JPH06293489A - Moving yoke type lifting magnet - Google Patents

Abstract

PURPOSE:To perform reliable decision of whether a work is attracted to a moving yoke even when the shape and the attraction posture of the work are not kept in a constant state. CONSTITUTION:An output signal from a first magnetic sensor 31 to detect a magnetic flux passing through a main iron core 21 and an output signal from a second magnetic sensor 32 to detect a magnetic flux passing through an auxiliary iron core 24 are compared with each other by means of a deciding means 35 and decision of whether a work 15 is attracted to moving yokes 23a and 23b is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movable yoke type lifting magnet for lifting a work by electromagnetic force,
In particular, the present invention relates to a movable yoke type lifting magnet capable of surely determining whether or not a work is attracted.

[0002]

2. Description of the Related Art By providing a main iron core provided with an exciting coil and an auxiliary iron core different from the main iron core, the attracting force of a movable yoke is increased to prevent the work from slipping and dropping during the work transfer, and to stabilize the work. A lifting magnet that makes it possible to convey a work is disclosed in Japanese Patent Publication No. 4-38679.

8 and 9 show an example of a conventional movable yoke type lifting magnet provided with an auxiliary iron core. In such a movable yoke type lifting magnet, when the coil 2 wound around the main iron core 1 is energized, a magnetic flux passing through the work 3 side and a magnetic flux passing through the auxiliary iron core 4 side are generated. Of these, the magnetic flux passing through the work 3 side generates a suction force on the contact surfaces of the movable yokes 5a, 5b and the work 3, and if the suction force is larger than the weight of the work, the work can be lifted.

On the other hand, due to the magnetic flux passing through the auxiliary iron core 4, an attractive force is generated on the contact surface between the movable yokes 5a and 5b and the main iron core 1 and on the contact surface between the auxiliary iron core 4 and the movable yokes 5a and 5b. As a result, an attractive force due to the combined magnetic flux of the two magnetic fluxes is generated in the movable yokes 5a and 5b, and
A large frictional force acts on the contact surface between 5b and the main iron core 1. Therefore, the movable yokes 5a and 5b are integrated with the main iron core 1 and the auxiliary iron core 4, and the attraction force of the movable yokes 5a and 5b is significantly increased.

As described above, by using the movable yoke-type lifting magnet using the auxiliary iron core as shown in FIGS. 8 and 9, it is possible to form a perforated work or a draw work which is difficult to be attracted by the vacuum cup. Work can be adsorbed, and work can be automatically conveyed.

[0006]

However, the movable yoke type lifting magnet shown in FIGS. 8 and 9 still has a problem to be solved.

Even when a plurality of workpieces randomly placed on a pallet or the like are conveyed one by one by the movable yoke type lifting magnets shown in FIGS. 8 and 9, the workpieces are lifted due to the deviation of the suction position and the overlapping state of the workpieces. May fail. Therefore, only the lifting magnet is conveyed to a predetermined position without adsorbing the work, and it may be noticed that there is no work for the first time, and there is a problem that transport time is lost.

As a countermeasure against such a problem, an overcurrent sensor or the like for detecting a work is attached to the surface of the movable yoke type lifting magnet facing the work, or an optical sensor or the like is arranged at a point where the suspended work passes. The presence or absence of the work is detected. However, in such a method, it is difficult to detect the work when the shape of the work is not constant or when the suction posture of the work is not constant. Further, even if the work can be detected, the equipment for the work detection becomes large in scale, which causes a problem in cost.

In view of the above problems, the present invention provides a movable yoke type lifting magnet capable of reliably determining whether or not a work is attracted to a movable yoke even when the shape or attraction posture of the work is not constant. The purpose is to provide.

[0010]

To achieve this object, a movable yoke type lifting magnet according to the present invention comprises a main iron core made of a magnetic material, and a magnetic material arranged at a distance from the main iron core. An auxiliary iron core, a movable yoke made of a magnetic material arranged so as to slide in a direction straddling the main iron core and the auxiliary iron core, and a coil wound around the main iron core and connected to a power source. A first magnetic sensor for detecting a magnetic flux passing through the main iron core, a second magnetic sensor for detecting a magnetic flux passing through the auxiliary iron core, an output signal from the first magnetic sensor and a second magnetic sensor Determination means for determining whether or not the work is attracted to the movable yoke by relative comparison with the output signal from the.

