Anodizing-assisted grinding apparatus and anodizing-assisted grinding method

Abstract

To efficiently perform grinding while more efficiently anodizing the surface of a workpiece.SOLUTION: An anodized film is formed on the surface of a workpiece 1 by passing a direct current between an anode 6, a cathode 7, and the workpiece 1 via an electrolyte W, and the anodized film is ground away by a grinding wheel 12. The anode 6 is provided separately from the grinding wheel 12, and power is supplied while the anode 6 is pressed against the workpiece 1 by pressure applied by pressure applying means 16. The anode 6 is made of a conductive material that is softer than the workpiece 1. The electrolyte W is supplied from the electrode 6, 7 sides of the anode 6 and the cathode 7.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an anodic oxidation-assisted grinding apparatus and an anodic oxidation-assisted grinding method for grinding the surface of a workpiece by applying an anodic oxidation reaction that occurs on the surface of the workpiece when a direct current is passed through the workpiece via an electrolyte solution.

Background Art

[0002] Conventionally, there has been an anodic oxidation-assisted grinding apparatus for use in a surface grinding apparatus for grinding a workpiece such as a SiC wafer (Patent Document 1). This anodic oxidation-assisted grinding apparatus includes a container for storing an electrolyte solution. When processing the workpiece, the workpiece is immersed in the electrolyte solution stored in the container, and a direct current is passed between the anode, the cathode, and the workpiece through the electrolyte solution. The surface of the workpiece is then ground with a grinding wheel by utilizing the anodic oxidation reaction that occurs on the surface of the workpiece.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such an anodic oxidation-assisted grinding apparatus, even when grinding a workpiece such as a SiC wafer, the surface of the SiC wafer becomes soft due to anodic oxidation, so it becomes possible to use a grinding wheel with general abrasive grains such as cerium oxide or free abrasive grains. Compared with the case of grinding with a diamond grinding wheel, the damage to the surface of the SiC wafer is reduced, the surface roughness after processing is improved, and there is an advantage that the tool cost can be reduced due to non-superabrasive grains of the grinding wheel.

[0005] However, conventional anodizing-assisted grinding equipment has several drawbacks: the workpiece is immersed in an electrolyte solution stored in a container, making the entire grinding apparatus large and complex; and grinding debris generated by grinding the workpiece with the grinding wheel accumulates in the electrolyte solution in the container, making it difficult to collect the debris and perform maintenance.

[0006] Therefore, the present inventors proposed a new anodic oxidation-assisted grinding apparatus as Japanese Patent Application No. 2022-71617. Unlike conventional anodic oxidation-assisted grinding apparatuses that immerse the workpiece in an electrolyte stored in a container, this apparatus eliminates the need for a container to store the electrolyte by supplying the electrolyte in a flow-through manner between the cathode and the workpiece. This allows for a smaller overall apparatus and has the advantage of eliminating the need to collect grinding debris accumulated in the container, thus simplifying maintenance.

[0007] However, the prior art anodic oxidation-assisted grinding apparatus used the grinding wheel as the anode and supplied power through this grinding wheel. As a result, the grinding wheel itself underwent an oxidation reaction, reducing the grinding efficiency of the grinding wheel. Furthermore, there were problems such as significant loss of electrical energy when anodizing the surface of the workpiece. Consequently, it was not possible to efficiently grind the surface of the workpiece with the grinding wheel while more efficiently anodizing the surface of the workpiece.

[0008] In view of these problems, the present invention aims to provide an anodizing-assisted grinding apparatus and an anodizing-assisted grinding method that can efficiently grind a workpiece while more efficiently anodizing the surface of the workpiece. [Means for solving the problem]

[0009] The anodic oxidation-assisted grinding apparatus according to the present invention generates an anodic oxide film on the surface of a workpiece by passing a direct current through an electrolyte between an anode, a cathode, and a workpiece, and grinds the anodic oxide film with a grinding wheel. The apparatus comprises an electrolyte supply means that, separately from the grinding wheel, arranges the anode and cathode facing the workpiece's work surface, supplies the electrolyte onto the workpiece's work surface, and supplies power while pressing the anode against the workpiece under pressure. Furthermore, the anode can be switched between a contact state and a non-contact state with respect to the workpiece, depending on the grinding stage of the workpiece. It is 。

[0010] The present invention relates to an anodizing-assisted grinding method comprising the steps of: generating an anodic oxide film on the surface of a workpiece by passing a direct current through an electrolyte between an anode, a cathode and a workpiece; and grinding the anodic oxide film with a grinding wheel, wherein the method provides the electrolyte to the workpiece while supplying power to the workpiece while applying pressure to the anode of the anode and cathode, which are positioned opposite the workpiece surface separately from the grinding wheel, and pressing the anode against the workpiece. death, The anode is controlled to be in contact with the workpiece and not in contact with the workpiece according to the grinding stage of the workpiece. It is . [Effects of the Invention]

[0011] According to the present invention, since power is supplied while an anode, which is provided separately from the grinding wheel, is pressed against the workpiece by pressurization, there is an advantage in that the surface of the workpiece can be anodized more efficiently and the grinding process can be performed efficiently compared to when power is supplied via the grinding wheel. [Brief explanation of the drawing]

[0012] [Figure 1] This is an elevation view of an anodizing-assisted grinding apparatus showing a first embodiment of the present invention. [Figure 2] This is a plan view of the anodic oxidation-assisted grinding apparatus. [Figure 3] This is a cross-sectional view of the main part of the anodizing-assisted grinding apparatus. [Figure 4]This is a plan cross-sectional view of the main part of the anodizing-assisted grinding apparatus. [Figure 5] (a) and (b) are cross-sectional views of the electrode. [Figure 6] (a) and (b) are plan cross-sectional views of an oscillating type anodic oxidation-assisted grinding apparatus showing a second embodiment of the present invention. [Figure 7] This is a cross-sectional view of the anode showing a third embodiment of the present invention. [Figure 8] This is a plan cross-sectional view of a main part showing a fourth embodiment of the present invention. [Figure 9] This is an explanatory diagram of a first processing example showing a fifth embodiment of the present invention. [Figure 10] This is an explanatory diagram of the second processing example. [Figure 11] This is an explanatory diagram of the third processing example. [Figure 12] (a) is a diagram showing the configuration of the electrode, and (b) is an explanatory diagram of the fourth processing example. [Best Mode for Carrying Out the Invention]

