JPH0583345B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides an automatic screwdriver configured to eliminate the influence of inertia of a driver bit when screw tightening is completed and to reliably tighten screws with a desired screw tightening torque. The present invention relates to a control device for a tightening machine.

Prior Art Generally, when controlling screw tightening torque, a driver bit is rotated by a rotary drive source, the load torque applied to the driver bit is detected using an appropriate detection means, and the torque is detected until the detected value reaches a set value. For example, a device that stops a rotational drive source is common. In this device, 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 to the correct tightening torque. There is a need for a screw tightening machine that can accurately tighten screws even at a low set tightening torque.

Problems to be Solved by the Invention As disclosed in Japanese Patent Publication No. 57-13211, the present invention has a rotary drive source configured such that 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. The rotation of the driver bit is reduced to zero without any problems, and the output torque at this time is used to maintain the tightening torque, and the output shaft of the automatic transmission self-locks when the screw tightening is completed and the rotational drive source is stopped. This is an attempt to solve the problem of damaging the head of a screw when lifting a driver bit whose rotation is restricted.

Means for Solving the Problems The present invention aims to solve the above problems, and includes an input disk that rotates in response to rotation of a rotary drive source, and a circumferential groove that frictionally engages with the outer periphery of the input disk. a planetary cone held in the planetary cone; a cam disk coaxially located with the input disc and frictionally engaged with the flat surface on the back side of the planetary cone; and a cam disk frictionally engaged with the conical surface of the planetary cone while rotating. A transmission mechanism is composed of a transmission ring held by an arm so as to be able to slide along a conical surface, and a spring that biases this transmission ring in a direction in which the arm stands upright. The transmission ring is configured to transmit a driver bit and receive a reaction force applied to the speed change ring due to a load torque related to the driver bit.

On the other hand, a forward rotation voltage supply section and a reverse rotation voltage supply section that supplies a voltage lower than the forward rotation voltage are connected to the rotational drive source via a switching means.

Further, there are provided a first detection means for detecting the torque applied to the driver bit when tightening the screw, and a second detection means for detecting that the detected value reaches a set value A and the screw tightening is completed. The switching means is actuated by the output of the second 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 rotation drive source.

Further, a third detection means is provided for detecting the stoppage of the drive shaft of the rotational drive source, and the forward rotation voltage supply section is cut off by the operation of the switching means, and the rotational drive source is stopped by the third detection means. After confirming that, the reversing voltage of the reversing voltage supply section may be supplied to the rotational drive source.

Function: In the control device for the automatic screw tightening machine described above, a normal rotation voltage is supplied to the rotation drive source to drive the rotation drive source, and the rotation is controlled by the driver bit at a reduction ratio determined by the frictional engagement position of the speed change ring with respect to the conical surface of the planetary cone. transmit and tighten the screws. When the screw is tightened, a reaction force is applied to the speed change ring according to the load on the driver bit, and when the speed change ring rotates, it moves in the direction of its axis, and its reduction ratio increases until it reaches infinity, and the driver Bit rotation stops. on the other hand,
As the load is applied to the driver bit, the load current of the rotary drive source increases, and this is detected by the first detection means. When the detected value reaches the set value A, it is detected by the second detection means, and completion of screw tightening is detected. The switching means is actuated by the output signal of the second detection means, and the supply of normal rotation voltage to the rotational drive source is cut off. Thereafter, a reverse voltage that is lower than the normal rotation voltage is supplied from the reverse voltage supply section to the rotation drive source. Therefore, the rotational drive source rotates in the opposite direction, and the load applied to the driver bit is reduced from the rotational drive source side, so that the speed change ring returns to its original position along the conical surface of the planetary cone. After that, the driver bit rises, but since the speed change ring has returned to the initial state where the reduction ratio is small, the driver bit is in a free state, so the head of the screw is not damaged. Prepare for the next task.

Furthermore, the timing for applying the reverse voltage to the rotary drive source is set after confirming that the output signal is transmitted from the third detection means and the rotation of the rotary drive source has completely stopped. There is no possibility that current flows in two directions, even transiently, in the forward and reverse directions, and the rotary drive source can be rotated in the reverse direction without damage or malfunction.

