JPH06287B2 - Automatic screw tightener control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is configured to eliminate the influence of inertia of a driver bit at the time of completion of screw tightening and securely perform screw tightening with a desired screw tightening torque. The present invention relates to a control device for an automatic screw tightener.

[Prior Art] Recently, there has been developed an automatic screw tightening machine configured to eliminate the influence of inertia of a driver bit at the time of completion of screw tightening and securely perform screw tightening with a desired screw tightening torque. This automatic screw tightener has a motor 2 fixed to one end of a driver body 1 as shown in FIGS. 3 and 4, and the motor may be AC or DC. Any of a brushless motor may be used. An input disc 4 forming a part of the differential planetary gear mechanism 3 is arranged in the motor 2 so as to rotate integrally with the motor 2 in response to the rotation thereof. A plurality of planetary cones 5 are arranged on the outer circumference of the input disc 4, and circumferential grooves 5a of the planetary cones 5 are frictionally engaged with the input disc 4 to rotate. On the flat surface 5b located on the back surface of the conical surface 5c of the planetary cone 5, a cam disk 6 rotating concentrically with the input disk 4 is arranged so as to frictionally engage with it. Moreover, this cam disc 6
The driver bit 8 is connected to the driver so as to rotate integrally therewith, and the rotation of the motor 2 is transmitted to the driver bit 8.

Further, a transmission ring 7 is arranged on the outer periphery of the planetary cone 5 so as to rotate by frictionally engaging with the conical surface 5c thereof, and the transmission ring 7 is supported by an arm 9 rotatably held at one end thereof. It is rotatably held. Moreover, the speed change ring 7 is biased by the spring 10 so that its frictional engagement position is located on the high speed side, and the elastic force holding member composed of the spring 10 and the arm 9 causes the speed change ring 7 to be frictionally engaged. The position is regulated, and the maximum value of the reduction ratio and the tightening torque are determined.

[Problems to be Solved by the Invention] In this automatic screw tightener, when the motor 2 rotates to start screw tightening, the transmission ring 7 rotates due to a reaction torque generated according to the tightening torque applied to the driver bit 8. . The amount of movement of the speed change ring 7 in the axial direction due to the rotation thereof is regulated by the spring 10. Therefore, the reaction force torque exerts a pressing force on the spring 10 on the speed change ring 7 and an elastic force generated by the bending of the spring 10. Shift ring 7 to balance position
Moves. When the load on the driver bit 8 increases, the speed change ring 7 further gradually moves to the edge of the planet cone 5, the driver bit 8 is decelerated to zero rotation, and the screw is moved as shown in the characteristic curve of FIG. Tightening can be done without problems. In this case, since the completion of tightening is detected by the rotation stop of the driver bit 8,
If the motor does not rotate as prescribed due to a power failure, insufficient adjustment, motor abnormality, etc., or if the driver bit rotates extremely slowly despite no load due to bit bending, etc., the driver bit 8 It is detected that the rotation of the motor has stopped, the rotation command to the motor 2 is not transmitted, the voltage supply to the motor 2 is immediately cut off, the motor 2 stops, and the screw tightening work cannot be performed. Is occurring. Also, during tightening the screw, the sensor of the rotation detection part (not shown) provided on the driver bit 8 may be broken, the contact between the sensor and the control device may be poor, or dust may be attached to the detection surface of the sensor. Then, if the output pulse is not transmitted, the voltage supply to the motor 2 is immediately cut off as the tightening is completed even though the tightening is in progress, and the motor 2 may stop. At this time, although the tightening is defective, the normal tightening is displayed, and the tightening cannot be accurately determined.

The present invention aims to eliminate the above-mentioned drawbacks, and detects that the transmission ring of the differential planetary mechanism has moved to the zero rotation position on the conical surface of the planet cone and the tightening is completed by stopping the rotation of the driver bit. At the same time, it is an object of the present invention to provide a control device configured to detect the rotation stop of the driver bit after confirming that the driver bit has rotated.

[Means for Solving the Problems] In order to solve the above-described problems, the present invention solves the above problems by providing an input disc that is rotated by a motor to rotate, a planet cone that frictionally engages the outer periphery of the input disc, and a cam that frictionally engages the planet. The driver bits are connected via the disk. A speed change ring frictionally engaged with the planetary cone is arranged on the outer circumference of the planetary cone, and the speed change ring receives a reaction force by the load of the driver bit, and the elastic force retaining member receives the reaction force. .