[0011]

In the movable yoke type lifting magnet constructed as above, the magnetic flux passing through the main iron core is detected by the first magnetic sensor, and the magnetic flux passing through the auxiliary iron core is detected by the second magnetic sensor.
Is detected by the magnetic sensor of. Here, since the main iron core and the auxiliary iron core are constantly in contact with each other, the magnetic flux passing through the main iron core, the auxiliary iron core, and the movable yoke as a loop hardly changes depending on whether or not the work is attracted, and the second magnetic sensor The output signal from is almost unchanged.

On the other hand, the magnetic flux passing through the main iron core greatly changes depending on whether or not the work is attracted. When the work is not attracted to the movable yoke, only the magnetic flux that passes through the main iron core, the auxiliary iron core, and the movable yoke as a loop is generated when the coil is energized, but when the work is attracted to the movable yoke, the main iron core and the auxiliary iron core. And a magnetic flux passing through the movable yoke as a loop and a magnetic flux passing through the main iron core, the workpiece, and the movable yoke as a loop.

Thus, when the work is attracted to the movable yoke, both the magnetic flux passing through one loop and the magnetic flux passing through the other loop pass through the main iron core. This allows
When a work is attracted, the number of magnetic fluxes increases compared to when the work is not attracted, and the output signal from the first magnetic sensor changes greatly. Therefore, by comparing the output signal from the first magnetic sensor with the output signal from the second magnetic sensor by the determination means, it is possible to reliably determine whether or not the work is attracted to the movable yoke. Become.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the movable yoke type lifting magnet according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 6 show a first embodiment of the present invention.
1 to 3, reference numeral 21 indicates a main iron core.
The main iron core 21 is made of a soft magnetic material such as mild steel. A coil 22 for excitation is arranged on the outer periphery of the main iron core 21. The coil 22 is made by winding an enameled copper wire a large number of times and subjected to an insulation treatment.

The movable yoke 2 is provided on both end surfaces of the main iron core 21.
3a and 23b are arranged. Movable yoke 23a, 2
3b is made of a soft magnetic material. Above the main iron core 21, the auxiliary iron core 2 is provided at a predetermined distance from the main iron core 21.
4 are arranged. The movable yokes 23a and 23b are arranged so as to be able to slide in the direction in which they are in contact with the main iron core 21 and the auxiliary iron core 24.

The tips of the movable yokes 23a and 23b are tapered. The movable yokes 23a and 23b are shown in FIG.
Not only the flat plate-shaped work 15 shown in FIG. The coil 22 is the switch 2
5 is connected to the DC power supply 26. Switch 2
When 5 is turned on and the coil 22 is excited, a magnetic flux φ _w passing through the work 15 side and a magnetic flux φ _a passing through the auxiliary iron core 24 side are generated, and the work 15 moves the movable yoke 23.
Adsorbed on a and 23b.

The main iron core 21 is divided into two parts in the left-right direction from a substantially central portion. A recess 27 is formed in the center of one of the divided surfaces of the main iron core 21. The split surface of the main iron core 21 is
They are connected via a spacer 28. The recess 27 of the main iron core 21 is provided with a first magnetic sensor 31 that detects a magnetic flux passing through the main iron core 21.

The auxiliary iron core 24 is divided into two parts in the left-right direction from a substantially central portion. A recess 29 is formed in the center of one side of the split surface of the auxiliary iron core 24. The split surfaces of the auxiliary iron core 24 are joined via a spacer 30. The recess 29 of the auxiliary iron core 24 is provided with a second magnetic sensor 32 for detecting the magnetic flux passing through the auxiliary iron core 21.

The first magnetic sensor 31 includes a first amplifier 3
3 and the output signal from the first magnetic sensor 31 is amplified by the first amplifier 33. The second magnetic sensor 32 is connected to the second amplifier 34, and the output signal from the second magnetic sensor 32 is amplified by the second amplifier 34. Each magnetic sensor 31, 32 is composed of, for example, a Hall element or a magnetoresistive element.

