JPH0468097B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is configured to completely eliminate the influence of inertia of a driver bit when screw tightening is completed, and to ensure screw tightening with a desired screw tightening torque. This invention relates to a control device for an automatic screw 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 motor, a planetary cone which frictionally engages with the outer periphery of the input disk, and a cam disc which 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 motor via a switching means.

Further, as the detection means for detecting the completion of screw tightening, the first detection means detects the load current of the motor, and the second detection means outputs an output signal when the detected value reaches a current value close to the saturation current. is arranged, and the switching means is actuated by the output of the detection means, the forward rotation voltage supply section is cut off, and the reverse rotation voltage of the reverse rotation voltage supply section is supplied to the motor for a predetermined period of time. .

Function The control device for the automatic screw tightening machine described above drives the motor by supplying normal rotation voltage, and transmits the rotation to the driver bit at a reduction ratio determined by the frictional engagement position of the speed change ring with the conical surface of the planetary cone. and then tighten the screws. 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, the speed change ring rotates and moves in the direction of its axis, and its reduction ratio increases until it reaches infinity, and the driver bit stops rotating, completing screw tightening. do.
Along with this, the load current of the motor increases and reaches a saturated state at a constant value, but during this time the load current reaches the set value just before reaching the saturated state, the completion of screw tightening is detected, and the detection output is output. Ru. This output signal activates the switching means to cut off the supply of normal rotation voltage to the motor. At this time, since the straight line connecting the contact points of the planetary cone, the speed change ring, and the cam disk is approximately parallel to the planetary cone, the cam disk is locked by the wedge action. Thereafter, a reverse voltage is supplied from the reverse voltage supply section to the motor for a predetermined period of time, and the motor rotates slightly in reverse and then stops. Therefore, the planetary cone and speed change ring are slightly reversed from the motor, and the frictional engagement position is slightly returned to the high speed side. By returning the frictional engagement position to the high speed side, the gear ring, cam disc and planetary cone are unlocked.
At the same time, the load on the driver bit is reduced by reversing the motor, so the speed change ring returns to the high speed side to a position corresponding to this load, and finally returns to its original position. After that, the driver bit increases and prepares for the next operation. At this time, since the load on the driver bit is completely reduced, the driver bit and screw can be smoothly separated, and there is no damage to the driver bit or the screw. Moreover, since there is no mechanical torque detection mechanism, the output torque of the differential planetary mechanism can be transmitted to the driver bit without loss, and tightening can be completed accurately using the output torque of the differential planetary mechanism.

Embodiments Hereinafter, embodiments will be described with reference to the drawings. In FIGS. 1 and 2, A is a control device for the automatic screw tightening machine 1, which is configured to be driven according to the flowchart shown in FIG. Prior to explaining the control device A, the automatic screw tightening machine of the present invention shown in FIG. 4 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 an input disk 21 forming a part of a differential planetary mechanism 20 is rotated by the motor 19. arranged to rotate.
Further, a plurality of planetary cones 23 are arranged on the outer periphery of this input disk 21, and a circumferential groove 23a is provided in the planetary cones 23.
is configured to rotate while being frictionally engaged with the input disk 21. A cam disk 24 that rotates concentrically with the input disk 21 is provided on a flat surface 23b located on the back side of the conical surface 23c of the planetary cone 23.
are arranged so as to frictionally engage with each other. Moreover,
A driver bit (not shown) 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.

Further, a speed change ring 25 is arranged on the outer periphery of the planetary cone 23 so as to rotate while frictionally engaging with the conical surface 23c.
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 The maximum value of the reduction ratio and the tightening torque determined by the position are regulated. In this automatic screw tightening machine 1,
The speed change ring 25 rotates due to the reaction torque generated in response to the tightening torque applied to the driver bit. The amount of movement in the axial direction due to the rotation of the speed change ring 25 is regulated by the spring 31;
Spring 3 generated in speed change ring 25 due to reaction torque
The speed change ring 25 is configured to move to a position where the pressing force on the spring 31 and the elastic force generated by the deflection of the spring 31 are balanced. Therefore, when the load on the driver bit increases, the speed change ring 25 moves to the edge of the planetary cone 23, the driver bit is decelerated to zero rotation, and the screw is tightened as shown in the characteristic curve shown in Figure 5. .

