JP5121047B2 - Spindle device using hydrodynamic bearing and radial hydrodynamic bearing - Google Patents

Description

  The present invention relates to a hydrodynamic bearing using a wedge function of a fluid such as a tilting pad bearing and a spindle apparatus using the same. More specifically, the present invention relates to a support bearing mechanism for a high-speed spindle for holding a small-diameter grinding wheel or cutting tool and rotating it with high speed and high accuracy in a machine tool or the like.

  In a high-speed spindle that grips and drives a small-diameter grinding wheel or cutting tool, an increase in spindle rotation speed is required as the tool diameter decreases in order to maintain an optimum cutting speed. However, as the spindle rotation speed increases, the vibration amplitude of the spindle increases. As a result, the tool also vibrates, so that the processing accuracy is lowered.

In order to maintain and improve the rotational accuracy of the spindle, it is effective to improve the accuracy of the spindle support bearing and increase the bearing rigidity. For example, when using a rolling bearing, the vibration of the spindle can be reduced by improving the shape accuracy of the rolling elements incorporated in the bearing. However, the allowable spindle vibration amplitude in precision / ultra-precision machining is on the order of submicron, and the operable rotation speed at which good machining results can be obtained with a spindle using a rolling bearing is at most about 30,000 min ⁻¹ . Therefore, the tool diameter is below 1mm, 50,000min ^-1, more rotational accuracy is high, the less air friction losses and hydraulic fluid in the case of requiring a high-speed rotation exceeding 100,000Min ^-1 The use of plain bearings is appropriate, and various types of hydrodynamic bearings and hydrostatic bearings have been proposed.

  First, as an air dynamic pressure bearing, for example, there is a tilting pad bearing. In this bearing, the bearing surface is not integrated but is composed of a plurality of parts. As a result, processing and assembly are complicated, and the shape accuracy of the bearing surface cannot be so high. Therefore, high rotational accuracy could not be expected for the spindle supported by such a dynamic pressure bearing. There are also dynamic pressure bearings (such as a perfect circle bearing and a herringbone bearing) having a single bearing surface, but in the case of a perfect circle bearing with a simple bearing surface shape, the generated dynamic pressure is insufficient. Therefore, in order to generate the dynamic pressure necessary to support the load, it is necessary to create a complicated shape on the bearing surface as seen in herringbone bearings and the like, resulting in difficulties in processing and assembly techniques. Moreover, these dynamic pressure bearings have a fatal disadvantage in that sufficient load capacity and rigidity cannot be obtained during low-speed rotation, and the spindle and the bearing surface come into contact with each other.

  On the other hand, an aerostatic bearing has a sufficient and stable lubricating film even at low speed rotation, and the spindle and the bearing surface do not contact each other. However, the bearing rigidity is not always sufficient due to the limitation of the bearing size, and an increase in vibration amplitude accompanying high-speed rotation of the spindle becomes a problem. Thus, structures that increase the bearing area with limited bearing dimensions, such as porous bearings and surface constricted bearings, have been proposed, but problems such as difficulty in manufacture and complicated structures arise. Moreover, the load supporting operation in these hydrostatic bearings is passive, and the vibration suppressing effect must be limited.

  Therefore, as a bearing that reduces the displacement and vibration of the spindle by active control, for example, in Patent Document 1, an active self-contained throttle using a piezoelectric element is incorporated in a hydrostatic bearing, and axial displacement is actively controlled. This has an aperture with an opening that supplies fluid pressure at the tip, forming a diaphragm with a small gap between the opposing plane between two opposing planes, and the aperture is expanded and contracted in a uniaxial direction relative to the fixed side. A hydrostatic element is provided which is fixed and protrudes from the mounting plane, and a hydrostatic bearing is formed between the two planes facing each other by the fluid supplied from the throttle by the minute gap, and the distance between the two planes is set from the outside. A setting device to set and a measuring device to measure the distance between two planes are provided, and the output signal of the measuring device is compared with the setting signal of the setting device. When the output signal is smaller than the set signal, the hydrostatic bearing is controlled so that the opening surface is separated from the counterpart plane, and the distance between the two planes is controlled to the distance set by the setting device.

