JP4230608B2 - Number discrimination device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet number discriminating apparatus that discriminates the number of plates to be inspected, such as metal plates, into one sheet and two or more sheets.
[0002]
[Prior art]
Conventionally, the following number discriminating devices have been used.
[0003]
FIG. 3 is a schematic diagram illustrating an example of a number discriminating apparatus that discriminates the number of metal plates.
[0004]
For example, on the most upstream side of a line for bending or punching a metal plate, a number of stacked metal plates 1 are sucked and lifted one by one by a suction cup 2 and supplied to the line. The At that time, as shown by a one-dot chain line in FIG. 3, if the two metal plates are lifted by the suction cup 2 while being adsorbed to each other and are supplied to the line as they are, a great load is applied to the processing mold for processing the metal plates. In order to avoid this, it is detected that two metal plates 1 have been lifted, and when two are lifted, the metal plates are not supplied to the line. It is necessary to take measures such as removing it next to it.
[0005]
Therefore, here, a number discriminating device 3 for detecting that two metal plates are lifted is provided.
[0006]
The number discriminating apparatus 3 includes a transmission head 31. The transmission head 31 is provided with a drive coil (not shown), and the drive coil is driven by a coil drive circuit 32 to generate an alternating magnetic field. The coil drive circuit 32 can drive the drive coil with drive signals of various frequencies by automatic or manual switching.
[0007]
The number discriminating apparatus 3 is provided with a receiving head 33 so as to face the transmitting head 31. The receiving head 33 is provided with a detection coil (not shown), and an alternating magnetic flux emitted from the transmission head 31 and transmitted through the metal plate 1 is detected by the detection coil. The magnetic flux detected by the detection coil in the receiving head 33 is appropriately amplified by the amplifier circuit 34 and its effective value is obtained by the rectifier circuit 35 and then input to the comparison circuit 36. The threshold value generated by the threshold value generation circuit 37 is also input to the comparison circuit 36, and whether or not the magnetic flux detected by the reception head 33 is equal to or higher than a predetermined strength, that is, one metal plate 1 is provided. It is determined whether the magnetic flux has a strength when only passing through it or a magnetic flux having strength when passing through two (or more) metal plates 1, whereby one metal plate 1 is sucked by the suction cup 2. It is determined whether it is lifted only by two or more. The determination result is input to a metal plate supply device provided with a suction cup 2 to control the movement of the suction cup 2 so that the metal plate 1 is supplied to the line only when the suction cup 2 lifts only one metal plate 1. By controlling, it is possible to avoid the supply of the double metal plates to the line.
[0008]
[Problems to be solved by the invention]
The number discriminating apparatus as described above detects two overlaps based on a change in the level of a signal received by the receiving head 33. Therefore, the frequency of an alternating magnetic field for detecting the two overlaps, that is, the transmission head 31 is detected. As the drive frequency for driving the drive coil, the received signal levels when the frequency f is one and two metal plates are overlapped are V _1f and V _2f , respectively, and the difference between the received signal levels is ΔV _f When V = _{f 1} −V _2f , it is considered best to select a frequency that maximizes the difference ΔV _f . However, in that case, the following problems cannot be avoided.
[0009]
FIG. 4 is a schematic diagram showing a state in which the metal plate 1 is gradually inserted between the transmission head 31 and the reception head 32, and FIG. 5 is a diagram showing a change in the reception signal level at that time.
[0010]
When the metal plate 1 is gradually inserted between the transmission head 31 and the reception head 33 and the tip 1a of the metal plate 1 reaches each of the positions a, b, c, d, e, the received signal level Changes as a, b, c, d, e in FIG. That is, when the metal plate 1 is a non-magnetic material such as aluminum and is thin, the signal level changes gradually as the metal plate 1 is gradually inserted, but when the metal plate 1 is a magnetic material such as an iron plate, While the metal plate 1 is gradually inserted, a phenomenon that the signal level is once reduced greatly and then restored to a normal level is observed. When the metal plate 1 is once lowered, the double-layered metal plate is inserted. It can also drop beyond the signal level. According to our experiments, the phenomenon that the signal level decreases once during the insertion process occurs in a non-magnetic material with a thickness of 6 mm or more or a metal plate with a magnetic material of 0.1 mm or more. As the metal plate is thicker, the excessive signal level is greatly reduced.
[0011]
In FIG. 5, the non-magnetic material and the magnetic material are shown as if they have the same signal level, but here they are standardized for ease of understanding, and the actual signal level is The non-magnetic material and the magnetic material are greatly different, and greatly differ depending on the plate thickness and the frequency of the alternating magnetic flux.
