JP2009083033A - Screw fastening tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw fastening tool having small noise and vibration, quietness and excellent operability. <P>SOLUTION: This screw fastening tool 1 is provided with: a gear shaft 8 transmitted with rotation from a motor to be a driving source via a gear 7; a socket (spindle) 10 relatively rotatably supported on the gear shift 8; a driving clutch portion 11 fixed to the gear shaft 8; and a driven clutch portion 19 supported to be rotatable and movable in a shaft direction in relation to the gear shaft 8. A driving claw 14 of the driving clutch portion 11 and a driven claw 21 of the driven clutch portion 19 are formed into fan shapes extending from an axial center. Each angle of the fan shapes of both of the claws 14 and 21 is set in the range of 9° to 36°. During an initial engagement, at least two sheets or less of each of the driving claws 14 and the driven claws 21 are engaged with other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a screw fastening tool using power, and more particularly, to a screw fastening tool provided with a clutch mechanism that cuts off torque applied to a screw at a predetermined fastening depth while continuously rotating a motor.

  For example, a screw driver is conventionally known as a screw fastening tool. As this screw driver, a stopper whose position can be adjusted in the axial direction is provided in a part, and an operator can screw until the stopper comes into contact with a material to be fastened. After the screw driver main body is pushed through the stopper and the stopper comes into contact with the material to be fastened, the clutch is disengaged with claws or the like.

  In such a screwdriver, the operation is performed while continuously rotating the motor at a high speed in order to increase the work efficiency. Therefore, if the clutch pawl is simply interposed between the gear and the spindle, Large noise and vibration are generated by interference, that is, collision between clutch claws at the start of screw tightening and re-collision between clutch claws after completion of screw tightening. Such noise and vibration not only cause discomfort to the surroundings and the workers themselves, but also the nails tend to wear out, which is a problem in terms of life. For this reason, a comfortable screw fastening tool with good operability has been desired.

  In order to improve noise, vibration, operability and life, the clutch after screwing should be completely disengaged. In Patent Document 1, a gear meshed with a pinion provided in a motor is integrally formed. Between the driving clutch pawl and the output clutch pawl provided on the spindle shaft holding the screwdriver screw bit, a third rotatable and axially slidable clutch that is always engaged with the output clutch pawl. There has been proposed a screwdriver in which an intermediate clutch pawl is provided and a spring is disposed so as to have a certain distance between the driving clutch pawl and the intermediate clutch pawl.

  The screw tightening operation using such a screw driver is performed by attaching the screw to the driver bit while rotating the motor, that is, by pressing the screw driver against the material to be fastened while rotating the gear and the driving clutch pawl. The In this case, the spindle shaft moves together with the driving clutch pawl and the intermediate clutch pawl to the driving clutch pawl side, the intermediate clutch pawl and the driving clutch pawl mesh with each other, torque is transmitted to the spindle shaft, and the screw The drive clutch pawl and the intermediate clutch pawl are disengaged at a predetermined position, and torque transmission is interrupted. After the torque transmission is cut off, a constant distance is maintained between the driving clutch pawl and the intermediate clutch pawl by a spring that is compressed between the driving clutch pawl and the intermediate clutch pawl, and the clutch pawls collide again. As a result, the noise and vibration after the screw tightening are reduced.

  Patent Document 2 discloses a drive-side clutch that can move in the axial direction via a plurality of balls to a drive gear that meshes with a pinion provided in a motor for the purpose of improving noise and vibration at the start of screw tightening. And a driven-side clutch member that is movable in the axial direction via a plurality of balls in the same manner on the spindle that is supported so as to be rotatable with respect to the housing and movable in the axial direction. A screw driver has been proposed in which power is transmitted and disconnected between the drive gear and the spindle by disengaging each other.

  The feature of this screw driver is that it has an engagement promoting mechanism that smoothly engages the pawl of the driving clutch member that is rotating at the initial stage of screw tightening with the pawl of the driven clutch member that is stationary. In other words, during screw tightening, when the screw is attached to the driver bit and the screw driver is pressed against the material to be fastened, the spindle and the spindle-side driven clutch member move to the drive-side clutch member side, immediately before both claws engage. The pawls of the driven clutch member are pushed against the pawls of the drive side clutch member by the balls so that the pawls are engaged with each other.

