Magnetic clamp device

Abstract

To reconsider a contact area between a mold and a magnetic pole and to optimize the contact area between the mold and the magnetic pole.SOLUTION: A magnetic clamp device 1 includes a plate main body 2 and a magnetic pad 3 arranged in a housing chamber 2a. The magnetic pad 3 includes a magnetic pole 6 having a pad surface PS, a polarity-reversible magnet 8 that is provided between the magnetic pole 6 and a bottom 2b of the housing chamber 2a and can reverse its polarity, and a polarity-unreversible magnet 7 provided between the magnetic pole 6 and a side face 2e of the inner periphery of the housing chamber 2a and surrounding the magnetic pole 6. The pad surface PS is provided with a control recess 5 that controls the area of the pad surface PS to make the area M of the magnetic pole of the polarity-unreversible magnet 7 coincide with the area A of the pad surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic clamping device.

[0002] A magnetic clamp device for an injection molding machine that utilizes magnetic attraction is known as a fixing device for an object to be fixed, such as a mold. The magnetic clamp device is a device that magnetically fixes a mold to a plate body made of a magnetic material attached to a platen of an injection molding machine. The plate body is provided with a plurality of magnetic pads, and each magnetic pad has a non-reversible magnet (e.g., a neodymium magnet) that is provided around a magnetic pole and a reversible magnet (e.g., an alnico magnet) that is reversible and that is arranged on the back side of the magnetic pole. By controlling the magnetic polarity of the alnico magnet with a coil, it is possible to switch between a magnetic circuit that is closed within the plate body and a magnetic circuit that passes through the mold.

[0003] For example, according to Patent Document 1, the magnetic clamp device has a plate body made of a magnetic material and a magnetic pad. The magnetic pad is cylindrical and is disposed in a bottomed accommodation chamber drilled on the front side of the plate body. The magnetic clamp device has a magnetic pole, a non-reversible magnet disposed around the magnetic pole, a reversible magnet disposed on the back side of the magnetic pole, and a coil disposed around the reversible magnet. A through hole is drilled in the center of the magnetic pole, into which a bolt is inserted. This through hole is provided with a deep countersunk hole that hides the head of the bolt. The magnetic pad is fixed by inserting the bolt into the through hole and screwing it into a female screw hole provided at the bottom of the hollow portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5301117 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] As shown in Patent Document 1, the magnetic pole of the magnetic pad is designed to have a large contact area with the die in order to allow the magnetic flux of the non-reversible magnet to pass through the die without leaking, and to attract the die. A through hole with a deep countersunk hole is drilled in the center of the magnetic pole, which reduces the contact area between the die and the magnetic pole, and the deep countersunk hole is designed to have a diameter as close as possible to the size of the bolt head. The deep countersunk hole is designed to be as close as possible to the size of the bolt head in order to prevent the accumulation of dirt such as iron powder and oil. The contact area between the die and the magnetic pole is currently large, and no further consideration has been given to this.

[0006] The object of the present invention is to reconsider the contact area between the mold and the magnetic pole and to optimize the contact area between the magnetic pole and the mold. [Means for solving the problem]

[0007] The present invention is a magnetic clamping device comprising a plate body made of a magnetic material having a bottomed storage chamber on its surface, and a magnetic pad placed in the storage chamber, wherein the magnetic pad has a magnetic pole having a pad surface that comes into contact with an object of the magnetic material to be fixed, a reversible magnet whose polarity can be reversed that is arranged between the magnetic pole and the bottom of the storage chamber, and a non-reversible magnet that is arranged between the magnetic pole and the side of the inner circumference of the storage chamber and surrounds the magnetic pole, and is characterized in that an adjustment recess for adjusting the area of ​​the pad surface is provided on the pad surface to match the area of ​​the magnetic pole of the non-reversible magnet and the area of ​​the pad surface. Effect of the Invention

[0008] According to the present invention, the area of ​​the pad surface can be adjusted to be equal to the area of ​​the magnetic pole of the non-reversible magnet by the adjustment recess, thereby increasing the attractive force. [Brief description of the drawings]