On the other hand, a power supply unit is connected to the motor via a switching means.

Further, a rotation detector for detecting the rotation of the driver bit for a predetermined time and a counter for counting the output pulse of the rotation detector are provided. Further, an AND circuit is provided which opens the gate by the count end signal of the counter to pass the output pulse. The output of this AND circuit is connected to a stop determination unit that detects the pulse width of the output pulse that passes through the AND circuit and determines the stop of the driver bit. It is connected to a control unit which sends a forward rotation voltage cutoff command signal for cutting off the rotation voltage to the switching unit and also sends a reverse rotation command signal for supplying a reverse rotation voltage from the power supply unit to the motor to the switching unit.

[Operation] In the above automatic screw tightener, the switching means is activated by the work start signal, a predetermined voltage is supplied to the motor, and the motor rotates. The rotation of the motor is transmitted to the driver bit at a reduction ratio determined by the frictional engagement position between the planet cone and the speed change ring, and the driver bit tightens the screw. at the same time,
The rotation of the driver bit is detected by the rotation detector. The output pulse of the rotation detector is counted by the counter for a certain period of time, and when it reaches a set value, a count end signal is transmitted. The count end signal opens the gate of the AND circuit, and the output pulse of the rotation detection unit is sent to the stop determination unit. The stop determination unit starts detecting the pulse width of the output pulse.

In this state, when the screw tightening is started and a reaction force torque is applied to the shift ring according to the load applied to the driver bit, the shift ring moves in the axial direction while rotating. Further, when the motor continues to rotate, the speed change ring moves in the axial direction of the axis, the reduction ratio increases, and finally the infinity becomes infinite, the driver bit stops, and the stop determination unit detects stop. Output is emitted. This stop detection output is sent to the switching means, and the voltage from the power supply unit is cut off. At the same time, a reverse rotation command signal is sent to the switching means, and the control unit for rotating the motor in reverse operates. Therefore, the motor reversely rotates, the planetary cone and the speed change ring slightly reversely, and the frictional engagement positions of these are returned to the original position on the high speed side, and the next work can be prepared.

On the other hand, after the motor is started by the work start signal, the motor does not rotate as prescribed due to power supply abnormality, insufficient adjustment, motor abnormality, etc., or the driver bit rotates extremely even when there is no load due to bending of the driver bit etc. If the output pulse is not transmitted due to slowness, the sensor in the rotation detection unit is defective, there is a contact failure between the sensor and the control device, or dust is attached to the detection surface of the sensor. The output pulse is not added to the counter within a fixed time, and the counter does not send the count end signal.
Therefore, in such a case, the output pulse is not sent to the stop determination unit, the stop of the driver bit is not detected, and the tightening failure is detected due to the cycle time over.

Embodiments Embodiments will be described below with reference to the drawings. In FIG. 1, A is a controller for the automatic screw tightener shown in FIG. 3, and this controller A controls a motor (a DC motor will be described in this embodiment) 2 of the automatic screw tightener. Is configured. The control device A has a work starting unit 11, and the work starting unit 11 is connected to a lifting means 12. This work start unit 11 is connected to a counter 14a of a rotation confirmation unit 14 described later, a latch circuit 14b, and a flip-flop 15a of a stop determination unit 15 via an initial cut pulse generation unit 13 in order to prevent a malfunction at the time of start, Latch output of rotation confirmation unit 14 and stop determination unit 15 described later
The reset outputs of the flip-flops are reset and the set value of the setter 14c described later is set in the counter 14a. The work starting section 11 is connected to a normal rotation control section 16, and the normal rotation control section 16 is configured to send a normal rotation command signal to a switching means 17 described later. Further, the normal rotation control unit 16 is configured to receive the inverted output of the flip-flop 15a that constitutes the stop determination unit and transmit the cutoff command signal.

On the other hand, a power supply section 18 is connected to the motor 2 via a switching means 17, and the switching means 17 receives a signal from a second pulse generating section 29 described later and transmits a reverse rotation command signal. The reverse rotation control unit 20 is connected to the power supply unit 18, and is configured to supply a reverse rotation voltage lower than the normal rotation voltage to the motor 2.