Further, when the claws start to engage with each other, the drive-side clutch member is instantaneously moved to the driven-side clutch member side by a ball interposed between the drive gear and the drive-side clutch member, and the claws are engaged more deeply. ing. Then, when the claw of the spindle side clutch member is disengaged from the claw of the drive side clutch member at the end of screw tightening, the drive side clutch is secured so that a certain distance is secured between the drive side clutch member and the spindle side clutch member by the action of the spring. The member returns to the initial position, and an appropriate space is formed between the drive-side clutch member on the gear side and the driven-side clutch member on the spindle side, so that a silent clutch is realized and noise and vibration are reduced.
Japanese Patent Publication No. 3-005952 JP 2006-116656 A

  In the screw driver described in Patent Document 1, a great effect is obtained after the completion of screw tightening. However, in recent years, the motor tends to rotate at a high speed in order to increase the screw tightening operation speed. There is a problem that smooth engagement may not be achieved.

  In order to mesh the driving clutch pawl that is rotating and the stationary intermediate clutch pawl at the initial stage of screw tightening, it is necessary to increase the moving speed of the driving clutch pawl, and the operator must vigorously move the screw driver. It was dealt with by pushing, but it was a work to get tired of the arm.

  On the other hand, by slowing down the moving speed, that is, by pushing the screwdriver with a light pressing force, the work becomes easier, but the clutch pawls do not engage immediately, and the tips of the claws collide with each other shockingly, causing large noise and Interference caused by vibrations occurred, and it also caused accelerated wear on the nails.

  Further, the invention described in Patent Document 2 corresponds to the increase in speed and was made to compensate for the drawbacks of the screw driver described in Patent Document 1. When an operator presses a screw driver through a screw against the urging force of a spring arranged between the driven clutch member and the driving clutch member, the spindle driven shaft pushes the ball, and the ball steps the step of the support shaft. By moving over, the driven clutch member is instantaneously moved to the driving clutch member, and the operator pushes the screw driver with a large thrust to obtain the same effect as moving the spindle and the driven clutch member at high speed. It is. Furthermore, when the pawl of the drive side clutch member and the pawl of the driven side clutch member are engaged, the drive side clutch member instantaneously slides on the spindle side driven side clutch member and both engage deeply to transmit power, thereby transmitting power. This is also a reliable way of blocking.

  However, in this method, the number of parts increases and the structure must be complicated. Further, in addition to the biasing force of the spring, when the ball gets over the step of the support shaft, a force for pushing a larger screw driver is required, and the burden on the operator is not yet reduced.

  Furthermore, since the pawls of the driven clutch member and the pawls of the drive side clutch member are instantaneously moved in the meshing direction, the clutch members collide at high speed in the axial direction even if they are meshed with each other without interference. Large noise and impact force will be generated. There is an increasing demand for a screw fastening tool having a good feeling, including noise and vibration at the time of transmission and interruption of power and overall operability.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw fastening tool with low noise and vibration, quiet and easy to operate.

  In order to achieve the above object, a first aspect of the present invention is directed to a gear shaft to which rotation is transmitted from a motor as a drive source via a gear, a spindle supported so as to be relatively rotatable with respect to the gear shaft, and a gear. A drive clutch portion fixed to the shaft, and a driven clutch portion supported on the gear shaft so as to be rotatable and movable in the axial direction, and engaging / engaging between the drive claws of the drive clutch portion and the driven claws of the driven clutch portion; The rotation of the motor is transmitted / blocked to / from the spindle by detachment, and the driving claw and the driven claw are separated from each other after the blocking, thereby performing screw tightening and loosening operations while continuously driving the motor to rotate. In the screw fastening tool, the shape of the drive claw of the drive clutch portion and the follower claw of the driven clutch portion is a fan shape extending from the axis, and the fan of both claws Angle was set in the range of 9 ° ~ 36 °, at the time the initial engagement is characterized by drive pawl and the follower pawl is configured to mate with at least each of two or less.

  According to a second aspect of the present invention, in the first aspect of the invention, at least the gear and the drive clutch portion are separated and loosely fitted so as to be relatively rotatable, and an elastic body is interposed therebetween. It is characterized by.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a low drive claw having a lower height than the drive claw is separately formed in the drive clutch portion, and the driven clutch portion is formed by the driven claw. Further, a low driven claw having a low height is formed separately.

