Indexing device

Abstract

To provide configuration that can reliably prevent of immersion of coolant liquid into a frame in an indexing device which includes a first gear attached to an output shaft of a drive motor, a second gear attached to a drive shaft for driving a drive object, and an intermediate gear which transmits rotation of the first gear to the second gear and is supported rotatably with respect to the intermediate shaft fixed to the frame, and comprises a drive transmission mechanism in which the intermediate shaft is inserted into a storage hole for the frame.SOLUTION: In an indexing device, an intermediate shaft has a bottomed hole-shaped accommodation recess and a plurality of open holes, a fixation mechanism for fixing the intermediate shaft to a frame includes: a pressing member having a tapered surface and an insertion hole; a steel ball located in each open hole; and a screw member which is inserted into the insertion hole and screwed onto the intermediate shaft. In a state that the pressing member is accommodated in the accommodation recess and the steel ball contacts the tapered surface and a storage hole, a gap exists between the pressing member and a bottom part of the accommodation recess.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an indexing device that uses a drive motor as a drive source to index the angular position of a driven object, and that includes a first gear attached to the output shaft of the drive motor, a second gear attached to a drive shaft that drives the driven object, and an intermediate gear that transmits the rotation of the first gear to the second gear and is rotatably supported on an intermediate shaft fixed to a frame, and the indexing device is equipped with a drive transmission mechanism in which the intermediate shaft is inserted at its end into an accommodation hole formed in the frame. [Background technology]

[0002] An example of an indexing device used in a machine tool is a rotary indexing device that includes a spindle with a table on one end of which a workpiece is placed, and a drive motor as a drive source for rotating the spindle, and that is configured to rotate the spindle with the drive motor to index the angular position of the table, which is the object to be driven. The rotary indexing device also includes a drive transmission mechanism within its frame for transmitting the drive of the drive motor to the spindle. The drive transmission mechanism also includes a drive shaft for rotating the spindle (table), as well as a gear (first gear) attached to the output shaft of the drive motor and a gear (second gear) attached to the drive shaft. Some such drive transmission mechanisms also include a gear (intermediate gear) for transmitting the rotation of the first gear to the second gear. Patent Document 1 discloses an example of a rotary indexing device that includes such an intermediate gear.

[0003] The device of Patent Document 1 is a rotary indexing device in which the drive shaft in the drive transmission mechanism is a worm shaft. That is, the drive transmission mechanism in the rotary indexing device of Patent Document 1 (hereinafter referred to as the "conventional device") includes a so-called worm gear mechanism consisting of a worm wheel attached to the main shaft and a worm shaft including a worm meshing with the worm wheel. In the drive transmission mechanism, the intermediate gear is supported at its end by an intermediate shaft that is fitted into a shaft hole (accommodation hole) in the frame. The intermediate shaft is fixed to the frame so as not to rotate, and the intermediate gear is supported rotatably on the intermediate shaft.

[0004] In conventional devices, a locking mechanism using a setscrew and steel balls is used as a mechanism (fixing mechanism) for fixing the intermediate shaft to the frame. More specifically, the intermediate shaft has a plurality of female screw holes (threaded holes) that open onto the end surface and extend in the axial direction at the end that is inserted into the receiving hole, and a through hole (pass-through hole) that penetrates from each female screw hole toward the outer circumferential surface. The setscrew is threaded into the female screw hole at the end of the intermediate shaft and is a so-called pointed setscrew with a tapered surface at the tip.

[0005] In the fixing mechanism, steel balls are placed in the through holes at the end of the intermediate shaft, and set screws are threaded into the female threaded holes, so that the steel balls are placed between the tapered surface of the set screws and the inner peripheral surface of the accommodation hole. Then, by tightening the set screws so as to displace the steel balls in the axial direction, a pressing force in the axial direction acts on the steel balls, and a radial force acts on the inner peripheral surface of the accommodation hole via the steel balls, fixing the intermediate shaft to the frame. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Jitsuzen Showa 63-067052 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in conventional devices that use the above-mentioned fixing mechanism, there is a risk that the coolant used when machining the workpiece will seep into the frame, reducing the lubricating performance of the lubricating oil stored in the frame.

[0008] Specifically, when machine tools perform machining such as cutting and grinding, the machining is performed while a large amount of coolant is sprayed onto the contact area between the tool and the workpiece, and therefore a large amount of coolant is also sprayed onto the rotary indexing device on which the workpiece is placed during the machining process.

[0009] In conventional devices employing the above-described fixing mechanism, the end face of the intermediate shaft is exposed to the outside, and therefore the openings of the female threaded holes formed at the end of the intermediate shaft are also exposed to the outside. Then, a set screw is threaded into each female threaded hole, closing the female threaded hole. However, because the female threaded holes and the set screws are threadedly engaged, a small gap exists between them. Furthermore, in such a configuration, it is not possible to provide a sealing member between them.

