JP2015178168A - Main spindle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a main spindle device effectively suppressing temperature rise by heat evolution from a free side bearing, achieving lifetime extension of the free side bearing, i.e., lifetime extension of the main spindle device, and capable of improving processing precision.SOLUTION: A cooling path 40 into which a cooling medium can flow is formed between an outer peripheral surface 16b of a bearing sleeve 16 to which free side bearings 14 and 14 are internally fitted, and an inner peripheral surface 33a of a rear housing 33. The cooling path 40 comprises a plurality of spiral grooves 41A and 41B formed on the outer peripheral surface 16b of the bearing sleeve 16, and formed between one end side to the other end side in the axial direction of the sleeve on the outer peripheral surface of the sleeve. The housing includes a plurality of supply ports 51A and 51B which are communicated with one ends of respective spiral grooves, and to which the cooling medium is supplied, and a plurality of discharge ports 52A and 52B which are communicated with the other ends of respective spiral grooves, and from which the cooling medium flowing in the spiral groove is discharged.

Description

  The present invention relates to a spindle device, and more particularly to a spindle device of a rotating machine that rotates at high speed, such as a machine tool spindle, a high-speed motor, a centrifugal separator, or a turbo refrigerator.

The speedup of machine tool spindles has been remarkably developed, and oil-air lubrication and oil mist lubrication have been adopted as lubrication methods for enabling speedup of the spindle. As another lubrication method, from the viewpoint of environmental protection, grease lubrication that does not discharge lubricating oil to the outside has been reconsidered, and a lightweight ceramic rolling element (for example, silicon nitride) that has high speed rotation and excellent seizure resistance has been reviewed. Etc.) is used together with rolling bearings.
Further, as a driving method for the high-speed rotating main shaft, a so-called motor built-in main shaft in which a motor is built in the main shaft dominates rather than gear driving, belt driving, or direct coupling driving by coupling.

  In the high-speed main shaft having such a configuration, heat generation from the built-in motor (stator and rotor) is large in addition to heat generation from the rolling bearing that supports the main shaft. In the case of a machine tool spindle, if the temperature rise of the spindle is high, thermal deformation occurs and machining accuracy decreases. For this reason, means for flowing cooling oil from the outside to the housing which is the main shaft outer cylinder is used so as to suppress the temperature rise of the main shaft. Since the deformation of the main shaft due to thermal expansion occurs in the axial direction with the front bearing on the fixed side as the origin, the outer periphery of the front bearing on the fixed side and the stator of the motor is often cooled.

  For example, as shown in FIG. 11, a conventional cooling device 100 that suppresses heat generation from the front bearing is provided on an outer peripheral surface of a front housing 104 in which a pair of front bearings 102 and 103 that support the front side of the main shaft 101 are fitted. A circumferential groove 105 is provided. A cooling medium is circulated between the outer peripheral surface of the front housing 104 and the inner peripheral surface of the other housing 106 to cool the front bearings 102 and 103.

  Patent Document 1 discloses a machine tool in which a cooling medium passage is provided in an inner ring spacer disposed between a front bearing and a rear bearing, and the inner ring spacer is cooled by a cooling medium pumped from a pump or the like. Discloses a spindle cooling device.

  On the other hand, the rear bearing, which is the free bearing, is often used with a bearing that is slightly smaller in size than the front bearing (for example, the inner diameter of the bearing is about 10 to 30 mm smaller than the fixed bearing). . For this reason, the dmn value of the bearing is reduced, and the temperature rise is correspondingly reduced. In addition, the rear bearing is a free side, and the thermal deformation of the rear part of the main shaft has a smaller influence on the machining accuracy than the front bearing (for example, the rotating shaft is less than the non-rotating part. The rear bearing has a complicated cooling structure due to the fact that the rear side of the spindle slides backwards even if it expands relative to the direction, and it is difficult to appear in the displacement of the front side of the spindle where the blade is mounted. Is often not added.

Japanese Utility Model Publication No. 4-133555

  By the way, recent high-speed main shafts have increased dmn values of bearings to be used of 1 million or more, or more than 1.5 million, and more than 2 million, and accordingly, the dmn value of the rear bearing is also increased. Increasing and generating fever. If the rear bearing generates a large amount of heat, the lubricating oil viscosity decreases due to an increase in the internal temperature of the bearing, and seizure may occur due to poor oil film formation at the rolling contact portion.

