JP3440324B2 - Two-sheet suction detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-sheet suction detecting device for detecting a two-sheet suction abnormality of an iron plate work which is sucked and lifted by an electromagnetic force of an electromagnetic chuck.

[0002]

2. Description of the Related Art Conventionally, it is extremely important to accurately supply a flat iron plate work piece by piece in a step of conveying a flat iron plate work piece to a press machine for press working.

If two or more workpieces are supplied at the same time, there is a possibility that the pressed product will be a defective product and the press die may be damaged or the press itself may be destroyed.

[0004]

As a conventional preventive measure, there is a method of measuring the plate thickness from the vertical direction of the work using a non-contact distance measuring device or the like during the conveyance of the work to detect the adsorption of two sheets. It was being done. But this method
There is a problem that the detection accuracy is insufficient because two detectors are required above and below, and the detectors cannot be brought close to the work (if they are brought too close, they interfere with each other due to the vibration of the work being conveyed, etc.). there were.

The cause of the two-sheet feeding (two-sheet suction) is the sticking of the oil adhered to the work itself from the beginning, the sticking due to the vacuum between the plates, and the suction magnetic flux when the work is sucked by the electromagnetic chuck. Adhesion by penetrating the second sheet is also possible. As measures against this, generally, a method of using a separating device such as a separator or blowing air to the edge of the work has been adopted.

However, in adsorbing and transporting a work, even if various separating means are provided, there is no guarantee that only one work will be picked up. Therefore, whether one work or two or more works are detected. Had to do.

The present invention has been made in view of the above, and an object of the present invention is to provide a two-sheet suction detecting device capable of simply and reliably detecting the two-sheet suction of a work.

The present invention has been made to achieve the above object, and the two-sheet adsorption detection device of the present invention is an electromagnetic chuck.
A two-piece attraction detection device for a workpiece that is attracted to and lifted from the electromagnetic chuck , which is provided separately from a backpack, wherein one end has one magnetic pole capable of contacting the workpiece and the other end has the workpiece. A detector comprising an iron core forming another magnetic pole capable of contacting in the vicinity of the contact portion, an exciting coil wound around the iron core, and a detection coil wound around the iron core, and a synchronization signal.
A square wave oscillator that generates a square wave voltage having a signal width T ₃ to excite the exciting coil of the detector, an integrator that integrates the output of the detecting coil of the detector, and an output of the integrator are stored in advance. A two-sheet suction detection device, comprising: an arithmetic processing unit that determines whether one workpiece is sucked by comparing the table with a suction number table.

Further, the iron core of the detector is composed of a rod portion and a lower end portion which forms one magnetic pole, and a main pole portion which is formed of a cylindrical portion and is coaxially arranged outside the main pole portion so as to have a lower end. At least 8 of the plate thickness of the work piece on which the exciting coil and the detection coil are wound around the main pole part, and the diameter of the main pole part is attracted. It is desirable that it is doubled.

Further, it is desirable to add the exciting current of the exciting coil of the detector to a value close to the magnetic saturation of the work.

[0011]

The present invention is configured as described above, and the detector is placed on the work that is attracted and lifted by the electromagnetic chuck, and the pair of magnetic poles are in contact with the work. The exciting coil of the detector is excited by the square wave oscillator, and the magnetic flux generated thereby passes through the path from one magnetic pole to the other magnetic pole via the workpiece.

The magnetic flux connecting the two magnetic poles is proportional to the number of workpieces when the thickness of the workpieces is constant. The detection coil detects this magnetic flux and outputs the induced voltage, and the integrator integrates the output of the detection coil.

The arithmetic processing unit compares the output of the integrator with the suction number table, and determines whether the number of suctioned works is one or more.

[0014]

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

FIG. 1 is a block diagram showing the construction of a two-sheet suction detection device according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a state in which the detector of this device is attached to an electromagnetic chuck.

The two-sheet adsorption detection device of the present invention comprises a detector 1
, A square wave oscillator 15, an integrator 17, and an arithmetic processing unit 20 having a suction number table 21.

