JP2013082018A - Spindle device of built-in motor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle device of a built-in motor system, the device capable of suppressing rise in temperature of a rotary shaft or a bearing due to heat generation of a rotor, and capable of improving machining accuracy.SOLUTION: In a spindle device 10 of a built-in motor system, a rotary shaft 12 includes: a first cylindrical member 71 made of metal material; and a second cylindrical member 72 made of carbon fiber composite material, which is positioned on the outer peripheral surface of the first cylindrical member 71 and into the outer peripheral surface of which a rotor 20 fits; and third cylindrical members 73, 74 made of metal material, which are positioned on the outer peripheral surface of the second cylindrical member 72 and into the outer peripheral surface of which inner ring 52, 62 of front or rear bearing 50, 60 fits.

Description

  The present invention relates to a motor built-in spindle device, and more particularly to a motor built-in spindle device that can be applied to a multi-axis control machine tool and can rotate at a high speed with a dmn of 1 million or more.

  Because the spindle of the spindle device applied to machine tools etc. receives a machining load while rotating at high speed, it is necessary to maintain rigidity against the machining load or deformation suppression characteristics against centrifugal force during high-speed rotation. As the material, metal is mainly used. In addition, since the rotating shaft is used by exchanging tools, it needs to have wear resistance and hardness. For this reason, depending on the physical properties of the metal, there are limits to eigenvalues and thermal expansion, and the rotational speed and acceleration / deceleration time are also limited.

  In the machine tool described in Patent Document 1, a horizontal boring machine using a fiber-reinforced composite material as a rotating shaft is described. In this horizontal boring machine, a rotating shaft that moves in the axial direction within the sleeve while rotating is disclosed, and while reducing weight and reducing thermal expansion, impact resistance required for the rotating shaft, surface From the viewpoint of hardness and strength by mechanical processing, metal or ceramic is provided at a necessary portion of the rotating shaft.

  In the spindle device described in Patent Document 2, the rotary shaft is rotatably supported by an air bearing, and a fiber layer is formed on the outer peripheral surface of the rotary shaft to suppress expansion of the rotary shaft and improve rigidity. It is described. Further, in the spindle device described in Patent Document 3, a groove is formed on both sides of the outer peripheral surface to which the rolling bearing of the rotating shaft is attached, and a carbon fiber layer is formed in the groove, thereby suppressing expansion due to centrifugal force. It is described. In the tool holder described in Patent Document 4, the tapered portion, the flange portion, and the tool holding portion are integrally formed, and a collet attached to the tool is inserted into a tapered hole formed in the tool holding portion. A tool for fixing a tool by tightening a nut screwed to a screw formed on the outer periphery is described, and a carbon fiber layer is wound around the outer peripheral surface of the nut to prevent deformation of the nut.

Japanese Patent Laid-Open No. 2-167602 Japanese Patent Laid-Open No. 7-51903 JP-A-6-226506 (FIG. 3) JP-A-6-218608

  By the way, as a main shaft device capable of rotating at a high speed, a motor built-in type in which a motor is built in between a front bearing and a rear bearing that support a rotating shaft is used. For this reason, when the rotor fitted to the rotating shaft generates heat, this heat is transmitted to the rotating shaft, and the rotating shaft expands, which may affect the processing accuracy. In addition, the heat transmitted to the rotating shaft is also transmitted to the inner ring of the bearing, the temperature of the inner ring rises, and a temperature difference occurs between the inner and outer rings. Therefore, the bearing preload becomes excessive, and the PV value of the rolling contact portion increases. There is a risk of problems such as burn-in.

  Usually, in order to suppress the thermal displacement due to the temperature rise of the entire spindle device, a method of circulating the cooling oil in the vicinity of the stator and bearing outer diameter portion in the housing is used, but the cooling effect hardly affects the rotating shaft, An imbalance occurs in which the temperature of the rotating shaft is higher than the temperature of the housing. When an axial thermal expansion difference occurs due to such an unbalanced state, the relative position of the fixed-side front bearing and the free-side rear bearing fluctuates. An abnormal load is generated due to the tension between them, which leads to damage such as seizure of the bearing.

  The spindle devices described in Patent Documents 1 to 4 do not describe a motor built-in type device and do not recognize the above problem.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a motor built-in system that can suppress a temperature rise of a rotating shaft and a bearing due to heat generation of a rotor and can improve machining accuracy. It is to provide a spindle device.

