JPH02100838A - Control device for automatic thread fastening machine - Google Patents

Abstract

PURPOSE:To correct the fastening quality by forming the structure of feeding a reversing voltage to a motor by cutting off the normal rotation voltage fed from a power feeding part at the time when the stop detection output of a driver bit and non-urinal stall output of a motor stall detection part are received. CONSTITUTION:A normal rotation voltage is fed to a motor 2, transmitted to a driver bit at the deceleration ratio that the rotation thereof is determined by the friction engaging position of a planetary cone 5 and speed change ring 7 and the driver bit tightens a screw. When a reaction force torque is applied on the speed change ring 7 according to the load related to the driver bit, the speed change ring 7 is moved in the shaft center direction with turning. When the motor 2 continues its rotation without reducing the output and not becoming in a stall state, then, non-stall output is output, the speed change ring 7 is moved in the shaft center direction, the deceleration ratio becomes larger and finally infinite, the driver bit is stopped and a stoppage detection output is transmitted. Then, this stop detection output becomes effective, as the stall signal is not transmitted yet and the control part reversing the motor 2 is actuated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention eliminates the influence of inertia 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.

[Prior Art] Recently, an automatic screw tightening machine has been developed which is configured to eliminate the influence of inertia of a driver bit when screw tightening is completed and to reliably tighten a screw using torque as desired. This automatic screw tightening machine has a motor 2 fixed to one end of a driver body 1, as shown in FIGS. , brushless motor. An input disk 4, which forms part of a differential planetary mechanism 3, is arranged in the motor 2 so as to rotate together with the input disk 4, which forms a part of a differential planetary mechanism 3 in response to the rotation of the motor. A cone 5 is arranged so that its circumferential groove 5a frictionally engages with the input disk 4 and rotates. A flat surface 5b located at the center 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. Furthermore, 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, and this speed change ring 7 is connected to an arm 9 which is rotatably held at one end. It is rotatably held by. Moreover, the speed change ring 9 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 caused by the elastic holding member consisting of the spring 10 and the arm 9. The position is regulated, and the maximum value of the reduction ratio and the tightening torque are determined.

[Problem to be Solved by the Invention 1] In this automatic screw tightening), the speed change ring 7 is rotated by the reaction torque generated in response to the torque applied to the driver bit 8. The amount of movement in the axial direction due to rotation of the speed change ring 7 is regulated by the spring 10, and the pressing force on the spring 10 generated on the speed change ring 7 due to reaction torque and the elastic force generated due to the deflection of the spring 10 are combined. The speed change ring 7 moves to a position where the two are balanced. The driver bit 8
As the load related to the gear increases, the speed change ring 7 gradually moves further to the edge of the planetary cone 5. At this time, the driver bit 8 is decelerated until it reaches zero rotation, and the screw is tightened as shown in the characteristic curve shown in FIG.

In this screw tightening machine, the speed change ring 7 is temporarily attached to the planetary cone 5.
When the conical surface 5C of the planetary cone 5 moves to the zero rotation position, even if the motor 2 is stopped and the load on the driver bit 8 is zero, the speed change ring 7 does not return to its original position on the high speed side of the conical surface 5C of the planetary cone 5. Therefore, in this screw tightening machine, each time a screw is tightened, the motor 2 is rotated in the reverse direction to the extent that the tightened screw does not come loose, and the speed change ring 7 is rotated in the cone of the planetary cone 5 according to the load in the reverse direction on the driver bit 8. It is moved along the surface 5C and returned to its original position. In this case, the completion of screw tightening is generally detected by a sensor that detects the stoppage of the driver bit 8.

However, in the case of the motor 2, the control elements, especially the FET that controls the power, are affected by aging, initial troubles, and a decrease in the cooling effect within the control device.

If the SCR etc. is damaged, the motor drive section may be damaged. In addition, in the case of DC motors, aging of the smoothing electrolytic capacitor and brushes in the power supply section, increased resistance due to poor connection of the power supply line, or mistakes in volume adjustment that occur when the motor 2 is driven 4H, etc. , this may lead to a decrease in rotational speed. In general, when the motor 2 is used as a substitute when it breaks down, a motor with a small output is sometimes used. In such a case, the motor 2 stalls and the driver bit 8 stops. In this case, in the method of detecting the completion of tightening by detecting the stoppage of the driver bit 8, the stoppage of the driver bit 8 is detected as the completion of screw tightening, resulting in drawbacks such as poor tightening. .

The present invention aims to eliminate the above-mentioned drawbacks, and in order to return the differential planetary mechanism to its original position, it detects that the motor is not stalled and removes the driver bit that occurs when the motor is not stalled. This is necessary because it is intended to provide a control device that reverses the motor in response to a stop detection signal.

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

On the other hand, a power supply section is connected to the motor via a switching means. Further, a motor stall detection unit is connected to the motor to detect a stall state of the motor.