Further, the control device A is configured to control a motor 19 that is a rotational drive source of the automatic screw tightening machine. This control device A has a work start section 41, and this work start section 41 is connected to a normal rotation control section 42. A forward rotation voltage supply section 43 and a reverse rotation voltage supply section 44 that supplies a reverse rotation voltage lower than the normal rotation voltage are connected to the motor 19 via a switching means 45. This switching means 4
5 supplies a forward rotation voltage to the motor 19 in response to a signal from the forward rotation control section 42, and after cutting off the forward rotation voltage in response to a conversion completion signal from an A/D converter 54 to be described later, a reverse rotation control section The motor 19 is configured to supply a reverse voltage to the motor 19 based on a signal from the motor 46 . Moreover, this switching means 45 is configured so that the forward rotation voltage and the reverse rotation voltage are not supplied at the same time.

Further, a first detection means 47 is connected to the motor 19 for detecting the load current flowing through the armature winding, and as the load on the driver bit increases, the detected value increases and the motor The structure is such that when the driver bit stops during 19 rotations, it is in a saturated state. This first detection means 47 includes a filter 48 and a gain correction section 4.
9, and is configured so that the determination described later can be easily performed. Moreover, this first detection means 47 has a second detection means 5 for detecting the completion of screw tightening.
Connected to 0. The second detection means 50 includes:
A first setting device 5 which has a voltage value lower than the constant voltage value at the time of load current saturation corresponding to the desired tightening torque as a set value A in order to detect the completion of screw tightening.
1. A first step that compares this set value A and the detected value.
A comparator 52 and a first delay circuit 53 which receives an AND output signal of the output signal of the first comparator 52 and the output signal of the third detection means 55 described later and transmits an output signal after a predetermined time (T1). ing. This first delay circuit 53 is connected to an A-D converter 54 which will be described later.
The converter is configured to transmit a conversion command signal to the converter.

Further, the first detection means 47 is connected to a third detection means 55 that detects whether the motor 19 has stopped rotating. This third detection means 55 includes a second setter 56 having a set value close to zero in order to detect rotation stoppage of the motor 19, and a second comparator 57 for comparing this set value with the detected value. and when the set value and the detected value match, the second comparator 5
It is configured such that an output signal is transmitted from 7.

The detected value of the first detecting means 47 is supplied to the A/D converter 54, and the output signal of the second detecting means 50 starts digital conversion of the analog detected value at the time when screw tightening is completely completed. After completion of the conversion, the conversion data is outputted at the same time as a conversion completion signal is sent from the A/D converter 54. Further, the conversion data is supplied to a torque display unit 58, and is configured to be displayed as a torque value upon receiving the conversion completion signal.

On the other hand, the conversion completion signal is transmitted to the forward rotation control section 42.
The normal rotation voltage supplied to the motor 19 is cut off by a signal from the work start section 41. Further, this conversion completion signal is supplied to the second delay circuit 59, and is configured to be delayed by the time (T2) necessary for the normally rotating motor 19 to stop. At the same time, this conversion completion signal is supplied to the pulse generator 60 after waiting for an output signal from the third detection means 55 to confirm that the rotation of the motor 19 has completely stopped. Said motor 1
At 9, an output signal corresponding to the pulse of the desired reversal time (T3) is input to the reversal control section 46, and while the switching means 45 is actuated by the signal from this reversal control section 46, the output signal is inputted via the machine cycle completion detection section 61. The driver bit is configured to be raised and returned to its original position by operating the driver bit lifting means 62.

