JPH0373410B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides an automatic screwdriver configured to eliminate the influence of inertia of a driver bit when screw tightening is completed and to reliably tighten screws with a desired screw tightening torque. Regarding tightening machines.

Prior Art Generally, when controlling screw tightening torque, a driver bit is rotated by a rotary drive source, the load torque applied to the driver bit is detected using an appropriate detection means, and the torque is detected until the detected value reaches a set value. For example, a device that stops a rotational drive source is common. With this device, if the set value of the screw tightening torque is low, the tightening torque will exceed the set value due to the influence of the inertia of the rotary drive unit when the screw tightening is completed, and the screw cannot be accurately tightened with the set tightening torque. There is a need for a screw tightening machine that can accurately tighten screws even with a low set tightening torque.

Problems to be Solved by the Invention As disclosed in Japanese Patent Publication No. 57-13221, the present invention is characterized in that the transmission system that connects the rotary drive source from the input shaft to the output shaft includes a plurality of planetary cones with planetary motion. , a non-rotating speed change ring that frictionally engages in common with the conical surfaces of the plurality of planetary cones, a concave transmission surface that frictionally engages the input disk on the input shaft, and a cam disk on the output shaft. In a frictionless transmission in which a flat transmission surface that frictionally engages with the planetary cone is provided on a planetary cone, the speed change ring is automatically moved in the direction of decreasing the rotational speed of the output shaft as the load torque increases. The output side of this automatic transmission is connected to a driver bit and screws are tightened, and when the tightening torque reaches the set value,
To provide an automatic screw tightening machine which maintains the tightening torque even with the output torque at this time by reducing the rotation of the driver bit to zero without stopping the rotational drive source, and which has excellent durability. .

Means for Solving the Problems In the present invention, a rotary drive source is fixed to one end of the driver body, and an input disk is arranged so as to rotate in response to rotation of the drive shaft. A plurality of planetary cones are arranged at predetermined intervals on the circumference surrounding the axis of the input disk, and the planetary cones have a conical surface, a flat surface located on the back surface thereof, and a circumferential groove. have. The input disk is disposed in the circumferential groove, and a cam disk rotating concentrically with the input disk is disposed in the flat surface so as to frictionally engage with the input disk,
A driver bit is connected to this cam disk so as to rotate together with the cam disk.

On the other hand, a speed change ring is arranged on the outer periphery of the planetary cone so that it can be rotated in response to the load torque applied to the driver bit by frictionally engaging with the conical surface of the planetary cone, and can slide in the axial direction along the conical surface. has been done. This speed change ring is urged by a spring to be positioned on the high speed side, and an arm that limits the amount of movement of this speed change ring on the high speed side is provided between the speed change ring and the inner cylindrical portion.

Locking pieces are provided at both ends of the arm, and at least one of these locking pieces is shaped like a key. One of these locking pieces is loosely inserted into the speed change ring 25, the other locking piece is loosely inserted into the fixed side, and the key-shaped locking piece is configured to be locked in a locking hole drilled in the jaw. has been done.

Further, the locking piece may be bent on the same plane, but it is also possible to bend the key-shaped tip so that it is positioned in advance in the opposite direction to the direction in which the arm rotates as the arm tilts. .

Function In the above automatic screw tightening machine, the driver bit tightens the screw, and when a load torque is applied to the driver bit, a reaction torque corresponding to the load is applied to the speed change ring, and the speed change ring rotates in the opposite direction to the driver bit. do. In response to the rotation of the speed change ring, the arm tilts, the speed change ring moves in its axial direction, and its frictional engagement position moves toward the larger diameter side of the conical surface of the planetary cone. Therefore, the driver bit gradually tightens the screw at low speed and high torque, but when the head of the screw seats and the rotational speed of the driver bit suddenly decreases, the speed change ring suddenly moves to near the edge of the conical surface. Even though the input disc is rotating, the driver bit rotates at zero while maintaining a constant torque, so the tightening torque does not exceed the set value due to the influence of the inertia of the rotary drive unit. Complete screw tightening.

