Polishing Tool And Polishing Device

Abstract

A grinding machine (10) composed of a support table (12) for supporting an object (11) to be ground, a rotating shaft (13a) vertically arranged above the support table, and a grinding tool (40) connected to a lower end of the rotating shaft in parallel with the support table, in which the grinding tool is composed of a grind stone-holding member (32) on which a circular ultrasonic vibrators (31a, 31b) electrically connectable to an electric source are fixed and a circular grind stone (33) attached to a lower end of a periphery of the grind stone-holding member, in which the grind stone-holding member of the grinding tool has a continuous or discontinuous circular air space area (36) composed of multiple circular air space regions which are composed of circularly formed or arranged discontinuous air spaces between a position of the circular ultrasonic vibrator and a position at which the grind stone-holding member is connected to the rotating shaft, whereby the multiple circular air space area keeps an ultrasonic wave generated from the circular ultrasonic vibrator from linearly propagating to an area on an opposite side where the rotating shaft is connected, can grind an object to be ground with high precision because the ultrasonic wave generated in the ultrasonic vibrator is efficiently applied to the grind stone.

Description

FIELD OF THE INVENTION

[0001] This invention relates to a grinding tool (or polishing tool) and a grinding machine (or polishing device) which is favorably employable for grinding a surface of an object such as glass material or silicon material.

BACKGROUND OF THE INVENTION

[0002] Heretofore, various substrates such as glass substrates, silicon substrates, silicon nitride substrates, sapphire substrates, or silicon carbide substrates are employed for manufacturing thin film electronic devices. These substrates are ground on their surfaces using a grinding machine to give smoothened surfaces. In addition, optical devices such as a lens and a prism can be ground to give smoothened surfaces. Thus, the grinding machine has been employed for grinding these objects on their surface to give smoothened surface or to adjust the thickness of the objects by repeated grinding procedures.

[0003] FIG. 1 is a plan view of a grinding tool attached to a grinding machine illustrated in Patent Publication 1 (WO 06/137453). FIG. 2 is a sectional view of the grinding tool 1 taken along the line I-I indicated in FIG. 1.

[0004] The grinding tool 1 shown in FIG. 1 and FIG. 2 comprises a connecting plate 2 to be connected to a rotating shaft of a rotation driving means (e.g., motor), a circular elastic member 4 which is connected to the periphery of the connecting plate 2 via connecting means 3 composed of plural connecting portions 3a and space portions 3b, ultrasonic vibrators 5 fixed on the periphery of the circular elastic member 4 in the form of a circle, and grind stone 6 attached to the lower end at the periphery of the circular elastic member 4. The connecting plate 2 of the grinding tool 1 is connected to the rotating shaft via a disc-shaped attachment. The connecting plates have four holes 7 each of which receives a bolt for attaching the connecting plate to the disc-shaped attachment.

[0005] In the use of the grinding machine equipped with the above-mentioned grinding tool, the grinding tool 1 is rotated by driving the rotating shaft and the bottom of the grinding stone is brought into contact to an object to be ground, while the ultrasonic wave generated in the ultrasonic vibrator 5 is applied to the grinding stone 6 via the circular elastic member 4. Thus, the object is ground on its surface.

[0006] The circular elastic member 4 of the grinding tool 1 is largely vibrated in the areas between the adjoining connecting portions as compared with the areas continuing from the connecting portions 3a. Therefore, the ultrasonic vibration generated in each ultrasonic vibrator 5 hardly propagates to the rotating shaft via the connecting portion 3a and the connecting plate 2, and most of the generated ultrasonic vibration is applied to the grinding stone. When the ultrasonic vibration is efficiently applied to the grinding stone 6, the grinding stone 6 vibrates with a large amplitude so as to reduce friction between the grinding stone and the object to be ground, and generation of undesirable vibration of the machine is kept low. For this reason, the object can be ground with high precision by means of the grinding tool 1 disclosed in the Patent Publication 1.

[0007] The grinding tool disclosed in the Patent Publication 1 can grind an object with high precision. It has been found, however, that a portion of the ultrasonic vibration generated in the ultrasonic vibrator still propagates to the rotating shaft via the connecting portion of the connecting means and the connecting plate. Therefore, a small amount of the energy of the ultrasonic vibration is lost.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a grinding tool and a grinding machine in which the ultrasonic vibration generated in the ultrasonic vibrator is applied to the grinding stone more efficiently.

[0009] There is provided by the invention a grinding machine comprising a support table on which an object to be ground is supported, a rotating shaft vertically arranged above the support table, and a grinding tool connected to a lower end of the rotating shaft in parallel with the support table, the grinding tool comprising a grind stone-holding member on which a circular ultrasonic vibrator electrically connectable to an electric source is fixed and a circular grind stone attached to a lower end of a periphery of the grind stone-holding member, in which the grind stone-holding member of the grinding tool has a continuous or discontinuous circular air space area between a position of the circular ultrasonic vibrator and a position at which the grind stone-holding member is connected to the rotating shaft, the continuous or discontinuous circular air space area comprising multiple circular air space regions which comprise circularly formed or arranged continuous or discontinuous air spaces, whereby the circular air space area keeps an ultrasonic wave generated from the circular ultrasonic vibrator from linearly propagating to an area on an opposite side where the rotating shaft is connected.

[0010] Preferred embodiments of the grinding machine of the present invention are set forth below.

[0011] (1) The circular air space area comprises plural inner penetrating grooves intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating grooves intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer penetrating grooves and each of the outer connecting areas being arranged to face each of the inner penetrating grooves.

[0012] (2) The circular air space area comprises plural inner penetrating holes intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating holes intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer through holes and each of the outer connecting areas being arranged to face each of the inner through holes.

