JPH09239672A - Impact driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimizing the reaction of a body for the prevention of the falling of a screw by integrating a sun pinion, first gear, carrier with a built-in third gear and a fixed ring gear into a planet gear section. SOLUTION: A second gear 2b rotates on its axis through a first gear 2a in the same direction as a sun pinion 1. A third gear 2c also rotate on its axis in the same direction as the sun pinion 1. The third gear 2c rotates a carrier 2 in the direction opposite to that of the sun pinion 1 through a fixed ring gear 3. Accordingly, the impact mechanism section connected to the carrier 2 rotates in the direction opposite to the rotation direction of a motor, offsetting the rotation moment of the motor, resulting in minimizing the reaction when the motor is started. Therefore, this constitution can minimize such failure as falling a screw.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed reduction mechanism for a T-shaped impact driver.

[0002]

2. Description of the Related Art T-shaped impact drivers are widely used because they have a good balance when held in the hand and are easy to use. However, when a wood screw or a tex screw for steel frame is to be tightened while making a hole on the surface without the prepared hole, there is a drawback that the screw falls down at the moment when the motor is started. This is because at the moment the motor is started, the bit shakes sideways due to the reaction of the motor, and at the same time, the screw has not yet bite and the screw falls. The bit that fell off the screw head when it fell down could damage the decorative plate and window frame and ruin it.

This is because the main body as a whole is rotated by the reaction force of the motor with the handle portion held by the hand as a fulcrum, so that the body portion of the main body and the bit shaft swing sideways. The impact driver, in which the driving battery is housed at the tip of the handle, is easily rotated because the center of gravity itself shifts from the main body to the handle portion due to the weight of the driving battery, which causes a larger lateral shake. The planetary gear mechanism impact driver with the ring gear fixed, the sun pinion as the input shaft, and the carrier as the output shaft has the same rotation direction of the sun pinion and the carrier, so the rotation direction of the motor and the impact mechanism is the same. In the same way, the reaction force of the impact mechanism was added to the reaction force of the motor.

Therefore, the trigger switch is set to shift,
A method has been adopted in which an operator slowly activates the motor to reduce the lateral shake of the main body. In addition, since the recent motor is small enough to balance with the rotation moment of the impact mechanism, the planet gear is fixed to the carrier, the sun pinion is used as the input shaft, and the ring gear is used as the output shaft. By changing the rotation direction of the input shaft and the output shaft by making it a star type, and rotating the motor and the impact mechanism part in the opposite direction, the rotation moment of the motor is changed to the rotation moment of the impact mechanism part. There was a thing to offset it and reduce the recoil.

[0005]

However, a slow starter requires a long time since it is operated slowly until the screw bites, or it is necessary to make an intermittent motion between the chuncheon and the trigger switch.

The star type gear mechanism has an effect of rotating the input shaft and the output shaft in the opposite directions, but has a drawback that the reduction ratio is smaller than that of the planetary type. Set the number of teeth of the sun pinion to Z
a, the number of teeth of the idle gear is Zb, the number of teeth of the ring gear is Z
c, and when the rotation direction of the output shaft is the same as that of the input shaft, it is represented by +, and when it is opposite, it is represented by a sign of +, {/ ((Zc / Za) +1} ...
……… (1) Star type is –1 / (Zc / Za) ……………………
……… (2). For example, if Za is 7, Zb is 20, and Zc is 47, (1) is + 1 / 7.714 ...
(2) becomes -1 / 6.714 ... In the star type, the output shaft rotates in the opposite direction to the input shaft, but (2)
Has less one denominator than (1) and a smaller reduction ratio. In order to make (2) the same as (1), there is a method of reducing Za or increasing Zc. However, in the case of a practical impact driver, since Za is reduced to the limit of the strength surface in order to obtain a predetermined reduction gear ratio, it is necessary to actually increase Zc. The diameter has increased, the body has become thicker, and the center height has increased. In addition to the one that can't make the ring gear bigger, another length reduction gear is added, so the total length is longer. These are major drawbacks for impact drivers who often work in narrow spaces or corners.

An object of the present invention is to rotate the motor and the impact mechanism part in opposite directions without increasing the center height or length of the motor, and thereby rotate the motor.
This is to reduce the reaction of the main body and the failure of the screw to fall by offsetting the rotation moment of the motor as much as possible.

[0008]

The above-mentioned problems are solved by the planetary gear unit including a sun pinion connected to a motor, a carrier incorporating a first gear, a second gear and a third gear, and a fixed ring gear. The second gear and the third gear are coaxially integrated or connected,
This is achieved by the sun pinion meshing with the first gear, the first gear meshing with the second gear, and the third gear meshing with the ring gear.

[0009]

FIG. 1 shows an example of an embodiment of the present invention.
2 to FIG. FIG. 1 is a sectional view showing a gear relationship of a reduction gear unit of a T-shaped impact driver according to the present invention. In the figure, 1 is a sunpinion connected to the motor. 2 is a carrier connected to the impact mechanism section. Reference numeral 3 is a fixed ring gear. Two
Reference numeral a is a first gear which is built in the carrier 2 and meshes with the sun pinion 1. Reference numeral 2b is a second gear which is built in the carrier 2 and meshes with the first gear 2a. 2c is built in the carrier 2 and the second gear 2b
Ring gear 3 which is integrated or connected coaxially with
It is a third gear that meshes with.

