JP2709678B2 - Permanent electromagnetic chuck control 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 chuck used for fixing and holding a work in a machine tool, and more particularly to a control device for a permanent electromagnetic chuck which is turned on and off by attaching a permanent magnet, demagnetizing the magnet.

[0002]

2. Description of the Related Art Permanent electromagnetic chucks are roughly classified into a method of turning on and off by attaching and removing a permanent magnet, and a method of turning on and off by changing the polarity of a permanent magnet.

[0003] When the two are compared in terms of demagnetization of the work, which is a problem when the work is removed, the former, that is, the magnet demagnetization method is advantageous.

[0004] According to other classification methods, there are three methods: an attenuation control method by DC excitation, a capacitor charging adjustment attenuation method, and a pulse time control attenuation method.

[0005] Among them, in the damping control method by DC excitation, the number of turns of the coil is increased as much as the electromagnetic chuck to limit the magnetizing current. Also, in the capacitor charge adjustment / decay method, the number of turns is reduced and magnetization is performed by discharging a large instantaneous pulse, and demagnetization is performed by controlling the charge amount of the capacitor to perform attenuating discharge control. However, this demagnetization method has never been used for a permanent electromagnetic chuck. Further, the pulse time control damping method has never been attempted with a permanent electromagnetic chuck.

Conventionally, when the chuck is of the detachable magnetic type, the work is demagnetized by performing the first type of "decay control method by DC excitation", but when the chuck is of the polarity conversion type. Does not consider demagnetization of a workpiece by performing only magnetization in the second method, “capacitor charging / discharging method”.

[0007]

According to the first method,
The demagnetization of the work is performed together with the demagnetization of the permanent magnet.Therefore, when the work is made of a material having a relatively large coercive force, there is a problem that the demagnetization is deteriorated. There is a problem. On the other hand, in the second method, a capacitor as a power supply is charged in order to allow a large pulse current to flow. However, this charging time is required, and a sufficient discharge current cannot be obtained due to a problem of the capacitor capacity. It takes more time to complete the magnetization by repeating charge and discharge, and demagnetization is not performed.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and has as its object to provide a control device for a permanent electromagnetic chuck in which the time required for magnetizing and demagnetizing the chuck is short and the workpiece can be demagnetized. Aim.

[0009]

According to the present invention, there is provided a control apparatus for a permanent electromagnetic chuck which is turned on and off by magnetizing or demagnetizing a permanent magnet.
A permanent magnet type chuck including a plurality of iron cores including a permanent magnet serving as a magnetomotive source and configured to have a long cross section, and a coil wound on the iron core with a small number of turns; and When the chuck is turned on, a pulsed large current is supplied as the magnetizing current, and when the chuck is turned off, a pulse time control type power supply is provided, in which an alternating decay current is directly passed by a large half-pulse current control. And a controller for a permanent electromagnetic chuck.

[0010]

[Effect] The permanent electromagnetic chuck is effective for the skin effect phenomenon that hinders the exciting magnetic flux because the cross section is long,
A large magnetic field generated by a large current excitation method using a coil having a small number of turns can be obtained, and the time for attaching and detaching magnets can be shortened. Since the permanent electromagnetic chuck is easy to attach and detach, the pulse current from the pulse time control type power supply or the alternating half-wave decay current is applied to the permanent electromagnetic chuck to effectively attach it to the workpiece. , Demagnetization is performed.

[0011]

As described above, according to the present invention, the permanent magnet type chuck which is easily attached and detached is energized from the pulse time control type power supply, so that attachment and detachment can be performed efficiently. Therefore, the detachable magnetizing time, which required several seconds in the conventional apparatus, is greatly reduced, and the ON state can be completed in 0.15 seconds and the OFF state can be completed in 2 seconds.

[0012]

1 and 2 show a magnetic pole pattern used in an embodiment of the present invention. Among them, FIG. 1 is referred to as a vertical magnetic pole pattern, and has a cross-sectional shape suitable for an elongated core. FIG. 2 shows a horizontal magnetic pole pattern, which is the most commonly used shape, but shows an example in which the magnetic pole width is reduced in order to form a slender shape, and the magnetic pole interval is accordingly reduced.