Further, in a tilting pad bearing, which is a kind of dynamic pressure bearing, as shown in Patent Document 2, a part of the bearing surface is made a flexible surface, and the flexible surface is deformed by a piezoelectric element to thereby generate axial vibration. Trying to attenuate. Furthermore, in Patent Document 3 (paragraphs [0021] and [0022]), a displacement sensor for the rotation shaft is provided, and when the rotation shaft vibrates in the vertical direction, for example, the gap between the displacement sensor and the rotation shaft changes. A control device that detects and receives the displacement signal supplies a voltage having a height determined based on the detection signal to the piezoelectric element. The supplied piezoelectric element stretches to increase the inclination angle of the free end of the flexible pad, thereby changing the gap distribution between the rotating shaft and the flexible pad, changing the pressure distribution, the gap, the spring constant, and the damping coefficient. The displacement of the rotating shaft is attenuated by changing the vibration and suppressing the vibration. Furthermore, a dash pot is provided to suppress vibration.

On the other hand, as a compound bearing, in Patent Document 4, the protective bearing of the active magnetic bearing spindle is a hydrostatic bearing, and the active magnetic bearing gap is added to the hydrostatic bearing gap to add the rated allowable displacement of the hydrostatic bearing. The spindle is supported by the active magnetic bearing and the hydrostatic bearing at the same time during spindle operation to satisfy the function as a protective bearing and reduce the shaft clearance during spindle operation. The precision and rigidity of the spindle spindle are improved by increasing the sensitivity of the magnetic bearing.
Japanese Patent No. 3746199 Japanese Patent No. 2659829 JP 2000-205251 A Japanese Patent Publication No. 7-30789

    However, in the active control hydrostatic bearing as in Patent Document 1, the frequency characteristics are not sufficient, the control cannot catch up with the increase in the rotational speed, and a sufficient control effect is not obtained at high speed rotation. Further, in Patent Documents 2 and 3, the bearing surface is divided into a plurality of parts, and it is difficult to maintain the processing and assembly accuracy of the bearing, and the bearing surface shape error is large and high rotation accuracy is expected. Can not. Moreover, since the bearing surface clearance cannot be controlled with high accuracy, the bearing clearance is large, and the flexible part may come into contact with the rotating spindle during control. Not suitable for speed and high accuracy. Also in the vibration damping, as in Patent Document 3, only the vibration damping control that deteriorates the frequency characteristic like the dash pod can be performed, and the control with high accuracy and high response cannot be performed. Furthermore, in the combination with the active magnetic bearing as in Patent Document 4, the structure and control device on the magnetic bearing side are large, complicated, expensive, and require advanced adjustment.

  Thus, in the conventional spindle technology, there is no effective technology for suppressing an increase in vibration accompanying an increase in rotational speed, which has been an obstacle to realizing a high-speed spindle for precision machining with a small diameter tool.

  In view of the conventional problems, an object of the present invention is to provide a hydrodynamic bearing with low vibration and high rotational accuracy even at high speed rotation, and further, at high speed rotation required by a small-diameter tool, It is an object of the present invention to provide a dynamic pressure bearing and a spindle device using the dynamic pressure bearing capable of controlling a vibration amplitude to a submicron order.

In the present invention, there is provided a dynamic pressure bearing in which a plurality of bearing pads for generating dynamic pressure are formed by forming an inclined surface with respect to the opposing side surface, and the pad surface of the bearing pad is relative to the side surface. A flexible pad that can be moved back and forth by an externally controllable actuator, and a fixed portion is provided between the bearing pads, and the bearing pad including all the pad surfaces and the fixed portion are continuous. The flexible pad is connected by a surface, and the flexible pad has a thick part, a first thin part provided on one end side in the relative movement direction of the thick part, and the other end in the relative movement direction of the thick part. And a second thin portion whose relative movement direction length is longer than that of the first thin portion, each of which is connected to the fixed portion by a continuous surface, and the opposite side surface of the thick portion To the thick part by the actuator And solve the problems described above by providing a hydrodynamic bearing which is in retractable said pad surface to the counterpart side by changing the pressure.

  That is, the conventional one has a large and sufficiently large pad surface, and the influence of the fluid distribution at the start point and end point of the pad surface is not taken into consideration. However, when the present inventors are small and high-speed, the fluid distribution functioning as a hydrodynamic bearing formed by the pad surface at the start point and the end point is interrupted, resulting in an unstable distribution, and it becomes difficult to control the pad surface. I knew that the performance would drop. With this knowledge, in the present invention, the tilting pad type pad surface and the fixed portion are formed as a continuous surface, that is, formed as a single unit, and formed by moving the pad surface forward and backward with the bearing pad as a flexible pad. The surface forms a hydrodynamic bearing with a wedge-shaped film. By keeping the bearing surface of the hydrodynamic bearing continuous, the shape accuracy can be maintained, and a stable fluid distribution with little influence before and after the pad surface can be maintained.