[0013] Hereinafter, embodiments of the invention will be described in detail based on the drawings. FIGS. 1 to 5 show a first embodiment of an anodic oxidation-assisted grinding apparatus employed in a surface grinding apparatus. As shown in FIGS. 1 and 2, this anodic oxidation-assisted grinding apparatus includes a workpiece rotating device 2 on which a disk-shaped workpiece 1 is detachably mounted concentrically on the upper surface and rotates in the direction indicated by arrow a in FIG. 1 around the vertical axis 2a, a grinding wheel shaft 3 that rotates in the direction indicated by arrow b in FIG. 1 around the vertical axis 3a and can move forward and backward in the vertical direction (the vertical direction is synonymous with the vertical direction. The same applies hereinafter), a grinding wheel 5 that is detachably mounted on the grinding wheel flange 4 at the lower end of the grinding wheel shaft 3 and can grind the upper surface of the workpiece 1 on the workpiece rotating device 2, an anode 6 that is disposed near the outer peripheral side of the workpiece 1 on the workpiece rotating device 2 and is pressed against the upper surface of the workpiece 1 by pressure so as to be relatively movable in the rotation direction of the workpiece 1, a cathode 7 that is disposed between the grinding wheel 5 and the anode 6 and is disposed in a non-contact state with a minute gap S above the workpiece 1 on the workpiece rotating device 2, an electrolyte supply means 8 that is disposed on the outer peripheral side of the workpiece 1 with respect to the electrodes 6 and 7 of the anode 6 and the cathode 7 and supplies an electrolyte W in a flowing manner between the workpiece 1, the anode 6, and the cathode 7, and a DC power source 9 that passes a DC current from the anode 6 through the workpiece 1 to the cathode 7 via the electrolyte W.

[0014] Note that this anodic oxidation-assisted grinding apparatus is composed of an upper unit U1 by the grinding wheel 5, the anode 6, the cathode 7, the electrolyte supply means 8, etc., and a lower unit U2 by the workpiece rotating device 2, etc.

[0015] The workpiece rotating device 2 is adapted to detachably adsorb the workpiece 1 by the chuck means 10 at the upper end. The chuck means 10 has a porous adsorption plate for adsorbing the workpiece 1. The workpiece 1 is, for example, a conductive SiC wafer, but other conductive materials may also be used as long as they are conductive.

[0016] The grinding wheel 5 constitutes a grinding wheel (grinding means) for grinding the workpiece 1, and has a grinding wheel base material 11 that can be detachably attached to the lower side of the grinding wheel shaft flange 4, and a non-conductive cup-shaped grinding wheel 12 fixed to the lower side of the grinding wheel base material 11. The cup-shaped grinding wheel 12 has an outer diameter greater than or equal to the outer diameter of the workpiece 1, and is positioned so that its cutting edge width passes through the center of the workpiece 1. The cup-shaped grinding wheel 12 is a non-conductive grinding wheel such as a general grinding wheel. It is also possible to use a grinding wheel other than the cup-shaped grinding wheel 12, and depending on the material of the workpiece 1, a grinding wheel other than a general grinding wheel, a conductive one, etc. may be used.

[0017] The anode 6 is a vertically oriented rod and is made of a conductive material softer than the workpiece 1 so as not to damage the workpiece 1 even when sliding over it. As shown in Figure 3, the anode 6 is held so as to be vertically movable by a holding case 14 and an anode holder 15, and is pressed downward against the workpiece 1 by the pressure of a spring-type pressurizing means 16. It can also be lifted away from the workpiece 1 against the pressurizing means 16 by an air-operated lifting means 17 to a non-contact state. The anode 6 is connected to the positive potential terminal of the DC power supply 9 via a power supply member 18, anode holder 15, and positive potential side power supply line 19.

[0018] The power supply device is composed of an anode 6 and a cathode 7. Furthermore, a closed circuit is formed between the workpiece 1, electrolyte W, DC power supply 9, anode 6, and cathode 7, through which a DC current is passed to the workpiece 1 to generate an anodic oxide film on the surface of the workpiece 1.

[0019] The anode 6, cathode 7, and electrolyte supply means 8 are provided on the support member 21. The support member 21 is supported so as to be slidable in the vertical direction by a pair of guide shafts 26 of the oscillating frame 25 via a bracket 23 and a sliding part 24, and can be raised and lowered by the drive of a lifting drive means (not shown). The oscillating frame 25 is supported so as to be oscillable around a vertical axis, and can swing between a processing position (shown in Figures 1 and 2) where the anode 6, cathode 7, and electrolyte supply means 8 are located on the workpiece rotating device 2, and a retracted position laterally away from the workpiece rotating device 2.

[0020] As shown in Figure 2, the anode 6, cathode 7, and electrolyte supply means 8 are arranged in approximately a straight line in the order of grinding wheel 5, cathode 7, anode 6, and electrolyte supply means 8 on a line segment X that passes through approximately the center of the workpiece 1 at the processing position. The anode 6 is positioned between the grinding wheel 5 and the cathode 7, and corresponds to the outer circumference of the workpiece 1.

[0021] As shown in Figures 3 and 4, the anode 6 is held in an insulating holding case 14 by a bush 27 so as to be able to slide up and down, and has a flange-shaped piston portion 28 located above the bush 27 and a convex portion 29 that protrudes downward from the holding case 14 and can contact the upper surface of the workpiece 1. A power supply member 18 that can abut against the upper end of the anode 6 is housed in the anode holder 15, and a coil spring 30 is interposed between this power supply member 18 and the top of the anode holder 15. The holding case 14 and the anode holder 15 are detachably attached to the support member 21.