  According to the first aspect of the present invention, it is possible to obtain the same effect as when the operator increases the axial movement speed of the driven clutch portion. However, in practice, the axial movement speed of the driven clutch portion is increased. As a result, there is no large single noise or vibration in the axial direction due to the collision between the drive clutch unit and the driven clutch unit, and even if the claws do not instantly mesh with each other and the claws interfere with each other, they interfere. Since the number of claws is small, the number of impacts per unit time is reduced, and generation of large noise and vibration can be prevented. And if the shape of the drive claw of a drive clutch part and the follower claw of a driven clutch part is made into the fan shape extended from an axial center, and the angle of the fan shape of both claws is set in the range of 9 degrees-36 degrees, noise and vibration will be generated. It was experimentally confirmed that it can be reduced.

  According to the second aspect of the present invention, at least the gear and the drive clutch portion are separated and both are loosely fitted so as to be relatively rotatable, and the elastic body is interposed between the two. The impact at the time of meshing is absorbed and relaxed by elastic deformation of the elastic body, further reducing noise and vibration, and even if they interfere with each other because they do not mesh instantaneously, the impact force is mitigated Wear of gear teeth and drive claws of the drive clutch can be prevented.

  According to the third aspect of the present invention, when the drive claws of the drive clutch portion and the driven claws of the driven clutch portion are worn, the pressing force increases until the two mesh with each other. Since the low driven claw meshes, the screw tightening operation can be continued with a small pressing force. Further, even if the driving claw and the driven claw are damaged due to wear, torque can be transmitted by the low driving claw and the low driven claw and the screw tightening operation can be continued as it is.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
1 is a side sectional view of a main part of a screw fastening tool according to Embodiment 1 of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a plan view of a drive clutch part of the screw fastening tool. 4 is a cross-sectional view taken along the line BB in FIG. 3, FIG. 5 is a plan view of the cap of the screw fastening tool, FIG. 6 is an exploded view of the clutch portion showing a state immediately before the claw engagement of the screw fastening tool, FIG. FIG. 8 is a developed view of the clutch portion showing a state of engaging the claws during screw tightening of the screw fastening tool, and FIG. 8 is a plan view showing the dimensional shape of the drive clutch portion of the screw fastening tool.

  In the screw fastening tool 1 according to the present embodiment, as shown in FIG. 1, a cylindrical stopper sleeve 3 whose depth can be adjusted is attached to the lower end portion of the gear cover 2 by screwing. By rotating the stopper sleeve 3 by hand, the relative distance between the stopper sleeve 3 and the gear cover 2 can be adjusted, whereby the screw feed distance can be adjusted.

  In addition, a motor (not shown) as a drive source is accommodated in the housing 4, and a handle (not shown) for holding the screw fastening tool 1 and a motor (not shown) are activated at the end of the housing 4. A switch (not shown) for stopping / stopping is provided. Further, the output shaft of the motor passes through the inner cover 6 and protrudes downward from the inner cover 6. The pinion 5 engraved at the end of the motor is engaged with the gear 7, and the gear shaft 8 is attached to the inner cover 6. A bearing 9 to be held is press-fitted and fixed. The gear shaft 8 is loosely fitted in the shaft of a socket 10 that is a spindle, and a drive clutch portion 11 is press-fitted and fixed thereto.

  As shown in FIGS. 3 and 4, the drive clutch portion 11 is composed of a large-diameter boss 12 and a small-diameter boss 13 that are drive clutch plates, and two drives are provided on the surface facing the socket 10 on the large-diameter boss 12 side. The claw 14 is integrally formed. These drive claws 14 have a trapezoidal shape in the height direction, have a fan shape that spreads from the center of the large-diameter boss 12 in plan view, and are provided symmetrically at positions 180 ° apart in the circumferential direction. Yes.

  The gear 7 is loosely fitted to the small-diameter boss 13 of the drive clutch portion 11 so as to be rotatable and slidable. Teeth are engraved on the outer periphery thereof, and the inner surface side thereof is bilaterally symmetrical with respect to the central axis. Two spaces 15 are formed (see FIG. 2).

  The cap 16 shown in FIG. 5 has two projections 17 projecting vertically in the height direction toward the surface on the gear 7 side and symmetrically projecting in a fan shape with a 180.degree. . The cap 16 is press-fitted and fixed to the gear shaft 8. One end of the cap 16 is in contact with the bearing 9, and the surface on which the protrusion 17 is provided contacts the end surface of the small-diameter boss 13. Since the end face and the outer periphery are attached so as to cover the gear 7 with a gap, the gear 7 can move between the protrusions 7 in the rotational direction by the gap between the large-diameter boss 12 and the cap 16 in the axial direction. .

