JPH0468096B2 - - 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. The present invention relates to a control device for a tightening machine.

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 common method is to stop the rotational drive source. In this method, 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 tightened with accurate tightening torque. Therefore, 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 disc 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. This method reduces the rotation of the driver bit to zero without causing any problems, and maintains the tightening torque with the output torque at this time, and also solves the problem of biting between the driver bit and the screw head that occurs when screw tightening is completed. .

Means for Solving the Problems The present invention aims to eliminate the above-mentioned drawbacks.
The driver bit is connected through an input disk which rotates in response to the rotation of the rotational drive source, a planetary cone that frictionally engages with the outer periphery of the input disk, and a com disk that frictionally engages with the input disk. Further, a speed change ring is disposed on the outer periphery of the planetary cone and is frictionally engaged with the conical surface thereof, and is configured such that the reaction torque applied to the speed change ring due to the load torque related to the driver bit is received by an elastic holding member. ing.

On the other hand, a forward rotation voltage supply section and a reverse rotation voltage supply section are connected to the rotational drive source via a switching means. Further, rotation stop detection means for detecting stoppage of the driver bit is arranged, and the output of the rotation stop detection means operates the switching means to cut off the forward rotation voltage supply section and reverse rotation of the reverse rotation voltage supply section. It is configured to supply voltage to the rotary drive source for a predetermined period of time.

Function The control device for the automatic screw tightening machine described above supplies a normal rotation voltage to the rotational drive source and transmits the rotation to the driver bit at a reduction ratio determined by the frictional engagement position between the planetary cone and the speed change ring. Tighten the screw. When the screw is tightened, reaction torque is applied to the speed change ring according to the load on the driver bit. Along with this, when the speed change ring rotates, it moves in the direction of its axis, and its reduction ratio increases until it reaches infinity and the rotation of the driver bit stops. Accordingly, the rotation stop detection means for detecting rotation stop of the driver bit is activated, and the switching means is activated by its output signal.
Cut off the supply of normal rotation voltage to the rotation drive source. At this time, since the straight line connecting the contact points of the planetary cone, the speed change ring, and the cam disk is almost parallel to the planetary cone, the cam disk is locked by the wedge action, and the driver bit outputs the tightening torque value.

Thereafter, a reverse voltage is supplied from the reverse voltage supply section to the rotational drive source for a predetermined period of time. Therefore, the rotational drive source rotates slightly in the opposite direction and stops, but the planetary cone and the speed change ring are slightly reversed from the rotational drive source side, and the frictional engagement position returns slightly to the high speed side.
Therefore, the speed change ring, cam disk, and planetary cone are unlocked, and at the same time, the speed change ring returns along the conical surface of the planetary cone to a position corresponding to the load on the driver bit that has been reduced by reversing the rotational drive source. Eventually it returns to its original position. After that, the driver bit increases and prepares for the next operation.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In FIG. 1, A is a control device for an automatic screw tightening machine 1. Prior to this control device A, the automatic screw tightening machine shown in FIG. 3 will be explained. This automatic screw tightening machine 1 has a motor 19 as a rotational drive source fixed to one end of a driver main body 18, and receives the rotation of an input disk 2 that forms a part of a differential planetary mechanism 20.
1 is arranged to rotate. Further, a plurality of planetary cones 23 are provided on the outer periphery of the input disk 21.
is arranged, and its circumferential groove 23a is connected to the input disk 2.
1 and is configured to rotate by frictionally engaging with it. A cam disk 24 rotating concentrically with the input disk 21 is arranged so as to frictionally engage with a flat surface 23b located on the back side of the conical surface 23c of the planetary cone 23. Furthermore, a driver bit 26 is connected to the cam disk 24 so as to rotate together with the cam disk 24, and the rotation of the motor 19 is transmitted to the driver bit 26.

Furthermore, a speed change ring 25 is arranged on the outer periphery of the planetary cone 23 so as to rotate by frictionally engaging with the conical surface 23c of the speed change ring 25.
is rotatably held by an arm 32 whose one end is rotatably held. In addition, the speed change ring 25 is biased by a spring 31 so that its frictional engagement position is located on the high speed side, and the frictional engagement of the speed change ring 25 is location is regulated,
The maximum value of the reduction ratio and the tightening torque are determined. In this automatic screw tightening machine 1, the speed change ring 25 is rotated by a reaction torque generated in response to the tightening torque applied to the driver bit 26. The amount of movement in the axial direction due to the rotation of the speed change ring 25 is regulated by the spring 31, so that the pressing force on the spring 31 generated on the speed change ring 25 due to reaction torque and the elastic force generated due to the deflection of the spring 31 are combined. The speed change ring 25 is configured to move to a position where the speed change ring 25 is balanced. Therefore, when the load on the driver bit 26 increases, the speed change ring 25 moves to the edge of the planetary cone 23, and the driver bit 26 is decelerated to zero rotation.
Screw tightening is performed as shown in the characteristic curve shown in FIG.

