Patent Application
20070246372
This application is based on and incorporates by reference Japanese Patent Application No. 2004-272505, which was filed on Sep. 17, 2004 and Japanese Patent Application No. 2005-207881, which was filed on Jul. 15, 2005.
The present invention relates to electrochemical machining (ECM), and more specifically to an electrochemical machining tool and a method of machining using the electrochemical machining tool for manufacturing a high quality product, such as a bearing sleeve, at a low cost.
Conventional electrochemical machining equipment for deburring, as described, for example, in Japanese Unexamined Patent Application H10-277842, includes electrodes and a pulse current supply with a direct current power supply and a control device for applying a pulse current to a workpiece and to the electrodes. The electrodes include machining electrodes for deburring the workpiece and electrodes for detecting the position of the workpiece. An electrolyte is supplied between the workpiece and the electrodes, and the workpiece is aligned at a designated position relative to the electrodes.
With regard to the direct current power supply, the positive terminal (+) is connected to the workpiece, and the negative terminal (−) is connected to the workpiece machining electrodes and to the electrodes for detecting the workpiece position via the control device. It should be noted however, that the above document describes the workpiece machining electrodes for deburring and the pulse current supply as general concepts not easily practiced by one of ordinary skill in the art.
It is also known, as described for example in Japanese Unexamined Patent Application 2000-198042, that during electrochemical machining ultrasonic oscillation having an approximately uniform intensity can be directly propagated to the internal wall surface of the processing hole of the workpiece using a hone electrode tool having a structure that serves as both a hone tool for ultrasonic machining and an electrode tool for electrochemical machining. At the same time, an electrochemical effect is applied based on the electrochemical machining on the internal wall surface of the processing hole of the workpiece. As a result, parts having recesses where a conventional brush would not reach are effectively cleaned due to the action of the ultrasonic oscillation and the electrochemical effect. Metal chips and burrs, such as fine particles and shavings, can be effectively removed.
Further, it is known that, during conventional electrochemical machining including electrochemical deburring and electrochemical polishing processes, either one of the deburring or polishing processes can be carried out individually or both can be carried out simultaneously. Further, the electrolyte used in machining can be composed in a certain manner to achieve specific results associated with machining while ensuring that the electrolyte has stable conduction properties. For example, the electrolyte can include an oxidizing reagent capable of promoting surface oxidation in order to dissolve the metal surface of the workpiece to be machined, a polarization enhancer capable of maintaining the concentration polarization, and an inhibitor capable of inhibiting corrosion of the metal surface of the workpiece by the etching component. Japanese Unexamined Patent Application H07-316899 describes an electrolyte solution including one or a combination of electrolytes having one, two, or all three of the oxidizing reagent, the polarization enhancer or the inhibitor.
Still further, as described for example in Japanese Unexamined Patent Application H11-207530, electrochemical machining equipment may have processing electrodes configured to form a groove with a designated shape by electrochemical machining of an inner circumferential surface of a sleeve member. The processing electrodes can include groove machining electrodes capable of forming one or more grooves and finishing electrodes capable of carrying out a finishing process in which the sleeve member and the processing electrodes are moved in a designated relative direction, the groove machining electrodes form a groove on the inner circumferential surface of the sleeve member, and the finishing electrodes finish the inner circumferential surface.
However, while the above discussed reference generally describes machining of a radial dynamic pressure generating groove on the inner circumference of a sleeve, it fails to describe machining of an axial dynamic pressure generating groove at a designated position on the edge of the sleeve.
To overcome the above limitations of known machining tools and processes, the present invention provides an electrochemical machining tool and machining process using the electrochemical machining tool described herein, that are capable of producing a high quality machined product at a low cost. More specifically, the electrochemical machining tool and machining process of the present invention reduces the number of steps associated with machining a workpiece such as a hydrodynamic pressure bearing sleeve, as placement or setting of the workpiece sleeve, and setting of the electrochemical machining tool, need only be performed once.