[0010] Therefore, if coolant gets on the rotation indexing device as described above and reaches the openings of the female screw holes exposed to the outside in the intermediate shaft as described above, the coolant may pass through the gap between the female screw hole and the set screw and seep into the frame via the through hole communicating with the female screw hole.In that case, the coolant will mix with the lubricating oil stored in the frame to lubricate the drive transmission mechanism, causing a problem of reduced lubricating performance of the lubricating oil.

[0011] In order to prevent the coolant from seeping in through the gap between the female screw hole and the set screw, it is possible to apply a liquid sealant to the male thread portion of the set screw, but because the sealant is applied manually by an operator, uneven application may occur depending on the operator, and this approach lacks reliability in preventing the coolant from seeping in.

[0012] In view of the above circumstances, an object of the present invention is to provide an indexing device having a configuration that can more reliably prevent coolant from entering the frame. [Means for solving the problem]

[0013] The present invention is based on an indexing device that uses a drive motor as a drive source to index the angular position of a driven object, and includes a first gear attached to the output shaft of the drive motor, a second gear attached to the drive shaft that drives the driven object, and an intermediate gear for transmitting the rotation of the first gear to the second gear, the intermediate gear being rotatably supported on an intermediate shaft fixed to a frame, and the indexing device is equipped with a drive transmission mechanism in which the intermediate shaft is inserted at its end into an accommodation hole formed in the frame.

[0014] The present invention provides an indexing device based on the above-described premise, wherein the intermediate shaft has a bottomed hole-shaped accommodating recess formed at an end thereof, the accommodating recess opening to the end face and having a center aligned with the center of the outer periphery of the end face as viewed in the axial direction, and a plurality of through holes radially penetrating a peripheral wall around the accommodating recess. The indexing device of the present invention is characterized in that the fixing mechanism for fixing the intermediate shaft to the frame includes a cylindrical pressing member having a tapered surface on its peripheral surface and an insertion hole penetrating the axial direction at a central position, the pressing member being arranged so that the tapered surface faces a bottom surface of the accommodating recess and at least a portion of the tapered surface is positioned within the accommodating recess, steel balls disposed in each through hole, the steel balls having a diameter larger than the thickness of the peripheral wall, and a screw member inserted through the insertion hole of the pressing member and screwed into a female threaded hole opening at the bottom surface, wherein a gap exists between the pressing member and the bottom surface when the pressing member is accommodated in the accommodating recess and the steel balls accommodated in each through hole abut against the tapered surface and the inner circumferential surface of the accommodating hole. [Effects of the Invention]

[0015] In the indexing device according to the present invention, in a fixing mechanism utilizing a tapered surface and a steel ball, a mechanism (displacement mechanism) that axially displaces a pressing member that abuts against the steel ball on the tapered surface to apply an axial pressing force to the steel ball is not a screw mechanism between the pressing member and the intermediate shaft as in conventional devices, but uses a screw member that is inserted into the insertion hole formed in the pressing member as described above and is screwed into the female screw hole in the intermediate shaft. Specifically, the displacement mechanism is configured so that the screw member, which is displaced axially by tightening against the intermediate shaft, pushes the pressing member as it is displaced, thereby displacing the pressing member in the axial direction.

[0016] By configuring the displacement mechanism in this manner, the fixing mechanism can be configured so that the outer peripheral surface of the pressing member abuts against the surrounding portion (member) over the entire circumference within the housing hole of the frame. With the fixing mechanism configured in this manner, it becomes possible to arrange a sealing member such as an O-ring between the outer peripheral surface of the pressing member and the surrounding portion. Therefore, with the indexing device according to the present invention having the fixing mechanism (displacement mechanism) configured as described above, by appropriately arranging the sealing member in this manner, it is possible to prevent coolant from entering the frame as much as possible, and to prevent a decrease in the lubricating performance of the lubricating oil. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing an overall view of one embodiment of an indexing device according to the present invention; [Figure 2] FIG. 2 is a cross-sectional front view taken along line XX in FIG. [Figure 3] FIG. 3 is a partial cross-sectional front view showing the main part in FIG. 2. [Figure 4] FIG. 4 is a partial cross-sectional front view showing the main part in FIG. 3. [Figure 5] FIG. 10 is a partially sectional front view showing a main part of another embodiment of an indexing device according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0018] An embodiment (example) of an indexing device to which the present invention is applied will be described below with reference to Figures 1 to 5. In this example, the indexing device is a so-called rotary table device that includes a table on which a workpiece is placed and is configured to index the angular position of the table.

[0019] 1 is a diagram showing a schematic view of the exterior of a rotary table device 1. The rotary table device 1 comprises, as its components, a frame 10 that is placed on an installation surface (not shown) of a machine tool, and a table 3 on which a workpiece is placed. In the example shown, the rotary table device 1 is a so-called vertically-mounted rotary table device that is installed so that the surface of the table 3 on which the workpiece is placed is perpendicular to the installation surface. The rotary table device 1 is configured to use a drive motor as a drive source, and to rotate the table 3, which is the object to be driven, by the drive motor to determine its angular position.

