JPH0333078B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a device for detecting the bottom dead center of a press. The present invention relates to a bottom dead center detection device for a press that outputs an abnormal signal when an error occurs.

(Prior art) Conventionally, as a means of detecting the bottom dead center of a press, the bottom dead center is used to hold the lowest point position in the process of lowering the upper mold stripper during the processing stroke, and detect that position as the bottom dead center. The peak hold method is now available. In the case of this bottom dead center peak hold method, in the case of a mold with a shell or a mold with a strong stripper spring, even if the scraps rise, the scraps will be crushed and no change will appear at the bottom dead center, so the scraps will rise. The problem was that it was difficult to detect.

In addition, as another means of conventional bottom dead center detection, an external synchronization signal that is synchronized with the stroke position of the upper stripper is used to identify the point where the upper stripper begins to hit the scrap that has risen. There was a means to detect the peak hold value up to that point as the bottom dead center. however,
The bottom dead center detection means using an external synchronization signal requires a synchronization signal generation circuit to output the external synchronization signal, and furthermore, the external synchronization signal must be readjusted precisely every time the stroke speed of the press is changed. There was a problem that it was impractical because it had to be done.

(Problems to be Solved by the Invention) Therefore, in order to solve the above-mentioned problems, the present invention has developed a proximity sensor that detects the position of the upper die stripper and outputs a signal during the working stroke of the press, and when it starts outputting a signal, The output signal of the proximity sensor is sampled and input at time intervals, and the changes are successively calculated. When the amount of change in the signal becomes less than the set value, the sampling input is stopped, and the sampled value at this time is used as the bottom dead center data. The solution is to store the data and compare it with the bottom dead center data of the previous machining stroke or the average value of the bottom dead center data of the previous N times, and output an abnormal signal if the difference exceeds the allowable value. This is a technical issue that should be addressed.

(Means for solving the problem) The technical means for solving the above problem is to use a press bottom dead center detection device to detect the stroke position of the upper mold stripper during the processing stroke of the press and respond to that position. a proximity sensor that outputs a proximity signal; a sampling start signal output means that outputs a sampling start signal when the first proximity signal output from the proximity sensor is input for each working stroke of the press; and an output from the proximity sensor. A/D conversion sampling means for converting the proximity signal to a digital signal and performing a sampling operation for holding sampling data based on the digital signal at time intervals set corresponding to the operating characteristics of the press; a sampling start means for causing the A/D conversion sampling means to start the sampling operation when receiving the sampling start signal output from the sampling start signal output means; a subtraction means for calculating a difference between a signal corresponding to the held digital signal and the latest proximity signal from the proximity sensor, and a value subtracted by the subtraction means is set in advance in accordance with processing stroke characteristics of the press. When the A/
sampling stop means for stopping the sampling operation by the D conversion sampling means, and reading the sampling data held in the A/D conversion sampling means when the proximity signal from the proximity sensor is turned off; data storage means for storing as bottom dead center data for the current stroke; and a data storage means for storing the bottom dead center data of the previous stroke stored in the data storage means or the average value of the bottom dead center data of arbitrary previous strokes and the current stroke. a comparison calculation means for calculating the difference between the bottom dead center data and the bottom dead center data in the stroke of the press; and an abnormality signal output means for outputting an abnormality signal when the threshold is exceeded.

(Function) During the processing stroke operation of the press, the upper die stripper approaches the proximity sensor, the proximity sensor starts outputting a signal, and when the first signal is input, the sampling start signal output means outputs a signal to the sampling start means. outputs the sampling start signal. Upon receiving the sampling start signal, the sampling start means puts the A/D conversion sampling means into a sampling operation state. When in a sampling operation state, the A/D conversion sampling means converts the proximity signal output from the proximity sensor into a digital signal, holds sampling data based on the digital signal at preset time intervals, and converts the digital signal into a digital signal. The signals corresponding to the subtraction means are sequentially output to the subtraction means. The subtraction means calculates the difference between the signal and the closest signal from the proximity sensor, and when the difference becomes smaller than a reference value preset in accordance with the working stroke characteristics of the press, the sampling stop means stops the sampling operation of the A/D conversion sampling means.

