JPH0428494B2 - - 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-X 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 position and pitch is approximately 2 mm, even if the workpiece is fixed on a pallet and supplied, the relative positional relationship with the screw tightening machine will deviate significantly, so the screw tightening data will not be accurate. screws cannot be tightened due to
It had the disadvantage of not being able to respond immediately to automated production systems.

In order to solve the above conventional problems, the present inventors have already proposed a numerically controlled screw tightening machine having a function of correcting screw tightening position deviation.

FIG. 2 is a block diagram of a numerically controlled screw tightening machine already proposed by the present inventors. Also the third
The figure is a schematic perspective view of the present numerically controlled screw tightening machine.
In FIG. 2, this numerically controlled screw tightening machine includes a conventional numerically controlled screw tightening machine, a hole position detection section 26 that detects the screw hole position of a workpiece using an ultrasonic wave transmitting/receiving element 53, and the numerically controlled screw tightening machine described above. The hole position detection section 26 uses information from the central processing section 13 of the
Detection start signal output unit 2 that outputs a detection start signal to
4 and a detection completion signal input section 25 that provides information for selecting a specific program to the central processing section 15 based on the output signal from the hole position detection section 26.
The hole position detection unit 26 accurately detects the screw hole position of the target workpiece.
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 deviates significantly, the screw tightening position deviation can be corrected and the screw tightening can be carried out independently.

On the other hand, the numerically controlled screw tightening machine with the above configuration has a third
As shown in the figure, the center position of the electric screwdriver 21 and the center position of the beam of the ultrasonic transceiver element 53 are offset, and it is desired to simplify the operation of inputting the amount of offset.

OBJECTS OF THE INVENTION The present invention eliminates all of the above-mentioned conventional drawbacks, and provides an apparatus that allows the screw tightening position and the offset amount of the ultrasonic wave transmitting/receiving element to be input simply and with high precision.

Composition of the Invention The numerically controlled screw tightening machine of the present invention includes a table that can be moved and positioned within a predetermined range, a screw tightening machine body that is attached to the table and tightens screws on a workpiece, and an ultrasonic wave transmitting/receiving element arranged with an offset of
The hole position detection unit includes a control device that controls the drive of the table and the screw tightening machine body, and a hole position detection unit that outputs a signal when the center position of the hole is detected using the ultrasonic wave transceiver element. When a signal is output from It has the feature that input can be performed easily and with high precision.

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

The configuration diagram of the numerically controlled screw tightening machine in this embodiment is the same as that shown in FIG. 2, and the details of the configuration will be explained below.

In FIG. 2, reference numeral 13 denotes a control device, which is composed of a central processing section 15, a program storage section 14, a first 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. has been done. 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. Further, an ultrasonic transmitting/receiving element (hereinafter referred to as an ultrasonic transducer) 53 of the hole position detecting section 26 is fixedly arranged near the head section 20 as shown in FIG. It is configured to be able to operate on two axes, X and Y.

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 performs detection and arithmetic processing of reflected signal strength according to a program input and stored in advance from the FDD 60.

Next, regarding the input operation of the offset amount between the center position of the beam of the ultrasonic transducer 53 of the numerically controlled screw tightening machine configured as described above and the screw tightening position (center position of the electric screwdriver), as shown in FIG. The transmitting/receiving wave surface of the ultrasonic transducer 53 is arranged to face the workpiece 27 in a plane, and a case will be described in which parallel scanning is performed while keeping a constant distance from the workpiece 27.

The offset amount is input in accordance with the program procedure 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 X and Y coordinates of the hole 28 on the workpiece 27 at the reference position are input. The input is to lower the electric screwdriver 21 (not shown) and input the X, Y coordinates (X ₀ , Y 0 ) of the XY table 19 when the center position of the electric screwdriver 21 and the center position of the hole 28 on the workpiece ₂₇ match to the control device. This is done by memorizing.

Next, in step 2, an offset amount is tentatively input.