The above object of the present invention can be achieved by the following constitution.
(1) a rotating shaft;
Front and rear bearings that respectively support the rotary shaft rotatably with respect to the housing;
A motor having a rotor fitted to the rotary shaft between the front and rear bearings, and a stator disposed around the rotor;
A motor built-in spindle device comprising:
The rotation axis is
A first cylindrical member made of a metal material;
A second cylindrical member which is disposed on the outer peripheral surface of the first cylindrical member, the rotor is fitted to the outer peripheral surface, and which is made of a material having a higher specific elastic modulus and a smaller linear expansion coefficient than the metal material of the first cylindrical member When,
The second cylindrical member is disposed on the outer peripheral surface at a position spaced axially from the outer peripheral surface to which the rotor is fitted, and the inner ring of the front or rear bearing is fitted to the outer peripheral surface, and a third made of a metal material. A cylindrical member;
A motor built-in spindle device characterized by comprising:
(2) The second cylindrical member has a stepped portion so that an outer peripheral surface on which the third cylindrical member is disposed has a small diameter,
The third built-in spindle device according to (1), wherein the third cylindrical member has a flange portion sandwiched between an axial side surface of the stepped portion and an axial end surface of the inner ring.
(3) The motor built-in spindle device according to (1) or (2), wherein the third cylindrical member is a thin sleeve that fits to an outer peripheral surface of the second cylindrical member.
(4) The motor built-in according to (1) or (2), wherein the third cylindrical member is a thin film member bonded to an outer peripheral surface of the second cylindrical member by an electric or chemical method. System spindle device.
(5) In any one of (1) to (4), the third cylindrical member includes two third cylindrical members into which inner rings of the front bearing and the rear bearing are respectively fitted. The motor built-in spindle device as described.
(6) The motor built-in spindle device according to any one of (1) to (5), wherein the second cylindrical member is a carbon fiber composite material.

  According to the motor built-in spindle device of the present invention, the rotation shaft is disposed on the first cylindrical member made of a metal material and the outer peripheral surface of the first cylindrical member, and the rotor is fitted to the outer peripheral surface, and the first The second cylindrical member made of a material having a specific modulus greater than that of the metal material of the cylindrical member, a low coefficient of linear expansion, and a low thermal conductivity, and an outer circumferential surface on which the rotor of the second cylindrical member is fitted in the axial direction. And a third cylindrical member made of a metal material, the inner ring of the front or rear bearing being fitted to the outer peripheral surface. Therefore, the second cylindrical member can suppress the temperature rise of the rotating shaft and the bearing due to the heat generated by the rotor, and the processing accuracy can be improved. In addition, the surface hardness of the third cylindrical member and the inner ring of the bearing can be made equal, the interference fit between them can be easily performed, and when the bearing is replaced, The occurrence of defects such as galling and scratches can be suppressed. In addition, the heat generated in the bearing from the fitting portion of the third cylindrical member and the inner circumferential surface of the bearing inner ring (the entire circumferential surface of the fitting portion becomes the heat transfer area) is passed through the inner ring spacer, One cylindrical member can be transmitted. That is, it is possible to suppress the occurrence of troubles such as seizure due to heat stagnating in the bearing inner ring and excessive preload due to the temperature difference between the bearing inner and outer rings.

It is sectional drawing of the main axis | shaft apparatus which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the coupling | bonding method of the 1st cylindrical member and 2nd cylindrical member of a rotating shaft. It is sectional drawing of the main axis | shaft apparatus which concerns on the modification of this invention. It is sectional drawing of the main axis | shaft apparatus which concerns on the other modification of this invention.

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

(First embodiment)
As shown in FIG. 1, the spindle device 10 is a motor built-in system, and a hollow rotary shaft 12 is provided at the axial center, and a draw bar 13 slides on the axis of the rotary shaft 12. It is freely inserted. The draw bar 13 urges the collet portion 15 that fixes the tool holder 14 in the counter-tool side direction (right direction in the figure) by the force of the disc spring 17, and the tool holder 14 has a tapered surface 18 of the rotary shaft 12. Mates with. A tool (not shown) is attached to the tool holder 14, and as a result, the rotary shaft 12 clamps the tool at one end (left side in the figure) so that the tool can be attached.

  The rotary shaft 12 is rotatably supported by the housing H by two rows of front bearings 50 and 50 that support the tool side and two rows of rear bearings 60 and 60 that support the opposite tool side. Yes. The housing H includes a front cover 40, a front bearing outer ring retainer 29, an outer cylinder 19, a rear housing 24, and a rear lid 26 in order from the tool side.

  The rotor 20 is fitted on the outer peripheral surface of the rotary shaft 12 between the front bearings 50 and 50 and the rear bearings 60 and 60 by shrink fitting. The stator 22 arranged around the rotor 20 is fixed to the outer cylinder 19 by fitting a cooling jacket 23 shrink-fitted to the stator 22 into the outer cylinder 19 constituting the housing H. Therefore, the rotor 20 and the stator 22 constitute a motor, and by supplying electric power to the stator 22, a rotational force is generated in the rotor 20 and the rotating shaft 12 is rotated.