For this reason, in the cooling device 110 shown in FIG. 12, it is conceivable to cool the rear bearing while simplifying the peripheral structure. In this case, a sleeve 114 into which a pair of free-side bearings 112, 113 that support the rear side of the main shaft 101 is fitted is fitted in the rear housing 115, and a circumferential groove 116 is provided on the outer circumferential surface of the rear housing 115. Then, the free side bearings 112 and 113 are cooled by circulating a cooling medium between the outer peripheral surface of the rear housing 115 and the inner peripheral surface of the other housing 117.
However, in the structure shown in FIG. 12, the cooling part is disposed at a position radially away from the heat generating part (bearings 112 and 113), and the sleeve 114 and the rear housing 115 that are fitted by clearance fitting are arranged. Since the heat transfer efficiency between them is low, there is a problem that the cooling efficiency is low. Therefore, although the rear housing is cooled, the sleeve is not efficiently cooled, and there is a possibility that a gap between the rear housing and the sleeve becomes small and a sliding failure occurs. For this reason, a tensile load due to thermal expansion is generated between the front bearing (fixed side bearing) and the rear bearing (free side bearing), and there is a possibility that an excessive load is applied to the bearing and the bearing is damaged. Alternatively, preload loss may occur, causing abnormal noise or abnormal vibration.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to increase the life of the rear bearing, that is, the life of the main spindle device by suppressing the temperature increase due to heat generated from the rear bearing with high efficiency. An object of the present invention is to provide a spindle device that can be extended and improved in machining accuracy.

The above object of the present invention can be achieved by the following constitution.
(1) a housing;
A rotating shaft relatively rotatable with respect to the housing;
A fixed-side bearing in which an inner ring is fitted on one end side of the rotating shaft and an outer ring is fixed to the housing;
A sleeve disposed in the housing on the other end side of the rotating shaft and movable in the axial direction of the rotating shaft;
A free side bearing in which an inner ring is fitted on the other end side of the rotary shaft, and an outer ring is fitted in the sleeve;
A spindle device having
A cooling path through which a cooling medium can flow is formed between the outer peripheral surface of the sleeve and the inner peripheral surface of the housing facing each other.
The cooling path is a plurality of spiral grooves formed on the outer peripheral surface of the sleeve between one end side in the axial direction of the sleeve and the other end side.
The housing communicates with one end of each of the plurality of spiral grooves and supplies the cooling medium, and communicates with the other end of each of the plurality of spiral grooves and flows through the spiral grooves. And a plurality of outlets through which the cooling medium is discharged.
(2) An annular elastic member that seals between the outer peripheral surface of the sleeve and the inner peripheral surface of the housing in a liquid-tight manner is disposed on both sides in the axial direction of the cooling path. The spindle device according to (1).
(3) The chamfered portion is formed at both end edge portions of the outer peripheral surface facing the inner peripheral surface of the housing of the sleeve or both end edge portions of the inner peripheral surface of the housing (1). Or the spindle apparatus as described in (2).
(4) The spindle device according to any one of (1) to (3), wherein a side wall surface of the spiral groove is formed to be inclined with respect to a direction orthogonal to the axial direction.
(5) The spiral groove is characterized in that the one end and the other end are arranged with a phase difference of 180 ° in the circumferential direction of the outer peripheral surface of the sleeve. ) The spindle device according to any one of the above.
(6) The plurality of spiral grooves are characterized in that the one end portions and the other end portions are arranged with different phases within 45 ° in the circumferential direction of the outer peripheral surface of the sleeve ( The spindle apparatus as described in any one of 1)-(5).

  According to the spindle device of the present invention, the cooling path through which the cooling medium can flow is formed between the outer peripheral surface of the sleeve and the inner peripheral surface of the housing that face each other. The cooling path is formed on the outer peripheral surface of the sleeve, and has a plurality of spiral grooves formed on the outer peripheral surface of the sleeve between one end side in the axial direction of the sleeve and the other end side. A plurality of supply ports through which the cooling medium is supplied in communication with one end of each spiral groove, and a plurality of exhausts through which the cooling medium flowing through the spiral groove is communicated with the other end of each of the plurality of spiral grooves. And an exit. For this reason, the sleeve in which the bearing is fitted can be directly cooled, and the free-side bearing can be cooled with high efficiency. Moreover, the cooling control accuracy of the sleeve or the free-side bearing is improved by supplying and discharging the cooling medium independently with respect to the plurality of spiral grooves. As a result, the internal temperature of the bearing is lowered, and it is difficult for the lubricating oil film to be cut off due to a decrease in viscosity at the rolling contact portion and the cage guide surface during rotation, thereby preventing a reduction in life due to poor lubrication and bearing seizure. Since both the housing and the sleeve are cooled at the same time, the amount of radial contraction of both the members becomes uniform, the gap between the slide portions (the gap between the housing and the sleeve) is not clogged, and the occurrence of a sliding failure due to the insufficient gap. Can be prevented. Further, by using a spiral groove as the cooling path, the flow of the cooling medium in the spiral groove becomes smooth, the entire sleeve can be cooled uniformly, and deformation distortion due to cooling does not occur. As a result, there is no distortion of the bearing that fits inside, the rotation accuracy of the main shaft is maintained with high accuracy, and the processing accuracy of the main shaft is improved.

It is sectional drawing which shows the whole spindle apparatus structure of this invention. It is an expanded sectional view of the free side bearing vicinity shown in FIG. It is a fragmentary sectional view corresponding to FIG. 2 which shows the outer peripheral surface of a bearing sleeve for demonstrating a spiral groove. It is an A direction arrow directional view of FIG. It is a fragmentary sectional view which shows the outer peripheral surface of the bearing sleeve seen from the B direction of FIG. It is sectional drawing of a spiral groove. It is sectional drawing of the spiral groove of various modifications. It is a fragmentary sectional view of the bearing sleeve by which the chamfered part was formed in the outer peripheral surface both-ends edge part. It is a fragmentary sectional view of the bearing sleeve in which the chamfered part was formed in the shoulder part of a spiral groove. It is a graph which compares and shows the temperature rise by the difference in the cooling structure of a free side bearing. It is sectional drawing which shows the structure of the conventional fixed side bearing. It is sectional drawing which shows the structure of the conventional free side bearing.