[0013] (3) The circular air space area comprises a circular upper unpenetrating groove which extended downwardly from an upper surface of the grind stone-holding member and a circular lower unpenetrating groove which extended upwardly from a lower surface of the grind stone-holding member, a total of a depth of the upper groove and a depth of the lower groove being larger than thickness of the grind stone-connecting member.

[0014] (4) The circular air space area comprises circular porous material arranged in the grind stone-holding member on an inner side of the circular ultrasonic vibrator.

[0015] (5) The grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises upper plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member and lower plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member, each of the upper connecting areas being arranged to face each of the lower penetrating grooves and each of the lower connecting areas being arranged to face each of the upper penetrating grooves.

[0016] (6) The grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular outer unpenetrating grooves which extend inwardly from an outer surface of the cylinder member and circular inner unpenetrating grooves which extend outwardly from an inner surface of the cylinder member, a total of a depth of the outer groove and a depth of the inner groove being larger than thickness of the cylinder member.

[0017] (7) The grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular porous material arranged in the cylinder member on an upper side of the circular ultrasonic vibrator.

[0018] (8) The support table rotates.

[0019] There is further provided by the invention a grinding tool comprising a grind stone-holding member on which a circular ultrasonic vibrator electrically connectable to an electric source is fixed, said grind stone-holing member having a center portion to be connected to a rotating shaft, and a circular grind stone attached to a lower end of a periphery of the grind stone-holding member, in which the grind stone-holding member of the grinding tool has a continuous or discontinuous circular air space area between a position of the circular ultrasonic vibrator and a position at which the grind stone-holding member is connected to the rotating shaft, the continuous or discontinuous circular air space area comprising multiple circular air space regions which comprise circularly formed or arranged continuous or discontinuous air spaces, whereby the circular air space area keeps an ultrasonic wave generated from the circular ultrasonic vibrator from linearly propagating to an area on an opposite side where the rotating shaft is connected.

[0020] Preferred embodiments of the grinding tool of the invention are the grinding tools described above for the preferred embodiments (1) to (7) of the grinding machine.

[0021] In the specification, the term of "circular ultrasonic vibrator" can be a set of plural ultrasonic vibrators arranged in the form of circle. The term of "circular grinding stone" can be a set of plural grinding stone pieces arranged in the form of a circle.

[0022] In the grinding stone-holding means of the grinding tool of the invention, there is formed a circular air space area in which circular air space regions (or zones) are arranged. A ultrasonic vibration generated in the circular ultrasonic vibrator of the grinding tool is reflected at any of the ultrasonic wave reflecting faces provided by the plural air space areas constituting the circular air space areas, whereby the ultrasonic wave does not propagate to the rotating shaft. Therefore, the ultrasonic vibration is applied to the circular grinding stone with prominent high efficiency, so that the circular grinding stone vibrates with a large amplitude and the friction between the circular grinding stone and the object to be ground reduces. For this reason, an object can be ground with prominently high precision by the use of the grinding tool of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The grinding machine of the invention is described below, referring to the attached drawings.

[0024] FIG. 3 is a front view of one embodiment of the grinding machine according to the invention. FIG. 4 is a plan view illustrating the grinding machine of FIG. 3 that is given by sectioning the rotating shaft 13a taken along the II-II line. FIG. 5 is an enlarged sectional view of the grinding tool 40 of FIG. 4 taken along the line III-III.

[0025] As is shown in FIG. 3 to FIG. 5, the grinding machine 10 of the invention comprises a support table 12 on which an object 11 to be ground is supported; a rotating shaft 13a vertically arranged above the support table 12, and a grinding tool 40 (a grinding tool of the invention connected to a lower end of the rotating shaft 13a in parallel with the support table 12, the grinding tool comprising a grind stone-holding member 32 on which circular ultrasonic vibrators 31a, 31b electrically connectable to an electric source 14 is fixed and a circular grind stone 33 attached to a lower end of a periphery of the grind stone-holding member 32. The grinding machine 10 is characteristic in that the grind stone-holding member 32 has a circular air space area 36 (which comprises two circular air space regions comprising circularly arranged discontinuous air spaces) between a position 34a of the circular ultrasonic vibrator 31a, 31b and a position 34b (the position at which the grinding tool 40 is connected to the rotating shaft) at which the grind stone-holding member 32 is connected to the rotating shaft 13a, whereby the circular air space area 36 keeps an ultrasonic wave generated from the circular ultrasonic vibrators 31a, 31b from linearly propagating to the position 34a where the rotating shaft is connected.

[0026] The support table 12 is rotatably supported on a rotary shaft 16a of a rotation-driving apparatus 16 (e.g., motor) placed on a base 15. The support table can be made to move horizontally.

[0027] Above the support table 12, a grinding-assisting liquid supplying apparatus 18 equipped with a pipe 18a for supplying a grinding-assisting liquid (e.g., water) onto an object 11 to be ground. The supplying apparatus 18 is supported by a pole 21 fixed on the base 15. The pole 21 is arranged behind the support table 12 as shown in FIG. 3. The grinding-assisting liquid may be supplied onto an upper surface of the object to be ground through a through-hole formed in the grind stone-holding member on the inner side of the circular grind stone.

[0028] The grinding tool 40 is connected to the rotating shaft 13a of the rotation-driving unit 13. The rotation-driving unit 13 is supported by a nut 23b of a feed screw 23. A screw axis 23a of the feed screw 23 is connected with a rotation-driving apparatus 17 placed on the base 15. The rotation-driving unit 13 supported by the nut 23b is moved upwardly or downwardly with the grinding tool 40 when the screw axis 23a is rotated by driving the rotation-driving apparatus 17. The nut 23b is connected to a bearing 24 attached to a pole 22 which stands on the base 15 in parallel with the screw axis 23a. Therefore, the nut 23b, rotation-driving unit 13 and grinding tool 40 are not rotated around the screw axis 23a.