As noted, high quality and low cost manufacturing of workpieces such as bearing sleeves can be achieved by reducing the number of set-up related procedures and other procedures used for sleeve manufacturing. For example, the piece and electrochemical machining tool can be set up once, and procedures can be conducted with an electrochemical machining tool in accordance with the present invention to simultaneously or selectively perform machining of a radial dynamic pressure generating groove at a designated position on the inner circumferential surface of the workpiece, machining of an axial dynamic pressure groove at a designated position on the edge surface of the piece or sleeve, and deburring to remove machine processed burrs at an oil pool on the inner circumferential surface of the piece or sleeve.
It will be appreciated that the electrochemical machining tool and machining process can be used to machine workpieces and thereby produce products machined for demanding high speed, high accuracy applications, such as in a hydrodynamic pressure bearing capable of use in a hard disk spindle motor. Thus, in describing the electrochemical machining tool and machining process of the present invention, while the focus of the description will be on singular aspects of the present invention such as the formation of a radial dynamic pressure generating groove and axial dynamic pressure generating groove, a series of such grooves are formed on various surfaces as will be described herein for operation of, for example, a sleeve for a hydrodynamic pressure bearing. In describing the inventive electrochemical machining tool and method, the term workpiece may be used in place of sleeve since, in producing a product such as a sleeve, the tool and method of the present invention are applied to a workpiece, such as a piece of metal stock or the like, in accordance with the invention.
The electrochemical machining tool includes an electrode body, which can be configured to carry out any of the electrochemical machining procedures, such as axial groove machining, radial groove machining, and deburring, and further includes an insulated guiding tool having an electrolyte passage forming function and a positioning function for locating the machining electrodes relative to the workpiece or sleeve. In one embodiment, the electrode body is provided with electrochemical machining electrodes for machining an axial and a radial groove, and an electrochemical deburring electrode. In such an embodiment, all machining processes can be carried out simultaneously.
The electrochemical machining tool is configured to move reciprocally back and forth as necessary along an axis, such that the electrochemical machining tool can move away from or move toward and contact a workpiece such as a sleeve, which can be supported by a supporting tool. Very close contact can be achieved by way of pressing the edge of the guiding tool against the edge of the sleeve on which the axial dynamic pressure groove is to be formed, or against the top surface of the supporting tool. With the edge of the guiding tool pressed accordingly, an electrochemical machining gap can be assured for containing a flow of electrolyte.
More specifically, the guiding tool can have a projecting portion configured to be pressed together with the edge of the workpiece on which the axial dynamic pressure groove is to be formed, or with the edge of the workpiece supporting tool in order to assure the electrochemical machining gap for forming an electrolyte passage. The guiding tool and electrode body can be made movable relative to each other by a sliding mechanism and a screw to enable the two components to be adjusted related to one another. Therefore when, for example, the projecting portion is worn out, the guiding tool and the electrode body can be readjusted to ensure close contact and pressure is maintained during operation. Accordingly, by changing the relative position of the guiding tool and the electrode body, they can be readjusted relative to each other.
In accordance with a first embodiment of the present invention, an electrode body of the electrochemical machining tool can include machining electrodes configured to simultaneously form an axial dynamic pressure generating groove on the edge of the workpiece, a radial dynamic pressure generating groove on the inner circumferential surface of the workpiece and can remove the machined burrs of an oil pool. The machined burrs are associated with separate machining of the oil pool, which is mechanically machined on the inner circumferential surface of the workpiece. The oil pool formed by the mechanical machining can be provided anywhere on the inner circumferential surface of the workpiece. For example, it can be mechanically machined on the inner side between radial dynamic pressure generating grooves, or on the external side of the radial dynamic pressure generating grooves.
Alternatively, the electrode body of the electrochemical machining tool can include machining electrodes configured to simultaneously form an axial dynamic pressure generating groove on the edge of the workpiece and a radial dynamic pressure generating groove on the inner circumferential surface of the workpiece. The deburring to remove the machined burrs of the oil pool is performed separately.
In accordance with a second embodiment of the present invention, an electrode body of the electrochemical machining tool can include electrochemical machining electrodes configured to simultaneously form an axial dynamic pressure generating groove on the edge of the workpiece, and to electrochemically deburr or remove the machined burrs of the oil pool, which are mechanically machined on the inner circumferential surface of the workpiece. Electrochemical machining of a radial dynamic pressure generating groove on the inner circumferential surface of the workpiece is performed separately.