  Hereinafter, embodiments of a spindle device of the present invention will be described in detail with reference to the drawings.

First, with reference to FIG. 1, the whole structure of the spindle device of the present invention will be described.
The spindle device 10 has a housing 11 and a tool (not shown) attached to one end (left side in the figure), a rotary shaft 12 that is rotatable relative to the housing 11, and a front end side (left side in the figure) of the rotary shaft 12. A pair of fixed side bearings (angular ball bearings in this embodiment) 13 and 13 and a pair of free side bearings (this embodiment) arranged on the rear end side (right side in the figure) of the rotary shaft 12. , Angular ball bearings) 14 and 14 and a sleeve 15 that is inserted in the housing 11 and is slidable in the axial direction.

  The housing 11 includes a substantially cylindrical housing body 31, a front housing 32 fitted and fixed to the front end side of the housing body 31, and a rear housing 33 fitted and fixed to the rear end side of the housing body 31. ing. A front lid 34 is fastened and fixed to the front end of the front housing 32, and a rear lid 36 is fastened and fixed to the rear end of the rear housing 33.

  A stator 38 of a built-in motor 37 is fixed to the sleeve 29 that fits inside the inner peripheral surface 31 a of the housing body 31. In addition, a rotor 39 is fixed to an intermediate portion in the axial direction of the rotating shaft 12 so as to face the stator 38, and a rotating force is given by a rotating magnetic field generated by the stator 38 to rotationally drive the rotating shaft 12. A plurality of annular grooves 29 a are formed on the outer peripheral surface of the sleeve 29, and a cooling path 28 is formed between the inner peripheral surface 31 a and the inner groove 31 a by being fitted inside the housing body 31.

  The fixed side bearings 13 and 13 have outer rings 18 and 18 fitted in the front housing 32 and inner rings 19 and 19 fitted on the rotary shaft 12 so as to rotatably support the front end side of the rotary shaft 12. The outer rings 18, 18 of the fixed side bearings 13, 13 are sandwiched by the step 32 a of the front housing 32 and the front lid 34 via the outer ring spacer 20, and are positioned in the axial direction with respect to the front housing 32. The inner rings 19, 19 are clamped by the front step portion 12 a of the rotating shaft 12 through the inner ring spacer 21 and a nut 22 screwed to the rotating shaft 12, and are positioned in the axial direction with respect to the rotating shaft 12. . A plurality of annular grooves 32 b are formed on the outer peripheral surface of the front housing 32, and the cooling path 30 is formed between the inner peripheral surface 31 b of the housing main body 31 by being fitted into the housing main body 31. .

  A substantially cylindrical bearing sleeve 16 that is movable in the axial direction is fitted to the inner peripheral surface 33 a of the rear housing 33. Further, an outer ring presser 17 that extends radially outward from the outer peripheral surface of the bearing sleeve 16 is attached to the end surface of the bearing sleeve 16 opposite to the tool mounting side by screws (not shown). The bearing sleeve 16 and the outer ring presser 17 constitute a sleeve 15.

  The rear housing 33 is formed with a plurality of spring chambers 55 that open on the end surface (the right side surface in the drawing) opposite to the tool mounting side, and an outer ring presser extending radially outward from the bearing sleeve 16. It opposes the tool attachment side end surface of 17 flange parts. The coil spring 56 is accommodated in the spring chamber 55 and interposed between the flange portion of the outer ring presser 17 and the spring chamber 55. The coil spring 56 applies an elastic force in the axial direction (right direction in the drawing) to the sleeve 15, thereby applying a constant pressure preload to the fixed side bearings 13 and 13 and the free side bearings 14 and 14.

  The free-side bearings 14 and 14 have outer rings 23 and 23 fitted in the bearing sleeve 16 and inner rings 24 and 24 fitted on the rotary shaft 12 so as to rotatably support the rear end side of the rotary shaft 12. The outer rings 23, 23 of the free-side bearings 14, 14 are sandwiched by the step 16 a of the bearing sleeve 16 and the annular convex portion 17 a of the outer ring retainer 17 via the outer ring spacer 25, and are pivoted with respect to the bearing sleeve 16. Positioned in the direction. The inner rings 24, 24 are clamped by the rear step portion 12 b of the rotating shaft 12 through the inner ring spacer 26 and a nut 27 screwed to the rotating shaft 12, and are positioned in the axial direction with respect to the rotating shaft 12. The

  As shown in FIGS. 2 and 3, the outer circumferential surface 16 b of the bearing sleeve 16 has a plurality of (two in the illustrated example) spiral grooves 41 between one end side and the other end side in the axial direction of the bearing sleeve 16. Is provided. In the spiral groove 41 of this configuration, a first spiral groove 41A and a second spiral groove 41B are arranged in parallel. By fitting the bearing sleeve 16 to the inner peripheral surface 33 a of the rear housing 33, a cooling path 40 is formed between the outer peripheral surface of the bearing sleeve 16 and the inner peripheral surface 33 a of the rear housing 33 facing each other. A cooling medium such as cooling oil flows through the cooling path 40. A cooling medium is independently supplied to and discharged from the first spiral groove 41A and the second spiral groove 41B through a housing cooling path by a cooling device (not shown).

