JP2003245866A - Electric tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make engaging shapes of a torque transmitting part highly durable and cold-forge the engaging shapes, and facilitate the dimension management of the engaging shape for a rotary strike tool employing a split anvil method. <P>SOLUTION: The engaging shapes are formed into teeth profile comprising smooth curves. The teeth profile of each engaging shape is made in such a way that the side shape of it is composed of two planes symmetrical and parallel to each other, the bottom shape is composed of two planes that makes each teeth bottom in a symmetrical position across the axis of the engaging shape parallel to each other, and the outer periphery shape is composed of arcs having its center as the axis. The teeth profiles are rounded at a spot where each engaging shape crosses each other. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noise reduction of a rotary impact tool.

[0002]

2. Description of the Related Art Rotary impact tools are widely used nowadays because of their small reaction force transmitted to the hand and high tightening ability. However, noise is a serious problem due to the mechanism that uses impact.

FIG. 2 shows a structural sectional view of a hitting mechanism portion of a general rotary hitting tool which has been conventionally used. The striking mechanism is operated by the driving force of the motor to strike the anvil to impart a rotary striking force to the tip tool.

The striking mechanism will be described below. The driving force of the motor 1 rotates the spindle 9 via the planetary gear mechanism 2. Spindle 9 and hammer 5 are cam balls 10
And a V-shaped cam groove 9a. Further, the hammer 5 is always urged forward by the spring 4. The functions of the cam and spring 4 are as follows. That is, when the spindle 9 and the hammer 5 are relatively twisted, the hammer 5 is retracted toward the motor 1 side by the action of the V-shaped cam groove 9a cut in the V shape.
When released from the twist, the spring 4 accelerates to rotate and move forward. Further, the hammer 5 and the anvil 14 respectively have a hammer convex portion 5a and an anvil convex portion 14a symmetrically arranged at two positions on the rotation plane, and the hammer convex portion 5a and the anvil convex portion 14a are in a position where they are engaged with each other in the rotational direction. It is in. The rotation striking force is transmitted by the engagement of the convex portions. With the above configuration, the operation of the rotary impact proceeds as follows. The rotational force of the spindle 9 is transmitted to the hammer 5 via the cam mechanism and starts to rotate together. Before half a turn, the protrusions of the hammer 5 and the anvil 9 mesh with each other. The spindle 9 and the hammer 5 are twisted relative to each other, and the hammer 5 starts retracting while compressing the spring 4. Eventually, the height of the convex portion can be overcome and the meshing can be solved. Hammer 5
In addition to the rotational force of the spindle 9, the elastic energy stored in the spring 4 accelerates in the rotational direction and starts the forward movement. While the hammer 5 is being accelerated, the convex portions are fitted again, but at this time, a strong rotary impact force is applied to the anvil 14 and is transmitted to the tightened member. And the hammer 5 starts to retreat again.

The above is the cycle of rotary impact. In this cycle, the hammer 5 moves back and forth at the same time as the rotary motion, but hits the member to be tightened in the axial direction through the anvil 14, the tip tool 13, and the screw 16 to make a loud noise.

By the way, the noise during the operation of the rotary impact tool is
It is known that there are two, that is, the amount generated from the tool body and the amount generated from the member to be clamped, of which the noise energy from the member to be clamped occupies a large proportion. In order to reduce noise, it is a priori to reduce the impact force in the axial direction transmitted to the member to be tightened. JP-A-7-237
In 152, the anvil is divided into two parts, and a means for buffering the axial force is provided. It is an anvil divided into two
Fit the cushioning material so that it can slide in the axial direction, and
It was arranged between the divided anvils. By this method, the vibration force in the axial direction transmitted to the tightened member is reduced, and the noise from the tightened member is reduced.

The fitting of the anvils divided into two parts was based on a square as shown in FIG.

An important issue here is the durability of the torque transmission part fitted by the two anvils divided into two parts. The striking force in the rotating direction and the exciting force in the axial direction are simultaneously applied to the anvil. That is, the torque transmission section repeats sliding under high torque. For this reason, the torque transmission part needs to have a strength that can withstand a rotational impact force and a surface hardness that can withstand friction under high surface pressure. On the other hand, in recent years, in order to improve the tightening performance of the rotary impact tool, the rotary impact force tends to be increased. Under such circumstances, the torque transmission part cannot secure sufficient durability simply by improving the strength and hardness of the material. Therefore, when designing the torque transmitting portion, it is necessary to consider a fitting shape that reduces the load on the material. In addition, it is required to suppress the manufacturing cost as much as possible in mass production. Cold forging is desirable, but in principle,
It is unavoidable that the shapes of the corners and the corners are rounded, and a shape having many fine teeth such as an involute spline cannot be manufactured.