Further, the data storage means reads the sampling data held in the A/D conversion sampling means when the upper stripper leaves the proximity sensor and the proximity signal is turned off, and stores the data at the bottom dead center in the current stroke. Store as data. The comparison calculation means compares and calculates the bottom dead center data of the previous stroke stored in the data storage means or the average value of the bottom dead center data of arbitrary previous strokes and the bottom dead center data of the current stroke, When the difference exceeds a tolerance value determined in accordance with the working stroke characteristics of the press, the abnormality signal output means outputs an abnormality signal.

(Embodiment) Next, the configuration of an embodiment of the present invention will be described with reference to the electric circuit block diagram shown in FIG.

A proximal body 3 formed of, for example, an iron plate is attached to the stripper 2 attached to the upper die 1 of the press together with a body plate 1A and a stripper spring 1B.
When the object approaches the proximity sensor 5 fixed to the lower mold 4, the proximity sensor 5 outputs a proximity signal corresponding to the proximity distance 6 to the object 3. A sensor signal amplification circuit 7 for amplifying the proximity signal output from the proximity sensor 5 is provided, and the sensor signal amplification circuit 7 outputs a sensor amplification signal 7A.

A Schmitt circuit 9 is provided for converting the sensor amplified signal 7A output from the sensor signal amplification circuit 7 into a logic signal, and the signal converted into the logic signal by the Schmitt circuit 9 samples the stroke position of the stripper 2. The operation start signal 9A is output to the arithmetic control circuit 10.
The arithmetic control circuit 10 is composed of a circuit such as a microcomputer having memory, arithmetic and control functions, and when the operation start signal 9A from the Schmitts circuit 9 is input, the operation is performed according to a built-in arithmetic control program. A sampling start signal 13A is output to the sampling start command circuit 12A, and a sampling prohibition register reset signal 13B is output to the sampling prohibition register circuit 12B.

Further, the clock frequency dividing circuit 11 outputs an A/D conversion clock signal 16 obtained by dividing the frequency of the reference clock 14 of, for example, 800 KHz output from the arithmetic control circuit 10 to 400 KHz to the A/D conversion sampling circuit 15, and also outputs the A/D conversion clock signal 16 to the A/D conversion sampling circuit 15. The circuit is configured to output a sampling interval clock signal 17 whose frequency is divided into KHz to the sampling start command circuit 12A and the sampling prohibition register circuit 12B. The A/D conversion sampling circuit 27 first processes digital data by the internal operation of the successive approximation register circuit 15, which is executed in synchronization with the A/D conversion clock signal 16 from the time when the sampling interval clock signal 17 rises. Signal 18
When the MSB is set to a logic signal 1, the analog data signal output from the D/A conversion circuit becomes 1/2 full scale, and if the result of comparison with the sensor amplified signal 7A by the analog comparator 8 is a logic signal 1, the MSB is set to 1. Leave it as 1, and if it is 0, return the MSB to 0, set the next 1/4 full scale bit to 1, compare in the same way, and then sequentially compare and decide each bit from the upper bit to the LSB. , after all bits are completed, a digital data signal 18 and an analog data signal 21 that match the sensor amplified signal 7A are obtained. Further, the analog subtraction circuit 22 outputs the analog signal data 2 output from the D/A conversion circuit 19.
1 and the sensor amplified signal 7A output from the sensor signal amplification circuit 7 are input, analog subtraction is performed, and a subtraction signal 23 is output. The analog comparator 26 is operated by inputting the subtraction signal 23 output from the analog subtraction circuit 22 and the reference voltage 25 from the reference voltage generation circuit 24 that generates a voltage equal to the minimum limit value of the subtraction signal 23. In a state where the subtraction signal 23 is greater than the reference voltage 25, a logic signal 1 is output. Therefore, when the stripper 2 begins to hit scrap or material (not shown) during the downward stroke process, its displacement suddenly decreases, so that the sensor amplified signal 7A input to the analog subtraction circuit 22
As the voltage difference between the reference voltage 25 and the analog data signal 21 becomes smaller, the subtraction signal 23 output from the analog subtraction circuit 22 becomes smaller, and when the subtraction signal 23 becomes smaller than the reference voltage 25, the analog comparator 26 outputs a logic signal 0.

Logic signal from analog comparator 26 is 0
When the signal is input to the sampling prohibition register circuit 12B by the sampling interval clock 17, the sampling prohibition register circuit 12B is set and the sampling prohibition signal 13C is input to the sampling trigger signal circuit 12.
Output to C. As a result, the A/D conversion sampling circuit 27 stops sampling and inputting the signal corresponding to the stroke position of the stripper 2. Incidentally, the sampling trigger differential clock signal 14A is used to make the sampling trigger signal two clocks longer than the A/D conversion clock signal 16.

