JP2016129921A - Rotary table - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary table which stabilizes a vertical position of the table by using a simple structure without increasing costs of the table and increasing energy needed when the table is driven.SOLUTION: A rotary table 1 includes: a base 3 having a shaft member 9 which extends upward; and a table 5 which may rotate around an axis of the shaft member 9 of the base 3. The rotary table 1 is configured so that the table 5 is supported on the base 3 by a static pressure bearing structure that supplies a fluid to a fluid passage between the base 3 and the table 5. The static pressure bearing structure includes a thrust ball bearing 25 including an outer ring 45 fixed to the table 5 and supporting the table 5 in a vertical direction relative to the base 3. The rotary table 1 includes a bolt 41 and a fixing ring 31 which apply a downward pre-load to an inner ring 43 of the thrust ball bearing 25.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotary table, and more particularly, to a rotary table using a hydrostatic bearing.

  Conventionally, it is known to use a rotary table for rotating a workpiece in a machine tool such as a horizontal boring slicer or an NC lathe. A rotary table includes a rotatable table and a base fixed at a fixed position, and supports a table rotatably with respect to the base using a hydrostatic bearing. A rotary table using a hydrostatic bearing has a fluid pressure chamber between the table and the base, and a fluid film is interposed between the base and the table by supplying fluid under pressure to the fluid pressure chamber. Thus, the table and the base are configured not to contact each other directly (for example, Patent Document 1).

JP 2005-138216 A

  In the rotary table of the machine tool described in Patent Document 1, the workpiece on the table is rotated at a high speed by rotating the table on which the workpiece is placed on the base. When precise machining is performed on the workpiece on the table, it is necessary to stabilize the position of the workpiece. For this purpose, the machining table and the vertical position of the table are strictly set with respect to the base. It needs to be adjusted. However, even if the vertical position between the table and the base is adjusted before placing the work piece on the table, the vertical position of the table changes depending on the weight of the work piece when the work piece is placed on the table. In other cases, the load applied to the table by the workpiece when the workpiece is being processed changes, and the vertical position of the table relative to the base may change accordingly. And if the vertical position with respect to the base of a table changes, processing accuracy will fall. The same problem also occurs when the fluid pressure due to the fluid film interposed between the table and the base is insufficient. This problem becomes more prominent as the weight of the workpiece decreases.

  As a means for suppressing a change in the vertical position between the table and the base, there is known a method in which a force is applied in advance to the table in the base direction before the workpiece is placed on the table. By applying preload to the table, the static pressure rigidity (hardness of movement) of the table with respect to the base is improved, and even when the load applied to the table via the workpiece changes, the table and the base are perpendicular to each other. The position is difficult to change.

  As a method of applying a preload to the table, it is conceivable to increase the weight of the table. However, increasing the weight of the table is not preferable because the cost of the table increases and the energy required to rotate the table increases.

  As another method, a ring-shaped back plate may be provided above the table along the periphery of the table, and a fluid film may be interposed between the table and the back plate. In this case, the fluid pressure is applied to the table from below by the fluid film between the table and the base, and at the same time, the fluid pressure is also applied to the table from above by the fluid film between the table and the back plate. However, when the back plate is provided, it is necessary to provide a fluid passage between the back plate and the table. In this case, the number of parts for constituting the structure for applying the preload increases, which is not preferable.

  Therefore, the present invention has been made to solve such a problem, and does not increase the cost of the table, does not increase the energy required for driving the table, and uses a simple structure. An object of the present invention is to provide a rotary table capable of stabilizing the vertical position of the rotary table.

  In order to solve the above-described problems, the present invention includes a base having a shaft member extending upward, and a table rotatable around the axis of the shaft member of the base, and a fluid passage between the base and the table. A rotary table that supports a table on a base by a hydrostatic bearing structure for supplying fluid, wherein the hydrostatic bearing structure is a bearing in which one race is fixed to the table and the table is supported in a direction perpendicular to the base The table further includes a preload structure that applies a downward preload to the other race of the bearing.

  According to the present invention configured as described above, a preload can be applied to the table by a simple preload structure that applies a downward force to the other race of the bearing.

  In this case, the bearing is a thrust bearing in which one race is fixed to the table, and the hydrostatic bearing structure further includes a radial bearing interposed between the table and the shaft member of the base.