It is also important to facilitate the dimension control of the fitting shape. This is because the contact state changes greatly due to the dimensional deviation, which affects the life etc. For example, when a fitting shape using a plurality of tooth shapes is used, due to dimensional deviation, excess weight is concentrated only on a part of the tooth shapes, which may lead to damage. Further, the two-division anvil method is to alleviate the axial force by making the torque transmitting portion move smoothly in the axial direction. For this purpose, it is necessary for the fitting of the torque transmitting portion to have an appropriate clearance. As described above, dimensional control of the fitting shape is important in terms of strength and noise reduction. Inspection using a gauge is generally used for dimensional control of the fitting part of mass-produced products. This is to prepare a gauge manufactured at the upper limit of the dimensional tolerance and a gauge manufactured at the lower limit, and inspect whether the dimension of the component is within the allowable range by checking whether the gauge passes or stops in the component. . The advantage is that inspection can be done by simple work, but the dimensional values themselves cannot be measured. Therefore, when a part fails, another additional inspection is required to identify which dimensional elements are out of order. If you can measure with a caliper, you can directly measure the dimension value, but if it is not, you have to prepare a dedicated gauge, and the measurement is indirect and it is difficult to grasp the dimension value quantitatively. Become. Therefore, the fitting shape should be a shape that can be measured with a caliper.
It is desirable in terms of manufacturing cost and dimensional accuracy. The fitting shape by the quadrangle in FIG. 6 is adopted because it has a simple shape, is suitable for cold forging, and is easy in dimensional control, but has poor durability. During long use, the anvils that were divided into two parts sometimes bite at the fitting part, making it impossible to buffer the axial force.

[0010]

In the two-division anvil system, a fitting shape with high durability is required. Also,
From the viewpoint of manufacturing cost, cold forging is required. It is also important to ensure dimensional accuracy, and it is required to facilitate dimensional control.

The object of the present invention is to provide a rotary impact tool adopting a two-divided anvil system, in which the fitting shape of the torque transmission portion is made highly durable, cold forging is possible, and dimensional control is performed. It is easy to do.

[0012]

The above-mentioned object is to provide a spindle for transmitting a rotation, a hammer that rotates and reciprocates by the action of a cam groove of the spindle, a spring that constantly urges the hammer, and a convex portion of the hammer. In a power tool consisting of a striking anvil and a tool holding part such as a bit, the anvil is divided into two parts, the two parts are fitted together, and a two-part anvil type in which torque can be transmitted to each other and axially movable In addition, the fitting shape of the torque transmission part is a spline shape in which a plurality of teeth and tooth grooves that engage with each other with a tooth profile of similar shape are circumferentially arranged at equal intervals, and the tooth profile is configured by a smooth curve. To be achieved.

[0013]

FIG. 1 shows one of the embodiments according to the present invention. A two-division anvil system is used for a general rotary impact tool of the prior art. The anvil includes a first anvil 6, a second anvil 8, a damper 7, and a washer 15. 4 and 5 show three-dimensional views of the first anvil 6 and the second anvil 8, respectively. The first anvil 6 and the second anvil 8 are engaged with each other by the tooth portion 6c and the tooth groove 8b in the torque transmission portion 6b. A rubber damper 7 is arranged between the first anvil 6 and the second anvil 8, and a washer 15 is arranged between the first anvil 6 and the damper 7. The first anvil 6 and the second anvil 8 are provided with a cylindrical portion 6d coaxial with the torque transmitting portion 6b and a cylindrical hole portion 8a, and they fit with each other with a slight clearance. Further, the first anvil 6 has a first through hole 6e,
A cavity 8c and a second through hole 8d are provided on the bottom of the hole of the second anvil.

The operation of the two-division anvil system will be described with reference to FIG. The hammer 5 rotates while advancing in the axial direction, and strikes the first anvil convex portion 6a in an oblique direction. At this time, the force acting on the first anvil protrusion 6a is also in the oblique direction. This force can be divided into a rotational direction component and an axial direction component as shown in the figure. The direction component of rotation functions to turn the screw. The axial component is a cause of striking the material to be tightened and generating noise.