  The continuous surface has no discontinuous steps and reduces the influence on the dynamic pressure of the bearing pad. More preferably, in a state where the flexible pad is not in operation, the pad surface and the fixed portion are formed as an integral continuous surface, that is, the same circumferential surface for radial bearings and the same plane for thrust bearings. It is made to become. Further, a bearing pad including a flexible pad elastically deforms a part of the bearing surface (pad surface) with an actuator, thereby forming a rust film without the need for dynamic pressure generation while ensuring strength and reproducibility.

Further, when the pad surface is formed by the thick portion and the thick portion is pressed by the actuator, the thin portion is deformed and the thick portion approaches the other side surface to reduce the gap. At this time, since the second thin portion is longer than the first thin portion, the second thin portion side is more deformed and the thick portion forms a slope with the first thin portion side as the center. A rust-like film can be formed without the need for dynamic pressure generation. Needless to say, it is preferable to keep the thin portion within the elastic deformation range.

Further, the actuator high response, control ease, it is preferable that the piezoelectric element in terms of equal is a small (claim 2). Furthermore, the the fixing portion can be by providing a displacement sensor for measuring the displacement of the mating side, and the active form dynamic pressure bearing capable of feedback control (claim 3). When a displacement sensor is provided in the fixed part, a mounting hole or a detection hole is required in a part of the continuous surface in the fixed part. However, the size and position of the hole has the least influence on the dynamic pressure of the bearing pad. To be. If possible, it is desirable that the tip of the displacement sensor be shaped to match the continuous surface of the fixed part.

  As a result, the output of each sensor is observed, the pad surface on the side where the distance from the spindle is decreased is pushed up by an actuator such as a piezoelectric element, the amount of elastic deformation is increased, the generated dynamic pressure on the pad surface is increased, and the spindle is Push back. On the other hand, the pad surface on the side where the distance to the spindle increases increases the actuator push-down position to lower the pad surface by elastic force (decreasing the amount of elastic deformation), and reduces the generated dynamic pressure to pull the spindle. By controlling in this way, it is possible to suppress the vibration amplitude generated with the rotation of the rotary spindle.

Further, the counterpart side if the outer periphery of the rotary shaft, can be applied to the radial dynamic pressure bearing (Claim 4). Furthermore, the counterpart side if the axial side surface of the rotating disk unit, can be applied to the thrust hydrodynamic bearing (Claim 5).

When such a dynamic pressure bearing is used for a rotating spindle, there are few problems if the spindle is light, but such a dynamic pressure effect is insufficient to support the spindle load at a low rotational speed. Therefore, in the invention described in claim 6, wherein the mating side is a part of the outer peripheral surface provided al to an output end of the rotating spindle, the rotary spindle is further more hydrostatic bearing or rolling The spindle device uses a radial dynamic pressure bearing supported by the bearing.

  As a result, the spindle is supported by the hydrostatic bearing or the like as described above in the low speed and medium speed regions. On the other hand, the dynamic pressure bearing can generate sufficient dynamic pressure and load capacity in the high rotational speed region which is an object of the present invention, and the generated dynamic pressure can be used to control the position of the spindle to suppress vibration. In Patent Document 4, both ends of the spindle are supported by both magnetic and hydrostatic bearings. In contrast, in the present invention, a hydrostatic bearing or the like is supported at both ends, the spindle is always held, and one end on the outer side thereof is a dynamic pressure bearing, and control of only minute vibration at the tool tip is controlled using the dynamic pressure bearing. Therefore, the structure and control are simple.

  In the present invention, the bearing pad including the flexible pad of the hydrodynamic bearing that advances and retracts the flexible pad surface and the fixed portion are integrated on a continuous surface, and the shape accuracy is maintained by continuing the bearing surface. Since the stable fluid distribution with little influence before and after the surface can be maintained, the influence of the bearing surface shape on the rotation accuracy of the spindle can be minimized. Furthermore, since the bearing surface can be a single component of an integral structure, and the shape of the bearing surface can be basically a simple geometric shape such as a perfect circle (radial bearing) or a true plane (thrust bearing), an active bearing mechanism The bearing surface can be processed with high accuracy, and the shape accuracy of the bearing surface and the arrangement accuracy with other bearing surfaces can be maintained at a high level during assembly. As a result, the bearing clearance can be kept smaller, and high rotational accuracy can be expected.

