JPH0117819B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a numerically controlled screw tightening machine that uses ultrasonic waves to detect the screw hole position of a workpiece, corrects screw tightening position deviations, and independently tightens screws. It is related to.

Configuration of conventional example and its problems As shown in FIG. It consists of a numerical control device 1 having a control section 7, a screw tightening machine main body 2 consisting of a table drive section 8, an X-Y table 9, a head section 10, an electric screwdriver 11, and a screw supply section 12. A screw hole in a target workpiece that is accurately positioned and in a predetermined relative positional relationship with the screw tightening machine 2 is tightened using screw tightening data. However, in the above configuration, the work must be accurately positioned at a predetermined position on the conveyor line, and the conveyor requires a modular conveyor that can perform highly accurate positioning, rather than a conventional roller conveyor. It had the disadvantage of being expensive. Furthermore, when tightening screws on many types of workpieces, the usual method is to manufacture a special pallet for each workpiece, position the workpieces on the pallet, and then feed the pallets using a modular conveyor. It has the disadvantage of being expensive. Furthermore, for workpieces such as large structural parts where the machining accuracy of screw hole positions and pitches is approximately 2 mm, even if they are fixed on a pallet and supplied, the relative positional relationship with the screw tightening machine will be greatly deviated, so the screw tightening data will not be accurate. It had the disadvantage that screws could not be tightened by hand, and it could not be quickly adapted to an automated production system.

Purpose of the Invention The present invention solves all of the above-mentioned conventional drawbacks, and is a numerically controlled screw tightening system that has a simple configuration and can correct screw tightening position deviations at the same time as detecting the relative positional relationship with the screw hole of the workpiece. The purpose is to supply machines.

Composition of the Invention The present invention provides a numerically controlled screw tightening machine equipped with an electric screwdriver having a conventional configuration, an ultrasonic wave transmitting/receiving element arranged so that its axis coincides with that of the electric driver on the work surface, and the ultrasonic a hole position detection circuit that detects the screw hole position of the workpiece using a wave transmitting/receiving element; a detection start signal output unit that outputs a detection start signal to the hole position detection circuit based on information from the central processing unit; and the hole It consists of a detection completion signal input section that supplies information for executing a specific program to the central processing unit using the output signal from the position detection circuit, and simultaneously detects the hole position of the workpiece using the hole position detection circuit Since the screw tightening position deviation can be corrected, there is no need to correct the screw tightening position deviation even if the relative positional relationship between the numerically controlled screw tightening machine of the present invention and the screw hole of the target workpiece is greatly deviated, and screw tightening can be performed quickly and with high positional accuracy. It has the unique effect of being able to perform tightening and being compatible with automated production systems.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of a numerically controlled screw tightening machine in an embodiment of the present invention. Further, FIG. 3 is a perspective view of a numerically controlled screw tightening machine in an embodiment of the present invention.

In FIG. 2, 13 is a numerical control device, which includes a central processing unit 15, a program storage unit 14, and a first
It is composed of a numerical control section 16, a second numerical control section 17, a detection start signal output section 24, and a detection completion signal input section 25. 23 is a screw tightening machine main body, which includes a table drive section 18, an X-Y table 19, a head section 20, an electric screwdriver 21, and a screw supply section 2.
It is composed of 2. Further, ultrasonic transducers 53 and 54 for detecting hole positions are fixedly arranged orthogonally near the head section 20 as shown in FIG.
It has a configuration that allows it to operate on two axes, Y. The ultrasonic transducer 53 is used exclusively for detecting the center position of the hole 28 in the Y-axis direction, and the ultrasonic transducer 54 is used exclusively for detecting the center position of the hole 28 in the X-axis direction.

Furthermore, FIGS. 4a and 4b show the mounting positions of the ultrasonic transducers 53 and 54 relative to the screw tightening position (center position of the electric screwdriver), and the axes 63 and 64 of the ultrasonic transducers 53 and 54 and the screw The ultrasonic transducers 53 and 54 are mounted inclined to the surface of the workpiece 27 so that the center 62 of the tightening position (the axis of the electric screwdriver) coincides with the surface of the workpiece 27.