  As shown in FIG. 2, four elastic bodies 18 having a constricted portion 36 at the center are mounted in a space divided into four by two spaces 15 of the gear 7 and two protrusions 17 of the cap 16. Further, a driven clutch portion 19 is loosely fitted on the gear shaft 8 so as to be slidable and rotatable in the axial direction between the socket 10 and the drive clutch portion 11.

  In the driven clutch portion 19, two first driven claws 21 having the same shape as the drive claws 14 are provided at equal intervals on the driven clutch plate 20 facing the drive clutch portion 11 so as to face each other by 180 °. Further, as shown in FIGS. 6 and 7, three second driven claws 22 are provided at equal intervals on the surface of the driven clutch portion 19 facing the socket 10 side. The three driven claws 24 of the driven clutch portion 23 provided integrally with the socket 10 are always engaged.

  As shown in FIG. 6, the second driven claw 22 has a gently inclined surface 25 from the surface facing the driven clutch portion 23, and then has a vertical lateral surface 26 and is connected to the tip surface 27. When viewed from the socket 10 side, each of the surfaces 25, 26, 27 has a fan shape extending from the center to the outer peripheral surface, and all of the three second driven claws 22 have the same shape. Similarly, the driven claw 24 has an inclined surface 28, a lateral surface 29, and a tip surface 30, has the same shape as the second driven claw 22, and is provided in the same number (three).

  As shown in FIG. 1, a holding portion 32 that holds a bit 31 to which a screw 33 is attached at the tip is formed on the other end side of the driven clutch portion 23 of the socket 10. The socket 10 is held in the gear cover 2 by a bearing 34 so as to be rotatable and slidable in the axial direction. A spring 35 is mounted between the drive clutch portion 11 and the driven clutch portion 19 and, as shown in FIG. 1, the drive claw 14 and the first driven claw 21 are not engaged with each other at a distance from each other in the initial state. The second driven claw 22 and the driven claw 24 are always in contact with each other.

  Next, operation | movement of the screw fastening tool 1 comprised as mentioned above is demonstrated.

  When an operator holds a handle (not shown) and pulls a switch (not shown) to start the motor, the pinion 5, the gear 7, the drive clutch unit 11, the gear shaft 8, and the cap 16 rotate. At this time, the driven clutch portion 19 and the socket 10 do not rotate.

  When the screw 33 is attached to the tip of the bit 31 and the operator of the screw fastening tool 1 presses the screw fastening tool 1 against the fastened material 37 via the screw 33 from this state, the socket 10, the driven clutch portion 23, and the driven clutch portion. 19 moves against the biasing force of the spring 35 toward the gear 7, and the first driven claw 21 starts to engage with the driving claw 14 of the rotating driving clutch portion 11. Here, the impact force generated when the driving claw 14 and the first driven claw 21 mesh with each other is caused by the action of the elastic body 18 between the gear 7 and the driving clutch portion 11 so that the constricted portion 36 having a low spring constant is first crushed and deformed. Then, the whole is gradually deformed to obtain a large buffering effect and damping effect.

  FIG. 6 shows a state immediately before the drive claw 14 of the drive clutch portion 11 and the first driven claw 21 of the driven clutch portion 19 start to mesh with each other, and the arrow indicates the rotational direction of the drive clutch portion 11. Here, when the first driven claw 21 of the driven clutch portion 19 is engaged with the driving claw 14 of the driving clutch portion 11, the second driven claw 22 of the driven clutch portion 19 is inclined to the inclined surface 28 of the driven claw 24 of the driven clutch portion 23. As shown in FIG. 7, the drive clutch portion 11, the driven clutch portion 19, and the driven clutch portion 23 rotate integrally with each other while the lateral surfaces 26 and 29 mesh with each other.

