JPS6359816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing collisions in machine tools, particularly collisions between moving bodies such as tools or tool rests and fixed bodies such as spindle rests and tailstocks.

As shown in Fig. 1, a machine tool such as an NC (numerical control) lathe has a workpiece 2 mounted on a chuck 1 held by a tailstock 3, and a cutting tool 6 mounted on a turret 5 of a tool post 4. Workpiece 2 is now machined. During machining, the tool bar 6 is moved according to a predetermined operation program, so problems such as collisions do not occur. 4 may collide with the workpiece 2 or the tailstock 3, damaging the workpiece 2 or damaging the cutting tool 6. For this reason, conventional methods have been to prevent collisions with tools, etc. by using insulation from the drive system using a shear pin mechanism in the servo feed system, a chuck barrier using NC software, and a detection mechanism using inductance. However, with these conventional detection mechanisms and devices, it is necessary to adjust the range when the shape of the tool or workpiece changes, and it is said that it is impossible to detect the distance at which the servo system can suddenly stop. There were flaws. It is therefore an object of the invention to provide a collision prevention device that does not have these drawbacks.

This invention will be explained below.

In this invention, as shown in FIGS. 2 and 3,
A TV camera 10 that moves in conjunction with the tool rest 4 is attached, and a video signal VS near the cutting edge of the cutting tool 6 is processed by a graphic processing device 20, and the servo control system is controlled by the stop signal DT. . In addition, in Fig. 3, 7 is the headstock, and the tool rest 4
A middle stand 8 that is moved by a feed screw 31 connected to a servo motor 30 is provided at the bottom of the servo motor 30 .

Thus, the command from the tape 32 is input to the function generator 34 stored in the command value register 33, and the instantaneous command value P from the function generator 34 and the position detector 35 indicating the current position of the byte 6 are input. The current position A is compared with the comparator 36, and the deviation
The ER is converted into an analog signal by the DA converter 37 and sent to the servo motor 30 via the servo drive circuit 38.
It is becoming more and more like driving. The graphic processing device 20 also includes a video signal binarization circuit 21 that inputs the video signal VS from the TV camera 10 and converts it into a binary signal of "1" and "0" corresponding to black and white of the image; A sampling circuit 22 that samples the binary signal from the video signal binarization circuit 21 at a predetermined timing, and counters 23 and 2 that count the sampling data SD from this sampling circuit 22.
4, a memory circuit 25 that stores the count value of the counter 23, and a memory circuit 25 that stores the value stored in the memory circuit 25 and the count value of the counter 23.
4, and outputs a stop signal DT when the values are different. Note that the counter 23 is operated to count by the set signal TS generated when the cutting tool 6 is attached to the turret 5, and the counter 24 is operated to count by the fast-forward signal EM generated when the fast-forward mode is operated. It's getting old.

In such a configuration, the TV camera 10 is installed so as to display the vicinity of the cutting edge of the cutting tool 6, and the image thereof is, for example, as shown in section 6A in FIG. 5. Note that 6A shows an image of the tip of the cutting tool 6. However, TV camera 10
The video signal VS is input to the graphic processing device 20 and processed. First, the operation of the servo system will be explained. The operation command for the servo system is given by a tape 32, which is once stored in a command value register 33, then inputted to a function generator 34, and given to a comparator 36 as a predetermined instantaneous command value P. and,
The current position A from the position detector 35 is input to the other side of the comparator 36, and its deviation (P-A) is converted into an analog signal by the DA converter 37, which drives the servo motor 30 via the servo drive circuit 38. Drive.
In this way, the middle platform 8 is moved by the feed screw 31, the current position A of the position detector 35 also changes, and the deviation
The ER is controlled to be 0. Therefore, the intermediate platform 8, ie, the cutting tool 6, is moved according to the instructions on the tape 32, thereby processing the workpiece 2. Here, a stop signal DT is output from the graphic processing device 20, and this is transmitted to the servo drive circuit 3.
8, the drive of the servo motor 30 is stopped. It should be noted that while the cutting tool 6 moves in conjunction with the movement of the middle platform 8, the TV camera 10 also moves, but since the TV camera 10 is fixed to the table 8, its image position is the same.
In other words, it is near the cutting edge of the cutting tool 6.

Next, the operation of the graphic processing device 20 will be explained.
The video signal VS from the TV camera 10 is the video signal VS
A video signal binarization circuit 21 binarizes the black portion of the image into a binary signal of “1” and the white portion of the image as “0”. Therefore, in the case of an image as shown in FIG. 5, the area 6A is converted to "1" and the other areas are converted to "0". Then, this binary signal is sampled at a predetermined timing by the sampling circuit 22, and this sampling data SD is sent to the counter 2.
3 and 24. In this state, since the set signal TS is input, the counter 23 performs a counting operation, and the counter 23 counts all "1" signals from the sampling data SD. In other words, the counter 23 counts the area of the image area 6A in digital quantities. The count value of the counter 23 is stored in the storage circuit 25, and the comparison circuit 26
is input as reference area data. Note that during machining with the cutting tool 6, the fast forward signal EM is not generated, so the counter 24 does not perform a counting operation.
Therefore, the stop signal DT is not outputted from the comparison circuit 26.