[0029] The grinding tool 40 comprises a grind stone-holding member 32 equipped with circular ultrasonic vibrators 31a, 31b and a circular grind stone 33 attached to the lower surface of the grind stone-holding member 32 at its periphery.

[0030] The circular grind stone 33 can be composed of abrasives such as diamond grains and a binder such as metal bond or resin bond. Generally, the abrasive can have a mean diameter in the range of 0.1 to 50 .mu.m.

[0031] The circular grind stone can be composed of plural (e.g., 2 to 50) stone pieces arranged to form of a circle. The grind stone composed of plural stone pieces can be favorably utilized to prepare a circular grind stone having a large size. In addition, the grind stone composed of plural stone pieces is highly resistant to damage (such as formation of cracks) in the case that the ultrasonic vibration is applied to the grind stone or the grind stone is kept in contact with the object to be ground under friction. This is because the stress produced in the grind stone decreases.

[0032] The grind stone-holding member 32 can be made of material capable of transmitting ultrasonic vibrations such as metallic material, for instance, aluminum, bronze, stainless steel or aluminum alloy (e.g., duralmin) or ceramic material.

[0033] The grinding stone-holding member 32 comprises a sleeve 32a placed around the rotating shaft 13a and fixed with a bolt 38a, a holding disc 32b fixed to the lower surface of the sleeve 32a with a bolt 38b, and a grind stone-holding ring 32c which is fixed to the lower surface of the holding disc 32b with a combination of an adhesive (e.g., hot-melt adhesive) and a bolt 38c.

[0034] The sleeve 32a, holding disc 32b and holding ring 32c can be made to form a single unit. However, if the sleeve 32a and holding disc 32b are made separable from each other and the holding disc 32b is made to have a small thickness, the holding disc 32b and grind stone 33 can vibrate with a large amplitude when the circular ultrasonic vibrators 31a, 31b generate ultrasonic vibration. In addition, if the sleeve 32a is made to have a large length, the holding disc 32b can be firmly fixed to the rotating shaft 13a via the sleeve 32a. If the holding disc 32b and grinding stone-holding ring 32c are made separable from each other, the grinding stone 33 can be easily replaced with a fresh grinding stone when the grinding stone is worn out by the grinding procedures by detaching the holding ring 32c with the worn grinding stone 33 without removing the below-described wirings 28b, 28c for connecting the circular ultrasonic vibrators 31a, 31b to the electric energy-receiving unit 25b of the below-described rotary transformer 25.

[0035] The grinding stone-holding member 32 is preferably made to be symmetrical around the rotating axis so that the grinding stone can be rotated stably. For instance, the holding disc can be made in the form of a circular disc or a polygonal disc.

[0036] In the grinding stone-holding member 32, there is formed a circular air space area 36 composed of two circular air space regions comprising circularly arranged discontinuous air spaces between the position 34a of the circular ultrasonic vibrators 31a, 31b and the position 34b for connecting with the rotating shaft 13a. Thus formed circular air space area 36 keeps an ultrasonic wave generated from the circular ultrasonic vibrators 31a, 31b from linearly propagating to an area on an opposite side near to the position 34b (the inner side of the illustrated grinding tool 40) where the rotating shaft is connected. The function of the circular air space area 36 will be described later in more detail.

[0037] The term of "position of the ultrasonic vibrator(s)" means "position on which the ultrasonic vibrator(s) is fixed". In the case that the circular air space area 36 is formed in the grinding stone-holding member 32 on the inner side of the circular ultrasonic vibrators 31a, 31b, the position of the ultrasonic vibrator(s) corresponds to the inner periphery of the circular ultrasonic vibrators 31a, 31b on the grinding stone-holding member 32. In the case that plural circular ultrasonic vibrators having different inner diameters are fixed to the grinding stone-holding member 32, the inner periphery of the circular ultrasonic vibrators means an inner periphery of the circular ultrasonic vibrator having the least inner diameter. The term of "position connecting the rotation shaft) means a position at which the grinding stone-holding member is attached to the rotating shaft 13a.

[0038] Each of the circular ultrasonic vibrators 31a, 31b may comprise a piezoelectric material 41 and a pair of electrodes 42 which are placed on their both surfaces. The piezoelectric material 41 can be made of piezoelectric ceramic material of lead zirconate titanate. The electrode 42 can be made of silver or phosphor bronze.

[0039] Each piezoelectric material 41 of the circular ultrasonic vibrators 31a, 31b is polarized, for instance, in the thickness direction. For example, the piezoelectric material 41 of the circular ultrasonic vibration 31a is polarized upwardly in the perpendicular direction, while the piezoelectric material 41 of the circular ultrasonic vibration 31b is polarized downwardly in the perpendicular direction.

[0040] Each of the circular ultrasonic vibrators 31a, 31b is fixed to the grind stone-holding member 32, for instance, via an epoxy resin. The epoxy resin can serve to insulate each of the circular ultrasonic vibrators 31a, 32 from the grind stone-holding member 32. The circular ultrasonic vibrators 31a, 31b can be coated with insulating coat material to keep the pair of the electrodes of the ultrasonic vibrator from electrically connecting with each other when the electrodes are brought into contact with the grinding assisting liquid (e.g., water).

[0041] The circular ultrasonic vibrator can be composed of plural (e.g., 2 to 30) ultrasonic vibrating pieces arranged to form a circle. If the circular ultrasonic vibrator can be preferably composed of plural pieces in the case that a circular ultrasonic vibrator in a large diameter is manufactured.

[0042] Practically, one or plural (preferably up to 4) circular ultrasonic vibrators can be used. The circular grind stone can be vibrate with a large amplitude if a great number of circular ultrasonic vibrators are used. However, if a large number of circular ultrasonic vibrators is attached to the grind stone-holding member, the wiring to transmit electric energy to the circular ultrasonic vibrators is complicated.

