JPH058023Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is configured to eliminate the influence of inertia of the driver bit when screw tightening is completed, and ensure screw tightening with the desired screw tightening torque. Regarding the automatic screw tightening machine.

Prior Art Generally, when controlling screw tightening torque,
A driver bit is rotated by a motor, the load current of the motor is detected, which varies according to the load applied to the driver bit, and when this detected value reaches a set value, the screw is tightened to stop the motor after a certain period of time from that point. Devices equipped with a completion detection section, or devices equipped with a screw tightening completion detection section that detects the reaction torque applied to the driver bit using a torque detector such as a strain gauge and stop the motor when this reaches a certain value are common. It is true. In these devices, if the set value of the screw tightening torque is low, the tightening torque will be far from the set value due to the influence of the inertia of the rotary drive unit when the screw tightening is completed, and the screw will be accurately tightened to the desired value. There is a need for a screw tightening machine that can accurately tighten screws even at low tightening torque settings. In line with this demand, new automatic screw tightening machines have been developed. This automatic screw tightening machine 1
As shown in FIGS. 3 and 4, this has a driver stand 3 that is raised and lowered by the operation of a cylinder 2. A motor 5 is attached to the driver stand 3 via a driver body 4 with its drive shaft facing downward. An automatic transmission housed within the driver body 4 is connected to the drive shaft of the motor 5. The automatic transmission 15 is composed of a differential planetary mechanism 6 and has an input disk 7 that rotates in response to the rotation of the motor 5. A plurality of planetary cones 8 held by a cone holder 8d are arranged on the outer periphery of the input disk 7 so as to rotate through frictional engagement. It has a circumferential groove 8a that engages in friction, a conical surface 8b, and a flat surface 8c located on the back surface thereof.
A cam disk 9 that rotates concentrically with the input disk 7 is arranged so as to be frictionally engaged with the flat surface 8c of the planetary cone 8, and the frictional engagement between the speed change ring 10 and the planetary cone 8, which will be described later, is The speed reduction ratio is configured to change continuously depending on the position. The cam disc 9 also includes a pressure regulating mechanism 11.
An output shaft 12 of the automatic transmission is connected to the automatic transmission through the holder, and the output shaft 12 is rotatably held in an inner cylinder portion 4a fixed to the driver stand 3 side. This output shaft 12 includes a first spring locking ring 13a integrally fixed thereto, a second spring locking ring 13b rotatable with respect to the first spring locking ring 13a, and a connecting spring having an end portion locked to these. 13c is connected to the buffer mechanism 13. Furthermore, the second
A driver bit 15 is connected to the spring locking ring 13b via a connecting mechanism 14 that rotates together with the spring locking ring 13b, so that the rotation of the motor 5 is transmitted to the driver bit 15.

Furthermore, a bottom cover 4 is provided inside the driver body 4.
An arm 18 is rotatably locked through a fixture 17 fixed to a, and a speed change ring 10 is rotatably supported at the upper end of the arm 18, and the conical surface 8b of the planetary cone 8 is held movably along the The speed change ring 10 has a first spring 19 so that its frictional engagement position is located on the high speed side.
The first spring 19 and the arm 18 are configured to regulate the maximum rotational speed and tightening torque of the driver bit 15 determined by the frictional engagement position of the speed change ring 10. .