Further, the detected value of the first detection means 47 is supplied to a third comparator 64 of a tightening quality determination section 63, and is compared with a voltage value corresponding to the lower limit tightening torque set in a third setting device 69. It is composed of This third comparator 64 is configured to issue an output signal when these match, and is configured to detect insufficient tightening when this output signal is not issued. Further, the tightening quality determination section 63 adjusts the conversion data of the A-D converter 54 to the range of upper and lower limit values of the tightening torque set in the fourth setting device 65 and the fifth setting device 66. It is configured to receive output signals from a fourth comparator 67 and a fifth comparator 68 that determine whether or not there is. In addition, the tightening quality determination section 63
has a determination unit (not shown) that determines whether the time from the start of screw tightening to the completion of screw tightening is within a predetermined time, and receives the conversion completion signal and determines whether the screw tightening is complete. It is configured such that the quality is determined and the quality is comprehensively displayed on the tightening quality display section 70.

In the control device for the automatic screw tightening machine described above, as shown in FIGS. 2a and 2c, the output signal of the work start section 41 is supplied to the lifting means 62 of the driver bit, the lifting means 62 is operated, and the driver bit is lowered. . At the same time, the output signal of the work start section 41 is supplied to the forward rotation control section 42, and the switching means 45 is actuated by the signal from the forward rotation control section 42.
As shown in FIG. 2 , the normal rotation voltage is supplied to the motor 19 from the normal rotation voltage supply section 43 . As the motor 19 rotates, the driver bit rotates via a differential planetary mechanism consisting of an input disk, a planetary cone, a cam disk, and a speed change ring, and screw tightening is started.
At this time, the speed change ring rotates in response to the load applied to the driver bit, and its reduction ratio increases continuously until the reduction ratio reaches infinity and the rotation of the driver bit stops. On the other hand, as shown in FIG. 2d, the load current of the motor 19 increases in accordance with the load related to the driver bit, so this load current is detected by the first detection means 47, and as shown in FIG. 2e, the load current of the motor 19 increases. The detected value is the setting value A of the first setting device 51
compared to When the detected value and the set value A match, a conversion command signal is sent to the A-D converter 54 after a predetermined time (T1) from that point, as shown in FIG.
The A/D converter 54 converts the detected value at that point into digital data, and this converted data is displayed on the torque display section 58. At the same time as this conversion is completed, a conversion completion signal is supplied to the normal rotation control section 42 as shown in FIG. 2g, and the rotation of the motor 19 is stopped.

On the other hand, the conversion completion signal is delayed by the time (T2) necessary for the motor 19 to normally stop, as shown in FIG. 2h. At the same time, this conversion completion signal is supplied to the pulse generator 60 after waiting for the output signal of the third detection means 55 and confirming that the motor 19 has stopped rotating, as shown in FIG. 2i. The pulse generator 60 generates a pulse signal with a predetermined time width (T3) as shown in FIG. 2j, and supplies this to the reverse rotation controller 46. This reversal control section 46 operates the switching means 45 while the pulse signal is being transmitted,
A reverse voltage is supplied to the motor 19 from the reverse voltage supply section 44 . The motor 19 rotates slightly in the reverse direction and then stops, but as the motor 19 rotates in the reverse direction, the planetary cone and the speed change ring reverse. Therefore, the frictional engagement position between the planetary cone and the speed change ring returns to the high speed side, the speed change ring, cam disc and planetary cone are unlocked from the motor 19 side, and the reaction torque corresponding to the load on the driver bit changes the speed. transmitted to the ring. At this time, the load applied to the driver bit is reduced as the motor 19 rotates in reverse, so the speed change ring returns along the conical surface of the planetary coil according to the load, and finally returns to its original position. do. Further, the pulse signal from the pulse generator 60 shown in FIG. 2j is supplied to the machine cycle completion detector 61, and its output signal
As shown in Figure K, it is supplied to the lifting means, which is operated to raise the driver bit in preparation for the next operation.

At this time, the reverse rotation voltage is sufficiently lower than the forward rotation voltage as shown in Figure 2b, so even if the reverse rotation time of the motor 19 is long, the driver bit receives a load in the reverse direction, but this load is small. , the driver bits are never reversed.