In the embodiment, the detector 1 comprises an iron core 3, an exciting coil 10 and a detecting coil 11. The iron core 3 is composed of a rod-shaped main pole portion 4 and a cylindrical portion, and is located outside the main pole portion 4. And a yoke portion 6 integrally arranged coaxially. The main coil 4 has an exciting coil 1 on the upper side of the bobbin 12.
0 is wound and electrically connected to the square wave oscillator 15 by the cable 13, the detection coil 11 is wound on the lower side of the bobbin 12, and electrically connected to the integrator 17 by the cable 13.

The lower end surface of the main pole portion 4 and the lower end surface of the yoke portion 6 are formed on the same plane, and they form the magnetic pole 5 and the magnetic pole 7 when the exciting coil 10 is energized.
Further, a mounting portion 8 formed of a female screw is provided on the upper portion of the iron core 3.

The square wave oscillator 15 is so constructed as to output a square wave having a period longer than the time constant of the exciting coil 10, and is controlled by the arithmetic processing unit 20 to output a square wave voltage V ₁ at a predetermined timing. Is formed. In the figure, R ₀ is a resistor for adjusting the time constant.

The integrator 17 is provided with an FET for discharging the integration capacitor C, is configured to integrate the output voltage of the detection coil 11 and output the integrated value. The integrator output voltage V ₂ is , A / D converter 18, and is input to the arithmetic processing unit 20.

The arithmetic processing unit 20 is mainly composed of a microcomputer, and C for executing arithmetic processing.
Stores programs for PU and CPU,
Number of workpieces adsorbed by the thickness of workpiece W and integrator output voltage V
₂ is provided with a RAM and a ROM that store the relationship with ₂ in advance as a suction number table 21, and outputs a synchronization signal of a predetermined cycle T ₂ to output the work suction number determined by the suction number table 21 to the display 23. It is configured.

The detector 1 thus constructed is attached, for example, in the vicinity of an electromagnetic chuck 30 for lifting and conveying a work, as shown in FIG.

In the electromagnetic chuck 30, the main pole portion 31 and the yoke portion 32 form a tubular iron core, and the coil 34 is energized via the cable 36 so that the main pole portion 31 and the yoke portion 32 are electrically connected to each other. In addition, an attracting magnetic flux is generated. The electromagnetic chuck 30 is attached to a carrying device such as a robot via a connecting rod 38, and a supporting plate 25 extending laterally is fixed to the electromagnetic chuck 30. Note that reference numeral 39 is a detent for the support plate 25.

A free insertion hole 26 penetrating in the vertical direction is provided at the tip of the support plate 25, and a connection rod 28 standing on the mounting portion 8 of the detector 1 is provided in the free insertion hole 26. It is movably inserted in the vertical direction. The detector 1 is arranged as close as possible to the workpiece adsorption portion of the electromagnetic chuck 30 and is capable of contacting the upper surface of the workpiece W outside the magnetic field of the electromagnetic chuck 30. When the electromagnetic chuck 30 is in the non-adsorbed state of the workpiece, the detector 1 has its lower surface lowered from the lower surface of the electromagnetic chuck 30 due to its own weight, and its upper and lower positions are restricted by the brim portion 28a of the connecting rod 28. There is.

Next, the operation of the two-sheet suction detecting device thus constructed will be described with reference to FIGS.

First, the electromagnetic chuck 30 and the detector 1 are moved onto the iron plate works W stacked in large numbers, and the detector 1
Is slightly raised by the loose insertion hole 26, and the magnetic poles 5 and 7 contact the upper surface of the work W of the electromagnetic chuck 30. When the electromagnetic chuck 30 is energized, the electromagnetic chuck 30 moves the work W.
Adsorb.

When the electromagnetic chuck 30 is raised, the work W on the upper side is separated from the other work groups and rises, and the detector 1 also rises. After that (after the time T ₁ elapses), the synchronization signal of the cycle T ₂ is transmitted from the arithmetic processing unit 20 to the square wave oscillator
5, output to the integrator 17. The period T ₂ is set to be equal to or longer than the magnetic flux saturation time of two workpieces W having a predetermined thickness.