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.
In addition, a plurality of planetary cones 23 are arranged on the outer periphery of the input disk 21, and a circumferential groove 2 is formed in the neck of the planetary cone 23.
3a is configured to frictionally engage with the input disk 21 and rotate. A cam disk 24 rotating concentrically with the input disk 21 is arranged so as to frictionally engage with a flat surface 23b located on the back side of the conical surface 23c of the planetary cone 23. Furthermore, a driver bit (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.

Furthermore, a speed change ring 25 is disposed so as to surround the outer periphery of the planetary cone 23 and is slidable along the conical surface 23c while frictionally engaging with a part of the conical surface 23c. The ring 25 is rotatably held by an arm 32 whose one end is rotatably held. Moreover, this speed change ring 25 is biased by a spring 31 so that its frictional engagement position is located on the high speed side.
1 and the arm 32 regulates the maximum reduction ratio and tightening torque determined by the frictional engagement position of the speed change ring 25, and the input disk 21, the planetary cone 23, the cam disk 24, Speed change ring 25, arm 32 and spring 3
1 constitutes a transmission mechanism. In this automatic screw tightening machine 1, the speed change ring 25 is rotated by 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, so that the pressing force on the spring 31 generated on the speed change ring 25 due to reaction torque and the elastic force generated due to the deflection of the spring 31 are combined. The speed change ring 25 is configured to move to a position where the speed change ring 25 is balanced.
Therefore, when the load on the driver bit 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 as a rotational drive source of the automatic screw tightening machine. This control device A includes a work start section 4
1, and this work start section 41 is connected to a forward rotation control section 42. A positive voltage supply section 43 and a reverse voltage supply section 44 that supplies a reverse voltage having a lower voltage than the forward rotation voltage are connected to the motor 19 via a switching means 45. This switching means 45
is the motor 1 according to the signal from the normal rotation control section 42.
The motor 9 is configured to cut off the supply of forward rotation voltage to the motor 19, and to supply a reverse rotation voltage to the motor 19 in response to a signal from a reverse rotation control section 46, which will be described later. 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, the motor 19 is connected to a first detection means 47 for detecting the load current flowing through the armature winding, and this first detection means 47 is connected to the filter 4.
8 and a gain correction section 49, and this first detection means 47 is connected to a second detection means 50 for detecting completion of screw tightening. This second detection means 50 compares this set value A with the detected value with a first setting device 51 that sets a voltage value lower than the voltage value corresponding to the desired tightening torque in order to detect the completion of screw tightening. a first comparator 52; a first delay circuit 53 which receives an AND output signal of an output signal of the first comparator 52 and an output signal of a third detection means 55, which will be described later, and transmits an output signal after a predetermined time (T1); It is made up of This first delay circuit 53 is configured to send a conversion command signal to an AD converter 54, which will be described later.

Further, the first detecting means 47 is connected to a third detecting means 55 for detecting the stoppage of rotation of the motor 19, and the third detecting means 55 detects the stoppage of rotation of the motor 19, so that the third detecting means 55 has a value close to zero. It consists of a second setter 56 having a set value, and a second comparator 57 that compares the set value with the detected value.When the set value and the detected value match, the second comparator 57 compares the set value with the detected value.
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 converting the detected value at the time when the screw tightening is completely completed. The conversion data is output from the A-D converter 54 at the same time as the conversion completion signal is sent.
Further, the conversion data is supplied to the display section 58,
It is configured to receive the conversion completion signal and display it as a torque value.

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 delayed by the time (T2) necessary for the normally rotating motor 19 to stop, and also indicates that the rotation of the motor 19 has completely stopped. The third detection means 55 for checking
Waiting for an output signal from the motor 19, the pulse generator 60 is supplied to a pulse generator 60, and the pulse generator 60 is configured to transmit a pulse signal of a desired reversal time (T3) to the motor 19. The pulse generating section 60 is connected to the reverse rotation control section 46, and uses the pulse signal to operate the reverse rotation control section 46, and at the same time operates the driver bit lifting means 62 via the machine cycle completion detection section 61 to raise and lower the driver bit. It is configured to raise and return.