The stripper 2 enters the rising process, and the proximity sensor 5
When the timing signal exceeds the sensing range of , the signal output from the Schmitt circuit 9 becomes a logic signal 0, so the arithmetic control circuit 10 determines this timing signal as the read start signal 9B and holds it in the A/D conversion sampling circuit 27. The digital data signal 18 is read.

FIG. 2 shows an example of an electronic circuit diagram corresponding to the electrical circuit block diagram shown in FIG. 1 with the above-described configuration. The block name and attached number of each block in the electric circuit block diagram in FIG. 1 are shown in the corresponding electronic circuit section in FIG.

As shown in FIG. 2, the analog comparators 8 and 26 and the Schmitt circuit 9 are, for example, the voltage comparator LM319 manufactured by National Semiconductor, and the arithmetic control circuit 10 is a microcomputer such as the Z80 manufactured by Zilog, as described above. . In addition, the clock frequency dividing circuit 1
1 uses Motorola's 7-stage ripple counter MC14024, and Motorola's D-type flip-flop MC14013 is used for sampling start command circuit 12A, sampling inhibit register circuit 12B, and sampling trigger signal circuit 12C.
is used.

Further, the successive approximation register circuit 15 is, for example, a cascade connection of successive approximation registers (SAR) MC14549 and MC14559 manufactured by Motorola. Further, for the D/A conversion circuit 19, for example, a 12-bit binary multiplication D/A converter DAC1220 manufactured by National Semiconductor Corporation is used.

As the analog subtraction circuit 22, for example, an operational amplifier LM318 manufactured by National Semiconductor Corporation is used.

Next, the operation of this embodiment will be explained with reference to the electric circuit block diagram of FIG.

During the working stroke of the press, when the proximity body 3 attached to the upper mold stripper 2 approaches the proximity sensor 5 fixed near the lower mold 4 and enters the sensing range of the proximity sensor 5, a second As shown in FIG. 3, a proximity signal corresponding to the distance to the nearby object 3 is output. The proximity signal output from the proximity sensor 5 is input to the sensor signal amplification circuit 7,
After being amplified, it is output from the sensor signal amplification circuit 7 as a sensor amplification signal 7A. The sensor amplified signal 7A output from the sensor signal amplification circuit 7 is input to the Schmitt circuit 9, where the waveform is shaped and outputted to the arithmetic control circuit 10 in the state of logic signal 1. When the logic signal 1 output from the Schmitts circuit 9 is input to the arithmetic control circuit 10 as the operation start signal 9A, the arithmetic control circuit 10 starts the sampling start command circuit 12 according to the built-in control program.
Sampling start signal 13A to A, and
A sampling prohibition register reset signal 13B is output to the sampling prohibition register circuit 12B. The arithmetic control circuit 10 constantly transmits a reference clock 14 of, for example, 800 KHz to the clock frequency divider circuit 11.
The clock frequency dividing circuit 11 divides the reference clock 14 and sends the A/D conversion clock signal 16 having a period of 2.5 μs, that is, a frequency of 400 KHz to the successive approximation register circuit 15 of the A/D conversion sampling circuit 27. . The successive approximation register circuit 15 first receives the digital data signal by the internal operation of the successive approximation register circuit 15, which is executed periodically according to the A/D conversion clock signal 16 from the time when the sampling interval clock signal 17 rises. When the MSB of 18 is set to logic signal 1, the analog data signal that is the output of the D/A conversion circuit becomes 1/2 full scale,
Sensor amplified signal 7 by analog comparator 8
If the result compared with A is a logical signal 1, leave the MSB as 1, and if it is 0, return the MSB to 0 and select the next 1/4
The full-scale bit is set to 1 and compared in the same way, and then each bit from the upper bit to the LSB is sequentially compared and determined. After all bits are completed, the digital data signal 18 and analog data that match the sensor amplified signal 7A are obtained. Obtain signal 21.