In accordance with a third embodiment, the electrode body of the electrochemical machining tool can include machining electrodes configured to simultaneously form a radial dynamic pressure generating groove on the inner circumferential surface of the workpiece and to deburr or remove the machined burrs of the oil pool. Electrochemical machining of an axial dynamic pressure generating groove on the edge of the workpiece is performed separately.
The electrode body of the electrochemical machining tool of the present invention, and the ECM methods described herein can produce a sleeve. The sleeve is manufactured, for example, from a piece of metal stock by electrochemical machining using the electrochemical machining tool of the present invention. Alternatively, the sleeve can further embody a hydrodynamic pressure bearing having the above described sleeve for use in a spindle motor, such as a hard disk spindle motor.
The electrochemical machining tool and electrochemical machining method of the present invention allow axial dynamic pressure generating groove machining at a designated position of the edge of the workpiece, radial dynamic pressure generating groove machining at a designated position of the inner surface of the workpiece, and deburring machining of the oil pool on the inner surface of the workpiece to be conducted simultaneously as a single process while the positions of the workpiece and machining electrodes are set only once. Depending on the individual instance, the electrochemical machining tool and the electrochemical machining method allow flexible handling of the workpiece by allowing simultaneous or sequential procedures or a combination thereof to be performed as noted above.
For example, axial dynamic pressure generating groove machining and deburring machining having similar electrochemical machining conditions can be carried out first, and then radial dynamic pressure generating groove machining can be carried out. As a result, the number of individual process steps can be reduced as compared to the prior art where electrochemical machining is carried out one process step at a time. Moreover, in accordance with the present invention, the workpiece and machining electrodes remain stationary while the position of the workpiece and the machining electrodes are set, thereby maintaining and not reducing precision. Still further, the prior art brushing process typically required after the deburring process can be omitted, allowing further reduction in cost and maintaining or improving precision.
The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the separate views and which, together with the detailed description below, are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
The present invention will now be described in detail in accordance with the drawings. The illustration and description of some components are omitted where their inclusion would not be necessary for one skilled in the art to understand the present invention.
As shown with reference to
As noted, the present invention allows simultaneous machining in connection with an axial dynamic pressure generating groove machining process conducted at a designated position on the edge of the workpiece, a radial dynamic pressure generating groove machining process conducted at a designated position on the inner circumferential surface of the workpiece, and a deburring machining process configured to remove machine processed burrs at, for example, an oil pool on the inner circumferential surface of the workpiece.
Alternatively, the axial dynamic pressure generating groove electrochemical machining and electrochemical deburring of an oil pool having similar electrochemical machining conditions can be carried out simultaneously using the electrode body 11, followed by a separate step of radial dynamic pressure generating groove electrochemical machining using, for example, another electrode body (not shown). It should be noted that, in accordance with the present embodiment, the electrode body 11 can include only the machining electrode 13 as shown, for example, in
Furthermore, the radial dynamic pressure generating groove machining at a designated position on the inner circumferential surface of the workpiece can be carried out first, followed by simultaneous machining of the axial dynamic pressure generating groove, and the deburring.
It should be noted that after mechanical machining of the inner circumferential surface of the sleeve 4 is carried out and an oil pool 41 is formed in the sleeve 4 as shown, for example, in
The electrochemical machining tool 1 of the present invention can include, as shown for example in
The electrochemical machining tool 1 of the present invention includes the electrode body 11, and further includes an insulated guiding tool 2 having an electrolyte passage forming function and an electrode positioning function for locating the electrode body 11 and the sleeve 4. The electrochemical machining tool 1 can move reciprocally back and forth along an axis, as required, to a designated position and the sleeve 4 can freely be installed and removed. The movement of the electrochemical machining tool 1 assures the flow of the electrolyte in the electrochemical machining gap by closely contacting the edge of the insulated guiding tool 2 to the axial dynamic pressure groove side edge of the sleeve 4, which can be supported by supporting tool 3, or to the top edge of the supporting tool 3 with a certain pressure. Accordingly, leakage of the electrolyte to locations other than the electrochemical machining gap is prevented.
