Fluid polishing apparatus and fluid polishing method

Abstract

To provide a technique for further improving the polishing efficiency in fluid polishing.SOLUTION: A fluid polishing device comprises: a shaft body which can rotate around a shaft line extending in a prescribed direction; a main magnetic body in which a conductive layer having conductivity is formed on a portion or the whole of a cylindrical magnet surrounding the shaft line and is provided so as to be rotatable driven by the shaft body; a sub magnetic body which is made of a cylindrical magnetic material that surrounds the shaft line and has a diameter different from that of the main magnetic body, and is provided so as to be rotatable driven by the shaft body in a state of being received inside the main magnetic body or receiving the main magnetic body therein; and an electrical field path in which one of electrode poles in a pair is connected to the conductive layer of the main magnetic body, meanwhile the other is provided at a prescribed distance from the main magnetic body, and which becomes a conductive path that generates an electrical field involving electric conduction into between the electrode poles.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fluid polishing apparatus for polishing an object to be processed by using a processing fluid. [Background technology]

[0002] Fluid polishing involves polishing the surface of the workpiece by displacing the workpiece relative to the tool body, which is made of a magnetic body, with a processing fluid containing abrasive grains interposed between the workpiece and the tool body. In recent years, a method has been proposed to improve polishing efficiency by polishing under magnetic and electric fields (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-116722 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, simply performing polishing under a magnetic field and an electric field does not necessarily result in a sufficiently high polishing efficiency, and there is still room for improvement.

[0005] The present invention has been made to solve such problems, and an object of the present invention is to provide a technique for further improving the polishing efficiency in fluid polishing. [Means for solving the problem]

[0006] In a first aspect for solving the above problem, there is provided a magnetic recording medium comprising: a shaft body rotatable about an axis extending in a predetermined direction; a cylindrical magnet surrounding the axis, on which a conductive layer is formed in part or the whole; a main magnetic body provided to be rotatable in accordance with the shaft body; a sub-magnetic body surrounding the axis and made of a cylindrical magnetic body having a diameter different from that of the main magnetic body, and housed inside the main magnetic body or provided to be rotatable in accordance with the shaft body while housing the main magnetic body inside; and a pair of electrodes, one of which is connected to the conductive layer of the main magnetic body while the other is provided at a position spaced a predetermined distance from the main magnetic body, and a current generating means for generating an electric field when a current is passed between these electrodes. and an electric field path which serves as an electric path, wherein the main magnetic body is positioned such that one end thereof protrudes from one end of the shaft body by a predetermined length, and the sub-magnetic body is positioned such that one end thereof protrudes from one end of the shaft body by the same length as the main magnetic body or an approximate length less than a predetermined threshold value, and the fluid polishing device realizes magnetic fluid polishing of the workpiece by rotating the shaft body under a magnetic field generated by the main magnetic body and an electric field generated by the electric field path, with a processing fluid in which non-magnetic and non-conductive abrasive grains are contained in a magnetic fluid, being interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a processing surface of the workpiece arranged opposite this area.

[0007] In the fluid polishing apparatus in this aspect, the magnetic field generated by the magnet forms magnetic clusters centered on the magnetic particles in the processing fluid along the direction of the magnetic field lines leading to the workpiece.

[0008] Here, the magnetic field lines of the magnet tend to spread inward and outward due to the influence of the sub-magnetic body, so the magnetic particles are distributed so as to spread inward and outward along the magnetic field lines, and are also gathered on the magnet side due to the influence of the magnetic field. Meanwhile, the abrasive grains are displaced to the area of ​​weak magnetic field, i.e., the surface to be processed, due to magnetic buoyancy (the force that displaces a non-magnetic body to the area of ​​weak magnetic field), but due to the flow of the processing fluid accompanying the rotation of the magnetic body, they tend to displace to the area of ​​weak magnetic field radially outside the magnetic body. In the fluid polishing device in this aspect, the electric field generated by the electric field path can apply a force to the abrasive grains to aggregate along the electric field lines against such displacement, so that the abrasive grains are suppressed from displacing radially outward due to this force, and the number of abrasive grains present on the surface to be processed can be prevented from decreasing.

[0009] Furthermore, agglomerates of abrasive grains are formed in the processing fluid due to the effect of the electric field generated by the electric field path, and the apparent viscosity of the processing fluid increases locally, so that the magnetic clusters are pressed against the workpiece with even stronger force. Agglomerates of abrasive grains are formed because the non-magnetic and non-conductive abrasive grains are affected by the dielectric polarization caused by the electric field, causing a bias in the electric charge on a particle-by-particle basis, and adjacent particles tend to aggregate together to cancel out this biased electric charge.

[0010] Then, by rotating the main magnetic body and the sub magnetic body together with the shaft body in the above-mentioned state, the surface of the workpiece facing the area formed by both magnetic bodies (including the gap between both magnetic bodies) at one end side of the shaft body is polished by the abrasive grains in the processing fluid. At this time, the magnetic clusters are distributed in the inner and outer directions, and the abrasive grains can be widely arranged and acted on the surface of the workpiece, so that the polishing efficiency of the fluid polishing can be further improved.