[0009] [Figure 1]1A and 1B are diagrams showing a magnetic clamp device, in which FIG. 1A is a diagram showing the magnetic clamp device from the front side, and FIG. 1B is a cross-sectional view of one magnetic pad. [Diagram 2] 2A is a cross-sectional view of a magnetic pad, FIG. 2B is a view showing a magnetic pole and a non-reversible magnet arranged around it, and FIG. 2C is an enlarged cross-sectional view of an adjustment recess (the area circled by the dotted line in FIG. 2A). [Diagram 3] 3A and 3B are diagrams for explaining the evaluation environment, where FIG. 3A is a diagram for explaining the evaluation tool, and FIG. 3B is a diagram for explaining the range of the magnetic pads to be evaluated. [Figure 4] FIG. 13 is a diagram showing experimental results. [Diagram 5] FIG. 13 is a diagram for explaining another embodiment. BEST MODE FOR CARRYING OUT THEINVENTION

[0010] If the cross-sectional area through which the magnetic flux passes is large, the magnetic flux density decreases and the adhesive force per unit area decreases, but the adhesive force of the non-reversible magnet to the mold should remain unchanged when considered in terms of the total area. On the other hand, if the cross-sectional area through which the magnetic flux passes is narrow, the magnetic flux density increases and the adhesive force per unit area increases, but magnetic flux leakage becomes more likely, and the adhesive force of the non-reversible magnet to the mold should decrease when considered in terms of the total area.

[0011] However, according to the inventors' verification, it has become clear that it is not always better to have a large contact area between the magnetic object to be fixed (e.g., a mold) and the magnetic pole. It is difficult to predict all of the paths that the magnetic flux will take, but the magnetic flux will move forward searching for an easy path to pass through and establish a path. The inventors deduced that the magnetic flux would be most powerful when it is allowed to move forward searching for an easy path to pass through when the magnetic flux density is at its highest, and then establish a path, and so conducted verification.

[0012] The configuration according to the present invention is such that the area of ​​the magnetic pole of the non-reversible magnet is made to match the area of ​​the magnetic pole that contacts the mold. Since the magnetic force of the reversible magnet is weaker than that of the non-reversible magnet, and it is considered that there is almost no magnetic flux of the reversible magnet passing through the surface of the magnetic pole that contacts the mold, the area of ​​the magnetic pole that contacts the mold is determined based on the area of ​​the magnetic pole of the non-reversible magnet. The following describes an embodiment of the present invention. [Example 1]

[0013] Fig. 1 is a diagram showing a magnetic clamp device 1. Fig. 1A is a diagram showing the magnetic clamp device 1 as viewed from the front side, and Fig. 1B is an enlarged perspective view of a magnetic pad 3 portion.

[0014] 1A, the magnetic clamp device 1 has a plate body 2 made of a magnetic material and a number of magnetic pads 3 provided on the surface of the plate body 2. The surface of the plate body 2 is also provided with a proximity sensor, a through hole into which an ejector rod (not shown) is inserted, and the like.

[0015] In FIG. 1B, the magnetic pad 3 is disposed in the bottomed accommodation chamber 2a of the plate body 2. In the figure, the magnetic pad 3 at the upper right is removed. The magnetic pad 3 is cylindrical, and the pad surface PS comes into contact with a mold (not shown). A deep countersink 4 is drilled in the center of the surface of the magnetic pad 3. Visible in the deep countersink 4 is the head 12a of the bolt 12. The bolt 12 fixes the magnetic pad 3 to the female screw hole 2c in the bottom 2b of the accommodation chamber 2a. Around the deep countersink 4, an adjustment recess 5 is provided that is lower than the pad surface PS. The adjustment recess 5 is provided to adjust the area of ​​the pad surface. Due to the deep countersink 4 and the adjustment recess 5, the head 12a of the bolt 12 is lower than the pad surface PS by 0.2 mm or more. In addition, the cavity 2d is a cavity for wiring to the magnetic pad 3.

[0016] FIG. 2 is a diagram illustrating the magnetic pad 3, where FIG. 2A is a cross-sectional view, FIG. 2B is a diagram showing the magnetic pole 6 and the non-reversible magnet 7 arranged around it, and FIG. 2C is an enlarged cross-sectional view of the adjustment recess 5 (the area circled by the dotted line in FIG. 2A).

[0017] 2A, the magnetic pad 3 has a magnetic pole 6, a non-reversible magnet 7 (e.g., a neodymium magnet) that is provided so as to surround the magnetic pole 6 in a circular manner and that allows polarity reversal, a reversible magnet 8 (e.g., an alnico magnet) that is provided on the back side of the magnetic pole 6 and allows polarity reversal, a bobbin 9 that is provided around the reversible magnet 8, and a coil 10 that is wound around the bobbin 9. The magnetic pole 6 has a circular outer periphery, and one end face is the pad surface PS.

