JPH02152733A - Controller for automatic screw clamper - Google Patents

Abstract

PURPOSE:To make a clamping failure surely judgeable by detecting an output pulse being transmitted with rotation of a driver bit, and after confirmation of output pulse transmitting, detecting a clamping end by pulse width. CONSTITUTION:A selector means 17 operates when work is started, and rotation of a motor 2 is transmitted to a driver bit 8 via a shift mechanism consisting of a planetary cone and a speed change ring, and simultaneously with a screw clamped, a pulse is generated out of a rotation detecting means 22, and it is counted by a counter 14a as long as the specified time of a rotation checking part 14. When it is not reached to the specified counting within the specified time, it is detected as a trouble (clamping failure). On the other hand, when it is reached to the setting value, an AND circuit is opened, and the output pulse is fed to a stop judging part 15, starting detection of feed pulse width, and when reaction acts on the speed change ring according to load, a reduction gear ratio grows larger, turning to infinity finally, and the driver bit 8 is stopped, so that this fact is detected by the pulse width, stopping the motor 2. Thus, any clamping failure is surely judgeable.

Description

[Detailed Description of the Invention] E-Industrial Application Field] The present invention eliminates the influence of the characteristics of the driver bit when screw tightening is completed, and ensures that the desired screw tightening is performed using torque. The present invention relates to a control device for an automatic screw tightening machine.

[Conventional techniques] Recently, an automatic screw tightening machine has been developed that is configured to eliminate the influence of the characteristics of the driver bit when screw tightening is completed, and to ensure that the desired screw tightening is performed using torque. . This automatic screw tightening machine has a motor 2 fixed to one end of a driver body 1, as shown in FIGS. It may be either a motor or a brushless motor. An input disk 4, which forms a part of the differential planetary mechanism 3, is arranged on the motor 2 so as to rotate together with the input disk 4, which forms a part of the differential planetary mechanism 3. A plurality of planet cones 5 are arranged on the outer periphery of the input disk 4, and the circumferential grooves 5a of the planet cones 5 are configured to frictionally engage with the input disk 4 to rotate. A flat surface 5b located on the back surface of the conical surface 5C of this planetary cone 5
includes a cam disk 6 that rotates concentrically with the input disk 4;
are arranged so as to frictionally engage with each other. Moreover, a driver bit 8 is connected to the cam disc 6 so as to rotate together with the cam disc 6, and the rotation of the motor 2 is transmitted to the driver bit 8.

Roughly speaking, a speed change 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 this speed change ring 7 is attached to an arm 9 which is rotatably held at one end. It is rotatably held by. Moreover, the speed change ring 7 is biased by a spring 10 so that its frictional engagement position is located on the high speed side, and the frictional engagement of the speed change ring 7 is The structure is such that 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 tightening machine, when the motor 2 rotates and starts screw tightening, the tightening applied to the driver bit 8 is caused by the reaction torque generated in accordance with the torque, which causes the speed change ring 7 to rotate. move. Movement M in the axial direction due to rotation of this speed change ring 7
The shift ring 7 moves to a position where the pressure on the spring 10 produced by the reaction torque on the shift ring 7 and the elastic force produced by the deflection of the spring 10 are balanced. When the load on the driver bit 8 increases, the speed change ring 7 gradually moves to the edge of the planetary cone 5, and the driver bit 8 is decelerated to zero rotation, as shown in the characteristic curve shown in FIG. Screw tightening is performed without any problem. In this case, since the completion of tightening is detected when the driver bit 8 stops rotating, the motor may not rotate at the specified speed due to a power supply abnormality, lack of adjustment, motor abnormality, etc. If the rotation of the driver bit is extremely slow due to bending, etc. even when there is no load, it will be detected that the rotation of the driver bit 8 has stopped at this point, and a rotation command will not be sent to the motor 2, but the rotation will be stopped immediately. The voltage supply to the motor 2 is cut off, and the motor 2 stops, making it impossible to tighten screws. Also, when tightening the screw, there is a rotation detecting section (
If the sensor (not shown in the figure) is damaged, there is poor contact between the sensor and the control device, or there is dirt, etc. on the detection surface of the sensor, and the output pulse is not transmitted, the tightening may be interrupted. Despite this, the tightening is completed and motor 2 is immediately turned on.
The voltage supply to the motor 2 may be cut off and the motor 2 may stop. At this time, there are drawbacks such as normal tightening is displayed even though the tightening is defective, and accurate tightening cannot be determined.

