Workpiece support mechanism and machine tool

Abstract

To provide a technology that is able to prevent deformation of a rotary table in a workpiece support mechanism.SOLUTION: A workpiece support mechanism includes: a base; a rotation shaft; a rotary table disposed on the base and configured to rotate about an axis in conjunction with the rotation shaft; a bearing configured to rotatably support the rotary table; a force generation mechanism configured to apply a vertically downward force to a pressure receiving portion; a displacement sensor configured to detect a displacement of an outer peripheral part of the table along a vertical direction; and a force adjustment unit configured to adjust a magnitude of the force generated by the force generation mechanism, in accordance with a detection result of the displacement sensor. The rotary table has a table central-part and a diameter larger than that of the base. The rotation shaft is engaged with the table central part so as to transmit a force applied to the pressure receiving portion of the base to the table central-part.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a technique for a workpiece supporting mechanism. [Background technology]

[0002] Conventionally, there has been known a workpiece support mechanism having a base, a rotary table provided on the base, and a hydrostatic bearing provided on the base for rotatably supporting the rotary table (Patent Document 1). The workpiece support mechanism supports a workpiece to be machined on the rotary table. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-238297 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a conventional technology, when a large workpiece is to be machined, a rotary table having a diameter larger than that of a base may be used to support the workpiece. In this case, the weight of the workpiece may easily cause deformation of the rotary table, with the outer periphery of the rotary table displacing downward and the center displacing upward. If the rotary table is deformed, problems such as a decrease in the machining accuracy of the workpiece may occur. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one embodiment of the present disclosure, there is provided a workpiece support mechanism, comprising: a base, a rotating shaft rotatable about an axis along a vertical direction, and a rotating table arranged on the base and rotating about the axis in conjunction with the rotating shaft, the rotating table supporting a workpiece, a bearing rotatably supporting the rotating table, a force generating mechanism that applies a vertically downward force to a pressure receiving portion of the base closer to a base center through which the rotating shaft is inserted than to an outer periphery of the base, a displacement sensor that detects a displacement along the vertical direction at a table outer periphery of the rotating table that is positioned radially outward from the base, and a force adjusting portion that adjusts the magnitude of the force generated by the force generating mechanism according to a detection result of the displacement sensor, the rotating table having a table center where an upper end of the rotating shaft is located and that includes a center in the radial direction, and a diameter larger than that of the base, and the rotating shaft is engaged with the table center so as to transmit the force applied to the pressure receiving portion of the base to the table center. According to this embodiment, by applying a vertically downward force to the pressure receiving part by the force generating mechanism, a vertically downward force can be applied to the center of the turntable via the rotation shaft, which suppresses (cancels) deformation of the turntable, which is caused by the load from the workpiece displacing the outer periphery of the table downward and the center of the table upward. (2) In the above embodiment, the force generating mechanism may apply the force to the pressure receiving portion by supplying a force pressurized fluid to the pressure receiving portion. According to this embodiment, the force can be easily applied to the pressure receiving portion by the force pressurized fluid. (3) In the above embodiment, a hydrostatic bearing member may be disposed radially between the base and the rotating shaft, the hydrostatic bearing member having the rotating shaft inserted therethrough, the hydrostatic bearing member including a shaft supply line for supplying a shaft pressurized fluid to a radial gap between the hydrostatic bearing member and the rotating shaft, and a force supply line for supplying the force pressurized fluid toward the pressure-receiving portion. According to this embodiment, by providing the force supply line in the hydrostatic bearing member, it is not necessary to provide another member