[0011] In particular, when the main magnetic body and sub-magnetic body are rotated for a long period of time, the centrifugal force causes the abrasive grains to displace outward, which tends to reduce the polishing efficiency. However, in the fluid polishing device of this aspect, a force acts on the abrasive grains to aggregate along the electric field lines, preventing the abrasive grains from displacing radially outward, resulting in the excellent effect that the polishing efficiency is less likely to decrease even when the main magnetic body and sub-magnetic body are rotated for a long period of time.

[0012] In this aspect, the magnetization direction of the magnet in the main magnetic body is not particularly limited, and it is possible to set it as in the second or third aspect shown below.

[0013] In a second aspect, the main magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in an axial direction, which is the direction in which the axis extends.

[0014] In this aspect, the magnetic clusters can be distributed inward and outward along the magnetic field lines extending from one end of each of the main magnetic body and the sub-magnetic body to the other end.

[0015] In a third aspect, the main magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in an inward and outward direction that intersects with the axis.

[0016] In this aspect, the magnetic clusters can be distributed inwardly and outwardly across the main magnetic body and the sub-magnetic body.

[0017] In each of the above aspects, the other electrode in the electric field path may be provided at a position spaced a predetermined distance from the main magnetic body, and may be provided at a position spaced apart in the axial direction between the main magnetic body and the workpiece, for example. In this case, if the workpiece is made of a conductive material, the other electrode may be provided in contact with the workpiece, so that the workpiece itself functions as an electrode.

[0018] The other electrode in the electric field path may be provided at a position spaced apart from the main magnetic body in the inward / outward direction, for example, on the sub-magnetic body side. In this case, the fourth aspect shown below may be adopted.

[0019] In a fourth aspect, the sub-magnetic body has a conductive layer formed on part or the entirety of a cylindrical magnetic body and is electrically insulated from the main magnetic body, and the electric field path is such that the other electrode is connected to the conductive layer of the sub-magnetic body.

[0020] In this aspect, the main magnetic body and the sub magnetic body function as electrodes arranged at a distance from each other, and an electric field can be generated between the two magnetic bodies. As a result, the pair of electrodes is integrated with the fluid polishing device, so that it is possible to reduce the effort of providing the other electrode at a distance from the main magnetic body, for example, by providing the other electrode on the workpiece each time polishing is performed.

[0021] In this aspect, the sub-magnetic body may be a magnetic body made of a material that affects the magnetic field, but a magnet formed by magnetizing a magnetic body may also be used.

[0022] In this case, it is possible to proceed as shown in the fifth and sixth steps below. In a fifth aspect, the sub-magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body but with an opposite arrangement of magnetic poles.

[0023] In this aspect, if the main magnetic body and the sub magnetic body are magnetized in the axial direction, opposite magnetic poles are arranged at intervals in the inward and outward directions on one end of the shaft, so that magnetic clusters can be distributed widely in the inward and outward directions along the magnetic field lines going from one side to the other.

[0024] On the other hand, if the main magnetic body and the sub magnetic body are magnetized in the inward and outward directions, the two magnetic bodies are arranged at one end of the shaft so that their identical magnetic poles face each other in the inward and outward directions, and independent inward and outward magnetic field line loops are formed for each, so that magnetic clusters can be distributed widely in the inward and outward directions along these magnetic field lines.

[0025] In a sixth aspect, the sub-magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in a direction intersecting the magnetization direction of the main magnetic body and such that the area facing the main magnetic body on one end side of the shaft body has the same magnetic pole as the main magnetic body.

[0026] In this aspect, both magnetic bodies are arranged with the same magnetic poles facing each other in the inward and outward directions on one end of the shaft body, and independent inward and outward magnetic field line loops are formed, so that magnetic clusters can be distributed widely in the inward and outward directions along these magnetic field lines.

[0027] Moreover, the above fifth and sixth aspects may be modified as in the seventh aspect shown below. In a seventh aspect, the main magnetic body and the sub magnetic body are spaced apart inward and outward by a distance determined so that the magnetic flux density at the midpoint between them does not fall below a value determined as the magnetic flux density required for fluid polishing. More specifically, as in an eighth aspect, the main magnetic body and the sub magnetic body may be spaced apart inward and outward by a distance determined so that the magnetic flux density at the midpoint between them does not fall below 0.18 T.

[0028] In this aspect, the magnetic flux density between the main magnetic body and the sub-magnetic body is equal to or greater than the magnetic flux density required for fluid polishing, as described below, and therefore, fluid polishing can be carried out effectively, as described below.

[0029] In addition, each of the above aspects may be modified as in the ninth aspect described below. In a ninth aspect, the device includes a power supply unit that applies a voltage to the electric field path, and the power supply unit generates a voltage of 2.0 kV / mm or less between electrodes in the electric field path by applying a voltage to the electric field path.

[0030] In this aspect, an electric field suitable for placing abrasive grains on the surface of the workpiece facing the main magnetic body, the sub magnetic body, and the gap region between the two magnetic bodies can be generated via the electric field path without the processing fluid between the electrodes becoming electrically conductive due to dielectric breakdown.