[0012]
As shown in FIG. 5, when the signal level changes greatly in a transient manner, it is detected that the two metal plates 1 are overlapped while the metal plate 1 is being inserted between the transmission head 31 and the transmission head 32. The result is that discrimination becomes impossible.
[0013]
In order to avoid this, a sensor for detecting that the metal plate 1 is in a transitional state being inserted between the transmission head 31 and the reception head 33 is provided, and the determination is avoided in the transitional state. A method is also conceivable, but originally this number discriminating device also serves as a sensor that detects whether or not the metal plate has been carried, and the sensor is provided separately from this number discriminating device. It is not preferable, and providing such a sensor is disadvantageous in terms of cost and space.
[0014]
In view of the above circumstances, the present invention is capable of accurately discriminating whether a test plate is a single plate or a double plate (or more) without providing another sensor for detecting the presence of the test plate. An object of the present invention is to provide a discriminating device capable of discriminating sheets.
[0015]
[Means for Solving the Problems]
The number discriminating device of the present invention that achieves the above object receives a transmission head that generates an alternating magnetic flux having a variable frequency, and an alternating magnetic flux generated from the transmission head, which are arranged at a predetermined interval between each other. A receiving head for obtaining a received signal, and based on the received signal, discriminates whether one or more inspected plates are arranged between the transmitting head and the receiving head. In the discriminating device, the discriminating frequency setting means for setting the driving frequency of the transmission head prior to discrimination for discriminating whether the number of the plates to be inspected is one or two or more, and the discrimination frequency is provided. When the setting means generates an alternating magnetic flux having a frequency f from the transmission head by placing one or two test plates between the transmission head and the reception head in a stack for testing. Subtracting the [Delta] V _f of the signal level to each other of each received signal obtained by the reception head, frequency to avoid erroneous detection in transient state which is being inserted between the inspected board said reception head and the transmission head Assuming that the upper limit frequency of the region is f _th and the threshold value for determining whether the test plate is single or double is Th , the frequency is equal to or lower than the frequency f _th and satisfies ΔV _f ≧ Th. When one or more frequencies are present, a predetermined frequency among the one or more frequencies that satisfy the frequency f _th or less and satisfies ΔV _f ≧ Th is set as the drive frequency. .
[0016]
Here, the discrimination frequency setting means, the frequency f _th or less, and [Delta] V _{when f} ≧ Th frequency which satisfies the existence of one or more of the lowest of the one or more frequencies that satisfy the [Delta] V _f ≧ Th The frequency may be set as the drive frequency.
[0017]
Further, the discrimination frequency setting means, when there is no frequency that is equal to or less than the frequency f _th and that satisfies ΔV _f ≧ Th, a frequency at which ΔV _{f of the} entire range that can be taken as the drive frequency is maximum, The driving frequency may be set.
[0018]
According to the knowledge obtained by the inventor through experiments, the phenomenon that the signal level once greatly decreases during the insertion process described with reference to FIG. 4 and FIG. In addition to being generated in a metal plate of magnetic material with a plate thickness of 1 mm or more, the higher the thickness of the metal plate and the higher the driving frequency of the drive coil of the transmission head, the more the transient signal level. Is greatly reduced. Here, as a result of further experiments, even at a frequency lower than a certain frequency, for example, less than 150 Hz, even if the thickness of the magnetic material is as thick as about 20 mm, for example, as described with reference to FIG. It has been found that there is no phenomenon that falls beyond the level of double stacking, and it is possible to discriminate between one and two or more with sufficient accuracy.
[0019]
Further, as shown in FIG. 6, when the drive frequency of the transmission head is increased or the plate thickness is increased, the signal level of the magnetic material is drastically decreased as compared with the non-magnetic material. However, a low driving frequency such as 100 Hz is used.
[0020]
The present invention is based on the above knowledge. First, a threshold value Th that can discriminate between one sheet and two sheets at a frequency f _th or less at which a transient false detection does not occur even if the plate thickness is thick is set. It is determined whether or not there is a frequency that can obtain a signal level difference ΔV _f that exceeds the frequency level. If there is a frequency that is equal to or lower than the frequency f _th and ΔV _f ≧ Th, the driving frequency is set to that frequency. Sheets and double sheets can be discriminated with high accuracy. In that case, the frequency satisfying the condition is searched from the lower frequency, and the frequency when the frequency satisfying the condition is first found (that is, the lowest frequency satisfying the condition) is adopted. As a result, the time required for setting the drive frequency is short.
[0021]
The fact that there is no frequency satisfying ΔV _f ≧ Th at a frequency equal to or lower than the frequency f _th is a non-magnetic material or a transient decrease in the signal level as described above even if it is a magnetic material. Since it is a thin plate thickness that is hardly seen, the discrimination accuracy can be increased by removing the restriction of the frequency f _th or less and setting the frequency at which the signal level ΔV _f is maximum as the driving frequency.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0023]
FIG. 1 is a block diagram of an embodiment of the number discriminating apparatus of the present invention.