Furthermore, the detection 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. The third comparator 64 is configured to transmit an output signal when they match, and is configured to detect insufficient tightening when this output signal is not transmitted. Also,
The tightening quality determining section 63 is connected to the A-D converting section 54.
The fourth setter 65 and the fifth
It has a fourth comparator 67 and a fifth comparator 68 that determine whether the tightening torque is within the upper and lower limit setting values set in the setting device 66. Further, the tightening quality determining unit 63 includes a determining 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,
In response to the conversion completion signal, the quality of screw tightening is comprehensively determined and 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 driver bit elevating means 62 is actuated by the output signal from the work start section 41, and the driver bit is lowered. At the same time, the output signal of the work start section 41 is supplied to the switching means 45 via the forward rotation control section 42, the switching means 45 is activated, and the normal rotation voltage is supplied from the forward rotation voltage supply section 43 as shown in FIG. is supplied to the motor 19. Motor 1
9, the driver bit rotates via the differential planetary mechanism 20 consisting of the input disk 21, planetary cone 23, cam disk 24, and speed change ring 25, and screw tightening is started. At this time, depending on the load applied to the driver bit, the speed change ring 25
rotates, its reduction ratio increases continuously, and finally 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 according to the load on 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 value is compared with the setting value of the first setting device 51, and if they match, a conversion command signal is supplied to the A-D converter 54 after a predetermined time (T1) from that point, as shown in FIG. The -D conversion section 54 converts the detected value at that point into digital data, and this converted data is displayed on the 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, and is output from the third detection means 55 as shown in FIG. After waiting for a signal and confirming that the motor 19 has stopped rotating, it is supplied to the pulse generator 60. The pulse generator 60 generates a pulse signal having a predetermined time width (T3) as shown in FIG. 2J, and supplies this to the reverse rotation controller 46. The reversal control section 46 operates the switching means 45 while the pulse signal is being transmitted, and supplies a reversal voltage to the motor 19 from the reversal voltage supply section 44 .
When the motor 19 rotates slightly in the opposite direction, the load applied to the driver bit is reduced from the motor 19 side.
The speed change ring 25 gradually returns along the planetary cone 23, and the locked state of the driver bit is released. Further, the pulse signal from the pulse generator 60 is supplied to a machine cycle completion detector 61,
The output signal is supplied to the lifting means as shown in FIG. 2k, which is actuated to raise the driver bit in preparation for the next operation.

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

Further, a third comparator 69 of the tightening quality determination section 63 compares the set value corresponding to the lower limit tightening torque of the third setter 65 with the detected value,
The torque transmission system is monitored for any abnormalities. 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 quality of the screw tightening work is determined comprehensively, and the tightening quality display section 70
is displayed.

Note that the display section 58 and the tightening quality display section 7
0 is 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. The movement is regulated by an elastic member, and the completion of screw tightening is detected from the load current that fluctuates according to the load applied to the driver bit by supplying forward voltage to the rotational drive source, and after screw tightening is completed, the rotational drive source is Since the structure is configured so that the supply of forward rotation voltage is stopped and then a reverse rotation voltage of a value lower than the forward rotation voltage is supplied to the rotation drive source, the differential planetary mechanism is locked when the screw tightening is completed. Even if the motor stops in this state, the lock state can be released from the rotational drive source side, and the gear ring of the differential planetary mechanism can be gradually returned to its original position, making it possible to provide a quiet device with no noise. Even when the driver bit is raised and returned to its original position, the driver bit is smoothly removed from the screw, there is no lifting of the workpiece, and there is no damage to the screw head or the driver bit. Furthermore, the present invention is configured to cut off the forward rotation voltage of the rotation drive source, and after confirming that the rotation drive source has stopped, supply the reverse voltage to reverse the rotation drive source. There is no transient flow of current in the forward and reverse directions, which has the advantage of extending the life of the drive unit.