for providing the force supply line, and therefore the number of parts can be reduced. (4) In the above embodiment, the hydrostatic bearing member may have an opposing surface formed directly above the pressure-receiving portion, opposing the pressure-receiving portion with a gap in the vertical direction, and a supply opening which is the downstream end of the force supply line may be formed in the opposing surface. According to this embodiment, by forming a supply opening in the opposing surface of the hydrostatic bearing member, a vertically downward force can be efficiently applied to the pressure-receiving portion by the force pressurized fluid flowing from the supply opening toward the pressure-receiving portion. (5) In the above embodiment, three or more of the supply openings may be formed at equal intervals in the circumferential direction. According to this embodiment, since three or more of the supply openings are formed at equal intervals in the circumferential direction, it is possible to reduce the possibility that the vertical downward force applied to the pressure-receiving portion will be non-uniform in the circumferential direction. (6) In the above embodiment, the force adjustment unit may set the force to be larger as the vertical downward displacement of the outer periphery of the table represented by the detection result of the displacement sensor becomes larger. According to this embodiment, the force applied to the pressure receiving unit is increased as the vertical downward displacement of the outer periphery of the table becomes larger, thereby making it possible to further displace the central part of the table vertically downward. This makes it possible to suppress deformation of the turntable regardless of the magnitude of the displacement of the outer periphery of the table. (7) In the above-described embodiment, the bearing may be a hydrostatic bearing. According to this embodiment, the rotary table can be rotatably supported by the hydrostatic bearing. (8) In the above aspect, the displacement sensor may be a non-contact sensor. According to this aspect, the non-contact displacement sensor can detect the displacement of the outer periphery of the table in the vertical direction. (9) According to another aspect of the present disclosure, there is provided a machine tool including a gripping mechanism configured to grip a tool for machining a workpiece, and any one of the workpiece support mechanisms described above. According to this embodiment, by applying a vertically downward force to the pressure receiving portion by the force generating mechanism, a vertically downward force can be applied to the table center of the rotary table via the rotation axis. This makes it possible to suppress (cancel) deformation of the rotary table, which would otherwise occur due to the load from the workpiece, such as the table outer periphery being displaced downward and the table center being displaced upward. This makes it possible to suppress deviation of the position of the workpiece from the target position, allowing the workpiece to be machined with high precision. The present disclosure may be realized in various forms other than the workpiece support mechanism and the machine tool, for example, in the form of a control method for the workpiece support mechanism, a manufacturing method for the machine tool, a computer program, and a recording medium on which the computer program is recorded. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a machine tool according to an embodiment as viewed from the front; [Diagram 2] FIG. 1 is a schematic diagram of a workpiece and a rotary table. [Diagram 3] FIG. 4 is a schematic diagram showing a bearing arrangement member of the base as viewed from directly above. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] Schematic diagram of region Rg5 in Figure 5. [Figure 7] 6A and 6B are diagrams for explaining a table adjustment process. [Figure 8] 13 is a flowchart of a table adjustment process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A. Embodiment: 1 is a schematic diagram of a machine tool 10 according to an embodiment, seen from the front. The machine tool 10 includes a workpiece support mechanism 50 that supports a workpiece 120, two gripping mechanisms 30, 40 that grip a processing tool for machining the workpiece, a machine body 20 that slidably supports the gripping mechanisms 30, 40, three columns 12, 13, 14, and a control device 90. The workpiece support mechanism 50 has a rotary table 52, which will be described later. Of the two gripping mechanisms 30, 40, the gripping mechanism 30 is also referred to as a first gripping mechanism 30, and the gripping mechanism 40 is also referred to as a second gripping mechanism 40. The control device 90 controls the operation of the machine tool 10.