[0020] In the rotary table device 1, as shown in Figure 2, the frame 10 is mainly composed of a main frame section 11 that occupies the majority of the frame. The rotary table device 1 also has a main shaft 2 to which a table 3 is attached at one end. The main shaft 2 is rotatably supported by the frame 10 (main frame section 11) via bearings (not shown) in an accommodation space formed within the main frame section 11 of the frame 10. The table 3 is attached to the main shaft 2 in such a way that the mounting surface is exposed to a surface of the main frame section 11 that is perpendicular to both side surfaces.

[0021] The main frame portion 11 of the frame 10 has a worm shaft hole 11a that accommodates a worm shaft of a drive transmission mechanism (described later). The worm shaft hole 11a is formed to penetrate the main frame portion 11, communicating with the accommodation space and opening on both side surfaces of the main frame portion 11.

[0022] The frame 10 also includes a sub-frame portion 12 to which a drive motor 4, which is a drive source, is attached. The sub-frame portion 12 has a generally rectangular parallelepiped appearance and has an internal space (internal space) 12a, which is mainly made up of four peripheral walls, a peripheral wall portion 12b, and a plate-like lid portion 12c that is combined with the peripheral wall portion 12b to close the upper opening of the peripheral wall portion 12b.

[0023] The drive motor 4 is attached to the outer surface of one of the peripheral walls (mounting wall) of the peripheral wall portion 12b of the sub-frame portion 12, with the output shaft 4a facing the sub-frame portion 12. The mounting wall of the peripheral wall portion 12b has a through-hole formed therethrough to allow for the attachment of the drive motor 4. As a result, when the drive motor 4 is attached to the mounting wall of the peripheral wall portion 12b, the output shaft 4a passes through the mounting wall, and its end is located within the internal space 12a of the sub-frame portion 12.

[0024] The sub-frame portion 12 is attached to the top surface (the surface opposite to the surface installed on the machine tool) of the main frame portion 11 in such a manner that the outer surface of the peripheral wall parallel to the mounting wall in the width direction of the frame 10 (the penetration direction of the worm shaft hole 11a) is aligned with the position of one of the side surfaces of the main frame portion 11. The portion of the top surface of the main frame portion 11 to which the sub-frame portion 12 is attached is formed to protrude upward. The protruding portion (protruding portion) 11c of the main frame portion 11 has a space (communicating space) 11d therein that communicates with the worm shaft hole 11a, and is configured to have an opening on the top surface so that the communicating space 11d is open upward. Therefore, when the sub-frame portion 12 is attached to the main frame portion 11 (protruding portion 11c), the worm shaft hole 11a in the main frame portion 11 and the internal space 12a in the sub-frame portion 12 are in communication with each other via the communicating space 11d in the protruding portion 11c.

[0025] The rotary table device 1 also includes a drive transmission mechanism 30 for transmitting the drive of the drive motor 4 to the main shaft 2. The drive transmission mechanism 30 includes a worm gear mechanism 20 consisting of a worm wheel 21 attached to the main shaft 2 and a worm shaft 22 meshing with the worm wheel 21.

[0026] In the worm gear mechanism 20, the worm wheel 21 is attached in the accommodation space in the frame 10 (main frame portion 11) at a position overlapping with the worm shaft hole 11a in the axial direction of the main shaft 2 so as to be non-rotatable relative to the main shaft 2. The worm shaft 22 includes a worm 22a that meshes with the worm wheel 21. The worm shaft 22 is supported in the worm shaft hole 11a in the main frame portion 11 by bearings 23 and 24 on both sides of the worm 22a so as to be rotatable relative to the main frame portion 11 (worm shaft hole 11a). The worm shaft 22 meshes with the worm wheel 21 at its worm 22a.

[0027] The drive transmission mechanism 30 also includes a gear train 31 made up of a combination of multiple gears, and is configured to connect the worm shaft 22 to the output shaft 4a of the drive motor 4 via the gear train 31. The gear train 31 includes a first gear 32 attached to the end of the output shaft 4a of the drive motor 4, and a second gear 33 attached to the shaft portion 22b of the worm shaft 22 on one end side (the side closer to the one side than the bearing 23) facing the worm 22a.

[0028] Furthermore, the gear train 31 includes an intermediate gear 34 for transmitting rotation of the first gear 32 to the second gear 33. The intermediate gear 34 is configured to connect the first gear 32 and the second gear 33. In this embodiment, the intermediate gear 34 is a so-called two-stage gear formed by combining two gears with different numbers of teeth. One of the two gears of the intermediate gear 34 is connected to the first gear 32, and the other is connected to the second gear 33. The intermediate gear 34 is supported by an intermediate shaft 35 provided in the communication space 11d and spanning both side walls 11c1 and 11c2 of the protruding portion 11c of the main frame portion 11.

[0029] The intermediate shaft 35 supporting the intermediate gear 34 has a through-hole 11b formed as an accommodation hole in the outer side wall 11c1 (the side of one of the sides of the main frame 11) of the side walls 11c1, 11c2, of the protruding portion 11c of the main frame 11, on which the intermediate shaft 35 is installed. This allows the intermediate shaft 35 to be inserted into the protruding portion 11c from the accommodation hole 11b side. The inner diameter of the accommodation hole 11b is approximately the same as the outer diameter of one end portion 35a of the intermediate shaft 35. The one end portion 35a of the intermediate shaft 35 is inserted into the accommodation hole 11b and supported by the outer side wall 11c1 of the protruding portion 11c.