When the fast-forward mode is entered by an operation by an operator or the like, the counter 24 enters a counting operation by the fast-forward signal EM, and the sampling circuit 22
The sampling data SD from is calculated by the counter 24, and this count value is input to the comparison circuit 26. Comparison circuit 26 compares the reference area data from storage circuit 25 and the count value of counter 24, and outputs a stop signal DT only when the values differ.
Therefore, if there is no change in the area of the image from the state in which the TV camera 10 was initially set, the two inputs of the comparator circuit 26 will match, so the stop signal DT will not be output, and as shown in FIG. As shown in FIG. 2, when an obstacle image 11 such as a workpiece appears near the cutting tool 6, the area of the black area in the image changes and the count value of the counter 24 also increases. Thus, counter 2
Since the count value of 4 no longer matches the value stored in the memory circuit 25, a stop signal DT is output from the comparator circuit 26, and the servo system suddenly stops, preventing a collision with the obstacle that appeared in the image of bite 6. Prevented. By the way, the reason why only the vicinity of the part-time job can be shown on the TV camera 10 as shown in part 6A of FIG. 5 will be described. As is clear from FIG. 3, the vicinity of the cutting edge of the cutting tool 6 and the workpiece 2 are approximately equidistant from each other when viewed from the TV camera 10, but on the other hand, the table, bed guide, etc. (not shown) are This is because the image is far away and can be ignored. In other words, so that only the vicinity of the cutting edge of the cutting tool 6 and the image of the workpiece 2 around it are clearly shown on the TV camera,
This involves adjusting the placement of the TV camera, focal length settings, etc. Further, paint or the like may be used as necessary to further reduce the difference in brightness between the clearly imaged portion and the less clearly imaged portion. In this case, it is of course possible to make the parts that are clearly imaged black and the parts that are not clearly imaged white. As a result, the brightness of the image captured by the TV camera is high, and the low brightness of the image is weak.

Therefore, the strength or weakness of the luminous intensity is converted into an analog voltage via a photoelectric conversion means, and compared with a preset threshold voltage. ), the other imaged portions below the threshold are converted into digital signals of logic “0” (or “1”) by the binarization circuit 21, and are processed by the byte 6.
Pattern recognition is performed on the image of the workpiece 2 in the vicinity of the cutting edge and its surroundings. (Note that there is a pattern recognition device using this type of ITV camera and binarization circuit in Japanese Patent Publication No. 53-7112.) Furthermore, FIG. 6 shows an example of an image according to another embodiment of the present invention. The image area corresponds to a composite image of the tool rest and the cutting tool, and the area separated by a certain distance L from the edge thereof is defined as the detection area RA. Therefore, when the area of the image 12 is used as a reference area and the image area changes such as when the image 3A of the tailstock 3 appears in the detection area RA, the same stop signal DT as described above is output and the servo system is activated. make it stop. This also makes it possible to prevent collisions between the moving body and the fixed body. Furthermore, Figure 7 shows an example of a circuit that realizes this.
The video signal VS from 0 is input to the area setting circuit 27 in the graphic processing device 20A, and the detection area RA as described above is set here. Therefore, in this case, the TV camera 10 needs to be installed so as to display the entire cutting tool and tool rest. Note that the area signal from the area setting circuit 27 is input to the video signal binarization circuit 21, and the following processing is the same as in the above case.

As described above, according to the present invention, the reference image area is determined by a TV camera fixed to a moving object, and the servo system is stopped depending on the change in the image area, so that the servo system is stopped during fast forwarding. Irregular collisions can be prevented. Furthermore, even if the shape of the tool or workpiece changes, the reference image area can be automatically set, which is superior in terms of operation and maintenance.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic configuration of the vicinity of the processing section of a machine tool, Fig. 2 is a diagram showing the arrangement of a TV camera according to the present invention, and Fig. 3 is a block configuration diagram showing an embodiment of the present invention. , Fig. 4 is a block circuit diagram showing an example of the graphic processing device in detail, and Fig. 5 is a block circuit diagram showing an example of the graphic processing device in detail.
FIG. 6 is a diagram showing an image taken by a TV camera, FIG. 6 is a diagram for explaining another embodiment of the present invention, and FIG.
The figure is a block circuit diagram showing an example of a graphic processing device in this case. 1...chuck, 2...workpiece, 3...tailstock, 4...turret, 5...turret, 6...bite, 7...headstock, 8...middle stock, 10...TV Camera, 11... Obstacle image, 20, 20A... Graphic processing device, 21... Video signal binarization circuit, 22...
...Sampling circuit, 23, 24...Counter,
25... Memory circuit, 26... Comparison circuit, 27...
Area setting circuit, 30... Servo motor, 31...
Feed screw, 32... Tape, 33... Command value register, 34... Function generator, 35... Position detector, 36... Comparator, 37... DA converter, 38
...Servo drive circuit.

Claims (1)

[Claims] 1. A TV camera arranged and fixed to a moving body of a machine tool via a holding member, and a tool near the moving body that processes video signals from the TV camera and whose settings are initially stored. a graphic processing device that compares an image area of the tool with an image area in the fast-forward mode and outputs a stop signal to the moving body when the image area in the fast-forward mode exceeds a previously set and stored image area of the tool; , when the stop signal is output, suddenly stopping a servo drive circuit that drives the movable body according to an instantaneous command value based on a processing command for the movable body while returning the current position of the movable body; A collision prevention device for a machine tool, characterized in that it prevents a collision between the movable body and the fixed body.