[0031] In addition, in order to solve the above-mentioned problems, a fluid polishing method according to a tenth aspect includes a shaft body rotatable about an axis extending in a predetermined direction, and a cylindrical magnet surrounding the axis, the cylindrical magnet having a conductive layer formed on a part or the whole of the magnet, the main magnetic body being provided rotatably in a manner following the shaft body, and a sub-magnetic body surrounding the axis and having a cylindrical magnetic body with a diameter different from that of the main magnetic body, the sub-magnetic body being accommodated inside the main magnetic body or being provided rotatably in a manner following the shaft body while the main magnetic body is accommodated inside the sub-magnetic body, and one of a pair of electrodes is connected to the conductive layer of the main magnetic body, In contrast, the other electrode is provided at a position a predetermined distance away from the main magnetic body, and an electric field path serves as a current path that generates an electric field when current is passed between these electrodes.A processing fluid containing non-magnetic and non-conductive abrasive grains is interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a surface to be processed of the workpiece that is positioned opposite this area, and the shaft body is rotated under the magnetic field generated by the main magnetic body and the electric field generated by the electric field path, thereby achieving magnetic fluid polishing of the workpiece.

[0032] The fluid polishing method according to this aspect is suitable for implementing fluid polishing using each of the fluid polishing apparatuses described above. [Brief description of the drawings]

[0033] [Figure 1]A front cross-sectional view of a fluid polishing apparatus taken along a plane intersecting an axial direction (1) [Diagram 2] A front cross-sectional view (2) of a fluid polishing apparatus taken along a plane intersecting the axial direction. [Diagram 3] A front cross-sectional view (3) of a fluid polishing apparatus taken along a plane intersecting the axial direction. [Figure 4] A front cross-sectional view (4) of a fluid polishing apparatus taken along a plane intersecting the axial direction. [Diagram 5] A front cross-sectional view (5) of a fluid polishing apparatus taken along a plane intersecting the axial direction. [Figure 6] A front cross-sectional view (6) of a fluid polishing apparatus taken along a plane intersecting the axial direction. [Figure 7] A diagram (front cross-sectional view) showing the distribution of magnetic and electric field lines generated between the main magnetic body and the sub-magnetic body, and the state of the magnetic clusters generated between them. [Figure 8] A diagram (bottom view) showing the distribution of magnetic and electric field lines generated between the main magnetic body and the sub-magnetic body, and the state of the magnetic clusters generated between them. [Figure 9] Graph showing the results of magnetic field analysis DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (1) Equipment overview The fluid polishing device 1 is a device for performing fluid polishing on the surface of a workpiece 100 by rotating a processing fluid 200, which is a magnetic fluid containing non-magnetic and non-conductive abrasive grains, relative to the workpiece 100 while being interposed between the workpiece 100 and the fluid.

[0035] (2) Overall structure As shown in Figure 1, the fluid polishing apparatus 1 comprises a shaft body 10 that can rotate around an axis extending in a predetermined direction (up and down in the figure), a main magnetic body 20 and a sub-magnetic body 30 which are cylindrical magnetic bodies that each surround the axis, an electric field path 40 equipped with a set of electrodes, a rotational drive unit 50 that rotates the shaft body 10, a control unit 60 that controls the operation of the entire apparatus, and a power supply unit 70 that applies a voltage to the electric field path 40.

[0036] The shaft body 10 is a cylindrical member extending along an axis and made of a conductive material. The shaft body 10 is electrically insulated from the rotation drive unit 50.

[0037] The main magnetic body 20 is a magnet formed by magnetizing a cylindrical magnetic body in the direction in which the axis extends (hereinafter referred to as the "axial direction"), and is provided so as to be rotatable following the shaft body 10 with the same axis as the center of rotation. Here, the shaft body 10 is magnetized so that one end (the lower end in FIG. 1; the same applies below) is an S pole, and the other end (the upper end in FIG. 1; the same applies below) is an N pole. Note that the main magnetic body 20 may also be magnetized so that the other end of the shaft body 10 is an S pole, and one end is an N pole.

[0038] The main magnetic body 20 has a conductive layer 21 formed over a part or the whole (the whole in this embodiment) of the main magnetic body 20. The conductive layer 21 is made of a material that is soft magnetic, highly conductive, and highly hard, and is formed so as to cover the surface of the main magnetic body 20. In this embodiment, the conductive layer 21 is formed by plating the entire main magnetic body 20 with nickel or chromium.

[0039] It is sufficient that this conductive layer 21 covers only the area of ​​the surface of the main magnetic body 20 that is connected to the electric field path 40 (the upper end surface 21u connected to the cylindrical body 13 described later), the area for generating an electric field between the sub-magnetic body 30 (here, the end surface 21d on one end side), and the area for connecting these areas (here, the inner surface 21i or the outer surface 21o).

[0040] The main magnetic body 20 is provided in a positional relationship in which one end thereof protrudes a predetermined length from one end of the shaft body 10. Here, one end of the main magnetic body 20 may be at the same position as one end of the shaft body 10.

[0041] The sub-magnetic body 30 is made of a cylindrical magnetic body having a smaller diameter than the main magnetic body 20, and is accommodated inside the main magnetic body 20 and is arranged to be rotatable in accordance with the shaft body 10 around the same axis as the center of rotation.

[0042] The sub-magnetic body 30 is a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body 20 but with the magnetic poles arranged in the opposite direction. Here, one end of the shaft body 10 is magnetized as the N pole and the other end as the S pole. Note that the sub-magnetic body 30 may also be magnetized so that the other end of the shaft body 10 is the N pole and one end as the S pole, in accordance with the magnetic pole arrangement of the main magnetic body 20.

