large. Also, even in the half-balanced system and the overbalanced system, a large inertial unbalanced force remains in the direction of piston movement or in the direction perpendicular to it. The present invention has been made based on the above-mentioned matters, and by reducing the inertial unbalanced force in any direction, vibrations generated by the inertial unbalanced force are reduced.
The object of the present invention is to provide an electric hammer that can reduce the burden of muscular labor on a worker and suppress the occurrence of vibration disorders.

The present invention is characterized by an electric hammer that crushes concrete by striking the hammer with a striker pushed out by air pressure compressed by the reciprocating motion of a piston, in which a piston is attached to one end via a piston pin. The other end of the cone rod is extended beyond the crank pin, a swinging balance wheel weight is attached to this extension, and a rotating balance wheel bell is attached to the crank pin. .

An embodiment of the electric hammer of the present invention will be described below with reference to FIG.

In FIG. 4, the same reference numerals as in FIG. 2 indicate the same parts.

A piston (not shown) is attached to one end of the cone rod 13 via a piston pin 6 as in the conventional case, and the other end is formed to extend beyond the crank pin 4.

A vibration balancing wheel weight 14 is attached to the extension of the cone rod 13 in order to reduce the unbalanced force in the direction of piston movement. Further, a rotating balance weight 15 is attached to the crank pin 4 of the crankshaft 2, and the weights and arm lengths of these weights 14 and 16 are determined according to the following relational expression. (WP10W^10W2)Y=WB
RB...{1}R^=0, Hiro ~ 0.8L
・・・・・・■W＾=WP
...'31■, W instead of glue type
^・RA=(0.5-0.6)WP・L may also be used.

In the above formula, RA: Length of the arm of the oscillating counterweight 14 W^: Weight of the oscillating counterweight 14 WB: Weight of the rotating counterweight 15 RB: Length of the arm of these R ^, RB, W^ and W8 as above '11
, {21, {3} by choosing to satisfy the expression
It is possible to reduce the inertial unbalanced forces in the piston movement direction and the direction perpendicular thereto by 4, and to average out the inertial unbalanced forces.

When the electric hammer of the present invention is expressed in a concentrated weight system, it becomes as shown in FIG.

In the present invention, the inertial unbalanced force U and the inertial unbalanced torque M are U=IP+IA+120 IBi (WPL-W^R^) (
i and ten 2) e-i? /g In the above equation, 1^: Inertial force acting on the oscillating balance weight 14 = -k[r(WPL-W
^R^)X {A COS (01a) Ichizu Sin (80◇)
}/g-pCOS8{r■2(WPL-WAR^)Si
n (8 tenya) tena (WPze+W^R^2 tengJ)}/
Battle os◇2o].

Figures 6a, b, and c compare the electric hammer system of the present invention and the conventional electric hammer system. In c, the vertical axis represents the unbalanced torque (k9 one skin), and the horizontal axis represents the rotation angle. The solid line represents the method of the present invention, the dotted line represents the conventional rotational balance method, and the dashed line represents the half balance method. The method is shown.

Figure 6a shows the unbalanced force in the direction of piston movement,
Compared to conventional methods, the inertial unbalanced force is extremely small. FIG. 6b shows the unbalanced force in the direction perpendicular to the piston, and FIG. 6c shows the inertial unbalanced torque, both of which are slightly smaller than those of the conventional system. Figure 7 compares the vibrations in the piston movement direction of an electric hammer embodying the present invention and a conventional electric hammer (rotational balance type), with the vertical axis representing the vibration acceleration (g) and the axis representing the frequency. (Hz), the solid line shows the case of the present invention, and the dotted line shows the conventional case, and the vibration in the hammer of the present invention is much smaller.

In the figure, ISO c・f=1 or 5 is an index measured by ISO to prevent vibration damage, for example, c
- When f=5, if you work for 4 to 8 hours while taking regular breaks, you need at least 40 minutes of break time per hour, and when c'f=1, you need 20 minutes. The conventional method does not pass the ISO standard, but the present invention does. According to the present invention, since the oscillating balance bell and the rotating balance weight are attached to the electric hammer, it is possible to reduce the inertial unbalanced force generated by the inertial unbalanced force, especially in the direction of piston movement. Reduces vibrations caused by
It can reduce the burden of muscular labor on workers and suppress the occurrence of vibration disorders.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a conventional electric hammer, with Figure 1 being an overall view, Figure 2 showing the piston-crank mechanism, and Figure 3 concentrating the piston-crank mechanism shown in Figure 2. 4 is a cross-sectional view of a part of the piston-crank mechanism of the electric hammer of the present invention, and FIG. 5 is a diagram showing the concentrated weight of the piston-crank mechanism shown in FIG. Figures 6a, b, and c are diagrams comparing the inertial unbalanced force and inertial unbalanced torque of the present invention and the conventional method, and Figure 7 is a diagram comparing the vibrations of the electric hammer implementing the present invention and the conventional electric hammer. be. 4... Crank pin, 6... Piston pin, 13... Corn rod, 14... Oscillating balance wheel weight, 15... Rotating balance weight. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 6

Claims (1)

[Claims] 1. In an electric hammer that crushes concrete, etc. by hitting it with a hammer with a striker pushed out by air pressure compressed by the reciprocating motion of the piston, the other end of the cone rod to which the piston is pivotally connected via a piston pin. An electric hammer, characterized in that the electric hammer is formed by extending beyond the crank pin, a swinging counterweight is attached to the extended portion, and a rotating counterweight is attached to the crankpin.