JPH0780103B2 - Automatic screw tightener - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention eliminates the influence of the inertia of the driver bit at the time of detecting the completion of tightening of screws, bolts, etc., and securely performs the tightening work with a desired tightening torque. And an automatic screw tightener configured as described above.

[Prior Art] and "Problems to be Solved by the Invention" Generally, when controlling tightening torque of screws, bolts, etc., a driver bit is rotated by a rotary drive source, and a load torque applied to the driver bit is adjusted to an appropriate value. It is a general method to detect using a detecting means and to stop the rotary drive source when the detected value reaches a set value. In this method, when the tightening torque is set to a low value, the tightening torque exceeds the set value due to the influence of the inertia of the rotary drive unit when the completion of tightening is detected, and the screw or bolt cannot be tightened with an accurate tightening torque. Therefore, there is a demand for a screw tightening machine that can accurately tighten these even with a low set tightening torque. In response to this demand, as a means for mitigating the influence of inertia, Japanese Utility Model Publication No. 63-107536 has a differential planetary cone mechanism or Japanese Utility Model Publication No. 62-47936 has a two-stage differential planetary gear mechanism. The described screw tightener has been developed. With these screw tighteners, the influence of the motor inertia at the completion of tightening is mitigated, but the torque value detected by the torque detection part changes abruptly at the moment the screw is seated on the workpiece, so the torque detection part is distorted. When a flexible detecting member such as a pipe is used, the deformation itself of the detecting member is also affected by inertia. Therefore, there are drawbacks such that the torque applied to the driver bit cannot be accurately detected. Further, since a sudden force is applied to the detecting member in the rotational direction, repeated occurrence of such a drawback causes a shortage of the detecting member, and the like. Therefore, an automatic screw tightener that eliminates these drawbacks is desired.

[Means for Solving the Problems] In view of the above demand, the driver bit is connected to the rotary drive source via two differential planetary mechanisms, and the torque applied to the driver bit is connected to one differential planetary mechanism. In an automatic screw tightener equipped with a torque detection unit that detects a torque detection unit and a tightening completion detection unit that outputs a tightening completion signal when the output signal of the torque detection unit reaches a preset value corresponding to a predetermined tightening torque value, As a differential planetary mechanism connected to the rotary drive source side, an input disc that rotates in response to the rotation of the rotary drive source, a planet cone that frictionally engages with the outer circumference of the input disc, and a planetary cone that frictionally engages with this and rotates integrally with the driver bit There is provided a differential planetary cone mechanism comprising a cam disk and a transmission ring frictionally engaged with the outer periphery of the planetary cone and rotatably held by an arm. As a differential planetary mechanism connected to the driver bit side, a sun gear that rotates integrally with the cam disk,
A differential planetary gear mechanism consisting of a planetary gear base that holds a planetary gear that rotates around it and that rotates together with the driver bit, and a ring gear unit that has an internal gear that meshes with the planetary gear is provided. The ring gear is rotatably held and the torque detector is connected to the ring gear.

[Operation] In the above automatic screw tightener, the rotation of the rotary drive source is transmitted to the driver bit via the differential planetary gear mechanism at the reduction ratio determined by the friction engagement position between the planet cone and the speed change ring, and the screw is transferred to the workpiece. Fastened to. When the screw is fastened to the work, the ring gear portion of the differential planetary gear mechanism receives a force in the direction of rotation in the direction opposite to the driver bit from the planet gear according to the load applied to the driver bit. At the same time, the cam disk of the differential planetary cone mechanism also receives a load via the sun gear, and the gear shift ring rotates around the planetary cone in response to this load, and accordingly moves in the axial direction to reduce the reduction ratio. Increase.

When the screw is seated on the work, the load on the driver bit suddenly increases and receives a large force from the planetary gear, but this is transmitted not only to the ring gear but also to the differential planetary cone mechanism via the sun gear. . Therefore, the ring gear portion tries to rotate rapidly, but at the same time, the cam disk of the differential planetary cone mechanism also receives a sudden load, and the transmission ring rotates around the planetary cone. Along with this, the transmission ring moves in the axial direction thereof, the reduction ratio of the differential planetary cone mechanism further increases, and the speed of the driver bit decreases. Due to the decrease in the speed of the driver bit, the abrupt rotation of the ring gear portion is alleviated, and the abrupt load of the cam disk is alleviated by the rotation of the ring gear portion. Can be rotated with a relatively long time, and the torque value can be detected accurately by the torque detection unit. Further, even if the torque detecting section is repeatedly detected, the detecting member is never destroyed.