More specifically, the insulated guiding tool 2, which is mounted on the electrode body 11 as will be described in greater detail hereinafter, can move back and forth along with the electrochemical machining tool 1. The insulated guiding tool 2 can be positioned to come into close contact with the supporting tool 3 by pressing together the projecting portion 22 of the insulated guiding tool 2, which is the portion projecting slightly from the large diameter portion of the electrode body 11, and the edge of the supporting tool 3 for supporting the sleeve 4, as can be seen, for example, in
By pressing the projecting portion 22 of the insulated guiding tool 2 in the above described manner, an electrolyte passage in the sleeve machining portion is formed, and the electrolyte can be introduced from the inlet 21 of the insulated guiding tool 2, allowing electrochemical machining of the designated portion of the edge and inner circumferential surface of the sleeve 4. It should be noted that the insulated guiding tool 2 can be formed using commercially available ceramic or commercially available synthetic resin. It will be appreciated that synthetic resin is preferably used to achieve a desired flexibility, since flexibility of the projecting portion 22 of the insulated guiding tool 2 makes it difficult for the electrolyte to leak when the insulating guiding tool 2 is placed into close contact under a pressure with the edge of the supporting tool 3 or the sleeve 4 as noted above.
In addition to movement of the insulated guiding tool 2 as described above, the insulated guiding tool 2 and the supporting tool 3 for the sleeve 4 can move back and forth, allowing the projecting portion 22 of the insulated guiding tool 2 to come into contact under a pressure with the edge of the sleeve 4 or the edge of the supporting tool 3 for the sleeve 4. Consequently, the electrolyte can be introduced from the inlet 21 of the electrolyte passage without leakage, and creating an electrolyte passage in the sleeve machining portion, and therefore, allowing electrochemical machining of the designated portion of the edge and inner circumferential surface of the sleeve 4.
To better understand how electrochemical machining and formation of the electrolyte passages is accomplished as described herein above, several observations can be made with reference to the electrode body 11 as shown in
It should be noted however that the projecting portion 22 can become worn, for example, since the projecting portion 22, as shown in detail in
It will be appreciated by those of skill in the art that conductive materials are used for the electrodes to achieve the electrochemical machining results described herein. Examples of the electrode body material including the processing or machining electrodes used for the electrochemical machining tool of the present invention are copper alloys or iron alloys. An example of a copper alloy is brass, and an example of an iron alloy is austenitic stainless steel known in the art as steel having, for example, a Japanese Industrial Standards (JIS) designation of SUS303, SUS304, or the like. While many materials can be used as the insulation resin to insulate portions of the electrode body other than the electrodes, insulating material should have a high resistance against electrolytes such as NaNO3 (sodium nitrate) and should provide a good adherence to the electrode body material. An epoxy resin, a urethane resin, or a polyimide resin should ideally be chosen, with epoxy resins exhibiting superior performance characteristics. The ideal base material for the exemplary workpiece such as the sleeve 4 can also be chosen from copper alloys or iron alloys. As noted above, an example of a copper alloy is brass, and an example of an iron alloy is austenitic stainless steel such as SUS303, SUS304, or the like.
While the next section presents detailed examples and embodiments, they are presented for illustrative purposes. The present invention is not limited by these embodiments.
In accordance with a first embodiment, radial dynamic pressure generating groove electrochemical machining, axial dynamic pressure generating groove electrochemical machining and electrochemical machining for deburring are carried out simultaneously using the electrochemical machining tool 1 of the present invention.
It will be appreciated that the oil pool 41 is formed by a mechanical machining process. The sleeve 4, which as noted is formed from a blank machined austenitic stainless alloy, will be electrochemically machined using the electrochemical machining tool 1 of the present invention.
As shown in
The electrochemical machining tool 1, the insulated guiding tool 2, the supporting tool 3, which hold the sleeve 4, can be set or placed into designated or predetermined positions. The sleeve 4 to be electrochemically machined is placed in the concave supporting portion of the supporting tool 3. The electrochemical machining tool 1 is then lowered and, with a certain amount of force, the edge of the projecting portion 22 of the insulated guiding tool 2 is pushed against the edge of the sleeve 4, assuring the flow of the electrolyte in the electrochemical machining gap for performing electrochemical machining.
