JPH0724992B2 - Automatic screw tightener - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when a screw bit such as a bolt, a nut or a screw is fastened to a work by using a box bit or a driver bit which is rotated by the rotation of a motor, the head of the screw component is seated. The present invention relates to an automatic screw tightener configured to reduce the impact of a shocking reaction torque when tightening.

[0002]

2. Description of the Related Art Generally, when controlling the tightening torque of bolts, nuts, screws, etc., a motor rotates a box bit or a driver bit (hereinafter, the driver bit will be described) and is applied to the driver bit. A detector that detects the load current of the motor that changes according to the load is provided, and if the detected value reaches the set value, the device configured to stop the motor after a certain time from that point, or the reaction added to the driver bit A general device is configured so that the force torque is converted into a strain amount by a strain tube, the strain amount is detected by a detection unit such as a strain gauge, and the motor is stopped if the strain amount reaches a constant value. In these devices, if a shocking reaction force torque occurs when the head of the screw is seated immediately before the completion of tightening, this is detected by the detection unit, and when the set tightening torque value is low, the detected value is set instantaneously. Since the value exceeds the value, there is a defect that the tightening cannot be completed with the desired tightening torque. In addition, in these devices, if tightening is started and the detected value reaches the set tightening torque, the actual tightening torque is always the set tightening torque due to the influence of inertia when the motor is stopped because the motor is stopped. However, there are drawbacks such as not being able to perform accurate tightening work.

As a device for eliminating these drawbacks, an automatic screw tightener having an automatic transmission that stops only the rotation of the driver bit while the motor continues to rotate when the set tightening torque is reached has been devised. . As shown in FIG. 4, the automatic transmission 7 of the automatic screw tightener 1 has a motor 6
An input disc 8 which is rotationally driven by a plurality of planetary cones 9 having a circumferential groove 9a frictionally engaged with the input disc 8, a cam disk 10 frictionally engaged with a flat surface 9c on the back surface thereof, and the planetary cone 9 A speed change ring 11 frictionally engaged along the conical surface 9b of the, and an arm 12 rotatably holding the speed change ring 11.
It is composed of a spring 15 for urging the speed change ring 11 toward the high speed side. When the speed change ring 11 is rotated and the arm 12 is tilted, the friction engagement position between the speed change ring 11 and the planetary cone 9 is changed to decelerate. The ratio is configured to change continuously.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the automatic screw tightener 1 having the automatic transmission 7 as described above, a screw (not shown) is used.
Even if a shocking reaction torque occurs due to the inertia of the driver bit when the head of the vehicle is seated,
It is considerably absorbed by the rotation of 1 and is hardly transmitted as the output torque of the driver bit. Moreover, with the rotation of the speed change ring 11, the speed change ring 11 moves to the larger diameter side along the conical surface 9b of the planet cone 9, the reduction ratio increases, and the driver bit is decelerated.
When the time point at which the reduction ratio becomes infinite is the tightening completion time point, the rotation of the driver bit (not shown) stops despite the rotation of the motor 6 at the completion of the tightening operation. Since the influence of the inertia of the automatic transmission can be mitigated and tightening can be performed with the output torque of the automatic transmission at this time, the automatic screw tightener 1 has a high evaluation as a highly accurate screw tightener. There is.

The applicant uses the automatic screw tightening machine 1 to provide a means for detecting the torque applied to the driver bit not only when the driver bit is stopped, but also to complete the tightening before the driver bit is stopped. Even with this structure, we have devised an automatic screw tightener that can perform high-precision tightening. Although this automatic screw tightener can largely mitigate the influence of the inertia of the motor at the time of seating, the effect of the inertia after the power supply to the motor is stopped remains slightly, and the deceleration of the automatic transmission decreases as the tightening progresses. The output torque of the driver bit is affected by the sudden operation, which makes it impossible to perform highly accurate tightening, and the large load is applied to the motor to shorten the life of the motor. However, there is a demand for improvement.

The present invention has been made in view of the above demands, and provides an automatic screw tightening machine capable of performing high-precision tightening in a wide tightening torque range by mitigating the impact of shocking torque immediately before the completion of tightening. It is the one we are trying to provide.