The synchronizing signal width T ₃ is the ON time of the FET for discharging the integrating capacitor C, and is set to several ms in the embodiment. This discharging of the integrating capacitor C prevents the charging voltage of the integrating capacitor C from shifting due to the bias of the magnetic circuit (residual magnetism) and the +/− imbalance of the square wave voltage.

The square wave oscillator 15 is controlled by the synchronizing signal and applies the square wave voltage V ₁ to the exciting coil 10 to detect the detector 1.
To excite. At this time, in the detector 1, a magnetic flux φ reaching the magnetic pole 7 from the magnetic pole 5 via the work W is generated. The magnetic resistance between the magnetic poles 5 and 7 is large when the number of the attracted works W is one, and the magnetic resistance becomes small when the number of the works W is two, and the magnetic flux φ passing through the detection coil 11 is opposite to that. It will be proportional.

The detection coil 11 outputs an output voltage proportional to the magnetic flux φ, and the integrator 17 outputs a saturation value V ₂ (when one work W is used) or V ₂ 'of the integrator output voltage corresponding thereto.
(When the work W is 2 sheets) is output. FIG. 4 shows the excitation coil 1
The relationship between the exciting current I of 0 and the magnetic flux φ of the work W is shown, and the work W is magnetized to a state close to magnetic saturation.
The difference between one sheet and two sheets can be clearly detected.

The integrator output voltage V ₂ (or V ₂ ') is A
The integrator output voltage V ₂ (V ₂ '), which is taken into the arithmetic processing unit 20 via the / D converter 18 and compared with the adsorption number table 21 corresponding to the plate thickness of the work W, is W
Judge whether it is 1 or 2. And the result is display 2
3 and the number of works W is two or more, the operation of the transport device is stopped.

By the excitation of the detector 1, the magnetic flux of the detector 1 itself acts on the work W to suppress the vibration of the work W, and at the time of adsorbing the two, the space between the first and second sheets is increased. It acts to generate a suction force and reduce the gap between them.

FIG. 5 is a curve diagram showing the relationship between the work W plate thickness t and the integrator output voltage V _{2 in} the embodiment. As shown in the figure, when the plate thickness t is 1.2 mm or less, it is extremely easy to distinguish between one and two plates, and it is considered that the practical range is up to about 1.5 mm.

FIG. 6 is a view showing the relationship between the thickness of the work W and the detector 1. The detector 1 only needs to measure the magnetic characteristics of the work W, but in reality, the magnetic characteristics of the detector 1 itself and the characteristics of a minute gap on the contact surface with the work W are also included.

In FIG. 6, what is affected by the magnetic characteristics of the work W is the portion of L ₂ (the portion shown by the oblique broken line in FIG. 7 and its peripheral portion). In order to properly capture the magnetic characteristics of this portion (including the case of two workpieces W), it is necessary for the detector 1 to further facilitate the passage of magnetic flux.

[0036] The condition detector 1 and if the workpiece W using the material of the same magnetic properties, D ₁ of the cross-sectional area> D ₁ of the circumferential area of the workpiece W2 sheets diameter (S ₁₎ π / ^{_{4 · D 1 2> πD 1}} · 2t words, it is desirable to D _1> 8t.

In the detector 1 of this embodiment, D ₁ = 12, and therefore t <1.5 mm, which is suitable for detecting the work W having a plate thickness of 1.5 mm or less. Also, the magnetic pole 7
Sectional area of the thickness of a portion of the (D ₃ -D ₂₎ shall not be smaller than the cross-sectional area of the D _1. Further, L _{1 in} FIG. 6 is
The average magnetic path length of the detector 1 is shown.

In general, the iron plate serving as the work W is a cold rolled steel plate or a general structural rolled steel plate, and its magnetic characteristics are magnetically saturated at a magnetomotive force of about 2400 AT / m. The iron core 3 of the detector 1 has a holding force (Hc) higher than that of the work W material,
It is desirable to use pure iron having excellent saturation magnetic flux density (Bm). It may also be a TM alloy (a type of permalloy).

The detector 1 may be hung on the support plate 25 by a coil spring or the like whose axis is flexible and which can be expanded and contracted in the vertical direction. As a result, even if the work W suspended by the electromagnetic chuck 30 is warped, the magnetic poles 5 and 7 of the detector 1 can be properly attracted to the work W surface.