[0009] The columns 12, 14 at both ends are erected on either side of the rotary table 52. The central column 13 is erected on the rear side of the rotary table 52. The three columns 12, 13, 14 support the machine body 20.

[0010] The machine body 20 is a member that extends in the horizontal direction. The machine body 20 has a first rail 22 and a second rail 24 that extend in the horizontal direction. The first rail 22 guides the horizontal movement of the first gripping mechanism 30. The second rail 24 guides the horizontal movement of the second gripping mechanism 40.

[0011] The first gripping mechanism 30 performs cutting, drilling, and the like, depending on the type of the first processing tool 35. The first gripping mechanism 30 has a first gripping shaft 34 and a first processing tool 35 gripped at one end of the first gripping shaft 34. In the example shown in FIG. 1, the first processing tool 35 is a grindstone. The first gripping shaft 34 is configured to be movable in the Y direction along the vertical direction by a motor (not shown). In addition, the first gripping shaft 34 can be rotated in the direction indicated by the arrow Y1a around the rotation axis RA1 by a motor (not shown). This adjusts the inclination of the first gripping shaft 34 with respect to the Y direction. The first gripping shaft 34 has an axis and can rotate the first processing tool 35 around the axis.

[0012] The second gripping mechanism 40 performs grinding to process a special shape. The second gripping mechanism 40 has a second gripping shaft 44, a rotating shaft 47 attached to one end of the second gripping shaft 44, and a second processing tool 45 held at one end of the rotating shaft 47. In the example shown in FIG. 1, the second processing tool 45 is a grindstone. The second gripping shaft 44 is configured to be movable in the Y direction by a motor (not shown). In addition, the second gripping shaft 44 can be rotated in the direction indicated by the arrow Y1b around the rotation axis RA2 by a motor (not shown). This adjusts the inclination of the second gripping shaft 44 with respect to the Y direction. The rotating shaft 47 has an axis and can rotate the second processing tool 45 around the axis.

[0013] The workpiece support mechanism 50 includes a base 110, a rotating shaft 180 rotatable around an axis RX along the vertical direction, a rotating table 52 supporting a workpiece 120 placed on the base 110, and a displacement sensor 92 detecting the displacement of the rotating table 52.

[0014] The base 110 has a seat 200 that is placed on an installation surface, and a bearing arrangement member 60. The base 110 is cylindrical. The bearing arrangement member 60 is placed on the seat 200. The bearing arrangement member 60 is provided with a bearing that rotatably supports the rotary table 52. The bearing is a hydrostatic bearing. The bearing will be described in detail later.

[0015] The rotary table 52 has a table body 53 and a chuck 54. The table body 53 is disk-shaped. A plurality of chucks 54 are arranged at equal intervals in the circumferential direction of the table body 53. The chucks 54 grip the workpiece 120.

[0016] The displacement sensor 92 is disposed directly below the rotary table 52 with a gap therebetween. The displacement sensor 92 detects the distance to the rotary table 52 along the vertical direction. The number of displacement sensors 92 may be one or more. In this embodiment, three displacement sensors 92 are disposed at equal intervals in the circumferential direction around the axis RX. The detection result by the displacement sensor 92 is transmitted to the control device 90. The displacement sensor 92 is a non-contact type displacement sensor. An example of the non-contact type displacement sensor is a laser displacement sensor. By using the non-contact type displacement sensor as the displacement sensor 92, the degree of freedom in arranging the displacement sensor 92 is improved.

[0017] The machine tool 10 further includes a first oil source 94, a second oil source 96, and a third oil source 98. The first oil source 94 stores oil to be supplied to a bearing that rotatably supports the rotary table 52. The oil supplied from the first oil source 94 to the bearing is pressurized by a first pump 124 arranged on a first supply line L1 and supplied to the bearing. The second oil source 96 stores oil to be supplied to a gap between the rotating shaft 180 and a non-rotating element spaced apart in a radial direction perpendicular to the axis RX. The oil supplied to this gap is pressurized by a second pump 126 arranged on a second supply line L2 and supplied to the gap. The third oil source 98 stores oil to be supplied to a force generating mechanism, which will be described later. The force generated by the force generating mechanism is proportional to the pressurized state of the oil supplied to the force generating mechanism. The magnitude of this force is adjusted by a third pump 128 as a force adjusting unit arranged on a third supply line L3. For example, by increasing the rotation speed of the third pump 128, the pressure of the oil supplied to the force generating mechanism also increases, and the force generated by the force generating mechanism increases. The third pump 128 as a force adjustment unit adjusts the magnitude of the force generated by the force generating mechanism, which will be described later, according to the detection result of the displacement sensor 92. The manner in which the force magnitude is adjusted will be described in detail later. The third pump 128 is a component of the work support mechanism 50.

[0018] 2 is a schematic diagram of the workpiece 120 and the rotary table 52. The workpiece 120 is, for example, an outer ring or an inner ring of a bearing used in a wind power generator or the like, and is a large workpiece. The rotary table 52 places the workpiece 120 thereon and grips the workpiece 120 with a chuck 54 shown in FIG. 1. As a result, the rotary table 52 rotates about the axis RX, and the workpiece 120 rotates about the axis RX.