  When the screw 33 is further tightened in the above state, the stopper sleeve 3 comes into contact with the fastened material 37, and the driving claw 14 of the driving clutch portion 11 and the first driven claw 21 of the driven clutch portion 19 form a trapezoidal shape. Therefore, the driving claw 14 and the first driven claw 21 receive a force in a direction in which the driving claw 14 and the first driven claw 21 are separated from each other by the component force of the rotation torque, and the driven clutch portion 19 is pushed out to the fastening material 37 side by the action of the spring 35. As a result, the drive claw 14 and the first driven claw 21 are disengaged. Thereafter, the driven clutch portion 19 returns to the initial position shown in FIG. A gap is ensured and contact between the two does not occur, and quietness is ensured.

  Here, as shown in FIG. 8, the ratio of the occupied area of the drive claw 14 to the large-diameter boss 12 of the drive clutch part 11 and the occupied area ratio of the first driven claw 21 to the driven clutch plate 20 of the driven clutch part 19 are engaged. Table 1 and FIG. 9 show the results of measuring how the noise changes. As a condition, both the driving claw 14 and the first driven claw 21 have the same number of claws and have a shape extending in a fan shape from the center of the clutch portions 11 and 19 to about 25 in the height direction. ° It has a trapezoidal shape with an inclination.

図８の大径ボス１２に示されるように扇形の角度θは駆動爪１４の底面と上面の平均角度とし、駆動クラッチ部１１が回転したときに駆動爪１４が描く軌道面積Ｓｍｍ² に対する駆動爪の面積ｓｍｍ² との比をＰ％とし、角度θを変数として初期噛み合い時の騒音を計測した。従動クラッチ部２０も同様である。

As shown in the large-diameter boss 12 in FIG. 8, the fan-shaped angle θ is an average angle between the bottom surface and the top surface of the driving claw 14, and the driving claw with respect to the track area Smm ² drawn by the driving claw 14 when the driving clutch portion 11 rotates. The noise at the time of initial meshing was measured with the ratio of the area smm ² to P% and the angle θ as a variable. The same applies to the driven clutch unit 20.

  At this time, S, s, and P are respectively expressed by the following equations.

S = 3.14 ((D / 2) ^2- (d / 2) ² )
s = 2Sθ / 360
P = (s / S) × 100 = (2θ / 360) × 100
As shown in FIG. 8, assuming that the outer diameter of the large-diameter boss 12 is D and the space necessary for arranging the spring 35 is d, d is about 12 mm, and D at this time is about 22 mm. This was the limit on space and production, and this minimum diameter was considered. The number of rotations of the drive clutch unit 11 was examined at 6000 rpm, which is currently considered to be the highest speed and efficient. Further, the pressing force of the screw fastening tool 1 was set to 3 kgf, which is light, and 10 kgf, which is strengthened. As an example currently used in products, P is 45%, that is, θ is 81 ° as a maximum, and θ is reduced from this.

  From the results shown in Table 1 and FIG. 9, the noise during the load is larger than the noise 77 dBA during no load, but the distance between the driving claws 14 and the first driven claws 21 increases as the angle θ decreases. It can be seen that the chance of interference between the claws 14 and 21 is reduced and the noise is reduced. Further, it has been found that by increasing the pressing force and increasing the meshing speed, the interference between the claws 14 and 21 during meshing is similarly reduced, and the noise is reduced. In FIG. 9, ◯ indicates the case where the pressing force is 3 kgf, and ● indicates the case where the pressing force is 10 kgf.

  Therefore, it is said that if 6 dBA can be reduced with respect to the noise value when θ is 81 °, the noise energy is halved and the difference can be clearly seen. From the measurement results, a reduction of 6 dBA can be obtained when the pressing force is 3 kgf and 93 dBA is 87 dBA, and when the pressing force is 10 kgf, 89 dBA is 83 dBA. Both θ are about 36 ° and P is about 20% or less. I found it good.

On the other hand, from the viewpoint of strength, the screwdriver is a tool for attaching a gypsum board to an iron plate called wood or light sky with screws 33, and it is sufficient if there is a torque of about 400 kgf · mm as a regular torque. When the stress is calculated considering the occupied area S of the claws 14 and 21 when θ is 9 ° as a cross-sectional area, the force applied to the centers in the radial direction of the claws 14 and 21 is an average,
400kgf · mm ÷ 17mm = 23.5kgf
When this is calculated with an occupied area P = 5% and s = 13 mm ² , the stress is
23.5 kgf ÷ 13 mm ² = 2 kgf / mm ²
And there will be no problem at all.