It will be appreciated that by applying a machining voltage as will be described in greater detail hereinafter to the sleeve 4 and the electrode body 11 including the machining electrodes 12 and 13 and deburring electrode 14 thereon, the electrolyte in the electrochemical machining gap will carry a current from the electrode surface through the electrolyte to the sleeve 4 and react with the surface of the sleeve 4 to ionize and remove molecules associated with a localized surface of the sleeve 4 through an electrochemical reaction. The groove or grooves are thereby formed in the sleeve 4 corresponding to the exposed electrode patterns on the electrode body 11.
As is well known, the electrolyte can be recycled. For example, the electrolyte in the electrolyte bath can be supplied to a sludge removal device (not shown) for removing the sludge generated during the electrochemical machining. The electrolyte from which sludge is removed can be returned, recycled, or otherwise re-supplied to the electrolyte supplying source. The recycled electrolyte in the electrolyte supplying source can be supplied to the electrolyte bath with a supply pump (not shown). It should be noted that the inlet 21 of the electrochemical machining tool 1 of the present invention can include, as described for example in Japanese Unexamined Patent Application H11-207530 noted above, a well-known electrolyte recycling device to circulate the electrolyte in the electrolyte bath (not shown) during the electrochemical machining. The electrolyte is supplied to and from the electrolyte recycling device including, for example, a sludge removal device with a filter, a container tank to contain the electrolyte, and a supply pump to supply the electrolyte.
The electrochemical machining tool 1 can include an electrode body 11. The electrode body 11 can include the radial dynamic pressure generating groove machining electrode 12 as previously described, the axial dynamic pressure generating groove machining electrode 13, and the deburring electrode 14. A drive control unit and a drive control circuit (not shown) intervenes between the electrodes 12, 13 and 14 and a direct current power supply. The drive control circuit is used to apply a desired machining voltage to the electrodes 12, 13 and 14 through the electrode body 11. The insulated guiding tool 2 can move back and forth by way of a control means (not shown) and establish a position corresponding to the designated position of the sleeve 4 to be machined. The sleeve 4 is contained in the concave supporting portion of the supporting tool 3 and supported at the designated position.
By controlling the size of the small diameter portion of the electrode body 11 or the size of the inner diameter of the sleeve 4, the gap between the inner surface of the sleeve 4 and the electrodes 12, 13 and 14 of the electrode body 11 can be controlled to a distance of several tens of micrometers (μm) at the position where the center of the sleeve 4 and the center of the machining electrodes 12 and 14 coincide. The importance of control over the gap distance will be appreciated by one of ordinary skill in the art of ECM. In addition, regarding the gap between the electrode 13 and the edge of the supported sleeve 4, the height of the projecting portion 22 is set in advance so that the gap becomes several tens of micrometers (μm) in a state of close contact under a pressure. The edge of the projecting portion 22 of the insulated guiding tool 2 and the edge of the supported sleeve 4 are placed into close contact under a constant pressure, and are kept stationary. Electrolyte is fed to the electrochemical machining gap while the sleeve 4 and the electrochemical machining tool 1 are stationary.
It should be noted that the electrolyte supplied from the electrolyte supplying source (not shown) is fed into the inlet 21 of the insulated guiding tool 2. An electrolyte passage is formed from the gap between the axial dynamic pressure generating groove machining electrode 13 and the edge of the sleeve 4, to the gaps between the inner circumferential surface of the sleeve 4, the radial dynamic pressure generating groove machining electrode 12, and the deburring electrode 14. Electrolyte is thus able to flow through the passage such that electrochemical machining can be performed as described herein.
Between the electrodes 12, 13 and 14 and the direct current power source, the drive control circuit (not shown) is provided. Electrolyte is further supplied as noted above. By applying the machining voltage to the three electrodes, 12, 13 and 14 using the drive control circuit, an axial dynamic pressure generating groove 44 on the edge of sleeve 4, and a radial dynamic pressure generating groove 43 on the inner circumferential surface of the sleeve 4 are formed as shown in
Alternatively, radial dynamic pressure generating groove electrochemical machining and axial dynamic pressure generating groove electrochemical machining may be carried out simultaneously using the electrochemical machining tool 1 of the present invention. Unlike the first embodiment, electrochemical machining for deburring is performed separately. In this alternative scenario, the electrode body 11 only includes the radial dynamic pressure generating groove machining electrode 12 and the axial dynamic pressure generating groove machining electrode 13.