  The rear housing 33 shown in FIG. 1 communicates with one end that is the groove start end of the first spiral groove 41A, and supplies a cooling medium into the spiral groove 41A (indicated by an arrow IN (A) in the figure). The cooling medium flowing through the spiral groove 41A is discharged in communication with the supply port 51A of the supply path 57A and the other end portion of the first spiral groove 41A (in the figure, the arrow OUT (A)). A discharge port 52A is formed.

  The rear housing 33 communicates with one end that is the groove start end of the second spiral groove 41B, and is supplied with a cooling medium (indicated by an arrow IN (B) in the drawing) 51B The cooling medium that has flowed through the spiral groove 41B is discharged (indicated by an arrow OUT (B) in the drawing) to communicate with the other end portion of the spiral groove 41B of the second spiral groove 41B. Yes.

  The supply port 51A is formed so as to open toward the one end 41Aa of the spiral groove 41A located closest to the built-in motor 37 side. The discharge port 52A is formed so as to open toward the other end portion 41Ab of the spiral groove 41A farthest from the built-in motor 37, and is formed in a phase different from the supply port 51A by 180 ° in the circumferential direction.

  As described above, the first spiral groove 41A and the second spiral groove 41B have the circumferential phase of one end 41Aa (corresponding position of the supply port 51A) and 41Ba (corresponding position of the supply port 51B) of 0. In addition to ° and 0 ° (hereinafter referred to as (0 ° -0 °)), it may be (0 ° -180 °), and the other end 41Ab of the first spiral groove 41A (of the discharge port 52A). Corresponding position), 41Bb (corresponding position of the discharge port 52B), the phase in the circumferential direction may be (0 ° -180 °) in addition to (180 ° -180 °).

  Next, the first spiral groove 41A and the second spiral groove 41B have a circumferential phase of one end portions 41Aa and 41Ba (0 ° -45 °) and the other end portions 41Ab and 41Bb in the circumferential direction. A case where the phase is (0 ° -45 °) will be described.

  FIG. 4 shows a view in the direction of arrow A in FIG. In the case of this configuration, the supply path 57A and the discharge path 58A formed in the rear housing 33 and the rear lid 36 are arranged in a phase different by 180 ° in the circumferential direction. The supply path 57B for supplying the cooling medium into the spiral groove 41B has a phase different from the supply path 57A in the circumferential direction by an angle α (α = 45 ° in the illustrated example) around the axis Ax of the bearing sleeve 16. Has been placed. The discharge path 58B is arranged with a phase that is 180 ° different from the supply path 57B in the circumferential direction.

  Similarly to the spiral groove 41A, the supply port 51B of the supply path 57B for supplying the cooling medium to the spiral groove 41B is formed to open toward one end portion 41Ba of the spiral groove 41B located closest to the built-in motor 37. Yes. The discharge port 52B of the discharge path 58B for discharging the cooling medium opens toward the other end portion 41Bb of the spiral groove 41B farthest from the built-in motor 37, and is formed with a phase that is 180 ° different from the supply port 51B.

  FIG. 5 shows a partial cross-sectional view of the outer peripheral surface of the bearing sleeve viewed from the direction B of FIG. As described above, the one end 41Aa, which is the groove start end of the spiral groove 41A, and the other end 41Ab, which is the groove end of the spiral groove 41A, are arranged in a phase different by 180 ° in the circumferential direction of the bearing sleeve 16. . That is, when one end portion 41 </ b> Aa of the spiral groove 41 </ b> A on the bearing sleeve 16 is viewed from the front in the direction perpendicular to the axis, the other end portion 41 </ b> Bb of the spiral groove 41 is disposed at a position overlapping the axis Ax of the bearing sleeve 16.

  The one end 41Ba, which is the groove start end of the spiral groove 41B, is arranged in a phase different from the one end 41Aa of the spiral groove 41A and the circumferential direction of the bearing sleeve 16 by an angle α (for example, α = 45 °). Further, the one end portion 41Ba of the spiral groove 41B and the other end portion 41Bb of the spiral groove 41B are arranged in a phase different by 180 ° in the circumferential direction of the bearing sleeve 16. Accordingly, the other end portion 41Bb of the spiral groove 41B is disposed at a phase different from the other end portion 41Ab of the spiral groove 41A by an angle α in the circumferential direction of the bearing sleeve 16.

  By supplying and discharging the cooling medium from the independent housing cooling paths to the spiral grooves 41A and 41B, the flow rate and temperature of the cooling medium can be controlled for each of the spiral grooves 41A and 41B. And the free-side bearing temperature can be accurately and stably controlled.