[0040]

As is apparent from the above description, according to the two-sheet suction detection device of the present invention, the magnetic flux passing through the suction work can be detected from the upper surface of the work that is sucked and lifted by the electromagnetic chuck. It is possible to easily detect the adsorption of two workpieces.

Further, by forming the diameter of the main pole portion of the iron core at least 8 times the plate thickness of the suction work, the magnetic flux difference between one suction work and two suction works is made clear, and two suction works are ensured. Can be detected.

Further, the exciting voltage of the exciting coil of the detector is
Excited with a positive and negative square wave voltage having a sync signal width T _3.
Therefore, the bias of the magnetic circuit (remanent magnetism) and the square wave voltage
To prevent deviation of the detector output due to +/- imbalance of
You can

Further, by adding the exciting current up to a value close to the magnetic saturation of the work, it is possible to clearly detect the magnetic flux difference between the one and the two work, and to improve the detection accuracy.

Further, since the detector of this apparatus exerts an attraction force on the work by its exciting current, the close contact with the work is improved and the vibration of the work when the work is conveyed by the electromagnetic chuck is suppressed. You can In addition, even when there is a slight gap between the two workpieces during suction, the magnetic flux of the detector itself generates an attractive force between the first and second workpieces to close the gap and detect It has the effect of maintaining accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a two-sheet suction detection device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a state in which a detector is attached to an electromagnetic chuck.

FIG. 3 is a time chart showing an operation state of the present apparatus.

FIG. 4 is an excitation characteristic curve diagram of an excitation coil.

FIG. 5 is a curve diagram showing the number of workpieces and the integrator output voltage for each plate thickness.

FIG. 6 is an explanatory diagram of a dimensional configuration of a detector.

FIG. 7 is a lower surface portion of FIG.

[Explanation of symbols]

1 detector 3 iron core 4 main pole 5,7 magnetic pole 6 Yoke part 10 Excitation coil 11 Detection coil 15 Square wave oscillator 17 Integrator 20 arithmetic processing unit 21 Adsorption number table 30 electromagnetic chuck

Continuation of front page (56) Reference JP-A-55-22145 (JP, A) JP-A-60-188802 (JP, A) JP-A 61-122503 (JP, A) JP-A 52-49440 (JP , A) JP 63-241304 (JP, A) JP 59-114247 (JP, A) Actual development Sho 53-164187 (JP, U) Actual development Sho 54-3167 (JP, U) Actual development Sho 60-52036 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 7/06 B65H 7/12 B66C 1/08

Claims (3)

(57) [Claims] 1. An electromagnetic chuck provided separately from the electromagnetic chuck.
A two-piece suction detection device for a workpiece that is attracted and lifted by the electromagnetic chuck , wherein one end has one magnetic pole capable of abutting the workpiece and the other end abuts in the vicinity of the workpiece abutting portion. A detector comprising an iron core forming another possible magnetic pole, an exciting coil wound around the iron core, and a detection coil wound around the iron core; and generating a square wave voltage having a sync signal width T ₃ A square wave oscillator that excites the exciting coil of the detector, an integrator that integrates the output of the detecting coil of the detector, and an output of the integrator compared with a pre-stored adsorption number table A two-sheet suction detection device, comprising: an arithmetic processing unit that determines whether or not one sheet is adsorbed. 2. The two-sheet adsorption detection device according to claim 1, wherein the iron core of the detector is composed of a rod-shaped portion, a main pole portion whose lower end portion forms one magnetic pole, and a cylindrical portion. A yoke portion coaxially arranged outside the pole portion and having a lower end portion forming another magnetic pole, and the excitation coil and the detection coil are wound around the main pole portion, and the main pole portion. The two-sheet suction detecting device is characterized in that it is formed to have a diameter of at least 8 times the plate thickness of the workpiece to be sucked. 3. The two-sheet adsorption detector according to claim 1, wherein the exciting current of the exciting coil of the detector is added up to a value close to the magnetic saturation of the workpiece. Detection device.