[0043] The sub-magnetic body 30 is formed by forming a conductive layer 31 over a part or the whole (the whole in this embodiment) of the cylindrical magnetic body, and is electrically insulated from the main magnetic body 20. This conductive layer 31 is made of a material that is soft magnetic, highly conductive, and highly hard, and is formed so as to cover the surface of the sub-magnetic body 30. In this embodiment, the conductive layer 21 is formed by plating the entire sub-magnetic body 30 with nickel or chromium.

[0044] Furthermore, this conductive layer 31 only needs to cover at least the area of ​​the surface of the sub-magnetic body 30 that is connected to the shaft body 10 (one end side on the inner surface 31i) and the area for generating an electric field between the sub-magnetic body 30 and the main magnetic body 20 (here, the end face 31d on the one end side).

[0045] Here, in order to electrically insulate the main magnetic body 20 from the sub-magnetic body 30, an insulating material 11 is provided at least between the main magnetic body 20 and the sub-magnetic body 30. In this embodiment, the insulating material 11 is filled between the magnetic bodies and between the main magnetic body 20 and the shaft body 10.

[0046] The sub-magnetic body 30 is provided in a positional relationship such that one end thereof protrudes from one end of the shaft body 10 by a length equal to or approximately equal to that of the main magnetic body 20 but less than a predetermined threshold value.

[0047] The electric field path 40 has one electrode 41 connected to the conductive layer 21 of the main magnetic body 20 and the other electrode 43 located at a position spaced a predetermined distance from the main magnetic body 20, and serves as a current path that generates an electric field when current is passed between these electrodes.

[0048] In this embodiment, a conductive cylindrical body 13 is provided which surrounds the shaft body 10 outside the sub-magnetic body 30 and is disposed adjacent to the conductive layer 21 of the main magnetic body 20 in the axial direction, and one of the electrode elements 41 is connected to this cylindrical body 13. In other words, the main magnetic body 20 is electrically connected to one of the electrode elements 41 via the cylindrical body 13 and the conductive layer 21, and functions as an electrode of the electric field path 40. This electrode element 41 is formed as an electrically conductive brush.

[0049] In this embodiment, the conductive layer 31 of the sub-magnetic body 30 and the shaft body 10 are connected to a side surface at one end of the shaft body 10, and the other electrode element 43 is connected to the other end of the shaft body 10. In other words, the sub-magnetic body 30 is electrically connected to the other electrode element 43 via the shaft body 10, and functions as an electrode of the electric field path 40. Here, the other electrode element 43 is formed as an electrically conductive brush.

[0050] In this electric field path 40, a voltage is applied between a pair of electrodes (each region functioning as an electrode; in this embodiment, the main magnetic body 20 connected to one electrode 41 and the sub magnetic body 30 connected to the other electrode 43) by the power supply unit 70. In this embodiment, a voltage is applied according to the magnetic field strength of the magnet, the components of the processing fluid 200, the distance from the workpiece 100, and the like. In this embodiment, a voltage of 2.0 kV / mm or less is applied as a voltage selected so that the members (particularly the processing fluid 200) that may exist between the main magnetic body 20 and the sub magnetic body 30 do not become conductive due to dielectric breakdown. In other words, the main magnetic body 20 and the sub magnetic body 30 are separated in the inner and outer directions by a distance determined so as to prevent conduction due to dielectric breakdown in relation to the voltage applied from the power supply unit 70 and the members that may exist between the two magnetic bodies.

[0051] A non-conductive magnetic fluid containing non-conductive and non-magnetic abrasive grains is used as the processing fluid 200. In the processing fluid 200, magnetic particles having a particle size of 5 nm to 10 μm are selectively used as the magnetic particles according to the magnetic field strength of the magnet, the distance from the workpiece 100, the composition of the base liquid, and the like.

[0052] The abrasive grains contained in this processing fluid 200 are selected from materials having a dielectric constant at least equal to or greater than that of the base liquid in the magnetic fluid, such as general abrasive grains made of ceramic materials such as alumina or silicon carbide, or super abrasive grains such as diamond or cubic boron nitride (cBN), suitable for the workpiece 100.

[0053] In this embodiment, in addition to the above, a certain amount of fibrous material having a predetermined length is distributed in the processing fluid 200. Specifically, α-cellulose having a length approximately equal to or shorter than the distance to the processing object 100 is distributed. This fibrous material can promote and strengthen the bonding and adhesion between magnetic clusters, which will be described later.

[0054] In the fluid polishing apparatus 1 configured in this manner, with the processing fluid 200 interposed between the region formed by the main magnetic body 20 and the sub magnetic body 30 at one end side of the shaft body 10 and the surface to be processed of the workpiece 100 arranged opposite this region, the shaft body 10 is rotated under the magnetic field of the magnet and the electric field of the electric field path 40, thereby achieving magnetic fluid polishing of the workpiece 100. Fig. 1 illustrates an example of a configuration in which the top surface of the planar workpiece 100 is processed along one end face of each magnetic body.