  Each front bearing 50 is an angular ball bearing having an outer ring 51, an inner ring 52, a ball 53 as a rolling element arranged with a contact angle, and a cage (not shown). Is an angular ball bearing having an outer ring 61, an inner ring 62, balls 63 as rolling elements, and a cage (not shown). The front bearings 50 and 50 (parallel combination) and the rear bearings 60 and 60 (parallel combination) are arranged to cooperate with each other to form a back combination.

  The outer rings 51, 51 of the front bearings 50, 50 are fitted into the outer cylinder 19, and are pivoted with respect to the outer cylinder 19 via the outer ring spacer 30 by the front bearing outer ring presser 29 that is bolted to the outer cylinder 19. Positioned and fixed in the direction. Further, the inner rings 52, 52 of the front bearings 50, 50 are externally fitted to the rotating shaft 12, and are axially connected to the rotating shaft 12 via the inner ring spacer 32 by a nut 31 fastened to the rotating shaft 12. Positioning is fixed.

  The outer rings 61, 61 of the rear bearings 60, 60 are fitted inside a sleeve 25 that is slidable in the axial direction with respect to the rear housing 24 inside the rear housing 24. It is positioned and fixed in the axial direction with respect to the sleeve 25 via the outer ring spacer 34 by the rear bearing outer ring presser 33 fastened with bolts. Between the rear housing 24 and the rear bearing outer ring retainer 33, a coil spring 38 for biasing the rear bearing outer ring retainer 33 toward the rear end is interposed, and the rear bearing outer ring retainer 33 and the sleeve 25 are interposed. The outer rings 61, 61 and the outer ring spacer 34 move integrally to the rear end side, the outer rings 61, 61 are pressed in the axial direction, and a constant pressure preload corresponding to the urging force of the coil spring 38 is applied. It has become so. Inner rings 62, 62 of the rear bearings 60, 60 are fitted on the rotary shaft 12, and are inserted into the inner ring spacer 36 and the detected portion 37 of the speed sensor by another nut 35 fastened to the rotary shaft 12. The positioning is fixed.

  Here, the rotating shaft 12 is disposed on a first cylindrical member 71 made of a metal material such as high-tensile steel or carbon steel, and an outer peripheral surface of the first cylindrical member 71, and the rotor 20 is fitted on the outer peripheral surface. A second cylindrical member 72 made of a fiber composite material (CFRP), an inner ring 52, 52 of the front bearings 50, 50, and an inner ring of the rear bearings 60, 60 are arranged on the outer peripheral surface of the second cylindrical member 72. 62 and 62 have two 3rd cylindrical parts 73 and 74 which consist of a metal material which each fits.

  The first cylindrical member 71 is formed longer than the second cylindrical member 72 and regulates the axial positions of the small diameter portion 71a where the second cylindrical member 72 is disposed and the inner rings 52, 52 of the front bearings 50, 50. A large-diameter portion 71c having a male screw portion 71b to which the nut 31 is fastened. Further, a male screw portion to which another nut 35 for restricting the axial position of the inner rings 62 and 62 of the rear bearings 60 and 60 is fastened to the end portion on the side opposite to the tool of the small diameter portion 71a extending from the second cylindrical member 72. 71d is formed. A collet portion 15, a draw bar 13, and a disc spring 17 that move in the axial direction are housed inside the first cylindrical member 71, and the collet portion 15, the draw bar 13, A plurality of sliding contact surfaces 71e, 71f, 71g for slidably guiding the disc spring 17 are formed, and a tapered surface 18 to which the tool holder 14 is attached is formed on the inner peripheral surface on the tool side.

The second cylindrical member 72 has the third cylindrical members 73 and 74 disposed at the front and rear portions that are spaced apart from each other in the axial direction with respect to the axial intermediate portion where the rotor 20 is fitted to the outer peripheral surface. Step portions 72a and 72b are provided so that the outer peripheral surface has a small diameter. The third cylindrical members 73 and 74 are fitted with the sleeve portions 73a and 74a on the outer peripheral surface having a small diameter in front of the stepped portion 72a and rearward of the stepped portion 72b, and the nuts of the sleeve portions 73a and 74a. Flange portions 73b, 74b extending radially outward from the side end portions are sandwiched between the axial side surfaces of the stepped portions 72a, 72b and the axial end surfaces of the inner rings 52, 62.
The outer diameter of the flange portion 74b is set to be equal to or smaller than the outer diameter of the outer peripheral surface to which the rotor 20 is fitted so as not to interfere when the rotor 20 is fitted to the second cylindrical member 72.