The analog data signal 21 input to the analog subtraction circuit 22 is compared with the real-time sensor amplified signal 7A, and the difference is output as a subtraction signal 23. The subtraction signal 23 output from the analog subtraction circuit 22 is a reference voltage 25 that is preset in accordance with the stroke characteristics of the press.
is input to the analog comparator 26 and calculated, and if the subtraction signal 23 becomes smaller than the reference voltage 25, that is, if the stripper 2 hits a piece of scrap (not shown) or a material during the downward stroke, the stripper 2 Since the change in the subtraction signal 23 suddenly becomes small, the magnitude of the subtraction signal 23 becomes small, so the reference voltage 25 becomes larger and a logic signal 0 is output from the analog comparator 26 in synchronization with the sampling interval clock 17 to the sampling start command circuit. 12
A and the sampling inhibit register circuit 12B. As a result, the sampling prohibition register circuit 12B
A sampling stop signal is output to C, and sampling is stopped until the operation start signal 9A is output in the next stroke.

On the other hand, the arithmetic control circuit 10 is a Schmitt circuit 9
When the logic signal output from the A/D conversion sampling circuit 27 changes to 0, this timing signal is input as the read start signal 9B, and the digital data signal 18 output from the A/D conversion sampling circuit 27 is read as bottom dead center data. The difference is calculated and compared with the bottom dead center data stored in the previous stroke or the average value of the bottom dead center data in any N previous strokes, and the difference is set in advance according to the stroke characteristics of the press. If the value exceeds the above value, it is determined that an abnormal condition such as scrap rising has occurred, and the arithmetic control circuit 10 outputs an abnormal signal 10A.
This is to bring the press operation to an emergency stop.

(Effects of the Invention) As described above, according to the present invention, when the upper stripper starts to hit the scrap or material, the displacement suddenly decreases, so by calculating the displacement difference, it is possible to easily detect the point at which the stripper starts hitting the scrap or material. The position can be detected, and even in the case of a shell-mounted mold, the position can be detected when the stripper is still being pushed by only a small pressure from the stripper spring before it is mounted, so even small scraps can be accurately detected. Since it can detect and output an abnormality signal, it has the effect of reliably stopping the press.

[Brief explanation of drawings]

Fig. 1 is an electric circuit block diagram of an embodiment of the present invention, Fig. 2 is an electronic circuit diagram corresponding to the electric circuit block diagram of Fig. 1, and Fig. 3 is an operational explanatory diagram of an embodiment of the invention. be. 1... Upper die, 2... Stripper, 3... Proximity body, 4... Lower die, 5... Proximity sensor, 7... Sensor signal amplification circuit, 8... Analog comparator,
9... Schmitt circuit, 10... Arithmetic control circuit,
11... Clock frequency divider circuit, 12A... Sampling start command circuit, 12B... Sampling prohibition register circuit, 12C... Sampling trigger signal circuit, 15... Successive approximation register circuit, 1
9...D/A conversion circuit, 22...Analog subtraction circuit, 24...Reference voltage generation circuit, 26...Analog comparator, 27...A/D conversion sampling circuit.

Claims (1)

[Scope of Claims] 1. A proximity sensor that detects the stroke position of the upper die stripper during the processing stroke of the press and outputs a proximity signal corresponding to the position; a sampling start signal output means for outputting a sampling start signal when a first proximity signal is input to the press; A/D conversion sampling means that performs a sampling operation to hold sampling data based on the digital signal at set time intervals; and upon receiving the sampling start signal output from the sampling start signal output means, sampling start means for causing the A/D conversion sampling means to start the sampling operation; and a difference between a signal corresponding to the digital signal held in the A/D conversion sampling means and the latest proximity signal from the proximity sensor. and a subtracting means for calculating the sampling operation by the A/D conversion sampling means when the value subtracted by the subtracting means becomes smaller than a preset reference value corresponding to the processing stroke characteristics of the press. a sampling stop means for stopping the proximity signal from the proximity sensor; and when the proximity signal from the proximity sensor is turned off, reading the sampling data held in the A/D conversion sampling means and applying the data to the bottom dead center of the current stroke. a data storage means for storing data, and bottom dead center data of the previous stroke stored in the data storage means, or an average value of bottom dead center data of arbitrary previous strokes, and bottom dead center data of the current stroke. and outputting an abnormal signal when the difference between the bottom dead center data calculated by the comparison calculation means exceeds a tolerance determined in accordance with the processing stroke characteristics of the press. An apparatus for detecting a bottom dead center of a press, comprising an abnormality signal output means.