[0022] The pressurizing means 16 consists of an anode holder 15, a coil spring 30, etc. The lifting means 17 consists of a cylinder chamber 31 formed between a bush 27 and a piston portion 28 within the holding case 14, an air pipeline 32 connected to the cylinder chamber 31, and a coil spring 30. The air pipeline 32 is connected to an air source 39 via a control valve 33.

[0023] The anode 6 can be switched between a contact state (see Figures 1 and 3) where it is in contact with the workpiece 1 and a non-contact state (see Figure 5(b)) where it is separated from the workpiece 1 by the raising and lowering operation of the lifting mechanism 17 by operating the control valve 33. Specifically, when the control valve 33 is operated to the upward position, air is supplied to the cylinder chamber 31 of the lifting mechanism 17 via the air pipeline 32, causing the anode 6 to rise via the piston portion 28 as shown in Figure 5(b), and the convex portion 29 separates from the upper surface of the workpiece 1, resulting in a non-contact state. Conversely, when the control valve 33 is operated to the downward position, the air is released from the cylinder chamber 31 of the lifting mechanism 17 by the pressurization of the coil spring 30, and the anode 6 returns to a contact state where it is in contact with the workpiece 1 as shown in Figure 3.

[0024] Therefore, by operating the control valve 33 according to the processing status of the workpiece 1, the lifting means 17 moves in the upward or downward direction, allowing arbitrary selection between a contact state in which the anode 6 is in contact with the workpiece 1 and a non-contact state in which the anode 6 is separated from the workpiece 1.

[0025] The anode 6 is composed of graphite, carbon, or a composite material thereof, which is softer than the workpiece 1. However, the anode 6 can be made of any material softer than the workpiece 1, and is not limited to graphite or carbon.

[0026] The cathode 7 is flat and is positioned approximately parallel to the upper surface of the workpiece 1 with a predetermined gap, for example, a small gap S, between them. As the workpiece 1 rotates on the workpiece rotating device 2, the cathode 7 is shaped to face approximately the entire upper surface of the workpiece 1, from the outer periphery to the center. That is, as shown in Figure 2, the cathode 7 is approximately semicircular in shape, with a long side portion 7a in the approximately diametrical direction of the workpiece 1 on the side closer to the grinding wheel 5, and an arc-shaped portion 7b on the side opposite to the grinding wheel 5 relative to this long side portion 7a. An approximately V-shaped notch 7c is provided in the center of the arc-shaped portion 7b, leading to the grinding wheel 5. An anode unit, including the anode 6 and the holding case 14, is positioned within the notch 7c.

[0027] In other words, the cathode 7 has a shape and size that corresponds to approximately half of the workpiece 1 on the anode 6 side, and is provided with a pair of cathode portions 7d on both sides of the line segment X, with the outer circumference of the workpiece 1 widening, so that the entire upper surface of the workpiece 1 corresponds to each cathode portion 7d through relative rotation with respect to the workpiece 1. Note that the cathode 7 only needs to correspond to the entire workpiece 1 through relative movement such as rotation and oscillation (described later) of the workpiece 1, so for example, only one of the pair of cathode portions 7d in Figure 2 may be used.

[0028] The cathode 7 is fixed to the lower side of the support member 21 via an insulating mounting member (not shown), and a power supply member 36 that penetrates the support member 21 and protrudes upward is also fixed to it. The power supply member 36 is connected to the negative potential terminal of the DC power supply 9 via a negative potential side power supply line 37.

[0029] The gap between the workpiece 1 and the cathode 7 is specifically a minute gap S of 1 mm or less, preferably 500 μm or less. Hereinafter, this gap will be referred to as the minute gap S, but it does not refer to a gap of a specific size. During power supply, a closed circuit is formed between the workpiece 1, the electrolyte W, the DC power supply 9, the anode 6, and the cathode 7.

[0030] The electrolyte supply means 8 supplies electrolyte W from the electrode 6 and 7 sides of the anode 6 and cathode 7 to the workpiece 1 side, forming a layer of electrolyte W between the workpiece 1, anode 6, and cathode 7, and is positioned on the opposite side of the grinding wheel 5 from the anode 6 and cathode 7.

[0031] This electrolyte supply means 8 includes a pair of downward-facing supply ports 41, a supply conduit 43 that supplies electrolyte W from a supply source 34 to the supply ports 41, and a guide 44 that receives the electrolyte W from the supply ports 41 and guides it onto the workpiece 1 from the anode 6 and cathode 7 side.

[0032] The supply port 41 is arranged approximately symmetrically with respect to line segment X and is fixed in a vertically adjustable manner by adjustment means 42 such as nuts provided on both the upper and lower sides of the bracket 23. Note that multiple supply ports 41 may be provided, or there may be just one.

[0033] The guide device 44 comprises a peripheral wall portion 45 surrounding the supply port 41 and a receiving portion 46 provided on the bottom side of the peripheral wall portion 45. The peripheral wall portion 45 is provided with a guide opening 47 that opens towards the workpiece 1. The guide device 44 is fixed to the lower side of the support member 21. The guide opening 47 of the peripheral wall portion 45 is almost entirely blocked by the holding case 14 of the anode unit, except for the lower side, and the electrolyte W is supplied onto the workpiece 1 through the space between the lower side of the holding case 14 of the anode unit and the receiving portion 46.

[0034] The electrolyte supply means 8 may also supply the electrolyte W onto the workpiece 1 via the outer circumference of the anode unit's holding case 14. The guide opening 47 of the receiving portion 46 is provided with a notch 49 so as not to interfere with the anode 6. The supply opening 41 of the electrolyte supply means 8 is attached to the bracket 23 and the guide 44 is attached to the support member 21, but the entire electrolyte supply means 8 may also be attached to the support member 21.

[0035] The power lines 19, 37, air conduit 32, and supply conduit 43 are appropriately flexible so as not to hinder the movement of the anode 6, cathode 7, electrolyte supply means 8, etc., such as swinging and lifting. Insulating materials are used for the support member 21, bracket 23, and guide 44.

