JPH0117818B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a numerically controlled screw tightening machine that detects the screw hole position of a workpiece using ultrasonic waves, corrects screw tightening position deviation, 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. The screw hole of the target workpiece, which 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 has a simple configuration, and uses numerical control that detects the relative positional relationship with the screw hole of the workpiece, corrects the screw tightening position deviation, and tightens the screw. The purpose is to provide screw tightening machines.

Composition of the Invention The present invention comprises a conventionally configured numerically controlled screw tightening machine, a hole position detection unit that detects the screw hole position of a workpiece using an ultrasonic wave transmitting/receiving element, and a central processing unit of the numerically controlled screw tightening machine. a detection start signal output section that outputs a detection start signal to the hole position detection section based on the information; and a detection completion signal that provides the central processing section with information for selecting a specific program based on the output signal from the hole position detection section. The screw hole position of the target workpiece is accurately detected by the hole position detection unit, so that the numerical control screw tightening machine of the present invention and the relative positional relationship between the screw hole of the target workpiece are largely deviated. This method also has the unique effect of being able to correct screw tightening position deviations and perform screw tightening independently, and being compatible with an automated production system.

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, a first numerical control unit 16, a second numerical control unit 17, a detection start signal output unit 24, and a detection completion signal input unit 25. It is configured. Reference numeral 23 denotes the main body of the screw tightening machine, which is composed of a table drive section 18, an X-Y table 19, a head section 20, an electric screwdriver 21, and a screw supply section 22. Also, the hole position detection section 26
The ultrasonic transducer 53 is fixedly arranged near the head section 20 as shown in FIG.
It is configured to be able to operate in two axes, X and Y, in synchronization with the operation of the Y table 19.

Furthermore, the attachment of the ultrasonic transducer 53 to the screw tightening position (the center position of the electric screwdriver) corresponds to the center position 62 of the ultrasonic beam transmitted and received from the ultrasonic transducer 53, as shown in FIGS. 4a and 4b. The screw tightening positions 63 coincide in the X-axis direction, and are offset by a length L in the Y-axis direction.

Next, the hole position detection section 26 including the ultrasonic transducer 28 will be explained. FIG. 5 is a system diagram showing a schematic configuration of the hole position detection section 26 of this embodiment. As shown in FIG. 4, the ultrasonic transducer 53 uses an oscillator 55 to transmit ultrasonic waves of a predetermined frequency toward the hole 28 of the workpiece 27, and also receives reflected signals from the workpiece 27. . The received signal output from the ultrasonic transducer 53 passes through a received signal amplifier 56, is converted into a digital value by an analog-to-digital converter 57 (hereinafter referred to as an A/D converter), and is stored in a memory 58. be done. Furthermore, a data processing control device 51 is provided, which includes an interface control unit 59 (hereinafter referred to as ICU) and a floppy disk drive device 60 (hereinafter referred to as ICU).
It's called FDD. ) and small electronic computer 61 (hereinafter
It is called CPU. ). ICU29 is FDD
60 and CPU 61, and outputs a control signal for operating the oscillator 55, pre-processes input data transferred from the memory 58, and outputs a detection start signal from the detection start signal output section 24 of the numerical control device 1 described above. It inputs a control signal and outputs the control signal to the detection completion signal input section 25 of the numerical control device 1 described above. The CPU 61 detects and calculates the reflected signal strength according to a program input and stored in advance from the FDD 60.

Next, the operation of the hole position detection section 26 configured as described above will be explained. FIG. 4 is a side view of the hole position detection according to this embodiment, and the transmitting and receiving wave surface of the ultrasonic transducer 53 shown in FIG. A case will be described in which the center position of the hole in the X-axis direction is detected by performing parallel scanning while maintaining a distance.

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 53 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 transmit the reflected signal from the work 27 to the memory 58. to be memorized. In FIG. 4a, 62 indicates the center position of the ultrasonic beam transmitted from the ultrasonic transducer 53. 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 obtained reflected signal strength P ₁
Determine whether is a local minimum value. Judgment is made by comparing the previous value, and the reflected signal strength P ₁ obtained with respect to the previous value
If the value 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 control signal from the detection start signal output section 24 described above is output. Wait for Step 2,
Repeat step 3.

FIG. 8 shows the reflected signal intensity P ₁ from the workpiece 27 when the ultrasonic transducer 53 is scanned parallel to the
3, and the reflected signal strength _P1 is plotted on the vertical axis, and the point 64 where the reflected signal strength _P1 shows the minimum value corresponds to the center position of the hole 28 in the workpiece 27 in the X-axis direction. and from now on hole 28
The center position in the X-axis direction can be detected.
In addition, in this example, point 6 where the value of the previous value comparison becomes large
5 is detected, but the position information can be easily corrected by using the central processing unit 15 described above, and the center position of the hole 28 of the workpiece 27 in the X-axis direction can be detected. Although detailed explanation is omitted, hole 28
The center position in the Y-axis direction can also be detected in the same way.