[0018] The magnetic pole 6 is made of a ferromagnetic material such as steel. The magnetic pole 6 and the reversible magnet 8 have through holes 6a and 8a, respectively, along the central axis c, and the through holes 6a and 8a are in communication with each other. The through holes 6a and 8a are through holes without threads. A deep countersink 4 is provided at the entrance of the through hole 6a to accommodate the head 12a of a bolt 12. The bolt 12 fixes the magnetic pole 6 and the reversible magnet 8 to the bottom 2b of the accommodation chamber 2a via a sealing material 12b (seal washer).

[0019] The magnetic pole 6 is in contact with the non-reversible magnet 7 along its outer periphery 6b. Above the non-reversible magnet 7, between the magnetic pole 6 and the plate body 2, the outer periphery 6b of the magnetic pole 6 extends with a thin thickness until it comes into contact with / or is close to the inner periphery 2e of the plate body 2. A sealing material 11 (O-ring) is provided below the outer periphery 6b for sealing to improve watertightness.

[0020] In FIG. 2B, the irreversible magnet 7 is polarized to N and S poles in the radial direction of the magnetic pole 6. The irreversible magnet 7 is divided into a plurality of arcuate sides 7a-7d of the same shape in the circumferential direction, and each arcuate piece is a 45-degree arc. The arcuate sides 7a-7d are combined to form a ring-shaped irreversible magnet 7. The arcuate sides 7a-7d are arranged so that there is as little gap as possible between the inner peripheral side 2e of the accommodation chamber 2a and the outer peripheral surface of the magnetic pole 6. The arcuate sides 7a-7d are arranged so that the magnetic poles are aligned on the inner peripheral side and the outer peripheral side. When the mold is attracted, the magnetic poles of the irreversible magnet 7, either the N pole or the S pole, that are in contact with the magnetic pole 6 on the inner peripheral side of the arcuate sides 7a-7d, appear on the pad surface PS.

[0021] The adjustment recess 5 is a recess having a circular outer periphery with a diameter d centered on the central axis c of the magnetic pole 6, which is similar to the outer periphery of the magnetic pole 6 or the circular shape of the inner periphery of the non-reversible magnet 7. The adjustment recess 5 is provided around the deep countersink 4 and at the center of the pad surface PS. The reason why the adjustment recess 5 is not provided on the outer periphery of the magnetic pole 6 is that if the adjustment recess 5 is provided on the outer periphery of the magnetic pole 6, only a long path will remain from the non-reversible magnet 7 to the die.

[0022] In FIG. 2C, the cross section of the adjustment recess 5 has an inclined surface 5b with an inclination angle θ extending from the pad surface PS to the bottom surface 5a of the adjustment recess. By providing this inclined surface 5b, iron and oil stains can be quickly removed. The inclination angle θ is set to 30 degrees. The depth h of the adjustment recess 5 is set to 0.5 mm, which is greater than the measurement limit of 0.2 mm of a proximity sensor generally used in the magnetic clamp device 1 to detect the drop of a mold. The depth h of the adjustment recess 5 is significantly shallower than the depth of the deep countersink 4.

[0023] The evaluation of the size of the adjustment recess 5 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram illustrating the evaluation environment, Fig. 3A is a diagram illustrating the evaluation tool 20, and Fig. 3B is a diagram illustrating the range of the magnetic pad 3 to be evaluated. Also, Fig. 4 shows the evaluation results.

[0024] In FIG. 3A, the evaluation tool 20 includes a leg 21 attached to the magnetic clamping device 1, a movable part 24 on which a dummy die 23 is attached by moving up and down the track of a guide rod 22, a driving part 25 for lifting the movable part 24, and a load sensor 27 for measuring the tensile force between the output shaft 26 of the driving part 25 and the movable part 24. The evaluation tool 20 is attached to the magnetic clamping device 1, and the dummy die 23 is attracted by the magnetic pad 3. In FIG. 3B, the dummy die 23 has a size shown by a dotted line 28. In this example, a total of four bipolar poles consisting of four N-pole magnetic pads and four S-pole magnetic pads are attracted to the dummy die 23. The movable part 24 is lifted by the driving part 25, and the tensile force when the dummy die 23 is peeled off from the magnetic pad 3 is measured by the load sensor 27.