[0007]

There is provided a driver stand that moves up and down by the operation of a lifting drive source, and a casing is arranged so as to move integrally with the driver stand.
A bottom lid having a sleeve portion protruding inward is fixed to the bottom of the casing, and the casing is configured to be filled with lubricating oil. Also,
In the casing, an input disc rotated by rotational driving of a motor, a plurality of planet cones having a circumferential groove frictionally engaged with the input disc, and a cam disk frictionally engaged with the back surface thereof are arranged. There is. An output shaft is connected to the cam disk, and a driver bit that integrally rotates is connected to the output shaft. Further, a speed change ring is arranged in frictional engagement along the conical surface of the planet cone, and one end of an arm is locked to the speed change ring. The other end of the arm is locked to a locking member that is rotatably arranged around the sleeve portion of the bottom lid, and the transmission ring is rotatably held around the planetary cone. The locking member is biased and fixed by an elastic member in a direction in which the arm stands upright, and the locking member is configured to gradually rotate as the transmission ring rotates. Further, the shift ring is biased toward the high speed side by a spring, and an automatic transmission is constructed in which the reduction gear ratio is continuously changed by the rotation of the shift ring.

[0008]

In the above automatic screw tightener, the load applied to the driver bit increases as the head of the screw is seated on the work, and the shift ring of the automatic transmission receives the reaction torque and rotates. Therefore, the arm that holds this transmission ring tilts, the transmission ring is pulled down on the conical surface of the planet cone along the generatrix direction toward its large diameter side, the reduction ratio of the automatic transmission begins to increase, and the driver bit Be slowed down. At the same time, one end of the arm is locked to the speed change ring along with the rotation of the speed change ring, and the other end of the arm is engaged with the lock member. It starts to rotate slightly in the rotating direction of the speed change ring against the elastic force of. Therefore, the arm slowly inclines, the transmission ring is smoothly pulled down with respect to the planet cone, and the automatic transmission of the driver bit is smoothly decelerated.

During this time, even if the tightening torque of the driver bit is detected and reaches the predetermined tightening torque value and the power supply to the motor is stopped, the motor bit continues to rotate for a predetermined time due to the inertia of the motor. However, since the influence of inertia of this motor is mitigated by the speed change ring, the arm and the retaining member that retains elasticity, the output torque of the driver bit is hardly affected, and even in the low tightening torque range, Highly accurate tightening can be performed.
Further, since the automatic transmission smoothly increases the reduction gear ratio, not only a sudden load is not applied to the motor, but also wear of parts constituting the automatic transmission can be reduced.

[0010]

Embodiments Embodiments will be described below with reference to the drawings. In FIGS. 1 and 2, reference numeral 1 denotes an automatic screw tightener, which is a driver base (not shown) that is moved up and down by the operation of a cylinder (not shown), which is an example of an elevation drive source, and a predetermined position with a predetermined distance from the driver base. It has a chuck base (not shown) having a chuck unit through which the driver bit 21 described later can be integrally inserted. In the driver stand,
A bottom lid 3 having a sleeve portion 3a for rotatably guiding an output shaft 2 described later is fixed via a mount (not shown) so as to move integrally. A casing 4 is fixed to the bottom lid 3, and an upper lid 5 is fixed to the upper portion of the casing 4 so that the casing 4 is filled with lubricating oil. A motor (not shown) is attached to the upper lid 3 via an integrally attached bracket 5a, and the rotation of the motor causes the casing 4 to rotate.
It is configured to be transmitted to the input disc 8 of the automatic transmission 7 built in the.