  Further, the phases of the supply ports 51A and 51B of the spiral grooves 41A and 41B and the phases of the discharge ports 52A and 52B are equally spaced in the circumferential direction, that is, between the supply port 51A and the supply port 51B. By equalizing the phase difference and the phase difference between the discharge port 52A and the discharge port 52B, the cooling effect along the circumference of the bearing sleeve 16 is averaged, and thermal deformation due to cooling around the bearing sleeve 16 becomes uniform. . Thereby, the rotation accuracy of the main shaft can be maintained, the generation of vibration is suppressed, and the processing accuracy is improved.

  Further, the one end portions 41Aa and 41Ba of the spiral grooves 41A and 41B and the other end portions 41Ab and 41Bb may be arranged in different phases within 45 ° in the circumferential direction of the bearing sleeve 16. Thereby, it can arrange | position, without making a supply port and a discharge port interfere.

  In the processing of the spiral groove 41 of the bearing sleeve 16 described above, first, an end mill tool is cut in the sleeve radial direction from one of the end portions in the sleeve axial direction to dig a groove. Thereafter, the end mill tool is fed in a spiral shape while maintaining the cut, and the spiral groove is processed. Then, when reaching the vicinity of the other end in the sleeve axial direction, the feed is stopped, and the end mill tool is pulled up to form a groove.

  In general, processing of a spiral groove on a cylindrical member has been very difficult until now, and it has been disadvantageous in that it is difficult to improve processing accuracy and increase processing cost. However, in recent years, multi-axis machines and multi-task machines have come to be widely used, and the spiral groove 41 of this configuration can be machined easily, with high accuracy and at low cost. Thereby, for example, the phase error in the circumferential direction between the supply ports 51A and 51B and the discharge ports 52A and 52B can be reduced, and uniform cooling can be achieved.

  The cooling medium pumped from a pump (not shown) is supplied from the supply ports 51A and 51B, flows in the cooling path 40, cools the periphery of the cooling path 40, and then is discharged from the discharge ports 52A and 52B. Is done. By supplying the cooling medium from the one end portions 41Aa and 41Ba of the spiral grooves 41A and 41B close to the built-in motor 37, a portion with a large amount of generated heat, that is, the temperature is likely to rise, is cooled with a lower temperature cooling medium. Can be cooled with high efficiency. Further, the supply ports 51A, 51B and the discharge ports 52A, 52B are arranged with a phase difference of 180 ° in the circumferential direction, so that the cooling paths 40 of the first and second spiral grooves 41A, 41B can be provided. Each of them has a symmetric arrangement, and the free-side bearing portion can be cooled more uniformly.

  Although the phase difference between the supply ports 51A and 51B and the discharge ports 52A and 52B is (0 ° -45 °) in this configuration, it can be arbitrarily changed according to the arrangement of peripheral components. For example, the phase difference may be (0 ° -180 °).

  Furthermore, the axial groove widths of the spiral grooves 41A and 41B may be the same or different. The helical axial pitch can also be set arbitrarily. In this configuration, the motor side is the cooling medium supply side, and the spindle end side is the cooling medium discharge side, but this is not a limitation.

  A pair of annular grooves 44 are formed on the outer peripheral surface 16 b of the bearing sleeve 16 on the outer side in the axial direction from the cooling path 40. An O-ring 45 that is an elastic member is attached to the annular groove 44 to seal the fitting portion between the inner peripheral surface 33 a of the rear housing 33 and the bearing sleeve 16. The crushing allowance of the O-ring 45 is preferably in the range of 0.1 mm to 2.0 mm, and in order to more easily solve the sliding failure of the bearing sleeve 16, the range of 0.2 mm to 0.5 mm is used. Is desirable. Further, the fitting gap between the bearing sleeve 16 and the rear housing 33 may have a difference in diameter, that is, the dimension indicated by the inner diameter of the rear housing 33 minus the outer diameter of the bearing sleeve 16 within a range of 5 μm to 100 μm. Preferably, in order to easily eliminate the sliding failure due to insufficient gap or inclination of the bearing sleeve 16, it is desirable to set the range of 15 μm to 50 μm.

  As materials for the O-ring 45, in addition to general nitrile rubber, acrylic rubber, etc., heat resistant silicon rubber and various elastomers corresponding to the heat generated by the motor built-in spindle, or swelling resistance and oil resistance corresponding to the cooling medium A suitable fluororubber is selected as necessary. Note that the sliding amount of the bearing sleeve 16 and the rear housing 33 in this embodiment is a displacement that escapes deformation due to processing load and thermal axial expansion of the spindle, and is at most ± 0.5 mm or less. ± 1 mm or less. Therefore, the problem of degradation of sealing performance due to sliding wear due to large and fast stroke as seen in the piston ring mounted on the movable cylinder is small, and creep resistance due to aging (heat and initial interference fit) It is desirable to select a material with excellent characteristics.