Embodiments Embodiments will be described below with reference to the drawings. In FIG. 1 and FIG. 2, reference numeral 1 is an automatic screw tightening machine, and the automatic screw tightening machine 1 is a driver main body fixed via a gear case 3 to a driver base 2 which is moved up and down by the operation of a lifting drive source 26. Have four. Lubricant oil is filled in the driver main body 4 so as to cover the periphery of a differential planetary cone mechanism 6 described later. A motor 5 as a rotary drive source is fixed to one end of the driver body 4, and a drive shaft of the motor 5 is a differential planetary cone mechanism 6 as an example of a differential planetary mechanism located on the motor 5 side. The input discs 7 forming a part are connected to each other, and are arranged so as to rotate integrally with the rotation of the motor 5. A plurality of planet cones 8 are arranged on the outer circumference of the input disc 7, and the circumferential grooves 8a of the planet cones 8 are frictionally engaged with the input disc 7 to rotate. A cam disk 9 that rotates concentrically with the input disk 7 is arranged so as to frictionally engage with the flat surface 8b located on the back surface of the conical surface 8c of the planetary cone 8.

A transmission ring 10 has a conical surface on the outer periphery of the planetary cone 8.
It is arranged so as to rotate by frictionally engaging with 8c. One end of this transmission ring 10 is rotatable by an arm 13 which is rotatably held by a fixed ring 12 arranged on the side of a bottom lid 11 described later. Held in. Moreover, the transmission ring 10 is biased by the spring 14 so that the frictional engagement position is located on the high speed side, and the spring 14 and the arm 13 constitute an elastic holding member. This elastic holding member is configured to regulate the frictional engagement position of the speed change ring 10 and determine the maximum value of the reduction ratio and the maximum tightening torque. The spring 14 is mounted on a spring seat 15 which is movable along the cylindrical portion 11a of the bottom cover 11, and the spring seat 15 is screwed onto an adjusting bolt 16 rotatably held on the bottom cover 11. However, the position can be arbitrarily selected.

The cam disk 9 has an output shaft 17 rotatably held by a cylindrical portion 11a of a bottom lid 11 which constitutes a part of the driver body 4.
The connecting shaft 18 is connected via the cam disc 9,
The output shaft 17 and the connecting shaft 18 are configured to rotate integrally. A sun gear 19a of a differential planetary gear mechanism 19 provided in the gear case 3 is connected to the lower end of the connecting shaft 18 as a differential planetary mechanism located on the driver bit 23 side, which will be described later. Three planet gears 19b that mesh with each other at equal intervals are supported and arranged on the planet gear base 19c. The planet gear 19b is a ring gear portion having an internal gear that is rotatably held in the gear case 3.
It meshes with the internal gear 19d, and is configured to reduce the rotation of the connecting shaft 18 to a predetermined ratio and transmit the rotation to the planetary gear base 19c. A strain tube as an example of a torque detection unit arranged so as to include the connecting shaft 18 in the ring gear unit 19d.
20 is fixed, and the upper end of the strain tube 20 is the bottom lid 11
Is fixed to the cylindrical portion 11a side. A strain gauge 21 for detecting the amount of strain is attached to the strain tube 20, and the strain amount of the strain tube 20 is detected to detect the reaction torque applied to the ring gear portion 19d.

A driver bit 23 is connected to the planetary gear base 19c via a transmission mechanism 22, and the rotation of the motor 5 is transmitted to the driver bit 23.

Further, the control device 24 of the automatic screw fastening machine outputs a work start signal to the work start section 25, a lift drive source 26 which starts the operation upon receiving the work start signal, and a power to the motor 5 upon receipt of the work start signal. Power supply unit to supply
27, a torque detector 2 that receives the output signal of the strain gauge 21 and detects the reaction torque applied to the driver bit 23.
8. When the output signal of the torque detection unit 28 reaches a set value corresponding to the tightening torque preset by the torque setting unit 29, a stop signal for stopping the power supply to the motor 5 is output and the lifting drive source 26 is restored. The tightening completion detecting unit 30 is provided. The torque detection unit 28 includes a filter unit 28a, a zero point correction unit 28b, and a gain correction unit 28c, and is configured to obtain a detected value corresponding to the tightening torque value by calibration. Although the detected value is an analog value, it may be changed to a digital value. Further, if the control device 24 is provided with a switching portion (not shown) for rotating the motor 5 in the reverse direction, even if the differential planetary mechanism 6 is in a stalled state, it can be released.

