JPH0373411B2 - - 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. 13221/1983, the present invention provides a rotary drive source in which the transmission system from the input shaft to the output shaft includes a plurality of planetary cones with planetary motion. A non-rotating speed change ring that is commonly frictionally engaged with the conical surfaces of the plurality of planetary cones, and a concave transmission surface that is frictionally engaged with the input disk on the input shaft and a cam on the output shaft. In a frictionless transmission in which a flat transmission surface that frictionally engages with a disk is provided on a planetary cone, a speed change ring is automatically moved in a direction to reduce the rotational speed of an output shaft as 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 a set value, the rotational drive source is stopped. 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 causing any problems, and which has excellent durability.

Means for Solving the Problems The present invention has a rotary drive source at one end of the driver body, and an input disk is arranged 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 as a transmission surface and a flat surface on the back surface adjacent to the conical surface. It has a circumferential groove located in the same direction. An input disk is disposed in the circumferential groove, and a cam disk that rotates concentrically with the input disk is arranged in frictional engagement with the flat surface, and the cam disk rotates integrally with the cam disk. The driver bits are connected like this.

A speed change ring is disposed on the outer periphery of the conical surface so as to be rotatable and move along the load torque of the driver bit. This speed change ring is biased by a spring to be positioned on the high speed side, and an arm that limits the amount of movement of the speed change ring toward the high speed side is located between the speed change ring and a fixed ring fixed to the inner cylinder. It is provided.

Locking pieces are provided at both ends of the arm, and these locking pieces are bent in a direction forming a predetermined angle. One of the locking pieces is loosely inserted into the speed change ring and rotatably attached, and the other locking piece is loosely inserted into the fixed ring and rotatably held. Furthermore, the locking piece is configured to be located in a direction opposite to the direction in which the arm pivots as the arm tilts.

Function In the automatic screw tightening machine described above, as the input disk rotates in response to the rotation of the rotary drive source, the planetary cone rotates at that position, and the rotation of the planetary cone is transmitted to the cam disk, causing the driver bit to rotate. rotates while being reduced in speed at a reduction ratio determined by the frictional engagement position between the speed change ring and the conical surface of the planetary cone, and tightens the desired screw onto the workpiece.

When the driver bit tightens the screw, a reaction torque corresponding to the load torque of the driver bit is applied to the speed change ring, causing the speed change ring to rotate in the opposite direction to the driver bit. As the speed change ring rotates, the arm tilts, and the friction engagement position of the speed change ring moves toward the larger diameter side of the conical surface of the planetary cone, so that the reduction ratio becomes larger and larger. Therefore, the driver bit gradually tightens the screw at low speed and high torque, but when the screw is seated and the load torque on the driver bit suddenly increases, the speed change ring rotates further and suddenly tightens to near the edge of the conical surface. Moving. Therefore,
Even though the input disk is rotating, the driver bit rotates at zero while maintaining a constant torque. Therefore, due to the influence of the inertia of the rotating drive part, the tightening torque does not exceed the set value and the screws can be tightened. complete.

During this screw tightening process, the arm that locks between the speed change ring and the fixed ring tilts in accordance with the rotation of the speed change ring, and the locking piece that is locked to the fixed ring rotates accordingly. . The rotation of this locking piece reaches its maximum when the screw tightening is completed, but since this locking piece is bent in advance in the opposite direction to the direction of rotation, the locking piece is raised in the direction of rotation as it turns. The arm only moves up and does not come into contact with the inner wall of the fixed ring, and the arm can smoothly rotate relative to the speed change ring and the fixed ring. Therefore, the arm does not twist, and even if the screws are repeatedly tightened, the durability will not be impaired.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In Fig. 4, reference numeral 1 denotes an automatic screw tightening machine, and this automatic screw tightening machine 1 includes a driver mounting base 3 that is raised and lowered by the operation of a cylinder 2, and a driver mounting base 3 that is movable integrally and relatively movable at a predetermined interval. It has a large desk 4. In addition, the driver mounting base 3
A driver unit 5 is fixed to the upper part of the screwdriver, and the driver unit 5 is configured to rotate the driver bit 7 via a connecting mechanism 6. On the other hand, a chuck unit 8 is fixed to the chuck base 4, and the driver bit 7 is inserted into the chuck unit 8 and screwed into a predetermined position with a screw (not shown) held by a chuck pawl 8a. It is composed of