[0030] Furthermore, a circular groove (circular groove) opening to the inner circumferential surface is formed in the inner sidewall 11c2 of the protrusion 11c (the sidewall facing the outer sidewall 11c1). The circular groove is formed so that its center coincides with the center of the accommodating hole 11b when viewed in the width direction, and its inner diameter is approximately the same as the inner diameter of the accommodating hole 11b. The other end of the intermediate shaft 35 is supported by the inner sidewall 11c2 of the protrusion 11c, being inserted into the circular groove. The intermediate shaft 35 is formed such that its one end 35a, which is inserted into the accommodating hole 11b, has a larger outer diameter than the remaining portion. That is, the outer diameter of the one end 35a of the intermediate shaft 35 is larger than the outer diameter of the other end. A bushing 36 is fitted into the circular groove, and the other end of the intermediate shaft 35 is supported by being fitted into the bushing 36.

[0031] In addition, in the state where the intermediate shaft 35 is supported in this manner, it is made non-rotatable with respect to the protruding portion 11c by a fixing mechanism described later. The intermediate gear 34 is rotatably supported on the intermediate shaft 35 via a bearing.

[0032] In the rotary table device 1 configured as described above, the fixing mechanism for fixing the intermediate shaft 35 to the frame 10 according to the present invention includes a pressing member having a tapered surface and accommodated in a recessed accommodating member formed in one end 35a of the intermediate shaft 35; a screw member inserted into an insertion hole of the pressing member and screwed into the female threaded hole of the intermediate shaft 35; and a steel ball disposed in a through hole formed in the intermediate shaft 35 and interposed between the tapered surface of the pressing member and the inner circumferential surface of the accommodating hole 11b. In this embodiment, the entire tapered surface of the pressing member is positioned within the recessed accommodating member, and the pressing member slides along the inner circumferential surface of the recessed accommodating member. The configuration of the rotary table device 1 including such a fixing mechanism will be described in detail with reference to FIGS. 3 and 4.

[0033] First, regarding the intermediate shaft 35, an accommodating recess 35c, which is a recess that opens into an end face on one end side, is formed in one end 35a of the intermediate shaft 35. The accommodating recess 35c is circular when viewed in the axial direction of the intermediate shaft 35, and its center is formed to coincide with the axis of the intermediate shaft 35 (the center of the outer periphery at the one end 35a). That is, the one end 35a of the intermediate shaft 35 is configured to have a space that is open to the outside within a peripheral wall 35d around the accommodating recess 35c. The intermediate shaft 35 is also formed with three through holes 35e (only one visible in the cross section is shown in the drawing) that radially penetrate the peripheral wall 35d around the accommodating recess 35c. The three through holes 35e are formed at equal intervals in the circumferential direction of the peripheral wall 35d.

[0034] Furthermore, with regard to the components of the fixing mechanism 40, the pressing member 42 is primarily a member formed in a cylindrical shape. However, one end side of the circumferential surface of the pressing member 42 is formed to have a tapered surface 42a1. In this manner, the pressing member 42 is made up of a tapered portion 42a, which is the portion of the circumferential surface on one end side formed as the tapered surface 42a1, and a cylindrical portion 42b, which is the portion on the other end side of the tapered portion 42a. Furthermore, the outer diameter of the cylindrical portion 42b is approximately the same as the inner diameter of the installation recess 35c in the intermediate shaft 35.

[0035] In this embodiment, the pressing member 42 is formed so that its dimension in the axial direction is approximately the same as the depth dimension of the accommodating recess 35c in the intermediate shaft 35. Furthermore, the pressing member 42 is configured so that the dimension of the tapered portion 42a and the dimension of the cylindrical portion 42b in the axial direction are approximately the same, that is, one end side from approximately the middle position is the tapered portion 42a, and the other end side is the cylindrical portion 42b.

[0036] Furthermore, the pressing member 42 is formed with an insertion hole 42c that penetrates the pressing member 42 in the axial direction. The insertion hole 42c is formed so that its center coincides with the axis of the pressing member 42 (cylindrical portion 42b) when viewed in the axial direction of the pressing member 42. However, the insertion hole 42c is formed so that its inner diameter changes at approximately the middle position in the axial direction of the pressing member 42, with the inner diameter at one end side (the tapered portion 42a side) being smaller than the inner diameter at the other end side (the cylindrical portion 42b side). In other words, the insertion hole 42c is formed so as to have a step therein that includes an end face 42d facing the other end side.