[0043] The rotary transformer 25 attached to the grinding machine 10 serves to supply electric energy to each of the circular ultrasonic vibrators 31a, 31b rotating with the grinding tool 40 when the object 11 is being ground.

[0044] The rotary transformer 25 comprises a power supply unit 25a and a power receiving unit 25b adjacently arranged to each other with a small space. Both of the power supply unit 25a and power receiving unit 25b are in an annular form. The power supply unit 25a is fixed to the bottom of the rotation driving unit 13. The power receiving unit 25b is fixed to the top of the grind stone-holding member 32.

[0045] The power supply unit 25a comprises an annular stator core 26a and a stator coil 27a, and the power receiving unit 25b comprises an annular rotor core 26b and a rotor coil 27b. Each of the stator core 26a and rotor core 26b is made of magnetic material such as ferrite and has annular grooves arranged along the periphery of the core. Each of the stator coil 27a and rotor coil 27b comprises a conductive wiring coiled along the annular grooves formed on each of the stator core 26a and rotor core 26b.

[0046] To the stator coil 27a is electrically connected a power source 14 via an electric wiring 28a, and to the rotor coil 27b is electrically connected each of the circular ultrasonic vibrators 31a, 31b via an electric wiring 28b, 28c. The electric wiring 28c is electrically connected to the lower ultrasonic vibrators 31b through a through hole 32d formed in the grind stone-holding member 32.

[0047] When an electric energy generated by the power source 14 is supplied to the stator coil 27a of the rotary transformer 25, the stator coil 27a and rotor coil 27b are magnetically coupled to each other. For the reason, the electric energy supplied to the stator coil 27a is transmitted to the rotor coil 27b when the rotor coil 27b (i.e., the power receiving unit 25b) is rotated simultaneously with the rotating shaft 13a. Hence, the electric energy generated by the power source 14 can be transmitted to each of the ultrasonic vibrators 31a, 31b rotating together with both of the rotating shaft 13a and grinding tool 40 when the object 11 is being ground.

[0048] The electric energy (e.g., a.c. alternating voltage) generated by the power source 14 is transmitted to each of the ultrasonic vibrators 31a, 31b (in more detail, each electrode of the piezoelectric vibrator serving as ultrasonic vibrator) to cause generation of ultrasonic vibration in the ultrasonic vibrators 31a, 31b, and the ultrasonic vibration is then applied to the circular (annular) grind stone 33 via the grind stone-holding member 32.

[0049] The rotary transformer serving as a transmission unit for transmitting the electric energy to ultrasonic vibrator can be replaced with a slip ring. The rotary transformer is advantageous in that it can stably transmit the electric energy to the ultrasonic vibrator rotating together with the rotating shaft at a rotation rate up to 100,000 r.p.m., because the electric energy is transmitted through the power supply unit and power receiving unit which are arranged with no contact. On the other hand, the slip ring cannot stably transmit the electric energy to the rotating ultrasonic vibrator when the rotation rate exceeds approx. 5,000 r.p.m.

[0050] The procedures for grinding the object by means of the grinding machine 10 are described below.

[0051] The object 11 is temporarily fixed, for instance, to an iron-made holder (not shown) using a hot-melt adhesive. The holder to which the object 11 is fixed is then fixed onto the support table 12, for instance, by means of magnetic force.

[0052] Thereafter, the rotation driving apparatus 16 is actuated to rotate the rotating shaft 16a together with the support table 12. A liquid is supplied from the pipe 18a of the liquid supply means 18 on the object 11. The electric energy generated by the power source 14 is transmitted to the ultrasonic vibrators 31a, 31b via the rotary transformer 25, whereby each ultrasonic vibrator generates ultrasonic vibration. The generated ultrasonic vibration is then transmitted to the circular grind stone 33 via the grind stone-holding member 32.

[0053] The driving unit 13 is then driven to rotate the rotating shaft 13a and the grinding tool 40. Subsequently, the driving apparatus 17 is driven to gradually move the grinding tool downwardly. By these operations, the circular grinding stone 33 under application of ultrasonic vibration is brought into contact with the object 11 under such condition that an outer surface of a portion in the vicinity of the lower end of the grind stone is brought into contact with a portion in the vicinity of the upper end of the object 11, whereby a whole upper surface of the object 11 is ground or polished. The grinding tool is further moved downwardly to grind the object to have a predetermined thickness.

[0054] The circular air space area 36 provided to the grind stone-holding member 32 of the grinding tool 40 is explained below.

[0055] The circular air space area 36 of the grinding tool 40 comprises an inner circular air space region 36a comprising four air spaces 35a and an outer circular air space region 36b comprising four air spaces 35b.

[0056] It is known that when two different material having greatly different inherent acoustic impedances are in contact with each other to form a interface, a most portion of a sound wave propagating in one material toward another material is reflected on the interface so that almost no sound wave propagates to the later material. The sound impedance is defined as a product of a density of the material and a sound velocity. Since solid material and air have largely different densities from each other, most of a sound wave propagating in the solid material is reflected on the interface between the solid material and air and does not propagate to the air.

[0057] Accordingly, if the grind stone-holding member 32 has air space areas 35a, 35b, an ultrasonic (vibration) reflecting face is formed on the interfaces between the solid grind stone-holding member 32 and the air spaces 35a, 35b.

[0058] Thus, in the grinding tool 40, the ultrasonic vibration generated in the circular ultrasonic vibrators 31a, 31b does not linearly propagate to the area on the side of the position 34b at which the rotating shaft is connected, that is an inner side area in the case of the grinding tool 40, because the circular air space area 36 comprising a combination of a circular air space regions 36a, 36b does not transmit the ultrasonic vibration.