However, when the claws 14 and 21 mesh with each other in an impact, an impact torque of 1600 kgf · mm or more, which is about four times the normal torque, may occur. In the present embodiment, the impact is greatly relieved by the elastic body 18, but in consideration of the state in which the elastic body 18 disappears due to progress of wear and plastic deformation of the elastic body 18, Recalculating assuming that only one nail receives torque, on average,
1600kgf · mm ÷ 17mm = 94kgf
It becomes. If this force is received with one nail and s = 6.5 mm ² , the stress will be 15 kgf / mm ² , and the safety factor will be 2 if the allowable stress of the sintered material is 30 kgf / mm ^2. However, when θ is 9 ° or less and P is 5% or less, the safety factor is 2 or less. Therefore, for safety, θ is preferably 9 ° or more in consideration of manufacturing errors and tolerances.

  FIG. 10 shows a state where the driving claw 14 of the driving clutch portion 11 and the first driven claw 21 of the driven clutch portion 19 are worn. In such a state, the trapezoidal shape of the meshing surface collapses, and the force that separates the driving claw 14 and the first driven claw 21 due to the component force due to the torque increases, so that the screw is always tightened with a larger pressing force until and after the meshing. Tool 1 must be kept pressed. If this is repeated, the claws 14 and 21 are thinned and damaged at the end. An embodiment for solving this problem will be described below.

<Embodiment 2>
In the present embodiment, as shown in FIG. 11, two low drive claws 40 are arranged in the drive clutch portion 11 and their phases are shifted by 90 ° with respect to the drive claws 14. Here, the low drive claw 40 has the same shape as that of the drive claw 14 and is only reduced in height by 0.5 mm.

  An example in which the low first driven claw 41 having the same shape as the low drive claw 40 is similarly arranged on the first driven claw 21 of the driven clutch portion 19 is shown in the development view of FIG.

  When the drive claw 14 and the first driven claw 21 are worn, the pressing force increases until they are engaged with each other. The screwing operation can be continued with a small pressing force. Further, even if the driving claw 14 and the first driven claw 21 are damaged due to wear, torque can be transmitted by the low driving claw 40 and the low first driven claw 41, and the screw tightening depth at that time is adjusted by a stopper. This can be handled by the sleeve 3.

  However, when a phenomenon occurs in which the driving claw 14 and the low first driven claw 41 first mesh in a new state in which the driving claw 14 and the first driven claw 21 are not worn, that is, the four claws 14, 21. , 40 and 41 are simultaneously engaged with each other, noise and vibration become high.

  Therefore, FIG. 13 shows a developed surface of only the drive clutch portion 11 and the driven clutch portion 19 to confirm whether or not the above phenomenon occurs.

Assuming that P of the driving claw 14 and the first driven claw 21 is 20%, θ is 36 °, s is 53 mm ² , and the distance L between the outermost circumferences of the first driven claw 21 and the low first driven claw 41 is It becomes about 10.3 mm. The height difference between the drive claw 14 and the low first driven claw 41 is 0.5 mm, and the rotation speed of the drive claw 14 is 6000 rpm.

  Generally, when screw tightening is performed with a pressing force of 10 kgf or less and the screw fastening tool 1 is pressed with a pressing force of 10 kgf, the axial movement speed of the driven claw 14 is about 300 mm / sec or less by actual measurement.

Therefore, the driving claw 14 at 6000 rpm should not mesh with the low first driven claw 41 between L10.3 mm from the state shown in FIG. The time required for the low first driven claw 41 to move 0.5 mm in the axial direction is 1.7 × 10 ⁻³ sec.

On the other hand, the moving speed of the drive claw 14 is 2.5 × 10 ⁷ mm / sec at the position of the outer diameter of 22 mm, and the time required to move L10.3 mm is about 4 × 10 ⁻⁷ sec.

  Even if the moving speed of the driven clutch portion 19 is increased under the above conditions and the driving claw 14 and the low first driven claw 41 are engaged with each other, the pressing force becomes large at that time, and there is almost no interference between the claws 14 and 41. It is thought that there is no problem as well.

  As long as the driving claw 14 and the low first driven claw 41 do not mesh with each other, the rotational speed of the driving claw 14 and the height difference between the claw 14 and 40 and the claw 21 and 41 can be changed within an allowable range. . In the present embodiment, the outer diameter of the driven clutch plate 20 is 22 mm. However, the outer diameter may be increased if the ratio of θ and P does not change. If the number of the drive claw 14 and the first driven claw 21 is one by one, the effect is further enhanced. However, although there is a possibility that a biased load is applied and the life of the parts is affected, the claw having a low height as described above. By arranging 40 and 41, the problem can be solved, and the number of claws 40 and 41 having a low height can be arbitrarily set within the design range.