Further, the control device A may be anywhere as long as it does not hinder the lifting and lowering of the driver bit 8 of the automatic screw tightener.
It has a rotation detecting means 22 for detecting the rotation of the driver bit 8. The rotation detecting means 22 includes a slit disc 23 which can be raised and lowered integrally with a driver body (not shown) and which rotates integrally with the driver bit 8, and a rotation detecting portion 24 arranged corresponding to the movement path of the slit at one end thereof. And have. The rotation detection unit 24 is configured to transmit an output pulse during detection of passage of the slit of the slit disk 23, and the output pulse detects the amplification unit 25, the waveform shaping unit 26, and the edge of the output pulse. It is configured to be sent to the rotation confirmation unit 14 via the differentiating circuit 27.

The rotation confirmation unit 14 sets the first delay circuit 28 in which the time T1 from the transmission of the work start signal to the normal motor 2 reaching a high speed is set, and the setting of the counter 14a which is usually described later by receiving the delay output. A first pulse generator 19 that generates a pulse having a pulse width corresponding to a time T _p1 that is slightly longer than the value obtained by multiplying the value by the output pulse width under a predetermined high-speed rotation, and the first pulse generator 19 AND circuit 30 which emits an output while the pulse and the high-speed command signal are transmitted, and a second AND circuit which opens the gate and transmits the output pulse while the output is transmitted from the first AND circuit 30. And a circuit 31.

The rotation confirmation unit 14 is a counter that sequentially subtracts the set value set in the setter 14c by the input of the output pulse.
14a, a latch circuit 14b for temporarily holding the count end signal of the counter 14a, and a third AND circuit 32 for opening the gate and passing the output pulse by the latch output, that is, the rotation confirmation signal.

The counter 14a can count while the gate of the second AND circuit 31 is open, that is, while the pulse is being output from the first pulse generator 19, and the output pulse is output from the first pulse generator 19. It is configured to be in the reset state when not performed.

The output of the latch circuit 14b is configured to open the gate of the third AND circuit 32 while being connected to the OR circuit 33 via an inverter to reset the timer 15b of the stop determination unit 15.

The stop determination unit 15 outputs a timer 15b which is an example of a pulse width detector, a second delay circuit 34 which delays the output signal of the third AND circuit 32 and sets the timer 15b, and a time-up signal of the timer 15b. It is composed of a flip-flop 15a which is an example of a storage device for storing. When the rotation confirmation signal is transmitted from the latch circuit 14b of the rotation confirmation unit 14, the timer 15b is reset by the edge detection pulse obtained by differentiating the output pulse from the rotation detection unit 24 and the second delay. It is designed to be set immediately after a very short time determined by the circuit 34. Further, when the timer 15b is set and the next output pulse is not transmitted from the rotation detecting unit 24 even if the predetermined time Ta has passed, the timer 15b transmits a time-up signal and outputs it to the flip-flop 15a.
Configured to output to. Further, the flip-flop 15a is configured to receive the time-up signal of the timer 15b, invert its output, and cut off the normal rotation command signal transmitted from the normal rotation control unit 16 by the inverted output. . Further, the inverted output of the flip-flop 15a is sent to the third delay circuit 35, delayed by the time T3 required for stopping the motor 2 which is normally rotating, and then the second delay circuit.
It is configured to be supplied to the pulse generator 29. When the second pulse generating section 29 receives the output signal of the third delay circuit 35, it sends a pulse signal of the desired reverse rotation time T _P2 to the reverse rotation control section 20 to switch the reverse rotation command signal from the reverse rotation control section 20. To the motor 2 from the power supply unit 18 for a predetermined time.
It is configured to supply a reverse voltage to. Further, the second pulse generating section 29 is configured to operate the elevating means 12 of the driver bit 8 via the machine cycle completion detecting section 36 to raise and restore the driver bit 8.

Further, although not shown, the work start signal is configured so that the cycle time over detection unit operates, and its output is supplied to the normal rotation control unit 16 as a normal voltage cutoff command signal, and The signal is supplied to the 3-delay circuit 35 and an abnormality is displayed.