[0036] Furthermore, it is sufficient for the anode 6, cathode 7, and electrolyte supply means 8 to be positioned between the grinding wheel 5 and the electrolyte supply means 8; it is not necessary to arrange the anode 6, cathode 7, and electrolyte supply means 8 in a roughly straight line along line segment X. In addition, the anode 6, cathode 7, and electrolyte supply means 8 may be attached to a common support member 21, or they may be individually and movably attached to separate members.

[0037] Furthermore, the electrolyte supply means 8 can be either a single-use type that discards the electrolyte W applied to the workpiece 1 each time grinding is performed without recirculation, or a recirculating type in which the electrolyte W used once for grinding is recovered at an appropriate location such as downstream of the workpiece rotating device 2, purified by filtering or chemical reaction treatment, and then recirculated and supplied to the workpiece 1 again. Therefore, the supply of electrolyte W in this embodiment includes both the case in which the electrolyte W is applied to the workpiece 1 and then passed through, and the case in which the electrolyte W applied to the workpiece 1 is recovered, purified, recirculated, and then applied to the workpiece 1 again.

[0038] The amount of electrolyte W supplied is at least enough to fill the space between the electrodes 6 and 7 of the anode 6 and cathode 7 and the workpiece 1 during grinding. Therefore, it is sufficient for the electrolyte W to accumulate at least between the anode 6 and cathode 7 and the workpiece 1. The electrolyte W supplied from the anode 6 and cathode 7 to the area around the workpiece 1 can also be an electrolytic coolant such as water that is circulated to cool the grinding heat of the grinding wheel 5 and wash away grinding chips. Therefore, the electrolyte W can be any liquid that can conduct direct current, and water-soluble coolant or tap water may be used.

[0039] The gap between the cathode 7 and the workpiece 1 is set to a minute gap S necessary for the workpiece 1 on the workpiece rotating device 2 to rotate around the vertical axis 2a without contacting the cathode 7. Therefore, the electrolyte W poured onto the workpiece 1 accumulates in the minute gap S on the workpiece 1 and flows outwards due to the centrifugal force of the workpiece 1. Furthermore, when the anode 6 is in contact with the workpiece 1, although there is pre-pressure from the coil spring 30, it is desirable for a film of electrolyte W to form between the two.

[0040] During the grinding process of the workpiece 1, the workpiece rotating device 2, with the workpiece 1 mounted on its upper surface, is rotated in the direction indicated by arrow a. At the same time, the upper unit U1, including the grinding wheel 5, anode 6, cathode 7, and electrolyte supply means 8, is moved toward the processing position, and then the upper unit U1 is lowered to a predetermined position.

[0041] For example, when moving the upper unit U1 between the retracted position and the machining position, the entire power supply device, including the anode 6 and cathode 7, is held in an elevated position above the workpiece 1. In this elevated position, as shown in Figure 5(a), the cathode 7 rises and moves away from the workpiece 1, while the anode 6 is pushed down by the pressure of the coil spring 30, and descends to a position where the piston portion 28 of the anode 6 contacts and is restricted by the bush 27. At this time, the air in the cylinder chamber 31 is removed.

[0042] When grinding of the workpiece 1 by the grinding wheel 5 begins, the power supply device is lowered until a small gap S exists between the cathode 7 and the workpiece 1, as shown in Figure 5(b). If the control valve 33 is operated at this time to release the air from the cylinder chamber 31, the convex portion 29 at the lower end of the anode 6 will begin to contact the upper surface of the workpiece 1 as the power supply device descends, as shown in Figure 3. As the power supply device descends, the coil spring 30 of the pressurizing means 16 compresses, and the pressurizing means 16 generates pressure that presses the anode 6 against the workpiece 1. This results in a contact state where the anode 6 is in contact with the upper surface of the workpiece 1 at a predetermined pressure.

[0043] Conversely, when the power supply device is in the raised position, air is supplied to the cylinder chamber 31 to raise the anode 6. After lowering the power supply device until there is a small gap S between the cathode 7 and the workpiece 1, the air is released from the cylinder chamber 31, and the anode 6 is pressed against the workpiece 1 by the pressurization of the coil spring 30.

[0044] In the contact state where the anode 6 is pressed against the workpiece 1, the anode 6 is pushed back relative to the coil spring 30, creating a gap between the piston portion 28 of the anode 6 and the upper end of the bush 27, and a gap between the piston portion 28 and the lower end of the anode holder 15. but Yes, it is possible. Furthermore, in the state shown in Figure 3, by adjusting the air pressure in the cylinder chamber 31, the air pressure and the amount of pressure applied to the coil spring 30 can be offset, so it is also possible to adjust the force with which the anode 6 is pressed against the workpiece 1. Therefore, the pressure applied to the anode 6 can be appropriately adjusted according to the oxidation reaction status on the upper surface of the workpiece 1.

[0045] When the anode 6 is in contact with the workpiece 1, supplying air to the cylinder chamber 31 causes the anode 6 and the power supply member 18 to rise against the pre-pressure of the coil spring 30 until the anode 6 contacts the lower surface of the anode holder 15, as shown in Figure 5(b). When the piston portion 28 of the anode 6 contacts the lower surface of the anode holder 15, a gap is created between the anode 6 and the workpiece 1, and the anode 6 and the workpiece 1 become non-contact.

[0046] Even in this non-contact state, the electrolyte W fills the space between the anode 6 and the workpiece 1, so the anode 6 and the workpiece 1 maintain electrical conductivity through the electrolyte W. However, compared to the contact state where the anode 6 and the workpiece 1 are in contact, the electrical resistance between the anode 6 and the workpiece 1 increases because the conductivity is through the electrolyte W, and the anodic oxidation reaction of the workpiece 1 decreases.

[0047] Therefore, in the rough grinding region immediately after starting the grinding process of the workpiece 1, the anodic oxidation efficiency of the workpiece 1 is increased by supplying power with the anode 6 in contact with the workpiece 1. At the end of the grinding process, in the finish grinding region or the spark-out region, the anode 6 is removed from the workpiece 1 to create a non-contact state, intentionally lowering the anodic oxidation efficiency. By prioritizing the removal by grinding with the grinding wheel 5 over grinding by anodic oxidation, it becomes possible to finish the workpiece 1 to a surface with less damage from anodic oxidation.