  As the carbon fiber composite material constituting the second cylindrical member 72, a material having a higher specific elastic modulus, a lower specific gravity, and a smaller linear expansion coefficient than the metal material constituting the first cylindrical member 71 is used. In particular, the specific elastic modulus of the carbon fiber composite material is preferably at least twice, more preferably at least three times that of the metal material used in order to suppress expansion due to the centrifugal force of the rotating shaft 12 to an appropriate value. . The carbon fiber composite material is anisotropic depending on the fiber direction, but the fiber direction is determined during molding in accordance with the direction of the load. Moreover, you may make it isotropic by making a fiber direction cross. Further, the fiber direction may be determined so that the specific elastic modulus in the circumferential direction is increased.

  As a method of joining the second cylindrical member 72 and the first cylindrical member 71, separately formed members may be joined by interference fitting or adhesion, or may be integrally formed. Furthermore, as shown in FIG. 2, in order to transmit a sufficient rotational torque, a key 80 may be inserted between the second cylindrical member 72 and the first cylindrical member 71, or spline fitting may be performed.

  Further, the carbon fiber composite material that constitutes the second cylindrical member 72 located on the radially outer side has a higher specific modulus, a lower specific gravity, and a wire than the metal material that constitutes the first cylindrical member 71 located on the inner side. Since the expansion coefficient is small, there is no gap in the fitting portion between them due to centrifugal force action and temperature change, and problems such as increased vibration during rotation and reduced rigidity do not occur.

  For example, the carbon fiber composite material constituting the second cylindrical member 72 is a fabric in which yarns made of carbon fibers made of PAN (polyacrylonitrile) as a main raw material are arranged in parallel, or a fabric made of yarns made of carbon fibers. The sheet is manufactured by laminating a number of layers of a sheet formed by impregnating a thermosetting resin such as an epoxy resin containing a curing agent, winding the sheet around a cored bar, etc., and curing the sheet by heating.

As characteristics of the carbon fiber composite material, for example, when carbon fiber type: HTA of Toho Tenax Co., Ltd. is used, the tensile strength is 2060 MPa, the tensile elastic modulus is 137 GPa, and the specific gravity is 1.55 g / cc. The tensile strength is equivalent or higher, and the specific gravity is about 1/5. Moreover, since the coefficient of thermal expansion can be made −5 to + 5 × 10 ⁻⁶ (K ⁻¹ ) by optimizing the fiber direction and angle, it is ½ to 1 compared to conventional carbon steel. / 10 or so.

  The rotor 20 and the second cylindrical member 72 are fitted with an interference due to shrink fitting. If the interference at the mating part decreases due to centrifugal force, rotational slippage due to torsional torque will occur, and if it becomes a clearance, the vibration of the main shaft may increase or machining may be defective. There is.

  For this reason, the interference is set in advance in advance in consideration of reduction of interference due to centrifugal force. For example, considering the reduction in interference due to centrifugal force, the interference is the same clearance as (the centrifugal expansion amount of the inner diameter of the rotor 20 minus the centrifugal expansion amount of the outer diameter of the second cylindrical member 72) or more. Set to. Specifically, the winding angle at the time of molding the carbon fiber composite material is set to an appropriate value, for example, “specific elastic modulus = E (longitudinal elastic modulus) / ρ (density)” is set to an appropriate value, or the rotor Adjust the radial thickness of 20 and the radial thickness of the carbon fiber composite material to an appropriate ratio or value, or select the rotor material and carbon fiber composite material (select the fiber diameter and binding resin material). Is set. Further, these methods may be combined, or other factors that affect centrifugal expansion may be set to appropriate values.

  In addition, if the linear expansion coefficient of the carbon fiber composite material is set to be smaller than that of the rotor 20 depending on the winding angle at the time of molding, it is considered that the interference is reduced due to a rise in the temperature of the rotor 20 and a clearance is formed. For this reason, it is preferable that the interference is set to be equal to or larger than (the above-mentioned centrifugal expansion amount + a decrease in interference due to temperature rise).

  Alternatively, a metal sleeve (not shown) may be interposed between the second cylindrical member 72 of the rotor 20, or as described in Patent Document 1, the outer peripheral surface of the carbon fiber composite material Alternatively, metal plating or ceramic may be sprayed.

  In addition to fitting with interference, a spline or key may be formed on at least a part of the rotor 20 and the second cylindrical member 72 to integrally mold the carbon fiber composite material.

  The third cylindrical members 73 and 74 are thin-walled sleeves fitted to the outer peripheral surface of the second cylindrical member 72, and are metal materials having a surface hardness equivalent to that of the first cylindrical member 71, such as high-tensile steel or carbon steel. Is preferably selected. The third cylindrical members 73 and 74 formed of such a thin sleeve are covered with the outer peripheral surface of the second cylindrical member 72 by shrink fitting, or by using a slight interference and bonding together. The outer peripheral surface of the member 72 is coupled. The inner rings 52, 52 of the front bearings 50, 50 and the inner rings 62, 62 of the rear bearings 60, 60 are fitted to the outer peripheral surfaces of the third cylindrical members 73, 74 with interference.