  In this case, the bearing may be a tapered roller bearing in which one race is fixed to the table and the other race is fixed to the shaft member of the base.

  Preferably, in the present invention, the table has a receiving portion for receiving the shaft member of the base in the vicinity of the rotation center of the lower surface thereof, and one race of the bearing is fixed to the peripheral wall of the receiving portion. The upper surface of the table is inclined so as to rise toward the center of rotation.

  According to the present invention configured as described above, even if a downward preload is applied to the peripheral wall of the receiving portion provided near the rotation center of the table and the vicinity of the rotation center on the upper surface of the table is pulled downward, By subjecting the top surface of the table to a tilting process, the top surface of the table can be leveled when preload is applied.

  As described above, according to the present invention, it is possible to stabilize the vertical position of the table using a simple structure without increasing the cost of the table, without increasing the energy required for driving the table. .

It is a sectional side view of the turntable by 1st embodiment of this invention. It is a top view of the base of the turntable by 1st embodiment of this invention. It is a sectional side view of the turntable by 2nd embodiment of this invention. It is a sectional side view of the turntable by the modification of embodiment of this invention.

  Hereinafter, a rotary table according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a turntable according to an embodiment of the present invention, and FIG. 2 is a top view of a base of the turntable.

  As shown in FIG. 1, the rotary table 1 includes a base 3 and a table 5, and is configured to support the table 5 on the base 3 by a hydrostatic bearing structure.

  The base 3 has a substantially disk shape, and an annular support portion 7 is formed on the upper surface of the base 3 along the periphery thereof. A substantially cylindrical shaft member 9 extending upward from the upper surface of the base 3 is formed near the center of the base 3. The annular support portion 7 is formed by increasing the thickness along the periphery of the upper surface of the base 3. A fluid pressure chamber 13 defined by the side wall 11 is formed on the annular support portion 7. The fluid pressure chamber 13 has a rectangular plane defined by, for example, four side walls 11, and the bottom of the fluid pressure chamber 13 guides oil supplied from an oil supply source (not shown) to the fluid pressure chamber 13. The outlet of the conduit 15 is formed. As shown in FIG. 2, the base 3 of the turntable 1 according to the present embodiment is provided with four rectangular parallelepiped fluid pressure chambers 13 at equal angular intervals.

  The table 5 has a substantially disk shape having the same diameter as the base 3 and is supported so as to be rotatable around the shaft member 9 of the base 3 by a hydrostatic bearing structure described later. The upper surface of the table 5 is formed horizontally so that the workpiece can be arranged. The vicinity of the center of the table 5 is hollowed out in a cylindrical shape, and this hollowed out portion constitutes a receiving portion 17 for receiving the shaft member 9 of the base 3. The receiving portion 17 is surrounded by a peripheral wall 19 extending vertically, and the center thereof is formed at a position overlapping the rotation axis of the table 5, that is, the axis of the shaft member 9. Further, a lid 21 is placed on the upper portion of the receiving portion 17, and a uniform horizontal plane is formed by the upper surface of the lid 21 and the upper surface of the table 5. And a workpiece is arrange | positioned on a horizontal surface.

  Further, an annular support portion 23 is provided on the lower surface of the table 5 so as to face the annular support portion 7 of the base 3 along the peripheral edge thereof. The annular support portion 23 of the table 5 is formed by increasing the thickness along the peripheral edge of the lower surface of the table 5, and the lower surface of the annular support portion 23 has substantially the same width as the annular support portion 7 of the base 3. An annular plane is formed. Further, the annular support portion 23 of the table 5 has a minute gap between the upper end of the side wall 11 of the fluid pressure chamber 13 when the table 5 is supported on the base 3 by a hydrostatic bearing structure described later. It is positioned.

  In addition, the rotary table 1 includes two bearings for supporting the table 5 on the base 3. Specifically, the rotary table 1 includes a thrust ball bearing 25 for receiving axial thrust, and a cylindrical roller bearing 27 for receiving radial radial. In the rotary table 1, a hydrostatic bearing structure is formed by a mechanism for supplying oil between the base 5 and the table 5 such as the fluid pressure chamber 13 and the conduit 15 for guiding the oil therethrough.