Next, the ultrasonic transducers 53 and 54 and the hole position detection circuit 26 will be explained. FIG. 5 is a system diagram schematically showing the hole position detection circuit 26 of this embodiment. As shown in FIG. 4, the ultrasonic transducers 53 and 54 transmit ultrasonic waves of a predetermined frequency toward the hole 28 of the workpiece 27 using an oscillator 55, and receive reflected signals from the workpiece 27. ing.

Note that the oscillator 55 is the ultrasonic transducer 5
The configuration is such that it is possible to transmit and receive ultrasonic waves by selecting either one of 3 and 54. ultrasonic transducer 53,
The received signal outputted by 54 passes through a received signal amplifier 56 and is then sent to an analog-to-digital converter 57 (hereinafter referred to as A/
It is called a D converter. ) is converted into a digital value and stored in the memory 58. Furthermore, a data processing control device 51 is provided, which includes an interface control unit 59 (hereinafter referred to as ICU), a floppy disk drive device 60 (hereinafter referred to as FDD), and a small electronic computer 61 (hereinafter referred to as FDD). CPU). The ICU 59 is connected to the FDD 60 and the CPU 61, and outputs a control signal for operating the oscillator 55 described above, pre-processes input data transferred from the memory 58, and outputs the detection start signal 24 of the numerical control unit 1 described above. input of control signals from,
Detection completion signal input section 25 of the numerical control device 1 described above
Outputs control signals to. With CPU61,
Detection and arithmetic processing of reflected signal strength is performed according to a program input and stored in advance from the FDD 60.

Next, the operations of the ultrasonic transducer 54 and hole position detection circuit 26 configured as described above will be explained using FIG. 4a. The wave transmitting/receiving surface of the ultrasonic transducer 54 shown in FIG.
The center position in the X-axis direction is detected.

Hole position detection is performed according to the procedure of the hole position detection program shown in the flowchart of FIG. 6, which is input and stored in advance from the FDD 60.

In the flowchart of FIG. 6, first in step 1, the ultrasonic transducer 54 shown in FIG.
When the ICU 59 receives the control signal from the detection start signal output section 24, the oscillator 5
At the same time, the A/D converter 57 and the memory 58 are operated to store the reflected signal from the work 27 in the memory. 58
to be memorized. In FIG. 4a, 62 indicates the center position of the ultrasonic beam transmitted from the ultrasonic transducer 54. In FIG. Further, FIG. 7 shows the reflected signal from the workpiece 27 stored in the memory 58.

Next, in step 2, the reflected signal stored in the memory 58 is transferred to the CPU 61 via the ICU 59.
The CPU 61 detects the reflected signal strength P ₁ according to a program input and stored in advance from the FDD 60 .

Next, in step 3, the reflected signal strength obtained is
Determine whether P ₁ is a local minimum value. Judgment is made by comparing the previous value, and the reflected signal strength obtained against the previous value
If P ₁ is large, the ICU 59 outputs a control signal to the detection completion signal input section 25 described above. If the reflected signal strength P ₁ obtained is smaller than the previous value, the process returns to step 1 and the ultrasonic transducer 53 is moved by a predetermined amount in the direction of arrow A and the detection start signal output unit 24 is With the control signal, repeat steps 2 and 3. Figure 8 shows the workpiece 27 when the ultrasonic transducer 54 is scanned parallel to the X-axis direction.
The horizontal axis represents the parallel scanning amount of the ultrasonic transducer 54, and the vertical axis represents the reflected signal strength _P1.
It is plotted by taking the reflected signal strength.
The point 68 where P ₁ shows the minimum value is the hole 28 of the workpiece 27
The center position of the hole 28 in the X-axis direction can be detected from this. In this embodiment, the point 69 where the value of the previous value comparison becomes large is detected.
5, the position information can be easily corrected and the center position of the hole 28 of the workpiece 27 in the X-axis direction can be detected. Although detailed explanation will be omitted, the center position of the hole 28 in the Y-axis direction can also be detected in the same manner.