Further, a rotation stop detection means for detecting a stop of the driver bit is provided, and when receiving the stop detection output of the rotation stop detection means and the non-stall output of the motor stall detection section, a positive signal from the power supply section is provided. A control section is provided for supplying a reversing voltage to the motor from the power supply section after cutting off the reversing voltage.

[Function] In the above automatic screw tightening machine, a normal rotation voltage is supplied to the motor, and the rotation is transmitted to the 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. . When a reaction torque is applied to the speed change ring in accordance with the load on the driver bit, the speed change ring rotates and moves in its axial direction. At this time,
If the motor output decreases for some reason and the motor stalls during tightening, this will be detected by the motor stall detector, an abnormality will be displayed, and the power supply to the motor will be immediately cut off.

At the same time, even if the motor is in a stall state and a stop detection output is sent due to driver error 1~, a stall signal is still being sent from the motor stall detection section.
The stop detection output is disabled, and the control unit that rotates the motor in reverse is not activated.

When the motor continues to rotate without reducing its output or entering a stall state, a non-stall output is being output. In this state, the speed change ring moves in the direction of its axis, and its reduction ratio increases until it reaches infinity. When the driver bit stops and a stop detection output is sent, a stall signal is generated. Since no signal is being generated, this stop detection output becomes valid, and the control section that reverses the motor operates. 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.

[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 (in this embodiment, a DC motor will be explained) of the automatic screw tightening machine.

This control device A has a work start part 11, and this work start part 11 is connected to a lifting means 12. Further, this work start section 11 is connected to a stop judgment section 17 (to be described later) via a first delay circuit 32 in order to prevent malfunctions at the time of startup.
The flip-flop 17b is connected to the flip-flop 17b, and is configured to reset the latch output of the flip-flop 17b. Further, the section 11 to the work star 1 is connected to a normal rotation control section 13, and is configured to send a normal rotation command signal from the normal rotation control section 13 to a switching means 16, which will be described later. The motor 2 has a power supply section 14 connected to the switching means 1.
6. This switching means 16 is configured to supply a forward rotation voltage to the motor 2 in response to a signal from the forward rotation control section 13. Moreover, this switching means 1
6 is a stop judgment unit 17 which will be described later via a first OR circuit 41.
signal from or motor stall detection unit 19 (described later)
The motor is configured to receive a reverse rotation command signal from a reverse rotation control unit 18 that is activated in response to a stall signal, and in response to this reverse rotation command signal, a reverse rotation voltage having a voltage value lower than the normal rotation voltage is supplied from the power supply unit 14 to the motor 2. It is configured as follows.

A motor stall detecting section 19 is connected to the motor 2, and the output of the motor stall detecting section 19 is sent to the stop determining section 17. The motor stall detection section 19 includes a current detection section 20 that detects a load current flowing through the armature winding of the motor 2, and a filter section 21.
, an amplifier 22, a setter 23 whose set value is a current value close to the stall current value, a comparator 24 which compares the load current amplified by the amplifier 22 with the set value, and a coincidence signal of this comparator and the first delay. It consists of a first AND circuit 37 that checks whether the output of the circuit 32 and the normal rotation command signal match. The output of the first AND circuit 37, that is, the stall output of the motor stall detection section 19, is sent to the forward rotation control section 13 via the first OR circuit 41 to cut off the supply of forward rotation voltage, and also directly to the abnormality display section. 25 to display a tightening abnormality. Further, the stall output is connected to a fourth AND circuit 40 via a second OR circuit 42 and a second delay circuit 33 activated by this output, and waits for a time-up signal from a timer 17a (described later) of the stop determination section 17. The screwdriver is configured to be ready for returning the screwdriver to its original position. Further, the stall output of the motor stall detection section 19 is sent to the third AND circuit 39 of the stop judgment section 17 via an inverter, and the gate thereof is closed.

Further, the control device may be placed 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.
Rotation stop detection means 2 for detecting stop of driver bit 8
6. This rotation stop detection means 26 is a slit disk 27 that can be raised and lowered integrally with the driver body (not shown) and rotates integrally with the driver bit 8, and a rotating member arranged corresponding to the movement path of the slit disk 27 at one end thereof. The rotation detecting section 28 is configured to emit an output pulse when detecting passage of the slit disk 27 through the slit disk 27, and this output pulse is transmitted to an amplifier 29, It is configured to be applied to the stop determination section 17 via a second AND circuit 38 that checks the coincidence with the output of the waveform shaping section 30, the differentiation circuit 31, and the first delay circuit 32.