[0055] Here, the distance between the area formed by the main magnetic body 20 and the sub magnetic body 30 at one end side of the shaft body 10 and the surface to be processed of the workpiece 100 arranged opposite this area is a distance selected (in this embodiment, a distance selected from the range of 0.5 to 2.0 mm; more specifically, 1 mm) so as to achieve the desired distribution of magnetic and electric field lines depending on the parameters of the magnet (magnetic flux density, magnetic field strength, etc.) and the parameters of the electric field generated by the electric field path 40 (voltage, electric field strength, etc.).

[0056] Meanwhile, the above-mentioned main magnetic body 20 and sub magnetic body 30 are separated inwardly and outwardly by a distance determined so that the magnetic flux density at the midpoint between them does not fall below a value determined as the magnetic flux density required for fluid polishing.

[0057] In a fluid polishing device that performs polishing at the tip side of a magnetic body, which is a magnet body, a certain magnetic flux density (0.18 T or more; hereinafter referred to as the "required magnetic flux density") is required to hold a processing fluid at the tip side and realize polishing with this processing fluid (Shinji Ikeda et al., "Design of a tool for surface polishing using magnetic functional fluid", 42nd Japan Magnetics Society Academic Lecture Abstracts, 2018, p.221). This is because the magnetic cluster formed at the tip side of the magnetic body needs to be held with a force that can withstand polishing, and even in a configuration consisting of the main magnetic body 20 and the sub magnetic body 30 as in this embodiment, the magnetic cluster formed so as to extend between the two in the inner and outer directions needs to be held with a similar force. In other words, the main magnetic body 20 and the sub magnetic body 30 are desirably separated by a predetermined distance so that the magnetic flux density between them decreases and the force holding the magnetic clusters becomes weaker, especially at the intermediate position between them (especially the intermediate position at the bottom surface) does not fall below the value determined as the magnetic flux density required for fluid polishing.

[0058] Regarding this, the applicant has determined the change in magnetic flux density B(0.5δ)[T] at the intermediate position with an increase in the distance δ between the main magnetic body 20 and the sub magnetic body 30 (hereinafter referred to as the "gap distance"), using the magnetic flux density B(0.5)[T] at the intermediate position (one end surface) between the main magnetic body 20 and the sub magnetic body 30 (hereinafter referred to as the "reference magnetic flux density") as a reference when the two are separated by a predetermined distance of 0.5[mm] along the inner and outer sides. Then, the applicant has confirmed the extent to which the necessary magnetic flux density can be secured at the intermediate position of the bottom surface at the maximum distance between the main magnetic body 20 and the sub magnetic body 30. The analysis was performed for magnets of the same material, height, and thickness for the main magnetic body 20 and the sub magnetic body 30. The magnetic field analysis has analyzed the maximum distance δmax at which the necessary magnetic flux density can be secured, and as a result, it has been found that the distance δmax can be expressed by the formula [δmax≦8.3×B(0.5)-1.4] with the reference magnetic flux density B(0.5) as a variable (see FIG. 9). In other words, selecting a spacing distance δ that is equal to or less than “8.3×B(0.5)−1.4” means that the magnetic flux density will not fall below the level necessary to achieve polishing, and will not hinder efficient polishing.

[0059] Needless to say, the above-mentioned fluid polishing apparatus 1 can be configured to achieve magnetic fluid polishing by placing the workpiece 100 on a stage and displacing this stage along the x-y axis or the x-yz axis using a displacement mechanism, or by similarly displacing the fluid polishing apparatus 1 using a displacement mechanism.

[0060] (3) Variations It goes without saying that the present invention is not limited to the above-described embodiment, and various other forms can be adopted as long as they fall within the technical scope of the present invention.

[0061] For example, in the above embodiment, the main magnetic body 20 and the sub magnetic body 30 are magnets formed by magnetizing cylindrical magnetic bodies in the axial direction. However, these magnetic bodies may be magnets magnetized in the inward and outward directions intersecting the axis.

[0062] Also, in the above embodiment, the sub-magnetic body 30 has a smaller diameter than the main magnetic body 20 and is housed inside the main magnetic body 20. However, the sub-magnetic body 30 may have a larger diameter than the main magnetic body 20 and be provided rotatably following the shaft body 10 with the main magnetic body 20 housed inside.

[0063] In the present embodiment, a magnet formed by magnetizing a magnetic body is used as the sub-magnetic body 30. However, the sub-magnetic body 30 does not have to be a magnet as long as it is a magnetic body made of a material that affects the magnetic field, as shown in FIG.

[0064] In this embodiment, the sub-magnetic body 30 is electrically connected to the other electrode element 43 via the shaft body 10, and is configured to function as an electrode spaced apart from the main magnetic body 20 in the inward and outward directions in the electric field path 40. However, the function of an electrode in the electric field path 40 may be performed by the other electrode element 43 itself, and as a specific example, the other electrode element 43 may be disposed with a gap in the axial direction between the main magnetic body 20 and the workpiece 100, as shown in Fig. 3. In this case, it is preferable to divide one electrode element 41 into two and connect them to the main magnetic body 20 side (cylindrical body 13) and the sub-magnetic body 30 side (shaft body 10), respectively.