[0019] FIG. 3 is a schematic diagram of the bearing arrangement member 60 of the base 110, seen from directly above. The bearing arrangement member 60 has a disk-shaped member body 61 and a plurality of bearings 63, 66 provided on the member body 61. The plurality of bearings 63, 66 are hydrostatic bearings. Of the plurality of bearings 63, 66, the bearing arranged radially inward is also called the inner bearing 63. Of the plurality of bearings 63, 66, the bearing arranged radially outward of the inner bearing 63 is also called the outer bearing 66. Six inner bearings 63 are provided at equal intervals in the circumferential direction. When the six inner bearings 63 are to be distinguished from one another, the reference symbols 63a to 63f are used. Twelve outer bearings 66 are provided at equal intervals in the circumferential direction. When the twelve outer bearings 66 are to be distinguished from one another, the reference symbols 66a to 66l are used.

[0020] 4 is a diagram for explaining the bearings 63, 66. The bearings 63, 66 have a pocket 65 provided on a sliding surface 61f, which is the surface of the member body 61 facing the rotary table 52, and a nozzle 67 that discharges pressurized oil into the pocket 65. The nozzle 67 is connected to the first supply line L1. The nozzle 67 discharges pressurized oil toward the rotary table 52 through the pocket 65. The rotary table 52 is lifted slightly by this pressurized oil. As a result, a gap is formed between the rotary table 52 and the sliding surface 61f.

[0021] Fig. 5 is a schematic vertical cross-sectional view of the work support mechanism 50. The configuration of the work support mechanism 50 will be further described with reference to Fig. 5. The table body 53 of the rotating table 52 has a first body 53a on which the work 120 is placed, and a second body 53b located on the back side of the first body 53a. The second body 53b is attached to the first body 53a by a mounting member such as a bolt. The diameter of the rotating table 52 is Φ1. The diameter Φ1 corresponds to the diameter of the first body 53a.

[0022] The work support mechanism 50 further includes a rotating shaft 180 inserted through the bearing arrangement member 60 of the base 110, and a hydrostatic bearing member 70, which is a non-rotating element, disposed between the bearing arrangement member 60 of the base 110 and the rotating shaft 180 in the radial direction. The hydrostatic bearing member 70 is disposed between the base 110 and the rotating shaft 180 in the radial direction perpendicular to the axis RX. The hydrostatic bearing member 70 is cylindrical, and the rotating shaft 180 is inserted through it. The hydrostatic bearing member 70 supplies pressurized oil toward the rotating shaft 180, thereby forming a certain gap between the hydrostatic bearing member 70, which is a non-rotating element, and the rotating shaft 180, which is a rotating element. This allows the rotating shaft 180 to rotate stably around the axis RX. The hydrostatic bearing member 70 and the rotating shaft 180 will be described in detail later.

[0023] The base 110 has a diameter Φ2. The diameter Φ2 is the diameter of the bearing arrangement member 60 of the base 110. The diameter Φ1 of the rotary table 52 is larger than the diameter Φ2 of the base 110.

[0024] The displacement sensor 92 detects a vertical displacement of a table outer periphery 52t of the turntable 52, which is located radially outward of the base 110. The table outer periphery 52t is located radially closer to the periphery 52p of the turntable 52 than the axis RX.

[0025] 6 is a schematic diagram of the region Rg5 in FIG. 5. The rotating shaft 180 includes an upper end 180a, which is the end on the vertically upper side, a lower end 180b, which is the end on the vertically lower side, and a shaft portion 180c connecting the upper end 180a and the lower end 180b. In this embodiment, the shaft portion 180c has a double tube structure. The lower end side of the shaft portion 180c is inserted into the bottom of the bearing arrangement member 60.