  As shown in FIG. 1, the spindle device 10 cools the fixed side bearings 13 and 13, the cooling path 30 that cools the stator 38 of the built-in motor 37, and the cooling paths that cool the free side bearings 14 and 14. In the case of having a plurality of 40 cooling paths, the cooling device (not shown) is also provided in a separate system from the other cooling paths 28 and 30 for optimal cooling of the free-side bearings 14 and 14, and is used for the cooling path 40. It is preferable to arrange them independently. Thereby, the temperature adjustment of the cooling medium can be performed without being affected by the conditions of the other cooling paths 28 and 30.

  However, if it is practically difficult, the cooling device may not be made independent but only the cooling path 40 may be made independent. In this case, an optimum cooling condition can be adjusted by providing a throttle somewhere in the supply side piping to the cooling path 40 and controlling the supply amount of the cooling medium.

  In the case of the one-path cooling configuration, after passing the cooling medium through the cooling path 28 that cools the stator 38 that tends to generate a large amount of heat, the cooling path 40 that cools the free-side bearings 14 and 14. If the path configuration is to be circulated, the temperature of the spindle device 10 as a whole can be lowered more efficiently. Further, when it is desired to cool the free-side bearings 14 and 14 more efficiently, a cooling medium having a lower temperature may be circulated through the cooling path 40 as a path configuration opposite to the above, and as required. Can be selected.

  As described above, according to the spindle device 10 of the present embodiment, the cooling path 40 through which the cooling medium can flow is formed between the outer peripheral surface 16 b of the bearing sleeve 16 and the inner peripheral surface 33 a of the rear housing 33. Is done. The cooling path 40 is formed on the outer peripheral surface 16 b of the bearing sleeve 16, and has a plurality of spiral grooves formed on the outer peripheral surface of the bearing sleeve 16. The rear housing 33 communicates with one end portions 41Aa and 41Ba of the plurality of spiral grooves, and supplies a plurality of supply ports 51A and 51B to which a cooling medium is supplied, and the other end portion 41Ab of each of the plurality of spiral grooves 41A and 41B. , 41Bb and a plurality of discharge ports 52A, 52B through which the cooling medium flowing through the spiral groove is discharged. For this reason, the bearing sleeve 16 in which the free-side bearings 14 and 14 are fitted can be directly cooled, and the free-side bearings 14 and 14 can be cooled with high efficiency.

  Further, by using the plurality of spiral grooves 41A and 41B in the cooling path 40, the cooling medium smoothly flows in one direction along the spiral groove toward the discharge side, and the thermal cooling efficiency is improved. The bearing sleeve 16 is supplied with a cooling medium from supply ports 51A and 51B communicating with one end portions of the spiral grooves 41A and 41B, and from the discharge ports 52A and 52B respectively communicating with the other end portions of the spiral grooves 41A and 41B. The cooling medium that has flowed through is discharged.

  That is, since the supply and discharge paths of the cooling medium communicate directly with the spiral groove 41, the coolant flows in the entire groove from one end to the other end of the spiral groove 41 without stagnation. As a result, efficient heat exchange is possible. Furthermore, the space in the axial direction of the bearing sleeve 16 can be saved as compared with the case where a circumferential annular groove serving as a cooling medium supply path and a discharge path is formed on both ends of the spiral groove 41.

  Further, since a further spiral groove can be formed in the space of the circumferential annular groove, the cooling path and the cooling heat transfer area can be increased, that is, the groove length can be increased, and the cooling efficiency can be increased. Note that the circumferential phase shift between the rear housing 33 and the bearing sleeve 16 in assembly can be eliminated by an existing key member that prevents the rear housing 33 and the bearing sleeve 16 from rotating during rotation. There is no need to add an anti-rotation member.

  With the above configuration, the internal temperature of the free-side bearings 14 and 14 is lowered, and it is difficult for the lubricating oil film to break due to a decrease in viscosity at the rolling contact portion and the cage guide surface during rotation. 14 and 14 are prevented from being seized.

  Further, since both the members of the rear housing 33 and the bearing sleeve 16 are cooled at the same time, the amount of radial contraction of both the members becomes uniform, and the gap between the slide portions (the gap between the rear housing 33 and the bearing sleeve 16) is not clogged. It is possible to prevent the occurrence of a slide failure due to insufficient gap. Furthermore, the flow of the cooling medium in the groove of the spiral groove 41 becomes smooth, and the entire bearing sleeve 16 is uniformly cooled, so that deformation distortion due to cooling does not occur. As a result, the free-side bearings 14 and 14 fitted therein are not distorted, the rotational accuracy of the rotary shaft 12 is maintained with high accuracy, and the processing accuracy of the spindle device 10 is improved.

  In addition, since the cooling oil constantly circulates in the slide portion, the friction coefficient is small, and there is an effect that the slide performance is further improved. There is a method in which a ball guide (ball bush) or the like is arranged on the slide portion to improve the slidability by rolling action, but problems such as generation of vibration and reduction of the natural frequency of the spindle occur due to the reduction in rigidity. On the other hand, if the preload clearance (that is, the radial clearance between the inner diameter of the housing, the ball, and the outer diameter of the sleeve) is increased in order to increase the rigidity, on the contrary, there arises a problem that the slidability becomes worse than the sliding by sliding.