  In the present embodiment, the gear 7 is loosely coupled, but the drive clutch portion 11 may be loosely coupled and the gear 7 may be press-fitted and fixed to the gear shaft 8, and loosely coupled between the socket 10 and the driven clutch portion 23. Anyway. Further, although the elastic body 18 is used, the impact mitigating effect can be obtained by merely providing play between the gear 7 and the gear shaft 8 and between the socket 10 and the driven clutch portion 23 without using the elastic body 18. .

It is a sectional side view of the principal part of the screw fastening tool which concerns on Embodiment 1 of this invention. It is the sectional view on the AA line of FIG. It is a top view of the drive clutch part of the screw fastening tool principal part which concerns on Embodiment 1 of this invention. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is a top view of the cap of the screw fastening tool which concerns on Embodiment 1 of this invention. It is an expanded view of the clutch part which shows the state immediately before the nail | claw meshing of the screw fastening tool which concerns on Embodiment 1 of this invention. It is an expanded view of the clutch part which shows the nail | claw meshing state during the screw fastening of the screw fastening tool which concerns on Embodiment 1 of this invention. It is a top view which shows the dimension shape of the drive clutch part of the screw fastening tool which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the angle (theta) of the nail | claw of the clutch part of the screw fastening tool which concerns on Embodiment 1 of this invention, and noise. It is an expanded view which shows the abrasion state of the nail | claw of the clutch part of the screw fastening tool which concerns on Embodiment 1 of this invention. It is a top view of the drive clutch part of the screw fastening tool which concerns on Embodiment 2 of this invention. It is an expanded view of the clutch part of the screw fastening tool which concerns on Embodiment 2 of this invention. It is an expanded view of the clutch part of the screw fastening tool which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw fastening tool 2 Gear cover 3 Stopper sleeve 4 Housing 5 Pinion 6 Inner cover 7 Gear 8 Gear shaft 9 Bearing 10 Socket (spindle)
11 Drive clutch 12 Large diameter boss (Drive clutch plate)
13 Small-diameter boss (drive clutch plate)
DESCRIPTION OF SYMBOLS 14 Driven claw 15 Space 16 Cap 17 Protrusion 18 Elastic body 19 Driven clutch part 20 Driven clutch plate 21 First driven claw 22 Second driven claw 23 Driven clutch part 24 Driven claw 25 Inclined surface of the second driven claw 26 Second driven claw 27 Side surface of second driven claw 28 Inclined surface of driven claw 29 Side surface of driven claw 30 End surface of driven claw 31 Bit 32 Holding portion 33 Screw 34 Bearing 35 Spring 36 Constricted portion of elastic body 37 Fastened material 40 Low drive claw 41 Low first follower claw

Claims (3)

A gear shaft to which rotation is transmitted from a motor that is a driving source via a gear, a spindle that is supported so as to be relatively rotatable with respect to the gear shaft, a drive clutch portion that is fixed to the gear shaft, and a gear shaft that is rotatable And a driven clutch portion supported so as to be movable in the axial direction, and transmitting / cutting off the rotation of the motor to and from the spindle by engagement / disengagement of the driving claw of the driving clutch portion and the driven claw of the driven clutch portion. In a screw fastening tool for performing screw tightening and loosening operations by continuously rotating the motor by separating the drive claw and the driven claw after being shut off,
The drive claws of the drive clutch portion and the driven claws of the driven clutch portion are fan-shaped extending from the axial center, and the fan-shaped angle of both claws is set in the range of 9 ° to 36 °. A screw fastening tool characterized in that the driving claw and the driven claw are configured to mesh with each other at least two pieces or less.   2. The screw fastening tool according to claim 1, wherein at least the gear and the drive clutch portion are separated and loosely fitted so as to be relatively rotatable, and an elastic body is interposed therebetween. A low driving claw having a lower height than the driving claw is separately formed in the driving clutch portion, and a low driven claw having a lower height than the driven claw is separately formed in the driven clutch portion. Item 3. A screw fastening tool according to item 1 or 2.

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