  The outer peripheral surface of the second cylindrical member 72 made of a carbon fiber composite material combined with the first cylindrical member 71 is subjected to a finishing process in order to ensure proper fitting with the third cylindrical members 73 and 74. Further, the outer peripheral surfaces of the third cylindrical members 73 and 74 made of a metal material are also subjected to a finishing process in order to ensure proper fitting with the inner rings 52 and 62.

  By the way, although the carbon fiber composite material which comprises the 2nd cylindrical member 72 is excellent in a metal material in specific elastic modulus, surface hardness tends to depend on the resin material used as a base material, and is comparatively soft. Further, the fitting between the rotating shaft 12 and each of the inner rings 52 and 62 needs to be an interference fit with at least a clearance of 0 or more in order to increase the rigidity of the main shaft and improve the rotation accuracy of the shaft.

  There is no problem even if the interference value is small for a main shaft with a relatively low rotational speed, but in the case of a main shaft used at high speed rotation, the expansion of the inner rings 52 and 62 due to centrifugal force is larger than that of the rotation shaft 12. Become. For this reason, if the interference is small, the clearance becomes large and problems such as vibration of the rotating shaft and fretting occur. Therefore, it is necessary to increase the interference. Under these conditions, when the carbon fiber composite material and the inner ring are fitted together locally (only in the axial width portion of the inner ring), the contact surface pressure between them increases locally, and the carbon fiber composite There is a possibility that the mating part cannot be joined well due to the crushing or deformation of the surface of the material.

  On the other hand, as in the present embodiment, by using the third cylindrical members 73 and 74, the carbon fiber composite material (second cylindrical member 72) and the third cylindrical members 73 and 74 are coupled in a wide range in the axial direction. In addition, by using a thin sleeve, even if it is fitted with a carbon fiber composite material with a large interference, elastic deformation on the third cylindrical members 73 and 74 side can be expected. Can be reduced. Note that the contact surface pressure does not increase if both are bonded together as a small interference fit instead of a large interference fit.

  Thereafter, even when the inner rings 52, 62 are fitted to the outer peripheral surfaces of the third cylindrical members 73, 74 with a large interference, a local surface pressure is not directly applied to the surface of the carbon fiber composite material. A load acts through the cylindrical members 73 and 74, and the compressive force due to the fitting is dispersed. By such a buffering action, the surface of the carbon fiber composite material is not crushed or deformed.

  Further, since the linear expansion coefficient is different between the inner ring and the carbon fiber composite material, the clearance of the fitting portion changes in the same manner as the centrifugal force effect when the temperature of the main shaft rises as the rotation increases. Therefore, in consideration of these conditions, the fitting clearance between the third cylindrical members 73 and 74 and the inner rings 52 and 62 during operation (for example, at the maximum rotation of the target spindle) is 0 to the interference side. It is desirable to set the fit when assembled.

  Further, when the bearing is replaced due to periodic maintenance or sudden bearing failure, the inner rings 52, 62 are pulled out from the third cylindrical members 73, 74 made of a metal material. Since this drawing structure is the same as the conventional structure in which the inner ring is fitted to the rotating shaft of the metal material, there is no problem.

Further, as described above, since the third cylindrical members 73 and 74 are provided with the flange portions 73b and 74b, the inner rings of the bearings 50 and 60 are provided together with the nuts 31 and 35 and the inner ring spacers 32 and 36 on the opposite side. The axial fixing of the end can be an intermetal bond. Since the carbon fiber composite material uses a synthetic resin material as a base material, when the inner rings 52 and 62 and the carbon fiber composite material are tightly bonded with a certain load, the inner ring end portion and the contact portion of the carbon fiber composite material are between Elastic deformation tends to be large, and the tightening connection by the nuts 31 and 35 may be weakened. That is, if the tightening force is extremely increased with emphasis on rigidity, there is a concern that the carbon fiber composite material may be broken or cracked. On the other hand, in order to ensure cutting accuracy, axial deformation rigidity is required. Therefore, these problems can be solved by providing the third cylindrical members 73 and 74 with the flange portions 73b and 74b.
When the surface hardness of the carbon fiber composite material is relatively high, the axial end surfaces of the inner rings 52 and 62 and the stepped portions 72a and 72b of the second cylindrical member 72 are not provided without providing the flange portions 73b and 74b. And may be directly joined.
Further, the sleeve portions 73a and 74a and the flange portions 73b and 74b may be constituted by different members.