[0065] In this configuration, if the workpiece 100 is made of a conductive material, the other electrode element 43 can be placed in contact with the workpiece 100, allowing the entire workpiece 100 to function as an electrode in the electric field path 40. If the contact surface of the electrode element 43 and the workpiece 100 is flat, the electrode element 43 can also be formed flat and the flat surfaces can be brought into contact with each other, or the electrode element 43 can be formed by a conductive brush and pressed against the contact surface with the workpiece 100 to bring them into contact.

[0066] In the above embodiment, the main magnetic body 20 is a magnet formed by magnetizing a cylindrical magnetic body in the axial direction, and the sub magnetic body 30 is a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body 20 and with the magnetic poles arranged in the opposite direction. However, as for these magnetic bodies, as shown in Fig. 4, the main magnetic body 20 may be a magnet formed by magnetizing a cylindrical magnetic body in the inward and outward directions, and the sub magnetic body 30 may be a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body 20 and with the magnetic poles arranged in the opposite direction.

[0067] In this example, the main magnetic body 20 is magnetized so that the inside is an S pole and the outside is an N pole, and the sub magnetic body 30 is magnetized so that the inside is an N pole and the outside is an S pole.

[0068] In the above embodiment, the sub magnetic body 30 is a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body 20 and with the magnetic poles arranged in the opposite direction. However, the sub magnetic body 30 may be a magnet formed by magnetizing a cylindrical magnetic body in a direction intersecting the magnetization direction of the main magnetic body 20 and such that the region facing the main magnetic body 20 at one end side of the shaft body 10 has the same magnetic pole as the main magnetic body 20.

[0069] Specifically, as shown in Figure 5, when the inside of the main magnetic body 20 is magnetized so that the inside is a south pole and the outside is a north pole, it is possible to use a magnet as the sub-magnetic body 30, which is a cylindrical magnetic body magnetized in the axial direction and so that the area facing the main magnetic body 20 on one end side of the shaft body 10 is magnetized to have the same magnetic pole as the main magnetic body 20, that is, an south pole.

[0070] In this configuration, the sub-magnetic body 30 may be configured to be a magnet in which the inside of the cylinder is filled with a magnetic body, as shown in FIG.

[0071] Furthermore, in this embodiment, the fluid polishing apparatus 1 is configured to rotate relative to the workpiece 100, but the workpiece 100 may be configured to rotate.

[0072] (4) Effects In the fluid polishing apparatus 1 of the above embodiment, the magnetic field generated by the magnet forms magnetic clusters centered on magnetic particles in the processing fluid along the direction of the magnetic field lines leading to the workpiece 100 (see Figures 7 and 8).

[0073] Here, the magnetic field lines of the magnet tend to spread inward and outward due to the influence of the sub-magnetic body 30, so the magnetic particles are distributed so as to spread inward and outward along the magnetic field lines, and are also gathered on the magnet side due to the influence of the magnetic field. On the other hand, the abrasive grains are displaced to the area of ​​weak magnetic field, i.e., the surface to be processed, due to magnetic buoyancy (the force that displaces a non-magnetic body to an area of ​​weak magnetic field), but the flow of the processing fluid accompanying the rotation of the magnetic body tries to displace them to the area of ​​weak magnetic field radially outward of the magnetic body. In this embodiment, the electric field generated by the electric field path can apply a force to the abrasive grains to aggregate along the electric field lines against such displacement, so that the abrasive grains are suppressed from displacing radially outward due to this force, and the number of abrasive grains present on the surface to be processed can be prevented from decreasing.

[0074] Furthermore, agglomerates of abrasive grains are formed in the processing fluid 200 due to the effect of the electric field generated by the electric field path 40, and the apparent viscosity of the processing fluid 200 increases locally, so that the magnetic clusters are pressed with even stronger force against the workpiece 100. Agglomerates of abrasive grains are formed because the non-magnetic and non-conductive abrasive grains are affected by dielectric polarization due to the electric field, causing charge imbalance on a particle-by-particle basis, and adjacent particles tend to aggregate together to cancel out this biased charge.

[0075] Then, by rotating the main magnetic body 20 and the sub magnetic body 30 together with the shaft body 10 in the above-mentioned state, the machining surface of the workpiece 100 facing the area formed by both magnetic bodies (including the gap between both magnetic bodies) at one end side of the shaft body 10 is polished by the abrasive grains attached to the magnetic clusters. At this time, the magnetic clusters are distributed in the inner and outer directions, and the abrasive grains can be widely arranged and acted on the surface of the workpiece 100, so that the polishing efficiency as a fluid polishing can be further improved.

[0076] In particular, when the main magnetic body 20 and the sub magnetic body 30 are rotated for a long period of time, the centrifugal force tends to displace the abrasive grains outward, resulting in a decrease in polishing efficiency. However, in this embodiment, a force acts on the abrasive grains to aggregate them along the electric field lines, preventing the abrasive grains from displacing outward, resulting in the excellent effect that the polishing efficiency is less likely to decrease even when the main magnetic body 20 and the sub magnetic body 30 are rotated for a long period of time.

[0077] Furthermore, in the above embodiment, if each magnetic body is configured to function as an electrode in the electric field path 40, an electric field can be generated between the main magnetic body 20 and the sub magnetic body 30. As a result, a pair of electrodes is integrated with the fluid polishing apparatus 1, which makes it possible to reduce the effort of providing the other electrode 43 at a distance from the main magnetic body 20, for example, by providing the other electrode on the workpiece each time polishing is performed.