In the embodiment, the motor is configured to rotate at the same time as the elevating source is activated, but it may also be configured to rotate after the motor has descended to a predetermined position. Further, the motor may be an AC motor, and in this case, it is preferable to use a torque sensor such as a strain gauge as the first detection means.

[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...Display unit, 59...Second delay circuit, 60...Pulse generator, 61...Machine cycle completion detection unit, 62...Lifting means, 63...Tightening quality determination unit, 64... ...Third comparator, 65...Fourth setting device, 66...Fifth setting device, 67...Fourth comparator, 68...Fifth comparator, 69...Third setting device, 70...Tightening Placement pass/fail display section.

Claims (1)

[Scope of Claims] 1. An input disk 21 that rotates in response to the rotation of a rotational drive source, a planetary cone 23 having a circumferential groove 23a in its neck that frictionally engages with the outer periphery of the input disk 21, and this planetary cone 2.
a cam disk 24 that is located concentrically with the input disk 21 and frictionally engages with the flat surface 23b on the back side of the input disk 21;
and a speed change ring 25 held by an arm 32 so as to be able to slide along the conical surface 23c while rotating while frictionally engaging with the conical surface 23c of the planetary cone 23; A transmission mechanism is constituted by a spring 31 that urges the transmission link 25 in the direction of standing upright, and is configured to receive a reaction force applied to the transmission link 25 due to the load torque related to the driver bit. The forward rotation voltage supply section 43 and the reverse rotation voltage supply section 44 which supplies a voltage lower than the forward rotation voltage are connected through the first detection means 47 and A second detection means 50 is provided for detecting that the detected value has reached the set value A, and the output of the second detection means 50 operates the switching means 45 to switch between the rotational drive source and the normal rotation voltage supply section 43. After cutting off the rotational drive source, the rotational drive source and the reverse voltage supply section 44 are connected, and by reversing the rotational drive source, the speed change ring 25 is moved from the low speed side to the high speed side along the planetary cone 23. A control device for an automatic screw tightening machine, characterized in that the load applied to the driver bit is reduced by returning the screwdriver bit to the original state. 2. The control device for an automatic screw tightening machine according to claim 1, wherein the switching means 45 supplies the reverse voltage of the reverse voltage supply section 44 to the rotational drive source for a predetermined set time. 3. The automatic screw tightening according to claim 1, wherein the second detection means 50 detects the completion of screw tightening after a predetermined time after the detection value of the first detection means 47 reaches the set value A. Machine control device. 4. An input disk 21 that rotates in response to rotation of a rotational drive source, a planetary cone 23 having a circumferential groove 23a in its neck that frictionally engages with the outer periphery of the input disk 21, and this planetary cone 2.
a cam disk 24 that is located concentrically with the input disk 21 and frictionally engages with the flat surface 23b on the back side of the input disk 21;
and a speed change ring 25 held by an arm 32 so as to be able to slide along the conical surface 23c while rotating while frictionally engaging with the conical surface 23c of the planetary cone 23; A transmission mechanism is constituted by a spring 31 that urges the transmission ring 25 in the direction of standing upright, and is configured to receive a reaction force applied to the transmission ring 25 due to the load torque related to the driver bit. The forward rotation voltage supply section 43 and the reverse rotation voltage supply section 44 which supplies a voltage lower than the forward rotation voltage are connected through the first detection means 47 and A second detection means 50 is provided for detecting that the detected value has reached the set value A, and the output of the second detection means 50 operates the switching means 45 to switch between the rotational drive source and the normal rotation voltage supply section 43. A third detection means 55 is provided to detect the stoppage of the rotational drive source, and upon receiving an output signal of the third detection means 55, the rotational drive source and the reverse voltage supply section 44 are connected. By supplying a reversing voltage to the rotational drive source and reversing the rotational drive source, the speed change ring 25
A control device for an automatic screw tightening machine, characterized in that the load applied to the driver bit is reduced by returning the screwdriver bit from a low speed side to a high speed side along a planetary cone 23.