[0048] When grinding the workpiece 1 with the grinding wheel 6, electrolyte W is poured from the electrolyte supply means 8 onto the upper surface of the workpiece 1 of the workpiece rotating device 2, and a direct current is passed from the anode 6 through the workpiece 1 to the cathode 7 via the electrolyte W, while processing is carried out sequentially through roughing, finishing, and spark-out processes.

[0049] When the electrolyte W is applied to the upper surface of the workpiece 1 from the electrolyte supply means 8, the electrolyte W is poured onto the workpiece 1 from the electrode side of the anode 6 and cathode 7. This ensures that the electrolyte W flowing on the upper surface of the workpiece 1 is reliably supplied to the electrode side 6 and 7. The electrolyte W on the upper surface of the workpiece 1 flows from the outer circumference of the workpiece 1 to the outer circumference of the workpiece rotating device 2, maintaining its thin film state due to the centrifugal force or surface tension of the workpiece 1, and penetrates into the gap between the workpiece 1 and the anode 6, and the gap between the workpiece 1 and the cathode 7, respectively, forming an electrolyte layer of a thickness appropriate to the size of each gap.

[0050] In sync with the supply of electrolyte W, the power supply device descends to apply a direct current to the workpiece 1, forming an anodic oxide film on the upper surface of the workpiece 1 through an anodizing reaction. When the grinding wheel 5 is rotating, the electrolyte W also penetrates between the rotating grinding wheel 5 and the workpiece 1, functioning as a coolant.

[0051] As the grinding wheel 5, which is rotating around the grinding wheel shaft 3, is advanced toward the workpiece 1 in the direction indicated by arrow c, the grinding wheel 5 comes into contact with the workpiece 1, and the rough grinding process of the workpiece 1 by the grinding wheel 5 begins. Meanwhile, when the power supply device is lowered to a predetermined position, a small gap S is created between the workpiece 1 and the cathode 7, and the anode 6 comes into contact with the upper surface of the workpiece 1 due to the pressure of the coil spring 30, and a direct current flows from the anode 6 to the cathode 7 through the workpiece 1 and the electrolyte W.

[0052] At this time, the anode 6 is in direct contact with the upper surface of the workpiece 1, and the electrical resistance between the anode 6 and the workpiece 1 becomes small. As a result, the entire region of the upper surface of the workpiece 1 facing the cathode 7 becomes positively charged, and this positively charged region expands as the workpiece 1 rotates. Therefore, the upper surface of the workpiece 1 can be efficiently anodic-oxidized, preventing wasted power consumption.

[0053] Furthermore, since the anode 6 is provided separately from the grinding wheel 5, there is no need to pass a DC current through the grinding wheel 5. Therefore, the anodic oxidation reaction of the grinding wheel 5 that occurs when a DC current is passed through the grinding wheel 5 to the workpiece 1 is eliminated, resulting in no wasted power consumption and preventing deterioration of the grinding wheel 5 due to the anodic oxidation reaction. This allows the grinding efficiency of the grinding wheel 5 to be maintained over a long period, enabling efficient processing of the workpiece 1. Moreover, since the anode 6 is made of a material softer than the workpiece 1, damage to the upper surface of the workpiece 1 by the anode 6 can be prevented, even though the anode 6 slides along the upper surface of the workpiece 1.

[0054] Furthermore, the anode 6 may be made of a material softer than the workpiece 1. The tip of the anode 6 that contacts the workpiece 1 may be made flat to make surface contact with the workpiece 1, or it may be made curved to minimize sliding resistance. The tip of the anode 6 may also be made to make rolling contact via a roller, sphere, or the like.

[0055] Since the anode 6 is in contact with the workpiece 1 via pressure from the pressure-applying means 16, the anode 6 can make stable contact with the workpiece 1 with lower electrical resistance compared to the case without pressure. Furthermore, even if the anode 6 is damaged due to wear or other reasons, it can be pushed towards the workpiece 1, allowing the anode 6 to be used for a long period of time and reducing the frequency of anode 6 replacement.

[0056] Furthermore, when the anode 6 comes into direct contact with the workpiece 1, a positive potential is directly applied from the anode 6 to the workpiece 1, further reducing the electrical resistance between the anode 6 and the workpiece 1. As a result, the portion of the workpiece 1 facing the cathode 7 becomes more susceptible to anodizing, and as the upper surface of the workpiece 1 becomes anodized, the upper surface of the workpiece 1 rapidly undergoes anodizing, creating a soft anodic oxide film on the upper surface of the workpiece 1.

[0057] Furthermore, by supplying power while pressing the anode 6 against the workpiece 1 using the pressurizing means 16, the electrical resistance at the contact point between the workpiece 1 and the anode 6 is stably reduced, allowing for efficient grinding while anodizing the workpiece 1. This improves the grindability of the upper surface of the workpiece 1, and by cutting into it with the grinding wheel 5, the anodic oxide film on the surface of the workpiece 1, which has softened due to the anodizing reaction, can be ground and removed. Note that the anodic oxide film on the upper surface of the workpiece 1 is formed more efficiently as the minute gap S between the workpiece 1 and the cathode 7 becomes smaller.

[0058] Of course, with this anodizing-assisted grinding apparatus, there is no need to immerse the workpiece 1 in an electrolyte solution stored in a container, as in conventional methods. Therefore, compared to conventional methods where a container was essential, the entire apparatus can be made smaller and simpler. Furthermore, since the anodized film is ground and removed by the grinding wheel 5 while the electrolyte solution W is flowing over it, the grinding debris can be washed away by the flowing electrolyte solution W. As a result, the grinding debris can be easily collected outside the machine, and the maintenance of the apparatus can be made easier.

[0059] When the grinding wheel 5 cuts into the workpiece 1, there are several control methods, including a constant speed control method that controls the cutting speed to a constant cutting speed, a constant load control method that controls the cutting load to a constant cutting load, an arbitrary load control method that controls the cutting speed to an arbitrary rotational load, and an oxidation rate response method that controls the cutting speed according to the anodizing rate of the surface of the workpiece 1. In the case of the arbitrary load control method, the smaller the rotational load, the faster the cutting speed is achieved, and if the rotational load becomes too high, the grinding wheel 5 is controlled to move away from the workpiece 1.