During this screw-tightening process, the arm that engages between the speed change ring and the inner cylinder tilts as the speed change ring rotates, but the arm that engages between the speed change ring and the inner cylinder part is tilted, and the arm has a rotatable lock formed in a key shape at both ends of the arm. One of the locking pieces is loosely inserted into the locking hole of the jaw and the other is loosely inserted into the locking hole of the speed change ring, so even if the arm is tilted, the locking pieces at both ends of the arm will prevent the arm from tilting. Since the arm is rotated vertically around its parallel portion and horizontally around its tip end, no twisting of the arm occurs.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In FIG. 4, 1 is an automatic screw tightening machine, and this automatic screw tightening machine 1 has a driver mounting base 8 which is raised and lowered by the operation of a cylinder 7, and a driver mounting base 8 which is movable integrally and relatively movably at a predetermined interval. It has a desk 10. In addition, the driver mounting base 8
A driver unit 12 is fixed to the upper part of the screwdriver, and this driver unit 12 is configured to rotate a driver bit 14 via a connecting mechanism 13. On the other hand, a chuck unit 15 is fixed to the chuck base 10, and the driver bit 14 is inserted into the chuck unit 15 and screwed into a predetermined position with a screw (not shown) held by a chuck pawl 15a. It is composed of

The driver unit 12 has a driver main body 18 as shown in FIGS. 1 and 2, and has a motor 19 as a rotational drive source at one end, and an internal motor 19 fixed to the driver mounting base 8 at the other end. Cylinder part 17
is fixed. Drive shaft 19 of the motor 19
An input disk 21 of a differential planetary mechanism 20 forming an automatic transmission is connected to a. A plurality of planetary cones 23 are arranged on the circumference surrounding the axis of the input disk 21 at predetermined intervals by a cone holder 22, and the planetary cones 23 have a conical surface 23c as a transmission surface. A flat surface 23b on the back surface thereof and a circumferential groove 23a having a concave cross-section located adjacent thereto are formed. Further, the input disk 21 is placed in the circumferential groove 23a, and the cam disk 24 that rotates concentrically with the input disk 21 is placed in the flat surface 23b.
The cam disk 24 is arranged to frictionally engage with the cam disk 24, and the cam disk 24 is configured to transmit its rotation to the driver bit 14 via the buffer mechanism 29 and the link mechanism 13.

On the other hand, the driver bit 14 is frictionally engaged with the conical surface 23c of the planetary cone 23 on its outer periphery.
A speed change ring 25 is arranged so as to be rotatable and move along the load according to the load, and this speed change ring 25 is urged by a spring 31 to be located on the high speed side. Moreover, this speed change ring 25 is held in the inner cylindrical portion 17 via a rotatable arm 32, and this arm 32
is configured to limit the amount of movement of the speed change ring 25 toward the high speed side.

The speed change ring 25 is connected to the driver bit 1.
When the arm 32 is rotated by the reaction torque corresponding to the load related to 4, the arm 32 is tilted and moves in its axial direction, and due to the pressing force on the spring 31 and the deflection of the spring 31 generated on the speed change ring 25 by the reaction torque. It is configured to stop at a position where the generated elastic force is balanced. Furthermore, when the speed change ring 25 reaches the position shown in FIG.
4 is configured to have zero rotation, and the rotation of the cam disk 24 is steplessly changed from high speed to low speed according to the load, so that the load torque of the driver bit 14 is changed as shown in FIG. At its greatest,
It is configured so that the rotation becomes zero.