The attachment of the ultrasonic transducer 53 to the screw tightening position (the center position of the electric screwdriver) is performed at the center position 6 of the ultrasonic beam transmitted and received from the ultrasonic transducer 53, as shown in FIGS.
2 and the screw tightening position 63 are almost the same in the X-axis direction, and are offset by the length L in the Y-axis direction, so the control device knows that the offset amount in the X-axis direction = 0 and the offset amount in the Y-axis direction. Input =L and memorize it.

Next, in steps 3, 4, 5, and 6, detailed offset amounts in the X-axis direction are input.

First, in step 3, the control device 13 is used to
The Y table 19 is driven, and the ultrasonic transducer 53 is set to the fourth position in consideration of the above-mentioned temporary offset amount.
When moving to the position shown in Figure a (position in the X-axis direction outside the range where the hole 28 on the workpiece 27 causes positional deviation), the ICU
59 receives the control signal from the detection start signal output section 24, it operates the oscillator 55, and the ultrasonic transducer 53 transmits waves at a predetermined frequency toward the ultrasonic workpiece 27, and at the same time, the A/D converter 5
7. Operate the memory 58 and store the reflected signal from the workpiece 27 in the memory 58. In FIG. 4a, 62 indicates the center position of the ultrasonic beam transmitted from the ultrasonic transducer 53. In FIG. Also the 7th
The figure shows a reflected signal from the workpiece 27 stored in the memory 58.

Next, in step 4, 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 5, 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 _P1 obtained is smaller than the previous value, the process returns to step 3 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 is output. Wait for Step 3,
Repeat step 4.

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. From this, the center position of the hole 28 in the X-axis direction can be detected.

At this time, the control device 13 stores the X and Y coordinates (X ₁ , Y ₁ ) of the X-Y table 19 at the time when the control signal was output from the ICU 59, and from this it calculates the detailed offset amount X _s in the X-axis direction. was calculated by X _s =X ₀ to _{X 1} (1), and was able to be converted into a temporary offset amount and stored in the program storage unit 14. Although a detailed explanation will be omitted, the detailed offset amount _Y0 in the Y-axis direction was similarly calculated by steps 7 to 10, and was able to be stored in the program storage section 14.

Effects of the Invention As described above, the numerically controlled screw tightening machine of the present invention allows the screw tightening position to match the center position of the hole on the workpiece when inputting the offset amount between the screw tightening position and the beam center of the ultrasonic wave transmitting/receiving element. X when doing
- Since the offset amount is stored by comparing and calculating the coordinates of the Y table and the coordinates of the X-Y table when the signal is output from the hole position detection section, it is possible to input the offset easily and with high precision. Its practical effects are significant.

[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 already proposed by the present inventors, FIG. 3 is a schematic perspective view of the same screw tightening machine, and FIGS. 4 a and b are hole position detection in an embodiment of the present invention. A schematic diagram of the main parts of the head section showing
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 for inputting an offset amount, FIG. 7 is a diagram showing operation waveforms for hole position detection, and FIG. FIG. 3 is a diagram arranging operation waveforms of a hole position detection section. 19...table, 23...screw tightening machine body,
53... Ultrasonic transducer, 13... Control device, 26... Hole position detection unit, 27... Work.

Claims (1)

[Claims] 1. A table that can be moved and positioned within a predetermined range, a screw tightening machine body that is attached to the table and tightens screws on a workpiece, and a screw tightening machine that is arranged with a predetermined offset amount from the screw tightening machine body and that tightens screws on a workpiece. an ultrasonic transceiver element that detects the center position of the hole on the workpiece; a control device that stores positional information of the hole on the workpiece at the screw tightening position and controls the driving of the table and the screw tightening machine body; and a hole position detection section that outputs a signal when the center position of the hole is detected using an ultrasonic transceiver element, and the control device detects the coordinates of the table when the signal is output from the hole position detection section. A numerically controlled screw tightening machine configured to detect the offset amount, compare it with position information at the screw tightening position of the hole, and calculate and store the offset amount.