In the control device for the automatic screw tightener, as shown in FIGS. 2A and 2B, the elevating means 12 is activated by the output signal of the work starting section 11 and the driver bit 8 is lowered. At the same time, the output signal of the work start section 11 is switched via the forward rotation control section 16 to the switching means.
2, the forward rotation voltage x is supplied from the power supply unit 18 to the motor 2 as shown in FIG. 2c. As the motor 2 rotates, an input disk (not shown) and a planet cone (not shown) are shown. No.), a cam disk (not shown), and a differential planetary mechanism (not shown) consisting of a speed change ring (not shown) rotate the driver bit 8 to start screw tightening.

After the motor 2 is started, as shown in d1 and d2 of FIG. 2, the motor 2 does not rotate in a predetermined manner due to an abnormality in the power supply, insufficient adjustment of the motor 2, abnormality in the motor 2, bending of the bit, etc. Due to this, the rotation of the driver bit 8 is extremely slow in spite of no load, the sensor in the rotation detecting section 24 of the rotation detecting means 22 is out of order, the contact between the sensor and the control device is poor, and the detection surface of the sensor. If dust or the like adheres to the output pulse and the output pulse is not transmitted, the counter 1 is set within the time T _p1 determined by the pulse of the first pulse generator 19.
Since the set value of 4a is not subtracted to zero, the counter 14a does not send the count end signal as shown in e1 of FIG.
Therefore, the gate of the third AND circuit 32 is held in the closed state, no output pulse is input to the stop determination unit 15, and the timer 15b is held in the reset state. In this state, when the motor 2 continues to rotate, the cycle time over detection unit can detect the cycle time over and notify the outside as a tightening failure.

On the other hand, when the output pulse is normally transmitted from the rotation detection unit 24 after the motor 2 is started, this output pulse is
After the waveform is shaped as shown in FIG. D3, it is sent to the counter 14a of the rotation confirmation unit 14. When the output pulse is converted and counted by the set value set in the setter 14c within the time T _p1 determined by the pulse of the first pulse generator 19, the counter
A count end signal is transmitted from 14a, and the count end signal is temporarily held by the latch circuit 14b as shown in FIG. 2e2. Since the output signal of the latch circuit 14b is sent to the third AND circuit 32 as a rotation confirmation signal, its gate is opened, and the subsequent output pulse is supplied to the stop judging section 15 by the timer 15b, which counts the predetermined set time Ta. If the output pulse is continuously supplied before starting, the timer 15b is reset by the next output pulse, and the timer 15b does not emit the time-up signal. Also, the timer 15b is set immediately after resetting and is ready for the next output pulse.
In this state, screw tightening progresses, the transmission ring rotates according to the load applied to the driver bit 8, its reduction ratio increases continuously, and finally the reduction ratio becomes infinite. 8 rotation stops. When the rotation of the driver bit 8 is stopped, the output pulse from the rotation detection unit 24 is not transmitted and the timer 15b counts the predetermined time Ta,
Send a time-up signal. The time-up signal is applied to the flip-flop 15a, and the output of the flip-flop 15a is inverted as shown in FIG. This reverse output operates the normal rotation control unit 16 and the switching means 17, and the voltage supply from the power supply unit 18 to the motor 2 is cut off.

At the same time, the inverted output of the flip-flop 15a is supplied to the third delay circuit 35 and, as shown in FIG.
The signal is delayed by the time T3 required for the normal stop, and is supplied to the second pulse generator 29.

The second pulse generator 29 transmits a pulse signal having a predetermined time width T _p2 as shown in FIG. 2 h and supplies it to the reverse rotation controller 20. The reverse rotation control unit 20 sends a reverse rotation command signal to the switching means 17 while the pulse signal is transmitted, and supplies the reverse rotation voltage y lower than the normal rotation voltage x to the motor 2 from the power supply unit 18. The motor 2 slightly rotates in the reverse direction and stops, but with the reverse rotation of the motor 2, the planet cone and the speed change ring reversely rotate. Therefore, the friction engagement position between the planetary cone and the speed change ring returns to the original position on the high speed side according to the load in the reverse rotation direction related to the driver bit 8, and the speed change ring, the cam disk and the planetary cone are locked from the motor 2 side. It will be canceled.