Further, at both upper and lower ends of the arm 32, as shown in FIGS. 1 and 3, key-shaped locking pieces 32a and 3 having parallel portions a1 and b1 and tip portions a2 and b2 are provided.
2b is provided, and these locking pieces 32a, 32
b are bent on the same plane. Moreover, the tip b2 of the lower locking piece 32b is bent so that the angle formed with the bending surface is a predetermined angle θ,
When located in a second locking hole 17b, which will be described later, it is configured to be located in a direction opposite to the direction in which the arm 32 rotates as the arm 32 inclines. The upper locking piece 32a is loosely inserted into a first locking hole 25a formed in the speed change ring 25, and as the arm 32 inclines, the first locking piece 32a closes around the parallel portion a1 of the arm 32.
It is configured to be able to rotate in the vertical direction. On the other hand, the tip of the lower locking piece 32b is connected to the inner cylinder portion 1.
The arm 32 is loosely inserted into a second tapered locking hole 17b drilled in the jaw 17a of the arm 32, and as the arm 32 tilts, it rotates vertically around its parallel portion b1, and at the same time the tip The locking piece 32b rotates in the horizontal direction around the part b2, and the tip part b2 of the locking piece 32b
It is configured to be pivotable within the locking hole 17a.

On the other hand, a torque adjustment ring 36 is slidably disposed on the outer periphery of the inner cylindrical portion 17, and a torque adjustment ring 36 is provided on the side of the torque adjustment ring 36 at regular intervals to interfere with the inclination of the arm 32. A recessed portion 36b is formed so that there is no gap, and a spring seat portion 36a is formed on the upper surface of the recessed portion 36b. As shown in FIG. 2, three pairs of springs 31 are arranged in the spring seat portion 36a so as to be parallel to and surround the connecting shaft 28 at equal intervals.
is configured so that it is biased towards the high speed side. The torque adjustment ring 36 also includes the inner cylinder portion 1.
An adjustment bolt 37, which is rotatably held at that position, is screwed into the bottom of the housing 7.

Further, an oil seal mechanism is arranged around the drive shaft 19a and the connecting shaft 28, and oil is filled between the driver body 18 and the inner cylinder part 17 to prevent wear of the differential planetary mechanism 20. It is configured to

In the above automatic screw tightening machine, when the motor 19 rotates, the rotation is transmitted from the input disk 21 to the cam disk 24 via the planetary cone 23, and the speed change ring 25 frictionally engages with the conical surface 23c of the planetary cone 23. The speed is reduced at a speed reduction ratio determined by the position and transmitted to the driver bit 14.

As the driver bit 14 tightens the screw to the workpiece (not shown) and a load torque is applied to the driver bit 14, a reaction torque corresponding to the load is applied to the speed change ring 25, as shown in FIG. The speed change ring 25 rotates in a direction opposite to the direction of rotation of the driver bit 14. When the speed change ring 25 rotates, the arm 32 rotates and tilts relative to the speed change ring 25 and the jaw portion 17a, respectively. Due to the inclination of this arm 32, the speed change ring 25
descends along the conical surface 23c of the planetary cone 23, so its reduction ratio becomes larger and larger. As the screw is seated on the workpiece, the tightening torque increases rapidly, and when the speed change ring 25 rapidly moves and reaches the edge of the conical surface 23c, the input disc 21 rotates. Despite this, the cam disc 24 reaches zero rotation and stops while outputting a constant output torque as shown in FIG.
Screw tightening is completed.

During this screw tightening process, the arm 32 that locks between the speed change ring 25 and the inner cylindrical portion 17 tilts in accordance with the rotation of the speed change ring 25. Along with this, the upper locking piece 32a rotates about its parallel portion a1 within the first locking hole 25a. At the same time, as shown in FIG. 8, the lower locking piece 32b rotates vertically around its parallel portion b1 and horizontally around its tip b2. During this time, the tip b2 of the locking piece 32b pivots within the second locking hole 17b, but even when the arm 32 is tilted to its maximum angle, the angle of rotation is small, and furthermore, the tip b2 of the locking piece 32b rotates in the direction of rotation. Since the locking piece 32b is located in the opposite direction to the tapered second
The arm 32 can smoothly rotate relative to the speed change ring 25 and the jaw 17a without coming into contact with the inner wall of the locking hole 17b, and the arm 32 is not twisted.