The automatic transmission 7 has an input disc 8 which is rotated by the rotation of a drive shaft 6a of the motor, and a plurality of planetary cones 9 having a circumferential groove 9a which is frictionally engaged with the outer periphery thereof.
However, a cam disk 10 is arranged on the planetary cone 9 so as to frictionally engage with a flat surface 9c located on the rear surface of the conical surface 9b of the planetary cone 9 and to rotate concentrically with the input disk 8. ing. Further, a speed-change ring 11 is frictionally engaged with the conical surface 9b of the planetary cone 9 and is rotatably arranged. The speed reduction ratio is determined by the frictional engagement position between the speed-change ring 11 and the planetary cone 9. It is configured to change continuously. Further, one end of an arm 12 is engaged with the speed change ring 11 at a plurality of positions on the outer circumference thereof, and the other end of the arm 12 is locked by a locking sleeve 13 which is an example of a locking member described later, and The amount of movement of the ring 11 on the high speed side is limited. Moreover, the speed change ring 11 is biased upward by the spring 15 held by the spring holding sleeve 14 arranged around the sleeve portion 3a of the bottom cover 3, and the locking sleeve 13 is always pulled up via the arm 12. Is configured.

A locking sleeve 13 is rotatably arranged at that position around the sleeve portion 3a of the bottom lid 3, and the locking sleeve 13 has a peripheral edge portion with which one end of the arm 12 is engaged. It has a collar portion 13a. A spring locking pin 16 is planted upright on the collar portion 13a of the locking sleeve 13 so that one end of a tension spring 17 described later is locked to the spring locking pin 16. It is configured. Further, the collar portion 13 of the locking sleeve 13
Slots 13b are formed at two locations in a, and spring fixing pins 18 planted in the bottom cover 3 project from the slots 13b. The other end of the tension spring 17 is fixed to the spring fixing pin 18, and the tension spring 17 locks the locking sleeve 13 into the spring fixing pin 18.
Is configured to be urged in the direction of coming into contact with and to be stopped to one side.

An output shaft 2 rotatably guided by a sleeve portion 3a of the bottom lid 3 is connected to the cam disk 10 via a pressure adjusting mechanism 19, and the output shaft 2 is connected to the output shaft 2. A connecting shaft 20 that is rotatably held is connected to the driver base side. A driver bit 21 is configured to rotate integrally with the connecting shaft 20 via a transmission mechanism (not shown).

Further, the connecting shaft 20 is provided with torque detecting means (not shown), and when the detected value and the reduction ratio of the automatic transmission 7 become infinite, the driver bit 21 stops. It is configured such that an arbitrary set value up to the output torque value of the automatic transmission 7 is compared and the tightening can be completed with an arbitrary tightening torque.

In the above automatic screw tightening machine, when the motor is driven to start tightening and the screw is seated on the work, the load applied to the driver bit 21 increases, and the automatic transmission 7 changes according to the load applied to the driver bit 21. Shift ring 1
1 rotates in the direction opposite to the tightening direction along the conical surface 9b of the planet cone 9. By the rotation of the transmission ring 11,
The arm 12 holding the speed change ring 11 is inclined, and the speed change ring 11 is pulled down on the conical surface 9b of the planet cone 9 along the generatrix direction toward the large diameter side. This shift ring 1
With the rotation of 1, the inclination angle of the arm 12 increases and the reduction gear ratio of the automatic transmission 7 starts to increase rapidly, but one end is locked to the speed change ring 11 and the locking sleeve is locked to the other end of the arm 12. Since the sleeve 13 is locked, the locking sleeve 1
A force is generated in 3 to rotate in the same direction as the speed change ring 11. When the rotational force of the locking sleeve 13 is smaller than the elastic force of the tension spring 17, the locking sleeve 13 is in contact with the spring fixing pin 18, but as shown in FIG. Becomes larger than the elastic force of the tension spring 17, the locking sleeve 13 moves to the tension spring 1
The arm 12 starts to rotate slightly against the elastic force of 7, and the fixed side of the arm 12 moves in the same direction as the transmission ring 11. Therefore, the inclination of the arm 12 advances slowly, and the reduction gear ratio of the automatic transmission 7 gradually increases.

During this time, even if the detected value of the torque detecting means reaches the set value and the power supply to the motor is stopped, the motor continues to rotate for a predetermined time due to the inertia of the motor, but the influence of the inertia of the motor Is relaxed by the speed change ring 11, the arm 12 and the locking sleeve 13, so that the driver bit 21 can be immediately stopped without being affected by the inertia of the motor, and the tightening torque value within the low tightening torque range can be obtained. Even if there is, high-precision tightening can be performed. Further, even immediately before the completion of tightening, the inclination of the arm 12 advances slowly and the deceleration of the automatic transmission 7 gradually increases. Therefore, not only a large load is not applied to the motor, but the life of the motor can be extended. Therefore, it is possible to minimize the wear of each component forming the automatic transmission 7. Further, since the automatic transmission 7 smoothly increases the reduction ratio, the output torque of the motor is transmitted to the driver bit 21 without loss, and it is not necessary to increase the capacity of the motor excessively, and a motor having a small capacity can be used.