The driver unit 5 has a driver main body 9, as shown in FIG. 5, and has a motor 10 as a rotational drive source at one end, and an inner cylindrical portion 11 fixed to the driver mounting base 3 at the other end. Fixed. An input disk 13 of a differential planetary mechanism 12 constituting an automatic transmission is connected to a drive shaft 10a of the motor 10. A plurality of planetary cones 1 are arranged at predetermined intervals on the circumference surrounding the axis of the input disk 13.
4 is arranged, and this planetary cone 14 has a conical surface 14a as a transmission surface and a flat surface 14 on the back surface of the conical surface 14a.
b and a circumferential groove 1 with a concave cross section located adjacent thereto.
4c is formed. Further, the circumferential groove 14
The input disk 13 is disposed at c, and a cam disk 15 rotating concentrically with the input disk 13 is disposed on the flat surface 14b so as to frictionally engage with the input disk 13.
Moreover, the cam disk 15 is configured to transmit its rotation to the driver bit 7 via the buffer mechanism 16 and the link mechanism 6.

On the other hand, a speed change ring 17 is disposed on the outer periphery of the planetary cone 14 so as to be rotatable by the load torque of the driver bit 7 and move along this. is biased so that it is located at Furthermore, an arm 19 that limits the amount of movement of the speed change ring 17 on the high speed side is provided between the speed change ring 17 and a fixed ring 20 fixed to the inner cylinder portion 11. Further, when the speed change ring 17 reaches the position shown in FIG. 6 (a position that substantially satisfies a:b=c:d) by its movement, the cam disc 15 is configured to rotate at zero. The rotation of the cam disk 15 is changed steplessly from high speed to low speed according to the load, so that when the load torque of the driver bit 7 is maximum, the rotation becomes zero.

As shown in FIGS. 1 to 3, the arm 19 has locking pieces 19a and 19b at both ends, and each of the locking pieces 19a and 19b is bent in different directions around the arm 19. , the angle formed by these is θ. The upper locking piece 19a is also bent downward, and the angle it makes with the direction in which the arm 19 extends is θ1.
It is configured to do the following. Further, the lower locking piece 19b is also bent upward, and is configured to form an angle θ2 with the direction in which the arm 19 extends. Moreover, the locking piece 19a
is the first locking hole 1 bored in the speed change ring 17.
7a, and is configured to be able to pivot within the first locking hole 17a as the arm 19 tilts. On the other hand, the lower locking piece 19b is loosely inserted into a second locking hole 20a formed in the fixing ring 20, and as the arm 19 tilts, it moves into the second locking hole 20a. It is configured so that it can be rotated. Further, this locking piece 19b is configured in advance to be positioned in the opposite direction to the rotation direction thereof, and is configured so that it does not come into contact with the inner wall of the fixing ring 20 even when the arm 19 is tilted to its maximum. . The first locking hole 17a and the second locking hole 2
Both ends of 0a are chamfered so that the locking pieces 19a, 19b can rotate smoothly.

In the automatic screw tightening machine described above, when the motor 10 rotates and its rotation is transmitted to the driver bit 7, the driver bit 7 tightens the screw onto the workpiece. When the screw is tightened and a load torque is applied to the driver bit 7, a reaction torque corresponding to the load is applied to the speed change ring 17, and as shown in FIG. rotates. When the speed change ring 17 rotates, the locking pieces 19a and 19b of the arm 19 rotate and tilt within the first locking hole 17a of the speed change ring 17 and the second locking hole 20a of the fixed ring 20, thereby shifting the speed. The ring 17 moves in the axial direction along the conical surface 14c of the planetary cone 14, the reduction ratio is changed, and finally the rotation of the driver bit 7 becomes zero and the screw tightening is completed.

During this screw tightening process, the arm 19 tilts in accordance with the rotation of the speed change ring 17, and the locking pieces 1 at both ends of the arm 19 tilt.
9a and 19b rotate within the speed change ring 17 and fixed ring 20, respectively. These locking pieces 19a, 19
The rotation of the locking piece b reaches its maximum when the screw tightening is completed, but since the lower locking piece 32b is bent in advance in the opposite direction to the turning direction, the locking piece 19b
As shown in the figure, the arm 19 only rises as it turns and does not come into contact with the inner wall of the fixed ring 20, allowing the arm 19 to rotate smoothly relative to the speed change ring 17 and the fixed ring 20. .
Therefore, the arm 19 will not be twisted, and its durability will not be impaired even if the screws are repeatedly tightened.