Further, the control device A is configured to control a motor 19 as a rotational drive source of the automatic screw tightening machine, and as shown in FIG.
1, and this work start section 41 is connected to a forward rotation control section 42. The motor 19 has a forward rotation voltage supply section 43 and a reverse rotation voltage supply section 44 that supplies a reverse rotation voltage lower than the forward rotation voltage.
5. This switching means 45 controls the motor 19 by a signal from the normal rotation control section 42.
In addition to supplying normal rotation voltage to the stop judgment unit 5
After cutting off the forward rotation voltage in response to a signal from the motor 6, the reverse rotation voltage is supplied to the motor 19 in response to a signal from the reverse rotation control section 46.

Further, a rotation stop detection means 50 for detecting rotation stop of the driver bit 26 is disposed in a position where the driver bit 26 does not interfere with its elevation. This rotation stop detection means 50 is connected to the driver main body 1.
A slit disk 51 that can be raised and lowered together with the driver bit 8 and rotates together with the driver bit 26, and a rotation detection section 5 that is disposed corresponding to the movement path of the slit at one end of the slit disk 51.
2. The rotation detecting section 52 is configured to transmit an output pulse when detecting passage of the slit disk 51 through the slit. This rotation detecting section 52 is connected to a stop determining section 56 via an amplifying section 57, a waveform shaping section 54, and a differentiating circuit 55. This stop judgment section 56 consists of a timer 56a which is an example of a pulse width detection section and a flip-flop 56b which is an example of a memory device.
After a predetermined time (T4) determined by the delay circuit 53 has elapsed, the timer 56a is reset by an output pulse from the rotation detection section 52, and after a very short time determined by the third delay circuit 56c has elapsed, the timer 56a is immediately set. It is composed of Furthermore, this timer 56a is set so that if an output pulse is not transmitted from the rotation detecting section 52 for a predetermined period of time (T1), the output signal is passed to the flip-flop 5.
6b, and upon receiving this output signal, flip-flop 56b is configured to output the output signal of stop determination section 56.

The output signal of the stop determination section 56 is supplied to the forward rotation control section 42, and is configured to cut off the forward rotation voltage supplied to the motor 19 based on the signal from the work start section 41. Further, this output signal is supplied to the second delay circuit 59, delayed by the necessary time (T2) for the normally rotating motor 19 to stop, and then supplied to the pulse generator 60. There is. This pulse generator 60 is configured to transmit a pulse signal of a desired reversal time (T3) to the reversal control section 46, so that the motor 19 can be reversed for a predetermined period of time. Further, the pulse generating section 60 is configured to operate a lifting means 62 for the driver bit 26 via a machine cycle completion detecting section 61 to raise and return the driver bit 26.

In the control device for the automatic screw tightening machine described above, as shown in FIGS. 2a and 2b, the elevating means 62 is actuated by the output signal from the work start section 41, and the driver bit 26 is lowered. At the same time, the output signal of the work start section 41 is transmitted to the switching means 45 via the forward rotation control section 42.
The switching means 45 is activated, and the normal rotation voltage is supplied to the motor 19 from the normal rotation voltage supply section 43 as shown in FIG. 2c. As the motor 19 rotates, the driver bit 26 rotates via a differential planetary mechanism 20 consisting of an input disk 21, a planet cone 23, a cam disk 24, and a speed change ring 25, and screw tightening is started. Along with this, the slit disk 51 rotates, so that the rotation detection section 52 outputs an output pulse. After this output pulse is waveform-shaped, it is supplied to the stop determination section 56 as shown in FIG. 2d. If this output pulse is continuously supplied before the timer 56a has counted the predetermined time (T1), the timer 56a is reset by the next output pulse as shown in FIG. does not emit an output signal. Also, the timer 56a is set immediately after being reset to prepare for the next output pulse. In this state,
As the screw tightening progresses, the speed change ring 25 rotates in response to the load applied to the driver bit 26, and its reduction ratio increases continuously, until the reduction ratio reaches infinity and the rotation of the driver bit 26 increases. stops. When the rotation of the driver bit 26 stops,
The output pulse from the rotation detection section 52 is no longer transmitted, the timer 56a counts a predetermined time (T1),
An output signal is generated as shown in FIG. 2e. Therefore, as shown in FIG. 2f, the flip-flop 5
The output of 6b is inverted, and the output signal reaches the normal rotation control section 42 to cut off the normal rotation voltage. At the same time, the output signal of the flip-flop 56b is supplied to a second delay circuit 59, delayed by the time (T2) necessary for the motor 19 to normally stop, and supplied to the pulse generator 60, as shown in FIG. 2g. Ru.