  As described above, according to the spindle device 10 of the present embodiment, since the carbon fiber composite material used for the second cylindrical member 72 has a low thermal conductivity, the rotor 20 is externally fitted to the second cylindrical member 72. The heat generated by the rotor 20 is difficult to be transmitted to the inner rings 52 and 62 of the front and rear bearings 50 and 60 via the rotating shaft 12, and the temperature difference between the inner and outer rings 51, 52, 61 and 62 is suppressed, and an appropriate preload is achieved. Maintained. Further, since the linear expansion coefficient is small, the expansion of the rotary shaft 12 itself is also suppressed, so that good machining accuracy can be obtained.

  Moreover, since the rotating shaft 12 is provided with the 1st cylindrical member 71 which consists of metal materials inside the 2nd cylindrical member 72, the taper surface 18 to which the sliding contact surface 71f of the draw bar 13 and the tool holder 14 are attached is the 1st. It is comprised by the cylindrical member 71, and the abrasion resistance in a specific site | part can also be ensured.

  Further, since the rotor 20 is fitted to the second cylindrical member 72 with a margin, it is possible to prevent a gap from occurring even if a centrifugal force or a temperature rise of the rotor 20 occurs, and the rotor 20 rotates. In addition, an increase in vibration of the rotating shaft 12 can be suppressed.

The first cylindrical member 71 includes a small-diameter portion 71a in which the second cylindrical member 72 is disposed, and a large-diameter portion 71c having a male screw portion 71b to which the nut 31 that regulates the axial position of the front bearing 50 is tightened. Thus, the nut 31 can be securely fastened to the male screw portion 72b.
Further, since the heat generation of the inner rings 52, 52 of the front bearings 50, 50 is transmitted from the inner ring spacer 32 and the nut 31 to the metal member such as the tool holder 14 via the first cylindrical member 71, the inner rings 52, 52 are transmitted. Temperature rise can be suppressed.

  Further, in the motor built-in spindle device, the distance between the front bearing 50 and the rear bearing 60 becomes long, and the natural frequency of the rotating shaft in the radial direction tends to be small. In the case of machine tool spindles, it may be used in all areas up to the maximum number of revolutions, depending on the workpiece and machining conditions, rather than being used at a specific number of revolutions. If the frequency is not greater than the frequency at the maximum rotation, there is a possibility that machining cannot be performed due to the resonance action, or abnormal vibration of the rotating shaft 12 in the resonance region may occur. In this embodiment, a carbon fiber composite material having a larger specific modulus than that of a metal material is used. Therefore, in the case of the same bearing span, the natural frequency of the rotating shaft system (particularly, the natural frequency in the radial direction) is increased. The maximum number of rotations of the spindle device can be increased, and the machining rotation area can be widened.

  In addition, since the carbon fiber composite material is excellent in vibration damping properties compared to the metal material, the dynamic rigidity of the rotating shaft 12 can be improved, and as a result, chatter vibration is hardly generated in severe processing conditions and finishing processing. The surface roughness is improved, the quality and glossiness of the processed surface are improved, and the processing accuracy is stabilized.

Further, the machining time and deceleration time of the spindle device depend on the size of the rotary inertia J. Here, the rotational inertia of the hollow cylinder is given by the following calculation formula and is in a relationship proportional to the fourth power of the diameter.
J = (D ⁴ −d ⁴ ) · L · η · π / 32
Here, D is the outer diameter of the hollow cylinder, d is the inner diameter of the hollow cylinder, L is the axial length of the hollow cylinder, and η is the specific gravity.

  Therefore, by applying a carbon fiber composite material having a small specific gravity as the rotating shaft 12 occupying a large weight ratio among the main components of the main shaft device, the weight of the rotating shaft 12 as a whole is reduced, and the rotating shaft 12 is separated from the center of rotation. Since the carbon fiber composite material is applied to the second cylindrical member 72, the rotational inertia can be reduced, the machining time and the deceleration time of the spindle device can be greatly shortened, and the machining tool replacement time can be shortened, thereby achieving high efficiency machining. Is possible.

  In addition, since the metal material is present on the inner diameter side or both end sides, the outer diameter of the rotating shaft and the reference surface for inner diameter finish grinding are ensured, and finish grinding can be performed with high accuracy. When a reference surface is provided on the carbon fiber composite material, wear and deformation are likely to occur, and it is difficult to ensure the coaxiality and roundness required for the high-speed main shaft. If the coaxiality and roundness are poor, the unbalance is large, causing vibration during high-speed rotation and poor machining accuracy.

  Furthermore, according to the present embodiment, the inner ring 52 of the front and rear bearings 50, 60 is provided on the outer peripheral surface of the second cylindrical member 72 at a position spaced axially from the outer peripheral surface with which the rotor 20 is fitted. , 62 are fitted, and the third cylindrical members 73, 74 made of a metal material are disposed, so that the surface hardness of the third cylindrical members 73, 74 and the inner rings 52, 62 of the bearings 50, 60 are made equal. Interference fit between the two can be easily performed, and when the bearings 50 and 60 are replaced, the occurrence of problems such as galling or scratches on the mating surfaces can be suppressed.