[0037] A spherical steel ball 41 is placed in each through hole 35e of the intermediate shaft 35. The installation recess 35c is formed such that the thickness of the peripheral wall 35d around the installation recess 35c, in which the through hole 35e is formed, is slightly smaller than the diameter of the steel ball 41. In other words, the diameter of the steel ball 41 is slightly larger than the thickness of the peripheral wall 35d. The through holes 35e are also formed such that the inner diameter thereof is approximately the same as the diameter of the steel ball 41. Therefore, when the steel ball 41 is placed (received) in each through hole 35e of the intermediate shaft 35, whose one end 35a is inserted into the installation hole 11b, the steel ball 41 abuts against the inner peripheral surfaces of the through holes 35e and the installation hole 11b, and a portion of the steel ball 41 protrudes inward from the inner peripheral surface of the peripheral wall 35d.

[0038] Furthermore, in the fixing mechanism 40, the pressing member 42 is accommodated in the accommodating recess 35c of the intermediate shaft 35 so that its axial direction coincides with the axial direction of the intermediate shaft 35 and its tapered portion 42a faces the bottom surface 35g of the accommodating recess 35c relative to the cylindrical portion 42b. As a result, the tapered surface 42a1 of the tapered portion 42a of the pressing member 42 a abuts against the steel ball 41 protruding from the inner circumferential surface of the peripheral wall 35d as described above. In other words, when the pressing member 42 is accommodated in the accommodating recess 35c in this manner, the steel ball 41 is sandwiched between the tapered surface 42a1 of the tapered portion 42a of the pressing member 42 and the inner circumferential surface of the accommodating hole 11b.

[0039] As described above, in this embodiment, the fixing mechanism 40 is configured so that, when the pressing member 42 is accommodated in the installation recess 35c, the pressing member 42 (cylindrical portion 42b) slides against the inner circumferential surface of the installation recess 35c. Therefore, with respect to the axial direction of the intermediate shaft 35, the position of the steel ball 41 at the one end 35a, i.e., the position where the through hole 35e in which the steel ball 41 is accommodated, is formed, is closer to (close to) the bottom surface 35g of the installation recess 35c. Also, as described above, the inner diameter of the through hole 35e is approximately the same as that of the steel ball 41, but the dimension in the axial direction of the intermediate shaft 35 of the peripheral wall 35d where the through hole 35e is formed (the depth dimension of the installation recess 35c) is approximately half the size of the one end 35a in terms of the dimension in the axial direction of the intermediate shaft 35.

[0040] Furthermore, the tapered portion 42a of the pressing member 42 is formed so that the angle of the tapered surface 42a1 is large enough to create a gap 44 between the end face 42e on one end side of the pressing member 42 and the bottom surface 35g of the accommodating recess 35c when the pressing member 42 is accommodated in the accommodating recess 35c as described above and the steel ball 41 is in contact with the tapered surface 42a1 and the inner circumferential surface of the accommodating hole 11b (accommodated state).

[0041] Specifically, when the diameter of the steel ball 41 is specified and the arrangement of the steel ball 41 within the installation recess 35c in the axial direction of the intermediate shaft 35 (the position of the through hole 35e) is specified, the position on the tapered surface 42a1 of the tapered portion 42a of the pressing member 42 of the contact point P between the steel ball 41 and the tapered surface 42a1 and the distance A from the contact point P to the bottom surface 35g of the installation recess 35c in the axial direction of the intermediate shaft 35 depends on the angle of the tapered surface 42a1, more specifically, the angle (taper angle) θ that the tapered surface 42a1 forms with respect to the axis of the pressing member 42 ( FIG. 4 ). Furthermore, the distance B from the contact point P to the end surface 42e on one end of the pressing member 42 depends on the position of the contact point P on the tapered surface 42a1. Incidentally, the larger the taper angle θ, the larger the distances A and B, and vice versa. However, when the taper angle θ is changed, the change in the distances A and B is greater than the change in the distance B.

[0042] Furthermore, with respect to the taper angle θ, when a pressing force is applied to the pressing member 42 in its axial direction, that pressing force also acts on the steel ball 41, and the action of the tapered surface 42a1 causes a radial force to act on the steel ball 41. Furthermore, the radial force increases as the taper angle θ decreases.

[0043] Therefore, the taper angle θ of the tapered portion 42a of the pressing member 42 is set to an angle such that a desired degree of radial force is applied to the steel ball 41 when a predetermined pressing force is applied to the pressing member 42. At the same time, the taper angle θ is set to an angle such that distance A is greater than distance B, that is, such that a gap 44 exists between the end face 42e on one end side of the pressing member 42 and the bottom surface 35g of the installation recess 35c when the tapered portion 42a is in contact with the steel ball 41.

[0044] Additionally, the fixing mechanism 40 is provided with a screw member 43 that applies a force to the pressing member 42 in the housed state to displace it toward the bottom surface 35g of the housing recess 35c. As described above, the screw member 43 is inserted into the insertion hole 42c of the pressing member 42 in the housed state and is threadedly inserted into the intermediate shaft 35. The intermediate shaft 35 is formed with a female threaded hole 35f that opens to the bottom surface 35g of the housing recess 35c and whose center coincides with the center of the insertion hole 42c of the pressing member 42 in the housed state when viewed in the axial direction of the intermediate shaft 35. The screw member 43 is threadedly inserted into the female threaded hole 35f.