[0078] Furthermore, in the above embodiment, if the main magnetic body 20 is a magnet magnetized in the axial direction, magnetic clusters can be distributed inward and outward along the magnetic field lines extending from one end to the other at each of the main magnetic body 20 and the sub-magnetic body 30.

[0079] On the other hand, in the above embodiment, if the main magnetic body 20 is a magnet magnetized in the inward and outward directions, the magnetic clusters can be distributed in the inward and outward directions across the main magnetic body 20 and the sub-magnetic body 30.

[0080] Furthermore, in the above embodiment, if the main magnetic body 20 and the sub magnetic body 30 are magnets magnetized in the axial direction with opposite magnetic pole arrangements, the opposite magnetic poles are arranged with a gap in the inward and outward directions on one end side of the shaft body 10, so that magnetic clusters can be distributed widely in the inward and outward directions along the magnetic field lines going from one side to the other.

[0081] On the other hand, if the main magnetic body 20 and the sub magnetic body 30 are magnets magnetized in the inward and outward directions and with opposite magnetic pole arrangements, then the two magnetic bodies are arranged at one end of the shaft body 10 with the same magnetic poles facing each other in the inward and outward directions, and independent inward and outward magnetic field line loops are formed in each, so that magnetic clusters can be distributed widely in the inward and outward directions along these magnetic field lines.

[0082] Furthermore, in the above embodiment, if the sub-magnetic body 30 is a magnet that is magnetized in a direction that intersects the magnetization direction of the main magnetic body 20 and so that the area facing the main magnetic body 20 at one end side of the shaft body 10 has the same magnetic pole as the main magnetic body 20, then both magnetic bodies are arranged so that their same magnetic poles face each other in the inward and outward directions at one end side of the shaft body 10, and independent magnetic field line loops are formed in the inward and outward directions, so that magnetic clusters can be distributed widely in the inward and outward directions along these magnetic field lines.

[0083] In addition, in the above embodiment, an electric field suitable for placing abrasive grains on the surface of the workpiece facing the main magnetic body 20, the sub-magnetic body 30, and the gap area between the two magnetic bodies can be generated via the electric field path 40, without the processing fluid between the electrodes becoming electrically conductive due to dielectric breakdown.

[0084] Furthermore, in the above embodiment, as described above, the magnetic flux density between the main magnetic body 20 and the sub magnetic body 30 is equal to or greater than the magnetic flux density required for fluid polishing, which makes it possible to carry out fluid polishing effectively. [Explanation of symbols]

[0085] 1...fluid polishing device, 10...shaft body, 11...insulating material, 13...cylindrical body, 15...conductive material, 20...main magnetic body, 21...conductive layer, 30...sub-magnetic body, 31...conductive layer, 40...electric field path, 41...electrode, 43...electrode, 50...rotary drive unit, 60...control unit, 70...power supply unit, 100...workpiece, 200...processing fluid.

Claims

1. A shaft body that is rotatable around an axis extending in a predetermined direction; A main magnetic body is provided in such a manner that a conductive layer is formed on a part or the whole of a cylindrical magnet surrounding the axis and that the main magnetic body is rotatable in accordance with the shaft body; a sub-magnetic body that surrounds the axis and is made of a cylindrical magnetic body having a diameter different from that of the main magnetic body, and is accommodated inside the main magnetic body or is provided so as to be rotatable following the shaft body while the main magnetic body is accommodated inside the sub-magnetic body; one of a pair of electrodes is connected to the conductive layer of the main magnetic body, while the other electrode is provided at a position spaced a predetermined distance from the main magnetic body, and an electric field path serves as a current path for generating an electric field associated with current flow between the electrodes; the main magnetic body is provided in a positional relationship such that one end thereof protrudes a predetermined length from one end of the shaft body, the sub-magnetic body is provided in a positional relationship such that one end of the sub-magnetic body protrudes from one end of the shaft body by the same length as the main magnetic body or a length approximately equal to or less than a predetermined threshold value; A processing fluid containing non-magnetic and non-conductive abrasive grains is interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a surface to be processed of the workpiece disposed opposite this area, and the shaft body is rotated under a magnetic field generated by the main magnetic body and an electric field generated by the electric field path, thereby realizing magnetic fluid polishing of the workpiece; moreover, The sub-magnetic body is a cylindrical magnetic body having a conductive layer formed thereon in part or the entirety thereof, and is electrically insulated from the main magnetic body. The electric field path is such that the other electrode is connected to the conductive layer of the sub-magnetic body, The sub-magnetic body is a magnet obtained by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body but with the magnetic poles arranged in the opposite direction. Fluid polishing equipment.