[0026] The upper end 180a is attached to the first main body 53a of the table main body 53. The upper end 180a engages with the table main body 53 in the circumferential direction around the axis RX. As a result, when the rotating shaft 180 rotates around the axis RX by the power of a driving motor (not shown), the rotating table 52 rotates around the axis RX in conjunction with the rotating shaft 180. In addition, the upper end 180a engages with the table main body 53 in the vertical direction. As a result, a vertical force applied to the rotating shaft 180 is transmitted to the rotating table 52. The above-mentioned engagement around the axis and in the vertical direction is performed, for example, by using a plurality of bolts BT. The plurality of bolts BT vertically engage the upper end 180a with the table center portion 52M of the first main body 53a.

[0027] The lower end 180b is disposed within the seat 200 of the base 110. In other words, the lower end 180b is located vertically below the bearing arrangement member 60. The lower end 180b faces the bearing arrangement member 60 in the vertical direction.

[0028] The rotary table 52 has a table central portion 52M where the upper end portion 180a of the rotary shaft 180 is located. The table central portion 52M is an area including the center 52Ce in the radial direction. The table central portion 52M is located radially inward of the table outer peripheral portion 52t (FIG. 5). The base 110 also has a pressure-receiving portion 110S that is closer to the base central portion 110M through which the rotary shaft 180 is inserted than the base outer peripheral portion 110p (FIG. 5). The pressure-receiving portion 110S is located vertically below the hydrostatic bearing member 70 and is a surface that faces the hydrostatic bearing member 70.

[0029] The hydrostatic bearing member 70 has a through hole penetrating along the axis RX. This through hole is defined by an inner peripheral surface 70f of the hydrostatic bearing member 70 having a circular cross section. The rotating shaft 180 is inserted into this through hole. The hydrostatic bearing member 70 includes a plurality of shaft supply lines 72 for supplying a shaft pressurized fluid, and a plurality of force supply lines 74 for supplying a force pressurized fluid toward the pressure receiving portion 110S. The plurality of force supply lines 74 function as a force generating mechanism. In this embodiment, the shaft pressurized fluid and the force pressurized fluid are oil. The shaft supply line 72 constitutes the downstream portion of the second supply line L2. The force supply line 74 constitutes the downstream portion of the third supply line L3. In this embodiment, three shaft supply lines 72 are provided. The number of upstream lines in the second supply line L2 that communicate with the three shaft supply lines 72 may be one, or may be multiple depending on the number of the shaft supply lines 72. When there are multiple upstream lines, the number of second pumps 126 provided corresponds to the number of upstream lines. Openings 72e, which are the downstream ends of each of the three shaft supply lines 72, are formed at equal intervals in the circumferential direction. Three openings 72e are formed on the inner circumferential surface 70f. The shaft supply line 72 supplies oil, which is a pressurized fluid, to a radial gap between the hydrostatic bearing member 70 and the rotating shaft 180.

[0030] The hydrostatic bearing member 70 has an opposing surface 76 formed directly above the pressure-receiving portion 110S. The opposing surface 76 faces the pressure-receiving portion 110S with a small gap therebetween in the vertical direction. The normal direction of the opposing surface 76 is vertically downward.

[0031] Three or more force supply lines 74 are provided as a force generating mechanism. In this embodiment, four force supply lines 74 are provided. The number of upstream lines of the third supply line L3 communicating with the four force supply lines 74 may be one, or multiple lines corresponding to the number of force supply lines 74. When there are multiple upstream lines, multiple third pumps 128 are provided corresponding to the number of upstream lines. The downstream end of the force supply line 74 is a supply opening 74e.

[0032] Three or more supply openings 74e are formed at equal intervals in the circumferential direction on the opposing surface 76. In this embodiment, four supply openings 74e are formed at 90° intervals in the circumferential direction.