[0024]
The difference between the block diagram shown in FIG. 1 and the block diagram shown in FIG. 3 is that the drive frequency setting unit 38 is shown, and the operation of the other parts is the same as in FIG. Therefore, in the following, description of other parts is omitted, and the drive frequency setting unit 38 will be described.
[0025]
FIG. 2 is a flowchart showing the operation of the drive frequency setting unit 38.
[0026]
First, in a state in which one metal plate is disposed for testing between the transmission head 31 and the reception head 33, the frequency is changed stepwise and the reception signal level (output of the rectifier 35) at each frequency is stored. (Step a).
[0027]
Next, two metal plates are placed for testing between the transmission head 31 and the reception head 33, and in that state, the frequency is changed stepwise, and the received signal level at each frequency is stored (step b).
[0028]
Next, the frequency f is sequentially changed from the lowest frequency f _min (step c) toward the high frequency side (step f) up to a predetermined frequency f _th (step g), and when the frequency is one or two at the same time. The difference ΔV _f = V _1f −V _2f between the signal levels V _1f and V _2f is compared with the threshold Th to determine whether ΔV _f ≧ Th (step d). In the above process, when there is a frequency f that satisfies ΔV _f ≧ Th at any frequency below the frequency f _th , the frequency f is set as the drive frequency (step e). On the other hand, if there is no frequency satisfying ΔV _f ≧ Th even after searching up to the frequency f _th , the frequency at which ΔV _f is maximized is searched (step f), and the maximum ΔV _f is obtained. The frequency is set as the drive frequency (step i).
[0029]
The drive frequency once set in this manner is used for detecting the overlap of the metal plates until the next calibration.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible to discriminate with high accuracy whether the inspection plate is a single sheet or a stack of two sheets without separately providing a sensor for detecting the presence of the inspection plate.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a sheet number discriminating apparatus according to the present invention.
FIG. 2 is a flowchart showing an operation of a drive frequency setting unit.
FIG. 3 is a block diagram of a conventional discriminating device for discriminating the number of metal plates.
FIG. 4 is a schematic diagram showing a state where a metal plate is gradually inserted between a transmission head and a reception head.
FIG. 5 is a diagram illustrating a change in a received signal level.
FIG. 6 is a diagram showing changes in received signal level with respect to drive frequency and plate thickness.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal plate 2 Suction cup 3 Number discriminating device 31 Transmission head 32 Coil drive circuit 33 Reception head 34 Amplification circuit 35 Rectifier 36 Comparison circuit 37 Threshold generation circuit 38 Drive frequency setting part

Claims (3)

A transmission head that generates an alternating magnetic flux with a variable frequency, and a reception head that receives the alternating magnetic flux emitted from the transmission head and obtains a reception signal, the reception signal being arranged with a predetermined interval between them; On the basis of the number discriminating device for discriminating whether one plate to be inspected is arranged between the transmitting head and the receiving head or two or more overlapping plates,
A discriminating frequency setting means for setting the driving frequency of the transmission head for discriminating whether the number of the plates to be inspected is one or two or more, prior to discrimination,
When the discrimination frequency setting means arranges one and two test plates between the transmission head and the reception head for test and generates an alternating magnetic flux having a frequency f from the transmission head, the reception frequency is set. The difference between the signal levels of each received signal obtained by the head is ΔV _f , and the frequency domain avoids erroneous detection in a transient state where the board to be inspected is being inserted between the transmitting head and the receiving head. Assuming that the upper limit frequency is f _th and the threshold value for determining whether there is one or two test plates is Th , the frequency is equal to or lower than the upper limit frequency f _th and satisfies ΔV _f ≧ Th. When one or more frequencies are present, a predetermined frequency among the one or more frequencies satisfying ΔV _f ≧ Th and the upper limit frequency f _th or less is set as the drive frequency. Sheets Number discrimination device. Said discrimination frequency setting means, the upper limit frequency f _th or less, and [Delta] V _{when f} ≧ Th frequency which satisfies the existence of one or more lowest frequency of the one or more frequencies that satisfy the [Delta] V _f ≧ Th The number discriminating apparatus according to claim 1, wherein: is set as the drive frequency. When the discrimination frequency setting means has a frequency that is equal to or lower than the upper limit frequency f _th and does not satisfy ΔV _f ≧ Th, a frequency at which ΔV _{f of the} entire range that can be taken as the drive frequency is maximized, The number discriminating apparatus according to claim 1, wherein the number discriminating apparatus is set as the driving frequency.

Images