Further, the pad surface is formed by the thick portion supported by the first and second thin portions, and the pad portion is pushed up so that the thick portion is centered around the first thin portion on both sides of the pad surface. The structure can be made simple by forming a wedge-shaped film on the slope, making it easy to design and analyze in the elastic deformation region, and to design and manufacture easily. Moreover, because of the use of piezoelectric elements in the actuator, it is easy to compact and produced (Claim 2).

Also, by providing a displacement sensor in the fixed part, an active dynamic pressure bearing capable of feedback control can be obtained, so that the vibration amplitude generated with the rotation of the rotating spindle can be suppressed, and high-precision control can be achieved. (Claim 3) . Further, if the opposite side surface is the outer periphery of the rotary shaft, it can be applied to a radial dynamic pressure bearing (Claim 4) , and if the opposite side surface is an axial side surface, it can be applied to a thrust dynamic pressure bearing (Claim 5) . It can be applied to various dynamic pressure bearings.

Furthermore, in the invention described in claim 6 , the hydrostatic bearing is supported at both ends, the spindle is always held, the outer end is used as the hydrodynamic bearing, and only the slight vibration of the tool tip is controlled using the hydrodynamic bearing. Therefore, it is not necessary to increase the angle of the “wedge film” because the hydrostatic bearing is responsible for the load at a low rotational speed with little dynamic pressure effect. Furthermore, in the case of active control of the hydrostatic bearing, there has been a problem of insufficient control force as the rotational speed increases. However, in the present invention, the generated dynamic pressure increases as the rotational speed increases, resulting in greater control. As a result, the vibration amplitude of the spindle can be suppressed to the submicron order at the time of high-speed rotation required by a small-diameter tool.

  A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a radial type active dynamic pressure bearing showing a first embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1 showing a state of elastic deformation of the flexible bearing pad of the present invention. FIG. 3 is a longitudinal sectional view of a spindle head of a spindle apparatus using the radial type active hydrodynamic bearing of the present invention. As shown in FIGS. 1 and 3, a radial type active dynamic pressure bearing (hereinafter simply referred to as “dynamic pressure bearing”) 1 of the present invention is attached to a spindle head 11 of a spindle device 10 fixed to a work table (not shown) at a tip portion. It is inserted into the drilled through hole 11a. The outer periphery 2a and inner periphery 2b of the main body 2 of the hydrodynamic bearing 1 are concentric. Four bearing pads 3 are equally arranged along the inner peripheral surface, and the fixing portion 4 is arranged between the bearing pads.

  The pad surface 5 a of the bearing pad 3 is separated from the main body 2 in the radial direction by a slit 6 at a distance from the inner peripheral surface 2 b, thereby forming a thick portion 5. A small-diameter hole 7 is formed in the vicinity of the inner periphery 2b on one end side in the circumferential direction of the pad surface 5a to form a first thin portion 7b. In addition, a long hole 8 is formed along the inner periphery in the vicinity of the inner periphery on the other end side of the pad surface, and a second thin portion 8b is formed. The pad surface 5a is supported by first and second thin portions 7b, 8b having different elastic deformation amounts at both ends in the circumferential direction, and constitutes a bearing pad 3 that is a flexible pad. The inner periphery 2b of the fixed portion 4, the inner peripheral side surface 7a of the first thin portion 7b, the pad surface 5a, the inner peripheral side surface 8a of the second thin portion 8b, and the inner periphery 2b of the adjacent fixed portion 4 form a perfect circle. Connected by continuous surfaces. The pad surface 5a is determined so as to deform within the elastic deformation region by adjusting the thickness of the first and second thin portions 7b, 8b.