Furthermore, the third comparator 64 that sends the output signal of the tightening quality determination section 63 compares the set value corresponding to the lower limit tightening torque of the third setter 69 with the detected value, and confirms that there is no abnormality in the torque transmission system. How it goes is monitored. The conversion data of the A-D converter 54 is compared with the upper and lower limit settings of the tightening torque of the fourth setting device 65 and the fifth setting device 66, respectively, to determine whether the screw tightening torque is good or bad. The required time is compared with the set time and the tightening state is determined based on the screw tightening time, and the tightening quality judgment unit 63 comprehensively determines the quality of the screw tightening work, which is displayed on the tightening quality display unit 70. .

The torque display section 58 and the tightening quality display section 70 are reset by a signal from the next work start section 41.

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, the motor is configured to detect the load current of the motor, and when it reaches a predetermined value, cut off the forward rotation voltage to the motor and supply reverse rotation voltage, causing the motor to rotate slightly in the reverse direction. Therefore, 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 motor side, and the position of friction engagement can be slightly changed to reverse the speed change ring. The driver bit can be rotated and returned to its original position according to the load on the driver bit in the direction, and the load on the driver bit can be completely reduced, and even when the driver bit is raised and returned, the driver bit will move smoothly. There is no need to separate from the screw and lift the workpiece.
There are advantages such as no damage to screw heads or driver bits. Furthermore, since the present invention is configured to detect the completion of screw tightening due to forward rotation of the motor from the load current of the motor, extra rotation detection means, that is, attached to the driver bit, is required to detect the stoppage of the driver bit. This eliminates the need for extra mechanical components such as slit discs, which eliminates extra load on the driver bit, and the output torque of the differential planetary mechanism is applied to the driver bit without loss. Tightening can be completed accurately.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a signal waveform diagram at each point in Fig. 1, Fig. 3 is a flowchart showing the operation of the present invention, and Fig. 4 is an automatic screw tightening machine according to the present invention. FIG. 5 is a sectional view of a main part of the present invention, and FIG. 5 is a torque-rotational speed characteristic curve diagram of the output shaft of the automatic transmission according to the present invention. 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 disk, 25...
...Speed ring, 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 section, 4
7...first detection means, 48...filter, 49...
...Gain correction section, 50...Second detection means, 51...
...first setter, 52...first comparator, 53...first delay circuit, 54...A-D converter, 55...third detection means, 56...second setter, 57... Second
Comparator, 58...torque display section, 59...second delay circuit, 60...pulse generation section, 61...machine cycle completion detection section, 62...lifting means, 63...
...Tightening quality determination section, 64...Third comparator, 65...
...Fourth setter, 66...Fifth setter, 67...Fourth comparator, 68...Fifth comparator, 69...Third setter, 70...Tightening quality display unit.

Claims (1)

[Claims] 1. An input disk 21 that rotates in response to the rotation of the motor 19, 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 gear change ring 25 that connects the driver bit with the drive bit through the cam disc 24 that frictionally engages with the outer periphery of the planetary cone 23.
is arranged so that the elastic holding member receives the reaction force applied to the speed change ring 25 due to the load torque related to the driver bit, while the forward rotation voltage supply section 43 and the reverse rotation voltage supply section 43 and reverse rotation voltage are supplied to the motor 19 via the switching means 45. 44, and a first detection means for detecting the load current flowing through the motor 19, and a second detection means for outputting an output signal when the detection value of this detection means reaches a current value close to its saturation current. Detecting means are provided, and the outputs of these detecting means actuate the switching means 45 to cut off the forward rotation voltage supply section 43 and, after detecting the stoppage of the motor, switch the reverse rotation voltage of the reverse rotation voltage supply section 44 to the motor for a predetermined period of time. 19, and is slightly reversed to release the locked state and return the frictional engagement position between the planetary cone 23 and the speed change ring 25 from the motor 19 side to the slightly high speed side, so that the motor 19 A control device for an automatic screw tightening machine, characterized in that the speed change ring 25 is rotated back to the high speed side by the elastic force of an elastic holding member in response to the load related to the driver bit which is reduced by the reversal of the speed change ring 25.