FIGS. 3 to 6 and FIGS. 7 to 10
3 to 6 show specific chuck suction surfaces and internal structures. FIGS. 3 to 6 show a permanent electromagnetic chuck for a grinding machine, and FIGS. 7 to 10 show a permanent electromagnetic chuck for cutting.

In the examples of FIGS. 3 to 6, the upper surface of the elongated core 2 is an attraction surface, and a plurality of permanent magnets 4 serving as a magnetomotive source are arranged on the bottom plate 1a on the lower surface as shown in FIG. Have been. Then, as shown in FIG. 3 and FIG.
, Side plates 1b and 1c and an intermediate plate 1d are alternately arranged with an iron core.

Then, as shown in FIG. 6, the side plates 1b, 1c
An insulated electric wire (generally, a vinyl electric wire) is wound around the iron core 2 and the permanent magnet 4, which are framed on the intermediate plate 1 d, several tens times into a coil shape to form a coil 5. It is continuously contracted into coils.

Further, as shown in FIG. 6, an induction magnetic pole 3 is provided above the respective coils 5 and between the iron core 2 and the intermediate plate 1d with a separator 6a interposed therebetween. The shape is so fine that even small workpieces can be easily absorbed.

The example shown in FIG. 7 to FIG. 10 is a strong type in which iron cores 2 are arranged side by side with different polarities, are formed directly as counter electrodes without a middle plate via a separator 6a, and are used for a chuck for cutting. .

The separator 6a is made of a brass plate or other non-ferrous metal to form the adsorption surface, and thus has much better mechanical structural characteristics than a resin.

FIGS. 11 and 12 illustrate the difference between the coil arrangements shown in FIGS. 3 to 6 and the coil arrangements shown in FIGS. 7 to 10. FIG. In FIG. 11, the iron core 2 and the yoke (intermediate plate) 1d are alternately arranged,
The coil 5 is wound only on the iron core (the iron core magnetic pole 2 and the permanent magnet 4). In FIG. 12, only the iron cores (the iron core magnetic poles 2 and the permanent magnets 4) are arranged side by side, and the coils 5 are wound and connected so as to have mutually different polarities.

FIG. 13 shows a method of forming the magnetic pole interval in the above embodiment. That is, in order to reliably maintain the gap between the induction magnetic pole 3 and the iron core magnetic pole 2 and the intermediate plate 1d,
The gap is replaced with a spacer 6c instead of the separator 6a to facilitate assembly. The gap is finally integrated with the separators 6a and 6b by filling with resin. And the polarity of the iron core is the same polarity arrangement, and the intermediate plate and the side plate are opposite poles.

In the chuck having the above-described structure, an alnico magnet or a rare earth magnet having a large residual magnetic flux density is used for the iron core. When a chuck is turned on from a power supply circuit (not shown) (for example, refer to Japanese Patent Application No. 3-99195), a large positive pulse current flows through the coil to magnetize it. As a result, a magnetic circuit returns to the permanent magnet through the permanent magnet 4, the iron core magnetic pole 2, the work, the yoke (side plate 1b or intermediate plate 1d) of the counter electrode, and the bottom plate 1a.

When the counter electrode is the same permanent magnet core instead of the yoke, they are arranged in an NS relationship. Next, in the case of chuck-off, an alternating damping control current of a half-wave time control method is applied to the coil to demagnetize. In order to sufficiently cope with the magnetic flux change in this case, the shapes of the permanent magnet 4 and the iron core 2 and the number of turns of the coil 5 are important matters.

Table 1 shows that, for a chuck having a size of 300 mm × 600 mm, three types of work materials having a size of 105 mm × 101 mm × 19 mm were used, and a peeling force at the time of chuck-off (residual magnetism) for a raw material and a quenched material. Is shown by actual measurement.