The pulse generator 60 generates a pulse signal with a predetermined time width (T3) as shown in FIG. 2h, and supplies this to the reverse rotation controller 46. This reversal control section 4
6 is the switching means 4 while the pulse signal is being transmitted.
5 is activated, and a reversing voltage is supplied to the motor 19 from the reversing voltage supply section 44. The motor 19 rotates slightly in the opposite direction and then stops, but as the motor 19 rotates in the opposite direction, the planet cone 23 and the speed change ring 25 rotate in the opposite direction. Therefore, the frictional engagement position between the planetary cone 23 and the speed change ring returns to the high speed side, and the lock of the speed change ring 25, cam disc 24, and planetary cone 23 is released from the motor 19 side, and the load on the driver bit 26 can be handled. The generated reaction torque is transmitted to the speed change ring 25. At this time, the load applied to the driver bit 26 is reduced as the motor 19 rotates in reverse, so the speed change ring 25 returns along the conical surface of the planetary cone 23 in accordance with the load, and finally the original Return to position. Moreover, since the reverse rotation voltage is sufficiently smaller than the forward rotation voltage as shown in FIG. It is small and there is no possibility of the driver bit being reversed.

Further, the pulse signal from the pulse generating section 60 is supplied to the machine cycle completion detecting section 61, and its output signal is supplied to the elevating means as shown in FIG. and prepare for the next work.

Effects of the Invention As explained above, the present invention transmits the rotation of the motor to the driver bit through a differential planetary mechanism consisting of an input disk, a planetary cone, a cam disk, and a speed change ring, thereby shifting the speed in the axial direction of the speed change ring. In addition to regulating the movement with an elastic holding member, a rotation stop detection means is provided to detect the stoppage of the driver bit, and its output signal stops the supply of forward rotation voltage to the rotation drive source, and then applies reverse rotation voltage to the rotation drive source. Since the configuration is such that the supply is only supplied for a predetermined period of time, even if the differential planetary mechanism stops in a locked state when the screws are tightened, the planetary cone and the speed change ring can be reversed from the rotational drive source side, and the planetary cone and the speed change ring can be rotated slightly. By changing the frictional engagement position, the speed change ring can be returned to its original position according to the load on the driver bit, and even when the driver bit is raised and returned to its original position, the driver bit can be smoothly detached from the screw and the workpiece can be removed. There are advantages such as no need to lift the screw, and no damage to the screw head or driver bit.

In the embodiment, after the motor is rotated in the normal direction, the motor is configured to be reversed by detecting that the output pulse from the rotation detection section is no longer transmitted. The motor may be configured to rotate in the reverse direction if the number of output pulses is less than a predetermined number. In addition, the rotation detection section is composed of a slit disk and a photoelectric sensor, but instead of the combination of the slit disk and the photoelectric sensor, a combination of a disk with a magnet embedded in the outer periphery and a magnetic sensor is used. You can also. Furthermore, an opto-encoder or a magnetic encoder can also be used as the rotation detection section.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a time chart at each point in FIG. It is a torque-rotation speed characteristic curve diagram of the output shaft of the automatic transmission. A...Control device, 1...Automatic screw tightening machine, 18
... Driver body, 19 ... Motor, 20 ... Differential planetary mechanism, 21 ... Input disk, 23 ... Planet cone, 23a ... Circumferential groove, 23b ... Flat surface, 2
3c...conical surface, 24...cam disc, 25...
...Speed ring, 26...Driver bit, 31...
... Spring, 32 ... Arm, 41 ... Work start section, 42 ... Forward rotation control section, 43 ... Forward rotation voltage supply section, 44 ... Reverse rotation voltage supply section, 45 ... Switching means, 46 ... Reverse rotation Control unit, 50...Rotation stop detection means, 51...Slit disk, 52...Rotation detection unit, 53...First delay circuit, 54...Waveform shaping unit, 55...Differential circuit, 56...Stop Judgment department, 5
6a...Timer, 56b...Flip-flop,
56c...Third delay circuit, 57...Amplification section, 59
...Second delay circuit, 60...Pulse generator, 61
. . . Machine cycle completion detection section, 62 . . . Lifting means.

Claims (1)

[Claims] 1. An input disk 21 that rotates in response to the rotation of a rotational drive source, and a planetary cone 2 that frictionally engages with the outer periphery of the input disk 21.
3 and a cam disc 24 that frictionally engages with the driver bit 26, and a speed change ring 25 that frictionally engages with the outer periphery of the planetary cone 23 is arranged so that the speed change ring is controlled by the load torque applied to the driver bit 26. 25 is configured so that the reaction force applied to the driver bit 26 is received by the elastic holding member, and the forward rotation voltage supply section 43 and the reverse rotation voltage supply section 44 are connected to the rotational drive source via the switching means 45, and the driver bit 26 is A rotation stop detection means 50 for detecting a stop is provided, and after the output of the rotation stop detection means 50 operates the switching means 45 to cut off the forward rotation voltage supply section 43, the reverse rotation voltage of the reverse rotation voltage supply section 44 is set to a predetermined value. The rotational drive source is slightly reversed to release the locked state, and the planetary cone 2
The driver bit 26 is reduced as the rotational drive source is reversed by returning the frictional engagement position between the speed change ring 25 and the rotational drive source from the rotational drive source side to a slightly higher speed side.
A control device for an automatic screw tightening machine, characterized in that the speed change ring 25 is configured to rotate back to the high speed side by the elastic force of an elastic holding member in response to a load related to the above.