After the desired electrochemical machining is carried out, the sleeve 4 is removed and can be brushed or otherwise cleaned to remove the sludge caused by the electrochemical machining. The sleeve 4 can then be rinsed and dried. As a result, a sleeve 4 having a radial dynamic pressure generating groove and an axial dynamic pressure generating groove is obtained.
In accordance with a second embodiment, axial dynamic pressure generating groove electrochemical machining and deburring are carried out simultaneously, and radial dynamic pressure generating groove electrochemical machining is carried out separately.
As shown in
The insulated guiding tool 2 can move reciprocally back and forth along an axis as necessary, by way of a control device (not shown) and can establish a position corresponding to the designated position of the sleeve 4 to be machined. The sleeve 4 is contained in the concave supporting portion of the supporting tool 3 and is thereby supported at the designated position. By controlling the size of the small diameter portion of the electrode body 11, or the size of the inner diameter of the sleeve 4, the gap between the inner surface of the sleeve 4 and the electrodes 12 and 14 of the electrode body 11 can be controlled to a distance of several tens of micrometers (μm) at the position where the center of the sleeve 4 and the center of the machining electrodes 12 and 14 coincide to facilitate electrochemical machining as described herein.
In addition, regarding the gap between the electrode 13 and the edge of the sleeve 4, the height of the projecting portion 22 can be set in advance so that the gap becomes several tens of micrometers (μm) when the projecting portion 22 and the edge of the sleeve 4 are closely contacted under a pressure. The edge of the projecting portion 22 of the insulated guiding tool 2 and the edge of the supported sleeve 4 are placed into close contact under a predetermined pressure and held motionless in a stationary position. Electrolyte is fed into the electrochemical machining gap while the sleeve 4 and electrochemical machining tool 1 are stationary.
The electrochemical machining tool 1 of the present embodiment can include an electrode body 11 positioned at a front end or the edge thereof. The electrode body 11 can include the axial dynamic pressure generating groove machining electrode 13 and the deburring electrode 14. A radial dynamic pressure generating groove on the inner circumferential surface of the sleeve 4 is formed separately.
In the present embodiment, as noted above, the axial dynamic pressure generating groove electrochemical machining and deburring machining are simultaneously carried out. Using the drive control circuit described above (not shown), the machining voltage is applied to the axial dynamic pressure generating groove machining electrode 13 and the deburring electrode 14. As shown in
The electrolyte supplied from the electrolyte supplying source (not shown) can be fed from the inlet 21 of the insulated guiding tool 2. An electrolyte passage is formed from the gap between the axial dynamic pressure generating groove machining electrode 13 and the edge of the sleeve 4, to the gaps between the inner circumferential surface of the sleeve 4 and the deburring electrode 14. The electrolyte can thus flow through the gaps.
Between the electrodes 13 and 14 and the direct current power source, the drive control circuit (not shown) is provided as noted. The electrolyte can be supplied and, by applying the machining voltage to the two electrodes 13 and 14, for example using the driving circuit, an axial dynamic pressure generating groove 44 can be machined on the edge of sleeve 4 and the machined burr 42 at the oil pool 41 can be removed by deburring electrode 14. In a separate procedure, an electrochemical machining tool 1 using an electrode body 11 with only a radial dynamic pressure generating groove electrochemical machining electrode 12 can be used to machine a radial dynamic pressure generating groove.
After the desired electrochemical machining is carried out, the sleeve 4 is removed and can be brushed or otherwise cleaned to remove the sludge caused by the electrochemical machining. The sleeve 4 can then be rinsed and dried. As a result, a sleeve 4 having a radial dynamic pressure generating groove and an axial dynamic pressure generating groove is obtained.
In accordance with a third embodiment, an electrochemical machining tool of the present invention simultaneously performs an electrochemical machining process for forming a radial dynamic pressure generating groove and an electrochemical machining process for removing burrs occurring from a mechanical machining process. An electrochemical machining process for forming an axial dynamic pressure generating groove is performed separately.