The present invention aims to eliminate the above-mentioned drawbacks, and detects when the speed change ring of the differential planetary mechanism has moved to the zero rotation position on the conical surface of the planetary cone and tightening has been 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 that the driver bit has stopped rotating after confirming that the driver bit has rotated.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an input disk that rotates in response to rotation of a motor, a planetary cone that frictionally engages with the outer periphery of the input disk, and a cam that frictionally engages with the input disk. A driver bit is connected to the disc via the disc. Further, a speed change ring is disposed on the outer periphery of the planetary cone and is frictionally engaged with the planetary cone, and the speed change ring receives a reaction force due to the load related to the driver bit, and the elastic holding member receives this reaction force. .

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

Further, a rotation detection section that detects the rotation of the driver bit for a certain period of time and a counter that counts output pulses of this rotation detection section are provided. Furthermore, an AND circuit is provided which opens a gate in response to a count end signal of the counter and allows the output pulse to pass through. The output of this AND circuit is connected to a stop judgment section that detects the pulse width of the output pulse passing through the AND circuit and judges whether or not the driver bit is stopped. It is connected to a control section that sends a forward voltage cutoff command signal for cutting off the rotational voltage to the switching means, and also sends a reverse rotation command signal to the switching means for supplying the motor with the reverse rotation voltage from the power supply section.

[Operation] In the automatic screw tightening machine described above, 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 this motor is transmitted to the lower driver bit at a reduction ratio determined by the frictional engagement position between the planetary cone and the speed change ring, and the driver bit tightens the screw. at the same time,
Rotation of the driver bit is detected by a rotation detection section. The output pulses of the rotation detection section are counted by a counter for a certain period of time, and when a set value is reached, a count end signal is transmitted.

This count end signal opens the gate of the AND circuit, and the output pulse of the rotation detecting section is sent to the stop determining section. The stop determination section starts detecting the pulse width of the output pulse.

In this state, when screw tightening is started and a reaction torque is applied to the speed change ring according to the load on the driver bit, the speed change ring rotates and moves in its axial direction. Roughly speaking, as the motor continues to rotate, the speed change ring moves in the direction of its axis, and its reduction ratio increases until it reaches infinity, causing the driver bit to stop, and the stop judgment unit to stop the motor. A detection output is transmitted. This stop detection output is sent to the switching means, and the voltage from the power supply section is cut off. At the same time, a reverse rotation command signal is sent to the switching means, and a control section that reverses the motor is activated. Therefore, the motor rotates in reverse, the planetary cone and the speed change ring rotate slightly in reverse, and their frictional engagement positions return to their original positions on the high speed side, making it possible to prepare for the next operation.

On the other hand, after the motor is started by the work start signal, the motor may not rotate as expected due to power supply abnormality, insufficient adjustment, motor abnormality, etc., or the driver bit may rotate excessively even under no load due to bending of the driver bit, etc. If the sensor in the rotation detection section is malfunctioning, there is poor contact between the sensor and the control device, or there is dust on the detection surface of the sensor, the output pulse may not be transmitted. , no output pulse is applied to the counter within a certain period of time, and the counter does not issue a count end signal.

Therefore, in such a case, the output pulse is not sent to the stop determination section, and stoppage of the driver bit is not detected, and a tightening failure is detected due to cycle time over.

[Example] Hereinafter, an example will be described with reference to the drawings. In FIG. 1, A is a control device for the automatic screw tightening machine shown in FIG. 3,
This control device is configured to control the motor (a) 2 of the automatic screw tightening machine (in this embodiment, a DC motor will be explained).

This control device A has a work start section 11, and this work start 1 part 11 is connected to a lifting means 12.