In the embodiment, the locking sleeve 13 is biased in one direction by the tension spring 17, but a compression spring (not shown) may be used in place of the tension spring 17, or both directions may be used. It may be biased to move to.
Further, other known elastic members other than these springs can be used.

[0018]

As described above, according to the present invention, the input disc, the planetary cone that rotates by the rotation thereof, the cam disk that frictionally engages with the flat surface of the back surface thereof, and the frictional engagement with the conical surface of the planetary cone. A gear shift ring, an arm that holds the gear rotatably, a spring that biases the gear shift ring so that the arm is always upright, and a locking member that holds one end of the arm and is rotatably held elastically. Since an automatic transmission is installed and a driver bit is connected to the output shaft of this automatic transmission so as to rotate integrally, there is no impact that may occur when the screw head is seated on the workpiece as tightening progresses. The reaction torque and the influence of the inertia of the motor after stopping the power supply to the motor can be mitigated by the rotation of the speed change ring, the arm and the locking member, and the output torque of the driver bit is Can do well without being little power supply stop during the influence of the motor, a low clamping accurate tightening even tightening torque range. Further, according to the present invention, since the arm is slowly tilted and the reduction ratio of the automatic transmission is gradually increased, not only an unreasonable load is not applied to the motor,
It is possible to minimize the wear of the respective parts constituting the automatic transmission and extend the life of the machine. Further, according to the present invention, since the reduction ratio of the automatic transmission is gradually increased, the power of the motor is reliably transmitted to the driver bit without loss, and it is necessary to increase the capacity of the motor. It is possible to provide a compact screw tightening machine.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view taken along the line AA of FIG.

FIG. 2 is a longitudinal sectional view of an essential part of the automatic transmission according to the present invention.

FIG. 3 is a diagram illustrating the operation of the main part of the present invention.

FIG. 4 is a longitudinal sectional view of a main part of a conventional automatic screw fastening machine.

[Explanation of symbols]

 1 Automatic Screw Tightening Machine 2 Output Shaft 3 Bottom Lid 3a Sleeve Part 4 Casing 5 Top Lid 5a Bracket 6 Motor 6a Drive Shaft 7 Automatic Transmission 8 Input Disc 9 Planetary Cone 9a Circular Groove 9b Cone Face 9c Flat Face 10 Cam Disc 11 Speed change ring 12 Arm 13 Locking sleeve 13a Collar part 13b Oblong hole 14 Spring holding sleeve 15 Spring 16 Spring locking pin 17 Pulling spring 18 Spring fixing pin 19 Pressure adjusting mechanism 20 Connecting shaft 21 Driver bit

Claims (1)

[Claims] 1. A casing is arranged so as to move integrally with a driver stand that is elevated and lowered by the operation of an elevation drive source, and a bottom lid having a sleeve portion projecting inward is fixed to the bottom portion of the casing, and the casing is fixed in the casing. An input disc that is configured to be filled with lubricating oil and that is rotated by the rotational driving of a motor in the casing, a plurality of planet cones having a circumferential groove that frictionally engages with the input disc, and a friction member on the back surface thereof. A mating cam disk is arranged, and further, a transmission ring is arranged in friction engagement along the conical surface of the planetary cone,
The transmission ring is rotatably held by an arm whose one end is locked to the driver base side and is urged to the high speed side by a spring, while the output shaft is integrally connected to the cam disk. In an automatic screw tightener in which a driver bit that rotates integrally with the above is connected, a locking member that rotates around the sleeve portion of the bottom lid is arranged on the driver base side, and this locking member is biased by an elastic member. The automatic screw tightener is characterized in that the other end of the arm that holds the transmission ring is locked to the locking member while being fixed.