[0033] The force supply line 74 as a force generating mechanism applies a vertically downward force to the pressure receiving portion 110S by injecting pressurized oil, which is a force pressurized fluid, toward the pressure receiving portion 110S. The third pump 128 as a force adjusting portion sets the pressure of the pressurized oil flowing through the force supply line 74 to a higher value by increasing the rotation speed according to a command from the control device 90, as the vertically downward displacement of the table outer peripheral portion 52t indicated by the detection result of the displacement sensor 92 increases. As a result, the pressure of the pressurized oil injected from the supply opening 74e increases, and the vertically downward force applied to the pressure receiving portion 110S increases. In other words, the third pump 128 as a force adjusting portion sets the force applied to the pressure receiving portion 110S to a higher value as the vertically downward displacement of the table outer peripheral portion 52t indicated by the detection result of the displacement sensor 92 increases. The detection result may be, for example, an average value or a maximum value of the detection results of the multiple displacement sensors 92. When a vertically downward force is applied to the pressure-receiving portion 110S, the pressure-receiving portion 110S and the base central portion 110M through which the rotating shaft 180 surrounded by the pressure-receiving portion 110S is inserted are displaced vertically downward in the bearing arrangement member 60. The vertically downward displacement of the pressure-receiving portion 110S and the base central portion 110M increases as the force applied to the pressure-receiving portion 110S from the force supply line 74 as a force generating mechanism increases.

[0034] Here, the rotating shaft 180 is engaged with the table center portion 52M so as to transmit the force applied to the pressure receiving portion 110S to the table center portion 52M of the rotating table 52. Specifically, the lower end portion 180b of the rotating shaft 180 is pushed vertically downward by the base center portion 110M due to the vertical downward displacement of the base center portion 110M, and is displaced vertically downward. As a result, the upper end portion 180a of the rotating shaft 180 is also displaced vertically downward. The upper end portion 180a is engaged with the table center portion 52M of the first main body 53a in the vertical direction by a plurality of bolts BT. As a result, the table center portion 52M is displaced vertically downward in conjunction with the vertical downward displacement of the upper end portion 180a.

[0035] Fig. 7 is a diagram for explaining the table adjustment process. Fig. 8 is a flowchart of the table adjustment process. The table adjustment process is a process for reducing deformation of the rotary table 52 when the rotary table 52 is deformed due to the weight of the workpiece 120.

[0036] As shown in FIG. 7, when the workpiece 120 is placed on the rotary table 52, a large load may be applied unevenly to the table outer periphery 52t depending on the weight, shape, and size of the workpiece 120. As a result, the rotary table 52 is deformed so that the table outer periphery 52t is displaced vertically downward and the table center 52M is displaced vertically upward, as shown by the two-dot chain line. When the rotary table 52 is deformed as described above, various problems may occur, such as the following. For example, the position of the workpiece 120 may deviate from the target position, resulting in a decrease in the machining accuracy of the workpiece 120, or the gap between the table center 52M and the hydrostatic bearing (for example, the pocket 65 shown in FIG. 4) may become large, preventing the hydrostatic bearing from functioning properly. In addition, for example, a problem may occur in which the rigidity of the rotary table 52 is reduced. On the other hand, if the diameter Φ2 of the base 110 on which the hydrostatic bearing is provided is set to be equal to or larger than the diameter Φ1 of the turntable 52 in order to support the load applied to the table outer periphery 52t, and the hydrostatic bearing is disposed directly below the workpiece 120, the base 110 will become larger. In the table adjustment process of this embodiment, it is possible to suppress deformation of the turntable 52 due to the workpiece 120 while suppressing an increase in the size of the base 110. A specific example of the table adjustment process will be described below with reference to FIG. 8.

[0037] 8 is executed after the workpiece 120 is placed on the rotary table 52 and gripped by the chuck 54, and after the first pump 124 is driven to supply pressurized oil to the pocket 65 to provide the hydrostatic bearing function. The table adjustment process is executed before the rotary table 52 rotates to machine the workpiece 120. The table adjustment process may be executed by a user, or may be executed automatically by the control device 90.

[0038] First, in step S10, the detection value of the displacement sensor 92 is obtained. When the user executes step S10, the detection value is obtained by checking the detection value of the displacement sensor 92 displayed on a display unit such as an LCD monitor. On the other hand, when the control device 90 executes step S10, the detection value is obtained by receiving a signal indicating the detection value from the displacement sensor 92 via wired or wireless communication.