This work start section 11 is connected to a counter 14a of a rotation confirmation section 14, a latch circuit 14b, and a flip-flop 15a of a stop judgment section 15, which will be described later, through an initial cut pulse generation section 13 in order to prevent malfunctions during startup. Latch output of rotation confirmation section 14 and stop judgment section 1 to be described later
In addition to resetting the inverted outputs of the flip-flops 5 and 5, the set values of the setting device 14c, which will be described later, are set on the counter 1.
4a. Further, the work start section 11 is connected to a forward rotation control section 16,
The normal rotation control section 16 is configured to send a normal rotation command signal to a switching means 17, which will be described later. Further, the normal rotation control section 16 is configured by a flip-flop 1 constituting a stop determination section.
It is configured to receive the inverted output of 5a and transmit a cutoff command signal.

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

Further, the control 1iIiI device is provided with a rotation detecting means 22 for detecting the rotation of the driver bit 8, which may be located at any position as long as it does not hinder the lifting and lowering of the driver bit 8 of the automatic screw tightening machine. The rotation detecting means 22 includes a slit disk 23 that can be raised and lowered integrally with the driver body (not shown) and rotates integrally with the driver bit 8, and a rotation detecting section 24 disposed corresponding to the movement path of the slit at one end thereof. It has This rotation detecting section 24 is connected to the slit disk 2.
When passing through the slit No. 3 is detected, an output pulse is emitted during that time, and this output pulse is passed through an amplifying section 25, a waveform shaping section 26, and a differentiating circuit 27 that detects the edge of the output pulse to confirm rotation. 14.

The rotation confirmation unit 14 includes a first delay circuit 28 in which a time T1 from when a work start signal is issued until the motor 2 normally reaches high speed is set, and a counter 14a which receives this delay output and which is normally described later. a first pulse generator 19 that generates a pulse with a pulse width corresponding to 1 for a time slightly longer than the time obtained by directly multiplying the output pulse width under a predetermined high speed rotation; an M1 AND circuit 30 that transmits an output while the pulse No. 19 and the high-speed command signal are being transmitted, and a second AND circuit that opens the gate and allows the output pulse to pass while the first AND circuit 30 is transmitting the output. It has a circuit 31.

Further, the rotation confirmation unit 14 includes a counter 14a that sequentially subtracts a set value set in a setter 14c according to the input of the output pulse, and a latch circuit 14 that temporarily holds a count end signal of the counter 14a. b, and a third AND circuit 32 which opens the gate in response to the latch output thereof, that is, the rotation confirmation signal, and allows the output pulse to pass through.

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

The output of the latch circuit 14b is sent to the third AND circuit 32.
OR circuit 3 through the inverter while opening the gate of
3 to reset the timer 15b of the stop determination section 15.

The stop determination unit 15 includes 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 records a time-up signal of the timer 15b. It consists of a flip-flop 15a, which is an example of a hidden device. When the rotation confirmation signal is transmitted from the latch circuit 14b of the rotation tTC recognition section 14, the timer 15b is reset by an edge detection pulse obtained by differentiating the output pulse from the rotation detection section 24, and also Delay circuit 34
It is configured to be set immediately after a very short period of time determined by . Also, this timer 15b
Even if the predetermined time Ta has elapsed since the rotation detector 24
When the next output pulse is not generated, a time-up signal is generated and outputted to the flip-flop 15a. Roughly, the flip-flop 1
5a is configured to invert its output upon receiving the time-up I word from the timer 15b, and to cut off the normal rotation command signal transmitted from the normal rotation control section 16 by the inverted output. Further, the inverted output of the foot flop 15a is sent to the third delay circuit 35, and after being delayed by the time T3 necessary for the normally rotating motor 2 to stop,
It is configured to be supplied to the second pulse generator 29 (
,enter. This second pulse generating section 29 is connected to a third delay circuit 35.
When the output signal is received, a pulse signal of desired reversal time T92 is sent to the reversal control section 20, a reversal command signal is sent from the reversal control section 20 to the switching means 17, and the power supply section 18 switches the motor 2 for a predetermined period of time. The circuit is configured to provide a reversing voltage. Further, the second pulse generating section 29 detects the driver pin 1 through the machine cycle completion detecting section 36.
The driver bit 8 is configured to be raised and returned to its original state without operating the lifting means 12 of the driver bit 8.