  In addition, the amount of heat generated by the bearing is reduced by the inner ring spacer 32, from the fitting portion of the inner peripheral surface of the third cylindrical members 73, 74 and the bearing inner rings 52, 62 (the entire circumferential surface of the fitting portion becomes the heat transfer area). It can be transmitted to the front bearing nut 31 and the first cylindrical member 71 via 36. That is, it is possible to suppress the occurrence of problems such as seizure due to heat stagnating in the bearing inner rings 52 and 62 and excessive preload due to the temperature difference between the bearing inner and outer rings.

  Further, the third cylindrical members 73 and 74 have flange portions 73b and 74b sandwiched between the axial side surfaces of the stepped portions 72a and 72b of the second cylindrical member 72 and the axial end surfaces of the inner rings 52 and 62. Even when the nuts 31 and 35 on the opposite side are strongly tightened, the inner ring ends of the bearings 50 and 60 can be fixed in the axial direction without causing damage such as cracking or chipping of the second cylindrical member 72.

  In the present embodiment, the third cylindrical members 73 and 74 are thin sleeves that fit on the outer peripheral surface of the second cylindrical member 72, but the third cylindrical members 73 and 74 are outer peripheral surfaces of the second cylindrical member 72. It may be a thin film member bonded to the surface by an electrical or chemical method. For example, when the following metal plating is used, a strong film can be formed. For example, on the surface of the second cylindrical member 72 (that is, the outer peripheral surface and the axial end surfaces of the stepped portions 72a and 72b), a base treatment layer for thermal spraying, a metal spray treatment layer, an intermediate plating layer, and an outermost plating layer, By forming sequentially from the inside, a metal plating layer that is firmly bonded can be obtained.

Here, the base treatment layer has, for example, a thermal conductivity of 0.001 cal · cm ⁻¹ · sec ⁻¹ · deg ⁻¹ or more and λ · S ≧ 0.05 (λ: thermal conductivity, S: m Carbon fiber composite material by blending a non-flat inorganic filler satisfying ² / g) or a specially shaped metal or inorganic powder, such as an inorganic filler having complex irregularities on the surface, with a thermosetting resin It is formed by applying to the surface and thermosetting. The material of the metal spray-treated layer is not particularly limited as long as it can be electroplated on the surface, such as Cu, Ni, Al, and Fe. The material of the intermediate plating layer is selected from the viewpoint of sealing performance and corrosion resistance. As a result of various experiments for such purposes, Cu or Ni is particularly effective. Further, the material of the outermost plating layer is appropriately selected depending on the application, but Ni and Cu are generally employed, and Cu plating is preferable when surface hardness is particularly required.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
For example, in the above-described embodiment, the front bearing and the rear bearing are configured by a pair of angular ball bearings, but the type and number of the bearings are not limited thereto, and can be appropriately designed according to the use state.

  Further, as shown in FIG. 3, the inner rings 52, 52 of the front bearings 50, 50 are attached to the rotating shaft 12 by a fixing sleeve 81 that is fitted around the first cylindrical member 71 of the rotating shaft 12 with an interference. On the other hand, it may be configured to be positioned and fixed in the axial direction. The fixing sleeve 81 is incorporated into the first cylindrical member 71 by shrink fitting, and the fixing sleeve 81 is disassembled from the first cylindrical member 71 between the fixing sleeve 81 and the first cylindrical member 71. This is done by applying hydraulic pressure to the hydraulic chamber 83.

  In such a configuration, since the fixing sleeve 81 and the first cylindrical member 71 are fitted to each other, the effective contact area between the fixing sleeve 81 and the first cylindrical member 71 is increased, so that the thermal conductivity is increased. As a result, the heat generation of the inner ring 52 of the front bearing 50 can be efficiently released to the first cylindrical member 71 via the fixed sleeve 81.

  Further, since the fixed sleeve 81 is configured to directly contact the inner ring 52 without using a spacer or the like, the axial length of the fixed sleeve 81 can be set long. Therefore, the axial length of the fitting portion between the fixed sleeve 81 and the first cylindrical member 71 is increased, and the contact area for heat conduction can be further increased.

  As described above, the heat generation of the inner ring 52 of the front bearing 50 can be more efficiently transmitted to the first cylindrical member 71 side via the fixed sleeve 81, so that the temperature of the inner ring 52 decreases and the inner ring 52 and the outer ring 51 The temperature difference can be reduced. Therefore, an increase in the preload during rotation of the front bearing 50 is reduced, and the PV values of the rolling contact portions of the inner ring 52 and the ball 53 and the outer ring 51 and the ball 53 can be suppressed, so that the front bearing 50 can be prevented from being seized. .