The electrochemical machining tool 1 of the present embodiment corresponds to the electrochemical machining tool 1 as shown, for example, in
It will be appreciated that in accordance with the present embodiment, the electrochemical machining process for forming an axial dynamic pressure generating groove on the end surface of the sleeve is performed separately by using an electrochemical machining tool 1, of which the electrode body 11 has only electrode 13 for electrochemically machining an axial dynamic pressure generating groove. Except for the structural differences in the exemplary electrode body 11 described above in connection with the present embodiment, the machining method is the same as in the second embodiment, and the same results are obtained; therefore, a detailed explanation of the electrochemical machining process is omitted.
The electrochemical machining tool of the present invention, in accordance with the above described embodiments, can be used to manufacture a hydrodynamic pressure bearing as shown in
As shown in
A rotary shaft 6 to which a flange 61 is fit on one end thereof, can be inserted or assembled within the sleeve 4 so that it rotates freely. An end cap 7 and a tubular sleeve 9 can be used to contain components of the hydrodynamic pressure bearing. The end cap 7 can be provided with axial dynamic pressure generating grooves formed using, for example, principles described herein, on an edge surface thereof. An outer circumference of the end cap 7 and an end portion of the tubular sleeve 9 can be welded to form a cup shape. The tubular sleeve 9 is fit to the outer circumference of the sleeve 4 of the hydrodynamic pressure bearing and is sealed in an airtight condition at the outer circumferential surface of hydrodynamic pressure bearing with an adhesive 15 so that the top and bottom edges of the flange 61 are facing respectively the axial dynamic pressure generating grooves 44 of sleeve 4 and the axial dynamic pressure generating grooves 71 formed on the end cap 7.
The distance between the end surface of the hydrodynamic pressure bearing and the surface of the end cap 7 can be configured using a spacer 8 to form a suitably sized gap, space, cavity, or the like in which the rotary shaft 6 and the flange 61 can be suspended. The space or gap formed with the hydrodynamic pressure bearing, the end cap 7, and the rotary shaft 6 including the flange 61 is filled with a lubricant oil 10 to promote lubrication and suspension of the rotary shaft 6 including the flange 61 by the generation of dynamic pressure in the oil 10 by the action of the dynamic pressure generating grooves discussed and described herein during rotation as will be further described.
When the rotary shaft 6 with the flange 61 rotates, axial and radial dynamic pressures are generated in the lubricant oil 10, between the rotary shaft 6 and the radial dynamic pressure generating grooves 43 on the inner circumferential surface of the sleeve 4, and between the flange 61 and the axial dynamic pressure generating grooves 44 formed on the edge portion of sleeve 4, and axial dynamic pressure generating grooves 71 formed on the end plate 7. By the lifting action associated with the dynamic pressures generated during rotation, the rotary shaft 6 with the flange 61 can freely rotate. It is important to note that while machining of an axial pressure generating groove and machining of a radial pressure generating groove are described herein in accordance with the invention, suspension of the rotary shaft 6 with the flange 61 are accomplished with a series of such grooves formed, in the above described manner, around, for example, the circumference of the sleeve 4, or around the edge surface of the sleeve 4 as shown, for example, in the figures.
The electrochemical machining tool and electrochemical machining method of the present invention allow radial dynamic pressure generating groove machining, axial dynamic pressure generating groove machining at a designated position of the inner surface of the sleeve 4, and deburring machining of the oil pool 41 at the inner surface of the sleeve 4 as a single process, while the positions of the sleeve 4 and the machining electrodes 12, 13 and 14 are set only once. Electrochemical machining of the radial dynamic pressure generating groove, axial dynamic pressure generating groove and burrs associated with the oil pool, and the resulting sleeve allow for superior mass production capacity leading to high industrial availability of related parts or subassemblies.
The disclosure is intended to explain how to fashion and use various embodiments in accordance with the invention and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications or variations are possible in light of the above teachings. The embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and modifications as are suited to the particular use contemplated, and which fall within the scope of the invention as determined by the appended claims, and all equivalents thereof, when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-272505 | Sep 2004 | JP | national |
| 2005-207881 | Jul 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/30072 | 8/25/2005 | WO | 3/6/2007 |