[0059] Accordingly, the ultrasonic vibration generated in the ultrasonic vibrators 31a, 31b is reflected on the interfaces formed by the air spaces 35a, 35 and propagates through the outer side of the grinding stone-holding member 32 to the circular grind stone 33 so as to efficiently cause ultrasonic vibration of the grind stone 33 with large amplitude. If the circular grind stone 33 is vibrates with large amplitude, friction caused between the grind stone 33 and the object 11 decreases so that unfavorable mechanical vibration decreases. For this reason, the grinding tool 40 can grind the object with high precision.

[0060] As is shown in FIG. 4, the circular air space area 36 comprises plural (e.g., four) inner penetrating grooves (inner through grooves) 43a intermittently formed via connecting areas 37a and plural (e.g., four) outer penetrating grooves (outer through grooves) 43b intermittently formed via connecting areas 37b, in which each of the inner connecting areas 37a is arranged to face each of the outer penetrating grooves 43b and each of the outer connecting areas 37b is arranged to face each of the inner penetrating grooves 43a. Under this structure, most of the ultrasonic vibration generated in the circular ultrasonic vibrators 31a, 31b is reflected on any of the ultrasonic wave-reflecting faces formed by the air spaces 35a, 35b, and is efficiently utilized to cause the ultrasonic vibration of the circular grind stone 33.

[0061] The penetrating groove can be easily formed by discharge processing or cutting processing.

[0062] FIG. 6 is a plan view of other embodiment of the grinding tool of the invention. FIG. 7 is an enlarged sectional view of the grinding tool 60 of FIG. 6 taken along the line IV-IV.

[0063] The grinding tool 60 shown in FIG. 6 and FIG. 7 is similar to the grinding tool 40 of FIG. 4 except that a circular air space area 66 comprises a circular upper unpenetrating groove 73a which extends downwardly from an upper surface of the grind stone-holding member 62 and a circular lower unpenetrating groove 73b which extends upwardly from a lower surface of the grind stone-holding member 62 and a total of a depth of the upper groove and a depth of the lower groove is larger than thickness of the grind stone-holding member.

[0064] In the grinding tool 60, a circular air space region 66a is formed of an air space (circular continuous air space) 65a inside of the upper groove 73a and a connecting area 67a, while a circular air space region 66b is formed of an air space 65b inside of the lower groove 73b and a connecting area 67b. The circular air space region 66a and circular air space region 66b is combined to give a circular air space area 66.

[0065] Each of the air spaces 65a, 65b and connecting areas 67a, 67b is in the form of circle. Therefore, the grinding tool 60 is advantageous over the grinding tool 40 of FIG. 4, because the circular grind stone 33 can vibrate more uniformly along the grind stone when the ultrasonic vibration is applied, and hence the object can be ground more precisely.

[0066] The total of the depth of the upper groove 73a and lower groove 73b is more than the thickness of the grind stone-holding member 62, preferably not more than 1.5 times, more preferably not more than 1.1 times.

[0067] FIG. 8 is a plan view of other embodiment of the grinding tool of the invention. FIG. 9 is an enlarged sectional view of the grinding tool 80 of FIG. 8 taken along the line V-V.

[0068] The grinding tool 80 shown in FIG. 8 and FIG. 9 is similar to the grinding tool 40 of FIG. 4 except that a circular air space area 86 comprises circular porous material 93 arranged in the grind stone-holding member 82 on an inner side of the circular ultrasonic vibrators 31a, 31b.

[0069] The circular air space area 86 of the grinding tool 80 comprises circular porous material 93 which is formed of plural circular air space regions comprising air spaces 85 arranged in the circular direction of the circular porous material 93.

[0070] The air spaces comprises a great number of pores dispersed uniformly in the circular porous material 93. Therefore, the grinding tool 80 is advantageous over the grinding tool 40 of FIG. 4, because the circular grind stone 33 can vibrate more uniformly along the grind stone when the ultrasonic vibration is applied and moreover the grind stone-holding member 82 has an increased rigidity, and hence the object can be ground more precisely.

[0071] The substrate disc 82b of the grind stone-holding member 82 can be easily manufactured by the steps of preparing an outer portion of the substrate disc 82b and an inner portion of the substrate disc 82b independently, arranging the circular porous material 93 between both portions, and binding the outer and inner portions via the porous material by welding or by the use of an adhesive.

[0072] The circular porous material 93 can be porous metal material. The porous material 93 can be prepare by molding a power (or fibers) of metal such as bronze, stainless steel, nickel or titanium under compression. The pores of the porous material 93 generally have diameters in the range of 10 nm to several mm.

[0073] The porous material 93 preferably has a bulk density in the range of 5 to 75% of the density of the substrate disc 82 on the outer side.

[0074] FIG. 10 is a plan view of other embodiment of the grinding tool of the invention. FIG. 11 is an enlarged sectional view of the grinding tool 100 of FIG. 10 taken along the line VI-VI.

[0075] The grinding tool 100 shown in FIG. 10 and FIG. 11 is similar to the grinding tool 40 of FIG. 4 except that a circular air space area 106 comprises inner plural penetrating holes (through holes) 113a intermittently formed via connecting areas 107a and outer plural penetrating holes (through holes) 113b intermittently formed via connecting areas 107b both formed in the grind stone-holding member 102 and that the inner connecting areas 107a face the outer penetrating holes 113b and the outer connecting areas 107b face the inner penetrating holes 113a.

[0076] In the grinding tool 100, one circular air space region 106a is composed of an air spaces 105a inside of the plural penetrating holes 113a and the connecting areas 107a, and another circular air space region 106b is composed of an air spaces 105b inside of the plural penetrating holes 113b and the connecting areas 107b. The circular air space region 106a and circular air space region 106b are combined to give a circular air space area 106.

[0077] The grinding tool 100 may be advantageous over the grinding tool 40 of FIG. 4 because the penetrating holes 113a, 113b can be easily formed by perforating method using a drill.