Effects of the Invention As explained above, the present invention is configured to transmit the rotation of a rotary drive source to a driver bit via a differential planetary mechanism having a planetary cone, and
A locking piece is provided at both ends of an arm that holds the speed change ring of the differential planetary mechanism so as to be rotatable relative to the fixed side and movable in the axial direction thereof, and at least one of the locking pieces is formed in a key shape, Since this key-shaped locking piece is configured to be loosely inserted into a locking hole drilled in the jaw, the differential planetary mechanism 20
By continuously increasing the reduction ratio of Not only is tightening with extremely high precision possible without being affected by the inertia of the parts, but even if the gear ring repeatedly returns to rotation due to repeated screw tightening operations, the arm will only tilt and the arm will not move. There are advantages such as being able to provide an automatic screw tightening machine that does not twist itself and therefore has excellent durability. Furthermore, since the locking piece at the end of the arm is shaped like a key, the present invention has the advantage that the arm will not come off from the speed change ring and the fixed side.

[Brief explanation of drawings]

1 is an enlarged sectional view of the main part of the present invention, FIG. 2 is an enlarged sectional view of the main part taken along line A-A in FIG. 1, FIG. 3 is an enlarged front view of the arm according to the present invention, The figure is an overall explanatory diagram of the present invention, Figure 5 is a cross-sectional view of the main part showing the operating state of the differential planetary mechanism according to the present invention, and Figure 6 is the torque-rotation of the output shaft of the stepless reduction mechanism according to the present invention. FIG. 7 is an explanatory diagram of the operation of the main part of the present invention, and FIG. 8 is an explanatory diagram of the operation of the main part showing the turning state of the arm of the present invention. 1...Automatic screw tightener, 7...Cylinder, 8...Driver mounting stand, 8a...Notch hole, 10...Chuck stand,
12...Driver unit, 13...Connection mechanism, 14
...Drive bit, 15...Chuck unit, 1
5a...chuck pawl, 17...inner cylinder part, 17a...flange part, 17b...second locking hole, 18...driver body,
19... Motor, 19a... Drive shaft, 20... Differential planetary mechanism, 21... Input disk, 22... Cone holder, 2
3... Planetary cone, 23a... Circumferential groove, 23b... Flat surface, 23c... Conical surface, 24... Cam disk, 25
...speed change ring, 25a...first locking hole, 27...pressure regulating mechanism, 28...connection shaft, 29...buffer mechanism, 31...spring, 32...arm, 32a, 32b...locking piece, a
1, b1...Parallel part, a2, b2...Tip part, 36...
Torque adjustment ring, 36a...spring seat, 36...recess, 37...adjustment bolt.

Claims (1)

[Scope of Claims] 1. A rotary drive source is fixed to one end of the driver body 18, and an input disk 21 is arranged so as to rotate in response to the rotation of the drive shaft 19a, and the axis of the input disk 21 is A plurality of planetary cones 23 are arranged at predetermined intervals on a circumference surrounding the planetary cone 23, and a conical surface 23c, a flat surface 23b located on the back surface of the planetary cone 23, and a circumferential groove 23a are formed on the planetary cone 23,
The input disk 21 is placed in the circumferential groove 23a, and the flat surface 21
A cam disk 24 that rotates concentrically with the input disk 21 is arranged at b so as to be frictionally engaged with the input disk 21, and a driver bit 14 is connected to the cam disk 24 so as to rotate together with the cam disk 24, thereby reducing the load on the driver bit 14. Rotatable by torque and the conical surface 23
The speed change ring 25 is slid in the axial direction along c.
The gear ring 25 is biased by a spring 31 to be positioned on the high speed side, and an arm 32 that limits the amount of movement of the gear ring 25 toward the high speed side is connected to the gear ring 25 and the inner cylindrical portion 17. Locking pieces 32a, 32 are provided at both ends of the arm 32.
b, and at least one of them is formed into a key shape, and this key-shaped locking piece 32b is inserted into the locking hole of the jaw part 17a provided in the inner cylinder part 17, and the other locking piece 32a
are respectively locked in the locking holes of a speed change ring 25. 2 The tip of the key-shaped locking piece 32b is attached to the arm 3
2. The automatic screw tightening machine according to claim 1, wherein the automatic screw tightening machine is bent to form a predetermined angle with the extending direction of the screw.