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 fret chart 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 wave transmitted and received by the ultrasonic transducer 53 outside the range 65 where the hole 28 on the workpiece 27 causes positional deviation when the workpiece 27 comes to the front of the screw tightening body 23 by the conveyor line 64. This refers to the position where the center position 62 of the beam is located, and is input into the program storage unit 14 in advance. 66 is the intersection point between the center position 62 of the ultrasonic beam and the workpiece 27 at this time, 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 unit 26. Upon receiving the command, the detection start signal output section 24 outputs the ICU 59 of the hole position detection section 26.
When a control signal is issued to the workpiece 27, the ultrasonic transducer 53 transmits and receives ultrasonic waves to and from the workpiece 27 to detect the center position of the hole 28 in the X-axis direction, and the ICU 59 outputs the aforementioned detection completion signal. A control signal is output to the input section 25. The detection completion signal input section receives this control signal and sends it to the central processing section 15. The central processing section 15 corrects the position information of the X-Y table 19 according to a pre-stored program, Detects the center position in the axial 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 program storage unit 14 is preliminarily stored so that the center position of the ultrasonic beam transmitted and received by the ultrasonic transducer 53 is located outside the ultrasonic transducer 53. 67 is the intersection of the center position 62 of the ultrasonic beam and the workpiece 27 at this time. From now on, the X-Y table 19 will be set to this point 67.
Move by a predetermined amount in the Y-axis direction based on . Next, in the same way as step 1, make the hole 28 of the workpiece 27
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. Also, the second
The numerical control section 17 controls the electric screwdriver 21 at the same time as the head section 20 is lowered, and causes the screw to be tightened until a predetermined torque value is reached.When the predetermined torque value is reached, the screw tightening completion signal is processed by central processing. At the same time, the electric screwdriver 21 stops rotating.The 15 sends a screw tightening completion command to the first numerical control section 16, and the 16 receives it, raises the head section 20, and moves the electric screwdriver 21 to the workpiece 27. keep away from

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

As described above, according to this embodiment, the ultrasonic transducer 5 is located at a predetermined position near the head 20.
3 is roughly positioned outside the range where the hole 28 of the workpiece 27 causes positional deviation, and the head 20 is moved to operate the hole position detection section 26 using the detection start signal output section 24, and the control signal is received at the detection completion signal input section. After detecting the exact position of the hole 28 (screw tightening position), move the X-Y table 19 to the detected screw tightening position.
The workpiece 27 fed by the roller conveyor 64 can be tightened by moving the workpiece 27.
Even if the relative positional relationship between the hole position and the screw tightening machine main body 23 deviated greatly, all screws could be tightened.

Effects of the Invention As described above, the present invention provides a numerically controlled screw tightening machine having a conventional configuration, a hole position detection section that detects the screw hole position of a workpiece using an ultrasonic wave transmitting/receiving element, and a center of the numerically controlled screw tightening machine described above. A detection start signal output section outputs a detection start signal to the hole position detection section based on information from the arithmetic processing section, and information for selecting a specific program based on the output signal from the hole position detection section is sent to the central processing section. The hole position detector accurately detects the screw hole position of the target workpiece, so the relative positional relationship between the numerically controlled screw tightening machine of the present invention and the screw hole of the target workpiece can be determined. Even if there is a large deviation, the screw tightening position deviation can be corrected and the screw tightening can be performed independently, and it can be immediately adapted to an automated production system, which has great practical effects.

[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 a hole position detection section according to an embodiment of the present invention, FIG. 6 is a schematic flowchart of hole position detection, and FIG.
Figure 8 is a diagram illustrating operation waveforms of hole position detection, Figure 8 is a diagram arranging operation waveforms of the hole position detection section, and Figure 9 is a schematic flowchart of screw tightening by a screw tightening machine in an embodiment of the present invention. , FIG. 10 is a perspective view of the main part of the head section. 13... Numerical control unit, 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 section.

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. a processing unit; a screw hole center position detection unit that detects the center position of the screw hole in the workpiece by determining the minimum value of the reflected signal intensity of the ultrasonic beam emitted from the ultrasonic transceiver element to the workpiece; A detection start signal output unit outputs a detection start signal to the hole position detection unit based on information from the central processing unit, and a central processing unit processes information for executing a specific program using the output signal from the hole position detection unit. A numerically controlled screw tightening machine consisting of a detection completion signal input section and a detection completion signal input section.