[0024]

[Table 1] In this measurement, the number of turns of the coil was 30, and an on time of about 0.15 seconds and an off time of about 2 seconds were obtained. This is a remarkable improvement in performance in comparison with the conventional capacitor charging / discharging method that required about 7.5 seconds. As for demagnetization, what could not be done by the conventional capacitor charging / discharging method can be made, which is essentially different.

The peeling force (residual magnetism) is 1.8 k
gf-2.2 kgf, and when the work weight 1.6 kg is subtracted, the weight is 0.6 kg.

The residual magnetism after peeling is 9 G-30 G, which is 15 G-134 G by the conventional capacitor charging / discharging method.
It can be seen that even if the difference is the smallest, a considerable difference occurs. This is because the coil according to the present invention has a small number of turns, whereas the conventional coil has a relatively large number.

FIG. 14 shows the relationship between the shape of the iron core and the releasability and adsorbability of the work. That is, the width B of the iron core and the elongation ratio, that is, the ratio (A / B) of the length A to the width B in FIGS. Taking the force F results in the two curves shown.

These curves show that as the width B increases and the ratio A / B decreases, the peeling force f and the attracting force F both increase, and the peeling force f decreases significantly in a region where the width is relatively large. On the other hand, the adsorption force F tends to decrease significantly in a region where the ratio A / B is large.

Therefore, it is necessary to select a dimension such as A / B = 10 so as to obtain a required suction force and an appropriate peeling force.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a magnetic pole pattern used in an embodiment of the present invention.

FIG. 2 is an explanatory view showing a magnetic pole pattern used in the embodiment of the present invention.

FIG. 3 is a plan view showing a specific chuck suction surface used in the present invention.

FIG. 4 is an enlarged plan view of a specific chuck suction surface shown in FIG. 3;

FIG. 5 is a partial front sectional view of the specific chuck shown in FIG. 3;

FIG. 6 is a partial sectional side view of the specific chuck shown in FIG. 3;

FIG. 7 is a plan view showing another specific chuck suction surface used in the present invention.

FIG. 8 is an enlarged plan view of a specific chuck suction surface shown in FIG. 7;

FIG. 9 is a partial front sectional view of the specific chuck shown in FIG. 7;

FIG. 10 is a partial sectional side view of the specific chuck shown in FIG. 7;

FIG. 11 is a sectional view showing a coil arrangement according to the configuration of FIGS. 3 to 6;

FIG. 12 is a sectional view showing a coil arrangement according to the configuration of FIGS. 7 to 10;

FIG. 13 is an explanatory diagram showing a method of forming a magnetic pole interval in the embodiment of the present invention.

FIG. 14 is a characteristic diagram showing the relationship between the shape of an iron core and the releasability and adsorption of a workpiece.

[Explanation of symbols]

 1a Bottom plate 1b Side plate 1c Side plate 1d Intermediate plate 2 Iron core 3 Induction pole 4 Permanent magnet 5 Coil 6a Separator 6b Separator 6c Spacer A Length B Width

Claims (4)

(57) [Claims] 1. A control device for a permanent electromagnetic chuck which is turned on and off by magnetizing or demagnetizing a permanent magnet, comprising a permanent magnet serving as a magnetomotive source and having a long cross section. A permanent magnet chuck having a plurality of iron cores, and a coil wound around the iron core with a small number of turns, and when a large pulse current is supplied as a magnetizing current when the permanent electromagnetic chuck is turned on and off, A permanent electromagnetic chuck control device comprising a pulse time control type power supply for directly supplying an alternating decay current by a large current time control of a pulse half-wave. 2. An apparatus according to claim 1, wherein an iron core of said chuck is configured such that a magnetic pole extends along a longitudinal direction of said chuck. 3. The apparatus according to claim 1, wherein the iron core of the chuck is configured such that a magnetic pole extends in a direction perpendicular to a longitudinal direction of the chuck, and the width of the magnetic pole is reduced so that the pole face is elongated. Control device for permanent magnet type chuck. 4. The control device according to claim 1, wherein the coil is formed by directly winding an insulated wire for wiring around the iron core.