In the automatic screw tightener 1, when the work start signal is received, power is supplied to the motor 5 and the motor rotates.
With the rotation of the motor 5, the rotation is transmitted to the driver bit 23 via the differential planetary cone mechanism 6 and the differential planetary gear mechanism 19 which are composed of the input disc 7, the planetary cone 8, the cam disk 9 and the speed change ring 10. The screw arranged at the tip of the driver bit 23 is fitted into the prepared hole of the predetermined work, and the tightening is started. When the screw is screwed into the work (not shown) and the load of the driver bit 23 becomes large, the reaction torque corresponding to this load is applied to the ring gear portion 19d of the differential planetary gear mechanism 19, and the ring gear portion 19d becomes The driver bit 23 rotates in a direction opposite to the rotating direction. At the same time, the load applied to the sun gear 19a also increases, and a reaction torque corresponding to the load of the driver bit 23 is generated on the output shaft 17 and the connecting shaft 18 that are integral with the cam disk 9 of the differential planetary cone mechanism 6. The reaction ring torque causes the transmission ring 10 to rotate, but the transmission ring 10
Is held by the arm 13 having a constant length, the rotation of the transmission ring 10 causes the transmission ring 10 to move in its axial direction. At this time, the amount of movement is such that the speed change ring 10 is regulated by the spring 14, and the position where the pressing force to the spring 14 generated in the speed change ring 10 by the reaction torque and the elastic force generated by the bending of the spring 14 are balanced. Shifting ring up to 10
Moves.

When the screw is seated on the work, the load applied to the driver bit 23 suddenly increases and the ring gear portion 19d becomes the planetary gear 1
A large force in the direction opposite to the rotation direction is received from 9b, but this is transmitted not only to the ring gear portion 19d but also to the differential planetary cone mechanism 6 via the sun gear 19a. Therefore, the ring gear portion 19d tries to rotate rapidly, but at the same time, the cam disk 9 of the differential planetary cone mechanism 6 also receives a sudden load, and the transmission ring 10 rotates around the planetary cone 8 in accordance with the load. Move. The speed change ring 10 moves in the axial direction along with the rotation to further increase the speed reduction ratio and reduce the speed of the driver bit 23. Due to the decrease in the speed of the driver bit 23, the abrupt rotation of the ring gear portion 19d is alleviated, and the abrupt load of the cam disk 9 is alleviated by the rotation of the ring gear portion 19d, so that the transmission ring 10 and the ring gear portion Each of the 19d rotates with a relatively long time. Therefore, the deformation of the strain tube 20 fixed to the ring gear portion 19d also progresses without the influence of inertia, and the torque value can be detected accurately.

Further, when the speed change ring 10 moves to the vicinity of the edge of the planetary cone 8 as the load on the driver bit 23 increases, the rotation of the output shaft 17 and the connecting shaft 18 decreases to near zero rotation, and the driver bit 23 The speed is reduced to near zero rotation, and the tightening of the screw is performed while outputting the tightening torque indicated by the characteristic curve shown in FIG.

Meanwhile, as the load on the driver bit 23 increases, the ring gear portion 19d further receives the reaction torque and further rotates, and the strain gauge 21 detects the strain amount of the strain tube 20 due to this rotation. When the detection signal of the strain gauge 21 is amplified and reaches a set value corresponding to the tightening torque preset in the torque setting section 29, a tightening completion signal is output from the tightening completion detecting section 30 to supply power to the motor 5. Is stopped. At this time, since the driver bit 23 is close to zero rotation, the inertia that the driver bit 23 itself has hardly occurs, and when the power supply to the motor 5 is stopped, the inertia that the motor 5 itself has becomes differential. Although the input disc 7 is transmitted by being transmitted to the input disc 7 of the planetary cone mechanism 6, the rotation of the input disc 7 is hardly transmitted to the output shaft 17 and the connecting shaft 18 by the operation of the differential planetary cone mechanism 6. From this aspect as well, the driver bit 23 is not affected by the inertia, and the driver bit 23 can stop its rotation at the same time when the power supply to the motor 5 is stopped, and the screw is securely tightened with a predetermined tightening torque. be able to.