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 an automatic transmission made of a differential planetary mechanism having a planetary cone, and to change the speed of the differential planetary mechanism. Since both ends of the arm that holds the ring rotatably and movably in the axial direction are bent in advance to form a predetermined angle, the reduction ratio of the motor can be continuously increased according to the tightening torque. When the desired tightening torque is reached, screw tightening can be completed with the driver bit set to zero rotation regardless of the rotation of the rotary drive source, and the screw tightening can be completed without being affected by the inertia of the rotating part of the rotary drive source. Not only does this enable extremely high-precision tightening, but even if the gear ring repeatedly returns to rotation due to repeated screw tightening operations, the arm will only tilt and the arm itself will not twist, resulting in increased durability. It has advantages such as being able to provide an excellent automatic screw tightening machine.

[Brief explanation of drawings]

Figure 1 is a front view of the arm according to the present invention, Figure 2 is a front view of the arm according to the present invention;
The figure is a plan view of the arm in Figure 1, Figure 3 is a front view of the main part of the present invention, Figure 4 is an overall explanatory diagram of the present invention, and Figure 5 is a plan view of the arm in Figure 1.
The figure is an enlarged sectional view of the main part of the present invention, FIG. 6 is a sectional view of the main part showing the operating state of the differential planetary mechanism according to the present invention, and FIG. 7 is an explanatory diagram showing the operating state of the main part of the present invention, FIG. 8 is a sectional view of a main part showing the operating state of the arm according to the present invention. DESCRIPTION OF SYMBOLS 1...Automatic screw tightener, 2...Cylinder, 3...Driver mounting base, 4...Chuck stand, 5...Driver unit, 6...Connection mechanism, 7...Driver bit, 8...
Chuck unit, 8a... Chuck claw, 9... Driver body, 10... Motor, 10a... Drive shaft, 11
...Inner cylinder part, 12...Differential planetary mechanism, 13...Input disk, 14...Planetary cone, 14a...Conical surface, 14b
... Flat surface, 14c... Circumferential groove, 15... Cam disc, 16... Buffer mechanism, 17... Speed change ring, 17a
...first locking hole, 18...spring, 19...arm, 19
a, 19b...locking piece, 20...fixing ring, 20a
...Second locking hole.

Claims (1)

[Scope of Claims] 1. A rotary drive source is fixed to one end of the driver body 9, and an input disk 13 is arranged so as to rotate in response to the rotation of the drive shaft 10a, and the axis of the input disk 13 is A plurality of planetary cones 14 are arranged at predetermined intervals on a circumference surrounding the planetary cone 14, and the planetary cone 14 has a conical surface 14a as a transmission surface, a flat surface 14b on the back surface thereof, and a circumferential groove located adjacent to the conical surface 14a as a transmission surface. 14c, the input disk 13 is formed in the circumferential groove 14c, and the input disk 1 is formed in the flat surface 14b.
A cam disc 15 rotating concentrically with the cam disc 15 is frictionally engaged with the cam disc 15, and a driver bit 7 is connected to the cam disc 15 so as to rotate together with the cam disc 15.
A speed change ring 17 is arranged so as to be rotatable by the load torque of the driver bit 7 and move along the conical surface 14a.
A rotatable arm 19 is fixed to the speed change ring 17 and the inner cylindrical portion 11 to bias the speed change ring 17 to the high speed side by a spring 18 and limit the amount of movement of the speed change ring 17 toward the high speed side. A locking piece 19 is provided between the ring 20 and the arm 19 at both ends thereof.
a, 19b are provided, and these locking pieces 19a, 19b
is bent in a direction forming a predetermined angle, one of the locking pieces 19a is loosely inserted into the speed change ring 17 to be freely rotatable, and the other locking piece 19b is loosely inserted into the fixed ring 20 so that it can be freely rotated. The automatic screw tightening machine is characterized in that the locking piece 19b is previously positioned in a direction opposite to the direction in which the arm 19 rotates as the arm 19 inclines.