FIG. 2 shows an overall side view of an impact driver adopting the present invention. The features of the reduction gear unit having the above configuration will be described.

First, the direction of rotation will be described. The second gear 2b rotates in the same rotation direction as the rotation of the sun pinion 1 via the first gear 2a. Similarly, the third gear 2c also rotates in the same rotation direction as the rotation of the sun pinion 1. The third gear 2c rotates the carrier 2 in the direction opposite to the sun pinion 1 by the fixed ring gear 3. For this reason, the impact mechanism connected to the carrier 2 rotates in the direction opposite to the rotation direction of the motor to cancel the rotation moment of the motor and reduce the reaction at the time of starting.

Second, the reduction ratio will be described. The reduction gear ratio of the reduction gear portion having the above-described structure is such that the number of teeth of the sun pinion 1 is Za, the number of teeth of the first gear 2a is Zb1, the number of teeth of the second gear 2b is Zb2, and the number of teeth of the third gear 2c is Zb.
3, when the number of teeth of the ring gear is Zc, -1 / {(Z
c / Za) * (Zb2 / Zb3) -1} ... (3).

For example, Za is 7, Zb1 is 15, Zb2
Is set to 17, Zb3 is set to 13, and Zc is set to 47, then (3) becomes −1 / 7.780 ... (3) is a reduction ratio equivalent to the planetary type reduction ratio (1). Zb2, Z
A larger reduction ratio can be obtained by devising the relationship of b3. First gear 2a and third gear 2c
Can be disposed between the sun pinion 1 and the ring gear 3, so that the diameter of the ring gear is not larger than that of the planetary type.
The second gear 2b is also the ring gear 3 rather than the ring gear 3.
Since you can choose not to stick out so that you cannot fix it, do not make the body part thick.

If it is not necessary to reduce the reduction ratio, the third gear 2b can be eliminated and the second gear 2b can be meshed with the ring gear 3. The reduction ratio at this time is −1 / {(Zc / Za) −1} ... (4).

For example, Za is 7, Zb1 is 15, and Zb2 is
Is set to 17 and Zc is set to 47, (4) becomes -1/5.
714 ...

Thirdly, the tooth width will be described. When comparing the strength of each gear in the planetary gear unit of a practical impact driver, the sun pinion is the weakest. In some cases, it is less than half that of idle gear and ring gear. Therefore, the tooth width of the gear that first meshes with the sun pinion is one of the dimensions that determines the minimum width dimension of the planetary gear unit. In terms of strength, the second gear 2b, the third gear 2c, and the ring gear 3 need only have a blade width that is approximately half that of the sun pinion 1. Therefore, the second gear 2b and the second gear 2c
Can be arranged between the blade width of the first gear meshing with the sun pinion 1 or in a slightly larger range. Further, the first gear 2a can be disposed inside the ring gear 3 with a number of teeth having a strength sufficient to mesh with the second gear 2b having a blade width half that of the sun pinion 1. Therefore, the total length of the main body portion can be reduced to a slight extent even if the length is increased.

[0017]

According to the present invention, the speed reduction ratio can be made equal to or more than that of the planetary type, the first gear and the third gear can be arranged in the gap between the sun pinion and the ring gear, and the second gear can be more effective than the ring gear. It can be selected so that it does not protrude significantly, and since the second gear and the third gear can be arranged within the same width as the blade width of the first gear that meshes with the sun pinion, the body part of the main body can be thickened and the overall length can be lengthened. I do not do it. Further, since the carrier and the impact mechanism section are rotated in the direction opposite to the rotation direction of the motor, it is possible to reduce the recoil at the time of startup in the T-shaped driver and reduce the failure of the screw to fall.

[Brief description of drawings]

FIG. 1 is a state diagram showing an embodiment of a reduction gear according to the present invention.

FIG. 2 is a partially longitudinal side view showing an impact driver adopting the present invention.

[Explanation of symbols]

1 is a sun pinion, 2 is a carrier, 2a is a first gear, 2b is a second gear, 2c is a third gear, and 3 is a ring gear.

Claims (3)

[Claims] 1. A main body portion including a motor portion of a drive source, a planetary gear portion for reducing the rotation of the motor portion, and an impact mechanism portion, and a bar-shaped handle portion substantially at the center of the main body portion. The planetary gears are arranged in a substantially T-shape, and the planetary gear part is a sun pinion and a far
The second gear and the third gear are coaxially integrated with or connected to each other, and the sun pinion and the first gear are composed of a carrier having a built-in streak gear, a second gear, and a third gear, and a fixed ring gear. Mesh,
The first gear meshes with the second gear, and the second gear engages with the second gear.
An impact driver characterized in that the do gear meshes with the ring gear. 2. The carrier includes the first gear and the second gear, the sun pinion meshes with the first gear, the first gear meshes with the second gear, and the second gear meshes with the ring gear. The impact driver according to claim 1, wherein the impact driver engages with each other. 3. A power source unit for accommodating a driving battery is arranged at the tip of the handle.
The impact driver according to claim 2.