  On the back surface (outer peripheral surface) 5b of the pad surface 5a, through holes 2c and 11b penetrating the main body in the radial direction are formed so that the piezoelectric element 9 can press the back surface 5b of the pad surface. The piezoelectric element 9 is screwed and positioned with a screw 11c formed in the spindle head 11. By supplying a predetermined voltage to the piezoelectric element 9 from the outside, the back surface 5b of the pad surface 5a is pressed, and due to the difference in the amount of elastic deformation of the thin portions 7b, 8b, the pad surface is centered on the first thin portion side. 5a forms a slope, and a rust-like film can be formed without the need for generating dynamic pressure. Thereby, the rotary spindle 20 is supported.

  A bearing clearance 31 similar to that of a general hydrostatic bearing is provided between the inner peripheral surface 2 b and the spindle 20, and a sensor 12 for observing the change in the clearance, that is, vibration, is provided on the fixed portion 4. It is attached to a through hole 4b opened in a substantially central radial direction. The tip 12a of the sensor 12 is formed in the same shape as the inner periphery 2b, and the inner periphery 7a, 5a, 8a, 2b, 12a of the bearing pad 3 and the fixed portion 4 is formed into a perfect circle when no piezoelectric element is applied. Has been. In order to process such a shape, the outer periphery 2a of the main body and the slit 6, the small diameter hole 7, the long hole 8 and the like may be processed, and finally the inner periphery 2b may be processed. At this time, if a receiving screw is provided in place of the piezoelectric element 9 to support the back surface 5b of the thick portion 5, roundness defects due to machining escape can be reduced. Further, if a plurality of receiving screws are provided in the axial direction, the roundness accuracy can be improved.

  The operation of the dynamic pressure bearing will be described. The bearing surface (inner peripheral surface 2b) is a continuous true circle when no voltage is applied to the piezoelectric element. As shown in FIG. 2, when the spindle 20 reaches a predetermined number of rotations, an initial voltage is applied to each piezoelectric element 9 by an appropriate control device installed outside, and the piezoelectric element pushes the thick part back surface 5b, The bearing pad 3 bends as shown by a solid line from the dotted line 3 ', and a state where the bearing clearance is narrowed in a "wedge shape" is formed on the pad surface 5a to generate an initial dynamic pressure.

  When vibration is generated with the rotation of the spindle 20 (in the direction of the arrow in the figure), this vibration, that is, the change in the bearing clearance (the clearance between the spindle outer periphery 20a and the fixed portion 4) 31 is caused by the sensor 12 as shown in FIG. Detected and sent to the control device 14 via the sensor amplifier 13. Then, the control device increases the amount of elastic deformation by increasing the voltage applied to the piezoelectric element in the region where the bearing clearance is reduced via the piezoelectric element driving amplifier 15 by an appropriate control algorithm. As a result, as shown in FIG. 2, the generated dynamic pressure is increased by reducing the outlet clearance 32 and increasing the “wedge angle” with respect to the entrance clearance 31 of the “wedge region” 30. On the other hand, in the region where the bearing clearance increases, the amount of elastic deformation 33 is reduced to reduce the dynamic pressure. By doing so, the spindle can be pushed back to the original position, so that the generation of vibration can be suppressed. Note that the control method, control circuit, and the like are the same as those in the prior art, and thus description thereof is omitted.

Next, the hydrodynamic bearing according to the first embodiment of the present invention described above and the aerodynamic pressure bearing and the air hydrodynamic bearing having excellent rotational accuracy and low friction loss during high-speed operation are used in combination for the spindle support. A spindle apparatus according to a second embodiment will be described. In addition, about the structure similar to the above-mentioned, the same code | symbol is attached | subjected and a part of description is abbreviate | omitted. In this spindle apparatus, the spindle's own weight is first supported by a normal-type hydrostatic bearing to prevent the spindle from coming into contact with the bearing surface when the spindle is stopped and when rotating at a low speed. When the spindle supported by the hydrostatic bearing is accelerated to a rotational speed suitable for machining with a small-diameter tool, for example, tens of thousands of min ^-1 , the spindle generates minute vibrations according to the load characteristics of the hydrostatic bearing. When processing is performed, the processing accuracy is reduced.

  The basic idea of the second embodiment is to actively control a dynamic pressure air bearing incorporated in the spindle when such a minute vibration is generated to suppress the minute vibration. However, since the vibration level of the spindle in the controlled state is on the order of submicrons, high shape accuracy is also required for the bearing surface of the hydrodynamic bearing used here.