[Effects of the Invention] As described above, the present invention connects a driver bit to a rotary drive source through two differential planetary mechanisms, and
An input circle that rotates while receiving the rotation of the rotary drive source as a differential planetary mechanism that is connected to one of the differential planetary mechanisms and that detects the torque related to the driver bit, while being connected to the rotary drive source side. A plate and a planet cone that frictionally engages the outer periphery thereof, a cam disk that frictionally engages the plate and that rotates integrally with the driver bit, and frictionally engages the outer periphery of the planet cone and is rotatably held by the arm. A differential planetary cone mechanism composed of a speed change ring is used as a differential planetary mechanism connected to the driver bit side, and a sun gear that rotates integrally with the cam disk and a planetary gear that rotates around the sun gear are held and used as a driver bit. A differential planetary gear mechanism consisting of a planetary gear stand that rotates integrally and a ring gear part that has an internal gear that meshes with the planetary gear is provided, and this ring gear part is rotatably held. The torque detecting portion is connected to the ring gear portion. Therefore, even if the ring gear portion receives a force to rapidly rotate when the screw is seated on the work, this is transmitted not only to the ring gear portion but also to the differential planetary cone mechanism via the sun gear, By operating the differential planetary cone mechanism, it is possible to increase the speed reduction ratio of the driver bit, reduce the speed of the driver bit, and suppress abrupt rotation of the ring gear portion. Also, the sudden load on the cam disk is alleviated by the rotation of the ring gear, and the speed change ring and the ring gear interact with each other so that both rotary parts can rotate in a relatively long time. The detection member is deformed without inertia, and accurate torque detection is possible. Moreover, even if repeated measurement is performed, the torque detection unit is not impacted, so that a device with a long life can be provided.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of an essential part of the present invention, FIG. 2 is an overall explanatory view of the present invention, and FIG. 3 is a torque-rotational speed characteristic diagram of an output shaft of a differential planetary cone mechanism according to the present invention. . 1 ... Automatic screw tightener, 2 ... driver base, 3 ... gear case, 4 ... driver body, 5 ... motor, 6 ... differential planetary cone mechanism, 7 ... input disk, 8 ... Planetary cone, 8a ... circumferential groove, 8b ... flat surface, 8c ... conical surface, 9 ... cam disk, 10 ... transmission ring, 11 ... bottom lid, 11a ... cylindrical part, 12 ... fixed Ring, 13 ... Arm, 14 ... Spring, 15 ... Spring seat, 16 ... Adjusting bolt, 17 ... Output shaft, 18 ... Connecting shaft, 19 ... Differential planetary gear mechanism, 19a ... Sun gear , 19b ...... Planetary gear, 19c ...... Planetary gear stand, 19d ...... Ring gear part, 20 ...... Strain tube, 21 ...... Strain gauge, 22 ...... Transmission mechanism, 23 ...... Driver bit, 24 ...... Control device , 25 …… Work start part, 26 …… Lifting drive source, 27 …… Power supply part, 28 …… Torque detection part, 28 a …… Filter part, 28 b …… Zero correction part, 28 c …… Inn correction unit, 29 ...... torque setting section, 30 ...... tightening completion detection unit,

Claims (1)

[Claims] 1. A torque detector for connecting a driver bit to a rotary drive source via two differential planetary mechanisms, and a torque detector connected to one differential planetary mechanism for detecting a torque applied to the driver bit, When the output signal of the torque detection unit reaches the set value corresponding to the predetermined tightening torque value, the automatic screw tightener equipped with the tightening completion detection unit that outputs the tightening completion signal outputs the difference connected to the rotary drive source side. As a dynamic planetary mechanism, an input disc that is rotated by the rotation of a rotary drive source, a planet cone that is frictionally engaged with the outer periphery of the input disc, a cam disk that is frictionally engaged with the disc and that rotates integrally with the driver bit, and the planet cone are provided. A differential planetary cone mechanism that is frictionally engaged with the outer periphery and is rotatably held by an arm, and a differential planetary cone mechanism that is connected to the driver bit side; Then, from the sun gear that rotates integrally with the cam disk, the planetary gear base that retains the planetary gear that rotates around it and that rotates integrally with the driver bit, and the ring gear that has the internal gear that meshes with the planetary gear. An automatic screw tightener characterized in that a differential planetary gear mechanism is provided, the ring gear portion is rotatably held, and a torque detection portion is connected to the ring gear portion.