[0078] As is shown in FIG. 11, two (or more) rotary transformers 115a, 115b can be arranged around the rotating shaft 13a to be connected to the grinding tool 100. To the circular ultrasonic vibrators 31a, 31b can be supplied electric energy by means of the rotary transformers 115a, 115b. The rotary transformers 115a, 115b are magnetically shielded from each other by means of a permalloy-made cylinder 116 placed between them.

[0079] In the above-mentioned arrangement of the rotary transformers, the circular ultrasonic vibrators 31a, 31b can receive an alternating voltage (e.g., sine wave voltage) of the same phase via the rotary transformers 115a, 115b, so that the ultrasonic vibrators 31a, 31b can vibrate in the radial direction with the same phase. As a result, when the ultrasonic vibrator 31a vibrates to increase its diameter, the ultrasonic vibrator 31b vibrates simultaneously to increase its diameter, so that the outer periphery of the grind stone-holding member 102 is displaced outwardly. Then, when the ultrasonic vibrator 31a vibrates to decrease its diameter, the ultrasonic vibrator 31b vibrates simultaneously to decrease its diameter, so that the outer periphery of the grind stone-holding member 102 is displaced inwardly. Therefore, the outer periphery of the grind stone-holding member 102 vibrates in the direction indicated by an arrow 119a shown in FIG. 11 (that is a direction in parallel with the surface of the object to be ground) together with the circular grind stone 33.

[0080] The vibration of the circular grind stone 33 in the direction in parallel with the surface of an object to be ground can improve precision of the grinding processing.

[0081] Otherwise, the circular ultrasonic vibrators 31a, 31b can receive an alternating voltage (e.g., sine wave voltage) of the opposite phase via the rotary transformers 115a, 115b, so that the ultrasonic vibrators 31a, 31b can vibrate in the radial direction with the opposite phase. As a result, when the ultrasonic vibrator 31a vibrates to increase its diameter, the ultrasonic vibrator 31b vibrates to decrease its diameter, so that the grind stone-holding member 102 is deformed to move its outer periphery downwardly. Then, when the ultrasonic vibrator 31a vibrates to decrease its diameter, the ultrasonic vibrator 31b vibrates to increase its diameter, so that the outer periphery of the grind stone-holding member 102 is deformed to move its outer periphery upwardly. Therefore, the outer periphery of the grind stone-holding member 102 vibrates in the direction indicated by an arrow 119b shown in FIG. 11 (that is a direction substantially perpendicular to the surface of the object to be ground) together with the circular grind stone 33.

[0082] The vibration of the circular grind stone 33 in the direction perpendicular to the surface of an object to be ground can grind the object at an increased rate (or within shortened period of time).

[0083] In the use of the grinding machine equipped with the rotary transformers 115a, 115b, the object can be first submitted to rough grinding by applying alternating current with opposite phase to the ultrasonic vibrators 31a, 31, to grind the object at a higher rate. Subsequently, the object can be submitted to precise grinding by applying alternating current with same phase to the ultrasonic vibrators 31a, 31, to grind the object at a higher precision. As a result, an object can be roughly ground within a short period of time and then ground with high precision.

[0084] The above-mentioned procedures utilizing a circular ultrasonic vibrator composed of plural ultrasonic vibrating pieces and plural rotary transformers are described in detail in the aforementioned Patent Publication 1.

[0085] FIG. 12 is a plan view of other embodiment of the grinding tool of the invention. FIG. 13 is an enlarged sectional view of the grinding tool 120 of FIG. 12 taken along the line VII-VII.

[0086] The grinding tool 120 shown in FIG. 12 and FIG. 13 is similar to the grinding tool 40 of FIG. 4 except that the grind stone-holding member 122 comprises a disc substrate 112a and a cylinder member 122b downwardly extended from a periphery of the disc substrate 122a, and the circular air space area 126 comprises upper plural penetrating grooves 133a intermittently formed via connecting areas 127a formed in the cylinder member 122b and lower plural penetrating grooves 133b intermittently formed via connecting areas 127b formed in the cylinder member 122b. Each of the upper connecting areas 127a are arranged to face each of the lower penetrating grooves 133b and each of the lower connecting areas 127b are arranged to face each of the upper penetrating grooves 133a.

[0087] In the grinding tool 120, one circular air space region 126a is composed of air spaces 125a inside of the upper plural penetrating grooves 133a and plural connecting areas 127a and another air space region 126b is composed of air spaces 125b inside of the lower plural penetrating grooves 133b and plural connecting areas 127b. The circular air space region 126a and circular air space region 126b are combined to form a circular air space area 126.

[0088] Most of the ultrasonic vibration generated in the circular ultrasonic vibrator 31 propagating to the circular air space area 126 is reflected to an ultrasonic wave reflecting faces provided by the air spaces 125a, 125b and then propagates to the circular grinding stone 33 via the grind stone-holding member 122. Thus, the generated ultrasonic vibration is efficiently applied to the grind stone.

[0089] The grinding tool 120 may be advantageous in that the grinding stone can vibrate with a large amplitude in the direction in parallel with an object to be ground if the cylinder member 122b is so manufactured as to have a thin thickness.

[0090] In the case that the circular air space area 126 is formed in the grind stone-holding member 122 above the circular ultrasonic vibrator 31, the term of "position on which the circular ultrasonic vibrator is fixed to the grind stone-holding member" means the top end position of the ultrasonic vibrator.

[0091] FIG. 14 is a partly broken view of other embodiment of the grinding tool of the invention. FIG. 15 is an enlarged sectional view of the grinding tool 140 of FIG. 14 taken along the line VIII-VIII.