[0025] In Fig. 4, the tensile force was measured by changing the diameter d of the adjustment recess 5. As shown in Fig. 2C, the diameter d of the adjustment recess 5 changes by a length depending on the inclination angle θ and the depth h between the pad surface PS side and the bottom surface 5a side of the adjustment recess. In this embodiment, the diameter d is the length measured on the pad surface PS side.

[0026] For the measurements, magnetic poles 6 were prepared with adjustment recess diameters d of 22 mm, 25 mm, 28 mm, and 32 mm. The other configurations of the magnetic poles 6 are common to all the magnetic poles. The pad surface PS is a circle with diameter D, and the deep countersink 4 is a circle with diameter Z, where D is 70 mm and Z is 18 mm. Meanwhile, the area M of the magnetic pole of the non-reversible magnet 7 is calculated as M=D×π×H (H is the height of the arcuate sides 7a-7d). In this example, the total area of ​​the inner peripheral faces (SA, SB, SC, SD) of the arcuate sides 7a-7d (see FIG. 2B) is M=3421.9 mm 2 The bolt 12 is an M8 bolt.

[0027] The area A of the pad surface PS that comes into contact with the die is calculated as A = (Dd) × 2π / 4. When the diameter d of the adjustment recess 5 is 22 mm, 25 mm, 28 mm, and 32 mm in this order, the area A of the pad surface PS is 3657.51 mm 2 , 3546.77mm 2, 3421.89mm 2 ,3233.39mm 2 With respect to the area M of the magnetic pole of the non-reversible magnet 7, the areas A are 106.69% (rounded off to the second decimal place, the same applies below), 103.65%, 100.00%, and 94.49%, respectively.

[0028] As a result of the measurement, the attracting forces were 22.8KN, 23.4KN, 24.6KN, and 22.0KN for diameters d of the adjustment recesses 5 of 22mm, 25mm, 28mm, and 32mm, respectively. Note that in the experiment, the dummy die 23 was attracted and measured by a total of four bipolar poles consisting of four N-pole magnetic pads 3 and four S-pole magnetic pads 3, so the attracting force with one bipolar pole was 1 / 4 of this.

[0029] Among these, when the diameter d of the adjustment recess 5 is 28 mm, it matches the area M of the magnetic pole of the non-reversible magnet. When the diameter d of the adjustment recess 5 is 28 mm, the path through which the magnet enters and exits the pseudo die 23 remains the same as the area of ​​the magnetic pole of the non-reversible magnet 7, and this is the case in which the magnetic flux density that the non-reversible magnet 7 can generate is maximized. And when the diameter d of the adjustment recess matches the area M of the magnetic pole of the non-reversible magnet 7, the adsorptive force becomes maximum.

[0030] Thus, according to this experimental example, the area A of the pad surface PS is desirably in the range of less than 106.69% (rounded off to two decimal places; the same applies below) and not less than 100.00% of the area M of the magnetic pole of the irreversible magnet 7, or preferably in the range of not more than 103.65% and not less than 100.00%. By providing an adjustment recess 5 in the center of the magnetic pole 6 and adjusting the area of ​​the pad surface PS in contact with the mold so that it is equal to the area of ​​the magnetic pole of the irreversible magnet 7, the adsorptive force can be increased.

[0031] [Example 2] In the first embodiment, a through hole 6a with a deep countersunk 4 is drilled in the center of the surface of the magnetic pole 6, and the bolt 12 penetrates the center of the magnetic pad 3 to fix the magnetic pad 3 to the bottom 2b of the accommodation chamber 2a. In this embodiment, as shown in FIG. 5A, there is no deep countersunk 4 in the center of the surface of the magnetic pole 6, and the bolt 12 protrudes from the back side of the plate body 2 through the bottom 2b into the accommodation chamber 2b. A bottomed female screw hole 6d opening toward the bottom 2b is drilled in the magnetic pole 6, and the bolt 12 is screwed into the female screw hole 6d. In this embodiment, the adjustment recess 5 is also provided in the center of the pad surface PS, and the area of ​​the pad surface PS in contact with the mold is adjusted to match the area M of the magnetic pole of the non-reversible magnet 7. The outer peripheral shape of the adjustment recess 5 is a circle similar to that of the magnetic pole 6 or the non-reversible magnet 7. Other configurations with the same reference symbols are the same as those in the embodiment.