[0045] The screw member 43 is a screw member such as a bolt having a head. Furthermore, the inner diameter of one end (the tapered portion 42a side) of the insertion hole 42c of the pressing member 42, through which the screw member 43 is inserted, is smaller than the size (outer diameter) of the head. Furthermore, the inner diameter of the other end (the cylindrical portion 42b side) of the insertion hole 42c is larger than the size of the head. Therefore, when the screw member 43 is inserted into the insertion hole 42c as described above, the head of the screw member 43 can abut against the end surface 42d of the insertion hole 42c of the pressing member 42. The screw member 43 is screwed into the female threaded hole 35f of the intermediate shaft 35, so that the head of the screw member 43 abuts against the end surface 42d. The female screw hole 35f is formed to have a depth dimension that allows the screw member 43 to be further screwed in after the head of the screw member 43 abuts against the end surface 42d.

[0046] Furthermore, a seal member 51 is interposed between the head of the screw member 43 and an end surface 42d of the pressing member 42. Furthermore, seal members 52, 53 such as O-rings are interposed between the outer peripheral surface of the cylindrical portion 42b of the pressing member 42 and the inner peripheral surface of the peripheral wall 35d of the intermediate shaft 35, and between the outer peripheral surface of the peripheral wall 35d and the inner peripheral surface of the accommodating hole 11b, respectively. However, the seal member 53 interposed between the outer peripheral surface of the peripheral wall 35d and the inner peripheral surface of the accommodating hole 11b is provided outside the position of the through hole 35e in the axial direction of the intermediate shaft 35 (on the opposite side to the bottom surface 35g of the accommodating recess 35c).

[0047] In the rotary table device 1 configured as described above, when the head of the screw member 43 is in contact with the end face 42d of the pressing member 42 in the accommodated state, if the screw member 43 is further rotated in the tightening direction, an action occurs in which the screw member 43 tries to displace toward the bottom surface 35g of the accommodation recess 35c of the intermediate shaft 35, and therefore the pressing member 42 in contact with the head of the screw member 43 receives a force (pressing force) from the head toward the bottom surface 35g of the accommodation recess 35c. As a result, the pressing force acts on the steel ball 41 that is interposed between the tapered surface 42a1 of the pressing member 42 and the inner circumferential surface of the accommodation hole 11b and is sandwiched between them.

[0048] When the pressing member 42 is in a state in which it applies the pressing force to the steel ball 41, a radial force toward the inner peripheral surface of the receiving hole 11b is applied to the steel ball 41 by the action of the tapered surface 42a1, and the steel ball 41 is pressed against the inner peripheral surface of the receiving hole 11b. As a result, a frictional force corresponding to the pressing force causes the steel ball 41 to be fixed to the inner peripheral surface of the receiving hole 11b in the main frame portion 11. As a result of the steel ball 41 being fixed to the inner peripheral surface of the receiving hole 11b in the main frame portion 11 (frame 10) in this way, the intermediate shaft 35 is fixed to the frame 10 via the pressing member 42 and the screw member 43.

[0049] In the fixing mechanism 40 for fixing the intermediate shaft 35 to the frame 10, as described above, the pressing member 42 is displaced (a force for displacing) toward the bottom surface 35g of the accommodation recess 35c, and the pressing force acts on the steel balls 41. The mechanism for displacing the pressing member 42 in the fixing mechanism 40 is not a conventional mechanism in which a screw action for displacement occurs directly on the pressing member by screwing the pressing member onto the intermediate shaft, but rather a mechanism in which the screw member 43 provided on the pressing member 42 is screwed into the intermediate shaft 35 as described above, and the screw action for displacement acts indirectly on the pressing member 42 via the screw member 43.

[0050] As a result, in the fixing mechanism 40, the outer peripheral surface of the cylindrical portion 42b of the pressing member 42 and the intermediate shaft 35 can be formed flat, and the inner peripheral surface of the accommodating recess 35c can be configured so that the pressing member 42 and the intermediate shaft 35 abut on each other at that surface. This configuration makes it possible to dispose a seal member such as an O-ring between the outer peripheral surface of the cylindrical portion 42b and the inner peripheral surface of the accommodating recess 35c. Therefore, in the fixing mechanism 40, the seal member 52 is disposed between the pressing member 42 and the intermediate shaft 35 as described above. Therefore, even if coolant that has splashed on the rotary table device 1 reaches the portion between the pressing member 42 and the intermediate shaft 35, the seal member 52 prevents the coolant from entering the frame 10 between the pressing member 42 and the intermediate shaft 35.

[0051] In the fixing mechanism 40, the screw member 43, which functions as described above, is inserted into the insertion hole 42c of the pressing member 42, with its head abutting against the end face 42d perpendicular to the insertion direction. Therefore, this configuration allows a seal member to be disposed between the screw member 43 and the pressing member 42. In the fixing mechanism 40, the seal member 51 is also disposed between the head of the screw member 43 and the end face 42d of the pressing member 42, as described above. This prevents coolant from penetrating into the frame 10 between the screw member 43 and the pressing member 42 by the seal member 51. The fixing mechanism 40 configured as described above appropriately disposes the seal member as described above to prevent coolant from penetrating into the frame 10, thereby minimizing the occurrence of problems such as a decrease in the lubricating performance of the lubricating oil stored in the frame 10.