[0060] The electrolyte W is supplied by the guide 44 from the side of the anode 6 and cathode 7 closest to the electrodes 6 and 7. This prevents unnecessary consumption of the electrolyte W while ensuring a reliable supply of the electrolyte W between the electrodes 6 and 7 and the workpiece 1. In particular, since the rod-shaped anode 6 is positioned on the side of the guide 44, and the cathode 7 is positioned approximately parallel to the workpiece 1 on the opposite side of the guide 44, the electrolyte W supplied onto the workpiece 1 can smoothly penetrate into the gap between the anode 6 and cathode 7 and the workpiece 1.

[0061] Furthermore, since the guide opening 47 of the guide device 44 is blocked by the anode 6 holding case 14 except for the lower position on the bottom side, the electrolyte W is supplied onto the workpiece 1 via the underside of the holding case 14, and the electrolyte W can be supplied concentrated near the workpiece 1.

[0062] Furthermore, during the machining of the workpiece 1, especially near the end of grinding or when machining has progressed to the end, the anode 6 can be raised to a non-contact state depending on the situation at that time. This reduces the efficiency of anodizing the upper surface of the workpiece 1 while the anode 6 is not in contact. As a result, the upper surface of the workpiece 1 can be finished with less damage due to anodizing.

[0063] The non-contact state of the anode 6 may be maintained for a predetermined time during the finishing stage or spark-out, depending on the grinding status of the workpiece 1, or it may be intermittently repeated between the non-contact state and the contact state at short time intervals after the rough grinding is completed. In either case, the workpiece 1 can be finished with minimal damage from anodizing.

[0064] Figure 6 illustrates a second embodiment of the present invention. This anodizing-assisted grinding apparatus is of the oscillating type, and as shown in Figures 6(a) and (b), an upper unit U1 including a grinding wheel 5, an anode 6, a cathode 7, and an electrolyte supply means 8, and a lower unit U2 including a workpiece rotating device 2 that supports a workpiece 1 are configured to oscillate relative to each other in the substantially radial direction of the workpiece 1 (directions indicated by arrows d and e) by an oscillating means (not shown).

[0065] In Figure 6, the lower unit U2 is positioned in a fixed location and the upper unit U1 is moved back and forth in the oscillation direction. However, the upper unit U1 may be positioned in a fixed location and the lower unit U2 may be moved back and forth in the oscillation direction, or both may be moved back and forth in opposite directions. Other configurations are the same as in the first embodiment.

[0066] By performing grinding of the workpiece 1 while the upper unit U1 and the lower unit U2 oscillate relative to each other in this manner, the anodizing of the upper surface of the workpiece 1 and the grinding of the upper surface of the workpiece 1 by the grinding wheel 5 are efficiently carried out.

[0067] In other words, when using a cup-shaped grinding wheel 5, the grinding position is adjusted so that the center Y of the workpiece 1 passes through the width of the cutting edge of the cup-shaped grinding wheel 12, as shown in Figure 6(a). However, because the center Y of the workpiece 1 is not below the cathode 7, the anodizing efficiency near the center Y of the workpiece 1 is drastically reduced.

[0068] However, by causing the upper unit U1 and the lower unit U2 to oscillate relative to each other, the area near the center Y of the workpiece 1 can more easily correspond to the area below the cathode 7, as shown in Figure 6(b), allowing for efficient anodizing of the upper surface of the workpiece 1 and grinding of the upper surface of the workpiece 1 by the cup-shaped grinding wheel 12. Therefore, the workpiece rotating device 2 is reciprocated in the approximately radial direction of the workpiece 1 until the center Y of the workpiece 1 is below or near the cathode 7, and the oscillating motion of the grinding wheel 5 and the cathode 7 relative to the workpiece 1 is repeated. This has the advantage that even when using the cup-shaped grinding wheel 12, the amount of overlap between the workpiece 1 and the cathode 7 increases, significantly improving the anodizing efficiency of the workpiece 1.

[0069] If sparking occurs before the grinding process is complete, turn off the DC power supply 9. to The anodizing of the upper surface of the workpiece 1 may be stopped, and the oscillation operation may be continued in the same state as normal grinding.

[0070] Figure 7 illustrates a third embodiment of the present invention. In this anodizing-assisted grinding apparatus, the anode 6 is configured to be pressed against the workpiece 1 by the pressure exerted by the anode 6's own weight. The anode 6 is supported by bushings 27 inside a holding case 14 so as to be able to slide up and down on both sides. The anode 6 protrudes upward through a through hole 21a in a support member 21, and a positive potential side power supply line 19 is connected to its upper end. The anode 6 also has a piston portion 28 in the middle in the vertical direction, and this piston portion 28 is located in a cylinder chamber 31. The piston portion 28, cylinder chamber 31, etc. constitute a lifting means 17, similar to the first embodiment, and the cylinder chamber 31 is connected to a control valve (not shown) via an air pipeline 32.

[0071] In this case, the anode 6 can be pressed against the workpiece 1 with a predetermined pressure by its own weight, thus ensuring stable contact between the anode 6 and the workpiece 1. Furthermore, by supplying air to the cylinder chamber 31, the anode 6 can be lifted via the piston 28 and maintained in a non-contact state with the workpiece 1.

[0072] Therefore, the pressurizing means 16 only needs to be capable of applying a predetermined pressurizing force in a direction that presses the anode 6 against the workpiece 1. In addition to a spring type that utilizes a coil spring 30 or the like as shown in the first embodiment, a cylinder type that uses an air cylinder to press the anode 6 against it may also be used, or a gravity type that utilizes the weight of the anode 6 itself may be adopted.