As shown in FIG. 3, the spindle device 10 according to the second embodiment of the present invention has a hydrostatic bearing member 21 constituting a normal hydrostatic radial bearing portion 21 a at the center portion of the spindle head 11. It is inserted and fixed in the central part 11d. The hydrostatic thrust bearing portion 22 is disposed at the rear end portion (right side in the drawing) 11e of the spindle head, and the above-described dynamic pressure bearing 1 is disposed at the distal end portion 11a (left end in the drawing). A built-in motor 24 is further provided on the rear end side of the spindle 20 via an intermediate member 23 (right end in the figure), and is connected to the spindle 20 so as to drive the spindle 20 to rotate.

This spindle device 10 is based on the premise that the weight of the spindle 20 and the processing load are basically supported by the hydrostatic bearing portion 21a. That is, the spindle 20 is supported to a certain degree of stability by the hydrostatic bearing 21a and rotates from the stop state to the high-speed operation state. After the spindle reaches a specified rotational speed, for example, tens of thousands of min ⁻¹ , machining is started by a small-diameter tool installed at the tip. The magnitude of the radial vibration amplitude generated at this time is It affects the machining accuracy. Therefore, the radial radial vibration amplitude can be suppressed using the active radial dynamic pressure bearing 1 at the left end. The spindle diameter is 25 mm, the length from the spindle tip to the motor mounting end is about 200 mm, the dynamic pressure bearing width is about 25 mm, and the static pressure bearing width is about 100 mm.

Next, the performance of the spindle device 10 will be described. FIG. 4 shows the relationship between the amount of elastic deformation at one location (horizontal axis) and the load capacity of the bearing surface due to the generated dynamic pressure (vertical axis) in the elastic deformation region of the pad surface 5a of the bearing surface in the spindle device of the present invention. It is a result. However, the rotation speed of the spindle is 100,000 min ⁻¹ . The initial bearing clearance 31 is 15 μm, and the bearing clearance is the same as that of the aerostatic radial bearing arranged coaxially. As shown in FIG. 4, when the amount of elastic deformation is 0 μm, the bearing clearance remains the entrance clearance 31 and does not change, so no dynamic pressure is generated. As the bearing surface is deformed by the piezoelectric element to reduce the clearance 32 on the bearing surface and the angle of the “wedge film” is increased, dynamic pressure is generated and load capacity is generated. Since the rigidity of the hydrostatic radial bearing in this example is about 1 N / μm, a radial displacement of about 1 μm can be generated in the spindle per one place in the elastic deformation region of the pad surface 5a of the active dynamic pressure bearing from FIG. Recognize.

  FIG. 5 is a calculation result of the relationship between the change in the rotation speed (horizontal axis) and the generated load capacity (vertical axis) of the spindle device of the present invention. However, the bearing clearance 31 at the entrance of the “wedge film” region of the bearing surface is 12 μm, and the amount of elastic deformation is 2 μm (the clearance 32 at the exit is 10 μm). From FIG. 5, it can be seen that the generated dynamic pressure at the elastically deforming portion increases as the rotational speed increases, and it can be seen that the present invention can operate effectively in the high rotational speed region.

Next, actual measurement results of the spindle device 10 described above will be described. FIG. 6 shows the results of actual measurement of the relationship between the rotational speed change (horizontal axis) and the spindle displacement (vertical axis) of the spindle device of the present invention. As shown in FIG. 6, the effect per one place of the pad surface 5a of the bearing pad 3 is shown for each rotational speed. As a result of measuring the spindle displacement when the applied voltage is 80 V with reference to the spindle position when no voltage is applied to the piezoelectric element (0 V), the spindle is 40 to 160 nm (nanometer) by applying the voltage to the piezoelectric element. ) Confirmed to move away from the pad surface. Further, as shown in FIG. 6, it can be seen that the generated dynamic pressure on the pad surface increases and the spindle displacement increases as the rotational speed increases even with the same applied voltage. The rotational speed has been measured only up to 30,000 min ^−1, but the displacement is about 0.2 μm, which is effective for suppressing vibrations in the submicron region. Such an operation is consistent with the result of theoretical calculation.