The operation of the numerically controlled screw tightening machine configured as described above will be explained below.

Hole position detection and screw tightening are performed according to the procedure stored in the program storage section 14 shown in FIG. FIG. 10 is a perspective view of FIG. 4 showing hole position detection. In FIG. 10, reference numeral 65 indicates a range where the hole 28 of the workpiece 27 fed by the roller conveyor is displaced.

In the flowchart of FIG. 9, first, in step 1, the center position of the hole 28 in the X-axis direction is detected.
The central processing unit 15 issues a command to the first numerical control unit 16 to move the X-Y table 19 to a predetermined position. The first numerical control unit 16 receives the command.
controls the table drive unit 18 and moves the X-Y table 1
9 is moved to the called position data to perform positioning. The above-mentioned position data is the ultrasonic beam transmitted and received by the ultrasonic transducer 54 outside the range 65 where the hole 28 on the workpiece 27 causes positional deviation when the workpiece 27 is brought to the front of the screw tightening body by the conveyor line 64. This indicates the position where the center position 62 of is located, and is input into the program storage section 14 in advance. 66 is the center position 6 of the ultrasonic beam at this time
2 and the work 27, and thereafter the X-Y table 19 moves by a predetermined amount in the X-axis direction with this point as a reference.

Next, the central processing unit 15 issues a command to the detection start signal output unit 24 to output a control signal to the hole position detection circuit 26. Upon receiving the command, the detection start signal output section 24 outputs a control signal to the ICU 59 of the hole position detection circuit 26, and as described above, the ultrasonic transducer 54 transmits and receives ultrasonic waves to and from the workpiece 27 to detect the hole 28. Detect the center position in the X-axis direction of
The ICU 59 outputs a control signal to the detection completion signal input section 25 described above. A detection completion signal is received from this control and sent to the central processing unit 15, which corrects the position information according to a pre-stored program and detects the center position of the workpiece 27 in the X-axis direction.

Next, in step 2, the center position of the hole 28 in the Y-axis direction is detected. The central processing unit 15 positions the X-Y table 19 at a predetermined position in the same manner as in step 1 described above. X at this predetermined position
The axis is the one detected in step 1 above, and the Y axis is the range 6 where the hole 28 of the workpiece 27 causes positional deviation.
The center position of the ultrasonic beam transmitted and received by the ultrasonic transducer 53 is set to be outside of the ultrasonic transducer 53. 6
7 is the intersection of the center position 62 of the ultrasonic beam and the workpiece 27 at this time. From now on, X-Y table 19
is moved by a predetermined amount in the Y-axis direction based on this point 67. Next, do the same as step 1, and then
Detects the center position in the axial direction.

Next, in step 3, the central processing unit 15 sends a command to the first numerical control unit 16 to move the X-Y table 19 to the position of the hole 28 (screw tightening position) detected in steps 1 and 2, and a second After the movement of the table is completed, a command to drive the electric screwdriver is sent to the numerical control unit 17. The first person to receive orders
The numerical control section 16 controls the table driving section 18,
The X-Y table 19 is moved to the called screw tightening position data to perform positioning, and after the positioning is completed, the head portion 20 is lowered and the electric screwdriver 21 is brought closer to the workpiece. Further, the second numerical control section 17 controls the electric screwdriver 21 at the same time as the head section 20 is lowered to perform screw tightening until a predetermined torque value is reached, and when the predetermined torque value is reached, a screw tightening completion signal is sent. The central processing unit 15
At the same time, the rotation of the electric screwdriver 21 is stopped, and the screw tightening completion command 15 is sent to the first numerical control section 16, which receives it, raises the head section 20, and moves the electric screwdriver 21 away from the workpiece 27.

As described above, all the screw tightening of the work 27 is completed by repeating the screw tightening after detecting the hole position on the work 27.