  Even when initial fretting wear powder is generated between the rear housing 33 and the bearing sleeve 16 due to chatter vibration or the like that may occur during heavy cutting, the cooling medium carries away the fine wear powder to the outside. Therefore, it is possible to suppress further progress of fretting by using the abrasion powder as an auxiliary agent.

  Further, on both sides of the cooling path 40 in the axial direction, O-rings 45 are disposed for liquid-tight sealing between the outer peripheral surface 16b of the bearing sleeve 16 and the inner peripheral surface 33a of the rear housing 33. Leakage is prevented, and the damping characteristic of the spindle device 10 is improved by the elasticity of the O-ring 45, which contributes to the improvement of dynamic rigidity, which particularly affects the machining characteristics of difficult-to-cut materials. In addition, a damping action due to the damper effect of the cooling medium flowing through the slide portion is also added.

  In the above embodiment, as shown in FIG. 6, the spiral groove 41 is formed in a rectangular cross-sectional shape by the bottom surface 41a and the side wall surface 41b. The size of the groove width B and the depth T of the spiral groove 41 having the rectangular cross-sectional shape can be selected as appropriate.

  When B> T, since the radial depth of the spiral groove 41 is shallow, the radial thickness of the bearing sleeve 16 is ensured, and the sleeve rigidity can be increased. Such a shape is applied when importance is placed on improving the processing accuracy of the sleeve or when the rigidity of the main shaft is improved. If B <T, the radial depth of the spiral groove 41 is deep, so the spiral groove 41 is formed near the bearing, and the vicinity of the bearing can be cooled more efficiently. As a result, the cooling efficiency of the main shaft can be improved. Such a shape is applied when importance is placed on improving the cooling characteristics of the spindle. When B = T, the above effects can be balanced.

  Further, the cross-sectional shape of the spiral groove 41 can be various shapes as shown in FIGS. For example, as shown in FIGS. 7A and 7B, the side wall surface 41b of the spiral groove 41 may be formed to be inclined with respect to the direction orthogonal to the axial direction, that is, the radial direction.

Specifically, the spiral groove 41 of the bearing sleeve 16 shown in FIG. 7A is a trapezoidal groove whose groove width B gradually increases from the bottom surface 41a of the spiral groove 41 toward the outer peripheral surface 16b of the bearing sleeve 16. . That is, in the trapezoidal spiral groove 41, the cross-sectional shape of the spiral groove 41 is such that the angle formed by the bottom surface 41a and the side wall surface 41b is an obtuse angle (θ ₁ ), and thus there is no interference with the inner peripheral surface 33a of the rear housing 33 , Improved slideability. Further, the spiral groove 41 of the bearing sleeve 16 shown in FIG. 7B is a so-called dovetail in which the groove width B gradually decreases from the bottom surface 41 a of the spiral groove 41 toward the outer peripheral surface 16 b of the bearing sleeve 16. Yes. That is, in the dovetail spiral groove 41, the cross-sectional shape of the spiral groove 41 is a portion close to the free-side bearings 14 and 14, which are heat sources, because the angle formed by the bottom surface 41a and the side wall surface 41b is an acute angle (θ ₂ ). Therefore, the heat of the free-side bearings 14 and 14 can be efficiently transmitted to the cooling medium, and the cooling performance is improved.

  Further, since the spiral groove 41 of the bearing sleeve 16 shown in FIG. 7C has a semicircular cross section with a radius of curvature R, it can be machined with a round bite, and the bite is less worn during machining. Workability can be improved.

Further, as shown in FIG. 8, chamfered portions 43 may be formed at both ends of the outer peripheral surface 16 b facing the inner peripheral surface 33 a of the rear housing 33 of the bearing sleeve 16. Angle theta ₃ with respect to the outer peripheral surface 16b of the chamfer 43, 3 ° to 45 °, more preferably, it is preferable to 3 ° to 30 °. Thereby, even if the bearing sleeve 16 is inclined in the rear housing 33, interference with the inner peripheral surface 33a of the rear housing 33 is prevented, and slidability is ensured.

Further, as shown in FIG. 9, if a chamfered portion 46 is formed on the top (shoulder) of the side wall of the spiral groove 41 in addition to the chamfered portions 43 at both ends of the bearing sleeve 16, the inner periphery of the rear housing 33 can be formed. Interference with the surface 33a is further prevented, and slidability is maintained. Bevel angle theta ₄ of the shoulder portion of the spiral groove 41, 3 ° to 45 °, more preferably 3 to 30 °.

  In addition, this invention is not limited to each embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.

  For example, in the above-described embodiment, the spindle device in which the preload is applied by the constant pressure preload between the fixed side bearing and the free side bearing has been described. The present invention can also be applied to the main spindle device, and the same effect can be obtained. For this reason, as a free side bearing, it is not limited to an angular ball bearing, Other rolling bearings, such as a cylindrical roller bearing, may be applied.