[0039] Following step S10, in step S20, a vertically downward force to be applied to the pressure receiving portion 110S is set by the multiple force supply lines 74 as a force generating mechanism according to the acquired detection value. When the user executes step S20, the target rotation speed of the third pump 128 as a force adjusting portion is input to the control device 90. As a result, the control device 90 transmits an operation command value according to the target rotation speed to the third pump 128, so that the third pump 128 operates at the target rotation speed. When the control device 90 automatically executes step S20, an operation command value of the third pump 128 is generated so as to achieve the target rotation speed according to the acquired detection value, and transmitted to the third pump 128. In step S20, the larger the vertically downward displacement indicated by the detection value, the larger the target rotation speed is, and the larger the vertically downward force (pressure) to be applied to the pressure receiving portion 110S is. In step S20, the larger the vertical downward displacement of the table outer peripheral portion 52t, the larger the force applied to the pressure-receiving portion 110S, so that the table central portion 52M can be further displaced vertically downward. This makes it possible to suppress deformation of the turntable 52 regardless of the magnitude of the displacement of the table outer peripheral portion 52t.

[0040] While maintaining the rotation speed of the third pump 128 set in step S20, the machine tool 10 rotates the workpiece 120 about the axis RX to machine the workpiece 120. Note that every time the workpiece 120 is set on the rotary table 52, the table adjustment process shown in Fig. 8 is performed.

[0041] According to the above embodiment, as shown in FIG. 6, a vertically downward force can be applied to the pressure receiving portion 110S by injecting pressurized oil from the third supply line L3 as a force generating mechanism toward the pressure receiving portion 110S. This allows a vertically downward force to be applied to the table central portion 52M via the rotating shaft 180, and thus it is possible to suppress (cancel) deformation of the rotating table 52, in which the table outer peripheral portion 52t is displaced downward and the table central portion 52M is displaced upward due to the load from the workpiece 120, while suppressing an increase in size of the base 110. In addition, by suppressing deformation of the rotating table 52, it is possible to suppress the occurrence of the above-mentioned various defects. For example, it is possible to suppress deviation of the position of the workpiece 120 from the target position, and therefore it is possible to machine the workpiece 120 with high precision.

[0042] According to the above embodiment, the third supply line L3 as a force generating mechanism applies a vertically downward force to the pressure receiving portion 110S by supplying pressurized oil, which is a force pressurized fluid, to the pressure receiving portion 110S. This allows the work support mechanism 50 to easily apply a vertically downward force to the pressure receiving portion 110S by the pressurized oil. According to the above embodiment, as shown in FIG. 6, by providing the force supply line 74 to the hydrostatic bearing member 70, it is not necessary to newly arrange another member for providing the force supply line 74. This allows the number of parts of the work support mechanism 50 to be reduced.

[0043] According to the above embodiment, as shown in Fig. 6, by forming the supply opening 74e on the facing surface 76 of the hydrostatic bearing member 70, the pressurized oil flowing from the supply opening 74e toward the pressure receiving portion 110S can efficiently apply a vertically downward force to the pressure receiving portion 110S. According to this embodiment, three or more supply openings 74e are formed at equal intervals in the circumferential direction, so that the possibility that the vertically downward force applied to the pressure receiving portion 110S will be uneven in the circumferential direction can be reduced. As a result, the rotating shaft 180 can be more reliably pressed down vertically, so that the vertically downward force can be efficiently transmitted to the table center portion 52M via the rotating shaft 180.

[0044] B. Other embodiments: B-1. Alternative embodiment 1: In the above embodiment, the bearing that rotatably supports the rotary table 52 is a hydrostatic bearing. Other bearings such as rolling bearings and plain bearings may also be used.

[0045] B-2. Alternative embodiment 2: In the above embodiment, the force generating mechanism applies a vertically downward force to the pressure receiving portion 110S by the force pressurized fluid, but the force generating mechanism is not limited to the above as long as it is configured to apply a vertically downward force to the pressure receiving portion 110S. For example, the force generating mechanism may be a rod that can extend and contract in the vertically downward direction. In this case, the rod applies a vertically downward force by pushing the pressure receiving portion 110S vertically downward.

[0046] B-3. ​​Alternative embodiment 3: According to the above embodiment, the force supply line 74 is formed in the hydrostatic bearing member 70, but it is also possible to arrange another member for the force supply line 74 separately and form the force supply line 74 in the other member.