Although not shown, a cycle time over detection section is configured to operate in response to a work start signal, and its output is supplied to the forward rotation control section 16 as a forward rotation voltage cutoff command signal. 3 delay circuit 35, and an abnormality is displayed.

The control device for the automatic screw tightening machine is shown in FIG. 2a.

As shown in b, the elevating means 12 is actuated by the output signal from the work start section 11, and the driver bit 8 is lowered. At the same time, the output signal of the work start section 11 is transmitted to the forward rotation control section 16.
The normal rotation voltage X is supplied to the switching means 17 via the power supply section 18 as shown in FIG. 2C. As the motor 2 rotates, a differential planetary mechanism (
The driver bit 8 is rotated via the screw (not shown), and screw tightening is started.

After starting the motor 2, as shown in FIG.
Due to bending, etc., the rotation of the driver bit 8 is extremely slow even when there is no load, or the lens in the rotation detection section 24 of the rotation detection means 22 is malfunctioning, there is a poor contact between the sensor and the control device, or the sensor If the output pulse is not emitted due to dust etc. adhering to the detection surface of the counter 14a, the set value of the counter 14a will not be subtracted to zero within the time Tp1 determined by the pulse of the first pulse generator 19. 2. As shown in FIG. 1, the counter 14a does not issue a count end signal. Therefore, the gate of the third AND circuit 32 is kept closed, no output pulse is input to the stop determination section 15, and the timer 15b is kept in the reset state. When the motor 2 continues to rotate in this state, the cycle time over detecting section detects one major cycle time over, and can notify the outside as a tightening failure.

On the other hand, after the motor 2 is started, when an output pulse is normally transmitted from the rotation detecting section 24, this output pulse is waveform-shaped as shown in FIG.
4 is sent to the counter 14a. When the output pulse is decremented by 1 shift set in the setting device 14c within the time T, 1 determined by the pulse of the first pulse generator 19, a count end signal is transmitted from the counter 14a, and the count end signal is emitted from the counter 14a. 2. As shown in FIG. 2, the count end signal is temporarily held in the latch circuit 14b. This latch circuit 1
Since the output No. 4b, No. 1, 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 judgment section 15. If output pulses are continuously supplied before the timer 15b counts the predetermined set time Ta, the timer 15b is reset by the next output pulse, and the timer 15b does not issue a time-up signal. Further, the timer 15b is set immediately after being reset to prepare for the next output pulse.

In this state, the screw tightening progresses, the speed change ring rotates in response to the load applied to the driver bit 8, and its reduction ratio increases continuously, until finally, the reduction ratio becomes infinite.
The rotation of the driver bit 8 stops. driver bit 8
When the rotation of the rotation detecting section 24 stops, the output pulse from the rotation detecting section 24 is no longer transmitted, and the timer 15b counts a predetermined time Ta and transmits a time-up signal. The time-up signal is applied to the flip-flop 15a, and as shown in FIG.
The output of the flip-flop 15a is inverted as shown in FIG. This inverted output prevents the normal rotation control section 16 and the l;IIJ conversion means 17 from operating, and the voltage supply from the power supply section 18 to the motor 2 is cut off.

At the same time, the inverted output of the flip-flop 15a is the third
The signal is supplied to the delay circuit 35, delayed by the time (T3) necessary for the motor 2 to normally stop, as shown in the second diagram, and then supplied to the second pulse generator 29.

The second pulse generator 29 generates two pulse signals within a predetermined time period, as shown in the second diagram, and supplies them to the reverse rotation controller 20. This reversal control section 20 sends a reversal command signal to the switching means 17 while the pulse signal is being transmitted,
Reverse rotation voltage y lower than forward rotation voltage X from power supply section 18
is supplied to motor 2. The motor 2 rotates slightly in the opposite direction and then stops, but as the motor 2 rotates in the opposite direction, the planetary cone and the speed change ring are reversed. Therefore, in response to the load in the reverse direction on the driver bit 8, the freezing engagement position between the planetary cone and the speed change ring returns to the original position on the high speed side, and the lock of the speed change ring, cam disc, and planet cone is locked on the motor 2 side. be canceled from.