[0073] Figure 8 illustrates a fourth embodiment of the present invention. In this anodic oxidation-assisted grinding apparatus, a substantially V-shaped cathode 7 is employed. This cathode 7 comprises a pair of strip-shaped cathode portions 7d made of plate-shaped conductive members, and both cathode portions 7d are connected in a substantially V-shape at a connection portion 7e on the power supply member 36 side. There is a notch 7c on the side of the cathode 7 opposite the grinding wheel 5, and the anode 6, electrolyte supply means 8, etc. are provided in the notch 7c, and other configurations are the same as in the first embodiment.

[0074] Even when a cathode 7 is used with a strip-shaped cathode portion 7d arranged in a roughly V-shape, the workpiece 1 rotates around its center during grinding, allowing the cathode 7 to cover the entire surface of the workpiece 1. Therefore, each time the cathode 7 passes over the workpiece 1, the portion corresponding to the cathode 7 is intermittently anodized with high current efficiency, while the portion outside the cathode 7 is anodized with low current efficiency. By considering the material of the workpiece 1, the rotation speed of the workpiece 1, the width of the cathode portion 7d, etc., it is possible to process efficiently while minimizing damage to the workpiece 1's surface.

[0075] Figures 9 to 12 illustrate the first to fourth machining examples when grinding a workpiece 1 as a fifth embodiment of the present invention. Figure 9 shows the first machining example. In this first machining example, the entire machining process is divided into a rough machining process, a finish machining process, and a spark-out process. In the rough machining process, the anode 6 is in contact and energized; in the finish machining process, the anode 6 is in a non-contact state and energized; and in the spark-out process, the anode 6 is in a non-contact state and the energization is stopped.

[0076] In this way, the efficiency of current supply to the workpiece 1 is increased during the rough machining process, and the oxidation efficiency of the upper surface of the workpiece 1 is increased, thereby improving the machining efficiency of the workpiece 1. On the other hand, in the finishing process, the current supply efficiency can be intentionally reduced by supplying current from the non-contact anode 6 to the workpiece 1 via the electrolyte W. Therefore, the oxidation efficiency of the workpiece 1 is reduced, preventing damage from the oxidation reaction on the surface of the workpiece 1, and also preventing the occurrence of contact marks from the anode on the surface of the workpiece 1. In the spark-out process, there are no contact marks from the anode 6 and no damage from the oxidation reaction, so the surface finish of the workpiece 1 can be improved.

[0077] Figure 10 shows a second machining example. In this second machining example, the entire grinding process is divided into a roughing process, a finishing process, and a spark-out process. In the roughing and finishing processes, the anode 6 is intermittently brought into contact with the workpiece 1 while the current is still flowing. In the roughing process, the contact time t1 of the anode 6 with the workpiece 1 is made longer, and in the finishing process, the contact time t2 of the anode 6 with the workpiece 1 is made shorter compared to the roughing process.

[0078] This increases the efficiency of current supply to the workpiece 1 during the rough machining process, thereby improving the machining efficiency of the workpiece 1. However, in the finishing process, the current supply efficiency is intentionally reduced to prevent damage from oxidation reactions on the surface of the workpiece 1. In the spark-out process, the anode 6 is kept in a non-contact state, and the current is also stopped.

[0079] Figure 11 shows a third machining example. In this third machining example, the entire machining process is divided into a rough machining process, a finish machining process, and a spark-out process. In the rough machining and finish machining processes, the anode 6 is kept in contact and current is continuously supplied, but the current value is increased in the rough machining process and decreased in the finish machining process.

[0080] As a result, the efficiency of current supply to the workpiece 1 can be increased in the rough machining process, but the efficiency of current supply to the workpiece 1 decreases in the finishing process, preventing damage to the surface of the workpiece 1 due to oxidation reactions. In the spark-out process, the anode 6 is kept in a non-contact state and the current supply is stopped.

[0081] In this third machining example, as shown by the dotted line, the anode 6 may be kept in contact with the workpiece 1 from the rough machining process to partway through the finishing process, and then separated from the workpiece 1 to a non-contact state from partway through the finishing process onward.

[0082] Figure 12 shows a fourth machining example. In this fourth machining example, as shown in Figure 12(a), multiple (for example, 5) anode rods 6a to 6e are arranged on the anode 6 side corresponding to the cathode 7. In the rough machining process, as shown in Figure 12(b), all anode rods 6a to 6e are in contact with the workpiece 1 and current is passed through many anode rods 6a to 6e. In the finishing machining process, anode rods 6b and 6d among the anode rods 6a to 6e are made non-contact, reducing the number of contacting anode rods 6a, 6c, and 6e.

[0083] This increases the processing efficiency of the workpiece 1 during the roughing process, but reduces the electrical conductivity of the workpiece 1 during the finishing process, preventing damage to the surface of the workpiece 1 due to oxidation reactions. In the spark-out process, all anode rods 6a to 6e are made non-contact, and the current is stopped. Regardless of the increase or decrease in the number of anode rods, it is desirable that the relationship between the multiple anode rods 6a to 6e and the cathode 7 be such that the current flows approximately equally between each anode rod 6a to 6e and the cathode 7.

[0084] The processing examples are not limited to these first to fourth processing examples, and it goes without saying that there are many processing procedures depending on the processing conditions of the workpiece 1. For example, it is also possible to use the oscillation operation of the second embodiment in combination with any of the first to fourth processing examples.

[0085] Alternatively, the rough machining process may be divided into two stages. In the first stage, the anode 6 is brought into contact with the workpiece 1 and current is applied, resulting in a highly efficient process for the workpiece 1. In the second stage, the anode 6 is repeatedly brought into contact with the workpiece 1, resulting in a less efficient process than the first stage. After this, the process may proceed from the finishing stage to the spark-out stage. The spark-out stage involves grinding with the grinding wheel 12 for a predetermined time while the cutting depth of the grinding wheel 12 is stopped, but this spark-out stage may be omitted.

[0086] Although the embodiments of the present invention have been illustrated above, the present invention is not limited to these embodiments, and various modifications are possible without departing from the spirit of the invention. For example, in each embodiment, a flow-type anodic oxidation-assisted grinding apparatus is illustrated in which the electrolyte W is supplied to the workpiece 1 by flowing it over it. However, the present invention can be similarly applied to an anodic oxidation-assisted grinding apparatus in which the workpiece 1, anode 6, cathode 7, and grinding wheel are immersed in the electrolyte W stored in a container, as long as the anode 6, which is provided separately from the grinding wheel 5, is pressed against the workpiece 1 by pressurization and power can be supplied. In other words, the present invention can be similarly applied to both flow-type and immersion-type electrolyte W, and is not limited to one or the other.