  Further, since the fixing sleeve 81 and the first cylindrical member 71 of the rotating shaft 12 are fitted to each other, the tilting of the fixing sleeve 81 with respect to the rotating shaft 12 is suppressed, and the inner ring 52 can be fixed uniformly. This makes it possible to improve the processing accuracy.

Even when the inner ring 52 is positioned and fixed in the axial direction by the nut 31 as in the above-described embodiment, the axial length of the nut 31 is ensured long, or the screw pitch is shortened (fine screw). By adopting specifications such as extremely small fitting gaps between the nut 31 and the first cylindrical member 71 and between the spacer 32 and the second cylindrical member 72 (for example, intermediate fitting) It is possible to increase the effective contact area of conduction and release the heat generated in the inner ring 52.
Similarly, even when the inner ring 52 is positioned and fixed in the axial direction by the nut 31, by correcting the inclination when the nut 31 is assembled, the inner ring 52 can be fixed uniformly and processing accuracy can be ensured. It is.

  In addition, the front side bearing 50 arrange | positioned at the tool side is a bearing which loads a cutting load, and the emitted-heat amount becomes high with the said load. Further, since the taper surface 18 for holding the tool holder 14 is provided on the tool side of the spindle device 10, a wall thickness is required to ensure the shaft rigidity and the natural frequency of the shaft system, and the front bearing 50 Tends to increase, and as a result, the dmn value of the front bearing 50 increases. Therefore, it is very effective to provide the fixed sleeve 81 as described above so as to efficiently release the heat generated by the front bearing 50.

  On the other hand, the rear bearing 60 disposed on the side opposite to the tool is not directly subjected to a cutting load as compared with the front bearing 50 and is smaller in size than the front bearing 50. Therefore, as in the above-described embodiment. A configuration in which the nut 35 is positioned in the axial direction may be used. However, the inner rings 62, 62 of the rear bearings 60, 60 have an interference with the first cylindrical member 71 without using the nut 35 as necessary, for example, when there is a margin for securing an axial space. Then, it may be configured to be positioned and fixed in the axial direction with respect to the rotating shaft 12 by a fixing sleeve fitted outside (not shown).

Moreover, the structure which a fixed position preload is each given to the front bearings 50 and 50 and the rear bearings 60 and 60 may be sufficient like the main axis | shaft apparatus which concerns on the other modification of this invention shown in FIG. In this case, the front bearings 50 and 50 and the rear bearings 60 and 60 are arranged so as to be a back combination.
Even in such a spindle device, the same effects as those of the above-described embodiment can be obtained.

  Further, the spindle device to which the present invention is applied is constituted by a pair of angular ball bearings so that a fixed position preload is applied to the front bearings 50, 50, and the rear bearing 60 is constituted by a single row cylindrical roller bearing. It may be something like that.

DESCRIPTION OF SYMBOLS 10 Main shaft apparatus 12 Rotating shaft 20 Rotor 22 Stator 50 Front side bearing 60 Rear side bearing 71 1st cylindrical part 72 2nd cylindrical part H Housing

Claims (6)

A rotation axis;
Front and rear bearings that respectively support the rotary shaft rotatably with respect to the housing;
A motor having a rotor fitted to the rotary shaft between the front and rear bearings, and a stator disposed around the rotor;
A motor built-in spindle device comprising:
The rotation axis is
A first cylindrical member made of a metal material;
A second cylindrical member which is disposed on the outer peripheral surface of the first cylindrical member, the rotor is fitted to the outer peripheral surface, and which is made of a material having a higher specific elastic modulus and a smaller linear expansion coefficient than the metal material of the first cylindrical member. When,
The second cylindrical member is disposed on the outer peripheral surface at a position spaced axially from the outer peripheral surface to which the rotor is fitted, and the inner ring of the front or rear bearing is fitted to the outer peripheral surface, and a third made of a metal material. A cylindrical member;
A motor built-in spindle device characterized by comprising: The second cylindrical member has a stepped portion so that an outer peripheral surface on which the third cylindrical member is disposed has a small diameter,
2. The motor built-in spindle device according to claim 1, wherein the third cylindrical member has a flange portion sandwiched between an axial side surface of the stepped portion and an axial end surface of the inner ring.   3. The motor built-in spindle device according to claim 1, wherein the third cylindrical member is a thin sleeve fitted to an outer peripheral surface of the second cylindrical member.   3. The motor built-in spindle device according to claim 1, wherein the third cylindrical member is a thin film member bonded to an outer peripheral surface of the second cylindrical member by an electric or chemical method.   5. The motor according to claim 1, wherein the third cylindrical member has two third cylindrical members into which inner rings of the front bearing and the rear bearing are respectively fitted. Built-in spindle device.   The motor-built-in spindle device according to any one of claims 1 to 5, wherein the second cylindrical member is a carbon fiber composite material.

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