  The thrust ball bearing 25 is disposed between the shaft member 9 of the base 3 and the peripheral wall 19 of the receiving portion 17 of the table 5 so that the rotation axis of the thrust ball bearing 25 overlaps the axis of the shaft member 9. The upper race 29 of the thrust ball bearing 25 is fixed to the shaft member 9 via an annular fixing ring 31 and a spacer 33. The lower race 35 of the thrust ball bearing 25 is fixed on an annular pedestal 37 that is integrally formed with the peripheral wall 19 of the receiving portion 17 and extends radially inward from the peripheral wall 19. A step 39 extending in the circumferential direction is formed on the outer periphery of the shaft member 9, and the spacer 33 is disposed on the upper surface of the step 39. The fixing ring 31 is disposed on the spacer 33, and the fixing ring 31 and the spacer 33 are bolted to the step 39 of the shaft member 9. The rotary table 1 is configured such that the position of the fixing ring 31 is adjusted by adjusting the thickness of the spacer 33, thereby adjusting the strength with which the fixing ring 31 pushes the thrust ball bearing 25 downward. Yes.

  The cylindrical roller bearing 27 is disposed below the thrust ball bearing 25, the inner peripheral surface of the inner ring 43 is fixed to the outer peripheral surface of the shaft member 9, and the outer peripheral surface of the outer ring 45 is the table 5. Is fixed to the peripheral surface of the receiving portion 17. An inner ring fixing portion 47 is formed on the outer peripheral surface of the shaft member 9 to sandwich the inner ring 43 of the cylindrical roller bearing 27 from above and below to fix the position in the vertical direction. Similarly, an outer ring fixing portion 49 for holding the outer ring 45 of the cylindrical roller bearing 27 in the vertical direction and fixing the vertical position thereof is formed on the peripheral surface of the receiving portion 17 of the table 5. In addition, as an upper member of the outer ring fixing portion 49, an annular pedestal 37 to which the lower race 35 of the thrust ball bearing 25 described above is fixed may be used, or a member different from the annular pedestal 37 may be used. Also good.

  Next, the operation of the rotary table 1 will be described in detail.

  As described above, the rotary table 1 can adjust the force by which the fixing ring 31 pushes the upper race 29 of the thrust ball bearing 25 downward by adjusting the thickness of the spacer 33. A downward force can be applied from the base 3 to the table 5 through the thrust ball bearing 25 that receives the force. More specifically, when a relatively thin spacer 33 is used, the fixing ring 31 is pushed downward together with the bolt 41 when the fixing ring 31 is tightened. When the fixing ring 31 is pushed downward, the upper race 29 of the thrust ball bearing 25 disposed on the lower side of the fixing ring 31 is pushed downward by the fixing ring 31. When the upper race 29 of the thrust ball bearing 25 is pushed downward, the force is transmitted to the thrust ball bearing 25 and the pedestal 37 that supports the thrust ball bearing 25 from the lower side. When the pedestal 37 is pushed downward, the table 5 on which the pedestal 37 is integrally formed is also pushed downward. Thereby, a downward force can be applied to the table 5 by the base 3.

  Then, by applying a downward force to the table 5 by the base 3, the gap between the base 3 and the table 5 can be reduced. Thereby, when oil is supplied from the conduit 15 to the fluid pressure chamber 13 and oil is supplied between the table 5 and the base 3, the oil passage through which the oil passes is made narrower than the conventional one. Can do. Thereby, when the oil film is formed between the table 5 and the base 3 and the table 5 is supported with respect to the base 3, the operating area of the table 5 in the vertical direction can be reduced. The table 5 can be stabilized in the vertical direction with respect to the base 3 by reducing the vertical operating area of the table 5.

  Next, the second embodiment of the present invention will be described in detail. FIG. 3 is a side sectional view of the turntable according to the second embodiment. In addition, since the turntable concerning 2nd embodiment has the structure similar to the turntable 1 concerning 1st embodiment, the same code | symbol is used about the same structure.