With the two-anvil method, the axial component forces are damped as follows. That is, the force of the axial component is transmitted from the first anvil convex portion 6 a to the washer 15 and dispersed, and is damped by the damper 7. As a result, the tightened member 1
The power to hit 7 is reduced.

Besides, FIG. 1 also includes a structure having an effect of improving the life.

A cylindrical portion 6d is formed at the base of the tooth portion 6c of the first anvil 6, and a cylindrical hole portion 8a to be fitted therein is provided in the second anvil 8. By fitting these without clearance, the first anvil 6 and the second anvil 8 do not become misaligned, and the life is improved.

Further, by providing the first through hole 6e in the first anvil 6 and providing the space portion 8c at the hole bottom of the second anvil 8, the grease in the hammer case 3 passes through the first through hole 6e and becomes a space. Accumulation in the portion 8c does not impede lubrication to the fitting portion, and the life is improved.

Next, the fitting shape of the torque transmitting portion 6b will be described. The two-division anvil system requires a fitting shape with high durability. Further, it is required that the manufacturing be suitable for cold forging, which is inexpensive, and that dimensional control be easy.

FIG. 7 shows an example of a fitting shape according to the present invention. It is composed of 6 tooth profiles with smooth curves. With such a shape, cold forging becomes possible. Further, by forming the tooth shape, the drive angle can be reduced, the surface pressure of the contact surface of the fitting portion can be reduced, damage of the contact surface can be reduced, and biting of the fitting portion can be prevented. Increasing the number of teeth also has the effect of reducing the surface pressure of the contact surface of the fitting portion. These effects and the meaning of the drive angle will be described in detail later. Regarding the difference from the quadrangle in FIG. 6, the difference in contact surface pressure can be seen from the difference in the magnitude of the force F acting on the contact surface shown in the figure. This will also be described in detail later.

The effect of increasing the number of teeth and the effect of reducing the drive angle will be described below with reference to FIG.

First, the effect of increasing the number of teeth will be described. When the distance r between the contact surface and the central axis is the same, the rotational force fc carried by one tooth can be reduced by increasing the number of teeth n. When expressed by an equation, the transmission torque is represented by the following equation.

Fc = T / (r · n) Next, the meaning of the drive angle and the effect of reducing it will be described with reference to FIG. In FIG. 7, F is a vector representing the force acting on the contact surface. The direction of the arrow indicates the direction of the force, and the length indicates the magnitude of the force. At this time,
Since the grease is properly lubricated and the frictional force is small, we will simply ignore the friction and calculate. F can be considered as being divided into a rotational direction component and a radial direction component, and they are referred to as fc and fr, respectively. Here, fb has one tooth as the second
It means the rotational force that tries to rotate the anvil. The angle formed by F and fb will be called the drive angle θ. Then, it can be seen that if the rotational force fc is kept constant and θ is increased, F will be gradually increased. This means that in the fitting shape in which the drive angle θ is large, even if the rotational force fc applied to the teeth is the same, the force F acting on the contact surface becomes large and the contact surface pressure becomes large. Therefore, reducing the drive angle θ is an effective means for reducing the contact surface pressure and preventing the engagement portion from biting. The above relationship can be expressed as the following equation. The value of F in the figure is calculated by the following equation.

F = fc / cos θ = T / (r · n · cos θ) FIG. 8 shows another example of the fitting shape according to the present invention. It is composed of four tooth profiles that are configured by using a number of parallel two surfaces. The details of the tooth profile are two planes that are symmetrical and parallel for the side shape, two planes that are parallel to each other at the target position about the axis for the tooth bottom shape, and rotate for the outer peripheral shape. It consists of a circular arc centered on the axis, and the intersection of these shapes is rounded.

The tooth profile is relatively smooth and cold forging is possible. In addition, even though it has a complicated fitting shape, it is possible to measure the opposite side with a vernier caliper by using a lot of parallel two surfaces, which simplifies dimensional control. B1 and B shown in the figure
2, φD is the main dimension that defines the fitting shape,
All of these can be measured by calipers.

The contact surface pressure is also smaller than that of the quadrangle in FIG. 6, as indicated by the magnitude of the force F acting on the contact surface in the figure.