[0032] [Example 3] In the above embodiment, the irreversible magnet is a ring-shaped magnet consisting of four arcuate sides 7a-7d. In this embodiment, the outer periphery of the magnetic pole 6 is track-shaped. Therefore, the irreversible magnet 7 surrounding the magnetic pole 6 is also track-shaped, with four arcuate sides 7a-7d combined with straight sides 7e and 7f. Even in this case, the area A of the pad surface PS in contact with the die is adjusted to match the area of ​​the magnetic pole of the irreversible magnet 7. In this embodiment, the outer periphery of the adjustment recess 5 is a track-shaped shape similar to that of the magnetic pole 6 or the irreversible magnet 7. The position of the adjustment recess 5 is provided at the center of the pad surface PS. Even if the outer periphery of the magnetic pole 6 is rectangular and the irreversible magnet 7 is a rectangle (including a square) with only four straight sides, the adjustment recess 5 adjusts the area A of the pad surface to match the area M of the magnetic pole of the irreversible magnet 7. In this case, it is also preferable to make the outer periphery of the adjustment recess 5 a rectangle similar to that of the magnetic pole 6 or the irreversible magnet. In any case, the non-reversible magnet 7 is in the shape of a circle, and the outer peripheral shape of the adjustment recess 5 is similar to that of the non-reversible magnet. Also, as in the second embodiment, the present invention can be applied to a case where the deep countersink 4 is not provided at the center of the surface of the magnetic pole 6, and the bolt 12 penetrates the bottom 2b from the back side of the plate body 2 and protrudes into the accommodation chamber 2b. [Explanation of symbols]

[0033] 1 Magnetic clamping device 2 Plate body 2a Containment Room 2b bottom 2c Female screw hole 2d cavity 2e side 3 Magnetic Pads 4 Deep countersinking 5 Adjustment recess 5a Bottom 5b Slope 6 Magnetic pole 6a, 8a through hole 6b Outer periphery 6c Female screw hole 7 Non-reversible magnets 7a-7d Circular arc 7e, 7f straight side 8 Reversible Magnets 9. Bobbin 10 Coil 11 Sealing material 12 Volts 12a head 12b Sealing material 20 Evaluation Instruments 21 Legs 22 Guide Rod 23 Pseudo-mold 24 Moving parts 25 Drive unit 26 Output shaft 27 Load Sensor 28 Dotted Line A area D diameter M area PS pad surface Z diameter c Center axis d diameter θ Tilt angle

Claims

1. A magnetic clamping device comprising a plate body made of a magnetic material having a bottomed accommodation chamber on a surface thereof, and a magnetic pad disposed in the accommodation chamber, The magnetic pad includes a magnetic pole having a pad surface that contacts the magnetic body to be fixed, a reversible magnet capable of reversing polarity that is provided between the magnetic pole and the bottom of the storage chamber, and a non-reversible magnet that is provided between the magnetic pole and the side surface of the inner circumference of the storage chamber and surrounds the magnetic pole; A bolt is inserted into the center of the pad surface to fix the magnetic pad to the plate body, and a through hole that passes through the magnetic pole and a deep countersink that receives the head of the bolt are provided. An adjustment recess shallower than the deep countersink is provided around the deep countersink for adjusting an area of ​​the pad surface; and A magnetic clamping device characterized in that the area A of the pad surface adjusted by the adjustment recess is 100.00% equal to or at most 106.69% of the area M of the surface where the magnetic pole of the non-reversible magnet contacts the magnetic pole.

2. A magnetic clamping device comprising a plate body made of a magnetic material having a bottomed accommodation chamber on a surface thereof, and a magnetic pad disposed in the accommodation chamber, The magnetic pad includes a magnetic pole having a pad surface that contacts the magnetic body to be fixed, a reversible magnet capable of reversing polarity that is provided between the magnetic pole and the bottom of the storage chamber, and a non-reversible magnet that is provided between the magnetic pole and the side surface of the inner circumference of the storage chamber and surrounds the magnetic pole; The magnetic pole has a bottomed female screw hole that opens toward the bottom of the accommodation chamber, The bolt protruding from the bottom of the housing chamber is screwed into the female screw hole, An adjustment recess shallower than the deep countersink is provided at the center of the pad surface for adjusting the area of ​​the pad surface; and A magnetic clamping device characterized in that the area A of the pad surface adjusted by the adjustment recess is 100.00% equal to or at most 106.69% of the area M of the surface where the magnetic pole of the non-reversible magnet contacts the magnetic pole.

3. 3. The magnetic clamping device according to claim 1, wherein the outer circumferential shape of the adjustment recess is similar to the outer circumferential shape of the magnetic pole.

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