  The rotary table 101 according to the second embodiment has a conical roller bearing 103 instead of the thrust ball bearing 25 and the cylindrical roller bearing 27 as a hydrostatic bearing structure. In the conical roller bearing 103, the inner periphery of the inner ring 105 is in contact with the outer periphery of the shaft member 9, and the outer periphery of the outer ring 109 is fixed to the fixed portion 111 and the peripheral wall 19 of the receiving portion 17 of the table 5. The conical roller bearing 103 is disposed between the shaft member 9 and the table 5 so that the sharpened portion of the tapered roller faces downward so that downward force can be supported. Further, the rotary table 101 includes a nut 113 that is disposed on the upper side of the inner ring 105 of the conical roller bearing 103 and screwed to the shaft member 9, and a spacer 115 that is disposed between the nut 113 and the inner ring 105. The nut 113 is screwed into a thread cut in the vertical direction on the outer periphery of the shaft member 9. Also in the second embodiment, by adjusting the thickness of the spacer 115, the force for pushing the inner ring 105 downward can be adjusted.

  Similarly to the turntable 1 according to the first embodiment, the turntable 101 also adjusts the downward force on the inner ring 105 of the conical roller bearing 103 by adjusting the thickness of the spacer 115. Therefore, by increasing the thickness of the spacer 115, the downward force on the inner ring 105 is increased, thereby causing the downward force to act on the outer ring 109 fixed to the table 5, and applying the downward force to the table 5. It is configured to add. Also with such a configuration, the gap between the table 5 and the base 3 can be narrowed, whereby the table 5 can be stabilized in the vertical direction with respect to the base 3.

  Next, modifications of the first and second embodiments described above will be described in detail.

  FIG. 4 is a side sectional view of a turntable according to a modification. In FIG. 4, the bearing is omitted for simplification, but this modification is applicable to both the rotary table 1 according to the first embodiment and the rotary table 101 according to the second embodiment.

  As shown in FIG. 4, the top surface of the table 123 included in the rotary table 121 is inclined so that the thickness increases toward the center. Thereby, the upper surface of the table 123 has a shape that rises toward the center.

  As described in the first and second embodiments, the rotary table 121 is preliminarily pushed downward by the fixing ring 31 or the nut 113 via the bearings 25 and 103. That is, when a downward force is applied to the table 123, the vicinity of the center of the table 123 is deformed downward, and the flatness of the upper surface of the table 123 is impaired.

ここで、Ｐは、荷重、ｒは、テーブル１２３の中心からの距離、νは、ポアソン比、Ｄは、曲げ剛性を示し、中実であれば、Ｄは、数式２によって算出される。

Therefore, the upper surface of the table 123 can be kept flat by applying a tilting process to the upper surface of the table 123 even after a downward force is applied to the table 123. At this time, the shape of the upper surface of the table 123 by the tilting process is determined by, for example, calculating the deformation amount in advance using Equation 1 below.

Here, P is a load, r is a distance from the center of the table 123, ν is a Poisson's ratio, D is a bending rigidity, and D is calculated by Equation 2 if solid.

  In addition, this invention is not limited to the above-mentioned embodiment and its modification, Each structure of embodiment and modification can be suitably changed in the range which does not deviate from the meaning of this invention.

1, 101, 121 Rotary table 3 Base 5, 123 Table 25 Thrust ball bearing 27 Cylindrical roller bearing 29 Upper race 31 Fixing ring 35 Lower race 41 Bolt 103 Conical roller bearing 105 Inner ring 113 Nut

Claims (4)

A base having a shaft member extending upward;
A table rotatable around the axis of the shaft member of the base, and
A rotary table that supports the table on the base by a hydrostatic bearing structure that supplies fluid to a fluid passage between the base and the table;
The hydrostatic bearing structure includes a bearing in which one race is fixed to a table and supports the table in a vertical direction with respect to the base.
The rotary table further includes a preload structure that applies a downward preload to the other race of the bearing. The bearing is a thrust bearing in which one race is fixed to the table,
The rotary table according to claim 1, wherein the hydrostatic bearing structure further includes a radial bearing interposed between the table and a shaft member of the base.   The rotary table according to claim 1, wherein the bearing is a tapered roller bearing in which one race is fixed to the table and the other race is fixed to the shaft member of the base.   The table has a receiving portion for receiving the shaft member of the base in the vicinity of the rotation center of the lower surface thereof, and one race of the bearing is fixed to a peripheral wall of the receiving portion, The turntable according to any one of claims 1 to 3, wherein an upper surface of the plate is inclined so as to rise toward the center of rotation.

Images