[0027]

EFFECTS OF THE INVENTION By forming the fitting shape with a tooth shape consisting of a smooth curve, the drive angle can be made as small as 40 ° or less, the contact surface pressure at the fitting portion can be reduced, the damage on the contact surface can be reduced, and the fitting can be reduced. It is possible to prevent biting of parts. In addition, cold forging is possible and the manufacturing cost can be reduced.

Further, the mating tooth profile is composed of two planes which are laterally symmetrical and parallel with respect to the side surface shape, and two tooth planes which are parallel to each other at the object positions with respect to the axis about the tooth root shape. As for the outer peripheral shape, it consists of an arc centered on the rotation axis, and by making the tooth shape where these shapes intersect rounded, the drive angle can be reduced to 25 ° or less as in the above, and the contact of the fitting part Surface pressure can be reduced, contact surface damage can be reduced, and engagement of the fitting portion can be prevented. In addition, cold forging is possible and the manufacturing cost can be reduced. In addition, the fitting shape can be measured with a caliper, which simplifies dimensional control. By providing the cylindrical portion in which the first anvil and the second anvil are fitted to each other, misalignment of the tooth portion can be prevented and the life can be improved.

Further, due to the effect of the first through hole of the first anvil and the space for accumulating grease, grease lubrication is always performed on the tooth portion where a high surface pressure acts, and biting prevention and life extension are achieved.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing one embodiment of a striking mechanism portion of a rotary striking tool having a two-division anvil system according to the present invention.

FIG. 2 is a structural cross-sectional view showing an example of a striking mechanism portion of a general rotary striking tool which is a conventional technique.

FIG. 3 is a diagram showing forces acting on a two-division anvil system.

FIG. 4 is a perspective view of a first anvil according to a two-division anvil system.

FIG. 5 is a perspective view of a second anvil according to a two-division anvil system.

FIG. 6 is an example of using a square as a fitting shape, which is a conventional technique.

FIG. 7 is an example of using a tooth profile formed by a smooth curve in a fitting shape according to the present invention.

FIG. 8 is an example using a tooth profile according to the present invention, which is configured by frequently using two surfaces parallel to the fitting shape.

[Explanation of reference numerals] 1 is a motor, 2 is a planetary gear mechanism, 3 is a hammer case, 4
Is a spring, 5 is a hammer, 5a is a hammer convex portion, 6 is a first anvil, 6a is an anvil convex portion, 6b is a torque transmitting portion, 6c is a tooth portion, 6d is a cylindrical portion, 6e is a first through hole, 7
Is a damper, 8 is a second anvil, 8a is a cylindrical hole, 8b is a tooth groove, 8c is a space, 8d is a second through hole, 9 is a spindle, 9a is a V-shaped cam groove, 10 is a cam ball, 11 is a Metal, 12 is an oil seal, 13 is a tip tool, 14 is an anvil, 14a is an anvil protrusion, 15 is a washer, 16
Is a screw, and 17 is a member to be tightened.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuma Saito             Hitachiko, 1060 Takeda, Hitachinaka City, Ibaraki Prefecture             Machine Co., Ltd.

Claims (4)

[Claims] 1. A spindle that transmits rotation, a hammer that rotates and reciprocates by the action of a cam groove of the spindle, a spring that constantly urges the hammer, an anvil that is struck by a convex portion of the hammer, a bit, etc. In the electric tool composed of the tool holding part, the anvil is divided into two
The parts are fitted together, the torque can be transmitted to each other, and it is a two-part anvil type that is movable in the axial direction, and the fitting shape of the torque transmitting part is such that a plurality of teeth and tooth grooves that are engaged with each other with a tooth profile of a similar shape are A power tool, characterized in that it has a spline shape arranged at regular intervals, and the tooth profile is composed of smooth curves. 2. The tooth profile is composed of two planes which are symmetrical and parallel to each other in terms of a side surface shape, and two plane surfaces in which the tooth roots at target positions about an axis are parallel to each other in terms of a tooth bottom shape, and an outer periphery thereof. The electric tool comprises a circular arc centered on the rotation axis, and a rounded tooth profile is provided at the intersection of these shapes. 3. An anvil divided into a first anvil and a second anvil, wherein a cylindrical shaft portion is provided on the first anvil and a hole portion is provided on the second anvil, separately from the torque transmitting portion, and the fitting is performed. The electric power tool according to claim 1, which is characterized in that. 4. An anvil divided into a first anvil and a second anvil, wherein a through hole is provided on the axis of the first anvil and a space is provided between the first anvil and the second anvil. The electric power tool according to claim 1.