Problems to be Solved by the Invention In the automatic screw tightening machine described above, during normal screw tightening, the driver bit 15 is not engaged until the bearing surface of the screw (not shown) comes into contact with the workpiece (not shown). Since the applied load is small and almost constant, there is almost no movement of the speed change ring 10, and the driver bit 15 can rotate at high speed to tighten the screw. After that, when the bearing surface of the screw comes into contact with the workpiece,
The load on the driver bit 15 increases rapidly. At the same time, the speed change ring 10 receives a reaction torque according to the load on the driver bit 15, and the driver bit 1
Rotate in the opposite direction to 5. At this time, the gear ring 10
Since it is held by the arm 18, the position of frictional engagement with the planetary cone 8 changes, and its reduction ratio increases rapidly. Therefore, the rotation of the driver bit 15 is rapidly decelerated, the rotation reaches zero rotation, and screw tightening is completed, and the screw tightening is performed accurately and quickly without being affected by the inertia of the rotating part of the motor 5. It can be carried out. However, in this automatic screw tightening machine 1, when the screw tightening is completed, the speed change ring 10 moves along the conical surface 8b of the planetary cone 8 and reaches a position where its reduction ratio becomes infinite. Even if the voltage to 5 is cut off, the speed change ring 10 and the planetary cone 8 are self-locked.
In this state, when the driver bit 15 rises,
If the driver bit 15 bites into the screw head and lifts the workpiece, or if the driver bit 15 is forcibly removed from the screw head when rotational torque is applied, the screw head or the tip of the driver bit 15 is damaged. There is a fear that this will happen. To prevent this, it is necessary to release the self-lock between the speed change ring 10 and the planetary cone 8 when the driver bit 15 is raised. Therefore, an appropriate screw tightening completion detection section (not shown) is provided in the control section (not shown) of the motor 5, and the motor 5 is slightly reversed for a predetermined period of time based on the output signal, and the speed change ring 10 and the planetary The self-lock between the cone 8 and the cone 8 has been released. However, since this self-lock is released instantaneously, if this time is set too long, the reverse rotation of the motor 5 will be transmitted to the driver bit 15, which may cause the screw to tighten once it has been tightened. is occurring.

Means for Solving the Problems The present invention aims to eliminate the above-mentioned problems, and includes a driver stand that is raised and lowered by the operation of a cylinder. A motor is attached to this driver stand so that it moves up and down as one unit, and this motor includes an input disk that rotates in response to the rotation of the motor, a planetary cone that frictionally engages with the outer periphery of the input disk, and a planetary cone that frictionally engages with the input disk. A driver bit is connected via a cam disc. Further, an arm whose one end is rotatably locked on the driver stand side is arranged. At the other end of this arm, a speed change ring is rotatably held in a position where it frictionally engages with the conical surface of the planetary cone, and the speed change ring is biased toward the high speed side by a first spring and held in position. is configured to do so.

On the other hand, the control section of the motor is provided with a screw tightening completion detection section, and the output signal of the screw tightening completion detection section stops the forward rotation of the motor and causes the motor to rotate slightly in reverse for a predetermined period of time. It is configured as follows.

Furthermore, a connecting shaft that rotates together with the cam disk and has a non-circular fitting protrusion is connected to the cam disk, and a connection shaft is provided between the connecting shaft and the driver bit in the reverse direction of the cam disk and the connecting shaft. A lap spring clutch is connected to prevent rotation. The lap spring clutch is rotatable with respect to a drive shaft portion having a fitting recess that fits into a fitting protrusion of the connecting shaft, and a drive shaft portion inserted through a storage hole drilled in the drive shaft portion. a driven shaft portion having an engaging portion; a second spring that contacts the expanded diameter portion of the driven shaft portion and is tightly wound around the circumferential surfaces of the drive shaft portion and the driven shaft portion; A stop ring is fixed and restricts the spring length of the second spring.

Further, a portion of each of the driving shaft portion and the driven shaft portion on the joint side side is formed to be a small diameter portion, and the second spring is configured to be separated from the circumferential surface in this small diameter portion.

Function In the automatic screw tightening machine described above, when the motor is driven, normal rotation of the motor is transmitted to the cam disc at a reduction ratio determined by the frictional engagement position of the speed change ring with the conical surface of the planetary cone. As the cam disc rotates, the output shaft and the drive shaft portion of the lap spring clutch rotate together. When the drive shaft portion rotates in the forward direction, the second spring is further twisted in a direction to wrap around the drive shaft portion and the driven shaft portion, so that the drive shaft portion and the driven shaft portion rotate together,
The rotation is transmitted to the driver bit, and the screw is tightened into a predetermined position on the workpiece. When the screw is tightened, a reaction force is applied to the speed change ring according to the reaction torque of the driver bit, and when the speed change ring rotates, the arm tilts, the speed change ring moves in the direction of its axis, and its reduction ratio changes. growing.

When the seat surface of the screw comes into contact with the workpiece, the load on the driver bit increases rapidly, so the reduction ratio increases rapidly and finally reaches infinity. At this time, when reaction torque is transmitted to the driven shaft of the lap spring clutch in order to rapidly rotate the speed change ring, the impact is applied to the second spring around the small diameter portion of the drive shaft and driven shaft. It is absorbed by the buffer mechanism. Therefore, the impact is not transmitted to the output shaft and the cam disc, and therefore the speed change ring of the differential planetary mechanism moves gradually, albeit rapidly, and the speed change ring moves without excessive rotation due to inertial force. can do.