[0047] The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention can be appropriately replaced or combined to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0048] 10...machine tool, 12,13,14...column, 20...machine body, 22...first rail, 24...second rail, 30...first gripping mechanism, 34...first gripping shaft portion, 35...first processing tool, 40...second gripping mechanism, 44...second gripping shaft portion, 45...second processing tool, 47...rotating shaft portion, 50...work support mechanism, 52...rotating table, 52Ce...center, 52M...table center portion, 52p...periphery portion, 52t...table outer periphery portion, 53...table body, 53a...first body, 53b...second body, 54...chuck, 60...bearing arrangement member, 61...member body, 61f...sliding surface, 63...inner circumference side bearing, 65...pocket, 66...outer circumference side bearing, 67...nozzle, 70...hydrostatic bearing member, 7 0f...inner surface, 72...shaft supply line, 72e...opening, 74...force supply line, 74e...supply opening, 76...opposing surface, 90...control device, 92...displacement sensor, 94...first oil source, 96...second oil source, 98...third oil source, 110...base, 110M...center of base, 110p...outer periphery of base, 110S...pressure receiving portion, 120...work, 124...first pump, 126...second pump, 128...third pump, 180...rotating shaft, 180a...upper end, 180b...lower end, 180c...shaft portion, 200...base, BT...bolt, L1...first supply line, L2...second supply line, L3...third supply line, RA1...rotating shaft, RA2...rotating shaft, RX...axis line

Claims

1. A work support mechanism, The base and A rotation shaft that can rotate around an axis line along a vertical direction; a rotary table that is disposed on the base and rotates about the axis in conjunction with the rotation shaft and supports a workpiece; a bearing that rotatably supports the rotary table; a force generating mechanism that applies a vertically downward force to a pressure receiving portion of the base that is closer to a center portion of the base through which the rotation shaft is inserted than to an outer periphery of the base; a displacement sensor that detects a displacement along the vertical direction at an outer periphery of the rotary table that is located radially outward of the base; a force adjustment unit that adjusts the magnitude of the force generated by the force generation mechanism in accordance with a detection result of the displacement sensor, the rotary table has a table center portion where an upper end portion of the rotary shaft is located and includes a center in a radial direction, and a diameter larger than that of the base, A work support mechanism, wherein the rotating shaft is engaged with a center portion of the table so as to transmit the force applied to the pressure-receiving portion of the base to the center portion of the table.

2. The workpiece support mechanism according to claim 1 , The force generating mechanism applies the force to the pressure receiving portion by supplying a force pressurized fluid to the pressure receiving portion.

3. The workpiece support mechanism according to claim 2, The hydrostatic bearing member is disposed between the base and the rotating shaft in the radial direction, and the rotating shaft is inserted through the hydrostatic bearing member. The hydrostatic bearing member is a shaft supply line for supplying a shaft pressurized fluid to a radial gap between the hydrostatic bearing member and the rotating shaft; a force supply line that supplies the force pressurized fluid toward the pressure receiving portion.

4. The workpiece support mechanism according to claim 3, the hydrostatic bearing member has an opposing surface formed directly above the pressure-receiving portion and opposing the pressure-receiving portion with a gap therebetween in the vertical direction, A workpiece supporting mechanism, wherein a supply opening which is a downstream end of the force supply line is formed in the opposing surface.

5. The workpiece supporting mechanism according to claim 4, A work supporting mechanism, wherein three or more supply openings are formed at equal intervals in the circumferential direction.

6. The workpiece support mechanism according to claim 1 , A workpiece support mechanism, wherein the force adjustment unit sets the force to be larger as the vertical downward displacement of the outer periphery of the table represented by the detection result of the displacement sensor becomes larger.

7. The workpiece support mechanism according to claim 1 , The work support mechanism, wherein the bearing is a hydrostatic bearing.

8. The workpiece support mechanism according to claim 1 , The workpiece supporting mechanism, wherein the displacement sensor is a non-contact sensor.

9. A machine tool, A gripping mechanism that grips a processing tool for processing a workpiece; A work support mechanism according to any one of claims 1 to 8; A machine tool comprising:

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