FIG. 7 shows the experimental results of the spindle vibration suppression effect by the dynamic pressure bearing 1 of the spindle device 20 of the present invention (spindle speed is 12,000 min ⁻¹ ). As shown in FIG. 7, the left side without control has an amplitude of about 40 nm and the eccentricity is about 20 nm, while the right side with control has an amplitude of about 20 nm and the eccentricity is almost 0 nm. As described above, the spindle drift observed before the control is extinguished by the servo lock due to the start of the control, and the spindle vibration amplitude is suppressed to about 10 nm, so that the spindle vibration can be actively controlled. I understand that. Thus, in the present invention, an active dynamic pressure bearing and a spindle device capable of suppressing vibration of a spindle rotating at a high speed to a submicron order are provided, and further, a control means for the active dynamic pressure bearing is provided. became.

  In the embodiment of the present invention, it has been described that the spindle's own weight and the like are mainly supported by the hydrostatic bearing, but the present invention can also be applied to other types, for example, vibration suppression of a spindle supported by a rolling bearing. Regarding the vibration direction, the active hydrodynamic bearing that suppresses radial vibration has been described as an example, but the same configuration can be applied to a thrust active hydrodynamic bearing that suppresses thrust vibration. Although the example of air is shown here as the working fluid, a fluid such as lubricating oil can be used as the working fluid. Further, although a piezoelectric element is used as the driving element, a linear solenoid or the like may be used. Further, the displacement sensor is not limited to this embodiment, for example, various sensors such as laser and sound can be used.

It is the AA sectional view taken on the line of FIG. 3 of the radial type active dynamic pressure bearing which shows 1st embodiment of this invention, and the conceptual diagram of the control system. It is the elements on larger scale of FIG. 1 which shows the mode of the elastic deformation of the flexible bearing pad of this invention. It is a longitudinal cross-sectional view of the spindle apparatus using the radial type active dynamic pressure bearing of this invention. It is a theoretical graph which shows the change of the load capacity (vertical axis) of the bearing surface by the generated dynamic pressure when increasing the elastic deformation (horizontal axis) of the pad surface of the bearing surface in the spindle device of the present invention. It is a theoretical graph which shows the rotation speed change (horizontal axis) and the change of generated load capacity (vertical axis) of the spindle apparatus of this invention. It is an actual measurement graph of the spindle displacement (vertical axis) when the spindle rotation of the spindle device of the present invention is changed several times (horizontal axis). It is the measurement graph which showed the vibration suppression effect when operating the active dynamic pressure bearing of the spindle device of the present invention.

Explanation of symbols

1 Hydrodynamic bearing (active hydrodynamic bearing)
3 Bearing pads (flexible pads)
4 Fixed part 5 Thick part 5a Pad surface 5b Opposite side of thick part (back)
7b 1st thin part 8b 2nd thin part 9 Actuator (piezoelectric element)
DESCRIPTION OF SYMBOLS 10 Spindle apparatus 12 Displacement sensor 20 Rotating spindle 20a Opposite side surface (spindle outer periphery, rotating shaft outer periphery)
21a Bearing (hydrostatic bearing)

Claims (6)

A hydrodynamic bearing in which a plurality of bearing pads for generating dynamic pressure is formed by forming an inclined surface with respect to a counterpart moving side surface, and the pad surface of the bearing pad can be controlled from the outside with respect to the counter side surface such a flexible pad that is in retractable by the actuator, wherein the inter-bearing pads are stationary part is provided, and the all of the bearing pad and the fixing portion including a pad surface are connected by a continuous surface And the flexible pad is provided on the other end of the thick portion, the first thin portion provided on one end side in the relative movement direction of the thick portion, and on the other end in the relative movement direction of the thick portion. An actuator provided on the opposite side surface of the thick portion, each of which is connected to the fixed portion by a continuous surface. To change the pressing force to the thick part Dynamic bearing, characterized in that the pad surface is in retractable Against side by the. The hydrodynamic bearing according to claim 1 , wherein the actuator is a piezoelectric element. The hydrodynamic bearing according to claim 1, wherein a displacement sensor for measuring a displacement with respect to the other side surface is provided in the fixed portion. The radial dynamic pressure bearing according to claim 1, wherein the opposite side surface is an outer periphery of a rotating shaft. The thrust dynamic pressure bearing according to any one of claims 1 to 3 , wherein the opposite side surface is an axial side surface of a rotating circle portion. Wherein the counterpart side is a part of the outer circumferential surface was found provided on the output end side of the rotating spindle, the rotary spindle is further more static pressure or, characterized in that it is supported by the rolling bearing A spindle device using the radial dynamic pressure bearing according to Item 4 .

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