2. A shaft body that is rotatable around an axis extending in a predetermined direction; A main magnetic body is provided in such a manner that a conductive layer is formed on a part or the whole of a cylindrical magnet surrounding the axis and that the main magnetic body is rotatable in accordance with the shaft body; a sub-magnetic body that surrounds the axis and is made of a cylindrical magnetic body having a diameter different from that of the main magnetic body, and is accommodated inside the main magnetic body or is provided so as to be rotatable following the shaft body while the main magnetic body is accommodated inside the sub-magnetic body; one of a pair of electrodes is connected to the conductive layer of the main magnetic body, while the other electrode is provided at a position spaced a predetermined distance from the main magnetic body, and an electric field path serves as a current path for generating an electric field associated with current flow between the electrodes; the main magnetic body is provided in a positional relationship such that one end thereof protrudes a predetermined length from one end of the shaft body, the sub-magnetic body is provided in a positional relationship such that one end of the sub-magnetic body protrudes from one end of the shaft body by the same length as the main magnetic body or a length approximately equal to or less than a predetermined threshold value; A processing fluid containing non-magnetic and non-conductive abrasive grains is interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a surface to be processed of the workpiece disposed opposite this area, and the shaft body is rotated under a magnetic field generated by the main magnetic body and an electric field generated by the electric field path, thereby realizing magnetic fluid polishing of the workpiece; moreover, The sub-magnetic body is a cylindrical magnetic body having a conductive layer formed thereon in part or the entirety thereof, and is electrically insulated from the main magnetic body. The electric field path is such that the other electrode is connected to the conductive layer of the sub-magnetic body, The sub-magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in a direction intersecting the magnetization direction of the main magnetic body and such that a region facing the main magnetic body at one end side of the shaft body has the same magnetic pole as the main magnetic body. Fluid polishing equipment.

3. The main magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in the axial direction, which is the direction in which the axis extends.

3. The fluid polishing apparatus according to claim 1 or 2.

4. The main magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in an inward and outward direction, which is a direction intersecting the axis.

3. The fluid polishing apparatus according to claim 1 or 2.

5. The main magnetic body and the sub magnetic body are spaced apart inward and outward directions by a distance determined so that the magnetic flux density at the intermediate position between them does not fall below a value determined as the magnetic flux density required for fluid polishing. The fluid polishing apparatus according to claim 1 .

6. The main magnetic body and the sub magnetic body are spaced apart inward and outward directions by a distance determined so that the magnetic flux density at the intermediate position between them does not fall below 0.18 T.

6. The fluid polishing apparatus according to claim 5.

7. A power supply unit that applies a voltage to the electric field path, The power supply unit generates a voltage of 2.0 kV / mm or less between the electrodes in the electric field path by applying a voltage to the electric field path.

7. The fluid polishing apparatus according to claim 1.

8. A shaft body that is rotatable around an axis extending in a predetermined direction; A main magnetic body is provided in such a manner that a conductive layer is formed on a part or the whole of a cylindrical magnet surrounding the axis and that the main magnetic body is rotatable in accordance with the shaft body; a sub-magnetic body that surrounds the axis and is made of a cylindrical magnetic body having a diameter different from that of the main magnetic body, and is accommodated inside the main magnetic body or is provided so as to be rotatable following the shaft body while the main magnetic body is accommodated inside the sub-magnetic body; one of a pair of electrodes is connected to the conductive layer of the main magnetic body, while the other electrode is provided at a position spaced a predetermined distance from the main magnetic body, and an electric field path serves as a current path for generating an electric field associated with current flow between the electrodes; moreover, the sub-magnetic body is a cylindrical magnetic body having a conductive layer formed thereon in part or the entirety thereof, and is electrically insulated from the main magnetic body; The electric field path is such that the other electrode is connected to the conductive layer of the sub-magnetic body, In the case where the sub-magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in the same direction as the main magnetic body but with the magnetic poles arranged in the opposite direction, A processing fluid containing non-magnetic and non-conductive abrasive grains is interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a surface to be processed of the workpiece disposed opposite to this area, and the shaft body is rotated under a magnetic field generated by the main magnetic body and an electric field generated by the electric field path, thereby realizing magnetic fluid polishing of the workpiece. Fluid polishing method.

9. A shaft body that is rotatable around an axis extending in a predetermined direction; A main magnetic body is provided in such a manner that a conductive layer is formed on a part or the whole of a cylindrical magnet surrounding the axis and that the main magnetic body is rotatable in accordance with the shaft body; a sub-magnetic body that surrounds the axis and is made of a cylindrical magnetic body having a diameter different from that of the main magnetic body, and is accommodated inside the main magnetic body or is provided so as to be rotatable following the shaft body while the main magnetic body is accommodated inside the sub-magnetic body; one of a pair of electrodes is connected to the conductive layer of the main magnetic body, while the other electrode is provided at a position spaced a predetermined distance from the main magnetic body, and an electric field path serves as a current path for generating an electric field associated with current flow between the electrodes; moreover, the sub-magnetic body is a cylindrical magnetic body having a conductive layer formed thereon in part or the entirety thereof, and is electrically insulated from the main magnetic body; The electric field path is such that the other electrode is connected to the conductive layer of the sub-magnetic body, The sub-magnetic body is a magnet formed by magnetizing a cylindrical magnetic body in a direction intersecting the magnetization direction of the main magnetic body and such that a region facing the main magnetic body at one end side of the shaft body has the same magnetic pole as the main magnetic body side, A processing fluid containing non-magnetic and non-conductive abrasive grains is interposed between an area formed by the main magnetic body and the sub-magnetic body at one end side of the shaft body and a surface to be processed of the workpiece disposed opposite to this area, and the shaft body is rotated under a magnetic field generated by the main magnetic body and an electric field generated by the electric field path, thereby realizing magnetic fluid polishing of the workpiece. Fluid polishing method.

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