When the speed reduction ratio becomes infinite due to the movement of the speed change ring, the rotation of the driver bit stops and tightening is completed. As the rotation of the driver bit is stopped, an output signal is transmitted from the screw tightening completion detection section, and the normal rotation of the motor is stopped. At the same time, a reverse rotation command is given to the motor, and the motor is slightly reversed for a predetermined period of time. Therefore, the input disk and the planet cone are reversed, the self-lock between the speed change ring and the planet cone is released, and the speed change ring returns to the high speed side along the planet cone. At this time, since the speed change ring returns instantly, the reverse rotation of the motor is transmitted to the cam disk for a while after the speed change ring returns. This reversal of the cam disc is transmitted to the output shaft, causing the drive shaft portion of the lap spring clutch to rotate in the opposite direction. When this drive shaft portion rotates in the reverse direction, the second spring wound around the drive shaft portion and the driven shaft portion is twisted in the direction of separation, and the rotation of the drive shaft portion is no longer transmitted to the driven shaft portion, and the drive shaft portion only is reversed. Therefore, reverse rotation is not transmitted to the driver bit, and the tightened screw will not loosen.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. 1 and 2, reference numeral 1 denotes an automatic screw tightening machine, which has an automatic transmission that rotates in response to the rotation of a motor 5 that moves up and down together with a driver stand (not shown). This automatic transmission includes an input disk 7 that rotates in response to the rotation of the drive shaft of a motor 5, a plurality of planetary cones 8 that rotate by frictionally engaging the outer periphery of the input disk 7, and a plurality of planetary cones 8 located on the back side of the conical surface 8b of the planetary cones 8. flat surface 8c
It has a cam disk 9 that frictionally engages with the input disk 7 and rotates concentrically with the input disk 7, and an output shaft 12 that is connected to the cam disk 9 via a pressure regulating mechanism 11. This output shaft 12 is rotatably held by an inner cylindrical portion 4b of a bottom cover 4a attached to the driver stand 3. The automatic transmission also includes an arm 1 whose one end is rotatably locked to the driver stand 3 side.
2 and a speed change ring 10 held at the upper end thereof and frictionally engaged with the conical surface 8b of the planetary cone 8, and this speed change ring 10 has a first spring 19
is biased towards high speed. Further, this speed change ring 10 continuously changes its reduction ratio depending on the position of frictional engagement with the planetary cone 8, and the output shaft 12
It is configured such that the rotation of is decelerated. The output shaft 12 has a non-circular fitting protrusion 12a at one end, and the fitting protrusion 12a of the output shaft 12 forms a part of a lap spring clutch 20 disposed within the inner cylindrical portion 4b. It fits into a fitting recess 21a at one end of the drive shaft portion 21. A storage hole 21b is bored in the other end of the drive shaft portion 21 in the axial direction thereof, and an engaging portion 22a of the driven shaft portion 22 is disposed in the storage hole 21b. In addition, this engaging portion 22
a has a circumferential groove 22b, into which a pin 23 is press-fitted orthogonally to the drive shaft portion 21.
is positioned so that the drive shaft portion 21 and the driven shaft portion 22 do not separate from each other, and the drive shaft portion 21 is configured to be rotatable relative to the driven shaft portion 22. On the outer periphery of the drive shaft portion 21 and the driven shaft portion 22, there is provided a second shaft which is closely connected thereto and whose one end is in contact with the enlarged diameter portion of the driven shaft portion 22.
A spring 24 is wound around the second spring 24.
The length of the spring is determined by a stop ring 25 fixed to the drive shaft 24. When the drive shaft portion 21 rotates normally, the second spring 24
1 and the driven shaft portion 22, and when the drive shaft portion 21 reverses, it separates from the drive shaft portion 21 and the driven shaft portion 22, and is configured such that only the drive shaft portion 21 rotates in the reverse direction. has been done. Moreover, a part of the driving shaft part 21 and the driven shaft part 22 on the joint side forms small diameter parts 26a and 26b, and the second spring 24 is located away from the circumferential surface, and the buffer mechanism is activated in this part. It is already configured. Further, a driver bit (not shown) is connected to one end of the driven shaft portion 22 via a connecting mechanism (not shown) so as to rotate together with the driven shaft portion 22.