[0092] The grinding tool 140 shown in FIG. 14 and FIG. 15 is similar to the grinding tool 40 of FIG. 4 except that the grind stone-holding member 142 comprises a disc substrate 142a and a cylinder member 142b downwardly extended from a periphery of the disc substrate 142a, and the circular air space area 146 comprises circular outer unpenetrating grooves 153a which extend inwardly from an outer surface of the cylinder member 142 and circular inner unpenetrating grooves 153b which extend outwardly from an inner surface of the cylinder member 142. A total of a depth of the outer groove 153a and a depth of the inner groove 153b is larger than thickness of the cylinder member 142b. The circular ultrasonic vibrator 31 is fixed to the lower surface of the cylinder member 142b.

[0093] In the grinding tool 140, one circular air space region 146a is composed of air space 145a inside of the outer groove 153a and the connecting area 147a, and another air space region 146b is composed of air space 145b inside of the inner groove 153b and the connecting area 147b. A circular air space area 146 is composed of the circular air space region 146a and circular air space region 146b.

[0094] The grinding tool 140 of FIG. 14 is also advantageous for the same reason described for the grinding tool 60 of FIG. 6.

[0095] The total of the depth of the outer groove 153a and inner groove 153b is more than the thickness of the cylinder member 142, preferably not more than 1.5 times, more preferably not more than 1.1 times.

[0096] FIG. 16 is a schematic view of other embodiment of the grinding tool of the invention. FIG. 17 is an enlarged sectional view of the grinding tool 160 of FIG. 16 taken along the line IX-IX.

[0097] The grinding tool 160 shown in FIG. 16 and FIG. 17 is similar to the grinding tool 40 of FIG. 4 except that the grind stone-holding member 162 comprises a disc substrate 162a and a cylinder member 162b downwardly extended from a periphery of the disc substrate 162a, and the circular air space area 166 comprises circular porous material 173 arranged in the cylinder member 162 on an upper side of the circular ultrasonic vibrator 31.

[0098] Thus, the circular are space area 166 of the grinding tool 160 comprises plural circular air space regions which contain pores (air spaces) 165 which are arranged in the circular porous material 173 in the axis direction.

BRIEF DESCRIPTION OF THE DRAWING

[0099] FIG. 1 is a front view of a grinding tool attached to a conventional grinding machine.

[0100] FIG. 2 is a sectional view of the grinding tool 1 of FIG. 1 taken along the line I-I.

[0101] FIG. 3 is a front view of one embodiment of the grinding machine according to the invention.

[0102] FIG. 4 is a plan view illustrating the grinding machine of FIG. 3 that is given by sectioning the rotating shaft 13a taken along the II-II line.

[0103] FIG. 5 is an enlarged sectional view of the grinding tool 40 of FIG. 4 taken along the line III-III.

[0104] FIG. 6 is a plan view of other embodiment of the grinding tool of the invention.

[0105] FIG. 7 is an enlarged sectional view of the grinding tool 60 of FIG. 6 taken along the line IV-IV.

[0106] FIG. 8 is a plan view of other embodiment of the grinding tool of the invention.

[0107] FIG. 9 is an enlarged sectional view of the grinding tool 80 of FIG. 8 taken along the line V-V.

[0108] FIG. 10 is a plan view of other embodiment of the grinding tool of the invention.

[0109] FIG. 11 is an enlarged sectional view of the grinding tool 100 of FIG. 10 taken along the line VI-VI.

[0110] FIG. 12 is a plan view of other embodiment of the grinding tool of the invention.

[0111] FIG. 13 is an enlarged sectional view of the grinding tool 120 of FIG. 12 taken along the line VII-VII.

[0112] FIG. 14 is a partly broken view of other embodiment of the grinding tool of the invention.

[0113] FIG. 15 is an enlarged sectional view of the grinding tool 140 of FIG. 14 taken along the line VIII-VIII.

[0114] FIG. 16 is a schematic view of other embodiment of the grinding tool of the invention.

[0115] FIG. 17 is an enlarged sectional view of the grinding tool 160 of FIG. 16 taken along the line IX-IX.

[0116] The numerals mean the following:

1 grinding tool, 2 connecting plate, 3a connecting means, 3b connecting portion, 4 elastic body, 5 ultrasonic vibrator, 6 grind stone, 7 screw hole, 10 grinding machine, 11 object to be ground, 12 support table, 13 rotation-driving unit, 13a rotating shaft, 14 power source, 15 base, 16, 17 rotation driving apparatus, 16a rotating shaft, 18 grinding assisting liquid-supplying means, 18a pipe, 21, 21 pole, 23 feed screw, 23a screw axis, 23b nut, 24 bearing, 25 rotary transformer, 25a power supply unit, 25b power-receiving unit, 26a stator core, 26b rotor core, 27a stator coil, 27b rotor coil, 28a, 28b, 28c wiring, 31, 31a, 31b circular ultrasonic vibrator, 32 grind stone-holding member, 32a sleeve, 32b substrate disc, 32c grind stone-holding ring, 32d through hole, 33 circular grind stone, 34a position on which the circular ultrasonic vibrator is fixed, 34b position connecting the rotating shaft, 35a, 35b air space, 36 circular air space area, 36a, 36b circular air space region, 37a, 37b connecting area, 38a, 38b, 38c bolt, 40 grinding tool, 41 piezoelectric material, 42 electrode, 43a, 43b penetrating groove, 44a position on which the circular ultrasonic vibrator is fixed, 60 grinding tool, 62 grind stone-holding member, 66 circular air space area, 65a, 65b air space, 66a, 66b circular air space region, 67a, 67b connecting area, 73a circular upper groove, 73b circular lower groove, 80 grinding tool, 82 grind stone-holding member, 82b disc substrate, 85 pores (air space), 86 circular air space area, 83 circular porous material, 100 grinding tool, 102 grind stone-holding member, 105a, 105b air space, 106 circular air space area, 106a, 106b circular air space region, 107a, 107b connecting area, 113a, 113b penetrating hole, 115a, 115b rotary transformer, 116 cylinder member, 119a, 119b arrow indicating direction of the vibration of the circular grind stone 33, 120 grinding tool, 122 grind stone-holding member, 122a disc member, 122b cylinder member, 125a, 125b air space, 126 circular air space area, 126a, 126b circular air space region, 127a, 127b connecting area, 133a, 133b penetrating groove, 140 grinding tool, 142 grind stone-holding member, 142a disc member, 142b cylinder member, 145a, 145b air space, 146 circular air space area, 146a, 146b circular air space region, 147a, 147b connecting area, 153a circular outer groove, 153b circular inner groove, 160 grinding tool, 162 grind stone-holding member, 162a, disc member, 162b cylinder member, 165 pores (air space), 166 circular air space area, 173 circular porous material