The stop determination section 17 includes a timer 17a which is an example of a pulse width detector and a flip-flop 1 which is an example of a memory device.
7b and a third AND circuit 39 that opens and closes the gate according to the output of the motor stall detection section 19,
After a predetermined time (T1) determined by the first delay circuit 32 has elapsed after the work start signal is transmitted, the timer 17a is reset by the output pulse from the rotation detector 28, and the third
The timer 17a is configured to be set immediately after a very short period of time determined by the delay circuit 34 has elapsed. Furthermore, the timer 17a is configured to output an output signal to the flip-flop 17b if no output pulse is generated from the rotation detection section 28 even after a predetermined time (T) has been set. The flip-flop 17b
receives this output signal and sends the output signal to the third AND circuit 39, and the motor stall detection section 1 is sent to the third AND circuit 39.
The output of the flip-flop 17b passes through the third AND circuit 39 and is output as the output signal of the stop determination section 17 when the non-stall signal is being transmitted from the stop determination section 17. The flip-flop 17b is reset by the next output of the first delay circuit 32.

The output signal of the stop determination section 17 is supplied to the forward rotation control section 13, and is configured to cut off the forward rotation voltage supplied to the motor 2 based on the signal from the work start section 11. Further, this output signal is supplied to the second delay circuit 33, and after being delayed by the time (T2) necessary for the normally rotating motor 2 to stop, a second delay circuit 33 is checked to see if it matches the time-up signal of the timer 17a. The output signal is sent to a 4-AND circuit 40, and the output of this 4-AND circuit 40 is roughly supplied to the pulse generator 35. This pulse generating section 35 outputs a desired reversal time (4 seconds) to the reversal control section 18.
A pulse signal is transmitted, a reverse rotation command signal is sent to the switching means 16, a reverse rotation voltage is supplied from the power supply section 14 to the motor 2, and the motor 2 is rotated in the reverse direction for a predetermined period of time. Further, the pulse generating section 35 detects the lifting means 1 of the driver pin 1-8 via the machine cycle completion detecting section 36.
2 is activated to raise and return the driver bit 8. Note that the stall signal of the motor stall signal is input to the second delay circuit 33 by the second OR circuit 4.
2, and is configured such that it is always output to the pulse generator 35 when the screw tightening machine is reset.

In the control device for the automatic screw tightening machine described above, as shown in FIGS. 2a and 2b, the elevating means 12 is actuated by the output signal from the work start section 11, and the driver pin 1-8 is lowered. At the same time, the output signal of the work start section 11 is supplied to the switching means 16 via the forward rotation control section 13, and the forward rotation voltage X is supplied from the power supply section 14 to the motor 2 as shown in FIG. 2C. . As the motor 2 rotates, the input disk (not shown)
, planetary cone (not shown), cam disc (not shown)
The driver bit 8 is rotated via a differential planetary mechanism (not shown) consisting of a variable speed ring (not shown) and a speed change ring (not shown), and screw tightening is started.

When the motor 2 outputs a predetermined output, the slit disk 27 rotates, so that the rotation detection section 28 emits an output pulse. After this output pulse is waveform-shaped, it is supplied to the stop determination section 17 as shown in FIG. 2d. If this output pulse is continuously supplied before the timer 17a counts the predetermined time (King), the timer 17a is reset by the next output pulse, and the timer 17a is reset by the next output pulse.
a does not emit an output signal. Further, the timer 17a is set immediately after reset 1 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. Dry pitch 88
When the zero rotation stops, the output pulse from the rotation detection section 28 is no longer transmitted, and the timer 178 counts a predetermined time (T) and outputs an output signal as shown in FIG. 28. Therefore, the output of the flip-flop 17b is inverted, and the output signal is applied to the third AND circuit 39. At this time, the motor 2 continues to rotate, the motor 2 does not enter a stall state, and the load current of the motor 2 is sufficiently smaller than the predetermined stall current. The match signal is not transmitted from the device 24, and the stall signal is not transmitted from the first AND circuit 37 either. That is, the motor stall detection section 19 is transmitting a non-stalling signal, and this non-stalling signal is supplied to the third AND circuit 39 via the inverter, and as shown in FIG. The 3-AND circuit 39 has its gate open.

Therefore, as shown in the second diagram, the output signal of the flip-flop 17b passes through the third AND circuit 39, reaches the forward rotation control section 13, and cuts off the forward rotation voltage. At the same time, the second
The pulse signal is supplied to the delay circuit 33, delayed by the time required for the motor 2 to normally stop (2) as shown in the second diagram, and supplied to the pulse generator 35 via the fourth AND circuit 40.

This pulse generator 35 emits a pulse signal with a predetermined time width (T4) as shown in FIG.
Supply to 8. While the pulse signal is being transmitted, the reverse rotation control section 18 sends a reverse rotation command signal to the switching means 16, and the power supply section 14 supplies the motor 2 with a reverse rotation voltage y lower than the normal rotation voltage x. 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, driver bit 8
In response to the load in the reverse direction, the frictional engagement position between the planetary cone and the speed change ring returns to the high speed side, and the speed change ring, cam disc, and star cone are unlocked from the motor 2 side. Moreover, since the load applied to the driver bit 8 in the reverse direction is almost zero, the speed change ring returns along the conical surface of the planetary cone in accordance with the load, and finally returns to its original position.