Further, the pulse signal from the second pulse generating section 29 is supplied to the machine cycle completion detecting section 36, and its output signal is supplied to the elevating means 12 as shown in FIG. [・Raise 8 and move on to the next work.

[Effects of the Invention] As explained above, the present invention transmits the rotation of the motor to the driver hit via a differential planetary mechanism consisting of an input disk, a planetary cone, a cam disk, and a speed change ring, thereby adjusting the axis of the speed change ring. The movement in the direction is restricted by an elastic holding member, and the output pulse emitted as the driver bit rotates is detected. After confirming that this output pulse is reliably emitted, the pulse width of the output pulse is adjusted. Since the structure is configured to detect the completion of one dimension of tightening by detecting the Sometimes the driver bit rotates extremely slowly, sometimes the sensor inside the rotation detecting part is malfunctioning, sometimes there is poor contact between the sensor and the control device, or there is dust etc. on the detection surface of the sensor. If the specified output pulse is not emitted as the driver bit rotates,
This has the advantage that this can be reliably detected and the tightening can be determined to be defective, and that the tightening can be reliably performed with a predetermined torque. In addition, the present invention is configured to confirm that the driver bit is rotating reliably, confirm that the driver bit has stopped after τ, and detect the completion of tightening. There are advantages such as being able to indirectly investigate the cause of abnormal tightening by visually observing the rotation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a time chart of Fig. 1, Fig. 3 is an overall explanatory diagram of the automatic screw tightening machine according to the present invention, and Fig. 4 is a diagram of the automatic screw tightening machine of Fig. 3. FIG. 5 is a sectional view of a main part and a torque-rotational speed characteristic curve of the output shaft of the differential planetary mechanism according to the present invention. 8 Control device, 1 Driver main body, 3 Differential planetary mechanism, 5 Planetary cone, 5b Flat surface, 6 Cam disk, 8 Driver bit, 10 Spring, 12 Lifting means, 14 Rotation confirmation part, 14b latch circuit, 2 Motor, 4 Manual disc, 5a Circumferential groove, 50 Conical surface, 7 Speed ring, 9 Arm, 11 Work start part, 13 Initial cut pulse generator, 14a Counter, 14C setting device, Stop judgment part, 15a Flip-flop, timer, 16 Forward rotation control section, switching means,
18 power supply section, first pulse generation section, 20
Reversal control section, rotation detection means, 23 slit disk, rotation detection section, 25 amplification section, waveform shaping section, 27 differentiation circuit, first delay circuit,
29 Second pulse generator, first AND circuit, 3
1 2nd AND circuit, 3rd AND circuit, 33
OR circuit, second delay circuit, 35 third delay circuit, machine cycle completion detection section,

Claims (1)

[Claims] A motor (2) is fixed to one end of the driver body (1), and an input disk (2) that rotates in response to the rotation of the motor (2).
4), a planetary cone (5) that frictionally engages with the outer periphery of the driver bit (8), and a cam disc (6) that frictionally engages with the planetary cone (5).
A speed change ring (7) that frictionally engages with the outer periphery of the speed change ring (7) is arranged so that the speed change ring (
In an automatic screw tightening machine configured so that the reaction force applied to the motor (7) is received by an elastic holding member, a power supply section (18) is connected to the motor (2) via a switching means (17), and a driver bit (8) is connected to the power supply section (18) through a switching means (17). ) is provided for a certain period of time, a counter (14a) is provided for counting the output pulses of this rotation detection section (24), and the gate is opened by the count end signal of this counter (14a). an AND circuit for passing the output pulse, and a stop determination unit (15) that detects the pulse width of the output pulse passing through the AND circuit to determine whether the driver bit is stopped.
), and upon receiving the output of the stop determination section (15), sends a forward voltage cutoff command signal for cutting off the forward voltage from the power supply section (18) to the switching means (17), and also sends a forward voltage cutoff command signal to the switching means (17). ) A control device comprising a control unit that sends a reverse rotation command signal to a switching means (17) for supplying a reverse rotation voltage to a motor (2).