Claims

1. A grinding machine comprising a support table on which an object to be ground is supported, a rotating shaft vertically arranged above the support table, and a grinding tool connected to a lower end of the rotating shaft in parallel with the support table, the grinding tool comprising a grind stone-holding member on which a circular ultrasonic vibrator electrically connectable to an electric source is fixed and a circular grind stone attached to a lower end of a periphery of the grind stone-holding member, in which the grind stone-holding member of the grinding tool has a continuous or discontinuous circular air space area between a position of the circular ultrasonic vibrator and a position at which the grind stone-holding member is connected to the rotating shaft, the continuous or discontinuous circular air space area comprising multiple circular air space regions which comprise circularly formed or arranged continuous or discontinuous air spaces, whereby the circular air space area keeps an ultrasonic wave generated from the circular ultrasonic vibrator from linearly propagating to an area on an opposite side where the rotating shaft is connected.

2. The grinding machine of claim 1, in which the circular air space area comprises plural inner penetrating grooves intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating grooves intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer penetrating grooves and each of the outer connecting areas being arranged to face each of the inner penetrating grooves.

3. The grinding machine of claim 1, in which the circular air space area comprises plural inner penetrating holes intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating holes intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer through holes and each of the outer connecting areas being arranged to face each of the inner through holes.

4. The grinding machine of claim 1, in which the circular air space area comprises s circular upper unpenetrating groove which extends downwardly from an upper surface of the grind stone-holding member and a circular lower unpenetrating groove which extends upwardly from a lower surface of the grind stone-holding member, a total of a depth of the upper groove and a depth of the lower groove being larger than thickness of the grind stone-holding member.

5. The grinding machine of claim 1, in which the circular air space area comprises circular porous material arranged in the grind stone-holding member on an inner side of the circular ultrasonic vibrator.

6. The grinding machine of claim 1, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises upper plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member and lower plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member, each of the upper connecting areas being arranged to face each of the lower penetrating grooves and each of the lower connecting areas being arranged to face each of the upper penetrating grooves.

7. The grinding machine of claim 1, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular outer unpenetrating grooves which extend inwardly from an outer surface of the cylinder member and circular inner unpenetrating grooves which extend outwardly from an inner surface of the cylinder member, a total of a depth of the outer groove and a depth of the inner groove being larger than thickness of the cylinder member.

8. The grinding machine of claim 1, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular porous material arranged in the cylinder member on an upper side of the circular ultrasonic vibrator.

9. The grinding machine of claim 1, in which the support table rotates.

10. A grinding tool comprising a grind stone-holding member on which a circular ultrasonic vibrator electrically connectable to an electric source is fixed, said grind stone-holing member having a center portion to be connected to a rotating shaft, and a circular grind stone attached to a lower end of a periphery of the grind stone-holding member, in which the grind stone-holding member of the grinding tool has a continuous or discontinuous circular air space area between a position of the circular ultrasonic vibrator and a position at which the grind stone-holding member is connected to the rotating shaft, the continuous or discontinuous circular air space area comprising multiple circular air space regions which comprise circularly formed or arranged continuous or discontinuous air spaces, whereby the circular air space area keeps an ultrasonic wave generated from the circular ultrasonic vibrator from linearly propagating to an area on an opposite side where the rotating shaft is connected.

11. The grinding tool of claim 10, in which the circular air space area comprises plural inner penetrating grooves intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating grooves intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer penetrating grooves and each of the outer connecting areas being arranged to face each of the inner penetrating grooves.

12. The grinding tool of claim 10, in which the circular air space area comprises plural inner penetrating holes intermittently formed in the grind stone-holding member via connecting areas and plural outer penetrating holes intermittently formed in the grind stone-holding member via connecting areas, each of the inner connecting areas being arranged to face each of the outer through holes and each of the outer connecting areas being arranged to face each of the inner through holes.

13. The grinding tool of claim 10, in which the circular air space area comprises circular upper unpenetrating grooves which extend downwardly from an upper surface of the grind stone-holding member and circular lower unpenetrating grooves which extend upwardly from a lower surface of the grind stone-holding member, a total of a depth of the upper groove and a depth of the lower groove being larger than thickness of the grind stone-holding member.

14. The grinding tool of claim 10, in which the circular air space area comprises circular porous material arranged on an inner side of the circular ultrasonic vibrator.

15. The grinding tool of claim 10, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises upper plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member and lower plural penetrating grooves intermittently formed via connecting areas formed in the cylinder member, each of the upper connecting areas being arranged to face each of the lower penetrating grooves and each of the lower connecting areas being arranged to face each of the upper penetrating grooves.

16. The grinding tool of claim 10, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular outer unpenetrating grooves which extend inwardly from an outer surface of the cylinder member and circular inner unpenetrating grooves which extend outwardly from an inner surface of the cylinder member, a total of a depth of the outer groove and a depth of the inner groove being larger than thickness of the cylinder member.

17. The grinding tool of claim 10, in which the grind stone-holding member comprises a disc substrate and a cylinder member downwardly extended from a periphery of the disc substrate, and the circular air space area comprises circular porous material arranged in the cylinder member on an upper side of the circular ultrasonic vibrator.