Moreover, since the reverse rotation voltage y is sufficiently smaller than the forward rotation voltage X as shown in FIG. The load is small, and the tightened screw will not loosen due to the driver bit 8 rotating in the opposite direction.

Further, the pulse signal from the pulse generating section 35 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. Avoid rising and prepare for the next work.

On the other hand, if the output of the motor 2 is avoided for some reason, the tightening torque corresponding to the output torque is reached, and the motor 2 enters a stall state during tightening. Therefore, the driver bit 8 stops during tightening as shown in FIG. 2 d', and the rotation stop detection means 26 outputs a stop detection output to the stop judgment unit 17 as shown in FIG. It is sent to the third AND circuit 39. At this time, the load current of the motor 2 detected by the current detection section 20 suddenly reaches the stall current value, so a coincidence signal is transmitted from the comparator 29. A ratio signal is transmitted, the signal is sent to the abnormality display section 25,
An error message is displayed. At the same time, the third AND circuit 39
Since a stall signal is added to , the signal shown in Fig. 2 [.

As shown in FIG. 2, the gate of the third AND circuit 39 is closed, and the stop determination section 17 does not produce any output as shown in FIG. Further, the stall signal is configured to wait for the timer 17a of the stop judgment section 17 to time up, and then send a signal to the pulse generation section 35 to return the automatic screw tightening machine to its original position and prepare for the next operation. .

[Effects of the Invention] As explained above, the present invention transmits the rotation of the motor to the driver bit 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. In addition to regulating movement in the direction by an elastic holding member, a detection unit is provided to detect a stall state of the motor, and a rotation stop detection means is provided to detect a stoppage of the driver bit. Since the configuration is such that the supply of forward rotation voltage to the motor is stopped by the output signal of It is possible to judge when the bit rotation has stopped and when the driver bit has stopped due to normal tightening, which not only makes it possible to accurately judge whether the tightening is good or bad, but also makes it possible to It has the advantage of being able to check for abnormalities in the system, especially the motor operation.

In the embodiment, after the motor is rotated in the normal direction, the motor is rotated in the reverse direction 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. Further, 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 9- is used. or other rotation detection means such as an opto-encoder or a magnetic encoder. In general, the motor stall detection section may use a conventionally known rotation detection means, or in the case of an AC servo motor or an AC brushless motor, a signal from a Hall sensor or a resolver may be used.

[Brief explanation of drawings]

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 an automatic screw tightening machine according to the present invention, and Fig. 4 is an automatic screw tightening machine of Fig. 3. FIG. 5 is a sectional view of a main part, and FIG. 5 is a torque-rotational speed characteristic curve diagram of the output shaft of the differential planetary mechanism according to the present invention. 8 control device, 1 driver body, 2 3 differential planetary mechanism, 4 5 planetary cone, 5a 5b flat surface, 5C 6 cam disc, 7 8 driver bit, 9 10 spring, 11 motor, input disk, circumferential groove, Circular surface, speed change ring, arm, work start section, lifting means, 13 forward rotation control section, power supply section, switching means, 17 stop judgment section, timer,
17b flip-flop, reversal control section,
19 Motor stall detection section, current detection section,
21 filter section, amplifier, 23 setting device, comparator, 25 abnormality display section, rotation stop detection means, 27 slit disk, rotation detection section,
29 Amplifier, waveform shaping section, 31
Differentiation circuit, first delay circuit, 33 second delay circuit, third delay circuit, 35 pulse generation section, machine cycle completion detection section,

Claims (1)

[Scope of Claims] A driver bit 8 is connected via an input disk 4 that rotates in response to the rotation of the motor 2, a planetary cone 5 that frictionally engages with the outer circumference of the input disk 4, and a cam disk 6 that frictionally engages with this. At the same time, a speed change ring 7 that is frictionally engaged with the outer periphery of the planetary cone 5 is arranged so that the reaction force applied to the speed change ring 7 due to the load torque related to the driver bit 8 is received by the elastic holding member. power supply 14 via switching means 16 to
A motor stall detection unit 19 is provided to connect the motor 2 and detect the stall state of the motor 2, and further, a rotation stop detection unit 26 is provided to detect the stop of the driver bit 8, and a stop detection output of the rotation stop detection unit 26 is provided. and a non-stall detection output of the motor stall detection section 19, the motor is characterized by being provided with a control section that cuts off the forward rotation voltage from the power supply section 14 and then supplies the reverse rotation voltage from the power supply section 14 to the motor 2. A control device for an automatic screw tightening machine.