As described above, according to this embodiment, the ultrasonic transducers 53 and 54, which are arranged at predetermined positions near the head 20 and inclined with respect to the surface of the workpiece 27, are arranged in a range where the hole 28 of the workpiece 27 causes positional deviation. After roughly positioning the hole 28, the head 20 is moved, the hole position detection circuit 26 is operated by the detection start signal output section 24, and the detection completion signal input section receives a control signal to determine the exact position of the hole 28 (screw tightening position). ) is detected and the wide X-Y table 1 moves to the screw tightening position at the same time.
All screws can be tightened even if the relative position of the hole position of the work 27 supplied by the roller conveyor 64 and the screw tightening machine main body 23 is significantly different from each other. I was able to do that. Furthermore, higher hole detection sensitivity could be obtained than in the case where the ultrasonic transducer was arranged parallel to the surface of the workpiece 27, and screw tightening could be performed with high positional accuracy.

Effects of the Invention As described above, the present invention provides a numerically controlled screw tightening machine equipped with an electric screwdriver having a conventional configuration, an ultrasonic wave transmitting/receiving element arranged so that the axis of the driver coincides with that of the work surface, and an ultrasonic a hole position detection circuit that detects the screw hole position of the workpiece using a wave transmitting/receiving element; a detection start signal output section that outputs a detection start signal to the hole position detection circuit based on information from the central processing section; It consists of a detection completion signal part that gives information to the central processing unit to execute a specific program based on the output from the hole position detection circuit. Since the tightening position deviation can be corrected, even if the relative positional relationship between the numerically controlled screw tightening machine of the present invention and the screw hole of the target workpiece is significantly deviated, there is no need to correct the screw tightening position deviation, and screw tightening can be performed quickly and with high positional accuracy. It can be easily adapted to automated production systems, and its practical effects are great.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional screw tightening machine, Figure 2
The figure is a block diagram of a screw tightening machine according to an embodiment of the present invention, FIG. 3 is a schematic perspective view of a screw tightening machine according to an embodiment of the present invention, and FIGS. 4 a and 4 b are head sections showing hole position detection, respectively. Fig. 5 is a block diagram of the hole position detection section, Fig. 6 is a schematic flowchart of hole position detection, Fig. 7 is a diagram showing operation waveforms of hole position detection, and Fig. 8 is a block diagram of the hole position detection section. FIG. 9 is a schematic flowchart of screw tightening in a screw tightening machine according to an embodiment of the present invention, and FIG. 10 is a perspective view of the main parts of the head section. 13... Numerical control device, 14... Program storage unit, 15... Central processing unit, 16... First numerical control unit, 17... Second numerical control unit, 24... Detection start signal output unit, 25 ...Detection completion signal input section, 26 ... Hole position detection section, 23 ... Screw tightening machine main body, 20 ... Head section, 21 ... Electric screwdriver, 18 ... Table drive section, 19 ... X-Y table , 22... Screw supply unit, 53, 54... Ultrasonic transducer.

Claims (1)

[Claims] 1 A table supported movably within a predetermined range, a table drive unit that drives and positions the table, a numerical control unit that controls the table drive unit, and an electric screwdriver that tightens screws to the workpiece. a screw tightening machine body, a program storage section that stores a program in which position information is set, and a central processing unit that selects a specific program from the storage section and controls the numerical control section according to this program to execute the program. Ultrasonic waves emitted to the workpiece from a processing unit and two ultrasonic wave transmitting/receiving elements arranged at an angle with respect to the workpiece surface so that their axes coincide with the axis of the electric screwdriver on the workpiece surface. a screw hole center position detection unit that detects the center position of the screw hole in the workpiece by finding the minimum value of the reflected signal intensity of the beam; and a detection start signal that outputs a detection start signal to the position detection circuit based on information from the central processing unit. A numerically controlled screw tightening machine comprising an output section and a detection completion signal input section that supplies information for executing a specific program to a central processing section using an output signal from the hole position detection circuit.