[0087] The power supply devices such as the anode 6 and cathode 7, and the electrolyte supply means 8 are made movable up and down by a lifting mechanism via a support member 21, etc. The lifting mechanism may be manual or automatic, and any type of mechanism such as screw type or cylinder type can be used. The cylinder type may be either air pressure type or hydraulic type. However, in relation to the machining accuracy of the workpiece 1, it is desirable to use a lifting mechanism with high positioning accuracy.

[0088] The anode 6, cathode 7, and electrolyte supply means 8 may be insulated from the support portion that supports them so as to be able to move up and down by using an insulating material for the support member 21. The anode 6 and cathode 7 and the power supply system that supplies power to them may be made of conductors, and the electrolyte supply means 8 may be made entirely or partially of insulating material.

[0089] The shapes of the anode 6 and cathode 7 can be arbitrarily selected and are not limited to each embodiment. The contact surface of the anode 6 with respect to the workpiece 1 may be circular or rectangular. Also, when a power supply member 18 is provided above the rod-shaped anode 6, the anode 6 and the power supply member 18 may be integrated or separate. On the other hand, the shape of the cathode 7 is also arbitrary. However, if at least one of the anode 6 and cathode 7 is elongated in the planar direction of the workpiece 1, it is desirable that the electrical resistance between the anode 6 and cathode 7 be approximately the same at any position. Since the anode 6 contacts the workpiece 1 and the surface of the workpiece 1 facing the cathode 7 is anodized, it is desirable for the cathode 7 to be wider than the anode 6 in terms of processing efficiency.

[0090] The pressurizing means 16 that applies pressure to the anode 6 may utilize a coil spring 30 or its own weight, or it may utilize the elastic force of rubber or other elastic material, air pressure, or the magnetic force of a magnet. The lifting means 17 can also be any type, similar to the pressurizing means 16. For example, a magnetic lifting means 17 can be used to move the anode 6 up and down using magnetic force. In that case, the lifting means 17 can also serve as part or all of the biasing means 16.

[0091] The anode 6 is preferably made of a conductive material that is softer than the workpiece 1. However, a material with the same hardness as the workpiece 1, or a material that is harder than the workpiece 1, may be used for the anode 6, as long as it does not leave contact marks or other damage to the workpiece 1.

[0092] In this embodiment, a non-conductive grinding wheel is used, but a conductive one may also be used. When a conductive grinding wheel is used, it is desirable to prevent the DC current from the anode 6 from flowing to the grinding wheel.

[0093] When supplying power via the anode 6, the oxidation reaction on the upper surface of the workpiece 1 can be precisely controlled by bringing the anode 6 into contact with or away from the workpiece 1 according to the processing status of the workpiece 1 (amount removed by the grinding wheel). As a result, the workpiece 1 can be processed efficiently, and it is possible to prevent the oxidized layer from remaining on the upper surface of the workpiece 1.

[0094] By supplying power via the anode 6, it is not necessary to use a conductive material for the grinding wheel 5, which has the advantage of increasing the range of grinding wheel options. Furthermore, when using the grinding wheel as the anode, it is not possible to switch between contact and non-contact of the anode with respect to the workpiece 1, so the adjustment of the oxidation reaction on the upper surface of the workpiece 1 was limited to controlling the current value. However, by using both contact and non-contact of the anode 6 with respect to the workpiece 1, the range of options is increased.

[0095] The electrolyte W may be supplied through the grinding wheel spindle 3. Alternatively, when supplying the electrolyte W separately from the anode 6 via a supply port 41, the anode 6, cathode 7, and supply port 41 may be arranged in a different positional relationship than in the first embodiment, such as by positioning the supply port 41 so as to be directed towards the intermediate portion between the anode 6 and cathode 7. However, it is necessary to fill the space between the anode 6 and cathode 7 and the workpiece 1, and the surface of the workpiece 1, with the electrolyte W. If the cathode 7 is flat, multiple grooves may be provided on the surface of the cathode 7 facing the workpiece 1 to facilitate the flow of the electrolyte W between it and the workpiece 1. This ensures that fresh electrolyte W is always supplied without the accumulation of old electrolyte between the cathode 7 and the workpiece 1, thus preventing a decrease in electrolysis efficiency. [Explanation of symbols]

[0096] 1 Workpiece 2 Workpiece rotation device 5 Grinding Wheels 6 Anode 7 Cathode 8 Electrolyte supply means 9 DC power supply 16 Pressurization means 17 Lifting and lowering means W Electrolyte

Claims

1. An anodizing-assisted grinding apparatus that generates an anodic oxide film on the surface of a workpiece by passing a direct current through an electrolyte between the anode, cathode and workpiece, and then grinds the anodic oxide film with a grinding wheel, In addition to the grinding wheel, the anode and cathode are arranged facing the workpiece surface. The system includes an electrolyte supply means for supplying the electrolyte onto the workpiece surface, The anode is pressed against the workpiece by pressurization while power is supplied, Depending on the grinding stage of the workpiece, the anode can be switched between a contact state and a non-contact state with respect to the workpiece. An anodizing-assisted grinding apparatus characterized by the following features.

2. A step of generating an anodic oxide film on the surface of a workpiece by passing a direct current between the anode, cathode and workpiece via an electrolyte, An anodizing-assisted grinding method comprising the step of grinding the anodic oxide film with a grinding wheel, While supplying the electrolyte to the workpiece surface, power is supplied to the workpiece by applying pressure to the anode, which is one of the anodes and cathodes positioned opposite the workpiece surface separately from the grinding wheel, The anode is controlled to be in contact with the workpiece and not in contact with the workpiece according to the grinding stage of the workpiece. A grinding method using anodic oxidation, characterized by the following features.

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