On the other hand, the motor 5 is controlled by a control section including a screw tightening completion detection section that detects the completion of screw tightening by the driver bit and sends a detection signal. It is configured to stop the forward rotation of the motor 5 and to slightly rotate the motor 5 in the reverse direction based on a detection signal from the detection section. Furthermore, even if the screw tightening completion detection section detects the load current flowing through the motor 5 and stops the motor 5 after a predetermined time from this point when it reaches a set value, the The configuration may be such that the force/torque is detected using a strain tube (not shown) and a strain gauge (not shown), and when a predetermined value is reached, the motor is stopped after a predetermined time from that point. .

In the automatic screw tightening machine described above, the motor 5 is driven and the forward rotation of the motor 5 is transmitted to the output shaft 12 of the automatic transmission at a reduction ratio determined by the frictional engagement position of the speed change ring 10 with the conical surface 8b of the planetary cone 8. Ru. This rotation of the output shaft 12 is transmitted to the drive shaft portion 21 of the lap spring clutch 20, and the second spring 24 wound around this is further wound around the drive shaft portion 21 and the driven shaft portion 22, and the second spring 24 is wound around the drive shaft portion 21 and the driven shaft portion 22. The rotation is transmitted to the driven shaft portion 22 and further transmitted to the driver bit via the connecting mechanism 14, and the screw is tightened in a predetermined position on the workpiece. When the screw is tightened and the seat surface of the screw comes into contact with the workpiece, the load on the driver bit increases rapidly, and the speed change ring 10 rotates in response to the load on the driver bit, causing the arm 18 to tilt. Along with this, the speed change ring 10
moves in the direction of its axis, and its reduction ratio increases rapidly. At this time, the shock caused when the rotation of the driver bit is suddenly decelerated is absorbed by the buffer mechanism formed by a part of the second spring 24 of the lap spring clutch 20, and the rotation of the speed change ring 10 is rapid but smooth. The speed change ring 10 will not rotate beyond a predetermined level due to its inertia, and no tightening torque greater than the final tightening torque will be output at this point.

Thereafter, when the speed change ring 10 rotates further and the reduction ratio reaches infinity, the rotation of the driver bit stops and the tightening is completed. At this time, a self-lock is activated between the speed change ring 10 and the planetary cone 8 of the automatic transmission, but as the driver bit stops rotating, an output signal is sent from the screw tightening completion detection section, and the motor 5 is The rotation stops. At the same time, a reverse rotation command is given to the motor 5, and the motor 5 is slightly reversed for a predetermined period of time. By reversing the motor 5, the differential planetary mechanism 6 is reversed, and its cam disk 9 is also reversed. At the same time, the drive shaft section 21 is reversely rotated, and the second spring 24 is unscrewed so as to be wound around it and separated from the drive shaft section 21 and the driven shaft section 22, and the rotation of the drive shaft section 21 is transferred to the driven shaft section 22. No more transmission occurs, and only the drive shaft portion 21 rotates in reverse. Therefore, the self-lock between the gear ring 10 of the automatic transmission and the planetary cone 8 can be released without transmitting reverse rotation to the driver bit, and the screwdriver fitted into the head of the screw that has been tightened can be released. Only the load on the bit is reduced and the screw does not loosen.

Effects of the Invention As explained above, the present invention transmits the rotation of the motor to the driver bit through an automatic transmission consisting of an input disk, a planetary cone, a cam disk, and a speed change ring, and also transmits the rotation of the motor to the control section of the motor. The automatic transmission is configured to connect a mounting completion detection section and use its output signal to stop the forward rotation of the motor and cause the rear motor to rotate slightly in the reverse direction for a predetermined period of time. The drive shaft of the lap spring clutch that transmits the transmission is connected to the driver bit, and a driver bit is connected to the driven shaft, and a second spring with a specified spring length is tightly wound around the circumferential surfaces of both to achieve forward rotation. Since the structure is configured so that only the rotation in the direction of Even if the shaft is reversed and reversed, due to the action of the lap spring, the drive shaft only reverses, the driven shaft does not reverse, and the driver bit is held in a stopped state, reducing the load on the driver bit. There are advantages such as being able to tighten the screws reliably without having to loosen the screws once they have been tightened. In addition, in the present invention, a part of the lap spring on the joint side between the drive shaft part and the driven shaft part is a small diameter part, and the second spring in this part forms a buffer mechanism, so when the screw is seated, The shock is absorbed by this buffer mechanism, and the reaction force applied to the gear ring is applied rapidly but gradually.The gear ring rotates without being affected by inertia, and the impact when the screw is seated causes the final rotation. There is no possibility that a tightening torque higher than the tightening torque is outputted, and even when tightening a screw with a low tightening torque, there is an advantage that accurate tightening can be performed.