  Here, the cooling structure of the present invention in which the cooling path is provided on the outer peripheral surface of the bearing sleeve 16, the cooling structure shown in FIG. 12 in which the cooling path is provided on the outer peripheral surface of the rear housing, and the bearing sleeve and the rear housing are cooled. The temperature rise values from the inner diameter of the bearing sleeve to the outer diameter of the housing were compared using a structure without cooling without a passage. FIG. 10 is a graph comparing temperature rise values from the inner diameter of the bearing sleeve to the outer diameter of the housing due to different cooling structures.

  As is apparent from FIG. 10, the temperature rise due to each cooling structure is the smallest in the temperature rise value of the cooling structure of the present invention in which the cooling path 40 is provided on the outer peripheral surface of the bearing sleeve 16, and the spindle device 10 is cooled with high efficiency. You can see that In addition, the difference in temperature rise between the inner diameter of the housing (the sleeve inner fitting portion) and the bearing sleeve is extremely small compared to the outer cylinder cooling structure shown in FIG. 12, and the sliding gap of the slide portion is reduced due to the difference in thermal expansion. It can be made small and good sliding characteristics can be maintained.

Specifically, the temperature difference between the bearing sleeve and the inner diameter of the housing is 1.5 ° C. in the configuration of the present invention compared to 8.5 ° C. in the case of the outer cylinder cooling structure shown in FIG. is there. If the sliding part (= sleeve outer diameter dimension) is φ150 mm and the linear expansion coefficient of the bearing sleeve and the housing (carbon steel) is 11.5 × 10 ⁻⁶ , the difference in the thermal expansion amount between them is
11.5 × 10 ⁻⁶ (/ ° C.) × 150 (mm) × 7 (° C.) = 0.012 (mm)
It becomes.

  That is, in the case of the configuration of the present invention, it is possible to maintain good slide characteristics even if the set clearance of the slide portion is 12 μm smaller than the appropriate set clearance in the conventional structure (outer cylinder cooling). As a result, the bearing temperature rise is relatively low and the temperature difference between the slide parts is small. At the time of heavy cutting at low speed rotation, the conventional structure has insufficient rigidity due to excessive clearance of the slide parts, generation of vibration, and fretting. Where problems occur, the configuration of the present invention provides an effect of preventing these problems.

  Further, since the temperature of the bearing sleeve is about 12 ° C. lower, the bearing temperature is lowered, the base oil viscosity of the lubricant can be maintained, and the oil film formation at the rolling contact portion is also improved. In the case of grease lubrication, it becomes difficult for the base oil to separate from the thickener (oil separation), the grease outflow to the outside of the bearing is reduced, and the grease life can be extended.

DESCRIPTION OF SYMBOLS 10 Main shaft apparatus 11 Housing 12 Rotating shaft 13 Fixed side bearing 14 Free side bearing 16 Bearing sleeve (sleeve)
16b Outer peripheral surface of sleeve 18, 23 Outer ring 19, 24 Inner ring 28, 30, 40 Cooling path 31 Housing body 32 Front housing 33 Rear housing (housing)
33a Inner circumferential surface 41 of the housing Spiral groove 41A First spiral groove 41B Second spiral groove 41Aa One end part 41Ab of the first spiral groove Other end part 41Ba of the first spiral groove One end part 41Bb of the second spiral groove The other end portion 43 of the second spiral groove Chamfered portion 45 O-ring (elastic member)
51 Supply port 52 Discharge port

Claims (6)

A housing;
A rotating shaft relatively rotatable with respect to the housing;
A fixed-side bearing in which an inner ring is fitted on one end side of the rotating shaft and an outer ring is fixed to the housing;
A sleeve disposed in the housing on the other end side of the rotating shaft and movable in the axial direction of the rotating shaft;
A free side bearing in which an inner ring is fitted on the other end side of the rotary shaft, and an outer ring is fitted in the sleeve;
A spindle device having
A cooling path through which a cooling medium can flow is formed between the outer peripheral surface of the sleeve and the inner peripheral surface of the housing facing each other.
The cooling path is a plurality of spiral grooves formed on the outer peripheral surface of the sleeve between one end side in the axial direction of the sleeve and the other end side.
The housing communicates with one end of each of the plurality of spiral grooves and supplies the cooling medium, and communicates with the other end of each of the plurality of spiral grooves and flows through the spiral grooves. And a plurality of outlets through which the cooling medium is discharged.   2. An annular elastic member for liquid-tightly sealing between the outer peripheral surface of the sleeve and the inner peripheral surface of the housing is disposed on both sides in the axial direction of the cooling path. Spindle device described in 1.   The chamfered portion is formed at both end edges of the outer peripheral surface of the sleeve facing the inner peripheral surface of the housing or both end edges of the inner peripheral surface of the housing. 2. The spindle device according to 2.   4. The spindle device according to claim 1, wherein a side wall surface of the spiral groove is formed to be inclined with respect to a direction orthogonal to the axial direction. 5.   5. The spiral groove according to claim 1, wherein the one end and the other end are arranged with a phase difference of 180 ° in the circumferential direction of the outer peripheral surface of the sleeve. A spindle device according to claim 1.   The plurality of spiral grooves are arranged such that the one end portions and the other end portions are arranged in different phases within 45 ° in the circumferential direction of the outer peripheral surface of the sleeve. The spindle device according to claim 5.

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