The pulse signal from the second pulse generator 29 is supplied to the machine cycle completion detector 36, and its output signal is supplied to the lifting means 12 as shown in FIG. Raise 8 to prepare for the next task.

As described above, according to the present invention, the rotation of the motor is transmitted to the driver bit via the differential planetary mechanism including the input disc, the planet cone, the cam disk and the speed change ring to transmit the shaft center of the speed change ring. Directional movement is regulated by the elastic holding member, the output pulse transmitted with the rotation of the driver bit is detected, and after confirming that this output pulse is transmitted reliably, the pulse width of the output pulse Is detected to detect the completion of tightening, the motor does not rotate as prescribed due to power supply abnormality, insufficient adjustment, motor abnormality, etc. Despite this, the rotation of the driver bit is extremely slow, the sensor in the rotation detection unit is defective, the contact between the sensor and the control device is poor, and dust on the detection surface of the sensor If a predetermined output pulse is not transmitted due to the rotation of the driver bit due to the adherence etc., this can be reliably detected and it can be judged as a tightening failure, and it is possible to securely tighten with the predetermined torque. Can be performed. Further, since the present invention is configured to recognize that the driver bit is rotating surely, confirm the stop of the rear driver bit, and detect the completion of tightening, the motor and driver bit of the motor and the driver bit are displayed when an error is displayed. There is an advantage that the cause of abnormal tightening can be indirectly investigated by visually observing the rotation.

[Brief description of drawings]

1 is a block diagram of the present invention, FIG. 2 is a time chart of FIG. 1, FIG. 3 is an overall explanatory view of an automatic screw tightener according to the present invention, and FIG. 4 is an automatic screw tightener of FIG. FIG. 5 is a sectional view of a main part of FIG. 5, and is a torque-rotational speed characteristic curve diagram of the output shaft of the differential planetary gear mechanism according to the present invention. A control device, 1 driver body, 2 motor, 3 differential planetary mechanism, 4 input disk, 5 planetary cone, 5a circumferential groove, 5b flat surface, 5c conical surface, 6 cam disk, 7 speed change ring, 8 driver bit , 9 arms, 10 springs, 11 work starting part, 12 lifting means, 13 initial cutting pulse generating part, 14 rotation confirming part, 14a counter, 14b latch circuit, 14c setting device, 15 stop judging part, 15a flip-flop, 15b Timer, 16 forward rotation control section, 17 switching means, 18 power supply section, 19 first pulse generation section, 20 reverse rotation control section, 22 rotation detection means, 23 slit disk, 24 rotation detection section, 25 amplification section, 26 waveform Shaping section, 27 differentiating circuit, 28 first delay circuit, 29 second pulse generating section, 30 first AND circuit, 31 second circuit AND circuit, 32 third AND circuit, 33 OR circuit, 34 second delay circuit, 35 third delay circuit, 36 machine cycle completion detection unit,

Claims (1)

[Claims] 1. A motor (2) is fixed to one end of a driver body (1), an input disc (4) is rotated by the rotation of the motor (2), and a planet cone is frictionally engaged with its outer circumference. The driver bit (8) is connected via the (5) and the cam disk (6) frictionally engaged therewith, and the speed change ring (7) frictionally engaged with the outer periphery of the planetary cone (5) is arranged. Driver Bit (8)
In an automatic screw tightener configured to receive the reaction force applied to the speed change ring (7) by the load holding torque related to the elastic holding member, the motor (2) is connected to the power supply section (18) via the switching means (17). While connected, a rotation detector (24) for detecting the rotation of the driver bit (8) for a certain period of time is provided, and a counter (14a) for counting the output pulses of the rotation detector (24) is provided. An AND circuit is provided to open the gate by the count end signal to pass the output pulse, and a stop determination unit (15) for determining the stop of the driver bit by detecting the pulse width of the output pulse passing through the AND circuit is provided. When the output of this stop determination unit (15) is received, a forward rotation voltage cutoff command signal for cutting off the forward rotation voltage from the power supply unit (18) is sent to the switching means (17) and at the same time from the power supply unit (18). Reverse voltage to motor
A control device provided with a control section for sending a reverse rotation command signal supplied to (2) to a switching means (17).