[Brief explanation of the drawing]

Fig. 1 is an enlarged sectional view of the main parts of the present invention, Fig. 2 is a sectional view of the main parts along line A-A in Fig. 1, Fig. 3 is an overall explanatory diagram of a general automatic screw tightening machine, FIG. 4 is an enlarged sectional view of the main parts of a conventional automatic transmission. 1...Automatic screw tightening machine, 2...Cylinder, 3...
... Driver stand, 4 ... Driver body, 4a ... Bottom cover, 4b ... Inner cylinder part, 5 ... Motor, 6 ... Differential planetary mechanism, 7 ... Input disk, 8 ... Planetary cone,
8a... Circumferential groove, 8b... Conical surface, 8c... Flat surface, 8d... Cone holder, 9... Cam disk, 10... Speed change ring, 11... Pressure regulating mechanism, 1
2... Output shaft, 12a... Fitting protrusion, 13... Buffer mechanism, 13a... First spring locking ring, 13b
...Second spring locking ring, 13c...Connection spring,
14...Connection mechanism, 15...Driver bit, 1
6..., 17... Fixture, 18... Arm, 19
...First spring, 20...Lap spring clutch, 21...Drive shaft portion, 21a...Fitting recess, 2
1b... Storage hole, 22... Driven shaft portion, 22a...
Engaging portion, 22b...Circumferential groove, 23...Pin, 24
...Second spring, 25...Stop spring, 26
a, 26b...Small diameter part.

Claims (1)

[Scope of claim for utility model registration] Driver stand 3 that moves up and down by the operation of cylinder 2
A motor 5 is fixed to the driver base 3 so as to move up and down integrally with the input disc 7, which rotates in response to the rotation of the motor 5, and a planetary cone 8 that frictionally engages with the outer periphery of the input disc 7. A driver bit 15 is connected to the cam disk 9 so as to rotate together with the cam disk 9, and an arm 18 is rotatably locked at one end on the driver stand 3 side. is arranged, and a speed change ring 10 is arranged at the upper end of this arm 18 so as to be frictionally engaged with the outer periphery of the planetary cone 8 and rotatably arranged,
Further, a screw tightening completion detecting section is provided which biases the speed change ring 10 toward the high speed side by the first spring 19, and detects the completion of screw tightening by the driver bit 15 and sends a detection signal. In an automatic screw tightening machine equipped with a control section for the motor 5 that stops forward rotation of the motor 5 and slightly reverses the rotation of the motor 5 based on a detection signal from a completion detection section, the cam disk 9 has an output that rotates integrally with the motor 5. A shaft 12 is connected to the output shaft 12, and a non-circular fitting protrusion 12a is provided on the output shaft 12.
The drive shaft portion 21 has a fitting recess 21a that fits into the drive shaft portion 21.
and a driven shaft portion 22 having an engaging portion 22a which is inserted through the storage hole 21b bored in the axial direction and rotatable with respect to the drive shaft portion 21; a second spring 24 that is in contact with and closely wound around the circumferential surfaces of the drive shaft portion 21 and the driven shaft portion 22; and a stop ring 25 that is fixed to the drive shaft portion 21 and regulates the spring length of the second spring 24.
The driver bit 15 is connected to the driven shaft portion 22 of the lap spring clutch 20, and the drive shaft portion 21 and the driven shaft portion 22 of the lap spring clutch 20 are connected to each other. A part of the joining part side is made into small diameter part 26a, 26b, and this small diameter part 26
An automatic screw tightening machine characterized in that the second spring 24 is separated from the circumferential surface at points a and 26b.