[0052] The above describes one embodiment of an indexing device to which the present invention is applied (hereinafter referred to as "the embodiment"). However, the present invention is not limited to the embodiment, and can be implemented in other embodiments (variations) such as those described below.

[0053] (1) Regarding the fixing mechanism, the fixing mechanism 40 of the above embodiment is configured such that the outer diameter of the cylindrical portion 42b of the pressing member 42 is substantially the same as the inner diameter of the accommodating recess 35c of the intermediate shaft 35, and the pressing member 42 is inserted into the accommodating recess 35c at the cylindrical portion 42b, thereby allowing the pressing member 42 to slide in the axial direction relative to the intermediate shaft 35. However, in the present invention, the fixing mechanism is not limited to one configured such that the sliding of the pressing member is guided by the intermediate shaft as described above, and may also be one configured such that the sliding of the pressing member is guided by a portion of the frame side located outside the intermediate shaft (for example, the inner circumferential surface of the accommodating hole).

[0054] 5, the intermediate shaft 35 and the screw member 43 are configured the same as in the above-described embodiment, but the pressing member 62 is formed so that the outer diameter of its cylindrical portion 62b is approximately the same as the inner diameter of the accommodating hole 11b in the frame 10. The fixing mechanism is configured so that the pressing member 62 is provided with its tapered portion 62a inserted into the accommodating recess 35c of the intermediate shaft 35 and its cylindrical portion 62b fitted into the accommodating hole 11b in the frame 10. Therefore, in this configuration, the cylindrical portion 62b of the pressing member 62 is guided in sliding movement along the inner circumferential surface of the accommodating hole 11b formed in the frame 10 (main frame portion 11).

[0055] In this configuration, the tapered portion 62a is formed to have a dimension such that, when the pressing member 62 (tapered portion 62a) is in contact with the steel ball 41, the tapered portion 62a protrudes outward from the intermediate shaft 35 (accommodating recess 35c) in the axial direction of the pressing member 62. In other words, the dimension is such that a gap exists between the end face of one end side (the tapered portion 62a side) of the cylindrical portion 62 and the end face of one end side (the tip of the peripheral wall 35d) of the intermediate shaft 35. Therefore, in the fixing mechanism, the tapered surface 62a1 of the pressing member 62 is not entirely located within the accommodating recess 35c as in the above embodiment, but rather is partially located within the accommodating recess 35c. In the fixing mechanism configured in this manner, a sealing member such as an O-ring is provided between the outer peripheral surface of the cylindrical portion 62b of the pressing member 62 and the inner peripheral surface of the accommodating hole 11b to prevent coolant from entering the frame 10.

[0056] Furthermore, with regard to the pressing member, in the above embodiment, the pressing member 42 is made up only of the tapered portion 42a, which is the portion that comes into contact with the steel ball 41 at the tapered surface 42a1, and the cylindrical portion 42b, which is the portion that slides relative to the intermediate shaft 35. However, in the present invention, the pressing member is not limited to being made up only of the tapered portion and cylindrical portion, but may also be made up to have, in addition to the tapered portion and cylindrical portion, for example, a cylindrical portion that continues on the opposite side of the cylindrical portion relative to the tapered portion.

[0057] In the above embodiment, the insertion hole 42c of the pressing member 42 is formed as a hole whose inner diameter at one end is smaller than the head of the screw member 43 and whose inner diameter at the other end is larger than the head of the screw member 43, and the head of the screw member 43 is inserted into the portion at the other end. However, in the fixing mechanism of the present invention, the insertion hole in the pressing member is not limited to being formed so that the inner diameter at the other end is larger, and may be a hole whose inner diameter is uniform throughout and smaller than the head of the screw member. In this case, in the fixing mechanism, when the screw member is fastened to the intermediate shaft 35, the head of the screw member abuts against the end face at the other end of the pressing member (applying a pressing force to the end face at the other end).

[0058] Furthermore, with regard to the fixing mechanism, in the above embodiment, the fixing mechanism 40 has three through holes 35e in the intermediate shaft 35, and three steel balls 41 are disposed in each of the three through holes 35e. However, in the fixing mechanism of the present invention, the number of steel balls is not particularly limited as long as it is two or more. The number of through holes is also not limited to the same number as the number of steel balls, and it is sufficient as long as it is equal to or greater than the number of steel balls. In other words, it is not limited to disposing steel balls in all of the through holes. For example, n (n≧3) through holes may be formed, and steel balls may be disposed in appropriate through holes selected from a number less than n.

[0059] (2) Regarding the drive transmission mechanism, in the above-described embodiment, the drive transmission mechanism 30 is configured so that the intermediate gear 34 is a so-called two-stage gear formed by combining two gears. However, in the present invention, when it is not necessary to change the reduction ratio by using an intermediate gear, the drive transmission mechanism may be configured so that the intermediate gear is a so-called single-stage gear (idle gear) formed by one gear, rather than a two-stage gear as in the above-described embodiment.