The output signals from the magnetic sensors 31 and 33 amplified by the amplifiers 33 and 34 are input to a comparator 35 as a judging means. The comparator 35 has a function of determining whether or not the work 15 is attracted to the movable yokes 23a and 23b by relative comparison between the output signal from the first magnetic sensor 31 and the output signal from the second magnetic sensor 32. Have

FIG. 5 shows the coil input voltage and each amplifier 33,
34 shows the relationship with the output signals V _m and V _a from 34.
The characteristic (a) in FIG. 5 is that the work 15 has the movable yoke 23a,
23B shows an output signal from the first amplifier 33 when the work 15 is not attracted to the movable yokes 23a and 23b, and a characteristic (b) shows an output signal from the first amplifier 33 when the work 15 is attracted to the movable yokes 23a and 23b. Shows the signal. Characteristics (C)
Indicates the output signal from the second amplifier 34.

As shown in FIG. 5, the second amplifier 34 is
The output signal from the second magnetic sensor 32 that detects the magnetic flux φ _a passing through the auxiliary iron core 24 is amplified, and the output signal V _a from the second amplifier 34 is almost left or right depending on whether or not the work 15 is attracted. Not done. On the other hand, the output signal V _m from the first amplifier 33 that amplifies the output signal from the first magnetic sensor 31 greatly changes depending on whether or not the work 15 is attracted. Therefore, by grasping the change in the output signal V _m of the first amplifier 33 with respect to the output signal V _a of the second amplifier 34, it is possible to reliably determine whether or not the work 15 is attracted to the movable yokes 23a and 23b. It becomes possible.

The comparator 35 includes an LED as a display means.
(Light emitting diode) 36 is connected. Comparator 35
When the work 15 is determined not to be attracted to the movable yokes 23a and 23b, the LED 36 is turned on.

Next, the operation of the first embodiment will be described. When a current is supplied to the coil 22 from the DC power supply 26 via the switch 25, a magnetic flux φ _w passing through the work 15 side and a magnetic flux passing through the auxiliary iron core φ _a are generated.

Here, when the thickness of the work 15 is T ₁ , the thickness of the main iron core 21 is T ₂ , and the thickness of the auxiliary iron core 24 is T ₃ , if T ₂ > (T ₁ + T ₃ ), the main iron core 21 There is a margin in the generated magnetic flux, and since there is magnetic flux φ _a , the magnetic flux φ _w
Will never decrease. Therefore, an attraction force is generated on the attraction surface of the main iron core 21 by the combined magnetic flux of the magnetic fluxes φ _w and φ _a , and an attraction force is generated on the attraction surface of the auxiliary iron core 24 by the magnetic flux φ _a .

On the attracting surfaces of the movable yokes 23a and 23b,
An attractive force is generated by the magnetic flux φ _w , and if the attractive force is larger than the work weight, the movable yokes 23a and 23b can lift the work 15. The lifting magnet that has lifted the work 15 is transported to a predetermined position by a transport unit (not shown).

When the work 15 is attracted, a part of the magnetic flux (φ _a + φ _w ) passing through the main iron core 21 passes through the first magnetic sensor 31 and gives a magnetic flux density B _m there. Similarly, the auxiliary core 24
A part of the magnetic flux passing through passes through the second magnetic sensor 32 and gives the magnetic flux density B _a there. It is known that when a Hall element is used as the magnetic sensor, its output voltage is proportional to the bias current and the magnetic flux density B.

The basis of the magnetic circuit in the present invention is the relationship between the output voltages from the magnetic sensors 31 and 32, and the relationship of V _m > V _a must be established when the work 15 is adsorbed. Therefore, the excitation condition is set so that the auxiliary iron core 24 is in a magnetic saturation state or a state close thereto.

When using the lifting magnet, the amplifiers 33 and 34 are adjusted in advance. First, in the non-excited state of the coil 22, the two amplifiers 3
Zero adjustment is performed so that the output voltages V _m and V _a from 3, 34 become zero. Next, the rated voltage is applied to the coil 22 and the output voltage V _a of the amplifier 34 is applied to the amplifier 33 without adsorbing the work 15 to the movable yokes 23a and 23b.
Output voltage V _{m of} several percent (for example, V _a = 1.05 V
_m ) Increase. This completes the adjustment of the amplifiers 33 and 34.

[0031] When the work 15 by the excitation of the coil 22 is attracted to the movable yoke 23a, 23b, magnetic flux passing through the main core 21 increases from phi _a to φ _a + φ _w, given to the first magnetic sensor 31 The magnetic flux density increases and each amplifier 3
The relationship of the output signals from 3, 34 is V _a > V _m .

FIG. 5 shows changes in the output voltages of the amplifiers 33 and 34 depending on whether or not the work 15 is adsorbed. Second
The output voltage V _a of the amplifier 34 is almost independent of whether or not the work 15 is adsorbed. On the other hand, the first amplifier 3
The output voltage V _{m of} 3 is smaller than the output voltage V _a of the second amplifier 34 when the work 15 is not adsorbed, and is larger than the output voltage V _a when the work 15 is adsorbed. In addition, the input voltage of the coil 22 is 60 to 120%
Be varied in the range of the output voltage V _a is the output voltage V _m1, V
_It will be located almost in the middle between _m2 and stable operation can be obtained.

As described above, in this embodiment, the output voltages V _m and V _a of the amplifiers 33 and 34 based on the output signals from the magnetic sensors 31 and 32 are relatively compared by the comparator 35 to obtain V
_{If a} > V _m , it is determined that the work 15 is not adsorbed,
If V _a <V _m , it is determined that the work 15 has been adsorbed. When it is determined that the work 15 is not sucked,
Depending on the output signal from the comparator 35, L as a display means
The ED 36 lights up.

By turning on the LED 36, the work 15
Is stopped, and the work 15 is sucked again. In the present embodiment, the non-adsorption of the work 15 is controlled by the LED 3
Although the display is made by turning on 6, the output signal from the comparator 35 may be input to the conveying means (not shown). With such a configuration, even if the work 15 falls during the conveyance, the conveyance can be immediately stopped by the output signal from the comparator 35, and appropriate measures can be taken.

The comparator 35 also has the following functions.
Volatile. Workpiece attracted to the movable yokes 23a and 23b
15 is a flat plate, and the work 15 is always placed at a fixed position.
As long as the suction is possible, it depends on the number of suctioned workpieces 15.
Output voltage V of amplifier 33 _mChanges as shown in Figure 6.
It

In FIG. 6, V _m2 indicates the output voltage of the amplifier 33 when one work 15 is adsorbed, and V _m3 indicates the output voltage of the amplifier 33 when two work 15 are adsorbed. . Therefore, when the output voltage from the amplifier 33 exceeding V _m3 is output to the comparator 35, the work 1
By providing a function of outputting a signal indicating that two sheets are detected as 5 sheets, it is possible to display the conveyance failure as a display different from the work suction failure.

The function of detecting two workpieces as described above becomes very effective when a flat plate workpiece is put into a press machine. Further, if the function is to detect only the two-sheet suction, the output of the amplifier is adjusted so that the output voltage has _a relationship of V _a > V _{m in} the state where one workpiece 15 is sucked, and the two workpieces are sucked. In this state, the output of the amplifier may be adjusted so that the output voltage has _a relationship of V _a <V _m .

Second Embodiment FIG. 7 shows a second embodiment of the present invention. The second embodiment is different from the first embodiment only in the arrangement of the magnetic sensor, and the other parts are the same as those in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are applied to the corresponding parts. Description of parts will be omitted, and only different parts will be described.

FIG. 5 shows an arrangement example of the magnetic sensors 31 and 32. The work 15 has movable yokes 23a and 23b.
When it is attracted to the entire attracting surface of each of the magnetic sensors 31,
32 may be provided in the central portions of the main iron core 21 and the auxiliary iron core 24, respectively, but when the work 15 is adsorbed only at the end portions, the distance between the work 15 and the magnetic sensors 31 and 32 becomes large, and Output voltage V _m2 from the magnetic sensor 31 of
May not exceed the output voltage V _a from the second magnetic sensor 32.