[0060] In the above embodiment, the drive transmission mechanism 30 is configured to include only one set of an intermediate gear 34 and an intermediate shaft 35 supporting the intermediate gear 34. That is, the drive transmission mechanism 30 is configured so that the first gear 32 and the second gear 33 are directly connected via one intermediate gear 34. Note that among the indexing devices that are the premise of the present invention, there are also ones configured so that the first gear and the second gear referred to in the present invention are connected via two or more intermediate gears. The present invention is also applicable to such indexing devices (drive transmission mechanisms) that include two or more intermediate gears and intermediate shafts supporting the respective intermediate gears.

[0061] In the above embodiment, the intermediate shaft 35 supporting the intermediate gear is formed so that the outer diameter of one end 35a that is inserted into the receiving hole 11b is larger than the outer diameter of the other portion. However, in the indexing device that is the premise of the present invention, the intermediate shaft is not limited to being formed in this manner, and may be formed so that the outer diameter is uniform over the entirety.

[0062] In the above embodiment, the drive transmission mechanism 30 employs a so-called worm gear mechanism 20 including a worm wheel 21 attached to the main shaft 2 and a worm shaft 22 having a worm 22a meshing with the worm wheel 21. However, in the indexing device on which the present invention is based, the drive transmission mechanism is not limited to one employing such a worm gear mechanism. For example, the drive transmission mechanism may employ a roller gear cam mechanism including a roller gear with multiple rollers arranged in the circumferential direction and a roller cam shaft having a spiral cam groove meshing with the roller gear. Alternatively, the drive transmission mechanism may employ a so-called ball drive mechanism (ball reducer) in which the worm wheel and the worm shaft are indirectly engaged with each other via balls serving as engaging members.

[0063] (3) In the above-described examples of the indexing device to which the present invention is applied, the present invention is applied to a so-called rotary table device that includes a table on which a workpiece is placed and is configured to index the angular position of the table. However, the indexing device to which the present invention is applied is not limited to such a rotary table device, and may also be, for example, another indexing device such as a milling head (spindle head) that includes a main shaft spindle as a driven object supported by a support shaft corresponding to the main shaft and is configured to index the angular position of the main shaft spindle around the axis of the support shaft.

[0064] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0065] 1 Rotary table device (indexing device) 2 main shaft 3 tables 4 Drive motor 4a Output shaft 10 frames 11 Main frame section 11a Worm shaft hole 11b Through hole (receiving hole) 11c Protrusion 11c1 Outer side wall 11c2 Inner side wall 11d Communication space 12 Sub-frame section 12a Interior space 12b Peripheral wall part 12c Lid 20 Worm gear mechanism 21 Worm wheel 22 Worm shaft (drive shaft) 22a Warm 22b Shaft 23 Bearings 24 Bearings 30 Drive transmission mechanism 31 Gear train 32 First Gear 33 Second Gear 34 Intermediate gear 35 Intermediate shaft 35a One end 35c Recessed storage area 35d peripheral wall 35e through hole 35f female screw hole 35g bottom 36 Bush 40 Fixing mechanism 41 steel ball 42 Pressing member 42a Tapered section 42a1 tapered surface 42b Cylindrical part 42c Insertion hole 42d End surface facing the other end 42e End face on one end 43 Screw material 44 Gap 51 Sealing material 52 Sealing material 53 Sealing material 62 Pressing member 62a Tapered section 62a1 tapered surface 62b Cylindrical part

Claims

[Claim 1] An indexing device that uses a drive motor as a drive source to index the angular position of a driven object, the indexing device including: a first gear attached to an output shaft of the drive motor; a second gear attached to a drive shaft that drives the driven object; and an intermediate gear for transmitting rotation of the first gear to the second gear, the intermediate gear being rotatably supported on an intermediate shaft fixed to a frame, the intermediate gear having an end portion of the intermediate shaft being fitted into an accommodation hole formed in the frame, the intermediate shaft has an accommodating recess in the form of a bottomed hole formed at the end portion, the accommodating recess opening to the end face and having a center aligned with the center of an outer peripheral edge of the end face as viewed in the axial direction, and a plurality of through holes radially penetrating a peripheral wall around the accommodating recess, The fixing mechanism for fixing the intermediate shaft to the frame includes a cylindrical pressing member having a tapered surface on its peripheral surface and an insertion hole penetrating in the axial direction at a center position, the pressing member being arranged so that the tapered surface faces the bottom surface of the accommodating recess and at least a portion of the tapered surface is located within the accommodating recess; steel balls disposed in each of the through holes, the steel balls having a diameter larger than the thickness of the peripheral wall; and a screw member that is inserted into the insertion hole of the pressing member and screwed into a female screw hole that opens into the bottom surface, and is configured so that a gap exists between the pressing member and the bottom surface when the pressing member is accommodated in the accommodating recess and the steel balls accommodated in each of the through holes are in contact with the tapered surface and the inner peripheral surface of the accommodating hole. An indexing device characterized by:

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