When the attraction of the work as described above is expected, as shown in FIG. 7, the magnetic sensors 31 and 32 are arranged also at both ends of the main iron core 21 and the auxiliary iron core 24, and three magnetic sensors are provided. The output voltage V _m2 having the largest output voltage among the output signals 31 and 32 is input to the comparator 35. As a result, even if the suction position is shifted, it is possible to reliably determine whether or not the work 15 is sucked.

[0041]

According to the present invention, the following effects can be obtained.

(1) The output signal from the first magnetic sensor for detecting the magnetic flux passing through the main iron core and the output signal from the second magnetic sensor for detecting the magnetic flux passing through the auxiliary iron core are relatively compared by the judging means. Since the presence / absence of suction of the work is determined, it is possible to reliably determine the presence / absence of suction of the work on the movable yoke even when the shape and the suction posture of the work are not constant. Therefore, it is possible to prevent only the lifting magnet from being conveyed without adsorbing the work, and it is possible to reduce the conveyance loss time.

(2) By comparing the output signal from the first magnetic sensor and the output signal from the second magnetic sensor, it is possible to determine whether or not a plurality of workpieces are attracted, and two workpieces are supplied. It is very effective in press molding operations that should not be done.

(3) Since it is determined whether or not the work is adsorbed by the relative comparison between the output signal from the first magnetic sensor and the output signal from the second magnetic sensor, the preset value and the preset value Compared to the configuration in which the output signal from the magnetic sensor of No. 1 is compared, it is less likely to be affected by disturbance, and stable performance can be exhibited even when the coil input voltage fluctuates.

(4) Instead of externally detecting the work adsorbed by the lifting magnet by an optical sensor or the like as in the conventional case, the presence or absence of the work adsorption is determined based on the change of the magnetic flux. This is also a significant advantage in terms of reliability and cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a movable yoke type lifting magnet according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an operating state of the apparatus of FIG. 1 when a work is not adsorbed.

FIG. 3 is a cross-sectional view showing a state of magnetic flux generated when a work is attracted by the apparatus of FIG.

FIG. 4 is a cross-sectional view showing a mounted state of a first magnetic sensor in the apparatus of FIG.

5 is a characteristic diagram showing the relationship between the presence or absence of workpiece adsorption and the output voltage of the amplifier in the apparatus of FIG.

FIG. 6 is a characteristic diagram showing the relationship between the number of workpieces attracted and the output voltage of the amplifier in the apparatus of FIG.

FIG. 7 is a front view showing an arrangement of magnetic sensors in a movable yoke type lifting magnet according to a second embodiment of the present invention.

FIG. 8 is a front view showing an example of a conventional movable yoke type lifting magnet.

9 is a side view of FIG.

[Explanation of symbols]

15 work 21 main iron core 22 coil 23a movable yoke 23b movable yoke 24 auxiliary iron core 31 first magnetic sensor 32 second magnetic sensor 35 determination means 36 display means φ _w magnetic flux φ _a magnetic flux

Front page continuation (72) Inventor Hideo Niwa 6-10 Ushimakicho, Mizuho-ku, Nagoya, Aichi Sanmei Electric Co., Ltd.

Claims (1)

[Claims] 1. A main iron core made of a magnetic material, an auxiliary iron core made of a magnetic material arranged at a distance from the main iron core, and sliding in a direction in which the main iron core and the auxiliary iron core are in contact with each other. A movable yoke made of a magnetic material that is arranged as much as possible, a coil wound around the main iron core and connected to a power source, a first magnetic sensor that detects a magnetic flux passing through the main iron core, and the auxiliary iron core. Whether or not the work is attracted to the movable yoke is determined by relative comparison between the output signal from the second magnetic sensor that detects the passing magnetic flux and the output signal from the first magnetic sensor. A movable yoke type lifting magnet, comprising: a determining unit.